Yeonhwa Park, for giving me a great opportunity to pursue my Ph.D. study in her lab and for her continuous guidance, support, and patience during the four years. Without her kind help and encouragement, I cannot make it here. My sincere thanks also go to my thesis committee, Dr. McLandsborough and Dr. Kim, for their great support and guidance during my study here. I would like to give special thanks to Dr. Decker, the department head, and Mr. Peter Salmon, the CFS CPP of IFN Consulting, who generously gave great help, financial support, and gracious encouragement to me.