iii TABLE OF CONTENTS

ii ACKNOWLEDGMENTS First of all, I would like to give my deepest thankful wish to my graduate advisor Dr. Nicholas Materer for his great help and guidance during my graduate school life. I have received a lot of benefit from his teaching and suggestions. His prolific knowledge and experience have greatly expanded my science insight. I would also like to thank Dr. John Gelder for his generous help with my teaching assistant career at OSU. I wish to thank Dr. Allen Apblett, Dr. Jeffery White and Dr. John Mintmire for being my committee members and spending efforts and time on helping me with my dissertation. I want to appreciate Dr. Asfaha Iob for his great support to my teaching assistant career, Dr. Richard Bunce for his thoughtful and interesting conversations. I want to thank our formal group member Dr. Dane Scott for his help with my research and my living at Stillwater. He has always been a good and helpful friend. I also wish to thank my college mates in China. They have been very supportive to my study and research experiences at the States in many ways. Finally, I want to give my gratitude to my beloved parents. They are my first tw