Graphic summary
  • Show / hide key
  • Information


Scientific and technological production
  •  

1 to 50 of 78 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.

  • Scheduling commercial advertisements for television

     García Villoria, Alberto; Salhi, Said
    International Journal of Production Research
    DOI: 10.1080/00207543.2014.951095
    Date of publication: 2014
    Journal article

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

    The problem of scheduling the commercial advertisements in the television industry is investigated. Each advertiser client demands that the multiple airings of the same brand advertisement should be as spaced as possible over a given time period. Moreover, audience rating requests have to be taken into account in the scheduling. This is the first time this hard decision problem is dealt with in the literature. We design two mixed integer linear programming (MILP) models. Two constructive heuristics, local search procedures and simulated annealing (SA) approaches are also proposed. Extensive computational experiments, using several instances of various sizes, are performed. The results show that the proposed MILP model which represents the problem as a network flow obtains a larger number of optimal solutions and the best non-exact procedure is one that uses SA.

    The problem of scheduling the commercial advertisements in the television industry is investigated. Each advertiser client demands that the multiple airings of the same brand advertisement should be as spaced as possible over a given time period. Moreover, audience rating requests have to be taken into account in the scheduling. This is the first time this hard decision problem is dealt with in the literature. We design two mixed integer linear programming (MILP) models. Two constructive heuristics, local search procedures and simulated annealing (SA) approaches are also proposed. Extensive computational experiments, using several instances of various sizes, are performed. The results show that the proposed MILP model which represents the problem as a network flow obtains a larger number of optimal solutions and the best non-exact procedure is one that uses SA.

  • Renewable energy projects to electrify rural communities in Cape Verde

     Ranaboldo, Matteo; Domenech Lega, Bruno; Vilar, David; Ferrer Marti, Laia; Pastor Moreno, Rafael; García Villoria, Alberto
    Applied energy
    Vol. 118, p. 280-291
    Date of publication: 2014
    Journal article

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

    Even though Cape Verde has high wind and solar energy resources, the conventional strategy for increasing access to electricity in isolated rural areas is by centralized microgrids with diesel generators. In this study, the design of 2 off-grid electrification projects based on hybrid wind¿photovoltaic systems in Cape Verde is developed and analyzed. The design considers some significant novelty features in comparison with previous studies. First a detailed wind resource assessment is carried out combining meso-scale wind climate data and a specialized micro-scale wind flow model. Then a mathematical model is used for the design of off-grid projects considering a combination of individual systems and microgrids. In this study, locations far from the demand points are also considered as possible generation points. Various design configurations are analyzed and compared. The proposed configurations exploit the highest wind potential areas and are economically beneficial in comparison with diesel generator systems.

    Even though Cape Verde has high wind and solar energy resources, the conventional strategy for increasing access to electricity in isolated rural areas is by centralized microgrids with diesel generators. In this study, the design of 2 off-grid electrification projects based on hybrid wind–photovoltaic systems in Cape Verde is developed and analyzed. The design considers some significant novelty features in comparison with previous studies. First a detailed wind resource assessment is carried out combining meso-scale wind climate data and a specialized micro-scale wind flow model. Then a mathematical model is used for the design of off-grid projects considering a combination of individual systems and microgrids. In this study, locations far from the demand points are also considered as possible generation points. Various design configurations are analyzed and compared. The proposed configurations exploit the highest wind potential areas and are economically beneficial in comparison with diesel generator systems.

  • Journal of heuristics

     García Villoria, Alberto
    Collaboration in journals

     Share

  • MILP-based tabu search using corridor method for an assembly line balancing problem with accessibility windows

     Corominas, Albert; García Villoria, Alberto; Calleja Sanz, Gema; Pastor Moreno, Rafael
    Triennial Conference of the International Federation of Operational Research Societies
    p. 192
    Presentation's date: 2014-07-17
    Presentation of work at congresses

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

    In this work, we present an MILP-TS matheuristic for an assembly line balancing problem with accessibility windows. The proposed matheuristic uses an MILP model embedded in a tabu search (TS) algorithm to iteratively solve reduced portions of the original solution space. We use the paradigm of the corridor method to impose exogenous constraints of the original mathematical formulation and, subsequently, we apply an MILP solver to optimally solve the constrained problem. Computational results show the effectiveness of the proposed matheuristic.

