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Optimal sub-Gaussian variance proxy for truncated Gaussian and exponential random variables
No full textInternational audienceThis paper establishes the optimal sub-Gaussian variance proxy for truncated Gaussian and truncated exponential random variables. The proofs are based initially on reducing each distribution to their standardized versions. Geometrically, for the normal distribution, our argument consists of fitting a parabola to another parabola-looking function, which emerges from its moment generating function. For the exponential case, we show that the optimal variance proxy is the unique solution to a pair of equations and then provide this solution explicitly. Moreover, we demonstrate that truncated Gaussian variables exhibit strict sub-Gaussian behavior if and only if they are symmetric, meaning their truncation is symmetric with respect to the mean. Conversely, truncated exponential variables are shown to never exhibit strict sub-Gaussianity
Amoeba Measures of Random Plane Curves
No full text41 pages, 1 figureInternational audienceWe prove that the expected area of the amoeba of a complex plane curve of degree is less than and once rescaled by , is asymptotically bounded from below by . In order to get this lower bound, given disjoint isometric embeddings of a bidisc of size in the complex projective plane, we lower estimate the probability that one of them is a submanifold chart of a complex plane curve. It exponentially converges to one as the number of bidiscs grow to
Étude de la microstructure et des propriétés émissives des membranes ultrafines MoSiN nanocomposites autoportantes
No full textThe growing demand for compact, energy-efficient, and robust mid-infrared (mid-IR) light sources is driving the development of advanced thermal emitters for next-generation hightemperature gas sensing technologies. Mid-IR gas sensors, in particular, benefit from this spectral range due to the strong and selective molecular absorption features of most gases. However, their development remains constrained by the lack of efficient, low-power, and thermally stable emitter materials capable of reaching the high temperature (600-1000°C) needed for strong emission across the mid-IR broadband range. Conventional microheaterbased emitters suffer from high power consumption, slow thermal response, and material degradation during repeated heating cycles. Addressing these limitations requires materials that combine high emissivity, thermal stability, and mechanical resilience at nanoscale thicknesses. Reducing the membrane thickness lowers thermal mass, minimizing power consumption and enabling faster heating and cooling for enhanced thermal response. For nanoscale membranes where both high emissivity and mechanical strength are critical, integrating these attributes within a composite material offers an effective and promising solution. In this context, this study develops and investigates ultrathin freestanding MoSiN nanocomposite membranes, examining their structural, optical, and thermal properties to assess their suitability as efficient, low-power, and thermally stable mid-IR emitters for compact and reliable gas sensing applications. Freestanding MoSiN membranes, 6-16 nm thick with lateral dimensions of 10 mm × 10 mm supported on silicon frames, were fabricated and characterized. The microstructure and composition of the ultrathin MoSiN membranes were thoroughly studied to elucidate the distribution of intermetallic and dielectric phases. The microstructural analysis reveals that MoSiN possess a complex nanocomposite structure, comprising intermetallic phases (MoSi2 and Mo5Si3) and silicon oxynitride (SiOxNy) dielectric phase. The intermetallic phases facilitate free-carrier absorption in the mid-IR region, while the dielectric phase enhances mechanical integrity and provides strong resistance to oxidation. Membrane exhibits metal-like emissivity (~0.41) and retains thermal and mechanical stability at high temperature (900°C). Repeated laser pulsed-heating experiments confirm rapid thermal response, excellent repeatability, and efficient radiative cooling, validating its potential as a durable microheater emitter material. FTIR spectroscopy shows broadband absorption in the 2-8 µm range, dominated by free-carrier processes, with negligible phonon absorption beyond 8 µm. Emissivity shows a strong thickness dependence due to interference effects, as confirmed by optical modeling using Fresnel equations and the generalized matrix method. Electrical characterization shows resistivity (~10 -4 Ω•cm) with a positive temperature coefficient, indicating metallic conduction. Overall, MoSiN behaves as a semimetal combining metallic absorption and dielectric-induced stability. These results highlight ultrathin freestanding MoSiN membranes as a compelling platform for mid-infrared emitters, offering a synergistic combination of low power, thermal iii efficiency, mechanical durability, and CMOS compatibility for gas sensing applications in harsh environments.To my dearest Daddy, Mummy, and Neethu-Your boundless love, selfless sacrifices, and quiet strength have sustained me in ways words cannot fully captureLa demande croissante en sources lumineuses compactes, écoénergétiques et robustes dans le domaine de l'infrarouge moyen (IR moyen) stimule le développement d'émetteurs thermiques avancés pour les technologies de détection de gaz à haute température de nouvelle génération. Les capteurs de gaz à infrarouge moyen, en particulier, tirent parti de cette gamme spectrale en raison des caractéristiques d'absorption moléculaire fortes et sélectives de la plupart des gaz. Cependant, leur développement reste limité par le manque de matériaux émetteurs efficaces, à faible consommation d'énergie et thermiquement stables, capables d'atteindre la température élevée (~900°C) nécessaire pour une émission forte dans toute la gamme à large bande de l'infrarouge moyen. Les émetteurs conventionnels à micro-réchauffeurs souffrent d'une consommation d'énergie élevée, d'une réponse thermique lente et d'une dégradation des matériaux lors de cycles de chauffage répétés. Pour remédier à ces limitations, il faut des matériaux qui combinent une émissivité élevée, une stabilité thermique et une résilience mécanique à des épaisseurs nanométriques. La réduction de l'épaisseur de la membrane diminue la masse thermique, minimise la consommation d'énergie et permet un chauffage et un refroidissement plus rapides pour une réponse thermique améliorée. Pour les membranes à l'échelle nanométrique où une émissivité élevée et une résistance mécanique sont essentielles, l'intégration de ces propriétés dans un matériau composite offre une solution efficace et prometteuse. Dans ce contexte, cette étude développe et examine des membranes nanocomposites MoSiN ultrafines autonomes, en étudiant leurs propriétés structurelles, optiques et thermiques afin d'évaluer leur adéquation en tant qu'émetteurs infrarouges moyens efficaces, à faible consommation d'énergie et thermiquement stables pour des applications compactes et fiables de détection de gaz. Des membranes MoSiN autonomes, d'une épaisseur de 6 à 16 nm et de dimensions latérales de 10 mm × 10 mm, supportées par des cadres en silicium, ont été fabriquées et caractérisées. La microstructure et la composition des membranes MoSiN ultrafines ont été étudiées de manière approfondie afin d'élucider la distribution des phases intermétalliques et diélectriques. L'analyse microstructurale révèle que le MoSiN possède une structure nanocomposite complexe, comprenant des phases intermétalliques (MoSi2 et Mo5Si3) et une phase diélectrique d'oxynitrure de silicium (SiOxNy). Les phases intermétalliques facilitent l'absorption des porteurs libres dans la région de l'infrarouge moyen, tandis que la phase diélectrique améliore l'intégrité mécanique et offre une forte résistance à l'oxydation. La membrane présente une émissivité de type métallique (~0.41) et conserve sa stabilité thermique et mécanique à haute température (900°C). Des expériences répétées de chauffage par impulsions laser confirment une réponse thermique rapide, une excellente répétabilité et un refroidissement radiatif efficace, validant son potentiel en tant que matériau émetteur micro-chauffant durable. La spectroscopie FTIR montre une absorption à large bande dans la gamme 2-8 µm, dominée par des processus de porteurs libres, avec une absorption phononique négligeable au-delà de 8 µm. L'émissivité montre une forte dépendance à l'épaisseur due à des effets d'interférence, comme le confirment la modélisation optique à l'aide des équations de Fresnel et la méthode matricielle généralisée. La caractérisation électrique montre une résistivité (~10-4 Ω·cm) avec un coefficient de température positif, indiquant une conduction métallique. Dans l'ensemble, le MoSiN se comporte comme un semi-métal combinant une absorption métallique et une stabilité induite par diélectrique. Ces résultats mettent en évidence les membranes MoSiN ultrafines autonomes comme une plateforme convaincante pour les émetteurs infrarouges moyens, offrant une combinaison synergique de faible puissance, d'efficacité thermique, de durabilité mécanique et de compatibilité CMOS pour les applications de détection de gaz dans des environnements difficiles
Vortex-induced vibration attenuation on tubular monopole telecommunications towers using a nonlinear absorber
No full textInternational audienceWe investigate the nonlinear passive control of vortex-induced vibrations of tubular telecommunication monopoles. The use of nonlinear energy sinks as an alternative to the commonly used tuned mass dampers for the control of vortex-induced vibrations is explored. The behaviors of the monopole coupled to a purely cubic nonlinear energy sink are analyzed using the complexification averaging method, while the linear dynamics of the system coupled with a tuned mass damper are studied through classical methods. The monopole is modeled as an Euler–Bernoulli beam, and the aerodynamic forces are represented by a simplified model from the literature, allowing the influence of wind speed and vortex shedding frequency to be considered. A design procedure for the nonlinear energy sink is proposed in order to estimate its optimal parameters. The validation of the developed analytical tools is carried out through numerical integration of the governing equations and also via simulations performed using the finite element method. Comparisons show that a nonlinear passive absorber can effectively control vortex-induced vibrations under certain conditions
A comprehensive review on autonomous and plan-based QoS-aware service composition approaches in service community
No full textInternational audienceIn the evolving landscape of the Internet of Things (IoT), many smart devices provide basic functionalities as services that often fail to meet users’ requirements. To address this gap, fine-grained services are combined to create coarse-grained services, giving rise to the QoS-aware service composition challenge. The growing number of IoT devices has resulted in numerous fine-grained services with similar functional properties (inputs and outputs) but different non-functional properties, typically related to quality of service (QoS). The QoS-aware service composition approaches can be categorized into two main classes: plan-based approaches and autonomous ones. Existing surveys in this domain primarily focus on either a single class or technical aspects, such as composition representation and utility functions. In contrast, this study offers a comprehensive and systematic review of both classes, emphasizing resolution and validation methodologies. The contributions of this paper are fourfold: 1) introduce a novel taxonomy that classifies QoS-aware service composition approaches from the past decade based on their reliance on preexisting abstract composition plans, 2) provide a detailed comparative analysis of these approaches using the most relevant criteria in the service composition field, 3) investigate their resolution and validation methodologies along with the quality and appropriateness of the datasets used in the reviewed approaches, and 4) discuss future directions for advancing the field. This review not only bridges the knowledge gap in understanding these approaches but also serves as a foundation for researchers to develop more robust and efficient QoS-aware service composition methods
