1. School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an 710049, China
2. School of Mathematics and Statistics, Xi’an Key Laboratory of Scientific Computation and Applied Statistics, Northwestern Polytechnical University, Xi’an 710129, China
3. School of Mathematics, Northwest University, Xi’an 710127, China
4. Institute of Applied Physics and Computational Mathematics, Beijing 100088, China