  • 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

  • A MILP model to design hybrid wind¿photovoltaic isolated rural electrification projects in developing countries

     Ferrer Marti, Laia; Domenech Lega, Bruno; García Villoria, Alberto; Pastor Moreno, Rafael
    European journal of operational research
    Vol. 226, num. 2, p. 293-300
    DOI: 10.1016/j.ejor.2012.11.018
    Date of publication: 2013-04-16
    Journal article

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

    Electrification systems based on the use of renewable energy sources are a suitable option for providing electricity to isolated communities autonomously. Wind and hybrid wind-photovoltaic (PV) systems are increasingly getting attention. To electrify scattered communities, designs that combine individual systems and microgrids have recently proven advantageous. In this paper we present a mathematical programming model to optimize the design of hybrid wind-PV systems that solves the location of the wind-PV generators and the design of the microgrids, taking into account the demand of the consumption points and the energy potential. The criterion is the minimization of the initial investment cost required to meet the demand. The proposed hybrid model is tested with realistic size instances and results show the instances are efficiently solved.

    Electrification systems based on the use of renewable energy sources are a suitable option for providing electricity to isolated communities autonomously. Wind and hybrid wind–photovoltaic (PV) systems are increasingly getting attention. To electrify scattered communities, designs that combine individual systems and microgrids have recently proven advantageous. In this paper we present a mathematical programming model to optimize the design of hybrid wind–PV systems that solves the location of the wind–PV generators and the design of the microgrids, taking into account the demand of the consumption points and the energy potential. The criterion is the minimization of the initial investment cost required to meet the demand. The proposed hybrid model is tested with realistic size instances and results show the instances are efficiently solved. Moreover, the model is applied to real case studies in Peru; obtained results verify that the hybrid model efficiently finds solutions that significantly reduce cost.

  • Minimising maximum response time

     García Villoria, Alberto; Pastor Moreno, Rafael
    Computers & operations research
    Vol. 40, num. 10, p. 2314-2321
    DOI: 10.1016/j.cor.2013.03.014
    Date of publication: 2013-10
    Journal article

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

    The minmax response time problem (mRTP) is a scheduling problem that has recently appeared in the literature and can be considered as a fair sequencing problem. This kind of problems appears in a wide range of real-world applications in mixed-model assembly lines, computer systems, periodic maintenance and others. The mRTP arises whenever products, clients or jobs need to be sequenced in such a way that the maximum time between the points at which they receive the necessary resources is minimised. The mRTP has been solved in the literature with a greedy heuristic. The objective of this paper is to improve the solution of this problem by means of exact and heuristic methods. We propose one mixed integer linear programming model, nine local search procedures and five metaheuristic algorithms. Extensive computational experiments are carried out to test them.

    The minmax response time problem (mRTP) is a scheduling problem that has recently appeared in the literature and can be considered as a fair sequencing problem. This kind of problems appears in a wide range of real-world applications in mixed-model assembly lines, computer systems, periodic maintenance and others. The mRTP arises whenever products, clients or jobs need to be sequenced in such a way that the maximum time between the points at which they receive the necessary resources is minimised. The mRTP has been solved in the literature with a greedy heuristic. The objective of this paper is to improve the solution of this problem by means of exact and heuristic methods. We propose one mixed integer linear programming model, nine local search procedures and five metaheuristic algorithms. Extensive computational experiments are carried out to test them.

  • Erratum to ¿A solution procedure for type E simple assembly line balancing problem"

     García Villoria, Alberto; Pastor Moreno, Rafael
    Computers and industrial engineering
    Vol. 66, num. 1, p. 201-202
    DOI: 10.1016/j.cie.2013.05.015
    Date of publication: 2013-10-01
    Journal article

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

    The objective of SALBP-E is to minimize the product on the number of workstations by the cycle time. Recently Wei and Chao [Comput. Ind. Eng. 61 (2011) 824¿830] have proposed an exact procedure for solving this problem. It is based on solving iteratively SALBP-2 by means of a MILP model. SALBP-E has not been much studied and hence the high interest of their work. However, the article has several errors that make its understanding harder and, moreover, impede the correct implementation of their procedure for solving SALBP-E. Therefore, it is important to correct them.

    The objective of SALBP-E is to minimize the product on the number of workstations by the cycle time. Recently Wei and Chao [Comput. Ind. Eng. 61 (2011) 824–830] have proposed an exact procedure for solving this problem. It is based on solving iteratively SALBP-2 by means of a MILP model. SALBP-E has not been much studied and hence the high interest of their work. However, the article has several errors that make its understanding harder and, moreover, impede the correct implementation of their procedure for solving SALBP-E. Therefore, it is important to correct them.

