This thesis would not have been possible without the support from many sides. First and foremost, I would like to express my sincerest gratitude to my supervisor, Assistant Professor Poh Chueh Loo, for his patience, enthusiasm, motivation, and enormous knowledge in this area. His continuous support helped me greatly in all the time of my Ph.D. study and research, and writing this thesis. His guidance has not only given me the knowledge in scientific area but also made me a better researcher and person, with patience, confidence, and responsibilities. I could not have imagined having a better supervisor and mentor for my Ph.D. study.