1 School of Mathematical Sciences, Nankai University, Tianjin 300071, China ; Division of Biomedical Engineering, University of Saskatchewan, Saskatoon, SK, Canada S7N 5A9.
2 School of Information Science and Engineering, Central South University, Changsha 410083, China.
3 School of Mathematical Sciences, Nankai University, Tianjin 300071, China.
4 School of Computing, Clemson University, Clemson, SC 29634, USA.