263134 research outputs found
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How I Learned to Stop Worrying and Drop Justified True Belief
No full textsponsorship: Fonds Wetenschappelijk Onderzoek|12AAT25Nstatus: Accepte
The evolutionary role of mutational robustness: theoretical insights
No full textMutational robustness, the ensemble of mechanisms that allow organisms to maintain a stable phenotype despite genetic mutations, affects adaptive evolution in several ways. Many models have attempted to explain how mutational robustness might evolve and shape adaptation, but the variety of approaches and assumptions complicates a clear synthesis. Here, we categorize and critically discuss the main approaches for modeling the evolutionary causes and consequences of mutational robustness. We discuss how robustness can emerge from aspects of biological organization (e.g., modularity, critical dynamics) and selection (e.g., stabilizing selection) and how robustness can both enhance and constrain evolvability [e.g., through cryptic genetic variation (CGV)]. We conclude by discussing challenges related to model complexity and computational cost and outline the foremost outstanding questions.sponsorship: KU Leuven|ZKE3820, KU Leuven Research Council, KU Leuven|C16/23/007status: Published onlin
Bearing housing as a sensor: Estimation of lumped bearing loads using accurate housing models
No full textAccurate knowledge of bearing loads is crucial for assessing structural health state, estimating Remaining Useful Life (RUL), and optimizing performance in various mechanical systems. However, direct measurement of these loads is often intrusive and costly. This study presents a model-based virtual sensing framework for estimating lumped bearing loads using the bearing housing as a sensor. The approach relies on a finely tuned Finite Element (FE) model of the housing, combined with strategically placed strain and acceleration sensors. The linear FE model is integrated into an Augmented Kalman Filter (AKF) scheme to estimate both system states and input loads. A rigorous model updating procedure enhances the accuracy of the FE model, while a calibration-based Boundary Condition (BC) identification method enables strain gauge placement close to the boundaries, achieving a high Signal-to-Noise Ratio (SNR) of the strain measurements. To evaluate its effectiveness, the BC identification method is first assessed through a numerical example. Experimental validation on a setup with industrial complexity demonstrates that the proposed method enables load estimation across both quasi-static and higher frequency dynamic ranges. In comparison to existing virtual sensing methods, utilizing the high SNR locations and BC identification in this study has led to accurate estimation of individual bearing loads, without modeling the rotating components, and only using non-intrusive sensors placed on the housing. The results highlight the feasibility of transforming even stiff bearing housings into cost-effective and scalable virtual sensors for load estimation in various industrial applications.sponsorship: The Research Foundation - Flanders (FWO) is gratefully acknowledged for its support through research grant no. S006119N. This research was partially supported by Flanders Make, the strategic research center for the manufacturing industry. Additionally, the authors gratefully acknowledge the Internal Funds KU Leuven and the Chinese Scholarship Council for their support. (Research Foundation - Flanders (FWO)|S006119N, Flanders Make, Internal Funds KU Leuven, Chinese Scholarship Council)status: Published onlin
A Systematic Approach to Study Preferences for Complexity at Different Levels of Order
No full textsponsorship: This work has been supported by a PhD fellowship and a junior postdoctoral fellowship from the Research Foundation-Flanders (FWO), both awarded to Eline Van Geert (Grants 11D3621N and 1244825N), and by a long-term structural funding from the Flemish Government awarded to Johan Wagemans (METH/21/02). The data, materials, and analysis code for the experiment are available as the additional online materials on the Open Science Framework (https:/doi.org/10.17605/osf.io/ur7g5). (Research Foundation-Flanders (FWO)|11D3621N, Research Foundation-Flanders (FWO)|1244825N, Flemish Government|METH/21/02)status: Published onlin
Gebonden Toestanden en Stromen
No full textThis thesis comprises a wide range of topics. The first work revolves around an active matter system, where a bound state between two run-and-tumble probe particles is induced by a thermal medium, whose interactions with the probe are purely repulsive. The bound state is then induced by the self-trapping behavior of the active particles and the density profile of the thermal particles. There is a surprising analogy between the formation of these bound states and the formation of Cooper pairs in superconductors. The electron, as described by the Dirac equation, may be seen as obeying a master equation of precisely the same form as the master equation of the run-and-tumble particle. Taking this view literally, Cooper pairs are bound states of two run-and-tumble particles whose binding is enabled by the thermal medium in which they reside.
The second chapter revolves around these zig-zag electrons which are described by this master-equation formulation of the Dirac equation. This zig-zag behavior may be visualized by the calculation of trajectories that form an extension of Bohmian trajectories. These tools of visualization are then applied to the famous Stern-Gerlach experiment.
The third part of the thesis concerns superconductivity, and more specifically the Josephson effect. Josephson junctions form the cornerstone of superconducting quantum technology, providing anharmonicity to qubits and phase sensitivity to SQUIDs. The physics of Josephson junctions is very rich, with features such as Andreev bound states playing a crucial part in the understanding of the Josephson current and the current-phase relation. Yet the microscopic modeling of Josephson junctions remains challenging, and many things remain unexplained. One of the issues addressed in this thesis is the issue of current conservation in the modeling of Josephson junctions, but also in mean-field superconductivity generally. We show that ensuring current conservation has a dramatic effect on the Andreev states and on the current-phase relation, challenging assumptions which have long become standard in the literature.
