Academic literature on the topic 'Vents de particules'
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Journal articles on the topic "Vents de particules"
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Minaker, Leia M., Meghan Lynch, Brian E. Cook, and Catherine L. Mah. "Analyse de données sur les ventes lors d'une intervention axée sur un dépanneur santé de Toronto : le projet FRESH sur l'environnement de la vente d’aliments au détail comme déterminant de la santé." Promotion de la santé et prévention des maladies chroniques au Canada 37, no. 10 (October 2017): 383–91. http://dx.doi.org/10.24095/hpcdp.37.10.04f.
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Introduction Les interventions en santé de la population dans le secteur de l’alimentation de détail, comme celles réalisées dans les dépanneurs, visent à transformer le type de signaux envoyés aux consommateurs afin qu'ils choisissent des aliments plus sains. Peu de recherches abordent les aspects financiers des interventions réalisées dans le milieu de la vente au détail, en particulier les mesures de résultat comme les ventes en magasin, pourtant au centre du processus décisionnel de la vente au détail. Cette étude examine l'évolution des ventes en magasin et les ventes par catégories de produits dans le cadre d’une intervention axée sur un dépanneur santé situé dans un quartier à faible revenu de Toronto (Ontario). Méthodologie Les données sur les ventes effectuées entre août 2014 et avril 2015 ont été regroupées par catégories de produits et par jour. Nous avons utilisé des tableaux croisés dynamiques Excel afin de résumer et de présenter visuellement les données sur ces ventes. Nous avons mené des tests t afin d’étudier les différences au niveau des ventes de chaque catégorie de produits en fonction des jours de vente « de pointe » (jours d’affluence) par rapport aux autres jours de vente. Résultats Les ventes globales du magasin culminaient les derniers jours de chaque mois, soit à la période à laquelle les prestations d’assistance sociale sont versées. La hausse des revenus lors des jours de pointe était principalement imputable aux ventes de laissez-passer de transports en commun. La moyenne des ventes de collations non nutritives et de cigarettes était légèrement plus élevée lors des jours de pointe par rapport aux autres jours. Les stratégies novatrices employées pour augmenter les ventes de fruits et légumes frais ont semblé accroître considérablement les revenus générés par ces catégories de produits. Conclusion Les données sur les ventes en magasin constituent un paramètre important de mesure du succès des interventions en environnement alimentaire. De plus, les prises de décision des détaillants fondé sur ces données peuvent se révéler déterminantes lors de l’adaptation des interventions. Les responsables des recherches et des interventions futures devraient envisager d’établir des partenariats et d’utiliser d'autres indicateurs de rendement lors des interventions ciblant l'environnement de la vente au détail d’aliments dans divers contextes canadiens.
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Bonnivard, Eric, Olivier Catrice, Juliette Ravaux, Spencer C. Brown, and Dominique Higuet. "Survey of genome size in 28 hydrothermal vent species covering 10 families." Genome 52, no. 6 (June 2009): 524–36. http://dx.doi.org/10.1139/g09-027.
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Knowledge of genome size is a useful and necessary prerequisite for the development of many genomic resources. To better understand the origins and effects of DNA gains and losses among species, it is important to collect data from a broad taxonomic base, but also from particular ecosystems. Oceanic thermal vents are an interesting model to investigate genome size in very unstable environments. Here we provide data estimated by flow cytometry for 28 vent-living species among the most representative from different hydrothermal vents. We also report the genome size of closely related coastal decapods. Haploid C-values were compared with those previously reported for species from corresponding orders or infraorders. This is the first broad survey of 2C values in vent organisms. Contrary to expectations, it shows that certain hydrothermal vent species have particularly large genomes. The vent squat lobster Munidopsis recta has the largest genome yet reported for any anomuran: 2C = 31.1 pg = 30.4 × 109 bp. In several groups, such as Brachyura, Phyllodocida, and Veneroida, vent species have genomes that clearly rank at the high end of published values for each group. We also describe the highest DNA content yet recorded for the Brachyura (coastal crabs Xantho pilipes and Necora puber ). Finally, analysis of genome size variation across populations revealed unexpected intraspecific variation in the vent shrimp Mirocaris fortunata that could not be attributed simply to ploidy changes.
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Cardoso, Silvana S. S., and Julyan H. E. Cartwright. "On the differing growth mechanisms of black-smoker and Lost City-type hydrothermal vents." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2205 (September 2017): 20170387. http://dx.doi.org/10.1098/rspa.2017.0387.
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Black smokers and Lost City-type springs are varieties of hydrothermal vents on the ocean floors that emit hot, acidic water and cool, alkaline water, respectively. While both produce precipitation structures as the issuing fluid encounters oceanic water, Lost City-type hydrothermal vents in particular have been implicated in the origin of life on the Earth. We present a parallel-velocity flow model for the radius and flow rate of a cylindrical jet of fluid that forms the template for the growth of a tube precipitated about itself and we compare the solution with previous laboratory experimental results from growth of silicate chemical gardens. We show that when the growth of the solid structure is determined by thermal diffusion, fluid flow is slow at the solid–liquid contact. However, in the case of chemical diffusive transport, the fluid jet effectively drags the liquid in the pores of the solid precipitate. These findings suggest a continuum in the diffusive growth rate of hydrothermal vent structures, where Lost City-type hydrothermal vents favour contact between the vent fluid and the external seawater. We explore the implications for the road to life.
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Leignel, V., L. A. Hurtado, and M. Segonzac. "Ecology, adaptation and acclimatisation mechanisms of Bythograeidae Williams, 1980, a unique endemic hydrothermal vent crabs family: current state of knowledge." Marine and Freshwater Research 69, no. 1 (2018): 1. http://dx.doi.org/10.1071/mf17007.
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Diversified fauna have colonised the deep-sea hydrothermal vents, an environment characterised by high metallic concentrations and sulfide-rich waters. In 1977–79, brachyuran crabs were collected in hydrothermal vents around the Galapagos Rift, allowing description in 1980 of Bythograea thermydron and the new family Bythograeidae (and the superfamily Bythogreoidea). This family has a worldwide distribution and currently includes 13 species classified in 6 genera: Allograea (1 species), Austinograea (3 species), Bythograea (5 species), Cyanagraea (1 species), Gandalfus (2 species) and Segonzacia (1 species). These crabs have distinctive morphological and physiological characteristics, which reflect adaptations to particular deep-sea hydrothermal vent conditions. This review is the first on Bythograeidae, documenting the state of our knowledge regarding their taxonomy, evolution, ecology, morphology and physiology (i.e. osmoregulation, oxygen consumption, sulfide and metal detoxification, temperature tolerance). We also report on recent progress in maintaining bythograeids in an artificial ex situ environment.
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Bevilacqua, Andrea, Alvaro Aravena, Augusto Neri, Eduardo Gutiérrez, Demetrio Escobar, Melida Schliz, Alessandro Aiuppa, and Raffaello Cioni. "Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador volcanic complex (El Salvador) and Nejapa-Chiltepe volcanic complex (Nicaragua)." Natural Hazards and Earth System Sciences 21, no. 5 (May 28, 2021): 1639–65. http://dx.doi.org/10.5194/nhess-21-1639-2021.
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Abstract. The San Salvador volcanic complex (El Salvador) and Nejapa-Chiltepe volcanic complex (Nicaragua) have been characterized by a significant variability in eruption style and vent location. Densely inhabited cities are built on them and their surroundings, including the metropolitan areas of San Salvador (∼2.4 million people) and Managua (∼1.4 million people), respectively. In this study we present novel vent opening probability maps for these volcanic complexes, which are based on a multi-model approach that relies on kernel density estimators. In particular, we present thematic vent opening maps, i.e., we consider different hazardous phenomena separately, including lava emission, small-scale pyroclastic density currents, ejection of ballistic projectiles, and low-intensity pyroclastic fallout. Our volcanological dataset includes: (1) the location of past vents, (2) the mapping of the main fault structures, and (3) the eruption styles of past events, obtained from critical analysis of the literature and/or inferred from volcanic deposits and morphological features observed remotely and in the field. To illustrate the effects of considering the expected eruption style in the construction of vent opening maps, we focus on the analysis of small-scale pyroclastic density currents derived from phreatomagmatic activity or from low-intensity magmatic volcanism. For the numerical simulation of these phenomena we adopted the recently developed branching energy cone model by using the program ECMapProb. Our results show that the implementation of thematic vent opening maps can produce significantly different hazard levels from those estimated with traditional, non-thematic maps.
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Ferreira de Lima, Neilson, Marcos Antônio Chaves Freire, Josimar José dos Santos, and Rodrigo Ricardo Cavalcante de Albuquerque. "CORRELAÇÃO DE LONGO ALCANCE TEMPORAL DA VELOCIDADE DO VENTO NOS MUNICÍPIOS DE CEARÁ-MIRIM E NATAL NO RIO GRANDE DO NORTE." HOLOS 8 (December 31, 2017): 56. http://dx.doi.org/10.15628/holos.2017.5491.
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A energia eólica é uma fonte natural de energia renovável e utilizada em diversos países para o abastecimento energético de residências, fábricas e empresas. Para os países que possuem hidrelétricas como a principal fonte geradora de energia, como o Brasil, por exemplo, a energia eólica é muito importante, porque ela não consome água, é renovável, limpa e não causa danos ambientais como outras fontes energéticas poluentes e sujas. Diversos estudos são realizados a fim de observar o comportamento do vento, em particular às correlações com outras variáveis como radiação solar, temperatura máxima ou mínima e umidade relativa do ar. Para fazerem inferência das observações do vento pesquisadores tem empregado diversas ferramentas estatísticas como médias móveis, média móvel ponderada e suavização exponencial. Nosso interesse é verificar as correlações de curto ou longo alcance persistente/antipersistente em séries temporais de ventos dos municípios Natal e Ceará-Mirim. Para realizar o estudo da correlação do vento se aplicou os métodos estatísticos denominados Detrended Fluctuation Analysis (DFA) e Detrended Cross-Correlation Analysis –DCCA, isto é análise da flutuação sem tendências e análise da correlação cruzada sem tendências. Nesta pesquisa observou-se que a série temporal do vento tem uma forte correlação de longo alcance persistente, significando que valores altos de velocidade do vento tem maior probabilidade de ser seguido por valores altos; e, valores baixos na velocidade do vento tem maior probabilidade de ser seguido por valores baixos.
