1. Department of Mathematics, National Institute of Technology Manipur, Langol, Imphal 795004, Manipur, India
2. Department of Electric Machines and Drives, Technical University of Cluj-Napoca, 26-28 Baritiu Str., 400027 Cluj-Napoca, Romania
3. Department of Physics and Chemistry, Technical University of Cluj-Napoca, 103-105 Muncii Blvd., 400641 Cluj-Napoca, Romania