Publications scientifiques de l'Université de Reims Champagne-Ardenne
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A Note on the Limiting Corner Angle of Liquid Drops in the Lubrication Approximation
No full textInternational audienceThe derivation of thin-film equations for liquid drops on an inclined plane is analyzed. It was found that the limiting corner angle of the contact line for such a drop should be close to 25 degrees, in accordance with observations. This is achieved by the method of Fuchsian reduction, which yields a more complete solution of the equation for the profile of drops than other methods
Impact of Input Data Augmentation on Lithium-Ion Battery SOC Estimation: Comparison Between LSTM and GRU
No full textInternational audienceThis paper investigates the impact of input variable selection on the accuracy of lithium-ion battery state-of-charge estimation (SOCE). Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) algorithms were used for SOCE. Traditional methods use voltage, current, and temperature as inputs. In contrast, this work considers additional signals from the vehicle’s CAN bus including speed, engine torque, and heater power to determine whether a richer set of inputs enhances prediction performance. The approach applies a wavelet transform to remove signal noise and employs correlation analysis followed by principal component analysis (PCA) to lower dimensionality and improve signal quality by removing collinear variables. Two modeling strategies are compared: one using features selected by correlation analysis, and the other using only three physically meaningful variables (voltage, current, and temperature). Experimental validation on real-world driving data of a 2014 BMW i3 (60 Ah) over 70 trips under varied environmental conditions confirms that more input data does not systematically lead to better accuracy. The results highlight the importance of variable selection and the benefits of simplicity when key variables are well chosen
Traitements orthodontiques chez les patients atteints de parodontite de stade IV
No full textLa parodontite de stade IV se caractérise par une perte osseuse sévère, des migrations dentaires et des altérations fonctionnelles et esthétiques majeures. Par ailleurs, de plus en plus de patients présentant des malocclusions et une maladie parodontale sollicitent un traitement orthodontique, ce qui nécessite d’évaluer les bénéfices et les risques associés à une telle prise en charge. Cette thèse présente les spécificités du traitement orthodontique chez ces patients, en en définir les indications, les limites et les adaptations nécessaires, et en proposant un protocole clinique fondé sur les donné actuelles. Après avoir décrit les caractéristiques de la maladie et ses répercussions sur les conditions du traitement orthodontique, le travail détaille les conditions requises pour débuter un traitement. Les principes biomécaniques adaptés à un parodonte réduit y sont développés. L’accent est enfin mis sur la nécessité d’une collaboration interdisciplinaire étroite et d’un suivi parodontal régulier tout au long du traitement, éléments essentiels pour assurer une prise en charge durable
PET Imaging in Head and Neck Squamous Cell Carcinoma: from Staging to Response Assessment
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On informative state vectors for discrete dynamic estimation in switched systems using the model-based minimum distance method
No full textInternational audienceThis technical note addresses the discrete dynamic estimation problem in switched linear systems using the model-based minimum distance method (MB-MDM). Prior work has shown that, for this method, the state vector must be sufficiently far from the origin to guarantee an accurate estimation of the discrete dynamic, thereby confirming inherent conflicts between discrete dynamic estimation and feedback control objectives in switched systems. To enhance the accuracy of the MB-MDM, this work focuses on characterizing the region of state vectors that enable exact discrete dynamic estimation, termed informative state vector (ISV). The contributions of this paper are twofold. Firstly, a necessary and sufficient condition based on linear matrix inequalities is derived to determine whether a state vector is informative, revealing that ISV must lie outside a specific ellipsoid. Based on this observation, an ellipsoid-based approach is then proposed to estimate the ISV region
Modélisation haute résolution des panaches de méthane : validation et expériences de sensibilité pour explorer les approches de quantification des émissions
No full textInternational audienceMethane (C H 4 ) emissions from natural gas, waste, and industrial sources are routinely detected by satellite and aerial platforms; however, quantifying these plumes remains challenging due to their complex structure and rapidly changing fine-scale atmospheric dynamics. This study directly addresses the resulting uncertainties in UAV flight measurements by employing the Fire Dynamics Simulation (FDS) in Large Eddy Simulation (LES) mode, leveraging mean wind data derived from LiDAR datasets. The FDS model was validated with in-situ CH 4 concentration data collected by Uncrewed Aerial Vehicles (UAVs) during controlled release experiments. Our analysis of ten extensively sampled plumes shows that FDS accurately reproduces the magnitude and spatiotemporal variations of the observed plumes for sufficiently large pipes (diameter > 0.6 cm). We found