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141.
This paper deals with ultrasound medical image processing, particularly to filter the noise while preserving the edges and
structures of information. The mathematical processing consists in solving by a numerical way a nonlinear evolutive boundary
value problem. Several numerical semi-implicit time marching schemes are considered and analyzed. At each time step, parallel
synchronous or asynchronous Schwarz alternating methods are used to solve the linear system and its convergence is studied.
Lastly, the results of sequential and parallel simulations are presented.
相似文献
142.
局部方差在图像质量评价中的应用 总被引:4,自引:0,他引:4
将灰度图像的局部方差分布(QLS)作为表征图像结构信息的一个重要特征,对局部方差分布矩阵进行奇异值分解,计算得到相应的奇异值特征向量;通过计算降质图像与原参考图像局部方差矩阵奇异值特征向量的夹角大小度量两图像的结构相似度,实现了对降质图像的质量评价。实验结果表明:局部方差分布更能突出图像的结构特征,评价结果优于传统的均方误差(MSE)、峰值信噪比(PSNR)、结构相似度(SSIM)以及直接评价图像像素分布的奇异值分析(SVD)等方法,与人眼视觉感知效果的一致性较好。 相似文献
143.
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145.
Lung-Hui Chen 《复变函数与椭圆型方程》2015,60(5):707-731
We study the inverse spectral problem in an interior transmission eigenvalue problem. The Cartwright’s theory in value distribution theory gives a connection between the distributional structure of the eigenvalues and the asymptotic behaviours of its defining functional determinants. Given a sufficient quantity of transmission eigenvalues, we prove a uniqueness of the refraction index in inhomogeneous medium as an uniqueness problem in entire function theory. The asymptotically periodical structure of the zero set of the solutions helps to locate infinitely many eigenvalues of infinite degree of freedom. 相似文献
146.
147.
148.
In this paper, we derive the asymptotic expansions of the moments of normalized partial maxima for general error distribution. A byproduct is to deduce the convergence rates of the moments of normalized maxima to the moments of the corresponding extreme value distribution. 相似文献
149.
Well‐posedness and approximation of solutions of linear divergence‐form elliptic problems on exterior regions 下载免费PDF全文
This paper describes well‐posedness, spectral representations, and approximations of solutions of uniformly elliptic, second‐order, divergence form elliptic boundary value problems on exterior regions U in when N ≥ 3. Inhomogeneous Dirichlet, Neumann, and Robin boundary conditions are treated. These problems are first shown to be well‐posed in the space E1(U) of finite‐energy functions on U using variational methods. Spectral representations of these solutions involving Steklov eigenfunctions and solutions subject to zero Dirichlet boundary conditions are described. Some approximation results for the A‐harmonic components are obtained. Positivity and comparison results for these solutions are given. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
150.
Fredholm boundary value problems for perturbed systems of dynamic equations on time scales 下载免费PDF全文
Ravi P. Agarwal Martin Bohner Alexandr Boı̆chuk Olexandr Strakh 《Mathematical Methods in the Applied Sciences》2015,38(17):4178-4186
This paper offers conditions ensuring the existence of solutions of linear boundary value problems for systems of dynamic equations on time scales. Utilizing a method of Moore–Penrose pseudo‐inverse matrices leads to an analytical form of a criterion for the existence of solutions in a relevant space and, moreover, to the construction of a family of linearly independent solutions of such problems in a general case with the number of boundary conditions (defined by a linear vector functional) not coinciding with the number of unknowns of a system of dynamic equations. As an example of an application of the presented results, the problem of bifurcation of solutions of boundary value problems for systems of dynamic equations on time scales with a small parameter is considered. 相似文献