Meta-raps: Un enfoque de solución eficaz para problemas combinatorios

Este artículo introduce una metaheurística denominada Meta-RaPS (Meta-heuristic for Randomized Priority Search) para problemas de optimización combinatoria. Meta-RaPS es un sistema de múltiples iteraciones que balancea el uso de heurísticas de construcción y mejoramiento de soluciones en cada iteración. Una de las características principales de Meta-RaPS es la dosificación del uso de aleatoriedad como mecanismo para mejorar heurísticas de construcción. En este artículo se presenta el enfoque y se entregan resultados de aplicaciones a cuatro problemas de optimización combinatoria. Este artículo es un extracto de la tesis doctoral titulada: “Meta-RaPS: An Effective Solution Approach for Combinatorial Problems” (Moraga, 2002). La tesis representa la culminación de una investigación desarrollada por las Universidades de Central Florida y Louisville en un esfuerzo por extender un enfoque heurístico clásico denominado COMSOAL a problemas combinatorios. (Nota: esta tesis doctoral es una de las tres tesis que recientemente obtuvieron el Premio “2003 Pritsker Doctoral Dissertation Award”, otorgado por el Institute of Industrial Engineering en la última Conferencia de Investigación en Ingeniería Industrial celebrada en Portland, Oregon, USA, Mayo 2003.

Garden Table

A handicapped accessible work table having a horizontal transparent table top, with removable plant trays, cushioned arm rest edges, and vertical legs with caster wheels. The tabletop is supported by parallel identical one piece aluminum franes. Each frame is formed from bending an aluminum bar at several points. Each side frame has vertical legs that have upper portions that bend to form supports for the table top and an upwardly bent mid-section that passes through a slot in the table top. A cross-brace bar connects the top of the opposite upwardly bent mid-sections of each frame to give the table structural support above the tabletop. Thus, wheelchairs have no obstacles when positioned about and under the edges of the table. An ultraviolet light source can be connected to the cross-brace bar so that plantings in the trays can have an adequate light source for growth when the table is used for gardening. The tabletop can include a solid working surface. The tabletop can be used fo

La decisión de localización en la cadena de suministro

En esta publicación nosotros mostramos la importancia de la decisión de localización en el diseño de la cadena de suministro. Luego revisamos algunos modelos clásicos de localización como P-Center y P-Mediana además, revisamos dos modelos de localización que permiten incorporar otras decisiones de la cadena de suministro, como: Multi-product capacitated plant and warehouse location y warehouse location-routing. Para, por último, aplicar los modelos revisados en esta publicación a un caso en estudio.In this paper we show the importance of the facility location decisions in the supply chain design. Then we review some classical models of facility locations like P-Center and P-Mediana, also we review two models of facility locations what allow incorporate other supply chain decisions like: Multi-product capacitated plant and warehouse location and warehouse location-routing. For finally apply these review models in this paper to a case study

INTRODUCCIÓN DE ELEMENTOS DE MEMORIA EN EL MÉTODO SIMULATED ANNEALING PARA RESOLVER PROBLEMAS DE PROGRAMACIÓN MULTIOBJETIVO DE MÁQUINAS PARALELAS INTRODUCTION OF MEMORY ELEMENTS IN SIMULATED ANNEALING METHOD TO SOLVE MULTIOBJECTIVE PARALLEL MACHINE SCHEDULING PROBLEMS

El presente artículo introduce una variante de la metaheurística simulated annealing, para la resolución de problemas de optimización multiobjetivo. Este enfoque se demonina MultiObjective Simulated Annealing with Random Trajectory Search, MOSARTS. Esta técnica agrega al algoritmo Simulated Annealing elementos de memoria de corto y largo plazo para realizar una búsqueda que permita balancear el esfuerzo entre todos los objetivos involucrados en el problema. Los resultados obtenidos se compararon con otras tres metodologías en un problema real de programación de máquinas paralelas, compuesto por 24 trabajos y 2 máquinas idénticas. Este problema corresponde a un caso de estudio real de la industria regional del aserrío. En los experimentos realizados, MOSARTS se comportó de mejor manera que el resto de la herramientas de comparación, encontrando mejores soluciones en términos de dominancia y dispersión.This paper introduces a variant of the metaheuristic simulated annealing, oriented to solve multiobjective optimization problems. This technique is called MultiObjective Simulated Annealing with Random Trajectory Search (MOSARTS). This technique incorporates short an long term memory concepts to Simulated Annealing in order to balance the search effort among all the objectives involved in the problem. The algorithm was tested against three different techniques on a real life parallel machine scheduling problem, composed of 24 jobs and two identical machines. This problem represents a real life case study of the local sawmill industry. The results showed that MOSARTS behaved much better than the other methods utilized, because found better solutions in terms of dominance and frontier dispersion

