|
|
Study of ultrafine-grained materials prepared with different methods of severe plastic deformation
Krajňák, Tomáš ; Mathis, Kristián (advisor) ; Hadzima, Branislav (referee) ; Kalvoda, Ladislav (referee)
Title: Study of ultrafine-grained materials prepared with different methods of severe plastic deformation Author: RNDr. Tomáš Krajňák Department: Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University in Prague Supervisor: Doc. RNDr. Kristián Máthis, PhD., Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University in Prague Abstract: Interstitial free steel with ultrafine-grained (UFG) structure was prepared by high-pressure torsion (HPT). The development of the microstructure as a function of the number of HPT turns was studied at the centre, half-radius and periphery of the HPT-processed disks by X-ray line profile analysis (XLPA), positron annihilation spectroscopy (PAS) and electron microscopy. The dislocation densities and the dislocation cell sizes determined by XLPA were found to be in good agreement with those obtained by PAS. The evolution of the dislocation density, the dislocation cell and grain sizes, the vacancy cluster size, as well as the high-angle grain boundary (HAGB) fraction was determined as a function of the equivalent strain. It was found that first the dislocation density saturated, then the dislocation cell size reached its minimum value and finally the grain size got saturated. For very high strains after the...
|
|
|
Resident's perception of tourism - Karlštejn
Oberman, Radek ; Fialová, Dana (advisor) ; Krajňák, Tomáš (referee)
The Bachelor thesis aims to find out the opinions and attitudes of residents of the municipality of Karlštejn on tourism. In particular, the method of semi-structured conversations, as well as the mapping of the functional use of buildings, is used to achieve this goal. The work in the introduction presents tourism, related literature and selected terms associated with it, possible ways to access it and the impacts it can have on a particular destination. The case study then focuses on tourism in Karlštejn, especially its perception by residents, who play an important role in tourism. In conclusion, the research results are summarised and compared with the situation in similar destinations. Keywords tourism, tourism perceptions, semi-structured talks, Karlštejn
|
|
|
Political-Military Risks for Tourism in the Middle East
Krajňák, Tomáš
Political-Military Risks for Tourism in the Middle East Abstract The master's thesis analyses the perception of political-military risks for incoming tourism in the Middle East from the perspective of Czech potential tourists. The examined area of the Middle East bears some geographic and geopolitical ideas, that are still absent in the Czech scientific milieu. Tourism in the Middle East also operates in the environment of political-military risks. Scholarly literature suggests that these risks represent one of the main factors influencing the choice of destination. The paper deepens understanding of this relationship by focusing on the perception of political-military risks in space, in terms of their typological diversity, and analyses determinants of this perception. The main research tool, a questionnaire, served to collect data that was analysed through descriptive statistics and statistical inference, as a paired t-test, analysis of variance (ANOVA) and correlation analysis. The findings are mostly in consensus with theoretical knowledge and previous studies. Individual types of political- military risks showed different impact on the perception for realization of tourism. A statistically significant difference exists between violent and non-violent political-military risks. In some cases, however,...
|
|
|
Microstructural evolution of equal-channel angular pressed IF steel
Krajňák, Tomáš
Equal channel angular pressing (ECAP) belongs to advanced technologies for improving mechanical properties of materials. In the present work the influence of number of pressing by route BC on grain size, density and type of dislocation, evolution of microstructure and mechanical properties of IF steel has been investigated by means of optical microscopy, electron back-scattering diffraction (EBSD), diffraction profile analysis, microhardness testing and tensile deformations. It has been found, that the grain size decreasing with increasing number of passes. Simultaneously, the microhardness, density of dislocation and maximum true strength has been increased. The evolution of microstructure with increasing pressing number, particularly the forming of high-angle boundaries has been also examined.
|
|
|
Deposition of large organic molecules under UHV
Krajňák, Tomáš ; Novák,, Jiří (referee) ; Čechal, Jan (advisor)
In this thesis, large organic molecules (DM15N, DM18N, Cu(dbm)2) were deposited. These molecules are cannot be deposited by thermal sublimation due the fact that they decompose at lower temperature than they sublime. The employed molecules to single molecular magnets, which can be potentially used as quantum bites (qubit). The new method of deposition atomic layer injection made by Bihur Crystal company was introduced and tested. The method uses liquid solution with molecules which is driven by argon gas through pulse valve to the sample placed in ultra-high vacuum chamber. During the deposition, droplets of solution are formed on the sample surface. The solvent can be removed by light annealing or by keeping the sample in the vacuum for couple of days. The molecules were investigated by x-ray photoelectron spectroscopy and by scanning electron microscopy to determine fragmentation of the molecules, to study topography of the resultant surface and homogeneity of the deposited layer. We found conditions at which the intact molecules are deposited on the sample surfaces and form molecular nano- and micro- crystals.
|
|
|
Mechanical properties and microstructure of ultrafine-grained magnesium alloys containg neodymium and zinc
Šašek, Stanislav ; Stráská, Jitka (advisor) ; Krajňák, Tomáš (referee)
Two experimental magnesium alloys containing neodymium and zinc (Mg- 5Nd-1Zn and Mg-1Nd-1Zn) were processed by severe plastic deformation (SPD) method - equal channel angular pressing (ECAP). The influence of the processing on the microstructure was studied by light optical microscopy (LOM), transmis- sion electron microscopy (TEM) and also scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD). A significant grain refinement was observed after the final stage of ECAP in both alloys resulting in homogenous ultra-fine grained condition. Microstructure development had a significant influ- ence on mechanical properties which were investigated by microhardness measu- rements and compression deformation tests. Both the yield compression strength σ0,2 and the microhadness significantly increased compared to the extruded/as- cast counterparts. 1
|
|
|
Political-Military Risks for Tourism in the Middle East
Krajňák, Tomáš
Political-Military Risks for Tourism in the Middle East Abstract The master's thesis analyses the perception of political-military risks for incoming tourism in the Middle East from the perspective of Czech potential tourists. The examined area of the Middle East bears some geographic and geopolitical ideas, that are still absent in the Czech scientific milieu. Tourism in the Middle East also operates in the environment of political-military risks. Scholarly literature suggests that these risks represent one of the main factors influencing the choice of destination. The paper deepens understanding of this relationship by focusing on the perception of political-military risks in space, in terms of their typological diversity, and analyses determinants of this perception. The main research tool, a questionnaire, served to collect data that was analysed through descriptive statistics and statistical inference, as a paired t-test, analysis of variance (ANOVA) and correlation analysis. The findings are mostly in consensus with theoretical knowledge and previous studies. Individual types of political- military risks showed different impact on the perception for realization of tourism. A statistically significant difference exists between violent and non-violent political-military risks. In some cases, however,...
|
|
| |
|
| |
|
|
Attitudes toward retirement system of the Czech Republic – November 2018
Krajňák, Tomáš
In November, the Public Opinion Research Centre asked a set of questions related to attitudes of the Czech citizens towards the retirement system in the Czech Republic. Questions focused mainly on the current condition of the retirement system and its possible changes. Respondents also expressed level of their support for concrete measures and actions within the retirement system. The last question focused on the opinion whether the received finances from the social security system can cover funding of the pensions.
|
guest ::
