
Thin accretion disks with magnetic advective term
Vavřička, Radek ; Bursa, Michal (advisor) ; Horák, Jiří (referee)
Accretion disks around black holes with gas radiating out parts of its gravitational potential energy have long served as objects of both theoretical and observational studies. By solving the structure equations of the disk it is possible to predict the outgoing radia tive flux and the observed spectrum of the disk and test the validity of the theory against direct observations. The standard thin disk model (ShakuraSunyaev, NovikovThorne) shows, however, a still unexplained nonnegligible deviance in the observed spectrum at higher mass accretion rates. To amend to the set of proposed explanations, in this thesis we examine the effect of the magnetic pressure on the trapping of some of the internal energy generated by viscous dissipation processes in the disk and advecting this energy to the black hole. A phenomenological description of heat advection mediated by a highly heterogenous magnetic field will be given, as well as its effect on the spectrum and observed effective temperature. 1


Propagation of waves in polytropic disks
Horák, Jiří
We derive an analytic dispersion relation for waves in threedimensional polytropic disks. The problem can be separated to two onedimensional problems of radial and vertical wave propagation. For the vertical problem, we use and generalize firstorder perturbation method for waves near the vertical resonance introduced previously by several authors. Based on comparison of the analytical solutions with numerical integration, we find a surprisingly large region of validity of our dispersion relation including both pmode and gmode oscillations.


Android Application Design and Monetization Strategy
Doležel, Filip ; Horák, Jiří (referee) ; Luhan, Jan (advisor)
The bachelor's thesis deals with the design of a mobile application for the Android platform. It assesses the implementation tools designed for this development, then contains design of implementation and testing which is an integral part of the application development process. The next section is dedicated to an elaborated analysis of possible ways of monetization of an Android application and selection of a suitable monetization strategy for the developed application. It also includes an example of a typical user of the application according to analysis.


3D printed directional antenna
Dvořák, Václav ; Horák, Jiří (referee) ; Láčík, Jaroslav (advisor)
This master thesis deals with a study of directional antennas, followed by their design and optimization of horn antenna based on SIW for Ka band (26,5 40 GHz). The first part of the thesis contains the theoretical analysis of the different types of directional antennas, also the SIW technology is described here. It also describes the 3D printing technology by means of which the final antenna should be made. The next part of this work is about design of horn antenna based on SIW. Simulation and optimization of the antenna will be done using the CST Microwave Studio. The horn antenna was modeled with three different dielectric loads. The horn antenna with an experimental triangular dielectric load was chosen for fabrication. The fabricated antenna has reached almost the whole bandwidth to cover Ka. The antenna gain was 9,38 dBi for 33 GHz frequency.


3D printed directional antenna
Dvořák, Václav ; Horák, Jiří (referee) ; Láčík, Jaroslav (advisor)
This master thesis deals with a study of directional antennas, followed by their design and optimalization of horn antenna based on SIW for Ka band (26,5 40 GHz). The first part of the thesis contains the theoretical analysis of the different types of directional antennas, also the SIW technology is described here. It also describes the 3D printing technology by means of which the final antenna should be made. The next part of this work is about design of horn antenna based on SIW. Simulation and optimization of the antenna will be done using the CST Microwave Studio. The final part of the thesis deals with evaluation of achieved results.


Periodic structure design for directivity enhancement of dielectric resonator antennas
Slavíček, Radek ; Horák, Jiří (referee) ; Láčík, Jaroslav (advisor)
The thesis deals with linearly polarized dielectric rectangular resonator antenna (DRA) operating in the basic mode TEy11 and higher order mode TEy131 at f0 = 10GHz surrounded by an electromagnetic band gap structure (EBG). The dielectric resonator antennas, the EBG structure were designed and a method of integration of both components was developed. The simulated results show a significant improvement of the radiation pattern in the Eplane radiation pattern (narrower main beam, lower level of side lobes, higher directivity) in comparison to a conventional DRA. This was verified by the TEy11 measurement.


Financing the Construction og a Low Energy House
Horák, Jiří ; Tománek, Jindřich (referee) ; Zeman, Václav (advisor)
This thesis describes the design of optimal options for financing the construction og a low energy house. In the introductory section describes the characteristics of the two products designed to finance housing, mortgage loan and building savings. Another section is devoted to the characteristics and principles of construction of a low energy house, which is related to low energy and less than saving the house. The final section focuses on the selection of a suitable vision of the comparable financial products.

 

Epicyclic oscillations of thick relativistic disks
Horák, Jiří ; Straub, O. ; Šrámková, E. ; Goluchová, K. ; Török, G.
We study epicyclic oscillations of thick relativistic tori with constant specific angular momentum distribution using the finite element numerical method. We have compared frequencies of the axisymmetric and nonaxisymmetric modes with the analytic formulae obtained by Straub and Šrámková (2009) and Fragile et al. (2016). We have found excellent agreement in the case of axisymmetric radial epicyclic modes. In the case of the axisymmetric vertical epicyclic modes and nonaxisymmetric modes in general, the analytic approximation agrees with numerical results only for tori of moderate thicknesses. Our analysis also revealed an instability of the thick constant angular momentum tori with respect to the radial epicyclic oscillation.


Wave excitation at Lindblad resonances using the method of multiple scales
Horák, Jiří
In this note, the method of multiple scales is adopted to the problem of excitation of non–axisymmetric acoustic waves in vertically integrated disk by tidal gravitational fields. We derive a formula describing a waveform of exited wave that is uniformly valid in a whole disk as long as only a single Lindblad resonance is present. Our formalism is subsequently applied to two classical problems: trapped p–mode oscillations in relativistic accretion disks and the excitation of waves in infinite disk.
