1. School of Economics, Ocean University of China, Qingdao, Shandong 266100, China
2. College of Mathematics and Information Science, Hebei University, Baoding, Hebei 071002, China
3. Department of Mathematics, Faculty of Sciences, Erciyes University, Kayseri 38039, Turkey
4. LinDa Institute of Shandong Provincial Key Laboratory of Network Based Intelligent Computing, Linyi University, Linyi, Shandong 276005, China
5. School of Information Science and Engineering, Linyi University, Linyi, Shandong 276005, China