TIGRÉ : LA GUERRE OUBLIÉE DE LA CORNE DE L'AFRIQUE: Entre centralisation autoritaire et fédéralisme ethnique, un conflit de haute intensité aux ramifications régionales (2020-2022) Entre centralisation autoritaire et fédéralisme ethnique, un conflit de haute intensité aux ramifications régionales (2020-2022)

International audienc

Development and assessment of an adhesively bonded assembly geometry adapted for both ELS test and toward hygro-mechanical aging evaluation

International audienceStructural adhesive bonding has gained significant attention in recent years. However, its durability in harsh environments, such as marine ones, remains insufficiently examined due to a lack of comprehensive research. One reliable approach for assessing the strength of bonded assemblies is the fracture mechanics, which involves conducting experimental tests in different loading modes to determine their fracture toughness. These tests can be performed before and after aging conditions to evaluate the mechanical properties evolution of the bonded assembly in response to aging. While mode I may occur, mode II is usually dominant in bonded joints; thus, only mode II is considered in this study. The selected mode II test is the End-Loaded Split (ELS) test. Most studies have focused on either the mechanical test setup or the aging setup, but have lacked a combined approach. This paper introduces a new sample configuration that merges both the ELS test setup and the hygro-mechanical frame. To validate the new sample design, a comparison of the fracture toughness values and of the cohesive zone models (CZMs), obtained after fracture data elaboration, is made between this new configuration and a standard ELS sample geometry. For the fracture toughness measurement, all specimens were instrumented with distributed optical fiber sensor to monitor crack propagation as well as Digital Image Correlation system to calculate the J-integral values from which the CZM can be derived. One major conclusion is that the results are repeatable, confirming that the new sample design is valid for the upcoming aging study

Unprecedented polyvinyl polymer loading on SWCNTs in the liquid phase

International audienceOutstanding adsorption capacities of three polyvinyl polymers on single-walled carbon nanotubes

Marketing: Le marketing au service de la décarbonation des marchés (Management décarboné)

International audienceDans cet ouvrage, nous proposons de comprendre le processus de décarbonation des organisations et de leurs activités via le marketing, en tant que levier d’information et de transformation des marchés.La décarbonation se structure par jalons progressifs. L’ouvrage s’inscrit dans la démarche marketing, depuis la décarbonation des organisations, des business models, de l’offre et de la communication, jusqu’à la transformation des imaginaires.Les réflexions présentées sont nourries de dialogues interdisciplinaires entre des cadres théoriques mobilisés par les chercheurs en marketing avec ceux de l’économie de la fonctionnalité, l’économie circulaire et les communs. Ils sont illustrés de pratiques marketing décarbonées

Designing and Producing a Library's Catalogue for an Engineering School in 19th Century France: The Ecole des Ponts et Chaussées' First General Printed Catalogue (1872)

International audienceThis article is devoted to the first general printed catalogue of the École des Ponts et Chaussées (EPC) library, which was published in 1872 and whose production spanned several decades. The article opens with a historical account of the EPC library, and proceeds to examine the principal episodes that shaped the conception, maturation, and implementation of the 1872 catalogue, while its last part is concerned with the place of mathematical sciences—rational and applied mechanics included—within that document. Finally, the article’s conclusion offers some general reflections on the process of designing and crafting library catalogues for engineering schools dedicated to the production of State engineers in 19th century France, while a special attention is given to the “patrimonialization” work carried out by those involved in the devising of the 1872 catalogue

Evaluation of the accuracy of markerless algorithms in a paediatric population for upper limb movements in everyday life

International audienc

The Wasserstein gradient flow of the Sinkhorn divergence between Gaussian distributions

We study the Wasserstein gradient flow of the Sinkhorn divergence when both the source and the target are Gaussian distributions. We prove the existence of a flow that stays in the class of Gaussian distributions, and is unique in the larger class of measures with strongly-concave and smooth log-densities. We prove that the flow globally converges toward the target measure when the source's covariance matrix is not singular, and provide counter-examples to global convergence when it is, giving a first answer to an open question raised in [Carlier et al. 2024, §4.2]. When the covariance matrix of the source distribution commutes with that of the target, we derive more quantitative results that showcase exponential convergence toward the target when the source and the target share their support, but dropping to linear rates (O(t^{-1})) if the target is concentrated on a strict subspace of the source's support.</div

