Thus, {TAIL ~ the forces} required for closing {HEAD ~ the packing} can be more accurately calculated, wherefore the exact time of closure can be determined, which is critical 
Thus , { TAIL ~ the forces } required for closing { HEAD ~ the packing } can be more accurately calculated , wherefore the exact time of closure can be determined , which is critical
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH