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Spectral analysis of the B[e] star FS CMa
Kříček, Radek ; Korčáková, Daniela (advisor) ; Mayer, Pavel (referee)
The thesis is dealing with spectral analysis of the B[e] star FS CMa, a prototype of FS CMa stars group. These objects are characterized by huge amount of matter in sourrounding shell which origin is not explained for many years. However, solving this issue could enrich stellar astrophysics by enhanced stellar evolution models. The goal of this thesis is to improve our understanding of FS CMa. We described spectral variability on various time scales and simulated spectra for different forms of the system in HDUST code. On the basis of new obtained spectra we confirmed long-term changes in variability of some spectral features and rapid variability of some spectral lines. We gained an estimate of the gas density. The simulations showed that spectral type of FS CMa is not certain and that the star could be surrounded by extended disk, many stellar radii wide. 1
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Identification of rate type fluids suitable for modeling geomaterials
Tůma, Karel ; Málek, Josef (advisor) ; Čadek, Ondřej (referee) ; Vohralík, Martin (referee)
In the present thesis we study and compare different viscoelastic rate-type fluid models capable of describing response of geomaterials such as asphalt. Using new thermodynamic approach proposed by Rajagopal and Srinivasa (2000) we derive several classes of non-linear viscoelastic models that generalize standard Oldroyd-B and Burgers models. We show that the new models achieve better results in fitting experimental data with asphalt than the previously considered models (Oldroyd-B, Burgers, Rajagopal and Srinivasa (2000)). In particular they are able to capture the behavior of asphalt observed recently in experiments (torque overshoot and two relaxation mechanisms), which is not possible to describe by the other models. Using both the standard and the newly derived models we compute full simulations of viscoelastic flow with the finite element method in fixed domains and incorporating the Arbitrary Lagrangian-Eulerian description also in deforming domains. For example, we study rolling of asphalt or creation of ruts in the road with the real material parameters obtained by fitting the experiments. Powered by TCPDF (www.tcpdf.org)
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Adaptivní hp nespojitá Galerkinova metoda pro nestacionární stlačitelné Eulerovy rovnice
Korous, Lukáš ; Feistauer, Miloslav (advisor) ; Dolejší, Vít (referee)
The compressible Euler equations describe the motion of compressible inviscid fluids. They are used in many areas ranging from aerospace, automotive, and nuclear engineering to chemistry, ecology, climatology, and others. Mathematically, the compressible Euler equations represent a hyperbolic system consisting of several nonlinear partial differential equations (conservation laws). These equations are solved most frequently by means of Finite Volume Methods (FVM) and low-order Finite Element Methods (FEM). However, both these approaches are lacking higher order accuracy and moreover, it is well known that conforming FEM is not the optimal tool for the discretization of first-order equations. The most promissing approach to the approximate solution of the compressible Euler equations is the discontinuous Galerkin method that combines the stability of FVM, with excellent approximation properties of higher-order FEM. The objective of this Master Thesis was to develop, implement and test new adaptive algorithms for the nonstationary compressible Euler equations based on higher-order discontinuous Galerkin (hp-DG) methods. The basis for the new methods were the discontinuous Galerkin methods and space-time adaptive hp-FEM algorithms on dynamical meshes for nonstationary second-order problems. The new algorithms...
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Seismic Site Effects (Data Analysis and Modelling)
Caserta, Arrigo ; Zahradník, Jiří (advisor) ; Růžek, Bohuslav (referee) ; Burjánek, Jan (referee)
A comprehensive study of the soil shaking under the seismic wave-field ex- citation is presented. It includes theoretical, geological, geotechnical, data analysis and numerical simulations aspects. The aim is to quantify the main parameters allowing the estimate of the soil shaking in urban areas for better mitigating seismic risk due to future earthquakes. The city of Rome has been chosen as a case study because of its high density of popula- tion and large concentration of historical monuments with high earthquake vulnerability. This study improves significantly the knowledge concerning the detailed near-surface geology of the chosen study area of Rome, ful- fills the absence both of knowledge concerning its geotechnical properties and earthquake data recordings in the city. Among others, it allows for a better explanation of the spatial damage pattern observed in the city due to earthquakes in the past. The main innovations include the construction and long-term operation a seismic array in the city, analysis of the natural seismic noise, and instrumental recordings of the 2009 L'Aquila earthquake sequence. The 3D array (including a borehole sensor at 70-m depth) is the first one in Italy planned, realized and operated within an urban area, and the first one that recorded a significant earthquake in...
