Portail HAL IMT Mines Albi
Not a member yet
5440 research outputs found
Sort by
Quantitative analysis of supercritical CO 2 jet structure from Schlieren imaging in free and impinged configurations
No full textInternational audienceIn recent years supercritical carbon dioxide (sCO) has emerged as a promising technology for machining assistance. Its contribution to the tool lifetime relies on both tribological and thermal actions on the control of the cutting zone. The present contribution proposes an experimental investigation of the flow features of a sCO jet. It intends to address primary data regarding the influence of the operating parameters on the shock structures and the flow characteristic (laminar–turbulent). It also intends to provide some explanations for the thermal behavior of such flow already observed in other published papers. This work addresses both free and impinged jets and investigates the influence of the impingement on the nature of the flow through Schlieren imaging and flow velocity estimation
Effect of Eu3+ Doping on the Interfacial Fracture Toughness of Yttria-Stabilized Zirconia Thermal Barrier Coatings in Flame Thermal Shock Condition
No full textInternational audienceThis study mainly focuses on the effect of small amount additions of Eu3+ in substitution for Y3+ on the thermal conductivity of YSZ TBCs, and the evaluation of coatings resistance to severe thermal shock cycles. Eu3+ doped and undoped YSZ coatings were prepared by APS method. Thermal conductivity of the two coatings was measured and both types of coatings were subjected to thermal shock condition under a steady propane flame at 1100 °C. Results showed that thermal conductivity of the YSZ:Eu coating is 10–19% lower than that of the YSZ coating at the same temperature, indicating that only 2 mol% Eu3+ doping can effectively reduce the thermal conductivity of the YSZ TBCs. For the same treatment conditions, the interfacial fracture toughness of the YSZ:Eu coating is slightly higher than that of the YSZ coating and the TGO thickness is thinner, indicating that 2 mol% Eu3+ doping is prone to inhibit the growth of TGO and improve the coating’s interfacial properties. Comparison between flame thermal shock and furnace isothermal / cyclic oxidation treatment confirmed that flame thermal shock is a more severe and destructive treatment as it results in higher densities of micro-cracks and pores within the TGO, thus inducing a lower interfacial fracture toughness value
Comparative analysis of methods for solving conduction-radiation coupling in heterogeneous materials
No full textInternational audienceThis article sets out a collaborative operation of seven French research teams to compare the numerical simulation methods currently developed by each of them for coupled conductionradiation heat transfer resolution in heterogeneous semi-transparent media. The different deterministic and stochastic methodologies are succinctly presented, emphasizing the distinctiveness of each simulation strategy. The teams work on a common configuration encompassing shared thermal model, thermophysical parameters, boundary conditions and mesh description files. The results produced, i.e. the radiative, conductive and total net heat flux profiles and the temperature profiles, are analyzed and discussed. This study highlights the strengths and limitations of each method regarding the chosen configuration, with each offering a distinct perspective that complements the others. An overview of current strategies for addressing thermal coupling in heterogeneous media is offered, emphasizing that the selection of a method should align with the initial physical inquiry
Developing a mobile application and dashboard for proactive management of patient no-shows via geolocation and dynamic scheduling
No full textInternational audienceMissed medical appointments (no-shows) remain a pervasive source of wasted capacity, idle clinical time, and workflow disruptions in hospitals. Existing approaches—from automated reminders to overbooking and waitlists—are mostly reactive and provide little real-time visibility into whether a patient is actually en route or likely to arrive. This paper introduces a proactive solution that continuously tracks patients from home to the point of care by combining outdoor GPS with indoor real-time location systems (RTLS), computes a dynamic Estimated Time of Arrival (ETA), and triggers scheduling adjustments through lightweight replanning heuristics. Our architecture couples a patient-facing mobile app, a hospital dashboard for operational oversight, and a backend that processes geolocation signals to update ETA on contextual events (traffic slowdowns, f loor changes, site entry). The approach aims to be win–win: improving patient guidance and communication while increasing resource utilization and schedule robustness on the hospital side
Analyse du potentiel des systèmes de fabrication en réseau pour saisir de nouvelles opportunités de production
