共查询到20条相似文献,搜索用时 31 毫秒
1.
We introduce and analyze a discontinuous Galerkin method for a time-harmonic eddy current problem formulated in terms of the magnetic field. The scheme is obtained by putting together a DG method for the approximation of the vector field variable representing the magnetic field in the conductor and a DG method for the Laplace equation whose solution is a scalar magnetic potential in the insulator. The transmission conditions linking the two problems are taken into account weakly in the global discontinuous Galerkin scheme. We prove that the numerical method is uniformly stable and obtain quasi-optimal error estimates in the DG-energy norm. 相似文献
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映射域漂移和偏见性预测问题使得现有的方案无法很好地应对广义零样本学习挑战.在CADA-VAE模型的基础上,提出了基于模态融合的半监督学习方案,就如何利用未标注样本及语义辅助模型进行模态内自学习提供了一种思路.该方案使用潜层向量空间作为视觉和语义模态融合的桥梁,提出了视觉质心和异类语义潜层向量概念,用以指导模态间互学习;... 相似文献
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R. Bürger K.H. Karlsen N.H. Risebro J.D. Towers 《Computing and Visualization in Science》2004,6(2-3):83-91
Clarifier-thickener units treating ideal suspensions can be modeled as an initial-value problem for a nonconvex scalar conservation
law whose flux depends on a vector of discontinuous parameters. This problem can be treated by the well-known Engquist-Osher
scheme if the discontinuous parameters are discretized on a grid staggered against that of the conserved variable. We prove
convergence of this scheme to a weak solution of the problem and illustrate its application to the clarifier-thickener setup
by a numerical example. 相似文献
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《IEEE transactions on audio, speech, and language processing》2006,14(2):524-532
In this paper, we use the Gaussian mixture model (GMM) based multidimensional companding quantization framework to develop two important quantization schemes. In the first scheme, the scalar quantization in the companding framework is replaced by more efficient lattice vector quantization. Low-complexity lattice pruning and quantization schemes are provided for the E/sub 8/ Gossett lattice. At moderate to high bit rates, the proposed scheme recovers much of the space-filling loss due to the product vector quantizers (PVQ) employed in earlier work, and thereby, provides improved performance with a marginal increase in complexity. In the second scheme, we generalize the compression framework to accommodate recursive coding. In this approach, the joint probability density function (PDF) of the parameter vectors of successive source frames is modeled using a GMM. The conditional density of the parameter vector of the current source frame based on the quantized values of the parameter vector of the previous source frames is used to generate a new codebook for every current source frame. We demonstrate the efficacy of the proposed schemes in the application of speech spectrum quantization. The proposed scheme is shown to provide superior performance with moderate increase in complexity when compared with conventional one-step linear prediction based compression schemes for both narrow-band and wide-band speech. 相似文献
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Gradient meshes are a 2D vector graphics primitive where colour is interpolated between mesh vertices. The current implementations of gradient meshes are restricted to rectangular mesh topology. Our new interpolation method relaxes this restriction by supporting arbitrary manifold topology of the input gradient mesh. Our method is based on the Catmull‐Clark subdivision scheme, which is well‐known to support arbitrary mesh topology in 3D. We adapt this scheme to support gradient mesh colour interpolation, adding extensions to handle interpolation of colours of the control points, interpolation only inside the given colour space and emulation of gradient constraints seen in related closed‐form solutions. These extensions make subdivision a viable option for interpolating arbitrary‐topology gradient meshes for 2D vector graphics. 相似文献
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作战方案评估是当今军事领域一个急需解决又具有相对难度的课题。针对目前的作战方案大多是由专家评估这一现实状况,提出了基于支持向量机的方案评估方法。以某次作战为研究背景,客观分析了影响作战方案实施的各因素,建立方案评估指标体系,将支持向量机的回归方法应用于作战方案评估模型的建立中。最后,通过实验验证了评估模型的可行性。 相似文献
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Jiaheng Zhao Ilhan Özgen-Xian Dongfang Liang Tian Wang Reinhard Hinkelmann 《Computers & Mathematics with Applications》2019,77(2):576-596
This paper describes an improved vector manipulation multislope monotone upstream-centred scheme for conservation laws (MUSCL) reconstruction for solving the shallow water equations on unstructured grids. This improved MUSCL reconstruction method includes a bigger stencil for the interpolation and saves time for determining the geometric relations compared to the original vector manipulation method, so it is computationally more efficient and straightforward to implement. Four examples involving an analytical solution, laboratory experiments and field-scale measurements are used to test the performance of the proposed scheme. It has been proven that the proposed scheme can provide comparable accuracy and higher efficiency compared to the original vector manipulation method. With the increasing of the number of cells, the advantage of the proposed scheme becomes more apparent. 相似文献
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介绍了基于开关函数的三电平并联型有源电力滤波器工作原理,建立了该种有源电力滤波器的数学模型,并提出一种三电平并联型有源电力滤波器的无差拍控制方案。该方案采用ipiq法检测谐波电流,根据当前采样时刻得到的负载电流和补偿电流值预测出下一采样时刻的电流参考值,并计算出有源电力滤波器在下一个采样时刻的输出电压参考值,最后采用电压空间矢量算法得出桥臂开关信号,从而达到电流跟踪控制的目的。仿真结果表明,采用该方案的三电平并联型有源电力滤波器能够很好地对检测电流进行跟踪控制,有效抑制了谐波,且具有良好的动态响应效果。 相似文献
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S.R. Mulpuru 《Mathematics and computers in simulation》1983,25(4):309-320
Using the technique of flux vector splitting, it is shown that one-dimensional, inviscid, compressible-flow equations possess a split conservation form. Some attractive features of this form for the design of finite-difference solution schemes are discussed. Based on the split form, two solution chemes are designed. One is a first-order accurate ‘upwind’ scheme and the other is similar to the Lax-Wendroff scheme. A hybrid scheme, based on a nonlinear weighting of these two schemes, is demonstrated to yield results superior to either of the two in the solution of an ideal shock-tube problem. 相似文献
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Li WC Vallet B Ray N Lévy B 《IEEE transactions on visualization and computer graphics》2006,12(5):1315-1322
Accurately representing higher-order singularities of vector fields defined on piecewise linear surfaces is a non-trivial problem. In this work, we introduce a concise yet complete interpolation scheme of vector fields on arbitrary triangulated surfaces. The scheme enables arbitrary singularities to be represented at vertices. The representation can be considered as a facet-based "encoding" of vector fields on piecewise linear surfaces. The vector field is described in polar coordinates over each facet, with a facet edge being chosen as the reference to define the angle. An integer called the period jump is associated to each edge of the triangulation to remove the ambiguity when interpolating the direction of the vector field between two facets that share an edge. To interpolate the vector field, we first linearly interpolate the angle of rotation of the vectors along the edges of the facet graph. Then. we use a variant of Nielson's side-vertex scheme to interpolate the vector field over the entire surface. With our representation, we remove the bound imposed on the complexity of singularities that a vertex can represent by its connectivity. This bound is a limitation generally exists in vertex-based linear schemes. Furthermore, using our data structure, the index of a vertex of a vector field can be combinatorily determined. We show the simplicity of the interpolation scheme with a GPU-accelerated algorithm for a LIC-based visualization of the so-defined vector fields, operating in image space. We demonstrate the algorithm applied to various vector fields on curved surfaces. 相似文献
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Islam SM Das S Ghosh S Roy S Suganthan PN 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2012,42(2):482-500
Differential evolution (DE) is one of the most powerful stochastic real parameter optimizers of current interest. In this paper, we propose a new mutation strategy, a fitness-induced parent selection scheme for the binomial crossover of DE, and a simple but effective scheme of adapting two of its most important control parameters with an objective of achieving improved performance. The new mutation operator, which we call DE/current-to-gr_best/1, is a variant of the classical DE/current-to-best/1 scheme. It uses the best of a group (whose size is q% of the population size) of randomly selected solutions from current generation to perturb the parent (target) vector, unlike DE/current-to-best/1 that always picks the best vector of the entire population to perturb the target vector. In our modified framework of recombination, a biased parent selection scheme has been incorporated by letting each mutant undergo the usual binomial crossover with one of the p top-ranked individuals from the current population and not with the target vector with the same index as used in all variants of DE. A DE variant obtained by integrating the proposed mutation, crossover, and parameter adaptation strategies with the classical DE framework (developed in 1995) is compared with two classical and four state-of-the-art adaptive DE variants over 25 standard numerical benchmarks taken from the IEEE Congress on Evolutionary Computation 2005 competition and special session on real parameter optimization. Our comparative study indicates that the proposed schemes improve the performance of DE by a large magnitude such that it becomes capable of enjoying statistical superiority over the state-of-the-art DE variants for a wide variety of test problems. Finally, we experimentally demonstrate that, if one or more of our proposed strategies are integrated with existing powerful DE variants such as jDE and JADE, their performances can also be enhanced. 相似文献
