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Queries with External Predicates
No full textInternational audienceReal-life query languages feature external predicates such as user-defined functions or built-in arithmetic and string operations. These predicates are often infinite, potentially leading to unsafe or non-computable queries. To overcome this, traditional languages such as SQL, put significant syntactic restrictions on the use of external predicates. These restrictions have been relaxed in a number of modern query languages, each doing it in their own way. Our goal therefore is to provide a theoretical basis for querying with external predicates. To this end, we formalize queries with external predicates based on the notion of access patterns. We develop a suitable evaluation model, based on Turing machines with oracles, and tailor the classical notion of query safety to it. Since query safety is undecidable in general, we can only produce sufficient conditions for guaranteeing safety. We do so by developing an inference system to derive safety and computability for relational algebra, first-order logic, as well as for a language that combines them both
Optimisation de mortiers d'impression 3D à faible impact environnemental
No full textClimate change is compelling the entire construction industry to adopt more sustainable practices. This thesis contributes to the ongoing industrialization of the sector, which must be concurrent with a reduction in its environmental footprint. Extrusion-based 3D printing is rapidly advancing in both academic and industrial fields, showcasing significant technical progress throughout the process. However, mix design strategies for materials that meet the rheological requirements of these systems are still lacking, particularly when it comes to alternative binders. Yet, one of the most promising avenues for achieving substantial decarbonization (over 30%) in 3D printing lies in optimizing mortar constituents and proportions, thus maximizing strength per unit volume of cement, known to be the primary contributor to greenhouse gas emissions in mortars. In this context, mix design procedures tailored specifically to 3D printing must be explored, with a strong emphasis on environmental performance. This thesis introduces two optimization strategies for mortars with very low cement content. The first approach associates a contextualized life cycle assessment model with the prediction abilities of artificial neural networks for the multi-objective optimization of a mortar containing three types of supplementary cementitious materials. The second approach utilizes a granular packing model to guide the design of LC3-type mortars, destined for acceleration with aluminium sulfates. This provides a critical analysis of the pozzolanic contribution of calcined clay in regard to its negative effect on overall packing density across various application ranges. Finally, this research highlights the largely unexplored potential of ternary and quaternary binders for sustainable 3D printing.La crise climatique impose à toute la chaîne de valeur du secteur de la construction d'entamer une transition vers des pratiques plus vertueuses. Ce projet de recherche doctoral s'inscrit dans un mouvement nécessaire d'industrialisation du domaine de la construction, qui doit s'accompagner d'une baisse de son impact environnemental. L'impression 3D de mortier par extrusion se développe de manière spectaculaire dans les milieux académiques et industriels, dévoilant des avancées remarquables au niveau du procédé. En parallèle, peu de stratégies existent pour la formulation de matériaux adaptés à ces systèmes exigeants du point de vue rhéologique, notamment concernant des liants alternatifs. Pourtant, une des pistes les plus accessibles pour une décarbonation significative (> 30%) de l'impression 3D est l'optimisation des constituants et dosages de mortiers, maximisant ainsi la résistance par unité de volume de ciment, principale contributeur des émissions de gaz à effet de serre dans les mortiers. Dans ce contexte, des méthodologies de formulation spécifiques à l'impression 3D doivent être explorées sous le prisme de la performance environnementale. Ainsi, cette thèse propose deux solutions d'optimisation de mortiers à très faible teneur en ciment, pour la réduction des impacts environnementaux. La première approche permet d'associer un calcul d'analyse de cycle de vie contextualisé et la capacité de prédiction des réseaux de neurones artificiels pour l'optimisation multi-objectifs d'un mortier contenant trois types d'ajouts cimentaires. La deuxième approche exploite un modèle physique d'empilement granulaire pour faciliter la formulation de mortiers de type LC3 destinés à être accélérés. Une analyse critique sur la contribution pouzzolanique de l'argile calcinée à la microstructure, par rapport à son effet délétère sur la compacité globale est émise pour plusieurs gammes d'application. Finalement, ce travail contribue à confirmer le potentiel encore peu exploré des liants ternaires et quaternaires pour l'impression 3D bas-carbone
Modeling Access Ergonomics to Daily Life Resources Using Sustainable Modes within the Eurométropole de Strasbourg
No full textInternational audienceSince the 1980s, many cities in Europe, including the Eurométropole de Strasbourg, have implemented policies to reduce transportation and mobility related negative impacts, especially those caused by individual cars. In the Eurométropole de Strasbourg, measures have been introduced to limit car use while promoting sustainable transport. This includes developing public transportation, enhancing shared and active modes (walking, cycling) usage, and urban planning focused on a “proximity metropolis” model to support sustainable mobility.Furthermore, the Eurométropole de Strasbourg has restricted motorized mobility, particularly internal combustion engine vehicles, by creating a Low Emission Zone covering its 33 municipalities. The city also supports energy transition, encouraging the adoption of electric vehicles including electric bikes through purchase subsidies. The central question is how well the Eurométropole de Strasbourg enables its residents to access essential daily-life resources, efficiently, comfortably, and at low cost (financial cost, effort, risk, emissions, energy and time) while using sustainable transport modes.To address this, spatial ergonomics (Saint-Gérand, 2002) which studies the capacity for a territory to fulfil the needs of its inhabitants at least costs, and especially its subdomain access ergonomics (Hached, 2019) which provides an approach through mobility, offer a relevant analytical framework. This approach assesses accessibility while focusing on its conditions not only regarding travel duration but also considering daily-life resources and infrastructure quality (facilities, safety, comfort, environment) adapted to each transport mode.The hypothesis is that a high-quality environment helps to promotes sustainable transport, especially for active modes. Mobility behaviors, including route choices, are influenced by safety, comfort, and environmental factors (Piombini, 2013). Access ergonomics integrates these factors into a synthetic access ergonomics score composed of several sub-indicators to identify socio-spatial inequalities in accessing daily resources.Previous studies (Saint-Gérand et al., 2021) showed significant variability in access across the Eurométropole de Strasbourg; however, they did not consider emerging mobility forms, such as electric vehicles and micromobility. The rise of micromobility and intermodality requires adaptation of these analyses.Activity-based models are used for evaluating accessibility through a trip completion rate by measuring the proportion of the trips below a certain threshold (Somranath et al., 2025). This approach however does not consider key parts of access ergonomics (safety and convenience of trips).Our study aims to improve realism and precision in evaluating access ergonomics. A new methodology has been developed to overcome limitations from previous works. Multi-agent modeling is used to simulate mobility behaviors based on detailed socio-spatial profiles, considering diverse socio-economic and demographic data at a fine scale (200 × 200 m). These profiles are fed to a geographic information system to assess access conditions using various transport modes (active, shared, motorized, intermodal).Trips are analyzed within activity chains, where each activity (work, leisure, services) can be interconnected. The model also considers resource availability and transport service schedules, identifying potential inconsistencies that impact access ergonomics.The study relies on open geographic and statistical data covering the Eurométropole de Strasbourg. The synthetic population is generated using eqasim (Hörl and Balac, 2021), and user profiles are adjusted based on socio-demographic data and mobility surveys.The goal is also to develop a tool which will generate an access ergonomics score for each inhabited grid square, providing a detailed and comprehensive view of socio-spatial inequalities. The synthetic score will be broken down into sub-indicators (travel time, safety, comfort, etc.) and transport modes, enabling comparison across the territory.These results will help to identify actions for improving access ergonomics and for reducing inequalities. In further studies, the developed tool will be improved by considering the aspect of energy transition, especially to take its consequences into account on the access ergonomics
Political Brinkmanship and Compromise
No full textInternational audienceWe study how do‐or‐die threats ending negotiations affect gridlock and welfare when two opposing parties bargain. Failure to agree on a deal in any period implies a continuation of the negotiation. However, under brinkmanship, agreement failure in any period may precipitate a crisis with a small chance. In equilibrium, such brinkmanship threats improve the probability of an agreement, but also increase the risk of crisis. Brinkmanship reduces welfare when one might think it is most needed: severe gridlock. In this case, despite this global welfare loss, a party has incentives to use brinkmanship strategically to obtain a favorable bargaining position
Frederick Tryon and the Decoupling of Energy and Economic Growth in the 1920s
No full textInternational audienceThe roots of the decoupling debate do not begin in the 1970s, during a period riven by energy crises, as one might expect, nor do they begin in the 1980s, with the rise of the notion of "sustainable development". The earliest instantiation of the principles of decoupling can be found in the 1920s, when the North American economist Frederick G. Tryon published his article "An Index of Consumption of Fuels and Water Power" in the Journal of the American Statistical Association. This chapter reviews and analyzes Tryon's contribution in the context of the early 20th century, and in view of today's energy and ecological challenges
Commuting Patterns and Emissions in Paris-Île-de-France: A Comparative Study of Interregional and Intraregional Travel
No full textThe Paris-Île-de-France (IDF) region, as the capital of France, exerts significant influence extending beyond its borders. Its robust economy and job market attract a substantial number of commuters from across the country. Interregional commuting to IDF is characterized by longer distances, lower frequencies, and an exclusive reliance on motorized transportation compared to intraregional commuting. To explore this phenomenon, we segmented the French territory into concentric rings centered on Paris and examined the evolution and geographical distribution of interregional commuters to IDF ("outsiders") relative to their distance from Paris. Key commuting variables-distance, frequency, and mode share-were calculated based on the origin and destination rings of the commuters.Our findings indicate that although outsider drivers constitute only 9% of the regional carcommuting workforce, they cover a total distance nearly equivalent to that of intraregional car commuters. Furthermore, an analysis of commuting emissions revealed that outsiders represent 29% of the total emissions related to IDF employment, with zones outside the Parisian basin contributing 11%. Surprisingly, even though IDF jobs make up 21% of national employment, they only contribute 14.6% of France's total commuting emissions. These results suggest that carbon mitigation policies should be directed not only toward emission-intensive suburban commuters but also those from outside the Parisian basin. The study highlights a significant disparity in commuting emissions among IDF commuters, largely due to the high number of outsiders.</div
Machine learning in the prediction of human wellbeing
No full textInternational audienceSubjective wellbeing data are increasingly used across the social sciences. Yet, despite the widespread use of such data, the predictive power of approaches commonly used to model wellbeing is only limited. In response, we here use tree-based Machine Learning (ML) algorithms to provide a better understanding of respondents’ self-reported wellbeing. We analyse representative samples of more than one million respondents from Germany, the UK, and the United States, using data from 2010 to 2018. We make three contributions. First, we show that ML algorithms can indeed yield better predictive performance than standard approaches, and establish an upper bound on the predictability of wellbeing scores with survey data. Second, we use ML to identify the key drivers of evaluative wellbeing. We show that the variables emphasised in the earlier intuition- and theory-based literature also appear in ML analyses. Third, we illustrate how ML can be used to make a judgement about functional forms, including the existence of satiation points in the effects of income and the U-shaped relationship between age and wellbeing
Diurnal and Seasonal Variations of Gravity Waves in the Lower Atmosphere of Mars as Observed by InSight
No full textInternational audienceWe investigate Gravity Waves (GWs) in the lower atmosphere of Mars based on pressure timeseries acquired by the InSight lander. We compile a climatology showing that most GW activity detected at the InSight landing site takes place after the sunrise and sunset; they are almost absent during the aphelion season, and more prominent around the equinoxes, with variations during dust events and interannual variations. We find GWs with coherent phases in different sols, and a previously unnoticed coincidence of GW activity with those moments in which the diurnal cycle (of tidal origin) exhibits the fastest increases in absolute pressure. We explore the possibility that some of these GWs might actually be high-order harmonics of thermal tides transiently interfering constructively to produce relevant meteorological patterns, and discuss other interpretations based on wind patterns. The so-called Terminator Waves observed on Earth might also explain some of our observations. Plain Language Summary Gravity waves are oscillations in a fluid, observed for example, in the surface of water when it is perturbed. These waves are common in planetary atmospheres and play a key role in their dynamics; however, they are difficult to reproduce in computer models. Based on the comprehensive observations of pressure acquired by the InSight lander, we analyze the occurrence of these waves on Mars at different seasons and times of the day in unprecedented detail. We find that these waves are much more common after the sunrise and the sunset. Also, they tend to repeat synchronously in consecutive days, and they seem to happen at those moments when the absolute atmospheric pressure is increasing. Interpreting these observations is challenging, and we propose various plausible explanations
