National Repository of Grey Literature 36 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Measurment of Equivalent Circuit of Piezoelectric Resonator
Vomočil, Vojtěch ; Frk, Martin (referee) ; Kazelle, Jiří (advisor)
This theis deals with the general overview of the piezoelectric theory, focused both on the mathematical description and on the attributes of piezoelectric materials. It further focuses on the description of piezoelectric resonators with a more detailed explantation of their equivalent scheme and measurement methods of its single elements. The practical part of the thesis rests on the proposal of a measurement apparatus which will serve to measuring the equivalent circuit piezoelectric resonator elements. The realization of the apparatus and its functionality testing are described. In the experimental part of the thesis, the measured rates are processed and levels of the electric equivalent circuit elements of the used piesoelectric resonator for the basic and the two higher closest resonance frequency are set. The measured results are compiled into a standard measurement protocol. This thesis should place basics to the growing laboratory. It should also be a source of necessary theoretical and practical information for this lab.
Degradation of epoxy resins vith various aditives by solar radiation
Škarabelová, Lenka ; Novák, Vítězslav (referee) ; Kazelle, Jiří (advisor)
This master’s thesis is focused on the study of chemical and physical properties of dielectric materials with main focus on epoxy resins. It includes possible processes that can influence the properties of epoxy resins, both processes that improve polymer properties and processes that cause material degradation. Next part of the thesis is a description of diagnostic methods suitable for measurement of basic electrical quantities of material and design of a suitable method for measuring properties of epoxy resins with different additives, influencing the samples by solar radiation. At the end, the work includes an experiment dedicated to the degradation of epoxy resins with various additives by solar radiation and the evaluation of the experiment.
Calibration of contact and non-contact thermometers
Skalický, David ; Kazelle, Jiří (referee) ; Frk, Martin (advisor)
This work deals with the calibration of contact and contactless thermometers. The theoretical part describes physical laws, which are important for contact and contactless measuring of temperature, requirements for thermometers, suitability of use different types of thermometers and materials used for construction of temperature sensors. The following part describes metrology with the focus on metrology system of the Czech Republic. This thesis also describes errors and uncertainties of measurments, especially on their division, sources of uncertainties and methodology of type A and type B uncertainty determination. The practical part is focused on the calibration of thermometers within the Czech Metrological Institute and the Faculty of Electrical Engineering and Communication in Brno.
Thermal degradation of alternative electrical insulating liquids
Vodička, Tomáš ; Kazelle, Jiří (referee) ; Frk, Martin (advisor)
This thesis deals with alternative thermal degradation of electrical insulating liquids. The theoretical part describes the current state of the problem, electrical insulating liquids, their classification and types. There are described properties of electrical insulating liquids, their models of aging and diagnostic methods in accordance with the appropriate standards. In the practical part are chosen by representatives of alternative electrical insulating liquids and there are determined their dielectric characteristics in the initial state. According to the measured values is chosen five candidates for which it is designed and implemented an accelerated degradation test. During the test are measured dielectric parameters of the selected oils. Measured dependencies are mathematically approximated. In conclusion, the results are compared and physically interpreted in view of oxidation stability.
Study of Electrochemical Insertion Cations to the Oxides of Transitive Metals
Svoboda, Vít ; Kadlec, Jaromír (referee) ; Trnková, Libuše (referee) ; Kazelle, Jiří (advisor)
Electrochromic devices are based on the intercalation processes to the active layer mostly WO3. The optical properties of active layer are changed by intercalation ions from the electrolyte. For that purpose are used Li ions. The mass of thin layer can be observed by the QCM method. This method is based on the changes of the resonance frequency of a quartz crystal resonator. The investigated substance is deposited on the surface of the resonator. Various metals (Pt, Au, Ag) and their compounds should be plated on the resonator. Most frequently, the resonators for the frequency 5,0 MHz are used. This frequency change is used for the detection of chemical changes of the electrode surface and is very sensitive.
Dielectric properties of epoxy resins
Matoušová, Klára ; Novák, Vítězslav (referee) ; Kazelle, Jiří (advisor)
This diploma thesis deals with the fundamental properties of epoxide mixtures, as determining of these fundamental properties of epoxide mixtures could in the case of favorable results lead to diminishing the amount of defects in epoxide-embedded instrument transformers. As the influence of effects in the manufacturing process of transformers causing poor quality is very extensit, the biggest emphasis is laid capitally on the influence of the epoxide casting mixture composition. The thesis describes the manufacture technology including used methodics and materials. The compositions of epoxide resins and the mechanisms of their curing. Also, the definitions of fundamental properties of dielectric materials and the description of diagnostic methods used to relative permitivity, dissipation factor and inner resistivity are included. suitable casts of acquired samples were set and dried out within the experimental part, followed by measurement of fundamental electrical properties in temperature and frequency relations. Hereafter a comparison of individual samples and the evaluation of their electrical properties will be carried out.
Cooling of Two-channel audio power-amplifier using FVM
Němec, Radek ; Kazelle, Jiří (referee) ; Vyroubal, Petr (advisor)
This bachelor´s thesis is dealing with the design and construction of two-channel audio Leach type power-amplifier, including the necessary additional components and subsequent design of the amplifier cooling using Flow Simulation tool included in the SolidWorks design system. The opening chapters is about theoretical analysis of audio amplifiers, heat transfer and description of SolidWorks design system. The main part of this thesis contains the design and construction of amplifier and design of each variants of amplifier cooling, including the best variation designed. The last part of the thesis is about assembling the amplifier and evaluation of economic aspects of its production.
Comparation of the properties of the perovskit photovoltaic cells
Mudroch, Michal ; Kazelle, Jiří (referee) ; Novák, Vítězslav (advisor)
In this bachelor’s thesis it is introduced production technology and conversion of electromagnetic radiation into electric energy employing perovskites. In this paper are also described known types of perovskite photovoltaic cell structures and materials that are used to produce them. Furthermore, the theoretical part describes properties of perovskite photovoltaic cells, measured electric quantities and methods of measurement such as photospectroscopy photoimpedance spectroscopy and impedance spectroscopy that are also used to analyze cells functionality. In the following practical part is described fabrication of perovskite cells and evaluation of measured results of the perovskite cell.
Electrical properties analysis of epoxy resins with various fillers
Horák, Luděk ; Kazelle, Jiří (referee) ; Frk, Martin (advisor)
Presented bachelor thesis is focused on studying electroinsulating epoxy resin-based sealings. It describes the chemical composition, production, properties and measuring methods of basic electric quantities of these materials. This work also embodies a preparation of composite epoxy resin samples with different kinds of micro-ground siliceous sand as a filling. The samples given are measured on the temperature dependency of relative permitivity, dissipation factor and inner resistivity.
Drying and preheating in potting process of epoxides
Matoušová, Klára ; Novák, Vítězslav (referee) ; Kazelle, Jiří (advisor)
The bachelor's thesis is dealing with the defects in epoxy resin flooded transformer devices. Since these can be damaged severely in terms of quality by numerous forces, the main focus is dedicated to the impact of moisture. The thesis describes the manufacturing technology including the methods applied and materials used. It further encompasses the composition of epoxy resin and the mechanisms used for their hardening processes. Additionally, the description of the moisture, the impact of adverse forces and the method of their elimination using drying is presented. In the experimental part of the paper, a moisture of the banding materials was measured. On the basis of the results acquired, the paper reaches a conclusion on the ideal time frame of drying, the sufficiency of materials in terms of drying and in two cases two substitutes for contemporary uneasily dryable samples were considered.

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