Number of found documents: 1104
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Remarks on inverse of matrix polynomials
Fischer, Cyril; Náprstek, Jiří
2017 - English
Analysis of a non-classically damped engineering structure, which is subjected to an external excitation, leads to the solution of a system of second order ordinary differential equations. Although there exists a large variety of powerful numerical methods to accomplish this task, in some cases it is convenient to formulate the explicit inversion of the respective quadratic fundamental system. The presented contribution uses and extends concepts in matrix polynomial theory and proposes an implementation of the inversion problem. Keywords: matrix polynomial; polynomial eigenvalues; structural vibration Available at various institutes of the ASCR
Remarks on inverse of matrix polynomials

Analysis of a non-classically damped engineering structure, which is subjected to an external excitation, leads to the solution of a system of second order ordinary differential equations. Although ...

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

Popis měření. Velkoplošné scany obrazů s vysokým rozlišením
Kumpová, Ivana; Vopálenský, Michal
2017 - Czech
Bylo provedeno skenování čtyř historických obrazů v souvislosti s jejich restaurováním na zařízení TORATOM v Centru excelence Telč Large-area scanning of four historical paintings was performed in association with their restoration. The work was done using TORATOM device in the Centre of Excelence Telč. Keywords: historical paintings; TORATOM; large-area scanning Available at various institutes of the ASCR
Popis měření. Velkoplošné scany obrazů s vysokým rozlišením

Bylo provedeno skenování čtyř historických obrazů v souvislosti s jejich restaurováním na zařízení TORATOM v Centru excelence Telč...

Kumpová, Ivana; Vopálenský, Michal
Ústav teoretické a aplikované mechaniky, 2017

Research report 2013-11-18 Calcite SSS6
Kumpová, Ivana; Vopálenský, Michal; Vavřík, Daniel
2017 - English
Porosity was measured on a irregular sample of calcite, designated Calcite_SSS6, using the TORATOM device in the Centre of Excellence Telč. Keywords: calcite; TORATOM; measuring Available at various institutes of the ASCR
Research report 2013-11-18 Calcite SSS6

Porosity was measured on a irregular sample of calcite, designated Calcite_SSS6, using the TORATOM device in the Centre of Excellence Telč.

Kumpová, Ivana; Vopálenský, Michal; Vavřík, Daniel
Ústav teoretické a aplikované mechaniky, 2017

Three-dimensional characterization of polymer foams using X-ray dark-field imaging
Senck, S.; Plank, B.; Gusenbauer, C.; Salaberger, D.; Vavřík, Daniel; Santer, W.; Kastner, J.
2017 - English
Due to the low cost, the ease of processing, and excellent material properties, polymer foams are used in various applications, e.g. packaging, building and construction, furnitures and bedding, and the automotive and aerospace sector. The mechanical response of polymer foams is primarily influenced by density and morphology. While foam density can be determined with high precision, cell morphology is more difficult to determine since the size distribution of foam cells differs in three dimensions. However, using conventional methods, e.g. optical light microscopy or scanning electron microscopy, it is very difficult to obtain three-dimensional information and to differentiate between the strut system and cell walls. An alternative for the three-dimensional characterization of foam morphology is micro-computed tomography (XCT). But even non-destructive techniques like XCT are not able to characterize anisotropic foams if the thickness of single struts and cell walls is below the physcial resolution of the respective XCT system. In this contribution we therefore investigate different polymeric foam samples using a Talbot-Lau grating interferometer XCT (TLGI-XCT) system. We show that the obtained darkfield contrast images show a high contrast and a strong signal at struts and cell walls, facilitating the segmentation of foam cells in various examples. Keywords: foam; micro-computed tomography; Talbot-Lau grating interferometer XCT; dark-field imaging Fulltext is available at external website.
Three-dimensional characterization of polymer foams using X-ray dark-field imaging

Due to the low cost, the ease of processing, and excellent material properties, polymer foams are used in various applications, e.g. packaging, building and construction, furnitures and bedding, and ...

Senck, S.; Plank, B.; Gusenbauer, C.; Salaberger, D.; Vavřík, Daniel; Santer, W.; Kastner, J.
Ústav teoretické a aplikované mechaniky, 2017

Wind-tunnel simulation of thermally unstable atmospheric flow in complex terrain
Pospíšil, Stanislav; Kuznetsov, Sergeii; Kozmar, H.; Michalcová, V.
2017 - English
The paper presents the characteristics of thermal effects in wind-tunnel simulations of the atmospheric boundary layer (ABL) flow developing above complex terrain. The differences and instable stratification effects between the windward and leeward sides of a hill model were investigated for different wind characteristics. Particularly, the buoyancy effects on the structure of the ABL simulation in a wide range of stability conditions expressed by Richardson number are studied. Keywords: instable stratification; wind tunnel; Richardson number Available at various institutes of the ASCR
Wind-tunnel simulation of thermally unstable atmospheric flow in complex terrain

The paper presents the characteristics of thermal effects in wind-tunnel simulations of the atmospheric boundary layer (ABL) flow developing above complex terrain. The differences and instable ...

