"So a year ago,in 2009, when you had a majority being optimistic about American policy in the Middle East, only 29 percent said Iran having nuclear weapons would be positive for the Middle East.

VOA: standard.2010.08.06

One major difference between electron affinity and ionization energy is that when we talked about ionization energy, remember ionization energy always has to be positive.

电子亲和能,与电离能之间最大的不同就在于,当我们提到电离能的时候，记得电离能总是正的。

麻省理工公开课 - 化学原理课程节选

It turns out that it's going to be a little bit different when we're talking about positive ions here.

结果是当我们讨论阳离子时,有一些不同。

麻省理工公开课 - 化学原理课程节选

And in terms of thinking about the phase of this p orbital, the phase is going to be positive anywhere where z is positive.

对于ｐ轨道的相位，在ｚ大于零的地方都是正的。

麻省理工公开课 - 化学原理课程节选