Examinando por Materia "Combinatorial optimization"
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Ítem A case study on scheduling university timetables using a three-phase matheuristic(Universidad EAFIT, 2022) Rodríguez Garzón, Camilo Andrés; Rivera, Juan CarlosÍtem An approach for printing the maximum possible number of images(Institute of Industrial Engineers, 2017-01-01) Rojas-Santiago M.; Barbosa R.C.; Muthuswamy S.; Hulett M.; Velez-Gallego M.C.; Universidad EAFIT. Departamento de Ingeniería de Producción; Gestión de Producción y LogísticaThis paper considers a real life application of a printing process in a lithographic company that manufactures food packaging bags. The focus area of this problem is to print a variety of 2D images of bags on a surface area for maximum press layouts, with a constraint that the orientation of all bags is fixed and they should be placed parallel to the edges of the impression material. The problem under study is NP-hard and is an extension of the classical knapsack problem. An algorithm to maximize the number of rectangular images of bags that can be placed within the printing material is proposed. The results were compared with a Particle Swarm Optimization (PSO) metaheuristic. Several numerical experiments show that our procedure outperforms the PSO algorithm and improves the lithography's performance.Ítem Diseño de líneas de transporte público con consideraciones ambientales(Universidad EAFIT, 2021) Bolaños Nuñez, Sara Alejandra; Rivera Agudelo, Juan CarlosÍtem Environmental improvement of operating supply chains: a multi-objective approach for the cement industry(Universidad EAFIT, 2017) Cadavid Giraldo, Nora; Vélez Gallego, Mario CésarNowadays companies worldwide face a growing pressure to reduce the environmental impact of their manufacturing activities -- However, the strategies used to achieve this goal are not clearly defined because of their conflicting relations with financial outcomes -- In parallel, globalization trends imply that as companies grow, usually through mergers and acquisitions, their supply chains become more complex -- The environmental improvement of these supply chains imply not only technical retrofit decisions aiming at adopting cleaner production technologies but also decisions regarding the structure of the supply chain itself -- Making these decisions becomes a difficult task because of the large number of variables involved, and the diversity of the interactions among them -- To tackle this problem, this research aims at providing a multi-objective solution approach for making technological retrofit decisions within an operating supply chain, so that both environmental and financial goals are best met -- The proposed solution approach is applied to the case of an operating cement supply chain in Colombia -- Several computational experiments were conducted, obtained results demonstrates that the proposed model is an e effective tool for multi-objective improvement decisions making, towards a more sustainable production processÍtem Estimación de parámetros de un UAV tipo ala volante mediante algoritmos metaheurísticos(Universidad EAFIT, 2014) Benjumea Giraldo, Jorge Alejandro; Vélez Sánchez, Carlos MarioEn este trabajo se describe el desarrollo y prueba de una herramienta en Matlab/Simulink para la estimación de parámetros aerodinámicos de un vehículo aéreo no tripulado (UAV) tipo ala volante a partir de las entradas y salidas observables del sistema, por medio de métodos metaheurísticos -- Para ello se procede con la descripción de un modelo matemático tipo caja gris implementado en Simulink, el cual representa la dinámica general de una aeronave descrita por las derivadas de estabilidad como coeficientes de las fuerzas y momentos inherentes al cuerpo rígido del sistema -- Igualmente se describen los algoritmos metaheurísticos utilizados por el software de estimación (algoritmos genéticos y optimización por enjambre de partículas), los cuales brindan las características más representativas del comportamiento social y evolutivo presente en esta disciplina -- A continuación, se realizan simulaciones con un modelo generador de datos con perturbaciones y un modelo caja gris para la estimación, de manera que se puedan validar la aplicabilidad, eficacia, problemas y bondades del método -- Finalmente, se realizan estimaciones de algunos parámetros en condiciones de vuelo longitudinal y se comparan los resultados con los datos teóricos -- Los resultados, obtenidos a partir de datos simulados con un modelo de un ala volante, muestran que la herramienta, principal aporte de este trabajo, permite estimar los parámetros de una manera amigable y eficiente, con desviaciones y tiempos de cómputo aceptables para once parámetrosÍtem Formulaciones matemáticas y heurísticos simples para solucionar problemas de programación de proyectos con recursos limitados(Universidad EAFIT, 2017) Viveros Gutiérrez, René; Rivera Agudelo, Juan CarlosEn este artículo se trata el Problema de Programación de Proyectos con Recursos Limitados, más conocido como RCPSP (sigla de Resource Constrained Project Scheduling Problem) -- El RCPSP es un problema proveniente del área de programación de producción y de construcción, aunque sus aplicaciones se extienden a diversas áreas del conocimiento -- En esta investigación se evalúan cinco formulaciones matemáticas diferentes que se encuentran en la literatura, se presenta un heurístico simple compuesto por nueve procedimientos de solución independientes y se comparan diferentes propuestas para combinar las soluciones heurísticas obtenidas con la formulación que presenta los mejores resultados -- Entre los métodos resultantes se encuentran tanto soluciones exactas como heurísticas -- El desempeño de los algoritmos es evaluado utilizando las instancias de la libraría PSPLIB de la literatura -- Los resultados obtenidos comprueban que tener buenas soluciones heurísticas puede ser útil para acelerar la convergencia de los modelos matemáticos en la búsqueda de soluciones óptimas -- Sin embargo, el uso de nuevas restricciones, añadidas de manera heurística, en los modelos matemáticos no es garantía de obtener buenas soluciones ni menores tiempos de cómputoÍtem Heuristic to allocate intermediate buffer storage capacities in a production line subject to machine breakdowns(Production and Operations Management Society (POMS), 2013-05-03) Vélez Gallego, Mario César; Jaramillo Jiménez, Jhull Breynner; Universidad EAFIT. Departamento de Ingeniería de Producción; marvelez@eafit.edu.co; Gestión de Producción y LogísticaIn this research proposal we consider a production line subject to random failures at each workstation and operating under a make-to-stock policy -- Every time a workstation fails, a corrective maintenance activity is triggered to repair the workstation -- In order to palliate the effect of the random failures in the performance of the system, intermediate buffers are placed in-between workstations -- An inventory holding cost is associated to eachbuffer -- The research objective in this work is to allocate capacity to each intermediate buffer in the line so that the average cost per time unit is minimized while the average service level is kept above a minimum pre-specified value -- In this paper we assume that unsatisfied demand is lost and the service level is defined as the long term proportion of satisfied demand -- A greedy simulation–based heuristic is presented to find a feasible solution to the problemÍtem Implementación de un filtro de Kalman para la estimación del dinero lavado a través de remesas familiares en Colombia(Universidad EAFIT, 2013) Gómez Restrepo, Jackelyne; Vélez Sánchez, Carlos MarioÍtem Makespan minimization in a job shop with a BPM using simulated annealing(Springer London, 2013-03-08) Rojas Santiago, Miguel; Vélez Gallego, Mario César; Damodaran, Purushothaman; Muthuswamy, Shanthi; Rojas Santiago, Miguel; Vélez Gallego, Mario César; Damodaran, Purushothaman; Muthuswamy, Shanthi; Universidad EAFIT. Departamento de Ingeniería de Producción; marvelez@eafit.edu.co; Gestión de Producción y LogísticaA scheduling problem commonly observed in the metal working industry has been studied in this research effort -- A job shop equipped with one batch processing machine (BPM) and several unit-capacity machines has been considered. Given a set of jobs, their process routes,processing requirements, and size, the objective is to schedule the jobs such that the makespan is minimized -- The BPM can process a batch of jobs as long as its capacity is not exceeded -- The batch processing time is equal to the longest processing job in the batch -- If no batches were to be formed, the scheduling problem under study reduces to the classicaljob shop problem with makespan objective, which is known to be nondeterministic polynomial time-hard -- A network representation of the problem using disjunctive and conjunctive arcs, and a simulated annealing (SA) algorithm are proposed to solve the problem. The solution quality and run time of SA are compared with CPLEX, a commercial solver used to solve the mathematical formulation and with four dispatching rules -- Experimental study clearly highlights the advantages, in terms of solution quality and run time, of using SA to solve large-scale problemsÍtem Metaheurísticos: una alternativa para la solución de problemas combinatorios en Administración de Operaciones(Revista EIA, 2007-12) Vélez, Mario César; Montoya, José Alejandro; Universidad EAFIT. Departamento de Ingeniería de Producción; marvelez@ eafit.edu.co; jmonto36@eafit.edu.co; Gestión de Producción y LogísticaThe scarce diffusion given to the newest techniques for solving complex operations management problems has as a direct consequence that companies lose opportunities to operate at lower costs and higher efficiency -- The objective of this article is to introduce and explain the fundamental ideas behind metaheuristics, a solution technique for combinatorial problems that has received the most attention from the academiccommunity in the last few years -- In order to illustrate these ideas, an example of a classical combinatorial problem in the sequencing of operations area is presented, and a solution algorithm making use of some of these techniques is proposedÍtem A Mixed-Integer Linear Programming Model for a Selective Vehicle Routing Problem(Springer Verlag, 2018-01-01) Posada A.; Rivera J.C.; Palacio J.D.; Posada A.; Rivera J.C.; Palacio J.D.; Universidad EAFIT. Departamento de Ciencias; Matemáticas y AplicacionesIn this paper, we propose a new vehicle routing problem variant. The new problem is a type of selective vehicle routing model in which it is not necessary to visit all nodes, but to visit enough nodes in such a way that all clusters are visited and from which it is possible to cover all nodes. Here, a mixed-integer linear programming formulation (MILP) is proposed in order to model the problem. The MILP is tested by using adapted instances from the generalized vehicle routing problem (GVRP). The model is also tested on small size GVRP instances as a special case of our proposed model. The results allow to evaluate the impact of clusters configuration in solver efficacy. © 2018, Springer Nature Switzerland AG.