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AIKON : un environnement de recherche collaboratif pour l’étude visuelle de corpus historiques
No full textThe article presents the AIKON digital research environment, developed as a response to methodological questions raised by the integration of artificial intelligence (AI) in the field of Digital humanities. Designed for the visual study of large historical corpora, this platform articulates three stages of the historian's work: corpus construction, image analysis and exploitation of results. AIKON takes a pragmatic and collaborative approach. Historians, Digital humanities engineers, and Computer vision specialists co-developed this platform, ensuring that the tasks entrusted to algorithms, such as image extraction and vectorisation or similarity searches, can also be performed manually on a smaller scale. The platform allows historians to maintain critical control over processing, thanks to interfaces that enable them to validate and correct algorithmic results. AIKON is thus positioned as a powerful, modular and interoperable tool that reaffirms the central role of human expertise while offering new perspectives for the study of visual heritage
Rethinking the Informal Economy and the Hugo Effect
No full textInternational audienceThis paper offers a new approach to measuring the size of the informal economy based on VAT data for the European Union. Although data intensive, our evading value added duty economy (EVADE) measure is simpler and more transparent than existing measures. EVADE also shows more variation across countries of Europe than earlier measures, including higher informality in Greece, Italy, and Spain, for example. Moreover, we find considerably higher variation within countries across time; in a cross-country time series regression, controlling for tax rates, we confirm that the informal economy grows significantly in recessions and decreases in booms, which we term the “Hugo effect”
Do Financial Concerns Make Workers Less Productive?
No full textInternational audienceWorkers who are worried about their personal finances may find it hard to focus at work. If so, reducing financial concerns could increase productivity. We test this hypothesis in a sample of low-income Indian piece-rate manufacturing workers. We stagger when wages are paid out: some workers are paid earlier and receive a cash infusion while others remain liquidity constrained. The cash infusion leads workers to reduce their financial concerns by immediately paying off debts and buying household essentials. Subsequently, they become more productive at work: their output increases by 7% (0.11 std. dev.), and they make fewer costly, unintentional mistakes. Workers with more cash on hand thus not only work faster but also more attentively, suggesting improved cognition. These effects are concentrated among more financially constrained workers. We argue that mechanisms such as gift exchange or nutrition cannot account for our results. Instead, our findings suggest that financial strain, at least partly through psychological channels, has the potential to reduce earnings exactly when money is most needed
Comparing the influence of Atlantic Multidecadal Variability and spring soil moisture on European summer heat waves
No full textInternational audienceIn this work, we study and compare the influence of the Atlantic Multidecadal Variability (AMV) and spring soil moisture in Southern Europe on the duration and intensity of European summer heat waves. We study heat waves with return times of a few years and also propose a new methodological approach, return time maps, that allows us to study rare heat waves with return times of 10 or 50 years. We use the outputs from three climate models, namely IPSL-CM6A-LR, EC-Earth3, and CNRM-CM6-1, in which North Atlantic sea surface temperatures are restored towards the observed AMV anomalies. The three models give consistent results, with the exception of EC-Earth simulating a much greater influence of soil moisture. Our main conclusion is that spring soil moisture in Southern Europe is a slow driver of greater importance than the AMV for European summer heat waves, both in terms of the extension of the region of influence and in terms of amplitude. While the influence of the AMV concentrates over the very south of Europe, around the Mediterranean Basin, spring soil moisture influence extends over large parts of Europe. As might be expected, a positive AMV phase or low soil moisture generally induces hotter and longer heat waves. For more extreme events, the influences of the AMV and soil moisture increase, according to regional patterns that seem to be the same as for typical heat waves. However, confirming this statement would require datasets with more extreme events
Flow patterns in shallow rectangular reservoirs with open channel inlet or pipe flow inlet at various depths: An experimental study
No full textInternational audienceThis study experimentally assesses the influence of varying the inlet boundary condition on the flow patterns in rectangular shallow reservoirs. Two types of inlet boundary conditions were compared: a free surface inlet channel, and a pressurized circular inlet jet positioned at three different elevations over the flow depth (centroid of the inlet jet situated at 25%, 50%, or 75% of the flow depth). The outlet boundary condition was a free surface channel in all cases. Twenty-two experiments were done with two distinct reservoir lengths (length-to-width ratios of 1.1 and 2.0) and three hydraulic boundary conditions (Froude numbers of 0.14, 0.16, and 0.21). Velocity fields were measured with Large-Scale Particle Image Velocimetry (LSPIV) at the surface, and with an Acoustic Doppler Velocity Profiler(ADVP) at several cross sections. The flow patterns are greatly influenced by the inlet boundary condition and the reservoir geometry, but to a lesser extent by the hydraulic boundary condition. For an inlet circular jet located near the reservoir bottom, an unstable flow type, changing over time in a chaotic manner, was observed regardless of the reservoir length and of the inlet flow rate. The same type of unstable flow pattern was observed for a relatively long reservoir and the lowest tested flow rate, irrespective of the vertical positioning of the inlet jet. In all other tested configurations, a steady reattached jet was found in the reservoir equipped with a pressurized inlet jet. In addition to providing new knowledge on flow patterns in shallow reservoirs with an inlet jet, the experimental data presented here will prove valuable for evaluating flow computational models
