for serving as my committee members and providing valuable suggestions and comments for this dissertation. A big "thank you" goes to Dr. Bicheng Zhu for all his help in fundamental research problem discussions, encouragement, and suggestions for life. Further thanks go to the lab colleagues and friends, including Omer Yaman, Yunpeng Li, Hang Yin, and Kai Sun, for their good suggestions in my research work. Special thanks go to Dr. Xianrui Wang and Dr. Xu Yan, for their friendship and support across the world. I also want to thank my friends Dr. Jing Wang, Zhengyi Song, and Daiyang Gao for their companionship in graduate school. Finally, I would like to acknowledge the most important persons in my life-my parents Zhijian Zhang and Huiying Jia for their unconditional love. Without their support, I could not overcome all the challenges I faced all these years. v