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So now let's go around the cycle and just compare notes on what happens to the thermodynamic quantities as we do that.
现在让我们推导一下这个循环,比较一下这个过程中,热力学性质的变化。
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So we're going to go through a thermodynamic cycle, and here's what I want to calculate when we do this.
那么我们要推导,一个热力学循环,这是这个过程中我要计算的东西。
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As soon as I detect with what we'll call a condition if I'm touching the edge I have to essentially spin around 180 degrees and then continue looping.
一旦我检测到这种情况,当我碰到边界时,我需要转180°然后继续这一循环过程。
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And what's this little loop say to do? This little loop says I'm going to write a function or procedures that takes in two messages.
这个小循环是做什么的,这个小的循环是,我要写一个函数或者过程来接受两条消息。
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If you repeatedly go through this cycle of denaturing, synthesizing, denaturing, synthesizing you'll get many, many copies of DNA.
如果你不断重复这个变性-复制,变性-复制的循环过程,你就会得到很多很多的DNA复制产物
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Of course there are lots of ways we can execute the cycle, but this is a simple one, and these are steps that we're all familiar with at this point.
当然循环过程,可以有很多种方法，这是一个简单的例子，这是循环过程,循环中的每一步我们都很熟悉。
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As long as it's reversible, you know what the efficiency has to be, and in principle, you could break it down into a bunch of steps that you could formulate as isothermal and adiabatic.
只要这个循环过程是可逆的，你们知道效率是多少，从理论上说，可以将总过程,分解成一系列绝热,和等温的小过程。
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Now if you look at my derivation here, there's one spot where I could have just stopped and proven my point without going through the whole thing.
如果仔细检查我的推导过程，你会发现其实,我们不用研究整个循环过程,就可以证明我们要证的公式。
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You couldn't just run something successfully in a cycle and get work out of it, using the heat from the hot reservoir, without also converting some of the heat that came in to heat that would flow into a cold reservoir.
如果一样东西在循环工作过程中,只有热从高温热源中流出，而没有热流入低温热源，那么此过程,不可能对外做功,不可能把所有热。
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There's no change in them, and then we also looked at some at non-state functions, work and heat, and saw that those aren't zero going around a cycle. Of course you can do work in a cyclic process, and heat can be exchanged with the environment at the same time.
它们不会有变化，然后我们研究了,一些非态函数，功和热量，并看到,沿着循环行进一周的话,它们并不是零，当然你可以在,一个循环过程中做功，而同时热量可以在系统,与外界环境之间进行交换。
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What is counting my way through this process?
什么东西在数着我循环这个过程多少次了？
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So there is our set of individual processes that's going to constitute our cycle, right.
那么这就是组成这个,循环的一组反应过程。
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By two, by two, by two, and here it just conceptually is why this thing doesn't infinitely loop.
除以2，除以2，除以2，这里只是概念性地说明这一,过程为何不会无限循环。
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Now, if we go back to our Carnot cycle which is a set of reversible paths, it's useful to compare this to what happens in an irreversible case.
如果回到卡诺循环,它是由一系列可逆过程组成，我们将它,和不可逆过程的情况相比较。
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And the cycle it's going to undertake is called a Carnot cycle, and it works the following way: we're going to do pressure volume work.
它的循环过程,叫做卡诺循环，过程如下：,这是个压强体积系统。
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Now what I want to do is put up a specific example of the cycle that can be undertaken inside here in an engine, and we can just calculate from what you've already seen of thermodynamics.
现在我想做的是,举一个例子,来具体说明热机内部的循环过程，同时我们可以利用热力学定律进行计算,看看热力学参量发生了什么变化。
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Going around in a cycle the integral of dq over T is less than or equal to zero.
对一个循环过程作dq除以T的积分,小于等于零。
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So you know your cycle, you know, you could have a whole complicated sequence on a p v diagram of steps going back.
因此，对某一的循环过程，可以在pV图上画出,一系列很复杂的小步骤。
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So the question was, why is this return down at this level, it says, well if I ever execute out of this FOR loop, I get to the end of the FOR loop without hitting that branch that took me through the return, then and only then do I want to actually say, gee, I got to this place, there isn't any value to return, none I'm going to return none and none.
问题是，为什么它是在这个级别上返回值呢，意思就是如果我出了这个for循环,就意味着我运行的过程中没有走到任何,带return的支路上去,这时也只有这时我才能说天呐,我终于走到这儿了，这时不会返回任何值，只会返回none和。
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