Excentricité et forme des sections transversales de bois. Définitions, méthodologie, exemples sur l'épicéa commun (Picea abies Karst.)

Cette note fait le point sur plusieurs définitions importantes lorsqu'il s'agit de caractériser l'asymétrie de la croissance du bois en section transversale. Lorsque le contour des rondelles est discrétisé par intersection avec un certain nombre de rayons pairs (2n) équirépartis en direction sur [0.2pi) et originaires de la moelle, il est possible de définir le centre de gravité des points, de la surface et du contour. Ces points sont généralement distincts et sensibles au nombre de rayons utilisés ainsi qu'à leurs orientations. Pour calculer l'excentricité (position de la moelle par rapport au centre de gravité de la surface de la rondelle), ou le méplat (rapport entre le plus grand diamètre de la rondelle et son perpendiculaire, passants tous deux par le centre de la rondelle) l'utilisation de I'un ou l'autre de ces points donne des résultats très différents. Les applications sont réalisées pour des figures géométriques simples (cercle. ellipse) et pour 168 rondelles d'épicéa commu

Processus d’acculturation et problèmes de traduction : le théâtre de Wole Soyinka

Processus d'acculturation et problèmes de traduction : le théâtre de WoIe Soyinka — Cette étude traite des déterminations linguistiques et culturelles que fait peser une culture-source peu familière sur la traduction en français du théâtre de langue anglaise de l'auteur nigérian WoIe Soyinka, prix Nobel de littérature (1986). L'ethnie yoruba fournit à ces pièces une langue polytonale, une civilisation enracinée dans le sacré et un théâtre ambulant opératique. Les influences occidentales se reconnaissent à l'utilisation de l'anglais standard par les personnages membres de l'élite cultivée, de mots-clés révélateurs d'idéologies par les personnages représentatifs et de modèles littéraires occidentaux. La composante anglo-nigériane, synthèse plus ou moins cohérente, mais toujours très riche, de toutes les influences, se distingue par l'emploi de l'anglais pidgin, d'un anglais nigérianisé et d'un style heurté, parfois hermétique, exprimant la souffrance et la rébellion. Les trois composantes de ce théâtre (indissociables dans la réalité) exigent du traducteur des techniques variées, une culture étendue et une grande sensibilité poétique. Il revient au traducteur francophone de trouver des équivalents français susceptibles de rendre des faits de civilisation africains, issus de processus d'acculturation complexes.Acculturation process and translation problems: the theatre of WoIe Soyinka — This paper deals with the linguistic and cultural determinations imposed by a little-known (Anglo-African) source-culture on translations into French of plays by the Anglophone Nigerian writer, 1986 Nobel-prize winner, WoIe Soyinka. The Yoruba background provides these plays with a tone-language, a culture rooted in animism and techniques borrowed from a partly traditional, partly modern itinerant operatic theatre. Western influences show through in the use of standard English by the plays' Western-educated protagonists, of key-words and phrases pointing to the plays' ideologies and of Western literary models. The Anglo-Nigerian elements, forming a rich though at times hardly coherent synthesis of every source and influence, stand forth in the prevalence of Nigerian pidgin, image-laden Nigerianized English and a tense, jerky and even abstruse style expressing both suffering, rebellion and a search for ultimate truths

Directed transport in a classical lattice with a high-frequency driving

We analyze the dynamics of a classical particle in a spatially periodic potential under the influence of a periodic in time uniform force. It was shown in [S.Flach, O.Yevtushenko, Y. Zolotaryuk, Phys. Rev. Lett. 84, 2358 (2000)] that despite zero average force, directed transport is possible in the system. Asymptotic description of this phenomenon for the case of slow driving was developed in [X. Leoncini, A. Neishtadt, A. Vasiliev, Phys. Rev. E 79, 026213 (2009)]. Here we consider the case of fast driving using canonical perturbation theory. An asymptotic formula is derived for the average drift velocity as a function of the system parameters and the driving law. We show that directed transport arises in an effective Hamiltonian that does not possess chaotic dynamics, thereby clarifying the relation between chaos and transport in the system. Sufficient conditions for transport are derived.Comment: 5 page

Multivariate dynamic model for ordinal outcomes

Individual or stand-level biomass is not easy to measure. The current methods employed, based on cutting down a representative sample of plantations, make it possible to assess the biomasses for various compartments (bark, dead branches, leaves, . . .). However, this felling makes individual longitudinal follow-up impossible. In this context, we propose a method to evaluate individual biomasses by compartments when these biomasses are taken as ordinals. Biomass is measured visually and observations are therefore not destructive. The technique is based on a probit model redefined in terms of latent variables. A generalization of the univariate case to the multivariate case is then natural and takes into account the dependency between compartment biomasses. These models are then extended to the longitudinal case by developing a Dynamic Multivariate Ordinal Probit Model. The performance of the MCMC algorithm used for the estimation is illustrated by means of simulations built from known biomass models. The quality of the estimates and the impact of certain parameters, are then discussed

On fundamental mechanisms in dye sensitized solar cells through the behaviour of different mesoporous titanium dioxide films

Understanding mechanisms in DSSCs is fundamental for their improvement; this includes the nanocrystalline semiconducting layer behaviour. Different mesoporous TiO2 layers are fabricated and analyzed for possible use in DSSC solar cells. The preparations included the addition of P123 triblock copolymer as structuring agent to the synthesized anatase sol. This preparation was also mixed with Degussa P25 nanoparticles in one case and polystyrene latex in another. Mesoporous mixed TiO2-SiO2 thin layers were also analyzed. The diverse morphology and features are studied by microscopic techniques and by means of spectral quantum efficiency of a photoelectrochemical cell (PEC) that uses as photoelectrode the unsensitized porous TiO\_2 layer. Contact angle measurements are also performed. We have found that a very high specific area due to very small nanocrystals and small pores can hinder electrolyte penetration in the pores formed by TiO\_2 nanograins, affecting photoelectrodes efficiency

Survey on Solar X-ray Flares and Associated Coherent Radio Emissions

The radio emission during 201 selected X-ray solar flares was surveyed from 100 MHz to 4 GHz with the Phoenix-2 spectrometer of ETH Zürich. The selection includes all RHESSI flares larger than C5.0 jointly observed from launch until June 30, 2003. Detailed association rates of radio emission during X-ray flares are reported. In the decimeter wavelength range, type III bursts and the genuinely decimetric emissions (pulsations, continua, and narrowband spikes) were found equally frequently. Both occur predominantly in the peak phase of hard X-ray (HXR) emission, but are less in tune with HXRs than the high-frequency continuum exceeding 4 GHz, attributed to gyrosynchrotron radiation. In 10% of the HXR flares, an intense radiation of the above genuine decimetric types followed in the decay phase or later. Classic meter-wave type III bursts are associated in 33% of all HXR flares, but only in 4% are they the exclusive radio emission. Noise storms were the only radio emission in 5% of the HXR flares, some of them with extended duration. Despite the spatial association (same active region), the noise storm variations are found to be only loosely correlated in time with the X-ray flux. In a surprising 17% of the HXR flares, no coherent radio emission was found in the extremely broad band surveyed. The association but loose correlation between HXR and coherent radio emission is interpreted by multiple reconnection sites connected by common field line