Surface integral equations for electromagnetic testing: the low-frequency and high-contrast case

International audienceThis study concerns boundary element methods applied to electromagnetic testing, for a wide range of frequencies and conductivities. The eddy currents approximation cannot handle all configurations, while the common Maxwell formulation suffers from numerical instabilities at low frequency or in presence of highly contrasted media. We draw on studies that overcome these problems for dielectric configurations to treat conductive bodies, and show how to link them to eddy current formulations under suitable assumptions. This is intended as a first step towards a generic formulation that can be modified in each sub-domain according to the corresponding medium

A multi-step solution algorithm for Maxwell boundary integral equations applied to low-frequency electromagnetic testing of conductive objects

International audienceWe consider the solution, using boundary elements (BE), of the surface integral equation system arising in electromagnetic testing of conducting bodies, with emphasis on situations such that $o(1) \leq \sqrt{\omega\varepsilon_{0}/\sigma} \leq O(1)$, $L \sqrt{\omega\sigma\mu_{0}} =O(1)$ which includes in particular the case of eddy current testing) and assuming $L\omega\sqrt{\varepsilon_0 \mu_{0}}\leq 2\pi$, i.e. low-frequency conditions ($L$: diameter of conducting body). Earlier approaches for dielectric objects at low frequencies are not applicable in the present context. After showing that a simple normalization of the BE system significantly improves its conditioning, we propose a multi-step solution method based on block SOR iterations, which facilitates the use of direct solvers and converges within a few iterations for the considered range of physical parameters. This novel, albeit simple, treatment allows to perform eddy current-type analyses using standard Maxwell SIE formulations, avoiding the adverse consequences of ill-conditioning for low frequencies and high conductivities. Its performance and limitations are studied on three numerical examples involfing low frequencies and high conductivities

The contribution of ontologies to the creation of knowledge bases for the management of legal compliance in occupational health and safety

International audienceOccupational health and safety (OHS) is at the heart of corporate policies and the increasing trend towards litigation has contributed to the inflated number of regulatory texts published each year. OHS professionals are therefore faced with the need to process a growing amount of data in order to remain in compliance. They train themselves in law, draw upon internal expertise (the company's legal department) or external consultants (advisory and enforcement agencies) and equip themselves with information systems. These systems are mainly 'judicial monitoring' databases that contain regulatory texts and associated comments. For the most part, this data is complex to interpret and difficult to exploit given the growing number of texts, the expertise needed to understand them and the difficulty in being sure that they are relevant to the activities of the company. This need for clarity may be met by models and methods from artificial intelligence. Amongst these, we have selected the concepts of the ontology and the knowledge base. An ontology is a model of a particular domain of knowledge created for a specific purpose. Mainly used for the formalization of knowledge, it can also be used to define a common language between an information system and a community of actors (i.e. OHS professionals). A knowledge base is a set of knowledge that is specific to a given domain that can be exploited by a technology. The coupling between the ontology and the knowledge base makes it possible to automate certain tasks, such as monitoring, auditing, ensuring compliance, etc. This three-part article describes a methodology and an associated software tool that can ensure compliance. The first part identifies elements used in the definition and the proven benefits of ontologies and knowledge bases. The second describes the approach taken in the design of the ontology and its implementation as a rule base using a bespoke knowledge base editor. Finally, a concrete example of the formalization of regulatory knowledge (using the theme of harassment and violence at work) is presented to demonstrate the contributions and the limitations of the tool

Apports des ontologies à la création de bases de connaissances pour la maîtrise des conformités légales en santé et sécurité au travail

La "Santé-Sécurité au Travail" (SST) est au coeur des politiques d'entreprise et la judiciarisation de la société concourt à une inflation du nombre de textes réglementaires publiés chaque année. Les préventeurs sont donc confrontés au traitement croissant de données afin de rester en conformité. Ils se forment au droit et s'entourent de compétences interne (direction juridique) ou externe (bureaux de contrôle et de conseil) et se dotent de systèmes d'information. Ces derniers sont principalement des bases de données de "veille juridique" proposant des textes réglementaires accompagnés de commentaires. L'ensemble de ces données demeure complexe à interpréter et à exploiter en raison du nombre croissant de textes, de l'expertise nécessaire à fin de les comprendre et de la difficulté à s'assurer qu'ils concernent les activités de l'entreprise. Ce besoin peut être satisfait par le recours aux modèles et méthodes de l'intelligence artificielle. Parmi ceux-ci, les concepts d'ontologies et de bases de connaissances ont été retenus. Une ontologie est un modèle d'un domaine particulier de connaissances réalisé dans un but précis

