National Repository of Grey Literature 10 records found  Search took 0.00 seconds. 
Genetic Algorithms driven by MCTS
Havránek, Štěpán ; Hric, Jan (advisor) ; Moudřík, Josef (referee)
Evolutionary and genetic algorithms are problem-solving methods designed according to a nature inspiration. They are used for solving hard problems that we cannot solve by any efficient specialized algorithm. The Monte Carlo method and its derivation the Monte Carlo Tree Search (MCTS) are based on sampling and are also commonly used for too complex problems, where we are dealing with enormous memory consumption and it is impossible to perform a complete searching. The goal of this thesis is to design a general problem solving method that is built from these two completely different approaches. We explain and implement the new method on one example problem: the Traveling salesman problem (TSP). Second part of this thesis contains various tests and experiments. We compare different settings and parametrizations of our method. The best performing variant is then compared with the classical evolutionary TSP solution or, for example, with greedy algorithms. Our method shows competitive results. The best results were achieved with the cooperation of our method and the classical evolutionary TSP solution. This union shows better results than any of its parts separately, which we find as a great success.
Financial stability and the impact of instability on the real economy
Havránek, Štěpán ; Hlaváček, Michal (advisor) ; Mertlík, Pavel (referee)
This thesis focuses on the problematic of financial stability - its maintenance and the detection of possible sources of instability. In the first theoretical part, a summary of the role of financial stability for properly working financial system is followed by identification of threats to stability and historical examples of instability. The thesis continues with an analysis of the recent subprime crisis. In the second empirical part, vector autoregression is used to estimate interconnections between financial instability indicators. This is followed by impulse response analysis. Although some assumed relationships are affirmed, their scop does not answer the fundamental question: why do values of these indicators change so vigorously during the time of distress.
Pathophysiological consequences of different cardiac support regimens in cardiorespiratory insufficiency
Lacko, Stanislav ; Kittnar, Otomar (advisor) ; Havránek, Štěpán (referee) ; Rohn, Vilém (referee)
Introduction: Veno-arterial extracorporeal membrane oxygenation (VA ECMO) is a rapidly applicable type of mechanical circulatory support that overcomes acute hemodynamic breakdowns, whether in acute or chronic heart failure or cardiac arrest. In recent years, the method has seen a very significant increase in use. VA ECMO can fully replace the function of the heart and lungs, delivering about 5 l / min of fully saturated blood. However, the method is burdened with a number of risks. Currently much-discussed issue is the effect of circulatory support on left ventricular residual function as VA ECMO increases its work and the risk of developing left ventricular distension and subsequent pulmonary edema. A detailed analysis of these pathophysiological mechanisms is a key objective of this work. Methods: The focus of the work is three series of experiments on a large biomodel (domestic pig). First, we developed a new model of acute hypoxic-ischemic heart failure by proximal occlusion of one of the main branches of the left coronary artery with a balloon catheter with a lumen for controlled perfusion of deoxygenated venous blood behind the balloon. Furthermore, we monitored the hemodynamic response and energy parameters in detail in the porcine biomodel of acute and chronic heart failure with a gradual...
Hemodynamic adaptation mechanisms of heart failure to percutaneous venoarterial extracorporeal circulatory support
Hála, Pavel ; Kittnar, Otomar (advisor) ; Szárszoi, Ondrej (referee) ; Havránek, Štěpán (referee)
Introduction: Venoarterial extracorporeal membrane oxygenation (VA ECMO) is widely used in the treatment of circulatory failure, but repeatedly, its negative effects on the left ventricle (LV) have been observed. The purpose of this study is to assess the influence of ex- tracorporeal blood flow (EBF) on systemic hemodynamic changes and LV performance parameters during VA ECMO therapy of decompensated heart failure. Methods: Porcine models of low-output chronic and acute heart failure were developed by long-term fast cardiac pacing and coronary hypoxemia, respectively. Profound signs of circulatory decompensation were defined by reduced cardiac output and tissue hypoperfusion. Sub- sequently, under total anesthesia and artificial ventilation, VA ECMO was introduced. LV performance and organ specific parameters were recorded at different levels of EBF using an LV pressure-volume loop analysis, arterial flow probes on carotid and subclavian arteries, and transcutaneous probes positioned to measure cerebral and forelimb regional tissue oxygen saturations. Results: Conditions of severely decompensated heart failure led to systemic hypotension, low tissue and mixed venous oxygen saturations, and increase in LV end-diastolic pressure. By increasing the EBF from minimal flow to 5 L/min, we observed a...
Using of non-invasive cardiac imaging for precise evaluation of atrium size and prediction of atrial wall fibrosis in patients with atrial fibrillation
Fingrová, Zdeňka ; Havránek, Štěpán (advisor) ; Kittnar, Otomar (referee) ; Skála, Tomáš (referee)
Atrial fibrillation is the most prevalent arrhythmia worldwide and remains one of the major causes of morbidity and mortality. Atrial fibrillation is an arrhythmia that has a various etiology and takes number of clinical forms. Due to the heterogenity of atrial fibrillation, it is necessary to individualize the optimal treatment strategy, ie conservative pharmacological therapy or interventional therapy as catheter ablation. Inncorrect indication of catheter ablation of atrial fibrillation leads to low success rate of the procedure and increases the risk of the procedure. The success rate of catheter ablation of atrial fibrillation depends on many clinical parameters, including the size and volume of the left atrium and the presence of pathological tissue in the atrial myocardium. In everyday practice, echocardiography (2D-echocardiography) is the most dominant method in estimation of the left atrial parameters, for it's simplicity, non- invasiveness, financial costs and the absence of ionizing radiation. Different methods for assesment of left atrial parameters are cardiac CT, cardiac magnetic resonance imaging and methods of 3-D echocardiography or 3-D angiography. The results of the present studies show that in patients with non-valvular atrial fibrillation who are indicated for catheter...
