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Investigation of composite material degradation indicators using acoustic measurement: comparison with laser vibrometry
Fíla, Tomáš ; Urushadze, Shota ; Kytýř, Daniel ; Valach, Jaroslav ; Šperl, Martin
This paper deals with investigation of acoustic material degradation indicator (attenuation decrement drop of selected natural frequency) measured by a custom-built experimental device. Samples of C/PPS fibre composite material were analyzed. Acoustic signals were recorded and processed using spectral analysis and sound signal regression. Data measured by this method were verified by comparative experiment. Specimens were simultaneously measured using both acoustic experimental device and laser vibrometer. Modal analysis of the specimen were carried out prior to the experiment. This enabled assessment of specimens natural modes and therefore the best impact zone. In total, 10 measurements were performed for each specimen at the same level of degradation. Measured data were then processed and compared. The specimens were repetitively measured after designated number of loading cycles.
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Sustainable tourism development of Vysocina Region
Veselá, Markéta ; Macháček, Jaroslav (advisor) ; Vondráková, Zuzana (referee)
The diploma thesis deals with the topic of sustainable tourism development at the regional level. This phenomenon is elaborated on the example of Vysocina Region. To evaluate sustainability of its development, the potential of this touristic destination is researched regarding various areas, including key products. These are subjected to comparisons with recommendations of significant tourism organization for the purpose of assessing the sustainability of tourism. The diploma thesis also includes a comparison with other Czech regions experience as a touristic destination. Vysocina Region has favourable initial conditions for its sustainable development, especially regarding supply of key products, which include both environmentally friendly goods and cultural attractiveness contributing to the personal development of individuals and promoting intercultural tolerance. The main issue appears to be the spatial imbalance of its development in the region, caused mainly by the concentration of tourist activities to certain areas and low local initiative in the less attractive areas. The diploma thesis proposes a number of solutions, such as utilization of geocaching and products of gastroturism, supporting the foundation of local destination management organisations, promoting cycling tourism and the foundation of highly visited tourist destinations.
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Small mammals in diet of barn owl in the Eastern Meditarranean
Šindelář, Jiří ; Horáček, Ivan (advisor) ; Anděra, Miloš (referee)
The extensive material of skeletal remains of mammals from a diet of barn owl in the eastern Mediterranean has been processed and evaluated with different techniques of chorological and morphometric analysis. At least 8400 individuals of 45 species of insectivores, rodents and bats were found in our total collection of samples, which represents a significant portion of fauna of the region. We have evaluated a chorological composition of the taphocoenoses and the interregional differences, manifested primarily by differences in the representation of satellite and accessory elements. We found a highly significant impoverishment of the isolated island taphocenoses (Cyprus, Karpathos, partly on Crete), where Cricetidae, Arvicolidae, C. leucodon etc. are missing. On the other hand the essential part of the dominance structure takes up the Rattus rattus, which acts here as an invasive species, significantly more successful than in the ragged continental contexts. The species diversity of the examined samples is positively correlated with the geographic latitude (taphocenoses of the northern regions are significantly richer) and negatively with the island effect and the degree of aridization. The morphometric analysis of the three most abundant species of Soricidae within the studied region showed...
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The stability of biologically active compounds in elderberry (Sambucus nigra L.) inflorescence during processing
SUCHÁ, Renata
This thesis examines the stability of rutin in the inflorescences of the elder during processing. Elder (Sambucus nigra L.) is a medicinal plant that was used for medical purposes as early as in the Middle Ages. Both flowers (Flos Sambuci) and fruit (Fructus Sambuci) of the elder are on the list of official medicinal products of the State Institute for Drug Control. The main active phenolic substance is flavonoid rutin. Flavonoids are phenolic substances of plant origin. Among the best known properties of these substances is their antioxidant activity. They protect the low density blood lipoproteins from the oxidation modifications that cause the development of arteriosclerosis and hypertension. As a medical plant, the elder is used especially for the preparation of a medicinal drink. It is also commonly used as a material for the preparation of syrup. This product serves as a basis for a refreshing and tasty drink and lately is has also started to be sold in shops. For comparison, five single-flower syrups from the elderflower by different producers were bought. A method of preparation of the elderflower syrup was devised, based in one case on frozen elder inflorescences and in the other on dried inflorescences. The plant material came from wildly growing shrubs and it was collected in June 2013. Altogether, 8 syrups were prepared in the laboratory, 4 of them from fresh material and 4 from dried material. Two different methods were used. The first one was based on extraction using sugar solution, the second one on extraction using water solution where sugar was added afterwards. Another added substance was ethanol. The method for measuring the amount of rutin in the samples was a combination of two extraction steps. The first step was the usual exraction using aqueous methanol and the second step was extraction using a solid sorbent (SPE). The analysis of fresh and dried material concluded that dried elderflowers contain many times more rutin than fresh elder. Among the commercially produced syrups, the "Kitl Syrob Bezový" contained most rutin; a little less rutin was found in "Hamé Bylinný sirup Bezový květ". The concentration of rutin in the syrups prepared in the laboratory was much higher than in the commercial products. By using different methods of syrup preparation and their subsequent analysis, it was found that the syrups prepared from the dried inflorescences contained a higher amount of rutin than the syrups produced in the same way, but from frozen material. Addition of a small amount of ethanol had no effect on extraction of rutin from inflorescences. Free quercetin, which indicate a decomposition of rutin, wasn´t found in any of produced syrups. The produced syrups were used for the preparation of a drink and then underwent sensory analysis. The paired two-sided preference test included pairs of drinks consisting of a fresh elder drink and dried elder drink. The results showed that the evaluators preferred syrups from dried elderflowers in two of the cases, while in the other two evaluated pairs, the results were not statistically significant. In all cases, the evaluators most often found small and middle differences. The gained results show that the best method of syrup preparation uses dried plant material and sucrose solution as the extraction agent. The syrup prepared in this way contained most rutin and at the same time showed the smallest losses of this substance, which is beneficial to human health. Furthermore, it also tasted better in comparison with syrup prepared in the same way, but from fresh material.
