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Wyświetlanie 1-15 z 18
Tytuł:
The reflection and transmission of waves at interface between two nonlocal orthotropic thermoelastic halfspaces
Autorzy:
Tung, D. X.
Powiązania:
https://bibliotekanauki.pl/articles/38695697.pdf
Data publikacji:
2022
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
inhomogeneous
attenuation
orthotropic
nonlocal thermoelastic
Opis:
The present article deals with the propagation of inhomogeneous waves in an orthotropic medium based on Eringen’s nonlocal thermoelasticity. For chosen directions of propagation and a real finite inhomogeneity parameter, a complex slowness vector is specified to define the propagation of inhomogeneous incident wave. Then the reflection, transmission of plane waves at a plane interface between two nonlocal orthotropic thermoelastic halfspaces are discussed. In this incidence, horizontal slowness determines the slowness vectors for all reflected, transmitted waves. For each reflected, transmitted wave, the corresponding slowness vector is resolved to define its phase direction, phase velocity and attenuation angle. Appropriate boundary conditions on this wave-field determine the amplitude ratios for reflected, transmitted waves relative to the incident wave. The numerical examples are provided to show the effect of the inhomogeneity of incident wave, nonlocal parameter on the propagation characteristic of the reflected, transmitted waves.
Źródło:
Archives of Mechanics; 2022, 74, 5; 373-389
0373-2029
Pojawia się w:
Archives of Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic propagation in inhomogeneous fluids: regularization via the introduction of fine particles
Autorzy:
Jordan, P. M.
Powiązania:
https://bibliotekanauki.pl/articles/38440473.pdf
Data publikacji:
2020
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
inhomogeneous fluids
Laplace transform
particle-laden flow
singular surface theory
Opis:
It is shown, using analytical methodologies, that the velocity field blow-up suffered by vertically ascending acoustic waves in an isothermal atmosphere can be eliminated via the introduction of fine particles. Assuming the inhomogeneous generalization of the particle-laden flow model known as the (linearized) Marble–Thompson model-1, it is established that bounded, exponentially decreasing, shock amplitudes can be obtained provided the mass fraction of particles exceeds a critical value, for which an exact expression is derived. Lastly, supporting numerical results are presented, special cases are discussed, and possible follow-on studies are noted.
Źródło:
Archives of Mechanics; 2020, 72, 1; 59-73
0373-2029
Pojawia się w:
Archives of Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic Scattering of Inhomogeneous Plane Wave by Ensemble of Cylinders
Autorzy:
Dinia, Lorenzo
Mangini, Fabio
Frezza, Fabrizio
Powiązania:
https://bibliotekanauki.pl/articles/309062.pdf
Data publikacji:
2020
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
electromagnetic scattering
inhomogeneous wave dispersion
lossy media
multi-cylinders scattering
vectorial cylindrical-harmonics
Opis:
The interaction between an ensemble of cylinders and an inhomogeneous plane wave is introduced and is determined, in the present paper, through a rigorous theoretical approach. Scattered electromagnetic field generated by an indefinite number of infinite circular cylinders is analyzed by the application of the generalized vector cylinder harmonics (VCH) expansion. The exact mathematical model relied upon to represent this scenario considers the so-called complex-angle formalism reaching a superposition of vectorial cylindrical-harmonics and Foldy-Lax Multiple scattering equations (FLMSE) to account for the multiscattering process between the cylinders. The method was validated by comparing the numerical results obtained with the use of the finite element method and a homemade Matlab code.
Źródło:
Journal of Telecommunications and Information Technology; 2020, 3; 86-92
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On three methods for bounding the rate of convergence for some continuous-time Markov chains
Autorzy:
Zeifman, Alexander
Satin, Yacov
Kryukova, Anastasia
Razumchik, Rostislav
Kiseleva, Ksenia
Shilova, Galina
Powiązania:
https://bibliotekanauki.pl/articles/329966.pdf
Data publikacji:
2020
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
inhomogeneous continuous time Markov chains
weak ergodicity
Lyapunov function
differential inequalities
forward Kolmogorov system
łańcuchy Markowa z czasem ciągłym
funkcja Lapunowa
nierówność różniczkowa
system Kołmogorowa
Opis:
Consideration is given to three different analytical methods for the computation of upper bounds for the rate of convergence to the limiting regime of one specific class of (in)homogeneous continuous-time Markov chains. This class is particularly well suited to describe evolutions of the total number of customers in (in)homogeneous M/M/S queueing systems with possibly state-dependent arrival and service intensities, batch arrivals and services. One of the methods is based on the logarithmic norm of a linear operator function; the other two rely on Lyapunov functions and differential inequalities, respectively. Less restrictive conditions (compared with those known from the literature) under which the methods are applicable are being formulated. Two numerical examples are given. It is also shown that, for homogeneous birth-death Markov processes defined on a finite state space with all transition rates being positive, all methods yield the same sharp upper bound.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2020, 30, 2; 251-266
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic Scattering by a Cylinder in a Lossy Medium of an Inhomogeneous Elliptically Polarized Plane Wave
Autorzy:
Mangini, Fabio
Dinia, Lorenzo
Frezza, Fabrizio
Powiązania:
https://bibliotekanauki.pl/articles/309521.pdf
Data publikacji:
2019
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
electromagnetic scattering
inhomogeneous wave dispersion
vectorial cylindrical-harmonics
Opis:
In this paper, a rigorous theoretical approach, adopted in order to generalize the Vectorial CylindricalHarmonics (VCH) expansion of an inhomogeneous elliptically polarized plane wave, is presented. An application of the VCH expansion to analyze electromagnetic field scattered by an infinite circular cylinder is presented. The results are obtained using the so-called complex-angle formalism reaching a superposition of Vectorial Cylindrical-Harmonics. To validate the method, a Matlab code was implemented. Also, the validity of the methodology was confirmed through some comparisons between the proposed method and the numerical results obtained based on the Finite Element Method (FEM) in the canonical scenario with a single cylinder.
