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Contact erosion of switchgear under real conditions
Holoubek, Josef ; Bušov, Bohuslav (referee) ; Valenta, Jiří (advisor)
This bachelor thesis is focused on the material loss - contacts erosion during switching process of the switchgears. First part is focused on the switchgears generally, their dividing and functions. Then there is closer look on the contacts of switchgears and what is necessary to be considered during their designing a operating. In this part there is also section devoted to the theory of the contacts erosion including the formulas for material loss calculation, which I found in existing literature. Practical part is focused on the contact system model and the measuring performed on this model. Measuring was also performed on the real switchgears for common use. There is also part devoted to this measuring. In the last part of thesis the analyze of the measured values is performed.
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Influence of multiple cyclic loading on the selected parameters of lightweight concrete
Alexa, Martin ; Misák, Petr (referee) ; Kocáb, Dalibor (advisor)
The diploma thesis deals with the observation of the values of selected parameters (especially the static modulus of elasticity) of light-weight concrete in compression before and after multiple cyclic loading. The deformation of test specimens during multiple cyclic loading were measured with resistive strain gauges. Test specimens (cylinders with a diameter of 150 mm and height of a 300 mm) were cyclically loaded and up to 4 500 loading cycles were performed. The aim of this thesis is assessment changes in the values of static modulus of elasticity depending on the number of loading cycles.
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Contact erosion of switching devices
Píška, Jakub ; Šimek, David (referee) ; Valenta, Jiří (advisor)
This bachelor thesis deals with the erosion of contacts, as one of the negative phenomena affecting contacts of switchgears. In its first part, it briefly summarizes the other negative influences that must be considered when designing switching devices. In the following part, the physical mechanism of erosion and the primary criterion of assessment - weight loss are approached. The last and main part of the work deals with design of the contact system for comparing this loss for for frequently used materials and testing on a real switchgear. After the tests, the results were analyzed primarily from the perspective of ignition angles, the polarities of the current pulse and the current flowing through the arc. Taking into account the influence of the material composition, the size of the contacts and the presence of the arc-runner.
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Bones implants based on Fe and Mg
Košíček, Adam ; Zatloukal, Miroslav (referee) ; Sedlaříková, Marie (advisor)
This paper work deals with properties of metallic biomaterials in terms of their suitability for use as a temporary metal implants. The work focuses on biodegradable materials based on iron and suitable alloying elements, which would create a perfect implant. A part of this work describes procedure of creating biodegradable metallic samples with alloying element Magnesium and measuring the corrosion rates. There are a few theoretical chapters concerning permanent implants, function and composition of human bones, iron and magnesium in human body and biodegradable materials.
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Posouzení trvanlivosti vybraných druhů dřev pro obchodovatelný výrobek
Sion, Matěj
In this thesis, the problem of the resistance of terrace boards to biological degradation. The following woods were chosen for the experiment: 1) Garapa (Apuleia leiocarpa Vog.) → is a representative of tropical woods and at the same time a species required by customers. 2) Mulberry (Morus) → a possible alternative in future years. 3) Acetylated European alder wood (Alnus glutinosa) → a possible alternative, when this method of modification appears to be very effective. The selected woods were tested according to the ČSN EN 350 standard for resistance to the wood decay fungi of white rot (Trametes versicolor) and brown rot (Gloeophyllum trabeu) and Coniophora puteana). The second part of this thesis was the determination of the total content of extractive substances (ES), phenolic substances (FS), carbohydrates (C), and pH values of aqueous leachate selected wood species. All samples were tested and compared with each other. The wood of the mulberry tree was evaluated and as to how these properties change along the radius of the trunk. The selected woods have been found to be suitable for decking. Weight losses (white and brown rot) were in negative values, so the fungi were not able to attack the wood and it was classified in durability class 1 "very durable". From the point of view of chemical composition, it was found that the most chemical substances are contained in the wood of the mulberry tree, garapa, and the least acetylated alder. In the case of the mulberry tree, it was also found that the amount of chemical substances varies depending on the position along the stem radius. The high resistance of garapa and mulberry to wood-rotting fungi is mainly caused by the content of chemical substances. The resistance of acetylated alder was due to the acetylation process.
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Laboratorní korozní zkoušky kovových materiálů
Gajdošík, Miroslav
Subject of my bachelor's thesis is "Laboratory corrosion tests of metallic materials" examines the impact of aggressive environment and heat processing on the change of losing the weight and mechanical properties structural steel of claas 12 050. The theoretical part simply describes forms, kinds of corrosion and possibly ways how to protect machines against the corrosion. Next point in the theoretical part is corrosion tests. In the practical part is described in detail effect of corrosion degradation to change of weight loss and mechanical properties of structural steel of claas 12 050. The first part of experiment compares results of weight loss after the corrosion degradation of heat-affected and untouched samples also. In the second part exposed samples were subjected to a tensile test followed by conducting the comparison of the measured values. Practical measurement is continuously supplemented by images gradual degradation of corrosion test samples.
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Možnosti využití méně známých druhů zelenin
Fojt, Robin
The bachelor thesis describes the species of vegetables and the detail of the radish that I chose for my work. The practical part is monitored shelf content substances and sensory evaluation. In terms of shelf life and sensory evaluation was the best variety Miyashige and in terms of content materials was the best variety Mantanghong, although not statistically confirmed. Among the storage options, XTend was the best result, which significantly prolonged the shelf life of radish, which was statistically confirmed. Conventional storage is more of a need for shorter storage. The overall rating was the best Miyashige variety, which is most similar to our radish that the European consumer is accustomed to.
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Contact erosion of switching devices
Píška, Jakub ; Šimek, David (referee) ; Valenta, Jiří (advisor)
This bachelor thesis deals with the erosion of contacts, as one of the negative phenomena affecting contacts of switchgears. In its first part, it briefly summarizes the other negative influences that must be considered when designing switching devices. In the following part, the physical mechanism of erosion and the primary criterion of assessment - weight loss are approached. The last and main part of the work deals with design of the contact system for comparing this loss for for frequently used materials and testing on a real switchgear. After the tests, the results were analyzed primarily from the perspective of ignition angles, the polarities of the current pulse and the current flowing through the arc. Taking into account the influence of the material composition, the size of the contacts and the presence of the arc-runner.
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Influence of multiple cyclic loading on the selected parameters of lightweight concrete
Alexa, Martin ; Misák, Petr (referee) ; Kocáb, Dalibor (advisor)
The diploma thesis deals with the observation of the values of selected parameters (especially the static modulus of elasticity) of light-weight concrete in compression before and after multiple cyclic loading. The deformation of test specimens during multiple cyclic loading were measured with resistive strain gauges. Test specimens (cylinders with a diameter of 150 mm and height of a 300 mm) were cyclically loaded and up to 4 500 loading cycles were performed. The aim of this thesis is assessment changes in the values of static modulus of elasticity depending on the number of loading cycles.
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