I would like to express my deep gratitude to my supervisor, Professor Choi San Shing, for his invaluable guidance, help and encouragement throughout my research. My special thanks go to Associate Professor D. M. Vilathgamuwa and Assistant Professor S. Rajakaruna, for their invaluable advice and help throughout my research. The research would not be possible without the financial support provided by Nanyang Technological University in the form of a research scholarship. For this I am most grateful. I am also deeply thankful to Ms Chew-Sim Annie, Mr.Yeoh Tiow Koon, and Mr. Lee Ting Yeng for the technical support they have given me in the course of my research. Last but not at least, to my fiancé, Heyi, for his unfailing support, patience and cooperation that have made the completion of the research work possible. And also my parents for their invaluable support and understanding over these three years or so of my graduate program.