LpL p ASYMPTOTIC STABILITY OF 1D DAMPED WAVE EQUATION WITH NONLINEAR DAMPING

International audienceIn this paper, we study the one-dimensional wave equation with localized nonlinear damping and Dirichlet boundary conditions, in the L p framework, with p ∈ [1, ∞).We begin by addressing the well-posedness problem, establishing the existence and uniqueness of weak and strong solutions for p ∈ [1, ∞), under suitable assumptions on the damping function.Next, we study the asymptotic behaviour of the associated energy when p ∈ (1, ∞), and we provide decay estimates that appear to be almost optimal compared to similar problems with boundary damping. Our work is motivated by earlier studies, particularly, those by Chitour, Marx and Prieur [Journal of Differential Equations, 269 (2020)], and Haraux [C.R.A.S Paris, 287 (1978)]. The proofs combine arguments from Kafnemer, Mebkhout and Chitour [ESAIM: COCV, 28 (2022)] for wave equation in the L p framework with a linear damping, techniques of weighted energy estimates introduced in Martinez [ESAIM: COCV, 4 (1999)], new integral inequalities for p > 2, and convex analysis tools when p ∈ (1, 2)

A Deep Look Into the Temporal I/O Behavior of HPC Applications

International audienceThe increasing gap between compute and I/O speeds in high-performance computing (HPC) systems imposes the need for techniques to improve applications' I/O performance. Such techniques must rely on assumptions about I/O behavior in order to efficiently allocate I/O resources such as burst buffers, to schedule accesses to the shared parallel file system or to delay certain applications at the batch scheduler level to prevent contention, for instance. In this paper, we verify these common assumptions about I/O behavior, specifically about temporal behavior, using over 440,000 traces from real HPC systems. By combining traces from diverse systems, we characterize the behaviors observed in real HPC workloads. Among other findings, we show that I/O activity tends to last for a few seconds, and that periodic jobs are the minority, but responsible for a large portion of the I/O time. Furthermore, we make projections for the expected improvement yielded by popular approaches for I/O performance improvement. Our work provides valuable insights to everyone working to alleviate the I/O bottleneck in HPC

Quantum Reservoir Computing and Risk Bounds

We propose a way to bound the generalisation errors of several classes of quantum reservoirs using the Rademacher complexity. We give specific, parameter-dependent bounds for two particular quantum reservoir classes. We analyse how the generalisation bounds scale with growing numbers of qubits. Applying our results to classes with polynomial readout functions, we find that the risk bounds converge in the number of training samples. The explicit dependence on the quantum reservoir and readout parameters in our bounds can be used to control the generalisation error to a certain extent. It should be noted that the bounds scale exponentially with the number of qubits n. The upper bounds on the Rademacher complexity can be applied to other reservoir classes that fulfill a few hypotheses on the quantum dynamics and the readout function.</div

Monotonicity and convergence of two-relaxation-times lattice Boltzmann schemes for a non-linear conservation law

We address the convergence analysis of lattice Boltzmann methods for scalar non-linear conservation laws, focusing on two-relaxation-times (TRT) schemes. Unlike Finite Difference/Finite Volume methods, lattice Boltzmann schemes offer exceptional computational efficiency and parallelization capabilities. However, their monotonicity and $L^{\infty}$-stability remain underexplored. Extending existing results on simpler BGK schemes, we derive conditions ensuring that TRT schemes are monotone and stable by leveraging their unique relaxation structure. Our analysis culminates in proving convergence of the numerical solution to the weak entropy solution of the conservation law. Compared to BGK schemes, TRT schemes achieve reduced numerical diffusion while retaining provable convergence. Numerical experiments validate and illustrate the theoretical findings

Leveraging Prompt-based Large Language Models for Code Smell Detection: A Comparative Study on the MLCQ Dataset