Ítem A Mixed-Integer Linear Programming Model for a Selective Vehicle Routing Problem(Springer Verlag, 2018-01-01) Posada A.; Rivera J.C.; Palacio J.D.; Posada A.; Rivera J.C.; Palacio J.D.; Universidad EAFIT. Departamento de Ciencias; Modelado MatemáticoIn this paper, we propose a new vehicle routing problem variant. The new problem is a type of selective vehicle routing model in which it is not necessary to visit all nodes, but to visit enough nodes in such a way that all clusters are visited and from which it is possible to cover all nodes. Here, a mixed-integer linear programming formulation (MILP) is proposed in order to model the problem. The MILP is tested by using adapted instances from the generalized vehicle routing problem (GVRP). The model is also tested on small size GVRP instances as a special case of our proposed model. The results allow to evaluate the impact of clusters configuration in solver efficacy. © 2018, Springer Nature Switzerland AG.Ítem On adequate robustness measures for the resource-constrained project scheduling problem(Universidad EAFIT, 2024) Franco Ardila, Julio César; Escudero Marín, Paula Alejandra; Rivera Agudelo, Juan Carlos; Escudero Marín, Paula Alejandra; Rivera Agudelo, Juan CarlosÍtem Optimización de empaques aplicando lineamientos de diseño para el ensamble validado en los contextos de empaque, transporte y desempaque(Universidad EAFIT, 2013) Betancur Muñoz, Pamela; Martínez Cadavid, José Fernando; Duque Lombana, Juan FernandoÍtem Optimización de parámetros y de valores de inicio para el modelo de Holt basado en señales de rastreo(Revista EIA, 2010-12) Castro Zuluaga, Carlos Alberto; Uribe Cadavid, Diana Cecilia; Universidad EAFIT. Departamento de Ingeniería de Producción; ccastro@eafit.edu.co; pfdianauribe@eia.edu.co; Gestión de Producción y LogísticaTime series models are quantitative techniques commonly used to forecast the behavior of variables -- These models include the exponential smoothing with trend or Holt model that requires the definition of the smoothing constants α and β and the initialization values, both required for the model upgrade -- This paper proposes a different way to obtain the parameter values and initial conditions of the Holts model, optimizing the tracking signal range (TSR), in order to achieve a more robust model from the viewpoint of accuracy of the results and historical performance -- Some comparisons between the proposed approach and the traditional methods based on the mean absolute deviation (MAD) and the mean square error (MSE) are provided -- These are the measurestraditionally used to determine the degree of accuracy of a model, and a better model performance is obtainedÍtem Planeación de rutas de vehículos en sistemas con flota privada y pública(Universidad EAFIT, 2013) Toro Hincapié, Ángela María; Vélez Gallego, Mario CésarEn este proyecto se propone un método heurístico de solución para el problema de planeación de rutas de vehículos en sistemas con flota privada y pública, conocido en la literatura como vehicle routing problem with private fleet and common carrier (VRPPC) Este problema de optimización combinatoria consiste en diseñar una serie de rutas donde cada cliente debe ser atendido una vez, ya sea por un vehículo de la flota privada o asignado a una empresa de transporte público de manera que los costos totales de operación sean mínimos. Para su solución se propone un heurístico de búsqueda de vecindario variable, conocido en la literatura como VNS, que parte de una solución inicial para luego mejorarla por medio de la exploración sistemática de múltiples vecindarios. Para evaluar el desempeño del heurístico propuesto se compararon los resultados obtenidos con los de otros métodos disponibles en la literatura. Los experimentos computacionales demuestran que el heurístico propuesto es efectivo en encontrar soluciones de buena calidad a un costo computacional razonable.Ítem Surveillance Camera Location Models on a Public Transportation Network(Universidad EAFIT, 2017-04-24) Solano-Pinzón, Nathaly; Pinzón-Marroquín, David; Guerrero, William Javier; Escuela Colombiana de Ingeniería Julio GaravitoÍtem A variable neighborhood search algorithm to minimize the total weighted tardiness on a batch processing machine(Revista Ingeniería Industrial, 2011-08-11) López Jiménez, Juan Diego; Vélez Gallego, Mario César; López Jiménez, Juan Diego; Vélez Gallego, Mario César; Universidad EAFIT. Grupo de Investigación Gestión de Producción y Logística; Universidad EAFIT. Departamento de Ingeniería de Producción; marvelez@eafit.edu.co; Gestión de Producción y LogísticaThis paper presents the results of a research project conducted to solve a production scheduling problem observed in a system in which meeting customer due dates is the primary objective -- Each job to be scheduled is defined by its processing time, ready time, due date, weight and size -- The Batch Processing Machine (BPM) can process several jobs simultaneously as a batch as long as its capacity is not violated -- The processing time of a batch is the largest processing time among the jobs in the batch, and the batch ready time is the largest ready time among the jobs in the batch -- Given that the problem is NP-hard we propose a Variable Neighborhood Search (VNS) heuristic to minimize the total weighted tardiness on a single BPM -- The computational experiments conducted to assess the quality of the solutions found show that in a computational time restricted to a maximum of 30 minutes, the proposed heuristic finds solutions considerably better than the solutions obtained after implementing a mixed integer programming model available in the literature in a commercial solver