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Sample records for convection naturelle le

  1. 1 Étude numérique de la convection naturelle tridimensionnelle ...

    African Journals Online (AJOL)

    TOSHIBA

    naturelle thermique laminaire de type couche limite au voisinage d'un cône à surface lisse. Bapuji et al. [2] ont étudié le courant de la convection naturelle laminaire instable avec un cône vertical isotherme. Pop et. Tsung Yen [3] ont étudié les effets de la compressibilité dans la convection naturelle laminaire autour d'un.

  2. Etude numérique de la convection naturelle dans une enceinte ...

    African Journals Online (AJOL)

    Mots-clés: convection naturelle, chaos, méthode de Lattice Boltzmann, methode des différences finies. Numerical Study of natural convection in an inclined enclosure. Lattice Boltzmann Method (LBM ) , Finite Difference Explicit ( DFE ) , Hybrid combines the two previous methods and Finite Elements (FE) are used to study ...

  3. Natural convection between parallel vertical plates; Convection naturelle entre plaques paralleles verticales

    Energy Technology Data Exchange (ETDEWEB)

    Robin, M; Schwab, B [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    In the thermal study of a 'swimming-pool' type of pile, the flow of water between vertical plates of 'combustible' material must be investigated. Therefore starting from general equations of natural convection, we have determined, the law of distribution of velocities, then that of temperatures, and finally the value of the Biot-Nusselt number, assuming steady-state conditions (both dynamic and thermal) and a constant heat flow at the surface. An abacus (fig. 7, 8 and 9) allows working power to be related to the average velocity and to the heating of the water which passes through the pile. For purposes of comparison, the curves on the calculation presented by S. GLASSTONE (31) have been drawn. (author) [French] L'etude thermique d'une pile du type 'piscine' necessite l'etude de l'ecoulement de l'eau entre les plaques verticales de materiau 'combustible'. Nous avons donc, a partir des equations generales de la convection naturelle, determine la loi de repartition des vitesses, puis celle des temperatures et enfin la valeur du nombre de Biot-Niisselt, en supposant les regimes, dynamique et thermique, etablis et la densite de flux calorifique a la paroi constante. Un abaque (fig. 7, 8 et 9) permet de relier a la puissance de fonctionnement, la vitesse moyenne de l'echauffement de l'eau qui traverse la pile. On a trace a titre de comparaison, les courbes du calcul presente par S. GLASSTONE (3). (auteur)

  4. Gestion communautaire des ressources naturelles dans le Parc ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    En 2002, le Mozambique, l'Afrique du Sud et le Zimbabwe ont signé un accord établissant le Parc transfrontalier du Grand Limpopo (Greater Limpopo Trans Frontier Conservation Area), qui relie entre eux des parcs nationaux des trois pays et un ensemble de terres relevant pour la plupart de régimes fonciers communaux.

  5. Dynamique des ressources naturelles dans le Parc national de Manda: Cartographie et analyse pour le Développement durable

    Science.gov (United States)

    Ballah Solkam, Rosalie; Médard, Ndoutorlengar

    2018-05-01

    Au Tchad, le réseau d'aires protégées couvre près de 10,2% de la surface du pays et reste globalement représentatif de toute la diversité des écosystèmes de la région. Cependant, ce réseau n'est pas constitué d'écosystèmes intacts car de nombreuses altérations y ont été apportés (certaines espèces sont déjà au seuil critique d'extinction (Addax, gazelle dama, lamantin), voire ont disparu (Rhinocéros noir et blanc, Oryx)) surtout dans les parcs nationaux. Ce qui nous amène à nous interroger sur la dynamique des ressources naturelles et le degré de conservation du parc national de Manda? Une évaluation de la diversité biologique et des ressources hydrographiques de 1951 à 1999 sur la base de la bibliographie existante, de la carte topographique de 1956, des images satellitaires Landsat 5 et 7 TM et ETM+ de 2 périodes (1986, 1999), complétée par des interviews semi-structurés et des transects sur le terrain, permettra de mieux appréhender la dynamique des ressources et les actions de conservation de la biodiversité réalisées à cet effet. Les résultats montrent une dynamique progressive de la faune de 1951 à 1970, puis une dynamique régressive de 1970 à 1989. Après cette tumultueuse période, un repeuplement du parc s'opère de 1989 à 2002. Par contre, la flore est relativement bien conservée avec quelques cours d'eau, des mares, champs et plantations. Et cela grâce aux multiples projets de conservation de la biodiversité. La promotion de l'écotourisme serait une alternative au développement durable de ce parc.

  6. Natural convection in an uniformly heated vertical channel with rectangular cross section (1962); Convection naturelle dans un canal vertical de section rectangulaire chauffe uniformement (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Vernier, Ph [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1962-07-01

    The study is experimental and theoretical. The theory is only for fully developed laminar flow. The experimental study is made with water at low temperature. The uniform heat flux varies from 0 to 16 000 BTU/hr ft{sup 2} and the distance between the heated plates from 0.2 to 0.48 inches. The experimental correlations give the mean velocity and the temperature rise of the water, the Nusselt number versus the Rayleigh number. Experience and theory agree well for heat fluxes sufficiently low. Using a special apparatus, one measures the velocity and temperature profiles between the plates and finds interesting results on the flow properties. The profiles show that the flow is not fully developed and not a Poiseuille flow. (author) [French] L'etude est theorique et experimentale. La theorie ne traite que le cas des ecoulements laminaires completement developpes. Pour toute l'etude experimentale le fluide est de l'eau a la temperature ambiante. La densite de flux de chaleur uniforme a varie entre 0 et 5 W/cm{sup 2} tandis que l'espace compris entre les deux parois chauffantes a varie entre 5 et 12 mm. On obtient des correlations empiriques qui permettent de connaitre la vitesse moyenne et rechauffement de l'eau, ainsi que le nombre de Nusselt en fonction du nombre de Rayleigh. La correspondance entre theorie et experience est assez bonne pour des puissances de chauffage suffisamment faibles. La mesure, faite a l'aide d'une sonde speciale, des profils des vitesses et des temperatures a la sortie du canal donne des renseignements interessants sur les proprietes de l'ecoulement. Ces profils montrent notamment que l'ecoulement n'est pas developpe et ne s'effectue pas 'a la Poiseuille'. (auteur)

  7. Le changement comme tradition dans la recherche et la formation a la recherche en biotechnologie et en peripherie Etude de cas en sciences de la sante, sciences naturelles et genie

    Science.gov (United States)

    Bourque, Claude Julie

    Le champ de la recherche scientifique et de la formation a la recherche est traverse depuis quelques dizaines d'annees par plusieurs courants et discours associes au changement, mais peu de travaux empiriques permettent de comprendre ce qui change concretement. C'est la contribution originale de cette these au champ de l'education, plus specifiquement a l'etude sociologique de l'enseignement superieur ou sont concentrees les activites liees a la triade thematique du programme doctoral dans lequel elle a ete produite : recherche, formation et pratique. L'enquete-terrain a ete realisee en 2009 et 2010 aupres de 808 repondants affilies a 60 etablissements au Quebec et a produit un vaste materiau de nature mixte (donnees quantitatives et qualitatives). Un portrait de la nebuleuse biotechnologique qui touche les secteurs des sciences de la sante, des sciences naturelles et du genie a ete realise. Ce domaine concerne des dizaines de disciplines et se revele de nature transdisciplinaire, mais les pratiques n'y sont pas davantage marquees par le changement que celles d'autres domaines connexes. Les dynamiques sociales ont fait l'objet d'analyses comparatives dans quatre contextes: le choix des programmes, des objets et des methodes, le financement, la diffusion et la planification de la carriere. Les resultats indiquent que les echanges entre les agents traditionnellement situes au coeur des activites de recherche dominent ces dynamiques dans tous les contextes etudies. L'etude des representations au fondement des pratiques a revele l'existence de trois ecoles de pensee qui coexistent dans le champ scientifique: academique, pragmatique et economiste. Ces ecoles permettent de categoriser les agents en fonction des zones de fractures qui marquent leurs oppositions tout en identifiant ce qu'ils ont en commun. Les representations et les pratiques liees a la formation temoignent d'un habitus plutot homogene, alors que les contradictions semblent plus souvent ancrees dans des

  8. Regeneration naturelle des especes ligneuses dans la foret de Ngotto

    African Journals Online (AJOL)

    Republique Centrafricaine). OD Yongo, J Kassin'dja, MS Tiebre, B de Foucault. Abstract. L'étude envisagée a pour objectif d'analyser le potentiel de la régénération naturelle des espèces ligneuses de la forêt de Ngotto (République Centrafricaine).

  9. L'hybridation dans les populations naturelles de salmonidés dans le Sud-Ouest de l'Europe et en milieu expérimental

    Directory of Open Access Journals (Sweden)

    BEALL E.

    1997-01-01

    Full Text Available L'hybridation interspécifique entre le saumon atlantique et la truite commune dans la nature a été mise en évidence dans différents pays d'Europe et au Canada. Une étude a été entreprise pour examiner son incidence dans des populations de salmonidés de certaines rivières des Asturies (nord de l'Espagne et du sud-ouest de la France. Elle a été complétée par des expériences en milieu contrôlé pour déterminer les causes et les conditions de la disparition des barrières comportementales permettant le maintien de l'isolement reproducteur. Les hypothèses de travail étaient que l'hybridation pouvait être favorisée par le comportement de «sneaker» des tacons mâles précoces et par les repeuplements en juvéniles des deux espèces. Les résultats obtenus confirment que l'hybridation entre la truite et le saumon est un phénomène répandu, qui peut affecter localement des fractions significatives des populations (9,4 % sur la rivière Narcea dans les Asturies. Dans l'aire originelle de distribution des deux espèces, le croisement s'effectue dans le sens femelle saumon x mâle truite. Dans les conditions normales de sympatrie, les barrières d'isolement reproducteur pré-appariement paraissent solides en raison du comportement agressif du mâle conspécifique dominant qui parvient à écarter efficacement les mâles compétiteurs hétérospécifiques. En l'absence de mâle conspécifique, l'hybridation peut avoir lieu. Cependant, les femelles modifient leur comportement, ralentissent leur activité de frai et le succès reproducteur, particulièrement chez la truite, diminue. Par ailleurs, les hypothèses de travail ne sont pas vérifiées. Pour éviter l'hybridation, il est recommandé au gestionnaire de veiller à la qualité et à la quantité des zones de reproduction, de maintenir l'équilibre des populations de géniteurs et de limiter les repeuplements en sujets non autochtones.

  10. Intelligence Naturelle et Intelligence Artificielle

    OpenAIRE

    Dubois, Daniel

    2011-01-01

    Cet article présente une approche systémique du concept d’intelligence naturelle en ayant pour objectif de créer une intelligence artificielle. Ainsi, l’intelligence naturelle, humaine et animale non-humaine, est une fonction composée de facultés permettant de connaître et de comprendre. De plus, l'intelligence naturelle reste indissociable de la structure, à savoir les organes du cerveau et du corps. La tentation est grande de doter les systèmes informatiques d’une intelligence artificielle ...

  11. L'influence d'un stage d'enseignement dans un musee de sciences naturelles sur le sentiment d'autoefficacite en sciences de futurs enseignants

    Science.gov (United States)

    Deblois, Annick

    Cette etude qualitative multicas est ancree dans l'approche sociale-cognitive de la theorie de l'autoefficacite de Bandura (1977). Elle s'interesse a quatre stages a l'enseignement qui se sont deroules au Musee canadien de la nature a Ottawa, Canada, en 2009. L'utilisation de donnees secondaires issues du questionnaire STEBI-B traduit et modifie (Dionne et Couture, 2010) ainsi que des entrevues semi-dirigees ont permis une analyse du changement du sentiment d'autoefficacite en sciences chez les stagiaires. Les elements les plus interessants de cette recherche sont l'apprentissage vicariant et la possibilite de repetition qui favorise une meilleure connaissance de soi et une pratique reflexive. Les resultats, dans l'ensemble positifs, illustrent bien le potentiel d'un tel stage afin de rehausser le sentiment d'autoefficacite en sciences chez des stagiaires en enseignement, particulierement chez ceux qui se destinent a enseigner a l'elementaire puisque ceux-ci ont souvent une formation academique dans un domaine autre que les sciences.

  12. L'hybridation dans les populations naturelles de salmonidés dans le Sud-Ouest de l'Europe et en milieu expérimental

    OpenAIRE

    BEALL E.; MORAN P.; PENDAS A.; IZQUIERDO J.; GARCIA VAZQUEZ E.; GLISE S.; VIGNES J. C.; BARRIERE L.

    1997-01-01

    L'hybridation interspécifique entre le saumon atlantique et la truite commune dans la nature a été mise en évidence dans différents pays d'Europe et au Canada. Une étude a été entreprise pour examiner son incidence dans des populations de salmonidés de certaines rivières des Asturies (nord de l'Espagne) et du sud-ouest de la France. Elle a été complétée par des expériences en milieu contrôlé pour déterminer les causes et les conditions de la disparition des barrières comportementales permetta...

  13. Direct numerical simulation and modeling of turbulent natural convection in a vertical differentially heated slot; Simulation numerique directe et modelisation de la convection naturelle turbulente dans un canal differentiellement chauffe

    Energy Technology Data Exchange (ETDEWEB)

    Boudjemadi, R.

    1996-03-01

    The main objectives of this thesis are the direct numerical simulation of natural convection in a vertical differentially heated slot and the improvements of second-order turbulence modelling. A three-dimensional direct numerical simulation code has been developed in order to gain a better understanding of turbulence properties in natural convection flows. This code has been validated in several physical configurations: non-stratified natural convection flows (conduction solution), stratified natural convection flows (double boundary layer solution), transitional and turbulent Poiseuille flows. For the conduction solution, the turbulent regime was reached at a Rayleigh number of 1*10{sup 5} and 5.4*10{sup 5}. A detailed analysis of these results has revealed the principal qualities of the available models but has also pointed our their shortcomings. This data base has been used in order to improve the triple correlations transport models and to select the turbulent time scales suitable for such flows. (author). 122 refs., figs., tabs., 4 appends.

  14. Gestion communautaire des ressources naturelles au Bénin (Afrique de l’Ouest : le cas de la vallée du Sitatunga

    Directory of Open Access Journals (Sweden)

    Pricette Dovonou-Vinagbè

    2009-09-01

    Full Text Available Le Bénin, pays de l’Afrique de l’Ouest est confronté à la destruction des terres humides particulièrement dans la partie sud du pays. Les terres humides riches biodiversité sont importantes tant pour les humains que pour milieu naturel. La menace la plus importante est la pression du anthropique. Même si ce territoire est reconnu par la Convention Ramsar, la destruction continue. En 1995 le gouvernement a décidé de créer une aire de gestion communautaire pour ces territoires. L’objectif de  cette recherche est de comprendre les grands défis liés à la mise en œuvre de la gestion communautaire des milieux humides à travers une étude de cas, en l’occurrence celui de la vallée du Sitatunga. Pour atteindre cet objectif, un séjour de 3 mois a été effectué sur le site. Des entrevues semi-dirigées ont été alors réalisées. Les résultats montrent que la vallée du Sitatunga est considérée comme inutile voire nuisible par les populations riveraines rencontrées dans le cadre de l’étude, qui sont davantage préoccupées à se sortir de leur état de pauvreté. Les traditions et valeurs autrefois attribuées à la conservation des milieux humides ont quasiment disparues et l’individualisme est grandissant. Il importe de tenir compte de tous ces facteurs pour espérer véritablement préserver ces milieux. D’un autre côté, parlant de gestion de l’environnement et plus particulièrement de gestion des milieux humides à l’échelle béninoise, le constat n’est pas reluisant. En effet, l’État étant donné son état de sous-développement et donc de manque de ressources, à du mal à coordonner ces activités. Il est de même pour les ONG. La situation est accentuée par l’état des relations entre ONG et structures de l’État qui se considèrent davantage comme des adversaires que comme des partenaires ce qui affecte l’efficacité des activités menées. Pour que la gestion communautaire devienne une

  15. Vers une narratologie naturelle de la musique

    Directory of Open Access Journals (Sweden)

    Nicolas Marty

    2011-12-01

    Full Text Available Grâce à l’étude du modèle de la narratologie « naturelle » de Monika Fludernik, nous souhaitons montrer qu’il est possible d’envisager une narratologie « naturelle » de la musique, prenant en compte tous les phénomènes sémiotiques, sémantiques et narratifs présents dans l’écoute de la musique. Nous ouvrons de plus la question de la différence observable entre les « narrativisations » opérées par les musiciens experts et celles opérées par les non-experts.Following Monika Fludernik’s frame for a “natural” narratology, we wish to demonstrate that it is in fact possible to think of “natural” narratology for music, which would consider every semiotic, semantic and narrative phenomenon found in the listening of music. We then open the question of the apparent difference between music experts’ and non-experts’ “narrativizations”.

  16. Effet de la combinaison de la chaux et de la pouzzolane naturelle sur le compactage et la résistance des sols mous argileux Effect of the combination of lime and natural pozzolana on the compaction and strength of soft clayey soils

    Directory of Open Access Journals (Sweden)

    Kenai S.

    2012-09-01

    Full Text Available La stabilisation des sols mous a été pratiquée longtemps en mélangeant des ajouts, tels que le ciment, la chaux et les cendres volantes au sol pour augmenter sa résistance. Cependant, il y a un manque d’investigations sur l’utilisation de la pouzzolane naturelle seule ou combinée avec la chaux pour les applications d’amélioration des sols. Un programme expérimental a été entrepris pour étudier l’effet de la chaux, la pouzzolane naturelle ou leur combinaison sur les caractéristiques géotechniques des sols mous. La chaux ou la pouzzolane naturelle ont été ajoutées aux sols par des teneurs de 0-10% et 0-20% respectivement. Les échantillons préparés ont été soumis aux essais de compactage et de résistance à la compression non confinée. Les échantillons ont subis des périodes de cure de 1, 7, 28 et 90 jours après quoi ils ont été soumis aux essais de la résistance à la compression non confinée. Basé sur les résultats favorables obtenus, ilpeut être conclu que les sols mous argileux peuvent être stabilisés avec succès par l’action combinée de la chaux et de la pouzzolane naturelle. Puisque la pouzzolane naturelle est beaucoup moins chère que la chaux, l’addition de la pouzzolane naturelle dans le mélange chaux-sol peut en particulier devenir attirante et avoir comme conséquence une réduction des coûts de la construction. Soft soil stabilization has been practiced for quite some time by mixing additives, such as cement, lime and fly ash to the soil to increase its strength. However, there is a lack of investigations on the use of natural pozzolana alone or combined with lime for ground improvement applications. An experimental program was undertaken to study the effect of using lime, natural pozzolana or a combination of both on the geotechnical characteristics of soft soils. Lime or natural pozzolana was added to soft soils at ranges of 0-10% and 0-20%, respectively. In addition, combinations of

  17. Le séchage combiné convection-micro-ondes : modelisation-validation-optimisation

    OpenAIRE

    Constant , Thiéry

    1992-01-01

    Not available; Ce travail est consacré à l'étude du séchage combiné convection-micro-ondes, le matériau choisi pour l'étude étant un béton cellulaire. Il comporte une partie théorique et une partie expérimentale. D’un point de vue théorique, deux points sont plus particulièrement discutés: la formulation du terme source volumique d'énergie et la modélisation des transferts de chaleur et de masse avec prise en compte du gradient de pression totale de la phase gazeuse. D’un point de vue expérim...

  18. La cogestion des Ressources naturelles

    International Development Research Centre (IDRC) Digital Library (Canada)

    L'eau, le sol, les nutriments, la lumière du soleil — ce sont des choses de la vie. .... habitent encore ces régions, soit de 9 % à 14 % de la population mondiale. ...... La guerre civile a fait vivre au Cambodge des années de chaos, d'anarchie et ...... et les allégeances politiques sont des facteurs qu'il est impossible d'ignorer.

  19. Movement of Radioactive Effluents in Natural Waters at Hanford; Le Mouvement des Effluents Radioactifs dans les Eaux Naturelles a Hanford; 0414 0412 0418 0416 0414 ; Movimiento de los Efluentes Radiactivos en Aguas Naturales en Hanford

    Energy Technology Data Exchange (ETDEWEB)

    Honstead, J. F.; Foster, R. F.; Bierschenk, W. H. [Hanford Laboratories Operation, Hanford Atomic Products Operation, General Electric Company, Richland, WA (United States)

    1960-07-01

    ) [French] L'installation de Hanford se trouve dans une region semi-aride-de sediments non consolides en couche tres epaisse, qui ont ete deposes par les eaux et reposent sur un lit rocheux basaltique. Ces roches forment deux couches geologiques, la couche inferieure etant beaucoup moins permeable que la couche superieure. La Columbia traverse les terrains de l'installation et ce n'est qu'a environ 55 kilometres en aval du dernier reacteur qu'on commence a utiliser les eaux pour la consommation humaine. Les effluents de faible intensite provenant des reacteurs sont evacues dans la Columbia apres un sejour d'une a trqis heuges dans des reservoirs. Dans les effluents, on a pu identifier plus de 60 radioisotopes, qui, pour la plupart, ont y une tres courte periode. On a observe l'appauvrissement de l'eau fluviale en plusieurs radioisotopes par suite de mecanismes autres que la desintegration. Cet appauvrissement atteint 40% en moyenne sur les 55 kilometres qui separent les reacteurs et Pasco; il serait du a des processus d'assimilation biologique et de sedimentation. Les solutions de dechets de faible intensite provenant des usines de traitement chimique sont evacuees dans le sol ou elles filtrent a travers les sediments sur une profondeur de 70 a 120 metres avant d'atteindre la nappe aquifere. Pendant leur passage a travers le sol, la plupart des substances radioactives sont retenues par adsorption ou par d'autres reactions. L'eau et les quelques contaminants qui atteignent le niveau hydrostatique se deplacent avec les eaux souterraines en direction de la Columbia. La vitesse et la direction de ce deplacement sont determines par la forme de la surface piezometrique et les caracteristiques hydrauliques de l'aquifere. La configuration locale de la nappe a ete fortement influencee par l'evacuation de grandes quantites d'eau. Compte tenu du gradient hydraulique et du degre de permeabilite des aquiferes, on estime a 180 annees la duree moyenne du deplacement de J'eau. On reconnait

  20. Aide à la décision en agriculture et gestion des ressources naturelles : note introductive

    OpenAIRE

    Jallas , Eric; Crétenet , Michel

    2003-01-01

    International audience; L'aide à la décision n'a pas pour but de se substituer aux décideurs en leur proposant des solutions "toutes faites". Elle cherche plutôt à les éclairer et à les guider vers des décisions dont ils conservent la responsabilité. Dans le domaine agricole et dans celui de la gestion des ressources naturelles, il existe aujourd'hui de nombreux outils d'aide à la décision. Les systèmes experts utilisent une base de connaissances afin de fournir des solutions, équivalentes à ...

  1. On the phenomenon of the reversal of the cooling current in the hot pipes of a swimming-pool type pile cooled by forced convection; Sur un phenomene de renversement du courant de refrigeration dans les canaux chauds d'une pile piscine refroidie en convection forcee

    Energy Technology Data Exchange (ETDEWEB)

    Boure, J [Commissariat a l' Energie Atomique, Grenoble (France).Centre d' Etudes Nucleaires

    1961-07-01

    It is shown, for a swimming-pool type pile cooled by forced convection (general flow downwards), that a permanently stable regime with downward flow in all the channels is not possible when the flow is below a critical value for a given power. In the hot channels the natural convection then becomes preponderant, the direction of the flow is reversed and a permanently stable regime exists for which the flow is upwards in the hot channels. Calculations are made, with simplifying hypotheses in the case of Melusine. (author) [French] Pour une pile piscine refrigeree en convection forcee (ecoulement global descendant), on montre qu'un regime permanent stable avec ecoulement descendant dans tous les canaux est impossible lorsque le debit est inferieur a une valeur critique pour une puissance donnee. Dans les canaux chauds, la convection naturelle l'emporte alors, le sens du courant s'inverse et un regime permanent stable existe, pour lequel le courant est ascendant dans les canaux chauds. On fait les calculs, avec des hypotheses simplificatrices, dans le cas de Melusine. (auteur)

  2. Contribution méthodologique pour la connaissance du rôle des acteurs locaux dans la réalisation d’un projet de territoire : le cas du projet de la réserve naturelle de Réghaia dans la zone côtière Est de l’Algérois

    Directory of Open Access Journals (Sweden)

    Mohamed Larid

    2010-12-01

    Full Text Available Dans le domaine de la gestion territoriale, on peut constater le manque et l’insuffisance des outils d’analyse des stratégies des acteurs. Ceci est encore plus ressenti dans les sociétés du monde en développement, où les mécanismes de gestion et d’administration du territoire sont souvent dysfonctionnels. Une meilleure connaissance des relations entre les intervenants dans l’application d’un projet territorial, permet des éclairages sur le contexte de sa réalisation et des orientations suceptibles d’avantager sa réussite. Les repères sur les logiques de comportement aident à cerner les enjeux et à poser les questions clés, pour atteindre les objectifs fixés et conforter l’accomplissement des actions arrêtées. Le présent article rend compte des résultats d’une expérience de terrain, réalisée dans une zone côtière humide de la région algéroise. Il propose une contribution, sur le plan méthodologique, pour la collecte d’informations pertinentes sur le comportement et les possibilités des acteurs dans la réalisation d’un projet local, orienté vers la valorisation et la protection d’un patrimoine naturel important.In the field of territorially management, we can see the insufficiency of analysis tools on the strategies of actors. This is even more crucial in case of the developing world, where the management and territorially administration are often dysfunctional. Better knowledge of the roles of stakeholders in the implementation of a territorial project, provides insights of the context of its implementation and guidance likely to favor its success. The logical behavior help to identify issues and key questions, to achieve the objectives and ensure the completion of actions agreed. This article reports the results of a field experiment conducted in a coastal wetland in the region of Algiers. It offers a contribution, on the methodology for collecting information on the behavior and capabilities of

  3. Le Sanskrit

    CERN Document Server

    Balbir, Nalini

    2013-01-01

    Cet ouvrage est destiné à tous ceux qui souhaitent se mettre ou se remettre à l'étude du sanskrit et ne peuvent y consacrer que quelques minutes par jour. En suivant le principe de la méthode quotidienne Assimil, vous acquerrez progressivement le vocabulaire et la grammaire de base qui sont nécessaires à la lecture des textes de la littérature sanskrite classique. Vous trouverez dans cette méthode une approche vivante de la langue et de la culture sanskrite classique à travers des textes d'abord adaptés pour le débutant puis authentiques. En quelques mois, vous manierez la langue sans efforts ni hésitation, de manière très naturelle. Les enregistrements reprennent l'intégralité des textes en sanskrit des leçons et des exercices de traduction du livre. Ils sont interprétés, à un rythme progressif, par des locuteurs natifs professionnels.

  4. Publications | Page 132 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Rapport technique final / projet "Les Technologies de l'Information et de la Communication (TIC) dans la gestion des ressources naturelles et le développement : les Systèmes d'Information Géographique Participatifs (SIG - P) dans le développement local... (open access) ...

  5. Treatment of uranium ores by natural leaching in Portugal; Traitement par lixiviation naturelle des minerais uraniferes portugais

    Energy Technology Data Exchange (ETDEWEB)

    Lacerda, J de [Junta de Energia Nuclear, Lisbonne (Portugal)

    1967-06-15

    The technique described for treating uranium ores by natural leaching has been developed as a result of research carried out in Portugal with a view to determining and eliminating the causes of uranium migration in ores stored in the open. With the natural leaching method, which has been successfully applied to primary uranium ores, the ore is piled up on a waterproof surface and sprayed intermittently with mine water. Pyrite and ferrous sulphate are used as solid reagents and are mixed with the ore in amounts averaging 0.4% and 0.2% respectively. Over 70 000 tons of ore with a U{sub 3}O{sub 8} content of between 0.076 and 0.150% have been treated at five natural leaching plants. The average recovery in these operations was between 57.7 and 85.9%. The average cost was US $3.31/lb U{sub 3}O{sub 8}. (author) [French] Le traitement des minerais uraniferes par lixiviation naturelle est le fruit des recherches effectuees au Portugal dans le but de determiner et d'eliminer les causes de la migration de l'uranium contenu dans les minerais emmagasines a ciel ouvert. La methode de lixiviation naturelle, appliquee avec succes aux mineraux primaires d'uranium, consiste essentiellement en l'arrosage intermittent, avec l'eau des mines, du minerai entasse sur des aires impermeabilisees. On utilise comme reactifs solides la pyrite et le sulfate ferreux melanges avec le minerai a raison de 0,4% et 0,2% respectivement en moyenne. Plus de 70 000 t de minerai, dont les teneurs en U{sub 3}O{sub 8} etaient comprises entre 0,076% et 0,150%, ont ete traitees dans cinq installations de lixiviation naturelle ou on a obtenu des recuperations moyennes oscillant entre 57,7% et 85,9%, pour le prix de revient moyen de 3,31 dollars par livre de U{sub 3}O{sub 8}. (author)

  6. Pourquoi Hume et Kant ont eu tort de rejeter la théologie naturelle

    Directory of Open Access Journals (Sweden)

    Richard Swinburne

    2012-07-01

    Full Text Available La théologie naturelle faisait partie de la tradition philosophique occidentale jusqu’à ce que Hume et Kant affirment qu’il y a des limites fondamentales à l’intelligibilité, ou au moins au savoir possible, de ce qui dépasse l’expérience ; et donc qu’il ne peut exister d’arguments solides partant du monde naturel et concluant à l’existence de Dieu. Je défends que, bien que nos concepts doivent en effet être dérivés de notre expérience, ils peuvent avoir une application bien au-delà de notre expérience ; et que la science moderne nous a montré comment des théories à propos de choses au-delà de notre expérience pouvaient être rendues probables par les données de l’expérience. Un point important dans les arguments de Hume et de Kant est que le concept de ‘cause’ n’a d’application que pour les successions régulières d’événements observables. J’argumente contre eux en montrant que, puisque nous dérivons originairement ce concept de notre propre expérience quand nous sommes cause d’événements, son application n’est en aucun cas limitée aux successions régulières d’événements observables. J’en conclus que les arguments de Hume et Kant n’ont pas du tout de force pour montrer l’impossibilité d’une théologie naturelle solide.

  7. LA COGESTION DES RESSOURCES NATURELLES - Abrégé ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    6 oct. 2011 ... L'ENJEU Selon les estimations, de 600 à 900 millions de paysans pauvres habitent les régions marginales, écologiquement fragiles, des pays en développement. Leur survie dépend largement de l'accès aux ressources naturelles qui les entourent, mais la croissance démographique et l'extraction ...

  8. Le chrome en milieu marin

    OpenAIRE

    Chiffoleau, Jean-francois

    1994-01-01

    Le présent document constitue une synthèse des connaissances sur le cycle biogéochimique du chrome. Les sources naturelles et anthropiques sont étudiées, les échanges entre les différents compartiments géochimiques sont évalués, avec une attention particulière portée à la quantification des apports aussi bien des fleuves que de l'atmosphère au milieu marin. Les niveaux de concentration dans ces compartiments sont évalués, et montrent que l'on rencontre dans certaines régions des contamination...

  9. Publications | Page 79 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le Sri Lanka mieux préparé aux futurs tsunamis. Les collectivités côtières vulnérables du Sri Lanka sont désormais mieux outillées pour survivre aux tsunamis, cyclones et autres catastrophes naturelles survenant soudainement. Ce degré accru de.

  10. Publications | Page 112 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le sans fil, un outil de gestion des ressources au Mozambique. Au Mozambique, il faut aimer la solitude pour être garde forestier ou garde-chasse, un métier parfois dangereux. L'année dernière, par exemple, un garde-chasse a essuyé le feu d'un braconnier dans une nouvelle réserve naturelle de la.

  11. Contribution to the study of the thermal and hydrodynamical properties of a two-phase natural circulation flow of normal helium (He I) for the cooling of superconducting magnets; Contribution a l'etude des proprietes thermiques et hydrodynamiques d'un ecoulement d'helium normal (He I) diphasique en circulation naturelle pour le refroidissement des aimants supraconducteurs

    Energy Technology Data Exchange (ETDEWEB)

    Benkheira, L

    2007-06-15

    The method of cooling based on the thermosyphon principle is of great interest because of its simplicity, its passivity and its low cost. It is adopted to cool down to 4,5 K the superconducting magnet of the CMS particles detector of the Large Hadron Collider (LHC) experiment under construction at CERN, Geneva. This work studies heat and mass transfer characteristics of two phase He I in a natural circulation loop. The experimental set-up consists of a thermosyphon single branch loop mainly composed of a phase separator, a downward tube, and a test section. The experiments were conducted with varying several parameters such as the diameter of the test section (10 mm or 14 mm) and the applied heat flux up to the appearance of the boiling crisis. These experiments have permitted to determine the laws of evolution of the various parameters characterizing the flow (circulation mass flow rate, vapour mass flow rate, vapour quality, friction coefficient, two phase heat transfer coefficient and the critical heat flux) as a function of the applied heat flux. On the base of the obtained results, we discuss the validity of the various existing models in the literature. We show that the homogeneous model is the best model to predict the hydrodynamical properties of this type of flow in the vapour quality range 0{<=}x{<=}30%. Moreover, we propose two models for the prediction of the two phase heat transfer coefficient and the density of the critical heat flux. The first one considers that the effects of the forced convection and nucleate boiling act simultaneously and contribute to heat transfer. The second one correlates the measured critical heat flux density with the ratio altitude to diameter. (author)

  12. Théorie mathématique des catégories en biologie et notion d'équivalence naturelle chez Robert Rosen

    OpenAIRE

    Varenne , Franck

    2011-01-01

    L'objectif de cet article est de rendre compte de la justification épistémologique de la proposition faite, dès 1958, par le biomathématicien Robert Rosen d'introduire le concept mathématique de " catégorie " et celui - corrélatif - d'" équivalence naturelle " dans la modélisation mathématique appliquée au vivant. Nos questions sont les suivantes : en quoi la notion mathématique de catégorie permet-elle, selon Rosen, de donner accès à des formalismes plus " naturels " pour la modélisation du ...

  13. Usages des TIC et rapports a l’incertitude en situation de catastrophes naturelles

    Directory of Open Access Journals (Sweden)

    Claire Brossaud

    2008-11-01

    Full Text Available Cet article montre comment des professionnels et des sinistrés qui ont été confrontés à des catastrophes naturelles sur trois territoires distincts - la tempête à Limoges en 1999, les inondations à Abbeville (2001 et à Bourg-en-Bresse (2005 - ont construit une histoire commune du risque au moyen des technologies de l’information et de la communication (TIC : Internet, téléphone portable, bases de données, outils de travail partagés, etc. Les usages des TIC sont d’abord resitués concrètement avant, pendant et après les événements dans un contexte historique où les sciences et techniques sont de plus en plus sollicitées pour réduire les incertitudes liées aux menaces sanitaires et écologiques. On voit ensuite s’élaborer une culture du risque sur la base de compétences socio-cognitives et relationnelles particulières face aux événements et à leur prise en charge technologique. Nous examinons en dernier ressort lele des TIC dans l’apprentissage d’une argumentation et d’une délibération collective sur les catastrophes, notamment grâce à la mise en place d’outils dédiés à l’étude sur le site http://www.technorisque.net.This article shows how professionnals and disaster victims involved in natural catastrophes in three different areas - Limoges storm in 1999, Abbeville and Bourg-en-Bresse floods in 2001 and 2005 – built a commun risk story with Information and communication technologies (ICT : Internet, mobiles, data bases, groupware, etc. At first, ICT uses are concretely approached before, during and after the events in a historic context where sciences and technology are growing up to reduce uncertainties of medical and ecological threats. Then, in the second part of this article, a risk culture is supported by socio-cognitive and relationnal competences towards events and their technological holding. At last, we examine ICT place in a collective argumentation and deliberation about the

  14. Récupérer l'espoir | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    14 oct. 2010 ... En octobre 2007, André Casault, professeur d'architecture à l'Université ... du soleil et permettrait un meilleur contrôle de la lumière naturelle et de l'aération. ... Depuis plusieurs années, l'Institut africain de gestion urbaine ...

  15. Appréhender le changement climatique dans une interface Homme ...

    African Journals Online (AJOL)

    tion au développement et de recherche scientifique dans le do- maine forestier ont été ... grande échelle en ce qui concerne la dévolution de droits d'usage aux populations ..... de la Gestion Communautaire des Ressources Naturelles: Coopération,. Contradictions, Conflits. Actes du Colloque International 1–3 juillet 2008,.

  16. Animal Certifié Conforme: Déchiffrer nos Relations avec le Vivant

    Directory of Open Access Journals (Sweden)

    Daniel W. Gade

    2014-01-01

    Full Text Available Review of Animal Certifié Conforme: Déchiffrer nos Relations avec le Vivant. Bernadette Lizet and Jacqueline Milliet, eds. 2012. Dunod/Muséum National d’Histoire Naturelle, Paris. Pp 256. €22 (paperback. ISBN 9782100582853.

  17. Sexospécificités | Page 239 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Read more about Taxation and Gender Equity : A Comparative Analysis of Direct and Indirect Taxes in Developing and Developed Countries. Langue French. Ce livre révèle les voies par lesquelles l'innovation en matière de gestion des ressources naturelles peut contribuer à la réduction de la pauvreté en milieu rural.

  18. Processus hydrogéochimiques et origine des sources naturelles ...

    African Journals Online (AJOL)

    Dr Gatsing

    minéralisées. La signature chimique des eaux de sources marquée par de faibles conductivités se rapproche nettement de celle des eaux de puits qui captent les altérites, et s'éloigne de celle des eaux de forages qui interceptent le socle fissuré. Le calcul des indices de saturation par rapport à la dolomie et la calcite, et.

  19. Les vélins du Muséum national d’histoire naturelle : une collection mise en lumière

    OpenAIRE

    Cardinal, Catherine

    2018-01-01

    Une exposition unique au Cabinet d’histoire du Jardin des plantes Très rarement, le public a pu voir la collection d’images de fleurs, de plantes, d’oiseaux et de mammifères, déposée à la bibliothèque centrale du Musée national d’histoire naturelle. La fragilité des peintures sur vélin au contact de l’air humide et de la lumière explique les précautions prises à leur égard. L’exposition d’environ cent cinquante pièces au sein du Cabinet d’histoire, d’octobre 2016 à janvier 2017, a donc consti...

  20. etude socio-anthropologique de la gestion des ressources naturelles

    African Journals Online (AJOL)

    SECRETARIAT

    Le Burkina Faso est un pays sahélien dont l'économie est essentiellement agricole. ... dégradation sont, entre autres, l'érosion hydrique et éolienne, les changements climatiques, les actions .... Figure 3 : Présentation globale de la zone.

  1. Promouvoir la bonne gouvernance des ressources naturelles dans ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Il encouragera l'émergence et le renforcement du leadership féminin, la promotion des ... The main objective of this competitive research fund is to support applied ... The Science Granting Councils Initiative in sub-Saharan Africa wins Science ...

  2. Les Cabinets de curiosités dauphinois dans les origines scientifiques du Muséum d'histoire naturelle de Grenoble (XVIII e -XIX e siècles)

    OpenAIRE

    Rochas , Joëlle

    2008-01-01

    Les actes du colloque de Poitiers concernant les cabinets de curiosités seront déposés sur le site web www.curiositas.org, site européen dédié aux cabinets de curiosités (Université de Poitiers).; Le Cabinet d'histoire naturelle de Grenoble, ancêtre du Muséum actuel, a été créé en 1773. Un premier historique de la fin du XVIIIe siècle mentionne les trois principaux cabinets d'où il était issu : un cabinet dauphinois - celui des Antonins - et deux cabinets grenoblois - celui du négociant greno...

  3. un_focus - La cogestion des ressources naturelles : Réduire la ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    M. Tyler était auparavant chef d'équipe du programme Gestion communautaire des ressources naturelles du CRDI en Asie. Dans ces fonctions, il a administré pendant sept ans un portefeuille de plus de 75 projets exécutés dans 12 pays. Il a obtenu un doctorat en aménagement urbain et régional de l'Université de la ...

  4. De quoi le genre est-il le nom ?

    OpenAIRE

    Andrieu, Bernard

    2013-01-01

    Cette note de lecture présente une courte évolution des travaux sur le genre sous l’angle du rapport au corps en démontrant comment la dénaturalisation du corps et du sexe biologique a conduit à une description culturaliste des fonctions individuelles et des rôles sociaux. Si le genre dénaturalise le corps c’est en refusant toute référence au sexe ou à la sexualité en tant qu’ils seraient des données naturelles. Depuis son apparition en 1947, sous la plume de John Money, psychologue chargé du...

  5. La Gestion Locale Sécurisée (GELOSE : L’expérience malgache de gestion décentralisée des ressources naturelles

    Directory of Open Access Journals (Sweden)

    Bruno Sarrasin

    2009-09-01

    Full Text Available Marqué par une biodiversité exceptionnelle et une grande pauvreté humaine, la destruction rapide des ressources naturelles à Madagascar place le territoire et son appropriation au centre des enjeux de développement. Dans ce contexte, cet article s’intéresse à l’émergence et à la mise en œuvre d’une politique publique touchant la Gestion LOcale SÉcurisée (GELOSE dont le principal objectif vise à transférer la gestion de ces ressources, de l’État vers les communautés locales, dans le but de les protéger plus efficacement. Cette lecture montre cependant que les objectifs, les ressources et les stratégies des principaux acteurs concernés sont difficilement conciliables et que le système de relation qu’il induit n’est pas nécessairement en phase avec les finalités poursuivies.Marked by exceptional biodiversity and extreme human poverty, Madagascar is experiencing a rapid destruction of its natural resources, placing territory and its appropriation at the heart of development issues. From this perspective, this article will look at the development and implementation of a public policy, the Gestion LOcale SÉcurisée (GELOSE, for the local management of natural renewable resources. This regulation seeks to transfer the management of these resources from the government to local communities in the goal of protecting them more effectively. We will see, however, that the objectives, resources and strategies of the primary actors concerned are difficult to reconcile at best and that the relational system to which the policy gives rise is not necessarily in keeping with the goals being pursued.

  6. Conditions of competition between the production of water by desalination and natural resources; Les conditions de concurrence entre la production d'eau par dessalement et les ressources naturelles

    Energy Technology Data Exchange (ETDEWEB)

    Gaussens, J [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1969-07-01

    A close examination of the local supply and demand for fresh water is involved when considering a sea water desalination plant in a given region. This examination makes it possible in most cases to undertake a thorough study of the natural resources, resulting in the use of desalination being rejected. After confirming this fact by precise examples, the authors consider that the preliminary study should be extended, taking into account the complementary character of natural resources and desalination systems: contribution to peak demand, contribution to base demand. This analysis results in a classification of the main user regions according to certain economic criteria defining their suitability for the use of desalination processes. (author) [French] Envisager une installation d'eau de mer dans une region donnee, entraine un examen attentif de l'offre et de la demande locale en eau douce. Cet examen permet de conduire dans la plupart des cas a une etude approfondie des ressources naturelles qui aboutit a ecarter le recours au dessalement. Apres avoir constate ce fait, par des exemples precis, les auteurs estiment que l'on doit pousser plus loin l'etude preliminaire en tenant compte de la complementarite entre les ressources naturelles et les systemes de dessalement: contribution a la demande de pointe, contribution a la demande de base. Cette analyse conduit a classer les regions utilisatrices essentielles selon certains criteres economiques definissant leur aptitude a l'utilisation des procedes de dessalement. (auteur)

  7. Conditions of competition between the production of water by desalination and natural resources; Les conditions de concurrence entre la production d'eau par dessalement et les ressources naturelles

    Energy Technology Data Exchange (ETDEWEB)

    Gaussens, J. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1969-07-01

    A close examination of the local supply and demand for fresh water is involved when considering a sea water desalination plant in a given region. This examination makes it possible in most cases to undertake a thorough study of the natural resources, resulting in the use of desalination being rejected. After confirming this fact by precise examples, the authors consider that the preliminary study should be extended, taking into account the complementary character of natural resources and desalination systems: contribution to peak demand, contribution to base demand. This analysis results in a classification of the main user regions according to certain economic criteria defining their suitability for the use of desalination processes. (author) [French] Envisager une installation d'eau de mer dans une region donnee, entraine un examen attentif de l'offre et de la demande locale en eau douce. Cet examen permet de conduire dans la plupart des cas a une etude approfondie des ressources naturelles qui aboutit a ecarter le recours au dessalement. Apres avoir constate ce fait, par des exemples precis, les auteurs estiment que l'on doit pousser plus loin l'etude preliminaire en tenant compte de la complementarite entre les ressources naturelles et les systemes de dessalement: contribution a la demande de pointe, contribution a la demande de base. Cette analyse conduit a classer les regions utilisatrices essentielles selon certains criteres economiques definissant leur aptitude a l'utilisation des procedes de dessalement. (auteur)

  8. Le sans fil, un outil de gestion des ressources au Mozambique ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    3 févr. 2011 ... ... nouvelle réserve naturelle de la province septentrionale de Niassa. Heureusement, son téléphone sans fil à haute fréquence lui a permis d'appeler sa station de base à l'aide. Malgré la distance, ses collègues ont pu lui porter secours en demandant à une pourvoirie d'envoyer un petit avion le cueillir.

  9. Le monde a besoin de plus de femmes scientifiques | CRDI - Centre ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    24 oct. 2017 ... Les femmes sont très sous-représentées en sciences, ne constituant que 28 p. 100 de tous les chercheurs à l'échelle mondiale; la disparité est encore plus grande dans les domaines des sciences naturelles et du génie. Bien que le nombre de femmes qui poursuivent des études doctorales et ...

  10. le traitement chirurgical des poches de rétraction tympaniques

    African Journals Online (AJOL)

    16 juin 2006 ... L'évolution naturelle de l'otite atelectasique vers la maladie cholestéatomateuse complique d'avantage la prise en charge des poches de rétraction. ... risque de cholestéatome résiduel était important. Après un recul minimum de 21 mois, le résultat anato- mique été satisfaisant dans 88%. Ailleurs ...

  11. Des chercheurs palestiniens appliquent les leçons de l'évaluation à ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    1 févr. 2011 ... L'institut a recensé les terres et les ressources naturelles dont dispose le peuple palestinien et les répercussions que cela suppose sur l'économie et sur les collectivités locales. Les chercheurs ont interrogé des dirigeants locaux et des ménages et étudié des images satellite, pour analyser aussi bien les ...

  12. Heat Convection

    Science.gov (United States)

    Jiji, Latif M.

    Professor Jiji's broad teaching experience lead him to select the topics for this book to provide a firm foundation for convection heat transfer with emphasis on fundamentals, physical phenomena, and mathematical modelling of a wide range of engineering applications. Reflecting recent developments, this textbook is the first to include an introduction to the challenging topic of microchannels. The strong pedagogic potential of Heat Convection is enhanced by the follow ing ancillary materials: (1) Power Point lectures, (2) Problem Solutions, (3) Homework Facilitator, and, (4) Summary of Sections and Chapters.

  13. Surimpressions naturelles et volontaires chez les surréalistes. Un regard multiple sur Paris Voluntary and natural multiple exposure among Surrealists. A manifold view on Paris

    Directory of Open Access Journals (Sweden)

    Héloïse Pocry

    2009-10-01

    Full Text Available La surimpression photographique, simple accident technique consistant à impressionner plusieurs fois une même surface sensible, fut mise à profit par les avant-gardes photographiques des années 1920 et 1930 pour révéler les aspects insolites ou poétiques du paysage urbain et traduire les sensations démultipliées dans cet environnement. Les reflets dans les vitrines sont également pourvoyeurs de superpositions visuelles dans la ville. Les avant-gardes vont s’intéresser à ce phénomène comme une surimpression à l’état naturel, en particulier les surréalistes, portés par leur goût du hasard et de la déambulation urbaine. Surimpressions volontaires et naturelles sont deux procédés permettant de rendre compte de l’expérience multiple du passant dans le paysage urbain. La surimpression est-elle la transposition photographique de l’expérience des reflets de vitrine ? Dans quelle mesure ces deux procédés réussissent-ils à reproduire efficacement les perturbations sensitives qui peuvent assaillir le passant dans le paysage urbain ? Nous mettrons en évidence à travers un corpus de textes et de photographies principalement issu du surréalisme des années 1920 et 1930 les enjeux des surimpressions naturelles et volontaires. Nous étudierons comment elles ont été utilisées par les surréalistes parisiens pour conduire le spectateur vers une perception et une compréhension nouvelles du paysage urbain de la capitale française.Photographic multiple exposure, a simple technical accident consisting in exposing several times the same sensitized material, was capitalized on by the photographic avant-garde in the 1920s and 1930s. Their aim was to reveal unusual or poetic aspects within urban landscape and convey its multiple sensations. Reflections on windows also provide visual urban superpositions. Avant-gardists conceived of this phenomenon as a natural multiple exposure. Surrealists were particularly fond of this

  14. Des SIG-P pour sauver le complexe forestier de la basse rivière Tana?

    International Development Research Centre (IDRC) Digital Library (Canada)

    L'objectif général de ce programme panafricain est de contribuer à rendre disponibles des systèmes d'information de bonne qualité, fiables et accessibles grâce à l'usage de SIG-P en vue d'améliorer la gestion des ressources naturelles (eau, terres, forêts, etc.) et de promouvoir la sécurité alimentaire. Le programme ...

  15. Le cas des beurres végétaux et des cires d’origine naturelle

    Directory of Open Access Journals (Sweden)

    Rossow Véronique

    2008-07-01

    Full Text Available Natural waxes such as Beeswax, Carnauba wax and Candelilla wax are widely used in the Cosmetic and Food industries. Thanks to their composition, and besides a compulsory high safety, they provide desirable properties such as strength, gloss, emolliency, barrier effect, making them essential in numerous applications. For example, lots of candies are coated with either one or a mix of these 3 waxes, while for Cosmetics, the waxy part of lipsticks contains various combinations of such waxes. Within the cosmetic industry, the “green wave” – natural products – which is developing to the detriment of synthetic or mineral raw materials, has generated know-hows to enlighten new values to natural resources. Several types of developments have occurred: managing to substitute materials facing bad press (ex: petrolatum, lanolin, mimicking trendy “butter-like” textures either by adequate mixture or by chemical reaction to offer alternatives to overused Shea or Cupuaçu Butter, or as a result of more recent research programs, identifying natural waxes acting more like active ingredients than “just” like excipients (Mimosa Flower wax, Lemon Peel or Orange Peel waxes, etc..

  16. The dating of the fourth volume of Guillaume-Antoine Olivier's "Entomologie, ou histoire naturelle des insectes".

    Science.gov (United States)

    Bousquet, Yves

    2018-01-01

    Despite the title page is dated 1795, the fourth volume of Olivier's Entomologie, ou histoire naturelle des insectes was issued in two parts, one probably in 1795 and the second in 1800. All new taxa made available in this work have previously been dated 1795 in the literature. A list of new species described in 1795 and a list of those that have to be dated 1800 are appended. The genus Necrobia should be credited to Latreille, 1797, not Olivier, 1795.

  17. Facteur 4 : le chantier social et politique

    Directory of Open Access Journals (Sweden)

    Mathilde Szuba

    2011-03-01

    Full Text Available Émergeant au milieu des années 1990, la notion de « facteur 4 » fait référence, en premier lieu, à la capacité dont disposeraient nos systèmes techniques de réduire la consommation de ressources naturelles de façon significative : emblématiquement d’un facteur 4, soit une diminution de 75 %. Le concept a été popularisée par un rapport destiné au Club de Rome, édité en 1995 : "Factor Four : Doubling Wealth, Halving Resource Use" avec pour auteurs, les époux Lovins et le fondateur du Wuppertal ...

  18. National Convective Weather Diagnostic

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current convective hazards identified by the National Convective Weather Detection algorithm. The National Convective Weather Diagnostic (NCWD) is an automatically...

  19. Accès des femmes à la terre et aux ressources naturelles dans les ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Realties of women facing multiple exclusion in accessing land and land-based resources in pastoralist and forest dwelling communities in Uganda. Téléchargez le PDF. Documents. Access to land and land based resources among women in pastoralist and forest-dependent communities in East Africa. Téléchargez le PDF.

  20. The French Muséum national d'histoire naturelle vascular plant herbarium collection dataset

    Science.gov (United States)

    Le Bras, Gwenaël; Pignal, Marc; Jeanson, Marc L.; Muller, Serge; Aupic, Cécile; Carré, Benoît; Flament, Grégoire; Gaudeul, Myriam; Gonçalves, Claudia; Invernón, Vanessa R.; Jabbour, Florian; Lerat, Elodie; Lowry, Porter P.; Offroy, Bérangère; Pimparé, Eva Pérez; Poncy, Odile; Rouhan, Germinal; Haevermans, Thomas

    2017-02-01

    We provide a quantitative description of the French national herbarium vascular plants collection dataset. Held at the Muséum national d'histoire naturelle, Paris, it currently comprises records for 5,400,000 specimens, representing 90% of the estimated total of specimens. Ninety nine percent of the specimen entries are linked to one or more images and 16% have field-collecting information available. This major botanical collection represents the results of over three centuries of exploration and study. The sources of the collection are global, with a strong representation for France, including overseas territories, and former French colonies. The compilation of this dataset was made possible through numerous national and international projects, the most important of which was linked to the renovation of the herbarium building. The vascular plant collection is actively expanding today, hence the continuous growth exhibited by the dataset, which can be fully accessed through the GBIF portal or the MNHN database portal (available at: https://science.mnhn.fr/institution/mnhn/collection/p/item/search/form). This dataset is a major source of data for systematics, global plants macroecological studies or conservation assessments.

