This work was supported by the National Science Foundation of China under Grant (No. 61202470 ), the Self-Determined Research Funds of CCNU from the Colleges’ Basic Research and Operation of MOE (Nos. CCNU11A02008 and CCNU10A02008 ), the Initial Scientific Research Fund of CCNU (Nos. 1200050487 and 1200050486 ), the National Science Foundation Key Project of China under Grant (No. 60832002 ), Important National Science & Technology Specific Project of China under Grant (No. 2010ZX03004-003-03 ).