{HEAD ~ The percent area A} of the plane in {TAIL ~ the slide surface} is set in a range of A≧50% 
{ HEAD ~ The percent area A } of the plane in { TAIL ~ the slide surface } is set in a range of A≧50 %
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH