1. Department of Materials Processing, Faculty of Engineering, Tohoku University, Aramaki-Aza-Aoba, Aoba-ku, Sendai 980, Japan
2. Department of Mechanical Engineering, Tokyo National College of Technology, Kunugida-Machi 1220-2, Hachioji 193, Japan
3. Department of Mechanical Engineering, Campus Box 427, University of Colorado, Boulder, CO 80309-0427