that factors such as gas exit velocity, obstacles, and terrain topography significantly affect the near-field dynamics of the plumes. To a lesser extent, the temperature of the gas influences plume behaviour at higher mass-flow rates. We highlight the added value of high-resolution LES modelling to understand CH 4 plume dynamics captured by various sensors, aiming to improve current emissions quantification methodsLes émissions de méthane (CH4) provenant du gaz naturel, des déchets et des sources industrielles sont couramment détectées par des plateformes satellitaires et aériennes ; cependant, la quantification de ces panaches reste complexe en raison de leur structure multidimensionnelle et de la dynamique atmosphérique fine, qui évolue rapidement. Cette étude traite directement les incertitudes résultant des mesures par vol de drones (UAV) en employant la simulation de dynamique d'incendie (FDS) en mode de simulation des grandes échelles (LES), en exploitant les données de vent moyen dérivées de jeux de données LiDAR. Le modèle FDS a été validé avec des données de concentration de CH4 recueillies in situ par des drones lors d'expériences de rejets contrôlés. Notre analyse de dix panaches largement échantillonnés montre que le modèle FDS reproduit avec précision l'ampleur et les variations spatiotemporelles des panaches observés pour des conduites de diamètre suffisant (diamètre > 0,6 cm). Nous avons constaté que des facteurs tels que la vitesse de sortie du gaz, les obstacles et la topographie du terrain affectent de manière significative la dynamique en champ proche des panaches. Dans une moindre mesure, la température du gaz influence le comportement du panache à des débits massiques plus élevés. Nous soulignons la valeur ajoutée de la modélisation LES à haute résolution pour comprendre la dynamique des panaches de CH4 captée par divers capteurs, dans le but d'améliorer les méthodes actuelles de quantification des émissions
Unlocking Parallel Efficiency in Monte Carlo Particle Transport Applications on Manycore Architectures
No full textInternational audienceMany Monte Carlo Particle Transport (MCPT) applications exist to simulate complex physical problems like nuclear reactor modeling using random sampling to simulate particles. They often involve complex interacting data structures, and huge and qualitative input to provide accurate results. These operations are often complex to parallelize, involving communications and synchronizations between processes. Modern supercomputers have evolved to answer the need for more computational power, and now present complex and massive architectures, regrouping tens of thousands of manycore nodes. Parallelizing complex algorithms such as MCPT is challenging, especially on modern architectures, since the number of cores keeps increasing. Most existing MCPT applications focus their effort of parallelization on scaling across nodes, to benefit from the increasing number of computations nodes on most systems. It is mainly because most of these applications have been developed before the standardization of manycore nodes in supercomputers. These applications don't use intra-node parallelization to its full potential. In this paper, our objective is to maximize intra-node parallelism since manycore architectures are multiplying on modern supercomputers. We target shared memory MCPT parallelization and found how to overcome the following limitations: the storage of particles across levels of memory, the cost of reduction operations, and the structure of the algorithm forcing synchronizations. In this paper, we focused on how to tackle them incrementally up to an asynchronous implementation, which achieves a scaling superior to 80% on a 128 cores node
Improving Leishmania isolation in field conditions: Efficacy of caspofungin against yeasts contamination
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First steps in walking, the potential beginnings of resonance? The inaugural experience of mountain walking among vocational high school students
No full textInternational audienceInspired by Merleau-Ponty's phenomenology of perception, the sociology of relations to the world, developed by Harmut Rosa (2018), explores how a connection is established with the world, with oneself, and with others. After analyzing several canonical works on walking, written by naturalists, anthropologists and philosophers, providing detailed accounts of walks, this study explores how walking in nature can represent a potential opportunity for resonance for high school students who are unfamiliar with this environment. More specifically, it seeks to identify the potential beginnings of a resonance string, the promises and early signs of vibration, likely to lead, if repeated and consolidated, to the internalisation of a singular area of resonance regarding the relationship to the body and the environment. Three main results emerge based on three types of relationships: 1. a relationship of alienation develops among high school students during this first walking experience (between repulsion and indifference towards the environment); 2. a relationship based on resistance (as a ridgeline between alienation and resonance) emerges depending on the hostility of the terrain, the nature of the effort, and the sense of self-efficacy of the practitioners; 3. a vibrant chord of resonance is revealed in some high school students during the walk as they are affected by the silence, the landscape, and the connection to others