The Experts below are selected from a list of 113004 Experts worldwide ranked by ideXlab platform
Xifeng Fang - One of the best experts on this subject based on the ideXlab platform.
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improving mid tone quality of Variable Coefficient error diffusion using threshold modulation
International Conference on Computer Graphics and Interactive Techniques, 2003Co-Authors: Bingfeng Zhou, Xifeng FangAbstract:In this paper, we describe the use of threshold modulation to remove the visual artifacts contained in the Variable-Coefficient error-diffusion algorithm. To obtain a suitable parameter set for the threshold modulation, a cost function used for the search of optimal parameters is designed. An optimal diffusion parameter set, as well as the corresponding threshold modulation strength values, is thus obtained. Experiments over this new set of parameters show that, compared with the original Variable-Coefficient error-diffusion algorithm, threshold modulation can remove visual anomalies more effectively. The result of the new algorithm is an artifact-free halftoning in the full range of intensities. Fourier analysis of the experimental results further support this conclusion.
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improving mid tone quality of Variable Coefficient error diffusion using threshold modulation
International Conference on Computer Graphics and Interactive Techniques, 2003Co-Authors: Bingfeng Zhou, Xifeng FangAbstract:In this paper, we describe the use of threshold modulation to remove the visual artifacts contained in the Variable-Coefficient error-diffusion algorithm. To obtain a suitable parameter set for the threshold modulation, a cost function used for the search of optimal parameters is designed. An optimal diffusion parameter set, as well as the corresponding threshold modulation strength values, is thus obtained. Experiments over this new set of parameters show that, compared with the original Variable-Coefficient error-diffusion algorithm, threshold modulation can remove visual anomalies more effectively. The result of the new algorithm is an artifact-free halftoning in the full range of intensities. Fourier analysis of the experimental results further support this conclusion.
Bingfeng Zhou - One of the best experts on this subject based on the ideXlab platform.
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improving mid tone quality of Variable Coefficient error diffusion using threshold modulation
International Conference on Computer Graphics and Interactive Techniques, 2003Co-Authors: Bingfeng Zhou, Xifeng FangAbstract:In this paper, we describe the use of threshold modulation to remove the visual artifacts contained in the Variable-Coefficient error-diffusion algorithm. To obtain a suitable parameter set for the threshold modulation, a cost function used for the search of optimal parameters is designed. An optimal diffusion parameter set, as well as the corresponding threshold modulation strength values, is thus obtained. Experiments over this new set of parameters show that, compared with the original Variable-Coefficient error-diffusion algorithm, threshold modulation can remove visual anomalies more effectively. The result of the new algorithm is an artifact-free halftoning in the full range of intensities. Fourier analysis of the experimental results further support this conclusion.
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improving mid tone quality of Variable Coefficient error diffusion using threshold modulation
International Conference on Computer Graphics and Interactive Techniques, 2003Co-Authors: Bingfeng Zhou, Xifeng FangAbstract:In this paper, we describe the use of threshold modulation to remove the visual artifacts contained in the Variable-Coefficient error-diffusion algorithm. To obtain a suitable parameter set for the threshold modulation, a cost function used for the search of optimal parameters is designed. An optimal diffusion parameter set, as well as the corresponding threshold modulation strength values, is thus obtained. Experiments over this new set of parameters show that, compared with the original Variable-Coefficient error-diffusion algorithm, threshold modulation can remove visual anomalies more effectively. The result of the new algorithm is an artifact-free halftoning in the full range of intensities. Fourier analysis of the experimental results further support this conclusion.
Wenhui Shi - One of the best experts on this subject based on the ideXlab platform.