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《Computers & Mathematics with Applications》2005,49(2-3):239-252
This paper proposes a second-order scheme of precision integration for dynamic analysis with respect to long-term integration. Rather than transforming into first-order equations, a recursive scheme is presented in detail for direct solution of the homogeneous part of second-order algebraic and differential equations. The sine and cosine matrices involved in the scheme are calculated using the so-called 2N algorithm. Numerical tests show that both the efficiency and the accuracy of homogeneous equations can be improved considerably with the second-order scheme. The corresponding particular solution is also presented, incorporated with the second-order scheme where the excitation vector is approximated by the truncated Taylor series. 相似文献
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Stationary properties of a recently suggested windup prevention scheme for recursive parameter estimation are investigated in the case of insufficient excitation. When the regressor vector contains data covering the whole parameter space, the algorithm has only one stationary point, the one defined by a weighting matrix. If the excitation is insufficient, the algorithm is shown to possess a manifold of stationary points and a complete parametrization of this manifold is given. However, if the past excitation conditions already caused the algorithm to converge to a certain point, the stationary solution would not be affected by current lack of excitation. This property guarantees good anti-windup properties of the studied parameter estimation algorithm. 相似文献
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A. F. Shorikov 《Automation and Remote Control》2014,75(3):458-469
We consider a dynamical system consisting of three objects whose dynamics is given by vector linear discrete recurrent equations. The system contains two levels of managerial decision making, basic and secondary, that have different operational criteria and are united by informational and managerial connections defined in advance. For the dynamical system in question, we propose a mathematical formalization in the form of solving a multistage problem of two-level hierarchical minimax program control over the approach process with incomplete information and give a general scheme for its solution. 相似文献
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H.Theisel 《Computer Graphics Forum》2002,21(3):595-604
We introduce a scheme of control polygons to design topological skeletons for vector fields of arbitrary topology. Based on this we construct piecewise linear vector fields of exactly the topology specified by the control polygons. This way a controlled construction of vector fields of any topology is possible. Finally we apply this method for topology‐preserving compression of vector fields consisting of a simple topology. 相似文献
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An efficient method-of-lines approach is presented for the Euler and Navier-Stokes equations. The governing equations are spatially discretized by a central finite-difference approximation. The rational Runge-Kutta scheme is used for the time integration. Attention is focused on improving the efficiency and accuracy of the solution. A remarkable improvement in the efficiency is achieved by adopting a combination of the present scheme with the residual averaging and multigrid (M.G.) techniques. The M.G. method and the high suitability of the present scheme to a vector computer partly reduce the computational load imposed on a numerical simulation with a finer grid. The steady-state convergence obtained with the scheme is comparable with those of diagonalized implicit approximate factorization schemes for inviscid and viscous flow equations. The reliability and accuracy of the scheme have also been improved by adopting the artificial dissipation terms scaled down to the minimum level required for stability. The facilities of the scheme are demonstrated in a series of numerical experiments for two- and three-dimensional transonic flows. 相似文献