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In-situ Study of Surface Topography Changes in Elastohydrodynamic Contact
Šperka, Petr ; Dzimko, Marián (referee) ; Návrat, Tomáš (referee) ; Dobeš, Petr (referee) ; Hartl, Martin (advisor)
This dissertation thesis deals with elastohydrodynamic lubrication (EHL) of surfaces with real roughness. Systematic study of surface harmonic components behaviour, during their passage of the EHL contact, by other authors led to retrieval of a uniform principle according which individual harmonic components deform inside the contact. Although the amplitude attenuation model can provide rapid tool for more accurate surface assessment in design process it has not been validated on real surfaces till now. The thesis represents pioneering work on quantitative analysis of real surfaces EHD measurements. It contains original and new results with real and model roughness features that in many cases confirm theoretical expectations. Deeper understanding of surface roughness behaviour inside EHL contact, which is typical for machine parts like bearings, gears, cams etc., can help to improve design process of the components and ultimately enable machines and equipment to work with lower energy requirements and higher durability.
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Limiting and Degradation Processes of Magnetorheological Suspension Dampers
Roupec, Jakub ; Bauer, František (referee) ; Ondrůšek, Čestmír (referee) ; Dobeš, Petr (referee) ; Mazůrek, Ivan (advisor)
This work deals with the research of degradation of magnetorheological (MR) fluid during long-term loading under conditions that correspond to the real load in the linear MR devices such as dampers. The behaviour of MR fluid is described by a Bingham model of viscoplastic fluid. The parameters of this model are the yield stress and viscosity. Their values are determined by the shear rate from 1 to 2,8104 s-1. Results of durability tests show a significant decrease in viscosity of MR fluid, a gradual increase in yield stress in the off-state and a significant decrease in MR effect. The paper also described the effect of temperature on these parameters and there is also designed a method of non-assembly diagnostic of the MR fluid state in the damper using the "rate of pulsation."
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THIN LUBRICANT FILMS STUDY USING SPECTROSCOPIC REFLECTOMETRY
Čudek, Vladimír ; Dzimko, Marián (referee) ; Navrátil, Karel (referee) ; Dobeš, Petr (referee) ; Křupka, Ivan (advisor)
ectroscopic reflectometry is measurement technique that enables the study of the thickness and refractive index of thin layers. This thesis deals with its use for the study of lubrication films within EHD contact and verifies a new approach suggested in recent publications. It is focused on the development of an optical arrangement and mathematical model for the lubrication film thickness measurement within the entire EHD contact. This technique brings the possibility to study the pressure distribution within the contact area through the evaluation of changes in lubricant refractive index.
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Experimental Study of Lubrication Films Formation During Start-up and Reversal Motion of Rubing Surfaces
Svoboda, Petr ; Dzimko, Marián (referee) ; Čermák, Jan (referee) ; Dobeš, Petr (referee) ; Křupka, Ivan (advisor)
This dissertation is focused on the effects of both artificially produced and real roughness features on mixed lubrication film formation during start-up and reversal of non-conformal contacts operated under rolling/sliding conditions. The start-up operation of mixed lubricated contacts represents one of the transient conditions that bring the risk of the surface damage because of asperities interactions. Chromatic interferograms captured by CMOS high-speed camera during start up of the motion enabled to observe the detailed changes in lubrication film caused by surface features. The observation of the effects of surface dents artificially produced on the ball surface helped to understand better the behaviour of real surface topography. It was found that the presence of shallow surface features can help to separate mixed lubricated rubbing surfaces more efficiently than it could be suggested from the results obtained with smooth surfaces. It can be suggested from the obtain results that properly designed topography of the rubbing surfaces can help to reduce the asperities interactions under transient operational conditions.
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Reconstruction of AXMAT Testing Station
Gergel, Matej ; Dobeš, Petr (referee) ; Dvořáček, Jiří (advisor)
The master´s thesis deals with reconstruction of RCF test rig AXMAT. Main goal is design new hydraulic load system and his realization. The first part of thesis describes similar experimental machines and their pros and cons. This analysis is base for complete reconstruciton of AXMAT. New hydraulic load system allows dynamic programmable load cycles. Control system with close loop and feedback was created in software Matlab – Simulink. Main frame was reconstructed too. Control and action parts were asseble to station. Output of thesis is function sample.
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Revitalization of hydraulic circuits control tester
Korsa, Filip ; Dobeš, Petr (referee) ; Nevrlý, Josef (advisor)
High-quality simulation of hydraulic mechanism saves the time and other costs associated with the changes of inappropriately designed circuit. The aim of this thesis is to revitalize the test rig intended for simulating hydraulic circuits in order to verify the results of the simulation program Hyvos used internally by Bosch Rexroth Company. It is expected that the simulation of the hydraulic machinery cycles under the influence of disturbances will be carry out on the test rig and measured data are compared with results of the virtual models which are designed using the mentioned software Hyvos. The work deals with the so called position and pressure control which represent the classical modes of pressing machines or hydraulic press brakes operation cycles. The parameters of the hydraulic closed-loop axis controller for electrohydraulic drives (HACD) are set using the software Bodac.
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Comparison of the gaseous and liquid releases of the Czech and world nuclear power plants
DOBEŠ, Petr
In this work, which deals with problematics of releases from nuclear power plants, I tried to make an overview of various types of nuclear power plants and radioizotopes which are released through liquid and gasseous effluents. As a part of this comparison evaluation of czech and world nuclear power plants gaseous and liquid releases was made. Introductory part of this work contains information about different types of nuclear power plants and radioizotopes, which are produced in their reactors. It continues with today{\crq}s legislative and information about releasing levels and methods and systems used for measurement of radioactive gaseous and liquid effluents from nuclear power plants. Second part of this work describes the aim of this work and hypothesis. Third part explains the methods, which were used for completing of this work. Fourth part contains results in the form of tables and graphs. Fifth part represents discussion of the results. Last part is a summarization of the results.
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Management of Six Sigma projects
Dobeš, Petr ; Chocholatý, Drahomír (advisor) ; Hřebíček, Vladimír (referee)
Diploma thesis of "Management of Six Sigma projects" is dealing with possibilities of using this technique in specific continuous improvement projects. Main goal is to analyse tools of this method on real situation and proof that Six Sigma is usable to manage this kind of projects. This work will include necessary theoretical basics from project management scope based on generally approved PMBOK methodology. Part of this analysis will be concerned on comparison of PMBOK principles and Six Sigma method. Explanation of Six Sigma basics won't be omitted as well through the fact this method has achieved a significant value in recent times. Practical part of this paper will be composed as case study example of a logistics project in DHL Exel Supply Chain company where I have been employed in United Kingdom.
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Informační systémy veřejné správy
Dobeš, Petr ; Klas, Jan (advisor) ; Novotný, Jakub (referee)
Práce si klade za cíl seznámit čtenáře s možnostmi Portálu veřejné správy. Tento portál je základním informačním systémem celé české veřejné správy. Měl by plnit funkci jakési elektronické brány, kde se spolu setkávají různé skupiny uživatelů. Při jeho analýze se nejprve zaměřím na prezentační část, poté se budu věnovat funkcím transakčního jádra portálu. Součástí práce je také krátký přehled o veřejné správě, e-governmentu a teorie elektronického podpisu. Hlavním přínos práce spočívá v celkovém objektivním zhodnocení portálu na základě soustavy určitých obodovaných kritérií.
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