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  • 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
    Date of publication: 2014
    Journal article

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    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.

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

     García Villoria, Alberto; Pastor Moreno, Rafael
    International Journal of Production Research
    Date of publication: 2013-05-29
    Journal article

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  • 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
    Date of publication: 2013-02
    Journal article

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

     García Villoria, Alberto; Pastor Moreno, Rafael
    Computers and industrial engineering
    Date of publication: 2013-10-01
    Journal article

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    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.

  • Minimising maximum response time

     García Villoria, Alberto; Pastor Moreno, Rafael
    Computers & operations research
    Date of publication: 2013-10
    Journal article

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    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.

  • Metodología para el diseño de sistemas autónomos de electrificación rural con energías renovables

     Domenech Lega, Bruno; Ferrer Marti, Laia; Pastor Moreno, Rafael
    International Covention on Environment and Development
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Los sistemas de electrificación autónomos basados en el uso de las energías eólica y solar han demostrado ser adecuados para electrificar comunidades rurales aisladas de países en desarrollo. Éstas pueden ser utilizadas en lugar de otras, como los generadores diésel, contribuyendo, así, a una mejor gestión ambiental y un desarrollo más sostenible. En este trabajo se presenta una metodología para ayudar en el diseño de dichos sistemas. A diferencia de otras herramientas de diseño, la propuesta considera en detalle las soluciones de electrificación; aspectos económicos, técnicos, sociales y ambientales; y la opinión de todos los actores involucrados en el proyecto. La metodología se divide en 3 etapas: ¿ Consiste en recopilar información característica de la comunidad. ¿ Es el proceso de diseño y se divide en 3 niveles de decisión, en función de la importancia de las decisiones a tomar. Se estudia la influencia sobre el coste de modificaciones en la demanda eléctrica (nivel 1), la gestión del sistema (nivel 2) y la seguridad del suministro (nivel 3). En cada nivel se generan diversas alternativas de electrificación incluyendo consideraciones técnicas y sociales, y luego se selecciona la alternativa más adecuada según criterios económicos, técnicos y sociales. ¿ Permite intentar mejorar el coste de la solución obtenida, manteniendo las decisiones previamente tomadas. Para ilustrar el funcionamiento de la metodología, se presenta el diseño del sistema de electrificación de una supuesta comunidad. Se observa la pertinencia de la metodología al permitir adecuar la toma de decisiones a las peculiaridades de cada comunidad

  • 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

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  • 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

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

     Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    TOP
    Date of publication: 2013-07
    Journal article

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  • 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
    Date of publication: 2013-06
    Journal article

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    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
    Date of publication: 2013
    Journal article

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    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
    Date of publication: 2013-04
    Journal article

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    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

  • A dispatching algorithm for flexible job-shop scheduling with transfer batches: an industrial application

     Calleja Sanz, Gema; Pastor Moreno, Rafael
    Production planning and control
    Date of publication: 2013-05-03
    Journal article

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    In this study, we present a dispatching algorithm to solve a real-world case of the flexible job-shop scheduling problem with transfer batches and the objective of minimising the average tardiness of production orders. The proposed algorithm considers two variants: (i) an ordered variant, where the priority dispatching rules are applied in a predefined order, and (ii) a randomised variant, where the user can assign probabilities (weights) to the priority rules. Using the information of the number of units and due dates requested by the only customer, the algorithm provides the sequence of operations that must be performed on each machine, as well as the start and completion times of operations. In order to reduce the impact of unexpected events on a generated schedule, several robustness rules are considered. The obtained results substantially improve the former method used in the company in terms of minimising average tardiness. Additionally, other important benefits are obtained, including significant saving in the time spent on scheduling, simplicity of use of the proposed procedure, robustness against unexpected events, reduction of idle times, improvement of decision-making information, and improvement of on-time delivery performance.

  • 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
    Date of publication: 2013-04-16
    Journal article

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    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.

  • Task assignment considering cross-training goals and due dates

     Olivella Nadal, Jorge; Corominas Subias, Albert; Pastor Moreno, Rafael
    International Journal of Production Research
    Date of publication: 2013-02-01
    Journal article

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  • 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
    Defense's date: 2013-06-28
    Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya
    Theses

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    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.

