Time flies, after several months of hard work, my graduation thesis will be successfully completed.

First of all, I would like to thank my tutor, who guided me with a solid theoretical foundation and rich professional knowledge, and deeply influenced me with a serious and responsible work attitude and approachable attitude. From topic selection, literature review, opening report to writing, the teacher gave me a lot of valuable advice, and always took time out of his busy schedule to revise my paper again and again, which helped me a lot.

At the same time, I would also like to thank the teachers who guided my thesis. It is the teachers' serious and rigorous teaching attitude that helped me to perfect my graduation thesis and improve my professional theoretical level. Here, I would like to express my deep gratitude to them.

In addition, I would like to thank my classmates and friends who helped me in the process of completing my thesis, especially for their enlightenment.

In a word, I got a lot of help in the process of my thesis, and I thank all the people who helped me.