But it is not easy to get at. Specks of gold embedded in the mountain rock can only be extracted by blasting and crushing the rock to powder.

VOA: standard.2010.04.22

Just to be clear, so it's heat extracted over the work in.

这等于取出的热量除以做的功，我重写一下这个式子。

麻省理工公开课 - 热力学与动力学课程节选

These plots are extracted from these two regions and represent trials in which you're about to buy a product or you are about not to buy a product.

这些图是两个区域的切片,分别代表着受试者是否会,购买商品的不同试验。

斯坦福公开课 - 7个颠覆你思想的演讲课程节选