27 research outputs found
A place-focused model for social networks in cities
The focused organization theory of social ties proposes that the structure of
human social networks can be arranged around extra-network foci, which can
include shared physical spaces such as homes, workplaces, restaurants, and so
on. Until now, this has been difficult to investigate on a large scale, but the
huge volume of data available from online location-based social services now
makes it possible to examine the friendships and mobility of many thousands of
people, and to investigate the relationship between meetings at places and the
structure of the social network. In this paper, we analyze a large dataset from
Foursquare, the most popular online location-based social network. We examine
the properties of city-based social networks, finding that they have common
structural properties, and that the category of place where two people meet has
very strong influence on the likelihood of their being friends. Inspired by
these observations in combination with the focused organization theory, we then
present a model to generate city-level social networks, and show that it
produces networks with the structural properties seen in empirical data.Comment: 13 pages, 7 figures. IEEE/ASE SocialCom 201
Group colocation behavior in technological social networks.
We analyze two large datasets from technological networks with location and social data: user location records from an online location-based social networking service, and anonymized telecommunications data from a European cellphone operator, in order to investigate the differences between individual and group behavior with respect to physical location. We discover agreements between the two datasets: firstly, that individuals are more likely to meet with one friend at a place they have not visited before, but tend to meet at familiar locations when with a larger group. We also find that groups of individuals are more likely to meet at places that their other friends have visited, and that the type of a place strongly affects the propensity for groups to meet there. These differences between group and solo mobility has potential technological applications, for example, in venue recommendation in location-based social networks.This is the final manuscript published by PLOS One. It was originally published here: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0105816
Caractérisation du comportement au feu des matériaux de l'habitat : Influence de l'effet d'échelle.
The origin of home fires can be as diverse as poor wiring, a smoldering cigarette, poor maintenance of a fireplace... This manuscript deals with the flammability of various household materials exposed to a radiative source. Several parameters such as dimension, orientation and nature of materials were investigated in similar operating conditions. These studies led to the development of new experimental device enabling working at different scales: RAPACES (RAdiant PAnel Concentrator Experimental Setup). The results obtained on PMMA showed that geometric factors play a major role (i) on ignition (variation of thermal radiative properties) and (ii) on combustion dynamics through structural phenomena (destabilization, collapsing and polymer melting). This approach was also applied to complex materials (plywood, tapestry, carpet). A numerical model was used to validate some hypothesis regarding the fire behavior of PMMA. Finally, original configurations including material assemblies were performed and clearly evidenced the effect of fuel interactions on ignition and flame propagation.L’origine des incendies domestiques peut être aussi diverse qu’une mauvaise installation électrique, une cigarette mal éteinte, un mauvais entretien d’une cheminée… Ce mémoire traite de l’inflammabilité de différents matériaux de l’habitat face à une source radiative. Plusieurs paramètres tels que la dimension, l’orientation et la nature des matériaux ont été étudiés dans des conditions opératoires similaires. Ces travaux ont conduit au développement d’un nouveau dispositif expérimental permettant de travailler à différentes échelles : le RAPACES (RAdiant PAnel Concentrator Experimental Setup). Les résultats obtenus sur le PMMA ont permis de mettre en évidence que les facteurs géométriques jouent un rôle prépondérant; d’une part sur l’ignition (variation des propriétés thermo-radiatives) et d’autre part sur la dynamique de combustion à travers des phénomènes structuraux (déstabilisation structurelle, affaissement et écoulement du matériau). Cette démarche a également été appliquée à des matériaux plus complexes (contreplaqué, tapisserie, moquette). L’utilisation d’un modèle numérique a permis de valider certaines hypothèses concernant le comportement au feu du PMMA. Enfin, des configurations originales constituées d’assemblages de matériaux ont été testées et ont permis de mettre en évidence les interactions entre combustibles en termes d’ignition et de propagation de flamme
Immobilization of Metal Hexacyanoferrate Ion-Exchangers for the Synthesis of Metal Ion Sorbents—A Mini-Review
Metal hexacyanoferrates are very efficient sorbents for the recovery of alkali and base metal ions (including radionuclides such as Cs). Generally produced by the direct reaction of metal salts with potassium hexacyanoferrate (the precursors), they are characterized by ion-exchange and structural properties that make then particularly selective for Cs(I), Rb(I) and Tl(I) recovery (based on their hydrated ionic radius consistent with the size of the ion-exchanger cage), though they can bind also base metals. The major drawback of these materials is associated to their nanometer or micrometer size that makes them difficult to recover in large-size continuous systems. For this reason many techniques have been designed for immobilizing these ion-exchangers in suitable matrices that can be organic (mainly polymers and biopolymers) or inorganic (mineral supports), carbon-based matrices. This immobilization may proceed by in situ synthesis or by entrapment/encapsulation. This mini-review reports some examples of hybrid materials synthesized for the immobilization of metal hexacyanoferrate, the different conditionings of these composite materials and, briefly, the parameters to take into account for their optimal design and facilitated use
Les nouveaux entrants de l'information locale: un journalisme de rupture?
