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Development of calibration methods for hypoplastic models
Šula, Igor ; Mašín, David (advisor) ; Janda, Tomáš (referee)
The calibration application named ExCalibre was developed at Technical University in Prague, Faculty of Civil Engineering. This application can automatically process experimental data and create set of parameters of hypoplastic models which are designed for saturated clays or sands. The aim of this master thesis was to support development of application for calibration with testing it on real experimental data sets. Automatic calibration of these data sets was compared with calibration by hand for identical data. The development of the application and main phase of testing took place in two stages, where the main calibration errors of calibration application were identified. After the final testing of application where the minor bugs and errors were overcome a user-friendly web application (soilmodel.com/excalibre/) was introduced. This final testing has gone beyond this thesis. The results from the main phases of testing are discussed in this thesis as well as the description of database of fine-grained and coarse-grained samples which were used to testing of application. Knowing the calibration of the model is crucial for its using, you can find description of the used constitutive models in this thesis, which are used in the calibration application, as well as a description of procedure for...
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Dynamics of spin polarization in semiconductors
Janda, Tomáš
In this work we study ultrafast laser-induced magnetization dynamics in samples of ferromagnetic semiconductor Ga1−xMnxAs with a nominal concentration of Mn within the range of x = 0,015-0,14. To get information about magnetization movement we use magneto-optic phenomena PKE and MLD in a time-resolved pump & probe experiment. Thorough analysis of the measured magneto-optical signal allows us to disentangle contributions due to angular movement of magnetization and due to demagnetization and to reconstruct 3D motion of magnetization vector without any numerical modeling. First we explain the basis of this experimental method and we demonstrate its utilization on the measured data. After that we study angular movement of magnetization vector and its dependence on the external magnetic field, excitation intensity and Mn concentration. The pump pulse helicity dependent and independent dynamics were treated separately. In the case of demagnetization we have been able to observe not only its intensity and Mn doping dependence but also the magnetic field dependence, which has not been reported so far in the literature.
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Investigation of spin structure and dynamics in magnetically ordered thin films
Janda, Tomáš ; Němec, Petr (advisor) ; Hamrle, Jaroslav (referee) ; Reiss, Günter (referee)
Title: Investigation of spin structure and dynamics in magnetically ordered thin films Author: Tomáš Janda Abstract: This thesis is devoted to the development of methods for imaging and ultrafast manipulation of magnetic textures, such as magnetic domains and domain walls (DWs), and to the investigation of the corresponding magnetiza- tion dynamics. We focused on techniques that are, besides ferromagnets (FMs), applicable also to antiferromagnets (AFs), in particular, AF thin films. The employed excitation techniques were mostly based on direct or indirect effects of ultrashort laser pulses. We studied the DW motion induced by a transfer of angular momentum from circularly polarized femtosecond laser pulses in a FM GaMnAsP and we found that the observed macroscopic DW displacement is only possible due to its inertia. In a distinct experiment, picosecond current pulses were generated by an absorption of the ultrashort laser pulses in a verti- cal PIN diode-based photoconductive switch and used to excite a magnetic film deposited directly on top of the diode. For imaging of AF domain patterns, we developed a simple table-top laser-scanning technique, which is based on a magneto-thermoelectric response of the AF textures in the presence of a local laser-induced heating. We first used the method to image the...
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Theory of magneto-optics
Zálešák, Ondřej ; Ostatnický, Tomáš (advisor) ; Janda, Tomáš (referee)
Magnetic properties of matter have an effect on their optical response. These properties depend on the microscopic structure of the matter and we distinguish several basic types of magnetism. In the latest research, scientists focus on tri- angualr antiferromagnets and their use in technology, for example in spintronics. We describe the magnetic material by permittivity tensor. Description of the response of the material is derived from Maxwell equations and the reflected light is described by its polarization and ellipticity. Then we model triangular antiferromagnets Γ5g and Γ4g configuration. 1
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Development of calibration methods for hypoplastic models
Šula, Igor ; Mašín, David (advisor) ; Janda, Tomáš (referee)
The calibration application named ExCalibre was developed at Technical University in Prague, Faculty of Civil Engineering. This application can automatically process experimental data and create set of parameters of hypoplastic models which are designed for saturated clays or sands. The aim of this master thesis was to support development of application for calibration with testing it on real experimental data sets. Automatic calibration of these data sets was compared with calibration by hand for identical data. The development of the application and main phase of testing took place in two stages, where the main calibration errors of calibration application were identified. After the final testing of application where the minor bugs and errors were overcome a user-friendly web application (soilmodel.com/excalibre/) was introduced. This final testing has gone beyond this thesis. The results from the main phases of testing are discussed in this thesis as well as the description of database of fine-grained and coarse-grained samples which were used to testing of application. Knowing the calibration of the model is crucial for its using, you can find description of the used constitutive models in this thesis, which are used in the calibration application, as well as a description of procedure for...
