1st round checking

Modify:

1. re-arrange the sections
2. add more pictures
3. delete unnecessary descriptions
4. modify the formulas
5. simplify the cites

TODO:

1. reduce the formula
2. reduce the unnecessary cites of figure and formula
3. use more short but accurate words
4. maybe merge some subsection
5. The likelihood of waveform and its reconstruction

Signed-off-by: dw839566105 839566105@qq.com