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Courant algebroid connections and string effective actions
Jurčo, B.; Vysoký, Jan
2017 - English
Courant algebroids are a natural generalization of quadratic Lie algebras, appearing in various contexts in mathematical physics. A connection on a Courant algebroid gives an analogue of a covariant derivative compatible with a given fiber-wise metric. Imposing further conditions resembling standard Levi-Civita connections, one obtains a class of connections whose curvature tensor in certain cases gives a new geometrical description of equations of motion of low energy effective action of string theory. Two examples are given. One is the so called symplectic gravity, the second one is an application to the the so called heterotic reduction. All necessary definitions, propositions and theorems are given in a detailed and self-contained way. Keywords: Courant algebroid connections; low-energy effective actions; Levi-Civita connections Available on request at various institutes of the ASCR
Courant algebroid connections and string effective actions

Courant algebroids are a natural generalization of quadratic Lie algebras, appearing in various contexts in mathematical physics. A connection on a Courant algebroid gives an analogue of a covariant ...

Jurčo, B.; Vysoký, Jan
Matematický ústav, 2017

Influence of surface morphology on fatigue behavior of metastable austenitic stainless steel AISI 347 at ambient temperature and 300°C
Smaga, M.; Skorupski, R.; Mayer, P.; Kirsch, B.; Aurich, J. C.; Raid, I.; Seewig, J.; Man, Jiří; Eifler, D.; Beck, T.
2017 - English
The effect of surface modification by cryogenic turning on fatigue behavior of metastable austenitic stainless steel AISI 347 was investigated in stress-controlled fatigue tests at ambient temperature (AT) and 300 °C in air. Five different surface morphologies were manufactured by the variation of turning parameters. Surface and near surface morphology were comprehensively characterized by various experimental techniques. The experimental data on the cyclic deformation behavior, stress-strain response and fatigue life for all surface morphologies are reported. Keywords: metastable austenitic stainless steel; cryogenic turning; fatigue; surface morphology; martensite Available at various institutes of the ASCR
Influence of surface morphology on fatigue behavior of metastable austenitic stainless steel AISI 347 at ambient temperature and 300°C

The effect of surface modification by cryogenic turning on fatigue behavior of metastable austenitic stainless steel AISI 347 was investigated in stress-controlled fatigue tests at ambient temperature ...

Smaga, M.; Skorupski, R.; Mayer, P.; Kirsch, B.; Aurich, J. C.; Raid, I.; Seewig, J.; Man, Jiří; Eifler, D.; Beck, T.
Ústav fyziky materiálů, 2017

On the scientific utilisation of low power research reactors
Mikula, Pavol; Strunz, Pavel
2017 - English
In our contribution we focus our attention on the scientific utilisation of the beam tubes at the low power research reactor LVR-15. Namely, it will be reported about the neutron scattering instrumentation development and the educational possibilities at the low power neutron sources. The feasibility of carrying out the methodology and instrumental development research at the low power neutron sources will be demonstrated on designs of several high resolution and good luminosity neutron scattering instruments exploiting Bragg diffraction optics. Some of them have been already realized e.g. for small angle neutron scattering studies or residual strain/stress measurements. As the mentioned instrumental development and testing can be carried out at the low power neutron sources, due to the much lower safety requirements in comparison with the medium and high flux sources, they offer excellent educational and training programmes in neutron scattering or imaging for students. Keywords: low power reactor; research with thermal neutrons; LVR-15 Available at various institutes of the ASCR
On the scientific utilisation of low power research reactors

In our contribution we focus our attention on the scientific utilisation of the beam tubes at the low power research reactor LVR-15. Namely, it will be reported about the neutron scattering ...

Mikula, Pavol; Strunz, Pavel
Ústav jaderné fyziky, 2017

Do Invasive Alien Species Affect Diversity of Local Communities?
Kindlmann, Pavel; Honěk, A.; Martinková, Z.
2017 - English
Here we present results of simulation models to investigate the diversity dynamics in a theoretical system consisting of an "original" community of native species and an invasive alien species that invades this community, thus creating a "new" community. See Kindlmann et al. (2017) for full details of the simulations and results. Keywords: invasive species; local diversity Available at various institutes of the ASCR
Do Invasive Alien Species Affect Diversity of Local Communities?

Here we present results of simulation models to investigate the diversity dynamics in a theoretical system consisting of an "original" community of native species and an invasive alien species that ...

Kindlmann, Pavel; Honěk, A.; Martinková, Z.
Ústav výzkumu globální změny , 2017

Detekce plasticity v tenkých hliníkových vrstvách pomocí bulge testu
Holzer, Jakub; Pikálek, Tomáš; Buchta, Zdeněk; Lazar, Josef; Tinoco, H.A.; Chlupová, Alice; Náhlík, Luboš; Sobota, Jaroslav; Fořt, Tomáš; Kruml, Tomáš
2017 - English
The Bulge test proved to be a useful tool for measuring elastic properties of thin films and\nfree standing membranes, particularly Young’s modulus and residual stress. The basic principle\nof bulge test is application of differential pressure on one side of the a membrane, measurement of\nthe shape of bulged surface as a function of pressure, in this case via laser interferometer, and\nevaluation of a pressure-deflection relationship. In this study, bilayer membrane consisting of a\nsilicon nitride supporting layer and an aluminium layer deposited by means of magnetron\nsputtering is subjected to the bulge test. The results clearly show signs of a non-linear behavior\nthat is caused by plastic deformation in the aluminium layer. Finite element analysis is being\ndeveloped to describe this behavior because analytical model using deflection of central point and\npressure relation falls apart in case of non-linearity. Keywords: Bulge test; thin films; mechanical test Available at various institutes of the ASCR
Detekce plasticity v tenkých hliníkových vrstvách pomocí bulge testu

The Bulge test proved to be a useful tool for measuring elastic properties of thin films and\nfree standing membranes, particularly Young’s modulus and residual stress. The basic principle\nof bulge ...

