1. a Tokyo Metropolitan Technical College , 1-10-40 Higashiohi Shinagawa-ku, Tokyo , 140 , Japan
2. b Department of Physics, Faculty of Science , Science University of Tokyo, 1-3 Kagurazaka , Shinjuku-ku, Tokyo , 162 , Japan
3. c Hitachi Keisoku Engineering Co., Ltd., 882 Ichige , Katsuta-shi , Ibaraki 312 , Japan