Lively data: discover, browse and access ocean altimetry data on internet

International audienceThe Products and Services (P&S) department in the Space Oceanography Division at CLS (Collecte, Localisation, Satellites) is in charge of distributing and promoting altimetry and operational oceanography data. The department is thus involved in the Aviso satellite altimetry project (the French service which distributes altimetry products since 1992), in the Mercator ocean operational forecasting system, and in the European Godae/Mersea ocean portal. Aiming to a standardisation and a common vision and management of all these ocean data, all these projects, led to the implementation of several Opendap/LAS Internet servers (Baudel et al., 2004). Some of the possibilities of the tools, as well as how-to information will be highlighted, as they are in the "Lively data'' section of Aviso website (see http://www.aviso.oceanobs.com/html/donnees/las/). Moreover, with a two-year experience we now have some feedback and analysis of how people – users, would-be users and students alike – are using this tool, some ideas for possible enhancements, etc

Characterization of Bonding Defects in Carbon Fiber-Epoxy Plates via Thermal Wave Imaging

Thermal wave imaging (TWI), a technology based on heat conduction and radiation through materials, is a relatively new addition to current non-destructive inspections (NDI) systems. Bonding of composites, an extremely important step in manufacturing and repair of laminates, could be affected by defects originating from faulty manufacturing processes or damages during the operation of the products. Bonding defects are typically characterized by NDI as part of quality control in manufacturing and routine and unscheduled maintenance checks. The present work is focused on the application of TWI for identification of debonds in carbon fiber – epoxy laminates and specifically TWI resolution and accuracy will be evaluated. Various techniques for the simulation of bonding defects, using film adhesive and polylactic acid, were designed for calibration purposes and experimentally evaluated. The system showed an average accuracy of 13.4% in determining a defect’s location, and average accuracy of 314.6% in determining a defect's size. An exponential decay trend between the aspect ratio of a defect and error in the estimation of the defect’s size, was confirmed. Aspect ratio however seems not to significantly affect estimates of the location of the defects. Furthermore, the system's resolution, defined by the defect’s aspect ratio, was estimated to be around 2 with the minimum defect size visible at 3mm

Scattering by a cylinder covered with an arbitrary distribution of impedance and application to the optimization of a tramway noise abatement system

International audienceA semi-analytical solution for the two-dimensional scattering of a line source by a cylinder with an arbitrary distribution of surface impedance and its image with respect to a vertical baffle is derived. This description is used to model the shadowing due to a low-height semi-cylindrical noise barrier close to a tramway. After validation against the boundary element method, this solution is used in a gradient-based optimization approach of the admittance distribution to maximize the broadband insertion loss in a given receiver zone. First, a hypothetical but passive distribution is found, showing an improvement of more than 20 dB(A) with respect to a purely rigid barrier. Second, a feasible optimized surface treatment made of a porous layer and a micro-perforated resonant panel is proposed, with an improvement of 14 dB(A) with respect to an entirely rigid barrier and 8 dB(A) with respect to a uniform absorbent barrier. The optimization provides an automatic way of tuning the resonant panel so that the attenuation is enhanced in the frequency band where the source has the most spectral content. The benefit of using a non-uniform admittance distribution is evaluated in this idealized context to be about 8 dB(A)

Thermographic Testing Applied to Fiber Reinforced Polymers

Non-destructive testing is a methodology to inspect production and operational parts for potential flaws, defects, or damages. The present work is based on pulsed wave thermography, a thermal imaging method based on heat conduction to identify surface and subsurface defects potentially present in a component. Pulsed wave thermography applies a fast pulse of heat energy on the specimen’s surface while heat conduction through the material is recorded through an infrared camera. Test procedures are established with the objective of comparing system performance between homogeneous and fiber reinforced polymers. Preliminary tests on aluminum alloy have shown reliable defect detection using profile graphs with noisy data due to high metal heat conductivity. Tests on fiber reinforced polymer samples confirmed pulsed wave thermography can detect defects within carbon composites, however only surface level data can be detected in fiberglass and sandwich panels applying the basic level analysis as performed in the current work. Advanced data processing for better performance on a wider range of composites will be applied in the continuation of the research. An educational laboratory procedure for teaching the basic operation of the system in an undergraduate and graduate class environment has been developed.Key Words: Non-destructive testing, thermography, composite, non-homogenous, homogenous, fiber reinforced polymers

