Modéliser l'efficacité d'un réseau: Le cas de la poste aux chevaux dans la France pré-industrielle (1632-1833)

National audienceThe topic deals with the question of relationships between the creation of a new transportation network and its effects, in terms of space shaping, here in the “Ancien Regime” France. Using a modelization approach, we aim to build the postal relation space of pre-industrial France and its evolution through two centuries. Postal roads are digitalized from historical lists of post houses, at seven different dates. Using a 900 points grid, we calculate the accessibility “at every place in France”, with a Shimbel index, and we take into account a secondary road network, characterized by a slower transportation speed. We weight the accessibility values by geometrical accessibility, and we generalize the results by interpolation methods. This methodology enlightens major regional differences, with some regions that have been favored by postal roads creations and other, less provided. The regional differentiations and their evolution reveal some planned decisions taken by French State as soon as the 18e century.Nous abordons la question des effets structurants d'un nouveau réseau de transport sur un territoire, ici la France d'Ancien Régime. Pour cela, nous reconstituons par la modélisation l'espace des relations postales et son évolution sur deux siècles. Les routes de poste sont numérisées à partir de la liste des relais à sept dates différentes. Grâce à l'établissement d'une grille de 900 points, nous évaluons l'accessibilité « en tout point de la France » par le calcul de l'indice d'accessibilité de Shimbel, en tenant compte d'un réseau de voies secondaires de circulation plus lente. Nous généralisons ensuite les valeurs obtenues par lissage et nous les pondérons par l'accessibilité géométrique des lieux. Cette méthode met en évidence de forts contrastes régionaux, entre des zones qui ont été particulièrement favorisées par l'implantation du réseau postal et d'autres, moins bien pourvues. L'analyse des dénivellations régionales d'accessibilité et de leur évolution met en lumière une action volontaire d'aménagement de l'espace par les routes de poste dès le 18ème siècle

La carte du sang de l'immobilier chinois, un cas de cyber-activisme

International audienceThe aim of this paper is to explore new forms of social mobilization in urban areas that use the Internet technologies. The development of online social networks offers new possibilities of expression and protest. Web 2.0 is transformed into a digital public space complementary to the traditional physical public space especially when this one is particularly controlled. The Chinese bloody map of real estate is particularly representative of these changes. Published in October 2010, this map uses cooperative knowledge of Internet users to list real estate developments that led to physical violence. These can range from simple protest repression to self-immolation. The checked version of the map shows 85 events and the open version 199 cases. The diffusion of the news of this map in the Chinese and international medias helped to put this social issue on the international political agenda related to urban development and real estate in China.L'objectif de cet article est d'explorer les nouvelles formes de mobilisation sociale en milieu urbain qui utilisent les technologies de l'Internet. Le développement des réseaux sociaux en ligne offre en effet de nouvelles possibilités d'expression et de contestation. Le Web 2.0 se transforme ainsi en un espace public numérique complémentaire de l'espace public physique traditionnel surtout lorsque celui-ci est particulièrement contrôlé. Le cas de la " carte du sang de l'immobilier chinois " est particulièrement représentatif de ces transformations. Mise en ligne en octobre 2010, cette carte coopérative fait appel à la connaissance des internautes pour répertorier les développements immobiliers ayant donné lieu à des violences physiques. Celles-ci peuvent aller de la simple répression de manifestations à des immolations par le feu. La version vérifiée de la carte présente 85 événements et la version ouverte 199 cas. La publication de cette carte a été reprise dans les médias chinois et internationaux, participant ainsi à l'inscription sur l'agenda politique international des enjeux sociaux liés au développement urbain et immobilier chinois

Urban monitoring using NetKDE and VGI: network based kernel density estimation on volunteered geographic information applied to Baghdad, Iraq

This paper presents a methodology for urban monitoring using volunteered geographic information (VGI) and journalism data Iraq war logs with network based kernel density estimation (NetKDE). It investigates, using spatio-temporal analysis, the evolution of urban events in Baghdad between 2004 and 2009. The extracted street network is based on the data distributed by OpenStreetMap (OSM). A total of 21,876 logged events, 66,648 network segments, 22,644 gridpoints (200m resolution grid) and 362,304 gridpoints (50m resolution grid) are used for the analysis. The methodology combines and adapts these VGI data and is mainly based on open source and/or publicly available software. It handles very large datasets with multiscale, multi-resolution and temporal perspectives. Fuzzy-set map comparison (FMC) is used to identify level of changes between each period of time. The methodology is already used in other fields of research being biology, urban planning, criminology or economic evelopment. It should help stakeholders in respective domain to analyze the evolution of network constrained events in multiple contexts. This paper is divided in three parts. Firstly, conceptual background of VGI, NetKDE and FMC is presented. Secondly, the methodology is illustrated using data Iraq war logs, OSM data and grids with two different resolutions. Thirdly, spatio-temporal analysis results are presented and discussed.Peer Reviewe

Cold, Optically Dense Samples of Atomic Rubidium

Cold and optically dense gases of atomic rubidium are produced using buffer gas cooling in combination with rapid, high-flow vapor injection. The observed rubidium density is 3 × 10$^{12}$cm$^{−3}$ at a gas temperature of ∼20 K, leading to an optical density of the order of 200.Physic

Crowdsourcing the georeferencing of historical pictures

Countless organizations own archive pictures which are not used due to the difficulty of localizing them. Only the participation of volunteers can help to identify the image content. Through an accessible web interface called smapshot, citizens are able to georeference historical images without any prior specific competence. To avoid the volunteers to face the complexity of 3D digitization and navigation, we implemented a state of the art photogrammetry camera orientation algorithm in the platform. Currently several thousand images from all around Switzerland have been georeferenced by the crowd. At this time the tool is mainly used by the population for the visualization experience and the nostalgia behind it. The ambition is to support scientists to analyze landscape evolution

Cash Flow Optimization on Synthetic CDOs

Collateralized Debt Obligations are not as widely used nowadays as they were before 2007 Subprime crisis. Nonetheless there remains an enthralling challenge to optimize cash flows associated with synthetic CDOs. A Gaussian-based model is used here in which default correlation and unconditional probabilities of default are highlighted. Then numerous simulations are performed based on this model for different scenarios in order to evaluate the associated cash flows given a specific number of defaults at different periods of time. Cash flows are not solely calculated on a single bought or sold tranche but rather on a combination of bought and sold tranches. With some assumptions, the simplex algorithm gives a way to find the maximum cash flow according to correlation of defaults and maturities. The used Gaussian model is not realistic in crisis situations. Besides present system does not handle buying or selling a portion of a tranche but only the whole tranche. However the work provides the investor with relevant elements on how to know what and when to buy and sell

Cash Flow Optimization on Synthetic CDOs

Collateralized Debt Obligations are not as widely used nowadays as they were before 2007 Subprime crisis. Nonetheless there remains an enthralling challenge to optimize cash flows associated with synthetic CDOs. A Gaussian-based model is used here in which default correlation and unconditional probabilities of default are highlighted. Then numerous simulations are performed based on this model for different scenarios in order to evaluate the associated cash flows given a specific number of defaults at different periods of time. Cash flows are not solely calculated on a single bought or sold tranche but rather on a combination of bought and sold tranches. With some assumptions, the simplex algorithm gives a way to find the maximum cash flow according to correlation of defaults and maturities. The used Gaussian model is not realistic in crisis situations. Besides present system does not handle buying or selling a portion of a tranche but only the whole tranche. However the work provides the investor with relevant elements on how to know what and when to buy and sell

Law of spreading of the crest of a breaking wave

Wave breaking can be seen as the manifestation of a singularity in the dynamics of the fluid surface. We show theoretically and experimentally that, for shallow water waves, their crests expand in the span-wise direction as the square root of time. We then explore another configuration where the focusing of the initially parabolic waves induces a widening of the breaking proportional to the power 3/2 of time as it follows the Huygens cusp shape

SERS detection of biomolecules using lithographied nanoparticles towards a reproducible SERS biosensor

International audienceIn this paper we highlight the accurate spectral detection of bovine serum albumin and ribonuclease-A using a Surface-Enhanced Raman Scattering (SERS) substrate based on gold nanocylinders obtained by Electron-Beam Lithography (EBL). The nanocylinders have diameter from 100 to 180 nm with a gap of 200 nm. We demonstrate that optimizing the size and the shape of the lithographied gold nanocylinders, we can obtain SERS spectra of proteins at low concentration. This SERS study enabled us to estimate high enhancement factors (105 for BSA and 107 for RNase-A) of important bands in the protein Raman spectrum measured for 1mM concentration. We demonstrate that to reach the highest enhancement it is necessary to optimize the SERS signal and that the main parameter of optimization is the LSPR position. The LSPR have to be suitably located between the laser excitation wavelength which is 632.8 nm and the position of the considered Raman band. Our study underlines the efficiency of gold nanocylinders arrays in spectral detection of proteins