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The Suggestion Small Water Resources
Knápek, Michal ; Mastný, Petr (referee) ; Matoušek, Antonín (advisor)
This Bachelor’s paper deals with design of a micro hydro power plant. First, a suitable location for the plant is chosen. Second, technology for the plant, along with technical equipment and enginery, is proposed. Third, electrical part of the project, including power feeding into the grid, is proposed. Last, economical projection of costs and benefits of the plant is calculated.
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Design of Home Theater
Knápek, Michal ; Buganská, Tamara (referee) ; Křenek, Ladislav (advisor)
The main aim of my bachelor´s thesis is to find new approaches and new ergonomic, technical and esthetic solutions which satisfy the latest requirements for domestic devices of today. The result should be a design that is modern in appearance and technology should also show a new direction for the design of home theater could take. Another aim is also to fulfill psychological and social function and in order to appeal more to the public and suspended to its beauty.
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The assessment of advantages of construction of large hydroelectric power plants in the area of Cukrova bouda, district Sumperk
Knápek, Michal ; Kopřiva,, Miroslav (referee) ; Mastný, Petr (advisor)
The subject matter of the master´s thesis is, in particular, an evaluation of the advantageousness of the construction of a pumped-storage hydroelectric power station in the vicinity of Cukrová Bouda. In the master´s thesis introduction the utilisation of pumped-storage hydroelectric power stations in providing reserve power generation to the operator of a power transmission system is discussed. The thesis then focuses on a technical design solution where two alternatives are drawn up for which the nominal parameters of individual designs for a pumped-storage hydroelectric power station are specified. The following part deals with the impact of the structure and the plant’s subsequent operation on the environment. A further key part is the determination of investment and subsequent operating costs and an evaluation of the plant according to economic pointers. The final part of the master´s thesis contains a SWOT analysis and an assumed programme of works for the plant’s preparation and actual construction. The conclusion contains an overall evaluation.
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Experimental study of the deformation mechanisms in cobalt by advanced in-situ techniques
Greš, Adam ; Knapek, Michal (advisor) ; Mathis, Kristián (referee)
The behaviour of pure polycrystalline cobalt in compressive deformation is influenced by the presence of high temperature fcc phase. To investigate this influence samples are prepared using annealing at different temperatures (600 řC- 1100 řC) with ≈ 6-10% of residual fcc phase. Additional sets of samples are also subjected to thermal cycling around the phase transformation temperature for ten or twenty cycles with the goal of stabilising the microstructure and creating material with no fcc fraction. Samples are tested in compression and a decrease in ductility and strength is observed after the the fcc phase is removed using thermal cycling. The interrupted deformation experiment shows that the transformation is rather sluggish and the main contribution of fcc grains to deformation is their ability to accommodate shape change. The presence of 71ř boundaries also sug- gests that the transformation is not fully stabilised and further thermal cycling could lead to further evolution of microstructure. Additionally the slow transfor- mation does not seem to produce detectable acoustic emission (AE) signal. The energies of AE events (recorded mostly around the yield point) follow a power law distribution. This is in line with recent investigations of the collective nature of dislocation motion and the...
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Study of cooperative dislocation phenomena in solids by the acoustic emission technique
Knapek, Michal ; Chmelík, František (advisor) ; Haušild, Petr (referee) ; Landa, Michal (referee)
Title: Study of cooperative dislocation phenomena in solids by the acoustic emis- sion technique Author: Michal KNAPEK Department: Department of Physics of Materials Supervisor: doc. RNDr. František Chmelík, CSc., Department of Physics of Materials Abstract: Plastic deformation of micron-scale crystalline materials differs con- siderably from bulk specimens, as it is characterized by random strain bursts. Three categories of metallic samples were investigated in this thesis: micron- scale copper micropillars with varied geometries, submillimeter-scale aluminum microwires, and aluminum and aluminum-magnesium salt-replicated foams. Very precise fabrication methods and sensitive measurement set-ups consisting of uni- axial compression and tensile tests with concurrent acoustic emission (AE) record- ing were developed. These fine methods allowed for investigations of effects re- lated to plastic deformation at micrometer scales, i.e. the dislocation dynamics associated with the stress drops. Size effects in plastic deformation, as well as clear correlations between the stress drops and the AE events, were found in mi- crosamples, confirming that dislocation avalanches are indeed responsible for the stochastic character of deformation processes also at microscales. Open-cell pure aluminum and aluminum-magnesium...
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Mechanical and thermophysical properties of illite-based ceramic materials.
