Dept of Mechanical Engg

DEPT OF MECHANICAL ENGG

Researcher : Au Yeung KL

List of Research Outputs

Au Yeung K.L., Sze K.Y., Sham M.H. and Chan B.P., Development of a micromanipulator-based loading device for mechanoregulation study of human mesenchymal stem cells in three-dimensional cellagen constructs , Tissue Engineering, Part C Methods. 2010, 16(1): 93-107.

Researcher : Au-yeung KL

List of Research Outputs

Au-yeung K.L., Sze K.Y., Sham M.H. and Chan B.P., Development of a micromanipulator-based loading device for mechanoregulation study of human mesenchymal stem cells in 3D collagen constructs., WACBE (World Association for Chinese Biomedical Engineers) World Congress on Bioengineering 2009. 26-29 Jul 2009, Hong Kong, China.. 2009, 53.

Chan B.P., Li C.H., Au-yeung K.L., Sze K.Y. and Ngan A.H.W., Research Output Prize 2009, Faculty of Engineering. 2009.

Researcher : Bai C

List of Research Outputs

Bai C. and Wang L., Constructal allocation of nanoparticles in nanofluids, Journal of Heat Transfer. 2010, 132: 052404/1-052404/6.

Bai C. and Wang L., Constructal design of nanofluids for one-dimensional steady heat conduction systems, NANO. 2010, 5: 39-51.

Researcher : Chan ATY

Project Title:	Strategic guidelines for future development to achieve sustainable air quality in urban areas
Investigator(s):	Chan ATY
Department:	Mechanical Engg
Source(s) of Funding:	Other Funding Scheme
Start Date:	09/1999

Abstract:

To develop a list of comprehensive strategic planning and development guidelines for urban area development in order to achieve sustainable air quality in Hong Kong.

Project Title:	Evaluation of air pollution indication system in Hong Kong
Investigator(s):	Chan ATY
Department:	Mechanical Engg
Source(s) of Funding:	Pollution Studies in Hong Kong
Start Date:	01/2000

Abstract:

To produce an objective assessment of its air quality and an effective mean of control measures through the analysis air quality and air pollution indices of various countries.

Project Title:	16th Engineering Mechanics Conference (ASCE) Drag Effect on Mountain Waves by Flow Over Topography
Investigator(s):	Chan ATY
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	07/2003

Abstract:

N/A

Project Title:	Indoor/outdoor air quality relationships of respirable suspended particulates, nitrogen oxides and carbon monoxides in urban buildings
Investigator(s):	Chan ATY, Li Y
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	09/2003

Abstract:

To investigate experimentally and computationally indoor-outdoor (IO) relationships in buildings and to develop semi-empirical models for various situations.

Project Title:	Correlation between urban morphological attributes and air pollution in urban areas in Hong Kong
Investigator(s):	Chan ATY
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	09/2004

Abstract:

To identify the urban morphological attributes that are responsible for air pollution in urban areas through analytical and experimental investigation.

Project Title:	15th United States National Congress on Theoretical and Applied Mechanics Indoor/outdoor Air Quality Relationship in an Urban Street Canyon
Investigator(s):	Chan ATY
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2006

Abstract:

N/A

Researcher : Chan BP

Project Title:	Photochemical crosslinking (PC) technology in fabrication of collagen-based scaffolds for tissue engineering
Investigator(s):	Chan BP
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2004

Abstract:

To develop an innovative photochemical crosslinking technology, which is the light activation of a photosensitizing compound leading to the crosslinking of collagen.

Project Title:	International Society for Stem Cell Research 4th ISSCR Annual Meeting A Novel 3-Dimensional Culture System for Human Mesenchymal Stem Cells
Investigator(s):	Chan BP
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2006

Abstract:

N/A

Project Title:	Collagen biomaterial and bone marrow derived mesenchymal stem cell (MSCs) based therapy - Second generation tissue engineering solutions for cartilage repair
Investigator(s):	Chan BP, Chan GCF, Chan D, Cheung KMC, Sze KY
Department:	Mechanical Engg
Source(s) of Funding:	Guangdong-Hong Kong Technology Cooperation Funding Scheme
Start Date:	08/2007
Completion Date:	07/2009

Abstract:

This project aims to develop second generation tissue engineering solutions for cartilage repair using MSC-collagen microshpheres and photochemically crosslinked collagen membranes. Specifically, we aim to (1) optimize the conditions for construction of an automatic and high throughput facility for fabrication of collagen-cell microspheres; (2) optimize the conditions for fabrication of stable and injectable collagen-MSC microspheres using the microencapsulation technology; (3) optimize the conditions for fabrication of collagen-based artificial bone sheath graft using photochemical crosslinking technology; and (4) conduct the in vivo evaluation of the repair in a rabbit model.

Project Title:	Migratory and invasion activities of human mesenchymal stem cells cultured in 3D collagen microspheres and their surface chemokine receptors expression
Investigator(s):	Chan BP, Chan GCF
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	04/2008
Completion Date:	09/2009

Abstract:

Mesenchymal stem cell (MSCs)-based therapy is promising for regenerative medicine [1-2]. However, the functional outcomes of existing MSC-based therapies have not been satisfactory because of the poor engraftment of the delivered cells in particular the systemically delivered ones. Previous studies on hMSCs systemic infusion showed <1% engraftment rate in different organs in irradiated NOD/SCID mice [3] and in lumbar dorsal root ganglia in rats after sciatic nerve constriction [4], and <5% engraftment in bones in children with osteogenic imperfecta [5]. As a result, strategies improving MSC engraftment rate in local injured tissues may improve the functional outcomes of MSC-based therapies. Response of cells towards concentration gradients of chemo-attractants and the subsequent invasion through the endothelial barrier are the prerequisites of successful engraftment at local tissue injury site. As a result, increased sensitivity of MSCs toward chemoattractants concentration gradients may improve the engraftment rate. Migration of hMSCs is mediated by chemoattractants such as MSCP1, IGF1, fractalkine, SDF1/CXCL12 and their respective receptors CCR2, IGF1R, CXCR1 and CXCR4 [6-8]. In our lab, we have developed a 3D collagen microsphere system encapsulating human MSCs for 3D culture and local delivery [9]. The encapsulated MSCs are able to survive, proliferate and differentiate in the 3D microspheres. Moreover, the encapsulated MSCs can also invade and migrate through the collagen microspheres (Fig. 1 – see Section VI) with retained multi-differentiating potential and immunophenotype. What is even more interesting is that we recently found a better migratory response in these MSCs (Fig. 2 – see Section VI) towards chemo-attractants including SDF1 and fractalkine (Fig. 3 – see Section VI). We therefore hypothesize that interactions between MSCs and the 3D collagen microspheres may up-regulate the expression of chemoattractant receptors on MSC surface and enhance their migratory activities. In this proof-of-principle study, we would like to (1) find out the 3D microsphere culture conditions with optimized migratory and invasion responses of MSCs towards different chemoattractants; (2) investigate whether the MSC surface receptors towards various chemo-attractants are up-regulated in 3D cultures comparing with those in traditional 2D cultures.

Project Title:	Collagen biomaterial and bone marrow derived mesenchymal stem cell (MSCs) based therapy - Second generation tissue engineering solutions for cartilage repair
Investigator(s):	Chan BP
Department:	Mechanical Engg
Source(s) of Funding:	Innovation and Technology Fund Internship Programme
Start Date:	07/2008

Abstract:

Project Title:	Collagen biomaterial and bone marrow derived mesenchymal stem cell (MSCs) based therapy - Second generation tissue engineering solutions for cartilage repair
Investigator(s):	Chan BP
Department:	Mechanical Engg
Source(s) of Funding:	Innovation and Technology Fund Internship Programme
Start Date:	08/2008

Abstract:

Project Title:	Creating Stable Tissue Interfaces for Bioengineered Intervertebral Disc Segment
Investigator(s):	Chan BP, Cheung KMC, Luk KDK
Department:	Mechanical Engg
Source(s) of Funding:	Innovation and Technology Support Programme (Tier 3)
Start Date:	10/2008
Completion Date:	03/2010

Abstract:

IVD degeneration is a common disorder. In late stage degeneration, disc replacement is the only option for motion preservation. Currently, artificial IVD using metal and rubber provides functional replacement. However, its long term usage is uncertain. A biological functional replacement is the ideal treatment. Recently, allograft transplantation has been shown promising but donor availability, immunogenicity, degenerative changes and lack of remodeling cells are issues remained to be solved. The technological challenges for bioengineering an IVD replacement are multifold. First, disc is a complex structure of heterogeneous tissues with differential biological and mechanical properties. We have previously established methods in fabricating bone, cartilage and disc (annulus and nucleus) structures with favorable biological and mechanical properties. Second, disc cells play important roles in remodeling the extracellular matrix upon physiological and mechanical stimulation during daily activities. We have previously demonstrated that bone marrow mesenchymal stem cells (MSCs) are able to survive, proliferate, migrate, differentiate and secrete specific extracellular matrix in collagen biomaterials used for fabricating various tissue structures. Third, there are several important interfaces such as bone to endplate and endplate to disc interfaces, which serve important biomechanical and biological functions in native tissues. In this project, we aim to develop stable biological integration between multiple tissue components of the bioengineered IVD segment. The outcomes of this study would be the prerequisite to future development of intact and functional bioengineered IVD segment as a potential therapeutic treatment with long term efficacy for late stage IVD degeneration.

Project Title:	A Novel Cell Delivery Technology Injectable Collagen-Cell Microspheres For Intervertebral Disc Regeneration
Investigator(s):	Chan BP, Chan D, Chan GCF, Cheung KMC, Leung YL, Sze KY
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2009

Abstract:

(1) To determine the best fabrication parameters, by optimizing cell seeding density and collagen concentration, for collagen- MSC microspheres; (2) To investigate the long term fate of the delivered MSCs by labeling the cells with GFP and monitoring their local engraftment and functional remodeling; (3) To compare the efficacy of MSC-collagen microspheres in treating IVD degeneration with that of the traditional delivery approaches using saline or hydrogel; (4) To augment the biological potency of the encapsulated MSCs on IVD regeneration by pre-differentiation with Transforming Growth Factor-beta3.

Project Title:	Creating Stable Tissue Interfaces for Bioengineered Intervertebral Disc Segment
Investigator(s):	Chan BP
Department:	Mechanical Engg
Source(s) of Funding:	Innovation and Technology Fund Internship Programme
Start Date:	02/2009

Abstract:

Project Title:	Creating Stable Tissue Interfaces for Bioengineered Intervertebral Disc Segment
Investigator(s):	Chan BP
Department:	Mechanical Engg
Source(s) of Funding:	Innovation and Technology Fund Internship Programme
Start Date:	05/2009

Abstract:

Project Title:	Fabrication of osteoinductive microparticles for bone tissue engineering
Investigator(s):	Chan BP, Luk KDK, Cheung KMC
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2009

Abstract:

There is a demonstrated clinical need for bone graft materials for treating bone disorders [1-3]. Autologous bone grafts are still the “gold standard” for bone repair and regeneration [4]. This is mainly because of the absence of immunogenicity and the presence of three favorable characteristics for bone regeneration namely osteoinductivity, osteoconductivity and osteogenicity [1,3,5]. Nevertheless, invasive nature of the harvesting procedure, donor site morbidities and limited availability are the main drawbacks of autologous bone grafting irrespective of the excellent performance of this approach. Allogenic or xenogenic bone grafts do not have the donor site morbidity and the availability issues but present the immunogenicity problem and have compromised the biological performance as compared to autografts [6-7]. Upon Urist’s initial report on the osteoinductivity of demineralized and freeze-dried allogenic grafts [8], the active compounds inducing bone formation namely bone morphogenic proteins (BMPs) have been identified and researched extensively [9-10] and the demineralized bone matrix (DBM) possessing osteoinductivity have been developed into various formulations [2,11]. Nevertheless, multiple injections of BMPs are needed and better carriers are therefore needed to control their release upon injection so as to make it an affordable option. While for the DBM, carriers and augmentation formulations are needed to improve their handling capability [2]. Osteoconductive materials provide the three dimensional porous structures facilitating cell and nutrient infiltration for bone growth [1,3]. Many osteoconductive matrix materials have been developed as bone graft substitutes to provide readily available scaffolds facilitating bone ingrowth [12]. Examples include calcium phosphate-based materials such as insoluble hydroxyapatites and soluble calcium sulfates [1,12,13] and collagen type I [14]. Osteogenic activity refers to the provision of bone forming cells such as osteoblastic cells from fresh bone grafts or bone marrow [1,15]. Bone marrow derived mesenchymal stem cells (MSCs) are multipotent cells able to differentiate into osteogenic lineages [16] and therefore can be used as an osteogenic cell source. Important roles of bone marrow derived MSCs treating bone disorders have been reported [17-19]. Moreover, the availability of MSCs from adults provides the opportunity to use autologous cells for bone regeneration with better biological performance. We previously developed a novel collagen microencapsulation technology [7], which entraps bone marrow MSCs in a self-assembled biomimetic collagen matrix consisting of collagen fiber meshwork. Stable and injectable microspheres providing a physiologically relevant microenvironment to support MSC viability, proliferation, migration and differentiation have been produced for cell delivery and tissue engineering [9]. Recently, we successfully induced the encapsulated bone marrow mesenchymal stem cells into chondrogenic lineage, which remodels to form cartilage-specific matrix, and produced injectable cartilage tissue micro-masses [19]. In this study, we aim to produce alternatives for fresh bone grafts with osteoinductivity, osteoconductivity and osteogenicity using human mesenchymal stem cells and collagen materials. Specifically, we aim to microencapsulate human mesenchymal stem cells, which serve as the osteogenic cell source, in osteoconductive collagen fiber meshwork, and to differentiate the encapsulated MSCs towards osteogenic lineage in the 3D microspheres. Osteogenic differentiation markers in hMSCs such as the early marker alkaline phosphatase and the late stage marker calcium deposition will be evaluated. SEM and EDX analysis will also be conducted to evaluate the microstructure and composition of bones formed. Moreover, osteoinductivity will be investigated via co-culture of the microspheres with undifferentiated MSCs and expression and secretion of BMPs from the differentiating MSCs.

Project Title:	Research Output Prize
Investigator(s):	Chan BP, Li CH, Sze KY, Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Research Output Prize (in Faculty)
Start Date:	12/2009

Abstract:

To identify and recognize the best research outputs in different faculties.

Project Title:	Selection of human mesenchymal stem cells (hMSCs) sub-populations with better migratory activities using a collagen barrier - A strategy to enhance stem cell engraftment?
Investigator(s):	Chan BP, Chan GCF, Yang Z
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2010

Abstract:

1) To optimize the selection process by studying the effects of various process parameters on the migratory properties of the selected subpopulations; 2) To associate the in vitro migratory activities with the in vivo stem cell engraftment rate by using a hepatectomized NOD/SCID mice model; 3) To understand the mechanisms of the selection process by profiling a number of molecular markers associated with several key steps in the engraftment process.

Project Title:	Decellularization of intervertebral disc cell-encapsulated collagen microspheres – A 3D model to study the effects of acellular matrix on stem cell fate
Investigator(s):	Chan BP
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2010

Abstract:

Objectives Stem cell niche is collectively made up of several different cell types, a specialized extracellular matrix (ECM) consisting of many different constituents and a variety of growth factors [Watt & Hogan 2000]. Existing experimental models studying the effect of particular ECM on stem cell fate are usually supplementation of secreted factors and free ECM to 2D monolayer cultures. Nevertheless, it has recently been demonstrated that cells interact with their ECM differently when they are in a 3D configuration compared with in 2D monolayer cultures [Cukierman et al. 2001]. As a result, experimental models reconstituting the ECM microenvironment in a 3D configuration will significantly enhance our understanding of how stem cells interact with and respond to the ECM niche before effective scaffolding strategies with appropriate controls over the stem cell fates can be developed. Recently, we have used a microencapsulation technology developed in our lab [Chan et al. 2007] and a decellularization technique to establish a 3D experimental model for investigation of the effects of the cell-specific ECM microenvironment on stem cell fate. As a feasibility test, we have demonstrated that mesenchymal stem cells (MSCs) respond to chondrocytes-produced glycosaminoglycan-rich extracellular matrix within the collagen microsphere by committing towards chondrogenic lineages, indicating that the matrix niche laid down by chondrocytes may be chondroinductive [Cheng et al. 2009]. In this study, we hypothesize that the extracellular matrix niche deposited by intervertebral disc cells are instructive to mesenchymal stem cells. Specifically, we aim to investigate whether a nucleus pulposus (NP) cell-specific extracellular matrix niche in the 3D microsphere is able to induce the differentiation of MSCs towards disc cells. We also aim to conduct a pilot animal study to evaluate the feasibility to inject microspheres deposited with disc matrix niche and repopulated with MSCs into degenerative discs for regeneration.

Project Title:	Development of a selection kit for mesenchymal stem cells with better migratory properties from various tissue sources
Investigator(s):	Chan BP, Chan GCF, Yu CS
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Applied Research
Start Date:	06/2010

Abstract:

MSC based therapy is promising but so far the clinical outcomes of injected MSCs are not satisfactory. This is largely due to the poor engraftment which is less than 5% in most cases. Better migratory activities of MSCs are important for engraftment. Attempts to enhance migration have been made but most involve either expensive chemokine treatments or genetically manipulation of these cells, making their long term use unpredictable. We have previously developed a collagen barrier platform to process MSCs from bone marrow and found that the selected MSCs dramatically increased in migratory activities. The selected MSCs retained the same stem cell characteristics such as immunophenotype, self-renewal capacity and multiple differentiating potential. In a pilot animal model, we further found that the selected cells are able to engraft to a liver injury and preliminary finding demonstrated that a longer term survival and better engraftment is resulted. We further demonstrated that the migratory activities of the selected MSCs increase as the collagen concentrations used in the selection process increased, suggesting the haptotactic nature of the MSC migration within the selection barrier. MSCs can be isolated from different tissue sources including bone marrow, fat and cord blood. Nevertheless, it is well kwnow that it is a heterogenous mixture of cells. Moreover, there is so far no agreed specific cell surface marker for MSCs. Previous efforts in using FACS sorting on particularly marker such as Stro-1 could not be reproducibly produce meaningful number of MSCs. Moreover, the sorted cells cannot be used clinically. As a result, a simple selection and sorting process to process the heterogenous mixture of the isolated MSCs or the crude bone marrow aspirate is required to provide better MSCs for clinical application. Before we can develop the concept into real useful kit, we would like to ask the following critical questions: 1. Whether cells from other tissues such as adipose tissue and cord blood can also be selected by this selection process? 2. Whether MSCs respond to biomaterials with haptotactic gradients such as collagen and fibrinogen can also be used? 3. Whether the selected subpopulations also have other favorable properties such as better resistance to inflammatory response and lower immunogenicity.

List of Research Outputs

Au Yeung K.L., Sze K.Y., Sham M.H. and Chan B.P., Development of a micromanipulator-based loading device for mechanoregulation study of human mesenchymal stem cells in three-dimensional cellagen constructs , Tissue Engineering, Part C Methods. 2010, 16(1): 93-107.

Au-yeung K.L., Sze K.Y., Sham M.H. and Chan B.P., Development of a micromanipulator-based loading device for mechanoregulation study of human mesenchymal stem cells in 3D collagen constructs., WACBE (World Association for Chinese Biomedical Engineers) World Congress on Bioengineering 2009. 26-29 Jul 2009, Hong Kong, China.. 2009, 53.

Chan B.P., Biomedical applications of photochemistry, Tissue Engineering Part B. 2010, 16: 1-14.

Chan B.P., Collagen microencapsulation and its applications, Biomedical Engineering Seminar, The Hong Kong University of Science and Technology. 2009.

Chan B.P. and Kwok C.B., Compression-induced reorientation of human mensenchymal stem cells (hMSCs) in 3D collagen matrix – Dependence on collagen concentration and integrin beta 1. , ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #W-55, p237.

Chan B.P., Extracellular matrix niche and stem cell differentiation, International Course on Stem Cell Biology and Regenerative Medicine, Hong Kong. 2009.

Chan B.P., Hui T.Y., Wong M.Y. and Chan G.C.F., Formation of injectable and osteoinductive bone-like microparticles using mesenchymal stem cell-collagen microspheres., 7th Annual Meeting of International Society for Stem Cell Research, Jul 8-11, 2009. Barcelona, Spain.. 2009, 1263.

Chan B.P., In vitro formation of osteochondral interface using mesenchymal stem cells and collagen, CRDG Research Meeting, Hong Kong. 2009.

Chan B.P., Cheng H.W., Chik T.K., Cheung K.M.C. and Luk K.D.K., Methods for Complex Tissue Engineering, Provisional Patent Application (filed on 15 June 2010) (Application No. 61/354,869). 2010.

Chan B.P., Wong H.L., Wong M.Y., Chan G.C.F. and Yang Z., Methods to Enhance Mesenchymal Stem Cell Migration, Provisional Patent Application (filed on 15 June 2010) (Application No. 61/354,871). 2010.

Chan B.P., Li C.H., Au-yeung K.L., Sze K.Y. and Ngan A.H.W., Research Output Prize 2009, Faculty of Engineering. 2009.

Chan B.P., Stem cell-based tissue engineering in Orthopaedics, AOTAP Clinical Research Workshop, Hong Kong. 2009.

Cheng H.W., Tsui Y.K., Cheung K.M.C., Chan D. and Chan B.P., Decellularization of chondrocyte-encapsulated collagen microspheres - a 3D model to study the effects of acellular matrix on stem cell fate, Tissue Engineering Part C Methods . 2009, 15(4): 697-706.

Cheng H.W., Tsui Y.K., Cheung K.M.C., Chan D. and Chan B.P., Decellularization of chondrocyte-encapsulated collagen microspheres. , WACBE (World Association for Chinese Biomedical Engineers) World Congress on Bioengineering 2009. 26-29 Jul 2009, Hong Kong, China. . 2009, 58.

Cheng H.W., Tsui Y.K., Cheung K.M., Chan D. and Chan B.P., Decellularization of chondrocyte-encapsulated collagen microspheres: a three-dimensional model to study the effects of acellular matrix on stem cell fate , Tissue Engineering, Part C Methods. 2009, 15(4): 697-706.

Cheng H.W., Chan D. and Chan B.P., Fabrication of an osteochondral construct with an intact interface using rabbit mesenchymal stem cells (rMSCs) and collagen gel, ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #Y-40, p239.

Cheng H.W. and Chan B.P., Fabrication of osteochondral composite with intact interface using rabbit mesenchymal stem cells and collagen gel., TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S234: 893.

Chik T.K., Sze K.Y. and Chan B.P., A feasibility study on applying dynamic torsional loading to cylindrical collagen-fibroblast constructs. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. S211: 801.

Chik T.K., Luk K.D.K., Cheung K.M.C. and Chan B.P., Creation of a tissue interface between bone-like construct and soft tissue-like construct. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. S211: 802.

Choy T.H.A., Au-yeung C., Tam H., Lau I. and Chan B.P., Fabrication and characterization of a gel-like collagen-glycosaminoglycan structure for nucleus pulposus replacement. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S215: 817.

Li C.H., Ngan A.H.W., Sze K.Y. and Chan B.P., Association between elastic modulus and extracellular matrix components of collagen-mesenchymal stem cell microsphres during chondrogenic differentiation. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. (Best Poster Presentation Award). 2009, S210:795.

Li C.H., Sze K.Y. and Chan B.P., Microplate manipulation of human mesenchymal stem cells collagen microspheres. , WACBE (World Association for Chinese Biomedical Engineers) World Congress on Bioengineering 2009. 26-29 Jul 2009, Hong Kong, China.. 2009, 65.

Li Y.Y., Cheng H.W., Wong M.Y., Cheung K.M.C., Chan D. and Chan B.P., Collagen-mesenchymal stem cell microspheres for cartilage tissue engineering. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S69:222.

Li Y.Y., Cheng H.W., Chan P.M., Wong M.Y., Teng W.K., Chow S.T., Cheung K.M.C., Chan D. and Chan B.P., Repair of osteochondral defects with collagen-mesenchymal stem cell microspheres in a rabbit model. , ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #W-50, p250.

Liu T., Teng W.K., Chan B.P. and Chew S.Y., Photochemical Crosslinked Electrospun Collagen Nanofibers: Synthesis, Characterization & Neural Stem Cell Interactions. , J. Biomed Mater Res A.. 2010, 276-282.

Wong H.C.T., Wong M.Y., Chan B.P. and Yu A.C.H., Ultrasound-enhanced osteogenesis of human mesenchymal stem cells encapsulated in collagen meshwork, IEEE Ultrasonics Symposium. 2009, 361-364.

Wong H.L., Wong M.Y., Chan G.C.F., Yang Z. and Chan B.P., Functionally selecting human mesenchymal stem cell subpopulations with better migratory activities using a collagen barrier. , 7th Annual Meeting of International Society for Stem Cell Research, Jul 8-11, 2009. Barcelona, Spain.. 2009, 1265.

Yeung C.W., Cheah K.S.E., Chan D. and Chan B.P., Effects of reconstituted collagen matrix on fates of mouse embryonic stem cells before and after induction for chondrogenic differentiation, 7th Annual Meeting of International Society for Stem Cell Research, Jul 8-11, 2009. Barcelona, Spain.. 2009, 369.

Yuan M. and Chan B.P., Culture of rabbit nucleus pulposus cells in 3D collagen microspheres – A comparison with traditional 2D culture. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S217: 824.

Researcher : Chan CW

Project Title:	IFAC Symposium on Artificial Intelligence in Real Time Control AIRTC-2000 Adaptive Control of Stochastic Nonlinear Systems Using Neurofuzzy Networks Modelling of Nonlinear Dynamic Systems Using Support Vector Neural Networks
Investigator(s):	Chan CW
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	10/2000

Abstract:

N/A

Project Title:	International Federation of Automatic Control 15th IFAC World Congress Asymptotic Local Approach in Fault Detection with Faults Modeled by Neurofuzzy Networks
Investigator(s):	Chan CW
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	07/2002

Abstract:

N/A

Project Title:	Installation of wave suppressor in the Victoria Harbour
Investigator(s):	Chan CW
Department:	Mechanical Engg
Source(s) of Funding:	Utility Information Ltd.
Start Date:	06/2006

Abstract:

To study the installation of wave suppressor in the Victoria Harbour.

Project Title:	Neurofuzzy network based adaptive control for nonlinear networked control systems
Investigator(s):	Chan CW
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2008

Abstract:

1. Since the communication network forms an important part of a NCS, models for the time delays and data dropouts will be derived taking into account data traffics based on the protocols of the networks, e.g., Profibus, switched Ethernet and Controller Area Network. Also, the models should be able to detect and adapt to changes in the number of devices in the network, which may affect the data traffics. From this result, a network will be selected for the simulation studies and networked control of the three-tank liquid level control rig. 2. An adaptive nonlinear controller for networked control based on neurofuzzy networks is developed, which are trained online by computation efficient algorithm proposed by the PI. As NITD is an important factor that affects the performance and stability of the NCS, it is included as an input in the proposed controller. Since these time delays are generally unknown, the estimates obtained from the time-delay model derived in Objective 1 are used to compute the control by the proposed controller. 3. Techniques to minimize the effect of the uncertain time delays and data dropouts are developed based on the estimated time delays from the model obtained in Objective 1. The method that uses the output from the NFN approximating the system for minimizing the NITD and data dropouts will be investigated. 4. To illustrate the implementation and performance of the proposed controller for networked control, simulations are conducted first to control a simulated three-tank liquid level control system with simulated data traffics and changes in the configuration of the NCS using the selected communication network. The proposed controller is also applied to control the three-tank liquid level rig.

Project Title:	Wireless networked control of unmaaned mini-helicopters based on neurofuzzy networks
Investigator(s):	Chan CW
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	12/2008

Abstract:

A recent research area of immense interest is the control of rotorcraft-based unmanned aerial vehicle (RUAV), popularly referred to as the unmanned mini-helicopters [1-3]. The RUAV is notoriously difficult to control, as its dynamics change drastically during a maneuver that involves vertical, lateral, longitudinal and yaw attitude motion. Although linear controllers are proposed, they only perform well only over part, but not the full range of the maneuver. It is therefore necessary to develop nonlinear control laws that can handle the changing dynamics of the RUAV during a maneuver. A further complication is that the nonlinear dynamics of the RUAV are often unknown and may even be time-varying. It is therefore necessary that any proposed nonlinear controllers must be able to handle time-varying nonlinearities. As neurofuzzy networks are known to be able to approximate any nonlinearity with arbitrary accuracy, and that they can be trained online to handle time-varying nonlinearities, they are used in this project to develop the adaptive nonlinear controller for the RUAV. This is a joint project with Professor Pei Hai Long of the South China University of Technology in Guangzhou. Our role is to provide expertise on intelligent control to develop adaptive nonlinear controllers for controlling the RUAV, and he will provide the fleet of unmanned mini-helicopters that he and his team have constructed in the past decade. Details of the objectives of the project are as follows: (1) The first task of the project is to develop computer software to simulate reliably and accurately the dynamics of the RUAV over a wide range of operating conditions. Since Professor Pei and his team have already developed a simulation package using SIMULINK, our first task is to transfer their simulation package onto our computer. This simulation package will be thoroughly tested using benchmark examples. (2) As we have already developed an adaptive nonlinear controllers based on neurofuzzy networks (NFN) that have the adaptive ability to handle time-varying nonlinear dynamics, they are used here to control the RUAV. For real-time control of the RUAV, the implementation of the proposed controllers needs to be computationally efficient. The proposed controller is therefore implemented using C++ on the computer, and incorporated in the simulation package written using SIMULINK. The proposed controller will be thoroughly tested under different working conditions. After verification, the proposed controller written in C++ will be incorporated into the real time control software for real time control of the mini-helicopter. (3) The design of the proposed controller will be investigated and appropriate design rules devised based on the dynamic model of the RUAV. Extensive simulations will be conducted to validate the implementation of the proposed controller, and to test the design rules for the proposed controller. The robustness of the proposed controller will also be studied. Further, these simulation examples will also provide important knowledge in selecting and initializing the parameters of the proposed controller. (4) From experience learnt in the simulation examples, field tests will be conducted in collaboration with Professor Pei and his team in Guangzhou to validate and to assess the performance and robustness of the proposed controller for real time control of the unmanned mini-helicopter. References [1] L Marconi and R Naldi, Robust full degree-of-freedom tracking control of a helicopter, Automatica, Vol. 43(11), 1909-1920, Nov. 2007. [2] LC Lai, CC Yang and CJ Wu, Time-optimal control of a hovering quad-rotor helicopter, Journal of Intelligent & Robotic System, Vol. 45(2), 115-135, Feb. 2006. [3] A Rahideh, HM Shaheed and AH Bajodah, Adaptive non-linear model inversion control of a twin rotor multi-input multi-output system using artificial intelligence, Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering, Vol. 221(G3), 343-351, Jun. 2007.

Researcher : Chan KW

Project Title:	Computer-aided mould design and manufacture of thermoformed PVC sheets
Investigator(s):	Chan KW
Department:	Mechanical Engg
Source(s) of Funding:	Other Funding Scheme
Start Date:	01/2002

Abstract:

To develop a computer-aided design and manufacturing process for producing thermoformed PVC sheets for packaging purpose.

Project Title:	Design and development of implantable artifical finger joints for biological repair
Investigator(s):	Chan KW, Chow SP, Lu WW, Chiu PKY, Ngan AHW, Luk KDK
Department:	Mechanical Engg
Source(s) of Funding:	Guangdong-Hong Kong Technology Cooperation Funding Scheme
Start Date:	06/2007

Abstract:

(1) Create an Asian finger bone DATABASE for determining the manufacturing sizes of artificial finger joint for Asian patients and development of a 3D CAD SYSTEM for finger joint design. (2) Enhance ONE-PIECE artificial finger joint DESIGN and TWO-PIECE artificial finger joint DESIGN. (3) Identify appropriate manufacturing PROCESSES and MATERIALS for manufacturing artificial finger joints. (4) Produce functional PROTOTYPES for conducting mechanical tests and tests on animal models. (5) Conduct phase 1 CLINICAL TRIALS on human subject for assessment. (6) REFINE finger joint design based on test results and manufacturing considerations. (7) Solicit and facilitate potential investors to COMMERCIALIZE the developed artificial finger joints.

Project Title:	Design and development of implantable artifical finger joints for biological repair
Investigator(s):	Chan KW
Department:	Mechanical Engg
Source(s) of Funding:	Innovation and Technology Fund Internship Programme
Start Date:	10/2009

Abstract:

Project Title:	Design and development of implantable artifical finger joints for biological repair
Investigator(s):	Chan KW
Department:	Mechanical Engg
Source(s) of Funding:	Innovation and Technology Fund Internship Programme
Start Date:	10/2009

Abstract:

Researcher : Chan PM

List of Research Outputs

Li Y.Y., Cheng H.W., Chan P.M., Wong M.Y., Teng W.K., Chow S.T., Cheung K.M.C., Chan D. and Chan B.P., Repair of osteochondral defects with collagen-mesenchymal stem cell microspheres in a rabbit model. , ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #W-50, p250.

Researcher : Chan WH

List of Research Outputs

Chan W.H., Fabrication of Aligned Carbon Nanotubes Layer and Interfacting with Nafion Membrane for Potential Application in Fuel Cells, MPhil Thesis. Hong Kong, The University of Hong Kong, 2009, 1-125.

Researcher : Chan YF

List of Research Outputs

Chan Y.F., Neurofuzzy Network Based Adaptive Nonlinear PID Controllers, MPhil Thesis. Hong Kong, The University of Hong Kong, 2009, 1-126.

Researcher : Chan YL

List of Research Outputs

Chan Y.L., Ngan A.H.W. and King N.M., Degraded prism sheaths in the transition region of hypomineralized teeth, Journal of Dentistry. 2010, 38: 237-244.

Chan Y.L. and Ngan A.H.W., Invariant elastic modulus of viscoelastic materials measured by rate-jump tests, Polymer Testing. Elsevier Ltd., 2010, 29: 558-564.

Researcher : Chen K

Project Title:	Virtual component modelling for components made of a multiphase perfect material
Investigator(s):	Chen KZ
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2005

Abstract:

The main objectives of the project are: 1) To verify the fesibility of the manufacturing principle for the CMMPM, a model of the virtually manufactured CMMPM has to be established first and is used to check whether the precisions of the virtually manufactured CMMPM meet all the requirements specified in its CAD model. 2) To faithfully evaluate the manufacturability of CMMPMs and the feasibility of the proposed manufacturing principle, and to discover any manufacturing defects introduced by the manufacturing principle and process, the used tools and facilities, and the related technologic parameters.

Researcher : Chen KZ

Project Title:	Virtual component modelling for components made of a multiphase perfect material
Investigator(s):	Chen KZ
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2005

Abstract:

Researcher : Chen X

List of Research Outputs

Chen X. and Soh A.K., On the inverse phase characteristics of Gaussian beams in negative refractive index materials, Journal of Optics A - Pure and Applied Optics. Bristol, England, IOP Publishing, 2009, 11(10): Article No.: 105101.

Chen X., Theoretical and Numerical Studies of Left-handed Materials: Transmission Properties, Beam Propagation and Localization, PhD Thesis. Hong Kong, The University of Hong Kong, 2009, 1-137.

Researcher : Chen YH

Project Title:	Realistic Modeling and Rendering of Dynamic Torques and Forces in Bone Drilling
Investigator(s):	Chen YH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	09/2007
Completion Date:	08/2009

Abstract:

Manual bone drilling/milling, used in many important surgical operations such as the insertion of pins or screws during the repair of fractures or installation of prosthetic devices requires high skills to prevent tissue damages and superfluous heat generation resulting in thermal necrosis. In such clinical operations, there is no room for mistakes. The ultimate goal of computer aided surgery is therefore to help the surgeon to plan and rehearse a clinical operation as if he/she is working on a real patient. Given the latest development in MRI scanning, computing hardware and software, robotics, haptic technology, and most of all, devoted researchers in these areas, the ultimate goal is achievable in the foreseeable future. In this project, research in computer aided surgery will be focused on bone drilling and milling which are important steps in clinical operations such as craniofacial surgery, head cancer tumor removal, and the insertion of pins/screws during the repair of fractures or installation of prosthetic devices, etc. The success of the proposed research will be dependent on the accurate measurements in experimental bone drilling and milling. The measurement data also provides important information for surgical robot control which is also a hot research area in recent years. The following are the key issues identified for the proposed project. 1.Accurate measurement of thrust forces in bone drilling and milling: All experiments in this project will be conducted on pig bones. Due to the diversity of drilling tool geometry, together with large variations of drilling process parameters, a large number of experiments must be done. 2. Measurement of torques in roll, yaw and pitch: while in drilling, the major toque is in the roll direction while other torques are only present when the drilling tool is tilted. However, for accurate modeling, torques in pitch and yaw muct be measured too. 3. Real-time haptic force and torque rendering algorithms: recently there are some research publications about bone drilling simulation. However, none of the publications has mentioned the force and torque variation as a parameter of drilling/milling parameter settings such as thrust force, rotational speed, feed rate, and tool geometry, mainly because they did not have experimental data. Realistic torque rendering in 3D space is a challenging task itself as torques in roll, pitch and yaw must be considered simultaneously. In this research, torque rendering will be investigated based on quaternion calculus. 4. Parametric representation of heterogeneous properties of bone structure: A bone is composed of heterogeneous materials. Current computer aided design systems only support the modeling of object made of homogeneous material. Even though a lot of research has been done in heterogeneous material modeling recently, there is no method that can effectively represent complicated object shape such as bone with none-uniform property changes and porous material structures. In this research, the representation of heterogeneous bone properties will be simplified as a parametric model. The parametric model will be developed based on experimental data from actual bone drilling and milling. 5. Efficient Multi-modal integration: Visual, audio and haptic renderings dictate different refresh rates. For visual rendering, only 30Hz will be sufficient in most cases while in audio rendering, up to as high as 10kHz is needed for 3D sound effect. The most challenging of all is the rendering of forces and torques that require a refresh rate of around 1kHz. The high refresh rate of torque and force presents a problem for computing power of today's computers. For example, collision detection, force and torque computation that work on a lot of data must be computed in a very short time of 1ms. The problem will be investigated by looking into both multi-resolution geometry representation and multi-rate haptic rendering.

Project Title:	Measurements and Multi-modal Modeling of Bone Drilling and Milling
Investigator(s):	Chen YH
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2008

Abstract:

(1) Accurate temperature change and thermal distribution measurement in bone drilling and milling: so far, there have been limited attempts in doing such measurements mainly because of the difficulties involved. Bone is composed of heterogeneous material thus the thermal distribution is not symmetric or uniform; further more, thermal distribution is a three dimensional problem, therefore, finite point measurements are not accurate. In this research, a pulsed thermography method will be developed to measure the heat generation and thermal distribution. Measurement results will be validated by measuring temperature at finite points from pre-installed thermo-couples. All bone drilling/milling experiments will be conducted on pig bones. (2) Development of a mathematical model for thermo-mechanics relationship in bone drilling and milling: based on measurements from experiments, a parametric model of thermo-mechanics will be developed. The model will be used to predict how the temperature varies over time in the volume surrounding the drill/mill tool for a given set of process parameters such as rotational speed, feed rate, drill geometry, and thrust force. This model will not only be used for the rendering of thermo distribution in drilling/milling, but also is invaluable for surgical robot control. (3) Real-time haptic force and torque rendering algorithms: recently there are some research publications about bone drilling simulation. However, none of the publications has mentioned the force and torque variation as a parameter of drilling/milling parameter settings such as thrust force, rotational speed, feed rate, etc., mainly because they did not have experimental data. Realistic torque rendering in 3D space is a challenging task itself as torques in roll, pitch and yaw must be considered simultaneously. In this research, torque rendering will be investigated based on quaternion calculus. (4) Parametric representation of heterogeneous properties of bone structure: A bone is composed of heterogeneous materials. Current computer aided design systems only support the modeling of object made of homogeneous material. Even though a lot of research has been done in heterogeneous material modeling recently, there is no method that can effectively represent complicated object shape such as bone with none-uniform property changes and porous material structures. In this research, the representation of heterogeneous bone properties will be simplified as a parametric model. The parametric model will be developed based on experimental data from actual bone drilling and milling. (5) Efficient Multi-modal integration: Visual, audio and haptic renderings dictate different refresh rates. For visual rendering, only 30Hz will be sufficient in most cases while in audio rendering, up to as high as 10kHz is needed for 3D sound effect. The most challenging of all is the rendering of forces and torques that require a refresh rate of around 1kHz. The high refresh rate of torque and force presents a problem for computing power of today’s computers. For example, collision detection, force and torque computation that work on a lot of data must be computed in a very short time of 1ms. The problem will be investigated by looking into both multi-resolution geometry representation and multi-rate haptic rendering.

Project Title:	Modeling of compliant needle insertion in minimum invasive surgery (MIS)
Investigator(s):	Chen YH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2008

Abstract:

With recent rapid advances in high speed computation, high resolution image assembly of a patient’s body has been greatly facilitated, creating new opportunities for image guided surgical procedures. Even though high resolution images can provide a clear road map for doctor’s planned surgical treatment, the navigation of medical instruments such as long and flexible needles and catheters deep inside human body has presented a big problem. The difficulty of accurate steering has prohibited doctors from performing some surgical operations that could save thousands of lives. The main objective of this project is therefore to investigate ways of accurately steering a flexible instrument deep inside human tissues. The ability to steer away from a critical structure or blood vessel is a very important feature desired by doctors in some major treatments such as brain tumors and stroke. As brain tumor and stroke are major killers in many places including Hong Kong (Stroke alone is the third leading cause of death in Hong Kong: http://cme.medcomasia.com/cmequiz/quizview.asp?id=133), the success of the proposed project is of great value to advance the treatment of such illness. The Major Objectives of the proposed projects are 1. To study stereotactic techniques and develop a compliant needle/catheter that can accurately steer inside tissues. Needle and catheter insertion into human body is a minimally invasive surgery (MIS) performed manually by experienced doctors. However, the wide applications of such MIS procedures to more advanced treatment are restricted by limited degrees of freedom of straight needles, or the complicated nature of human organs. For instance, it is very difficult or impossible for a needle or catheter to access a deep zone of brain because currently used needles or catheters have no ability to steer around critical structures or blood vessels. The steering capability of a needle or catheter will be investigated from two approaches: passive steering and positive steering. In passive steering, the steering force will be generated from the contact force in needle/catheter thrusting, whilst in positive steering, a magnetic force is utilized to deflect the needle/catheter head causing the needle to switch thrust direction. A compliant flexible needle will be developed for the analysis and experimental testing of the two steering approaches. 2. To develop mechanics models for various compliant needles in insertion and steering operations: needles with various diameters, compliant hinge layouts, and material properties will be optimized. Since different human tissues have different mechanical properties such as density and Young’s Module, the same compliant needle may behave differently in different tissues. It is therefore desirable to optimize the compliant needle design for different tissues. 3. To investigate ways of constructing transparent human tissue phantoms from CT and MRI data. Various modern manufacturing technologies will be explored such as reverse engineering techniques for the computer modeling of human tissue, rapid prototyping (RP) techniques for the physical shaping of a tissue model, and various molding techniques for the conversion of a hard RP tissue model to a phantom that has similar mechanical properties of a real tissue. 4. Based on the constructed phantoms, a number of experiments for the proposed compliant needle or catheter insertion and steering will be conducted. Measurement data from these experiments will be used to develop a computer aided-pre-operative planning system for needle/catheter insertion. 5. To develop a computer aided pre-operative planning system for flexible needle or catheter insertion and path planning. A haptic device will be used for force feedback in the proposed implementation. Before a surgical operation, a patient’s MRI image can be taken. These images can be re-constructed in a 3D system for both visualization and interaction by doctors. Currently, many commercial systems such as Mimics are very good in visualizing such models. However, interaction with such models is awkward, not to mention pre-operative rehearsal on such models. In this project, experimental measurement data will be used to drive the development of a haptic pre-operative planning system so that doctors can plan and rehearse the surgery operations with good fidelity to real operations.

Project Title:	Design and Development of A Common Robotic Flatform for Computer-Aided Orthopaedic Surgery Research
Investigator(s):	Chen YH, Yau WP
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2009

Abstract:

Robot assisted surgery for orthopaedic procedures is a concept which is still in its infancy. Most of the developments in the field have happened in the last decade or so and only recently some of the robotic devices are being allowed for limited clinical uses. As is quite evident from different studies the main emphasis of robotic assisted orthopaedic surgery has been in relation to specific applications such as hip replacement, knee arthroplasty, spine and pelvic surgery and femur bone reduction. However, since there are immense variations in the type of bony trauma, and current researches are limited to specific aspects of trauma surgery, it is highly desired to develop a common robotic platform for all type of trauma surgeries. In this project, the main objective is to develop a common robotic platform that can be configured to specific needs of a trauma surgery. Based on the proposed robotic platform, more in-depth study related to surgical planning, adaptive motion control and force control will be initiated for a GRF proposal in 2009. The following is an itemized description of the project objectives. Major objectives of the proposed project: 1. Conceptual development of a six-degrees-of-freedom robotic platform: bone has definite rigid structure and dimensions and behaves very predictably in the clinical setting. If a bone fractures, the fragments displace in a certain predictable way. Because of the high strength of bone, the load required for bone related surgeries is very high. This causes problems in robotic design as it is desirable to have a small size robot, yet it must carry a large load. In this project, parallel structures will be investigated as they can normally carry load with high rigidity. Since the angular or linear bone displacement can be quite large, the robot design must allow a large range of motion for each of its degree of freedom. 2. Kinematic analysis of robot: displacement transformation is very important for a given robotic mechanism. Once a proposed robotic platform is conceptualized, forward and inverse transformation of displacement and velocity will be performed. These transformations provide necessary data for motion control of the robot. 3. Kinetic analysis of the robot: dynamic analysis of the robotic mechanism must be done to ensure the rigidity and stability of the robot in operation. 4. Motion control analysis of the robot: when the robotic mechanism design is ready, a motion control system must be developed to control the motion. This task will be performed with the help of a commercial software package LABVIEW. 5. Prototype fabrication of the robotic mechanism design: this is one of the major objectives of the project as a prototype of the robotic mechanism must be built to verify the feasibility of the design. 6. Experimental test on femur reduction and fixation: based on the prototype robot, a number of experimental tests will be done on different cases of femur reduction and fixation on a phantom leg model. While testing, some measurements such as force and vibration can be carried out.