  • 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

  • Simulated annealing for improving the solution of the response time variability problem

     García Villoria, Alberto; Pastor Moreno, Rafael
    International Journal of Production Research
    Vol. 51, num. 16, p. 4911-4920
    DOI: 10.1080/00207543.2013.775522
    Date of publication: 2013-05-29
    Journal article

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

  • 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.

  • Heuristic indicators for the design of community off-grid electrification systems based on multiple renewable energies

     Ranaboldo, Matteo; Ferrer Marti, Laia; García Villoria, Alberto; Pastor Moreno, Rafael
    Energy
    Vol. 50, p. 501-512
    Date of publication: 2013
    Journal article

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

    Off-grid rural electrification project configurations which consider hybrid generation systems based on multiple renewable sources and the implementation of micro-grids are the most promising design solutions. The efficient design of those systems is a complex task that is facing several technical issues such as limited time and resources available for the purpose, especially in developing countries. This study proposes indicators for supporting and improving the design of community off-grid electrification projects considering hybrid generation and micro-grids. A (Grid Generation Score) GGS is defined in order to identify most promising locations for being the generation point of a micro-grid. The (No- Generation Score) NGS and the (Independent Generation Score) IGS evaluate respectively if a point should be reliably connected to a micro-grid or should better be an independent generation point. All indicators could be easily and quickly calculated at a very first stage of the plan of a community project requiring as input data only demand and resource distributions in the studied area. It is shown that the utilization of proposed indictors can enhance the design of stand-alone community electrification projects based on renewable energies.

  • 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

  • Dyna

     García Villoria, Alberto
    Collaboration in journals

     Share

  • 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.

  • Design of autonomous rural electrification systems for isolated Spanish communities

     Domenech Lega, Bruno; Ranaboldo, Matteo; Ferrer Marti, Laia; García Villoria, Alberto; Pastor Moreno, Rafael
    International Conference on Microgeneration and Related Technologies
    p. 88
    Presentation's date: 2013-04-15
    Presentation of work at congresses

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

  • 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.

  • Corridor method heuristics to solve rural electrification projects

     Triado Aymerich, Joan; Ferrer Marti, Laia; García Villoria, Alberto; Pastor Moreno, Rafael
    International Workshop on Simulation-Optimization & Internet Computing
    Presentation's date: 2013-07-11
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • MILP based heuristics to solve rural electrification projects

     Triado Aymerich, Joan; Ferrer Marti, Laia; García Villoria, Alberto; Pastor Moreno, Rafael
    European Conference on Operational Research
    p. 39
    Presentation's date: 2013-07-03
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Metodología para el diseño de proyectos de electrificación autónomos con energías eólica y solar, y consideraciones técnicas y sociales

     Ranaboldo, Matteo; Domenech Lega, Bruno; Ferrer Marti, Laia; García Villoria, Alberto; Pastor Moreno, Rafael
    Simposio internacional en energía eolica de pequeña escala
    Presentation's date: 2013-11
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • An Adaptive search for the response time variability problem

     Salhi, Said; García Villoria, Alberto
    Journal of the Operational Research Society
    Vol. 63, num. 5-6, p. 597-605
    DOI: 10.1057/jors.2011.46
    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

    The Response Time Variability Problem (RTVP) is an NP-hard combinatorial scheduling problem, which has recently been reported and formalised in the literature. This problem has a wide range of real-world applications in mixed-model assembly lines, multi-threaded computer systems, broadcast of commercial videotapes and others. The RTVP arises whenever products, clients or jobs need to be sequenced in such a way that the variability in the time between the points at which they receive the necessary resources is minimised. We propose a greedy but adaptive heuristic that avoids being trapped into a poor solution by incorporating a look ahead strategy suitable for this particular scheduling problem. The proposed heuristic outperforms the best existing methods, while being much faster and easier to understand and to implement.

  • 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

  • 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

  • Journal of scheduling

     García Villoria, Alberto
    Collaboration in journals

     Share

  • Premi extraordinari de doctorat en l'ambit d'Enginyeria Industrial

     García Villoria, Alberto
    Award or recognition

     Share

  • 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.

