1,473 research outputs found
Toward a structural understanding of turbulent drag reduction: nonlinear coherent states in viscoelastic shear flows
Nontrivial steady flows have recently been found that capture the main
structures of the turbulent buffer layer. We study the effects of polymer
addition on these "exact coherent states" (ECS) in plane Couette flow. Despite
the simplicity of the ECS flows, these effects closely mirror those observed
experimentally: Structures shift to larger length scales, wall-normal
fluctuations are suppressed while streamwise ones are enhanced, and drag is
reduced. The mechanism underlying these effects is elucidated. These results
suggest that the ECS are closely related to buffer layer turbulence.Comment: 5 pages, 3 figures, published version, Phys. Rev. Lett. 89, 208301
(2002
Digital modelling and stereolithographic production of a Homo Erectus skull
The National Museum of Natural History has been carrying out, over the last several years, a study of hominid fossil skulls, which have been discovered in different regions of the world. The aim of the palaeoâanthropological study of these skulls is to reconstruct the genealogic tree of the evolution of man and to understand better, the diversity of the homo Erectus species on the different continents. Currently, digital techniques and those of rapid prototyping offer a solution to these problems by allowing the virtual or physical reconstitution of the skulls for scientific study. This paper presents this new perspective for the world of palaeontology
Did the first inhabitants of the Caune de lâArago between 700,000 and 400,000 years BP have domesticated fire? Did they know how to light the fire at will?
This note is a comment to the article âSearch for early traces of fire in the Caune de lâArago at Tautavel (Eastern Pyrenees, France), combining magnetic susceptibility measurements, microscopic observations, and Raman analysisâ by Deldicque et al., published online on July 29, 2021, in Comptes Rendus GĂ©oscience in Volume 353, 2021, pages 247-264, https://doi.org/10.5802/crgeos.66. The authorsâ response to this comment has also been published in Comptes Rendus GĂ©oscience in Volume 354, 2022, pages 47-50, https://doi.org/10.5802/crgeos.114
Did the first inhabitants of the Caune de lâArago between 700,000 and 400,000 years BP have domesticated fire? Did they know how to light the fire at will?
This note is a comment to the article âSearch for early traces of fire in the Caune de lâArago at Tautavel (Eastern Pyrenees, France), combining magnetic susceptibility measurements, microscopic observations, and Raman analysisâ by Deldicque et al., published online on July 29, 2021, in Comptes Rendus GĂ©oscience in Volume 353, 2021, pages 247-264, https://doi.org/10.5802/crgeos.66. The authorsâ response to this comment has also been published in Comptes Rendus GĂ©oscience in Volume 354, 2022, pages 47-50, https://doi.org/10.5802/crgeos.114
Un gisement Levalloisien dans la DrĂŽme, au Buis les Baronies
Ce gisement dĂ©couvert par les frĂšres Catelan et briĂšvement signalĂ© par H. Muller est situĂ© dans la ville mĂȘme du Buis les Baronies, au lieu-dit Bas-Guillotte. L'outillage accompagnĂ© d'un peu de faune a Ă©tĂ© trouvĂ© dans la partie supĂ©rieure d'une terrasse de l'OuvĂšze, Ă 25 m au dessus du thalweg actuel ; il fut dĂ©posĂ© au MusĂ©e Calvet d'Avignon par le Dr Arlaud sur la demande de F. Bourdier. MM GagniĂšre et Germand nous ont facilitĂ© son Ă©tude, faite en utilisant la mĂ©thode statistique de F. Bordes et sa nomenclature
Correlation of Quaternary Shorelines in Meridional France With the Alpine Glacial Chronology
