The work was done by Md. Mahbub Alam, Dr. Sujaul Chowdhury (email@example.com) and Sudipta Saha as M.S. thesis of Md. Mahbub Alam in 2011 in Department of Physics, Shahjalal University of Science and Technology: http: //www.sust.edu, Sylhet 3114, Bangladesh. Dr Chowdhury is a faculty of the Department; he has a glorious record of academic, scientific, teaching and research achievements; details in http: //schowdhury-phy.weebly.com/. Sudipta Saha is a Scientific Officer, Bangladesh Atomic Energy Commission: http: //www.baec.org.