International audienceCode smells are indicators of potential issues in software code that can make maintenance more challenging. Traditional approaches to detecting code smells have primarily relied on handcrafted rules and heuristics, while recent advances have explored Machine Learning (ML) and Deep Learning (DL) techniques. In this paper, we investigate the application of prompt-based Large Language Models (LLMs) for code smell detection, utilizing state-of-the-art models, namely Generative Pretrained Transformer-4 (GPT-4) and Large Language Model Meta AI (LLaMA). We conduct an extensive analysis of the Machine Learning Code Quality (MLCQ) dataset, focusing on how these LLMs perform when prompted to identify and classify code smells. By systematically evaluating each model’s performance, we provide insights into their precision, recall and ability to generalize across different types of code smells. Our results aim to demonstrate the potential of LLMs as a promising tool for automating certain types of code smells while underperforming for others.\keywords{Code Smells \and GPT-4 \and Large Language Models \and LLaMA \and LLMs \and Machine Learning

Inferring Time-Varying Internal Models of Agents Through Dynamic Structure Learning

Abstract Reinforcement learning (RL) models usually assume a stationary internal model structure of agents, which consists of fixed learning rules and environment representations. However, this assumption does not allow accounting for real problem solving by individuals who can exhibit irrational behaviors or hold inaccurate beliefs about their environment. In this work, we present a novel framework called Dynamic Structure Learning (DSL), which allows agents to adapt their learning rules and internal representations dynamically. This structural flexibility enables a deeper understanding of how individuals learn and adapt in real-world scenarios. The DSL framework reconstructs the most likely sequence of agent structures—sourced from a pool of learning rules and environment models—based on observed behaviors. The method provides insights into how an agent’s internal structure model evolves as it transitions between different structures throughout the learning process. We applied our framework to study rat behavior in a maze task. Our results demonstrate that rats progressively refine their mental map of the maze, evolving from a suboptimal representation associated with repetitive errors to an optimal one that guides efficient navigation. Concurrently, their learning rules transition from heuristic-based to more rational approaches. These findings underscore the importance of both credit assignment and representation learning in complex behaviors. By going beyond simple reward-based associations, our research offers valuable insights into the cognitive mechanisms underlying decision-making in natural intelligence. DSL framework allows better understanding and modeling how individuals in real-world scenarios exhibit a level of adaptability that current AI systems have yet to achieve

Optimizing stilbene recovery from cell cultures media: A comprehensive study of the adsorption process

International audienceStilbenes are of significant interest due to their potential health benefits and applications in pharmaceuticals and nutraceuticals. Traditional extraction methods often involve organic solvents, which pose environmental and safety concerns.This study investigates the extraction of stilbenes (E-resveratrol, labruscol, leachianol, ε-viniferin, and δ-viniferin) from grapevine (Vitis vinifera and Vitis labrusca) cell cultures using adsorption technology. Five food-grade resins (XAD-7, XAD-16, XAD-4, XAD-1180, and FPX-66) were tested for stilbene adsorption. XAD-7 was chosen as the optimum adsorbent, displaying the highest adsorbed quantity (86.94 ± 4.90 mgstilbenes/gdry resin) and desorbed quantity (74.28 ± 0.38 mgstilbenes/gdry resin). Adsorption kinetics using XAD-7 followed a pseudo-second-order model, with intraparticle diffusion limiting approximately 10 % of total adsorption. Desorption occurs more rapidly than adsorption, achieving equilibrium in about 60 min. Isotherm curves fitted well to a multicomponent Langmuir model, indicating a maximum adsorption capacity of 0.280–0.360 mmolstilbenes/gdry resin, close to the experimental value of 0.271 mmolstilbenes/gdry resin. Stilbene affinity for XAD-7 decreased in the following order: ε-viniferin &gt; (labruscol, E-resveratrol, leachianol) &gt; δ-viniferin. The optimal desorbed quantity of 59.74 ± 0.14 mgstilbenes/gdry resin was achieved with a 70 % ethanol solution and a 160:1 desorption solution-to-adsorbent ratio (v/w). XAD-7 resin coupled with an optimized washing step increased stilbene purity by 4.6 times (from 5.41 ± 0.05 % to 23.19 ± 0.31 % w/w). XAD-7 can be reused for multiple cycles with consistent adsorption capacity and desorption yield, maintaining the same stilbenes purity after 5 cycles.This study underscores the viability of polymeric resin adsorption as an eco-friendly and efficient method for stilbene extraction from grapevine cell cultures, paving the way for sustainable production processes in the nutraceutical and pharmaceutical industries

