1. Division of Computer Science, University of Aizu, Fukushima, Japan
2. Graduate School, Army Engineering University of PLA, Nanjing, China
3. Department of Computer Science, City University of Hong Kong, Hong Kong, SAR, China
4. College of Computer Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, China
5. Department of Computer Science, Kennesaw State University, Marietta, GA, USA