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Measurement of nucleation rate in corrossive mixtures
Krejčí, A. Petr
For a complete description of two-phase flow a basic informationabout liquid phase formation is needed. The information is fulfilled in terms ofnucleation rate and its dependency on quantities characteristic for gas-phaseflow. One of devices used for measuring of nucleation rate in multi-componentsystems of vapors and gases is a shock tube. Unique modification of this devicedesigned for measuring in chemically aggressive mixtures is described.
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Study of the synthesis and structure of ceramic perovskite materials for energy applications
Strejček, Josef ; Bartoníčková, Eva (referee) ; Cihlář, Jaroslav (advisor)
Method, so called “glycin- nitrate process”, combined with high temperature solid state reaction, of preparation multi- component ceramic perovskite materials was studied. Two types of perovskite systems were prepared by this method. Firs one, based on LaNiO3 doped by calcium and aluminium and second one, based on SmFeO3 doped by calcium and nickel or cobalt. This method made possible preparation of one phase perovskite or perovskites with few percent of nickel in form of oxide. In systems containing both nickel and calcium another phases rich in calcium and nickel appeared.
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Ab initio studie Lavesových fází v systémech Fe-Cr, Fe-Mo a Fe-Ta
Houserová, Jana ; Šob, Mojmír
Binary systems Fe-Cr, Fe-Mo and Fe-Ta can be found in many kinds of steels where the Laves-phase can be considered as a potential candidate for strengthening provided size and distribution of the particles are within certain limits. We performed electronic structure calculations to study the thermodynamic and structural properties of the C14 Laves phase with various compositions. In the frame of the thermodynamic study, we have evaluated the total energies of formation of Laves phase structure with different occupations of sublattices (Fe2Fe, Fe2X, X2Fe, X2X, where X stands for Cr, Mo and Ta) with respect to the Standard Element Reference (SER) states. These energies of formation are of great importance for prediction of stability of studied configurations.
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Ellipsometry of Thin Films
Novotný, Zbyněk ; Navrátil, Karel (referee) ; Nebojsa, Alois (advisor)
Diploma thesis deals with ageing process of thin films of Co and Cu on Si substrate, prepared by the IBAD method. The process of film ageing, which depends on time of exposition to the atmosphere at room conditions, was investigated with spectroscopic ellipsometry (VIS+UV) and atomic force microscopy. In case of thin Co films, approximately four days long incubation period was observed. During this time period, a change in the optical parameters of the film occurs without a measurable change of the film topography. Using non-contact atomic force microscopy, a growth of the transitional film in the island growth regime was observed. During the ageing of thin Cu films, two stages of growth of the transitional layer were observed - nucleation stage and growth stage. Both of these time periods of the transitional layer growth show direct logarithmic dependence. Using non-contact atomic force microscopy, the growth of the transitional film was observed. Using atomic force microscopy in non-contact regime, time dependent measurement was done and the process of forming of one monolayer of the transitional layer was documented. Within the diploma thesis, a series of experiments on ultra high vacuum system were performed in order to investigate phase transformation of thin Fe films (22 monolayers) on Cu(100) stabilized by CO absorption. The transformation from fcc phase to bcc phase was induced by Ar+ ion beam bombardment with the ion energy in the range (0.5-4) keV. The process of phase transformation was observed by surface magneto-optic Kerr effect, Auger electron spectroscopy and low energy electron diffraction.
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Aroma profile of cheese analogues
Součková, Šárka ; Pšenáková, Ivana (referee) ; Vítová, Eva (advisor)
This Bachelor’s thesis deals with the issue of processed cheese analogues. It will explain what they are, their chemical composition and properties. The aim is to examine a number of cheese analogue samples with added various types of vegetable fats and identify and quantify the volatile aroma active substances present. Aroma compounds were isolated from samples using the Solid Phase Microextraction (SPME), a fiber with polar stationary phase (CARTM/PDMS) was used and the captured substances were then determined by gas chromatography. The evaluated cheese analogues varied in the type of the contained fat. In total 27 aroma active compounds in different amounts were identified. Cheese analogue with sunflower oil contained the most compounds (24) and the smallest number of aroma substances (16) has been detected in the cheese analogue with coconut fat. The highest concentration of aromatic compounds was found in the analogue with coconut fat and lowest in the cheese analogue with palm fat. Ethanol occurred in all types of analogues in the largest concentration. In conclusion it can be argued that the various analogues varied in the type and the amount of aromatic compounds, depending on the type of fat used.
