加氢装置临氢系统进行初始气密阶段()。
A、气密、置换同步进行
B、先气密,后置换,节省氮气
C、先空气试压、再氮气置换、
D、先氮气置换合格,再气密
参考答案:D
关于激光的英文“laser”,以下哪一项是正确的()
A.Lightactivation by stimulation emanation of radiation
B.Luminant amplimeter by stimulation emission of radiation
C.Lightactivation by pemission of radiation
D.Luminant activation before p emission of radiation
E.Light amplification by stimulation emisssion of radiation
择伐