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91.
Stephan Dahlke Massimo Fornasier Miriam Primbs Thorsten Raasch Manuel Werner 《Numerical Methods for Partial Differential Equations》2009,25(6):1366-1401
This article is concerned with adaptive numerical frame methods for elliptic operator equations. We show how specific noncanonical frame expansions on domains can be constructed. Moreover, we study the approximation order of best n‐term frame approximation, which serves as the benchmark for the performance of adaptive schemes. We also discuss numerical experiments for second order elliptic boundary value problems in polygonal domains where the discretization is based on recent constructions of boundary adapted wavelet bases on the interval. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009 相似文献
92.
Let M be a differentiable manifold and [0, )×MM be a C1 map satisfying the condition (0, p)=p for all pM. Among other results, we prove that when the degree (also called Hopf index or Euler characteristic) of the tangent vector field wMTM, given by w(p)=(/)(0, p), is well defined and nonzero, then the set (of nontrivial pairs) admits a connected subset whose closure is not compact and meets the slice {0}×M of [0, )×M. This extends known results regarding the existence of harmonic solutions of periodic ordinary differential equations on manifolds. 相似文献
93.
94.
Serhii Gryshchuk Massimo Lanza de Cristoforis 《Mathematical Methods in the Applied Sciences》2014,37(12):1755-1771
Let be a bounded open domain of . Let denote the outward unit normal of . We assume that the Steklov problem Δu = 0 in and on has a simple eigenvalue of . Then we consider an annular domain obtained by removing from a small‐cavity size of ε > 0, and we show that under proper assumptions there exists a real valued and real analytic function defined in an open neighborhood of (0,0) in and such that is a simple eigenvalue for the Steklov problem Δu = 0 in and on for all ε > 0 small enough, and such that . Here denotes the outward unit normal of , and δ2,2 ≡ 1 and δ2,n ≡ 0 if n ≥ 3. Then related statements have been proved for corresponding eigenfunctions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
95.
Using five alternative data sets and a range of specifications concerning the underlying linear predictability models, we study whether long-run dynamic optimizing portfolio strategies may actually outperform simpler benchmarks in out-of-sample tests. The dynamic portfolio problems are solved using a combination of dynamic programming and Monte Carlo methods. The benchmarks are represented by two typical fixed mix strategies: the celebrated equally-weighted portfolio and a myopic, Markowitz-style strategy that fails to account for any predictability in asset returns. Within a framework in which the investor maximizes expected HARA (constant relative risk aversion) utility in a frictionless market, our key finding is that there are enormous difference in optimal long-horizon (in-sample) weights between the mean–variance benchmark and the optimal dynamic weights. In out-of-sample comparisons, there is however no clear-cut, systematic, evidence that long-horizon dynamic strategies outperform naively diversified portfolios. 相似文献
96.
97.
Massimo Rudan 《Numerical Functional Analysis & Optimization》2013,34(3-4):501-529
An analysis is carried out of the multi-dimensional extension of the Scharfetter-Gummel method. It shown that, within the frame of the drift-diffusion model of semiconductor devices, the assumption of constant electric field and current densities over suitable subelements of the discretization grid preserves the necessary degrees of freedom of the problem and, at the same time, provides some information about the current-density field. These informations are exploited for treating a case in which the dependence of the model's coefficients on the current density is strong, namely, impact ionization. 相似文献
98.
Adaptive frame methods for elliptic operator equations: the steepest descent approach 总被引:2,自引:0,他引:2
Dahlke Stephan; Raasch Thorsten; Werner Manuel; Fornasier Massimo; Stevenson Rob 《IMA Journal of Numerical Analysis》2007,27(4):717-740
99.
Near a Mott transition, strong electron correlations may enhance Cooper pairing. This is demonstrated in the dynamical mean field theory solution of a twofold-orbital degenerate Hubbard model with an inverted on-site Hund rule exchange, favoring local spin-singlet configurations. Close to the Mott insulator (which here is a local version of a valence bond insulator) a pseudogap non-Fermi-liquid metal, a superconductor, and a normal metal appear, in striking similarity with the physics of cuprates. The strongly correlated s-wave superconducting state has a larger Drude weight than the corresponding normal state. The role of the impurity Kondo problem is underscored. 相似文献
100.
Abstract GARR is engineering its next generation of the Italian Research and Education Network (GARR-X), which will exploit a countrywide optical infrastructure based on DWDM equipment and advanced multi-domain services. The trend is common in all National Research and Education Networks [1] in Europe and worldwide. NRENs are relying more and more on direct use of optical equipment to fulfill the researchers' requirements. These hybrid networks are built to provide services on a multi-domain environment both at the circuit and at the IP layer for researchers in, for example, radio astronomy (eVLBI [2]), GRID computing (EGEE [3], LHC [4]), high-performance computing (DEISA [5]). This article outlines the status and issues of ongoing research activities in GARR [6] and NRENs to provide, manage, and evolve dedicated optical-based networks for providing multi-domain end-to-end services. The research is performed mainly in the framework of the European Commission co-funded project GÉANT2 [7]. 相似文献