Today, the trend is to increase {HEAD ~ the temperature} of {TAIL ~ operation} of gas turbine engines 
of
Today , the trend is to increase { HEAD ~ the temperature } of { TAIL ~ operation } of gas turbine engines
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH