Portail HAL Nantes Université
Not a member yet
120169 research outputs found
Sort by
Modelling a single-mode 915 MHz microwave applicator for low-moisture food treatment: comparison between COMSOL Multiphysics ® and CST Studio Suite ®
No full textInternational audienceTwo computational models were developed by using COMSOL Multiphysics® and CST Studio Suite® to simulate the microwave heating process of paprika and to compare the electromagnetic results obtained from each modelling software. The dielectric properties of paprika were initially measured at room temperature using the cavity perturbations technique and then estimated as a function of temperature. Experimental validation was performed in a rectangular waveguide with iris openings of 125 (Configuration 1) and 88 mm (Configuration 2). The impact of variations in both dielectric constant and dielectric loss on temperature prediction was examined, along with the sensitivity of the results to the positioning of probes. Simulated and experimental temperatures were compared at two positions inside the product: the centre (T1) and the bottom (T2). Additionally, the distribution of the electromagnetic field and the microwave reflected power were examined. The results highlight the strong impact of dielectric property variations on local temperature prediction and provide valuable insights for optimizing industrial microwave heating processes for food powders
Channel Charting for Efficient Precoding in Cell-Free Massive MIMO
No full textInternational audienceCell-free massive MIMO (CF-mMIMO) systems promise enhanced spectral efficiency and uniform service by deploying numerous distributed access points (APs) that jointly serve users. However, centralized precoding, which offers optimal performance by leveraging global channel state information (CSI), imposes significant fronthaul overhead due to the extensive CSI exchange between APs and the central processing unit (CPU). In contrast, distributed precoding reduces fronthaul demands, but undergoes performance degradation due to the lack of coordination between APs. This paper introduces a novel framework that strikes a balance between these two scenarios by employing channel charting (CC) as a lightweight CSI compression mechanism at each AP. CC maps high-dimensional CSI into a low-dimensional pseudo-location space, capturing essential channel characteristics. These pseudo-locations are transmitted to the CPU with minimal overhead, where advanced machine learning models are employed to infer effective downlink precoding vectors, thereby approximating centralized performance while reducing fronthaul signaling. Extensive simulations on realistic synthetic datasets demonstrate that our approach achieves very promising results. This work highlights the potential of integrating CC and machine learning to enhance scalability and efficiency in CF-mMIMO networks.</div
« Opposition à une saisie-appréhension par un tiers détenteur : contours et conditions », JEX TJ Paris, 7 juill. 2025, RG no 25/80329
No full textInternational audienc
Effets d’un schème trompeur et de remédiations
No full textInternational audienceThis study aims to investigate a misleading scheme that occurred in an aeronautic workshop, and to test possible forms of remediation. A misleading scheme is a scheme activated by deceptive characteristics of the situation which might reduce performance. Such a scheme had been identified among operators in a metal frame stretching workshop: they used the results obtained on one frame to program a stretching machine for subsequent frames. As it proved difficult to study this misleading scheme in the real workshop, the microworld paradigm was used for this research to evaluate two forms of remediation: a brief training course in the inhibition of the misleading scheme and a real-time simulation program. The misleading scheme appeared among the “naïve” participants in the same way it had appeared among the operators in the real workshop. Moreover, in the microworld the misleading scheme led to a decrease in performance. The real-time simulation tool did not lead to the disappearance of the misleading scheme, even though it seemed to allow users to learn how to refine the rules guiding the machine tool settings. The article thus raises the question of the persistence of a misleading scheme and the relevance of using real-time simulation without support to avoid its use in a situation where it is not relevant.Cette étude cherche à investiguer un schème trompeur, apparu dans un atelier d’aéronautique, elle cherche également à tester des formes de remédiations possibles. Un schème trompeur est un schème activé par des caractéristiques trompeuses de la situation et qui peut diminuer la performance. Un tel schème avait été identifié chez des opérateurs dans un atelier d’étirage de cadres métalliques. Il se manifestait par l’utilisation des résultats obtenus sur un cadre afin de paramétrer une machine d’étirage pour les cadres suivants. L’étude de ce schème trompeur s’étant révélée difficile dans l’atelier réel, le paradigme du micromonde est utilisé afin d’évaluer deux formes de remédiation : une formation succincte à l’inhibition du schème trompeur et une simulation en temps réel. Le schème trompeur apparaît chez les participants « tout venant » dans l’étude sur le micromonde comme il apparaissait chez les opérateurs de l’atelier. De plus, dans le micromonde, le schème trompeur provoque une diminution des performances. L’outil de simulation en temps réel ne permet pas de faire disparaître le schème trompeur même s’il semble permettre aux utilisateurs d’apprendre à affiner les règles guidant le réglage de la machine-outil. L’article pose ainsi la question de la persistance d’un schème trompeur et de la pertinence de l’utilisation de la simulation en temps réel sans accompagnement pour éviter son utilisation dans une situation où il n’est pas pertinent
