1. School of Mathematics and Systems Science, Beihang University, Beijing 100191, China
2. Key Laboratory of Mathematics Informatics Behavioral Semantics (LMIB), Ministry of Education, Beijing 100191, China
3. School of Mathematical Sciences, Dalian University of Technology, Dalian 116024, China
4. Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032, USA