Experimental study of parametric subharmonic instability for internal waves

Internal waves are believed to be of primary importance as they affect ocean mixing and energy transport. Several processes can lead to the breaking of internal waves and they usually involve non linear interactions between waves. In this work, we study experimentally the parametric subharmonic instability (PSI), which provides an efficient mechanism to transfer energy from large to smaller scales. It corresponds to the destabilization of a primary plane wave and the spontaneous emission of two secondary waves, of lower frequencies and different wave vectors. Using a time-frequency analysis, we observe the time evolution of the secondary waves, thus measuring the growth rate of the instability. In addition, a Hilbert transform method allows the measurement of the different wave vectors. We compare these measurements with theoretical predictions, and study the dependence of the instability with primary wave frequency and amplitude, revealing a possible effect of the confinement due to the finite size of the beam, on the selection of the unstable mode

Optimisation du traitement thermique des tubes d'aluminium 6063 étirés à froid

L'étirage à froid des tubes d'aluminium extrudés améliore leur fini de surface et augmente leur résistance ; cependant cela diminue leur ductilité. Pour atteindre la ductilité exigée lors des opérations subséquentes de pliage, les tubes sont traités thermiquement après l'étirage à froid. Pour résoudre un problème industriel, ce projet vise à déterminer les conditions de traitement thermique optimales (temps et température) pour obtenir des propriétés mécaniques (limite élastique, limite ultime et allongement à la rupture) exigées par la condition T832 de l’alliage 6063 spécifiée par la norme ASTM associée et éliminer les pertes dues à des ruptures lors du pliage des tubes. De plus, le projet expose l’influence de la quantité de déformation par étirage sur les propriétés après le traitement thermique. Enfin, il cherche à déterminer si le temps de montée en température du four peut contribuer au traitement thermique afin d'augmenter la productivité du procédé.Cold drawing of extruded aluminium tubes not only improves the surface quality but also increases their strength, however ductility of the tubes decreases. To improve the ductility required for the following bending operations, tubes are heat treated after the cold drawing operation. To resolve an industrial problem, this research aims to determine the optimal heat treatment conditions for obtaining the required mechanical properties (yield strength, ultimate tensile strength and elongation to fracture) based on the ASTM 6063-T832 temper and also avoiding scraps caused by failure during the bending operation. Moreover, this research investigates the effect of the amount of prestrain imposed by cold drawing on mechanical properties after the heat treatment. Finally, it is interesting to know if the heating period inside the furnace before reaching the targeted temperature could be exploited as part of the required heat treatment to increase the productivity of the process

Finite-size effects in parametric subharmonic instability

The parametric subharmonic instability in stratified fluids depends on the frequency and the amplitude of the primary plane wave. In this paper, we present experimental and numerical results emphasizing that the finite width of the beam also plays an important role on this triadic instability. A new theoretical approach based on a simple energy balance is developed and compared to numerical and experimental results. Because of the finite width of the primary wave beam, the secondary pair of waves can leave the interaction zone which affects the transfer of energy. Experimental and numerical results are in good agreement with the prediction of this theory, which brings new insights on energy transfers in the ocean where internal waves with finite-width beams are dominant

VLTI status update: a decade of operations and beyond

We present the latest update of the European Southern Observatory's Very Large Telescope interferometer (VLTI). The operations of VLTI have greatly improved in the past years: reduction of the execution time; better offering of telescopes configurations; improvements on AMBER limiting magnitudes; study of polarization effects and control for single mode fibres; fringe tracking real time data, etc. We present some of these improvements and also quantify the operational improvements using a performance metric. We take the opportunity of the first decade of operations to reflect on the VLTI community which is analyzed quantitatively and qualitatively. Finally, we present briefly the preparatory work for the arrival of the second generation instruments GRAVITY and MATISSE.Comment: 10 pages, 7 figures, Proceedings of the SPIE, 9146-1

The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI

The GRAVITY instrument has been revolutionary for near-infrared interferometry by pushing sensitivity and precision to previously unknown limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer (VLTI) in GRAVITY+, these limits will be pushed even further, with vastly improved sky coverage, as well as faint-science and high-contrast capabilities. This upgrade includes the implementation of wide-field off-axis fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser guide stars in an upgraded facility. GRAVITY+ will open up the sky to the measurement of black hole masses across cosmic time in hundreds of active galactic nuclei, use the faint stars in the Galactic centre to probe General Relativity, and enable the characterisation of dozens of young exoplanets to study their formation, bearing the promise of another scientific revolution to come at the VLTI.Comment: Published in the ESO Messenge

