1. National Institute of Standards (NIS), Tersa St, El-Haram, PO Box 136, Code 12211, Giza, Egypt
2. Department of Physics, Faculty of Science, Al-Azhar University, Assiut 71542, Egypt
3. Central Metallurgical Research and Development Institute (CMRDI), P.O. BOX. 87 Helwan, Egypt 11421