Affiliation: | a Graduate School of Engineering, Osaka University, 1 Yamadaoka, Suita, Osaka 565-0871, Japan b Joining and Welding Research Institution, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan c Hokkaido University, 5 Niow, Kita-ku, Sapporo, Hokkaido 060-0810, Japan |