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Micro and nanocomposites in the microstructure of metallic materials
Olivo, Tomas ; Adam, Ondřej (referee) ; Jan, Vít (advisor)
This bachelor thesis focuses on the field of metal matrix nanocomposites. Firstly, the research covers the general mechanical characteristics of materials utilized in nanocomposites. Subsequently, the research defines the mentioned matrix and its different types, that are regularly applied during the production of nanocomposites. Secondly, the research analyses the types of reinforcing (strengthening) components and their use in matrix advancement. This will further lead to introducing the individual mechanisms that reinforce nanocomposites. Thirdly, this research describes the methods employed in the production of nanocomposites – both continuously or discontinuously reinforced. Moreover, the focus shifts to the individual types of materials that satisfy the required characteristics of composites. This outlines the specific types of composites created by the reactions within the materials. Finally, the research summarises the benefits of using nanocomposites.
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Fairytales about selfdetermination.
Sachrová, Tereza ; Babáková, Bernardeta (referee) ; Klímová, Barbora (advisor)
In my bachelor thesis I present a text named Tales from Beztrudy land in an author book. It’s 12 stories about Lutynka and Hynek living in an abandoned narrow gauge railway near a train station in a land called Beztrudy. They live with eighteen dogs, with a cat without one leg Prlenka, with half dog half fox Bařinka and one domesticated bird. Together with their friends, they face everyday problems (getting food, changing seasons, growing a group of dogs, bottling honey, going to the ball, etc.), as well as traumas, social abnormalities, problems with the dominance of the powerful or the absence of a stable background for life. The setting of the stories - Beztrudy is a paraphrase of the Beskydy Mountains, which are the main inspiration for the stories. The goal of the thesis was to create an ecofeminist text similar to fairy tale series, which would thematize non-hierarchical interpersonal relationships, the relationship with nature or coping with abandonment. In the text part of the thesis, I also deal with the role of dialect in society or when working with language. Furthermore, I thematize here the eternal struggle to preserve the integrity of the landscape and the role of this theme in fairy tale production.
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Optimization of Machining Technologies for Special Applications
Ohnišťová, Petra ; Maňková, Ildikó (referee) ; Neslušan, Miroslav (referee) ; Píška, Miroslav (advisor)
This thesis is focused on the optimization of the milling technologies for special applications with respect to the required fatigue properties of aircraft components. The theoretical part of the thesis describes in detail the key features of the high-speed and high-feed milling, surface integrity after milling and fatigue characteristics of the studied component. The key aim of the work is devoted to the analysis of the influence of the cutting conditions of the high-speed peripheral and high-feed face milling of the bottom wing panel from aluminium alloy 7475-T7351 on the surface integrity in relation to the final fatigue properties. Therefore, the part of the work is a study of metallographic structure of the material, measurement of the accompanying machining phenomenon and quantities, advanced analysis of the surface integrity (amplitude characteristics, S-N parameters), manufacturing of the highly accurate fatigue samples and fatigue testing. Furthermore, the development of sample damage during in situ tensile loading and the development of sample damage during cyclic in situ fatigue tensile loading is also studied. The achieved results and fractography of fracture surfaces show that the studied cutting conditions have a significant effect on the quality of machining and resistance to mechanical stress, but they are not a decisive factor in terms of the fatigue crack nucleation. The effect of the achieved topography for the studied cutting conditions is suppressed by the presence of large intermetallic inclusions (Al7Cu2Fe; Al-Cr-Fe-Cu-Si) with a size from 2 µm to 20 µm, being the origin on the fatigue crack nucleation.
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Micro and nanocomposites in the microstructure of metallic materials
Olivo, Tomas ; Adam, Ondřej (referee) ; Jan, Vít (advisor)
This bachelor thesis focuses on the field of metal matrix nanocomposites. Firstly, the research covers the general mechanical characteristics of materials utilized in nanocomposites. Subsequently, the research defines the mentioned matrix and its different types, that are regularly applied during the production of nanocomposites. Secondly, the research analyses the types of reinforcing (strengthening) components and their use in matrix advancement. This will further lead to introducing the individual mechanisms that reinforce nanocomposites. Thirdly, this research describes the methods employed in the production of nanocomposites – both continuously or discontinuously reinforced. Moreover, the focus shifts to the individual types of materials that satisfy the required characteristics of composites. This outlines the specific types of composites created by the reactions within the materials. Finally, the research summarises the benefits of using nanocomposites.
