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Study of CdTe sensor properties
Vašíček, Martin ; Holcman, Vladimír (referee) ; Grmela, Lubomír (advisor)
This Bachelor Thesis is focused on studies of CdTe detector characteristics. It is to describe the analysis of transport and noise characteristics of CdTe samples at different temperatures. Evaluation of our results proves that CdTe junction behaves like an antiseries connection of a pair of diodes. The courses of VA characteristics are noted for linear or slightly exponential growth. When temperature is growing , conductivity of the samples is growing too. Our measurements demonstrated difference in conductivity of samples tested at the same temperature. It is also obvious that within very low range of frequencies the factor of noise 1/f is dominating. From 10Hz frequency the effect of thermal noise prevails.
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Design of algorithms for a continuous steam quality measurement system
Hanák, Tomáš ; Tofel, Pavel (referee) ; Holcman, Vladimír (advisor)
This bachelor thesis deals with proposal of algorithm for continuous system of sterilizated steam. At the beginning we deal with the process of sterilization and its methods. Later on we talk over about the saturated steam and parameters of saturated steam. At the end of the bachelors thesis we discuss about current measurement of sterilization steam quality. Then, the procedure of simultaneous measurement of sterilization steam quality is described here. The last part is the evaluation of measured data and presentation of their results.
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Processing of electromagnetic and acoustic emission signals during mechanical stressing of solids
Šopík, Martin ; Holcman, Vladimír (referee) ; Koktavý, Pavel (advisor)
Electromagnetic emission and acoustic emission are physical phenomena evoked in non-conductive material by the sudden release of energy that generate rising cracks in material structure. The significant is a fact that these emission signals are detected already in stadium of materials loading whereof can be used e.g. at non-destructive diagnostics of building materials and constructions. In the appropriate manner processing of the emitted signals then make possible to obtain valuable informations for study physical properties of cracks. Master’s thesis describes methods designed for important signal data ascertainment in time, frequency even time-frequency domain. It can be e.g. start time, maximum value, dominant frequency in spectrum etc. All these methods are implemented into main program. Next load is formularization of source signal transformation which is given by used measuring circuit. Analytical method is chosen for solving. It means finding out reserve electrical circuit with constant element values. Resultant circuit approaches original circuit with less square error than existing way. The signal transformation is described by differential equation of second order with constant coefficients. MATLAB software is used for all computations and projections.
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Continuous measurement of the quality of steam
Rageh, Akram ; Sedlák, Petr (referee) ; Holcman, Vladimír (advisor)
Diplomová práce se zabývá měřením, analýzou a následným nalezením vhodných fyzikálních parametrů pro analýzu kvality syté sterilizační páry. Tato práce si klade za cíl určit, kritické parametry systému vyvíječe páry pro provoz dle norem ČSN. Dílčí částí projektu je popis fyzikální sterilizace, syté páry, metod a senzorů pro kontrolu sterilizační páry.
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Preparation and optimization of electrospun materials suitable as electricity generators
Pokorná, Romana ; Holcman, Vladimír (referee) ; Tofel, Pavel (advisor)
This master's thesis is focused on energy harvesting and is divided into two parts: theoretical and practical part. The theoretical part of the thesis contains the dielectric parameters, the meaning of the piezoelectric and triboelectric effect and the principles of electric energy gain in energy havesting. The last chapter of the theoretical part is devoted to various electrospun materials suitable for energy harvesting. The practical part of the work deals with nanofibers as an energy generator and describes their dielectric parameters. In this part the relative permittivity and loss factor of selected types of nanofibers are measured. Also the triboelectric nanogenerator is made and it's properties are measured.
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Development of application for simulation of physicals effects
Polách, Milan ; Šimek, Milan (referee) ; Holcman, Vladimír (advisor)
The aim of this bachelor's thesis was to create an educational system for more effective teaching physical phenomena and the replacement of older systems used. Whole project is composed of several parts. At the begining, the theoretical information are shown on website. Next is a simulation of physical phenomena and in conclusion, how the phenomena looks like in a real situation is presented. Animations for simulations are created in Blender, using programming language Phyton.
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Dielectric Relaxation Spectroscopy of Composite Systems
Holcman, Vladimír ; Liedermann, Karel (advisor)
The subject of this doctoral thesis is the study of dielectric properties of a binary composite made up of a polymer matrix and metallic filler. Properties of such composites have been extensively examined in the past and they turned out to depend on temperature, frequency and in particular on filler concentration. The objective of this work was first to experimentally establish and second to describe quantitatively the effect of the size of metallic particles on the properties of the composite concerned, yet at the same filler concentration. This study was carried out on the model system ethylene-vinylacetate copolymer – nickel. The acquisition of experimental results required extensive measurements in a wide frequency and temperature interval, as well as a manufacture and preparation of a large set of samples with different concentrations and Ni filler sizes. Measurements were in part carried out at the Centre for Electronic Correlations and Magnetism, Institute of Experimental Physics V of the University of Augsburg (Germany) and, after the installation of a new cryogenic system, at the Department of Physics at FEEC, BUT Brno. Measurements were performed on a number of meters (Alpha-Analyzer of Novocontrol, HP4284A and HP4285A of Hewlett Packard and E4991A of Agilent) in the frequency range 1 Hz – 1 MHz and in the temperature interval 10 K – 300 K. The nickel concentration in systems studied varied from 0 % to 75 % and nickel particles were of a spherical shape with diameters between 35 and 115 m. The measurement results have shown that in the above frequency and temperature window just a single relaxation and a single conductivity mechanism occur. It was also proved that the frequency dependence of complex permittivity is for different Ni particle sizes at the same concentration different. These results have been quantified and a simple mathematical formula based on the Lichtenecker mixture rule has been proposed for their description. The physical origin of the effect of particle size at the same total nickel concentration is sought in different surface areas of internal interfaces between nickel and polymer in the composite
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Wavelet transform and characterization of acoustic signal emision for cluster analysis
Blažek, Petr ; Holcman, Vladimír (referee) ; Sedlák, Petr (advisor)
This work describes the usage application of wavelet transform for on characterization of acoustic emission signals in cluster analysis. Acoustic emission, which are among the passive non-destructive methods, offering a huge potential due to quantization evaluating their options, such as localization and characterization of emission sources, i.e. wide spectrum of degradation processes in the material. In this work, I focused on testing the input parameters AE, selection of a suitable mother wavelet in the application of DWT and WPT for characterization of AE sources and the selection of a suitable mother wavelet noise reduction when using DWT.
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Electrical characterization of flexible nanofiber piezoelectric materials
Pokorná, Romana ; Holcman, Vladimír (referee) ; Tofel, Pavel (advisor)
This bacherol thesis is focused on piezoelectric nanofibrous materials. The first part describes the formation, use and possible aplications of nanofibers. It further analyze the principle of piezoelectric effect. It is a conversion of mechanical energy into electric energy and conversely. The second part is focused on design of experimental workplace for measurement of functional material properties. The last section of the thesis is dedicated to the electrical characterization of PVDF nanofibers and to the measurement of the piezoelectric charge constant.
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Proposal for a new system of continuous quality measurement pairs
Foltová, Anežka ; Sedlák, Petr (referee) ; Holcman, Vladimír (advisor)
This paper deals with proposal of new continual system for quality measurement of sterilization steam. At the begining the process of sterilization is introduced. Then the concept of saturated streams, parameters for sterilization and sensors for measurement are described. Then the current process of measurement of steam quality is described and in the last part the proposal of the new system is introduced. After the draft was the measurement data, analysis and evalution.
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