1. Research Institute of Electrical Communication, Tohoku University, Japan
2. Department of Electrical Engineering, Yamagata University, Japan
3. CREST, Japan Science and Technology Agency, Japan
4. Center for Interdisciplinary Research, Tohoku University, Japan
5. Dept. of Electrical Engineering, Nagaoka University of Technology, Japan
6. Dept. of Materials Science and Technology, Hirosaki University, Japan