1. Fracture Research Laboratory, Faculty of New Science and Technologies, Univ. of Tehran, P.O. Box 13741-4395, Tehran, IR.
2. Dept. of Management and Engineering, Univ. of Padova, Stradella, S. Nicola 3-36100 Vicenza, IT.
3. Dept. of Management and Engineering, Univ. of Padova, Stradella, S. Nicola 3-36100 Vicenza, IT (Corresponding author), e-mail: berto@gest.unipd.it