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Kaliska, Agnieszka K. "Prédicats et verbes supports d’occurrence météorologiques dans une perspective contrastive franco-polonaise." Lingvisticæ Investigationes. International Journal of Linguistics and Language Resources 34, no. 2 (December 8, 2011): 169–203. http://dx.doi.org/10.1075/li.34.2.01kal.
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The common co-occurrence of words in a given context reflects both the extra-linguistic knowledge of a language user, and the specific intra-linguistic rules. We can say that lexicon and grammar are interpreters of the extra-linguistic reality. The purpose of our research is to consider, in French-Polish constrastive perspective, the relation between the pronoun and the meteorological verb (such as il and venter in Il vente) on the one hand and, on the other, the relation between the meteorological noun and the special kind of support verb named verbe d’occurrence on the Lexicon-Grammar ground (such as vent and mugir in Le vent mugit). We then raise the question of the particular status of meteorological nouns in the grammatical subject position and explain the non-predicative character of verbs in constructions such as Le vent mugit. In the end, we present a list of Polish and French examples containing meteorological support verbs or their stylistic and aspectual variants.
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Appolloni, Luca, Daniela Zeppilli, Luigia Donnarumma, Elisa Baldrighi, Elena Chianese, Giovanni Fulvio Russo, and Roberto Sandulli. "Seawater Acidification Affects Beta-Diversity of Benthic Communities at a Shallow Hydrothermal Vent in a Mediterranean Marine Protected Area (Underwater Archaeological Park of Baia, Naples, Italy)." Diversity 12, no. 12 (December 4, 2020): 464. http://dx.doi.org/10.3390/d12120464.
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One of the most important pieces of climate change evidence is ocean acidification. Acidification effects on marine organisms are widely studied, while very little is known regarding its effects on assemblages’ β-diversity. In this framework, shallow hydrothermal vents within a Marine Protected Area (MPA) represent natural ecosystems acting as laboratory set-ups where the continuous carbon dioxide emissions affect assemblages with consequences that can be reasonably comparable to the effects of global water acidification. The aim of the present study is to test the impact of seawater acidification on the β-diversity of soft-bottom assemblages in a shallow vent field located in the Underwater Archeological Park of Baia MPA (Gulf of Naples, Mediterranean Sea). We investigated macro- and meiofauna communities of the ‘Secca delle fumose’ vent system in sites characterized by sulfurous (G) and carbon dioxide emissions (H) that are compared with control/inactive sites (CN and CS). Statistical analyses were performed on the most represented macrobenthic (Mollusca, Polychaeta, and Crustacea), and meiobenthic (Nematoda) taxa. Results show that the lowest synecological values are detected at H and, to a lesser extent, at G. Multivariate analyses show significant differences between hydrothermal vents (G, H) and control/inactive sites; the highest small-scale heterogeneities (measure of β-diversity) are detected at sites H and G and are mainly affected by pH, TOC (Total Organic Carbon), and cations concentrations. Such findings are probably related to acidification effects, since MPA excludes anthropic impacts. In particular, acidification markedly affects β-diversity and an increase in heterogeneity among sample replicates coupled to a decrease in number of taxa is an indicator of redundancy loss and, thus, of resilience capacity. The survival is assured to either tolerant species or those opportunistic taxa that can find good environmental conditions among gravels of sand.
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Santos, Tailine C. dos, Michelle Simões Reboita, and Vanessa Silveira Barreto Carvalho. "Investigação da Relação entre Variáveis Atmosféricas e a Concentração de MP10 E O3 no Estado de São Paulo." Revista Brasileira de Meteorologia 33, no. 4 (December 2018): 631–45. http://dx.doi.org/10.1590/0102-7786334006.
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Resumo O presente estudo tem como objetivo identificar relações entre variáveis atmosféricas e concentrações de material particulado inalável (MP10) e ozônio (O3) registradas no estado de São Paulo. Para isso, foram utilizados dados entre 2005 a 2014 de cinco estações de monitoramento de qualidade do ar. O estudo foi baseado em duas metodologias: Análise de Componentes Principais (ACP) e campos médios meteorológicos. Nas ACP para as concentrações de O3, encontraram-se correlações positivas entorno de 0,5 e 0,6 com temperatura do ar, e correlações negativas, entre 0,4 e 0,6 com umidade relativa do ar. As contribuições das componentes do vento nas concentrações de O3 diferem de uma localidade para outra, sendo em Cubatão e Bauru maior a relação com ventos meridionais e nas demais a maior contribuição é da componente zonal, contudo, em todas as localidades as correlações são negativas com o O3. Para o MP10 teve-se as menores correlações, negativas para umidade, e praticamente nulas para temperatura. As correlações com as componentes do vento variam de acordo com a localidade. Com isso, é possível concluir que relações de MP10 com umidade são mais significativas e no caso do O3, dentre todas as variáveis, destaca-se a correlação com temperatura como a mais importante, já com relação ao vento ressalta-se a forte ligação deste com as características locais e particulares de cada estação. Os campos médios das variáveis atmosféricas revelam durante altas concentrações de MP10 e O3 a predominância da atuação do Anticiclone Subtropical do Atlântico Sul (ASAS) sobre a região Sudeste do Brasil. Com relação à temperatura do ar, as maiores concentrações de ozônio ocorreram em dias com temperaturas elevadas, e sem diferença significativa em dias de altas concentrações de MP10. Por fim, as maiores concentrações de MP10 e O3 ocorreram em dias secos e de ventos fracos.
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MacKay, D. K. "Ice Conditions in the Gulf of St.Lawrence and Cabot Strait (with particular reference to the Sydney Bight Area)." Cahiers de géographie du Québec 7, no. 14 (April 12, 2005): 211–28. http://dx.doi.org/10.7202/020427ar.
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Les glaces qui, au printemps, se trouvent dans le détroit de Cabot et tout particulièrement dans la région de la baie Sydney, gênent souvent les traversées des bateaux passeurs entre Port-aux-Basques, Terre-Neuve et North Sydney, Nouvelle-Ecosse. Des données sur les principaux relevés des glaces dans le golfe Saint-Laurent et le détroit de Cabot ont été recueillis et étudiées en tenant compte de ce problème. Les relations qui existent entre les nuances de température, les vents et l'étendue des glaces ont été étudiées à la lumière de la statistique. La somme des températures de décembre et janvier correspond assez bien aux principales étendues des glaces qui se trouvaient dans le golfe et le détroit durant ces deux mois. L'étude des vents indique un véritable mouvement de la glace à partir du golfe en direction du détroit durant les années où des observations ont été faites. Si l'on additionne les températures et les vents et les exprime en termes de glace de dérive, on découvre que ces deux éléments sont très étroitement liés l'un à l'autre.
Dissertations / Theses on the topic "Vents de particules"
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Forot, Michael. "Accélération de particules au sein des vents relativistes de pulsar : simulation et contraintes observationelles avec le satellite INTEGRAL." Paris 7, 2006. http://www.theses.fr/2006PA077049.
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Le but de cette thèse est de poser de nouvelles contraintes sur les différents mécanismes d'accélération de particules opérant au sein de la géométrie complexe de l'environnement d'une étoile à neutrons, c'est à dire dans la magnétosphère du pulsar, dans le jet, dans le plan équatorial ainsi qu'au choc terminal. Proche de la surface l'accélération est produite par l'entraînement du très fort champ magnétique par la rotation de l'étoile. Au delà du cylindre de lumière, les particules sont également accélérées dans le plan équatorial par reconnexions magnétiques. Ces processus ont pour principale signature observationnelle une émission puisée pouvant être observée dans tous les domaines de longueurs d'onde. Un des outils les plus puissants afin de contraindre ces mécanismes est l'étude de la polarisation suivant la phase de rotation. C'est dans cet esprit que nous avons utilisé le mode Compton d'IBIS à bord du satellite S\gammaS INTEGRAL. En effet ce dernier permet par la mesure de la distribution selon l'angle azimuthal de diffusion, des événements diffusés entre les deux plans détecteurs d'IBIS, de remonter à la direction et à la fraction de polarisation d'une source au delà de 200 keV. Une méthode d'analyse et de traitement de données a donc été développée dans ce but. La sensibilité atteinte permet de mesurer la polarisation de sources persistantes fortes ainsi que celle de sursauts S\gammaS. Cette méthode a été appliquée au pulsar du Crabe ainsi qu'a sa nébuleuse. Pour la première fois la polarisation d'une source a été mesurée dans le domaine S\gammaS entre 0. 2 et 0. 8 MeV. L'évolution de cette dernière avec la phase de rotation est en accord avec celle trouvée en optique dans les régions centrales, c'est à dire pour des régions S<0. 01S pc du pulsar. Dans le domaine non puisé l'angle de polarisation semble aligné le long de l'axe de rotation, ce qui suggère un rayonnement venant principalement du jet ou bien du point brillant proche du pulsar. Le fait qu'aucune polarisation ne soit observée juste après les pics en émission pourrait être la signature d'effets caustiques sur de grandes distances le long de la dernière ligne de champ ouverte dans la magnétosphère du pulsar. Dans ce cas le modèle du \textit{slot gap} pourrait être responsable de l'émission puisée et donc de la réaccélération de particules proche du pulsar. Afin de mieux contraindre les processus d'accélération par la polarisation il est alors nécessaire d'utiliser une configuration de champ magnétique la plus réaliste possible. Ce paramètre est en effet à la base de tous les modèles d'accélération et d'émission hautes énergies. Jusqu'à maintenant cette géométrie fut supposée dipolaire. C'est donc dans l'optique d'établir une configuration du champ E et B plus réaliste que les équations d'Einstein et de Maxwell furent résolues proche de la surface et dans le vide en utilisant la librairie LORENE. Cette librairie est basée sur les décompositions spectrales, méthode bien adaptée à la résolution des équations de type Poisson. La géométrie obtenue diffère légèrement de celle d'un dipôle classique pour de faibles rotations et les zones d'accélération sont elles localisées proche des calottes polaires. Il est maintenant nécessaire de poursuivre cette étude dans le cas d'une magnétosphère chargée. Dans la magnétosphère lointaine et plus particulièrement proche du choc terminal, les particules peuvent être réaccélérées par absorption d'ondes cyclotrons émises par les ions ainsi que par processus de Fermi relativiste. Des contraintes spectrales comme l'énergie maximum ou l'indice spectral de la distribution de particules permettent de contraindre de façon très efficace ces processus. Pour remonter à de telles informations et notamment à l'énergie maximum qui est en général de l'ordre de S10*{l4-15}S TeV, il est en général nécessaire d'utiliser les émissions synchrotron dans le domaine des X durs (>20 keV). Le champ magnétique doit dans ce cas être connu de manière très précise. C'est dans cet esprit que nous avons étudié les émissions au delà de 20 keV de PSR B1509-58. Ce pulsar produit une longue traine observée en X et au TeV, traine qui a été interprète comme étant du à un jet. Dans le domaine non puisée, de son émission, où la contribution du pulsar par rapport au vent qu il crée est minimum, 1'imageur IBIS détecta lui aussi entre 20 et 200 keV une source s'étendant dans la direction de ce jet et ayant un spectre coupé vers 160 keV. Le champ magnétique a été contraint à des valeurs comprises entre 2 et 3 nT en utilisant la variation de la longueur apparente du jet avec l'énergie entre 0. 