1. Faculty of Science, Osaka University, Toyonaka, Osaka 560
2. Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-11
3. Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305
4. Faculty of Engineering, Toyama Prefectural University, Toyama 939-03
5. National Research Institute for Metals, Tsukuba, Ibaraki 305
6. College of Integrated Arts and Sciences, University of Osaka Prefecture, Sakai, Osaka 593