  • Metodología para el diseño de sistemas de electrificación autónomos para comunidades rurales.  Open access

     Domenech Lega, Bruno
    Defense's date: 2013-06-20
    Department of Business Administration, Universitat Politècnica de Catalunya
    Theses

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    Los sistemas de electrificación autónomos basados en el uso de energías renovables son adecuados para electrificar comunidades rurales aisladas. Para su diseño existen herramientas de apoyo a la toma de decisiones, pero no abarcan algunas consideraciones técnicas y sociales, y/o no entran en el detalle específico del proyecto. En este contexto, el objetivo de esta tesis doctoral es desarrollar una metodología para ayudar en el diseño de sistemas de electrificación autónomos basados en las energías eólica y solar, que sea adecuada a las características económicas, técnicas y sociales de comunidades rurales de países en desarrollo, y que considere la opinión de todos los actores involucrados en el proyecto. La metodología de diseño propuesta se divide en 3 etapas principales: - La primera etapa consiste en realizar evaluaciones iniciales (socioeconómica, energética y técnica) para recopilar la información característica de la comunidad a electrificar. - La segunda etapa es el propio proceso de diseño en sí y se divide en 3 niveles de decisión, ordenados en función de la importancia de las decisiones a tomar. En concreto se estudia la influencia sobre el coste de modificaciones en la demanda (nivel 1), la gestión del sistema (nivel 2) y la seguridad del suministro (nivel 3). Cada nivel de decisión se estructura en 2 pasos: primero se generan diversas alternativas de electrificación con un modelo de programación lineal, incluyendo consideraciones técnicas y sociales; y segundo se selecciona la alternativa más adecuada en función de criterios económicos, técnicos y sociales, mediante la técnica multicriterio de la programación compromiso. - La tercera etapa, opcional, permite intentar mejorar el coste de la solución obtenida, manteniendo las decisiones previamente tomadas. Para la validación de este trabajo de investigación, dos expertos en el campo de la electrificación rural han actuado como hipotéticos usuarios de la metodología de diseño, y han realizado todo el proceso para las comunidades reales de El Alumbre y Alto Perú, ambas en Cajamarca (Perú). Se valida, de esta forma, que la metodología propuesta es adecuada para diseñar sistemas de electrificación autónomos. En concreto, permite personalizar la toma de decisiones de forma clara y estructurada, evaluando una gran cantidad de alternativas de electrificación y obteniendo unos resultados que concuerdan con las preferencias del usuario.

    Autonomous electrification systems based on the use of renewable energies are suitable to electrify isolated rural communities. For its design there are decision-making support tools, but they do not cover some technical and social constraints and do not consider the specific detail of the project. In this context, the aim of this PhD is to develop a methodology for helping to the design of autonomous electrification systems based on wind and solar energies, which is appropriate to the economic, technical and social aspects of rural communities in developing countries, and which considers the views of all stakeholders involved in the project. The proposed design methodology is divided into 3 principal stages: - In the first stage characteristics from the community to electrify are gathered through some initial assessments (socio-economic, resource and technical). - The second stage is the design process itself and is divided into 3 decision levels, ordered according to the importance of the decisions to take. Specifically the influence on the cost of modifications on the demand (level 1), the system management (level 2) and the security of supply (level 3) are studied. Each decision level is divided into 2 steps: first several electrification alternatives are generated through a linear programming model, including technical and social considerations; second the most appropriate alternative is selected based on economic, technical and social criteria, through compromise programming multicriteria technique. - The third stage, optional, allows trying to improve the cost of the obtained solutions, maintaining previously taken decisions. To validate this research work, two experts in the field of rural electrification have acted as hypothetical users of the design methodology, and have carried out all the process for the real communities of El Alumbre and Alto Peru, both in Cajamarca (Peru). Thus, it is validated that the proposed methodology is suitable to design autonomous electrification systems. Specifically, it allows personalizing decision-making in a clear and structured way, evaluating many electrification alternatives and obtaining results that match user’s preferences up.

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    Urban freight transport: Description and classification of existing measures and implementation of two nobel solutions  Open access

     Sanz, Guillem; Pastor Moreno, Rafael; Benedito Benet, Ernest
    Dyna (Medellín)
    Date of publication: 2012
    Journal article

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    En este trabajo se describen y clasifican las soluciones existentes para la distribución urbana de mercancías (DUM) y se proponen dos soluciones novedosas aplicables a la DUM. La descripción de las soluciones proviene de una extensa revisión de la literatura existente. La clasificación de las soluciones existentes es fruto del análisis realizado por los autores, gracias al cual se propone una nueva clasificación en 6 categorías distintas. En cuanto a las soluciones novedosas, se describen y se analiza su utilidad mediante dos pruebas piloto en España en establecimientos de las enseñas Eroski, Caprabo y Mercadona. A lo largo de las pruebas piloto queda patente que dichas dos soluciones pueden ser de gran utilidad para el sector de la DUM.

