1. Postdoctoral Research Associate, Dept. of Aerospace Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea (corresponding author).
2. Professor and Head, Dept. of Aerospace Engineering, Auburn Univ., Auburn, AL, 36849.
3. Professor, Dept. of Aerospace Engineering, Chonbuk National Univ., Jeonju, 560-756, Republic of Korea.