Number of found documents: 1115
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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

Large-area scans of paintings with high resolution
Vopálenský, Michal; Kumpová, Ivana
2019 - Czech
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. 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. Keywords: large-area X-ray scanning; radiography of fine-art objects; restoration of paintings Available at various institutes of the ASCR
Large-area scans of paintings with high resolution

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 ...

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

Reconstruction of the Renaissance sand-coloured sgraffito based on the material copy
Válek, Jan; Skružná, Olga; Kozlovcev, Petr; Waisserová, J.; Wichterlová, Z.; Jiroušek, Josef
2019 - Czech
The aim of the method is to provide a methodical design for the preparation of sand made sgraffito mortar and show its use on a specific example. Cílem památkového postupu je poskytnout metodický návrh přípravy maltového doplňku pískového\nsgrafita a ukázat jeho využití na konkrétním příkladu. Keywords: renaissance sgraffito; repairs of plasters; traditional building technologies; traditional lime techniques Available in a digital repository NRGL
Reconstruction of the Renaissance sand-coloured sgraffito based on the material copy

The aim of the method is to provide a methodical design for the preparation of sand made sgraffito mortar and show its use on a specific example.

Válek, Jan; Skružná, Olga; Kozlovcev, Petr; Waisserová, J.; Wichterlová, Z.; Jiroušek, Josef
Ústav teoretické a aplikované mechaniky, 2019

Tomographical investigation of the historical metal bracelets
Kumpová, Ivana; Vopálenský, Michal
2019 - Czech
The work was focused on the method definition for the investigation of historical metal artifacts employing the X-ray tomography. Two metal bracelets made of brass and plated with silver were investigated in the laboratory. The goal was to determine the technology of manufacturing and damages, possible also to visualize the silver layer. Práce byla zaměřena na vytvoření metodiky využívající rentgenové (RTG) tomografické zobrazování pro průzkumy historických artefaktů na bázi kovů. V laboratoři byly touto metodou zkoumány dva kovové náramky z mosazi s postříbřeným povrchem. Průzkum byl proveden za účelem odhalení technologie výroby a případných poškození, případně řešení napojení stříbrné vrstvy. Keywords: X-ray tomography; investigation of historical objects; metal artifacts Available at various institutes of the ASCR
Tomographical investigation of the historical metal bracelets

The work was focused on the method definition for the investigation of historical metal artifacts employing the X-ray tomography. Two metal bracelets made of brass and plated with silver were ...

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

The research of wooden dowel-type connectors
Kunecký, Jiří; Hasníková, Hana; Hataj, M.; Milch, J.; Tyrová, M.; Suchomelová, P.
2019 - Czech
The carpentry joints, some of them secured by wooden connectors, are part of historical timber roof structures. Originally, a wooden dowel rather secured the position of timber elements in a joint than transferring loads (e.g. dovetail joints). But in some joints it can also transfer the forces between the structural members, therefore its behaviour influences the stiffness and load-bearing capacity of the whole structure directly. This type of connectors can be used nowadays as well; while reconstructions, a new timber building construction, or manufacturing individual structural timber elements (e.g. panels). Current technical standards do not prescribe a suitable computing procedure for the joints with wooden connectors. Moreover, a complex failure criteria for various fibre directions are missing. The article introduces an ongoing project, whose ambition is to cover the knowledge gap. Součástí historických krovových soustav jsou tesařské spoje, z nichž některé jsou zajištěny dřevěnými spojovacími prostředky. Původně dřevěný kolík spíše zajišťoval polohu prvků ve spoji než by primárně přenášel zatížení (např. rybinové spoje). V některých spojích však mezi jednotlivými konstrukčními prvky může síly také přenášet, a jeho působení tak má přímý vliv na tuhost i únosnost celé konstrukce. Tento typ spojovacích prostředků je možné využít i v současnosti, při rekonstrukcích, výstavbě nových dřevostaveb nebo pro výrobu jednotlivých dřevěných konstrukčních prvků (např. panelů). Současné technické normy však spojům s dřevěnými spojovacími prostředky nepředepisují dostatečný výpočetní postup, navíc chybí i komplexní model porušení v různých směrech k vláknům. Článek představuje aktuální projekt, který má ambici tuto mezeru vyplnit. Keywords: wooden dowel; load-bearing capacity; stiffness; creep; carpentry joints Available at various institutes of the ASCR
The research of wooden dowel-type connectors

The carpentry joints, some of them secured by wooden connectors, are part of historical timber roof structures. Originally, a wooden dowel rather secured the position of timber elements in a joint ...

