Graphic summary
  • Show / hide key
  • Information


Scientific and technological production
  •  

1 to 50 of 465 results
  • Combining matheuristics and MILP to solve the accessibility windows assembly line balancing problem level 2 (AWALBP-L2)

     Calleja Sanz, Gema; Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Computers & operations research
    Vol. 48, p. 113-123
    DOI: 10.1016/j.cor.2014.03.009
    Date of publication: 2014-08-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    We propose an approach combining a matheuristic and a MILP model to solve the variant Level 2 of the Accessibility Windows Assembly Line Balancing Problem (AWALBP-L2). This is a novel problem that arises in those real-world assembly lines where, in contrast to the most common ones, the length of the workpieces is larger than the widths of the workstations. This means that, at any time, a workstation cannot access an entire workpiece, but only a restricted portion of a workpiece or two consecutive workpieces. As a result, a workstation can only perform, at any time, the subset of tasks that fall inside its accessible area. The problem is to solve the task assignment and the movement scheme subproblems, while minimizing the cycle time. The proposed solving approach consists of (i) a matheuristic to generate good feasible solutions and compute bounds and (ii) a MILP model that makes use of the obtained bounds. A computational study is carried out to compare the performance of the proposed approach with the existing literature. (C) 2014 Elsevier Ltd. All rights reserved.

    We propose an approach combining a matheuristic and a MILP model to solve the variant Level 2 of the Accessibility Windows Assembly Line Balancing Problem (AWALBP-L2). This is a novel problem that arises in those real-world assembly lines where, in contrast to the most common ones, the length of the workpieces is larger than the widths of the workstations. This means that, at any time, a workstation cannot access an entire workpiece, but only a restricted portion of a workpiece or two consecutive workpieces. As a result, a workstation can only perform, at any time, the subset of tasks that fall inside its accessible area. The problem is to solve the task assignment and the movement scheme subproblems, while minimizing the cycle time. The proposed solving approach consists of (i) a matheuristic to generate good feasible solutions and compute bounds and (ii) a MILP model that makes use of the obtained bounds. A computational study is carried out to compare the performance of the proposed approach with the existing literature. (C) 2014 Elsevier Ltd. All rights reserved.

  • A review of mathematical programming models for strategic capacity planning in manufacturing

     Martinez Costa, M. Carmen; Mas Machuca, Marta; Benedito Benet, Ernest; Corominas Subias, Albert
    International journal of production economics
    Vol. 153, p. 66-85
    DOI: 10.1016/j.ijpe.2014.03.011
    Date of publication: 2014-07
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This paper offers an up-to-date review on strategic capacity planning in manufacturing companies, with two main objectives: (1) to describe and analyze the strategic capacity planning problems; and (2) to review the mathematical programming models proposed in the literature for dealing with these problems. The main search was conducted in the Web of Science using critical keywords and was complemented by using other search engines. Cross checking of citations of all the articles was also carried out. Papers were selected that have formulated discrete time, finite horizon, multi-period models. The major decisions addressed and the main conditioning factors of the strategic capacity problem in the literature are identified and described. A structured overview of the main strategic capacity planning mathematical programming models is given. A classification of the models is proposed and their main characteristics, solution procedures and industrial applications are identified. Based on the review of the existing studies, a framework for capacity planning is presented, consisting of three main phases: problem definition (considering context, characteristics of the manufacturing system and specific factors that could influence the decision-making process), model design and solution procedure. Closing the paper, some future lines of research are suggested. The review should help both practitioners and academic researchers in developing useful models and processes to aid decision-making in strategic capacity planning.

  • Metaheuristic algorithms hybridized with variable neighbourhood search for solving the response time variability problem

     Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    TOP
    Vol. 21, num. 2, p. 296-312
    DOI: 10.1007/s11750-011-0175-y
    Date of publication: 2013-07
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Task assignment considering cross-training goals and due dates

     Olivella Nadal, Jorge; Corominas Subias, Albert; Pastor Moreno, Rafael
    International Journal of Production Research
    Vol. 51, num. 3, p. 952-962
    DOI: 10.1080/00207543.2012.693645
    Date of publication: 2013-02-01
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Technical note: A systematic procedure based on CALIBRA and the Nelder & Mead algorithm for fine-tuning metaheuristics

     Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Journal of the Operational Research Society
    Vol. 64, num. 2, p. 276-282
    DOI: 10.1057/jors.2012.51
    Date of publication: 2013-02
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Supply chains: What they are and the new problems they raise

     Corominas Subias, Albert
    International Journal of Production Research
    Vol. 51, num. 23-24, p. 6828-6835
    DOI: 10.1080/00207543.2013.852700
    Date of publication: 2013-11-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The term supply chain has been, perhaps surprisingly, highly successful since it was proposed. This paper discusses the material and theoretical roots from which the concept arises, as well as its content and implications. It focuses especially on the question of whether the term is useful only to, say, put old wine into new wineskins or responds to a very different reality from that we had a few decades ago. The latter poses new problems, some of which are pointed out, whose resolution requires new theoretical and computational tools. The obvious inadequacy of the term to describe the reality it refers to is emphasised. Some challenges, opportunities and switchpoints for the future of the supply chain are listed as well.

  • A MILP model for the Accessibility Windows Assembly Line Balancing Problem (AWALBP).