  1. The French Muséum national d’histoire naturelle vascular plant herbarium collection dataset

    Science.gov (United States)

    Le Bras, Gwenaël; Pignal, Marc; Jeanson, Marc L.; Muller, Serge; Aupic, Cécile; Carré, Benoît; Flament, Grégoire; Gaudeul, Myriam; Gonçalves, Claudia; Invernón, Vanessa R.; Jabbour, Florian; Lerat, Elodie; Lowry, Porter P.; Offroy, Bérangère; Pimparé, Eva Pérez; Poncy, Odile; Rouhan, Germinal; Haevermans, Thomas

    2017-01-01

    We provide a quantitative description of the French national herbarium vascular plants collection dataset. Held at the Muséum national d’histoire naturelle, Paris, it currently comprises records for 5,400,000 specimens, representing 90% of the estimated total of specimens. Ninety nine percent of the specimen entries are linked to one or more images and 16% have field-collecting information available. This major botanical collection represents the results of over three centuries of exploration and study. The sources of the collection are global, with a strong representation for France, including overseas territories, and former French colonies. The compilation of this dataset was made possible through numerous national and international projects, the most important of which was linked to the renovation of the herbarium building. The vascular plant collection is actively expanding today, hence the continuous growth exhibited by the dataset, which can be fully accessed through the GBIF portal or the MNHN database portal (available at: https://science.mnhn.fr/institution/mnhn/collection/p/item/search/form). This dataset is a major source of data for systematics, global plants macroecological studies or conservation assessments. PMID:28195585

  2. Le chaos et l'harmonie la fabrication du Réel

    CERN Document Server

    Xuan Thuan, Trinh

    1998-01-01

    Cette fin de siècle a vu un véritable bouleversement dans notre façon de concevoir le monde. Après avoir dominé la pensée occidentale pendant trois cents ans, la vision newtonienne d'un univers fragmenté, mécaniste et déterministe a fait place à celle d'un monde exubérant de créativité. Le Réel n'est plus déterminé seulement par des lois naturelles appliquées à des conditions initiales particulières, mais aussi moulé et façonné par une suite d'événements contingents et historiques qui peuvent bouleverser la réalité à son niveau le plus profond. Celui du bolide rocailleux venu percuter la Terre il y a quelque 65 millions d'années et responsable de la mort des dinosaures en est un exemple. Les lois physiques ont perdu leur rigidité. Avec l'avènement de la mécanique quantique, le hasard est entré en force dans le monde subatomique. Le monde macroscopique n'a pas été épargné. Avec la théorie du chaos, le hasard et le non-déterminisme ont envahi non seulement la vie de tous le...

  3. L'hybridation naturelle entre le barbeau commun et le barbeau méridional en France : compte rendu de dix années de recherche

    Directory of Open Access Journals (Sweden)

    CRESPIN L.

    1994-07-01

    Full Text Available Les deux espèces de barbeaux de France s'hybrident spontanément dans plusieurs bassins. Les modalités de cette hybridation ont été recherchées au travers de nombreuses études relevant de disciplines différentes (biogéographie, éthologie, génétique et parasitologie. Cet article se veut une synthèse des différents travaux consacrés à cette hybridation en même temps qu'une caractérisation de l'état de l'hybridation dans toute la France.

  4. Cogestion des ressources naturelles en dépit de différences ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Si le projet proposé vise les collectivités Yshiro du Paraguay, un volet sera mené au Labrador en collaboration avec la nation innue et le gouvernement des Inuits du Nunatsiavut. Les trois cas combinés permettront de généraliser et de faire passer à grande échelle les résultats de la recherche sous forme de techniques et ...

  5. : tous les projets | Page 575 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Accroissement de l'efficacité des applications et outils TIC dans la gestion des catastrophes naturelles dans les Caraïbes. Projet. D'août à novembre 2005, neuf ouragans ont dévasté les Caraïbes, causant le décès d'au moins 2 000 personnes et des dommages évalués à 60 milliards de dollars américains. Date de début ...

  6. Caractérisation intégrée du vignoble alsacien : aspects méthodologiques et application à l'étude des composantes naturelles des principaux terroirs

    Directory of Open Access Journals (Sweden)

    Éric Lebon

    1993-12-01

    Full Text Available Parmi les méthodes utilisées en vue de la définition des potentialités viticoles, l'approche intégrée des terroirs fondée sur la notion de séquence écogéopédologique développée en Moyenne Vallée de la Loire par l'INRA d'Angers s'est révélée particulièrement performante. Son application à la caractérisation du vignoble d'Alsace, fondamentalement différent sur le plan de sa structure géologique, nécessite un certain nombre d'aménagements méthodologiques liés à une variabilité paysagère marquée. Ainsi, une typologie des paysages s'appuyant sur des paramètres tels que l'ouverture du paysage, la répartition et l'orientation des masques est proposée. Elle vient compléter les descripteurs stationnels classiques (altitude, pente et exposition. Le concept de séquence écogéopédologique reste pertinent dans ce contexte moyennant l'adjonction du paramètre exposition, dans le cas des terroirs sur versants. Dans cette optique, les caractéristiques des composantes naturelles des grands types de terroirs alsaciens sont présentées à partir de l'étude de cas concrets.

  7. National Convective Weather Forecast

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NCWF is an automatically generated depiction of: (1) current convection and (2) extrapolated signficant current convection. It is a supplement to, but does NOT...

  8. La gestion des ressources naturelles dans la commune de Hong Ha ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    approvisionnement utilisée par l'armée nord-vietnamienne dans les années 1960 et 1970, la commune de Hong Ha — qui .... J'ai remboursé le prêt et utilisé les profits pour acheter de la nourriture et envoyer mes enfants à l'école. ».

  9. Gestion des ressources naturelles pour une sécurité alimentaire ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Au Sahel, le déficit de la production agricole et pastorale, combiné à la hausse générale des prix des denrées, ont augmenté l'insécurité alimentaire. Pour garantir leur sécurité alimentaire, les populations rurales utilisent des techniques de production agricole visant à maximiser leur production sans nécessairement se ...

  10. Les catastrophes naturelles présentent une menace pour les ...

    African Journals Online (AJOL)

    toufik

    L'événement sismique a été simulé en utilisant le catalogue algérien des failles actives. Les résultats obtenus montrent que les constructions les plus endommagées sont celles qui reposent sur des sols meubles. Mots-clés : SIG, risque sismique, probabilité de dommages, courbes de fragilité, Hazus. Abstract. Use of a GIS ...

  11. L’interface Habitat / Habitant : quand le lieu de vie est porteur de maladie - Le cas du radon en PACA

    Directory of Open Access Journals (Sweden)

    Cissé E.

    2012-10-01

    Full Text Available Les préoccupations sont croissantes pour étudier les liens entre des conditions environnementales spécifiques et la fréquence de certaines pathologies. Nous proposons d’analyser ici le lien présupposé entre une exposition au radon et le cancer du poumon. Le radon, est un gaz radioactif d’origine naturelle (issu de la désintégration naturelle de l’uranium présent dans la croûte terrestre et plus particulièrement dans certaines formations géologiques. A partir du sol et de l’eau, le radon se diffuse dans l’air (exhalation et se trouve, par effet de confinement, à des concentrations plus élevées à l’intérieur des bâtiments qu’à l’extérieur. Les descendants solides du radon sont alors inhalés avec l’air respiré et se déposent dans le poumon. Il est établi par diverses études scientifiques que le radon a un impact non négligeable sur certains cancers, notamment du poumon (augmentation de 16 % du risque de cancer du poumon par tranche de 100 Bq/m3, et des cancers digestifs via la consommation d’eau qui s’est chargée en radon au contact du socle. Le nombre annuel de décès par cancer du poumon attribuable à l’exposition domestique au radon en France métropolitaine varie entre 1 200 à 3 575 en fonction des relations exposition-réponse utilisées. Plusieurs régions en France se caractérisent par une problématique radon reconnue et étudiée depuis longtemps (Bretagne, Massif central, Corse. Or, si le radon ne recouvre pas l’ensemble de la région PACA, certaines zones géographiques sont particulièrement concernées et méritent d’être étudiées : le Massif des Maures dans le Var, du Mercantour dans les Alpes-Maritimes et du Briançonnais dans les Hautes-Alpes. La région PACA est une des régions de France et d’Europe les plus touchées par la pollution atmosphérique principalement due à l’augmentation du trafic routier et des contributions de régions industrialisées telles que

  12. Renforcer la résilience dans les collectivités touchées par le tsunami ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Lors du tsunami qui a frappé l'Asie du Sud en décembre 2004, des études ont indiqué qu'une épaisse végétation côtière, telles les mangroves, avait permis de sauver des vies et de réduire les pertes matérielles en servant de barrières naturelles. Par ailleurs, des villageois, comme ceux de Nallavadu dans le territoire de ...

  13. Briançon, 24 juillet 1995: autopsie et enseignements d'une catastrophe naturelle

    Directory of Open Access Journals (Sweden)

    Philippe LAHOUSSE

    1998-06-01

    Full Text Available L'épisode pluvio-orageux du 24 juillet 1995 dans le Briançonnais est à l'origine d'une série de crues torrentielles et de coulées de débris dévastatrices. L'approche cartographique, combinée à l'enquête historique, permet de mesurer l'ampleur du phénomène et contribue à une meilleure évaluation des dangers. Elle permet de mieux fonder la politique de prévention des risques.

  14. Incidence et regulation naturelle de la chenille mineuse de l'epi de ...

    African Journals Online (AJOL)

    Au Sénégal, la mineuse de l'épi, Heliocheilus albipunctella (Lepidoptera, Noctuidae) a commencé à causer des dégâts dans les cultures de mil suite à une longue période de sécheresse au début des années 70. Le suivi d'un réseau de 45 parcelles de producteurs à Bambey en 2013, a permis d'évaluer la situation du ...

  15. Le Parti des Paysans de Bessarabie et la rivalite entre Pantelimon Halippa et Ion Inculeţ

    Directory of Open Access Journals (Sweden)

    Andrei Cemârtan

    2011-12-01

    Full Text Available L’effervescence du mouvement national en Bessarabie en 1917 a apporté en premier plan la question de l’organisation de la vie politique. Anterieurement il n’y avait pas des partis politiques proprement dits et en étant animés par le meme but, les leaders de ce mouvement ont formé Le Parti National Moldave. Halippa a été un des représentants marquants qui a contribué à la formation de la vie politique en Bessarabie, il a fondé le Parti National Moldave, ulterieurement transformé en Parti des Paysans de Bessarabie, dont Halippa a été le président durant toute sa vie (1918-1926. Cet étude souligne lele joué par Halippa dans Le Parti des Paysans de Bessarabie et sa contribution à la fusion avec le Parti des Paysans dans le Vieux Royaume. Le conflit d’opinions entre Halippa et Inculeţ et, plus précisément le conflit entre les visions liés à l’avenir du parti, ont influencé l’évolution de l’organisation. L’intégration du Parti des Paysans de Bessarabie dans le système politique roumain a été la suite naturelle de l’Union et des processus complexes de formation de la Grande Roumanie, mais la formation d’un parti des paysans uni a représenté un progrès pour la vie politique roumaine.

  16. Observing Convective Aggregation

    Science.gov (United States)

    Holloway, Christopher E.; Wing, Allison A.; Bony, Sandrine; Muller, Caroline; Masunaga, Hirohiko; L'Ecuyer, Tristan S.; Turner, David D.; Zuidema, Paquita

    2017-11-01

    Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network.

  17. Architecture naturelle et architecture symbolique au Néolithique. L’exemple des abris peints des gorges de la Nesque (Vaucluse, France

    Directory of Open Access Journals (Sweden)

    Philippe HAMEAU

    2009-12-01

    Full Text Available RÉSUMÉ: L’expression schématique rupestre, pariétale ou mobilière du Néolithique dans le sud de la France est à placer, essentiellement, aux IVe et IIIe millénaires av.J.C. Pourtant, certaines peintures pourraient être plus anciennes et le décor céramique est de style schématique dès le Néolithique ancien. On décrit ici un groupe de dix abris ornés dans un contexte de gorges: leur topographie, leurs peintures et éventuellement leur mobilier archéologique. La diversité des teintes utilisées et des cas de superpositions de traits nous font supposer plusieurs phases graphiques et une complémentarité des sites. Malgré leur apparente disparité, ces abris répondent à des critères précis qui déterminent leur choix par les Néolithiques, notamment la présence d’un ruissellement périodique. A ce titre, plusieurs concrétions résultant des écoulements d’eau sont rehaussées de colorant rouge. Deux abris sont manifestement des sites de réclusion: la condamnation du couloir du premier, le perchement du second, isolent automatiquement leurs usagers du reste de la communauté. En outre, leurs particularités topographiques et pariétales en font des sites propices à des rites de passage. Par comparaison, les grands porches seraient plutôt des lieux de rassemblement. Toutes ces hypothèses traduisent une volonté de considérer les singularités naturelles des lieux (gorges, abris, parois comme autant d’éléments symboliques participant à la constitution des sanctuaires au Néolithique.RESUMEN: La expresión esquemática rupestre, parietal o mobiliaria del Neolítico en el sur de Francia, se tiene que integrar, principalmente, en los IV y III milenios a.C. A pesar de todo, algunas pinturas podrían ser más antiguas y la decoración cerámica es de estilo esquemático desde el Neolítico antiguo. Se describe aquí un grupo de diez abrigos pintados en un contexto de gargantas: su topografía, sus pinturas y

  18. Convective heat transfer

    CERN Document Server

    Kakac, Sadik; Pramuanjaroenkij, Anchasa

    2014-01-01

    Intended for readers who have taken a basic heat transfer course and have a basic knowledge of thermodynamics, heat transfer, fluid mechanics, and differential equations, Convective Heat Transfer, Third Edition provides an overview of phenomenological convective heat transfer. This book combines applications of engineering with the basic concepts of convection. It offers a clear and balanced presentation of essential topics using both traditional and numerical methods. The text addresses emerging science and technology matters, and highlights biomedical applications and energy technologies. What’s New in the Third Edition: Includes updated chapters and two new chapters on heat transfer in microchannels and heat transfer with nanofluids Expands problem sets and introduces new correlations and solved examples Provides more coverage of numerical/computer methods The third edition details the new research areas of heat transfer in microchannels and the enhancement of convective heat transfer with nanofluids....

  19. Quelles pratiques agroécologiques pour contrôler les bioagresseurs dans un système pérenne, le verger de pommiers?

    OpenAIRE

    Simon, Sylvaine; Marliac, Gaëlle; Capowiez, Yvan

    2015-01-01

    Les vergers constituent un habitat pérenne, multi-strate et complexe, potentiellement favorable dans le temps et dans l’espace, au maintien des chaînes trophiques et à la régulation naturelle des ravageurs. Or, ils dépendent fortement de l’utilisation des pesticides, ce qui compromet leur durabilité et l’expression de ce potentiel de régulation. Deux expérimentations en verger de pommiers ont analysé (1) la réduction de l’utilisation des pesticides permise par la combinaison de plusieurs levi...

  20. Le laboratoire, le temple et le marché

    International Development Research Centre (IDRC) Digital Library (Canada)

    De manière générale, les auteurs insistent sur le fait que c'est leur foi qui leur a .... nettement que dans de nombreux cercles, le besoin était vivement ressenti de ... Le Dr Kapur présente tout d'abord une brève discussion sur sa vision du ...... pour les soins aux enfants orphelins et aux pauvres et pour la renaissance des ...

  1. Protection of personnel against atmospheric contamination by plutonium in the laboratory (1963); Protection du personnel contre la contamination atmospherique par le plutonium, dans les laboratoires (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Feliers, P; Pomarola, J; Risselin, A [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1963-07-01

    Various problems about measurement of atmospheric contamination by plutonium in laboratories are considered. In particular are studied sampling methods, continuous measurement for alarm, criteria used for fixation of the concentrations to be measured, sensitivity of apparatus and effects of natural atmospheric contamination. The means actually available for measurement of contamination and their limits of use are briefly analysed. (authors) [French] Les differents problemes a resoudre pour realiser un controle satisfaisant de la contamination atmospherique par le plutonium, dans les laboratoires, sont abordes. On etudie en particulier les differents modes d'echantillonnage, le controle continu en vue de l'alarme, les criteres qui servent a la fixation des concentrations a mesurer, la sensibilite a donner aux moyens de mesure, les difficultes provenant de la contamination atmospherique naturelle. Les moyens actuellement disponibles pour le controle de la contamination et leurs moyens limites d'emploi sont analyses sommairement. (auteurs)

  2. QUALITÉ NUTRITIVE DE L’ALIMENTATION NATURELLE DU TILAPIA OREOCHROMIS NILOTICUS EN ÉLEVAGE EXTENSIF DANS DES ÉTANGS DE BARRAGE (CÔTE D’IVOIRE

    Directory of Open Access Journals (Sweden)

    BLE M. C.

    2007-04-01

    Full Text Available La composition chimique des sources alimentaires (périphyton, matières en suspension et sédiment et celle des contenus stomacaux d’Oreochromis niloticus en élevage extensif dans deux barrages situés en zone rurale (Gueyo, Sud-Ouest de la Côte d’Ivoire ont été déterminées afin d’apprécier la qualité de la nourriture naturelle ingérée par ces poissons. Les proportions des différents constituants chimiques mesurés dans ces trois sources alimentaires laissent apparaître la part importante que représentent les matières organiques hydrolysables dans le périphyton (65 et 67 % aux barrages 1 et 2, respectivement, alors que les matières minérales constituent plus de la moitié du poids sec total des matières en suspension (59 et 63 % et de la ressource sédimentaire (76 et 63 %. Sur les deux sites, les fibres représentent moins de 15 % de ces trois ressources. Les teneurs en protéines (19 % et le ratio Protéines/Énergie (17 mg.kJ-1 observés dans la ressource périphytique sont respectivement 2 et 3 fois supérieurs aux valeurs mesurées dans les deux autres ressources. L’analyse biochimique des contenus stomacaux montre que les protéines sont présentes en très faibles proportions dans la nourriture ingérée par O. niloticus (7 et 11 % dans les deux barrages. Par contre, les proportions en fibres (12 et 16 % et lipides (11 et 8 % de même que les ratios Protéines/Énergie (6 et 12 mg.kJ-1 caractérisant l’alimentation semblent répondre aux exigences de croissance chez cette espèce de tilapia. Les poids moyens des poissons en fin de cycle d’élevage traduisent la capacité d’O. niloticus à présenter une croissance correcte à partir d’une alimentation pauvre en matières azotées pourvu qu’une faible densité soit appliquée dans les sites d’élevage.

  3. Contrat comme loi naturelle (rationnelle, penser le fondement de la validité du contenu du contrat en droit français et iranien des contrats

    Directory of Open Access Journals (Sweden)

    Mahdi Shahabi

    2015-12-01

    Full Text Available The contract looks like the natural law. This means the negation of the principle of the autonomy of the will and the will of Legislator as a basis for the validity of contractual content would be rejected. For, the foundation of creation and validity of natural law would not the will, but natural justice and natural equity. Therefore, the foundation of the validity for such a contract- similar to such a law- must be sought in justice and equity. Adopting such an approach, the principle of contractual justice and fairness- not the principle of the autonomy of the will or the principle of obligatory force of a contract- surface dominant. Such an approach could become more conductive to Iranian contract law. Neither will of legislator nor the principle of the autonomy of the will could be considered as the foundation of the validity of the contractual content in the Iranian legal system, all in order to deter the contract to be praised. It is God's will that determines the foundation of the validity of the contract and this will gives priority to the La Zarar and the negation of Hardship over other contractual principles.

  4. Antioxidant effect of naturally occurring xanthines on the oxidative damage of DNA bases; Effet antioxydant de xanthines naturelles sur le dommage oxydant des bases de l`ADN

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, A.J.S.C.; Telo, J.P.; Pereira, H.F.; Patrocinio, P.F. [Instituto Superior Tecnico, Lisbon (Portugal); Dias, R.M.B. [Instituto Tecnologico e Nuclear, Sacavem codex (Portugal). Dept. de Quimica

    1999-01-01

    The repair of the oxidised radicals of adenine and guanosine by several naturally occurring xanthines was studied. Each pair of DNA purine/xanthine was made to react with the sulphate radical and the decrease of the concentration of both compounds was measured by HPLC as a function of irradiation time. The results show that xanthine efficiently prevents the oxidation of the two DNA purines. Theophylline and para-xanthine repair the oxidizes radical of adenine but not the one from guanosine. Theobromine and caffeine to do not show any protecting effect. An order of the oxidation potentials of all the purines studied is proposed. (authors) 10 refs.

  5. Simulating deep convection with a shallow convection scheme

    Directory of Open Access Journals (Sweden)

    C. Hohenegger

    2011-10-01

    Full Text Available Convective processes profoundly affect the global water and energy balance of our planet but remain a challenge for global climate modeling. Here we develop and investigate the suitability of a unified convection scheme, capable of handling both shallow and deep convection, to simulate cases of tropical oceanic convection, mid-latitude continental convection, and maritime shallow convection. To that aim, we employ large-eddy simulations (LES as a benchmark to test and refine a unified convection scheme implemented in the Single-column Community Atmosphere Model (SCAM. Our approach is motivated by previous cloud-resolving modeling studies, which have documented the gradual transition between shallow and deep convection and its possible importance for the simulated precipitation diurnal cycle.

    Analysis of the LES reveals that differences between shallow and deep convection, regarding cloud-base properties as well as entrainment/detrainment rates, can be related to the evaporation of precipitation. Parameterizing such effects and accordingly modifying the University of Washington shallow convection scheme, it is found that the new unified scheme can represent both shallow and deep convection as well as tropical and mid-latitude continental convection. Compared to the default SCAM version, the new scheme especially improves relative humidity, cloud cover and mass flux profiles. The new unified scheme also removes the well-known too early onset and peak of convective precipitation over mid-latitude continental areas.

  6. Le vieillard et le chevalier

    Directory of Open Access Journals (Sweden)

    Mélanie JECKER

    2010-05-01

    Full Text Available La fin du Moyen Âge fascine. Deux facteurs principaux expliquent l’attraction qu’exerce cette période : elle apparaît d’une part comme un moment historique riche car double, phase de transition entre le Moyen Âge et la Renaissance, où se mêlent des cadres de représentation anciens et nouveaux. L’insinuation d’une pensée humaniste balbutiante s’y traduirait notamment par l’émergence de la notion d’individu, qui constitue l’un des objets de ce travail. Il faut invoquer, d’autre part, l’image macabre d’un bas Moyen Âge hanté par l’idée de la maladie et de la mort depuis l’épidémie de peste noire de 1348, obsédé par la brièveté de la vie humaine. Ces deux facettes de « l’automne du Moyen Âge » tel que l’évoque avec poésie Joan Huizinga sont-elles autre chose qu’une plaisante image d’Epinal? Cette étude cherche précisément à déterminer le degré de validité de ces deux topiques, à travers l’analyse de la représentation des âges de la vie dans un corpus bien défini, celui de la biographie chevaleresque castillane du XVe siècle. L’intérêt porté à l’individu, la conscience de la singularité impliquent en effet celle du caractère mouvant de la personne, or quel thème mieux que celui des âges permet de confirmer ou d’infirmer l’hypothèse du surgissement d’une nouvelle manière de concevoir l’homme, proprement « renaissante », en ce siècle de transition , La nature même du corpus retenu – des récits biographiques – suggère en effet une mutation dans l’appréhension de la personne, une attention prêtée à sa progressive transformation. L’étude de la représentation de la vieillesse, en particulier, révèle non seulement à quel point était alors réelle cette prétendue obsession de la déchéance physique et de la mortalité, mais aussi dans quelle mesure étaient soulignés et valorisés les changements individuels parallèles à l

  7. Convection and stellar oscillations

    DEFF Research Database (Denmark)

    Aarslev, Magnus Johan

    2017-01-01

    for asteroseismology, because of the challenges inherent in modelling turbulent convection in 1D stellar models. As a result of oversimplifying the physics near the surface, theoretical calculations systematically overestimate the oscillation frequencies. This has become known as the asteroseismic surface effect. Due...... to lacking better options, this frequency difference is typically corrected for with ad-hoc formulae. The topic of this thesis is the improvement of 1D stellar convection models and the effects this has on asteroseismic properties. The source of improvements is 3D simulations of radiation...... atmospheres to replace the outer layers of stellar models. The additional turbulent pressure and asymmetrical opacity effects in the atmosphere model, compared to convection in stellar evolution models, serve to expand the atmosphere. The enlarged acoustic cavity lowers the pulsation frequencies bringing them...

  8. Active control of convection

    Energy Technology Data Exchange (ETDEWEB)

    Bau, H.H. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    1995-12-31

    Using stability theory, numerical simulations, and in some instances experiments, it is demonstrated that the critical Rayleigh number for the bifurcation (1) from the no-motion (conduction) state to the motion state and (2) from time-independent convection to time-dependent, oscillatory convection in the thermal convection loop and Rayleigh-Benard problems can be significantly increased or decreased. This is accomplished through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid`s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such a way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary`s temperature/heat flux are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behavior at relatively low Rayleigh numbers.

  9. Convective transport in tokamaks

    International Nuclear Information System (INIS)

    D'Ippolito, D.A.; Myra, J.R.; Russell, D.A.; Krasheninnikov, S.I.; Pigarov, A.Yu.; Yu, G.Q.; Xu, X.Q.; Nevins, W.M.

    2005-01-01

    Scrape-off-layer (SOL) convection in fusion experiments appears to be a universal phenomenon that can 'short-circuit' the divertor in some cases. The theory of 'blob' transport provides a simple and robust physical paradigm for studying convective transport. This paper summarizes recent advances in the theory of blob transport and its comparison with 2D and 3D computer simulations. We also discuss the common physical basis relating radial transport of blobs, pellets, and ELMs and a new blob regime that may lead to a connection between blob transport and the density limit. (author)

  10. Physics of Stellar Convection

    Science.gov (United States)

    Arnett, W. David

    2009-05-01

    We review recent progress using numerical simulations as a testbed for development of a theory of stellar convection, much as envisaged by John von Newmann. Necessary features of the theory, non-locality and fluctuations, are illustrated by computer movies. It is found that the common approximation of convection as a diffusive process presents the wrong physical picture, and improvements are suggested. New observational results discussed at the conference are gratifying in their validation of some of our theoretical ideas, especially the idea that SNIb and SNIc events are related to the explosion of massive star cores which have been stripped by mass loss and binary interactions [1

  11. Parameterizing convective organization

    Directory of Open Access Journals (Sweden)

    Brian Earle Mapes

    2011-06-01

    Full Text Available Lateral mixing parameters in buoyancy-driven deep convection schemes are among the most sensitive and important unknowns in atmosphere models. Unfortunately, there is not a true optimum value for plume mixing rate, but rather a dilemma or tradeoff: Excessive dilution of updrafts leads to unstable stratification bias in the mean state, while inadequate dilution allows deep convection to occur too easily, causing poor space and time distributions and variability. In this too-small parameter space, compromises are made based on competing metrics of model performance. We attempt to escape this “entrainment dilemma” by making bulk plume parameters (chiefly entrainment rate depend on a new prognostic variable (“organization,” org meant to reflect the rectified effects of subgrid-scale structure in meteorological fields. We test an org scheme in the Community Atmosphere Model (CAM5 with a new unified shallow-deep convection scheme (UW-ens, a 2-plume version of the University of Washington scheme. Since buoyant ascent involves natural selection, subgrid structure makes convection systematically deeper and stronger than the pure unorganized case: plumes of average (or randomly sampled air rising in the average environment. To reflect this, org is nonnegative, but we leave it dimensionless. A time scale characterizes its behavior (here ∼3 h for a 2o model. Currently its source is rain evaporation, but other sources can be added easily. We also let org be horizontally transported by advection, as a mass-weighted mean over the convecting layer. Linear coefficients link org to a plume ensemble, which it assists via: 1 plume base warmth above the mean temperature 2 plume radius enhancement (reduced mixing, and 3 increased probability of overlap in a multi-plume scheme, where interactions benefit later generations (this part has only been implemented in an offline toy column model. Since rain evaporation is a source for org, it functions as a time

  12. Mathematical models of convection

    CERN Document Server

    Andreev, Victor K; Goncharova, Olga N; Pukhnachev, Vladislav V

    2012-01-01

    Phenomena of convection are abundant in nature as well as in industry. This volume addresses the subject of convection from the point of view of both, theory and application. While the first three chapters provide a refresher on fluid dynamics and heat transfer theory, the rest of the book describes the modern developments in theory. Thus it brings the reader to the ""front"" of the modern research. This monograph provides the theoretical foundation on a topic relevant to metallurgy, ecology, meteorology, geo-and astrophysics, aerospace industry, chemistry, crystal physics, and many other fiel

  13. Convective aggregation in realistic convective-scale simulations

    OpenAIRE

    Holloway, Christopher E.

    2017-01-01

    To investigate the real-world relevance of idealized-model convective self-aggregation, five 15-day cases of real organized convection in the tropics are simulated. These include multiple simulations of each case to test sensitivities of the convective organization and mean states to interactive radiation, interactive surface fluxes, and evaporation of rain. These simulations are compared to self-aggregation seen in the same model configured to run in idealized radiative-convective equilibriu...

  14. Le beau et le vrai

    Directory of Open Access Journals (Sweden)

    Létitia Mouze

    2006-05-01

    Full Text Available La vie des abeilles de Maeterlinck est un ouvrage à la fois scientifique et littéraire, non pas parce qu’il appartiendrait à la science par son exactitude et à la littérature par son style, mais en ce qu’il invite à penser l’unité des deux domaines. Les aspects littéraires de l’ouvrage (beauté de l’écriture, usage des images, de l’analogie, etc. ne sont pas des accessoires, mais des outils indispensables à l’élaboration d’un authentique savoir sur les abeilles, c’est-à-dire un savoir qui reconnaît la part d’inconnu et le mystère qui subsistent en dépit de toutes les explications physiques et mécaniques que l’on peut par ailleurs donner des phénomènes observés. Etre scientifique, dans cette perspective, c’est-à-dire donner à connaître, c’est donc être littéraire. Cette conception de la science repose en dernière instance sur une conception philosophique de l’univers comme un tout où toutes choses sont reliées, unies, par des relations d’analogies, ce qui fonde et justifie l’emploi d’un style symboliste.The life of bees, one of Maeterlinck’s works, is together a scientific and literary book, not because of it scientific exactness and its literary style, but for the reason it suggests the unity of both these domains. Literay’s aspects of this work (writing’s beauty, use of images, analogy, etc. are not secondary but necessary to elaborate an authentic knowledge about bees, that means a knowledge which admit the unknown part and the mistery that subsist despite all the physical and mechanical explanations we can give moreover about the observed phenomenons. Be a scientist, in this sense, that is give something to know, therefore means be literary. Finally, this conception of science consist in a philosophiacl conception of Universe as a whole where everything links together, and is united by analogical relations, that base and justify the use of a symbolist style.

  15. The dating of the fourth volume of Guillaume-Antoine Olivier’s “Entomologie, ou histoire naturelle des insectes”

    Science.gov (United States)

    Bousquet, Yves

    2018-01-01

    Abstract Despite the title page is dated 1795, the fourth volume of Olivier’s Entomologie, ou histoire naturelle des insectes was issued in two parts, one probably in 1795 and the second in 1800. All new taxa made available in this work have previously been dated 1795 in the literature. A list of new species described in 1795 and a list of those that have to be dated 1800 are appended. The genus Necrobia should be credited to Latreille, 1797, not Olivier, 1795. PMID:29674858

  16. CDM Convective Forecast Planning guidance

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The CDM Convective Forecast Planning (CCFP) guidance product provides a foreast of en-route aviation convective hazards. The forecasts are updated every 2 hours and...

  17. Presentation on Tropical Mesoscale convective Systems and ...

    Indian Academy of Sciences (India)

    IAS Admin

    Shallow convection- 70% of the storm heights are below 6 km. ♢ Deep convection ... Decay convection, the convective top is found at a higher altitude than deep .... Stratospheric Fountain – Two step process. Warm tropopause- preferable for.

  18. Convective overshooting in stars

    NARCIS (Netherlands)

    Andrássy, R.

    2015-01-01

    Numerous observations provide evidence that the standard picture, in which convective mixing is limited to the unstable layers of a star, is incomplete. The mixing layers in real stars are significantly more extended than what the standard models predict. Some of the observations require changing

  19. Le CRDI en Colombie

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le CRDI appuie la recherche en Colombie dans des domaines tels ... Le CRDI a soutenu des activités de longue haleine qui ont eu pour ... Des travaux subventionnés par le CRDI ont aidé une fondation à intégrer Internet à son programme ...

  20. Convective Propagation Characteristics Using a Simple Representation of Convective Organization

    Science.gov (United States)

    Neale, R. B.; Mapes, B. E.

    2016-12-01

    Observed equatorial wave propagation is intimately linked to convective organization and it's coupling to features of the larger-scale flow. In this talk we a use simple 4 level model to accommodate vertical modes of a mass flux convection scheme (shallow, mid-level and deep). Two paradigms of convection are used to represent convective processes. One that has only both random (unorganized) diagnosed fluctuations of convective properties and one with organized fluctuations of convective properties that are amplified by previously existing convection and has an explicit moistening impact on the local convecting environment We show a series of model simulations in single-column, 2D and 3D configurations, where the role of convective organization in wave propagation is shown to be fundamental. For the optimal choice of parameters linking organization to local atmospheric state, a broad array of convective wave propagation emerges. Interestingly the key characteristics of propagating modes are the low-level moistening followed by deep convection followed by mature 'large-scale' heating. This organization structure appears to hold firm across timescales from 5-day wave disturbances to MJO-like wave propagation.

  1. Forced heat convection in annular spaces; Convection forcee de la chaleur dans les espaces annulaires

    Energy Technology Data Exchange (ETDEWEB)

    Pelce, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1960-02-15

    This report deals with the experimental study of forced heat convection in annular spaces through which flow of air is passing when a uniform heat flux is dissipated across the inner wall. These observations took place chiefly in the region where thermal equilibrium are not yet established. Amongst other things it became apparent that, both in the region where thermal equilibrium conditions are on the way to establishment and where they are already established, the following relationship held good: the longitudinal temperature gradient, either on the wall or in the fluid stream, is proportional to the heat flux dissipated q, and inversely proportional to the average flow rate V: dT/dx = B (q/V). From this result the next step is to express the variations of the local convection coefficient {alpha} (or of the Margoulis number M) in a relationship of the form: 1/M = {psi}(V) + F(x). If this relationship is compared with the classical empirical relationship {alpha} = KV{sup n} (where n is close to 0.8), the relationship: 1/M = {xi}V{sup 1-n} + F(x) is obtained ({xi} is a constant for a given annular space); from this it was possible to coordinate the whole set of experimental results. (author) [French] Il s'agit precisement de l'etude experimentale de la convection forcee de la chaleur dans des espaces annulaires parcourus par de l'air en ecoulement turbulent, lorsqu'on dissipe a travers la paroi interieure un flux de chaleur uniforme. Ces observations ont eu lieu principalement dans la region ou le regime thermique n'est pas encore etabli. Il est apparu, entre autre, qu'il existait, tant dans la region ou le regime thermique est en voie d'etablissement qu'en regime etabli, la relation suivante: le gradient longitudinal des temperatures, que ce soit sur la paroi ou dans l'ecoulement fluide, est proportionnel au flux de la chaleur dissipee q, et inversement proportionnel a la vitesse moyenne V de l'ecoulement: dT/dx = B (q/V). Ce resultat a pour consequence de traduire

  2. Convection heat transfer

    CERN Document Server

    Bejan, Adrian

    2013-01-01

    Written by an internationally recognized authority on heat transfer and thermodynamics, this second edition of Convection Heat Transfer contains new and updated problems and examples reflecting real-world research and applications, including heat exchanger design. Teaching not only structure but also technique, the book begins with the simplest problem solving method (scale analysis), and moves on to progressively more advanced and exact methods (integral method, self similarity, asymptotic behavior). A solutions manual is available for all problems and exercises.

  3. Concepts of magnetospheric convection

    International Nuclear Information System (INIS)

    Vasyliunas, V.M.

    1975-01-01

    Magnetospheric physics, which grew out of attempts to understand the space environment of the Earth, is becoming increasingly applicable to other systems in the Universe. Among the planets, in addition to the Earth, Jupiter, Mercury, Mars and (in a somewhat different way) Venus are now known to have magnetospheres. The magnetospheres of pulsars have been regarded as an essential part of the pulsar phenomenon. Other astrophysical systems, such as supernova remnant shells or magnetic stars and binary star systems, may be describable as magnetospheres. The major concepts of magnetospheric physics thus need to be formulated in a general way not restricted to the geophysical context in which they may have originated. Magnetospheric convection has been one of the most important and fruitful concepts in the study of the Earth's magnetosphere. This paper describes the basic theoretical notions of convection in a manner applicable to magnetospheres generally and discusses the relative importance of convective corotational motions, with particular reference to the comparison of the Earth and Jupiter. (Auth.)

  4. Induction précoce de l'ovulation chez le saumon Atlantique Salmo salar élevé entièrement en eau douce

    Directory of Open Access Journals (Sweden)

    JALABERT B.

    1980-10-01

    Full Text Available Des essais réalisés sur une population de Saumon Atlantique de l'Allier, élevée entièrement en eau douce, ont démontré la possibilité d'induire artificiellement l'ovulation avec une avance d'au moins 15 jours sur la date d'ovulation naturelle. Le traitement le plus avantageux (dose minimale de gonadotropine de Saumon partiellement purifiée. G.S.P.P. de 0,1 mg/kg fournissant une réponse rapide est constitué par deux injections successives de G.S.P.P. (0,05 mg/kg suivies d'une injection de 17 x hydroxy-20 β dihydroprogestérone (2 mg/kg.

  5. Inventory of refrigeration training in Quebec given within the framework of the intervention program of Natural Resources Canada's CETC-Varennes and the AEE of Ressources naturelles du Quebec; Inventaire de la formation en refrigeration au Quebec dans le cadre du programme d'intervention initie par le CTEC-Varennes de ressources naturelles Canada et l'AEE de ressources naturelles du Quebec

    Energy Technology Data Exchange (ETDEWEB)

    Garant, G.J. [Association des Arenas du Quebec Inc., Montreal, PQ (Canada)

    2004-03-01

    This paper relates information concerning vocational courses in refrigeration in Quebec, with reference to the newly formed National Committee on Vocational and Technical Educational Programs. The aim of the paper was to collect data on the availability of refrigeration courses. A description of course outlines was provided, with reference to requirements in high school and at the college level. Requirement details for additional courses in heating and electricity refrigeration were also provided. The status of diplomas was also discussed, with reference to employment opportunities in management and analysis upon completion of the Diploma of Collegial Studies, which requires additional courses in energy conservation. Opportunities in the labour market were reviewed, as well as information on privately run courses. Particular reference was made concerning the Canadian Energy Technology Centre (CETC) as a leading research facility for refrigeration concepts and design. It was noted that very few courses on refrigeration technology are offered at the university level, and that currently only one distance education course on refrigeration has been recognized. As a result of this investigation, the Quebec Arena Association has determined that development of new courses is a priority, especially given that only the CETC currently offers courses on refrigeration for arenas and curling rinks. New courses should focus on arena and rink refrigeration technologies, with particular reference to new technologies and developments in energy efficiency. tabs., figs.

  6. Le corps sportif1

    OpenAIRE

    Brulé, Pierre

    2015-01-01

    Le nu et le cuit Si, pas plus que l’Auvergne, le monde grec antique n’a été le théâtre d’un quelconque « miracle », il n’a pas manqué, toutefois, de « distinctions » diverses, d’exceptions même, qui le singularisent absolument. Une, c’est la pédérastie. Quelle culture l’a autant valorisée, autant instrumentalisée, l’a autant érigée en modèle ? Nous n’en avons pas encore mesuré toutes les conséquences. La place inhabituelle que prend là et alors cette polyvalence rare de la libido masculine de...

  7. Bidispersive-inclined convection

    Science.gov (United States)

    Mulone, Giuseppe; Straughan, Brian

    2016-01-01

    A model is presented for thermal convection in an inclined layer of porous material when the medium has a bidispersive structure. Thus, there are the usual macropores which are full of a fluid, but there are also a system of micropores full of the same fluid. The model we employ is a modification of the one proposed by Nield & Kuznetsov (2006 Int. J. Heat Mass Transf. 49, 3068–3074. (doi:10.1016/j.ijheatmasstransfer.2006.02.008)), although we consider a single temperature field only. PMID:27616934

  8. Prévention des catastrophes naturelles à l'échelle des collectivités ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    5 juin 2012 ... Grâce à un outil de planification à l'échelle locale créé avec l'appui du CRDI, des ... hors de danger, et ce, au moyen des données générées grâce au SIGA. ... ÉTUDE DE CAS — Amérique latine : Un point de départ pour le ...

  9. Le Bon, Gustave

    DEFF Research Database (Denmark)

    Borch, Christian

    2017-01-01

    Gustave Le Bon (1841–1931) was a French physician and crowd psychologist who published extensively on themes such as crowds, war, race, revolution, socialism, and war. His work on crowd psychology in particular was highly influential, including beyond scholarly circles. Le Bon argued that crowds...

  10. A Generalized Evolution Criterion in Nonequilibrium Convective Systems

    Science.gov (United States)

    Ichiyanagi, Masakazu; Nisizima, Kunisuke

    1989-04-01

    A general evolution criterion, applicable to transport processes such as the conduction of heat and mass diffusion, is obtained as a direct version of the Le Chatelier-Braun principle for stationary states. The present theory is not based on any radical departure from the conventional one. The generalized theory is made determinate by proposing the balance equations for extensive thermodynamic variables which will reflect the character of convective systems under the assumption of local equilibrium. As a consequence of the introduction of source terms in the balance equations, there appear additional terms in the expression of the local entropy production, which are bilinear in terms of the intensive variables and the sources. In the present paper, we show that we can construct a dissipation function for such general cases, in which the premises of the Glansdorff-Prigogine theory are accumulated. The new dissipation function permits us to formulate a generalized evolution criterion for convective systems.

  11. Le commerce des fleurs naturelles dans une métropole tropicale; implications socioéconomiques et spatiales: le cas de la ville de Yaoundé au Cameroun

    Directory of Open Access Journals (Sweden)

    Clotaire Ndzie Souga

    2017-06-01

    Full Text Available . The economic crises of the years 1980-1990 weakened the power of African states to create decent jobs, fight against poverty and ameliorate the living conditions of the population. Just as other African countries, Cameroon has been hard hit by this crisis as well as the damaging effects of the structural adjustment plan. Currently, Cameroonian towns with the example of Yaoundé are at the centre of socioeconomic innovations, indigenous know how and circular economy. This situation is shown on the spot by the interest given by the populations to the novel initiatives and the creation of income generating activities. Such is the case with the horticulture trade in the towns of Douala and Yaoundé. In effect, the sale of natural flowers is an activity that is increasing in proportion in these two towns of Cameroon. Here, flowers are no longer only vegetation species meant for decoration. They are more than ever sold and give employment to a wide variety of people young and old. In the town of Yaoundé, a flower market has been created at avenue Foch at ABBIA. This study analyses the socioeconomic and spatial implications of this market. A survey, of 38 of the 73 vendors in the flower market of the town of Yaoundé in 2015, shows that the sale of natural flowers is part of the socioeconomic landscape of Yaoundé. Today, it generates enormous income that contributes in the amelioration of the lives of those involved in it. It contributes to significant spatial flux in Yaoundé and the entire Cameroon. But it is important for it to be organised and made popular so that its actors can draw significant income for an emerging Cameroonian economy.

  12. Lele des chefs traditionnels au Ghana : un modèle inspirant ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    8 févr. 2011 ... Avec ses partenaires du Sud, avec aussi le soutien du Centre de recherches pour le développement international ( CRDI ), organisme canadien, Ray a étudié lele des chefs traditionnels au Ghana dans la lutte contre le VIH et le sida. Les collectivités politiques antérieures au colonialisme sont une ...

  13. Frontières administratives et identités communales. Le cas de la France, XVIII-XXe siècles

    Directory of Open Access Journals (Sweden)

    Claude Motte

    2009-01-01

    Full Text Available Parmi les différentes déclinaisons du terme "frontière" (naturelle, politique, administrative, identitaire, existe-t-il une combinaison d'entre elles qui résisterait le plus farouchement à l'épreuve du temps? Le cas de la France qui, au sein de l'Europe, connaît une exception administrative particulière, est intéressant à observer. Ses nombreuses frontières intérieures ont repoussé avec obstination toute tentative de réduction de leur nombre. Sans doute parce que, laissée à l'initiative des populations locales et respectée par les successifs gouvernements, la définition des territoires s'est appuyée sur la reconnaissance des identités communales construites au cours des siècles par le quotidien des habitants. La correspondance cartographique établie entre le tissu paroissial du XVIIIe siècle en France, et le maillage communal d'aujourd'hui illustre, en dépit des quelques variations observées, la remarquable stabilité de ses frontières administratives.

  14. Convection in Porous Media

    CERN Document Server

    Nield, Donald A

    2013-01-01

    Convection in Porous Media, 4th Edition, provides a user-friendly introduction to the subject, covering a wide range of topics, such as fibrous insulation, geological strata, and catalytic reactors. The presentation is self-contained, requiring only routine mathematics and the basic elements of fluid mechanics and heat transfer. The book will be of use not only to researchers and practicing engineers as a review and reference, but also to graduate students and others entering the field. The new edition features approximately 1,750 new references and covers current research in nanofluids, cellular porous materials, strong heterogeneity, pulsating flow, and more. Recognized as the standard reference in the field Includes a comprehensive, 250-page reference list Cited over 2300 times to date in its various editions Serves as an introduction for those entering the field and as a comprehensive reference for experienced researchers Features new sections on nanofluids, carbon dioxide sequestration, and applications...

  15. Temperature-Driven Convection

    Science.gov (United States)

    Bohan, Richard J.; Vandegrift, Guy

    2003-02-01

    Warm air aloft is stable. This explains the lack of strong winds in a warm front and how nighttime radiative cooling can lead to motionless air that can trap smog. The stability of stratospheric air can be attributed to the fact that it is heated from above as ultraviolet radiation strikes the ozone layer. On the other hand, fluid heated from below is unstable and can lead to Bernard convection cells. This explains the generally turbulent nature of the troposphere, which receives a significant fraction of its heat directly from the Earth's warmer surface. The instability of cold fluid aloft explains the violent nature of a cold front, as well as the motion of Earth's magma, which is driven by radioactive heating deep within the Earth's mantle. This paper describes how both effects can be demonstrated using four standard beakers, ice, and a bit of food coloring.

  16. Convection in porous media

    CERN Document Server

    Nield, Donald A

    1992-01-01

    This book provides a user-friendly introduction to the topic of convection in porous media The authors as- sume that the reader is familiar with the basic elements of fluid mechanics and heat transfer, but otherwise the book is self-contained The book will be useful both as a review (for reference) and as a tutorial work, suitable as a textbook in a graduate course or seminar The book brings into perspective the voluminous research that has been performed during the last two decades The field has recently exploded because of worldwide concern with issues such as energy self-sufficiency and pollution of the environment Areas of application include the insulation of buildings and equipment, energy storage and recovery, geothermal reservoirs, nuclear waste disposal, chemical reactor engineering, and the storage of heat-generating materials such as grain and coal Geophysical applications range from the flow of groundwater around hot intrusions to the stability of snow against avalanches

  17. Géographie et politiques de l’aide d’urgence au Bangladesh ; les désastres engendrés par le typhon Sidr, le 16 novembre 2007

    Directory of Open Access Journals (Sweden)

    Mouhssine Ennaïmi

    2008-04-01

    Full Text Available Le typhon Sidr a frappé le Sud du Bangladesh le 16 novembre 2007 (4 000 victimes, 8 millions de déplacés et sans abris. La réputation controversée de ce pays mal connu lui a valu l’attention de l’opinion internationale. Le Bangladesh a une longue expérience en matière de catastrophes naturelles, et est doté d’un large réseau d’organisations de solidarité. La prévention de l’aléa et la gestion de l’aide d’urgence ont permis de limiter les pertes humaines. Grâce à cette bonne coordination, la phase de reconstruction a été amorcée rapidement. La situation demeure difficile et le pays n’est pas encore sorti du marasme économique et social qui le caractérise.Sidr typhoon struck the Southern districts in Bangladesh on November 16, 2007 (4000 victims, 8 millions of displaced people / homeless. The discussed reputation of this country supports the attention of the international opinion to him. Thanks to its experience about natural hazards and to a broad humanitarian organizations network, the prevention of the catastrophe and the management of emergency aid made it possible to limit the human lives losses. A good relief aid management offered the opportunity of quickly switching from an emergency to a development stage.Still, the situation remains complex and the country has not overcome the economic and social depression which characterizes it.

  18. Stellar convection and dynamo theory

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, R L

    1989-10-01

    In considering the large scale stellar convection problem the outer layers of a star are modelled as two co-rotating plane layers coupled at a fluid/fluid interface. Heating from below causes only the upper fluid to convect, although this convection can penetrate into the lower fluid. Stability analysis is then used to find the most unstable mode of convection. With parameters appropriate to the Sun the most unstable mode is steady convection in thin cells (aspect ratio {approx equal} 0.2) filling the convection zone. There is negligible vertical motion in the lower fluid, but considerable thermal penetration, and a large jump in helicity at the interface, which has implications for dynamo theory. An {alpha}{omega} dynamo is investigated in isolation from the convection problem. Complexity is included by allowing both latitudinal and time dependence in the magnetic fields. The nonlinear dynamics of the resulting partial differential equations are analysed in considerable detail. On varying the main control parameter D (the dynamo number), many transitions of behaviour are found involving many forms of time dependence, but not chaos. Further, solutions which break equatorial symmetry are common and provide a theoretical explanation of solar observations which have this symmetry. Overall the behaviour was more complicated than expected. In particular, there were multiple stable solutions at fixed D, meaning that similar stars can have very different magnetic patterns, depending upon their history. (author).

  19. Analytical and Numerical Study of Soret and Dufour Effects on Double Diffusive Convection in a Shallow Horizontal Binary Fluid Layer Submitted to Uniform Fluxes of Heat and Mass

    Directory of Open Access Journals (Sweden)

    A. Lagra

    2018-01-01

    Full Text Available Combined Soret and Dufour effects on thermosolutal convection induced in a horizontal layer filled with a binary fluid and subject to constant heat and mass fluxes are investigated analytically and numerically. The thresholds marking the onset of supercritical and subcritical convection are predicted analytically and explicitly versus the governing parameters. The present investigation shows that different regions exist in the N-Du plane corresponding to different parallel flow regimes. The number, the extent, and the locations of these regions depend on whether SrDu>-(1+Le2/2Le2=f(Le or SrDu<-(1+Le2/2Le2. Conjugate effects of cross-phenomena on thresholds of fluid flow and heat and mass transfer characteristics are illustrated and discussed.

  20. The convection patterns in microemulsions

    International Nuclear Information System (INIS)

    Korneta, W.; Lopez Quintela, M.A.; Fernandez Novoa, A.

    1991-07-01

    The Rayleigh-Benard convection in the microemulsion consisting of water (7.5%), cyclohexan (oil-61.7%) and diethylenglycolmonobutylether (surfactant-30.8%) is studied from the onset of convection to the phase separation. The five classes of convection patterns are observed and recorded on the video: localized travelling waves, travelling waves, travelling waves and localized steady rolls, steady rolls and steady polygons. The Fourier transforms and histograms of these patterns are presented. The origin of any pattern is discussed. The intermittent behaviour close to the phase separation was observed. Possible applications of the obtained results are suggested. (author). 6 refs, 4 figs

  1. Le Mouvement Social

    OpenAIRE

    FRIDENSON, Patrick

    2003-01-01

    J'ai la faiblesse d'affirmer que parmi les revues françaises d'histoire Le Mouvement Social est la revue qui a publié le plus d'articles et de comptes rendus en matière d'histoire des femmes et du gender. Chacun peut le vérifier grâce à nos pages Web sur le site Internet du Dictionnaire créé par Jean Maitron. Elles comportent la table des matières complète de la revue depuis sa fondation en 1960. Notre rédaction est extrêmement fière de ce résultat. Mais elle reconnaît qu'il a été difficile à...

  2. Le CRDI en Afghanistan

    International Development Research Centre (IDRC) Digital Library (Canada)

    Depuis près de 40 ans, le CRDI collabore étroitement avec les chercheurs des pays en développement et les appuie dans leur quête de moyens de créer des sociétés en meilleure santé, plus équitables et plus prospères. Centre de recherches pour le développement international. CP 8500, Ottawa (Ontario) Canada K1G ...

