1. Laboratory of Mechanics, Materials, Structure and Production, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon
2. Fundamental Physics Laboratory, Department of Physics, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon
3. Mechanics Laboratory (lme), Rheology of Thin Films and Environment, University of Laghouat, Laghouat, Algeria