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Cesser le feu: Crudivorisme, science et contre-connaissance
No full textCesser le feuCrudivorisme, science et contre-connaissance
Towards a finer heat flux partitioning modeling with detailed validation for boiling flows simulations
No full textInternational audienceA new heat flux partitioning model for to vertical boiling flows has been developed. The goal was to perform separate validation for each closure law (nucleation site density, bubble sliding, etc.) using large literature database. The model is finally validated against a recent boiling experiments where several physical parameters have been simultaneously measured
Modèle de canopée urbaine amélioré avec du lancer de rayons pour l'énergétique du bâtiment
No full textInternational audienceThe urban heat island (UHI) affects energy consumption as well as heating and cooling demand in cities. Traditional urban canopy models, such as the Urban Weather Generator (UWG), can be used to estimate the impact of the UHI on the outdoor air temperature. They simplify urban morphology by assuming idealized averaged street canyons. This limits the accuracy of solar radiation modeling, a critical component of urban energy balance. To address this, we propose integrating detailed ray tracing solar calculations into UWG, leveraging Building Information Models (BIM) to enhance geometric precision. A case study on a real neighborhood shows the impact on shortwave irradiance and air temperature predictions, with measurable but limited impacts on cooling demand.L'îlot de chaleur urbain (ICU) influe sur la consommation d'énergie ainsi que sur les besoins en chauffage et en climatisation dans les villes. Les modèles traditionnels de canopée urbaine, tels que Urban Weather Generator (UWG), peuvent être utilisés pour estimer l'impact de l'ICU sur la température de l'air extérieur. Ils simplifient la morphologie urbaine en supposant des canyons urbains idéalisés et moyennés. Cela limite la précision de la modélisation du rayonnement solaire, un élément essentiel du bilan d'énergie à la maille urbaine. Pour remédier à cela, nous proposons d'intégrer une méthode de calculs solaires détaillés par lancer de rayons dans UWG, en tirant parti d'une chaîne logicielle de BIM to BEM (BIM) pour obtenir une géométrie plus détaillée. Une étude de cas sur un quartier réel montre l'impact sur l'irradiance et la température de l'air, avec des effets mesurables mais limités sur la demande en refroidissement
Microarchitectural signals analysis platform for the implementation of Hardware Security Counters
No full textInternational audienceDetecting malicious software or hardware behavior during the operation of a computer system requires observables from one or more abstraction layers of the system. This abstraction, however, tends to limit the ability to detect behavioral deviations, especially for attack classes that exploit vulnerabilities very close to the target hardware. Conversely, too low a level of abstraction tends to significantly increase the complexity of the system model, and therefore poses a number of difficulties for the extraction and selection of relevant observables for a given class of attack.Hardware performance counters in particular have been used as an indirect means of observing micro-architecture behavior and detecting software attempting to exploit hardware vulnerabilities. In order to improve the various detection methods, we propose the construction of hardware metrics designed from the outset for security, by studying the correlation between signals from the micro-architecture and the various classes of attack in the literature, targeting both conventional IT and industrial OT systems. By extension, this work aims to detect attacks originating from hardware Trojans, the latter having the effect of changing the behavior of a given micro-architecture
Base données Epos-France des mouvements du sols dus aux séismes en France métropolitaine
No full textNational audienceCet article présente la base de données Epos-France des séismes en France métropolitaine. Cette base met à jour et améliore celle compilée par Traversa et al. (2020). Elle s’étend de janvier 1996 jusqu’à décembre 2021, et est composée de plus de 16 000 enregistrements correspondant à plus de 600 séismes s’étant produits en France métropolitaine ou dans les pays alentours
Eigenvalue falls in thin broken quantum strips
No full textWe are interesting in the spectrum of the Dirichlet Laplacian in thin broken strips with angle α. Playing with symmetries, this leads us to investigate spectral problems for the Laplace operator with mixed boundary conditions in thin trapezoids characterized by a parameter ε small. We give an asymptotic expansion of the first eigenvalues and corresponding eigenfunctions as ε tends to zero. The new point in this work is to study the dependence with respect to α. We show that for a small fixed ε>;0, at certain particular angles α_k , k = 0, 1, . . . , that we characterize, an eigenvalue dives, i.e. moves down rapidly, below the normalized threshold π^2 /ε^2 as α>0 increases. We describe the way the eigenvalue dives below π^2 /ε^2 and prove that the phenomenon is milder at α_0 = 0 than at α_k for k ≥ 1
Convergence rates of curved boundary element methods for the 3D Laplace and Helmholtz equations
No full textInternational audienceWe establish improved convergence rates for curved boundary element methods applied to the three-dimensional (3D) Laplace and Helmholtz equations with smooth geometry and data. Our analysis relies on a precise analysis of the consistency errors introduced by the perturbed bilinear and sesquilinear forms. We illustrate our results with numerical experiments in 3D based on basis functions and curved triangular elements up to order four
SerpentFlow: Generative Unpaired Domain Alignment via Shared-Structure Decomposition
No full textDomain alignment refers broadly to learning correspondences between data distributions from distinct domains. In this work, we focus on a setting where domains share underlying structural patterns despite differences in their specific realizations. The task is particularly challenging in the absence of paired observations, which removes direct supervision across domains. We introduce a generative framework, called SerpentFlow (SharEd-structuRe decomPosition for gEnerative domaiN adapTation), for unpaired domain alignment. SerpentFlow decomposes data within a latent space into a shared component common to both domains and a domain-specific one. By isolating the shared structure and replacing the domain-specific component with stochastic noise, we construct synthetic training pairs between shared representations and target-domain samples, thereby enabling the use of conditional generative models that are traditionally restricted to paired settings. We apply this approach to super-resolution tasks, where the shared component naturally corresponds to low-frequency content while high-frequency details capture domain-specific variability. The cutoff frequency separating low- and high-frequency components is determined automatically using a classifier-based criterion, ensuring a data-driven and domain-adaptive decomposition. By generating pseudo-pairs that preserve low-frequency structures while injecting stochastic high-frequency realizations, we learn the conditional distribution of the target domain given the shared representation. We implement SerpentFlow using Flow Matching as the generative pipeline, although the framework is compatible with other conditional generative approaches. Experiments on synthetic images, physical process simulations, and a climate downscaling task demonstrate that the method effectively reconstructs high-frequency structures consistent with underlying low-frequency patterns, supporting shared-structure decomposition as an effective strategy for unpaired domain alignment
Résilience à température ambiante et à température cryogénique d'un acier inoxydable 316L élaboré par fabrication additive arc-fil
No full textInternational audienceIn this study, the impact toughness behavior of wire-arc additively manufactured 316L stainless steel (WAAM 316L) was characterized at room temperature and at -193 ◦C. Microstructure – toughness relationships were determined, as well as the influence of recrystallization on microstructural evolution and impact properties. At the stress-relived state, WAAM 316L exhibited a ductile fracture and an impact toughness of 139 ± 10 J/cm2 at room temperature, whereas a partially brittle fracture was obtained at -193 ◦C leading to a low impact toughness of 28 ± 10 J/cm2. Recrystallization and homogenization heat treatment induced a significant increase in impact toughness both at room temperature (+60 %) and at -193 ◦C (+475 %). As in other additively manufactured 316L, oxide particles appeared to be the microstructural feature controlling ductile fracture of WAAM 316L and the cause of its low impact toughness compared to conventionally processed 316L. Brittle fracture observed at -193 ◦C occurred by cleavage of the δ-ferrite domains. A comparison of the results obtained with WAAM 316L with those reported by the literature for LPBF 316L allowed to identify the localization of oxide particles as a key factor in determining the relevance of recrystallization heat treatments, regarding the fracture behavior
Unintended capital value destruction. The qualification of energy inefficient housing as "bads" in the French real estate markets
No full textInternational audienceAs dangerous thresholds of GHG emissions are overstepped and planetary boundaries breached (Ripple et al. 2024; Rockström et al. 2024), as no effective global governing action of the issue is in sight (Dahan 2016; De Pryck and Hulme 2022) and at a time when public policies aimed at reconciling ecology and the economy, such as the European ‘Green Deal’, are under threat from all sides, can we still believe that markets offer a way to coordinate much needed action to tackle climate change challenges? Can we really believe, as the proponents of market studies seem to have done, that it is possible to integrate political issues into the workings of the market economy? (Callon 2007; Geiger et al. 2015). More specifically, can markets themselves be entrusted with the task of eliminating goods that are considered to be morally or environmentally harmful?Market studies have offered analysis of the moral legitimacy of certain markets (Steiner and Trespeuch 2019) and of the multiple values that enter the production of ‘concerned’ markets (Geiger et al. 2015). The ability of markets to endorse political contestation has been shown in studies that have drawn the attention to activists and consumers protesting against certain types of goods (Stolle and Micheletti 2013; Bereni and Dubuisson-Quellier 2020). While these processes sometimes lead to the re- articulation of practices outside the market sphere (Dubuisson-Quellier and Lamine 2004; Bailly, Barbier, and Daniel 2022), they also often lead to the production of alternative products and markets. Labelling or ranking processes (Laurent and Mallard 2020; Bergeron, Castel, and Dubuisson-Quellier 2014) are part of the range of responses to contestation. They also contribute to the disappearance of poor-quality products, even though labels are often seen primarily from the point of view of their ability to differentiate qualities and promote products deemed to be of better quality. An important point is that in linking products to the political and moral externalities they create, non-market actors who protest engage in struggles over the valuation of goods (Dubuisson-Quellier 2021; Cova and D’Antone 2016). Finally, in drawing attention to the process of detachment (Brembeck, Cochoy, and Hawkins 2021) make visible the established dependencies and embedded infrastructures that are part of real markets and make their transformation often long and effortful. In so doing, the angle taken on detachment pays full tribute to Callon's definition of markets, not as interfaces but as complex sets of relations involving various entities - humans, objects, discourses, among others (Callon 2016; 2021). There has been however a lack of studies specifically focussing on the use of market means to destroy capital value. Drawing on the foundational 'economy of qualities' (Callon, Méadel and Rabeharisoa 2002), which demonstrated the crucial importance of the work of characterising the unique qualities of the good for the establishment and functioning of markets, and on the demonstration of the thickness and interconnectedness of markets (Callon, 2021), we’ll be looking at the case of energy over- consuming dwellings in France. In this instance, a process of requalification of certain dwellings as ‘bads” and their progressive phasing out of the rental market by governmental regulation has led not to the expected improvement of the living and environmental condition of dwellings but first and foremost to the sudden disappearance of the monetary value of certain properties and to protests from landlords who consider themselves spoliated.Over the past few years, French public authorities have been implementing a banning programme of excessively energy inefficient housing that they want to see disappear from the building stock. This includes the notion of ‘energy-inefficient housing’ or “energy sieves” in the categories of public action, a branding of energy sieves as such in real estate ads, the freezing of rents and the ban on renting out these homes, which will come into force gradually depending on the energy consumption of the property (from 2025 for the most energy-intensive, then in 2028 and 2034). These are supposed to lead to a process of eradication that will see energy sieves disappear from the French housing stock – and its overall energy performance improve. As it has entered into force, the regulation has provoked a stir among landlords.In just a few years in the property sector, energy performance - and the notion of ‘sieve’ that characterises it so emblematically - has established itself as a new way of looking at property. This form of qualification is coming to the property sales and rental markets, where properties are traditionally viewed in terms of a range of different qualities: surface area, number of rooms, relationship to light (north/south orientation, sunlight), geographical location, view, old or new character, ‘charm’ or practicality in terms of how the space is used, modernity and performance of equipment, but also the potential for enhancement and capital value conservation and increase. Tenants and landlords, buyers and sellers, residents and investors are now being led to understand the new qualities of housing, which impact on both comfort and quality of life, the durability of the property as an asset, but also the value and investment required. In other words, property has a number of market commitments: to be lived in (which means it needs to be heated and well insulated), to be rented out, and to serve as a store of value. And it is in relation to this multiplicity of markets associated with the property that we need to re-examine the question of transforming them into bads.This article will show that these three processes are at play in the case of energy sieves. We will be looking at the collective nature of the requalification process of some dwellings as “bads”, which involves a range of players (public authorities, activist associations, property owners, market intermediaries such as estate agents). We will also look at the way in which the property itself is involved in several markets: property ownership, housing, works and renovation. The issue of reclassification as ‘bad’ in one market raises the question of how values and qualities are reconstituted in other markets. Finally we will suggest that the lack of production of alternatives, namely the deficiencies of the retrofit market, helps accounts for the tumultuous detachment of energy sieves from the building stock in France. The research on which this paper is based on 18 interviews with stakeholders of the energy label reform and of the emergence of the energy sieve notion ; on 15 interviews with real estate commercial agents; and on extensive documentary press and internet review1