Some optional items that I found useful are as follows.

一些可选项目，我发现有用的内容如下。

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The research items are follows:(1) The significance of researches and some results on CCV were generalized. At the same time, the contents and ways of this study were proposed.

阐述了汽油机非稳定工况燃烧过程研究的意义及其现状，提出了本文的研究内容与研究思路。

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