Źródło:
Journal of Telecommunications and Information Technology; 2019, 4; 36-42
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bounds on the rate of convergence for one class of inhomogeneous Markovian queueing models with possible batch arrivals and services
Autorzy:
Zeifman, A.
Razumchik, R.
Satin, Y.
Kiseleva, K.
Korotysheva, A.
Korolev, V.
Powiązania:
https://bibliotekanauki.pl/articles/330534.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
inhomogeneous birth process
inhomogeneous death process
weak ergodicity
rate of convergence
sharp bounds
logarithmic norm
forward Kolmogorov system
proces narodzin
proces śmierci
stopień konwergencji
norma logarytmiczna
system Kołmogorowa
Opis:
In this paper we present a method for the computation of convergence bounds for four classes of multiserver queueing systems, described by inhomogeneous Markov chains. Specifically, we consider an inhomogeneous M/M/S queueing system with possible state-dependent arrival and service intensities, and additionally possible batch arrivals and batch service. A unified approach based on a logarithmic norm of linear operators for obtaining sharp upper and lower bounds on the rate of convergence and corresponding sharp perturbation bounds is described. As a side effect, we show, by virtue of numerical examples, that the approach based on a logarithmic norm can also be used to approximate limiting characteristics (the idle probability and the mean number of customers in the system) of the systems considered with a given approximation error.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2018, 28, 1; 141-154
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The complex phenomenological model for prediction of inhomogeneous deformations of railway ballast layer after tamping works
Autorzy:
Sysyn, M.
Gerber, U.
Kovalchuk, V.
Nabochenko, O.
Powiązania:
https://bibliotekanauki.pl/articles/224218.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
track geometry
phenomenological modeling
track unevenness
uniform subsidence
inhomogeneous subgrade
tamping works
geometria toru
modelowanie fenomenologiczne
nierówności
osiadanie jednolite
podłoże niejednorodne
Opis:
The given article considers the method of calculating the track geometry deformation with respect to uneven accumulation of residual deformations along the track. The technique proposes two significant changes in existing approaches to calculating the efficiency of the ballast layer. The transition from the approach of allowable stresses design in the ballast layer to the deformative approach of accumulations of track geometry deformations allows us to draw conclusions regarding the intervals of track tamping and the duration of ballast layer life cycle. The transition from the determinative to probabilistic approaches makes it possible to draw conclusions not only from the average unevenness, but also with regard to all possible facts of unevenness. The method is based on the mechanism of sudden and gradual deformations occurrence, which depends on a number of key factors: dynamic stresses on the ballast, non-uniformity of track elasticity, performance of current maintenance work. Based on the experimental studies results, the dependencies of sudden deformations and the intensity of gradual deformations on the level of stress on the ballast layer were established. The experimental results of the influence of the subballast base elasticity on the intensity of accumulation of residual deformations are shown. On the basis of the developed method, the prediction of track geometry deterioration for a given structure of the track, the rolling stock and the permissible level of geometric deviations for track maintenance is presented.
Źródło:
Archives of Transport; 2018, 47, 3; 91-107
0866-9546
2300-8830
Pojawia się w:
Archives of Transport
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamic projection operator method in the theory of hyperbolic systems of partial differential equations with variable coefficients
Autorzy:
Leble, S.
Vereshchagina, I.
