Permeability of a porous, sheet like sample is determined using a device that is designed to measure {HEAD ~ the pressure differential} between {TAIL ~ a first stream} of fluid applied across an entire thickness of a test sample and a second stream of fluid applied across an entire thickness of a reference sample 
between
Permeability of a porous , sheet like sample is determined using a device that is designed to measure { HEAD ~ the pressure differential } between { TAIL ~ a first stream } of fluid applied across an entire thickness of a test sample and a second stream of fluid applied across an entire thickness of a reference sample
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH