supported by the National Natural Science Foundationof China ( Grant Nos .40839910 , 40762001 and 40902003) ;the Foundation of the Mobile Projectof Science and Technology of Guizhou Province(Grant No . Gui Ji 2007-4004) ;the key project ofInternational cooperation of Guizhou Science andTechnology ( Gui . Co . G.[2008]700110]) ;the Major Basic Research Projects of MSTof China(2006CB806401)