Holzer, Jakub; Pikálek, Tomáš; Buchta, Zdeněk; Lazar, Josef; Tinoco, H.A.; Chlupová, Alice; Náhlík, Luboš; Sobota, Jaroslav; Fořt, Tomáš; Kruml, Tomáš
Ústav fyziky materiálů, 2017

Flows along arch filaments observed in the GRIS `very fast spectroscopic mode'
Gonzalez Manrique, S. J.; Denker, C.; Kuckein, C.; Pastor Yabar, A.; Collados Vera, M.; Verma, M.; Balthasar, H.; Diercke, A.; Fischer, C.E.; Gömöry, P.; Bello González, N.; Schlichenmaier, R.; Cubas Armas, M.; Berkefeld, T.; Feller, A.; Hoch, S.; Hofmann, A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Schmidt, D.; Schmid, W.; Sigwarth, M.; Sobotka, Michal; Solanki, S.K.; Soltau, D.; Staude, J.; Strassmeier, K.G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.A.
2017 - English
A new generation of solar instruments provides improved spectral, spatial, and temporal resolution, thus facilitating a better understanding of dynamic processes on the Sun. High-resolution observations often reveal multiple-component spectral line profiles, which provides information about the chromospheric velocity and magnetic fine structure. We observed an emerging flux region, including two small pores and an arch filament system, on 2015 April 17 with the "very fast spectroscopic mode" of the GREGOR Infrared Spectrograph (GRIS) situated at the 1.5-meter GREGOR solar telescope at Observatorio del Teide, Tenerife, Spain. We discuss this method of obtaining fast (one per minute) spectral scans of the solar surface and its potential to follow dynamic processes on the Sun. We demonstrate the performance of the "very fast spectroscopic mode" by tracking chromospheric high-velocity features in the arch filament system. Keywords: Sun; chromosphere; photosphere Available at various institutes of the ASCR
Flows along arch filaments observed in the GRIS `very fast spectroscopic mode'

A new generation of solar instruments provides improved spectral, spatial, and temporal resolution, thus facilitating a better understanding of dynamic processes on the Sun. High-resolution ...

Gonzalez Manrique, S. J.; Denker, C.; Kuckein, C.; Pastor Yabar, A.; Collados Vera, M.; Verma, M.; Balthasar, H.; Diercke, A.; Fischer, C.E.; Gömöry, P.; Bello González, N.; Schlichenmaier, R.; Cubas Armas, M.; Berkefeld, T.; Feller, A.; Hoch, S.; Hofmann, A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Schmidt, D.; Schmid, W.; Sigwarth, M.; Sobotka, Michal; Solanki, S.K.; Soltau, D.; Staude, J.; Strassmeier, K.G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.A.
Astronomický ústav, 2017

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

Measurements and usage of cross sections of various (n,chi n) threshold reactions
Chudoba, Petr; Vrzalová, Jitka; Svoboda, Ondřej; Krása, Antonín; Kugler, Andrej; Majerle, Mitja; Suchopár, Martin; Wagner, Vladimír
2017 - English
Current trend in nuclear reactor physics is a transition from technologies using thermal neutrons to technologies utilizing fast neutrons. Unfortunately focus was put mainly on the thermal neutrons for a long time and lead to very good knowledge about this low energy region, but very scarce coverage of the high energy region. This means that there is a gap in the knowledge of excitation functions for higher energies. This gap spreads from 20 MeV up to 1 GeV and higher. This is exactly the energy region needed for description of advanced nuclear systems such as accelerator driven systems (ADS). Our group from Nuclear Physics Institute (NPI) of the CAS is a member of an international collaboration Energy & Transmutation of Radioactive Waste (E&T RAW). This collaboration focuses on ADS for many years. In order to measure neutron field within ADS models it is necessary to know excitation functions of reactions used to monitor the neutron field. In many cases there are almost no experimental data for suitable reactions. Worse and quite common case is that there are no data at all. Therefore we are also focusing on measurements of these data in order to fill the databases as well as to allow further improvements of codes for nuclear data calculations. Keywords: cross section; NPI; E&T RAW Available at various institutes of the ASCR
Measurements and usage of cross sections of various (n,chi n) threshold reactions

Current trend in nuclear reactor physics is a transition from technologies using thermal neutrons to technologies utilizing fast neutrons. Unfortunately focus was put mainly on the thermal neutrons ...

Chudoba, Petr; Vrzalová, Jitka; Svoboda, Ondřej; Krása, Antonín; Kugler, Andrej; Majerle, Mitja; Suchopár, Martin; Wagner, Vladimír
Ústav jaderné fyziky, 2017

Genus two prime form formula for vertex operator characters
Zuevsky, Alexander
2017 - English
We find an expression for the self-sewn genus two Riemann surface counterpart of the torus formula for for an $n$-vertex operator character for the Heisenberg vertex operator algebra an $n$-point correlation function for a vertex operator algebra module with complex parameterization of corresponding states. Keywords: prime forms; vertex operator algebras; correlation functions; prime form identities Available at various institutes of the ASCR
Genus two prime form formula for vertex operator characters

We find an expression for the self-sewn genus two Riemann surface counterpart of the torus formula for for an $n$-vertex operator character for the Heisenberg vertex operator algebra an $n$-point ...

Zuevsky, Alexander
Matematický ústav, 2017

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