Number of found documents: 388
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Observing how future primary school teachers reason and generalize: the case of number triangles and Concept Cartoons
Samková, L.; Tichá, Marie
2017 - English
The contribution focuses on the possibility to use an educational tool called Concept Cartoons as a diagnostic instrument in problem solving and problem posing activities of future primary school teachers. The aim of the presented study is to observe which aspects of future primary school teachers' knowledge related to reasoning and generalization could be investigated through Concept Cartoons that are based on a substantial learning environment called "Number triangles". Keywords: future primary school teachers; reasoning; generalization Available at various institutes of the ASCR
Observing how future primary school teachers reason and generalize: the case of number triangles and Concept Cartoons

The contribution focuses on the possibility to use an educational tool called Concept Cartoons as a diagnostic instrument in problem solving and problem posing activities of future primary school ...

Samková, L.; Tichá, Marie
Matematický ústav, 2017

Average contra-rotation and co-rotation of line segments for flow field analysis
Šístek, Jakub; Kolář, Václav
2017 - English
The earlier concept of the average co-rotation of infinitesimal radial line segments near a point is extended to the case of contra-rotation. The tensor of the contra-rotation is introduced and averaged over "all planar cross sections" going through the examined point. Both the average contra-rotation and co-rotation, representing shear-free quantities, are applied to describe a complex flow structure. Keywords: fluid mechanics; contra-rotation Available on request at various institutes of the ASCR
Average contra-rotation and co-rotation of line segments for flow field analysis

The earlier concept of the average co-rotation of infinitesimal radial line segments near a point is extended to the case of contra-rotation. The tensor of the contra-rotation is introduced and ...

Šístek, Jakub; Kolář, Václav
Matematický ústav, 2017

Crandall-Rabinowitz type bifurcation for non-differentiable perturbations of smooth mappings
Recke, L.; Väth, Martin; Kučera, Milan; Navrátil, J.
2017 - English
We consider abstract equations of the type ..., where lambda is a bifurcation parameter and tau is a perturbation parameter. We suppose that ... for all lambda and tau, F is smooth and the unperturbed equation ... describes a Crandall-Rabinowitz bifurcation in lambda=0, that is, two half-branches of nontrivial solutions bifurcate from the trivial solution in lambda=0. Concerning G, we suppose only a certain Lipschitz condition; in particular, G is allowed to be non-differentiable. We show that for fixed small ... there exist also two half-branches of nontrivial solutions to the perturbed equation, but they bifurcate from the trivial solution in two bifurcation points, which are different, in general. Moreover, we determine the bifurcation directions of those two half-branches, and we describe, asymptotically as ..., how the bifurcation points depend on tau. Finally, we present applications to boundary value problems for quasilinear elliptic equations and... Keywords: nonsmooth equation; Lipschitz bifurcation branch; formula for the bifurcation direction Available on request at various institutes of the ASCR
Crandall-Rabinowitz type bifurcation for non-differentiable perturbations of smooth mappings

We consider abstract equations of the type ..., where lambda is a bifurcation parameter and tau is a perturbation parameter. We suppose that ... for all lambda and tau, F is smooth and the unperturbed ...

Recke, L.; Väth, Martin; Kučera, Milan; Navrátil, J.
Matematický ústav, 2017

Clusterization of correlation functions
Zuevsky, Alexander
2017 - English
Using the Zhu recursion formulas for correlation functions for vertex operator algebras, we introduce a cluster algebra structure over a non-commutative set of variables. Keywords: vertex algebras; correlation functions; cluster algebras Available on request at various institutes of the ASCR
Clusterization of correlation functions

Using the Zhu recursion formulas for correlation functions for vertex operator algebras, we introduce a cluster algebra structure over a non-commutative set of variables.

Zuevsky, Alexander
Matematický ústav, 2017

On the boundary conditions in the numerical simulation of stably stratified fluids flows
Bodnár, Tomáš; Fraunié, P.
2017 - English
This paper presents the results of a numerical study of the stably stratified flow over a low smooth hill. The emphasize is on certain problems related to artificial boundary conditions used in the numerical simulations. The numerical results of three-dimensional simulations are shown for a range of Froude and Reynolds numbers in order to demonstrate the varying importance of these boundary issues in different flow regimes. The simulations were performed using the Boussinesq approximation model solved by a high-resolution numerical code. The in-house developed code is based on compact finite-difference discretization in space and Strong Stability Preserving Runge-Kutta time integration. Keywords: Boussinesq approximation; stable stratification; compact finite-difference Available on request at various institutes of the ASCR
On the boundary conditions in the numerical simulation of stably stratified fluids flows

This paper presents the results of a numerical study of the stably stratified flow over a low smooth hill. The emphasize is on certain problems related to artificial boundary conditions used in the ...

