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On the distribution of the first exit time from an interval of a threshold Ornstein-Uhlenbeck process
No full textWe investigate the threshold Ornstein-Uhlenbeck process, a diffusion process where the drift and volatility coefficients change across thresholds. On each statespace interval delimited by the thresholds, it follows the dynamics of a classical Ornstein-Uhlenbeck process. We give explicit series representations for the transition density of the process killed at the boundaries of an interval and for the distribution of its first exit time. These results are obtained using spectral methods. Particular cases with a single threshold and without threshold are obtained as direct consequences of the general framework.</div
Numerical Modelling of Granular Flow and Workpiece Interaction in Vibratory Finishing.
No full textInternational audienceNumerical Modelling of Granular Flow and Workpiece Interaction in Vibratory Finishing
Analyse et modélisation multi-physique du phénomène de « Spring-Back » pour des structures composites
No full textInternational audienceAnalyse et modélisation multi-physique du phénomène de « Spring-Back » pour des structures composite
Unsupervised Energy-Based Model for the Identification of Out-Of-Distribution Copy Detection Patterns
No full textInternational audienceThe recent advances in deep neural networks have led us to revisit the safety of current mechanisms for the authentification of people's identities and validating the provenance of traded goods. This paper studies the problem of identifying counterfeits of Copy Detection Patterns (CDPs). CDPs are used on product packaging to identify counterfeiting by relying on the information loss principle. Current verification techniques rely on a supervised machine learning paradigm, which needs examples from real and fake CDPs to learn a model capable of differentiating both classes of CDPs. This paper proposes an unsupervised forensic approach that is capable of training an Energy-Based Model for detecting out-of-distribution (OOD) images (fake CDP examples in our case) using only original CDP images. This paper also introduces a novel thresholding technique that only requires original CDPs for threshold value selection. We validate our approach on the Indigo dataset, with results demonstrating comparable counterfeit detection capabilities to prior work but using a method trained on less data
Enhanced Optoelectronic Properties of Silicon Clathrate Films via Sodium Extraction by Vacuum Annealing
No full textInternational audienceSilicon clathrates, which exhibit a direct or near‐direct bandgap, represent a promising alternative to conventional diamond cubic silicon for optoelectronic applications. They combine the elemental abundance and nontoxicity of Si with a more favorable bandgap and higher optical absorption at room temperature. Their open cage‐like frameworks allow for reversible guest atom incorporation with minimal lattice distortion, making them attractive not only for optoelectronics but also for energy storage applications. However, conventional synthesis methods typically require the use of sodium as a structure‐directing agent to stabilize the metastable clathrate lattice during thermal decomposition. The resulting sodium incorporation degrades the optoelectronic properties and complicates device integration. Herein, a nontoxic, scalable, vacuum‐annealing approach is utilized that effectively removes sodium from silicon clathrates films without the use of hazardous chemicals, such as iodine, HF, or SF 6 . Optoelectronic characterization reveals a significant improvement in semiconducting behavior, including enhanced surface photovoltage response, marking a critical step toward developing sodium‐free silicon clathrate thin films as efficient light absorbers. This vacuum annealing process is compatible with large‐area substrates and offers a key step toward a safer, and more sustainable approach to integrating exotic Si phases into the next‐generation optoelectronic devices
Étude des groupes et corps dans certaines théories modérées
No full textThis thesis is dedicated to the study of algebraic structures within a certain class of the model-theoretic classification of structures, namely that of NSOP1 theories.We begin by presenting how the classification developed in general and the study of NSOP1 in particular, as well as the various model-theoretic tools used in this context, namely independence relations, forking-independence, and especially Kim-independence.We then address the construction of NSOP1 theories. In Chapter 2, we consider generic extensions of certain theories. We show that under certain assumptions, these generic extensions are NSOP1, and in that case we characterize Kim-independence and forking independence in them. This provides us, among other things, with an example of a definable group in an NSOP1 theory.Other examples of NSOP1 theories are studied in Chapter 3. These concern