If you have a real gas and you write du is Cv dT and your path is not a constant volume path, then you are making a mistake. But for an ideal gas, you can always write this. And this turns out to be very useful to remember.

对于真实气体，如果其变化过程,不是恒容的，du=Cv*dT就不成立，但对于理想气体,这条规则永远成立,这一点非常有用，请记住。

麻省理工公开课 - 热力学与动力学课程节选

So, what made you change your career path?

是什么促使你改变了你的职业道路呢？

换专业的理由 - SpeakingMax英语口语达人

Depending on what you call external and internal environment, this path that I'm tracing here, deep within your digestive system, is really directly connected to the outside world through both ends.

基于你们所谓的外环境和内环境,我在这里我所指的消化系统内部通路,它的两端确实与外界环境直接相通

耶鲁公开课 - 生物医学工程探索课程节选

So if you need the help of the notes it's in there but I would urge you to work through it on your own, and it's the following: let's start with the same path A, all right?

如果你需要帮助，可以去看讲义,但我还是希望你们自己去推导它,它是这样的，让我们从：,相同的路径A开始，好吗？

麻省理工公开课 - 热力学与动力学课程节选