1. a Intelligent Systems Research Center, Sungkyunkwan University, Suwon 440-746, South Korea;, Email: ojhee@cnu.ac.kr
2. b Department of Aerospace Engineering, Tohoku University, Aoba-yama 6-6-01, Sendai 980-8579, Japan
3. c Department of Aerospace Engineering, Tohoku University, Aoba-yama 6-6-01, Sendai 980-8579, Japan