1. Textile Engineering Department, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Yugoslavia, Institute of Physics, P.O. Box 68, 11080 Zemun,Yugoslavia, and Deutsches Wollforschungsinstitut an der RWTH Aachen, Veltmanplatz 8, 52062 Aachen, Deutschland