1 et 100 keV. Dans ce champ les particules y rayonnant à 160 keV possèdent une énergie comprise entre 400 et 730 TeV. Pour des pulsars plus vieux, le vent relativiste est confiné par la pression du au déplacement de l'étoile dans le milieu interstellaire. La morphologie de ce dernier est alors modifiée et la simple hypothèse de vent sphérique utilisée dans le modèle standard de Kennel et Corroniti ou bien de jet cylindrique, s'évanouit alors au profit de 1'apparation d'un choc en étrave. C'est pourquoi un simple modèle MHD analytique des émissions synchrotrons d'un vent relativiste choqué de pulsar fut développé dans une telle géométrie. Ce modèle fut appliqué au cas de Geminga récemment observé avec XMM et Chandra. Dans cette géométrie l'amplification du champ magnétique le long de la discontinuité de contact permet d'expliquer les flux observés alors que l'énergie maximum nécessaire pour reproduire les observations est incompatible avec celle donnée par un processus de Fermi relativiste. L'énergie maximum de l'ordre de 400 TeV nécessite d'utiliser l'intégralité du potentiel dipolaire aux calottes polaires. Ce simple modèle montre également combien l'évaluation du champ magnétique est primordiale pour interpréter les donnéesThe context of this thesis is to gain new constraints on the different particle accelerators that occur in the complex environment of neutron stars: in the pulsar magnetosphere, in the striped wind or wave zone outside the light cylinder, in the jets and equatorial wind, and at the wind terminal shock. Near the star, the accelerator is powered by the rotation of the intense magnetic field and can be probed by the pulsed radiation at all wavelengths. An additional powerful tool to investigate the magnetic geometry in the radiative zones, therefore the accelerator location, is polarimetry, especially at high photon energy. The shocked wind of the Crab nebula and a handful of other wind nebulae are known to host 1014-15 eV particles, but thé energy estimates are always subject to the uncertain evaluation of the local magnetic field strength. The famous spherical model of Kennel and Coroniti (1984) has been challenged by high-resolution X-ray and TeV images that show a growing wealth of jets and equatorial flows, confined by asymmetric pressure gradients in a supernova remnant or by interstellar bow shocks. An important tool to constrain both the magnetic field and primary particle energies is to image the synchrotron ageing of the population, but it requires a careful modelling of the magnetic field evolution in the wind flow. The current models and understanding of these different accelerators, the acceleration processes, and open questions have been reviewed in the first part of the thesis. In this context, the thesis work is three-fold: instrumental, observational, and theoretical. On board INTEGRAL, the IBIS imager provides images with 12' resolution from 17 keV to MeV energies where the SPI spectrometer takes over up, to 10 MeV, but with a reduced 2° resolution. The first part of the work provides a new method for using the double-layer IBIS imager as a Compton telescope with coded mask aperture. Its performance has been measured. The new concept takes advantage of the coded mask deconvolution for high resolution and background rejection to construct images with a 12' resolution, over a 29°x29° field of view, at the 0. 1-0. 4 Crab sensitivity level, in the 0. 2-1 MeV range. The Compton scattering information and the achieved sensitivity also open a new window for polarimetry in gamma rays. A method has been developed to extract the linear polarization properties and to check the instrument response for fake polarimetric signais in the various backgrounds and projection effects. The achieved sensitivity of 0. 3-1 Crab for polarized emission allows the study of bright sources and AGN flares, gamma-ray bursts and solar flares for the first time at high energy. The INTEGRAL data recorded for the Crab pulsar and nebula show good evidence for a high degree of polarization for both the pulsed and the unpulsed emissions in the 0. 2-0. 8 MeV band. The measured polarization closely follows the optical one from the central < 0. 01 pc region around the pulsar. The polarization orientation along the rotation axis is consistent with emission from the jet and bright knot, not with DC emission from the pulsar beams. No polarization has been detected on the trailing sides of the pulsed peaks. It could sign the caustic effects that characterize emission along a fair fraction of the last open field lines on the trailing sides of the pulsar magnetosphere. A dipolar magnetic field geometry is assumed in the magnetosphere and a split-monopole one outside, but they can be questioned for very intense stellar fields or very compact magnetospheres. As a first step to map this field in general relativity, Einstein and Maxwell equations have been solved near the pulsar, in vacuum, using the LORENE library to find the rotating star metric together with the associated magnetic and electric fields. This library is based on spectral methods well adapted for Poisson type equations. The resulting field geometry differs slightly from a dipole and the acceleration regions are closed to the polar caps. Studying the geometry in a charged magnetosphere with potential currents will be the next step. INTEGRAL synchrotron data above 30 keV is best suited to probe the most energetic wind particles and their ageing in the flow by comparison with lower-energy images. The wind from PSR B1509-58 powers a long X-ray jet and TeV tail. The unpulsed emission recorded by INTEGRAL-IBIS at 20-200 keV has been used to detect a slightly extended source along the jet axis, with a power-law spectrum up to 160 keV. The variation of the apparent jet length with energy from 0. 1 to 100 keV has been interpreted as synchrotron ageing in a simple cylindrical jet. This allows to constrain both the average jet magnetic field to 2 or 3 nT and the electron energies near the cut-off to 400-700 TeV. Many older wind nebulae are confined into a bow shock geometry by the ram pressure of their motion into the interstellar medium. This morphology modifies the MHD flow by providing an exit for the kinetic and magnetic energy and stationary conditions. Very hard synchrotron X-ray tails have been imaged around the nearby, 0. 3 Myr-old, Geminga pulsar. A first attempt at modelling the emission shows that Fermi acceleration at the wind terminal shock or at the bow shock cannot produce the required particle energies. As for the Crab, the particles must somehow tap the potential drop from the pulsar unipolar inductor. We also find that the particles are too few and/or the magnetic field to low to account for the observed X rays. The prediction falls short by 2 or 3 orders of magnitude. A simple analytical MHD model has been developed to show that the magnetic field advection toward the bow-shock contact discontinuity and the resulting amplification can explain the observed flux. Electron energies of 400 TeV are found. This 'toy model1 proves the importance of a careful modelling of the magnetic flow to interpret the data
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Voshchepynets, Andrii. "Interaction faisceau-plasma dans un plasma aleatoirement non-homogene du vent solaire." Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2035/document.
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Dans cette thèse nous avons présenté un modèle probabiliste auto cohérent décrivant la relaxation d'un faisceau d'électrons dans un vent solaire dont les fluctuations aléatoires de la densité ont les mêmes propriétés spectrales que celles mesurées à bord de satellites. On a supposé que, le système possédait différentes échelles caractéristiques en plus de l'échelle caractéristique des fluctuations de densité. Ceci nous a permis de décrire avec précision l'interaction onde-particule à des échelles inférieures à l'échelle caractéristique des fluctuations de densité en supposant que des paramètres d'onde sont connus: notamment, la phase, la fréquence et l'amplitude. Cependant, pour des échelles suffisamment plus grandes que l'échelle caractéristique des irrégularités de densité, l'interaction des ondes et des particules ne peut être caractérisée déterminé que par des quantités statistiques moyennes dans l'espace des vitesses à savoir: le taux de croissance/amortissement et le coefficient de diffusion des particules. En utilisant notre modèle, nous décrivons l'évolution de la fonction de distribution des électrons et d'énergie des ondes de Langmuir. Le schéma 1D suggérée est applicable pour des paramètres physiques de plasma du vent solaire à différentes distances du Soleil. Ainsi, nous pouvons utiliser nos calculs pour décrire des émissions solaires de Type III, ainsi que les interactions de faisceau avec le plasma, à des distances d'une Unité Astronomique du Soleil dans l'héliosphère et au voisinage des chocs planétairesThis thesis is dedicated to effects of plasma density fluctuations in the solar wind on the relaxation of the electron beams ejected from the Sun. The density fluctuations are supposed to be responsible for the changes in the local phase velocity of the Langmuir waves generated by the beam instability. Changes in the wave phase velocity during the wave propagation can be described in terms of probability distribution function determined by distribution of the density fluctuations. Using these probability distributions we describe resonant wave particle interactions by a system of equations, similar to well known quasi-linear approximation, where the conventional velocity diffusion coefficient and the wave growth rate are replaced by the averaged in the velocity space. It was shown that the process of relaxation of electron beam is accompanied by transformation of significant part of the beam kinetic energy to energy of the accelerated particles via generation and absorption of the Langmuir waves. We discovered that for the very rapid beams the relaxation process consists of two well separated steps. On first step the major relaxation process occurs and the wave growth rate almost everywhere in the velocity space becomes close to zero or negative. At the seconde stage the system remains in the state close to state of marginal stability enough long to explain how the beam may be preserved traveling distances over 1 AU while still being able to generate the Langmuir waves
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Bénit, Jean. "Effets d'irradiation par des ions de grande énergie dans de la glace H₂O et applications astrophysiques." Paris 11, 1987. http://www.theses.fr/1987PA112229.
