1. Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, China
2. Department of Computer Science, Montclair State University, Montclair, NJ, USA
3. State Key Laboratory of Novel Software Technology, Department of Computer Science and Technology, Nanjing University, Nanjing, Jiangsu, China
4. Center for Networked Computing, Temple University, Philadelphia, PA, USA