First of all, I would like to deeply and gratefully thank my supervisor, Prof. Fei Richard Yu, for his invaluable support from all aspects and wonderful supervision. His excellent research insight and ongoing encouragement bring me an amount of momentum to explore the research. His comments and suggestions on my works not only increase the quality of the research but also provide a source of thought for my career. This work is as much his contribution as is mine for the fact that he has always wholeheartedly supported every decision I have made during this wonderful study. He has better prepared me for the world and I will always be indebted to him for anything I achieve in my future life. I would like to thank Dr. Helen Tang, for her valuable comments and suggestions during my research and study. Besides, I want to thank Dr. Shengrong Bu and Dr. Zhexiong Wei for giving me a lot of support and valuable advice in my research.