作者机构:[1]Department of Mathematics and Information Science, Zhoukou Normal University, Zhoukou 466001, China, [2]Department of Mathematics, Shanghai University, Shanghai 200444, China
相关基金:Foundation item: Supported by the Natural Science Foundation of China(61072147, 11071159); Supported by the Shanghai Leading Academic Discipline Project(J50101); Supported by the Youth Foundation of Zhoukou Normal University(zknuqn200917)