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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.
721

Měření částečných výbojů u vysokonapěťových kabelů / Partial discharge measurement of middle and high voltage cables

Pelikán, Luděk January 2018 (has links)
The main topic of this work is the analysis of the measurement of partial discharge measurements on high voltage cables. The thesis also deals with other measurements, including the measurement of the loss factor and the voltage retention and breakdown test. Part of the text describes the issue of partial discharge, its measurement by galvanic method and methods of elimination of disturbing influences that affect this method in terms of sensitivity and accuracy of the measured values. Thesis also describes the construction of the cables, their marking and the tests carried out on them. There is also a description of the cable terminals used for measuring, especially water terminals, which are designed for high voltages and which are carried out in the practical part of the thesis. The next part deals with problems prior to the commissioning of water terminals and their preparation for certain tests, including description and evaluation of the results of the measurements.
722

Synthèse de couches optiques par co-dépôt pour les miroirs de LIGO

Lalande, Émile 04 1900 (has links)
En 2015, le Laser Interferometer Gravitational-Wave Observatory (LIGO) a observé pour la première fois des ondes gravitationnelles générées par la fusion de deux trous noirs. Cette observation résulte de 40 ans d’efforts afin de réduire au minimum les sources de bruit qui affectent l’interféromètre. À ce jour, la sensibilité de LIGO, dans son domaine de fréquence le plus sensible, est limitée par la granularité de la lumière d’une part et, d’autre part, par un phénomène de fluctuations thermiques résultat de la dissipation mécanique dans les couches minces qui constituent ses miroirs, en particulier dans le matériau ayant un haut indice de réfraction : l’oxyde de tantale. Une amélioration de la sensibilité permettrait d’observer davantage d’événement, d’autres phénomènes gravitationnels, ainsi que des détails importants permettant de mieux les comprendre. Ce mémoire présente les résultats de nos recherches afin de diminuer le bruit causé par la dissipation mécanique interne dans les couches à haut indice de réfraction. Pour ce faire, des couches d’oxyde de tantale ont été dopées soit au zirconium ou à la fois au zirconium et au titane, par co-dépôt. Des couches avec différentes quantités de dopant ont été synthétisées par pulvérisation cathodique magnétron sur des substrats de silice semblables à ceux de LIGO. Par la suite, la dissipation mécanique, l’épaisseur, la rugosité, la composition, la densité surfacique, et la microstructure ont été caractérisées par suspension nodale, ellipsométrie résolue spectralement, spectrométrie de rétrodiffusion de Rutherford et la spectroscopie Raman. Il appert que le zirconium permet d’augmenter la température de recuit avant la cristallisation, ce qui permet de diminuer plus amplement la dissipation mécanique interne, mais ne change pas la dissipation à une température de recuit donnée. Il a aussi été déterminé que la concentration de titane permettait de diminuer l’angle de perte, peu importe la concentration de zirconium. Une combinaison des deux dopages et un recuit à haute température permet ainsi de recuire par un facteur d’environ 1.5 la dissipation mécanique interne. La différence de coefficient d’expansion thermique durant les recuits à haute température induit cependant des problèmes de craquement des couches, partiellement résolus par l’application d’une couche de recouvrement en silice. / In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) observed for the first time gravitational waves generated by the merger of two black holes. This observation was the resut of 40 years of efforts to minimize the noise source which affect the the interferometer. To this date, the sensitivity of LIGO, in its most sensitive frequency domain, is limited by the granularity of the light on one hand, on the other, by a phenomenon of thermal fluctuations resulting from the mechanical dissipation in the thin film of the miroir, in particular in the high refractive index material: tantala. An improvement of the sensitivity would allow the measurement of more events, other gravitational phenomena and some details that would result in a better understanding. This master’s thesis presents results of our research to reduce the noise caused by internal mechanical dissipation in high refractive index layers. To do so, tantala layers were doped with either zirconium and titanium by co-deposition. Layers with different amounts of dopant were synthesized by magnetron sputtering on fused silica substrate similar to those of LIGO. Subsequently, mechanical dissipation, thickness, roughness, composition, areal density and microstructure were characterized by gentle nodal suspension, spectrally resolved ellipsometry, Rutherford backscattering spectroscopy, and Raman spectroscopy. It appears that zirconium allows the annealing temperature to be increased before crystallization which further decreases internal mechanical dissipation, but does not change dissipation at a given annealing temperature. It was also determined that the concentration of titanium reduced the loss angle regardless of the zirconium concentration. A combination of the two dopant and high annealing temperatures thus enables the internal mechanical dissipation to be lower by a factor of 1.5.The difference in thermal expansion coefficient during high temperature annealing, however, induces layer cracking problems, partially resolved by the application of a silica cap.
723

