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Arc optical diagnostics
Čermák, Jiří ; Valenta, Jiří (referee) ; Dohnal, Petr (advisor)
The aim of this bachelor thesis is to sort out the individual types of electric discharges, explain the ionization inside the plazma of the electric arc and the elucidation of the energetic balance inside the plazma. The electric arc is an undesirable and hardly predictable phenomenon occurring in switching devices during switching on and switching off the electric circuit. Some older methods of image processing obtained by a high-speed camera are also mentioned. Based on the images obtained from the camera, it is possible to make an equidensity or an equidensitogram that is used to monitor the arc in a quenching chamber. The second part includes the description of an experiment performed in a laboratory and the description of the high-speed camera used during this experiment. A modern method of the image processing using software Matlab is also described. An equidensitogram showing different levels of radioation was made in Matlab from the obtained images.
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Tribological behavior of detonation nanodiamond dispersed in lubricants
Dočekal, Martin ; Čermák, Jan (referee) ; Svoboda, Petr (advisor)
Currently tribological laboratories are looking for a new type of solid ingredients, to create a lubricating composition with minimal friction, heat resistant, with particles well dispersed in oils, sedimentation stable, improving the running properties and to minimize the concentration of solids. Nanodiamonds (DND) could exhibit the possible solution. These particles (in nanometers size) have very good physical and chemical properties, high hardness and resistance. The main advantages are effectiveness at low concentrations, compatibility with various types of oils or environmental safety (carbon additive, unlike metal) in a comparison with other types of additives. However, it is necessary to study these ingredients. The aim of research was to examine the influence of diamond nanoparticles on friction in a lubricated contact (elastohydrodynamic mode). Using tribological equipment, 3D optical profilometer and a microscope, we compared and evaluated using oil with diamond nanoparticles as well as without them. The research focused on the behavior of nanoparticles in contact and the effect they have on friction. To assess these properties of nanodiamonds, EHD optical tribometer was used (this is a device designed for the study of thin lubricating films). 3D optical profilometer and a microscope to assess the wear. And to determine the relationship between the coefficient of friction (COF) and time, Mini Traction Machine was used.
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Experimental study of the starved lubrication
Novotný, Antonín ; Čermák, Jan (referee) ; Košťál, David (advisor)
This master’s thesis deals with the experimental study of an elastohydrodynamic contact under conditions of insufficient lubricant supply. Starvation level of this type of the contact may be experimentally determined based on the input position of the meniscus, but this way can’t determine all its levels of starvation. Consequent development in the field of tribology achieved theoretical model that can determine at all levels of starvation depending on the thickness of the lubricant film entering the contact, but it is relatively difficult for experimental verification. The main goal of this work is an experimental study and describes the behavior of elastohydrodynamic contact at an exactly defined thickness of the lubricant film at the contact input. The benefit of this work is a validation of that mentioned theoretical model for base oils and greases made from them, and mutual comparison of their behavior.
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Physics Simulation for Pinball Game
Čermák, Jakub ; Polok, Lukáš (referee) ; Zachariáš, Michal (advisor)
The objective of this work is to create a library for physical simulation and using the library to create a game of pinball, on which you can test functionality of the library. Problems that appeared during the creation of the library, are described in this paper along with their solutions. In particular, tunneling, detection and results of collisions. Subsequent optimization solutions to these problems for our specific library. Of no smaller importance are principles which reduce the requirements of the final simulation. Among the most important ones are the correct choice of limits, detection of rolling and sleep of slowly moving dynamic objects.
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Calculation of the size of the surface area of deciduous trees and their potential for eventual use in a forensic-expert practice
Honzová, Markéta ; Čermák, Jan
Calculation of the surface area of above ground parts of the tree of chosen species individuals (oak, ash, small-leaved lime) was based on a set of data measured in a flood plain forest in Lednice in southern Moravia. The basic principle is to convert volume values of the tree skeleton (stem, branches) in thickness classes into the size of the area. There was reviewed the importance of these parameters in relation to forensic ecotechnique. In particular, there was assessed usefulness of results for determine functions of trees in terms of allometric relationships (e.g. cambium area in relation to base), importance of the size of bark area to capture dust particles, water interception or absorption of noise.
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Experimental Study of the Lubricant Film under Starved Conditions
Košťál, David ; Čermák, Jan (referee) ; Dzimko, Marián (referee) ; Ali, Fadi (referee) ; Křupka, Ivan (advisor)
The dissertation thesis deals with an experimental study of an elastohydrodynamic contact under insufficient lubricant supply. Theoretical studies published in this research area focus mainly on the development of theoretical models and there is an insufficient number of experimental studies which validate these models. There are two basic methods of starvation severity control in published theoretical models: by positioning of an inlet meniscus and by setting the thickness of an oil layer in the vicinity of contact inlet. The second method is more suitable when considering a wide range of operating conditions, however it is difficult to ensure experimentally. This thesis presents original experimental results and aims to describe the starvation severity level as a function of the inlet film thickness. Deeper understanding of fundamental processes in starved elastohydrodynamic contacts enables the development of more precise models, better ability of prediction of the starvation and improves the ability to avoid starvation in the early design process of key tribological components.
