1. Department of Mathematics, National Institute of Technology Warangal, Warangal 1 , Telangana 506 004, India
2. Department of Mathematics, University College of Science, Osmania University 2 , Hyderabad, Telangana 500 007, India
3. Department of Mechanical Engineering, National Institute of Technology Warangal 3 , Warangal, Telangana 506 004, India