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Biogeography of the herpetofauna of the Aegean Islands
Sýkorová, Marta ; Šmíd, Jiří (advisor) ; Papežík, Petr (referee)
In the last thirty years, the biogeography of the herpetofauna of the Aegean Sea has been the subject of thorough research. In evolutionary biology, islands are considered to be model ecosystems. Morphological, physiological and behavioral changes in some species can be observed on them. These changes are described as so-called "island syndromes". The occurrence of these syndromes depends on the size of the island, its distance from the mainland and the age of the island as well as on population density, availability of resources and presence of predators. The specific manifestations of these syndromes in reptiles of the Aegean islands are: the occurrence of endemism, gigantism and dwarfism, color changes, more frequent tail autotomy, cannibalism and food specialization. Most of these changes are described in lizards of the Podarcis genus, especially on Podarcis erhardii, as it is the most widespread reptile in this area. The second very widespread and therefore often researched reptile is Mediodactylus kotschyi. Changes often take place on small islands, so individuals tend to be compared with members of the same species from a larger island or mainland. The number of endemic species is significantly higher on islands that are longer separated from the mainland. The existence of gigantism and...
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Mechanical properties of entropy stabilized ceramic materials
Ronschak, Johana ; Mařák, Vojtěch (referee) ; Salamon, David (advisor)
This work focuses on the topic of the currently novel high entropy materials (HEM). The focus is put primarily on high entropy carbides (HEC) and the effect of carbon content in the matrix of a high entropy alloy (HEA) on its microstructure and hardness. Additionally, the effect of mechanical preparation, sintering temperatures and carbon diffusion from within the sintering die is observed on the samples. Several samples were sintered using the Spark Plasma Sintering (SPS) method under different temperatures. Density, phase and structure analyses were put in correlation to Vickers hardness tests, X-Ray Diffraction (XRD) analysis as well as on some samples to nanohardness tests and Energy Dispersive Spectroscopy (EDS) analysis. Powder milling has been implemented in order to reduce the final material’s porosity, which could negatively impact the accuracy of the hardness reading. Thus, a higher density of the HEA VNbTaMoW has been reached compared to literature by 7 %. Additionally, this result was obtained using lower sintering temperatures. The milled VNbTaMoW had a density of 100 % along with a hardness of 6,9 GPa. Two single-phase HEC materials VNbTaMoW-C0,8 and VNbTaMoW-C0,9 reached hardnesses of 20,46 GPa and 16,87 GPa respectively, whilst densities of 100 % and 97,9 % were observed. The heterogeneous material of VNbTaMoW-C0,5 showed an average hardness of 16,83 GPa. Within this material, nanohardness was measured of the lamellar areas as 20,4 GPa whilst the homogenous areas reached up to 29,3 GPa. The effect of the C diffusion was observed on all samples with the most significant being that of the VNbTaMoW and VNbTaMoW-C0,5 microstructures, where a heterogeneous and homogenous phase of the VNbTaMoW-C0,8 composition was created respectively. C has reached a depth of ~180 m within the VNbTaMoW through diffusion and ~200 m in VNbTaMoW C0,5, where an increase of hardness was observed from 18,4 GPa in the core material to 22,6 GPa on the surface. This work observed a positive impact of mechanical powder milling on the final microstructure and density. Additionally, the implementation of milling has resulted in a lower needed sintering temperature than reported in literature, whilst reaching higher densities. An increase of hardness has been observed in the HEC depending on the C content, with the highest being measured on the VNbTaMoW-C0,8. The material VNbTaMoW-C0,9 showed lower hardness, most likely due to its higher porosity, which lowers the effective hardness of the material. This points towards a possible direction of further studies in regard to the optimalization of HEC powder preparation and sintering temperatures with the goal of obtaining a full-density material with content of C > 80 mol %.
