1. Beijing Key Laboratory of Intelligent Telecommunications Software and Multimedia, Beijing University of Posts and Telecommunications (BUPT), Beijing, China
2. Chongqing Engineering Laboratory of Internet and Information Security, Chongqing University of Posts and Telecommunications (CQUPT), no. 2 Chongwen Road, Nanan District, Chongqing 400065, China
3. Samsung Research, San Jose, CA, USA
4. Web Intelligence Laboratory, Konkuk University, Seoul, Republic of Korea