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Sidorov, K. (author), Correia, Gonçalo (author), de Weerdt, M.M. (author), Demirović, E. (author)People want to rely on optimization algorithms for complex decisions but verifying the optimality of the solutions can then become a valid concern, particularly for critical decisions taken by non-experts in optimization. One example is the shortest-path problem on a network, occurring in many contexts from transportation to logistics to...journal article 2024
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Hanou, I.K. (author), de Weerdt, M.M. (author), Mulderij, J. (author)The Train Unit Shunting Problem concerns the parking of trains outside their scheduled use on so-called shunting yards. This is an NP-hard problem, and the current algorithm used by the Netherlands Railways cannot detect whether an instance is infeasible. So, infeasible instances can cause needlessly long computation times. Therefore, this...journal article 2023
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Serna Suarez, I.D. (author), Morales-Espana, G. (author), de Weerdt, M.M. (author), Carrillo-Caicedo, G. (author), Ordóñez-Plata, G. (author), Quiroga, O. A. (author)The integration of Distributed Energy Resources (DERs) in distribution networks comes with challenges, like power quality concerns, but also opens up new opportunities, e.g., DERs can offer competitive energy prices for final users by leveraging time arbitrage. A suitable method to fully exploit such opportunities is to compute the optimal...journal article 2023
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Bliek, Laurens (author), Guijt, A. (author), Karlsson, R.K.A. (author), Verwer, S.E. (author), de Weerdt, M.M. (author)Surrogate algorithms such as Bayesian optimisation are especially designed for black-box optimisation problems with expensive objectives, such as hyperparameter tuning or simulation-based optimisation. In the literature, these algorithms are usually evaluated with synthetic benchmarks which are well established but have no expensive objective...journal article 2023
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van der Linden, J.G.M. (author), de Weerdt, M.M. (author), Demirović, E. (author)Global optimization of decision trees has shown to be promising in terms of accuracy, size, and consequently human comprehensibility. However, many of the methods used rely on general-purpose solvers for which scalability remains an issue. Dynamic programming methods have been shown to scale much better because they exploit the tree structure by...conference paper 2023
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van den Houten, K.C. (author), de Weerdt, M.M. (author), Tax, D.M.J. (author), Freydell, Esteban (author), Christoupoulou, Eva (author), Nati, Alessandro (author)We study a highly complex scheduling problem that requires the generation and optimization of production schedules for a multi-product biomanufacturing system with continuous and batch processes. There are two main objectives here; makespan and lateness, which are combined into a cost function that is a weighted sum. An additional complexity...conference paper 2023
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Wen, J. (author), Abeel, T.E.P.M.F. (author), de Weerdt, M.M. (author)Global soft fruit supply chains rely on trustworthy descriptions of product quality. However, crucial criteria such as sweetness and firmness cannot be accurately established without destroying the fruit. Since traditional alternatives are subjective assessments by human experts, it is desirable to obtain quality estimations in a consistent and...journal article 2023
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van der Linden, J.G.M. (author), de Weerdt, M.M. (author), Demirović, E. (author)Interpretable and fair machine learning models are required for many applications, such as credit assessment and in criminal justice. Decision trees offer this interpretability, especially when they are small. Optimal decision trees are of particular interest because they offer the best performance possible for a given size. However, state-of...conference paper 2022
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Wu, J. (author), Everhardt, Rob (author), Stepanovic, K. (author), de Weerdt, M.M. (author)District heating system (DHS) optimization is becoming an increasingly important problem because of the unused potential in flexibility that could allow less energy being wasted and the integration of renewable energy. While new optimization methods are proposed every year to tackle this problem, the literature lacks a good way to benchmark...conference paper 2022
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- Stepanovic, K. (author), Wu, J. (author), Everhardt, Rob (author), de Weerdt, M.M. (author) abstract 2022
