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Structure and fatigue properties of selected titanium alloy
Prudíková, Alena ; Kohout, Jan (referee) ; Věchet, Stanislav (advisor)
Main topic of the thesis was to evaluate fatigue properties of the titanium alloy Ti-A13-V2,5, labelled by ASTM as Grade 9. Most attention was focused on fatigue behaviour of the alloy in the range of high cycle fatigue. Fatigue testing was realised to detect the fatigue properties and consequently to generate the Wöhler curve and the Haigh diagram. In addition to this, tension and bending tests were performed. Metallographic and fractographic analyses of fatigue fracture form part of the overview about material properties, which was accomplished by use of REM. Experimental part of the thesis was backed by the literature research. The first half of it contains a short summary of basic information about the titanium and its alloys, so as some chapters about the history and properties of titanium, the way of its production, classification of titanium alloys and its thermic treatment. The fatigue is thoroughly scrutinised in the second half of the background research. Here can also be found the information about the fatigue process, its stages, the fatigue life and the most significant attributes of the fatigue fracture. The last chapters of the thesis are dedicated to the alloy Ti-A13-V2,5 - being examined in the experimental part - so as to its fatigue properties. The main benefit of this thesis is the completion of the missing information concerning the fatigue behaviour of the alloy, which is – according to the literature research - generally not available.
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Study of the properties of hyperpolarized xenon-129 for magnetic resonance imaging
Rychnovský, Jan ; Nováková,, Sabina (referee) ; Kohout,, jJaroslav (referee) ; Bartušek, Karel (advisor)
Produkce hyperpolarizovaných plynů, především helia (3He) nebo xenonu (129Xe), nachází stále rostoucí rozsah aplikací v zobrazování magnetickou rezonancí (MRI). Helium ani xenon nejsou obyčejně obsaženy v těle a experimenty tedy nejsou ovlivněny nechtěným signálem z okolních tkání. Ukázalo se, že několika hyperpolarizačními technikami může být magnetická polarizace (magnetizace) jader vzácných plynů zvýšena na hladinu, se kterou jsou praktické aplikace proveditelné. Hyperpolarizované plyny mohou tedy být užitečným nástrojem pro neinvazivní zkoumání lidského dýchání, dovolující statické zobrazování během zadržení dechu nebo zkoumání dynamiky výdechu nebo nádechu, nebo funkčního zobrazování. V neživé přírodě, mohou být hyperpolarizovaný plyny využity jako kontrastní látka při studiu mikroporézních materiálů, jako jsou zeolity, stavební látky a hmoty, atd. V této doktorské práci je popsán vývoj a konstrukce aparatury pro hyperpolarizaci xenonu (izotopu 129Xe). Nákup hyperpolarizovaného xenonu od jiných výzkumných center v zahraničí a jeho dovážení by ovšem nebylo efektivní a to zejména z důvodu náročnosti zajištění potřebných fyzikálních podmínek pro přepravu hyperpolarizovaného plynu. Toto bylo hlavní motivací k vývoji vlastní technologie pro přípravu hyperpolarizovaného xenonu. Se zvládnutou technologií by bylo možné navázat spolupráci s medicínskými zařízeními, nebo s týmy zabývající se živou nebo neživou přírodou (např. při studiu mikroporézních materiálů, gelů, v zemědělských aplikacích nebo při výzkumu využívajících zvířat, atd.). Cílem této práce je studium teorie hyperpolarizovaných vzácných plynů se zaměřením na 129Xe a experimentální ověření a změření relaxačních časů pomocí jaderné magnetické rezonance. Vzhledem k tomu, že je možné hyperpolarizované vzácné plyny skladovat pro pozdější využití, se tato práce také zabývá možnostmi zásobníku hyperpolarizovaného vzácného plynu a jeho teoretickým a experimentálním řešením. V této práci jsou popsány především dva základní typy experimentů přípravy hyperpolarizovaného xenonu. V obou jsou využity zatavené válcové skleněné vzorky naplněné xenonem a doplňujícím plynem – dusíkem, heliem. První z experimentů se zabývá měřením vlastností termálně polarizovaného xenonu a druhý měřením vlastností hyperpolarizovaného xenonu. Pro hyperpolarizaci 129Xe bylo použito výkonového laseru a experimentálně byla zkoumána jednak míra polarizace na základě změny spektrální hustoty čerpacího laserového svazku a dále pak optimální doba optického čerpání 129Xe a relaxační časy xenonu.
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The Effect of Temperature Annealing on Structure-Property Relationship of Oriented Polypropylene
Sadílek, Jiří ; Jančář, Josef (referee) ; Kohout,, Jan (referee) ; Hell,, Jaroslav (referee) ; Kučera, Jaroslav (advisor)
The aim of this work is to study the effect of thermal history to structure and properties not only of oriented polypropylene monofilaments with different orientation but of course of isotropic non-oriented polypropylene. Term thermal history includes thermal regimes from alpha relaxation temperature (T?) to melting temperature (Tm). This work consists of three parts. The changes of dynamic mechanical properties, strength, deformation and tensile modulus of polypropylene samples according to annealing temperature (Ta) are described in the first part of this work. In the second part, the changes of crystal phase are observed. Preferentially, calorimetric behaviour (DSC), changes of crystal dimensions and orientation function of crystal phase (X-ray) are observed. Measured values from the first and the second part of this work were used for calculation of total orientation function of PP samples. Rheological measurements are shown in the third part of this thesis. Rheological measurements consist of short isothermal creep, shrinkage of free tapes and static deformation at higher temperatures. Measured rheological values were performed using rheological models. Using these models characteristics of entropic spring, instantaneous elasticity and viscosity and tendency to get to state of ease were calculated.
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DLMS security suite implementation
Kohout, David ; Sláčik, Ján (referee) ; Mlýnek, Petr (advisor)
This thesis is focused on smart meters cyber security using DLMS Security Suite standard. Security is more important every day and DLMS specifies multiple methods of authentication and message encryption which is defined in Security Suites. For message creation there are multiple possible formats that can be used. For a better understanding all formats are analysed and compared using a specific example. Main part of this work is about making a testing application called VUT DLMS Tester which is used for testing this standard for real usage in distribution network. Whole development is cooperated with distribution companies and smart meter manufacturers. Application also implements higher levels of security which DLMS specifies. This application is used for testing multiple scenarios regarding security impact on data volume.
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Marketing communication analysis of the Czech Olympic team during the 2022 Olympic Games
Kohout, Jakub ; Turková, Kateřina (advisor) ; Halada, Jan (referee)
My bachelor thesis "Marketing communication analysis of the Czech Olympic team during the 2022 Olympic Games" examines the complex marketing communication of the Czech Olympic Team using available data. In the thesis I first describe the theoretical foundations of the field of marketing and sports marketing, then I introduce the issues of marketing communication within the Olympic Games. In the practical part, with the help of semi-structured interviews with members of the Czech Olympic Team marketing team and SWOT analysis, I draw conclusions and offer recommendations for further marketing communication strategy of the Czech Olympic Team. The thesis examines in detail all marketing tools and channels of the Czech Olympic Team.
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Analysis of the Causes and Nature of Ethnic Conflicts
Kohout, Jan ; Plechanovová, Běla (advisor) ; Parízek, Michal (referee)
The aim of this thesis is to analyze factors responsible for onset of ethnic conflicts and selected characteristics. By comparing to non-ethnic conflicts it was determined, if there are any differences in onset mechanisms of these two types of conflicts and thus if there is a space for explanatory role of ethnicity as a cause of ethnic conflicts. Selection of examined factors is congruent with the relevant literature and existing analyses and reflects the context of contemporary conflict research. The influence of male unemployment rate, level of Human development index and its inequality-adjusted version, human rights and finally the influence of conflicts in neighbouring countries on the onset of conflict is tested by statistical methods in component analyses. Also the intensity of ethnic and non-ethnic conflicts, war years and HDI are also compared. The comparative style of the research helps to understand the true nature of causes of intrastate conflicts and indicates, that there is no difference between the two types. Empirical character of this thesis is also the reason for assessing it within the context of other quantitative studies of conflict, comparing the results and defining the proper level of analysis for reaching tangible contributions.
