|
Simulation of the human vocal fold vibrations – sensitivity to the material parameters
Vampola, T. ; Horáček, Jaromír ; Klepáček, I.
A 3D finite element (FE) fully parametric model of the human larynx was developed and used for numerical simulation of vocal folds vibrations excited by a prescribed intraglottal aerodynamic pressure. The complex model consists of the arytenoid, thyroid and cricoid cartilages. The vocal fold tissue is modelled as a three layered orthotropic material and the FE contact elements are used for modelling the vocal folds collisions. The principal and shear stresses on the surface the vocal fold tissue are computed in time domain.
|
|
Deskripce zubní úrazovosti u chlapců staršího školního věku v mikroregionu České Budějovice a návrh zdravotně edukačního materiálu.
TOBOLKOVÁ, Andrea
Diplomová práce se zabývá problematikou zubní úrazovosti u chlapců staršího školního věku v mikroregionu České Budějovice. Úraz znamená náhlé poškození zdraví působením vnějších faktorů o síle přesahující adaptační možnosti lidského organismu. V oblasti zubní úrazovosti jsou nejvíce ohroženou skupinou populace děti. Nejčastějším důvodem úrazu malých dětí je jejich nedokonalá stabilita. V případě starších dětí a mládeže převažují úrazy vzniklé vlivem sportu. Teoretická část diplomové práce je zaměřena na vymezení období staršího školního věku, dále pak na anatomii a fyziologii chrupu. Součástí práce je i výčet zubních úrazů a jejich následná léčba. Pozornost také patří protetické stomatologii a vlivu úrazů na fyzické a psychické zdraví jedince. V závěru teoretické části je uveden postup při vyšetření zraněného, poúrazová dentální hygiena a výživa pacienta po úrazu zubů. Výzkumná část práce zjišťuje pomocí dotazníkového šetření druhy úrazů zubů, okolnosti vzniku úrazů a vliv úrazů na fyzické a psychické zdraví jedinců dané věkové kategorie. Dotazníkové šetření bylo vyhodnoceno a následně zpracováno v grafické části práce. Součástí diplomové práce je i zdravotně edukační materiál, který slouží ke zkvalitnění dentální hygieny a k prevenci vzniku zubních úrazů u žáků 2. stupně základní školy.
|
| |
|
HYDROGENATION PROPERTIES OF BALL-MILLED Mg-Ti-C-Zr COMPOSITE
Král, Lubomír ; Čermák, Jiří ; Roupcová, Pavla
The hydrogen storage properties of ball-milled Mg-Ti-Zr-C composite (1.8 wt.% Ti, 1.9 wt.% Zr and 0.2 wt.% C) were investigated. It has been previously shown, that the addition of Ti, Zr and C improved its storage properties. This beneficial effect of additives upon hydrogen storage properties can be explained by catalysis by the particles rich in Ti or Zr located on the surface of Mg grains. They provide effective pathways for the hydrogen diffusion into the MgH2. The morphological and microstructural characteristics were investigated by scanning electron microscopy and by X-ray diffraction. The hydrogen sorption was measured by Sieverts method using Setaram PCT-Pro device. In this paper, sorption behaviour of the composite after ball-milling and after aging on the air was compared. The ball-milled composite adsorbed 3.5 wt.% H2 within 10 min at 623 K. However, hydrogen storage capacity of the composite aged on the air for 7 months remarkably decreased: The aged composite adsorbed within 10 min only 2 wt.% H2 at 623 K and the sorption capacity decreased from 4.7 wt.% H2 to 2.1 wt.% H2.
|
|
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.
|
|
Changes in structure and phase composition in the surface of tram rail
Švábenská, Eva ; Roupcová, Pavla ; Schneeweiss, Oldřich
We have investigated structure and phase composition of surface layer of tram rails after long time running and the results were compared with those obtained on the original part of material. Changes due to effects of severe plastic deformation together with thermal shocks by friction process were expected. The information about structure and phase composition was obtained by optical and scanning electron microscopy, X-Ray Powder Diffraction, Mössbauer Spectroscopy and Glow Discharge Emission Spectroscopy (GDOES) and this was completed by microhardness measurements. The results show that the surface layer in comparison with the original material exhibits important changes in grain structure, an increase in microhardness and high content of iron oxide and hydrooxides. According to the depth profile of the chemical composition measured by GDOES there is an increase in carbon content in the surface layer which can be effect of up-hill diffusion.
|
|
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
|
|
Deposition of Titania from Solution by Hybrid Water-Stabilized Plasma Torch
Mušálek, Radek ; Medřický, Jan ; Tesař, Tomáš ; Kotlan, Jiří ; Lukáč, František
Thermal spraying with liquid feedstock presents a novel route for deposition of functional coatings. In this study, possibility of preparation of titania coatings from solution by hybrid water stabilized plasma torch is presented. Coatings were prepared from solution of titanium isopropoxide Ti[OCH(CH3)2]4 in anhydrous ethanol. Fragmentation of feedstock stream in the plasma jet was monitored by shadowgraphy. Deposition was carried out on steel samples mounted to the cooled rotating carousel. Cross-sectional images from SEM microscope showed successful formation of the deposit with dual morphology consisting of fine feather-like features combined with bigger droplets. X-ray diffraction revealed formation of nanometric rutile crystallites.
|
|
Black Chromia Coatings on Metal Tubes for the Solar Collectors
Brožek, V. ; Mastný, L. ; Novák, M. ; Vilémová, Monika ; Kubatík, Tomáš František
This paper describes the results of the first phase of the study preparation, structure and properties of coatings modification of black chromium oxide on copper, aluminium, iron and zirconium tubes for solar collectors. The coatings are prepared by plasma spraying of liquid chromate method which is known as liquid precursor plasma spraying. Coatings have the function of an energy trap for thermal radiation wavelengths of 1 μm – 3 μm i.e. in the IR region. At the same time, the coating increases the corrosion resistance of metal substrates. The nanometric structure and thickness of the coating depend of the feeding distance and the concentration of chromate precursors. For the deposition of nanometric splats of melt chromiumIII oxide, a new type of feeder that injects precursors into the water stabilized thermal plasma produced by the WSP® generator has been\ndeveloped.\n
|
| |
host ::
