supported by NSFC(No.10771058,No.11071062);Natural Science Foundation of Hunan Province(No.10jj3065);Scientific Research Foundation of Hunan Provincial Education Department(No.10A033)
Supported by the Scientific Research Fund of Hunan Provincial Education Department(07c268);the Hunan Provincie Natural Science Foundation of China(06jj20053);the Scientific Research Fund of Hunan Province Education Department(06A017)