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The role of sonication of PEO solutions with magnetic nanoparticles on morphology of the resulting nanofibrous mats
Peer, Petra ; Stěnička, M. ; Filip, Petr ; Pizúrová, Naděžda ; Babayan, V.
Properties of the resulting polymer nanofibres are often tailored by sonication technique applied prior or past an electrospinning process. The aim of this contribution is to evaluate morphology of nanofibrous mats formed by poly(ethylene oxide) with distributed magnetic nanoparticles (about 20nm in diameter) in dependence on time of sonication of the used polymer solutions. The solutions were exposed to sonication (intensity 200W, frequency 24 kHz) for 10, 30, and 60 minutes. It was shown that rheological characteristics (viscosity, storage and loss moduli) strongly depend on time of sonication (particularly phase angle) in contrast to electric conductivity and surface tension. For analysis of homogeneous distribution of magnetic field and magnetorheological efficiency (a relation of corresponding ciscosities) was process of electrospinning and resulting wuality of the obtained nanofibrous mats.
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Komunikační strategie modelové řady Škody Fabia
Trnka, Eduard ; Halík, Jaroslav (vedoucí práce) ; Filip, Petr (oponent)
Diplomová práce se zabývá problematikou marketingové komunikace vozu Škoda Fabia třetí generace. Zaměřuje se na dosud nevyužívaný, a přitom velmi přesvědčivý prodejní argument, umožňující komplexní vyčíslení nákladů spojených s vlastnictvím vozidla. Nástroj je znám pod zkratkou TCO (Total Cost of Ownership) a své uplatnění dosud nachází převážně u provozovatelů velkých firemních flotil. Dílčím cílem této práce je posouzení konkurenceschopnosti modelu Fabia z hlediska ukazatele TCO. K tomu bude využit specializovaný nástroj CarCostExpert od společnosti EurotaxGlass. Na základě tohoto srovnání s konkurencí a dotazování v prodejní síti bude navržen koncept komunikační strategie založené na TCO. Součástí konceptu je odhad finančního potenciálu navrženého řešení i analýza souvisejících hrozeb a příležitostí.
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Spinnability of PEO solutions with respect to their aging
Zelenková, Jana ; Peer, Petra ; Filip, Petr
Non - negligible portion of pol ymer commodity suffers from ageing that participates in sometimes significant changes of products attributes. Rheology represents a useful tool for a description of this process. The aim of this contribution is to evaluate possible ageing of PEO solution ( polyethylen e oxide ( M w =300,000 g/mol) dissolved in water at 10 wt.% concentration) based both on rheological characterization and on quality of electrospun fibres. Rheological measurements in steady shear and oscillatory modes were carried out using a rota tional rheometer MCR 501 (Anton Paar, Austria) equipped with the concentric cylinders geometry. The electrospinning measurements were executed with the help of a proposed laboratory device. The tip - to - collector distance attained 20 cm, applied voltage rang ed from 20 to 30 kV. The obtained electrospun fibres were analysed using a scanning electron microscope (VEGA 3, Tescan, Czech Republic). Both types of measurements were carried out in the period of several months during which the solution studied was plac ed in a dark and tempered box (25°C). The measurements indicate no ageing impact on rheological characteristics or quality of electrospun fibres. This guarantees more or less the identical quality of non - woven textiles prepared from PEO solutions regardles s of time period during which the solutions are deposited.
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Tvorba manažerského simulátoru pro řízení zásob ve vybrané společnosti
Prokop, Tomáš ; Mildeová, Stanislava (vedoucí práce) ; Filip, Petr (oponent)
Cílem diplomové práce je vytvoření softwarové aplikace manažerského simulátoru jako základního nástroje pro provádění vlastních simulací. Navržený manažerský simulátor je vytvořen v kontextu taxonomie systémů pro podporu rozhodování. Jde o modelově orientovaný systém, jehož základem jsou mnou navržené modely a nad nimi vytvořené uživatelské rozhraní. V tomto konkrétním případě, kterým se práce zabývá, se jedná o společnost Dynavix, která působí v odvětví výroby navigačních zařízení. Po úvodních teoretických informacích o modelech, počítačových technikách pro modelování systémů a jednotlivých fázích simulačního procesu následuje případová studie. S využitím přístupů systémové dynamiky (vytvořeného modelu a jeho testování) se snaží najít a doporučit vhodné řešení výkyvů v potřebě nákupu navigačních zařízení společnosti Dynavix. Doporučené řešení je ověřeno na základě stanovené hypotézy a jejím testování dle předem vytvořeného testovacího scénáře.
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Motion of multiple cylinders in potential flow of ideal fluid
Kharlamov, Alexander A. ; Filip, Petr
The flow field past multiple arbitrarily moving cylinders is calculated using a generalisation of the conventional images method. The flow is presented by a flow from an infinite set of dipoles. For calculation purposes the infinite series must be, however, truncated. The kinetic energy of fluid is presented as a sum over all modelling dipoles. A rather good convergence of the method is observed. However, if the distances between any cylinders tend to zero, the method fails in zones close to the contact point. Nevertheless, even for the case of touching cylinders the series for the kinetic energy remain convergent. In case of just two cylinders the method projects on the classical method of images. Method is validated by several comparisons with solutions known from the literature.
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On the electrospinning of PVB solutions
Švrčinová, Petra ; Filip, Petr ; Lubasová, D.
Extension rheological characteristics belong to the principal description of polymer jet formation during a process of electrospinning. However, in spite of nearly absence of shear deformation of polymer solutions during the process of their spinnability, it seems that shear electrorheological characteristics can serve as an indicator of good or bad quality of an electrospun template. The experiments were carried out with four polyvinylbutyral (PVB) solutions in concentration of 10 wt%. Shear viscosities in absence (η0) and presence (η) of electric field were measured using a rotational rheometer equipped with an electrorheological cell. It was shown that the good solvents of PVB exhibit an almost constant curve of η/η0 vs. electric field strength, whereas the viscosity curves for the poor solvents exhibit enhancement. This enhancement corresponds to better quality of electrospun templates (obtained for polymer solutions of PVB with poor solvents).
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On behaviour of PVB solutions in electrospinning
Švrčinová, Petra ; Lubasová, D. ; Filip, Petr ; Martinová, L.
Electrospinning produces nanofibre sheets from polymer solutions under high electric field. Rheological properties of these solutions play a substantial role in a nanofibre formation simultaneously with properties of polymers and solvents applied. This contribution aims at a determination of dependence of shear viscosity of polyvinylbuthyral (PVB) on the intensity of electric field to which PVB solutions are exposed. PVB was dissolved consecutively in a series of solvents as 10% wt. solution. It was found that the viscosity ratio (viscosity of a solution in presence of electric field/viscosity of a solution in absence of electric field) depends on the polarity of solvent. This pre-determines the possibility of application of the individual solvents for the process of electrospinning.
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A note to the simplification in description of some molecular-based polymer models
Kharlamov, Alexander ; Filip, Petr
One type of integral is frequently met in various description of behaviour of polymer materials through molecular-based models starting with the classical Doi-Edwards one. The integrand in this integral for which an integrated region represents a solid angle is formed by a product of a unit vector (pointed at an element of this region) with a deformation gradient tensor. This product is raised to an exponent that is not usually an integer. The aim of this contribution is to derive substantially simplified expression for this integral respecting high accuracy of an approximation.
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