1. Laboratory of Mathematics and Their Interactions, University Center of Mila, Algeria
2. Laboratoire de Mathématiques J.A. Dieudonné, Université Côte d’Azur, Parc Valrose, 06108 Nice Cedex 02, France
3. Department of Electrical Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR, P. R. China