She said each new performance was different from the next one.

VOA: special.2009.12.18

And so instead of defining efficiency the way you've got it written there, I'm going to define what's called something different for a refrigerator which is called the coefficient of performance.

现在我们不用,效率的那个定义，我给出一个,有关制冷机的,新的定义,叫做制冷系数。

麻省理工公开课 - 热力学与动力学课程节选

So,I'm telling you from the beginning, but don't dream and think that somehow the Final's going to be so much different from your regular day-to-day performance, but to give you some reason to live after the Midterm.

所以我在开始告诉你们,但是,不要以为你们的最终成绩,和你们的平时表现,没什么关系,但这能让你们不至于期中的时候就绝望了

耶鲁公开课 - 基础物理课程节选