Dept of Mechanical Engg

DEPT OF MECHANICAL ENGG

Researcher : Afrin N

List of Research Outputs

Ngan A.H.W., Wo P.C., Zuo L., Li H. and Afrin N., The strength of submicron-sized materials, International Journal of Modern Physics B. World Scientific Publishing Company, 2006, 20(25), 26 & 27: 3579-3586.

Researcher : Au-yeung KL

List of Research Outputs

Au-yeung K.L., Sze K.Y. and Chan B.P., A setup for mechanoregulation studies of cells in 3D configuration, NANOBIO - TOKYO 2006. p151-154.

Researcher : Bakountouzis LN

Project Title:	Petrol engine fuel quality requirements
Investigator(s):	Bakountouzis LN
Department:	Mechanical Engg
Source(s) of Funding:	University Research Committee / Committee on Research and Conference Grants - General Award
Start Date:	07/1992

Abstract:

To investigate the effect of the quality of present-day fuels, available in Hong Kong, on the performance of typical petrol engines; to establish the requirements for a safe margin of protection against detonation and to quantify the loss of performance incurred, for the same protection, for a range of engines/fuels.

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:	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:	Competitive Earmarked Research Grants (CERG)
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:	Competitive Earmarked Research Grants (CERG)
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:	Study of carbon fibres and their applications in domestic electrical appliances
Investigator(s):	Chan ATY, Cheung DHK, Cheung KC
Department:	Mechanical Engg
Source(s) of Funding:	Matching Grant for Joint Research
Start Date:	05/2005
Completion Date:	08/2006

Abstract:

Carbon fibres are electrical conductors with electrical, mechanical and thermal properties very different from that of a traditional metallic or alloy conductor. By corretly dopting it with impurities, the properties of carbon fibre may be altered to suit specific appliction requirement as heating elements in domestic applicances. The following body of knowledge is requried to systematically apply the material to consumer product applications: relationship between the physical and chemical composition of the carbon fibres and its electrical, mechanical and thermal properties; the electrical, mechanical and thermal properties of "carbon-fibre based" materials such as thin film and emulsion. The university is in the position to provide the know-how and research facilities to collect and compile the said body of knowledge which will allow the applicant company to apply it the design of new types of key components in domestic electrical applicances to improve their performances and thus provide the necessary competitive edge in the international marketplace.

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:	A novel photochemically crosslinked collagen scaffold for intervertebral disc replacement
Investigator(s):	Chan BP, Cheung KMC, Lu WW, Wang M, Chan D, Luk KDK, So KF
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	10/2005

Abstract:

To develops a better solution for biological disc replacement by considering both the mechanical requirement and the biocompatibility of the scaffolds simultaneously; to fabricate and engineer a novel collagen scaffold with desired properties for disc replacement using a new crosslinking technology; to evaluate the in vitro biocompatibility of the scaffold in supporting growth and ECM production of bone marrow derived mesenchymal stem cells (MSCs).

Project Title:	Stem cell encapsulation in collagen microspheres – A platform technology for 3D cultures and cell delivery
Investigator(s):	Chan BP, Chan GCF
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	01/2006

Abstract:

The ultimate goal of the whole project is to develop collagen based cell encapsulation system for 3D culture expansion and cell delivery. The investigators would like to apply for the seed funding for a pilot study with the following specific objectives: 1. Build a prototype fabrication setup for cell encapsulation in collagen microspheres; 2. Investigate the influence of parameters (e.g. nozzle size) on the physical properties (e.g. size) of the microspheres. 3. Investigate the influence of the encapsulation process parameters (e.g. timing of harvest) and the matrix parameters (e.g. collagen density) on the cellular fate processes in particular viability, proliferation and differentiation potential of hMSCs.

Project Title:	Mechanoregulation studies of mesenchymal stem cells in 3D configuration
Investigator(s):	Chan BP, Chan D, Ngan AHW, Sze KY, Cheung KMC, Chan GCF
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	01/2007

Abstract:

(1) investigate the effects of cyclic compression on cellular activities of MSCs including chondrogenic differentiation using collagen-MSC microspheres as the physiologically relevant model (2) study the role of focal contact expression as the adhesion-dependent mechanosensing mechanism in the mechanical stimulation-induced cellular changes

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:	06/2007

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.

List of Research Outputs

Au-yeung K.L., Sze K.Y. and Chan B.P., A setup for mechanoregulation studies of cells in 3D configuration, NANOBIO - TOKYO 2006. p151-154.

Chan B.P., A novel cell delivery technology - Stable and injectable collagen-MSC microspheres, Stem cell Workshop, Li Ka Shing Faculty of Medicine, The University of Hong Kong. 2006.

Chan B.P., Cheung K.M.C., Chan G.C.F., Chan D. and Hui T.Y., Bioengineered intervertebral disc and Methods for Their Preparation., US Regular Patent Application No. 11/742,040 (filed on 30 April 2007). 2007.

Chan B.P., Chan G.C.F., Wong H.L., Cheung P.T., Cheah K.S.E. and Chan D., Cell-Matrix Microsphere, Associated Products, Methods for Preparation and Applications., US Regular Patent Application No. 11/750,863 (filed on 18 May 2007).. 2007.

Chan B.P., Hui T.Y., Chan C.M., So K.F., Lu W., Cheung K.M.C., Salomatina E. and Yaroslavsky A., Photochemical cross-linking for collagen-based scaffolds: a study on optical properties, mechanical properties, stability, and hematocompatibility, Tissue Engineering. 2007, 13(1): 73-85.

Chan B.P. and Chan G.C.F., Self-Assembled Collagen-Human mesenchymal stem cell (hMSCs) microspheres – novel bio-devices for cell delivery, International Society for Stem Cell Research 5th Annual Meeting. Jun 15-21 2007. Cairns, Queensland, Australia. 2007, p59.

Chan B.P., Fu S.C., Qin L., Rolf C. and Chan K.M., Supplementation-time dependence of growth factors in promoting tendon healing, Clinical Orthopaedics and Related Research. 2006, 448: 240-247.

Chan C.M., So K.F. and Chan B.P., Photochemically crosslinked collagen microspheres for controlled drug release, Proceedings on the Conference on Biomedical Engineering, BME2006. Hong Kong, p65.

Hui T.Y., Chan D., Cheung K.M.C., Chan G.C.F., Cheung W.L. and Chan B.P., Chondrogenic differentiation of human mesenchymal stem cells in three-dimensional collagen/chondroitin-6-sulfate gels: Influences of cell seeding density and collagen concentration, International Society for Stem Cell Research 5th Annual Meeting. Jun 15-21 2007. Cairns, Queensland, Australia. 2007, p155.

Tse T.H., Chan B.P., Chan C.M. and Lam J., Mathematical modeling of guided neurite growth in an engineered conduit with multiple concentration gradients of nerve growth factor (NGF), Annals of Biomedical Engineering. 2007, 35(9): 1561-1572.

Yeung C.W., Cheah K.S.E., Chan D. and Chan B.P., A novel 3-dimensional culture system for mouse embryonic stem cells, International Society for Stem Cell Research 5th Annual Meeting. Jun 15-21 2007. Cairns, Queensland, Australia. 2007, p340.

Researcher : Chan CF

List of Research Outputs

Chan C.F., Computer-aided Design and Manufacturing of Tactile Maps, M.Phil. Thesis. Hong Kong, The University of Hong Kong, 2007, 1-112.

Researcher : Chan CM

List of Research Outputs

Chan B.P., Hui T.Y., Chan C.M., So K.F., Lu W., Cheung K.M.C., Salomatina E. and Yaroslavsky A., Photochemical cross-linking for collagen-based scaffolds: a study on optical properties, mechanical properties, stability, and hematocompatibility, Tissue Engineering. 2007, 13(1): 73-85.

Chan C.M., So K.F. and Chan B.P., Photochemically crosslinked collagen microspheres for controlled drug release, Proceedings on the Conference on Biomedical Engineering, BME2006. Hong Kong, p65.

Tse T.H., Chan B.P., Chan C.M. and Lam J., Mathematical modeling of guided neurite growth in an engineered conduit with multiple concentration gradients of nerve growth factor (NGF), Annals of Biomedical Engineering. 2007, 35(9): 1561-1572.

Researcher : Chan CM

List of Research Outputs

Researcher : Chan CW

Project Title:	A unified framework for the compensation of memoryless actuator nonlinearity in feedback control
Investigator(s):	Chan CW
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	11/2003

Abstract:

To develop a general compensator for unknown memoryless actuator non-linearity, but known upper or lower bounds, and to derive conditions for the compensated system to be globally stable, by extending the actuator saturation compensator; to devise methods to design the saturation compensator from the stability conditions in both the time and frequency domain; to develop special guidelines for designing the actuator compensator for this class of controllers, and to investigate stability of the compensated system.

Project Title:	A time series approach to detect the transcriptional start sites of genes
Investigator(s):	Chan CW
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	01/2006

Abstract:

After sequencing, the next important task is to extract the hidden meaning behind the genetic information based on the four-letter alphabet {A, C, T, G}, by first finding the genes, then determining how their expression is regulated and the functions of the proteins they encode. These results would be essential to analyze the association between gene mutations and diseases, and to discover measures to cure the diseases. Two common approaches to identify genes are: to compare with known genes using e.g., data mining methods, and to identify special features in the DNA sequence that signify the possible existence of genes. The difficulties in the first approach are to choose suitable gene sequences for comparison and to select the thresholds in the comparison. Further, it is also difficult to identify new genes, as comparisons are made only with known genes. The second approach is more general, as it is based on the detection of the Transcriptional Start Site (TSS), e.g., the CpG island, which does not rely on the knowledge of existing genes. Although several techniques are available, they are developed based on the basic genetic information data. As sudden changes in the counts of CpGs that characterize the CpG islands are similar to faults in engineering systems, the detection of TSSs can be formulated as a fault detection problem, and well developed fault detection techniques for engineering systems can be applied to detect genes in the DNA sequence. The proposed techniques involve transforming first the genetic data into a time series before applying statistical techniques to detect the surges in the counts of CpG. The objectives of the project are:(1) To devolop statistical techniques based on the asymptotic local approach for detecting the surges in the counts of CpGs for detecting the TSS of CpG rich genes,(2) To apply the methods developed in this project to identify genes in human chromosomes, and to compare its performance with other existing techniques.

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.

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:	04/2007

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.

List of Research Outputs

Niu C. and Chan K.W., Tool path strategies for direct rib milling, In: Dr. I. Gibson, International Conference on Manufacturing Automation ICMA 2007. Singpapore, 866-877.

Researcher : Chan SH

List of Research Outputs

Chan S.H. and Ngan A.H.W., Statistical distribution of forces in stressed 2-D low-density materials with random microstructures, Mechanics of Materials. Elsevier Ltd., 2006, 38: 1199-1212.

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:

List of Research Outputs

Chen K.Z., Feng X.Y., Wang F. and Feng X.A., A virtual manufacturing system for components made of a multiphase perfect material, Computer-Aided Design. Exeter, U.K., Elsevier Ltd., 2007, 39: 13.

Chen K.Z., Wang F., Feng X.Y. and Feng X.A., Behavior modeling for the spraying device in the layered manufacturing process for the components made of a multiphase perfect material, Journal for New Generation Sciences. Bloemfontein, South Africa, Central University of Technology, 2006, 4: 13.

Chen K.Z., Design, modeling, and manufacture of heterogeneous components, Dalian Jiaotong University, Dalian, China. 2007.

Chen K.Z., Design, modeling, and manufacture of heterogeneous components, Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong. 2006.

Chen K.Z., I was awarded a Natural Science Prize (the second class) by the Ministry of Education in China in January 2007 for my achievement in the area of "Research on computer pattern recognition technology" together with the achievement in the same area made by Nanjing University, China., The Ministry of Education in China . 2007.

Chen K.Z., Wang F. and Feng X.A., Modeling of virtually manufactured components with a multiphase perfect material, 2006 IEEE International Conference on Virtual environments, human-computer interfaces and measurement systems. La Coruna, Spain, 2006, 6.

Wang F., Chen K.Z. and Feng X.A., Engraving behaviour modelling for manufacturing components with a periodic microstructure, International Conference on Manufacturing Automation. Singapore, 2007, 8.

Researcher : Chen X

List of Research Outputs

Yang J.S., Soh A.K. and Chen X., Acoustic leakage in electromagnetic waveguides made from piezoelectric materials , Journal of Applied Physics. USA, American Inst. of Physics, 2007, 101 (6): Art. No. 066105.

Researcher : Chen YH

Project Title:	Haptic sculpting of computer generated holography (CGH) for conceptual design
Investigator(s):	Chen YH
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	11/2002
Completion Date:	10/2006

Abstract:

This project will investigate some major issues in developing a 3D haptic interaction system based on Computer Generated Holography (CGH). CGH is the only 3D display technology supplying the 3d depth cues used by human visual system. The study will look into 3 major issues: 1) developing data reduction schemes for CGH visualization; 2) building a simplied dynamic model for the interaction between a haptic device and a 3d solid model; and 3) the volumetric models from haptic sculpting will be converted to StereoLithography (STL) files from which physical prototypes can be built using rapid prototyping techniques.

Project Title:	Haptic modelling and filtering in reverse engineering model refinement
Investigator(s):	Chen YH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	01/2005

Abstract:

1) To develop a haptic interface and surface filtering algorithm for haptically guided mark-up of feature edges for surface smoothing, and perform local, haptic-based smoothing of noise regions. 2) To develop a hatpic based algorithm to allow a user to easily add extra data with reference to the existing model or based on the user's new concepts.

Project Title:	Interactive Haptic Shape Modeling of Heterogeneous Objects
Investigator(s):	Chen YH
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	11/2005

Abstract:

The objectives of this project are: 1. To develop Physical Models for haptic interaction; 2. To develop representation schemes for heterogeneous property representation; 3. To study the haptic stability; 4. Collision detection and response algorithm studies; 5. Model simplification algorithm studies.

Project Title:	haptic interacting and editing of multi-material product in computer aided design
Investigator(s):	Chen YH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	07/2006

Abstract:

The major purpose of the proposed investigation is to develop a multi-material physical model and related rendering algorithms that are suitable for real-time haptic interaction between a multi-material object and an external tool. This investigation is mainly driven by recent research in computer aided modeling and representation of multi-material objects in engineering design and enormous interest in surgical simulation. The proposed project is made feasible with the latest technological development in haptic technologies, and the increasing computational power of today’s desktop computers. In graphical visualization, the rendering rate is only about 30 to 60 Hz. In haptic interaction, both graphical rendering and force rendering must be considered at the same time. Realistic force rendering presents a big challenge as the required force rendering rate is about 1kHz. Therefore, there are far more difficult problems to be considered and solved than only considering graphic modeling as in existing computer aided systems. Among many of the key issues to be considered in the haptic interaction are: * Force models used for the haptic interaction; * Haptic stability; * Collision detection and response techniques; * Intermediate representation (buffering) to ensure loop (both haptic and simulation loops) synchronization. The above issues must be considered for haptic interaction of object with isotropic mechanical properties. For haptic interaction of multi-material objects that have anisotropic mechanical properties, even more issues such as efficient force vector modeling must be considered. Multi-material objects, composed of different materials, are increasingly being used in engineering applications, current Computer-Aided Design (CAD) systems are excellent tools for the modeling of part geometry, but are unable to model and edit local material information of a part. It is also difficult for a part to be decomposed into a number of parts with free-form surfaces. The proposed investigation is critical for the successful development of CAD systems for multi-material objects as it allows the perception of different material properties in a part.

Researcher : Cheung C

List of Research Outputs

Cheung C., Effect of Heat Flux on Wind Flow and Pollutant Dispersion in an Urban Street Canyon, M.Phil. Thesis. Hong Kong, The University of Hong Kong, 2006, 1-201.

Researcher : Cheung KC

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.

Researcher : Cheung WL

List of Research Outputs

Fan K.M., Wong K.W., Cheung W.L. and Gibson I., Reflectance and transmittance of TrueForm^TM powder and its composites to Co₂ laser, Rapid Prototyping Journal. Bradford, UK, Emerald Group Publishing Ltd., 2007, 3: 175-181.

Hui T.Y., Chan D., Cheung K.M.C., Chan G.C.F., Cheung W.L. and Chan B.P., Chondrogenic differentiation of human mesenchymal stem cells in three-dimensional collagen/chondroitin-6-sulfate gels: Influences of cell seeding density and collagen concentration, International Society for Stem Cell Research 5th Annual Meeting. Jun 15-21 2007. Cairns, Queensland, Australia. 2007, p155.

Leung F.K.P., Cheung W.L., Lin X.D., Jia D. and Chung C.Y., Poly(ethylene terephthalate)/polypropylene microfibrillar composites. III. Structural development of poly(ethylene terephthalate) microfibers, Journal of Applied Polymer Science. Hoboken, NJ, USA, John Wiley & Sons, 2007, 104: 137-146.

Zhou W., Cheung W.L. and Wang M., Biodegradable composite scaffolds produced by selective laser sintering, Transactions of the Society for Biomaterials 2007 Annual Meeting. Chicago, USA, Society for Biomaterials, 2007, p. 170.

Zhou W., Wang M. and Cheung W.L., Fabrication and characterization of composite microspheres containing carbonated hydroxyapatite nanoparticles, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1221-1224.

Zhou W., Wang M. and Cheung W.L., Fabrication and characterization of composite microspheres containing carbonated hydroxyapatite nanoparticles, Proceedings of 5th Asian-Australiasian Conference on Composite Materials (ACCM-5). Hong Kong, The Hong Kong University of Science and Technology, 2006, 416-H.

Zhou W., Wang M. and Cheung W.L., Microstructures of carbonated hydroxyapatite nanospheres and CHAP/PLLA nanocomposite microspheres, Proceedings of Conference on Biomedical Engineering, BME2006. Hong Kong, Biomedical Division, HKIE, 104-107.

Zhou W., Lee S.H., Cheung W.L., Wang M. and Ip W.Y., Selective laser sintering of porous scaffolds from poly(L-lactide) microspheres and its nanocomposite with carbonated hydroxyapatite nanospheres, Proceedings of 20th European Conference on Biomaterials. Nantes, France, European Society for Biomaterials, 2006, T175.

Zhou W., Lee S.H., Wang M. and Cheung W.L., Selective laser sintering of tissue engineering scaffolds using Poly(L-lactide) microspheres, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1225-1228.

Zhou W., Lee S.H., Wang M. and Cheung W.L., Selective laser sintering of tissue engineering scaffolds using microspheres of poly(L-lactide)-Based nanocomposite, Proceedings of 5th Asian-Australiasian Conference on Composite Materials (ACCM-5). Hong Kong, The Hong Kong University of Science and Technology, 2006, 417-H.

Researcher : Ching WH

List of Research Outputs

Leung M.K.H., Ching W.H., Leung Y.C. and Lam G.C.K., Fluid dynamics and heat transfer in cold water thawing, Journal of Food Engineering. 2007, 78: 1221-1227.

Researcher : Chow HN

List of Research Outputs

Chow H.N., Tan S.T. and Sze W.S., An overview and discussion on designed porous structures and selected biomedical applications, Proceedings of International Conference on Manufacturing Automation (ICMA07). 2007, 243-251.

Chow H.N., Tan S.T. and Sze W.S., Layered modeling of porous structures with voronoi diagrams, Computer-Aided Design & Applications. 2007, 4(1-4): 321-330.

Researcher : Chow HYP

List of Research Outputs

Chow H.Y.P., Complexity Reduction of Mechanical Assemblies for Layered Manufacturing, M.Phil. Thesis. Hong Kong, The University of Hong Kong, 2006, 1-152.

Researcher : Chow KW

Project Title:	Periodic patterns in coupled hydrodynamical and optical waveguides
Investigator(s):	Chow KW
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	01/2005

Abstract:

To examine if wave propagation will persist for coupled waveguides of increasing complexity. Existence of solitary periodic, or generally these 'clusters' of solitary waves will promote our ability to characterize the physical problem under investigation, and will reveal the significant underlying structure of the model employed.

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:	Competitive Earmarked Research Grants (CERG)
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.

List of Research Outputs

Chow K.W., Editor, Applied Mathematical Sciences. 2007.

Chow K.W., Renewable and Sustainable Energy Fund - Generation of energy from waves by a tapered channel, The China Light and Power Company, Hong Kong. 2006.

Chow K.W., Malomed B.A., Liu W.M. and Xiong B., Singular nonlinearity management for matter wave solitons in normal and inverted parabolic potentials, Journal of the Physical Society of Japan. 2006, 75: 114004 (6 pages).

Chow K.W., The Best Teacher Award 2006-2007 Academic Year, Faculty of Engineering, HKU. 2007.

Conte R.M.J. and Chow K.W., Periodic waves of a discrete higher order nonlinear Schrodinger equation, Communications in Theoretical Physics. 2006, 46: 961 - 966.

Grimshaw R.H.J., Nakkeeran K., Poon C.K. and Chow K.W., Solitary wave solution for a non-integrable, variable coefficient nonlinear Schrodinger equation, Physica Scripta. 2007, 75: 620-623.

Gurarie D., Yip L.P., Chow K.W. and Zhang D., Relaxation and stationary vortex patterns for two dimensional channel flows, The Fifth International Conference on Nonlinear Mechanics, Shanghai, China. 2007.

Hu H.C., Lou S.Y. and Chow K.W., New interaction solutions of multiply periodic, quasi-periodic and non-periodic waves for the (n+1)-dimensional double sine Gordon equations, Chaos, Solitons and Fractals. 2007, 31: 1213-1222.

Tang X., Chow K.W. and Lou S., Nonlinear excitations and peakons of a (2+1) dimensional generalized Broer Kaup system, Acta Mechanica Sinica . 2007, DOI 10.I007/s10409-007-0062-9.

Yip L.P., Chow K.W. and Gurarie D., The role of geometry on the equilibrium configurations of two dimensional inviscid channel flows, 59th American Physical Society Division of Fluid Dynamics Meeting, Tampa, Florida, USA. 2006.

Researcher : Chwang ATY

Project Title:	An investigation of hydrodynamic interaction between two bodies
Investigator(s):	Chwang ATY
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	11/2003
Completion Date:	10/2006

Abstract:

To conduct research analytically as well as numerically on the hydrodynamic interaction between two immersed bodies involving translation, rotation and vibration. Fundamental solutions for three-dimensional non-spherical bodies will be derived by means of transformations of harmonics between two corresponding coordinate systems. Properties and dynamic behavior of a two-body system will be determined by solving the dynamical equations of motion. Experimental verification of some basic analytical and numerical results on the trajectories of floating bodies will also be conducted.