the theory of a generic symmetric bilinear form over a field K. We show that if the field K is NSOP1, then this theory is as well, and we characterize Kim-independence over models in it. We also demonstrate more precise results about this theory by adding conditions on the theory of the field K. We provide a counterexample to a conjecture concerning a link between Kim-independence and forking-independence in the case where K is an algebraically closed field.In Chapter 4, we focus on model-theoretic tools for studying definable groups, and we aim to generalize them to the NSOP1 context. We define the Kim-stabilizer and show that in several examples of NSOP1 theories, we obtain a type-definable subgroup. We also define certain assumptions on a field K under which, using the Kim-stabilizer, we can establish a connection between a definable group in K and the K-rational points of an algebraic group over K.In the appendix, we focus on a generalization of the stable deviation conjecture to the setting of NSOP1 theories and Kim-deviation.Cette thèse est dédiée à l’étude des structures algébriques dans une certaine classe de la classification modèle-théorique des structures, celle des théories NSOP1.On commence par présenter comment s’est développée la classification en général et l’étude de NSOP1 en particulier, ainsi que les différents outils modèle-théoriques que l’on utilise dans ce contexte, c’est-à-dire les relations d’indépendance, la Shelah-indépendance et surtout la Kim-indépendance.On aborde ensuite la construction de théories NSOP1. Dans le Chapitre 2 on considère des extensions générique de certaines théories. On démontre que sous certaines hypothèses ces extensions génériques sont NSOP1 et on caractérise la Kim-indépendance et la Shelah-indépendance dans celles-ci. Ceci nous fournit entre autres un exemple de groupe définissable dans une théorie NSOP1.D’autres exemples de théories NSOP1 sont étudiés dans le Chapitre 3. Il s’agit de la théorie d’une forme bilinéaire symétrique générique sur un espace vectoriel sur un corps K. On démontre que si le corps K est NSOP1 alors cette théorie l’est aussi et on caractérise la Kim-indépendance sur des modèles dans celle-ci. On démontre aussi des résultats plus précis sur cette théorie en ajoutant des conditions sur la théorie du corps K. On fournit un contre-exemple à une conjecture portant sur un lien entre Kim-indépendance et Shelah-indépendance dans le cas où K est un corps algébriquement clos.Dans le Chapitre 4 on s’intéresse aux outils modèle-théoriques pour étudier les groupes définissables, et on cherche à les généraliser au contexte de NSOP1. On définit le Kim-stabilisateur et on démontre que dans plusieurs exemples de théories NSOP1 on obtient un sous-groupe type-définissable. On définit aussi certaines hypothèses sur un corps K sous lesquelles en utilisant le Kim-stabilisateur on peut établir un lien entre un groupe définissable dans K et les points K-rationnels d’un groupe algébrique sur K.Dans l’appendice on s’intéresse à une généralisation de la conjecture de la déviation stable au cadre des théories NSOP1 et de la Kim-déviation
Exploring weighted network backbone extraction: A comparative analysis of structural techniques
No full textInternational audienceBackbone extraction simplifies complex networks while retaining essential features. It reduces complexity without losing critical structural information. However, selecting the most suitable method remains challenging due to the diverse behaviors of existing techniques. This study evaluates eight structural backbone extraction methods designed for weighted networks. These methods leverage network topology rather than statistical weight distributions. A dataset of 33 real-world networks is analyzed, covering diverse sizes, topologies, and domains. Key metrics, such as Jaccard similarity and Overlap Coefficient, reveal distinct method behaviors. A hierarchical relationship emerges among methods. Primary Linkage Analysis (PLAM) captures the most substantial edges, forming the simplest backbone. Minimum Spanning Tree (MSP), Ultrametric Backbone (UMB), and Metric Backbone (MB) build on this structure, progressively adding connectivity and detail. The Doubly Stochastic Filter excels at preserving weight and degree distributions, connectivity, and transitivity. By contrast, the H-Backbone prioritizes high-weight edges but disrupts connectivity. Metric Backbone and Planar Maximally Filtered Graph ensure complete node preservation and maintain high reachability. These insights advance the understanding of structural backbone extraction techniques for weighted networks. They benefit applications in fields like biology, social networks, and transportation. Practitioners can better achieve goals like network simplification for visualization or property preservation for analysis
Hamiltonian representation of isomonodromic deformations of general rational connections on
