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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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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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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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Purpose of epicentrum agency and marketpace for a new agency after its closure
Kohout, Jan ; Trunečková, Ludmila (advisor) ; Osvaldová, Barbora (referee)
This thesis recapitulates activities of Epicentrum agency which was reporting from the crisis places in the world and due to its termination of activities it attempts to define the meaning of Epicentrum. There is no doubt that Epicentrum was unique, but the important thing is to understand the causes and circumstances of its establishment and actions and to describe the way Epicentrum worked, including the both positive and negative aspects. Since the days of Epicentrum the world of media has changed fundametally (although it has not been that long). There is the phenomenon of media internetisation which the traditional media do not know how to deal with. Consequences of digitization have meant significant changes in journalists' work and the theme of this thesis is how could similar agency operate in these days. Today the proccess of producing the reports from the field is faster and cheaper which is advantage, on the other hand it is much easier to gather the large amount information for free these days and it is hard to convince media to buy it from such an agency. Therefore the integral part of this work is also a reflection on the value of on-the-spot reporting and its subsequent application possibilities on the market.
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Basic Mechanism of Fatigue and Combined Fatigue/Creep Damage of Ni-based Superalloys MAR-M 247 and IN 713LC
Horník, Vít ; Kohout, Jan (referee) ; Pantělejev, Libor (referee) ; Kunz, Ludvík (advisor)
The thesis is focused on clarifying fatigue damage mechanisms and fatigue-creep damage mechanisms of MAR-M 247 and IN 713LC polycrystalline Ni-based superalloys. This thesis begins with basic information about nickel-based superalloys and their microstructure, followed by a description of fatigue and creep mechanisms and their mutual interaction. The next part contains experimentally obtained results describing the behavior of MAR-M 247 and IN 713LC superalloys under various sets of conditions. Three testing temperatures - 800, 900 and 950 °C were used for the measurement of fatigue properties under symmetrical loading cycle, because in the temperature range 800 – 950 °C, the mechanism of fatigue crack propagation of both superalloys should change from the originally crystallographic at "lower" temperatures (800 °C) to non-crystallographic at "higher" temperatures (950 °C). In addition the effect of processing technology on fatigue properties was studied on the superalloy IN 713LC. High-frequency cyclic loading (about 120 Hz) with high mean stress at elevated temperatures was applied to induce fatigue-creep interaction. The combined fatigue-creep loading was performed on the IN 713LC superalloy at 800 °C and on the MAR-M 247 superalloy at 900 °C.
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Extremely low cycle fatigue life of non-ferrous alloys
Judas, Jakub ; Kohout, Jan (referee) ; Zapletal, Josef (advisor)
This thesis is focused on fatigue behaviour of aluminium alloy 2024-T351 in low cycle and extremely low cycle fatigue regime. Test specimens were firstly subjected to quasi-static tensile and compression tests to establish basic mechanical properties of the experimental material. Fatigue tests were conducted in strain-control mode, when cyclic plastic response and S-N curves were determined. All of the experiments were conducted at room temperature. Shapes of mechanical hysteresis loops are dependent on the strain amplitude and clearly exhibit cyclic plasticity of the alloy. Cyclic deformation curve was fitted by power regression function and subsequently compared with the tensile test. Experimental data of the S-N curves were fitted by Manson-Coffin and Wöhler-Basquin law. The discrepancy of the fatigue data was observed in the extremely low cycle fatigue regime. Based on this phenomenon, new regression function was used to overcome shortening of fatigue life in the extremely low cycle regime.
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Influence of asymmetry loading cycle on fatigue crack growth of alloy Inconel 625
Kander, Jan ; Kohout, Jan (referee) ; Věchet, Stanislav (advisor)
The main subject of this bachelor thesis was to evaluate influence of asymmetry of loading cycle on fatigue crack growth rate in a nickel-based superalloy Inconel 625. Experimental part of this thesis was carried out in Material and metallurgical research Ltd. Company in Ostrava, it’s main aim was to study the influences of loading cycles with parameter of asymmetry R = 0,1 and R = 0,7 on crack growth rate. Theoretical part deals with structure of nickel-based superalloys and fatigue crack growth rate.
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Využití dronů v konkrétních podmínkách zemědělského podniku
KOHOUT, Jan
The thesis deals with the use and utilization of drones, especially in agricultural conditions, where the drones are used more and more frequently in recent years, especially in combination with precision farming, thanks to the great number of advantages that this technology currently brings, not only to agricultural sector. In the thesis there are types of drones that are used for precision agriculture. In addition, there are described the functions of drones used and their distribution according to their deployment on the farm. Finally, questions will be answered about the amount of investment in this technology and the assessment of the effectiveness of the systems.
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Analysis of an accuracy of laser scanning
Vacová, Dominika ; Kohout, Jan (referee) ; Volařík, Tomáš (advisor)
The main goal of this master thesis is processing a point cloud with respect of possibilities of a registration clouds based on reference objects or on objects in general. This thesis studies transformations to the reference coordinate system S –JTSK. The first part of this thesis describes a theoretical background of the laser scanning and its use. A practical part shows the results and the evaluation of whole research.
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Evaluation of laser scanning for 3D modelling
Oboňová, Veronika ; Kohout, Jan (referee) ; Volařík, Tomáš (advisor)
The aim of the diploma thesis is to create a 3D model of the given object using laser scanning technology. Subsequent adjustments of the model and its separate preparation for possible 3D printing will be done through appropriate programs. The next 3D model of the identical object will be made based on the created photos and will be edited and prepared in the same way for possible 3D printing.
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