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Does Tax-Benefit Linkage Matter for the Incidence of Payroll Taxes?
No full textWe analyse earnings responses to six large payroll tax and income tax reforms in France. Our findings indicate full pass-through to workers when there is a strong and transparent link between contributions and expected benefits. In contrast, employer payroll taxes with no tax-benefit linkage exhibit limited pass-through to workers, while income tax nominally borne by employees show nearly full pass-through. Together with a meta-analysis of the literature, we interpret these results as empirical support for the long-standing hypothesis that tax-benefit linkage matters for the incidence of payroll taxes. In the absence of such linkage, our findings suggest that the individual-level incidence of payroll taxes aligns with their statutory incidence
The Household Demand for Leisure, the Price of Time and the Full Cost of Children: A Structural Model and Evidence from the PSID
No full textWe propose a novel approach to estimating the full cost of children -the sum of monetary and time costs -by endogenizing the price of parental time rather than assuming it is equal to the parents' wage rate. In this approach, the price of time depends on how parents perceive their time with children, whether as a leisure-like activity or more as a labor-like activity. We then develop a simplified collective model of leisure demand for working couples, incorporating individual preferences and childcare technology, and estimate it using 2019 PSID data. This allows us to recover the price of parental time and the full cost of children. We find that mothers perceive 44% of their childcare time as labor, compared to 35% for fathers. Our results also highlight that a substantial portion of the full cost of children is non-monetary.</div
La demande d’actifs risqués des épargnants après les réformes fiscales et la Covid-19
No full textInternational audienceEntre 2004 et 2014, le nombre d’actionnaires en France a diminué d’environ 50 %. Cependant, cette frilosité des épargnants observée après la crise de 2008 semble, aujourd’hui, moins d’actualité, d’autant plus que l’année 2017 a été marquée par une réforme fiscale visant à soutenir l’actionnariat : mise en place d’une flat tax et suppression de l’impôt de solidarité sur la fortune (ISF), remplacé par l’impôt sur la fortune immobilière (IFI). Mais c’était sans compter sur la crise sanitaire de la Covid-19, durant la période 2020-2021, et ses conséquences sur le marché boursier (chute des cours, augmentation du taux d’épargne, risques accrus, etc.), qui ont pu affecter l’efficacité de ces mesures. Dans ce contexte, nous proposons d’étudier les portefeuilles risqués (actions et assurances-vie en unités de compte) des ménages français, à partir des trois dernières vagues (2014-2015, 2017-2018 et 2020-2021) de l’enquête « Histoire de vie et patrimoine » de l’Insee qui présentent, aujourd’hui, l’avantage d’être panélisées
Universal Functions with Ekman Spiral and Monin–Obukhov Surface Layers
No full textInternational audienceToday, computational fluid dynamics (CFD) is widely used for atmospheric dispersion at building scale. This type of simulation requires boundary conditions for wind, turbulence, and temperature. A classical way of imposing representative flow at open boundaries is to derive (universal) functions corresponding to idealised situations (e.g. constant shear stress, constant heat flux, such as in the Monin–Obukhov theory). In this paper, we first propose an analysis of universal functions for the surface layer and compare them to a 5-year data base of measurement on the SIRTA observatory (France). The conclusion is that these functions are in good agreement with the experimental data for moderate ratios of (distance to the ground divided by Obukhov length), but most of them do not fulfil asymptotic behaviours in the very stable or convective limit. We also compare the measurements with the extensions proposed by Gryning et al. (Bound Layer Meteorol 124(2):251–268, 2007), which take into account the height of the atmospheric boundary layer. Then, following the work of Nieuwstadt (Noct Bound Layer J Atmos Sci 41(14):2202–2216, 1984. https://doi.org/10.1175/1520-0469(1984)0412202:TTSOTS2.0.CO;2 ), we propose universal functions able to reproduce the Ekman spiral and consistent with moment-turbulence closures for stably stratified atmospheres
Derivation of model-consistent universal functions for second-order turbulence models and their implications on Lagrangian stochastic methods for thermally stratified atmospheric surface boundary layer flows
No full textInternational audienceThe aim of this paper is to provide a description of high-Reynolds-number thermally stratified surface-boundary-layer flows consistent with given turbulence models and to study their implications on Lagrangian stochastic approaches. The emphasis is first put on the relations between the selected turbulence models and the resulting universal functions used to describe the first- and second-order moments for temperature and velocity. To this end, a methodology for deriving model-consistent mean profiles that agrees with the Monin–-Obukhov theory is presented. This methodology is based on the derivation of algebraic solutions for the thermal and dynamic second-order moments, and on an iterative resolution of the turbulent dissipation rate. With adequate models for the dissipation rate, it is shown that the derived universal functions for the first- and second-order moments retrieve the correct asymptotic behaviors for both the stable and unstable limits. Based on these formulations, the consequences on Lagrangian stochastic models are then investigated since the turbulent model corresponding to the Lagrangian description must be consistent with the one used in the moment approach. For example, when using wall-function formulations, we highlight the importance of applying an-elastic wall-boundary conditions for both velocity and thermal instantaneous properties. Finally, an application to the case of linear-source dispersion is analyzed in the frame of hybrid moment–probability density function methods. It is shown that these methods can adequately account for stability effects and that models of instantaneous thermal quantities have a great impact on both buoyant plume rise and dispersion
Modelling chemically active porous media: material evolution and multiphysics couplings
No full textInternational audienceChemically active porous media are a common occurence in building materials, from the traditional cement-based materials to geopolymers, for instance. Their common feature is a drastic evolution of material properties induced by chemical processes taking place in the pore space. This evolution concerns not only the mechanical behaviour of the material, but also thermal and hydraulic aspects. The ability to model this evolution, taking into account external factors such as temperature and relative humidity conditions is paramount to the development of new materials (e.g. low-carbon cement) and new technologies associated with them (such as 3D printing, for instance). However, from a thermodynamics point of view, treating porous media for which chemical processes alter the behaviour, seemingly irreversibly, is not straightforward. Indeed, even reversible processes such as elasticity can lead to irreversible deformations due to the advancement of chemical reactions. Herein, we propose a thermodynamics framework taking into account chemical processes, showing the ability to recover the traditional constitutive equations of thermo-poroelasticity by introducing a chemically frozen free energy of the solid skeleton. In addition, we also show how in the case of precipitation reactions, the standard equations of thermo-poroplasticity can be extended to describe the fluid-like behaviour of a material for which a connected solid network does not exist. Couplings with thermal processes through the thermo-activation of chemical reactions, as well as with hydraulic processes in the case of water-based reactions, are of primary importance when looking at the time evolution of such porous media. Following the theoretical analysis, we propose an implementation of a fully-coupled chemo-thermo-poromechanical material model, with applications to cement-based materials. In particular, we show how such a model is able to reproduce numerically the impact of loading history (be it mechanical, thermal or ambient relative humidity) on the behaviour at the hardened state, in various scenarii from deep well cementing to 3Dconcrete printing.Les milieux poreux chimiquement actifs sont répandus parmi les matériaux de construction, allant des matériaux cimentaires traditionnels aux géopolymers, par exemple. Leur caractéristique commune réside dans l’évolution drastique de leur propriétés induite par des processus chimiques ayant lieu dans les pores. Cette évolution concerne les propriétés mécaniques, mais également thermiques et hydriquesdu matériau. La modélisation de cette évolution en prenant en compte des facteurs externes tels que la température et l’humidité relative est indispensable au développement de nouveaux matériaux (e.g. ciments bas-carbone) et de nouvelles technologies qui leur sont associées (comme l’impression 3D, par exemple). Toutefois, du point de vue de la thermodynamique, le traitement de ces matériaux poreux pour lesquels des processus chimiques modifie le comportement de manière irréversible n’est pasdirect. En effet, des processus réversibles comme l’élasticité peuvent conduire à des déformations irréversibles à cause de l’avancement de réactions chimiques. Ici, nous proposons un cadre thermodynamique prenant en compte des processus chimiques qui permet de retrouver les équations classiques de thermo-poroelasticité par l’introduction d’une énergie libre bloquée pour le squelette poreux. De plus, nous montrons également que dans le cas de réactions de précipitation de solide, les équations classiquespeuvent être étendues à la description de l’état fluide d’un matériau pour lequel un réseau solide connecté n’est pas encore formé. Les couplages thermochimiques, et également hydrochimiques dans le cas de réaction impliquant l’eau comme réactif, sont d’une importance capitale pour l’évolution dans le temps de ces matériaux. Après une analyse théorique, nous proposons une implémentation d’un modèle couplé chemo-thermo-poromécanique pour les matériaux cimentaires. En particulier, nous montronscomment un tel modèle peut reproduire les effets de l’histoire de chargement (mécanique, thermique, ou d’humidité relative) sur le comportement à l’état durci des matériaux cimentaires, dans des applications allant de la cimentation des puits à l’impression 3D
Méthodes d'ordre réduit pour simuler la propagation de fissures dans les milieux hétérogènes fragiles
No full textInternational audienceWe present a variational perturbation approach in linear elastic fracture mechanics to model coplanar crack propagation in heterogeneous brittle materials. This method can be qualified as a reduced-order method as we model 3D crack growth from the meshing of the sole 1D crack front. By minimizing the sum of potential and dissipated energies under irreversibility constraints, the method compute state equilibria, with unparalleled numerical efficiency. Implemented using a conjugate gradient method with trustregion, bound constraints, matrix-free implementation, preconditioning and FFT speedup, it naturally incorporates the impact of long-range elastic forces, geometric nonlinearities, and material disorder on crack growth. In particular, it reveals a transition from material weakening to strengthening as crack size exceeds the heterogeneity scale, linked to the occurrence of instabilities.Dans ce travail, nous proposons une approche variationnelle perturbative en mécanique linéaire élastique de la rupture pour modéliser la propagation coplanaire de fissures dans des matériaux fragiles hétérogènes. Cette méthode peut-être qualifiée d’ordre réduit puisqu’elle permet de décrire la croissance d’une fissure 3D à partir du maillage du front de fissure 1D. En minimisant la somme des énergies potentielle et dissipée sous contrainte d’irréversibilité, notre algorithme détermine les positions d’équilibre du front de fissure, avec une efficacité numérique supérieure aux méthodes traditionnelles. Implémentéesvia une méthode du gradient conjugué sans matrice, sous contraintes d’inégalité, avec région de confiance et préconditionnement et accélérées par la transformée de Fourier rapide, nos simulations intègrent l’effet combiné des forces élastiques de longue portée, des non-linéarités géométriques et du désordre matériel sur la croissance de la fissure. Elles mettent notamment en évidence une transition entre un affaiblissement et un renforcement du matériau lorsque la taille de la fissure dépasse celle deshétérogénéités, en lien avec l’apparition d’instabilités
Teleconsultation cabins: a response to France’s healthcare access crisis?
No full textInternational audienceThe article analyzes the implementation of the teleconsultation cabins in spaces accessible to the public in France from 2018 to March 2025. The cabins are connected devices located in places generally not dedicated to providing healthcare consultations and treatments, enabling residents to receive such services from medical professionals through connected devices. These devices, developed by private companies, were identified and promoted by the French government as part of its French Tech policy. As such, they were presented as a tool to fight against medical desertification. This study compares this promise with the reality of its implementation. A spatial analysis is proposed, based on a database of all 6105 cases already installed in France, collected specifically for the study, showing that the new teleconsultation facilities appear primarily in territories already relatively well-equipped with access to medical care and less frequently directly in response to medical desertification. The study also shows that what mainly determines the location of these devices is the prior presence of pharmacies on the territory. The article concludes with three proposed scenarios on future development of teleconsultation cabins in public places in France.Similar c
Investigation of the ageing behaviour of triple mesoscopic perovskite solar cells under outdoor working conditions
No full textInternational audienceThe photovoltaic industry’s dependence on critical raw materials such as silver raises sustainability concerns. This work explores rare-metal-free triple mesoscopic solar cells (m-TiO₂/m-ZrO₂/m-Carbon), easily fabricated by screen printing or doctor blading. The study focuses on the mesoporous carbon layer, acting as both hole-transporting and hole-collecting material, and on developing a conductive carbon ink with suitable rheology for thin film deposition. Applied to MAPbI₃ perovskite cells, these structures are evaluated under real outdoor conditions at the SIRTA site, demonstrating their potential for sustainable, low-cost photovoltaic technologies
La cérémonie royale du décintrement du pont de Neuilly (1772). Fabrique et lectures d’un événement
No full textInternational audienceCet article analyse une cérémonie festive, organisée en présence du roi et de la cour le 22 septembre 1772 et immortalisée par le peintre Hubert Robert : le décintrement du pont de Neuilly. Il en reconstitue le déroulement, les principaux protagonistes et l’agencement spatial. Il s’intéresse surtout aux enjeux et effets attendus de cette fête-spectacle au motif si singulier, à partir de l’étude de ses préparatifs et des commentaires qu’elle a suscités. L’enquête menée s’appuie sur une analyse critique des traces de l’évènement, attentive au fait qu’elles le construisent autant qu’elles l’enregistrent. Elle permet de mettre en lumière les efforts déployés par les organisateurs pour saturer l’espace narratif de représentations officielles. À travers les détails de cette manifestation, qui s’avérera être la dernière apparition publique de Louis XV, se lisent les tensions qui traversent la société à la fin de son règne, ainsi que les relations nouées entre savoirs techniques et pouvoir politique