No full textInternational audienceIn this paper, we study and build the Hamiltonian system attached to any meromorphic connection with an arbitrary number of non-ramified poles of arbitrary degrees. In particular, we propose the Lax pairs and Hamiltonian evolutions expressed in terms of irregular times and monodromies associated to the poles as well as Darboux coordinates defined as the apparent singularities arising in the oper gauge. Moreover, we also provide a reduction of the isomonodromic deformations to a subset of non-trivial isomonodromic deformations. This reduction is equivalent to a map reducing the set of irregular times to only non-trivial isomonodromic times. We apply our construction to all cases where the associated spectral curve has genus 1 and recover the standard Painlev\'{e} equations. We finally make the connection with the topological recursion and the quantization of classical spectral curve from this perspective.</div
State-of-the-Art Research on Hf-ZrO2 Ferroelectric and Antiferroelectric Capacitors
No full textInternational audienceIn 2011, NamLab reported ferroelectricity in Si-doped HfO2 [1], sparking widespread interest due to its CMOS compatibility. Since then, HfO2-based materials have been investigated for various applications, mainly in memory devices (FeRAM, FeFET, FTJ), but also in energy storage, IR detection, electrocaloric cooling devices, and pyroelectric/piezoelectric systems.This presentation reviews the development of ferroelectric and antiferroelectric capacitors (FeCaps and AFeCaps) at Institut des Nanotechnologies de Lyon (INL). We describe the fabrication of Hf1-xZrxO2 (HZO)-based capacitors by reactive sputtering using metallic [2] and ceramic [3] targets, and more recently by ALD [4]. Structural characterization and electrical performance—endurance (via DHM, PUND, DLCC), retention, leakage, and imprint—will be discussed. For FeCaps, the orthorhombic phase associated with ferroelectricity is observed, with 2Pr exceeding 40 µC/cm² using both sputtering and ALD. Endurance strongly depends on the cycling protocol. In AFeCaps, a tetragonal phase is identified [5]. Recent advances in understanding antiferroelectricity in HZO will be discussed.References[1] Böscke, T. S., et al. Applied Physics Letters 99.10 (2011).[2] Bouaziz, Jordan, et al. APL Materials 7.8 (2019).[3] Bouaziz, Jordan, et al. ACS Applied Electronic Materials 1.9 (2019): 1740-1745.[4] Magagnin, Grégoire, et al. APL Materials 12.7 (2024).[5] Cervasio, Rebecca, et al. ACS Applied Materials & Interfaces 16.3 (2024): 3829-3840
Représentations dynamiques, virtuelles et tangibles de la ville
No full textThe objective of this thesis is to develop new forms of territorial representations based on 3D urban data. Behind these representations, we focus on three forms of representations: multimedia, spatio-temporal, and tangible. The integration of multimedia such as archival images, videos, and documents into a virtual 3D scene allows for the enhancement of a historical district or provides additional information on urban objects. Alongside this contextualization of urban data, we seek to introduce a temporal dimension into the digital city. This involves diachronic management of information integrated into a 3D environment, enabling the representation of the city's evolution, comparison of different versions, and visualization of morphological changes in buildings within the same context. Finally, beyond digital representations, physical models of a neighborhood or area can improve understanding by providing another form of mediation. Augmented models facilitate the organization of mediation workshops on urban themes. To enhance the comprehension process, we propose interactions with these devices to further engage the user.L'objectif de cette thèse est de développer de nouvelles formes de représentations territoriales basées sur des données urbaines 3D. Derrière ces représentations, nous nous intéressons à trois formes de représentations : multimédia, spatio-temporelles et tangibles. L'intégration de multimédias tels que des images d'archives, des vidéos et des documents dans une scène 3D virtuelle permet de mettre en valeur un quartier historique ou d'apporter des informations complémentaires sur des objets urbains. Parallèlement à cette contextualisation des données urbaines, nous cherchons à introduire une dimension temporelle dans la ville numérique. Cela passe par une gestion diachronique des informations intégrées dans un environnement 3D, permettant de représenter l'évolution de la ville, de comparer différentes versions et de visualiser les changements morphologiques des bâtiments dans un même contexte. Enfin, au-delà des représentations numériques, les modèles physiques d'un quartier ou d'une zone peuvent améliorer la compréhension en apportant une autre forme de médiation. Les maquettes augmentées facilitent l'organisation d'ateliers de médiation sur des thèmes urbains. Pour améliorer le processus de compréhension, nous proposons des interactions avec ces dispositifs afin d'impliquer davantage l'utilisateur