1. Department of Mechanical Science and Technology, Kim Chaek University of Technology, Pyongyang 950003, Democratic People’s Republic of Korea
2. Department of Mechanical Engineering, Pyongyang University of Mechanical Engineering, Pyongyang 999093, Democratic People’s Republic of Korea
3. Department of Organic Chemistry, Hamhung University of Chemical Engineering, Hamhung, Democratic People’s Republic of Korea
4. Department of Information Engineering, Chongjin Mine and Metal University, Chongjin 999091, Democratic People’s Republic of Korea
5. Faculty of Geology, Kim Il Sung University, Pyongyang 999093, Democratic People’s Republic of Korea