1. International School for Optoelectronic Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, P. R. China
2. School of Mathematics and Statistics, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, P. R. China
3. Rehabilitation Center, Qilu Hospital of Shandong University, Jinan 250012, P. R. China
4. Shandong Institute of Scientific and Technical Information, Jinan 250101, P. R. China