1. Department of Applied Mathematics, Bharathiar University , Coimbatore 641046, India ; , Coimbatore 641032, India
2. Department of Mathematics, Karpagam College of Engineering , Coimbatore 641046, India ; , Coimbatore 641032, India
3. Department of Applied Mathematics, Bharathiar University , Coimbatore 641046, India
4. School of Electrical Engineering, Chungbuk National University , Cheongju 28644, South Korea