we can run the engine backward and build a refrigerator, if you've got your lecture notes from last period your 8-9, well, they're labeled 8-9 lecture notes, I made an attempt to define something which was a little bit misguided.

现在我们可以把热机倒过来,制作一台制冷机，如果你们拿出上节课的笔记,也就是8-9节，好的，他们在8-9节，当时我试着,定义了一些,有些误导你们的物理量。

麻省理工公开课 - 热力学与动力学课程节选

But the other reason to go through the thermodynamic cycles and really to develop great facility with them is because there are just an awful lot of things in nature and things that we build that run in cycles, where we want to calculate the thermodynamics, right.

但是要推导热力学,循环并为之发展一套,完善方法的另外一个原因是,自然界中或人造的那些,我们想计算它们的热力学的东西,有很多是以循环的方式运作的。

麻省理工公开课 - 热力学与动力学课程节选