HEPA filters capture almost all particles in the air that are zero point three microns in size or larger.

VOA: special.2009.07.14

So, when the voltage difference between the plates is zero, or when we just don't have the plates there at all, the cathode rays are not bent, they just go right in a straight line, and they can be detected on this screen.

拐弯来测试它们是否带电,当两板之间电压为零，或者根本就,没有这两个板时，阴极射线是一条直线,它可以在屏幕上。

麻省理工公开课 - 化学原理课程节选

pV=RT p plus a over v bar squared times v bar minus b equals r t. All right if you take a equal to zero, these are the two parameters, a and b. If you take those two equal to zero you have p v is equal to r t.

我们就回到,也就是理想气体,状态方程,下面我们来看看,这个方程。

麻省理工公开课 - 热力学与动力学课程节选

The atoms or molecules in the gas don't know that there are other atoms and molecules in the gas, and then you end up with this universal property. All right, so gases that have this universal property, even when the pressure is not zero, those are the ideal gases.

可以忽略,这样就得到了理想气体的性质,在有限压强下,依然能保持这些性质的气体，被称为理想气体，本课中我们把大部分气体，都作为理想气体来处理。

麻省理工公开课 - 热力学与动力学课程节选