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Study of starvation in a grease-lubricated elastohydrodynamic contact
Kuňák, Jiří ; Hartl, Martin (referee) ; Svoboda, Petr (advisor)
This diploma thesis is an experimental study of grease lubrication in a starved elastohydrodynamic lubricated (EHL) contact. Lubricating film thickness is measured with tribological experimental device ball-on-disc using optical interferometry and high speed camera. The experiment is aimed at a comparison of results acquired by ball-on-disc device and full scale axial bearing. In addition, this paper also investigates the influence of number of the rolling elements (overrolling time) on the resulting film thickness.
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Study of lubrication films formation under starved lubrication conditions
Košťál, David ; Hartl, Martin (referee) ; Křupka, Ivan (advisor)
The purpose of this thesis is to reveal production mechanisms of lubrication films between non-conformal surfaces in situations, when is not possible to designate lubrication regime as fully flooded elastohydrodynamic contact. Under certain conditions of lubrication volume, rolling speeds, temperatures, lubrication properties or loads could lubrication film decrease under values determined by fully flooded formulas. This regime is designated as starvation at it includes risk of increased wear. In this thesis the methodology and the new simulator of starving contact are described. Obtained film thickness results are compared with existing numerical models.
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Archive+
Šana, Václav ; Hora, Jan (referee) ; Kristek, Jan (advisor)
The proposal deals with the architecture archive concept on a wider social scale. The goal is to treat the information as a certain relative value, when the individual spaces are conceived with emotional surprise. There is a controlled collision between old and new approaches where attractive spaces serve purely rational mechanical systems. A person going through the archive should perceive emotional experiences and, after leaving the archive, perceive information in a more complex way.
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Effect of surface texturing on starved contact
Jordán, Jakub ; Náhlík, Luboš (referee) ; Křupka, Ivan (advisor)
The diploma thesis deals with the analysis of the effects surface texturing on starved contact. Experimental verification was realized on apparatus simulating contact between a steel ball and glass disc using colorimetric interferometry and high-speed camera. The work deals with lubrication regimes, problems with starved contacts and surface texturing which can reduce effects of starvation on non-conformal surface contacts.
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Experimental study of the starved lubrication
Novotný, Antonín ; Čermák, Jan (referee) ; Košťál, David (advisor)
This master’s thesis deals with the experimental study of an elastohydrodynamic contact under conditions of insufficient lubricant supply. Starvation level of this type of the contact may be experimentally determined based on the input position of the meniscus, but this way can’t determine all its levels of starvation. Consequent development in the field of tribology achieved theoretical model that can determine at all levels of starvation depending on the thickness of the lubricant film entering the contact, but it is relatively difficult for experimental verification. The main goal of this work is an experimental study and describes the behavior of elastohydrodynamic contact at an exactly defined thickness of the lubricant film at the contact input. The benefit of this work is a validation of that mentioned theoretical model for base oils and greases made from them, and mutual comparison of their behavior.
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Experimental Study of the Lubricant Film under Starved Conditions
Košťál, David ; Čermák, Jan (referee) ; Dzimko, Marián (referee) ; Ali, Fadi (referee) ; Křupka, Ivan (advisor)
The dissertation thesis deals with an experimental study of an elastohydrodynamic contact under insufficient lubricant supply. Theoretical studies published in this research area focus mainly on the development of theoretical models and there is an insufficient number of experimental studies which validate these models. There are two basic methods of starvation severity control in published theoretical models: by positioning of an inlet meniscus and by setting the thickness of an oil layer in the vicinity of contact inlet. The second method is more suitable when considering a wide range of operating conditions, however it is difficult to ensure experimentally. This thesis presents original experimental results and aims to describe the starvation severity level as a function of the inlet film thickness. Deeper understanding of fundamental processes in starved elastohydrodynamic contacts enables the development of more precise models, better ability of prediction of the starvation and improves the ability to avoid starvation in the early design process of key tribological components.
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Vývoj potravinové bezpečnosti ve vybraných zemích jihovýchodní Afriky
Hendrychová, Marcela
The diploma thesis deals with monitoring the development of food security in Malawi, Zimbabwe and Zambia. The specific criteria for the selection of three states were the HDI indicator and the geographical location of the selected states. Through individual indicators from different pillars of food security, the work evaluates the most significant factors that cause food insecurity in the monitored countries. The theoretical part of the thesis explains the basic facts and the background of the problem, contains an explanation of key terms and terms, and defines individual causes and consequences of food security at the level of selected countries. The work also describes the most used indicators measuring food safety. The practical part based on the development of monitored indicators (average protein intake; average protein intake of animal origin; prevalence of moderate or severe food insecurity; prevalence of severe food shortage; percentage of the population using basic hygiene services; percentage of the population with access to drinking water; percentage of children under 5 years, suffering from stunting; prevalence of anemia in women of reproductive age; variability of food production per person; political stability and absence of violence/terrorism) in the period 2009-2019 examines the factors that influenced changes in these indicators. In the work, it was found that the most important factors influencing the development of food security in the observed states of Malawi, Zambia and Zimbabwe are climatic conditions, political and economic situation, low education of the population and infectious diseases. These factors slow down the economic growth of countries and prevent growth from developing to developed countries and result in food insecurity and consequences.
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Fasting and its importance for spiritual and personality development
POCHOPOVÁ, Veronika
The thesis deals with the influence of fasting on the personality development of man. The theoretical part characterizes diet and fasting. It looks at fasting through the eyes of the world´s most important religions, explains their motivation, practices and goals. Furthermore, it describes the mental and spiritual development of personality from the perspective of psychology and philosophy, putting it in context with the teaching profession. The practical part confirms the influence of fasting on the respondens. They prove the positive impact of fasting not only on health, the maturation of the human personality and transcendental beliefs, but also on the acceptance of everything that surrounds us and what we are a part of.
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miRNA analysis of small extracellular vesicles isolated from plasma after diet intervention
Kratochvílová, Michala ; Koc, Michal (advisor) ; Šrámek, Jan (referee)
The aim of this thesis was to establish a protocol for the isolation of small extracellular vesicles (sEVs) from human plasma. Plasma samples were collected from 44 healthy women who underwent a 60-hour dietary intervention in the form of fasting as part of a clinical trial. These women were divided into two groups based on their BMI - lean and obese. Plasma was collected from each participant before and after the dietary intervention and sEVs were isolated using the polyethylene glycol precipitation method. Each sample was then characterized by the size of sEVs and their concentration. The amount of sEVs in plasma before the dietary intervention was the same for both groups and did not change with dietary intervention. However, the 60-hour fasting resulted in a change in sEVs size in the lean group. Another goal of this thesis was to analyze miRNA expression in sEVs. There were differences found in the expression of certain miRNA between the two groups. More specifically, differences were observed in the expression of hsa-miR-17-5p, hsa-miR-20a-5p and hsa-let-7b-5p. The 60-hour fasting period resulted in an increased expression of hsa-miR-5100 in the lean group and hsa- miR-27a-3p and hsa-miR-27b-3p in the obese group. However, these changes induced by the dietary intervention were not evaluated...
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