Improvement to Defect Detection by Ultrasonic Data Processing: The DTVG Method

In the case of coarse grained austenitic stainless steel, an important diminution in the defect detection possibilities is noted. The wave amplitude is attenuated and can also be deviated, according to the importance of anisotropy and/or heterogeneity

Development of a New Method for the Inspection of a 3D Volume of Ultrasonic Data

NDT technologies by ultrasounds are in constant progress. The advance is considerable for sensors and acquisition systems. The means for data processing follow this evolution. In order to meet the demand for processing very high volumes of data, we propose in this paper a method of volume automatic thresholding. The application concerns the testing of austenitic steel or else, for the nuclear industry. The thresholding techniques from the image histogram are inadequate as the ultrasonic image histogram is unimodal. The study of the image with the cooccurrence matrix which is a two dimensionnal histogram allows to clearly show the noise-defect transition. Several authors have elaborated on thresholding techniques of an image from the cooccurrence matrix. These vary according to the type of exploited image [1–2]. We showed the good results of thresholding by cooccurrence matrix on images with a defect. We develop in this paper a two-part study. Firstly, after a brief account of the matrix exploitation, we show the limits of this method in bearing simulated images. We then describe the chosen approach to extend the method to the volume thresholding problem. We give results from a data volume obtained on austenitic steel testing

Non destructive examination of immersed structures within liquid sodium

International audienceThe In Service Inspection of internal structures of future liquid sodium cooled fast reactors implies, among different options, the use of ultrasounds from the outside of sodium circuit. In these conditions, ultrasounds have to propagate through the metallic envelope of main vessel, then other immersed plates. Thus the study aims at mastering ultrasonic propagation in these multilayered structures in order to determine the best conditions allowing NDT of a plate behind some screens. The necessity of propagating a maximum of energy through bounded media orientated the study towards Lamb waves. Those are often employed for singles plates or solid layers but they are less usual for liquid/solid alternations. Theoretical results are obtained using transfer matrix method. They are compared to in water experimental measurements. Cases with one, two and three parallel plates without then with an artificial defect are presented for identical and different thicknesses of plates. Results show that an artificial crack defect is obviously detected in a plate located behind one and two screens. Measured attenuation is compatible with industrial NDT conditions. Thus a promising potential is shown for this inspection technique

Modelling of ultrasound transmission through a solid-liquid interface comprising a network of gas pockets

International audienceUltrasonic inspection of sodium-cooled fast reactor requires a good acoustic coupling between the transducer and the liquid sodium. Ultrasonic transmission through a solid surface in contact with liquid sodium can be complex due to the presence of microscopic gas pockets entrapped by the surface roughness. Experiments are run using substrates with controlled roughness consisting of a network of holes and a modeling approach is then developed. In this model, a gas pocket stiffness at a partially solid-liquid interface is defined. This stiffness is then used to calculate the transmission coefficient of ultrasound at the entire interface. The gas pocket stiffness has a static, as well as an inertial component, which depends on the ultrasonic frequency and the radiative mass

Optimal co-occurrence matrix for automatic segmentation of ultrasonic images

This paper introduces a new method of segmentation using automatic thresholding adapted to the NDT ultrasonic images . This study is based on image analysis through co-occurrence matrixes . It shows an optimization of the r and 0 parameters of the co-occurrence matrix enabling to define more acurately the border between noise and defect echoes . The segmentation is obtained by automatically taking into account a threshold derived from a determination curve calculated front the co-occurrence matrix . This curve, called Average Product of Variances Measure, is an analysis of the distribution of the matrix coefficients . The results show behaviors of the co-occurrence matrixes and of the threshold selection curves that justify perfectly the analysis performed on the characteristics of the image .Cet article présente une nouvelle méthode de segmentation par seuillage automatique, adaptée aux images obtenues en contrôle non destructif par ultrasons. Cette étude est fondée sur l'analyse d'image par matrice de co-occurrence. On présente une optimisation des paramètres r et Θ de la matrice de co-occurrence permettant de mieux définir la frontière qui sépare le bruit des échos de défauts. La segmentation s'obtient par la prise en compte automatique d'un seuil issu d'une courbe de détermination calculée à partir de la matrice de co-occurrenc