A Revision of the Quality Metrics of Physical Unclonable Functions
No full textInternational audiencePhysical unclonable functions (PUFs) leverage process variability to generate unique signatures in electronic devices. They are a strong alternative to conventional security mechanisms as they do not rely on non-volatile memories (NVMs) to store the secrets. However, PUFs can be influenced by external factors and may exhibit biased output distributions, leading to vulnerabilities that could compromise their uniqueness and resistance to cloning. The quality of a PUF is evaluated through a common set of metrics such as uniformity, bit-aliasing, uniqueness, and reliability. However, the lack of standardized methodologies hinders effective comparisons between diverse PUF designs, limiting the broader understanding of their performance. Besides, the underlying physics and mechanisms of PUFs makes them difficult to study and mitigate potential vulnerabilities and attacks. Overall, the quality metrics for PUFs are still evolving, and there is ongoing research to address these challenges and develop more robust and reliable PUFs. In this article, we demonstrate the limitations of current PUF evaluation metrics using experimental data and introduce a novel set of metrics that provide a more rigorous and comprehensive assessment.</p
Molecular Insights into the Tribological Confined Interface via Surface Forces Measurements
No full textSurface forces act at the interface between two media or phases, such as liquid/solid/gas or non miscible liquids. When confined between two solid surfaces, typically with a film thickness to contact size ratio of 1/1000, film properties can differ from those of the bulk. Measuring forces across confined films requires precise, high-resolution equipment, to provide valuable insights into the origins of these interactions and the properties of the confined films. This chapter first presents an overview of the historical development of surface forces measurements, followed by a review of the three main techniques currently used in tribology research. Technical details are provided and representative examples illustrate recent advances, highlighting the influence of structuring of ionic liquid-based lubricants, the effect of molecular structure, and the role of surface chemistry and roughness on the tribological behavior of confined interfaces
Looking for stabilizers in NSOP
No full textIn this work we study some examples of groups definable and type-de nable in NSOP1theories. We exhibit some behaviors of these groups that differ from the ones of groups definable insimple theories. We take interest in the notions of generics and stabilizers, and define the Kim-stabilizer.We apply the notion of Kim-stabilizer and the notion of stabilizer from Hrushovski to the context of agroup G definable in an NSOP1 field F satisfying some assumptions to show that in this context thereexist a finite to one embedding of a type-definable subgroup of G of bounded index into an algebraicgroup over F. We then show that definable groups in Frobenius fields of characteristic 0 satisfy theseconditions
Multi-Score Reinforcement Learning for High-Tg Polyimide Design
No full textInternational audienceThis study explores strategies to guide the generation of polyimides with high glass transition temperatures (Tg > 750 K) through reinforcement learning. We present a systematic computational framework for analyzing and combining multiple scoring functions into a single score in reinforcement learning (RL) for molecular design. Rather than relying solely on a single scoring function based on a predictive model, we examine a range of complementary scores, including a novel naı̈ve high-Tg score and various Tanimoto similarity-based scores. We analyze these scores both individually and in combination with the predictive model-based score in order to assess their influence on the structural diversity and quality of the generated polymers. In addition, we investigate several methods for combining scores, such as arithmetic, geometric, and harmonic means, as well as a novel exponential–logarithmic function, referred to as ExpAgg. We evaluate how these aggregation strategies affect the outcomes of molecular generation across different reinforcement learning configurations. Our findings show that the choice of score combination method significantly impacts both the quality and diversity of generated polymers. The proposed ExpAgg achieves superior performance in multiple settings, revealing nontrivial interactions between score compatibility and model convergence. While the predictive model exhibits underestimation in the out-of-distribution region (>800 K), our multiscore framework successfully generates chemically reasonable high-Tg candidates. Based on these insights, we provide practical guidelines for selecting aggregation functions when fusing two scores. This case study on high-Tg polyimide generation demonstrates how score aggregation strategies influence molecular RL outcomes; broader generalizability to other molecular design tasks remains to be investigated. This work emphasizes the importance of moving beyond simple weighted averages in order to enhance targeted molecular design
Problèmes ouverts en géométrie symplectique quantitative et étude des billards
No full textThis document collects contributions to the Open Problem List in Billiards and Quantitative Symplectic Geometry, compiled following discussions during the workshop "Billiards and quantitative symplectic geometry" that took place at the University of Heidelberg on July 14-18, 2025