1. Department of Aerospace Engineering, Chosun University, Gwangju 501-759, Republic of Korea
2. Future Convergence Research Division, Korea Aerospace Research Institute, Daejeon 305-806, Republic of Korea
3. Department of Aerospace Engineering, KAIST, Daejeon 305-701, Republic of Korea
4. Texas A&M University, College Station, TX 77843-3141, USA