简述选用密封垫片的原则。
参考答案:
应根据介质的工作压力、工作温度、密封介质的腐蚀性、结合面的形式选用垫片。
Neil has three friends in the school. They are all________.
A.woman teacher
B.woman teachers
C.women teacher
D.women teachers
CQ40型、CQ40A型、CQ40B型机械式钢筋切断机中40的含义是()
A.切断钢筋的最大直径是40mm
B.切断钢筋的最小直径是40mm
C.切断机的转速是40r/min
D.切断机的功率是40Kw