|
|
Stochastic cooperative games
Ryzák, David ; Černý, Martin (advisor) ; Lachout, Petr (referee)
Stochastic cooperative games - abstrakt (EN) Bc. David Ryz'ak May 2024 This thesis explores stochastic cooperative games, viewed here as cooperative games with a stochastic characteristic function, representing a generalization of the classical deterministic model by von Neumann and Morgenstern. To address the inherent randomness, it is essential to either access additional information about the game or understand its stochastic structure thoroughly. The main contribution of this thesis is the exploration of solution concepts within the stochastic context, defined by assuming the risk averse behaviors of the play- ers. This is particularly achieved through the application of the second order stochastic dominance (SSD). We both define and examine the notion of the SSD-dominating core across various distributions of the characteristic function and apply it to the multiple newsvendors problem. Our findings concerning the nonemptiness of the SSD-dominating core offer a framework for addressing risk aversion in stochastic cooperative games without requiring specific assumptions about the levels of risk aversion among players. 1
|
|
|
Aquatic insects versus fish: adaptations to fish predation
Chawner, Adam Mark ; Černý, Martin (advisor) ; Jor, Tomáš (referee)
in English In this thesis, I review how aquatic insects have adapted to fish predation in various habitats during all phases of their life cycles. Aquatic insects are a large group of heterogeneous species and this review introduces these orders and species, including the environments they inhabit. Fish are some of the most common and most impactful predators of aquatic insects and this thesis identifies a wide range of behavioural, morphological, chemical and life history defence mechanisms of various complexity and uniqueness aquatic insect orders have developed to counter fish predation. Most aquatic insects are subject to predation during their aquatic larval stage. A few orders also inhabit the water as adults, as is the case most notably for aquatic Coleoptera. More complex adaptations to fish predation are presented in this order. Oviposition is noted as a strategy used to negate fish predation even before individuals hatch. The use of fish predation as means to control mosquito larvae communities is presented and reviewed. Keywords: aquatic insects, fish predation, defence mechanisms, adaptation to predation
|
|
|
Effect of global climate change on areal and phenology shifts of dragoflies species
Perthen, Ervín ; Černý, Martin (advisor) ; Bílková, Eva (referee)
Climate change in recent decades affects the distribution and phenology of dragonflies. The main factor causing these changes is the increase in the average global temperature, but other factors, such as loss of habitats or changes in precipitation regime, also play a role. As a result of climate change, phenological processes are accelerating. We can therefore observe a faster egg development rates, an earlier emergence of adults, a longer flight period and also a shift in voltinism towards a greater number of generations per year. Good dispersal abilities allow dragonflies to respond to changing environmental conditions also by shifting their distribution. The ranges of most species are currently expanding towards the poles. Generalists and species capable of using temporary waters expand their ranges the most, while specialized species with a narrow niche are the most threatened by climate change. Shifts are also visible in the altitudinal distribution, increasing temperatures allow warm- adapted species to expand their ranges to higher altitudes. Keywords: climate change, dragonflies, distribution, phenology, temperature, altitudinal shift
|
|
|
Visual orientation of dragonflies - using polarized light
Kalavská, Tereza ; Černý, Martin (advisor) ; Kolář, Vojtěch (referee)
Polarized light is a physical phenomenon that is quite common in the nature. It has been known for a long time that some animals use such kind of light for various purposes in their lives. This group also includes dragonflies, which use horizontally polarized light to detect areas of water where mating and egg-laying takes place. The aim of this bachelor's thesis is to summarize the current knowledge of the visual orientation of dragonflies in space using polarized light. In my thesis, I focus on habitat selection and in which spectrum range dragonflies can perceive polarized light. Furthermore, I focus on the area of perception of polarized light by dragonfly larvae in the aquatic environment, which has not been properly researched yet as there are very few studies. Key words: orientation, insects, dragonflies, visual, polarized light, habitat selection
|
|
|
Ab initio study of phase stability of multicomponent alloys
Fikar, Ondřej ; Brož, Pavel (referee) ; Černý, Miroslav (referee) ; Zelený, Martin (advisor)
Ab initio methods are based on purely theoretical findings of quantum physics that can be used to predict among others physical, chemical and mechanical properties of materials. Due to rapid increase in accessibility of computational resources in the recent decades the theoretical prediction of material properties became an integral part of materials design. This work is focused on theoretical prediction of phase stability and solubility of solid solutions. Ab initio calculations based on Density Functional Theory were performed using Projector-Augmented Waves method and thermal dependencies of thermodynamic quantities were obtained using phonon calculations and Monte Carlo simulations. Attention is paid to alloys mainly based on aluminium, silver and magnesium, which were investigated in order to assess the reliability and precision of theoretical predictions of solubility in the solid state. Phase stability of solid solutions was evaluated multiple times including different energy contributions and using various methods in order to determine the influence of each contribution and method on the prediction accuracy. Calculated solubilities are compared with experimental data provided using the CALPHAD method.
|
|
|
Processing of grapes into non-traditional products
Černý, Marek ; Pacasová, Viktorie-Alexandra (referee) ; Mikulíková, Renata (advisor)
This bachelor’s thesis focuses on the processing of grapes into non-traditional products, mainly on grape jelly with the addition of spices, herbs and juices. The aim of this work is to investigate, which combination of herbs, spices or juices leads to the best sample. In the theoretical part of the thesis is described morfology of grapevine, it’s technological processing and variation of uses in food industry. Sensory analysis is also described, which represents a big part of thesis. The experimental part focuses on the desription of preparation of flavoured jelly and on it’s sensory analysis. Vitamin C was also studied with the usage of HPLC. Based on the sensory analysis data, the best sample was with lemon balm. Vitamin C was evaluated using HPLC and was determined to be around 0,017 – 0,028 mg per jelly.
