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Modulated ultrasonic water jet cutting – optimization of the liquid wave guide shape
Veselý, Radek ; Foldyna, Josef (referee) ; Habán, Vladimír (advisor)
High speed water jets have un-substitutable place in unconventional technologies in the machining of materials. Indeed its larger spreading is limited above all by its really high purchase price and also high costs of the operation. Certain possibility is represented by high-speed pulsating jets, which don’t put such a high pretension on arrangement of generating the pressure during the comparable operation. Probably the most effective method of the generating of pulsating water jets is ultrasonic modulation. This work could benefit to understanding spreading of pressure impulses between ultrasonic generator and output nozzle. Pulsating is solved by the numerical calculation using transfer matrix method.
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Audio Pre-Amplifier for Laboratory Measurements
Friml, Vilém ; Hanák, Pavel (referee) ; Kratochvíl, Tomáš (advisor)
This thesis deals with a design of audio pre-amplifier with fixed frequency filters and a choice between amplification using integrated circuits and solidstate circuit. The thesis includes a design of attenuation circuit, an amplifier with an integrated circuit, an amplifier with transistors, a RIAA filter, a speech filter, a physiological filter, a rock preset filter and a power supply circuit. The thesis describes design of the circuit board, solution of oscillations of the amplifier with transistors and a measurement of the constructed device. The aim of the thesis is the design and construction of laboratory equipment.
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Rheology of hyaluronane solutions
Hlisnikovská, Kristýna ; Soukupová, Lenka (referee) ; Pekař, Miloslav (advisor)
Předmětem tohoto studia bylo prozkoumat reologické chování vodných roztoků vysokomolekulárního hyaluronanu. Byl studován vliv zvyšující se koncentrace biopolymeru v roztoku, která se pohybovala v rozmezí od 1 do 3 hmotnostních procent, a také vliv vzrůstající iontové síly rozpouštědla, způsobené přídavkem chloridu sodného, na viskoelasticitu a stabilitu těchto roztoků. Pro obsáhlejší popis viskoelasických vlastností roztoků byla použita, vedle běžných oscilačních měření, také metoda ceepových testů, ze které bylo možno určit důležité veličity, jako je procentuální poměr viskozní a elastické složky vzorku, rovnovážná poddajnost, viskozita při nulovém smykovém napětí a retardační čas. Ty byly následně porovnávány s výstupy z jiných typů měření, jako jsou právě oscilační a tokové křivky, nebo nesly dopňující informace důležité pro detailnější popis viskoelastických vlastností těchto roztoků. Ke studiu stability vzorků během namáhání pak byla použita metoda peak-hold, která ukázala na velmi dobou mechanickou i časovou odolnost roztoků hyaluronanu a naznačila hranice, za kterými už dochází k trvalému poškození struktury a degradaci řetězců hyaluronanu a je s němi proto potřeba při manipulaci s roztoky tohoto biopolymeru pro jejich další použití v aplikacích počítat.
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Study of CO oxidation on platinum by UHV-SEM
Jaroš, Antonín ; Kolíbal, Miroslav (referee) ; Bábor, Petr (advisor)
This bachelor’s thesis is focused on the study of heterogeneous catalytic oxidation of CO on the surface of platinum, but also in the confined space between platinum and graphene. The thesis is separated into two parts – theoretical and experimental. In the theoretical part, there is a general explanation of important principles regarding this thesis, such as the stucture of scanning electron microscope, growth of graphene, evolution of the catalytic oxidation of CO and oscillatory mode of this reaction, and lastly evolution of the same reaction under the graphene. The experimental part is chronologically concerned about individual tasks of bachelor’s thesis.
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Study of catalytic reaction waves by SIMS
Jaroš, Antonín ; Willinger, Marc Georg (referee) ; Bábor, Petr (advisor)
Katalytické reakce jsou klíčové pro mnoho technologických oblastí. Abychom docílili jejich zlepšení, je potřeba porozumět jejich mechanismu, k čemuž je důležité vyvíjet nové in-operando techniky. Operando spektroskopie jsou obecně rozděleny do dvou kategorií: velkoplošné techniky, které poskytují zprůměrované informace z celé analyzované oblasti, přičemž nemusí zaznamenat signál z důležitých aktivních míst, a lokalizované techniky, které poskytují informace na atomární úrovni, ovšem nemusí relevantní aktivní místa obsahovat vůbec. V této práci je demonstrováno, že hmotnostní spektrometrie sekundárních iontů je bezprecedentní způsob, jak v reálném čase sledovat oscilační vlny během oxidace CO, poskytující mikro-spektroskopická data, která jsou klíčová pro rozluštění složitého katalytického mechanismu. Ukazuje se, že v nízkých tlacích jsou reakční vlny tvořeny střídajícími se vlnami oxidu platiny a adsorbovaného oxidu uhelnatého. Mechanismus reakce spočívá v redukci oxidu pomocí CO. Navíc jsou oxid platiny a CO adsorbáty nehomogenně rozloženy napříč vln, což je nejvíce patrné na reakční vlnoploše.