Recommandations de Conception issues du Contrôle Non Destructif (RCC-MRx)

National audienceUne réflexion a été initiée en 2008 par les concepteurs de centrales nucléaires RNRrefroidies au sodium, avec l’aide de spécialistes du LCND (Université Aix-Marseille).L’objectif était d’insuffler une culture CND, un réflexe pour les besoinsd’inspectabilité/réparabilité. Le constat qui a motivé cette réflexion était que toutes les règlesrelatives aux CND présentes dans le code RCC-MR (édition 2007) étaient spécifiquementdévolues aux contrôles de fabrication. Un Groupe de Travail Thématique (GTT) a produit fin2012 une révision de l’Annexe A20 «Dispositions constructives associées aux visites desurveillance en exploitation» du code RCC-MRx, résultant de la fusion des codes RCC-MRet RCC-MX dédié aux réacteurs expérimentaux. Cette révision est volontairement peuprescriptive car le GTT a montré que, vis-à-vis de la complexité des problèmes posés, ledialogue entre concepteur, fabricant et contrôleur semble être le meilleur moyen pour trouverun compromis entre conception, fabrication et besoin d’inspection en service. Le GTT aconsidéré indispensable d’accompagner cette Annexe d’un document qui fournisse lesfondements des recommandations (criteria), et qui permette de comprendre et justifier lessolutions apportées avec les moyens techniques de contrôles actuels. Certaines mises enperspective sont également indiquées. La présente communication montre le principe de larévision retenue, et présente quelques exemples extraits des criteria

A RasGAP SH3 Peptide Aptamer Inhibits RasGAP-Aurora Interaction and Induces Caspase-Independent Tumor Cell Death

The Ras GTPase-activating protein RasGAP catalyzes the conversion of active GTP-bound Ras into inactive GDP-bound Ras. However, RasGAP also acts as a positive effector of Ras and exerts an anti-apoptotic activity that is independent of its GAP function and that involves its SH3 (Src homology) domain. We used a combinatorial peptide aptamer approach to select a collection of RasGAP SH3 specific ligands. We mapped the peptide aptamer binding sites by performing yeast two-hybrid mating assays against a panel of RasGAP SH3 mutants. We examined the biological activity of a peptide aptamer targeting a pocket delineated by residues D295/7, L313 and W317. This aptamer shows a caspase-independent cytotoxic activity on tumor cell lines. It disrupts the interaction between RasGAP and Aurora B kinase. This work identifies the above-mentioned pocket as an interesting therapeutic target to pursue and points its cognate peptide aptamer as a promising guide to discover RasGAP small-molecule drug candidates

The Politics of (and Behind) the UNFCCC’s Loss and Damage Mechanism

Despite being one of the most controversial issues to be recently treated within climate negotiations, Loss and Damage (L&D) has attracted little attention among scholars of International Relations (IR). In this chapter we take the “structuralist paradox” in L&D negotiations as our starting point, considering how IR theories can help to explain the somewhat surprising capacity of weak parties to achieve results while negotiating with stronger parties. We adopt a multi-faceted notion of power, drawing from the neorealist, liberal and constructivist schools of thought, in order to explain how L&D milestones were reached. Our analysis shows that the IR discipline can greatly contribute to the debate, not only by enhancing understanding of the negotiation process and related outcomes but also by offering insights on how the issue could be fruitfully moved forward. In particular, we note the key importance that discursive power had in the attainment of L&D milestones: Framing L&D in ethical and legal terms appealed to standards relevant beyond the UNFCCC context, including basic moral norms linked to island states’ narratives of survival and the reference to international customary law. These broader standards are in principle recognised by both contending parties and this broader framing of L&D has helped to prove the need for action on L&D. However, we find that a change of narrative may be needed to avoid turning the issue into a win-lose negotiation game. Instead, a stronger emphasis on mutual gains through adaptation and action on L&D for both developed and developing countries is needed as well as clarity on the limits of these strategies. Examples of such mutual gains are more resilient global supply chains, reduction of climate-induced migration and enhanced security. As a result, acting on L&D would not feel as a unilateral concession developed countries make to vulnerable ones: it would rather be about elaborating patterns of collective action on an issue of common concern