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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Studium anizotropie tvorby mechanických dvojčat v hořčíkové slitině AZ31 / Study of twinning anisotropy of AZ31 magnesium alloy

Zdražilová, Zuzana January 2011 (has links)
In the present work the deformation behaviour of magnesium-based alloy AZ31 which was produced by horizontal continual casting is investigated. Samples with two different orientations are deformed in tension and compression at strain rate of 10-3 s-1 in temperature range of 20 řC to 300 řC. Simultaneously, the acoustic emission is recorded and studied with focused on mechanical twinning. The mechanisms of plastic deformation of material and anisotropy between tension and compression are discussed. Dependence of deformation behaviour on temperature is analyzed. The microstructure of original and deformed material is also studied by means of optical microscopy.
32

Roztoková dynamika komplexů LnIII s monofosforovými deriváty H4dota sledovaná metódou NMR / NMR study of solution dynamics of LnIII complexes of monophosphorus H4dota analogues

Svítok, Adam January 2021 (has links)
Lanthanides have several specific properties which cannot be found for other elements in the periodic table. Among various applications of lanthanides, complexes of LnIII ions are used in medicine, e.g., as contrast agents in MRI, as luminescent probes or as radiopharmaceuticals, where their specific properties are important. These complexes must be kinetically inert to prevent release of highly toxic "free" LnIII ions. This requirement is fulfilled with pre-organized ligands such as analogues of H4dota (1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid). Many of important properties of LnIII complexes of H4dota, such as relaxivity, isomerism and fluxionality, depend on the solution dynamics of the complexes. However, the knowledge of this solution dynamics is limited for LnIII complexes of H4dota derivatives with phosphonate or phosphinate pendant arms. Recently, a new dynamical process where phosphonate oxygen atoms interchange through a bidentate phosphonate intermediate ("a phosphonate rotation") has been proposed by DFT calculations but unconfirmed experimentally. To prove the process experimentally, solution dynamics of LnIII complexes of monophosphonate and monophosphinate derivatives of H4dota was investigated. Especially, to examine the "P-rotation", 17 O NMR spectroscopy was used...
33

Příprava a charakterizace hybridních materiálů na grafenové bázi / Preparation and Characterization of Graphene Based Hybrid Materials

Hrubý, Jakub January 2017 (has links)
Grafen v kombinaci s komplexy kovů by mohl poskytnout nové přísutpy v hybridních materiálech založených na grafenové bázi a v oblasti molekulárního magnetismu. Obě témata jsou velmi diskutovaná jako taková, nicméně, výzkumu vedoucího k možnosti jejich míchání není mnoho. Vzorky byly připraveny sonikací grafitu v kapalné fázi, což vedlo k exfoliaci grafenu. Následně byly nadeponovány pomocí modiikované Lagmuirovy– Schaeferovy depoziční metody různé komplexy kovů na substrát pokrytý grafenem. Klíčovým krokem bylo určení vlastností takto připraveného materiálu. Proto byly následně vlastnosti takového hybridního materiálu charakterizovány pomocí vysokofrekvenční elektronové paramagnetické rezonance (angl. HFEPR), rastrovacího elektronového mikroskopu, (angl. SEM), Ramanovou spektroskopií a čtyř bodovou metodou měření odporu. V této práci jsme potvrdili naši presumpci, že je možné vytvořit hybridní materiál smícháním exfoliovaného grafenu s molekulárními magnety pro získání nových magnetických a elektronických vlastností, které by mohly být využity v další generaci detektorů a elektroniky.
34

Posouzení environmentální zátěže technologií práškového lakování / Environmental Impact Assessment for Powder Coating Technology

Havlíček, Lukáš January 2018 (has links)
This diploma thesis is focused on evaluating an environmental impact of using LCA methodology. LCA is a methodology of powder varnishing. The first part of the thesis is concerned with technologies modifying metal surfaces. An analysis of LCA technology was executed and a technological process was described. As a part of theoretical part, a description of available methods evaluating environmental impact was made. According to description the LCA methodology was chosen. In practical part of the thesis an analysis of material and energetic inputs of each process was made.
35

In-situ elektronová mikroskopie / In-situ electron microscopy

Bukvišová, Kristýna January 2019 (has links)
Cílem diplomové práce je popsat oxidaci nanotrubic sulfidu wolframičitého za zvýšených teplot v přítomnosti vodní páry. Na jejich povrchu se nejprve vytvoří nanočástice oxidu wolframu, ze kterých potom vyrůstají nanodráty. Na základě in-situ experimentů v rastrovacím elektronovém mikroskopu je navržen mechanismus reakce a ten je zjednodušeně popsán analyticky. Ukazuje se, že elektronový svazek má zásadní vliv na reakci.
36