Correspondence about the article “Effect of hydrocortisone on mortality in patients with severe community-acquired pneumonia. The REMAP-CAP corticosteroid domain randomized clinical trial”
No full textInternational audienc
Exploring the molecular cargos associated with extracellular vesicles extracted from bone tissue to identify novel players in osteoblast function
No full textInternational audienceExtracellular vesicles (EVs), composed of proteins, lipids, and nucleic acids, are key mediators of intercellular communication across various tissues. However, research on EVs isolated directly from bone tissue remains limited. Here, we identified for the first time and characterized two EV subpopulations extracted from bone tissue and enhanced our understanding of their roles in bone physiology. These two EV subpopulations were reproducibly isolated: a large EV population (lEV; 237.7 ± 8.8 nm) and a small EV population (sEV; 109.2 ± 8.3 nm), both exhibiting the expected shape and presence of EV and bone cell markers. Comparative analysis of their cargos revealed unique or enriched proteins and miRNA profiles for each, suggesting shared functional characteristics with bone cells, including osteocytes, osteoblasts, and osteoclasts. Notably, lEVs contained proteins such as FHL2 and pleiotrophin, along with miRNAs including miR-15b-5p, miR-29a-3p, and miR-128-3p, all of which are involved in early osteogenic signaling pathways such as Hippo, TGF-β, and Wnt. Furthermore, sEVs contained ALP, PAPSS2, and miR-125b, both known regulators of matrix mineralization. Both EV subpopulations were internalized by stromal ST2 and preosteoblastic MC3T3-E1 cells. We present evidence that lEVs significantly enhanced ALP activity in ST2 cells, indicating early osteogenic stimulation, whereas sEVs partially promoted matrix mineralization in primary osteoblasts. Our findings provide novel insights into the role of bone-derived EVs as possible complementary mediators of osteogenesis in vivo and highlight the potential of their cargos in advancing bone regeneration strategies.NEW & NOTEWORTHY This study identifies for the first time two extracellular vesicle (EV) subpopulations isolated from young male mice bone tissue, with distinct mean size and molecular signature. Analysis of the protein and miRNA cargos of these EVs indicates that the large and small EVs are involved in different stages of osteogenesis, from commitment to the formation of mineralized tissue. These findings provide new insights into the role of bone-derived EVs in bone physiology
Regular Lagrangians are smooth Lagrangians
No full text16 pages, 2 figures. v2: Revised, to appear in J. Math. Soc. Japa
Rien sur nous sans nous
No full textfanzineCe fanzine est le résultat de l'atelier collectif et participatif "Livres sensibles : Éditer, une pratique alternative d’écriture" animé par Magali Avezou (curatrice, Archipelago) et Laurence Bizien (documentaliste) lors des journées annuelles de recherche-création du CIREC (Centre de recherche-création en sciences sociales) autour du care et de ses représentations, organisées dans le cadre du programme Industries culturelles et créatives PEPR ICCARE (Journées d’accélération de l'ICCARE-LAB – arts visuels et arts numériques). Le fanzine, inspiré des interventions des journées et du ressenti des participants, a été réalisé grâce à une collecte de documents (photographies, dessins, poèmes ..), une sélection et mise en page des planches lors de l'atelier et a été imprimé en risographie. Publication collective restituant les journées, il en est le témoignage sensible. L'ensemble des contributeurs/contributrices et acteurs/actrices de ce commun est cité sur la 4e de couverture
3D Electron diffraction on nanoparticles: minimal size and associated dynamical effects
No full textInternational audienceOver the past decade, advances in electron diffraction (ED) have significantly improved the determination and refinement of crystal structures, making it a viable alternative to traditional X-ray diffraction (XRD), especially for very small volumes, such as nanoparticles (NPs). This work evaluates the application of advanced 3D ED techniques to the analysis of isolated NPs, focusing on their efficacy and limitations in terms of crystal size and accuracy of results. Our investigation begins by addressing the challenges of obtaining 3D ED data for NPs, including sample preparation, instrument capabilities, and the choice of 3D ED methods. We find that 3D ED can provide highly accurate structure refinements for crystals in the 50-100 nm range and is also effective for the analysis of NPs as small as 10 nm. While kinematical approximations often provide accurate refinements similar to those obtained from powder XRD, the accuracy depends on the specific data set and may not always align with traditional reliability indicators.Our study shows that dynamical scattering effects, even in tiny crystals, challenge the assumption that they are negligible in thin crystal scenarios. Addressing these effects through full dynamical refinement significantly improves the accuracy and reliability of the structure determination. This report suggests a paradigm shift in viewing dynamic scattering effects not as mere obstacles but as opportunities to explore crystal structures in greater detail on smaller scales. By embracing these complexities, 3D ED can provide precise and reliable structural insights that are critical to the advancement of nanotechnology and materials science