Bodnár, Tomáš; Fraunié, P.
Matematický ústav, 2017

Higher dimensional Robinson-Trautman spacetimes sourced by p-forms: static and radiating black holes
Ortaggio, Marcello; Podolský, J.; Žofka, M.
2017 - English
We summarize results about Robinson-Trautman spacetimes in the presence of an aligned p-form Maxwell field and an arbitrary cosmological constant in n >= 4 dimensions. While in odd dimensions the solutions reduce to static black holes dressed with an electric and a magnetic field (with an Einstein space horizon), in even dimensions 2p = n they may also describe black holes gaining (or losing) mass by receiving (or emitting) electromagnetic radiation. The Weyl type of the spacetimes is also briefly discussed in all the possible cases. Keywords: Robinson-Trautman spacetimes; p-form fields; black holes Available on request at various institutes of the ASCR
Higher dimensional Robinson-Trautman spacetimes sourced by p-forms: static and radiating black holes

We summarize results about Robinson-Trautman spacetimes in the presence of an aligned p-form Maxwell field and an arbitrary cosmological constant in n >= 4 dimensions. While in odd dimensions the ...

Ortaggio, Marcello; Podolský, J.; Žofka, M.
Matematický ústav, 2017

On type N and III universal spacetimes
Hervik, S.; Pravda, Vojtěch; Pravdová, Alena
2017 - English
We briefly summarize our recent results on type N and III universal spacetimes. Keywords: generalized theories of gravity; universal spacetimes Available on request at various institutes of the ASCR
On type N and III universal spacetimes

We briefly summarize our recent results on type N and III universal spacetimes.

Hervik, S.; Pravda, Vojtěch; Pravdová, Alena
Matematický ústav, 2017

On type II universal spacetimes
Hervik, S.; Málek, Tomáš; Pravda, Vojtěch; Pravdová, Alena
2017 - English
We briefly summarize our recent results on type II universal metrics of the Lorentzian signature. These metrics simultaneously solve all vacuum field equations of theories of gravity with the Lagrangian being a polynomial curvature invariant constructed from the metric, the Riemann tensor and its covariant derivatives of arbitrary order. It turns out that the results critically depend on the dimensionality of the spacetime. While we discuss examples of type II universal metrics for all composite number dimensions, we have no examples for prime number dimensions. Furthermore, we have proven the non-existence of type II universal spacetimes in five dimensions. Keywords: generalized theories of gravity; universal spacetimes Available on request at various institutes of the ASCR
On type II universal spacetimes

We briefly summarize our recent results on type II universal metrics of the Lorentzian signature. These metrics simultaneously solve all vacuum field equations of theories of gravity with the ...

Hervik, S.; Málek, Tomáš; Pravda, Vojtěch; Pravdová, Alena
Matematický ústav, 2017

The effect of irregular interfaces on the BDDC method for the Navier-Stokes equations
Hanek, M.; Šístek, Jakub; Burda, P.
2017 - English
We investigate the effect of interface irregularity on the convergence of the BDDC method for Navier-Stokes equations. A benchmark problem of a sequence of contracting channels is proposed to evaluate the robustness of the iterative solver with respect to element aspect ratios at the interface. Partitioners based on graph of the mesh and the geometry of the domain are compared. It is shown, that the convergence is significantly improved by avoiding irregular interfaces for the benchmark problem as well as for an industrial problem of oil flow in hydrostatic bearing. Keywords: Navier Stokes equations; domain decomposition methods; hydrostatic bearings Available at various institutes of the ASCR
The effect of irregular interfaces on the BDDC method for the Navier-Stokes equations

We investigate the effect of interface irregularity on the convergence of the BDDC method for Navier-Stokes equations. A benchmark problem of a sequence of contracting channels is proposed to evaluate ...

Hanek, M.; Šístek, Jakub; Burda, P.
Matematický ústav, 2017

Observing how future primary school teachers reason about fractions
Samková, L.; Tichá, Marie
2017 - English
The contribution focuses on the possibility to use an educational tool called Concept Cartoons in future primary school teachers' education, especially as an instrument for observing how future primary school teachers reason about fractions. The task which we adapted to the Concept Cartoons form belongs to primary school mathematics, i.e. it focuses on the concept of a fraction per se, in particular on the parts-and-whole decision and on comparison of two pre-partitioned models with diverse wholes. Using Concept Cartoons, we observe which statements about the issue our respondents consider as correct, and which kinds of reasoning they use in their justifications. We also mention other related concepts (percentages), and related tasks from entrance exams to lower-secondary selective schools. Keywords: concept Cartoons; fractions; future primary school teachers Available at various institutes of the ASCR
Observing how future primary school teachers reason about fractions

The contribution focuses on the possibility to use an educational tool called Concept Cartoons in future primary school teachers' education, especially as an instrument for observing how future ...

Samková, L.; Tichá, Marie
Matematický ústav, 2017

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