1. National Engineering School of Tunis, University of Tunis El Manar, ENIT-LAMSIN, B.P. 37, 1002Tunis, Tunisia
2. University of Aix-Marseille, 58 boulevard Charles Livon, 13284Marseille, France; and Faculty of Sciences of Bizerte, University of de Carthage, 7021 Jarzouna Bizerte, Tunisia