作者机构:[1]College of Sciences, Shanghai University, Shanghai 200444, P. R. China, [2]School of Mathematics and Information, Jiaxing University, Jiaxing 314001, Zhejiang Province, P. R. China, [3]College of Mathematical and Physical Sciences, Chongqing University, Chongqing 400030, P. R. China, [4]Department of Mathematics and Statistics, Lixin University of Commerce, Shanghai 201620, P. R. China
相关基金:Project supported by the National Natural Science Foundation of China (No. 60872060) and the Key Projects of Shanghai Municipal Commission of Education (No. 06ZZ84)