1. Faculty of Physical Engineering, Kim Chaek University of Technology, Pyongyang 999093, Democratic People’s Republic of Korea
2. Department of Light Industry Machinery Engineering, Pyongyang University of Mechanical Engineering, Pyongyang 999093, Democratic People’s Republic of Korea
3. Faculty of Forest Science, Kim Il Sung University, Pyongyang 999093, Democratic People’s Republic of Korea
4. College of Ship and Ocean Technology, Kim Chaek University of Technology, Pyongyang 999093, Democratic People’s Republic of Korea
5. Department of Agricultural Machinery Engineering, Pyongyang University of Mechanical Engineering, Pyongyang 999093, Democratic People’s Republic of Korea