Diagnostic de défauts d'isolement dans des lignes de transmission électriques : application aux cables de signalisation SNCF

This thesis work focuses on the detection of insulation faults in very long transmission lines. This is detecting soft defects related to the insulation between the conductors of a long cable which are represented by the leakage conductance parameter. Detect these faults, signs of a possible future short-circuit, is an important issue but requires a noninvasive method. For example, in the case of railway signaling cables, it is to develop a method of diagnosis of very low leakage conductances in signaling cables along railways compatible with the movement of trains. Be aware estimate from measurements in one point of the cable, strong resistance distributed over several hundred meters without disturbing the continuous frequency range to 40 kHz, reserved for service signals. Indeed, the signal cables from the train that interest us have an average length 1500 m and are used in the frequency band 0-40 kHz.We propose so a frequency method for estimating low defects to medium frequency in uniform transmission lines with losses. It is based on two main ideas : a detailed analysis of joint effects of dissipation and dispersion and a method of comparing two lines having the same characteristics and differing only leak conductance parameter. This method of comparison was widespread in the case of multiconductor lines by adopting a statistical approach.This thesis has brought new results : losses estimation formulas resulting from the detailed analysis of a share of joint effects of dissipation and dispersion and also the method of comparing two lines. Numerical simulations were made in both cases to validate the proposed frequency method. Experiments were performed to validate the statistical analysis in the case of multiconductor lines.Ces travaux de thèse portent sur la détection de défauts d'isolement dans des lignes de transmission de grandes longueurs. Il s'agit de détecter des défauts non francs liés à l'isolant entre les conducteurs d'un câble de grande longueur qui sont représentés par le paramètre de conductance de fuite. Détecter ces défauts, signes d'un possible futur court-circuit, est un enjeu important mais nécessite une méthode non invasive. Par exemple, dans le cas des câbles de signalisation SNCF, il s'agit de développer une méthode de diagnostic de très faibles conductances de fuite dans les câbles de signalisation le long des voies ferrées compatible avec la circulation des trains. Il faut savoir estimer, à partir de mesures en un seul point du câble, de fortes résistances distribuées sur plusieurs centaines de mètres sans perturber la bande de fréquences du continu à 40 kHz, réservée aux signaux de service. En effet, les câbles de signalisation de la SNCF qui nous intéressent ont une longueur moyenne de 1500 m et sont utilisés dans la bande de fréquence 0-40 kHz. Nous proposons donc une méthode fréquentielle permettant d'estimer de faibles défauts à moyenne fréquence dans des lignes de transmission uniformes avec pertes. Elle repose sur deux idées principales : une analyse fine des effets conjoints de la dissipation et de la dispersion et une méthode de comparaison de deux lignes ayant les mêmes caractéristiques et ne différant que du paramètre de conductance de fuite. Cette méthode de comparaison a été généralisée dans le cas de lignes multiconducteurs en adoptant une démarche statistique.\\Cette thèse a apporté de nouveaux résultats : des formules d'estimation de pertes découlant de l'analyse fine d'une part des effets conjoints de la dissipation et de la dispersion et d'autre part de la méthode de comparaison de deux lignes. Des simulations numériques ont été faites dans les deux cas afin de valider la méthode fréquentielle proposée. Des expériences ont été réalisées afin de valider l'analyse statistique développée dans le cas de lignes multiconducteurs

Une double discordance cardiaque complexe décompensée, à propos d’un cas et revue de la littérature

AbstractDouble discordance is an extremely rare complex congenital heart disease; It ischaracterized by atrioventricular discordance followed by another ventriculo-arterialdiscordance. Its diagnosis is usually made in adulthood by imaging examinations.Its prognosis depends mainly on other associated congenital heart defects,arrhythmias and disorders of the conduction, as well as systolic function of theright ventricle in the systemic position.We report the case of a 23-year-old patient with a complex cyanogen heart disease.It is a double discordance associated to an interventricular communicationwith reverse shunt and an hypoplasia of the pulmonary artery.This Diagnosis wasconfirmed in multimodal imaging. Non-operated, the patient saw his functionalstatus worsen rapidly with dyspnea which went from stage I to stage III-IV of theNew York Heart Association (NYHA), and appearance of hypoxic and congestivesigns.Through this observation, we have clarified the anatomoclinical characteristics ofthis complex congenital cyanogens heart disease, the necessary explorations andthe different therapeutic options, as well as the pejorative role of its associationwith other congenital malformations. RésuméLa double discordance est une cardiopathie congénitale complexe extrêmement rare,elle se caractérise par une discordance auriculo-ventriculaire suivie d’une autre discordanceventriculo-artérielle. Son diagnostic est posé généralement à l’âge adulte par desexamens d’imagerie. Son pronostic dépend essentiellement des autres malformationscongénitales cardiaques associées, des arythmies et des troubles de la conduction, ainsique de la fonction systolique du ventricule droit en position systémique.Nous rapportons le cas d’un patient âgé de 23 ans, porteur d’une cardiopathie congénitalecomplexe cyanogène. Il s’agit d’une double discordance associée à une largecommunication interventriculaire sous aortique avec un shunt inversé et une hypoplasiede l’artère pulmonaire. Ce diagnostic a été confirmé par l’imagerie multimodale. Nonopéré, le patient a vu son stade fonctionnel s’aggraver rapidement avec une dyspnéequi est passée d’un stade I à un stade III-IV de la New York Heart Association (NYHA), etapparition de signes hypoxiques et congestifs.A travers cette observation, nous avons précisé les caractéristiques anatomocliniques decette cardiopathie congénitale complexe cyanogène, son exploration, ses options thérapeutiques,ainsi que le rôle péjoratif de son association avec d’autres malformationscongénitales

Combined synchrotron X-rays and image correlation analyses of biaxially deformed W/Cu nanocomposite thin films on Kapton

International audienceAbstract In-situ biaxial tensile tests within the elastic domain were conducted with W/Cu nanocomposite thin films deposited on a polyimide cruciform substrate thanks to a biaxial testing machine developed on the DiffAbs beamline at SOLEIL synchrotron. The mechanical behavior of the nanocomposite was characterized at the micro-scale and the macro-scale using simultaneously synchrotron X-ray diffraction and digital image correlation techniques. Strain analyses for equi-biaxial and non equi-biaxial loading paths have been performed. The results show that the two strain measurements match to within 1 × 10-4 in the elastic domain for strain levels less than 0.3% and for both loading paths

Effects of colocynth alkaloids and glycosides on Wistar rats fed high-fat diet. A biochemical and morphological study

Introduction. In traditional medicine, Citrullus colocynthis is used to treat diabetes, hyperlipidemia, cardiovascular diseases, inflammation, and oxidative stress, all of which can appear when a diet rich in vegetable fats, such as palm oil, is continuously consumed. Such high-fat diets are chronic stressors of the hypothalamic–pituitary–adrenal axis. The objective of our study was to analyze and evaluate the effects of colocynth total alkaloids and glycosides on metabolic, hormonal, and structural disorders of the adrenal medulla in Wistar rats fed a high-fat diet. Material and methods. Twenty six Wistar rats were distributed as follows: six control animals received a standard laboratory diet; twenty experimental rats received the standard laboratory diet supplemented with palm oil — the high-fat diet (HFD). After seven months of this diet, the HFD group was subdivided into rats treated for the next 2 months with either alkaloid extract (HFD-ALk group) or ethanol extract of glycosides (HFD-GLc) or animals on HFD only. Plasma metabolites and ACTH concentrations were measured by standard methods. Sections of adrenal medulla were stained by Heidenhain-Azan method and Sudan Black. Results. The adrenal medulla of the HFD rats showed prominent structural changes, such as hypertrophy of chromaffin and ganglion cells, vacuolation, inflammatory foci, and fibrosis. The biochemical and hormonal parameters were significantly improved in the HFD rats treated with alkaloid and glycoside extracts of Citrullus colocynthis. Moreover, the morphological changes of the adrenal medulla were attenuated in HFD-ALk and HFD-Glc rats. Conclusions. The results of the study indicate that phytotherapy using Citrullus colocynthis alkaloids may correct metabolic and hormonal perturbations as well as adrenal medulla structure of rats maintained on HFD.

Deformation-Induced Martensite: A New Paradigm for Exceptional Steels

Atom-probe tomography (APT) and synchrotron X-ray diffraction (XRD) were combined to study the carbon supersaturation of ferrite for two pearlitic steel-wire compositions, eutectoid and hypereutectoid. The samples were cold-drawn at different strains up to true drawing strains for the eutectoid steel and the hypereutectoid steel, respectively. The wire diameters range from 1.7 mm down to 0.058 mm for the eutectoid steel and from 0.54 mm down to 0.02 mm for the hypereutectoid steel. The findings reveal that cold-drawing of pearlitic steel wires leads to a carbon-supersaturated ferrite causing a spontaneous tetragonal distortion of the ferrite unit cell through a strain-induced deformation driven martensitic transformation. We fi nd that the drawing process induced a significant increase in the carbon content inside the originally nearcarbon-free ferrite until a steady state is approached at drawing strains larger than ca. 4 for the wires. The change of carbon concentration in the ferrite grains during the drawing process is closely related to the tetragonal distortion of the ferrite unit cell

Élasticité et endommagement sous chargement bi-axial de nano-composites W/Cuen couches minces sur polyimide (apport des techniques synchrotrons)

