According to the process for the production of convex-concave ends local fracture, optimization is proposed.
本文针对生产过程中出现的凸凹端头局部断裂问题，提出优化方案。
2
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。
3
Water surges from the cells on the inside of the leaf to those on the outside, causing the leaf to rapidly flip in shape from convex to concave, like a soft contact lens.