{HEAD ~ means} for delivering {TAIL ~ the energy} from the source to the inner surface of the tubular portion 
for delivering
{ HEAD ~ means } for delivering { TAIL ~ the energy } from the source to the inner surface of the tubular portion
HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH