Fund Project:Supported by the National Natural Science Foundation of China (Grant No.11201005), the Natural Science Foundation of Anhui Province (Grant Nos.1308085QA13; 1208085MA11), the Key Project of Natural Science Foundation of of Universities in Anhui Province (Grant No.KJ2012A135) and the Key Project of Distinguished Young Talents of Universities in Anhui Province (Grant No.2012SQRL028ZD).