http://hdl.handle.net/10397/200 Search the Channel search http://repository.lib.polyu.edu.hk/jspui/simple-search http://hdl.handle.net/10397/3870 Title: Fabrication of nano-structured HA/CNT coatings on Ti6Al4V by electrophoretic deposition for biomedical applications<br/><br/>Authors: Zhang, Bokai; Kwok, Chi-tat; Cheng, Fai Tsun; Man, H. C.<br/><br/>Abstract: In order to improve the bone bioactivity andosteointegration of metallic implants, hydroxyapatite (HA) is often coated on their surface so that a real bond with the surrounding bone tissue can be formed. In the present study, cathodic electrophoretic deposition (EPD) has been attempted fordepositing nanostructured HA coatings on titanium alloy Ti6Al4V followed by sintering at 800 °C. Nano-sized HA powder was usedin the EPD process to produce dense coatings. Moreover, multi-walled carbon nanotubes (CNTs) were also used to reinforce the HA coating for enhancing its mechanical strength. The surface morphology, compositions and microstructure of the monolithic coating of HA and composite coatings of HA with different CNT contents (5 to 20%) on Ti6Al4V were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-raydiffractometry, respectively. Electrochemical corrosion behavior of the various coatings in Hanks’ solution at 37 °C was investigated by means of open-circuit potential measurement and cyclic potentiodynamic polarization tests. Surface hardness, adhesion strength and bone bioactivity of the coatings were also studied. The HA and HA/CNT coated Ti6Al4V had a thickness of about 10 µm without cracks, with corrosion resistance higherthan that of the substrate and adhesion strength higher than that of plasma sprayed HA coating. The properties of the compositecoatings were optimized by varying the CNT contents. The enhanced properties could be attributed to the use of nano-sized HA particles and CNTs. Compared with the monolithic HA coating, the CNT-reinforced HA coating markedly increased the coating hardness without deteriorating the corrosion resistance or adhesion strength.<br/><br/>Description: DOI: 10.1109/INEC.2010.5425191 http://hdl.handle.net/10397/1662 Title: Leakage field modeling of spiral winding transformer for contactless power converters<br/><br/>Authors: Cheng, K. W. Eric; Lu, Yan; Chan, K. W. Kevin; Kwok, Yi-lin; Kwok, Kin-wing; Kwok, K. F.; Xue, Xiangdang<br/><br/>Abstract: The leakage inductance of the spiral winding transformer is examined. Two dimensional leakage field is modeled and leakage field linkage is then obtained to calculate the leakage inductance. The transformer is an air core based with a separation between the primary and secondary. The application is for contactless power conversion. http://hdl.handle.net/10397/1608 Title: General study on piezoelectric transformer<br/><br/>Authors: Kwok, K. F.; Dong, Ping; Cheng, K. W. Eric; Kwok, Kin-wing; Ho, Y. L.; Wang, X. X.; Chan, Helen L. W.<br/><br/>Abstract: Piezoelectric Transformer (PZT) is a devicewhich transforms voltage by piezoelectric effect and converse piezoelectric effect of ceramic material. Compared with electromagnetic transformer, it has favorable characteristics of miniaturization,electromagnetic-noise free and the variable voltage gain with frequency and impedance. The modeling of Piezoelectric Transformer is the base of control and optimize. The principle of transforming voltage ispresented in this paper. In addition, different modeling methods were brought into comparisons. Merits, shortcomings and the future work in modeling of PZT were given. http://hdl.handle.net/10397/1556 Title: LED lighting development for intelligent clothing<br/><br/>Authors: Cheng, K. W. Eric; Kwok, Kin-wing; Kwok, Yi-lin; Chan, K. W. Kevin; Cheung, C. Norbert; Ho, Y. K.; Kwok, K. F.<br/><br/>Abstract: LED lighting is applied to clothing. It allows a flexible method to provide illumination of lighting. A family of converter topologies is proposed to give this simply method of power conversion. Analysis for the circuits in terms of output power, efficiency and general operation are provided. Two types of LED lighting clothing are developed. One is using super-bright LED embedded on the cloth. This gives active lighting instead of passive lighting. Another one is using optical fibre with grating to form lighting pattern.