Project Title:	CSME Forum 2010 Cutting Tool Path Verification for robot machining systems
Investigator(s):	Chen YH
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2010

Abstract:

N/A

Project Title:	Design, analysis and fabrication of microfluidic device for biomedical applications
Investigator(s):	Chen YH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2010

Abstract:

The major objectives of this project are: 1. To investigate and explore an appropriate flow focusing technique that is appropriate for use in flow cytometric application with characteristics of high flow speed, simple fabrication, and low cost. 2. To study feasible precise flow focusing designs based on the appropriate flow focusing technique. 3. To simulate, analyze and optimize the proposed designs using various simulation packages. 4. To plan and fabricate a final design using MEMS fabrication techniques and to obtain experimental results based on the design. 5. To compare the theoretical, experimental and simulation results for design optimization. Since many biomedical/clinical applications need advanced micro fluidic devices for cell sorting, detection for medical diagnosis, it is important to design precise micro fluidic devices with low cost and simple fabrication while maintaining high efficiency. Yet it has been a challenge for researchers to achieve this. Some improvements in design and fabrication of micro channels have been made during the past decade. Micro channels have many applications such as manipulation of biological cells, On-chip cell counting, separation, isolation, drug delivery applications, fluid mixing at micron level and many other industrial/bio related applications. This project will focus on the study of micro flow cytometers with the following two key issues to be studied. * Material Selection and design optimization Flow cytometer is one of the devices which focus human cells/particles in the micro channel which is then detected by using laser and sorted out according to its properties. Due to increased demand of medical diagnosis in clinical applications, it becomes necessary to increase the cell detection speed. It is not an easy task to detect the cells at a high speed. It needs a precise flow focusing device for cell sorting at high speed. The high speed can be achieved by applying high pressure to the sample fluid. The micro fluidic device should not burst due to high pressure. Hence there is a need to find such a strong material to withstand the necessary pressure. Currently there are many types of fabrication materials available like silicon, glass, quartz, PMMA, biocompatible SU-8 polymers, PDMS etc. The proper selection of material and its suitability for optimized design feature is very important here and will be studied. *Flow focusing methodlogies The flow focusing device is one of the important components of the flow cytometry. The cells in a sample solution are initially randomly distributed in three dimensional space. To detect the cells individually, the sample solution needs to be directed into a stream of single cells that can be interrogated by the detection system. There are three basic techniques to give the motion to the sample fluid. These are hydrodynamic flow focusing, electro kinetic flow focusing and dielectrophoretic flow focusing. Hydrodynamic flow focusing needs sheath fluid to move the sample fluid through a micro channel. The use of sheath fluid increases size, cost and fabrication complexity. To overcome these limitations, 2D and 3D hydrodynamic flow focusing devices will be studied. Many researchers have used electrokinetic flow focusing technique to reduce the cost of flow cytometers. The sheath flow is not required in this method hence it avoids the waste of sheath fluid ultimately reducing the cost. Such technique doesn’t need very complex structure like hydrodynamic focusing, but it is only applicable for conducting liquids. Dielectrophoresis (DEP) flow focusing techniques are also developed by some researchers. In dielectrophoresis, a force generated by a non-uniform electric field is exerted on a dielectric particle. But DEP three-dimensional flow focusing requires complex fabrication technology such as e-beam evaporation and accurate alignment of electrodes with a substrate. Moreover extras electronics is required to integrate DEP electric field generation. Only liquids with specific conductivities can be used in DEP flow focusing.

Researcher : Cheng HW

List of Research Outputs

Chan B.P., Cheng H.W., Chik T.K., Cheung K.M.C. and Luk K.D.K., Methods for Complex Tissue Engineering, Provisional Patent Application (filed on 15 June 2010) (Application No. 61/354,869). 2010.

Cheng H.W., Tsui Y.K., Cheung K.M.C., Chan D. and Chan B.P., Decellularization of chondrocyte-encapsulated collagen microspheres - a 3D model to study the effects of acellular matrix on stem cell fate, Tissue Engineering Part C Methods . 2009, 15(4): 697-706.

Cheng H.W., Tsui Y.K., Cheung K.M.C., Chan D. and Chan B.P., Decellularization of chondrocyte-encapsulated collagen microspheres. , WACBE (World Association for Chinese Biomedical Engineers) World Congress on Bioengineering 2009. 26-29 Jul 2009, Hong Kong, China. . 2009, 58.

Cheng H.W., Tsui Y.K., Cheung K.M., Chan D. and Chan B.P., Decellularization of chondrocyte-encapsulated collagen microspheres: a three-dimensional model to study the effects of acellular matrix on stem cell fate , Tissue Engineering, Part C Methods. 2009, 15(4): 697-706.

Cheng H.W., Chan D. and Chan B.P., Fabrication of an osteochondral construct with an intact interface using rabbit mesenchymal stem cells (rMSCs) and collagen gel, ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #Y-40, p239.

Cheng H.W. and Chan B.P., Fabrication of osteochondral composite with intact interface using rabbit mesenchymal stem cells and collagen gel., TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S234: 893.

Li Y.Y., Cheng H.W., Wong M.Y., Cheung K.M.C., Chan D. and Chan B.P., Collagen-mesenchymal stem cell microspheres for cartilage tissue engineering. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S69:222.

Li Y.Y., Cheng H.W., Chan P.M., Wong M.Y., Teng W.K., Chow S.T., Cheung K.M.C., Chan D. and Chan B.P., Repair of osteochondral defects with collagen-mesenchymal stem cell microspheres in a rabbit model. , ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #W-50, p250.

Researcher : Cheng HW

List of Research Outputs

Researcher : Cheng WC

List of Research Outputs

Cheng W.C. and Liu C.H., Analysis of the momentum and pollutant transport at the roof level of 2D idealized street canyons: a large-eddy simulation solution, European Geosciences Union, General Assembly 2010, Vienna, Austria, May 2-7, 2010 . 2010.

Cheng W.C. and Liu C.H., Effects of thermal stratifications on the flow & pollutant dispersion in urban street canyon: a large-eddy simulation approach, 9th American Meteorological Society Symposium on the Urban Environment, Keystone, Colorado, USA, August, 2-6, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Large-eddy simulation of street canyon flow and pollutant transport in neutral and unstable stratifications, 90th Annual Meeting of the American Meteorological Society, Atlanta, GA, January 17-21, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Large-eddy simulation of turbulent transports in urban street canyons in different thermal stabilities, 5th International Symposium on Computational Wind Engineering, Chapel Hill, North Carolina, USA, May 23 to 27, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Large-eddy simulation of ventilation and pollutant removal in neutrally and unstably stratified street canyons, American Geophysical Union Fall Meeting 2009, San Francisco, December 14-18, 2009.

Cheng W.C., Liu C.H. and Leung Y.C., On the wind statistics and pollutant re-entrainment in street canyons by large-eddy simulation, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Periodic Flow & Pollutant Removal of Street Canyon in Wind-Buoyancy-Driven Condition Using the URANS Model, ICUC-7, 29/6-3/6, 2009, Yokohama, Japan. 2009.

Liu C.H., Cheng W.C., Leung T.C.Y. and Leung Y.C., On the mechanism of air pollutant re-entrainment in two-dimensional idealized street canyons, Atmospheric Environment. 2010.

Researcher : Cheung KC

Project Title:	14th World Congress of International Federation of Automatic Control A Fast On-Line Training Algorithm for Neurofuzzy Networks
Investigator(s):	Cheung KC
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	07/1999

Abstract:

N/A

Project Title:	A study on the use of fuel cells as replacement for lead-acid batteries in solar-based electrical power generation
Investigator(s):	Cheung KC
Department:	Mechanical Engg
Source(s) of Funding:	Low Budget High Impact Programme
Start Date:	11/2001

Abstract:

To address the following issues: (1) the performance of small sized (in the order of kilowatts) fuel cells under varying d.c. and a.c. loads; (2) the feasibility of using water electrolysis as a means to store surplus solar-generated electrical power, especially under the climatic condition of hong Kong in which days of overcast follow days of sunny spells.

Project Title:	A study on solar-powered water electrolysis for hydrogen production
Investigator(s):	Cheung KC
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	11/2002

Abstract:

To study the use of solar panels to generate electrical power for water electrolysis.

Project Title:	Operator and artificial intelligence based approaches to construct the sound perceived by human beings
Investigator(s):	Cheung KC, Huang L, Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2009

Abstract:

Tinnitus is a symptom recognised for thousands of years. Sufferers of tinnitus "hear" sounds when there is no external stimulation. The phantom sound affects the daily life and general well-being of the sufferers. Different causes for the phantom hearing sensation have been proposed and different therapy methods have been developed to treat tinnitus. Up to now, there is no definite cause to explain the "sound" heard by tinnitus sufferers. A common description of tinnitus was proposed in the Committee on Hearing, Bioacoustics and Biomechanics report entitled "Tinnitus Facts, Theories and Treatments" as "the conscious experience of sound that originates in the head" [1]. This definition includes the auditory hallucinations of schizophrenia and a variety of somatosounds as well as sensation resulting from a malfunction of the cochlea or auditory nerve. Many different phenomena unrelated to tinnitus are thus encompassed by it. Effective treatment of tinnitus is hindered as the definition is too broad. A narrower definition of tinnitus is given as the perception of sound that results exclusively from activity within the nervous system without any corresponding mechanical, vibratory activity within the cochlea, and not related to external stimulation of any kind [2]. Sufferers of tinnitus perceive sense of hearing without excitation from a real noise source. Various studies estimate that six to thirty per cent of people experience continuous tinnitus [3, 4, 5, 6, 7]. Tinnitus causes sleep deprivation which seriously impairs the quality of life of its sufferers. Current therapy strategy aims to identify the frequency band and amplitude of the perceived noise. The patient is given different pure tones to match the noise perceived by the patient. So far, no patient has reported exact match of sound quality between the tinnitus and the external pure-tone stimulus. The proposed research uses non-pure-tone sounds comprising a range of frequencies and a continuous distribution of amplitude and phase across the frequency range to match the tinnitus. The aim is to design and build a "sound generator" that allows the user to change the frequency band and the distribution of the amplitude and phase within the selected frequency band. In the first stage of the work, an operator-controlled tinnitus synthesizer will be designed and built. The user can adjust the frequency band and the distribution of the amplitude and phase angle within the band so as to achieve an exact match with an externally-produced sound. The "sound generator" can then be used by tinnitus sufferers to reproduce the sound that they perceived. The second stage of the work uses artificial intelligence techniques such as neural network and fuzzy logic to tune the "sound generator." Neuro-fuzzy systems has been used in adaptive control [8], self-tuning control [9], modelling [10] and fault-diagnosis [11]. The ability of fuzzy systems to use linguistic variables to represent non-crisp perception (e.g., close match, pitch too low, not loud enough, etc.) together with the non-linear representation capability of neural networks will be employed to tune the parameters of the "sound generator" so that users do not have to manipulate the controls in order reproduce the sound. For instance, by using linguistic feedback such as "too loud", "pitch too low", "just right", the user can reproduce the sound that he hears. It is expected that tinnitus sufferers can use this system to easily generate the phantom perception that they have. Successful completion of this project will provide information on the phantom sound heard by tinnitus sufferers. This will help to validate the current definition of tinnitus and establish new theories on retraining for tinnitus sufferers. Medical practitioners can use this knowledge to develop new therapeutic tools. [1] McFadden, D. Tinnitus: Facts, Theories, and Treatments. Washington, DC: National Academy Press. http://books.nap.edu/books/0309033284/html/R1.html [2] Jastreboff, P.J. Tinnitus as a phantom perception: theories and clinical perception. In Mechanisms of Tinnitus, ed. Vernon, J & Moller, A.R., pp. 73-94. Boston, MA: Allyn & Bacon, 1995. [3] Coles, R.R.A. Epidemiology of tinnitus. In Tinnitus, ed. Hazell, J.W.P., pp. 46-70. Edinburgh: Churchill Livingstone, 1987. [4] Coles, R.R.A. Epidemiology, atieology and classification. In Proceedings of the Fifth International Tinnitus Seminar, ed. Vernon, J.A. & Reich, G., pp. 25-30. Portland, OR: American Tinnitus association, 1996. [5] Davis, A. The aetiology of tinnitus: risk factors for tinnitus in the UK population - a possible role for conductive pathologies? In Proceedings of the Fifth International Tinnitus Seminar, ed. Vernon, J.A. & Reich, G., pp. 25-30. Portland, OR: American Tinnitus association, 1996. [6] Davis, A & El Rafaie, A. Epidemiology of tinnitus. In Tinnitus Handbook, ed. Tyler, R., pp. 1-23. San Diego, CA: Singular, Thomson Learning, 2000. [7] George, R.N. and Kemp, S. A survey of New Zealanders with tinnitus. Br. J. Audio., 25, pp. 331-336, 1991. [8] Yeung W.K., Chan C.W. and Cheung K.C., Adaptive control of stochastic nonlinear systems using neurofuzzy networks, Preprints IFAC Symposium AI in Real Time Control - 2000. Budapest, Hungary, , 235-240. [9] Yeung W.K., Chan C.W. and Cheung K.C., Self-tuning control for nonlinear systems based on neurofuzzy networks, Proceedings UKACC - CONTROL 2000. Cambridge, UK, , 142. [10] Chan W.C., Chan C.W., Cheung K.C. and Harris C.J., On the modelling of nonlinear dynamic systems using support vector neural networks, Eng. Appl. Artificial Intelligence. 2001, 14: 105-113. [11] Wang Y., Chan C.W. and Cheung K.C., On-line fault diagnosis of nonlinear systems based on neural networks using the asymptotic local approach, Asian Journal of Control, Special issue: Selections from The 3rd Asian Control Conference. 2001, 3, (1): 73-78

Project Title:	Stability analysis of uncertain stochastic neural networks with delays
Investigator(s):	Cheung KC, Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	01/2010

Abstract:

Over the past decades, neural networks have been extensively studied due to their important applications in static image processing, pattern recognition, fixed-point computation, associative memory, combinatorial optimization and other engineering areas. Since the stability of neural networks is a prerequisite for the applications, the problem of stability analysis for neural networks has attracted considerable attention in recent years. On the other hand, time delays are frequently encountered in various engineering, biological and economic systems. Due to the finite speed of information processing and the inherent communication time of neurons, the existence of time delays often causes oscillation or even instability of neural networks. Therefore, it is of both theoretical and practical importance to study the stability of neural networks with time delays. Recently, various results on the robust stability and exponential stability for neural networks with various types of time delays (either constant or time-varying) have been reported in the literature, see [CYL06, XLHZ04, XL06, LCZL08]. The stability criteria for neural networks with time delays can be generally classified into two categories, namely, delay-independent criteria and delay-dependent criteria, where the former is more conservative than the latter when the size of the delay is small [HLR07, LCZ02, XLHZ05] [MGLQ08]. Moreover, another type of time-delays is distributed delay, which has drawn much research interest, due to the fact that there may exist a distribution of propagation delays over a period of time in some cases [WFL08, RBL08]. Therefore, we should introduce both discrete and distributed delays into the model of a realistic neural network [RF04, LZL06, SW08]. As previously mentioned, it is significant to investigate the stability of neural networks with discrete and distributed delays [WLFL06, LCZL08]. It is also worth noting that the synaptic transmission is a noisy process brought on by random fluctuations from the release of neurotransmitters in real nervous systems. It is well known that a neural network could be stabilized or destabilized by certain stochastic inputs [BML01]. Thus, it is of practical importance to investigate the stability for stochastic neural networks with time delays, see [WLFL07, WFL08] for example. Furthermore, the connection weights of the neurons depend on certain resistance and capacitance values which include uncertainties (modelling errors). When modelling neural networks, we should consider the parameter uncertainties (also called variations or fluctuations). Therefore, it is important to investigate the robust stability of uncertain stochastic neural networks, see [CL08]. Recently, some results on stability of stochastic neural networks with finite distributed delays have been reported in [LCZF08, RBL08]. In view of the importance of robust stability of uncertain stochastic neural networks with discrete and distributed time-vary delays, some researchers have begun to study how to reduce the conservatism (namely obtain larger allowable upper bounded of time delays). However, there is room for improving the delay-dependent conditions for uncertain stochastic neural networks with discrete and distributed time-vary delays through constructing new Lyapunov functional and utilizing the delay partitioning idea. The resulting delay-dependent robust condition could be less conservative than some published conditions in the literature. In this project, a considerable amount of attention will be focused on the robust stability of uncertain stochastic neural networks with discrete and distributed time-varying delays. The delays are both discrete and distributed time-varying, while the uncertainties are assumed to be norm bounded uncertainties. Attention will be focused on the problem of robust stability analysis for the stochastic neural networks. By constructing a novel Lyapunov functional and utilizing the delay partitioning idea, some robust stability criteria will be derived and then formulated in term of linear matrix inequalities (LMIs). These new criteria could prove to be much less conservative than the existing ones, and the conservatism can be notably reduced as the fractioning goes thinner. Moreover, the problems of synchronization and passivity analysis will also be investigated in this framework. Some numerical examples will be provided to illustrate the effectiveness and advantage of the proposed theoretical results. Neural networks have been applied to solve various engineering problems such as fault detection [CCZW99] and non-linear modelling [CCC99].

Researcher : Cheung OP

List of Research Outputs

Cheung O.P. and Liu C.H., Effects of Building Interference on Natural Ventilation for High-Rise Residential Buildings, ISHVAC09, November, 6-9, 2009, Southeast University, Nanjing, China. 2009.

Cheung O.P., Liu C.H. and Yam M.C.H., Impact of building separation on natural ventilation behavior and performance for low-rise structures, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Researcher : Cheung WL

Project Title:	Selective Laser Sintering of Porous Biopolymer/Biocomposite Scaffolds for Bone Tissue Engineering
Investigator(s):	Cheung WL, Ip WY, Wang M
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	09/2005

Abstract:

To study the feasibility of using the SLS technology to fabricate porous scaffolds from biopolymers and biocomposites for bone tissue engineering applications, and to characterize the in vitro degradation and biological characteristics of these scaffolds.

List of Research Outputs

Wong K.L., Wong C.T., Liu W.C., Pan H., Fong M.K., Lam W.M.R., Cheung W.L., Tang W.M., Chiu P.K.Y., Luk K.D.K., Lu W.W., Wong K.L., Wong C.T., Liu W.C., Pan H., Fong M.K., Lam W.M., Cheung W.L., Tang W.M., Chiu P.K.Y., Luk K.D.K. and Lu W.W., Mechanical properties and in vitro response of strontium-containing hydroxyapatite/polyetheretherketone composites, Biomaterials. Elsevier Ltd, 2009, 30: 3810-3817.

Zhou W., Duan B., Wang M. and Cheung W.L., Crystallization behavior of Poly(L-Lactide)/Carbonated hydroxyapatite nanocomposite microspheres, Journal of Applied Polymer Science. Wiley Periodicals, Inc, 2009, 113: 4100-4115.

Zhou W., Wang M., Cheung W.L. and Ip W.Y., Selective Laser Sintering of Poly(L-Lactide)/Carbonated Hydroxyapatite Nanocomposite Porous Scaffolds for Bone Tissue Engineering, In: Daniel Eberli , Tissue Engineering. Vienna, Austria, IN-TECH, 2010, 179-204.

Researcher : Chik TK

List of Research Outputs

Chan B.P., Cheng H.W., Chik T.K., Cheung K.M.C. and Luk K.D.K., Methods for Complex Tissue Engineering, Provisional Patent Application (filed on 15 June 2010) (Application No. 61/354,869). 2010.

Chik T.K., Sze K.Y. and Chan B.P., A feasibility study on applying dynamic torsional loading to cylindrical collagen-fibroblast constructs. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. S211: 801.

Chik T.K., Luk K.D.K., Cheung K.M.C. and Chan B.P., Creation of a tissue interface between bone-like construct and soft tissue-like construct. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. S211: 802.

Researcher : Ching WH

List of Research Outputs

Ching W.H., Leung M.K.H. and Leung Y.C., An efficient approach to transient turbulent dispersion modeling by CFD-statistical analysis of a many puff system, Fluid Dynamics Research. 2009, 41(3): 035512.

Researcher : Chiu HS

List of Research Outputs

Chiu H.S. and Chow K.W., Effect of birefringence on the modulation instabilities of a system of coherently coupled nonlinear Schrodinger equations, Physical Review A. 2009, 79: 065803 (4 pages).

Chiu H.S. and Chow K.W., Periodic and solitary waves in systems of coherently coupled nonlinear envelope equations (invited article), International Journal of Computers and Mathematics, special issue on 'Novel Methods to Solve Nonlinear Equations'. 2010, 87: 1083-1093.

Chiu H.S., Stability and Interaction of Waves in Coupled Nonlinear Schrödinger Type Systems, MPhil Thesis. Hong Kong, The University of Hong Kong, 2009, 1-91.

Chiu H.S., Chow K.W. and Tsang C.H., Studies of freak or rogue waves by the nonlinear Schrodinger model, The 33rd IAHR Congress - Water Engineering for a Sustainable Environment, Vancouver, BC, Canada. 2009.

Researcher : Chiu HS

List of Research Outputs

Chiu H.S., Stability and Interaction of Waves in Coupled Nonlinear Schrödinger Type Systems, MPhil Thesis. Hong Kong, The University of Hong Kong, 2009, 1-91.

Researcher : Chow KW

Project Title:	Nonlinear localized modes and their dynamics: applications in hydrodynamics and optics
Investigator(s):	Chow KW, Rogers C
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2006

Abstract:

The main objective of this project is to examine the evolution of similar modes in hydrodynamic and optical systems. Interactions among waves of different scales will be investigated.

Project Title:	The nonlinear Schrödinger models with novel nonlinearities: their applications in capillarity and physics of optical fibers
Investigator(s):	Chow KW, Rogers C
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2008

Abstract:

(1) To compute wave patterns asscoiated with isolated or coupled NLS models with novel nonlinearities, especially the saturable or the resonant type. (2) To study coupled NLS models with saturable nonlinearities in optical waveguides - In addition to the conventional self phase and cross phase modulation effects, these models possess saturable nonlinearities of the algebraic and/or rational types. (3) To examine the applications of NLS in hydrodynamics - Besides free surface and internal waves, NLS is also relevant in the phase field descriptions of capillarity. Earlier studies have demonstrated that proper choices of a thermodynamic free energy function lead to NLS, possibly with a 'resonant' nonlinearity. The search for various wave modes and extension to higher spatial dimensions will be examined. (4) To investigate nonlinear pulse propagation in periodic structures, possibly with saturable nonlinearities - Optical periodic structures or photonic band gap materials such as fiber Bragg gratings have relatively large dispersion locally, and will permit interactions of nonlinearity and dispersion over a relatively short distance. Models of Bragg gratings, perhaps in the presence of saturable nonlinearities, their wave profiles, their modulational instabilities, and practical applications will be assessed.

Project Title:	Wave propagation in non-uniform media: Effects of amplification / attenuation and marginal stability
Investigator(s):	Chow KW
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2009

Abstract:

1. Year 1 (Theory) - The precise conditions on the cubic nonlinearity, linear and nonlinear gain/loss for a robust solitary pulse to exist will be identified. The dispersion profile is assumed to be given, which is readily realized in practice. The Hirota bilinear method is employed. A combination of (a) a modified Hirota transform proposed earlier in the literature, and (b) the idea of spatially dependent wavenumber proposed by the Principal Investigator recently will be utilized.; 2.Year 1 (Applications) - A spatially varying dispersion only will cause the pulse to broaden or be compressed. The intriguing dynamics now is to add the competition among the distributed dispersion, linear gain (or loss) and nonlinear loss (or gain) respectively. The merit of a complete analytical description is to monitor the energy or intensity of the pulse in full details.; 3. Year 2 (Theory) - The regime around the neutral point of a plane or continuous wave has frequently been termed marginal stability in the literature, and this terminology will be adopted here. Higher order dispersive and/or nonlinear effects must be restored. An analytical algorithm to treat wave propagation in a non-uniform medium will reveal new, solvable variable coefficient evolution systems.; 4. Year 2 (Applications) - For wavepackets, marginal stability refers to the regime of vanishing group velocity dispersion (GVD) or cubic nonlinearity. In optics, zero GVD is related to the power in generating a bright solitary pulse. In hydrodynamics, cubic nonlinearity vanishes when kh is about 1.363, where k is the wave number and h is the undisturbed depth. Considerations will now be extended to waves in an inhomogeneous medium in the regime of marginal stability.; 5. Year 3 (Applications) - New solitary pulses discovered in this project must be stable to be observable or useful in practice. Numerical schemes to trace a perturbed wave packet will be developed. The Hopscotch and the split step Fourier methods will be employed.; 6. Year 3 (Educational) - Coding numerical schemes will typically be an instructive training ground for graduate students.

Project Title:	Competing nonlinearities in systems of hydrodynamic waves
Investigator(s):	Chow KW, Zhang D
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2010

Abstract:

Background on Optical Waveguides Wave propagation is related to the transmission of signals and energy, and as such is critically important in Nature and engineering. The goal here is to investigate one particular aspect of wave motion, namely, the competition of quadratic and cubic effects, which has been studied intensively in optical waveguides in the past two decades. The goal here is to examine if the new knowledge and insight gained in physical optics can be transferred, directly or indirectly, to the field of internal waves in oceans. The science of optics has attained spectacular achievements in the last fifty years. Examples are optical waveguides and systems, e.g. fibers, with enormous capacity for information. One possible mode to transmit signals and information along fibers is to adopt a binary code, where a '1' is represented by a solitary pulse, and a '0' is recorded by an absence of any signal. Rigorous asymptotic, multiple-scale expansions of the governing physics, namely, the Maxwell's equations, are then performed, leading to the well established nonlinear Schrodinger model. Group velocity dispersion and Kerr effects are the dominant factors in analysing the properties of the pulses [1, 2]. Group velocity dispersion measures the variation of group velocities with respect to changes in wave numbers. Kerr effect is a nonlinear property of light propagation whereby the refractive index of the medium changes with the intensity of the incoming light beam. The balance of these effects can lead to permanent, localized pulses, commonly known as 'solitons'. This nonlinear Schrodinger (NLS) model involves cubic nonlinearity, or third order in amplitude, and roughly speaking, invokes mode with one wave number only. In the past fifteen years, another regime of wave interactions has received intensive attention. Commonly known as quadratic resonance, this differs from the NLS model in two aspects. First, a second order in amplitude expansion is necessary, in contrast with a third order one in NLS. Second, and more important, two waves, the fundamental frequency (FF) and its second harmonic (SH), are necessary. More precisely, the wave numbers and frequencies of FF and SH need to match certain precise resonance condition for this scenario to occur. Historically, theoretical predictions for such second harmonic resonance were made in the Russian literature as far back as forty years ago. However, the lack of suitable optical materials to sustain such experiments has led to a general neglect of such questions. The situation changed in the early 1990s, when high quality semi-conductors can be fabricated. Experiments with properly directed lasers then showed such resonance. Synergy with Hydrodynamics The motivation to submit the present proposal rests with the visits of the Co-Investigators to HKU earlier in 2009. Dr. Ee visited the campus in August 2009 during his summer vacation in his home country of Singapore. Professor Choi presented a seminar on internal waves at the Department of Mechanical Engineering, HKU, in late October 2009. Both of them expressed interests in collaborating with our research group. A theme common to both of them is their interests to examine fully nonlinear waves in fluids, i.e. waves of higher order nonlinearity. The present proposal is the result of these fruitful and ongoing dialogues. Weakly nonlinear waves in fluids have been studied for many years too. In the long wave regime, the Korteweg - de Vries model is the first approximation, while a NLS model is valid for the finite depth case. The second harmonic resonance and cubic NLS model cannot easily occur simulataneously in a fluid, mainly due to the difficulty in matching the group velocities. Hence, for the current project with a modest scope, the focus is on the long wave regime. For surface waves, quadratic nonlinearity never vanishes and cubic effects are always subdominant. Hence one needs to consider internal waves, which are nevertheless very important themselves (Section VI below). After extensive assessment of the literature, regimes where analytical progress can be made are identified. An existing body of knowledge deals with KdV model with cubic term, but we shall deal with how such effects can also be accomplished by introduction of novel boundary conditions. Furthermore, we shall study weakly stratified fluids, where long wave dispersion is balanced by the weak changes in density, and wave amplitude can be arbitrarily large, but the amplitudes are still governed by analogous equations. Details will be presented in Section VII. The main goal here is to develop a theoretical framework for this class of fluid flows, in preparation for a RGC GRF proposal to be submitted Autumn 2010 or 2011. [1] Y. S. Kivshar, G. P. Agrawal, Optical Solitons: From Fibers to Photonic Crystals, Academic Press, San Diego, USA (2005). [2] G. P. Agrawal, Nonlinear Fiber Optics, Academic Press, San Diego, USA (2007).

List of Research Outputs

Chiu H.S. and Chow K.W., Effect of birefringence on the modulation instabilities of a system of coherently coupled nonlinear Schrodinger equations, Physical Review A. 2009, 79: 065803 (4 pages).

Chiu H.S. and Chow K.W., Periodic and solitary waves in systems of coherently coupled nonlinear envelope equations (invited article), International Journal of Computers and Mathematics, special issue on 'Novel Methods to Solve Nonlinear Equations'. 2010, 87: 1083-1093.

Chiu H.S., Chow K.W. and Tsang C.H., Studies of freak or rogue waves by the nonlinear Schrodinger model, The 33rd IAHR Congress - Water Engineering for a Sustainable Environment, Vancouver, BC, Canada. 2009.

Chow K.W., An exact, periodic solution of the Kaup - Newell equation (invited article), Nonlinear Science Letters A. 2010, 1: 83-89.

Chow K.W. and Ng T.W., Nontrivial phase solutions of the Chen-Lee-Liu equation, accepted and to appear in the Journal of Computational and Applied Mathematics, special issue on the International Conference on Engineering Mathematics. 2010.

Chow K.W., Yip L.P. and Gurarie D., Two exact solutions of the Tzitzeica - Bullough - Dodd equation, International Journal of Nonlinear Sciences and Numerical Simulations. 2009, 10: 935-943.

Ee B.K., Grimshaw R.H.J., Zhang D. and Chow K.W., Steady transcritical flow over a hole: Parametric map of solutions of the forced Korteweg - dr Vries equation, Physics of Fluids. 2010, 22: 056602 (9 pages).

Fan Y., Qing K., Cheng S.W.K. and Chow K.W., Computational studies of thoracic aortic dissection, The 8th Asian Computational Fluid Dynamics Conference, Hong Kong. 2010.

Fan Y., Qing K., Cheng S.W.K. and Chow K.W., Studies of thoracic aortic dissection by computational fluid dynamics, The Fifth European Conference on Computational Fluid Dynamics, Lisbon, Portugal, 2010.

Kraenkel R.A., Nakkeeran K. and Chow K.W., Integrable NLS equation with time dependent nonlinear coefficient and self-similar attractive BEC , accepted and to appear in Communications in Nonlinear Sciences and Numerical Simulations. 2010.

Lai D.W.C., Chow K.W., Rogers C.W. and Yan Z., Anti-dark solitons and periodic solutions of the resonant nonlinear Schrodinger equation, Advances in Nonlinear Waves and Symbolic Computations. Nova, 2009, 101-110.

Pak O.S., Lam C.K., Nakkeeran K., Malomed B.A., Chow K.W. and Senthilnathan K., Dissipative solitons in coupled complex Ginzburg Landau equations, Journal of the Physical Society of Japan. 2009, 78: 084001 (8 pages).

Senthilnathan K., Nakkeeran K., Li Q., Wai P.K.A. and Chow K.W., Chirped optical solitons, In: Z. Y. Yan, Advances in Nonlinear Waves and Symbolic Computations. 2009, 1-17.

Senthilnathan K., Nakkeeran K., Chow K.W., Li Q. and Wai P.K.A., Chirped optical solitons, In: Z. Y. Yan, Advances in Nonlinear Waves and Symbolic Computations. Nova, 2009, 1-17.

Tang X., Chow K.W. and Rogers C.W., Propagating wave patterns for the 'resonant' Davey - Stewartson system, Chaos, Solitons and Fractals. 2009, 42: 2707-2712.

Tsang C.H., Malomed B.A. and Chow K.W., Exact solutions for periodic and solitary matter waves in nonlinear lattices (invited article), accepted and to appear in Discrete and Continuous Dynamical Systesm, special issue on the Seville, Spain Meeting on Dynamical Systems. 2010.

Tsang C.H., Lam C.K., Malomed B.A. and Chow K.W., Solitons pinned to hot spots, European Physical Journal D, special issue on 'Dissipative Optical Solitons' (invited article). 2010, 59: 81-89.

Yan Z., Chow K.W. and Malomed B.A., Exact stationary wave patterns in three coupled nonlinear Schrodinger / Gross Pitaevskii equations, Chaos, Solitons and Fractals. 2009, 42: 3013-3019.

Researcher : Chow ST

List of Research Outputs

Li Y.Y., Cheng H.W., Chan P.M., Wong M.Y., Teng W.K., Chow S.T., Cheung K.M.C., Chan D. and Chan B.P., Repair of osteochondral defects with collagen-mesenchymal stem cell microspheres in a rabbit model. , ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #W-50, p250.

Researcher : Choy THA

List of Research Outputs

Choy T.H.A., Au-yeung C., Tam H., Lau I. and Chan B.P., Fabrication and characterization of a gel-like collagen-glycosaminoglycan structure for nucleus pulposus replacement. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S215: 817.

Researcher : Chung NH

List of Research Outputs

Chung N.H. and Liu C.H., Large-eddy simulation & k-epsilon turbulence modeling of pollutant transfer coefficient for street canyon of different aspect ratios, Western Pacific Geophysical Meeting, Taipei, Taiwan, June 22-25, 2010.

Chung N.H. and Liu C.H., Pollutant transfer coefficient in different flow regimes using large-eddy simulation, 14th Annual Conference of HKSTAM 2009-2010, Hong Kong, March 13, 2010.

Chung N.H. and Liu C.H., Pollutant transfer coefficient in street canyons of different aspect ratios, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Researcher : Deng Y

List of Research Outputs

Leung Y.C., Deng Y. and Leung M.K.H., Design optimization of a cost-effective micro wind turbine, Proceedigns World Engineering Congress 2010. London, UK, International Association of Engineers, 2: 988-993.

Researcher : Du B

List of Research Outputs

Du B., Stability Analysis and Controller Synthesis of Continuous-time Linear Time-delay Systems, PhD Thesis. Hong Kong, The University of Hong Kong, 2010, 1-185.

Du B., Lam J. and Shu Z., Strong stabilization by output feedback controller for input-delayed linear systems, ICINCO 2010. Funchal, Portugal, 141-146.

Feng Z., Lam J., Gao H. and Du B., Improved stability and stabilization results for discrete singular delay systems via delay partitioning, Joint 48th IEEE Conference on Decision and Control and 28th Chinese Control Conference. Shanghai, P.R. China, 2009, 7210-7215.

Y Z.H.A.O., Gao H., Lam J. and Du B., Stability and stabilization of delayed T-S fuzzy systems: A delay partitioning approach, IEEE Transactions on Fuzzy Systems. 2009, 17(4): 750-762.

Researcher : Duan B

List of Research Outputs

Duan B., Wang M., Li Z. and Lu W.W., Bone morphogenetic protein incorporated nanocomposite scaffolds and induction of osteogenic differentiation of mesenchymal stem cells, Proceedings of the Tissue Engineering and Regenerative Medicine International Society – EU Meeting -2010. Galway, Ireland, Paper #459.

Duan B., Wang M., Li Z. and Lu W.W., Ca-P/PHBV nanocomposite scaffolds modified by gelatin and heparin and their biological evaluation, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 94.

Duan B., Wang M., Li Z. and Lu W.W., Cytocompatibility and osteoconductivity of three-dimensional selective laser sintered nanocomposite scaffolds, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 95.

Duan B. and Wang M., Design, selective laser sintering, properties and In Vitro biological evaluation of osteoconductive nanocomposite scaffolds for bone tissue engineering, Transactions of the Society For Biomaterials 2010 Annual Meeting. Seattle, WA, USA, 2010, Paper #116.

Duan B. and Wang M., Fabrication of Ca-P/PHBV nanocomposite scaffolds via selective laser sintering and biocompatibility of the scaffolds, Proceedings of the 1st Forum on Surface Engineering of Biomedical Materials. Chengdu, China, 2009, 1pp.

Duan B., Wang M., Li Z. and Lu W.W., In Vitro Biological assessment of nanocomposite scaffolds for bone tissue engineering, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 20.

Duan B. and Wang M., Modification of selective laser sintered Ca-P/PHBV nanocomposite scaffolds, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 44.

Duan B. and Wang M., Surface modification and biocompatibility of Ca-P/PHBV nanocomposite scaffolds, Proceedings of the 1st Forum on Surface Engineering of Biomedical Materials. Chengdu, China, 2009, 1pp.

Duan B., Wang M., Li Z. and Lu W.W., Surface modification of selective laser sintered nanocomposite scaffolds and osteogenic differentiation of mesenchymal stem cells on the scaffolds, Transactions of the Society For Biomaterials 2010 Annual Meeting. Seattle, WA, USA, 2010, Paper #421.

Zhou W., Duan B., Wang M. and Cheung W.L., Crystallization behavior of Poly(L-Lactide)/Carbonated hydroxyapatite nanocomposite microspheres, Journal of Applied Polymer Science. Wiley Periodicals, Inc, 2009, 113: 4100-4115.

Researcher : Duggan BJ

List of Research Outputs

Chang C.S.T. and Duggan B.J., Relationships between rolled grain shape, deformation bands, microstructures and recrystallization textures in A1-5%Mg, Acta Materialia. Elsevier Ltd., 2009, 58: 476-489.

Chang C.S.T. and Duggan B.J., The effects of different precipitation states on the annealing behaviour of AA6111, International Conference on Processing & Manufacturing of Advanced Materials Processing, Fabrication, Properties, Applications (THERME'2009). Switzerland, Trans Tech Publication, 2009, 638-642: 2817-2822.

Duggan B.J., Tse Y.Y. and Liu G.L., Deformation banding and origins of rolling and annealing textures in low carbon and interstitial free steels, Materials Science and Technology. 2009, 26(4): 404-409.

Quadir M.Z., Chang C.S.T. and Duggan B.J., Formation of the goss texture in a thin foil experiment on Fe-3.2%Si, ISIJ International. ISIJ, 2009, 50(2): 264-271.

Researcher : Fan J

List of Research Outputs

Fan J. and Wang L., Constructal design of nanofluids, International Journal of Heat and Mass Transfer. 2010, 53: 4238-4247.

Fan J. and Wang L., Effective thermal conductivity of nanofluids: effects of microstructure, Journal of Physics D: Applied Physics. 2010, 43: 165501/1-165501/10.

Fan J. and Wang L., Effects of microscale physics on macroscale thermal properties in nanofluids, The 2nd ASME Micro/Nanoscale Heat and Mass Transfer International Conference. 2009, ASME MNHMT2009-18386.

Fan J. and Wang L., Is classical energy equation adequate for convective heat transfer in nanofluids?, Advances in Mechanical Engineering (Special issue on Heat Transfer in Nanofluids). 2010, DOI: 10.1155/2010/719406.

Wang L. and Fan J., Nanofluids research: key issues, Nanoscale Research Letters. 2010, 5: 1241-1252.

Zhang Y., Fan J. and Wang L., Formation of nanoliter droplets in a confined microfluidic T-shaped junction: formation time and droplet volume, Current Nanoscience. 2009, 5: 519-526.

Researcher : Fan Y

List of Research Outputs

Fan Y., Qing K., Cheng S.W.K. and Chow K.W., Computational studies of thoracic aortic dissection, The 8th Asian Computational Fluid Dynamics Conference, Hong Kong. 2010.

Fan Y., Qing K., Cheng S.W.K. and Chow K.W., Studies of thoracic aortic dissection by computational fluid dynamics, The Fifth European Conference on Computational Fluid Dynamics, Lisbon, Portugal, 2010.

Researcher : Fan Y

List of Research Outputs

Fan Y., Qing K., Cheng S.W.K. and Chow K.W., Computational studies of thoracic aortic dissection, The 8th Asian Computational Fluid Dynamics Conference, Hong Kong. 2010.

Researcher : Fu X

List of Research Outputs

Fu X., Wang X.X., Ding Z.X., Leung Y.C., Zhang Z.Z., Long J.L., Zhang W.X., Li Z.H. and Fu X.Z., Hydroxide ZnSn(OH)₆ : A new promising photocatalyst for benezene degradation, Applied Catalysis B: Environmental. Elsevier, 2009, 91: 67-72.

Fu X., Wang X.X., Chen Z.X., Leung Y.C., Li Z.H., Wu L. and Fu X.Z., Photocatalytic performance of tetragonal and cubic b-In 2S3 for water splitting under visible light irradiation, Applied Catalysis B: Environmental. Elsevier, 2010, 95: 393-399.

Leung Y.C., Fu X., Wang C.F., Ni M., Leung M.K.H., Wang X.X. and Fu X.Z., Hydiogen production over titania-based photocatalysts, ChemSusChem. Wiley Inter Science, 2010, 3: 681-694.

Researcher : Grimshaw RHJ

List of Research Outputs

Ee B.K., Grimshaw R.H.J., Zhang D. and Chow K.W., Steady transcritical flow over a hole: Parametric map of solutions of the forced Korteweg - dr Vries equation, Physics of Fluids. 2010, 22: 056602 (9 pages).

Researcher : Gurarie D

List of Research Outputs

Chow K.W., Yip L.P. and Gurarie D., Two exact solutions of the Tzitzeica - Bullough - Dodd equation, International Journal of Nonlinear Sciences and Numerical Simulations. 2009, 10: 935-943.

Researcher : Hang J

List of Research Outputs

Hang J., Sandberg M. and Li Y., Age of air and air exchange efficiency in idealized city models, Building and Environment. 2009, 44: 1714-1723.

Hang J., Sandberg M., Li Y. and Claesson L., Flow mechanisms and flow capacity in idealized long-street city models, Building and Environment. 2010, 45: 1042-1053.

Hang J., Li Y. and Lina Y.A.N.G., Macroscopic numerical simulations of wind conditions in high-rise building clusters using a porous turbulence model, The 8th Asian Computational Fluid Dynamics Conference. 2010.

Hang J., Sandberg M., Li Y. and Claesson L., Pollutant dispersion in idealized city models with different urban morphologies, Atmospheric Environment. 2009, 43: 6011-6025.

Hang J. and Li Y., Ventilation strategy and air change rates in idealized high-rise compact urban areas , Building and Environment . 2010, 45: 2754-2767.

Hang J., Wind Conditions and Urban Ventilation in Idealized City Models, PhD Thesis. Hong Kong, The University of Hong Kong, 2009, 1-365.

Hang J. and Li Y., Wind Conditions in Idealized Building Clusters: Macroscopic Simulations Using a Porous Turbulence Model, Boundary-Layer Meteorol. 2010, 136: 129-159.

Hang J., Sandberg M. and Li Y., Wind conditions and ventilation in high-rise long street models, Building and Environment. 2010, 45: 1353-1365.

Researcher : Hang J

List of Research Outputs

Hang J., Sandberg M. and Li Y., Age of air and air exchange efficiency in idealized city models, Building and Environment. 2009, 44: 1714-1723.

Hang J., Sandberg M., Li Y. and Claesson L., Flow mechanisms and flow capacity in idealized long-street city models, Building and Environment. 2010, 45: 1042-1053.

Hang J., Sandberg M., Li Y. and Claesson L., Pollutant dispersion in idealized city models with different urban morphologies, Atmospheric Environment. 2009, 43: 6011-6025.

Hang J. and Li Y., Ventilation strategy and air change rates in idealized high-rise compact urban areas , Building and Environment . 2010, 45: 2754-2767.

Hang J., Wind Conditions and Urban Ventilation in Idealized City Models, PhD Thesis. Hong Kong, The University of Hong Kong, 2009, 1-365.

Hang J. and Li Y., Wind Conditions in Idealized Building Clusters: Macroscopic Simulations Using a Porous Turbulence Model, Boundary-Layer Meteorol. 2010, 136: 129-159.

Hang J., Sandberg M. and Li Y., Wind conditions and ventilation in high-rise long street models, Building and Environment. 2010, 45: 1353-1365.

Researcher : Hong L

List of Research Outputs

Hong L. and Soh A.K., Control of domain states in individual PbTiO3 nanoparticles by prescribed strains , Materials Structure & Micromechanics of Fracture (MSMF6). VUTIUM Brno, 2010, 1: 67.

Hong L., On Nanoferroelectric Domain Structures and Distributions of Defects in Ferroelectrics, PhD Thesis. Hong Kong, The University of Hong Kong, 2010, 1-129.

Hong L., Soh A.K., Liu S. and Lu L., Vortex structure transformation of BaTi0₃ nanoparticles through the gradient function, Journal of Applied Physics. USA, Amer. Inst. Physics, 2009, 106(2): Article no.: 024111.

Hong L. and Soh A.K., Vortex structure transformation of BaTiO3 nanoparticles through the gradient function by phase field method, 2009 MRS Fall Meeting. 2009.

Liu S., Soh A.K. and Hong L., Lateral surface induced effects on ultra-thin amorphous Co nanowire, Journal of Physics D - Applied Physics. Bristol, England, IOP Publishing, 2009, 42(21): Article No.: 215002.

Liu S., Soh A.K. and Hong L., Monte Carlo Simulation to the magnetic properties of amorphous Co nanowires, 2009 MRS Fall Meeting. 2009.

Liu S., Soh A.K., Hong L. and Lu L., Surface characterization of amorphous Co_xGd_1-x nanowires and magnetic properties of their arrays, Journal of Physical Chemistry C. Washington, USA, Amer Chemical Soc., 2009, 113(39): 16934-16938.

Shi Y., Hong L. and Soh A.K., 3-D ferroelectric domain reversal mechanism , The 14th Annual Conference of HKSTAM 2009-2010 cum The 7th Shanghai – Hong Kong Forum on Mechanics and Its Application . HKSTAM, 2010, 1: 36.