Project Title:	Wrist pulse contour screening programme
Investigator(s):	Chwang ATY, Lau CP
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2004

Abstract:

To set up a WPC Screening Centre to provide the WPC evaluation service to local adult subjects at the age of 18 years or above.

Project Title:	Fundamental Study of Nanofluids in Nanochannels of Various Shapes
Investigator(s):	Chen G
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	01/2006

Abstract:

The main objective of this email is to develop analytical models of nanofluid dynamics. Implications for designing nanofluidic circuits will be summarized for applications.

List of Research Outputs

Wang X., Xin H., Leonard J...N., Chen G., Chwang A.T.Y. and Jiang Q., The Oscillatory Characteristics of a 2C₆₀CNT Oscillator System, Journal Nanoscience and Nanotechnology . 2007, 7: 1512-1517.

Xie X., Li Y., Chwang A.T.Y., Ho P.L. and Seto W.H., How far droplets can move in indoor environments – Revisiting Wells evaporation-falling curve of droplets., Indoor Air. 2007, 17 (3): 211-225.

Zhao Y., Ma C.C., Wong L.H., Chen G., Xu Z.P., Zheng Q.S. and Chwang A.T.Y., Quasi-Reversible Energy Flows in Carbon-Nanotube-Based Oscillation, Journal Computational Theoretical Nanoscience. 2006, 3, 852: 852.

Zheng J., Zheng X., Zhao Y., Xie Y., Yam C.Y., Chen G., Jiang Q. and Chwang A.T.Y., Maxwell's Demon and Smoluchowskis Trap Door, Physical Review E. 2007, 75: 041109-1 - 041109-6.

Researcher : Conte RMJ

List of Research Outputs

Conte R.M.J. and Chow K.W., Periodic waves of a discrete higher order nonlinear Schrodinger equation, Communications in Theoretical Physics. 2006, 46: 961 - 966.

Researcher : Duggan BJ

List of Research Outputs

Chen Q.Z., Quadir M.Z. and Duggan B.J., Shear band formation in IF steel during cold rolling at medium reduction levels, Philosophical Magazine. Taylor & Francis, 2006, 86(23): 3633-3646.

Duggan B.J., Quadir M.Z. and Penelle R., An examination of cluster nucleation of goss oriented grains formed during secondary recrystallisation in an Fe-3.2% Si electrical steel, The Third International Conference on Recrystallization and Grain Growth (ReX & GG III). Switzerland, Trans Tech Publications, 2007, 558-559: 723-728.

Duggan B.J., Quadir M.Z., Tse Y.Y., Shen K., Liu G.L. and Chen Q.Z., The development of homo and heterogeneous rolling microstructures in rolled low carbon and interstitial-free steel, The Third International Conference on Recrystallization and Grain Growth (ReX & GG III). Switzerland, Trans Tech Publications, 2007, 558-559: 61-70.

Quadir M.Z. and Duggan B.J., A microstructural study of the origins of g recrystallization textures in 75% warm rolled IF steel, Acta Materialia. Elsevier Ltd., 2006, 54: 4337-4350.

Quadir M.Z. and Duggan B.J., Shear band thickening during rolling of interstitial free steel, ISIJ International. 2006, 46(10): 1495-1499.

Shen K. and Duggan B.J., Microbands and crystal orientation metastability in cold rolling interstitial-free steel, Acta Materialia. Elsevier Ltd., 2006, 55: 1137-1144.

Researcher : Grimshaw RHJ

List of Research Outputs

Grimshaw R.H.J., Nakkeeran K., Poon C.K. and Chow K.W., Solitary wave solution for a non-integrable, variable coefficient nonlinear Schrodinger equation, Physica Scripta. 2007, 75: 620-623.

Researcher : Gurarie D

List of Research Outputs

Gurarie D., Yip L.P., Chow K.W. and Zhang D., Relaxation and stationary vortex patterns for two dimensional channel flows, The Fifth International Conference on Nonlinear Mechanics, Shanghai, China. 2007.

Yip L.P., Chow K.W. and Gurarie D., The role of geometry on the equilibrium configurations of two dimensional inviscid channel flows, 59th American Physical Society Division of Fluid Dynamics Meeting, Tampa, Florida, USA. 2006.

Researcher : He M

List of Research Outputs

He M., Analysis of Underground Thermal Energy Storage Systems with Ground Water Advection in Subtropical Regions, M.Phil. Thesis. Hong Kong, The University of Hong Kong, 2007, 1-117.

Researcher : Hu R

List of Research Outputs

Hu R. and Soh A.K., Micromagnetic simulation of size effects on the properties of ferromagnetic materials , Fifth Asian-Australasian Conference on Composite Materials (ACCM-5). 2006.

Liang W., Soh A.K. and Hu R., Vibration analysis of a ferromagnetic plate subjected to an inclined magnetic field , International Journal of Mechanical Sciences. England, Pergamon-Elsevier Science Ltd, 2007, 49 (4): 440-446.

Song Y., Hu R. and Soh A.K., Microscopic simulations of the behavior of ferroelectrics and ferromagnetics, 2nd International Symposium on Functional Materials. 2007.

Researcher : Huang L

Project Title:	Braodband duct noise control at very low frequencies
Investigator(s):	Huang L
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	12/2003

Abstract:

A lot of noise sources are low-frequency in nature, such as the heavy road traffic, marine traffic, and the indoor air conditioning system. More discussion on the general impact of noise on our daily life in crowded cities like Hong Kong will be given in the next section. In this section, however, a special problem of noise induced combustion instability is adopted to illustrate the technological significance and objectives of the proposed topic, bearing in mind though that a direct solution of the combustion instability problem is beyond the scope of the project. Low frequency sound may induce flow instabilities that cause structural damage to devices like combustion engines. For example, diesel engines are known to emit a lot more nitrogen oxides when it operates in the fuel-rich regime than in the fuel-lean regime. However, fuel-lean combustion tends to feed part of the heat into unstable waves which may extinguish the flame. It does so by a productive coupling between the unsteady thermal expansion of gases with the sound waves bouncing back and forth in the combustion chamber which acts as a half-wavelength organ pipe. In order to quench the thermoacoustic coupling and stabilize the flame, the sound waves have to be absorbed at a sufficient rate according to the Rayleigh criterion. The techniqy of active noise control can certainly work in laboratory (Bloxsidge et al 1988, Dowling 2000, see References of Section 3, P.9), but manufacturers still prefer passive control as the ultimate solution for the design of lean combustors for vehicles, power plants as well as fighter jets fitted with afterburners. The challenge now is how to absorb or manipulate these menacing sound waves for a wide range of working conditions, and in a space much smaller than the combustor which itself measures only half a wavelength. The objectives are: a) to seek an anlytical understanding of how the essentially incompressible wave behaves with such a configuration, and b) to explore the full potential of the dipole motion in order to cross the low-frequency barrier in broadband, passive noise control in both ideal and realistic settings.

Project Title:	The suppression of multiple tones for small axial-flow fans
Investigator(s):	Huang L
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
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:	Stability of flow over a broadband wave reflector
Investigator(s):	Huang L
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	01/2007

Abstract:

1. To understand the flow-acoustic-structural interaction for flow induced vibration of a tensioned membrance, especially the role of the acoustic boundary condition on the observed instability. 2. To provide guidelines on how the new device (US Patent 10/697, 493 and its development) should be applied with regard to flow. 3. Research plan step 1 (8 months): numerical simulation of the instability problem (coding and initial analysis). This step will develop codes to identify the eigenvalues of the coupled system. The method of Chebyshev collocation will be used in either frequency domain or time domain. Initial coding will focus on the model with the compressible, potential flow interacting with the membrance, while the shear flow effect will be explored if the results of this model does not seem to account for the qualitative observations in the experiment. 4. Research plan step 2 (8 months): parametric study of controlling parameters. The anticipated key parameters include the flow speed, membrane length, mass and tension, the existence and geometry of the cavity, and the acoustic impedance at the upstream and downstream boundaries. 5. Research plan step 3 (8 months): experiment-simulation comparison on key mechanisms. In addition to the existing qualitative experimental observations, measurements will be taken to map out the instability regions. The qualitative instability observations (divergence vs flutter, vibration frequency and mode) will be compared with results from the numercial simulation. The agreement should reveal the key mechanisms of the instability, thus pointing to the directions in which the new device can be correctly and successfully employed in future design.

List of Research Outputs

Chiu Y.H., Cheng L. and Huang L., Drum-like silencers using magnetic forces in a pressurized cavity, Journal of Sound and Vibration. 2006, 297: 895-915.

Wang C.H., Han J. and Huang L., Optimization of a clamped plate silencer, Journal of the Acoustical Society of America. 2007, 121: 949-960.

Wang J. and Huang L., Active control of drag noise from a small axial flow fan, Journal of the Acoustical Society of America. 2006, 120: 192-203.

Researcher : Huang S

List of Research Outputs

Huang S., Ng C.O. and Guo Q., Experimental investigation of the effect of flow turbulence and sediment transport patterns on the adsorption of cadmium ions onto sediment particles, Journal of Environmental Sciences. Beijing, China, Science Press of China, 2007, 19(6): 696–703.

Huang S. and Ng C.O., Hydraulics of a submerged weir and its applicability in navigational channels: Basic flow structures, International Journal for Numerical Methods in Engineering. Chichester, UK, John Wiley & Sons, 2007, 69: 2264–2278.

Researcher : Hui SCM

List of Research Outputs

Hui S.C.M., Analysis of climatic data for sustainable buildings in Hong Kong, In: Meng, Qinglin, et al., Green Building Design and Technologies: Experience in Southern China and Hong Kong. Guangzhou, China, China Architectural and Building Press, 2006, 135-143.

Hui S.C.M., Benefits and potential applications of green roof systems in Hong Kong, Proceedings of the 2nd Megacities International Conference 2006. Guangzhou, China, Department of Architecture, the University of Hong Kong, 351-360.

Hui S.C.M., Internet resources on sustainable buildings, HKIA Journal. Hong Kong, PACE Publishing Limited, 2007, 48(1): 60-61.

Hui S.C.M., Latest trends in building automation and control systems, CAI Symposium 2007 on Intelligent Facility Management and Intelligent Transport. Hong Kong, Hong Kong Institution of Engineers CAI Division, 2007, 10pp.

Researcher : Hui TY

List of Research Outputs

Chan B.P., Cheung K.M.C., Chan G.C.F., Chan D. and Hui T.Y., Bioengineered intervertebral disc and Methods for Their Preparation., US Regular Patent Application No. 11/742,040 (filed on 30 April 2007). 2007.

Chan B.P., Hui T.Y., Chan C.M., So K.F., Lu W., Cheung K.M.C., Salomatina E. and Yaroslavsky A., Photochemical cross-linking for collagen-based scaffolds: a study on optical properties, mechanical properties, stability, and hematocompatibility, Tissue Engineering. 2007, 13(1): 73-85.

Hui T.Y., Chan D., Cheung K.M.C., Chan G.C.F., Cheung W.L. and Chan B.P., Chondrogenic differentiation of human mesenchymal stem cells in three-dimensional collagen/chondroitin-6-sulfate gels: Influences of cell seeding density and collagen concentration, International Society for Stem Cell Research 5th Annual Meeting. Jun 15-21 2007. Cairns, Queensland, Australia. 2007, p155.

Researcher : Hui TY

List of Research Outputs

Researcher : Kou X

List of Research Outputs

Kou X. and Tan S.T., A systematic approach for integrated computer-aided design and finite element analysis of funtionally graded objects, Materials and Design. UK, Elsevier Science, 2006, 28: 2549-2565.

Kou X. and Tan S.T., Heterogeneous object modeling: a review , Computer-Aided Design. 2007, 39: 284.

Researcher : Lam CW

List of Research Outputs

Lam C.W., Development of Photocatalytic Oxidation Technology for Purification of Air adn Water, M.Phil. Thesis. Hong Kong, The University of Hong Kong, 2007, 1-115.

Lam C.W., Leung M.K.H., Leung Y.C., Vrijmoed L.L.P., Yam W.C. and Ng S.P., Photocatalytic honeycomb reactor for removal of nitric oxide, Proceedings of the Renewable Energy 2006. Chiba, Japan, ISES, CD-ROM: 4pp.

Researcher : Lam HN

Project Title:	Design and production of an automatic cleaning and air drying system for kitchen floors
Investigator(s):	Lam HN
Department:	Mechanical Engg
Source(s) of Funding:	The OSH Enhancement Scheme for SMEs
Start Date:	01/2005

Abstract:

To carry out study on design and production of an automatic cleaning and air drying system for kitchen floors.

Project Title:	Innovative Environmentally Friendly Building-Integrated Ground-Source Heat Pump Systems for Building Air Conditioning
Investigator(s):	Lam HN
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	04/2006

Abstract:

The objectives of the research project are to investigate the feasibility and detailed technical performance of a ground-source heat pump system for building air conditioning with the heat exchanger pipes embedded in the concrete building foundation piles so that its potential for energy saving and environmental protection can be identified. Conventional ground-source heat pump systems utilise the mass of the earth as a heat sink when they operate in the cooling mode for comfort air conditioning. These systems are highly energy-efficient and environmentally friendly on account of the steady and lower temperature of the ground and the absence of heat rejection into the ambient air. A large number of deep bore holes down to a depth of at least 50 m are drilled in the ground to accommodate the vertical heat exchanger pipes. Besides being costly, these bore hole drillings also impose a great demand for availability of land which is scarce in Hong Kong. An innovative approach to solve this problem is therefore proposed in which the concrete building foundation piles will be used to accommodate the vertical heat exchanger pipes. Since most buildings in Hong Kong are high-rise buildings, the foundation piles are deeper and more piles are needed to ensure structural rigidity. In view of this, the potential of using the foundation piles for dissipation of heat to the ground from the embedded heat exchanger pipes is expected to be high.

List of Research Outputs

Lee C.K. and Lam H.N., Computer Modeling of Displacement Ventilation Systems Based on Plume Rise in Stratified Environment, Energy and Buildings. 2007, 39(4): 427-436.

Leung M.K.H., Leung Y.C., Lam H.N., Kung C.Y. and Liu C.H., Integrated Heat Pump with Fuzzy-Genetic Control for Instantaneous Cooling and Heating. 2006, 22(49): Publication number: 1873350.

Tan J. and Lam H.N., A Liquid Desiccant Cooling System with Heat Pump for Energy Conservation, Global Conference on Renewable Energy Approaches for Desert Regions. 2006, Paper No. 27, 1-6.

Researcher : Lam J

Project Title:	Synthesis Techniques for Multidimensional Dynamic Systems with Delay and Stochastic Effects
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	11/2004

Abstract:

To study: (1) stability analysis for multidimensional systems with delay and stochastic effects; (2) development of performance-based synthesis and filtering techniques.

Project Title:	Development of improved LMI-Type stability and performance conditions for retarded systems
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	11/2004
Completion Date:	10/2006

Abstract:

To develop stability and performance conditions in terms of linear matrix inequality which are suitable for a wide class of retarded systems with reduced conservatism. A new formulation with multiple time-dependent delay components will be considered.

Project Title:	Admissibility Conditions and Performance-Based Stabilization of Singular Switched Systems
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	10/2005

Abstract:

The main objectives of this project are: 1: Admissibility Analysis for Singular Switched Systems To derive regularity, stability, and non-impulsiveness (causality) conditions for continuous and discrete singular switched systems. Both deterministic and stochastic techniques will be used for different switching mechanisms. 2: Development of Performance-based Stabilization Techniques To develop conditions for stabilization of switched systems based on the worst-gain and energy-to-peak gain performance theories. Both deterministic and stochastic stabilization methodologies involving full and reduced order control will be studied and compared. Numerically reliable and efficient design algorithms will be constructed.

Project Title:	Design of Feedback Controllers for Systems with Random Transmission Signal Failures
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2006

Abstract:

In control engineering applications, the performance of feedback systems is dependent upon a continuous flow of measurement and control signals. Apart from possibly noise corruption, measurement and control signals may be delayed or even lost in the transmission process. A typical situation is when the control loop is implemented over a networked environment. Issues like networked-induced delay, data dropout and disordering are inevitable. This will naturally lead to a significant level of performance degradation or, in critical situations, instability of the closed-loop systems. In the past decade, more severe forms of control loop failures such as those due to the outage of sensors or actuators have been considered. These failures are consequences of hardware problems. In these situations, the signals involved will cease to transmit to the plants or the controllers, or fix at some constant values prior to the failures. Due to the severe stability and performance implications in the event of control system failure, there have been continuing efforts devoted to designing reliable feedback systems that guarantee the stability and basic performance even under the occurrence of these types of sensor or actuator faults. However, previous work in the synthesis of controllers to give reliable systems with faults are often unrealistic or conservative due to the assumptions imposed on the set of failure-prone sensors/actuators. Moreover, the faults considered in earlier developments are often treated as irrecoverable failures. These assumptions lead to controller synthesis results unnecessarily conservative. Instead, our focus will be on the possible signal transmission failures in the control channels. When properly modeled, the failures may be viewed as recoverable and governed by certain probabilistic descriptions. Such failures include intermittent lost of signal data (due to network conditions) or, in the extreme case, system component failures (rare but with slow recovery). In this project, feedback control design techniques will be developed with the aim of relaxing the restriction that a specific subset of sensors or actuators is only allowed to fail and that the failures are irrecoverable. Instead, a probabilistic description will be introduced to cater possibly random transmission signal failures over the whole set (or a subset) of sensors or actuators. Moreover, control over a networked environment will be considered with data packet dropouts or delay. Stabilization incorporating additional control objectives such as the H-infinity and H2 measures will also be studied. To facilitate the computation of the required controllers, numerical algorithms will be developed for the solution of these performance-based reliable controllers in the form of convex optimization.

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:	Competitive Earmarked Research Grants (CERG)
Start Date:	11/2006

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:	Model Simplification of Systems with Structural Constraints
Investigator(s):	Lam J
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2007

Abstract:

In the state-space modelling of certain engineering, economic and biological processes, the state variables used to represent the physical parameters often have fixed signs. The time evolution trajectories of these physical variables are therefore confined to an orthant in the state space. For instance, quantities such as time, money, animal and plant populations, concentration of chemicals can only admit positive values and thus imposing strong structural constraints on the system dynamics. Under appropriate diffeomorphisms, these systems can be transformed into different classes of positive systems. Systems with positivity have received a lot of attention in recent years. Apart from addressing the fundamental system-theoretic issues like stability, controllability, and realizability, most of the research results are focused on fairly restrictive classes of positive systems. Due to the technical difficulties in handling the positivity constraints, comparatively very little analysis and synthesis results obtained for general state-space systems have been extended to systems under such constraints. Another type of structural constraints imposed to systems modelled by the finite element approach is the positive semidefiniteness of system matrices. For instance, the dynamic models describing the vibration of engineering structures are invariably given in the form of second-order matrix differential equations. The mass, stiffness, and damping matrices are typical positive semidefinite in nature. Feedback control with collocated actuators and sensors will preserve such a property. In practical applications of these two types of structurally constrained systems, the number of state variables may be huge in order to accurately describe the behaviour of these models. To improve the modelling accuracy the dynamics of engineering systems or physical processes, mathematical models describing their dynamics, be they obtained from finite element modelling or identification techniques, are often necessarily of high orders. The large number of state variables in such models not only will decrease the efficiency of analysis, they may even lead to excessive computational time to an extent that simulation or real-time applications become impossible. On the other hand, from a synthesis point of view, the construction of controllers or filters for such dynamic systems based on these high-order models will encounter implementation difficulties. This is because modern performance-based synthesis techniques based on dynamic output feedback will give rise to controller dimensions no less than those of the system models (assuming that frequency weightings and full-order controllers are used). Consequently, there is a need to simplify these high-order models so that they are of size amenable to analysis and synthesis.In this project, model simplification techniques will be developed to reduce the dimensions of structurally constrained systems. Two types of structurally constrained systems will be considered, one involves the positivity of the system dynamics and the other has positive (semi)definite system matrices. Approaches based on controllability and observability measures, as well as optimality related to control-oriented performance indices, will be used to generate the reduced-order models with possibly guaranteed accuracy. Numerically reliable and efficient computational algorithms will be constructed for the computation of desired reduced models.

List of Research Outputs

Du H., Lam J. and Huang B., Constrained H₂ approximation of multiple input-output delay systems using genetic algorithm, ISA Transactions. 2007, 46(2): 211-221.

Du H. and Lam J., Energy-to-peak performance controller design for building via static output feedback under consideration of actuator saturation, Computers and Structures. 2006, 84(31-32): 2277-2290.

Du H., Lam J. and Zhang N., Modelling of a magneto-rheological damper by evolving radial basis function networks, Engineering Applications of Artificial Intelligence. 2006, 19(8): 869-881.

Galkowski K., Cichy B., Rogers E. and Lam J., Stabilization of a class of uncertain ‘wave’ discrete linear repetitive processes, IEEE Conference on Decision and Control 2006. San Diego, 1435-1440.

Gao H., Chen T. and Lam J., A new model for yime-delay systems with application to network based control, Chinese Control Conference 2006. Harbin, China, 56-61.

Gao H., Lam J., Mao X. and Shi P., H_¥ filtering for uncertain bilinear stochastic systems, Nonlinear Dynamics and Systems Theory. 2007, 7(2): 151-168.

Gao H., Lam J. and Wang C., Model simplification for switched hybrid systems, IEEE Transactions on Automatic Control. 2006, 55(12): 2015-2021.

Gao H., Lam J. and Chen G., New synchronization stability for general complex dynamic networks with coupling delays, Physics Letters A. 2006, 360(2): 263-273.

Gao H., Lam J., Chen T. and Wang C., Stability analysis of uncertain discrete-time systems with time-varying state delay: a parameter-dependent lyapunov functional approach, Asian Journal of Control. 2006, 8(4): 433-440.

Ho D.W.C., Jiang J. and Lam J., Global exponential stability of impulsive high-order BAM neural networks with time-varying delays, Neural Networks. 2006, 19(10): 1581-1590.

Lam J., Associate Editor , International Journal of Applied Mathematics and Computer Science. 2007.

Lam J., Associate Editor, Asian Journal of Control. 2007.

Lam J., Associate Editor, Conference Editorial Board of IEEE Control Systems Society. 2007.

Lam J., Associate Editor, IEEE Transactions on Signal Processing. 2007.

Lam J., Associate Editor, International Journal of Systems Science. 2007.

Lam J., Associate Editor, Journal of Sound and Vibration. 2007.

Lam J., Associate Editor, Journal of The Franklin Institute. 2007.

Lam J. and Zhou S., Dynamic output feedback H_¥ control of discrete-time fuzzy systems: a fuzzy-basis-dependent lyapunov function approach, International Journal of Systems Science. 2007, 38(1): 25-37.

