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Investigating the Impact of Alignment Angle Between Copper Turns and Magnetic Core on Magnetic Field Coupling in PCB Integrated Inductors
No full textInternational audienceThis study investigates the influence of copper trace alignment relative to the magnetic core in PCB-embedded inductors, focusing on the effects of the alignment angle on perpendicular magnetic flux density that shall cause eddy currents in AC applications. Although aligning traces at right angles is common in traditional inductor winding, it may not be feasible for PCB designs due to manufacturing constraints. The study proposes an investigation of the angular-shift effects on magnetic flux while maintaining practical PCB manufacturability in potential applications like static power converters. By evaluating how the angular shift impacts magnetic flux behavior in copper traces, this research is part of a study that aims to address efficiency losses and heating caused by eddy currents. Through Finite Element Method (FEM) simulations using Ansys Maxwell software and experimental validation, the results demonstrate that smaller alignment angles, particularly at 0°, reduce perpendicular flux what shall mitigate eddy current formation in AC applications, improving inductor performance
Euclid. I. Overview of the Euclid mission
No full textInternational audienceThe current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015-2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14,000 deg^2 of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance
Evaluation of cancer cells mechanical phenotype associated with the resistance to treatment in myeloid leukemia
No full textInternational audienceAcute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by an abnormal proliferation of leukemic cells (or blasts) that build up in the bone marrow and the blood. Despite the recent progress in therapies, which consist essentially in intensive cycles of chemotherapy or the use of targeted therapies, most of the AML patients do not recover, having a five-year survival rate of 20%. This poor prognosis may be explained by tumor cell heterogeneity, which could be related to cellular differentiation, as well as to the tumor microenvironment. Indeed, the rapid clonal expansion of leukemic blasts within the bone marrow alters the physical characteristics of the tumor microenvironment and decreases the available space for each cell type. This project seeks to establish a correlation between drug resistance and leukemic cell intrinsic stiffness, in the context of the dynamic dialogue between leukemic cells and their microenvironment.One of the most widely utilized passive microfluidic methods in literature for measuring cellular mechanical properties with high throughput involves the monitoring of cell deformations as they flow passively through constricted channels. Here we propose an original readout traducing the way the cell perturbs the pressure distribution within the device, as it blocks the flow when passing through the constriction. Preliminary results suggest different mechanical profile associated with AML cell lines that are sensitive or resistant to chemotherapy, consistent with findings in the literature, hence demonstrating the pertinence of our approach. Furthermore, our data suggests that the mechanical properties of resistant AML cell lines may be treatment-dependent, varying with the applied therapeutic agent
Algebres de Jordan libres et representations de sl(2,J)
No full textLet J be a unital Jordan algebra. When J is the free Jordan algebra J(D) on D generators, a formula for the dimension of its homogeneous components has been conjectured in [22].Let sl2(J) be the universal central extension of the Tits-Kantor-Koecher Lie algebra T KK(J). In the present paper, we connect the conjecture with the representation theory of sl2(J). For example, we prove the conjecture under the hypothesis that the Lie algebra sl2(J(D)) is F P∞, or if certain modules admit a good filtration.However, most of our results are unconditional. For example, we prove that sl2(J) is finitely presented if J is finitely presented. We also show that the standard modules are finite dimensional. Surprisingly the proofs make use of some deep results of E. Zelmanov.</div
Design, manufacture and characterization of compact optics for micro-CPV
No full textInternational audienceConcentrator photovoltaics (CPV) modules are complex, heavy and bulky which hinders the deployment of this technology. Over the past few years, the miniaturization of this technology, called micro-CPV, promises to make more compact and less expensive modules. This article focuses on the design, fabrication and characterization of a 350× single-stage concentrator optic made of PMMA. A matrix of 16 lenses has been produced, and a prototype module has been fabricated and characterized outdoors, achieving an optical efficiency of over 80%
Développement de modèles basse et moyenne fidélité pour l'étude du flottement gyroscopique d'hélices à pales rigides ou flexibles