  3. Le CRDI au Bhoutan

    International Development Research Centre (IDRC) Digital Library (Canada)

    Il en résulte des solutions locales, novatrices et durables, qui offrent des choix aux personnes qui en ont le plus besoin et font changer les choses. Centre de recherches pour le développement international. CP 8500, Ottawa (Ontario) Canada K1G 3H9. Pour en savoir plus, consulter la page. Web du Bureau régional de ...

  4. Le CRDI au Kenya

    International Development Research Centre (IDRC) Digital Library (Canada)

    afin d'y favoriser la croissance et le développement. Il en résulte des solutions novatrices et durables qui ont pour but d'améliorer les conditions de vie et les moyens de subsistance. Centre de recherches pour le développement international. CP 8500, Ottawa (Ontario) Canada K1G 3H9. Pour en savoir plus, consulter.

  5. Le CRDI en Jordanie

    International Development Research Centre (IDRC) Digital Library (Canada)

    ... dans les pays en développement afin d'y favoriser la croissance et le développement. Il en résulte des solutions novatrices et durables qui ont pour but d'améliorer les conditions de vie et les moyens de subsistance. Centre de recherches pour le développement international. CP 8500, Ottawa (Ontario) Canada K1G 3H9.

  6. Le CRDI au Mali

    International Development Research Centre (IDRC) Digital Library (Canada)

    de ces technologies et tentent de déterminer si un régime de microcrédit pourrait encourager leur adoption. On cherche par cela à accroître la sécurité alimentaire de même que le rendement des cultures de dolique, de sorgho et de mil. □ Menaces pesant sur les moyens de subsistance. Financement octroyé pour le Mali :.

  7. Le faussaire roman

    CERN Document Server

    D'Anna, Gianfranco

    2016-01-01

    À l'aube du XXIe siècle, le monde de la science est sur le point de vivre une révolution. Le jeune physicien allemand Albert Hendrick Thebell, des célèbres laboratoires de recherche B-Labs, à Summit, dans le New Jersey, publie, dans les plus grandes revues scientifiques internationales, une série d'articles dans lesquels il prétend avoir obtenu des résultats extraordinaires qui pourraient révolutionner les bases mêmes de la technologie. Rapidement, la communauté scientifique puis les médias saluent en lui un futur prix Nobel; on compare même son génie à celui d'Albert Einstein. Le progrès scientifique semble avoir franchi une étape décisive, susceptible d'amener un futur meilleur. Mais ces découvertes sont-elles authentiques ? Car pendant ce temps, dans les mêmeslaboratoires, des voix s'élèvent pour contester non seulement les théories de Thebell mais aussi la légitimité même de ses expériences ; certains le soupçonnent d'avoir combiné la plus grande fraude scientifique de tous l...

  8. Aide à la décision pour l’analyse de la vulnérabilité des réseaux d’infrastructure face à une crise de catastrophe naturelle

    OpenAIRE

    Kamissoko, Daouda

    2013-01-01

    Cette thèse traite de la Vulnérabilité des réseaux face aux catastrophes naturelles. Elle part du constat que les infrastructures telles que les réseaux d’eau, d’électricité influencent considérablement les conséquences indirectes des catastrophes naturelles. Elle vise donc à modéliser la vulnérabilité dans de telles situations pour une prise de décision efficace. La démarche scientifique est divisée en deux parties complémentaires. La première traite de la vulnérabilité des dits systèmes, ta...

  9. A new method for dosing rhodamine B in natural water; Dosage de la rhodamine B dans les eaux naturelles

    Energy Technology Data Exchange (ETDEWEB)

    Marichal, M.; Benoit, R. [Commissariat a l' energie atomique et aux energies alternatives - CEA, Centre de Marcoule, Centre de Production de Plutonium de Marcoule, Service de Protection contre les Radiations (France)

    1961-07-01

    A simple and sensitive method well adapted to hydrological research. The dye is first extracted from the water sample by isoamyl alcohol and then the fluorescence of the alcoholic solution, after excitation by ultraviolet radiation, is measured spectrophotometrically. The sensitivity of the method is about 10{sup -12}, that is, a millionth of a milligram of dye per litre. Reprint of a paper published in 'Chimie Analytique', N. 2, Feb 1962, p. 70-72 [French] Methode simple et sensible convenant bien aux recherches hydrologiques. Le colorant est prealablement extrait de l'echantillon d'eau par l'alcool isoamylique; la fluorescence de la solution alcoolique eclairee en lumiere ultraviolette est ensuite mesuree au spectrophotometre. La sensibilite de la methode est de l'ordre de I0{sup -12}, soit un millionieme de milligramme de colorant par litre. Reproduction d'un article publie dans 'Chimie Analytique', N. 2, Feb 1962, p. 70-72.

  10. Réglementation et ressources naturelles : l’exemple de la forêt en Comtat Venaissin

    OpenAIRE

    Leroy, Nicolas

    2009-01-01

    À travers l’exemple de la forêt dans le Comtat Venaissin et la Principauté d’Orange voisine, sont approchées les réglementations visant à assurer une gestion raisonnée de la ressource bois. À la fin du Moyen Âge, la prise de conscience de la raréfaction des forêts est incontestable dans la région. Plusieurs seigneurs et communautés élaborent alors des mesures visant à concilier conservation et exploitation indispensable aux villageois. Celles-ci vont de l’interdiction assez stricte d’accès et...

  11. Study of a method of detection for natural carbon-14 using a liquid scintillator, recent variations in the natural radio-activity due to artificial carbon-14 (1963); Etude d'une methode de detection du carrons 14 naturel, utilisant un scintillateur liquide - variations recentes de l'activite naturelle dues au carbone 14 artificiel (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Leger, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-06-15

    Among the various natural isotopes of carbon, a radioactive isotope, carbon-14, is formed by the action of secondary neutrons from cosmic rays on nitrogen in the air. Until 1950, the concentration of this isotope in ordinary carbon underwent weak fluctuations of about 2-3 per cent. The exact measurement of this concentration 6 X 10{sup 12} Ci/gm of carbon, and of its fluctuations, are difficult and in the first part of this report a highly sensitive method is given using a liquid scintillator. Since 1950 this natural activity has shown large fluctuations because of the carbon-14 formed during nuclear explosions, and in the second part, the evolution in France of this specific activity of carbon in the atmosphere and biosphere is examined. In the last part is studied the local increase in carbon activity in the atmosphere around the Saclay site, an increase caused by the carbon-14 given off as C{sup 14}O{sub 2}, by the reactors cooled partially with exterior air. (author) [French] Parmi les differents isotopes naturels du carbone, un isotope radioactif, le carbone 14, est forme par l'action de neutrons secondaires due aux rayons cosmiques sir l'azote de l'air. Jusqu'en 1950, la concentration de cet isotope dans le carbone ordinaire est soumise a des fluctuations de faible amplitude, de l'ordre de 2 a 3 pour cent. Les mesures precises de cette concentration, 6. 10{sup -12} Ci/g de carbone, et de ses fluctuations sont delicates, et dans la premiere partie de ce rapport, on decrit une methode de detection a grande sensibilite utilisant un scintillateur liquide. Depuis 1950, cette activite naturelle subit des fluctuations importantes dues au carbone 14 forme lors des explosions nucleaires, et dans la seconde partie, on examine l'evolution en France de l'activite specifique du carbone de l'atmosphere et ce la biosphere. Dans la derniere partie, on etudie l'accroissement local de l'activite du carbone de l'air aux environs du site de Saclay, accroissement provoque par le

  12. Study of a method of detection for natural carbon-14 using a liquid scintillator, recent variations in the natural radio-activity due to artificial carbon-14 (1963); Etude d'une methode de detection du carrons 14 naturel, utilisant un scintillateur liquide - variations recentes de l'activite naturelle dues au carbone 14 artificiel (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Leger, C. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-06-15

    Among the various natural isotopes of carbon, a radioactive isotope, carbon-14, is formed by the action of secondary neutrons from cosmic rays on nitrogen in the air. Until 1950, the concentration of this isotope in ordinary carbon underwent weak fluctuations of about 2-3 per cent. The exact measurement of this concentration 6 X 10{sup 12} Ci/gm of carbon, and of its fluctuations, are difficult and in the first part of this report a highly sensitive method is given using a liquid scintillator. Since 1950 this natural activity has shown large fluctuations because of the carbon-14 formed during nuclear explosions, and in the second part, the evolution in France of this specific activity of carbon in the atmosphere and biosphere is examined. In the last part is studied the local increase in carbon activity in the atmosphere around the Saclay site, an increase caused by the carbon-14 given off as C{sup 14}O{sub 2}, by the reactors cooled partially with exterior air. (author) [French] Parmi les differents isotopes naturels du carbone, un isotope radioactif, le carbone 14, est forme par l'action de neutrons secondaires due aux rayons cosmiques sir l'azote de l'air. Jusqu'en 1950, la concentration de cet isotope dans le carbone ordinaire est soumise a des fluctuations de faible amplitude, de l'ordre de 2 a 3 pour cent. Les mesures precises de cette concentration, 6. 10{sup -12} Ci/g de carbone, et de ses fluctuations sont delicates, et dans la premiere partie de ce rapport, on decrit une methode de detection a grande sensibilite utilisant un scintillateur liquide. Depuis 1950, cette activite naturelle subit des fluctuations importantes dues au carbone 14 forme lors des explosions nucleaires, et dans la seconde partie, on examine l'evolution en France de l'activite specifique du carbone de l'atmosphere et ce la biosphere. Dans la derniere partie, on etudie l'accroissement local de l'activite du carbone de l'air aux

  13. Convection in the Labrador Sea

    National Research Council Canada - National Science Library

    Davis, R

    1997-01-01

    The long-term goal of this grant was to describe the process of deep oceanic convection well enough to provide critical tests of, and guidance to, models used to predict subsurface ocean conditions...

  14. Convective heat flow probe

    Science.gov (United States)

    Dunn, James C.; Hardee, Harry C.; Striker, Richard P.

    1985-01-01

    A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packer-type seals are provided along the probe above and below the heater pads.

  15. Convection-enhanced water evaporation

    OpenAIRE

    B. M. Weon; J. H. Je; C. Poulard

    2011-01-01

    Water vapor is lighter than air; this can enhance water evaporation by triggering vapor convection but there is little evidence. We directly visualize evaporation of nanoliter (2 to 700 nL) water droplets resting on silicon wafer in calm air using a high-resolution dual X-ray imaging method. Temporal evolutions of contact radius and contact angle reveal that evaporation rate linearly changes with surface area, indicating convective (instead of diffusive) evaporation in nanoliter water droplet...

  16. Tumelo le Moruo

    Directory of Open Access Journals (Sweden)

    Vuyani S. Vellem

    2015-03-01

    Full Text Available Paleng ya rona batho ba batsho, tumelo ya boKreste e fihlile lefatsheng la rona la Afrika Borwa mmoho le dikgoka tsa ditjhaba tsa boPhirima. BoKreste bo fihlile ka nako ya dintwa tseo mohopolo wa tsona e neng e le ho hapa lefatshe la, batho ba batsho. Ka mantswe amang, rona batho ba batsho, re ile ra qetella re le setjhaba se ileng sa hlolwa, mme lefatshe la rona la nkuwa ka dikgoka. Ka hare ho dikgoka tsena, ho ne ho dutse tumelo ya boKreste. Makgowa a ile are: �A re kwaleng mahlo re rapeleng, rona ra kwala mahlo, mme ha re qeta hore Amen, re bula mahlo, ra fumana lefatshe le nkuwe matsohong a rona ho setse Bibele.� Re ile ra sala le Bibele eo ka yona re lekileng dilemong tse fitileng ho lwana ntwa ya topollo, kapa tokoloho hofihlela selemong sa 1994. Le ha re ile ra fumana tokoloho ka selemo seo, hare so ka re lokoloha ho tsa moruo. E kaba sena se bolela eng mabapi le tumelo ya rona ya boKreste? Segolweng sena re leka ho araba potso ena. Tumelo ke eng ho batho ba sa lokolohang moruong wa naha ya bona? Re lekola pale ya boKreste, tumelo ya batho le maemo a kereke ntlheng ya ho tadimana le tokoloho ka tumelo.Faith and economics. In our history from a black perspective, Christianity arrived through violent conquest from the west. Evidentially, this faith coincided with wars of dispossession and the ultimate defeat of black Africans. It is difficult to separate the violent defeat of black Africans from the arrival of Christian faith. This well-known statement within the circles of black Theology of liberation: When the white man arrived in our land he said, �let us pray and after prayer, when we opened our eyes, our land was taken and only the Bible was left in our hands,� captures the black sentiment of this history. Ironically, it was this Bible that black Africans used to wage their struggle for liberation up to the demise of apartheid in 1994.Nonetheless, political liberation is not enough as the struggle for economic liberation

  17. Le vernis des apparences

    Directory of Open Access Journals (Sweden)

    Grazia Nicosia

    2010-04-01

    Full Text Available Le but de cet article est de comprendre l’incidence sémiotique du nettoyage d’un tableau ainsi que la résultante cognitive induite sur l’observateur. Cette étude confronte l’analyse des phénomènes visuels engendrés par le jaunissement du vernis et son retrait, à des entretiens réalisés à dessein. Le retrait d’un vernis jauni change considérablement l’image. L’heure, le climat, la saison et l’activité même des personnages s’en trouvent ainsi modifié. La patine peut être perçue, soit comme un obstacle à l’exploration, soit pour ceux qui l’apprécient, comme le medium d’une relation plus intime entre l’œuvre et l’observateur.The purpose of this article is to understand the semiotic impact of the cleaning of a painting and the cognitive effects induced on the observer. This study analyses conjointly the visual phenomenon generated by yellowing varnish and its removal and controlled interviews of observers.The removal of yellowing varnish modifies considerably the perception of the picture. Daytime, climate, season and characters activities are modified. The patina may be perceived either as an obstacle to the painting exploration, or, for those who appreciate it, as a medium for a closer relationship between the painting and the observer.

  18. Storicizzare le teorie psicocritiche

    Directory of Open Access Journals (Sweden)

    Roberto Talamo

    2015-07-01

    Full Text Available Le teorie psicoanalitiche della letteratura, dopo una fase di alterne fortune, sono oggi praticate da una cerchia di adepti sempre più ristretta. Le nuove koinè critico-teoriche tendono infatti a relegare la dottrina freudiana all’interno di un sapere letterario (e non interpretativo o a sostituire ad essa strumenti ritenuti più efficaci nella descrizione della sfera del mentale in letteratura (neuroestetica e neuronarratologia. La proposta storiografica che qui si avanza non vuole prendere parte in questo dibattito pro o contro la psicocritica, ma vuole leggere le proposte di teoria psicoanalitica della letteratura alla luce di una riflessione sul concetto di ibridazione, concetto sul quale queste teorie hanno costruito il loro confronto con i paradigmi teorici di volta in volta egemoni.

  19. Le Bestiaire d'amour de Gustave Flaubert (1

    Directory of Open Access Journals (Sweden)

    Loïc Windels

    2010-09-01

    Full Text Available « Désirer, c'est tuer ». Voilà ce qu’un Ministère de la Prévention fera bientôt imprimer sur le bandeau accompagnant les ventes du second des Trois contes. Du reste, il est certain que sa carte du Tendre empiète quelque peu sur les géographies du Cruel. Qui se penche sur son bestiaire en relève généralement assez vite le caractère symbolique et la couleur pré-freudienne. Flaubert ferait, avec le légendaire médiéval, ce que Freud peu après avec la mythologie grecque. Ces remarques et quelques autres ont parfois été faites1, et nul doute qu'elles ne soient familières à l'amateur de cette prose dense et suggestive qu'est La Légende de Saint Julien L'Hospitalier. Aussi le présent article (comme celui qui le suivra voudrait-il moins rouvrir à nouveaux frais un débat déjà bien nourri que l'aborder de façon quelque peu différente : en choisissant, parmi les épisodes où les animaux tiennent un rôle prépondérant, ceux qui semblent s'apparier pour former – à sauts et à gambades – un récit sous l'histoire, et ceux qui, en même temps, paraissaient désirer qu'on les confronte à d'autres textes (reste de l'œuvre, bestiaires médiévaux, histoires naturelles anciennes et modernes, mythographies et à quelques images.In The Legend of Saint Julian the Hospitalier – the middle of Flaubert’s Three Tales – to desire and to kill are but one thing, and its Map of Tendre encroaches somewhat on the topographies of Cruelty. He who looks into his bestiary is usually rather quick to detect its symbolic character and pre-Freudian overtones. It is as if Flaubert did with Medieval legends what Freud would do a little later with Greek mythology. These observations and other similar ones have already been made, and there is no doubt that the reader who loves the dense and suggestive prose that is The Legend of Saint Julian is familiar with them. Thus, the present article (and the one that will follow strive less to

  20. Mantle Convection on Modern Supercomputers

    Science.gov (United States)

    Weismüller, J.; Gmeiner, B.; Huber, M.; John, L.; Mohr, M.; Rüde, U.; Wohlmuth, B.; Bunge, H. P.

    2015-12-01

    Mantle convection is the cause for plate tectonics, the formation of mountains and oceans, and the main driving mechanism behind earthquakes. The convection process is modeled by a system of partial differential equations describing the conservation of mass, momentum and energy. Characteristic to mantle flow is the vast disparity of length scales from global to microscopic, turning mantle convection simulations into a challenging application for high-performance computing. As system size and technical complexity of the simulations continue to increase, design and implementation of simulation models for next generation large-scale architectures is handled successfully only in an interdisciplinary context. A new priority program - named SPPEXA - by the German Research Foundation (DFG) addresses this issue, and brings together computer scientists, mathematicians and application scientists around grand challenges in HPC. Here we report from the TERRA-NEO project, which is part of the high visibility SPPEXA program, and a joint effort of four research groups. TERRA-NEO develops algorithms for future HPC infrastructures, focusing on high computational efficiency and resilience in next generation mantle convection models. We present software that can resolve the Earth's mantle with up to 1012 grid points and scales efficiently to massively parallel hardware with more than 50,000 processors. We use our simulations to explore the dynamic regime of mantle convection and assess the impact of small scale processes on global mantle flow.

  1. Convective behaviour in severe accidents

    International Nuclear Information System (INIS)

    Clement, C.F.

    1988-01-01

    The nature and magnitude of the hazard from radioactivity posed by a possible nuclear accident depend strongly on convective behaviour within and immediately adjacent to the plant in question. This behaviour depends upon the nature of the vapour-gas-aerosol mixture concerned, and can show unusual properties such as 'upside-down' convection in which hot mixtures fall and cold mixtures rise. Predictions and criteria as to the types of behaviour which could possibly occur are summarised. Possible applications to present reactors are considered, and ways in which presently expected convection could be drastically modified are described. In some circumstances these could be used to suppress the radioactive source term or to switch its effect between distant dilute contamination and severe local contamination. (author). 8 refs, 2 figs, 2 tabs

  2. Topology Optimization for Convection Problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe

    2011-01-01

    This report deals with the topology optimization of convection problems.That is, the aim of the project is to develop, implement and examine topology optimization of purely thermal and coupled thermomechanical problems,when the design-dependent eects of convection are taken into consideration.......This is done by the use of a self-programmed FORTRAN-code, which builds on an existing 2D-plane thermomechanical nite element code implementing during the course `41525 FEM-Heavy'. The topology optimizationfeatures have been implemented from scratch, and allows the program to optimize elastostatic mechanical...

  3. Experimental methods in natural convection

    International Nuclear Information System (INIS)

    Koster, J.N.

    1982-11-01

    Some common experimental techniques to determine local velocities and to visualize temperature fields in natural convection research are discussed. First the physics and practice of anemometers are discussed with emphasis put on optical anemometers. In the second and third case the physics and practice of the most developed interferometers are discussed; namely differential interferometry for visualization of temperature gradient fields and holographic interferometry for visualization of temperature fields. At the Institut fuer Reaktorbauelemente these three measuring techniques are applied for convection and pipe flow studies. (orig.) [de

  4. Le vase de Pandore

    Directory of Open Access Journals (Sweden)

    Nicola Panichi

    2000-06-01

    Full Text Available Il s’agit ici de suivre les stratégies discursives par lesquelles Érasme situe sa Lingua sous le patronage symbolique de deux mythes des plus opératoires à la Renaissance : le vase de Pandore et la tour de Babel, tous deux verrouillant le texte, l’un en guise d’incipit, l’autre d’explicit, dans un dialogue où chacun use de l’autre pour renforcer les significations et instaurer le régime sémantique du texte, tant linguistique qu’éthique. Ce sont ces jeux complexes entre différents niveaux de discours dont dépend le sens ultime de l’œuvre que cet article s’attache à saisir.Se trata de seguir aquí las estrategias discursivas mediante las cuales Erasmo sitúa su Lingua bajo el dominio simbólico de dos de los mitos más funcionales del Renacimiento: el vaso de Pandora y la torre de Babel, los cuales limitan el texto, uno a modo de íncipit, otro de excipit, en un diálogo en el que se valen el uno del otro para reforzar los significados y establecer el régimen semántico del texto, tanto lingüístico como ético. Son esos juegos complejos entre diferentes niveles de discurso, de los que depende el sentido último de la obra, que este artículo intenta captar.

  5. Segregation and convection in dendritic alloys

    Science.gov (United States)

    Poirier, D. R.

    1990-01-01

    Microsegregation in dentritic alloys is discussed, including solidification with and without thermal gradient, the convection of interdendritic liquid. The conservation of momentum, energy, and solute is considered. Directional solidification and thermosolutal convection are discussed.

  6. Boiling Suppression in Convective Flow

    International Nuclear Information System (INIS)

    Aounallah, Y.

    2004-01-01

    The development of convective boiling heat transfer correlations and analytical models has almost exclusively been based on measurements of the total heat flux, and therefore on the overall two-phase heat transfer coefficient, when the well-known heat transfer correlations have often assumed additive mechanisms, one for each mode of heat transfer, convection and boiling. While the global performance of such correlations can readily be assessed, the predictive capability of the individual components of the correlation has usually remained elusive. This becomes important when, for example, developing mechanistic models for subcooled void formation based on the partitioning of the wall heat flux into a boiling and a convective component, or when extending a correlation beyond its original range of applications where the preponderance of the heat transfer mechanisms involved can be significantly different. A new examination of existing experimental heat transfer data obtained under fixed hydrodynamic conditions, whereby the local flow conditions are decoupled from the local heat flux, has allowed the unequivocal isolation of the boiling contribution over a broad range of thermodynamic qualities (0 to 0.8) for water at 7 MPa. Boiling suppression, as the quality increases, has consequently been quantified, thus providing valuable new insights on the functionality and contribution of boiling in convective flows. (author)

  7. Le plurilinguisme du perroquet

    Directory of Open Access Journals (Sweden)

    Manuel Mühlbacher

    2012-05-01

    Full Text Available La figure du perroquet occupe une position ambiguë face à la question de la traduction. Il est capable d’imiter des paroles en toutes les langues, mais il n’est capable d’en comprendre aucune — il ne peut que répéter des sons, c’est-à-dire des signifiants. Le traducteur semble faire le contraire quand il passe d’une langue à une autre en tâchant de transmettre une signification semblable par d’autres signes. L’article vise à discuter lele du traducteur et sa relation, éventuellement équivoque, au perroquet, en analysant la traduction allemande de Trois Contes par André Stoll et Cora van Kleffens. Un décalage au niveau sémantique peut éclairer l’interprétation du texte, par exemple en explicitant des allusions sous-jacentes, tandis que le transfert de la syntaxe française en allemand pose souvent des problèmes considérables. Comment le traducteur peut-il reproduire des structures syntaxiques qui n’existent pas en allemand, mais qui ne cessent de revenir dans le texte français ? Que faire si le texte se met à jouer au perroquet et finit par se singer lui-même ? André Stoll et Cora van Kleffens ont su trouver des stratégies pour affronter ces difficultés.The figure of the parrot holds an ambiguous position towards the question of translation. It is able to imitate all languages, but it will never understand any of them – its only skill is to mimic sounds, i.e. mere signifiers. On the contrary, the translator seems to be the antithesis of the parrot when he moves from one language to another. He endeavours to convey a similar meaning, but by different signs. The article aims at discussing the role of the translator and his or her eventually equivocal relation to the parrot by means of analysing the German translation of Trois Contes by André Stoll and Cora van Kleffens. Whereas a semantic divergence can result in a different tendency on the level of interpretation, as in the case of an underlying

  8. Le cru, le cuit et le pourri dans _Le vice-consul_ de Marguerite Duras

    Directory of Open Access Journals (Sweden)

    Hélène Caron

    2011-05-01

    Full Text Available Bien que plusieurs articles critiques aient déjà avancé de nouvelles perspectives sur le texte Le Vice-Consul (LVC de Marguerite Duras, l’analyse de la représentation de la nourriture dans ce roman n’a fait l’objet d’aucune étude. Cet article tente donc de combler cette lacune en proposant d’analyser les images du cru et du cuit, images qui se rejoignent sous les notions du pourri et de l’abject, tout en offrant quelques interprétations de l’un des passages critiques du roman où la folle mendiante croque la tête d’un poisson vivant.

  9. Le charme slave

    Directory of Open Access Journals (Sweden)

    Antonella Mauri

    2012-09-01

    Full Text Available Antonella Mauri analyse l’image des femmes slaves immigrées en Italie telle qu’elle apparaît à travers la publicité, la littérature romanesque (La ballata dei lavavetri de Peter Del monte, Luce Profuga de Valerio Aiolli, Pornokiller de Bruno Ventavoli, le cinéma, la bande dessinée (Danilo Maramotti, image qu’elle oppose aux résultats d’une enquête qu’elle a menée sur le terrain. Elle s’interroge en particulier sur la permanence des stéréotypes liés à la femme slave.

  10. Le Brahmane du Komintern

    Directory of Open Access Journals (Sweden)

    Elizabeth Burgos

    2008-01-01

    Full Text Available Le Brahmane du Komintern, largometraje documental del realizador francés Vladimir León, constituye un ejercicio ejemplar de investigación histórica y  de lograda factura de realización. Y, pese a no haber contado con la ayuda de ninguno organismo público, se trata de un ambicioso proyecto que cubre una amplia extensión geográfica que abarca: Estados Unidos, México, Moscú, Berlín, y la India. Gira en torno a una figura que tuvo en su tiempo su hora de gloria. Un bengalí, hijo de braman, la c...

  11. Le monde quantique

    CERN Document Server

    Aspect, A; Bensaude-Vincent, B; Castiel, A; Chevalley, C; Darrigol, O; Deligeorges, S; D'Espagnat, B; Laloë, F; Lévy-Leblond, J-M; Messiah, A; Paty, M; Vuillemin, J; Wheaton, B R

    1984-01-01

    Le monde quantique La physique quantique, après trois quarts de siècle, n'en finit pas d'être moderne. Elle est présente quotidiennement dans les laboratoires où les physiciens étudient atomes, noyaux et particules. Elle est entrée dans l'industrie où lasers, transistors et supraconducteurs lui doivent d'exister. Et elle continue à alimenter le débat philosophique sur la nature de la réalité dont elle montre la non-séparabilité fondamentale. Ses concepts de base, son développement, ses applications, ses controverses sont ici présentés par une pléiade de physiciens, d'historiens et de philosophes.

  12. Le CRDI au Ghana

    International Development Research Centre (IDRC) Digital Library (Canada)

    pour prévenir le paludisme, des études ayant démontré que leur utilisation pouvait réduire considérablement la mortalité infantile. Les chercheurs ont également suggéré aux gouvernements différents moyens pour inciter les gens à acheter les moustiquaires et à les utiliser correctement. Les TI au service de la démocratie.

  13. Le Culture preistoriche

    OpenAIRE

    Tanda, Giuseppa

    1987-01-01

    Le più antiche manifestazioni della presenza dell'uomo, nella provincia di Sassari (e in Sardegna), risalgono al Quaternario: sono state osservate nel 1979, nel bacino del rio Altana-Anzos, situato nel territorio dei comuni di Laerru e Perfugas. Il presente lavoro propone un excursus dal Paleolitico al Neolitico (antico, medio e recente) fino all'Età del Rame e all'Età del Bronzo (II metà del III millennio-1600 a.C.).

  14. Le CRDI en Chine

    International Development Research Centre (IDRC) Digital Library (Canada)

    les employés du secteur non structuré ont de meilleures conditions de travail. □ les citoyens influencent les décisions relatives aux dépenses publiques. Soutien accordé par le CRDI depuis 1981. 222 activités d'une valeur de 59 millions CAD. Chercheurs et agriculteurs s'emploient à améliorer les moyens de subsistance.

  15. Le CRDI en Tunisie

    International Development Research Centre (IDRC) Digital Library (Canada)

    les citoyens arabes sont plus présents sur Internet. Soutien accordé depuis 1975. 49 activités. 8 millions cad. Dans la foulée du Printemps arabe, les chercheurs conçoivent des réformes visant à assurer l'essor de la démocratie et en examinent la validité. CRDI centre de recherches pour le développement international.

  16. A transilient matrix for moist convection

    Energy Technology Data Exchange (ETDEWEB)

    Romps, D.; Kuang, Z.

    2011-08-15

    A method is introduced for diagnosing a transilient matrix for moist convection. This transilient matrix quantifies the nonlocal transport of air by convective eddies: for every height z, it gives the distribution of starting heights z{prime} for the eddies that arrive at z. In a cloud-resolving simulation of deep convection, the transilient matrix shows that two-thirds of the subcloud air convecting into the free troposphere originates from within 100 m of the surface. This finding clarifies which initial height to use when calculating convective available potential energy from soundings of the tropical troposphere.

  17. Le Conseil des gouverneurs | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le Conseil des gouverneurs guide le travail du CRDI en lui fournissant une orientation stratégique, en examinant ses activités et en approuvant ses budgets. Les gouverneurs – un maximum de 14 – sont nommés par le gouverneur en conseil du Canada pour un mandat d'au plus quatre ans, qui peut être reconduit. La Loi ...

  18. Le FIVB annonce le financement de cinq autres projets | CRDI ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    10 avr. 2018 ... En partenariat avec la Fondation Bill et Melinda Gates et Affaires mondiales Canada, le CRDI est heureux d'annoncer la prochaine série de projets soutenus par le Fonds d'innovation en matière de vaccins pour le bétail (FIVB). À ce jour, 11 projets ont obtenu un financement total de 13,6 millions de CAD ...

  19. Le nouveau modèle africain | IDRC - International Development ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    22 juil. 2011 ... L'annulation de la dette, un commerce plus équitable, davantage d'aide : voilà le plan d'action mondial dont on convient qu'il faut de toute urgence mettre en oeuvre en vue d'accélérer le développement en Afrique. Or, ce serait rater le bateau que de ne pas s'engager dans la voie tout autre que les ...

  20. Numerical simulation of double-diffusive mixed convective flow in rectangular enclosure with insulated moving lid

    Energy Technology Data Exchange (ETDEWEB)

    Teamah, M.A. [Faculty of Engineering, Alexandria University, Mech. Eng. Dept, Alexandria (Egypt); El-Maghlany, W.M. [Faculty of Engineering, Suez Canal University, Ismailia (Egypt)

    2010-09-15

    The present study is concerned with the mixed convection in a rectangular lid-driven cavity under the combined buoyancy effects of thermal and mass diffusion. Double-diffusive convective flow in a rectangular enclosure with moving upper surface is studied numerically. Both upper and lower surfaces are being insulated and impermeable. Constant different temperatures and concentration are imposed along the vertical walls of the enclosure, steady state laminar regime is considered. The transport equations for continuity, momentum, energy and spices transfer are solved. The numerical results are reported for the effect of Richardson number, Lewis number, and buoyancy ratio on the iso-contours of stream line, temperature, and concentration. In addition, the predicted results for both local and average Nusselt and Sherwood numbers are presented and discussed for various parametric conditions. This study was done for 0.1 <= Le <= 50 and Prandtl number Pr = 0.7. Through out the study the Grashof number and aspect ratio are kept constant at 10{sup 4} and 2 respectively and -10 <= N <= 10, while Richardson number has been varied from 0.01 to 10 to simulate forced convection dominated flow, mixed convection and natural convection dominated flow. (authors)

  1. Convective aggregation in realistic convective-scale simulations

    Science.gov (United States)

    Holloway, Christopher E.

    2017-06-01

    To investigate the real-world relevance of idealized-model convective self-aggregation, five 15 day cases of real organized convection in the tropics are simulated. These include multiple simulations of each case to test sensitivities of the convective organization and mean states to interactive radiation, interactive surface fluxes, and evaporation of rain. These simulations are compared to self-aggregation seen in the same model configured to run in idealized radiative-convective equilibrium. Analysis of the budget of the spatial variance of column-integrated frozen moist static energy shows that control runs have significant positive contributions to organization from radiation and negative contributions from surface fluxes and transport, similar to idealized runs once they become aggregated. Despite identical lateral boundary conditions for all experiments in each case, systematic differences in mean column water vapor (CWV), CWV distribution shape, and CWV autocorrelation length scale are found between the different sensitivity runs, particularly for those without interactive radiation, showing that there are at least some similarities in sensitivities to these feedbacks in both idealized and realistic simulations (although the organization of precipitation shows less sensitivity to interactive radiation). The magnitudes and signs of these systematic differences are consistent with a rough equilibrium between (1) equalization due to advection from the lateral boundaries and (2) disaggregation due to the absence of interactive radiation, implying disaggregation rates comparable to those in idealized runs with aggregated initial conditions and noninteractive radiation. This points to a plausible similarity in the way that radiation feedbacks maintain aggregated convection in both idealized simulations and the real world.Plain Language SummaryUnderstanding the processes that lead to the organization of tropical rainstorms is an important challenge for weather

  2. Soil-plant-atmosphere conditions regulating convective cloud formation above southeastern US pine plantations.

    Science.gov (United States)

    Manoli, Gabriele; Domec, Jean-Christophe; Novick, Kimberly; Oishi, Andrew Christopher; Noormets, Asko; Marani, Marco; Katul, Gabriel

    2016-06-01

    Loblolly pine trees (Pinus taeda L.) occupy more than 20% of the forested area in the southern United States, represent more than 50% of the standing pine volume in this region, and remove from the atmosphere about 500 g C m-2 per year through net ecosystem exchange. Hence, their significance as a major regional carbon sink can hardly be disputed. What is disputed is whether the proliferation of young plantations replacing old forest in the southern United States will alter key aspects of the hydrologic cycle, including convective rainfall, which is the focus of the present work. Ecosystem fluxes of sensible (Hs) and latent heat (LE) and large-scale, slowly evolving free atmospheric temperature and water vapor content are known to be first-order controls on the formation of convective clouds in the atmospheric boundary layer. These controlling processes are here described by a zero-order analytical model aimed at assessing how plantations of different ages may regulate the persistence and transition of the atmospheric system between cloudy and cloudless conditions. Using the analytical model together with field observations, the roles of ecosystem Hs and LE on convective cloud formation are explored relative to the entrainment of heat and moisture from the free atmosphere. Our results demonstrate that cloudy-cloudless regimes at the land surface are regulated by a nonlinear relation between the Bowen ratio Bo=Hs/LE and root-zone soil water content, suggesting that young/mature pines ecosystems have the ability to recirculate available water (through rainfall predisposition mechanisms). Such nonlinearity was not detected in a much older pine stand, suggesting a higher tolerance to drought but a limited control on boundary layer dynamics. These results enable the generation of hypotheses about the impacts on convective cloud formation driven by afforestation/deforestation and groundwater depletion projected to increase following increased human population in the

  3. CRUCIB: an axisymmetric convection code

    International Nuclear Information System (INIS)

    Bertram, L.A.

    1975-03-01

    The CRUCIB code was written in support of an experimental program aimed at measurement of thermal diffusivities of refractory liquids. Precise values of diffusivity are necessary to realistic analysis of reactor safety problems, nuclear waste disposal procedures, and fundamental metal forming processes. The code calculates the axisymmetric transient convective motions produced in a right circular cylindrical crucible, which is surface heated by an annular heat pulse. Emphasis of this report is placed on the input-output options of the CRUCIB code, which are tailored to assess the importance of the convective heat transfer in determining the surface temperature distribution. Use is limited to Prandtl numbers less than unity; larger values can be accommodated by replacement of a single block of the code, if desired. (U.S.)

  4. Fluid convection, constraint and causation

    Science.gov (United States)

    Bishop, Robert C.

    2012-01-01

    Complexity—nonlinear dynamics for my purposes in this essay—is rich with metaphysical and epistemological implications but is receiving sustained philosophical analysis only recently. I will explore some of the subtleties of causation and constraint in Rayleigh–Bénard convection as an example of a complex phenomenon, and extract some lessons for further philosophical reflection on top-down constraint and causation particularly with respect to causal foundationalism. PMID:23386955

  5. Cryogenic helium gas convection research

    International Nuclear Information System (INIS)

    Donnelly, R.J.

    1994-10-01

    This is a report prepared by a group interested in doing research in thermal convection using the large scale refrigeration facilities available at the SSC Laboratories (SSCL). The group preparing this report consists of Michael McAshan at SSCL, Robert Behringer at Duke University, Katepalli Sreenivasan at Yale University, Xiao-Zhong Wu at Northern Illinois University and Russell Donnelly at the University of Oregon, who served as Editor for this report. This study reports the research and development opportunities in such a project, the technical requirements and feasibility of its construction and operation, and the costs associated with the needed facilities and support activities. The facility will be a unique national resource for studies of high-Reynolds-number and high-Rayleigh-number and high Rayleigh number turbulence phenomena, and is one of the six items determined as suitable for potential funding through a screening of Expressions of Interest. The proposed facility is possible only because of the advanced cryogenic technology available at the SSCL. Typical scientific issues to be addressed in the facility will be discussed. It devolved during our study, that while the main experiment is still considered to be the thermal convection experiment discussed in our original Expression of Interest, there are now a very substantial set of other, important and fundamental experiments which can be done with the large cryostat proposed for the convection experiment. We believe the facility could provide several decades of front-line research in turbulence, and shall describe why this is so

  6. Thermosolutal convection during dendritic solidification

    Science.gov (United States)

    Heinrich, J. C.; Nandapurkar, P.; Poirier, D. R.; Felicelli, S.

    1989-01-01

    This paper presents a mathematical model for directional solidification of a binary alloy including a dendritic region underlying an all-liquid region. It is assumed initially that there exists a nonconvecting state with planar isotherms and isoconcentrates solidifying at a constant velocity. The stability of this system has been analyzed and nonlinear calculations are performed that show the effect of convection in the solidification process when the system is unstable. Results of calculations for various cases defined by the initial temperature gradient at the dendrite tips and varying strength of the gravitational field are presented for systems involving lead-tin alloys. The results show that the systems are stable for a gravitational constant of 0.0001 g(0) and that convection can be suppressed by appropriate choice of the container's size for higher values of the gravitational constant. It is also concluded that for the lead-tin systems considered, convection in the mushy zone is not significant below the upper 20 percent of the dendritic zone, if al all.

  7. Le regard anachronique

    Directory of Open Access Journals (Sweden)

    Jean-Paul Aubert

    2011-01-01

    Full Text Available Cet article a pour objet l’anachronisme dans le film historique. Il s’appuie sur l’étude du long métrage Goya à Bordeaux, réalisé en 1999 par le cinéaste espagnol Carlos Saura. Cette biographie filmée du peintre Francisco de Goya fait mieux que composer avec l’anachronisme inhérent à toute reconstitution historique. Il l’assume et le revendique. La mise en cause de la chronologie et l’effacement de l’Histoire prennent sens dans la perspective d’une réflexion originale sur l’Histoire de l’art conçue comme un dialogue entre les œuvres et entre les époques.Este artículo está dedicado al problema del anacronismo en las películas históricas. Se basa en el estudio de Goya en Burdeos, un largo metraje rodado en 1999 por el director de cine español Carlos Saura. Esta biografía de Goya no sólo se acomoda con el anacronismo propio de la reconstitución histórica sino que lo asume y lo reivindica. El cuestionamiento de la cronología y el desinterés por la Historia cobran un nuevo sentido en el marco de una reflexión original sobre la Historia del arte concebida como un diálogo entre las obras y entre las épocas.

  8. La piraterie sur le web

    CERN Multimedia

    2002-01-01

    Les échanges de toutes sortes sont facilités à l'extrême par le web: des forums, des vidéoconférences, le commerce à distance, ou tout simplement la célérité des courriers électroniques ou la convivialité des chats, tout cela participe de la société de communication. Une certaine partie du monde découvre le nouvel horizon des échanges quasi instantanés, mais... les transactions sur le web sont-elles vraiment s res?

  9. Le commerce du Nord

    OpenAIRE

    Pourchasse, Pierrick; Bouëdec, Gérard Le

    2015-01-01

    Au XVIIIe siècle, la France s'approvisionne abondamment dans les pays du Nord : bois, chanvre et goudron de la Baltique, tonnellerie de Poméranie, pêche de rogue de Norvège, graines de lin de Courlande, barres de fer suédois… Sa balance commerciale est pourtant positive grâce aux sels, aux vins et surtout des nouvelles marchandises coloniales. Or, la plupart des transactions passent par l’incontournable intermédiaire hollandais. Les explications sur l’absence des Français dans le Nord sont re...

  10. Le survivant sans le syndrome Schreber

    Directory of Open Access Journals (Sweden)

    Richard Figuier

    2006-09-01

    Full Text Available On a pensé la catastrophe, mais a-t-on suffisamment pensé la survivance et la figure du survivant ? Ce n'est pas un hasard si celle-ci est au centre de Masse et puissance, oeuvre dans laquelle Canetti interroge la « mauvaise » survivance responsable de la poursuite de la logique de guerre. Mais où trouver la « bonne » ? Revenir de la catastrophe ne suffit pas pour être un « survivant authentique », selon l'expression de Kafka. Il faut avoir dépassé, avec Primo Levi et Robert Antelme, l'opposition de la vie comme croissance continue et de la mort comme son horrible contraire, par le don, dans la pauvreté solidaire, de cette vie retrouvée.Hemos reflexionado acerca de la catástrofe, pero ¿hemos meditado lo suficiente sobre la supervivencia y el superviviente? No es una coincidencia si el superviviente es el tema principal de Masse et puissance, obra en la cual Canetti analiza la «mala» supervivencia responsable de la persistencia de la lógica de guerra ¿Dónde sin embargo podemos encontrar la «buena» supervivencia? Superar la catástrofe no es suficiente para ser un «auténtico superviviente», según Kafka. Es fundamental ir más allá, con Primo Levi y Robert Antelme, de la oposición entre la vida, como crecimiento continuo, y la muerte, como su espantoso contrario, mediante la donación de forma solidaria de esta vida reencontrada.Disaster is the theme of many studies, but what about survival and of the figure of the survivor? This issue is central in Mass and power, work in which Canetti questions the “bad” survival, responsible for the continuation of the logic of war. But is there any “good” survival? Coming back from the catastrophe is not enough to be an “authentic survivor”, according to Kafka’s expression. To achieve this, it is necessary to have exceeded, with PrimoLevi and Robert Antelme, the opposition of life as a continuous growth and of death as its horrible opposite, by the gift, in a

  11. Le Conseil des gouverneurs | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    2 nov. 2010 ... La gouvernance du CRDI. Reddition de comptes, transparence et efficacité. Au cours de l'exercice 2009–2010, le Conseil des gouverneurs du CRDI a adopté un nouveau cadre stratégique quinquennal, Le développement par l'innovation. Pendant de nombreux mois, les gouverneurs et les membres de la ...

  12. Le tournoi des ombres

    CERN Document Server

    Treille, Daniel

    2017-01-01

    Le lecteur, transporté avec le narrateur dans une région hors norme, est invité à partager sa fascination pour la beauté du lieu, à découvrir la chronique de son passé, rude et pittoresque. Il va côtoyer une galerie de personnages très attachants, mais aux destinées bousculées par l histoire, et assister à l agitation montante du présent dans un contexte d une actualité brûlante. Ce quatrième roman de Daniel Treille, mêlant hardiment les genres, du quotidien trivial au récit épique, de considérations géopolitiques à quelques avancées de la science moderne, confirme son talent à mener, d une écriture très aboutie, une histoire complexe, peuplée de héros singuliers

  13. Le Dominique Interactif

    Directory of Open Access Journals (Sweden)

    Valérie Ouellette

    2005-09-01

    Full Text Available Cet article présente le Dominique Interactif, une bande dessinée interactive et multimédia unique, servant à évaluer sept troubles de la santé mentale chez les jeunes. La version pour les six à onze ans est adaptée aux limites cognitives des enfants et comporte plusieurs avantages. Malgré quelques limites, cet instrument permet d’obtenir des informations fiables de la part de l’enfant sur sa santé mentale. La fidélité et la validité de cet outil sont meilleures que celles des autres instruments traditionnels servant à mesurer la santé mentale des enfants. En combinant les résultats de ce questionnaire avec les informations des parents, professionnels et enseignants, le Dominique Interactif permet aussi d’effectuer une évaluation complète de la santé mentale de l’enfant. Enfin, son utilisation simple et rapide facilite l’évaluation clinique des enfants par les professionnels, permet l’évaluation de programmes d’intervention et favorise l’intervention précoce (Valla et al., 2000.

  14. Le principe roman

    CERN Document Server

    Ferrari, Jérôme

    2015-01-01

    Fasciné par la figure du physicien allemand Werner Heisenberg (1901-1976), fondateur de la mécanique quantique, inventeur du célèbre "principe d'incertitude" et Prix Nobel de physique en 1932, un jeune aspirant-philosophe désenchanté s'efforce, à l'aube du XXIe siècle, de considérer l'incomplétude de sa propre existence à l'aune des travaux et de la destinée de cet exceptionnel homme de sciences qui incarne pour lui la rencontre du langage scientifique et de la poésie, lesquels, chacun à leur manière, en ouvrant la voie au scandale de l'inédit, dessillent les yeux sur le monde pour en révéler la mystérieuse beauté que ne cessent de confisquer le matérialisme à l'œuvre dans l'Histoire des hommes.

  15. Convective overshoot at the solar tachocline

    Science.gov (United States)

    Brown, Benjamin; Oishi, Jeffrey S.; Anders, Evan H.; Lecoanet, Daniel; Burns, Keaton; Vasil, Geoffrey M.

    2017-08-01

    At the base of the solar convection zone lies the solar tachocline. This internal interface is where motions from the unstable convection zone above overshoot and penetrate downward into the stiffly stable radiative zone below, driving gravity waves, mixing, and possibly pumping and storing magnetic fields. Here we study the dynamics of convective overshoot across very stiff interfaces with some properties similar to the internal boundary layer within the Sun. We use the Dedalus pseudospectral framework and study fully compressible dynamics at moderate to high Peclet number and low Mach number, probing a regime where turbulent transport is important, and where the compressible dynamics are similar to those of convective motions in the deep solar interior. We find that the depth of convective overshoot is well described by a simple buoyancy equilibration model, and we consider implications for dynamics at the solar tachocline and for the storage of magnetic fields there by overshooting convection.

  16. The convection electric field in auroral substorms

    DEFF Research Database (Denmark)

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    2001-01-01

    Dynamics Explorer 2 (DE 2) electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge-type auroral substorms. Thirty-one individual DE 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained...... this database enabled us to compile a model of the ionospheric convection electric field. The characteristics of the premidnight convection reversal show a pronounced local time dependency. Far west of the surge it is a fairly well defined point reversal or convection shear. Approaching the surge and within...... the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields. Therefore we adopt the term Harang region rather than the Harang discontinuity for the premidnight convection reversal. A relatively narrow convection...

  17. The pattern of convection in the Sun

    International Nuclear Information System (INIS)

    Weiss, N.O.

    1976-01-01

    The structure of solar magnetic fields is dominated by the effects of convection, which should be incorporated in any model of the solar cycle. Although mixing length theory is adequate for calculating the structure of main sequence stars, a better description of convection is needed for any detailed dynamo model. Recent work on nonlinear convection at low Prandt numbers is reviewed. There has been some progress towards a theory of compressible convection, though there is still no firm theoretical evidence for cells with scales less than the depth of the convecting layer. However, it remains likely that the pattern of solar convection is dominated by granules, supergranules and giant cells. The effects of rotation on these cells are briefly considered. (Auth.)

  18. Equazioni: le icone del sapere

    NARCIS (Netherlands)

    Bais, S.

    2009-01-01

    Il mistero del cosmo è scritto nel linguaggio della matematica, e le equazioni sono le frasi che ne esprimono la bellezza e la profondità. Cercare di spiegare la scienza senza equazioni è come cercare di spiegare l’arte senza illustrazioni: partendo da questo presupposto, Sander Bais presenta una

  19. Le cerveau sous effet placebo

    OpenAIRE

    Touzet , Claude

    2017-01-01

    International audience; Comment le fait de croire qu’on nous injecte de la morphine (alors qu’il s’agit de sérum physiologique) peut-il faire disparaître la douleur ? Investigation sur le cerveau sous placebo.

  20. Titan Balloon Convection Model, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This innovative research effort is directed at determining, quantitatively, the convective heat transfer coefficients applicable to a Montgolfiere balloon operating...

  1. REVERSALS IN THE 6-CELLS CONVECTION DRIVEN

    Directory of Open Access Journals (Sweden)

    G.M. Vodinchar

    2015-12-01

    Full Text Available We describe the large-scale model geodynamo, which based on indirect data of inhomogeneities in the density of the Earth’s core. Convection structure is associated with spherical harmonic Y24 , which defines the basic poloidal component of velocity. Coriolis drift of this mode determines the toroidal component of velocity. Thus, 6 convective cells are formed. The model takes into account the feedback effect of the magnetic field on convection. It was ascertained that the model contains stable regimes of field generation. The velocity of convection and the dipole component of the magnetic field are close to the observed ones.

  2. Scale analysis of convective clouds

    Directory of Open Access Journals (Sweden)

    Micha Gryschka

    2008-12-01

    Full Text Available The size distribution of cumulus clouds due to shallow and deep convection is analyzed using satellite pictures, LES model results and data from the German rain radar network. The size distributions found can be described by simple power laws as has also been proposed for other cloud data in the literature. As the observed precipitation at ground stations is finally determined by cloud numbers in an area and individual sizes and rain rates of single clouds, the cloud size distributions might be used for developing empirical precipitation forecasts or for validating results from cloud resolving models being introduced to routine weather forecasts.

  3. Characterizing Convection in Stellar Atmospheres

    International Nuclear Information System (INIS)

    Tanner, Joel; Basu, Sarbani; Demarque, Pierre; Robinson, Frank

    2011-01-01

    We perform 3D radiative hydrodynamic simulations to study the properties of convection in the superadiabatic layer of stars. The simulations show differences in both the stratification and turbulent quantities for different types of stars. We extract turbulent pressure and eddy sizes, as well as the T-τ relation for different stars and find that they are sensitive to the energy flux and gravity. We also show that contrary to what is usually assumed in the field of stellar atmospheres, the structure and gas dynamics of simulations of turbulent atmospheres cannot be parameterized with T eff and log(g) alone.

  4. Le Baratze (ou

    Directory of Open Access Journals (Sweden)

    Jacques Blot

    1998-01-01

    Full Text Available El círculo de piedras Mendizabal 7, de 8 metros de diámetro,   presenta una corona externa constituida de grandes bloques   hincados en la tierra, y otra interna y tangente, de elementos idénticos sólo puestos en el suelo. El cajón central está compuesto de cuatro losas y una tapa. No hay depósito de huesos ni de carbón de leña ; sólo se encuentran dos herraduras, entre las cuales una completa de tipo medieval, que podrían permitir de pensar en una construcción del círculo en el periodo histórico.

