Ano (102)
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102
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Excessive extrapolations of Einstein's equations
Křížek, Michal; Somer, L.
2020 - anglický
The standard cosmological model is surprisingly quite thoroughly investigated even though it possesses many paradoxes. We present several arguments indicating why excessive extrapolations of Einstein's equations to cosmological distances are questionable. First, we show how to express explicitly the first of Einstein's 10 partial differential equations to demonstrate their extremely large complexity. Therefore, it would be very difficult to find their solution for two or more bodies to model, e.g., the evolution of the Solar system. Further, we present some unexpected failures of the Schwarzschild and Friedmann solution of these equations. Then we explain why application of Einstein's equations to the whole universe represents incorrect extrapolations that lead to dark matter, dark energy, and several unrealistic situations. Finally, we give 10 further arguments showing why celebrated Einstein's equations do not describe reality well.
Klíčová slova:
Einstein's equations; Schwarzschild solution; Friedmann equation
Dokument je dostupný na externích webových stránkách.
Excessive extrapolations of Einstein's equations
The standard cosmological model is surprisingly quite thoroughly investigated even though it possesses many paradoxes. We present several arguments indicating why excessive extrapolations of ...
The effect of submeso motions on second-order moment budgets in the stable atmospheric boundary layer
Schiavon, M.; Tampieri, F.; Caggio, M.; Bodnár, Tomáš
2020 - anglický
The effect of submeso motions on small-scale turbulence is studied considering the budget of the vertical flux of stream-wise momentum, ⟨uw⟩, in the atmospheric stable boundary layer (SBL). A parameter expressing the strength of the submeso effect is defined, and the budget is evaluated from observations both for small and large submeso effect. It results that submeso motions affect the efficiency of the vertical transport by small-scale turbulence, having implications on the terms composing the momentum flux budget and on its corresponding closures.
Klíčová slova:
submeso motions; pressure redistribution; second-order moment equations
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
The effect of submeso motions on second-order moment budgets in the stable atmospheric boundary layer
The effect of submeso motions on small-scale turbulence is studied considering the budget of the vertical flux of stream-wise momentum, ⟨uw⟩, in the atmospheric stable boundary layer (SBL). A ...
On the influence of diffusion stabilization in Oldroyd-B fluid flow simulations
Pires, M.; Bodnár, Tomáš
2020 - anglický
This work presents some numerical tests of finite element solution of incompressible Oldroyd-B fluid flows. The effect of numerical stabilization using artificial stress diffusion is investigated in detail. The limits of Weissenberg number We for which it is possible to obtain the numerical solution were studied depending on the Reynolds number Re and the diffusion parameter. Series of numerical tests were performed for steady two-dimensional Oldroyd-B fluid flow in corrugated channel (tube). The numerical results clearly proved the advantage (higher attainable We) of stabilized numerical method over the classical formulation without the artificial stress diffusion.
Klíčová slova:
finite element method; Oldroyd-B fluid; numerical stabilization; stres diffusion
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
On the influence of diffusion stabilization in Oldroyd-B fluid flow simulations
This work presents some numerical tests of finite element solution of incompressible Oldroyd-B fluid flows. The effect of numerical stabilization using artificial stress diffusion is investigated in ...
Cosmology on Small Scales 2020: Excessive extrapolations and selected controversies in cosmology
Křížek, Michal; Dumin, Y. V.
2020 - anglický
According to the modern cosmological paradigm, about 2/3 of the energy of the Universe is in dark form and about 5/6 of the matter is invisible. However, numerous recent independent attempts to detect dark-matter particles failed, and a number of other problems with the existence of dark energy and dark matter (such as the anomalous friction in the dark-matter halos of galaxies) become now more and more obvious. All these problems raise the question if the 'dark' substance is merely a result of the use of erroneous assumptions or incorrect models based e.g. on excessive extrapolations. Consequently, it is timely to gather specialists from various branches of astronomy and astrophysics to discuss these questions.
Klíčová slova:
cosmology
Dokument je dostupný na externích webových stránkách.
Cosmology on Small Scales 2020: Excessive extrapolations and selected controversies in cosmology
According to the modern cosmological paradigm, about 2/3 of the energy of the Universe is in dark form and about 5/6 of the matter is invisible. However, numerous recent independent attempts to detect ...
A critical review of paradoxes in the special theory of relativity
Křížek, Michal
2020 - anglický
We show that the Doppler effect and aberration of light can produce more dominant and entirely opposite effects for relativistic speeds than those predicted by the Special Theory of Relativity, in particular, the clock paradox, time dilatation, and length contraction. For instance, an observer will measure a higher frequency of an approaching clock than the same clock has at rest. We also prove that under certain conditions an approaching bar on a photo may seem to have a larger length for a relativistic speed than at rest.
Klíčová slova:
Lorentz transformation; theory of groups; inertial systems
Dokument je dostupný na externích webových stránkách.
A critical review of paradoxes in the special theory of relativity
We show that the Doppler effect and aberration of light can produce more dominant and entirely opposite effects for relativistic speeds than those predicted by the Special Theory of Relativity, in ...
Recent results on the problem of motion of viscous fluid around a rotating rigid body
Deuring, P.; Kračmar, Stanislav; Nečasová, Šárka
2020 - anglický
We consider the linearized incompressible flow around rotating and translating body in the exterior domain R³D‾, where D⊂R³ is open and bounded, with Lipschitz boundary. We derive the pointwise estimates for the pressure. Further, we consider the linearized problem in a truncation domain DR:=BRD‾ of the exterior domain R³D‾ under certain artificial boundary conditions on the truncating boundary ∂BR, and then compare this solution with the solution in the exterior domain R³D‾ to get the truncation error estimate.
Klíčová slova:
pointwise decay; artificial boundary; error estimates
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Recent results on the problem of motion of viscous fluid around a rotating rigid body
We consider the linearized incompressible flow around rotating and translating body in the exterior domain R³D‾, where D⊂R³ is open and bounded, with Lipschitz boundary. We derive the pointwise ...
Note on the problem of compressible non-Newtonian fluids
Caggio, M.; Nečasová, Šárka
2019 - anglický
The aim of the paper is to consider the compressible non-Newtonian fluids of power law type when the viscosity coeffcients depend not only on invariants of velocity field but also on the density. We introduce approximation scheme using model of multipolar fluids. After then passing with higher viscosity to zero we get the measure valued solution of the problem.
Klíčová slova:
non-Newtonian fluid; compressible fluid; multipolar fluid; measure-valued solution
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Note on the problem of compressible non-Newtonian fluids
The aim of the paper is to consider the compressible non-Newtonian fluids of power law type when the viscosity coeffcients depend not only on invariants of velocity field but also on the density. We ...
Programs and Algorithms of Numerical Mathematics 19 : Hejnice, June 24-29, 2018 : proceedings of seminar
Chleboun, J.; Kůs, Pavel; Přikryl, Petr; Rozložník, Miroslav; Segeth, Karel; Šístek, Jakub; Vejchodský, Tomáš
2019 - anglický
These proceedings contain peer-reviewed papers that are based on the invited lectures, survey lectures, short communications, and posters presented at the 19th seminar Programs and Algorithms of Numerical Mathematics (PANM) held in the International Center for Spiritual Rehabilitation, Hejnice, Czech Republic, June 24-29, 2018. The seminar was organized by the Institute of Mathematics of the Czech Academy of Sciences under the auspices of EU-MATHS-IN.cz, Czech Network for Mathematics in Industry, and with the financial support provided by the RSJ Foundation. It continued the previous seminars on mathematical software and numerical methods held (biennially, with only one exception) in Alšovice, Bratříkov, Janov nad Nisou, Kořenov, Lázně Libverda, Dolní Maxov, and Prague in the period 1983-2016. The objective of this series of seminars is to provide a forum for presenting and discussing advanced topics in numerical analysis, computer implementation of numerical algorithms, new approaches to mathematical modeling, and single- or multi-processor applications of computational methods.
Klíčová slova:
numerical mathematics
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Programs and Algorithms of Numerical Mathematics 19 : Hejnice, June 24-29, 2018 : proceedings of seminar
These proceedings contain peer-reviewed papers that are based on the invited lectures, survey lectures, short communications, and posters presented at the 19th seminar Programs and Algorithms of ...
On the mechanisms of dimensional transition in stably stratified turbulent fluid layers
Caggio, M.; Bodnár, Tomáš; Schiavon, M.
2019 - anglický
The purpose of this short review communication is to present some recent results on the effects of stable density stratification on the three-dimensional turbulent dynamics of 'thin' fluid layers forced at intermediate scales. In particular, how the strati cation and the confinement affect the mechanism of kinetic and potential energy transfer between different scales. Results on two-dimensional vertically stratifed flows and possible applications for stably stratifed atmospheric boundary layer will be shortly discussed.
Klíčová slova:
stable density stratification; kinetic and potential energy transfer; atmospheric boundary layer
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
On the mechanisms of dimensional transition in stably stratified turbulent fluid layers
The purpose of this short review communication is to present some recent results on the effects of stable density stratification on the three-dimensional turbulent dynamics of 'thin' fluid layers ...
Multivariate smooth interpolation that employs polyharmonic functions
Segeth, Karel
2019 - anglický
We study the problém of construction of the smooth interpolation formula presented as the minimizer of suitable functionals subject to interpolation constraints. We present a procedure for determining the interpolation formula that in a natural way leads to a linear combination of polyharmonic splines complemented with lower order polynomials therms. In general, such formulae can be very useful e.g. in geographic information systems or computer aided geometric design. A simple computational example is presented.
Klíčová slova:
data interpolation; smooth interpolation; polyharmonic spline; radial basis function
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Multivariate smooth interpolation that employs polyharmonic functions
We study the problém of construction of the smooth interpolation formula presented as the minimizer of suitable functionals subject to interpolation constraints. We present a procedure for determining ...
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