In the meridional Alps, between the horizon corresponding to the maximum plancian transgression and actual sea level, a number of transgressive shorelines occur at approximately the following altitudes : 165 m - end of Pliocene or lower Calabrian transgression ; 108 m - Donau-GĂŒnz interglacial or upper Calabrian transgression ; 83 m - GĂŒnz-Mindel interglacial or Sicilian ; 33 m - Inter-Mindel ; 26 m - Inter-Mindel ; 23 m - Mindel-Riss interglacial or Milazian ; 17 m - Inter-Riss ; 12 m - Riss-WĂŒrm interglacial or Tyrrhenian ; 5 m - Inter-WĂŒrm or Neo-Tyrrhenian.The shorelines have been dated on the basis of their stratigraphic relations to prehistoric horizons and paleontologic content at localities where excavations have been made (Vallonet, Terra Amata, Lazaret). These Quaternary beaches have been uplifted as a result of isostacy, to altitudes that cross-cut, in terms of time elapsed since their desposition. The western end of the meridional Alps has been raised at the rate of about 10 m every 100 000 years.Dans les Alpes Maritimes, entre le niveau correspondant au maximum de la transgression plaisancienne et celui de la mer actuelle, de nombreuses lignes de rivage transgressif s'Ă©chelonnent aux altitudes approximatives de 165 m (fin du PliocĂšne ou Calabrien transgressif infĂ©rieur), 108 m (Donau-GĂŒnz ou Calabrien transgressif supĂ©rieur) 83 m (GĂŒnz-Mindel ou Sicilien) 33 m (Inter-Mindel), 26 m (Inter Mindel) 23 m (Mindel-Riss ou Milazzien), 17 m (Inter-Riss), 12 m (Riss-WĂŒrm ou TyrrhĂ©nien), 5 m (Inter-WĂŒrm ou NĂ©o thyrrhĂ©nien).Elles ont pu ĂȘtre datĂ©es grĂące Ă leur relation avec des gisements prĂ©historiques et palĂ©ontologiques (Vallonnet, Terra Amata, Lazaret) dans lesquels nous avons effectuĂ© des fouilles. Ces lignes de rivage quaternaire, ont Ă©tĂ© portĂ©es Ă des altitudes croissantes en fonction du temps Ă©coulĂ© depuis leur dĂ©pĂŽt, par les phĂ©nomĂšnes d'isostasie qui ont soulevĂ© l'extrĂ©mitĂ© mĂ©ridionale du Massif Alpin au rhyhme d'environ 10 m tous les 100 000 ans
Shell Model for Drag Reduction with Polymer Additive in Homogeneous Turbulence
Recent direct numerical simulations of the FENE-P model of non-Newtonian
hydrodynamics revealed that the phenomenon of drag reduction by polymer
additives exists (albeit in reduced form) also in homogeneous turbulence. We
introduce here a simple shell model for homogeneous viscoelastic flows that
recaptures the essential observations of the full simulations. The simplicity
of the shell model allows us to offer a transparent explanation of the main
observations. It is shown that the mechanism for drag reduction operates mainly
on the large scales. Understanding the mechanism allows us to predict how the
amount of drag reduction depends of the various parameters in the model. The
main conclusion is that drag reduction is not a universal phenomenon, it peaks
in a window of parameters like Reynolds number and the relaxation rate of the
polymer
Tende â Mont Bego : attelages de la zone IV, secteur des Merveilles
Identifiant de l'opĂ©ration archĂ©ologique : 7881 Date de l'opĂ©ration : 2007 (RE) Inventeur(s) : De Lumeley Henry (CNRS) ; Ăchassoux Annie (SUP) ; Romain Odile (MUS) Le relevĂ© des gravures rupestres de la rĂ©gion du mont Bego entrepris par Henry de Lumley, sur un territoire dâenviron 2 000 ha Ă lâest de Tende, est en cours de vĂ©rification (BSR PACA, 2006 : 94-96). Chaque annĂ©e de nouvelles roches, gĂ©nĂ©ralement peu gravĂ©es, sâinscrivent dans le corpus : il sâagit souvent dâun groupe de cupules Ă©p..
Nice â Grotte du Lazaret, unitĂ© archĂ©ostratigraphique UA27
Identifiant de l'opĂ©ration archĂ©ologique : 7880 Date de l'opĂ©ration : 2007 (FP) Inventeur(s) : De Lumeley Henry (CNRS) ; Desclaux Emmanuel (COL) ; Valensi Patricia (COL) La grotte du Lazaret, situĂ©e sur les pentes du mont Boron Ă Nice, livre une succession dâoccupations humaines attribuĂ©es aux AntĂ©nĂ©andertaliens (derniers Homo erectus dâEurope) (Lumley et al., 2004). Le chantier de fouille sâĂ©tend sur environ 90 m2 et se situe en arriĂšre du porche de lâentrĂ©e, dans la partie est de la caverne..
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