     Calleja Sanz, Gema; Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    International Journal of Production Research
    Vol. 51, num. 12, p. 3549-3560
    DOI: 10.1080/00207543.2012.751514
    Date of publication: 2013-06
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This work studies a novel assembly line balancing problem that has recently appeared in the literature, which we name Accessibility Windows Assembly Line Balancing Problem (AWALBP). AWALBP is a real-world industrial problem that arises in those assembly lines where, as opposed to the most common ones, the length of the workpiece is larger than the widths of the workstation. This means that, at any time, a workstation cannot access one whole workpiece, but only a restricted portion of one or two consecutive workpiece. In our problem the cycle decomposes into stationary stages separated by forward steps, according to a cyclic movement scheme. The aim of this paper is (i) to formalise the AWALBP and its variants, and (ii) to propose a Mixed Integer Linear Programming (MILP) model using two alternative formulations to solve the variant AWALBP-L2. This variant involves solving the task assignment and the movement scheme sub-problems (with the objective of minimising the cycle time). An extensive computational experiment is carried out to study the behaviour of the proposed model for different instance sizes. To the best of our knowledge, this is the first work in the literature which provides optimal solutions for AWALBP-L2. In addition, a set of benchmark instances is provided, which can be further used by the research community.

  • A branch and bound algorithm for the response time variability problem

     García Villoria, Alberto; Corominas Subias, Albert; Delorme, Xavier; Dolgui, Alexandre; Kubiak, Wieslaw; Pastor Moreno, Rafael
    Journal of scheduling
    Vol. 16, num. 2, p. 243-252
    DOI: 10.1007/s10951-012-0277-x
    Date of publication: 2013-04
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The response time variability problem (RTVP) is an NP-hard scheduling problem that has been studied intensively recently and has a wide range of real-world applications in mixed-model assembly lines, multithreaded computer systems, network environments and others. The RTVP arises whenever products, clients or jobs need to be sequenced in order to minimise the variability in the time between two successive points at which they receive the necessary resources. To date, the best exact method for solving this problem is a mixed integer linear programming (MILP) model, which solves to optimality most of instances with up to 40 units to be scheduled in a reasonable amount of time. The goal of this paper is to increase the size of the instances that can be solved to optimality. We have designed an algorithm based on the branch and bound (B&B) technique to take advantage of the particular features of the problem. Our computational experiments show that the B&B algorithm is able to solve larger instances with up to 55 units to optimality in a reasonable time.

    The response time variability problem (RTVP) is an NP-hard scheduling problem that has been studied intensively recently and has a wide range of real-world applications in mixed-model assembly lines, multithreaded computer systems, network environments and others. The RTVP arises whenever products, clients or jobs need to be sequenced in order to minimise the variability in the time between two successive points at which they receive the necessary resources. To date, the best exact method for solving this problem is a mixed integer linear programming (MILP) model, which solves to optimality most of instances with up to 40 units to be scheduled in a reasonable amount of time. The goal of this paper is to increase the size of the instances that can be solved to optimality. We have designed an algorithm based on the branch and bound (B&B) technique to take advantage of the particular features of the problem. Our computational experiments show that the B&B algorithm is able to solve larger instances with up to 55 units to optimality in a reasonable time

  • Resolución del problema de flujo general flexible con fechas comprometidas y costes dependientes del intervalo de realización de las operaciones  Open access

     González Vargas, Néstor Andrés
    Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    En el marco de la problemática de la programación de operaciones en taller, en esta tesis se introduce un nuevo problema, que se identifica como problema de flujo general flexible (fJSP) con fechas comprometidas y costes dependientes del intervalo de realización de las operaciones. En el fJSP se deben tratar dos subproblemas, el de asignación de las operaciones a las máquinas que pueden ejecutarlas y el de secuenciación de las operaciones en cada una de las máquinas. Para este problemase propone, como función objetivo, minimizar la suma de los costes asociados a los adelantos y retrasos que se generan con respecto a la fecha de entrega comprometida y unos costes dependientes del intervalo de realización de las operaciones. De entre estos últimos se utiliza el coste de la energía necesaria para ejecutar las operaciones de los jobs (tareas) en las máquinas.Para resolver el problema propuesto se plantea un procedimiento dividido en tres pasos. En el Paso 1 se obtiene una secuencia inicial de jobs; en el Paso 2 se genera una solución inicial mediante un procedimiento que se basa principalmente en realizar,simultáneamente, la construcción y búsqueda del camino mínimo en un grafo polietápico para cada job; y en el Paso 3 se emplean procedimientos de mejora de la solución inicial. También se exponen los resultados de la experiencia computacionalque evalúa el procedimiento de resolución propuesto. En los resultados se observa que el procedimiento favorece la programación de las operaciones respetando las fechas de entrega, y ayuda a reducir la factura de la empresa eléctrica, ya queen las soluciones de un conjunto de tipos de ejemplares se observa cómo se asignan, mayoritariamente, operaciones a máquinas con menor consumo de energía, y principalmente en aquellos intervalos de tiempo en los que el coste de la energíaes menor. Al analizar los resultados de la experiencia computacional se observa, además, que el procedimiento encuentra la solución de ejemplares de diferente dimensión en un tiempo de proceso de ordenador razonable.

