1. State Key Laboratory of Computer Science, Institute of Software, Chinese Academy of Sciences, Beijing, China
2. Beijing Key Lab of Human–Computer Interaction, Institute of Software, Chinese Academy of Sciences, Beijing, China
3. School of Digital Media and Design Arts, Beijing University of Posts and Telecommunications, Beijing, China
4. College of Information Sciences and Technology, The Pennsylvania State University, University Park, Pennsylvania, USA
5. School of Information, Kochi University of Technology, Kochi, Japan