DepartmentofComputerScience;
BeijingNormalUniversity;
Beijing100875//NationalLaboratoryofPatternRecognition;
InstituteofAutomation;
ChineseAcademyofSciences;
Beijing100080;
DepartmentofComputerScience;
BeijingNormalUniversity;
Beijing100875;
NationalLaboratoryofPatternRecognition;
InstituteofAutomation;
ChineseAcademyofSciences;
Beijing100080;