No full textIn today’s volatile, uncertain, complex, and ambiguous manufacturing context, firms must adapt their production systems to stay competitive. Traditional risk management based on static data often fails to address unforeseen production requirements. Reconfiguration, defined as adjusting system parameters without new resources, offers a strategic response but requires collaboration across networks. This thesis proposes a framework with two contributions: an ontology-based model to identify configuration alternatives using available capabilities, and an optimization model to evaluate them through cost, feasibility, and logistics criteria. Applied to folding bicycle and hydroalcoholic gel production, the framework shows how firms can leverage shared resources to seize new production opportunities efficiently.Dans le contexte actuel de fabrication volatile, incertain, complexe et ambigu, les entreprises doivent adapter leurs systèmes de production pour rester compétitives. La gestion traditionnelle des risques basée sur des données statiques ne permet souvent pas de répondre à des exigences de production imprévues. La reconfiguration, définie comme l'ajustement des paramètres du système sans nouvelles ressources, offre une réponse stratégique mais nécessite une collaboration entre les réseaux. Cette thèse propose un cadre comportant deux contributions : un modèle ontologique permettant d'identifier les alternatives de configuration à partir des capacités disponibles, et un modèle d'optimisation permettant de les évaluer selon des critères de coût, de faisabilité et de logistique. Appliqué à la production de vélos pliants et de gel hydroalcoolique, ce cadre montre comment les entreprises peuvent tirer parti des ressources partagées pour saisir efficacement de nouvelles opportunités de production
Nouvelle approche basée sur Monte Carlo pour la modélisation des systèmes chimiquement réactifs : application à la pyrolyse de la biomasse lignocellulosique
No full textA new stochastic approach based on the "Monte Carlo Integral Formulation" is presented in this thesis to model the degradation kinetics of lignocellulosic biomass during pyrolysis. Pyrolysis, defined as the thermal degradation of biomass in the absence of dioxygen, is a complex process involving primary and secondary reactions influenced by heat and mass transfer, with physical properties of the biomass varying according to its chemical composition. This complexity is accentuated by the coupling of various physical phenomena and chemical reactions. To address this, Monte Carlo statistical methods are adopted, as they are insensitive to the complexity of the integration domains, making them particularly well-suited for the simulation of such processes. In the first case study, the kinetic/kinetic coupling under isothermal conditions was explored, modeling first-order coupled chemical reactions (in parallel, successive, and/or reversible). The kinetic model was formulated as a system of coupled expectations, and this coupling was addressed using the double randomization method. Stiffness scenarios were also tackled by using importance sampling, guided by classical approximations such as partial equilibrium and quasi-stationary state approximations, allowing results similar to analytical solutions to be obtained while extending the method to more complex reaction schemes. In the second case study, non-isothermal conditions are considered. It is assumed that the temperature and rate constants are known and prescribed. To model the coupling between thermal dynamics and kinetics, null-reaction algorithms are introduced. This approach was applied to the Broido-Shafizadeh model for cellulose pyrolysis, showing that a null-reaction algorithm without rejection is optimal for simple reactions, while an algorithm with rejection is found to perform better for reaction schemes with coupled reactions. Finally, in the third case study, this approach was extended to handle nonlinear thermal/kinetic coupling with a non-prescribed thermal model, formulated as an expectation. This case presents a particular challenge due to the non-linearity of the coupling law (Arrhenius law). A method to bypass this non-linearity using null collisions is proposed, and it is shown that this approach provides results comparable to deterministic solutions in simple cases. However, improvements are still required for more complex scenarios due to high computational costs and slow convergence. This thesis contributes to the multi-scale and multiphysics modeling of pyrolysis by addressing the main challenges associated with thermal/kinetic coupling and non-linearity. It also opens up perspectives for future research aimed at improving these methods for more complex systems.Une nouvelle approche stochastique basée sur le "Monte Carlo Formulation Intégrale" est présentée dans cette thèse pour modéliser la cinétique de dégradation de la biomasse lignocellulosique au cours de la pyrolyse. La pyrolyse, définie comme la dégradation thermique de la biomasse en absence de dioxygène, est un processus complexe impliquant des réactions primaires et secondaires influencées par les transferts de chaleur et de matière, avec des propriétés physiques de la biomasse qui varient en fonction de sa composition chimique. Cette complexité est accentuée par le couplage de divers phénomènes physiques et réactions chimiques. Pour y faire face, des méthodes statistiques de Monte Carlo