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Decision Support for Dimensioning an Innovative Rail-Road Transport System
No full textInternational audienceThis paper proposes an optimization algorithm to support decision makers in the dimensioning of a new type of public transport service. In particular, vehicles capable of traveling on both rail and road are exploited to revitalize capillary railway lines, characterized by low demand but very high societal impact. To support decisions on infrastructure modifications and fleet size, we propose an algorithm based on the solution of a mixed-integer linear programming model. In particular, the infrastructure modifications considered consist in the construction of road-type sidings
Conflict detection and resolution for distance-to-go railway signalling
No full textInternational audienceConflict detection and resolution models typically consider train separation distances based on a number of blocks corresponding to conventional fixed-block signalling systems. However, modern distance-to-go railway signalling systems, such as the European Train Control System (ETCS), use braking curve supervision, resulting in train-and speed-dependent train separation distances. This paper proposes a modelling approach that incorporates train-and speed-dependent brake indication points and the resulting blocking times, enhancing conflict detection and resolution models for distance-to-go signalling. By integrating these enhancements into the state-of-the-art RECIFE-MILP model, a mixed integer linear programming formulation explicitly representing fixed-block distance-to-go signalling is obtained. The enhanced model is evaluated considering the state-of-practice fixed-block distance-to-go signalling system ETCS Level 2, and is compared with the original model for conventional fixed-block signalling in two real-world case studies. Results show that the shorter train separation under distance-to-go signalling leads to different rescheduling decisions, including a significant number of reroutings and some reorderings. With that, reductions in total train delay are achieved for 98% and 55% of the respective case study instances. While the mean reductions are below 1%, reductions of up to 7% are observed. These findings illustrate the operational relevance of incorporating distance-to-go principles into conflict detection and resolution modelling
Contamination des sédiments d’un bassin d’infiltration par les particules d’usure des pneus et de la route
No full textInternational audienceLes bassins d’infiltration jouent un rôle essentiel dans la gestion des eaux de ruissellement, mais aussi dans la réduction de la charge polluante dans l’environnement. Les eaux de ruissellement des routes lessivent des polluants, notamment des métaux lourds et des particules d’usure des pneus et des routes (TRWP). Afin d’améliorer nos connaissances sur les niveaux de TRWP dans ces ouvrages et leur capacité à réduire la charge de TRWP, nous avons étudié les niveaux de contamination, la distribution spatiale et en taille des TRWP et leur relation avec les métaux dans les sédiments d’un bassin d’infiltration du périphérique nantais. Les résultats ont montré une contamination significative des sédiments en TRWP de l’ordre du mg/g. Le fractionnement en taille révèle une distribution bimodale, indiquant deux types distincts de TRWP. Le premier est caractérisé par de faibles diamètres (63-160 μm), suggérant des TRWP moins intégrées aux particules minérales et organiques. Le second type, caractérisé par des diamètres plus mportants (200-500 μm), suggère une intégration plus prononcée avec ces mêmes particules minérales et organiques. Une corrélation positive significative entre les TRWP et les éléments traces métalliques a été mise en évidence (r > 0,74, p < 0,05) et suggère que les TRWP ou les phases uxquelles elles sont associées peuvent jouer un rôle de vecteur de la contamination métallique. Enfin, un bilan de masse entre les apports de TRWP et la quantité retenue dans les sédiments a confirmé le rôle des bassins d’infiltration en tant que « puits » vis-à-vis des TRWP
The hindered development of continuing education in French universities. A paradoxical approach
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Le préconstruit dans les subordonnées temporelles en when, after et before
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Dynamique des allocataires du RSA à Paris
No full textRapport du Laboratoire Interdisciplinaire d’Évaluation des Politiques Publiques (LIEPP) de Sciences Po réalisé dans le cadre d'une convention de recherche avec de la Ville de Paris et la Caf de ParisL’objet du présent travail est d’analyser en profondeur la dynamique du nombre d’allocataires du RSA dans le département de Paris. La revue de littérature restitue les principaux éléments de connaissance récents sur les effets des politiques d’accompagnement et d’activation sur la sortie des minima sociaux. Une analyse en statistique descriptive explore l’évolution du nombre d’allocataires à Paris : le pic du nombre d’allocataires a été particulièrement marqué en 2020 et la décrue moins forte que dans d’autres départements. Cette spécificité doit se comprendre sur le temps long : Paris avait été particulièrement épargné par la hausse du nombre d’allocataire et la dégradation de l’emploi dans le reste de la France en 2010-2015. Nous proposons enfin un modèle agrégé de prévision des flux et du nombre d’allocataires, principalement basé sur les observations passées des flux d’entrées et de sorties. Ce modèle, facilement appropriable, produit une prédiction de bonne qualité à un mois, et une prévision utile à horizon de six mois
Étude en laboratoire de l'influence des cycles de geldégel sur du calcaire -projet PermaPyrenees
No full textInternational audienceDans le contexte de changement climatique, la dégradation du pergélisol, observée par l'approfondissement de sa couche active (qui gèle et dégèle de façon saisonnière), entraîne une modification de l’intensité et de la fréquence des cycles de gel-dégel au sein de cette dernière. Dans le cadre du Projet Interreg Poctefa PermaPyrénées (EFA 063/01), une étude expérimentale a été menée dans le but d’étudier le lien entre ces cycles de gel-dégel et la micro et macro fracturation des roches.Des cycles de 12h entre -10 et 20°C ont été réalisés dans une enceinte climatique sur des éprouvettes saturées et non saturées de calcaire de Saint-Maximin. La masse, les dimensions et les vitesses des ondes P et S à travers ces échantillons ont été mesurées chaque semaine pour évaluer l’évolution du volume des vides et donc la fissuration de l’échantillon. De plus, deux échantillons, un saturé et l’autre non saturé, ont été suivis par microtomographie à rayons X afin d’observer l’évolution de la microfissuration de la roche due à la succession de cycles de gel-dégel
How are the data from the OZCAR RI critical zone observatories used by local stakeholders?
No full textInternational audienceThe long-term observatories of the OZCAR Critical Zone Research Infrastructure (https://www.ozcar-ri.org/ ) were initially set up to answer scientific questions of local interest to society. To answer these questions, a series of variables documenting meteorological conditions, hydro-geochemistry of surface water or aquifers, land surface fluxes and soils, as well as land use and practices are collected, sometimes over several decades. In the context of open science, these data are shared according to the FAIR (Findable, Accessible, Interoperable, Reusable) principles. However, a recurring question is the usefulness of making this data available and the use made of it by local stakeholders or citizens. To answer this question, observatory managers were asked to provide information on - The measured variables from their observatory used by local actors, - The stakeholders who use their data- The type of data used (raw data or data already transformed/digested by scientists) - The type of interactions they have with stakeholders.The results of the consultation show that the data is primarily used in universities or as part of initial training. Long-term involvement in the study-areas has also led to the establishment of long-lasting relationships with stakeholders (e.g. local authorities, hydropower companies, river basins management authorities, water agencies, Regional Natural Parks, state agencies (e.g. forest managers), associations, farmers and the public. Often, but not always, these stakeholders make direct use of the data produced by the observatories included in OZCAR RI. Qualified data from several monitored sites are used to manage the drinking water supply of several towns or municipalities, flood warning systems (in this case in near-real time or in a a posteriori analysis of problematic episodes), quantify water resources (quantity, quality), understand soil quality, or monitor wetland restoration. Nevertheless, in the face of increasingly strong and frequent pressures and disturbances, local stakeholders are increasingly questioning critical zone observatories to obtain data, trends and projections on the impact of climate change or land use. This information will help them to draw up regulatory documents and make decisions on the future habitability of their areas. Scientists are also called upon to provide scientific mediation and make the results of their research accessible to non-specialists. In addition to data, decision-makers, elected representatives and the public expect scientists to provide them with indicators that can be used more directly than raw data. In order to provide satisfactory responses to these new needs, it is necessary to co-construct the various actions, which requires time and a strong investment by scientists and stakeholders. As a result, new missions and new jobs are emerging, making observatories meeting places for local stakeholders and scientists. Observatories are becoming places, named Living Labs, where knowledge and research questions can be co-constructed, where citizens can be involved in metrology (participatory science), in order to better respond to the challenges of the Earth's habitability in the various areas
Evolution Mechanisms of an Artificial Calco-Magnesian Agglomerate in Seawater: Analysis of Powder by Experiments and Numerical Modeling
No full textInternational audienceThe aim of this work was to investigate the evolutionary mechanisms of an artificial sedimentary agglomerate formed by cathodic polarization in natural seawater during its abandonment to a natural environment. Previous studies indicate that the mineralogical evolution of the material is controlled by kinetic factors and/or the local precipitation of aragonite on the brucite surface. However, the observation of the precipitation of metastable phase precipitation during the initial immersion of this material (in powder form) has suggested the possibility of a more complex mechanism. The present study builds upon previous experimental work and includes thermogravimetric analysis and infrared spectrometry. The results are analyzed using numerical experimentation to evaluate the proposed hypotheses. Findings show that the transformation mechanism is characterized by the precipitation of metastable calcium carbonate phases. Under supersaturation conditions, these hydrated phases form on the brucite surface, limiting the mineral’s contact with the solution. The subsequent transformation of these amorphous phases into aragonite further reduces brucite–solution interaction, which explains the persistence of brucite both in the residual powder after 120 h of immersion and in the consolidated material after more than 20 years of exposure to natural seawater