So, in this class we'll be talking about energy a lot, and it's often useful to draw some sort of energy diagram to visualize the differences in energy that we're discussing.

所以，这堂课我们会讨论很多,关于能量的问题，讨论时，画能级图来使能量差别,形象化常常是很有用的。

麻省理工公开课 - 化学原理课程节选

Just to plant a couple of seeds so that you've seen it before and then we can revisit in more useful context.

前人多栽树,后人易乘凉。

哈佛公开课 - 计算机科学课程节选

Now we know so much about these, they've turned out to be so useful in biotechnology.

现在我们对限制性内切酶了解这么深入,它们在生物技术方面又这么有用

耶鲁公开课 - 生物医学工程探索课程节选

So this isn't the most useful form that we can have, but what we'll see shortly is that from this, we can then derive further criteria for essentially any set of variables or any set of external constraints, like constant temperature or pressure or volume and so forth that we might set.

所以这不是我们所能得到的最有用的形式，但是我们会很快看到，我们能够进一步推导出包含任意变量,或者任意约束的自发过程判断标准，比如说恒定的温度，压强,体积或者其他我们能够给出的约束。

麻省理工公开课 - 热力学与动力学课程节选

Newton says F = ma, so to make it a useful result of this problem, we know the mass of this guy.

牛顿指出 F = ma,这对于解决这个问题很有用,我们知道这个物体的质量

耶鲁公开课 - 基础物理课程节选

So we are actually using the C99 version of C, which really means nothing useful today other than to realize we are using that version.

所以我们在使用的C语言的C99版本，这对今天来说是没多大用处的,只是告诉我们使用的是那个版本而已。

哈佛公开课 - 计算机科学课程节选