Powiązania:
https://bibliotekanauki.pl/articles/1940707.pdf
Data publikacji:
2017
Wydawca:
Politechnika Gdańska
Tematy:
hyperbolic PDE
idempotents
inhomogeneous media
acoustics
Opis:
We consider a generalization of the projection operator method for the case of the Cauchy problem in 1D space for systems of evolution differential equations of first order with variable coefficients. It is supposed that the dependence of coefficients on the only variable χ is weak, that is described by the introduction of a small parameter. Such problem corresponds, for example, to the case of wave propagation in a weakly inhomogeneous medium. As an example, we specify the problem to adiabatic acoustics in waveguides with a variable cross-section. Projection operators are constructed for the Cauchy problem to fix unidirectional modes. The method of successive approximations (perturbation theory) is developed and based on the pseudodifferential operators theory. The application of projection operators adapted for the case under consideration allows deriving approximate evolution equations corresponding to the separated directed waves.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2017, 21, 2; 109-120
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of Darboux transformation to multidimensinal inhomogeneous problems
Autorzy:
Kwiatkowski, G.
Powiązania:
https://bibliotekanauki.pl/articles/1938593.pdf
Data publikacji:
2016
Wydawca:
Politechnika Gdańska
Tematy:
Darboux transform
Green function
interwine relation
ladder operator
inhomogeneous partial differential equation
Opis:
General properties of ladder operators applied to inhomogeneous problems are studied in the context of their usefulness for solving practical problems with stress put on the possibility of embedding the interwine relation onto a wider class of operators. From those general remarks an algorithm using the Darboux transform for construction of the Green function for linear partial differential equations is formed and a sample implementation thereof is shown along with some examples of solutions.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2016, 20, 2; 187-195
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mathematical modeling of random concentracion field and its second moments in semispace with Erlangian distributions of layerd inclusions
Autorzy:
Chernukha, O.
Bilushchak, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1938608.pdf
Data publikacji:
2016
Wydawca:
Politechnika Gdańska
Tematy:
diffusion process
randomly inhomogeneous stratified structure
Erlangian distribution
field dispersion
correlation function
Neumann series
averaging over the ensemble of phase configurations
Opis:
The processes of admixture diffusion in a two-phase stratified semispace with random disposition of syblayers are studied by the approach where internal random nonhomogeneities are considered as inner sources and the solution is found in the form of a Neumann series. The diffusion equations are formulated for one-connected regions of each phase and non-ideal contact conditions for the concentration on interphases are imposed. By the theory of generalized functions the contact problem is reduced to the equation of mass transfer in the whole body, which operator includes explicitly jump discontinuities of the concentration function and its derivatives. The obtained initial-boundary value problem of mass transfer is reduced to the equivalent integro-differentual equation. The solution is constructed in the form of a Neumann series and averaged over the ensemble of phase configurations with Erlangian and exponential distributions of inclusions. Dispersion and the two-point correlation function of the concentration field for diffusion are determined taking into account the probable distribution of inclusions, pair interaction of sublayers and the function of phase correlation. The dependence of the behavior of the averaged admixture concentration, field dispersion and the correlation function in the semispace with Erlangian and exponential distributions of inclusions on different medium characteristics is investigated and established.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2016, 20, 3; 295-334
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ergodicity and perturbation bounds for inhomogeneous birth and death processes with additional transitions from and to the origin
Autorzy:
Zeifman, A.
Korotysheva, A.
Satin, Y.
Korolev, V.
Shorgin, S.
Razumchik, R.
Powiązania:
https://bibliotekanauki.pl/articles/331214.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
inhomogeneous birth process
inhomogeneous death process
ergodicity bound
perturbation bound
Opis:
Service life of many real-life systems cannot be considered infinite, and thus the systems will be eventually stopped or will break down. Some of them may be re-launched after possible maintenance under likely new initial conditions. In such systems, which are often modelled by birth and death processes, the assumption of stationarity may be too strong and performance characteristics obtained under this assumption may not make much sense. In such circumstances, time-dependent analysis is more meaningful. In this paper, transient analysis of one class of Markov processes defined on non-negative integers, specifically, inhomogeneous birth and death processes allowing special transitions from and to the origin, is carried out. Whenever the process is at the origin, transition can occur to any state, not necessarily a neighbouring one. Being in any other state, besides ordinary transitions to neighbouring states, a transition to the origin can occur. All possible transition intensities are assumed to be non-random functions of time and may depend (except for transition to the origin) on the process state. To the best of our knowledge, first ergodicity and perturbation bounds for this class of processes are obtained. Extensive numerical results are also provided.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2015, 25, 4; 787-802
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelowanie tolerancyjne przewodzenia ciepła w materiałach periodycznie niejednorodnych
Tolerance modelling of heat conduction in periodically non-homogeneous materials
Autorzy:
Jurczak, T.
