Be thankful for what you have; you’ll end up having more. If you concentrate on what you don’t have, you will never, ever have enough.
奈奎斯特准则提供了一种图形方法来确定闭环系统的稳定性。
Time is a concept that humans have created to make sense of the universe, but the universe itself is timeless.
It is a capital mistake to theorize before one has data.