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Cette thèse est consacrée à l'étude expérimentale des effets induits par l'irradiation d'ions de grande énergie (0,1 à 4,5 MeV/uma) dans des glaces, fabriquées par condensation sous vide de gaz sur des supports refroidis à 80 K. Les ions émis pendant l'irradiation ont été analysés grâce à un spectromètre de masse par temps de vol. Les cibles ont été étudiées in-situ en infrarouge, par un spectromètre à Transformée de Fourier. Les principaux résultats concernent tout d'abord les processus conduisant à l'érosion des glaces induite par l'irradiation. Elle provient principalement de la dissociation des molécules constitutives des glaces, suivies de recombinaisons en composés volatils pouvant diffuser hors des cibles irradiées. On obtient ainsi des taux d'érosion très élevés, qui dépendent linéairement de l'épaisseur des cibles traversées par les ions incidents. Ceci atteste de ce que l'érosion se produit tout au long de la trace des ions dans la cible. En second lieu, il a été possible de suivre la désorption d'ions depuis la surface irradiée. L'ensemble des espèces ionisées ont été détectées, jusqu'à des masses supérieures à 400 uma. Un des résultats les plus marquants est l'abondance relative élevé d'amas ionisés de grande masse. Enfin, nous avons mis en évidence la synthèse de composés moléculaires nouveaux dans les glaces irradiées. L'ensemble de ces résultats a des implications astrophysiques directes. En particulier, ils permettent de rendre compte de la présence de composés moléculaires complexes dans de nombreux sites, dans le Système Solaire (comètes, satellites), dans les nuages interstellaires et les cavités stellairesThis thesis presents the study of radiation effects induced in H20 ice by MeV/u ions: desorption of ionized species, "erosion" of the irradiated film and molecular synthesis within the ice. The desorption is analysed by time of flight mass spectroscopy. We describe the mass spectra of the desorbed ions, both positively and negatively charged, up to 400 uma. The absolute yields are given, as well as their dependence with the energy and energy loss of the primary ions. The "erosion" of the ice is analysed by infrared spectroscopy, on line during the irradiation. Absolute yields are derived, as a function of the ions beam flux, the mass and energy of the ions, and the thickness of the samples. A linear dependence of the yield with the thickness is interpretated as follows: the erosion comes primarely from the dissociation of the molecules all along the ion tracks. Some astrophysical implications of the results are discussed in the framework of irradiation of icy material in a variety of environments: magnetospheres of giant planets, cometary nuclei, circumstellar shells and molecular clouds. Lt is emphasized that the irradiation by energetic ions plays a major role in cosmochemistry
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Flint, Hannah Christina. "Diversity of meiofauna at deep-sea hydrothermal vents and cold seeps with particular reference to nematodes." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/63135/.
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Deep-sea hydrothermal vents and cold seeps are remarkable for their spectacular megaand macrofauna, many of which appear to have a high level of endemism to these chemosynthetic environments. It is not clear whether the patterns of biodiversity, faunal zonation and biogeography documented in these size categories, are also present in the meiofauna. This thesis examines the diversity and density patterns of the meiofauna (with particular reference to nematodes) in quantitative samples collected from: Bathymodiolus mussel beds in a deep-sea hydrothermal vent field on the East Pacific Rise; Bathymodiolus mussel beds at an Atlantic methane seep site; an Atlantic hydrothermal vent sediment mound and a reference non-chemosynthetic sediment site on the Mid-Atlantic Ridge. Results suggested that deep-water chemosynthetic substrata will generally harbour assemblages exhibiting lower diversity and elevated dominance. The densities of meiobenthos appeared to vary in accordance with the presence of macrofauna. From the study of the meiobenthos of hydrothermal vent mussel beds spanning 27 degrees of latitude on the EPR, the nematodes share the same, if not a larger biogeographical province as the macrofauna. From comparison of data collected from the vent mussel beds and the Atlantic methane seep mussel bed, it was evident that the species composition of the nematode assemblage was completely different. Density levels and major taxa composition were very similar as a result of similar local factors acting within the mussel beds. Based on a comparison of data collected from all mussel bed samples and the hydrothermal sediment core, it was evident that the nematode assemblages were significantly different. Factors determining all the observed differences are discussed.
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Le, Chat Gaétan. "Étude du vent solaire à grande échelle." Phd thesis, Université Paris-Diderot - Paris VII, 2010. http://tel.archives-ouvertes.fr/tel-00547571.
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Depuis les premières mesures in situ du vent solaire en 1960, les propriétés macroscopiques et microscopiques de ce plasma éjecté par le Soleil ont été intensivement étudiées, tant du point de vue théorique qu'observationnel. Aujourd'hui encore, certaines des propriétés du vent solaire sont incomprises, comme par exemple le transport de l'énergie dans un plasma peu collisionnel. Mesurer précisément la température des électrons et leurs propriétés non thermique est nécessaire pour comprendre les propriétés du transport. Pour ce faire, la spectroscopie du bruit quasi-thermique est un outil fiable, en étant moins sensible aux perturbations produites par le satellite que les détecteurs de particules classiques. Le bruit quasi-thermique est produit par les fluctuations du champ électrique causées par le mouvement des charges du plasma directement mesurées par une paire d'antennes reliée à un récepteur radio suffisamment sensible. L'étude de ce bruit permet de déterminer les moments des distributions de vitesses des particules. De nombreux résultats ont ainsi été obtenus à partir du récepteur radio de la sonde Ulysse, en décrivant les distributions des électrons par une somme de Maxwelliennes. Cependant une limitation de l'instrument ne permet pas de mesurer avec une précision suffisante la température totale des électrons avec un tel modèle de fonctions de distribution. Pour pallier à ce problème, une nouvelle méthode d'analyse des spectres de bruit quasi-thermique, utilisant une distribution des électrons de type kappa est proposée. Son application aux données de la sonde Ulysse permet de mesurer les variations avec la distance de la température totale des électrons et de leurs propriétés super thermiques dans le vent solaire. Le profil de température montre un comportement intermédiaire entre adiabatique et isotherme, et le paramètre kappa est constant avec la distance au Soleil. Ces résultats sont en accord avec les modèles exosphériques. Le vent solaire est également en interaction avec l'ensemble des objets du Système Solaire. Deux exemples d'interactions plasma-poussières sont présentés dans la deuxième partie de cette thèse : l'accélération des nanoparticules et leurs découvertes dans le vent solaire à une unité astronomique ; et la modification du champ magnétique interplanétaire par les poussières cométaires. Enfin, un point de vue plus global est adopté. Une comparaison du flux d'énergie, qui dans le cas du vent solaire est observé comme étant très stable temporellement et spatialement, est effectuée pour de nombreux vents stellaires. Cette comparaison met en évidence une similitude entre les étoiles de types solaire et les géantes froides, ainsi qu'une éventuelle conséquence de l'accrétion de matière sur les vents stellaires des T-Tauri.
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Debesse, Philippe. "Vers une mesure du vent thermoacoustique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00445461.
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Les phénomènes non-linéaires présents dans les systèmes thermoacoustiques sont responsables de l'apparition des écoulements continus secondaires qui se superposent aux oscillations acoustiques dominantes, pénalisant l'efficacité des systèmes. L'objectif de cette étude est de caractériser le champ acoustique dans un résonateur contenant un générateur d'onde thermoacoustique et de mettre en évidence les écoulements secondaires. Nous mesurons le champ de vitesse par vélocimétrie par images de particules (PIV). Les premières mesures enregistrées sans relation de phases avec la période acoustique, permettent de reconstruire la composante acoustique sur une période, en réordonnant les vitesses suivant leur phase avec une technique de projection par décomposition aux valeurs singulières (SVD). Celle-ci fait partie d'une batterie de post-traitements qui permettent d'obtenir des résultats concordant avec l'acoustique linéaire. Ils mettent en évidence un contenu harmonique important et le caractère non-linéaire de l'écoulement acoustique. Le calcul du champ de vitesse moyenné en temps montre l'existence d'un écoulement continu différent de celui de Rayleigh-Schlichting. Dans la fenêtre de mesure, il est composé de cellules de convection dont l'extension radiale tend à croître avec le rapport moteur. Il fait aussi apparaître un caractère tridimensionnel. Un deuxième type de mesures PIV synchronisées aux mesures de pression, apporte un complément d'information sur les écoulements secondaires et confirme globalement les résultats obtenus à partir des premières mesures. Cependant ces mesures synchronisées se révèlent moins précises que les premières.
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Cierco, François-Xavier. "Étude des instationnarités du transport de neige par le vent." Phd thesis, Grenoble 1, 2007. http://www.theses.fr/2007GRE10270.
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Le transport de neige par le vent occasionne des nuisances qui entravent certaines activités du secteur des transports et du tourisme. Il déplace les dépôts de neige et modifie la structure du manteau neigeux. A ce titre, il participe à l'augmentation du risque d'avalanche. Ces différents aspects justifient l'activité de recherche menée depuis plusieurs années au Cemagref de Grenoble et dans laquelle cette étude trouve naturellement sa place. Ainsi les travaux précédents ont contribué à la modélisation physique et numérique de prévision du transport de neige par le vent. Cela dit, le transport éolien de particules met en jeu différents phénomènes complexes que les connaissances actuelles ne suffisent pas à décrire avec précision. Dans ce contexte, des travaux expérimentaux ont été conduits à la fois en soufflerie et sur le terrain. Ces derniers ont permis des premières investigations sur le comportement des fluctuations de concentration en régime permanent, en particulier par le biais de traitements d'images et d'analyses spectrales. Cette thèse a également porté sur la variabilité des profils de concentration en conditions naturelles, c'est-à-dire dans un écoulement turbulent instationnaire. Tous les résultats in-situ ont nécessité l'usage d'instruments adaptés dont certains ont du être réétalonnés de manière spécifiqueBlowing snow causes disturbances that affect both tourism and transportation. Moreover, snowdrifts and accelerated snow metamorphosis dramatically increase the risk of avalanches. These observations call for more scientific and technical researches like those realized in Cemagref, Grenoble, France, where this Ph-D was achieved. Past works contributed to the development of physical and numerical models about blowing snow but the difficulties encountered to match the results get in the field and the general complexity involved in Aeolian particle transport required more studies. That’s why new experimental measurements were recorded either in a wind-tunnel or in the field. On one hand, image processing and spectral analysis were used to investigate the fluctuations of particle concentration blown in a stationary turbulent flow. On the other hand, the variability of concentration profiles during natural events of blowing snow was studied thanks to flux measurements. These latter required some dedicated sensors with specific calibration
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Herrero, Crespo Angel. "El proceso de adopción de nuevos sistemas de venta: aplicación al comercio electrónico entre particulares y empresas." Doctoral thesis, Universidad de Cantabria, 2005. http://hdl.handle.net/10803/10589.
