-
1دورية أكاديمية
المؤلفون: Dombrovskaya Zh.O., Belov A.A., Govorukhin V.A.
المصدر: Journal of Physics: Conference Series
مصطلحات موضوعية: Electromagnetic wave propagation, Maxwell equations, Mesh generation, Adaptive meshes, Dielectric interface, Dielectric structure, Error values, Finite-difference solution, High refractive index, Maxwell's curl equations, Uniform mesh, Refractive index
الوصف: We consider spatial step selection for finite-difference solution of Maxwell's curl equations in presence of dielectric interfaces. If the contrast of the refractive indices is high, the wave number in optically thick medium decreases greatly and the fields oscillate fast. To improve accuracy, we propose a special quasi-uniform mesh which provides fine enough meshes in the vicinity of the interface and does not impose abundant computations in optically thin medium. The fundamental advantage of quasi-unform meshes in finite-difference is the possibility to obtain the solution simultaneously with its error value. We describe the corresponding procedure. © 2020 IOP Publishing Ltd.
العلاقة: https://doi.org/10.1088/1742-6596/1461/1/012031Test; https://repository.rudn.ru/records/article/record/64824Test/
-
2دورية أكاديمية
المؤلفون: Babourova O.V., Frolov B.N., Khetzeva M.S., Markova N.V.
المصدر: Journal of Physics: Conference Series
مصطلحات موضوعية: Electromagnetic waves, Relativity, Set theory, Topology, Wave propagation, Anti-symmetric, Arbitrary functions, Lie derivative, Lorentz transformations, Metric spaces, Minkowski space, Plane electromagnetic waves, Tangent space, Elastic waves
الوصف: Using the analogy with the properties of plane electromagnetic waves in Minkowski space, a definition of an affine-metric space of the plane wave type is given, which is characterized by the null action of the Lie derivative on the 40 components of the nonmetricity 1-form in the 4-dimensional affine-metric space. This leads to the conclusion that the nonmetricity of a plane wave type is determined by five arbitrary functions of delayed time. A theorem on the structure of the nonmetricity of the plane wave type is proved, which states that parts of the nonmetricity 1-form irreducible with respect to the Lorentz transformations of the tangent space, such as the Weyl 1-form, the trace 1-form, and the symmetric 1-form, are defined by one arbitrary function each, and the antisymmetric 1-form is defined by two arbitrary functions. Presence of arbitrary functions in the description of nonmetricity plane waves allows transmitting information with the help of nonmetricity waves. © Published under licence by IOP Publishing Ltd.
العلاقة: https://doi.org/10.1088/1742-6596/1557/1/012012Test; https://repository.rudn.ru/records/article/record/64639Test/
-
3دورية أكاديمية
المؤلفون: Popova I., Leonteva L., Danilov I.
المصدر: IOP Conference Series: Materials Science and Engineering
مصطلحات موضوعية: Acoustic noise, Acoustic wave propagation, Asbestos, Felt, Felts, Mineral wool, Noise abatement, Railroads, Sound insulating materials, Wool, Yarn, Cladding steel, Glass wool, Noise reducing, Railway transport, Russian federation, Sound absorbing materials, Sound absorption, Track machines, Acoustic wave absorption
الوصف: The article discusses the types and features of the operation of transport technological machines of the railways of the Russian Federation on the example of the most frequently used track machines, and presents methods for noise reducing on the railways of the Russian Federation. The most effective method to reduce the noise arising during the operation of track machines is identified - this is the installation of a steel soundproofing hood (casing) over the electric motor. The calculation of the effectiveness of sound-absorbing materials used for cladding steel bonnet is given. According to the results of the calculation, the material «asbestos felt» turned out to be the most effective, but the other materials under consideration, and in particular, «glass wool», «mineral wool» and «construction felt», turned out to be also applicable to the lining of the steel bonnet, since the calculations revealed the applicable level of sound absorption, which is less than a decibel in terms of noise reduction to the material «asbestos felt». © Published under licence by IOP Publishing Ltd.
العلاقة: https://doi.org/10.1088/1757-899X/675/1/012045Test; https://repository.rudn.ru/records/article/record/54889Test/
-
4دورية أكاديمية
المؤلفون: Bessonov N., Bocharov G., Touaoula T.M., Trofimchuk S., Volpert V.
المصدر: Discrete and Continuous Dynamical Systems - Series B
مصطلحات موضوعية: Delay reaction-diffusion equation, Nonlinear dynamics, Wave propagation
الوصف: Nonlinear dynamics of a reaction-diffusion equation with delay is studied with numerical simulations in 1D and 2D cases. Homogeneous in space solutions can manifest time oscillations with period doubling bifurcations and transition to chaos. Transition between two regions with homogeneous oscillations is provided by quasi-waves, propagating solutions without regular structure and often with complex aperiodic oscillations. Dynamics of space dependent solutions is described by a combination of various waves, e.g., bistable, monostable, periodic and quasi-waves. © 2019 American Institute of Mathematical Sciences. All Rights Reserved.
العلاقة: https://doi.org/10.3934/dcdsb.2019085Test; https://repository.rudn.ru/records/article/record/38664Test/
-
5دورية أكاديمية
المؤلفون: Nikolaev N.E., Pavlov S.V., Chekhlova T.K.
المصدر: Journal of Communications Technology and Electronics
مصطلحات موضوعية: Electromagnetic wave propagation, Electromagnetic waves, Optical waveguides, Refractive index, Sol-gel process, Temperature distribution, Effective refractive index, Mathematical descriptions, Propagation of electromagnetic waves, Sol-gel materials, Temperature coefficient, Temperature dependence, Varying temperature, Waveguide parameter, Sol-gels
الوصف: Features of the temperature dependence of effective refractive index neff (ERI) of optical waveguides based on sol-gel materials have been studied and behavior of the ERI temperature coefficient (TC) have been determined. It has been found experimentally and theoretically that, with properly selected film parameters, the ERI TC can have a negative, zero, or even small positive value within a certain temperature range. Clear mathematical description of the dependence of the ERI TC on the waveguide parameters and the partial power of the wave in the waveguide has been given. © 2018, Pleiades Publishing, Inc.
العلاقة: https://doi.org/10.1134/S1064226918110074Test; https://repository.rudn.ru/records/article/record/36243Test/
-
6دورية أكاديمية
المؤلفون: Moiseev V.S., Kotovskaya Y.V., Kobalava Z.D.
المصدر: Kardiologiia
مصطلحات موضوعية: central arterial pressure, pulse wave analysis, applanation tonometry, pulse wave propagation velocity
الوصف: Most of large controlled randomized trials have not revealed superiority of "new" over "old" anti hypertensive drugs and posed a question of value of surrogate criteria for comparison of various treatment regimes. Data of ASCOT-CAFE trials allow to assume that estimation of central blood pressure (BP) opens novel perspectives in this direction. Most affordable methods of noninvasive measurement of central BP are radial artery applanation tonometry with subsequent computer transformation of peripheral to central pulse wave, and carotid artery applanation tonometry. Contrary to peripheral BP central BP level is modulated by elastic properties of major arteries and structural-functional state of medium caliber arteries and microcirculatory vascular bed, and thus is an index indirectly reflecting the state of the whole cardiovascular bed. Differences between central and peripheral BP levels are most clearly expressed in young age and diminish in the elderly. Effects of anti hypertensive drugs on central BP may vary at the account of difference of points of application of their effects in vascular bed. Prognostic and clinical value of the central BP requires further investigation.
-
7دورية أكاديمية
المؤلفون: Metin A.D., Pelinovsky E., Yalciner A.C., Zaytsev A., Tarakcioglu G.O., Yalciner B., Kurkin A.
