1. Department of Aeronautics and Astronautics, Kyoto University, Kyoto 615-8540, Japan
2. Shinko Seiki Co., Ltd., Shiga 524-0051, Japan
3. SANKEN (The Institute of Scientific and Industrial Research), Osaka University, Osaka 567-0047, Japan
4. Hyogo Prefectural Institute of Technology, Hyogo 654-0037, Japan