No full textAs the aviation industry strives to push the boundaries of traditional design, aircraft are increasingly incorporating larger diameter engines and higher aspect-ratio wings. While these innovations promise enhanced performance, they also raise important concerns about their influence on whirl flutter. This aeroelastic instability, which can impact traditional propeller-driven aircraft but also more advanced configurations with open rotors, manifests as a divergent precessional motion of the engine's rotational axis. Addressing whirl flutter is therefore essential to ensure the safety and reliability of future aircraft generations.The work presented in this thesis aims to develop various modeling approaches for this instability, with the goal of deepening its understanding and providing methods for efficiently conducting stability studies. In this context, the developed models are based on certain simplifying assumptions, placing them within low- to mid-fidelity levels. The simplest models, which are easier to use, rely on two-dimensional aerodynamic theories (low-fidelity), while others, more comprehensive but also more complex to implement, are based on external numerical codes that inherently incorporate three-dimensional flow effects using potential flow theory (mid-fidelity). Special attention is given to blade flexibility, which has long been overlooked in whirl flutter studies, and is considered in the low-fidelity models.These various modeling methods for whirl flutter are applied to evaluate the stability of two systems. The first, a simplified model with few degrees of freedom, simulates a propeller mounted on a flexible pylon. The second, more detailed but computationally more expensive, is a finite element model of an actual wing/nacelle/propeller mock-up used in wind tunnel testing. While the first system, due to its simplicity, is intended for numerous parametric studies, the second offers the possibility of evaluating whirl flutter onset in a realistic case.Results show that the low-fidelity models developed in this thesis offer more accurate stability predictions compared to some existing models. Meanwhile, mid-fidelity models remain crucial for studying complex configurations, such as non-axial flow scenarios, where whirl flutter is found to be less likely to occur. A detailed analysis of the impact of blade flexibility, expected to play an increasingly important role in novel engine configurations, reveals that it gives rise to new instability phenomena. Notably, it induces instabilities in a forward whirl motion, contrasting with the classical whirl flutter observed in rigid-blade propellers, where instability manifests as a backward whirl motion. Overall, for typical blade stiffness values, flexibility tends to significantly stabilize the system.Alors que les avions de nouvelle génération tendent à intégrer des moteurs de plus grand diamètre sur des ailes d’allongement croissant, des préoccupations émergent concernant l'impact de ces évolutions sur le flottement gyroscopique. Cette instabilité aéroélastique, pouvant affecter les avions à hélice classiques comme des configurations plus complexes équipées d'open rotors, se manifeste par un mouvement de précession divergent de l'axe de rotation du moteur. Il est donc essentiel de s'intéresser à ce phénomène pour garantir la sécurité et la fiabilité des prochaines générations d'avions.Les travaux présentés dans cette thèse ont pour objectif de modéliser et d'approfondir la compréhension du flottement gyroscopique. Plusieurs modèles aéroélastiques, reposant sur une modélisation aérodynamique basse fidélité (modèles analytiques) ou moyenne fidélité (Vortex Particle Method), sont développés afin d'étudier la stabilité de deux configurations. La première est un système simplifié avec peu de degrés de liberté représentant une hélice montée sur un pylône flexible. La seconde configuration, plus détaillée mais également plus complexe, est un modèle éléments finis d’une véritable maquette d’aile/nacelle/hélice utilisée pour des essais en soufflerie. Une attention particulière est apportée à la prise en compte de la flexibilité des pales, un facteur amené à jouer un rôle prépondérant pour les moteurs de prochaine génération.Les résultats montrent que les modèles de basse fidélité développés dans cette thèse offrent de meilleures prédictions du flottement gyroscopique que certains modèles existants. Les modèles de moyenne fidélité demeurent essentiels pour l'étude de configurations complexes, telles que les situations d'écoulements non axiaux, où il a été observé que le flottement gyroscopique est moins susceptible de se manifester. Une analyse approfondie de l'impact de la flexibilité des pales, qui devrait jouer un rôle de plus en plus important dans les nouvelles générations de moteurs, révèle qu'elle engendre l'apparition de nouvelles phénoménologies d'instabilité. En particulier, elle induit des instabilités avec un mouvement de précession direct, contrastant avec le flottement gyroscopique classique observé pour les hélices à pales rigides, qui se manifeste par un mouvement de précession indirect. De manière générale, pour des valeurs réalistes de rigidité des pales, leur flexibilité tend à stabiliser significativement le système
Selective Transparent Contacts Based on a Hafnium‐Titanium Oxide Alloy with Optimized Band Alignment for c‐Si Solar Cells
No full textInternational audienceIn this study, the potential of hafnium-titanium oxide (HfxTi1-xOy, HTO) thin films is explored and deposited by low-temperature (75 °C) atomic layer deposition (ALD) as selective contacts for crystalline silicon (c-Si) solar cells. Through a comprehensive analysis of their selectivity, optical and chemical properties, and band alignment characteristics, the HTO films are shown to exhibit remarkable electron selectivity. They formed efficient ohmic contacts on n-type silicon, while exhibiting diode-like characteristics on p-type silicon, confirming their selective behavior. Band alignment analysis at the HTO/n-Si interface revealed a high valence band offset and a low conduction band offset, facilitating efficient electron extraction and blocking hole transport. Optical measurements demonstrate the high optical transparency of the HTO films with a bandgap above 3.5 eV, making them suitable for photovoltaic applications. A proof-of-concept photovoltaic device is evaluated, and significant improvements are observed in all solar cell parameters following the incorporation of HTO, highlighting the potential of low-temperature ALD-deposited HTO films as efficient electron-selective contacts for next-generation c-Si solar cells
Plagiat en éducation et intégrité scientifique à l'ère de l'IA générative : IAgiat ?
