The last hemispheric gathering, in Argentina in 2005, was marred by riots and fierce demonstrations against then-U.S.President George W.Bush.
VOA: standard.2009.04.19
Delta u, delta H, familiar state functions, q w changes in their values, q, w, heat and work.
U,△H,很熟悉的态函数,它们的值在变化;
For isothermal expansion, that means that delta u does not change, but delta q is equal to delta w?
在等温过程中,是不是内能不变,Δq等于Δw?
The agreement to be signed Thursday replaces the START-1 treaty, which U.S.President George H.W.Bush and Soviet President Mikhail Gorbachev signed in 1991.
VOA: standard.2010.04.04
U OK, so let's look at delta u. Delta u is q plus w.
好的,让我们看看Δ
president's actions are the same as his predecessor. (Speech) Larijani argued two actions last week showed that little had changed in U.S.policy since the presidency of George W.Bush.
VOA: standard.2009.11.15
u=q+w We have a relationship between them.
它们之间有关系Δ
u=q+w All right, what is delta u? delta u is q plus w.
好,Δu是多少?Δ
w Now, we have u, q and w.
现在我们有u,q和。
w This is just q plus w. There's w, RT1 ln q has to be R T1 log of V2 over V1.
而U等于q加,那是w,q应该是。
q Work is zero. Delta u is w plus q, work plus heat. This is zero, this isn't.
功是零,△U是w加,功加上热量,这个是零。
U And then if we can also determine delta u, then we know this, we know delta u is q plus w w, then we can determine work as well, right?
然后,如果我们也能定出△,然后我们知道这个,我们知道△U等于q加?
And of course, in either case, w delta u is q plus w, so it's q irreversible plus w irreversible, u being a state function it's the same in either case.
当然了,在这两个过程中,Δu都等于q加,因此现在是q不可逆加w不可逆,同时u在这两个过程中都是态函数。
Delta u is q plus w. Delta u isn't zero.
U是q+w,△U不是零。
U It's u, because u is to q plus w right, heat and work, but it's adiabatic. So there's no heat, exchange with the environment, and it's constant volume, so there's no p dV work, right.
什么是零?是U,因为,等于q加w,热量和功,但这是绝热的,所以系统与环境间没有热量交换;,同时它是灯体的,所以也没有pdV形式的功。
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。
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