Number of found documents: 1034
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Zpráva o výsledcích chemické a mineralogické analýzy malt z hradu Bečov
Slížková, Zuzana; Koudelková, Veronika; Kozlovcev, Petr; Šterner, Adam
2018 - Czech
Pomocí chemické a mikroskopické analýzy bylo určeno, že analyzovaný vzorek malty z 13. stol. je vápenná malta s převážně křemenným a silikátovým pískem a vnitřní omítka z 13. stol. byla provedena z malty vápenohliněné s převážně silikátovým plnivem. Omítka obsahuje příměs dřevěných či rostlinných částic, byly identifikovány piliny. Malta obsahuje kousky strusky. Using chemical and microscopic analysis, it was determined that the analyzed sample of bedding mortar from the 13th century (Czech castle Bečov) is the air lime mortar with the quartz and silicate sand enriched by some content of slag grains. The internal plaster from the same building period of the castle was made using the lime-earthen mortar with predominantly silicate sand. The plaster contained an admixture of wood or plant particles, sawdust has been identified.\n\n Keywords: chemical composition; survey; material characterization; binder; aggregate; historic plaster; historic render Available at various institutes of the ASCR
Zpráva o výsledcích chemické a mineralogické analýzy malt z hradu Bečov

Pomocí chemické a mikroskopické analýzy bylo určeno, že analyzovaný vzorek malty z 13. stol. je vápenná malta s převážně křemenným a silikátovým pískem a vnitřní omítka z 13. stol. byla provedena z ...

Slížková, Zuzana; Koudelková, Veronika; Kozlovcev, Petr; Šterner, Adam
Ústav teoretické a aplikované mechaniky, 2018

Asymmetry of the response probability density of a system with parametric random noises
Náprstek, Jiří; Fischer, Cyril
2018 - English
Recording of time variable processes is accompanied by various internal disturbing effects as a rule. They influence parameters of the measuring facility, transducer-device transmission, etc. These parasitic processes are usually of the random character and, consequently, they exercise as parametric noises. Moreover, the input signal mostly consists of a useful signal which can be taken as composed from deterministic and random additive part. Various combinations of these noises are the origin of random and also systematic measuring errors which can have under certain circumstances a cumulative character, deteriorate the output signal quality and can lead finally to the stochastic stability loss. These effects can be theoretically described using differential systems with stochastic coefficients and stochastic right hand side considering all input and output processes to be of the Markov type. Keywords: random vibration; signal reconstruction; parametric noise; response asymmetry Available at various institutes of the ASCR
Asymmetry of the response probability density of a system with parametric random noises

Recording of time variable processes is accompanied by various internal disturbing effects as a rule. They influence parameters of the measuring facility, transducer-device transmission, etc. These ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2018

Zpráva o výsledcích mikroskopické analýzy malt použitých pro opravu vnější omítky objektu Petschkova vila, V sadech 2, Praha 6
Slížková, Zuzana; Koudelková, Veronika; Frankeová, Dita; Šterner, Adam
2018 - Czech
Cílem práce bylo zjištění složení opravné malty použité na fasádě Petschkovy vily, V sadech 2, Praha 6 za účelem průzkumu fasády vily před restaurováním. Bylo provedeno SEM-EDX vyšetření nábrusu malty, výsledkem je charakterizace kameniva a pojiva malty. Pomocí analýz bylo určeno, že se jedná o cementovou maltu překrytou vápenocementovým štukem. The aim of this work was to analyze the repair mortar from Petschek villa, by means of SEM-EDX analysis in order to characterize the aggregate and the binder in the mortar sample. The analyses proved the cement mortar covered with lime-cement mortar. Keywords: chemical composition; survey; material characterization; binder; aggregate; repair mortar Available at various institutes of the ASCR
Zpráva o výsledcích mikroskopické analýzy malt použitých pro opravu vnější omítky objektu Petschkova vila, V sadech 2, Praha 6

Cílem práce bylo zjištění složení opravné malty použité na fasádě Petschkovy vily, V sadech 2, Praha 6 za účelem průzkumu fasády vily před restaurováním. Bylo provedeno SEM-EDX vyšetření nábrusu ...