Analýza zubů a kostí metodou spektroskopie laserem buzeného plazmatu / Analysis of teeth and bones by laser-induced breakdown spectroscopy

Šindelářová, Anna January 2021 (has links)
The presented diploma thesis deals with the elemental composition of hard tissues – human and murine jaws studied by laser-induced plasma spectroscopy (LIBS). Samples of human teeth contained a disease called ankylosis and the difference in elemental composition of healthy and diseased tissue was observed to localize ankylosis in the tooth. When evaluating the map of the spatial distribution of phosphorus and calcium, a decrease in the concentration of these elements in the ankylosis infected area was observed. Furthermore, murine jaws containing lead were analyzed. When assessing the spatial distribution of lead in tissue, it was found that lead was incorporated in murine teeth in the enamel at the tip of the incisor and molars. In conclusion, LIBS method achieved good results considering the detection of the elemental distribution of hard tissues. It enables to differentiate parts of the tooth in terms of elemental composition and tissue hardness and also to detect changes in the matrix caused by a disease or bioaccumulation of heavy metals.
37

Možnosti odstranění zelených řas z betonových konstrukcí / The possibilities of green algae removal from concrete structures

Cochlárová, Milena January 2014 (has links)
This master´s thesis deals with the suppression of algal growth on concrete structures. The subject of the work is to design and coatings their own structural concretes containing protective element in order to inhibit the growth of algae. As the coating are tested commercially avaiable and newly created systems. Testing systems are based on the portland cement and chelates of metal (Cu, Ni, Co, Mn, Zn, Al).
38

Technologie řezání plazmovým paprskem / Technology Plasma Beam Machining

Sedlák, Ondřej January 2011 (has links)
This diploma thesis focuses on the unconventional method of metal separation, namely on the cutting technology based on the plasma arc. The introductory part deals with studies which focus on the given issue from a theoretical point of view. The core of the work rests in the practical part which is dedicated to the production of samples using a plasma burning machine called Hypertherm HPR 260. The burned samples are monitored and assessed for the surface quality and dimensional accuracy for every created part. The final part of the work is dedicated to the techno-economic assessment of the burned parts. In the end, the evaluation of the attained results is made.
39

Vliv oxidů těžkých kovů na tvorbu a vlastnosti portlandského slínku / Influence of heavy metal oxides on the formation and properties of Portland clinker

Kašpárková, Kateřina January 2016 (has links)
The Master’s thesis is focused on a study of the effect of increased content of heavy metals present in a raw meal on the formation and properties of prepared clinker and acquired cement. Main attention is devoted to changes on the physical, mechanical, microstructural and hydration properties. The theoretical part contains an overview of clinker minerals occurring in Portland cement including the possibility of incorporation of heavy metals into their structure and affecting the properities of the cement. In the experimental part, there is compared the effect of heavy metal oxides on the composition and hydration properties of portland clinker and physical-mechanical and microstructural properities of cement pastes prepared from this clinker.
40

Teoretické studium aplikačního potenciálu nových dvourozměrných materiálů / Theoretical investigation of novel two-dimensional materials with application potential

Lyu, Pengbo January 2019 (has links)
Electron confinement due to the two-dimensional (2D) nature of layered materials accounts for their fascinating electronic properties and for their applications in new-generation electronic devices. Moreover, the large specific surface area of 2D materials also enables their use in surface-related applications, such as catalysis and adsorption. In addition, these 2D materials are promising photocatalysts thanks to the shorter migration distance of photogenerated electrons and of electron holes. The research reported in this thesis aimed to provide atomistic insight into 2D layered materials, particularly into their structures, electronic properties and potential applications in the field of catalysis, photocatalysis and alkali metal ion batteries. Our findings are not only theoretically relevant but also open new research avenues for our experimental collaborators to improve specific properties and activities of their materials. The main results from this thesis, for five different classes of 2D materials, are summarized below. 2D covalent organic frameworks (COFs). CTF-type COFs with similar topology but different nitrogen-to-carbon ratios were investigated for their potential in photocatalytic water splitting. More specifically, torsion and bending effects on structure stability were investigated in...

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