基金Supported by the vital study foundation of hunan university of artsand science(No.JJZD0701)foundation of education department ofhunan province(No.07C444)
基金This work is supported by Science Foundation of Hunan University of Arts and Sci-ences(JJZD0701)the Natural Science Foundation of Fujian Province of China(S0650036)theScience Foundation of Provincial Education Department of Hunan(07C444)