Low thickness platform on soft soil reinforced with rigid inclusions: 2D rolling load tests in centrifuge

International audienceThe effect of rolling loads on a thin granular subgrade, reinforced with rigid inclusions (RIs) and based on soft soil, is investigated using centrifuge modelling with a 2D scale model at 1/10th scale. The inclusion coverage rate is 10%. The model consists of a sand mattress—optionally reinforced with a geogrid sheet—an analog soft soil made of expanded polystyrene, and regularly spaced vertical metal plates. This setup is placed in a transparent container to facilitate the analysis of loading images. Traffic loading is simulated using a weighted roller, and results reveal an evolution of the load transfer platform (LTP) behavior during the traffic. Both unidirectional and bidirectional rolling tests are performed to replicate linear service traffic. Arching effects and geogrid-induced confinement within the sand mattress are measured using flexible tactile sensors and load cells embedded in the RIs. The efficiency of reinforcement in terms of load distribution is quantified for the different test configurations. Experimentally, load transfer to the RIs is found to be greater when the geogrid reinforcement (GGR) is placed at mid-height of the thin LTP, compared to placement directly on the RI heads. Finally, a simplified analytical model is proposed to estimate the vertical load at the top of the RIs, induced by the combined weight of the mobile roller and the resistance to forward motion at the LTP surface

Experimental investigation of passive alternating flow heating strategies for PEMFC cold start

International audiencePassive cold start remains a major challenge to Proton Exchange Membrane Fuel Cells (PEMFCs), with thermal imbalance during warm-up being a key challenge. Uneven temperatures can cause startup failure and long-term degradation. This study experimentally evaluates a new passive heating strategy using alternating coolant flow to improve thermal management. Experiments are conducted using a 3-cell thermal-emulation stack (100 cm2 per cell, ≈230 W thermal power), designed to replicate the edge and central-cell thermal behavior of real PEMFC stacks at −10 °C. The proposed method relies on alternating-flow operation, in which the coolant periodically reverses direction inside the cooling channels, enhancing heat retention and redistribution. This configuration is systematically compared with conventional no-flow (no coolant circulation) and unidirectional-flow (constant flow direction) using key thermal metrics, including temperature rise, vertical and horizontal uniformity, and forced-convection losses. Results show that the no-flow configuration enables rapid heating but induces significant inter-cell temperature differences, resulting in poor horizontal uniformity. Unidirectional configuration provides better horizontal uniformity but limits heating capability and leads to vertical temperature stratification at the cell level due to convective heat removal. The proposed alternating-flow strategy outperforms both reference cases, achieving a 32.3 °C temperature rise in 85 s, reducing vertical gradients by 90 %, and decreasing inter-cell temperature dispersion by more than 57 %. Under these conditions, the active surface exceeds 0 °C, enabling safe cold start. An adaptive strategy is proposed, dynamically switching flow modes based on internal thermal monitoring. This scalable approach offers a promising passive solution for cold-start management in PEMFCs

Bayesian calibration with missing data and model discrepancies: Application to high-speed train with uncertain control

International audienceWith the increasing complexity of engineering systems, the calibration of physical models has become a key step in ensuring predictive accuracy for industrial applications. In practice, however, calibration is often hindered by latent environmental variables whose influence on system behavior cannot be directly observed or controlled. Standard calibration techniques typically presume full knowledge of input variables — an assumption that, when violated, can lead to biased estimates and degraded model performance. This issue is exacerbated in dynamic systems, where both inputs and outputs are time-dependent functions, and measurements are inherently noisyand approximate. To address these limitations, we formulate the calibration problem within a Bayesian framework, treating the unknown environmental variables as random inputs with an associated probabilitydistribution. Rather than optimizing calibration parameters for a fixed set of inputs, we compute their posterior distribution and marginalize over the distribution of the unobserved variables. This approach propagates input uncertainty through the model and provides a natural mechanism for regularizing model error, thereby enhancing both robustness and interpretability. We demonstrate the practical benefits of this method on a railway dynamics case study, where it outperforms standard calibration in terms of both accuracy and reliability under uncertainty