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Dynamic change in optical response of nanostructures
Vančík, Michal ; Veis, Martin (advisor) ; Zázvorka, Jakub (referee)
Title: Dynamic change in optical response of nanostructures Author: Michal Vančík Institute: Institute of Physics of Charles University Supervisor: RNDr. Martin Veis, Ph.D., Institute of Physics of Charles University Abstract: At the present time, properties of thin layers and multilayered nanos- tructures are intensively reseacrched. Because of different properties than bulk materials, thin layers have found application in various fields and play a key role in many technologies. Nanostructures containing GdOxare intensively studied since their properties can be modified by voltage application. It is assumed, that this change is caused by migration of ions in the structure. This thesis conducts re- search on multilayered structures, whose optical response changes reversibly by applying voltage. In these samples, the change is likely caused by migration of hydrogen ions into the GdOx layer. The goal of this thesis is to describe the opti- cal properties of individual layers of the structure and to describe the dynamic change in optical properties. The measurements were conducted with the help of spectroscopic ellipsometry, which allowed in situ voltage application. Keywords: spectroscopic ellipsometry, gadolinium oxide, multilayered nanostruc- tures, in situ
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Bioaktivní látky ve vodním prostředí a jejich vliv na ryby - zaměření na cytochromy P450 v rybách
SAKALLI, Sidika
The term "biologically active compounds" covers a wide range of substances originating from natural or synthetic origins. These compounds can enter the aquatic environment through wastewater treatment plants, manufactural discharge or they are naturally present in the aquatic plants or microorganisms. Their adverse effects on fish has been widely studied and accepted. This thesis is focussed on the adverse effect of several bioactive compounds (i.e. pharmaceuticals, phytochemicals, or complex mixture of pollutants) on fish using different experimental design as in vitro, in vivo and in situ. In the first part of this thesis, in vitro effects of pharmaceuticals and phytochemicals or their combinations on fish CYP system were investigated. Moreover, effects of standard carrier solvents used in enzyme activity assays were also investigated. An important finding in this study was the lack of effects of either dexamethasone, quercetin, or indole-3-carbinol on EROD activity; however, when these agents were combined, EROD activity was strongly inhibited. This demonstrates that combination of compounds might exert different effects than single compounds, and the effects of mixture compounds cannot be predicted from the effects of individual compounds. In the second part of the thesis, the effects of chronic exposures of rainbow trout to dexamethasone and clotrimazole were investigated. The results regarding dexamethasone showed similarities with in vitro studies, and both in vitro and in vivo exposure of dexamethasone did not alter the CYP enzyme activities. On the other hand, in vivo exposure of clotrimazole yielded conflicting results with findings from the in vitro studies. Clotrimazole induced EROD activity in chronically exposed rainbow trout, and BFCOD activity showed biphasic pattern in which it was inhibited at environmentally relevant concentrations and induced at high concentrations. Thus, the observed effects suggest that clotrimazole could negatively affect fish CYPs at environmentally relevant concentrations. However, in the environment, the effects of clotrimazole and dexamethasone on fish CYPs system might be modified because of unknown compounds in these mixtures. Therefore, further investigations were done to identify the effects of mixture compounds using an in situ model. The last part of the dissertation addresses the effects of cocktail PPCPs on common carp under natural conditions. In situ studies provide valuable information on both hepatic and intestinal CYP activities. Both EROD and BFCOD activities were affected by the PPCPs that are present in the exposed fish. Moreover, changes in intestinal CYP activities suggest that fish can ingest some of these contaminants through their feed. Therefore, the intestines might be responsible for elimination of some of these pollutants and act as the first barrier of pollutant entry in fish. Despite the extensive studies concerning aquatic pollution, further studies are necessary. Development of new pharmaceuticals, their occurrence in the aquatic environment, and their effects on non-target organisms should be continuously monitored.
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In situ weathering experiments of sulphides and silicates
Jarošíková, Alice ; Mihaljevič, Martin (advisor) ; Drahota, Petr (referee)
Weathering is a natural process which is occuring on the Earth's surface. Its effect on minerals and other materials is significant. Besides mechanical alteration, the result of weathering can reach the chemical reactions, which can lead to contamination of the environment (e.g. ground water and soils). Not only for this reason has weathering become an object of intensive studies. In situ weathering experiments are one way of research. The aim of this bachelor thesis is to review the advantages and disadvantages of these experiments, to describe their course and the complications which can happen during the experiments, and how to use knowledge of these observations. Attention is also focused on several concrete experiments which were concerned with the weathering of sulphides and silicates, and where it is possible to observe these things on them.
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Ruminal effective degradability of neutral detergent fibre in ruminants
KOUKOL, Ondřej
Seven clover sampes (Trifolium pratense L.) were collected at three different miters A (n = 3), B (n = 3) a C (n = 1) during the growing season from 10th of May to 3rd of August. The samples were analyzed for chemical composition, gross energy (BE) content, in vivo sheep digestibility of organic matter (KS OH) and gross energy (KS BE) and in situ rumen degradability of neutral detergent fibre (NDF). The contents of ash, crude protein (NL), crude fibre (CF), NDF, acid detergent fibre (ADF), acid detergent lignin (ADL) and BE were significantly (P {>} 0,05) affected by the date of cutting time. The averaged values were for ash 119,2 g/kg of dry matter, NL 197,7 g/kg of dry matter, CF 236,5 g/kg of dry matter, NDF 400,7 g/kg of dry matter, ADF 296,2 g/kg of dry matter, ADL 73,8 g/kg of dry matter and BE 18,2 MJ/kg of dry matter. KS OH and KS BE generally decreased with higher dates of cutting time. On average KS OH and KS BE amounted 72,4 % and 70,2 %, respectively. The effective ruminal degradability (ED) of NDF generally decreased (P {>} 0,05) with increasing date of cutting time with values of 66,1 % (May 10), 63,6 % (May 18), 59,2 % (May 25), 64,8 % (June 29), 57,4 % (July 7), 56,9 % (July 13) a 51,6 % ( August 3). In situ characteristics were in average 77,1 % for the potential degradable NDF fraction (parameter b), 0,0703 h-1 for the fractional rate of degradation (parameter c) and 77,8 % for the digestible NDF (parameter DNDF).
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