1. Sciencotech, 780 Girad St. NW, Washington, DC 20001, U.S.A.
2. Department of Physics and Techno Physics, Vidyasagar University, Midnapore 721 102, West Bengal, India. Currently with the Dept of Electronic Engineering, Chang Gung University, Keei-Shan Tao-Yuan, Taiwan 333, Republic of China