1. School of Mathematics and Computer Science, Guangdong Ocean University, Zhanjiang, Guangdong 524025, P. R. China
2. College of Mathematics and Statistics, Sichuan University of Science and Engineering, Zigong, Sichuan 643000, P. R. China
3. The Key Laboratory of Higher Education of Sichuan Province for Enterprise Informationalization and Internet of Things, Zigong, Sichuan 643000, P. R. China