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Subsolidus thermal convection as a key to understanding volatile evolution and internal dynamics of large icy bodies
Ninneman, Brendan ; Kalousová, Klára (advisor) ; Šrámek, Ondřej (referee)
Titan is a unique moon in the solar system as it is the only one with a thick atmo- sphere, and surface lakes and seas. Observations made by the Cassini/Huygens probe showed the potential of a subsurface ocean hidden below the outer crust made of ice. This thesis analyzes the heat transfer through the crust of Titan to understand the long term evolution of the ocean. We developed a finite element model of the heat transfer through a thickening ice crust and investigated the effect of viscosity, internal heat flux, and ammonia concentration in the ocean. While other explanations cannot be ruled out, it was found high values of viscosity and possible ammonia presence could keep the ocean liquid for long periods. 1
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Effects of crustal rheology on stresses generated in subducting lithosphere
Pokorný, Jakub ; Čížková, Hana (advisor) ; Šrámek, Ondřej (referee)
In this thesis we present the results of the numerical models of lithospheric subduction focused on the influence of rheological properties of the crust. We use a two-dimensional Cartesian model with non-linear rheology, including the major phase transitions at the depths of 410 km and 660 km. The separation of the subducting and overriding plates is facilitated by a low-viscosity crust, prescribed on the top of the subducting plate. Previous studies have shown that the mechanical properties of this crust significantly influence the deformation of the subducted plate in the transition zone. Here we focus 1) on a detailed analysis of the combined effects of the crustal thickness and viscosity on the slab deformation and its ability to penetrate to the lower mantle and 2) the implementation of the non-linear crustal rheology and testing the influence of its parameters. In the case of models with constant viscosity we show that the increase of the crustal thickness and/or the decrease of its viscosity makes it easier for the subducting plate to move and therefore leads to increasing the subduction velocity and rollback. If the ratio between the crustal viscosity and its thickness à · 3:3 č 1016 à · 3:3 č 1016 Pa s m-1 the slab stagnates above the boundary at the depth of 660 km. For higher ratio ÃÃ...
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Business plan
Šrámek, Ondřej ; Khelerová, Vladimíra (advisor) ; Vojtíšek, Zdeněk (referee)
The goal of this bachelor is thesis is to create an ideal structure of a business plan, which will be used as the guide for creators of a project but also as a valid source of needed information for the reader. Everything with maximal focus on customer needs. The goal is also to create clear criteria for determining whether a project can be called "startup" and if it is suitable to use franchising for expanding to other countries. This plan and criteria are followed by practical test and example.
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Thermal Convection in Terrestrial Planetary Mantles
Benešová, Nina ; Čížková, Hana (advisor) ; Hejda, Pavel (referee) ; Šrámek, Ondřej (referee)
In this thesis, we present results of a numerical modelling study focused on the thermal evolution of the Earth and terrestrial planets. We focus particularly on two problems: I) constraining the internal structure of Venus and Mercury using their geoid and surface topography data and II) evaluating the effects of a rhe- ologically distinct post-perovskite on the secular cooling of the Earth. In part I, we performed simulations in a broad group of models of the Venusian man- tle, characterised by different rheological descriptions, and we compared spectra of their geoid and their surface topography with the observed quantities. Our analysis suggested that the geoid and the surface topography of Venus are con- sistent with a radially symmetric viscosity model with a strong 200 km thick lithosphere, without an asthenosphere and with a gradual viscosity increase in the underlying mantle. In the case of Mercury, none of our models was able to predict observed data, thus suggesting other than a dynamic origin of observed geoid and topography. In part II, we investigated style of Earth's mantle con- vection and its long-term evolution in the models that take into account a weak post-perovskite. We conclude that the presence of the weak post-perovskite en- hances the core cooling. This effect is comparable in...
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Studium rovnováhy mezi klesajícími kapkami železa a roztavenými silikáty v magmatických oceánech
Ulvrová, Martina ; Velímský, Jakub (advisor) ; Šrámek, Ondřej (referee)
During the Earth's accretion process deep magma oceans were episodically formed. Differentiation of iron took place within the melted zone and small droplets of iron were sinking to the base of the magma ocean due to the density contrast. In the present work we study the process of equilibration between dispersed metal droplets and surrounding silicates that proceeds by the advection transport and diffusion at the rim. We allow for steady state ow of a spherical liquid blob falling in a host liquid and establish the numerical code in axisymmetric spherical coordinates computing the chemical evolution of such heterogeneous system. We focus on determining the time scales of equilibration for which we propose an analytical model based on the boundary layer analysis. The obtained characteristic times are especially for low silicate viscosities very short that supports the idea that the drops attained equilibrium while sinking.
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Real-time visualization of terrain data
Šrámek, Ondřej ; Pelikán, Josef (referee) ; Maršálek, Lukáš (advisor)
The rendering of huge terrain data is an actual problem in many application areas like interactive games or virtual environments. To keep rendering interactive it was necessary to implement computationally intensive LOD techniques, because the graphical systems were incapable of rendering enough geometry to represent the whole terrain accurately. Due to the raw processing power of current systems (with respect to rasterization) which enables to render hundreds of millions of triangles per second, new methods for rendering these data emerge. They are based on observation that this is enough to render pixel-sized triangles while keeping reasonable output resolution. The aim of this work was to develop a practical implementation based on such approach. The main algorithm chosen was Geometry Clipmaps and its modi ed version was created. The solution devoloped is capable of rendering almost 300M samples terrain in the real-time with avarage 56 frames per seconds.
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Critical evaluation of Šik s reform
Šrámek, Ondřej ; Szobi, Pavel (advisor) ; Dufek, Pavel (referee)
The thesis deals with the so called Šik s reform, which was a reform, that tried to implement certain elements of market economy in the centrally planned economy of Czechoslovakia in the sixties of the twentieth century. Firstly the thesis describes the course of the reform, when the importance of the central plan was significantly reduced, the position of enterprises was strengthened and the price system was rebuild. Lately the thesis examines and compares opinions on reform and new economic system of foreign and domestic experts. The goal of the thesis is to discover mistakes and imperfections of implementing of new systém, which could endanger its functioning.
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