Monodisperse Dry Granular Flows on Inclined Planes : Role of Roughness

Recent studies have pointed out the importance of the basal friction on the dynamics of granular flows. We present experimental results on the influence of the roughness of the inclined plane on the dynamics of a monodisperse dry granular flow. We found experimentally that it exists a maximum of the friction for a given relative roughness. This maximum is shown to be independent of the angle of the slope. This behavior is observed for four planes with different bump sizes (given by the size of the beads glued on the plane) from 200 microns to 2 mm. The relative roughness corresponding to the maximum of the friction can be predicted with a geometrical model of stability of one single bead on the plane. The main parameters are the size of the bumps and the size of the flowing beads. In order to obtain a higher precision, the model also takes into account of the spacing between the bumps of the rough plane. Experimental results and model are in good agreement for all the planes we studied. Other parameters, like the sphericity of the beads, or irregularities in the thickness of the layer of glued particles, are shown to be of influence on the friction.Comment: 17 pages, 15 figures, submitted to EPJ

Discharge flow of a granular media from a silo: effect of the packing fraction and of the hopper angle

International audienceSilos are widely used in the industry. While empirical predictions of the flow rate, based on scaling laws, have existed for more than a century (Hagen 1852, translated in [1]-Beverloo et al. [2]), recent advances have be made on the understanding of the control parameters of the flow. In particular, using continuous modeling together with a mu(I) granular rheology seem to be successful in predicting the flow rate for large numbers of beads at the aperture (Staron et al.[3], [4]). Moreover Janda et al.[5] have shown that the packing fraction at the outlet plays an important role when the number of beads at the apeture decreases. Based on these considerations, we have studied experimentally the discharge flow of a granular media from a rectangular silo. We have varied two main parameters: the angle of the hopper, and the bulk packing fraction of the granular material by using bidisperse mixtures. We propose a simple physical model to describe the effect of these parameters, considering a continuous granular media with a dilatancy law at the outlet. This model predicts well the dependance of the flow rate on the hopper angle as well as the dependance of the flow rate on the fine mass fraction of a bidisperse mixture

Les opérations de réforme foncière à Poya (Nouvelle Calédonie) : le rôle de l'Office foncier

Cette étude s'attache à analyser les opérations de réforme foncière menées à Poya (commune de la côte ouest de Nouvelle-Calédonie) de 1978 à 1986. La redistribution foncière en faveur de l'ethnie mélanésienne a d'abord été mise en oeuvre par le Territoire, puis par l'Office Foncier, établissement public d'Etat créé en 1982 par un texte reconnaissant pour la première fois des droits fonciers coutumiers à la communauté canaque. Ce travail aborde en premier lieu les motifs culturels et historiques de la revendication foncière mélanésienne, avant d'examiner en détail, pour chaque tribu de Poya, le déroulement des opérations de redistribution de terres. Sont enfin analysées les expériences de mise en valeur sur les terrains rétrocédés, où se sont constitués des G.I.E. d'élevage bovin. Au-delà d'une approche purement technique, cette étude de cas permet de révéler l'importance des mécanismes culturels, politiques et historiques, qui, trop souvent ignorés ou négligés, ont conduit à l'échec des expériences de mise en valeur économique sur les terres redistribuées. (Résumé d'auteur

Identidade: do conceito ao produto final - criação e desenvolvimento de uma coleção de jóias através do acto criativo e artístico