From Sea to Sea: Canada's Three Oceans of Biodiversity

Evaluating and understanding biodiversity in marine ecosystems are both necessary and challenging for conservation. This paper compiles and summarizes current knowledge of the diversity of marine taxa in Canada's three oceans while recognizing that this compilation is incomplete and will change in the future. That Canada has the longest coastline in the world and incorporates distinctly different biogeographic provinces and ecoregions (e.g., temperate through ice-covered areas) constrains this analysis. The taxonomic groups presented here include microbes, phytoplankton, macroalgae, zooplankton, benthic infauna, fishes, and marine mammals. The minimum number of species or taxa compiled here is 15,988 for the three Canadian oceans. However, this number clearly underestimates in several ways the total number of taxa present. First, there are significant gaps in the published literature. Second, the diversity of many habitats has not been compiled for all taxonomic groups (e.g., intertidal rocky shores, deep sea), and data compilations are based on short-term, directed research programs or longer-term monitoring activities with limited spatial resolution. Third, the biodiversity of large organisms is well known, but this is not true of smaller organisms. Finally, the greatest constraint on this summary is the willingness and capacity of those who collected the data to make it available to those interested in biodiversity meta-analyses. Confirmation of identities and intercomparison of studies are also constrained by the disturbing rate of decline in the number of taxonomists and systematists specializing on marine taxa in Canada. This decline is mostly the result of retirements of current specialists and to a lack of training and employment opportunities for new ones. Considering the difficulties encountered in compiling an overview of biogeographic data and the diversity of species or taxa in Canada's three oceans, this synthesis is intended to serve as a biodiversity baseline for a new program on marine biodiversity, the Canadian Healthy Ocean Network. A major effort needs to be undertaken to establish a complete baseline of Canadian marine biodiversity of all taxonomic groups, especially if we are to understand and conserve this part of Canada's natural heritage

Comparaison des techniques CLHP-UV, UV/visible-IRTF et Spectroscopie Raman, appliquées au contrôle de qualité analytique libératoire des préparations injectables en milieu de soins (application à la classe des anthracyclines en cancérologie)

PARIS-BIUP (751062107) / SudocSudocFranceF

L'exploration de l'image dans l'abîme de la discursivité (une analyse picturale de The Tunnel de William H. Gass)

Univers cauchemardesque et rappel d'un siècle où images et discours ont été mis au service de la propagande de régimes fascistes et totalitaires, The Tunnel ne fait pas que s'interroger sur le rôle de l'image aux côtés du discours mais met véritablement en crise la représentation en renvoyant l'image au discours et inversement. William Gass crée à partir de ce jeu intersémiotique la possibilité d'un espace de résistance et de désobéissance face à une narration dont la visée destructrice et autoritaire donne à voir les fondements de la mentalité de ce qu'il a nommé le fascisme du cœur . L'objectif de cette thèse a été par conséquent d'observer la façon dont l'image négocie sa place dans le textepour rivaliser avec le discours. Alors que la première partie de cette étude porte sur le statut de l'image par rapport au discours, sur leur altérité en somme, la deuxième partie analyse, à l'appui de la notion d' iconotexte définie par Michael Nerlich et Alain Montandon, les expérimentations intersémiotiques qui visent à redonner au langage sa portée dialogique, de la lettre protéiforme à la phrase-calligramme. La troisième partie de cette étude vise à observer comment les transactions formelles entre narration et photographie dans The Tunnel participent à l'instauration d'une écriture photographique rejoignant la poétique du pictural définie par Liliane Louvel. Le récit de rêve, lieu privilégié du dédoublement dans l'élaboration d'une fiction au carré , fait quant à lui l'objet de la dernière partie de cette étude consacrée à l'image produite par le texte de métafiction, ou discours imagé .The Tunnel questions representation as it sets images against discourse and reminds us of a century where image and discourse have served the propaganda of fascist and totalitarian regimes. The complex inter-semiotic play developed by William Gass creates a space of disobedience and résistance against a narration whose authoritarian and destructive goals exposes a mentality that the author called the "fascism of the heart".The objective of this dissertation is to observe the way image negotiates its place in the text in order to compete with a narrative discourse. In the first part of this study, I focus on the opposite roles of image and speech. The second part deals with the notion of "iconotext", as defined by Michael Nerlich and Alain Montandon, through the analysis of inter-semiotic experimentations in an attempt to restore the dialogic dimension of language from protean letters to sentences that shape calligrams. The third part of this study observes how a formal transaction between narration and photography participates in the foundation of a photographical writing that echoes the pictorial poetics defined by Liliane Louvel. The fourth and last part is dedicated to dream narratives, that relate to metafiction as they are stories within stories, and investigates images as products of figurative speech.PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

La mer cache en ses flots ... Poésie de Paul Bourget. Adaptation musicale par Ph. Bellenot.

4 p. 34 cm. For spoken voice and piano with superlinear French words. In binders collection