1. School of Mathematics and Statistics, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, China; and School of Statistics and Mathematics, Yunnan University of Finance and Economics, Kunming, Yunnan, China
2. Faculty of Information Engineering and Automation, Kunming University of Science and Technology, Kunming, Yunnan, China
3. School of Statistics and Mathematics, Yunnan University of Finance and Economics, Kunming, Yunnan, China