Kunecký, Jiří; Hasníková, Hana; Hataj, M.; Milch, J.; Tyrová, M.; Suchomelová, P.
Ústav teoretické a aplikované mechaniky, 2019

Strategies for computation of Lyapunov exponents estimates from discrete data
Fischer, Cyril; Náprstek, Jiří
2019 - English
The Lyapunov exponents (LE) provide a simple numerical measure of the sensitive dependence of the dynamical system on initial conditions. The positive LE in dissipative systems is often regarded as an indicator of the occurrence of deterministic chaos. However, the values of LE can also help to assess stability of particular solution branches of dynamical systems. The contribution brings a short review of two methods for estimation of the largest LE from discrete data series. Two methods are analysed and their freely available Matlab implementations are tested using two sets of discrete data: the sampled series of the Lorenz system and the experimental record of the movement of a heavy ball in a spherical cavity. It appears that the most important factor in LE estimation from discrete data series is quality of the available record. Keywords: dynamical system; Lyapunov exponents; stability; data analysis Available at various institutes of the ASCR
Strategies for computation of Lyapunov exponents estimates from discrete data

The Lyapunov exponents (LE) provide a simple numerical measure of the sensitive dependence of the dynamical system on initial conditions. The positive LE in dissipative systems is often regarded as an ...

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

Chemical and mineralogical analyses of plaster samples from State Castle Bečov
Slížková, Zuzana; Koudelková, Veronika; Kozlovcev, Petr; Šterner, Adam
2018 - Czech
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 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. Keywords: chemical composition; survey; material characterization; binder; aggregate; historic plaster; historic render Available at various institutes of the ASCR
Chemical and mineralogical analyses of plaster samples from State Castle Bečov

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 ...

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

Proposal for loading tests of bridges - simulation and laboratory experiments
Bayer, Jan; Urushadze, Shota; Černý, Miloš
2018 - English
A new dynamic load testing of bridges is proposed and theoretically investigated. A transient analysis of passing vehicle over a bridge in ANSYS and an analytical program in MATLAB for the transient solution of piecewise linear mechanical structures were developed to assess the effects of the proposed dynamic load on a bridge model. According to the first laboratory experiments, it seems that the proposed travelling impulse load could surpass some of the shortcomings and limitations of the currently applied methods of bridge testing. The investigation is a part of a project aimed at drive-by identification of dynamic properties of bridges and further experimental and analytical research will follow. Keywords: dynamic loading tests; transient analysis; vibrations; vehicle-bridge interaction Fulltext is available at external website.
Proposal for loading tests of bridges - simulation and laboratory experiments

A new dynamic load testing of bridges is proposed and theoretically investigated. A transient analysis of passing vehicle over a bridge in ANSYS and an analytical program in MATLAB for the transient ...

Bayer, Jan; Urushadze, Shota; Černý, Miloš
Ústav teoretické a aplikované mechaniky, 2018

Characterization of historical renders and plasters sampled from the Castle Freudenstein (also called Slikuv Castle), tower „Slikovka“, Ostroh nad Jachymovem (Zamecký vrsek u Jachymova)
Slížková, Zuzana; Frankeová, Dita; Koudelková, Veronika
2018 - Czech
SEM and SEM-EDS analyses was used for determination of renders and plasters microstructure and components Vzorky vnějších a vnitřních omítek byly zkoumány za účelem zjištění jejich struktury a chemického složení pomocí metod SEM a SEM-EDS Keywords: render; plaster; slag; cement; SEM-EDS analysis Available at various institutes of the ASCR
Characterization of historical renders and plasters sampled from the Castle Freudenstein (also called Slikuv Castle), tower „Slikovka“, Ostroh nad Jachymovem (Zamecký vrsek u Jachymova)

SEM and SEM-EDS analyses was used for determination of renders and plasters microstructure and components

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

Footbridge in Radotín - wind load according to EN 1991-1-4 and wind tunnel experiments
Göringer, J.; Hračov, Stanislav; Macháček, Michael
2018 - Czech
Due to the atypical design of the footbridge in Radotín the procedures for evaluation of the force coefficients presented in EN 1991-1-4 were experimentally verified in the wind tunnel. For the lack of the information about the structure behaviour on the edge of the aerodynamic instability the critical velocity for flutter was experimentally verified as well. The paper presents comparison of the approaches from EN 1991-1-4 with the results of the experiment. S ohledem na atypickou konstrukci lávky v Radotíně bylo nutno v rámci statického ověření řešit nestandardní účinky zatížení větrem, kdy EN 1991-1-4 poskytuje pro takto atypické konstrukce jen málo podpory. Zatížení větrem u takovéto konstrukce nevystupuje pouze jako náhradní statický účinek, ale zejména je nutné posoudit případné ztráty aerodynamické stability. Příspěvek předkládá postup stanovení problematiky podle EN 1991-1-4 včetně porovnání s výsledky z větrného tunelu. Keywords: wind load; footbridge; wind tunnel experiments Available at various institutes of the ASCR
Footbridge in Radotín - wind load according to EN 1991-1-4 and wind tunnel experiments

Due to the atypical design of the footbridge in Radotín the procedures for evaluation of the force coefficients presented in EN 1991-1-4 were experimentally verified in the wind tunnel. For the lack ...

Göringer, J.; Hračov, Stanislav; Macháček, Michael
Ústav teoretické a aplikované mechaniky, 2018

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