National Repository of Grey Literature 65 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
The Impact of Short-term Interest Rate on Stock Prices in the Czech Republic
Michlian, Štefan ; Princ, Michael (advisor) ; Brechler, Josef (referee)
This thesis focuses on the relationship between short-term interest rate and stock prices. The main idea is that if interest-rate increases, it makes holding stocks less attractive relative to fixed income securities. Therefore, investors change the structure of their portfolios and switch capital from stocks to banks, which results in stock prices decrease. In our thesis, we apply GJR-GARCH-t-M model to study the impact of Czech interest rate (14-day PRIBOR) on the Prague Stock Exchange (the PX index). In contrast to the majority of research on this topic, we have found no impact of the PRIBOR rate on the PX index- neither on its mean nor on its volatility. We attribute the absence of a significant relationship to exceptional composition of the PX index. Furthermore, we have found that the recent crisis has significantly changed the behavior of the Czech stock market.
The Evaluation of the Heavy Convective Precipitation Forecast
Zacharov, Petr ; Řezáčová, Daniela (advisor) ; Brechler, Josef (referee) ; Pešice, Petr (referee)
The thesis deal with the evaluation of the quantitative convective precipitation forecast and its uncertainty. Five convective events that produced heavy local rainfall in the Czech Republic were studied. The nonhydrostatic local model LM COSMO was run with a horizontal resolution of 2.8 km and an ensemble of 13 forecasts was created by modifying the initial and boundary conditions. Forecasts were verified by gauge-adjusted radar-based rainfalls. Ensemble skill and ensemble spread were determined using the Fractions Skill Score (FSS). The spread represents the differences between the control forecast and the forecasts provided by each ensemble member, while the skill evaluates the difference between the precipitation forecast and radar-based rainfalls. The numerical experiments used the FSS-skill and spread values related to four events to estimate the skill-spread relationship. The relationship was applied to a fifth event to estimate the QPF ensemble skill given the ensemble FSS-spread. A couple of test of FSS computing were performed. The analysis of these events proved, that the application of the new fuzzy verification scores in high resolution QPF is highly advisable. The new scores are more suitable then the traditional verification scores based on the contingency table. In order to asses the...
Wind-tunnel Modelling of Turbulent Flow Inside the Street Canyon
Kellnerová, Radka ; Jaňour, Zbyněk (advisor) ; Brechler, Josef (referee) ; Jonáš, Pavel (referee)
Turbulent flow inside a street canyon was investigated in an open circuit wind tunnel and in a blow-down wind channel. Two geometries were used for comparison purposes: buildings with pitched roofs and with flat roofs. Both generate the flow of a different category, so the induced ventilation regimes are fundamentally different. Quadrant, Fourier and Wavelet analysis, Proper Orthogonal Decomposition (POD) and vortex detection methods are used to identify coherent structures in the flow and establish their impact on the ventilation of pollution. Two types of the organised motions are detected: the compact areas of sweep and ejection with the scale comparable to the size of building and the small vortices generated in the shear layer behind the building roof. POD identifies the most dominant modes with high coherency in the flow and evaluates the relative contributions of each mode to the overall kinetic energy of turbulence. Rigorous analysis of the correctness of the physical interpretation for such a decomposition is carried out. Wavelet analysis is applied to the time-series of the POD expansion coefficients in order to reveal control mechanism of the dynamics of the modes. Vorticity, calculated from the original velocity data, is decomposed by POD as well. Finally, the correlation between the vorticity...
Immersed boundary methods in air-flow models
Benešová, Stanislava ; Brechler, Josef (advisor) ; Hron, Jaroslav (referee)
This work focuses on the immersed boundary methods and their aplications to modeling flow in urban areas. In the first part Navier-Stokes equations are derived. In the second part we describe the main priciples of the immersed boundary methods. Two main groups of methods are introduced accompanied by examples. Based on the properties of these methods one method is selected which is suitable to describe the geometry in the modeling of airflow in urban areas. The method MIB from the article Mark et al. (2008) is chosen. This method is compared with the method introduced in the article Kim et al. (2001). Both methods are described in detail and compared according to several criteria in the third chapter. Such a criterion is the accuracy of the continuity equation. Simulations of a several test problems were carried out for the purpose of comparison of the chosen methods. Flow around a circular cylinder and a square cylinder for Reynolds numbers of 10 and 30 is solved. The divergence value of~the~velocity field in the modeled area was observed during the calculation of both methods. The results yields that MIB method solves the continuity equation more accurate.
