As an example,he says Soviet war veterans exert political pressure against negative portrayals of events they participated in and that the Kremlin has its own interest in creating the historical truth commission.

VOA: standard.2009.12.25

Negative pressure doesn't make any sense, right?

负的压强没有意义？

麻省理工公开课 - 热力学与动力学课程节选

So if delta v is negative, in this case delta v is negative, OK, delta v is negative, pressure is a positive number, negative times negative is positive, work is greater than zero.

也就是当活塞,压缩气体的时候，做的功是正的，按照这一规定,我们需要在这里，加上一个负号，这是习惯规定。

麻省理工公开课 - 热力学与动力学课程节选