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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

Terahertzové záření v nanostrukturách / Terahertz radiation in nanostructures

Klimovič, Filip January 2019 (has links)
V této teoretické práci se zabýváme kvantově mechanickými jevy, jež jsou spjaté s vodi- vostními elektrony uzavřenými v kvantových tečkách. Nejprve je odvozen model nanokrys- talu jakožto potenciálové jámy. Při tom se ukazuje, že pouze objem, ne tvar, je významným parametrem modelu pro účely terahertzové spektroskopie. Studované geometrie jsou tak vzájemně zaměnitelné a výběr mezi nimi m·že zjednodušit dané úlohy. Pro zkoumání depo- larizačních efekt·, které jsou zahrnuty v depolarizačním faktoru v Maxwell Garnettově teorii efektivního prostředí, je zvolena sférická symetrie. V rámci poruchy prvního řádu je vyřešena Poissonova rovnice pro elektrony rozmístěné uvnitř koule podle vlnové funkce a je určen depo- larizační faktor. Zatímco v klasické limitě tento nabývá p·vodní hodnoty, pro nanokrystaly se zvyšuje a maxima je dosaženo v ne-degenerovaném režimu, kdy je obsazen pouze základní stav. Navýšení depolarizačního faktoru posouvá plasmonovou rezonanci směrem k vyšším frekvencím. 1
32

Identifikace bodových zdrojů znečištění povrchových vod a jejich kvantifikace na vybraných povodích na Šumavě / Identification of point sources of surface water pollution and their quantification in selected catchments in the Šumava Mountains.

TOMKOVÁ, Zdeňka January 2010 (has links)
An evaluation of chemical parameters of surface waters proceed in the three small basin areas in Šumava Mountains, in the area of Svatý Tomáš highlands, during the year 2009: Bukový (woods), Mlýnský (semi{--}intensive and drained pasture, part of Pasečná village) and Horský stream (wetlands, woods, mowed meadows, a part of Svatý Tomáš village). The aim was to chart the three main periods during the year. The spring sampling (the 12th May) should illustrate the beginning of growing season with higher water flow rates. The summer sampling (the 21st July) is the period on the top of growing and touristic season, seasonal works in wood and especially in agriculture (grazing and mowing meadows). The last sampling (the 21st October) represents the season at the end of growing season, generally with the lowest flow rates in the stream, the end of touristic season and the end of full{--}area grazing. Already during the field research, involving the water sampling and conductivity measurement, there were some inflows with increased concentrations of dissolved solids found. Whereas in Bukový stream, as has been assumed, these inflows didn´t more or less occur, in Horský stream they had, relatively surprisingly but significantly, appeared immediately in headwater area. The elevated concentrations of dissolved solids occurred in Mlýnský stream in the whole area of basin, as has been assumed regarding to drainage and full{--}area grazing. One year monitoring proved the advantage of water quality evaluation using simple measurement of conductivity in field. High water conductivity in field was subsequently confirmed by laboratory analysis of selected ions. On the basis of identification of point sources of pollution, the recommendation improving present condition was suggested.
33

Spektrální a transportní vlastnosti korelovaných elektronů v neuspořádaných slitinách / Spectral and transport properties of correlated electrons in disordered alloys

Pokorný, Vladislav January 2013 (has links)
We develop methods how to calculate charge transport in disordered systems applicable in all disorder regimes. They allow to calculate vertex corrections to the electrical conductivity and the diffusion coefficient in models of elastically scattered electrons in the presence of random scatterers. These methods are based on an asymptotic limit to high spatial dimensions. The resulting formulas lead to reliable results free of unphysical behavior, as illustrated on a gallery of numerical examples.
34

Regulation of stomatal development by environmental conditions and physiological processes in the leaf

VRÁBLOVÁ, Martina January 2017 (has links)
Stomatal development and its regulation by environmental conditions (light, CO2 concentration) and physiological processes in the leaf of higher plants were investigated. The study was based on the assumptions that stomatal development should be regulated by signals coming from both external environment and leaf interior, and that the signal should be transduced from cotyledons to leaves. Transgenerational effect in stomatal development was also studied. Molecular and physiological approaches were applied to reveal the relationship between leaf environment, stomatal development, stomatal function and leaf physiology.
35