Researcher : Huang H

Project Title:	Destruction of multiple indoor air pollutants using photocatalysis irradiated by ozone-producing UV lamp
Investigator(s):	Huang H, Leung YC, Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	10/2009

Abstract:

Indoor air pollution causes great harm not only to environment but also to human health. It may be responsible for up to 2.4 million premature deaths a year (1). People spend 80~90% of their time indoors. We work, study, eat, drink, sleep, travel and play in enclosed environments where air circulation may be restricted that affects the air quality. Indoor air pollution is also serious in public places such as hospitals, supermarkets, waiting halls and underground parking, etc. Thus, indoor environment may impose important effects on human health and work efficiency. There are many sources of indoor air pollution. Fox example, VOCs, one of the most important indoor air pollutants, are emitted from numerous sources such as furniture, decorations and combustion products while micro-organisms grow on dirty and humid surfaces, such as components of systems for heating, ventilating, and air conditioning (2). Indoor air pollution mainly includes particulate matters, biological pollutants, and gaseous pollutants (3). There are many air cleaners in the market but most of them are only capable to remove a single pollutant and many of them may not fully meet with the local or international regulation. Few studies have been conducted on the destruction of multiple indoor air pollutants simultaneously. UV lamp and O3 is a conventional sterilization technology commonly used. However, UV lamp has the limitation of light holdback. While the main drawback of the O3 sterilization system is its high cost and space requirements, and creation of O3 residue. The UV lamp and O3 technology has little effect on the removal of gaseous and particle pollutants. Heterogeneous photocatalysis has become one of the most adopted methods to destruct indoor air pollutants and a great number of patents and commercial equipments are generated every year (3-8). Unfortunately, photocatalysis has several disadvantages, such as photocatalyst deactivation, low removal efficiency and energy yield, hindering its development and application (9-11). It has been proved that the combination of O3 with photocatalysis enhanced the removal efficiency (4, 12, 13). However, additional O3 increases the complexity and cost. Sterilization using ozone-producing UV lamp (O3-UV) is a new technology that can overcome the above-mentioned drawbacks. The previous studies (including our preliminary study) show that gaseous pollutants can be destructed by ozone-producing UV lamp directly (14, 15). Nevertheless, the ozone-producing UV lamp alone is limited by in usage due to the formation of O3 byproduct and low-efficiency. The photocatalysis irradiated by ozone-producing UV lamp (O3-UV photocatalysis) cannot only efficiently remove gaseous and biological pollutants simultaneously, but also further enhance the pollutants destruction due to O3 decomposition. O3 can be completely removed by a photocatalyst. Strong UVC and photocatalysis can break down various viruses, air pollutants and VOCs. O3-UV photocatalysis has advantages of much greater efficiency, higher stability and durability, and lower energy consumption over conventional photocatalysis. Furthermore, some particulate pollutants in air can be filtered by a photocatalyst mesh. The main objective of the proposed study is to develop an O3-UV photocatalysis process for the destruction of biological and gaseous pollutants simultaneously without any O3 byproduct (Fig. 1). Specifically the following study will be conducted: a. To develop a series of photocatalysts with high photocatalysis activity and ozone-destruction efficiency; b. To study the destruction of biological and gaseous pollutants in the O3-UV and conventional photocatalysis; c. To optimize the operating parameters in the O3-UV photocatalysis; d. To investigate the mechanism of air pollutants destruction. Key issues and problems to be addressed: Few studies have been conducted on O3-UV photocatalysis targeting on more than one pollutant. The destruction of multiple pollutants in this process is not fully understood at present. Both of the photocatalysts and O3-UV lamp are vital to the destruction performance. Preparation of photocatalysts with high activity and ozone-destruction efficiency, the selection of optimum UV sources, etc, are most important factors that affect the destruction performance. The analysis of intermediate and final products of pollutants destruction, generation and destruction of O3 are not only helpful to the mechanism investigation, but also essential for future practical application. The working mechanism of O3-UV photocatalysis is much more complicated than that of photocatalysis only and is not fully known presently. Photolysis, photocatalysis, and O3 in the O3-UV photocatalysis process may affect each other and result in synergistic effect. Therefore, it is important to study the individual effect while fixed other parameters. References: (1) UNEP, United Nations Environment Programme Report (2006). (2) M. P. Paschoalino and W. F. Jardim, Indoor Air, 18, 473-479 (2008). (3) B. F. Yu, Z. B. Hu, M. Liu, H. L. Yang, Q. X. Kong and Y. H. Liu, International Journal of Refrigeration, 32, 3-20 (2009). (4) P. Y. Zhang, F. Y. Liang, G. Yu, Q. Chen and W. P. Zhu, Journal of Photochemistry and Photobiology a-Chemistry, 156, 189-194 (2003). (5) J. Peral, X. Domenech and D. F. Ollis, Journal of Chemical Technology and Biotechnology, 70, 117-140 (1997). (6) A. Vohra, D. Y. Goswami, D. A. Deshpande and S. S. Block, Applied Catalysis B: Environmental, 64, 57-65 (2006). (7) U. I. Gaya and A. H. Abdullah, Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 9, 1-12 (2008). (8) J. M. Herrmann, C. Duchamp, M. Karkmaz, B. T. Hoai, H. Lachheb, E. Puzenat and C. Guillard, Journal of Hazardous Materials, 146, 624-629 (2007). (9) M. Kang, B.-J. Kim, S. M. Cho, C.-H. Chung, B.-W. Kim, G. Y. Han and K. J. Yoon, Journal of Molecular Catalysis A: Chemical, 180, 125-132 (2002). (10) L. X. Cao, Z. Gao and S. L. Suib, American Chemical Society, 220, U269-U269 (2000). (11) U. Siemon, D. Bahnemann, J. J. Testa, D. Rodriguez, M. I. Litter and N. Bruno, Journal of Photochemistry and Photobiology a-Chemistry, 148, 247-255 (2002). (12) K. P. Yu and G. W. M. Lee, Applied Catalysis B-Environmental, 75, 29-38 (2007). (13) H. Qi, D. Z. Sun and G. Q. Chi, Journal of Environmental Sciences-China, 19, 1136-1140 (2007). (14) L. Yang, Z. Liu, J. Shi, Y. Zhang, H. Hu and W. Shangguan, Separation and Purification Technology, 54, 204-211 (2007). (15) T. Alapi and A. Dombi, Chemosphere, 67, 693-701 (2007).

List of Research Outputs

Huang H. and Leung Y.C., Destruction of indoor air pollutants using photocatalysis irradiated by ozone-producing UV lamp, 4th Japan-China Workshop on Environmental Catalysis and Eco-materials. 2009.

Huang H. and Leung Y.C., Enhanced Destruction of Toluene by Photocatalysis combined with Ozone, The 2nd International Workshop on Regional Air Quality Management in Rapidly Developing Economic Regions. 2009.

Researcher : Huang L

Project Title:	The suppression of multiple tones for small axial-flow fans
Investigator(s):	Huang L
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	12/2005

Abstract:

The underlying objective of the project is to bridge the gap between the fan aerodynamics and aeroacoustics in the following sense. Acoustic design normally follows aerodynamic design and is treated as a modification exercise. This project seeks to integrate the two and answer the question of whether an essentially toneless fan is possible without sacrificing the aerodynamic performance. Here, a toneless fan is defined as a fan whose discrete noises are at most a couple of decibels above the level of broadband noise associated with a descent flow condition in which the flow can be turbulent but is attached to profiled blades. Tonal noise is radiated at the blade passing frequency (BPF) and many of its harmonics with frequency f=mxBPF, m=1,2,3... For small axial flow fans with few blades, tones of m>=4 are rarely above the broadband with a significant margin, so the emphasis of the project is on the suppression of multiple tones of small order m. A fresh perspective and the key issue: The main source of tonal noise is the interaction between the rotor blades and nearby stationary parts, such as the motor struts and/or inlet/exit guidevanes. The blade tip speed of a small fan is typically below 50m/s. Noise generated byt he steady aerodynamic loading, i.e. the Gutin noise, is far below the interaction noise and is therefore ignored. To make a fan toneless means the simultaneous suppression of noise at multiple frequencies, say for m=1,2,3. The general consensus in the acoustics community is that it is difficult, if not impossible. However, the results of our recent work (Huang 2003a, Wong & Huang 2003, see end of Section 3 for references) on computer cooling fans show that there is a lot of potential in suppressing the tonal noise by self-cancellation of sound waves made by different sites of rotor-stator interaction. This strategy differs from the usual approach of trying to weaken each interaction event. Specifically, the major BPF peak can be suppressed by suitable choice of the numbers of rotor and stator blades. The simultaneous suppression of higher harmonics is also shown to be possible if the waveform of the unsteady loading arising from the rotor-stator interaction can be fine-tuned by design. The key issue is the thorough understanding of the interaction process and factors that shape the temporal characteristics of the unsteady loading on the rotor blades.

Project Title:	Blower noise source identification and mitigation for notebook PCs
Investigator(s):	Huang L
Department:	Mechanical Engg
Source(s) of Funding:	Intel Corporation - General Award
Start Date:	05/2007

Abstract:

(A) Intel's Goal. To have University perform certain experiments involving noise source modeling and mitigation in order to determine feasibility of improving design to reduce fan noise. If successful, the results of University's experiments and modeling will be incorporated for use with Intel platforms so that Intel's OEM/ODM's can have sufficient availability of products in the marketplace ideally suited for platforms based on genuine Intel architecture. (B) University's Goal. To have research for noise source modeling and mitigation funded, the results of the research published, and the results of University's experiments incorporated for use with platforms based on genuine Intel architecture in order to make or have made these optimized products for potential sale to Intel's OEM/ODMs.

Project Title:	Broadband Duct Noise Control Inspired by the Middle Ear Mechanisms
Investigator(s):	Huang L
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2009

Abstract:

1. Numerical solution and physics understanding. Construct a full numerical simulation for the bio-inspired silencer, and compare the solution with the asymptotic, closed-form solution obtained by a low-frequency approximation. An acceptable agreement between the two solutions would help identify the major physics ingredients needed to achieve a broadband performance for a side-branch silencer. One main concern here is the spectral trough between two neighbouring peaks. 2. Parametric study and optimization. Identify the key factors controlling the volume and the axial length required for a given silencing task. These factors may include the structural mass of the ossicular mechanism, the area ratio between the two moving ends emulating the eardrum and the oval window, and their elasticity. In addition, the influence of the structural boundary conditions of these moving parts will also be investigated. A single-digit performance index will be used for the low-frequency, broadband silencer taking into account several technical concerns, and the performance of the new device will be compared with the previous device of drumlike silencer. 3. Experimental validation or demonstration of the bio-inspired device. Experiments will be conducted to demonstrate the working mechanism of the device and identify potential problems that may occur in real applications.

Project Title:	Exploring a new approach of ground noise control for the over-land supersonic transportation
Investigator(s):	Huang L
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2009

Abstract:

Flying Concord used to be a luxury reserved for the rich and the noble, but the aviation industry has never given up the pursuit of building supersonic planes that are environmentally friendly and economically viable for ordinary business travellers. One of the main challenges of building such a jumble jet is the excessive and unpleasant noise (sonic boom) that rattles buildings and startles humans. As a result, Concord was only allowed to travel over the ocean and banned from all overland routes in the US. Partly because of this, its operational cost was extremely high and its eventual grounding became an inevitable history (Candel 2004; references listed at the end of Sec VII). Since the launch of Concord in 1970s, the aviation industry has actually made great strides in design (Farhat et al 2007) and the noise level for supersonic passenger aircraft has decreased by a very respectable amount of 35 dB (Volz 2003). In other words, the ratio of sound energy to the old plane is 1:3162. There is now a real prospect that supersonic flights with 50% or more time savings from the current commercial jets will become a sustainable reality. The American Federal Aviation Administration (FAA) called for extensive noise acceptability studies from 2003 (Heron et al 2006, Locey et al 2007) as part of the legislation relaxation process to usher in a new era of quiet supersonic commercial flights. NASA and various companies, e.g. Boeing, Gulfstream, are preparing to launch their first supersonic jumble jet in the middle of the coming decade. The current proposal assumes that the new age of supersonic travel will become a reality, and aims at tackling one of the crucial noise abatement problems that will be faced by metropolitan cities, such as Hong Kong, that will be served by such jumble jets. The problem is the effective shielding of the sonic boom by buildings so that residents near the flight path will not be excessively affected by such flights. As has been discussed above, sonic booms have already been weakened by the latest aircraft design technology, but a low-boom is still a boom, and it is found to be 5 dB more annoying than blast noise of equal energy (Schomer & Sias 1998). It must be pointed out that, while the fundamental solution of the subsonic flight noise lies with the airplane design itself, the problem of supersonic flight noise straddles across both noise source and receiver. Unlike subsonic noise, the shock waves created by supersonic flights, i.e. the sonic booms, are more or less unavoidable and the strength is primarily determined by the weight of the loaded aircraft, which has to be heavy to be economically viable. Although a lot of research work is carried out on how to “trim” the waveform so that a major portion of that sound energy does not bother human ears, equal emphasis should be placed on how buildings can be designed to better protect its inhabitants from such powerful waves. An effective solution here would be a major boost for the march towards a sustainable supersonic aviation. In this aspect, research efforts should not and will not be confined to Seattle or Toulouse, or America and Europe at large. We all have a shared opportunity to make contributions. The specific contribution we seek to make in this exploratory project is the following. Most existing work focuses on two questions in the receiver side. The first is how sonic boom is transmitted to rooms via windows and how that transmission can be reduced by strengthening window panels. The second is how to gauge human reaction to different boom signatures such that the most acceptable type can be used to guide the airplane design, which mainly involves lift re-distribution along the aircraft length. The current project explores a possibility of draining the energy of the sonic boom through a passage next to windows, much like a lightning rod (or conductor) protects a building. In parallel with the existing effort of gauging human reaction to the sonic boom spectra, we shall also investigate the special silencers that should be used for sonic booms as opposed to usual transportation noise. Therefore, this project has two specific objectives. (a) Explore the concept of acoustic “lightning rod” by studying the interaction of sonic boom with two acoustic passages, window plus a parallel silencer, which may or may not be connected physically. The result should point to directions of how the wave energy can be directed away from the window passage. More specifically, the necessary condition for the bypass silencer should be established theoretically. (b) Investigate the special silencer characteristics required of sonic booms. This silencer can be either part of the bypass described above or additional silencer installed to deal with the residual weak boom that may otherwise enter a room.

Project Title:	The 16th International Congress on Sound and Vibration ATTENUATION OF LOW FREQUENCY DUCT NOISE BY A FLUTE-LIKE SILENCER
Investigator(s):	Huang L
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	07/2009
Completion Date:	07/2009

Abstract:

N/A

Project Title:	Study of two prototype problems of confined noise sources
Investigator(s):	Huang L
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2010

Abstract:

Mathematically, sound sources are categorized into three basic types, monopole, dipole and quadrupole. Dipole can be considered as the result of combining two monopoles of opposite signs and so is quadrupole in terms of dipoles (Lighthill 1978). Physically, monopole is related to the expansion and contraction of volume such as that arising from unsteady combustion inside an engine. Dipole is related to the vibration of rigid objects or unsteady air pressure acting on rotary or stationary blades (Blake 1986), while quadrupole describes the noise radiation by turbulence at the absence of rigid structures (Lighthill 1952). It may be said that the practical problem of quadrupole noise from jet engine is already settled with the development of high bypass ratio turbofan engines. What is left today is monopole and dipole problem. Practical monopole sources are relatively rare, except by the distortion of non-compact structural vibrations. That leaves us with dipole as the dominant feature of today’s noisy world. For an ideal point dipole, it has a radiation axis and no noise is found in the direction perpendicular to this axis. The front and the back of the dipole has exactly the opposite phase angles. These simple and yet very distinct features of dipole radiation does not seem to have been fully exploited so far. This is evidenced by the fact that most theoretical studies and illustrations of theories use monopoles, apparently due to its simplicity. The fundamental objective of this project is to change this situation in acoustics. We shall consider two prototype problems using dipole as sound source and illustrate how very differently the basic principles of sound attenuation should be reconstructed. To do so, it would be convenient to begin with simple situation in which sound propagation is confined to some extent. Fan noise in an industrial tube and vehicle noise in a road tunnel are two such examples. The fundamental difference in the way noise attenuation should be considered is that, in the case of dipole, noise from the two sides of the source must be dealt with simultaneously leading to maximum control effect. In the first prototype problem, we consider the suppression of dipole noise radiation inside an infinitely long tube. The main purpose of such a theoretical model is not primarily inspired by the mathematical beauty or convenience. Rather, it is based on the following considerations. When the sound power output from the two sides of the duct is minimized, the source itself is said to be suppressed and very little sound is ever created in the first place. Interaction with features far upstream and far downstream becomes trivial. When the sound radiation is not minimized, however, the above statement is incorrect. The result of infinite duct study serves to provide the source characterization only, which is also unique. In the second prototype problem, we consider a semi-infinite duct problem. This is further divided into two sub-problems, 2A and 2B. In problem 2A, the concern is the sound minimization inside the duct, such as the problem of ventilation noise inside a tunnel where the source is near to one open-end with distinctive features of sound reflection. In problem 2B, the concern is the sound radiation out of the duct from perhaps multiple sources inside the duct. To summarize, the objectives of the project are as follows. (a) To study the fundamental difference between noise attenuation for monopole and dipole sources. This will be achieved through two prototype problems in which the sound radiation conditions are distinct from each other. (b) To explore possible direct application of the two prototype problems for confined noise sources. Some of the results will be tested experimentally.

List of Research Outputs

Choy Y.S. and Huang L., Multiple drumlike silencer for low frequency duct noise reflection, Applied Acoustics. Elsevier Ltd., 2009, 70(11-12): 1422-1430.

Choy Y.S., Huang L. and Wang C., Sound propagation in and low frequency noise absorption by helium-filled porous material, Journal of the Acoustical Society of America. Journal of the Acoustical Society of America, 2009, 126(6): 3008-3019.

Huang J.C., Ma X. and Huang L., Experimental study and control of noise from a window-type ventilation fan, Noise Control Engineering Journal. 2009, 57(4): 335-340.

Huang L., Attenuation Of Low Frequency Duct Noise By A Flute-like Silencer, In: M Crocker et al, Proceedings of the 16th International Congress on Sound and Vibration. Krakow, Poland, 2009, 8 pages.

Huang L., Attenuation of low frequency duct noise by a flute-like silencer, Journal of Sound and Vibration. 2009, 326(1-2): 161-176.

Huang L., Suppression of ducted dipole noise by an expansion segment around the source, The Joint Meeting of the 159th Meeting of the Acoustical Society of America and Noise-Con 2010. Baltimore, Maryland, Journal of the Acoustical Society of America, 127(3), Pt.2: 1838, Paper 2pNSs10.

Wang C. and Huang L., TIME-DOMAIN SIMULATION OF ACOUSTIC WAVE PROPAGATION BY CHEBYSHEV COLLOCATION, the 39th International Congress and Exposition on Noise Control Engineering. 2010, paper 784.

Researcher : Hui SCM

List of Research Outputs

Hui S.C.M., ASHRAE Distinguished Lecturer (2009-2011), American Society of Heating, Refrigerating and Air Conditioning Engineers. 2009.

Hui S.C.M. and Lee R.K.H., Development of energy labels for residential buildings in Hong Kong, In: N/A, Proceedings of the 10th Asia Pacific Conference on the Built Environment: Green Energy for Environment, 5-6 November 2009, Kaohsiung, Taiwan. Kaohsiung, Taiwan, ASHRAE Taiwan Chapter, 2009, 8 pages.

Hui S.C.M., Green Roof Systems and Technology, ASHRAE-HKC / CIBSE-HKB / HKIE-BSD Joint Function Technical Talk, 30 July 2009 (Thu), HKIE Headquarters. Hong Kong, Hong Kong Institution of Engineers, 2009, n/a.

Hui S.C.M. and Chu C.H.T., Green roofs for stormwater mitigation in Hong Kong, In: N/A, Proceedings of the Joint Symposium 2009: Design for Sustainable Performance, 25 November 2009, Kowloon Shangri-La Hotel, Hong Kong. Hong Kong, The Symposium organiser, 2009, 10.1-10.11.

Hui S.C.M., Operation and maintenance to improve energy efficiency and sustainability of existing buildings, Invited presentation for the Green Buildings: Better Quality of Life Conference, 11 June 2010 (Fri), L'hotel Nina et Convention Centre, Tsuen Wan. 2010.

Hui S.C.M., Study of Thermal and Energy Performance of Green Roof Systems: Final Report, Department of Mechanical Engineering, The University of Hong Kong, Hong Kong (submitted to Energy Efficiency Office, Electrical and Mechanical Services Department, Hong Kong). Hong Kong, Department of Mechanical Engineering, The University of Hong, 2009, 136 pages.

Hui S.C.M., Study of zero energy building and zero carbon building, 探討零能耗建築和零碳建築, Intelligent Building Technology. 智能建築科技, Shanghai, China, Shanghai Intelligent Building Network 上海智能建築網 www.eastib.com, 2010, 43: 1-8.

Hui S.C.M., Zero energy and zero carbon buildings: myths and facts, In: Asian Institute of Intelligent Buildings (AIIB), Proceedings of the International Conference on Intelligent Systems, Structures and Facilities (ISSF2010): Intelligent Infrastructure and Buildings, 12 January 2010, Kowloon Shangri-la Hotel, Hong Kong. Hong Kong, Asian Institute of Intelligent Buildings (AIIB), 2010, 15-25.

Researcher : Hui TY

List of Research Outputs

Chan B.P., Hui T.Y., Wong M.Y. and Chan G.C.F., Formation of injectable and osteoinductive bone-like microparticles using mesenchymal stem cell-collagen microspheres., 7th Annual Meeting of International Society for Stem Cell Research, Jul 8-11, 2009. Barcelona, Spain.. 2009, 1263.

Researcher : Ip RWL

Project Title:	Axial-fugal Flow Turbo-machines: A New Family Group of Airflow Machines for Specific Industrial Applications
Investigator(s):	Ip RWL
Department:	Mechanical Engg
Source(s) of Funding:	Matching Grant for Joint Research
Start Date:	03/2010

Abstract:

A. To generate an idea for the design of a new turbo-machine family group for specific industrial applications. B. To define sets of algorithms for the design of machine impellers and volutes for specific operations requiring high head and large flow. C. To design the aero-mechanical structure of the machines, including the geometrical shape of the impellers and volutes. D. To design and manufacture prototypes to validate the machine performance, characteristics and efficiency. E. To measure the machine output performance and efficiency, and suggest improvement strategies. F. To develop a turn-key software program for potential users to support their use of the developed algorithms for specific airflow system design.

List of Research Outputs

Hung Y.Y., Chen Y.S., Ng S.P., Liu L., Huang Y.H., Luk B.L., Ip R.W.L., Wu C.M.L. and Chung P.S., Review and comparison of shearography and active thermography for nondestructive evaluation, Materials Science and Engineering Report. 2009, 64: 73-112.

Ip R.W.L., Cheng M.T., Lao S.H. and Wan I.C., A finite element analytical approach for the design of industrial type heat exchangers, Annual Journal of Institute of Industrial Engineers. 2010, 30: 11-20.

Siak J.K., Shek C.H., Chung C.Y., Ip R.W.L. and Cheung T.L., A method and apparatus for production a lightweight metal alloy, 2009, HK Patent no. 09110127.6.

Researcher : Kang J

List of Research Outputs

Kang J., Wang M. and Yuan X.T., Bicomponent fibrous scaffolds of controlled composition for tissue engineering applications, Proceedings of the 2009 ASME International Mechanical Engineering Congress & Exposition (IMECE 2009). Lake Buena Vista, Florida, USA, 2009, 9pp.

Kang J., Wang M. and Yuan X.Y., Biodegradable micro- and nanofibers fabricated through electrospinning for tissue engineering and controlled release applications, Proceedings of the 2009 ASME International Mechanical Engineering Congress & Exposition (IMECE 2009). Lake Buena Vista, Florida, USA, 2009, 7pp.

Kang J., Wang M. and Yuan X.Y., Electrospinning of PLLA Micro- and nanofibers: Effects of electrospinning parameters on fiber diameter and morphology, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 37.

Kang J., Wang M. and Yuan X.Y., Fibrous scaffolds of genipin-crosslinked gelatin fabricated through electrospinning, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 81.

Kang J., Wang M. and Yuan X.Y., Gelatin-PLLA bicomponent fibrous scaffolds for tissue engineering applications, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 120.

Researcher : Kang J

List of Research Outputs

Kang J., Wang M. and Yuan X.Y., Fibrous scaffolds of genipin-crosslinked gelatin fabricated through electrospinning, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 81.

Researcher : Kong T

List of Research Outputs

Wei X., Kong T., Zhu H.T. and Wang L., CuS/Cu₂S nanofluids: synthesis and thermal conductivity, International Journal of Heat Mass Transfer. 2010, 53: 1841-1843.

Researcher : Kou X

List of Research Outputs

Kou X. and Tan S.T., An XML implementation for data exchange of heterogeneous object models, In: Xun Xu and Andrew Y. C. Nee, Springer Series in Advanced Manufacturing, Advanced Design and Manufacturing based on STEP. London, Springer, 2009, 419-438.

Kou X., Xue S. and Tan S.T., Knowledge-guided inference for voice-enabled CAD, Computer Aided Design. Elsevier, 2010, 42: 545-557.

Kou X., Liu X.C. and Tan S.T., Quadtree based mouse trajectory analysis for efficacy evaluation of voice-enabled CAD, International Conference on Virtual Environment, Human-Computer Interfaces, and Measurements Systems (VECIMS). Hong Kong, 2009, 196-201.

Xue S., Kou X. and Tan S.T., Natural voice-enabled CAD: Modeling via natural discourse, Computer-Aided Design and Applications. 2009, 6(1): 125-136.

Researcher : Kwok CB

List of Research Outputs

Chan B.P. and Kwok C.B., Compression-induced reorientation of human mensenchymal stem cells (hMSCs) in 3D collagen matrix – Dependence on collagen concentration and integrin beta 1. , ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #W-55, p237.

Researcher : Lai DWC

List of Research Outputs

Lai D.W.C., Chow K.W., Rogers C.W. and Yan Z., Anti-dark solitons and periodic solutions of the resonant nonlinear Schrodinger equation, Advances in Nonlinear Waves and Symbolic Computations. Nova, 2009, 101-110.

Researcher : Lam CK

List of Research Outputs

Pak O.S., Lam C.K., Nakkeeran K., Malomed B.A., Chow K.W. and Senthilnathan K., Dissipative solitons in coupled complex Ginzburg Landau equations, Journal of the Physical Society of Japan. 2009, 78: 084001 (8 pages).

Tsang C.H., Lam C.K., Malomed B.A. and Chow K.W., Solitons pinned to hot spots, European Physical Journal D, special issue on 'Dissipative Optical Solitons' (invited article). 2010, 59: 81-89.

Researcher : Lam HN

Project Title:	GIS -based Intelligent Management of Building Facilities and Security System
Investigator(s):	Lam HN
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	11/2007

Abstract:

Building services engineering systems serving modern commercial buildings have become increasingly sophisticated. In order to operate and maintain these systems effectively and efficiently, integrated planning, monitoring, control and maintenance are required. Computerised systems are available from the market for handling these different job requirements. However, there is almost no integration or coordination among these systems, resulting in a poor overall system performance. The objectives of the research project are to investigate the development and performance analysis of an innovative computerised system based on the concept of Geographic Information System (GIS) and artifical intelligence for the co-ordinated management of various facilities and security system for buildings.

Project Title:	Intelligent Control Strategy for Direct Expansion Air Conditioning Systems
Investigator(s):	Lam HN
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	12/2008

Abstract:

Comfort air conditioning systems for buildings account for a major proportion of the total whole-building energy consumption. In view of the escalating cost of electricity and the growing concern for the grave consequences of climate change due to release of greenhouse gases into the atmosphere, building owners are increasingly keen at searching for solutions to tackle the problem of high electrical energy consumption and and costly electricity bill for air conditioning systems. The air conditioning systems which operate on the principles of vapour compression and direct expansion, including the split-type, variable-refrigerant type and window type, are traditionally controlled by a relatively simple control system. There are ample rooms for improvement in the control strategies to be adopted so that energy efficiency is enhanced without compromising the provision of the required comfort level. The objectives of the research project are to investigate detailed dynamic computer modelling of such air conditioning systems to identify the feasibility of reduction in energy demand and to design artificial-intelligence-based algorithms for optimal system control.

Project Title:	Powerline-based Smart Energy System for User Decision Support and Energy Saving
Investigator(s):	Lam HN
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	12/2009

Abstract:

There is now a worldwide concern about the sustainability of the enironment due to excessive energy consumption by mankind and the consequent high emission of greenhouse gases and climate change. To help combat this climate change, much attention has been paid to the demand-side management of electrical energy consumption with the aim of improving the efficiency of energy utilisation and reducing energy wastage. The major obstacles confronting effective demand-side management strategies lie in the difficulty in designing a system capable of providing useful information to the users for supporting decision-making on the level of energy saving desired at the expense of reduced comfort level. The need for laying dedicated control wiring for networking the system components also adds to the system cost and imposes inflexibility on relocation of components due to requirement of changes in the future. The objectives of the research project are to investigate how the concept of smart energy systems can be applied to domestic dwellings by designing a powerline-based network system for the monitoring, control and management of all services systems and appliances inside the buildings, capable of providing the users with useful information about strategy for energy saving without the need for laying dedicated signal wirings.

List of Research Outputs

Lam H.N., Application of Far Infrared Radiation to Food Processing , Workshop on Application and Productization Design for Far Infrared Rays (FIR) Technology – Food Processing . 2009.

Lam H.N., Effects of FIR on Health , Workshop on Application and Productization Design for Far Infrared Rays (FIR) Technology – Healthcare Products. 2009.

Lam H.N., From CAD to BIM to GIS, BuilTech Conference 2009. 2009.

Lam H.N., Optimising Energy Cost Savings for Building Air Conditioning Systems by Using Phase Change Materials, Forum on Latest Researches on Energy Efficiency and Conservation organised by Electrical & Mechanical Services Department, HKSAR Government . 2010.

Lam H.N., Study of Liquid Desiccant Dehumidification Utilising Far Infrared Radiation for Moisture Control in Air Conditioning Applications , Workshop on Application and Productization Design for Far Infrared Rays (FIR) Technology - Industrial Heating and Drying. 2009.

Lam H.N., The Implementation of Standardization and Certification for FIR Products in Hong Kong, Conference on Far Infrared Rays Technology for the Food Processing & Healthcare Industries . 2010.

Lam H.N., The Need for Standardization and Certification for FIR Products in Hong Kong , Conference on Far Infrared Rays Technology for the Food Processing & Healthcare Industries. 2010.

Researcher : Lam J

Project Title:	Decay rate estimation and synthesis of functional differential systems via semi-definite programming
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	11/2006
Completion Date:	04/2010

Abstract:

(1) To develop stability conditions with decay rates for functional differential systems Estimating the decay rate of dynamic systems has long been an area of both theoretical and practical concern. Most long-established methods for decay rate estimation are either imprecise or require the solution of transcendental equations, while more recent approaches involve certain levels of conservatism in their estimates. The improved delay-dependent stability conditions to be developed will give enhanced decay rate estimates. This involves novel construction of Lyapunov-Krasovskii functionals and techniques to introduce degrees of freedom in the stability criteria. To facilitate computation, the estimation problems will be formulated as semi-definite programming tasks. The results should enable the decay characteristics in many engineering applications involving functional differential equations to be properly quantified for the first time, and will also suggest techniques for reducing the conservatism of stability and performance conditions related to these systems. (2) To extend the decay rate estimation techniques for general uncertain dynamic systems Many important classes of functional differential systems employed to describe engineering processes involve impulsive and stochastic characteristics. Based on improved conditions and techniques, the objective is to develop decay rate estimates for these classes of systems. As this requires specialized analytical tools, relatively little research has been done in this area. As the knowledge of their decay rates is important in assessing the stability profile of these systems, the results developed will be useful not only for system analysis but also for synthesis tasks. Neural networks represent another class of functional differential systems. Most exponential stability conditions and decay rate estimates developed in this area are conservative since strong bounding techniques are often involved in their derivations. The results developed in this project will provide novel ideas and techniques for exponential estimates in these areas. (3) To design controllers and filters for functional differential systems with specified/optimized decay rates Little research has been done on design performance-based controllers or filters for functional differential systems with explicit decay rate specification. The reason is partly due to a lack of easily utilizable decay rate conditions, which can be incorporated into synthesis tasks with performance. We aim to fill this gap by applying the decay rate estimation results developed to synthesize controllers and filters which give exponentially stable closed-loop and filtering characteristics with prescribed/optimized decay rates amongst other application-oriented performances. Numerically reliable algorithms will be constructed based on the linear matrix inequality approach. The results will provide designers with the necessary theoretical and numerical tools for their applications.

Project Title:	Fuzzy Control of Nonlinear Systems with Unreliable Communication Links
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	11/2007
Completion Date:	10/2009

Abstract:

Most physical systems and processes in the real world are nonlinear. The inherent nonlinearity of these systems and processes makes it difficult to address the control and regulation problems. Amongst the many models to represent nonlinear systems, Takagi-Sugeno (T-S) fuzzy system modelling is arguably one of the most effective approaches to describe nonlinear systems. T-S fuzzy systems with affine terms can approximate any smooth nonlinear function to any specified accuracy within any compact set. This provides a firm theoretical foundation for using T-S fuzzy models to represent complex nonlinear systems approximately. T-S fuzzy models include two kinds of knowledge: one is the qualitative knowledge represented by fuzzy IF-THEN rules, and the other is the quantitative knowledge represented by local linear models. T-S fuzzy models have a compatible two-level control structure, with the lower level providing basic feedback control and the higher level providing supervisory control or scheduling. By using T-S fuzzy models, one can amalgamate these two kinds of knowledge into a unified mathematical framework that enables the possibility of developing a systematic analysis and design method for complex nonlinear control systems. In recent years, many researchers have shown great interests in T-S fuzzy modelling, and a number of important results related to stability analysis, stabilizing and H∞ control design, and state estimation of T-S fuzzy systems have been reported in the literature. Most of the available results concerning T-S fuzzy systems are based on the implicit assumption that the communications between the physical plant and controller are perfect. In many practical situations, however, there may be a nonzero probability that some measurements or control inputs will be lost during their transmission. This is more obvious and important for the emerging networked control systems (NCSs) where feedback control loops are closed via digital communication channels. In a typical NCS [IB05], several components communicate over a shared network, and information flows among the sensor, actuator and controller according to some rules. NCSs are becoming more and more popular for the reason that they have several advantages over traditional systems, such as low cost, reduced weight and power requirements, simple installation and maintenance, and high reliability. However, the insertion of the communication networks in the feedback loops makes the analysis and synthesis problems much more complex. In particular, among a few others, data packet dropout is an important issue to be taken into consideration for the analysis and synthesis of communication-based control systems. In view of the importance of unreliable communications in modern control systems, some researchers have begun to study how to design control systems with the simultaneous consideration of communication issues. It is worth mentioning that most of the results obtained till now are concerning linear systems [YHL05], while nonlinear systems under unreliable communication links have received little attention, and still remain challenging. In this project, our focus will be on the analysis and synthesis of nonlinear systems under unreliable communication links, where the nonlinear systems will be modelled as T-S fuzzy systems. The communication links, existing between the plant and controller, are assumed to be imperfect (that is, data-packet dropouts occur intermittently), and stochastic variables with the Bernoulli random binary distribution are utilized to model the unreliable communication links. Attention will be focused on the stability analysis, stabilizing and H∞ controller design. Moreover, the problem of model reference control and state estimation will also be investigated in this framework. To maximize the reduction of conservatism, the idea of basis-dependent Lyapunov function will be utilized for these problems, and extensive comparisons will be carried out.

Project Title:	Synthesis of Networked Dynamic Systems with Improved Stability and Performance
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2008

Abstract:

Establishment of mathematical conditions for designing networked control systems Stability and performance characteristics of systems with signal transmission through network will be studied. Improved stability and performance conditions for networked systems modeled as functional differential equations or difference equations with multiple (time-varying, random) delay components and stochastic packet loss will be derived. Development of synthesis techniques with delayed and missing information Various synthesis approaches aimed at enhancing closed-loop performance under delayed and missing information will be studied. Different performance criteria will be used for (sub-)optimal controller design. Stability and performance robustness will be considered. Numerically reliable computational algorithms for controller synthesis will be given.

Project Title:	Outstanding Researcher Award 2007-2008
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Outstanding Researcher Award
Start Date:	10/2008

Abstract:

The Awards are intended to recognize, reward, and promote exceptional research accomplishments of academic and research staff.

Project Title:	Robust Synthesis of Quantum Systems
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	01/2009

Abstract:

The first theoretical work on feedback for quantum systems appeared in quantum optics, where feedback was used to treat the fluctuations of the photocurrent and to generate squeezed state [HY86]. In the early 90s, study was conducted on the instantaneous feedback of some measured photocurrent onto the dynamics of a quantum system and the master equation with Markovian evolution (so called Markovian quantum feedback) [WM93]. The Markovian quantum feedback theory has been applied to the control of squeezed state and stabilization of a two-level atom [WW01]. More general schemes have been developed where the best estimates of the dynamical variables are obtained continuously from the measurement record and fed back to control the system (called Bayesian quantum feedback). In Bayesian quantum feedback, control algorithms are divided into an estimation step and a feedback control step, and the resulting dynamics is non-Markovian. Quantum filtering theory has also drawn some attention in the physics community. There is also a little work on quantum filtering for control of quantum systems. Recently an introduction to quantum filtering theory was provided from the perspective of quantum control and quantum filtering equations for system-probe models from quantum optics were obtained [BvHJ07]. From the perspective of control theory, robust filtering and feedback control theories and methods have been widely and successfully applied to many practical engineering systems. It is necessary to develop a series of filtering and feedback theories being adapted to emergent quantum engineering applications. However, the task is nontrivial for several reasons. In classical control, feedback is a key factor in control design for dealing with the uncertainties of systems to be controlled and many important results have been obtained about the robust control of linear control systems. However, quantum control systems must evolve according to quantum theory and cannot usually be modeled as linear control systems. Furthermore, filtering analysis and feedback control for quantum systems have essential differences since any observation (or measurement) on a quantum system generally destroys its state and leads to the loss of quantum coherence. The no-cloning theorem prohibits the precise copy of arbitrary unknown quantum information. Hence, it is necessary to develop new methods for robust filtering and feedback design of quantum systems and the results may provide important tools for engineering the quantum world. The objectives of this project are as follows: (1) Robust filter design of quantum systems –– Filtering and filter design have achieved many successful applications in the field of signal processing and control systems. The filtering problem of quantum systems has also started to draw the attention of both physicists and engineers in recent years. However, existing results mainly focus on either simple quantum systems or a noncommutative probability space. The filter design and the robustness of filtering problem have only a few results. We will investigate new methods for the robust filter design of quantum systems including H2 filtering and H∞ filtering for quantum systems described by linear/nonlinear stochastic models; (2) Feedback control strategies of quantum systems –– Feedback control is an effective method for enhancing the robustness of control systems and it has been used to control design of quantum systems. Research has shown that feedback strategy is also useful for some specific quantum control tasks. However, much work still needs to be further considered and the exploration and comparison of different feedback strategies are necessary. Here we will focus on Lyapunov-based feedback control design and incoherent quantum feedback control.

Project Title:	Dissipativity Analysis and Related Reduced-Order Synthesis for Stochastic Delay Systems
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	11/2009

Abstract:

1) Establish mathematical conditions for the dissipativity property of stochastic delay systems. Stability and dissipativity of dynamic systems with time delay and internal/external stochasticity will be studied. New delay-dependent dissipativity characterizations for such systems will be derived; 2) Develop synthesis techniques for related reduced-order compensators. A new framework for reduced-order dissipative synthesis will be established. New design conditions, algorithms, and optimization techniques, for reduced-order dissipative synthesis with enhanced capability and improved solvability will be developed. In addition, stability and performance robustness will be considered.

Project Title:	48th IEEE Conference on Decision and Control and 28th Chinese Control Conference Filters for Linear Continuous-Time Singular Systems
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	12/2009
Completion Date:	12/2009

Abstract:

N/A

Project Title:	Design of Distributed Filters for Multi-agent Systems
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	01/2010

Abstract:

In recent years, the problems of distributed coordination and control for multi-agent networks have attracted considerable attention from researchers in various fields including control engineering, statistical physics, biology, applied mathematics, and computer science. The practical applications of multi-agent systems in various areas including robotics have proved their capacity to propose models enabling to better understand the functioning of biological systems and physical phenomena. The principal objective of using multi-agent systems is to collectively reach goals that are difficult to achieve by an individual agent. To this end, there is a necessity for research efforts to be paid towards the arrangement of local operational performance criteria to the overall performance of a whole system. Coordination among agents is essential for achieving the goals and acting in a coherent manner since an agent performs its activity in a group in which other agents exist. Also coordination is a means to achieve the coherent behavior of the entire system. With nodes representing dynamic units and links indicating the interconnections between them, graph theory appears to be a natural framework for modeling and handling networks of dynamic agents. The characterization of properties of such systems then relies closely on the structure and interconnection topology of the graph associated with the network. This brings new features and challenges for the coordination and control of multi-agent systems, and central to the investigation of coordination control is to answer how the dynamic process is affected by the structure of networks. In the project, the study will be carried out by carefully examining the topology structure of interconnection graphs. Conventional centralized filtering suffers from serious drawbacks in terms of speed, accuracy, economic considerations, and a large amount of energy for communications and has the potential for a critical failure to occur at the central node. Distributed strategies represent an attractive alternative, since they are in general more robust, requiring fewer communications and allowing parallel processing. In practice, real-world sensor networks often confront uncertainties caused by, for example, the noises contaminated information received/sensed by each agent. Accordingly, coordination and control of multi-agent systems in a noisy environment become a fundamental problem. In particular, distributed estimation via design of observers/filters for multi-agent coordination calls for intensive study, which will contribute to the applications especially in sensor networks and robot networks, among many others. However, very few results have been obtained to date along this line and the associated measurement-based dynamic neighbor-based control design. This motivates the research proposed in the project. The objective is to extend the conventional observer/filter designs to the distributed observer and filter designs for the coordination and control of multi-agent systems. Decentralized filtering involves state estimation using a set of local filters that communicate with all other nodes. In the project, we will mainly concentrate on scalable or distributed filtering algorithms in which each node only communicates messages with its neighbors on a network. The primary purpose of this proposed project is: (i) to propose new distributed filter algorithms to solve consensus problem in a noisy environment; (ii) to construct novel neighbor-based rules by designing distributed observers/filters for the consensus of multi-agent systems.

List of Research Outputs

Dong D., Lam J. and Petersen I.R., Robust incoherent control of qubit systems via switching and optimization, International Journal of Control. 2010, 83(1): 206-217.

Du B., Lam J. and Shu Z., Strong stabilization by output feedback controller for input-delayed linear systems, ICINCO 2010. Funchal, Portugal, 141-146.

Feng J., Lam J. and Xu S., Filters for linear continuous-time singular systems, Joint 48th IEEE Conference on Decision and Control and 28th Chinese Control Conference. Shanghai, P.R. China, 2009, 229-234.

Feng J., Lam J., Shu Z. and Wang Q., Internal positivity preserved model reduction, International Journal of Control. 2010, 83(3): 575-584.

Feng J., Lam J. and Wei Y., Spectral properties of sums of certain kronecker products, Linear Algebra and Its Applications. 2009, 431(9): 1691-1701.

Feng J., Lam J. and Shu Z., Stabilization of markovian systems via probability rate synthesis and output feedback, IEEE Transactions on Automatic Control. 2010, 55(3): 773-777.

Feng Z., Lam J., Gao H. and Du B., Improved stability and stabilization results for discrete singular delay systems via delay partitioning, Joint 48th IEEE Conference on Decision and Control and 28th Chinese Control Conference. Shanghai, P.R. China, 2009, 7210-7215.

Gao H., Meng X., Chen T. and Lam J., Stabilization of networked control systems via dynamic output-feedback controllers, SIAM Journal of Control and Optimization. 2010, 48(5): 3643-3658.

Haidar A., Boukas E.K., Xu S. and Lam J., Exponential stability and static output feedback stabilization of singular time-delay systems with saturating actuators, IET Control Theory and Applications. 2009, 3(9): 1293-1305.

Hu Y., Lam J. and Liang J., Consensus problem of multi-agent systems with markovian communication failure, ICINCO 2010. Funchal, Portugal, 373-376.

Lam J., Appreciated Reviewer, IEEE Transactions on Automatic Control. 2010.

Lam J., Associate Editor , International Journal of Applied Mathematics and Computer Science. 2009.

Lam J., Associate Editor, Asian Journal of Control. 2009.

Lam J., Associate Editor, Asian Journal of Control. 2010.

Lam J., Associate Editor, Automatica. 2010.

Lam J., Associate Editor, Conference Editorial Board of IEEE Control Systems Society. 2009.

Lam J., Associate Editor, Dynamics of Continuous, Discrete, and Impulsive Systems – Series B. 2009.

Lam J., Associate Editor, IEEE Transactions on Signal Processing. 2009.

Lam J., Associate Editor, International Journal for Information and Systems Sciences. 2010.

Lam J., Associate Editor, International Journal of Systems Science. 2009.

Lam J., Associate Editor, International Journal of Systems Science. 2010.

Lam J., Associate Editor, Journal of Sound and Vibration. 2009.

Lam J., Associate Editor, Journal of The Franklin Institute. 2010.

Lam J., Best Paper , 3rd International Symposium on Systems and Control on Aeronautics and Astronautics . 2010.

Lam J., Editoral Member, Journal of Electrical and Computer Engineering. 2009.

Lam J., In: Donghua University, Fixed Order Multi-Objective Synthesis: A System Augmentation Framework. 2009.

Lam J., Fixed Order Multi-Objective Synthesis: A System Augmentation Framework, Hangzhou Dianzi University. 2010.

Lam J., Fixed Order Multi-Objective Synthesis: A System Augmentation Framework, Nanjing University of Science and Technology. 2010.

Lam J., Fixed Order Multi-Objective Synthesis: A System Augmentation Framework, Shadong University. 2010.

Lam J., Fixed Order Multi-Objective Synthesis: A System Augmentation Framework, Zhejiang University of Technology. 2010.

Lam J., International Journal of Systems Science Prize Paper, International Journal of Systems Science. 2010.

Lam J., Member of Editorial Advisory Board, Central European Journal of Engineering. 2010.

Lam J., Member of Editorial Board , Multidimensional Systems and Signal Processing. 2010.

Lam J., Member of Editorial Board, IET Control Theory and Applications. 2010.

Lam J., Member of Editorial Board, International Journal of Sensors, Wireless Communications and Control . 2010.

Lam J., Member of Editorial Board, International Journal of Systems, Control and Communications. 2010.

Lam J., Member of Editorial Board, Multidimensional Systems and Signal Processing. 2010.

Lam J., Member of Editorial Board, The Open Automation and Control Journal. 2010.

Lam J., Member of Editorial Board, The Open Electrical and Electronic Journal. 2010.

Lam J., Subject Editor, Journal of Sound and Vibration. 2010.

Lam J., Transient and Steady-State Estimates of Interval Genetic Regulatory Networks, Zhejiang University. 2010.

Li P. and Lam J., Decentralized H_¥ control for air traffic flow networks modeled by A class of compartmental systems, 3rd International Symposium on Systems and Control in Aeronautics and Astronautics. Harbin, China, 2010, CD-Rom: 6pp.

Li P., Lam J. and Wang Z., H_¥ model reduction for positive systems, Proc. 2010 American Control Conference. Baltimore, 2010, 6244-6249.

Li P., Lam J. and Shu Z., On the transient and steady-state estimates of interval genetic regulatory networks, IEEE Transactions on Systems, Men, and Cybernetics, Part B. 2010, 40(2): 336-349.

Li P., Lam J. and Shu Z., Positive observers for positive interval linear discrete-time delay systems, Joint 48th IEEE Conference on Decision and Control and 28th Chinese Control Conference. Shanghai, P.R. China, 2009, 6107-6112.

Li Y., Lam J. and Luo X., Hankel norm model reduction of uncertain neutral stochastic time-delay systems, International Journal of Innovative Computing, Information and Control. 2009, 5(9): 2819-2828.

Liang J. and Lam J., Robust state estimation for stochastic genetic regulatory networks, International Journal of Systems Science. 2010, 41(1): 47-63.

