Design of an axial segment bearing simulator

Bakalářská práce se zabývá konstrukčním návrhem simulátoru axiálního segmentového ložiska. Experimentální zařízení je navrženo pro studium tenkého mazacího filmu mezi segmentem axiálního ložiska a skleněným diskem. Snahou konstrukce je co nejvíce se přiblížit reálnému provozu ložiska. Použitím snímačů, způsobu zatěžování a mazání je zajištěna opakovatelnost podmínek experimentu. Práce obsahuje přehled zkonstruovaných zařízení a užitých metod měření, návrhy konstrukčních variant a popis navrhovaného zařízení.The bachelor thesis deals with an engineering design of a hydrodynamic thrust bearing simulator. The experimental apparatus has been designed to study the oil-film thickness between the pad and the glass disc. The goal of this thesis is to approach real operating conditions. The repeatability of the experimental conditions is provided by using transducers, way of loading and lubrication. The bachelor thesis contains a summary of rigs designed and measuring methods used, designs of constructional variations and a description of the engineered apparatus are also included.

Magnetorheology of dimorphic magnetorheological fluids based on iron nanorods

The aim of this paper is to document suitability of partial substitution of magnetic carbonyl iron (CI) microspheres with iron nanorods to obtain dimorphic magnetorheological (MR) suspensions with comparable MR performance to conventional MR suspensions exclusively based on (CI) microspheres while the sedimentation stability is considerably improved. The morphology of CI and iron nanorods was analyzed via scanning electron microscopy and transmission electron microscopy, respectively, and magnetic properties via vibrating sample magnetometry. The steady shear flow and small-amplitude dynamic oscillatory shear measurements were carried out to confirm effective MR performance. The sedimentation test showed positive role of dimorphic composition of dispersed phase on the sedimentation stability. © Published under licence by IOP Publishing Ltd.Grant Agency of the Czech Republic [14-32114P]; Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504

BE BORN AS SUCCESSFUL MATHEMATICS OR LANGUAGE LEARNER: MYTHS, TRUE OR FALSE?

Applied mathematics and English language belong among consequential subjects within the Faculty of Economics and Management curriculum. The authors focused on these two subjects and apart from their description they deal with entrance exam analysis for bachelor degree at the Faculty of Economics and Management, which is a part of the University of Defence. In an endeavour to widen the understanding referring to factors predicting academic achievement in tertiary education, the authors compare the entrance test results and try to find out whether there is an independent relationship between success in the English language test and success in the Learning Potential Test. Exploratory statistics and methods of non-parametric statistics for testing of the hypothesis regarding this relationship is described in the last part of this article

Tracking the University Student Success: Statistical Quality Assessment

Higher education institutions are continually striving to make education relevant to the working environment students will encounter upon graduation. One of the tools for enhancing an institution’s quality and sufficiently informing students about their outcomes and learning opportunities is a quality assessment. Quality assessment is a long process which establishes measurable student learning outcomes, then analyses and interprets them. This enables students to receive feedback on their learning and helps them to improve their performance. The authors’ objective was to gather empirical data on students´ learning in order to improve the process of learning and to refine study programmes. A longitudinal study was used to observe students’ performance and outcomes from entrance exams to state exams. Statistical analysis revealed that there is a correlation between the results of the admission tests and the study results, especially the connection between the results of the entrance test and the chance of successful completion of studies. No statistically significant correlation was found between the overall results of military students’ studies. An interesting issue is a comparison between military and civilian students, as well as civilian students´ results. As a continuous process, assessment of students’ performance was observed up until the Final State Examination

Rheology of uncured magnetorheological elastomers

The aim of this paper is to study rheological properties of uncured magnetorheological elastomers comprising iron particles dispersed in silicon elastomer in relation to particle rearrangement by external magnetic field into oriented structures as this process is strongly affected by viscosity. Studied systems vary in used filler volume concentration (0 to 30 vol. %). From measured flow curves flow consistency index is extracted first by fitting experimental data to Herschel-Bulkley model followed by applying two concentration dependency models (Maron-Pierce and Krieger-Dougherty) to normed consistency. Results and model predictions are discussed. © Published under licence by IOP Publishing Ltd.Czech Science FoundationGrant Agency of the Czech Republic [17-24730S]; Ministry of Education, Youth and Sports of the Czech Republic -Program NPU I [LO1504

