José Ismael Gutiérrez

A new characterization for the dynamic lot size problem with bounded inventory

In this paper, we address the dynamic lot size problem with storage capacity. As in the unconstrained dynamic lot size problem, this problem admits a reduction of the state space. New properties to obtain optimal policies are introduced. Based on these properties a new dynamic programming algorithm is devised. Superiority of the new algorithm to the existing procedure is demonstrated. Furthermore, the new algorithm runs in O(T) expected time when demands vary between zero and the storage capacity. Computational results are reported for randomly generated problems.

A polynomial algorithm for the production/ordering planning problem with limited storage

This paper concerns the dynamic lot size problem where the storage capacity is limited and shortages are allowed. The planning horizon is divided into T periods and, for each period, concave functions to define the holding/stockout and production costs are considered. It is proved that the results derived in a previous work for the dynamic lot size problem assuming time-varying storage capacities remain valid for the case with backlogging.

The Multiscenario Lot Size Problem With Concave Costs

Abstract The dynamic single-facility single-item lot size problem is addressed. The finite planning horizon is divided into several time periods. Although the total demand is assumed to be a fixed value, the distribution of this demand among the different periods is unknown. Therefore, for each period the demand can be chosen from a discrete set of values. For this reason, all the combinations of the demand vector yield a set of different scenarios. Moreover, we assume that the production/reorder and holding cost vectors can vary from one scenario to another. For each scenario, we consider as the objective function the sum of the production/reorder and the holding costs. The problem consists of determining all the Pareto-optimal or non-dominated production plans with respect to all scenarios. We propose a solution method based on a multiobjective branch and bound approach. Depending on whether shortages are considered or not, different upper bound sets are provided. Computational results on several randomly generated problems are reported.

The biobjective undirected two-commodity minimum cost flow problem

We address the two-commodity minimum cost flow problem considering two objectives. We show that the biobjective undirected two-commodity minimum cost flow problem can be split into two standard biobjective minimum cost flow problems using the change of variables approach. This technique allows us to develop a method that finds all the efficient extreme points in the objective space for the two-commodity problem solving two biobjective minimum cost flow problems. In other words, we generalize the Hus theorem for the biobjective undirected two-commodity minimum cost flow problem. In addition, we develop a parametric network simplex method to solve the biobjective problem.

A new bound and an O( mn ) algorithm for the undesirable 1-median problem (maxian) on networks

The problem of locating an undesirable facility on a network with n nodes and m edges so as to maximize its total weighted distance to all nodes is addressed. We propose a new upper bound to the problem. Likewise, we develop a new algorithm in O(mn) time which dynamically updates this new upper bound. Computational results on low and high dense networks, as well as planar networks, are presented.

An O ( T log T ) Algorithm for the Dynamic Lot Size Problem with Limited Storage and Linear Costs

In this paper the dynamic lot size problem with time varying storage capacities and linear costs is addressed. Like in the uncapacitated version, this problem can be formulated as a network flow problem. Considering the properties of the underlying network, we devise an O(T log T) greedy algorithm to obtain optimal policies and we report computational results for randomly generated problems.

Oficio de Ángel, de Miguel Barnet: la memoria en un espejo fragmentado

La evocacion infantil y juventil le ha servido al escritor cubano Miguel Barnet como recurso para articular un discurso fragmentado que oscila entre el genero testimonial y la escritura autobiografica. Oficio de Angel (1989) es un testimonio que adopta la forma de la ficcion y una novela que recrea enganosamente la vida real.

Por una revisión de los cuentos de Manuel Gutiérrez Nájera

Manuel Gutierrez Näjera (1859-1895) ocupa un puesto estelar en las letras mexicanas e hispanoamericanas de finales del siglo XIX. De ello no cabe la menor duda. Asi lo han juzgado tanto los contemporaneos del autor que leyeron con gusto sus escritos publicados en revistas y periodicos de la epoca como la multidud de criticos posteriores que han indagado en su dispersa obra. Ya en fechas proximas a su muerte, acaecida en 1895, empieza a perfilarse toda una retahüa de juicios ditirämbicos que ha gozado de enorme fortuna. Entre los mäs conocidos-y que aun hoy se siguen repitiendo a la hora de ponderar su produccion literaria, asi como la singularidad de su temple artistico y personal-esta la idea de que el escritor es un maestro en el cultivo de la cronica, que su estilo posee una elegancia solo matizada por la gracia, que es un cosmopolita influenciado por los autores franceses del momento, que-aunque espiritu exquisite-siente tambien compasion por los seres mas necesitados, entre ellos las mujeres y los niftos, etc., etc. Todos estas valoraciones y otras, sostenidas una y otra vez por la critica hasta la actualidad, no nos dan una idea cabal del alcance de la obra najeriana, de sus peculiaridades. El lugar comun, aunque no siempre carente de bases reales pero si necesitado de argumentos que lo justifiquen, dificilmente puede ser cuestionado en una situacion de precariedad. Porque sucede que hasta hace algunos anos el conocimiento de la obra de nuestro autor, que aun en parte permanece inedita en forma de libro, era bastante escaso debido a que la totalidad de la misma vio la luz en su dia en las päginas efimeras de diversas publicaciones periodicas. De ahi que con el tiempo cayera parcialmente en el olvido, cuando no en la simplification