Variational segmentation models provide effective tools for image processing applications. Although existing models are continually refined to increase their capabilities, solution of such models is often a slow proce...
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Variational segmentation models provide effective tools for image processing applications. Although existing models are continually refined to increase their capabilities, solution of such models is often a slow process, since fast methods are not immediately applicable to nonlinear problems. This paper presents an efficient multi-grid algorithm for solving the Chan-Vese model in three dimensions, generalizing our previous work on the topic in two dimensions, but this direct generalized method is low performance or unfeasible. So here, we first present two general smoothers for a nonlinear multi-grid method and then give our three new adaptive smoothers which can choose optimal a parameter of the smoothers automatically, also we analyse them using a local Fourier analysis and our theorem to inform how to obtain an optimal parameter and the best smoother selection. Finally, various advantages of our recommended algorithm are illustrated, using both synthetic and real images.
The partial differential equations are often used in science and engineering *** solutions cannot be got analytical,so the numerical methods are often used to get approximate *** achieve high precision,more computing ...
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The partial differential equations are often used in science and engineering *** solutions cannot be got analytical,so the numerical methods are often used to get approximate *** achieve high precision,more computing time is *** the long time in practical applications is not often allowed,so the precision of final results has to be *** on cluster system,this paper studies the parallel multi-grid method and its application in the numerical analysis of heat *** results from the sample show that the method not only can expand the size of solved problems efficiently,but also can gain excellent parallel efficiency;therefore it is a method suitable for network parallel environment based on cluster system.
The assumptions of both a Couette flow dominance and a quadratic temperature profile across the film are commonly used in the analysis of thermal non-Newtonian elastohydrodynamic lubrication. In such calculations, the...
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The assumptions of both a Couette flow dominance and a quadratic temperature profile across the film are commonly used in the analysis of thermal non-Newtonian elastohydrodynamic lubrication. In such calculations, the conduction across the film and the energy dissipation are assumed to be the main phenomena in the prediction of temperature rise. Consequently the gradients of the physical properties across the film as well as the reverse flow and the heat convection in all directions are assumed to have no or little impact on the general characteristics of the temperature profiles and therefore can be neglected. The objective of this paper is to assess the quality of these approximations. A comparison between both the simplified and the complete non-Newtonian thermal approach is made for the line contact problem. The complete solution is based upon the resolution of a two-dimensional energy equation, which is fully coupled with the non-Newtonian Reynolds equation. The analysis reveals some local discrepancies between both the simplified and the complete solutions. These differences are clearly visible at the inlet of the contact where a bump in the temperature profiles disappears in the simplified approach. The results also show a significant difference in the levels of temperature predicted within the high-pressure region between the simplified and complete approach. In regard to the friction coefficient, the simplified calculation forecasts a lower coefficient than that obtained with the complete formulation.
The aim of this paper is to present a new method for skin tumor segmentation in the 3D ultrasound images. We consider a variational formulation, the energy of which combines a diffuse interface phase field model (regu...
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The aim of this paper is to present a new method for skin tumor segmentation in the 3D ultrasound images. We consider a variational formulation, the energy of which combines a diffuse interface phase field model (regularization term) and a log-likelihood computed using nonparametric estimates (data attachment term). We propose a multi-grid implementation with the exact solutions which has the advantage to avoid space discretization and numerical instabilities. The resulting algorithm is simple and easy to implement in multi-dimensions. Concerning applications, we focus on skin tumor segmentation. The clinical dataset used for the experiments is composed of 12 images with the ground truth given by a dermatologist. Comparisons with the reference methods show that the proposed method is more robust to the choice of the volume initialization. Moreover, thanks to the flexibility introduced by the diffuse interface, the sensitivity increases by 12% if the initialization is inside the lesion, and the Dice index increases by 59%, if the initialization covers the entire lesion. These results show that this new method is well designed to tackle the problem of underestimation of tumor volumes.
In this paper, a multi-grid algorithm is applied to a large-scale block matrix that is produced from a Beam and Warming scheme. The Beam and Warming scheme is used in the simulation of unsteady flow in an open channel...
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In this paper, a multi-grid algorithm is applied to a large-scale block matrix that is produced from a Beam and Warming scheme. The Beam and Warming scheme is used in the simulation of unsteady flow in an open channel. The Gauss-Seidel block-wise iteration method is used for a smoothing process with a few iterations. It is also shown that the governing equations determine the type of prolongation and restriction operators for the multi-grid algorithm.
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