1. Department of Engineering Machine, Pyongyang University of Mechanical Engineering, Pyongyang, Democratic People’s Republic of Korea
2. College of Mechanical Science and Technology, Kim Chaek University of Technology, Pyongyang, Democratic People’s Republic of Korea
3. Institute of Nano-Physical Engineering, Kim Chaek University of Technology, Pyongyang,
4. Information Center, Kim Chaek University of Technology, Pyongyang, Democratic People’s Republic of Korea
5. Department of Organic Chemistry, Hamhung University of Chemical Engineering, Hamhung, Democratic People’s Republic of Korea