设有泵体密封环，而叶轮密封环为可选用件。
Sealing ring is fitted on pump body, while impeller sealing ring is an optional part.
年前，我刚刚开始山地自行车运动的时候，我更愿意选用零件尽可能少尽可能简单的自行车。
When I started mountain biking 10 years ago, I went for the simplest possible bike with the fewest possible components.
着重说明了车削淬火钢件时，如何通过合理地选用刀具材料、刀具几何参数及切削用量达到理想的切削效果，并提出车削淬火钢件时应注意的若干问题。
The author gave us the reasonable selection of tool materials, tool parameters and cutting parameters during turning of hardened steel in order to get the ideal cutting result.
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