providing financial supports during early years of my study. Furthermore, I would like to thank my wife, Lingyuan, for cheering me up on numerous occasions and giving me a home always full of joys. Finally, I would like to thank my parents, General and Mrs. Yeh-Kai Wang, for their never-ending supports from the day I was born. Their love and encouragement make my pursuit of higher education possible. I therefore dedicate this dissertation to them.