المصدر: 13th International MEDCOAST Congress on Coastal and Marine Sciences, Engineering, Management and Conservation, MEDCOAST 2017
مصطلحات موضوعية: Equations of motion, Nonlinear equations, Sea level, Water levels, Wave propagation, Coastal morphology, High pressure zones, Long-period waves, Low atmospheric pressures, Non-linear shallow water equations, Small amplitude, Spatial and temporal changes, Static water level, Atmospheric pressure
الوصف: The cause of the occurrence of ebb or abnormal waves which are occasionally observed on the coasts is related to the spatial and temporal changes of atmospheric pressure. Because, low atmospheric pressure leads to static water level rise in a part of the marine area and high atmospheric pressure leads to static water level drop in another zone, water level throughout the entire marine area is deformed. This deformation moves as wave, sometimes amplifies on the shore. Due to the changes of atmospheric pressure, the respective small amplitude long waves propagate along the entire marine area. This type of waves can propagate through long distances and can also be amplified due to resonant effects in the enclosed basins and nearshore/offshore coastal morphology. The investigation of the amplification of the long-period waves which occurred by the spatial and temporal changes of atmospheric pressure is the one of the objectives of this study. For the different types of regular shaped basins, tests are conducted by numerical modeling solving nonlinear shallow water equations. In the tests, basins with flat, triangular, shelf, upward and downward sloping sections are simulated by using high pressure zone propagating with certain velocity (faster, equal or slower than wave velocity). The change in the sea level is calculated and compared with the theoretical outcomes.
-
8دورية أكاديمية
المؤلفون: Uvarova L.A., Galakhov E.I., Salieva O.A.
المصدر: International Journal of Fluid Mechanics Research
مصطلحات موضوعية: Chemical modification, Computational mechanics, Gravity waves, Korteweg-de Vries equation, Nonlinear analysis, Nonlinear equations, Stochastic systems, Wave propagation, Wavefronts, KdV equations, Molecular mechanism, Phase surface, Physicochemical process, Evaporation
الوصف: In this paper we consider the impact of evaporation on formation of a gravitational wave in a potential approximation and study the condition of its existence in the form of a soliton. We study a nonlinear modified KdV equation, which takes into account the impact of a molecular mechanism (evaporation) at the dividing boundary "wave front - environment" on wave propagation. A nonlinear analysis is given. It is shown that, in general, modification of the KdV equation by introducing an additional stochastic term determined by a certain physical or physico-chemical process gives rise to solutions that are not Jacobi functions. © 2016 Begell House, Inc.
العلاقة: https://doi.org/10.1615/InterJFluidMechRes.v43.i5-6.20Test; https://repository.rudn.ru/records/article/record/4144Test/
-
9دورية أكاديمية
المؤلفون: Bessonov N., Bocharov G., Volpert V.
المصدر: Mathematics
مصطلحات موضوعية: Genotype, Infection progression, Nonlocal interaction, Virus density distribution, Wave propagation
الوصف: The paper is devoted to a nonlocal reaction-diffusion equation describing the development of viral infection in tissue, taking into account virus distribution in the space of genotypes, the antiviral immune response, and natural genotype-dependent virus death. It is shown that infection propagates as a reaction-diffusion wave. In some particular cases, the 2D problem can be reduced to a 1D problem by separation of variables, allowing for proof of wave existence and stability. In general, this reduction provides an approximation of the 2D problem by a 1D problem. The analysis of the reduced problem allows us to determine how viral load and virulence depend on genotype distribution, the strength of the immune response, and the level of immunity. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
العلاقة: https://doi.org/10.3390/math10010096Test; https://repository.rudn.ru/records/article/record/84320Test/
-
10دورية أكاديمية
المؤلفون: Divakov D.V., Tyutyunnik A.A.
المصدر: Programming and computer software
مصطلحات موضوعية: Eigenvalues and eigenfunctions, Guided electromagnetic wave propagation, Numerical methods, Waveguides, Computer algebra systems, Functional equation, Guided modes, Homogeneous system, Irregular waveguides, Numerical computations, Spectral characteristics, Spectral problem, Symbolic methods, Systems of algebraic equations, Functional analysis
الوصف: This paper considers a homogeneous system of functional equations that occurs when solving a spectral problem the eigenfunctions of which describe guided modes of smoothly irregular waveguides. The resulting system of functional equations is a homogeneous system of algebraic equations for any fixed argument. A symbolic method for solving systems of functional equations of this type is proposed. The method is implemented in the Maple computer algebra system. Results of numerical computations are presented to demonstrate the effectiveness of the developed symbolic-numerical method in comparison with the approach based on only numerical techniques. © 2022, Pleiades Publishing, Ltd.
العلاقة: https://doi.org/10.1134/S0361768822020049Test; https://repository.rudn.ru/records/article/record/83699Test/