Kušnír, Jakub ; Knapek, Michal (advisor) ; Chmelík, František (referee)
Title: Mechanical and thermophysical properties of illite-based ceramic materials. Author: Jakub Kušnír Department: Department of Physics of Materials Supervisor: RNDr. Michal Knapek, Ph.D, Department of Physics of Materials Abstract: This work examines high purity illite-based ceramic material (illite) with varying porosity, illite with fly-ash addition and textured illite- and kaolin-based ceramics. Investigated illitic clay originated from the Tokaj region in Hungary and contained 84 wt.% of illite. Kaolinitic clay (Sedlecký Kaolin Inc.) contained 88-94 wt.% of kaolinite. Samples were prepared using different heating regimes based on the type of material, with maximum firing temperature of 1100 řC. The porosity was controlled by adding charcoal powder to the green body before firing. Fly-ash waste from the combustion of powdered oil shale from Estonia was used as another additive. The microstructure of samples was analyzed by scanning electron microscopy. Mechanical properties were studied by compression tests with concurrent application of advanced investigation methods: Acoustic emission (AE) and Digital image correlation. By means of thermal analyses and AE we also investigated the frost resistance of samples with porosity created by charcoal combustion. Keywords: illite; kaolinite; ceramics;...
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Study of cooperative dislocation phenomena in solids by the acoustic emission technique
Knapek, Michal ; Chmelík, František (advisor)
Title: Study of cooperative dislocation phenomena in solids by the acoustic emis- sion technique Author: Michal KNAPEK Department: Department of Physics of Materials Supervisor: doc. RNDr. František Chmelík, CSc., Department of Physics of Materials Abstract: Plastic deformation of micron-scale crystalline materials differs con- siderably from bulk specimens, as it is characterized by random strain bursts. Three categories of metallic samples were investigated in this thesis: micron- scale copper micropillars with varied geometries, submillimeter-scale aluminum microwires, and aluminum and aluminum-magnesium salt-replicated foams. Very precise fabrication methods and sensitive measurement set-ups consisting of uni- axial compression and tensile tests with concurrent acoustic emission (AE) record- ing were developed. These fine methods allowed for investigations of effects re- lated to plastic deformation at micrometer scales, i.e. the dislocation dynamics associated with the stress drops. Size effects in plastic deformation, as well as clear correlations between the stress drops and the AE events, were found in mi- crosamples, confirming that dislocation avalanches are indeed responsible for the stochastic character of deformation processes also at microscales. Open-cell pure aluminum and aluminum-magnesium...
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Investigation of deformation mechanisms in textured magnesium alloy
Dittrich, J. ; Čapek, J. ; Knapek, Michal ; Minárik, P.
Advanced in-situ and ex-situ methods were used to reveal active deformation mechanisms during deformation of magnesium alloy with a strong texture. Three sets of samples were prepared from the rolled sheet of commercial AZ31 alloy with respect to its strong basal texture - normal direction (ND), rolling direction (RD) and 45 degrees between RD and ND, and were deformed in both compression and tension. The signal of acoustic emission (AE) was measured concurrently during the deformation. Electron backscattered diffraction (EBSD) was used to study the microstructure after the selected stages of the deformation. It is shown that the extension twinning played an important role during the plastic deformation in the samples having favorably oriented basal texture component, whereas in the unfavorably oriented samples, the role of twinning was marginal. Pronounced activation of twinning only in some samples caused a considerable variation in the deformation behavior and AE response. A consistent link between the energy and amplitudes of the AE signal and the microstructure changes investigated by EBSD was established.
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Mechanical properties of WN43 magnesium alloy prepared by spark plasma sintering
Knapek, Michal ; Minárik, P. ; Greš, A. ; Zemková, M. ; Cinert, Jakub ; Král, R.
The spark plasma sintering (SPS) method was used to prepare bulk materials form WN43 magnesium alloy atomized powder. Compression tests were carried out in order to investigate the effect of different sintering regimes (10 min at 400, 450, or 500 degrees C) on the mechanical properties of the material. Furthermore, complementary in-situ acoustic emission (AE) recording was employed to reveal the dynamics of deformation processes during compression. It was shown that by increasing the sintering temperature, the ultimate compressive strength and ductility were significantly improved. The AE data and microstructure observations suggest that pronounced twin nucleation takes place around the yield point whereas twin growth and dislocation activity are the dominant deformation mechanisms in the later stages of deformation.
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Effect of aluminum content and precipitation on the corrosion behavior and acoustic emission response of AZ31 and AZ80 magnesium alloys
Veverková, E. ; Knapek, Michal ; Minárik, P.
In this study, we investigated the effect of aluminum content and precipitation on the corrosion behavior of the AZ31 and AZ80 magnesium alloys. The investigated alloys were received in the as-extruded condition in order to retain comparable grain size and texture. First, solid solution treatment was performed on the samples of both alloys. Subsequently, the samples were isothermally aged at 200 degrees C for 20 hours. The scanning electron microscopy was used to study the grain size and microstructure. The corrosion properties of samples were studied by potentiodynamic polarization measurements and the AE signal was concurrently recorded. Solution treated AZ80 and AZ31 samples exhibited similar behavior. The aged AZ80 sample showed lower corrosion rate. Also, a strong breakdown appeared in the later (compared to other samples) stage of the potentiodynamic test. The breakdown was found to be easily recognized by AE parameters.
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