GNOM - Grup d'Optimització Numèrica i Modelització

 


El treball del grup comprèn l'optimització numèrica, la modelització de problemes resolubles amb optimització, i l'aplicació de tècniques adients a problemes de l'enginyeria, la indústria, la logística i les tecnologies de la informació. L'optimització numèrica inclou l'estudi de les propietats del problemes estudiats, l'anàlisi de nous algorismes d'optimització (lineal, no lineal, contínua, entera i combinatòria), el desenvolupament de procediments numèrics per a la seva implementació computacional eficient i la comparació amb algorismes previs, si existeixen. La part de modelització implica la cerca de formulacions escaients que permetin la resolució de problemes reals, sovint de gran dimensió. Els problemes reals en que el grup està treballant actualment són: protecció i privacitat de dades estadístiques; i generació òptima d'electricitat en un entorn multimercat.

The group works on both the numerical optimisation and the modelling of problems that can be solved through optimisation. Its work on numerical optimisation includes the analysis of new optimisation algorithms (linear, nonlinear, continuous and integer) and their convergence, the development of numerical procedures for their efficient computational implementation, and the comparison to existing algorithms. The work on modelling focuses on the solution of real problems, which are often large-scale, by finding an equivalentmathematical formulation leading to an optimisation problem, and applying a suitable solver, that has either been specially developed or is commercially available. The modelling languages that are available are used.

The group works on both the numerical optimisation and the modelling of problems that can be solved through optimisation. Its work on numerical optimisation includes the analysis of new optimisation algorithms (linear, nonlinear, continuous and integer) and their convergence, the development of numerical procedures for their efficient computational implementation, and the comparison to existing algorithms. The work on modelling focuses on the solution of real problems, which are often large-scale, by finding an equivalentmathematical formulation leading to an optimisation problem, and applying a suitable solver, that has either been specially developed or is commercially available. The modelling languages that are available are used.

Recent Submissions

  • A specialized interior-point algorithm for huge minimum convex cost flows in bipartite networks 

    Castro Pérez, Jordi; Nasini, Stefano (Elsevier, 2021-05)
    Article
    Restricted access - publisher's policy
    The computation of the Newton direction is the most time consuming step of interior-point methods. This direction was efficiently computed by a combination of Cholesky factorizations and conjugate gradients in a specialized ...

  • Recent advances in optimization techniques for statistical tabular data protection 

    Castro Pérez, Jordi (Elsevier, 2012-01-16)
    Article
    Open Access
    One of the main services of National Statistical Agencies (NSAs) for the current Information Society is the dissemination of large amounts of tabular data, which is obtained from microdata by crossing one or more categorical ...

  • A new interior-point approach for large separable convex quadratic two-stage stochastic problems 

    Castro Pérez, Jordi; Lama Zubirán, Paula de la (2020-11-03)
    Article
    Open Access
    Two-stage stochastic models give rise to very large optimization problems. Several approaches havebeen devised for efficiently solving them, including interior-point methods (IPMs). However, usingIPMs, the linking columns ...

  • Stabilized Benders methods for large-scale combinatorial optimization, with application to data privacy 

    Baena, Daniel; Castro Pérez, Jordi; Frangioni, Antonio (2020-07)
    Article
    Open Access
    The Cell Suppression Problem (CSP) is a very large Mixed-IntegerLinear Problem arising in statistical disclosure control. However, CSPhas the typical structure that allows application of the Benders de-composition, which ...

  • An online optimization-based procedure for the assignment of airplane seats 

    Castro Pérez, Jordi; Sarachaga, Fernando (Springer, 2021)
    Article
    Open Access
    Due to the large number of air flights these days, all procedures involved in their operational management should be carefully optimized. This work presents a novel approach to the seat assignment problem, which focuses ...

  • Using a stabilized Benders algorithm for cell suppression 

    Baena Mirabete, Daniel; Castro Pérez, Jordi; Frangioni, Antonio (John Wiley & sons, 2019)
    Conference report
    Restricted access - publisher's policy
    The cell suppression problem (CSP) is one of the most widely applied post-tabular protection methods for tabular data. Given a set of sensitive cells to be protected, its aim is to find set of additional cells whose removal ...

  • Evaluation of the end-of-life of electric vehicles according to the state-of-health 

    Canals Casals, Lluc; Rodriguez, Marta; Corchero García, Cristina; Carrillo, Rafael E. (2019)
    Conference report
    Open Access
    As a result of monitoring thousands of electric vehicle charges around Europe, this study builds statistical distributions that model the amount of energy necessary for trips between charges, showing that most of trips are ...

  • Overview of the regulation on aggregator agents in Europe 

    Barbero, Mattia; Igualada González, Lucía; Corchero García, Cristina (Institute of Electrical and Electronics Engineers (IEEE), 2018)
    Conference report
    Restricted access - publisher's policy
    Demand Response (DR) mechanisms promise to increase competition in the electricity sector and grid's reliability. Balancing and ancillary services could be offered by consumers for frequency balances but a new actor is ...

  • A hazard ratio was estimated by a ratio of median survival times, but with considerable uncertainty 

    Cortés Martínez, Jordi; González Alastrué, José Antonio; Campbell, Michael J.; Cobo Valeri, Erik (2014-10-01)
    Article
    Open Access
    Objectives: To evaluate the empirical concordance between the hazard ratio (HR) and the median ratio (MR) in survival cancer studies. Study Design and Setting: We selected all cancer survival articles from the New England ...

  • The impact of COVID-19 on teaching in statistics and operations research in higher education 

    Vega Hernández, Maria Concepción; González Alastrué, José Antonio; Morales Arsenal, Roberto; Pinar Pérez, Jesús María (Sociedad de Estadística e Investigación Operativa (SEIO), 2020-07)
    Article
    Open Access
    This study analyzed the current situation of education in the context of the pandemic caused by COVID-19. The worldwide health emergency situation has caused the confinement of people and with it, the closure of centers ...

  • An algorithm for the microaggregation problem using column generation 

    Gentile, Claudio; Spagnolo Arrizabalaga, Enric; Castro Pérez, Jordi (2020-06)
    External research report
    Open Access
    The field of Statistical Disclosure Control aims at reducing the risk of re-identification of an individualwhen disseminating data, and it is one of the main concerns of national statistical agencies. OperationsResearch ...

  • Battery electric buses participation in electricity markets and power systems 

    Chapman, Nick; Barbero, Mattia; Corchero García, Cristina (Institute of Electrical and Electronics Engineers (IEEE), 2019)
    Conference report
    Restricted access - publisher's policy
    Many European cities have committed to procure only zero-emission buses by 2025, considering battery electric buses as the first choice to achieve this objective. However, whilst this technology promises to solve several ...

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