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Sobre la base de la revisión teórica efectuada, se propone un modelo teórico de adopción del comercio electrónico por parte de los consumidores finales. De esta forma, se pretende analizar cuales son los factores que determinan la intención de compra futura en Internet por parte de los individuos particulares. Con objeto de dar respuesta a estas cuestiones se realiza un estudio cualitativo mediante entrevistas en profundidad a expertos en comercio electrónico, y una investigación cuantitativa mediante encuesta personal dirigida a usuarios habituales de Internet. La investigación cuantitativa pretende analizar las actitudes de los sujetos respecto a la compra electrónica, la influencia social que experimentan, el control que perciben en las transacciones virtuales, el riesgo asociado al comercio electrónico, su propensión a innovar y los atributos percibidos en el sistema. Así mismo, se examina el efecto de estas variables en el proceso de adopción de la compra en Internet.Taking as a basis an extensive literature review, a theoretical model of e-commerce acceptance by consumers is proposed. Thus, we aim to analyse which are the factors that determine consumers' intention to buy in Internet in the future. With this objective a qualitative study is developed, consisting in in-depth interviews with experts in the field of e-commerce. Subsequently, a quantitative research based in a personal survey aimed to habitual Internet users is developed. This quantitative research aims to analyse consumers' attitudes towards e-commerce, normative influence in the behaviour, perceived behavioural control felt, perceived risk associated to virtual purchase, individual's innovativeness and the attributes perceived in Internet as a shopping channel. More over, the effect of these variables in the process of e-commerce adoption is evaluated through SEM methodology.
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Moreau, Thomas. "Etude numérique et développement de spectromètres embarquables de particules chargées." Toulouse 3, 2003. http://www.theses.fr/2003TOU30032.
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Atig, Mérouane. "Non-linéarité acoustique localisée à l'extrémité ouverte d'un tube. Mesure, modélisation et application aux instruments à vent." Phd thesis, Université du Maine, 2004. http://tel.archives-ouvertes.fr/tel-00009283.
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L'étude porte sur les pertes acoustiques non-linéaires localisées à la sortie d'un tube cylindrique. Trois aspects sont envisagés : tout d'abord la mise en évidence du phénomène par la mesure de l'impédance terminale du tube, puis la modélisation physique du phénomène et enfin l'application aux instruments de musique à vent. Le travail comprend trois parties qui traitent des trois aspects envisagés.Dans une première partie, des mesures de l'impédance terminale réalisées à l'aide d'une méthode à deux microphones montrent que les pertes à la sortie du tube - partie réelle de l'impédance terminale dans le cadre de l'approximation du premier harmonique - augmentent avec l'amplitude de la vitesse acoustique. Les résultats montrent que l'importance de ces pertes dépend fortement du rayon de courbure des bords intérieurs à la sortie de tube. En outre, pour les faibles rayons de courbure, deux régimes sont mis en évidence. L'existence de ces deux régimes est confirmée par des observations utilisant la vélocimétrie par imagerie de particules (PIV) réalisées en collaboration avec l'Université d'Edimbourg : dans les deux cas un anneau tourbillonnaire est formé à la sortie du tube mais dans le cas du premier régime (faibles vitesses acoustiques) l'anneau reste accroché aux bords du tube alors que dans le cas du second régime (fortes vitesses acoustiques) il est expulsé.
La seconde partie concerne la modélisation du phénomène dans le but de mieux comprendre les mécanismes physiques mis en jeu. La théorie du bruit tourbillonnaire (``vortex sound theory'') est appliquée afin d'estimer directement les pertes à la sortie du tube. Trois calculs utilisant cette théorie sont menés : le premier, analytique, sur la base d'un unique anneau tourbillonnaire fixe ou mobile, le second à partir des mesures par PIV et le troisième par la méthode numérique dite des réseaux de Boltzmann. Les trois calculs conduisent à des résultats similaires qui démontrent que les pertes non linéaires trouvent leur origine dans la formation d'anneaux tourbillonnaires en sortie de tube. Ces résultats sont confrontés avec succès aux résultats issus des mesures d'impédance.
La troisième partie analyse les conséquences que peuvent avoir les pertes non linéaires dans le fonctionnement d'un instrument de musique à trous latéraux. Il est montré expérimentalement et à l'aide de simulations numériques que la dynamique de jeu d'un instrument à vent dépend directement des pertes dans l'instrument et que cette dynamique peut être étendue lorsque les pertes à la sortie sont minimisées par exemple en chanfreinant les bords des trous latéraux.
Books on the topic "Vents de particules"
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Laflamme, J. C. K. Notes sur un fait météorologique particulier à Québec. [S.l: s.n., 1986.
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Gagnon, Philéas. Courte liste d'ouvrages rares sur l'Amérique et sur le Canada en particulier recemment [sic] procurés et offert [sic] en vente par le soussigné P. Gagnon ... [S.l: s.n., 1987.
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Arroyo, Dulio. 5 años de jurisprudencia de las Salas Primera (de lo Civil) y tercera (de lo contencioso-administrativo) de la Corte Suprema de Justicia de Panamá, 1981-1985: DE CONTRATO DE COMPRA Y VENTA EN PARTICULAR. Panamá: [s.n.], 1988.
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Ontario. Esquisse de cours 12e année: Le droit canadien et international cln4u cours préuniversitaire. Vanier, Ont: CFORP, 2002.
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Ontario. Esquisse de cours 12e année: Étude de l'alimentation et de la nutrition hfa4m cours préuniversitaire. Vanier, Ont: CFORP, 2002.
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Ontario. Esquisse de cours 12e année: Atelier d'écriture fae4o cours ouvert. Vanier, Ont: CFORP, 2002.
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Ontario. Esquisse de cours 12e année: Histoire de l'Occident et du monde chy4u. Vanier, Ont: CFORP, 2002.
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Ontario. Esquisse de cours 12e année: Géométrie et mathématiques discrètes mga4u cours préuniversitaire. Vanier, Ont: CFORP, 2002.
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Ontario. Esquisse de cours 12e année: Français des affaires faf4o. Vanier, Ont: CFORP, 2002.
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Ontario. Esquisse de cours 12e année: L'église et la culture hre4m. Vanier, Ont: CFORP, 2007.
Find full textBook chapters on the topic "Vents de particules"
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Kruszewski, Łukasz. "Fossil Fuel Fires: A Forgotten Factor of Air Quality." In Environmental Sustainability - Preparing for Tomorrow. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96294.
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Spontaneous fossil fuel fires, especially coal fires, are known worldwide. They occur in numerous sites, both completely natural (coal seam outcrops) and anthropogenic (burning mining waste heaps, or BMWHs). Coal and waste/barren rock fires produce gaseous emanations, acting within exhalative processes. This factor is rarely being considered as influencing quality of the atmospheric air. The paper shortly discusses most important available methods for field gas analysis, with an emphasis on a portable FTIR spectrometer. It summarizes results of gas analyses from Polish BMWHs, using a multi-tool approach. It also lists a number of additional analyses from 53 vents of these environmentally important objects, with the main purpose of enlarging the knowledge of the span of concentrations of the particular compounds. This is especially true for formaldehyde, pyridine, CO, 1,1,1-trichloroethene, 1,1-dichloroethene, cumene, SO2, and, to a lesser extent, NO2, CCl4, ethane, propane, ethene, and thiophene. The latter, and DMS, are confirmed as gaseous S source more frequent and rich than SO2.
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"APÉNDICE. Novelas a la venta en librerías españolas del Siglo de Oro (1600-1650), (BHi, 110, 1, juin 2008, pp. 92-109)." In Literatura (novela, poesía, teatro) en bibliotecas particulares del Siglo de Oro español (1600-1650), 139–58. Vervuert Verlagsgesellschaft, 2010. http://dx.doi.org/10.31819/9783865279767-009.
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Brun-Hurtad, Elisabeth, and Christophe GUITTON. "16 - Chargé de clientèle particulier dans la banque de détail : un équilibre délicat entre vente et conseil." In Les professions intermédiaires, 223. Armand Colin, 2013. http://dx.doi.org/10.3917/arco.guit.2013.01.0223.
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Berressem, Hanjo. "The Birth of Philosophy." In Gilles Deleuze's Luminous Philosophy, 21–48. Edinburgh University Press, 2020. http://dx.doi.org/10.3366/edinburgh/9781474450713.003.0002.
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The chapter focuses on the beginning of Deleuze’s career, charting his confrontation with Simondon, from whose work he takes the notion of crystal individuation. It then turns to Deleuze’s early reading of Lucretius’ De Rerum Natura. Stressing in particular Lucretius’ notion of the ‘light of Venus’, the chapter reads Deleuze’s luminous ontology against Thomas Nail’s argument that Lucretius’ work proposes a fluid and processual ontology. The chapter concludes that the ideas Deleuze distils from Lucretius concern a love of the multiplicity of the world and of life, and that Deleuzian philosophy is a response to the question of where Lucretius’ love of life and of a given multiplicity takes philosophy. Nowhere in Deleuze’s work is the positivity and affirmation that he finds in Lucretius put into question. All horrors are immanent to this more profound love of a multiplicitous life and light, which Deleuze also finds in Nietzsche and Bergson.
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Koneva, Sophie, and Cyril Pshenichny. "Conceptualization of the Dike Distribution Analysis Aiming at Identification of Eruptive Centers." In Advances in Web Technologies and Engineering, 119–54. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-5261-1.ch006.
