As a part-time student, my study for the degree of master of engineering will never become possible without the excellent guidance and great help from the people mentioned below. Firstly, I wish to express my sincere and deepest appreciation to my supervisor, Associate Professor Joe Hsieh Jang-Hsing, for his continuous support, encouragement, and invaluable guidance throughout this work. I would like to thank my co-supervisor, Dr. Tung Siew Kong, for his continuous support, encouragement, and invaluable discussions and suggestions in this study. As a working mother, doing part-time research study is a really tough job. Without Professor Hsieh and Dr. Tung's continuous encouragement and understanding, I would not be able to achieve the goal. I also thank sincerely my institute directors, Dr. Lim Ser Yong and Dr. Lee Loke Chong, for their kind support in this study. I would like to express my deep appreciation to my colleagues, Ms.