1. Department of Computer Science, The George Washington University, Washington, DC, USA
2. School of Computer Science and Technology, Shandong University, Qingdao, China
3. Faculty of Information Science, Beijing University of Technology, Beijing, China
4. School of Computer Science, University of Sydney, Sydney, Australia
5. School of Computer Science and Technology, Qilu University of Technology Shandong Academy of Sciences and Shandong Computer Science Center National Supercom- puter Center in Jinan, Jinan, China