According to another object of the invention, the middle member comprises {HEAD ~ a sandwich} of {TAIL ~ wire trusses} and polystyrene materials 
of
According to another object of the invention , the middle member comprises { HEAD ~ a sandwich } of { TAIL ~ wire trusses } and polystyrene materials
OTH 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