    En este trabajo se describen y clasifican las soluciones existentes para la distribución urbana de mercancías (DUM) y se proponen dos soluciones novedosas aplicables a la DUM. La descripción de las soluciones proviene de una extensa revisión de la literatura existente. La clasificación de las soluciones existentes es fruto del análisis realizado por los autores, gracias al cual se propone una nueva clasificación en 6 categorías distintas. En cuanto a las soluciones novedosas, se describen y se analiza su utilidad mediante dos pruebas piloto en España en establecimientos de las enseñas Eroski, Caprabo y Mercadona. A lo largo de las pruebas piloto queda patente que dichas dos soluciones pueden ser de gran utilidad para el sector de la DUM

  • Heuristics for the response time variability problem

     Corominas Subias, Albert; Kubiak, Wieslaw; Pastor Moreno, Rafael
    European journal of industrial engineering
    Date of publication: 2012
    Journal article

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  • 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
    Date of publication: 2012
    Journal article

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    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.

  • 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
    Presentation's date: 2012-04-13
    Presentation of work at congresses

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    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.

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    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
    Presentation's date: 2012-07
    Presentation of work at congresses

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    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
    Presentation's date: 2012-07
    Presentation of work at congresses

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    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
    Presentation's date: 2012-07-18
    Presentation of work at congresses

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    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.

  • Access to the full text
    Diseño de sistemas autónomos de electrificación rural con consideraciones técnicas y sociales  Open access

     Domenech Lega, Bruno; Ferrer Marti, Laia; Pastor Moreno, Rafael
    International Conference on Industrial Engineering and Industrial Management
    Presentation's date: 2012-07
    Presentation of work at congresses

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    Los sistemas de electrificación basados en el uso de energía eólica y solar, y que combinan la distribución en microrred e individual, son adecuados para electrificar comunidades aisladas de forma autónoma. Para diseñarlos existen modelos que consideran restricciones técnicas y económicas. Entre las diferentes soluciones posibles, algunas pueden tener problemas en la continuidad del suministro o resultan difíciles de gestionar. Este trabajo analiza estos condicionantes y propone mejoras a incorporar en los modelos, que se validan mediante la aplicación a la comunidad de Alto Perú (Cajamarca, Perú). Se demuestra que las mejoras propuestas permiten obtener unas soluciones con unos beneficios sociales que compensan ampliamente los pequeños incrementos de coste.

  • Cocktail of heuristics for solving hard problems

     Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Dyna
    Date of publication: 2012-05
    Journal article

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  • Pure and hybrid metaheuristics for the response time variability problem

     García Villoria, Alberto; Corominas Subias, Albert; Pastor Moreno, Rafael
    Date of publication: 2012-08-16
    Book chapter

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  • Distribución urbana de mercancías: descripción y clasificación de soluciones existentes e implementación de dos soluciones novedosas

     Sanz Marzà, Guillem; Pastor Moreno, Rafael; Benedito Benet, Ernest
    Date: 2012-04-24
    Report

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    En este trabajo se describen y clasifican las soluciones existentes para la distribución urbana de mercancías (DUM) y se proponen dos soluciones novedosas aplicables a la DUM. La descripción de las soluciones proviene de una extensa revisión de la literatura existente. La clasificación de las soluciones existentes es fruto del análisis realizado por los autores, gracias al cual se propone una nueva clasificación en 6 categorías distintas. En cuanto a las soluciones novedosas, se describen y se analiza su utilidad mediante dos pruebas piloto en establecimientos de la enseña Eroski, Caprabo y Mercadona. A lo largo de las pruebas piloto ha quedado patente que dichas dos soluciones pueden ser de gran utilidad para el sector de la DUM.

