Supported by National Natural science Foundation-of P.R.Chlna (60474038, 60774022), Specialized Research Fund for the Doctoral Program of Higher Educatlon(20060004002)
Supported by National Natural Science Foundation of P.R.China(60474038);Science Research Foundation of Beijing Jiaotong University(2005SM005);Specialized Research Fund for the Doctoral Program of Higher Education(20060004002)