Number of found documents: 14683
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A limited-memory optimization method using the infinitely many times repeated BNS update and conjugate directions
Vlček, Jan; Lukšan, Ladislav
2018 - English
Keywords: Unconstrained minimization; variable metric methods; limited-memory methods; the repeated BFGS update; global convergence; numerical results Available in digital repository of the ASCR
A limited-memory optimization method using the infinitely many times repeated BNS update and conjugate directions

Vlček, Jan; Lukšan, Ladislav
Ústav informatiky, 2018

Soupis publikovaých prací pana prof. Ing. Mirko Nováka, DrSc. zpracovaný ke dni 13. dubna 2018 knihovnou Ústavu informatiky AV ČR, v. v. i. s ohledem na dostupnost uvedených prací
Nývltová, Ludmila; Ramešová, Nina; Šírová, Tereza
2018 - Czech
Keywords: bibliografie Available in digital repository of the ASCR
Soupis publikovaých prací pana prof. Ing. Mirko Nováka, DrSc. zpracovaný ke dni 13. dubna 2018 knihovnou Ústavu informatiky AV ČR, v. v. i. s ohledem na dostupnost uvedených prací

Nývltová, Ludmila; Ramešová, Nina; Šírová, Tereza
Ústav informatiky, 2018

Evaluation of thin discontinuities in planar conducting materials using the diffraction of electromagnetic field
Savin, A.; Nový, F.; Fintová, Stanislava; Steigmann, R.
2017 - English
The current stage of nondestructive evaluation techniques imposes the development of new electromagnetic (EM) methods that are based on high spatial resolution and increased sensitivity. In order to achieve high performance, the work frequencies must be either radifrequencies or microwaves. At these frequencies, at the dielectric/conductor interface, plasmon polaritons can appear, propagating between conductive regions as evanescent waves. In order to use the evanescent wave that can appear even if the slits width is much smaller that the wavwelength of incident EM wave, a sensor with metamaterial (MM) is used. The study of the EM field diffraction against the edge of long thin discontinuity placed under the inspected surface of a conductive plate has been performed using the geometrical optics principles. This type of sensor having the reception coils shielded by a conductive screen with a circular aperture placed in the front of reception coil of emission reception sensor has been developed and 'transported' information for obtaining of magnified image of the conductive structures inspected. This work presents a sensor, using MM conical Swiss roll type that allows the propagation of evanescent waves and the electromagnetic images are magnified. The test method can be successfully applied in a variety of applications of maxim importance such as defect/damage detection in materials used in automotive and aviation technologies. Applying this testing method, spatial resolution can be improved. Keywords: Electromagnetic fields; Electromagnetic wave reflection; Electromagnetic waves; Geometrical optics; Image resolution; Nondestructive examination; Testing Available at various institutes of the ASCR
Evaluation of thin discontinuities in planar conducting materials using the diffraction of electromagnetic field

The current stage of nondestructive evaluation techniques imposes the development of new electromagnetic (EM) methods that are based on high spatial resolution and increased sensitivity. In order to ...

Savin, A.; Nový, F.; Fintová, Stanislava; Steigmann, R.
Ústav fyziky materiálů, 2017

Crack initiation in austenitic stainless steel sanicro 25 subjected to thermomechanical fatigue
Petráš, Roman; Škorík, Viktor; Polák, Jaroslav
2017 - English
Thermomechanical fatigue experiments were performed with austenitic stainless Sanicro 25 steel. Several amplitudes of mechanical strain in a wide temperature interval (250-700 °C) were applied to the specimens. Mechanical response was recorded and fatigue lives were obtained. Scanning electron microscopy combined with FIB technique was used to study the mechanism of crack initiation in in-phase and in out-of-phase thermomechanical cycling. Different mechanisms of the crack initiation were found in these two types of loading. During in-phase loading fatigue cracks start in grain boundaries by cracking of the oxide. Cracks grew preferentially along grain boundaries which resulted in rapid crack initiation and low fatigue life. In out-of-phase loading multiple cracks perpendicular to the stress axis developed only after sufficiently thick oxide layer was formed and cracked in low temperature loading half-cycle. The cracks in oxide allowed localized repeated oxidation and finally also cracking. The cracks grow transgranularly and result in longer fatigue life. Keywords: Damage mechanism; FIB cutting; Localized oxidation-cracking; Sanicro 25 steel; Thermomechanical fatigue Available at various institutes of the ASCR
Crack initiation in austenitic stainless steel sanicro 25 subjected to thermomechanical fatigue

Thermomechanical fatigue experiments were performed with austenitic stainless Sanicro 25 steel. Several amplitudes of mechanical strain in a wide temperature interval (250-700 °C) were applied to the ...