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Numerical simulations of magnetoacoustic waves in solar corona
POKORNÝ, Jan
The topic of the master thesis are the numerical simulations of magnetoacoustic waves in the solar corona in relation to the reconnection of magnetic field. The first part is devoted to the basic description of the Sun, its atmosphere and the processes that occur in it. Other sections are devoted to the description of reconnection of magnetic field and the description of solar flares taking place in the solar corona in relation to the mechanisms of magnetic field reconnection. Then the attention is focused on plasma waves and oscilations. The last section aims to simulate the startup options of the reconnection of magnetic field by oscillations and waves in the Harris current-sheet. Numerical simulations are implemented in FLASH 3.3.
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Coulomb Interactions in Electron Beams
Jánský, Pavel ; Janík,, Ján (referee) ; Kolařík,, Robert (referee) ; Lencová, Bohumila (advisor)
The thesis deals with numerical simulations of a hairpin thermionic electron gun, an electron source of the electron-beam welding machine. Simulations showed that the space charge in the electron gun has a significant influence on the beam current and electron trajectories. Simulation outputs are in a sufficient agreement with the experimental measurements.
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Prediction of welding joint distortion by computer simulation.
Vaněk, Mojmír ; Slováček, Marek (referee) ; Daněk, Ladislav (advisor)
In this master’s thesis there are set down dependencies of distortion of T-joints on the size of heat input and welding speed. Dependencies were found for single- and double-fillet welds, for single- and multiple-pass welding. The computer simulations were carried out in programs Visual-Weld and SYSWELD. The size of the melted zones, stress fields, material structure and hardness of the weld specimens were specified. Simulation results were compared with experimentally detected values.
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Numerical simulation of mold filling and casting solidification
Kolda, Vlastimil ; Herman,, Aleš (referee) ; Krutiš, Vladimír (advisor)
The object of this diploma thesis is to analyze, persuant to numerical simulation of current technology of production aluminous casting roller-reck V9X, causes of the rise of cold lap and laminations defects. Consequently, to work up a project of variant solution of the shape of casting so, as to come to elimination mentioned defects. This variant solving will be tested with numerical simulation as well. Fruitfulness of these designed changes will be verified by testing molten of the casting. In terms of solve the problem the simulation of cycling of the mold and subsequently the filling of the casting will be effected. During the analyse of filling of the die the first phase of filling will be effected too.It means the movement of the piston throught the chambre. Simulation of solidification of the casting wont be effected because of the type of the defect.
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Numerický model odezvy stromu během tahové zkoušky
Vojáčková, Barbota
The numerical simulation of the tree pulling test was carried out in the thesis. ANSYS Parametric Design Language was used for the simulation. The parametric design enables use of simulation for variations of tree dimensions, material properties and device positions. Results from numerical solution were compared with a field experiment and analytical solution in cases of three oaks. To found significant influence of input parameters probabilistic analysis was carried out. The analysis found that there is a significant correlation among stem diameter, root volume and tree inclination and nodes displacement on the tree stem. The influence of stem defect and root-plate damage on ability of devices was found as well. Numerical model can be used for the simulation of tree pulling test in wide variety of different configurations, for example change of geometry, material properties and defects extension and position of stem and root-plate system. The practical impact of results and further development of numerical simulation are discussed at the end.
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Numerical simulations of MHD waves in the solar corona with gravitational field
ŠEBÍK, Matěj
The aim of this bachelor?s thesis is to numerically simulate propagation of impulsively generated waves and oscillations in a plasma of the solar corona using a numerical code FLASH. This program is used to create a model of propagation of the MHD waves in a so-called current-sheet layer. The model should correspond with an observations obtained by modern solar probes. There are clues implying that a gravitationally stratified solar atmosphere affects the progression of the MHD waves in a time evolution. Therefore the gravitation effect is inducted in the calcullation. The last part of the text discusses the given differences with and without gravitation.
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