Ce travail de thèse porte sur la déformation bi-axiale contrôlée de nano-composites W/Cu en couches minces déposées sur des substrats polyimides. La nano-structuration est obtenue par stratification de deux matériaux immiscibles (W et Cu) par pulvérisation ionique avec contrôle de la taille des grains au sein du film mince par contrôle de l'épaisseur selon la direction decroissance du film. Nous avons développé une procédure permettant de caractériser le comportement mécanique des échantillons à deux échelles différentes. L'essai de traction biaxial est couplé à la diffraction des rayons X (déformation microscopique) et à la corrélation d'images numériques (déformation macroscopique). Nous avons utilisé une machine de tractionbi-axiale développée dans le cadre d un projet ANR sur la ligne de lumière DiffAbs du synchrotron SOLEIL. Elle permet de contrôler les contraintes dans des films minces supportés par des substrats polyimides. La confrontation des résultats obtenus par ces deux techniques dans le domaine d'élasticité a montré que la déformation est intégralement transmise via l interfacefilm - substrat. La seconde étape de notre travail a consisté à étudier les déformations du nanocomposite W/Cu au-delà du domaine d élasticité. Nous avons mis en évidence trois domaines de déformation associés à différents mécanismes de déformation. La limite d'élasticité du nanocomposite W/Cu a été déterminée en comparant la déformation élastique du film mince à la déformation macroscopique du substrat. Enfin, l'étude de la limite d'élasticité du nanocomposite W/Cu pour différents ratios de force a révélé un comportement fragile du nanocomposite W/Cu.This thesis focuses on the biaxial deformation of W/Cu nanocomposite thin films deposited on polyimide substrates. The grain size in the thin film is controlled by stratification of two immiscible materials (W and Cu) employing sputtering techniques. We developed a procedure to characterize the mechanical behavior of samples at two different scales. A biaxial tensile test is coupled to X-ray diffraction (microscopic deformation) and digital image correlation (macroscopic deformation) techniques. We used a biaxial tensile setup developed in the framework of an ANR project on the DiffAbs beamline at synchrotron SOLEIL allowing forthe control of stresses in thin films supported by polyimide substrates. By comparing the strains obtained by these two techniques, the applied strain is determined to be transmitted unchanged in the elastic domain through the film - substrate interface. The second part of our work was to study the deformation of W/Cu nanocomposite beyond the elastic range. We have highlighted three domains of deformation associated with different deformation mechanisms. The elastic limit of the W/Cu nanocomposite was determined by comparing the elastic deformation of the thin film to the macroscopic deformation of the substrate. Finally, the elastic limit of W/Cu nanocomposite was studied for different load ratios. The overall results emphasized the brittle behavior of these nanocomposites.POITIERS-SCD-Bib. électronique (861949901) / SudocSudocFranceF

Synchrotron X-ray diffraction experiments with a prototype hybrid pixel detector

International audienceA prototype X-ray pixel area detector (XPAD3.1) has been used for X-ray diffraction experiments with synchrotron radiation. The characteristics of this detector are very attractive in terms of fast readout time, high dynamic range and high signal-to-noise ratio. The prototype XPAD3.1 enabled various diffraction experiments to be performed at different energies, sample-to-detector distances and detector angles with respect to the direct beam, yet it was necessary to perform corrections on the diffraction images according to the type of experiment. This paper is focused on calibration and correction procedures to obtain high-quality scientific results specifically developed in the context of three different experiments, namely mechanical characterization of nanostructured multilayers, elastic-plastic deformation of duplex steel and growth of carbon nanotubes

Controlled biaxial deformation of nanostructured W/Cu thin films studied by X-ray diffraction

The deformation behaviour of 150. nm thick W/Cu nanocomposite deposited on polyimide substrates has been analysed under equi-biaxial tensile testing coupled to X-ray diffraction technique. The experiments were carried out using a biaxial device that has been developed for the DiffAbs beamline of SOLEIL synchrotron source. Finite element analysis has been performed to study the strain distribution into the cruciform shape substrate and define the homogeneous deformed volume. X-ray measured elastic strains in tungsten sub-layers could be carried out for both principal directions. The strain field was determined to be almost equi-biaxial as expected and compared to finite element calculations

Synchrotron X-ray diffraction experiments with a prototype hybrid pixel detector

A prototype X-ray pixel area detector (XPAD3.1) has been used for X-ray diffraction experiments with synchrotron radiation. The characteristics of this detector are very attractive in terms of fast readout time, high dynamic range and high signal-to-noise ratio. The prototype XPAD3.1 enabled various diffraction experiments to be performed at different energies, sample-to-detector distances and detector angles with respect to the direct beam, yet it was necessary to perform corrections on the diffraction images according to the type of experiment. This paper is focused on calibration and correction procedures to obtain high-quality scientific results specifically developed in the context of three different experiments, namely mechanical characterization of nanostructured multilayers, elastic-plastic deformation of duplex steel and growth of carbon nanotubes