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Merida, Venezuela

The University of the Andes is the second-oldest university in Venezuela, whose main campus is located in the city of Mérida, Venezuela. ULA is the largest public university in the Venezuelan Andes, having one of the largest student bodies in the country. Wikipedia.


Aguilar J.,University of Los Andes, Venezuela
Applied Soft Computing Journal | Year: 2013

We study in this work the problem of adaptation on cognitive maps (CMs). We review different approaches of adaptation for CM, based on the idea that the causal relationships of the CM change during their phase of execution (runtime). Particularly, we study three dynamic causal relationships: the first one where the relationships between the concepts are defined as fuzzy rules, and the concepts and the relationship are fuzzy variables; the second one where mathematical models that describe the real system are used to define the causal relationships; and finally, in the last one the causal relationships are defined by generic logic rules based on the state of the concepts of the map. Each one can be used to model different types of systems, because each one exploits specific characteristics of the modeled system. These approaches are tested in different problems, giving very good results, and demonstrating that the utilization of CM as dynamic models is reliable and good. © 2012 Elsevier B.V.


Herrera L.,University of the Basque Country | Barreto W.,University of Los Andes, Venezuela
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We set up in detail the general formalism to model polytropic general relativistic stars with anisotropic pressure. We shall consider two different possible polytropic equations, all of which yield the same Lane-Emden equation in the Newtonian limit. A heuristic model based on an ansatz to obtain anisotropic matter solutions from known solutions for isotropic matter is adopted to illustrate the effects of the pressure anisotropy on the structure of the star. In this context, the Tolman mass, which is a measure of the active gravitational mass, is invoked to explain some features of the models. Prospective extensions of the proposed approach are pointed out. © 2013 American Physical Society.


Herrera L.,University of the Basque Country | Barreto W.,University of Los Andes, Venezuela
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We set up the general formalism to model polytropic Newtonian stars with anisotropic pressure. We obtain the corresponding Lane-Emden equation. A heuristic model based on an ansatz to obtain anisotropic matter solutions from known solutions for isotropic matter is adopted to illustrate the effects of the pressure anisotropy on the structure of the star. In particular, we calculate the Chandrasekhar mass for a white dwarf. It is clearly displayed how the Chandrasekhar mass limit changes depending on the anisotropy. Prospective astrophysical applications of the proposed approach are discussed. © 2013 American Physical Society.


The effect of group improvisational music therapy on depression in adolescents and adults with substance abuse was investigated. It was hypothesized that group improvisational music therapy would relieve depressive symptoms. Twenty-four Spanish-speaking patients receiving treatment for substance abuse at Fundación José Felix Ribas (FJFR) in Mérida-Venezuela participated in the study. Participants completed the Beck Depression Inventory (BDI) and the Hamilton Rating Scale for Depression (HRSD) before being randomly assigned to experimental or control groups, each consisting of three cohort groups recruited over a nine-month period. The experimental group received 12 group improvisation sessions over a three-month period, along with the standard treatment program provided at the facility, and the control group received only the standard treatment program. Post-test measures were completed at the end of each three-month treatment cycle. Differences between the groups (pre-test-post-test scores) were calculated (Mann-Whitney U Test). Results showed that both groups were equally matched on all pre-test measures. As for post-test measures, significant differences were found between the groups on HRSD but not the BDI. The experimental group was significantly less depressed after treatment than the control group, as measured by the HRSD. Improvisational music therapy led to statistically significant greater improvements in psychologist-rated depression (HRSD) when compared with the regular treatment program alone; improvisational music therapy had a clinically significant effect. Among limitations of the study were: a small sample size and the absence of a depression assessment tool for substance abuse. © 2011 The Grieg Academy Music Therapy Research Centre.


Paredes J.L.,University of Los Andes, Venezuela | Arce G.R.,University of Delaware
IEEE Transactions on Signal Processing | Year: 2011

In this paper, we propose a simple and robust algorithm for compressive sensing (CS) signal reconstruction based on the weighted median (WM) operator. The proposed approach addresses the reconstruction problem by solving a l 0-regularized least absolute deviation (l0-LAD) regression problem with a tunable regularization parameter, being suitable for applications where the underlying contamination follows a statistical model with heavier-than-Gaussian tails. The solution to this regularized LAD regression problem is efficiently computed, under a coordinate descent framework, by an iterative algorithm that comprises two stages. In the first stage, an estimation of the sparse signal is found by recasting the reconstruction problem as a parameter location estimation for each entry in the sparse vector leading to the minimization of a sum of weighted absolute deviations. The solution to this one-dimensional minimization problem turns out to be the WM operator acting on a shifted-and-scaled version of the measurement samples with weights taken from the entries in the measurement matrix. The resultant estimated value is then passed to a second stage that identifies whether the corresponding entry is relevant or not. This stage is achieved by a hard threshold operator with adaptable thresholding parameter that is suitably tuned as the algorithm progresses. This two-stage operation, WM operator followed by a hard threshold operator, adds the desired robustness to the estimation of the sparse signal and, at the same time, ensures the sparsity of the solution. Extensive simulations demonstrate the reconstruction capability of the proposed approach under different noise models. We compare the performance of the proposed approach to those yielded by state-of-the-art CS reconstruction algorithms showing that our approach achieves a better performance for different noise distributions. In particular, as the distribution tails become heavier the performance gain achieved by the proposed approach increases significantly. © 2011 IEEE.

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