  5. Le tourisme alpin

    Directory of Open Access Journals (Sweden)

    Andrea Macchiavelli

    2009-06-01

    Full Text Available La forte croissance qu’ont connue les pays alpins dans les dernières décennies a surtout été fondée sur l’offre des activités du ski, avec comme conséquence, un massif développement immobilier, la multiplication d’infrastructures et l’extension des domaines. Aujourd’hui, le marché du ski semble arriver à saturation, la Convention alpine a mis un frein à la poursuite du développement des domaines skiables et on observe donc avec intérêt la diversification de l’offre soutenue par l’innovation. Après avoir rappelé les facteurs de changement en cours les plus significatifs dans le tourisme montagnard, l’article présente une grille interprétative de l’évolution des destinations touristiques alpines, identifiant les phases qui ont caractérisé son développement. Puis il propose une réflexion sur certaines conditions qui peuvent favoriser l’innovation dans le tourisme alpin, ainsi que sur les contradictions qui les accompagnent souvent. Dans la plupart des cas l’innovation est le résultat d’un processus qui a été lancé et qui s’est développé au sein de la communauté alpine, souvent favorisé et soutenu par des institutions nationales et internationales, et grâce auquel les difficultés structurelles qui ont déjà été abordées précédemment ont pu être surmontées avec succès.The spectacular increase in tourism in the Alps in recent decades has been founded mainly on the boom in skiing, resulting in both strong real estate development and an increasing array of infrastructures and ski runs. Today the ski market seems to have virtually reached saturation point and the winter sports sector needs to diversify its offer through innovation. After a review of the main factors of change in mountain tourism, the paper presents a grid for interpreting the life cycle of alpine destinations, identifying the phases that characterize their evolution. The conditions that may favour innovation in alpine

  6. Le citoyen rieur

    Directory of Open Access Journals (Sweden)

    Anna Rycman

    2009-11-01

    Full Text Available Dans la Pologne d’aujourd’hui, l’évolution des modèles d’engagement civique et politique s’opère plus particulièrement auprès des jeunes générations. Parmi les expériences nouvelles de participation politique, les nouvelles technologies de l’information et de la communication offrent des opportunités radicales de reconfigurer l’espace public. La jeunesse polonaise investit en masse le Web. Dans le flux de paroles affranchies circulant et dialoguant dans le cyberespace, nous nous intéressons ici au développement d’un discours qui emprunte au registre de la dérision et de la satire politiques. Une multitude de sites critiques, de nature apparemment contestataire, des sites d’opposition fondés sur le genre satirique, ont émergé comme réponse apportée à la situation politique. Cet espace public électronique représente une forme moderne de « folklore politique », contribuant au processus de socialisation des jeunes citoyens polonais.The laughing citizen. A modern form of civic commitment in democratic Poland?In present day Poland, the evolution of civic and political commitment models is above all the affaire of the younger generations. Among the current opportunities for political participation, the new information and communication technologies offer radical opportunities to reconfigure the public arena. Polish youth are flocking to the Web. Amongst the flux of frank points of views circulating and dialoguing in cyberspace, our interest here is the development of a discourse inspired by political and satirical derision. A multitude of critical, apparently anti-establishment, sites and general opposition sites using the satirical style have emerged as a response to the political situation. This public electronic space represents a modern form of « political folklore », contributing to the socialising processes of young polish citizens.El ciudadano que rie. ¿Nueva forma del compromiso cívico en la

  7. Le grand inventaire

    Directory of Open Access Journals (Sweden)

    Michel Melot

    2012-05-01

    Full Text Available Depuis quarante ans qu’il existe, l’Inventaire général des monuments et des richesses artistiques de la France n’a pas seulement progressé, couvrant près de dix mille communes, documentant plus de vingt mille dans cinq millions de pages, trois millions de photographies, et cent mille dessins. Il est devenu ce que ses fondateurs désiraient qu’il fût. Il n’est pas une liste d’objets plus ou moins singuliers qu’on aurait oubliés, mais l’observation méthodique de l’émergence dans le monde de l’ar...

  8. INVESTIR DANS LE SAVOIR : le soutien que le CRDI consent à des ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    5 nov. 2010 ... ... 40 ans, le Cenre de recherches pour le développement international (CRDI), en plus d'appuyer des travaux de recherche dans l'ensemble des pays en développement, encourage des générations successives de jeunes chercheurs par l'entremise de son Programme de formation et de bourses (PFB).

  9. Le recours aux catégories dans la gestion du choix au cours d’un repas au restaurant

    Directory of Open Access Journals (Sweden)

    Hugol-Gential Clémentine

    2012-07-01

    Full Text Available Ce travail, ancré dans le champ de l’Analyse Conversationnelle (Sacks, 1992, s’intéresse à une question centrale à laquelle les clients sont perpétuellement confrontés lors de la prise d’un repas au restaurant : le choix. Plus précisément, nous nous intéressons à son caractère situé et à son déploiement en interaction en nous basant sur un corpus audiovisuel collecté en situation « naturelle » de production, lors de repas au restaurant, afin d’étudier la parole-en-interaction telle qu’elle est localement produite et organisée par les participants (Heath, Hindmarsch & Luff, 2010. Après avoir exposé le lien entre identité et alimentation et la notion de catégorisation telle qu’elle a été développée en Analyse Conversationnelle, nous proposerons deux analyses de séquences de prise de commande pendant lesquelles les choix des clients sont discutés et négociés avec le sommelier ou le serveur. Grâce à des analyses séquentielles basées sur des transcriptions fines, nous soulignerons que les participants à l’interaction manifestent de façon reconnaissable qui ils sont (clients experts, non experts, habitués... afin d’organiser de façon intelligible leurs actions et de permettre à leurs partenaires de s’y ajuster. Nous analyserons finement les catégories utilisées par les participants, et nous décrirons les différents procédés mobilisés afin d’organiser et d’orienter la prise de commande. Ainsi, dans un premier extrait, nous verrons que les clients s’orientent, tout d’abord, vers l’exhibition de leur propre identité, tandis que dans un deuxième extrait, c’est le plat à la carte qui fait l’objet d’une première catégorisation. L’ensemble de ce travail nous permettra de montrer que les catégories sont structurantes pour l’organisation du choix et que leur déploiement séquentiel au cours de l’interaction est constitutif des affiliations ou des désaffiliations lors

  10. Two-dimensional turbulent convection

    Science.gov (United States)

    Mazzino, Andrea

    2017-11-01

    We present an overview of the most relevant, and sometimes contrasting, theoretical approaches to Rayleigh-Taylor and mean-gradient-forced Rayleigh-Bénard two-dimensional turbulence together with numerical and experimental evidences for their support. The main aim of this overview is to emphasize that, despite the different character of these two systems, especially in relation to their steadiness/unsteadiness, turbulent fluctuations are well described by the same scaling relationships originated from the Bolgiano balance. The latter states that inertial terms and buoyancy terms balance at small scales giving rise to an inverse kinetic energy cascade. The main difference with respect to the inverse energy cascade in hydrodynamic turbulence [R. H. Kraichnan, "Inertial ranges in two-dimensional turbulence," Phys. Fluids 10, 1417 (1967)] is that the rate of cascade of kinetic energy here is not constant along the inertial range of scales. Thanks to the absence of physical boundaries, the two systems here investigated turned out to be a natural physical realization of the Kraichnan scaling regime hitherto associated with the elusive "ultimate state of thermal convection" [R. H. Kraichnan, "Turbulent thermal convection at arbitrary Prandtl number," Phys. Fluids 5, 1374-1389 (1962)].

  11. Livres | Page 22 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Large Mines and the Community : Socioeconomic and Environmental Effects in Latin America, Canada, and Spain. Les humains s'établissent à proximité des ressources naturelles depuis des centaines d'années. Directeur(s) : Gary McMahon et Felix Remy. Maison(s) d'édition : Banque mondiale, CRDI. ISBN: Épuisé.

  12. Dans le tourbillon des particules

    CERN Document Server

    Zito, Marco

    2015-01-01

    Accélérateurs géants, détecteurs complexes, particules énigmatiques... La physique subatomique peut sembler bien intimidante pour le novice. Et pourtant, qui n a jamais entendu parler du boson de Higgs et du CERN, le laboratoire européen où il a été découvert en 2012 ? Nul besoin d être un spécialiste pour comprendre de quoi il s agit. Aujourd hui, une théorie extraordinairement élégante, le Modèle Standard, décrit tous les résultats des expériences dans le domaine. Trente-sept particules élémentaires et quatre forces fondamentales : c est tout ce dont nous avons besoin pour expliquer la matière et l Univers ! Ce livre, destiné à un large public, raconte sans équations le long parcours qui a abouti au Modèle Standard. Ce parcours, parfois sinueux, a été entamé lorsque les Grecs anciens, et peut-être d autres avant eux, ont imaginé que la matière est composée de petites « billes ». Il faudra attendre plusieurs siècles pour qu on réalise que la matière, à l échelle micros...

  13. Benard convection in gaps and cavities

    International Nuclear Information System (INIS)

    Mueller, U.

    1981-04-01

    The article contains two parts. In the first part a condensed review of the most striking phenomena in Benard convection in laterally confined fluid layers is given. In the second part recent experimental and theoretical work on Benard convection in gaps is presented an analysed. (orig.) [de

  14. Convective mixing and accretion in white dwarfs

    International Nuclear Information System (INIS)

    Koester, D.

    1976-01-01

    The evolution of convection zones in cooling white dwarfs with helium envelopes and outer hydrogen layers is calculated with a complete stellar evolution code. It is shown that white dwarfs of spectral type DB cannot be formed from DA stars by convective mixing. However, for cooler temperatures (Tsub(e) [de

  15. : tous les projets | Page 517 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    amélioration des cultures et de gestion des ressources naturelles sont compromises. Date de début : 30 ... Sujet: WATER SHORTAGE, CLIMATE CHANGE, ADAPTATION TO CHANGE, DISASTER PREPAREDNESS. Région: Burkina Faso, Ivory Coast, ...

  16. Southern Ocean Convection and tropical telleconnections

    Science.gov (United States)

    Marinov, I.; Cabre, A.; Gnanadesikan, A.

    2014-12-01

    We show that Southern Ocean (SO) temperatures in the latest generation of Earth System Models exhibit two major modes of variation, one driven by deep convection, the other by tropical variability. We perform a CMIP5 model intercomparison to understand why different climate models represent SO variability so differently in long, control simulations. We show that multiyear variability in Southern Ocean sea surface temperatures (SSTs) can in turn influence oceanic and atmospheric conditions in the tropics on short (atmospheric) time-scales. We argue that the strength and pattern of SO-tropical teleconnections depends on the intensity of SO deep convection. Periodic convection in the SO is a feature of most CMIP5 models under preindustrial forcing (deLavergne et al., 2014). Models show a wide distribution in the spatial extent, periodicity and intensity of their SO convection, with some models convecting most of the time, and some showing very little convection. In a highly convective coupled model, we find that multidecadal variability in SO and global SSTs, as well as SO heat storage are driven by Weddell Sea convective variability, with convective decades relatively warm due to the heat released from the deep southern ocean and non-convective decades cold due to the subsurface storage of heat. Furthermore, pulses of SO convection drive SST and sea ice variations, influencing absorbed shortwave and emitted longwave radiation, wind, cloud and precipitation patterns, with climatic implications for the low latitudes via fast atmospheric teleconnections. We suggest that these high-low latitude teleconnection mechanisms are relevant for understanding hiatus decades. Additionally, Southern Ocean deep convection varied significantly during past, natural climate changes such as during the last deglaciation. Weddell Sea open convection was recently weakened, likely as a consequence of anthropogenic forcing and the resulting surface freshening. Our study opens up the

  17. Le FIVB annonce le financement de huit autres projets | CRDI ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    5 avr. 2018 ... Découvrez les derniers récents projets soutenus par le Fonds d'innovation en matière de vaccins pour le bétail : Maladie de Newcastle · Pleuropneumonie contagieuse caprine – cowdriose · Plateforme de modification génétique CRISPR/cas9 · Entérotoxémie, la bactérie Pasteurella et la fièvre de la vallée ...

  18. Topology Optimisation for Coupled Convection Problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe

    This thesis deals with topology optimisation for coupled convection problems. The aim is to extend and apply topology optimisation to steady-state conjugate heat transfer problems, where the heat conduction equation governs the heat transfer in a solid and is coupled to thermal transport...... in a surrounding uid, governed by a convection-diffusion equation, where the convective velocity field is found from solving the isothermal incompressible steady-state Navier-Stokes equations. Topology optimisation is also applied to steady-state natural convection problems. The modelling is done using stabilised...... finite elements, the formulation and implementation of which was done partly during a special course as prepatory work for this thesis. The formulation is extended with a Brinkman friction term in order to facilitate the topology optimisation of fluid flow and convective cooling problems. The derived...

  19. Convective penetration in a young sun

    Science.gov (United States)

    Pratt, Jane; Baraffe, Isabelle; Goffrey, Tom; MUSIC developers group

    2018-01-01

    To interpret the high-quality data produced from recent space-missions it is necessary to study convection under realistic stellar conditions. We describe the multi-dimensional, time implicit, fully compressible, hydrodynamic, implicit large eddy simulation code MUSIC. We use MUSIC to study convection during an early stage in the evolution of our sun where the convection zone covers approximately half of the solar radius. This model of the young sun possesses a realistic stratification in density, temperature, and luminosity. We approach convection in a stellar context using extreme value theory and derive a new model for convective penetration, targeted for one-dimensional stellar evolution calculations. This model provides a scenario that can explain the observed lithium abundance in the sun and in solar-like stars at a range of ages.

  20. Numerical simulations of convectively excited gravity waves

    International Nuclear Information System (INIS)

    Glatzmaier, G.A.

    1983-01-01

    Magneto-convection and gravity waves are numerically simulated with a nonlinear, three-dimensional, time-dependent model of a stratified, rotating, spherical fluid shell heated from below. A Solar-like reference state is specified while global velocity, magnetic field, and thermodynamic perturbations are computed from the anelastic magnetohydrodynamic equations. Convective overshooting from the upper (superadiabatic) part of the shell excites gravity waves in the lower (subadiabatic) part. Due to differential rotation and Coriolis forces, convective cell patterns propagate eastward with a latitudinally dependent phase velocity. The structure of the excited wave motions in the stable region is more time-dependent than that of the convective motions above. The magnetic field tends to be concentrated over giant-cell downdrafts in the convective zone but is affected very little by the wave motion in the stable region

  1. Magnetic Fields in the Solar Convection Zone

    Directory of Open Access Journals (Sweden)

    Fan Yuhong

    2004-07-01

    Full Text Available Recent studies of the dynamic evolution of magnetic flux tubes in the solar convection zone are reviewed with focus on emerging flux tubes responsible for the formation of solar active regions. The current prevailing picture is that active regions on the solar surface originate from strong toroidal magnetic fields generated by the solar dynamo mechanism at the thin tachocline layer at the base of the solar convection zone. Thus the magnetic fields need to traverse the entire convection zone before they reach the photosphere to form the observed solar active regions. This review discusses results with regard to the following major topics: 1. the equilibrium properties of the toroidal magnetic fields stored in the stable overshoot region at the base of the convection zone, 2. the buoyancy instability associated with the toroidal magnetic fields and the formation of buoyant magnetic flux tubes, 3. the rise of emerging flux loops through the solar convective envelope as modeled by the thin flux tube calculations which infer that the field strength of the toroidal magnetic fields at the base of the solar convection zone is significantly higher than the value in equipartition with convection, 4. the minimum twist needed for maintaining cohesion of the rising flux tubes, 5. the rise of highly twisted kink unstable flux tubes as a possible origin of d -sunspots, 6. the evolution of buoyant magnetic flux tubes in 3D stratified convection, 7. turbulent pumping of magnetic flux by penetrative compressible convection, 8. an alternative mechanism for intensifying toroidal magnetic fields to significantly super-equipartition field strengths by conversion of the potential energy associated with the superadiabatic stratification of the solar convection zone, and finally 9. a brief overview of our current understanding of flux emergence at the surface and post-emergence evolution of the subsurface magnetic fields.

  2. Expression Study of LeGAPDH, LeACO1, LeACS1A, and LeACS2 in Tomato Fruit (Solanum lycopersicum

    Directory of Open Access Journals (Sweden)

    Pijar Riza Anugerah

    2015-10-01

    Full Text Available Tomato is a climacteric fruit, which is characterized by ripening-related increase of respiration and elevated ethylene synthesis. Ethylene is the key hormone in ripening process of climacteric fruits. The objective of this research is to study the expression of three ethylene synthesis genes: LeACO1, LeACS1A, LeACS2, and a housekeeping gene LeGAPDH in ripening tomato fruit. Specific primers have been designed to amplify complementary DNA fragment of LeGAPDH (143 bp, LeACO1 (240 bp, LeACS1A (169 bp, and LeACS2 (148 bp using polymerase chain reaction. Nucleotide BLAST results of the complementary DNA fragments show high similarity with LeGAPDH (NM_001247874.1, LeACO1 (NM_001247095.1, LeACS1A (NM_001246993.1, LeACS2 (NM_001247249.1, respectively. Expression study showed that LeACO1, LeACS1A, LeACS2, and LeGAPDH genes were expressed in ripening tomato fruit. Isolation methods, reference sequences, and primers used in this study can be used in future experiments to study expression of genes responsible for ethylene synthesis using quantitative polymerase chain reaction and to design better strategy for controlling fruit ripening in agroindustry.

  3. Le Valais et ses Reines

    Directory of Open Access Journals (Sweden)

    Alberto Campi

    2012-06-01

    Full Text Available Combat de ReinesAu premier plan (la corde dans la main, un propriétaire de vaches. Dans l'arène se trouve le rabatteur. Les Reines sur la photo sont des reines de première catégorie (ainsi que le montre le « I » sur leur cuisse .Dimanche 6 mai 2012, « Schakira », la vache numéro 42, a gagné, non sans polémique, le titre de Reine. Elle peut donc être considérée comme la Reine des Reines, titre qu’elle a gagné en se battant contre ses rivales dans différents combats, qui ont commencé pour Sch...

  4. Actively convected liquid metal divertor

    International Nuclear Information System (INIS)

    Shimada, Michiya; Hirooka, Yoshi

    2014-01-01

    The use of actively convected liquid metals with j × B force is proposed to facilitate heat handling by the divertor, a challenging issue associated with magnetic fusion experiments such as ITER. This issue will be aggravated even more for DEMO and power reactors because the divertor heat load will be significantly higher and yet the use of copper would not be allowed as the heat sink material. Instead, reduced activation ferritic/martensitic steel alloys with heat conductivities substantially lower than that of copper, will be used as the structural materials. The present proposal is to fill the lower part of the vacuum vessel with liquid metals with relatively low melting points and low chemical activities including Ga and Sn. The divertor modules, equipped with electrodes and cooling tubes, are immersed in the liquid metal. The electrode, placed in the middle of the liquid metal, can be biased positively or negatively with respect to the module. The j × B force due to the current between the electrode and the module provides a rotating motion for the liquid metal around the electrodes. The rise in liquid temperature at the separatrix hit point can be maintained at acceptable levels from the operation point of view. As the rotation speed increases, the current in the liquid metal is expected to decrease due to the v × B electromotive force. This rotating motion in the poloidal plane will reduce the divertor heat load significantly. Another important benefit of the convected liquid metal divertor is the fast recovery from unmitigated disruptions. Also, the liquid metal divertor concept eliminates the erosion problem. (letter)

  5. Le bal du loup

    CERN Multimedia

    Happy Children's Home

    2013-01-01

    The Bord'eau amateur theatre group will graciously perform a play of their creation Le bal du loup Saturday 19 October 2013 at 20:00 Sunday 20 October at 17:00 in the Théâtre des Grottes Rue Louis Favre 43, 1201 Genève Children from age 12 upwards. Summary: The new-elected mayoress of a small village would like to clean up the town by prohibiting alcohol and getting rid of its prostitutes. Then along comes « Massimo Lupo » the pimp... The performances will be given to support the Happy Children's Home charity, which runs a foster-home in Pokhara for Nepali children:  http://www.happychildrenshome.org/ Admission : minimum charge of 10 CHF per person requested, to cover the cost of technical assistance and theatre rental. Any profit will be used solely for the foster-home. At the end of each performance members of the HCH charity will be happy to answer any questions you may have. The theatre has 86 seats, thank you for reserv...

  6. Un oiseau "sabote" le CERN

    CERN Multimedia

    Colson, Sébastien

    2009-01-01

    Un oiseau, un simple oiseau, est parvenu à bloquer à lui tout seul l'accélérateur à particules à 3,7 milliards d'euros. UNe histoire quasiment bulresque qui a toutefois impacté le fonctionnement de la machine durant près de cinq jours, puisque c'est le système de refroidissement qui a été affecté. (1 page)

  7. Le CRDI dans les Philippines

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le CRDI appuie la recherche dans les. Philippines depuis 1972. Le travail qu'y ont accompli des universités et des instituts de recherche vigoureux et la participation active de la société civile ont entraîné d'importantes améliorations dans les domaines de l'agriculture, du suivi de la pauvreté et de la gestion des forêts.

  8. Étude méthodologique de la conservation de ressources génétiques de ray-grass anglais (graminée fourragère) par multiplication en pools de populations naturelles

    OpenAIRE

    Balfourier , François; Charmet , G

    1994-01-01

    À partir d’une collection de 547 populations naturelles de ray-grass anglais, préalablement étudiées pour des caractères d’intérêt agronomique, 42 populations sont choisies à l’aide d’analyses multivariables et en fonction de critères agronomiques et écogéographiques, afin de constituer 9 pools typés et représentatifs de la diversité observée. Cette méthode de constitution de pools est présentée comme une étape de présélection, permettant la conservation de la diversité et la préparation...

  9. Le modèle spatial de la capitale allemande

    Directory of Open Access Journals (Sweden)

    Antoine Laporte

    2013-06-01

    Full Text Available En Allemagne, en 1999, le Chancelier fédéral et son gouvernement ont quitté Bonn pour Berlin. Ce transfert du pouvoir est accompagné de celui d’une grande partie de l’appareil d’État et de la haute administration, et des fonctions qui leur sont traditionnellement attribuées comme la presse, les lobbys ou encore la diplomatie. Le déplacement du statut de capitale effective de l’Allemagne de Bonn à Berlin est le résultat des évolutions géopolitiques d’un pays ayant recouvré son unité et sa pleine et entière souveraineté. Installer le pouvoir exécutif et législatif à Berlin était une démarche hautement symbolique, visant à normaliser la position de l’ancienne capitale de la RDA et du IIIe Reich comme véritable centre politique de l’Allemagne. Or le déplacement des institutions fédérales n’est pas qu’un acte symbolique. Il entraîne également à l’échelle intra-urbaine des dynamiques très concrètes sur le tissu urbain et participe à la mise en place de nouvelles centralités dans la ville. En effet, le statut de capitale d’État prédestine l’agglomération à la coprésence de nombreuses fonctions urbaines spécifiques plus ou moins directement liées à l’exercice ou à la symbolique du pouvoir.

  10. Le livre sur le livre traité de documentation

    CERN Document Server

    Otlet, Paul

    2015-01-01

    Paul Otlet est considéré comme le père des sciences de l'information. Ouvrage fondateur et fondamental, le Traité de documentation. Le livre sur le livre (1934) est l'aboutissement de son travail inlassable pour rassembler, classer et partager les connaissances. Otlet y propose une remarquable synthèse du savoir sur le livre et le document en même temps qu'il anticipe Internet et l'hypertexte. La réédition du Traité de documentation, 70 ans après la disparition de son auteur, coïncide avec la réouverture du Mundaneum à Mons, où le fabuleux héritage documentaire légué par Paul Otlet et Henri La Fontaine est conservé. « Ici, la table de travail n'est plus chargée d'aucun livre. À leur place se dresse un écran et à portée un téléphone. Là-bas, au loin, dans un édifice immense, sont tous les livres et tous les renseignements. De là, on fait apparaître sur l'écran la page à lire pour connaître la réponse aux questions posées par téléphone. » Préfaces de Benoît Peeters (éc...

  11. Biopsie et mesure de l'activité Na+/K+ ATPasique branchiale : validité et impact sur le développement du smolt de saumon Atlantique (Salmo salar L.

    Directory of Open Access Journals (Sweden)

    SIEGLER L.

    1996-01-01

    Full Text Available Une biopsie de fragment de tissu branchial a été effectuée, durant toute la période de smoltification, sur des juvéniles de saumons Atlantique (Salmo salar élevés en pisciculture. Le microdosage de l'activité de la Na+/K+ ATPase branchiale, effectué sur ce fragment de tissu, a été comparé au macrodosage obtenu à partir des branchies entières. Aucune mortalité n'a été observée chez les saumons biopsies dont le taux de croissance (linéaire et pondérale est resté identique à celui des poissons témoins. La bonne correspondance des cinétiques de l'activité enzymatique obtenues par les deux méthodes valide la technique de microdosage et confirme l'absence d'influence sur le développement physiologique ultérieur du smolt biopsie. Nos résultats montrent les modifications envisageables pour améliorer la sensibilité de la méthode. Cette technique est très prometteuse pour l'analyse des populations naturelles

  12. Study and development of an optical method for the measurement of convection coefficients; Etude et developpement d'une methode optique pour la mesure du coefficient de convection

    Energy Technology Data Exchange (ETDEWEB)

    Crowther, David J.

    1990-03-06

    This research thesis addresses the field of fluid-wall thermal exchanges in which the notion of exchange coefficient is notably useful to design, size and optimise devices. A first part reports a bibliographical study which gives an overview of solutions envisaged to determine the convection coefficient in permanent regime with the use of flow sensors, as well as in transient regime. Then, the author reports the development of an unsteady method which is based on the analysis of the cooling kinetics of the front face of a convecting wall, after a unique energetic perturbation (an infinitely brief pulse, or a finite duration energy step). This method is applied to the general case (wall with finite thickness) and to the case of a semi-infinite wall which is typical of materials which are weak thermal conductors. This is extended to the case of good thermal conductors by considering a thermally thin wall. After a detailed description of the experimental bench, above-mentioned solutions are applied to insulating and good thermal conducting materials. In order to validate results of an analysis in transient regime, they are compared with measurements performed in permanent regime with a flow-metering technique. The study of the principle of the dissipation-based flow sensor, and its operation are reported. Experimental results are presented for both methods (pulse and flow sensor), and compared in order to highlight the interest of the unsteady method [French] Difficile a mesurer, le coefficient de convection reste cependant une grandeur necessaire au calcul et a l'optimisation de tout systeme thermique. L'amelioration des capteurs thermiques permet aujourd'hui de concevoir une methode optique, utilisable a distance, et non destructive. Nous proposons dans ce but, un procede de mesure en regime transitoire base sur la radiometrie photothermique impulsionnelle. L'analyse du regime de relaxation d'une paroi, apres une brusque elevation de temperature, permet de remonter

  13. A thermodynamically general theory for convective vortices

    Science.gov (United States)

    Renno, Nilton O.

    2008-08-01

    Convective vortices are common features of atmospheres that absorb lower-entropy-energy at higher temperatures than they reject higher-entropy-energy to space. These vortices range from small to large-scale and play an important role in the vertical transport of heat, momentum, and tracer species. Thus, the development of theoretical models for convective vortices is important to our understanding of some of the basic features of planetary atmospheres. The heat engine framework is a useful tool for studying convective vortices. However, current theories assume that convective vortices are reversible heat engines. Since there are questions about how reversible real atmospheric heat engines are, their usefulness for studying real atmospheric vortices is somewhat controversial. In order to reduce this problem, a theory for convective vortices that includes irreversible processes is proposed. The paper's main result is that the proposed theory provides an expression for the pressure drop along streamlines that includes the effects of irreversible processes. It is shown that a simplified version of this expression is a generalization of Bernoulli's equation to convective circulations. It is speculated that the proposed theory not only explains the intensity, but also sheds light on other basic features of convective vortices such as their physical appearance.

  14. Lele des chefs traditionnels au Ghana : un modèle inspirant ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    8 févr. 2011 ... Ray est également coordonnateur international du Traditional Authority ... Marketing social : le chef traditionnel acquiert une certaine expertise et ... Nadine Robitaille est rédactrice à la Division des communications du CRDI .

  15. Boundary Layer Control of Rotating Convection Systems

    Science.gov (United States)

    King, E. M.; Stellmach, S.; Noir, J.; Hansen, U.; Aurnou, J. M.

    2008-12-01

    Rotating convection is ubiquitous in the natural universe, and is likely responsible for planetary processes such magnetic field generation. Rapidly rotating convection is typically organized by the Coriolis force into tall, thin, coherent convection columns which are aligned with the axis of rotation. This organizational effect of rotation is thought to be responsible for the strength and structure of magnetic fields generated by convecting planetary interiors. As thermal forcing is increased, the relative influence of rotation weakens, and fully three-dimensional convection can exist. It has long been assumed that rotational effects will dominate convection dynamics when the ratio of buoyancy to the Coriolis force, the convective Rossby number, Roc, is less than unity. We investigate the influence of rotation on turbulent Rayleigh-Benard convection via a suite of coupled laboratory and numerical experiments over a broad parameter range: Rayleigh number, 10310; Ekman number, 10-6≤ E ≤ ∞; and Prandtl number, 1≤ Pr ≤ 100. In particular, we measure heat transfer (as characterized by the Nusselt number, Nu) as a function of the Rayleigh number for several different Ekman and Prandtl numbers. Two distinct heat transfer scaling regimes are identified: non-rotating style heat transfer, Nu ~ Ra2/7, and quasigeostrophic style heat transfer, Nu~ Ra6/5. The transition between the non-rotating regime and the rotationally dominant regime is described as a function of the Ekman number, E. We show that the regime transition depends not on the global force balance Roc, but on the relative thicknesses of the thermal and Ekman boundary layers. The transition scaling provides a predictive criterion for the applicability of convection models to natural systems such as Earth's core.

  16. L'étang de Dombes. Insertion dans le paysage agraire

    Directory of Open Access Journals (Sweden)

    BILLARD A.

    1979-01-01

    Full Text Available Les étangs constituent en Dombes centrale un élément original et un facteur de complexité du paysage agraire. Ils sont situés dans des dépressions au sol imperméable établies entre des collines glaciaires barrées par des digues d'argile et sont de forme irrégulière ; leur alimentation est à peu près exclusivement assurée par les eaux de pluie. Ces étangs, d'une superficie courante de 20 à 30 ha, sont soumis à un assolement pas toujours régulier qui fait alterner la production de poissons (évolage et la production de céréales ou de mais (assec. Constituant un niveau de base local, la nappe d'eau de l'étang en évolage limite les phénomènes d'érosion et assure un rôle d'équilibre. L'étang représente une forme d'adaptation aux conditions naturelles mais il est indissociable des formes d'habitat dispersé et des grandes parcelles de l'exploitation d'un seul tenant. L'origine des étangs remonte au Moyen-Age. Mais le rythme des constructions se serait accéléré à partir des 15ème et 16ème siècles. L'analyse du paysage agraire, Jointe aux données d'un manuscrit en date de 1704, suggère que le développement des étangs serait lié à un phénomène de concentration foncière qui a donné naissance aux grands domaines de la Dombes. Avec sa production de poisson réservé au propriétaire à l'exclusion des paysans, l'étang représentait dans une région, alors très pauvre, l'introduction de l'économie de marché.

  17. Le nouveau modèle africain | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    22 juil. 2011 ... Or, ce serait rater le bateau que de ne pas s'engager dans la voie tout autre que les Africains proposent maintenant — à savoir se défaire du syndrome de la dépendance qui afflige l'Afrique depuis des décennies. Le Canada et les autres pays riches du Nord reconnaissent généralement qu'ils ne peuvent ...

  18. Lele des intervenants non gouvernementaux dans le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Ce projet servira à déterminer les facteurs stratégiques et réglementaires qui ont contribué ou nui aux efforts visant à permettre aux fournisseurs non gouvernementaux de participer au renforcement des systèmes de santé. Lele des fournisseurs de ... Climate Change and Water Adaptation Options. The impacts of climate ...

  19. Le dualisme Chipaya

    Directory of Open Access Journals (Sweden)

    1974-01-01

    Full Text Available L’auteur, partant des observations de Métraux sur Chipaya, apporte des idées neuves sur les ayllu constituant le village, basées sur une enquête approfondie et un plan détaillé du village : deux divisions principales apparaissent, celles-ci se divisant a leur tour en quatre ayllu. La chute brutale de la démographie depuis la seconde moitié du XVIe siècle a fait disparaître les 4 ayllu originels mais l’examen des archives permet d’observer un très vigoureux redressement démographique à partir des derniers 150 ans. Ce redressement démographique semble précipiter un nouvel éclatement de la communauté chipaya. El autor partiendo de las observaciones de Métraux sobre Chipaya, aporta sobre los ayllu que constituían el pueblo, basadas en una encuesta profunda y un plano detallado del pueblo: aparecen dos divisiones principales, dividiéndose éstas a su vez en cuatro ayllu. La caída brutal de la demografía desde la segunda mitad del siglo XVI ha hecho desaparecer los 4 ayllu primitivos pero el examen de los archivos permite observar un resurgimiento vigoroso a partir de los últimos 150 años. Este resurgimiento demográfico parece precipitar una nueva explosión de la comunidad chipaya.

  20. Le pompage optique naturel dans le milieu astrophysique

    Science.gov (United States)

    Pecker, J.-C.

    The title of this lecture abstracts only a part of it : the importance in astrophysics of the study of non-LTE situations has become considerable, as well in the stellar atmospheres as, still more, in the study of fortuitous coincidences as a mechanism of formation of emission line nebular spectra, or of molecular interstellar « masers ». Another part of this talk underlines the role of Kastler in his time, and describes his warm personality through his public reactions in front of the nuclear armement, of the Viet-Nam and Algerian wars, of the problems of political refugees... Kastler was a great scientist ; he was also a courageous humanist. 1976 : Les accords nucléaires du Brésil : allocution d'ouverture (19 mars). Colloque sur le sujet ci-dessus. 1976 : La promotion de la culture dans le nouvel ordre économique international, allocution à l'occasion d'une table ronde sur ce thème par l'UNESCO (23-27 juin 1976) ; « Sciences et Techniques », octobre 1976. 1979 : La bête immonde (avec J.-C. Pecker), « Le Matin », 20 mars. 1979 : Appel à nos ministres (avec J.-C. Pecker), « Le Monde », 13 décembre. 1979 : Le flou, le ténébreux, l'irrationnel (avec J.-C. Pecker), « Le Monde », 14 septembre. 1980 : Education à la paix, Préface, in : Publ. UNESCO. 1981 : Le vrai danger, « Le Monde », 6 août 1981. 1982 : Nucléaire civil et militaire, « Le Monde », 1er juin 1982. 1982 : Les scientifiques face à la perspective d'holocauste nucléaire (texte inédit). Le titre de cette communication en résume seulement une partie : l'importance prise en astrophysique par l'analyse des situations hors ETL est devenue considérable, qu'il s'agisse des atmosphères stellaires, ou plus encore, des coïncidences fortuites de la formation des spectres d'émission nébulaires, ou des « masers » moléculaires interstellaires. Une autre partie de cet exposé souligne lele de Kastler dans son époque, et décrit sa personnalité généreuse à travers ses r

  1. Measuring Convective Mass Fluxes Over Tropical Oceans

    Science.gov (United States)

    Raymond, David

    2017-04-01

    Deep convection forms the upward branches of all large-scale circulations in the tropics. Understanding what controls the form and intensity of vertical convective mass fluxes is thus key to understanding tropical weather and climate. These mass fluxes and the corresponding conditions supporting them have been measured by recent field programs (TPARC/TCS08, PREDICT, HS3) in tropical disturbances considered to be possible tropical storm precursors. In reality, this encompasses most strong convection in the tropics. The measurements were made with arrays of dropsondes deployed from high altitude. In some cases Doppler radar provided additional measurements. The results are in some ways surprising. Three factors were found to control the mass flux profiles, the strength of total surface heat fluxes, the column-integrated relative humidity, and the low to mid-tropospheric moist convective instability. The first two act as expected, with larger heat fluxes and higher humidity producing more precipitation and stronger lower tropospheric mass fluxes. However, unexpectedly, smaller (but still positive) convective instability produces more precipitation as well as more bottom-heavy convective mass flux profiles. Furthermore, the column humidity and the convective instability are anti-correlated, at least in the presence of strong convection. On spatial scales of a few hundred kilometers, the virtual temperature structure appears to be in dynamic balance with the pattern of potential vorticity. Since potential vorticity typically evolves on longer time scales than convection, the potential vorticity pattern plus the surface heat fluxes then become the immediate controlling factors for average convective properties. All measurements so far have taken place in regions with relatively flat sea surface temperature (SST) distributions. We are currently seeking funding for a measurement program in the tropical east Pacific, a region that exhibits strong SST gradients and

  2. Transient Mixed Convection Validation for NGNP

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Barton [Utah State Univ., Logan, UT (United States); Schultz, Richard [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-10-19

    The results of this project are best described by the papers and dissertations that resulted from the work. They are included in their entirety in this document. They are: (1) Jeff Harris PhD dissertation (focused mainly on forced convection); (2) Blake Lance PhD dissertation (focused mainly on mixed and transient convection). This dissertation is in multi-paper format and includes the article currently submitted and one to be submitted shortly; and, (3) JFE paper on CFD Validation Benchmark for Forced Convection.

  3. Convective cells and transport in toroidal plasmas

    International Nuclear Information System (INIS)

    Hassam, A.B.; Kulsrud, R.M.

    1978-12-01

    The properties of convective cells and the diffusion resulting from such cells are significantly influenced by an inhomogeneity in the extermal confining magnetic field, such as that in toroidal plasmas. The convective diffusion in the presence of a field inhomogeneity is estimated. For a thermal background, this diffusion is shown to be substantially smaller than classical collisional diffusion. For a model nonthermal background, the diffusion is estimated, for typical parameters, to be at most of the order of collisional diffusion. The model background employed is based on spectra observed in numerical simulations of drift-wave-driven convective cells

  4. Transient Mixed Convection Validation for NGNP

    International Nuclear Information System (INIS)

    Smith, Barton; Schultz, Richard

    2015-01-01

    The results of this project are best described by the papers and dissertations that resulted from the work. They are included in their entirety in this document. They are: (1) Jeff Harris PhD dissertation (focused mainly on forced convection); (2) Blake Lance PhD dissertation (focused mainly on mixed and transient convection). This dissertation is in multi-paper format and includes the article currently submitted and one to be submitted shortly; and, (3) JFE paper on CFD Validation Benchmark for Forced Convection.

  5. Plutonium separation and the measurement of its concentration in natural waters (1963); Separation du plutonium et mesure de sa concentration dans les eaux naturelles

    Energy Technology Data Exchange (ETDEWEB)

    Scheidhauer, J; Messainguiral, L; Meiraneisio, A M [Commissariat a l' Energie Atomique, Centre de Production de Plutonium, Marcoule (France). Centre d' Etudes Nucleaires

    1963-07-01

    After concentration by chemisorption on a calcium fluoride suspension, the plutonium is purified and isolated by xylene extraction of the complex formed with T.T.A. The radioelement is measured by counting with a ZnS (Ag) scintillator after evaporation or electrolysis. (authors) [French] Apres concentration par chimisorption sur une suspension de fluorure de calcium, le plutonium est purifie et isole par extraction au xylene du complexe forme avec la T.T.A. La mesure du radioelement est effectuee par comptage au scintillateur S Zn (Ag) apres evaporation ou electrolyse. (auteurs)

  6. Hyperloop : le droit et le devoir de douter...

    OpenAIRE

    Crozet , Yves

    2016-01-01

    National audience; C’est comme si c’était fait ! Les journaux les plus sérieux (Les Echos) nous annoncent que le premier test du prototype Hyperloop dans le désert du Nevada est un succès. Le projet futuriste d’Elon Musk se concrétise. Un véhicule terrestre de transport collectif va bientôt se déplacer à plus de 1000 km/h entre San Francisco et Los Angeles. Comme pour donner du crédit à cette information, la SNCF, via sa filiale SYSTRA va devenir partenaire du projet. Déjà les journaux de Pro...

  7. Convection in complex shaped vessel; Convection dans des enceintes de forme complexe

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-07-01

    The 8 november 2000, the SFT (Societe Francaise de Thermique) organized a technical day on the convection in complex shaped vessels. Nine papers have been presented in the domains of the heat transfers, the natural convection, the fluid distribution, the thermosyphon effect, the steam flow in a sterilization cycle and the transformers cooling. Eight papers are analyzed in ETDE and one paper dealing with the natural convection in spent fuels depository is analyzed in INIS. (A.L.B.)

  8. Los Dioramas de Le Corbusier = Le Corbusier's Dioramas

    Directory of Open Access Journals (Sweden)

    José Ramón Alonso Pereira

    2013-10-01

    Full Text Available ResumenLe Corbusier simboliza el urbanismo moderno racional, cuyo esfuerzo riguroso de planificación exige un esfuerzo paralelo de comprensión. Se opone a ese urbanismo contemporáneo que quiere percibir y disfrutar la ciudad sensiblemente. Sentimiento y razón, sin embargo, no son opuestos y Le Corbusier nos dio en su momento las claves para intentar una síntesis, uniéndolos de modo singular por medio de sus ‘boîte à miracles’ o ‘cajas mágicas’: esos "espectáculos arquitectónicos de síntesis" que definiría en el Ciam de 1951. Pretendemos aproximarnos aquí a la primera de esos ‘espectáculos’: el ‘diorama’, viéndolo como estrategia corbuseriana de mediación entre lo racional y lo sensible en la ciudad moderna y contemporánea.Palabras claveLe Corbusier, diorama, Ville Contemporaine, Plan Voisin, Plan MaciáAbstractLe Corbusier symbolizes the modern rational urbanism, whose rigorous effort of town planning demands a parallel effort of comprehension. It opposes to these contemporary urbanism that wish to perceive and to enjoy cities in a sensible way. Nevertheless, sentiment and reason are not adverses and Le Corbusier gives us at his  moment keys to intent a synthesis, joined them in a singular way by means of his ‘boîtes à miracles’ or ‘magic boxes’: those "architectural spectacles of synthesis" that he defined in 1951 Ciam. Here we try to approach to the first of those ‘spectacles’: the ‘diorama’, considering it as a corbusean strategy of mediation between rational and sensible in modern and contemporary city.Key wordsLe Corbusier, diorama, Ville Contemporaine, Plan Voisin, Plan Maciá.

  9. Steady, three-dimensional, internally heated convection

    International Nuclear Information System (INIS)

    Schubert, G.; Glatzmaier, G.A.; Travis, B.

    1993-01-01

    Numerical calculations have been carried out of steady, symmetric, three-dimensional modes of convection in internally heated, infinite Prandtl number, Boussinesq fluids at a Rayleigh number of 1.4x10 4 in a spherical shell with inner/outer radius of 0.55 and in a 3x3x1 rectangular box. Multiple patterns of convection occur in both geometries. In the Cartesian geometry the patterns are dominated by cylindrical cold downflows and a broad hot upwelling. In the spherical geometry the patterns consist of cylindrical cold downwellings centered either at the vertices of a tetrahedron or the centers of the faces of a cube. The cold downflow cylinders are immersed in a background of upwelling within which there are cylindrical hot concentrations (plumes) and hot halos around the downflows. The forced hot upflow return plumes of internally heated spherical convection are fundamentally different from the buoyancy-driven plumes of heated from below convection

  10. Convective Radio Occultations Final Campaign Summary

    Energy Technology Data Exchange (ETDEWEB)

    Biondi, R. [Atmospheric Radiation Measurement, Washington, DC (United States)

    2016-03-01

    Deep convective systems are destructive weather phenomena that annually cause many deaths and injuries as well as much damage, thereby accounting for major economic losses in several countries. The number and intensity of such phenomena have increased over the last decades in some areas of the globe. Damage is mostly caused by strong winds and heavy rain parameters that are strongly connected to the structure of the particular storm. Convection over land is usually stronger and deeper than over the ocean and some convective systems, known as supercells, also develop tornadoes through processes that remain mostly unclear. The intensity forecast and monitoring of convective systems is one of the major challenges for meteorology because in situ measurements during extreme events are too sparse or unreliable and most ongoing satellite missions do not provide suitable time/space coverage.

  11. Ignition in Convective-Diffusive Systems

    National Research Council Canada - National Science Library

    Law, Chung

    1999-01-01

    ... efficiency as well as the knock and emission characteristics. The ignition event is clearly controlled by the chemical reactions of fuel oxidation and the fluid mechanics of convective and diffusive transport...

  12. Understanding and controlling plasmon-induced convection

    Science.gov (United States)

    Roxworthy, Brian J.; Bhuiya, Abdul M.; Vanka, Surya P.; Toussaint, Kimani C.

    2014-01-01

    The heat generation and fluid convection induced by plasmonic nanostructures is attractive for optofluidic applications. However, previously published theoretical studies predict only nanometre per second fluid velocities that are inadequate for microscale mass transport. Here we show both theoretically and experimentally that an array of plasmonic nanoantennas coupled to an optically absorptive indium-tin-oxide (ITO) substrate can generate >micrometre per second fluid convection. Crucially, the ITO distributes thermal energy created by the nanoantennas generating an order of magnitude increase in convection velocities compared with nanoantennas on a SiO2 base layer. In addition, the plasmonic array alters absorption in the ITO, causing a deviation from Beer-Lambert absorption that results in an optimum ITO thickness for a given system. This work elucidates the role of convection in plasmonic optical trapping and particle assembly, and opens up new avenues for controlling fluid and mass transport on the micro- and nanoscale.

  13. What favors convective aggregation and why?

    Science.gov (United States)

    Muller, Caroline; Bony, Sandrine

    2015-07-01

    The organization of convection is ubiquitous, but its physical understanding remains limited. One particular type of organization is the spatial self-aggregation of convection, taking the form of cloud clusters, or tropical cyclones in the presence of rotation. We show that several physical processes can give rise to self-aggregation and highlight the key features responsible for it, using idealized simulations. Longwave radiative feedbacks yield a "radiative aggregation." In that case, sufficient spatial variability of radiative cooling rates yields a low-level circulation, which induces the upgradient energy transport and radiative-convective instability. Not only do vertically integrated radiative budgets matter but the vertical profile of cooling is also crucial. Convective aggregation is facilitated when downdrafts below clouds are weak ("moisture-memory aggregation"), and this is sufficient to trigger aggregation in the absence of longwave radiative feedbacks. These results shed some light on the sensitivity of self-aggregation to various parameters, including resolution or domain size.

  14. Le LHC, un tunnel cosmique

    CERN Multimedia

    CERN. Geneva

    2009-01-01

    Et si la lumière au bout du tunnel du LHC était cosmique ? En d’autres termes, qu’est-ce que le LHC peut nous apporter dans la connaissance de l’Univers ? Car la montée en énergie des accélérateurs de particules nous permet de mieux appréhender l’univers primordial, chaud et dense. Mais dans quel sens dit-on que le LHC reproduit des conditions proches du Big bang ? Quelles informations nous apporte-t-il sur le contenu de l’Univers ? La matière noire est-elle détectable au LHC ? L’énergie noire ? Pourquoi l’antimatière accumulée au CERN est-elle si rare dans l’Univers ? Et si le CERN a bâti sa réputation sur l’exploration des forces faibles et fortes qui opèrent au sein des atomes et de leurs noyaux, est-ce que le LHC peut nous apporter des informations sur la force gravitationnelle qui gouverne l’évolution cosmique ? Depuis une trentaine d’années, notre compréhension de l’univers dans ses plus grandes dimensions et l’appréhension de son comportement aux plus peti...

  15. Antartic observations of plasma convection

    International Nuclear Information System (INIS)

    Hansen, H.J.

    1983-01-01

    This thesis is concerned with the use of whistler duct tracking as a diagnostic for the behaviour of plasma in the plasmasphere. As a setting for the results given in the thesis, a broad review is presented which embraces pertinent aspects of previous experimental and theoretical studies of the plasmasphere. From a study of 24 hours of continuous whistler data recorded at Sanae, (L = 3,98), it is shown that associated with quiet magnetic conditions (Av Ksub(p)=1), there exists two plasmasphere bulges centred on about 1700 and 0100 UT. There is evidence that these plasmasphere bulge structures are part of a ground-state or reference base drift pattern. Electric field measurements provide some evidence that quiet time plasmasphere drift behaviour is controlled by the internal ionospheric current systems of dynamo origin, rather than being controlled by magnetospheric convection. Finally, this thesis describes an application of the whistler duct tracking technique to whistler data recorded simultaneously at two ground-based stations (Sanae (L = 3,98) and Halley (L = 4,23)). The identification of common whistler components on each station's data set provides a means of estimating the lifetimes of the associated whistler ducts. Duct lifetimes of as little as 30 minutes are found. Such short lived ducts have important implications for current theories of duct formation

  16. Le paludisme, le tsunami silencieux d'Afrique | IDRC - International ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    12 janv. 2011 ... Dans un élan de compassion fort justifié, le monde s'est porté au secours des victimes du tsunami qui a touché récemment la région de l'océan Indien. Mais il ignore qu'un « tsunami silencieux », le paludisme, s'abat sans cesse sur l'Afrique et y fait chaque année plus de 1,5 million de victimes, surtout de ...

  17. Optimisation des propriétés pharmacologiques des substances naturelles par la méthode numérique Volsurf

    Directory of Open Access Journals (Sweden)

    S. DJEDDI

    2015-03-01

    Full Text Available L'expérience a montré que le maintien de la richesse de la biodiversité végétale ainsi que la connaissance des thérapeutiques traditionnelles, sont susceptibles de mener à bien la recherche de nouvelles molécules aux activités biologiques. Dans ce contexte nous nous sommes intéressés à étudier de manière approfondie l'extraction et l'identification des substances secondaires actives isolées de Centaurea pullata L. (Asteraceae utilisée en médecine traditionnelle algérienne récoltée à Blida. Après l'identification des différentes substances secondaires (huiles essentielles, flavonoïdes, sesquiterpènes lactones, les substances nouvelles isolée et identifiées ont été investiguées pour leurs pouvoirs antimicrobiens (antibactérien et antifongique et anticancéreux. Sachant que les propriétés clefs pour la découverte des médicaments sont l'absorption, la distribution, le métabolisme et l'excrétion (ADME, nous avons alors réalisé la prédiction des propriétés pharmacologiques de quelques substances nouvelles via la méthode computationnelle Volsurf.

  18. Dynamics of acoustic-convective drying of sunflower cake

    Science.gov (United States)

    Zhilin, A. A.

    2017-10-01

    The dynamics of drying sunflower cake by a new acoustic-convective method has been studied. Unlike the conventional (thermal-convective) method, the proposed method allows moisture to be extracted from porous materials without applying heat to the sample to be dried. Kinetic curves of drying by the thermal-convective and acoustic-convective methods were obtained and analyzed. The advantages of the acoustic-convective extraction of moisture over the thermal-convective method are discussed. The relaxation times of drying were determined for both drying methods. An intermittent drying mode which improves the efficiency of acoustic-convective extraction of moisture is considered.

  19. Influence d'un ecran thermique sur le bilan energetique et le microclimat nocturnes d'une serre

    OpenAIRE

    Baille, M.; Laury, J.C.; Baille, Alain

    1984-01-01

    Dans cet article, on présente les résultats expérimentaux concernant les effets d’un écran thermique sur les déperditions énergétiques et le microclimat nocturnes de deux serres identiques, mais de matériaux de couverture différents : verre horticole ordinaire (V.O.) et verre à faible émissivité (V.F.E.). lorsque l’écran est déployé, on constate une diminution significative des pertes thermiques globales dans les deux serres. L’écran agit surtout au niveau des pertes par convection et par...

  20. Building a better energy future for the remote communities: sustainable energy supply strategy for the village of Inukjuak; Batir un meilleur avenir energetique pour les communautes eloignees: Strategie d'approvisionnement en energie renouvelable pour le village d'Inukjuak

    Energy Technology Data Exchange (ETDEWEB)

    St-Pierre, Stephane; Bui-Quang, Hung; Atagotaaluk, Eric; Benedetti, Bruno

    2010-09-15

    Remote regions of Canada, notwithstanding their natural resources, suffer from a development lag because of a lack of affordable energy. The production in an isolated network comes from thermal sources, highly responsible for global warming. To replace thermal production by renewable energy necessitate the implementation of electricity prices by the public utility who favors the investment. The tariff is actually applied in order to reflect the high production cost. This article shows the actual rate situation, some possible solutions to encourage investment and the hydro electrical development in Inukjuak, where the sale of electricity at the cost of not using fossil fuels would allow to make the investments profitable. [French] Les regions eloignees du Canada, malgre leurs richesses naturelles, accusent un retard dans leur developpement vu le manque d'energie abordable. La production en reseau isole provient de sources thermiques, grandement responsables du rechauffement climatique. Remplacer la production thermique par des energies renouvelables requiert d'implanter des prix d'achat d'electricite par l'utilite publique favorisant l'investissement. Le tarif est presentement applique afin de refleter le cout eleve de production. Ce papier presente la situation tarifaire actuelle, des pistes de solution pour encourager l'investissement, et le developpement hydroelectrique Inukjuak, ou la vente d'electricite au cout d'evitement des combustibles fossiles permettrait de rentabiliser les investissements.

  1. CONVECTION IN CONDENSIBLE-RICH ATMOSPHERES

    Energy Technology Data Exchange (ETDEWEB)

    Ding, F. [Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States); Pierrehumbert, R. T., E-mail: fding@uchicago.edu [Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom)

    2016-05-01

    Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case—water vapor in Earth’s present climate—the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO{sub 2} is the condensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamental ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-convective simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere for both steady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.

  2. Le CERN et les Institutions

    CERN Document Server

    Barbalat, Oscar

    1996-01-01

    Une première partie de l'exposéŽ sera consacrée àˆ une brève description des principaux organes de l'Union EuropéŽennne: Conseil, Parlement et Commission ainsi que la structure de la Commission. On passera ensuite en revue le Programme-Cadre de Recherche et DéŽveloppement Technologique et les principaux programmes spéŽcifiques auxquels participe le CERN (ESPRIT, ACTS, TMR) On situera ensuite les autres organisations et initiatives scientifiques européŽennes (ESA, ESO, ESRF, JET, ISTC, EUREKA, ...) pour terminer par une brève revue des relations entre le CERN avec ces difféŽrentes institutions en déŽveloppant plus particulièrement celles avec la Commission.

