1. state key laboratory of Integrated Services Networks, Xidian University, Xi'an, China
2. Departments of Mathematics and Computer and Information Science, Westfield State University, Westfield, MA, USA
3. School of Artificial Intelligence, Optics and Electronics (iOPEN), Northwestern Polytechnical University, Xi'an, Shaanxi, China
4. Chongqing Key Laboratory of Image Cognition, Chongqing University of Posts and Telecommunications, Chongqing, China