Portable automated radio-frequency scanner for non-destructive testing of carbon-fibre-reinforced polymer composites

A portable automated scanner for non-destructive testing of carbon-fibre-reinforced polymer (CFRP) composites has been developed. Measurement head has been equipped with an array of newly developed radio-frequency (RF) inductive sensors mounted on a flexible arm, which allows the measurement of curved CFRP samples. The scanner is also equipped with vacuum sucks providing mechanical stability. RF sensors operate in a frequency range spanning from 10 up to 300 MHz, where the largest sensitivity to defects buried below the front CFRP surface is expected. Unlike to ultrasonic testing, which will be used for reference, the proposed technique does not require additional couplants. Moreover, negligible cost and high repeatability of inductive sensors allows developing large scanning arrays, thus, substantially speeding up the measurements of large surfaces. The objective will be to present the results of an extensive measurement campaign undertaken for both planar and curved large CFRP samples, pointing out major achievements and potential challenges that still have to be addressed

J Neurosci Methods

BACKGROUND: Spatial memory and navigation have been widely studied using animal models, most of them were performed with rodents and only few of them with non-human primates. Also, most of these studies were achieved in simple and small-scale mazes. NEW METHOD: In order to test navigation strategy in macaque monkeys, we used a double-cross virtual maze in which they could freely move using a joystick and a procedure adapted from previous studies with rodents. The monkeys had first to learn several routes from a specific starting point to reach separate positions, each one containing distinct symbols, and then to associate each route with these symbols. After this phase, the monkeys had to reach these targets from a second starting point positioned at the other end of the maze, requiring the use an allocentric strategy. In order to evaluate monkey's strategy, we analyzed monkey's first choice as a function of the symbol presented. RESULTS: The monkeys were able to learn routes and to associate routes with symbols but were not able to use an allocentric strategy. They also did not use the procedural strategy and seemed disoriented or adopted a stereotypical behavior. COMPARISON WITH EXISTING METHOD(S): Contrary to the few studies using small-scale environments, the monkeys seemed unable to solve the allocentric task. The studies using virtual mazes seemed not to specifically analyze monkey's navigation strategy. CONCLUSIONS: Supplementary experiments will be necessary to explain the origin of the monkey's inability to use an allocentric strategy. Modified learning conditions could also incite the monkeys to develop an allocentric representation

Shearography: A Tool for Imaging Lamb Waves in Composites and their Interaction with Delaminations

Composite materials, especially in aeronautics, often present themselves as thin structures of large lateral size. Their control is generally performed by pulse-echo technique using ultrasonic bulk waves. A way of reducing the inspection time could be to use Lamb waves. These guided waves present a relatively low attenuation which thus allows to inspect large areas more rapidly. Furthermore, one can select a propagation mode offering no « dead zone » inside the plate [1]. Lamb waves can be generated by piezo transducers with contact, water coupling or, more recently, with air coupling [1,2]. Research is underway to generate Lamb waves through imbedded optical fibers delivering laser pulses [3]. Then the inspection consists in detecting for each considered emission direction either an echo (reflection mode) or an increased attenuation (transmission mode) [1,2]. These indications reveal the presence of a defect in the insonicated area. Depending on the minimal size of the defects and of the induced diffraction pattern, the angular discretization of the « inspection web » around each emission transducer has to be optimized.</p

Shearographic visualization of lamb waves in carbon epoxy plates interaction with delaminations

This article presents an application of a speckle interferometry technique with video doubling, called "shearography". This technique can be used for near real time imaging of Lamb waves in continuous or burst modes, revealing the presence of delaminations in a carbon epoxy plate. The amplitude of the displacements is measured with a typical uncertainty of the order of 1 nm. The nominal Lamb wave can be suppressed from the shearographic image by optical filtering, to show only the wave interaction with any defects that may exist in the plate. This method is especially advantageous for non-destructive testing

Shearography: A Tool for Imaging Lamb Waves in Composites and their Interaction with Delaminations