  3. La preuve par le nombre

    Directory of Open Access Journals (Sweden)

    Hélène Verdier

    2012-04-01

    Full Text Available S’il en était besoin, la question des usages et de la finalité des résultats de l’inventaire général pourrait être abordée par le nombre : nombre d’œuvres répertoriées, de communes inventoriées, de clichés photographiques réalisés, de dossiers, de consultations des notices dans les bases de données… Les additions aujourd’hui sont éloquentes, mais elles laissent dans l’ombre lele de l’inventaire qui, en mettant en œuvre une démarche systématique de connaissance, participe à l’ identificatio...

  4. Le Corbusier’s Dioramas

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    José Ramón Alonso Pereira

    2013-10-01

    Full Text Available AbstractLe Corbusier symbolizes the modern rational urbanism, whose rigorous effort of town planning demands a parallel effort of comprehension. It opposes to these contemporary urbanism that wish to perceive and to enjoy cities in a sensible way. Nevertheless, sentiment and reason are not adverses and Le Corbusier gives us at his  moment keys to intent a synthesis, joined them in a singular way by means of his ‘boîtes à miracles’ or ‘magic boxes’: those "architectural spectacles of synthesis" that he defined in 1951 Ciam. Here we try to approach to the first of those ‘spectacles’: the ‘diorama’, considering it as a corbusean strategy of mediation between rational and sensible in modern and contemporary city.Key wordsLe Corbusier, diorama, Ville Contemporaine, Plan Voisin, Plan Maciá

  5. Le bord de la solitude

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    Jean-Paul Galibert

    2010-04-01

    Full Text Available La solitude a un bord, et non un seuil, parce que sinon, ce ne serait pas la solitude. Car le seuil a ceci de merveilleux qu’il sépare un dedans et un dehors, en sorte qu’il reste franchissable, et que l’on peut toujours sortir, et rentrer à sa guise. De ce fait, où que soient les autres, le seuil garantit donc que je pourrais les rejoindre, et me délasser, en changeant de lieu, des inconvénients croisés de l’intérieur et de l’extérieur. Dans le seuil, la métaphore implicite de la maison nous...

  6. Hidrelétricas no Rio Madeira-RO: tensões sobre o uso do território e dos recursos naturais na Amazônia Hydroélectriques dans la rivière Madeira-RO: les tensions sur l´usage du territoire et des les ressources naturelles d’Amazonie Hydroelectric at the Madeira River: tensions about the territory using and the natural resources in the Amazon

    Directory of Open Access Journals (Sweden)

    Leonardo José Cordeiro Santos

    2012-06-01

    Full Text Available A construção das usinas hidrelétricas (Jirau e Santo Antônio, iniciadas em 2008, no Rio Madeira, município de Porto Velho-RO, confere à parte da Amazônia Sul Ocidental Rondoniense, uma (revalorização diante do contexto nacional e internacional devido ao potencial energético e ainda por compor parte de complexos para circulação e energia Sul-Americana. A materialização da obra incide sobre a intensificação dos conflitos sobre o uso do território e de seus recursos, fato comprovado a partir das análises feitas sobre as escalas de atuação dos atores e as estratégias na utilização dos recursos naturais na área de estudo. Os resultados ratificam que na Amazônia Rondoniense as políticas de infraestrutura estabelecidas são resultantes de interesses externos a região e, quando implantadas, desestruturam a lógica de organização local, elevando as tensões ambientais e sociais.La construction des usines hydroélectriques (Jirau et Santo Antônio, commencée en 2008, sur le Rio Madeira, dans le município Porto Velho-RO, (revalorise la partie d’ Amazonie Sud Occidentale dú Rondônia en raison du potentiel énérfetique qu’elle gènére et son inscription dans le réseau d’alimentation électrique de l’Amérique du Sud. Mais l´rélisation des ouvrages intensifie les conflits d’utilisation du territoire et de ses ressources, comme le conferment les analyses produites par cette recherché sur les échelles d’intervention des acteurs et les estratégies d’utilisation des ressources naturelles dans la zone d’éstude. Les résultats montrent que dans l’Amazonie du Rondônia, les politiques d’infrastructure telles qu’elles sont conçues resultant d’intérêts externes à la région et, lorsqu’wlles sont implantées, déstructurent les logiques d’organisation locale et provoquent des tensions environnementales et sociales.The building of the hydroelectric plants (Jirau and Santo Antônio, which started

  7. Le front oriental de Lille

    Directory of Open Access Journals (Sweden)

    Étienne Poncelet

    2011-06-01

    Full Text Available De la porte d’eau de la Basse Deûle jusqu’au fort Saint-Sauveur, le front oriental de Lille, fortifié à l’époque espagnole, glisse ses courtines dans les entrelacs du périphérique et des gares. L’enjeu urbain actuel consiste à s’appuyer sur ces murs historiques pour « passer malgré tout » à travers cet écheveau urbain et retisser les fils de la continuité des promenades au cœur de la ville. Moins connus que le front occidental de la reine des citadelles, ces anciens espaces militaires sont une chance pour l’urbanisme de demain dont les opérations en cours de la Porte de Gand et de la Basse Deûle témoignent déjà.The east wall, at Lille, fortified during the period of Spanish occupation, extends from the Porte d'Eau de la Basse-Deûle to the Saint-Sauveur fort. Its curtain walls emerge today in a landscape of ring roads and railway territories. The issue today is to profit from these historic walls in order to make some sense of the urban chaos and to reinstate some urban continuity in the city-centre walkways. Although they are not as well known as the western wall of this major fortified city, these former military properties are an exciting opportunity for tomorrow's town-planners, as the operations already underway at the Porte de Gand et de la Basse Deûle suggest.

  8. La détermination de l'âge par scalimétrie chez le saumon atlantique (Salmo salar dans son aire de répartition méridionale : utilisation pratique et difficultés de la méthode

    Directory of Open Access Journals (Sweden)

    BAGLINIÈRE J. L.

    1985-07-01

    Full Text Available Ce rapport confirme les critères d'interprétation scalimétrique utilisés pour âger le saumon atlantique en eau douce et en mer à l'aide d'exemples typiques. Il synthétise également les difficultés rencontrées pour la détermination d'âge des populations naturelles et d'élevage en les illustrant à l'aide d'exemples atypiques. Enfin, il propose un certain nombre de recommandations pour permettre une meilleure connaissance des populations de saumon atlantique dans son aire de répartition méridionale.

  9. Agir sur le gaspillage alimentaire

    OpenAIRE

    Jan, Sophie; Baron, Florence

    2016-01-01

    On estime aujourd'hui à 25% les pertes d'aliments post-récolte et en aval, en raison de leur altération par des microorganismes. L'étude menée ici illustre le risque d'altération engendré par une rupture dans la chaîne du froid, en prenant comme modèle un aliment liquide pasteurisé et réfrigéré, riche en nutriments et dont la température ne doit pas dépasser 4°C.

  10. Vertical natural convection: application of the unifying theory of thermal convection

    NARCIS (Netherlands)

    Ng, C.S.; Ooi, A.; Lohse, Detlef; Chung, D.

    2015-01-01

    Results from direct numerical simulations of vertical natural convection at Rayleigh numbers 1.0×10 5 –1.0×10 9 and Prandtl number 0.709 support a generalised applicability of the Grossmann–Lohse (GL) theory, which was originally developed for horizontal natural (Rayleigh–Bénard) convection. In

  11. Epidémiologie et contrôle des infections à Pseudodactylogyrus dans les élevages intensifs d'anguilles : données actuelles

    Directory of Open Access Journals (Sweden)

    BUCHMANN K.

    1993-01-01

    Full Text Available Dans une première partie, l'auteur considère successivement divers aspects qui conditionnent l'épidémiologie des infections observées, chez l'Anguille européenne, par Pseudodactylogyrus anguillae et P. bini, en élevage intensif, en eau chaude. La température optimale pour la croissance des Anguilles est aussi celle qui correspond à une reproduction optimale de ces deux Monogènes. L'influence des conditions de recyclage de l'eau et de son traitement par le formol sur les réinfestations parasitaires sont discutées. Il existe une distribution différentielle des deux espèces congénériques sur les branchies, qui varie en fonction de la taille de l'hôte. Les relations entre la taille de l'hôte et la charge parasitaire sont discutées en fonction des conditions d'élevage et les conditions naturelles. Une relative résistance à la réinfestation parasitaire a été observée. Dans une seconde partie, une étude thérapeutique basée sur les effets antihelmintiques des 22 produits est présentée. Si le mebendazole s'est avéré le plus efficace, des phénomènes de résistance après traitements répétés sont évoqués.

  12. Rapport sur le développement dans le monde sur le thème du rôle ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    ... rural et sont tributaires principalement de l'agriculture pour assurer leur subsistance. Ce projet permettra de veiller à ce qu'une place soit accordée aux travaux de recherche financés par le CRDI, aux points de vue différents et aux auteurs de l'hémisphère Sud dans le Rapport sur le développement dans le monde 2008.

  13. Le CRDI en Indonésie

    International Development Research Centre (IDRC) Digital Library (Canada)

    l'État dans l'île de Java. Soutenu par le CRDI, l'institut Lembaga Alam Tropika Indonesia. (ou LATIN) a conçu un modèle de cogestion des forêts qui met à contribution les collec- tivités et le gouvernement dans trois dis- tricts. Ainsi, les agriculteurs disposent d'un meilleur accès aux ressources de la forêt. Évaluation des ...

  14. Le Kenya nomme le titulaire de sa première chaire de recherche

    International Development Research Centre (IDRC) Digital Library (Canada)

    14 avr. 2016 ... De concert avec le CRDI, la National Commission for Science, Technology and Innovation (NACOSTI) du Kenya a inauguré sa première chaire de recherche à Nairobi, le 31 mars 2015. Le professeur Fabian Omoding Esamai, qui dirige actuellement le College of Health Sciences de la Moi University, a été ...

  15. Rapport financier trimestriel pour le trimestre qui a pris fin le 31

    International Development Research Centre (IDRC) Digital Library (Canada)

    Office 2004 Test Drive User

    31 déc. 2015 ... Le CRDI finance des travaux de recherche appliquée ... recherches pour le développement international (CRDI, le Centre) et ..... voie de développement et sur la mise en oeuvre des connaissances scientifiques, techniques et autres en .... Les accords expirent à des dates différentes, et le dernier prend fin.

  16. pour le trimestre qui a pris fin le 30 juin 2015

    International Development Research Centre (IDRC) Digital Library (Canada)

    Office 2004 Test Drive User

    30 juin 2015 ... Le CRDI finance des travaux de recherche appliquée ... recherches pour le développement international (le Centre) et de ..... voie de développement et sur la mise en oeuvre des connaissances scientifiques, techniques et autres en .... Les accords expirent à des dates différentes, et le dernier prend fin en.

  17. pour le trimestre qui a pris fin le 31 décembre 2014

    International Development Research Centre (IDRC) Digital Library (Canada)

    Office 2004 Test Drive User

    31 déc. 2014 ... Le CRDI finance des travaux de recherche appliquée ... recherches pour le développement international (le Centre) et de ...... voie de développement et sur la mise en oeuvre des connaissances scientifiques, techniques et autres en vue .... Les accords expirent à des dates différentes, et le dernier prend fin.

  18. Rapport financier trimestriel pour le trimestre qui a pris fin le 30

    International Development Research Centre (IDRC) Digital Library (Canada)

    Office 2004 Test Drive User

    30 sept. 2015 ... Le CRDI finance des travaux de recherche appliquée ... recherches pour le développement international (le Centre) et de ..... voie de développement et sur la mise en oeuvre des connaissances scientifiques, techniques et autres en .... Les accords expirent à des dates différentes, et le dernier prend fin en.

  19. Variabilité selon le captureur de l'efficacité de répulsifs à base d'huiles végétales dans la protection individuelle contre les piqûres de Simulium damnosum s. l.

    Directory of Open Access Journals (Sweden)

    Sylla M.

    2002-12-01

    Full Text Available Dans le présent article, nous faisons état de la variabilité selon le captureur de l'efficacité de répulsifs à base d'huiles végétales appliquées sur la peau contre les piqûres de Simulium damnosum s. l. Les expérimentations ont été effectuées en zones de savane (Chaussée-Niaka et de forêt (Soubré de Côte d'Ivoire. Les formulations (lotions, crèmes] testées lors de ces travaux ont été obtenues à partir d'huiles d'amande de palme (Elaeis guineensis, de coco (Cocos nucifera et de gobi (Carapa procera. La technique classique de capture sur homme à l'aide de tubes à hémolyse en matière plastique a été utilisée. Pour chaque journée d'expérimentation, un captureur non traité (jambes non enduites de répulsif servait de témoin. Les résultats indiquent qu'en savane, quels que soient le répulsif et le captureur, la densité simulidienne se situait de 1 à 4, 1 à 6 et de 2 à 10 simulies par homme et par jour lorsque le captureur était respectivement protégé avec le coco, le palmiste et le gobi. Avec les mêmes répulsifs, en zone de forêt, l'agressivité simulidienne variait de 9 à 16, de 2 à 30 et de 8 à 49 piqûres par jour. En comparaison, le témoin recevait de 67 à 90 et de 310 à 533 piqûres par jour, respectivement en zones de savane et de forêt. Malgré les variations importantes dans le nombre de simulies capturées en fonction du captureur choisi, nos résultats montrent que quels que soient le répulsif et l'espèce simulidienne, une protection similaire est conférée à tous les captureurs. Ils indiquent également que le recours à des substances naturelles locales, utilisées comme répulsifs en application dermique, est l'une des meilleures méthodes de protection personnelle contre les simulies.

  20. Lutter contre le paludisme sans DDT

    International Development Research Centre (IDRC) Digital Library (Canada)

    Nancy Minogue

    La participation de la collectivité aux stratégies de contrôle, une surveillance ... Le contrôle de la maladie passe par une meilleure gestion de l'environnement. En vertu de ... de la santé humaine, ou écosanté, est un processus dynamique qui.

  1. Le CERN ouvre ses entrailles au public

    CERN Multimedia

    2004-01-01

    "Le CERN se lance dans une grande opération de relations publiques pour son cinquantième anniversaire. Le centre de recherche organisera une journée portes ouvertes le 16 octobre. Quelque 50 sites pourrant être visités" (1/2 page)

  2. Eau, terre et vie : Communication participative pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Dans domaine de la recherche sur la gestion des ressources naturelles, les meilleurs modèles sont ceux qui, lors de la prise de décision et de l'identification du projet de recherche et des paramètres de développement, intègrent la participation des membres de la collectivité, des équipes de recherche ou de ...

  3. Convective transport resistance in the vitreous humor

    Science.gov (United States)

    Penkova, Anita; Sadhal, Satwindar; Ratanakijsuntorn, Komsan; Moats, Rex; Tang, Yang; Hughes, Patrick; Robinson, Michael; Lee, Susan

    2012-11-01

    It has been established by MRI visualization experiments that the convection of nanoparticles and large molecules with high rate of water flow in the vitreous humor will experience resistance, depending on the respective permeabilities of the injected solute. A set of experiments conducted with Gd-DTPA (Magnevist, Bayer AG, Leverkusen, Germany) and 30 nm gadolinium-based particles (Gado CELLTrackTM, Biopal, Worcester, MA) as MRI contrast agents showed that the degree of convective transport in this Darcy-type porous medium varies between the two solutes. These experiments consisted of injecting a mixture of the two (a 30 μl solution of 2% Magnevist and 1% nanoparticles) at the middle of the vitreous of an ex vivo whole bovine eye and subjecting the vitreous to water flow rate of 100 μl/min. The water (0.9% saline solution) was injected at the top of the eye, and was allowed to drain through small slits cut at the bottom of the eyeball. After 50 minutes of pumping, MRI images showed that the water flow carried the Gd-DTPA farther than the nanoparticles, even though the two solutes, being mixed, were subjected to the same convective flow conditions. We find that the convected solute lags the water flow, depending on the solute permeability. The usual convection term needs to be adjusted to allow for the filtration effect on the larger particles in the form (1- σ) u . ∇ c with important implications for the modeling of such systems.

  4. LE CORBUSIER: CONCURSOS Y PALACIOS / Le Corbusier: competitions and palaces

    Directory of Open Access Journals (Sweden)

    Fernando Zaparaín Hernández

    2012-11-01

    Full Text Available RESUMEN Cuando Le Corbusier ya había pasado de los cuarenta años se enfrentó a dos concursos internacionales: el Palacio de las Naciones en Ginebra (1926–31 y el Palacio de los Soviets en Moscú (1931–32 con los que intentaba acceder a grandes encargos de estado con mayor escala urbana en los que poner a prueba su ideario moderno sobre arquitectura y urbanismo. En ambos casos estuvo entre los vencedores pero por conveniencia e indecisión, los poderes políticos optaron por soluciones academicistas. Al conocer las decisiones definitivas, Le Corbusier y todos sus contactos del Movimiento Moderno orquestaron diversas polémicas ante los medios de comunicación y los gobernantes por entender que el progreso se veía lastrado por el triunfo de propuestas reaccionarias. Mediante el estudio de la correspondencia con personas particulares como Moser, Giedion, Colly o Stonorov, conservada en la Fundación Le Corbusier, se analizan las relaciones y el tono ideológico en torno a aquellas protestas. En esos textos quedan reflejados los principales rasgos que caracterizan la modernidad como su internacionalización, la seguridad en la propia misión, la defensa de lo nuevo o el método dialéctico. SUMMARY When Le Corbusier had already passed the age of forty he confronted two international competitions: the Palais des Nations in Geneva (1926–1931 and the Palace of the Soviets in Moscow (1931–32, with which he attempted to access large state commissions, with greater urban scale, in which to test his ideas about modern architecture and urbanism. In both cases he was among the winners, but through convenience and indecision the political powers opted for solutions from academicians. Upon knowing the final decisions, Le Corbusier and all his contacts in the Modern Movement orchestrated several controversies with the media, and the people in power, to convey that progress seemed burdened by the triumph of reactionary proposals. The relationships

  5. Le contrôle de gestion des entreprises familiales : un contrôle non-financiarisé ?

    OpenAIRE

    Barbelivien , Dominique

    2016-01-01

    Nous examinons la tendance décrite dans la littérature quant à la financiarisation de la fonction de contrôle de gestion en nous appuyant sur le cas d’une entreprise de taille intermédiaire familiale. Nous constatons que le contrôle de gestion dans le cas étudié correspond à une rationalisation des décisions opérationnelles et développons les raisons qui peuvent expliquer la persistance d’un contrôle de gestion très opérationnel. Le contexte d’entreprise familiale dans laquelle il y a confusi...

  6. Le droit, l'économie et le fondamental

    OpenAIRE

    Gérard Farjat

    2005-01-01

    MAITRE Grégory, préf. MUIR WATT Horatia, La Responsabilité civile à l’épreuve de l’analyse économique du droit, Paris, L.G.D.J., coll. Droit &Économie, 2005,315 p. LE TOURNEAU Philippe, L’Éthique des affaires et du management au XXIe siècle, Paris, Dalloz, Paris, Dunod, 2000,269 p. DELMAS-MARTY Mireille, Le Relatif et l’universel : les forces imaginantes du droit, Paris, Seuil, coll. La Couleur des idées, 2004,440 p. FRISON-ROCHE Marie-Anne, BONFILS Sébastien, Les Grandes Questions du droit é...

  7. Convective mixing in helium white dwarfs

    International Nuclear Information System (INIS)

    Vauclair, G.; Fontaine, G.

    1979-01-01

    The conditions under which convective mixing episodes take place between the helium envelopes and the underlying carbon layers in helium-rich white dwarfs are investigated. It is found that, for essentially any value of the initial helium content less than the maximum mass a helium convection zone can have, mixing does occur, and leads, in the vast majority of cases, to an almost pure carbon superficial composition. Mixing products that show only traces of carbon while retaining helium-dominated envelopes are possible only if the initial helium content is quite close to the maximum possible mass of the helium convection zone. In the presence of turbulence, this restriction could be relaxed, however, and the helium-rich lambda4670 stars may possibly be explained in this fashion

  8. 48. Le pavillon Liliane de Stewart

    OpenAIRE

    Cameron, Christina; Déom, Claudine; Valois, Nicole

    2018-01-01

    Le pavillon Liliane de Stewart Le pavillon Liliane de Stewart est situé à l’arrière du pavillon Marguerite-d’Youville, qui lui est mitoyen. Il en constitue en quelque sorte un agrandissement, mais il s’en différencie par son plus petit volume (trois étages). Les deux pavillons partagent quelques caractéristiques architecturales, dont le plan angulaire et le revêtement de brique chamois. Le pavillon Liliane de Stewart se distingue cependant par sa fenestration, surtout celle de la façade avant...

  9. LE FRANÇAIS DANS LA PRESSE ECRITE DU NORD-CAMEROUN : DIAGNOSTIC, CRITIQUES ET ORIENTATIONS

    Directory of Open Access Journals (Sweden)

    Moïse MBEY MAKANG

    2013-11-01

    Full Text Available La présente réflexion tire son origine de la crise linguistique observée au sein de la presse écrite du Nord-Cameroun. Celle-ci fait échos des irrégularités de la langue de Voltaire dans la presse écrite de cette partie du pays. De plus en plus, on y assiste à une émergence des déviances syntaxiques et une profusion des écarts langagiers à connotation dépréciative. L’indécence verbale de la société, la mauvaise prestation des élèves en classe et lors des examens officiels en sont des indicateurs pertinents. Il est important de mentionner que la cohabitation entre les langues camerounaises et le français, la sous-scolarisation et ou l’ignorance, le laxisme des rédacteurs en chef, etc. sont les mobiles profonds de cette incorrection. Pourtant, nous savons tous que les media sont une forteresse où la langue doit être préservée de toute entorse et représentent un modèle pour la société. Néanmoins, des traits caractéristiques du français de la presse écrite du Nord-Cameroun s’inscrivent en faux par rapport à cette vocation naturelle des media. Dès lors, la question que nous pouvons nous poser est celle de savoir si ces mobiles ci-dessus cités sont des éléments qui favorisent l’émergence de cette dialectalisation du français. En clair qu’est-ce qui caractérise le français des journalistes? Quelle est la structure morphosyntaxique du français des rédacteurs des journaux? S’agit-il d’un français conforme à une norme locale ou (y retrouvons-nous des énoncés exogènes ? Quel type de morphosyntaxe utilisent les rédacteurs ? Une morphosyntaxe endogène, morphosyntaxe qui leur est propre, ou plutôt une morphosyntaxe exogène, supposée unique à tous les francophones ? Peut-on parler d’alternance codique, d’argotisation, ou de créolisation ? La présente analyse a pour ambitions de s’interroger sur les mobiles profonds qui incitent des journalistes à s’écarter de la norme du fran

  10. Le black-bass (Micropterus salmoides Lacép. dans les eaux italiennes. Un antagoniste du brochet ?

    Directory of Open Access Journals (Sweden)

    ALESSIO G.

    1984-01-01

    Full Text Available Le black-bass à grande bouche est largement répandu dans les eaux italiennes et fait l'objet de repeuplement. Les alevins et estivaux nécessaires proviennent le plus souvent de la vidange automnale des étangs à cyprinidés avec lesquels ils sont élevés. Il n'y a pas vraiment d'élevage contrôlé de cette espèce en Italie, mais seulement une série d'essais qui portent sur la reproduction naturelle en étangs-frayères, l'introduction de nids artificiels dans le milieu et l'induction de la ponte par traitement hypophysaire (avec HCG, essais qui donnent des résultats satisfaisants. Dans le milieu naturel, la croissance en longueur et en poids du black-bass en Italie est comparable et quelquefois meilleure que celle enregistrée sur ses lieux d'origine. La croissance annuelle est d'abord lente (printemps, puis rapide (été, ensuite à nouveau lente (automne pour être finalement modeste ou pratiquement nulle en hiver. La population qui, avec des fluctuations annuelles, représente 0,5 à 1,6 % de l'ichthyofaune des eaux étudiées (fleuves Pô, Sesia et Ticino, est constituée surtout de sujets jeunes : environ 40 % des individus sont âgés de 2 hivers et ne dépassent pas un poids de 400 g et une longueur totale de 28 cm. La survie est considérée comme bonne avec une durée de vie de 8 à 9 hivers. La nourriture présente un spectre très large et est basée de préférence sur des petits poissons et sur les amphibiens, avec une large partie d'invertébrés (surtout des insectes. La reproduction intervient aux mois de mai et juin, mais elle peut être aussi plus précoce et, le plus souvent, plus tardive. Le black-bass est très sensible aux pollutions, mais ne semble pas particulièrement affecté par des épizooties ou du parasitisme. Par rapport à la niche écologique occupée, à son spectre trophique, à son rôle dans les équilibres biologiques et à ses caractéristiques éthologiques, le black-bass ne peut pas être consid

  11. Le cosmos et le lotus confessions d'un astrophysicien

    CERN Document Server

    Trinh, Xuan Thuan

    2011-01-01

    Que nous dit vraiment la science sur la nature de l'univers, sur son origine et son avenir ? Par quel mystère le langage mathématique, pure création de l'esprit humain, se révèle-t-il aussi performant pour nous décrire les phénomènes physiques, de l'infiniment petit à l'infiniment grand ? S'il existe un ordre du monde, ce que nous en disent la physique quantique et la théorie de la relativité est-il compatible avec ce qu'enseigne le bouddhisme ? Et que peut-on en conclure concernant notre propre vie ? A ces questions passionnantes et à beaucoup d'autres, le célèbre astrophysicien Trinh Xuan Thuan répond ici d'une façon personnelle, en s'appuyant sur son expérience. Son itinéraire l'a placé d'emblée à la confluence de trois cultures : issu d'une famille de lettrés vietnamiens imprégnée de traditions bouddhiste et confucéenne, il a reçu une éducation à la française puis une formation scientifique à l'américaine. Une telle richesse de points de vue lui permet d'apporter, non pas de...

  12. Bulletin #109 | CRDI - Le Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    ... offres d'emploi. Appel à propositions de recherche sur les villes résilientes en Amérique latine. Date butoir : 13 juin 2016. Programme de recherche sur le virus Zika Canada-Amérique latine et Caraïbes Date butoir : 12 juillet 2016. POSSIBILITÉS D'EMPLOIS Agent de ressources humaines · Analyste des opérations de TI.

  13. Vaincre le vampire violet | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    26 janv. 2011 ... ... de s'assurer que l'arme fongique découverte par Alan Watson ne se transforme en mercenaire et cause la destruction d'autres espèces végétales, Fusarium oxysporum a été soumis pendant deux ans à une batterie de tests dans les laboratoires hautement sécurisés de McGill, sur le campus Macdonald.

  14. Le futur du travail | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    12 juin 2017 ... Trois hommes qui travaillent sur le projet de livraison de drone au Rwanda. Sarah Farhat / Banque mondiale. La numérisation, l'automatisation et les communications en réseau façonnent de plus en plus les sociétés, les marchés du travail et les occasions d'emploi à l'échelle mondiale. Les changements ...

  15. Natural Convective Heat Transfer from Narrow Plates

    CERN Document Server

    Oosthuizen, Patrick H

    2013-01-01

    Natural Convective Heat Transfer from Narrow Plates deals with a heat transfer situation that is of significant practical importance but which is not adequately dealt with in any existing textbooks or in any widely available review papers. The aim of the book is to introduce the reader to recent studies of natural convection from narrow plates including the effects of plate edge conditions, plate inclination, thermal conditions at the plate surface and interaction of the flows over adjacent plates. Both numerical and experimental studies are discussed and correlation equations based on the results of these studies are reviewed.

  16. Introductory analysis of Benard-Marangoni convection

    International Nuclear Information System (INIS)

    Maroto, J A; Perez-Munuzuri, V; Romero-Cano, M S

    2007-01-01

    We describe experiments on Benard-Marangoni convection which permit a useful understanding of the main concepts involved in this phenomenon such as, for example, Benard cells, aspect ratio, Rayleigh and Marangoni numbers, Crispation number and critical conditions. In spite of the complexity of convection theory, we carry out a simple and introductory analysis which has the additional advantage of providing very suggestive experiments. As a consequence, we recommend our device for use as a laboratory experiment for undergraduate students of the thermodynamics of nonlinear and fluid physics

  17. Might electrical earthing affect convection of light

    International Nuclear Information System (INIS)

    Budrikis, Z.L.

    1982-01-01

    Partial convection of light by moving media was predicted by Fresnel and verified by Fizeau, Zeeman and others. It is accepted as an important argument in favour of the Special Theory of Relativity. The suggestion is made here that the convection is partial only when the propagating medium is moved with respect to its electrically earthed surroundings and that it would be total if an earthed shield was co-moving with the medium. This is based on a reinterpretation of Maxwell's equations wherein they are seen as macroscopic relationships that are in each case valid only in respect of a particular inertial frame of reference, the local electrical earth frame. (Auth.)

  18. Introductory analysis of Benard-Marangoni convection

    Energy Technology Data Exchange (ETDEWEB)

    Maroto, J A [Group of Physics and Chemistry of Linares, Escuela Politecnica Superior, St Alfonso X El Sabio, 28, University of Jaen, E-23700 Linares, Jaen (Spain); Perez-Munuzuri, V [Group of Nonlinear Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Romero-Cano, M S [Group of Complex Fluids Physics, Department of Applied Physics, University of Almeria, E-04120 Almeria (Spain)

    2007-03-15

    We describe experiments on Benard-Marangoni convection which permit a useful understanding of the main concepts involved in this phenomenon such as, for example, Benard cells, aspect ratio, Rayleigh and Marangoni numbers, Crispation number and critical conditions. In spite of the complexity of convection theory, we carry out a simple and introductory analysis which has the additional advantage of providing very suggestive experiments. As a consequence, we recommend our device for use as a laboratory experiment for undergraduate students of the thermodynamics of nonlinear and fluid physics.

  19. Topology Optimisation for Coupled Convection Problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe; Andreasen, Casper Schousboe; Aage, Niels

    stabilised finite elements implemented in a parallel multiphysics analysis and optimisation framework DFEM [1], developed and maintained in house. Focus is put on control of the temperature field within the solid structure and the problems can therefore be seen as conjugate heat transfer problems, where heat...... conduction governs in the solid parts of the design domain and couples to convection-dominated heat transfer to a surrounding fluid. Both loosely coupled and tightly coupled problems are considered. The loosely coupled problems are convection-diffusion problems, based on an advective velocity field from...

  20. Lattice BGK simulation of natural convection

    International Nuclear Information System (INIS)

    Chen, Yu; Ohashi, Hirotada; Akiyama, Mamoru

    1995-01-01

    Recently a new thermal lattice Bhatnagar-Gross-Krook fluid model was suggested by the authors. In this study, this new model was applied into the numerical simulation of natural convection, namely the Rayleigh Benard flow. The critical number for the onset of convective phenomenon was numerically measured and compared with that of theoretical prediction. A gravity dependent deviation was found in the numerical simulation, which is explained as an unavoidable consequence of the incorporation of gravity force in the lattice BGK system. (author)

  1. Comparing convective heat fluxes derived from thermodynamics to a radiative-convective model and GCMs

    Science.gov (United States)

    Dhara, Chirag; Renner, Maik; Kleidon, Axel

    2015-04-01

    The convective transport of heat and moisture plays a key role in the climate system, but the transport is typically parameterized in models. Here, we aim at the simplest possible physical representation and treat convective heat fluxes as the result of a heat engine. We combine the well-known Carnot limit of this heat engine with the energy balances of the surface-atmosphere system that describe how the temperature difference is affected by convective heat transport, yielding a maximum power limit of convection. This results in a simple analytic expression for convective strength that depends primarily on surface solar absorption. We compare this expression with an idealized grey atmosphere radiative-convective (RC) model as well as Global Circulation Model (GCM) simulations at the grid scale. We find that our simple expression as well as the RC model can explain much of the geographic variation of the GCM output, resulting in strong linear correlations among the three approaches. The RC model, however, shows a lower bias than our simple expression. We identify the use of the prescribed convective adjustment in RC-like models as the reason for the lower bias. The strength of our model lies in its ability to capture the geographic variation of convective strength with a parameter-free expression. On the other hand, the comparison with the RC model indicates a method for improving the formulation of radiative transfer in our simple approach. We also find that the latent heat fluxes compare very well among the approaches, as well as their sensitivity to surface warming. What our comparison suggests is that the strength of convection and their sensitivity in the climatic mean can be estimated relatively robustly by rather simple approaches.

  2. Le colonel Rol-Tanguy

    OpenAIRE

    Bourderon, Roger

    2009-01-01

    Ouvrier métallurgiste, syndicaliste et communiste, le futur colonel Rol-Tanguy, né en 1908, se passionne pour le métier des armes lors de son service militaire. Son expérience dans les Brigades internationales est décisive. Il l’enrichit dans les FTP puis comme chef régional FFI : il prépare et conduit l’insurrection parisienne avec un état-major comportant de nombreux cadres de l’armée. Compagnon de la Libération, il se distingue dans la campagne d’Allemagne et est intégré dans l’armée avec ...

  3. Le glaive de la parole

    Directory of Open Access Journals (Sweden)

    Luce Marchal-Albert

    2006-09-01

    Full Text Available Chacun sait, selon le mot de Pierre Viret, « en quelle confusion est la Chrestienté » au xvie siècle en Europe. C’est le deuxième quart du siècle qui nous intéressera ici, et en particulier l’année 1545, qui constitue une année charnière qui voit vaciller l’Église romaine, flamber et culminer la chasse aux hérétiques en même temps qu’elle voit la jeune Église réformée se renforcer et se positionner avec succès dans un champ religieux plus que chaotique. Les ouvrages polémiques réformés écrits...

  4. Le CRDI au Costa Rica

    International Development Research Centre (IDRC) Digital Library (Canada)

    région ont-elles besoin du commerce, mais elles doivent en outre acquérir de nouvelles compétences afin de pouvoir prospérer dans l'économie du savoir. La capacité d'utiliser les technologies de l'information, entre autres, est désormais une nécessité. Le CRDI subventionne la Fundación. Omar Dengo afin qu'elle puisse ...

  5. High Ra, high Pr convection with viscosity gradients

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. High Ra, high Pr convection with viscosity gradients. Weak upward flow through mesh. Top fluid more viscous. Unstable layer Instability Convection.

  6. Stretched flow of Carreau nanofluid with convective boundary ...

    Indian Academy of Sciences (India)

    journal of. January 2016 physics pp. 3–17. Stretched flow of Carreau nanofluid with ... fluid over a flat plate subjected to convective surface condition. ... the steady laminar boundary layer flow over a permeable plate with a convective boundary.

  7. Georges et le big bang

    CERN Document Server

    Hawking, Lucy; Parsons, Gary

    2011-01-01

    Georges et Annie, sa meilleure amie, sont sur le point d'assister à l'une des plus importantes expériences scientifiques de tous les temps : explorer les premiers instants de l'Univers, le Big Bang ! Grâce à Cosmos, leur super ordinateur, et au Grand Collisionneur de hadrons créé par Éric, le père d'Annie, ils vont enfin pouvoir répondre à cette question essentielle : pourquoi existons nous ? Mais Georges et Annie découvrent qu'un complot diabolique se trame. Pire, c'est toute la recherche scientifique qui est en péril ! Entraîné dans d'incroyables aventures, Georges ira jusqu'aux confins de la galaxie pour sauver ses amis...Une plongée passionnante au coeur du Big Bang. Les toutes dernières théories de Stephen Hawking et des plus grands scientifiques actuels.

  8. Micro manometer and pitot tube for measuring the velocity distribution in a natural convection water stream between two vertical parallel plates (1961); Micromano metre et tube de pitot destines a l'exploration du profil de vitesse dans un ecoulement d'eau de convection naturelle entre deux plaques verticales paralleles (1961)

    Energy Technology Data Exchange (ETDEWEB)

    Santon, L; Vernier, Ph [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1961-07-01

    For heat transfer studies in certain cases of cooling in swimming-pool type nuclear reactors, a knowledge of the distribution of the velocities between two heating elements is of prime importance. A Pitot tube and a micro-manometer have been developed for making these measurements on an experimental model. (authors) [French] Pour l'etude du transfert de chaleur dans certains cas de refroidissement des reacteurs nucleaires du type piscine, la connaissance de la repartition des vitesses entre deux elements chauffants est primordiale. On a mis au point un tube de Pitot et un micromanometre pour effectuer ces mesures sur une maquette experimentale. (auteurs)

  9. An infinite-dimensional model of free convection

    Energy Technology Data Exchange (ETDEWEB)

    Iudovich, V.I. (Rostovskii Gosudarstvennyi Universitet, Rostov-on-Don (USSR))

    1990-12-01

    An infinite-dimensional model is derived from the equations of free convection in the Boussinesq-Oberbeck approximation. The velocity field is approximated by a single mode, while the heat-conduction equation is conserved fully. It is shown that, for all supercritical Rayleigh numbers, there exist exactly two secondary convective regimes. The case of ideal convection with zero viscosity and thermal conductivity is examined. The averaging method is used to study convection regimes at high Reynolds numbers. 10 refs.

  10. Education: DNA replication using microscale natural convection.

    Science.gov (United States)

    Priye, Aashish; Hassan, Yassin A; Ugaz, Victor M

    2012-12-07

    There is a need for innovative educational experiences that unify and reinforce fundamental principles at the interface between the physical, chemical, and life sciences. These experiences empower and excite students by helping them recognize how interdisciplinary knowledge can be applied to develop new products and technologies that benefit society. Microfluidics offers an incredibly versatile tool to address this need. Here we describe our efforts to create innovative hands-on activities that introduce chemical engineering students to molecular biology by challenging them to harness microscale natural convection phenomena to perform DNA replication via the polymerase chain reaction (PCR). Experimentally, we have constructed convective PCR stations incorporating a simple design for loading and mounting cylindrical microfluidic reactors between independently controlled thermal plates. A portable motion analysis microscope enables flow patterns inside the convective reactors to be directly visualized using fluorescent bead tracers. We have also developed a hands-on computational fluid dynamics (CFD) exercise based on modeling microscale thermal convection to identify optimal geometries for DNA replication. A cognitive assessment reveals that these activities strongly impact student learning in a positive way.

  11. Evolution of Excited Convective Cells in Plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans; Juul Rasmussen, Jens; Sugai, H.

    1984-01-01

    Convective cells are excited externally in a fully ionized magnetized plasma and their space-time evolution is investigated by two-dimensional potential measurements. A positive cell is excited externally by control of the end losses in the 'scrape off' layer of a plasma column produced by surface...

  12. Free convection film flows and heat transfer

    CERN Document Server

    Shang, Deyi

    2010-01-01

    Presents development of systematic studies for hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, and accelerating film flow of non-Newtonian power-law fluids. This book provides a system of analysis models with a developed velocity component method.

  13. Penetrative convection at high Rayleigh numbers

    Science.gov (United States)

    Toppaladoddi, Srikanth; Wettlaufer, John S.

    2018-04-01

    We study penetrative convection of a fluid confined between two horizontal plates, the temperatures of which are such that a temperature of maximum density lies between them. The range of Rayleigh numbers studied is Ra=[0.01 ,4 ]106,108 and the Prandtl numbers are Pr=1 and 11.6. An evolution equation for the growth of the convecting region is obtained through an integral energy balance. We identify a new nondimensional parameter, Λ , which is the ratio of temperature difference between the stable and unstable regions of the flow; larger values of Λ denote increased stability of the upper stable layer. We study the effects of Λ on the flow field using well-resolved lattice Boltzmann simulations and show that the characteristics of the flow depend sensitively upon it. For the range Λ = , we find that for a fixed Ra the Nusselt number, Nu, increases with decreasing Λ . We also investigate the effects of Λ on the vertical variation of convective heat flux and the Brunt-Väisälä frequency. Our results clearly indicate that in the limit Λ →0 the problem reduces to that of the classical Rayleigh-Bénard convection.

  14. Radiative-convective equilibrium model intercomparison project

    Science.gov (United States)

    Wing, Allison A.; Reed, Kevin A.; Satoh, Masaki; Stevens, Bjorn; Bony, Sandrine; Ohno, Tomoki

    2018-03-01

    RCEMIP, an intercomparison of multiple types of models configured in radiative-convective equilibrium (RCE), is proposed. RCE is an idealization of the climate system in which there is a balance between radiative cooling of the atmosphere and heating by convection. The scientific objectives of RCEMIP are three-fold. First, clouds and climate sensitivity will be investigated in the RCE setting. This includes determining how cloud fraction changes with warming and the role of self-aggregation of convection in climate sensitivity. Second, RCEMIP will quantify the dependence of the degree of convective aggregation and tropical circulation regimes on temperature. Finally, by providing a common baseline, RCEMIP will allow the robustness of the RCE state across the spectrum of models to be assessed, which is essential for interpreting the results found regarding clouds, climate sensitivity, and aggregation, and more generally, determining which features of tropical climate a RCE framework is useful for. A novel aspect and major advantage of RCEMIP is the accessibility of the RCE framework to a variety of models, including cloud-resolving models, general circulation models, global cloud-resolving models, single-column models, and large-eddy simulation models.

  15. Vortex statistics in turbulent rotating convection

    NARCIS (Netherlands)

    Kunnen, R.P.J.; Clercx, H.J.H.; Geurts, B.J.

    2010-01-01

    The vortices emerging in rotating turbulent Rayleigh-Bénard convection in water at Rayleigh number Ra=6.0×108 are investigated using stereoscopic particle image velocimetry and by direct numerical simulation. The so-called Q criterion is used to detect the vortices from velocity fields. This

  16. Phenomenology of convection-parameterization closure

    Directory of Open Access Journals (Sweden)

    J.-I. Yano

    2013-04-01

    Full Text Available Closure is a problem of defining the convective intensity in a given parameterization. In spite of many years of efforts and progress, it is still considered an overall unresolved problem. The present article reviews this problem from phenomenological perspectives. The physical variables that may contribute in defining the convective intensity are listed, and their statistical significances identified by observational data analyses are reviewed. A possibility is discussed for identifying a correct closure hypothesis by performing a linear stability analysis of tropical convectively coupled waves with various different closure hypotheses. Various individual theoretical issues are considered from various different perspectives. The review also emphasizes that the dominant physical factors controlling convection differ between the tropics and extra-tropics, as well as between oceanic and land areas. Both observational as well as theoretical analyses, often focused on the tropics, do not necessarily lead to conclusions consistent with our operational experiences focused on midlatitudes. Though we emphasize the importance of the interplays between these observational, theoretical and operational perspectives, we also face challenges for establishing a solid research framework that is universally applicable. An energy cycle framework is suggested as such a candidate.

  17. Oscillatory Convection in Rotating Liquid Metals

    Science.gov (United States)

    Bertin, Vincent; Grannan, Alex; Aurnou, Jonathan

    2016-11-01

    We have performed laboratory experiments in a aspect ratio Γ = 2 cylinder using liquid gallium (Pr = 0 . 023) as the working fluid. The Ekman number varies from E = 4 ×10-5 to 4 ×10-6 and the Rayleigh number varies from Ra = 3 ×105 to 2 ×107 . Using heat transfer and temperature measurements within the fluid, we characterize the different styles of low Pr rotating convective flow. The convection threshold is first overcome in the form of a container scale inertial oscillatory mode. At stronger forcing, wall-localized modes develop, coexisting with the inertial oscillatory modes in the bulk. When the strength of the buoyancy increases further, the bulk flow becomes turbulent while the wall modes remain. Our results imply that rotating convective flows in liquid metals do not develop in the form of quasi-steady columns, as in Pr = 1 planetary and stellar dynamo models, but in the form of oscillatory motions. Therefore, convection driven dynamo action in low Pr fluids can differ substantively than that occurring in typical Pr = 1 numerical models. Our results also suggest that low wavenumber, wall modes may be dynamically and observationally important in liquid metal dynamo systems. We thank the NSF Geophysics Program for support of this project.

  18. Natural convection in horizontal fluid layers

    International Nuclear Information System (INIS)

    Suo-Antilla, A.J.

    1977-02-01

    The experimental work includes developing and using a thermal convection cell to obtain measurements of the heat flux and turbulent core temperature of a horizontal layer of fluid heated internally and subject to both stabilizing and destabilizing temperature differences. The ranges of Rayleigh numbers tested were 10 7 equal to or less than R/sub I/ equal to or less than 10 13 and -10 10 equal to or less than R/sub E/ equal to or less than 10 10 . Power integral methods were found to be adequate for interpolating and extrapolating the data. The theoretical work consists of the derivation, solution and use of the mean field equations for study of thermally driven convection in horizontal layers of infinite extent. The equations were derived by a separation of variables technique where the horizontal directions were described by periodic structures and the vertical being some function of z. The derivation resulted in a coupled set of momentum and energy equations. The equations were simplified by using the infinite Prandtl number limit and neglecting direct intermodal interaction. Solutions to these equations are used to predict the existence of multi-wavenumber flows at all supercritical Rayleigh numbers. Subsequent inspection of existing experimental photographs of convecting fluids confirms their existence. The onset of time dependence is found to coincide with the onset of the second convective mode. Each mode is found to consist of two wavenumbers and typically the velocity and temperature fields of the right modal branch are found to be out of phase

  19. Unstable mixed convective transport in groundwater

    International Nuclear Information System (INIS)

    Schincariol, R.A.; Schwartz, F.W.

    1990-01-01

    This study is an experimental investigation of variable density groundwater flow in homogeneous and lenticular porous media. A solution of 500 mg/l Rhodamine WT dye served as the carrier for various concentrations of solute (NaCl) introduced into a two-dimensional flow tank at concentrations ranging from 1000 to 100,000 mg/l. At the scale of the experiments, mass transport depends upon both forced and free convection. In addition, density differences as low as 0.008 g/cm 3 (1000 mg/l NaCl) between a plume of dense water and ambient groundwater in homogeneous medium produces gravitational instabilities at realistic groundwater velocities. These instabilities are manifest by lobe-shaped protuberances that formed first along the bottom edge of the plume and later within the plume. As the density difference increases to 0.0015 g/cm 3 (2000 mg/l NaCl), 0.0037 g/cm 3 (5000 mg/l NaCl) or higher, this unstable mixing due to convective dispersion significantly alters the spreading process, resulting in a large degree of vertical spreading of the plume. In a lenticular medium the combination of convective dispersion and nonuniform flow due to heterogeneities results in relatively large dispersion. Scale considerations indicate that convective dispersion may provide an important component of mixing at the field scale. (Author) (30 refs., 12 figs., 3 tabs.)

  20. Solar Hot Water Heating by Natural Convection.

    Science.gov (United States)

    Noble, Richard D.

    1983-01-01

    Presents an undergraduate laboratory experiment in which a solar collector is used to heat water for domestic use. The working fluid is moved by natural convection so no pumps are required. Experimental apparatus is simple in design and operation so that data can be collected quickly and easily. (Author/JN)

  1. A 'backward' free-convective boundary layer

    NARCIS (Netherlands)

    Kuiken, H.K.

    1981-01-01

    In this paper the cooling of a low-heat-resistance sheet that moves downwards is considered. The free-convective velocities are assumed to be much larger than the velocity of the sheet. As a result the motion of the fluid is mainly towards the point where the sheet enters the system and a ‘backward’

  2. Natural convection inside an irregular porous cavity

    International Nuclear Information System (INIS)

    Beltran, Jorge I. LLagostera; Trevisan, Osvair Vidal

    1990-01-01

    Natural convection flow induced by heating from below in a irregular porous cavity is investigated numerically. The influence of the modified Rayleigh number and geometric ratios on heat transfer and fluid flow is studied. Global and local Nusselt for Rayleigh numbers covering the range 0 - 1600 and for several geometric ratios. The fluid flow and the temperature field are illustrated by contour maps. (author)

  3. Convection in Slab and Spheroidal Geometries

    Science.gov (United States)

    Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.

    2000-01-01

    Three-dimensional numerical simulations of compressible turbulent thermally driven convection, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one convection cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale convective motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local convection. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.

  4. Preserving Symmetry in Convection-Diffusion Schemes

    NARCIS (Netherlands)

    Verstappen, R.W.C.P.; Veldman, A.E.P.; Drikakis, D.; Geurts, B.J.

    2002-01-01

    We propose to perform turbulent flow simulations in such manner that the difference operators do have the same symmetry properties as the corresponding differential operators. That is, the convective operator is represented by a skew-symmetric difference operator and the diffusive operator is

  5. Theories for convection in stellar atmospheres

    International Nuclear Information System (INIS)

    Nordlund, Aa.

    1976-02-01

    A discussion of the fundamental differences between laboratory convection in a stellar atmosphere is presented. The shortcomings of laterally homogeneous model atmospheres are analysed, and the extent to which these shortcoming are avoided in the two-component representation is discussed. Finally a qualitative discussion on the scaling properties of stellar granulation is presented. (Auth.)

  6. Terminal project heat convection in thin cylinders

    International Nuclear Information System (INIS)

    Morales Corona, J.

    1992-01-01

    Heat convection in thin cylinders and analysis about natural convection for straight vertical plates, and straight vertical cylinders submersed in a fluid are presented some works carry out by different authors in the field of heat transfer. In the part of conduction, deduction of the equation of heat conduction in cylindrical coordinates by means of energy balance in a control volume is presented. Enthalpy and internal energy are used for the outlining of the equation and finally the equation in its vectorial form is obtained. In the convection part development to calculate the Nusselt number for a straight vertical plate by a forces analysis, an energy balance and mass conservation over a control volume is outlined. Several empiric correlations to calculate the Nusselt number and its relations with other dimensionless numbers are presented. In the experimental part the way in which a prototype rode is assembled is presented measurements of temperatures attained in steady state and in free convection for working fluids as air and water are showed in tables. Also graphs of Nusselt numbers obtained in the experimental way through some empiric correlations are showed (Author)

  7. Influence of convective conditions on three dimensional mixed convective hydromagnetic boundary layer flow of Casson nanofluid

    Energy Technology Data Exchange (ETDEWEB)

    Rauf, A., E-mail: raufamar@ciitsahiwal.edu.pk [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Siddiq, M.K. [Centre for Advanced Studies in Pure and Applied Mathematics, Department of Mathematics, Bahauddin Zakariya University, Multan 63000 (Pakistan); Abbasi, F.M. [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Meraj, M.A. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Ashraf, M. [Centre for Advanced Studies in Pure and Applied Mathematics, Department of Mathematics, Bahauddin Zakariya University, Multan 63000 (Pakistan); Shehzad, S.A. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan)

    2016-10-15

    The present work deals with the steady laminar three-dimensional mixed convective magnetohydrodynamic (MHD) boundary layer flow of Casson nanofluid over a bidirectional stretching surface. A uniform magnetic field is applied normal to the flow direction. Similarity variables are implemented to convert the non-linear partial differential equations into ordinary ones. Convective boundary conditions are utilized at surface of the sheet. A numerical technique of Runge–Kutta–Fehlberg (RFK45) is used to obtain the results of velocity, temperature and concentration fields. The physical dimensionless parameters are discussed through tables and graphs. - Highlights: • Mixed convective boundary layer flow of Casson nanofluid is taken into account. • Impact of magnetic field is examined. • Convective heat and mass conditions are imposed. • Numerical solutions are presented and discussed.

