1. School of Mathematics and Computational Science, and Hunan Key Laboratory for Computation and Simulation in Science and Engineering, Xiangtan University, Xiangtan, China
2. School of Mathematics and Computational Science, and Hunan National Applied Mathematics Center, Xiangtan University, Xiangtan, China
3. Centre for Mathematical ImagingTechniques, Department of Mathematical Sciences, The University of Liverpool, Liverpool, U.K.
4. School of Mathematics and Computational Science, and the Key Laboratory of Intelligent Computing & Information Processing of the Ministry of Education, Xiangtan University, Xiangtan, China