Liang L., Lam J. and Wang Z., State estimation for markov-type genetic regulatory networks with delays and uncertain mode transition rates, Physics Letters A. 2009, 373(47): 4328-4337.

Meng X., Lam J., Du B. and Gao H., A delay-partitioning approach to stability analysis of discrete delay systems, Automatica. 2010, 46(3): 610-614.

Shu Z., Lam J. and Hu Y., Fixed-order H_¥ filtering for discrete-time markovian jump linear systems with unobservable jump modes, 7th Asian Control Conference. Hong Kong, 2009, 424-429.

Shu Z., Lam J. and Li P., On positive filtering with H_¥ performance for compartmental networks, International Journal of Systems Science. 2009, 40(9): 961-971.

Shu Z., Lam J. and Li P., Simultaneous H_¥ stabilization via fixed-order controllers: Equivalence and computation, Joint 48th IEEE Conference on Decision and Control and 28th Chinese Control Conference. Shanghai, P.R. China, 2009, 3244-3249.

Shu Z., Lam J. and Xiong J., Static output-reedback stabilization of discrete-time markovian jump linear systems: A system augmentation approach, Automatica. 2010, 46(4): 687-694.

Wang Q. and Lam J., Optimal H₂ model reduction for mechanical systems, International Journal of Innovative Computing, Information and Control. 2010, 6(5): 2045-2054.

Wei G., Wang Z., Lam J., Fraser K., Rao G.P. and Liu X., Robust filtering for stochastic genetic regulatory networks with time-varying delay, Mathematical Biosciences. 2009, 220(2): 73-80.

Wu L., Lam J., Paszke W., Galkowski K., Rogers E. and Kummert A., Control and filtering for discrete linear repetitive processes with H_¥ and 1₂-1_¥ performance, Multidimensional Systems and Signal Processing. 2009, 20(3): 235-264.

Wu L., Ho D.W.C. and Lam J., H_¥ model reduction for continuous-time switched stochastic hybrid systems, International Journal of Systems Science. 2009, 40(12): 1241-1251.

Wu L. and Lam J., Weighted H_¥ filtering for switched hybrid systems with time-varying delay: An average dwell time approach, Circuits, Systems, and Signal Processing. 2009, 28(6): 1017-1036.

Xu S., Lam J., Shi P., Boukas E.K. and Zou Y., Guaranteed cost control for uncertain neutral stochastic systems via dynamic output feedback controllers, Journal of Optimization Theory and Applications. 2009, 143(1): 207-223.

Xu S., Lam J., Zhou Y. and Li J., Robust admissibility of time-varying singular systems with commensurate time delays, Automatica. 2009, 45(11): 2714-2717.

Y Z.H.A.O., Gao H., Lam J. and Du B., Stability and stabilization of delayed T-S fuzzy systems: A delay partitioning approach, IEEE Transactions on Fuzzy Systems. 2009, 17(4): 750-762.

Yang R., Gao H., Lam J. and Shi P., New stability criteria for neural networks with distributed and stochastic discrete delay, Circuits, Systems, and Signal Processing. 2009, 28(4): 505-522.

Yue D., Tian E., Wang Z. and Lam J., Stabilization of systems with probabilistic interval input delays and its applications to networked control systems, IEEE Transactions on Systems, Man, and Cybernetics (A). 2009, 39(4): 939-945.

Zhang B., Lam J. and Xu S., Absolute exponential stability criteria for A class of nonlinear time-delay systems, Nonlinear Analysis Series B: Real World Applications. 2010, 11, Issue 3: 1963-1976.

Zhang Z., Mou S., Lam J. and Gao H., New passivity criteria for neural networks with time-varying delay, Neural Networks. 2009, 22(7): 864-868.

Zhao Y., Gao H., Lam J. and Chen K., Stability analysis of discrete-time recurrent neural networks with stochastic delay, IEEE Transactions on Neural Networks. 2009, 20(8): 1330-1339.

Zhou B., Lam J. and Duan G.R., An ARE approach to semi-global stabilization of discrete-time descriptor linear systems with input saturation, Systems and Control Letters. 2009, 58(8): 609-616.

Zhou B., Lam J. and Duan G., Full delayed state feedback pole assignment of discrete-time time-delay systems, Optimal Control Applications and Methods. 2010, 31(2): 155-169.

Zhou B., Lam J. and Duan G.R., Gradient based maximal convergence rate iterative method for solving linear matrix equations, International Journal of Computer Mathematics. 2010, 87(3): 515-527.

Zhou B., Lam J. and Duan G.R., On Smith-Type iterative algorithms for the stein matrix equation, Applied Mathematics Letters. 2009, 22(7): 1038-1044.

Zhou B., Duan G.R. and Lam J., On absolute stability method for quantized feedback control, Automatica. 2010, 46(2): 337-346.

Researcher : Lam KF

List of Research Outputs

Lam K.F., Experimental Investigation for Designing Passive Fences to Orient Parts by Pushing, MPhil Thesis. Hong Kong, The University of Hong Kong, 2009, 1-84.

Researcher : Lam LL

List of Research Outputs

Lam L.L., Gain-Scheduled PID Controllers in Networked Control Systems, MPhil Thesis. Hong Kong, The University of Hong Kong, 2009, 1-127.

Researcher : Lee WC

List of Research Outputs

Lee W.C. and Wang M., Drug incorporation and release from electrochemically deposited Apatite/Collagen coatings on Ti alloy, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Researcher : Leung MKH

Project Title:	Indoor air quality control and mitigation measures for printing plants
Investigator(s):	Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	Occupational Safety and Health Council - Research Grant Projects
Start Date:	03/2003

Abstract:

To study the existing IAQ conditions and develop useful Engineering Control Measures for the printing industry in Hong Kong. A self-assessment software kit will also be developed to facilitate IAQ surveys and audits.

Project Title:	Local exhaust ventilation for protection against nosocomial infection of SARS
Investigator(s):	Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	VCO SARS Research Fund
Start Date:	07/2003

Abstract:

To develop a local exhaust ventilation system that removes droplets and bioaersols effectively so as to reduce the risk of nosocomial SARS infection during the peformance of intubation and surgical procedures for SARS patients.

Project Title:	Environmental friendly cold water thawing for catering industry
Investigator(s):	Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	Environmental Research, Technology Demonstration Projects
Start Date:	07/2003

Abstract:

To carry out a Computational Fluid Dynamic (CFD) analysis for the abovementioned defrosting processes and optimise the process parameters, including the position of the frozen meat and flow rate of the town water; to investigate computationally the additional use of a rotating mechanism inside the deforesting water pail to enhance the cold water thawing process; to conduct experimental study to verify the performance of the best cold water thawing process identified from the above analytical investigation; to conduct field test in selected restaurants and collect data to determine the saving in water consumption.

Project Title:	Novel local exhaust ventilation device for printing industry
Investigator(s):	Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	The OSH Enhancement Scheme for SMEs
Start Date:	10/2004

Abstract:

To design a novel Local Exhaust Ventilation (LEV) device to protect the workers by removing the VOCs effectively.

Project Title:	Domestic Single-Phase Heat Pump Water Heater and Air Conditioner
Investigator(s):	Leung MKH, Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	CLP Power Hong Kong Ltd. - General Award
Start Date:	08/2007

Abstract:

(1) The main purpose of this project is to develop an effective single phase domestic electric water heater that can supply hot water instantaneously to fulfill the specified requirements (water flow rate = 6 l/min, water temperature increase = 40oC). (2) The actual performance characteristics of the water heater, in terms of heating effect, electricity consumption and coefficient of performance (COP), will be tested under various operating conditions. (3) The lifecycle factors of the prototype, in terms of safety, reliability and maintainability, will be evaluated by multiple operation cycles.

Project Title:	Modeling, design and optimization of micro wind turbines for low-cost clean energy
Investigator(s):	Leung MKH, Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Applied Research
Start Date:	02/2008
Completion Date:	01/2010

Abstract:

Micro wind turbine system is an innovative approach to harness wind energy for production of electricity. Conceptually, multiple small wind turbines (250 to 500 mm diameter) are engaged together with gears to form a large-scale wind energy collector. Each micro turbine contributes to build up an accumulative torque. The torque is so strong that it can drive a motor generator to produce electricity (see Figure 1 in Section VI). We have conducted some initial wind tunnel experiments and the results reveal that the wind-to-electricity efficiency of micro wind turbines is comparable to that of conventional 3-blade wind turbines. More importantly, it is found that micro wind turbines can function at even low wind speed, i.e. 2 m/s. Compared with the typical cut-in wind speed of 6 m/s for conventional 3-blade wind turbines, micro wind turbines are potentially much more productive. Low cost is another important advantage of micro wind turbines. The cost is low because micro wind turbines can adopt inexpensive injection molding for mass production. Installation, maintenance and repair works are also rather simple. In our recent initial experiments, the micro wind turbine prototype tested was built based on the preliminary design. Some promising results have shown the feasibility of micro wind turbines. In order to further enhance the wind-to-electricity conversion efficiency, more in-depth modeling and design optimization analyses should be conducted. We propose to carry out comprehensive computational fluid dynamics (CFD) modeling study with laboratory validation tests to achieve the following objectives: (1) to enhance micro wind turbine design; (2) to optimize design parameters, such as aerodynamics of turbine blades, turbine dimensions, system configuration etc.; (3) to enhance structural support design for stability under dynamic loading condition; (4) to minimize noise impact on the surrounding environment and (5) to simulate the year-round performance for various local climatic conditions. The proposed research works on CFD modeling and design optimization should put us in a better position to apply for larger scale external research funding, such as ITF fund.

Project Title:	Enhancement of integrated heat pumps for energy savings in hot water and air-conditioning at home
Investigator(s):	Leung MKH, Leung YC, Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	Environment and Conservation Fund
Start Date:	06/2008

Abstract:

(1) Research and technology demonstration. The air pollution and climate change problems have reached alarming levels in Hong Kong, other major cities in Mainland China and many other parts of the world. The main cause of the problems is the emission due to increasing burning of fossil fuels to generate power for our high energy demand. Besides the environmental problems, we shall soon face the adverse impacts of energy crisis as the data from the oil industry indicate that the Hubbert peak of oil production will occur within the next decade. The development of clean energy technologies to replace fossil fuel based technologies is the ultimate solution for sustainable development. Meanwhile, we should immediately practise high energy efficiency so as to slow down the burning rate of fossil fuel. The objective of this research is to develop compact, energy-efficient integrated heat pumps for domestic hot water and air-conditioning. Other heating applications, such as laundry drying and space heating, will be studied as well. Theoretical modelling and experimental study will be conducted. The environmental performance will be quantified by the energy savings achieved and the equivalent reduction in carbon footprint. (2) Public awareness and environmental education. To enhance the public awareness of the energy conservation at home and the benefits of domestic integrated heat pumps. The following dissemination and awareness activities will be conducted: (2a) Workshops, seminars as well as conference presentations will be conducted to disseminate the research findings. The investigators will also invite interested parties (property developers, engineering consultants, home appliance manufacturers etc.) to visit The University of Hong Kong for demonstration of the domestic integrated heat pump prototype. The investigators will take these opportunities to promote energy conservation practices at home. (2b) The research findings will be published in journals and conference proceedings for widespread dissemination to relevant groups of audience.

Project Title:	Carbon audit guidelines and carbon calculator for SMEs to conduct life-cycle carbon footprint analysis
Investigator(s):	Leung MKH, Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	Small and Medium Enterprises Development Fund
Start Date:	12/2008
Completion Date:	11/2009

Abstract:

The main objective of this project is to facilitate carbon audits for SMEs by provision of a carbon audit tool kit. The tool kit to be developed in this project will provide necessary carbon audit guidelines and carbon calculator to enable the majority SMEs to perform self assessments of the life-cycle carbon footprints for their business operations. The tool kit can also help SMEs identify ways to improve their environmental performance.

Project Title:	Study of manifold airflow dynamics and NOx formation mechanisms in solar gas turbine for performance enhancement
Investigator(s):	Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	12/2008

Abstract:

Solar gas turbine (see Fig. 1 in Section VI) can convert solar energy into electricity for large-scale power supply in an energy-efficient and cost-effective manner [1-3]. A solar gas turbine system mainly consists of multiple solar collectors, gas turbine and generator. Each solar collector is built with a solar concentrator and a thermal receiver to collect concentrated radiation up to 1000 suns. Air is selected as the working fluid as it is the most convenient substance to use and it is totally free of charge. Air is pressurized and passed through the irradiated receivers to gain heat to a temperature of 1000 deg C or above. The hot air will drive the gas turbine and generator to produce electricity. The overall solar-to-electricity conversion efficiency achieved is as high as 30%. In this project, there are two main objectives for enhancement of solar gas turbine: (1) Uniform manifold airflow distribution A basic solar gas turbine system consists of one gas turbine and multiple solar collectors. All the solar collectors are connected to the gas turbine via a manifold ductwork (see Fig. 2 in Section VI) [4,5]. It is important to properly design and operate a manifold so that each solar collector supplies hot air at the same temperature and same flow rate. It is not an easy task because the different manifold channel lengths, varying solar radiation, temperature-dependent air properties and mixed laminar/turbulent flow tend to yield highly irregular airflow distribution. In this project, effective design and control algorithms will be developed to manipulate the complex manifold fluid flow. The design algorithms will determine the detailed dimensions of each channel section of the manifold ductwork. The control algorithms will regulate the variable-speed fans to ensure uniform airflow drawn by each solar collector under dynamic solar radiation conditions. (2) NOx control In general, with the hot air produced at a higher temperature, the solar gas turbine can operate at a higher solar-to-electricity conversion efficiency. In fact, there exists a limitation. When the hot air is heated above 800 deg C, harmful NOx will start to form due to the presence of nitrogen, oxygen and sufficient heat. For this reason, it is important to identify the operating condition under which the energy conversion efficiency is high and, at the same time, the NOx emission is low. The design and control algorithms developed in this project will take into account the NOx factor. References: [1] Peter Schwarzbozl, Reiner Buck, Chemi Sugarmen, Arik Ring, M Jesus Marcos Crespo, Peter Altwegg, Juan Enril, Solar gas turbine systems: Design, cost and perspectives, Solar Energy 80 (2006) 1231-1240. [2] Peter Heller, Markus Pfander, Thorsten Denk, Felix Tellez, Antonio Valverde, Jesus Fernandez, Arik Ring, Test and evaluation of a solar powered gas turbine system, Solar Energy 80 (2006) 1225–1230. [3] A. Kribus, P. Doron, R. Rubin, J. Karni, R. Reuven, S. Duchan, E. Taragan, A multistage solar receiver: the route to high temperature, Solar Energy 67 (1999) 3–11. [4] Ephraim M. Sparrow, Jimmy C. K. Tong, Fluid flow in a system with separate laminar and turbulent zones, Numerical Heat Transfer, Part A, 53 (2008) 341–353. [5] Jimmy C. K. Tong, Ephraim M. Sparrow, John P. Abraham, Attainment of flowrate uniformity in the channels that link a distribution manifold to a collection manifold, ASME Journal of Fluids Engineering 129 (2007), 1186-1192.

Project Title:	ISES Solar World Congress 2009 PERFORMANCE CHARACTERISTICS OF AIRFOIL-BLADE MICRO WIND TURBINES
Investigator(s):	Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	10/2009
Completion Date:	10/2009

Abstract:

N/A

Project Title:	TiO2-WO3 nanotube array coated on glass substrate for enhanced photoelectrocatalysis
Investigator(s):	Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2010

Abstract:

TiO2 is regarded as one of the most effective photocatalysts for environmental applications such as photocatalytic degradation of pollutants (Adachi, Murata et al. 2000; Zhang, Yuan et al. 2008) , solar cell (Macak, Tsuchiya et al. 2005; Rattanavoravipa, Sagawa et al. 2008), and gas sensors (Rella, Spadavecchia et al. 2007; Seo, Yuasa et al. 2009) due to its high photocatalytic activity, photo-stability, cost effectiveness and non-toxicity. However, the photocatalytic reaction is limited by its wide band gap (3.2 eV) which causes high recombination rate of photogenerated electrons and holes. The wide band gap also limit the utilization of solar spectrum since TiO2 can be activated only by UV irradiation (λ<380nm) for photocatalytic activation and UV light accounts for merely 4-5% of the solar energy (Han, Kambala et al. 2009). Tremendous work has been done to increase the photocatalytic activity of TiO2 and to extend its spectral response range to the visible region. Research includes doping metal or nonmetal into the TiO2 lattice, (Ghicov, Schmidt et al. 2007; Zhang, Lei et al. 2009), deposition of noble metals (Sclafani and Herrmann 1998; Wang, Liu et al. 1998; Paramasivam, Macak et al. 2008), and dye photosensitization on the TiO2 surface (Vinodgopal, Wynkoop et al. 1996; Wang, Zhao et al. 2009). Comparatively, coupling TiO2 with a narrower band gap semiconductor which presents suitable potential energies can effectively facilitate charge separation by isolating electrons and holes in two different particles. Since the band gap energy of WO3 is about 2.4 to 2.8eV, photoexcitation with radiation of energy greater than 2.4 to 2.8eV promotes an electron in WO3 from the valence band to the conduction band. The photo-generated electron then transfers to the TiO2 nanotube-array, leaving holes in WO3 particles for reacting with organic pollutants. In addition, crystal cavities are introduced into the nanostructures of TiO2 when doping of WO3 into TiO2, reducing the band gap energy of it. Both effects mentioned above would improve the visible-light photocatalytic activity of TiO2. To further increase the photocatalytic efficiency of TiO2, fabrication of TiO2 photocatalyst in form of nanotube structure has been suggested due to the high surface-to-volume ratios and size dependent properties of nanotubes. Sol-gel template synthesis (Zhang, Bando et al. 2001), seeded growth (Tian, Voigt et al. 2003), hydrothermal processes (Ou and Lo 2007) and anodization (Mor, Varghese et al. 2006) are some of the common techniques to produce TiO2 nanotubes. Compared with other fabrication methods, TNT arrays produced by anodization are highly ordered, more firmly attached to the support and its dimensions can be precisely controlled by tailoring the anodization parameters. However, TNT arrays fabricated by anodization method are usually grown on titanium foils, which limit the applications of this material architecture. For example, dye-sensitized solar cells or electrochromic devices require their metal oxide electrode to be transparent. Recently, some researchers (Tang et al, 2008; Leenheer et al, 2007) have successfully developed the technology to grow TNT on glass using anodization method. Presently, limited literatures report the formation of highly ordered, self-assembled TNT-arrays coupled with W growing on glass by anodization method. This study suggests to fabricate such material by first depositing Ti-W alloy thin film on a conducting glass by RF magnetron sputtering method and then anodized it in an aqueous (NH)4F electrolyte solution at room temperature. The effect of different anodization conditions on the microstructure of anodized thin films is investigated. The photoelectrocatalytic (PEC) activity of TiO2-WO3 nanotubes is evaluated by PEC degradation of Acid Blue 80 under UV or visible light irradiation. If the transparent TiO2-WO3 nanotubes can be successfully grown on glass by anodization method, not only the metal material can be saved, the application of it can also be extended.

List of Research Outputs

Ching W.H., Leung M.K.H. and Leung Y.C., An efficient approach to transient turbulent dispersion modeling by CFD-statistical analysis of a many puff system, Fluid Dynamics Research. 2009, 41(3): 035512.

Leung M.K.H., Leung Y.C. and Chan A...H...C..., Carbon Audit for Small and Medium Enterprises in Hong Kong, Proceedings of 2010 International Conference on Process Engineering and Advanced Materials (ICPEAM2010). 2010.

Leung M.K.H., Leung Y.C. and Chan A.H.S., Carbon audit toolkit for small & medium enterprises in Hong Kong, Book. Hong Kong, The University of Hong Kong, 2010, 1-90.

Leung Y.C., Wu X. and Leung M.K.H., A review on biodiesel production using catalyzed transesterification, Applied Energy. Elsevier, 2010, 87: 1083-1095.

Leung Y.C., Deng Y. and Leung M.K.H., Design optimization of a cost-effective micro wind turbine, Proceedigns World Engineering Congress 2010. London, UK, International Association of Engineers, 2: 988-993.

Leung Y.C., Fu X., Wang C.F., Ni M., Leung M.K.H., Wang X.X. and Fu X.Z., Hydiogen production over titania-based photocatalysts, ChemSusChem. Wiley Inter Science, 2010, 3: 681-694.

Li G., Zhang D., Yu J...C... and Leung M.K.H., An efficient bismuth tungstate visible-light-driven photocatalyst for breaking down a smog precursor nitric oxide, Environmental Science & Technology. 2010, 44: 4176-4281.

Lim B.L., Leung Y.C., Yung K.F., Leung M.K.H., Mah D.N.Y., Lam J.C.K. and Hills P.R., Conference Presentation: "Development of Biofuel Technologies and Policy", at the Initiative on Clean Energy and Environment’s Review Workshop, Shenzhen, January 8, 2010.

Ni M., Leung Y.C. and Leung M.K.H., Ammonia fed solid oxide fuel cells for power generation - A review, International Journal of Energy Research. Wiley Inter Science, 2009, 33: 943-959.

Ni M., Leung Y.C., Leung M.K.H., Xuan J. and Wang H.Z., Thermo-electrochemical modeling of the transport phenomena and electrochemical reactions in ammonia fed solid oxide fuel cells, Proceedings International Conference on Applied Energy 2010. Singapore, National University of Singapore, CD-Rom: 10pp.

Wang H., Leung Y.C. and Leung M.K.H., Energy analysis of hydrogen and electricity production from aluminum-based processes, Proceedings International Conference on Applied Energy 2010. Singapore, National University of Singapore, CD-Rom: 10pp.

Xuan J., Leung M.K.H., Leung Y.C. and Ni M., A review of biomass-derived fuel processors for fuel cell systems, Renewable and Sustainable Energy Reviews. 2009, 13: 1301-1313.

Xuan J., Leung M.K.H. and Leung Y.C., Gravitational effects on the performance of membraneless micro fuel cells, Proceedings International on Applied Engergy 2010. Singapore, National University of Singapore, CD-Rom: 10pp.

Xuan J., Leung M.K.H., Leung Y.C. and Ni M., Integrating chemical kinetics with CFD modeling for autothermal reforming of biogas, International Journal of Hydrogen Energy. Elesvier, 2009, 34: 9076-9086.

Xuan J., Leung M.K.H. and Leung Y.C., Modeling analysis of membraneless micro fuel cell working under critical conditions, Proceedings International Conference on Applied Energy 2010. Singapore, Natioanl University of Singapore, CD-Rom: 10pp.

Researcher : Leung YC

Project Title:	Production of biodiesel fuel using grease trap waste oil
Investigator(s):	Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	Dynamic Progress International Ltd. - General Award
Start Date:	08/2005

Abstract:

To study the production of biodiesel fuel using grease trap waste oil.

Project Title:	Photocatalytic production of clean and renewable hydrogen fuel
Investigator(s):	Leung YC, Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2006

Abstract:

The objectives of this project are: (1) To investigate characteristics of nano-semiconductor photocatalytic hydrogen production. (2) To develop a new photocatalyst with high energy conversion efficiency using the visible light spectrum and to study its characteristics in hydrogen production. (3) To develop and validate a simulation model to predict hydrogen production using the newly developed photocatalyst, based on experimental work.

Project Title:	Hong Kong Biogenic VOCs emission study
Investigator(s):	Leung YC, Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	Environment Protection Department - General Award
Start Date:	07/2007

Abstract:

To determine the amount of biogenic VOCs emission from different parts of Hong Kong.

Project Title:	Study on the use of wet scrubber for cleaning the exhaust gas from ferry
Investigator(s):	Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	Urban and Environmental Studies - General Award
Start Date:	11/2007

Abstract:

To conduct a feasibility study on whether wet scrubbing can be used to clean the exhaust of ferry; to design, construct and install a wet scrubber in a ferry for performance testing.

Project Title:	Study on the wind flow in Chek Lap Kok Airport and its influence on aircraft landing and taking off
Investigator(s):	Leung YC, Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	01/2009
Completion Date:	12/2009

Abstract:

Problems Turbulent flow is generated in the wake behind buildings, structures or obstacles such as terrains, which imposes different effects on the surrounding environments [1,2]. The effect may vary from as small as just affecting the thermal comfort of people or as large as affecting the structural safety of buildings, bridges or aircraft operation. Special attention is paid on the turbulences generated in the airport as they may have significant adverse effects on the aircrafts operation, during landing and taking off using nearby runways. The Hong Kong International Airport (HKIA) was built in Chek Lap Kok and commissioned in 1998. The airport was constructed with distinct features in that it is surrounded by a number of buildings in the near field (less than 500m) and complex terrains in the far field (greater than 2000m), while the runways are situated near the terminal building (within 500m). Due to the existence of these structures and the complex terrain on Lantau Island, the wind blowing from both north-westerly and south to south-easterly will affect the aircraft operation, particularly the south runway. Up to now, no official analyses have been performed to investigate the effects of the building wakes on the aircrafts’ operation on the runways. A system has already been installed in the airport to measure the wind shear in the vicinity of the airport and provide information to pilots in the area. On 22 August 1999, a serious accident occurred in the HKIA involving a landing China Airlines aircraft, which lost control during landing, ended up in an inverted, reversed position on a grass area just to the right of the runway, killing 3 passengers and more than 200 injured. In the investigation report [3], abrupt change in the approaching wind was supposed to be one of the reasons of the incident which was based on the report of the pilot. However, no details or justification has been made in the investigation report. Key issues In 2007 a preliminary investigation has been conducted by the PI and Co-I to study the effect of the terminal building on the aircraft operation. From the simulated results, it was found that when the wind direction is between 300˚ and 330˚ with wind speed over certain critical value, there will occur a significant velocity drops of over 3.6 m/s in the wake of the terminal building close to the runway. That means when an aircraft is approaching the south runway along the glide path it will experience a sudden drop in wind speed, which will lead to a sudden loss of lifting force of the aircrafts. Vibrations and sudden loss of stability of different degrees will be experienced under such situation. More interesting is that strong north-westerly wind was blown on the accident day that matched the simulation result. From this alarming result, there is an imminent need to conduct a more detailed investigation on the effect of the approaching wind on the aircraft operation in the HKIA, particularly under severe conditions. Objectives 1. To study experimentally the characteristics of wind flow in the wake of the terrains in Lantau Island near the HKIA, which may have direct effect on aircraft operations. 2. To investigate, using CFD, the wind flow characteristics in the vicinity of the runways due to the combined influence of terrains and airport buildings. 3. To develop, from the results obtained in 2 above, guidelines for safe aircraft operation under certain meteorological conditions and establish guidelines for the construction of new building in the airport area. Reference 1. S. Senthooran and Dong-Dae Lee, ‘A computational model to calculate the flow-induced pressure fluctuations on buildings’, Journal of Wind Engineering and Industrial Aerodynamics 92 (2004) 1131–1145. 2. Q.S. Li, ‘Numerical evaluation of wind effects on a tall steel building by CFD’. Journal of Constructional Steel Research 63 (2007) 612–627 3. Report on the accident to Boeing MD11 B-150 at Hong Kong International Airport on 22 August 1999, Aircraft Accident Report 1/2004, Accident Investigation Division, Civil Aviation Dept, Hong Kong.

Project Title:	NOx removal from flue gas by an integrated absorption and biological denitrification process in a bioreactor
Investigator(s):	Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	01/2010

Abstract:

Gaseous nitrogen oxides (NOx) are primary air pollutants, which arise naturally in the atmosphere by the action of lighting and microbial biodegradation of organic nitrogenous compounds in soils. NOx are also produced from a variety of anthropogenic activities, such as combustion of fossil fuels and synthesis of nitrogenous fertilizers. NOx consist of nitric oxide (NO), and nitrogen dioxide (NO2). More than 95% of the NOx emitted from combustion sources is NO (a colorless and odorless gas), part of which is oxidized to NO2 (a reddish-brown toxic gas) in ambient air. NOx cause serious environmental problems, such as a contribution to global warming and eutrophication, increase of the tropospheric ozone, and the loss of biodiversity, leading to the formation of acid rain and particulate matter. Exposure to NO2 has been associated with an increased risk of respiratory illness, such as cough and irritation of the respiratory tract. Continued exposure may produce an abnormal accumulation of fluid in the lungs (pulmonary edema) (Ferris, 1978). Also, many research groups suggest that cellular oxidative damage occurring in Parkinson’s disease might result from actions of the altered production of NO (Aquilano et al., 2008). Therefore, emission of NOx to the atmosphere not only threatens our environment but is also harmful to plants, animals and human health. As a result of the rapidly growing economy powered by the generation of energy from fossil fuels, large increases in NOx emissions have been predicted for the next couple of decades, particularly from developing countries such as China and India (Richter et al., 2005). Thus, NOx emissions from combustion systems are facing increasingly stringent regulations throughout the world due to the increased demand for clean air. Currently, conventional post-combustion controls include selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), adsorption and absorption methods (Flagan and Seinfeld, 1988; Rhoads et al., 1990). The major drawback of conventional systems is the prohibitive cost for treating large volumes of air containing low to moderate concentrations of NOx. In addition, most of the conventional systems generate secondary wastes such as wastewater, often requiring further treatment (Jin et al., 2005). In contrast, biological air pollution control technologies (bioreactors) are simple to construct and operate, and both the capital and operating costs are generally considerably less (Schroeder, 2002). A bioreactor is a reactor that can destruct biological pollutants using micro-organisms. They require much less energy and do not produce residual products that require further disposal (Min et al., 2002). They use media that provide increased surface area per unit volume, with structured components that virtually eliminate problems of compaction and collapse (Boswell, 2002). Bioreactor appears is superior to conventional technologies in terms of simplicity and economy in operation, low process energy requirements, and easy treatment of residual products. Key issues: In recent years, a number of researchers have investigated the removal of NOx using conventional gas phase bioreactors such as biofilters, biotrickling filters and bioscrubbers. However, no matter which type of bioreactor, for biodegradation to occur, gas-phase NO must first diffuse through a thin aqueous layer surrounding the biofilm. Since NO is poorly soluble in water, mass transfer limitation may play an important role during the biological treatment processes (Flanagan et al., 2002). The effects of oxygen to the NOx removal efficiency did not have a consistent conclusion in denitrification process (Lee et al., 2001; Wang et al., 2006). Proposed study: In this project, I propose to use hemoglobin as a bridge between the absorption and denitrification. Recent research indicate that the low solubility of NO can be overcome by the use of an aqueous solution of hemoglobin, which has the ability to form stable complexes with NO, and therefore provides high absorption efficiencies for gaseous NO pollutant. After the absorption process by hemoglobin, the denitrification process by the micro-organism will convert NOx to benign N2. Hemoglobin can react with NO in both oxygenated and deoxygenated states, with a kinetic rate limited only by diffusion. This implies that oxygen may have little effect to the reaction between hemoglobin with NO. Hence the efficiency of absorption will not be affected by the presence of oxygen in the flue gas. Since hemoglobin has never been used in a bioreactor for the removal of NOx, this research will investigate the availability of hemoglobin as a bridge between the poorly soluble NO to the micrograms. Also hemoglobin is an expensive material, so the recycling of it is importance for its sustainability. The main objective of the study is to develop a technology to improve NOx removal efficiency using hemoglobin and microorganisms. Our target is to raise the NO removal efficiency to a reasonable level for industrial application. The objectives of the proposed study therefore consist of the following: • To study the mechanism of the absorption of NO by hemoglobin; • To develop a suitable approach to improve the mass transfer from NO to micrograms and to decrease the effect of oxygen on the removal efficiency; • To develop method to limit the accumulation of nitrite formed during denitrification process; • To evaluate those micro-organisms with the best removal efficiency and study its denitrification mechanism in a bioreactor; Reference: Aquilano K, Baldelli S, Rotilio G, Ciriolo MR (2008) Neurochemical Research 33:2416-2426. Boswell J (2002) Chemical engineering progress 98:48-53. Ferguson SJ, Richardson DJ, van Spanning RJM, Hermann B, Stuart JF, William EN (2007) In: Biology of the Nitrogen Cycle. Elsevier: Amsterdam. pp 209-222. Ferris BG (1978) Journal of the air pollution control association 28:482-497. Flanagan WP, Apel WA, Barnes JM, Lee BD (2002) Fuel 81:1953-1961. Jin YM, Veiga MC, Kennes C (2005) Journal of chemical technology and biotechnology 80:483-494. Lee BD, Apel WA, Smith WA (2001) Environmental progress 20:157-166. Min KN, Ergas SJ, Harrison JM (2002) Environmental Engineering Science 19:575-583. Rhoads TW, Marks JR, Siebert.P.C (1990) Environmental progress 9:126-130. Richter A, Burrows JP, Nu¨ß H, Granier C, Niemeier U (2005) Nature 437:129-132. Schroeder ED (2002) Re/Views in environmental science and bio/technology 1:65-67. Wang JD, Wu CQ, Chen JM, Zhang HJ (2006) Chemical Engineering Journal 121:45-49.

Project Title:	The 2010 International Conference of Mechanical Engineering (WCE 2010) Design Optimization of a Cost-Effective Micro-Wind Turbine
Investigator(s):	Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2010
Completion Date:	07/2010

Abstract:

N/A

List of Research Outputs

Chan P.W., Lo W.Y. and Leung Y.C., Low level wind effects of the hangers at the Hong Kong International Airport, Proceedings 5th International Symposium on Computational Wind Engineering. North Carolina, USA, Int. Ass. for Wind Engineering, 2010, CD-Rom: 8pp.

Cheng W.C., Liu C.H. and Leung Y.C., Large-eddy simulation of street canyon flow and pollutant transport in neutral and unstable stratifications, 90th Annual Meeting of the American Meteorological Society, Atlanta, GA, January 17-21, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Large-eddy simulation of turbulent transports in urban street canyons in different thermal stabilities, 5th International Symposium on Computational Wind Engineering, Chapel Hill, North Carolina, USA, May 23 to 27, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Large-eddy simulation of ventilation and pollutant removal in neutrally and unstably stratified street canyons, American Geophysical Union Fall Meeting 2009, San Francisco, December 14-18, 2009.

Cheng W.C., Liu C.H. and Leung Y.C., On the wind statistics and pollutant re-entrainment in street canyons by large-eddy simulation, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Periodic Flow & Pollutant Removal of Street Canyon in Wind-Buoyancy-Driven Condition Using the URANS Model, ICUC-7, 29/6-3/6, 2009, Yokohama, Japan. 2009.

Ching W.H., Leung M.K.H. and Leung Y.C., An efficient approach to transient turbulent dispersion modeling by CFD-statistical analysis of a many puff system, Fluid Dynamics Research. 2009, 41(3): 035512.

Fu X., Wang X.X., Ding Z.X., Leung Y.C., Zhang Z.Z., Long J.L., Zhang W.X., Li Z.H. and Fu X.Z., Hydroxide ZnSn(OH)₆ : A new promising photocatalyst for benezene degradation, Applied Catalysis B: Environmental. Elsevier, 2009, 91: 67-72.

Fu X., Wang X.X., Chen Z.X., Leung Y.C., Li Z.H., Wu L. and Fu X.Z., Photocatalytic performance of tetragonal and cubic b-In 2S3 for water splitting under visible light irradiation, Applied Catalysis B: Environmental. Elsevier, 2010, 95: 393-399.

Huang H. and Leung Y.C., Destruction of indoor air pollutants using photocatalysis irradiated by ozone-producing UV lamp, 4th Japan-China Workshop on Environmental Catalysis and Eco-materials. 2009.

Huang H. and Leung Y.C., Enhanced Destruction of Toluene by Photocatalysis combined with Ozone, The 2nd International Workshop on Regional Air Quality Management in Rapidly Developing Economic Regions. 2009.

Leung M.K.H., Leung Y.C. and Chan A...H...C..., Carbon Audit for Small and Medium Enterprises in Hong Kong, Proceedings of 2010 International Conference on Process Engineering and Advanced Materials (ICPEAM2010). 2010.

Leung M.K.H., Leung Y.C. and Chan A.H.S., Carbon audit toolkit for small & medium enterprises in Hong Kong, Book. Hong Kong, The University of Hong Kong, 2010, 1-90.

Leung Y.C., Wu X. and Leung M.K.H., A review on biodiesel production using catalyzed transesterification, Applied Energy. Elsevier, 2010, 87: 1083-1095.

Leung Y.C., Deng Y. and Leung M.K.H., Design optimization of a cost-effective micro wind turbine, Proceedigns World Engineering Congress 2010. London, UK, International Association of Engineers, 2: 988-993.

Leung Y.C., Fu X., Wang C.F., Ni M., Leung M.K.H., Wang X.X. and Fu X.Z., Hydiogen production over titania-based photocatalysts, ChemSusChem. Wiley Inter Science, 2010, 3: 681-694.

Leung Y.C., Wong P., Cheung B.K.H. and Guenther A., Improved landcover and emission factors for modelling biogenic volatile organic compounds emissions from Hong Kong, Atmospheric Environment. Elsevier, 2010, 44: 1456-1468.

Leung Y.C., Wong P., Cheung B.K.H. and Lau B.M.P., Modeling of biogenic volatile organic compounds (BVOC) emissions in Hong Kong using improved laucover and emission facters, 2nd International Workshop on Regional Air Guality Management in Rapidly Developing Economic Regions. China, 2009, Poster.

Leung Y.C., The development of Innovative Micro-Wind Turbines for Harnessing Wind Power (Invited speech), Techology Conference on Renewable Energy. Hong Kong, Hong Kong Polytechnic University, 2010.

Lim B.L., Leung Y.C., Yung K.F., Leung M.K.H., Mah D.N.Y., Lam J.C.K. and Hills P.R., Conference Presentation: "Development of Biofuel Technologies and Policy", at the Initiative on Clean Energy and Environment’s Review Workshop, Shenzhen, January 8, 2010.

Liu C.H., Leung Y.C., Man A.C.S. and Chan P.W., CFD simulation of the wind flow over an airport terminal building, Journal of Zhejiang University-Science A (Appl. Phys. & Eng.). Springer, 2010, 11: 389-401.

Liu C.H., Cheng W.C., Leung T.C.Y. and Leung Y.C., On the mechanism of air pollutant re-entrainment in two-dimensional idealized street canyons, Atmospheric Environment. 2010.

Memon R.A., Leung Y.C. and Liu C.H., An investigation of urban heat island intensity (UHII) as an indicator of urban heating, Atmospheric Research. Elsevier, 2009, 94: 491-500.

Ni M., Leung Y.C. and Leung M.K.H., Ammonia fed solid oxide fuel cells for power generation - A review, International Journal of Energy Research. Wiley Inter Science, 2009, 33: 943-959.

Ni M., Leung Y.C., Leung M.K.H., Xuan J. and Wang H.Z., Thermo-electrochemical modeling of the transport phenomena and electrochemical reactions in ammonia fed solid oxide fuel cells, Proceedings International Conference on Applied Energy 2010. Singapore, National University of Singapore, CD-Rom: 10pp.

Wang H., Leung Y.C. and Leung M.K.H., Energy analysis of hydrogen and electricity production from aluminum-based processes, Proceedings International Conference on Applied Energy 2010. Singapore, National University of Singapore, CD-Rom: 10pp.

Xuan J., Leung M.K.H., Leung Y.C. and Ni M., A review of biomass-derived fuel processors for fuel cell systems, Renewable and Sustainable Energy Reviews. 2009, 13: 1301-1313.

Xuan J., Leung M.K.H. and Leung Y.C., Gravitational effects on the performance of membraneless micro fuel cells, Proceedings International on Applied Engergy 2010. Singapore, National University of Singapore, CD-Rom: 10pp.

Xuan J., Leung M.K.H., Leung Y.C. and Ni M., Integrating chemical kinetics with CFD modeling for autothermal reforming of biogas, International Journal of Hydrogen Energy. Elesvier, 2009, 34: 9076-9086.

Xuan J., Leung M.K.H. and Leung Y.C., Modeling analysis of membraneless micro fuel cell working under critical conditions, Proceedings International Conference on Applied Energy 2010. Singapore, Natioanl University of Singapore, CD-Rom: 10pp.

Yang H.X., Leung Y.C. and Yan J.Y., Special Issue of the Ist International Conference on Applied Energy, Hong Kong, Jan. 5-7, 2009, International Journal of Green Energy. Philadephia, USA, Taylor & Francis, 2010, 7: 223-360.

Researcher : Li C

List of Research Outputs

Wang L.Y., Yin G.G., Li C. and Zheng W.X., Signal estimation with binary-valued sensors , In: Lei Guo, Journal of Systems Science and Complexity. China, Springer, 2010, 23: 622-639.

Researcher : Li CH

List of Research Outputs

Chan B.P., Li C.H., Au-yeung K.L., Sze K.Y. and Ngan A.H.W., Research Output Prize 2009, Faculty of Engineering. 2009.

Li C.H., Ngan A.H.W., Sze K.Y. and Chan B.P., Association between elastic modulus and extracellular matrix components of collagen-mesenchymal stem cell microsphres during chondrogenic differentiation. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. (Best Poster Presentation Award). 2009, S210:795.

Li C.H., Characterization on the Biochemical Composition of Collagen-hMSCs Microspheres and their Mechanical Property During Chondrogenic Differenctiation, MPhil Thesis. Hong Kong, The University of Hong Kong, 2009, 1-97.

Li C.H., Sze K.Y. and Chan B.P., Microplate manipulation of human mesenchymal stem cells collagen microspheres. , WACBE (World Association for Chinese Biomedical Engineers) World Congress on Bioengineering 2009. 26-29 Jul 2009, Hong Kong, China.. 2009, 65.

Researcher : Li G

List of Research Outputs

Li G., Zhang D., Yu J...C... and Leung M.K.H., An efficient bismuth tungstate visible-light-driven photocatalyst for breaking down a smog precursor nitric oxide, Environmental Science & Technology. 2010, 44: 4176-4281.

Researcher : Li J

List of Research Outputs

Li J. and Ngan A.H.W., Nanoscale fast relaxation events in polyethylene, Scripta Materialia. Elsevier Ltd., 2010, 62: 488-491.

Researcher : Li P

List of Research Outputs

Li P. and Lam J., Decentralized H_¥ control for air traffic flow networks modeled by A class of compartmental systems, 3rd International Symposium on Systems and Control in Aeronautics and Astronautics. Harbin, China, 2010, CD-Rom: 6pp.

Li P., Lam J. and Wang Z., H_¥ model reduction for positive systems, Proc. 2010 American Control Conference. Baltimore, 2010, 6244-6249.

Li P., Lam J. and Shu Z., On the transient and steady-state estimates of interval genetic regulatory networks, IEEE Transactions on Systems, Men, and Cybernetics, Part B. 2010, 40(2): 336-349.

Li P., Lam J. and Shu Z., Positive observers for positive interval linear discrete-time delay systems, Joint 48th IEEE Conference on Decision and Control and 28th Chinese Control Conference. Shanghai, P.R. China, 2009, 6107-6112.

Shu Z., Lam J. and Li P., On positive filtering with H_¥ performance for compartmental networks, International Journal of Systems Science. 2009, 40(9): 961-971.

Shu Z., Lam J. and Li P., Simultaneous H_¥ stabilization via fixed-order controllers: Equivalence and computation, Joint 48th IEEE Conference on Decision and Control and 28th Chinese Control Conference. Shanghai, P.R. China, 2009, 3244-3249.

Researcher : Li S

List of Research Outputs

Li S. and Wang M., Synthesis of Au nanoparticles and their characterization, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Researcher : Li Y

Project Title:	World Renewable Energy Congress VII Analysis and Design of Hybrid Ventilation and Cooling in Buildings
Investigator(s):	Li Y
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2002

Abstract:

N/A

Project Title:	Full-scale study of air conditioning systems for SARS wards
Investigator(s):	Li Y
Department:	Mechanical Engg
Source(s) of Funding:	Other Funding Scheme
Start Date:	06/2006

Abstract:

This project proposal is to undertake a preliminary research study to construct a full-scale mock-up test chamber for SARS wards and to investigate the performance of a new air-conditioning system designed by SARS-Busters. The full-scale test room was completed in less than 4 weeks time between late May and middle June. The air conditioning system tests was completed in another four weeks time between middle June and middle July, 2003.

Project Title:	Healthy Buildings 2006 - Creating a Healthy Indoor Environment for People How Far Respiratory Droplets Move in Indoor Environments?
Investigator(s):	Li Y
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2006

Abstract:

N/A

Project Title:	BioPassVent - a theory of enclosure ventilation for purging combined pollutants
Investigator(s):	Li Y
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	09/2006
Completion Date:	08/2009

Abstract:

1. Study particle deposition and bacterial survival on surfaces 2. Study of the removal of combined pollutants in simple systems 3. New ventilation strategies for removing combined pollutants 4. BioPassVent air distribution strategy for isolation rooms

Project Title:	CityVent A Theory of Ventilation of a Dense and High-Rise City by Wind and Buoyancy Forces
Investigator(s):	Li Y
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	09/2007
Completion Date:	02/2010

Abstract:

(1) To develop a fundamental understanding of ventilation flow rates and efficiencies for dense high-rise cities, and a part of a city, due to wind penetration, canopy “roof” turbulence exchange and buoyancy-driven flows (i.e. natural ventilation of a city). (2) To develop guidelines for ventilation strategies for urban environments.

Project Title:	ConnectVent - Ventilation of"connected"indoor environments in controlling airborne disease transmission
Investigator(s):	Li Y, Leung GM
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	12/2008

Abstract:

1. To develop a fundamental understanding of the relative effectiveness of building ventilation in a connected indoor environments in a city of 7 million population and 3-5 million indoor environments, as compared to other intervention measures. The ventilation rates in different indoor environments will be based on the literature data. 2. To develop a new approach for studying the relative effectiveness of building ventilation as compared to other engineering and personal methods such as use of filters, use of ultraviolet germicidal irradiation (UVGI), personal masks etc as an intervention measure in airborne disease epidemics.