    En el marco de la problemática de la programación de operaciones en taller, en esta tesis se introduce un nuevo problema, que se identifica como problema de flujo general flexible (fJSP) con fechas comprometidas y costes dependientes del intervalo de realización de las operaciones. En el fJSP se deben tratar dos subproblemas, el de asignación de las operaciones a las máquinas que pueden ejecutarlas y el de secuenciación de las operaciones en cada una de las máquinas. Para este problema se propone, como función objetivo, minimizar la suma de los costes asociados a los adelantos y retrasos que se generan con respecto a la fecha de entrega comprometida y unos costes dependientes del intervalo de realización de las operaciones. De entre estos últimos se utiliza el coste de la energía necesaria para ejecutar las operaciones de los jobs (tareas) en las máquinas. Para resolver el problema propuesto se plantea un procedimiento dividido en tres pasos. En el Paso 1 se obtiene una secuencia inicial de jobs; en el Paso 2 se genera una solución inicial mediante un procedimiento que se basa principalmente en realizar, simultáneamente, la construcción y búsqueda del camino mínimo en un grafo polietápico para cada job; y en el Paso 3 se emplean procedimientos de mejora de la solución inicial. También se exponen los resultados de la experiencia computacional que evalúa el procedimiento de resolución propuesto. En los resultados se observa que el procedimiento favorece la programación de las operaciones respetando las fechas de entrega, y ayuda a reducir la factura de la empresa eléctrica, ya que en las soluciones de un conjunto de tipos de ejemplares se observa cómo se asignan, mayoritariamente, operaciones a máquinas con menor consumo de energía, y principalmente en aquellos intervalos de tiempo en los que el coste de la energía es menor. Al analizar los resultados de la experiencia computacional se observa, además, que el procedimiento encuentra la solución de ejemplares de diferente dimensión en un tiempo de proceso de ordenador razonable

    In the context of the job-shop scheduling problem, this thesis introduces a new problem, which is identified as the flexible job-shop scheduling problem (fJSP) with due dates and energy costs that are dependent on the time interval in which the operations are processed. The fJSP involves two subproblems: that of assigning operations to the machines that can process them and that of sequencing the operations on each of the machines. For this problem, we propose an objective function that minimizes the sum of the costs of earliness and tardiness with respect to the due date and the costs that depend on the time interval in which the operations are processed. Regarding these costs, we have focused primarily on the cost of the energy required to process the jobs on the machines. To solve the proposed problem, we suggest a solution procedure that is divided into three steps. Step 1 involves obtaining an initial sequence of jobs, Step 2 involves generating an initial solution using a procedure based primarily on simultaneously constructing and finding the shortest path in a multistage graph for each job, and Step 3 involves implementing procedures for improving the initial solution. We report the results of the computational experiment used to test the proposed solution procedure. We were able to conclude from the results that the procedure is useful for scheduling operations while respecting due dates and that it could help reduce electricity bills, since the solutions to a set of example types demonstrated that operations were generally assigned to machines with a lower energy consumption, and mainly in time intervals in which the energy costs is low. When analysing the results of the computational experiment, we also observed that the procedure found the solution for examples of varying sizes in a fairly reasonable computer processing time.

  • Using tabu search and MILP for the accessibility windows assembly line balancing problem (AWALBP)

     Calleja Sanz, Gema; Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Congreso Nacional de Estadística e Investigación Operativa
    p. 117
    DOI: 10.6035/e-TIiT.2013.16
    Presentation's date: 2013-09-12
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The AWALBP arises in those assembly lines where, in contrast to standard ones, the length of the workpieces is larger than the accessibility windows of the workstations. Because of this, only a limited portion of one or two consecutive workpieces can be reached from each station at any moment. In our problem, the cycle decomposes into stationary stages separated between them by forward steps, according to a cyclic movement scheme. Several procedures were previously proposed to solve the problem to optimality and instances up to a certain size limit were solved. In this study, we propose a tabu search (TS) and a combination procedure using TS and a mixed integer linear programming (MILP) model in order to solve larger instances. The neighborhood search is performed in the space of the movement schemes. Results show that a better solution is obtained in most of the cases that could not be previously solved optimally.

  • Using simulated annealing and MILP for the accessibility windows assembly line balancing problem (AWALBP)

     Calleja Sanz, Gema; Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    European Conference on Operational Research
    p. 38
    Presentation's date: 2013-07-01
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The AWALBP is an assembly line balancing problem where the length of the workpieces is larger than the width of the workstations. A procedure using a matheuristic and a mixed integer linear programming (MILP) model was previously tested to solve the AWALBP and it succeeded in finding optimal solutions to instances up to a certain size. We propose simulated annealing (SA) and a hybrid procedure using SA and MILP in order to find good quality solutions for larger instances. Results show that a better solution is obtained in most of the cases that could not be previously solved optimally.

  • The experience of the summer school in Optimization and Decision Support Systems for Supply Chains

     Bruno, Giuseppe; Amaro, Ana; Casquilho, Miguel; Corominas Subias, Albert; Genovese, Andrea; García López, Juan-Manuel; Lusa Garcia, Amaia; Magnusson, Johan; Matos, Henrique; Miranda, Joao; Rubio Lacoba, Sergio
    European Conference on Operational Research
    p. 293
    Presentation's date: 2013-07-03
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Optimising the extraction rate of a non-renewable non-durable resource: a mathematical programming approach

     Corominas Subias, Albert; Fossas Colet, Enric
    European Conference on Operational Research
    p. 52
    Presentation's date: 2013-07-01
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Optimal manufacturing policy in a reverse logistic system with dependent stochastic returns and limited capacities

     Benedito Benet, Ernest; Corominas Subias, Albert
    International Journal of Production Research
    Vol. 51, num. 1, p. 189-201
    DOI: 10.1080/00207543.2012.655863
    Date of publication: 2012-03-02
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The stochastic models of systems with reverse logistics usually assume that the quantity of products returned is independent of sales. This hypothesis is obviously not true and can lead to suboptimal production policies. In this paper a new sales-dependent returns model is described. In this model, the returns depend on the useful life of the products sold and on the probability of an end-of-life product being returned. A Markov decision problem is formulated in order to obtain the optimal manufacturing policy. A numerical example is provided to illustrate the use of the defined model. An approximated Markov decision model is defined where the optimal policy is easily obtained. The optimal policies of the original and the approximated models are compared.