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the Variable Coefficient thin obstacle problem carleman inequalities
Advances in Mathematics, 2016Co-Authors: Herbert Koch, Angkana Ruland, Wenhui ShiAbstract:Abstract In this article we present a new strategy of addressing the (Variable Coefficient) thin obstacle problem. Our approach is based on a (Variable Coefficient) Carleman estimate. This yields semi-continuity of the vanishing order, lower and uniform upper growth bounds of solutions and sufficient compactness properties in order to carry out a blow-up procedure. Moreover, the Carleman estimate implies the existence of homogeneous blow-up limits along certain sequences and ultimately leads to an almost optimal regularity statement. As it is a very robust tool, it allows us to consider the problem in the setting of Sobolev metrics, i.e. working on the upper half ball B 1 + ⊂ R + n + 1 , the Coefficients are only W 1 , p regular for some p > n + 1 . These results provide the basis for our further analysis of the free boundary, the optimal regularity of solutions and a first order asymptotic expansion of solutions at the regular free boundary which is carried out in a follow-up article, [21] , in the framework of W 1 , p , p > 2 ( n + 1 ) , regular Coefficients and W 2 , p , p > 2 ( n + 1 ) , regular non-zero obstacles.
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the Variable Coefficient thin obstacle problem carleman inequalities
arXiv: Analysis of PDEs, 2015Co-Authors: Herbert Koch, Angkana Ruland, Wenhui ShiAbstract:In this article we present a new strategy of addressing the (Variable Coefficient) thin obstacle problem. Our approach is based on a (Variable Coefficient) Carleman estimate. This yields semi-continuity of the vanishing order, lower and uniform upper growth bounds of solutions and sufficient compactness properties in order to carry out a blow-up procedure. Moreover, the Carleman estimate implies the existence of homogeneous blow-up limits along certain sequences and ultimately leads to an almost optimal regularity statement. As it is a very robust tool, it allows us to consider the problem in the setting of Sobolev metrics, i.e. the Coefficients are only $W^{1,p}$ regular for some $p>n+1$. These results provide the basis for our further analysis of the free boundary, the optimal ($C^{1,1/2}$-) regularity of solutions and a first order asymptotic expansion of solutions at the regular free boundary which is carried out in a follow-up article in the framework of $W^{1,p}$, $p>2(n+1)$, regular Coefficients.
Yi-tian Gao - One of the best experts on this subject based on the ideXlab platform.
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soliton management for a Variable Coefficient modified korteweg de vries equation
Physical Review E, 2011Co-Authors: Zhiyuan Sun, Yi-tian Gao, Ying LiuAbstract:The concept of soliton management has been explored in the Bose-Einstein condensate and optical fibers. In this paper, our purpose is to investigate whether a similar concept exists for a Variable-Coefficient modified Korteweg--de Vries equation, which arises in the interfacial waves in two-layer liquid and Alfv\'en waves in a collisionless plasma. Through the Painlev\'e test, a generalized integrable form of such an equation has been constructed under the Painlev\'e constraints of the Variable Coefficients based on the symbolic computation. By virtue of the Ablowitz-Kaup-Newell-Segur system, a Lax pair with time-dependent nonisospectral flow of the integrable form has been established under the Lax constraints which appear to be more rigid than the Painlev\'e ones. Under such Lax constraints, multisoliton solutions for the completely integrable Variable-Coefficient modified Korteweg--de Vries equation have been derived via the Hirota bilinear method. Moreover, results show that the solitons and breathers with desired amplitude and width can be derived via the different choices of the Variable Coefficients.
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Variable-Coefficient balancing-act method and Variable-Coefficient KdV equation from fluid dynamics and plasma physics
European Physical Journal B, 2001Co-Authors: Bo Tian, Yi-tian GaoAbstract:Although their Coefficient functions often make the studies very hard, the Variable-Coefficient nonlinear evolution equations (vcNLEEs) are of current interests since they are able to model the real world in many fields of physical and engineering sciences. In this paper, based on the computerized symbolic computation, a Variable-Coefficient balancing-act method is proposed. Being concise and straightforward, it can be applicable to certain vcNLEEs, to get the solitonic features out, along with other exact analytic solutions, all beyond the travelling waves. By virtue of the method, such new solutions are demonstrated for a Variable-Coefficient KdV equation arising from fluid dynamics, plasmas and other fields. Special attention is paid to the one- and two-soliton-type solutions. Sample applications and physical interests are discussed, such as coastal waters of the world oceans, plasma physics, liquid drops and bubbles. Nonlinear interaction hallmarked by the phase shifts is pictured. Comparisons are made with other results in the literature.
