I am very grateful and indebted to my thesis advisor, Dr. Chita Ranjan Das, who
guided me with patience during my doctoral studies at Penn State University. He not
only supported me as an advisor, but also is my role model as a researcher because of
his great enthusiasm and passion in doing research and tackling challenging problems. I
would also like to express my appreciation to my other committee members, Dr. Wang
Chien Lee, Dr. Thomas La Porta, Dr. C. Lee Giles, and Dr. Dongwon Lee, for their
insightful commentary on my work.
I am thankful to many colleagues with whom I have had the privilege to work.
Let me also express my gratitude for the many friends and church members who have
been with me during my graduate studies. I have been very fortunate to have had the
chance to know them and will never forget their kindness and warm hearts.
I am very thankful for my parents, who have always believed in me and have
been a great support for me, and for my sisters, Jin kyon, Jin sook, and Jin ee, their
husbands, and their children, whom I love from bottom of my heart.
Lastly, I want most of all to thank my husband, Gyu Sang. He is the kindest and
nicest person in the world. Our discussion regarding my research were very simulating