sont adoptées, étant insensibles à la complexité des domaines d'intégration, ce qui les rend particulièrement adaptées à la simulation de tel procédé. Dans le premier cas d’étude, le couplage cinétique/cinétique en conditions isothermes a été exploré, en modélisant des réactions chimiques (en parallèle, successives et/ou réversibles) de premier ordre couplées. Le modèle cinétique a été formulé sous forme d'un système d’espérances couplées, et ce couplage a été traité à l'aide de la méthode de double randomisation. Des scénarios de raideur ont également été abordés en étant traités à l'aide d'un échantillonnage par importance, guidé par des approximations classiques telles que l'équilibre partiel et l'approximation des états quasi-stationnaires, permettant ainsi d'obtenir des résultats similaires aux solutions analytiques, tout en étendant la méthode à des schémas réactionnels plus complexes. Dans le deuxième cas d'étude, des conditions non-isothermes sont considérées. Il est supposé que la température et les constantes de vitesses sont connues et prescrites. Pour modéliser ce couplage entre la dynamique thermique et la cinétique, des algorithmes à réactions nulles sont introduits. Cette approche a été appliquée au modèle de Broido-Shafizadeh pour la pyrolyse de la cellulose, montrant qu'un algorithme à réactions nulles sans rejet est optimal pour les réactions simples, tandis qu'un algorithme avec rejet s'avère plus performant pour des schémas réactionnels avec des réactions couplées. Enfin, dans le troisième cas d’étude, cette approche a été étendue pour traiter le couplage thermique/cinétique non-linéaire avec un modèle thermique non-prescrit, formulé sous forme d'espérance. Ce cas présente un défi particulier en raison de la non-linéarité de la loi de couplage (loi d'Arrhenius). Une méthode permettant de contourner cette non-linéarité en utilisant les collisions nulles est proposée, et il est démontré que cette approche fournit des résultats comparables à ceux des solutions déterministes dans des cas simples. Cependant, elle nécessite encore des améliorations pour des scénarios plus complexes, en raison des coûts de calcul élevés et de la lenteur de convergence. La modélisation multi-échelle et multiphysique de la pyrolyse est contribué par cette thèse en abordant les principaux défis associés au couplage thermique/cinétique et à la non-linéarité. Des perspectives pour des recherches futures visant à améliorer ces méthodes pour des systèmes plus complexes sont également ouvertes
Thermo-Metallo-Mechanical Modeling of Case-Hardened Steel Parts for Prediction of Distortions during Intermittent Gas Quenching
No full textInternational audienceTo develop a behavior model, properties such as Young's modulus, viscous stress, kinematic hardening, isotropic hardening, yield strength and transformation-induced plasticity parameter (TRIP) for austenite and martensite were determined using a specially developed experimental set-up
Development of Stereo DIC Measurement on thermal energy storage tank: Determination of mechanical response
No full textInternational audienc
Technical Appendix for Bimodal Depth-First Search for Scalable GAC for AllDifferent
No full textThis document is the technical appendix for the paper entitled "Bimodal Depth-First Search for Scalable GAC for AllDifferent" accepted at IJCAI 2025. Section 1 presents the complete proof of Theorem 2. Section 2 details the bimodal algorithm for finding a maximum matching in the variable-value graph. Section 3 details the bimodal algorithm for computing the strongly connected components in the residual graph and finding the variable-value pairs to prune
Advection, diffusion and linear transport in a single path-sampling Monte-Carlo algorithm: Getting insensitive to geometrical refinement
No full textInternational audienceWe address the question of numerically simulating the coupling of diffusion, advection and one-speed linear transport, with a specific focus on managing geometrical complexity. We base our work on recent advances from the computer graphics community, which has developed Monte Carlo algorithms simulating linear radiation transport in physically realistic scenes, with numerical costs that remain unaffected by geometrical refinement: adding more details to the scene description does not impact the computation time. The resulting benefits in terms of engineering flexibility are already fully integrated into the cinema industry and are gradually being adopted by the video game industry. Here we demonstrate that the same insensitivity to the geometric complexity can be achieved when considering not only one-speed linear transport, but also its coupling with diffusion and advection. In this case, pure linear-transport paths are replaced with advection-diffusion/linear-transport paths, which are composed of subpaths. Each subpath represents one of the three physical phenomena, and coupling is handled by switching from one subpath (i.e. phenomenon) to another. This approach is illustrated using a porous medium involving up to 10,000 pores, with the computation time being strictly independent of the number of pores, showing its ability to facilitate engineering calculations in complex geometries