Proportion Of True Null Hypotheses In Non High-Dimensional Multiple Testing Problems: Procedures And Comparison

An electromagnetic clutch for use with a compressor for an automobile air conditioning system includes a back cover provided at an end wall (26) of an armature (15) which moves to engage and disengage a rotor. The back cover has visored slits (30) with visors (30a) which align with arcuate slots (24) of an armature (28). The air between the armature and the rotor is released through the slits to prevent over compression of the air when the armature is attracted to the rotor. The visor of the back cover prevents an oil leaking from the compressor from invading into the contacting surfaces of the clutch through the arcuate slots of the armature (15).