O trabalho de investigação proposto teve como objetivo, o desenvolvimento de uma coleção de joias com uma vertente comercial, destinada a um determinado segmento de mercado. Este trabalho busca suprir a escassez de projetos de investigação direcionados para a área comercial do setor, procurando novas possibilidades para o desenvolvimento de coleções de joias através de pequenas e médias empresas. Para isso, foi proposto o desenvolvimento de uma coleção, a partir de uma pequena mostra de joias conceptuais, que representam a expressão artística do seu criador e que foi levada ao extremo. Numa primeira fase, procurou-se analisar as diferentes vertentes da joalharia, tendo como base um levantamento histórico e conceitual da joia e do design, visto que ainda existe falta de consenso sobre tais vertentes. Numa segunda fase foi necessário o estudo de mercado e de marca, com o objetivo de se obter as características necessárias para gerar interesse por parte dos consumidores e agregar valor às joias. Não menos importante, foi o estudo sobre o corpo que possui relação direta com a joia, sendo este último necessário para a sua existência. Numa terceira fase, foi desenvolvida a coleção conceptual de três peças que serviram como base para o desenvolvimento e produção da coleção de joias de vertente comercial. Nesta fase também foram descritas todas as etapas da criação à produção das joias, exemplificando-as com imagens, desenho técnicos e suas devidas observações. Numa quarta e ultima fase, foram realizadas entrevistas semi-estruturadas com quatro pessoas influentes em áreas da joalharia, a fim de validar e consolidar o trabalho realizado

TRIM33 switches off Ifnb1 gene transcription during the late phase of macrophage activation

Despite its importance during viral or bacterial infections, transcriptional regulation of the interferon-β gene (Ifnb1) in activated macrophages is only partially understood. Here we report that TRIM33 deficiency results in high, sustained expression of Ifnb1 at late stages of toll-like receptor-mediated activation in macrophages but not in fibroblasts. In macrophages, TRIM33 is recruited by PU.1 to a conserved region, the Ifnb1 Control Element (ICE), located 15 kb upstream of the Ifnb1 transcription start site. ICE constitutively interacts with Ifnb1 through a TRIM33-independent chromatin loop. At late phases of lipopolysaccharide activation of macrophages, TRIM33 is bound to ICE, regulates Ifnb1 enhanceosome loading, controls Ifnb1 chromatin structure and represses Ifnb1 gene transcription by preventing recruitment of CBP/p300. These results characterize a previously unknown mechanism of macrophage-specific regulation of Ifnb1 transcription whereby TRIM33 is critical for Ifnb1 gene transcription shutdown

Automatic Sleep Stages Classification Combining Semantic Representation and Dynamic Expert System

International audienceInterest in sleep has been growing in the last decades, considering its benefits for well-being, but also to diagnose sleep troubles. The gold standard to monitor sleep consists of recording the course of many physiological parameters during a whole night. The human interpretation of resulting curves is time consuming. We propose an automatic knowledge-based decision system to support sleep staging. This system handles temporal data, such as events, to combine and aggregate atomic data, so as to obtain high-abstraction-levels contextual decisions. The proposed system relies on a semantic reprentation of observations, and on contextual knowledge base obtained by formalizing clinical practice guidelines. Evaluated on a dataset composed of 131 full night polysomnographies, results are encouraging, but point out that further knowledge need to be integrated

Profils de vitesse des écoulements granulaires

Nous présentons une étude expérimentale et numérique de l'écoulement sur plan incliné de milieux granulaires monodisperse et bidisperse ségrégé. Après présentation des profils de vitesse théoriques attendus, et ceux observés expérimentalement et numériquement, que l'augmentation de la vitesse d'écoulement par la présence de grandes particules à la surface a lieu sur les écoulements de faibles épaisseurs. Dès que l'écoulement est plus épais, on retrouve numériquement la superposition des deux profils monodisperses, contrairement au cas expérimental

Image quality metrics for restricted gamut images produced by laser-induced printing on plasmonic films

Laser-induced printing is a low-cost, high-speed, non-contact method of marking large, high-resolution images. Implemented on thin films containing metallic nanoparticles, the technique allows for the printing of color images with visual effects. However, these images typically have a limited color gamut compared to inkjet printing. This limitation is due to the inability to achieve high levels of saturation for all colors and to cover the sRGB hue range. While common quality metrics focus primarily on aspects such as resolution or blur, they rarely address the color aspect. This study proposes a methodology to provide image quality metrics adapted to color gamuts with unusual shapes and volumes. It aims to rank them in terms of image quality performance for any given image. In particular, this work focuses on gamuts measured in transmission and reflection that are not necessarily centered on the CIE a*b* plane and may exhibit low contrast. Psychophysical studies have been conducted to evaluate the quality of images simulated with different color gamuts. The same images were evaluated using different metrics, and an analysis based on the ANOVA model was used to determine a set of metrics that explain observers’ preferences

