1. College of Computer Science and Engineering Northwest Normal University No. 967 Anning East Road Lanzhou Gansu 730070 China
2. College of Civil and Transportation Engineering Shenzhen University 3688 Nanhai Avenue Shenzhen Guangdong 518060 China
3. College of Geography and Environmental Science Northwest Normal University No. 967 Anning East Road Lanzhou Gansu 730070 China