基金Foundation item:supported by the Natural Science Foundation of Hunan Province(00JJyz0110)and Scientific Research Fund of Hunan Provincial Education Department(01C022)
基金Supported by the National Natural Science Foundation of China(20476046 and 20776069)the Key Natural Science Foundation for Univer-sities of Jiangsu Province(06KJA53012)the Program for Changjiang Scholars and Innovative Research Team in Universities(PCSIRT 0732)