  • Access to the full text
    Heurística basada en un indicador de demanda y potencial para diseñar sistemas de electrificación  Open access

     Ranaboldo, Matteo; Ferrer Marti, Laia; García Villoria, Alberto; Pastor Moreno, Rafael
    International Conference on Industrial Engineering and Industrial Management
    p. 1057-1066
    Presentation's date: 2012-07
    Presentation of work at congresses

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

  • Access to the full text
    Heurística basada en PLEM para resolver proyectos de electrificación rural  Open access

     Triadó-Aymerich, Joan; Ferrer Marti, Laia; García Villoria, Alberto; Pastor Moreno, Rafael
    International Conference on Industrial Engineering and Industrial Management
    p. 1137-1144
    Presentation's date: 2012-07
    Presentation of work at congresses

    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 la literatura se ha propuesto un modelo matemático para diseños de electrificación rural con generación eólica y solar en el que tiene que decidirse la localización de cada uno de los componentes de generación y distribución de energía eléctrica. Cuando la cantidad de viviendas a electrificar excede de un cierto número, la resolución del modelo matemático requiere un tiempo computacional que puede ser inviable en la práctica. En este artículo se presenta un método heurístico basado en programación lineal entera y mixta para la resolución de ejemplares con gran número de viviendas. Para ello proponemos un proceso en dos etapas. En la primera etapa se resuelve el modelo con algunas de las variables relajadas. En la segunda etapa se fijan algunas variables enteras resultado de la etapa 1 y se resuelve el modelo sin relajar. En este artículo se presenta una extensa experiencia computacional para evaluar la heurística propuesta y se constata una mejora de las soluciones obtenidas.

  • 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

  • A Heuristic procedure for solving the Lexicographic Bottleneck Assembly Line Balancing Problem (LB-ALBP)

     Pastor Moreno, Rafael; Chueca, Ignacio; García Villoria, Alberto
    International Journal of Production Research
    Vol. 50, num. 7, p. 1862-1876
    DOI: 10.1080/00207543.2011.578164
    Date of publication: 2011-07-25
    Journal article

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

  • Journal of the Operational Research Society

     García Villoria, Alberto
    Collaboration in journals

     Share

  • SORT: statistics and operations research transactions

     García Villoria, Alberto
    Collaboration in journals

     Share

  • Omega: the international journal of management science

     García Villoria, Alberto
    Collaboration in journals

     Share

  • Assembly automation

     García Villoria, Alberto
    Collaboration in journals

     Share

  • International Journal of Engineering, Science and Technology

     García Villoria, Alberto
    Collaboration in journals

     Share

  • 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

  • Electrificación rural con energía eólica y solar

     García Villoria, Alberto; Pastor Moreno, Rafael; Coves Moreno, Anna Maria; Santos Lopez, M. Antonia de Los; Villafafila Robles, Roberto; Domenech Lega, Bruno; Ferrer Marti, Laia
    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

  • Desarrollo metodológico para la ubicación de microaerogeneradores a escala comunal

     Domenech Lega, Bruno; Ferrer Marti, Laia; Pastor Moreno, Rafael; García Villoria, Alberto
    Simposio Internacional de Energía Eólica de Pequeña Escala
    Presentation's date: 2011-11
    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.

  • 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

  • Solving the response time variability problem by means of the electromagnetism-like mechanism

     García Villoria, Alberto; Pastor Moreno, Rafael
    International Journal of Production Research
    Vol. 48, num. 22, p. 6701-6714
    DOI: 10.1080/00207540902862545
    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

    The response time variability problem (RTVP) is an NP-hard combinatorial scheduling problem that has been recently formalised in the literature. The RTVP has a wide range of real-life applications such as in the automobile industry, when models to be produced on a mixed-model assembly line have to be sequenced under a just-in-time production. 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. In two previous studies, three metaheuristic algorithms (a multi-start, a GRASP and a PSO algorithm) were proposed to solve the RTVP. We propose solving the RTVP by means of the electromagnetism-like mechanism (EM) metaheuristic algorithm. The EM algorithm is based on an analogy with the attraction-repulsion mechanism of the electromagnetism theory, where solutions are moved according to their associated charges. In this paper we compare the proposed EM metaheuristic procedure with the three metaheuristic algorithms aforementioned and it is shown that, on average, the EM procedure improves strongly on the obtained results.

  • Solving the response time variability problem by means of a genetic algorithm

     García Villoria, Alberto; Pastor Moreno, Rafael
    European journal of operational research
    Vol. 202, num. 2, p. 320-327
    DOI: 10.1016/j.ejor.2009.05.024
    Date of publication: 2010-04
    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 a hard scheduling problem that has recently been defined in the literature 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 such a way that the variability in the time between the points at which they receive the necessary resources is minimized. Since the RTVP is a complex problem, heuristic and metaheuristic techniques are needed to solve it. The best results in the literature for the RTVP have been obtained with a psychoclonal algorithm. We propose a genetic algorithm (GA) that is adapted to solve the RTVP. A computational experiment is carried out and it is shown that, on average, the GA produces better results than the psychoclonal algorithm.

  • 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.