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Formation of dikes is typical for most of the volcanic centers. Different types of eruptive centers tend to create different patterns of dike distribution by strike. Looking at this distribution, one may suggest, by purely geometrical reasons, where the vent should be (if buried) or should have been (if removed by denudation or new eruptions). However, wide application of this technique raises the issue of interpretation of the results in the context of the geological history of a particular volcano. Impartial and universal interpretation may be possible in a framework of knowledge of eruptive center evolution that can be built by means of the event bush method. Such a framework, however, may have wide application in volcanology extending far from the initial task it has been developed for.
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Poon, Damon Chi Him, and Louis Leung. "Effects of Narcissism, Leisure Boredom, and Gratifications Sought on User-Generated Content Among Net-Generation Users." In Evolving Psychological and Educational Perspectives on Cyber Behavior, 49–63. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-1858-9.ch004.
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This research identifies the gratifications sought by the Net-generation when producing user-generated content (UGC) on the internet. Members of the Net-generation want to vent negative feelings, show affection to their friends and relatives, be involved in others’ lives, and fulfill their need to be recognized. These gratifications, to a large degree, were found to be significantly associated with the users’ various levels of participation in UGC (e.g., Facebook, blogs, online forums, etc.). What’s more, narcissism was predictive of content generation in social networking sites, blogs, and personal webpages, while leisure boredom was significantly linked to expressing views in forums, updating personal websites, and participating in consumer reviews. In particular, the results showed that Net-geners who encountered leisure boredom had a higher tendency to seek interaction with friends online. Implications of findings are discussed.
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Gibellini, Pietro. "Un viaggio tra i Fiori di Baudelaire." In «Un viaggio realmente avvenuto». Venice: Edizioni Ca' Foscari, 2019. http://dx.doi.org/10.30687/978-88-6969-344-1/010.
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The author analyzes the journey motif in the poetic masterpiece of Charles Baudelaire, signaling and commenting all the texts where the term voyage and derivatives appears and considers in particular the poems where the keyword appears in the title: Bohémiens en voyage, L’Invitation au voyage, Un Voyage à Cythère, Le Voyage. In the passage from one text to another, the journey becomes little by little a physical experience to become, finally, a mental and spiritual dimension: in Bohémiens there is still a residue of romantic oleography; in the Invitation one dreams an exotic country, a mythical place, an earthly paradise that only the imagination can reach, in Le voyage à Cythère, the sacred island of Venus no longer has the legendary face of the classical world, but the dark and dramatic of modernity and evil; once all the illusions of earthly wanderings have fallen, only the last departure remains, Le voyage par excellence, to know the mystery that awaits beyond death. The textual analysis, conducted with a diachronic and synchronic method, becomes a cognitive analysis, a literary hermeneutic essay.
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Mulvenna, Gareth. "Football, Flags and Fighting (1970–71)." In Tartan Gangs and Paramilitaries. Liverpool University Press, 2017. http://dx.doi.org/10.5949/liverpool/9781781383261.003.0004.
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Chapter Three places the oral histories in the context of the growth of republican violence and in particular focuses on the last weekend of June 1970, when events occurred which led to the formation of the UVF in East Belfast and the organisation of a small militant grouping of young loyalists in North Belfast which would become known as the Red Hand Commando. The chapter explains the importance of John McKeague as a leading loyalist and the way in which his protest against nationalist residents at the Unity Flats interface at the foot of the Shankill Road in 1970 became an ongoing focal point for young loyalists, most notably Tartans and Linfield supporters who were eager to vent their frustrations at the declining security situation in Northern Ireland. Furthermore, the chapter describes how the Tartan movement gained momentum as the first half of 1971 proved to be a dire period for Ulster Protestants.
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Rosello, Mireille. "Jeanne Duval." In Postcolonial Realms of Memory, 307–13. Liverpool University Press, 2020. http://dx.doi.org/10.3828/liverpool/9781789620665.003.0028.
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This particular attempt at imagining a site of memory made of words may appear irreverent at first, but it has been crafted as an homage to a formidable woman: Jeanne Duval. I have taken the liberty of fictionalizing a first-person narrator who will talk about ‘herself’, at the risk of usurping her voice and her identity. Jeanne (whose name was or was not Duval) was a woman of colour and she had a long-term turbulent relationship with the enfant terrible of French nineteenth-century poetry, Charles Baudelaire. As a result, historical accounts both magnify and marginalize her. Trying to do justice to a historical character who was so much more than a muse but may not have been happy to embrace the role of exemplary black foremother, this text puts together the numerous and often incompatible portraits of Jeanne Duval. She appears and disappears in biographies (Emmanuel Richon), novels (Fabienne Pasquet), short stories (Angela Carter), academic studies (Claude Pichois). She is both present and absent, celebrated and erased in the so-called ‘Black Venus cycle’ of Baudelaire’s Flower of Evil as well as in paintings by Edouard Manet (Baudelaire’s Mistress, Reclining) and Gustave Courbet (The Painter’s Studio). The objective was to question the process of memorialization that might silence or appropriate her instead of providing her with a safe space of memory. It remains to be seen to what extent Jeanne is here celebrated or betrayed.
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Maynard Smith, John, and Eors Szathmary. "Symbiosis." In The Major Transitions in Evolution. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780198502944.003.0015.
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The establishment of a permanent and obligate coexistence of genetic entities that were once capable of independent existence played an important part in the origin of the eukaryotes, and, if our earlier speculations are correct, in the origin of cells and chromosomes. In this chapter, we discuss other examples of symbiosis. The term is used to include all cases in which two or more different kinds of organism live in close association: thus it extends from parasitism to mutualism. Mutualism has been defined as a relationship from which both partners benefit. However, as will become clearer below, it is hard to measure, or even to define, ‘benefits’: in what sense is a mitochondrion today better off than its once free-living ancestors? The two questions that we shall ask are: • What are the selective force acting on the two partners in present-day symbioses? • Could such selective forces lead to the establishment of permanent and obligate coexistence? First, however, we review briefly some of the ecologically more important symbioses (for further examples, see Pirozynski & Hawksworth, 1988; Margulis & Fester, 1991). We mention only a fraction of the known mutualistic associations. Others, including cases of interaction between animals and prokaryotes, are discussed below. It is striking that symbiotic relationships have been important in the utilization by plants of nutrient-poor soils, the colonization of bare rock, life in deep-sea vents, the construction of coral reefs, and the utilization of plant material by several groups of insects. Sonea (1991; see also Sonea & Panisset, 1983) has pictured the world of bacteria as a single superorganism, whose individual component cells rely for their survival on ecological exchange of metabolites, and on genetic exchange via plasmids and phages. This picture has the virtue of emphasizing the important role played by plasmids and temperate phages in conferring on individual bacterial cells capacities needed in particular environments—for example, resistance to antibiotics, tolerance of heavy metals and new metabolic abilities. But the picture suffers from the drawback that is fatal to all holistic models of evolution, from the Gaia hypothesis downwards, of losing all sight of the units of selection, and hence of lacking any model of the dynamics of evolutionary change.
Conference papers on the topic "Vents de particules"
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Anderson, Kevin R., Christopher McNamara, and Ariel Gatti. "Analysis of a Multi-Cascade Methyl Linoleate / SCO2 / Transcritical CO2 / R-410A Refrigeration Cycle for Use in High Temperature High Pressure Environments." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65547.
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This paper presents the results of an analysis of a hybrid cascaded Methyl Linoleate / Supercritical (SCO2) / Transcritical CO2 / R-410A cycle for extreme environment refrigeration applications. The particular application of this cascaded CO2 refrigeration cycle stems from a space exploration application of a Venus lander mission. The payload of the Venus lander is subject an extremely harsh environment, i.e. the objective is to maintain a 1 cubic meter payload cavity at 35 °C, with dissipation of 500 W to an environmental temperature of 465 °C. Complicating the situation is the Venus local atmosphere is 9 MPa, and the atmosphere is mainly comprised of CO2 (95.5% by volume, 3.5% N2 by volume). Because this temperature is so high, to stay under the saturation dome we need some fairly exotic fluids to do a normal vapor compression system. Some of the only fluids with critical points allowing for this particular application are sulfuric acid and Fatty Acid Methyl Ester (FAME) type bio-diesels such as Methyl Linoleate (MLL). The actual heat rejection process and throttling processes are the primary challenges of this research topic. Results of a COP comparison and a lift curve are carried out in order to determine efficiency and guide feasibility of realizing the actual hardware to be used in the cycle.
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Zimmermann, H., A. Kammerer, R. Fischer, and D. Rebhan. "Two-Phase Flow Correlations in Air/Oil Systems of Aero Engines." In ASME 1991 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1991. http://dx.doi.org/10.1115/91-gt-054.
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A strategy is outlined on how to introduce two-phase flow correlations into air/oil system calculations for aero engines. The importance of two-phase flow effects is highlighted by demonstrating their particular significance for the high altitude performance of a vent system. For air/oil mixtures very little can be obtained from the literature and correlations derived from air/water test results have to be corrected. For critical flow conditions in restrictors an improved method is developed. Some test data obtained for air/oil mixtures show, that the proposed correlations agree fairly well. Furthermore, it is shown how numerical methods for this complex field of fluid dynamics can be used in the future by the example of phase demixing by centrifugal forces.
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Busam, S., J. Ebner, and S. Wittig. "An Experimental Study of Liquid Film Thickness in Annular Air/Oil Flow in a Vertical Pipe Using a Laser Focus Displacement Meter." In ASME Turbo Expo 2001: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/2001-gt-0116.
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The development of modern aero-engines is leading to increased pressure and temperature levels which makes increasing demands on the engines’ safety and reliability. In particular the vent-system of the bearing chambers located in the hot section of the engine represents a critical component in the design process due to the complex two-phase flow phenomena. The air/oil mixture that is discharged out of the bearing chambers has a strong influence on the overall pressure losses and it shows locally enhanced heat transfer where oil coking or oil fires with the risk of flashback into the bearing chamber can occur. In order to gain a deeper insight into the interacting flow of air and oil, a glass pipe test section with a inner tube diameter of 10 mm was integrated into the vent-line of the high speed bearing chamber test rig operated at the Institut für Thermische Strömungsmaschinen, University of Karlsruhe, Germany. Therewith, an experimental study of the oil film along the wall in vertical annular upflow was performed by use of a laser focus displacement meter. This instrument which was introduced by Takamasa et al. [1] allows accurate measurements of film thickness to be made in real time with a sensitivity of 2 microns and a datarate of 1.5 kilohertz. Comprehensive measurements were conducted at two locations of the pipe 320 mm apart in flow direction. A wide range of oil and air flow rates was examined to study their impact on the local film thickness. Both fluids were heated up to the same temperature of 70°C and 100 °C, respectively, to vary the oil viscosity by a factor of 2.
