Department of Mathematics, Shanghai Normal University, Shanghai 200234, China.|Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute and Harvard School of Public Health, Boston 02215, MA, USA and.|Department of Mathematics, Shanghai Normal University, Shanghai 200234, China.|Department of Mathematics, Shanghai Normal University, Shanghai 200234, China.|Department of Biostatistics and Bioinformatics, Emory University, Atlanta, GA 30322, USA.|Department of Mathematics, Shanghai Normal University, Shanghai 200234, China.