1. a Department of Electronics and Computer Science, College of Science and Engineering , Iwaki Meisei University , 5-5-1 Iino, Chuohdai, Iwaki, Fukushima , 970-8551 , Japan
2. b Department of Electrical Engineering, School of Science and Engineering , Meisei University , 2-1-1 Hodokubo, Hino-shi, Tokyo , 191-8506 , Japan