SELEÇÃO DE LOCAIS DE ABRIGO POR Caluromys philander (DIDELPHIMORPHIA, DIDELPHIDAE), UTILIZANDO NINHOS ARTIFICIAIS, EM ÁREA DE MATA ATLÂNTICA, GUAPIMIRIM, RJ, BRASIL

Os abrigos são recursos importantes para a biologia dos organismos, mas os mecanismos pelos quais os indivíduos escolhem determinado abrigo são pouco conhecidos. Entre 2004 e 2009, foi avaliado se há seleção de abrigos por Caluromys philander por meio do método de Ninhos Artificiais (NA). As hipóteses testadas foram: (1) que haveria relação positiva entre os NA mais usados e a estrutura da vegetação que favorecessem o acesso aos NA, e (2) os NA mais usados estariam localizados próximos às estruturas do habitat que pudessem ser usadas como indicadoras de fontes de alimentos, como forma de redução de gasto energético de forrageamento. O Micro-habitat Descritivo das Árvores e o Micro-habitat Descritivo foram medidos em 63 estações, contendo três NA cada, localizados em três alturas (0 m, 2,5 m e 5 m), nos quais 22 variáveis foram avaliadas (11 para cada tipo) com relação à frequência de ocorrência de C. philander nos NA. Os modelos foram gerados a partir da regressão de Poisson, os quais foram selecionados pelo Critério de Informação de Akaike. Houve 118 registros de 21 indivíduos de C. philander, 80% deles no estrato mais alto (5 m de altura). As árvores selecionadas por C. philander eram altas, com troncos grossos com baixa abundância de bromélias e cipós, circundadas por árvores mortas, dossel aberto e relevo plano. Ambas as hipóteses foram negadas, pois C. philander selecionou os abrigos que priorizavam sua proteção, pois estavam em locais inacessíveis, exceto pelo uso do próprio tronco das árvores. Esse posicionamento e a relação negativa com as variáveis indicadoras de fontes de alimento mostram que C. philander se comporta de forma diferente ao selecionar locais de descanso e abrigo com os de fontes de alimento, e é possível esperar que este seja um comportamento difundido em outras espécies relacionadas de marsupiais arborícolas neotropicais.Shelters are important resources for the biology of organisms, but the mechanisms by which individuals choose a particular shelter are poorly understood. Between 2004 and 2009, using the Artificial Nests (AN) method, we evaluated if there is shelter selection by Caluromys philander and which microhabitat variables influence this choice. The hypotheses tested were: (1) there would be a positive relationship between the most used AN and components of vegetation structure that favor the arboreal habit of the species and its access to AN, and (2) the most used AN would be located near habitat features used as food sources proxies, to reduce energy expenditure during foraging. We measured the Descriptive Microhabitat of the Trees containing AN station and the Descriptive Microhabitat around each AN. There were 63 AN station measured, containing three AN at three heights each (0 m, 2.5 m and 5 m). We evaluated 21 variables (11 of each microhabitat scale) and related it to the frequency of C. philander in the AN. Models were generated from Poisson regression, which were selected by Akaike’s Information Criteria. There were 118 records of 21 individuals of C. philander, 80% of them in the highest stratum (5 m of height). The trees selected by C. philander were tall, with thick trunks, and low bromeliads and lianas abundance, surrounded by dead trees, open canopy, and flat relief. Both hypotheses were denied, as C. philander selected shelters that may prioritize their protection, as they were positioned in inaccessible places except by using tree trunk itself. This positioning and the negative relationship with food sources proxy variables show that C. philander behave differently when selecting resting and sheltering sites from food source sites, and it is possible to expect this to be a widespread behavior in other related species of small Neotropical arboreal marsupials