Slížková, Zuzana; Koudelková, Veronika; Frankeová, Dita; Šterner, Adam
Ústav teoretické a aplikované mechaniky, 2018

Možnosti využití rentgenové tomografie ke kvantifikaci poškození teplotně namáhaného betonu
Rozsypalová, I.; Kumpová, Ivana; Daněk, P.; Šimonová, H.; Keršner, Z.
2018 - Czech
Působení vysokých teplot na beton ovlivňuje vnitřní strukturu tohoto kompozitního materiálu. V příspěvku se otevírá otázka možnosti využití výpočetní rentgenové tomografie ke kVantifikaci míry poškození betonového tělesa, které bylo odvrtáno z vybraného experimentálního panelu zatěžovaného vysokými teplotami na požární peci Centra AdMaS (Advanced Materials, Structures and Technologies) FAST VUT v Brně. Nominální hodnota maxima teploty v peci činila 1000 °C. Pokročilé zařízení TORATOM (Twinned Orthogonal Adjustable Tomograph) v Centru excelence Telč (CET) kombinuje dva páry „rentgenka–detektor“ v ortogonálním uspořádání, které umožňuje dvojnásobné zrychlení procesu sběru dat pro tomografické rekonstrukce. Zařízení má plně motorizované osy pro nastavování vzdáleností „rentgenka–vzorek–detektor“. Tím lze měnit zvětšení zhruba od 1,2× po 100× (ve speciálních případech i více). Při dané velikosti pixelů detektoru je možné měnit rozlišení CT rekonstrukcí, tj. velikost jednoho prostorového bodu modelu, od 0,2 milimetrů až po mikrometrické. Další výhodu zařízení TORATOM představuje možnost paralelního zobrazování objektu ve dvou spektrech RTG záření. Tento postup umožňuje zvýraznit rozdíly mezi materiálovými komponentami, které mají v plném RTG spektru podobný útlum. Pokud se vzorek skládá pouze ze dvou materiálů, lze tyto materiály jednoznačně odlišit. U vícesložkových materiálů lze rozdíly pouze zdůraznit. The effect of high temperatures on concrete affects the internal structure of this composite material. The paper opens the question of the possibility of using a computed X–ray tomography to quantify the degree of damage of a concrete specimen that was drilled from the selected experimental panel loaded in a fire furnace with high temperatures at the AdMaS (Advanced Materials, Structures and Technologies) research centre at Faculty of Civil Engineering Brno University of Technology. The nominal value of the maximum temperature on the heated side of the panel was 1000 °C. Advanced workstation computer X–ray tomography TORATOM at Centre of Excellence Telč (CET) is parallel imaging of an object in two spectra of X–ray radiation, that allows to highlight differences between the material components to the full X–ray spectrum similar to the attenuation of the radiation. Keywords: TORATOM; concrete; high temperature; computed tomography Available at various institutes of the ASCR
Možnosti využití rentgenové tomografie ke kvantifikaci poškození teplotně namáhaného betonu

Působení vysokých teplot na beton ovlivňuje vnitřní strukturu tohoto kompozitního materiálu. V příspěvku se otevírá otázka možnosti využití výpočetní rentgenové tomografie ke kVantifikaci míry ...

Rozsypalová, I.; Kumpová, Ivana; Daněk, P.; Šimonová, H.; Keršner, Z.
Ústav teoretické a aplikované mechaniky, 2018

Analysis of mini-jack technique for in situ measurement of strength
Kloiber, Michal; Tippner, J.; Kunecký, Jiří; Sebera, V.; Milch, J.; Hrivnák, Jaroslav
2017 - English
The paper presents a recently developed diagnostic technique for in situ determination of modulus of deformability (MODL) and conventional strength (CSL) parallel to the grain using the mini-jack inserted in bored hole. The mini-jack compression technique simulates the standard compression test, it is compared to that to examine its prediction strength (correlation coefficients). The paper shows an influence of moisture content of wood on experimental measurements using this technique. The measurement was carried out at spruce samples at three moisture contents of 12, 18 and 24%. The results of the tests prove a very good correlation of the strength determined by the proposed technique and wood density and strength determined at universal testing machine in compression parallel to the grain. The effect of the moisture content on the measurement by the mini-jack technique was proved to be significant. Beside that, the newly-developed instrument was also studied using digital image correlation (DIC) technique to analyze induced strains around the bored hole. This was studied on halved spruce samples. The DIC revealed symmetric character of the loading and significant differences between strains induced in tangential and longitudinal directions. Keywords: non-destructive testing; mini-jack technique; wood; in-situ testing; compression strength Available at various institutes of the ASCR
Analysis of mini-jack technique for in situ measurement of strength

The paper presents a recently developed diagnostic technique for in situ determination of modulus of deformability (MODL) and conventional strength (CSL) parallel to the grain using the mini-jack ...

Kloiber, Michal; Tippner, J.; Kunecký, Jiří; Sebera, V.; Milch, J.; Hrivnák, Jaroslav
Ústav teoretické a aplikované mechaniky, 2017

Mechanical analysis of scarf joint fastened using cylindrical wooden dowel
Tippner, J.; Milch, J.; Kunecký, Jiří; Kloiber, Michal; Brabec, M.; Sebera, V.
2017 - English
Traditional all-wooden woodworking joints play an important role in the behaviour of timber structures. These joints are also widely used when historically valuable constructions are being reconstructed and the connections are usually the masterpieces that testify to the high carpentry skills and knowledges of the overall mechanical behaviour. Within historical timber structures traditional carpentry joints were used while wooden dowel fixed mutual position of elements. Main aim of this study was to contribute to knowledge base about prediction and analysis of the mechanical performance of frequently used scarf joints made from spruce wood fastened using oak dowels. The objectives were to determine the joints' slip moduli and load-carrying capacity by means of theoretical and experimental approaches, in next to assess the mechanical behaviour of dowels through experimental investigation, and finally to perform a strain analysis of dowels. For these purposes, the optical technique employing three-dimensional full-field digital image correlation was used. The experiments were done on the full-scale specimens meeting the requirements of European standards (EN 383 and EN 26891), which were made from Norway spruce (Picea abies L. Karst.) and English oak (Quercus robur L.). The mechanical load consisted in tensile parallel and perpendicular to grain direction within the main components. The results of this study showed good correlation between theoretical approach based on based on Beam on Elastic Foundation theory and European yield model theory and experimental observations. Keywords: all-wooden joints; scarf joint; dowel; spruce; oak; digital image correlation Available at various institutes of the ASCR
Mechanical analysis of scarf joint fastened using cylindrical wooden dowel

Traditional all-wooden woodworking joints play an important role in the behaviour of timber structures. These joints are also widely used when historically valuable constructions are being ...

Tippner, J.; Milch, J.; Kunecký, Jiří; Kloiber, Michal; Brabec, M.; Sebera, V.
Ústav teoretické a aplikované mechaniky, 2017

Iron alloys outdoor corrosion and laboratory simulation - comparison
Majtás, Dušan; Mácová, Petra; Kreislová, Kateřina; Příhoda, J.
2017 - English
Simulation of iron alloy corrosion is widespread used to predict corrosion resistance. The simulation using corrosion chambers or climatic chambers provides reasonable information on corrosion resistance, the corrosion rate however must be compared to real exposition as the corrosion in simulated environment is accelerated compared to real situation. However the composition of corrosion products and its structure is different question. The corrosion products composition is dependent on corrosion process. The phases present are most likely the same, most voluminous hydrated oxides and oxy-hydroxides on the outside where the less voluminous oxides are present in the lower layers. However this macroscopic phase structure may not fully describe the layered structure of corrosion products, thickness of corrosion products or mechanical properties. In the vicinity of crack in corrosion products the structure is more likely to be similar to the structure near the surface. Keywords: corrosion; wrought iron; accelerated ageing; corrosion simulation Available at various institutes of the ASCR
Iron alloys outdoor corrosion and laboratory simulation - comparison

Simulation of iron alloy corrosion is widespread used to predict corrosion resistance. The simulation using corrosion chambers or climatic chambers provides reasonable information on corrosion ...

