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Design of synchronous reluctance motor with permanent magnets
Knebl, Ladislav ; Huzlík, Rostislav (referee) ; Ondrůšek, Čestmír (advisor)
V dnešní době je kladen vysoký nárok na účinnost elektrických zařízení a to jak ze strany provozovatele, tak i legislativy. Nejlepší účinnosti dosahují synchronní motory s permanentními magnety umístěnými na povrchu rotoru (SMPM), se kterými lze i u malých motorů dosáhnout účinnosti nad 90%. Nicméně tyto motory jsou z důvodů použití magnetů ze vzácných zemin, např. NdFeB, drahé a jsou schopny provozu pouze s frekvenčním měničem. Z cenových důvodů jsou hledány levnější alternativy k SMPM motorům. Jedním z typů motorů, kterým lze SMPM nahradit je synchronní reluktanční motor s permanentními magnety (PMASR). Tento motor je cenově výhodnější, protože používá menší množství magnetů, při zachování podobných, mnohdy i lepších vlastností, nicméně neodpadá potřeba použití frekvenčního měniče. Navíc je zde možnost použití levnějších feritových magnetů a tím ještě výrazněji snížit cenu motoru. V této práci bude PMASR topologie popsána důkladněji včetně elektromagnetického návrhu metodou konečných prvků. Bude provedena i mechanická analýza zvoleného optimálního modelu. Výsledky dosažené metodou konečných prvků budou následně porovnány s analytickým modelem. Z navrženého modelu bude vyroben prototyp a naměřené výsledky budou porovnány s výpočty.
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High temperature conductivity measurements of ceramic materials
Grochal, Peter ; Kazelle, Jiří (referee) ; Novák, Vítězslav (advisor)
The aim of this work is to get acquainted with the detailed structure of yttrium-stabilized zirconia, focusing mainly on conductivity. Coating platinum electrodes by screen printing. Solution of complexity of conductivity segregation by electrode geometry. Measurement of the conductivity of macroscopic samples of ceramics by impedance spectroscopy to determine the electrical behavior of the system. Creating equivalent circuits to measured data. Detect system behavior when excited by different AC voltage and electrode geometry values.
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Diagnostic properties of concrete exposed to high temperatures
Hudský, Petr ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
This master’s thesis studies the problems of high temperatures on cement concretes, their following diagnostics from pre-treatment to rehabilitation, the emphasis was on the use of high-speed water jet. In the experimental part of the design of a concrete composition with basalt aggregate. Were reviewed the physico-mechanical properties after thermal loading. The influence of pressure water jet on the thermal load on concrete, pull-off test, the volume of the removed concrete with a strength evaluation and comparison.
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Response to abiotic stress in plants growing in green façades of temperate urban environment
Hrochová, Růžena ; Lhotáková, Zuzana (advisor) ; Havelková, Lenka (referee)
With increasing urbanization the temperature of cities is increasing and an effect of urban heat island arises. Vegetation, particularly vertical greenery systems: facades and walls, is mitigating urban heat island and reducing temperature. The aim of this work was to define these systems, their effects on the urban microclimate, to create an overview of the most used plants for greenery systems and to summarize their reactions to abiotic stresses of cities in a temperate region. Mediterranean studies were used in this work due to the scarcity of temperate climate research, which results could become valuable with climate change. Selecting proper vegetation can be done using habitat template, plants that are acclimated or adapted to the urban environment. Plants affect the urban microclimate through shading and transpirational cooling, which ideally contribute to reducing the heat island effect with optimal irrigation. Stressors followed in this work were drought, high temperature and irradiance, air pollution and salinity. To all these stressors plants reacted with limiting physiological functions and reducing growth. The common reaction was a decrease photosynthesis rate and chlorophyll content. Ractions of plants of vertical greenery systems to different stressors and their combinations are...
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Study of resistance of selected aggregates to high temperatures
Holanec, Aleš ; Sitek,, Libor (referee) ; Bodnárová, Lenka (advisor)
The thesis deals with the monitoring of changes taking place in natural stones and aggregates under high temperatures. The theoretical part of the work provides information about basic groups of rocks, the technology of processing the natural stone and primarily about the study of behavior of natural stone and aggregates at high temperatures. Also some findings from different research works aimed at monitoring the behavior of rocks at high temperatures are presented. In the experimental part a selection of rocks with a higher expected resistance to high temperatures is made, including detailed information and description. Further in this section we provide the comparison of the properties of individual rocks. Later we describe the most important methods of testing, the procedure of preparation of rock samples and we design an experiment to use for evaluation of resistance of rocks and aggregates under high temperatures.
