HAL Portal Univ-Côtedazur
Not a member yet
95391 research outputs found
Sort by
Application des réseaux de neurones informés par la physique aux équations de Maxwell
No full textIn the last decade, the study of electromagnetic waves has been a primary concern in many applications such as designing radar or antenna technology as well as cloaking devices and metalenses which fill the role of a lens through the use of metamaterials. The electromagnetic field follows the Maxwell equations that in most applications have no analytic solutions. Traditional ways to solve this system, which are based on numerical methods such as the finite difference or the finite element methods, are computationally expensive. This becomes a problem when a lot of simulations need to be done such as when doing numerical optimisation. Physics-informed neural networks (PINNs) have been introduced only recently in the world of Scientific Machine Learning (SciML) as a novel way to solve systems of partial differential equations. Therefore, in this study we would like to study the concept of PINNs for the Maxwell equations to generate surrogate models, trading accuracy for faster results. We pursue three objectives: (1) establish an appropriate PINN framework for the Maxwell equations ; (2) assess this PINN framework on a collection of simple cases to eventually build towards complex and realistic applications ; (3) complete the basic PINN implementation with additional techniques to improve results and test them on the previous cases. In the end, we found that our framework was effective to solve the simpler cases considered but that more difficult cases benefited greatly from the addition of techniques.Durant la dernière décennie, l’étude des ondes électromagnétiques a été une préoccupation majeure dans de nombreux domaines. Notamment pour la conception de radars ou d’antennes ainsi que pour les technologies furtives et les métalentilles qui remplissent le rôle de lentille grâce à l’utilisation de métamatériaux. Le champ électromagnétique suit les équations de Maxwell qui, dans la plupart des applications, n’ont pas de solution analytique. La façon traditionnelle de résoudre ce système, avec la méthode des éléments finis, est coûteuse en termes de temps de calcul. Cela devient un problème lorsque de nombreuses simulations doivent être effectuées, par exemple lors d’une optimisation. Les réseaux de neurones informés par la physique (PINN) n’ont été introduits que récemment dans le monde de l’apprentissage automatique scientifique comme nouvelle façon de résoudre des systèmes d’équations aux dérivées partielles. Par conséquent, dans cette étude, nous aimerions utiliser les PINN avec les équations de Maxwell pour générer des modèles de substitution, quitte à perdre un peu de précision pour avoir des résultats plus rapidement. Nous avons trois objectifs : (1) établir un modèle PINN pour les équations de Maxwell ; (2) évaluer ce modèle sur un ensemble de cas simples pour éventuellement aller vers des applications complexes et réalistes ; (3) compléter le PINN avec des techniques supplémentaires pour améliorer les résultats et les tester sur les cas précédents. En fin de compte, nous avons constaté que les PINNs pouvaient résoudre les cas les plus simples, mais que les plus difficiles nécessitaient l’ajout de techniques appropriées.</div
Statistical Insights into Fibronectin Networks in the Extracellular Matrix
No full textInternational audienc
Euclid. IV. The NISP Calibration Unit
No full textInternational audienceThe near-infrared calibration unit (NI-CU) onboard Euclid's Near-Infrared Spectrometer and Photometer (NISP) is the first astronomical calibration lamp based on light-emitting diodes (LEDs) to be operated in space. Euclid is a mission in ESA's 'Cosmic Vision 2015-2025' framework, to explore the dark universe and provide a next-level characterisation of the nature of gravitation, dark matter, and dark energy. Calibrating photometric and spectrometric measurements of galaxies to better than 1.5% accuracy in a survey homogeneously mapping ~14000 deg^2 of extragalactic sky requires a very detailed characterisation of near-infrared (NIR) detector properties, as well their constant monitoring in flight. To cover two of the main contributions - relative pixel-to-pixel sensitivity and non-linearity characteristics - as well as support other calibration activities, NI-CU was designed to provide spatially approximately homogeneous (<12% variations) and temporally stable illumination (0.1%-0.2% over 1200s) over the NISP detector plane, with minimal power consumption and energy dissipation. NI-CU is covers the spectral range ~[900,1900] nm - at cryo-operating temperature - at 5 fixed independent wavelengths to capture wavelength-dependent behaviour of the detectors, with fluence over a dynamic range of >=100 from ~15 ph s^-1 pixel^-1 to >1500 ph s^-1 pixel^-1. For this functionality, NI-CU is based on LEDs. We describe the rationale behind the decision and design process, describe the challenges in sourcing the right LEDs, as well as the qualification process and lessons learned. We also provide a description of the completed NI-CU, its capabilities and performance as well as its limits. NI-CU has been integrated into NISP and the Euclid satellite, and since Euclid's launch in July 2023 has started supporting survey operations
Euclid. II. The VIS Instrument
No full textInternational audienceThis paper presents the specification, design, and development of the Visible Camera (VIS) on the ESA Euclid mission. VIS is a large optical-band imager with a field of view of 0.54 deg^2 sampled at 0.1" with an array of 609 Megapixels and spatial resolution of 0.18". It will be used to survey approximately 14,000 deg^2 of extragalactic sky to measure the distortion of galaxies in the redshift range z=0.1-1.5 resulting from weak gravitational lensing, one of the two principal cosmology probes of Euclid. With photometric redshifts, the distribution of dark matter can be mapped in three dimensions, and, from how this has changed with look-back time, the nature of dark energy and theories of gravity can be constrained. The entire VIS focal plane will be transmitted to provide the largest images of the Universe from space to date, reaching m_AB>24.5 with S/N >10 in a single broad I_E~(r+i+z) band over a six year survey. The particularly challenging aspects of the instrument are the control and calibration of observational biases, which lead to stringent performance requirements and calibration regimes. With its combination of spatial resolution, calibration knowledge, depth, and area covering most of the extra-Galactic sky, VIS will also provide a legacy data set for many other fields. This paper discusses the rationale behind the VIS concept and describes the instrument design and development before reporting the pre-launch performance derived from ground calibrations and brief results from the in-orbit commissioning. VIS should reach fainter than m_AB=25 with S/N>10 for galaxies of full-width half-maximum of 0.3" in a 1.3" diameter aperture over the Wide Survey, and m_AB>26.4 for a Deep Survey that will cover more than 50 deg^2. The paper also describes how VIS works with the other Euclid components of survey, telescope, and science data processing to extract the cosmological information
Civil Liability in the Age of Smart Cities: New Legal Challenges
No full textInternational audienceThe emergence of smart cities, driven by AI and the IoT, challenges traditional civil liability frameworks. The complexity of multi-stakeholder environments, the autonomy of intelligent systems, and mass data collection necessitate new legal approaches. Recent European initiatives seek to modernize liability regimes, ensuring a balance between technological innovation, accountability, and the protection of fundamental rights
Exercise Recommendations and Practical Considerations for Asthma Management—An EAACI Position Paper
No full textInternational audienceABSTRACT Exercise is an important treatment for people with asthma and should be considered alongside pharmacological therapy when developing personalised asthma management plans. Despite this, there remains limited guidance concerning the practicalities of asthma‐specific exercise prescription. This European Academy of Allergy and Clinical Immunology task force was therefore established to achieve three fundamental aims: first, to provide an up‐to‐date perspective concerning the role of exercise for asthma management (i.e., describe the disease modifying potential of exercise and associated impact on asthma‐related extrapulmonary comorbidities); second, to develop pragmatic recommendations to facilitate safe and effective exercise prescription; and third, to identify key unmet needs and provide focused direction for future research. The position paper is structured as a practically focused document, with recommendations formulated according to best available scientific evidence and expert opinion, with an emphasis on providing healthcare providers with pragmatic advice that can be implemented during routine asthma review
Characterisation of magnetic activity of M dwarfs: Possible impact on surface brightness
No full textInternational audienceContext. M dwarfs are an ideal laboratory for hunting Earth-like planets, and the study of chromospheric activity is an important part of this task. On the one hand, according to the study of short-term activity their high levels of magnetic activity can affect habitability and make it difficult to detect exoplanets orbiting around them. On the other hand, however, long-term activity studies can show whether or not these stars exhibit cyclical behaviour in their activity, facilitating the detection of planets in periods of low magnetic activity.Aims. The long-term cyclical behaviour of magnetic activity can be detected by studying several spectral lines and explained by different stellar dynamo models (such as αΩ or α2 dynamos). In the present work, we studied the Mount Wilson S index to search for evidence of long-term activity possibly driven by a solar-type dynamo.Methods. We studied a sample of 35 M dwarfs with different levels of chromospheric activity and spectral classes ranging from dM0 to dM6. To do this, we used 2965 spectra in the optical range from different instruments installed in the southern and northern hemispheres to construct time series with extensions of up to 21 years. We analysed these time series with different time-domain techniques to detect cyclical patterns. In addition, using 2MASS-KS and