Majtás, Dušan; Mácová, Petra; Kreislová, Kateřina; Příhoda, J.
Ústav teoretické a aplikované mechaniky, 2017

Deformation behaviour of gellan gum based artificial bone structures under simulated physiological conditions
Krčmářová, N.; Šleichrt, J.; Fíla, Tomáš; Koudelka_ml., Petr; Kytýř, Daniel
2017 - English
The paper deals with investigation of deformation behaviour of gellan gum (GG) based\nstructures prepared for regenerative medicine purposes. Investigated material was synthesized as porous spongy-like scaffold reinforced by bioactive glass (BAG) nano-particles in different concentrations. Deformation behavior was obtained employing custom designed experimental setup. This device equipped with bioreactor chamber allows to test the delivered samples under simulated physiological conditions with controlled flow and temperature. Cylindrical samples were subjected to uniaxial quasi-static loading in tension and compression. Material properties of plain scaffold buffered by 50 wt% and 70 wt% BAG were derived from a set of tensile and compression tests. The results are represented in form of stress-strain curves calculated from the acquired force and displacement data. Keywords: gellan gum scaffold; reinforcement; uni-axial loading; simulated physiological conditions Available at various institutes of the ASCR
Deformation behaviour of gellan gum based artificial bone structures under simulated physiological conditions

The paper deals with investigation of deformation behaviour of gellan gum (GG) based\nstructures prepared for regenerative medicine purposes. Investigated material was synthesized as porous ...

Krčmářová, N.; Šleichrt, J.; Fíla, Tomáš; Koudelka_ml., Petr; Kytýř, Daniel
Ústav teoretické a aplikované mechaniky, 2017

Acta Polytechnica CTU Proceedings 7
Kytýř, Daniel; Zlámal, Petr
2017 - English
The International Symposium on Experimental Methods and Numerical Simulation in Engineering Sciences continues the tradition of the Czech-German bilateral symposium founded by prof. Karl-Hans Laermann and prof. Stanislav Holý in 1985. In the following years, the symposium was extensively developed by prof. Josef Jíra. The symposium shall bring together mainly young scientists who are actively involved in experimental solid mechanics, theoretically and practically, in order to exchange experience, to report on the present state-of-art as well as on running research projects, to discuss due questions and problems and to promote the co-operation between individuals as well as between institutions. Therefore in the symposium discussions will play a highly significant role. Keywords: experimental solid mechanics; numerical simulation Available at various institutes of the ASCR
Acta Polytechnica CTU Proceedings 7

The International Symposium on Experimental Methods and Numerical Simulation in Engineering Sciences continues the tradition of the Czech-German bilateral symposium founded by prof. Karl-Hans Laermann ...

Kytýř, Daniel; Zlámal, Petr
Ústav teoretické a aplikované mechaniky, 2017

Non-holonomic planar and spatial model of a ball-type tuned mass damping device
Náprstek, Jiří; Fischer, Cyril
2017 - English
The area of tuned mass dampers is a wide field of inspiration for theoretical studies in non-linear dynamics and dynamic stability. The studies attempt to estimate behaviour of diverse damping devices and their reliability. The current paper deals with the response of a heavy ball rolling inside a spherical cavity under horizontal kinematic excitation. The non-linear system consists of six degrees of freedom with three non-holonomic constraints. The contact between the ball and the cavity surface is supposed to be perfect without any sliding. The mathematical model using the Appell-Gibbs function of acceleration energy is developed and discussed. Comparison with previous planar (SDOF) model which is based on the Lagrangian procedure is given. The system has an auto-parametric character and therefore semi-trivial solutions and their dynamic stability can be analysed. The most important post-critical regimes are outlined and qualitatively evaluated in resonance domain. Numerical experiments were performed when excitation frequency is slowly swept up and down to identify different modes of response. Some applications in civil engineering as a tuned mass damper, which can be used on slender structures, are mentioned. The proposed device is compared with a conventional pendulum damper. Strengths and weaknesses of both absorbers types are discussed. Keywords: tuned mass damper; moving ball; Appell-Gibbs formulation Available at various institutes of the ASCR
Non-holonomic planar and spatial model of a ball-type tuned mass damping device

The area of tuned mass dampers is a wide field of inspiration for theoretical studies in non-linear dynamics and dynamic stability. The studies attempt to estimate behaviour of diverse damping devices ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2017

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