International audienc
Les nouveaux entrants de l'information locale: un journalisme de rupture?
International audienc
Contester l’hégémonie médiatique locale: Entre engagement journalistique et repolitisation des territoires
International audienceThis article examines the ability of the new players of local news to renew the process of democratic debate in their zone of distribution, in the face of hegemonic regional daily press. We thus hypothesize that local journalism, built in opposition to or alongside dominant players, could catalyze the transformations at work in the journalistic field by championing the introduction of dissenting voices (Benson & Neveu, 2005; Smyrnaios & Thiong-Kay, 2023) in territories characterized until now by the media’s construction of consensus. Based on the "multi-referential" conception of territory put forward by Boure and Lefebvre (2000), we consider it to be structured by the opposition between, on the one hand, the exercise of institutional power and the crystallization of collective social time and, on the other, asymmetrical social relationships and plural or competing enactments of meaning. Ultimately, our aim was to understand the "territorial work" of the media (Noyer & Raoul 2011). Our study focused on 11 media located in the Auvergne RhĂ´ne-Alpes region, each of which had at least one professional journalist on its editorial staff. Through semi-structured interviews, combined with a focus on the media's meta-discourse, we examined the media's relationship with its territory from three perspectives (market, field and local public space). Our results confirm, among the actors studied, the structuring dynamics of professionalization previously observed in alternative media (Ferron 2006). They also reveal a form of polarization between two journalistic ideal-types, which we characterize in the light of Nielsen's work (2015). Indeed, while some media aim to reduce disparities in access to knowledge of public affairs among citizens (reduction of the "knowledge gap"), others seem above all committed to fostering civic and political engagement among citizens in the local space (reduction of the "engagement gap").Este artĂculo se propone examinar la capacidad de los nuevos operadores de la informaciĂłn local para renovar el proceso de alimentaciĂłn del debate democrático en sus territorios de difusiĂłn, frente a una Prensa Diaria Regional hegemĂłnica. De este modo, nuestra hipĂłtesis es que un periodismo local, construido en contra o al lado del actor hegemĂłnico, serĂa capaz de catalizar las transformaciones en marcha en el campo periodĂstico, defendiendo la introducciĂłn de voces disidentes (Benson y Neveu, 2005; Smyrnaios y Thiong-Kay, 2023) en territorios hasta ahora marcados por la construcciĂłn mediática del consenso. Partiendo de la concepciĂłn "multirreferencial" del territorio propuesta por Boure y Lefebvre (2000), consideramos que este está estructurado por la oposiciĂłn entre el ejercicio de un poder institucional y la cristalizaciĂłn de un tiempo social compartido, por un lado, y las relaciones sociales asimĂ©tricas y las significaciones plurales o concurrentes, por el otro. En definitiva, lo que hemos tratado de comprender es el "trabajo territorial" de los medios de comunicaciĂłn (Noyer y Raoul, 2011). Nuestro estudio se ha centrado en 11 medios de comunicaciĂłn situados en la regiĂłn de Auvernia-RĂłdano-Alpes y que cuentan con al menos un periodista profesional en su redacciĂłn. Mediante entrevistas semiestructuradas, complementadas con una atenciĂłn al metadiscurso de los medios de comunicaciĂłn, consideramos su relaciĂłn con el territorio en una dimensiĂłn triple (mercado, terreno y espacio pĂşblico local). Nuestros resultados confirman en primer lugar, entre los actores estudiados, una dinámica estructurante de profesionalizaciĂłn previamente observada en los medios alternativos (Ferron, 2006). Pero tambiĂ©n revelan una forma de polarizaciĂłn entre dos ideales-tipos periodĂsticos, que caracterizamos a la luz de los trabajos de Nielsen (2015). En efecto, mientras que algunos medios de comunicaciĂłn pretenden reducir las disparidades en el acceso al conocimiento de los asuntos pĂşblicos entre los ciudadanos (reducciĂłn de la brecha del conocimiento o knowledge gap), otros parecen sobre todo comprometidos con el fomento del compromiso cĂvico y polĂtico de los ciudadanos a nivel local (reducciĂłn de la brecha del compromiso o engagement gap).FR. Cet article propose de questionner la