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The separation of microplastics from environmental matrices
Pařízková, Mia Victoria ; Řezáčová, Veronika (referee) ; Doležalová Weissmannová, Helena (advisor)
This bachelor’s thesis deals with methods of separation microplastics from soil and the follow up application of quantitative methods of gravimetry, ATR-FTIR and Py-GC/MS. Samples containing model soil and PET or PLA microplastics of different concentrations were prepared. These samples were separated using potassium carbonate solution of known density. The effectivity of separation was measured by gravimetry. The samples were also analysed using ATR-FTIR and Py-GC/MS methods the results of which were compared by correlation coefficients. It was found that ATR-FTIR is a more suitable method, thus it was used for analysis of prepared samples of ten different real soils and PET or PLA microplastics.
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Polyvinyl alcohol hydrogels with gradient structure in crosslinking density
Ščotková, Romana ; Kalina, Michal (referee) ; Smilek, Jiří (advisor)
The presented thesis introduce one of the many possibilities for the physical preparation of PVA hydrogels with a gradient in the crosslinking density. Based on the research conducted, the main focus of which was the preparation methods of gradient hydrogels and the characterization of their properties, a cyclic freezing and thawing method was selected and optimized with a focus on the selected preparation parameters. The next step was to perform pilot experiments leading to the confirmation and characterization of the resulting gradient structure by selected instrumental techniques such as rheology, scanning electron microscopy or a method based on monitoring the loss of dispersion during drying of the samples. In addition to the confirmation of the gradient structure, one of the parameters studied was the effect of the addition of polysaccharide on the resulting mechanical properties. Gradient hydrogels with different molecular weights or biopolymer additions were compared in the second part of the experimental work based on diffusion experiments using methylene blue. At the end of the work, all the results obtained were discussed and additional measurements were proposed for a deeper understanding of the subject.
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Weighted inequalities, limiting real interpolation and function spaces
Grover, Manvi ; Opic, Bohumír (advisor) ; Persson, Lars-Erik (referee) ; Nekvinda, Aleš (referee)
This thesis is focused on studying limiting interpolation spaces with weight func- tions of slowly varying type and properties of operators defined on them. In Paper 1 we establish conditions under which K-spaces in the limiting real interpolation involving slowly varying functions can be described by means of J-spaces and we also solve the reverse problem. Further, we apply our results to obtain density theorems for the corresponding limiting interpolation spaces. In paper 2 we study the properties of compactness of operators defined on lim- iting interpolation spaces and derive the quantitative estimates of measure of non-compactness. In paper 3 we estimate dual spaces of limiting interpolation spaces that involve weight functions of slowly varying type. 1
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Trajectory Data Preprocessing Framework for Discovering Semantic Locations
Ostroukh, Anna ; Burgetová, Ivana (referee) ; Ismael, Mazen (advisor)
Cílem práce je vytvoření přehledu o existujících přístupech pro předzpracování dopravních dat se zaměřením na objevování sémantických trajektorií a návrh a vývoj rámce, který integruje dopravní data z GPS senzorů se sémantikou. Problém analýzy nezpracovaných trajektorií spočíva v tom, že není natolik vyčerpávající, jako analýza trajektorií, které obsahují smysluplný kontext. Po nastudování různých přístupů a algoritmů sleduje návrh a vývoj rámce, který objevuje semantická místa pomocí schlukovací metody záložené na hustotě, aplikované na body zastavení v trajektoriích. Návrh a implementace rámce byl zhodnotěn na veřejně přístupných datových souborech obsahujících nezpracované GPS záznamy.
