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Synthesis of Heterostructure Particles by CVD Method in a Tube Flow Reactor
Moravec, Pavel ; Smolík, Jiří ; Levdansky, V.V. ; Keskinen, H.
Powders of mixed or heterostructure fine particles are of even greater value than the single component ones. During last decade we prepared single component fine particles of silica, alumina, titania and zirconia by decomposition of organoelement precursors in an externally heated tube flow reactor. On the basis of experience with the synthesis of single component particles we prepared mixed or coated multicomponent particles Al2O3-SiO2, TiO2-SiO2 and ZrO2SiO2 by simultaneous decomposition of two precursors in one reactor.
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Factors affecting the occurrence of aquatic macrophytes in the Lipno reservoir
KROLOVÁ, Monika
This RNDr. thesis focuses on the species composition and cover in the littoral of the Lipno Reservoir in 2006. Aquatic macrophytes are an essential component of littoral communities in lakes. Their reasonable development positively affects biodiversity and stability of the aquatic ecosystems and water quality. The aim of this study was to characterise the development of littoral macrophytes in Lipno Reservoir, an artificial lake with seasonal water level fluctuation, and highlight controlling factors for macrophyte occurrence. The development of macrophytes was examined at 114 segments of the shoreline, each 50 m long, situated along the whole reservoir perimeter in regular 1km distances. The segments were surveyed for phytocenology, shore morphology, pedological characteristics of substrate, and anthropogenic impact. The survey identified 53 macrophyte species (24 hydrophilic terrestrial, 17 emergent,1 floating-leaved, 2 free-floating, 4 submersed, and 5 amphibious). The average vegetation cover of the examined segments was 14 %, with approximately one third of the segments without any macrophytes and another third with vegetation cover less than 10 %. Macrophytes occurred only in the uppermost eulittoral zone down to the level of 75 % probability of water surface exceedance. On the basis of a correlation analysis, the major factors affecting macrophyte occurrence in the littoral zone were shore morphology, light conditions in water and erosion effect of waves that together with water level fluctuation caused loss of fine particles from and degradation of the substrate in the littoral zone.
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Fine and coarse aerosol particles in a student's club before and after a smoking ban
Valchářová, Tereza ; Ondráček, Jakub (referee) ; Hovorka, Jan (advisor)
This master thesis was tasked to find out how the parameter of interior atmosphere changes at student's club "Mrtvá Ryba", that means atmospheric aerosols sized from 0,524 to 20 micrometers. This work tries to show indoor aerosols before and after the smoking ban and its comparison. This work describes concentrations PM1 and PM10, and their behavior per day. Concentrations was measured by APS (Aerodynamic particle sizer). The measurement was the first step in the non-smoking club, then processing with retrieved informations in CoPlot, CoStat and Excel, where the statistical method has done, and comparison with previous values. T-tests was used for statistics and linear regresion. The result confirms, what was it supposed to, so concentracion values are significantly different. The average concentration of all measured days (six) of smoking campaign was at PM1 13,28 µg.m-3 and at PM10 23,38 µg.m-3. The average concentration of all measured days (thirty six) of non-smoking campaign was at PM1 4,88 µg.m-3 and at PM10 24,61 µg.m-3. Resulting concentration of aerosol particles was explicity lower at non-smoking period than at smoking period. Contamination of interior enviroment is influenced by many factors. The most important factor is presence of persons and their number, concentration of outdoor...
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Ultrafine Particle Concentrations: Importance of Local Sources and New Particle Formation in Two Central European Cities
Wonaschuetz, A. ; Wagner, R. ; Aschauer, I. ; Haindl, R. ; Ludwig, W. ; Zecha, G. ; Ondráček, Jakub ; Vodička, Petr ; Zíková, Naděžda ; Ždímal, Vladimír ; Schwarz, Jaroslav ; Hitzenberger, R.
In this study, the importance of local primary sources and new particle formation as sources of fine and ultrafine particles is investigated for winter and summer in two central European cities. Particular attention is given to the impact of local meteorological characteristics: air mass origins play a large role in the characteristics of the background aerosol and the concentrations of trace gases associated with new particle formation and growth, and precipitation and thus the condensational sink.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_C22013091713550 - PDF
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Urban and Suburban Intermodal Fraction of Atmospheric Aerosol in Winter 2014
Kozáková, Jana ; Hovorka, J. ; Schwarz, Jaroslav
Fine (PM1) and coarse (PM10-2.5) aerosols differ not only in size but also in the chemical composition, health effects, type of sources, and others. A dividing line between fine and coarse aerosol is not clearly defined. These fractions overlap in the aerodynamic particle size range 1-2.5 μm, also called the intermodal fraction. Sources of both coarse and fine aerosols contribute to the intermodal fraction to a different extent relating to different meteorological conditions and types of locations. According to several studies, the intermodal fraction highly correlated with coarse aerosol in dry areas during high wind speed episodes. In contrast, other studies have shown higher or comparable correlation with fine aerosol. The aim of this study is to characterize the intermodal fraction in urban and suburban localities and estimate to what extent fine/coarse aerosol sources contribute to this fraction.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22014102013540 - PDF
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Current state and prospects of scintillation materials for detectors in SEM
Schauer, Petr ; Bok, Jan
The two principal quantities are important for assessing the quality of each imaging system. Firstly, it is the detective quantum efficiency (DQE), which is primarily a measure of image noise. As the DQE is determined by signal to noise ratio (SNR), the efficient and noise-free components are the key to the high DQE. Second, not less important indicator of image quality is also the modulation transfer function (MTF). MTF describes the ability of adjacent pixels to change from black to white in response to patterns of varying spatial frequency, and hence it determines the actual capability to show fine detail, whether with full or reduced contrast. Using a scanning imaging system the fast components are the key to the good MTF. In a scintillation electron detector of scanning electron microscope (SEM) the scintillator is the most crucial component, because it significantly influences both the DQE and MTF. The aim of this study is to assess the scintillation materials suitable for SEM detectors characterized by the both high efficiency and fast decay characteristic.
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Concentration of HCl, HF and Sulfur Compounds in Fuel Gas from Fluidized Bed Gasification of Coals and Wood by Steam-Oxygen Mixtures
Svoboda, Karel ; Pohořelý, Michael ; Jeremiáš, Michal ; Kameníková, Petra ; Skoblia, S. ; Beňo, Z. ; Šyc, Michal
We have concentrated in our study on FB gasification of two kinds of coals differing in reactivity, ash content and composition and hard wood at temperature 850 oC. Our attention was particularly devoted to speciation of sulfur compounds, presence of HCl, HF and tar compounds in fuel gas. Silica sand and mixture of silica sand with gradually added dolomite was used as basic particulate bed material in FB gasification. The results have shown that presence of dolomite particles in the fluidized bed and presence of dolomite dust reduces concentrations of all sulfur species, but the reduction of thiophene concentration is more pronounced. Presence of dolomite in FB causes substantial decrease of HCl concentration and moderate decrease of HF concentration in fuel gas. Accumulation of char and ash with active calcium based components leads to moderate reduction of HCl and sulfur compounds concentration in fuel gas.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22012102413551 - PDF
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