A method, device, and system for controlling {HEAD ~ a flow} of {TAIL ~ a fluid} moving through a pipe are presented 
A method , device , and system for controlling { HEAD ~ a flow } of { TAIL ~ a fluid } moving through a pipe are presented
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 OTH OTH