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Cesium Microcell Optical Reference at 459 nm With Short-Term Stability Below 2.5 × 10−13 at 1 s
No full textInternational audienceWe report on the development and short-term stability characterization of lasers stabilized onto the 6S1/2-7P1/2 transition of Cs atom at 459 nm using a microfabricated vapor cell. A laser beatnote, obtained between two quasi-identical systems, demonstrates an instability below 2.5 × 10−13 at 1 s, in good agreement with the noise budget, and limited by the laser frequency noise through the FM-AM conversion process and theintermodulation effect. The dependence of the laser frequency to the laser power at the cell input and the cell temperature variations are also measured. These results are promising for the demonstration of microcell-based optical references with stability performances approaching those of hydrogen masers in a simple architecture
Observer-based <i>H</i><sub>∞</sub> control for stochastic parabolic systems
No full textInternational audienceThis paper proposes an observer-based H∞ fault-tolerant controller for a class of stochastic parabolic systems (SPSs) subject to actuator failures. An augmented SPS that includes both the state vector and the error vector is given. The coupling difficulty between faults and system states is solved by using matrix decompositions and inequality techniques. The designed observer-based controller ensures that the SPSs achieve the mean square finite horizon H∞ performance. Finally, a simulation of CPU chip thermal fault is provided to illustrate the effectiveness of the proposed scheme
Parties prenantes et performance post-succession au sein des PME françaises : l’impact de la structure du capital, de l’origine et de l’expérience du dirigeant
No full textInternational audienceBased on a questionnaire administered to 180 SME managers, this article aims to see the link between stakeholders and the post-succession performance recorded by managers whose experiences and origins differ in a context where capital can be diluted or concentrated. The SEM-PLS approach was used, and the data processed with smartPLS3. Our results indicate that regardless of the origin of the succession, the capital structure and the manager’s experience, the involvement of stakeholders in strategic decisions does not impact on post-succession performance. The new leaders seek to act independently to carry out the strategic orientations of the companies taken over. Our results also show that stakeholders who succeed in participating in operational decision-making processes lead to a drop in post-succession performance, when the new managers do not hold most of the capital or if they come from outside or again when they are not experienced. The latter would have to exploit relations with their stakeholders to strengthen their legitimacy.Basado en un cuestionario administrado a 180 administradores de PYME, este artículo tiene como objetivo ver el vínculo entre las partes interesadas y el desempeño post-sucesión registrado por administradores cuyas experiencias y orígenes difieren en un contexto donde el capital puede diluirse o concentrarse. Se utilizó el enfoque SEM-PLS y los datos se procesaron con smartPLS3. Nuestros resultados indican, independientemente del origen de la sucesión, la estructura de capital y la experiencia del gerente, que la participación de los interesados en las decisiones estratégicas no impacta el rendimiento posterior a la sucesión. Los nuevos directivos buscan actuar de forma autónoma para llevar a cabo las orientaciones estratégicas de las empresas adquiridas. Nuestros resultados también muestran que las partes interesadas que logran participar en los procesos de toma de decisiones operativas conducen a una disminución en el desempeño post-sucesión, cuando los nuevos gerentes no poseen la mayoría del capital o si provienen del exterior o incluso cuando no tienen experiencia. Estos últimos se verían inducidos a utilizar las relaciones con sus partes interesadas para fortalecersu legitimidad.À partir d’un questionnaire administré à 180 dirigeants de PME, cet article a pour objectif de voir le lien entre les parties prenantes et la performance post-succession enregistrée par des dirigeants dont les expériences et les origines diffèrent dans un contexte où le capital peut être dilué ou concentré. L’approche SEM-PLS a été utilisée et les données traitées avec smartPLS3. Nos résultats indiquent et peu importe l’origine de la succession, la structure du capital et l’expérience du dirigeant, que l’implication des parties prenantes dans les décisions stratégiques n’impacte pas la performance post-succession. Les nouveaux dirigeants cherchent à agir de manière autonome pour effectuer les orientations stratégiques des entreprises reprises. Nos résultats font apparaître également que les parties prenantes qui réussissent à participer aux processus de décisions opérationnelles entraînent une baisse de la performance post-succession, lorsque les nouveaux dirigeants ne détiennent pas la majorité du capital ou s’ils sont issus de l’extérieur ou encore lorsqu’ils ne sont pas expérimentés. Ces derniers seraient amenés à instrumentaliser les relations avec leurs parties prenantes pour renforcer leur légitimité
Electrolyse basse-température en fonctionnement intermittent : caractérisation des impacts et aide au pilotage
