Then I would like to extend my genuine thanks to my prestigious and edifying teachersof school of foreign languages in East China University of Science and Technology, ProfessorShao Zhihong,Professor Yu Yuguo,Professor Yan Jinglan,Professor Wang Jianguo,Professor Wang Zhiqin, Professor Chen Li and all the other responsible teachers andprofessors. Their classes,lectures and suggestions shed invaluable enlightenment on me andwill have great influence on my fiiture study.

　　Finally,my sincere gratitude goes to my family and friends for their unweaving supportand understanding which encourages me to overcome academic struggle and support me tospend three years' life here. With the help of such selfless individuals, I am glad to dedicatemy heartfelt thanks to all of you.

论文致谢五：

　　Time is a bird forever on the wing. For the past two years' post-graduate study, Ireally had a fulfilling life here. Not only have I met many knowledgeable teachers, butalso truthful friends. I would like to give my deep gratitude to many of them. First of all, Iam most grateful to Professor Zhang Ruwen, my supervisor, who offers me invaluableguidance and help both in my study and my life. Without her enlightening suggestions andinstructions, it would be a tough task for me to finish my thesis. Besides, I also appreciatemany other teachers who have offered their useful suggestions and inspire me a lot. Mythanks also go to my parents, grandparents, my classmates and my loving friends. Theircompany is a great consolation to me. I wish everyone could live in peace and happiness.