作者机构:[1]Department of Mathematics, Hubei Institute for Nationalities, Enshi 445000, China, [2]College of Mathematics and Information Sciences, East China Institute of Technology, Fuzhou, Jiangxi 344000, China
相关基金:Supported by the National Natural Science Foundation of China (60875034), the Natural Science Foundation of Education Committee of Hubei Province(D20092901), and the Natural Science Foundation of Hubei Province (2009CDB340).