反馈是鲁棒控制系统的关键。

The only real prison is the one we build for ourselves.

Quality is never an accident; it is always the result of intelligent effort.

It is the preoccupation with possessions， more than anything else， that prevents us from living freely and nobly.

Sustainable development is not a slogan but a concept that must be practiced. We must keep the land forever vibrant.