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Vazamentos em tubos pressurizados geram ondas acústicas que se propagam através das paredes destes tubos, as quais podem ser captadas por acelerômetros ou por sensores de emissão acústica. O conhecimento de como estas paredes podem vibrar, ou de outro modo como as ondas acústicas se propagam neste meio, é fundamental em um processo de detecção e localização da fonte de vazamento. Neste trabalho, foi implementado um modelo analítico, através das equações de movimento da casca cilíndrica, com o objetivo de entender o comportamento da superfície do tubo em função de uma excitação pontual. Como a superfície cilíndrica é um meio fechado na direção circunferencial, ondas que iniciaram sua jornada, a partir de uma fonte pontual sobre a superfície, se encontrarão com outras que já completaram a volta na casca cilíndrica, tanto no sentido horário como no anti-horário, gerando interferências construtivas e destrutivas. Após um tempo suficiente, uma estacionariedade é atingida, criando pontos de picos e vales na superfície da casca, os quais podem ser visualizadas através de uma representação gráfica do modelo analítico criado. Os resultados teóricos foram comprovados através de medidas realizadas em uma bancada de testes composta de um tubo de aço terminado em caixa de areia, simulando a condição de tubo infinito. Para proceder à localização da fonte pontual sobre a superfície, adotou-se o processo de solução inversa, ou seja, conhecidos os sinais dos sensores dispostos na superfície do tubo, determina-se através do modelo teórico onde a fonte que gerou estes sinais pode estar. / Leaks in pressurized tubes generate acoustic waves that propagate through the walls of these tubes, which can be captured by accelerometers or by acoustic emission sensors. The knowledge of how these walls can vibrate, or in another way, how these acoustic waves propagate in this material is fundamental in the detection and localization process of the leak source. In this work an analytic model was implemented, through the motion equations of a cylindrical shell, with the objective to understand the behavior of the tube surface excited by a point source. Since the cylindrical surface has a closed pattern in the circumferential direction, waves that are beginning their trajectory will meet with another that has already completed the turn over the cylindrical shell, in the clockwise direction as well as in the counter clockwise direction, generating constructive and destructive interferences. After enough time of propagation, peaks and valleys in the shell surface are formed, which can be visualized through a graphic representation of the analytic solution created. The theoretical results were proven through measures accomplished in an experimental setup composed of a steel tube finished in sand box, simulating the condition of infinite tube. To determine the location of the point source on the surface, the process of inverse solution was adopted, that is to say, known the signals of the sensor disposed in the tube surface, it is determined through the theoretical model where the source that generated these signals can be.

Vazamentos em tubos pressurizados geram ondas acústicas que se propagam através das paredes destes tubos, as quais podem ser captadas por acelerômetros ou por sensores de emissão acústica. O conhecimento de como estas paredes podem vibrar, ou de outro modo como as ondas acústicas se propagam neste meio, é fundamental em um processo de detecção e localização da fonte de vazamento. Neste trabalho, foi implementado um modelo analítico, através das equações de movimento da casca cilíndrica, com o objetivo de entender o comportamento da superfície do tubo em função de uma excitação pontual. Como a superfície cilíndrica é um meio fechado na direção circunferencial, ondas que iniciaram sua jornada, a partir de uma fonte pontual sobre a superfície, se encontrarão com outras que já completaram a volta na casca cilíndrica, tanto no sentido horário como no anti-horário, gerando interferências construtivas e destrutivas. Após um tempo suficiente, uma estacionariedade é atingida, criando pontos de picos e vales na superfície da casca, os quais podem ser visualizadas através de uma representação gráfica do modelo analítico criado. Os resultados teóricos foram comprovados através de medidas realizadas em uma bancada de testes composta de um tubo de aço terminado em caixa de areia, simulando a condição de tubo infinito. Para proceder à localização da fonte pontual sobre a superfície, adotou-se o processo de solução inversa, ou seja, conhecidos os sinais dos sensores dispostos na superfície do tubo, determina-se através do modelo teórico onde a fonte que gerou estes sinais pode estar. / Leaks in pressurized tubes generate acoustic waves that propagate through the walls of these tubes, which can be captured by accelerometers or by acoustic emission sensors. The knowledge of how these walls can vibrate, or in another way, how these acoustic waves propagate in this material is fundamental in the detection and localization process of the leak source. In this work an analytic model was implemented, through the motion equations of a cylindrical shell, with the objective to understand the behavior of the tube surface excited by a point source. Since the cylindrical surface has a closed pattern in the circumferential direction, waves that are beginning their trajectory will meet with another that has already completed the turn over the cylindrical shell, in the clockwise direction as well as in the counter clockwise direction, generating constructive and destructive interferences. After enough time of propagation, peaks and valleys in the shell surface are formed, which can be visualized through a graphic representation of the analytic solution created. The theoretical results were proven through measures accomplished in an experimental setup composed of a steel tube finished in sand box, simulating the condition of infinite tube. To determine the location of the point source on the surface, the process of inverse solution was adopted, that is to say, known the signals of the sensor disposed in the tube surface, it is determined through the theoretical model where the source that generated these signals can be.

No description available.

L’eau est abondante sur terre, cependant, elle n’est pas répartie de façon équitable sur le globe. C’est ainsi, que des systèmes de distribution d’eau ont été conçus pour répondre aux différents besoins. Dans ce cadre, pour rendre fertiles les terres au-dessus de la source, des réseaux d’irrigation ont été mis en oeuvre en exploitant des systèmes de pompage. Cependant, les réseaux sous pression sont sources de dépenses énergétiques colossales et de pertes en eau qui représentent des enjeux économiques importants. Ceci constitue un défi majeur en vue de l’optimisation des dépenses énergétiques. La présente thèse vise l’analyse du coût énergétique d’un réseau d’irrigation avec application au canal de Carpentras. L’objectif de ce travail est de minimiser les dépenses énergétiques du réseau. Pour ce faire, trois approches ont été explorées. Dans une première partie, une étude s’est focalisée sur l’optimisation des contrats d’électricité d’un point de vue administratif. Le but a été de proposer une méthodologie permettant d’optimiser le coût de la facture d’électricité en agissant sur des éléments du choix de l’exploitant. Dans la deuxième partie, une méthodologie pour la détection et localisation de fuites éventuelles, dans le réseau d’irrigation, est proposée. Cette méthode est fondée sur l’analyse de la circulation de l’eau. La troisième partie a été dédiée au dimensionnement d’un système de production énergétique basé sur l’utilisation des sources renouvelables / Water is abundant on earth, however, it is not evenly distributed on the globe. Thus, water distribution systems have been designed to meet different needs. In this context, to make fertile lands above the source, irrigation networks were implemented by operating pumping systems. However, pressurized networks are a source of huge energy expenditures and water losses that represent important economic issues. This is a major challenge for optimizing energy expenditure. The present thesis aims to analyze the energy cost of an irrigation network with application to the Carpentras canal.The objective of this work is to minimize the energy expenditure of the network. To do so, three approaches have been explored. Firstly, a study focused on the optimization of electricity contracts from an administrative point of view. The aim was to propose a methodology to optimize the cost of the electricity bill by acting on elements chosen by the operator. Secondly, a methodology for the detection and localization of possible leaks, in the irrigation network, is proposed. This method is based on the analysis of the circulation of water. Finally, a part was dedicated to the sizing of an energy production system based on the use of renewable sources

