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The production technology of clarinet reeds and possible modifications
Žitný, Radek ; HLAVÁČ, Jiří (advisor) ; MAREŠ, Vlastimil (referee)
In my thesis I describe the known technologies of clarinet and saxophone reed making. These range from purely hand-made fabrication (as in the case of the production of oboe and bassoon reeds) to technologies with an extensive use of machine work, which allows for refined and accelerated production. I also describe what precedes the manufacturing of a reed itself, that is growing and harvesting of cane wood of which the reeds are made. Clarinet and saxophone reeds are the subject of much speculation in terms of durability, usage, warm-up, storage and especially their possible customization to the needs of each individual player. That is why in the second part of this thesis I focus on possible personilised modifications of reeds. To conclude I quote and comment on the most comprehensive records of reed adjustments available in the existing specialist literature. The aim of my research is to provide clarinetists and saxophonists with a manual where I present facts and methods of reed adjustment they may put in practice themselves, and therefore avoid having to rely on „selecting the best of the mediocre reeds available in the music shop". The thesis includes an illustrated appendix of sketches, adjustments, reeds and their packaging, cases and tools.
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Numerical Modelling of Grate Combustion
Juřena, Tomáš ; Klemeš,, Jiří (referee) ; Žitný, Rudolf (referee) ; Hájek, Jiří (advisor)
Předkládaná práce je zaměřena na numerické modelování spalování tuhých paliv na roštu metodami výpočtové dynamiky tekutin (CFD). Jelikož výsledky CFD simulací roštového spalování závisí na kvalitě vstupních dat, která zahrnují i údaje o teplotě, hmotnostním toku a chemickém složení spalin vystupujících z lože, pozornost je věnována především procesům, probíhajícím v loži během spalování na roštu. Velká část práce je věnována vývoji spolehlivého modelu spalování v sypaných ložích, jelikož může napomoci zkvalitnit výsledky simulací i rozšířit znalosti principů spalování tuhých paliv v sypaných ložích. V rámci práce byl vyvinut jednorozměrný nestacionární model spalování v experimentálním reaktoru a implementován do počítačového programu GRATECAL 1.3 včetně grafického uživatelského rozhraní. Zvláštní důraz byl kladen na konzervativnost modelu. Proto byla vyvinuta metoda pro kontrolu hmotnostní a energetické bilance systému a následně aplikována v řadě studií, v rámci nichž byly odhaleny některé chyby týkající se definic zdrojových členů, které byly převzaty z literatury a opraveny. Pomocí modelu byla provedena analýza šíření čela sušení a reakce hoření koksu po výšce lože pšeničné slámy. Na základě výsledků těchto analýz bylo doporučeno zahrnout i modelování změny porozity částic paliva, aby šířka reakční zóny byla predikována korektně v případě, že je uvažována změna porozity celého lože. Rovněž vyvinutá bilanční metoda byla použita k analýze vlivu kritérií konvergence na hmotnostní a energetickou nerovnováhu simulovaného systému. Bylo zjištěno, že škálovaná rezidua rovnic všech veličin by měla poklesnout aspoň na hodnotu $10^{-6}$, aby bylo dosaženo nízké hmotnostní a energetické nerovnováhy a tudíž uspokojivě přesných výsledků ze simulací v loži. Druhá část práce je věnována vývoji a implementaci knihovny uživatelem definovaných funkcí pro komerční CFD nástroj ANSYS FLUENT, které slouží k propojení modelu lože s modelem komory reálné spalovací jednotky, aby byla umožněna dynamická změna okrajových podmínek na vstupu do komory v závislosti na výstupech ze simulací v loži. Vytvořené rozhraní pro propojení těchto dvou modelů je dostatečně obecné pro aplikaci na širokou škálu modelů roštových kotlů. Popsané výsledky přispívají k lepšímu porozumění numerickému modelování spalování na roštu, a to zejména ve fázi sestavování numerického modelu a nastavení parametrů řešiče pro kontrolu konvergence.
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Methods for Determination of Characteristic Parameters of Combustion Processes on the Basis of Experiments and Modeling
Bělohradský, Petr ; Klemeš,, Jiří (referee) ; Žitný, Rudolf (referee) ; Stehlík, Petr (advisor)
The present thesis is concerned with methods for determination and modeling of characteristic parameters of combustion of gaseous fuels. The focus is stressed on formation of nitrogen oxides and heat transfer from hot flue gases into combustion chamber’s walls. Experimental work, which is focused on testing of two burners with suppressed formation of nitrogen oxides, is an important part of the thesis. Its aim is to obtain data that is necessary for further processing and modeling. The work presents two methods that may be used in modeling of characteristic combustion parameters, namely the method based on statistical processing of data and the method based on computational fluid dynamics. The approaches are applied to two devices (burner with two-staged fuel supply, burner with two-staged air supply) with the objective to analyze their parameters. First approach covers detailed planning of burner test prior to its own carrying out (definition of the goal of experiment, choice of input factors and response, experimental plan) and subsequent statistical processing of experimental data. On the contrary, CFD approach offers simulations as an alternative option to traditional experimental methods. The simulation of combustion includes building of computational grid, setup of boundary conditions, turbulence model, heat transfer model and chemical kinetics. Results of simulations are compared with experimental measured data.
