1. School of Electrical and Information Engineering, Tianjin University, Tianjin, China
2. School of Big Data and Software Engineering, Chongqing University, Chongqing, China
3. School of Computer Science, Aberystwyth University, UK
4. School of Computer Science and Center for OPTical IMagery Analysis and Learning (OPTIMAL), Northwestern Polytechnical University, Xi'an, P.R. China