principle role主体作用principlen.原理；原则；主义；信念principle of proportionality比例原则principle of equal treatment平等待遇原理principle of legal certainty法律确定性原则principle of being a teacher师道principle of controls design控制器的设计原理principle of differentiation区别原则principle of excluded middle排中律PRINCIPLE OF AIR PISTON PUMP气动柱塞泵的工作原理principle of rationalization合理原则principle of Fraud Exception信用证欺诈例外原则