Lam J., Guest Professorship, Central South University. 2006.

Lam J., Member of Editorial Board, IET Control Theory and Applications. 2007.

Lam J., Member of Editorial Board, Journal of Applied Functional Differential Equations. 2007.

Lam J., Member of Editorial Board, Research Letters in Signal Processing. 2007.

Lam J., Member of Editorial Board, The Open Automation and Control Journal. 2007.

Lam J., Member of Editorial Board, The Open Electrical and Electronic Journal. 2007.

Lam J., Model Reduction of Dynamic Systems, Nanjing University of Science and Technology. 2006.

Lam J., Model Reduction of Switched Systems, Central South University. 2006.

Lam J. and Xu S., On improvement of robust stability conditions for discrete-time polytopic systems, Dynamics of Continuous, Discrete and Impulsive Systems: Series A. 2007, 14(2): 301-308.

Lam J. and Huang S.D., Output feedback decentralized H_¥ control and fault tolerance analysis for symmetric cmposite systems, Dynamics of Continuous, Discrete, and Impulsive Systems: Series B. 2007, 14(3): 445-462.

Lam J., Shu Z., Xu S. and Boukas E.K., Robust H_¥ control of descriptor discrete-time mrkovian jump systems, International Journal of Control. 2007, 80(3): 374-385.

Lam J., Gao H. and Wang C., Stability analysis for continuous systems with two additive time-varying delay components, Systems and Control Letters. 2007, 56(1): 16-24.

Lam J., Stabilization of Markovian Jump Linear Systems via Time-Delayed Controllers, Nanjing University of Science and Technology. 2007.

Li Y., Gao H., Lam J. and Wang C., Robust peak-to-peak model reduction for linear systems: continuous- and discrete-time cases, Dynamics of Continuous, Discrete, and Impulsive Systems (Series B). 2007, 14(2): 291-304.

Paszke W., Lam J., Galkowski K., Xu S. and Kummert A., Delay-dependent stability condition for uncertain linear 2-D state-delayed systems, IEEE Conference on Decision and Control 2006. San Diego, 2783-2788.

Paszke W., Galkowski K., Rogers E., Lam J. and Xu S., Stability of differential linear repetitive processes with delays along two directions, MTNS 2006. Kyoto, Japan, 816-820.

Shu Z. and Lam J., Delay-dependent exponential estimates of stochastic neural networks with time delay, ICONIP 2006. Hong Kong, Part I: LNCS 4232-0332.

Shu Z. and Lam J., Global exponential estimates of stochastic cohen-grossberg neural networks with time delay, International Conference on Control and Automation. Guangzhou, China, 2007, 6pp.

Shu Z., Lam J. and Xu S., Robust stabilization of markovian delay systems with delay-dependent exponential estimates, Automatica. 2006, 42(11): 2001-2008.

Sulikowski B., Galkowski K., Rogers E., Kummert A. and Lam J., New A'casual output control for discrete linear repetitive processes, International Conference on Control and Automation. Guangzhou, China, 2007, 5pp.

Tse T.H., Chan B.P., Chan C.M. and Lam J., Mathematical modeling of guided neurite growth in an engineered conduit with multiple concentration gradients of nerve growth factor (NGF), Annals of Biomedical Engineering. 2007, 35(9): 1561-1572.

Wang H., Wang J. and Lam J., Robust fault detection observer design: iterative LMI approaches, Journal of Dynamic Systems, Measurement and Control. 2007, 129(1): 77-82.

Wang H., Wang J. and Lam J., Worst-case fault detection observer design: optimization approach, Journal of Optimization Theory and Applications. 2007, 132(3): 475-491.

Wang Q., Lam J., Gao H. and Wang Q., Energy-to-Peak model reduction for 2-D discrete systems described by fornasini-marchesini models, European Journal of Control. 2006, 12(4): 420-430.

Wang Q., Lam J., Xu S. and Zhou S., H_¥ model reduction for polytopic systems with time-varying delay, Journal of Systems and Control Engineering. 2006, 220(7): 627-639.

Wang Q., Lam J., Zhang Q.L. and Wang Q., Mixed optimization approach to model approximation of descriptor systems, Journal of Optimization Theory and Applications. 2006, 131(2): 265-280.

Wang Z., Lam J. and Liu X., Filtering for a class of nonlinear discrete-time stochastic systems with state delays, Journal of Computational and Applied Mathematics. 2007, 201(1): 153-163.

Wu L., Lam J., Paszke W., Galkowski K., Rogers E. and Kummert A., Filtering of discrete linear repetitive processes with H_¥ and l₂-l_¥ performance, IEEE International Symposium on Circuits and Systems. New Orleans, USA, 2007, 593-596.

Xiong J. and Lam J., Stabilization of linear systems over networks with bounded packet loss, Automatica. 2007, 43(1): 80-87.

Xu S., Lam J. and Zhong M., New exponential estimates for time-delay systems, IEEE Transactions on Automatic Control. 2006, 51(9): 1501-1505.

Xu S. and Lam J., On equivalence and efficiency of certain stability criteria for time-delay systems, IEEE Transactions on Automatic Control. 2007, 52(1): 95-101.

Xu S. and Lam J., Reduced-order H_¥ filtering for singular systems, Systems & Control Letters. 2007, 56(1): 48-57.

Zhou S., Lam J. and Zheng W., Control design for fuzzy systems based on relaxed nonquadratic stability and H_¥ performance conditions, IEEE Transactions on Fuzzy Systems. 2007, 15(2): 188-199.

Zhou S., Lam J. and Xue A., H_¥ filtering of discrete-time fuzzy systems via basis-dependent lyapunov function approach, Fuzzy Sets and Systems. 2007, 158(2): 180-193.

Researcher : Lam TF

List of Research Outputs

Lam T.F., Sze W.S. and Tan S.T., Nesting of complex sheet metal parts, Computer-Aided Design & Applications. 2007, 4(1-4): 169-179.

Researcher : Lau MW

List of Research Outputs

Ng C.O. and Lau M.W., Effects of boundary sorption on dispersion in oscillatory plane Couette flow, Proceedings of the International Conference on Frontiers in Fluid Mechanics, Bangalore, India, October 26-28. Bangalore, India, Sapna Book House, 2006, 62-86.

Researcher : Lee CK

List of Research Outputs

Lee C.K. and Lam H.N., Computer Modeling of Displacement Ventilation Systems Based on Plume Rise in Stratified Environment, Energy and Buildings. 2007, 39(4): 427-436.

Researcher : Lee SH

List of Research Outputs

Lee S.H., Feasibility Study of Selective Laser Sintering of Biopolymer Scaffolds for Tissue Engineering, M.Phil. Thesis. Hong Kong, The University of Hong Kong, 2006, 1-152.

Zhou W., Lee S.H., Cheung W.L., Wang M. and Ip W.Y., Selective laser sintering of porous scaffolds from poly(L-lactide) microspheres and its nanocomposite with carbonated hydroxyapatite nanospheres, Proceedings of 20th European Conference on Biomaterials. Nantes, France, European Society for Biomaterials, 2006, T175.

Zhou W., Lee S.H., Wang M. and Cheung W.L., Selective laser sintering of tissue engineering scaffolds using Poly(L-lactide) microspheres, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1225-1228.

Zhou W., Lee S.H., Wang M. and Cheung W.L., Selective laser sintering of tissue engineering scaffolds using microspheres of poly(L-lactide)-Based nanocomposite, Proceedings of 5th Asian-Australiasian Conference on Composite Materials (ACCM-5). Hong Kong, The Hong Kong University of Science and Technology, 2006, 417-H.

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:	Development of theoretical solutions to predict the transient phase-change heat and mass transfer for multiple industrial applications
Investigator(s):	Leung MKH, Leung YC, Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	04/2005

Abstract:

The main objectives of this research are: 1) To derive a general theoretical solution to this nonhomogeneous problem. 2) To design computational techniques that determine the movement of an interface whose behavior highly depends on the nature and characteristics of individual industrial process. 3) To define proper equivalent material properties that can be substitutes for any temperature-dependent material properties for accurate theoretical prediction.

Project Title:	Additional Columbarium at Diamond Hill Consultancy Services for the Joss Paper Burning, Smoke & Ash Treatment Systems
Investigator(s):	Leung MKH, Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	Architectural Services Department - General Award
Start Date:	10/2005
Completion Date:	08/2006

Abstract:

To conduct site visit(s) to existing columbaria to study the process of joss paper burning, associated equipment, inputs and other provisions as required for the burning tests and smoke and temperature measurements; to survey the weight of ash generated during the peak seasons and off-peak seasons at existing local columbaria; to estimate the weight of ash generated during the peak seasons and off-peak seasons at the new columbarium; to set up and perform on-site tests for the smoke flow and temperature measurements in a joss paper burner by simulating the peak and non-peak conditions. The measurements include: a) at the main chimney stack, airflow and smoke flow rates, and temperature, b) temperature at individual joss paper burners. The aforementioned measurements are used to determine the smoke / flue gas flow rate and temperature along the exhaust pathway during the burning process. Afterward, it is used to estimate the amount of smoke / flue gas exhaust from the new columbaria.

Project Title:	Solar Photocatalysis of Metal Ion Implanted Sol-Gel TiO2 Thin Film Coated on Light-Transmitting Substrate
Investigator(s):	Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	04/2006

Abstract:

Key issues and problems: Photocatalysis of transparent sol-gel nano titanium dioxide (TiO2) thin films coated on light-transmitting glass substrates has many potential applications in various aspects, including water purification, air purification, hydrogen production, and self-cleaning windows. The light-transmitting glass substrate can significantly increase the irradiated surface area due to the optic fiber effect. The useful spectral range can be extended from UV to visible light when the TiO2 catalyst is implanted with metal ion, such as chromium (Cr) or vanadium (V). Such monolith photoreactors are particularly suitable for the use of sunlight as the solar UV and visible light can be transmitted from the upper surface to the lower layers, resulting in complete activation of all immobilized photocatalyst. In this research, a theoretical model will be developed to simulate the heterogeneous photocatalytic kinetics of the thin film and the water/air purification effect of the monolith photoreactor. Preivous research has shown the promise of photoreactors made of UV-transmitting glass substrates coated with sol-gel TiO2 thin films [1-6]. Further development needed is to investigate the shift of absorption band from UVA to the full solar spectrum. Metal ion implantation has been identified as the most suitable method to shift the absorption band. The limited research works done on ion implanted TiO2 were mostly conducted by Anpo [7]. The effects of the thin film properties, photoreactor design, and operational parameters on the photocatalytic performance are not yet fully understood. The fundamental molecular photocatalytic kinetics of the ion-implanted catalyst is of particular importance. Further theoretical and experimental studies are needed to facilitate engineering design and control. Project objectives: In order to address the abovementioned issues, the research will be carried out with the following key objectives: (1) The promising photocatalytic module made of Cr- or V-implanted sol-gel nano-TiO2 thin film coated on light-transmitting glass substrate will be thoroughly characterized in four categories: (i) adsorption of chemicals, (ii) spectral absorption, (iii) photocatalytic degradation of organic compounds, and (iv) photocatalytic destruction of microorganisms. (2) A theoretical model will be developed to simulate and predict the electron-hole formation and recombination behaviors. The model will be used to optimize the design of the thin film with proper physical and chemical properties. (3) In conjunction with fluid dynamics and quantum mechanics, a computational model will be implemented to predict the performance of a thin film photoreactor on water and air purification. (4) The computational model will be used as a design tool to optimize the photoreactor design for water and air purification. (5) Experimental investigation on photocatalytic water/air detoxification and disinfection will be conducted in order to validate the computational model and to test the performance of the optimally designed photoreactor.

List of Research Outputs

Ao C.H., Leung M.K.H., Lam R.C.W., Leung Y.C., Vrijmoed L.P., Yam W.C. and Ng S.P., Photocatalytic decolorization of anthraquinonic dye by TiO₂ thin film under UVA and visible-light irradiation, Chemical Engineering Journal. 2007, 129(1-3): 153-159.

Lam C.W., Leung M.K.H., Leung Y.C., Vrijmoed L.L.P., Yam W.C. and Ng S.P., Photocatalytic honeycomb reactor for removal of nitric oxide, Proceedings of the Renewable Energy 2006. Chiba, Japan, ISES, CD-ROM: 4pp.

Lam R.C.W., Leung M.K.H., Leung Y.C., Vrijmoed L.L.P., Yam W.C. and Ng S.P., Visible-light-assisted photocatalytic degradation of gaseous formaldehyde by parallel-plate reactor coated with Cr ion-implanted TiO₂ thin film, Solar Energy Materials and Solar Cells. 2006, 91: 54-61.

Leung M.K.H., Ching W.H., Leung Y.C. and Lam G.C.K., Fluid dynamics and heat transfer in cold water thawing, Journal of Food Engineering. 2007, 78: 1221-1227.

Leung M.K.H., Leung Y.C., Lam H.N., Kung C.Y. and Liu C.H., Integrated Heat Pump with Fuzzy-Genetic Control for Instantaneous Cooling and Heating. 2006, 22(49): Publication number: 1873350.

Leung M.K.H., Integrated heat pump assisted desiccant dehumidifier , 6th Asia Pacific Conference on Sustainable Energy and Environmental Technologies APCSEET 2007. Thailand, CD-ROM.

Leung M.K.H., Tang S.M., Lam R.C.W., Leung Y.C., Yam W.C., Ng S.P. and Vrijmoed L.L.P., Parallel-plate solar photocatalytic reactor for air purification: semi-empirical correlation, modeling and optimization, Solar Energy. Oxford, UK, Elsevier Ltd., 2006, 80: 949-955.

Leung M.K.H., Yau J.K.F., Leung Y.C. and Kwong T.F.L., Sandwich-structured TiO₂/Cr/TiO₂ thin film for visible-light-assisted photocatalytic decolorization of dye, World Renewable Energy Congress–IX. 2006, CD-ROM.

Ni M., Leung M.K.H. and Leung Y.C., A modeling study on concentration overpotentials of a reversible solid oxide fuel cell, Journal of Power Sources. 2006, 163: 460-466.

Ni M., Leung M.K.H., Leung Y.C. and Sumathy K., A review and recent developments in photocatalytic water-splitting using TiO₂ for hydrogen production, Renewable and Sustainable Energy Reviews. 2007, 11(3): 401-425.

Ni M., Leung Y.C. and Leung M.K.H., Hydrogen production from biomass or biomass derived feedstock, Advances in Catalysis for Fuel Reforming and the Water Gas Shift Reaction. Pennsylvania, USA, Catalyst Group Resources Inc., 2006, 51-93.

Ni M., Leung M.K.H. and Leung Y.C., Micro-scale modeling analyses for advanced design of solid oxide steam electrolyzer to enhance hydrogen production, Proceedings of the Hydrogen Economy and Hydrogen Treatment of Materials (HTM). Ukraine, IAHE, 2007, 199-205.

Ni M., Leung M.K.H. and Leung Y.C., Micro-scale modeling of a functionally graded Ni-YSZ anode, Chemical Engineering & Technology. 2007, 30(5): 587-592.

Ni M., Leung M.K.H. and Leung Y.C., Micro-scale modelling of solid oxide fuel cells with micro-structurally graded electrodes, Journal of Power Sources. 2007, 168: 369-378.

Ni M., Leung M.K.H. and Leung Y.C., Modelling of proton conducting solid oxide fuel cells, Scientific Advances in Fuel Cell Systems. Turin, Italy, 2006, CD-ROM.

Ni M., Leung M.K.H. and Leung Y.C., Parametric study of solid oxide fuel cell performance, Energy Conversion & Management. 2007, 48: 1525-1535.

Ni M., Leung M.K.H., Sumathy K. and Leung Y.C., Potential of renewable hydrogen production for energy supply in Hong Kong, International Journal of Hydrogen Energy. Oxford, UK, Elsevier Ltd., 2006, 31: 1401-1412.

Ni M., Leung M.K.H. and Leung Y.C., Progress of dye-sensitized water-splitting for hydrogen production (Chinese), Chinese Journal of Power Sources. Tianjin, China, Ministry of Information Industry, 2006, 856-859.

Ni M., Leung M.K.H. and Leung Y.C., Technology development in nano-sized photocatalyst powder preparation technologies (in Chinese), Powder Metallurgy Technology. Beijing, China, China Association for Science and Technology, 2006, 379-383.

Ni M., Leung M.K.H., Leung Y.C. and Sumathy K., Theoretical modelling of TiO₂/TCO interfacial effect on dye-sensitized solar cell performance, Solar Energy Materials & Solar Cells. Amsterdam, Netherlands, Elsevier B.V., 2006, 90: 2000-2009.

Xie X., Liu C.H., Leung Y.C. and Leung M.K.H., Characteristics of air exchange in a street canyon with ground heating, Atmospheric Environment. Oxford, UK, Elsevier Ltd., 2006, 40: 6396-6409.

Yeung L.L., Lam C.K., Leung M.K.H. and Leung Y.C., Food Thawing Equipment. 2006, Application no. 200520017978.5.

Researcher : Leung YC

Project Title:	Development of a three-dimensional numerical model for air pollution study in urban street canyons
Investigator(s):	Leung YC, Lam KM
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	12/2003

Abstract:

To develop a three-dimensional computation model for street canyon flow; to validate and fine-tune the model using physical modelling technique; to investigate the characteristics of the flow in street canyons with different configurations using the validated model.

Project Title:	Numerical investigation of the physical and chemical processes of air pollutants in urban street canyons
Investigator(s):	Leung YC, Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	01/2005

Abstract:

To improve our understanding and to supplement experimental findings of the physical and chemical processes that occur in urban street canyons; to enhance current urban design practice and air polluation control strategy by conducting comprehensive sensitivity tests.

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
Completion Date:	07/2006

Abstract:

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

Project Title:	Performance test of a pilot FGD system
Investigator(s):	Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	Hong Kong Productivity Council - General Award
Start Date:	11/2005

Abstract:

To carry out performance test of a pilot FGD system.

Project Title:	Photocatalytic production of clean and renewable hydrogen fuel
Investigator(s):	Leung YC, Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
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:	Air pollution in Pearl River Delta region:sources and mitigations
Investigator(s):	Leung YC
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	05/2006

Abstract:

In recent years, vehicular emission control program implemented by the HKSAR Government has lowered the concentration of some of the air pollutants such as respirable suspended particulates and nitrogen oxides , mainly at the street level (HKEPD 2003). However, very little improvement in air quality can be felt by the general public. Many studies have revealed that the air pollution in Hong Kong is inherently a regional-scale problem. The increasing ground-level ozone concentration and decreasing visibility in our harbour served as a good indication of continuous deterioration of the regional air quality (Wang 2003). The problem is particularly serious for ozone and fine particles (smog) that cannot be solved solely by source control and managements in Hong Kong itself. In fact, these pollutants are secondary-pollutant formed from primary pollutants through a complex series of chemical reactions occurring in the atmospheric boundary layer and involve pollutants emitted from a variety of sources (e.g. vehicles, power plants and factories). A recent study (HKEPD 2002) found that the economy, population, electricity demand and vehicle mileage in the Pearl River Delta (PRD) region will grow by about two folds from 1997 to 2010. To cope with the deterioration in the regional air quality, the HKSAR Government and the Guangdong Provincial Government reached a consensus in 2002 for air pollutant emission reduction and jointly drew up the PRD Regional Air Quality Management Plan in 2003. Under the management plan, the two governments would set up a regional air quality monitoring network to be in operation in 2005. With the air quality data from the network, it is feasible to analyze the regional air quality problems in a wider aspect, which can help to develop comprehensive mitigation measures to combat the air pollution problems in the region. The followings are the objectives of the proposed study: 1. Identify long term trends and possible epidodic events of severe air pollution in the Pearl River Delta region;2. Establish the relationship between the air pollution in HK and PRD;3. Investigate the relative importance of local and transported air pollutants to air quality in HK and PRD.References:HKEPD (2003), Air Quality in Hong Kong 2003, Environmental Protection Dept., HKSAR.HKEPD (2002), Study of Air Quality in the Pearl River Delta Region, Environmental Protection Dept., HKSAR.Wang, T. (2003), Study of Visibility Reduction and its Causes in Hong Kong, Research Centre for Environmental Technology and Management, Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic University.

Project Title:	The impact of biogenic volatile organic compounds on regional-scale ozone episodes and air quality problems in Hong Kong
Investigator(s):	Leung YC, Liu CH
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	10/2006

Abstract:

(1) Project Purposes and Objectives The aim of this project is to determine the contribution of biogenic volatile organic compounds (VOCs) to the production of tropospheric ozone in the Hong Kong metropolitan region. In achieving this goal, we will accomplish the following objectives: (2) • compile a biogenic VOC emission inventory for air-quality application in Hong Kong; • configure a state-of-the-art air quality model for the region surrounding Hong Kong; • quantify the sensitivity of anthropogenic ozone precursors and biogenic VOCs on the regional-scale photochemical formation of tropospheric ozone over Hong Kong by making use of the biogenic VOC emission inventories, the mesoscale meteorological model and air quality model; • study the characteristics of and explain the frequent ozone episodes being encountered near the Hong Kong International Airport in the Tung Chung (suburban) and Tap Mun (rural) areas; • locate the photochemical-ozone regimes, such as nitrogen oxides (NOx)-sensitive or VOC-sensitive, of Hong Kong; • review the effectiveness of the current ozone abatement strategies employed in Hong Kong and recommend additional strategies, such as further restriction on NOx or VOC emissions, if necessary. (3) Key Issues and the Problems being Addressed • Tropospheric ozone is a secondary gaseous pollutant produced in the presence of solar radiation from NOx and VOCs. These air pollutants adversely affecting human health and agriculture products. • Vegetation emits a variety of biogenic VOCs as by-products of their metabolism with an estimated amount exceeding anthropogenic emissions, and under normal conditions biogenic VOCs are more chemically reactive than their anthropogenic counterparts. Studies have shown that biogenic VOCs contribute at least as much to tropospheric ozone formation at a level as anthropogenic VOCs. • The anthropogenic VOCs and ozone precursor emission inventories currently established in Hong Kong are reasonably reliable, but biogenic VOC emission inventories on a regional scale are not yet available for the Hong Kong territory and the industrialized Pearl River Delta Region. • Early ozone management strategies for the Hong Kong and Pearl River Delta Region have focused on limiting anthropogenic VOC emissions. This has worked well in metropolitan areas but less so in sub-urban and rural areas. • As anthropogenic VOC emissions have been falling due to more stringent control measures, biogenic VOCs will take on increasing importance in the development of effective ozone abatement strategies. (4) Possible Outcome and Long-Term Impact • Quantify the biogenic VOC emission inventory for Hong Kong and contrast its importance with the anthropogenic VOC emission inventory, particularly in the production of tropospheric ozone in HK. • Enhance our understanding of the physical and chemical behavior of ozone precursors, together with the nature and mechanisms leading to the ozone episodes in Hong Kong, and therefore help to implement effective environmental management strategies so as to improve the current severe air pollution problems in Hong Kong and Pearl River Delta Region. • Educate the general public, engineers, environmental consultants and urban planners on the ozone-formation potential of trees and plants during large-scale planting programs in metropolitan and urban areas so that these factors can be taken into account in future projects.