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Water hammer experiment in artificial blood vessel
Hromádka, D. ; Horný, L. ; Žitný, R. ; Chlup, Hynek
This paper presents a water hammer experiment performed on an artificial blood vessel and the latex tube. Artificial blood vessel was manufactured from latex tubes and textile rubber bands. These bands were wound on outer surface of latex tube and they imitated reinforcing effect of collagen fibres. Mathematical model describes pulsation of pressure after instantaneous closing of valve at outlet of pipeline a part of which is a short elastic tested tube. It is shown that the observed pressure responses can be approximated by a simplified mathematical model assuming linear relationship between internal pressure and inflated volume.
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Residual Strains of Arteries as Forensic Index
Adámek, T. ; Horný, L. ; Chlup, Hynek ; Žitný, R.
It has been known for long time that arteries are pre-strained in situ. These residual strains play crucial role in arterial load-bearing capacity. However, to the best of authors’ knowledge they have never been considered from forensics point of view. This paper concerns a possibility of employing the longitudinal pre-strain of human aortas as an indicator of human subject age. Lengths of abdominal aorta were measured within autopsies before and after segment resection. Longitudinal stretch ratio was calculated for 45 male and 12 female cadavers. It was found that both male and female data samples give approximately the same mean of the stretch ratio = 1.2. The correlation coefficients between the pre-strain and age were R=-0.7926, R=-0.8684 in male and female samples, respectively. Linear regression equation with confidence intervals was employed. The correlation between pre-strain and age seems to be suitable statistics to be used in forensic sciences.
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Neinvazivní potické měření deformací elastických trubic
Macková, H. ; Chlup, Hynek ; Žitný, R.
Noninvasive optical measurement and evaluation of the pulse wave velocity of a self-oscillating elastic tube was done. A latex tube was loaded by self-excited internal pulsatile flow as a simple model of human big arteries. The method is based on evaluation of high speed camera recordings and edges detection algorithm. Displacements of the tube edge were evaluated by a given scale factor from a standard gauge inserted to the recorded scene. Our goal is to recognize the pulse wave and measure its velocity along the tube.
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Konstitutivní modelování tepenné stěny
Horný, L. ; Chlup, Hynek ; Adámek, T. ; Zitny, R. ; Macková, H.
Inflation tests and uni–axial extension tests of arterial tissue were performed. Experimental data were used in nonlinear regression analysis to identify material model. Arterial tissue was assumed to be incompressible hyperelastic material. 5–parameter strain energy density function based on combination of isotropic Neo–Hookean expression and Fung–type orthotropic expression was used. Computational model for material parameters identification was based on thick–wall tube with axial pre–strains. Residual strains were included. Internal structure of arterial wall was not considered. Fitted material models correspond to experimental data very well.
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Optimalizace měření rychlosti pulzní vlny v tepnách
Macková, H. ; Chlup, Hynek ; Hulan, M. ; Žitný, R.
Measurements of the pulse wave velocity (PWV) in human arteries are important for two different reasons: an early diagnostics of atherosclerosis and identification of material properties of the vessel wall for numerical simulations. The PWV in blood vessels is not constant and classical methods of pressure wave shift between two points are not sufficient. We consider three methods: optical measurements of vessel wall displacement in several points by high speed camera, continual optical measurements of vessel wall displacement by correlator Q-450 and measurements of flow rate and displacements by ultrasonic device. The first method can determine the PWV only between several points. The second method can show 3D reconstruction of displacements with very good resolution. The ultrasound measurements need combination of Doppler ultrasound velocimetry and B-scan imagining. However, the common devices used in medicine do not have any data output. It causes bad resolution.
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Experimentální měření pulzní vlny v elastické trubici
Chlup, Hynek ; Macková, H. ; Žitný, R. ; Konvičková, S.
The pulse wave velocity (PWV) in blood vessels is one of the important hemodynamical parameters for detection of artery health condition. In our laboratory, the PWV in elastic tubes and arteries is measured in vitro. The method is based on optical measurements of displacement of the pulsating tube wall. A high frame rate camera was used. The obtained data were evaluated by several methods and compared. The measured pulse wave velocities were in the same order of magnitude as values based on theoretical calculations and published physiological data.
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