Konstrukční optimalizace dílu pro tepelný spínač / Structural optimization of the heat switch part

Zemek, Albert January 2020 (has links)
This diploma thesis deals with the design of a structure for heat transfer path of miniaturized heat switch. The focus is on production using SLM additive technology. The aim is to assess the possibilities of using metal 3D printing on a part intended primarily for heat transfer. This work presents several concepts of structure arrangement, which are further analysed and evaluated. The results show the potential of additive technologies in this area and the proposed structures meet the heat transfer requirement according to the calculations used.
36

Gelové polymerní elektrolyty s nanočásticemi oxidu hlinitého / Gel polymer electrolytes with nanoparticulars Al2O3

Procházka, Jaroslav January 2008 (has links)
This work deals with electrolytic conductivity of gel polymer electrolytes. In the theoretical part of the work the methacrylates, the polymerization and the basic outlines of gel polymer electrolytes conductivity are described. The preparation and electrical conductivity of gels based on PMMA are described in the experimental part.
37

Elektrická vodivost alternativních elektroizolačních kapalin / Electrical conduction of alternative electroinsulating liquids

Reňák, Ladislav January 2011 (has links)
This labor deals with features of alternative electrical insulating liquids and also petroleum-base liquids. It examines their usage in the electrotechnical industry. The practical part of the thesis deals with measurement of absorption charakteristics of biodegradable electrical insulating liquid MIDEL 7131 and the petroleum - based transformer oil TRAFO N. The results of the measurement are examined by the help of substitutional math function.
38

Elektrolyty s rozpouštědly typu sulfolanu / Electrolytes based on sulfolan and similar solvents

Máca, Josef January 2011 (has links)
Submitted thesis deal with study of aprotic electrolytes in order to increase the safety for use in lithno – ionts accumulators. Increase of safety is specified by measuring the flash point of each electrolytes, at the same time are evaluated also other parameters important for use in accumulators. For determine the window of temperatures where the electrolytes can work is measured by melting point. The melting point is measured by cryoscopy. From electrical properties is measured specific conductivity of the electrolyte.
39

Aprotické elektrolyty pro lithno-iontové akumulátory s vyšší teplotní stabilitou / Aprotic electrolytes for lithium-ion batteries with higher temperature stability

Bajer, Michal January 2013 (has links)
Master thesis deals with safety of aprotic electrolites used in lithium – ion accumulators. Beside conductivity and viscosity of electrolytes is work focused to flashpoint of electrolytes with flame retardants. In main part of work is shortly explained lithium ion accumulator used materials and fundamentals. Flame retardancy mechanisms and used materials are disscussed too. In practical part work deals with description of used measuring methods and evaluation of gauged data. At least optimal composition of electrolyte with flame retardant is proposed.
40

Syntéza a analýza kompozitních oxidových keramik v přítomnosti nekonvenčních energetických polí / Synthesis and Analysis of Composite Oxide Ceramics in Presence of Nonconventional Energetic Fields

Bartoníčková, Eva January 2010 (has links)
Synthesis and bulk analysis of composite ceramic oxide materials and materials with perovskite-defect structure is presented within this work. Syntheses of these advanced ceramics materials were carroed out by using of nonconventional techniques (microwave-assisted hydrothermal synthesis and polycondensation techniques) and by conventional mechanochemical activation followed by high temperature solid state reaction. X-Ray difraction (XRD), Rietveld analysis, scaning microscopy (SEM), microalysis EDS-SEM, thermal analysis (TG), infrared spectroscopy (IR), determination of particles size and specific surface area were used for description of synthesized products. In case of perovskite system based on La-Sr-Fe-Ti-O electrochemical properties were studied. Part of work was focused on chemical analysis of synthesized composite oxide materials and decomposition hard structured products by using of nonconventional fields.

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