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141.
Viscosity Approximation Methods for Generalized Multi-Valued Nonexpansive Mappings with Applications
AbstractIn this article, we study viscosity approximation methods for generalized multi-valued nonexpansive mappings and we present some new results related to strong convergence, variational inequality, convex optimization, split and common split feasibility problems (SFPs). Some numerical computations are also presented to illustrate our results. 相似文献
142.
Kriging is commonly used for developing emulators as surrogates for computationally intensive simulations. One difficulty with kriging is the potential numerical instability in the computation of the inverse of the covariance matrix, which can lead to large variability and poor performance of the kriging predictor. First, we study some causes of ill-conditioning in kriging. We then study the use of nugget in kriging to overcome the numerical instability. Some asymptotic results on its interpolation bias and mean squared prediction errors are presented. Finally, we study the choice of the nugget parameter based on some algebraic lower bounds and use of a regularizing trace. A simulation study is performed to show the differences between kriging with and without nugget and to demonstrate the advantages of the former. This article has supplementary materials online. 相似文献
143.
X-ray powder diffraction patterns of the AgNbO3 have been obtained in a wide temperature range: from room temperature up to 850 K. The type of distortion and the multiplicity of the pseudo-cubic perovskite cell has been determined from the splitting of the main diffraction lines and from analysis of the superlattice peaks. The scheme of oxygen octahedra tilting and the sequence of the distorted pseudocubic cell is: <artwork name="GPHT21121eu1"> 相似文献
144.
《偏微分方程通讯》2013,38(9-10):1751-1791
ABSTRACT On a riemannian manifold of dimension 3, it is possible to change the laplacian Δ at a single point p. This procedure gives the so-called Dirac potential, and we study the associated wave equation. We first show that the propagator can be written as a sum in which each operator takes into account n diffractions at p. We then show that the curve obtained by following, one after another, n geodesic segments emanating from, and returning to p, gives a singularity in the trace formula. The principal part of this singularity is also computed. 相似文献
145.
S. Plubtieng K. Ungchittrakool R. Wangkeeree 《Numerical Functional Analysis & Optimization》2013,34(5-6):737-749
The purpose of this paper is to study the weak and strong convergence of an implicit iteration process to a common fixed point for two finite families of nonexpansive mappings in Banach spaces. The results presented in this paper extend and improve the corresponding results of Xu and Ori, Numer. Funct. Anal. Optim. 2001; 22:767–773, Zhou and Chang, Numer. Fund. Anal. Optim. 2002; 23:911–921, Chidume and Shahzad, Nonlinear. Anal. 2005; 62: 1149–1156. 相似文献
146.
N. Hussain B. E. Rhoades G. Jungck 《Numerical Functional Analysis & Optimization》2013,34(9-10):1139-1151
A fixed point theorem of Ciric, Diviccaro et al., Fisher and Sessa, Gregus, Jungck, and Mukherjee and Verma is generalized to weakly compatible maps. As applications, common fixed point and approximation results for Gregus type I-contractions are obtained. Our results unify and generalize various known results to the more general classes of noncommuting mappings. 相似文献
147.
The purpose of this article is to introduce an implicit iteration process for approximating common fixed points of three finite families nonexpansive mappings and to prove weak and strong convergence theorems in uniformly convex Banach spaces. 相似文献
148.
Balmohan V. Limaye 《Numerical Functional Analysis & Optimization》2013,34(2):180-206
A condition number of an ordered basis of a finite-dimensional normed space is defined in an intrinsic manner. This concept is extended to a sequence of bases of finite-dimensional normed spaces, and is used to determine uniform conditioning of such a sequence. We address the problem of finding a sequence of uniformly conditioned bases of spectral subspaces of operators of the form T n = S n + U n , where S n is a finite-rank operator on a Banach space and U n is an operator which satisfies an invariance condition with respect to S n . This problem is reduced to constructing a sequence of uniformly conditioned bases of spectral subspaces of operators on ? n×1. The applicability of these considerations in practical as well as theoretical aspects of spectral approximation is pointed out. 相似文献
149.
给出了求解对流扩散方程的组合差商算法,构造了一类隐式差分格式,其精度为o(τ^2 h^2),按网比r=τ/h恒稳定,并分析了对角占优条件。数值例子验证了理论分析结果的有效性。 相似文献
150.
Bar-Shir A Avram L Ozarslan E Basser PJ Cohen Y 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,194(2):230-236
q-Space diffusion MRI (QSI) provides a means of obtaining microstructural information about porous materials and neuronal tissues from diffusion data. However, the accuracy of this structural information depends on experimental parameters used to collect the MR data. q-Space diffusion MR performed on clinical scanners is generally collected with relatively long diffusion gradient pulses, in which the gradient pulse duration, δ, is comparable to the diffusion time, Δ. In this study, we used phantoms, consisting of ensembles of microtubes, and mathematical models to assess the effect of the ratio of the diffusion time and the duration of the diffusion pulse gradient, i.e., Δ/δ, on the MR signal attenuation vs. q, and on the measured structural information extracted therefrom. We found that for Δ/δ 1, the diffraction pattern obtained from q-space MR data are shallower than when the short gradient pulse (SGP) approximation is satisfied. For long δ the estimated compartment size is, as expected, smaller than the real size. Interestingly, for Δ/δ 1 the diffraction peaks are shifted to even higher q-values, even when δ is kept constant, giving the impression that the restricted compartments are even smaller than they are. When phantoms composed of microtubes of different diameters are used, it is more difficult to estimate the diameter distribution in this regime. Excellent agreement is found between the experimental results and simulations that explicitly account for the use of long duration gradient pulses. Using such experimental data and this mathematical framework, one can estimate the true compartment dimensions when long and finite gradient pulses are used even when Δ/δ 1. 相似文献