Project Title:	Economic production of hydrogen fuel using scrap metals
Investigator(s):	Leung YC, Leung MKH
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	05/2007

Abstract:

Objectives:a. To investigate the chemical kinetics of the reaction between metals and seawaterb. To explore the characteristics of hydrogen production from the above process;c. To optimize the hydrogen production efficiency of the process. Key issues and problems to be addressed:Hydrogen is a clean, renewable, and efficient energy source, which may well replace existing fossil fuel based energy sources. There are lot of researches on developing economical and clean techniques for producing hydrogen that can be used for internal combustion engines or fuel cells. The use of waste metals is an innovative technology that has high potential for producing hydrogen economically and cleanly. Some metals and alloys, such as magnesium, possess high chemical energy that can produce hydrogen gas from hydrolysis of the metals as shown below (take magnesium as an example): Mg + 2 H2O --> Mg(OH)2 + H2However, the hydrogen production rate in the above chemical process is quite low under normal circumstances. Until its energy conversion efficiency can be improved hydrogen production by this means will remain uneconomic. One way of improvement is the use of catalyst (such as platinum) and NaCl aqueous solution for enhancing the reaction rate. The main challenge in this study is, therefore, to study the chemical kinetics of the reaction process so as to develop a way to produce hydrogen efficiently using scrap metals that have no commerical values. It is anticipated to obtain the best operation conditions for the reaction process. Possible outcomes and long-term impact:The study will provide a better understanding on the mechanisms of hydrogen production during the hydrolysis reaction between metals and its reactant. An innovative and economic method of producing hydrogen will be developed. The project will make an important contribution towards the development of a clean and sustainable hydrogen economy. Furthermore, the success of this project can help reducing the pressure of solid waste disposal.

List of Research Outputs

Ao C.H., Leung M.K.H., Lam R.C.W., Leung Y.C., Vrijmoed L.P., Yam W.C. and Ng S.P., Photocatalytic decolorization of anthraquinonic dye by TiO₂ thin film under UVA and visible-light irradiation, Chemical Engineering Journal. 2007, 129(1-3): 153-159.

Lam C.W., Leung M.K.H., Leung Y.C., Vrijmoed L.L.P., Yam W.C. and Ng S.P., Photocatalytic honeycomb reactor for removal of nitric oxide, Proceedings of the Renewable Energy 2006. Chiba, Japan, ISES, CD-ROM: 4pp.

Lam R.C.W., Leung M.K.H., Leung Y.C., Vrijmoed L.L.P., Yam W.C. and Ng S.P., Visible-light-assisted photocatalytic degradation of gaseous formaldehyde by parallel-plate reactor coated with Cr ion-implanted TiO₂ thin film, Solar Energy Materials and Solar Cells. 2006, 91: 54-61.

Leung M.K.H., Ching W.H., Leung Y.C. and Lam G.C.K., Fluid dynamics and heat transfer in cold water thawing, Journal of Food Engineering. 2007, 78: 1221-1227.

Leung M.K.H., Leung Y.C., Lam H.N., Kung C.Y. and Liu C.H., Integrated Heat Pump with Fuzzy-Genetic Control for Instantaneous Cooling and Heating. 2006, 22(49): Publication number: 1873350.

Leung M.K.H., Tang S.M., Lam R.C.W., Leung Y.C., Yam W.C., Ng S.P. and Vrijmoed L.L.P., Parallel-plate solar photocatalytic reactor for air purification: semi-empirical correlation, modeling and optimization, Solar Energy. Oxford, UK, Elsevier Ltd., 2006, 80: 949-955.

Leung M.K.H., Yau J.K.F., Leung Y.C. and Kwong T.F.L., Sandwich-structured TiO₂/Cr/TiO₂ thin film for visible-light-assisted photocatalytic decolorization of dye, World Renewable Energy Congress–IX. 2006, CD-ROM.

Leung Y.C. and Guo Y., Effect of water on alkaline-catalyzed biodiesel production, 6th Asia Pacific Conference on Sustainable Energy and Environmental Technology APCSEET. Bangkok, Thailand, Kasetsart University, 2007, CD-ROM: 5pp.

Leung Y.C., Hydrogen energy: Policy and applications in Hong Kong (Keynote Speech), Hydrogen Energy and Fuel Cells Technology, Taiwan Hydrogen Energy & Fuel Cells Association.. 2006.

Leung Y.C., Impact of biogenic VOCs emissions on regional photochemical ozone formation., Invited lecture by School of Life Sciences, Sun Yat-Sen University. 2007.

Leung Y.C., Potential of renewable hydrogen applications in Hong Kong, Hong Kong Institution of Engineers Seminar organized by Gas & Energy Division, HKIE. 2007.

Leung Y.C., Potential of renewable hydrogen production for limited energy supply in Hong Kong, Annual Conference of the Hong Kong Institution of Sciences, HKIS. 2006.

Leung Y.C. and Guo Y., Transestification of neat and used frying oil: Optimization for biodiesel production, Fuel Processing Technology. Amsterdam, Netherlands, Elsevier B.V., 2006, 87: 883-890.

Li X., Liu C.H., Leung Y.C. and Lam K.M., Recent progress in CFD modelling of wind field and pollutant transport in street canyons, Atmospheric Environment. Oxford, UK, Elsevier Ltd., 2006, 40: 5640-5658.

Liu C.H. and Leung Y.C., Turbulent transport of passive scalar behind line sources in an unstably stratified open channel flow, International Journal of Heat & Mass Transfer. 2006, 49: 4305-4324.

Ni M., Leung M.K.H. and Leung Y.C., A modeling study on concentration overpotentials of a reversible solid oxide fuel cell, Journal of Power Sources. 2006, 163: 460-466.

Ni M., Leung M.K.H., Leung Y.C. and Sumathy K., A review and recent developments in photocatalytic water-splitting using TiO₂ for hydrogen production, Renewable and Sustainable Energy Reviews. 2007, 11(3): 401-425.

Ni M., Leung Y.C. and Leung M.K.H., Hydrogen production from biomass or biomass derived feedstock, Advances in Catalysis for Fuel Reforming and the Water Gas Shift Reaction. Pennsylvania, USA, Catalyst Group Resources Inc., 2006, 51-93.

Ni M., Leung M.K.H. and Leung Y.C., Micro-scale modeling analyses for advanced design of solid oxide steam electrolyzer to enhance hydrogen production, Proceedings of the Hydrogen Economy and Hydrogen Treatment of Materials (HTM). Ukraine, IAHE, 2007, 199-205.

Ni M., Leung M.K.H. and Leung Y.C., Micro-scale modeling of a functionally graded Ni-YSZ anode, Chemical Engineering & Technology. 2007, 30(5): 587-592.

Ni M., Leung M.K.H. and Leung Y.C., Micro-scale modelling of solid oxide fuel cells with micro-structurally graded electrodes, Journal of Power Sources. 2007, 168: 369-378.

Ni M., Leung M.K.H. and Leung Y.C., Modelling of proton conducting solid oxide fuel cells, Scientific Advances in Fuel Cell Systems. Turin, Italy, 2006, CD-ROM.

Ni M., Leung M.K.H. and Leung Y.C., Parametric study of solid oxide fuel cell performance, Energy Conversion & Management. 2007, 48: 1525-1535.

Ni M., Leung M.K.H., Sumathy K. and Leung Y.C., Potential of renewable hydrogen production for energy supply in Hong Kong, International Journal of Hydrogen Energy. Oxford, UK, Elsevier Ltd., 2006, 31: 1401-1412.

Ni M., Leung M.K.H. and Leung Y.C., Progress of dye-sensitized water-splitting for hydrogen production (Chinese), Chinese Journal of Power Sources. Tianjin, China, Ministry of Information Industry, 2006, 856-859.

Ni M., Leung M.K.H. and Leung Y.C., Technology development in nano-sized photocatalyst powder preparation technologies (in Chinese), Powder Metallurgy Technology. Beijing, China, China Association for Science and Technology, 2006, 379-383.

Ni M., Leung M.K.H., Leung Y.C. and Sumathy K., Theoretical modelling of TiO₂/TCO interfacial effect on dye-sensitized solar cell performance, Solar Energy Materials & Solar Cells. Amsterdam, Netherlands, Elsevier B.V., 2006, 90: 2000-2009.

Xie X., Liu C.H., Leung Y.C. and Leung M.K.H., Characteristics of air exchange in a street canyon with ground heating, Atmospheric Environment. Oxford, UK, Elsevier Ltd., 2006, 40: 6396-6409.

Yeung L.L., Lam C.K., Leung M.K.H. and Leung Y.C., Food Thawing Equipment. 2006, Application no. 200520017978.5.

Researcher : Li H

List of Research Outputs

Ngan A.H.W., Wo P.C., Zuo L., Li H. and Afrin N., The strength of submicron-sized materials, International Journal of Modern Physics B. World Scientific Publishing Company, 2006, 20(25), 26 & 27: 3579-3586.

Researcher : Li X

List of Research Outputs

Li X., Liu C.H., Leung Y.C. and Lam K.M., Recent progress in CFD modelling of wind field and pollutant transport in street canyons, Atmospheric Environment. Oxford, UK, Elsevier Ltd., 2006, 40: 5640-5658.

Researcher : Li Y

Project Title:	A theory of enclosure ventilation driven by combined forces
Investigator(s):	Li Y, Chan ATY
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	09/2002

Abstract:

Ventilation flow in an enclosure driven by combined natural and mechanical forces is fundamental to hybrid ventilation as well as to smoke control by mechanical extract. The current study is to understand how each driving force contributes to the overall force (pressure), ventilation flow rate, and flow pattern.

Project Title:	Dispersion and ventilation control of exhalation pollutants in hospital wards
Investigator(s):	Li Y, Chwang ATY
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	11/2004

Abstract:

To investigate the dispersion of exhalation gases and droplets from a single person; to investigate the interaction of inhalation and exhalation flows bewteen two persons in hospital settings using both experimental and computational methods; to comparie the existing ventilation systems for large hospital wards using both experimental and computational methods; to develop of new ventilation systems for large hospital wards; to apply the present findings to transmission routes analysis.

Project Title:	Understanding droplets due to the use of nebulizers and respiratory activities
Investigator(s):	Li Y, Chwang ATY, Seto WH, Ho PL
Department:	Mechanical Engg
Source(s) of Funding:	Research Fund for the Control of Infectious Diseases - Full Grants
Start Date:	12/2004

Abstract:

The present project is to provide new data on the number and size distribution of droplets expelled during respiratory activities and when using a nebulizer and taking nasopharyngeal aspirates; and investigate how far droplets travel as well as how the size of droplets changes, with a vew of providing essential data for studying transmission routes of respiratory diseases such as SARS and their ventilation control.

Project Title:	Evaluating factors that affect ventilation effectiveness in SARS wards
Investigator(s):	Li Y, Leung MKH, Seto WH, Yu SCT
Department:	Mechanical Engg
Source(s) of Funding:	Research Fund for the Control of Infectious Diseases - Full Grants
Start Date:	12/2004

Abstract:

Between July and October 2003, the Hong Kong Government has constructed a large number of new SARS wards with more than 1,200 beds in 9 hospitals. A large number of these new SARS wards have multiple beds (2 or 4 beds). This project is to study the factors affecting the effectiveness of these new SARS wards in terms of air distribution and the removal of virus aerosols. The outcomes will facilitate decision making in various ventilation designs in different hospitals.

Project Title:	Interaction between natural ventilation and wind flow around a multi-storey building
Investigator(s):	Li Y, Seifert J
Department:	Mechanical Engg
Source(s) of Funding:	Germany/Hong Kong Joint Research Scheme
Start Date:	01/2005

Abstract:

To understand the mechanisms of interaction between wind flow around and through a multi-storey building; to improve the existing rediction methods for natural ventilation in multi-storey buildings.

Project Title:	Nonlinear coupling of thermal mass and natural ventilation in buildings
Investigator(s):	Li Y
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	09/2005

Abstract:

The objectives of this project are: 1. To develop a fundamental understanding of the nonlinear coupling of natural ventilation and thermal mass with a focus on night ventilation; 2. To develop effective simple design methods of using thermal mass and night ventilation for the conceptual and detailed design stage; 3. To evaluate the potential of using thermal mass and night ventilation in various Chinese locations, including Hong Kong. Work programme Phase I: Theoretical Development IA. Effect of internal thermal mass on night ventilation IB. Combined effect of insulation and external thermal mass with a constant ventilation flow rate ID. Combined effect of internal and external thermal mass on night ventilation Phase II: Design Methods and Potential Analysis IIA. Design parameters using virtual sphere for internal thermal mass IIB. Evaluating thermal mass effect in realistic buildings using combined multi-zone thermal and air flow modeling. The use of thermal mass and night ventilation will be tested in one existing full-scale test room in Dalian, (But not in Beijing, Shanghai, Xi’an and Hunan). (Software + one test = HK$75000+HK$55000=HK$130000) IIC. Understanding the potential of using thermal mass in China and Hong Kong

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:	BioPassVent - a theory of enclosure ventilation for purging combined pollutants
Investigator(s):	Li Y
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	09/2006

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

List of Research Outputs

Li Y., Associate Editor, In: Editor in Chief: Jan Sundel; Associate Editors: William Nazaroff, Yuguo Li and H. Jenny Su, Indoor Air - International Journal of Indoor Environment and Health. Blackwell, 2007.

Li Y., Qian H., Yu I.T.S. and Wong T.W., Chapter 16. Probable Roles of Bio-Aerosol Dispersion in the SARS Outbreak in Amoy Gardens, Hong Kong, In: A C Sleigh, C H Leng, B SA Yeoh, P K Hong and R Safman, Population Dynamics and Infectious Diseases in Asia. New Jersey, World Scientific, 2006, 305-327.

Li Y. and Li X., Guest Editor, In: Martin Liddament, International Journal of Ventilation. UK, VEETECH Ltd., 2006, 5 (3).

Li Y., Invited speaker: Airborne Transmission of Infectious Diseases and Effectiveness of Isolation Room Ventilation., The 3rd Annual Conference of the Korean Society for Indoor Environment (KOSIE), Seoul, Korea, 15 September 2006.. 2006.

Li Y., Invited speaker: Chinese Kangs – Today’s Rural Essential Home Heating System and Tomorrow’s Sustainable Energy Technologies. , The 37th Congress on Heating, Refrigerating and Air-Conditioning, Belgrade, December 6-8 2006.. 2006.

Li Y., Plenary Speech, Ventilation for Control of Infectious Disease in Built Environment. , The 9th International Conference on Air Distribution in Rooms, Roomvent 2007, Helsinki, Finland, 13-15 June 2007. . 2007.

Li Y., Leung G.M., Tang J.W., Yang X., Chao C.Y.H., Lin J.Z., Lu J.W., Niu J., Sleigh A.C. and Su H.J.J., Role of ventilation in airborne transmission of infectious agents in the built environment – a multidisciplinary systematic review., Indoor Air. 2007, 17 (1): 2-18.

Seifert J., Li Y., Axley J. and Rosler M., Calculation of wind-driven cross ventilation in buildings with large openings. , Journal of Wind Engineering and Industrial Aerodynamics. 2006, 94(12): 925-947.

Tang J.W., Li Y., Eames I., Chan P.K.S. and Ridgway G.L., Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises., Journal of Hospital Infection. Elsevier, 2006, 194(6).

Xie X., Li Y., Zhang T. and Fang H.H.P., Bacterial survival in evaporating deposited droplets on a teflon-coated surface. , Applied Microbiology and Biotechnology . 2006, 73: 703-712.

Xie X., Li Y., Chwang A.T.Y., Ho P.L. and Seto W.H., How far droplets can move in indoor environments – Revisiting Wells evaporation-falling curve of droplets., Indoor Air. 2007, 17 (3): 211-225.

Researcher : Lian L

List of Research Outputs

Lian L., Haptic Rendering of Three-dimensional Heterogeneous Features, Ph.D. Thesis. Hong Kong, The University of Hong Kong, 2007, 1-191.

Researcher : Liu CH

List of Research Outputs

Leung M.K.H., Leung Y.C., Lam H.N., Kung C.Y. and Liu C.H., Integrated Heat Pump with Fuzzy-Genetic Control for Instantaneous Cooling and Heating. 2006, 22(49): Publication number: 1873350.

Researcher : Liu F

List of Research Outputs

Liu F., Forced Convection in Curved Ducts: Multiplicity and Stability, Ph.D. Thesis. Hong Kong, The University of Hong Kong, 2006, 1-346.

Researcher : Liu X

List of Research Outputs

Sze K.Y. and Liu X., Some progress in computational analysis in drapes. Invited Paper, Book of Abstracts, The Fifth International Conference on Mechanics & Materials in Design. Porto, Portugal, 2006, 493-494.

Researcher : Liu Y

List of Research Outputs

Liu Y. and Wang M., Developing a composite materials for bone tissue repair, Current Applied Physics. Netherlands, Elsevier B.V., 2007, 7: 547-554.

Liu Y. and Wang M., Thermophysical and mechanical properties of b-tricalcium phosphate reinforced polyhydroxybutyrate and polyhydroxybutyrate-co-hydroxyvalerate composites, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1217-1220.

Wang M., Liu Y. and Tang L.Y., Injection moulded bioactive and biodegradable composites for hard tissue repair, Proceedings of the Biomedical Engineering Conference BME2006. Hong Kong, HKIE, 51-54.

Researcher : Lou S

List of Research Outputs

Tang X., Chow K.W. and Lou S., Nonlinear excitations and peakons of a (2+1) dimensional generalized Broer Kaup system, Acta Mechanica Sinica . 2007, DOI 10.I007/s10409-007-0062-9.

Researcher : Lu D

List of Research Outputs

Lu D. and Ng C.O., Interfacial capillary-gravity waves due to a Stokeslet, Proceedings of the Fifth International Conference on Nonlinear Mechanics, Shanghai, China, June 11–14. Shanghai, China, Shanghai University Press, 2007, 1055–1059.

Researcher : Malomed BA

List of Research Outputs

Chow K.W., Malomed B.A., Liu W.M. and Xiong B., Singular nonlinearity management for matter wave solitons in normal and inverted parabolic potentials, Journal of the Physical Society of Japan. 2006, 75: 114004 (6 pages).

Researcher : Muley AA

List of Research Outputs

Ng K.Y., Muley A.A., Chan Y.F., Ng M.C.A., Djurisic A. and Ngan A.H.W., Highly facetted metallic zinc nanocrystals fabricated by thermal evaporation, Materials Letters. Amsterdam, Elsevier B.V., 2006, 60: 2423-2427.

Researcher : Ng CO

Project Title:	Dispersion of a chemical species subject to sorptive exchange in a wave boundary layer
Investigator(s):	Ng CO
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	09/2002

Abstract:

The goal of the study is to study theoretically the transport of a sorbing chemical species in a wave boundary layer on the bottom of a body of water, where the transport is subject to the effects of kinetic mass exchange between an aqueous phase and a sorbed phase on suspended particles. The project also aims at constructing a mathematical model to describe these transport processes.

Project Title:	Nonlinear interaction between surface gravity waves and non-Newtonian fluid mud
Investigator(s):	Ng CO, Zhang D
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	12/2003

Abstract:

To study: (i) characterization of cohesive sediments in estuaries of China. (2) mass transport of non-Newtonian fluid mud induced by surface waves. (3) dispersion of contaminants in fluid mud under waves. (4) effect of watercraft on the erosion of botton sediment.

Project Title:	Dispersion mechanisms in biomechanics of synovial joints and coronary artery diseases
Investigator(s):	Ng CO
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	01/2005

Abstract:

To look into the transport phenomena in a synovial joint and in the coronary arteries in a human body, in connection with the associated diseases in these organs and the synthesis of artificial materials for the replacement of these human body parts; to investigate the problem in detail incorporating the concepts and requirements of a smart material based on various models for the dispersion mechanism and fluid rheology.

Project Title:	On the Control of Electroconvection in the Manufacture of Smart Materials Free From Impurities
Investigator(s):	Ng CO
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	01/2005

Abstract:

Purpose:- This project is to conduct a theoretical study on the control of electroconvection in a layer of fluid-saturated porous medium in the presence of a transverse temperature gradient and electric field, with a view of proposing efficient mechanisms to suppress electroconvective instability in the manufacture of smart materials free from impurities. Practical Issues:- Materials science processing applications require manufacture of new strong materials, like nano and smart materials, free from impurities. Smart materials are those that have both sensing and actuating properties. One of the most crucial and active areas of research in this direction is the solidification of different types of alloys, which may be dielectric or poorly electrically conducting, by cooling from below and heating from above. At present, ferroelectric (i.e., dielectric) ceramics have been widely used in making smart devices by virtue of their piezoelectric properties. Although much less studied, smart materials can also be manufactured from poorly electrically conducting alloys (like shape memory alloys made of nickel-titanium, aluminum oxides, electrochromic, particle reinforced aluminum matrix composites, self-assembled materials and so on), which have a small electrical conductivity. These smart and strong materials have built-in sensing, actuation and control features, which can be effectively used in the design of all types of structures having a high level of safety, reduced vibration and noise, high shape control with accompanying pay-off. Problems Addressed:- These smart materials are synthesized by solidifying poorly conducting alloys by cooling from below and heating from above. In this material science process, the physical process is as follows. The variation of electrical conductivity due to the temperature difference induces free charges in the bulk of the fluid. These free charges interacting with an induced, and/or applied electrical field will produce a force equal to the product of the charge and the strength of the electric field. This force may lead to a kind of convective instability called electroconvection, which in turn produces a mushy layer that is a solid-fluid mixture made up of dendrites. These dendrites produced by electroconvection are regarded as impurities. The problem here is therefore to propose mechanisms to suppress electroconvection in order to reduce the formation of dendrites in the manufacture of smart and strong materials, which are intended to be free from impurities.

