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Ítem 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 solverÍtem 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 The impact of supply chain decisions, using dynamic systems, of an aquatic garment manufacturing company(Revista Ingeniería Industrial, 2010-06) Peña Zapata, Gloria Elena; Pineda Toro, Mauricio; Escalante Ochoa, Daniel; Ramírez Echeverri, Sergio A.; Peña Zapata, Gloria Elena; Pineda Toro, Mauricio; Escalante Ochoa, Daniel; Ramírez Echeverri, Sergio A.; Universidad EAFIT. Grupo de Investigación Gestión de Producción y Logística; Universidad EAFIT. Departamento de Ingeniería de Producción; sramire@eafit.edu.co; Gestión de Producción y LogísticaThis article shows the supply chain model of the company Creaciones Nadar S.A. Thatmanufactures aquatic sports garments -- The chain links are the clients, the store, the warehousing, the internal and satellite plants and raw material supply -- The supply chain of Creaciones Nadar S.A. is a complex system given the different agents that form the feedback structures and delayed effects on behaviors -- The supply chain has different dynamic behaviors generated by changes in external factors such as garment’s demand, number of required workers in the company’s plant, the warehousing, and the store, among other -- A dynamic system methodology and the software Ithink® were used to model the chain; moreover, different scenarios were analyzed using simulation and taking into account the most representative variables to be modified -- The obtained results allow Creaciones Nadar S.A. to determine policies and parameters and to obtain the best kind of benefits for the companyÍtem Clasificación ABC Multicriterio: tipos de criterios y efectos en la asignación de pesos(2011-11-28) Vélez Gallego, Mario César; Castro Urrego, Jaime Andrés; Castro Zuluaga, Carlos Alberto; Vélez Gallego, Mario César; Castro Urrego, Jaime Andrés; Castro Zuluaga, Carlos Alberto; Universidad EAFIT. Grupo de Investigación Gestión de Producción y Logística; Universidad EAFIT. Departamento de Ingeniería de Producción; ccastro@eafit.edu.co; marvelez@eafit.edu.co; jcastrou@eafit.edu.co; Gestión de Producción y LogísticaABC classification is traditionally performed in companies in order to define and implement an inventory control policy for all the products within the same category -- The classification of products into categories is done according to their importance or relevance for some kind of criteria, usually the consumption or annual usage (for raw materials or spare parts) or demand or annual sales (for finished goods) using the well-know Pareto´s principle -- However, sometimes it is highly recommended and necessary to use additional criteria in order to make a more effective differentiation of stocks -- Therefore, this paper presents a collection of useful criteria for ABC classification; describes its meaning and how it must be measured -- Additionally, an example of a critical stage of a classification ABC with three criteria, shows that depending on the weights assigned and the characteristics of the products included in the classification process, the validity of some criteria are lost in the analysisÍtem Minimizing makespan in a two-machine no-wait flow shop with batch processing machines(Springer-Verlag, 2012-11-01) Muthuswamy, Shanthi; Vélez Gallego, Mario César; Rojas Santiago, Miguel; Maya Toro, Jairo; Muthuswamy, Shanthi; Vélez Gallego, Mario César; Rojas Santiago, Miguel; Maya Toro, Jairo; Universidad EAFIT. Grupo de Investigación Gestión de Producción y Logística; Universidad EAFIT. Departamento de Ingeniería de Producción; smuthuswamy@niu.edu; marvelez@eafit.edu.co; jmaya@eafit.edu.co; miguelrojas@uninorte.edu.co; Gestión de Producción y LogísticaGiven a set of jobs and two batch processing machines (BPMs) arranged in a flow shop environment,the objective is to batch the jobs and sequence the batches such that the makespan is minimized. The job sizes, ready times, and processing times on the two BPMs are knowN -- The batch processing machines can process a batch of jobs as long as the total size of all the jobs assigned to a batch does not exceed its capacity -- Once the jobs are batched, the processing time of the batch on the first machine is equal to the longest processing job in the batch; processing time of the batch on the second machine is equal to the sum of processing times of all the jobs in the batch -- The batches cannot wait between two machines (i.e., no-wait) -- The problem under study is NP-hard -- We propose a mathematical formulation and present a particle swarm optimization (PSO) algorithm -- The solution quality and run time of PSO is compared with a commercial solver used to solve the mathematical formulation Experimental study clearly highlights the advantages, in terms of solution quality and run time, of using PSO to solve large-scale problemsÍtem Benchmarking about Lean Manufacturing in the textile sector in Medellin(Journal of Economics, Finance and Administrative Science, 2010-06) Arrieta Posada, Juan Gregorio; Romano Martínez, María Jimena; Botero Herrera, Victoria Eugenia; Universidad EAFIT. Departamento de Ingeniería de Producción; jarrieta@eafit.edu.co; vboteroh@eafit.edu.co; mromanom@eafit.edu.co; Gestión de Producción y LogísticaThis document shows the results of a benchmarking study among different firms from the clothing industry that seeks to evaluate their degree of implementation in Lean Manufacturing during their respective productive processes -- The study mainly targets firms that produce blue jeans, cotton shirts and t-shirts -- Indeed, this industrial sector in the city of Medellin is highly developed and one of the most dynamic, thus the interest to perform an evaluation in this area -- To achieve the benchmarking, a questionnaire was designed and applied to the different firms that were visited -- The most significant result obtained was that Lean Manufacturing techniques were not prevalent within the general public -- Only those companies with years in the business, exporters or foreign trademarks licensees, were knowledgeable of their application and developmentÍtem 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 Games and practical exercises as support to the interactive courses for the Operations and Logistics Management area in the Production Engineering Pregraduated Program of the EAFIT University(Latin American and Caribbean Journal of Engineering Education, 2010-11-16) Rodríguez, Carlos