PROFESSOR BAWENDI: The only But it's hard to imagine an irreversible compression the way we can just imagine an irreversible expansion.
,但是我们很难,像描述不可逆膨胀一样,来描述不可逆压缩。
OK, important -- if you are part of this group here think about it and make sure you understand that.
好的,这很重要,如果刚才你选了可逆过程,请好好想想并且保证已经理解了这个问题。
Now,that thing that wakes up after this complete irreversible amnesia will no doubt eventually develop a personality,a set of beliefs,memories.
这人在经历了完全不可逆的失忆后醒来,最终发展出了自己的人格,信念和记忆。
It's been encrypted pretty naively, pretty simplistically, but it's actually an English sentence that's been somehow scrambled; but scrambled in a reversible way.
它被天真地,相当简单地加密了,但是它实际上是一个被加密的英语句子,但是加密方式是可逆的。
The other beauty about - beautiful thing about proteins is that if you make subtle conformational changes, often those changes are reversible.
蛋白质的另一个美妙之处就是,如果蛋白质发生一些小的构像改变,这些改变通常是可逆的
All right, let's try again. How many people vote that this is reversible? That looks like a majority to me. Irreversible?
好的,让我们再试试,有多少人认为这是可逆的?,看上去大多数人都这么认为?
Of course in the reversible case, you're always pushing against an external pressure, which is essentially equal to the internal pressure.
当然在可逆的情况下,外压力,总是,等于内部压力。
it becomes a gray area but it should be pretty clear if you can treat something is reversible are irreversible.
这是个灰色区域,但什么可以当作可逆过程处理,而什么要当作不可逆过程,这是相当清楚的。
How many people vote for that this is a reversible process? I've got one vote back there two votes, three votes, four votes. Anybody else?
有多少人认为,这是一个可逆过程?有一个,两个,三个,四个,还有别的人吗?
So for the reversible process, the work done is the integral under the pressure volume state function, the function of state.
对可逆过程,做的功,是压强体积态函数曲线下,的积分面积。
Because it's so important. And I should add and also under reversible work, where the external pressure is equal to the internal pressure.
而且我还要说应该在外部压强,和内部压强相等的,可逆过程中引入它。
Wrev w reversible. in this case here let's see this is it's a pressure is going down.
曲线下的面积,可逆过程的功,这个过程中。
get back to the initial point is going to require some input from outside, like heat or extra work or extra heat or something because you've done an irreversible process.
如果要逆转它,回到初始点,就需要外界的投入,比如额外的功,额外的热量等等,因为你进行了一个不可逆过程。
So we've got our reversible adiabatic path right.
那么我们有了这条可逆绝热路径。
So what this says is the efficiency of any reversible engine T1 has to be one minus T2 over T1.
这就是说,任何可逆热机的效率都是,负T2除以。
And all we know about this is that it's really for some irreversible reversible step.
我们知道,这个式子,对不可逆过程成立。
You have to do it awfully fast to get your irreversible compression.
我们要压缩得非常快,才能实现不可逆压缩。
OK, so now we're going to do the same kind of experiment, but irreversibly. An irreversible adiabatic.
现在来在,不可逆的条件下,完成相同的实验。
And I want to make sure everybody figured out that it really was an irreversible expansion.
或者多孔塞的,不可逆的等焓过程。
that instead of all the steps being reversible, let's just put in one irreversible step.
不是所有的过程都是可逆的,其中有一个过程不可逆。
We can do it reversibly, or we can do it irreversibly.
它可以是可逆的,也可以是不可逆的。
So w, the work is less for the irreversible process than the reversible process.
不可逆过程中系统对外界,做的功要比可逆过程时小。
This is equal to zero. So this irreversible process this Joule-Thomson process, is a constant enthalpy process. Delta h for this process is equal to zero.
等于0。所以这个不可逆过程,也就是焦耳-汤姆逊过程,是一个等焓过程。
All right, let's calculate the work that's involved with these two processes.
这些路径都是可逆的,可逆过程指的。
Let's just take our reversible engine and modify it a little bit.
我们就拿可逆热机为研究对象,并对它进行一点修改。
The reversible process is going to be colder because it has to expend more energy.
可逆过程降温更多,因为输出的能量更多。
T2 Is the temperature T2 in this process smaller or larger than if I were to do the process reversibly with the same endpoint pressure.
这里的末态温度,与经过可逆绝热过程,到达相同压强的末态温度相比哪个比较高呢?
And probably also in practice nothing is truly reversible.
或许在实践中,没有什么是真正可逆的。
No, pretty much things are either reversible or irreversible.
不,几乎所有的都是要么可逆,要么不可逆。
Like something is almost reversible and almost irreversible.
就像什么东西是几乎可逆的,或几乎不可逆的。
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