Project Title:	A Model for Mass Transport in Oscillatory Flow through a Curved Tube with Viscoelastic Absorbing Wall
Investigator(s):	Ng CO
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	01/2007

Abstract:

This project aims to develop a model for the mass transport associated with flow through a tube, when subject to the combination of the following effects: i) the flow is oscillatory; ii) the tube is curved; iii) the tube wall is made of viscoelastic and reactive material; iv) the fluid can be non-Newtonian; and v) it is during an early phase of the dispersion process. Dispersion is a mechanism that enhances the rate of broadening of a solute cloud in flow through a tube of channel, and can therefore be utilized as an effective means to accomplish dilution or mixing. It plays a central role in applications and processes as diverse as chromatographic separations in chemical engineering, the mixing and transport of drugs or toxins in physiological flows related to cardiovascular and respiratory systems, and contaminant transport in surface and subsurface waters, and so on. Dispersion is an interaction between lateral diffusion and velocity shear, and is therefore a function of the flow type, the geometry of the channel, and also properties of the substance. Other factors, like flow pulsation, chemical reactions, and boundary irregularities may also affect the dispersion. Despite the sizable literature on dispersion, the existing works are largely limited by the following aspects. First, many dispersion models are valid only for large times after injection, and hence applicable only to sufficiently long tubes/channels. Many systems, like blood circulation, involve short tubes, and it is important to understand the early development of dispersion in such systems. Second, many of the individual factors of dispersion have only been studied either separately or together with only a few others. The combined effects, when many of the factors are equally important at the same time, remain largely unknown. It is because the coupling of effects may lead to results that can be dramatically different from the sum of the individual effects. Moreover, many studies on dispersion have only presented mathematical formalism rather than tools for immediate practical use. In view of these issues, it is worth pursuing a study with the following intentions. (1) To perform a thorough review of the literature, since the classical work due to Taylor (1953), to find out what is the state-of-the-art understanding of the subject matter. (2) To develop relatively comprehensive numerical models for the flow and transport in a system that may be subject to many of the important factors, such as flow oscillation, tube curvature and tapering, reactions, wall viscoelasticity, and non-Newtonian fluid rheology. (3) To perform simulations that are relevant to, for examples, the cardiovascular and pulmonary systems so as to widen the current understanding on the mass transport processes in these systems.

List of Research Outputs

Devaraju N., Ng C.O. and Rudraiah N., Pulsating electrohydrodynamic flow in a pipe in the presence of transverse electric field, Proceedings of the International Conference on Frontiers in Fluid Mechanics, Bangalore, India, October 26-28. Bangalore, India, Sapna Book House, 2006, 788-805.

Huang S., Ng C.O. and Guo Q., Experimental investigation of the effect of flow turbulence and sediment transport patterns on the adsorption of cadmium ions onto sediment particles, Journal of Environmental Sciences. Beijing, China, Science Press of China, 2007, 19(6): 696–703.

Huang S. and Ng C.O., Hydraulics of a submerged weir and its applicability in navigational channels: Basic flow structures, International Journal for Numerical Methods in Engineering. Chichester, UK, John Wiley & Sons, 2007, 69: 2264–2278.

Lu D. and Ng C.O., Interfacial capillary-gravity waves due to a Stokeslet, Proceedings of the Fifth International Conference on Nonlinear Mechanics, Shanghai, China, June 11–14. Shanghai, China, Shanghai University Press, 2007, 1055–1059.

Ng C.O., 2006 Research Output Prize in Department of Mechanical Engineering, The University of Hong Kong. 2007.

Ng C.O., Concurrent Professor, since December 2006 , Shanghai University, China. 2006.

Ng C.O., Dispersion Subject to Reversible and Irreversible Wall Reactions, Invited Plenary Lecture at the Fourth Shanghai–Hong Kong Forum on Mechanics and Its Application, Shanghai, China, June 16. 2007.

Ng C.O., Dispersion in Oscillatory Tube and Plane Couette Flows Subject to Wall Reactions, Invited Special Lectures at the International Conference on Frontiers in Fluid Mechanics (ICFFM-06), Bangalore University, Bangalore, India, October 26-28. 2006.

Ng C.O., Dispersion in flows through a tube subject to wall reactions, Proceedings of the International Conference on Application of Fluid Mechanics in Industry and Environment, Kolkata, India, August 28-31. Chennai, India, Research Publishing Services, 2006, 100-106.

Ng C.O., Dispersion in open-channel flow subject to the processes of sorptive exchange on the bottom and air-water exchange on the free surface, Proceedings of the Conference of Global Chinese Scholars on Hydrodynamics, Shanghai, China, July 11-14. Shanghai, China, Shanghai University Press, 2006, 57-64.

Ng C.O., Effects of Viscoelastic Mud on Mass Transport in Water Waves, Invited Lectures (sponsored by the Scheme of Induction of Foreign Experts administered by the Ministry of Education, China) at School of Civil Engineering, Tianjin University, China, July 18-22. 2006.

Ng C.O. and Lau M.W., Effects of boundary sorption on dispersion in oscillatory plane Couette flow, Proceedings of the International Conference on Frontiers in Fluid Mechanics, Bangalore, India, October 26-28. Bangalore, India, Sapna Book House, 2006, 62-86.

Ng C.O., First Class Prize of Natural Science Award, 自然科學獎一等獎, State Ministry of Education, China. 中國教育部, 2007.

Ng C.O., Invited (international) Editorial Board Committee Member, since August 2003, Journal of Hydrodynamics. Shanghai, China, Publishing House for Journal of Hydrodynamics, 2006.

Ng C.O. and Zhang X., Mass transport in water waves over a thin layer of soft viscoelastic mud, Journal of Fluid Mechanics. Cambridge, UK, Cambridge University Press, 2007, 573: 105-130.

Ng C.O., Mass transport under waves in a two-layer fluid system, The Fourth Shanghai–Hong Kong Forum on Mechanics and Its Application, Shanghai, China, June 16. Shanghai, China, Shanghai Jiao Tong University, 2007, 25.

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

Rudraiah N. and Ng C.O., Dispersion in porous media with and without reaction: a review, In: Kambiz Vafai, Journal of Porous Media. CT, USA, Begell House Inc., 2007, 10(3): 219-248.

Rudraiah N., Ng C.O. and Nagaraj C., Effect of artificial cartilage made up of smart material of nanostructure on dispersion in poorly conducting macromolecular components in synovial joints, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1245–1248.

Rudraiah N., Ng C.O., Nagaraj C. and Nagaraj H.N., Electrohydrodynamic dispersion of macromolecular components in biological bearing, Journal of Energy, Heat and Mass Transfer. Chennai, India, Regional Centre for Energy, Heat and Mass Transfer, 2006, 28: 261-280.

Rudraiah N., Ng C.O., Nagaraj C. and Nagaraj H.N., Electrohydrodynamic dispersion of macromolecular components in biological bearing, Proceedings of the International Conference on Frontiers in Fluid Mechanics, Bangalore, India, October 26-28. Bangalore, India, Sapna Book House, 2006, 712-732.

Rudraiah N. and Ng C.O., Modeling of smart materials of nanostructure in a poorly electrically conducting fluid saturated composite material, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 441–444.

Shen Y...M., Zheng Y...H. and Ng C.O., 斜向波與任意多個長水平圓柱的相互作用, 中國科學Ｅ輯: 技術科學, Beijing, China, 中國科學院, 2007, 37(1): 107–126.

Zhang D. and Ng C.O., A numerical study on wave-mud interaction, Proceedings of the ICHD 2006, the Seventh International Conference on Hydrodynamics, Ischia, Italy, October 4-6. Naples, Italy, ICHD 2006 LOC, 2006, 477-484.

Zhang D. and Ng C.O., A numerical study on wave–mud interaction, China Ocean Engineering. Beijing, China, China Ocean Press, 2006, 20(3): 383-394.

Researcher : Ng KY

List of Research Outputs

Ng K.Y., Muley A.A., Chan Y.F., Ng M.C.A., Djurisic A. and Ngan A.H.W., Highly facetted metallic zinc nanocrystals fabricated by thermal evaporation, Materials Letters. Amsterdam, Elsevier B.V., 2006, 60: 2423-2427.

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:	Competitive Earmarked Research Grants (CERG)
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:	Energetic pathway prediction in dislocation processes by 3-D atomistic simulation
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	09/2003
Completion Date:	08/2006

Abstract:

To use atomistic simulation to study the energetic pathways in the following 3-D dislocation activation processes: (i) cross-slip, (ii) kink-pair processes, (iii) homogeneous dislocation nucleation as detected in nanoindentation.

Project Title:	Creep effects in high-temperature nanoindentation
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	09/2004

Abstract:

To investigate the characteristics of sub-micron indentation creep at room temperature, by using different materials with a variety of melting points; particular attention will be paid to the dependence of creep characteristics in a representative range of materials on melting temperature and indent size (or load); the effects of creep on elastic modulus and hardness measurements by the well-known Oliver-Pharr method will also be investigated.

Project Title:	Proposal on Seed Funding for Strategic Research Theme on Bio-nanotechnology
Investigator(s):	Ngan AHW, Che CM, Wong WT, Lu WW, Sze KY, Chan BP
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding for Strategic Research Theme
Start Date:	05/2005

Abstract:

To encourage staff to collaborate on the research theme by working and securing external research grants; to increase the visibility of HKU in the relevant research areas in the world scene.

Project Title:	Effects of Surface Adhesion on Mechanical Property Measurement of Viscoelastic Materials by Nanoindentation
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	09/2005

Abstract:

The main objectives of this project are: (1) To study how tip-sample adhesion affects the nanoindentation response of materials, and (2) To develop procedures to measure the elastic modulus and hardness of materials by nanoindentation when significant tip-sample adhesion is present.

Project Title:	Size Effect of Incipient Plasticity in Crystals Investigated by Spherical Nanoindentation
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2006
Completion Date:	01/2007

Abstract:

Dimiduk, Nix and co-workers have demonstrated that FIB-fabricated micro-pillars exhibit significant size effect in their initial yield strength [Science 50, 986 (2004)]. Smaller micro-pillars were found to yield at significantly higher stresses than larger micro-pillars. They attribute this to “dislocation starvation”. Although some of the pillars tested were in the range of dozens of microns and hence the chance of them containing no initial dislocations is small, Nix and co-workers believe that these initial dislocations quickly operate and become annihilated at the free surfaces, and hence fresh ones will have to be generated somewhere [private communication at ECI conference on Instrumented Indentation, Crete, 2005]. This ties in well with their experimental observation that the load-displacement curves exhibit serrations each of which is believed to represent a cycle in which dislocations are generated and then exhausted. The PI also demonstrated using nanoindentation with Berkovich indenter that the first pop-in loads recorded from bulk annealed crystals exhibit significant statistical scatter and time dependence [Phys. Rev. Lett., 94, 095501 (2005); Scripta Materialia, accepted]. Indentations performed at identical macroscopic conditions (e.g. within the same grain, similar surface conditions, etc.) do not exhibit the same pop-in load but instead the pop-in loads show statistical scatter. Holding the load in the initially elastic regime will also lead to an eventual pop-in, indicating that the “elastic-limit” of a small volume is dependent on time. The three aspects of sub-micron strength discussed so far, namely, size dependence, statistical scatter, and time dependence, are analogous to the well-known characteristics of the fracture strength of bulk ceramics. In ceramics, the reason of course is due to the statistical occurrence of flaws and their subcritical growth under corrosive environments. In the case of submicron crystals, Ngan recently proposed that these three aspects of strength are all related to the statistical occurrence of thermally agitated atomic locations for homogeneous dislocation nucleation. This belief was augmented by MD simulations on Ni3Al which show that in a block of perfect crystal under intense shear at finite temperatures, dislocation always originate from atomic sites, called “hot spots”, which are momentarily displaced significantly with respect to their neighbors. The occurrence of these hot spots is stochastic, as is similar to the occurrence of flaws of critical sizes in bulk ceramics, and hence the overall strength of the submicron crystal exhibits the three interesting aspects as discussed above. Based on this idea, the PI proposed a survival probability analysis, similar to the Weibull statistics in bulk ceramics, for the strength of submicron Ni3Al [Phys. Rev. Lett., 94, 095501 (2005); Scripta Materialia, accepted]. The theory uses input from MD simulations (mainly the occurrence probability of the “hot spots”), and is able to predict the failure (i.e. incipient plasticity) load in a general specimen geometry (e.g. conical indentation, compression of FIB-pillars, etc) given a prescribed survival probability. The idea therefore is to start from the behavior of very small “specimens” at femto-scale time scale (the MD simulation blocks), and then to project into micron-sized behavior at real time scales. This again is analogous to the use of Weibull statistics in bulk ceramics. The PI’s theory was found to work well for the indentation experiments on statistical scatter and time-dependence of strength in Ni3Al, as shown in fig. 1 and 2 in Section VI below. However, it overestimates the yield strengths of the FIB-fabricated Ni3Al pillars in Uchic et al.’s experiments by a few times, although the decreasing trend of the strength as size increases is predicted. The problem in applying the theory to the FIB-pillars lies on the fact that dislocation nucleation in these pillars probably starts from the free surfaces, which are probably implanted with Ga atoms as well during the FIB fabrication, but the theory is based on MD simulation which is difficult to capture the hot spot statistics at a free surface. The aim of this investigation is therefore to use spherical indentation to study the size dependence of incipient plasticity in annealed crystals.

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:	Competitive Earmarked Research Grants (CERG)
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:	Length-scale effects of mechanical properties of cortical bone
Investigator(s):	Ngan AHW
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2007

Abstract:

Currently, nanoindentation is widely used in biological research because it can measure the mechanical properties of materials from specified small material volumes. Biological tissues are challenging materials for nanoindentation because their structure is hierarchical down to the nanometer length scale, so that their properties should be strong functions of the material volume size from which the measurements are taken. Unfortunately, the effects of the maximum load or indent size on the measured properties of these materials are seldom rigorously considered in the literature. The PI has performed a preliminary but systematic study using goat femur samples as a prototype cortical bone material. Nanoindentation tests were conducted with a sharp diamond indenter in these cortical bone samples using a step-wise increasing load schedule shown in Fig. 1. This multi-cycle load schedule allowed the mechanical properties to be measured as a function of load or indent size on a specific sub-micron location in the bone sample, thus eliminating the effects of location-dependent inhomogeneity of the sample on the measured properties if different tests are carried out in different locations. The peak loads of the cycles in Fig. 1 ranged from 0.5 to 300 mN, resulting in indents 90nm to 4.2 microns deep. Fig. 2 shows the elastic modulus and hardness calculated from each cycle at 3 independent locations of the same bone sample. It can be seen that the elastic modulus at all three positions measured drops significantly from about 38 GPa at 90 nm indent depth to about 21 GPa at 4169 nm, and the hardness drops from 2.5 GPa to 0.9 GPa over same depth range. The properties measured at smaller indent depths show larger scatter. The saturating values of the measured properties at large indent depths in Fig. 2 are similar to values reported in the literature for cortical bone of large mammals, but the sharp increments at small indent depths are novel results unseen before in the literature. In a nanoindentation experiment, the size of the material volume probed is proportional to the indent depth, and so it is believed that the significant rise in the measured properties at small indent sizes is due to the hierarchical structure of cortical bone at the sub-micron level. Similar, although less systematic, results were also found in cortical bone samples from two strains of mice. However, control experiments on monolithic, amorphous materials such as polymers or fused quartz did not reveal any size dependence on the measured properties, as expected. The strong size dependence of mechanical properties is thus believed to be generic amongst bone of different species. Objectives – The present project aims at studying the size effect of mechanical properties as measured from nanoindentation tests in animals of different sizes, including goats, rabbits, mice, etc., to observe any generic trend amongst different animal species.

List of Research Outputs

Aladin K.D.M., Lu W.W., Cheung K.M.C., Ngan A.H.W., Chan D. and Luk K.D.K., " Nano Biomechanics Of Type Ii Collagens In Human Intervertebral Discs", Best Paper Award; Conference on Biomedical Engineering, BME 2006. Hong Kong. 2006.

Aladin Kaderbatcha D.M., Lu W.W., Cheung K.M.C., Ngan A.H.W., Chan D. and Luk K.D.K., Nano Structure and Biomechanics of Human Intervertebral Disc Collagens, International Society for the Study of the Lumbar Spine. 34th annual Meeting, June 10-14,Hong Kong . 2007.

Chan S.H. and Ngan A.H.W., Statistical distribution of forces in stressed 2-D low-density materials with random microstructures, Mechanics of Materials. Elsevier Ltd., 2006, 38: 1199-1212.

Chan Y.L., Yeung K.W.K., Ngan A.H.W., Cheung K.M.C., Lu W.W., Luk K.D.K., Liu X.M. and Chu P.K., Oxygen and sodium plasma-implanted nickel-titanium shape memory alloy: A novel method to promote hydroxyapatite formation and nickel suppression, 15th International Conference on Ion Beam Modification of Materials. Taormina, Sicily, Italy (Sep 18-22, 2006). 2006.

Chan Y.L., Yeung K.W.K., Lu W.W., Ngan A.H.W., Luk K.D.K., Chan D., Wu S.L., Liu X.M., Chu P.K. and Cheung K.M.C., Oxygen and sodium plasma-implanted nickel-titanium shape memory alloy: A novel method to promote hydroxyapatite formation and suppress nickel leaching, Nuclear Instruments & Methods In Physics Research Section B-Beam Interactions With Materials And Atoms. 2007, 257: 687-691.

Chiu Y.L., Feng G., Tang B. and Ngan A.H.W., An alternative method for continuous property measurement during depth-sensing indentation, International Journal of Surface Science and Engineering. Inderscience Enterprises Ltd., 2007, 1(1): 144-154.

Ng K.Y., Muley A.A., Chan Y.F., Ng M.C.A., Djurisic A. and Ngan A.H.W., Highly facetted metallic zinc nanocrystals fabricated by thermal evaporation, Materials Letters. Amsterdam, Elsevier B.V., 2006, 60: 2423-2427.

Ngan A.H.W., "Elasticity and Plasticity of Disordered Materials and Structures: A Non-thermal Statistical Mechanics Description", Keynote Lecture, The 13th International Symposium on Plasticity and Its Current Applications (Plasticity 2007), June 2-6, 2007, Alaska, USA. 2007.

Ngan A.H.W., Wo P.C. and Zuo L., Initiation of Plasticity In Submicron Crystals: Weibull-like Characteristics”, Invited Presentation, The 12th International Symposium on Plasticity and Its Current Applications (Plasticity 2006), July 17-22, 2006, Halifax, Canada.. 2006.

Ngan A.H.W., Journal of Nano Research, Member of the Editorial Board, Trans Tech Publishers, 2007.

Ngan A.H.W., Nanoindentation and Applications to Metallic, Nonmetallic and Biological Materials, invited lecture, Summer School on Multiscale Material Mechanics and Engineering Sciences: From Macro to Nano Scales, May 2-3, 2007, Thessaloniki, Greece.. 2007.

Ngan A.H.W., Non-thermal Statistical Mechanics of Disordered Structures and Materials, In: Z. Han, S.W. Lee, M. Nakagaki, Keynote Paper, Advances in Computational & Experimental Engineering and Sciences, Proceedings of ICCES'07 (International Conference on Computational & Experimental Engineering and Sciences, Miami, FL, 3-8 January 2007) . Tech Science Press, 2007, pp. 169-175.

Ngan A.H.W. and Thomson R., Nonequilibrium statistical mechanics of the evolution of dislocation structures, Physical Review B. The American Physical Society, 2007, 75: 014107-1 to 014107-11.

Ngan A.H.W., Rosenhain Medal and Prize, Institute of Materials, Minerals and Mining. 2007.

Ngan A.H.W., Statistical Mechanics of Non-thermal Structures and Materials, invited lecture in 1st World Symposium on Multiscale Material Mechanics and Engineering Sciences (Dedicated to the Memory of Frank Nabarro, Edward Hart and Ronald Rivlin), April 29-May 3, 2007, Thessaloniki, Greece.. 2007.

Ngan A.H.W., Wo P.C., Zuo L., Li H. and Afrin N., The strength of submicron-sized materials, International Journal of Modern Physics B. World Scientific Publishing Company, 2006, 20(25), 26 & 27: 3579-3586.

Ni G., Lu W.W., Ngan A.H.W. and Luk K.D.K., Nanomechanics of bone and bioactive bone-cement interfaces, In: Ling Qin, Harry K. Genant, James Griffith, Kwok-Sui Leung, Advanced Bioimaging Technologies in Assessment of the Quality of Bone and Scaffold Materials Techniques and Applications. Springer, 2007, 613-625.

Tang B., Ngan A.H.W. and Lu W.W., A novel method to measure the mechanical properties of bio-tissues using nanoindentation, Proceedings of University of Tokyo (UT) Symposium on Nanobio Integration NANOBIO-TOKYO 2006. 145-148.

Tang B., Ngan A.H.W. and Lu W.W., An improved method for the measurement of mechanical properties of bone by nanoindentation, Journal of Materials Science: Materials in Medicine. Springer, 2007, 18: 1875-1881.

Tang B., Ngan A.H.W. and Lu W.W., Nanoindentation size effects of cortical bone, Proceedings of University of Tokyo (UT) Symposium on Nanobo Integration NANOBIO-TOKYO 2006. 149-150.

Tang B., Ngan A.H.W. and Lu W.W., Viscoelastic effects during depth-sensing indentation of cortical bone tissues, Philosophical Magazine. Taylor & Francis, 2006, 86(33-35): 5653-5666.

Thomson R. and Ngan A.H.W., "Non-equilibrium Statistical Mechanics Applied To Dislocation Patterning Evolution During Metal Deformation", Keynote Lecture, The 12th International Symposium on Plasticity and Its Current Applications (Plasticity 2006), July 17-22, 2006, Halifax, Canada. 2006.

Researcher : Ni M

List of Research Outputs

Ni M., Leung M.K.H. and Leung Y.C., A modeling study on concentration overpotentials of a reversible solid oxide fuel cell, Journal of Power Sources. 2006, 163: 460-466.

Ni M., Leung M.K.H., Leung Y.C. and Sumathy K., A review and recent developments in photocatalytic water-splitting using TiO₂ for hydrogen production, Renewable and Sustainable Energy Reviews. 2007, 11(3): 401-425.

Ni M., Leung Y.C. and Leung M.K.H., Hydrogen production from biomass or biomass derived feedstock, Advances in Catalysis for Fuel Reforming and the Water Gas Shift Reaction. Pennsylvania, USA, Catalyst Group Resources Inc., 2006, 51-93.

Ni M., Leung M.K.H. and Leung Y.C., Micro-scale modeling analyses for advanced design of solid oxide steam electrolyzer to enhance hydrogen production, Proceedings of the Hydrogen Economy and Hydrogen Treatment of Materials (HTM). Ukraine, IAHE, 2007, 199-205.