capacitĂ© des nouveaux entrants de l’information locale Ă renouveler le processus d’alimentation du dĂ©bat dĂ©mocratique dans leur territoire de diffusion, face Ă une Presse Quotidienne RĂ©gionale en situation hĂ©gĂ©monique. Nous faisons ainsi l’hypothèse qu’un journalisme local, construit contre ou Ă cĂ´tĂ© de l’acteur hĂ©gĂ©monique, serait en mesure de catalyser les transformations Ă l’œuvre dans le champ journalistique en dĂ©fendant l’introduction de voix dissidentes (Benson & Neveu, 2005 ; Smyrnaios & Thiong-Kay, 2023) dans des territoires jusqu’ici marquĂ©s par la construction mĂ©diatique du consensus. Ă€ partir de la conception « multirĂ©fĂ©rentielle » du territoire avancĂ©e par Boure et Lefebvre (2000), nous envisageons en effet celui-ci comme structurĂ© par l’opposition entre, d’un cĂ´tĂ©, l’exercice d’un pouvoir institutionnel et la cristallisation d’un temps social partagĂ© et, de l’autre, des rapports sociaux dissymĂ©triques et des mises en sens plurielles ou concurrentes. Au final, c’est donc le « travail territorial » des mĂ©dias (Noyer & Raoul 2011) que nous avons cherchĂ© Ă apprĂ©hender. Notre Ă©tude a portĂ© sur 11 mĂ©dias situĂ©s en rĂ©gion Auvergne RhĂ´ne-Alpes et comportant dans leur rĂ©daction au moins un journaliste professionnel. Par le biais d’entretiens semi-directifs, complĂ©tĂ©s d’une attention au mĂ©ta-discours des mĂ©dias, nous envisageons leur rapport au territoire dans une triple dimension (marchĂ©, terrain et espace public local). Nos rĂ©sultats confirment d’abord, chez les acteurs Ă©tudiĂ©s, une dynamique structurante de professionnalisation prĂ©cĂ©demment observĂ©e dans les mĂ©dias alternatifs (Ferron 2006). Mais ils rĂ©vèlent Ă©galement une forme de polarisation entre deux idĂ©aux-types journalistiques, que nous caractĂ©risons Ă la lumière des travaux de Nielsen (2015). En effet, si certains mĂ©dias ambitionnent de rĂ©duire les disparitĂ©s d’accès Ă la connaissance des affaires publiques parmi les citoyens (rĂ©duction du « knowledge gap »), d’autres semblent avant tout attachĂ©s Ă susciter l’engagement civique et politique des citoyens dans l’espace local (rĂ©duction de l’« engagement gap »).O objeto deste artigo Ă© discutir como os novos atores do noticiário local podem renovar o processo de documentação do debate democrático em suas áreas de transmissĂŁo, frente Ă posição hegemĂ´nica da Imprensa Diária Regional. Levanta-se a hipĂłtese de que um jornalismo local, construĂdo contra ou ao lado do ator hegemĂ´nico, seja capaz de catalisar as transformações em curso no campo jornalĂstico ao defender a introdução de vozes dissidentes (Benson & Neveu, 2005; Smyrnaios & Thiong-Kay, 2023) em territĂłrios atĂ© entĂŁo marcados pela construção midiática do consenso. De fato, com base na concepção “multirreferencial” do territĂłrio apresentada por Boure e Lefebvre (2000), considera-se que o territĂłrio Ă© estruturado pela oposição entre, de um lado, o exercĂcio do poder institucional e a cristalização de um tempo social compartilhado e, de outro, as relações sociais assimĂ©tricas e as atribuições de sentidos plurais ou concorrentes. Dessa forma, em Ăşltima análise, o que procuramos compreender Ă© o “trabalho territorial” da mĂdia (Noyer & Raoul 2011). O estudo considerou 11 meios de comunicação localizados na regiĂŁo de Auvergne RhĂ´ne-Alpes, com pelo menos um jornalista profissional em sua equipe editorial. Por meio de entrevistas semiestruturadas, complementadas por um foco no metadiscurso da mĂdia, analisou-se a relação desses veĂculos com o territĂłrio sob uma tripla perspectiva (de mercado, em campo e no espaço pĂşblico local). Os resultados confirmam, em primeiro lugar, que há, entre os atores estudados, a mesma dinâmica estruturante de profissionalização já observada na mĂdia alternativa (Ferron, 2006). Mas evidencia-se tambĂ©m uma forma de polarização entre dois tipos de ideais jornalĂsticos, caracterizados aqui Ă luz do trabalho de Nielsen (2015). Com efeito, enquanto alguns meios de comunicação objetivam reduzir as disparidades no acesso ao conhecimento dos assuntos pĂşblicos entre os cidadĂŁos (redução do “knowledge gap”), outros parecem estar comprometidos principalmente com a promoção do engajamento cĂvico e polĂtico dos cidadĂŁos no espaço local (redução do “engagement gap”)
Characterization of the flammability of household materials subjected to high radiative flux
International audienc
Characterization of the flammability of household materials subjected to high radiative flux
International audienc