1. Department of Applied Physics and Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 724
2. Department of Physics, Faculty of Science, Hokkaido University, Kita-10, Nishi-8, Kita-ku, Sapporo 060
3. Department of Electronics, Iwaki-Meisei University, Chu-oh-dai Iino 5-5-1, Iwaki 970
4. Department of Basic Sciences, Ishinomaki Senshu University, Ishinomaki 986
5. Department of Physics, Faculty of Science, Kumamoto University, Kurokami 2-39-1, Kumamoto 860