  8. Testing particle filters on convective scale dynamics

    Science.gov (United States)

    Haslehner, Mylene; Craig, George. C.; Janjic, Tijana

    2014-05-01

    Particle filters have been developed in recent years to deal with highly nonlinear dynamics and non Gaussian error statistics that also characterize data assimilation on convective scales. In this work we explore the use of the efficient particle filter (P.v. Leeuwen, 2011) for convective scale data assimilation application. The method is tested in idealized setting, on two stochastic models. The models were designed to reproduce some of the properties of convection, for example the rapid development and decay of convective clouds. The first model is a simple one-dimensional, discrete state birth-death model of clouds (Craig and Würsch, 2012). For this model, the efficient particle filter that includes nudging the variables shows significant improvement compared to Ensemble Kalman Filter and Sequential Importance Resampling (SIR) particle filter. The success of the combination of nudging and resampling, measured as RMS error with respect to the 'true state', is proportional to the nudging intensity. Significantly, even a very weak nudging intensity brings notable improvement over SIR. The second model is a modified version of a stochastic shallow water model (Würsch and Craig 2013), which contains more realistic dynamical characteristics of convective scale phenomena. Using the efficient particle filter and different combination of observations of the three field variables (wind, water 'height' and rain) allows the particle filter to be evaluated in comparison to a regime where only nudging is used. Sensitivity to the properties of the model error covariance is also considered. Finally, criteria are identified under which the efficient particle filter outperforms nudging alone. References: Craig, G. C. and M. Würsch, 2012: The impact of localization and observation averaging for convective-scale data assimilation in a simple stochastic model. Q. J. R. Meteorol. Soc.,139, 515-523. Van Leeuwen, P. J., 2011: Efficient non-linear data assimilation in geophysical

  9. Novel Natural Convection Heat Sink Design Concepts From First Principles

    Science.gov (United States)

    2016-06-01

    CONVECTION HEAT SINK DESIGN CONCEPTS FROM FIRST PRINCIPLES by Derek E. Fletcher June 2016 Thesis Advisor: Garth Hobson Second Reader...COVERED Master’s Thesis 4. TITLE AND SUBTITLE NOVEL NATURAL CONVECTION HEAT SINK DESIGN CONCEPTS FROM FIRST PRINCIPLES 5. FUNDING NUMBERS 6...CONVECTION HEAT SINK DESIGN CONCEPTS FROM FIRST PRINCIPLES Derek E. Fletcher Lieutenant Commander, United States Navy B.S., Southwestern

  10. International symposium on transient convective heat transfer: book of abstracts

    International Nuclear Information System (INIS)

    1996-01-01

    The international symposium on convective heat transfer was held on 19-23 August 1996, in Cesme, Izmir, Turkey. The spesialists discussed forced convection, heat exchangers, free convection and multiphase media and phase change at the meeting. Almost 53 papers were presented in the meeting

  11. Basal melting driven by turbulent thermal convection

    Science.gov (United States)

    Rabbanipour Esfahani, Babak; Hirata, Silvia C.; Berti, Stefano; Calzavarini, Enrico

    2018-05-01

    Melting and, conversely, solidification processes in the presence of convection are key to many geophysical problems. An essential question related to these phenomena concerns the estimation of the (time-evolving) melting rate, which is tightly connected to the turbulent convective dynamics in the bulk of the melt fluid and the heat transfer at the liquid-solid interface. In this work, we consider a convective-melting model, constructed as a generalization of the Rayleigh-Bénard system, accounting for the basal melting of a solid. As the change of phase proceeds, a fluid layer grows at the heated bottom of the system and eventually reaches a turbulent convection state. By means of extensive lattice-Boltzmann numerical simulations employing an enthalpy formulation of the governing equations, we explore the model dynamics in two- and three-dimensional configurations. The focus of the analysis is on the scaling of global quantities like the heat flux and the kinetic energy with the Rayleigh number, as well as on the interface morphology and the effects of space dimensionality. Independently of dimensionality, we find that the convective-melting system behavior shares strong resemblances with that of the Rayleigh-Bénard one, and that the heat flux is only weakly enhanced with respect to that case. Such similarities are understood, at least to some extent, considering the resulting slow motion of the melting front (with respect to the turbulent fluid velocity fluctuations) and its generally little roughness (compared to the height of the fluid layer). Varying the Stefan number, accounting for the thermodynamical properties of the material, also seems to have only a mild effect, which implies the possibility of extrapolating results in numerically delicate low-Stefan setups from more convenient high-Stefan ones. Finally, we discuss the implications of our findings for the geophysically relevant problem of modeling Arctic ice melt ponds.

  12. Convective mass transfer around a dissolving bubble

    Science.gov (United States)

    Duplat, Jerome; Grandemange, Mathieu; Poulain, Cedric

    2017-11-01

    Heat or mass transfer around an evaporating drop or condensing vapor bubble is a complex issue due to the interplay between the substrate properties, diffusion- and convection-driven mass transfer, and Marangoni effects, to mention but a few. In order to disentangle these mechanisms, we focus here mainly on the convective mass transfer contribution in an isothermal mass transfer problem. For this, we study the case of a millimetric carbon dioxide bubble which is suspended under a substrate and dissolved into pure liquid water. The high solubility of CO2 in water makes the liquid denser and promotes a buoyant-driven flow at a high (solutal) Rayleigh number (Ra˜104 ). The alteration of p H allows the concentration field in the liquid to be imaged by laser fluorescence enabling us to measure both the global mass flux (bubble volume, contact angle) and local mass flux around the bubble along time. After a short period of mass diffusion, where the boundary layer thickens like the square root of time, convection starts and the CO2 is carried by a plume falling at constant velocity. The boundary layer thickness then reaches a plateau which depends on the bubble cross section. Meanwhile the plume velocity scales like (dV /d t )1 /2 with V being the volume of the bubble. As for the rate of volume loss, we recover a constant mass flux in the diffusion-driven regime followed by a decrease in the volume V like V2 /3 after convection has started. We present a model which agrees well with the bubble dynamics and discuss our results in the context of droplet evaporation, as well as high Rayleigh convection.

  13. Le principe non bis in idem et le droit communautaire

    OpenAIRE

    Hedabou, Aziz

    2018-01-01

    Le principe non bis in idem est une garantie fondamentale qui interdit que les mêmes faits soit poursuivi et puni deux fois. Il est reconnu par tous les droits internes et “appartient aux droit universel des nations”. Dès lors, sa lettre et son esprit ne sont plus cantonnés au droit interne et ont tendance à s’internationaliser. En droit communautaire, l’étude du principe non bis in idem peut être envisagée sous trois angles différents. D’abord en droit pénal international unilatéral où chaqu...

  14. Le tennis dans le monde: état et prospective

    Directory of Open Access Journals (Sweden)

    Pierre DUMOLARD

    1989-06-01

    Full Text Available Le tennis est peu ou prou pratiqué dans tous les pays du monde, mais avec de considérables variations d'intensité. Actuellement, ses points d'ancrage se situent dans les pays développés occidentaux et dans l'ancienne sphère d'influence britannique. En tenant compte de l'évolution démographique et économique possible des nations, des projections de pénétration de ce sport sont établies pour l'horizon 2000.

  15. A continuous and prognostic convection scheme based on buoyancy, PCMT

    Science.gov (United States)

    Guérémy, Jean-François; Piriou, Jean-Marcel

    2016-04-01

    A new and consistent convection scheme (PCMT: Prognostic Condensates Microphysics and Transport), providing a continuous and prognostic treatment of this atmospheric process, is described. The main concept ensuring the consistency of the whole system is the buoyancy, key element of any vertical motion. The buoyancy constitutes the forcing term of the convective vertical velocity, which is then used to define the triggering condition, the mass flux, and the rates of entrainment-detrainment. The buoyancy is also used in its vertically integrated form (CAPE) to determine the closure condition. The continuous treatment of convection, from dry thermals to deep precipitating convection, is achieved with the help of a continuous formulation of the entrainment-detrainment rates (depending on the convective vertical velocity) and of the CAPE relaxation time (depending on the convective over-turning time). The convective tendencies are directly expressed in terms of condensation and transport. Finally, the convective vertical velocity and condensates are fully prognostic, the latter being treated using the same microphysics scheme as for the resolved condensates but considering the convective environment. A Single Column Model (SCM) validation of this scheme is shown, allowing detailed comparisons with observed and explicitly simulated data. Four cases covering the convective spectrum are considered: over ocean, sensitivity to environmental moisture (S. Derbyshire) non precipitating shallow convection to deep precipitating convection, trade wind shallow convection (BOMEX) and strato-cumulus (FIRE), together with an entire continental diurnal cycle of convection (ARM). The emphasis is put on the characteristics of the scheme which enable a continuous treatment of convection. Then, a 3D LAM validation is presented considering an AMMA case with both observations and a CRM simulation using the same initial and lateral conditions as for the parameterized one. Finally, global

  16. Peut-on voyager dans le temps ?

    CERN Multimedia

    CERN. Geneva

    2008-01-01

    La possibilité de voyager dans le temps est régulièrement évoquée par les magazines scientifiques (et parfois même par les scientifiques). Elle est également le sujet de nombreux romans de science-fiction. Nous discuterons d’abord du sens qu’on peut donner à l’expression « voyager dans le temps », puis nous expliciterons ce que la physique contemporaine dit à ce propos.

  17. Le CRDI en Égypte

    International Development Research Centre (IDRC) Digital Library (Canada)

    afin d'y favoriser la croissance et le développement. Il en résulte des solutions locales, novatrices et durables, qui offrent des choix aux personnes qui en ont le plus besoin et font changer les choses. Centre de recherches pour le développement international. CP 8500, Ottawa (Ontario) Canada K1G 3H9. 1012 alexandrie.

  18. Le corps dans l'Antiquité

    Directory of Open Access Journals (Sweden)

    Sophie Lalanne

    2008-06-01

    Full Text Available Ouvrages générauxLaqueur Thomas, La fabrique du sexe. Essai sur le corps et le genre en Occident, trad. fr., Paris, Gallimard, 1992.Feher Michel, Naddaff Ramona, Tazi Nadia, Fragments for a History of the Human Body, 3 volumes, New York, Zone Books, 1989.Le Corps dans l’AntiquitéBodiou Lydie, Frère Dominique, Mehl Véronique dir., L’expression des corps. Gestes, attitudes, regards dans l’iconographie antique, Rennes, Presses Universitaires de Rennes, 2006.Bonnard Jean-Baptiste, Le complexe de ...

  19. Démocratie et le développement dans le monde arabe | IDRC ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le Rapport sur le développement humain dans le monde arabe 2002 souligne un " déficit en matière de libertés " fondamental dans le monde arabe se traduisant dans toute la région par des régimes autoritaires et la faiblesse de la démocratie. Cette subvention permettra aux chercheurs Samir Makdisi et Ibrahim Elbadawi ...

  20. ÉTUDE DE CAS — Cuba : Le logement et le capital humain à Cuba ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    10 janv. 2011 ... ÉTUDE DE CAS — Cuba : Le logement et le capital humain à Cuba ... Centre de recherches pour le développement international (CRDI) du Canada révèle ... Les ressources déjà limitées sont devenues encore plus rares. ... de l'Institut national pour l'hygiène, l'épidémiologie et la microbiologie (INHEM), ...

  1. Le CRDI et la lutte contre le paludisme | CRDI - Centre de ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    22 juil. 2011 ... D'autres interventions luttent également contre le paludisme, notamment les moustiquaires imprégnées d'insecticide et les médicaments visant à prévenir le ... Le CRDI appuie le GCRAI depuis les années 1970 et participe avec SIMA au financement de la recherche sur les interactions complexes entre ...

  2. Lele du langage de programmation dans la réalisation de code ...

    African Journals Online (AJOL)

    Lele du langage de programmation dans la réalisation de code de qualité, les cas de Delphi et C++ Nous discutons dans ce papier lele du langage de programmation dans la production d'un code de qualité. La qualité d'un code peut être atteinte en respectant certains critères simples au niveau de la programmation ...

  3. La spermiation chez le brochet.

    Directory of Open Access Journals (Sweden)

    DE MONTALEMBERT G.

    1980-01-01

    Full Text Available L'évolution quantitative et qualitative de la production de sperme au cours de la période de spermiation a été étudiée chez des brochets maintenus en captivité dans un étang de 400 m2. Le sperme est prélevé toutes les semaines à partir du début de février, et pendant près de 2 mois. La quantité de sperme recueillie est très faible et présente de fortes variations individuelles ; elle augmente progressivement jusqu'à la 5me semaine et décroit ensuite. La quantité moyenne de sperme récoltée par mâle est de l'ordre de 0,7 ml/semaine et varie considérablement d'un mâle à l'autre (0.07 à 1,5 ml. La concentration du sperme en spermatozoïdes varie entre 18 et 25 milliards par ml ( X = 21,5 109 + 2,11. La quantité de spermatozoïdes récoltée par semaine est de 28,5 106 + 26,4/kg de poids corporel. La qualité du sperme appréciée par l'intensité et la durée de motilité suit une évolution similaire à celle de la quantité de sperme récoltée avec des valeurs maximales à 4 semaines et minimales en début et fin de période de prélèvement. Les premières ovulations détectées sur des femelles stockées dans les mêmes conditions que les mâles ont été observées à la 6me semaine de prélèvements alors que les performances de spermiation avaient déjà fortement déclinées. Il est vraisemblable que les conditions expérimentales particulièrement traumatisantes pour les mâles ont affecté prématurément la spermiation, amplifiant ainsi le décalage fréquemment observé entre les périodes de spermiation et d'ovulation.

  4. Le groupe de travail EPNAC

    Directory of Open Access Journals (Sweden)

    MOLLE, Pascal

    2012-12-01

    Full Text Available En France, les procédés de traitement des eaux usées des petites et moyennes collectivités sont en constante évolution et leur diversité augmente fortement. Constitué à l'initiative d'Irstea, le groupe de travail EPNAC a pour objectif de mutualiser et de diffuser une information technique et cohérente sur ces procédés auprès des acteurs de l'assainissement.

  5. Behaviors and transitions along the path to magnetostrophic convection

    Science.gov (United States)

    Grannan, A. M.; Vogt, T.; Horn, S.; Hawkins, E. K.; Aggarwal, A.; Aurnou, J. M.

    2017-12-01

    The generation of magnetic fields in planetary and stellar interiors are believed to be controlled primarily by turbulent convection constrained by Coriolis and Lorentz forces in their electrically conducting fluid layers. Yet relatively few laboratory experiments are capable of investigating the different regimes of turbulent magnetohydrodynamic convection. In this work, we perform one laboratory experiment in a cylinder at a fixed heat flux using the liquid metal gallium in order to investigate, sequentially: Rayleigh-Bènard convection without any imposed constraints, magnetoconvection with a Lorentz constraint imposed by vertical magnetic field, rotating convection with a Coriolis constraint imposed by rotation, and finally the magnetostrophic convective regime where both Coriolis and Lorentz are imposed and equal. Using an array of internal and external temperature probes, we show that each regime along the path to magnetostrophic convection is unique. The behaviors and transitions in the dominant modes of convection as well as their fundamental frequencies and wavenumbers are investigated.

  6. Convective equilibrium and mixing-length theory for stellarator reactors

    International Nuclear Information System (INIS)

    Ho, D.D.M.; Kulsrud, R.M.

    1985-09-01

    In high β stellarator and tokamak reactors, the plasma pressure gradient in some regions of the plasma may exceed the critical pressure gradient set by ballooning instabilities. In these regions, convective cells break out to enhance the transport. As a result, the pressure gradient can rise only slightly above the critical gradient and the plasma is in another state of equilibrium - ''convective equilibrium'' - in these regions. Although the convective transport cannot be calculated precisely, it is shown that the density and temperature profiles in the convective region can still be estimated. A simple mixing-length theory, similar to that used for convection in stellar interiors, is introduced in this paper to provide a qualitative description of the convective cells and to show that the convective transport is highly efficient. A numerical example for obtaining the density and temperature profiles in a stellarator reactor is given

  7. Moisture Vertical Structure, Deep Convective Organization, and Convective Transition in the Amazon

    Science.gov (United States)

    Schiro, K. A.; Neelin, J. D.

    2017-12-01

    Constraining precipitation processes in climate models with observations is crucial to accurately simulating current climate and reducing uncertainties in future projections. Results from the Green Ocean Amazon (GOAmazon) field campaign (2014-2015) provide evidence that deep convection is strongly controlled by the availability of moisture in the free troposphere over the Amazon, much like over tropical oceans. Entraining plume buoyancy calculations confirm that CWV is a good proxy for the conditional instability of the environment, yet differences in convective onset as a function of CWV exist over land and ocean, as well as seasonally and diurnally over land. This is largely due to variability in the contribution of lower tropospheric humidity to the total column moisture. Boundary layer moisture shows a strong relationship to the onset during the day, which largely disappears during nighttime. Using S-Band radar, these transition statistics are examined separately for unorganized and mesoscale-organized convection, which exhibit sharp increases in probability of occurrence with increasing moisture throughout the column, particularly in the lower free troposphere. Retrievals of vertical velocity from a radar wind profiler indicate updraft velocity and mass flux increasing with height through the lower troposphere. A deep-inflow mixing scheme motivated by this — corresponding to deep inflow of environmental air into a plume that grows with height — provides a weighting of boundary layer and free tropospheric air that yields buoyancies consistent with the observed onset of deep convection across seasons and times of day, across land and ocean sites, and for all convection types. This provides a substantial improvement relative to more traditional constant mixing assumptions, and a dramatic improvement relative to no mixing. Furthermore, it provides relationships that are as strong or stronger for mesoscale-organized convection as for unorganized convection.

  8. Le salaire minimum n'est pas toujours le meilleur moyen d'accroître ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    4 mai 2016 ... De fait, cette intervention vigoureuse sur le marché du travail est une ... la mobilité des travailleurs entre le secteur structuré et le secteur non structuré, ... On peut certes se constituer rapidement du capital politique en faisant ...

  9. Rapport financier trimestriel pour le trimestre qui a pris fin le 30

    International Development Research Centre (IDRC) Digital Library (Canada)

    Sophie Comeau

    30 sept. 2011 ... politiques, de chercheurs et de collectivités de par le monde. ..... Financement : le CRDI est visé par l'Examen stratégique et ... Le Conseil des gouverneurs a amorcé la planification du recrutement du nouveau président.

  10. Rapport financier trimestriel pour le trimestre qui a pris fin le 30 juin ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Sophie Comeau

    30 juin 2017 ... Régi par la Loi sur le Centre de recherches pour le développement international ... des retombées; forme des leaders dans les secteurs de l'administration .... Au cours de la période de trois mois qui a pris fin le 30 juin 2017, ...

  11. Le facteur humain et la sûreté de fonctionnement dans le ...

    African Journals Online (AJOL)

    Elle permettait d'optimiser le couple « performance-coût », en identifiant, évaluant et maîtrisant les pannes qu'il ... gestion des risques deviennent une ...... Etre en mesure de détecter les .... variés qui s'y déroulent, avoir le contrôle du.

  12. Les femmes dans le secteur du travail domestique et le secteur ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Ce projet vise à rectifier le tir en faisant la lumière sur les caractéristiques ... le secteur du travail domestique et dans le secteur bancaire modifient la nature du travail ... des sciences sociales, des sciences humaines, de la santé publique ou.

  13. Coupling of convection and circulation at various resolutions

    Directory of Open Access Journals (Sweden)

    Cathy Hohenegger

    2015-03-01

    Full Text Available A correct representation of the coupling between convection and circulation constitutes a prerequisite for a correct representation of precipitation at all scales. In this study, the coupling between convection and a sea breeze is investigated across three main resolutions: large-eddy resolution where convection is fully explicit, convection-permitting resolution where convection is partly explicit and coarse resolution where convection is parameterised. The considered models are the UCLA-LES, COSMO and ICON. Despite the use of prescribed surface fluxes, comparison of the simulations reveals that typical biases associated with a misrepresentation of convection at convection-permitting and coarser resolutions significantly alter the characteristics of the sea breeze. The coarse-resolution simulations integrated without convective parameterisation and the convection-permitting simulations simulate a too slow propagation of the breeze front as compared to the large-eddy simulations. From the various factors affecting the propagation, a delayed onset and intensification of cold pools primarily explains the differences. This is a direct consequence of a delayed development of convection when the grid spacing is coarsened. Scaling the time the sea breeze reaches the centre of the land patch by the time precipitation exceeds 2 mm day−1, used as a measure for significant evaporation, yields a collapse of the simulations onto a simple linear relationship although subtle differences remain due to the use of different turbulence and microphysical schemes. Turning on the convection scheme significantly disrupts the propagation of the sea breeze due to a misrepresented timing (too early triggering and magnitude (too strong precipitation evaporation in one of the tested convection schemes of the convective processes.

  14. Natural convection in heat-generating fluids

    International Nuclear Information System (INIS)

    Bol'shov, Leonid A; Kondratenko, Petr S; Strizhov, Valerii F

    2001-01-01

    Experimental and theoretical studies of convective heat transfer from a heat-generating fluid confined to a closed volume are reviewed. Theoretical results are inferred from analytical estimates based on the relevant conservation laws and the current understanding of the convective heat-transfer processes. Four basic and one asymptotic regime of heat transfer are identified depending on the heat generation rate. Limiting heat-transfer distribution patterns are found for the lower boundary. Heat transfer in a quasi-two-dimensional geometry is analyzed. Quasi-steady-state heat transfer from a cooling-down fluid without internal heat sources is studied separately. Experimental results and theoretical predictions are compared. (reviews of topical problems)

  15. Topology optimisation of natural convection problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe; Aage, Niels; Andreasen, Casper Schousboe

    2014-01-01

    This paper demonstrates the application of the density-based topology optimisation approach for the design of heat sinks and micropumps based on natural convection effects. The problems are modelled under the assumptions of steady-state laminar flow using the incompressible Navier-Stokes equations...... coupled to the convection-diffusion equation through the Boussinesq approximation. In order to facilitate topology optimisation, the Brinkman approach is taken to penalise velocities inside the solid domain and the effective thermal conductivity is interpolated in order to accommodate differences...... in thermal conductivity of the solid and fluid phases. The governing equations are discretised using stabilised finite elements and topology optimisation is performed for two different problems using discrete adjoint sensitivity analysis. The study shows that topology optimisation is a viable approach...

  16. Convective instabilities in SN 1987A

    Science.gov (United States)

    Benz, Willy; Thielemann, Friedrich-Karl

    1990-01-01

    Following Bandiera (1984), it is shown that the relevant criterion to determine the stability of a blast wave, propagating through the layers of a massive star in a supernova explosion, is the Schwarzschild (or Ledoux) criterion rather than the Rayleigh-Taylor criterion. Both criteria coincide only in the incompressible limit. Results of a linear stability analysis are presented for a one-dimensional (spherical) explosion in a realistic model for the progenitor of SN 1987A. When applying the Schwarzschild criterion, unstable regions get extended considerably. Convection is found to develop behind the shock, with a characteristic growth rate corresponding to a time scale much smaller than the shock traversal time. This ensures that efficient mixing will take place. Since the entire ejected mass is found to be convectively unstable, Ni can be transported outward, even into the hydrogen envelope, while hydrogen can be mixed deep into the helium core.

  17. Natural convection heat transfer in SIGMA experiment

    International Nuclear Information System (INIS)

    Lee, Seung Dong; Lee, Gang Hee; Suh, Kune Yull

    2004-01-01

    A loss-of-coolant accident (LOCA) results in core melt formation and relocation at various locations within the reactor core over a considerable period of time. If there is no effective cooling mechanism, the core debris may heat up and commence natural circulation. The high temperature pool of molten core material will threaten the structural integrity of the reactor vessel. The extent and urgency of this threat depend primarily upon the intensity of the internal heat sources and upon the consequent distribution of the heat fluxes on the vessel walls in contact with the molten core material pools. In such a steady molten pool convection state, the thermal loads against the vessel would be determined by the in-vessel heat transfer distribution involving convective and conductive heat transfer from the decay-heated core material pool to the lower head wall in contact with the core material. In this study, upward and downward heat transfer fraction ratio is focused on

  18. An experimental study of mixed convection

    International Nuclear Information System (INIS)

    Saez, Manuel

    1998-01-01

    The aim of our study is to establish a reliable data base for improving thermal-hydraulic codes, in the field of turbulent flows with buoyancy forces. The flow considered is mixed convection in the Reynolds and Richardson number range: Re=10"3 to 6*10"4 and Ri=10"-"4 to 1. Experiments are carried out in an upward turbulent flow between vertical parallel plates at different wall temperatures. Part 1 gives a detailed data base of turbulent mixed flow of free and forced convection. Part II presents the installation and the calibration system intended for probes calibration. Part III describes the measurement technique (constant-temperature probe and cold-wire probe) and the method for measuring the position of the hot-wire anemometer from the wall surface. The measurement accuracy is within 0.001 mm in the present system. Part IV relates the development of a method for near wall measurements. This correction procedure for hot-wire anemometer close to wall has been derived on the basis of a two-dimensional numerical study. The method permits to obtain a quantitative correction of the wall influence on hot-wires and takes into account the velocity profile and the effects the wall material has on the heat loss. Part V presents the experimental data obtained in the channel in forced and mixed convection. Results obtained in the forced convection regime serve as a verification of the measurement technique close to the wall and give the conditions at the entrance of the test section. The effects of the buoyancy force on the mean velocity and temperature profiles are confirmed. The buoyancy strongly affects the flow structure and deforms the distribution of mean velocity. The velocity profiles are asymmetric. The second section of part V gives an approach of analytical wall functions with buoyancy forces, on the basis of the experimental data obtained in the test section. (author) [fr

  19. Convection and crystal settling in sills

    Science.gov (United States)

    Gibb, Fergus G. F.; Henderson, C. Michael B.

    1992-02-01

    It has been advocated that convective and crystal settling processes play significant, and perhaps crucial, roles in magmatic differentiation. The fluid dynamics of magma chambers have been extensively studied in recent years, both theoretically and experimentally, but there is disagreement over the nature and scale of the convection, over its bearing on fractionation and possibly over whether it occurs at all. The differential distribution of modal olivine with height in differentiated alkaline basic sills provides critical evidence to resolve this controversy, at least for small to medium-large magma chambers. Our own and others' published data for such sills show that, irrespective of overall olivine content, modal olivine contents tend to increase in a roughly symmetrical manner inwards from the upper and lower margins of the sill, i.e. the distribution patterns are more often approximately D-shaped rather than the classic S-shape generally ascribed to gravity settling. We concur with the majority of other authors that this is an original feature of the filling process which has survived more or less unchanged since emplacement. We therefore conclude that the magmas have not undergone turbulent convection and that gravity settling has usually played only a minor modifying role since the intrusion of these sills. We offer a possible explanation for the apparent contradiction between fluid dynamical theory and the petrological evidence by suggesting that such sills rarely fill by the rapid injection of a single pulse of magma. Rather, they form from a series of pulses or a continuous pulsed influx over a protracted interval during which marginal cooling severely limits the potential for thermal convection.

  20. Nonlinear Convective Models of RR Lyrae Stars

    Science.gov (United States)

    Feuchtinger, M.; Dorfi, E. A.

    The nonlinear behavior of RR Lyrae pulsations is investigated using a state-of-the-art numerical technique solving the full time-dependent system of radiation hydrodynamics. Grey radiative transfer is included by a variable Eddington-factor method and we use the time-dependent turbulent convection model according to Kuhfuss (1986, A&A 160, 116) in the version of Wuchterl (1995, Comp. Phys. Comm. 89, 19). OPAL opacities extended by the Alexander molecule opacities at temperatures below 6000 K and an equation of state according to Wuchterl (1990, A&A 238, 83) close the system. The resulting nonlinear system is discretized on an adaptive mesh developed by Dorfi & Drury (1987, J. Comp. Phys. 69, 175), which is important to provide the necessary spatial resolution in critical regions like ionization zones and shock waves. Additionally, we employ a second order advection scheme, a time centered temporal discretizaton and an artificial tensor viscosity in order to treat discontinuities. We compute fundamental as well first overtone models of RR Lyrae stars for a grid of stellar parameters both with and without convective energy transport in order to give a detailed picture of the pulsation-convection interaction. In order to investigate the influence of the different features of the convection model calculations with and without overshooting, turbulent pressure and turbulent viscosity are performed and compared with each other. A standard Fourier decomposition is used to confront the resulting light and radial velocity variations with recent observations and we show that the well known RR Lyrae phase discrepancy problem (Simon 1985, ApJ 299, 723) can be resolved with these stellar pulsation computations.

  1. Natural convective heat transfer from square cylinder

    Energy Technology Data Exchange (ETDEWEB)

    Novomestský, Marcel, E-mail: marcel.novomestsky@fstroj.uniza.sk; Smatanová, Helena, E-mail: helena.smatanova@fstroj.uniza.sk; Kapjor, Andrej, E-mail: andrej.kapjor@fstroj.uniza.sk [University of Žilina, Faculty of Mechanical Engineering, Department of Power Engineering, Univerzitná 1, 010 26 Žilina (Slovakia)

    2016-06-30

    This article is concerned with natural convective heat transfer from square cylinder mounted on a plane adiabatic base, the cylinders having an exposed cylinder surface according to different horizontal angle. The cylinder receives heat from a radiating heater which results in a buoyant flow. There are many industrial applications, including refrigeration, ventilation and the cooling of electrical components, for which the present study may be applicable.

  2. Aide au suivi du phénomène de dénitrification naturelle pour une gestion durable de la ressource en eau du Béthunois

    Directory of Open Access Journals (Sweden)

    Cherif Boulemia

    2006-11-01

    Full Text Available Les villes sont sujettes à des augmentations de population et d’activité industrielle, ce qui se traduit par une demande supplémentaire en eau. Notre objectif est de développer un outil de gestion et d’aide à la décision pour une meilleure connaissance de la ressource et pour soutenir les décisions de planification dans les services des eaux des moyennes collectivités locales. L’outil permettra une exploitation contrôlée du système aquifère et en particulier la préservation du phénomène de dénitrification naturelle ayant lieu dans la nappe de la craie du Béthunois au Nord de la France. Dans cet article, nous proposons la mise en place d’un tableau de bord à partir d’une plate-forme SIG couplée à un outil de modélisation hydrologique. Nos travaux de recherche sont appliqués au SIVOM de la Communauté du Béthunois.Cities face a substantial increase in population and in industrial activities which entails an increasing demand for water. Our aim is to develop a management and decision-making framework for a better knowledge of the resource and to support the planning and decisions in the water boards of medium-size local communities. The framework will allow the reasoned exploitation of the aquifer system and in particular the preservation of the natural denitrification process which occurs in the chalk aquifer in the Béthunois area in northern France. In this article, we propose the setting-up of a control panel thanks to a GIS platform coupled with a hydrological model. Our research work is applied to the SIVOM of the Béthunois.

  3. L’Association du personnel, le TREF, le Comité des Finances et le Conseil du CERN

    CERN Multimedia

    Staff Association

    2016-01-01

    L’Association du personnel, forte de son approche participative et consensuelle, recherche toujours le meilleur accord possible pour l’Organisation et son personnel. Pour ce faire, discussions et concertation avec la Direction, travail d’explication et de persuasion au TREF et ailleurs auprès des délégués des États membres sont nos principaux atouts. TREF (Tripartite Employment Conditions Forum), un Forum d’échanges, de discussions « L’objectif du Forum est d’améliorer le processus de prise de décision  en donnant aux personnes concernées la possibilité et le temps de comprendre pleinement la position de tous les participants. » (CERN/RTG/8) Le Forum tripartite sur les conditions d’emploi (TREF), créé par le Conseil du CERN en juin 1994, est composé de r...

  4. Study of mixed convection in sodium pool

    International Nuclear Information System (INIS)

    Wang Zhou; Chen Yan

    1995-01-01

    The mixed convection phenomena in the sodium pool of fast reactor have been studied systematically by the two dimensional modeling method. A generalized concept of circumferential line in the cylindrical coordinates was proposed to overcome the three dimensional effect induced by the pool geometry in an analysis of two dimensional modeling. A method of sub-step in time was developed for solving the turbulent equations. The treatments on the boundary condition for the auxiliary velocity field have been proposed, and the explanation of allowing the flow function method to be used in the flow field in presence of a mass source term was given. As examples of verification, the experiments were conducted with water flow in a rectangular cavity. The results from theoretical analysis were applied to the numerical computation for the mixed convection in the cavity. The mechanism of stratified flow in the cavity was studied. A numerical calculation was carried out for the mixed convection in hot plenum of a typical fast reactor

  5. Heat transport in bubbling turbulent convection.

    Science.gov (United States)

    Lakkaraju, Rajaram; Stevens, Richard J A M; Oresta, Paolo; Verzicco, Roberto; Lohse, Detlef; Prosperetti, Andrea

    2013-06-04

    Boiling is an extremely effective way to promote heat transfer from a hot surface to a liquid due to numerous mechanisms, many of which are not understood in quantitative detail. An important component of the overall process is that the buoyancy of the bubble compounds with that of the liquid to give rise to a much-enhanced natural convection. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh-Bénard convection process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 10(6) and 5 × 10(9). We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh-Bénard convection.

  6. Modeling mantle convection in the spherical annulus

    Science.gov (United States)

    Hernlund, John W.; Tackley, Paul J.

    2008-12-01

    Most methods for modeling mantle convection in a two-dimensional (2D) circular annular domain suffer from innate shortcomings in their ability to capture several characteristics of the spherical shell geometry of planetary mantles. While methods such as rescaling the inner and outer radius to reduce anomalous effects in a 2D polar cylindrical coordinate system have been introduced and widely implemented, such fixes may have other drawbacks that adversely affect the outcome of some kinds of mantle convection studies. Here we propose a new approach that we term the "spherical annulus," which is a 2D slice that bisects the spherical shell and is quantitatively formulated at the equator of a spherical polar coordinate system after neglecting terms in the governing equations related to variations in latitude. Spherical scaling is retained in this approximation since the Jacobian function remains proportional to the square of the radius. We present example calculations to show that the behavior of convection in the spherical annulus compares favorably against calculations performed in other 2D annular domains when measured relative to those in a fully three-dimensional (3D) spherical shell.

  7. Natural convection of nanofluids over a convectively heated vertical plate embedded in a porous medium

    Energy Technology Data Exchange (ETDEWEB)

    Ghalambaz, M.; Noghrehabadi, A.; Ghanbarzadeh, A., E-mail: m.ghalambaz@gmail.com, E-mail: ghanbarzadeh.a@scu.ac.ir [Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz (Iran, Islamic Republic of)

    2014-04-15

    In this paper, the natural convective flow of nanofluids over a convectively heated vertical plate in a saturated Darcy porous medium is studied numerically. The governing equations are transformed into a set of ordinary differential equations by using appropriate similarity variables, and they are numerically solved using the fourth-order Runge-Kutta method associated with the Gauss-Newton method. The effects of parametric variation of the Brownian motion parameter (Nb), thermophoresis parameter (Nt) and the convective heating parameter (Nc) on the boundary layer profiles are investigated. Furthermore, the variation of the reduced Nusselt number and reduced Sherwood number, as important parameters of heat and mass transfer, as a function of the Brownian motion, thermophoresis and convective heating parameters is discussed in detail. The results show that the thickness of the concentration profiles is much lower than the temperature and velocity profiles. For low values of the convective heating parameter (Nc), as the Brownian motion parameter increases, the non-dimensional wall temperature increases. However, for high values of Nc, the effect of the Brownian motion parameter on the non-dimensional wall temperature is not significant. As the Brownian motion parameter increases, the reduced Sherwood number increases and the reduced Nusselt number decreases. (author)

  8. Le contrôle de gestion environnementale d'une entreprise

    OpenAIRE

    Marquet-Pondeville, Sophie

    2001-01-01

    Dans cette recherche, nous étudions comment s’opère le contrôle de gestion environnementale. Cette problématique est abordée dans une perspective contingente et nous proposons un modèle théorique qui met en évidence l’impact de certaines variables sur les systèmes de contrôle de la gestion environnementale. Certains liens présents dans ce modèle sont discutés à travers une étude de cas.

  9. Le facteur humain et la sûreté de fonctionnement dans le ...

    African Journals Online (AJOL)

    Notre contribution porte sur lele fondamental du facteur humain dans le management intégré des risques d'une part et du rôle déterminant qu'il peut avoir à jouer pour que la sûreté de fonctionnement réponde à sa propriété d'autre part. Un rôle illustré à travers une analyse de risque dans un complexe de Gaz Naturel ...

  10. Le language des masques burkinabè

    African Journals Online (AJOL)

    hond

    2 juil. 2007 ... un faire transformateur cognitif devient un esprit qui a des fonctions hautement spirituelles, religieuses et aussi souvent esthétiques. Le langage et le discours des masques. Les masques sont un langage et un discours. Un langage est un système de communi- cation et d'expression. L'unité de base de ...

  11. Addendum waarde commerciële radiovergunningen

    NARCIS (Netherlands)

    Poort, J.; Kerste, M.; Akker, I.; Prins, J.

    2011-01-01

    Op 18 mei 2010 stuurde de Minister van Economische Zaken het SEO-rapport Waarde commerciële radiovergunningen naar de Tweede Kamer. Dat rapport doet verslag van een onderzoek naar de waarde van de commerciële radiovergunningen. Het vormde de grondslag voor het financieel instrument in de

  12. L'astronomie dans le monde

    Science.gov (United States)

    Manfroid, J.

    2008-09-01

    Fragmentation et astéroïdes binaires; Astéroïde géocroiseur triple; Rosetta sort de son hibernation; Messenger; Transit lunaire vu par Deep Impact; Titan; Phobos; Phoenix; Einstein avait raison; Le ballet des taches rouges; Le poids des lentilles;

  13. Le Débat des semences

    International Development Research Centre (IDRC) Digital Library (Canada)

    Solutions pour les lois nationales régissant le contrôle des ressources génétiques et des ...... des pouvoirs) qui reconnaissent, dans une certaine mesure, les droits de gestion collectifs des ...... documentés, les performances physiques, etc.

  14. Le barrage des trois Gorges (Chine

    Directory of Open Access Journals (Sweden)

    Luc Merchez

    1999-09-01

    Full Text Available Le barrage des Trois Gorges, en construction sur le Yangzijiang, sera le plus grand barrage au monde. Le gigantisme du projet et sa médiatisation croissante en Occident permettent d'en saisir les enjeux environnementaux et humains. On analyse les grandes caractéristiques du projet et ses conséquences premières avant d'aborder le travail de recherche de l'équipe SIG de l'IGA de Grenoble qui vise à préparer la relocalisation de plus d'un million d'habitants, et à modéliser les impacts démographiques et sociaux.

  15. Convective Heat Transfer Coefficients of the Human Body under Forced Convection from Ceiling

    DEFF Research Database (Denmark)

    Kurazumi, Yoshihito; Rezgals, Lauris; Melikov, Arsen Krikor

    2014-01-01

    The average convective heat transfer coefficient for a seated human body exposed to downward flow from above was determined. Thermal manikin with complex body shape and size of an average Scandinavian female was used. The surface temperature distribution of the manikin’s body was as the skin...... of the convective heat transfer coefficient of the whole body (hc [W/(m2•K)]) was proposed: hc=4.088+6.592V1.715 for a seated naked body at 20ºC and hc=2.874+7.427V1.345 for a seated naked body at 26ºC. Differences in the convective heat transfer coefficient of the whole body in low air velocity range, V

  16. Convergence behavior of idealized convection-resolving simulations of summertime deep moist convection over land

    Science.gov (United States)

    Panosetti, Davide; Schlemmer, Linda; Schär, Christoph

    2018-05-01

    Convection-resolving models (CRMs) can explicitly simulate deep convection and resolve interactions between convective updrafts. They are thus increasingly used in numerous weather and climate applications. However, the truncation of the continuous energy cascade at scales of O (1 km) poses a serious challenge, as in kilometer-scale simulations the size and properties of the simulated convective cells are often determined by the horizontal grid spacing (Δ x ).In this study, idealized simulations of deep moist convection over land are performed to assess the convergence behavior of a CRM at Δ x = 8, 4, 2, 1 km and 500 m. Two types of convergence estimates are investigated: bulk convergence addressing domain-averaged and integrated variables related to the water and energy budgets, and structural convergence addressing the statistics and scales of individual clouds and updrafts. Results show that bulk convergence generally begins at Δ x =4 km, while structural convergence is not yet fully achieved at the kilometer scale, despite some evidence that the resolution sensitivity of updraft velocities and convective mass fluxes decreases at finer resolution. In particular, at finer grid spacings the maximum updraft velocity generally increases, and the size of the smallest clouds is mostly determined by Δ x . A number of different experiments are conducted, and it is found that the presence of orography and environmental vertical wind shear yields more energetic structures at scales much larger than Δ x , sometimes reducing the resolution sensitivity. Overall the results lend support to the use of kilometer-scale resolutions in CRMs, despite the inability of these models to fully resolve the associated cloud field.

  17. Le projet de station touristique

    OpenAIRE

    Vlès, Vincent

    1996-01-01

    Cet ouvrage traite du savoir-faire du technicien, de l'ingénieur, du directeur d'office de tourisme qui façonne, depuis maintenant près de trois décennies, le territoire local de la production touristique : la station. Il analyse les stratégies, les mises en œuvre, les pratiques de l'aménagement et du développement touristique. Il propose une construction du projet de station, méthode qui est l'aboutissement d'expériences de terrain. Il présente un guide des interventions. Il décrit des modes...

  18. Le Squatteur, le Gentrifieur et le Promoteur. Une leçon de la géographie

    Directory of Open Access Journals (Sweden)

    Laurent Matthey

    2005-03-01

    Full Text Available Posées sur mon bureau : deux photos. Je les regarde. Silencieusement, je les décris et les commente. La première a été prise en novembre 1997. Angle rue Jean-Violette, rue Prévost-Martin, à Genève. On y voit un immeuble, ancien, des échafaudages. Entre cet immeuble et celui qui lui fait face, on a tendu des fanions verts, bleus, orange. Son rez-de-chaussée a été repeint dans une teinte un peu brique. La seconde date d’avril 2005. C’est le même immeuble, presque dix ans plus tard, rénové. Jaun...

  19. Vorticity imbalance and stability in relation to convection

    Science.gov (United States)

    Read, W. L.; Scoggins, J. R.

    1977-01-01

    A complete synoptic-scale vorticity budget was related to convection storm development in the eastern two-thirds of the United States. The 3-h sounding interval permitted a study of time changes of the vorticity budget in areas of convective storms. Results of analyses revealed significant changes in values of terms in the vorticity equation at different stages of squall line development. Average budgets for all areas of convection indicate systematic imbalance in the terms in the vorticity equation. This imbalance resulted primarily from sub-grid scale processes. Potential instability in the lower troposphere was analyzed in relation to the development of convective activity. Instability was related to areas of convection; however, instability alone was inadequate for forecast purposes. Combinations of stability and terms in the vorticity equation in the form of indices succeeded in depicting areas of convection better than any one item separately.

  20. A Thermodynamically General Theory for Convective Circulations and Vortices

    Science.gov (United States)

    Renno, N. O.

    2007-12-01

    Convective circulations and vortices are common features of atmospheres that absorb low-entropy-energy at higher temperatures than they reject high-entropy-energy to space. These circulations range from small to planetary-scale and play an important role in the vertical transport of heat, momentum, and tracer species. Thus, the development of theoretical models for convective phenomena is important to our understanding of many basic features of planetary atmospheres. A thermodynamically general theory for convective circulations and vortices is proposed. The theory includes irreversible processes and quantifies the pressure drop between the environment and any point in a convective updraft. The article's main result is that the proposed theory provides an expression for the pressure drop along streamlines or streamtubes that is a generalization of Bernoulli's equation to convective circulations. We speculate that the proposed theory not only explains the intensity, but also shed light on other basic features of convective circulations and vortices.

  1. Thermo-electro-hydrodynamic convection under microgravity: a review

    Energy Technology Data Exchange (ETDEWEB)

    Mutabazi, Innocent; Yoshikawa, Harunori N; Fogaing, Mireille Tadie; Travnikov, Vadim; Crumeyrolle, Olivier [Laboratoire Ondes et Milieux Complexes, UMR 6294, CNRS-Université du Havre, CS 80450, F-76058 Le Havre Cedex (France); Futterer, Birgit; Egbers, Christoph, E-mail: Innocent.Mutabazi@univ-lehavre.fr [Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology Cottbus-Senftenberg, Cottbus (Germany)

    2016-12-15

    Recent studies on thermo-electro-hydrodynamic (TEHD) convection are reviewed with focus on investigations motivated by the analogy with natural convection. TEHD convection originates in the action of the dielectrophoretic force generated by an alternating electric voltage applied to a dielectric fluid with a temperature gradient. This electrohydrodynamic force is analogous to Archimedean thermal buoyancy and can be regarded as a thermal buoyancy force in electric effective gravity. The review is concerned with TEHD convection in plane, cylindrical, and spherical capacitors under microgravity conditions, where the electric gravity can induce convection without any complexities arising from geometry or the buoyancy force due to the Earth’s gravity. We will highlight the convection in spherical geometry, comparing developed theories and numerical simulations with the GEOFLOW experiments performed on board the International Space Station (ISS). (paper)

  2. Sud du Sahara | Page 74 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Langue English. Read more about Les SIG-P au service d'une gestion durable des ressources naturelles et de la sécurité alimentaire en Afrique. Langue French. Read more about Adaptation aux changements climatiques en ce qui concerne l'agriculture et les ressources en eau dans la Corne de l'Afrique. Langue French.

  3. Sud du Sahara | Page 223 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    . Langue French. Read more about Pauvreté et vulnérabilité environnementale dans les bidonvilles en pleine croissance en Angola. Langue French. Read more about Les SIG-P au service d'une gestion durable des ressources naturelles et ...

  4. : tous les projets | Page 400 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Dans les deux tiers des pays d'Amérique latine et des Caraïbes, au moins la moitié des produits exportés découlent de l'exploitation des ressources naturelles. Date de début : 1 mars 2010. End Date: 1 janvier 2013. Sujet: RESOURCES EXPLOITATION, AGRICULTURAL DEVELOPMENT, FISHERY DEVELOPMENT, ...

  5. Santé | Page 25 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Dans cet ouvrage qui s'adresse aux planificateurs du développement et aux étudiants en nutrition, santé publique et anthropologie culturelle humaine, on aborde des enjeux de l'utilisation des sources naturelles d'aliments pour prévenir la carence en vitamine A. Read more about Culture, Environment, and Food to Prevent ...

  6. Le développement démocratique | IDRC - International ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    12 janv. 2011 ... Ces travaux peuvent sembler exempts de jugements de valeur, mais, ... Des études sur la gestion des ressources naturelles, notamment, peuvent .... factures et d'actes médicaux bâclés ayant mis la vie des gens en danger.

  7. Tirer le meilleur parti possible des produits de base | CRDI - Centre ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    10 avr. 2014 ... Pétrole, cuivre, diamants, or et bois d'oeuvre : L'Afrique est riche en ressources naturelles et en produits de base. La production de produits de base peut favoriser une croissance rapide, mais aussi exposer les pays à une croissance en dents de scie attribuable à l'incertitude des marchés mondiaux.

  8. Primary Issues of Mixed Convection Heat Transfer Phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Chae, Myeong-Seon; Chung, Bum-Jin [Kyung Hee University, Yongin (Korea, Republic of)

    2015-10-15

    The computer code analyzing the system operating and transient behavior must distinguish flow conditions involved with convective heat transfer flow regimes. And the proper correlations must be supplied to those flow regimes. However the existing safety analysis codes are focused on the Light Water Reactor and they are skeptical to be applied to the GCRs (Gas Cooled Reactors). One of the technical issues raise by the development of the VHTR is the mixed convection, which occur when the driving forces of both forced and natural convection are of comparable magnitudes. It can be encountered as in channel of the stacked with fuel elements and a decay heat removal system and in VHTR. The mixed convection is not intermediate phenomena with natural convection and forced convection but independent complicated phenomena. Therefore, many researchers have been studied and some primary issues were propounded for phenomena mixed convection. This paper is to discuss some problems identified through reviewing the papers for mixed convection phenomena. And primary issues of mixed convection heat transfer were proposed respect to thermal hydraulic problems for VHTR. The VHTR thermal hydraulic study requires an indepth study of the mixed convection phenomena. In this study we reviewed the classical flow regime map of Metais and Eckert and derived further issues to be considered. The following issues were raised: (1) Buoyancy aided an opposed flows were not differentiated and plotted in a map. (2) Experimental results for UWT and UHF condition were also plotted in the same map without differentiation. (3) The buoyancy coefficient was not generalized for correlating with buoyancy coefficient. (4) The phenomenon analysis for laminarization and returbulization as buoyancy effects in turbulent mixed convection was not established. (5) The defining to transition in mixed convection regime was difficult.

  9. Some problems of free convection in a macrocapillary

    Energy Technology Data Exchange (ETDEWEB)

    Luikov, A V; Berkovsky, B M; Kolpashchikov, V L

    1971-01-01

    Solution is given to a number of problems of free convection in incompressible viscous fluid in elementary macrocapillaries with nonuniform temperature distribution at the boundary. The fluid flow structure and effect of a magnetic field on convection in the case of conducting fluid has been studied in detail. The influence of macrocapillary properties on the flow structure, rate of convection, and temperature distribution has been estimated.

  10. Convective Cold Pool Structure and Boundary Layer Recovery in DYNAMO

    Science.gov (United States)

    Savarin, A.; Chen, S. S.; Kerns, B. W.; Lee, C.; Jorgensen, D. P.

    2012-12-01

    One of the key factors controlling convective cloud systems in the Madden-Julian Oscillation (MJO) over the tropical Indian Ocean is the property of the atmospheric boundary layer. Convective downdrafts and precipitation from the cloud systems produce cold pools in the boundary layer, which can inhibit subsequent development of convection. The recovery time is the time it takes for the boundary layer to return to pre convective conditions. It may affect the variability of the convection on various time scales during the initiation of MJO. This study examines the convective cold pool structure and boundary layer recovery using the NOAA WP-3D aircraft observations, include the flight-level, Doppler radar, and GPS dropsonde data, collected during the Dynamics of MJO (DYNAMO) field campaign from November-December 2011. The depth and strength of convective cold pools are defined by the negative buoyancy, which can be computed from the dropsonde data. Convective downdraft can be affected by environmental water vapor due to entrainment. Mid-level dry air observed during the convectively suppressed phase of MJO seems to enhance convective downdraft, making the cold pools stronger and deeper. Recovery of the cold pools in the boundary layer is determined by the strength and depth of the cold pools and also the air-sea heat and moisture fluxes. Given that the water vapor and surface winds are distinct for the convectively active and suppressed phases of MJO over the Indian Ocean, the aircraft data are stratified by the two different large-scale regimes of MJO. Preliminary results show that the strength and depth of the cold pools are inversely correlated with the surrounding mid-level moisture. During the convectively suppressed phase, the recovery time is ~5-20 hours in relative weak wind condition with small air-sea fluxes. The recovery time is generally less than 6 hours during the active phase of MJO with moist mid-levels and stronger surface wind and air-sea fluxes.

  11. Strategic Repositioning for Convection Business Case Study: AR Vendor

    OpenAIRE

    Anindita, Pratisara Satwika; Toha, Mohamad

    2013-01-01

    The study aims to determine suitable position and strategy in order to reach superiority in convection business based on the company strengths and weaknesses. A study conducted in late 2012 at AR Vendor, a home-based convection company which focus on the t-shirt screen printing service. In response to the issue of the below average profit margin, the company has to rethink their position and strategy in handling the convection business environment. While AR Vendor business may growth in accor...

  12. Convection Cells in the Atmospheric Boundary Layer

    Science.gov (United States)

    Fodor, Katherine; Mellado, Juan-Pedro

    2017-04-01

    In dry, shear-free convective boundary layers (CBLs), the turbulent flow of air is known to organise itself on large scales into coherent, cellular patterns, or superstructures, consisting of fast, narrow updraughts and slow, wide downdraughts which together form circulations. Superstructures act as transport mechanisms from the surface to the top of the boundary layer and vice-versa, as opposed to small-scale turbulence, which only modifies conditions locally. This suggests that a thorough investigation into superstructure properties may help us better understand transport across the atmospheric boundary layer as a whole. Whilst their existence has been noted, detailed studies into superstructures in the CBL have been scarce. By applying methods which are known to successfully isolate similar large-scale patterns in turbulent Rayleigh-Bénard convection, we can assess the efficacy of those detection techniques in the CBL. In addition, through non-dimensional analysis, we can systematically compare superstructures in various convective regimes. We use direct numerical simulation of four different cases for intercomparison: Rayleigh-Bénard convection (steady), Rayleigh-Bénard convection with an adiabatic top lid (quasi-steady), a stably-stratified CBL (quasi-steady) and a neutrally-stratified CBL (unsteady). The first two are non-penetrative and the latter two penetrative. We find that although superstructures clearly emerge from the time-mean flow in the non-penetrative cases, they become obscured by temporal averaging in the CBL. This is because a rigid lid acts to direct the flow into counter-rotating circulation cells whose axis of rotation remains stationary, whereas a boundary layer that grows in time and is able to entrain fluid from above causes the circulations to not only grow in vertical extent, but also to move horizontally and merge with neighbouring circulations. Spatial filtering is a useful comparative technique as it can be performed on boundary

  13. Transitions in rapidly rotating convection dynamos

    Science.gov (United States)

    Tilgner, A.

    2013-12-01

    It is commonly assumed that buoyancy in the fluid core powers the geodynamo. We study here the minimal model of a convection driven dynamo, which is a horizontal plane layer in a gravity field, filled with electrically conducting fluid, heated from below and cooled from above, and rotating about a vertical axis. Such a plane layer may be viewed as a local approximation to the geophysically more relevant spherical geometry. The numerical simulations have been run on graphics processing units with at least 960 cores. If the convection is driven stronger and stronger at fixed rotation rate, the flow behaves at some point as if it was not rotating. This transition shows in the scaling of the heat transport which can be used to distinguish slow from rapid rotation. One expects dynamos to behave differently in these two flow regimes. But even within the convection flows which are rapidly rotating according to this criterion, it will be shown that different types of dynamos exist. In one state, the magnetic field strength obeys a scaling indicative of a magnetostrophic balance, in which the Lorentz force is in equilibrium with the Coriolis force. The flow in this case is helical. A different state exists at higher magnetic Reynolds numbers, in which the magnetic energy obeys a different scaling law and the helicity of the flow is much reduced. As one increases the Rayleigh number, all other parameters kept constant, one may find both types of dynamos separated by an interval of Rayleigh numbers in which there are no dynamos at all. The effect of these transitions on energy dissipation and mean field generation have also been studied.

  14. What Determines Upscale Growth of Oceanic Convection into MCSs?

    Science.gov (United States)

    Zipser, E. J.

    2017-12-01

    Over tropical oceans, widely scattered convection of various depths may or may not grow upscale into mesoscale convective systems (MCSs). But what distinguishes the large-scale environment that favors such upscale growth from that favoring "unorganized", scattered convection? Is it some combination of large-scale low-level convergence and ascending motion, combined with sufficient instability? We recently put this to a test with ERA-I reanalysis data, with disappointing results. The "usual suspects" of total column water vapor, large-scale ascent, and CAPE may all be required to some extent, but their differences between large MCSs and scattered convection are small. The main positive results from this work (already published) demonstrate that the strength of convection is well correlated with the size and perhaps "organization" of convective features over tropical oceans, in contrast to tropical land, where strong convection is common for large or small convective features. So, important questions remain: Over tropical oceans, how should we define "organized" convection? By size of the precipitation area? And what environmental conditions lead to larger and better organized MCSs? Some recent attempts to answer these questions will be described, but good answers may require more data, and more insights.

