[1] Univ Carthage, Fac Sci Bizerta, Dept Math, Res Unit Math, UR13ES47,BP W, Zarzouna 7021, Bizerta, Tunisia
[2] Univ Carthage, Fac Sci Bizerta, Dept Math, Res Unit Applicat, UR13ES47,BP W, Zarzouna 7021, Bizerta, Tunisia
[3] Univ Nebraska, Dept Elect & Comp Engn, Lincoln, NE 68588 USA
[4] Univ Poitiers, XLIM UMR CNRS 7252, 11 Bd Marie & Pierre Curie, F-86073 Poitiers 9, France