作者机构:[1]Department of Mathematics, Harbin Institute of Technology Harbin 150006, China, [2]School of Mathematical Science, Harbin Normal University Harbin 150025, China
相关基金:The first author was supported by the NSF of HLJ Province (A200903) and the NSF of Education Department of HLJ Province (12511349), while the second author was supported by the NNSF of China (11171055, 11471090) and the NSF of HLJ Province (JC201004).