i am greatly in debt to a number of people, without whose help this thesis could not be completed. first of all, i must show my gratitude to my supervisor prof.导师名, whose helpful suggestions have contributed greatly to the completion of this thesis. i owe him special thanks for providing me solid and abundant materials and instructions.
my sincere thanks should go to mr. (某人), and miss （某人）, for their constant encouragement and support throughout the course of the research.
finally, i will express my thanks to my family who have shown patience and understanding to the entire period of this work. the biggest thanks must go to my parents who, though unable to support me theoretically, encourage me spiritually.