Modelování rušení pro xDSL / Interference modelling for xDSL

Čermák, Josef January 2008 (has links)
This work is focused on the subject of the interference modelling for xDSL technologies. First, the xDSL technologies are explained. Following is the presentation and description of the different kinds of the xDSL technologies. The next part deals with the basic parameters of metallic cable lines – especially the primary and secondary parameters. Nowadays wider bandwidths are used for the achievement of higher data transmission rates. During a higher frequency signal transmission a more intensive line attenuation appears. To identify the transfer characteristics of the lines while using an xDSL system, mathematic models of transmission lines are applied. That is why these mathematic models are dealt with in the next chapter. At the end of this section the mathematic models are compared using the modular and phase characteristics. The main aim of the work is to describe the different impacts which influence the efficiency of the xDSL systems. First, the causes interfering from the inside of the cable are deeply explained: Near End Crosstalk (NEXT), Far End Crosstalk (FEXT), Additive White Gaussian Noise (AWGN). Following is the explanation of the external interfering impacts: Radio Frequency Interference (RFI) and Impulse Noise. The next goal of this thesis is a design of a workstation for the tests of spectral features and the efficiency of the xDSL systems. The work also presents a designed GUI application and its description. The GUI application is an instrument for the choice or data entry of the final interference. The last chapter describes a realization of a measurement and shows the measured characteristics which were recorded on the ADSL tester and oscilloscope.
724

Časově proměnná filtrace signálů EKG / Time Varying Filters for ECG Signals

Peterek, Jan January 2013 (has links)
The aim of this master’s thesis is to create a multiband stop derived from Lynn filters for suppressing mains hum and baseline variation (drift). The first part of the thesis is focused on brief theoretical introduction to the distortion types affecting ECG signal and twelve lead connection. The following practical part describes free realizations of ECG filter and ECG signal filtration. The filter has been tested both on distorted and on non-distorted signal. Finally filters’ error rate was computed from CSE database signals.
725

Analýza a modelování přeslechů / Crosstalk analysis and modelling

Novotný, František January 2013 (has links)
The thesis concerns the problem of interference modelling for xDSL technologies and Ethernet. The introduction describes the origin of crosstalk, that arise during the operation of the systems and the physical properties of the lines, therefore, the next section describes the properties of the primary and secondary parameters of the homogenous line and their modelling. In order to achieve higher data rates on the metallic line, systems with larger frequency spectrum are applied, resulting in a greater attenuation of the line. This issue and the characteristics determination of the transmission systems are subjects of the mathematical models, which are divided according to the modelling of primary or secondary parameters. The main goal of this work is to describe the effects which influence the performance of data transfer via xDSL and Ethernet technology focusing on internal and external disturbances acting on the cable lines. This is the crosstalk at the near and far end, adaptive white noise, radio frequency interference RFI and impulse noise. Following part of the thesis deals with the properties of xDSL technologies, specifically ADSL2+ and VDSL2 and Ethernet. Another aim is to design applications which enable to test the performance of xDSL and Ethernet transmission systems with its own award simulations interference. The conclusion describes the design and implementation of laboratory experiments for measuring of the efficiency and spectral properties of xDSL. The proposed laboratory protocols are annexed to this thesis, including the measured waveforms.
726

Modelování LTI SISO systémů zlomkového řádu s využitím zobecněných Laguerrových funkcí / Fractional order LTI SISO systems modelling using generalized Laguerre functions

Kárský, Vilém January 2017 (has links)
This paper concentrates on the description of fractional order LTI SISO systems using generalized Laguerre functions. There are properties of generalized Laguerre functions described in the paper, and an orthogonal base of these functions is shown. Next the concept of fractional derivatives is explained. The last part of this paper deals with the representation of fractional order LTI SISO systems using generalized Laguerre functions. Several examples were solved to demonstrate the benefits of using these functions for the representation of LTI SISO systems.
727

Sociální události jako impuls ke studiu sociální práce / Experienced social incidents as an impulses for studying social work

Pondělíčková, Markéta January 2020 (has links)
The diploma thesis is called Social Events as an impulse to study social work. The thesis consists of two parts. The first part is theoretical and the second part is research. The theoretical part tries to map the personality of social workers and their motives for the study. The second part is research, where I tried to find out the motivation to study social work.
728

Increased delay discounting tracks with later ethanol seeking but not consumption

