Foreword

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Bounds for the first eigenvalue of the elastically supported membrane on convex domains

ISSN:1420-9039ISSN:0044-227

Bounds for the first eigenvalue of the elastically supportedmembrane on convex domains

Barta's principle and gradient bounds for the torsion function are the main tools for deriving lower bounds for the first eigenvalue. The optimal domains are an infinite strip, a disk or an annulus in different situation

Cost optimization in AGV applications

A otimização de custos em aplicações com veículos autónomos pode ser conseguida em diversas frentes. Nesta dissertação estudam-se e comparam-se soluções a três problemas: a interface entre instalador/operador do robô; a otimização de variáveis na solução de um problema de logística; e a escolha dos sensores afetos ao sistema de navegação

Yukawa potentials in systems with partial periodic boundary conditions II : Lekner sums for quasi-two dimensional systems

Yukawa potentials may be long ranged when the Debye screening length is large. In computer simulations, such long ranged potentials have to be taken into account with convenient algorithms to avoid systematic bias in the sampling of the phase space. Recently, we have provided Ewald sums for quasi-two dimensional systems with Yukawa interaction potentials [M. Mazars, {\it J. Chem. Phys.}, {\bf 126}, 056101 (2007) and M. Mazars, {\it Mol. Phys.}, Paper I]. Sometimes, Lekner sums are used as an alternative to Ewald sums for Coulomb systems. In the present work, we derive the Lekner sums for quasi-two dimensional systems with Yukawa interaction potentials and we give some numerical tests for pratical implementations. The main result of this paper is to outline that Lekner sums cannot be considered as an alternative to Ewald sums for Yukawa potentials. As a conclusion to this work : Lekner sums should not be used for quasi-two dimensional systems with Yukawa interaction potentials.Comment: 25 pages, 5 figures and 1 tabl

Investigations of an SLA Support System for Cloud Computing (SLACC)

Cloud Providers (CP) and Cloud Users (CU) need to agree on a set of parameters expressed through Service Level Agreements (SLA) for a given Cloud service. However, even with the existence of many CPs in the market, it is still impossible today to see CPs who guarantee, or at least offer, an SLA specification tailored to CU's interests: not just offering percentage of availability, but also guaranteeing, for example, specific performance parameters for a certain Cloud application. Due to (1) the huge size of CPs' IT infrastructures and (2) the high complexity with multiple inter-dependencies of resources (physical or virtual), the estimation of specific SLA parameters to compose Service Level Objectives (SLOs) with trustful Key Performance Indicators (KPIs) tends to be inaccurate. This paper investigates an SLA Support System for CC (SLACC) which aims to estimate in a formalized methodology - based on available Cloud Computing infrastructure parameters - what CPs will be able to offer/accept as SLOs or KPIs and, as a consequence, which increasing levels of SLA specificity for their customers can be reache

MMM2D: A fast and accurate summation method for electrostatic interactions in 2D slab geometries

We present a new method, in the following called MMM2D, to accurately calculate the electrostatic energy and forces on charges being distributed in a two dimensional periodic array of finite thickness. It is not based on an Ewald summation method and as such does not require any fine-tuning of an Ewald parameter for convergence. We transform the Coulomb sum via a convergence factor into a series of fast decaying functions which can be easily evaluated. Rigorous error bounds for the energies and the forces are derived and numerically verified. Already for small systems our method is much faster than the traditional 2D-Ewald methods, but for large systems it is clearly superior because its time demand scales like O(N^{5/3}) with the number N of charges considered. Moreover it shows a rapid convergence, is very precise and easy to handle.Comment: 29 pages, 6 figures, needs elsart.cls (provided

Logarithmic interaction under periodic boundary conditions: Closed form formulas for energy and forces

A method is given to obtain closed form formulas for the energy and forces for an aggregate of charges interacting via a logarithmic interaction under periodic boundary conditions. The work done here is a generalization of Glasser's results [M. L. Glasser, J. Math. Phys. 15, 188 (1974)] and is obtained with a different and simpler method than that by Stremler [M. A. Stremler, J. Math. Phys. 45, 3584 (2004)]. The simplicity of the formulas derived here makes them extremely convenient in a computer simulation

On the lowest eigenvalue of Laplace operators with mixed boundary conditions

In this paper we consider a Robin-type Laplace operator on bounded domains. We study the dependence of its lowest eigenvalue on the boundary conditions and its asymptotic behavior in shrinking and expanding domains. For convex domains we establish two-sided estimates on the lowest eigenvalues in terms of the inradius and of the boundary conditions