The second section is the introduction of basic concepts and theory.

第二部分是基本概念和理论的阐述。

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First, the second part, for the introduction and related basic concepts.

第一、第二部分，为绪论和相关基本概念。

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First, the second part, for the introduction and related basic concepts.

第一、第二部分，为绪论和相关基本概念。

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