Petráš, Roman; Škorík, Viktor; Polák, Jaroslav
Ústav fyziky materiálů, 2017

Trojan horse method with neutrons induced reactions: The 17O(n,alpha)14C reaction
Guardo, G. L.; Spitaleri, C.; Lamia, L.; Gulino, M.; Tang, X.; Bucher, B.; Burjan, Václav; Couder, M.; Davies, P.; deBoer, R.; Fang, X.; Kroha, Václav; La Cognata, M.; Ma, C.; Mrázek, Jaromír; Mukhamedzhanov, A.; Notani, M.; O'Brien, S.; Pizzone, R. G.; Rapisarda, G. G.; Roberson, D.; Sergi, M. L.; Tan, W.; Wiescher, M.
2017 - English
The experimental study of the 17O(n,alpha)14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To over-come the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. Keywords: reaction study; nucleosynthesis; Trojan Horse Method Available at various institutes of the ASCR
Trojan horse method with neutrons induced reactions: The 17O(n,alpha)14C reaction

The experimental study of the 17O(n,alpha)14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) ...

Guardo, G. L.; Spitaleri, C.; Lamia, L.; Gulino, M.; Tang, X.; Bucher, B.; Burjan, Václav; Couder, M.; Davies, P.; deBoer, R.; Fang, X.; Kroha, Václav; La Cognata, M.; Ma, C.; Mrázek, Jaromír; Mukhamedzhanov, A.; Notani, M.; O'Brien, S.; Pizzone, R. G.; Rapisarda, G. G.; Roberson, D.; Sergi, M. L.; Tan, W.; Wiescher, M.
Ústav jaderné fyziky, 2017

Lifetime Assessment of Particulate Ceramic Composite with Residual Stresses
Náhlík, Luboš; Majer, Zdeněk; Štegnerová, Kateřina; Hutař, Pavel
2017 - English
A micro-crack propagation in particulate ceramic based composite was studied using finite element method (FEM). Subcritical crack growth (SCG) was numerically simulated under complex load conditions (mechanical loading and loading by internal residual stresses). The effect of residual stresses on the crack propagation was studied. Two-dimensional computational model of particulate ceramic composite with material properties corresponding to low temperature co-fired ceramics (LTCC) was developed. The results indicate that the presence of residual stresses significantly reduces values of stress intensity factor in the vicinity of composite surface and the direction of residual stresses around the particles contributes to the micro-crack deflection from the particles. The time to failure of the composite under mechanical loading was determined. Results obtained contribute to a better understanding of the role of residual stresses during micro-crack propagation in ceramic particulate composites. Keywords: ceramic particulate composite; sub-critical crack growth; residual stresses Available at various institutes of the ASCR
Lifetime Assessment of Particulate Ceramic Composite with Residual Stresses

A micro-crack propagation in particulate ceramic based composite was studied using finite element method (FEM). Subcritical crack growth (SCG) was numerically simulated under complex load conditions ...

Náhlík, Luboš; Majer, Zdeněk; Štegnerová, Kateřina; Hutař, Pavel
Ústav fyziky materiálů, 2017

Theranostic Mercury Part 1: A New Hg/Au Separation by a Resin Based Method
Walther, M.; Lebeda, Ondřej; Preusche, S.; Pietzsch, H.-J.; Steinbach, J.
2017 - English
The development of a fast and efficient method for Mercury/Gold separation is described as a necessary precondition for large scale production of theranostic mercury Hg-197(m). To achieve this, the application of so called LN resin (LaNthanides) was studied. The results confirm the applicability of this resin for Au/Hg separation by high efficiency, high separation factor and reproducibility. Keywords: cyclotron; Hg-197(m); LaNthanides Available at various institutes of the ASCR
Theranostic Mercury Part 1: A New Hg/Au Separation by a Resin Based Method

The development of a fast and efficient method for Mercury/Gold separation is described as a necessary precondition for large scale production of theranostic mercury Hg-197(m). To achieve this, the ...

