ii @Copyright 2012, Xiaomeng Bian iii Dedication This dissertation is dedicated to all I have ever learnt from. Sincerely. iv Acknowledgement First, I would like to give my sincere thanks to my families: my parents, uncles and aunties, brothers and sisters, and my in-heaven grandparents. Their selfless love and firm support encourage me to face all the challenges in my study-and-life time.