1. Department of Computer Science and Technology, Shanghai Key Laboratory of Multidimensional Information Processing, East China Normal University, Shanghai 200062, P. R. China
2. School of Electronic and Electrical Engineering, Shanghai University of Engineering, Science Shanghai 201620, P. R. China
3. School of Information Engineering, Nanchang University, Nanchang 330031, P. R. China
4. Northeastern University, Boston, MA 02115, USA