A study of an aero-elastic twisted inverted wing in close ground proximity

Aero-elastic deformation of an inverted wing in close ground proximity can have an effect on the aerodynamic loads experienced and the downstream trajectory of the primary tip vortex. These differences have practical application to the front wing installations used in typical open-wheel auto-sport vehicle configurations. A series of moving ground wind tunnel measurements of aerodynamic lift and drag on a simplified inverted-wing-body configuration, at Re/m in the range 1.4 x 106 < Re/m < 2.8 x 106, were compared with RANS CFD simulations on both the un-deflected and deformed body. Measurements of model deformation were obtained using a videogrammetry technique. RANS CFD simulations appear to over-estimate the magnitude of the (-ve) lift coefficient, in very close ground proximity, compared to the experimental data. This may possibly be due to difficulty capturing the interaction between the wing tip vortex and a region of flow separation near the trailing edge, which is particularly apparent at low ground clearances

Influence des facteurs de l'environnement rhizosphérique sur la régulation de l'antagonisme de Pseudomonas spp. fluorescents vis-à-vis des pathogènes telluriques

International audienc

Semi-alicyclic polyimides as potential membrane oxygenators: Rheological implications on film processing, morphology and blood compatibility

Two polyimide structures were prepared from an alicyclic dianhydride and aromatic diamines, containing or lacking fluorine, and were tested as potential membrane oxygenators. First, the solution rheological properties were investigated to evaluate their effect on film processing by tape casting. Velocity and shear rates profiles were simulated to determine the shearing conditions during tape casting and transfer them in the flow curves. Proper films were obtained at a viscosity corresponding to a concentration in entangled regime, where pseudoplastic behavior is still noticed at shear rates beneath the blade. Theoretical predictions of gas permeability indicated a good oxygen (O2) exchange and carbon dioxide (CO2) removal through the studied polymers. Atomic force microscopy (AFM) scans revealed a morphology characterized by an intrinsic porosity. The pore size, uniformity and size distribution was affected by the structure of the diamine moiety. The interactions of blood with polyimide films indicated no prevalent adhesion of cells or plasma proteins. The results showed that the examined samples have adequate properties for potential membrane oxygenator applications

La présence de Ggt, agent du piétin-échaudage, favorise la colonisation des racines de blé par une souche antagoniste sélectionnée de Pseudomonas spp. fluorescent

International audienc

The influence of polysilane chemical structure on optical properties, rubbed film morphology and LC alignment

Polysilane films were prepared by the drop casting method and their optical and morphological properties have been analyzed in order to investigate their suitability as alignment layers for nematic molecules. The samples do not absorb the radiations in the visible domain, particularly those containing methylhydrosilyl units, and present a transmittance of about 90% starting from 390 to 1100 nm. The optical band-gap is higher than 3.26 eV for all polysilanes indicating a low probability of optical absorption processes in the visible range. The morphology of the pristine samples shows isotropically distributed granular formations. The polymer surface was oriented by rubbing with two types of velvet: one with short fibers and the other with long fibers. The latter generates higher surface anisotropy, as shown by the reduction of the surface texture direction index values. The presence of methylhydrosilyl units allows a denser packing of the polymer structure and thus finer surface periodicities, leading to better orientation of the nematic molecules on the polysilane surface

La lutte biologique contre les champignons pathogènes du sol: gestion des populations naturelles d'antagonistes et compatibilité avec l'introduction de microorganismes utiles

International audienc

Polyimide Layers with High Refractivity and Surface Wettability Adapted for Lowering Optical Losses in Solar Cells

