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Number of found documents:
426
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Note on the use of Camassa-Holm equations for simulation of incompressible fluid turbulence
Caggio, Matteo; Bodnár, Tomáš
2017 - English
The aim of this short communication is to briefly introduce the Camassa-Holm equations as a working model for simulation of incompressible fluid turbulence. In particular we discuss its application for turbulent boundary layer flows. This model (and related models) is studied for several years in mathematical community, starting from Leray [23]. It can be understood as a generalization of some classical fluid models (Navier-Stokes equations, Prandtl boundary layer equations), showing some interesting mathematical properties in the analysis of the behavior of it's solution (e.g. Layton and Lewandowski [22]). It has been found however, that the model predictions can lead to surprising extensions of the use of the model in technical applications, namely in simulating the turbulent fluid flows. This brief paper should be understood as an introductory note to this novel class of models for applied scientists.
Keywords:
Camassa-Holm equations; turbulent boundary layer
Available on request at various institutes of the ASCR
Note on the use of Camassa-Holm equations for simulation of incompressible fluid turbulence
The aim of this short communication is to briefly introduce the Camassa-Holm equations as a working model for simulation of incompressible fluid turbulence. In particular we discuss its application ...
Znovuobjevování geometrických konstrukcí
Roubíček, Filip
2016 - Czech
Článek je věnován uplatnění principů badatelsky orientovaného vyučování matematice v didaktickém semináři určeném studentům učitelství prvního stupně základní školy, konkrétně aktivitě zaměřené na konstruování známých geometrických útvarů v prostředí překládaného papíru. V článku je popsáno sedm studentských postupů konstrukce čtverce. The paper deals with the application of principles of inquiry based mathematics education in seminars of didactics for future primary school teachers, specifically with the activity focused on construction of known geometrical figures in the environment of folding paper. Seven students´ construction procedures of a square are presented in the paper.
Keywords:
mathematics education; inquiry; elementary geometry
Available at various institutes of the ASCR
Znovuobjevování geometrických konstrukcí
Článek je věnován uplatnění principů badatelsky orientovaného vyučování matematice v didaktickém semináři určeném studentům učitelství prvního stupně základní školy, konkrétně aktivitě zaměřené na ...
Cosmology on Small Scales 2016: Local Hubble Expansion and Selected Controversies in Cosmology
Křížek, Michal; Dumin, Y. V.
2016 - English
The problem of cosmological expansion on small scales (e.g., inside planetary systems) has a long history, dating back to the papers (McVittie, 1932, 1933), and quite many researchers dealt with this topic in the subsequent few decades. Although most of them concluded that the Hubble expansion should be strongly suppressed at small distances, there is no commonly-established criterion for such suppression at present. Moreover, some of the widely-used theoretical arguments against the local Hubble expansion contradict each other.
Keywords:
cosmology
Fulltext is available at external website.
Cosmology on Small Scales 2016: Local Hubble Expansion and Selected Controversies in Cosmology
The problem of cosmological expansion on small scales (e.g., inside planetary systems) has a long history, dating back to the papers (McVittie, 1932, 1933), and quite many researchers dealt with this ...
On the Friedmann equation for the three-dimensional hypersphere
Křížek, Michal; Mészáros, A.
2016 - English
The present standard cosmological model of the evolution of our universe, is based on the Friedmann equation, which was published by Alexander Friedmann in 1922. He applied Einstein’s equations to an expanding threedimensional sphere which enabled him to avoid boundary conditions. However, his description was very brief. Therefore, the main objective of this article is to detailed a derivation of the Friedmann equation for an unknown expansion function a = a(t) representing the radius of the universe. Furthermore, we present serious arguments showing why the validity of Einstein’s equations should not be extrapolated to the entire universe.
Keywords:
Einstein's equations; standard cosmological model; dark matter; dark energy
Available in digital repository of the ASCR
On the Friedmann equation for the three-dimensional hypersphere
The present standard cosmological model of the evolution of our universe, is based on the Friedmann equation, which was published by Alexander Friedmann in 1922. He applied Einstein’s equations to an ...
Badatelsky orientované vzdělávání jako jedna z cest ke zkvalitňování profesionality učitelů
Tichá, Marie; Samková, L.
2016 - Czech
Příspěvek je zaměřen na badatelsky orientované vzdělávání jako možnou cestu rozvíjení a zkvalitňování profesionality v přípravě učitelů 1. stupně základní školy. Vzhledem k tomu, že proces bádání vede k domněnkám, hypotetickým odpovědím a ty je třeba ověřit, zaměřili jsme se v poslední době také na rozvíjení uvědomování si potřeby argumentovat, vědomě zařazovat odůvodňování do vyučování matematice. This contribution focuses on inquiry-based education as one of the ways to develop and improve professionalism of future primary school teachers. Since the process of inquiry leads to conjectures and hypotheses that need to be verified, we recently turned our attention also to developing awareness of the need of proper argumentation and its incorporation into mathematics lessons.
Keywords:
inquiry-based education; teachers professionalism; primary school; argumentation
Available on request at various institutes of the ASCR
Badatelsky orientované vzdělávání jako jedna z cest ke zkvalitňování profesionality učitelů
Příspěvek je zaměřen na badatelsky orientované vzdělávání jako možnou cestu rozvíjení a zkvalitňování profesionality v přípravě učitelů 1. stupně základní školy. Vzhledem k tomu, že proces bádání vede ...
Developing open approach to mathematics in future primary school teachers
Samková, L.; Tichá, Marie
2016 - English
In our contribution we focus on the possibility to develop open approach to mathematics in future primary school teachers during a university course on mathematics conducted in inquiry-based manner. We analyse data obtained in the beginning and in the end of the course with respect to two main aspects related to open approach to mathematics: searching for all solutions of a task, and acceptance of different forms of notation of a given solution. Data analysis revealed in the participants three different shifts towards open approach to mathematics, and showed that after the active participation in the course each of the participants improved at least in one of the monitored aspects, and that none of the participants got worse in any of the aspects.
Keywords:
argumentaion; concept Cartoons; future primary school teachers; inquiry-based
Fulltext is available at external website.
Developing open approach to mathematics in future primary school teachers
In our contribution we focus on the possibility to develop open approach to mathematics in future primary school teachers during a university course on mathematics conducted in inquiry-based manner. ...
O některých miskoncepcích souvisejících se schopností argumentovat
Samková, L.; Tichá, Marie
2016 - Czech
Příspěvek se zaměřuje na různé způsoby prokazování pravdivosti obecných tvrzení (odkazy na autoritu, různé typy empirických argumentů, deduktivní argumenty). Podrobně sleduje argumentační schopnosti budoucích učitelů 1. Stupně ZŠ, zmiňuje často se vyskytující miskoncepce. Jako možnou cestu ke zlepšení argumentačních schopností nabízí badatelsky orientované vyučování. The contribution focuses on various ways of proving general statements (external convictions, various types of empirical arguments, deductive arguments). We observe in details argumentation skills of future primary school teachers, and mention often occurring misconceptions. We offer inquiry-based education as a possible way to development of argumentation skills.
Keywords:
general statements; argumentation skills; inqiry-based education
Fulltext is available at external website.
O některých miskoncepcích souvisejících se schopností argumentovat
Příspěvek se zaměřuje na různé způsoby prokazování pravdivosti obecných tvrzení (odkazy na autoritu, různé typy empirických argumentů, deduktivní argumenty). Podrobně sleduje argumentační schopnosti ...
Badatelské aktivity s geometrickým obsahem v přípravě studentů učitelství
Roubíček, Filip
2016 - Czech
Příspěvek je věnován otázkám uplatnění badatelského přístupu v semináři z didaktiky matematiky určených budoucím učitelům prvního stupně základní školy. Studentům byly předkládány badatelské výukové situace, jejichž základem bylo specifické geometrické prostředí. Studenti se zabývali řešením neurčitých geometrických úloh, které umožňovalo uplatnění badatelských postupů, jako jsou kladení otázek, navrhování postupů, experimentování, usuzování, ověřování, diskutování závěrů aj. V příspěvku jsou prezentovány tři ukázky badatelských aktivit realizovaných se studenty a jejich reflexe bádání. The paper deals with the issue of implementation of inquiry-based approach into seminars of didactics of mathematics for future primary school teachers. Inquiry -stimulating teaching situations based on specific geometrical environments were presented to students. Students engaged in the solving of undefined geometrical problems that enables application od inquiry procedures, such as posing of questions, designing of solving processes, making experiments, reasoning, verification, discussion of findings and others. Three illustrations of inquiry activities realised with students and their reflection of inquiry are presented in the paper.
Keywords:
inquiry activities; geometrical problems; preservice teacher education
Available on request at various institutes of the ASCR
Badatelské aktivity s geometrickým obsahem v přípravě studentů učitelství
Příspěvek je věnován otázkám uplatnění badatelského přístupu v semináři z didaktiky matematiky určených budoucím učitelům prvního stupně základní školy. Studentům byly předkládány badatelské výukové ...
Numerical modeling of magnetostrictive materials
Kholmetska, I.; Chleboun, J.; Krejčí, Pavel
2016 - English
An operator-differential model for magnetostrictive energy harvesting proposed in the literature is used to calculate the amount of harvested energy under some uncertainty in the Preisach density function. The uncertainty is modeled through a fuzzy set approach. In galfenol, an alloy of gallium and iron, however, the hysteresis phenomenon is present only weakly. This allows to propose a simpler, but computationally faster model without hysteresis. The new, simpler model has been identified from the measured magnetic and magnetostrictive cycles. The amount of harvested energy is of the same order in both models. Again, an uncertainty in the identified model can be considered and its impact on the amount of the harvested energy calculated.
Keywords:
magnetostrictive materials; hysteresis; energy harvesting
Available in digital repository of the ASCR
Numerical modeling of magnetostrictive materials
An operator-differential model for magnetostrictive energy harvesting proposed in the literature is used to calculate the amount of harvested energy under some uncertainty in the Preisach density ...
Anthropic principle and the local Hubble expansion
Křížek, Michal; Somer, L.
2016 - English
We claim that a local expansion of the universe, whose rate is comparable with the Hubble constant H0, had an essential influence on the development of intelligent life on the Earth. We present more than 10 examples showing that some antigravitational effects of the cosmological constant are observable locally in the Solar system. It is known that the luminosity of the Sun increased approximately linearly within the last 4.5Gyr starting at 70% of its present value. We give several independent arguments showing that the average Earth-Sun distance increases about 5m/yr due to antigravitational forces and such a large recession speed cannot be explained by solar wind, tidal forces, plasma outbursts from the Sun, or by the decrease of the Solar mass due to nuclear reactions. Models based on Newtonian mechanics can explain only a few cm per year.
Keywords:
antigravity; habitable zone; law of conservation of energy
Available in digital repository of the ASCR
Anthropic principle and the local Hubble expansion
We claim that a local expansion of the universe, whose rate is comparable with the Hubble constant H0, had an essential influence on the development of intelligent life on the Earth. We present more ...
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