Number of found documents: 1156
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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

Moving dynamic test loads for road bridges - a case study
Bayer, Jan; Urushadze, Shota
2019 - English
Two types of dynamic testing load for bridges - driving sprung mass and driving impulse load - areexamined from the drive-by identification point of view. Numerical studies in ANSYS using contact elements and in MATLAB using a modal solution together with coupling force were performed. Equations for the estimation of the impulse load caused by a rolling cogwheel were suggested. The experiments confirmed that a driving impulse load is more efficient in exciting bridge vibrations. This, together with the fact that impulse loading is not sensitive to surface roughness, leads to the conclusion that, as a method for bridge health monitoring, impulse loading is more promising than using a driving sprung mass Keywords: drive-by identification; bridge testing; moving sprung mass; impulse loading; vibration measurements; laboratory experiments Available at various institutes of the ASCR
Moving dynamic test loads for road bridges - a case study

Two types of dynamic testing load for bridges - driving sprung mass and driving impulse load - areexamined from the drive-by identification point of view. Numerical studies in ANSYS using contact ...

Bayer, Jan; Urushadze, Shota
Ústav teoretické a aplikované mechaniky, 2019

Probability density determination by means of Gibbs entropy probability density
Náprstek, Jiří; Fischer, Cyril
2019 - English
A method of random response investigation of a nonlinear dynam-ical system is discussed. In particular, the solution of the probability density of a single/multi-degree of freedom (SDOF/MDOF) system response is investigated. Multiple stable equilibrium states with possible jumps of the snap-through type among them are considered. The system is Hamiltonian with weak damping excited by a set of non-stationary Gaussian white noises. The solution, which is based on the Gibbs principle of the maximum entropy of probability, can be employed in various branches of engineering. The search for the extreme of the Gibbs entropy functional is formulated as a constrained optimization problem. The secondary constraints follow from the Fokker-Planck equation (FPE) for the system considered or from the system of ordinary di_erential equations for the stochastic moments of the response derived from the relevant FPE Keywords: Fokker-Planck equation; Gibbs entropy functional; maximum entropy; probability density principle Available at various institutes of the ASCR
Probability density determination by means of Gibbs entropy probability density

A method of random response investigation of a nonlinear dynam-ical system is discussed. In particular, the solution of the probability density of a single/multi-degree of freedom (SDOF/MDOF) system ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2019

System response with random imperfections in coefficients on the space of realizations
Náprstek, Jiří; Fischer, Cyril
2019 - English
The contribution is concerned with the analysis of the simultaneous effect of a random perturbation and a white noise in the coefficient of the system. The excitation of the system of the 1-st order is described by the sum of a deterministic signal and an additive white noise which is partly correlated with the parametric noise. The random perturbation in the parameter is considered as a statistics in a set of realizations. It reveals that the density of probability of perturbations must be limited in the phase space, otherwise the system would lose the stochastic stability in probability. The width of the permissible zone depends heavily on the intensity of the parametric noise, the extent of correlation with the additive excitation noise and the type of probability density. The general explanation is demonstrated on cases of normal, uniform and truncated normal densities of probability. Keywords: noisy signal; filtration; random imperfections Available at various institutes of the ASCR
System response with random imperfections in coefficients on the space of realizations

The contribution is concerned with the analysis of the simultaneous effect of a random perturbation and a white noise in the coefficient of the system. The excitation of the system of the 1-st order ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2019

Deformation response of polydimethylsiloxane substrates subjected to uniaxial quasi-static loading
Vinařský, V.; Martino, F.; Forte, G.; Šleichrt, Jan; Rada, Václav; Kytýř, Daniel
2019 - English
To investigate cellular response of cardiomyocytes to substrate mechanics, biocompatible material with stiffness in physiological range is needed. PDMS based material is used for construction of microfluidic organ on chip devices for cell culture due to ease of device preparation, bonding, and possibility of surface functionalization. However it has stiffness orders of magnitude out of physiological range. Therefore, we adapted recently available protocol aiming to prepare substrates which offer stiffness in physiological range 5−100 kPa using various mixtures of Sylgard. An in-house developer loading device with single micron position tracking accuracy and sub-micron position sensitivity was adapted for this experimental campaign. All batches of the samples were subjected to uniaxial loading. During quasi-static experiment the samples were compressed to minimally 40% deformation. The results are represented in the form of stress-strain curves calculated from the acquired force and displacement data and elastic moduli are estimated. Keywords: quasi-static loading; hyperelasticity; polydimethylsiloxane substrates; in-situ loading device Available at various institutes of the ASCR
Deformation response of polydimethylsiloxane substrates subjected to uniaxial quasi-static loading

To investigate cellular response of cardiomyocytes to substrate mechanics, biocompatible material with stiffness in physiological range is needed. PDMS based material is used for construction of ...

