And this one, I was skiing out in Salt Lake City and the name of a building out there was Reid with R-E-I-D and it sounded good at the time."

VOA: special.2009.07.06

So if we want to talk about the volume of that, we just talk about the surface area, which is 4 pi r squared, and we multiply that by the thickness d r.

如果我们要讨论它的体积，我们要用的是表面面积，也就是４πｒ的平方，乘以厚度ｄｒ

麻省理工公开课 - 化学原理课程节选

r And what that is the probability of finding an electron in some shell where we define the thickness as d r, some distance, r, from the nucleus.

在某个位置为,厚度为dr的壳层内,找到原子,的概率，我们来考虑下我们这里所说的。

麻省理工公开课 - 化学原理课程节选

Additional Home Secretary D.R.S.Chaudhary told a news conference Sunday authorities and citizens need to be vigilant, especially in five eastern states.

VOA: standard.2009.06.21

The most important result from last time was that if you took this r, and you took two derivatives of this to find the acceleration, d^2 r over dt^2, try to do this in your head.

上节课最重要的结论,就是如果你把 r 写成这样,对 r 求两次导就能得到加速度,d^2 r / dt^2,心算一下

耶鲁公开课 - 基础物理课程节选

"And,the President's budget for 2009 in the recovery act had the largest increase for R&D that we have seen in recent years."

VOA: standard.2009.08.31