In one aspect, the invention is a device for controlling {HEAD ~ a flow} of {TAIL ~ a fluid} moving through a pipe 
of
In one aspect , the invention is a device for controlling { HEAD ~ a flow } of { TAIL ~ a fluid } moving through a pipe
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH