In the process of writing this paper, I would particularly like to thank my guidance teacher for his guidance and supervision. Without the help of the teacher, there would be no today's paper. The course of study is hard but happy. During this process, Teacher Liang always demanded me strictly. Without any sloppyness, he was always able to provide targeted insights to some of my problems. At the same time, he paid more attention to the cultivation of my self-learning ability.