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Workplace for measuring capacity and rate-capability characteristics of lithium-ion batteries
Cápal, David ; Máca, Josef (referee) ; Libich, Jiří (advisor)
This master's thesis deals with the issues of lithium-ion batteries, describing common types of commercial lithium-ion batteries, their advantages, disadvantages, and characteristic properties. The thesis focuses in more detail on the influence of temperature on the characteristics of lithium-ion battery. The thesis describes the design and construction of a workplace for measuring capacity and rate-capability characteristics of lithium-ion batteries at low and high temperatures. The thesis also describes the implementation of a cooling and heating module using a system based on Peltier devices.
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Short-term application of elevated temperature and drought influences the isotopic composition of winter wheat grains
Pernicová, Natálie ; Urban, Otmar ; Čáslavský, Josef ; Klem, Karel ; Trnka, Miroslav
The study aimed to determine the differences in carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in grains of three winter wheat varieties grown under optimal and stress conditions. We found that the wheat variety has a significant effect on both δ13C and δ15N isotope ratios. Short-term (nine days) exposure to drought and high temperature during the heading or stem extension development phase significantly enhanced δ13C values, but only high temperature affected δ15N values. Enhanced δ15N values support the assumption that global warming causes a higher representation of the 15N isotope in plants. Moreover, significant interactive effects of temperature and water availability on the values of both isotopes were found implying that C and N metabolisms have been altered under the investigated stress conditions. We conclude that δ13C and δ15N isotope ratios of cereal grains are sensitive indicators of stress conditions, even short-term ones
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Use of organic fibers in fine-grained cement composites and their influence on the monitored properties
Mazán, Tomáš ; Ondráček, Michal (referee) ; Křížová, Klára (advisor)
The diploma thesis describes the possibilities of using organic fibres to improve the properties of cement composites at high temperatures. The theoretical part of the thesis deals with the behaviour of the different components of concrete and concretes in fire. A substantial part is devoted to the types of fibres, the method of dosage and the effect of their use on selected parameters. The practical part of the thesis is based on the developed methodology. On the basis of the results obtained, a summary of the behaviour and transformations of different types of organic fibres when exposed to temperatures from 20 to 800 °C was compiled. Furthermore, the observed parameters and the effect of the fibres, especially on the strength of the composite loaded at high temperature, are evaluated. The final of thesis concludes with recommendations for fibre dosage and the suitability of using recycled fibres.
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Conceptual design of a gear tester for space applications
Florián, Vojtěch ; Černohlávek, Mikuláš (referee) ; Košťál, David (advisor)
This bachelor thesis deals with the creation of a conceptual design of gears tester for space applications. The tester must simulate space conditions and test whether the gear can operate in those conditions. It is more important to test the wheel material than its geometry. The work is divided into theoretical and practical part. In the theoretical part, a search of current knowledge of the issue is created. The second part describes several conceptual designs of testers and their models. Subsequently, a concept that can most faithfully simulate real conditions in low orbit is selected and described in detail. The final design of this concept will facilitate the testing of gears and minimize their failure rate during operation.
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The effect of temperature on the charging and discharging characteristics of lithium-ion batteries
Doleželová, Eva ; Máca, Josef (referee) ; Libich, Jiří (advisor)
This thesis deals with operation principles of lithium-ion batteries, its degradation principles, capacity fade, materials used, formats, main characteristics, development, uses and mid to high temperature behaviour. The thesis aims to study aging characteristics of commercially available lithium-ion batteries. In the practical part of the thesis, the key parameters of selected types of commercially available lithium-ion batteries were measured under normal temperature conditions. The measurement was repeated at an elevated temperature. Results were analysed and effects of different temperatures on the selected characteristics were concluded both verbally and graphically. A conclusion evaluates short-term and long-term impacts of ambient temperature on rate capability, ageing, capacity fade and longevity.
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