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ON A Variable-Coefficient MODIFIED KP EQUATION AND A GENERALIZED Variable-Coefficient KP EQUATION WITH COMPUTERIZED SYMBOLIC COMPUTATION
International Journal of Modern Physics C, 2001Co-Authors: Yi-tian Gao, Bo TianAbstract:The Variable-Coefficient nonlinear evolution equations, although realistically modeling various mechanical and physical situations, often cause some well-known powerful methods not to work efficiently. In this paper, we extend the power of the generalized hyperbolic-function method, which is based on the computerized symbolic computation, to a Variable-Coefficient modified Kadomtsev–Petviashvili (KP) equation and a generalized Variable-Coefficient KP equation. New exact analytic solutions thus come out.
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Variable-Coefficient BALANCING-ACT ALGORITHM EXTENDED TO A Variable-Coefficient MKP MODEL FOR THE ROTATING FLUIDS
International Journal of Modern Physics C, 2001Co-Authors: Yi-tian Gao, Bo TianAbstract:The modified Kadomtsev–Petviashvili (MKP) models describe the large-scale motion of such rotating fluids as the atmosphere and oceans. Based on the computerized symbolic computation, we in this paper extend the power of the Variable-Coefficient balancing-act method, which is recently proposed, to a Variable-Coefficient MKP model. The model is re-written as a coupled set of partial differential equations, and the algorithm is re-written correspondingly. We obtain a new family of the soliton-like, exact analytic solutions, beyond the traveling waves.
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Generalized Variable-Coefficient KP Equation
International Journal of Theoretical Physics, 1998Co-Authors: Yi-tian Gao, Bo TianAbstract:The Variable-Coefficient generalizations of thecelebrated KP equation (GvcKPs) are realistic models forvarious physical and engineering situations. In thisnote, the application of symbolic computation and the truncated Painleve expansion leads toan auto-Backlund transformation and soliton-typedsolutions to a type of the GvcKPs.
Charbel Farhat - One of the best experts on this subject based on the ideXlab platform.
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a discontinuous enrichment method for Variable Coefficient advection diffusion at high peclet number
International Journal for Numerical Methods in Engineering, 2011Co-Authors: Irina Kalashnikova, Radek Tezaur, Charbel FarhatAbstract:A discontinuous Galerkin method with Lagrange multipliers is presented for the solution of Variable-Coefficient advection–diffusion problems at high Peclet number. In this method, the standard finite element polynomial approximation is enriched within each element with free-space solutions of a local, constant-Coefficient, homogeneous counterpart of the governing partial differential equation. Hence in the two-dimensional case, the enrichment functions are exponentials, each exhibiting a sharp gradient in a carefully chosen flow direction. The continuity of the enriched approximation across the element interfaces is enforced weakly by the aforementioned Lagrange multipliers. Numerical results obtained for two benchmark problems demonstrate that elements based on the proposed discretization method are far more competitive for Variable-Coefficient advection–diffusion analysis in the high Peclet number regime than their standard Galerkin and stabilized finite element comparables. Copyright © 2010 John Wiley & Sons, Ltd.
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A discontinuous enrichment method for Variable‐Coefficient advection–diffusion at high Péclet number
International Journal for Numerical Methods in Engineering, 2010Co-Authors: Irina Kalashnikova, Radek Tezaur, Charbel FarhatAbstract:A discontinuous Galerkin method with Lagrange multipliers is presented for the solution of Variable-Coefficient advection–diffusion problems at high Peclet number. In this method, the standard finite element polynomial approximation is enriched within each element with free-space solutions of a local, constant-Coefficient, homogeneous counterpart of the governing partial differential equation. Hence in the two-dimensional case, the enrichment functions are exponentials, each exhibiting a sharp gradient in a carefully chosen flow direction. The continuity of the enriched approximation across the element interfaces is enforced weakly by the aforementioned Lagrange multipliers. Numerical results obtained for two benchmark problems demonstrate that elements based on the proposed discretization method are far more competitive for Variable-Coefficient advection–diffusion analysis in the high Peclet number regime than their standard Galerkin and stabilized finite element comparables. Copyright © 2010 John Wiley & Sons, Ltd.