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Standardization of Remote Sensing Usage for Forensic Ecotechnique: forest and trees
Introvičová, Sabina ; Čermák, Jan (referee) ; Ulrich, Radomír (referee) ; Alexandr, Pavel (advisor)
The thesis presents the main points of standardization of remote sensing (RS) usage for Forensic Ecotechnique: forest and trees (FEft). Based on the study FEft expertise database, the types of expertise, which remote sensing data have already been used and the types where the use of remote sensing increases the exactness of solutions were analyzed. RS data are essential in a problematic situation when an examined object does not exist or has been changed at the time of the assignment. This situation may be solved by obtaining information about the investigated object via retrospective image data, as described in the model example. There are chosen categories of image data relevant to the needs of experts in this thesis. These categories of RS data and their products are described with an indication of their possible use in the expertise processing, including freely available or paid resources and archives of image data.
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The Calculation Of The Amount Of Material Injury Caused By The Forests In The Areas Of Implementation Of Water Management Structures
Bureš, Petr ; Čermák, Jan (referee) ; Vala,, Vlastimil (referee) ; Alexandr, Pavel (advisor)
Problem situations in damage to forests as a result of construction activities is the total of its quantification, because of not only to damage to the forest and the land intended for the performance of the function of the forest, but also to damage to the water feature of the forest. The emergence of the crop damage and forest grounds occurs at the same time damage to the management. Broken water conditions on the forest grounds, inter alia, that the environmental damage (or one of its components), are also material injury for the owner of the forest, because it directly affect the amount of the additional costs linked to its management in the forest. The existing decree MZe ČR no. 55/1999 Coll. on the method of calculating the amount of loss or damage caused to forests assesses only the injury or damage to the forest and the land intended for the performance of the functions of the forest, but does the forest and its other non-production function as a forest ecosystem. The damage (the material injury) on the water feature of the forest is not the above mentioned decree dealt with. Initially formulated the problem lies in finding the right way of solving how to objectively quantify the financial damage to the forest, inc. damage to the water feature of the forest and thus closer to the actual damage to the exaktnosti forest, resulting in direct connection with the location and the realisation of the buildings.
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Correlation of AE Signal Changes to Rolling Contact Damage Propagation
Nohál, Libor ; Čermák, Jan (referee) ; Hájek, Karel (referee) ; Hutař, Pavel (referee) ; Mazal, Pavel (advisor)
This PhD thesis deals with the experimental study of more precise rolling contact fatigue damage detection using acoustic emission method. A series of experiments was carried out on two representatives bearing steels and the analysis of sensitivity for the presence of contact damage was performed on selected parameters of acoustic emission. The extent of damage was classified into four classes and signal parameters the most characterizing the development of damage were correlated with the extent of damage. It was also verified the influence of lubricants on acoustic emission signals. The results have an impact on the implementation of more precise rolling contact fatigue tests and evaluation of parameters of acoustic emission signal. On the basis of experiments was established methodology for more precise RCF testing method using acoustic emission on test-rig AXMAT II.
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Stability of Neutral Delay Differential Equations and Their Discretizations
Dražková, Jana ; Čermák, Libor (referee) ; Šremr, Jiří (referee) ; Čermák, Jan (advisor)
Disertační práce se zabývá asymptotickou stabilitou zpožděných diferenciálních rovnic a jejich diskretizací. V práci jsou uvažovány lineární zpožděné diferenciální rovnice s~konstantním i neohraničeným zpožděním. Jsou odvozeny nutné a postačující podmínky popisující oblast asymptotické stability jak pro exaktní, tak i diskretizovanou lineární neutrální diferenciální rovnici s konstantním zpožděním. Pomocí těchto podmínek jsou porovnány oblasti asymptotické stability odpovídajících exaktních a diskretizovaných rovnic a vyvozeny některé vlastnosti diskrétních oblastí stability vzhledem k měnícímu se kroku použité diskretizace. Dále se zabýváme lineární zpožděnou diferenciální rovnicí s neohraničeným zpožděním. Je uveden popis jejích exaktních a diskrétních oblastí asymptotické stability spolu s asymptotickým odhadem jejich řešení. V závěru uvažujeme lineární diferenciální rovnici s více neohraničenými zpožděními.
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