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Flouros, Michael. "Analytical and Numerical Simulation of the Two Phase Flow Heat Transfer in the Vent and Scavenge Pipes of the Clean Engine Demonstrator." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50130.
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Advanced aircraft engine development dictates high standards of reliability for the lubrication systems, not only in terms of the proper lubrication of the bearings and the gears, but also in terms of the removal of the large amounts of the generated heat. Heat is introduced both internally through the rotating hardware and externally through radiation, conduction and convection. In case where the bearing chamber is in close proximity to the engine’s hot section, the external heat flux may be significant. This is, for example, the case when oil pipes pass through the turbine struts and vanes on their way to the bearing chamber. There; the thermal impact is extremely high, not only because of the hot turbine gases flowing around the vanes, but also because of the hot cooling air which is ingested into the vanes. The impact of this excessive heat on the oil may lead to severe engine safety and reliability problems which can range from oil coking with blockage of the oil tubes to oil fires with loss of part integrity, damage or even failure of the engine. It is therefore of great importance that the oil system designer is capable of predicting the system’s functionality. As part of the European Research program EEFAE (Efficient and Environmentally Friendly Aero Engine), the project CLEAN (Component vaLidator for Environmentally-friendly Aero-eNngine) [1], [2] was initiated with the goal to develop future engine technologies. Within the scope of this program, MTU Aero Engines has designed the lubrication system and has initiated an investigation of the heat transfer in the scavenge and vent tubes passing through the high thermally loaded TCF (Turbine Center Frame). The objective was to evaluate analytical and numerical models for the heat transfer into the air and oil mixtures and benchmark them. Three analytical models were investigated. A model which was based on the assumption that the flow of air and oil is a homogeneous mixture which was applied on the scavenge flow. The other two models assumed annular two-phase flows and were applied on the vent flows. Additionally, the two phase flow in the scavenge and vent pipes was simulated numerically using the ANSYS CFX package. The evaluation of the models was accomplished with test data from the heavily instrumented test engine with special emphasis on the TCF. Both the analytical and the numerical models have demonstrated strengths and weaknesses. The homogeneous flow model correlation and the most recent correlation by Dr. Busam for vent flows have demonstrated very good agreement between test and computed results. On the other hand the numerical analysis produced remarkable results, however at the expense of significant modeling and computing efforts. This particular work is unique compared to published investigations since it was conducted in a real engine environment and not in a simulating rig. Nevertheless, research in two-phase flow heat transfer will continue in order mitigate any deficiencies and to further improve the correlations and the CFD tools.
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Flouros, Michael, Georgios Iatrou, Kyros Yakinthos, Francois Cottier, and Markus Hirschmann. "Two-Phase Flow Heat Transfer and Pressure Drop in Horizontal Scavenge Pipes in an Aero Engine." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25011.
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In modern aero engines the lubrication system plays a key role due to the demand for high reliability. Oil is used not only for the lubrication of bearings, gears or seals, but it also removes large amounts of the generated heat. Also, air from the compressor at elevated temperature is used for sealing the bearing chambers and additional heat is introduced into the oil through radiation, conduction and convection from the surroundings. The impact of excessive heat on the oil may lead to severe engine safety and reliability problems which can range from oil coking (carbon formation) to oil fires. Coking may lead to a gradual blockage of the oil tubes and subsequently increase the internal bearing chamber pressure. As a consequence, oil may migrate through the seals into the turbo machinery and cause contamination of the cabin air or ignite and cause failure of the engine. It is therefore very important for the oil system designer to be capable to predict the system’s functionality. Coking or oil ignition may occur not only inside the bearing chamber but also in the oil pipes which carry away the air and oil mixture from the bearing chamber. Bearing chambers usually have one pipe (vent pipe) at the top of the chamber and also one pipe (scavenge pipe) at the bottom which is attached to a scavenge pump. The vent pipe enables most of the sealing air to escape thus avoid over-pressurization in the bearing compartment. In a bearing chamber sealing air is the dominant medium in terms of volume occupation and also the in terms of causing expansion phenomena. The scavenge pipe carries away most of the oil from the bearing chamber but some air is also carried away. The heat transfer in vent pipes was investigated by Busam [1], [2]. Busam has experimentally developed a Nusselt number correlation for an annular flow in a vent pipe. For the heat transfer predictions in scavenge pipes no particular Nusselt number correlation exist. This paper intends to close the gap in this area. As part of the European Union funded research programme ELUBSYS (Engine LUBrication System TechnologieS), an attempt was done to simplify the oil system’s architecture. In order to better understand the flow in scavenge pipes, high speed video was taken in two sections of the pipe (vertical and horizontal). In the vertical section the flow was a wavy annular falling film whereas the flow in the horizontal section was a an unsteady wavy stratified/slug flow. Heat transfer has been investigated in the horizontal section of the scavenge pipe, leaving the investigation on the vertical section for later. Thanks to the provided extensive instrumentation, the thermal field in, on and around the pipe was recorded, evaluated and also numerically modeled using ANSYS CFX version 14 [23]. Brand new correlations for two-phase flow heat transfer (Nusselt number) and for pressure drop (friction coefficient) in horizontal scavenge pipes are the result of this work. The Nusselt number correlation has been developed in such a way that smooth transition (i.e. no discontinuity) from two-phase into single phase flow is observed. This work was funded and conducted within the 7th EU Frame Programme for Aeronautics and Transport (AAT.2008.4.2.3).
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Kruger, Sunita, and Leon Pretorius. "The Effect of Bench Arrangements on the Natural Ventilation of a Multispan Greenhouse." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63304.
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In this paper, the influence of various bench arrangements on the microclimate inside a two-span greenhouse is numerically investigated using three-dimensional Computational Fluid Dynamics (CFD) models. Longitudinal and peninsular arrangements are investigated for both leeward and windward opened roof ventilators. The velocity and temperature distributions at plant level (1m) were of particular interest. The research in this paper is an extension of two-dimensional work conducted previously [1]. Results indicate that bench layouts inside the greenhouse have a significant effect on the microclimate at plant level. It was found that vent opening direction (leeward or windward) influences the velocity and temperature distributions at plant level noticeably. Results also indicated that in general, the leeward facing greenhouses containing either type of bench arrangement exhibit a lower velocity distribution at plant level compared to windward facing greenhouses. The latter type of greenhouses has regions with relatively high velocities at plant level which could cause some concern. The scalar plots indicate that more stagnant areas of low velocity appear for the leeward facing greenhouses. The windward facing greenhouses also display more heterogeneity at plant level as far as temperature is concerned.
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Marwah, Manish, Ratnesh K. Sharma, and Wilfredo Lugo. "Autonomous Detection of Thermal Anomalies in Data Centers." In ASME 2009 InterPACK Conference collocated with the ASME 2009 Summer Heat Transfer Conference and the ASME 2009 3rd International Conference on Energy Sustainability. ASMEDC, 2009. http://dx.doi.org/10.1115/interpack2009-89140.
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In recent years, there has been a significant growth in number, size and power densities of data centers. A significant part of data center power consumption is attributed to the cooling infrastructure, consisting of computer air conditioning units (CRACs), chillers and cooling towers. For energy efficient operation and management of the cooling resources, data centers are beginning to be extensively instrumented with temperature sensors. While this allows cooling actuators, such as CRAC set point temperature, to be dynamically controlled and data centers operated at higher temperatures to save energy, it also increases chances of thermal anomalies. Furthermore, considering that large data centers can contain thousands to tens of thousands of such sensors, it is virtually impossible to manually inspect and analyze the large volumes of dynamic data generated by these sensors, thus necessitating autonomous mechanisms for thermal anomaly detection. Also, in addition to threshold-based detection methods, other mechanisms of anomaly detection are also necessary. In this paper, we describe the commonly occurring thermal anomalies in a data center. Furthermore, we describe — with examples from a production data center — techniques to autonomously detect these anomalies. In particular, we show the usefulness of a principal component analysis (PCA) based methodology to a large temperature sensor network. Specifically, we examine thermal anomalies such as those related to misconfiguration of equipment, blocked vent tiles, faulty sensor and CRAC related anomalies. Furthermore, several of these anomalies normally go undetected since no temperature thresholds are violated. We present examples of the thermal anomalies and their detection from a real data center.
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Itani, Mariam, Nesreen Ghaddar, Kamel Ghali, Beatrice Khater, Djamel Ouahrani, and Walid Chakroun. "Experimental Study on Effective Placement of PCM Packets in Cooling Vest to Improve Performance in Warm Environment." In ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ht2017-4756.
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Global warming has increased the risk of heat stress of outdoor workers and one measure against heat stress is wearing passive personal cooling clothing. Passive body cooling systems, including phase change material (PCM) cooling vests, are considered as an effective solution to improve the working endurance of outdoor active workers. The objective of this study is to assess the effective placement of PCM packets in the cooling vest by examining the local and overall sensation and comfort when: (i) only the frontal segment of the human torso is covered (ii) only the back segment of the human torso is covered and (iii) both segments are covered. The PCM cooling vest is worn by human subjects performing cycling at about 3 Mets and for 30 minutes in a climatic chamber maintained at 28 °C and 60 % relative humidity. The used PCM melting temperature is 28 °C with a coverage area of 642 cm2 and total weight of the vest of 1.19 kg including 8 PCM packets (87.5 grams each). The physiological/thermal responses such as body core and mean skin temperatures, heart rate, and skin wittedness are monitored during the experiments while exercising and wearing the vest. In particular, the frontal and back torso skin temperatures are examined after being subjected to local cooling compared to the case when no PCM packets cover the torso segment. Moreover, subjective votes of thermal comfort, whole body and torso thermal sensations, skin and clothing wetness sensation and perceived exertion are recorded throughout the experiment. The experiment was repeated on five male subjects to ensure robustness of the obtained results. It was found that the core temperature changed slightly when wearing the vest, however the local skin temperature of the back and front torso segments decreased by about 5 °C and 3 °C at the end of the exercise, respectively. Gradual improvement in comfort that reaches a stable level when the PCM starts melting till the end of the exercise was also noticed.
