Finally, if this was all there it might be a simpler world, but Freud had a third component, that of the superego.

最后，如果只存在自我和本我,那么事情会简单得多，但弗洛伊德又提出了第三种结构，超我。

耶鲁公开课 - 心理学导论课程节选

But for now let's simply say that we have a diffraction which we know occurs only by wave-like behavior and it involves the use of x-rays. Why x-rays?

但现在让我们来简单假设一下,我们知道,只波才发生衍射,而且衍射涉及了X光的使用，为什么是X光？

麻省理工公开课 - 固态化学导论课程节选