Genetic Algorithms driven by MCTS
Havránek, Štěpán ; Hric, Jan (advisor) ; Moudřík, Josef (referee)
Evolutionary and genetic algorithms are problem-solving methods designed according to a nature inspiration. They are used for solving hard problems that we cannot solve by any efficient specialized algorithm. The Monte Carlo method and its derivation the Monte Carlo Tree Search (MCTS) are based on sampling and are also commonly used for too complex problems, where we are dealing with enormous memory consumption and it is impossible to perform a complete searching. The goal of this thesis is to design a general problem solving method that is built from these two completely different approaches. We explain and implement the new method on one example problem: the Traveling salesman problem (TSP). Second part of this thesis contains various tests and experiments. We compare different settings and parametrizations of our method. The best performing variant is then compared with the classical evolutionary TSP solution or, for example, with greedy algorithms. Our method shows competitive results. The best results were achieved with the cooperation of our method and the classical evolutionary TSP solution. This union shows better results than any of its parts separately, which we find as a great success.
3D akční hra v podivném městě
Havránek, Štěpán ; Balyo, Tomáš (advisor) ; Hauzar, David (referee)
This thesis deals with a conception and implementation of a real-time 3D action game. This game is placed in a bizzare surrounding that is not a subset of an ordinary real three- dimensional linear space. The work presents the whole game implementation process. It goes through various sets of techniques, algorithms and data structures used or considered during the development. It also describes different ways of solving specified problems and the choices between them. Moreover there are artificial beings situated in the town inside the surrounding. The player's goal is to capture the whole city. There is also an opponent, who systematically plans his tasks and tries to possess the city as well.
Fight against evasion in indirect taxation
Havránek, Štěpán ; Boháč, Radim (advisor) ; Kohajda, Michael (referee)
Thesis is focused on fight against indirect tax evasion. This topic was selected because it is a current issue. This is evidenced by media coverage regarding revealed tax evasion schemes; total estimated volume of tax evaded and increased activity of legislator in this field. The thesis is divided into three parts. In first part, I start with a general description of indirect taxes. I subsequently proceed with description of individual indirect taxes in the Czech Republic - value added tax, excise tax, and energy tax - and a brief summary of their evolution, main principles of functioning and their sources of law, both Czech and European. In second part, I tackle the problem of tax optimization, in particular the difference between legal and illegal methods of lowering ones tax. For this purpose, I go into more detail in explaining differences between tax planning, tax avoidance and tax evasion. I also draw attention to problems related to distinguishing these categories and to how these are interpreted differently by tax authorities in Anglo-Saxon and Continental area. After establishing theoretical background, I proceed by describing particular methods of evading tax, focusing mainly at illegal imports and carousel fraud, which, according to the Ministry of Finance, deprives Czech Republic of CZK 15...
Financial stability and the impact of instability on the real economy
Havránek, Štěpán ; Hlaváček, Michal (advisor) ; Mertlík, Pavel (referee)
This thesis focuses on the problematic of financial stability - its maintenance and the detection of possible sources of instability. In the first theoretical part, a summary of the role of financial stability for properly working financial system is followed by identification of threats to stability and historical examples of instability. The thesis continues with an analysis of the recent subprime crisis. In the second empirical part, vector autoregression is used to estimate interconnections between financial instability indicators. This is followed by impulse response analysis. Although some assumed relationships are affirmed, their scop does not answer the fundamental question: why do values of these indicators change so vigorously during the time of distress.
Comparison of QT dispersion and heart rate turbulence
Havránek, Štěpán ; Kittnar, Otomar (advisor) ; Horký, Karel (referee) ; Slavíková, Jana (referee)
Introduction: Both QT dispersion (QTD) and heart rate turbulence (HRT) were studied and tested like potential noninvasive markers for risk stratification. Aims: Compare QTD between different groups of patients with expected different mechanism of developing changes in QTD. Investigate if HRT is present following ventricular train drives and depends on left ventricular dysfunction. Test the hypothesis that QTD and HRT parameters assessed during programmed ventricular stimulation correlated to each other and there is association with iducibility of ventricular arrhythmia. Methods: We analysed body surface potential mapping (BSPM) recordings and vectorcardiographic T-loop parameters (T-loop width - Tw and T-loop amplitude - Ta) in 37 healthy women (20 - 36 yrs) in the 36th to 40th week of physiological pregnancy and 2 to 6 days after delivery. Control group contained 18 healthy women. Then we analysed BSPM recordings from 27 psychiatric outpatients treated with prophylactic doses of dosulepin (20 women, 44 ± 13 yrs) and compared to those obtained from 37 healthy volunteers. From these recordings the QTD was evaluated. This parameter was estimated using both BSPM recordings and 12 lead standard ECG. Acquired data were statistically correlated with Tw or Ta and dosulepin plasma levels, respectively. Distribution...

Interested in being notified about new results for this query?
Subscribe to the RSS feed.