So this one is a quadcopter. 这是一个四轴飞行器。 It's a small model helicopter. In a way, it's a toy, no? 一个小型的直升机模型。差不多是个玩具吧。 And so this one was military technology a few years ago, and now it's open-source,
There's only one little entrance to the entire building, 整座大楼只有一个小小的入口， and the 3,000 residents come in and out through that single door. 3000居民从这里通过这一个门进出。 Together, the inhabitants created publi
Hi everybody, and Happy Fourth of July weekend. On Monday, Michelle, Malia, Sasha, and I will celebrate the Fourth like most of you - in the backyard. We'll hang out with family and friends, throw
Now one of things that I believe is that change not only requires an understanding of human nature, change also requires clear-eyed realism, change requires a deep understanding of what is wrong, so t