A.; Ramírez, Sergio A.; Universidad EAFIT. Departamento de Ingeniería de Producción; carodri@eafit.edu.co; sramire@eafit.edu.co; Gestión de Producción y LogísticaThe following paper introduces the way on how play different games played in the subjects studied in engineering -- These games are a complement to the theory learnt in class and also facilitate students’ learning process. The games goal is to allow the student to have more control of his/her learning process, making it necessary to develop new ways of teaching class -- Teachers and students will be able to find the tools necessary to make the games a true learning process in this paperÍtem Analysis of chaotic behaviour in supply chain variables(Journal of Economics, Finance and Administrative Science, 2011-12) Peña Zapata, Gloria Elena; Ramírez Echeverri, Sergio Augusto; Universidad EAFIT. Departamento de Ingeniería de Producción; ramire@eafit.edu.co; gepena@unal.edu.co; Gestión de Producción y LogísticaIn this article we develop a supply chain model of four levels through the utilization of system dynamics with Ithink® and Mathlab® softwares to analyze data -- The supply chain is studied from the chaos theory perspective, which helps identifying the sensitive variables that can lead to a state of chaos -- A generic structure model that comprehends factory links, distribution, wholesale, retail and the client is constructed -- The difficulty of operations and logistics managers to decide how much to order and when to do it is simulated accordingly to what occurs in the links of the preceding and subsequent levels with two decision parameters: The first parameter denominated A indicates the participation (between 0 and 1) of the number of product units that are taken into account in the actual stock and the pending orders at the moment of performing an order – Thesecond parameter, denominated B, is the participation (between 0 and 1) of the number of units in the supply line (in transit) at the moment of performing orders of each of the links of the supply chainÍtem Allocation of intermediate buffer storage capacities in a production line(2013-07-24) Vélez Gallego, Mario César; Jaramillo Jiménez, Jhull B.; Universidad EAFIT. Departamento de Ingeniería de Producción; marvelez@eafit.edu.co; jjaram61@eafit.edu.co; Gestión de Producción y LogísticaIn this research proposal we consider a production line with random demand and subject to random failures at each workstation -- 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 that increases with the stage of the process is associated to each buffer -- 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 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 problem in a reasonable computational timeÍtem 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 Heurístico de simulación-optimización para la configuración de un sistema de estantería selectiva simple(Ingeniare. Revista chilena de ingeniería, 2012) Vélez Gallego, Mario César; Castro Zuluaga, Carlos Alberto; Valencia Ramírez, Diego Andrés; Universidad EAFIT. Departamento de Ingeniería de Producción; marvelez@eafit.edu.co; dvalenc8@eafit.edu.co; ccastro@eafit.edu.co; Gestión de Producción y LogísticaA discrete event simulation-optimization heuristic is presented for configuring a selective pallet rack system -- To the rack system under study pallets arrive dynamically over time to be stored for a given period of time -- The storage duration, arrival time and pallet height are assumed to be continuous random variables with known density functions -- In such a system, if there is no available slot in the rack to store an arriving pallet, it is placed on the floor -- The proposed heuristic aims at minimizing the number ofracking banks needed so that the long term proportion of pallets that are placed in a rack slot reaches a minimum pre-specified value -- The computational experiments conducted suggest that the proposed heuristic effectively solves the problem under studyÍtem Aspects to consider for high quality administration of Corporate Distribution Centers (Centros de Distribución, CEDIS)(Journal of Economics, Finance and Administrative Science, 2011-06) Arrieta Posada, Juan Gregorio; Universidad EAFIT. Departamento de Ingeniería de Producción; jarrieta@eafit.edu.co; Gestión de Producción y LogísticaIn this document we present different aspects that are necessary to perform an excellent administration and control of distribution centers that corporations may have -- If these ideas are implemented correctly in an efficient way, most of the productivity problems in the warehouse could be solved easily -- Thus, it is important to evaluate the products’ activity profile, thelayout of the warehouse and the products’ flow through the distribution center -- The objective of this process is to obtain the conditions of a world class warehouseÍtem Design of a didactic guide for learning in teh area of operations and logistics with the beer game in the software iThink®(Latin American and Caribbean Journal of Engineering Education, 2011) Peña, Gloria Elena; Rodríguez, Carlos A; Ramírez, Sergio; Universidad EAFIT. Departamento de Ingeniería de Producción; sramire@eafit.edu.co; carodri@eafit.edu.co; gepena@unal.edu.co; Gestión de Producción y LogísticaThe systems dynamics has charged significant importance as tool of support to the educational processes for the learning --An example is the the Beer Game, which, through the use of the software iThink®, simulates a chain of supplies, which permits the student to take decisions with regard to the behavior of the same one under certain conditions of simulation -- This work presents a didactic guide of the Play of the Beer by means of the use of the software iThink®, which has been developed as a complement in the processes of learning of the students of pregraduated level of Engineering of Production of the EAFIT University in Medellin, Colombia -- It is sought with this experience to develop a strategy that when it be played, the unique one that can create variations in the model is the player and the strategy can vary when be considered that is not throwing the results of form desired -- To be able to play should be determined the values of FAI and FLS that signify respectively; the first one is that so intense responds the inventory to the changes and the second is that weight in the quantity of inventory is found in transit for each position, With these concepts the variables are reinforced that disturb the effect whip in the supply chain