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1دورية أكاديمية
المؤلفون: Milantiev V.P.
المصدر: IEEE International Conference on Plasma Science
مصطلحات موضوعية: Acceleration, Cyclotron resonance, Electric fields, Electromagnetic wave polarization, Electromagnetic wave propagation, Light velocity, Magnetic fields, Vacuum, Velocity, Autoresonant electron motion, Phase velocity, Vacuum wave, Electromagnetic waves
الوصف: The possibility of autoresonance in a slow electromagnetic wave propagating along the straight lines of the external magnetic field is discussed. It turns out that the autoresonant regime of the motion in such a wave is possible if some rather restrictive relations between the electric drift velocity and the phase velocity of the wave take place. It also depends on the polarization of the wave. The general case of the elliptical polarization is considered. The optical regime corresponds to the wave with linear polarization in the direction of the constant electric field. For this case our calculations show that energy of the particle can unlimitedly increase or decrease. The rate of acceleration can be even larger than in the case of 'vacuum wave'. Radiative forces will restrict this process.
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2دورية 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.
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3دورية أكاديمية
المؤلفون: Milantiev V.P.
المصدر: Radiophysics and Quantum Electronics
مصطلحات موضوعية: Electromagnetic wave propagation, Electromagnetic waves, Electrostatics, Friction, Magnetic fields, Homogeneous magnetic field, Transverse electromagnetic waves, Wave particles, Charged particles
الوصف: We consider the autoresonant motion of a charged particle in the field of a transverse electromagnetic wave propagating with the speed of light along a stationary homogeneous magnetic field with allowance for radiative friction. It is shown that the loss of wave-particle synchronism due to radiative friction can be suppressed by an external electrostatic field that is parallel to the magnetic field. © 1997 Plenum Publishing Corporation.
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4دورية 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.
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5دورية أكاديمية
المؤلفون: Nikolaev N.E., Shevchenko V.V.
المصدر: Mathematical Methods in Electromagnetic Theory, MMET, Conference Proceedings
مصطلحات موضوعية: Algorithms, Electromagnetic wave propagation, Inverse problems, Least squares approximations, Mathematical models, Permittivity, Exponential power function, Permittivity profile synthesis, Planar buried waveguides, Propagation constants, Waveguides
الوصف: The method of finding the permittivity profile of graded-index single-mode planar waveguide after the given mode parameters is described. To solve this inverse problem, the same universal mathematical model of profile is proposed. Multiply repeated numerical solution of direct problem by special algorithm using the least-square method enables to select the function parameters for a certain set of mode parameters. Based on this procedure, the profile function in question is synthesized.
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6دورية 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://openrepository.ru/article?id=254688Test
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7دورية أكاديمية
المؤلفون: Shananin N.A.
المصدر: Mathematical Notes
مصطلحات موضوعية: Continuation of solutions, Distribution solution, Quasianalytic class, Wave propagation, Weakly nonlinear equation, Weighted homogeneity
الوصف: We obtain conditions sufficient for the set of distribution solutions of a weakly nonlinear differential equation with weights assigned to derivatives to be a quasianalytic class with respect to part of the variables. The class of equations considered in the paper contains a number of equations describing the propagation of nonlinear waves. © 2000 Kluwer Academic/Plenum Publishers.
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8مؤتمر
المؤلفون: Sulimov A., Karpov A.
المصدر: SCOPUS-2019-SID85072403396
مصطلحات موضوعية: Channel frequency response, Diffraction, Meteor burst communications, Meteor radio reflection, Nonreciprocal radio wave propagation
الوصف: © 2019 IEEE. The paper describes a method for simulation of frequency-selectivity of meteor scatter channel that takes into account its nonstationarity, nonreciprocity, and stochastic nature. The amplitude-frequency and phase-frequency responses of the channel obtained by averaging large number of single meteor radio reflections modeled for the typical meteor radio link of Moscow-Kazan of 720-km length are presented. A problem of nonsimultaneous detection of radio signals with large frequency diversity is discussed.
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9مؤتمر
المؤلفون: Dementyev V., Nasyrov I., Kogogin D., Shindin A., Grach S.
المصدر: SCOPUS-2019-SID85072392469
مصطلحات موضوعية: Artificial optical airglow of the ionosphere, Ionospheric plasma, Radio wave propagation, Ray tracing of decameter radio waves, Statistical analysis
الوصف: © 2019 IEEE. The paper presents statistical analysis results of experimental data obtained via heating experiments in recording artificial ionospheric airglow exposed to powerful short-wave radiation using the Sura facility. The data used in the analysis include the intensity values of optical airglow in the red oxygen line, the difference between the critical frequency of ionosphere and the pump wave frequency, the thickness of plasma resonance regions of ionosphere and the height of reflection of wave trajectories calculated via mathematical modeling. The key result is the detected correlation between the optical airglow magnitude and the difference between the critical frequency of ionosphere and the pump wave frequency. The statistical analysis shows that the interaction of short-wave electromagnetic radiation with the ionosphere is most effective when the difference between the critical frequency of ionosphere and the pump wave frequency ranges from 0 to 1 MHz.
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10مؤتمر
المؤلفون: Karpov A., Sulimov A., Sherstyukov O.
المصدر: SCOPUS-2019-SID85072385406
مصطلحات موضوعية: Encryption key, Meteor burst communications, Meteor radio reflection, Nonreciprocal radio wave propagation, Radar, Synchronization, Time scale
الوصف: © 2019 IEEE. The paper briefly outlines main key points in history of radio meteor research at the Kazan Federal University starting from the first radar observations of meteor radio reflections to development of unique radio systems for high-precision (nanosecond) distant synchronization of time scales. Recent achievements in designing of promising meteor systems for creation and secure distribution of secret encryption keys are considered. Main scientific and applied problems in studying nonreciprocal properties of radio wave propagation in meteor burst communications are discussed.