  • A detailed workforce planning model including non-linear dependence of capacity on the size of the staff and cash management

     Corominas Subias, Albert; Lusa Garcia, Amaia; Olivella Nadal, Jorge
    European journal of operational research
    Vol. 216, num. 2, p. 445-458
    DOI: 10.1016/j.ejor.2011.06.027
    Date of publication: 2012-01-01
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Cocktail of heuristics for solving hard problems

     Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Dyna
    Vol. 87, num. 3, p. 275-278
    DOI: 10.6036/4508
    Date of publication: 2012-05
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • A manufacturing and remanufacturing aggregate planning model considering a non-linear supply function of recovered products

     Corominas Subias, Albert; Lusa Garcia, Amaia; Olivella Nadal, Jorge
    Production planning and control
    Vol. 230, num. 2-3, p. 194-204
    DOI: 10.1080/09537287.2011.591651
    Date of publication: 2012
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • LETRIS: staffing service systems by means of simulation

     Corominas Subias, Albert; Lusa Garcia, Amaia
    Journal of industrial engineering and management (JIEM)
    Vol. 5, num. 2, p. 285-296
    Date of publication: 2012
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Purpose: This paper introduces a procedure for solving the staffing problem in a service system (i.e., determining the number of servers for each staffing period). Design/methodology: The proposed algorithm combines the use of queueing theory to find an initial solution with the use of simulation to adjust the number of servers to meet previously specified target non-delay probabilities. The basic idea of the simulation phase of the procedure is to successively fix the number of servers from the first staffing period to the last, without backtracking. Findings: Under the assumptions that the number of servers is not upper-bounded and there are no abandonments and, therefore, no retrials, the procedure converges in a finite number of iterations, regardless of the distributions of arrivals and services, and requires a reasonable amount of computing time. Originality / value: The new procedure proposed in this paper is a systematic, robust way to find a good solution to a relevant problem in the field of service management and it is very easy to implement using no more than commonly accessible tools.

  • Estimating the quality of service of sales in multiplex cinemas using a simulation model

     Ferrer Marti, Laia; Corominas Subias, Albert; Pastor Moreno, Rafael; Malaret, Anna
    International Journal of Modelling in Operations Management
    Vol. 2, num. 3, p. 309-326
    DOI: 10.1504/IJMOM.2012.047936
    Date of publication: 2012
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    One key decision for managers of multiplex cinemas is how many box offices to open to avoid overstaffing or poor service. We present a simulation model developed to support the capacity management of the Spanish leader of the multiplex cinema sector; the model uses ad hoc collected data. The user introduces the film schedule, the expected audience and the number of opened box offices and the model gives the expected level of service. The company has tested the model and considers that estimates the waiting time correctly and allows adjusting the open box offices to limit the waiting time without overstaffing.

  • Heuristics for the response time variability problem

     Corominas Subias, Albert; Kubiak, Wieslaw; Pastor Moreno, Rafael
    European journal of industrial engineering
    Vol. 6, num. 6, p. 751-764
    DOI: 10.1504/EJIE.2012.051077
    Date of publication: 2012
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Pure and hybrid metaheuristics for the response time variability problem

     García Villoria, Alberto; Corominas Subias, Albert; Pastor Moreno, Rafael
    DOI: 10.4018/978-1-4666-2086-5.ch010
    Date of publication: 2012-08-16
    Book chapter

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Quant paga l'estudiant?

     Arcas Abella, Oriol; Botella, J.; Corominas Subias, Albert; de la Villa, L.; França, J.; Sacristán Adinolfi, Vera
    Date of publication: 2012
    Book

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Enhanced MILP model for the Accessibility Windows Assembly Line Balancing Problem (AWALBP)

     Calleja Sanz, Gema; Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Congrès Annuel de la Société Française de Recherche Opérationnelle et d'Aide à la Décision
    p. 117-118
    Presentation's date: 2012-04-13
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The Accessibility Windows Assembly Line Balancing Problem (AWALBP) arises in those assembly lines where, as opposed to traditional assembly lines, the dimensions of the workpieces are larger than the width of the workstations. This means that, at any cycle, a workstation cannot access to one whole workpiece, but only to a restricted portion of one or two consecutive workpieces [1]. In our problem the cycle decomposes into stationary stages separated between them by forward steps, according to a cyclic movement scheme.

  • Modelo de PLEM mejorado para el Accessibility Windows Assembly Line Balancing Problem (AWALBP)

     Calleja Sanz, Gema; Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    International Conference on Industrial Engineering and Industrial Management. Congreso de Ingeniería de Organización
    p. 879-886
    Presentation's date: 2012-07-18
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The Accessibility Windows Assembly Line Balancing Prob-lem (AWALBP) occurs in those assembly lines where the length of the workpiec-es is large relative to the width of the workstations. As a result, each workstation can only access to the limited portion of workpiece(s) that is inside its accessibil-ity window. In previous works we proposed a mixed-integer linear programming (MILP) model and a heuristic decomposition approach to solve AWALBP. Com-putational results revealed the size limits of the instances that could be solved. In this work, we provide an enhanced MILP model using reformulations and addi-tional bound contraints, which significantly improves the percentage of the in-stances optimally solved.

