Thus, in the actuator extension example, the effective cross sectional area of the air mass volume exhaust is increased: in the actuator contraction instance {HEAD ~ the cross sectional area} of {TAIL ~ the air mass volume exhaust} is decreased 
Thus , in the actuator extension example , the effective cross sectional area of the air mass volume exhaust is increased : in the actuator contraction instance { HEAD ~ the cross sectional area } of { TAIL ~ the air mass volume exhaust } is decreased
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH