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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.
21

Termální konvekce v pláštích terestrických těles / Thermal Convection in Terrestrial Planetary Mantles

Benešová, Nina January 2015 (has links)
In this thesis, we present results of a numerical modelling study focused on the thermal evolution of the Earth and terrestrial planets. We focus particularly on two problems: I) constraining the internal structure of Venus and Mercury using their geoid and surface topography data and II) evaluating the effects of a rhe- ologically distinct post-perovskite on the secular cooling of the Earth. In part I, we performed simulations in a broad group of models of the Venusian man- tle, characterised by different rheological descriptions, and we compared spectra of their geoid and their surface topography with the observed quantities. Our analysis suggested that the geoid and the surface topography of Venus are con- sistent with a radially symmetric viscosity model with a strong 200 km thick lithosphere, without an asthenosphere and with a gradual viscosity increase in the underlying mantle. In the case of Mercury, none of our models was able to predict observed data, thus suggesting other than a dynamic origin of observed geoid and topography. In part II, we investigated style of Earth's mantle con- vection and its long-term evolution in the models that take into account a weak post-perovskite. We conclude that the presence of the weak post-perovskite en- hances the core cooling. This effect is comparable in...
22

DŮM NA ÚPATÍ - MĚSTSKÝ DŮM V HISTORICKÉM CENTRU BRNA / HOUSE ON THE FOOTHILL - TOWN HOUSE IN THE HISTORICAL CENTRE

Dvořáková, Eva January 2013 (has links)
The main objective of the master´s thesis was a design of the town house in the complicated topografical situation of the foothill of Pekařská street. The topography of the building site is influenced by its surroundings. The street Pekařská is lowering from east to west, but the road Anenská is rising from east to west. The biggest difference between the the lowest and the highest point of the site is 7,5 m. This situation enables to design three entrances to three different floors of the building. An outstanding point of the design of the house is a composition axis which is running up Pekařská street. The town house is facing this axis thus the main entrance of the house is accented. There was a compact house designed, which takes advantage of its very good position – there is a two-floor solution with a shopping mall. The hall in its middle is opening over two floors and it is lightened through a roof lightwell. On this platform is situated an „L“ shaped part of the building, which creates a protection against very noisy Pekařská street. The house is opening its form to the south, to a sunny roof garden. This garden is opened only for inhabitants of the house. The garden improves the quality of the living in the house and substitutes a green area, which used to be in this place. The shape of the building is lowering down from Pekařská street to Anenská road. There are some terraces designed this way to improve the living in the roof apartments and provide a beatiful view to the west.
23

Dynamické vyšetření Moiré a Pedoscan u pacientů se skoliózou / Moiré and Pedoscan dynamic examinations of patients with scoliosis

Klímová, Michaela January 2015 (has links)
Scoliosis is the most common deformity of the spine affecting from 3 to 6% of human population. The thesis "Moiré and Pedoscan dynamic examinations of patients with scoliosis" summarizes the findings of kinesiology of the spine, pelvis and hip joints and ontogenesis of axial organ straightening. It also deals with the issue of idiopathic scoliosis, its incidence, etiology, classification, diagnosis, treatment options and applied physiotherapy methods. The paper emphasizes the influence of physiotherapy that forms an integral part of medical treatment. A great part of the thesis is devoted to the rasterstereographic and pedobarographic examination. The main purpose of this thesis was to detect and evaluate parameters assessing posture and movement of patients suffering from scoliosis and compare them with a control group. For this purpose, a pedobarographic system Diers pedoscan was used, which detected the distribution of compressive forces on the feet when walking and standing. It was also used a rasterstereographic system Diers formetric III 4D, which allowed for capturing photogrammetric recording of the spine and pelvis using a video-rasterstereography based on the Moiré topography. The study was carried out with a group of 22 females with idiopathic scoliosis up to 40ř according to Cobb aged...
24

Hodnocení cyklického poškození slitin na bázi hliníku a hořčíku s využitím metody akustické emise / Evaluation of Cyclic Damage in Aluminum and Magnesium Alloys Using Acoustic Emission Technique

Vlašic, František January 2011 (has links)
The thesis deals with the application of nondestructive testing methods (acoustic emission, electron microscopy, X-ray diffraction topography) to description and identification of stages in the fatigue process in aluminium alloys. The main contribution of this dissertation thesis consists of the approach and evaluation methodology of cyclic damage in the materials. It dealt especially with the verification of measured data by using data obtained using other nondestructive methods. The experimental results show that the field of nondestructive testing materials can fundamentally uncover the process of fatigue damage and improve current knowledge in this area. Combination of used methods has become a powerful tool for the identification and monitoring of the whole fatigue degradation process of materials.
25

Optimalizace řídicích parametrů EDM stroje / Optimization of EDM process control parameters

Prokeš, Tomáš January 2021 (has links)
The dissertation thesis is focused on the optimization of control parameters of an EDM machine; the subject of optimization is cutting speed and surface topography. The first part of the thesis contains a research study on the technology of electrical discharge machining with the attention paid to the optimization methods use for control parameters of this process. The second part of the thesis is focused on real application of knowledge gained from studied sources. Here, a design of experiment aim at optimizing the parameters of the EDM machine is designed and carried on to maximize the cutting speed with the highest possible surface quallity. The result of the work is to build adequate regression models and find the optimal setting of machine control parameters.
26

Vliv složení synoviální kapaliny a topografie třecích povrchů na mazání kloubních náhrad / Effect of synovial fluid composition and surface topography modification on lubrication of joint replacements

Hekrle, Pavel January 2018 (has links)
The main objective of this diploma thesis is to determine the influence of synovial fluid compodition and the influence of surface microtextures on lubrication of hip join replacements. For all experiments, hip joint simulator based on the pendulum principle was utilized. Metal heads (CoCrMo) manufactured by B Braun company and and tailor made acetabular cups from optical glass were used as contact couples. Acetabulum dimensions were fabricated according to dimensions of real implants. Experiments with surface microtextures simulated walking cycle for 210 s and development of lubrication film over time was observed.Results have shown that all types of tested structures improved lubrication of contact area, where the best results were obtained for square and triangle shapes respectively. Second set of experiments was based on the fact, that the composition of synovial fluid of healthy people differs from the composition of patients with various stages of osteoarthritis. Therefore, experiments with different model fluids were compared, which in their composition correspond to different groups of patients. For the model fluid that corresponds to the largest number of cases, experiments with individual components and combinations thereof were subsequently performed to provide a more detailed description of how these components affect the film-forming mechanism. The results show, that a change in fluid composition of patients with osteoarthritis can have a major negative effect on fluid formation process within the pair.
27

Study of Correlation between Grease Film Formations and Mechanical Losses on Various Surfaces / Study of Correlation between Grease Film Formations and Mechanical Losses on Various Surfaces

Sakai, Kazumi January 2018 (has links)
Tato disertační práce se zaměřuje na studium závislosti mezi reakčním momentem ložiska mazaného plastickým mazivem s lithným mýdlem a vlastnostmi maziva, jako například tloušťka vytvářeného mazacího filmu, jeho reologie, struktura zpevňovadla, trakční vlastnosti či vliv topografie povrchu. Typ maziva poskytujícího nižší odpor závisí na podmínkách provozu ložiska, zejména rychlosti. Chování mazacího filmu za nízkých rychlostí má vliv na reakční moment ložiska v nízkých rychlostech. Mez toku a trakční chování koreluje s momentem ložiska za vysokých rychlostí. Schopnost zpevňovadla vstupovat do kontaktu má vliv na tloušťku filmu, vzhled kavitační oblasti na výstupu kontaktu a chování hladovění. Důvod vstupu zpevňovadla do kontaktu je jeho chemická struktura. Vysoká polárnost hydroxylových sloučenin zpevňovadla podporuje jeho vtažení kontaktními povrchy. Mazivo s nejvyšší polaritou prokázalo na površích obsahujících denty nejčastější vstup do prostoru dentů. Na základě předchozích pozorování je navržen popis principu mechanismu mazání.
28

Vliv topografie třecích povrchů na kontaktní únavu / Influence of topography of rubbing surfaces on rolling contact fatigue

Zahradník, Radek January 2010 (has links)
This master thesis deals with influence of topography of friction surfaces on rolling contact fatigue. This influence is examined by newly reconstructed R-MAT station, whose reconstruction and fully report about it, is part of this master thesis. Influence is examined on area with higher surface's roughness which it wasn't examined before. Further research is made on area of surfaces with topographical modification with higher surface's roughness.
29

Experimentální studium utváření mazacích filmů při reverzaci a rozběhu třecích povrchů / Experimental Study of Lubrication Films Formation During Start-up and Reversal Motion of Rubing Surfaces

Svoboda, Petr January 2009 (has links)
This dissertation is focused on the effects of both artificially produced and real roughness features on mixed lubrication film formation during start-up and reversal of non-conformal contacts operated under rolling/sliding conditions. The start-up operation of mixed lubricated contacts represents one of the transient conditions that bring the risk of the surface damage because of asperities interactions. Chromatic interferograms captured by CMOS high-speed camera during start up of the motion enabled to observe the detailed changes in lubrication film caused by surface features. The observation of the effects of surface dents artificially produced on the ball surface helped to understand better the behaviour of real surface topography. It was found that the presence of shallow surface features can help to separate mixed lubricated rubbing surfaces more efficiently than it could be suggested from the results obtained with smooth surfaces. It can be suggested from the obtain results that properly designed topography of the rubbing surfaces can help to reduce the asperities interactions under transient operational conditions.
30

Hodnocení cyklického poškození slitin na bázi hliníku a hořčíku s využitím metody akustické emise / Evaluation of Cyclic Damage in Aluminum and Magnesium Alloys Using Acoustic Emission Technique

Vlašic, František January 2011 (has links)
The thesis deals with the application of nondestructive testing methods (acoustic emission, electron microscopy, X-ray diffraction topography) to description and identification of stages in the fatigue process in aluminium alloys. The main contribution of this dissertation thesis consists of the approach and evaluation methodology of cyclic damage in the materials. It dealt especially with the verification of measured data by using data obtained using other nondestructive methods. The experimental results show that the field of nondestructive testing materials can fundamentally uncover the process of fatigue damage and improve current knowledge in this area. Combination of used methods has become a powerful tool for the identification and monitoring of the whole fatigue degradation process of materials.

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