Project Title:	City Ventilation by Valley Winds
Investigator(s):	Li Y
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2009

Abstract:

Purpose of the proposed project, • Objective 1 To develop a fundamental understanding of city ventilation by valley winds in an idealized city using analytical solutions, the small-scale water tank model and computational fluid dynamics. • Objective 2 To develop basic urban planning parameters for better ventilation of the high-rise dense Causeway Bay area and the Sha Tin area in Hong Kong, including the height of buildings, the urban porosity, building density, ventilation path (e.g. the Shing Mun Rover Channel in Sha Tin) and vegetation, using computational fluid dynamics and preliminary field measurement. Key issues and problems being addressed • Most existing studies of urban air pollution control focus on source control, but ignore the importance of ventilation removal of the airborne pollutants. However, past serious urban pollution episodes mostly resulted from poor city ventilation (Cheng and Lam 1998). The lack of studies on city ventilation has significant implication to urban planning. As the buildings become higher and denser in Hong Kong, the ability of city ventilation in removing airborne pollutants also becomes lower and lower, as shown by the data from Hong Kong Observatory. We thus identified a new research direction on city ventilation. •Existing urban design guidelines, such as for breezeways for example, are qualitative not quantitative. High-rise buildings, typically 40 to 60 stories, are densely packed along the 17 km long northern shore of Hong Kong Island, giving one of the most beautiful high-rise skylines in the world but also a challenging city ventilation problem. During fair-weather conditions, mountain slopes often induce upslope (downslope) air flows in the daytime (nighttime). Our hypothesis is that the combined/interacting slope and wall flows are responsible for ventilating (or trapping pollutants in) the high-rise dense city during fair-weather conditions. In this project, we like to focus on valley winds. Two of the most important valleys are the happy Valley and that of Sha Tin. • City ventilation supplies “external” rural air into an urban environment, and distributes this air within it. Understanding and quantifying city ventilation are important for the “pollutant island” and “heat island” phenomena, and also relevant to building energy consumption, indoor/outdoor air quality, and pedestrian thermal comfort. However, systematic and quantifying investigations of city ventilation are rare. • Valley winds originate from the upslope (anabatic winds) and downslope flows (katabatic winds). The ability by the slope winds and valley winds in transporting heat and air pollutants in complex terrain during fair-weather conditions is known in the meteorology literature. However, the focus of all existing studies has been on the slope flows or valley winds, not on the ventilation of the built-up areas. The existing field observations and the numerical mesoscale models also lack the horizontal resolution for the purpose of quantifying city ventilation. Existing studies of the interaction of building surface flows and the valley flows are rare, or non-existent.

Project Title:	Two-box models for the city-scale pollutant and heat transport
Investigator(s):	Li Y, Yang L
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2010

Abstract:

Background More than 50% of the world population now lives in cities. Enhancing the removal ability of heat and airborne pollutants is one of the major challenging scientific problems in mega-city air environment and energy. Rapid urbanization in China and India has led to renewed debate about high-rise compact cities in terms of saving land and offering better energy efficiency. Hong Kong has the lowest energy consumption per capita and per GDP dollars amongst developed countries/economies, which is often partly attributed to its high-rise compact city design. A high population density also, however, means concentrated human activities, and urban heat and pollutant generation. Urban air pollution and urban heat islands are caused by not only the concentrated heat and pollutant generation, but also the reduced ability of a city to remove airborne pollutants and heat. Systematic study of the heat and pollutant removal abilities of high-rise compact cities is currently lacking. Hong Kong has one of the highest population densities among the worlds’ largest cities and Hong Kong is an ideal city to carry out such studies. The study of the air, heat and pollutant budget as well as their removal at the overall city level is challenged by the difficulties in the large-scale field measurement, as well as the inability of existing computer simulation methods in resolving tens of thousands of buildings. Existing air pollution and urban heat islands research has mostly focused on monitoring and source control, while the meteorology studies have focused on the meso-scale wind climate considering city buildings as a roughness element. The existing street canyon and wind engineering often deal with one building or a building cluster. In this seeding funding project, we propose to use the simple box models as the first step of our major efforts to understand the major removal mechanisms of heat and pollutants in a large urban environment. Project objectives •To understand the removal mechanisms and determine the temporal budget of particles and CO and heat removed by air ventilation, vegetation, dry and wet deposition in different parts and the entire urban area of Hong Kong using a two box modeling approach. •To determine the impact of major urban and meteorological parameters (building height, density, vegetation areas and ventilation path, meso-scale winds, sea-land breeze, topography, etc.) on the removal of city heat and airborne pollutants. •To compare the removal ability of heat and pollutants of different mechanisms in Hong Kong to provide guidelines for future city design. Key issues and problems being addressed •The urban canopy layer (Figure 1) consists of buildings by street networks, parks and other open spaces. The urban canopy layer in a high-rise compact city such as Hong Kong can be more than 100 m deep on average. Most human activities occur here. Human activities including traffic within the urban canopy layer release airborne contaminants and heat. The urban canopy layer is also where the most human exposures of pollutant and heat occur. To understand and improve removal mechanisms of heat and airborne pollutants from the urban canopy layer, we need to analyze the air, heat and pollutant sources/sinks within it and surface fluxes. Such analysis may be obtained by simple analytical physical models, small-scale wind tunnel and water tank measurements, urban field measurement, satellite remote sensing, and meso-scale and city-scale coupling wind flow models. Although many of these aspects have been studied, focused study on removal mechanisms of heat and pollutants from the urban canopy layer are rare. In this proposed project, we focused on the simple analytical physical models. As mentioned, based on the physical mechanisms, the urban air environment can be divided into an urban canopy layer where the human activities are concentrated, and an urban dome/plume layer. Traditional single box models assume that the concentration of airborne pollutants is uniform below the mixing height. Such an assumption may be challenged as the concentration in the urban canopy layer is generally much higher due to the close proximity effect to the pollutant source. The new two box modeling approaches may shed new insights into the problem of urban heat and pollutant removal studies. •The study of air, heat and pollutant removal mechanism at the overall city level is challenged by the difficulties in large-scale field measurement, as well as the inability of existing computer simulation methods in resolving tens of thousands of buildings in a city. Existing air pollution and urban heat islands research mostly focuses on monitoring and source control, while meteorological studies focus on the meso-scale climate considering the city buildings as a roughness surface. The existing street canyon and wind engineering studies often deal with one building or a building cluster.

List of Research Outputs

Hang J., Sandberg M. and Li Y., Age of air and air exchange efficiency in idealized city models, Building and Environment. 2009, 44: 1714-1723.

Hang J., Sandberg M., Li Y. and Claesson L., Flow mechanisms and flow capacity in idealized long-street city models, Building and Environment. 2010, 45: 1042-1053.

Hang J., Li Y. and Lina Y.A.N.G., Macroscopic numerical simulations of wind conditions in high-rise building clusters using a porous turbulence model, The 8th Asian Computational Fluid Dynamics Conference. 2010.

Hang J., Sandberg M., Li Y. and Claesson L., Pollutant dispersion in idealized city models with different urban morphologies, Atmospheric Environment. 2009, 43: 6011-6025.

Hang J. and Li Y., Ventilation strategy and air change rates in idealized high-rise compact urban areas , Building and Environment . 2010, 45: 2754-2767.

Hang J. and Li Y., Wind Conditions in Idealized Building Clusters: Macroscopic Simulations Using a Porous Turbulence Model, Boundary-Layer Meteorol. 2010, 136: 129-159.

Hang J., Sandberg M. and Li Y., Wind conditions and ventilation in high-rise long street models, Building and Environment. 2010, 45: 1353-1365.

Lee J.H.W., Tang H.W., Wang W.P., Li Y. and Cheung V., State Science and Technology Awards, Second Prize, 2010, Ministry of Science and Technology, China. 2010.

Li Y., Plenary speaker. Ventilation and Airborne Infections, Healthy Buildings 2009 Conference and Exhibition in Syracuse, NY, September 13-17, 2009.. 2009.

Luo Z., Li Y. and Nazaroff W.W., Intake fraction of nonreactive motor vehicle exhaust in Hong Kong, Atmospheric Environment. 2010, 44: 1913-1918.

Qian H. and Li Y., Removal of exhaled particles by ventilation and deposition in a multibed airborne infection isolation room, Indoor Air. 2010, 20: 284-297.

Qian H., Li Y., Zhang X.S. and Liu J.P., Surface Temperature Distribution of Chinese Kangs, International Journal of Green Energy. 2010, 7: 347-360.

Shui P., Liu C.H. and Li Y., CFD Analysis of Pollutant Removal Mechanism in Urban Street Canyons, The 7th International Conference on Urban Climate, 29/6 to 3/7/2009, Yokohama, Japan. 2009.

Shui P., Liu C.H. and Li Y., Upward and sideward removal of air pollutants in three-dimensional street canyons, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Yang L. and Li Y., Dependence of City Ventilation by Thermal Buoyancy on Thermal Stratification, the 6th International Symposium on Heating, Ventilating and Air Conditioning (ISHVAC 2009). Nanjing, 2009.

Yang L. and Li Y., Urban Surface Temperature Profiles in Hong Kong, Clima2010, the 10th REHVA World Congress “Sustainable Energy Use in Buildings”. Turkey, 2010.

Yang L. and Li Y., Ventilation and thermal environment in a semi-enclosed open urban space, Clima2010, the 10th REHVA World Congress “Sustainable Energy Use in Buildings”. Turkey, 2010.

Zhuang Z., Li Y., Yang X., Chen B. and Liu J., Thermal and energy analysis of a Chinse kang, Front. Energy Power Eng. China. 2010, 4: 84-92.

Researcher : Li YY

List of Research Outputs

Li Y.Y., Cheng H.W., Wong M.Y., Cheung K.M.C., Chan D. and Chan B.P., Collagen-mesenchymal stem cell microspheres for cartilage tissue engineering. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S69:222.

Li Y.Y., Cheng H.W., Chan P.M., Wong M.Y., Teng W.K., Chow S.T., Cheung K.M.C., Chan D. and Chan B.P., Repair of osteochondral defects with collagen-mesenchymal stem cell microspheres in a rabbit model. , ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #W-50, p250.

Researcher : Lin Y

Project Title:	Cell motility meditated by adhesion
Investigator(s):	Lin Y
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	10/2008

Abstract:

A common feature of fibroblasts and other moving tissue cells is the formation of a broad, flat protrusion region, called lamellipodium, extending from the main cell body in the direction of movement [1,2]. Expansion of this protrusion is driven by active expansion of a network of actin filaments within the cell, with polymerization taking place at the filament ends pushing against the cell membrane [3,4]. It is commonly believed that the adhesion formed between the cell and substrate stabilizes the protrusion region and allows the generation and transmission of forces necessary for cell locomotion [5]. Several lines of evidence have suggested that mechanics plays an important role in cell motility, for example experimental observations have revealed that stable adhesion is more likely to form between a cell and a rigid substrate than with a soft one [6, 7]. Consequently, the cell movement is found to be guided by the rigidity of the substrate, meaning cells tend to move in the direction where the substrate is more rigid [8]. The nature of cell motility is still poorly understood. The main objective of this project is to examine the role of adhesion in cell motility from a mechanics point of view. We want to answer the question of how a cell regulates its adhesion with outside during locomotion, and how propelling forces necessary for cell movement are generated and transmitted through adhesions. Mechanics models, capturing the essential features involved in cell motility, will be developed at the end of the project from which testable predictions will be provided for the use and design of future experiments.

Project Title:	Investigation of the role of focal adhesion in mechanosensing
Investigator(s):	Lin Y
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2010

Abstract:

Adhesion is the primary way for a cell to anchor itself to extracellular matrix (ECM) which is essential for numerous important biological processes such as cell motility [1], cell signaling and proliferation [2]. The molecular bonds formed by receptors, which are transmembrane proteins, and their counter-parts from ECM, called ligands, are responsible for the formation of stable adhesion regions, often referred to as focal adhesions (FAs). Usually, these receptor-ligand bonds are laterally reinforced by a layer of proteins, including vinculin and paxillin etc. [3], that interconnect them together. As shown in Figure 1, this layer of proteins, often referred to as adhesion plaque, is then connected to the cytoskeleton of the cell through the so-called stress fibers, which are actin filaments and their associated myosin based molecular motors. Besides anchoring, the formation of FAs also allows a cell to probe the environment and exert forces to ECM through tensions generated within stress fibers [4,5]. Several compelling lines of evidence suggest that FAs have the remarkable ability to sense and respond to mechanical signals. First of all, it has been convincingly demonstrated that a FA, when subjected to external loading, tends to grow in the same direction as the applied force [6]. In addition, the rigidity of ECM has been found to affect the formation and maintenance of FAs as well. Basically, reduced rigidity in ECM leads to highly dynamic and unstable FAs, sometime called focal complexes (FXs) [7], with irregular shapes and smaller sizes [8]. As a result, cell movement was found to be guided by the rigidity of ECM, that is, cells tend to move in the direction where the substrate is more rigid because FAs are more likely to be formed there [9]. Theoretically, the role of FA as mechanosensors for a cell to explore the surrounding environment has been examined by many authors, see [10] for a comprehensive review. Roughly speaking, all the existing models in the literature can be categorized into two groups. In the first type of models, the mechanosensing ability of FAs relies on the existence of certain sensing proteins that can undergo conformational changes. Depending on the physical conditions experienced by these sensing proteins, such as stress or strain levels, they can fall into different “states”, or have different conformations, and behave differently. For example, a two-state model describing the transition, which is regulated by the substrate stiffness, from nascent adhesion sites to mature FA was presented by Bruinsma [11]. Nicolas and co-workers [12,13] proposed models based on the assumption that only parts of the whole adhesion region are subjected to shear forces, and the non-uniform deformations generated within FA, as consequence of this assumption, can then be captured by the sensing proteins. Models of the second type are based on physical arguments which do not need the presence of sensing molecules. Instead, FAs react to mechanical cues spontaneously, i.e. the responses occur naturally because they are energetically more favorable. For instance, Shemesh and co-workers [14] proposed a thermodynamic model which explains the force-induced growth of FA via a self-assembly mechanism. In working with Prof. L.B. Freund at Brown University, the PI has studied a number of issues concerning the formation, evolution and functioning of cell adhesions from a mechanics point of view since 2003. In a paper by the PI and his collaborator [15], a mechanics model describing the spontaneous growth of an adhesion patch has been proposed. The PI has also examined the role of thermal excitations in cell adhesions, and demonstrated that thermal undulations of the membrane itself do put a lot of restrictions on the formation of stable adhesion [16,17]. Lastly, the PI and his collaborators have conducted stochastic analyses on the strength of cell adhesions meditated by the enforced breaking and reforming of individual molecular bonds [18,19]. Despite all the aforementioned efforts, the exact mechanism by which FAs sense and respond to mechanical signals remains elusive. Specifically, we believe that several important issues need to be addressed here (i) The mechanics models for adhesion regions, adopted in the work mentioned above, are somewhat too simple. For example, the focal adhesion is treated as an elastic layer in [13]; in other studies, such as [19], the whole cell body is represented by an elastic half-space. While these assumptions greatly simplify the analyses, they surely overlook features of the real system as depicted in Figure 1. (ii) To the PI’s knowledge, no quantitative model predicting the evolution of focal adhesions in response to mechanical stimuli has been proposed. The PI has addressed the spontaneous growth of an adhesion patch in one of his papers [15], however, the internal structure of the adhesion region was largely neglected in that study and no mechanosensing mechanism was included in the analyses as well. (iii) Although the mechanosensing capability of FAs has been observed, there are very limited experimental data on how FAs evolve under various applied mechanical stimuli, such as a cyclic load in the tangential, as well as the normal, direction, which will undoubtedly be extremely valuable for the development of new theories in the future. In this application, we describe a research project involving both theoretical and experimental investigations to address the outstanding questions mentioned above. The objectives of this project are (1) To investigate how load is transmitted through focal adhesions (FAs) to extracellular matrix, as well as the mechanical responses, such as the induced stress and strain, within FAs when subjected to external stimuli. (2) To examine the possible mechanosensing mechanisms by which individual molecules, involved in the formation of FAs, detect and respond to mechanical cues, such as the changes in local stress or strain fields. (3) To develop theoretical models, on the basis of the work mentioned in (1) and (2), for the evolution and remodeling of FAs in response to mechanical signals. (4) To conduct carefully designed experiment to observe the evolution of FAs under different loading conditions.

Project Title:	16th US National Congress on Theoretical and Applied Mechanics (USNCTAM) A microscopic formulation of the motion of actin-driven Listeria
Investigator(s):	Lin Y
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2010
Completion Date:	07/2010

Abstract:

N/A

List of Research Outputs

Lin Y., A model of cell motility leading to biphasic dependence of transport speed on adhesive strength, Journal of the Mechanics and Physics of Solids. 2010, 58: 502-514.

Lin Y., Yao S. and Xu Q., Dynamic Adhesion Energy Between Surfaces Connected by Molecular Bonds and its Application to Peel Test , Cellular and Molecular Bioengineering. 2010, 3: 247-255.

Qian J., Wang J., Lin Y. and Gao H., Lifetime and strength of periodic bond clusters between elastic media under inclined loading, Biophysical Journal. 2009, 97: 2438-2445.

Wu Y., Chen G.L., Hui X.D., Liu C.T., Lin Y., Shang X.C. and Lu Z.P., A quantitative link between microplastic instability and macroscopic deformation behaviors in metallic glasses, Journal of Applied Physics. 2009, 106: 083512.

Researcher : Liu CH

Project Title:	Effects of Building Interference on Natural Ventilation, Thermal Comfort, and Air Quality in Residential Buildings.
Investigator(s):	Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2008
Completion Date:	02/2010

Abstract:

Summary Major side effects of rapid urbanization and expanding economy are dense built environment and large building energy consumption. The subsequent drawbacks are poor ventilation, thermal discomfort, and deteriorating air quality in our living environment. Improved architectural design and building planning, such as encompassing renewable resources and green features, are environmentally friendly solutions to the problems. Wind-induced fluctuation due to the buildings nearby modifies the micro-scale wind behaviours and pressure difference. Hence, proper building orientation and disposition would lead to favourable building interference that promotes natural ventilation performance. In this project, we propose to study the interference among adjacent buildings on micro-scale climate and wind environment. The feasibility of using building orientation and disposition for improved natural ventilation, thermal comfort, and air quality in residential buildings will be examined. Computational fluid dynamics (CFD) techniques will be used to identify the key factors related to building interference and natural ventilation performance. In particular, a series of CFD parametric tests will be performed to measure the environmental benefits of strategic building orientation and disposition for sustainable built environment. The results and experience earned in this project will be consolidated to some design and planning guidelines for housing estates in order to promote a sustainable living environment. Background By the end of 2006, the total residential housing stock in Hong Kong, including both private and public sectors, was up to 2,473, 900 flats (Hong Kong Year Book 2006). Housing and construction development has contributed to the economy in Hong Kong for decades, whereas, it has created considerable impacts on our natural and built environment. The residential sector consumes about 24% to 26% of electricity power in 1995 to 2005 (EMSD 2007) in which 40% of that residential consumption is used in space conditioning. Hence, reducing (improving) building energy consumption (efficiency), e.g. encompassing green features (JPN1 2001), has been a popular research topic in the recent years that is of fundamental importance to the sustainability of our living environment. Passive cooling of houses or apartments using natural ventilation is an effective alternative to air conditioning. In fact, natural (cross) ventilation, usually in the form of wind breeze passing through or over our indoor living zones, has been regarded as one of the most promising passive cooling means in hot and humid climate. By drawing in fresh outdoor air, effective ventilation helps maintain the indoor health environment as well as the thermal comfort at acceptable levels. Moreover, it dilutes and removes air pollutants so as to provide a healthy indoor habitat. Natural ventilation is an integration of the natural environment, architectural design, and engineering solution. Numerous studies have been performed to investigate the feasibility and performance of naturally ventilated buildings mainly for thermal comfort purposes (Ayad 1999, Li and Delsante 2001, Li et al. 2001, Eftekhari et al. 2003, Yang et al. 2005, Seifert et al. 2006, Andersen 2007). In particular, British Standard developed a code of practice that provided a framework for natural ventilation design (BS 5925 1991). In fact, effective natural ventilation is subject to skilful design of openings, building envelop, and the surrounding environment. However, most of the previous studies have focused on an isolated building and overlooked the influence of adjacent buildings. In the dense built environment, the situation of an isolated building rarely occurs. Some studies focusing on building interference have been performed. Generally, the wind flow behaviours and wind loads are significantly alternated by the adjacent buildings (e.g. Jóźwiak et al. 1995 and 1996, Ohba 1998, Khanduri et al. 1998). In fact, the wind behaviours around a building are complicated by the neighbouring structures. For example, the wind load or speed may either decrease or increase that depends mainly on the geometry and disposition of these structures (Niemann and Köpper 1998, Ferreira et al. 2002, He et al. 1997, Van Moeseke et al. 2005, Zhang et al. 2005, Xie and Gu 2004 and 2007). While the aforementioned studies have investigated the broad range of interference effects due to the nearby buildings on micro-scale climate and wind environment, they have focused on the outdoor environment but not the indoor one. Our understanding of the effects of adjacent buildings on the indoor environment of naturally ventilated buildings is limited. Thus, building interference should be taken into account for building natural ventilation studies. This is the key area to be explored in this project. Aims and Objectives This project aims to investigate the use of strategic building orientation and disposition to effectuate natural ventilation, enhance thermal comfort, and improve air quality inside and around residential buildings in the dense and high-rise built environment in Hong Kong and other metropolises. The specific objectives of this project are: 1. Advanced understanding of the modified micro-scale climate and wind environment in and around residential buildings, as well as the modified natural ventilation mechanism in the existence of adjacent buildings; 2. Elucidation of building interference for natural ventilation, thermal comfort, and air quality in residential apartments; and 3. Investigation of the building orientation and disposition that could improve natural ventilation, thermal comfort, and air quality of residential buildings in a dense built environment. Key Issues and Specific Problems In achieving the aforementioned objectives, the following key issues and specific problems will be addressed step by step: 1. Natural ventilation behaviours of apartments in high-rise residential buildings; 2. Characteristics of micro-scale climate and wind environment around a group of naturally ventilated residential buildings (i.e. a housing estate); 3. Building interference imposed by the adjacent buildings, and the subsequent modification on the micro-scale climate and wind environment in a dense built environment; 4. Effects of building interference on natural ventilation, thermal comfort, and air quality; 5. Sensitivity of building orientation and disposition on building natural ventilation performance, thermal comfort, and air quality; and 6. Identification of key factors, which are related to strategic building orientation and disposition, for the effectuation of natural ventilation for acceptable thermal comfort and efficient air pollutant removal.

Project Title:	On the Upward and Sideward Air Pollutant Removal in 3D Urban Street Canopies
Investigator(s):	Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2009

Abstract:

Background The major drawback of urbanization and industrialization is our deteriorating air quality. Street canyons and intersections are black spots of air pollution because of the large amount of vehicular exhaust nearby. In Hong Kong, the problem is especially serious due to the weakened air pollutant removal by the surrounding high-rise buildings and the close proximity between air pollutant sources and receptors. Previous studies have mainly focused on two-dimensional (2D) infinitely long (idealized) street canyons flanked by low-rise buildings and have laid a firm foundation of knowledge about upward air pollutant removal from the street level to the shear layer over urban areas. Because of our precious land resources, most of the buildings erected in the last decade are high-rise ones. Our conventional understanding of 2D street canyon ventilation and air pollutant removal only in the vertical direction is unable to fully explain the processes in narrower street canyons surrounded by high-rise buildings. Apart from the upward air pollutant removal, the sideward mean wind and turbulent mixing help remove air pollutants from three-dimensional (3D) finite-length street canyons, through street ends, to the connecting intersections and finally purge via the breezeways. Purposes of the Proposed Project In this project, we will use mathematical modeling techniques to investigate the characteristics of wind flow and air pollutant transport in 3D finite-length street canyons flanked by high-rise buildings. Computational fluid dynamics (CFD) will be used to perform a series of comprehensive sensitivity tests to elucidate the transport processes in street canyons. The Reynolds-averaged Navier-Stokes (RANS) equations equipped with two-equation k-ε turbulence models will be the core approach to the problems. We will compare the roles of mean and turbulent pollutant fluxes in, as well as the contributions of upward and sideward wind flow to, street canyon ventilation and air pollutant removal. Isothermal and stratified environment will be considered so as to account for the effects of solar radiation on the transport processes in daytime and nighttime street canyons. Moreover, the more sophisticated large-eddy simulation (LES) will be used to complement the findings from the RANS k-ε turbulence models, and examine the functions of intermittent wind and turbulence in street canyon air pollutant transport. Finally, we will analyze the wind flow and air pollutant transport, and determine the essential criteria for breezeway design so as to facilitate (upward and sideward) ventilation and air pollutant removal from 3D street canyons. Key Issues and Problems being Addressed In achieving the project goal, the following specific key issues and problems will be addressed step by step: 1/. The wind flow in 2D infinitely long street canyons is well defined into “isolated roughness”, “wake interference” and “skimming” flow regimes in accordance with the building-height-to-street-width ratio (H/W). The first issue to be addressed in this project is to define the characteristic wind flow and air pollutant transport in 3D finite-length street canyons as functions of the building geometries (i.e. building height and width, and street width). 2/. The mechanisms of (upward only) ventilation and air pollutant removal in 2D street canyons are well explored. Whereas, our understanding of the concurrent transport processes in the upward and sideward directions are rather limited. The in-depth elucidation of the mechanisms for ventilation and air pollutant removal, in terms of mean flow and intermittency, is deemed for better air quality in modern cities. 3/. Our recent 2D street canyon results showed that the heat dissipation on building facades induces updraft which substantially modifies the original wind-driven recirculation in the street canyons. Moreover, if the façade temperature is high enough (measured by the dimensionless parameter Richardson number Ri), the buoyancy force activates periodic wind flow which is different from our previous studies under isothermal conditions. Hence, the contribution of buoyancy (daytime and nighttime) to 3D finite-length street canyon ventilation and air pollutant transport should not be overlooked. 4/. Owing to the ground-level pollutant emissions, the amounts of air pollutant removal in the upward and sideward directions are obviously attributed to the geometry of the 3D street canyons. A series of sensitivity tests will be performed to determine the relative contributions of upward and sideward transports as functions of the geometric and meteorological factors. 5/. Our previous 2D street canyon results revealed the importance of pollutant re-entry in associated with the prolonged pollutant retention time. For 3D street canyons, we will study the roles and quantify the relative contributions of air pollutant removal/re-entry through mean and intermittent wind in the upward and sideward directions 6/. Neighborhood-scale turbulent mixing is a popular research topic because of its immediate impact on urban inhabitants. To advance our fundamental understanding, we will use fluid mechanics principles to examine the mechanisms of ventilation and air pollutant removal in details, e.g. the meandering of persistent recirculation in street canyons, penetration of recirculation into the roof-level shear zone, and the elongated low-speed streak over the street canyons. Objectives The primary objectives of the proposed project are using mathematical models and scientific computing to: 1/. Develop a robust CFD model which is able to calculate the wind flow and air pollutant transport in urban canopies using both the RANS k-ε turbulence model and the LES. 2/. Validate the aforementioned newly developed CFD model. 3/. Reveal the detailed transport processes and scientific principles of both mean and intermittent components for ventilation and air pollutant mixing, transport and removal in 3D finite-length street canyons in daytime and nighttime neighborhood-scale wind environment in urban canopies. 4/. Contrast the roles of mean and turbulent pollutant fluxes, as well as the relative contributions of upward and sideward ventilation to air pollutant removal for 3D finite-length street canyons under different building geometries and meteorological conditions. 5/. Identify, through a series of comprehensive CFD sensitivity tests, the key parameters and essential criteria for optimum street canyon design as well as effective implementation of breezeways in the perspective of better air quality. 6/. Critically examine the functionality of breezeways for ventilation and air pollutant removal in 3D finite-length street canyons in modern compact mega cities.

Project Title:	LESChem: Large-Eddy Simulation and Wind Tunnel Experiments for the Transport of Chemically Reactive Air Pollutants in Urban Canopies
Investigator(s):	Liu CH, Lam KM
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2010

Abstract:

1) Investigate the non-linear coupling between air pollution physics and chemistry; 2) Develop the computer model "LESChem" that simulates concurrently the physical and chemical processes of air pollutants in urban area; 3) Improve the component of vertical air pollutant fluxes in urban surface parameterizations.

Project Title:	European Geosciences Union General Assembly 2010 On the Pollutant Plume Dispersion in the Urban Canopy Layer over 2D Idealized Street Canyons: A Large-Eddy Simulation Approach Analysis of the Momentum and Pollutant Transport at the Roof Level of 2D Idealized Street Canyons: a Large-Eddy Simulation Solution
Investigator(s):	Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	05/2010
Completion Date:	05/2010

Abstract:

N/A

Project Title:	Wind and Air Pollutant Transport in the Urban Canopy Layer under Unstable Stratification: Development of an Experimental Dataset for Computer Model Validation Exercises
Investigator(s):	Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	06/2010

Abstract:

Background Street canopies lie down the bottom of the atmospheric boundary layer (ABL) where most people live. The transport processes in street canopies, such as heat (thermal comfort), momentum (ventilation) & mass (air quality), are crucial factors affecting our daily lives. While the realistic city morphology is often too complicated to be examined for the contributions of individual parameters (namely building geometry & meteorological conditions), idealized 2D street canyons are the conventional testing platforms for the studies of neighborhood-scale ventilation & pollutant removal in city environment. Basically, the transport processes are divided into two broad areas: 1. Momentum Transport: The prevalent wind over the urban canopies (in the shear layer) transfers momentum downward that subsequently induces the recirculating wind inside the street canyons. 2. Heat & Mass Transport: Heat dissipation & pollutant emission take place inside the street canyons, that are moved upward to the roof level, diluted & carried away from the urban canopies by the prevalent wind. The key component in the transport processes, either in the downward momentum or upward heat & mass transports, is the roof-level interface between the fast prevalent wind (in the shear layer) & the slow recirculations (inside the urban canopies). It is a layer of strong shear & turbulence flapping up & down to bridge the transport between the urban canopies & shear layer (Belcher 2005). The urban climate scientific community has devoted substantial efforts to portray the transport processes in isothermal conditions (nighttime). In fact, under daytime unstable stratification, the transport processes are tightly coupled with buoyancy, which, however, have been rarely addressed. We thus initiate this project, consisting of laboratory experiments and computational fluid dynamics (CFD) analyses, to bridge the aforementioned knowledge gap. Literature Review Owing to the rising public concern on climatic change & urban heat island, street canopy flow & pollutant removal have been popular research topics for many years. While the realistic urban morphology is often too complicated for theoretical analyses, idealized 2D urban canopies are the basic testing platforms for sensitivity tests & scenario analyses to enrich our in-depth fundamental understanding of ventilation & pollutant removal in urban environment. The major geometric parameter affecting the wind field in urban canopies is the building-height-to-street-width (aspect) ratio. Oke (1988) partitioned the flow into 3 regimes: a. Skimming flow; b. Wake interference & c. Isolated roughness, which are essentially functions of the aspect ratio (Figure 1). Thereafter, researches have been based on this parameter to examine the ventilation & pollutant removal mechanisms in different flow regimes under isothermal conditons (e.g., De Paul & Sheih 1986; Kastner-Klein & Plate 1999; Pavageau & Schatzmann 1999; Louka et al. 2000; Brown et al. 2000). Indeed, aspect ratio is not the only parameter governing the wind & pollutant removal in urban canopies. Computational fluid dynamics (CFD) works have shown that temperature stratifications, which are the results of heat dissipation on building facades & street surfaces, could substantially modify the flow regimes (Xie et al. 2006). Our theory of ventilation and pollutant removal originally developed under isothermal conditions should then be applied with caution. Temperature stratifications are commonly found in daytime ABL, however, measurement data of wind & pollutant transport for urban canopies are rather limited (e.g., Baik et al. 2000; Uehara et al. 2000; Kovar-Panskus et al. 2002). Therefore, CFD modelers are lack of datasets for comprehensive model validation exercises so the modeling quality is unavoidably affected. Purposes of the Proposed Project CFD have been employed to elucidate the mechanisms of ventilation & pollutant removal in urban canopies for some years, however, these (turbulent) processes are too complicated to be fully described by computer models. In particular, there is a lack of confidence to inform the scientific community the reliability of CFD under temperature stratifications. CFD development relies on comprehensive model validations but appropriate datasets are merely available. Obviously, more advanced laboratory measurements are deemed to develop systematic datasets for more innovative CFD model validation exercises & development. In view of the needs of the international scientific community, it is our initiative to develop a dataset and demonstrate a rigorous CFD model validation exercise for urban canopy ventilation & pollutant removal under temperature stratifications in order to 1. Assure the quality of CFD output 2. Arrive a consensus on CFD application, capability & limitation 3. Establish a systematic framework for CFD as a complementary methodology Key Issues & Problems being Addressed In achieving the project goal, the following specific key issues & problems will be addressed step by step 1. Identify the merits & weaknesses of CFD in urban canopy applications. 2. Review the accomplishment of existing modeling studies, laboratory experiments & observational datasets. 3. Formulate the strategy, by means of model validation exercises, to overcome the limitations of CFD in urban canopy applications. 4. Critically review CFD reliability by comparing with existing & the new datasets 5. Develop a protocol for comprehensive professional CFD model validation & benchmark. Objectives The primary objectives of this project are to: 1. Review & identify the weaknesses & limitations, if any, of existing datasets for urban canopy ventilation & pollution removal. 2. Develop a new dataset, with particular focus on temperature stratifications, to facilitate more advanced & comprehensive CFD model validation exercises. 3. Demonstrate a vigorous CFD validation protocol by performing a new intercomparison with existing & the newly developed datasets. References Baik, J.-J., Park, R.-S., Chun, H.-Y. & Kim, J.-J. (2000), J. Appl. Meteor., 38, 1576-1589. Belcher, S.E. (2005), Phil. Trans. R. Soc. A, 363, 2947-2968. Brown, M.J., Lawson, R.E., Decroix, D.S. & Lee, R.L. (2000), Proceedings of the 11th Joint AMS/AWMA Conference on Applied Air Pollution Meteorology, January 2000, Long Beach, CA. De Paul F.T. & Sheih, C.M. (1986), Atmos. Environ., 20, 455-459. Kastner-Klein, P. & Plate, E.J. (1999), Atmos. Environ., 33, 3973-3979. Kovar-Panskus, A., Moulinneuf, L., Savory, E., Abdelqari, A., Sini, J.-F., Rosant, J.-M., Robins, A. & Toy, N. (2002), Water Air Soil Pollut.: Focus, 2, 555-571. Oke, T.R. (1988), Energy Build., 11, 103-113. Pavageau, M. & Schatzmann, M. (1999), Atmos. Environ., 33, 3961-3971. Xie, X., Liu, C.-H., Leung, D.Y.C. & Leung, M.K.H. (2006), Atmos. Environ., 40, 6369-6409. Uehara, K., Murakami, S., Oikawa, S. & Wakamatsu, S. (2000), Atmos. Environ., 34, 1553-1562.

List of Research Outputs

Cheng W.C. and Liu C.H., Analysis of the momentum and pollutant transport at the roof level of 2D idealized street canyons: a large-eddy simulation solution, European Geosciences Union, General Assembly 2010, Vienna, Austria, May 2-7, 2010 . 2010.

Cheng W.C. and Liu C.H., Effects of thermal stratifications on the flow & pollutant dispersion in urban street canyon: a large-eddy simulation approach, 9th American Meteorological Society Symposium on the Urban Environment, Keystone, Colorado, USA, August, 2-6, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Large-eddy simulation of street canyon flow and pollutant transport in neutral and unstable stratifications, 90th Annual Meeting of the American Meteorological Society, Atlanta, GA, January 17-21, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Large-eddy simulation of turbulent transports in urban street canyons in different thermal stabilities, 5th International Symposium on Computational Wind Engineering, Chapel Hill, North Carolina, USA, May 23 to 27, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Large-eddy simulation of ventilation and pollutant removal in neutrally and unstably stratified street canyons, American Geophysical Union Fall Meeting 2009, San Francisco, December 14-18, 2009.

Cheng W.C., Liu C.H. and Leung Y.C., On the wind statistics and pollutant re-entrainment in street canyons by large-eddy simulation, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Cheng W.C., Liu C.H. and Leung Y.C., Periodic Flow & Pollutant Removal of Street Canyon in Wind-Buoyancy-Driven Condition Using the URANS Model, ICUC-7, 29/6-3/6, 2009, Yokohama, Japan. 2009.

Cheung O.P. and Liu C.H., Effects of Building Interference on Natural Ventilation for High-Rise Residential Buildings, ISHVAC09, November, 6-9, 2009, Southeast University, Nanjing, China. 2009.

Cheung O.P., Liu C.H. and Yam M.C.H., Impact of building separation on natural ventilation behavior and performance for low-rise structures, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Chung N.H. and Liu C.H., Large-eddy simulation & k-epsilon turbulence modeling of pollutant transfer coefficient for street canyon of different aspect ratios, Western Pacific Geophysical Meeting, Taipei, Taiwan, June 22-25, 2010.

Chung N.H. and Liu C.H., Pollutant transfer coefficient in different flow regimes using large-eddy simulation, 14th Annual Conference of HKSTAM 2009-2010, Hong Kong, March 13, 2010.

Chung N.H. and Liu C.H., Pollutant transfer coefficient in street canyons of different aspect ratios, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Grimmond C.S.B., Roth M., Oke T., Au Y., Best M., Betts R., Carmichael G., Cleugh H., Dabberdt W., Emmanuel R., Fortuniak E., Hanna S., Klein P., Kalkstein L.S., Liu C.H., Nickson A., Pearlmutter D., Sailor D. and Voogt J., Climate and more sustainable cities: climate information for improved planning and management of cities (producers/capabilities perspective), World Climate Conference 3, Geneva, Switzerland, August 31 to September 4, 2009.

Liu C.H., Leung Y.C., Man A.C.S. and Chan P.W., CFD simulation of the wind flow over an airport terminal building, Journal of Zhejiang University-Science A (Appl. Phys. & Eng.). Springer, 2010, 11: 389-401.

Liu C.H., Hong Kong Institute of Engineers Transactions, Associate Editor. 2010.

Liu C.H., Cheng W.C., Leung T.C.Y. and Leung Y.C., On the mechanism of air pollutant re-entrainment in two-dimensional idealized street canyons, Atmospheric Environment. 2010.

Memon R.A., Leung Y.C. and Liu C.H., An investigation of urban heat island intensity (UHII) as an indicator of urban heating, Atmospheric Research. Elsevier, 2009, 94: 491-500.

Poon H.C.C., Liu C.H. and Jim C.Y., Modelling the environment impacts of vegetation canopies with different lengths and leave area densities in urban scale, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Poon H.C.C., Liu C.H. and Jim C.Y., Turbulent flow within and over vegetation canopy with different length and drag forces, International Conference for Applied Energy (ICAE2010), April 21-23, 2010, Singapore. 2010.

Shui P., Liu C.H. and Li Y., CFD Analysis of Pollutant Removal Mechanism in Urban Street Canyons, The 7th International Conference on Urban Climate, 29/6 to 3/7/2009, Yokohama, Japan. 2009.

Shui P., Liu C.H. and Li Y., Upward and sideward removal of air pollutants in three-dimensional street canyons, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Wong C.C. and Liu C.H., On the pollutant plume dispersion in the urban canopy layer over 2D idealized street canyons: a large-eddy simulation approach, European Geosciences Union, General Assembly 2010, Vienna, Austria, May 2-7, 2010 , 2010 . 2010.

Wong C.C. and Liu C.H., Pollutant plume dispersion in the urban canopy layer over 2D idealized street canyons, 14th Annual Conference of HKSTAM 2009/2010, Hong Kong, March 13, 2010.

Researcher : Liu F

Project Title:	Hybrid Tandem and Quantum-Dot Solar Cells
Investigator(s):	Liu F
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	11/2009

Abstract:

1.1 Motivation Quantum dots have provided a new direction for photovoltaic (PV) solar power [1]. However, there are many existing issues for this new concept. Evidently, carrier transport and collection is an important issue that nearly all nanostructure-based solar cells have [2-3]. The inherent potentials in nanostructures allow quantum confinement effect, but also introduce an energy barrier for charge carrier transportation. Plus, the conventional approach, for example, the quantum dots grown by the Stranski–Krastanov (S-K) method, introduced a lot of recombination centers due to lattice mismatch, which greatly reduces the current collection efficiency. Here, we propose a hybrid tandem and QD structure (Fig. 1) to overcome these critical issues. The basic idea is to use large electric field (E) to effectively collect the photon-generated carriers in QDs, which act as an exciton source. We propose to utilize tandem cells to generate high built-in voltage [4], which can lead to a strong electric field on QDs. The efficiency of the tandem cells is not critical for the performance of such hybrid cells. Therefore, there are a variety of low-cost materials that can be used for the tandem cells, such as amorphous materials, polycrystalline materials, and wide bandgap materials. Thus, our proposed hybrid cells should be flexible, affordable, and highly efficient. 1.2 Objective The objective of this project is to experimentally prove the concept of the hybrid tandem and QD solar cells. To be more specific, we will test the impact of the electric field on the carrier collection in QD layers. In the short term (6 month) we will apply external bias to simulate the electric field on QDs provided by the tandem cells. If the concept works, we will fabricate actual hybrid tandem and QD solar cells, carry out electrical property measurement and structural characterization, and correlate experimental results with theoretical calculations in the literature.

Project Title:	2010 Materials Research Society Spring Meeting Grain boundaries and their behaviors in upgraded metallurgical-grade silicon for photovoltaics
Investigator(s):	Liu F
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	04/2010

Abstract:

N/A

List of Research Outputs

Liu F. and Wang L., Analysis on multiplicity and stability of convective heat transfer in tightly curved rectangular duct, International Journal of Heat and Mass Transfer. 2009, 52: 5849-5866.

Liu F., Case study: Effectively utilizing e-books and databases for conducting photovoltaic research, HKU and Elsevier. 2009.

Liu F., Ranked in the top 25% group in the SETL scores in the first semester of the academic year 2009-2010 (Engineering thermodynamics MECH 2002), HKU. 2010.

Liu F., Solar Cells: An Overview, The Hong Kong University of Science and Technology . 2009.

Liu F., Solar Cells: Converting Solar Energy into Electricity, College of Materials, South China Univ of Tech. 2009.

Liu F., Solar Cells: Harnessing Energy from the Sun, ICEE (Initiative on Clean Energy & Environment) at HKU . 2010.

Liu F., Ultra-High Material-Quality Silicon Pillars on Glass, The 34th IEEE Photovoltaic Specialists Conference. 2010.

Researcher : Liu F

List of Research Outputs

Liu F. and Wang L., Analysis on multiplicity and stability of convective heat transfer in tightly curved rectangular duct, International Journal of Heat and Mass Transfer. 2009, 52: 5849-5866.

Liu F., Case study: Effectively utilizing e-books and databases for conducting photovoltaic research, HKU and Elsevier. 2009.

Liu F., Ranked in the top 25% group in the SETL scores in the first semester of the academic year 2009-2010 (Engineering thermodynamics MECH 2002), HKU. 2010.

Liu F., Solar Cells: An Overview, The Hong Kong University of Science and Technology . 2009.

Liu F., Solar Cells: Converting Solar Energy into Electricity, College of Materials, South China Univ of Tech. 2009.

Liu F., Solar Cells: Harnessing Energy from the Sun, ICEE (Initiative on Clean Energy & Environment) at HKU . 2010.

Liu F., Ultra-High Material-Quality Silicon Pillars on Glass, The 34th IEEE Photovoltaic Specialists Conference. 2010.

Researcher : Liu G

List of Research Outputs

Liu G., Formulation of Multifield Finite Element Models for Helmholtz Problems, PhD Thesis. Hong Kong, The University of Hong Kong, 2010, 1-237.

Sze K.Y., Liu G. and Fan H., Four- and eight-node hybrid-Trefftz quadrilateral finite element models, Computer Methods Applied Mechanics & Engrg. 2010, 199: 598-614.

Researcher : Liu S

List of Research Outputs

Hong L., Soh A.K., Liu S. and Lu L., Vortex structure transformation of BaTi0₃ nanoparticles through the gradient function, Journal of Applied Physics. USA, Amer. Inst. Physics, 2009, 106(2): Article no.: 024111.

Liu S., Soh A.K. and Hong L., Lateral surface induced effects on ultra-thin amorphous Co nanowire, Journal of Physics D - Applied Physics. Bristol, England, IOP Publishing, 2009, 42(21): Article No.: 215002.

Liu S., Soh A.K. and Hong L., Monte Carlo Simulation to the magnetic properties of amorphous Co nanowires, 2009 MRS Fall Meeting. 2009.

Liu S., On the Fabrication, Characterization and Simulation of One Dimensional Cobalt and Gadolinium Nanostructures, PhD Thesis. Hong Kong, The University of Hong Kong, 2009, 1-126.

Liu S., Soh A.K., Hong L. and Lu L., Surface characterization of amorphous Co_xGd_1-x nanowires and magnetic properties of their arrays, Journal of Physical Chemistry C. Washington, USA, Amer Chemical Soc., 2009, 113(39): 16934-16938.

Researcher : Luo Z

List of Research Outputs

Luo Z., Li Y. and Nazaroff W.W., Intake fraction of nonreactive motor vehicle exhaust in Hong Kong, Atmospheric Environment. 2010, 44: 1913-1918.

Researcher : Ma X

List of Research Outputs

Huang J.C., Ma X. and Huang L., Experimental study and control of noise from a window-type ventilation fan, Noise Control Engineering Journal. 2009, 57(4): 335-340.

Ma X., Ducted Fan Noise Control, M.Phil. Thesis. Hong Kong, The University of Hong Kong, 2009, 1-86.

Researcher : Ma Y

List of Research Outputs

Ma Y. and Ng C.O., Numerical simulation of steady streaming in a two-dimensional channel, Proceedings of the 14th Annual Conference of Hong Kong Society of Theoretical and Applied Mechanics, and the 7th Shanghai-Hong Kong Forum on Mechanics and Its Application, Hong Kong, March 13. Hong Kong, HKSTAM, 2010, 56.

Ng C.O. and Ma Y., Lagrangian transport induced by peristaltic pumping in a closed channel, Physical Review E. USA, American Physical Society, 2009, 80(5): 056307.

Researcher : Mak HMH

List of Research Outputs

Mak H.M.H. and Ng C.O., Effect of channel height to pattern width ratio on superhydrophobic slip flow in microchannels, Proceedings of the 14th Annual Conference of Hong Kong Society of Theoretical and Applied Mechanics, and the 7th Shanghai-Hong Kong Forum on Mechanics and Its Application, Hong Kong, March 13. Hong Kong, HKSTAM, 2010, 57.

Researcher : Malomed BA

List of Research Outputs

Pak O.S., Lam C.K., Nakkeeran K., Malomed B.A., Chow K.W. and Senthilnathan K., Dissipative solitons in coupled complex Ginzburg Landau equations, Journal of the Physical Society of Japan. 2009, 78: 084001 (8 pages).

Tsang C.H., Malomed B.A. and Chow K.W., Exact solutions for periodic and solitary matter waves in nonlinear lattices (invited article), accepted and to appear in Discrete and Continuous Dynamical Systesm, special issue on the Seville, Spain Meeting on Dynamical Systems. 2010.

Tsang C.H., Lam C.K., Malomed B.A. and Chow K.W., Solitons pinned to hot spots, European Physical Journal D, special issue on 'Dissipative Optical Solitons' (invited article). 2010, 59: 81-89.

Yan Z., Chow K.W. and Malomed B.A., Exact stationary wave patterns in three coupled nonlinear Schrodinger / Gross Pitaevskii equations, Chaos, Solitons and Fractals. 2009, 42: 3013-3019.

Researcher : Memon RA

List of Research Outputs

Memon R.A., Leung Y.C. and Liu C.H., An investigation of urban heat island intensity (UHII) as an indicator of urban heating, Atmospheric Research. Elsevier, 2009, 94: 491-500.