Semantic vs. LLM-based approach: A case study of KOnPoTe vs. Claude for ontology population from French advertisements

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Concevoir des Interactions au Stylet pour la Productivité et la Créativité

Designed with the mouse and keyboard in mind, productivity tools and creativity support tools are powerful on desktop computers, but their structure becomes an obstacle when brought to interactive surfaces supporting pen and touch input.Indeed, the opportunities provided by the pen for precision and expressivity have been demonstrated in the HCI literature, but productivity and creativity tools require a careful redesign leveraging these unique affordances to take benefit from the intuitiveness they offer while keeping the advantages of structure. This delicate articulation between pen and structure has been overlooked in the literature.My thesis work focuses on this articulation with two use cases to answer the broad research question: “How to design pen-based interactions for productivity and creativity on interactive surfaces?” I argue that productivity depends on efficiency while creativity depends on both efficiency and flexibility, and explore interactions that promote these two dimensions.My first project, TableInk, explores a set of pen-based interaction techniques designed for spreadsheet programs and contributes guidelines to promote efficiency on interactive surfaces. I first conduct an analysis of commercial spreadsheet programs and an elicitation study to understand what users can do and what they would like to do with spreadsheets on interactive surfaces. Informed by these, I design interaction techniques that leverage the opportunities of the pen to mitigate friction and enable more operations by direct manipulation on and through the grid. I prototype these interaction techniques and conduct a qualitative study with information workers who performed a variety of spreadsheet operations on their own data. The observations show that using the pen to bypass the structure is a promising mean to promote efficiency with a productivity tool.My second project, EuterPen, explores a set of pen-based interaction techniques designed for music notation programs and contributes guidelines to promote both efficiency and flexibility on interactive surfaces. I first conduct a series of nine interviews with professional composers in order to take a step back and understand both their thought process and their work process with their current desktop tools. Building on this dual analysis, I derive guidelines for the design of features which have the potential to promote both efficiency with frequent or complex operations and flexibility in regard to the exploration of ideas. Then, I act on these guidelines by engaging in an iterative design process for interaction techniques that leverage the opportunities of the pen: two prototyping phases, a participatory design workshop, and a final series of interviews with eight professional composers. The observations show that on top of using the pen to leverage the structure for efficiency, using its properties to temporarily break the structure is a promising mean to promote flexibility with a creativity support tool.I conclude this manuscript by discussing several ways to interact with structure, presenting a set of guidelines to support the design of pen-based interactions for productivity and creativity tools, and elaborating on the future applications this thesis opens.Conçus pour une utilisation avec la souris et le clavier, les outils aidant à la productivité et à la créativité sont puissants sur les ordinateurs de bureau, mais leur structure devient un obstacle lorsqu'ils sont transposés sur des surfaces interactives offrant une saisie tactile et au stylet.En effet, les opportunités offertes par le stylet en termes de précision et d'expressivité ont été démontrées dans la littérature sur en IHM. Cependant, les outils de productivité et de créativité nécessitent une refonte minutieuse exploitant ces propriétés uniques pour tirer parti de l'intuitivité qu'ils offrent, tout en conservant les avantages liés à la structure. Cette articulation délicate entre le stylet et la structure a été négligée dans la littérature.Mon travail de thèse se concentre sur cette articulation à travers deux cas d'utilisation afin de répondre à la question de recherche générale : « Comment concevoir des interactions basées sur le stylet pour la productivité et la créativité sur des surfaces interactives ? » Je considère que la productivité dépend de l'efficacité, tandis que la créativité repose à la fois sur l'efficacité et la flexibilité, et j'explore des interactions qui favorisent ces deux dimensions.Mon premier projet, TableInk, explore un ensemble de techniques d'interaction basées sur le stylet et conçues pour les logiciels de tableurs, et propose des lignes directrices pour promouvoir l'efficacité sur les surfaces interactives. Je commence par analyser les logiciels commerciaux et par mener une étude d'élicitation pour comprendre ce que les utilisateurs peuvent faire et ce qu'ils aimeraient faire avec les tableurs sur des surfaces interactives. Sur la base de ces analyses, je conçois des techniques d'interaction qui exploitent les opportunités offertes par le stylet pour réduire les frictions et permettre plus d'opérations par manipulation directe sur et à travers la grille. Je prototype ces techniques d'interaction et mène une étude qualitative auprès d'utilisateurs qui effectuent diverses opérations sur tableurs avec leurs propres données. Les observations montrent que l'utilisation du stylet pour contourner la structure constitue un moyen prometteur de favoriser l'efficacité dans un outil de productivité.Mon deuxième projet, EuterPen, explore un ensemble de techniques d'interaction basées sur le stylet, et conçues pour les logiciels de notation musicale, et propose des lignes directrices pour promouvoir à la fois l'efficacité et la flexibilité sur les surfaces interactives. Je commence par une série de neuf entretiens avec des compositeurs professionnels afin de prendre du recul et de comprendre à la fois leur processus de réflexion et leur processus de travail avec leurs outils actuels sur ordinateur de bureau. Sur la base de cette analyse double, j'élabore des lignes directrices pour la conception de fonctionnalités ayant le potentiel de promouvoir à la fois l'efficacité pour les opérations fréquentes ou complexes et la flexibilité dans l'exploration des idées. Ensuite, je mets en œuvre ces lignes directrices à travers un processus de conception itératif : deux phases de prototypage, un atelier de conception participative et une série finale d'entretiens avec huit compositeurs professionnels. Les observations montrent qu'en plus d'utiliser le stylet pour profiter de la structure afin de favoriser l'efficacité, tirer parti de ses propriétés pour briser temporairement la structure constitue un moyen prometteur de promouvoir la flexibilité dans un outil de soutien à la créativité.Je conclus ce manuscrit en discutant de différentes manières d'interagir avec la structure, en présentant un ensemble de recommandations pour soutenir la conception d'interactions basées sur le stylet pour les outils de productivité et de créativité, et en élaborant sur les applications futures que cette thèse ouvre

