1. Graduate Student, Dept. of Mechanical and Aerospace Engineering, Seoul National Univ., 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea.
2. Professor, Dept. of Mechanical and Aerospace Engineering, Seoul National Univ., 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea; Institute of Advanced Aerospace Technology, Seoul National Univ., 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea (corresponding author).