  15. Natural convection in superposed fluid-porous layers

    CERN Document Server

    Bagchi, Aniruddha

    2013-01-01

    Natural Convection in Composite Fluid-Porous Domains provides a timely overview of the current state of understanding on the phenomenon of convection in composite fluid-porous layers. Natural convection in horizontal fluid-porous layers has received renewed attention because of engineering problems such as post-accident cooling of nuclear reactors, contaminant transport in groundwater, and convection in fibrous insulation systems. Because applications of the problem span many scientific domains, the book serves as a valuable resource for a wide audience.

  16. Urban Influences on Convection and Lightning Over Houston

    National Research Council Canada - National Science Library

    Gauthier, Michael L

    2006-01-01

    The research presented in this dissertation addresses a fundamental question regarding urban, ultimately anthropogenic, influences on convection as it relates to lightning production and precipitation structure...

  17. Effects of variable thermal diffusivity on the structure of convection

    Science.gov (United States)

    Shcheritsa, O. V.; Getling, A. V.; Mazhorova, O. S.

    2018-03-01

    The structure of multiscale convection in a thermally stratified plane horizontal fluid layer is investigated by means of numerical simulations. The thermal diffusivity is assumed to produce a thin boundary sublayer convectively much more unstable than the bulk of the layer. The simulated flow is a superposition of cellular structures with three different characteristic scales. In contrast to the largest convection cells, the smaller ones are localised in the upper portion of the layer. The smallest cells are advected by the larger-scale convective flows. The simulated flow pattern qualitatively resembles that observed on the Sun.

  18. Cumulus convection and the terrestrial water-vapor distribution

    Science.gov (United States)

    Donner, Leo J.

    1988-01-01

    Cumulus convection plays a significant role in determining the structure of the terrestrial water vapor field. Cumulus convection acts directly on the moisture field by condensing and precipitating water vapor and by redistributing water vapor through cumulus induced eddy circulations. The mechanisms by which cumulus convection influences the terrestrial water vapor distribution is outlined. Calculations using a theory due to Kuo is used to illustrate the mechanisms by which cumulus convection works. Understanding of these processes greatly aids the ability of researchers to interpret the seasonal and spatial distribution of atmospheric water vapor by providing information on the nature of sources and sinks and the global circulation.

  19. Mixing in heterogeneous internally-heated convection

    Science.gov (United States)

    Limare, A.; Kaminski, E. C.; Jaupart, C. P.; Farnetani, C. G.; Fourel, L.; Froment, M.

    2017-12-01

    Past laboratory experiments of thermo chemical convection have dealt with systems involving fluids with different intrinsic densities and viscosities in a Rayleigh-Bénard setup. Although these experiments have greatly improved our understanding of the Earth's mantle dynamics, they neglect a fundamental component of planetary convection: internal heat sources. We have developed a microwave-based method in order to study convection and mixing in systems involving two layers of fluid with different densities, viscosities, and internal heat production rates. Our innovative laboratory experiments are appropriate for the early Earth, when the lowermost mantle was likely enriched in incompatible and heat producing elements and when the heat flux from the core probably accounted for a small fraction of the mantle heat budget. They are also relevant to the present-day mantle if one considers that radioactive decay and secular cooling contribute both to internal heating. Our goal is to quantify how two fluid layers mix, which is still very difficult to resolve accurately in 3-D numerical calculations. Viscosities and microwave absorptions are tuned to achieve high values of the Rayleigh-Roberts and Prandtl numbers relevant for planetary convection. We start from a stably stratified system where the lower layer has higher internal heat production and density than the upper layer. Due to mixing, the amount of enriched material gradually decreases to zero over a finite time called the lifetime. Based on more than 30 experiments, we have derived a scaling law that relates the lifetime of an enriched reservoir to the layer thickness ratio, a, to the density and viscosity contrasts between the two layers, and to their two different internal heating rates in the form of an enrichment factor beta=1+2*a*H1/H, where H1 is the heating rate of the lower fluid and H is the average heating rate. We find that the lifetime of the lower enriched reservoir varies as beta**(-7/3) in the low

  20. Natural convection between two concentric spheres

    International Nuclear Information System (INIS)

    Blondel-Roux, Marie

    1983-01-01

    After an overview of researches on natural convection in a confined or semi-confined environment, this research thesis reports the use of the Caltagirone and Mojtabi numerical model and the study of its validity for different values of the Rayleigh and Prandtl numbers. Results obtained with this model are compared with experimental ones. Thermal transfer curves are presented and discussed, as well as the different temperature fields numerically obtained, flow function fields, velocities in the fluid layer, and temperature profiles with respect to the Rayleigh number [fr

  1. Measurement of natural convection by speckle photography

    International Nuclear Information System (INIS)

    Wernekinck, U.; Merzkirch, W.

    1986-01-01

    The principle of speckle photography can be applied to the measurement of density variations in fluids. A modification of existing experimental arrangements allows for the measurement of large values of the light deflection angles as they may occur in heat and mass transfer situations. The method is demonstrated for the case of a helium jet exhausting into still air and the natural convective flow along a heated plate. The obtained data are compared with results measured with classical optical interferometers, and good agreement is found. The advantages of the new technique over the classical optical methods are briefly discussed. 11 references

  2. Hamiltonian Description of Convective-cell Generation

    International Nuclear Information System (INIS)

    Krommes, J.A.; Kolesnikov, R.A.

    2004-01-01

    The nonlinear statistical growth rate eq for convective cells driven by drift-wave (DW) interactions is studied with the aid of a covariant Hamiltonian formalism for the gyrofluid nonlinearities. A statistical energy theorem is proven that relates eq to a second functional tensor derivative of the DW energy. This generalizes to a wide class of systems of coupled partial differential equations a previous result for scalar dynamics. Applications to (i) electrostatic ion-temperature-gradient-driven modes at small ion temperature, and (ii) weakly electromagnetic collisional DW's are noted

  3. Sunspots and the physics of magnetic flux tubes. VI - Convective propulsion. VII - Heat flow in a convective downdraft

    Science.gov (United States)

    Parker, E. N.

    1979-01-01

    The effect of negative aerodynamic drag in an ideal fluid subject to convective instability is considered. It is shown that a cylinder moving in such a fluid is propelled forward in its motion by the convective forces and that the characteristic acceleration time is comparable to the onset time of convective motions in the fluid. It is suggested that convective propulsion plays an important role in the dynamics of flux tubes extending through the surface of the sun. The suppression of the upward heat flow in a Boussinesq convective cell with free upper and lower boundaries by a downdraft is then analyzed. Application to the solar convection zone indicates that downdrafts of 1 to 2 km/s at depths of 1000 to 4000 km beneath the visible surface of the sun are sufficient to reduce the upward heat flux to a small fraction of the ambient value.

  4. Convectively coupled Kelvin waves in aquachannel simulations: 2. Life cycle and dynamical-convective coupling

    Science.gov (United States)

    Blanco, Joaquín. E.; Nolan, David S.; Mapes, Brian E.

    2016-10-01

    This second part of a two-part study uses Weather Research and Forecasting simulations with aquachannel and aquapatch domains to investigate the time evolution of convectively coupled Kelvin waves (CCKWs). Power spectra, filtering, and compositing are combined with object-tracking methods to assess the structure and phase speed propagation of CCKWs during their strengthening, mature, and decaying phases. In this regard, we introduce an innovative approach to more closely investigate the wave (Kelvin) versus entity (super cloud cluster or "SCC") dualism. In general, the composite CCKW structures represent a dynamical response to the organized convective activity. However, pressure and thermodynamic fields in the boundary layer behave differently. Further analysis of the time evolution of pressure and low-level moist static energy finds that these fields propagate eastward as a "moist" Kelvin wave (MKW), faster than the envelope of organized convection or SCC. When the separation is sufficiently large the SCC dissipates, and a new SCC generates to the east, in the region of strongest negative pressure perturbations. We revisit the concept itself of the "coupling" between convection and dynamics, and we also propose a conceptual model for CCKWs, with a clear distinction between the SCC and the MKW components.

  5. An application of the unifying theory of thermal convection in vertical natural convection

    Science.gov (United States)

    Ng, Chong Shen; Ooi, Andrew; Lohse, Detlef; Chung, Daniel

    2014-11-01

    Using direct numerical simulations of vertical natural convection (VNC) at Rayleigh numbers 1 . 0 ×105 - 1 . 0 ×109 and Prandtl number 0 . 709 , we provide support for a generalised applicability of the Grossmann-Lohse (GL) theory, originally developed for horizontal natural (Rayleigh-Bénard) convection. In accordance with the theory, the boundary-layer thicknesses of the velocity and temperature fields in VNC obey laminar-like scaling, whereas away from the walls, the dissipation of the turbulent fluctuations obey the scaling for fully developed turbulence. In contrast to Rayleigh-Bénard convection, the direction of gravity in VNC is parallel to the mean flow. Thus, there no longer exists an exact relation linking the normalised global dissipations to the Nusselt, Rayleigh and Prandtl numbers. Nevertheless, we show that the unclosed term, namely the global-averaged buoyancy flux, also exhibits laminar and turbulent scaling, consistent with the GL theory. The findings suggest that, similar to Rayleigh-Bénard convection, a pure power-law relationship between the Nusselt, Rayleigh and Prandtl numbers is not the best description for VNC and existing empirical power-law relationships should be recalibrated to better reflect the underlying physics.

  6. THE EFFECT OF SOLAR RADIATION ON AUTOMOBILE ENVIRONMENT THROUGH NATURAL CONVECTION AND MIXED CONVECTION

    Directory of Open Access Journals (Sweden)

    MD. FAISAL KADER

    2012-10-01

    Full Text Available In the present paper, the effect of solar radiation on automobiles has been studied by both experimentally and numerically. The numerical solution is done by an operation friendly and fast CFD code – SC/Tetra with a full scale model of a SM3 car and turbulence is modeled by the standard k-ε equation. Numerical analysis of the three-dimensional model predicts a detailed description of fluid flow and temperature distribution in the passenger compartment during both the natural convection due to the incoming solar radiation and mixed convection due to the flow from defrost nozzle and radiation. It can be seen that solar radiation is an important parameter to raise the compartment temperature above the ambient temperature during summer. During natural convection, the rate of heat transfer is fast at the initial period. In the mixed convection analyses, it is found that the temperature drops down to a comfortable range almost linearly at the initial stage. Experimental investigations are performed to determine the temperature contour on the windshield and the local temperature at a particular point for further validation of the numerical results.

  7. From convection rolls to finger convection in double-diffusive turbulence

    NARCIS (Netherlands)

    Yang, Yantao; Verzicco, Roberto; Lohse, Detlef

    2015-01-01

    Double-diffusive convection (DDC), which is the buoyancy-driven flow with fluid density depending on two scalar components, is ubiquitous in many natural and engineering environments. Of great interests are scalars’ transfer rate and flow structures. Here we systematically investigate DDC flow

  8. Le déficit de filles

    International Development Research Centre (IDRC) Digital Library (Canada)

    de la population est une tendance plus récente. C. Le déficit de filles. Le déséquilibre du ratio hommes-femmes en Inde. D. R. O. I. T. S. D. E. S. F. E. M. M. E. S. E. T. P. A. R. T. IC. I. P. A. T. IO. N. C. I. T. O. Y. E. N. N. E. CENTRE DE. RECHERCHES. POUR LE. DÉVELOPPEMENT. INTERNATIONAL. CRDI : Jason Taylor ...

  9. Le Parti paysan d’union sociale

    OpenAIRE

    Bensoussan, David

    2015-01-01

    La fondation, le 11 juillet 1945 à Paris, du Parti paysan n’a sans doute guère suscité l’attention des contemporains alors immergés dans le contexte tumultueux de l’immédiat après-guerre. Il faut d’ailleurs attendre la parution, quelque temps plus tard, le 6 octobre, du premier numéro de L’Unité Paysanne, organe hebdomadaire de cette nouvelle formation politique, pour que sa naissance soit publiquement officialisée. Sans vouloir surévaluer l’importance d’une organisation qui n’arrivera jamais...

  10. Le Corbusier, Alfred Roth y el color

    Directory of Open Access Journals (Sweden)

    Angelica Fernández-Morales

    2014-07-01

    Full Text Available This article discusses the relationship between Le Corbusier and Alfred Roth, a member of the Paris office between 1927 and 1928. It also deals with the influence that this period had with reference to an important factor in Roth’s professional development, as in Le Corbusier’s later works: the use of colour in his architecture. This article takes the position that Roth, given his close friendship with Mondrian, was an important figure in turning Le Corbusier’s work towards greater use of primary colours and aesthetic neoplasticism.

  11. Upscale Impact of Mesoscale Disturbances of Tropical Convection on Convectively Coupled Kelvin Waves

    Science.gov (United States)

    Yang, Q.; Majda, A.

    2017-12-01

    Tropical convection associated with convectively coupled Kelvin waves (CCKWs) is typically organized by an eastward-moving synoptic-scale convective envelope with numerous embedded westward-moving mesoscale disturbances. It is of central importance to assess upscale impact of mesoscale disturbances on CCKWs as mesoscale disturbances propagate at various tilt angles and speeds. Here a simple multi-scale model is used to capture this multi-scale structure, where mesoscale fluctuations are directly driven by mesoscale heating and synoptic-scale circulation is forced by mean heating and eddy transfer of momentum and temperature. The two-dimensional version of the multi-scale model drives the synoptic-scale circulation, successfully reproduces key features of flow fields with a front-to-rear tilt and compares well with results from a cloud resolving model. In the scenario with an elevated upright mean heating, the tilted vertical structure of synoptic-scale circulation is still induced by the upscale impact of mesoscale disturbances. In a faster propagation scenario, the upscale impact becomes less important, while the synoptic-scale circulation response to mean heating dominates. In the unrealistic scenario with upward/westward tilted mesoscale heating, positive potential temperature anomalies are induced in the leading edge, which will suppress shallow convection in a moist environment. In its three-dimensional version, results show that upscale impact of mesoscale disturbances that propagate at tilt angles (110o 250o) induces negative lower-tropospheric potential temperature anomalies in the leading edge, providing favorable conditions for shallow convection in a moist environment, while the remaining tilt angle cases have opposite effects. Even in the presence of upright mean heating, the front-to-rear tilted synoptic-scale circulation can still be induced by eddy terms at tilt angles (120o 240o). In the case with fast propagating mesoscale heating, positive

  12. The effect of convection and semi-convection on the C/O yield of massive stars

    International Nuclear Information System (INIS)

    Dearborn, D.S.

    1979-01-01

    The C/O ratio produced during core helium burning affects the future evolution and nucleosynthetic yield of massive stars. This ratio is shown to be sensitive to the treatment of convection as well as uncertainties in nuclear rates. By minimizing the effect of semi-convection and reducing the size of the convective core, mass loss in OB stars increases the C/O ratio. (Author)

  13. Changes in the convective population and thermodynamic environments in convection-permitting regional climate simulations over the United States

    Science.gov (United States)

    Rasmussen, K. L.; Prein, A. F.; Rasmussen, R. M.; Ikeda, K.; Liu, C.

    2017-11-01

    Novel high-resolution convection-permitting regional climate simulations over the US employing the pseudo-global warming approach are used to investigate changes in the convective population and thermodynamic environments in a future climate. Two continuous 13-year simulations were conducted using (1) ERA-Interim reanalysis and (2) ERA-Interim reanalysis plus a climate perturbation for the RCP8.5 scenario. The simulations adequately reproduce the observed precipitation diurnal cycle, indicating that they capture organized and propagating convection that most climate models cannot adequately represent. This study shows that weak to moderate convection will decrease and strong convection will increase in frequency in a future climate. Analysis of the thermodynamic environments supporting convection shows that both convective available potential energy (CAPE) and convective inhibition (CIN) increase downstream of the Rockies in a future climate. Previous studies suggest that CAPE will increase in a warming climate, however a corresponding increase in CIN acts as a balancing force to shift the convective population by suppressing weak to moderate convection and provides an environment where CAPE can build to extreme levels that may result in more frequent severe convection. An idealized investigation of fundamental changes in the thermodynamic environment was conducted by shifting a standard atmospheric profile by ± 5 °C. When temperature is increased, both CAPE and CIN increase in magnitude, while the opposite is true for decreased temperatures. Thus, even in the absence of synoptic and mesoscale variations, a warmer climate will provide more CAPE and CIN that will shift the convective population, likely impacting water and energy budgets on Earth.

  14. Simulating the convective precipitation diurnal cycle in a North American scale convection-permitting model

    Science.gov (United States)

    Scaff, L.; Li, Y.; Prein, A. F.; Liu, C.; Rasmussen, R.; Ikeda, K.

    2017-12-01

    A better representation of the diurnal cycle of convective precipitation is essential for the analysis of the energy balance and the water budget components such as runoff, evaporation and infiltration. Convection-permitting regional climate modeling (CPM) has been shown to improve the models' performance of summer precipitation, allowing to: (1) simulate the mesoscale processes in more detail and (2) to provide more insights in future changes in convective precipitation under climate change. In this work we investigate the skill of the Weather Research and Forecast model (WRF) in simulating the summer precipitation diurnal cycle over most of North America. We use 4 km horizontal grid spacing in a 13-years long current and future period. The future scenario is assuming no significant changes in large-scale weather patterns and aims to answer how the weather of the current climate would change if it would reoccur at the end of the century under a high-end emission scenario (Pseudo Global Warming). We emphasize on a region centered on the lee side of the Canadian Rocky Mountains, where the summer precipitation amount shows a regional maximum. The historical simulations are capable to correctly represent the diurnal cycle. At the lee-side of the Canadian Rockies the increase in the convective available potential energy as well as pronounced low-level moisture flux from the southeast Prairies explains the local maximum in summer precipitation. The PGW scenario shows an increase in summer precipitation amount and intensity in this region, consistently with a stronger source of moisture and convective energy.

  15. Biomass Smoke Influences on Deep Convection during the 2011 Midlatitude Continental Convective Clouds Experiment (MC3E)

    Science.gov (United States)

    Dong, X.; Logan, T.; Xi, B.

    2015-12-01

    Three deep convective cloud cases were selected during the 2011 Mid-Latitude Continental Convective Clouds Experiment (MC3E). Although biomass burning smoke advected from Mexico and Central America was the dominant source of cloud condensation nuclei (CCN) for deep convective cloud formation, the 11 May, 20 May, and 23 May cases exhibited different convective characteristics. The convection in the 11 May and 23 May cases formed in smoke laden environments in the presence of convective available potential energy (CAPE) values exceeding 1000 m2 s-2 and 3000 m2 s-2 along with low-level (0-1 km) shear of 10.3 m s-1 and 5.1 m s-1, respectively. The 11 May case had linear convection while the 23 May case featured discrete supercells. The 20 May case featured elevated linear convection that formed in a more moist environment with cleaner aerosol conditions, weak CAPE (9 km) suggesting a warm rain suppression mechanism caused by a combination of strong aerosol loading, large CAPE, and weak low-level wind shear. The observed results for the 20 May and 23 May cases agree well with recent modeling studies that simulated the convection and precipitation in these cases. Furthermore, the modeling of the 11 May case is suggested since the abundant amount of smoke CCN did not greatly enhance the overall precipitation amount and could be a possible aerosol-induced precipitation suppression case.

  16. Le soleil devient un mythe

    Directory of Open Access Journals (Sweden)

    Ildikó Lőrinszky

    2009-01-01

    Full Text Available Partant d’une phrase énigmatique datant de 1858 et puisée dans la Correspondance de Flaubert, cet article s’interroge sur la relation entre soleil et mythe, qui constituera l’un des éléments clefs de la dimension mythologique de Salammbô. Il se propose d’examiner la façon dont cette question apparaît dans deux ouvrages représentatifs des études mythographiques : d’une part, L’Origine de tous les cultes de Charles-François Dupuis, d’autre part, Les Religions de l’Antiquité..., publié sous les noms de Frédéric Creuzer et de son adaptateur français, Joseph-Daniel Guigniault. La version française de la grande synthèse de Creuzer, assortie d’une série importante de planches, a été richement exploitée par Flaubert au cours de la genèse du roman carthaginois. Dans Salammbô, le mythe apparaît sous de multiples formes. L’analyse de ce texte peut nous amener à réfléchir sur le « bon usage » du mythe auquel chaque créateur (et chaque lecteur se trouve nécessairement confronté.Starting from an enigmatic phrase in Flaubert’s correspondence, dating from 1858, this article examines the relation between the Sun and myth, which constitutes one of the key elements of the mythological dimension of Salammbô. It especially focuses on the treatment of this question in two representative works of mythographic studies, The Origin of All Religious Worship by Charles-François Dupuis, and Les Religions de l’Antiquité..., the French adaptation of Frédéric Creuzer’s Symbolik und Mythologie der alten Völker by Joseph-Daniel Guigniault. The French version of Creuzer’s great synthesis, supplied with a remarkable set of prints, was abundantly consulted by Flaubert when writing his Carthaginian novel. In Salammbô, myth takes on various forms. Analyzing this text might lead one to reconsider “the right way” to use myths — a problem all writers (and readers find themselves confronted with.

  17. Forced convection heat transfer in He II

    International Nuclear Information System (INIS)

    Kashani, A.

    1986-01-01

    An investigation of forced convection heat transfer in He II is conducted. The study includes both experimental and theoretical treatments of the problem. The experiment consists of a hydraulic pump and a copper flow tube, 3 mm in ID and 2m long. The system allows measurements of one-dimensional heat and mass transfer in He II. The heat transfer experiments are performed by applying heat at the midpoint along the length of the flow tube. Two modes of heat input are employed, i.e., step function heat input and square pulse heat input. The heat transfer results are discussed in terms of temperature distribution in the tube. The experimental temperature profiles are compared with numerical solutions of an analytical model developed from the He II energy equation. The bath temperature is set at three different values of 1.65, 1.80, and 1.95 K. The He II flow velocity is varied up to 90 cm/s. Pressure is monitored at each end of the flow tube, and the He II pressure drop is obtained for different flow velocities. Results indicate that He II heat transfer by forced convention is considerably higher than that by internal convection. The theoretical model is in close agreement with the experiment. He II pressure drop and friction factor are very similar to those of an ordinary fluid

  18. Vertical Slot Convection: A linear study

    International Nuclear Information System (INIS)

    McAllister, A.; Steinolfson, R.; Tajima, T.

    1992-11-01

    The linear stability properties of fluid convection in a vertical slot were studied. We use a Fourier-Chebychev decomposition was used to set up the linear eigenvalue problems for the Vertical Slot Convection and Benard problems. The eigenvalues, neutral stability curves, and critical point values of the Grashof number, G, and the wavenumber were determined. Plots of the real and imaginary parts of the eigenvalues as functions of G and α are given for a wide range of the Prandtl number, Pr, and special note is made of the complex mode that becomes linearly unstable above Pr ∼ 12.5. A discussion comparing different special cases facilitates the physical understanding of the VSC equations, especially the interaction of the shear-flow and buoyancy induced physics. Making use of the real and imaginary eigenvalues and the phase properties of the eigenmodes, the eigenmodes were characterized. One finds that the mode structure becomes progressively simpler with increasing Pr, with the greatest complexity in the mid ranges where the terms in the heat equation are of roughly the same size

  19. Land surface sensitivity of mesoscale convective systems

    Science.gov (United States)

    Tournay, Robert C.

    Mesoscale convective systems (MCSs) are important contributors to the hydrologic cycle in many regions of the world as well as major sources of severe weather. MCSs continue to challenge forecasters and researchers alike, arising from difficulties in understanding system initiation, propagation, and demise. One distinct type of MCS is that formed from individual convective cells initiated primarily by daytime heating over high terrain. This work is aimed at improving our understanding of the land surface sensitivity of this class of MCS in the contiguous United States. First, a climatology of mesoscale convective systems originating in the Rocky Mountains and adjacent high plains from Wyoming southward to New Mexico is developed through a combination of objective and subjective methods. This class of MCS is most important, in terms of total warm season precipitation, in the 500 to 1300m elevations of the Great Plains (GP) to the east in eastern Colorado to central Nebraska and northwest Kansas. Examining MCSs by longevity, short lasting MCSs (15 hrs) reveals that longer lasting systems tend to form further south and have a longer track with a more southerly track. The environment into which the MCS is moving showed differences across commonly used variables in convection forecasting, with some variables showing more favorable conditions throughout (convective inhibition, 0-6 km shear and 250 hPa wind speed) ahead of longer lasting MCSs. Other variables, such as convective available potential energy, showed improving conditions through time for longer lasting MCSs. Some variables showed no difference across longevity of MCS (precipitable water and large-scale vertical motion). From subsets of this MCS climatology, three regions of origin were chosen based on the presence of ridgelines extending eastward from the Rocky Mountains known to be foci for convection initiation and subsequent MCS formation: Southern Wyoming (Cheyenne Ridge), Colorado (Palmer divide) and

  20. Solutocapillary Convection Effects on Polymeric Membrane Morphology

    Science.gov (United States)

    Krantz, William B.; Todd, Paul W.; Kinagurthu, Sanjay

    1996-01-01

    Macro voids are undesirable large pores in membranes used for purification. They form when membranes are cast as thin films on a smooth surface by evaporating solvent (acetone) from a polymer solution. There are two un-tested hypotheses explaining the growth of macro voids. One states that diffusion of the non-solvent (water) is solely responsible, while the other states that solutocapillary convection is the primary cause of macro void growth. Solutocapillary convection is flow-caused by a concentration induced surface-tension gradient. Macrovoid growth in the former hypothesis is gravity independent, while in the latter it is opposed by gravity. To distinguish between these two hypotheses, experiments were designed to cast membranes in zero-gravity. A semi-automated apparatus was designed and built for casting membranes during the 20 secs of zero-g time available in parabolic aircraft flight such as NASA's KC-135. The phase changes were monitored optically, and membrane morphology was evaluated by scanning electron microscopy (SEM). These studies appear to be the first quantitative studies of membrane casting in micro-gravity which incorporate real-time data acquisition. Morphological studies of membranes cast at 0, 1, and 1.8 g revealed the presence of numerous, sparse and no macrovoids respectively. These results are consistent with the predictions of the solutocapillary hypothesis of macrovoid growth.

  1. Conjugate Problems in Convective Heat Transfer: Review

    Directory of Open Access Journals (Sweden)

    Abram Dorfman

    2009-01-01

    Full Text Available A review of conjugate convective heat transfer problems solved during the early and current time of development of this modern approach is presented. The discussion is based on analytical solutions of selected typical relatively simple conjugate problems including steady-state and transient processes, thermal material treatment, and heat and mass transfer in drying. This brief survey is accompanied by the list of almost two hundred publications considering application of different more and less complex analytical and numerical conjugate models for simulating technology processes and industrial devices from aerospace systems to food production. The references are combined in the groups of works studying similar problems so that each of the groups corresponds to one of selected analytical solutions considered in detail. Such structure of review gives the reader the understanding of early and current situation in conjugate convective heat transfer modeling and makes possible to use the information presented as an introduction to this area on the one hand, and to find more complicated publications of interest on the other hand.

  2. Mass transport in propagating patterns of convection

    International Nuclear Information System (INIS)

    Moses, E.; Steinberg, V.

    1988-01-01

    Recent studies of propagating waves in an oscillatory convection of binary mixtures arise questions about transport properties of this flow. Optical visualization of a field of refraction index due to a shadowgraph technique gives information on the temperature and concentration fields. However, experimental observation of rolls propagating along the cell as travelling waves (TW) does not necessarily imply that mass is transferred hydrodynamically by the convective motion along the cell. One of the possibilities discussed, e.g., is that TW observed is only a phase propagation. The traditional examples of such situations come from the domain of linear, superposition-oriented physics. Acoustic waves transfer momentum and energy, but do not cause the mass to make excursions for their equilibrium point that are larger than the oscillation amplitude. In the case of nonlinear physics we were aware that small amplitude surface waves cause only small oscillatory motion round the equilibrium point, while larger amplitudes can cause the mass to start moving in the direction of the TW. This paper discussed the different possibilities of mass transfer by TW. 27 refs., 20 figs

  3. Benard convection in liquid sodium layers

    International Nuclear Information System (INIS)

    Kek, V.

    1989-08-01

    In a sodium layer heated from below and cooled from above, the integral Nusselt numbers are determined in a range of Rayleigh numbers 1.5x10 3 5 . The experiments are performed in containers with dimensions of 500 mm in diameter and 15 mm and 45 mm in height. The relevant quantities are evaluated from measured temperature and heating power data. The experiments show that the heat transfer across the layer is determined mainly by heat conduction up to Rayleigh number Ra ≅ 10 4 . Beyond this value a significant increase of the convective heat transport is observed. At a Rayleigh number of 4x10 4 the Nusselt number achieves the value Nu = 1.7. This result differs from values given by Nusselt-Rayleigh number correlations reported in the literature for liquids with higher Prandtl number. A regression analysis of the experimental data results empirical correlations for the Nusselt number. A time series analysis of the time dependent temperature signals shows that the measured temperature fluctuations exhibit predominantly stochastic features. However, in the lower range of Rayleigh numbers 1.5x10 3 4 certain regular frequencies can be identified from peaks in broadband power density spectra. These frequencies correspond to fluctuations of a period of 80 to 200 seconds. These regular frequencies are explained by instabilities of the cellular pattern in the convection layer reported in the literature. (orig./HP) [de

  4. Effective diffusion in laminar convective flows

    International Nuclear Information System (INIS)

    Rosenbluth, M.N.; Berk, H.L.; Doxas, I.; Horton, W.

    1987-03-01

    The effective diffusion coefficient D* of a passive component, such as test particles, dye, temperature, magnetic flux, etc., is derived for motion in periodic two-dimensional incompressible convective flow with characteristic velocity v and size d in the presence of an intrinsic local diffusivity D. Asymptotic solutions for effective diffusivity D*(P) in the large P limit, with P ∼ vd/D, is shown to be of the form D* = cDP/sup 1/2/ with c being a coefficient that is determined analytically. The constant c depends on the geometry of the convective cell and on an average of the flow speed along the separatrix. The asymptotic method of evaluation applies to both free boundary and rough boundary flow patterns and it is shown that the method can be extended to more complicated patterns such as the flows generated by rotating cylinders, as in the problem considered by Nadim, Cox, and Brenner [J. Fluid Mech., 164: 185 (1986)]. The diffusivity D* is readily calculated for small P, but the evaluation for arbitrary P requires numerical methods. Monte Carlo particle simulation codes are used to evaluate D* at arbitrary P, and thereby describe the transition for D* between the large and small P limits

  5. Rapport financier trimestriel pour le trimestre qui a pris fin le 30 juin

    International Development Research Centre (IDRC) Digital Library (Canada)

    Office 2004 Test Drive User

    30 juin 2016 ... Le CRDI finance des travaux de recherche appliquée ... développement international (le Centre) et lʼévolution de la ..... voie de développement et sur la mise en oeuvre des connaissances scientifiques, techniques et autres en vue .... Les accords expirent à des dates différentes, et le dernier prend fin en.

  6. 205 Le Role de la Litterature dans le Developpement de la Nation ...

    African Journals Online (AJOL)

    Ike Odimegwu

    du plaisir en même temps qu'il le moralise. Elle fait naître dans ses lecteurs ou dans son audience des .... développement de l'esprit>>(319)Par cette définition nous comprenons que le développement signale qu'il du progrès ... qu'elle est une œuvre de l'imagination qui aide l'homme à transcender le monde physique.

  7. Le « modèle germanique » Français

    OpenAIRE

    Lefebvre , Armelle

    2009-01-01

    Resume Le concept d?Allemagne permet de reveler, selon une approche , l?ampleur des desaccords ayant preside a la definition du concept d?Etat en France. De ce dernier, l?on aborde divers emplois qu?illustrent des modeles d?Etat. Le opere ainsi dans un debat qui est le creuset de la connaissance politique moderne, avec ses apories: celles de la souverainete externe, de l?ordre interetatique, de la confederation. L?article expose alo...

  8. Social sciences and comparative research in Europe : cross-national and multi-disciplinary projects for urban development. The role of geography Sciences sociales et recherche comparative en Europe : projets transnationaux et projets multidisciplinaires de développement urbain. Lele de la géographie

    Directory of Open Access Journals (Sweden)

    Armando Montanari

    2012-12-01

    Full Text Available In the aftermath of the Second World War, UNESCO sought to build peace in the world through the exchange of knowledge. To this end, it developed a number of initiatives to encourage international cooperation among social scientists. These initiatives were of particular importance in Europe, where there was a clear divide between Eastern and Western European countries. After the fall of the Berlin Wall, comparative research came to signify the transfer of knowledge and the promotion of innovation. Over the past two decades the study of urban phenomena, alongside social and economic issues, has taken on a strategic role in reducing pollution, safeguarding the environment and improving the quality of life of inhabitants. The process of enlarging the scope and objectives of policy has also led to a change in the role played by geography, which is increasingly required to offer instruments of scientific communication between the natural and social sciences.Après la Seconde Guerre mondiale, l’UNESCO a tenté de construire la paix dans le monde à travers l’échange de savoirs. A cette fin, elle a mis sur pied un certain nombre d’initiatives visant à encourager la coopération scientifique. Celles-ci revêtaient une ampleur toute particulière en Europe, où existait un clivage net entre pays de l’Est et de l’Ouest. Suite à la chute du Mur de Berlin la recherche comparative signifia le transfert de savoirs et la promotion de l’innovation. Ces deux dernières décennies, l’étude des phénomènes urbains, de même que les questions sociales et économiques, ont pris un rôle stratégique par la réduction de la pollution, la sauvegarde de l’environnement et l’amélioration de la qualité de vie des habitants. Les processus d’élargissement du champ et des objectifs politiques ont également mené à une modification du rôle joué par la géographie, qui est de plus en plus sollicitée pour offrir des instruments de communication

  9. Publications | Page 200 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le CRDI collabore avec les chercheurs et les établissements des pays en développement au renforcement des capacités locales par le truchement du financement, de la mise en commun des connaissances et de la ... Le partage de l''information et des techniques de la communication favorise le développement durable.

  10. Publications | Page 17 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Publication du rapport de BSR sur le travail des enfants en Birmanie. Le CRDI finance plusieurs projets de recherche sur les facteurs expliquant le travail des enfants, incluant le rapport intitulé 'Child labor in Myanmar's Garment Sector' écrit récemment par l'organisme Business for Social Responsibility (BSR).

  11. Droits d'auteur | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Droits d'auteur détenus par le CRDI Sauf indication contraire, les droits d'auteur relatifs aux documents mis en ligne sur le présent site Web sont détenus par le Centre de recherches pour le développement international (CRDI).

  12. Publications | Page 103 | CRDI - Centre de recherches pour le ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Le FIE 2008 fait avancer le cadre écobiosocial de l'OMS. Le Programme spécial de recherche et de formation concernant les maladies tropicales (TDR) de l'OMS a élaboré le concept du champ « écobiosocial », qui combine les perspectives écologiques, biologiques et sociales « pour mieux.

  13. Savoir gérer le mal

    Directory of Open Access Journals (Sweden)

    Michel Maffesoli

    2015-09-01

    Full Text Available Le sens commun, conservatoire immémorial de la sagesse humaine « sait », de savoir incorporé, que le mal, l’ombre, la mort, la douleur sont des caractéristiques essentielles de l’existence en son entièreté. Dès lors les créatures quelles qu’elles soient, sont des manifestations de la vie et, dès lors, méritent une attitude « compassionnelle », fraternelle, parce qu’ensemble elles constituent le flux vital. C’est ainsi que l’on peut comprendre l’utilité sociale de ces divers « mondes intermédiaires » que sont les croyances, religieuses ou philosophiques, au « double », au « daimon », aux esprits et autres figures tutélaires ou effrayantes. Elles aident à vivre, au jour le jour, la souffrance en la communalisant.

  14. Jan Potocki et le "Gothic Novel"

    Science.gov (United States)

    Finne, Jacques

    1970-01-01

    Establishes a parallel between the supernatural and fantastic qualities of Le Comte Jan Potocki's literary works, and the English gothic novels by comparing the elements of terror, mysterious atmosphere, and the supernatural beings involved. (DS)

  15. Original Paper Le champignon arbusculaire Glomus aggregatum ...

    African Journals Online (AJOL)

    Le champignon arbusculaire Glomus aggregatum améliore la nutrition minérale de ... Salinity remains a major problem for soil fertility, especially in the Sahelian zone. However, many ...... environmental gradient in the Brazilian semiarid.

  16. le des universités dans le renforcement des technologies de l ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    le des universités dans le renforcement des technologies de l'information et de la communication au service du développement (TIC-D) en Asie. Jusqu'à maintenant, les efforts déployés dans le secteur de l'enseignement supérieur ont surtout été axés sur le téléapprentissage, l'apprentissage électronique et différentes ...

  17. Entre les violences conjugales et le harcèlement moral : le stalking .

    Directory of Open Access Journals (Sweden)

    Nicolas Desurmont

    2007-09-01

    Full Text Available Ce livre de la criminologue Murielle Anteo est le premier publié en langue française sur le stalking si l’on excepte les travaux encore inédits de Virginie Léon (2004. Comme le rappelle l’auteure, le terme est emprunté à l’anglais to stalk (hanter, rôder, et désigne un comportement menaçant, initié par un individu dont l’objectif conscient ou inconscient est l’objectivation de sa victime à des fins de domination. L’agression prend différentes formes : ...

  18. Nuevo León

    Directory of Open Access Journals (Sweden)

    Laura Nelly Medellín Mendoza

    2006-01-01

    Full Text Available El ensayo analiza la transición política nuevoleonesa a partir de un contexto de liberalización política. En Nuevo León el régimen político autoritario fue cediendo en el plano electoral, dada la presión que conjuntamente la sociedad política y la sociedad civil ejercieron por lograr reglas democráticas. Este avance gradual permitió garantizar un organismo electoral confiable y que determinó en buena medida la garantía de la alternancia en 1997. El pan fue el partido que capitalizó el bono democrático, pero una vez en la responsabilidad de gobierno, no pudo ampliar el proceso de liberalización política al mediatizar las reformas electorales y no comprometerse para sacar del atolladero legislativo las iniciativas que garantizaban mecanismos de participación ciudadana: referéndum y plebiscito.

  19. Surfactant-Enhanced Benard Convection on an Evaporating Drop

    Science.gov (United States)

    Nguyen, Van X.; Stebe, Kathleen J.

    2001-11-01

    Surfactant effects on an evaporating drop are studied experimentally. Using a fluorescent probe, the distribution and surface phase of the surfactant is directly imaged throughout the evaporation process. From these experiments, we identify conditions in which surfactants promote surface tension-driven Benard instabilities in aqueous systems. The drops under study contain finely divided particles, which act as tracers in the flow, and form well-defined patterns after the drop evaporates. Two flow fields have been reported in this system. The first occurs because the contact line becomes pinned by solid particles at the contact line region. In order for the contact line to remain fixed, an outward flow toward the ring results, driving further accumulation at the contact ring. A ‘coffee ring’ of particles is left as residue after the drop evaporates[1]. The second flow is Benard convection, driven by surface tension gradients on the drop[2,3]. In our experiments, an insoluble monolayer of pentadecanoic acid is spread at the interface of a pendant drop. The surface tension is recorded, and the drop is deposited on a well-defined solid substrate. Fluorescent images of the surface phase of the surfactant are recorded as the drop evaporates. The surfactant monolayer assumes a variety of surface states as a function of the area per molecule at the interface: surface gaseous, surface liquid expanded, and surface liquid condensed phases[4]. Depending upon the surface state of the surfactant as the drop evaporates, transitions of residue patterns left by the particles occur, from the coffee ring pattern to Benard cells to irregular patterns, suggesting a strong resistance to outward flow are observed. The occurrence of Benard cells on a surfactant-rich interface occurs when the interface is in LE-LC coexistence. Prior research concerning surfactant effects on this instability predict that surfactants are strongly stabilizing[5]. The mechanisms for this change in behavior

  20. Le Chatelier principle in replicator dynamics

    OpenAIRE

    Allahverdyan, Armen E.; Galstyan, Aram

    2011-01-01

    The Le Chatelier principle states that physical equilibria are not only stable, but they also resist external perturbations via short-time negative-feedback mechanisms: a perturbation induces processes tending to diminish its results. The principle has deep roots, e.g., in thermodynamics it is closely related to the second law and the positivity of the entropy production. Here we study the applicability of the Le Chatelier principle to evolutionary game theory, i.e., to perturbations of a Nas...

  1. Le CRDI au Brésil

    International Development Research Centre (IDRC) Digital Library (Canada)

    Les recherches subventionnées par le CRDI au Brésil ont permis d'éclairer les débats sur nombre de questions, dont la démocratie, la croissance économique, la santé, les services sociaux, l'innovation, la foresterie et l'eau. Pendant la dictature militaire, qui a pris fin en 1985, le CRDI s'est employé à assurer la survie de la ...

  2. Le CRDI en Cisjordanie et à Gaza

    International Development Research Centre (IDRC) Digital Library (Canada)

    Stress des adolescents et conflit qui perdure. En Cisjordanie, la violence politique et le conflit qui perdure ont aggravé le stress chez les adolescents, qui constituent près de la moitié de la population. À Ramallah, plus de 3 000 adolescents de 15 à 17 ans ont été interrogés par des chercheurs de l'Université de Birzeit et de ...

  3. Le désordre du monde

    African Journals Online (AJOL)

    sulaiman.adebowale

    Le début du XXIe siècle se caractérise par l'accumulation et la consécution ..... Unis a présidé à la naissance aux forceps de cet outil d'équilibre du monde en ... De toute évidence, l'ONU reste l'instrument qui a marqué le siècle dernier,.

  4. la lutte contre le SIDA au Cameroun

    African Journals Online (AJOL)

    Chantel

    Pour lutter contre cette pandémie, le Cameroun s'est organisé en mettant en place, avec l'aide de ses partenaires bilatéraux et ... la dérision qui faisait du SIDA 'le syndrome inventé pour décourager les ... rapidement donner une réponse médicale à la maladie. ... histoire politique, à ses susceptibilités historiques et à.

  5. LE MARCHE FINANCIER EN ALGERIE : SITUATION ET ...

    African Journals Online (AJOL)

    Administrateur

    marché en l'occurrence le marché financier ne représente pas un problème strictement ... variés de par le monde. Dans les pays en transition, la performance du .... Les valeurs mobilières sont constituées de deux types de titres : les titres de .... La COSOB (commission d'organisation et de surveillance des opérations de ...

  6. Le patrimoine et ses outils de gestion

    CERN Document Server

    Garcin, J

    2001-01-01

    Les principale taches de gestion du Patrimoine immobilier du CERN sont la saisie des données, leur mise à jour, l'archivage et la mise à disposition des informations. Les outils de gestion actuels : Le Système de Gestion de Base de Données Relationnelles alphanumérique ORACLE permet de gérer toutes les informations du Patrimoine, sur le réseau du CERN. Le logiciel de dessin Graphique MICROSTATION (Bentley) a été installé dans la division ST depuis fin 1991. Les plans de situation des sites, des bâtiments et locaux, des espaces confinés ont été réalisés avec ce logiciel. Les outils de demain : La mise en place du SIG (Système d'Information Graphique) STAR a été réalisée en 1993. Le transfert des plans de locaux de MICROSTATION vers STAR est en cours depuis une année environ. Le dessin de la cartographie des réseaux de canalisations Eaux Usées et Eaux Pluviales est en cours de réalisation. Le Web est l'outil de consultation de l'information par les utilisateurs.

  7. Convective losses through an air-filled gap

    Energy Technology Data Exchange (ETDEWEB)

    Baum, V A; Ovezsakhatov, N

    1976-01-01

    Simplified formulas for the heat fluxes with given parameters of the air are used to calculate the specific heat losses by convection in a number of solar-energy systems (water heater, thermal generator, double-glazed window, and still). Heat losses by convection and radiation are compared.

  8. Unravelling convective heat transfer in the Rotated Arc Mixer

    NARCIS (Netherlands)

    Speetjens, M.F.M.; Baskan, O.; Metcalfe, G.; Clercx, H.J.H.

    2014-01-01

    Thermal homogenization is essentially a transient problem and convective heat transfer by (chaotic) advection is known to accelerate this process. Convective heat transfer traditionally is examined in terms of heat-transfer coefficients at domain walls and characterised by Nusselt relations.

  9. Solar wind effects on ionospheric convection: a review

    DEFF Research Database (Denmark)

    Lu, G.; Cowley, S.W.H.; Milan, S.E.

    2002-01-01

    ), and travelling convection vortices (TCVs). Furthermore, the large-scale ionospheric convection configuration has also demonstrated a strong correspondence to variations in the interplanetary medium and substorm activity. This report briefly discusses the progress made over the past decade in studies...

  10. Modulated convection at high frequencies and large modulation amplitudes

    International Nuclear Information System (INIS)

    Swift, J.B.; Hohenberg, P.C.

    1987-01-01

    Modulated Rayleigh-Benard convection is analyzed for high frequencies and large modulation amplitudes. The linear theory of Gershuni and Zhukhovitskii is generalized to the nonlinear domain, and a subcritical bifurcation to convection is found in agreement with the experiments of Niemela and Donnelly. The crossover between the high-frequency (''Stokes layer'') regime and the low-frequency regime studied previously is analyzed

  11. Measurements of convective and radiative heating in wildland fires

    Science.gov (United States)

    David Frankman; Brent W. Webb; Bret W. Butler; Daniel Jimenez; Jason M. Forthofer; Paul Sopko; Kyle S. Shannon; J. Kevin Hiers; Roger D. Ottmar

    2012-01-01

    Time-resolved irradiance and convective heating and cooling of fast-response thermopile sensors were measured in 13 natural and prescribed wildland fires under a variety of fuel and ambient conditions. It was shown that a sensor exposed to the fire environment was subject to rapid fluctuations of convective transfer whereas irradiance measured by a windowed sensor was...

  12. Natural convection and vapor loss during underground waste storage

    International Nuclear Information System (INIS)

    Plys, M.G.; Epstein, M.; Turner, D.

    1996-01-01

    Natural convection and vapor loss from underground waste storage tanks is examined here. Stability criteria are provided for the onset of natural convection flow within the headspace of a tank, and between tanks and the environment. The flowrate is quantified and used to predict vapor losses during storage

  13. Heat removal by natural convection in a RPR reactor

    International Nuclear Information System (INIS)

    Sampaio, P.A.B. de

    1987-01-01

    In this paper natural convection in RPR reactor is analysed. The effect of natural convection valves size on cladding temperature is studied. The reactor channel heat transfer problem is solved using finite elements in a two-dimensional analysis. Results show that two valves with Φ = 0.16 m are suited to keep coolant and cladding temperatures below 73 0 C. (author) [pt

  14. Interaction of externally-driven acoustic waves with compressible convection

    International Nuclear Information System (INIS)

    Jones, P.; Merryfield, W.

    1992-01-01

    Two-dimensional numerical simulations are used to examine the interaction of acoustic waves with a compressible convecting fluid. Acoustic waves are forced at the lower boundary of the computational domain and propagate through a three-layer system undergoing vigorous penetrative convection. Energy exchange between the wave and the fluid is analyzed using a work integral formulation

  15. Efficiency of Heat Transfer in Turbulent Rayleigh-Benard Convection

    Czech Academy of Sciences Publication Activity Database

    Urban, Pavel; Musilová, Věra; Skrbek, L.

    2011-01-01

    Roč. 107, č. 1 (2011), 014302:1-4 ISSN 0031-9007 R&D Projects: GA AV ČR KJB200650902 Institutional research plan: CEZ:AV0Z20650511 Keywords : natural convection * thermal convection Subject RIV: BK - Fluid Dynamics Impact factor: 7.370, year: 2011

  16. Thermo-diffusion effect on free convection heat and mass transfer in a thermally linearly stratified non-darcy porous media

    KAUST Repository

    Murthy, P.V.S.N.

    2011-12-26

    Thermo-diffusion effect on free convection heat and mass transfer from a vertical surface embedded in a liquid saturated thermally stratified non - Darcy porous medium has been analyzed using a local non-similar procedure. The wall temperature and concentration are constant and the medium is linearly stratified in the vertical direction with respect to the thermal conditions. The fluid flow, temperature and concentration fields are affected by the complex interactions among the diffusion ratio Le, buoyancy ratio N, thermo-diffusion parameter Sr and stratification parameter ?. Non-linear interactions of all these parameters on the convective transport has been analyzed and variation of heat and mass transfer coefficients with thermo-diffusion parameter in the thermally stratified non-Darcy porous media is presented through computer generated plots.

  17. Thermo-diffusion effect on free convection heat and mass transfer in a thermally linearly stratified non-darcy porous media

    KAUST Repository

    Murthy, P.V.S.N.; El-Amin, Mohamed

    2011-01-01

    Thermo-diffusion effect on free convection heat and mass transfer from a vertical surface embedded in a liquid saturated thermally stratified non - Darcy porous medium has been analyzed using a local non-similar procedure. The wall temperature and concentration are constant and the medium is linearly stratified in the vertical direction with respect to the thermal conditions. The fluid flow, temperature and concentration fields are affected by the complex interactions among the diffusion ratio Le, buoyancy ratio N, thermo-diffusion parameter Sr and stratification parameter ?. Non-linear interactions of all these parameters on the convective transport has been analyzed and variation of heat and mass transfer coefficients with thermo-diffusion parameter in the thermally stratified non-Darcy porous media is presented through computer generated plots.

  18. Le Projet d’Ole Lando sur les Contrats

    DEFF Research Database (Denmark)

    Holle, Marie-Louise

    2017-01-01

    En 2016 le projet de recherche le plus important jusqu’à présent sur le droit nordique des contrats a pris fin et un livre, de presque 400 pages, en a marqué l’aboutissement. Le résultat du projet est un « restatement » tel qu’il existe aux États-Unis. Le Restatement porte sur les règles et les...

  19. Boundary-modulated Thermal Convection Model in the Mantle

    Science.gov (United States)

    Kurita, K.; Kumagai, I.

    2008-12-01

    Analog experiments have played an important role in the constructing ideas of mantle dynamics. The series of experiments by H. Ramberg is one of the successful examples. Recently, however the realm of the analog experiments seems to be overwhelmed by steady progress of computer simulations. Is there still room for the analog experiments? This might be a main and hidden subject of this session. Here we propose a working hypothesis how the convecting mantle behaves based on the analog experiments in the system of viscous fluid and particles. The essential part is the interaction of convecting flow with heterogeneities existing in the boundaries. It is proposed the preexisting topographical heterogeneity in the boundary could control the flow pattern of convecting fluid. If this kind of heterogeneity can be formed as a consequence of convective motion and mobilized by the flow, the convection also can control the heterogeneity. We can expect interactions in two ways, by which the system behaves in a self-organize fashion. To explore the mutual interactions between convection flow and heterogeneity the system of viscous fluid and particles with slightly higher density is selected as 2D Rayleigh-Benard type convection. The basic structure consists of a basal particulate layer where permeable convection transports heat and an upper viscous fluid layer. By reducing the magnitude of the density difference the convective flow can mobilize the particles and can erode the basal layer. The condition of this erosion can be identified in the phase diagram of the particle Shields"f and the Rayleigh numbers. At Ra greater than 107 the convection style drastically changed before and after the erosion. Before the erosion where the flat interface of the boundary is maintained small scaled turbulent convection pattern is dominant. After the erosion where the interface becomes bumpy the large scale convective motion is observed. The structure is coherent to that of the boundary. This

  20. Do tropical wetland plants possess a convective gas flow mechanism?

    DEFF Research Database (Denmark)

    Jensen, Dennis Konnerup; Sorrell, Brian Keith; Brix, Hans

    2011-01-01

    Internal pressurization and convective gas flow, which can aerate wetland plants more efficiently than diffusion, are common in temperate species. Here, we present the first survey of convective flow in a range of tropical plants. The occurrence of pressurization and convective flow was determined...... in 20 common wetland plants from the Mekong Delta in Vietnam. The diel variation in pressurization in culms and the convective flow and gas composition from stubbles were examined for Eleocharis dulcis, Phragmites vallatoria and Hymenachne acutigluma, and related to light, humidity and air temperature....... Nine of the 20 species studied were able to build up a static pressure of >50Pa, and eight species had convective flow rates higher than 1mlmin-1. There was a clear diel variation, with higher pressures and flows during the day than during the night, when pressures and flows were close to zero...

  1. Heat transfer of laminar mixed convection of liquid

    CERN Document Server

    Shang, De-Yi

    2016-01-01

    This book presents a new algorithm to calculate fluid flow and heat transfer of laminar mixed convection. It provides step-by-step tutorial help to learn quickly how to set up the theoretical and numerical models of laminar mixed convection, to consider the variable physical properties of fluids, to obtain the system of numerical solutions, to create a series of formalization equations for the convection heat transfer by using a curve-fitting approach combined with theoretical analysis and derivation. It presents the governing ordinary differential equations of laminar mixed convection, equivalently transformed by an innovative similarity transformation with the description of the related transformation process. A system of numerical calculations of the governing ordinary differential equations is presented for the water laminar mixed convection. A polynomial model is induced for convenient and reliable treatment of variable physical properties of liquids. The developed formalization equations of mixed convec...

