for their illuminating ideas, kind support, and precious friendship. V A special thanks to my parents Mrs. Pei Hualan and Mr. Yang Jiayi, and my husband Dr. Li Xian, for their love, care, dedication, encouragement, and the many years of support during my graduate studies. It was their immeasurable love that supports and keeps me motivated throughout my research. Last but not least, I would also like to thank Nanyang Technological University and Singapore Ministry of Education for providing me the opportunity and the resources to continue my research. VI CONTENTS STATEMENT OF ORIGINALITY .