# Revista de Matemáticas 8(1)

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Ítem Ajuste de un modelo VAR como predictor de los campos de anomalías de precipitación en centroamérica(2012-04-26 00:00:00) Alfaro Martínez, Eric J.; Soley Alfaro, Francisco JavierMás... Cluster analysis was used to identify common patterns of 15 precipitation points of the region, using their anomaly time series as grouping variables. Five clusters where identified through this process. A Vector Auto Regressive model was fitted tothe data to quantify the ocean-atmosphere interaction between the oceanic indices of the Tropical North and South Atlantic, the Tropical Eastern Pacific and the first empirical orthogonal functions of the regional rainfall clusters. This model shows that the Tropical North Atlantic has the largest influence over the region when compared with the influence of the other indices, having positive correlation with all the rainfall. The Tropical South Atlantic and the Niño 3 indices, instead, were found to have no correlation with the rainfall of the region when an stationary model is fitted. This work shows that the variability of the Tropical North Atlantic sea surface temperature anomaly presents stronger associations with the Central America rainfall than the Tropical Eastern Pacific sea surface temperature anomaly. The association is mainly related to the degree of development of the Tropical Upper Tropospheric Trough.Más... Ítem Experiencias con un nuevo índice de falta de ajuste en Tablas de Contingencia(2012-04-26 00:00:00) González Debén, Adalberto; Méndez Ramírez, IgnacioMás... Rudas, Clogg and Lindsay, en 1994, proposed a new index of lack of fit for contingency table analysis. For a contingency table P with N cells, and a model H, the new index is defined as the smallest \pi that satisfies the equationP_h=(1-\pi)\Pi_{1h}+\pi\Pi_{2h}, h=1,...,Nwith 0 \leq \pi \leq 1, and \Pi_1 and \Pi_2 the tables of probabilities for each latent class. The model H applies to \Pi_1 but not impose any restrictions on \Pi_2. The interpretation of the index of lack of fit is the proportion of individuals of the population intrinsically outside model H. In this work we propose the analysis of the second latent class to the study of the causes of lack of fit of a model and to detect outlying cells. At the same time, we propose the new index of lack of fit as a concepto of non-independence in the two simple configural frequency analysisMás... Ítem Isomorfismo de Conjuntos de Relaciones(2012-04-26 00:00:00) Bulat, MijailMás... It is recommended to use a solving method for relations sets in order to solve the isomorphism problem. This method allows to solve the same problem for big size graphs, homogeneous graphs, graph systems, k-signs logic functions and their systems.Más... Ítem On the Distribution of non-attacking Bishops on a Chessboard C(2012-04-26 00:00:00) Ansari Wahid, ShanazMás... It is shown how the placement of non-attacking bishops on a chessboard C is related to the matching polynomial of a bipartite graph. Reduction algorithms for finding the bishop polynomial of C are given. We interpret combinatorially the coefficients of this polynomial and construct some interesting boards. Some applications of the bishop polynomials are given.Más... Ítem Deformaciones isométricas infinitesimales de superficies multidimensionales ensambladas(2012-04-26 00:00:00) Markov, Pavel; Trejos, OlmanMás... The article introduces the concept of multidimensional pasted surfaces and considers the case of different dimensions in the surfaces to be pasted. Infinitesimal deformations of such surfaces are also considered. In a general way, it is proved that, if the surface pieces have first order infinitesimal rigidity, then the pasted surface contains infinitesimal rigidity of first order.Más... Ítem Fórmulas aproximadas del tipo Lévy-Khintchine(2009-02-19 00:00:00) Lobo Segura, JaimeMás... The problem of approximation of the characteristic functions defined by a PII in near intervals is studied. We establish some general properties of these functions and of the associated complex matingales, which, with the aid of the decomposition results in [4] and [5], lead to approximate formula of the Lévy-Khintchine type. As a consequence, we obtain the exact law for PII processes in continuous timeMás... Ítem Detecting constraint redundancy in 0-1 linear programming problems(2009-02-19 00:00:00) Muñoz, SusanaMás... In this paper we present a procedure for obtaining upper bounds on a linear function by means of certain families of packings, coverings and special ordered sets. We also present a new method for detecting redundant constraints in 0-1 linear programming problems based on these bounds that allows consideration of several constraints jointly. Furthermore, we show a redundancy situation which is detected by this new method, but not by the traditional methods, which consider the constraints individually.Keywords: Redundant constraints, packings, coverings, special ordered sets, admissible familiesMás...