2025-03-02
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2025-03-02
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O trhu a kapitálu poprvé souhrnně, teoreticky a česky. Josef Kaizl a jeho učebnice Národního hospodářství, in: Trh a kapitál v české kultuře 19. století.
Hlavačka, Milan
Text je postaven jako kritický rozbor okolností vzniku první vědecké učebnice národního hodpodářství publikované v českém jazyce z pera Josefa Kaizla v roce 1884. Autor poodhaluje stav českého ekonomického myšlení v době jeho univerzitní institucionalizace na Právnické fakultě Karlo-Ferdinandovy univerzity v Praze, kde právě probíhal proces dělení nejstaršího středoevropského univerzitního učení na českou a německou univerzitu a mimo tuto univerzitu vypukl spor mezi historickou školou národního hospodářství, reprezentovanou především Gustavem Schmollerem a Albertem Schäfflem a na druhé straně tzv. vídeňskou školou, která bude o něco později nazvána podle Mengerovy metody náhledu na politickou ekonomii školou mezního, respektive hraničního užitku. Politická ekonomie, respektive uvažování o trhu a kapitálu získalo tehdy definitivně svůj vlastní předmět výzkumu a také koncepčně myšlenkovou dynamiku, která se přesunula do střední Evropy.
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2025-03-02
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High-resolution neutron diffraction for finer studies of powder diffraction lines
Mikula, Pavol ; Ryukhtin, Vasyl
Feasibility of focusing high-resolution three axis diffractometer with the polycrystalline sample between the monochromator and the analyzer for studies of finer effects of diffraction lines is routinely used at the medium-power reactor LVR-15 in Řež. The focusing three-axis set-up equipped with bent perfect crystal monochromator and analyzer exploits both focusing in real and momentum space and provides the intensity and resolution parameters for measurements within a reasonable measurement time.
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2025-03-02
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Experimental equipments of Neutron physics laboratory for testing of metalic samples
Mikula, Pavol ; Strunz, Pavel
The use of neutron scattering for structural and property studies of technologically interesting materials as well as solution of industrial problems has been expanding in the last years. Correspondingly, demands for the beam time at neutron sources have been strongly increased. After using Bragg diffraction optics based on diffraction by curved perfect crystals some experiments of materials science - usually done with small sample volumes - can be effectively performed even at a medium power reactor, in our case at LVR-15 in Řež. Examples of unique experimental results obtained namely, by medium-resolution small-angle neutron scattering, residual strain/stress measurements and conventional powder diffraction at the reactor will be presented. An access to experiments for external users is also presented. \n
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2025-03-02
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Weak imposition of potential Dirichlet boundary conditions in piezoelasticity: Numerical study
Cimrman, Robert
Detailed modelling of piezoelastic structures often includes also an external circuit. This is tied with the need for a weak imposition of electric potential Dirichlet boundary conditions and questions of simulation accuracy arise. Several methods allowing the weak imposition, namely the non-symmetric Nitsche’s method, penalty method and their combinations, are evaluated and their numerical convergence w.r.t. uniform mesh refinement for various finite element approximation orders is reported. The numerical study is performed on a geometry corresponding to a piezoelectric sensor.
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2025-02-22
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X-ray computed tomography of the oscillating beam
Beneš, Pavel ; Rada, Václav ; Macháček, Michael ; Koudelka_ml., Petr ; Zlámal, Petr ; Fíla, Tomáš ; Šleichrt, Jan ; Vavřík, Daniel
This work presents X-ray computed tomography of a harmonically oscillating elastic beam. The tomographic imaging is achieved by obtaining projections of the object in its maximum amplitude to capture the eigenmode of the beam using a triggered computed tomography method synchronized with the oscillation of the beam. Related instrumentation, experimental methodology and data post-processing are presented. Results are demonstrated on the reconstructed 3D images of the polymeric oscillating beam in its deformed shape corresponding with the harmonic excitation using the first eigenfrequency. A comparison with conventional non-synchronized tomography of the oscillating beam in its first eigenfrequency is presented to highlight fundamental advantages on such tomographical imaging.
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2025-02-22
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Weld evaluation of eutectic high-entropy alloy and austenitic steel formed by EBW
Rončák, Ján ; Jozefovič, Patrik ; Zobač, Martin
AlCoCrFeNi2.1 alloy belongs to a group of materials called eutectic high-entropy alloys (EHEAs). These have gained attention due to the fact that there is no so-called “strength ductility trade-off”. At the same time, the material properties are stable over a wide temperature range due to the high entropy state of the eutectic structure. The generally good castability of eutectic alloys, which prevents segregation of the major chemical elements and precipitation of new phases, also extends the possibilities for future applications. Based on the above, AlCoCrFeNi2.1 alloy could be applied in critical structural locations subjected to severe conditions in terms of elevated temperatures and mechanical stresses. Alloy could replace, for example, austenitic steels with high ductility but lower tensile strength values. In order to make full use of a given material, its behaviour must be verified in bonding technologies with commercially used materials. Therefore, the following research deals with heterogeneous weld joints of AlCoCrFeNi2.1 with austenitic steel EN 1.4571 formed by electron beam welding. The evaluation of the weld consisted of observation of the resulting microstructure, determination of the chemical concentration of the elements in the fusion zone, phase analysis followed by mechanical properties testing in the form of Vickers hardness test and tensile test.
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2025-02-22
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On a Possibility of High-Resolution Neutron Scattering Observations of TiAl Substructure
Mikula, Pavol ; Michalcová, A. ; Ryukhtin, Vasyl
In this contribution, we present the feasibility of using two unconventional neutron scattering methods, namely, high-resolution neutron diffraction and small-angle neutron scattering, for substructure studies of TiAl alloys. The first one permits the finer studies of the diffraction line profiles and the second one the size distribution of pores on a rather large scale. The feasibility experiments were carried out on the three TiAl samples of the f = 9 mm diameter which were made from the 3D printed material of gamma titanium aluminides (Ti48Al2Cr2Nb) loaded on the bulk Ti substrate.
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2025-02-22
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Surface degradation of tungsten for plasma-facing components after thermal loading
Petráš, R. ; Peterka, Matěj ; Matějíček, Jiří ; Hajíček, M. ; Havlík, P. ; Čížek, O. ; Zýka, J. ; Vála, L.
During the operation of fusion devices, plasma facing components (PFCs) are subjected to high thermal loads. These result in mechanical stresses and various forms of degradation and microstructural changes in the material volume. In order to assess the viability of the PFC candidate materials, tungsten samples were subjected to high heat flux tests simulating heat load pulses caused by plasma instabilities. The presented study includes also a thermal model developed in ANSYS Fluent software to simulate the temperature profile at different depths of the sample and its evolution during the tests. Thermal loading was performed using an electron beam facility. Short pulses (~1 s) of up to 40 MW/m2 thermal load were applied to the top surface of 10 mm wide cylindrical samples. Homogeneous heat flux distribution over the circular area was achieved by scanning the electron beam in a dense pattern. The temperature evolution during the tests was monitored using a thermocouple inserted into the sample along with the surface temperature measurement with a pyrometer. Scanning electron microscopy was used to document surface degradation. A dense net of intergranular cracks typically formed on the loaded surface of the studied material. As a result of a qualitative comparison of the measured temperature profiles during the experiments with the profiles issued from ANSYS simulations, the computational thermal model was verified.
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2025-02-22
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