Beckwith, Steven Wesley 31 July 2014 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Assessments of delay discounting in rodent lines bidirectionally selected for home cage intake and preference of alcohol have had mixed findings. The current study sought to examine if delay discounting related differentially to alcohol seeking versus and alcohol drinking, two processes underlying alcohol intake and preference. Three strains of rats were utilized to answer this question Long Evans (LE), high alcohol drinking rats (HAD2), and alcohol preferring P rats. All strains were compared in an adjusting amount delay discounting task. Operant self-administration of alcohol was then assessed in the sipper tube model, and finally home cage drinking was assessed in a 24 hour 2 bottle choice paradigm. In the delay discounting it was found that the P rats were steeper discounters than both the LE and HAD2. In the sipper tube model, P rats displayed higher levels of seeking than both the HAD2s and the LE, but both the P rats and the HAD2s had higher intakes than the LE. During 24 hour home cage access, the P rats and the HAD2s had higher intake and preference for alcohol than the LE, but were not different from each other. These results show that increased discounting of delayed rewards tracks with appetitive processes versus consummatory factors and home cage intake of alcohol. This builds on prior findings using selected line pairs by providing an explanation for discordant results, and supports the hypotheses that increased delay discounting is an intermediate phenotype that predisposes individuals to alcohol use disorders.
729

Investigating reactivity to incentive downshift as a correlated response to selection for high alcohol preference and a determinant of rash action and alcohol consumption

Matson, Liana M. January 2014 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Losing a job or a significant other are examples of incentive shifts that result in negative emotional reactions. The occurrence of negative life events is associated with increased drinking, and alleviation of negative emotions has been cited as a drinking motive for individuals with problematic drinking patterns (Keyes et al., 2011; Adams et al., 2012). Further, there is evidence that certain genotypes drink alcohol in response to stressful negative life events (Blomeyer et al., 2008; Covault et al., 2007). It is possible that shared genetic factors contribute to both alcohol drinking and emotional reactivity, but there is a critical need for this relationship to be understood. The first aim of this proposal will use an incentive downshift paradigm to address whether emotional reactivity is elevated in mice predisposed to drink alcohol. The second aim of this proposal will address if reactivity to an incentive shift can result in rash action using a differential reinforcement of low rates of responding task, and whether this response is also associated with a predisposition for high drinking. The third aim of this proposal will investigate if experimenter administered ethanol reduces contrast effects, and if an incentive shift increases ethanol consumption in a high drinking line. The overall goal of this proposal is to investigate whether reactivity to incentive shift is an important mechanism underlying alcohol drinking in these mice, and the role an incentive shift may play in producing rash action and influencing ethanol consumption.
730

Zum Entladungsprozess der Spitze-Spitze-Elektrodenanordnung bei standardisierter und oszillierender Blitzspannung

Gürlek, Akif 02 March 2021 (has links)
Diese Dissertation widmet sich der Erfassung, Identifikation und Beschreibung von Entladungsprozessen, die an Überschlägen bei Blitzspannung auftreten. Es wird ein Messsystem entwickelt, welches die elektrischen und optischen Parameter der Entladungsprozesse an der Spitze-Spitze-Elektrodenanordnung bei standardisierter und oszillierender Blitzspannung mit hoher Empfindlichkeit und Synchronisationsgenauigkeit aufzeichnet. Mithilfe der Strommessungen und der fotografischen Aufzeichnungen von Entladungen können drei Phasen des Durchschlagprozesses identifiziert werden: In der Reihenfolge ihres Auftretens handelt es sich um die Streamerphase, die Kanalübergangsphase und die Kanalbildungsphase. Diese Phasen werden für die standardisierte und oszillierende Blitzspannung aufgezeigt, wobei Gemeinsamkeiten und Unterschiede herausgestellt werden. Anhand von statistischen Beschreibungen des Durchschlagverhaltens und des Entladungsverhaltens werden daraufhin Abhängigkeiten in den Entladungsprozessen abgeleitet. / This thesis is dedicated to the acquisition, identification and description of discharge processes, which occur under lightning impulse voltage. A measuring system has been developed that records the electrical and optical parameters of the discharge processes with a high sensitivity and synchronization accuracy on a rod-rod electrode arrangement under standardised and oscillated lightning impulse voltage. With the current measurements and the photographic records of discharges, three phases of the breakdown process can be identified. In order of their occurrence these are the streamer phase, the channel transition phase and the channel formation phase. These phases are shown for the standardised and oscillated lightning impulse voltage, whereby similarities and differences are presented in detail. Using statistical descriptions of the breakdown and the discharge behaviour, dependencies in the discharge process will be derived.

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