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Islam, A. K. M. Sadrul, M. Ruhul Amin, Shama F. Barna, Arafat A. Bhuiyan, and M. H. Banna. "Mixed Convection and Entropy Generation Characteristics Inside a Porous Cavity With Viscous Dissipation Effect." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-10883.
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This paper examines and explains two-dimensional, steady mixed convection flow in a porous square vented cavity. The interaction between the buoyancy stemming from one or more heated elements inside a microstructure filled vented enclosure and an imposed forced flow forms the topic of this investigation. Analysis has been carried out for two different boundary conditions. Initial investigations are carried out for walls of the enclosure being isothermal. A second stage of analysis is performed keeping only the left wall isothermal and other three walls adiabatic. Natural convection takes place due to temperature difference between the isothermal wall and the fluid. Forced convection condition is imposed by providing an inlet and a square vent inside the enclosure filled with fluid saturated porous medium. The mathematical model is developed using modified Darcy flow model and energy equation. Through the adaptation of the well known finite element method, solution to this numerical problem is obtained. Governing parameters chosen are Peclet Number (Pe), Rayleigh Number (Ra), Aspect ratio (AR) and the width of the inlet as a fraction of the width (I/W) of the enclosure. For detailed analysis different value of these parameters such as five Rayleigh Numbers (1, 50, 100, 500 and 1000) and seven different Peclet Numbers (0.1, 1, 5, 10, 20, 50 and 100) are considered. Effect of inlet to cavity width ratio is examined within the range 0.1 ≤ I/W ≤ 0.5 for a particular aspect ratio. The performance of the enclosure in both cases; are determined by flow visualization and by analyzing different parameters such as Bejan Number, Nusselt Number and Entropy Generation Number. Isotherms, streamlines show substantial variation in their pattern or magnitude. Average Nusselt number and average Bejan Number increases whereas Average energy flux density decreases with increasing I/W. These fluctuations also vary for different Rayleigh or Peclet numbers. The results for both the boundary conditions are also compared to find the most effective value of I/W.
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Aidarinis, J., D. Missirlis, K. Yakinthos, and A. Goulas. "CFD Modelling and LDA Measurements for the Air-Flow in an Aero-Engine Front Bearing Chamber." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23294.
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The constant development of aero engines towards lighter but yet more compact designs, without decreasing their efficiency, has led to gradually increased demands of the lubrication systems, such as the bearing chambers of the aero engine. For this reason, it is of particular importance to increase our level of understanding of the flow field inside the bearing chambers in order to optimize its design and performance. The flow field in such cases is of a complicated nature since there is a strong interaction between air-flow and lubricant oil together with the geometrical configurations and the shaft rotational speed inside the bearing chamber. The behavior of this interaction must be investigated in order to understand the flow field development inside the aero engine bearing and, at a next step, optimize its performance in relation to the lubrication and heat transfer capabilities. Such an effort is presented in this work where an investigation of the air-flow field development inside the front bearing chamber of an aero engine is attempted. The front bearing chamber is divided in two separate smaller sections where the flow passes from the first section partially through the bearing and the holding structure, to the second one where the vent and the scavenge are placed. The investigation was performed with the combined use of experimental measurements and Computational Fluid Dynamics (CFD) modeling. The experimental measurements were carried out with the use of a Laser Doppler Anemometry (LDA) system in an experimental rig modeling the front bearing chamber of an aero engine for real operating conditions taking into account both air-flow and lubricant oil-flow and for a varying number of shaft rotating speeds. The CFD modeling was performed with the use of a commercial CFD package. The air-flow inside the bearing was modeled with the adoption of a porous medium assumption. The experimental measurements and the CFD computations presented similar flow patterns and satisfactory quantitative agreement. At the same time the effect of the important parameters such as the air and oil mass flow together with the shaft rotation speed and the effect of the chamber inside geometry were identified. These conclusions can be exploited in future attempts in combination with the developed CFD model, in order to optimize the efficiency of the lubricant and cooling system. The latter forms the main target of this work which is the development of a useful engineering tool capable of predicting the flow field inside the aero engine bearing so as to be used for optimization efforts.
Reports on the topic "Vents de particules"
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Reporte de la situación del microcrédito en Colombia - Septiembre de 2020. Banco de la República de Colombia, October 2020. http://dx.doi.org/10.32468/rept-sit-micr-cred.tr3-2020.
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En este reporte se exponen los resultados de la Encuesta sobre la situación actual del microcrédito en Colombia del segundo trimestre de 2020. Esta encuesta fue diseñada por el Departamento de Estabilidad Financiera del Banco de la República, junto con Asomicrofinanzas, con el fin de conocer la percepción que tienen las entidades que realizan actividades de intermediación de microcrédito, incluyendo las que no son supervisadas por la Superintendencia Financiera de Colombia (SFC). Los objetivos de esta encuesta son indagar acerca del cambio en la percepción de oferta y demanda del mercado de microcrédito, la evolución de las políticas de asignación y evaluar, en particular, el riesgo de crédito de las entidades. De igual forma, se indaga sobre la frecuencia de prácticas relacionadas con reestructuraciones de microcrédito, venta de cartera y castigo de las deudas vencidas. Por último, se presentan los resultados de las preguntas de coyuntura que, para esta versión de la encuesta, continúan analizando la evolución de las medidas adoptadas por las entidades microcrediticias para hacer frente a la crisis sanitaria y, adicionalmente, pretenden evaluar el impacto de dichas medidas sobre el manejo del riesgo de crédito.
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Reporte de la situación del microcrédito en Colombia - Marzo de 2021. Banco de la República, April 2021. http://dx.doi.org/10.32468/rept-sit-micr-cred.tr1-2021.
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En este reporte se exponen los resultados de la Encuesta sobre la situación actual del microcrédito en Colombia del primer trimestre de 2021. Esta encuesta fue diseñada por el Departamento de Estabilidad Financiera del Banco de la República, junto con Asomicrofinanzas, con el fin de conocer la percepción que tienen las entidades que realizan actividades de intermediación de microcrédito, incluyendo las que no son supervisadas por la Superintendencia Financiera de Colombia (SFC). Los objetivos de esta encuesta son indagar acerca del cambio en la percepción de oferta y demanda del mercado de microcrédito, la evolución de las políticas de asignación y evaluar, en particular, el riesgo de crédito de las entidades. De igual forma, se indaga sobre la frecuencia de prácticas relacionadas con reestructuraciones de microcrédito, venta de cartera y castigo de las deudas vencidas. Por último, se presentan los resultados de las preguntas de coyuntura que, para esta versión de la encuesta, continúan analizando la evolución de las medidas adoptadas por las entidades microcrediticias para hacer frente a la crisis sanitaria, evalúan el impacto de dichas medidas sobre el manejo del riesgo de crédito e indagan sobre la implementación y uso de canales digitales en este tipo de entidades crediticias
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Reporte de la situación del microcrédito en Colombia - Junio de 2021. Banco de la República, August 2021. http://dx.doi.org/10.32468/rept-sit-micr-cred.tr2-2021.
Full textAbstract:
En este reporte se exponen los resultados de la Encuesta sobre la situación actual del microcrédito en Colombia del segundo trimestre de 2021. Esta encuesta fue diseñada por el Departamento de Estabilidad Financiera del Banco de la República, junto con Asomicrofinanzas, con el fin de conocer la percepción que tienen las entidades que realizan actividades de intermediación de microcrédito, incluyendo las que no son supervisadas por la Superintendencia Financiera de Colombia (SFC). Los objetivos de esta encuesta son indagar acerca del cambio en la percepción de oferta y demanda del mercado de microcrédito, la evolución de las políticas de asignación y evaluar, en particular, el riesgo de crédito de las entidades. De igual forma, se indaga sobre la frecuencia de prácticas relacionadas con reestructuraciones de microcrédito, venta de cartera y castigo de las deudas vencidas. Por último, se presentan los resultados de las preguntas de coyuntura que, para esta versión de la encuesta, continúan analizando la evolución de las medidas adoptadas por las entidades microcrediticias para hacer frente a la crisis sanitaria, evalúan el impacto de dichas medidas sobre el manejo del riesgo de crédito e indagan sobre el flujo de nuevos microcréditos tanto a nivel agregado como en cada sector productivo de este tipo de entidades crediticias.
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Reporte de la situación del microcrédito en Colombia - Diciembre de 2020. Banco de la República de Colombia, February 2021. http://dx.doi.org/10.32468/rept-sit-micr-cred.tr4-2020.
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En este reporte se exponen los resultados de la Encuesta sobre la situación actual del microcrédito en Colombia del cuarto trimestre de 2020. Esta encuesta fue diseñada por el Departamento de Estabilidad Financiera del Banco de la República, junto con Asomicrofinanzas, con el fin de conocer la percepción que tienen las entidades que realizan actividades de intermediación de microcrédito, incluyendo las que no son supervisadas por la Superintendencia Financiera de Colombia (SFC). Los objetivos de esta encuesta son indagar acerca del cambio en la percepción de oferta y demanda del mercado de microcrédito, la evolución de las políticas de asignación y evaluar, en particular, el riesgo de crédito de las entidades. De igual forma, se indaga sobre la frecuencia de prácticas relacionadas con reestructuraciones de microcrédito, venta de cartera y castigo de las deudas vencidas. Por último, se presentan los resultados de las preguntas de coyuntura que, para esta versión de la encuesta, continúan analizando la evolución de las medidas adoptadas por las entidades microcrediticias para hacer frente a la crisis sanitaria, evalúan el impacto de dichas medidas sobre el manejo del riesgo de crédito, inquieren sobre los retos que las microfinancieras perciben que enfrentarán en 2021 para incentivar la recuperación del tejido microempresarial del país, e indagan sobre la implementación y uso de canales digitales en este tipo de entidades crediticias.