Researcher : Ng CO

Project Title:	A Mathcad Worksheet to Evaluate Wave Properties in Water over a Stratified Muddy Bottom
Investigator(s):	Ng CO
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	01/2008
Completion Date:	12/2009

Abstract:

This project aims:- 1. to develop a Mathcad worksheet, which provides a user-friendly interface, to aid practicing engineers in the evaluation of the engineering properties of surface gravity waves propagating in water over a stratified muddy bottom; and 2. to investigate the effects of a stratified viscoelastic bottom on the attenuation of surface waves.

Project Title:	Shear Flow over a Superhydrophobic Surface
Investigator(s):	Ng CO
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	01/2009

Abstract:

1. To develop analytical models for Stokes shear flow over various types of microstructured surfaces. 2. To derive effective slip lengths based on the Stokes shear flow model. 3. To study effects of the microstructure on the effective slip lengths.

Project Title:	A homogenization-based model for roughness-induced apparent slip
Investigator(s):	Ng CO
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2010

Abstract:

1) To apply the multiple-scale method of homogenization to low Reynolds number flow of a liquid through a porous medium of periodic micro-structure with trapped vapor: - canonical boundary-value unit-cell problems to be formulated; - effective first- and second-order macroscale equations to be deduced by volume-averaging over a unit cell; 2) To develop solution methods for the boundary-value unit-cell problems for different types of roughness (posts, or holes): - semi-analytical eigen-function expansion method with domain decomposition; - finite-element or boundary-element methods; 3) To look into the following effects on the wall slippage - texture geometry (pattern type, dimensions, etc) relative to channel depth; - curvature of liquid-vapor interfaces, or penetration of liquid into the roughness; - weak inertia (Reynolds number) of the flow; - surface gradient of the material.

Project Title:	Mass transport in directional electroosmotic flow by interactive oscillatory electrical forcings
Investigator(s):	Ng CO
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2010

Abstract:

Background:- Much of the microfluidic technology relies on flow through a channel with very fine cross-section. Experiments in past decades have explored fluid flows in ever-smaller channels, which can now be miniaturized to microns or even smaller in cross-section. There is an increasing need to look for effective ways to drive fluids through such capillaries. The flow-rate for pressure-driven (also called Poiseuille) flow through a rectangular channel decreases according to the third power of the channel depth, and hence pressure pumping may become ineffective for very narrow channels. If the fluid is an electrolyte solution (e.g., water with dissolved ionic species, or a liquid with free charge), flow may result from electrokinetic phenomena as well. A common kind of such flow, termed electroosmotic flow (EOF), is driven by an electric potential difference across the channel. EOF has typically a plug-like velocity profile, which is determined by the electrical properties but not the channel depth. Electrokinetic phenomena stem from the distribution of free charges in the electrical double layer (EDL) that forms on the fluid–solid interface. Most substances acquire a surface electric charge when brought into contact with an electrolyte. Ions of opposite charge to that of the surface (counterions) will be attracted to the surface, while ions of the same charge (coions) are repelled from the surface. Such a redistribution of free ions in the solution, together with the surface charge, give rise to a two-layer structure: a single (Stern) layer of immobile ions attached to the surface, and a diffuse layer in which there is an excess of counterions over coions to neutralize the surface charge. The electric potential on the Stern interface is known as the zeta potential. Charge neutrality is not satisfied in the double layer, and hence, in the presence of an electric field, these ions will move, generating electric current in the channel. At the same time, the electric body force will drive the bulk fluid into motion as well. Such a phenomenon is called electroosmosis. If the channel is closed, electroosmotic pressure will be induced to produce a counterbalancing flow. One-dimensional steady EOF through a channel with uniform surface charge is a classical problem with known solutions. Issues:- In recent years, attention has been increasingly paid to alternating current (AC) electrokinetic systems. They have been successfully applied to separation of colloidal species, mixing enhancement, trapping particles in designated regions in micro-devices, and so on. Despite these successful applications, many fundamental aspects about AC EOF are yet to be fully understood. There exist only limited theories that have attempted to explain the mass transport and separation mechanisms due to AC EOF as functions of the controlling factors. Recently, a mechanism has been proposed to generate a steady directional EOF due to a nonlinear interaction between oscillatory axial electrical fields and oscillatory wall (zeta) potentials. This mechanism, which is unlike those previously developed, can produce a steady parallel flow without recirculation in a microchannel. Such a potentially useful mechanism, however, needs to be further explored in terms of its performance in mass transport and separation of species. This has formed the motivation of the present proposal, which is to achieve the following objectives. Objectives:- • To build a mathematical model to describe the mass transport and separation of species due to nonlinear interaction of oscillatory electrical field and oscillatory wall potential. • To derive explicit expressions for the time-averaged effective transport coefficients for the dispersion and convection. • To generate numerical results from the model in order to look into the various physical and chemical effects on the enhancement of mass transport and separation of species resulting from the flow.

Project Title:	The 20th International Offshore (Ocean) and Polar Engineering Conference (ISOPE 2010) Rheological Properties of Some Marine Muds Dredged from China Coasts
Investigator(s):	Ng CO
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2010
Completion Date:	06/2010

Abstract:

N/A

List of Research Outputs

Chu H.C.W. and Ng C.O., Stokes shear flow of liquid over grooves filled with vapour, Proceedings of the 14th Annual Conference of Hong Kong Society of Theoretical and Applied Mechanics, and the 7th Shanghai-Hong Kong Forum on Mechanics and Its Application, Hong Kong, March 13. Hong Kong, HKSTAM, 2010, 58.

Ma Y. and Ng C.O., Numerical simulation of steady streaming in a two-dimensional channel, Proceedings of the 14th Annual Conference of Hong Kong Society of Theoretical and Applied Mechanics, and the 7th Shanghai-Hong Kong Forum on Mechanics and Its Application, Hong Kong, March 13. Hong Kong, HKSTAM, 2010, 56.

Mak H.M.H. and Ng C.O., Effect of channel height to pattern width ratio on superhydrophobic slip flow in microchannels, Proceedings of the 14th Annual Conference of Hong Kong Society of Theoretical and Applied Mechanics, and the 7th Shanghai-Hong Kong Forum on Mechanics and Its Application, Hong Kong, March 13. Hong Kong, HKSTAM, 2010, 57.

Ng C.O. and Wang C.Y., Apparent Slip Arising From Stokes Shear Flow Over a Bidimensional Patterned Surface, SAP Endowment Lecture at the International Conference on Frontiers in Fluid Mechanics, Bangalore, India, September 1. 2009.

Ng C.O. and Wang C.Y., Apparent slip arising from Stokes shear flow over a bidimensional patterned surface, Abstracts of the International Conference on Frontiers in Fluid Mechanics, Bangalore, India, August 31–September 2. 2009, 5–6.

Ng C.O. and Wang C.Y., Apparent slip arising from Stokes shear flow over a bidimensional patterned surface, Microfluidics and Nanofluidics. Heidelberg, Germany, Springer Verlag, 2010, 8(3): 361–371.

Ng C.O., Associate Editor since August 2009, HKIE Transactions. Hong Kong, HKIE, 2009.

Ng C.O., Associate Editor since September 2009, Journal of Applied Fluid Mechanics. Iran, Physical Society of Iran, 2009.

Ng C.O., Editorial Advisory Board Member, since December 2007, The Open Ocean Engineering Journal. Bentham Science Publishers, 2009.

Ng C.O., Editorial Advisory Board Member, since October 2007, The Open Oceanography Journal. Bentham Science Publishers, 2009.

Ng C.O., Homogenization Technique Applied to Problems of Taylor Dispersion, Concurrent Professorship Lecture at the Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China, July 2. 2009.

Ng C.O., Homogenization Technique Applied to Problems of Taylor Dispersion, Invited Seminar in the Department of Mechanics and Engineering Science, Fudan University, Shanghai, China, July 3. 2009.

Ng C.O., ISST Journal of Mathematics & Computer Sciences, Editorial Board Member, since November 2009. India, Intellectuals Society for Socio-Techno Welfare, 2009.

Ng C.O., ISST Journal of Mechanical Engineering, Editorial Board Member, since November 2009. India, Intellectuals Society for Socio-Techno Welfare, 2009.

Ng C.O., Invited (international) Editorial Board Committee Member, since August 2003, Journal of Hydrodynamics. Shanghai, China, Publishing House for Journal of Hydrodynamics, 2009.

Ng C.O. and Ma Y., Lagrangian transport induced by peristaltic pumping in a closed channel, Physical Review E. USA, American Physical Society, 2009, 80(5): 056307.

Ng C.O., Mechanics of Water Waves over a Viscoelastic Muddy Bed, Invited Lecture at the Tainan Hydraulics Laboratory, National Cheng Kung University, Tainan, Taiwan, December 3. 2009.

Ng C.O., Member of the Editorial Board, since July 2006, Engineering Applications of Computational Fluid Mechanics. Hong Kong, The Hong Kong Polytechnic University, 2009.

Ng C.O., Sharing My Research Experiences, Invited Talk at the Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China, July 3. 2009.

Ng C.O. and Wang C.Y., Superhydrophobic Slip Flow Over a Grating, Keynote Speech at the Sixth Shanghai-Hong Kong Forum on Mechanics and Its Application, Shanghai, China, July 4. 2009.

Ng C.O. and Wang C.Y., Superhydrophobic slip flow over a grating, Proceedings of the Sixth Shanghai-Hong Kong Forum on Mechanics and Its Application, Shanghai, China, July 4. Shanghai, China, Shanghai Society of Mechanics, 2009, 1.

Soh A.K. and Ng C.O., Co-Editors, Proceedings of the 14th Annual Conference of Hong Kong Society of Theoretical and Applied Mechanics, and the 7th Shanghai-Hong Kong Forum on Mechanics and Its Application, March 13, 2010, Hong Kong. Hong Kong, HKSTAM, 2010.

Yang J., Ng C.O. and Zhang D., A numerical study on water waves generated by a submerged moving body in a two-layer fluid system, China Ocean Engineering. Nanjing, China, Chinese Ocean Engineering Society, 2009, 23(3): 441–458.

Zhang D., Yip T.L. and Ng C.O., Predicting tsunami arrivals: estimates and policy implications, Marine Policy. Netherlands, Elsevier Science, 2009, 33(4): 643–650.

Zhang D.X., Lu Z.M., Liu Y.L. and Ng C.O., Numerical simulation of the dispersion in oscillating flows with reversible and irreversible wall reactions, Journal of Hydrodynamics, Ser. B. Shanghai, China, Publishing House for Journal of Hydrodynamics, 2009, 21(4): 482–490.

Zhang X., Bai Y.C. and Ng C.O., Rheological properties of some marine muds dredged from China coasts, Proceedings of the Twentieth (2010) International Offshore and Polar Engineering Conference, Beijing, China, June 20–25. ISOPE, 2010, 455–461.

Researcher : Ng KS

List of Research Outputs

Ng K.S. and Ngan A.H.W., Deformation of micron-sized aluminium bi-crystal pillars, Philosophical Magazine. Taylor & Francis, 2009, 89(22): 3013-3026.

Ng K.S. and Ngan A.H.W., Effect of trapping dislocations within small crystals on their deformation behavior, Acta Materialia. Elsevier Ltd., 2009, 57: 4902-4910.

Ngan A.H.W. and Ng K.S., Formability of Micro-crystals: The Efects of Dislocation Confinement, invited talk, International Conference on Processing and Manufacturing of Advanced Materials (THERMEC’2009), Maritim Hotel, Berlin, Germany, August 25-29, 2009.. 2009.

Ngan A.H.W. and Ng K.S., Transition from deterministic to stochastic deformation, Philosophical Magazine. Taylor & Francis, 2010, 90(14): 1937-1954.

Researcher : Ng KY

List of Research Outputs

Ng K.Y., Zuo L. and Ngan A.H.W., Steady-state serrated deformation of metallic glass during indentation, Scripta Materialia. Elsevier Ltd., 2009, 61: 955-958.

Researcher : Ngan AHW

Project Title:	Stress-exponent measurement of nano-grained thin-films by nanoindentation
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	09/2002

Abstract:

The project attempts to investigate the deformation mechanism of nanograined thin film by measuring the stress exponent using depth-sensing indentation and by comparing with theoretical predictions. It is proposed to systematically vary the grain-size-to-indent-size ratio to investigate its effect on the measured properties.

Project Title:	Statistical distribution, size and time dependence of initial yield strength in submicron crystals
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	09/2006

Abstract:

1 (Objective 1) To investigate the mechanism for the rapid increase of the initial yield strength of annealed crystals as size decreases in the micron to submicron regime. 2 (Objective 2) To investigate the nature and mechanism of the statistical scatter of the initial yield strength data in the micron to submicron regime. 3 (Objective 3) To study the time dependence of the initial yield strength in the micron to submicron regime.

Project Title:	Outstanding Researcher Award 2006-2007
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Outstanding Researcher Award
Start Date:	11/2007

Abstract:

Nil

Project Title:	Nano-biotechnology
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding for Strategic Research Theme
Start Date:	07/2008

Abstract:

n/a

Project Title:	Stochastic nature of plastic deformation of small materials
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	09/2008

Abstract:

1. To understand the stochastic nature of plastic deformation of bulk metallic glass materials, in terms of the statistical distribution of burst sizes, correlation between successive bursts, etc., by performing compression experiments on micron-sized columns. 2 . To investigate how the specimen size in the sub-micron regime affects the burst size distribution, by performing compression experiments on a few representative materials (both crystalline and glassy) using a nanoindenter with flat-ended punch. 3. To investigate how the initial dislocation content affects the burst size distribution in crystalline materials. 4. To perform dislocation dynamics simulation, as well as Monte-Carlo based finite-element simulation, to investigate theoretically the dependence of the burst distribution on specimen size, in both crystalline and glassy cases respectively.

Project Title:	Microstructure and Mechanical properties of metal nano-wires
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Travel Grants for NSFC/RGC JRS
Start Date:	12/2008

Abstract:

Travel grants for NSFC/RGC JRS

Project Title:	Bio-nanomechanics Laboratory
Investigator(s):	Ngan AHW, Luk KDK, Lu WW, Wang M, Chan BP, Tang B
Department:	Mechanical Engg
Source(s) of Funding:	UGC One-off Special Equipment Grant Scheme
Start Date:	12/2008

Abstract:

1) A nanoindenter with a larger displacement stroke, suitable for testing in a wide variety of environments for biological specimens, such as immersion in fluid cells; 2) a nano-tensile tester

Project Title:	Mechanical Behaviour of Composite Micro-Pillars
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	04/2009

Abstract:

As revealed by recent experiments, micro-samples behave differently from their bulk counterparts in several aspects: (i) the yield strength increases as the pillar size decreases [1-10,12,13], (ii) the post-yield stress-strain behavior is jerky, with stochastic large strain bursts separated by elastic-like deformation [1-13], (iii) the dislocation density undergoes insignificant change after deformation [8, 12], and (iv) aluminium micro-pillars creep under constant load by the sporadic emission of bursts, in addition to a steady-state component that is 1 to 2 orders of magnitude slower than the bulk creep rate [11, 13]. For (i), if the specimen contains no or only a small quantity of initial dislocations, the size dependence of strength may be describable by a statistical model for homogeneous dislocation nucleation [19-20]. If dislocations pre-exist, the mean length of half-Frank-Read sources is expected to be shorter in a smaller sample, and so the yield strength is expected to be higher [16-18]. The size dependence of strength and the jerky flow are also predicted by dislocation dynamics [17-18, 23-25]. (ii) and (iii) are also in qualitative agreement with a “dislocation starvation” concept [6-8], in which the dislocations responsible for each burst zip through the crystal quickly, and hence the crystal returns to a “starved” state after each burst. Apart from the experimental evidence [8,12] mentioned above, that the dislocation density undergoes insignificant change was also confirmed by simulations [23], but whether this is true in a wider context, for example in different materials, needs to be confirmed by further studies. An analysis of the bursting probability also revealed that dislocation sources become successively exhausted as more bursts have been emitted [24]. The burst sizes were also found to exhibit power-law distributions [2, 4, 12], and to increase approximately exponentially with stress [12, 13]. For (iv), the stochastic and low steady-state creep rate was suggested to be due to the scattering and depletion of dislocations [11]. The above background suggests that, although small crystalline specimens are strong, their deformation is jerky under normal loading or creep conditions. The jerky deformation imposes great challenges to metal forming in the micro scale, since shape control would be impossible. As reviewed above, the jerky deformation of micro-specimens is possibly due to the fact that dislocations once generated inside the specimen can zip through it quickly, thus leaving the specimen in a more or less the same state as before. If this conjecture is true, then confining the dislocations within the specimen should smoothen the deformation and alleviate the problems in forming. One practical way to confine dislocations in a micro-specimen is to apply some foreign phase along the length of the specimen to form a micro-composite. The second phase can then prevent the dislocations from escaping from the micro-specimen. In this work, it is thus proposed to investigate the mechanical behaviour of micro-composites, in particular to study the post-yield behaviour, and the microstructure-property relation. References [1] M.D. Uchic, D.M. Dimiduk, J.N. Florando, W.D. Nix, Science 305 (2004) 986. [2] D.M. Dimiduk, M.D. Uchic, T.A. Parthasarathy, Acta Mater. 53 (2005) 4065. [3] M.D. Uchic, D.M. Dimiduk, Mater. Sci. Eng. A 400 (2005) 268. [4] D.M. Dimiduk, C. Woodward, R. LeSar, M.D. Uchic, Science 312 (2006) 1188. [5] D.M. Dimiduk, M.D. Uchic, S.I. Rao, C. Woordward, T.A. Parthasarathy, Modelling Simul. Mater. Sci. Eng. 15 (2007) 135. [6] J.R. Greer, W.C. Oliver, W.D. Nix, Acta Mater. 53 (2005) 1821. [7] J.R. Greer, W.D. Nix, Appl. Phys. A 80 (2005) 1625. [8] J.R. Greer, W.D. Nix, Phys. Rev. B 73 (2006) 245410. [9] C.A. Volkert, E.T. Lilleodden, Philo. Mag. 33 (2006) 5567. [10] N. Afrin, A.H.W. Ngan, Scripta Mater. 54 (2006) 7. [11] K.S. Ng, A.H.W. Ngan, Philos. Mag. Letts. 87 (2007) 967. [12] K.S. Ng, A.H.W. Ngan, Acta Mater. (2008) doi:10.1016/j.actamat.2007.12.016. [13] K.S. Ng, A.H.W. Ngan, submitted to Modelling Simul. Mater. Sci. Eng. (2008). [14] A.H.W. Ngan, L. Zuo, P.C. Wo, Proc. Phys. Soc. 462 (2006) 1661. [15] L. Zuo, A.H.W. Ngan, Philos. Mag. Letts. 86 (2006) 355. [16] T.A. Parthasarathy, S.I. Rao, D.M. Dimiduk, M.D. Uchic, R. Trinkle, Scripta Mater. 56 (2007) 313. [17] S.I. Rao, D.M. Dimiduk, M. Tang, T.A. Parthasarathy, M.D. Uchic, C. Woodward, Philos. Mag. 87 (2007) 4777. [18] A.A. Benzerga, N.F. Shaver, Scripta Mater. 54 (2006) 1937. [19] H. Tang, K.W. Schwarz, H.D. Espinosa, Acta Mater. 55 (2007) 1607. [20] F. Barlat, M.V. Glazov, J.C. Brem, D.J. Lege, Int. J. Plast. 18 (2002) 919. [21] D. Weygand, M. Poignant, P. Gumbsch, O. Kraft, Mater. Sci. Eng. A. 2007;doi:10.1016/j.msea.2006.09.183. [22] D.S. Balint, V.S. Deshpande, A. Needleman, Van der Giesssen E, Modelling Simul. Mater. Sci. Eng. 14 (2006) 409. [23] P.J. Guruprasad, A.A. Benzerga, J. Mech. Phys. Solids 56 (2008) 132. [24] K.S. Ng, A.H.W. Ngan, Philos. Mag. 88 (2008) 677.

Project Title:	Thermec 2009 International Conference on Processing & Manufacturing of Advanced Materials FORMABILITY OF MICRO-CRYSTALS: THE EFFECTS OF DISLOCATION CONFINEMENT
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	08/2009
Completion Date:	08/2009

Abstract:

N/A

Project Title:	Mechanical properties of submicron-sized materials and bio-tissues
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Croucher Senior Research Fellowships in Natural Sciences, Technology and Medicine
Start Date:	09/2009

Abstract:

Refer to hard copy

List of Research Outputs

Aladin K.D.M., Cheung K.M.C., Ngan A.H.W., Chan D., Leung Y.L., Lim C.T., Luk K.D.K. and Lu W.W., Nanostructure of Collagen Fibrils in Human Nucleus Pulposus and Its Correlation with Macroscale Tissue Mechanics, J. Ortho. Res.. 2009, 28: 497-502.

Aladin Kaderbatcha D.M., Cheung K.M.C., Ngan A.H.W., Chan D., Leung Y.L., Lim C.T., Luk K.D.K. and Lu W.W., Nano-structure of collagen fibrils in human nucleus pulposus and its correlation with macroscale tissue mechanics, Journal of Orthopedic Research. 2010, 28: 497-502.

Chan B.P., Li C.H., Au-yeung K.L., Sze K.Y. and Ngan A.H.W., Research Output Prize 2009, Faculty of Engineering. 2009.

Chan Y.L., Ngan A.H.W. and King N.M., Degraded prism sheaths in the transition region of hypomineralized teeth, Journal of Dentistry. 2010, 38: 237-244.

Chan Y.L. and Ngan A.H.W., Invariant elastic modulus of viscoelastic materials measured by rate-jump tests, Polymer Testing. Elsevier Ltd., 2010, 29: 558-564.

Li C.H., Ngan A.H.W., Sze K.Y. and Chan B.P., Association between elastic modulus and extracellular matrix components of collagen-mesenchymal stem cell microsphres during chondrogenic differentiation. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. (Best Poster Presentation Award). 2009, S210:795.

Li J. and Ngan A.H.W., Nanoscale fast relaxation events in polyethylene, Scripta Materialia. Elsevier Ltd., 2010, 62: 488-491.

Lu W.W., Aladin Kaderbatcha D.M., Cheung K.M.C., Ngan A.H.W., Chan D., Leung Y.L., Lim C.T. and Luk K.D.K., Correlation between the nano-structure and macro-mechanics of human nucleus pulposus, Combined SICOT/RCOST 2009 Annual Meeting, Pattaya, Thailand, October 29-November 1, 2009.

Ng K.S. and Ngan A.H.W., Deformation of micron-sized aluminium bi-crystal pillars, Philosophical Magazine. Taylor & Francis, 2009, 89(22): 3013-3026.

Ng K.S. and Ngan A.H.W., Effect of trapping dislocations within small crystals on their deformation behavior, Acta Materialia. Elsevier Ltd., 2009, 57: 4902-4910.

Ng K.Y., Zuo L. and Ngan A.H.W., Steady-state serrated deformation of metallic glass during indentation, Scripta Materialia. Elsevier Ltd., 2009, 61: 955-958.

Ngan A.H.W., Developments in Microscopy, invited talk in a meeting to celebrate the 80th birthday of Prof. R.E. Smallman CBE, FRS, FREng, and the 70th birthday of Prof. I. R. Harris FREng, University of Birmingham, July 31 – August 1, 2009. . 2009.

Ngan A.H.W. and Ng K.S., Formability of Micro-crystals: The Efects of Dislocation Confinement, invited talk, International Conference on Processing and Manufacturing of Advanced Materials (THERMEC’2009), Maritim Hotel, Berlin, Germany, August 25-29, 2009.. 2009.

Ngan A.H.W. and Tang B., Nanoindentation using atomic force microscope, extended invited talk, ECI Conference on Nanomechanical Testing in Materials Research and Development, October 11-16, 2009, Il Ciocco Hotel and Conference Center, Barga (Tuscany), Italy.. 2009.

Ngan A.H.W., Stochasticity in material elastostatics and deformation, invited talk, in Session “Modelling complex microstructures: materials behavior below the scale of the representative volume element”, 7th International Conference of Numerical Analysis and Applied Mathematics 2009 (ICNAAM 2009), Hotel Aquila Rithymna Beach, 18-22 September, 2009, Rethymno, Crete, Greece.. 2009.

Ngan A.H.W. and Ng K.S., Transition from deterministic to stochastic deformation, Philosophical Magazine. Taylor & Francis, 2010, 90(14): 1937-1954.

Researcher : Ni M

List of Research Outputs

Xuan J., Leung M.K.H., Leung Y.C. and Ni M., A review of biomass-derived fuel processors for fuel cell systems, Renewable and Sustainable Energy Reviews. 2009, 13: 1301-1313.

Researcher : Pak OS

List of Research Outputs

Pak O.S., Lam C.K., Nakkeeran K., Malomed B.A., Chow K.W. and Senthilnathan K., Dissipative solitons in coupled complex Ginzburg Landau equations, Journal of the Physical Society of Japan. 2009, 78: 084001 (8 pages).

Researcher : Poon HCC

List of Research Outputs

Poon H.C.C., Liu C.H. and Jim C.Y., Modelling the environment impacts of vegetation canopies with different lengths and leave area densities in urban scale, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Poon H.C.C., Liu C.H. and Jim C.Y., Turbulent flow within and over vegetation canopy with different length and drag forces, International Conference for Applied Energy (ICAE2010), April 21-23, 2010, Singapore. 2010.

Researcher : Qian H

List of Research Outputs

Qian H. and Li Y., Removal of exhaled particles by ventilation and deposition in a multibed airborne infection isolation room, Indoor Air. 2010, 20: 284-297.

Researcher : Rogers CW

List of Research Outputs

Lai D.W.C., Chow K.W., Rogers C.W. and Yan Z., Anti-dark solitons and periodic solutions of the resonant nonlinear Schrodinger equation, Advances in Nonlinear Waves and Symbolic Computations. Nova, 2009, 101-110.

Tang X., Chow K.W. and Rogers C.W., Propagating wave patterns for the 'resonant' Davey - Stewartson system, Chaos, Solitons and Fractals. 2009, 42: 2707-2712.

Researcher : Shabayek AAE

Project Title:	11th International Association of Management of Technology Conference (IAMOT) Government's Support for Small & Medium Enterprises (SMEs) for Prospering Hong Kong Economy: Impacts of Globalization & China Joining WTO
Investigator(s):	Shabayek AAE
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	03/2002

Abstract:

N/A

Researcher : Shi Y

List of Research Outputs

Shi Y., Hong L. and Soh A.K., 3-D ferroelectric domain reversal mechanism , The 14th Annual Conference of HKSTAM 2009-2010 cum The 7th Shanghai – Hong Kong Forum on Mechanics and Its Application . HKSTAM, 2010, 1: 36.

Researcher : Shu J

Project Title:	The Fourth International Conference on Hydrodynamics Impact of Breaking Wave on a Wall
Investigator(s):	Shu J
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	09/2000

Abstract:

N/A

Project Title:	International Conference on Applied Mathematics The Additivity of the Soliton Equation and Exact N-Envelope-Soliton Solutions of the Hirota Equation
Investigator(s):	Shu J
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	09/2000

Abstract:

N/A

Researcher : Shui P

List of Research Outputs

Shui P., Liu C.H. and Li Y., CFD Analysis of Pollutant Removal Mechanism in Urban Street Canyons, The 7th International Conference on Urban Climate, 29/6 to 3/7/2009, Yokohama, Japan. 2009.

Shui P., Liu C.H. and Li Y., Upward and sideward removal of air pollutants in three-dimensional street canyons, 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Paris, France, June 1-4, 2010.

Researcher : Soh AK

Project Title:	International Conference on Materials for Advanced Technologies 2007 Phase field simulation of surface roughening of heteroepitaxial films
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	07/2007

Abstract:

N/A

Project Title:	Development and application of a novel mesoscopic theory for the study of semiconducting ferroelectrics with crystal defects
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2008

Abstract:

(1) Establishment of a mesoscopic theoretical framework to incorporate the effect of charge-carrying defects of wide-band-gap semiconductors. (2) Theoretical analyses and numerical simulations of the domain structures and their evolutions in ferroelectrics. (3) Theoretical analyses and numerical simulations of the interfacial and surface effects in ferroelectrics. (4) Characterization of the domain and interfacial effects in ferroelectrics to provide experimental data for validation of the results obtained from the established theoretical model and numerical simulation.

Project Title:	Adhesive contact mechanics and its applications in biomechanics
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	04/2008
Completion Date:	03/2010

Abstract:

After a long period of evolution and development, many animals have achieved very special abilities in nature, such as navigation, identification, locomotion, synthesis and decomposition that the human being is inferior to, and many researchers were very surprised by their refinement, delicacy, speediness, high efficiency, reliability and immunity. Scientists have realized that nature has provided us many excellent examples for developing science and technology, and it is possible to learn from the nature and establish methods to solve difficult problems that we are encountering, such as energy sources, communications, materials and information. Many admirable solutions can be found from the nature, which explains why the subjects of biomechanics and biomimetics have caught the attention of the scientists. This is why more and more scientists in the fields of mechanics, materials, physics, chemistry and biology et al. have been attracted to the said topics of research. One of the special skills possessed by many animals and insects, such as geckos, spiders, flies, ants and grass hoppers, is adhesion that enables them not only to stay on a vertical wall, but also hung up-side-down on a ceiling. Among hundreds of animal species for which adhesion plays an important role for survival, gecko stands out in terms of body weight and its extraordinary ability to maneuver on vertical walls and ceilings. The tissue on gecko’s feet is made of hundreds of thousands of keratinous hairs called setae, the tips of which further contain hundreds of smaller hairs called spatulae with typical diameters on the order of a few hundred nanometers [1, 2]. While geckos and some insects have adopted hairy tissues, some other insects have smooth tissues [3]. Due to the proposed Johnson–Kendall–Roberts (JKR) model [4], contact mechanics theories have been widely used to investigate adhesion mechanisms [5-12]. The objective of this proposal is not only to develop the adhesive contact mechanics for visco-elastic materials and determine the factors influencing the adhesion force and adhesion strength, but also to investigate the adhesion mechanisms in biology and suggest possible designs for engineering applications. The sub-objectives of this project are as follows: (1) To achieve a better understanding of the influences of adhesion for fibrillar adhesive structure and determine an optimum geometry of the fibrillar structure for obtaining the desired adhesion force. While the adhesion of single seta in bio-adhesion system is robust, the condition of robust adhesion for fibrillar structures remains unclear. Moreover, the effects of the surface roughness and environmental humidity on the adhesion of fibrillar structures have yet to be explored. The geometry of a fibrillar adhesion system will be designed based on the above-mentioned factors. (2) To develop adhesive contact mechanics of visco-elasticity. Contact mechanics theories have been widely used to study adhesion mechanisms in both engineering and biology. Biological materials in general and attachment systems in particular exhibit pronounced visco-elastic effects, which require a more complete analysis using visco-elastic contact mechanics. (3) To understand the function of visco-elasticity in bio-adhesion. Several key issues and problems will be studied, such as the effect of visco-elasticity on the adhesion of single seta and fibrillar structures, the typical pull-off time for bio-adhesion system and the difference between elasticity and visco-elasticity adhesions in biology. (4) To propose some possible designs for engineering applications, such as biomimetic adhesive materials and adhesion sensors. References: [1] Autumn, K., Liang, Y.C., Hsieh, S. T., Zesch, W., Chan, W. P., Kenny, T. W., Fearing, R., Full, R.J., 2000. Adhesion forces of a single gecko foot-hair. Nature 405, 681-685. [2] Autumn, K., Sitti, M., Liang, Y.C., Peattie, A.M., Hansen, W.R., Sponberg, S., Kenny, T.W., Fearing, R., Israelachvili, J.N., Full, R.J., 2002. Evidence for van der Walls adhesion in gecko setae. Proc. Natl Acad. Sci. USA 99, 12252-12256. [3] Slifer, E.H., 1950. Vulnerable areas on the surface of the tarsus and pretarsus of the grasshopper (Acrididae, Orthoptera) with special reference to the arolium. Ann. Entomol. Soc. Am. 43, 173-188. [4] Johnson, K.L., Kendall, K., Roberts, A. D., 1971. Surface energy and the contact of elastic solids. Proc. R. Soc. A 324, 301–313. [5] Chen, S.H., Soh, A.K., 2007. Tuning the geometrical parameters of biomimetic fibrillar structures to enhance adhesion. Proc. R. Soc. Interface doi:10.1098/ rsif.2007.1121. [6] Artz, E., Gorb, S., Spolenak, R., 2003. From micro to nano contacts in biological attachment devices. Proc. Natl Acad. Sci. USA 100, 10603-10606. [7] Persson, B.N.J., 2003. Nanoadhesion. Wear 254, 832-834. [8] Glassmaker, N.J., Jagota, A., Hui, C.Y., Kim, J., 2004. Design of biomimetic fibrillar interface: 1. making contact. J. R. Soc. Interface 1, 23-33. [9] Hui, C.Y., Glassmaker, N.J., Tang, T., Jagota, A., 2004. Design of biomimetic fibrillar interface: 2. mechanics of enhanced adhesion. J. R. Soc. Interface 1, 35-48. [10] Gao, H., Wang, X., Yao, H., Gorb, S., Arzt, E., 2005. Mechanics of hierarchical adhesion structures of gecko. Mech. Mater. 37, 275-285. [11] Huber, G., Gorb, S., Spolenak, R., Artz, E., 2005. Resolving the nanoscale adhesion of individual gecko spatulae by atomic force microscopy. Biol. Lett. 1, 2-4. [12] Chen, S., Gao, H., 2007. Bio-inspired mechanics of reversible adhesion: orientation-dependent adhesion strength for non-slipping adhesive contact with transversely isotropic elastic materials. J. Mech. Phys. Solids 55, 1001-1015.

Project Title:	Mesoscopic study of magnetoelectroelastic coupling in multiferroic materials
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2009

Abstract:

1. Derivation of the fundamental solution for the distribution of electric and magnetic fields in a multiferroic material induced by point electric or magnetic charges, or by coupled magnetoelectric inclusions, which will serve as the cornerstone for the mesoscopic analysis of multiferroic materials. 2. Establishment of a mesoscopic theoretical framework to investigate the configurations and evolution of coupled magnetoelectric domains in multiferroic materials and the resulted cross-field switching, using thermodynamic principles and variational approach. 3. Application of the developed theoretical framework to investigate the coupled domain and cross-field switching in single-phase multiferroic crystal, the interfacial coupling and size effect in multiferroic superlattice, and the nanoscale cluster and morphotropic phase boundary in multiferroic solid solutions. 4. Fabrication and characterization of multiferroic thin films to provide experimental data for validation of the results obtained from the established theoretical model and numerical simulation.

Project Title:	Design and analysis of environmental friendly lead-free ferroelectric ceramics
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	05/2009

Abstract:

Ecological restrictions in many parts of the world are demanding the elimination of Pb from all consumer items. This prohibitive trend places the ceramics industry in a precarious position, as it has been for 50 years and remains entirely dependent on Pb-based perovskites for high piezoelectric applications. At this moment in the piezoelectric ceramics industry, there is no issue of more importance than the transition to lead free materials. Hundreds of companies worldwide are searching for answers on how to successfully make this transition. Many prior investigations have failed to develop high performance piezoelectric ceramics and the electrical properties of all the known nonlead materials have been inferior as compared to that of Pb(Zr,Ti)O3 (PZT). However, in the last few years, high piezoelectric properties have been discovered by Japanese Scientists in modified (Na1/2Bi1/2)TiO3–(K1/2Bi1/2)TiO3 (NBT-KBT), (Na1/2Bi1/2)TiO3–BaTiO3 (NBT-BT) and (Na0.5K0.5)NbO3 (KNN) ceramics of compositions close to a morphotrophic phase boundaries (MPBs) that possess significant degrees of grain orientation. Investigations have shown that {100} grain-orientation in these MPB ceramic systems results in significantly enhanced dielectric and piezoelectric properties [1-3]. This is a most important and timely discovery, about which much research and development remains to be done. It is unfortunately true for a period of over 40 years after the discovery of PZT that the community was unaware of the subtleties of the MPB in PZT. For all that time, the MPB was thought to be a near-vertical boundary in the composition-temperature (x-T) field, separating structurally similar phases that were distorted from each other, i.e., rhombohedral (R) and tetragonal (T). Only recently, a low temperature monoclinic phase near the MPB was discovered [4-6], and its strong role in the exceptional PZT piezoelectric properties explained [7]. In lieu of this discovery first principle investigations and theoretical models explaining the phenomenon for the enhancement of piezoelectricity at the MPB in Pb-based systems have been reformulated. For the new non-lead systems it is very important not to repeat this ignorance and to fully explore the family of stable and metastable phases, which may be associated with morphotropy in each case. This is significant because the polarization mechanism and chemical bonding differs from the Pb-based systems. The recent discovery of {100} grain-oriented NBT-KBT, NBT-BT and KNN ceramics for compositions close to the MPB may also be the result of ‘domain-engineered’ states, whose structural origins are as yet unidentified, and which may in fact be quite different than those previously reported in Pb-based perovskites. In order to elucidate the mechanism for high piezo responses in the non-Pb systems, it is important to develop a structural understanding of induced phase transitions in the MPB region of non-Pb-based systems; determine the presence of intermediate bridging phases under applied electric fields, and relate any such changes to the mechanism of enhanced piezoelectricity; and investigate the domain structure at various length scales. Over the period of 45 years after the discovery of PZT, there has been no other material reported in the literature which has the potential to replace the lead-based piezoelectric family until recently. Therefore, the objectives of the proposed project are: (i) Determination of the mechanism by which high piezoelectricity is achieved in non-Pb materials, and identification of the similarities and differences between MPBs in non-Pb and Pb-based systems. (ii) Employment of this understanding for optimization of piezoelectric properties in non-Pb systems. (iii) Search of the lead-free material system with strong piezoelectricity. References: 1. Fukuchi, E., Kimura, T., Tani, T. and Takeuchi, T., “Effect of potassium concentration on the grain orientation in bismuth sodium potassium titanate”, Journal of the American Ceramic Society, 85, 1461, (2002). 2. Kimura, T., Fukuchi, E., Takahashi, T. and Tani, T., “Factors Determining Crystallographic Texture in Bi1/2Na1/2TiO3-Based Piezoelectric Ceramics Made by Reactive Templated Grain Growth Method”, Ceramic Transactions, 150, Ed. Nair, K.M., Bhalla, A.S., Hirano, S.-I., Suvorov, D., Zhu, W. and Schwartz, R., (2004). 3. Tani, T., “Crystalline-oriented Piezoelectric Bulk Ceramics with a Perovskite-Type Structure”, J. Korean Phys. Soc., 32, 1217, (1998). 4. Noheda, B., Cox., D.E., Shirane, G., Gonzalo, J.A., Cross, L.E. and Park, S.E., Appl. Phys. Lett., 74, 2059, (1999). 5. Noheda, B., Cox, D.E., Shirane, G., Guo, R., Jones, B. and Cross, L.E., Phys. Rev. B, 63, 014103, (2000). 6. Noheda, B., Gonzalo, H.A., Cross, L.E., Guo, R., Park, S.E., Cox, D.E. and Shirane, G., Phy. Rev. B, 61, 8687, (2000). 7. Guo, R., Alberta, E., Thomas, A., Jones, B. and Cross, L.E., Ferroelectrics, 270, 265, (2002).

Project Title:	Development of nanoscale electro-mechanical coupling theory and functional design of nanoferroelectrics
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2010

Abstract:

(A) Purpose With the rapid development of nano-fabrication technology and miniaturization of sub-micron devices, nanoferroelectric devices, which are the important functional devices in nano-electro-mechanical systems (NEMS), have attracted the attention of many researchers. However, despite the fact that there have been vast improvements in material fabrication, theoretical modeling, numerical simulation and experimental characterization, many problems remain unresolved because of the complexity at nano-scale, such as constitutive relations, electro-mechanical coupling, depolarization, mechanical constraints on electric dipoles, etc. Moreover, although the existing theories and computational methods can be used to study the properties of nanoferroelectric devices, they encounter difficulties in effective prediction of the properties and providing guidance for optimization design. Thus, there is an urgent need to develop new theories and highly efficient simulation methods to better understand the size, surface, interfacial and mechanical constraint effects on nanoferroelectrics. (B) Key issues and problems being addressed Ultrathin ferroelectric films, ferroelectric nanowires and superlattices are the basic elements of nanoferroelectric devices, which are significantly affected by the thickness, surface, interfacial and mechanical constraint effects arising from nano-scale characteristics. Nanoferroelectric devices possess different dielectric, piezoelectric and ferroelectric properties, etc. compared with those of macroferroelectrics. Based on these unique properties, it is possible to design nano-electro-mechanical systems that possess ultrahigh storage density and ultra-sensitive transduction. For examples: (1) the storage density of ultrathin ferroelectric films could be 1 million times larger than that of the presently available devices. The research on ferroelectric nanowires demonstrated that the storage density would be increased to 1,000,000TB/cm3, which was 10 billion times larger than that of the present time. Ferroelectric superlattices have also illustrated their great potential in the application of high density storage. The superlattice dielectric constant was larger than 600 in the temperature range of 0~200 Deg. C. (2) The resolution of ultrasonic image was inversely proportional to the resonant frequency. The ultrasonic resolution could reach 20μm at 100MHz. The resonant frequency of ferroelectric superlattices was inversely proportional to the period of superlattice and was independent of the total thickness. It is easier for such superlattices to achieve ultrasonic excitation between 200MHz and 1GHz or even up to 10GHz. There is no doubt that ferroelectric superlattices provide a new development direction for fabrication of medical ultrasonic transducers with high resonance, bandwidth, sensitivity and power. (3) Nano-cantilever biosensors can be used to determine the mass of individual virus particles by detecting resonant frequency or deformation mode. However, the high precision of nano-cantilever biosensors could be affected by heat movement and environmental noise in resonance mode, and a complex optical system is required to ensure high precision measurement in the deformation mode. Our hypothesis is that a ferroelectric nanowire can be used as a cantilever biosensor, whose deformation data could be obtained by outputting voltage. Thus, single bio-molecule inspection can be realized without using a complex optical system. (C) Project Objectives 1. Preparation and characterization of nanoferroelectrics Ultrathin ferroelectric films, ferroelectric wires and superlattices will be fabricated, and their properties (Curie temperature, remanent polarization, coercive electric field, piezoelectric coefficient, depolarization, fatigue resistance) will be measured, which are significantly influenced by various factors, such as temperature, stress, size and absorption of atoms on the surface of the materials. The aim is to establish a standard for characterizing the properties of nanoferroelectrics, and to provide reliable experimental data for verifying our new nanoscale electro-mechanical coupling theory, and for designing and optimizing functional nanodevices. 2. Establishment of nanoscale electro-mechanical coupling theory At nanoscale, the surface effect and mechanical constraint on the ferroelectric properties become critical and the properties of nanodevices, such as Curie temperature, remanent polarization, piezoelectric coefficient, and coercive electric field, are size dependent. These phenomena are strongly correlated to the application of nanoferroelectric memories, actuators, nanosensors, etc. But the existing macroscale electro-mechanical coupling theories are no longer valid at nanoscale and, thus, they cannot be used to predict the said properties. Therefore, a general nano-electro-mechanical coupling theory (Lattice Model and a highly efficient electro-mechanical coupling atomic finite element method (EMC-AFEM)) will be developed to comprehensively study the novel physical properties of nanoferroelectrics and to meet the urgent requirement of carrying out functional design of nanoferroelectrics. On the other hand, due to the limitation of computational scale, the molecular dynamics (MD) and first principle methods are not suitable for simulation of nanoferroelectric properties or for application in functional design of nanoferroelectric devices. In order to overcome the said problem, an AFEM software incorporated with the capability of multifunctional design will be developed to simulate the properties of complex nanoferroelectrics and, hence, optimize the working conditions and parameters of NEMS. 3. Functional designs and optimization of device performance. Based on the experimental findings and the comprehensive understanding of nanoferroelectric properties, new functional designs for NEMS will then be proposed and simulated to optimize their properties. For example, by adjusting the thickness and the residual stress, which is caused by the misfit between the ultrathin film and the substrate, high polarization stability and long-life ferroelectric memories with ultrahigh storage density could be obtained. In addition, by making use of the sensitive electro-mechanical coupling properties of ferroelectric nanowires, new designs for NEMS, such as electromechanical tweezers that can pick up, store and release atoms or molecules in a controlled manner, and pressure, temperature, electrical or chemical sensors, will be proposed and simulated. Based on ferroelectric superlattices, various designs, such as ferroelectric memory devices that can work in large temperature range, actuators that can be actively controlled and infrared detector arrays that are much more sensitive to temperature than the existing types, will also be proposed. Our aim is to design basic nanodevices of optimal performance for NEMS.

Project Title:	14th INTERNATIONAL CONFERENCE ON APPLIED MECHANICS AND MECHANICAL ENGINEERING (AMME-14) Phase field simulation of ferroelectrics with defects
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	05/2010
Completion Date:	05/2010

Abstract:

N/A

List of Research Outputs

Chen X. and Soh A.K., On the inverse phase characteristics of Gaussian beams in negative refractive index materials, Journal of Optics A - Pure and Applied Optics. Bristol, England, IOP Publishing, 2009, 11(10): Article No.: 105101.

Hong L. and Soh A.K., Control of domain states in individual PbTiO3 nanoparticles by prescribed strains , Materials Structure & Micromechanics of Fracture (MSMF6). VUTIUM Brno, 2010, 1: 67.

Hong L., Soh A.K., Liu S. and Lu L., Vortex structure transformation of BaTi0₃ nanoparticles through the gradient function, Journal of Applied Physics. USA, Amer. Inst. Physics, 2009, 106(2): Article no.: 024111.

Hong L. and Soh A.K., Vortex structure transformation of BaTiO3 nanoparticles through the gradient function by phase field method, 2009 MRS Fall Meeting. 2009.

Li F.X., Zhou X.L. and Soh A.K., An optimization-based "phase field" model for polycrystalline ferroelectrics, Applied Physics Letters. USA, Amer. Inst. Physics, 2010, 96(15): Article No.: 152905.

Li F.X. and Soh A.K., An optimization-based computational model for domain evolution in polycrystalline ferroelastics, Acta Materialia. Oxford, England, Pergamon-Elsevier Sci., 2010, 58(6): 2207-2215.

Liu S., Soh A.K. and Hong L., Lateral surface induced effects on ultra-thin amorphous Co nanowire, Journal of Physics D - Applied Physics. Bristol, England, IOP Publishing, 2009, 42(21): Article No.: 215002.

Liu S., Soh A.K. and Hong L., Monte Carlo Simulation to the magnetic properties of amorphous Co nanowires, 2009 MRS Fall Meeting. 2009.

Liu S., Soh A.K., Hong L. and Lu L., Surface characterization of amorphous Co_xGd_1-x nanowires and magnetic properties of their arrays, Journal of Physical Chemistry C. Washington, USA, Amer Chemical Soc., 2009, 113(39): 16934-16938.

