"And I said to him that those were two easy promises to make because those two things I could not change."

VOA: standard.2009.10.01

and it's not really easy to change that.

这一点不容易改变。

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That tells us the direction of spontaneous change for ordinary processes, chemical processes, mixing and you name it, under conditions that are easy to achieve in the lab.

这个物理量告诉我们在实验室,能够实现的条件下通常的过程，化学过程，混合以及你所能想到的过程，自发进行的方向。

麻省理工公开课 - 热力学与动力学课程节选

I want to show you how easy it is to change the code. But, notice, once I've added this I actually have a problem. This is now an under-constrained problem. I have more unknowns than I have equations.

我加上这个条件后,我马上面临一个问题了,这就是现在是一个非约束性问题了,我的未知数比方程数多,你从代数中可以知道。

麻省理工公开课 - 计算机科学及编程导论课程节选

Often, for a particular state change, it is easy to calculate two of these, but not the third.

对于一些特定的状态变化，它们中的两个很好计算，但是第三个往往不容易计算。

麻省理工公开课 - 热力学与动力学课程节选

And the motivation for choosing a pair like that is easy to see, if we look at our condition for spontaneous change or general condition.

我们这样选择的动机,很明显，如果考察我们所考虑的自发变化的条件,或者更一般的条件。

麻省理工公开课 - 热力学与动力学课程节选

I've simply added this one extra constraint, nice thing about thinking about it this way is it's easy to think about it, and what do you think I'll have to do if I want to go change the code?

我已经加上这个额外的约束条件，思考这种方法有件好事,那就是以这种方式来思考很简答,你认为我要是想？

麻省理工公开课 - 计算机科学及编程导论课程节选

And because there is an explicit relationship between u, delta u, q and w, you can always find the easy way to derive the change in internal energy or the heat or the work.

因为Δu，q和w之间,有明确的关系，一般来说,内能或热或功的变化,易于计算。

麻省理工公开课 - 热力学与动力学课程节选