School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China. qwdong@insun.hit.edu.cn|School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China. qwdong@insun.hit.edu.cn|School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China. qwdong@insun.hit.edu.cn