  • Comparing ways of breaking symmetries in mathematical models for SALBP-1

     Pastor Moreno, Rafael; García Villoria, Alberto; Corominas Subias, Albert
    Assembly automation
    Vol. 31, num. 4, p. 385-387
    DOI: 10.1108/01445151111172970
    Date of publication: 2011
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Hyper-heuristic approaches for the response time variability problem

     García Villoria, Alberto; Salhi, Said; Corominas Subias, Albert; Pastor Moreno, Rafael
    European journal of operational research
    Vol. 211, num. 1, p. 160-169
    DOI: 10.1016/j.ejor.2010.12.005
    Date of publication: 2011-05-16
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Optimal production and storage capacities in a system with reverse logistics and periodic demand

     Benedito Benet, Ernest; Corominas Subias, Albert
    International journal of logistics systems and management
    Vol. 10, num. 3, p. 340-360
    DOI: 10.1504/IJLSM.2011.043121
    Date of publication: 2011
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Assembly line balancing: general resource-constrained case

     Corominas Subias, Albert; Ferrer Marti, Laia; Pastor Moreno, Rafael
    International Journal of Production Research
    Vol. 49, num. 12, p. 3527-3542
    DOI: 10.1080/00207543.2010.481294
    Date of publication: 2011
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Assessing the impact on optimal production capacities in a closed-loop logistics system of the assumption that returns are stochastically independent of sales

     Benedito Benet, Ernest; Corominas Subias, Albert
    Journal of industrial engineering and management (JIEM)
    Vol. 4, num. 3, p. 504-522
    DOI: 10.3926/jiem.2011.v4n3.504-522
    Date of publication: 2011
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Las Encrucijadas estratégicas de la universidad pública española

     Corominas Subias, Albert; Sacristán Adinolfi, Vera
    Revista de educación
    Vol. 355, p. 57-81
    Date of publication: 2011-05
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Designing greedy algorithms for the flow-shop problem by means of Empirically Adjusted Greedy Heuristics (EAGH)

     Corominas Subias, Albert; Pastor Moreno, Rafael
    Journal of the Operational Research Society
    Vol. 62, num. 9, p. 1704-1710
    DOI: 10.1057/jors.2010.131
    Date of publication: 2011-09
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Single-site strategic capacity planning considering renewal, maintenance, inventory, taxes and cash-flow management

     Benedito Benet, Ernest; Corominas Subias, Albert; Martinez Costa, M. Carmen; Mas Machuca, Marta
    Date: 2011-09-01
    Report

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this paper we propose a model of a single-site manufacturing system adressed to deal with the capacity planning from an strategic perspective. The model takes in account relevant business aspects, some of them not found in literature and others only partially considered. The model is formulated as a mixed-integer linear program with an objective function that maximize the after-tax cash balance at the end of the planning horizon. The model could be applied to several sectors especially in manufacturing industry. We present a computational experiment with 1792 business scenarios that test the computing time.

  • Task assignment considering cross-training goals and due dates

     Olivella Nadal, Jorge; Corominas Subias, Albert; Pastor Moreno, Rafael
    International Federation of Operational Research Societies
    p. 27
    Presentation's date: 2011-07-11
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Programación de tareas para la obtención de la polivalencia, teniendo en cuenta el aprendizaje y el olvido

     Corominas Subias, Albert; Cuatrecasas Arbos, Luis; García Villoria, Alberto; Calleja Sanz, Gema; Pastor Moreno, Rafael; Olivella Nadal, Jorge
    Competitive project

     Share

  • Planificación de la capacidad a largo plazo y diseño de la red de suministro

     Coves Moreno, Anna Maria; Mateo Doll, Manuel; Benedito Benet, Ernest; Mas Machuca, Marta; Martinez Costa, M. Carmen; Corominas Subias, Albert; Ribas Vila, Immaculada; Domenech Lega, Bruno; Lusa Garcia, Amaia
    Competitive project

     Share

  • Promoció de sistemes micro-eólics i solars per l'electrificació de comunitats de forma autònoma: anàlisis i desenvolupament d'eines de disseny i planificació per a diferents contextos i paisos II

     Pastor Moreno, Rafael; Ferrer Marti, Laia; García Villoria, Alberto; Corominas Subias, Albert; Villafafila Robles, Roberto; Ranaboldo, Matteo; Domenech Lega, Bruno; Triadó, Joan; Travesset, Oriol
    Competitive project

     Share

  • Heurísticas para el Visibility Windows Assembly Line Balancing Problem (VWALBP)

     Calleja Sanz, Gema; Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Congreso de Ingeniería de Organización
    p. 201-205
    Presentation's date: 2011-09-08
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    En este trabajo se trata el problema conocido como problema de equilibrado de líneas de montaje con ventanas de visibilidad o Visibility Windows Assembly Line Balancing Problem (VWALBP), que ocurre en varios entornos de producción automatizados. En particular este problema surge, por ejemplo, en la producción de placas de circuito impreso (PCIs) en líneas pick&place. Este tipo de líneas consta de varias estaciones en paralelo que montan los componentes en posiciones predefinidas sobre la superficie de la placa. El montaje se realiza de modo cíclico (en cada ciclo se completa una pieza) y consiste en escoger (pick) un componente de un alimentador, trasladarlo hacia la placa, y colocarlo (place) en su posición correspondiente

  • Prise en compte des objectifs de polyvalence et des dates d'échéance dans l¿affectation des tâches

     Olivella Nadal, Jorge; Corominas Subias, Albert; Pastor Moreno, Rafael
    Congrès Annuel de la Société Française de Recherche Opérationnelle et d'Aide à la Décision
    p. 1-2
    Presentation's date: 2011-03-02
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Exact and heuristic approaches for the Visibility Windows Assembly Line Balancing Problem (VWALBP)

     Calleja Sanz, Gema; Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    French National Society of Operations Research and Decision Science
    p. 583-584
    Presentation's date: 2011-03-04
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this paper, we consider the problem that we name Visibility Windows Assembly Line Balancing Problem (VWALBP) [1], which arises in some actual automated production lines. In contrast to traditional assembly lines, the length of the workpieces may be larger than the visibility windows of the workstations, and because of this, only a limited portion of the unit can be reached from any station at any time.

