她坚信阶级制度恒定不变。

She believed in the fixity of the class system.

《柯林斯英汉双解大词典》

就假定保持a恒定不变。

Let's say keep a constant.

youdao

首先，a是恒定不变的。

Well, first I said a is constant.

youdao

OK, so for a constant volume process, du we can write du, partial derivative of dT u with respect to T at constant V, dT, dv plus partial derivative of u at constant V, dV.

好，对于一个恒定体积的过程，我们可以写出,等于偏u偏T，V不变，加上偏u偏V，T不变。

麻省理工公开课 - 热力学与动力学课程节选