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The limits of movement and quantification of bedload amount for gravel-bed rivers
Roušar, Ladislav ; Matoušek, Václav (referee) ; Tůma, Antonín (referee) ; Veselý, Jaroslav (advisor)
Doctoral thesis in detail and comprehensively deals with mechanic of incipient bedload motion for gravel-bed rivers. This study based on theoretical knowledge, experimental researches, numerical models and field survey extends present knowledge concerning with incipient bedload motion and sediment transport at small relative height and hydraulically rough surface bed for turbulent unaerated free surface flow. Incipient bedload motion and sediment transport have been determined for homogeneous and inhomogeneous bed materials. For homogeneous bed material the velocity profiles have been described by different methods in near the bed. Further, hydraulic flow resistance has been evaluated. In the case of inhomogeneous bed material, static armouring and influence of surface layer sorting on hydraulic roughness have been investigated. The correctness of obtained knowledge has been confirmed on the object of nature-inspired river widening. Results shown, among others, that incipient bedload motion does not depend on relative height or final armouring of surface layer to what extend hydraulic roughness is influenced.
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Computational analysis of working roll surface layers in hot rolling
Luks, Tomáš ; Hajduk,, Daniel (referee) ; Pohanka, Michal (advisor)
This thesis is dealing with an analysis of thermal and mechanical loads on a work-roll. First, hot rolling focused on work-roll is described in general. A theoretical analysis of roll loads and the mechanisms affecting roll durability are presented here. The thesis is concentrated on creation of a model in FEM program ANSYS. The final model is loaded with different rolling schemes and monitored stresses in a surface layer. The parameters obtained from the measurements performed in a rolling mill are applied as boundary conditions within the model.
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Change in the durability of concrete made of recycled concrete by alternative addition of ceramic admixtures
Stavař, Tomáš ; Hoffmann, Oldřich (referee) ; Stehlík, Michal (advisor)
The master thesis dealing with problematic about durability of concrete, with use of recycled concrete and addition of silica additions. Predominant for resistance of concrete constructions is surface layer, through which aggressive gasses and liquids penetrate from surrounding environment. The most important indicator of concrete durability is ability of surface layer transmissions of aggressive substants. In experimental part will be defined the actual state of surface layer by normal testing methods. The transmissions of surface layer will be tested on concrete cubes. Tests for transmissions of air (method TORRENT), of water (method ISAT), of acid gases (dept of carbonation by quick test in 98% CO2) will be carried out and also strength tests. Assessment of positive or negative influence of additions and amount of cement on durability and mechanical properties of concrete will be discussed in conclusion.
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Study of bioceramic materials on the base of calcium phosphates
Kolář, Martin ; Maca, Karel (referee) ; Cihlář, Jaroslav (advisor)
The literature search on the topic of Bioceramic materials focused in layered materials based on calcium phosphates was written up. Based on knowledge obtained, experiments of preparation of calcium phosphates layered materials based on calcium phosphates by spin-coating method focused in optimalization of layer application conditions were designed and carried out. Experiments of preparation of hydroxyapatite bulk ceramics by uniaxial pressing followed by heat treatment were also performed. Prepared layered and bulk ceramics were characterized from bioactivity point of view by testing of their interaction with simulated body fluid.
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Analysis of the surface layer of the brake disk
Švábenská, Eva ; Roupcová, Pavla ; Podstranská, Ivana ; Petr, M. ; Filip, J. ; Schneeweiss, Oldřich
Our research is focused on the changes in thin surface layer of the brake disk due to the impact of severe plastic deformation and heating by friction process. The aim of this study is to compare structure, chemical and phase compositions of the surface layer in depth up to several hundreds of nanometers in the no affected central part of brake disk and the part which was in contact with brake pads by braking. The basic information on structure and phase composition was obtained by optical and scanning electron microscopy, X-Ray Powder Diffraction and Mössbauer Spectroscopy. The thin surface layer was studied using Conversion Electron Mössbauer Spectroscopy and X-ray Photoelectron Spectroscopy. We explain the observed changes with the knowledge on effects of plastic deformation and/or diffusion of alloying elements in the material of the brake disk.
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