Vinařský, V.; Martino, F.; Forte, G.; Šleichrt, Jan; Rada, Václav; Kytýř, Daniel
Ústav teoretické a aplikované mechaniky, 2019

Distribution of the external wind pressure coefficients on the surface of the façade of the high‐rise building "KINEUM" determined from the wind tunnel measurements
Hračov, Stanislav; Macháček, Michael
2019 - English
The report describes the procedure and results of the measurements of aerodynamic model of the planned high-rise building in Gothenburg in Sweden. The determined wind pressure distribution on individual surfaces of the building for several wind directions are presented in the form of external pressure coefficients. The obtained pressure coefficients are subsequently used by the client for the design of façade elements loaded by the wind. Keywords: external pressure coefficient; wind load; high-rise building Available at various institutes of the ASCR
Distribution of the external wind pressure coefficients on the surface of the façade of the high‐rise building "KINEUM" determined from the wind tunnel measurements

The report describes the procedure and results of the measurements of aerodynamic model of the planned high-rise building in Gothenburg in Sweden. The determined wind pressure distribution on ...

Hračov, Stanislav; Macháček, Michael
Ústav teoretické a aplikované mechaniky, 2019

Wind tunnel tests for lifetime estimation of bridge and mast cables exposed to vortex induced vibrations
Trush, Arsenii; Pospíšil, Stanislav; Kuznetsov, Sergeii
2019 - English
A significant number of TV and radio broadcasting masts in the Czech Republic was built in the 70-80s of the last century. At the moment is an actual issue is the reconstruction and determination of residual life of these structures. Guyed masts and particularly guy ropes have significant dimensions and comparatively low mass and damping with high flexibility. Therefore, aerodynamic and aeroelastic loads, such as vortex induced vibrations, galloping, wind gusts, etc., are key for them. As a tensile construction elements (guy ropes) for guyed masts the traditional open wire spiral strand cables are used. This type of cable has a characteristic helical surface roughness pattern that can act as vortex suppressor, high fatigue endurance, although somewhat lower corrosion resistance comparing to modern locked coil cables with non-circular shaped wires of outer layer and cables with protective polymer coatings. At the same time, on numerous bridges with the above-mentioned modern cable types the fatigue damage to wires in anchorage zones and destruction of protective coatings was detected. Present paper provides results of wind tunnel testing of three models of helical strake cable in order to evaluate separately impact of lay angle and surface roughness factors and reference smooth cylinder model in flow with grid generated turbulence of different intensities. The reduction of the lock-in range of helical strand cables comparing to reference smooth model was observed whereby the greatest impact was an increase of lay angle. Keywords: bridge cable; wind tunnel; vortex shedding Available at various institutes of the ASCR
Wind tunnel tests for lifetime estimation of bridge and mast cables exposed to vortex induced vibrations

A significant number of TV and radio broadcasting masts in the Czech Republic was built in the 70-80s of the last century. At the moment is an actual issue is the reconstruction and determination of ...

Trush, Arsenii; Pospíšil, Stanislav; Kuznetsov, Sergeii
Ústav teoretické a aplikované mechaniky, 2019

Velkoplošné scany obrazů s vysokým rozlišením
Vopálenský, Michal; Kumpová, Ivana
2019 - Czech
Cílem měření bylo získat radiografická data z historických maleb, zapůjčených Fakultou restaurování Univerzity Pardubice. Vzhledem k rozměru obrazů (až 90 × 110 cm) bylo třeba vytvořit vhodnou měřicí proceduru pro postupné skenování pláten v zařízení TORATOM. Výsledná data mají význam pro plánování restaurátorských prací na obrazech a mohou pomoci odhalit jinak neviditelné detaily v malbách, např. podmalby apod. The aim of the measurement was to obtain the radiographs from historical paintings from the Faculty of Restoration of the University Pardubice. Due to the dimensions of the paintings (up to 90 x 110 cm) it was necessary to develop a suitable measurement procedure for successive scanning of the paintings in the TORATOM device. The resulting data are important for the planning of the restoration processes of the paintings and can help to discover otherwise invisible details, like underpaintings etc. Keywords: large-area X-ray scanning; radiography of fine-art objects; restoration of paintings Available at various institutes of the ASCR
Velkoplošné scany obrazů s vysokým rozlišením

Cílem měření bylo získat radiografická data z historických maleb, zapůjčených Fakultou restaurování Univerzity Pardubice. Vzhledem k rozměru obrazů (až 90 × 110 cm) bylo třeba vytvořit vhodnou měřicí ...