Towards a Methodology for Monitoring and Analyzing the Supply Chain Behavior

In this chapter, the authors present general steps towards a methodology that contributes to the advancement of prediction and mitigation of undesirable supply chain behavior within short- and long- term horizons by promoting a better understanding of the structure that determines the behavior modes. Through the integration of tools such as system dynamics, neural networks, eigenvalue analysis, and sensitivity analysis, this methodology (1) captures the dynamics of the supply chain, (2) detects changes and predicts the behavior based on these changes, and (3) defines needed modifications to mitigate the unwanted behaviors and performance. In the following sections, some background information is given from literature, the general steps of the proposed methodology are discussed, and finally a case study is briefly summarized. © 2008, IGI Global

Towards A Methodology For Monitoring And Analyzing The Supply Chain Behavior

In this chapter, the authors present general steps towards a methodology that contributes to the advancement of prediction and mitigation of undesirable supply chain behavior within short- and long- term horizons by promoting a better understanding of the structure that determines the behavior modes. Through the integration of tools such as system dynamics, neural networks, eigenvalue analysis, and sensitivity analysis, this methodology (1) captures the dynamics of the supply chain, (2) detects changes and predicts the behavior based on these changes, and (3) defines needed modifications to mitigate the unwanted behaviors and performance. In the following sections, some background information is given from literature, the general steps of the proposed methodology are discussed, and finally a case study is briefly summarized. © 2008, IGI Global

Addressing Complexity Using Distributed Simulation: A Case Study In Spaceport Modeling

As the size, complexity, and functionality of systems to model and simulate continue to increase, benefits such as interoperability and reusability enabled by distributed discrete-event simulation are of interest, especially for distributed manufacturing and enterprise engineering. The High Level Architecture (HLA), a standard distributed simulation environment, is one technology that enables the interconnection of distributed model components. Many applications in industry are developed by a variety of Commercial Off-The-Shelf (COTS) simulation tools, which require some form of gateway to integrate the models into the HLA component-based simulation. This paper summarizes a study conducted to integrate COTS simulation models using gateway tools and visualization of the system states running as part of other simulation models under HLA. The study focused on the prototype of a virtual engineering environment, called the Virtual Test Bed, designed to analyze operations of current and future space vehicles, spaceports, and ranges as a distributed simulation environment

Heurística constructiva visionaria para el problema de máquinas paralelas no relacionadas con tiempos de setup dependientes de la secuencia

This paper presents a look-ahead constructive heuristic for solving the unrelated parallel machine problem with sequence dependent setup times, where the objective is to minimize the completion time of the last job, or makespan. This is an NP-hard problem. Although a variety of practical situations can be modeled using this problem, still a modest number of articles devoted to it can be found in literature. The constructive heuristic proposed in this paper has a look-ahead mechanism based on a saving criterion, which permits to improve the quality of solutions against another constructive heuristic rule already reported in literatureEste artículo presenta una heurística constructiva visionaria para resolver el problema de máquinas paralelas no relacionadas con tiempos de setup dependientes de la secuencia, donde el objetivo es minimizar el tiempo de completación del último trabajo, o makespan. Este es un problema NP-hard. A pesar de que una gran variedad de situaciones prácticas pueden ser modeladas usando este problema, existe una pequeña cantidad de artículos desarrollados que se puede encontrar en la literatura. La heurística constructiva propuesta en este artículo posee un mecanismo visionario basado en un criterio de ahorro, que permite mejorar la calidad de las soluciones que se obtienen al comparar este enfoque con otras reglas heurísticas encontradas en la literatura