• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 4
  • 2
  • 2
  • Tagged with
  • 8
  • 8
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Performance and Radiation Hardness of the ATLAS/SCT Detector Module

Eklund, Lars January 2003 (has links)
<p>The ATLAS experiment is a general purpose experiment being constructed at the Large Hadron Collider (LHC) at CERN, Geneva. ATLAS is designed to exploit the full physics potential of LHC, in particular to study topics con- cerning the Higgs mechanism, Super-symmetry and CP violation. The cross sections for the processes under study are extremely small, requiring very high luminosity colliding beams. The SemiConductor Tracker (SCT) is an essential part of the Inner Detector tracking system of ATLAS. The active elements of the SCT is 4088 detector modules, tiled on four barrel cylinders and eighteen endcap disks. As a consequence of the high luminosity, the detector modules will operate in a harsh radiation environment. This the- sis describes work concerning radiation hardness, beam test performance and methods for production testing of detector modules. The radiation hardness studies have been focused on the electrical performance of the front-end ASIC and the detector module. The results have identifed features of the ASIC failing after irradiation and conrmed the good performance of the re-designed ASIC. The beam tests have been performed in the late prototyping and the pre-production phase, verifying the specied performance of the detector modules. Special effort have been made to evaluate the performance of irradiated detector modules. The assembly, quality assurance and characterisation of the detector modules will be done in the collaborating institutes. The thesis reports on methods developed for use during the production, to assess the electrical performance.</p>
2

Performance and Radiation Hardness of the ATLAS/SCT Detector Module

Eklund, Lars January 2003 (has links)
The ATLAS experiment is a general purpose experiment being constructed at the Large Hadron Collider (LHC) at CERN, Geneva. ATLAS is designed to exploit the full physics potential of LHC, in particular to study topics con- cerning the Higgs mechanism, Super-symmetry and CP violation. The cross sections for the processes under study are extremely small, requiring very high luminosity colliding beams. The SemiConductor Tracker (SCT) is an essential part of the Inner Detector tracking system of ATLAS. The active elements of the SCT is 4088 detector modules, tiled on four barrel cylinders and eighteen endcap disks. As a consequence of the high luminosity, the detector modules will operate in a harsh radiation environment. This the- sis describes work concerning radiation hardness, beam test performance and methods for production testing of detector modules. The radiation hardness studies have been focused on the electrical performance of the front-end ASIC and the detector module. The results have identifed features of the ASIC failing after irradiation and conrmed the good performance of the re-designed ASIC. The beam tests have been performed in the late prototyping and the pre-production phase, verifying the specied performance of the detector modules. Special effort have been made to evaluate the performance of irradiated detector modules. The assembly, quality assurance and characterisation of the detector modules will be done in the collaborating institutes. The thesis reports on methods developed for use during the production, to assess the electrical performance.
3

Técnicas de otimização combinatória multiobjetivo aplicadas na estimação do desempenho elétrico de redes de distribuição. / Multiobjective combinatorial optimization techniques applied on electrical performance estimation of distribution networks.

Kleber Hashimoto 27 September 2004 (has links)
Neste trabalho são apresentadas contribuições para a estimação do desempenho elétrico na distribuição de energia elétrica, com implicações nos mais diversos problemas da operação e do planejamento da distribuição. Entende-se por desempenho elétrico, a avaliação dos parâmetros de congestionamento de redes, as perdas e o nível de tensão. A motivação deste trabalho está na agregação dos esforços advindos da campanha de medição compulsória das concessionárias de distribuição e da necessidade do órgão regulador de estabelecer parâmetros de avaliação do desempenho operacional das empresas, como previsto no documento intitulado “Procedimentos da Distribuição” da Aneel. A estimação do desempenho elétrico é formulada segundo um problema de otimização multiobjetivo onde as funções objetivo compõem uma avaliação de probabilidade de ocorrência e uma avaliação de proximidade dos parâmetros elétricos calculados com os valores obtidos por medição. Os valores das cargas são discretizados segundo probabilidades de ocorrência em cada intervalo, de modo que a formulação resulte em um problema de otimização combinatória multiobjetivo de dimensão exponencial. Propõe-se um procedimento de redução de rede, que diminua consideravelmente o espaço de decisões, e um procedimento de expansão de redes para recompô-la. Também são propostas heurísticas específicas para a obtenção de soluções com cargas diversificadas e desequilibradas. Para uma aplicação adequada destas heurísticas, propôs-se e aplicou-se um método evolucionário metaheurístico para composição das soluções factíveis, ordenadas de acordo com o conceito de dominância de Pareto. Para cada fronteira de dominância, ou conjunto de fronteiras, o aplicativo constrói a distribuição probabilística da corrente e fluxo de potência de cada trecho, o nível de tensão em todas as barras e as perdas técnicas totais do circuito. A formulação matemática de otimização é flexível o bastante para a aplicação prática, considerando os diversos estágios de implementação dos atuais sistemas supervisórios. O modelo evolucionário metaheurístico proposto foi aplicado para um caso ilustrativo evidenciando as suas potencialidades e os pontos a serem aprimorados. / This thesis aims at contributing for the estimation of electrical performance in the distribution of electrical energy. Electrical performance is assumed to be the evaluation of network congestion parameters, losses and voltage level. The development of this work was impelled due to distribution utilities compulsory measurement permanent campaigns, and due to the need of the regulatory agency in establishing operational performance standards, as stated in the Distribution Code of Aneel, the Brazilian Energy Regulatory Agency. The electrical performance estimation is formulated according to an optimization problem where the objective functions correspond to an evaluation of occurrence probability, and correspond to a proximity evaluation of calculated parameters with values obtained by measurement as well. Load values are discretized according to ocurrence probabilities within each interval, so that formulation results in a multiobjective combinatorial optimization of exponential dimension. Network reduction procedures to substantially reduce Decision Domain and network expansion procedures to recompose it are proposed. Specific heuristics are also proposed to get solutions with load diversity and unbalanced loads. In order to adequately apply these heuristics, a metaheuristic evolutionary method to build feasible solutions is proposed and applied, and ranked according to Pareto´s concept. For each dominance frontier or group of frontiers, the application builds the probabilistic: current and load flow distribution of for each branch, voltage level for each bar and circuit technical losses. The mathematical formulation of optimization is flexible enough to be effectively applied taking into account different levels of supervisory systems developed in the utilities. The metaheuristic evolutionary model proposed was applied to a representative case with main potentialities and weak points to be improved.
4

Técnicas de otimização combinatória multiobjetivo aplicadas na estimação do desempenho elétrico de redes de distribuição. / Multiobjective combinatorial optimization techniques applied on electrical performance estimation of distribution networks.

Hashimoto, Kleber 27 September 2004 (has links)
Neste trabalho são apresentadas contribuições para a estimação do desempenho elétrico na distribuição de energia elétrica, com implicações nos mais diversos problemas da operação e do planejamento da distribuição. Entende-se por desempenho elétrico, a avaliação dos parâmetros de congestionamento de redes, as perdas e o nível de tensão. A motivação deste trabalho está na agregação dos esforços advindos da campanha de medição compulsória das concessionárias de distribuição e da necessidade do órgão regulador de estabelecer parâmetros de avaliação do desempenho operacional das empresas, como previsto no documento intitulado “Procedimentos da Distribuição" da Aneel. A estimação do desempenho elétrico é formulada segundo um problema de otimização multiobjetivo onde as funções objetivo compõem uma avaliação de probabilidade de ocorrência e uma avaliação de proximidade dos parâmetros elétricos calculados com os valores obtidos por medição. Os valores das cargas são discretizados segundo probabilidades de ocorrência em cada intervalo, de modo que a formulação resulte em um problema de otimização combinatória multiobjetivo de dimensão exponencial. Propõe-se um procedimento de redução de rede, que diminua consideravelmente o espaço de decisões, e um procedimento de expansão de redes para recompô-la. Também são propostas heurísticas específicas para a obtenção de soluções com cargas diversificadas e desequilibradas. Para uma aplicação adequada destas heurísticas, propôs-se e aplicou-se um método evolucionário metaheurístico para composição das soluções factíveis, ordenadas de acordo com o conceito de dominância de Pareto. Para cada fronteira de dominância, ou conjunto de fronteiras, o aplicativo constrói a distribuição probabilística da corrente e fluxo de potência de cada trecho, o nível de tensão em todas as barras e as perdas técnicas totais do circuito. A formulação matemática de otimização é flexível o bastante para a aplicação prática, considerando os diversos estágios de implementação dos atuais sistemas supervisórios. O modelo evolucionário metaheurístico proposto foi aplicado para um caso ilustrativo evidenciando as suas potencialidades e os pontos a serem aprimorados. / This thesis aims at contributing for the estimation of electrical performance in the distribution of electrical energy. Electrical performance is assumed to be the evaluation of network congestion parameters, losses and voltage level. The development of this work was impelled due to distribution utilities compulsory measurement permanent campaigns, and due to the need of the regulatory agency in establishing operational performance standards, as stated in the Distribution Code of Aneel, the Brazilian Energy Regulatory Agency. The electrical performance estimation is formulated according to an optimization problem where the objective functions correspond to an evaluation of occurrence probability, and correspond to a proximity evaluation of calculated parameters with values obtained by measurement as well. Load values are discretized according to ocurrence probabilities within each interval, so that formulation results in a multiobjective combinatorial optimization of exponential dimension. Network reduction procedures to substantially reduce Decision Domain and network expansion procedures to recompose it are proposed. Specific heuristics are also proposed to get solutions with load diversity and unbalanced loads. In order to adequately apply these heuristics, a metaheuristic evolutionary method to build feasible solutions is proposed and applied, and ranked according to Pareto´s concept. For each dominance frontier or group of frontiers, the application builds the probabilistic: current and load flow distribution of for each branch, voltage level for each bar and circuit technical losses. The mathematical formulation of optimization is flexible enough to be effectively applied taking into account different levels of supervisory systems developed in the utilities. The metaheuristic evolutionary model proposed was applied to a representative case with main potentialities and weak points to be improved.
5

Welding methods for electrical connections in battery systems

Chamberlain, Alec, Larsson, Harald, Nilsson, Louise, Vasquez, Daniel, Schouri, Samir, Myrsell, Elin, Walin, Sally January 2019 (has links)
The demand for high energy battery assemblies is growing in sectors such as transportation. Alongwith it is the need for reliable, efficient and cost-effective ways to electrically connect the batteries toensure their performance. Battery cells are most often put into modules or packs when produced forelectrically driven vehicles. The variable of greatest influence when welding battery packs is thecontact resistance between the cell and the connection tab. It is crucial to minimize this variable asmuch as possible to prevent energy loss in the form of heat generation. The purpose of this project is to conduct a comparative literature study of different weldingtechniques for welding batteries. The compared techniques are resistance spot welding, laser beamwelding and ultrasonic welding. The performance was evaluated in terms of numerous factors such asproduction cost, degree of automation and weld quality. All three methods are tried and proven to function in the production of battery applications. Eachmethod has separate strengths and limitations which makes them complement each other. Thus, it isimportant to look at several factors when deciding which welding technique is the most suitable forthe desired application. The scale of production, economical aspects as well as battery cell geometrywere concluded to be the most important in making this decision.
6

Effets de la compensation du dopage sur les propriétés électriques du silicium et sur les performances photovoltaïques des cellules à base de silicium solaire purifié par voie métallurgique / Influence of the dopant compensation on the silicon electronic properties and on the performances of solar grade silicon solar cells

Veirman, Jordi 27 October 2011 (has links)
Ce travail a pour but de comprendre l’effet de la compensation du dopage sur les performances des cellules photovoltaïques à base de silicium de qualité solaire purifié par voie métallurgique. Après avoir développé la physique des matériaux compensés, l’influence de la compensation a été étudiée à l’échelle de la plaquette. Nous avons mis en évidence une forte réduction non prédite de la mobilité des porteurs. Au contraire, la compensation du dopage s’est avérée bénéfique à la durée de vie volumique. Nous avons précisé les propriétés recombinantes des dopants. L’étude a été transposée à l’échelle de la cellule. Des rendements de 16% ont été obtenus sur des cellules fortement dopées et compensées. La présence de nombreuses associations entre impuretés dopantes et défauts nous a conduits à l’élaboration d’un algorithme permettant de simuler la cinétique de ce type d’association. Enfin, deux techniques innovantes de mesure des teneurs en dopants et en oxygène interstitiel ont été présentées. / This study aims at understanding the influence of the dopant compensation on the performances of solar cells based on solar-grade silicon purified via metallurgical routes. We first detailed the physics of compensated semiconductors. The compensation effects were then studied at the wafer level. We found a sharp unpredicted reduction in carrier mobility at high compensation level. Conversely, the dopant compensation was shown to be very beneficial to the carrier lifetime. We specified the recombination properties of dopants. We then focused on the compensation effects at the solar cell level. We obtained conversion efficiencies of 16% on highly doped and compensated solar cells, revealing the photovoltaic potential of solar-grade silicon. Since numerous association reactions occur between dopants and defects, we built an algorithm in order to simulate the association kinetics of such reactions. Eventually, we presented two innovative characterisation techniques that allow the concentrations of dopants and light elements to be measured.
7

Analysis of the Annealing Budget of Metal Oxide Thin-Film Transistors Prepared by an Aqueous Blade-Coating Process

