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Segregation during solidification in austenitic-ferritic stainless steels
Kejha, Richard ; Čech, Jan (referee) ; Pernica, Vítězslav (advisor)
The master thesis deals with processes of segregation in austenitic-ferritic stainless steels. The introductory part consists of characteristics features of austenitic-ferritic steels and theoretical analysis of segregation processes. The second part shows practical measurements of segregation in experimental casting. Macrosegregation was measured on a spectrometric analyzer and simultaneously solved in the simulation program MAGMA. The aim of this thesis is to verify the effect of solidification time and dwell time between liquidus and solidus temperature on the chemical heterogeneity of duplex stainless steel casting of about 500 [mm]. Chemical heterogeneity was solved for selected alloying and accompanying elements such as C, Mo, Ni, Mn, Cr. The microsegregation was not addressed. Comparison of the mechanical properties of cast and heat treated duplex steel was done by tensile testing of samples cut from the center of the casting.
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Recovery and recrystallization of austenitic steel 08Cr18Ni10T
Čech, Jan ; Gregor, Martin (referee) ; Foret, Rudolf (advisor)
This thesis deals with influences of graded deformations, temperatures and holding times on the grains and subgrains size in steel 08Cr18Ni10T. In literary part of the thesis there are described static and dynamic annealing treatments, then also austenitic stainless steels and some selected types of their processing. In experimental part there is studied grain size on differently deformed samples annealed in temperature range 1050–1200 °C for 10, 50 and 100 minutes. Analysis of present structures units was perform by EBSD. Except of that, there were realized chemical analysis of selected inclusions and also hardness test were realised. Achieved measurement shown, that grain size of chosen steel is depended on all 3 variable values.
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Tři eseje o Josephu Stiglitzovi a informačních asymetriích
Pospíšil, Martin ; Mertlík, Pavel (advisor) ; Čech, Jan (referee)
This thesis contains three essays related to the work of economist Joseph Stiglitz. The first essay describes the contribution of Stiglitz to economic theory by analysing problems of information asymmetry, new Keynesian and institutional economics, rationality, and market theories. Shortcomings of neoclassical economics are described and possible solutions are outlined. The last part of this is essay summarizes the main critique to Stiglitz. The second essay applies the topic of information asymmetry by discussing whether the current level of economic development leads to convergence or divergence in the technology and information levels. The conclusion is that even though globalisation affects the level of technology and information, we do not see convergence as predicted by several theoretical models and information asymmetry remains an important element in the economy. The last essay links the Stiglitz-Greenwald theory of credit rationing using recent Czech data from years 2008 and 2009. Data confirm that credit rationing increases, information asymmetry increases, and the transmission mechanism does not function well during economic decline. I conclude that Czech banks increase their screening of clients and consequently credit rationing in the times uncertainty leading to ambiguous development...
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Evaluation of precision tennis forehand
Čech, Jan ; Kočíb, Tomáš (advisor) ; Pravečková, Petra (referee)
Name: Evaluation the accuracy of forehand in tenis Aim: The aim of the thesis is to verificate the own test of accuracy and the vigour of forehand and to compare its results with standard test of the international rating players, international tennis number (ITN). Methods: The test method was used. Also, an informal interview where open questions were held. The results obtained were arranged and tabulated for the purpose of presentation. The observation was focused on testing. The comparison method was used to compare the measured results in testing the ITN international test and my test for tennis forehand. Conclusion: The measured values were compared and processed. The results show us a comparison between the ITN International Test and my test for tennis forehand. Conclusion of processed data, where it is visible how the individual player was conducting in a certain test. Keywords: tennis, forehand, vigour, accuracy
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Design of linear motor with permanent magnets
Čech, Jan ; Bulín, Tomáš (referee) ; Knebl, Ladislav (advisor)
The first part of this thesis deals with the study of linear motors. The introduction of the thesis deals with the brief description of the linear motor, including its accessories. This part explains principle of linear motors, their general advantages and disadvantages. The next section contains an overview and division of the currently used linear motors. Each type of currently used linear motors is briefly introduced and also its principle and characteristics are described, including its specific application. The second part of the thesis deals with the design of an equivalent magnetic circuit model of a linear iron-core linear motor. Hereafter, the proposed design will be used to simulate the distribution of magnetic flux in the linear motor. The evaluated flux-density distribution in the air gap is later compared with the results obtained with finite element method. The thrust is then calculated from the flux-density and the estimated value is compared with the value listed in datasheet.
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Influence of solidification conditions on structure and properties of austenitic chrome-nickel steels
Ambrož, Ondřej ; Čech, Jan (referee) ; Záděra, Antonín (advisor)
The thesis deals with the influence of solidification conditions on structure and mechanical properties of austenitic stainless steels. The first part involves the distribution of stainless steels and a basic understanding of the issue of achieving the desired structure and mechanical properties. The second part is focused on austenitic steels and their basic characteristics. This section also describes the experiment and the results achieved. Finally, these results were evaluated and further research steps were recommended.
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Macrosegregation and microsegregation in austenitic CrNi steels
Ostratický, Marek ; Čech, Jan (referee) ; Záděra, Antonín (advisor)
This diploma thesis deals with segregation cycles in austenitic CrNi steels. In first section deals with theory of macrosegregation and microsegregation cycles. The second part is focused on this cycles in experimental casting. Macrosegregation was measured by spectrometric analyser and by MAGMA simulation program. Microsegregation was measured by electron microscope. The aim of this diploma thesis is verify the influence of setting conditions on heterogenity chemical composition in austenitic CrNi steel. For experimental casting with a wall thickness of about 500 mm will be verified effect of the setting time, residence time between solid and liquid phases and others parameters for macrosegregation and microsegregation in selected elements.
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Observation of twin boundaries in Ni-Mn-Ga alloys
Čech, Jan ; Jan, Vít (referee) ; Zelený, Martin (advisor)
This bachelor’s thesis is focused on observation of twin boundaries in a magnetic shape memory alloy based on Ni2MnGa with 10M martensitic structure. Theoretical part of the thesis describes materials with shape memory effect, their response on mechanical or magnetic loading, phenomenon of twinning, which is closely connected to the shape memory effect, and various levels of twinning. Experimental part studies different types of twin boundaries in monocrystal of alloy Ni49.2Mn30.4Ga20.4 using optical and electron microscopy. The thesis also deals with detection of structural orientations in different twin variants. A holder of samples was designed and constructed for real time observation of twin-boundary movement by optical microscopy. Deformation by pressure shows, that stress necessary for movement of Type II twin boundaries is ~0.2 MPa, whereas it is ~0.6 MPa for movement of Type I.
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Rule-of-Thumb Consumers in the New Keynesian Framework: The Implications for Fiscal Policy
Adam, Tomáš ; Baxa, Jaromír (advisor) ; Čech, Jan (referee)
iv Abstract This thesis investigates the effects of government spend- ing on aggregate economic variables in the Czech Republic. The standard RBC and New Keynesian models assume only forward-looking households despite the evidence of a sig- nificant fraction of non-optimizing households. These mod- els do not provide reasonable predictions for the response of consumption: both models predict its fall following a gov- ernment spending shock. Therefore, a variant of the New Keynesian model, where rule-of-thumb households coexist with optimizing households, is used for the analysis. We have found that fiscal policy has a positive impact on output, although government spending multiplier does not exceed one. Also, the impact on consumption is positive for several periods following a fiscal spending shock, which is consistent with the evidence. JEL Classification: C32, E32, E62 Keywords: fiscal policy, fiscal multipliers, fiscal VAR, rule- of-thumb consumers
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