,608 北京科技大学学报 2006年第6期 A method for attributes reduction based on scan vector EXu2),GAO Xuedong,YU Bin) 1)Department of Computer Science.Liaoning Institute of Technology.Jinzhou 121001,China 2)Management School.University of Science and Technology Beijing.Beijing 100083.China ABSTRACI In order to deal with attributes reduction,one of the major problems in rough set theory,an attributes reduction algorithm was proposed based on scan vector,and a new conception of discernible vec- tor was defined by which the information table can be transformed into discernible vector sets.Depending on the structural feature of the discernible vector,a plus rule for the discernible vector sets was defined,and a scan vector with concise structure but representing the information table can be obtained through scanning the discernible vector just one time.The item of attribute frequency in the scan vector was taken as heuris- tic information to improve the efficiency of attributes reduction.An illustration and experimental results in- dicate that the method proposed is much more effective. KEY WORDS rough set;information table;attributes reduction:discernible attributes set;scan vector (上接第586页) Numerical simulation on heat transfer of impinging slot jet LIU Guoyong,LI Mouwei,WANG Bangwen,ZHANG Shaojun,LI Shengyong,HUANG Yan Mechanical Engineering School.University of Science and Technology Beijing,Beijing 100083.China ABSTRACI Numerical simulation with the standard ke model was performed to study single phase con- vective heat transfer at the impinging zone of non-immersed slot jet.The factors considered were jet veloci- ty,spacing of nozzle to impinging plate (height),slot width,angle between jet direction and plate,tem- peratures of impinged plate and water (liquid)from the slot nozzle.The results show that jet velocity is the most remarkable factor influencing heat transfer at the impinging zone,and other factors such as water temperature and slot width are also non-negligible.The angle between jet direction and impinging plate on- ly influences the distribution of local convective heat transfer coefficient. KEY WORDS slot;impinging jet;convective heat transfer:k model;numerical simulationA method for attributes reduction based on scan vector E Xu 1‚2）‚GAO Xuedong 1）‚Y U Bin 1） 1） Department of Computer Science‚Liaoning Institute of Technology‚Jinzhou121001‚China 2） Management School‚University of Science and Technology Beijing‚Beijing100083‚China ABSTRACT In order to deal with attributes reduction‚one of the major problems in rough set theory‚an attributes reduction algorithm was proposed based on scan vector‚and a new conception of discernible vec￾tor was defined by which the information table can be transformed into discernible vector sets．Depending on the structural feature of the discernible vector‚a plus rule for the discernible vector sets was defined‚and a scan vector with concise structure but representing the information table can be obtained through scanning the discernible vector just one time．The item of attribute frequency in the scan vector was taken as heuris￾tic information to improve the efficiency of attributes reduction．An illustration and experimental results in￾dicate that the method proposed is much more effective． KEY WORDS rough set；information table；attributes reduction；discernible attributes set；scan vector （上接第586页） Numerical simulation on heat transfer of impinging slot jet LIU Guoyong‚LI Mouwei‚WA NG Bangwen‚ZHA NG Shaojun‚LI Shengyong‚HUA NG Y an Mechanical Engineering School‚University of Science and Technology Beijing‚Beijing100083‚China ABSTRACT Numerical simulation with the standard k—εmodel was performed to study single-phase con￾vective heat transfer at the impinging zone of non-immersed slot jet．The factors considered were jet veloci￾ty‚spacing of nozzle-to-impinging plate （height）‚slot width‚angle between jet direction and plate‚tem￾peratures of impinged plate and water （liquid） from the slot nozzle．The results show that jet velocity is the most remarkable factor influencing heat transfer at the impinging zone‚and other factors such as water temperature and slot width are also non-negligible．The angle between jet direction and impinging plate on￾ly influences the distribution of local convective heat transfer coefficient． KEY WORDS slot；impinging jet；convective heat transfer；k—εmodel；numerical simulation ·608· 北 京 科 技 大 学 学 报 2006年第6期