  • Optimal manufacturing and remanufacturing capacities of systems with reverse logistics and deterministic uniform demand

     Benedito Benet, Ernest; Corominas Subias, Albert
    Journal of industrial engineering and management (JIEM)
    Vol. 3, num. 1, p. 33-53
    DOI: 10.3926/jiem.2010.v3n1.p33-53
    Date of publication: 2010
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Using reverse logistics in production systems can help to reduce costs. However, it can also mean introducing a source of uncertainty in the system behavior. In this study we present a method for calculating the optimal manufacturing and remanufacturing capacities of a system with reverse logistics and steady demand taking into account the random behavior of the quantity, quality and timing of units that are collected thru the reverse logistics system. The collected units are remanufactured or disposed of. We also provide an example to illustrate the method.

  • A bicriteria integer programming model for the hierarchical workforce scheduling problem

     Pastor Moreno, Rafael; Corominas Subias, Albert
    Journal of modelling in management
    Vol. 5, num. 1, p. 54-62
    DOI: 10.1108/17465661011026167
    Date of publication: 2010
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • A model for the assignment of a set of tasks when work performance depends on experience of all tasks involved

     Corominas Subias, Albert; Olivella Nadal, Jorge; Pastor Moreno, Rafael
    International journal of production economics
    Vol. 126, num. 2, p. 335-340
    DOI: 10.1016/j.ijpe.2010.04.012
    Date of publication: 2010-08
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • A support tool for working time bargaining by considering individual time accounts and annual leave

     Pastor Moreno, Rafael; Corominas Subias, Albert; Olivella Nadal, Jorge
    Production planning and control
    Vol. 21, num. 1, p. 84-98
    DOI: 10.1080/09537280903318773
    Date of publication: 2010-01-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Working time accounts (WTAs) are employer-oriented flexibility systems that have been applied in industry but could be used far more. Their use is limited by the complexity of planning them, assessing their financial benefits and establishing suitable compensation for workers. To overcome these drawbacks we define a planning model that takes into account work performance per task per worker, individual annual leave, the use of WTAs and the use of overtime. A four-stage process is proposed: Stage 1 deals with annual leave and the linear consideration of the cost of the lack of capacity; Stage 2 with annual leave and the non-linear consideration of the lack of capacity (but only for the periods during which holidays can be established); Stage 3 with minimising costs (once the holidays selected in Stage 2 are fixed, i.e. the holidays are considered as data) and Stage 4 with minimising capacity slack and excess capacity by minimising costs. A computational experiment based on the different periods of annual leave is used to calculate the financial benefit generated by WTAs in each case and to assess possible compensations for workers.

  • A parametric multi-start algorithm for solving the response time variability problem

     Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Lecture notes in computer science
    Vol. 5910, p. 302-309
    DOI: 10.1007/978-3-642-12535-5_35
    Date of publication: 2010-01-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The Multi-start metaheuristic has been applied straight or hybridized with other metaheuristics to solve a wide range of optimisation problems. Moreover, this metaheuristic is very easy to be adapted and implemented for a wide variety of problems. In this study, we propose a parametric multi-start algorithm that keeps its original simplicity. To test the proposed algorithm, we solve the Response Time Variability Problem (RTVP). The RTVP is a NP-hard sequencing combinatorial optimisation problem that has recently defined in the literature. This problem has a wide range of real-life applications in, for example, manufacturing, hard real-time systems, operating systems and network environment. The RTVP occurs whenever products, clients or jobs need to be sequenced so as to minimise variability in the time between the instants at which they receive the necessary resources. The computational experiment shows the robustness of the proposed multi-start technique.

  • Fine-tuning a parametric Clarke and Wright heuristic by means of EAGH (Empirically Adjusted Greedy Heuristics)

     Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Journal of the Operational Research Society
    Vol. 61, p. 1309-1314
    DOI: 10.1057/jors.2009.89
    Date of publication: 2010
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Solving the response time variability problem by means of the cross-entropy method

     García Villoria, Alberto; Corominas Subias, Albert; Pastor Moreno, Rafael
    International journal of manufacturing technology and management
    Vol. 20, p. 316-330
    DOI: 10.1504/IJMTM.2010.032904
    Date of publication: 2010-05-01
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Reflexiones adogmáticas sobre la docencia universitaria

     Corominas Subias, Albert; Miró Sans, Joan M.
    Date of publication: 2010
    Book chapter

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Replanning working time under annualised working hours

     Corominas Subias, Albert; Pastor Moreno, Rafael
    International Journal of Production Research
    Vol. 48, num. 5, p. 1493-1515
    DOI: 10.1080/00207540802582227
    Date of publication: 2010
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Exact and non-exact procedures for solving the response time variability problem (RTVP)  Open access  awarded activity

