[1] Univ Yaounde I, Higher Teachers Training Coll, Dept Phys, Nonlinear Phys & Complex Syst Grp, POB 47, Yaounde, Cameroon
[2] Univ Douala, Fac Sci, Dept Phys, Pure Phys Lab,Grp Nonlinear Phys & Complex Syst, POB 24157, Douala, Cameroon
[3] Fotso Victor Univ, Dept Telecommun & Network Engn, Lab Automatique et Informat Apliquee LAIA, Inst Technol, POB 134, Bandjoun, Cameroon