143,749 research outputs found
Hierarchical bases for non-hierarchic 3Dtriangular meshes
We describe a novel basis of hierarchical, multiscale functions that are linear combinations of standard Rao-Wilton- Glisson (RWG) functions. When the basis is used for discretizing the electric field integral equation (EFIE) for PEC objects it gives rise to a linear system immune from low-frequency breakdown, and well conditioned for dense meshes. The proposed scheme can be applied to any mesh with triangular facets, and therefore it can be used as if it were an algebraic preconditioner. The properties of the new system are confirmed by numerical results that show fast convergence rates of iterative solvers, significantly better than those for the loop-tree basis. As a byproduct of the basis generation, a generalization of the RWG functions to nonsimplex cells is introduced
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Software tools for stochastic programming: A Stochastic Programming Integrated Environment (SPInE)
SP models combine the paradigm of dynamic linear programming with
modelling of random parameters, providing optimal decisions which hedge
against future uncertainties. Advances in hardware as well as software
techniques and solution methods have made SP a viable optimisation tool.
We identify a growing need for modelling systems which support the creation
and investigation of SP problems. Our SPInE system integrates a number of
components which include a flexible modelling tool (based on stochastic
extensions of the algebraic modelling languages AMPL and MPL), stochastic
solvers, as well as special purpose scenario generators and database tools.
We introduce an asset/liability management model and illustrate how SPInE
can be used to create and process this model as a multistage SP application
Trends and Spatial Patterns of Drought Affected Area in Southern South America
Based on 56 rainfall stations, which cover the period 1961–2008, we analyzed the presence of trends in the drought-affected area over southern South America (SSA) at different time scales. In order to define drought conditions, we used the standardized precipitation index, which was calculated on time scales of 1, 3, 6, 9 and 12 months. The trends were estimated following both a linear and a non-linear approach. The non-linear approach was based on the residual of the empirical mode decomposition, a recently proposed methodology, which is robust in presence of non-stationary data. This assessment indicates the existence of reversals in the trends of the drought affected, area around the 1990s, from decreasing trends during the first period to increasing trends during the recent period. This is indicative of the existence of a low-frequency variability that modulates regional precipitation patterns at different temporal scales, and warns about possible future consequences in the social and economic sectors if trends towards an increase in the drought affected area continue.Fil: Rivera, Juan Antonio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Penalba, Olga Clorinda. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Multipolar third-harmonic generation driven by optically-induced magnetic resonances
We analyze third-harmonic generation from high-index dielectric nanoparticles
and discuss the basic features and multipolar nature of the parametrically
generated electromagnetic fields near the Mie-type optical resonances. By
combining both analytical and numerical methods, we study the nonlinear
scattering from simple nanoparticle geometries such as spheres and disks in the
vicinity of the magnetic dipole resonance. We reveal the approaches for
manipulating and directing the resonantly enhanced nonlinear emission with
subwavelength all-dielectric structures that can be of a particular interest
for novel designs of nonlinear optical antennas and engineering the magnetic
optical nonlinear response at nanoscale.Comment: 24 pages, 6 figure
Circle-actions, quantum cohomology, and the Fukaya category of Fano toric varieties
We define a class of non-compact Fano toric manifolds, called admissible
toric manifolds, for which Floer theory and quantum cohomology are defined. The
class includes Fano toric negative line bundles, and it allows blow-ups along
fixed point sets. We prove closed-string mirror symmetry for this class of
manifolds: the Jacobian ring of the superpotential is the symplectic cohomology
(not the quantum cohomology). Moreover, SH(M) is obtained from QH(M) by
localizing at the toric divisors. We give explicit presentations of SH(M) and
QH(M), using ideas of Batyrev, McDuff and Tolman. Assuming that the
superpotential is Morse (or a milder semisimplicity assumption), we prove that
the wrapped Fukaya category for this class of manifolds satisfies the toric
generation criterion, i.e. is split-generated by the natural Lagrangian torus
fibres of the moment map with suitable holonomies. In particular, the wrapped
category is compactly generated and cohomologically finite. The proof uses a
deformation argument, via a generic generation theorem and an argument about
continuity of eigenspaces. We also prove that for any closed Fano toric
manifold, if the superpotential is Morse (or a milder semisimplicity
assumption) then the Fukaya category satisfies the toric generation criterion.
The key ingredients are non-vanishing results for the open-closed string map,
using tools from the paper by Ritter-Smith (we also prove a conjecture from
that paper that any monotone toric negative line bundle contains a
non-displaceable monotone Lagrangian torus). We also need to extend the class
of Hamiltonians for which the maximum principle holds for symplectic manifolds
conical at infinity, thus extending the class of Hamiltonian circle actions for
which invertible elements can be constructed in SH(M).Comment: 70 pages (51 pages + appendices). Version 2: rewrote the
Introduction, fixed a mistake (Remark 1.15), generation theorem generalized
to all admissible toric manifolds (Section 1.8
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