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。
2
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.