1. The College of Computer, Qinghai Normal University, Xining 810008, China
2. Academy of Plateau Science and Sustainability, People’s Government of Qinghai Province & Beijing Normal University, Xining 810004, China
3. The State Key Laboratory of Tibetan Intelligent Information Processing and Application, Qinghai Normal University, Xining 810008, China
4. School of Mathematics and Computer Science, Shanxi Normal University, Xi’an 710062, China