alternate motion

• 往复运动,交变运动

alternate motion的用法和样例：

例句

1. The steam-engine piston makes a cyclic motion.
   蒸汽机活塞做往复运动。
2. This is a mechanism using a slider to transit a rotation to reciprocating the linear motion skimpily.
   此机构利用一滑槽，即可简单的将圆周运动转成直线的简谐往复运动。