No full textThis paper examines the challenges posed by generative AI (GAI) to plagiarism and scientific integrity in education and research. It begins by defining plagiarism and scientific integrity, acknowledging variations in definitions across different contexts (e.g., US vs. European standards). The core question addressed is whether using GAI constitutes plagiarism. The answer is nuanced: it depends on the transparency of the AI's use. Openly using GAI without claiming authorship avoids plagiarism, while concealing its use constitutes both plagiarism and a breach of scientific integrity. The gray area lies in using GAI for improving writing style without explicitly mentioning it – a situation where the assessment of plagiarism becomes complex and context-dependent (hard vs. soft sciences).The paper highlights the significant increase in publications on scientific integrity, correlating it to the temptation to cheat under the growing pressure to publish. The use of GAI tools raises concerns about originality, as it potentially leads to the repetition of existing knowledge, even if reformulated. While GAI can detect plagiarism, it paradoxically struggles to detect its own use in generating text, creating a risk of unintentional plagiarism. Further risks associated with GAI include data fabrication, image manipulation, and the creation of "papermill" content (low-quality papers inflating publication metrics).The paper suggests two main strategies to mitigate these risks: (1) training students and scientists in responsible GAI use, and (2) revising assessment methods to evaluate critical thinking and originality, rather than solely focusing on the final product. The author proposes various approaches to training, such as providing guidelines for teaching writing with AI and encouraging students to critically analyze AI-generated content, including its references. Revised assessment methods could include prohibiting AI use during exams or requiring students to document and explain their use of GAI, emphasizing the critical thinking process involved. The paper concludes by noting a lack of evidence on the effectiveness of these recommendations, suggesting further research is needed to effectively address the challenges posed by GAI in academic settings
An informed machine learning based environmental risk score for hypertension in European adults
No full textInternational audienceBackground: The exposome framework seeks to unravel the cumulated effects of environmental exposures on health. However, existing methods struggle with challenges including multicollinearity, non-linearity and confounding. To address these limitations, we introduce SEANN (Summary Effect Adjusted Neural Network) a novel approach that integrates pooled effect sizes—a form of domain knowledge—with neural networks to improve the analysis and interpretation of hypertension risk factors.Methods: Based on data from 18,337 adults aged 40-65y participants in the GCAT cohort in Catalonia, covering a diverse selection of 53 environmental factors, we computed two environmental risk scores for hypertension prevalence using deep neural networks. An informed risk score using SEANN, integrating 11 different pooled effect size estimates from meta-analyses, and an agnostic counterpart for comparison. For each score, we computed Shapley values to extract and compare the learnt exposure-outcome relationships from each neural network model.Results: The obtained predictive performances were similarly good for the agnostic NN and SEANN (AUC 0.7). However, we demonstrate substantial improvements in the scientific validity of the informed risk score captured relationships. Directly informed variables were closer to their corresponding relationships observed in literature and other non-informed variables were successfully adjusted with their direction of associations more in line with previous studies. The mean delta SHAP distance averaged over all variables of the relationships extracted with both models and those observed in the literature, was 6 times lower with SEANN compared with the agnostic NN. The most influential environmental variables within the informed risk score included smoking intensity, Mediterranean diet adherence, coffee consumption and sedentary behaviour.Conclusions: This study demonstrates the added value of SEANN over conventional, purely data-driven machine learning approaches. By aligning learned relationships with established literature-based effect sizes, SEANN improves the disentanglement of exposure effects on hypertension