The check valves shall be modular and shall seal to the main valve body by the use of an O-ring.

这种止回阀应该是模块化的，并且应该采用一个O形环密封在主阀体上。

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This paper defines a new transformation of modules, discusses some of its basic characteristics, and proposes a modular isomorphic theorem of the ring transformation caused by induced functors.

本文定义了模的一种新的环变换，讨论了它的一些基本性质，并且给出了由诱导函子引起的环变换下的一个模的同构定理。

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