工程：the purposeful use of science. Engineering is about building useful systems.在整理东西的时候发现了这本笔记。我有幸在大一初接触电路时便跟随MIT的Anant Agarwal Jeffrey H.Lang教授学习并记下了这部分笔记，现分享给大家。The concept of abstraction pervades all of EECS.还有一句近期的感悟：The noise is the fact of life, We should penetrate the appearance to see the essence. Be Filter, my friend.