I wish to express my deepest and sincere gratitude to my supervisor, Associate Professor Dr. Wilawan Mahabusarakam, for her valuable instruction, expert guidance, excellent suggestion and kindness. I would also like to express my appreciation to Assist. Prof. Dr. Suda Chakthong my co-advisor and Dr. Moragot Kaewpet, for thesis correction and their kindness. Without their help, my thesis work would not be successful.