No full textThe large-scale integration of electrolyzers, when coupled with intermittent energy sources, presents significant operational challenges. The impact of intermittency on the energy performance, durability, and economic viability of electrolyzers remains insufficiently understood, hindering their widespread deployment. This thesis addresses this issue by adopting an approach combining experimental and modeling to evaluate the impact of intermittency on electrolyzers. Due to their industrial maturity and potential for intermittent operation, PEM and alkaline technologies have been the focus of this thesis. The first step involved a critical analysis of the literature, which synthesized the current knowledge on the impact of intermittency and identified several important gaps : the lack of standardized testing protocols, the shortage of quantitative studies at the industrial scale, and the absence of consensus on the degradation mechanisms induced by intermittency. These findings guided the research directions explored in the subsequent work. A key focus of this thesis was the definition and implementation of experimental protocols designed to characterize the impact of intermittency. Two large-scale systems were initially studied: a 3.5 MW alkaline electrolyzer and a 55 kW pressurized PEM electrolyzer. The results, consistent across both systems, showed that in the short term, intermittency had a limited impact on hydrogen production levels, electrical consumption, gas purity, and energy efficiency. This methodology was then applied to a 1 kW PEM stack, with the aim of incorporating a longer characterization timeline and examining the impact of intermittency on the aging of electrolyzers. Another area of work focused on the development of a generic performance model, initially calibrated and validated on a semi-industrial PEM electrolyzer. This model aims to simulate the dynamic behavior of industrial electrolyzers under various operational scenarios, over extended periods or under conditions that are difficult to reproduce experimentally. Additionally, it serves as a tool to optimize their design and management while contributing to techno-economic considerations regarding their deployment. Finally, several complementary research directions were proposed, including broadening the study scope to new performance indicators, expanding the utilization of the developed model, and discussing methods for evaluating degradation at the industrial system scale.L’intégration à grande échelle des électrolyseurs, lorsqu’ils sont couplés à des sources d’énergie intermittentes, pose des défis opérationnels considérables. L’impact de l’intermittence sur les performances énergétiques, la durabilité et la rentabilité des électrolyseurs demeure insuffisamment appréhendé, ce qui freine leur déploiement. Cette thèse s’inscrit dans ce contexte en adoptant une approche combinant expérimental et modélisation, afin d’évaluer l’impact de l’intermittence sur les électrolyseurs. En raison de leur maturité industrielle et de leur potentiel pour un fonctionnement intermittent, les technologies d’électrolyse basse-température PEM et alcalin, et plus spécifiquement la technologie PEM, ont été au coeur de cette thèse. Une première étape a consisté en une analyse critique de la littérature, permettant de synthétiser l’état des connaissances actuelles sur l’impact de l’intermittence et d’identifier plusieurs lacunes importantes : l’absence de protocoles de test standardisés, le manque d’études quantitatives menées à l’échelle industrielle, et l’absence de consensus sur les mécanismes de dégradation induits par l’intermittence. Ces constats ont orienté les axes de recherche explorés dans la suite du travail.Un axe majeur de cette thèse a porté sur la définition et la mise en oeuvre de protocoles de test dédiés à la caractérisation de l’impact de l’intermittence. Deux systèmes de grande envergure ont d’abord été étudiés : un électrolyseur alcalin de 3,5 MW et un électrolyseur PEM pressurisé de 55 kW. Les résultats obtenus, similaires aux deux systèmes étudiés, ont révélé qu’à court terme, l’intermittence exerce un impact limité sur le niveau de production d’hydrogène, la consommation électrique, la pureté du gaz et le rendement énergétique. Cette méthodologie a ensuite été appliquée à un stack PEM de 1 kW, dans le but d’intégrer une temporalité de caractérisation prolongée et d’étudier l’impact de l’intermittence sur le vieillissement des électrolyseurs. Ensuite, un modèle de performance générique, initialement calibré et validé sur un électrolyseur PEM semi-industriel, a été développé. Ce modèle a pour objectif de simuler le comportement dynamique des électrolyseurs industriels dans divers scénarios d’opération, sur des durées prolongées ou dans des conditions difficiles à reproduire expérimentalement. En outre, il constitue un outil d’aide à l’optimisation de leur conception et de leur gestion, tout en alimentant des réflexions technico-économiques sur leur déploiement. Enfin, plusieurs axes de recherche complémentaires ont été proposés, notamment l’élargissement du périmètre d’étude à de nouveaux indicateurs de performance, des perspectives d’exploitation du modèle développé, ainsi qu’une réflexion sur les méthodes d’évaluation de la dégradation à l’échelle des systèmes industriels
Dialogues sur les enjeux de la recherche-création pour les sciences humaines
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Pulsed heating atomic layer deposition of TiO2 thin films on soft substrates