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Development of mycorrhizal communities in primary succession
Mádle, Jan ; Kohout, Petr (advisor) ; Ponert, Jan (referee)
Primary succession is the process of ecosystem development that takes place in sites that were not suitable for colonization by plants and organisms dependent on them. These sites arise either naturally, for example after a volcanic eruption or glacial retreat, or anthropogenically, for example by strip mining. During primary succession, plants colonise the bare substrate and gradually modify its abiotic and biotic conditions. During primary succession, interactions between plants and the soil microbiome, especially with fungi and bacteria, occur. Plants and soil microorganisms influence each other's growth and development through various interactions. Plants, or rather their roots, form a specific niche for a wide range of soil microbial communities. Through their roots, plants provide a wide range of substances, organic acids, sugars, amino acids and other often carbon-rich compounds that can serve as a substrate for microorganisms. Plants are able to do this by producing litter, root exudates, and translocation of sugars for symbiotic fungi and bacteria. Soil microorganisms contri- bute to the release of nutrients and the decomposition of organic materials that would otherwise be unavailable to plants. Many soil microorganisms can form a symbiotic relationship with the plant; this relationship may be...
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The mounting jig concept for mounting the LED headlight module
Žlebek, Jan ; Kohout, Marek (referee) ; Zeizinger, Lukáš (advisor)
The aim of this thesis is to propose the concept of a universal preparation for mounting the LED module of the headlamp. The first part of the thesis is devoted to individual components of the headlamp, such as printed circuit boards, coolers, optical elements, etc. Furthermore, the thesis provides an overview of the types of modules currently used, from basic reflector technology to the most modern projection modules. The next part of the thesis is focused on conceptual designs for mounting the modules on pallets. It continues by the design of the pallet, which was further verified by the FEM method whether it complies with the given parameters. The last part of the thesis summarizes the advantages and disadvantages in the implementation of the proposed method into the production.
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Development of Long-pitch Corrugation in Curves of Small Radii
Valehrach, Jan ; Kohout,, Martin (referee) ; Lidmila,, Martin (referee) ; Plášek, Otto (advisor)
Throughout the operation, the rails are worn and deteriorate. With the increasing speed of rolling stock, along with higher track loads and especially in the vicinity of major traffic hubs with a higher frequency of trains, defects that did not occur to such an extent before or were not considered to be significant, are brought to the forefront of the concerns of track infrastructure managers. Even though these defects are not directly restrictive to traffic operation, they are, in any case, a source of noise and vibration. One of these defects on the railway track is the micro-geometry defect of the running surface of the railhead. In directional curves with radii of less than 600 m or 700 m, defects known as long-pitch corrugation occur on the inner rail. In curves with 300 m or smaller radii, these waves are so distinct that they are a significant source of noise and vibration. In particular, vibrations affect the track surroundings and the track itself, as they cause other defects in the track structure. This dissertation deals with long-pitch corrugation, focusing on the monitoring of wave generation and development over time. The verification of the possibility to track the development of slip waves over time is the basis for possible future models predicting the development of defects. Numerous measurements of geometric parameters of the track and microgeometry of the railheads, specifically slip waves, have been carried out in the framework of the problem. Using RMS and peak-to-peak methods, the rate of development of defects over time and the relationship with other track parameters were evaluated. Based on the obtained development curves, intervals for further maintenance interventions were estimated. A part of the thesis focuses on the deficiency or excess of cant concerning the development of long-pitch corrugation.
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Evolution of algorithm for artificial creatures
Kohout, Jan ; Holan, Tomáš (advisor) ; Mráz, František (referee)
The task of this work is to create an application which allows performing of experiments with evolution of artificial creatures. Behavior of each creature is managed by its algorithm. The algorithm is able to use creature's memory cells (which represent logical variables) and is the genome of the creature. By the crossing-over and mutation, the algorithm evolves. The second aim of this work is to make some tests with the application and describe their results.
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