  • Generación de alternativas para el diseño de sistemas de electrificación rural

     Domenech Lega, Bruno; Ferrer Marti, Laia; Pastor Moreno, Rafael
    Convención de Ingeniería Eléctrica
    Presentation's date: 2011-06
    Presentation of work at congresses

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  • 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
    Presentation's date: 2011-09-08
    Presentation of work at congresses

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    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

  • 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
    Date of publication: 2011-09
    Journal article

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  • Planning working time accounts under demand uncertainty

     Lusa Garcia, Amaia; Pastor Moreno, Rafael
    Computers & operations research
    Date of publication: 2011-02
    Journal article

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    Working timeaccounts(WTAs)areemployer-orientedflexibilitysystemsthathavebeenappliedin industrybutcouldbeusedfarmore.WTAsenablecapacitytobeadaptedtofluctuationsindemand.The requiredcapacity,whichisneededtoplanWTAs,usuallydependsonseveralfactors.Itisoften impossibletoreliablypredicttherequiredcapacityorunrealistictoadjustittoaprobability distribution.Insomecases,asetofrequired-capacityscenarioscanbedetermined,eachwitharelated probability.Thispaperpresentsamultistagestochasticoptimisationmodelthatisrobust(i.e.,provides a solutionthatisfeasibleforanypossiblescenario)andminimisestheexpectedtotalcost(which includesthecostofovertimeandthecostofthecapacityshortage).

  • Assembly line balancing: general resource-constrained case

     Corominas Subias, Albert; Ferrer Marti, Laia; Pastor Moreno, Rafael
    International Journal of Production Research
    Date of publication: 2011
    Journal article

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  • LB-ALBP: The lexicographic bottleneck assembly line balancing problem

     Pastor Moreno, Rafael
    International Journal of Production Research
    Date of publication: 2011-04-15
    Journal article

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  • 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
    Date of publication: 2011-07-25
    Journal article

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

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

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  • 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; Ferrer Marti, Laia
    Participation in a competitive project

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  • 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
    Date of publication: 2011-05-16
    Journal article

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  • Optimizing microwind rural electrification projects. A case study in Peru

     Ferrer Marti, Laia; Pastor Moreno, Rafael; Capó Plaza, Gregori Miquel; Velo Garcia, Enrique
    Journal of global optimization
    Date of publication: 2011
    Journal article

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

     Pastor Moreno, Rafael; García Villoria, Alberto; Corominas Subias, Albert
    Assembly automation
    Date of publication: 2011
    Journal article

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  • Mathematical programming modeling of the Response Time Variability Problem

     Corominas Subias, Albert; Kubiak, W; Pastor Moreno, Rafael
    European journal of operational research
    Date of publication: 2010-01
    Journal article

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  • An entropy-based measurement of working time flexibility

     Olivella Nadal, Jorge; Corominas Subias, Albert; Pastor Moreno, Rafael
    European journal of operational research
    Date of publication: 2010-01
    Journal article

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  • Capacity planning with working time accounts in services

     Corominas Subias, Albert; Olivella Nadal, Jorge; Pastor Moreno, Rafael
    Journal of the Operational Research Society
    Date of publication: 2010-02
    Journal article

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  • Solving the Response Time Variability Problem by means of psychoclonal approach

     García Villoria, Alberto; Pastor Moreno, Rafael
    Journal of heuristics
    Date of publication: 2010-06
    Journal article

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  • Diseño de sistemas autónomos de electrificación rural con energía eólica y solar

     Domenech Lega, Bruno; Ferrer Marti, Laia; Pastor Moreno, Rafael
    Conferencia Internacional de Ciencias Empresariales
    Presentation's date: 2010-10
    Presentation of work at congresses

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  • A new metaheuristic procedure for improving the solution of the response time variability problem

     Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    International Conference on Industrial Engineering and Industrial Management. Congreso de Ingeniería de Organización
    Presentation of work at congresses

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  • Programación de la producción en máquinas en paralelo con lotes de transferencia: un caso de estudio.

     Calleja Sanz, Gema; Pastor Moreno, Rafael
    International Conference on Industrial Engineering and Industrial Management. Congreso de Ingeniería de Organización
    Presentation's date: 2010-09-10
    Presentation of work at congresses

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  • Un procedimiento metaheurístico para mejorar la resolución del Response Time Variability Problem

     Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael
    Conferencia Internacional de Ciencias Empresariales
    Presentation of work at congresses

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  • 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
    Date of publication: 2010-01-01
    Journal article

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    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
    Date of publication: 2010-01-01
    Journal article

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    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.