HAL Université de Savoie
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On localisation of eigenfunctions of the Laplace operator
No full textInternational audienceWe prove (i) a simple sufficient geometric condition for localisation of a sequence of first Dirichlet eigenfunctions provided the corresponding Dirichlet Laplacians satisfy a uniform Hardy inequality, and (ii) localisation of a sequence of first Dirichlet eigenfunctions for a wide class of elongating horn-shaped domains. We give examples of sequences of simply connected, planar, polygonal domains for which the corresponding sequence of first eigenfunctions with either Dirichlet, or Neumann, boundary conditions -localise in
Does patellar resurfacing matter in robotic‐assisted total knee arthroplasty with functional alignment principles?
No full textInternational audienceAbstract Purpose While new philosophies in total knee arthroplasty (TKA) aim to optimize alignment and ligament balancing, restoring the anterior compartment and understanding the consequences of patella resurfacing remain challenging. This study evaluates the functional consequences of anterior compartment restoration, with a specific focus on patella resurfacing when performing robotic‐assisted TKA using functional alignment (FA) principles. Methods This retrospective comparative study included 268 patients affected by an end‐stage varus osteoarthritis who underwent robotic TKA according to FA principles. Patients were divided into two main groups based on whether patellar resurfacing procedure was performed (study group) or not (control group). Restoration of the anterior compartment and functional outcomes were evaluated using radiographic assessments, along with the Knee Society Score (KSS Knee and KSS Function), Forgotten Joint Score (FJS) and Kujala Score, all recorded at a minimum follow‐up of 2 years. Results One hundred thirty‐eight cases underwent patellar resurfacing and 130 did not. Patellar tilt and patellar translation were reduced by 74.63% ( p < 0.005) and 69.89% ( p < 0.005) in the resurfaced group compared to the non‐resurfaced group, respectively. The patellar offset values showed no significant differences between the two groups ( p = 0.873), although both groups showed a significant reduction in patellar offset in the post‐operative compared to the preoperative, 10.31% and 14.29%, respectively, in the resurfaced and non‐resurfaced groups ( p < 0.05). KSS knee and functional scores were higher in the non‐resurfaced group compared to the resurfaced group ( p = 0.023 and p = 0.017, respectively). Kujala and FJS scores were similar between the two groups. Conclusion Both resurfaced and non‐resurfaced approaches improve radiographic outcomes regarding the anterior knee compartment after TKA performed with FA and image‐based robotic system, without signs of superiority in clinical outcomes in the resurfaced group. The decision of patella resurfacing can be made on an individualized basis. Level of Evidence Level II
New experimental constraints on seismic velocities and densities across the α–β quartz transition at deep crustal conditions
No full textInternational audienceAt the pressure and temperature conditions of the lower crust, quartz undergoes a displacive phase transition from a trigonal (α) to a hexagonal phase (β). At room pressure, the α–β quartz transition occurs at 574.1 °C and it is associated with large changes in the thermodynamic and elastic properties. For that reason, it is interpreted as the cause of significant seismic velocity contrasts in the crust seen by seismic tomography. Existing thermodynamic models and Equations of State (EoS) of quartz are mostly constrained by data collected at room pressure (or at high pressure and room temperature). In this work we characterized the α–β quartz transition experimentally at simultaneous HP–HT conditions using synchrotron X-ray diffraction and acoustic measurements, and derived values of Vp, Vs, the adiabatic bulk modulus (Ks) and the shear modulus (G). The data collected in the α field agree with the models from the literature, so entrapment pressures of α -quartz inclusions calculated via elastic barometry with these EoS should be reliable. However, our measured Vp, Vs, and Ks are significantly lower than those predicted for β-quartz. Whatever the cause of this discrepancy, interpretations of seismic data in terms of the properties of β-quartz in the lower crust and calculations of entrapment conditions of quartz inclusions in the stability field of β-quartz should be treated with caution
On the development of breathing and vocalization in a prelinguistic child
No full textInternational audienceThis is an exploratory case study on respiration during vocalization in a prelinguistic infant (7;15 to 9;15). Respiratory data have been acquired using RespTrack system with two respiratory belts, acoustic data with a microphone and video data using camcorders. We labelled all acoustic events that the infant prouced with her mouth while interacting freely with her mother. We determined inhalation and exhalation windows during these intervals
Higher rates of meniscal and chondral lesions in second compared with first revision anterior cruciate ligament reconstructions
