supported by NSF of China(No.11161029,No.11261005);NSF of Guangxi(No.2010GXSFA013109,No.2012GXSFA276040);NSF of Guangxi University of Technology(No.1166218)
Supported by the Natural Science Foundation of China(11161029);the Natural Science Foundation of Guangxi(2010GXNSFA013109,2010GXNSFA013106);the Natural Science Foundation of Guangxi University of Technology(1166218)