1. 1Electrocom Corporation, P.O. Box 60317, Potomac, Maryland 20859-0317, USA
2. 2Department of Physics and Techno Physics, Vidyasagar University, Midnapore 721 102, West Bengal, India / Current address: Department of Electronic Engineering, Chang Gung University, Keei-Shan Tao-Yuan, Taiwan, 333, Republic of China