1. School of Artificial Intelligence and Automation, the Key Laboratory of Image Processing and Intelligent Control of Education Ministry of China, and the Hubei Key Laboratory of Brain-Inspired Intelligent Systems, Huazhong University of Science and Technology, Wuhan, China
2. IBM T. J. Watson Research Center, Yorktown Heights, NY, USA
3. School of Mathematics and Statistics, Wuhan University, Wuhan, China
4. School of Computer Science and the Hubei Provincial Key Laboratory of Artificial Intelligence and Smart Learning, Central China Normal University, Wuhan, China