Tang, Tianyu, Dacha, Preetam, Haase, Katherina, Kreß, Joshua, Hänisch, Christian, Perez, Jonathan, Krupskaya, Yulia, Tahn, Alexander, Pohl, Darius, Schneider, Sebastian, Talnack, Felix, Hambsch, Mike, Reineke, Sebastian, Vaynzof, Yana, Mannsfeld, Stefan C. B. 18 April 2024 (has links)
Metal oxide (MO) semiconductors are widely used in electronic devices due to their high optical transmittance and promising electrical performance. This work describes the advancement toward an eco-friendly, streamlined method for preparing thin-film transistors (TFTs) via a pure water-solution blade-coating process with focus on a low thermal budget. Low temperature and rapid annealing of triple-coated indium oxide thin-film transistors (3C-TFTs) and indium oxide/zinc oxide/indium oxide thin-film transistors (IZI-TFTs) on a 300 nm SiO2 gate dielectric at 300 °C for only 60 s yields devices with an average field effect mobility of 10.7 and 13.8 cm2 V−1 s−1, respectively. The devices show an excellent on/off ratio (>106), and a threshold voltage close to 0 V when measured in air. Flexible MO-TFTs on polyimide substrates with AlOx dielectrics fabricated by rapid annealing treatment can achieve a remarkable mobility of over 10 cm2 V−1 s−1 at low operating voltage. When using a longer post-coating annealing period of 20 min, high-performance 3C-TFTs (over 18 cm2 V−1 s−1) and IZI-TFTs (over 38 cm2 V−1 s−1) using MO semiconductor layers annealed at 300 °C are achieved.
8

Contribution au développement d'une mini-pelle tout-électrique : Approche prédictive pour la commande efficace et compliante des actionneurs électromécaniques / Contribution to the development of a full-electric mini-excavator : A predictive Approch to an efficient and compliant control of an electro-mechanical actuator

Gendrin, Martin 30 May 2016 (has links)
Les actionneurs électromécaniques supplantent les solutions d’actionnement hydrauliques concurrentes dans un nombre croissant d’applications industrielles, particulièrement en aéronautique. Ils le doivent à leurs rendements élevés et à une relative simplicité de commande. Fort de ces avantages, cette technologie a été mise en place dans le cadre du projet ELEXC, en vue de remplacer les vérins hydrauliques sur une mini-excavatrice tout-électrique et s’attaquant pour la première fois au secteur du bâtiment et des travaux publics. Cependant, cette intégration s’accompagne de doutes sur la performance et la durabilité de ces actionneurs dans ce cas précis d’utilisation. Pour répondre à ces interrogations, ce manuscrit se focalisera dans un premier volet sur la caractérisation des performances d’une structure spécifique, permise par la mise en place d’un banc de test multi-énergies instrumenté. Cette étude aboutira à la mise en place d’un modèle par lois physiques dont les paramètres auront été identifiés expérimentalement.Deux solutions innovantes vont ensuite être proposées, visant respectivement à réduire les répercussions, notamment énergétiques, de la caractéristique discrète du convertisseur à découpage, et à parer au manque de compliance de l’actionneur tout en conservant ses capacités de creusage. Elles seront toutes deux associées au concept de commande prédictive, mais offriront chacune une spécificité par rapport à l’implémentation standard de ce type de commande tout en conservant ses avantages. La première prendra la forme d’un modulateur fondé sur le principe d’une modulation de largeur d’impulsion vectorielle, dont la séquence sera sélectionnée par un contrôleur prédictif en rapport avec une fonction de coût alliant les ondulations de courant, les pertes par commutation et la tension de mode commun spécifiques aux séquences. La seconde consistera en un contrôleur d’impédance à boucle de position interne, dont les paramètres d’impédance seront variables et définis par un contrôleur prédictif afin de permettre une bonne pénétration dans l’environnement tout en limitant la dynamique et la valeur maximale de l’effort de compression sur la transmission. / Nowadays, the electro-mechanical actuators (EMA) are seen as an alternative to the conventional hydraulic cylinders in a growing number of industrial applications, including the aeronautic sector, thanks to their high efficiency and relatively simple commandability. According to this features, this actuator technology was selected to replace the hydraulic cylinders of the actuation system of a full-electric compact excavator in the ELEXC project. However, some concerns arose from the lack of existing examples with EMA functioning in relatively severe working conditions implying collisions of the actuators with stiff environments. Therefore, this manuscript will first focus on the characterization of the electro-mechanical actuator and of its performances in this specific case of application, enabled by the development of a multi-energy test-rig. Beside the validation of the EMA capacities, a physic law model will be developed, and its parameters tuned according to the experimental results. In a second part of this manuscript, two novel control laws will be proposed, aiming respectively to reduce the negative repercussions of the discrete characteristic of the electrical converter, and to counterpart the lack of natural compliance of the mechanical actuator. They will be both based on the concept of predictive control, but will differ from the conventional implementation of this type of controller. The first proposed topology is a modulator based on a vector Pulse Width Modulation, in which the PWM sequence to be used is defined online by a predictive controller according to a cost function that takes into account the current ripples, the switching losses and the common mode voltages specific to the sequences. Next, a position-based impedance controller, whose impedance parameters are defined online by a predictive controller, is introduced, in order to enable the EMA to penetrate a stiff environment with a relatively low dynamic increase of compression force on the mechanical transmission.

Page generated in 0.0756 seconds