1. Lecturer, Mechanical Engineering Dept., Faculty of Engineering and Technology, Univ. of Botswana, Gaborone, Botswana (corresponding author).
2. Professor, Dept. of Applied Mathematics, National Institute of Technology, Rourkela-769 008, Orissa, India.
3. Professor, Mechanical and Industrial Engineering Dept., Indian Institute of Technology Roorkee, Roorkee-247 667, Uttarakhand, India.