For example, the characteristic length may be a side length or a diagonal length when the transmission surface has {TAIL ~ a square shape}, or may be a diameter when {HEAD ~ the transmission surface} has a circular shape 
For example , the characteristic length may be a side length or a diagonal length when the transmission surface has { TAIL ~ a square shape } , or may be a diameter when { HEAD ~ the transmission surface } has a circular shape
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH