National Repository of Grey Literature 13 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
The framing of the topic of national indebtedness in MF DNES and Právo before the election to the chamber of deputies 2010
Šašek, Petr ; Němcová Tejkalová, Alice (advisor) ; Osvaldová, Barbora (referee)
The diploma thesis called "The Framing of the Topic of National Indebtedness in MF DNES and Právo before the Election to the Chamber of Deputies 2010" deals with a concrete example of framing in Czech media praxis. The national indebtedness was one of the key topics during the pre-election campaign. The coverage of this topic is analyzed in two Czech newpapers - Mladá fronta DNES and Právo. The diploma thesis describes the frames used in the coverage and compares framing in both newpapers.
Microscopic features of cement paste modified by fine perlite
Hrbek, V. ; Koudelková, Veronika ; Padevět, P. ; Šašek, Petr
The use of waste material and replacement of binder element in cementitious composites is in focus of material development. Perlite in the construction industry is usually used in form of lightweight aggregate enhancing the insulating performance of concrete. This paper focuses on integration of fine perlite into the cement matrix and possible replacement of the cement binder in the composition of the material. The macromechanical performance of the modified paste is tested on specimens with 5, 10, 15 and 20% fine perlite substitution and pure cement sample. To distinguish the effect of the perlite on the microstructural level, pure cement material and specimen containing 10% of fine perlite are investigated by the electron microscopy. Furthermore, the mechanical properties of individual phases are examined and compared on same samples by instrumented indentation. The presented results enabled estimation of fine perlite impact on the macro and microscopic performance of the material..
Qualitative and quantitative analysis of clay soils
Šašek, Petr ; Viani, Alberto ; Mácová, Petra
Smectite-to-illite conversion is an important mineralogical reaction that occurs during the diagenesis ofargillaceous sediment. Illite–smectite clay minerals are ubiquitous in sedimentary basins and they have been linked to the maturation, migration and trapping of hydrocarbons, rock cementation, evolution of porewater chemistry during diagenesis and the development of pore pressure. But, despite the importance of these clays, their structures are controversial. By combining layers of octahedra and tetrahedra several types of layered structures may be produced, which can form various types of clay minerals in nature. Clay minerals are divided into three main groups: kaolinite, smectite and illite. The aim of the study was to qualitatively and quantitatively analyse the clay minerals in soil samples and identification of unknown mineral found by exploration works. For this purpose XRD, Raman spectroscopy and SEM were employed.
Chemical and mineralogical analyses of stone sampled from Troja Castle, baroque staircase, Prague 7
Slížková, Zuzana ; Mácová, Petra ; Viani, Alberto ; Šašek, Petr ; Wolf, Benjamin
Chemical and mineralogical analyses of stone sampled from Troja Castle, baroque staircase, Prague 7.
Analysis of soils
Šašek, Petr ; Viani, Alberto ; Ševčík, Radek ; Mácová, Petra ; Machová, Dita
High concentrations of solid particles in the air may cause health problems. Sources of such particles can be natural processes, as well as human activity (e.g. coal mining, etc). Another source of contamination is the so-called secondary dustiness, which arises from vortex of already settled solids and dispersion into the atmosphere. Secondary dustiness formation is mainly affected by the surface moisture. The increase of humidity leads to agglomeration of the particles, resulting to their falling on ground, thus inhibiting their distribution in the atmosphere. The aim of the study was to analyse the soil dust particles collected on the filters of impactor, with respect to particle size and composition.
Microindentation assessment of climatic loading impacts on polymer sealants
Minster, Jiří ; Šašek, Petr
Sun light, especially the short-wave ultra-violet part of the sun spectrum, together with influence of moisture, are the most enlarged and the most effective sources of climatic damage of polymers. The effects of the both influences became stronger with enhanced temperature. Sun light on the one hand supports the forming of transverse chemical bonds between macromolecules and on the other hand results in their breakdown. This causes a strengthening or softening of polymers. The amount of changes and the dominant process depends on the radiation dose and on the influencing wave length. Every kind of chemical bond has its own critical wave length, which, with sufficient amount of energy, brings a reaction. Ageing, as a result of climatic loading, is therefore very closely connected with a structure of a real material. Microindentation is one of possible methods for assessing influences of a climatic loading on mechanical properties of polymers. Indentation test is checked by the history either of a power or an indent depth. The information about the hardness, Young modulus and viscoelastic properties of the investigated material can be received afterwards from measured data. The investigated materials were tested in their native standard form and also after four model types of physical-chemical ageing. Time-dependent properties of the sealants were assessed by the method of indentation creep. One hundred indentation creep tests were conducted for each sealant and type of ageing. A motivation for this work was a requirement to assess an influence of a climatic loading on the basic mechanical properties of sealants, used for a creation and a repair of mosaics.
Qualitative and quantitative analysis of clay soils
Šašek, Petr ; Viani, Alberto ; Ševčík, Radek ; Fabeš, Roman ; Řehoř, M.
Clay minerals are a group of aluminum silicates with a layered structure, which is formed by tetrahedrally and octahedrally arranged molecules with cations of potassium, magnesium, sodium and others. By combining layers of octahedra and tetrahedra several types of layered structures may be produced, which can form various types of clay minerals in nature. Clay minerals are divided into three main groups: kaolinite, smectite and illite. The aim of the study was to qualitatively and quantitatively analyse the clay minerals in soil samples; the main objective was to determine the phase transition on the boundary of smectite and illite phases. For this purpose XRD analysis with Rietveld refinement was employed.
Properties of commercially available, ready-to-use mortars for restoration of historic renders and masonry
Janotová, Dana ; Niedoba, Krzysztof ; Gláser, Petr ; Šašek, Petr ; Fabeš, Roman
There is a wide range of premixed, dry mortars, on the market, designed with the reconstruction of historic renders and masonry in mind. The use of such materials has some advantages, including good workability and standard quality, however, due to unknown composition, being a secret of a manufacturer, it is frequently impossible to predict their influence on the substrate and on the ageing. If the ready-to-use mortar is to be applied during the renovation of the historic masonry, it is necessary to know: how close the mortars’ properties match the properties of the original material; will the repair be durable enough and will it degrade faster than the original material. Technical information, provided by the manufacturer, does not contain such data. The only parameters given, are the strength, porosity of hardened mortar and water vapour diffusion coefficient, however, it is not specified in which conditions these values were measured.
Determination of the coefficient of linear thermal expansion of sintered PZT ceramics
Šašek, Petr
Působením teploty dochází v materiálech ke změnám velikosti. Toto může být problém v případě, že se jedná o vrstevnatý materiál, kdy jednotlivé vrstvy mají rozdílné vlastnosti. Cílem této studie bylo zjistit součinitel teplotní roztažnosti piezoelektrické keramiky s tenkou stříbrnou vrstvou. Teplotní rozsah byl od -20 do 60 °C, resp. od -30 do 160 °C. Rychlost ohřevu byla 1°C/min. Celkem byly měřeny 3 vzorky. Srovnání tepelné roztažnosti nám ukazuje, že jeden vzorek se liší od dvou vzorků, které mají podobné vlastnosti.

National Repository of Grey Literature : 13 records found   1 - 10next  jump to record:
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1 Šašek, Pavel
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