The final part of the thesis is concerned with superconducting qubits, and the effect of the precise shape of the CPR on qubit properties. We uncover resonances of the Andreev bound states, and show that these resonances correspond to lessened anharmonicity for transmon qubits.status: Publishe
Overheidsaansprakelijkheid in de PFAS-affaire: een cocktail van stilzittende overheden, het voorzorgsbeginsel, actieve openbaarheid en vorderingen door belangenverenigingen
No full textIn een wegens meerdere redenen belangrijk vonnis van 19 september 2024 veroordeelt de Brusselse rechtbank van eerste aanleg het Vlaamse Gewest en de OVAM omdat ze zich tussen september 2017 en juni 2021 op foutieve wijze onthielden van onderzoeks- en communicatiemaatregelen inzake de PFAS verontreiniging in woonwijken nabij de 3M-site te Zwijndrecht. In deze noot wordt toelichting gegeven bij markante onderdelen van dit vonnis, zoals de rol van het voorzorgsbeginsel binnen overheidsaansprakelijkheid, de wisselwerking met het Bodemdecreet, het belang bij deze vordering van niet alleen milieu- maar ook economische belangenverenigingen en de beperkingen van aansprakelijkheidsvorderingen die slechts door dergelijke verenigingen als onrechtstreekse schadelijders worden ingesteld. Daarnaast wordt stilgestaan bij de vraag of de overheden niet reeds voor september 2017 hadden moeten handelen, gelet op eerdere kennis over de PFAS-verontreiniging en de mogelijke gezondheidsrisico’s. Door dit af te wijzen, lijkt de rechtbank aan overheden een relatief passieve rol toe te kennen binnen een context van ‘novel entities’. Tot slot worden kritische bemerkingen geplaatst bij de beoordeling in het vonnis van de voor het bewijs van fout ingeroepen schendingen van art. 23 Grondwet, art. 2 en 8 EVRM en de actieve openbaarheid van milieu-informatie.sponsorship: Fonds Wetenschappelijk Onderzoek|12AA025Nstatus: Publishe
Mechanical, thermal and acoustic properties of hybrid flax-PP composites reinforced with CaCO3 produced via CO2 mineralization
No full textsponsorship: The research was supported by Fonds Wetenschappelijk Onder-zoek-Vlaanderen (FWO) . D.M. acknowledges support from FWO in the form of strategic basic research fellowships (File number: 1S13924N) . (Fonds Wetenschappelijk Onder-zoek-Vlaanderen (FWO), FWO|1S13924N)status: Publishe
Data-gedreven gezondheidsbeoordeling en prognostiek van technische systemen bij beperkte databeschikbaarheid
No full textPrognostics and Health Management (PHM) is a multidisciplinary framework for assessing the condition of engineering assets and forecasting their remaining useful lifetime to enable predictive maintenance. This thesis addresses the challenge of developing PHM models under limited data availability, a common constraint in real-world industrial systems and across diverse engineering domains. The research explores how hybrid and domain-informed learning frameworks can enhance model performance, interpretability, and reliability in such data-constrained environments.
The study is organized around three key objectives: (1) a comparative evaluation of conventional machine learning (ML) and deep learning (DL) methods for constructing health indicators (HIs) from limited time-series data; (2) the integration of domain knowledge into DL models through constraint-guided optimization to improve physical consistency and reduce dependence on annotated datasets; and (3) the quantification of predictive uncertainty to support more reliable decision-making.
These objectives are demonstrated across three case studies: (i) anomaly detection and fault diagnosis in a small household coffee vending machine using multi-sensor data; (ii) bearing degradation modeling using constraint-guided gradient descent (CGGD) to enforce monotonic degradation, bounded health states, and energy-aligned signal behavior; and (iii) hybrid modeling for remaining useful time estimation and uncertainty quantification in telecom base transceiver station backup batteries under forecasted variable load conditions.
The results demonstrate that embedding domain-informed constraints significantly improves the robustness and interpretability of DL models under limited data conditions. Hybrid frameworks that combine physics-based and data-driven approaches further enhance reliability and uncertainty estimation. Collectively, this work introduces new methods for constraint-guided learning and hybrid PHM modeling, advancing the development of data-efficient, explainable, and trustworthy predictive maintenance systems.status: Publishe
Binary imposters: Mergers in massive hierarchical triple stars
No full textsponsorship: FK would like to thank Eva Laplace, Jakob van den Eijnden, Julia Bodensteiner, Tomer Shenar, and Zsolt Keszthelyi for the helpful discussions. The authors also acknowledge support from the Netherlands Research Council NWO (VIDI 203.061 grant). (Netherlands Research Council NWO|VIDI 203.061)status: Publishe
Industry-Science-Interaction in Innovation: The Role of Transfer Channels and Policy Support
No full textWe investigate the effects of different channels of industry-science collaboration on new product sales at the firm-level and whether government subsidies for
collaboration make a difference. We distinguish four collaboration channels: joint R&D, consulting/contract research, IP licensing, human resource transfer. Employing firm-level panel data from the German Community Innovation Survey and a conditional difference-in-differences methodology, we find a positive effect of industry-science collaboration on product innovation success only for joint R&D, but not for the other three channels. The positive effect is limited to subsidized collaboration. Our results suggest that government subsidies are required to bring firms and public science into forms of collaboration that are effective in producing higher innovation output.status: Accepte