Collision avoidance behaviours in chronic non-specific low back pain participants: A prospective cohort study

International audienceObjective: Chronic non-specific low back pain (cNSLBP) is a leading cause of disability, influenced by bio-psycho-social factors. However, its impact on everyday activities such as navigating streets and interacting with other pedestrians remains underexplored. This study aimed to assess the effect of cNSLBP on perceptual-motor processes in a pedestrian crossing task, focusing on 1) collision avoidance behaviours, 2) the walker's role in avoiding collisions, and 3) the influence of pain perception.Methods: Seventeen asymptomatic adults (AA, 11 females, 46.4 ± 12.8 years) and seventeen cNSLBP participants (10 females, 47.9 ± 12.7 years) performed a task involving crossing paths at a 90° angle with another walker. Participants interacted in three groups pairings: AA-AA, AA-cNSLBP, and cNSLBP-cNSLBP. Key metrics included crossing order inversion, collision risk threshold informing movement adaptation, crossing distance, and the walker's contribution (speed/orientation).Results and discussion: No significant differences were observed between groups for the collision risk threshold (≈0.93 m) or crossing distance (≈0.8 m). However, cNSLBP participants exhibited distinct avoidance strategies, especially in cNSLBP-cNSLBP interactions, which showed more frequent inversions. When crossing first, cNSLBP participants contributed less, whereas when crossing second, they contributed more, primarily by adjusting their speed. A significant negative correlation emerged between depression scores and the level of contribution when cNSLBP participants crossed second.Conclusion: These findings suggest that pain perception may influence collision avoidance behaviours. Further research, potentially incorporating virtual reality, is needed to control environmental factors and deepen our understanding of these interactions