1. Development Division, Komatsu Ltd., 1200 Manda, Hiratsuka, Kanagawa 254-8567, Japan
2. KELK Ltd., 3-25-1 Shinomiya, Hiratsuka, Kanagawa 254-8543, Japan
3. Department of Materials Science, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan