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  • 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.
101

Contribution à la modélisation CEM d'une chaîne d'actionnement pour une application automobile / Contribution to the EMC modeling of an actuating system for an automotive application

Touré, Mohamed 19 March 2019 (has links)
Nos travaux portent sur l’étude d’une méthodologie de modélisation prédictive CEM en émission conduite pour une chaîne d’actionnement (CA). L’objectif ultime, lié à l’utilisation de ces modèles pour le dimensionnement de ce système, est basé sur une optimisation sous contraintes (conception sous contraintes). Au delà de l’application, nous cherchons à mettre en exergue les bénéfices d’une modélisation multi-niveaux dans la recherche d’un compromis entre la précision et la durée de simulation de ces modèles. Dès lors, le but sera d’obtenir un modèle prédictif pour les perturbations électromagnétiques (PEM) d’émission conduite provenant de la CA étudiée et de confronter les résultats de simulations aux résultats expérimentaux. Pour ce faire, le développement d’un premier modèle représentatif des différents phénomènes physiques intervenant dans le système est nécessaire de façon à simuler ces PEM. Dans le but d’améliorer la précision et la durée de simulation de ce premier modèle, nous nous sommes intéressés à l’application d’un algorithme de macromodélisation passive permettant d’obtenir un macromodèle précis et rapide à évaluer, ce qui permet d’en faire un prétendant idoine en vue d’une optimisation. Ensuite, dans le cadre d’une optimisation sous contraintes, nous avons proposé une illustration de l’utilisation du modèle CEM établi pour la CA étudiée. Cette optimisation par évolution différentielle se limitera au dimensionnement d’un filtre CEM, en faisant intervenir, à cette occasion, des contraintes reflétant la réduction des sources d’échauffement. / This phD dissertation is focused on the study of a methodology in order to predict the conducted electromagnetic interferences (EMI) arising from an actuating system (AS). The ultimate objective, linked to the use of these models for the sizing of this system, is based on an optimization under constraints (design under constraints).Beyond the application, we try to highlight the profits of multilevel modeling in looking for a tradeoff between the accuracy and the time cost of these models. Thereupon, the purpose will be to get a predictive model for the AS conducted EMI and to compare the simulation results to measurements.To that end, the development of a first representative model of the various physical phenomena occurring in the system is necessary so as to simulate the conducted EMI. In the purpose to improve the accuracy and the time cost of this first model, we were interested with care to a passive macromodeling algorithm allowing to obtain a fast and accurate macromodel to be estimated, what allows to make it an ideal pretender with the aim of an optimization.Then, within the framework of an optimization under constraints, we proposed an illustration of the use of the EMC model established for the studied AS. This optimization based on differential evolution will limit itself to the sizing of an EMI filter, by bringing in, on this occasion, constraints which reflect, in our case, thermal losses.
102

Properties and Distortion of Douglas-fir with Comparison to Radiata Pine

Wang, Eric Yunxin January 2009 (has links)
The objectives of this study were to investigate stability related basic wood properties and to determine stability performance of New Zealand grown Douglas-fir and those of radiata pine wood. In this study, nine 60-year old Douglas-fir trees and thirteen 26-year old radiata pine trees were selected from forests in Canterbury region. From these trees, 36 discs of 200 mm thick (13 for Douglas-fir and 23 for radiata pine) and 388 boards with dimensions of 100mm x 50mm x 4.8m (210 fro Douglas-fir and 178 fr radiata pine) were prepared. From the prepared discs, 515 specimens (204 for Douglas-fi and 211 for radiata pine) were prepared for green moisture content (MC) and basic density measurements, The same total number of 515 specimens (205 for Douglas-fir and 210 for radiata pine) were also prepared for shrinkage measurements. From the green MC specimens, green weight, volume and oven-dry weight were measured while for the shrinkage specimens, dimensions and weights were measured at equilibrium for nine humidity conditions. These data were used to analyse basic wood properties and moisture uptake characteristics for both Douglas-fir and radiata pine. Variation of shrinkage within a tree and between trees was also studied for both species. After this, selected specimens (36 for Doulas-fir and 36 for radiata pine) were further tested in water immersion for water repellence examination. The 388 full size boards (100mmx50mmx4.8m) were used for studies on distortion and acoustic properties at a sawmill (Southland Timber Ltd.). Dimensions, weights and acoustic velocity were measured from each board before and after drying. These data were used to analyse distortion and strength characteristics for both Douglas-fir and radiata pine. Comparison of the relative stability of full sized Douglas-fir and radiata pine structural timber was investigated in this study. The results from small sample study confirmed that Douglas-fir is much stronger, has lower longitudinal shrinkage and lower gradient in corewood which can be used to explain the better dimensional stability of Douglas-fir than radiate pine although there is significant variability in the shrinkage for both Douglas-fir and radiate pine. In water immersion tests, Douglas-fir has better water repellency property than radiata pine over 2000 hours period during water immersion. Under the same commercial practice in sawing and kiln drying, it is clearly shown that Douglas-fir timbers were straighter with lower levels of distortion than radiata pine at similar final moisture content. It is also interesting to note that the final moisture content in a range of 13-18% for Douglas-fir did not have significant impact on timber distortion but a negative trend was observed for radiata pine with MC in a range of 9 -14%. Tree heights showed clear influence on twist for radiata pine timbers, but it was not clearly observed from Douglas-fir timbers. Corewood proportion is found to have negative impact on the timber distortion for both Douglas-fir and radiata pine. Douglas-fir timbers showed much higher average acoustic MOE value than radiata pine timbers at similar final moisture content. Because of the various proportion of corewood, the shrinkage varied greatly along the stem height and along the disc radius direction for the two species. This variation caused the difference of distortion between corewood, outerwood and transition wood, but the difference between butt log, middle log and top log is inconsistent. Therefore, it is recommended that the corewood proportion to be a criterion for the timber pre-sorting. Variation of stability performance between trees was also found to be significant for the two species, and methods need to be developed for log sorting as well to reduce the timber distortion degradation. Non-destructive testing method such as acoustic tool may be offered to be a new approach for sorting logs, but it is also necessary to be aware of the significant difference between species. The outcome from this project includes better understanding of Douglas-fir for structural applications. The conclusion can be drawn that Douglas-fir has superior quality for its strength, durability and moisture resistance. Douglas-fir is also claimed to have uniform properties and thus to be more stable compared to radiata pine. Douglas-fir timbers showed much higher acoustic MOE value than radiate pine timbers as similar final moisture content.
103

Flash Diffractive Imaging in Three Dimensions

Ekeberg, Tomas January 2012 (has links)
During the last years we have seen the birth of free-electron lasers, a new type of light source ten billion times brighter than syncrotrons and able to produce pulses only a few femtoseconds long. One of the main motivations for building these multi-million dollar machines was the prospect of imaging biological samples such as proteins and viruses in 3D without the need for crystallization or staining. This thesis contains some of the first biological results from free-electron lasers. These results include 2D images, both of whole cells and of the giant mimivirus and also con- tains a 3D density map of the mimivirus assembled from diffraction patterns from many virus particles. These are important proof-of-concept experiments but they also mark the point where free-electron lasers start to produce biologically relevant results. The most noteworthy of these results is the unexpectedly non-uniform density distribution of the internals of the mimivirus. We also present Hawk, the only open-source software toolkit for analysing single particle diffraction data. The Uppsala-developed program suite supports a wide range fo algorithms and takes advantage of Graphics Processing Units which makes it very computationally efficient. Last, the problem introduced by structural variability in samples is discussed. This includes a description of the problem and how it can be overcome, and also how it could be turned into an advantage that allows us to image samples in all of their conformational states.
104

Phasing Two-Dimensional Crystal Diffraction Pattern with Iterative Projection Algorithms

January 2016 (has links)
abstract: Phase problem has been long-standing in x-ray diffractive imaging. It is originated from the fact that only the amplitude of the scattered wave can be recorded by the detector, losing the phase information. The measurement of amplitude alone is insufficient to solve the structure. Therefore, phase retrieval is essential to structure determination with X-ray diffractive imaging. So far, many experimental as well as algorithmic approaches have been developed to address the phase problem. The experimental phasing methods, such as MAD, SAD etc, exploit the phase relation in vector space. They usually demand a lot of efforts to prepare the samples and require much more data. On the other hand, iterative phasing algorithms make use of the prior knowledge and various constraints in real and reciprocal space. In this thesis, new approaches to the problem of direct digital phasing of X-ray diffraction patterns from two-dimensional organic crystals were presented. The phase problem for Bragg diffraction from two-dimensional (2D) crystalline monolayer in transmission may be solved by imposing a compact support that sets the density to zero outside the monolayer. By iterating between the measured stucture factor magnitudes along reciprocal space rods (starting with random phases) and a density of the correct sign, the complex scattered amplitudes may be found (J. Struct Biol 144, 209 (2003)). However this one-dimensional support function fails to link the rod phases correctly unless a low-resolution real-space map is also available. Minimum prior information required for successful three-dimensional (3D) structure retrieval from a 2D crystal XFEL diffraction dataset were investigated, when using the HIO algorithm. This method provides an alternative way to phase 2D crystal dataset, with less dependence on the high quality model used in the molecular replacement method. / Dissertation/Thesis / Doctoral Dissertation Physics 2016
105

