自动调节气压卸荷导轨利用压缩空气支承部分导轨载荷，以降低导轨面上的正压力，从而降低摩擦力。

In the automatic regulating pneumatic unloading guideways the compressed air is used to support part of the guideway load in order to reduce the normal force on the guideways.

youdao

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

This equation is telling you if you compress it, namely if x is negative, F will be then positive, because it's pushing you outwards.

这个方程告诉我们,如果压缩弹簧,即令 x 为负,F 就为正,因为推力的方向向外

耶鲁公开课 - 基础物理课程节选