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Kurzweil-Stieltjes integral and its generalizations
Konopka, Filip ; Slavík, Antonín (advisor) ; Mošna, František (referee)
The thesis deals with the HKSp α integral, which is generalization of the HKS integral, its properties and the concepts of ordinary oscillation and p-oscillation, which are needed for the construction of the integral. This integral is non-absolutely convergent and more general than the Lebesgue integral. This thesis is based on recent results in the theory of integrals and its goal is to introduce this integral to a wide readership interested in mathematical analysis. 1
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Study of CO oxidation on platinum by UHV-SEM
Jaroš, Antonín ; Kolíbal, Miroslav (referee) ; Bábor, Petr (advisor)
This bachelor’s thesis is focused on the study of heterogeneous catalytic oxidation of CO on the surface of platinum, but also in the confined space between platinum and graphene. The thesis is separated into two parts – theoretical and experimental. In the theoretical part, there is a general explanation of important principles regarding this thesis, such as the stucture of scanning electron microscope, growth of graphene, evolution of the catalytic oxidation of CO and oscillatory mode of this reaction, and lastly evolution of the same reaction under the graphene. The experimental part is chronologically concerned about individual tasks of bachelor’s thesis.
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Helioseismic inversions of plasma flows and sound-speed perturbations
Korda, David ; Švanda, Michal (advisor) ; Komm, Rudolf (referee) ; Roth, Markus (referee)
Local helioseismology consists of methods which study the propagation of the waves through the solar interior. The properties of the waves encode conditions in the plasma along their propagation trajectories. Local helioseismology allows us to learn about these conditions. The principal method utilised in this thesis is the time-distance local helioseismology. The time-distance method is based on measurements of travel times of the waves, hence it is sensitive especially to plasma flows and sound-speed perturbations, to which we focus. We utilised the inverse modelling, mainly using subtractive optimally localised averaging method with a minimisation of the cross-talk. This method was modified to allow for a simultaneous inversion of vector flows and sound-speed perturbation. This combination makes use of both the difference and the mean point-to-annulus averaging geometries of wave travel times in both the ridge and the phase-speed filtering approaches. The combined inversion provides us with more information about the inverted quantities. Moreover, the user can control the cross-talk and other important mathematical properties of the objects involved. The modified methodology was thoroughly tested. The main results may be summarised in five points. First, for successful inversions of the sound-speed...
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Helioseismic inversions of plasma flows and sound-speed perturbations
Korda, David ; Švanda, Michal (advisor) ; Komm, Rudolf (referee) ; Roth, Markus (referee)
Local helioseismology consists of methods which study the propagation of the waves through the solar interior. The properties of the waves encode conditions in the plasma along their propagation trajectories. Local helioseismology allows us to learn about these conditions. The principal method utilised in this thesis is the time-distance local helioseismology. The time-distance method is based on measurements of travel times of the waves, hence it is sensitive especially to plasma flows and sound-speed perturbations, to which we focus. We utilised the inverse modelling, mainly using subtractive optimally localised averaging method with a minimisation of the cross-talk. This method was modified to allow for a simultaneous inversion of vector flows and sound-speed perturbation. This combination makes use of both the difference and the mean point-to-annulus averaging geometries of wave travel times in both the ridge and the phase-speed filtering approaches. The combined inversion provides us with more information about the inverted quantities. Moreover, the user can control the cross-talk and other important mathematical properties of the objects involved. The modified methodology was thoroughly tested. The main results may be summarised in five points. First, for successful inversions of the sound-speed...
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Oscilační procesy v magnetických strukturách sluneční koróny
EFFENBERK, Kryštof
This diploma thesis is focused on waves and oscillations in the solar corona, which takes place in a large number of phenomena that occurs here. In recent years these waves have been observed in Earth observation same like as cosmic observation.The task of this thesis is to familiarize with the problems of waves and oscillations in solar corona and subsequent interpretation into numerical simulations that are performed by FLASH code. The aim of the work will be to modify numerical simulations and thus to achieve more realistic of the observed phenomena.
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