National Repository of Grey Literature 27 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Thermodynamic analysis of solid oxide cells
Vágner, Petr ; Maršík, František (advisor) ; Grmela, Miroslav (referee) ; Pekař, Miloslav (referee)
Thermodynamic analysis of solid oxide cells Petr Vágner The thesis deals with continuum thermodynamic modeling and analysis of phe- nomena in solid oxide electrochemical cells. A general description of the evo- lution of charged mixtures using partial mass densities, momentum density, entropy density, electric induction, magnetic field, polarization, and magnetiza- tion based on the GENERIC framework is formulated. The formulation is used to recover the Landau-Lifshitz magnetization relaxation model, the Single Re- laxation Time model for dielectrics, and the generalized Poisson-Nernst-Planck model. The latter model is consequently linked to the second part, where a novel double layer model of an yttria-stabilized zirconia interface is formulated within non-equilibrium thermodynamics. The model is solved for numerically in the time domain, and cyclic voltammetry of the system is analyzed. The last part of the thesis demonstrates the limits of Exergy Analysis on a simple solid oxide hydrogen fuel cell model with non-isothermal boundary. It is demon- strated that the minimization of entropy production does not necessarily lead to the maximization of the electric power for certain optimization scenarios. The thesis consists of a compilation of published and unpublished results of the author.
Magnetic loop antenna with electronic tuning for frequencies below 30MHz
Burda, Miroslav ; Vágner, Petr (referee) ; Urbanec, Tomáš (advisor)
This project deals with electronic tuning and automated adjustment of magnetic loop antennas, working in the High Frequencys. The whole work is divided into three parts tuning, adjustment and control). The tuning part is realized by changing the capacity of the array capacitors and adjustment is done by different changes of power points. The whole system is controlled by a microprocessor ATmega16. According to utility switches the microprocessor capacity, which tunes the antenna to the required frequency, processes information about power adjustment and autimatically fine-tuning the antenna by changing the position of charging.
Physical analysis of the main processes in the solid oxide fuel cells and their mathematical description
Vágner, Petr ; Maršík, František (advisor) ; Souček, Ondřej (referee)
Solid oxide fuel cells (SOFC) are mainly used as large stationary elec- tricity sources, therefore an every little improvement in their performance leads to considerable savings. In order to understand the fundamentals of the SOFC operation, we have developed a new model describing the main physical processes. The thermodynamical model of SOFC, developed in this thesis, concerns the gas transport, the transport of the charged particles in- cluding the thermoelectric effect and the electrochemical reactions. Linear irreversible thermodynamics is the key modelling framework, in which the dusty gas model and the Butler-Volmer equations are used. A new relation between the electrochemical affinity and the overpotential is introduced into the Butler-Volmer equation. A weakly formulated statinonary system en- dowed with boundary conditions is solved with the finite element method in one dimensional approximation. 1
Diagnostic of viral hepatitis B in the laboratory of serologic and molecular biology
Vagner, Petr ; Voxová, Barbora (advisor) ; Žáčková, Marta (referee)
Author: Petr Vagner Title: Diagnosis of viral hepatitis B in the serologic and molecular biology laboratory Field of study: Medical laboratory technician, combined type of study The aim of the study: The insight to the diagnosis of viral hepatitis B, with a focus on the examination of antibodies and antigens of Hepatitis B virus. Material and Methods: From 1st January 2011 to 31st December 2013 the serological laboratory of the Institute of Medical Biochemistry and Laboratory Medicine (ÚLBLD) in General University Hospital in Prague (VFN) 77,900 examinations were carried out by chemiluminescent immunoassay system ARCHITECT and system enzyme immunoassay AxSYM, which is used for detection of antibodies and antigens of the virus hepatitis B or detection of molecular biological methods for the detection of hepatitis B virus DNA, the determination of its genotype, drug resistance and pre-core mutations. Results: In total 92.90% of mentioned examinations were serological examinations and 7.10% molecular biological examinations. The examinations of serological markers of HBV were with the highest frequency of HBsAg testing (24, 033 tests) and 16 588 anti-HBs tests, the majority of requests was sent by The Center of Preventive Care (VFN), on the whole 4665 examinations of anti-HBs, from which 3,254 were...
