1. Researcher, Dept. of Aerospace and Mechanical Engineering, Korea Aerospace Univ., Goyang-si, Gyeonggi-do 10540, Korea.
2. Researcher, Production Engineering Research Institute, LG Electronics, Pyeongtaek-si, Gyeonggi-do 17709, Korea.
3. Researcher, Dept. of Reliability Assessment, Korea Institute of Machinery and Materials, Daejeon 34103, Korea.
4. Professor, School of Aerospace and Mechanical Engineering, Korea Aerospace Univ., Goyang-si, Gyeonggi-do 10540, Korea (corresponding author).