The performance of photovoltaics with superstrate configuration is limited by the rigidity and low refractivity of a classical glass cover. In this work, two polyimides (PIs) and two copolyimides combined in the main chain cycloaliphatic moieties, aromatic sequences, chalcogen atoms, and having/lacking fluorine atoms, are proposed as shielding covers for solar cells. The samples containing small cycloaliphatic moieties displayed high transmittance above 80% at 550 nm. The refractive index values under changeable wavelengths and temperatures were shown to influence the magnitude of the reflection losses. At the sample interface with the transparent electrode, optical losses were reduced (~0.26%) in comparison to the classical glass (~0.97%). The samples with the best optical features were further subjected to a surface treatment to render the self-cleaning ability. For this, a new approach was used residing in irradiation with the diffuse coplanar surface barrier discharge (DCSBD), followed by spraying with a commercial substance. Scanning electron microscopy and atomic force microscopy scans show that the surface characteristics were changed after surface treatment, as indicated by the variations in root mean square roughness, surface area ratio, and surface bearing index values. The proposed PI covers diminish the optical losses caused by total internal reflection and soiling, owing to their adapted refractivity and superhydrophobic surfaces (contact angles > 150°), and open up new perspectives for modern photovoltaic technologies

Daños macroscópicos y microscópicos causados por un aumento de la radiación ultravioleta-b en dos briófitos acuáticos del parque natural de sierra cebollera (La Rioja, norte de España)

El adelgazamiento de la capa de ozono estratosférico como consecuencia de la emisión antropogénica de halocarburos está causando un aumento en la radiación ultravioleta-B (UV-B: 280-315 nm) que llega a la superficie terrestre. Para evaluar los efectos que este aumento puede tener sobre los briófitos acuáticos y su capacidad bioindicadora, se han cultivado dos especies en el laboratorio durante 82 días bajo radiación UV-B suplementaria, y se han analizado las respuestas macro- y microscópicas. Así mismo, se ha comprobado el efecto de la temperatura de cultivo (2 º y 10ºC) en la aparición de daños. Las especies utilizadas han sido el musgo "Fontinalis antpyretica" y la hepática foliosa "Jungermannia exsertfolia" subsp. "cordifolia", procedentes del Parque Natural de Sierra Cebollera (La Rioja, norte de España). El musgo resultó sensible tanto al frío como al aumento en la radiación UV-B y los daños causados por ambos factores eran bastante parecidos: color marrón, depresión del crecimiento, desarrollo del cuerpo fibrilar central, desaparición de los cloroplastos, y presencia de protoplastos grumoso-vesiculosos, vacuolizados y en último término hialinos ("células vacías"). Estos síntomas son poco específicos y se han descrito en varios musgos pleurocárpicos como consecuencia de procesos de senescencia y estrés, tanto natural como antropogénico. La única respuesta específica al aumento en radiación UV-B fue un cambio de color en la pared celular, que pasaba de amarillo a marrón-anaranjado. Esto podría suponer o bien un aumento en la síntesis de compuestos absorbentes de radiación UV o bien la aparición de compuestos de degradación de la pared celular. La hepática estudiada resultó sensible a la radiación UV-B sólo cuando se combinaba con un estrés por frío, y entonces presentaba filidios de color marrón grisáceo y depresión del crecimiento, pero escasos daños celulares. El resto de muestras tenían un aspecto muy parecido entre sí y completamente normal, tanto a nivel macro- como microscópico. La mayor tolerancia de "Juogermannia exsertifolia" subsp. "cordifolia" respecto a "F. Antjpyretica" podría deberse a la presencia de compuestos absorbentes de radiación UV en los protoplastos de la primera especie. Esta tolerancia p tener un reflejo ecológico y corológico, de acuerdo con el carácter marcadamente montano de la hepática, puesto que tanto el frío como la radiación UY-E son Es sea habituales en sus hábitats típicos. Nuestros resultados indican que la sensibilidad de los briófítos acuáticos aumento en la radiación UY-B depende de la especie, y por lo tanto su utilización como bioindicadores debe estar basada en una adecuada selección de especies variables morfológicas. El cambio de color de las paredes de "E antipyretica" parece ser el síntoma más específico y adecuado para este objetivo