School of Mathematics, Sun Yat-sen University, Guangzhou 510275, China.|School of Statistics and Management, Shanghai University of Finance and Economics, Shanghai 200433, China Shanghai Key Laboratory of Financial Information Technology, Shanghai University of Finance and Economics, Shanghai 200433, China.|School of Mathematics, Sun Yat-sen University, Guangzhou 510275, China South China Center for Statistical Science, Sun Yat-sen University, Guangzhou 510275, China Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China.|School of Mathematics, Sun Yat-sen University, Guangzhou 510275, China South China Center for Statistical Science, Sun Yat-sen University, Guangzhou 510275, China.