DepartmentofMathematics&Physics;
HebeiVocational&TechnicalTeachereCollege;
Qinhuangdao066004;
China;
DepartmentofPrecisionInstruments;
TsinghuaUniversity;
Beijing100084;
China;
CollegeofBasicSciencesandTechnology;
ChinaAgriculturalUniversity;
Beijing100083;
China;
DepartmentofMathematics&Physics;
HebeiVocational&TechnicalTeachersCollege;
Qinhuangdao066004;
China;