1. Department of Information Engineering, Chongjin Mine and Metal University, Chongjin 999091, Democratic People’s Republic of Korea
2. Department of Engineering Machine, Pyongyang University of Mechanical Engineering, Pyongyang 999093, Democratic People’s Republic of Korea
3. Department of Material Engineering, Chongjin Mine and Metal University, Chongjin 999091, Democratic People’s Republic of Korea
4. Digital Library, Kim Chaek University of Technology, Pyongyang 950003, Democratic People’s Republic of Korea