1. School of Software, Nanjing University of Information Science and Technology, Nanjing, China
2. Department of Computer Engineering, Hankuk University of Foreign Studies, Yongin-si, South Korea
3. Faculty of Mathematics, University of Waterloo, Waterloo, Canada
4. College of Computer Science and Technology, China University of Petroleum (East China), Qingdao, China
5. College of Information Science and Technology, Xinjiang Production and Construction Corps, Geospatial Information Engineering Research Center, Shihezi University, Shihezi, China