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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.
211

Detecção da contração muscular através da tomografia de impedância elétrica. / Muscle contraction detection using electrical impedance tomograph

Olavo Luppi Silva 27 September 2012 (has links)
Atualmente existem diversos métodos e equipamentos disponíveis no mercado para análise da biomecânica do movimento humano. No entanto, mesmo uma equipe multidisciplinar, dispondo de um laboratório completo de análise do movimento, pode falhar na identificação de quais grupos musculares estão sendo recrutados durante um exercício. Sobretudo quando a musculatura de interesse é profunda. O objetivo desta tese é propor formas de detectar a contração muscular através da Tomografia por Impedância Elétrica (TIE). Um modelo de elementos finitos de condução elétrica é utilizado para resolver o problema inverso através do algoritmo de Newton-Raphson de forma a obter as imagens de TIE. Um novo modelo de eletrodo e o método de erro de discretização da malha são introduzidos como forma de melhorar as imagens de TIE. Além disso, a variabilidade da impeditividade de tecidos musculo-esqueléticos é medida experimentalmente, in vivo tanto em repouso quanto em exercício. Os resultados mostram que o sangue tem um papel importante nas mudanças de impeditividade e que as variações medidas durante as contrações musculares parecem estar relacionadas à taxa de contração do movimento. As imagens de TIE, obtidas in vivo de um voluntário, apresentam um aumento de resistividade durante a contração muscular. / Presently, there are several methods and equipment available in the market for the biomechanical analysis of human movement. However, even a well trained multidisciplinary team, equipped with a complete motion analysis laboratory, may fail to identify which muscle groups are being recruited during an exercise. Specially when deep muscles are being considered. The main objective of this work is to propose forms to detect muscle contraction from Electrical Impedance Tomography (EIT) images. A finite element electrical conduction model is used to solve an inverse problem with Newton-Raphson algorithm in order to produce EIT images. A new electrode model is proposed and the mesh discretization error method is implemented to improve EIT images. Additionally the variability of impeditivity of musculo-skeletal tissues is measured experimentally in vivo both at rest and during exercise. The results show that blood has an important role in muscle impeditivity changes and that resistivity variations during muscle contractions seem to be related to movement contraction rate. The EIT images, obtained in vivo from a volunteer, show an increase of resistivity during muscle contraction.
212

Downhole Physical Property Logging of the Blötberget Iron Deposit, Bergslagen, Sweden / Geofysisk borrhålsloggning i apatitjärnmalmer, norra Bergslagen

Johansson, Philip January 2017 (has links)
Geophysical methods are frequently applied in conjunction with exploration efforts to increase the understanding of the surveyed area. Their purpose is to determine the nature of the geophysical response of the subsurface, which can reveal the lithological and structural character. By combining geophysical measurements with the drill core data, greater clarity can be achieved about the structures and lithology of the borehole. The purpose of the project was to give the student an opportunity to discover borehole logging operations and to have a greater understanding of the local geology, in particular the iron mineralizations in the apatite iron ore intersected by the boreholes. In order to do this, the student participated in performing a geophysical borehole survey and analyzing the results. These were combined with a drill core log in order to cross plot the results and increase understanding. / Geofysiska metoder används ofta i samband med prospektering för att öka förståelsen av området. Utförda från ytan ger de en relativt god tolkning av vad som kan finnas på djupet och är även kostnadseffektiva jämfört med provborrning. Borrhålsloggning sker däremot efter att själva hålet borrats och ändamålet är ofta att utöka förståelsen om området omedelbart kring det loggade hålet. Genom att kombinera geofysisk fältdata med tolkning av borrkärnan kan man erhålla en ökad förståelse för borrhålets strukturer och litologi. Syftet med det här projektet var att utöka studentens förståelse inom borrhålsloggning, samt att avgöra hur relevant metoden är för att identifiera järnmineraliseringar i apatitjärnmalmen som kännetecknar norra Bergslagen
213

Modélisation et inversion de données électriques en courant continu : vers une prise en compte efficace de la topographie / Modeling and inversion of DC resistivity data : how to cope with topography effects

Penz, Sébastien 19 December 2012 (has links)
L'imagerie électrique est un outil de plus en plus important pour un large domaine d'applications relatives à la caractérisation de la subsurface proche. D'importants développements ont été réalisés au cours des vingt dernières années pour l'amélioration des systèmes d'acquisitions et des algorithmes d'inversions. L'acquisition et le traitement de gros jeux de données reste toutefois une tâche délicate, en particulier en présence de topographie. Afin d'améliorer la gestion de la topographie, nous avons développé un nouvel algorithme d'inversion électrique 2.5D et 3D. Nous avons proposé deux nouvelles formulations pour supprimer la singularité à la source. Le problème direct est résolu en utilisant la méthode des Différences Finies Généralisées et des maillages non structurés, permettant une représentation précise de la topographie. Le code d'inversion utilise la méthode de l'état adjoint pour calculer le gradient de la fonction objective de manière économique. Cette approche a donné de bons résultats avec des données synthétiques. Les premiers résultats sur des données réelles ont permis de retrouver les principales structures de la subsurface, ainsi que plusieurs zones de faibles résistivités pouvant correspondre à des zones fracturées. / DC resistivity imaging plays an important role for a wide range of applications related to the characterization of the shallow subsurface. Major developments have been made over the last two decades to improve acquisition systems as well as resistivity inversion. Nevertheless, large-scale data sets still represent a challenging task, in particular with arbitrary topography. In order to better take into account topography, we have developed a new 2.5D/3D tomographic inversion code. Two new formulations for the singularity removal have been proposed. The direct problem is solved in the framework of the Generalized Finite Differences Method, that allows the use of unstructured meshes yielding a fine represention of topography. The inversion code uses the adjoint state method to compute the gradient of the misfit function in a numerically efficient way, giving goodresults on synthetic data. First results on real data have shown the main subsurface structures, as well as several low resistivity zones possibly corresponding to fractured areas.
214

Permafrost Changes Along the Alaska Highway Corridor, Southern Yukon, from Ground Temperature Measurements and DC Electrical Resistivity Tomography

Maxime Arsène, Duguay January 2013 (has links)
Permafrost temperatures were measured by the Geological Survey of Canada (GSC) in 1977-1981 at boreholes along a proposed pipeline route in the southern Yukon. Analysis of climate station records indicate that mean annual air temperatures in the region have since increased by 0.5-1.0˚C. Renewed interest in the pipeline and the need to develop adaptation strategies for existing highway infrastructure have meant that information on permafrost and geotechnical conditions must be updated. To accomplish this goal, a total of eight GSC boreholes ranging in depth from 5-9 m were located, unblocked of ice and instrumented with thermistor cables and data-loggers to permit renewed ground temperature monitoring. Manual temperature measurements were also taken at four other shallow boreholes. Electrical resistivity tomography (ERT) surveys were conducted at each site. MAGTs below 1 m at permafrost sites in the study area range from -0.2˚C to -1.5˚C with permafrost depths greater than 25 m. The permafrost at the study sites can be classified as sporadic discontinuous and extensive discontinuous. Ground temperatures indicate that permafrost can persist under warmer climatic conditions as long as it remains protected by its ecosystem properties. Thermal monitoring for 2011-2012 shows an average increase of 0.5-1.0˚C when compared to the original 1978-1981 ground temperatures. This slow rate of ground warming is mainly attributed to a combination of limited climate change, especially in the south of the study area, ground temperatures close to 0˚C, and the possible disturbance of sites from the removal of vegetation prior to the original measurements being made. ERT surveys conducted at most borehole sites show deeper thaw or taliks where the cleared cut-line used for geophysical work in the 1970s is crossed. These results indicate the impacts of climate change and environmental change in the study area over the past three decades. They appear to match the relatively slow rates of ground warming observed elsewhere in northern Canada where permafrost temperatures are close to 0˚C and where warming also requires changes in latent heat due to internal thaw. TTOP equilibrium modelling suggests that if climate change is responsible for the ground warming, most of the change can be attributed to the step-like MAAT increase that occurred between 1975-1976.
215

Magnetron sputtering of highly transparent p-conductive NiO thin films / Magnetronsputtring av transparenta och p-ledande tunnfilmer av NiO

Book, Martin January 2020 (has links)
P-type transparent conductors are needed for a wide range of applicationssuch as solar cells and electrochromic smart windows. Solar power is animportant form of energy in today’s society as the threat of global warmingpushes the world towards fossil free energy. Hence a lot of solar cell typeshave been developed, among them tandem cells which are to different typesof solar cells stacked on top of each other. If one of the cells is based ona perovskite, a transparent p-type thin film electrode is needed as a holeconductor and electron blocking layer between the two cells. Nickel oxide(NiO) is a good candidate for this application as it has desired propertiessuch as good hole conduction, a high band gap and a matching work functionto the perovskite. The transmittance of as deposited NiO films by reactivemagnetron sputtered is limited so post deposition annealing is used to increasethe transmittance. This is not possible in this solar cell application as parts ofthe solar cell stack is temperature sensitive.Electrochromic smart windows contain a layer that can change its opticalproperties with the application of a voltage. Such windows are used inbuildings to increase energy efficiency and they contain an electrochromicdevice where NiO is used as an electrode as it has electrochromic properties,but just like with the solar cells, the transmittance of NiO is limited. Thisstudy investigates whether it is possible to make as deposited NiO by reactivemagnetron sputtering transparent, eliminating the need for post depositionannealing. Such a deposition process was found using different sputtermachines with the process point on the edge between metal and oxide modein terms of oxygen flow. This resulted in highly transparent and highlyresistive NiO films with a much higher deposition rate than in oxide mode.
216

Příprava vodivých struktur bezproudovým pokovením vytištěného prekurzoru / Fabrication of conducting patterns by material electroless plating of printed precursor

Kováčová, Silvia January 2021 (has links)
The subject of this diploma thesis is the preparation of conductive structures by electroless plating of an extruded precursor. The experimental part deals with the preparation of standard patterns based on the length of immersion time in a coppering bath. The precursor layers were applied with Fujifilm Dimatix to various receiver substrates. The individual substrates with the precursor layer were immersed in the copper solution within different time intervals. The structure of the layers of grown copper and their thickness was characterized by a profilometer.
217

Měření elektrické rezistivity půdy / Measurement of electrical soil resistivity

Matyska, Stanislav January 2018 (has links)
This master’s thesis deals with the measurement of the electrical soil resistivity. In the theoretical part there are described the methods by which the soil resistivity is measured – especially the Wenner’s method, which was used for the practical measurements. Then there is also described the one-layered and the two-layered model of this method. Furthermore, there is described the procedure for the measurement of soil resistivity using the OMICRON CPC 100 and PU 193 instruments used in the measurement. To verify the modeling of a two-layered soil model, the theoretical part of the thesis describes the soil modeling process using the program Ansys. As for the practical part of the thesis, the measurements were carried out in three localities: Brno – Královo Pole; Hrušovany nad Jevišovkou – Pravice; Hustopeče nad Bečvou – Vysoká. The measured values were processed using the Matlab’s graphical user interface (GUI) that was developed within this thesis. From these values, at least one two-layered soil model was created for each location and both meters – a total of 12 models were created. For these models, measurements were simulated in Ansys. The results of the simulations were then compared with the measured values. The aim of this thesis is to compare the measured data with the data obtained by the simulations and subsequently to describe the suitability / unsuitability of the substitution of the one-layered soil model for the two-layered one for given measurements.
218

Zpracování metodiky a podpory pro vyhodnocení naměřených hodnot uzemnění stožárů VVN v souvislosti s PNE 33 3300-1 / Development of methodology and supporting tool for evaluation of measured values of high voltage poles grounding systems according standard PNE 33 3300-1

Kováč, Frederik January 2020 (has links)
Diploma thesis is oriented on measuring and evaluation of grounding conditions of HV pylons. In theoretical part is described theory of grounding including related legislation, impact of electric current on human body, methods of measuring earth resistance, soil resitivity and description of available measurers. Practical part is focused on measuring earth resistance of selected pylons and measuring procedures followed by evaluation of measurements according to person's safety from dangerous touch voltage and impact of lightings. For evauluation of measured data is created supporting tool in MS Excel. In the last part of thesis are described recommendations for cutting-down touch voltages.
219

Design of a Polymeric Coating for Protecting Thermoelectric Materials from Sublimation and Oxidation

Chen, I Kang 08 1900 (has links)
Thermoelectric (TE) devices can undergo degradation from reactions in corrosive environments and at higher operating temperatures by sublimation and oxidation. To prevent the degradation, we have applied two high temperature polymers (HTPs) as coatings for TE materials. Sintering temperatures were from 250°C to 400°C. We explain why dip coating is better technique in our study and had two potential HTPs for tests. By applying TGA (thermogravimetric analysis), we were able to figure out which HTPs have better thermal resistivity. Besides, TGA also help us to find proper curing cycles for HTPs. EDS and SEM results show that the coatings prevent oxidation and sublimation of TE materials. We also shorten HTP curing cycle time and lower the energy costs.
220

Modifikace elektroizolačního laku mletou slídou / Modification of electroinsulating varnish with ground mica

Drápal, Aleš January 2009 (has links)
This master's thesis focuses on composite systems based on varnish combined with different filler ratios of micronized mica. The aim is to analyse impact of the filler on dielectric properties of the varnish, i.e. relative permittivity and loss factor as functions of frequency as well as charging and discharging currents as functions of time. Dielectric mixture formulas are applied on relative permittivity values. Calculated and measured values are compared.

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