Using polynomial regression, {TAIL ~ an empirical relationship} can be found between the density and {HEAD ~ pressure drop} 
Using polynomial regression , { TAIL ~ an empirical relationship } can be found between the density and { HEAD ~ pressure drop }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD