El lunes, 15 de Diciembre (ver horario) hay un nuevo seminario en el seminario IMUS del Edificio Celestino Mutis (Campus de Reina Mercedes). Las dos charlas son las siguientes.

Ponente: Antonio Manuel Rodríguez Chía
Autores: Martine Labbé y Antonio Manuel Rodríguez Chía.
Resumen:
In this paper we consider the problem of determining a hyperplane that separates, as “well” as possible, two sets of points in Rn. We consider a Support Vector Machine (SVM) approach by fixing in advance the maximal number of features that can be used in the process what implies a sort of feature selection. In order to do that, first, we provide a Mixed Integer Linear Programming formulation of the problem. Second, we study the structure of the problem and analyze different alternatives to solve it.  We run experiments on real-world benchmark datasets, comparing our approach with well-known techniques coming from Machine Learning area obtaining very competitive results.

Ponente: Valentina Gratta
Autores: Valentina Gratta, Isabella Lari, Justo Puerto,  Federica Ricca y Andrea Scozzari.
Resumen:
We consider a connected graph G with n vertices, p of which are centers, while the remaining ones are units; moreover for each unit-center pair there is a fixed assigning cost. We study the problem of partitioning G into p connected components such that each component contains only one center (p-centered partition). The proposal heuristic is based on local changes of a spanning tree of G; at each iteration it is applied an algorithm that solve the problem exactly in polynomial time.

El jueves, 20 de Marzo (ver horario) hay un nuevo seminario y reunión de coordinación en el campus de Jerez (ver ruta desde Sevilla) de la Universidad de Cádiz. El seminario tendrá lugar en el Seminario 2.780 en el Edificio de despachos y seminarios, 2ª planta. Las dos charlas son las siguientes.

Ponente: Antonia Castaño
Resumen:
Records are observations whose values are larger than all the previous ones. In recent years several generalizations of the concept of record have appeared in the literature, among these we can cite near records, epsilon-repeated records, delta-exceedance records, delta-records and geometric records. In this work we consider a continuous and strictly increasing real function psi, and introduce a new generalization of the concept of record, the upper psi-exceedances of records as those observations exceeding the function psi of the previous psi-exceedance. In the particular case of the identity function we obtain the ordinary record values, other choices provide some record-like variables of  interest like peaks over (fixed) threshold (POT), arithmetic and geometric exceedances. We study the basic distribution theory of psi-exceedances and in particular we investigate the cases of some common distributions like exponential, Pareto, Weibull among others.
Finally, we point out applications of these concepts to the theory of particle counters and telecommunications.

Ponente: Diego Ponce
Autores: Martine Labbé, Diego Ponce y Justo Puerto
Resumen:
El problema discreto de la mediana ordenada, conocido por su acrónimo en inglés DOMP, permite estudiar los problemas de localización discreta a través de una única formulación. En esta charla vamos a ver las nuevas formulaciones que han surgido basándose en similitudes con algunos de los conocidos como scheduling problems, las cuales nos han reportado grandes avances en el estudio poliédrico del problema. También introduciremos una formulación cuyas variables están basadas en un número exponencial de conjuntos, lo que nos llevará a aplicar la técnicas de generación de columnas y Branch & Price en nuestro problema.