Indiana University-Purdue University Indianapolis (IUPUI) / Compressed air is a powerful source of stored energy and is used in a variety of applications varying from painting to pressing, making it a versatile tool for manufacturers. Due to the high cost and energy consumption associated with producing compressed air and it’s use within industrial manufacturing, it is often referred to as a fourth utility behind electricity, natural gas, and water. This is the reason why air compressors and associated equipment are often the focus for improvements in the eyes of manufacturing plant managers. As compressed air can be used in multiple ways, the methods used to extract and transfer the energy from this source vary as well. Compressed air can flow through different types of piping, such as aluminum, Polyvinyl Chloride (PVC), rubber, etc. with varying hydraulic diameters, and through different fittings such as 90-degree elbows, T-junctions, valves, etc. which can cause one of the major concerns related to managing the energy consumption of an air compressor, and that is the waste of air through leaks. Air leaks make up a considerable portion of the energy that is wasted in a compressed air system, as they cause a multitude of problems that the compressor will have to make up for to maintain the steady operation of the pneumatic devices on the manufacturing floor that rely on compressed air for their application. When air leaks are formed within the compressed air piping network, they act as continuous consumers and cause not only the siphoning off of said compressed air, put also reduce the pressure that is needed within the pipes. The air compressors will have to work harder to compensate for the losses in the pressure and the amount of air itself, causing an overconsumption of energy and power. Overworking the air compressor also causes the internal equipment to be stretched beyond its capabilities, especially if they are already running at full loads, reducing their total lifespans considerably. In addition, if there are multiple leaks close to the pneumatic devices on the manufacturing floor, the immediate loss in pressure and air can cause the devices to operate inefficiently and thus cause a reduction in production. This will all cumulatively impact the manufacturer considerably when it comes to energy consumption and profits. There are multiple methods of air leak detection and accounting that currently exist so as to understand their impact on the compressed air systems. The methods are usually conducted when the air compressors are running but during the time when there is no, or minimal, active consumption of the air by the pneumatic devices on the manufacturing floor. This time period is usually called non-production hours and generally occur during breaks or between employee shift changes. This time is specifically chosen so that the only air consumption within the piping is that of the leaks and thus, the majority of the energy and power consumed during this time is noted to be used to feed the air leaks. The collected data is then used to extrapolate and calculate the energy and power consumed by these leaks for the rest of the year. There are, however, a few problems that arise when using such a method to understand the effects of the leaks in the system throughout the year. One of the issues is that it is assumed that the air and pressure lost through the found leaks are constant even during the production hours i.e. the hours that there is active air consumption by the pneumatic devices on the floor, which may not be the case due to the increased air flow rates and varying pressure within the line which can cause an increase in the amount of air lost through the same orifices that was initially detected. Another challenge that arises with using only the data collected during a single non-production time period is that there may be additional air leaks that may be created later on, and the energy and power lost due to the newer air leaks would remain unaccounted for. As the initial estimates will not include the additional losses, the effects of the air leaks may be underestimated by the plant managers. To combat said issues, a continuous method of air leak analyses will be required so as to monitor the air compressors’ efficiency in relation to the air leaks in real time. By studying a model that includes both the production, and non-production hours when accounting for the leaks, it was observed that there was a 50.33% increase in the energy losses, and a 82.90% increase in the demand losses that were estimated when the effects of the air leaks were observed continuously and in real time. A real time monitoring system can provide an in-depth understanding of the compressed air system and its efficiency. Managing leaks within a compressed air system can be challenging especially when the amount of energy wasted through these leaks are unaccounted for. The main goal of this research was to find a nonintrusive way to calculate the amount of air as well as energy lost due to these leaks using time series pressure measurements. Previous studies have shown a strong relationship between the pressure difference, and the use of air within pneumatic lines, this correlation along with other factors has been exploited in this research to find a novel and viable method of leak accounting to develop a Continuous Air Leak Monitoring (CALM) system.

In the atomic energy pile at Chalk River, heavy water (deuterium oxide, D2O) is to be used as a moderator. Early in 1944, it became evident that frequent determinations of the isotopic composition of D2O samples would be required. For this purpose, there was obtained from the American authorities a mass spectrometer specially designed for routine hydrogen isotope analysis. This instrument was assembled and put into operation at McMaster in the summer of 1944. During the course of subsequent work, two other deuterium mass spectrometers were built in this laboratory, following the design of the instrument sent from the United States; one of these has now been installed at the plant site, and a second is to follow at an early date. The studies reported below involved the determination of operating conditions, the measurement of grid leaks, of the order of 10^10 ohms, and the investigation of further applications of the deuterium mass spectrometer. / Thesis / Master of Science (MSc)

This study is a content analysis of the coverage in Time, Newsweek, and U. S. News & World Report on Spiro Agnew from August 13 to October 22, 1973, and is concerned with the use of leaks as determined by analyzing the levels of attribution and the attitudes of the magazines toward leaks. All three magazines used approximately equivalent amounts of material from concealed sources. Time and Newsweek defended the use of leaks; U. S. News & World Report attacked their use. The perils inherent in using information from concealed sources make it necessary to consult as many sources as feasible when following a controversial story.

Cette étude a pour objectif de déterminer dans quelle mesure les APR, dont les performances sont qualifiées pour des particules supérieures à 100 nm, sont efficaces pour des nanoparticules. En effet, dans le cas où l'utilisation d'une filtration collective est insuffisante, le port d'un Appareil de Protection Respiratoire (APR) est le dernier rempart préconisé. Une synthèse bibliographique a montré qu'aucune recherche n'a porté sur l'efficacité de demi-masques avec filtres pour des nanoparticules. Le banc d'ETude des NAnoparticules a été dimensionné et réalisé afin de pallier ces manques. Deux demi-masques ont été testés selon différentes configurations d'essais : débit constant et débit cyclique (débit moyen de 84 L/min) ; taille des particules (de 5 à 100 nm) ; pose du masque (scellée, libre, ou avec des fuites calibrées). Les résultats montrent que, dès lors que les APR utilisés contiennent des media (non électrets) efficaces pour des particules de la zone MPPS (100 nm - 300 nm), les APR sont plus efficaces pour les particules nanométriques. De plus, les résultats obtenus, en présence de fuites réelles et calibrées, ont mis en évidence l'importance des fuites au visage dans la détermination des performances des APR. Un modèle de calcul du facteur de protection a été établi, basé sur la différenciation des débits d'air traversant la fuite et le filtre. Cette modélisation a été validée à l'aide des mesures obtenues en présence des fuites calibrées, et appliquée pour l'analyse de nos résultats en pose libre / This study aims to determine how the respiratory protective devices (RPD), whose performances are qualified for particles above 100 nm, are effective for nanoparticles. Indeed, if the use of a collective filtration is inadequate, wearing a RPD is the last protection recommended. A literature review showed that no research concerned the effectiveness of half-masks for nanoparticles. The test bench ETNA has been sized and built to overcome these lacks. Two half masks were tested according to different configurations: constant flow rate and cyclic flow rate (average flow of 84 L /min) ; particle size (from 5 to 100 nm) ; positions of the mask (sealed, usual, or with calibrated leaks). The results show that, since the RPD contain high efficiency filter media (without charged fibers) for the most penetrating particle size (100 nm - 300 nm), the RPD is more efficient for nanoparticles. Furthermore, the results obtained in the presence of actual and calibrated leaks, highlighted the importance of faceseal leakages in determining the performance of RPD. A model for calculating the protection factor was established based on the balance between the airflow through the filter and the leak. This model was validated using measurements obtained in the presence of calibrated leaks, and applied for the analysis of our results in usual position