Ni M., Leung M.K.H. and Leung Y.C., Micro-scale modeling of a functionally graded Ni-YSZ anode, Chemical Engineering & Technology. 2007, 30(5): 587-592.

Ni M., Leung M.K.H. and Leung Y.C., Micro-scale modelling of solid oxide fuel cells with micro-structurally graded electrodes, Journal of Power Sources. 2007, 168: 369-378.

Ni M., Leung M.K.H. and Leung Y.C., Modelling of proton conducting solid oxide fuel cells, Scientific Advances in Fuel Cell Systems. Turin, Italy, 2006, CD-ROM.

Ni M., Leung M.K.H. and Leung Y.C., Parametric study of solid oxide fuel cell performance, Energy Conversion & Management. 2007, 48: 1525-1535.

Ni M., Leung M.K.H., Sumathy K. and Leung Y.C., Potential of renewable hydrogen production for energy supply in Hong Kong, International Journal of Hydrogen Energy. Oxford, UK, Elsevier Ltd., 2006, 31: 1401-1412.

Ni M., Leung M.K.H. and Leung Y.C., Progress of dye-sensitized water-splitting for hydrogen production (Chinese), Chinese Journal of Power Sources. Tianjin, China, Ministry of Information Industry, 2006, 856-859.

Ni M., Leung M.K.H. and Leung Y.C., Technology development in nano-sized photocatalyst powder preparation technologies (in Chinese), Powder Metallurgy Technology. Beijing, China, China Association for Science and Technology, 2006, 379-383.

Ni M., Leung M.K.H., Leung Y.C. and Sumathy K., Theoretical modelling of TiO₂/TCO interfacial effect on dye-sensitized solar cell performance, Solar Energy Materials & Solar Cells. Amsterdam, Netherlands, Elsevier B.V., 2006, 90: 2000-2009.

Researcher : Niu C

List of Research Outputs

Niu C. and Chan K.W., Tool path strategies for direct rib milling, In: Dr. I. Gibson, International Conference on Manufacturing Automation ICMA 2007. Singpapore, 866-877.

Researcher : Poon CK

List of Research Outputs

Grimshaw R.H.J., Nakkeeran K., Poon C.K. and Chow K.W., Solitary wave solution for a non-integrable, variable coefficient nonlinear Schrodinger equation, Physica Scripta. 2007, 75: 620-623.

Researcher : Qian H

List of Research Outputs

Li Y., Qian H., Yu I.T.S. and Wong T.W., Chapter 16. Probable Roles of Bio-Aerosol Dispersion in the SARS Outbreak in Amoy Gardens, Hong Kong, In: A C Sleigh, C H Leng, B SA Yeoh, P K Hong and R Safman, Population Dynamics and Infectious Diseases in Asia. New Jersey, World Scientific, 2006, 305-327.

Researcher : Rudraiah N

List of Research Outputs

Devaraju N., Ng C.O. and Rudraiah N., Pulsating electrohydrodynamic flow in a pipe in the presence of transverse electric field, Proceedings of the International Conference on Frontiers in Fluid Mechanics, Bangalore, India, October 26-28. Bangalore, India, Sapna Book House, 2006, 788-805.

Rudraiah N. and Ng C.O., Dispersion in porous media with and without reaction: a review, In: Kambiz Vafai, Journal of Porous Media. CT, USA, Begell House Inc., 2007, 10(3): 219-248.

Rudraiah N., Ng C.O. and Nagaraj C., Effect of artificial cartilage made up of smart material of nanostructure on dispersion in poorly conducting macromolecular components in synovial joints, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1245–1248.

Rudraiah N., Ng C.O., Nagaraj C. and Nagaraj H.N., Electrohydrodynamic dispersion of macromolecular components in biological bearing, Journal of Energy, Heat and Mass Transfer. Chennai, India, Regional Centre for Energy, Heat and Mass Transfer, 2006, 28: 261-280.

Rudraiah N., Ng C.O., Nagaraj C. and Nagaraj H.N., Electrohydrodynamic dispersion of macromolecular components in biological bearing, Proceedings of the International Conference on Frontiers in Fluid Mechanics, Bangalore, India, October 26-28. Bangalore, India, Sapna Book House, 2006, 712-732.

Rudraiah N. and Ng C.O., Modeling of smart materials of nanostructure in a poorly electrically conducting fluid saturated composite material, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 441–444.

Researcher : Shek CM

List of Research Outputs

Shek C.M., The Continuous and Discrete Extended-Korteweg De Vries Equations and Their Applications in Hydrodynamics and Lattice Dynamics, M.Phil. Thesis. Hong Kong, The University of Hong Kong, 2006, 1-90.

Researcher : Shu Z

List of Research Outputs

Lam J., Shu Z., Xu S. and Boukas E.K., Robust H_¥ control of descriptor discrete-time mrkovian jump systems, International Journal of Control. 2007, 80(3): 374-385.

Shu Z. and Lam J., Delay-dependent exponential estimates of stochastic neural networks with time delay, ICONIP 2006. Hong Kong, Part I: LNCS 4232-0332.

Shu Z. and Lam J., Global exponential estimates of stochastic cohen-grossberg neural networks with time delay, International Conference on Control and Automation. Guangzhou, China, 2007, 6pp.

Shu Z., Lam J. and Xu S., Robust stabilization of markovian delay systems with delay-dependent exponential estimates, Automatica. 2006, 42(11): 2001-2008.

Researcher : Soh AK

Project Title:	Toughening of ferroelectric ceramic nano-composites
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	10/2002

Abstract:

This project attempts to: 1) carry out experimental and theoretical studies on deformation and fracture of ferroelectric ceramic nano-composites (FNC); 2) examine different toughening mechanisms and develop models which are able to describe such mechanisms; and 3) investigate two types of FNC, one consisting of metal nano-particles and the other of dielectric ceramic nano-particles.

Project Title:	Mechanics of ultra-thin films and nanolaminates
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	10/2003

Abstract:

To develop modeling and simulation methods for prediction of the nanoscale mechanical properties of ultra-thin films and multilayer nanolaminates: to set-up innovative experiments ofr validation of these methods.

Project Title:	Interactive behaviour of carbon nanotubes with biological molecules
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2004
Completion Date:	01/2007

Abstract:

To investigate the interactive behavior of carbon nanotubes (CNTs) with chemical or biological molecules in the aqueous environment by using the molecular dynamics (MD) simulation; to study the dispersion and separation of the aggregate of CNT assisted by single strand DNA (ssDNA); to study the specific or selective binding of peptides or proteins on CNT.

Project Title:	Thermo-electro-chemical-mechanical multi-fields coupling behavior of intelligent biological materials
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	01/2005
Completion Date:	12/2006

Abstract:

Along with the development of modern medicinal engineering and rehabilitation technology, intelligent biological materials, especially the piezoelectric biological materials, have been a great concern to the researchers working in the field of medicinal engineering. Its development will accelerate the industrial revolution of medicinal and robotic engineering. Fukada [1] has studied the piezoelectric properties of the biological macromolecular materials, and observed that their tensile piezoelectric constants were stable below the temperature of 200 deg. C. Fotiadis et al. [2] have studied the wave propagation in the piezoelectric human long bone. An analytical solution for cylindrical magnetic piezoelectric long bones has been obtained by Ei-Naggar et al. [3]. Silva et al. [4] have measured the piezoelectric properties of collagen-hydroxyapatite films. Ahmed and Abd-Alla [5] have studied wave propatation in long bones with cavity on the basis of ref. [3]. Bocha et al. [6] have studied the biocompatibility of anionic collagen matrix as scaffold for bone healing. Guzelsu [7] and Johnson [8] have proposed models for dry bone cantilever subjected to an end load. By means of linear piezoelectric theory, Gjelsvik [9] has described the remodeling of piezoelectric bone. Williams et al. [10] explained the bending of piezoelectric bone cantilever by the strain gradient theory. Demiray [11] provided a general description for remodeling of bones. Aschero et al. [12- 13] have studied the statistical characterization of piezoelectric coefficients in cow bone. Xu [14] has proven that the piezoelectric effect of cartilage was due to the piezoelectricity of the helix polypeptide chains. Feng et al. [15] have studied the promotion of osteogenesis by a piezoelectric biological ceramic. To-date, the research outputs were mainly on the measurement of piezoelectric properties of bones and the theory for some special problems, and the existing theoretical results have no experimental data to compare with. Furthermore, the chemical potential corresponding to the cause of piezoelectric biological evolution has yet to be studied. It is important to note that the thermoelectroelastic effect and the chemical potential cannot be neglected in studying the properties of piezoelectric biological materials. However, at present there are no thermo-electro-mechanical-chemical multi-fields coupling theories for the study of piezoelectric biological materials. Therefore, it is important to carry out basic research on the study of the mechanism of multi-fields coupling. REFERENCES [1] Fukada E, Piezoelectricity of Biopolymers, Biorheology, 32, 593-609, 1995. [2] Fotiadis DI, Foutsitzi G, Massalas CV, Wave propagation in human long bones of arbitrary cross-section, Int. J. Eng. Sci., 38, 1553-1591, 2000. [3] El-Naggar AM, Abd-Alla AM, Mahmoud SR, Analytical solution of electro-mechanical wave propagation in long bones, Appl. Math. Comput., 119, 77-98, 2001. [4] Silva CC, et al, Collagen-hydroxyapatite films: piezoelectric properties, Mat. Sci. Eng., B86, 210-218, 2001. [5] Ahmed SM, Abd-Alla AM, Electromechanical wave propagation in a cylindrical poroelastic bone with cavity, Appl. Math. Comput., 133, 257-286, 2002. [6] Rocha LB, Goissis G, Rossi MA, Biocompatibility of anionic collagen matrix as scaffold for bone healing, Biomaterials, 23, 449-456, 2002. [7] Guzelsu N, A piezoelectric model for dry bone tissue, J. Biomechanics, 11, 257-267, 1978. [8] Johnson MW, Williams WS and Gross D, Ceramic models for piezoelectricity in dry bone, J. Biomechanics, 13, 565-573, 1980. [9] Gjelsvik A, Bone remodeling and piezoelectricity—I, J. Biomechanics, 6, 69-77, 1973. [10] Williams WS and Breger L, Analysis of stress distribution and piezoelectric response in cantilever bending of bone and tendon, Ann. N.Y. Acad. Sci., 238, 121-130, 1974. [11] Demiray H, Electro-Mechanical remodeling of bones, Int. J. Eng. Sci., 21, 1117-1126, 1983. [12] Aschero G, et al, Converse piezoelectric effect detected in fresh cow femur bone, J. Biomechanics, 29, 1169-1174, 1996. [13] Aschero G, Gizdulich P, Mango F, Statistical characterization of piezoelectric coefficient d23 in cow bone , J. Biomechanics, 32, 573-577, 1999. [14] Xu JZ, Soliton dynamics in the helix polypeptide chains, Chaos Solitons & Fractals, 11, 779-790, 2000. [15] Feng JP, Yuan HP, Zhang XD, Promotion of osteogenesis by a piezoelectric biological ceramic, Biomaterials, 18, 1531-1534, 1997.

Project Title:	Thermo-elastic behavior and properties of micro- and nano-oscillators
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	01/2005

Abstract:

To develop of analytical methodologies to study the thermo-elastic behavior and properties of two typical micro-/nano-structures, i.e. micro-oscillators and nano-beam oscillators, by considering both the time-and size-scale effects; to investigate the ab-initio molecular dynamics (MD) simulation, which would include both the wave effects and internal scattering, will be carried out to study the thermo-elastic behavior and properties of the above-mentioned micro-/nano-structures; a series of experiments will be designed and carried out to provide data for comparison with the corresponding analytical and numerical results.

Project Title:	Modeling and Analysis of the Electromagnetic Behavior of Left-handed Materials
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2006

Abstract:

Veselago[1] coined the term “left-handed materials (LHMs)” to categorize materials with simultaneously negative permittivity and permeability. Such materials have significantly different properties compared with the traditional materials in terms of transmission of electromagnetic wave (EM wave), which may lead to significant change of techniques that employ the principles of EM wave transmission. LHMs are expected to play an important role in communication, radar technique and wireless transmission. Veselago[1] predicted that many special properties, such as Doppler shift and Snell’s law, will be reversed in the case of LHMs. By employing an analytical model, Pendry et al.[2, 3] predicted that periodic structures of thin wires array might have negative effective permittivity, ε(eff) , in the GHz band. A rapid increase of interest in LHMs commenced after Pendry et al.[4] has predicted that structures of periodically arranged split ring resonators (SRRs) could possess, in a given frequency interval, a negative effective magnetic permeability. Pendry[5] has also predicted that “perfect lens” made of left-handed materials can breach the image sharpness limitation of the traditional lens. Smith et al.[6] carried out experimental fabrication of LHMs by combining a periodic array of interspaced conducting nonmagnetic SRRs and continuous wires. Smith et al.’s structure is left-handed only when the magnetic field of the incident EM wave is parallel to the SRR axis and the electric field parallel to the wires. Shelby et al.[7] removed anisotropy in the plane of incident by making each unit cell to contain six copper SRRs and two wire strips on two perpendicular thin fiberglass boards. Shelby et al.[8] were the first to observe the negative effective index of refraction (n) by measuring the scattering angle of the transmitted beam through a prism fabricated from a LHM. Markoš and Soukoulis[9] studied the relations between resonance frequency and structural parameters numerically using the transfer-matrix method (TMM). Some other researchers used commercial softwares, such as Microwave Studio[10], to estimate the position of the resonance frequency interval. Time-dependent analyses using various forms of finite difference time domain (FDTD) algorithms have also been carried out to study wave propagation in LHMs[11]. Smith et al.[12] analyzed the reflection and transmission coefficients calculated from transfer-matrix simulations to determine the negative effective permittivity and permeability, i.e., ε(eff ) and μ(eff) , of LHMs. Some researchers have predicted that other structures could also form LHMs, such as the Ω-like patterns[13, 14]. Huangfu et al.[15] reported both transmission and prism experiments on a one-dimensional metamaterial, which was realized using three connected Ω rings printed back-to-back and reversed on two sides of a dielectric substrate, and confirmed that such material was left-handed. Chui and Hu[16] showed, by adopting the approach of effective medium approximation, that by incorporating metallic magnetic nanoparticles into an appropriate insulating matrix and controlling the directions of magnetization of metallic magnetic components and their volume fraction, it might be possible to produce LHMs. By performing numerical simulations, Podolskiy et al.[17] showed that a composite of nanowires might possess a negative refractive index and act as a LHM in the optical range of the spectrum. To-date, only a few theoretical models[2, 4, 14, 16] have been proposed, and most of these models were only qualitatively consistent with experimental or numerical results. Moreover, the values of ε(eff) and μ(eff) are required in the entire range of frequencies, which are difficult to determine numerically. Therefore, it is important to devise a theoretical model, which can illustrate quantitatively the relations between the negative effective parameters and the microstructure of LHMs. The objective of this project is to study the microstructure of various types of LHMs. The works to be carried out include, among other things, theoretical modeling and numerical simulation, which are for studying the relations between the negative effective parameters and the microstructure of LHMs. In terms of fundamental research, the proposed project aims to develop: (1) a theoretical model to predict quantitatively the relations between the microstructure and negative effective parameters, i.e., ε(eff) and μ(eff), of LHMs; and (2) a software for numerical analysis of the dynamic propagation of EM wave in nonhomogeneous materials. A comparison will then be made between the theoretical and numerical results obtained. In terms of engineering applications, the proposed project is a preliminary study for investigation of the efficient methods for preparing LHMs. A method for designing the microstructure of a LHM will be established based on the theoretical model and numerical simulation. References: [1] Veselago, V.G., The electrodynamics of substances with simultaneously negative values of ε and μ, Soviet Physics Uspekhi, 10, 509-514, 1968. [2] Pendry, J.B., Holden, A.J. and Stewart, W.J., Extremely low frequency plasmons in metallic mesostructures, Phys. Rev. Lett., 76, 4773-4776, 1996. [3] Pendry, J.B., Holden, A.J., Robbins, D.J. and Stewart, W.J., Low frequency plasmons in thin-wire structures, J. Phys.: Condens. Matter., 10, 4785-4809, 1998. [4] Pendry, J.B., Holden, A.J., Robbins, D.J. and Stewart, W.J., Magnetism from conductors and enhanced nonlinear phenomena, IEEE Transactions on Microwave Theory and Techniques, 47, 2075-2084, 1999. [5] Pendry, J.B., Negative refraction makes a perfect lens, Phys. Rev. Lett., 85, 3966-3969, 2000. [6] Smith, D.R., Padilla, W.J., Vier, D.C., Nemat-Nasser, S.C. and Schultz, S., Composite medium with simultaneously negative permeability and permittivity, Phys. Rev. Lett., 84, 4184-4187, 2000. [7] Shelby, R.A., Smith, D.R., Nemat-Nasser, S.C. and Schultz, S., Microwave transmission through a two-dimensional isotropic left-handed metamaterial, Appl. Phys. Lett., 78, 489-491, 2001. [8] Shelby, R.A., Smith, D.R. and Schultz, S., Experimental verification of a negative index of refraction, Science, 292, 77-79, 2001. [9] Markoš, P. and Soukoulis, C.M., Numerical studies of left-handed materials and arrays of split ring resonators, Phys. Rev. E, 65, 036622, 2002. [10] Li, K., McLean, S.J., Greegor, R.B., Parazzoli, C.G. and Tanielian, M.H., Free-space focused-beam characterization of left-handed materials, Appl. Phys. Lett., 82, 2535-2537, 2003. [11] Ziolkowski, R.W. and Heyman, E., Wave propagation in media having negative permittivity and permeability, Phys. Rev. E, 64, 056625, 2001. [12] Smith, D.R., Schultz, S., Markoš, P. and Soukoulis, C.M., Determination of effective permittivity and permeability of metamaterials from reflection and transmission coefficients, Phys. Rev. B, 65, 195104, 2002. [13] Simovski, C.R., Tretyakov, S.A. and Sochava, A.A., Antenna model for conductive Omega particles, J. Electromagnetic Waves Appl., 11(11), 1509-1530, 1997. [14] Simovski, C.R. and Sauviac, B., Toward creating isotropic microwave composites with negative refraction, Radio Science, 39, RS2014, 2004. [15] Huangfu, J.T. et. al., Experimental confirmation of negative refractive index of a metamaterial composed of Ω-like metallic patterns, Appl. Phys. Lett., 84, 1537-1539, 2004. [16] Chui, S.T. and Hu, L.B., Theoretical investigation on the possibility of preparing left-handed materials in metallic magnetic granular composites, Physical Review B, 65, 144407, 2002. [17] Podolskiy V.A., Plasmon modes and negative refraction in metal nanowire composites, Optics Express, 11, 735-745, 2003.

Project Title:	Novel piezocrystals and their applications in medical ultrasonic transducers
Investigator(s):	Soh AK
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	10/2006

Abstract:

The objective of this proposal is not only to develop a new technique to manufacture PMNT single crystals of ultrahigh piezoelectric performance to satisfy the requirements of medical ultrasound transducers, but also to design and manufacture a prototype of high performance medical imaging transducers. The sub-objectives of this project are as follows: (1) To improve the integrated performance of PMNT single crystals by controlling the domain configuration; and to manufacture high quality large PMNT single crystals by controlling compositional variation due to segregation during crystal growth. This is to obtain the required uniform and consistent electromechanical properties for fabricating the next generation of medical ultrasonic transducers. (2) To achieve a better understanding of the influences of temperature, biased field and uniaxial stress on the performance of PMNT single crystals; and to establish an approach for optimizing the electromechanical properties of piezoelectric resonators. Hence, enhance the stability and reliability of novel medical ultrasonic transducers. (3) To design and optimize the device-structures of the next generation of medical ultrasonic transducers; and to establish a manufacturing process to fabricate wide-bandwidth and high-resolution medical imaging transducers.

List of Research Outputs

Fang D.N., Sun Y.X. and Soh A.K., Advances in thermoelastic damping in micro- and nano-mechanical resonators: a review, JSME International Journal - Series A: Journal of Solid Mechanics and Materials Engineering . Japan, Japan Society of Mechanical Engineers, 2007, 1(1): 1-17.

Hu R. and Soh A.K., Micromagnetic simulation of size effects on the properties of ferromagnetic materials , Fifth Asian-Australasian Conference on Composite Materials (ACCM-5). 2006.

Hu Z.Q., Soh A.K., Chen W.J. and Li X.W., Non-smooth nonlinear equations methods for solving 3D elastoplastic frictional contact problems , Computational Mechanics. USA, Springer, 2007, 39 (6): 849-858.

Liang W., Soh A.K. and Hu R., Vibration analysis of a ferromagnetic plate subjected to an inclined magnetic field , International Journal of Mechanical Sciences. England, Pergamon-Elsevier Science Ltd, 2007, 49 (4): 440-446.

Ni Y., Soh A.K. and He L.H., Dynamics of self-organized epitaxial island formation under controlled annealing, IUTAM Symposium - Mechanical behavior & micro-mechanics of nanostructured materials. Netherlands, Springer, 2007, 1: 218-228.

Peng P., Soh A.K., Yang R. and Hu Z.Q., First-principles study of alloying effect of Re on properties of Ni/Ni3Al interface , Computational Materials Science. Netherlands, Elsevier Science, 2006, 38 (2): 354-361.

Soh A.K., Lee K.L., Song Y. and Fang D.N., Experimental studies of peezoelectric/ferroelectric and soft ferromagnetic materials with defects , International Journal of Modern Physics B. Singapore, World Scientific Publishing Co Pte Ltd, 2006, 20 (25-27): 4643-4648.

Song Y., Hu R. and Soh A.K., Microscopic simulations of the behavior of ferroelectrics and ferromagnetics, 2nd International Symposium on Functional Materials. 2007.

Song Y., Soh A.K. and Ni Y., Phase field simulation of crack tip domain switching in ferroelectrics , Journal of Physics D - Applied Physics. England, IOP Publishing Ltd, 2007, 40 (4): 1175-1182.

Song Y. and Soh A.K., Phase field simulations of polarization switching and deformation in ferroelectrics, 中国科协青年科学家论坛 ---材料力学行为与微尺度效应 , 2006.

Wang Y., Fang D.N. and Soh A.K., Effects of radius and orientation of single-walled carbon nanotubes on their nonlinear tensile deformation behaviour , Chinese Physics Letters. England, IOP Publishing Ltd, 2007, 24 (1): 248-251.

Yang J.S. and Soh A.K., A new mass sensor based on thickness-twist edge modes in a piezoelectric plate , Europhysics Letters. France, EDP Sciences, 2007, 77 (2): Art. no. 28003.