Statistical modelling by neural networks in gamma-spectrometry

International audienceLayered Neural Networks are a class of models based on neural computation and have been applied to the measurement of uranium enrichment. The usual methods consider a limited number of $X$- and $\gamma$-ray peaks, and require calibrated instrumentation for each sample. Since the source-detector ensemble geometry conditions critically differ between such measurements, the spectral region of interest is normally reduced to improve the accuracy of such conventional methods by focusing on the $K_{\alpha}X$ region where the three elementary components are present. Such measurements lead to the desired ratio. Experimental data have been used to study the performance of neural networks involving a Maximum-Likelihood Method. The encoding of the data by a Neural Network approach is a promising method for the measurement of uranium ${}^{235}U$ and ${}^{238}U$ in infinitely thick samples

Combining microsatellites, growth, and adaptive traits for managing in situ genetic resources of Eucalyptus urophylla

International audienceGenetic diversity and structure of 17 populations representative of the natural range of Eucalyptus urophylla S.T. Blake in Indonesia were analysed with 10 microsatellite markers. Two provenance and progeny trials, using the same populations, were established in the Republic of the Congo and analysed for growth and survival at 37months. Observed microsatellite heterozygosity (Ho) was moderate to high within populations (Ho = 0.51-0.72). The index of fixation (FIS) was significantly different from zero for all populations (FIS = 0.13-0.31) and possibly resulted from a Wahlund effect. The differentiation parameter was low (FST = 0.04) and not significantly different from zero, which can be explained by effective gene flow via pollen. The genetic variances within and among provenances for survival and growth traits were significantly different from zero, representing 13%-23% and 14%-50% of the total variation, respectively. The differentiation between populations based on quantitative traits was marked (QST = 0.07-0.33). A negative relationship between altitude of the seed source and its performance in the Congo was observed (R2 = 0.59-0.67) and could be explained by the effect of natural selection along the altitudinal gradient. This marked differentiation for quantitative traits despite high apparent gene flow results in a clinal variation, which suggests the use of altitude of seed source as an important principle for in situ or ex situ management of E. urophylla genetic resources. À l'aide de 10 marqueurs microsatellites, les auteurs ont analysé la diversité et la structure génétiques de 17 populations représentatives de l'aire naturelle d'Eucalyptus urophylla S.T. Blake en Indonésie. La croissance et la survie après 37 mois ont été analysées dans deux essais établis en République du Congo et contenant les mêmes provenances et descendances. L'hétérozygotie observée (Ho) chez les marqueurs microsatellites variait de modérée à élevée au sein des populations (Ho = 0,51-0,72). L'indice FIS était significativement différent de zéro pour toutes les populations (FIS = 0,13-0,31) et était possiblement le résultat d'un effet de Wahlund. La différenciation de population était faible (FST = 0,04) et n'était pas significativement différente de zéro, ce qui peut s'expliquer par un flux génique efficace attribuable au pollen. Les variances génétiques au sein et parmi les provenances pour les caractères de survie et de croissance étaient significativement différentes de zéro, représentant respectivement 13% à 23% et 14% à 50% de la variation totale. La différenciation de population estimée à partir des caractères quantitatifs était élevée, avec une valeur de QST = 0,07-0,33. Une relation négative entre l'altitude des sources de semences et leur performance au Congo a été remarquée (R2 = 0,59-0,67). Cette relation pourrait s'expliquer par l'effet de la sélection naturelle le long du gradient altitudinal. Cette différenciation marquée chez les caractères quantitatifs, en dépit d'un flux génique apparent élevé, se manifeste par un patron de variation clinale, ce qui indique que l'altitude des sources de semences est un critère important qui devrait être utilisé pour la gestion in situ et ex situ des ressources génétiques d'E. urophyll

Ingénierie de la connaissance pour la prévention des risques en santé, sécurité au travail et environnement

Ce rapport de recherche dresse le bilan de cinq années (2009/2013) de collaboration de recherche entre la société Preventeo et le Centre de recherche sur les risques et les Crises (CRC) de MINES ParisTech. A cette fin, il présente les résultats de cinq thèses conduites sur la période. Deux d'entre elles portent sur la démarche de conception de modèles afin de caractériser la maîtrise des conformités en santé, sécurité au travail et environnement. Une troisième thèse traite du concept de culture de sécurité. Enfin, deux thèses ont permis de transformer les modèles en ingénierie, l'une sous la forme d'une ontologie, préalable indispensable à la création de bases de connaissances, l'autre sous la forme d'un tableau de bord pour le management de la santé et de la sécurité au travail