No full textInternational audienceOne of the strengths of the atomic layer deposition (ALD) technique is its ability to produce very thin and uniform deposits conform to the morphology of the substrates even in the case of high roughness or porosity. The range of potential substrates to support ALD films continues to expand. Among them, porous, flexible, organic and natural substrates are attracting increasing interest. Even though the deposition temperature is low in thermal ALD (the ALD window is commonly in between 150 and 400 °C for most metal-oxide deposits), the risk of degradation cannot be excluded for sensitive substrates. To reduce this risk, it would be interesting to limit heating on short periods of time in ALD cycles. Moreover, the energy cost of the production process would also be reduced. To date, several approaches have been proposed to provide additional energy in short periods oftime during an ALD process such as photo-assisted ALD using a pulse light source [1], atomic layer annealing (ALA) using in-situ plasma bombardment [2] and in-situ rapid thermal annealing introducing a heat pulse after a deposition cycle [3]. The goal was mainly to improve the quality of the ALD films by reducing the presence of defects and promoting the compound stoichiometry and the atomic arrangement in crystalline layers. In previous works [4,5], we reported the ALD synthesis of inverse opal TiO2 films using a template of polystyrene micro-beads deposited on a silicon substrate. A post-annealing treatment was used to remove the template to obtain inverse opal layers. The interest of these kind of films for photocatalysis and sensor applications was also shown. However, the possibility of reducing the size of PS beads, in order to increase the specific surface area, has run up against the problem of their softening, even at low ALD temperatures (90-100 °C). The aim of this work is to explore the possibility of using pulsed heating to preserve the morphology of the template, and more broadly to use soft thermal-sensitive substrates. In particular, we herein report the ALD synthesis of TiO2 films on flat substrates and PS micro-bead templates (Fig.1) using pulsed heating induced by short pulses of power supplied to infrared lamps. Several examples of TiO2 films deposited on soft substrates (polymer foams and natural material fibers) will also be presented. SEM observations, together with XPS and micro-Raman analysis, were carried out to study the morphology, stoichiometry and structure of the deposits
Assessing the consistency of numerical models for wind instrument impedance
No full textInternational audienceNumerical simulation of the input impedance of wind instruments is the basis of much work in music acoustics. However, the accuracy and reproducibility of such simulations across different contributors remain little documented. This study aims to benchmark the reliability of numerical simulations for pipe impedance, focusing on simple geometries such as cylindrical and conical pipes, and to identify key factors influencing simulation variability.A collaborative approach was adopted, involving multiple contributors employing various numerical models, including TMM, FEM (1D or 3D), etc., and eventually different physical models for the propagation, the boundary conditions, and the thermo-viscous effects. Significant variability in simulation results was observed due to differences in implementation, numerical precision, and boundary condition modelling. Incomplete convergence in some methods also contributed to discrepancies. Despite these challenges, the collaborative work and exchanges reduced variability and improved consistency across contributors. The study highlights the importance of such benchmark and the interest to adopt good practices including verification of the numerical tools through comparative analysis and identification of convergence criteria. This work provides a framework for improving the reproducibility an accuracy of numerical simulations in musical acoustics context
Evaluation of Polarimetric Fusion for Semantic Segmentation in Aquatic Environments
No full textAccurate segmentation of floating debris on water is often compromised by surface glare and changing outdoor illumination. Polarimetric imaging offers a single-sensor route to mitigate water-surface glare that disrupts semantic segmentation of floating objects. We benchmark state-of-the-art fusion networks on PoTATO, a public dataset of polarimetric images of plastic bottles in inland waterways, and compare their performance with single-image baselines using traditional models. Our results indicate that polarimetric cues help recover low-contrast objects and suppress reflection-induced false positives, raising mean IoU and lowering contour error relative to RGB inputs. These sharper masks come at a cost: the additional channels enlarge the models increasing the computational load and introducing the risk of new false positives. By providing a reproducible, diagnostic benchmark and publicly available code, we hope to help researchers choose if polarized cameras are suitable for their applications and to accelerate related research
Modèles génératifs de systèmes de villes hiérarchisés : action des individus et des entreprises
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Monitoring Pseudoprogression Using Circulating Small Extracellular Vesicles Expressing PD‐L1 in a Melanoma Patient Treated With Immune Checkpoint Inhibitors
No full textInternational audienceImmune checkpoint inhibitors (ICI) have revolutionized the treatment of metastatic malignancy. However, unique immune response patterns can occur, such as pseudoprogression, which corresponds to new lesion development or temporary tumour growth followed by regression. Misidentifying pseudoprogression may halt ICI therapy, due to the absence of biomarkers to distinguish progression from pseudoprogression. In 2020, our team proposed small extracellular vesicles expressing PD‐L1 (sEV‐PD‐L1) as a predictor of melanoma treatment response. We report a case of pseudoprogression in a patient treated with nivolumab and ipilimumab for metastatic melanoma, and showing reduced circulating sEV‐PD‐L1. To our knowledge, this is the first report of PD‐L1 monitoring in circulating sEV during pseudoprogression under ICI. A decrease in PD‐L1 in circulating sEV might be an early sign of disease response to ICI, and may help to diagnose pseudoprogression. This case supports further evaluation of sEV‐PD‐L1 to identify responder patients to ICI, especially in case of pseudoprogression. Trial Registration: EXOMEL1 P/2018/40 1 AC‐2015‐2496/DC‐2014‐2086. NCT05744076