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Charakterizace Božanského pískovce: pilotní lomové testy
Kumpová, I.; Rozsypalová, I.; Vavro, Leona; Vavro, Martin; Keršner, Z.
2020 - Czech
Cíl příspěvku představuje charakterizacipískovce zlomu Božanov u Broumova,Česká republika,pomocí pilotních lomových testů. Pět zkušebních těles z jádrových vývrtůnominálního průměru 50mm a délek 100 a125mm bylo před testy opatřeno koncentrátorem napětí ve tvaru šípového vrubu a zatěžováno spožadavkem konstantního přírůstku posunu vkonfiguraci tříbodového ohybu lisemLabTest 6.250 vlaboratoři Ústavu stavebního zkušebnictví FAST VUT vBrně. Snímaných diagramů síla–posun bylo po jejich korekci využito kvyčíslení základních lomově-mechanických parametrůstudovaného pískovce: statického modulu pružnosti, lomové houževnatosti, houževnatostia specifické lomové energie. The aim of this paper is a characterization ofsandstone from Božanov quarry near Broumov, Czech Republic,by means of the pilot fracture tests. Five drill-core test specimens withnominal diameter of 50mm and lengths of 100 and 125mmwere provided by an initial chevron type notch. Specimens were loaded in the configuration of the three-point bending as a displacement driven experimentusing LabTest 6.250 equipment in the laboratory of the Institute of Building Testing, Faculty of Civil Engineering, Brno University of Technology. The load versus displacement diagrams were used to quantify the basic mechanical fracture parameters of the studied sandstone: modulus of elasticity, fracture toughness, toughness, and specific fracture energy. Keywords: Božanov sandstone; drill-core specimen; chevron notch; fracture test; load–displacement diagram Fulltext is available at external website.
Charakterizace Božanského pískovce: pilotní lomové testy

Cíl příspěvku představuje charakterizacipískovce zlomu Božanov u Broumova,Česká republika,pomocí pilotních lomových testů. Pět zkušebních těles z jádrových vývrtůnominálního průměru ...

Kumpová, I.; Rozsypalová, I.; Vavro, Leona; Vavro, Martin; Keršner, Z.
Ústav geoniky, 2020

Random response of a dynamic system under polynomial of a white noise
Náprstek, Jiří; Fischer, Cyril
2020 - English
Many types of external additive random excitation of dynamic systems admit to be modelled as a combination of powers of a Gaussian noise. Such a type of excitation produces a non-Gaussian response even if the dynamic system is linear and the excitation is additive only. Although the excitation as a whole is non-Gaussian, the problem can be transformed into the form of a linear system with an additive and multiplicative white noise excitation which _nally produces a non-Gaussian response. The general method of transformation, the respective FPK equation, basic stochastic moments of the response, and a demonstrative example are discussed. Keywords: non-Gaussian excitation; nonlinear filtering; Kronecker algebra Available at various institutes of the ASCR
Random response of a dynamic system under polynomial of a white noise

Many types of external additive random excitation of dynamic systems admit to be modelled as a combination of powers of a Gaussian noise. Such a type of excitation produces a non-Gaussian response ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2020

Průzkum malt románské kaple ve věži hradu Landštejn
Válek, Jan; Skružná, Olga; Kozlovcev, Petr; Frankeová, Dita; Svoboda, Milan; Ševčík, Radek; Kotková, Kristýna
2020 - Czech
V rámci průzkumu byly odebrány čtyři vzorky malt z podlahy a dva vzorky z omítek v prostoru románské kaple nacházející se ve věži na hradě Landštejn. Cílem byla charakterizace použitých surovin, stanovení jejich poměru, charakterizace porozity malt a porovnání malt z jednotlivých stavebních fází. Four samples of floor mortars and two samples of plasters were analysed as a part of the survey in the Romanesque chapel located in the tower at Landštejn Castle. The aim was to characterize used raw materials, determine their ratio, characterize the porosity of mortars and compare mortars sorted to different phases of construction. Keywords: cultural heritage; Romanesque mortars; natural hydraulic lime; renders; floor mortars Available at various institutes of the ASCR
Průzkum malt románské kaple ve věži hradu Landštejn

V rámci průzkumu byly odebrány čtyři vzorky malt z podlahy a dva vzorky z omítek v prostoru románské kaple nacházející se ve věži na hradě Landštejn. Cílem byla charakterizace použitých surovin, ...

Válek, Jan; Skružná, Olga; Kozlovcev, Petr; Frankeová, Dita; Svoboda, Milan; Ševčík, Radek; Kotková, Kristýna
Ústav teoretické a aplikované mechaniky, 2020

Výzkumná zpráva. Sps_025: Keramika B4C + 1Ti, 1800°C, 2 min
Kumpová, Ivana; Vopálenský, Michal
2020 - Czech
Cílem práce bylo ověřit možnost pozorování stukturních detailů ve vzorcích B4C - Ti keramiky s 1 % titanu na základě 3D modelů z výpočetní tomografie. V laboratoři byl touto metodou zkoumán vzorek Sps_025: Keramika B4C + 1Ti, 1800°C, 2 min, ve tvaru válce o průměru 12 mm a výšce 10 mm. The aim of the measurement was to verify the feasibility of 3D computed tomography for observing structural details in samples of B4C - Ti ceramics with 1 % of Ti. Sample designated Sps_025: Keramika B4C + 1Ti, 1800°C, 2 min, in the form a cylinder with the diameter of 12 mm and the height of 10 mm was investigated by this method. Keywords: X-ray tomography; boron carbide ceramics; characterization of microstructures Available at various institutes of the ASCR
Výzkumná zpráva. Sps_025: Keramika B4C + 1Ti, 1800°C, 2 min

Cílem práce bylo ověřit možnost pozorování stukturních detailů ve vzorcích B4C - Ti keramiky s 1 % titanu na základě 3D modelů z výpočetní tomografie. V laboratoři byl touto metodou zkoumán vzorek ...

Kumpová, Ivana; Vopálenský, Michal
Ústav teoretické a aplikované mechaniky, 2020

Large Scale Motions in Turbulent Flows
Kellnerová, Radka; Jurčáková, Klára; Procházka, Pavel P.
2019 - English
Quadrant analysis based on the Reynolds decomposition was performed on the data from turbulent boundary layer flows above variously rough surfaces. An estimation of a convective velocity for events significant in terms of momentum flux, and the statistics of a length and amplitude of the individual events, together with their spectral analysis, was performed. Based on the analyses, we were able to detect a few individual sweep and ejection events with a length longer than 6δ, which could be considered as very large scale motions (VLSM). We also identified number of events with a longitudinal dimension equal to approximately 3δ labelled as large scale motions (LSM). The analyses were executed for various Reynolds numbers. The number of detected structures increases with the momentum of the flow. Keywords: wind tunnel; large scale motion; quadrant analysis Fulltext is available at external website.
Large Scale Motions in Turbulent Flows

Quadrant analysis based on the Reynolds decomposition was performed on the data from turbulent boundary layer flows above variously rough surfaces. An estimation of a convective velocity for events ...

Kellnerová, Radka; Jurčáková, Klára; Procházka, Pavel P.
Ústav termomechaniky, 2019

Assessing Quality of Boundary Layer Flows With the Diagnostic Plot
Jurčáková, Klára; Procházka, Pavel P.; Kellnerová, Radka
2019 - English
We experimentally investigated turbulent boundary layers over 4 rough surfaces and 1 smooth surface by particle image velocimetry for a range a free stream velocities. The obtained mean velocity vertical profiles were universally scaled by roughness length z₀ and friction velocity u*, but both parameters have to be obtained from the fit of the logarithmic or composite velocity pro le to the experimental data. Diagnostic plot, which relates turbulence intensity with the mean velocity showed good collapse of different free stream velocities for each surface. It became fully universal in its modified version when the roughness function was taken into an account. We found that turbulence intensities over our surfaces are higher than any published one and that they dependent on roughness length z₀*. Keywords: wind tunnel; turbulence intensity; rough-wall; friction velocity Fulltext is available at external website.
Assessing Quality of Boundary Layer Flows With the Diagnostic Plot

We experimentally investigated turbulent boundary layers over 4 rough surfaces and 1 smooth surface by particle image velocimetry for a range a free stream velocities. The obtained mean velocity ...

Jurčáková, Klára; Procházka, Pavel P.; Kellnerová, Radka
Ústav termomechaniky, 2019

Characterization of fine-grained montmorillonite fractions suitable for composite preparation
Valovičová, Věra; Vaculíková, Lenka; Plevová, Eva; Dolinská, S.; Znamenáčková, I.; Danková, Z.
2019 - English
The aim of this experimental study was to characterize a fine-grained fraction of montmorillonites (SAz-2, STx-1, SWy-2 and Kunipia-F). It was investigated in order to provide more precise information of used montmorillonites than could be obtained by analysis of the unfractioned montmorillonites. At first, the fine fraction of montmorillonites were prepared by sedimentation and activation by means of Na2CO3. The prepared clay materials were characterized by the X-ray diffraction analysis and FTIR spectroscopy. The thermal behaviour of the studied samples was determinated according to the characteristic temperatures obtained from TG/DTA curves. The temperatures of dehydratation and dehydroxylation were evaluated and kinetic parameters were also calculated. The porosity and surface properties of the studied samples were gained by the nitrogen adsorption measurements. The obtained results confirmed that the fine fraction of montmorillonites could be a suitable material for subsequent preparation of composites with enhanced sorption properties, especially montmorillonite/MnO2 composite. Keywords: montmorillonite; activation; characterization; composites Available in digital repository of the ASCR
Characterization of fine-grained montmorillonite fractions suitable for composite preparation

The aim of this experimental study was to characterize a fine-grained fraction of montmorillonites (SAz-2, STx-1, SWy-2 and Kunipia-F). It was investigated in order to provide more precise information ...

Valovičová, Věra; Vaculíková, Lenka; Plevová, Eva; Dolinská, S.; Znamenáčková, I.; Danková, Z.
Ústav geoniky, 2019

Note on the problem of compressible non-Newtonian fluids
Caggio, M.; Nečasová, Šárka
2019 - English
The aim of the paper is to consider the compressible non-Newtonian fluids of power law type when the viscosity coeffcients depend not only on invariants of velocity field but also on the density. We introduce approximation scheme using model of multipolar fluids. After then passing with higher viscosity to zero we get the measure valued solution of the problem. Keywords: non-Newtonian fluid; compressible fluid; multipolar fluid; measure-valued solution Available in digital repository of the ASCR
Note on the problem of compressible non-Newtonian fluids

The aim of the paper is to consider the compressible non-Newtonian fluids of power law type when the viscosity coeffcients depend not only on invariants of velocity field but also on the density. We ...

Caggio, M.; Nečasová, Šárka
Matematický ústav, 2019

Three-dimensionally ordered micromesoporous carbon as adsorbent for CO2 capture
Vorokhta, Maryna; Řimnáčová, Daniela; Pilař, Radim
2019 - English
In this work, ordered three-dimensionally micromesoporous carbon composed of large spherical mesopores 13 nm in diameter and small micropores with a mean micropore width of 1.46 nm, connecting the main spheres, was synthesized and investigated for CO2 capture ability at temperatures of 25°C, 35°C and 50°C, and at pressures up to 6.5 MPa. Because of the big pore volume occupying 3.62 cm3/g, composed of mesopores and micropores, the carbon sample showed very high adsorption capacity at high pressures. The highest CO2 adsorption capacity of 24.03 mmol/g was obtained at 25°C and at 5.5 MPa. As the temperature increased, the CO2 adsorption capacity decreased to 13.34 mmol/g at 50°C and at 6.5 MPa. The Freundlich fittings of the measured adsorption isotherms at pressures up to 2 MPa showed very high correlation coefficients. The estimated isosteric heats of adsorption in the range of 5.62-6.90 kJ/mol indicated a physical adsorption process, and suggested a stronger interaction between CO2 molecules than between CO2 molecules and the surface of the carbon sample. Keywords: 3DOmm carbon; CO2 adsorption; Freundlich fit; Isosteric heat Fulltext is available at external website.
Three-dimensionally ordered micromesoporous carbon as adsorbent for CO2 capture

In this work, ordered three-dimensionally micromesoporous carbon composed of large spherical mesopores 13 nm in diameter and small micropores with a mean micropore width of 1.46 nm, connecting the ...

Vorokhta, Maryna; Řimnáčová, Daniela; Pilař, Radim
Ústav struktury a mechaniky hornin, 2019

Lexicalized Syntactic Analysis by Restarting Automata
Mráz, F.; Otto, F.; Pardubská, D.; Plátek, Martin
2019 - English
We study h-lexicalized two-way restarting automata that can rewrite at most i times per cycle for some i ≥ 1 (hRLWW(i)-automata). This model is considered useful for the study of lexical (syntactic) disambiguation, which is a concept from linguistics. It is based on certain reduction patterns. We study lexical disambiguation through the formal notion of h-lexicalized syntactic analysis (hLSA). The hLSA is composed of a basic language and the corresponding h-proper language, which is obtained from the basic language by mapping all basic symbols to input symbols. We stress the sensitivity of hLSA by hRLWW(i)-automata to the size of their windows, the number of possible rewrites per cycle, and the degree of (non-)monotonicity. We introduce the concepts of contextually transparent languages (CTL) and contextually transparent lexicalized analyses based on very special reduction patterns, and we present two-dimensional hierarchies of their subclasses based on the size of windows and on the degree of synchronization. The bottoms of these hierarchies correspond to the context-free languages. CTL creates a proper subclass of context-sensitive languages with syntactically natural properties. Keywords: Restarting automaton; h-lexicalization; lexical disambiguation Fulltext is available at external website.
Lexicalized Syntactic Analysis by Restarting Automata

We study h-lexicalized two-way restarting automata that can rewrite at most i times per cycle for some i ≥ 1 (hRLWW(i)-automata). This model is considered useful for the study of lexical (syntactic) ...

Mráz, F.; Otto, F.; Pardubská, D.; Plátek, Martin
Ústav informatiky, 2019

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