Composite materials, especially in aeronautics, often present themselves as thin structures of large lateral size. Their control is generally performed by pulse-echo technique using ultrasonic bulk waves. A way of reducing the inspection time could be to use Lamb waves. These guided waves present a relatively low attenuation which thus allows to inspect large areas more rapidly. Furthermore, one can select a propagation mode offering no « dead zone » inside the plate [1]. Lamb waves can be generated by piezo transducers with contact, water coupling or, more recently, with air coupling [1,2]. Research is underway to generate Lamb waves through imbedded optical fibers delivering laser pulses [3]. Then the inspection consists in detecting for each considered emission direction either an echo (reflection mode) or an increased attenuation (transmission mode) [1,2]. These indications reveal the presence of a defect in the insonicated area. Depending on the minimal size of the defects and of the induced diffraction pattern, the angular discretization of the « inspection web » around each emission transducer has to be optimized

Effets d'enrichissements azotés sur la croissance des palourdes mises en élevage dans les claires du bassin de Marennes-Oléron

Etant donné que la production de mollusques (palourdes ou huîtres) est limitée à 0,8 kg à 1 kg au m2 soit 40 à 50 palourdes adultes de 20 g au m2, il est intéressant d'essayer de forcer cette production en augmentant la production primaire qui est le facteur limitant de la production de palourdes. Cette production primaire dépend des apports en sels nutritifs en effet les travaux antérieurs de Zanette (1979), de Zanette et Garnier (1980), de Robert (1984) ont mis en évidence que les biomasses phytoplanctoniques ne peuvent dépasser un certain seuil à cause de l'épuisement progressif en sels nutritifs. Robert et al. (1984) ont mis en évidence, dans les claires de la Baie de Bourgneuf que l'azote est le premier facteur limitant de la croissance phytoplanctonique et Flamion et al. (sous presse) ont confirmé que l'azote reste le facteur limitant dans les claires de la Seudre (bassin de Marennes-Oléron). Les amendements réalisés en 1983 dans les claires de la SATMAR ont mis en évidence que le nitrate d'ammonium induit des blooms de phytoflagellés pendant la période estivale (Flamion, 1983). Ainsi dans le cadre de cette expérimentation, il a été procédé à des enrichissements successifs de nitrate d'ammonium dans les claires où sont cultivées des palourdes à des densités et des tailles différentes, pendant l'été 1984

Oscillatory entrainment of subthalamic nucleus neurons and behavioural consequences in rodents and primates.

International audienceWe investigated the functional role of oscillatory activity in the local field potential (LFP) of the subthalamic nucleus (STN) in the pathophysiology of Parkinson's disease (PD). It has been postulated that beta (15-30 Hz) oscillatory activity in the basal ganglia induces PD motor symptoms. To assess this hypothesis, an LFP showing significant power in the beta frequency range (23 Hz) was used as a stimulus both in vitro and in vivo. We first demonstrated in rat brain slices that STN neuronal activity was driven by the LFP stimulation. We then applied beta stimulation to the STN of 16 rats and two monkeys while quantifying motor behaviour. Although stimulation-induced behavioural effects were observed, stimulation of the STN at 23 Hz induced no significant decrease in motor performance in either rodents or primates. This study is the first to show LFP-induced behaviour in both rats and primates, and highlights the complex relationship between beta power and parkinsonian symptoms

The development of an onsite sanitation system based on vermifiltration: the 'Tiger Toilet'

This paper describes the development of a novel onsite sanitation system based on vermifiltration, the ‘Tiger Toilet’. Initial laboratory experiments demonstrated that feed distribution was not required, a worm density of 2 kg/m2 could be used, worms preferred wetter environments, and system configuration did not affect effluent quality. Installing the first prototype in the UK proved that the process functioned when scaled, i.e., chemical oxygen demand and thermotolerant coliform reduction were found to be comparable with the laboratory results. Ten prototypes were then tested by households in rural India; all were working well after six months. The vermifilters were processing the amount of faeces entering the system on a daily basis, so faeces was not accumulating. It was estimated that they would require emptying after approximately five years, based on the depth of the vermicompost generated. With further development, it is believed that the Tiger Toilet has the potential to become a superior form of onsite sanitation, when compared with traditional onsite sanitation technologies