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Kinematic and dynamic characterization of a spacecraft deployable antenna mechanism
Troup, Mirko ; Marcián, Petr (referee) ; Hrstka, Miroslav (advisor)
This bachelor's thesis deals with a detailed description of the mechanism of a deployable antenna using two different methods: the Kinetostatic method and the Lagrange method. The resulting systems of equations are numerically calculated in Python. With the same input values, the solution is 2 identical results, which confirm the possibility of solving the system by both methods. Based on the result, optimal parameters are designed to maintain the correct functionality of the mechanism, first under conditions on Earth, then in space. Under the influence of gravity, much greater demands are required for springs and dampers. The subsequent comparison of the methods indicates that the most suitable solution is their combination, where the Lagrange method is more efficient for determining the individual accelerations of bodies, on the other hand, the kinetostatic method must be used to determine the values of the binding forces.
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Stress analysis of a connecting shackle
Bodo, Ondrej ; Hrstka, Miroslav (referee) ; Vaverka, Jiří (advisor)
The bachelor thesis deals with the stress analysis of a selected real connecting shackle using an analytical model based on the beam theory. In the first part, the basic classification of the used types of shackles according to their shape, removable pin or used materials is presented. The following part briefly presents the mechanical theory of linear elastic bars and beams complemented by the theory of curved beams, on the basis of which two analytical models differing in the use of symmetry are developed in the practical part. In both cases of the analytical models, the results with or without the use of the theory of curved beams are also compared, thus proving its applicability. The analytical section also includes an analysis of one ear of the shackle. Finally, the results obtained by the analytical solution are verified by computational modelling using the finite element method in ANSYS Workbench 2023 R2 software, where, in addition to the verification of the model calculated in the analytical solution, a more realistically distributed loading of the shackle is also considered, together with the verification of the maximum stresses of the ear using 3D solid elements.
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On the stress distribution near the tip of a sharp notch
Ostratický, Jakub ; Hrstka, Miroslav (referee) ; Profant, Tomáš (advisor)
The notch is a stress concentrator from the point of view of elasticity theory and the knowledge of the description of this stress in the vicinity of its tip is necessary for the correct functionality of a wide range of mechanical components and products. The stress at the tip of the notch is singular and it is technically impossible to prevent the initiation of cracks in its vicinity. However, it is known from fracture mechanics that the initiation and propagation of cracks is not influenced by the magnitude of the stress at their tips, but its intensity characterized by the so-called stress intensity factor. In the case of a notch, it is a generalized stress intensity factor or simply the amplitudes of the singular parts of the stress filed. These coefficients cannot be determined directly from the results of widely used numerical methods such as FEM, but it is necessary to use linear fracture mechanics methods based on the asymptotic solution of the equilibrium equations in elasticity. The presented work deals with the case of a symmetric sharp notch in an isotropic material under the mode I or II loadings. The stress singularity and the related stress intensity factor at the notch tip are analysed and evaluated. The derived asymptotic solution is compared with the results obtained from the FEM analysis.
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Vitamin C
Juráňová, Jana ; Hrstka, Miroslav (referee) ; Vespalcová, Milena (advisor)
The theme of this diploma thesis is an assessment of given nutritional parameters in selected kinds of lesser known fruits, specifically 10 varieties of sea buckthorn (Hippophae rhamnoides L.), 12 varieties of cornelian cherry (Cornus mas L.) and 6 varieties of blue honeysuckle (Lonicera caerulea var. kamtschatica). Harvests of two consecutive years (2011 and 2012) were analyzed in the case of blue honeysuckle. The theoretical part was focused on historical, morphological, taxonomic and nutritional aspects of individual plants and food or pharmaceutical utilization. The considerable part of the thesis is devoted to the characterization and the possibilities of determining the contained substances, namely ascorbic acid and polyphenolic compounds, especially anthocyanins. The content of the experimental part was a description of the methods and the results of the analysis of total solids, titratable acidity, total phenolics, total anthocyanins and ascorbic acid in fruits of the selected varieties of the above mentioned fruit species. Based on the measured results, the different varieties of fruits were compared to each other and evaluated.
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Methods for assessment of body composition
Krátká, Veronika ; Hrstka, Miroslav (referee) ; Vránová, Dana (advisor)
This bachelor thesis deals with the composition of the human body and methods of its analysis. The theoretical part is focused on basic food nutrients, nutrition recommendations, energy needs of the organism, body composition and methods for determining body composition. The experimental part contains a comparison of two methods for determining body composition – a method of bioelectrical impedance and a method NIR-spectrometry. Other section is devoted to a study of the eating habits of group of students, consisting of evaluation of diets and the questionnaires.
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Effects of elevated atmospheric carbon dioxide and nitrogen supply on grain quality of wheat
Chadimová, Klára ; Babák, Libor (referee) ; Hrstka, Miroslav (advisor)
The aim of this study was to examine the effect of elevated atmospheric carbon dioxide concentration and different nitrogen fertilization levels on wheat grain quality. Winter wheat cultivar Bohemia was grown under ambient carbon dioxide concentration (AC) and elevated carbon dioxide concentration (EC; 700 mol carbon dioxide per mol) half of the samples was fertilized with 200 kg N per ha (N+) and the other part stayed unfertilized (N-). Zeleny value and Hagberg-Perten value was determined. Bulk density was determined by routine method. Grain hardness, dry matter content, starch concentration and crude protein concentration was determined by NIR spektroscopy. No effect on grain quality was detected due to carbon dioxide enrichment. However nitrogen fertilizer influenced grain quality significantly. Zeleny value and crude protein concentration were decreased and starch concentration was increased in samples that stayed unfertilized. Other grain quality parameters stayed unaffected.
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Comparison of the properties of chokeberry spreads of different origins, comparison and different production technologies
Kapiton, Ulyana ; Hrstka, Miroslav (referee) ; Vespalcová, Milena (advisor)
This diploma thesis deals with comparison of the properties of chokeberry spreads of different origins, composition and different production technologies. The theoretical part contains a brief description of the chokeberry – Aronia melanocarpa, an overview of the most important substances contained in the chokeberry and examples of the use of aronia, not only in the food industry. Furthermore, the legislative requirements for the production of spreads and the production technology itself are described. In this thesis is also described a new patented technology of spread production using HTD technology. Another part of the theoretical part is a literature review of the determination of anthocyanins in chokeberry by HPLC method. The experimental part describes the laboratory procedures used for determination of dry matter, carbohydrates by HPLC with ELSD detector, anthocyanin dyes, total phenolic compounds and antioxidant activity. Another part of the work was a questionnaire survey and sensory analysis of selected chokeberry spreads. The panel members prefered the Lowicz chokeberry spread, for which was determined 29,39% dry matter, 15,15 mg.g-1 anthocyanins, 9,20 mg.g-1 total phenolic compounds, 158,42 mg.g-1 fructose and 151,26 mg.g-1 glucose and the antioxidant activity was determined to be 5,94 mg.g-1.
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Content of rutin in selected elderberry cultivars
Píšťková, Magdalena ; Hrstka, Miroslav (referee) ; Vespalcová, Milena (advisor)
The aim of this diploma thesis was to determine the rutin content in springs and leaves of 19 elderberry species (Sambucus nigra L.) with use of liquid chromatography. Furthermore the rutin content was determined in its significant sources – rue and buckwheat. The observed values were compared in order to answer the question whether it is useful to use the elderberry spring and leaves as a new source of rutin. Theoretical part of the thesis describes elderberry in general, its chemical composition and its usage in medicine. Following part concentrates on important substances contained in elderberry – flavonoids. Also principles of extraction techniques and HPLC are discussed. In practice the rutin was gained from plant matrix with use of pressurized hot water extraction (PHWE) which was performed in three five minutes long cycles. Conditions during the PHWE were set up to 80 °C and 150 bars. Obtained extract was purified with use of SPE columns and analyzed by HPLC with DAD detector (wave length – 360 nm). HPLC was performed with SUPELCOSILTMLC-8DB column. The mobile phase was composed of MeOH, H2O, and HCOOH in ration of 36:61,5:2,5. The set up flow of mobile phase was 1 ml/min. In the leaves the highest rutin content was determined in Pregarten – 26,34 ± 0,50 mg/g. On the other hand the lowest rutin content in leaves was determined in Körsör – 3,74 ± 0,13 mg/g. In springs the obtained results were as follow. The highest content was determined in Samyl – 4,87 ± 0,01 mg/g and the lowest content was determined in Heidegg 13 springs – 0,56 ± 0,01 mg/g. Also the HPLC detection limit – 6,3 . 10-5 mg/ml and quantitation limit – 2,1 . 10-4 mg/ml were determined for rutin.
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Computation of a closed curved beam deformation
Dvořáček, Jan ; Krepl, Ondřej (referee) ; Hrstka, Miroslav (advisor)
Presented bachelor's thesis deals with a computation of a closed curved beam (ring) deformation with a U-shaped cross section. The thesis consists of four parts. In the first part a brief summary of theories used for analytical solution is given. Specifically energy approach and related straight and curved beam theories, Timoshenko beam theory and Euler-Bernoulli beam theory are listed. The second part contains a complete analytical solution of given problem for both straight and curved beam theories. In the third part a design of computation models and numerical solution is described. In the last part, obtained values are compared and reviewed.
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Biological effects of substances isolated from Isoptera species
Dušková, Simona ; Hrstka, Miroslav (referee) ; Brázda, Václav (advisor)
This thesis was focused on monitoring the viability of eukaryotic and prokaryotic cells after exposure of termites-isolated chemicals. Recently, evidence of antibacterial and antifungal properties of these defense substances has grown, and they can find a wide range of uses not only in the pharmaceutical industry. In this work, three defensive substances from termites were studied: nerolidol, nitropentadecene and methylanthranilate. Their antibacterial effects, minimal inhibitory concentrations and minimal bactericidal concentrations against Escherichia coli STBL3 strain were monitored. Further, their cytotoxic effects on eukaryotic non-tumor (HEK293FT) and tumor cells (MCF7) as well as their effect on plasmid DNA were studied. Antibiotic ampicillin and cytostatic cisplatin were used as control substances for antibacterial and cytotoxic effects, respectively. In the case of the action of nerolidol, nitropentadecene and methylanthranilate on the STBL3 strain, antibacterial activity was not demonstrated. Cytotoxic effects were observed nerolidol and nitropentadecene. None of the examined substances modified the plasmid DNA.
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