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Investigation and Modelling of Concrete Carbonation
Rovnaníková, Markéta ; Keršner, Zbyněk (referee) ; Bajza, Adolf (referee) ; Havlica, Jaromír (advisor)
The corrosion of steel reinforcement is probably the most frequent type of degradation of reinforced concrete structures. Reinforcing bars are protected from corrosion by a thin iron oxide layer which is formed on their surface due to a high alkalinity of the surrounding concrete. Corrosion may start when this layer is destroyed (i) either by chloride ion penetration (when the concentration of dissolved chloride at the depth of the reinforcing steel exceeds a critical value) or (ii) by a reduction in the pH value of pore solution to values below 9.5. Such a reduction in alkalinity is the result of carbonation of the Ca(OH)2 in the concrete mass, i.e. of its reaction with the atmospheric CO2. The main aim of this work is an experimental investigation and modelling of carbonation process. The effect of relative humidity, curing period and replacement of Portland cement by supplementary cementing materials (SCM - fly ash, blast furnace slag and metakaolin) on carbonation process has been studied. Calcium hydroxide content in the presence of SCM and their pozzolanic activities have been also determined. Furthermore, lots of parametric studies and comparison of carbonation models have been provided. The software tools based on the introduced models and considering the input data to be statistically independent random variables have been described and used for other parametric studies.
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Switching mechanism in the molded case circuit breaker
Mejzlík, Tomáš ; Valenta, Jiří (referee) ; Dostál, Lukáš (advisor)
This paper deals with mechanical switch in circuit breaker designed for low voltage. The goal of this thesis was to analyze switching mechanism both theoretically and practically. Theoretical analysis consist of study different types of switching mechanism and analytical calculations of acceleration speed and trajectory. Practical analysis has been made taking a video with high speed camera of real switching mechanism of a circuit breaker and software analysis of the data. The next part of a thesis is about 3D modeling, animating and simulating of a switchgear switching mechanism.
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Computer modelling of courses of complex permittivity
Frybert, Jan ; Rozsívalová, Zdenka (referee) ; Frk, Martin (advisor)
The aim of this work was to create the program for modelling of frequencies courses of complex permittivity parts according to the basic empirical functions, which are described distribution of relaxation time. The main attention is concentrated on the influence of particular parameters on the courses of real and imaginary parts of complex permittivity. Whole program is written in Borland Builder C++.
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Reconfigurable multiband antenna
Havlín, Radomil ; Goňa, Stanislav (referee) ; Raida, Zbyněk (advisor)
This thesis deals with modeling and produce of reconfigurable multi-band planar antennas, which allow electrical shifting of frequency band. After antennas simulation with PIN diode and FET switch in a commercial program CST MW, another step is to optimize the antenna for a new substrate. The next step was to produce antennas. Finally, the optimized antennas are compared with the measurement on experimental antennas.
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