College of Electronic and Informational Engineering , HeBei University , Baoding 071002 , China
Physical department , Hebei University , Baoding 071002 , China
Industry and commerce institute , Hebei University , Baoding 071002 , China
Industry and commerce institute , Hebei University , Baoding 071002 , China
Physical department , Hebei University , Baoding 071002 , China
Physical department , Hebei University , Baoding 071002 , China
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