Application of admittance optimization to the design of a low-height tramway noise barriers

International audienceAn urban low-height barrier meant to attenuate tramway noise emission for nearby walking pedestrians or cyclists is studied. A numerical method coupling the two dimensional BEM and a gradient-based optimization algorithm is proposed to optimize the admittance distribution on the barrier in order to enhance the broadband insertion loss in the shadowing zone. The gradient of the broadband attenuation is calculated e ciently using the adjoint state approach which makes it possible to use a large number of parameters without significant increase of computation time and to consider a barrier of arbitrary shape. A few admittance designs coupling porous layers and micro-perforated resonant panels covering barriers of classical shapes are proposed, all showing an improvement of several dB(A) compared to more simple admittance distributions

Scattering of a cylinder covered with an arbitrary distribution of admittance and application to the design of a tramway noise abatement system

International audienceAn urban low-height barrier meant to attenuate tramway noise emission for nearby walking pedestrians or cyclists is studied. A semi-analytical solution for the two-dimensional scattering of a line source by a cylinder covered by an arbitrary distribution of impedance and its image with respect to a vertical baffle is derived. This description is used to model the shadowing due to a semi-cylindrical noise barrier close to a tramway. This solution is used in a gradient-based optimization approach of the admittance distribution to maximize the broadband insertion loss in a given receiver zone. A feasible optimized surface treatment made of a porous layer and a micro-perforated resonant panel is proposed, with an improvement of 14 dB(A) with respect to an entirely rigid barrier. The optimization gain with respect to a uniform absorbent admittance is about 8 dB(A). Extra tests with the boundary element method show that this gain is reduced but still significant if more realistic conditions are considered

Sensivity-based shape optimization of a rigid tramway low-height noise barrier

International audienceAn urban low-height barrier meant to attenuate tramway noise for nearby walking pedestrians or cyclists is considered. The efficiency of this type of device is known to depend on the shape of the cross section and the acoustic properties of the surface treatment. Some sort of absorptive material is often required to enhance the performance by preventing the multi-reflection phenomenon, however such materials can be costly compared to acoustically rigid materials such as concrete. In this study, a rigid barrier is assumed but its shape is optimized using a sensitivity-based shape optimization algorithm coupled to the two dimensional BEM. The shape is here described in a very general fashion by mesh nodes coordinates, which can involve a large number of variables. Sensitivities with respect to all coordinates are calculated efficiently using the adjoint state approach, without significant increase of computation time. Numerical results show that optimized shapes tend to be quite irregular but provide a significant improvement compared to simpler shapes, especially in the mid and high frequency range. Intensity calculations seem to suggest that this improvement is due to scattering of the incident acoustic energy in the upwards direction, therefore reducing the diffracted energy which reaches the shadow zone. Extra calculations show that the benefit of the optimized shapes can still be significant even in more realistic situations

In situ measurement of the acoustic performance of a full scale tramway low height noise barrier prototype

International audienceThe performance of a full scale low height barrier prototype meant to attenuate tramway noise is measured in situ. The prototype is made of a simple L-shape assembly of pressed wood boards covered on the source side with fibrous absorbing material, and has been set up temporarily in a residential area in the town of Saint-Martin-d'H` eres, near Grenoble, through which a tramway line passes. A series of pass-by measurements were made at a close receiver location corresponding to the typical height of human ears, with and without the device. The tram speed has been measured as well using an auxiliary microphone located very close to the track. A significant variability in pass-by levels has been found between the different trams, even when applying an approximate correction for speed. However it is shown that the barrier provides on average an attenuation of more than 10 dB(A), during the whole pass-by. Spectral analysis of the recorded signals is carried out as well to estimate the barrier insertion loss more accurately. Furthermore, comparisons between measurements and simplistic BEM calculations show that numerical predictions can yield rather good estimates of the actual in situ performance, within a few dB(A)

Constantes biologiques au Congo des moutons inoculés pour préparation du vaccin antirabique

Il a été tenté d'établir les valeurs moyennes de certains constituants sanguins du matériel animal utilisé pour la préparation du vaccin antirabique. Ces valeurs sont suivies chez les animaux inoculés, et les résultats obtenus sont comparés à ceux d'autres auteurs