Alcázar, Juan Gerardo
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Lávička, Miroslav
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Vršek, Jan
Computing symmetries of implicit algebraic surfaces We present a complete algorithm to compute the rotational, axial, reflectional and central symmetries of an algebraic surface defined by means of its implicit equation. The algorithms rely on the fact that the symmetries of the surface satisfy an algebraic condition verified by the... |
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Lávička, Miroslav
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Vršek, Jan
Polynomial curves with projections to PH curves Despite the fact that the orthogonal projection of a spatial Pythagorean hodograph (PH) curve into the plane is not a planar PH curve in general, we can find special cases such that the PH property is preserved when the curve is projected. In Farouki et al. (2021)&#x... |
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Bizzarri, Michal
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Lávička, Miroslav
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Vršek, Jan
Approximate symmetries of perturbed planar discrete curves We present a new algorithm to decide whether a discrete curve is symmetric or not. In the affirmative case we assign to each curve a particular symmetry group, and describe all rotational and reflectional symmetries (if they exist). The fundamental strategy of our approach is&... |
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Fencl, Martin
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López-Gómez, Julián
Nodal solutions of weighted indefinite problems This paper analyzes the structure of the set of nodal solutions, i.e., solutions changing sign, of a class of one-dimensional superlinear indefinite boundary value problems with indefinite weight functions in front of the spectral parameter. Quite surprisingly, the associated high-order eigenvalu... |
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Kabela, Adam
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Teska, Jakub
Trestles in the squares of graphs We show that the square of every connected S(K_{1,4})-free graph satisfying a matching condition has a 2-connected spanning subgraph of maximum degree at most 3. Furthermore, we characterise trees whose square has a 2-connected spanning subgraph of maximum degree at most k. This ge... |
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Horníková, Hana
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Vuik, Cornelis
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Egermaier, Jiří
A comparison of block preconditioners for isogeometric analysis discretizations of the incompressible Navier-Stokes equations We deal with numerical solution of the incompressible Navier-Stokes equations discretized using the isogeometric analysis (IgA) approach. Similarly to finite elements, the discretization leads to sparse nonsymmetric saddle-point linear systems. The IgA discretization basis has several specific properties d... |
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Bizzarri, Michal
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Lávička, Miroslav
Interpolation of Hermite data by clamped Minkowski Pythagorean hodograph B-spline curves Amorphous HfMSiBCN materials (M = Y, Ho, Ta, Mo or an enhanced Hf content instead of any other M) are investigated by ab initio calculations and magnetron sputtering. We focus on combining the high-temperature stability and oxidation resistance of these materials with optimised mec... |
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Bizzarri, Michal
,
Lávička, Miroslav
Construction of Minkowski Pythagorean hodograph B-spline curves Following and extending the recent results of Albrecht et all. (2017) for planar Pythagorean hodograph (PH) B-spline curves to the Minkowski 3-space, we introduce a class of Minkowski Pythagorean hodograph (MPH) B-spline curves. The distinguished property of these curves is that the Min... |
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Bizzarri, Michal
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Lávička, Miroslav
,
Vršek, Jan
Note on determining approximate symmetries of planar algebraic curves with inexact coefficients This paper$^{*}$ is devoted to a certain modification of the recently published method for an approximate reconstruction of inexact planar curves which are assumed to be perturbations of some unknown planar symmetric curves. The input curve is given by a perturbed polynomial and th... |
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Bizzarri, Michal
,
Lávička, Miroslav
,
Vršek, Jan
Approximate symmetries of planar algebraic curves with inexact input |
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Bizzarri, Michal
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Lávička, Miroslav
,
Vršek, Jan
Computing projective equivalences of special algebraic varieties This paper is devoted to the investigation of selected situations when computing projective (and other) equivalences of algebraic varieties can be efficiently solved via finding projective equivalences of finite sets of points on the projective line. In particular, we design a method th... |
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Pospíšil, Jan
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Sobotka, Tomáš
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Ziegler, Philippe
Robustness and sensitivity analyses for stochastic volatility models under uncertain data structure In this paper, we perform robustness and sensitivity analysis of several continuous-time stochastic volatility (SV) models with respect to the process of market calibration. The analyses should validate the hypothesis on importance of the jump part in the underlying model dynamics. Also ... |
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Alcazar, Juan Gerardo
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Lávička, Miroslav
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Vršek, Jan
Symmetries and similarities of planar algebraic curves using harmonic polynomials We present novel, deterministic, efficient algorithms to compute the symmetries of a planar algebraic curve, implicitly defined, and to check whether or not two given implicit planar algebraic curves are similar, i.e. equal up to a similarity transformation. Both algorithms are based on... |
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Aharoni, Ron
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Kaiser, Tomáš
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Zerbib, Shira
Fractional covers and matchings in families of weighted d-intervals A d-interval is a union of at most d disjoint closed intervals on a fixed line. Tardos [Combinatorica 15 (1995), 123-134] and the second author [Disc. Comput. Geom. 18 (1997), 195-203] used topological tools to bound the transversal number τ of a family H of d-intervals&#... |
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Gajarský, Jakub
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Hliněný, Petr
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Kaiser, Tomáš
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Král', Daniel
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Kupec, Martin
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Obdržálek, Jan
,
Ordyniak, Sebastian
,
Tůma, Vojtěch
First order limits of sparse graphs: Plane trees and path-width Nešetřil and Ossona de Mendez introduced the notion of first order convergence as an attempt to unify the notions of convergence for sparse and dense graphs. It is known that there exist first order convergent sequences of graphs with no limit modeling (an analytic representat... |
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Chhetri, Maya
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Girg, Petr
Globální bifurkace pro jistou třídu soustav eliptických PDR s nelinearitou typu "semipoziton" We study a class of semipositone elliptic systems depending on a parameter using bifurcation theory. We show that there are two disjoint unbounded connected components of the solution set and discuss the nodal properties of solutions on these components. Finally, as a consequence o... |
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Vršek, Jan
,
Lávička, Miroslav
Translation surfaces and isotropic nets on rational minimal surfaces We will deal with the translation surfaces which are the shapes generated by translating one curve along another one. We focus on the geometry of translation surfaces generated by two algebraic curves in space and study their properties, especially those useful for geometric modell... |
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Friesl, Michal
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Lenten, Liam J.A.
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Libich, Jan
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Stehlík, Petr
Zvyšování atraktivity ledního hokeje změnou pořadí střídání stran The popularity and business impact of major sports have been growing globally over time. This paper focuses on ice hockey, specifically the National Hockey League in North America. It reports a striking irregularity in ice hockey’s scoring dynamics relative to comparable sports such... |
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Bizzarri, Michal
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Lávička, Miroslav
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Vršek, Jan
Piecewise rational approximation of square-root parameterizable curves using the Weierstrass form In this paper we study situations when non-rational parameterizations of planar or space curves as results of certain geometric operations or constructions are obtained, in general. We focus especially on such cases in which one can identify a rational mapping which is a double... |
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Stehlík, Petr
Expoinenciální počet řešení Nagumovy rovnice na grafech We study the Nagumo reaction–diffusion equation on graphs and its dependence on the underlying graph structure and reaction–diffusion parameters. We provide necessary and sufficient conditions for the existence and nonexistence of spatially heterogeneous stationary solutions. Furthermore, we observe that&#... |
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Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 24
Collection's Items (Sorted by Submit Date in Descending order): 1 to 20 of 24