Four years of study and life are coming to an end in this season, but my life is just a comma, and I will face the beginning of another journey. With the strong support of teachers, relatives and friends, my four-year study career was very hard, but I also gained a lot. When my thesis was about to go to Fuzi, I had many ideas, and I couldn't calm down for a long time. I admire great men and celebrities, but I am more eager to dedicate my respect and praise to an ordinary person, my mentor. I am not your best student, but you are my most respected teacher. Your rigorous academic attitude, profound knowledge, profound thoughts and broad horizons have created a good spiritual atmosphere for me. It is better to teach people to fish than to teach them to fish. Being in it and deeply influenced by it, I not only accepted brand-new ideas, set up grand academic goals, but also understood the basic way of thinking. From the topic selection to the writing guidance, through your careful guidance and understanding after thinking, I often feel that "there is no doubt in the mountains and rivers, and there is a village."

Thanks to my parents, I can't get anything and I can't return it. My greatest wish is that you will be healthy and happy forever. When the paper is about to be completed, my mood can't be calm. How many respectable teachers, classmates and friends gave me wordless help from the beginning to the smooth completion of the thesis? Please accept my sincere thanks!

At the same time, I also thank the college for providing me with a good graduation design environment.

Finally, I would like to thank all my mentors, friends and classmates who helped me in my graduation project, as well as the authors of the works I quoted or referred to in my design.