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Kernelization in Parameterized Computation: A Survey
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作者 Qilong Feng Qian Zhou +1 位作者 Wenjun Li Jianxin Wang 《Tsinghua Science and Technology》 SCIE EI CAS 2014年第4期338-345,共8页
Parameterized computation is a new method dealing with NP-hard problems, which has attracted a lot of attentions in theoretical computer science. As a practical preprocessing method for NP-hard problems, kernelizaiton... Parameterized computation is a new method dealing with NP-hard problems, which has attracted a lot of attentions in theoretical computer science. As a practical preprocessing method for NP-hard problems, kernelizaiton in parameterized computation has recently become an active research area. In this paper, we discuss several kernelizaiton techniques, such as crown decomposition, planar graph vertex partition, randomized methods, and kernel lower bounds, which have been used widely in the kernelization of many hard problems. 展开更多
关键词 parameterized computation kernelization parameterized algorithm NP-hard
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Second-order sensitivity of eigenpairs in multiple parameter structures
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作者 陈塑寰 郭睿 孟广伟 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2009年第12期1475-1487,共13页
This paper presents methods for computing a second-order sensitivity matrix and the Hessian matrix of eigenvalues and eigenvectors of multiple parameter structures. Second-order perturbations of eigenvalues and eigenv... This paper presents methods for computing a second-order sensitivity matrix and the Hessian matrix of eigenvalues and eigenvectors of multiple parameter structures. Second-order perturbations of eigenvalues and eigenvectors are transformed into multiple parameter forms,and the second-order perturbation sensitivity matrices of eigenvalues and eigenvectors are developed.With these formulations,the efficient methods based on the second-order Taylor expansion and second-order perturbation are obtained to estimate changes of eigenvalues and eigenvectors when the design parameters are changed. The presented method avoids direct differential operation,and thus reduces difficulty for computing the second-order sensitivity matrices of eigenpairs.A numerical example is given to demonstrate application and accuracy of the proposed method. 展开更多
关键词 multiple parameter structures second-order sensitivity of eigenpairs efficient computational method
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On Unknown Small Subsets and Implicit Measures: New Techniques for Parameterized Algorithms 被引量:1
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作者 陈建二 冯启龙 《Journal of Computer Science & Technology》 SCIE EI CSCD 2014年第5期870-878,共9页
Parameterized computation is a recently proposed alternative approach to dealing with NP-hard problems.Developing efficient parameterized algorithms has become a very active research area in the current research in th... Parameterized computation is a recently proposed alternative approach to dealing with NP-hard problems.Developing efficient parameterized algorithms has become a very active research area in the current research in theoretical computer science. In this paper, we investigate a number of new algorithmic techniques that were proposed and initiated by ourselves in our research in parameterized computation. The techniques have proved to be very useful and promising,and have led to improved parameterized algorithms for many well-known NP-hard problems. 展开更多
关键词 parameterized computation randomized method implicit branching
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An IDDES study of the near-wake flow topology of a simplified heavy vehicle 被引量:3
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作者 Jie Zhang Zhanhao Guo +3 位作者 Shuai Han Siniša Krajnovi′c John Sheridan Guangjun Gao 《Transportation Safety and Environment》 EI 2022年第2期105-122,共18页
The complex wake flow of a GTS(ground transportation system)model contributes to large percentage of the aerodynamic drag force.Therefore,predicting accurate wake flow will help carry out the drag reduction strategies... The complex wake flow of a GTS(ground transportation system)model contributes to large percentage of the aerodynamic drag force.Therefore,predicting accurate wake flow will help carry out the drag reduction strategies.In this paper,the near-wake flow topology of the GTS was studied at Re=2.7×104 to assess the capability of a hybrid RANS/LES(Reynolds-averaged Navier–Stokes/large eddy simulation)approach,known as IDDES(improved delayed detached eddy simulation).The current study also aims to understand the effects of different computational parameters,e.g.the spatial resolution,time step,residual level,discretization scheme and turbulence model,on this asymmetrical wake flow configuration.A comparison of IDDES with previous water channel tests,wellresolved LES,partially averaged Navier–Stokes and URANS(unsteady RANS)was included to better understand the benefits of this hybrid RANS/LES approach.The results show that on the medium and fine grids,the IDDES produces an asymmetrical flow topology(known as flow state I)in the near-wake of the vertical midplane,as reported in previous studies.The recommended parameters for the time step(1×10^(–4 )s)and residual level(1×10^(–4))provide sufficient accuracy of wake predictions to show good agreement with experiments.For the convective term of the momentum equation in IDDES,the bounded central difference discretization scheme is proposed to be adopted for discretization.Additionally,URANS cannot accurately capture this asymmetrical flow field.IDDES proves to be capable of predicting thewake flowfield of this simplified heavy vehicle with high accuracy.All obtained conclusions can provide references for the aerodynamic drag reduction of the GTS. 展开更多
关键词 Heavy vehicle Asymmetrical wakes IDDES computational parameter
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