     García Villoria, Alberto
    Department of Business Administration, Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Cuando se ha de compartir un recurso entre demandas (de productos, clientes, tareas, etc.) competitivas que requieren una atención regular, es importante programar el derecho al acceso del recurso de alguna forma justa de manera que cada producto, cliente o tarea reciba un acceso al recurso proporcional a su demanda relativa al total de las demandas competitivas. Este tipo de problemas de secuenciación pueden ser generalizados bajo el siguiente esquema. Dados n símbolos, cada uno con demanda di (i = 1,...,n), se ha de generar una secuencia justa o regular donde cada símbolo aparezca di veces. No existe una definición universal de justicia, ya que puede haber varias métricas razonables para medirla según el problema específico considerado. En el Problema de Variabilidad en el Tiempo de Respuesta, o Response Time Variability Problem (RTVP) en inglés, la injusticia o irregularidad de una secuencia es medida como la suma, para todos los símbolos, de sus variabilidades en las distancias en que las copias de cada símbolo son secuenciados. Así, el objetivo del RTVP es encontrar la secuencia que minimice la variabilidad total. En otras palabras, el objetivo del RTVP es minimizar la variabilidad de los instantes en que los productos, clientes o trabajos reciben el recurso necesario. Este problema aparece en una amplia variedad de situaciones de la vida real; entre otras, secuenciación en líneas de modelo-mixto bajo just-in-time (JIT), en asignación de recursos en sistemas computacionales multi-hilo como sistemas operativos, servidores de red y aplicaciones mutimedia, en el mantenimiento periódico de maquinaria, en la recolección de basura, en la programación de comerciales en televisión y en el diseño de rutas para agentes comerciales con múltiples visitas a un mismo cliente. En algunos de estos problemas la regularidad no es una propiedad deseable por sí misma, si no que ayuda a minimizar costes. De hecho, cuando los costes son proporcionales al cuadrado de las distancias, el problema de minimizar costes y el RTVP son equivalentes. El RTVP es muy difícil de resolver (se ha demostrado que es NP-hard). El tamaño de las instancias del RTVP que pueden ser resueltas óptimamente con el mejor método exacto existente en la literatura tiene un límite práctico de 40 unidades. Por otro lado, los métodos no exactos propuestos en la literatura para resolver instancias mayores consisten en heurísticos simples que obtienen soluciones rápidamente, pero cuya calidad puede ser mejorada. Por tanto, los métodos de resolución existentes en la literatura son insuficientes. El principal objetivo de esta tesis es mejorar la resolución del RTVP. Este objetivo se divide en los dos siguientes subobjetivos : 1) aumentar el tamaño de las instancias del RTVP que puedan ser resueltas de forma óptima en un tiempo de computación práctico, y 2) obtener de forma eficiente soluciones lo más cercanas a las óptimas para instancias mayores. Además, la tesis tiene los dos siguientes objetivos secundarios: a) investigar el uso de metaheurísticos bajo el esquema de los hiper-heurísticos, y b) diseñar un procedimiento sistemático y automático para fijar los valores adecuados a los parámetros de los algoritmos. Se han desarrollado diversos métodos para alcanzar los objetivos anteriormente descritos. Para la resolución del RTVP se ha diseñado un método exacto basado en la técnica branch and bound y el tamaño de las instancias que pueden resolverse en un tiempo práctico se ha incrementado a 55 unidades. Para instancias mayores, se han diseñado métodos heurísticos, metaheurísticos e hiper-heurísticos, los cuales pueden obtener soluciones óptimas o casi óptimas rápidamente. Además, se ha propuesto un procedimiento sistemático y automático para tunear parámetros que aprovecha las ventajas de dos procedimientos existentes (el algoritmo Nelder & Mead y CALIBRA).

    When a resource must be shared between competing demands (of products, clients, jobs, etc.) that require regular attention, it is important to schedule the access right to the resource in some fair manner so that each product, client or job receives a share of the resource that is proportional to its demand relative to the total of the competing demands. These types of sequencing problems can be generalized under the following scheme. Given n symbols, each one with demand di (i = 1,...,n), a fair or regular sequence must be built in which each symbol appears di times. There is not a universal definition of fairness, as several reasonable metrics to measure it can be defined according to the specific considered problem. In the Response Time Variability Problem (RTVP), the unfairness or the irregularity of a sequence is measured by the sum, for all symbols, of their variabilities in the positions at which the copies of each symbol are sequenced. Thus, the objective of the RTVP is to find the sequence that minimises the total variability. In other words, the RTVP objective is to minimise the variability in the instants at which products, clients or jobs receive the necessary resource. This problem appears in a broad range of real-world areas. Applications include sequencing of mixed-model assembly lines under just-in-time (JIT), resource allocation in computer multi-threaded systems such as operating systems, network servers and media-based applications, periodic machine maintenance, waste collection, scheduling commercial videotapes for television and designing of salespeople's routes with multiple visits, among others. In some of these problems the regularity is not a property desirable by itself, but it helps to minimise costs. In fact, when the costs are proportional to the square of the distances, the problem of minimising costs and the RTVP are equivalent. The RTVP is very hard to be solved (it has been demonstrated that it is NP-hard). The size of the RTVP instances that can be solved optimally with the best exact method existing in the literature has a practical limit of 40 units. On the other hand, the non-exact methods proposed in the literature to solve larger instances are simple heuristics that obtains solutions quickly, but the quality of the obtained solutions can be improved. Thus, the solution methods existing in the literature are not enough to solve the RTVP. The main objective of this thesis is to improve the resolution of the RTVP. This objective is split in the two following sub-objectives: 1) to increase the size of the RTVP instances that can be solved optimally in a practical computing time; and 2) to obtain efficiently near-optimal solutions for larger instances. Moreover, the thesis has the following two secondary objectives: a) to research the use of metaheuristics under the scheme of hyper-heuristics, and b) to design a systematic, hands-off procedure to set the suitable values of the algorithm parameters. To achieve the aforementioned objectives, several procedures have been developed. To solve the RTVP an exact procedure based on the branch and bound technique has been designed and the size of the instances that can be solved in a practical time has been increased to 55 units. For larger instances, heuristic, heuristic, metaheuristic and hyper-heuristic procedures have been designed, which can obtain optimal or near-optimal solutions quickly. Moreover, a systematic, hands-off fine-tuning method that takes advantage of the two existing ones (Nelder & Mead algorithm and CALIBRA) has been proposed.