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Study of sterilization effect of dielectric barrier discharge on eucaryotic microorganisms
Vojkovská, Hana ; Ing.Hana Grossmannová, Ph.D. (referee) ; Kozáková, Zdenka (advisor)
Nowadays the wide spectrum of decontamination methods are used for the inactivation of microorganism on various materials and subjects. The serious disadvantage of the conventional decontaminations methods is stressing of the exposed material by heat or chemicals. The presented bachelor thesis discusses plasma sterilization, which is more friendly and more effective on the wide spectrum of procaryotic and eucaryotic microorganisms. Basically, the main inactivation factors for cells exposed to plasma are heat, UV radiation and various reactive species The work was focused on studying of the effect of the dielectric barrier discharge (DBD) operating at atmospheric pressure on bioindicator Aspergillus niger. Plasma was generated in nitrogen and argon. Paper and PET-foil wer used as the carrying medium. The influence of various working conditions on the efficiency of plasma sterilization was studied. Namely it was the influence of plasma exposition time, plasma power density, the type of operating gas and type of the medium supporting the microorganism. According to our results the efficiency of the plasma sterilization increases with increasing plasma power density, resp. the plasma exposition time. When comparing the results observed for the same conditions in argon and nitrogen the higher sterilization effect was reached in argon. The sterilization time was 40 – 120 second in dependence to plasma power density, gas and carrying medium. Furthermore the influence of the carrying medium on the sterilization efficiency was prooved. It was shown, that porous materials have a ”shadowing effect” for microorganisms. The microorganism may penetrate into the paper material and embed in pits and cavities. Such penetration could preclude the interaction of plasma with the microorganism, thereby decreasing the efficiency of spore inactivation. Additionaly paper porosity complicates the detachment of spores into solution, so it is reached less microorganisms as from the PET-foil. The discharge parameters were studied by means of the optical emission spectroscopy.
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Unmanned Aerial System design competition
Malinowski, Matěj ; Navrátil, Jan (referee) ; Pejchar, Jan (advisor)
Bakalářská práce se zabývá návrhem malého bezpilotního letounu určeného pro soutěž Air Cargo Challenge 2015. Práce je uspořádána dle postupu vývojových prací. Na prvotní koncepční návrh navazuje volba vhodného tvaru letounu a jeho profiláže. Následuje výpočet letových výkonů, maximální vzletové hmotnosti a centráže letounu. Poslední část práce se zabývá konstrukcí letounu a je provedena analýza závislosti užitečného zatížení na hustotě vzduchu.
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Computational modelling of function of the human vocal tract
Ryšavý, Antonín ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
In the first part of this bachelor's thesis is a brief summary of the biomechanics of the creation of the human voice and an overview of the published computational models of the vocal tract and the area around the head. The second part deals with the computational models of the human vocal tract set to the pronouncing the Czech vowels /a:/ and /i:/ with using the method of transfer matrices and the finite element method. By these methods is perform modal and harmonic analysis. Are investigated the natural frequencies and own vibration shapes of both vowels and course of sound pressure in a specific areas of the vocal tract. The method of transfer matrices is highly depend on the geometry of the tract, particularly on the density of the reference sections and its results in this thesis do not completely agree with the results in the literature. Finite element method is more accurate and its results agree well with results reported in the literature, but the opposite of the transfer matrices method is significantly time consuming. Method of the transfer matrices is more suitable for a large number of calculations or tuning certain parameters. Models created in this bachelor's thesis can serve for the analyse of pathology of voice production, eventually for prediction of surgical procedures in the area of the vocal tract.
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Computational modeling of radial hydrodynamic bearings for water machines
Pokorný, Jan ; Šimek,, Jiří (referee) ; Návrat, Tomáš (advisor)
The aim of this thesis is to calculate the stiffness and damping coefficients for radial hydrodynamic bearings. Cylindrical and lemon hydrodynamic bearings are considered. The solution to this problem mainly depends on the hydrodynamic pressure in the bearing. The numerical solution of the Reynolds equation is used to calculate the pressure. The effect of variable viscosity and density of the lubricant due to temperature changes is considered. The static equilibrium position of the journal centre is also solved. The stiffness and damping coefficients are determined using small amplitude journal motions about the equilibrium position. Three methods for determining these coefficients are presented. The outcome of this thesis is an algorithm for the calculation of stiffness and damping coefficients for cylindrical and lemon bearings. Results for lemon bearings are presented and comparison with the commercial software DynRot BR is made. The benefit of this thesis is the creation of an algorithm for the calculation of journal centre equilibrium position, a new way of incorporating the temperature changes in the viscosity and the density of the lubricant, and the modification of a method for calculating stiffness and damping coefficients based on experimental analogy.
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