1. Department of Informatics, Faculty of Engineering, Kindai University, 1 Takaya Umenobe, Higashi-Hiroshima 739-2116, Japan
2. Department of Informatics, The University of Electro-Communications, 1-5-1 Chofugaoka, Tokyo 182-8585, Japan
3. Graduate School of Advanced Science and Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8511, Japan
4. Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA