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Nestabilita akrečního disku jako zdroj energie pro kvaziperiodické oscilace
Horák, Jiří
We discuss a scenario, in which the energy for quasi-periodic oscillations comes from instabilities of the accretion disk. We demonstrate this mechanism on the interaction among stable and unstable modes of oscillations in slender accretion tori. In our model, the unstable non-axisymmetric corotation modes are nonlinearly coupled to stable acoustic modes of torus oscillations. The increasing energy of corotation modes is advected to the acoustic modes by the means of parametric instability. The stable modes may reach substantial amplitudes even if they are damped according to the linear theory.
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Creating conditions for evaluation of high-strength concrete characteristics using non-destructive testing methods
Procházka, David ; Horký,, Ondřej (referee) ; Kolář,, Karel (referee) ; Adámek, Jiří (referee) ; Brožovský, Jiří (advisor)
High-strength concrete (HSC) belongs in the recent years to frequently used types of concrete. It allows realization of static challenging structures and also shows due to its dense structure greater durability especially against aggressive media. Currently HSC construction realization abroad is not exceptional. It’s using in the Czech Republic is still limited. When realized, then in a small scale in civil engineering works. The realization of high-strength concrete structures is closely related with the concrete construction quality verification. Good efficiency of the quality control methods can provide non-destructive testing methods (NDT), especially when investigating strength of concrete built in structure. A lack on relevant data for non-destructive testing of HSC in technical and normative rules is to be considered as a significant deficiency. Evident for HSC generally is the lack in literature on deeper analysis of the factors affecting their non-destructive testing, as well a meaningful methodology or practically usable calibration relationships. HSC differs from ordinary concrete not only by used components, but also by more compact structure with different strength – elastic characteristics. Considering these differences, HSC strength prediction can not be performed by using calibration relationships developed for ordinary concrete. Moreover, the question is to what extent the current knowledge of the NDT results influencing factors can be considered as valid. The paper presents findings on the effects of the key factors affecting the measurement results of Schmidt hardness method and ultrasonic pulse method, including recommendations for the practical application of these methods. The problematic of static vs. dynamic modulus of elasticity was also solved. Calibration equations for predicting the compressive strength of HSC from the non-destructive testing parameter were elaborated, showing high cohesion among variables and practically usability.
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PROBLEMS OF DIAGNOSTIC IMAGING IN THE OBEZITY AND METABOLIC SYNDROM
VLKOVÁ, Renata
Metabolic syndrome is characterised by a combination of metabolic disorders and diseases with very serious consequences. Obesity is defined as being overweight with a high proportion of fatty tissue. According to the WHO, obesity is considered a serious epidemic of the 21st century. The aim of this work is to summarise mentioned issues from the available literature and to describe individual imaging modalities in diagnostic radiology related to metabolic syndrome, together with the evaluation of fat tissue distribution in the abdominal area, including its changes, after nutritional education and treatment in a monitored patient group. Participants have been randomised for the study group from the Centre for Adult Obesity and their BMI had to exceed 25. The main requirements were a voluntary cooperation, non-pharmacological methods of obesity treatment and weight limited to 140 kg. All of the addressed patients have shown their interest and willingness to continue this cooperation in the future.
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Non-energy Applications of Lignite
Majzlíková, Petra ; Maršálek, Roman (referee) ; Janoš, Pavel (referee) ; Pekař, Miloslav (advisor)
This thesis deals with various physical-chemical aspects of agricultural and environmental applications of the South Moravian lignite. The main attention was paid to the behavior of lignite in an aqueous environment and the application potential of lignite as a cheap, effective and universal sorbent. In the experimental part of the thesis, aqueous extracts of lignite were characterized in detail (by measurement of pH, conductivity, and by the qualitative and quantitative determination of inorganic constituents). The high sorption affinity towards polar (cationic dyes) and nonpolar compounds (petroleum products) was confirmed experimentally. At last, simple methods of the laboratory preparation of lignite granules was designed and optimized. The main aim of this part was to combine the unusual sorption properties of lignite with an improvement of the end-use properties of the product (user-friendly handling, controlled release of the lignite into the aqueous environment, etc.). The thesis represents a complex compilation of the results of pilot experiments which represent the starting point of detailed future works focused on the non-energetic application of this valuable natural material.
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Phase equilibria of carbon dioxide and methane gas-hydrates predicted with the modified analytical S-L-V equation of state
Vinš, Václav ; Jäger, A. ; Hrubý, Jan ; Span, R.
Gas-hydrates (clathrates) are non-stoichiometric crystallized solutions of gas molecules in the metastable water lattice. Two or more components are associated without ordinary chemical union but through complete enclosure of gas molecules in a framework of water molecules linked together by hydrogen bonds. The clathrates are important in the following applications: the pipeline blockage in natural gas industry, potential energy source in the form of natural hydrates present in ocean bottom, and the CO2 separation and storage. In this study, we have modified an analytical solid-liquid-vapor equation of state (EoS) [A. Yokozeki, Fluid Phase Equil. 222–223 (2004)] to improve its ability for modeling the phase equilibria of clathrates. The EoS can predict the formation conditions for CO2- and CH4-hydrates. It will be used as an initial estimate for a more complicated hydrate model based on the fundamental EoSs for fluid phases.
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Non-life Insurance {--} Contemporary Trends
KAMIŠOVÁ, Martina
Any man and any company can be endangered by risks. People can be mostly at risk of an accident, death, or destroying of his property. On the other hand, companies can be at risk of natural disasters or financial problems. Risks can endanger the existence of people as well as companies and for this reason insurance was created. The topic of this Bachelor work is Non-life Insurance {--} Contemporary Trends. The Bachelor work focuses on household insurance describes in detail its basic characteristics together with a comparison of this insurance product offered by two Czech insurance companies. It outlines advantages and disadvantages from the point view of potential clients. One section of the work is devoted to a comparison of household insurance offered by Allianz in the Czech Republic with the same product offered by the same insurance company in Slovakia.
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Health effects of ionizing and non-ionizing radiation
Gottvald, Martin ; Neoral, Jiří (referee) ; Bača, Petr (advisor)
This diploma thesis deals with electromagnetic radiation in its frequency spectrum. It also divides radiation into ionizing and non-ionizing. The principle of its effects and possible health problems from radiation exposure are also described. Hygienic limits – the maximum allowable and reference values of non-ionizing radiation are analysed too. The thesis should prove that the things of everyday need do not threaten the lives of human beings and are in compliance with the regulation No. 1/2008 Sb. on Health Protection Against Non-Ionizing Radiation. Measurement of low-frequency part is carried out with the cooperation of The National Institute of Public Health. Measurement of high-frequency part was carried out in 3 flats. The aim of this measurement was to find out the change of power density with the moving in a flat and the influence of the barriers (in this case walls).
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Study of volatile hydrocarbon decomposition in non-thermal plasma of gliding arc at atmospheric pressure
Töröková, Lucie ; Rašková, Zuzana (referee) ; Kozáková, Zdenka (advisor)
Diploma thesis deals with gliding arc discharge in non-equilibrium plasma, its properties and usage for dissociation of volatile organic compounds. Plasma techniques create a perspective alternative to classical methods such as adsorption, biofilters, thermal processes, freezing and condensation. The method used for analysis of dissociation products is described in the theoretical part as well. Method is gas chromatography and it is combined with mass spectroscopy. The experimental part contains the overall description of GlidArc reactor where volatile organic compounds were dissociated. The volatile organic compound is brought into the reactor from the reservoir by carrier gas (nitrogen); synthetic air was used as working gas. The reactor is connected to the device for sampling. This device has several openings for sampling by SPME fibre method, sorption tubes method and a special opening for probe entry from the device Testo 350 M/XL, which enables instant analysis of low-molecular compounds. GC-MS was used for determination of high-molecular products of dissociation. Products sorbed on SPME fibres were analysed directly, compounds sorbed by active carbon were extracted by carbon disulphide. Samples obtained using SPME fibres were analysed. The major products of the dissociaton were found due to this analysis, those major products are in the case of hexane: pentanal, 4 methyl-3-pentanal, 2-butoxy-ethanol, pentane a 2-hexene. Major products detected when dissociating cyclohexane were: l,3-dimethyl-butane, propanal, cyklohexanone, 5-hexenal a 2-pentyn-1-ol. Major products of xylene dissociation were methyl-benzene, benzaldehyde, 4-methyl-benzaldehyde, 1-nitroethyl-benzene a benzenmethanol. After analysis obtained using sorption tubes showed that mainly the dissociated compound was sorbed, but the products of the dissociation were presented in too low concentration for an adequate analysis. For that reason the sorption tubes were used only for quantitative determination of the compounds depending on the power supply. The dependence of the dissociation of the compounds on the power supply was observed using SPME fibres which were used for quantitative determination. The Results obtained by both obtained techniques were almost in accordance. Speaking of low-molecular compounds, dissociation of all compounds gave the same products, i.e. carbon dioxide, hydrogen, nitrogen oxide, nitrogen dioxide and water. The results show that the dissociation of VOC gives - besides many potentially dangerous dissociation products - significant amounts of nitrogen oxides which is harmful to the environment. Hence it is necessary to be concerned with problems studied in the future mainly with respect to limitation of NOx generation. It will be possible to optimalize the conditions of the VOC dissociation on the basis of future kinetic analysis.
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Alien fish species in the Odra basin on Moravien and Silesian
Lojkásek, B. ; Lusk, Stanislav ; Papoušek, Ivo
In the territory of Moravian and Silesian, the upper part of basin of the River Odra is found, where the riverine net is formed by smaller streams. The original ichthyofauna species structure is therefore, relative poor, representing 2 lamprey and 33 fish species, from which at present, 1 lamprey and 3 fish species are considered to be extinct. During the 19th and 20th centuries within human activities, 8 alien exotic species were introduced and 5 non-native species for this area were dislocated. All introduced and dislocated species are subject to fishery management. Regards to the fact that the species Carassius carassius and Pseudorasbora parva reproduce naturally, their relationships and influence are negative to the native species, they are assessed as invasive alien species.
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Non-destructive methods of control of welded joints
Černický, Martin ; Šlais, Miroslav (referee) ; Dohnal, Ivo (advisor)
The thesis elaborated in frame of bachelor studies branch mechanical engineering. The thesis is submitting research of present methods of non-destructive control of welded joints. Pursuant to of the literary pursuit the present methods of control of welded joints were written. First it mentioned problematics of defect of welded joints. After it is mentioned a summary of principles and application of methods of non-destructive control of welded joints.
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