No full textInternational audienceAims The aim of this study was to describe the rate of meniscal and chondral lesions in patients undergoing their first revision anterior cruciate ligament (ACL) reconstruction compared with those undergoing a second revision reconstruction. Methods This was a retrospective single-centre study, involving patients who underwent at least one revision ACL reconstruction between January 2012 and January 2022. Inclusion criteria were all patients aged between 16 and 60 years who underwent revision ACL reconstruction. Exclusion criteria were those with a multiligament knee injury, those who underwent a concomitant osteotomy, and those who had undergone ≥ three previous reconstructions. Results A total of 257 patients met the inclusion criteria. Of these, for 204 patients it was their first revision (R1), and for 51 it was their second revision (R2). Two patients who underwent a third revision were excluded. Medial meniscal tears were significantly more prevalent in the R2 group than in the R1 group – 40 (78.4%) compared with 106 (51.9%) (p < 0.001). There was no difference in the rates of the type of meniscal treatment in the medial and lateral compartments between the R1 and R2 groups. Chondral lesions were significantly more prevalent in the R2 group: 33 (64.7%) compared with 97 (47.6%) (p = 0.045). Medial and lateral compartment chondral lesions were significantly more prevalent in the R2 group (56.9% and 39.2%, respectively) compared with the R1 group (36.3% and 13.5%) (p = 0.012 and p = 0.001). Conclusion The rates of meniscal tears and chondral lesions were significantly higher in patients undergoing their second ACL revision reconstruction compared with those undergoing their first revision reconstruction, and were present in between 50% and 85% of patients. Medial and lateral compartment chondral lesions were significantly more prevalent in those undergoing a second ACL revision reconstruction group compared with those undergoing their first ACL revision reconstruction, with a nearly threefold higher rate in the lateral compartment. Cite this article: Bone Joint J 2025;107-B(7):723–727
Refroidissement par micro-canaux et nouvelles techniques d’interconnexion
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Optimal deployment of wind and solar electricity considering regional climates and demand patterns to minimize dispatchable supply
No full textInternational audienceDecarbonizing the global economy requires a massive deployment of low-carbon electricity sources, including nuclear, hydro, photovoltaic (PV) and wind power. Yet, most of today's electricity supply (60%) relies on dispatchable fossil fuel sources while options to deploy low-carbon electricity are limited. The relevance of deploying variable renewable energy sources (vRES), such as PV and wind, depends not only on their potential, which is geographically uneven, but also on electricity consumption patterns, which differ significantly across regions due to diverse usages and climatic conditions. In the pursuit of reducing greenhouse gases emissions and scaling up the development of intermittent renewable energy in a finite world, we seek an efficient and reasonable allocation of renewable capacities to minimize reliance on fossil-based dispatchable energy. Here, we investigate how production and consumption patterns affect optimal electricity mixes and residual reliance on dispatchable production across countries. Using linear programming optimization with hourly resolution, we size vRES capacities that minimize the use of dispatchable energy, for each country in the world. To focus only on the shapes of the temporal profiles of demand and vRES, we exclude economic considerations. Our findings reveal how climatic conditions and consumption patterns shape the suitability of PV and wind deployment, from an energy service perspective. Notably, seasonality of PV production has the most significant impact on the optimized shares of PV and wind energy in electricity mixes. While our approach reveals the possibility to reduce the reliance on dispatchable energy, it does not significantly lower the need for dispatchable power capacity. This work establishes a foundation for an optimized allocation of wind and PV capacities under environmental constraints on a global scale
Modèles de Flux Riemanniens pour l'Interférométrie SAR
No full textInternational audienceSAR interferometry (InSAR) enables the analysis of topological changes in natural sites or urban areas. However, the use of denoising algorithms is necessary to extract relevant information from interferograms. In this article, we exploit the cyclic structure of interferometric phases to design efficient distribution transports and ensure the validity of the data generated. We apply this approach to i) the generation of realistic interferograms for data augmentation, ii) the denoising of interferograms. Experiments on Sentinel-1 data illustrate the interest of these approaches.L'interférométrie SAR (InSAR) permet l'analyse des changements topologiques de sites naturels ou zones urbaines. Cependant, l'utilisation d'algorithmes de débruitage est nécessaire pour capturer l'information pertinente des interférogrammes. Dans cette article, nous exploitons la structure cyclique des phases interférométriques pour concevoir des modèles de transport de distributions efficaces et assurant la validité des données générées. Nous appliquons cette approche à i) la génération d'interférogrammes réalistes pour l'augmentation de données, ii) le débruitage d'interférogrammes. Nos expériences sur des données Sentinel-1 montrent l'efficacité des modèles de flux riemanniens pour ces applications
Extraction électrochimique du lithium appliquée au recyclage des batteries
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Thermally activated static friction can explain earthquake interactions
No full textUnlike e.g. meteorological hazards, tectonic earthquakes remain hardly predictable, re16 inforcing their deadly character. This is related to a strong time asymmetry, with few and nonsystematic foreshocks sometimes preceding large earthquakes, while aftershocks are ubiquitous and have been known for a long time. However, 130 years after Omori, the physical origin of this time asymmetry and of aftershocks remains highly debated. Slider-blocks models have been proposed to explain earthquakes physics and statistics. If these models can reproduce a Gutenberg-Richer distribution of slip magnitudes, they are unable to simulate aftershocks and time asymmetry except if introducing viscous relaxation in a deterministic way. Here, we model earthquake interactions and natural seismicity from a minimal number of fundamental mechanisms, namely elastic stress transfer and reaction rate theory applied to the simplest form of static friction. This allows introducing a microscopic timescale as well as temperature in a physically meaningful way, and to strikingly reproduce many aspects of seismicity and earthquake interactions, including time asymmetry