1. Department of Computer Science Xidian University Xi'an China
2. Multiscale Robotics Laboratory ETH Zurich Zurich Switzerland
3. Beijing Key Laboratory of Mobile Computing and Pervasive Device, Institute of Computing Technology Chinese Academy of Sciences Beijing China
4. University of Chinese Academy of Sciences Beijing China
5. Department of Computer Science University of Houston Houston TX USA
6. Department of Computer Science University of North Carolina at Chapel Hill Chapel Hill NC USA
7. Department of Computer Science University of Maryland College Park MD USA