Revista de Matemáticas 21(2)
URI permanente para esta colección
Examinar
Envíos recientes
Ítem MORTALITY AMONG YOUNG NICARAGUAN IMMIGRANTS TO COSTA RICA: AN APPLICATION OF GEOGRAPHICALLY WEIGHTED STATISTICAL REGRESSION(2014-07-01 00:00:00) Bonilla Carrión, Róger Enrique; Chavarría, Juan B.This paper applies a geographically weighted statistical regression (GWR) model to young Nicaraguan immigrant homicides in Costa Rica during the period 1998-2008 and identifies possible covariates. The pa- rameters for the GWR model are:Yi(g)=β0(g)+β1(g)x1 +β2(g)x2 +...+βk(g)xk +ε, which may be obtained from the solution ofβ(g) = (XT W (g)X)−1 XT W (g)Y.The GWR model is a more adequate model than the classic models, such as the log-linear Poisson model. In the GWR model, poverty was the most significant variable. The map of the estimators associated with the percentage of poor households suggests that the relationship between poverty and mortality by homicide for young Nicaraguan immigrants is stronger in the Caribbean region and neighboring zones. When the GWR model was run for homicides among young Costa Ricans, this effect was not observed, as it was among Nicaraguan immigrants.Ítem INTERACTIVE MULTIOBJECTIVE TABU/SCATTER SEARCH BASED ON REFERENCE POINT(2014-07-01 00:00:00) Beausoleil, Ricardo P.This paper presents multiobjective tabu/scatter search architecture with preference information based on reference points for problems of contin- uous nature. Features of this new version are: its interactive behavior, its deterministic approximation to Pareto-optimality solutions near the refer- ence point, and the possibility to change progressively the reference point to explore different preference regions. The approach does not impose any restrictions with respect to the location of the reference points in the objective space. On 2-objective to 10-objective optimization test problems the modified approach shows its efficacy and efficiency to find an adequate non-dominated set of solutions in the preferred region.Ítem GEODESIC DISTRIBUTION IN GRAPH THEORY: KULLBACK-LEIBLER-SYMMETRIC(2014-07-01 00:00:00) González, José Alejandro; Cascone, Marcos HenriqueKullback-Leibler information allow us to characterize a family of dis- tributions denominated Kullback-Leibler-Symmetric, which are distance functions and, under some restrictions, generate the Jensen’s equality shown by [1], in this paper denominated Jensen-Equal. On the other hand, [5] and [7] showed that graph theory gives conditions to define a new mea- surable space and, therefore, new distances, in particular, the distance characterized by [2], denominated Geodesic Distance. The interaction of these ideas allow us to define a new distribution, denominated Geodesic Distri- bution which, under graph theory as center and radius of a graph, we can to develop optimization methodologies based in probabilities of attendance. We obtain many applications and the proposal method is very adaptive. To illustrate, we apply this distribution in spatial statistics.Ítem MATHEMATICAL MODEL FOR TOXIN TRANSPORT IN A MARINE FOOD CHAIN(2014-07-01 00:00:00) Arbeláez A., Daniel; Ruiz V., Jorge MauricioSome cases of poisoning by consumption of contaminated fish, like the Ciguatera poisoning, occur unexpectedly and they are not easy to detect previously since the fish that carry the toxin do not have appearance and/or symptoms of illness. In this paper a mathematical model for transport and acumulation of a toxin through a food chain is proposed. The model is a stiff system of ordinary differential equations that describes the dynamic. We propose a numerical scheme that combines a third-order Runge-Kutta method and trapezoidal rule to avoid the stiffness of the system. Several scenarios of toxin outbreaks are simulated; the results show that the time it takes to the toxin disappear in the trophic chain, depends on the state of the dynamics population at the time of the outbreak. This information can be used to set a ban on fishing until the toxin be reduced to harmless levels for the human health.Ítem NONLINEAR FILTERS TO RECONSTRUCT ELECTROCARDIOGRAM SIGNALS(2014-07-01 00:00:00) Infante, Saba; Sánchez, Luis; Cedeño, FernandoECG signals have been used in cardiac pathology to detect disease heart. The main objective of this paper is to propose signal filtering techniques to reduce noise, extract information, to reconstruct the states and properties Morphological heartbeat. In addition, aims to represent the cardiac activity in a simple, informative, accurate, and easy to interpret for cardiologists. To achieve these objectives are proposed to implement the following algo- rithms: generic particle filter (GPF), resampling particle filter (RPF), un- scented Kalman filter (UKF) and the unscented particle filter (UFP) con- sidering the basic structure of synthetic dynamic model McSharry et al. (2003) [16]. The results show that filter performs very well in the recon- struction of the states heart rate system, while introducing small variations in the variances of the noises of the equation observation, ie, the methods have the ability to reproduce the original signal the synthetic model simu- lated and the synthetic model with real data accurately. Finally evaluates the performance of the filters in terms of the empirical standard deviation, showing little variability among the estimated errors and fast execution of algorithms.Ítem SUPERIOR ORDER G -STRUCTURES(2014-07-01 00:00:00) Rosales Ortega, JoséIn this article we study the basic facts about superior order G-structures, then we show that the set of infinitesimally automorphisms of a geometric G-structure is a closed Lie group.Ítem LENSING PROPERTIES OF THE EINASTO PROFILE IN TERMS OF THE MEIJER G FUNCTION(2014-07-01 00:00:00) Retana Montenegro, Edwin; Frutos Alfaro, FranciscoIn N-body simulations of cold dark matter, it has been found that three-parameter models, particularly the Einasto profile, yield better fits to a wide range of dark matter haloes than two parameter models like the Navarro-Frenk-White profile. Recently, the analytical properties of the Einasto profile has been studied, allowing closed expressions for its surface mass density and lensing properties in terms of the Fox H and Meijer G functions, using a Mellin transform formalism. These expressions are valid for all values of the Einasto index in terms of the Fox H function, and valid for integer and half-integer values of Einasto index in terms of the Meijer G function. In this paper, we derive expressions for lensing properties of the Einasto profile for all rational values of the Einasto index in terms of the Meijer G function. Equivalency between these expressions and other recent results is also discussed