Yang J.S., Soh A.K. and Chen X., Acoustic leakage in electromagnetic waveguides made from piezoelectric materials , Journal of Applied Physics. USA, American Inst. of Physics, 2007, 101 (6): Art. No. 066105.

Yang J.S., Song Y. and Soh A.K., Analysis of a circular piezoelectric semiconductor embedded in a piezoelectric semiconductor substrate , Archive of Applied Mechanics. USA, Springer, 2006, 76 (7-8): 381-390.

Zhu T.J., Lu L., Lai M.O. and Soh A.K., Thickness dependence of electrical properties in (001) oriented lead zirconate titanate films by laser ablation , Materials Science and Engineering B. Switzerland, Elsevier Science SA, 2007, 138 (1): 51-54.

Researcher : Song Y

List of Research Outputs

Soh A.K., Lee K.L., Song Y. and Fang D.N., Experimental studies of peezoelectric/ferroelectric and soft ferromagnetic materials with defects , International Journal of Modern Physics B. Singapore, World Scientific Publishing Co Pte Ltd, 2006, 20 (25-27): 4643-4648.

Song Y., Hu R. and Soh A.K., Microscopic simulations of the behavior of ferroelectrics and ferromagnetics, 2nd International Symposium on Functional Materials. 2007.

Song Y., Soh A.K. and Ni Y., Phase field simulation of crack tip domain switching in ferroelectrics , Journal of Physics D - Applied Physics. England, IOP Publishing Ltd, 2007, 40 (4): 1175-1182.

Song Y. and Soh A.K., Phase field simulations of polarization switching and deformation in ferroelectrics, 中国科协青年科学家论坛 ---材料力学行为与微尺度效应 , 2006.

Yang J.S., Song Y. and Soh A.K., Analysis of a circular piezoelectric semiconductor embedded in a piezoelectric semiconductor substrate , Archive of Applied Mechanics. USA, Springer, 2006, 76 (7-8): 381-390.

Researcher : Sultana N

List of Research Outputs

Sultana N. and Wang M., Fabrication and characterisation of polymer and composite scaffolds based on polyhydroxybutyrate and polyhydroxybutyrate-co-hydroxyvalerate, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1229-1232.

Sultana N. and Wang M., Hydroxyapatite/Polyhydroxybutyrate-co-hydroxyvalerate composite scaffolds for bone tissue engineering, Proceedings of the Biomedical Engineering Conference BME2006. Hong Kong, HKIE, 108-111.

Sultana N. and Wang M., Microstructure and mechanical properties of PHBV and HA/PHBV composite scaffolds for bone tissue engineering, Proceedings of the 5th Asian International Symposium on Biomaterials. Xiamen, China, 2006, 290-291.

Sultana N. and Wang M., Nano-hydroxyapatite/Polyhydroxybutyrate-co-valerate composite acaffolds for bone tissue engineering, Trans of Society For Biomaterials 2007 Annual Meeting. Chicago, USA, SFB, 2007, p. 365.

Sultana N. and Wang M., PHB- and PHBV-based osteoconductive composite scaffolds produced through an emulsion freeze-drying process, Proceedings of the 10th Annual Conference on Ceramics, Cells and Tissues, Faenza. Faenza, Italy, 2006, 201-208.

Wang M., Sultana N. and Fong N.L., PHB, PHBV and PLLA polymer scaffolds produced using the emulsion freeze-drying process, Proceedings of the Biomedical Engineering Conference BME2006, Hong Kong. Hong Kong, HKIE, 2006, 112-115.

Researcher : Sumathy K

List of Research Outputs

Ni M., Leung M.K.H., Sumathy K. and Leung Y.C., Potential of renewable hydrogen production for energy supply in Hong Kong, International Journal of Hydrogen Energy. Oxford, UK, Elsevier Ltd., 2006, 31: 1401-1412.

Ni M., Leung M.K.H., Leung Y.C. and Sumathy K., Theoretical modelling of TiO₂/TCO interfacial effect on dye-sensitized solar cell performance, Solar Energy Materials & Solar Cells. Amsterdam, Netherlands, Elsevier B.V., 2006, 90: 2000-2009.

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:	Competitive Earmarked Research Grants (CERG)
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:	Development of a rotation-free computational method for fabric drape simulation
Investigator(s):	Sze KY
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	12/2003

Abstract:

To develop an efficient computational method for simulating the mechanics responses of fabrics. Darts, folds and seams will be considered.

Project Title:	Trefftz computational method for simulating domain switching in ferroelectric materials.
Investigator(s):	Sze KY
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	12/2005

Abstract:

To formulate and implement a Trefftz computational method for simulating domain switching in ferroelectric materials.

Project Title:	Development of computational models for geometric nonlinear analysis of smart plate/shell structures
Investigator(s):	Sze KY
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	10/2006

Abstract:

Among smart structure technologies, vibration control of thin-walled and large-span light-weight structures attracts most of the research effort. Owing to the low flexural rigidity and low material damping, external load or maneuver-induced inertia force of these structures can trigger large-amplitude vibrations which take long time to decay. To minimize operational errors, structural instabilities and material fatigue, active damping has been pursued. The proposed project aims at developing robust and efficient computational models for analyses of geometrically nonlinear smart plate/shell structures. Objectives of the proposed project include: - Development of geometrically nonlinear computational models for piezoelectrics. - Development of incremental time formulation for geometric nonlinear analyses smart plate/shell structures.

List of Research Outputs

Au-yeung K.L., Sze K.Y. and Chan B.P., A setup for mechanoregulation studies of cells in 3D configuration, NANOBIO - TOKYO 2006. p151-154.

Lo S.H., Wan K.H. and Sze K.Y., Adaptive refinement analysis using hybrid-stress transition elements , Computers & Structures. Elsevier, 2006, 24: 2212-2230.

Sze K.Y. and Liu X., Some progress in computational analysis in drapes. Invited Paper, Book of Abstracts, The Fifth International Conference on Mechanics & Materials in Design. Porto, Portugal, 2006, 493-494.

Wang H.T. and Sze K.Y., A quasi-spherical coordinate system and its application to the determination of vertex-type singularities. Book of Abstract (p.263) and CD-ROM Proceedings, The 21st International Congress of Theoretical & Applied Mechanics. Warsaw, Poland, 2006, 11pp.

Wang H.T., Sze K.Y. and Yang X., Analysis of electromechanical stress singularity in piezoelectrics by computed eigensolutions and hybrid-Trefftz finite element models, Computational Mechanics. Springer, 2006, 38: 551-564.

Researcher : Sze WS

List of Research Outputs

Chow H.N., Tan S.T. and Sze W.S., An overview and discussion on designed porous structures and selected biomedical applications, Proceedings of International Conference on Manufacturing Automation (ICMA07). 2007, 243-251.

Chow H.N., Tan S.T. and Sze W.S., Layered modeling of porous structures with voronoi diagrams, Computer-Aided Design & Applications. 2007, 4(1-4): 321-330.

Lam T.F., Sze W.S. and Tan S.T., Nesting of complex sheet metal parts, Computer-Aided Design & Applications. 2007, 4(1-4): 169-179.

Researcher : Tan J

List of Research Outputs

Tan J. and Lam H.N., A Liquid Desiccant Cooling System with Heat Pump for Energy Conservation, Global Conference on Renewable Energy Approaches for Desert Regions. 2006, Paper No. 27, 1-6.

Researcher : Tan ST

Project Title:	Layered manufacturing and redesign of compliant assemblies
Investigator(s):	Tan ST
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	12/2002
Completion Date:	12/2006

Abstract:

The project is to investigate how and under what conditions 'compliant' assemblies can be built using layered manufacturing processes, and to construct algorithms for automatically merging those parts within the assembly that can be amalgamated without compromising on the strength and functionality of the assembly.

Project Title:	Heterogeneous solid modeling using materially defined geometric entities
Investigator(s):	Tan ST
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
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:	Competitive Earmarked Research Grants (CERG)
Start Date:	01/2007

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.

List of Research Outputs

Chow H.N., Tan S.T. and Sze W.S., An overview and discussion on designed porous structures and selected biomedical applications, Proceedings of International Conference on Manufacturing Automation (ICMA07). 2007, 243-251.

Chow H.N., Tan S.T. and Sze W.S., Layered modeling of porous structures with voronoi diagrams, Computer-Aided Design & Applications. 2007, 4(1-4): 321-330.

Kou X. and Tan S.T., A systematic approach for integrated computer-aided design and finite element analysis of funtionally graded objects, Materials and Design. UK, Elsevier Science, 2006, 28: 2549-2565.

Kou X. and Tan S.T., Heterogeneous object modeling: a review , Computer-Aided Design. 2007, 39: 284.

Lam T.F., Sze W.S. and Tan S.T., Nesting of complex sheet metal parts, Computer-Aided Design & Applications. 2007, 4(1-4): 169-179.

Researcher : Tang B

List of Research Outputs

Chiu Y.L., Feng G., Tang B. and Ngan A.H.W., An alternative method for continuous property measurement during depth-sensing indentation, International Journal of Surface Science and Engineering. Inderscience Enterprises Ltd., 2007, 1(1): 144-154.

Tang B., Ngan A.H.W. and Lu W.W., A novel method to measure the mechanical properties of bio-tissues using nanoindentation, Proceedings of University of Tokyo (UT) Symposium on Nanobio Integration NANOBIO-TOKYO 2006. 145-148.

Tang B., Ngan A.H.W. and Lu W.W., An improved method for the measurement of mechanical properties of bone by nanoindentation, Journal of Materials Science: Materials in Medicine. Springer, 2007, 18: 1875-1881.

Tang B., Ngan A.H.W. and Lu W.W., Nanoindentation size effects of cortical bone, Proceedings of University of Tokyo (UT) Symposium on Nanobo Integration NANOBIO-TOKYO 2006. 149-150.

Tang B., Ngan A.H.W. and Lu W.W., Viscoelastic effects during depth-sensing indentation of cortical bone tissues, Philosophical Magazine. Taylor & Francis, 2006, 86(33-35): 5653-5666.

Researcher : Tang X

List of Research Outputs

Tang X., Chow K.W. and Lou S., Nonlinear excitations and peakons of a (2+1) dimensional generalized Broer Kaup system, Acta Mechanica Sinica . 2007, DOI 10.I007/s10409-007-0062-9.

Researcher : Tong HW

List of Research Outputs

Tong H.W. and Wang M., Biodegradable microfibers containing hydroxyapatite nanospheres for bone tissue engineering, Trans of Society For Biomaterials 2007 Annual Meeting. Chicago, USA, 2007, p. 583.

Tong H.W. and Wang M., Effects of processing parameters on the morphology and size of electrospun PHBV micro- and nano-fibers, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1233-1236.

Tong H.W. and Wang M., Electrospinning of PHBV fibers: the processing window and elimination of defects, Proceedings of the Biomedical Engineering Conference BME2006. Hong Kong, HKIE, 55-58.

Tong H.W. and Wang M., Electrospinning of aligned biodegradable polymer fibers and composite fibers for tissue engineering applications, Proceedings of 2006 International Conference on Nano Science and Nano Technology. Gwangju, Korea, 2006, p. 13.

Tong H.W. and Wang M., Electrospun PHBV and PHBV-based composite fibrous membranes for tissue engineering applications, Proceedings of the 5th Asian International Symposium on Biomaterials. Xiamen, China, 2006, 263-264.

Tong H.W. and Wang M., Nanofibrous membranes consisting of aligned fibers and multilayered structures for tissue egineering applications, Society For Biomaterials 2007 Annual Meeting. Chicago, USA, 2007, p. 172.

Tong H.W. and Wang M., PHBV-based composite nanofibers for bone tissue engineering, Proceedings of the 10th Annual Conference on Ceramics, Cells and Tissues. Faenza, Italy, 2006, 192-200.

Tong H.W., Wang M., Lu W.W., Cheung K.M.C., Yeung K.W.K. and Luk K.D.K., Pedicle screws and rods made of a shape memory alloy for treating scoliotic patients, Proceedings of the Biomedical Engineering Conference BME2006. Hong Kong, HKIE, 127-130.

Researcher : Tsui KS

List of Research Outputs

Tsui K.S., Tool Path Generation for Protrusion Milling, M.Phil. Thesis. Hong Kong, The University of Hong Kong, 2006, 1-127.

Researcher : Wan KH

List of Research Outputs

Lo S.H., Wan K.H. and Sze K.Y., Adaptive refinement analysis using hybrid-stress transition elements , Computers & Structures. Elsevier, 2006, 24: 2212-2230.

Researcher : Wang F

List of Research Outputs

Chen K.Z., Feng X.Y., Wang F. and Feng X.A., A virtual manufacturing system for components made of a multiphase perfect material, Computer-Aided Design. Exeter, U.K., Elsevier Ltd., 2007, 39: 13.

Chen K.Z., Wang F., Feng X.Y. and Feng X.A., Behavior modeling for the spraying device in the layered manufacturing process for the components made of a multiphase perfect material, Journal for New Generation Sciences. Bloemfontein, South Africa, Central University of Technology, 2006, 4: 13.

Chen K.Z., Wang F. and Feng X.A., Modeling of virtually manufactured components with a multiphase perfect material, 2006 IEEE International Conference on Virtual environments, human-computer interfaces and measurement systems. La Coruna, Spain, 2006, 6.

Wang F., Chen K.Z. and Feng X.A., Engraving behaviour modelling for manufacturing components with a periodic microstructure, International Conference on Manufacturing Automation. Singapore, 2007, 8.

Researcher : Wang HT

List of Research Outputs

Wang H.T. and Sze K.Y., A quasi-spherical coordinate system and its application to the determination of vertex-type singularities. Book of Abstract (p.263) and CD-ROM Proceedings, The 21st International Congress of Theoretical & Applied Mechanics. Warsaw, Poland, 2006, 11pp.

Wang H.T., Sze K.Y. and Yang X., Analysis of electromechanical stress singularity in piezoelectrics by computed eigensolutions and hybrid-Trefftz finite element models, Computational Mechanics. Springer, 2006, 38: 551-564.

Researcher : Wang L

Project Title:	Multiplicity and stability of forced convection in curved pipes: numerical simulation
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2005
Completion Date:	12/2006

Abstract:

To numerically study the developing, three-dimensional (3D) bifurcation-driven multiplicity and the stability of forced convection in curved circular pipes, a phenomenon widely observed from piping systems for various fluids, the thermal control system of the Alpha magnetic spectrometer of searching for antimatter and darkmatter to blood flows in the human arterial system.

Project Title:	Experimental visualization of droplet formation and breakup in T-junctions of microchannels
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2006

Abstract:

We propose to develop and investigate a microfluidic technique for the formation of fine and monodispersed emulsions (dispersions of one liquid, dispersed liquid, in a second immiscible liquid, dispersing liquid). The technique exploits the microfluidic technology-offered capability of the precise handling of small fluid volume and is known as Two T-junction Emulsification (TTE).The technique has a number of advantages, including (1) the generation of one droplet at a time, allowing control over the formation of individual droplets and enabling the generation of highly monodispersed droplets; (2) the second T-junction in TTE, enabling generation of a smaller droplet size than that of microchannel cross-section; and (3) a simple microchannel structure without active/moving components, providing the capability for significant parallelization and high throughput. A fundamental understanding of droplet formation and breakup at T-junctions of microchannels is essential for the optimal design and process control of proposed novel emulsion generators. The project therefore seeks to achieve the following goals:(1) Visualize droplet formation and breakup experimentally by a high speed digital imaging system equipped with a long distance microscope; (2) Find the droplet formation/breakup pattern, the droplet diameter and the standard derivation in the droplet diameter as a function of flow rates of two fluids, geometrical parameters of the system and properties of two fluids (viscosity, interfacial tension, surfactant concentration); (3) Identify governing dimensionless parameters and develop phase diagram of droplet formation/breakup patterns and empirical relations to predict the droplet diameter and its standard derivation.

Project Title:	Nano-/pico-liter bubbles: formation and breakup
Investigator(s):	Wang L
Department:	Mechanical Engg
Source(s) of Funding:	Small Project Funding
Start Date:	12/2006

Abstract:

We propose to develop and investigate a microfluidic technique for the formation of monodispersed nano-/pico-liter bubbles (dispersions of a gas, dispersed liquid, in a second immiscible liquid, dispersing liquid). The technique exploits the microfluidic technology-offered capability of the precise handling of small fluid volume and is known as Two T-junction bubble generator (TTBG).The technique has a number of advantages, including (1) the generation of one bubble at a time, allowing control over the formation of individual bubbles and enabling the generation of highly monodispersed bubbles; (2) the second T-junction in TTBG, enabling generation of a smaller bubble size than that of microchannel cross-section; and (3) a simple microchannel structure without active/moving components, providing the capability for significant parallelization and high throughput. A fundamental understanding of bubble formation and breakup at T-junctions of microchannels is essential for the optimal design and process control of proposed novel bubble generators. The project therefore seeks to achieve the following goals:(1) Visualize bubble formation and breakup experimentally by a high speed digital imaging system equipped with a long distance microscope; (2) Find the bubble formation/breakup pattern, the bubble diameter and its standard derivation, and the bubble generation frequency as a function of pressures of two fluids, geometrical parameters of the system and properties of two fluids (viscosity, interfacial tension, surfactant concentration); (3) Identify governing dimensionless parameters and develop phase diagram of bubble formation/breakup patterns and empirical relations to predict the bubble diameter, its standard derivation and its generation frequency.

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:	Competitive Earmarked Research Grants (CERG)
Start Date:	01/2007

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.

List of Research Outputs

Yang D. and Wang L., Quasi-least-squates finite element method for steady flow and heat transfer with system rotation, Numerische Mathematik. Springer-Verlag, 2006, 104: 377-411.

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:	Competitive Earmarked Research Grants (CERG)
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 Metallic Scaffolds for Hard Tissue Repair
Investigator(s):	Wang M
Department:	Engineering Faculty
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	07/2006

Abstract:

The purpose of this project is to investigate production techniques for metallic scaffolds for tissue regeneration purposes and to evaluate the scaffolds produced. Key issues to be addressed in the project include:1) the feasibility of producing metallic scaffolds using Ti and Mg which have desired porous studctures;2) evaluating the structure and mechanical propoerties of the scaffolds;3) studying the bioactivity and biodegradation behaviour of the scaffolds.

Project Title:	Fibrous Membranes Consisting of Aligned Nanofibers and of Multilayered Structures for Tissue Engineering
Investigator(s):	Wang M
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	03/2007

Abstract:

The purpose of this project is to investigate the fabrication of fibrous membranes of aligned fibers and of multilayered structures for tissue engineering applications using the electrospinning technique and to characterise and evaluate the membranes produced. Key issues to be addressed in the project include:1) the feasibility of producing aligned nanofibers of biodegradable polymers using our own designed system;2) the investigation into making multilayered structures using aligned fibers and into producing composite fibers;3) preliminary study of the structure and mechanical propoerties of the fibrous membranes;4) preliminary study of the biodegradation behaviour and bioactivity of fibrous membranes produced

List of Research Outputs

Chen Y., Mak A.F.T. and Wang M., Formation of apatite within biodegradable scaffolds by an accelerated biomimetic process in the shaking condition and flow condition, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1213-1216.

Chen Y., Mak A.F.T., Wang M., Li J. and Wong M.S., PLLA scaffolds with biomimetic apatite coating and biomimetic apatite/collagen composite coating to enhance osteoblast-like cells attachment and activity, Surface & Coatings Technology. Netherlands, Elsevier B.V., 2006, 201: 575-580.

Liu Y. and Wang M., Developing a composite materials for bone tissue repair, Current Applied Physics. Netherlands, Elsevier B.V., 2007, 7: 547-554.

Liu Y. and Wang M., Thermophysical and mechanical properties of b-tricalcium phosphate reinforced polyhydroxybutyrate and polyhydroxybutyrate-co-hydroxyvalerate composites, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1217-1220.

Sultana N. and Wang M., Fabrication and characterisation of polymer and composite scaffolds based on polyhydroxybutyrate and polyhydroxybutyrate-co-hydroxyvalerate, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1229-1232.

Sultana N. and Wang M., Hydroxyapatite/Polyhydroxybutyrate-co-hydroxyvalerate composite scaffolds for bone tissue engineering, Proceedings of the Biomedical Engineering Conference BME2006. Hong Kong, HKIE, 108-111.

Sultana N. and Wang M., Microstructure and mechanical properties of PHBV and HA/PHBV composite scaffolds for bone tissue engineering, Proceedings of the 5th Asian International Symposium on Biomaterials. Xiamen, China, 2006, 290-291.

Sultana N. and Wang M., Nano-hydroxyapatite/Polyhydroxybutyrate-co-valerate composite acaffolds for bone tissue engineering, Trans of Society For Biomaterials 2007 Annual Meeting. Chicago, USA, SFB, 2007, p. 365.

Sultana N. and Wang M., PHB- and PHBV-based osteoconductive composite scaffolds produced through an emulsion freeze-drying process, Proceedings of the 10th Annual Conference on Ceramics, Cells and Tissues, Faenza. Faenza, Italy, 2006, 201-208.

Tong H.W. and Wang M., Biodegradable microfibers containing hydroxyapatite nanospheres for bone tissue engineering, Trans of Society For Biomaterials 2007 Annual Meeting. Chicago, USA, 2007, p. 583.

Tong H.W. and Wang M., Effects of processing parameters on the morphology and size of electrospun PHBV micro- and nano-fibers, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1233-1236.

Tong H.W. and Wang M., Electrospinning of PHBV fibers: the processing window and elimination of defects, Proceedings of the Biomedical Engineering Conference BME2006. Hong Kong, HKIE, 55-58.

Tong H.W. and Wang M., Electrospinning of aligned biodegradable polymer fibers and composite fibers for tissue engineering applications, Proceedings of 2006 International Conference on Nano Science and Nano Technology. Gwangju, Korea, 2006, p. 13.

Tong H.W. and Wang M., Electrospun PHBV and PHBV-based composite fibrous membranes for tissue engineering applications, Proceedings of the 5th Asian International Symposium on Biomaterials. Xiamen, China, 2006, 263-264.

Tong H.W. and Wang M., Nanofibrous membranes consisting of aligned fibers and multilayered structures for tissue egineering applications, Society For Biomaterials 2007 Annual Meeting. Chicago, USA, 2007, p. 172.

Tong H.W. and Wang M., PHBV-based composite nanofibers for bone tissue engineering, Proceedings of the 10th Annual Conference on Ceramics, Cells and Tissues. Faenza, Italy, 2006, 192-200.