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Guijt, A. (author), Luong, N.H. (author), Bosman, P.A.N. (author), de Weerdt, M.M. (author)Gene-pool Optimal Mixing Evolutionary Algorithms (GOMEAs) have been shown to achieve state-of-the-art results on various types of optimization problems with various types of problem variables. Recently, a GOMEA for permutation spaces was introduced by leveraging the random keys encoding, obtaining promising first results on permutation flow...journal article 2022
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van Hövell, Madeleine E.M.A. (author), Goverde, R.M.P. (author), Bešinović, Nikola (author), de Weerdt, M.M. (author)Trains consist of one or more railway vehicles called rolling stock, which need interior and exterior cleaning and small technical checks on a daily basis. These services are executed at service locations (SLs). Scheduling rolling stock servicing tasks during an operational day is important to guarantee the fulfilment of servicing deadlines....journal article 2022
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Neustroev, G. (author), Andringa, S.P.E. (author), Verzijlbergh, R.A. (author), de Weerdt, M.M. (author)Wind farms suffer from so-called wake effects: when turbines are located in the wind shadows of other turbines, their power output is substantially reduced. These losses can be partially mitigated via actively changing the yaw from the individually optimal direction. Most existing wake control techniques have two major limitations: they use...conference paper 2022
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Stepanovic, K. (author), Wu, J. (author), Everhardt, Rob (author), de Weerdt, M.M. (author)The integration of pipeline energy storage in the control of a district heating system can lead to profit gain, for example by adjusting the electricity production of a combined heat and power (CHP) unit to the fluctuating electricity price. The uncertainty from the environment, the computational complexity of an accurate model, and the scarcity...journal article 2022
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Veviurko, G. (author), Böhmer, J.W. (author), Mackay, Laurens (author), de Weerdt, M.M. (author)Many electric vehicles (EVs) are using today’s distribution grids, and their flexibility can be highly beneficial for the grid operators. This flexibility can be best exploited by DC power networks, as they allow charging and discharging without extra power electronics and transformation losses. From the grid control perspective, algorithms for...journal article 2022
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van der Linden, J.G.M. (author), Mulderij, J. (author), Huisman, B. (author), Den Ouden, Joris W. (author), Van Den Akker, Marjan (author), Hoogeveen, Han (author), de Weerdt, M.M. (author)When trains are finished with their transportation tasks during the day, they are moved to a shunting yard where they are routed, parked, cleaned, subject to regular maintenance checks and repaired during the night. The resulting Train Unit Shunting and Servicing problem motivates advanced research in planning and scheduling in general since...conference paper 2021
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Zomer, Jordi (author), Bešinović, Nikola (author), de Weerdt, M.M. (author), Goverde, R.M.P. (author)Due to increasing railway use, the capacity at railway yards and maintenance locations is becoming limiting to accommodate existing rolling stock. To reduce capacity issues at maintenance locations during nighttime, railway undertakings consider performing more daytime maintenance, but the choice at which locations personnel needs to be...journal article 2021
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- Agterberg, Pallas (author), Bijl, Maarten (author), Hurink, J. L. (author), la Poutré, J.A. (author), van de Vreede, Gerdien (author), de Weerdt, M.M. (author), Wilbrink, Tijs (author) report 2021
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van der Linden, J.G.M. (author), Lane, N.R. (author), de Weerdt, M.M. (author)Due to increasing numbers of intermittent and distributed generators in power systems, there is an increasing need for demand responses to maintain the balance between electricity generation and use at all times. For example, the electrification of transportation significantly adds to the amount of flexible electricity demand. Several methods...journal article 2021
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Bliek, L. (author), Guijt, A. (author), Verwer, S.E. (author), de Weerdt, M.M. (author)A challenging problem in both engineering and computer science is that of minimising a function for which we have no mathematical formulation available, that is expensive to evaluate, and that contains continuous and integer variables, for example in automatic algorithm configuration. Surrogate-based algorithms are very suitable for this type...conference paper 2021