visible photometry we also studied the potential impact of chromospheric activity on surface brightness.Results. Using the colour index (V − KS), we calculated the chromospheric emission levels and found that most of the stars in the sample have low emission levels, indicating that most of them are inactive or very inactive stars. For 31 stars of 35, we constructed time series using the S indexes, and we detected 13 potential cycles of magnetic activity. These cycles have an approximate duration of between three and 19 years, with false alarm probabilities (FAPs) less than 0.1%. For stars that do not show cyclic behaviour, we found that the mean value of the S index varies between 0.350 and 1.765, and its mean variability and chromospheric emission level are around 12% and −5.110 dex, respectively. We do not find any impact of chromospheric activity on the surface brightness in the domain of −5.6 < log R′H K < −4.5
Preparar os estudantes para o emprego na “Formação 4.0”: uma conceção didática multimodal baseada nos últimos desenvolvimentos tecnológicos no domínio profissional
No full textInternational audienceThis article examines the impact of emerging technologies on training professions, with a particular focus on the adaptation of the professionalization of educational engineers and adult trainers since 2019. The article demonstrates how economic and political changes have rapidly altered the nature of work in this field, forcing companies in a competitive environment to develop the digital skills of in-service trainers and those of students graduating from university. Based on a multimodal engineering model incorporating a variety of teaching practices, virtual reality and artificial intelligence, the text presents the action strategy and problem-solving implemented in a master’s degree course in France to manage this race to the top, while strengthening the quality of digital uses and remaining consistent with the skills at the heart of the professions involving interaction with others for which students are destined.Este artículo examina la evolución de las profesiones de la formación en relación con las tecnologías emergentes, con especial atención a la adaptación de la profesionalización de los ingenieros pedagógicos y los formadores de adultos desde 2019. El artículo demuestra cómo los cambios económicos y políticos han alterado rápidamente la naturaleza del trabajo en este campo, obligando a las empresas en un entorno competitivo a desarrollar las competencias digitales de los formadores en activo y las de los estudiantes que se gradúan en la universidad. Basándose en un modelo de ingeniería multimodal que incorpora diversas prácticas pedagógicas, la realidad virtual y la inteligencia artificial, el texto presenta la estrategia de acción y resolución de problemas puesta en práctica en un máster en Francia para gestionar esta carrera hacia la cima, reforzando al mismo tiempo la calidad de los usos digitales y siendo coherentes con las competencias que constituyen el núcleo de las profesiones que implican la interacción con los demás a las que están destinados los estudiantes.Cet article aborde l’évolution des métiers de la formation en lien avec les technologies émergentes en s’intéressant plus particulièrement à l’adaptation de la professionnalisation des ingénieurs pédagogiques et formateurs d’adultes depuis 2019. Il souligne comment les changements économiques et politiques ont modifié rapidement leur travail, obligeant les entreprises dans un environnement concurrentiel à faire évoluer les compétences numériques des formateurs en poste et celles des étudiants en cours de diplomation à l’université. À l’appui d’un modèle d’ingénierie multimodale intégrant des pratiques pédagogiques variées, la réalité virtuelle et l’intelligence artificielle, le texte présente la stratégie d’action et la résolution de problèmes mises en place dans un parcours de master en France pour gérer cette course en avant tout en renforçant la qualité des usages numériques et demeurer en cohérence avec les compétences au cœur des métiers de l’interaction avec autrui auxquels se destinent les étudiants.Este artigo analisa o impacto das tecnologias emergentes nas profissões da formação, com especial incidência na adaptação da profissionalização dos engenheiros educativos e dos formadores de adultos a partir de 2019. O artigo demonstra como as mudanças econômicas e políticas alteraram rapidamente a natureza do trabalho neste domínio, obrigando as empresas, num ambiente competitivo, a desenvolver as competências digitais dos formadores em exercício e as dos estudantes que terminam o ensino superior. Com base num modelo de engenharia multimodal que integra diversas práticas pedagógicas, realidade virtual e inteligência artificial, o texto apresenta a estratégia de ação e de resolução de problemas implementada num mestrado em França para gerir esta carreira em direção ao topo, reforçando a qualidade das utilizações digitais e sendo coerente com as competências que estão no cerne das profissões de interação com os outros para as quais os estudantes são destinados
Opérations de visite et de saisies par les agents de la DGCCRF, droits de la défense et secret professionnel
No full textInternational audience(Crim. 13 févr. 2024, no 23-90.020, inédit
