HAL Portal UBS (Université Bretagne Sud)
Not a member yet
14201 research outputs found
Sort by
Green's functions for the static curvature and deflection of two-phase peridynamic elastic Euler-Bernoulli beams with exponential kernels
No full textInternational audienc
Stationary internal waves in a two-dimensional aquarium at low viscosity
No full textWe prove the uniform solvability of a stationary problem associated to internal waves equation with small viscosity in a two dimensional aquarium with real-analytic boundary, under a Morse-Smale dynamical assumption. This is achieved by using complex deformations of the aquarium, on which the inviscid stationary internal wave operator is invertible
Analysis of slamming loads induced by breaking waves on vertical cylinders using fully nonlinear wave kinematics and semi-analytical load model
No full textInternational audienceMost offshore structures are made of vertical cylinders and may be exposed to breaking waves, which are known to generate impulsive forces that are challenging to estimate. In particular, engineering formulas are often based on an oversimplified representation of the breaking wave, leading to a poor estimate of the load time history. In this study, the wave shape and the fluid kinematics are obtained from a fully nonlinear potential flow solver to reduce the uncertainty on the wave characterisation. The slamming force is then estimated using a semi-analytical water impact model based on Wagner theory and the data from the fully nonlinear simulations. The modelled forces are compared with experimental data on a segmented cylinder impacted by breaking waves of various strengths. The influence of the distance between the cylinder and the breaking point is studied. The model is shown to reproduce accurately the force measurements on the two upper sections impacted by strong plunging breaking waves. The model is compared to other formulations and is shown to improve the estimation of the load time history. For waves of low and mid-breaking strength, the model highly overestimates the force acting on the upper section impacted by the wave crest. The presence of the cylinder in the wave field leads to run-up and diffraction effects that disturb the wave profile. Therefore, accounting for the unperturbed wave kinematics is a conservative approach to evaluate the force acting on the upper section, whereas the evolution of load in time on the lower section is accurately reproduced for all waves
Digital twin-based enhancement of vibration measurements for gearbox monitoring under data scarcity
No full textInternational audienc
Revue sur les stockage d'énergie thermique horizontal enterré à faible profondeur (HUTES)
No full textInternational audienceUnderground thermal energy storage (UTES) are widely recognised as one of the most promising technologies for building applications due to their high energy efficiency and low operating costs. In recent years, horizontal underground thermal energy storage (HUTES) have gained recognition as effective solutions for storing intermittent renewable energy. In these systems, heat exchangers play a crucial role as heat-conducting media, with a predominantly horizontal distribution. Many notable studies have been conducted in recent years. However, most existing reviews have focused on vertical UTES, addressing their design, performance and applications, as well as horizontal ground heat exchangers integrated into geothermal heat pump systems, named as Horizontal Ground source Heat Pump. A systematic synthesis analysing the thermodynamic performance of HUTES, enabling the use of energy from renewable resources, is therefore essential. This review aims to summarise the experimental benches and analytical and numerical models of shallow HUTES with linear, spring and spiral loops, as well as their advantages and disadvantages. Evaluations and comparisons between different configurations of HUTES are presented. Particular attention is paid to the various internal and external factors influencing the thermal properties of HUTES: geometric parameters, thermophysical properties of different materials, operating and climatic conditions. Finally, conclusions are drawn on the choices to be made in order to develop the most efficient HUTES. Finally, this review offers suggestions for future developments and recommendations for research directions related to HUTES, providing avenues for further research.Le stockage souterrain d'énergie thermique (UTES) est largement reconnu comme l'une des technologies les plus prometteuses pour les applications dans le bâtiment en raison de son rendement énergétique élevé et de ses faibles coûts d'exploitation. Ces dernières années, le stockage souterrain horizontal d'énergie thermique (HUTES) s'est imposé comme une solution efficace pour stocker l'énergie renouvelable intermittente. Dans ces systèmes, les échangeurs de chaleur jouent un rôle crucial en tant que moyens de conduction thermique, avec une distribution principalement horizontale. De nombreuses études notables ont été menées ces dernières années. Cependant, la plupart des analyses existantes se sont concentrées sur les UTES verticaux, abordant leur conception, leurs performances et leurs applications, ainsi que sur les échangeurs de chaleur horizontaux intégrés dans les systèmes de pompes à chaleur géothermiques, appelés « pompes à chaleur géothermiques horizontales ». Une synthèse systématique analysant les performances thermodynamiques des HUTES, permettant l'utilisation d'énergie provenant de ressources renouvelables, est donc essentielle. Cette revue vise à résumer les bancs d'essai expérimentaux et les modèles analytiques et numériques des HUTES peu profonds avec des boucles linéaires, à ressort et en spirale, ainsi que leurs avantages et leurs inconvénients. Des évaluations et des comparaisons entre différentes configurations de HUTES sont présentées. Une attention particulière est accordée aux différents facteurs internes et externes qui influencent les propriétés thermiques des HUTES : paramètres géométriques, propriétés thermophysiques des différents matériaux, conditions d'exploitation et climatiques. Enfin, des conclusions sont tirées sur les choix à faire afin de développer les HUTES les plus efficaces. Enfin, cette étude propose des suggestions pour les développements futurs et des recommandations pour les orientations de recherche liées aux HUTES, ouvrant ainsi la voie à de nouvelles recherches
Acceleration of implicit schemes for large systems of delay differential equations
No full textInternational audienceThe objective is to accelerate numerical implicit schemes for solving large linear or nonlinear delay differential equations. These schemes require solving large linear or nonlinear systems at each integration step, making effective initial guesses critical for rapid convergence. For nonlinear problems, an inexact Newton method is used, whose efficiency depends heavily on the quality of these initial guesses. To generate them, line search or trust-region algorithms are employed -each involving the solution of large linear systems. These linear systems are solved using a Krylov subspace method. Initial guesses are constructed via a Petrov-Galerkin process applied to low-dimensional approximation subspaces derived from previous steps. Error estimates are provided, linking the accuracy of the initial guesses to the timestep size, the scheme's order, and the subspace dimension. Numerical experiments show speedups of up to two orders of magnitude over standard predictor-based methods, when those converge
Molecular Pathogenesis and Targeted Therapeutic Advances in Langerhans Cell Histiocytosis: A Systematic Review
No full textInternational audienceIntroduction: Langerhans Cell Histiocytosis (LCH) is a rare myeloid neoplasm characterized by clonal proliferation of immature dendritic cells, primarily driven by constitutive activation of the MAPK signaling pathway through mutations in BRAFV600E, MAP2K1, and ARAF. Recent genomic and therapeutic advances have reshaped the understanding of LCH pathophysiology, highlighting differences between pediatric and adult presentations, particularly regarding skeletal involvement and prognosis.Aim: To systematically review the literature published between 2015 and 2025 addressing genetic alterations, immunopathogenic mechanisms, orthopedic manifestations, and targeted therapies in pediatric and adult Langerhans Cell Histiocytosis.Methods: A systematic review was conducted in accordance with PRISMA 2020 guidelines. Searches were performed in PubMed/MEDLINE, SciELO, and the Virtual Health Library (BVS). After screening, duplicate removal, and eligibility assessment, 38 studies were included. Due to methodological heterogeneity, data were synthesized through qualitative analysis, and no meta-analysis was performed.Results: The included studies demonstrated a predominance of BRAFV600E mutations (52–65%) and MAP2K1 mutations (15–25%), leading to sustained MAPK pathway activation and chronic inflammation. Pediatric patients more frequently presented with multifocal skeletal involvement, while adults predominantly exhibited unifocal disease with favorable prognosis. Targeted therapy with BRAF and MEK inhibitors achieved high response rates, with radiological regression and functional improvement; however, disease relapse after treatment discontinuation remained common in a subset of patients.Conclusion: Activation of the MAPK pathway is central to LCH pathogenesis and clinical behavior. Incorporation of molecular profiling enables precision-based therapeutic strategies, particularly with BRAF and MEK inhibitors. Orthopedic manifestations, especially in pediatric patients, require conservative and multidisciplinary management. Despite significant advances, randomized clinical trials and standardized treatment protocols are still needed to define optimal therapy duration and reduce relapse risk
High-resolution spatial estimation of abrupt heat flux fluctuations from infrared temperature measurements
No full textInternational audienc
Radial elastic heterogeneity in a high-modulus carbon fibre assessed by nano-indentation and micro-pillar compression
No full textInternational audienceUnderstanding the radial heterogeneity of carbon fibres is critical to optimising their performance in structural composites. In this study, we investigate the mechanical structure of a high-modulus PAN-based carbon fibre by combining instrumented nano-indentation (IIT) and micro-pillar compression (MCP). Nano-indentation mapping with 50 nm lateral resolution reveals a distinct layered skin–core structure. By combining IIT and MCP, we resolve for the first time the compressive modulus of individual radial layers within a single carbon fibre: a compliant core (110GPa at 0.45% compressive strain), a transitional middle layer, and a stiff outer skin (520 ± 100GPa, at 0.45% compressive strain). Our results confirm earlier indirect estimates and show that the skin modulus approaches that of highly oriented crystallites, whereas the core remains significantly softer due to misorientation. This integrated approach provides a robust framework for characterising anisotropic heterogeneous fibres and offers new insight into fibre-scale mechanical testing
Decoupling surface stiffness from surface chemistry: Impact on bacterial adhesion and retention under shear conditions
No full textInternational audienceUnderstanding how substrate mechanics influence bacterial adhesion and retention is essential for controlling biofilm formation on synthetic materials. Studies on soft polymers such as PDMS are often confounded by uncontrolled variations in surface chemistry and topography. In this work, a PS-PIB bilayer system was designed to decouple surface chemistry from mechanics, enabling independent control of stiffness while maintaining constant surface properties. Static adhesion assays with Pseudomonas aeruginosa PAO1 showed that initial attachment was insensitive to substrate modulus when surface chemistry and roughness were held constant. In contrast, retention under shear flow decreased with increasing stiffness and correlated more closely with the work of separation obtained from nanoindentation experiments. This parameter, which integrates both adhesive and dissipative contributions, is introduced as an empirical descriptor of interfacial mechanical resistance. Retention data were described by a power-law model consistent with stochastic frameworks of multivalent adhesion, reflecting population heterogeneity in the number and strength of adhesive contacts. Altogether, these findings suggest that viscoelastic dissipation is a key factor influencing P. aeruginosa PAO1 detachment under flow and highlight the need for future studies using bacterial mutants and diverse species to assess the generality of this correlation across different adhesion strategies