Méthodologie d'analyse CEM conduite d'un réseau multiconvertisseurs / Methodology for studying conducted EMC of an embedded network composed of several power converters

Foissac, Mikael 16 October 2012 (has links)
L’état de l’art aujourd’hui dans la CEM en électronique de puissance permet d’avoir une certaine connaissance des émissions conduites générées par un convertisseur statique sur un réseau fictif normalisé. L’objectif est maintenant de progresser vers la prise en compte de plusieurs convertisseurs connectés sur un réseau complexe de type « réseau de bord ». Dans le cadre du projet PEPS CEM intégré au projet plus vaste O2M, cette thèse propose une méthodologie d’analyse permettant de connaître les perturbations CEM conduites avec précision sur un réseau complexe connecté à de multiples convertisseurs. Une approche théorique sur l’idée originale de ces modèle CEM « système » a été développé sous forme d’un modèle type boîte noire prenant en compte l’ensemble du convertisseur avec sa charge et validé par des simulations complexes et l’expérimentation prenant en compte plusieurs convertisseurs statiques connectés sur le même réseau. / Today, the state of the art in EMC in power electronics allows to have some knowledge on conducted emissions generated by a converter on a Line Impedance Stabilization Network. Now, the new challenge is to include several converters connected in an embedded network. This PHD has been funded trhough the PEPS CEM sub-project, part of O2M project. It proposes a method to obtain the EMC interferences on a complex network including several converters. Based on the original idea of a “system” type EMC model, we came up with a theoretical approach based on a “Black Box” model. This model, including the converter load, has been validated through complex simulations as well as experimentations taking in account several static converters connected to the same network.
106

Contribution à la modélisation des systèmes mise à la terre : .en vue de la simulation des réseaux électriques du bâtiment / Contribution to the modeling of Grounding systems : for the simulation of building's electrical grid

Gouichiche, Zaki 23 January 2017 (has links)
Le bâtiment quel qu'il soit (industrie, tertiaire, domestique), s'électrifie toujours plus pour répondre entre autre au besoin de l'efficacité énergétique. Ainsi de nombreux équipements, en particulier d'électronique de puissance ou encore d'actionneurs sont présents et produisent des perturbations électromagnétiques tant conduites que rayonnées véhiculées ou propagées par les câblages électriques et dispositifs de protection, dimensionnés pour 50Hz et non les hautes fréquences. Ceci est à l’origine de la problématique CEM dans le bâtiment. La méthodologie de modélisation proposée consiste à chercher un schéma équivalent pour chaque constituant ou composant d’une installation. L’accès aux paramètres localisés de chacun est un des points fort de la méthode, tout en permettant l’association avec d’autres composants (couplages). Les modèles ainsi générés sont implantés automatiquement dans un logiciel circuit, en l’occurrence Spice, permettant la résolution et l’association d’autres équipements électriques complexes. La modélisation des différents composants, principalement le circuit de mise à la terre, permet la simulation et l’analyse de plusieurs configurations qui devraient nous permettre de dicter des règles de conception pour rendre plus robuste le bâtiment moderne fortement électrifié. / In order to answer the need for energy efficiency, building, whatever it is (industrial, commercial, domestic), still electrifies more and more. Hence many equipment, in particular power electronic or actuators are introduced and produce conducted and radiated electromagnetic disturbances. They propagate via cabling and protection devices which have been sized for 50Hz and not for high frequencies generated by the equipment. This constitutes the EMC problematic for building.The proposed modeling methodology is to evaluate an electrical equivalent circuit for each installation’s component. Access to lumped parameters of each component is one of the highlights of this method, allowing the other components association (couplings). The generated models are implemented in a circuit software such as Spice, enabling the resolution and the association of other electrical components.The modeling of the components, mainly the grounding circuit, allows the simulation of different configurations. The analysis of several configurations should help the elaboration of design rules to make today buildings more efficient.
107

