My deepest gratitude must go to my supervisor Dr. Maylor Leung, who is, by all means, a devoted teacher. His knowledge, vision, inspiration and encouragement have guided me through the wonder land of science and have taken me to the frontier of research. His refusal to accept any lowering of standards of any kind will affect all the rest of my life. I am greatly indebted to my parents for their encouragement throughout all these years. Their teaching about the value of hard work and independence is always my source of impetus. Thank for their consistent support behind me for both my success and failure.