Tong H.W., Wang M., Lu W.W., Cheung K.M.C., Yeung K.W.K. and Luk K.D.K., Pedicle screws and rods made of a shape memory alloy for treating scoliotic patients, Proceedings of the Biomedical Engineering Conference BME2006. Hong Kong, HKIE, 127-130.

Wang M., Biomedical engineering education and training in Hong Kong: meeting the challenges and competitions, Proceedings of ASAIHL Conference 2007 on Undergraduate Education. Hong Kong, 2007, CD-ROM: 9pp.

Wang M., Biomedical engineering education and training in Hong Kong: recent developments, Proceedings of the 3rd Kuala Lumpur International Conference on Biomedical Engineering. Kuala Lumpur, Malaysia, 2006, 244-247.

Wang M., Biomimetics, biomaterials, and tissue engineering, Proceedings of the 5th Asian International Symposium on Biomaterials. Xiamen, China, 2006, 28-29.

Wang M., Composite scaffolds for bone tissue engineering, American Journal of Biochemistry and Biotechnology. USA, Science Publications, 2006, 2: 80-83.

Wang M., Deformation and fracture of bioactive particle reinforced polymer composites developed for hard tissue repair, (Invited paper), Proceedings of the 16th European Conference of Fracture. Berlin, Springer, 2006, 1029-1030.

Wang M., Deformation and fracture of bioactive particle reinforced polymer composites developed for hard tissue repair, Fracture of Nano and Engineering Materials and Structures (CD-ROM Proceedings of the 16th European Conference of Fracture). Dordrecht, The Netherlands, Springer, 2006, CD-ROM: 7pp.

Wang M., Engineering in tissue repair, Proceedings of the 3rd Symposium on Advanced Technology for Health Care and Hygiene Control. Hong Kong, IMechE, H.K., 2006, 1pp.

Wang M., Expert Panel Member: Project Awarding Panel for Biophysics and Biomedical Engineering, NSFC, National Natural Science Foundation of China. China, 2007.

Wang M., Shum D.K.Y., Chu C.S. and Lam K.O., Fabrication and evaluation of chitosan devices for peripheral nerve regeneration: An initial study, Proceedings of the Biomedical Engineering Conference BME2006. Hong Kong, HKIE, 47-50.

Wang M., Guest Editor (2006 – 2007), Special Issue of Journal of Materials Science: Materials in Medicine. Springer, Germany, 2007.

Wang M., Liu Y. and Tang L.Y., Injection moulded bioactive and biodegradable composites for hard tissue repair, Proceedings of the Biomedical Engineering Conference BME2006. Hong Kong, HKIE, 51-54.

Wang M., Member (2004 - Present) of the Editorial Board, Journal of Materials Science: Materials in Medicine. Springer, Germany, 2007.

Wang M., Member (2004 - Present) of the Editorial Board, Surface and Coatings Technology. The Netherlands, Elsevier, 2007.

Wang M., Member (2006 – Present) of the Editorial Board, Biomedical Materials: Materials for Tissue Engineering & Regenerative Medicine. UK, Institute of Physics, 2007.

Wang M., Member (2006 – Present) of the Editorial Board, Composites Science and Technology. The Netherlands, Elsevier, 2007.

Wang M., Member (2006 – Present) of the Editorial Board, Journal of Biomimetics, Biomaterials and Tissue Engineering. Switzerland, TransTech Publications, 2007.

Wang M., Member (2007 – Present) of the Editorial Board, Frontiers of Materials Science in China: Selected Publications from Chinese Universities. China, and Springer, Germany, Higher Education Press, 2007.

Wang M., Member (2007 – Present) of the Editorial Board, IET Nanobiotechnology. UK, Institution of Engineering and Technology, 2007.

Wang M., Member of the Technical Committee: TC150 Implants for Surgery (2006 - present), International Organization for Standardization (ISO). 2007.

Wang M., Member of the Technical Committee: TC194 Biological Evaluation of Medical Devices (2006 - present), International Organization for Standardization (ISO). 2007.

Wang M., Member of the Technical Committee: TC229 Nanotechnologies (2006 - present), International Organization for Standardization (ISO). 2007.

Wang M., One of the Editors, In: J.K. Kim, D.Z. Wo, L.M. Zhou, H.T. Hunag, K.T. Lau and M. Wang, Advances in Composite Materials and Structures. Switzerland, Trans Tech Publications, 2007, Part I - Part II.

Wang M., Sultana N. and Fong N.L., PHB, PHBV and PLLA polymer scaffolds produced using the emulsion freeze-drying process, Proceedings of the Biomedical Engineering Conference BME2006, Hong Kong. Hong Kong, HKIE, 2006, 112-115.

Wang M., Strategies for developing tissue engineering scaffolds of various materials, Proceedings of the 10th Annual Conference on Ceramics, Cells and Tissues. Italy, Itallian Research Council, 2006, 49-54.

Wang M., Surface modification of biomaterials and tissue engineering scaffolds for enhanced osteoconductivity, Proceedings of the 3rd Kuala Lumpur International Conference on Biomedical Engineering. Kuala Lumpur, Malaysia, 2006, 22-27.

Wang M., The composite strategy for biomaterials development, Proceedings of the 5th Asian-Australian Conference on Composite Materials. Hong Kong, 2006, 126.

Wu J., Wang M. and Osaka A., Bioactive composite coating on titanium implants for hard tissue repair, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1249-1252.

Wu J.M., Wang M., Li Y., Zhao F., Ding X. and Osaka A., Crystallization of amorphous titania gel by hot water aging and induction of in vitro apatite formation by crystallized titania, Surface & Coatings Technology. Netherlands, Elsevier B.V., 2006, 201: 755-761.

Wu J.M., Zhang S.C., Li Y., Zhao F.D., Wang M. and Osaka A., Influence of film thickness on in vitro bioactivity of thin anatase films produced through direct deposition from an aqueous titanium tetrafluoride solution, Surface and Coatings Technology. Netherlands, Elsevier B.V., 2006, 201: 3181-3187.

Wu J.M., Huang B., Wang M. and Osaka A., Titania nanoflowers with high photocatalytic activity, Journal of the American Ceramic Society. USA, The American Ceramic Society, 2006, 89(8): 2660-2663.

Zhou W., Cheung W.L. and Wang M., Biodegradable composite scaffolds produced by selective laser sintering, Transactions of the Society for Biomaterials 2007 Annual Meeting. Chicago, USA, Society for Biomaterials, 2007, p. 170.

Zhou W., Wang M. and Cheung W.L., Fabrication and characterization of composite microspheres containing carbonated hydroxyapatite nanoparticles, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1221-1224.

Zhou W., Wang M. and Cheung W.L., Fabrication and characterization of composite microspheres containing carbonated hydroxyapatite nanoparticles, Proceedings of 5th Asian-Australiasian Conference on Composite Materials (ACCM-5). Hong Kong, The Hong Kong University of Science and Technology, 2006, 416-H.

Zhou W., Wang M. and Cheung W.L., Microstructures of carbonated hydroxyapatite nanospheres and CHAP/PLLA nanocomposite microspheres, Proceedings of Conference on Biomedical Engineering, BME2006. Hong Kong, Biomedical Division, HKIE, 104-107.

Zhou W., Lee S.H., Cheung W.L., Wang M. and Ip W.Y., Selective laser sintering of porous scaffolds from poly(L-lactide) microspheres and its nanocomposite with carbonated hydroxyapatite nanospheres, Proceedings of 20th European Conference on Biomaterials. Nantes, France, European Society for Biomaterials, 2006, T175.

Zhou W., Lee S.H., Wang M. and Cheung W.L., Selective laser sintering of tissue engineering scaffolds using Poly(L-lactide) microspheres, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1225-1228.

Zhou W., Lee S.H., Wang M. and Cheung W.L., Selective laser sintering of tissue engineering scaffolds using microspheres of poly(L-lactide)-Based nanocomposite, Proceedings of 5th Asian-Australiasian Conference on Composite Materials (ACCM-5). Hong Kong, The Hong Kong University of Science and Technology, 2006, 417-H.

Researcher : Wang Q

List of Research Outputs

Wang Q., Lam J., Gao H. and Wang Q., Energy-to-Peak model reduction for 2-D discrete systems described by fornasini-marchesini models, European Journal of Control. 2006, 12(4): 420-430.

Wang Q., Lam J., Xu S. and Zhou S., H_¥ model reduction for polytopic systems with time-varying delay, Journal of Systems and Control Engineering. 2006, 220(7): 627-639.

Wang Q., Lam J., Zhang Q.L. and Wang Q., Mixed optimization approach to model approximation of descriptor systems, Journal of Optimization Theory and Applications. 2006, 131(2): 265-280.

Wang Q., Model Reduction for Dynamic Systems with Time Delays: A Linear Matrix Inequality Approach, Ph.D. Thesis. Hong Kong, The University of Hong Kong, 2007, 1-154.

Researcher : Wo PC

List of Research Outputs

Ngan A.H.W., Wo P.C. and Zuo L., Initiation of Plasticity In Submicron Crystals: Weibull-like Characteristics”, Invited Presentation, The 12th International Symposium on Plasticity and Its Current Applications (Plasticity 2006), July 17-22, 2006, Halifax, Canada.. 2006.

Ngan A.H.W., Wo P.C., Zuo L., Li H. and Afrin N., The strength of submicron-sized materials, International Journal of Modern Physics B. World Scientific Publishing Company, 2006, 20(25), 26 & 27: 3579-3586.

Researcher : Wong HL

List of Research Outputs

Chan B.P., Chan G.C.F., Wong H.L., Cheung P.T., Cheah K.S.E. and Chan D., Cell-Matrix Microsphere, Associated Products, Methods for Preparation and Applications., US Regular Patent Application No. 11/750,863 (filed on 18 May 2007).. 2007.

Researcher : Wu J

List of Research Outputs

Wu J., Wang M. and Osaka A., Bioactive composite coating on titanium implants for hard tissue repair, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1249-1252.

Researcher : Xie X

List of Research Outputs

Xie X., Li Y., Zhang T. and Fang H.H.P., Bacterial survival in evaporating deposited droplets on a teflon-coated surface. , Applied Microbiology and Biotechnology . 2006, 73: 703-712.

Xie X., Li Y., Chwang A.T.Y., Ho P.L. and Seto W.H., How far droplets can move in indoor environments – Revisiting Wells evaporation-falling curve of droplets., Indoor Air. 2007, 17 (3): 211-225.

Researcher : Xie X

List of Research Outputs

Xie X., Li Y., Zhang T. and Fang H.H.P., Bacterial survival in evaporating deposited droplets on a teflon-coated surface. , Applied Microbiology and Biotechnology . 2006, 73: 703-712.

Researcher : Xiong J

List of Research Outputs

Xiong J. and Lam J., Stabilization of linear systems over networks with bounded packet loss, Automatica. 2007, 43(1): 80-87.

Researcher : Yang X

List of Research Outputs

Wang H.T., Sze K.Y. and Yang X., Analysis of electromechanical stress singularity in piezoelectrics by computed eigensolutions and hybrid-Trefftz finite element models, Computational Mechanics. Springer, 2006, 38: 551-564.

Researcher : Yeung CW

List of Research Outputs

Yeung C.W., Cheah K.S.E., Chan D. and Chan B.P., A novel 3-dimensional culture system for mouse embryonic stem cells, International Society for Stem Cell Research 5th Annual Meeting. Jun 15-21 2007. Cairns, Queensland, Australia. 2007, p340.

Researcher : Yip LP

List of Research Outputs

Gurarie D., Yip L.P., Chow K.W. and Zhang D., Relaxation and stationary vortex patterns for two dimensional channel flows, The Fifth International Conference on Nonlinear Mechanics, Shanghai, China. 2007.

Yip L.P., Chow K.W. and Gurarie D., The role of geometry on the equilibrium configurations of two dimensional inviscid channel flows, 59th American Physical Society Division of Fluid Dynamics Meeting, Tampa, Florida, USA. 2006.

Researcher : Yu X

List of Research Outputs

Yu X., Hemodynamic Analysis of Blood Flows in Carotid Bifurcations, Ph.D. Thesis. Hong Kong, The University of Hong Kong, 2007, 1-177.

Researcher : Zhang D

List of Research Outputs

Gurarie D., Yip L.P., Chow K.W. and Zhang D., Relaxation and stationary vortex patterns for two dimensional channel flows, The Fifth International Conference on Nonlinear Mechanics, Shanghai, China. 2007.

Zhang D. and Ng C.O., A numerical study on wave-mud interaction, Proceedings of the ICHD 2006, the Seventh International Conference on Hydrodynamics, Ischia, Italy, October 4-6. Naples, Italy, ICHD 2006 LOC, 2006, 477-484.

Zhang D. and Ng C.O., A numerical study on wave–mud interaction, China Ocean Engineering. Beijing, China, China Ocean Press, 2006, 20(3): 383-394.

Researcher : Zhang X

List of Research Outputs

Ng C.O. and Zhang X., Mass transport in water waves over a thin layer of soft viscoelastic mud, Journal of Fluid Mechanics. Cambridge, UK, Cambridge University Press, 2007, 573: 105-130.

Zhang X., Mechanics of Viscoelastic Mud Under Water Waves, M.Phil Thesis. Hong Kong, The University of Hong Kong, 2006, 1-146.

Researcher : Zhang X

List of Research Outputs

Ng C.O. and Zhang X., Mass transport in water waves over a thin layer of soft viscoelastic mud, Journal of Fluid Mechanics. Cambridge, UK, Cambridge University Press, 2007, 573: 105-130.

Zhang X., Mechanics of Viscoelastic Mud Under Water Waves, M.Phil Thesis. Hong Kong, The University of Hong Kong, 2006, 1-146.

Researcher : Zheng G

Project Title:	Experiment and simulation studies on the deformation mechanisms in nanocrystalline H.C.P. metals
Investigator(s):	Zheng G
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	10/2004
Completion Date:	09/2006

Abstract:

To study the mechanical deformation mechanisms in nanocrystalline (nc) metals by experiments and computer simulations.

Project Title:	Atomistic Simulation Study on Deformation Mechanisms in Nanocrystalline H.C.P. Metals
Investigator(s):	Zheng G
Department:	Mechanical Engg
Source(s) of Funding:	Competitive Earmarked Research Grants (CERG)
Start Date:	08/2005

Abstract:

The main objective of this project is to establish a systematic and quantitative approach for computer simulation of mechanical deformation in nanocrystalline (nc) metals. We focus our investigations on the deformation in nc hexagonal close-packed (hcp) metals.

Project Title:	Synthesis and Mechanical Properties of Amorphous Nanowires
Investigator(s):	Zheng G
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2006

Abstract:

Amorphous alloys or metallic glasses are known for large elastic strain, high fracture strength, high strength-to-density ratio, good thermal conductivity and corrosion resistance. Bulk metallic glasses (BMGs) are a new generation of structural materials desirable for industrial applications. Recently invented iron-based BMGs are even considered to form a very promising basis for affordable and high performance structural materials. They are so-called 'amorphous steel' and can be used in places where standard high strength steels are used, for examples, in sporting goods, building construction and military, etc.. However, metallic glasses including the iron-based BMGs are brittle. Unlike crystalline alloys, amorphous alloys do not have dislocation-like defects during deformation process and the deformation is localized in a few narrow regions, or shear bands. There is no work hardening during deformation process and fracture occurs along one of the shear bands when deformation inside the band becomes so large that it physically separates the system. The localized shear bands are about 10nm thick and orient in the direction of the maximum resolved shear stress. Because of these unique features of deformation behaviors in metallic glasses, it is generally believed that the confinement of nano-sized shear zones in composites of metallic glasses and nano-crystallites can improve the work hardening and plastic strain of metallic glasses. Unfortunately current theory fails to predict the atomistic deformation defects in metallic glasses, e.g., how and where the shear bands form and how they propagation. Since 1970's, a general theory of free-volume defect has been proposed to account for the shear banding in metallic glasses. It is suggested that atoms with loosely packed neighbors have extra volumes and can be moved to perform a local slip in disk shaped region typically of 1nm thickness. When accumulation of these dilated regions reaches a threshold density, localized shear band forms. Because of the lack of long range translational symmetry in metallic glasses and the rapid deformation process confined in narrowly localized shear zones, the free-volume defects hypothesized to be responsible for the shear banding can not been well characterized directly from electron microscopy. In searching for the deformation mechanisms in metallic glasses, we propose to investigate the size effect on the mechanical deformation in amorphous nanowire. This is because of the following reasons. First, the deformation defects are in atomistic scales and the corresponding shear banding is in nano-sized region. The only way to alternate the formation of shear bands without changing the composition and glassy nature of these alloys is to reduce one or two dimensions of amorphous alloys to a size compatible to the shear banding region. A good system that can fulfill this purpose is amorphous wire with diameter of about 100nm. If the free-volume defects are atomistic deformation defects responsible for the shear banding, significant size-dependent mechanical properties could be observed. Second, the deformation of amorphous nanowire can be compared with the atomistic simulation results. In molecular dynamics simulation, tensile deformation is usually performed in an amorphous nanowire with diameter within 100nm because of the limitation of computing power. Furthermore, the simulation results reveal a surprising feature that the strength and ductility of amorphous nanowire increase with decreasing nanowire diameter. This size-effect on deformation can be considered as a method to improve the ductility of metallic glasses and have to be confirmed by experiments. Third, deformation in nanometer scales is of scientific and engineering importance because of the rapid development of nano-electro-mechanical systems (NEMS). Although some mechanical behaviors of nanostructured crystalline solids have been revealed, little is known about the mechanical properties of nano-sized amorphous alloys.

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:	Competitive Earmarked Research Grants (CERG)
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:	: Mechanical properties of metal-coating carbon nanotubes
Investigator(s):	Zheng G
Department:	Mechanical Engg
Source(s) of Funding:	Seed Funding Programme for Basic Research
Start Date:	02/2007

Abstract:

Mechanical properties of light metals and alloys can be significantly enhanced by incorporating reinforcing fibers to form metal matrix composites. Because carbon nanotubes (CNTs) have nanoscale dimensions and ultra light weight (25% of the weight of steel), large Young's modulus (1-5TPa), high tensile strength (50-300GPa) and large uniform strain (40%), they are very promising in the producing of strong and light composite materials. Since the discovery of CNTs in 1991, the production costs of CNTs have been reduced dramatically [1]. Considerable attempts have been made to develop CNT composite materials with high strength-to-density ratio. Metal matrix composites with CNT reinforcements has attracted attention in the past decade because of the scientific and engineering needs for the strengthening of industrial metals and alloys, for examples aluminium or magnesium alloys, nanocrystalline metals and bulk metallic glasses. However, the mechanical properties of these composites are not as great as one would expect because of fabrication methods and the weak bonding between CNTs and the metal matrix. Pretreatment of CNTs by metal coating is needed prior to the fabrication of CNT-metal composites.There are two pivot issues that have not been resolved to allow widespread applications of CNT-reinforced metallic materials. First, at the atomistic scales the interaction among CNT and metal atoms or ions is unknown. Since the electronic structures of carbon in CNT are completely different with those in diamond and graphite, the interaction of metal atoms or ions with CNT may alternate the electrical, magnetic and mechanical properties of CNT but such changes have not been characterized experimentally or theoretically. Secondly, at the nano-scales the understanding of the electro-mechanical properties of CNT-metal interfaces is still lacking. The deformation mechanism of CNT-metal composite is determined by the electrical and mechanical responses of the interfaces. Therefore, understanding the mechanical behaviors of metal-coating CNTs is essential in developing metal-CNT composites with desired mechanical properties.The proposed research is designed to develop metal matrix composites using metal-coating CNTs. The objective of this research is to characterize the mechanical behaviors of CNTs coated with metallic materials. First, metal-coating CNTs will be synthesized by electrochemical techniques and their mechanical properties will be characterized. Second, mechanical properties of metal-coating CNTs will be predicted by atomistic modeling approaches and then compared with experimental results. The combination of experiments and modeling can optimize the mechanical properties of CNT coated with metallic materials and accelerate the development of CNT-metal nanocomposites.

List of Research Outputs

Zheng G. and Li M., Crystal instability in nanocrystalline materials, Acta Materialia . 2007, 55: 06013.

Researcher : Zhou W

List of Research Outputs

Zhou W., Cheung W.L. and Wang M., Biodegradable composite scaffolds produced by selective laser sintering, Transactions of the Society for Biomaterials 2007 Annual Meeting. Chicago, USA, Society for Biomaterials, 2007, p. 170.

Zhou W., Wang M. and Cheung W.L., Fabrication and characterization of composite microspheres containing carbonated hydroxyapatite nanoparticles, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1221-1224.

Zhou W., Wang M. and Cheung W.L., Fabrication and characterization of composite microspheres containing carbonated hydroxyapatite nanoparticles, Proceedings of 5th Asian-Australiasian Conference on Composite Materials (ACCM-5). Hong Kong, The Hong Kong University of Science and Technology, 2006, 416-H.

Zhou W., Wang M. and Cheung W.L., Microstructures of carbonated hydroxyapatite nanospheres and CHAP/PLLA nanocomposite microspheres, Proceedings of Conference on Biomedical Engineering, BME2006. Hong Kong, Biomedical Division, HKIE, 104-107.

Zhou W., Lee S.H., Cheung W.L., Wang M. and Ip W.Y., Selective laser sintering of porous scaffolds from poly(L-lactide) microspheres and its nanocomposite with carbonated hydroxyapatite nanospheres, Proceedings of 20th European Conference on Biomaterials. Nantes, France, European Society for Biomaterials, 2006, T175.

Zhou W., Lee S.H., Wang M. and Cheung W.L., Selective laser sintering of tissue engineering scaffolds using Poly(L-lactide) microspheres, Key Engineering Materials. Switzerland, Trans Tech Publications, 2007, 334-335: 1225-1228.

Zhou W., Lee S.H., Wang M. and Cheung W.L., Selective laser sintering of tissue engineering scaffolds using microspheres of poly(L-lactide)-Based nanocomposite, Proceedings of 5th Asian-Australiasian Conference on Composite Materials (ACCM-5). Hong Kong, The Hong Kong University of Science and Technology, 2006, 417-H.

Researcher : Zuo L

List of Research Outputs

Ngan A.H.W., Wo P.C. and Zuo L., Initiation of Plasticity In Submicron Crystals: Weibull-like Characteristics”, Invited Presentation, The 12th International Symposium on Plasticity and Its Current Applications (Plasticity 2006), July 17-22, 2006, Halifax, Canada.. 2006.

Ngan A.H.W., Wo P.C., Zuo L., Li H. and Afrin N., The strength of submicron-sized materials, International Journal of Modern Physics B. World Scientific Publishing Company, 2006, 20(25), 26 & 27: 3579-3586.

Researcher : Zuo L

List of Research Outputs

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