Shi Y., Hong L. and Soh A.K., 3-D ferroelectric domain reversal mechanism , The 14th Annual Conference of HKSTAM 2009-2010 cum The 7th Shanghai – Hong Kong Forum on Mechanics and Its Application . HKSTAM, 2010, 1: 36.

Soh A.K. and Ng C.O., Co-Editors, Proceedings of the 14th Annual Conference of Hong Kong Society of Theoretical and Applied Mechanics, and the 7th Shanghai-Hong Kong Forum on Mechanics and Its Application, March 13, 2010, Hong Kong. Hong Kong, HKSTAM, 2010.

Soh A.K., Zhao X. and Song Y., Crack tip domain switching in normal and relaxor ferroelectrics subjected to mechanical and electric loading , 5th International Conference on Materials for Advanced Technologies 2009 . 2009.

Soh A.K., HKU Overseas Fellowship Awards 2010-11, The University of Hong Kong. 2010.

Soh A.K., Mesoscopic studies of ferroelectric/ferromagnetic materials with defects , Invited lecture held in Nanyang Technological University (Singapore). 2010.

Soh A.K., Phase field simulations of normal and relaxor ferroelectrics, Invited lecture held in National University of Singapore. 2009.

Soh A.K., Visiting Professorship, Brown University (USA). 2010.

Soh A.K., Visiting Scientist, Nanyang Technological University (Singapore). 2010.

Tan X. and Soh A.K., Comment on "A simple and powerful analytical model for MEMS piezoelectric multimorphs", In: WE Booij, AH Vogl, DT Wang, F. Tyholdt, NP Stbo, H. R'der and K. Prume, Journal of Electroceramics. Dordrecht, Netherlands, Springer, 2010, 24(4): 313.

Tang M. and Soh A.K., Simulation of a Bio-adhesion System with Viscoelasticity , 8th International Conference on Fracture and Strength of Solids. 2010.

Tang M. and Soh A.K., Study of adhesion mechanism in gecko’s foot hair by FEM , The 14th Annual Conference of HKSTAM 2009-2010 cum The 7th Shanghai – Hong Kong Forum on Mechanics and Its Application . HKSTAM, 2010, 1: 37.

Zhao X., Soh A.K., Lu L. and Liu J.X., Influence of dipole defects on polarization switching in the vicinity of a crack in relaxor ferroelectrics, Philosophical Magazine Letters. Oxon, England, Taylor & Francis, 2010, 90(4): 251-260.

Zhao X. and Soh A.K., Phase field simulation of ferroelectrics with cracks, 8th International Conference on Fracture and Strength of Solids. 2010, 1: 117.

Zheng D.L., Chen S.D., Soh A.K. and Ma Y., Molecular dynamics simulations of glide dislocations induced by misfit dislocations at the Ni/Al interface, Computational Materials Science. Amsterdam, Netherlands, Elsevier Science BV, 2010, 48(3): 551-555.

Zhou J.X., Huang G.Y., Li M.E. and Soh A.K., Stress evolution in a phase-separating polymeric gel, Modelling and Simulation in Materials Science and Engineering. Bristol, England, IOP Publishing, 2010, 18(2): Article No.: 025002.

Researcher : Song Y

List of Research Outputs

Soh A.K., Zhao X. and Song Y., Crack tip domain switching in normal and relaxor ferroelectrics subjected to mechanical and electric loading , 5th International Conference on Materials for Advanced Technologies 2009 . 2009.

Researcher : Sultana N

List of Research Outputs

Sultana N. and Wang M., Coating PHBV- and PHBV/PLLA-based scaffolds with collagen and characteristics of collagen-coated scaffolds, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 34.

Sultana N., Fabrication of PHBV and PHBV-based Composite Tissue Engineering Scaffolds through the Emulsion Freezing/Freesz-drying Process and Evaluation of the Scaffolds, PhD Thesis. Hong Kong, The University of Hong Kong, 2009, 1-274.

Sultana N. and Wang M., Hydrolytic degradation and protein adsorption of PHBV/PLLA-based tissue engineering scaffolds, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 79.

Researcher : Sun T

List of Research Outputs

Sun T., Wang L.P. and Wang M., (Ti-O-N)/Ti composite coatings fabricated on NiTi shape memory alloy for medical applications, Materials Science & Technology 2009 Conference & Exhibition. Pittsburg, USA, 2009.

Sun T., Wang L.P. and Wang M., (Ti-O-N)/Ti composite coatings fabricated on NiTi shape memory alloy for medical applications, Proceedings of Materials Science & Technology 2009 Conference & Exhibition. Pittsburg, USA, 2009, CD-ROM: 1pp.

Sun T. and Wang M., A comparative study of apatite coating and apatite/collagen composite coating fabricated on NiTi SMA through electrochemical deposition, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 136.

Sun T. and Wang M., Electrochemical deposition of apatite/collagen composite coating on NiTi shape memory alloy and coating properties, Proceedings of the 2009 Materials Research Society Fall Meeting. Boston, MA, USA, 2009, 6pp.

Sun T. and Wang M., Electrochemically deposited Apatite coating on NiTi shape memory alloy, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 77.

Sun T. and Wang M., Electrochemically deposited apatite/collagen composite coating on NiTi shape memory alloy, Proceedings of the 2nd Asian Symposium on Advanced Materials. Shanghai, China, 2009, 89-90.

Sun T., Wang L.P. and Wang M., Fabrication and characterization of Ti-O/Ti composite coatings on NiTi sape memory alloy for medical applications, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 35.

Sun T., Wang L.P. and Wang M., Fabrication of (Ti-O)/Ti composite coating on NiTi shape memory alloy using PIIID and coating characterisation, Proceedings of the 2nd Asian Symposium on Advanced Materials. Shanghai, China, 2009, 54-56.

Sun T., Wang L.P. and Wang M., Fabrication of (Ti-O-N)/Ti composite coating on NiTi shape memory alloy via PIIID and its evaluation, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 135.

Sun T., Wang L.P. and Wang M., Fabrication of (Ti-O-N-Si)/Ti composite coating on NiTi shape memory alloy using PIIID and coating evaluation, Proceedings of the 2009 Materials Research Society Fall Meeting. Boston, MA, USA, 2009, 6pp.

Sun T., Wong H.W. and Wang M., Fabrication of an Apatite/Collagen composite coating on the NiTi shape memory alloy through electrochemical deposition and coating characterisation, Materials Science Forum. Switzerland, Trans Tech Publications, 2009, 618-619: 319-323.

Researcher : Sze KY

Project Title:	Computational methods for meso-electromechanical analysis of ferroelectrics and ferroelectric devices
Investigator(s):	Sze KY
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2001

Abstract:

To develop meso-scale constitutive and switching models of ferroelectrics suitable for finite element implementation. The project also aims to develop finite element procedure for determining the eigensolutions of the singular electromechanical fields at the boundary between ferroelectric grains with different polar directions and at electrode-ferroelectrics interfaces.

Project Title:	Efficient finite element models for large deformation analysis of hyperelastic materials.
Investigator(s):	Sze KY
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	10/2007
Completion Date:	03/2010

Abstract:

The proposed project will formulate efficient and reliable finite element models for large deformation analysis of hyperelastic materials. The proposed models will be tested by benchmarking examples and compared with the existing models.

Project Title:	Development of wave-based finite element families for plane, axial symmetric and three-dimensional Helmholtz problems.
Investigator(s):	Sze KY
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	11/2008

Abstract:

1. Formulate, implement and assess plane element family which comprises element models of different orders. 2. Formulate, implement and assess axial symmetric element family which comprises element models of different orders. 3. Formulate, implement and assess three-dimensional element family which comprises element models of different orders.

Project Title:	Development of efficient rotation-free triangles for shell and drape analyses.
Investigator(s):	Sze KY
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2010

Abstract:

1) Formulate, program and validate a rotation-free triangle for linear shell problems; 2) Formulate, program and validate a rotation-free triangle for geometric nonlinear shell problems; 3) Formulate, program and validate an adaptive mesh refinement scheme for the triangle developed in Objective 2; 4) Formulate, program and validate a rotation-free triangle for geometric and material linear shell problems; 5) Formulate, program and validate an adaptive scheme for the triangle developed in Objective 4.

List of Research Outputs

Au Yeung K.L., Sze K.Y., Sham M.H. and Chan B.P., Development of a micromanipulator-based loading device for mechanoregulation study of human mesenchymal stem cells in three-dimensional cellagen constructs , Tissue Engineering, Part C Methods. 2010, 16(1): 93-107.

Au-yeung K.L., Sze K.Y., Sham M.H. and Chan B.P., Development of a micromanipulator-based loading device for mechanoregulation study of human mesenchymal stem cells in 3D collagen constructs., WACBE (World Association for Chinese Biomedical Engineers) World Congress on Bioengineering 2009. 26-29 Jul 2009, Hong Kong, China.. 2009, 53.

Chan B.P., Li C.H., Au-yeung K.L., Sze K.Y. and Ngan A.H.W., Research Output Prize 2009, Faculty of Engineering. 2009.

Chan K.Y., Lu W.W., Sze K.Y., Leung Y.L., Tam V. and Cheung K.M.C., Development of decellularized intervertebral disc scaffold for tissue engineering, Orthopaedic Research Society. 2010.

Chen Y.Y., Chen S.H. and Sze K.Y., A hyperbolic Lindstedt-Poincaré method for homoclinic motion of a kind of strongly nonlinear autonomous oscillators, Acta Mechanica Sinica. 2009, 25: 721-729.

Chik T.K., Sze K.Y. and Chan B.P., A feasibility study on applying dynamic torsional loading to cylindrical collagen-fibroblast constructs. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. S211: 801.

Li C.H., Ngan A.H.W., Sze K.Y. and Chan B.P., Association between elastic modulus and extracellular matrix components of collagen-mesenchymal stem cell microsphres during chondrogenic differentiation. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. (Best Poster Presentation Award). 2009, S210:795.

Li C.H., Sze K.Y. and Chan B.P., Microplate manipulation of human mesenchymal stem cells collagen microspheres. , WACBE (World Association for Chinese Biomedical Engineers) World Congress on Bioengineering 2009. 26-29 Jul 2009, Hong Kong, China.. 2009, 65.

Lo S.H., Wu D. and Sze K.Y., Adaptive meshing and analysis using transitional quadrilateral and hexahedral elements, Finite Elements in Analysis & Design. 2010, 46: 2-16.

Sze K.Y., Liu G. and Fan H., Four- and eight-node hybrid-Trefftz quadrilateral finite element models, Computer Methods Applied Mechanics & Engrg. 2010, 199: 598-614.

Researcher : Tan ST

Project Title:	Heterogeneous solid modeling using materially defined geometric entities
Investigator(s):	Tan ST
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	04/2005

Abstract:

To extend and enchance the traditional homogeneous solid modeling methods by incorporating material information in the 1D, 2D and 3D geometric entities. Such a representation guarantees a more flexible material variation to be defined throughout the 3D space and the user's design intent can be intuitively captured. Moreover, a range of heterogeneous objects which are difficult or unable to be defined with existing methods can be represented. Unlike existing heterogeneous modeling schemes, this proposal defines the 1D and 2D heterogeneous geometric entities first and then hierarchically builds complex 3D solids from the lower level heterogeneous entities. To represent heterogeneous solids uniformly and generically, a Heterogeneous Feature Tree (HFT) is introduced and a material evaluation algorithm is proposed to dynamically determine or define the material information at a point.

Project Title:	Computer aided modeling of porous objects
Investigator(s):	Tan ST
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2007
Completion Date:	12/2009

Abstract:

This proposal aims to investigate the problems of porous objects modelling with a view to applying the models to some useful applications. For example, in Bio-CAD like bone implants where the bio-compability of the implants with human tissues is of huge concern. In drug delivery problems where the path and boundaries of the injected fluids are greatly influenced by the distribution of the pores. In the design of filters where the sizes and shapes of the pores are of paramount importance.

Project Title:	Voice enabled CAD modeling
Investigator(s):	Tan ST
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2009

Abstract:

1. To effect a faster and efficient CAD modeling process through voice commands. A very useful capability to have would be: "Chamfer Edge A of Part B" instead of conventionally and tediously driving the mouse to do this simple process on individual edges. 2. To investigate voice based approaches to boost the modeling efficiency as well as the overall productivities; 3. To investigate voice based approaches to improve the ease of use and user satisfactions; 4. To develop and implement a novel generation of voice enabled CAD system.

Project Title:	Adaptive mesh generation for the finite element analysis of heterogeneous objects
Investigator(s):	Tan ST
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2010

Abstract:

1) To investigate the influences of the mesh qualities on the solution accuracies and computational overheads in FEA of heterogeneous objects; 2) To provide a new adaptive meshing strategy which enables the material heterogeneity to be taken into account in the finite element analysis; 3) To introduce a new concept called “Material Curvature” (MC) to reflect and characterize the local material heterogeneities, the material curvature will be used to mimic and extend the classic local curvatures based adaptive meshing scheme; 4) To propose a new mathematical model in which the node spacing function [26] is modelled as the function of both the geometries as well as the material distributions; 5) To provide a set of algorithms to perform adaptive meshing of heterogeneous objects. Such algorithms should require minimum human supervision or manual intervention; 6) To test the feasibility and efficacy of using the generated mesh in contemporary FEA packages.

List of Research Outputs

Kou X., Xue S. and Tan S.T., Knowledge-guided inference for voice-enabled CAD, Computer Aided Design. Elsevier, 2010, 42: 545-557.

Kou X., Liu X.C. and Tan S.T., Quadtree based mouse trajectory analysis for efficacy evaluation of voice-enabled CAD, International Conference on Virtual Environment, Human-Computer Interfaces, and Measurements Systems (VECIMS). Hong Kong, 2009, 196-201.

Xue S., Kou X. and Tan S.T., Natural voice-enabled CAD: Modeling via natural discourse, Computer-Aided Design and Applications. 2009, 6(1): 125-136.

Researcher : Tan X

List of Research Outputs

Tan X. and Soh A.K., Comment on "A simple and powerful analytical model for MEMS piezoelectric multimorphs", In: WE Booij, AH Vogl, DT Wang, F. Tyholdt, NP Stbo, H. R'der and K. Prume, Journal of Electroceramics. Dordrecht, Netherlands, Springer, 2010, 24(4): 313.

Researcher : Tang B

Project Title:	Nanomechanical characterization of tissues in eye
Investigator(s):	Tang B, So KF, Wong DSH, Lo ACY, Ellis-Behnke RG
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	11/2007
Completion Date:	11/2009

Abstract:

Objectives: • To characterize the biomechanical properties of tissues in eye at different length scales, including cornea, lens, etc. • To analyze the relationship between the biomechanical properties of eye’s tissues and ocular diseases. The biomechanical properties of tissues in eye play an important role for the eye's normal physiological function but either diseases or surgical operations may alter them. For instance, in some cases, corneal thinning and softening is correlated with keratoconus, a common ocular disease that manifests as buckling of corneal tissue around apex [1] and it was reported that ablative refractive surgery may alter the biomechanical properties of cornea significantly [2]. Precise knowledge of the biomechanical properties of tissues in the eye therefore may lead to a better understanding of the pathogenesis of ocular diseases and help the clinicians to diagnose and monitor ocular diseases. Previously, a few studies were done to investigate the biomechanical properties of tissues in eye [3-14]. However, in most of these previous studies, the biomechanical properties were only qualitatively determined or only the mechanical properties in the bulk condition were provided. The nanomechanical properties of these tissues are still poorly understood. The PI therefore proposes a study to systematically investigate the mechanical properties of tissues in the eye at different length scales. In the present study, special attentions will be paid on cornea and lens, which are essentially important in eye's normal physiological function and whose mechanical properties may be directly associated with certain ocular diseases. The cornea is the transparent front part of the eye, and its major functions are to protect the eye from injury as a mechanical barrier and the helps the eye to focus by refracting light. Recent studies suggested that the biomechanical properties of cornea play an important role in glaucoma’s diagnose in clinical ophthalmology [14-17]. Glaucoma is a group of diseases that can damage the eye's optical nerve and result in permanent vision loss and is now the second leading cause of blindness in the world. In general, glaucoma is due to exorbitant intraocular pressure that may damage the optical nerve. A commonly used method to diagnose glaucoma is the intraocular pressure measurement (IOP), while previous studies reported that the accuracy of the IOP may be affected by the variation of biomechanical properties of cornea [14,15]. Moreover, it was also suggested that the central corneal thickness, which depends on the mechanical properties of tissues in or adjacent to the optical nerve, may also be associated with glaucoma risk [16-18]. A systematical study on the biomechanical properties of tissues in cornea therefore may improve the accuracy of intraocular pressure (IOP) measurement, and may lead to a better understanding of glaucoma risk and its assessment. Another interesting topic here is the biomechanics of cornea in relation to corneal ablative refractive surgeries. It has been pointed out that the local mechanical properties of cornea are important clinical risk factors for the sequelae of corneal refractive surgeries, such as post-LASIK ectasia, keratoconus, etc. [19]. The Lens is a transparent and lentil-shaped tissue in eye. The basic function of lens in eye is to help refracting light to be focused on the retina. By changing the refractive index, the lens allows the focusing of objects at various distances. However, pathological changes of lens may cause varied ocular diseases including cataract, which is a leading cause of blindness. Nowadays, a common treatment for cataract is to surgically remove the cataractous lens and replace it with an intraocular lens implant [20, 21]. A detailed study of the biomechanical properties of lens should therefore provide useful information for the development of a suitable lens implant [13]. Another interesting topic related to the mechanical properties of lens is the presbyopia. Presbyopia is the progressive loss of accommodation with age. The origin of presbyopia is various, but quite a number of studies pointed out that presbyopia should entail a loss of lens elasticity with age [11, 22, 23]. A wide range of testing technique was adopted to measure the mechanical properties of lens previously [9-13], and a few of these studies gave out absolute values of the mechanical properties. However, the mechanical properties given by these studies scatter severely, for example, the lens elasticity measured using DMA differed by several orders of magnitude [11-12]. Moreover, the nanomechanical properties of lens are seldom measured. In summary, the mechanical properties of tissues in the eye are associated with several crucial topics in ophthalmology. Although a number of studies have been done to investigate the mechanical behaviour of these tissues, the biomechanical properties of these tissues are still ambiguous. Furthermore, the nanomechanical properties of tissues in the eye are almost unknown. A systematic investigation of the various tissues in the eye at different scales is therefore necessary and meaningful.

Project Title:	Nanomechanical characterization of bone using AFM nanoindentation
Investigator(s):	Tang B, Lu WW
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	12/2008

Abstract:

1. To quantify the mechanical properties of the mineral platelets in dehydrated bone using AFM nanoindentation with the PI’s recently developed method. 2. To further modify the PI’s method to address the viscoelastic and adhesion effects, to establish a reliable measurement method for the mineral platelets and collagen fibrils in hydrated state, and other similar biological tissues in the future.

Project Title:	Mechanical nanolithography and characterization of polymer under elevated temperatures using atomic force microscope
Investigator(s):	Tang B
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2009

Abstract:

Nanofabrication now plays an important role in the manufacturing of integrated circuits, memory devices, display units, biochips and biosensors [1-3]. In nanofabrication, to create and pattern functional units less than 100 nm is one of the key challenges [4]. Various nano-patterning methods have been proposed and they can be divided into two categorizes: top-down and bottom-up. In top-down approaches, different lithographical techniques are applied to create nano-sized features from the starting bulk materials and AFM nanolithography is one of newly developed top-down nano-patterning techniques [5]. Compared with conventional lithographical techniques, such as photolithography, e-beam lithography or focused ion-beam lithography, the AFM nanolithography has several advantages: i) the cost of AFM nanolithography is relative cheap, ii) because of its very high spatial and force resolution, nano-patterns can be created on specified areas or locations with nano-sized precision, iii) it is versatile - it can be performed under different conditions, liquid, vacuum or in air, and it can create nano-patterns on various materials, insulating or conducting, and iv) AFM is a powerful imaging and mechanical characterization tool as well, and it enables in situ characterization and modification of the created nanopattern. Therefore, AFM nanolithography is one promising technique for nanoscale pattern formation and replication [4, 6-8]. The basic principle for AFM nanolithography is quite simple: while doing AFM lithography, the AFM tip (normally has a tip radius of 10-60 nm) is approached to the starting material, then suitable force and/or external field is applied on the AFM tip, and by this way, various localized physical deformation or chemical reaction can be introduced to the surface of the material and therefore desired nanostructures can be produced [4]. Various AFM nanolithography techniques have been developed ever since the invention of AFM, generally, these techniques can be divided into two groups: i) force-assisted AFM nanolithography and ii) bias-assisted AFM nanolithography. In bias-assisted AFM nanolithography, a bias voltage will be applied on the tip and a very localized electric field will be generated, which will assist the electrochemical reaction, electrostatic attraction, etc, therefore modify the chemical component locally to produce a desired nanostructure. However, most of the bias-assisted AFM nanolithography techniques require multiple-step processes and specified operational conditions, so the accessibility of these techniques is rather poor. Force-assisted AFM nanolithography is much more accessible than bias-assisted AFM nanolithography. In force-assisted AFM nanolithography, a suitable force will be applied on the tip, the morphology the substrate will be modified by pre-designed mechanically pulling, scratching, or pushing the molecules or atoms on the surface to create the desired nanostructure. Typical force-assisted AFM nanolithography techniques include mechanical indentation and plowing [9], dip-pen nanolithography [10], etc. However, in such techniques, it is very hard to obtain a nanostructure with very small feature size, since it is limited by the AFM tip radius [4, 9]. Moreover, usually these techniques can only be performed on soft materials. In several previous studies, various thermalmechanical writing techniques [11-13] has been proposed, in which the tip is heated to a relative high temperature to “soft” the substrate locally, so mechanical lithography can be achieved. However, it was reported that only a very small amount of heat is transferred from the tip to the substrate, and the nanostructure created by this way usually shows a distorted shape [4]. Heated substrates were usually adopted in nanoimprint techniques, and the volume shrinkage due to temperature decreasing or phase transition has been reported in many previous studies [14-18]. Since most of the AFM tips are made by silicon/silicon nitride, which has a very small thermal expansion coefficient and a rather stable phase, it is believed that a controllable nanostructure with feature size smaller than the AFM tip radius should be achieved by performing AFM nanolithography on a heated substrate, if the quantitative relationship between the volume shrinkage and temperature is well clarified. On the other hand, the nanomechanical properties of substrate materials at different temperatures, which are important parameters in both nanoimprint and thermal force-assisted AFM nanolithography, have been seldom reported because of the lack of reliable quantitative measurement techniques. Fortunately, the PI and his co-worker have proposed a quantitative measure method to characterize the nanomechanical properties of materials using AFM nanoindentation, whose validity has been verified on several types of polymers. In this preliminary study, different types of polymers will be used as the prototype materials, since polymers are widely used as masks or resists in various industrial fabrications [4, 15, 17]. The PI proposes, by performing AFM nanolithography and nanoindentation on polymer substrates at different temperatures, i) to figure out the quantitative relationship between the volume shrinkage and temperature during AFM force-assisted nanolithography, therefore enable controllable patterning of ultra-fine nanostructures; ii) to characterize the nanomechanical properties of various polymers at different temperatures using AFM nanoindentation, which will lead to a better understand of nanomechanical behaviour of the polymers.

Project Title:	International Conference on Materials for Advanced Technologies (ICMAT) 2009 A Novel Scheme for Quantitative Measurement of the Elastic Modulus of Materials at Nanoscale Using Atomic Force Microscope
Investigator(s):	Tang B
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2009
Completion Date:	07/2009

Abstract:

N/A

Project Title:	Investigation of Biomechanics and Biophysics of White Blood Cell using Optical Tweezer
Investigator(s):	Tang B, Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2010

Abstract:

The biomechanical properties of cells are directly determined by their protein structures and thus closely related to their biochemistry and genetics. Therefore, any physiological changes in the human body may result in alteration of the cells’ biomechanical properties [1-4]. On the other hand, our human body is constantly exposed to physical stress and strain, and biophysical interactions will happen in the cellular and molecular level as well as in musculoskeletal level. Such biophysical interactions are actually mechanical signals to cells and have been known to produce certain cells’ biological and biochemical responses, which may result in the change of the cells’ physiological functions, such as motility or differentiation, etc [5-9]. To study the biomechanics of cells may therefore be helpful in i) determining the health and function of the human body, ii) revealing quantitative relationship between the biomechanical properties of cells with the progression of certain diseases, e.g. glaucoma, cancer, etc., iii) better understanding the mechanotransduction process, in which mechanical signals are converted into biological and biochemical responses of cells. Therefore，quite a lot of cell mechanics studies have been performed. However, most of these studies used computer simulation and/or applied an external force field to numerous cells, and so the results obtained are qualitative rather than quantitative. Moreover, only a few studies have been done to investigate single cell mechanics. Leukaemia is a cancer of the blood or bone marrow due to an abnormal proliferation of blood cells, usually white blood cells. It usually can be classified into two groups: acute leukaemia and chronic leukaemia [10-11]. Acute leukaemia is caused by the rapid increase of immature blood cells, making the bone marrow not able to produce healthy blood cells. In acute leukaemia, the malignant cells rapidly progress and accumulate in the human body, split over into bloodstream and then spread out to other organs. Chronic leukaemia is due to the excessive build up of relatively mature, but still abnormal, white blood cells. The abnormal white blood cells are produced at a much higher rate than normal cells. According to the statistics done by Chinese Red Cross Foundation, China now has more than 4 million leukemia patients and the number increases at around 30,000 every year. Half of the leukemia patients are children, especially those aged 2 to 7. Leukaemia, especially acute leukaemia that usually happens in children, is therefore a major public health concern. Numerous studies have been done to investigate leukaemia, but only a few studies have been done to investigate the cell mechanics of leukaemia [12]. Moreover, the results for the single cell mechanics of leukaemia so far are ambiguous and debatable, due probably to the difficulties in simulating the in vivo conditions of white blood cells. Optical tweezers are a novel technique for manipulate small objects, in which a focused laser beam is utilized to provide an attractive or repulsive force (usually in piconewtons) to physically hold and move microscopic dielectric objects [13]. Because of its feasibility to perform test on biological samples in physiological conditions, it has been adopted by the biological community for cell manipulation, cell isolation, etc. Meanwhile, the feasibility of using the optical tweezers to study single cell mechanics has been demonstrated recently; the most pronounced study is to use this technique to investigate the elastic deformability of red blood cells suffering from malaria [14, 15]. It was found that red blood cells become stiffer with the progressing of malaria, and this provides very useful information in helping the malaria’s early detection. The following studies are proposed to be done: a) Investigate the biomechanical properties of normal white blood cells and the white blood cells suffering leukaemia (malignant cells) at different disease stages under a condition very close to its in vivo conditions using optical tweezers, which may i) lead to better understanding of the mechanical behaviour of single white blood cells; ii) enrich the biological database; iii) provide useful information in understanding the pathogenesis of leukaemia and build up the relationship between the biomechanical properties of white blood cells and the progressing of leukaemia. b) Investigate the normal white blood cells and malignant cells’ biomechanical, biological and biochemical responses due to a change of biophysical interactions by introducing quantitative mechanical signals to individual cells. In leukaemia, the rapid progressing and accumulation of malignant cells will not only change the cells’ biological and biochemical environment, but may also change the biomechanical environment, resulting in a change of biophysical interactions of cells. Therefore, it is necessary to understand how individual white blood cells and malignant cells respond to different mechanical signals, in order to clarify the role of biophysical changes in the progressing of leukaemia.

List of Research Outputs

Ngan A.H.W. and Tang B., Nanoindentation using atomic force microscope, extended invited talk, ECI Conference on Nanomechanical Testing in Materials Research and Development, October 11-16, 2009, Il Ciocco Hotel and Conference Center, Barga (Tuscany), Italy.. 2009.

Zhou W., Rabie A.B.M., Wong R.W.K. and Tang B., Nanocoating of Montmorillonite/Mg-β-Tricalcium Phosphate on Orthodontic Titanium Miniscrews, 3rd IEEE International NanoElectronics Conference (INEC). 2010, BC211.

Researcher : Tang M

List of Research Outputs

Tang M. and Soh A.K., Simulation of a Bio-adhesion System with Viscoelasticity , 8th International Conference on Fracture and Strength of Solids. 2010.

Tang M. and Soh A.K., Study of adhesion mechanism in gecko’s foot hair by FEM , The 14th Annual Conference of HKSTAM 2009-2010 cum The 7th Shanghai – Hong Kong Forum on Mechanics and Its Application . HKSTAM, 2010, 1: 37.

Researcher : Tang X

List of Research Outputs

Tang X., Chow K.W. and Rogers C.W., Propagating wave patterns for the 'resonant' Davey - Stewartson system, Chaos, Solitons and Fractals. 2009, 42: 2707-2712.

Researcher : Teng WK

List of Research Outputs

Li Y.Y., Cheng H.W., Chan P.M., Wong M.Y., Teng W.K., Chow S.T., Cheung K.M.C., Chan D. and Chan B.P., Repair of osteochondral defects with collagen-mesenchymal stem cell microspheres in a rabbit model. , ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #W-50, p250.

Liu T., Teng W.K., Chan B.P. and Chew S.Y., Photochemical Crosslinked Electrospun Collagen Nanofibers: Synthesis, Characterization & Neural Stem Cell Interactions. , J. Biomed Mater Res A.. 2010, 276-282.

Researcher : Tong HW

List of Research Outputs

Tong H.W., Wang M. and Lu W.W., Cell behaviour on electrospun biodegradable fibrous membranes: Effects of fiber diameter and fiber alignment, Proceedings of Materials Science & Technology 2009 Conference & Exhibition. Pittsburg, USA, 2009, CD-ROM: 1pp.

Tong H.W., Wang M., Li Z. and Lu W.W., Effects of the alignment, diameter and surface morphology of electrospun fibers on the behaviour of osteoblastic cells, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 107.

Tong H.W., Electrospinning of Ultrafine Fibers and its Application in Forming Fibrous Tissue Engineering Scaffolds, PhD Thesis. Hong Kong, The University of Hong Kong, 2009, 1-357.

Tong H.W. and Wang M., Electrospinning of fibrous polymer scaffolds using positive voltage or negative voltage: A comparative study, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 113.

Tong H.W., Wang M., Li Z., Lam W.M.R. and Lu W.W., Electrospinning of surface-porous fibers and In vitro biological study of these fibers, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 38.

Tong H.W. and Wang M., Electrospinning of ultrafine fibrous tissue engineering scaffolds: Effects of emitting electrode polarity, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Tong H.W. and Wang M., Electrospinning, characterization, and In Vitro degradation of PHBV micro- and submicron-fibers, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 78.

Tong H.W. and Wang M., Forming fibrous nanocomposite tissue engineering scaffolds through electrospinning: a comparative study of three fabrication routes, Proceedings of the 22nd International Symposium on Ceramics in Medicine (Bioceramics 22). Daegu, Korea, 2009, 197-200.

Tong H.W. and Wang M., Forming fibrous nanocomposite tissue engineering scaffolds through electrospinning: a comparative study of three fabrication routes, The 22nd International Symposium on Ceramics in Medicine (Bioceramics 22), Daegu, South Korea. 2009.

Tong H.W., Wang M. and Lu W.W., In Vitro Biological evaluation of fibrous PHBV polymer and CHA/PHBV nanocomposite scaffolds developed for tissue engineering applications, Proceedings of the 22nd International Symposium on Ceramics in Medicine (Bioceramics 22). Daegu, Korea, 2009, 453-456.

Tong H.W., Wang M., Li Z. and Lu W.W., In vitro biological assessment of electrospun composite fibers containing hydroxyapatite nanoparticles, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 108.

Tong H.W., Wang M. and Lu W.W., In vitro biological evaluation of fibrous PHBV polymer and CHA/PHBV nanocomposite scaffolds developed for tissue engineering applications, The 22nd International Symposium on Ceramics in Medicine (Bioceramics 22), Daegu, South Korea. 2009.

Tong H.W., Wang M., Li Z. and Lu W.W., The influence of fiber diameter, morphology and alignment on osteoblastic cell behaviour, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Tong H.W., Li Z., Wang M. and Lu W.W., 电纺纤维直径、表面形貌及排列状态对细胞的影响, 全国生物材料大会, 2010.

Tong H.W. and Wang M., 静电纺丝制备超细纤维组织工程支架—电极极性研究, 全国生物材料大会, 2010.

Researcher : Tong HW

List of Research Outputs

Tong H.W., Electrospinning of Ultrafine Fibers and its Application in Forming Fibrous Tissue Engineering Scaffolds, PhD Thesis. Hong Kong, The University of Hong Kong, 2009, 1-357.

Tong H.W., Li Z., Wang M. and Lu W.W., 电纺纤维直径、表面形貌及排列状态对细胞的影响, 全国生物材料大会, 2010.

Tong H.W. and Wang M., 静电纺丝制备超细纤维组织工程支架—电极极性研究, 全国生物材料大会, 2010.

Researcher : Tsang CH

List of Research Outputs

Chiu H.S., Chow K.W. and Tsang C.H., Studies of freak or rogue waves by the nonlinear Schrodinger model, The 33rd IAHR Congress - Water Engineering for a Sustainable Environment, Vancouver, BC, Canada. 2009.

Tsang C.H., Malomed B.A. and Chow K.W., Exact solutions for periodic and solitary matter waves in nonlinear lattices (invited article), accepted and to appear in Discrete and Continuous Dynamical Systesm, special issue on the Seville, Spain Meeting on Dynamical Systems. 2010.

Tsang C.H., Lam C.K., Malomed B.A. and Chow K.W., Solitons pinned to hot spots, European Physical Journal D, special issue on 'Dissipative Optical Solitons' (invited article). 2010, 59: 81-89.

Researcher : Wan IC

List of Research Outputs

Ip R.W.L., Cheng M.T., Lao S.H. and Wan I.C., A finite element analytical approach for the design of industrial type heat exchangers, Annual Journal of Institute of Industrial Engineers. 2010, 30: 11-20.

Researcher : Wang C

Project Title:	39th International Congress and Exposition on Noise Control Engineering (INTER-NOISE 2010) Time-Domain Simulation of Acoustic Wave Propagation by Chebyshev Collocation
Investigator(s):	Wang C
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	06/2010
Completion Date:	06/2010

Abstract:

N/A

List of Research Outputs

Choy Y.S., Huang L. and Wang C., Sound propagation in and low frequency noise absorption by helium-filled porous material, Journal of the Acoustical Society of America. Journal of the Acoustical Society of America, 2009, 126(6): 3008-3019.

Wang C., Cheng L. and Pan J., Cavity-Backed Microperforated Panel Sound Absorbers, Inter-noise 2009, Ottawa, Canada, August 23-26,2009,. 2009.

Wang C. and Wang M., Effects of de-ionized water and PBS buffer on the core-shell structure of emulsion electrospun fibers, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Wang C., Cheng L., Pan J. and Yu G., Sound absorption of a micro-perforated panel backed by an irregular shaped cavity, The Journal of the Acoustical Society of America. 2010, 127: 238-246.

Wang C. and Huang L., TIME-DOMAIN SIMULATION OF ACOUSTIC WAVE PROPAGATION BY CHEBYSHEV COLLOCATION, the 39th International Congress and Exposition on Noise Control Engineering. 2010, paper 784.

Researcher : Wang C

List of Research Outputs

Wang C., Cheng L. and Pan J., Cavity-Backed Microperforated Panel Sound Absorbers, Inter-noise 2009, Ottawa, Canada, August 23-26,2009,. 2009.

Wang C., Cheng L., Pan J. and Yu G., Sound absorption of a micro-perforated panel backed by an irregular shaped cavity, The Journal of the Acoustical Society of America. 2010, 127: 238-246.

Wang C. and Huang L., TIME-DOMAIN SIMULATION OF ACOUSTIC WAVE PROPAGATION BY CHEBYSHEV COLLOCATION, the 39th International Congress and Exposition on Noise Control Engineering. 2010, paper 784.

Researcher : Wang H

List of Research Outputs

Wang H., Leung Y.C. and Leung M.K.H., Energy analysis of hydrogen and electricity production from aluminum-based processes, Proceedings International Conference on Applied Energy 2010. Singapore, National University of Singapore, CD-Rom: 10pp.

Researcher : Wang L

Project Title:	Numerical and experimental investigations of developing, three-dimensional liquid flow in curved microchannels
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2007
Completion Date:	12/2009

Abstract:

(1) Purpose An understanding of liquid flow in curved microchannels is crucial to the optimal design and process control of various microfluidics devices and modern instruments used in chemical analysis and biomedical diagnostics. The goals of this project are to study characteristics of developing, three-dimensional (3D) flow in curved microchannels, to quantify when and to what extent various effects (channel curvature, disturbances, electric double-layer (EDL), entrance and three dimensional transport, initial conditions, surface roughness) become important in microchannels, to reconcile inconsistencies in the reported flow friction data in the literature, and to develop reliable design tools of correlating relations for friction factors. (2) Key Issues When transient flow has died away, flow in curved microchannels can have multiple states, each corresponding to different INITIAL conditions of flow. The flow in practical curved microchannels is also subject to the effect of disturbances. Both the initial conditions and the disturbances are normally unknown or cannot be accurately determined. Therefore, sets of steady flow states must be described (multiplicity study to address the effect of initial conditions); stable and experimentally observable subsets must be separated from the others (stability study to address the effect of disturbances). EDL and surface roughness effects, which are normally neglected for flow in macrochannels, must also be addressed. Another key issue is to find correlating relations of friction factors. (3) Possible outcomes 1. Solution structure: number of solution branches and their connectivity through different types of singular points; 2. Flow structure: flow patterns and distribution of friction factor for each flow state; 3. Dynamic responses of multiple flows to finite random disturbances; 4. Phenomena related to the transition to turbulence such as temporal/spatial oscillation of flows, period doubling, intermittency, and chaotic oscillation; 5. Quantification of effects of channel curvature, disturbances, EDL, three dimensional transport, initial conditions and surface roughness; 6. A general program package for continuation, bifurcation and stability analysis of three-dimensional curved microchannel flows; and 7. Reliable correlating relations for friction factors. (4 ) Significance This project will make a concrete contribution to the study of liquid flow in curved microchannels, which are of paramount importance for a variety of microfluidic systems. Understanding of flow in microchannels from this project will be of considerable general significance for novel, better and more efficient designs of microdevices used in the automotive industry, biomedical engineering, chemical processes, computer chips, lab-on-a-chip, microfluidic chips, micro mixers, micropower generation, microreactors and micro total analysis systems. More particularly, the project will provide more reliable design tools of correlating relations for friction factors for these microdevices. Microchannels are a very important area of emerging technology, and are playing an increasingly important role in the continuing advances of MEMS worldwide. The establishment of a critical technology base for Hong Kong in MEMS and biotechnology requires the development of local talent and expertise in this area. The project represents an important step in this direction.

Project Title:	Magic Microfluidic T-Junctions: Valving, Bubbling and Bubble-Manipulating
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	11/2007

Abstract:

Purpose We propose (i) to develop and characterize 4 kinds of microfluidic T-junctions (TJs) for valving microflows and generating monodispersed bubbles of nano/subnano liters; and (ii) to design, manufacture and test another 4 TJ types for manipulating (splitting, sorting, merging and encapsulating) bubbles at a scale of nano, pico and even femto liters. These two groups of four TJs are illustrated schematically below, at Fig. 1 (a)–(d) and (e)–(h) respectively, where TJs (e)-(h) refer to the 2nd TJs in the figure (attached Fig.1). Key Issues We will address the following 6 key issues as functions of geometrical parameters of the system, inlet pressures (or flow rates) and properties (viscosity, surface tension) of two fluids: (1) switch between valving and bubbling functions of TJs (a)–(d); (2) bubble formation process, bubble size, size distribution and bubble generation frequency at TJs (a)–(d); (3) characteristics of synchronized alternating bubble generation at the double TJ (c) and characteristics of bubble merging in the tapered expanding channel after the double TJ (d); (4) bubble splitting/sorting process and bubble size and its distribution in the two daughter branches of the channel at TJs (e) and (f); (5) bubble merging process and properties of merged bubbles (size and size distribution) at TJ (g); and (6) encapsulation process of bubbles into droplets of the dispersing liquid at TJ (h), droplet characteristics (size, size distribution and generation frequency), and characteristics of bubble distribution inside the droplets (position and numbers of bubbles in each droplet).

Project Title:	Nanofluids: Synthesis, Characterization and Thermal Conductivity
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2009

Abstract:

1. To systematically synthesize and characterize eight kinds of innovative nanofluids. 2. To reliably correlate synthesis parameters with microstructures and thermal conductivities of these nanofluids. 3.To rigorously obtain both microscale and macroscale-level understanding of how heat is transferred in nanofluids.

Project Title:	Synthesizing Nanofluids inside Microfluidic Droplets
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	04/2009

Abstract:

Nanofluids, fluid suspensions of nanometer-sized particles, have recently been demonstrated to have thermal conductivities far superior to that of the liquid alone. This and their other distinctive features offer unprecedented potential for many applications in various fields including energy, bio- and pharmaceutical industry, and chemical, electronic, environmental, material, medical and thermal engineering. Yet, the status quo of nanofluid research is rather confusing, and contradictory reports appear in nearly all aspects of nanofluids, mainly due to the unavailability of high-quality nanofluids with controllable and tailor-designed microstructures. We thus propose a one-step, continuous and scalable synthesis process for effective synthesis of nanofluids: the microfluidic-droplet-based wet-chemical technique that (i) replaces batch-based macroreactors in the one-step wet-chemical method by continuous-flow microfluidic droplets; and (ii) generates nanoparticles directly in the base fluids through chemical reactions in the liquid phase. Microfluidic droplets as microreactors exhibit numerous practical advantages, including safety, easy-manipulation, and numbering-up for industrial production, when compared with traditional macroreactors. It is also advantageous that the reactions can be controlled more accurately through efficient mixing, enhanced reaction/product selectivity, and effective mass and heat transfer, due to short diffusion paths and high surface-to-volume ratios at the microscale. Running the one-step chemical process in a continuous mode would not only increase its commercial viability, but also improve its repeatability significantly. Growth of nanoparticles directly in the base fluids through chemical reactions enables us to manipulate atoms and molecules in the liquid phase, thereby providing a powerful arsenal for synthesis of tailor-designed nanofluids using a bottom-up approach. Specifically, we will develop this promising technique by designing, fabricating and characterizing a microfluidic system for synthesizing two types of high-conductive nanofluids. The key issues include: (i) formatting fine and monodispersed droplets effectively; (ii) achieving a fast laminar-flow mixing between reactant fluids without introducing additional complexity to microfluidic fabrication and/or operation processes; and (iii) obtaining a reliable relationship among synthesis parameters, nanofluids’ microstructures, and their thermal conductivities. Here the synthesis parameters come from microfluidic-system geometry, type and concentration of reactants, and flow rate of reactant fluids and dispersing fluids. The microstructure includes nanoparticle size, size distribution, shape, morphology, liquid-particle interfacial property and agglomerating structure in nanofluids. The methods for fabricating droplets are plentiful, but most involve mixing two immiscible liquids in bulk processes, and many use turbulence to enhance the formation of dispersions. In these “top-down” approaches, little control over the formation of individual droplets is available, and a broad distribution of droplet sizes is typically produced. In an attempt to produce monodispersed droplets, a “bottom-up” approach—microfluidic T-junction emulsification (MTE)—has been recently proposed for fabricating emulsions at the level of individual droplets. In the MTE approach, the droplet is formed at the T-junction of two microfluidic channels conveying the dispersed liquid and dispersing liquid into the junction respectively. The instability responsible for the droplet formation at the T-junction comes from the competition between surface tension and shear forces. This approach operates in the laminar flow region and generates one droplet at a time at the T-junction. As the conditions for break-off are identical for every droplet, the droplets fabricated by this approach are highly monodispersed, with standard derivations in droplet size less than 2%. The energy requirement for this approach is also much lower than those demanded by conventional approaches. Therefore, we propose to use the MTE approach for formatting fine and monodispersed droplets that will serve as the microreactors for synthesizing nanofluids. Mixing has a decisive influence on the heat transfer, mass transfer, yield and selectivity of a reaction. Shrinking the reactor size to the microscale in the microfluidic droplets reduces the diffusion length between the reactant fluids, thus enhancing the mixing by molecular diffusion. The mixing by convection at the microscale is, however, weak because typically, flow in microchannels is laminar with Reynolds numbers well below the threshold for turbulence. Transverse secondary flows--which arise as a result of centrifugal effects experienced by fluids traveling along a curved trajectory and continuously expand interfacial area between reagent streams through stretching, folding and breakup processes--offer an attractive possibility of providing enhanced mixing in an easily-fabricated planar format by simply introducing curvature to the flow path. Expansion vortices or direct collision of slit fluid streams can also be generated by manipulating the geometrical structure of curved channels, and hence further enhance the mixing. Therefore, we propose a detailed study of the design, fabrication and characterization of a microfluidic system that is made of planar and smooth-walled curved microchannels on the one hand, and has a rapid laminar-flow mixing on the other hand. The reliable relationship among synthesis parameters, nanofluids’ microstructures, and their thermal conductivities depends very much on an accurate characterization of the microstructure and thermal conductivity of nanofluids. Inadequacies in doing this have yielded wide discrepancies and inconsistencies in the reported conductivity data. In many cases the microstructural parameters were not measured by the experimenters themselves but rather taken from the powder manufacturers’ nominal information. To reconcile these discrepancies and inconsistencies and to lay the foundations for better and more efficient designs of nanofluids, we propose to characterize the microstructure and thermal conductivity of nanofluids by state-of-the-art instrumentation of both in-vitro and in-vivo types. The purpose of the proposed project thus includes: (i) developing a microfluidic-droplet-based one-step wet-chemical technique for effectively synthesizing nanofluids with controllable microstructures; (ii) designing, fabricating and characterizing one microfluidic system for synthesis of two types of high-conductive nanofluids; and (iii) reliably correlating synthesis parameters, nanofluids’ microstructures, and their thermal conductivities.

Project Title:	Microfluidic Nanofluids: Synthesis and Characterization
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2010

Abstract:

1) To develop a microfluidic one-step wet-chemical technique for effectively synthesizing nanofluids with controllable microstructures; 2) To design, fabricate and characterize three microfluidic systems for synthesis of three types of high-conductive nanofluids; 3) To reliably correlate synthesis parameters, nanofluids’ microstructures, and their thermal conductivities.

Project Title:	Constructal Design of Nanofluids
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2010

Abstract:

Nanofluids—fluid suspensions of nanometer-sized structures (particles, fibers, tubes, droplets)—are research challenges of rare potential but daunting difficulty. The potential comes from both scientific and practical opportunities in many fields. The difficulty reflects the issues related to multiscales. Nanofluids involve at least four relevant scales: molecular scale, microscale, macroscale and megascale. The research and engineering practice in nanofluids aim to enhance system megascale performance through manipulating microscale physics (structures, properties and activities). Therefore, the success of nanofluid technology depends very much on how well we can address the issue such as how to optimize microscale physics for optimal megascale performance. For heat-conduction nanofluids, we propose to address this key issue with powerful constructal theory. Specifically, in this proposed project we will make a constructal design for five fundamental heat-conduction systems of nanofluids with two pre-specified types of microstructures (dispersed and tree configurations). The outcomes will thus include the constructal microstructure and performance in the five fundamental heat-conduction systems of nanofluids. The success of the project will revolutionize the way nanofluids are studied and applied and open the road for precise development of diverse multifunctional nanofluids. The project’s findings should also represent a revolutionizing step towards creating nanofluids by design and tailoring their microstructure to suit a desired application.