Vopálenský, Michal; Kumpová, Ivana
Ústav teoretické a aplikované mechaniky, 2019

Lomové parametry AAAS kompozitů s keramickým střepem
Šimonová, H.; Rozsypalová, I.; Kumpová, Ivana; Trčka, T.; Frantík, P.; Rovnaníková, P.; Keršner, Z.
2019 - Czech
Příspěvek se zabývá alkalicky aktivovanými aluminosilikátovými kompozity na bázi keramických prekurzorů z hlediska charakterizace lomově-mechanickými parametry. Byly vyšetřovány tři kompozity, vyrobené z cihelného prachu jako prekurzoru a alkalického aktivátoru se silikátovým modulem Ms = 1,0, 1,2 a 1,4. Zkušební tělesa měla nominální rozměry 40 × 40 × 160 mm a byla po 28 dnech opatřena zářezy uprostřed rozpětí do 1/3 výšky těles. Z každého kompozitu bylo zkoušeno nejméně 6 vzorků. Tělesa byla podrobována testům v tříbodovém ohybu, při kterých byly zaznamenávány diagramy síla vs. průhyb uprostřed rozpětí a síla vs. otevření ústí trhliny. Po korekci těchto diagramů se s využitím modelu efektivní trhliny, metody lomové práce a modelu dvojí-K stanovily hodnoty statického modulu pružnosti, efektivní lomové houževnatosti (včetně její iniciační složky) a specifické lomové energie. Po lomových testech se vždy na jednom ze zlomků určovaly hodnoty informativní pevnosti v tlaku. Všechna vyhodnocení zahrnovala určení aritmetických průměrů a výběrových směrodatných odchylek. Pro získání informace o vnitřní struktuře kompozitů před mechanickým testováním a po něm bylo vybrané těleso zkoumáno pomocí mikro-tomografie. Tomografická měření a zpracování obrazu byla provedena pro kvalitativní a kvantitativní vyhodnocení změn vnitřní struktury s důrazem na výpočet porozimetrických parametrů a také vizualizace lomové procesní zóny. Byla stanovena fraktální dimenze objektů lomu. The paper deals with alkali-activated aluminosilicate composites based on ceramic precursors with respect to their characterization by fracture-mechanical parameters. Three composites made of brick dust as a precursor and alkaline activator with silicate modulus Ms = 1.0, 1.2 and 1.4 were investigated. After 28 days of maturation, specimens with nominal dimensions of 40 × 40 × 160 mm were provided by an initial notch to 1/3 of the body height in the middle of the span. At least 6 samples were tested from each composite. Specimens were subjected to three-point bending tests during which force vs. deflection at midspan (F–d) and force vs. crack mouth opening displacement (F–CMOD) diagrams were recorded. By processing these diagrams, the values of the static modulus of elasticity, the effective fracture toughness (including its initiating component) and the specific fracture energy were determined using the effective crack model, Work-of-Fracture method, and Double-K fracture model. After the fracture experiments had been performed, compressive strength values were determined for informational purposes from one part of each specimen that remained after testing. All evaluations included the determination of arithmetic means and standard deviations. To obtain information about the internal structure of composites before and after mechanical testing, the selected body was examined by micro-tomography. Tomographic measurements and image processing were performed for qualitative and quantitative evaluation of internal structure changes with an emphasis on the calculation of porosimetric parameters as well as visualization of the fracture process zone. The fractal dimension of fracture objects was determined. Keywords: alkali-activated aluminosilicate (AAAS); ceramic precursor; fracture test; force-displacement diagram; X-ray micro-tomography Available at various institutes of the ASCR
Lomové parametry AAAS kompozitů s keramickým střepem

Příspěvek se zabývá alkalicky aktivovanými aluminosilikátovými kompozity na bázi keramických prekurzorů z hlediska charakterizace lomově-mechanickými parametry. Byly vyšetřovány tři kompozity, ...

Šimonová, H.; Rozsypalová, I.; Kumpová, Ivana; Trčka, T.; Frantík, P.; Rovnaníková, P.; Keršner, Z.
Ústav teoretické a aplikované mechaniky, 2019

In-situ compression test of artificial bone foams in controlled environment using X-Ray micro-computed tomography
Glinz, J.; Kytýř, Daniel; Fíla, Tomáš; Šleichrt, Jan; Schrempf, A.; Fürst, D.; Kastner, J.; Senck, S.
2019 - English
In this study, we investigated specimens of artificial bone foams, developed by the research group for surgical simulators at the UAS Linz, which are used to mimic the haptic feedback of physiologic and pathologic bone for more realistic surgery training. Specimens with two kinds of mineral filler material as well as different amounts of foaming agent were tested in an environmental in-situ loading stage developed by the ITAM CAS and scanned via X-ray micro-computed tomography. In this in-situ stage, specimens can be immersed in liquid and tested under temperature-controlled conditions. Consequently, a total amount of 12 specimens was subjected to compression loading; half of them immersed in water at 36.5 _C and half in dry condition. Results showed that there is no significant influence of liquid immersion to the compression outcome. However, foams with less amount of foaming agent appeared to have smaller pores resulting in higher compression strength. Keywords: x-ray micro-computed tomography; artificial bone foams; in-situ testing Available at various institutes of the ASCR
In-situ compression test of artificial bone foams in controlled environment using X-Ray micro-computed tomography

In this study, we investigated specimens of artificial bone foams, developed by the research group for surgical simulators at the UAS Linz, which are used to mimic the haptic feedback of physiologic ...

Glinz, J.; Kytýř, Daniel; Fíla, Tomáš; Šleichrt, Jan; Schrempf, A.; Fürst, D.; Kastner, J.; Senck, S.
Ústav teoretické a aplikované mechaniky, 2019

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