1. College of Biomedical Engineering, Taiyuan University of Technology, Shanxi Taiyuan 030024, China
2. Department of Mathematics, Taiyuan University of Technology, Shanxi Taiyuan 030024, China
3. Human Sciences Research Council (HSRC), South Africa
4. Department of Mathematics and Computer Science, Elizade University, Ilara-Mokin, Ondo State, Nigeria