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Emergent properties of the G1/S network
Dražková, Jana ; Tomášek, Petr (referee) ; Palumbo,, Pasquale (advisor)
Tato práce se zabývá buněčným cyklem kvasinky Saccgaromyces cerevisiae. Oblastí našeho zájmu je přechod mezi G1 a S fází, kde je naším cílem identifikovat velikosti buňky v době počátku DNA replikace. Nejprve se věnujeme nedávno publikovanému matematickému modelu, který popisuje mechanismy vedoucí k S fázi. Práce poskytuje detailní popis tohoto modelu, stejně jako časový průběh některých důležitých proteinů či jejich sloučenin. Dále se zabýváme pravděpodobnostním modelem aktivace replikačních počátků DNA. Nově uvažujeme vliv šíření DNA replikace mezi sousedícími počátky a analyzujeme jeho důsledky. Poskytujeme také senzitivní analýzu kritické velikosti buňky vzhledem ke konstantám popisujícím dynamiku reakcí v modelu G1/S přechodu.
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Costs reduction in production of Al-alloy castings
Nováková, Lucie ; Lána, Ivo (referee) ; Roučka, Jaromír (advisor)
This thesis deals with solving the most serious internal defects in castings made of aluminum alloys which are cast in sand molds in Slévárna a modelárna Nové Ransko Ltd. The problem solving contains a description of the problematic castings with the investigation of the structure and phases and subsequent detailed analysis of their production. The Author of this thesis also examines the influence of Fe and Mn on a possible formation of the internal porosity with the help of test meltings with the evaluation of the internal structural change. The Author’s design solution is a close checking of chemical composition with regard to the ratio Mn / Fe present in the alloy, the purchase of Foundry Degassing Unit to reduce gassiness of melted metals and better control of gassiness with the help of the appropriate equipment for the density Dichte index.
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Assesment of the Environmental Impact in the Design of Production Machines in Terms of Greenhouse Gas Emissions of Selected
Krbalová, Maria ; Pačaiová,, Hana (referee) ; Demeč, Peter (referee) ; Blecha, Petr (advisor)
The presented doctoral thesis is focused on environmental impact assessment of basic engineering materials used in a production machine construction. Ecological profile of the machine itself develops already in the phase of its design. It is not only about the choice of future machine parameters and materials that it is built from, but also about technologies used for its manufacture and operation conditions of the finished machine (consumption of energy and service fluids). The thesis occupies in detail with environmental impact analysis of the production machine design from the viewpoint of material production that mentioned machine consists of. The output from the performed analysis is methodology for evaluating of machine design from the viewpoint of greenhouse gas emissions. Created methodology enables evaluating of machine ecological profile and its possible adjustments even during pre-production stage. In the first part of the thesis the analysis of current legislation in the field of fighting against climate changes, reducing of products energy consumption and increasing of production machines energy efficiency is presented. Also in this part of the thesis description of methods that were used to achieve thesis goals is stated. Furthermore analysis of production machine as a system of structural components that fulfil the certain functions and description of used basic engineering materials are presented. The second part of the thesis is devoted to environmental impact analysis of the production machine design process. There the design process and environmental impact of machine design are described. This is followed by description of production machine life cycle and detailed analysis of undesirable substances emissions emitted during pre-production phases of machine life cycle (i.e. during the raw materials extraction and materials production). From this analysis the particular constituents’ pre-production phases which are sources of undesirable substances emissions (e.g. greenhouse gas emissions) were derived. The thesis also includes analysis of these constituents’ life cycles and description of electric power generation as a basic constituent of any phase of product life cycle. In this part of the thesis calculations of particular fuel type’s amounts that is required to produce 1 MWh of electric power and carbon dioxide amount produced during electric power generation are presented. The third part of the thesis contains created models of manufacturing processes of basic engineering materials and calculations of related emissions of selected greenhouse gases. The practical output from this part of the thesis is methodology that enables environmental impact assessment of machine design from the viewpoint of engineering materials used in its construction.
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Safety of technological systems
Jiříček, Petr ; Pavlík, Josef (referee) ; Hammer, Miloš (advisor)
The work deals with the safety of technological systems and can be divided into two main thematic units. The attention in the first theoretic unit is paid to aspects that affect the safety of technological systems during their technical life. It describes, together with elementary norms and acts solving the products safety, the most important principles for creating and analysing the safety. It clarifies the origin of company’s risk management, part of its quality management, mentions the faults in which products can be found and also describes the failures which have the biggest effect on these faults and of course on the safety too. Attention is further paid to the reliability analysis, as the tool that helps to create the products safety in the pre-manufacturing phase and also to technical diagnostic, as the tool to keep the safety in after-manufacturing phase. The second practical unit arithmetically analyses the safety of two high-voltage transformers. For that it was used the database of real operation numerical values that were gained during diagnostic investigations on these transformers. In addition it describes mentioned diagnostics methods and gives the new procedure for analyse of transformers’ safety by criteria matrix and weighted sum approach. The main contribution of the work can be considered the checkout and the evaluation of this procedure for use in elaboration of high-voltage transformers diagnostic values for analyzing their safety.
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