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Electrode Active Materials for Lithium-Ion Accumulators
Čech, Ondřej ; Oriňáková, Renáta (referee) ; Paidar,, Martin (referee) ; Sedlaříková, Marie (advisor)
This doctoral thesis deals with synthesis and characterisation of electroactive electrode materials for li-ion batteries and accumulators. The work is divided into two main parts. One deals with LiFePO4 based cathode composite electroactive material and in the second is described the synthesis and utilization of monoclinic TiO2(B) as an anode for li-ion cell. The main aim of the work is to relate the synthesis procedure and structural properties of both materials to its electrochemical preformance.
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Characterization of scanning transmission electron microscopy images of thin biological sections
Novotná, Veronika ; Nebesářová,, Jana (referee) ; Krzyžánek, Vladislav (advisor)
Diplomová práce popisuje fyzikální principy mikroskopů TEM, SEM a STEM spolu s jejich vhodností pro pozorování vzorků citlivých na elektrony, jako jsou zalévací média či biologické vzorky. Dále je popsána příprava vzorků pro STEM (TEM) a popis interakcí, ke kterým dochází mezi primárním elektronovým svazkem a vzorkem. Součástí práce je také pojednání o zpracování mikroskopických obrazů s podkapitolou o metodách kvantitativního porovnání obrazů ze STEM. Praktická část práce je zaměřena zejména na měření úbytku hmoty zalévacích médií (Epon, Spurr, LR White) způsobený primárním svazkem elektronů v nízkonapěťovém STEM. Ultratenké řezy několika tlouštěk byly zkoumány při různých nastaveních mikroskopu (urychlovací napětí, celková dávka, proud svazku, čištění povrchu vzorku a komory mikroskopu) a zobrazovacích módech (světlé a tmavé pole). Dále jsou zkoumány také biologické vzorky Krásnoočka štíhlého (Euglena gracilis) zalitého v pryskyřicích Epon a Spurr. Nasbírané snímky, vytvořené algoritmy a získané výsledky jsou diskutovány a zhodnoceny.
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Performance of YAG:Ce Scintillators for Low-Energy Electron Detectors in S(T)EM
Lalinský, Ondřej ; Bok, Jan ; Schauer, Petr ; Frank, Luděk
Cerium activated single crystals of yttrium aluminium garnet (YAG:Ce) Y3-xCexAl5O12 are widely used as scintillators in electron detectors for S(T)EM. Nowadays, it is sometimes necessary to detect low-energy electrons without post-acceleration. In such cases, extremely sensitive detectors are required that are able to detect even electrons with energies of only hundreds of eV while avoiding charging of the scintillator surface. However, commonly used scintillators strongly lose their light yield with the decrease of the incident electron energy. Moreover, a thinner conductive layer on the scintillator surface has to be used to allow low-energy electrons to pass through. Possible charging of the surface negatively affects its cathodoluminescence (CL) light yield. The low-energy electron excitation takes place closer to the scintillator surface where damage can be expected owing to its preparation, which also reduces the CL light yield. The aim was to study the influence of the scintillator and its conductive layer on the low-energy electron detection efficiency.
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Seasonal course of CO2 efflux in grassland and forest ecosystem in Beskydy mts
Dařenová, Eva ; Pavelka, Marian ; Acosta, Manuel ; Janouš, Dalibor
Our aim was to determine seasonal changes of CO2 efflux of the grassland and of the soil and stems in the Spruce forest at Bílý Kříž (Beskydy Mts). For elimination of the temperature dependency of CO2 efflux, standardized CO2 efflux R10 is used. Mean R10 was about 2.50, 5.0 and 0.97 umolCO2 m-2 s-1 for grassland, forest soil and stems. In grassland the R10 course did not show obvious trend. Whereas in the forest soil, the significant increase in R10 at the beginning and decrease at the end of the season occurred, but without any distinct maximum. Similar increase and decrease in R10 was observed in the stem CO2 efflux course as well. But there was a maximum in June and July. The temperature CO2 efflux sensitivity (Q10) was 3.04, 1.90 and 2.25 for the grassland, forest soil and stems. The temperature sensitivity in the forest soil increased shortly after rain. It resulted in a rapid increase in CO2 efflux of the soil as a response to rain.
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Kinetika doznívání scintilačních krystalů pro detektory elektronů v SEM
Schauer, Petr
A study of the decay kinetics of YAG:Ce single crystal scintillators for SEM is presented in this paper. The principal quantities of image quality in SEM are contrast, spatial resolution, and noise. However, to quantify the overall performance of an imaging system, the detective quantum efficiency (DQE) is a better tool as it includes both the modulation transfer function and the noise power spectrum. This means that for a detector to have high DQE, it should possess not only high efficiency and low noise, but also good kinetic properties. Utilizing of the cathodoluminescence decay results, a schematic kinetic model of radiative and nonradiative transitions in the YAG:Ce single crystals is presented.
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Rastrovací elektronová mikroskopie pomalými elektrony
Hrnčiřík, Petr ; Müllerová, Ilona
The largest sample thickness usable for transmission electron microscopy (TEM) is determined by the inelastic and elastic mean free paths (IMFP and EMFP). At primary electron energies normally used for TEM (>50 keV), both the mean free paths decrease as the primary energy is lowered. Attaining a sufficient penetration through a transmission sample of a given thickness is then simply a question of using a suitably high primary energy. As the primary energy is lowered below about 100 eV, however, IMFP is predicted to stop decreasing and to begin to grow again. This opens up the exciting possibility of very low voltage TEM, with poorer resolution but greatly reduced radiation damage compared to conventional TEM
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Výběr nového dodavatele ve firmě INVEST TEL AUTO s.r.o.
Hasmanová, Alena ; Fiala, Petr (advisor) ; Nejdl, Jaroslav (referee)
Cílem diplomové práce je aplikace modelů vícekriteriálního rozhodování na reálný rozhodovací problém ve firmě INVEST TEL AUTO s.r.o. V praktické části je pomocí několika metod vícekriteriálního hodnocení variant nejprve vybrána nejvhodnější automobilová značka, poté je pomocí metod spojitého vícekriteriálního rozhodování navržena skladba první objednávky vozů vybrané automobilové značky.
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