My foremost and tremendous appreciation goes to my major professor, Dr. Chen-Ching Liu, who provided me with his continuous support, inspirations, challenges and encouragement during my research work. This dissertation work could not have been completed without his insightful and invaluable technical advice. The precious experience of working with him as a teaching assistant and as a research assistant on a variety of projects will have a profound influence on my future career development. I would also like to express my sincere thanks to Prof. Venkataramana Ajjarapu, Prof. Manimaran Govindalasu, Prof. Dionysios Aliprantis and Prof. Dan Nordman for serving on my committee. Their valuable feedback and suggestions were essential in improving the dissertation. I am very grateful to my parents Zhen-Ju Zheng and Quan-Xi Li, my beloved husband, Nanpeng Yu, for their endless support and love as always.