作者机构:[1]College of Science, Shandong University of Science & Technology, Qingdao 266000, China, [2]Institute of Theoretical Physics, Lanzhou University, Lanzhou 730000, China
相关基金:Project supported by the National Natural Science Foundation of China (Grant Nos 10704031 and 1087150), the Scientific Research Foundation for Returned Scholars, Ministry of Education of China, the Foundation of Shandong Educational Committee, China (Grant No J08LI60), and the Research Project of ‘SUST Spring Bud', China (Grant No 2008AZZ093).