They drill down to the shale, then go sideways and inject high-pressure water, sand or other material into the rock.

VOA: special.2009.10.23

Wrev w reversible. in this case here let's see this is it's a pressure is going down.

曲线下的面积，可逆过程的功,这个过程中。

麻省理工公开课 - 热力学与动力学课程节选

So the force that you're pushing down on here is the external pressure times the area.

或者压缩功的概念,在活塞上施加压力。

麻省理工公开课 - 热力学与动力学课程节选

That is, it's easy to write down straight away that dG with respect to temperature at constant pressure S is minus S.

这就是说，可以很简单的写出dG在,恒定压强下对温度的偏导数,是负。

麻省理工公开课 - 热力学与动力学课程节选

Pressure, the piston goes down by some volume l.

我们只讨论膨胀功。

麻省理工公开课 - 热力学与动力学课程节选

So expansion work, for instance, or compression work, is if you have a piston with a gas in it. All right, you put a pressure on this piston here, and you compress the gas down. This is compression work.

力乘以距离，就是功，功有许多种：,电可以做功,驱动电机与电风扇,磁力也可以做功。

麻省理工公开课 - 热力学与动力学课程节选