Project Title:	Collaborative Conference on Interacting Nanostructures (CCIN 2010) Nanofluids Research: Key Issues
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	04/2010
Completion Date:	04/2010

Abstract:

N/A

List of Research Outputs

Bai C. and Wang L., Constructal allocation of nanoparticles in nanofluids, Journal of Heat Transfer. 2010, 132: 052404/1-052404/6.

Bai C. and Wang L., Constructal design of nanofluids for one-dimensional steady heat conduction systems, NANO. 2010, 5: 39-51.

Di Q.Q., Yang J.H., Sun M.D. and Wang L., Effect of microwave irradiation on the flow of micro-particle suspension (TiO2/H2O) in micro-scale porous structure, The 2nd ASME Micro/Nanoscale Heat and Mass Transfer International Conference. 2009, ASME MNHMT2009-18285.

Di Q.Q., Yang J.H., Sun M.D. and Wang L., Fractal characterization of astragalus slices under various microwave assisted extraction conditions, The 2nd ASME Micro/Nanoscale Heat and Mass Transfer International Conference. 2009, ASME MNHMT2009-18284.

Fan J. and Wang L., Constructal design of nanofluids, International Journal of Heat and Mass Transfer. 2010, 53: 4238-4247.

Fan J. and Wang L., Effective thermal conductivity of nanofluids: effects of microstructure, Journal of Physics D: Applied Physics. 2010, 43: 165501/1-165501/10.

Fan J. and Wang L., Effects of microscale physics on macroscale thermal properties in nanofluids, The 2nd ASME Micro/Nanoscale Heat and Mass Transfer International Conference. 2009, ASME MNHMT2009-18386.

Fan J. and Wang L., Is classical energy equation adequate for convective heat transfer in nanofluids?, Advances in Mechanical Engineering (Special issue on Heat Transfer in Nanofluids). 2010, DOI: 10.1155/2010/719406.

Liu F. and Wang L., Analysis on multiplicity and stability of convective heat transfer in tightly curved rectangular duct, International Journal of Heat and Mass Transfer. 2009, 52: 5849-5866.

Wang L., Design with constructal theory, In: A. Bejan and S. Lorente, International Journal of Energy Research. Hoboken, NJ (2008), Wiley, 2010, 1-529.

Wang L. and Wei X., Heat conduction in nanofluids, In: K. Sattler, Handbook of Nanophysics. Taylor & Francis, 2010, (Chapter 33), Vol. 3 (Nanoparticles and Quantum Dots): 33.1-33.15.

Wang L. and Fan J., Nanofluids research: key issues, Nanoscale Research Letters. 2010, 5: 1241-1252.

Wang L., Nanofluids research: key issues, The 2nd ASME Micro/Nanoscale Heat and Mass Transfer International Conference. 2009, ASME MNHMT2009-18126.

Wang L., Perspective and thermodynamic foundation of thermal-mass theory, Keynote lecture, Proceedings of the 38th CAST Academic Forum of New Ideas. 2010.

Wei X. and Wang L., 1+1>2: Extraordinary fluid conductivity enhancement, Current Nanoscience. 2009, 5: 527-529.

Wei X. and Wang L., A microfluidic method for synthesizing Cu₂O nanofluids, Journal of Thermophysics and Heat Transfer. 2010, 24: 445-448.

Wei X., Kong T., Zhu H.T. and Wang L., CuS/Cu₂S nanofluids: synthesis and thermal conductivity, International Journal of Heat Mass Transfer. 2010, 53: 1841-1843.

Wei X. and Wang L., Synthesis and thermal conductivity of microfluidic copper nanofluids, Particuology. 2010, 8: 262-271.

Yang J.H., Jiang Q., Di Q.Q. and Wang L., Preliminary study on the dynamic stability of TiO2-water based nanofluids flow in circular tube, The 2nd ASME Micro/Nanoscale Heat and Mass Transfer International Conference. 2009, ASME MNHMT2009-18282.

Zhang Y. and Wang L., Experimental investigation of bubble formation in a microfluidic T-shaped junction, Nanoscale and Microscale Thermophysical Engineering. 2009, 13: 228-242.

Zhang Y., Fan J. and Wang L., Formation of nanoliter droplets in a confined microfluidic T-shaped junction: formation time and droplet volume, Current Nanoscience. 2009, 5: 519-526.

Researcher : Wang M

Project Title:	Bioactive and biodegradable composites for bone tissue repair
Investigator(s):	Wang M, Lu WW
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	12/2005

Abstract:

The objectives of this project are: 1) to fabricate and develop bioceramic/PHBV composites; 2) to study the composites through structural, mechanical and biological analyses; 3) to investigate the bioactivity and biodegradation behaviour of the composites.

Project Title:	An investigation into controlled release of drug and protein in relation to bone tissue engineering
Investigator(s):	Wang M
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	04/2008
Completion Date:	03/2010

Abstract:

The purpose of this project is to explore the use of nanoparticles, microspheres and porous scaffolds for controlled release of drugs and proteins in relation to bone tissue engineering. Fabrication of these delivery vehicles containing a drug and/or a protein will be investigated and these vehicles will be evaluated for drug and/or protein loading and release. Key issues to be addressed in the project include: 1) fabrication of of good-quality delivery vehicles (nanoparticles, microspheres, scaffolds) containing a drug and/or a protein; 2) obtaining drug- and/or protein encapsulated delivery vehicles with sufficient loadings of drug and/or protein; 3) establishing the in vitro release profiles of drug and/or protein using different forms of delivery vehicles.

Project Title:	Compostie tssue engineering scaffolds and the synergetic effects of simultaneous controlled release of several bioactive substances
Investigator(s):	Wang M
Department:	Mechanical Engg
Source(s) of Funding:	Matching Fund for NSFC Academic Collaboration Award
Start Date:	01/2009

Abstract:

Compostie tssue engineering scaffolds and the synergetic effects of simultaneous controlled release of several bioactive substances

Project Title:	Electrospinning for Tissue Engineering Scaffolds: Effects of Emitting Electrode Polarity and Formation of Highly Aligned Fibrous Structures
Investigator(s):	Wang M, Lu WW
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	01/2009

Abstract:

1. To study the formation of electrospun tissue engineering scaffolds using negative electrospinning voltages. 2. To fully characterize electrospun tissue engineering scaffolds and evaluate the influence of positive and negative electrospinning voltages on scaffold properties. 3. To solve the technological problem of fabricating both thick and highly aligned-fiber fibrous structures for tissue engineering applications

Project Title:	An Investigation into the Fabrication and Properties of Bioactive and High Performance Coatings for NiTi Shape Memory Alloy
Investigator(s):	Wang M
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	05/2009

Abstract:

Due to its unique shape memory ability and superelastic property, NiTi shape memory alloy (NiTi SMA, which contains 50.8 at.% of Ni) has been investigated for clinical applications in orthodontics, orthopaedics, cardiovascular devices, etc. and has shown its potential as a major implantable metallic biomaterial. With the continual aging of the population around the world, there will be an increasing demand for the long-term implantation of implants made of NiTi SMA. However, there are critical problems that must be solved for the long-term implantation of NiTi SMA in human bodies: 1) improving the biocompatibility of NiTi SMA Ni is a strong sensitizer, being one of the most common causes of allergic contact dermatitis. At present, the incidence of Ni hypersensitivity within the general population is reported to be as high as 20-30%, with case reports of Ni hypersensitivity becoming more frequent in the medical literature. Adverse reactions related to Ni-containing orthodontic devices such as arch wires, brackets and buckles on headgear devices have been observed. In addition, high Ni ion concentrations may lead to, apart from allergen or particle-induced inflammation, tissue inflammation in the vicinity of a NiTi SMA implant in vivo and subsequently to implantation failure due to implant loosening. It has also been reported that the use of NiTi arch wires can convert Ni-nonsensitive subjects into Ni-sensitive subjects, with approximately a 20% conversion rate. Therefore, it is essential to prevent, or at least minimize, Ni ion release from NiTi SMA implants and hence improve the biocompatibility of the implants for their long-term implantation. 2) enhancing the bioactivity of NiTi SMA The long-term implant fixation and stability are major issues for metallic implants. Implant stability also depends on the fixation established with the surrounding tissue. One of the main reasons for the loosening of metallic implants during long-term implantation is the encapsulation of soft tissues. After being implanted into the body, NiTi SMA usually does not bond to the living bone directly due to its bioinertness and hence fibrous tissues form at the bone-implant interface, resulting in the instability of the implant and the eventual failure of implantation. Therefore, the NiTi SMA surface needs to be modified for possessing desired bioactivity. 3) increasing the wear resistance of NiTi SMA Another critical issue affecting the longevity of articulating implants (such as artificial hip or knee joints) made of NiTi SMA is the long-term wear resistance. Long-term wear and debris generation in implanted artificial joints result in bone necrosis. The wear debris can migrate and locate at the bone-implant stem interface, further promoting bone cell death. In addition, wear particles migrate from the intra-articular margin to the dome of the acetabulum along the bone-cement interface of artificial hip joints, inducing the formation of a fibrous tissue membrane and thereby resulting in the fixation instability and subsequent implant loosening. Thus, how to achieve better wear resistance and mitigate the creation of wear debris is very important for NiTi SMA implants. Fabricating dense, compact and uniform coatings on NiTi SMA implants is an effective way to achieve a good combination of biocompatibility, bioactivity and mechanical properties (including wear resistance) for the implants. Among many surface modification techniques, plasma immersion ion implantation (PIII) has been used by other research groups to produce coatings on NiTi SMA surfaces for medical applications. However, PIII has limitations in producing coatings of desired compositions and hence properties. The purpose of this project is to explore the use of the plasma immersion ion implantation and deposition (PIIID) technique to fabricate biocompatible, bioactive and wear-resistant coatings on the surface of NiTi SMA. The NiTi SMA with the coating thus formed should be suitable for long-term implantation in human bodies without causing adverse tissue reactions. Several types of coatings will be fabricated using PIIID and their structure and properties studied. Key issues to be addressed in this project include: 1) investigating the fabrication of durable biocompatible and bioactive coatings on NiTi SMA using PIIID and determining appropriate PIIID parameters for forming the coatings; 2) evaluating the structure and properties of coatings formed; 3) studying in vitro biocompatibility and bioactivity of the coatings.

Project Title:	Materials Science & Technology 2009 Conference & Exhibition (MS&T09) Nanoparticles, Nanofibers and Nanocomposites for Biomedical Applications
Investigator(s):	Wang M
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	10/2009
Completion Date:	10/2009

Abstract:

N/A

Project Title:	Emulsion Electrospinning and Formation of Bicomponent Fibrous Scaffolds for the Dual Growth Factor Delivery in Tissue Engineering
Investigator(s):	Wang M
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	12/2009

Abstract:

1) To study the formation of core-shell structured, biomolecule-encapsulated fibers through emulsion electrospinning; 2) To investigate the formation and characteristics of two types of bicomponent fibrous scaffolds containing different growth factors; 3) To study the in vitro biodegradation and growth factor release behaviour of mono- and bicomponent scaffolds and evaluate the synergetic effect of dual growth factor delivery.

Project Title:	Gold Nanoparticles and their Functionalization for Biomedical Applications
Investigator(s):	Wang M
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	04/2010

Abstract:

The purpose of this project is to explore the synthesis and functionalization of gold nanoparticles with dual diagnostic and therapeutic functions for cancer treatment. The surface modification and functionalization of gold nanoparticles of specific and desired shape and size will be investigated. These nanodevices will be characterized and then evaluated for targeting, imaging and hyperthermia effect. Key issues to be addressed in the project include: (1) controlled syntheses of gold nanoparticles of specific and desired shape and size; (2) fabrication of thin polyethyleneglycol film coated gold nanoparticles of desired shape and size that (i) improve the colloidal stability of the nanoparticles by minimizing their aggregation, (ii) improve the shape stability and biocompatibility of the nanoparticles, and (iii) allow for further modification of the surface of the nanoparticles; (3) production and preliminarily evaluation of folic acid-polyethyleneglycol-conjugated gold nanoparticles as a new targeting, imaging and hyperthermia agent for cancer treatment.

List of Research Outputs

Duan B., Wang M., Li Z. and Lu W.W., Bone morphogenetic protein incorporated nanocomposite scaffolds and induction of osteogenic differentiation of mesenchymal stem cells, Proceedings of the Tissue Engineering and Regenerative Medicine International Society – EU Meeting -2010. Galway, Ireland, Paper #459.

Duan B., Wang M., Li Z. and Lu W.W., Ca-P/PHBV nanocomposite scaffolds modified by gelatin and heparin and their biological evaluation, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 94.

Duan B., Wang M., Li Z. and Lu W.W., Cytocompatibility and osteoconductivity of three-dimensional selective laser sintered nanocomposite scaffolds, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 95.

Duan B. and Wang M., Design, selective laser sintering, properties and In Vitro biological evaluation of osteoconductive nanocomposite scaffolds for bone tissue engineering, Transactions of the Society For Biomaterials 2010 Annual Meeting. Seattle, WA, USA, 2010, Paper #116.

Duan B. and Wang M., Fabrication of Ca-P/PHBV nanocomposite scaffolds via selective laser sintering and biocompatibility of the scaffolds, Proceedings of the 1st Forum on Surface Engineering of Biomedical Materials. Chengdu, China, 2009, 1pp.

Duan B., Wang M., Li Z. and Lu W.W., In Vitro Biological assessment of nanocomposite scaffolds for bone tissue engineering, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 20.

Duan B. and Wang M., Modification of selective laser sintered Ca-P/PHBV nanocomposite scaffolds, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 44.

Duan B. and Wang M., Surface modification and biocompatibility of Ca-P/PHBV nanocomposite scaffolds, Proceedings of the 1st Forum on Surface Engineering of Biomedical Materials. Chengdu, China, 2009, 1pp.

Duan B., Wang M., Li Z. and Lu W.W., Surface modification of selective laser sintered nanocomposite scaffolds and osteogenic differentiation of mesenchymal stem cells on the scaffolds, Transactions of the Society For Biomaterials 2010 Annual Meeting. Seattle, WA, USA, 2010, Paper #421.

Kang J., Wang M. and Yuan X.T., Bicomponent fibrous scaffolds of controlled composition for tissue engineering applications, Proceedings of the 2009 ASME International Mechanical Engineering Congress & Exposition (IMECE 2009). Lake Buena Vista, Florida, USA, 2009, 9pp.

Kang J., Wang M. and Yuan X.Y., Biodegradable micro- and nanofibers fabricated through electrospinning for tissue engineering and controlled release applications, Proceedings of the 2009 ASME International Mechanical Engineering Congress & Exposition (IMECE 2009). Lake Buena Vista, Florida, USA, 2009, 7pp.

Kang J., Wang M. and Yuan X.Y., Electrospinning of PLLA Micro- and nanofibers: Effects of electrospinning parameters on fiber diameter and morphology, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 37.

Kang J., Wang M. and Yuan X.Y., Fibrous scaffolds of genipin-crosslinked gelatin fabricated through electrospinning, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 81.

Kang J., Wang M. and Yuan X.Y., Gelatin-PLLA bicomponent fibrous scaffolds for tissue engineering applications, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 120.

Lee W.C. and Wang M., Drug incorporation and release from electrochemically deposited Apatite/Collagen coatings on Ti alloy, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Li S. and Wang M., Synthesis of Au nanoparticles and their characterization, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Sultana N. and Wang M., Coating PHBV- and PHBV/PLLA-based scaffolds with collagen and characteristics of collagen-coated scaffolds, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 34.

Sultana N. and Wang M., Hydrolytic degradation and protein adsorption of PHBV/PLLA-based tissue engineering scaffolds, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 79.

Sun T., Wang L.P. and Wang M., (Ti-O-N)/Ti composite coatings fabricated on NiTi shape memory alloy for medical applications, Materials Science & Technology 2009 Conference & Exhibition. Pittsburg, USA, 2009.

Sun T., Wang L.P. and Wang M., (Ti-O-N)/Ti composite coatings fabricated on NiTi shape memory alloy for medical applications, Proceedings of Materials Science & Technology 2009 Conference & Exhibition. Pittsburg, USA, 2009, CD-ROM: 1pp.

Sun T. and Wang M., A comparative study of apatite coating and apatite/collagen composite coating fabricated on NiTi SMA through electrochemical deposition, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 136.

Sun T. and Wang M., Electrochemical deposition of apatite/collagen composite coating on NiTi shape memory alloy and coating properties, Proceedings of the 2009 Materials Research Society Fall Meeting. Boston, MA, USA, 2009, 6pp.

Sun T. and Wang M., Electrochemically deposited Apatite coating on NiTi shape memory alloy, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 77.

Sun T. and Wang M., Electrochemically deposited apatite/collagen composite coating on NiTi shape memory alloy, Proceedings of the 2nd Asian Symposium on Advanced Materials. Shanghai, China, 2009, 89-90.

Sun T., Wang L.P. and Wang M., Fabrication and characterization of Ti-O/Ti composite coatings on NiTi sape memory alloy for medical applications, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 35.

Sun T., Wang L.P. and Wang M., Fabrication of (Ti-O)/Ti composite coating on NiTi shape memory alloy using PIIID and coating characterisation, Proceedings of the 2nd Asian Symposium on Advanced Materials. Shanghai, China, 2009, 54-56.

Sun T., Wang L.P. and Wang M., Fabrication of (Ti-O-N)/Ti composite coating on NiTi shape memory alloy via PIIID and its evaluation, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 135.

Sun T., Wang L.P. and Wang M., Fabrication of (Ti-O-N-Si)/Ti composite coating on NiTi shape memory alloy using PIIID and coating evaluation, Proceedings of the 2009 Materials Research Society Fall Meeting. Boston, MA, USA, 2009, 6pp.

Sun T., Wong H.W. and Wang M., Fabrication of an Apatite/Collagen composite coating on the NiTi shape memory alloy through electrochemical deposition and coating characterisation, Materials Science Forum. Switzerland, Trans Tech Publications, 2009, 618-619: 319-323.

Tang G., Yang Y., Sun A., Song T., Zhao Y., Yuan X., Yuan X., Fan Y. and Wang M., Controlled release of dexamethasone from porous PLGA scaffolds under cyclic Loading, Science China Chemistry. Beijing, China and Berlin, Germany, Science China Press and Springer-Verlage Berlin Heidelberg, 2010, 53: 594-598.

Tang G.W., Yang Y.F., Zhao Y.H., Yuan X.Y., Wang M. and Fan Y.B., Controlled drug delivery from porous PLGA scaffolds under dynamic and static loading conditions, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 87.

Tong H.W., Wang M. and Lu W.W., Cell behaviour on electrospun biodegradable fibrous membranes: Effects of fiber diameter and fiber alignment, Proceedings of Materials Science & Technology 2009 Conference & Exhibition. Pittsburg, USA, 2009, CD-ROM: 1pp.

Tong H.W., Wang M., Li Z. and Lu W.W., Effects of the alignment, diameter and surface morphology of electrospun fibers on the behaviour of osteoblastic cells, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 107.

Tong H.W. and Wang M., Electrospinning of fibrous polymer scaffolds using positive voltage or negative voltage: A comparative study, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 113.

Tong H.W., Wang M., Li Z., Lam W.M.R. and Lu W.W., Electrospinning of surface-porous fibers and In vitro biological study of these fibers, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 38.

Tong H.W. and Wang M., Electrospinning of ultrafine fibrous tissue engineering scaffolds: Effects of emitting electrode polarity, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Tong H.W. and Wang M., Electrospinning, characterization, and In Vitro degradation of PHBV micro- and submicron-fibers, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 78.

Tong H.W. and Wang M., Forming fibrous nanocomposite tissue engineering scaffolds through electrospinning: a comparative study of three fabrication routes, Proceedings of the 22nd International Symposium on Ceramics in Medicine (Bioceramics 22). Daegu, Korea, 2009, 197-200.

Tong H.W. and Wang M., Forming fibrous nanocomposite tissue engineering scaffolds through electrospinning: a comparative study of three fabrication routes, The 22nd International Symposium on Ceramics in Medicine (Bioceramics 22), Daegu, South Korea. 2009.

Tong H.W., Wang M. and Lu W.W., In Vitro Biological evaluation of fibrous PHBV polymer and CHA/PHBV nanocomposite scaffolds developed for tissue engineering applications, Proceedings of the 22nd International Symposium on Ceramics in Medicine (Bioceramics 22). Daegu, Korea, 2009, 453-456.

Tong H.W., Wang M., Li Z. and Lu W.W., In vitro biological assessment of electrospun composite fibers containing hydroxyapatite nanoparticles, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 108.

Tong H.W., Wang M. and Lu W.W., In vitro biological evaluation of fibrous PHBV polymer and CHA/PHBV nanocomposite scaffolds developed for tissue engineering applications, The 22nd International Symposium on Ceramics in Medicine (Bioceramics 22), Daegu, South Korea. 2009.

Tong H.W., Wang M., Li Z. and Lu W.W., The influence of fiber diameter, morphology and alignment on osteoblastic cell behaviour, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Tong H.W., Li Z., Wang M. and Lu W.W., 电纺纤维直径、表面形貌及排列状态对细胞的影响, 全国生物材料大会, 2010.

Tong H.W. and Wang M., 静电纺丝制备超细纤维组织工程支架—电极极性研究, 全国生物材料大会, 2010.

Wang C. and Wang M., Effects of de-ionized water and PBS buffer on the core-shell structure of emulsion electrospun fibers, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Wang M., Biomaterials R & D: A personal experience and the current status in Hong Kong, Proceedings of the Chinese Academy of Engineering’s Forum on the Current Status and Future Trend of Biomaterials R & D in China. Beijing, China, 2009, 6pp.

Wang M., Biomaterials R & D: A personal experience and the current status in Hong Kong, The Chinese Academy of Engineering’s Forum on the Current Status and Future Trend of Biomaterials R & D in China. Beijing, China, 2009.

Wang M., Biomaterials and tissue engineering products: From Lab-scale fabrication to industrial production, International Conference on Quality Control of Biomaterials and Tissue Engineering Products. Tianjin, China, 2009.

Wang M., Biomaterials and tissue engineering products: From Lab-scale gabrication to industrial production, Proceedings of International Conference on Quality Control of Biomaterials and Tissue Engineering Product. Tianjin, China, 2009, 101-107.

Wang M., Biomedical composite materials: Design, manufacture and applications, 12th Annual National Conference of CSBME-BMB. Guangzhou, China, 2009.

Wang M., Biomedical composite materials: Design, manufacture and applications, Proceedings of the 12th Annual National Conference of CSBME-BMB. Guangzhou, China, 2009, 1pp.

Wang M., Chapter 6 Composite coatings for implants and tissue engineering scaffolds, In: Luigi Ambrosio, Biomedical Composites. Cambridge, UK and Boca Raton, USA, Woodhead Publishing Ltd. and CRC Press, 2010, 127-177.

Wang M., Composite materials, coatings and scaffolds for human tissue repair, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 31.

Wang M., Composite materials, coatings and scaffolds for human tissue repair, WACBE World Congress on Bioengineering 2009. Hong Kong, 2009.

Wang M., Editor, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 1-186.

Wang M., Editorial Board Member, Biomedical Materials: Materials for Tissue Engineering & Regenerative Medicine. UK, Institute of Physics, 2009.

Wang M., Editorial Board Member, Composites Science and Technology. The Netherlands, Elsevier, 2009.

Wang M., Editorial Board Member, Frontiers of Materials Science in China (in English). China and Germany, Higher Education Press and Springer, 2009.

Wang M., Editorial Board Member, IET Nanobiotechnology. UK, Institution of Engineering and Technology, 2009.

Wang M., Editorial Board Member, Journal of Biomimetics, Biomaterials and Tissue Engineering. Switzerland, TransTech Publications, 2009.

Wang M., Editorial Board Member, Journal of Bionanoscience. USA, American Scientific Publishers, 2009.

Wang M., Editorial Board Member, Journal of Materials Science: Materials in Medicine. Germany, Springer, 2009.

Wang M., Editorial Board Member, Journal of the Royal Society Interface. London, UK, The Royal Society, 2009.

Wang M., Editorial Board Member, Surface and Coatings Technology . The Netherlands, Elsevier, 2009.

Wang M., Nano-biomaterials for human tissue repair, National Biomaterials Congress. Chengdu, China, 2010.

Wang M., Nano-biomaterials for human tissue repair, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Wang M., Nanocomposite scaffolds for bone tissue engineering, 3rd Annual World Congress of Gene-2009 (WCG-2009). Foshan, China, 2009.

Wang M., Nanocomposite scaffolds for bone tissue engineering, Proceedings of the 3rd Annual World Congress of Gene-2009 (WCG-2009). Foshan, China, 2009, 1pp.

Wang M., Nanocomposites for human tissue repair and regeneration, 2nd Asian Symposium on Advanced Materials. Shanghai, China, 2009.

Wang M., Nanocomposites for human tissue repair and regeneration, Proceedings of the 2nd Asian Symposium on Advanced Materials. Shanghai, China, 2009, 243-244.

Wang M., Nanofibers and nanocomposites for biomedical applications, Proceedings of Materials Science & Technology 2009 Conference & Exhibition. Pittsburg, USA, 2009, CD-ROM: 1pp.

Wang M., Nanoparticles, nanofibers and nanocomposites for biomedical applications, Materials Science & Technology 2009 Conference & Exhibition. Pittsburg, USA, 2009.

Wang M., Surface modification of biomaterials and tissue engineering scaffolds using the composite approach, 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010.

Wang M., Surface modification of biomaterials and tissue engineering scaffolds using the composite approach, Proceedings of the 2nd International Symposium on Surface and Interface of Biomaterials (ISSIB-II). Hong Kong, 2010, 14.

Wang M., Surface modification of biomaterials: Technologies and applications, 1st Forum on Surface Engineering of Biomedical Materials. Chengdu, China, 2009.

Wang M., Surface modification of biomaterials: Technologies and applications, Proceedings of the 1st Forum on Surface Engineering of Biomedical Materials. Chengdu, China, 2009, CD-ROM: 1pp.

Wang M., Surface modification of metallic biomaterials for orthopaedic applications, 4th International Light Metals Technology Conference (LMT2009). Gold Coast, Australia, 2009.

Wang M., Surface modification of metallic biomaterials for orthopaedic applications, Materials Science Forum. Switzerland, Trans Tech Publications, 2009, 618-619: 285-290.

Wang M., Technical Commitee Member, International Organization for Standardization (TC150 Implants for surgery). 2010.

Wang M., Technical Committee Member, International Organization for Standardization (TC194 Biological evaluation of medical devices). 2010.

Wang M., Technical Committee Member, International Organization for Standardization (TC229 Nanotechnologies). 2010.

Wu J.M. and Wang M., Chapter 12 Bioactive bioceramic coatings. Part I: Coatings on non-metallic biomaterials, In: Ahmad Umar and Yoon-Bong Hahn, Metal Oxide Nanostructures and their Applications . California, USA, American Scientific Publishers, 2010, 4: 451-478.

Wu J.M. and Wang M., Chapter 13 Bioactive bioceramic coatings. Part II: Coatings on metallic biomaterials, In: Ahmad Umar and Yoon-Bong Hahn, Metal Oxide Nanostructures and their Applications. California, USA, American Scientific Publishers, 2010, 4: 479-509.

Yang Y., Tang G., Zhao Y., Yuan X., Yuan X., Fan Y. and Wang M., Controlled release of drugs from microsphere-attached scaffolds under static or cyclic loading, Proceedings of the National Biomaterials Congress. Chengdu, China, 2010, CD-ROM: 1pp.

Yang Y.F., Tang G.W., Zhang H., Zhao Y.H., Yuan X.T., Fan Y.B. and Wang M., Controlled release of bioactive agents from PLGA scaffolds under cyclic loading, Proceedings of WACBE World Congress on Bioengineering 2009. Hong Kong, 32.

Zhou W., Duan B., Wang M. and Cheung W.L., Crystallization behavior of Poly(L-Lactide)/Carbonated hydroxyapatite nanocomposite microspheres, Journal of Applied Polymer Science. Wiley Periodicals, Inc, 2009, 113: 4100-4115.

Zhou W., Wang M., Cheung W.L. and Ip W.Y., Selective Laser Sintering of Poly(L-Lactide)/Carbonated Hydroxyapatite Nanocomposite Porous Scaffolds for Bone Tissue Engineering, In: Daniel Eberli , Tissue Engineering. Vienna, Austria, IN-TECH, 2010, 179-204.

Researcher : Wei X

List of Research Outputs

Wang L. and Wei X., Heat conduction in nanofluids, In: K. Sattler, Handbook of Nanophysics. Taylor & Francis, 2010, (Chapter 33), Vol. 3 (Nanoparticles and Quantum Dots): 33.1-33.15.

Wei X. and Wang L., 1+1>2: Extraordinary fluid conductivity enhancement, Current Nanoscience. 2009, 5: 527-529.

Wei X. and Wang L., A microfluidic method for synthesizing Cu₂O nanofluids, Journal of Thermophysics and Heat Transfer. 2010, 24: 445-448.

Wei X., Kong T., Zhu H.T. and Wang L., CuS/Cu₂S nanofluids: synthesis and thermal conductivity, International Journal of Heat Mass Transfer. 2010, 53: 1841-1843.

Wei X. and Wang L., Synthesis and thermal conductivity of microfluidic copper nanofluids, Particuology. 2010, 8: 262-271.

Researcher : Wong CC

List of Research Outputs

Wong C.C. and Liu C.H., On the pollutant plume dispersion in the urban canopy layer over 2D idealized street canyons: a large-eddy simulation approach, European Geosciences Union, General Assembly 2010, Vienna, Austria, May 2-7, 2010 , 2010 . 2010.

Wong C.C. and Liu C.H., Pollutant plume dispersion in the urban canopy layer over 2D idealized street canyons, 14th Annual Conference of HKSTAM 2009/2010, Hong Kong, March 13, 2010.

Researcher : Wong HL

List of Research Outputs

Chan B.P., Wong H.L., Wong M.Y., Chan G.C.F. and Yang Z., Methods to Enhance Mesenchymal Stem Cell Migration, Provisional Patent Application (filed on 15 June 2010) (Application No. 61/354,871). 2010.

Wong H.L., Wong M.Y., Chan G.C.F., Yang Z. and Chan B.P., Functionally selecting human mesenchymal stem cell subpopulations with better migratory activities using a collagen barrier. , 7th Annual Meeting of International Society for Stem Cell Research, Jul 8-11, 2009. Barcelona, Spain.. 2009, 1265.

Researcher : Wong MY

List of Research Outputs

Chan B.P., Hui T.Y., Wong M.Y. and Chan G.C.F., Formation of injectable and osteoinductive bone-like microparticles using mesenchymal stem cell-collagen microspheres., 7th Annual Meeting of International Society for Stem Cell Research, Jul 8-11, 2009. Barcelona, Spain.. 2009, 1263.

Chan B.P., Wong H.L., Wong M.Y., Chan G.C.F. and Yang Z., Methods to Enhance Mesenchymal Stem Cell Migration, Provisional Patent Application (filed on 15 June 2010) (Application No. 61/354,871). 2010.

Li Y.Y., Cheng H.W., Wong M.Y., Cheung K.M.C., Chan D. and Chan B.P., Collagen-mesenchymal stem cell microspheres for cartilage tissue engineering. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S69:222.

Li Y.Y., Cheng H.W., Chan P.M., Wong M.Y., Teng W.K., Chow S.T., Cheung K.M.C., Chan D. and Chan B.P., Repair of osteochondral defects with collagen-mesenchymal stem cell microspheres in a rabbit model. , ISSCR 8th Annual Meeting. Jun 16-19, 2010, Moscone West, San Francisco, CA USA. . 2010, #W-50, p250.

Wong H.C.T., Wong M.Y., Chan B.P. and Yu A.C.H., Ultrasound-enhanced osteogenesis of human mesenchymal stem cells encapsulated in collagen meshwork, IEEE Ultrasonics Symposium. 2009, 361-364.

Wong H.L., Wong M.Y., Chan G.C.F., Yang Z. and Chan B.P., Functionally selecting human mesenchymal stem cell subpopulations with better migratory activities using a collagen barrier. , 7th Annual Meeting of International Society for Stem Cell Research, Jul 8-11, 2009. Barcelona, Spain.. 2009, 1265.

Researcher : Wong MY

List of Research Outputs

Wong H.C.T., Wong M.Y., Chan B.P. and Yu A.C.H., Ultrasound-enhanced osteogenesis of human mesenchymal stem cells encapsulated in collagen meshwork, IEEE Ultrasonics Symposium. 2009, 361-364.

Researcher : Wu D

List of Research Outputs

Lo S.H., Wu D. and Sze K.Y., Adaptive meshing and analysis using transitional quadrilateral and hexahedral elements, Finite Elements in Analysis & Design. 2010, 46: 2-16.

Wu D., Advanced Transition Finite Element Formulation for Adaptive Refinement Analysis of Solids and Structures, PhD Thesis. Hong Kong, The University of Hong Kong, 2010, 1-226.

Researcher : Wu X

List of Research Outputs

Leung Y.C., Wu X. and Leung M.K.H., A review on biodiesel production using catalyzed transesterification, Applied Energy. Elsevier, 2010, 87: 1083-1095.

Researcher : Xu Q

List of Research Outputs

Lin Y., Yao S. and Xu Q., Dynamic Adhesion Energy Between Surfaces Connected by Molecular Bonds and its Application to Peel Test , Cellular and Molecular Bioengineering. 2010, 3: 247-255.

Researcher : Xuan J

List of Research Outputs

Ni M., Leung Y.C., Leung M.K.H., Xuan J. and Wang H.Z., Thermo-electrochemical modeling of the transport phenomena and electrochemical reactions in ammonia fed solid oxide fuel cells, Proceedings International Conference on Applied Energy 2010. Singapore, National University of Singapore, CD-Rom: 10pp.

Xuan J., Leung M.K.H., Leung Y.C. and Ni M., A review of biomass-derived fuel processors for fuel cell systems, Renewable and Sustainable Energy Reviews. 2009, 13: 1301-1313.

Xuan J., Leung M.K.H. and Leung Y.C., Gravitational effects on the performance of membraneless micro fuel cells, Proceedings International on Applied Engergy 2010. Singapore, National University of Singapore, CD-Rom: 10pp.

Xuan J., Leung M.K.H., Leung Y.C. and Ni M., Integrating chemical kinetics with CFD modeling for autothermal reforming of biogas, International Journal of Hydrogen Energy. Elesvier, 2009, 34: 9076-9086.

Xuan J., Leung M.K.H. and Leung Y.C., Modeling analysis of membraneless micro fuel cell working under critical conditions, Proceedings International Conference on Applied Energy 2010. Singapore, Natioanl University of Singapore, CD-Rom: 10pp.

Researcher : Xuan J

List of Research Outputs

Xuan J., Leung M.K.H., Leung Y.C. and Ni M., A review of biomass-derived fuel processors for fuel cell systems, Renewable and Sustainable Energy Reviews. 2009, 13: 1301-1313.

Researcher : Xue S

List of Research Outputs

Kou X., Xue S. and Tan S.T., Knowledge-guided inference for voice-enabled CAD, Computer Aided Design. Elsevier, 2010, 42: 545-557.

Xue S., Kou X. and Tan S.T., Natural voice-enabled CAD: Modeling via natural discourse, Computer-Aided Design and Applications. 2009, 6(1): 125-136.

Researcher : Yan Z

List of Research Outputs

Lai D.W.C., Chow K.W., Rogers C.W. and Yan Z., Anti-dark solitons and periodic solutions of the resonant nonlinear Schrodinger equation, Advances in Nonlinear Waves and Symbolic Computations. Nova, 2009, 101-110.

Yan Z., Chow K.W. and Malomed B.A., Exact stationary wave patterns in three coupled nonlinear Schrodinger / Gross Pitaevskii equations, Chaos, Solitons and Fractals. 2009, 42: 3013-3019.

Researcher : Yang J

List of Research Outputs

Yang J., Ng C.O. and Zhang D., A numerical study on water waves generated by a submerged moving body in a two-layer fluid system, China Ocean Engineering. Nanjing, China, Chinese Ocean Engineering Society, 2009, 23(3): 441–458.

Researcher : Yang L

Project Title:	10th REHVA World Congress (Clima 2010) Urban Surface Temperature Profiles in Hong Kong Ventilation and Thermal environment in a semi-enclosed open urban space
Investigator(s):	Yang L
Department:	Mechanical Engg
Source(s) of Funding:	URC/CRCG - Conference Grants for Teaching Staff
Start Date:	05/2010
Completion Date:	05/2010

Abstract:

N/A

List of Research Outputs

Yang L., City Ventilation by Thermal Buoyancy for Better Urban Environment, URBAN ENVIRONMENTAL POLLUTION – Overcoming Obstacles to Sustainability and Quality of Life. Boston, USA, 2010.

Yang L., City Ventilation for Better Urban Air Environment and Energy Efficiency, Kyushu University G-COE Program: Novel Carbon Resources Science - Coal-Based Eco-Innovation, Forum III: Urban Environment in Asian Mega-City. 2010.

Yang L., City Ventilation of Hong Kong by Thermal Buoyancy, PhD Thesis. Hong Kong, The University of Hong Kong, 2009, 1-216.

Yang L. and Li Y., Dependence of City Ventilation by Thermal Buoyancy on Thermal Stratification, the 6th International Symposium on Heating, Ventilating and Air Conditioning (ISHVAC 2009). Nanjing, 2009.

Yang L. and Li Y., Urban Surface Temperature Profiles in Hong Kong, Clima2010, the 10th REHVA World Congress “Sustainable Energy Use in Buildings”. Turkey, 2010.

Yang L. and Li Y., Ventilation and thermal environment in a semi-enclosed open urban space, Clima2010, the 10th REHVA World Congress “Sustainable Energy Use in Buildings”. Turkey, 2010.

Yang L., Young Research Scientist Award at the Urban Environmental Pollution conference, Urban Environmental Pollution conference. 2010.

Researcher : Yang L

List of Research Outputs

Yang L., City Ventilation by Thermal Buoyancy for Better Urban Environment, URBAN ENVIRONMENTAL POLLUTION – Overcoming Obstacles to Sustainability and Quality of Life. Boston, USA, 2010.

Yang L., City Ventilation of Hong Kong by Thermal Buoyancy, PhD Thesis. Hong Kong, The University of Hong Kong, 2009, 1-216.

Yang L. and Li Y., Urban Surface Temperature Profiles in Hong Kong, Clima2010, the 10th REHVA World Congress “Sustainable Energy Use in Buildings”. Turkey, 2010.

Yang L. and Li Y., Ventilation and thermal environment in a semi-enclosed open urban space, Clima2010, the 10th REHVA World Congress “Sustainable Energy Use in Buildings”. Turkey, 2010.

Yang L., Young Research Scientist Award at the Urban Environmental Pollution conference, Urban Environmental Pollution conference. 2010.

Researcher : Yeung CW

List of Research Outputs

Yeung C.W., Cheah K.S.E., Chan D. and Chan B.P., Effects of reconstituted collagen matrix on fates of mouse embryonic stem cells before and after induction for chondrogenic differentiation, 7th Annual Meeting of International Society for Stem Cell Research, Jul 8-11, 2009. Barcelona, Spain.. 2009, 369.

Researcher : Yip LP

List of Research Outputs

Chow K.W., Yip L.P. and Gurarie D., Two exact solutions of the Tzitzeica - Bullough - Dodd equation, International Journal of Nonlinear Sciences and Numerical Simulations. 2009, 10: 935-943.

Researcher : Yuan M

List of Research Outputs

Yuan M. and Chan B.P., Culture of rabbit nucleus pulposus cells in 3D collagen microspheres – A comparison with traditional 2D culture. , TERMIS 2nd World Congress, Seoul, Korea, Aug 31- 3 Sep 2009. . 2009, S217: 824.

Researcher : Zhang D

List of Research Outputs

Ee B.K., Grimshaw R.H.J., Zhang D. and Chow K.W., Steady transcritical flow over a hole: Parametric map of solutions of the forced Korteweg - dr Vries equation, Physics of Fluids. 2010, 22: 056602 (9 pages).

Yang J., Ng C.O. and Zhang D., A numerical study on water waves generated by a submerged moving body in a two-layer fluid system, China Ocean Engineering. Nanjing, China, Chinese Ocean Engineering Society, 2009, 23(3): 441–458.

Zhang D., Yip T.L. and Ng C.O., Predicting tsunami arrivals: estimates and policy implications, Marine Policy. Netherlands, Elsevier Science, 2009, 33(4): 643–650.

Researcher : Zhang X

List of Research Outputs

Zhang X., Bai Y.C. and Ng C.O., Rheological properties of some marine muds dredged from China coasts, Proceedings of the Twentieth (2010) International Offshore and Polar Engineering Conference, Beijing, China, June 20–25. ISOPE, 2010, 455–461.

Researcher : Zhang Y

List of Research Outputs

Zhang Y. and Wang L., Experimental investigation of bubble formation in a microfluidic T-shaped junction, Nanoscale and Microscale Thermophysical Engineering. 2009, 13: 228-242.

Zhang Y., Fan J. and Wang L., Formation of nanoliter droplets in a confined microfluidic T-shaped junction: formation time and droplet volume, Current Nanoscience. 2009, 5: 519-526.

Researcher : Zhao X

List of Research Outputs

Soh A.K., Zhao X. and Song Y., Crack tip domain switching in normal and relaxor ferroelectrics subjected to mechanical and electric loading , 5th International Conference on Materials for Advanced Technologies 2009 . 2009.

Zhao X., Soh A.K., Lu L. and Liu J.X., Influence of dipole defects on polarization switching in the vicinity of a crack in relaxor ferroelectrics, Philosophical Magazine Letters. Oxon, England, Taylor & Francis, 2010, 90(4): 251-260.

Zhao X. and Soh A.K., Phase field simulation of ferroelectrics with cracks, 8th International Conference on Fracture and Strength of Solids. 2010, 1: 117.

Researcher : Zheng G

Project Title:	Theoretical investigation and atomistic simulation of deformation in iron-based bulk metallic glasses
Investigator(s):	Zheng G
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	08/2006

Abstract:

Purpose: The objective of this proposed research is to explore the deformation mechanisms in bulk metallic glasses (BMGs).We focus our research on iron-based BMG. Based on atomistic calculations, theory of mechanical deformation in these novel materials will be established. Key issues: BMGs are amorphous alloys with typical dimensions of millimeters to inches. They are known for high fracture strength, high strength-to-density ratio, and corrosion resistance. Unlike crystalline alloys, BMGs do not have dislocation-like defects during deformation process and the deformation is localized in nature. Although mechanical properties of BMG such as tensile or compression test, fracture and fatigue tests have been well studied in the past decade, a unified picture on microscopic deformation mechanisms governing their brittle nature is still lacking. Iron-based BMGs were invented in the past few years and have several features that deserve dedicated attention. First, iron-based BMGs are superior to other BMGs containing zirconium or palladium because theoretically they would possess larger strength and their main content, iron, is relatively cheap. Second, they are promising functional materials and structural materials in the industrial applications. Key issues: However, there are still several critical issues that have not been resolved to allow widespread applications of iron-based BMGs. First, they are brittle. Microscopic deformation mechanisms should be understood before materials design and processing techniques can be developed to increase their ductility. Second, is the role of iron atoms in the formation of atomistic defects called free-volume defects. Because of the lack of long range translational symmetry in BMG and the rapid deformation process confined in narrowly localized shear zones, the fundamental mechanisms of mechanical behavior in BMG are difficult, or sometimes impossible to be determined and understood by experiment alone. Calculations based on quantum mechanics and molecular dynamics (MD) simulations provide useful tools to explore the microscopic deformation defects in these materials. Possible outcomes and significance: In this proposed research we plan to develop a theory of deformation in iron-based BMG by gaining the knowledge needed through quantum mechanics calculation. First of all the electronic structures of deformation defects affected by the presentation of iron atoms will be determined by the density functional theory. The atomistic results will fulfill our ultimate goal to develop a phase-field transition theory for description, characterization and prediction of deformation behaviors of iron-based BMG. Successful execution of this proposed research will allow deformation defects to be characterized at the atomistic scale for the first time. The theory and simulation approaches will lay a solid foundation for the design and development of strong and ductile iron-based BMGs. Moreover, the research outcomes will have significant scientific impact on the deformation mechanisms of BMG and add significant value to the engineering applications of BMGs.

Project Title:	Atomistic Modeling of Mechanical Properties of Metal-Carbon Nanotube Composites
Investigator(s):	Zheng G
Department:	Mechanical Engg
Source(s) of Funding:	General Research Fund (GRF)
Start Date:	08/2007

Abstract:

1. The purpose of this research is to investigate the mechanical properties of metal-carbon nanotube (CNT) composites. Atomistic simulation approaches will be developed to predict and understand the mechanical behaviors of metal matrix composites with CNT reinforcement. 2. Multiscale computer modeling provides useful tools to explore the mechanical properties of CNT-metal composites, especially at the nano-scale where mechanical behavior of CNT-metal composite are difficult, or sometimes impossible to be determined and understood by experiment alone. However, these techniques are not well developed and validated for the CNT-metal composites. The proposed research is designed to develop the atomistic modeling approach which will allow us to predict and understand the mechanical behaviors of metal matrix composites with metallic CNT reinforcement. First-principles studies compared with available experimental data will be the expected products of this research. Such modeling products can accelerate the development of CNT-metal composites and optimize the fabrication of CNT-metal composites. 3. The atomistic simulations will also lay a solid foundation for design and development of strong and ductile industrial metals and alloys with CNT reinforcement. We plan to apply these approaches to CNT-reinforced aluminium alloy. CNTs have been considered as the ideal reinforcement component to improve the stiffness and toughness of these materials. The resulting nanocomposites could have broad applications in automobiles, aerospace, portable electronic devices and hydrogen storage 4. Successful execution of this proposed research will have significant scientific impacts on the understanding of the mechanical properties of CNT-metal composites and open up many opportunities to develop CNT-reinforced metals and alloys for engineering applications.

Researcher : Zhou W

List of Research Outputs

Zhou W., Duan B., Wang M. and Cheung W.L., Crystallization behavior of Poly(L-Lactide)/Carbonated hydroxyapatite nanocomposite microspheres, Journal of Applied Polymer Science. Wiley Periodicals, Inc, 2009, 113: 4100-4115.

Researcher : Zhuang Z

List of Research Outputs

Zhuang Z., Li Y., Yang X., Chen B. and Liu J., Thermal and energy analysis of a Chinse kang, Front. Energy Power Eng. China. 2010, 4: 84-92.

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