The letters H-E-P-A represent the words High Efficiency Particulate Air.

VOA: special.2009.07.14

Well, we would have to H+ have one of these hydrogen atoms go to an H plus, * plus an electron, right? **H --> H+ + e-** So, now we have a hydrogen ion here.

我们先要让,一个氢原子变成氢离子，加上一个电子，对么*,我们现在有一个氢离子了。

麻省理工公开课 - 固态化学导论课程节选

H- *H + e-> H-* And, clearly, we can't do both.

到一个电子生成*,但我们发现我们不能同时做到两个。

麻省理工公开课 - 固态化学导论课程节选

- There are a few equations that you need to memorize -- those are the very simple -- very, very simple equations, such as e equals h times nu -- hopefully you don't have to sit down and try to memorize that, hopefully we all know that already.

只有几个公式是需要记住的-,它们都非常简单，非常非常简单，比如，E，等于，h，乘以，ν,希望大家不需要再专门去背了，希望我们已经都记住了。

麻省理工公开课 - 化学原理课程节选