Affiliation: | 1. Department of Applied Physics , University of Dacca , Dacca, 2, Bangladesh;2. Department of Electrical Engineering , University of Salford , Salford, M5 4WT, England;3. Department of Electrical Engineering , University of Salford , Salford, M5 4WT, England;4. Department of Applied Physics , University of Dacca , Dacca, 2, Bangladesh |