Fund Project:Supported by the National Natural Science Foundation of China (Grant No.10961014), the Science and Technology Projects in Guangdong Province (Grant No.2010B010600039), the Guangdong Provincial Natural Science Foundation of China (Grant No.S2011010003681), the Anhui Provincial Excellent Youth Talent Foundation (Grant No.2012SQRL115ZD) and the University Natural Science Project of Anhui Province (Grant No.KJ2012B133) and the Fuyang Normal College Natural Science Foundation (Grant No.2007LZ01).