Powiązania:
https://bibliotekanauki.pl/articles/40730.pdf
Data publikacji:
2014
Wydawca:
Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Wydawnictwo Szkoły Głównej Gospodarstwa Wiejskiego w Warszawie
Tematy:
przewodnictwo cieplne
przeplyw ciepla
badania modelowe
modelowanie tolerancyjne
modele usrednione
przewodniki niejednorodne
thermal conductivity
heat flow
model research
tolerance modelling
average model
periodically inhomogeneous conductor
Opis:
Praca dotyczy modelowania przepływu ciepła w wybranych materiałach periodycznie niejednorodnych. Zastosowano technikę uśredniania tolerancyjnego do skonstruowania modelu uśrednionego przewodnictwa cieplnego dla materiałów periodycznie warstwowych. Otrzymano układ równań, który będzie prostszy do rozwiązania niż klasyczny układ równań Fouriera. Ponadto przedstawiono rozwiązania analityczne wybranych zagadnień początkowo-brzegowych oraz zweryfikowano je doświadczalnie
The paper concerns heat flow modeling in chosen periodically non-homogeneous materials. There will be applied the tolerance averaging technique to construct an averaged model of heat conduction for periodically multilayered materials. The set of equations in the constructed model will be simpler than the classical set of Fourier's equations. Apart of that, analytical solutions of chosen initial-boundary problems will be shown and experimentally verified.
Źródło:
Acta Scientiarum Polonorum. Architectura; 2014, 13, 2
1644-0633
Pojawia się w:
Acta Scientiarum Polonorum. Architectura
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Gaussian beam evolution in inhomogeneous nonlinear media with absorption
Autorzy:
Berczynski, P.
Powiązania:
https://bibliotekanauki.pl/articles/173434.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Gaussian beam diffraction and self-focusing
complex geometrical optics
inhomogeneous and nonlinear saturable fibres
Opis:
The method of complex geometrical optics (CGO) is presented, which describes Gaussian beam (GB) diffraction and self−fo− cusing in smoothly inhomogeneous and nonlinear Kerr type and saturable fibres. CGO reduces the problem of Gaussian beam evolution in inhomogeneous and nonlinear media to the system of the first order ordinary differential equations for the complex curvature of the wave front and for GB amplitude, which can be readily solved both analytically and numerically. As a result, CGO radically simplifies the description of Gaussian beam diffraction and self−focusing effects as compared to other methods of nonlinear optics such as variational method approach, method of moments and beam propagation method. The power of CGO method is presented on the example of Gaussian beam propagation in saturable fibres with either focu− sing and defocusing refractive profiles. Besides, the influence of initial curvature of the wave front, phenomenon of weak ab− sorption and effect of either transverse and longitudinal inhomogeneity on GB propagation in nonlinear fibres is discussed in this paper.
Źródło:
Optica Applicata; 2013, 43, 3; 583-595
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Surface waves in non-homogeneous, general magnetothermo, viscoelastic media of higher order
Autorzy:
Sethi, M.
Gupta, K. C.
Rani, M.
Powiązania:
https://bibliotekanauki.pl/articles/955273.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
fale powierzchniowe
lepkość
lepkosprężystość
inhomogeneous media
variable density
surface waves
viscosity
Opis:
The aim of the present paper is to investigate surface waves in a non-homogeneous, isotropic, visco-elastic solid medium of n-th order including the time rate of strain. The theory of generalised surface waves has firstly been developed and then it has been employed to investigate particular cases of waves, viz., Stoneley, Rayleigh and Love type. The wave velocity equations have been obtained for different cases and are in well agreement with the corresponding classical result, when the effects of viscosity, temperature, magnetism as well as nonhomogeneity of the material medium are ignored.
Źródło:
International Journal of Applied Mechanics and Engineering; 2013, 18, 4; 1221-1236
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Gaussian light beam propagation in inhomogeneous medium
Propagacja wiązki Gausowskiej w ośrodku niejednorodnym
Autorzy:
Pieszyński, K.
Powiązania:
https://bibliotekanauki.pl/articles/296458.pdf
Data publikacji:
2008
Wydawca:
Politechnika Łódzka. Wydawnictwo Politechniki Łódzkiej
Tematy:
wiązka gaussowska
propagacja
ośrodek niejednorodny
Gaussian light beam
propagation
inhomogeneous medium
Opis:
In this work the results of numerical calculations describing propagation of Gaussian light beam in inhomogeneous media is presented. Numerical calculation was based on scalar wave approximation. Additionally the split-step beam propagation method was exploited.
Praca przedstawia wyniki obliczeń numerycznych rozkładu natężenia wiązki lasera He-Ne w trakcie propagacji przez trzy niejednorodne ośrodki różniące się charakterem tejże niejednorodności. Do obliczeń wykorzystano przybliżenie pola skalarnego i rekurencyjnie liczono kolejne profile intensywności wiązki światła.
Źródło:
Scientific Bulletin. Physics / Technical University of Łódź; 2008, 29; 65-74
1505-1013
2449-982X
Pojawia się w:
Scientific Bulletin. Physics / Technical University of Łódź
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 18

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