1. Department of Mathematics, Harbin University of Science and Technology, Harbin, People's Republic of China
2. School of Engineering, University of South Wales, Pontypridd, UK
3. School of Measurement Control Technology Communication Engineering, Harbin University of Science and Technology, Harbin, People's Republic of China
4. School of Mathematics and Physics, Anhui Polytechnic University, Wuhu, People's Republic of China