DES modelling of the turbulent flow
Benešová, Stanislava ; Brechler, Josef (advisor) ; Dolejší, Vít (referee)
This thesis deals with the study of hybrid RANS/LES methods for modeling of turbulent flow with a focus on the DES method and its modifications. The theoretical part focuses on the description of turbulent flow and classical methods for its modeling. The following describes the hybrid RANS/LES methods, their principles and categories. Finally, the DES method is described in detail together with its improvement in form of DDES and IDDES methods. The practical part is devoted to the testing of DES and DDES on benchmark problems. We describe here used software OpenFOAM and numerical methods used to discretize the equations. One part is devoted to grid generation. The DES and the DDES methods are tested on two benchmarks: flat plate with zero pressure gradient and backward facing step. The simulaton results are compared with experimental data, with a focus on good modeling of the velocity profile near wall, turbulent viscosity and skin friction coefficient. Powered by TCPDF (
Microscale flow and diffusion characteristics inside the urban area
Kukačka, Libor ; Jaňour, Zbyněk (advisor) ; Brechler, Josef (referee)
Dispersion of pollutants in the atmosphere of urban areas is the important task in environmental sciences. The main goal was the quantitative studying of a flow in a symmetrical urban built-up area depending on a running on flow direction. There was given a theoretical base of the physical modeling of the atmospheric boundary layer in this work. The measurement was done with a model of the urban build-up area at a scale of 1:200 in the aerodynamic wind tunnel of the IT AS CR, v.v.i. in Nový Knín. The requirements to the similarity to a real atmospheric boundary layer and a model boundary layer in the wind tunnel were accomplished. Velocity fields, concentration fields and fields of scalar uxes were measured in the area of a rectangular intersection. Results of the experiment showed significant sensitivity of the velocity field about the running on flow direction that extensively inuenced ventilation of street canyons.
Zlepšení metod předpovědi termické konvekce pro účely letecké meteorologie
Dvořák, Petr ; Řezáčová, Daniela (advisor) ; Brechler, Josef (referee)
This rigorous thesis is engaging by some processes in boundary layer of the atmosphere, namely rise and running of thermals, focused on vertical motion and speeds of thermals, and on methods of their measurement and forecasting. It exploits data, measured by the GPS receivers and loggers aboard of gliders and paragliders during flying over Czech Republic, and data from aerological soundings, provided by Praha-Libus observatory. Measurement was in progress in so called cross-country flight season 2007 and 2008. The solution of this research is improvement of forecasting of vertical velocity of thermals and can be used in specialised forecasts for private and recreative flying and in forecasts of thermal turbulence.
Flow and diffusion characteristics inside the urban area
Chaloupecká, Hana ; Jaňour, Zbyněk (advisor) ; Brechler, Josef (referee)
Title: Flow and diffusion characteristics inside the urban area Author: Hana Chaloupecká Department: Department of meteorology and enviroment protection Supervisor: prof. RNDr. Zbyněk Jaňour, DrSc., IT AS CR, v. v. i. Supervisor's e - mail: Abstract: Uniqueness of different towns, consists of various shapes of buildings. The main topic of this work is to compare concentration diffusion within groups of buildings of various types. We pursued houses made of single blocks of two different lengths - they were placed parallel or in courtyards. For research of pollution diffusion within the housing estates a method of physical modelling has been used. For this purpose we summarized a theory of atmospheric boundary layer and physical modelling at first. Then we pursued experiments. Measuring took place in a model in scale 1 : 300 inside an aerodynamic wind tunnel of the Institute of Thermomechanics AS in Nový Knín. We checked out the requirements placed on similarity of the real boundary layer and boundary layer modelled in the tunnel. By the measuring of concentration in urban areas we weren't watching a plume from the pollution source but we were studying an inversion task. We measured concentrations in two fixed points from different point sources inside the defined areas. A sensitivity of...

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