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    The discontinuous Galerkin approximation of the grad-div and curl-curl operators in first-order form is involution-preserving and spectrally correct

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    International audienceThe discontinuous Galerkin approximation of the grad-div and curl-curl problems formulated in conservative first-order form is investigated. It is shown that the approximation is spectrally correct, thereby confirming numerical observations made by various authors in the literature. This result hinges on the existence of discrete involutions which are formulated as discrete orthogonality properties. The involutions are crucial to establish discrete versions of weak Poincaré-Steklov inequalities that hold at the continuous level

    Production Function Estimation with Multi-Destination Firms

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    We develop a procedure to estimate production functions, elasticities of demand, and productivity when firms endogenously select into multiple destination markets where they compete imperfectly, and when researchers observe output denominated only in value. We show that ignoring the multi-destination dimension (i.e., exporting) yields biased and inconsistent inference. Our estimator extends the two-stage procedure of Gandhi et al. (2020) to this setting, which allows for cross-market complementarities. In Monte Carlo simulations, we show that our estimator is consistent and performs well in finite samples. Using French manufacturing data, we find aver- age total returns to scale greater than 1, average returns to variable inputs less than 1, price elasticities of demand between -21.5 and -3.4, and learning-by-exporting effects between 0 and 4% per year. Alternative estimation procedures yield unrealistic estimates of returns to scale, demand elasticities, or both

    ARES VI: Are 1D retrieval models accurate enough to characterize exo-atmospheres with transmission spectroscopy in the era of JWST and Ariel?

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    International audienceThe observed exoplanets transit spectra are usually retrieved using one-dimensional models to determine atmospheric composition. However, planetary atmospheres are three-dimensional. With the new state-of-the-art James Webb Space Telescope (JWST) and future space telescopes such as Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large-survey), we will be able to obtain increasingly accurate transit spectra. The 3D effects on the spectra will be visible, and we can expect biases in the 1D extractions. In order to elucidate these biases, we have built theoretical observations of transit spectra, from 3D atmospheric modeling through transit modeling to instrument modeling. For that purpose, we used a Global Climate Model (GCM) to simulate the atmosphere, a 3D-radiative transfer model to calculate theoretical transmission spectra, and adapted instrument software from JWST and Ariel to reproduce telescope noise. Next, we used a 1D-radiative transfer inversion model to retrieve the known input atmosphere and disentangle any biases that might be observed. The study has been done from warm planets to ultra-hot planets to assess biases as a function of average planet temperature. Three-dimensional effects are observed to be strongly non-linear from the coldest to the hottest planets. These effects also depend on the planet's metallicity and gravity. Considering equilibrium chemistry, 3D effects are observed through very strong variations for certain features of the molecule, or very small variations over the whole spectrum. We conclude that we cannot rely on the uncertainty of retrievals at all pressures, and that we must be cautious about the results of retrievals at the top of the atmosphere. However the results are still fairly close to the truth at mid altitudes (those probed). We also need to be careful about the chemical models used for planetary atmosphere. If the chemistry of one molecule is not correctly described, this will bias all the others, as well as the retrieved temperature. Finally, although fitting a wider wavelength range and higher resolution has been shown to increase retrievals accuracy, we show that this could depend on the wavelength range chosen, due to the accuracy on modeling the different features. In any case, 1D retrievals are still correct for the detection of molecules, even in the event of an erroneous abundance retrieval

    Machine learning interatomic potentials for amorphous zeolitic imidazolate frameworks

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    International audienceAccurate microscopic models of amorphous metal–organic frameworks (MOFs) are difficult to create. Machine learning potentials based on data from ab initio molecular dynamics offer a novel way to achieve this goal

    Effect of temperature on the mechanical properties of fine-grained soils - A review

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    International audienceAbstract Swelling of clay–sulfate rocks is a serious and devastating geo-hazard, often causing damage to geotechnical structures. Therefore, understanding underlying swelling processes is crucial for the safe design, construction, and maintenance of infrastructure. Planning appropriate countermeasures to the swelling problem requires a thorough understanding of the processes involved. We developed a coupled hydro-mechanical (HM) model to reproduce the observed heave in the historic city of Staufen in south-west Germany, which was caused by water inflow into the clay–sulfate bearing Triassic Grabfeld Formation (formerly Gipskeuper = “Gypsum Keuper”) after geothermal drilling. Richards’ equation coupled to a deformation process with linear kinematics was used to describe the hydro-mechanical behavior of clay–sulfate rocks. The mathematical model is implemented into the scientific open-source framework OpenGeoSys. We compared the model calculations with the measured long-term heave records at the study site. We then designed a sensitivity analysis to achieve a deeper insight into the swelling phenomena. The synthetic database obtained from the sensitivity analysis was used to develop a machine learning (ML) model, namely least-squares boosting ensemble (LSBoost) model coupled with a Bayesian optimization algorithm to rank the importance of parameters controlling the swelling. The HM model reproduced the heave observed at Staufen with sufficient accuracy, from a practical point of view. The ML model showed that the maximum swelling pressure is the most important parameter controlling the swelling. The other influential parameters rank as Young’s modulus, Poisson’s ratio, overburden thickness, and the initial volumetric water content of the swelling layer

    Scalable 3D Panoptic Segmentation With Superpoint Graph Clustering

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    Accepted at 3DV 2024, Oral presentationInternational audienceWe introduce a highly efficient method for panoptic segmentation of large 3D point clouds by redefining this taskas a scalable graph clustering problem. This approach can be trained using only local auxiliary tasks, thereby eliminating the resource-intensive instance-matching step during training. Moreover, our formulation can easily be adapted to the superpoint paradigm, further increasing its efficiency. This allows our model to process scenes with millions of points and thousands of objects in a single inference. Our method, called SuperCluster, achieves a new state-of-the-art panoptic segmentation performance for two indoor scanning datasets: 50.1 PQ (+7.8) for S3DIS Area 5, and 58.7 PQ (+25.2) for ScanNetV2. We also set the first state-of-the-art for two large-scale mobile mapping benchmarks: KITTI-360 and DALES. With only 209k parameters, our model is over 30 times smaller than the best-competing method and trains up to 15 times faster. Our code and pretrained models are available at https://github.com/drprojects/superpoint_transformer

    The Effects of Electronic Monitoring on Offenders and their Families

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    Electronic monitoring (EM) has emerged as a popular tool for curbing the growth of large prison populations. Evidence on the causal effects of EM on criminal recidivism is, however, limited and it is unclear how this alternative to incarceration affects the labor supply of offenders and the outcomes of their family members. We study the countrywide expansion of EM in Sweden in 1997 wherein offenders sentenced to up to three months in prison were granted the option to substitute incarceration with EM. Our difference-in-differences estimates, which compare the change in the prison inflow rate of treated offenders to that of non-treated offenders with slightly longer sentences, show that the reform significantly decreased the number of incarcerations. Our main finding is that EM not only lowers criminal recidivism but also increases labor supply. Additionally, EM improves the educational attainment and early-life earnings of the children whose parents were exposed to the reform. The primary mechanisms through which EM operates appear to involve the preservation of offenders’ ties to the labor market, by reducing the barriers to both finding a job and changing employers. Our calculations suggest that the social benefits stemming from EM are about seven times larger than the fiscal savings associated with reduced prison expenditures, implying that the welfare gains from EM could be much greater than previously acknowledged

    The 1929 crash of the New York stock exchange as a liquidity crisis

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    International audienceWhat caused the 1929 crash of the New York Stock Exchange? This paper quantitatively studies liquidity during the 1929 crash of the NYSE. I evidence that the crash represented a liquidity crisis due to the liquidation of brokers’ margin loans. Applying recent estimators of effective spreads and liquidity conditions from contemporary finance literature suggests a four‐fold increase in spreads during the crash at the aggregate level. At the individual stock level, quoted bid‐ask spreads suggest that liquidity explains one‐fifth of the variance in daily stock returns during the crash

    Experimental Evidence from a Conditional Cash Transfer Program: Schooling, learning, fertility and labor market outcomes after 10 years

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    International audienceConditional cash transfer programs are the anti-poverty program of choice in manydeveloping countries, aiming to improve human capital and break the intergenerational transmission of poverty. A decade after a randomized 3-year CCT program began, earlier exposure during primary school ages when children were at risk of dropout led to higher labor market participation for young men and women and higher earnings for men. Results highlight the roles of the different program components with variation in timing of access to nutrition, health and education investments translating into substantial differential effects on learning for men and reproductive health outcomes for women

    QuadWire: an extended one dimensional model for efficient mechanical simulations of bead-based additive manufacturing processes

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    This paper presents the basis of a new mechanical model named QuadWire dedicated to efficient simulations of bead-based additive manufacturing processes in which elongated beads are assembled to form 3D parts. The key contribution is to use a multi-particular approach containing 4 particles per material point to develop an extended 1D model capable of capturing complex 3D mechanical states, while significantly reducing computation time with respect to conventional approaches. Indeed, 3D models usually require at least 3 to 4 elements across the bead section, which results in fine discretization along the tangential direction to avoid conditioning issues, and therefore very fine mesh of the entire 3D part. In the QuadWire model, the bead height and thickness are internal dimensions, enabling a significantly coarser mesh along the tangential direction. Thus, despite the QuadWire has 12 degrees of freedom per material point instead of 3 for classical models, the total number of degrees of freedom is reduced by several order of magnitudes for large parts. The proposed model is classically developed within the framework of the principle of virtual power and standard generalized elastic media. Furthermore, the proposed approach includes native and manageable kinematic constraints between successive beads so that the stress state properly evolves during fabrication. Finite element analysis is used for numerical implementation, and the QuadWire stiffness parameters are optimized so that the mechanical response fit conventional 3D approaches. To validate and demonstrate the capabilities of the proposed strategy, the evolution of displacements and stresses in fused deposition modeling of polylactide is simulated


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