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Risk Management in Electronic Business Operation
Janda, Tomáš ; Novák, Lukáš (referee) ; Koch, Miloš (advisor)
The diploma thesis deals with the issue of electronic commerce operation and risk analysis on a concrete example of a company that wants to break on the market through the internet shop. The thesis builds on a theoretical basis of e-business, e-commerce, e-shop features, information systems and risk engineering. Based on the theoretical backgrounds, were the risk analysis and suggestions made to prevent and potentially mitigate these risks to an acceptable level.
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Analysis of marketing mix of the company Comtessa
Djukič, Irina ; Říha, David (advisor) ; Janda, Tomáš (referee)
The main aim of my bachelor thesis considers to be the analysis of marketing mix of the company Comtessa, Czech chain providing womens fashion and to suggest relevant recommendations to make the company more competitive. I obtained all the information and data needed from the supervisors. The thesis is divided into two parts. The first one is a theoretical basis concerning marketing mix with links to the fashion. The second, practical part deals with the market analysis from the macro-economic (PEST analysis) and micro-economic perspective (Porter analysis 5F). Furthermore, it contains the SWOT analysis, which is based on the information obtained through the individual depth interview with supervisors. The last and most important part is the analysis of marketing mix, where each element is described into details. The result is recommendation for each element according to the previous analyses.
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Accounting for a spatial and experimental variability in numerical modelling of geotechnical structures
Kupa, Ondřej ; Mašín, David (advisor) ; Janda, Tomáš (referee)
This diploma thesis is focused on evaluation of influence of spatial and experimental variability of input data in numerical simulations of behaviour of geotechnical structures. Thanks to opportunity to use data source of sand from the only one location in order to evaluate spatial and experimental variability, the assessment was carried out using extracting the experimental uncertainty from the total spatial variability method. Primarily, an influence of different level of considered experimental variability on total response of material environment was investigated. Random field theory was used to model variabilities in parameters of geological underlay and Mohr-Coulomb ideal plastic constitutive soil model was taken into account. In order to achieve representative quantity of values for statistical quantification of resulting influence of considered variability level, Monte Carlo method was used. Presented method of extracting the experimental uncertainty from the total variability was verified on two geotechnical cases. First, a settlement of strip footing was solved. An increasing accuracy of settlement values depending on level of considered experimental variability was demonstrated. The second case was focused on assessment of variability influence on slope stability. In addition, a nonzero...
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Dynamics of spin polarization in semiconductors
Janda, Tomáš
In this work we study ultrafast laser-induced magnetization dynamics in samples of ferromagnetic semiconductor Ga1−xMnxAs with a nominal concentration of Mn within the range of x = 0,015-0,14. To get information about magnetization movement we use magneto-optic phenomena PKE and MLD in a time-resolved pump & probe experiment. Thorough analysis of the measured magneto-optical signal allows us to disentangle contributions due to angular movement of magnetization and due to demagnetization and to reconstruct 3D motion of magnetization vector without any numerical modeling. First we explain the basis of this experimental method and we demonstrate its utilization on the measured data. After that we study angular movement of magnetization vector and its dependence on the external magnetic field, excitation intensity and Mn concentration. The pump pulse helicity dependent and independent dynamics were treated separately. In the case of demagnetization we have been able to observe not only its intensity and Mn doping dependence but also the magnetic field dependence, which has not been reported so far in the literature.
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Dynamics of spin polarization in semiconductors
Janda, Tomáš ; Němec, Petr (advisor) ; Olejník, Kamil (referee)
In this work we study ultrafast laser-induced magnetization dynamics in samples of ferromagnetic semiconductor Ga1−xMnxAs with a nominal concentration of Mn within the range of x = 0,015-0,14. To get information about magnetization movement we use magneto-optic phenomena PKE and MLD in a time-resolved pump & probe experiment. Thorough analysis of the measured magneto-optical signal allows us to disentangle contributions due to angular movement of magnetization and due to demagnetization and to reconstruct 3D motion of magnetization vector without any numerical modeling. First we explain the basis of this experimental method and we demonstrate its utilization on the measured data. After that we study angular movement of magnetization vector and its dependence on the external magnetic field, excitation intensity and Mn concentration. The pump pulse helicity dependent and independent dynamics were treated separately. In the case of demagnetization we have been able to observe not only its intensity and Mn doping dependence but also the magnetic field dependence, which has not been reported so far in the literature.
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