Global solution of Quadratic Problems by Interval Methods and Convex Relaxations
No full textInternational audienceInterval branch-and-bound solvers provide reliable algorithms for handling non-convex optimization problems by ensuring the feasibility and the optimality of the computed solutions, i.e. independently from the floating-point rounding errors. Moreover, these solvers deal with a wide variety of mathematical operators. However, these solvers are not dedicated to quadratic optimization and do not exploit nonlinear convex relaxations in their framework. We present an interval branch-andbound method that can efficiently solve quadratic optimization problems. At each node explored by the algorithm, our solver uses a quadratic convex relaxation which is as strong as a semi-definite programming relaxation, and a variable selection strategy dedicated to quadratic problems. The interval features can then propagate efficiently this information for contracting all variable domains. We also propose to make our algorithm rigorous by certifying firstly the convexity of the objective function of our relaxation, and secondly the validity of the lower bound calculated at each node. In the non-rigorous case, our experiments show significant speedups on general integer quadratic instances, and when reliability is required, our first results show that we are able to handle medium-sized instances in a reasonable running time
A variational method for curve extraction
No full textInternational audienceWe propose a functional for extracting curves between a list of possible endpoints, based on a discretization of a variational energy and Smirnov's decomposition theorem for vector fields. It is then used to design a bi-level minimization approach to automatically extract curves and 1D structures from an image, which is mostly unsupervised
Socio-economic inequalities in access to COVID-19 tests in France in 2020: evidence from the EPICOV socio-epidemiological cohort
No full textInternational audienceTesting for COVID-19 has been strongly recommended for individuals experiencing COVID-19-like symptoms or those with a close relative who tested positive. In France, tests were free of charge until mid-October 2021 and became widely available after June 2020. Our main objective was to investigate whether access to COVID-19 testing in France was associated with socio-economic conditions, considering gender and ethno-racial status. Methods A random population-based cohort survey was conducted in France in May 2020 and November 2020, including 95,388 participants aged 18 and over. We used logistic regressions to identify how having been tested in 2020 was associated with socio-economic status and exposure factors among two groups of individuals. The first group consisted of individuals who had no close relative test positive but reported experiencing Covid-19-like symptoms, such as cough, fever, dyspnea, or sudden onset of ageusia, dysgeusia, or anosmia (N=12,729). The second group included individuals, with or without symptoms, who reported that a close relative had tested positive for Covid-19 (N=5,360). Findings In both groups, testing was more frequent among individuals living in urban areas. For individuals who had no close relative test positive but reported Covid-19-like symptoms, women were 1.04 (95%CI [1.01-1.06]) more likely than men to be tested, and testing decreased with age up to 35. Individuals holding a university degree were 1.08 [1.04-1.12]) more likely than those who only completed high school to be tested, as well as those in one of the three top income deciles with reference to the bottom decile (OR 1.07, [1.02-1.13] for the top decile). Ethno-racial status was not significantly associated with testing. For respondents who had a close relative test positive, testing was strongly associated with having experienced some symptoms, especially after September 1 (OR 1.34, 95%CI [1.30-1.39]). However, there was no link between testing and income, education, or ethno-racial status. Interpretation When an individual experiences symptoms but has no close relative who is positive, the motivation to test to avoid transmitting the virus to relatives by isolating oneself is particularly strong. This strategy makes sense when there are actual possibilities to isolate, which may explain why higher income and education positively impact the propensity to test. For individuals who had a close relative test positive, most socio-economic variables were no longer related to testing once infection risk was controlled for. The availability of tests at no cost is not sufficient in itself to eliminate socio-economic inequalities in testing
Condensation in Fleming--Viot particle systems with fast selection mechanism
No full textInternational audienceWe study the Fleming--Viot particle system in a discrete state space, in the regime of a fast selection mechanism, namely with killing rates which grow to infinity. This asymptotics creates a time scale separation which results in the formation of a condensate of all particles, which then evolves according to a continuous-time Markov chain with jump rates depending in a nontrivial way on both the underlying mutation dynamics and the relative speed of growth to infinity of the killing rate between neighbouring sites. We prove the convergence of the particle system and completely describe the dynamics of the condensate in the case where the number of particles is kept fixed, and partially in the case when the number of particles goes to infinity together with (but slower than) the minimal killing rate
