1. Department of Mechanical Engineering, Pyongyang University of Mechanical Engineering, Pyongyang 999093, Democratic People’s Republic of Korea
2. College of Mechanical Science and Technology, Kim Chaek University of Technology, Pyongyang 950003, Democratic People’s Republic of Korea
3. Institute of Nano-Physical Engineering, Kim Chaek University of Technology, Pyongyang 950003, Democratic People’s Republic of Korea
4. Department of Life Science, University of Science, Pyongyang 999093, Democratic People’s Republic of Korea