Reconstruction of signals from multiscale edges

We present a method for signal reconstruction based upon the location of its singularities which are identified by a wavelet transform technique. The reconstructed signal is an infconvolution spline approximant. The data for the interpolation problem which we solve comes from a compact signal coding procedure. Error bounds and convergence results for the calculated signal are given.     

Stability analysis of thermodynamic lubrication problems in journal bearings

A new numerical scheme (which combines FEM, FVM and BEM methods) for solving thermohydrodynamic lubrication transient problems with cavitation is described. The algorithm is then applied to study the stability of a journal-bearing system. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A strategy to find minimal energy nanocluster structures

An unbiased strategy to search for the global and local minimal energy structures of free standing nanoclusters is presented. Our objectives are twofold: to find a diverse set of low lying local minima, as well as the global minimum. To do so, we use massively the fast inertial relaxation engine algorithm as an efficient local minimizer. This procedure turns out to be quite efficient to reach the global minimum, and also most of the local minima. We test the method with the Lennard–Jones (LJ) potential, for which an abundant literature does exist, and obtain novel results, which include a new local minimum for LJ₁₃, 10 new local minima for LJ₁₄, and thousands of new local minima for . Insights on how to choose the initial configurations, analyzing the effectiveness of the method in reaching low‐energy structures, including the global minimum, are developed as a function of the number of atoms of the cluster. Also, a novel characterization of the potential energy surface, analyzing properties of the local minima basins, is provided. The procedure constitutes a promising tool to generate a diverse set of cluster conformations, both two‐ and three‐dimensional, that can be used as an input for refinement by means of ab initio methods. © 2013 Wiley Periodicals, Inc.     

Numerical modeling of ice behavior under high velocity impacts

In this work a constitutive relation for ice at high strain rates and an algorithm for its numerical integration are developed. This model is based on the Drucker–Prager plasticity criteria, which allows a different behavior in tension and in compression. In addition a failure criteria, based on pressure cut-offs, is implemented to describe the ice damage. In order to validate the constitutive model, numerical simulations were compared with experimental results, in which ice cylinders were impacted against a steel plate, allowing the measurement of the contact load. Three different numerical solvers are used in order to analyze its performance to appropriately modeling the ice behavior.     

Decomposition and reconstruction of multidimensional signals using polyharmonic pre-wavelets

In this paper, we build a multidimensional wavelet decomposition based on polyharmonic B-splines. The pre-wavelets are polyharmonic splines and so not tensor products of univariate wavelets. Explicit construction of the filters specified by the classical dyadic scaling relations is given and the decay of the functions and the filters is shown. We then design the decomposition/recomposition algorithm by means of downsampling/upsampling and convolution products.     

Pr3 +–Yb3 +‐codoped lanthanum fluorozirconate glasses and waveguides for visible laser emission

Pr^3 +–Yb^3 +‐codoped fluoride glass waveguides have been synthesized by Physical Vapor Deposition (PVD). A study of the evaporation of ternary mixture of rare earth fluorides LaF₃–PrF₃–YbF₃ has been necessary to control the doping of the evaporated glass. Optical and spectroscopic studies have been performed in both bulk and waveguide configuration. Red, orange, green and blue emissions in Pr^3 +–Yb^3 +-codoped lanthanum flurozirconate glasses called ZLAG have been investigated, by exciting in the blue or in the infra-red at 980 nm. Bulk samples with different dopant concentrations (0.25–3 mol% for Pr^3 + and 0–5 mol% for Yb^3 +) have been studied in order to optimize the Pr^3 + emission. It has been shown than the luminescence is similar in bulk and waveguide upon excitation at 980 nm.     

Influence of Temperature on Liquid–Liquid Equilibrium of Methanol + Toluene + Hexane Ternary Systems at Atmospheric Pressure

Phase equilibria of methanol?+?toluene?+?hexane ternary systems at (278.15, 283.15, 288.15 and 293.15) K at atmospheric pressure were investigated. The influence of temperature on the liquid–liquid equilibrium is discussed. All chemicals were quantified using gas chromatograph with a thermal conductivity detector coupled to a ChemStation and nitrogen as gas carrier, their mass fractions were higher than 0.999. From literature are found two articles from the same system at different temperatures studied here. Experimental data are compared with literature values. Values calculated using the NRTL and UNIQUAC equations are compared with the experimental data and it is found that the UNIQUAC equation fitted the experimental data better than the NRTL model for this ternary system.     

Intermolecular vibronic coupling and energy transfer in a flat molecular aggregate

Summary The migration of excitation within a small flat molecular aggregate composed of identical molecules is described using a Davidov-like model and a mechanism of excitation transfer of Förster type. We consider in this model the changes that take place in the equilibrium position of each molecule upon excitation and construct energy surfaces that describe paths, that is, conditions for excitation localization and transfer that govern, in first-order, the motion of excitation within the aggregate.Presented in part at XVIII Jornadas Chilenas de Química, Santiago, 1989