1. Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
2. Department of Electrical Engineering, Nagaoka University of Technology, Nagaoka 940-2188, Japan
3. Graduate School of Engineering, University of Fukui, Fukui 910-8507, Japan
4. Graduate School of Information Sciences, Hiroshima City University, Hiroshima 731-3194, Japan
5. Department of Physics, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan