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Media Slant is Contagious
No full textThis paper examines the diffusion of media slant. We document the influence of Fox News Channel (FNC) on the partisan slant of local newspapers in the U.S. over the years 1995-2008. We measure the political slant of local newspapers by scaling the news article texts to Republicans' and Democrats' speeches in Congress. Using channel positioning as an instrument for viewership, we find that higher FNC viewership causes local newspapers to adopt more right-wing slant. The effect emerges gradually, only several years after FNC's introduction, mirroring the channel's growing influence on voting behavior. A main driver of the shift in newspaper slant appears to be a change in local political preferences
Macroeconomic Instability, Migration, and the Option Value of Education
No full textInternational audienceMacroeconomic Instability, Migration, and the Option Value of Educatio
Charte de mutualisation et ouverture des données du projet Flex-Mediation
No full textThe charter applies to all researchers contributing to or supporting the research activities of the Flex-Mediation project, and participants undertake to respect the principles set out in the charter. The charter sets out a framework to facilitate collaborative research, the sharing of resources between team members (documents, raw data, etc.) and opening up research data.La charte concerne l’ensemble des chercheur.es contribuant à l’activité de recherche ou y apportant un appui dans le cadre du projet Flex-Mediation. Les participant.es s’engagent à respecter les principes énoncés dans la charte. Cette dernière fixe un cadre pour faciliter la recherche en collectif, la mutualisation des ressources (documents, données brutes, etc.) et l'ouverture des données
Multi-material topology optimization of structural load-bearing capacity using limit analysis
No full textInternational audienceWe extend the problem of finding an optimal structure with maximum load-bearing capacity to the case of multiple materials. We first consider a reinforcement optimization case where the structure consists of a fixed background matrix material with given strength properties and optimize the reinforcement topology within this material. We discuss the use of various isotropic and anisotropic strength criteria to model the reinforcing phase, including reinforcements with discrete orientations. In a second time, we investigate a bi-material formulation where we optimize the topology of two material phases simultaneously. Various choices for the material strength conditions are proposed and we apply this formulation to the optimization of pure tensile and compressive phases of a single material. In all cases, two optimization variants are proposed using concepts of convex optimization and limit analysis theory, namely maximizing the load-bearing capacity under a fixed volume constraint or minimizing the volume under a fixed loading. Both problems are convex and a penalization procedure is proposed. The underlying problems can be solved using conic programming solvers. Illustrative applications demonstrate the versatility of the proposed formulation, including the influence of the selected strength criteria, the possibility to obtain structures with members of fixed orientation or structures with different importance granted to tensile and compressive regions. Finally, we also draw a parallel with the generation of strut-and-tie models for the analysis of reinforced concrete structures
Uniform-in-time propagation of chaos for the Cucker-Smale model
No full textThis paper presents an elementary proof of quantitative uniform-in-time propagation of chaos for the Cucker--Smale model under sufficiently strong interaction. The idea is to combine existing finite-time propagation of chaos estimates with existing uniform-in-time stability estimates for the interacting particle system, in order to obtain a uniform-in-time propagation of chaos estimate with an explicit rate of convergence in the number of particles. This is achieved via a method that is similar in spirit to the classical 'stability + consistency implies convergence' approach in numerical analysis
A Data-Driven-based homogenization method to simulate the anisotropic damage of brittle heterogeneous structures
No full textInternational audienceAn efficient data-driven multiscale framework for modeling anisotropic damage (M-DDHAD) in heterogeneous structures is proposed, where the anisotropic damage model at the macro scale is constructed purely on the knowledge of Representative Volume Elements (RVE) of the material microstructure. The technique involves three main steps: the construction of a database, obtained by performing off-line calculations of crack propagation on Representative Volume Elements (RVE); the construction of an anisotropic damage model constructed from the database using Harmonic Analysis of Damage and off-line calculations, where damage is computed using the constructed model in tandem with a strain-gradient regularization technique. Using Harmonic Analysis of Damage, an anisotropic damage model defining the evolution of the macroscopic elastic tensor as a function of macro internal variables is provided without specific assumptions about the anisotropy related to the RVE geometry. A surrogate model is constructed to define their evolution. The macroscopic problem uses the constructed anisotropic damage model, and a modified strain-gradient regularization is applied to guarantee mesh-independence. The technique accuracy and robustness has been assessed on several structural problems with different microstructures, involving a strong initial and induced anisotropic fracture behavior, and compared with direct crack numerical simulations (DNS) of heterogeneous structures. Very good accuracy has been obtained both regarding the force-displacement curves as well as crack paths, while keeping the efficiency of classical Finite Element simulations
« Des horizons proches et lointains : une exploration des représentations sanatoriales au prisme de la linguistique »
No full textInternational audienceExpression of an architectural, geographical and medical thinking, in which the contemplation of the landscape is regarded as a therapeutic means (Luxembourg et al. 2023), the sanatorium occupies a distinctive position in the collective imagination. This exploratory article seeks to delineate the contours of this place by examining the contemporary representations that extend beyond its mere physical or geographical reality. Through a linguistic lens, our research addresses the following questions: Which terms belong to the semantic field of the sanatorium, and what proximity (or distance) do they have with our research object? How do these “keywords” contribute to shaping our understanding of sanatorium representations?We begin with a few etymological references to establish the general meaning of the concept of sanatorium, before exploring its semantic proximity by examining words that share similar or related meanings. Then, we conduct a detailed analysis of a corpus of scientific and journalistic articles published between 1991 and 2021, focusing on the most recurrent lexical forms that evoke contemporary representations of the sanatorium. Through this study, we aim to characterize specific facets of the sanatorium’s identity and trace its evolution over time.Expression d’une pensée architecturale, géographique et médicale, dans laquelle la contemplation du paysage est envisagée comme un moyen thérapeutique (Luxembourg et al. 2023), le sanatorium occupe une place singulière dans l’imaginaire collectif. Cet article exploratoire vise à esquisser les contours de ce lieu, en explorant les représentations contemporaines qui lui sont associées, et qui dépassent sa simple réalité physique ou géographique. Au prisme de la linguistique, notre recherche vise plus particulièrement à répondre aux questions suivantes : quels vocables font partie du champ sémantique du sanatorium, et quels liens de proximité (ou de distance), entretiennent-ils avec notre objet de recherche ? En quoi ces « mots-témoins » contribuent-ils à éclairer la compréhension des représentations sanatoriales ?Nous introduisons premièrement quelques repères étymologiques pour définir le sens général du concept de sanatorium, avant de prêter attention à sa proximité sémantique, via l’examen de certains mots qui lui sont plus ou moins proches du point de vue du sens. Ensuite, nous procédons à l’analyse plus détaillée d’un corpus d’articles scientifiques et journalistiques publiés entre 1991 et 2021, en nous penchant sur les formes lexicales les plus récurrentes qui évoquent les représentations sanatoriales contemporaines. Notre étude cherche ainsi à caractériser certaines facettes de l’identité du sanatorium et à documenter son évolution au cours du temps
Recognizing unit multiple interval graphs is hard
No full textAccepted in ISAAC 2023International audienceMultiple interval graphs are a well-known generalization of interval graphs introduced in the 1970s to deal with situations arising naturally in scheduling and allocation. A -interval is the union of intervals on the real line, and a graph is a -interval graph if it is the intersection graph of -intervals. In particular, it is a unit -interval graph if it admits a -interval representation where every interval has unit length. Whereas it has been known for a long time that recognizing 2-interval graphs and other related classes such as 2-track interval graphs is NP-complete, the complexity of recognizing unit 2-interval graphs remains open. Here, we settle this question by proving that the recognition of unit 2-interval graphs is also NP-complete. Our proof technique uses a completely different approach from the other hardness results of recognizing related classes. Furthermore, we extend the result for unit -interval graphs for any , which does not follow directly in graph recognition problems --as an example, it took almost 20 years to close the gap between and d> 2 for the recognition of -track interval graphs. Our result has several implications, including that recognizing -interval graphs and depth unit 2-interval graphs is NP-complete for every and every
Pricing and Calibration in the 4-Factor Path-Dependent Volatility Model
No full textInternational audienceWe consider the path-dependent volatility (PDV) model of Guyon and Lekeufack(2023), where the instantaneous volatility is a linear combination of a weighted sum of past returns and the square root of a weighted sum of past squared returns. We discuss the influence of an additional parameter that unlocks enough volatility on the upside to reproduce the implied volatility smiles of S&P 500 and VIX options. This PDV model, motivated by empirical studies, comes with computational challenges, especially in relation to VIX options pricing and calibration. We propose an accurate neural network approximation of the VIX which leverages on the Markovianity of the 4-factor version of the model. The VIX is learned as a function of the Markovian factors and the model parameters. We use this approximation to tackle the joint calibration of S&P500 and VIX options