1. School of Statistics and Mathematics, Zhejiang Gongshang University, Hangzhou, Zhejiang, China
2. School of Computer and Information Engineering, Zhejiang Gongshang University, Hangzhou, Zhejiang, China
3. Department of Environmental and Occupational Health, Epidemiology and Biostatistics Program, School of Community Health Sciences, University of Nevada Las Vegas, Las Vegas, NV