1. Department of Electronical and Information Engineering, Hubei Key Laboratory of Optical Information and Pattern Recognition, Wuhan Institute of Technology, Wuhan, China
2. School of Computer Science, The University of Manchester, Manchester, U.K.
3. Science and Technologies Facilities Council, Rutherford Appleton Laboratory, Didcot, U.K.
4. Department of Computer Science, The University of Liverpool, Liverpool, U.K.