多项选择题
A.金属—石棉垫B.金属垫C.塑料垫D.金属复合材料垫
A.开启、关闭B.开启、开启C.关闭、关闭D.关闭、开启
A.a=1.8~2.8B.a=1.0~2.0C.a=0.2~1.2D.a=1.2~2.2