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Stormwater management by urban trees: case of the SenseCity experimental device
No full textInternational audienc
Stormwater trees in urban runoff management: Water balance of the SenseCity Experimental Device
No full textInternational audienceFaced with high levels of soil sealing combined with the effects of climate change, stormwater trees offer an adaptive solution for stormwater management. A stormwater tree is a street tree that has been designed to manage runoff from the adjacent pavement, while enhancing its development and various ecosystem services. It's a natured based solution for sustainable source control of runoff that's developing more and more, but whose operation is not yet completely mastered. The aim of the present study is to analyze and better understand the hydrologic functioning of such a device for a better application in the city, based on an experimental prototype, implemented in SenseCity, in Paris conurbation. SenseCity is a mini-city made up of a roadway and walls simulating a Canyon Street, with ball maples (Acer platanoide Globosum) planted on either side, one side of which is fed by runoff from 88m2 of pavement - these are the stormwater trees. The three stormwater trees are planted in a 1.6m-diameter reservoir with two main substrate layers, the first consisting of 20cm of Rainclean, a depollution filter providing temporary storage before infiltration into the deeper 60cm layer of topsoil. The runoff infiltrates through these two layers before reaching the clayey natural underground, where it can be exfiltrated to the soil and excess water can be collected in an underdrain. Various sensors were installed to study this system. These include inflow (Krohne Optiflux electromagnetic flowmeter), soil water content (Campbell SoilVue TDR probe), sap flow (Edaphic Implexx sensor) which allows to assess the evapotranspiration flux from the trees, outflow from the underdrain (Précis Mécanique 2x1-liter auger) and meteorological parameters. Most parameters are measured at 15-minute time steps.The results obtained over one year (April 2022-March 2023) show exfiltration and transpiration rates on the system to represent respectively 53% and 27% of the inflow. Annual drainage accounts for around 19%. Exfiltration and transpiration are the main means of reducing runoff volumes. These different processes are not evenly distributed over the months. Transpiration rates are highest in summer, helping to cool the urban microclimate, while drainage and exfiltration is highest in winter. In summer, for example, transpiration rates were 41% and drainage 11%, while in winter transpiration was reduced to 5% and drainage increased to 32%
Hybrid Modeling for In Situ Artificial Fish Spawning Ground Stabilization
No full textInternational audienceErosion generally reduces the resilience of replenished gravel in rivers. As a result, structures are sometimes added to modify the upstream flow and stabilize artificial spawning grounds. In particular, rows of boulders can be placed around the replenishment area to limit the transport of replenished gravel during flood events. This study aims to optimize the arrangement of these rows, based on field experiments as well as physical and numerical models. A combined hydro-sedimentary numerical model is calibrated and validated by comparing simulated and measured morphological evolutions in nine laboratory experiments. The results show that boulders positioned downstream of the replenishment slow down the flow above the replenishment, decreasing shear stress over the gravel. The stabilization efficiency depends on both the positioning of the boulders and the arrangement of the replenished surface. To achieve sustainable spawning, prospective scenarios using the numerical model highlight the need to limit the width of the replenishment area. Experiments demonstrated that when the replenishment area spans the entire width flume, the erosion rate is significantly higher compared to a narrower replenishment area placed close to the edges. This effect is attributed to increased flow velocities in the center of the channel, leading to increased shear stress and gravel erosion
Vieillir chez soi dans les espaces peu denses : s’adapter pour maintenir un approvisionnement autonome
No full textIn low-density areas, ageing in place raises both mobility and accessibility issues. For some older people, shopping is not only an essential need: it is also about integration and participation in social life. Beyond urban centers, the retail offer is more sparsely meshed and distances to the nearest shop can be significant. The spatial distribution and nature of the retail offer have also changed considerably over the last few decades. Today's over-70s and 80-year-olds have seen the emergence of supermarkets, which are mainly accessible by car, first on the peripheries of cities and then in town centers. The rise of supermarkets was accompanied by a decline in specialist shops in low-density areas. Then, since the 2000s, new forms of supply have been developing, on the one hand promoting proximity through short distribution channels, and on the other with e-commerce and digital developments. The aim of this research is to better understand how older people living in low-density areas adapt their provisioning practices to the ageing process and to changes in their environment. It also raises the underlying question of autonomy and what it means to be autonomous when it comes to provisioning supplies.The theoretical framework developed for this thesis draws on a number of disciplines, combining approaches from urban planning and retail geography, the sociology of ageing and environmental gerontology, and the sociology of mobility and consumption. To provide empirical answers to the questions asked, a survey was carried out in the low-density areas surrounding two different cities: Dijon and Limoges. Semi-structured interviews were conducted with 70 people aged 70 or over who live at home. The interviewees described their provisioning practices, and how these practices have evolved in relation to changes in their environment and their ageing.The thesis highlights a number of changes that influence the provisioning practices of ageing people. The latter adopt a variety of strategies, such as spatio-temporal modifications to their provisioning universes or mutual aid relationships. Numerous forms of local are also observed, creating additional opportunities for supply. The thesis also sheds light on the role of values and perceptions of different modes of supply and travel. It provides a clear illustration of the importance of the representations associated with the perceived effects of digital transformations of the commercial offer and mobility services, and the influence that these representations have on e-shopping strategies. The strategies adopted in the face of digitalisation are particularly heterogeneous within the population interviewed. The analysis reveal inequalities between people in terms of their available resources and their ability to maintain an independent supply. These capacities depend on income levels, health conditions, residential and professional trajectories and gender. This research reveals how women's and men's supply practices evolve differently with advancing age. Finally, individual autonomy is expressed in a variety of ways through the strategies employed. This thesis opens up avenues for reflection on planning and public policies to support people as they age, and on the mobility services that could allow the different expressions of autonomy to be taken into accountDans les espaces peu denses, le vieillissement à domicile soulève des questions de mobilité et d’accessibilité aux commerces. L’approvisionnement, en plus d’être un besoin essentiel, relève également d’enjeux d’intégration et de participation à la vie sociale pour certaines personnes âgées. En dehors des centralités urbaines, le maillage de l’offre commerciale est plus lâche et les distances à parcourir pour rejoindre le commerce le plus proche peuvent être importantes. Par ailleurs, la répartition spatiale et la nature de l’offre ont beaucoup évolué depuis ces dernières décennies. Les personnes de plus de 80 ans aujourd’hui ont connu l’apparition des grandes et moyennes surfaces, dont l’accès repose principalement sur l’automobile, d’abord en périphérie des villes, puis dans les centres bourgs. L’essor de la grande distribution s’est effectué en parallèle d’une diminution des magasins spécialisés des communes peu denses. Puis, depuis les années 2000, de nouvelles formes d’approvisionnement se développent, valorisant la proximité à travers des circuits courts d’une part, et avec le commerce en ligne et les évolutions numériques d’autre part. Ce travail de recherche vise à mieux comprendre comment les personnes âgées qui vieillissent dans des espaces peu denses adaptent leurs pratiques d’approvisionnement aux conditions de leur vieillissement et aux modifications de leur environnement extérieur. Il interroge de manière sous-jacente la question de l’autonomie et ce que signifie être autonome pour s’approvisionner. Le cadre théorique construit pour cette thèse mobilise plusieurs disciplines, croisant des approches d’aménagement et de géographie du commerce, de sociologie du vieillissement et de gérontologie environnementale, et de sociologie de la mobilité et de la consommation. Pour fournir des éléments de réponse empirique aux questions posées, une enquête a été conduite sur deux terrains : les espaces peu denses des aires d’attraction de Limoges et Dijon. Des entretiens semi-directifs ont été menés avec 70 personnes âgées de 70 ans ou plus qui résident chez elles. Ces dernières ont fait le récit des évolutions de leurs pratiques d’approvisionnement au regard des transformations de leur environnement extérieur et de leur vieillissement. La thèse met en lumière une pluralité de changements ayant une influence sur ces pratiques. En réponse, les personnes vieillissantes adoptent des stratégies variées, telles que des modifications spatio-temporelles des univers d’approvisionnement ou l’appui sur des relations d’entraide. De nombreuses formes d’engagement dans l’espace local sont observées afin de créer des opportunités supplémentaires pour s’approvisionner. La thèse éclaire également le rôle des valeurs et des perceptions des différents modes d’approvisionnement. Elle illustre l’importance des représentations associées aux effets perçus des transformations numériques de l’offre commerciale et des services de mobilité et l’influence que ces représentations ont sur les stratégies d’approvisionnement en ligne. Les stratégies adoptées face à la digitalisation sont particulièrement hétérogènes. Il ressort des analyses des situations d’inégalités entre les personnes rencontrées quant à leurs ressources disponibles et leurs capacités à maintenir un approvisionnement autonome. Ces capacités dépendent ainsi du niveau de revenus, des conditions de santé, des trajectoires résidentielle et professionnelle et du genre. À propos de ce dernier critère, nos recherches révèlent les évolutions différenciées des pratiques d’approvisionnement des femmes et des hommes avec l’avancée en âge. Enfin, l’autonomie des personnes s’exprime sous des formes diverses à travers les stratégies employées. Cette thèse ouvre des pistes de réflexion quant aux politiques publiques d’accompagnement du vieillissement ou d’aménagement et les services de mobilité qui pourraient permettre de prendre en comptent les différentes formes d’expressions de l’autonomi
Comprendre les déterminants socio-spatiaux de l’achat en ligne par les choix de modes de livraison des ménages
No full textInternational audienceHouseholds increasingly buy goods online and use various delivery services, such as home deliveries and pick-up or click-and-collect services. Drawing on a questionnaire survey of 633 households in France, this article seeks to deepen understanding of the factors influencing online shopping practices, focusing on the type of goods purchased (food or non-food) and the chosen delivery services. The findings refine the innovations and efficiency hypotheses, that these factors have a greater influence on the choice of delivery methods than on the likelihood of shopping online. Beyond standard socio-demographic factors, residential location does not significantly impact the frequency of online purchases but significantly influences the selection of delivery options. Specifically, households in areas perceived or characterized as less densely populated, with fewer local stores and collection points, are more likely to opt for home delivery. Conversely, those in neighbourhoods perceived as well equipped with amenities are more inclined to choose a collection point. The conclusion, therefore, is that households in densely populated areas are more inclined to retrieve purchases from pick-up points, whereas those in less dense areas would more readily outsource these trips to a logistics provider for home delivery.Los hogares compran de manera creciente productos en línea y utilizan diversos servicios de entrega a domicilio o puntos de retiro/entrega. A partir de una encuesta aplicada en 633 hogares de Francia, este artículo busca profundizar en la comprensión de los factores que influyen en las prácticas de compras en línea, centrándose en el tipo de bienes comprados (alimenticios o no) y los servicios de entrega escogidos. Los resultados aportan en la hipótesis de innovación y eficiencia, respecto a la lógica de la importancia de los métodos de envío u/o retiro por sobre la compra misma. Más allá de los factores sociodemográficos, la localización de los hogares no permite explicar la frecuencia de las compras en línea, pero sí influye significativamente en la selección de las opciones de entrega. En particular, los hogares en áreas percibidas o caracterizadas como menos densamente pobladas, con menos tiendas locales o puntos de retiro, presentan mayores probabilidades de optar por la entrega a domicilio. Por el contrario, aquellas áreas percibidas como bien equipadas y con servicios, sus habitantes son más propensos a escoger un punto de retiro. Se concluye que los hogares en zonas densamente pobladas son más propensos a retirar las compras en puntos de retiro propiciando así desplazamientos de estos habitantes, mientras que, en las zonas menos densas, los habitantes estarían con una mayor disposición a contratar un proveedor de logística para la entrega a domicilio.Les ménages achètent de plus en plus en ligne en utilisant de nombreuses solutions de récupération, de la livraison à domicile à la mise à disposition dans des points de collecte hors domicile (point relais, drive alimentaire, consignes, etc.). En utilisant les résultats d’une enquête en ligne par questionnaire auprès de 633 ménages français, l’article a pour objectif de mieux comprendre les déterminants des pratiques d’achats en ligne, en considérant le type de marchandises achetée (alimentaire ou non alimentaire) et le mode de collecte choisi. Ce faisant, notre papier propose un raffinement des hypothèses d’innovations et d’efficience en montrant qu’elles joueraient moins sur la probabilité d’acheter en ligne et plus sur le choix des modes de livraison qui l’accompagnent. Au-delà des variables socio-démographiques usuelles, la localisation résidentielle des ménages ne permet pas d’expliquer l’intensité des achats en ligne, mais est déterminante dans le choix d’un mode de collecte. Le choix de la livraison à domicile est le fait de ménages qui vivent ou considèrent vivre dans des territoires moins denses, avec moins de commerces. Réciproquement, le choix du point relais concerne des ménages qui vivent en ville ou dans des quartiers qu’ils se représentent comme bien équipés en aménités. Dès lors, dans les aires denses, l’achat en ligne de produits matériels serait plus générateur de déplacements pour les ménages, alors que dans des territoires moins denses, les ménages auraient plus tendance à déléguer (ou sous-traiter) ces mêmes déplacements à des prestataires logistiques pour des livraisons à domicile
Foam coarsening in a yield stress fluid
No full textInternational audienceFoams coarsen because of pressure differences between bubbles of different sizes. We study the coarsening of quasi-2D foams made from model yield stress fluids: concentrated oil-in-water emulsions. We show that increasing the yield stress of the foamed emulsion continuous phase leads to both slower coarsening and irreversible structural change. The impact of the continuous phase rheology is stronger when the foamed emulsion is wetter or more confined. The bubble growth and organisation both become highly heterogeneous with an excess of small bubbles. We present a model that rationalises the impact of these three parameters by taking into account a resisting pressure required to displace the yield stress fluid around the bubbles
How (absent) fans influenced football during the COVID 19 pandemic?
No full textInternational audienceThe fact that home football teams win more games than away teams has been largely discussed in the literature. Crowd factors appear to be the most dominant cause of this home advantage . At the end of the 2019–2020 season, the COVID-19 pandemic forced European football teams to close their stadium to fans, allowing researchers to exploit this natural experiment to analyze the effects of crowd on match outcomes and referees' decisions. To answer to this question, we used match data played in the top two divisions of four of the main national professional leagues in European countries and Portugal in the 2018–19 and the 2019–20 seasons. We find that the total absence of a generally supportive crowd has a significant effect on home advantage. This results in a reduction of the chances of a home win, a poorer performance by the home team's players, and more severe refereeing decisions toward the home team and less severe toward the away team
Market failures and equilibria in Banach lattices
No full textDocuments de travail du Centre d'Economie de la Sorbonne 2018.37 (Version révisée) - ISSN : 1955-611XIn this paper, we consider an economy with infinitely many commodities and market failures such as increasing returns to scale and external effects or other regarding preferences. The commodity space is a Banach lattice possibly without interior points in the positive cone in order to include most of the relevant spaces in economics. We propose a new definition of the marginal pricing rule through a new tangent cone to the production set at a point of its (non-smooth)-boundary. The major contribution is the unification of many previous works with convex or non-convex production sets, smooth or non-smooth, for the competitive equilibria or for the marginal pricing equilibria, with or without external effects, in finite dimensional spaces as well as in infinite dimensional spaces. In order to prove the existence of a marginal pricing equilibria, we also provide a new properness condition on technologies.Dans ce papier, nous considérons une économie avec une infinité de biens et des imperfections de marché comme des rendements d'échelle croissants, des effets externes dans la production ou encore des préférences dépendantes des actions des autres agents. L'espace des biens est un lattice de Banach avec l'intérieur du cône positif qui peut être vide pour prendre en compte la plupart des espaces pertinents en économie. Nous proposons une nouvelle définition de la règle de tarification marginale grâce à un nouveau cône tangent pour les ensembles de production en un point de leur frontière. La contribution principale est l'unification de nombreux travaux antérieurs avec des ensembles de production convexes ou non, lisses ou non, avec des externalités ou non, pour l'équilibre compétitif ou pour l'équilibre de tarification marginale avec un nombre fini de biens ou un nombre infini. Pour obtenir l'existence d'un équilibre de tarification marginale, nous introduisons une nouvelle hypothèse de propreté sur les technologies lorsque l'intérieur du cône positif est vide
Dynamic Analysis of a Ballast-Less Railway Track Through a Periodically Supported Timoshenko Beam and Dynamical Forces Consideration
No full textInternational audienceThis article focuses on the extension of a ballast-less railway track analytical model to compute its dynamic responses due to the application of forces on the structure. Similarly to various existing models, the railway track is represented as a periodically supported Timoshenko beam on individual and independent supports. The supports consist of a two-stage damping spring system with a mass in between. The structure is subjected to mobile forces, representing the passage of trains, which move along the railway track at a constant speed. In existing models, the structure is subjected to static forces, representing trains as a moving mass. Since dynamic forces, resulting from wheel or track defects, can turn into the most important source of loads that can stress the structure, a new formulation of the force is introduced with the aim of taking into account the influence of dynamic forces on the behavior of the railway track. This new approach aims to improve the understanding of the railway track's response to a load that seeks to be more complete and faithful to real-world phenomena