La problématique développée dans cette thèse est le diagnostic des piles à combustible (PAC) de type « Proton Exchange Membrane » (PEM). Nous avons choisi d’axer ces travaux sur différentes méthodes de diagnostic, séparées en deux grandes thématiques, relativement différentes et donc indépendantes, qui forment les deux parties de cette thèse. Dans la première partie, intitulée « Méthodes de diagnostic des fuites internes », nous nous focaliserons sur un type de dégradation des PAC, celle de la membrane, et de sa conséquence principale, l’augmentation des fuites internes. Après avoir fait l’inventaire des différentes techniques de diagnostic possibles, nous avons eu l’opportunité d’en tester certaines sur un stack (empilement de cellules élémentaires) dégradé dont nous disposions. La voltammétrie cyclique semble la plus intéressante en terme de précision. Cependant, pour le diagnostic complet d’un stack, le niveau de fuite de chaque cellule doit être évalué. Il apparaît que cette opération est extrêmement chronophage ; nous avons donc dû mettre au point des méthodes alternatives à celles rencontrées fréquemment dans la littérature. Nous avons d’une part appliqué la voltammétrie cyclique directement aux bornes du stack et parallèlement nous avons mis au point une technique nouvelle de diagnostic des fuites internes d’une PAC. Ces méthodes seront testées sur trois stacks comportant chacun un nombre différent de cellules. La deuxième partie de ce manuscrit est intitulée « Méthodes de diagnostic en gaz actifs ». Nous aborderons dans un premier temps une méthode bien connue, la Spectroscopie d’Impédance Electrochimique (SIE). L’utilisation de cette technique soulève deux problématiques : le choix d’un modèle approprié pour décrire des phénomènes physico-chimiques variés puis la difficulté de converger vers un jeu unique de paramètres une fois le modèle établi. Partant de ce constat, nous avons développé une technique originale d’exploitation des SIE, basée sur un modèle électrique sans a priori, dont la construction va se faire automatiquement étape par étape. Cet algorithme sera validé de manière théorique sur des simulations, puis nous confirmerons son potentiel sur des données expérimentales issues d’essais de vieillissement de monocellules. Parallèlement, nous avons développé une technique alternative à la spectroscopie d’impédance, basée sur l’exploitation d’échelons de courant. Cette méthode permet d’extraire un spectre de constantes de temps sans passer par de l’identification paramétrique. Après une première validation théorique grâce à des simulations, nous avons éprouvé cette technique avec d’une part les données de vieillissement mentionnées précédemment ainsi qu’avec des données issues d’un essai d’engorgement d’une monocellule. Nous confirmerons que cette technique est bien adaptée pour effectuer du diagnostic en cours de fonctionnement. / This thesis deals with Proton Exchange Membrane Fuel Cell (PEMFC) diagnosis. Several methods will be treated, that have been divided into two main issues. These issues are quite independent and constitute the two parts of the manuscript. The first part, entitled “internal leakage detection methods”, concerns a major fault in PEMFC: membrane permeation. The consequence is the increase of internal leakage, or crossover. First, several diagnosis techniques are listed, and some of them are tested on a faulty stack. Cyclic voltammetry seems to be a good choice, but needs a lot of time to be performed on a large scale stack. Indeed, to achieve a satisfying level of diagnosis, the crossover of every cell in the stack has to be evaluated. New diagnosis techniques are needed to shorten the test phase. Cyclic voltammetry is performed directly at the stack level, while concurrently a new method is investigated to measure all cell crossovers simultaneously. Validation is done by experiments on three different stacks with different numbers of cells. The second part is entitled “diagnosis methods with active gases”. In a first time the well-known Electrochemical Impedance Spectroscopy (EIS) technique has been used as a characterization tool. But two issues arise from the EIS use: the choice of an appropriate model that describes all the electrochemical phenomena and the difficulty to obtain a unique set of parameters after the fitting stage. To solve these issues, an algorithm has been developed. It is based on an electrical circuit model built automatically step by step, which does not require the knowledge of every phenomenon of the studied system. The algorithm is validated theoretically by numerical simulations and then by experimental data collected from ageing tests with single cells. Secondly, a method alternative to EIS has been investigated, based on the fuel cell voltage response to current steps. A time-constant spectrum can be extracted from this response without the need of parameter identification process. After a first validation thanks to numerical simulations, this algorithm has been tested with the ageing data previously mentioned and also with a flooding experiment performed on a single cell. The time-constant spectrum seems to be an appropriate tool for fuel cell online diagnosis.