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一种基于压缩策略的高维空间子空间skyline查询算法 被引量:1
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作者 孟熠 刘玉葆 李启睿 《计算机研究与发展》 EI CSCD 北大核心 2013年第S1期101-108,共8页
skyline操作就是找出数据集中不被其他数据点支配的点的集合,但是随着数据属性维度的不断增多,通常人们只对数据集的某几个属性感兴趣,高维空间子空间skyline计算就是发现数据集中在某几个特定维度上不被其他点支配的点的集合,skyline... skyline操作就是找出数据集中不被其他数据点支配的点的集合,但是随着数据属性维度的不断增多,通常人们只对数据集的某几个属性感兴趣,高维空间子空间skyline计算就是发现数据集中在某几个特定维度上不被其他点支配的点的集合,skyline计算在数据量大时其时间花销是非常大的,快速的返回结果才是人们能接受的.基于此提出了一个RSky算法,在原有CSky算法的基础上,指出并改进了其存在的3处明显不足,并根据InvertS索引的特性提出了一个压缩扫描策略,通过设置每个维度的下限来控制要处理的桶,除去不必要处理的桶和不可能是skyline的点,从而减少了点与点之间的比较次数.实验结果表明了RSky算法的有效性. 展开更多
关键词 子空间skyline查询 InvertS索引 下限 压缩扫描法 渐进
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Numerical and Performance Analysis of one row Transonic Rotor with Sweep and Lean angle 被引量:4
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作者 Seyed Reza Razavi Masoud Boroom 《Journal of Thermal Science》 SCIE EI CAS CSCD 2014年第5期438-445,共8页
In this study,aerodynamic behaviors of swept and leaned blades were investigated.Axial and tangential blade curvatures impacts on compressor's operating parameters were analyzed separately.A commercial CFD program... In this study,aerodynamic behaviors of swept and leaned blades were investigated.Axial and tangential blade curvatures impacts on compressor's operating parameters were analyzed separately.A commercial CFD program which solves the Reynolds-averaged Navier-Stokes equations was used to find out the mentioned impact and the complicated flow field of transonic compressor-rotors.The CFD method that was used for solving flow field's equation was validated by experimental data of NASA Rotor 67.The results showed that the compressor with curved rotors had higher efficiency,rotor pressure ratio and stable operating range compared to the compressor with un-curved rotors.Using curved rotors mostly had higher impact on the overall stable operating range compared to the other operating parameters.Operating range involves choking point and stall point that were changed separately by using of bended blade.For finding the detailed impact of sweep and lean angle on transonic blades,various forms of lean and sweep angles were exerted to basic rotor.It was found that sweep angles increased overall operating range up to 30%,efficiency up to 2%and pressure ratio up to 1%.Leaning the blades increased the safe operating range,the pressure ratio and efficiency by 14%,4%and 2%respectively. 展开更多
关键词 compressor performance efficiency stable operational range surge improvement swept Rotor leaned rotor
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