Walther, M.; Lebeda, Ondřej; Preusche, S.; Pietzsch, H.-J.; Steinbach, J.
Ústav jaderné fyziky, 2017

In vivo study of diatom assemblages using low temperature method for ESEM
Tihlaříková, Eva; Neděla, Vilém; Fránková, Markéta
2017 - English
Diatoms are the most species-rich algal group represented by 12 000 described species and are recognized as powerful bio indicators and used for water quality monitoring. Diatom taxonomy is predominantly based on the morphology of ornate silicified cell wall called frustule composed of two overlapping parts (thecae). This frustule displays intricate patterns and designs unique to each species. For these studies conventional scanning electron microscopy (SEM) was and still is widely used. This method requires cleaning of diatom frustules in strong acids and peroxides followed by conductive coating.This aggressive procedure removes protoplast and damages delicate structures. Environmental scanning electron microscopy (ESEM) brings advantages of observation of fresh diatom material that are presence of whole intact diatom cells, not only empty diatom frustules, extracellular mucilaginous diatom secrets (e.g. pads, stalks, tubes) and whole diatom assemblages directly in situ together with other algal assemblages (e.g. cyanobacteria or green algae). However, in diatom research, ESEM is used mainly for elimination of conductive coating and observation of these organisms in their native wet state adhered directly on the host plant is not yet common. The ESEM observation of native aquatic samples is usually affected with radiation damage that can be lovered by the use of special methods like the Low Temperature Method (LTM) for the ESEM. Keywords: ESEM; diatom; morphology; LTM Available at various institutes of the ASCR
In vivo study of diatom assemblages using low temperature method for ESEM

Diatoms are the most species-rich algal group represented by 12 000 described species and are recognized as powerful bio indicators and used for water quality monitoring. Diatom taxonomy is ...

Tihlaříková, Eva; Neděla, Vilém; Fránková, Markéta
Ústav přístrojové techniky, 2017

Development of Creep Damage in Similar Weld Joints of P92 Steel Pipe
Král, Petr; Sklenička, Václav; Kuchařová, Květa; Svobodová, M.; Kvapilová, Marie; Dvořák, Jiří
2017 - English
The microstructure and creep behaviour of the welded joints of P92 steel pipe were\ninvestigated in order to determine the influence of orbital heat welding technology on the creep\nresistance. Creep specimens were machined from the welded joints. Tensile creep tests of welded\njoints were performed at 873 K using different stresses. The microstructure of tested specimens was\ninvestigated by scanning electron microscope Tescan equipped with an electron-back scatter\ndiffraction. The creep results showed that the creep fracture strain of the welded joints decreases\nwith decreasing value of applied stress. Microstructure investigation showed that fracture behaviour\nof welded joints is influenced by an enhanced cavity formation at grain boundaries in the heataffected\nzone causing lower fracture ductility. Keywords: P92 steel; welding; creep damage; creep fracture; microstructure Available at various institutes of the ASCR
Development of Creep Damage in Similar Weld Joints of P92 Steel Pipe

The microstructure and creep behaviour of the welded joints of P92 steel pipe were\ninvestigated in order to determine the influence of orbital heat welding technology on the creep\nresistance. Creep ...

Král, Petr; Sklenička, Václav; Kuchařová, Květa; Svobodová, M.; Kvapilová, Marie; Dvořák, Jiří
Ústav fyziky materiálů, 2017

Assessing a teacher’s competence for implementation of inquiry based mathematics education from a discussion of open geometrical situations
Roubíček, Filip
2017 - English
The study is focused on the possibility to assess and develop primary teachers’ abilities to implement some principles of inquiry based mathematics education into their teaching practice. The requirements on a primary teacher and their competence are assessed through a joint discussion of open geometrical situations presented through Concept Cartoons. Teachers’ written comments and notes and verbal statements expressed in the discussion of four geometrical problems were analysed and presented. Keywords: inguiry based mathematics education; primary teacher; elementary geometry Available at various institutes of the ASCR
Assessing a teacher’s competence for implementation of inquiry based mathematics education from a discussion of open geometrical situations

The study is focused on the possibility to assess and develop primary teachers’ abilities to implement some principles of inquiry based mathematics education into their teaching practice. The ...

Roubíček, Filip
Matematický ústav, 2017

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