Pospíšil, Stanislav; Kuznetsov, Sergeii; Kozmar, H.; Michalcová, V.
Ústav teoretické a aplikované mechaniky, 2017

Analytical approach of slender structure vibration due to random component of the wind velocity
Náprstek, Jiří; Hračov, Stanislav
2017 - English
Along wind random vibration of slender structures represents one of the most important aeroelastic effects resulting from wind - structure interaction. The theoretical model being based on one-dimensional elements with continuously distributed mass and stiffness has been introduced in this paper. The system has been considered to be linear self-adjoint with strongly non-proportional linear damping due to both material of the structure and presence of vibration dampers. The additive random excitation continuously distributed in time and space is Gaussian, therefore the response is Gaussian as well. Consequently, mathematical mean value and correlation function are satisfactory for the full description of the generalized solution of the respective PDE in the stochastic meaning. The general results have been obtained mostly in the form of analytical formulae for important cases of input spectral densities. A numerical example dealing with real structure is presented. Keywords: random vibrations; slender structures; wind load; non-proportional damping; distributed-parameter systems Fulltext is available at external website.
Analytical approach of slender structure vibration due to random component of the wind velocity

Along wind random vibration of slender structures represents one of the most important aeroelastic effects resulting from wind - structure interaction. The theoretical model being based on ...

Náprstek, Jiří; Hračov, Stanislav
Ústav teoretické a aplikované mechaniky, 2017

Stochastic stability of the generalized van der Pol system under random additive excitation
Náprstek, Jiří; Fischer, Cyril
2017 - English
The paper is motivated by a series of wind tunnel experiments investigating aeroelastic SDOF and TDOF section models of various shape and aeroelastic properties. It reveals that most of them can be theoretically modeled by the van der Pol – Duffing type equations or their combination adjusting degree of individual nonlinear terms or their coefficients. It should be emphasized that this character of the system response is very stable and is obvious in linear as well as in weakly nonlinear domain when the post-critical effect emerges. Moreover, many special effects identified by an experimental way evoke properties recognized in the pure theory of differential equations. Keywords: wind tunnel experiment; random excitation; stochastic stability Available at various institutes of the ASCR
Stochastic stability of the generalized van der Pol system under random additive excitation

The paper is motivated by a series of wind tunnel experiments investigating aeroelastic SDOF and TDOF section models of various shape and aeroelastic properties. It reveals that most of them can be ...

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

Mikroskopický laboratorní rozbor vzorku sgrafita z domu ve Venhudově ulici v Brně
Slížková, Zuzana; Kozlovcev, Petr; Koudelková, Veronika; Novák, Vladimír
2017 - Czech
Zpráva obsahuje výsledky mikroskopického rozboru vzorku sgrafita z 50.let 20. stol. na fasádě domu ve Venhudově ulici v Brně. Byla analyzována bílá povrchová vrstva a podkladní červenohnědá vrstva malty pomocí optické mikroskopie a elektronové mikroskopie ve spojení s prvkovou analýzou SEM-EDS. Report presents results of microscopic characterization of sgraffito from the the fifties of the twentieth century sampled from house façade in Brno, Venhudova street, CR. Light (optical) microscopy and electron microscopy SEM-EDS were used for characterization of the aggregate and the binder of two layers of sgraffito. Keywords: sgraffito, analysis; plaster; render; SEM-EDS; microscopy Available at various institutes of the ASCR
Mikroskopický laboratorní rozbor vzorku sgrafita z domu ve Venhudově ulici v Brně

Zpráva obsahuje výsledky mikroskopického rozboru vzorku sgrafita z 50.let 20. stol. na fasádě domu ve Venhudově ulici v Brně. Byla analyzována bílá povrchová vrstva a podkladní červenohnědá vrstva ...

Slížková, Zuzana; Kozlovcev, Petr; Koudelková, Veronika; Novák, Vladimír
Ústav teoretické a aplikované mechaniky, 2017

Výzkumná zpráva. Dýka v pochvě – Praha západ
Kumpová, Ivana
2017 - Czech
Byla provedena tomografie bronzové dýky z čerstvého archeologického nálezu a vytvořeny vizualizace. Výzkum byl proveden na zařízení TORATOM v Centru excelence Telč. Tomography of a bronze dagger from a recent archaeological finding was performed and visualizations were created. The research was done using the TORATOM device in the Centre of Excellence Telč. Keywords: bronze dagger; TORATOM; archaeology Available at various institutes of the ASCR
Výzkumná zpráva. Dýka v pochvě – Praha západ

Byla provedena tomografie bronzové dýky z čerstvého archeologického nálezu a vytvořeny vizualizace. Výzkum byl proveden na zařízení TORATOM v Centru excelence Telč....

Kumpová, Ivana
Ústav teoretické a aplikované mechaniky, 2017

Research report 2013-11-08 Calcite_S12
Kumpová, Ivana; Vopálenský, Michal; Vavřík, Daniel
2017 - English
Porosity was measured on a irregular sample of calcite, designated Calcite_S12, using the TORATOM device in the Centre of Excellence Telč. Keywords: calcite; TORATOM; measuring Available at various institutes of the ASCR
Research report 2013-11-08 Calcite_S12

Porosity was measured on a irregular sample of calcite, designated Calcite_S12, using the TORATOM device in the Centre of Excellence Telč.

Kumpová, Ivana; Vopálenský, Michal; Vavřík, Daniel
Ústav teoretické a aplikované mechaniky, 2017

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