1. Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan
2. Yamazaki Mazak Corporation, Aichi 480-0197, Japan
3. Joining and Welding Research Institute, Osaka University, Osaka 567-0047, Japan
4. Industrial Research Institute of Ishikawa, Ishikawa 920-8203, Japan
5. Muratani Machine Manufacture Co., Ltd., Ishikawa 920-0209, Japan
6. Graduate School of Science and Engineering, Kindai University, Osaka 577-8502, Japan