1. a Department of Aerospace Engineering, Tohoku University, Aoba 6-6-01, Sendai 980-8579, Japan;, Email: keiji@ieee.org
2. b Ricoh Co., Ltd, 810 Shimoizumi, Ebina, Kanagawa 243-0460, Japan
3. c Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 35-135A, Cambridge, MA 02139, USA
4. d Department of Aerospace Engineering, Tohoku University, Aoba 6-6-01, Sendai 980-8579, Japan
5. e Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama-shi, Okayama 700-8530, Japan