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Povrchová aktivita osmi běžných druhů chvostoskoků ve smrkových lesích a na pasekách po kůrovcové kalamitě v Národním parku Šumava, Česká republika
Brůhová, Jindřiška ; Rusek, Josef
Surface activity of eight common epigeic species of Collembola were studied in spruce forests, dead spruce forests and clearings in the Šumava National Park, South Bohemia, Czech Republic: .i.Lepidocyrtus lignorum, Leidocyrus cyaneus, Pogonognathellus longicornis, Tomocerus minutus, Tetracanthella stachi, Allacma fusca, Entomobrya nivalis, Dicyrtomina minuta./i.. Five pitfall traps were exposed at each of the 9 sites in the summer and autumn periods to study the impact of spruce forest die-off after bark beetle attack (dead forests) and on clearings. Material comprising 79435 specimens was evaluated in this study using the non-parametric Kruskal-Wallis test for comparing Collembola activity between the sites and seasons. Complete linkage (Euclidean distances) cluster analysis was used for comparing the collembolan activity in all nine sites.
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Effect of surface texturing on starved contact
Jordán, Jakub ; Náhlík, Luboš (referee) ; Křupka, Ivan (advisor)
The diploma thesis deals with the analysis of the effects surface texturing on starved contact. Experimental verification was realized on apparatus simulating contact between a steel ball and glass disc using colorimetric interferometry and high-speed camera. The work deals with lubrication regimes, problems with starved contacts and surface texturing which can reduce effects of starvation on non-conformal surface contacts.
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Optimization of Manufacturing and Assembling Technology of the Valve Bolt
Hrouzková, Andrea ; Zapletal, Josef (referee) ; Doležal, Pavel (advisor)
The thesis aimed to study the impact of manufacturing and assembly technology, the valve bolt fitted to diesel high pressure pump CP3 in the Bosch, which has been found to leak. As experimental material was chosen heat treated bolts M16x1,5 made of material 12 050th. Groups of samples were produced in two ranges hardness. Experimental determination of the optimum range of hardness was assessed on the basis of the results of the process of the screw and set the value of plastic deformation of the sealing surfaces of the parts. Experimental section also deals with the analysis of bearing surfaces on the pump and the components, after the screw process. To some extent, is observed as surface treatment
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development of fluorosenzor based on chemically modified electroluminescence diods.
Blažková, Ivona ; Jelínek, Ivan (advisor) ; Dejmková, Hana (referee)
Luminescence sensors based on LED were prepared by modification of LED poly- carbonate surface and following binding of luminescence dyes on this surface. Two methods of modification were utilized. The first one was the oxidation of the surface yielding free carboxylic groups. Such modified LEDs were then covered by cationic cresyl violet dye. The second modification consisted of nitration and consequent reduction to free amino groups followed by binding of anionic sulforhodamine dye. The stability of emission and the stability of dye binding were studied. Then, the response of constructed sensors to toluene as analyte in gas and liquid phase was measured.
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Changes in structure and phase composition in the surface of tram rail
Švábenská, Eva ; Roupcová, Pavla ; Schneeweiss, Oldřich
We have investigated structure and phase composition of surface layer of tram rails after long time running and the results were compared with those obtained on the original part of material. Changes due to effects of severe plastic deformation together with thermal shocks by friction process were expected. The information about structure and phase composition was obtained by optical and scanning electron microscopy, X-Ray Powder Diffraction, Mössbauer Spectroscopy and Glow Discharge Emission Spectroscopy (GDOES) and this was completed by microhardness measurements. The results show that the surface layer in comparison with the original material exhibits important changes in grain structure, an increase in microhardness and high content of iron oxide and hydrooxides. According to the depth profile of the chemical composition measured by GDOES there is an increase in carbon content in the surface layer which can be effect of up-hill diffusion.
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Passivation of Aluminum and Aluminum Alloys in passivation baths without Cr6+ Compounds
Macháč, Pavel ; Tulka,, Jaromír (referee) ; Molliková, Eva (advisor)
This diploma thesis deals with evaluation of efficiency of protection conversion coatings created by passivation metals and alloys in passivation baths without chromium compounds. The theoretical part is initially concerned with question of electrochemical corrosion of metals, consequently there are mentioned different methods of corrosion protection. The main section of theoretical part of this thesis deals with chromate conversion coatings, description of their protective efficiency (including their unique self-healing effect) and then with account of new chromate-free conversion coatings occurring as chromate alternatives, whose usage is constrained because of their content of hexavalent chromium, which is highly toxic, oxidizing and also carcinogenic and thereby very dangerous for human body and the environment. Experimental part of this thesis is concerned with evaluation of efficiency of particular conversion coating which is quite commonly use in some applications as chromate alternative. It is chromate-free conversion coating which is created by passivation of metals or alloys in passivation bath Pragokor BP, which contains zirconium fluorocomplexes and is without any chromium or other toxic or ecologically unhealthy compounds. The influence of sealing of the coating in preparation Pragokor Seal Al and also other surface treatments such as application of conservation wax WAXENG or cold application of zinc coating were tested too. Efficiency of mentioned surface treatments was then evaluated on aluminum and steel by laboratory accelerated and atmospheric corrosion testing.
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Embrittlement of TiAl intermetalics induced by surface oxidation
Fukátková, Pavla ; Jan, Vít (referee) ; Dlouhý, Ivo (advisor)
This work aimed to study the effect of surface oxidation of TiAl intermetallic alloys, its fracture behavior and study the formation and stability of picked coatings that could prevent these phenomena. ?-TiAl alloy (Ti46Al7Nb) was examined by three different coatings (AlCr, AlCrN and AlCrNAg). Firstly, it was carried out short-term exposure to high temperature in an inert atmosphere for all coatings. Secondly, there were experiments of cyclic exposure to high temperature in normal atmosphere and isothermal high-temperature exposure in a normal atmosphere. During high-temperature experiments in normal atmosphere mass gain was measured and it was monitored a surface texture. Finally, the most promising coatings were chosen, and those were evaluated in bending strength.
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Surface texturing of rubbing surfaces
Chlachula, Petr ; Čermák, Jan (referee) ; Křupka, Ivan (advisor)
Surface texturing of rubbing surfaces represents the way how to increase tribological performances by improving the lubrication film formation and diminishing friction and wear. Its application in machine components requires detailed understanding of the mechanism taking place between rubbing surfaces in microscopic scale. This diploma thesis is focused on the processes taking place in tribology systems to consider the possibility of surface texturing applications in highly loaded machine parts operated under transient operational conditions.
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Sorption and Stabilization of Metals/Mettalloids by Innovative Synthesized Sorbent Amochar.
Ouředníček, P. ; Trakal, L. ; Komárek, M. ; Pohořelý, Michael
Remediation of contaminated soil which is based on stabilization and immobilization of potential\nhazardous substance by sorption materials has been studied intensively nowadays. Biochar – activated organic carbon belongs to this group of stabilizing agents which can adsorb wide range of contaminants, including metals/metalloids. Surface area of the biochars is quite large in general and functional groups (e.g. COO–) can form chelates or alkaline elements on the surface, which is represented by cation exchange capacity. Altogether with the high pH values (7.00 – 10.00), biochars are quite effective sorbents and can adsorb metals/metalloids from the solution (ground water), especially in acidic soils (in the environments affected by intensive mining activities). Sorption\neffectiveness can be increased (especially for As (V) or Cr (VI) sorption) by modification of biochar by various types of secondary oxides. Innovative sorbent AMOchar (AMO + biochar) has been synthesized currently. The product was prepared by adding of biochar to the reaction solution during amorphous manganese oxide (AMO) synthesis. The AMOchar was formed mainly by Mn-oxalates which had coated surface of the pristine biochar. AMOchar composite was able to remove significantly higher amounts of various metal(loid)s from the solution despite the rather high pH of the material. Sorption effectiveness was high not only in case of Pb (II) sorption (almost 99%), and Cd(II) (51.2%), but also a very high amount of As(V), 91.4%. Additionally, both AMOchar composite was able to reduce Mn leaching. This can avoid potential post-contamination caused by the dissolution of less stable Mn-oxalates as observed in the pure AMO.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_22316111113040 - PDF
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