  2. Natural Convection Analysis with Various Turbulent Models Using FLUENT

    International Nuclear Information System (INIS)

    Park, Yu Sun

    2007-01-01

    The buoyancy driven convective flow fields are steady circulatory flows which were made between surfaces maintained at two fixed temperatures. They are ubiquitous in nature and play an important role in many engineering applications. Especially, in last decades, natural convection in a close loop or cavity becomes the main issue in the molecular biology for the polymerase chain reaction (PCR). Application of a natural convection can reduce the costs and efforts remarkably. This paper focuses on the sensitivity study of turbulence analysis using CFD for a natural convection in a closed rectangular cavity. Using commercial CFD code, FLUENT, various turbulent models were applied to the turbulent flow. Results from each CFD model will be compared each other in the viewpoints of flow characteristics. This work will suggest the best turbulent model of CFD for analyzing turbulent flows of the natural convection in an enclosure system

  3. The influence of convective current generator on the global current

    Directory of Open Access Journals (Sweden)

    V. N. Morozov

    2006-01-01

    Full Text Available The mathematical generalization of classical model of the global circuit with taking into account the convective current generator, working in the planetary boundary layer was considered. Convective current generator may be interpreted as generator, in which the electromotive force is generated by processes, of the turbulent transport of electrical charge. It is shown that the average potential of ionosphere is defined not only by the thunderstorm current generators, working at the present moment, but by the convective current generator also. The influence of the convective processes in the boundary layer on the electrical parameters of the atmosphere is not only local, but has global character as well. The numerical estimations, made for the case of the convective-unstable boundary layer demonstrate that the increase of the average potential of ionosphere may be of the order of 10% to 40%.

  4. Neutral beam injection and plasma convection in a magnetic field

    International Nuclear Information System (INIS)

    Okuda, H.; Hiroe, S.

    1988-06-01

    Injection of a neutral beam into a plasma in a magnetic field has been studied by means of numerical plasma simulations. It is found that, in the absence of a rotational transform, the convection electric field arising from the polarization charges at the edges of the beam is dissipated by turbulent plasma convection, leading to anomalous plasma diffusion across the magnetic field. The convection electric field increases with the beam density and beam energy. In the presence of a rotational transform, polarization charges can be neutralized by the electron motion along the magnetic field. Even in the presence of a rotational transform, a steady-state convection electric field and, hence, anomalous plasma diffusion can develop when a neutral beam is constantly injected into a plasma. Theoretical investigations on the convection electric field are described for a plasma in the presence of rotational transform. 11 refs., 19 figs

  5. Quantitative analysis of nickel in zirconium and zircaloy; Dosage du nickel dans le zirconium et dans le zircaloy

    Energy Technology Data Exchange (ETDEWEB)

    Rastoix, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    A rapid spectrophotometric has been developed for determination of 10 to 1000 ppm of Ni in zirconium and zircaloy using dimethylglyoxime. Iron, copper, tin and chromium, do not interfere at the concentration usually present in zirconium and its alloys. (author) [French] On determine colorimetriquenent 10 a 1000 ppm de Ni dans le zirconium et le zircaloy par photo colorimetrie a 440 m{mu} de la dimethylglyoxime nickelique. Le dosage est rapide. Le fer, le cuivre, l'etain, le chrome ne genent pas aux concentrations habituellement rencontrees dans le zirconium et ses alliages. (auteur)

  6. The sensitivity of Alpine summer convection to surrogate climate change: an intercomparison between convection-parameterizing and convection-resolving models

    Directory of Open Access Journals (Sweden)

    M. Keller

    2018-04-01

    Full Text Available Climate models project an increase in heavy precipitation events in response to greenhouse gas forcing. Important elements of such events are rain showers and thunderstorms, which are poorly represented in models with parameterized convection. In this study, simulations with 12 km horizontal grid spacing (convection-parameterizing model, CPM and 2 km grid spacing (convection-resolving model, CRM are employed to investigate the change in the diurnal cycle of convection with warmer climate. For this purpose, simulations of 11 days in June 2007 with a pronounced diurnal cycle of convection are compared with surrogate simulations from the same period. The surrogate climate simulations mimic a future climate with increased temperatures but unchanged relative humidity and similar synoptic-scale circulation. Two temperature scenarios are compared: one with homogeneous warming (HW using a vertically uniform warming and the other with vertically dependent warming (VW that enables changes in lapse rate.The two sets of simulations with parameterized and explicit convection exhibit substantial differences, some of which are well known from the literature. These include differences in the timing and amplitude of the diurnal cycle of convection, and the frequency of precipitation with low intensities. The response to climate change is much less studied. We can show that stratification changes have a strong influence on the changes in convection. Precipitation is strongly increasing for HW but decreasing for the VW simulations. For cloud type frequencies, virtually no changes are found for HW, but a substantial reduction in high clouds is found for VW. Further, we can show that the climate change signal strongly depends upon the horizontal resolution. In particular, significant differences between CPM and CRM are found in terms of the radiative feedbacks, with CRM exhibiting a stronger negative feedback in the top-of-the-atmosphere energy budget.

  7. The sensitivity of Alpine summer convection to surrogate climate change: an intercomparison between convection-parameterizing and convection-resolving models

    Science.gov (United States)

    Keller, Michael; Kröner, Nico; Fuhrer, Oliver; Lüthi, Daniel; Schmidli, Juerg; Stengel, Martin; Stöckli, Reto; Schär, Christoph

    2018-04-01

    Climate models project an increase in heavy precipitation events in response to greenhouse gas forcing. Important elements of such events are rain showers and thunderstorms, which are poorly represented in models with parameterized convection. In this study, simulations with 12 km horizontal grid spacing (convection-parameterizing model, CPM) and 2 km grid spacing (convection-resolving model, CRM) are employed to investigate the change in the diurnal cycle of convection with warmer climate. For this purpose, simulations of 11 days in June 2007 with a pronounced diurnal cycle of convection are compared with surrogate simulations from the same period. The surrogate climate simulations mimic a future climate with increased temperatures but unchanged relative humidity and similar synoptic-scale circulation. Two temperature scenarios are compared: one with homogeneous warming (HW) using a vertically uniform warming and the other with vertically dependent warming (VW) that enables changes in lapse rate. The two sets of simulations with parameterized and explicit convection exhibit substantial differences, some of which are well known from the literature. These include differences in the timing and amplitude of the diurnal cycle of convection, and the frequency of precipitation with low intensities. The response to climate change is much less studied. We can show that stratification changes have a strong influence on the changes in convection. Precipitation is strongly increasing for HW but decreasing for the VW simulations. For cloud type frequencies, virtually no changes are found for HW, but a substantial reduction in high clouds is found for VW. Further, we can show that the climate change signal strongly depends upon the horizontal resolution. In particular, significant differences between CPM and CRM are found in terms of the radiative feedbacks, with CRM exhibiting a stronger negative feedback in the top-of-the-atmosphere energy budget.

  8. Laminar Mixed Convection Heat Transfer Correlation for Horizontal Pipes

    International Nuclear Information System (INIS)

    Chae, Myeong Seon; Chung, Bum Jin

    2013-01-01

    This study aimed at producing experimental results and developing a new heat transfer correlation based upon a semi-empirical buoyancy coefficient. Mixed convection mass transfers inside horizontal pipe were investigated for the pipe of various length-to-diameters with varying Re. Forced convection correlation was developed using a very short cathode. With the length of cathode increase and Re decrease, the heat transfer rates were enhanced and becomes higher than that of forced convection. An empirical buoyancy coefficient was derived from correlation of natural convection and forced convection with the addition of L/D. And the heat transfer correlation for laminar mixed convection was developed using the buoyancy coefficient, it describes not only current results, but also results of other studies. Mixed convection occurs when the driving forces of both forced and natural convections are of comparable magnitude (Gr/Re 2 ∼1). It is classical problem but is still an active area of research for various thermal applications such as flat plate solar collectors, nuclear reactors and heat exchangers. The effect of buoyancy on heat transfer in a forced flow is varied by the direction of the buoyancy force. In a horizontal pipe the direction of the forced and buoyancy forces are perpendicular. The studies on the mixed convections of the horizontal pipes were not investigated very much due to the lack of practical uses compared to those of vertical pipes. Even the definitions on the buoyancy coefficient that presents the relative influence of the forced and the natural convections, are different by scholars. And the proposed heat transfer correlations do not agree

  9. Le concept d’ethos.

    Directory of Open Access Journals (Sweden)

    Bernard Fusulier

    2011-09-01

    Full Text Available Dans cet article, l’auteur traite de la signification et de l’usage du concept d’ethos. Dans la sociologie classique, ce dernier a été utilisé pour comprendre et qualifier la rationalité socialement et éthiquement encastrée des conduites sociales. Exprimant l’intériorisation d’un principe organisateur de pratiques, dessinant une matrice globale des comportements, il est porteur d’une vision qui paraît datée à l’heure du “brouillage des classes sociales”, de la “modernité liquide” et de “l’homme pluriel”. Néanmoins, si l’on reconnaît l’existence d’un univers social non entièrement liquéfié, c’est-à-dire où continuent à exister des milieux sociaux sédimentés qui imprègnent avec plus ou moins de profondeur le système de personnalité de celui qui s’y insère durablement, l’ethos reste un concept heuristique pour saisir et interpréter les récurrences de comportements qui peuvent s’y observer. Permettant de comprendre ce que les espaces d’insertion “font aux individus” ainsi que la façon dont les principes organisateurs de pratiques entrent en transaction (en consonance, en dissonance ou en concurrence, il garde toute sa pertinence dans la boîte à outils théoriques du sociologue et de l’anthropologue d’aujourd’hui.

  10. A model of the solar cycle driven by the dynamo action of the global convection in the solar convection zone

    International Nuclear Information System (INIS)

    Yoshimura, H.

    1976-01-01

    Extensive numerical studies of the dynamo equations due to the global convection are presented to simulate the solar cycle and to open the way to study general stellar magnetic cycles. The dynamo equations which represent the longitudinally-averaged magnetohydrodynamical action (mean magnetohydrodynamics) of the global convection under the influence of the rotation in the solar convection zone are considered here as an initial boundary-value problem. The latitudinal and radial structure of the dynamo action consisting of a generation action due to the differential rotation and a regeneration action due to the global convection is parameterized in accordance with the structure of the rotation and of the global convection. This is done especially in such a way as to represent the presence of the two cells of the regeneration action in the radial direction in which the action has opposite signs, which is typical of the regeneration action of the global convection. The effects of the dynamics of the global convection (e.g., the effects of the stratification of the physical conditions in the solar convection zone) are presumed to be all included in those parameters used in the model and they are presumed not to alter the results drastically since these effects are only to change the structure of the regeneration action topologically. (Auth.)

  11. Modes of convection in the magnetotail

    International Nuclear Information System (INIS)

    Baumjohann, Wolfgang

    2002-01-01

    The flow of plasma in the Earth's magnetotail cannot reach a steady state, since adiabatic convection would lead to exceedingly high pressure of the associated magnetic flux tubes closer to the Earth, the so-called pressure catastrophe. The natural way to avoid the pressure catastrophe is to significantly reduce the flux tube volume by reconnection, and observations show a near-Earth reconnection line typically around 20-25 Earth radii down tail. Earthward flows from this reconnection line are rather bursty and typically seen outside of 10 Earth radii. At this point they are strongly braked by the here dominant dipolar magnetic field. The pressure gradients piled up by the flow lead to the substorm current wedge, and possibly other substorm phenomena observed in the Earth's ionosphere. When more and more flux tubes are piled up, the dipolarization front moves tailward and finally shuts off near-Earth reconnection

  12. Mixed convection flow past a horizontal plate

    Directory of Open Access Journals (Sweden)

    Savić Lj.

    2005-01-01

    Full Text Available The mixed convection flow past a horizontal plate being aligned through a small angle of attack to a uniform free stream will be considered in the limit of large Reynolds number and small Richardson number. Even a small angle of inclination of the wake is sufficient for the buoyancy force to accelerate the flow in the wake which causes a velocity overshoot in the wake. Moreover a hydrostatic pressure difference across the wake induces a correction to the potential flow which influences the inclination of the wake. Thus the wake and the correction of the potential flow have to be determined simultaneously. However, it turns out that solutions exist only if the angle of attack is sufficiently large. Solutions are computed numerically and the influence of the buoyancy on the lift coefficient is determined.

  13. Imaging convection and magnetism in the sun

    CERN Document Server

    Hanasoge, Shravan

    2015-01-01

    This book reviews the field of helioseismology and its outstanding challenges and also offers a detailed discussion of the latest computational methodologies. The focus is on the development and implementation of techniques to create 3-D images of convection and magnetism in the solar interior and to introduce the latest computational and theoretical methods to the interested reader. With the increasing availability of computational resources, demand for greater accuracy in the interpretation of helioseismic measurements and the advent of billion-dollar instruments taking high-quality observations, computational methods of helioseismology that enable probing the 3-D structure of the Sun have increasingly become central. This book will benefit students and researchers with proficiency in basic numerical methods, differential equations and linear algebra who are interested in helioseismology.

  14. Design Aspects of the Rayleigh Convection Code

    Science.gov (United States)

    Featherstone, N. A.

    2017-12-01

    Understanding the long-term generation of planetary or stellar magnetic field requires complementary knowledge of the large-scale fluid dynamics pervading large fractions of the object's interior. Such large-scale motions are sensitive to the system's geometry which, in planets and stars, is spherical to a good approximation. As a result, computational models designed to study such systems often solve the MHD equations in spherical geometry, frequently employing a spectral approach involving spherical harmonics. We present computational and user-interface design aspects of one such modeling tool, the Rayleigh convection code, which is suitable for deployment on desktop and petascale-hpc architectures alike. In this poster, we will present an overview of this code's parallel design and its built-in diagnostics-output package. Rayleigh has been developed with NSF support through the Computational Infrastructure for Geodynamics and is expected to be released as open-source software in winter 2017/2018.

  15. Prediction of flow instability during natural convection

    International Nuclear Information System (INIS)

    Farhadi, Kazem

    2005-01-01

    The occurrence of flow excursion instability during passive heat removal for Tehran Research Reactor (TRR) has been analyzed at low-pressure and low-mass rate of flow conditions without boiling taking place. Pressure drop-flow rate characteristics in the general case are determined upon a developed code for this purpose. The code takes into account variations of different pressure drop components caused by different powers as well as different core inlet temperatures. The analysis revealed the fact that the instability can actually occur in the natural convection mode for a range of powers per fuel plates at a predetermined inlet temperature with fixed geometry of the core. Low mass rate of flow and high sub-cooling are the two important conditions for the occurrence of static instability in the TRR. The calculated results are compared with the existing data in the literature. (author)

  16. Translation and convection of Earth's inner core

    Science.gov (United States)

    Monnereau, M.; Calvet, M.; Margerin, L.; Mizzon, H.; Souriau, A.

    2012-12-01

    The image of the inner core growing slowly at the center of the Earth by gradual cooling and solidification of the surrounding liquid outer core is being replaced by the more vigorous image of a ``deep foundry'', where melting and crystallization rates exceed by many times the net growth rate. Recently, a particular mode of convection, called translation, has been put forward as an important mode of inner core dynamics because this mechanism is able to explain the observed East-West asymmetry of P-wave velocity and attenuation (Monnereau et al. 2010). Translation is a pure solid displacement of the inner core material (solid iron) within its envelop, implying crystallization of entering iron on one side of the inner core and melting on the opposite side. Translation is consistent with multiple scattering models of wave propagation. If they do not experience deformation, iron crystals grow as they transit from one hemisphere to the other. Larger crystals constituting a faster and more attenuating medium, a translation velocity of some cm/yr (about ten times the growth rate) is enough to account for the superficial asymmetry observed for P-wave velocity and attenuation, with grains of a few hundred meters on the crystallizing side (West) growing up to a few kilometers before melting on the East side, and a drift direction located in the equatorial plane. Among all hypotheses that have been proposed to account for the seismic asymmetry, translation is the only one based on a demonstrated link between the seismic data and the proposed dynamics, notably through a model of seismic wave propagation. This mechanism was also proposed to be responsible for the formation of a dense layer at the bottom of the outer core, since the high rate of melting and crystallization would release a liquid depleted in light elements at the surface of the inner core (Alboussiere et al 2010). This would explain the anomalously low gradient of P wave velocity in the lowermost 200 km of the

  17. Mixed convection in fluid superposed porous layers

    CERN Document Server

    Dixon, John M

    2017-01-01

    This Brief describes and analyzes flow and heat transport over a liquid-saturated porous bed. The porous bed is saturated by a liquid layer and heating takes place from a section of the bottom. The effect on flow patterns of heating from the bottom is shown by calculation, and when the heating is sufficiently strong, the flow is affected through the porous and upper liquid layers. Measurements of the heat transfer rate from the heated section confirm calculations. General heat transfer laws are developed for varying porous bed depths for applications to process industry needs, environmental sciences, and materials processing. Addressing a topic of considerable interest to the research community, the brief features an up-to-date literature review of mixed convection energy transport in fluid superposed porous layers.

  18. Convective heat transfer and infrared thermography.

    Science.gov (United States)

    Carlomagno, Giovanni M; Astarita, Tommaso; Cardone, Gennaro

    2002-10-01

    Infrared (IR) thermography, because of its two-dimensional and non-intrusive nature, can be exploited in industrial applications as well as in research. This paper deals with measurement of convective heat transfer coefficients (h) in three complex fluid flow configurations that concern the main aspects of both internal and external cooling of turbine engine components: (1) flow in ribbed, or smooth, channels connected by a 180 degrees sharp turn, (2) a jet in cross-flow, and (3) a jet impinging on a wall. The aim of this study was to acquire detailed measurements of h distribution in complex flow configurations related to both internal and external cooling of turbine components. The heated thin foil technique, which involves the detection of surface temperature by means of an IR scanning radiometer, was exploited to measure h. Particle image velocimetry was also used in one of the configurations to precisely determine the velocity field.

  19. Convectively Induced Meanflow in a Long Channel.

    Science.gov (United States)

    Grimm, Th.; Maxworthy, T.

    1997-11-01

    The similarity theory of Phillips (Deep Sea Res. 13, 1966) for the convectively induced motion in the Red Sea, predicts that the outflow buoyancy difference should scale as (B _0L) ^2/3/h :: , where B 0 is the surface buoyancy flux and L and h are the length and height of the channel above the sill crest, respectively. A friction-buoyancy balance leads to a modified expression [(B _0L) ^2/3/h][fracLh]^1/3 :: (2). The results can be applied also to a number of other natural flows including freezing-induced convection in fjords and polar seas. A series of Experiments have been conducted to check the predictions. A channel 300 cm long and 21 cm wide has been constructed. Within it segmented salt-water sources have been placed over a length of 250 cm. Their depth varied from 2 to 12 cm. A sill was placed in the exit region and its height was at least half the total depth of water in the channel. Density data were taken by withdrawing samples while velocity profiles were found by a DPIV technique. The meanflow consists of a two-layer stratification over a large fraction of the length of the channel. Our results suggest that the scaling (2) above is most closely realized with a constant of value 1.1. Analysis of the Red Sea data suggests a constant between 1.1 and 1.4 depending on the data set used. The exit Fr-number is unity. The amount of mixing within the channel is less than that predicted for the 'overmixed' state. Supported by the German Acad. Exchge. Serv. and the NSF Polar Programs.

  20. Engineering photochemical smog through convection towers

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, S.; Prueitt, M.L.; Bossert, J.E.; Mroz, E.J.; Krakowski, R.A.; Miller, R.L. [Los Alamos National Lab., NM (United States); Jacobson, M.Z.; Turco, R.P. [Los Alamos National Lab., NM (United States)]|[Univ. of California, Los Angeles, CA (United States). Atmospheric Sciences Dept.

    1995-02-01

    Reverse convection towers have attracted attention as a medium for cleansing modern cities. Evaporation of an aqueous mist injected at the tower opening could generate electrical power by creating descent, and simultaneously scavenge unsightly and unhealthful particulates. The study offered here assesses the influence to tower water droplets on the photochemical component of Los Angeles type smog. The primary radical chain initiator OH is likely removed into aqueous phases well within the residence time of air in the tower, and then reacts away rapidly. Organics do not dissolve, but nighttime hydrolysis of N{sub 2}O{sub 5} depletes the nitrogen oxides. A lack of HOx would slow hydrocarbon oxidation and so also ozone production. Lowering of NOx would also alter ozone production rates, but the direction is uncertain. SO{sub 2} is available in sufficient quantities in some urban areas to react with stable oxidants, and if seawater were the source of the mist, the high pH would lead to fast sulfur oxidation kinetics. With an accommodation coefficient of 10{sup {minus}3}, however, ozone may not enter the aqueous phase efficiently. Even if ozone is destroyed or its production suppressed, photochemical recovery times are on the order of hours, so that tower processing must be centered on a narrow midday time window. The cost of building the number of structures necessary for this brief turnover could be prohibitive. The increase in humidity accompanying mist evaporation could be controlled with condensers, but might otherwise counteract visibility enhancements by recreating aqueous aerosols. Quantification of the divergent forcings convection towers must exert upon the cityscape would call for coupled three dimensional modeling of transport, microphysics, and photochemistry. 112 refs.

  1. Influence of yield stress on free convective boundary-layer flow of a non-Newtonian nanofluid past a vertical plate in a porous medium

    International Nuclear Information System (INIS)

    Hady, F. M.; Ibrahim, F. S.; Abdel-Gaied, S. M.; Eid, M. R.

    2011-01-01

    The effect of yield stress on the free convective heat transfer of dilute liquid suspensions of nanofluids flowing on a vertical plate saturated in porous medium under laminar conditions is investigated considering the nanofluid obeys the mathematical model of power-law. The model used for non-Newtonian nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing boundary- layer equations are cast into dimensionless system which is solved numerically using a deferred correction technique and Newton iteration. This solution depends on yield stress parameter Ω, a power-law index n, Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. Analyses of the results found that the reduced Nusselt and Sherwood numbers are decreasing functions of the higher yield stress parameter for each dimensionless numbers, n and Le, except the reduced Sherwood number is an increasing function of higher Nb for different values of yield stress parameter

  2. True polar wander on convecting planets

    Science.gov (United States)

    Rose, Ian Robert

    Rotating planets are most stable when spinning around their maximum moment of inertia, and will tend to reorient themselves to achieve this configuration. Geological activity redistributes mass in the planet, making the moment of inertia a function of time. As the moment of inertia of the planet changes, the spin axis shifts with respect to a mantle reference frame in order to maintain rotational stability. This process is known as true polar wander (TPW). Of the processes that contribute to a planet's moment of inertia, convection in the mantle generates the largest and longest-period fluctuations, with corresponding shifts in the spin axis. True polar wander has been hypothesized to explain several physiographic features on planets and moons in our solar system. On Earth, TPW events have been invoked in some interpretations of paleomagnetic data. Large swings in the spin axis could have enormous ramifications for paleogeography, paleoclimate, and the history of life. Although the existence of TPW is well-verified, it is not known whether its rate and magnitude have been large enough for it to be an important process in Earth history. If true polar wander has been sluggish compared to plate tectonic speeds, then it would be difficult to detect and its consequences would be minor. I investigate rates of true polar wander on convecting planets using scaling, numerics, and inverse problems. I perform a scaling analysis of TPW on a convecting planet, identifying a minimal set of nondimensional parameters which describe the problem. The primary nondimensional numbers that control the rate of TPW are the ratio of centrifugal to gravitational forces m and the Rayleigh number Ra. The parameter m sets the size of a planet's rotational bulge, which determines the amount of work that needs to be done to move the spin axis. The Rayleigh number controls the size, distribution, and rate of change of moment of inertia anomalies, all of which affect the rate of TPW. I find that

  3. Le point sur le sida, l'alimentation et la nutrition | CRDI - Centre de ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    agriculture et l'alimentation ( FAO ), Stuart Gillespie a passé six mois à étudier le lien entre le VIH/sida et la sécurité alimentaire. Il a vite compris que l'épidémie risquait d'avoir, à long terme, des répercussions désastreuses sur la ...

  4. pour le trimestre qui a pris fin le 31 décembre 2013

    International Development Research Centre (IDRC) Digital Library (Canada)

    Sophie Comeau

    31 déc. 2013 ... IFRS 9 – Instruments financiers. Le CNCI a l'intention de remplacer la norme IAS 39 – Instruments financiers : comptabilisation et évaluation par la norme IFRS 9. La nouvelle norme guide la classification, la comptabilisation, la décomptabilisation et l'évaluation des actifs et des passifs financiers. Le Centre ...

  5. pour le trimestre qui a pris fin le 30 septembre 2016

    International Development Research Centre (IDRC) Digital Library (Canada)

    Office 2004 Test Drive User

    30 sept. 2016 ... Le CRDI finance des travaux de recherche appliquée ... internationales dʼinformation financière (normes IFRS). ..... voie de développement et sur la mise en oeuvre des connaissances scientifiques, techniques et autres en vue du .... Les accords expirent à des dates différentes, et le dernier prend fin en.

  6. Rapport financier trimestriel pour le trimestre qui a pris fin le 30 ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Sophie Comeau

    30 sept. 2017 ... Régi par la Loi sur le Centre de recherches pour le développement international ... forme des leaders dans les secteurs de l'administration publique, de la .... Plus des trois quart du manque à gagner prévu de 11,6 millions.

  7. Rapport financier trimestriel pour le trimestre qui a pris fin le 31 ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Sophie Comeau

    31 déc. 2017 ... Régi par la Loi sur le Centre de recherches pour le développement international ... optimiser les retombées; forme des leaders dans les secteurs de ... Centre dans ce domaine, et a animé une table ronde avec trois des quatre ...

  8. Le FIE 2008 fait avancer le cadre écobiosocial de l'OMS | CRDI ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    10 mai 2011 ... Le Programme spécial de recherche et de formation concernant les maladies tropicales (TDR) de l'OMS a élaboré le concept du champ « écobiosocial », qui combine les perspectives écologiques, biologiques et sociales « pour mieux comprendre la dynamique des maladies infectieuses à transmission ...

  9. pour le trimestre qui a pris fin le 30 juin 2013

    International Development Research Centre (IDRC) Digital Library (Canada)

    Office 2004 Test Drive User

    30 juin 2013 ... Conseil des gouverneurs du CRDI. Le mandat des gouverneurs suivants a pris fin le 27 mai 2013 : Margaret Biggs, d'Ottawa, en Ontario;. Faith Mitchell, de Washington, aux États-Unis; Elizabeth Parr-Johnston, de Chester Basin, en Nouvelle-Écosse; Gordon Shirley, de Kingston, en Jamaïque; l'honorable ...

  10. Le SRAS, le sida, et la santé publique | IDRC - International ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    22 juil. 2011 ... Certaines de ces leçons portent sur les interactions complexes entre la biologie, la culture et le pouvoir. D'autres traitent des moyens de .... HIV prevention policy in China. IDRC-funded research is using mathematical modelling to influence local and national policies in China to reduce HIV transmission.

  11. Juan Goytisolo: Le soi, le monde et la création littéraire

    Directory of Open Access Journals (Sweden)

    Pablo Romero Alegría

    2010-01-01

    Full Text Available Reseña de la obra: Yannick Llored. Le soi, le monde et la création littéraire. Presses Universitaires du Septentrion. Villeneuve d’Ascq (Francia. 2009. 421 págs. ISBN: 978-2-75740-0089-0

  12. LE LIEN ENTRE FINANCE ET ECONOMIE ISLAMIQUES VIA LE MODELE PRINCIPIEL "ZR"

    OpenAIRE

    BELABES, ABDERRAZAK

    2010-01-01

    A l'heure où certains évoquent l'intégration de la finance islamique à la finance globale, et d'autres rattachent la finance islamique à des thèmes en vogue telles que la finance éthique, la finance participative ou la finance socialement responsable, le présent papier explore le lien entre finance et économie islamiques à partir du modèle principiel "ZR", c’est-à-dire "Zakât" et "Ribâ". Ce modèle montre que les principes invariants de Zakât et Ribâ jouent un rôle central dans l’établissement...

  13. Le jeu de la création : Le mangeur (2005) de Ying Chen

    OpenAIRE

    Nicole Dunham

    2013-01-01

    Le théoricien James Hans définit le jeu comme une déconstruction structurante, un processus de perpétuelle remise en question. Dans Le Mangeur (2005) de Ying Chen, la narratrice revit un épisode d’une de ses vies passées où elle meurt mangée, avalée, par son père, descendant dans le « tunnel » du ventre de ce dernier. Cependant, suite à cet événement, elle se retrouve dans un autre espace-temps où elle rencontre son mari, A.. Une équivalence s’établit dans le roman entre les éléments suivants...

  14. Lele du pharmacien dans la fécondation in vitro

    OpenAIRE

    Hannoun , Odélia

    2017-01-01

    La procréation médicalement assistée regroupe plusieurs techniques venant en aide aux couples ayant des difficultés à concevoir. Environ 15% des couples en age de procréer consultent pour une difficulté à concevoir. Ce véritable problème de société nous incite à réfléchir sur le role que tient le pharmacien en tant que professionnel de santé dans le parcours de fécondation in vitro. Le pharmacien développe une relation étroite avec les patients au comptoir. Il est la pour expliquer le traitem...

  15. Bibliographie sélective sur le corps

    Directory of Open Access Journals (Sweden)

    Anne-Claire Rebreyend

    2007-11-01

    Full Text Available Ouvrages générauxBruit Zaidman Louise, Houbre Gabrielle, Klapisch-Zuber Christiane, Schmitt Pantel Pauline (dir., Le corps des jeunes filles de l'Antiquité à nos jours, Paris, Perrin, 2001.Vigarello Georges, Le propre et le sale. L'hygiène du corps depuis le Moyen Âge, Paris, Seuil, 1985.—, Le sain et le malsain : santé et mieux-être depuis le Moyen Âge, Paris, Seuil, 1993.—, Histoire de la beauté. Le corps et l'art d'embellir de la Renaissance à nos jours, Paris, Seuil, 2004.Le corps au Moy...

  16. Improved nowcasting of precipitation based on convective analysis fields

    Directory of Open Access Journals (Sweden)

    T. Haiden

    2007-04-01

    Full Text Available The high-resolution analysis and nowcasting system INCA (Integrated Nowcasting through Comprehensive Analysis developed at the Austrian national weather service provides three-dimensional fields of temperature, humidity, and wind on an hourly basis, and two-dimensional fields of precipitation rate in 15 min intervals. The system operates on a horizontal resolution of 1 km and a vertical resolution of 100–200 m. It combines surface station data, remote sensing data (radar, satellite, forecast fields of the numerical weather prediction model ALADIN, and high-resolution topographic data. An important application of the INCA system is nowcasting of convective precipitation. Based on fine-scale temperature, humidity, and wind analyses a number of convective analysis fields are routinely generated. These fields include convective boundary layer (CBL flow convergence and specific humidity, lifted condensation level (LCL, convective available potential energy (CAPE, convective inhibition (CIN, and various convective stability indices. Based on the verification of areal precipitation nowcasts it is shown that the pure translational forecast of convective cells can be improved by using a decision algorithm which is based on a subset of the above fields, combined with satellite products.

  17. Convective effects in a regulatory and proposed fire model

    International Nuclear Information System (INIS)

    Wix, S.D.; Hohnstreiter, G.F.

    1995-01-01

    Radiation is the dominant mode of heat transfer in large fires. However, convection can be as much as 10 to 20 percent of the total heat transfer to an object in a large fire. The current radioactive material transportation packaging regulations include convection as a mode of heat transfer in the accident condition scenario. The current International Atomic Energy Agency Safety Series 6 packaging regulation states ''the convection coefficient shall be that value which the designer can justify if the package were exposed to the specified fire''. The current Title 10, Code of Federal Regulations, Part 71 (10CFR71) packaging regulation states ''when significant, convection heat input must be included on the basis of still, ambient air at 800 degrees C (1475 degrees F)''. Two questions that can arise in an analysts mind from an examination of the packaging regulations is whether convection is significant and whether convection should be included in the design analysis of a radioactive materials transportation container. The objective of this study is to examine the convective effects on an actual radioactive materials transportation package using a regulatory and a proposed thermal boundary condition

  18. Modeling of plasma-sheet convection: implications for substorms

    International Nuclear Information System (INIS)

    Erickson, G.M.

    1985-01-01

    An answer is suggested to the question of why plasma and magnetic energy accumulate in the Earth's magnetotail to be released in sporadic events, namely substorms. It is shown that the idea of steady convection is inconsistent with the idea of slow, approximately lossless, plasma convection in a long, closed-field-line region that extends into a long magnetotail, such as occurs during Earthward convection in the Earth's plasma sheet. This inconsistency is argued generally and demonstrated specifically using several quantitative models of the Earth's magnetospheric magnetic field. These results suggest that plasma-sheet convection is necessarily time dependent. If flux tubes are to convect adiabatically earthward, the confining magnetic pressure in the tail lobes must increase with time, and the magnetotail must evolve into a more stretched configuration. Eventually, the magnetosphere must find some way to release plasma from inner-plasma-sheet flux tubes. This suggests an obvious role for the magnetospheric substorm in the convection process. To probe this process further, a two-dimensional, self-consistent, quasi-static convection model was developed. This model self consistently includes a dipole field and can reasonably account for the effects of inner-magnetospheric shielding

  19. Le patrimoine astronomique provençal

    Science.gov (United States)

    Rous, M.; Figon, P.; Guyot, S.

    2012-12-01

    L'OSU OAMP/Institut Pythéas porte les missions de conservation, inventaire et valorisation du patrimoine. Suite à la fusion de l'Observatoire de Marseille et du Laboratoire d'Astronomie Spatiale en 2000 pour créer le Laboratoire d'Astrophysique de Marseille, le déménagement des équipes sur le site de Château-Gombert en 2008 a soulevé le problème du devenir des collections des deux sites d'origine. Nous ferons le bilan des actions passées en matière de conservation et de valorisation de ce riche patrimoine : versement à l'inventaire général du Ministère de la Culture, classement de 22 instruments au titre des Monuments Historiques, inventaire et numérisation des archives anciennes, montage d'expositions et réalisation du catalogue Telescopium, 400 ans de lunettes et de télescopes. Nous présenterons les actions en cours: mesures de conservation préventive, inventaire des archives et des instruments. Nous parlerons enfin des projets: création d'un espace d'exposition permanente, participation à des expositions temporaires.

  20. Scaling of Convection and Plate Tectonics in Super-Earths

    Science.gov (United States)

    Valencia, D. C.; O'Connell, R. J.; Sasselov, D. D.

    2006-12-01

    The discovery of three Super-Earths around different stars, possible only in the last year, prompts us to study the characteristics of our planet within a general context. The Earth, being the most massive terrestrial object in the solar system is the only planet that exhibits plate tectonics. We think this might not be a coincidence and explore the role that mass plays in determining the mode of convection. We use the scaling of convective vigor with Rayleigh number commonly used in parameterized convection. We study how the parameters controlling convection: Rayleigh number (Ra), boundary layer thickness (δ), internal temperature (T_i) and convective velocities (u) scale with mass. This is possible from the scaling of heat flux, mantle density, size and gravity with mass which we reported in Valencia, et. al 2006. The extrapolation to massive rocky planets is done from our knowledge of the Earth. Even though uncertainties arise from extrapolation and assumptions are needed we consider this simple scaling to be a first adequate step. As the mass of a planet increases, Ra increases, yielding a decrease in δ and an increase in u, while T_i increases very slightly. This is true for an isoviscous case and is more accentuated in a temperature dependent viscosity scenario. In a planet with vigorous convection (high u), a thin lithosphere (low δ) is easier to subduct and hence, initiate plate tectonics. The lithosphere also has to be dense enough (cold and thick) to have the bouyancy necessary for subduction. We calculate that a convective cycle for an isoviscous planet is τ ~ M^{-0.3} considering whole mantle convection. Meaning that if these planets have continents, the timescale for continental rearrangement is shorter (about half the Earth's for a 5 earth-mass planet). Additionally, we explore the negative feedback cycle between convection and temperature dependent viscosity and estimate a timescale for this effect.

  1. Fédéralisme, identités nationales et critique des frontières naturelles : Pierre-Joseph Proudhon (1809-1865) géographe des « États-Unis d'Europe »

    OpenAIRE

    Ferretti , Federico; Castleton , Edward

    2016-01-01

    Cet article aborde la question de la « géographicité » de l’œuvre du philosophe et militant Pierre-Joseph Proudhon, dans le cadre des études sur les relations entre géographie et anarchisme, théorie politique dont Proudhon est considéré comme l’un des fondateurs. À partir de ses textes édits et inédits, nous interrogeons le rapport de Proudhon à la géographie, notamment dans la construction de ses approches du fédéralisme et du problème des nationalités. Au sein de l’immense corpus proudhonie...

  2. Double Diffusive Natural Convection in a Nuclear Waste Repository

    International Nuclear Information System (INIS)

    Y. Hao; J. Nitao; T.A. Buscheck; Y. Sun

    2006-01-01

    In this study, we conduct a two-dimensional numerical analysis of double diffusive natural convection in an emplacement drift for a nuclear waste repository. In-drift heat and moisture transport is driven by combined thermal- and compositional-induced buoyancy forces. Numerical results demonstrate buoyancy-driven convective flow patterns and configurations during both repository heat-up and cool-down phases. It is also shown that boundary conditions, particularly on the drip-shield surface, have strong impacts on the in-drift convective flow and transport

  3. Anomalous Convection Reversal due to Turbulence Transition in Tokamak Plasmas

    International Nuclear Information System (INIS)

    Sun Tian-Tian; Chen Shao-Yong; Huang Jie; Mou Mao-Lin; Tang Chang-Jian; Wang Zhan-Hui; Peng Xiao-Dong

    2015-01-01

    A critical physical model, based on the ion temperature gradient (ITG) mode and the trapped electron mode (TEM), trying to explain the spatio-temporal dynamics of anomalous particle convection reversal (i.e., the particle convective flux reverses from inward to outward), is developed numerically. The dependence of density peaking and profile shape on the particle convection is studied. Only the inward pinch could lead to the increase of the density peaking. The validation of the critical model is also analyzed. A comparison of the estimates calculated by the model and the experimental results from the Tore Supra tokamak shows that they are qualitatively both consistent. (paper)

  4. Convection with local thermal non-equilibrium and microfluidic effects

    CERN Document Server

    Straughan, Brian

    2015-01-01

    This book is one of the first devoted to an account of theories of thermal convection which involve local thermal non-equilibrium effects, including a concentration on microfluidic effects. The text introduces convection with local thermal non-equilibrium effects in extraordinary detail, making it easy for readers newer to the subject area to understand. This book is unique in the fact that it addresses a large number of convection theories and provides many new results which are not available elsewhere. This book will be useful to researchers from engineering, fluid mechanics, and applied mathematics, particularly those interested in microfluidics and porous media.

  5. Confinement and dynamical regulation in two-dimensional convective turbulence

    DEFF Research Database (Denmark)

    Bian, N.H.; Garcia, O.E.

    2003-01-01

    In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low......-frequency bursting in the fluctuation level and the convective heat flux integral, both resulting in a state of large-scale intermittency. The first one involves the control of convective transport by sheared mean flows. This regulation relies on the conservative transfer of kinetic energy from tilted fluctuations...

  6. Tests for removal of decay heat by natural convection

    International Nuclear Information System (INIS)

    Kashiwagi, E.; Wataru, M.; Gomi, Y.; Hattori, Y.; Ozaki, S.

    1993-01-01

    Interim storage technology for spent fuel by dry storage casks have been investigated. The casks are vertically placed in a storage building. The decay heat is removed from the outer cask surface by natural convection of air entering from the building wall to the roof. The air flow pattern in the storage building was governed by the natural driving pressure difference and circulating flow. The purpose of this study is to understand the mechanism of the removal of decay heat from casks by natural convection. The simulated flow conditions in the building were assumed as a natural and forced combined convection and were investigated by the turbulent quantities near wall. (author)

  7. Le mal et ses complots imaginaires

    OpenAIRE

    Frankfurter, David

    2012-01-01

    Les récits d’abus rituels sataniques que les médias ont largement diffusés, aux États-Unis et au Royaume-Uni, entre le début des années 1980 et la fin des années 1990, soutenaient le parallèle avec les allégations avancées, durant l’Antiquité et au début des Temps modernes, contre les chrétiens, les hérétiques, les juifs ou les sorcières. Quelle est la nature de ces parallèles ? Cet article examine plusieurs types de modèles convoqués lors de diverses occurrences historiques des peurs panique...

  8. Gisèle HALIMI, La Kahina

    OpenAIRE

    ALLOUCHE-BENAYOUN, Joëlle

    2010-01-01

    Est-ce un ouvrage historique ? Est-ce un roman ? Un roman historique ? Le lecteur est désemparé dès qu’il plonge dans l’ouvrage que Gisèle Halimi a consacré à la grande héroïne judéo berbère. Si l’on comprend bien l’intérêt de l’avocate féministe – par ailleurs juive et née en Tunisie – pour cette figure féminine de résistance, la gêne s’installe au fur et à mesure de la lecture, face à l’impossibilité de l’auteur de choisir un genre littéraire et de s’y tenir. Alors que le destin légendaire ...

  9. Le littoral face aux changements climatiques

    OpenAIRE

    Mulot, Vanessa; Vigneron, Anne-Laure; Lambert-Hadid, Marie-Laure

    2011-01-01

    Le changement climatique et l’anthropisation du littoral accentuent le risque de submersion marine sur l’ensemble des côtes. Malgré l’élévation en cours du niveau des mers, l’attractivité du littoral ne décroît pas malgré la connaissance du risque. Ce risque aggravera dans les années à venir les enjeux liés à la submersion marine, parmi lesquels le danger pour les vies humaines, comme l’a malheureusement illustré l’actualité (Xynhia), mais aussi la question de la propriété des biens et des te...

  10. Quand la musique donne le ton

    DEFF Research Database (Denmark)

    Reeh, Henrik

    2017-01-01

    Le lycée Sainte-Anne de Copenhague est un établissement réputé pour les résultats de ses élèves et pour être le foyer d’une intense tradition chorale et musicologique. L’article interroge les parcours de 32 élèves d’une même classe, tous reçus au baccalauréat 2014 avec une option musique et mathé...... de comprendre cette coexistence entre musique et éducation, la relation entre « individu » et « communauté » est examinée et la notion de « culture » désigne le point d’articulation qui peut rendre compte de la dynamique pédagogique en question....

  11. Investigation of tropical diurnal convection biases in a climate model using TWP-ICE observations and convection-permitting simulations

    Science.gov (United States)

    Lin, W.; Xie, S.; Jackson, R. C.; Endo, S.; Vogelmann, A. M.; Collis, S. M.; Golaz, J. C.

    2017-12-01

    Climate models are known to have difficulty in simulating tropical diurnal convections that exhibit distinct characteristics over land and open ocean. While the causes are rooted in deficiencies in convective parameterization in general, lack of representations of mesoscale dynamics in terms of land-sea breeze, convective organization, and propagation of convection-induced gravity waves also play critical roles. In this study, the problem is investigated at the process-level with the U.S. Department of Energy Accelerated Climate Modeling for Energy (ACME) model in short-term hindcast mode using the Cloud Associated Parameterization Testbed (CAPT) framework. Convective-scale radar retrievals and observation-driven convection-permitting simulations for the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) cases are used to guide the analysis of the underlying processes. The emphasis will be on linking deficiencies in representation of detailed process elements to the model biases in diurnal convective properties and their contrast among inland, coastal and open ocean conditions.

  12. Tectonic predictions with mantle convection models

    Science.gov (United States)

    Coltice, Nicolas; Shephard, Grace E.

    2018-04-01

    Over the past 15 yr, numerical models of convection in Earth's mantle have made a leap forward: they can now produce self-consistent plate-like behaviour at the surface together with deep mantle circulation. These digital tools provide a new window into the intimate connections between plate tectonics and mantle dynamics, and can therefore be used for tectonic predictions, in principle. This contribution explores this assumption. First, initial conditions at 30, 20, 10 and 0 Ma are generated by driving a convective flow with imposed plate velocities at the surface. We then compute instantaneous mantle flows in response to the guessed temperature fields without imposing any boundary conditions. Plate boundaries self-consistently emerge at correct locations with respect to reconstructions, except for small plates close to subduction zones. As already observed for other types of instantaneous flow calculations, the structure of the top boundary layer and upper-mantle slab is the dominant character that leads to accurate predictions of surface velocities. Perturbations of the rheological parameters have little impact on the resulting surface velocities. We then compute fully dynamic model evolution from 30 and 10 to 0 Ma, without imposing plate boundaries or plate velocities. Contrary to instantaneous calculations, errors in kinematic predictions are substantial, although the plate layout and kinematics in several areas remain consistent with the expectations for the Earth. For these calculations, varying the rheological parameters makes a difference for plate boundary evolution. Also, identified errors in initial conditions contribute to first-order kinematic errors. This experiment shows that the tectonic predictions of dynamic models over 10 My are highly sensitive to uncertainties of rheological parameters and initial temperature field in comparison to instantaneous flow calculations. Indeed, the initial conditions and the rheological parameters can be good enough

  13. Le jeu de la création : Le mangeur (2005 de Ying Chen

    Directory of Open Access Journals (Sweden)

    Nicole Dunham

    2013-11-01

    Full Text Available Le théoricien James Hans définit le jeu comme une déconstruction structurante, un processus de perpétuelle remise en question. Dans Le Mangeur (2005 de Ying Chen, la narratrice revit un épisode d’une de ses vies passées où elle meurt mangée, avalée, par son père, descendant dans le « tunnel » du ventre de ce dernier. Cependant, suite à cet événement, elle se retrouve dans un autre espace-temps où elle rencontre son mari, A.. Une équivalence s’établit dans le roman entre les éléments suivants : le ventre du père, les tableaux peints par ce dernier et l’espace-temps de A., et la fenêtre. Ces éléments deviennent des aires de jeu, remettant en question les concepts de l’intérieur et de l’extérieur et du créateur et de l’œuvre. En nous servant du texte « Le Tunnel » écrit par Ying Chen, nous démontrerons que cette notion du jeu s’applique également à l’ensemble de son œuvre.

  14. Le continu contre l'espace

    Science.gov (United States)

    Salanskis, Jean-Michel

    Disons pour conclure que, en tout état de cause, la façon de concevoir philosophiquement le conflit du continu et de l'espace que nous avons trouvée chez Hegel n'est pas homogène avec le style et les modalités de la pensée mathématique: 1) d'une part, le lien classique, le lien de référence entre continu et espace en mathématiques n'est pas que l'espace serait premier et privé de pensée, et le continu second, venant dissoudre l'espace en apportant la qualité, l'infini et la pensée, mais tout au contraire, il consiste en ce que l'espace est fondé sur l'abîme infinitaire du continu ; 2) d'autre part, l'éventuel divorce entre l'espace et le continu dans l'aire mathématique n'est pas celui d'une réflexivité purement conceptuelle du continu avec un positivisme géométrique, n'équivaut pas à une rupture disciplinaire ; il est plutôt le symptôme de la dérive d'une herméneutique à l'égard d'une autre, au sein d'un continent juridique commun définissant la discipline (la mathématique ensembliste), cette dérive pouvant, à la limite, induire une refonte de ce sol juridique, sans que jamais il soit question pour autant de nier l'unité des mathématiques, à comprendre ici comme l'unité ultime de responsabilité de la communauté mathématique à l'égard des trois questions Qu'est-ce que l'espace?”, “Qu'est-ce que le continu?” et “Qu'est-ce que l'infini?”.

  15. Le bonheur est dans les airs

    OpenAIRE

    Robène, Luc; Bodin, Dominique; Héas, Stéphane

    2010-01-01

    A partir des années 1880, en France, la dimension touristique des ascensions en ballon prend une importance croissante. En marge des pratiques strictement utilitaires de l'aérostation s’élabore un univers davantage tourné vers la communion et / ou vers le face-à-face de l'homme avec la nature en altitude. L'observation du milieu aérien, la confrontation avec la sauvagerie des éléments et le bien-être que l'environnement vierge des hauteurs est susceptible de procurer aux aéronautes constituen...

  16. Le CRDI au Népal

    International Development Research Centre (IDRC) Digital Library (Canada)

    Au cours des années 1980 et 1990, les recherches menées dans le domaine de la phytosélection ont donné lieu à l'amélio- ration du rendement de céréales telles que le mil et l'orge. Par la suite, d'autres activités de recherche ont rendu les agriculteurs mieux en mesure de préserver la diversité génétique de leurs cultures ...

  17. Le stéréotype dans le roman policier

    Directory of Open Access Journals (Sweden)

    Marion François

    2009-12-01

    Full Text Available Le roman policier offre à l’étude du stéréotype une grande variété de redondances, lexicales et structurelles, qui permettent d’éclairer le concept même de genre, en fait issu du constat de stéréotypie. Il est également manifeste que contrairement aux idées reçues, les clichés font du texte policier un texte littéraire, parce qu’ils naissent d’images associées, distinctes de la réalité, qui révèlent d’ailleurs le cheminement même de l’écriture. Par ailleurs ces images jouent un rôle fondamental dans le plaisir du lecteur, comme dans les contes de fées de notre enfance. Les clichés ouvrent la porte des fantasmes : le stéréotype rejoignant l’archétype, les clichés policiers réactivent de nombreux mythes, le texte évoquant l’Autre Scène. Le constat de stéréotypie provoque l’écriture, en particulier parodique, et stimule le renouvellement et l’essaimage des clichés dans toutes sortes de textes, qui bénéficieront de la présence du déjà-lu, laquelle donne au lecteur une assise pour affronter l’inconnu et une expérience pour apprécier la nouveauté.

  18. Heat and mass transfer by free convection in a porous medium along a surface of arbitrary shape

    International Nuclear Information System (INIS)

    Hossain, M.A.; Nakayama, A.

    1993-06-01

    Free convection flow of a viscous incompressible fluid in the presence of species concentration along a surface of arbitrary shape embedded in a saturated porous medium is investigated with non-uniform surface temperature and surface concentration distributions. The equations governing the flow, derived in the form of local similarity and nonsimilarity equations, are integrated numerically using the implicit finite difference approximation together with the Keller box method. Exact solutions of the local similarity equations are also obtained and compared with the finite difference solutions. All the solutions are shown graphically in terms of local Nusselt number, Nu χ , and local Sherwood number, Sh χ , against the physical parameter ξ (which characterizes the streamwise distance along the surface from the leading edge) taking the value of the Lewis number, Le, equals 1 0, 5, and 10 while N (which defines the ratio between the buoyancy forces arise due to thermal and mass diffusion) is unity. (author). Refs, 5 figs, 1 tab

  19. Lele de l'énergie dans le développement rural | CRDI - Centre de ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    21 oct. 2010 ... L'énergie est sans aucun doute l'un des principaux moteurs du ... de ses recherches sur l'énergie, l'environnement et le développement rural. ... Durban, Mumbai et Rio illustrent la croissance rapide et la transformation qui a ...

  20. Le Peer to Peer: Vers un Nouveau Modèle de Civilization

    Directory of Open Access Journals (Sweden)

    Michel Bauwens

    2006-06-01

    Full Text Available Le « peer to peer » est la dynamique intersubjective caractéristique des réseaux distribués. Le but de cet essai est de montrer qu'il s'agit d'une véritable nouvelle forme d’organisation sociale, apte à produire et échanger des biens, à créer de la valeur. Celle-ci est la conséquence d'un nouvel imaginaire social, et possède le potentiel de devenir le pilier d'un nouveau mode d'économie politique, voire d'un nouveau type de civilisation. Pour cela, nous allons d'abord définir le P2P, décrire en bref ces manifestations, et le différencier d'autres modalités d'échange intersubjectif tel que le marché, la hiérarchie, l'économie du don.Comme principale modalité P2P nous distinguons: Les processus de production P2P, comme troisième mode de production, qui n'est ni géré par un mode hiérarchique ou par l'état, ni répondant à des impératifs de profit ou qui sont modulés par le biais des prix. Les processus de gouvernance P2P, qui gouverne ces processus de production. Les formes de propriété P2P, qui sont destine a empecher l’appropriation prive de cette production pour le commun.Afin d’examiner les characteristiques de cette nouvelle dynamique sociale, nous utilisons la typologie intersubjective de l’anthropologue Alan Page Fisque, qui distingue: 1. l'échange égalitaire (Equality Matching, c..a.d l’economie du don. 2. La relation d’autorité (Authority Ranking tel qu’elle s’exprime dans le mode hierarchique. 3. le marché (Market Pricing. 4. la participation commune (Communal Shareholding.En conclusion, nous examinons les possibilites d’expansion de ce nouveau mode sociale et son insertion dans l’economie capitaliste, en nous nous posons la question: le P2P peut-il etre concu comme alternative sociale et economique aux modeles existants.