National Repository of Grey Literature 29 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
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.
Real-time visualization of terrain data
Šrámek, Ondřej ; Maršálek, Lukáš (advisor) ; Pelikán, Josef (referee)
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.
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...
Tidal Deformation of an Icy Moon with a Subsurface Ocean
Aygun, Burak ; Čadek, Ondřej (advisor) ; Šrámek, Ondřej (referee)
Enceladus is one of the icy moons in the outer solar system. The Cassini mis- sion has found out direct evidence on existing subsurface ocean. These evidences showed that the water contains organic molecules and nutrient, such that it could create suitable environment for emergence of life. However, the mechanism how the ocean is maintained in a liquid state, is still unknown. We studied the effect of the tidal force on maintaining the ocean in a liquid state, where the effect of the elastic ice shell is modelled through boundary condition. We modelled the ocean with the three dimensional linearised incompressible Navier-Stokes equa- tions in the time domain. Then, we solved the equations numerically with spectral method. The numerical methods are written in to Fortran 90 program. We tested the various properties of the numerical methods. We, then, investigate the tidal dissipation for various ocean thicknesses and viscosities. We conclude that the tidal dissipation heavily depends on the thickness and the viscosity. These results show us that the tidal force could have significant contribution to the total heat budget of Enceladus for given viscosities of the ocean. 1
Electrical conductivity of the mantle and its thermochemical and mineralogical state: Forward problem
Knopp, Ondřej ; Velímský, Jakub (advisor) ; Šrámek, Ondřej (referee)
With the increased availability of new geomagnetic data, mainly from the Swarm mission satellites, it is possible to obtain global mantle conductivity models. A subse- quent task is to interpret such models in terms of the thermal and chemical structure of the Earth's mantle. It can be done using the experimental conductivity data for major mantle minerals combined with the Gibbs energy minimization. Here I describe these methods and present a forward problem calculating the electrical conductivity of the Earth's mantle, from its temperature and chemical composition. I also present the modelling results for a-priori temperature and compositional settings. This software com- ponent will become part of the existing tools used for global inversion of electromagnetic data to constrain the thermochemical and mineralogical structure of the mantle. 1
Gravitational signal of Earth's crustal models
Jaroš, Jaroslav ; Šrámek, Ondřej (advisor) ; Martinec, Zdeněk (referee)
Global models of the Earth's crust, such as CRUST1.0, describe the 3-D distribution of seismic speeds and of material density in the crust. They are widely used in the geophysical community as reference models in local and regional seismic studies and are also the basis of current prediction models of geoneutrino flux from Earth's lithosphere. In this study we attempt to validate the seismology-based CRUST1.0 model using GOCE-derived gravity data. We calculate the anomalous gravitational potential and its first and second radial derivatives, induced at altitude of 250 km by the density distribution in the uppermost ~80 km thick shell of the Earth as described by CRUST1.0. We then compare the prediction with the GOCE model datasets inferred from the GOCE mission satallite gravity measurements. We find that the predicted signal is a factor of ~4 stronger than the measurement in terms of its root-mean-square value. The signal overestimation is consistent across the spherical harmonic spectrum and the spectral correlation of prediction vs. measurement is weak. Our findings motivate the need for improvement of CRUST1.0 and similar models by incorporating gravity data in the model inversion.
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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