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Optimalization of material flow in automotive industry
Kolář, Tomáš ; Jirsák, Petr (advisor) ; Vinš, Marek (referee)
This master thesis is focussed on optimalization of material flow in an automotive company. First part introduce theoretical background. Automotive industry and its actual trends on global markets. Follows short introduction of the company where project of this thesis was executed. Main theoretical part describes concept of lean management, its tools in practical examples, but it is also focussed on philosophical approach to the work and mindset of the company. Follows the aplication part based on theoretical background. The whole project of this master thesis is focussed on specific area called PC store. At first this area is showed in context of overall material flow. Shortly there are introduced processes and areas where full material packaging flows. Follows deeper analysis and optimalization of PC store itself. There are three approaches of stock and lead time reduction applied. Last part shows the comparison of initial and future state including performed changes.
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INFLUENCE OF LASER CUTTING AND PUNCHING ON MAGNETIC PROPERTIES\nOF ELECTRICAL STEEL M470-50A
Bulín, Tomáš ; Švábenská, Eva ; Hapla, Miroslav ; Ondrůšek, Č. ; Schneeweiss, Oldřich
Electrical steel M470-50A belongs to the most often used materials in electrical machines. Due to this fact, it is desirable to know the magnetic parameters after processing raw sheets into the required shape. Basic parameters of mechanical, electrical, and magnetic properties of the sheets are usually obtained from the producer but the magnetic properties are changing in dependence on additional machining processes. The aim of this study is to describe changes in parameters of magnetic behavior after punching, laser and spark cutting of the original sheets. The basic information of structure was obtained by optical and scanning electron microscopy. The magnetic parameters were acquired from the measuring of magnetic hysteresis loops in dependence on saturation fields and frequencies. The results are discussed from the point of view of applied\ncutting technology with the aim to obtain the best magnetic parameters and consequently a higher efficiency of the final product. Results can be used as input parameters in simulation of the electrical machine.
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STRAIN ENGINEERING OF THE ELECTRONIC STRUCTURE OF 2D MATERIALS
del Corro, Elena ; Peňa-Alvarez, M. ; Morales-García, A. ; Bouša, Milan ; Řáhová, Jaroslava ; Kavan, Ladislav ; Kalbáč, Martin ; Frank, Otakar
The research on graphene has attracted much attention since its first successful preparation in 2004. It possesses many unique properties, such as an extreme stiffness and strength, high electron mobility, ballistic transport even at room temperature, superior thermal conductivity and many others. The affection for graphene was followed swiftly by a keen interest in other two dimensional materials like transition metal dichalcogenides. As has been predicted and in part proven experimentally, the electronic properties of these materials can be modified by various means. The most common ones include covalent or non-covalent chemistry, electrochemical, gate or atomic doping, or quantum confinement. None of these methods has proven universal enough in terms of the devices' characteristics or scalability. However, another approach is known mechanical strain/stress, but experiments in that direction are scarce, in spite of their high promises.\nThe primary challenge consists in the understanding of the mechanical properties of 2D materials and in the ability to quantify the lattice deformation. Several techniques can be then used to apply strain to the specimens and thus to induce changes in their electronic structure. We will review their basic concepts and some of the examples so far documented experimentally and/or theoretically.
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ELECTRON BEAM REMELTING OF PLASMA SPRAYED ALUMINA COATINGS
Matějíček, Jiří ; Veverka, J. ; Čížek, J. ; Kouřil, J.
Plasma sprayed alumina coatings find numerous applications in various fields, where they enhance the properties of the base material. Examples include thermal barriers, wear resistance, electrical insulation, and diffusion and corrosion barriers. A typical structure of plasma sprayed coatings, containing a multitude of voids and imperfectly bonded interfaces, gives them unique properties - particularly low thermal conductivity, high strain tolerance, etc. However, for certain applications such as permeation barriers or wear resistance, these voids may be detrimental.\nThis paper reports on the first experiments with remelting of plasma sprayed alumina coatings by electron beam technology, with the purpose of densifying the coatings and thereby eliminating the voids. Throughout the study, several parameters of the e-beam device were varied - beam current, traverse velocity and number of passes. The treated coatings were observed by light and electron microscopy and the thickness, structure and surface morphology of the remelted layer were determined and correlated with the process parameters. Based on the first series of experiments, the e-beam settings leading to dense and smooth remelted layer of sufficient thickness were obtained. In this layer, a change of phase composition and a marked increase in hardness were observed.\n
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