|
|
|
The choice of material for the production of blade wheels of jet aircraft engines
Černý, Michal ; Hutařová, Simona (referee) ; Němec, Karel (advisor)
This bachelor's thesis provides a basic overview of the materials used in the production of turbine blades of jet aircraft engines. An aircraft engine can be divided into two parts - cold and hot part, each with very different requirements for the materials used in them. The conditions in the cold part are relatively mild and the requirements are more or less satisfied by the currently used materials. The goals for further development are primarily a reduction in density and an increase in strength and fatigue properties. The real challenge of the aerospace industry is to find materials capable of working under extreme conditions in the hot part, therefore this work devotes most of the scope to the given issue. The basic overview is created by synthesizing several sources. Most of the information is drawn from American books giving a comprehensive picture of materials and manufacturing processes for this use. After decades of research, nickel superalloys in combination with thermal coatings and cooling vents proved to be the most suitable materials. Their properties, structure and production process form the basis of knowledge on this topic. The main goal for the development is to increase the temperature at which these materials are able to function, as a higher temperature of the flue gas entering the turbine means higher efficiency and associated financial and ecological savings. Despite years of research and properties unmatched by any other material, I believe there is still room for improvement. With the advent of new technologies, the emergence of a new group of materials on a different basis than nickel superalloys is possible. A brief description of several promising newly tested groups of materials, as well as my view on the future of the industry, form the final part of this work.
|
|
|
Segmentation of Electrocardiographic Signals Using Deep Learning Methods
Hejč, Jakub ; Černý, Martin (referee) ; Halámek, Josef (referee) ; Kolářová, Jana (advisor)
The thesis deals with deep learning methods for the segmentation of surface and intracardiac electrocardiographic recording with focus on atrial activity. The theoretical part introduces current segmentation aproaches of electrocardiographic signals. Issues related to the development of deep learning models in context of standard ECG databases were also discussed. We proposed a pipeling for processing multimodal electrophysiology data from interventional procedures in order to build reliable training datasets. A deep model for segmentation of intracardiac recordings based on a modified residual architecture was proposed. A series of experiments was conducted to evaluate the effect of both model and dataset properties on segmentation quality. The annotation methodology of recordings with atrial fibrillation proved to be a crucial factor. Properties of loss function and type of data augmentation were revealed as secondary important parameters. A novel P wave segmentation method for incomplete references was proposed in the thesis. The approach was inspired by the deep contrast learning. It was modified to distinguish local segments of signals at different levels of abstraction of the extracted feature maps. Results were analyzed using standard quality metrics and post-hoc visual analysis. In some cases, a statistical comparison of experiments for different settings was performed. The results of the work showed that it is possible to use intracardiac signals for embedding a vector representation of local atrial activation into deep models.
|
|
|
Utilization of light emitting diode lighting
Podola, David ; Černý, Michal (referee) ; Paloušek, David (advisor)
This bachelor thesis deals with problems of illumination by LED diodes. Basic concepts of lighting technology are defined in the first part. The second part is dealing with the construction of body LED diodes and explains the principle of white light formation to LED. Introduces problems of cooling. Gives an overview of the available power sources for LEDs. Provides an overview of how to control lighting by using motion sensors and presence sensors. Will be made basic economic balance sheet, which will evaluate the advantages of using LED sources. Attachments provide the LED catalogs of manufacturers, accessories for LED and comment on other sources of information.
|
|
|
Hybrid Blends of Recycled Plastics
Černý, Miroslav ; Lehocký, Marián (referee) ; Balgová,, Vendula (referee) ; Jančář, Josef (advisor)
Work describes the relationship between structure and mechanical properties in case of hybrid mixtures. They are composed from polyurethane matrices (eventually polyurethane-urea or polyurethane-inorganic filler mixtures), different rubber fractions as filler and eventually reinforcement made from PET monofilaments. Mechanical behaviour was studied by tensile testing. Studied mechanical properties include tensile modulus, ultimate strength and strain and also specific energy need neccessary for ultimate strength achievement. Prepared materials are naturally porous. Therefore their mechanical behaviour has to be described generally for porous composites. The porosity occurence means, that it is difficult to describe them by models valid for mechanical behaviour (mainly elastic modulus) of nonporous composites. Models are also based on idealized structures on microscopic level. In case of porous composites, it is very difficult to create any idealized structure. The structure is changed with modifications of composition (change of components or their rates). These conditions have lead to utilizing of different approach how to describe the relationship between structure and mentioned mechanical properties. The chosen approach comes from knewledge about structural parametres coming from porosity. Structural parameters describe the structure on macroscopic level. They include interspace volume (volume lying between filler particles), interspace filling (how the matrix fills the interspace volume) and matrix volume fraction. Proposed parameters are used in relations, where they are fitted by exponents to interlay values of chosen mechanical properties for composites containing discrete matrix and filler. Found exponents are then described by properties of matrices to obtain relations describing properties of filled porous materials. Very similar approach was chosen for description in the case of reinforced composites. Proposed relation are potentially valid for materials containing binding matrix, infinity count of fillers and one kind of reinforcement.
|
guest ::