The surface modification of magnetic particles with polyamidoamine dendron

Magnetorheological elastomers are important kind of intelligent systems that can alter their properties upon an application of an external magnetic field. Crucial for their performance is interaction between polymer matrix and magnetic filler, thus, it is necessary to control the compatibility between the matrix and magnetic particles. In this study, polyamidoamine dendron was successfully introduced onto surface of carbonyl iron particles using divergent approach in order to provide novel magnetic particles for magnetorheological elastomers. The presence of a thin layer of polyamidoamine dendron on the carbonyl iron particles was confirmed by energy dispersive X-ray, infrared spectroscopy and transmission electron microscopy, which confirmed a thin layer in nanometers formed on the surface of the particles. The coated carbonyl iron particles exhibited superior chemical stability when compared to non-coated ones, while the saturation magnetization decreased only negligibly from 207.0 emu g-1 to 203.5 emu g-1 for pure carbonyl iron particles and polyamidoamine dendron-coated carbonyl iron particles, respectively. © 2018 Author(s).Czech Science Foundation [17-24730S]; Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504

Tailoring performance, damping, and surface properties of magnetorheological elastomers via particle-grafting technology

A novel concept based on advanced particle-grafting technology to tailor performance, damping, and surface properties of the magnetorheological elastomers (MREs) is introduced. In this work, the carbonyl iron (CI) particles grafted with poly(trimethylsilyloxyethyl methacrylate) (PHEMATMS) of two different molecular weights were prepared via surface-initiated atom transfer radical polymerization and the relations between the PHEMATMS chain lengths and the MREs properties were investigated. The results show that the magnetorheological performance and damping capability were remarkably influenced by different interaction between polydimethylsiloxane chains as a matrix and PHEMATMS grafts due to their different length. The MRE containing CI grafted with PHEMATMS of higher molecular weight exhibited a greater plasticizing effect and hence both a higher relative magnetorheological effect and enhanced damping capability were observed. Besides bulk MRE properties, the PHEMATMS modifications influenced also field-induced surface activity of the MRE sheets, which manifested as notable changes in surface roughness. © 2018 by the authors.Czech Science Foundation [17-24730S]; Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2017/004]; Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; Operational Program Research and Development for Innovations - European Regional Development Fund (ERDF); national budget of the Czech Republic [CZ.1.05/2.1.00/19.0409

Possibilities of utilisation of salt slags from aluminum production

Bakalářská práce se zabývá charakterizací solné strusky vznikající jako odpad při tavení hliníkového šrotu v rotačních pecích a navržením možností využití tohoto materiálu jako sekundární suroviny. Zkoumány byly vzorky odebrané z horní, střední a dolní částí kokily, do které je struska při odpichu nalita a kde chladne. Cílem práce je mimo jiné zhodnotit vliv přístupu vzduchu při chladnutí strusky na chemické a fázové složení strusky v různých částech kokily. U odebraných vzorků byla stanovena distribuce velikosti částic sítovou analýzou, obsah rozpustných látek ve strusce a chemické a fázové složení jednotlivých frakcí po sítové analýze. Dále bylo zkoumáno fázové i chemické složení rozpustných i nerozpustných podílů pomocí rentgenové práškové difrakce a rentgenové fluorescenční spektrometrie.Bachelor thesis deals with characterisation of salt slag formed during melting of aluminium scrap in rotary furnaces and proposes options of utilization of this material as a secondary raw material. Samples from top, middle and bottom part of mould, where slag cools down after the melting process is finished, were tested. Aim of the thesis is also to evaluate the effect of air access during the cooling process on phase and chemical composition of salt slag. Particle size distribution, content of soluble substances and composition were examined in collected samples. Phase and chemical compositions of both soluble and insoluble portion of idividual fractions were determined using X-ray powder diffraction and X-ray fluorescence spectrometry.

Trading strategies based on estimates of conditional distribution of stock returns

Tato práce vytváří novou obchodní strategii. Pomocí kvantilových regresí jsou odhadnuty podmíněné distribuční funkce tržních návratností. Na základě odhadnutých distribucí jsou produkovány signály pro nákup a prodej, které společně s funkcí vah, jež jsou odvozené od exponenciálních klouzavých průměrů, určují množství a čas nákupu a prodeje. Strategie má lepší výkonnost než trh na datech, na kterých byla odhadována, avšak při out-of-sample testování neposkytuje uspokojivé výsledky.In this thesis, a new trading strategy is proposed. By the help of quantile regression, the conditional distribution functions of stock market returns are estimated. Based on the knowledge of the distribution the strategy produced buying and selling signals which together with a weight function derived from exponential moving averages determines how much and when to buy or sell. The strategy performs better than the market in terms of absolute return and the Sharpe ratio in-sample, but it does not provide satisfactory results out-of-sample.Institut ekonomických studiíInstitute of Economic StudiesFaculty of Social SciencesFakulta sociálních vě