主动动机

She definitely had an ulterior motive in offering to help.

她主动提出帮忙, 肯定有不可告人动机。

When this method is applied to the spiral bevel gears of an airplane engine, the results show that it is more reasonable than TCA and the precontrol method.

提出在初始设计阶段就可保证弧锥具有预期加载接触性主动设计方法，并将其用于某航空发动机中央传动弧锥面综合。