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Study of xenobiotics and biologically active compounds degradation on titanium dioxide
Píšťková, Veronika ; Lisá,, Hana (referee) ; Vávrová, Milada (advisor)
Heterogenous photocatalysis using titanium dioxide seems to be a promising method for disposal xenobiotics from the environment. The aim of this diploma thesis is the study of degradation of selected xenobiotics and biologically active substrances applying this method. Theoretical part of diploma thesis deals with the principals of heterogenous photocatalysis by means of a semiconductor TiO2 and the examples of its possible application are mentioned too. The compounds which could be appropriate for a study of degradation were selected from the group of pharmaceuticals and pesticides. The properties of target substances and their environmental impact were described. Furthermore, a bibliographic search focused on the possibilities of their analytical determination was conducted. The experimental part of the thesis describes the experiments with photocatalyst in a form of powder as well as with immobilized photocatalyst in thin layer on a carrier. Identification and quantification of analytes was realized by high performance liquid chromatography with mass spectrometic detection.
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Stochastic analysis of shear failure of reinforced concrete beams
Kucek, Martin ; Doležel, Jiří (referee) ; Novák, Drahomír (advisor)
The diploma thesis is focused on a solution of the load reaction of the bridge construction from girders KA-73. Proposal methods of the nonlinear analysis by means of final elements on the stochastic and deterministic level are used for the solution of the load reaction. A simulation technique Latin Hypercube Sampling is used within the stochastic analysis. A material degradation in the form of the trussing corrosion is solved with the expected decrease of the construction lifetime. The conclusion of the thesis contains an evaluation of initial quantities of material parameters for the load reaction of the construction in the form of the sensitivity analysis.
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Possibilities of pesticide degradation by titanium dioxide
Píšťková, Veronika ; Veselý, Michal (referee) ; Vávrová, Milada (advisor)
The aim of this bachelor´s thesis is a selection of pesticides, which could be degradated using titanium dioxide. The first part of the paper deals with general pesticide characteristics, subdivision of pesticides, mode of action on target agents and transformations of pesticides within the environment – the metabolic and the non-metabolic tranformation. The second part of the paper deals with heterogeneous photocatalysis using semiconductor TiO2, which is activated by ultraviolet or solar radiation. Using this method pesticides could be transformed even into carbon dioxide, water and inorganic mineral salts. Furthermore, there are mentioned the factors, which affect degradation rate, analytical methods to determine kinetics of degradation and methods for monitoring transients and end products. By each group of pesticides there are stated the representatives from this group, which have been used for investigation of degradation methods. Furthermore are mentioned decomposition mechanisms of reaction and the intermediate products formed during the photocatalysis process.
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Study of degradation of biocompatible copolymers
Oborná, Jana ; Čáslavský, Josef (referee) ; Vávrová, Milada (advisor)
This diploma thesis is focused on biocompatible polymers degradation study. Copolymers were studied based on poly(lactic-co-glycolic) acid and poly(ethylene glycol) PLGA-PEG-PLGA and further these copolymers modified with itaconic acid ITA-PLGA-PEG-PLGA-ITA. This paper investigated the influence of pH phosphate solution on the degradation of polymers. Degradation of polymers occurred at 37 °C in phosphate solution with pH 4.2, 7.4 and 9.2. High performance liquid chromatography with UV-VIS detection of diode-array type was used for quantitative determination of lactic acid and glycolic acid as the final degradation products. For qualitative identification of additional degradation products were used tandem connection liquid chromatography and mass spectrometry. Gel permeation chromatography with refractive index detector was used to determine the molecular weight decrease polymer chain after the degradation.
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Thermal degradation of alternative electrical insulating liquids
Vodička, Tomáš ; Kazelle, Jiří (referee) ; Frk, Martin (advisor)
This thesis deals with alternative thermal degradation of electrical insulating liquids. The theoretical part describes the current state of the problem, electrical insulating liquids, their classification and types. There are described properties of electrical insulating liquids, their models of aging and diagnostic methods in accordance with the appropriate standards. In the practical part are chosen by representatives of alternative electrical insulating liquids and there are determined their dielectric characteristics in the initial state. According to the measured values is chosen five candidates for which it is designed and implemented an accelerated degradation test. During the test are measured dielectric parameters of the selected oils. Measured dependencies are mathematically approximated. In conclusion, the results are compared and physically interpreted in view of oxidation stability.
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Impact of Biomass Storing on Heating Value
Černý, Michal ; Špiláček, Michal (referee) ; Lisý, Martin (advisor)
The main aim of my bachelor´s work is the experimental verification of the landfill impact on the parameters biomass. The first part deals with definition, the formation of a basic biomass division. In the next section we find the issues concerning the burning, fuel composition and emissions during combustion. The last part deals with the influence of climatic conditions on the biomass degradation. In the experimental part were measured calorific calorimeter. The result was that, after a measured period of five months to avoid significant degradation of the fuel.
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Operational Parameters of LED and their Modelling
Pavelka, Tomáš ; Novák,, Tomáš (referee) ; Gašparovský, Dionýz (referee) ; Baxant, Petr (advisor)
Doctoral thesis deals with parameters of LED light sources and their static and dynamic changes due to variable operational conditions. Firstly there is briefly described the history of light emitting diodes, that brought LED from unintentional observation of luminescence to light source, which is generally used through the whole area of lighting techniques. Thesis focuses on light parameters analysis, which are specific for semiconductor light sources and their mutual relations. These relations in compliance with understanding the principles of light emission in semiconductor light sources enable establishing of basic connections and effects usable for LED behaviour model. Mutual relations of LED parameters and influencing factors are verified by measurement of chosen testing samples. For deeper understanding of diode parameter influencing mechanisms there are analysed current degradation models including degradation of partial components. On the basis of these facts there is created a model of LED luminaire operating with LED parameters together with cooling system that represent the integral part of the luminaire. Impact of supply drivers is also studied, because they are necessary for LED operation. Designed model supports the area of static changes of light parameters, as well as the dynamic changes of output parameters. Presented model is verified by testing measurements at basic operational states and partially outside of the common operational limits. There are also presented the possibilities of real use of the model that involve the evaluation of designed luminaire for specific light sources, searching for optimal operational limits, optimization of luminaire heatsink or using public lighting systems for regulation of electricity grid load fluctuations.
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Weathering and accelerated aging of high density polyethylene mixtures with regranulate
Bruzl, Dominik ; Tocháček, Jiří (referee) ; Bálková, Radka (advisor)
This master thesis deals with the effect of multiple extrusion (1, 2, 3) and the addition of 30, 60 and 90 % of this recycled material on the weathering and accelerated ageing of high density polyethylene (HDPE) copolymer. The weathering lasted 9 months and the accelerated ageing 1000 h at 65 °C. The degree of material degradation was assessed from changes in mechanical and physical properties and compositional changes using dynamic mechanical analysis and tensile testing, differential compensation calorimetry, thermogravimetric analysis and infrared spectrometry in the full attenuated reflection mode. The measurements showed that repeated extrusion as well as the addition of recycle material to the original one (R0) slightly slows down the photo-oxidative degradation during first month, but after that it does not have a negative or significant positive effect on the progress and rate of overall material degradation. A certain exception was the recycled material after the 3rd extrusion (R3), where the original properties comparable to R0 did not change much during ageing. The mechanical properties of the blends were better or comparable to R0 during ageing, but after months 6 and 9 the breaking strength of most of them decreased substantially as a result of the shortening of the chains. Accelerated ageing caused significant embrittlement in all samples, resulting in a reduction in yield strength by about half and almost immediate failure.
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Study of Polycaprolactone Biodegradability
Chamradová, Ivana ; Omelková, Jiřina (referee) ; Voběrková, Stanislava (advisor)
Aliphatic polyesters represent a group of degradable polymeric materials. These materials found their utilization almost in biomedical applications and as packing materials. In the theoretical part, the literature review on enzymatic and microbial degradation research of poly(?-caprolactone)(PCL) is summarized . In the experimental part, the methodology of biodegradation testing of PCL was formed and a series of experiments with a Bacillus Subtilis and Aspergilus-Lipase was carried out. Polymeric samples of Mn = 19 300 the film form with 100 µm thickness and 1 cm diameter were subjected to enzymatic degradation. Samples with 3 cm diameter were exposed to microbial degradation by the "solution casting" method. Biodegradable process was interpreted on the basis of changes of the molecular weight, melting point, crystallinity and changes on the surface of polymeric materials.
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