Termodynamická analýza procesů v palivových článcích s pevnými oxidy
Vágner, Petr ; Maršík, František (advisor) ; Némec, Tomáš (referee)
The fuel cells are the technology of the future. Although their discovery dates back to the 19th century the nature of how they work hasnt been adequately explained so far. This thesis focuses on description of solid oxides fuel cells (SOFC) for which ion conductive electrolyte and high operating temperature are distinctive. The mathematical model of SOFC developed in this thesis is formulated in terms of the mixture theory. The model development was constrained and simplified by isothermality, time-stationery and 1D approximation. The model equations characterize gas and ion transport and electric current flow in the fuel cell. Eventually comparison of the thesis model equations with the SOEC (solid oxides electrolysis cell) model developed at the Institute of Chemical Technology in Prague showed that both approaches lead to a similar conclusion. This thesis can be used as a basis for an experimental verification of the mixture theory. 1
Controll Module for Circuits with ADF4360 and Selected DDS
Lambor, Jiří ; Vágner, Petr (referee) ; Urbanec, Tomáš (advisor)
This bachelor’s thesis is focused on issues of communication between microprocessor unit and frequency synthesizer circuits - direct digital synthesis circuit (DDS), voltage control oscillator with phase lock loop (ADF). The basic theoretical function of DDS, ADF and SPI interface is described in the introduction. The solution and drafts of modules hardware are shown in next chapter. Last chapter describes programming of DDS and ADF circuits with examples of this code in C language. Schemes and board layouts of modules are attached in appendix.
Microstrip lowpass filter
Kubín, Petr ; Pítra, Kamil (referee) ; Vágner, Petr (advisor)
This thesis is focused on the design of an elliptic microstrip low pass filter. In the introduction, there is discussed theory of the filter design with discrete components. Then, the following part describes the design of the microstrip filter with distributed parameters. To simulate the characteristics of the designed filter structure, the simulator Ansoft Designer V2 was used. This software was also used for final optimization of the microstrip filter.
Miniaturized Measurement System for Wind Speed Estimation.
Štěpánek, Michal ; Vágner, Petr (referee) ; Urbanec, Tomáš (advisor)
This thesis is analysis of thermal anemometer, which contains design and realization. For measuring wind speed there are not used any mechanical moving parts in this way. This measuring uses two thermistors. One of these measures temperature of air, which is very important for compensation of whole system. Temperature of second thermistor is kept on constant value. This value is higher than surrounding air temperature about constant difference. Fluctuant air cools this sensor and because of that systém must supply more of heat. By analysis of value of supplied heat, we can calculate the wind speed value.
Selective Circuits - Laboratory Experiment
Košťál, Stanislav ; Vágner, Petr (referee) ; Urbanec, Tomáš (advisor)
The aim of this thesis is to describe the distribution and behavior of selective circuits and methods for their implementation. There are formulas provided for the calculation of the frequency components of selected second-order RLC filters. It further describes the choice of filter frequency components and computing relationships needed for the construction of coils. The work also includes a description and complete information needed for making measurements of the measurement of the RLC band-pass. The annex to this work includes all the materials needed for implementation of laboratory tasks designed to measure using the product.
PC Controlled PLL Synthesizer
Málek, Miroslav ; Šrámek, Petr (referee) ; Vágner, Petr (advisor)
The aim of this bachelor´s thesis is a practical realization of computer controlled PLL synthesizer using USB serial port. FT232RL was used as an interface between the PLL synthesizer ADF4110 and PC. A software with graphical user interface was also developed in order to control registers of the syntesizer.

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