1. New Industry Creation Hatchery Center, Tohoku University, Aoba, Sendai 980-8579, Japan
2. Fracture and Reliability Research Institute, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
3. The Electron Microscopy Center, Tohoku University, Aoba, Sendai 980-8577, Japan
4. National Institute of Technology, Sendai College, Natori 981-1239, Japan