Hard QCD Processes in the Nuclear Medium

Freese, Adam 29 March 2016 (has links)
The environment inside the atomic nucleus is one of the most fascinating arenas for the study of quantum chromodynamics (QCD). The strongly-interacting nature of the nuclear medium affects the nature of both QCD processes and the quark-gluon structure of hadrons, allowing several unique aspects of the strong nuclear force to be investigated in reactions involving nuclear targets. The research presented in this dissertation explores two aspects of nuclear QCD: firstly, the partonic structure of the nucleus itself; and secondly, the use of the nucleus as a micro-laboratory in which QCD processes can be studied. The partonic structure of the nucleus is calculated in this work by deriving and utilizing a convolution formula. The hadronic structure of the nucleus and the quark-gluon structure of its constituent nucleons are taken together to determine the nuclear partonic structure. Light cone descriptions of short range correlations, in terms of both hadronic and partonic structure, are derived and taken into account. Medium modifications of the bound nucleons are accounted for using the color screening model, and QCD evolution is used to connect nuclear partonic structure at vastly different energy scales. The formalism developed for calculating nuclear partonic structure is applied to inclusive dijet production from proton-nucleus collisions at LHC kinematics, and novel predictions are calculated and presented for the dijet cross section. The nucleus is investigated as a micro-laboratory in vector meson photoproduction reactions. In particular, the deuteron is studied in the break-up reaction γd → Vpn, for both the ϕ(1020) and J/ψ vector mesons. The generalized eikonal approximation is utilized, allowing unambiguous separation of the impulse approximation and final state interactions (FSIs). Two peaks or valleys are seen in the angular distribution of the reaction cross section, each of which is due to an FSI between either the proton and neutron, or the produced vector meson and the spectator nucleon. The presence and size of the latter FSI valley/peak contains information about the meson-nucleon interaction, and it is shown that several models of this interaction can be distinguished by measuring the angular distribution for the deuteron breakup reaction.
108

Development of Physics-based Models and Design Optimization of Power Electronic Conversion Systems

Nejadpak, Arash 21 March 2013 (has links)
The main objective for physics based modeling of the power converter components is to design the whole converter with respect to physical and operational constraints. Therefore, all the elements and components of the energy conversion system are modeled numerically and combined together to achieve the whole system behavioral model. Previously proposed high frequency (HF) models of power converters are based on circuit models that are only related to the parasitic inner parameters of the power devices and the connections between the components. This dissertation aims to obtain appropriate physics-based models for power conversion systems, which not only can represent the steady state behavior of the components, but also can predict their high frequency characteristics. The developed physics-based model would represent the physical device with a high level of accuracy in predicting its operating condition. The proposed physics-based model enables us to accurately develop components such as; effective EMI filters, switching algorithms and circuit topologies [7]. One of the applications of the developed modeling technique is design of new sets of topologies for high-frequency, high efficiency converters for variable speed drives. The main advantage of the modeling method, presented in this dissertation, is the practical design of an inverter for high power applications with the ability to overcome the blocking voltage limitations of available power semiconductor devices. Another advantage is selection of the best matching topology with inherent reduction of switching losses which can be utilized to improve the overall efficiency. The physics-based modeling approach, in this dissertation, makes it possible to design any power electronic conversion system to meet electromagnetic standards and design constraints. This includes physical characteristics such as; decreasing the size and weight of the package, optimized interactions with the neighboring components and higher power density. In addition, the electromagnetic behaviors and signatures can be evaluated including the study of conducted and radiated EMI interactions in addition to the design of attenuation measures and enclosures.
109

Pilotní zavádění DMS v bankovním prostředí / DMS pilot implementation in banking environment

Žáček, Jan January 2014 (has links)
The diploma thesis focuses on the analysis of a document management system (DMS) pilot implementation in the environment of a Czech bank. The thesis is divided into three parts; the first part is theoretical and remaining two parts are practical (analytical). The theoretical part is devoted to summarization of basic theoretical knowledge in the field of DMS and in a pilot deployment of information systems. The second part describes the EMC xCP 2.1 platform and evaluates its advantages and disadvantages compared to competing products. The third part describes the technological implementation and deployment of a new DMS pilot solution in a bank. Further it analyzes and describes the follow-up activities and related projects that increase the DMS usability in a real business applications. The diploma thesis concurrently focuses on the business requirements analysis including constrains of a new solution deployment, as well as the DMS technological aspects description and the solution design. The author of this thesis has been working as an analyst in the IT company and has been in a long-term cooperation with the DMS team in the bank. The motivation for choosing this topic is to make a summary and clarification of knowledge gained on projects in the the bank and to take an advantage of it in the future cooperation.
110

Monitorování rušení v síťovém napájení / Monitoring interference in the mains supply

Jirčík, Zdeněk January 2014 (has links)
This semester thesis describes design of electronic device adapted to monitoring of mains supply. Theoretical parts describes mains supply analysis, communication and management of files to memory. Next part is design electronics blocks and their cooperation. There are description of mains analyzer prototype and it’s parts and functions. Prototype was submitted to test measurement.

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