I would like to take this opportunity to express my sincere appreciation to many people who have helped me during my doctoral study at Nanyang Technological University. In the first place I would like to express my most sincere gratitude to my supervisor, Professor Er Meng Joo, for all these years of conscientious supervision, sound advices, invaluable guidance, constant encouragement and support. I would also like to express my special thanks to Dr Chen Weilong and Liu Fan for their valuable advices on my research work. I am deeply grateful to my family for their support and unfailing blessings, My dad, Mr. Lian Zhongxiang, my mum, Ms. Wang Suqin, and my wife, Ms. Han Lu. Their endless love, support, encouragement and care are a strong motivation for me. Last but not least, I would like to thank all my colleagues and friends for their friendship and countless help rendered during my graduate study.