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Analysis of degradation processes of the shock absorber rod
Sýkorová, Jitka ; Juliš, Martin (referee) ; Klakurková, Lenka (advisor)
The bachelor thesis deals with the analysis of degradation processes of the rods of the synchronizer generator. The theoretical part deals with the description of the generator, the analysis of the material, the properties of the brass for the production of the absorber rod and the possible parameters influencing its degradation. The experimental part of the thesis analyzes damaged bars of the shock absorber using destructive and non-destructive techniques, suggests non-destructive testing in-field and determines the dependence of electrical properties on the structure.
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Study of plasmachemical reduction of corrosive layers on brass
Řádková, Lucie ; Selucká, Alena (referee) ; Krčma, František (advisor)
The main topic of this bachelor thesis is plasmachemical treatment of archeological artifacts, especially plasma chemical treatment of brass corrosion layers. Low-pressure, low-temperature hydrogen plasma is used for this process. Nowadays, the technology is used mainly for iron or silver based materials but even for them the optimal conditions for the corrosion removal are not fully known yet. The knowledge about other metallic materials is fully missing. Two sets of brass samples were prepared in different corrosion atmospheres. The first atmosphere was prepared using saturated vapors of HCl. The samples were in this atmosphere during one month, and corrosion layers were orange-brown. The second set was prepared using ammonium solution, the samples were in this atmosphere for one day, corrosion layers were blue. The generation of capacitively coupled plasma in continuous mode by different supplied power was done. The experiments were carried out at 100 Pa with hydrogen gas flow of 50 sccm. Discharge power was varied in the interval 50 – 200 W and the treatment duration was 70 – 140 min. The optical emission spectroscopy of OH radical was used to find out all changes those have been resulting from plasmachemical reactions. The OH radical integral intensities were observed, they were used to monitoring plasma chemical reduction process. Spectral intensity of spectroscope was in the range 290 – 330 nm. After the plasmachemical treatment, it was very difficult to remove corrosion layers of HCl, but removing of NH3 corrosion layers was easy. It was caused by type of corrosion process (corrosion layers were influenced by time of corrosion process). This bachelor thesis is the start to find out conduct corrosion layers of brass in plasma treatment. In future, plasma treatment could be used to treatment of real archaeological artifacts.
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Reconstruction of the town spa in Malé Svatoňovice
Macek, Štěpán ; Špiller, Martin (referee) ; Guzdek, Adam (advisor) ; Kalousek, Lubor (advisor)
The aim of the bachelor thesis was to prepare a documentation for building permits and a part of the documentation for the building construction on the basis of an architectural study, developed in the „AG35 – Monuments Restoration Studio“ module. The topic of the studio work was to think about the appropriate use of a listed building in the historic center of the village of Malé Svatoňovice and to create an architectural study. I have proposed the following concept. The building should serve as a municipal house, so I have concentrated the corresponding functions here: the municipal office, the ceremonial hall, the museum, doctors labs, cosmetics, the pharmacy and finally the spa, which had a long tradition here. When restoring an object, I proceed synthetically. I examine the quality and preservation of individual layers. Then I highlight the best of each one. If some layer have not been preserved, but still have had its qualities, I remind it in a new language. I think it was Tadao Ando who said, "If the genius loci is to be legible, it must be revived and provoked by inventive inputs." I combine modern with historical using timelessness.
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Manufacture of cast Early Middle Age Viking Weapon parts
Brůža, František ; Mareček, Petr (referee) ; Záděra, Antonín (advisor)
The Bachelor’s project is concerned with the research and the following analysis of information and the period technologies needed for making a replica of the brass hilt of a 10th century sword. The project particularly focuses on the period casting technology. Next, the possibility of making a replica by a 3D scan and 3D print is discussed. The project also includes a comprehensive experiment consisting of casting parts of the hilt using the period technology. The functionality reproducing the hilt by 3D technology up to the printed model stage is also tested.
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Reduction of brass corrosion layers using hydrogen plasma
Řádková, Lucie ; Grossmannová, Hana (referee) ; Krčma, František (advisor)
The main topic of this Diploma thesis is the application of low-pressure low-temperature hydrogen plasma for the treatment model samples of rusted brass. Plasmachemical treatment of metallic artifacts is a relatively new way how to remove corrosion of artifacts. The temperature of an object should not exceed 150 °C during the treatment. Corrosion layers were prepared in an ammoniac corrosion atmosphere. The corrosion formation took two weeks. Energy Dispersive X-ray Microanalysis has shown that the corrosion layer was formed by carbon, oxygen, copper, zinc, and lead. The corrosion layers were blue-colored with white crystals on the surface. Except those two colors, brown color was observed on corrosion layers, too. The plasma reactor was a quartz tube with outer copper electrodes and supplied by the RF source of 13.54 MHz. The reactive atomic hydrogen was formed in plasma discharge. This atomic hydrogen reacted with the corrosive layer containing oxygen. This reaction created an unstable OH radical, which emitted light in the region of 305–320 nm. This radiation was detected by the optical emission spectroscopy and it was applied as process monitoring quantity. Rotational temperature and intensity of OH radicals were determined from obtained data. The sample temperature was measured by thermocouple installed inside the sample volume. Rusted samples were treated by low-pressure low-temperature hydrogen plasma. 16 samples were treated at different conditions – plasma power was 100 W, 200 W, 300 W, and 400 W at continuous mode and pulse mode with duty cycle of 25 %, 50 %, and 75 %. The pressure was between 140–160 Pa at hydrogen flow rate of 50 sccm. Samples after plasmachemical treatment were grey colored with white crystals on their surface. Corrosion layers were removed by spatula. The corrosion layers of some samples were easy removable, some others were difficult. Energy Dispersive X-ray Microanalysis, which was carried out after the treatment of 2 selected samples (400 W, 50% pulse mode and 400 W, 75% pulse mode), showed different amounts of carbon, oxygen, copper, zinc, and lead compared to the rusted sample. Other elements in the treated layer were silicon, sulfur, chlorine, and fluorine.
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Brass Corrosion Layers Reduction by Low-Pressure Low-Temperature Plasma
Řádková, Lucie ; Slavíček,, Pavel (referee) ; Zahoran,, Miroslav (referee) ; Krčma, František (advisor)
This thesis presents results of the corrosion layers removal which could be found on the archaeological artefact surfaces. The low pressure low temperature plasma reduction was used for this purpose. Brass samples were chosen for this study. Two different ways have been used to form model corrosion layers. Several sets of corrosion layers were prepared in laboratory in two different corrosion atmospheres, namely ammonia atmosphere and atmosphere of hydrochloric acid. These samples were placed into desiccator. Small quantities of sand were added to some sets of samples so samples with sandy incrustation were prepared. The corrosion layers had been usually formed during four weeks. The second way, which was used to prepare model corrosion layer, was the natural corrosion in soil or compost. In this case, the corrosion layers had been formed approximately 2 years. The samples were treated in the low pressure (150 Pa) cylindrical Quartz reactor (90 cm long and 9.5 cm in diameter) with a pair of external copper electrodes connected via the matching network to a radiofrequency generator (13.56 MHz). The flows of working gases were set by independent mass flow controllers. Whole system was continuously pumped by the rotary oil pump which was separated from the discharge reactor by liquid nitrogen trap with aluminium chips eliminating dust and reactive species from the gas flow. Each sample was placed on a glass holder at the reactor center. Plasma was generated in pure hydrogen or in mixture of hydrogen and argon. Total flow of working gas was 50 sccm. Different ratios of gas mixture were tested, the ratio 30 sccm hydrogen and 20 sccm argon flows was the best. RF discharge was used in a continuous and pulsed regime. Pulsed mode was carried out with various duty cycle at the frequency of 1000 Hz. There were two ways of temperature monitoring. The sample temperature during the treatment was monitored by a K-type thermocouple installed inside the sample in the first case. Thermometer optical probe was connected to the sample surface by a small stainless plate and allowed continuous sample temperature monitoring in the second way. Safe object temperature for copper and copper alloys is 100–120 °C. To avoid exceeding this temperature, power control or the duty cycle in pulse mode were automatically controlled if thermometer optical probe was used. Plasma chemical treatment is based on generation of reactive atomic hydrogen in plasma discharge. The main reactions during reduction were reactions between oxygen and chloride contained in the corrosion layer and the hydrogen ions and neutral atoms generated in the plasma. These reactions create an unstable OH radical, which emits light in the region of 306–312 nm. This radiation was detected by the optical emission spectroscopy using Ocean Optics HR4000 spectrometer with 2400 gr/mm grating. Data obtained from this method were used to calculate rotational temperatures and integral intensity of OH radicals that were used for the process monitoring. Corrosion layer was not completely removed during the reduction, but due to the reactions which occur in the plasma corrosion layer became brittle and after plasma chemical treatment can be removed easily. The SEM-EDS material analyses were carried out before and after treatment of some samples. Some samples were analysed by XRD analysis. EDS analysis showed that amount of oxygen and chloride was decreased, mainly at 400 W pulse mode.
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Influence of anticorrosive surface treatment of steel reinforcement fibers on the properties of ultrahigh-performace cement composite
Bocian, Luboš ; Ptáček, Petr (referee) ; Novotný, Radoslav (advisor)
This thesis characterized surface layer of brass on commercially available steel microfibers. Subsequently, it was studied how to remove this surface layer of brass off these microfibers. Additionally, this thesis investigated influence of removal of brass surface layer on mechanical and ballistic properties of RPC composites. It was also studied how previously mentioned surface layer of brass influences interface between steel microfibers and matrix. It was found out that the surface layer of brass on commercially available steel microfibers is uneven and that the brass fills scratches present on steel underneath the surface layer of brass. It was also found out that conc. HNO3 and mixture of NH3 and H2O2 in volume proportion of 3 : 1 can be used to remove the surface layer of brass. The only thing to consider is that steel microfibers from conc. HNO3 corrode. Flexural strength of composite made with fibers from mixture of NH3 and H2O2 is higher than flexural strength of composite made with commercially available steel microfibers with surface layer of brass after 28 and 95 days. Compression strength wasn’t significantly affected in any composite used in this thesis after 28 and 95 days. Composite made with fibers from mixture od NH3 and H2O2 showed slightly better ballistic resistance than composite made with commercially available steel microfibers with surface layer of brass. In terms of SEM analysis of interface between matrix and steel fibers of certain composite, it was found out that there was no evidence of infiltration of components of brass into matrix.
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New synagogue Jablonec nad Nisou
Gorčák, Lukáš ; Baranyai, René (referee) ; Dulenčín, Juraj (advisor)
The subject of this thesis is the design of a new synagogue in Jablonec nad Nisou. The construction should be an impetus for the return of Jewish traditions and culture to the city of Jablonec nad Nisou. In addition to the synagogue, the buildings also include spaces for the Jewish community and the general public. The building program envisages the design of a synagogue, on the ground floor of which is located the ritual purification bath of the mikveh, then the administrative premises of the Jewish community, a community center with a library, a classroom and a lecture hall, a public part in the form of a kosher restaurant, and a museum with an exhibition space dedicated to Judaism. An integral part of the design is an outdoor public space that offers the possibility of recreation and spending free time. The location of the synagogue has a strong connection with the place of worship of the original burned down synagogue in Jablonec nad Nisou. Spreading awareness and preventing the spread of anti-Semitism is very important to the Jewish community. The building of the synagogue is located in a lucrative area in close proximity to the city center, near an important water feature, the river Lužická nisa. The attractiveness of the area is also complemented by good transport accessibility, especially from the nearby bus station and train station. Good accessibility is also ensured for car and bicycle transport. The individual buildings are designed in a minimalist way, so that they disturb the original historical buildings as little as possible, especially from the period of Art Nouveau and historicism. The form is three imaginary blocks. One separate synagogue is embedded in the slope where the original burned down synagogue was located. Next, two blocks connected to each other by a neck, which are turned towards each other in such a way as to respect the street line and at the same time open up the public space by the river. The facades of individual buildings are finished with concrete screed plaster. The color of the individual buildings is connected with the decoration of the original burned down synagogue. The pure concrete appearance of the synagogue enhances the importance of the sacral space and leaves the possibility of accentuating the decorative brass facade with perforated ornament. The administration and community center building is decorated in yellow tones. The building, which includes a museum and a restaurant, is painted red.
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