1. Department of Informatics, Yamagata University, Yonezawa, Yamagata, Japan
2. nagai.t.aa@m.titech.ac.jp
3. Department of Intelligent Systems Engineering, Ichinoseki National College of Technology, Ichinoseki, Iwate, Japan
4. tsato@ichinoseki.ac.jp
5. Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi, Japan
6. ikuriki@riec.tohoku.ac.jp