  • Influence of reverse logistics on optimal manufacturing, remanufacturing, and storage capacities  Open access

     Benedito Benet, Ernest
    Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    El propósito de la presente tesis es estudiar la influencia de la logística inversa en las capacidades de fabricación, refabricación y almacenaje óptimas de un sistema industrial. El interés por la logística inversa ha crecido en los últimos años de forma paralela a la preocupación, creciente también, por las cuestiones medioambientales en el mundo industrializado. En el capítulo 2 se hace una introducción a la logística inversa, explicando su definición y los motivos por los que se ha creado esta área de gestión diferenciada de la logística tradicional; se describen los tipos de productos que intervienen en la logística inversa y los distintos procesos para recuperar su valor. Además, se analizan las características del comportamiento de un sistema con logística inversa, comparándolas con las de un sistema tradicional. En el capítulo 3 se revisa la literatura tanto en el ámbito de la gestión de las capacidades de fabricación y almacenaje en un sistema tradicional como en el ámbito de la logística inversa. Para cumplir con el objetivo de la tesis, en los capítulos 4, 5 y 6 se estudian tres modelos de un sistema en que el producto recuperado es indistinguible del producto nuevo. El proceso seguido para realizar el estudio ha sido el mismo en cada uno de los modelos presentados: en primer lugar se ha determinado la política de producción óptima utilizando una cierta función de coste y suponiendo que tenemos dadas unas capacidades fijas, en segundo lugar se ha determinado el valor óptimo de las capacidades que optimizan la función de coste y en tercer lugar se estudian las variaciones de las cantidades óptimas al variar algunos parámetros relacionados con la logística inversa. En el capítulo 4 se pone de manifiesto cómo influye la aleatoriedad de los retornos en las capacidades óptimas estudiando un sistema con demanda uniforme y retornos aleatorios. La función de coste a optimizar es el valor esperado del coste en un periodo. En el capítulo 5 se estudia un modelo en el que la demanda y los retornos son funciones conocidas, continuas y periódicas. La función de coste a optimizar es el coste incurrido en el periodo y el problema de determinar la política de fabricación óptima es un problema de control óptimo. El modelo presentado permite analizar la variación en las capacidades óptimas al variar el plazo entre la venta y los retornos de los productos. En el capítulo 6 se trata un modelo con demanda y retornos aleatorios. La función de coste a optimizar es el valor esperado del coste en un periodo. Para realizar el cálculo de las políticas óptimas se hace la hipótesis de independencia estocástica de los retornos, comúnmente utilizada en la literatura. Una vez calculadas las capacidades óptimas se contrasta la validez de la hipótesis mediante simulación. El modelo se utiliza para estudiar la dependencia de las capacidades respecto de la probabilidad de que el producto sea retornado y respecto de los costes variables de refabricación. Finalmente en el capítulo 7 se recogen las conclusiones y los futuros temas de investigación.

    The purpose of this thesis is to study the influence of reverse logistics in optimal manufacturing, remanufacturing and storage capacities of an industrial system. The interest in reverse logistics has grown in recent years in parallel with the increasing concern about environmental issues in the industrialized world. In chapter 2, we provide an introduction to reverse logistics: explaining the definition of reverse logistics and the reasons for which has been created as a differentiated area of management of traditional logistics, describing the types of products involved in reverse logistics and the different processes to recover its value, and examining the behavioral characteristics of a reverse logistics systems, compared with the traditional logistics system. In chapter 3 we review the literature both in the field of capacity management in traditional systems and in the field of reverse logistics. To meet the objective of the thesis, we study three models of a system in which the recovered product is indistinguishable from the new product. The process followed for the study was the same in each of the models presented: firstly, we determine the optimal production policy for every value of capacities; the second step is determining the optimal value of the capacities when optimal policies are applied and third we study the dependency of optimal capacities on some parameters related with reverse logistics. In chapter 4 we study a system with uniform demand and random returns to show the influence of the randomness of returns in the optimal capacities. The cost function to optimize is the expected value of cost in a period. In chapter 5 we study a model in which demand and returns are known functions, continuous and periodic. The cost function to optimize is the cost incurred in the period and the problem of determining the optimal production policy is an optimal control problem. Using this model, we analyze the dependence of optimal capacity on the time between sales and product returns. In chapter 6 we present a stochastic model where demand and returns are sequences of random variables. The cost function to optimize is the expected value of cost in a period. To perform the calculation of optimal policies we assume that returns are stochastically independent of demand (this assumption is commonly used in the literature). The hypothesis is validated by simulation after optimal capacity is calculated. The model is used to study the dependence of the optimal capacities on the probability that the product is returned and also on the variable costs of remanufacturing. Finally in chapter 7 we discuss the conclusions and future research topics.