Affiliation: | 1. International Chair in Mathematical Physics and Applications (ICMPA-UNESCO Chair), University of Abomey-Calavi, 072 P.O. Box 50, Cotonou, Benin;2. Laboratory of Mechanics, Materials and Structures, Department of Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon;3. Laboratory of Condensed Matter-Electronics and Signal Processing, Department of Physics, Faculty of Science, University of Dschang, P.O. Box 479, Dschang, Cameroon |