英语语法分析

Because there is no abrasion between the concave and convex, the nut is reusable.

由于凹面与凸面之间没有磨损，螺母可以重复使用。

A small curve in the sliding part of the convex top of the lower nut acts as the wedge.

下螺母凸顶的滑动零件上有一条小弧线充当楔块。

It is locally convex in the sense that it has no loops and the curvature never changes sign.

它的局部是凸的，因为它没有环路，且曲率永远不会改变符号。