193,916 research outputs found
A numerical method to solve the Stokes problem with a punctual force in source term
The aim of this note is to present a numerical method to solve the Stokes
problem in a bounded domain with a Dirac source term, which preserves
optimality for any approximation order by the finite-element method. It is
based on the knowledge of a fundamental solution to the associated operator
over the whole space. This method is motivated by the modeling of the movement
of active thin structures in a viscous fluid.Comment: Comptes Rendus M{\'e}canique, Elsevier, 2015,
http://www.sciencedirect.com/science/article/pii/S163107211400181
Benthic diatoms and some environmental conditions in three lowland streams
This article reports on the ecological preferences of benthic diatoms in relation to pH, conductivity and organic pollution-eutrophication and their tolerance spectrums. Three Pampean streams subjected to different human impacts were studied. The bottom substrate of these streams is mostly composed of slime-clay with low proportions of gravel and sand; in consequence, the epipelon is the most represented benthic community. Samples were taken seasonally between 1997-1998 at 9 sampling sites. In each sampling station ten sub-samples were collected by pipetting a superficial layer (5-10 mm) of sediment from different places. Physico-chemical parameters were measured. Considering the ranges of pH, conductivity and organic pollution-eutrophication the diatom's tolerance spectrums were established. 162 diatom species were identified. More than 50 % of species occurred in sites where the conductivity was lower than 600 ÎŒS cm-1. More than 50 % of species had their preference range in sites with moderate organic matter and nutrient content. Diatom species found show defined preferences for organic pollution-eutrophication, but show less consistent responses for conductivity and, particularly, hydrogen ions content.Fil: Licursi, Magdalena. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de LimnologĂa "Dr. RaĂșl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de LimnologĂa; ArgentinaFil: Gomez, Nora. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de LimnologĂa "Dr. RaĂșl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de LimnologĂa; Argentin
Advances in martensitic transformations in Cu-based shape memory alloys achieved by in situ neutron and synchrotron X-ray diffraction methods
This article deals with the application of several X-ray and neutron diffraction methods to investigate the mechanics of a stress induced martensitic transformation in Cu-based shape memory alloy polycrystals. It puts experimental results obtained by two different research groups on different length scales into context with the mechanics of stress induced martensitic transformation in polycrystalline environment
Programme D'appui Aux RĂ©formes du Secteur de L'Ă©nergie et Ă la Gouvernance FinanciĂšre
The report presents the aid give by BAD to reform industrial sector in Comoros
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Changement grammatical et discursif en français multiculturel de la région parisienne : éléments de comparaison
Cet article cherche Ă comparer la variation et le changement dans deux domaines linguistiques, Ă savoir la grammaire et le discours. Il prĂ©sente les rĂ©sultats du projet « Multicultural London English â Multicultural Paris French » et sâinterroge sur les diffĂ©rences dans lâusage des traits innovants et leur corrĂ©lation avec certaines catĂ©gories sociales. Du cĂŽtĂ© grammatical, la recherche se concentre en particulier sur lâusage des interrogatives indirectes in situ telles que 'je sais pas câest qui' et 'je sais ça veut dire quoi', frĂ©quemment utilisĂ©es Ă lâoral chez certains locuteurs. Du cĂŽtĂ© pragmatico-discursif, elle discute de lâutilisation des particules dâextension (et tout, et tout ça). LâĂ©tude rĂ©vĂšle que la distribution des innovations discursives nâest pas la mĂȘme que celle des innovations grammaticales, dont lâusage est davantage clivĂ© en fonction des catĂ©gories sociales. Lâarticle tente dâapporter des Ă©clairages sur les processus de grammaticalisation et de changement, en sâinterrogeant sur lâexistence dâun français multiculturel typiquement « jeune » ou typiquement « parisien »
Génératrice à aimants permanents à flux axial à grand diamÚtre avec entrefer immergé
Cette Ă©tude propose une mĂ©thode de modĂ©lisation et de conception adaptĂ©e aux machines Ă flux axial et Ă Double Stator (poly-entrefer) destinĂ©e Ă ĂȘtre intĂ©grĂ©e comme gĂ©nĂ©ratrice pour une hydrolienne RIM-DRIVEN de grande puissance. La particularitĂ© du concept RIM-DRIVEN ou Ă entrainement circonfĂ©rentiel rĂ©side dans le fait que la machine Ă©lectrique se situe sur la pĂ©riphĂ©rie de lâhĂ©lice. De plus, dans cette Ă©tude, lâentrefer de la machine est considĂ©rĂ© immergĂ© dans lâeau de mer. Les particularitĂ©s du systĂšme imposent de mettre au point des modĂšles de dimensionnement adaptĂ©s. Ainsi, un modĂšle Ă©lectromagnĂ©tique analytique 2D inversĂ© permettant le calcul des dimensions gĂ©omĂ©triques principales est prĂ©sentĂ©. De mĂȘme, un modĂšle thermique spĂ©cifique aux machines Ă entrefer immergĂ© est dĂ©crit. Ces modĂšles permettent dâestimer la masse et le coĂ»t des parties actives. Cette machine Ă flux axial est comparĂ©e en termes de coĂ»ts matiĂšres, masses et comportement thermique avec une machine Ă flux radial Ă aimants permanents dimensionnĂ©e pour un mĂȘme cahier des charges. Il en ressort clairement que la machine Ă flux axial double stator est thermiquement moins contrainte que les machines Ă simple stator
Development of an apparatus for obtaining molecular beams in the energy range from 2 to 200 eV
The formation and detection of molecular beams obtained by charge exchange from a low-energy ion source is discussed. Dispersion in energy of the ion source was measured and problems concerning detection of neutral beams were studied. Various methods were used, specifically secondary electron emissivity of a metallic surface and ionization of a gas target with a low ionization voltage. The intensities of neutral beams as low as 10 eV are measured by a tubular electron multiplier and a lock-in amplifier
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