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Showing papers on "Wave propagation published in 1976"


Journal ArticleDOI
TL;DR: In this paper, a reference record was created on 2005-11-18, modified on 2016-08-08 and used for the purpose of ondes ; chocs ; onde de : choc reference record.
Abstract: Keywords: ondes ; chocs ; onde de : choc Reference Record created on 2005-11-18, modified on 2016-08-08

4,774 citations


Journal ArticleDOI
TL;DR: In this article, a time-dependent three-space-dimensional laser beam propagation is described, where the authors use a discrete Fourier transform (DFT) method for diffraction problems.
Abstract: The computation of time-dependent three-space-dimensional laser beam propagation is described. The methods are applicable to the propagation of high energy laser beams through the atmosphere in the presence of a horizontal wind and turbulence for most situations of interest. Possible cases are propagation of cw beams through stagnation zones, multi-pulse propagation, including the self-consistent treatment of pulse self-blooming, and propagation involving transonic slewing. The solution of the Maxwell wave equation in Fresnel approximation is obtained by means of a discrete Fourier transform method, which, surprisingly, gives excellent results for diffraction problems. The latter provide a stringent test for the accuracy of any solution method. Considerable use is also made of discrete Fourier transform methods in solving the hydrodynamic equations. The treatment of turbulence is based on the generation of random phase screens at each calculation step along the propagation path. In a time-dependent calculation the random phase screens can be either made to move with the wind at a given propagation position or generated anew for each successive time.

1,105 citations


Journal ArticleDOI
TL;DR: In this paper, the origin of persistent wave propagation through medium of reactwn-diffusion type 1s is explored based on a generalized time-dependent Ginzburg-Landau equation for a complex field W, namely, the equation derived previously in connection with the instability problems in nonlinear chemical kinetics.
Abstract: The origin of persistent wave propagation through medium of reactwn-diffusion type 1s explored. Our theory is based on a generalized time-dependent Ginzburg-Landau equation for a complex field W, namely, the equation derived previously in connection with the instability problems in nonlinear chemical kinetics. For slow variation of lV in space and tune the above equation is further reduced to a Navier-Stokes-like one for the phase gradient of TV. Under a certain condition, the "viscosity" coefficient becomes negative, and at the :-;arne time the temporally ordered state of uniform concentrations becomes unstable. In :-;uch a situation we find a particular solution corresponding to a propagating concentratiOn wave with a wave-source or sink

914 citations


Journal ArticleDOI
29 Jan 1976
TL;DR: In this article, a technique to resolve the incident and reflected waves from the records of composite waves is presented, which is applicable to both regular and irregular trains of waves and is effective in the range outside the condition of the gauge spacing being even integer of half wavelength.
Abstract: A technique to resolve the incident and reflected waves from the records of composite waves is presented. It is applicable to both regular and irregular trains of waves. Two simultaneous wave records are taken at adjacent locations, and all the amplitudes of Fourier components are analyzed by the FFT technique. The amplitudes of incident and reflected wave components are estimated from the Fourier components, and the incident and reflected wave spectra are constructed by smoothing the estimated periodograms. The wave resolution is effective in the range outside the condition of the gauge spacing being even integer of half wavelength. The ratio of incident and reflected wave energies in the effective resolution range is employed in estimating the overall reflection coefficient. The incident and reflected wave heights are estimated from the composite wave heights by energy consideration.

731 citations


Journal ArticleDOI
TL;DR: In this article, a system of equations for propagation of waves in water of variable depth was derived by means of the incompressibility condition, the energy equation, the invariance requirements under superposed rigid-body motions, together with a single approximation for the (three-dimensional) velocity field.
Abstract: Within the scope of the three-dimensional theory of homogeneous incompressible inviscid fluids, this paper contains a derivation of a system of equations for propagation of waves in water of variable depth. The derivation is effected by means of the incompressibility condition, the energy equation, the invariance requirements under superposed rigid-body motions, together with a single approximation for the (three-dimensional) velocity field.

615 citations


01 Jun 1976
TL;DR: In this article, a system of equations for propagation of waves in water of variable depth was derived by means of the incompressibility condition, the energy equation, the invariance requirements under superposed rigid-body motions, together with a single approximation for the (three-dimensional) velocity field.
Abstract: Within the scope of the three-dimensional theory of homogeneous incompressible inviscid fluids, this paper contains a derivation of a system of equations for propagation of waves in water of variable depth. The derivation is effected by means of the incompressibility condition, the energy equation, the invariance requirements under superposed rigid-body motions, together with a single approximation for the (three-dimensional) velocity field.

525 citations


Journal ArticleDOI
TL;DR: In this paper, the stability of circularly polarized waves of finite amplitude propagating parallel to the magnetic field is studied. And the authors show that finite amplitude always promotes stability, while amplitude dependent stability conditions for long waves, previously obtained by the author, are confirmed.
Abstract: The stability of circularly polarized waves of finite amplitude propagating parallel to the magnetic field is studied. A set of equations for slowly varying waves of arbitrary amplitude is obtained. A discussion of the stability of the waces is based on this set of equations. Earlier results are confirmed; in addition we find that finite amplitude always promotes stability. An amplitude dependent stability condition for long waves, previously obtained by the author, is confirmed.

517 citations


Journal ArticleDOI
01 Dec 1976
TL;DR: The theory and recent applications of wave propagation in periodic structures are reviewed in this paper, and speculations about future problems and development in the field of waves in periodic structure are given.
Abstract: The theory and recent applications of waves in periodic structures are reviewed. Both the Floquet and coupled waves approach are analyzed in some detail. The theoretical part of the paper includes wave propagation in unbounded and bounded active or passive periodic media, wave scatterring from periodic boundaries, source radiation (dipole, Cerenkov, transition, and Smith-Purcell) in-periodic media, and pulse transmission through a periodic slab. The applications part covers the recent development in a variety of fields: distributed feedback oscillators, filters, mode convertors, couplers, second-harmonic generators, deflectors, modulators and transducers in the fields of integrated optics and integrated surface acoustics. We also review the work on insect compound eyes, mehanical structures ocean waves, pulse compressions, temperature waves, and cholestric liquid crystals. Particles interaction with crystals is briefly reviewed, especially in the case of zeolite crystals and supelattices. Recent advances in fabrication techniques for very fine gratings me also covered. Finally, speculations about future problems and development in the field of waves in periodic structures are given.

468 citations


Journal ArticleDOI
TL;DR: In this article, the basic nonlinear equation which describes the Alfven waves, with small but finite amplitude propagating along the magnetic field in cold plasmas, is derived modifying the reductive perturbation method proposed by Taniuti and Wei.
Abstract: The basic nonlinear equation which describes the Alfven waves, with small but finite amplitude propagating along the magnetic field in cold plasmas, is derived modifying the reductive perturbation method proposed by Taniuti and Wei. Then as a result, the nonlinear dispersion relation is obtained through a procedure which clarifies the physical meaning. Furthermore, the modified nonlinear Schrodinger equation which describes the modulated Alfven wave more correctly than the previous works is proposed. An example of the nonlinear phenomena is shown by the numerical calculations of the initial value problem, using our basic equation for the Alfven waves.

393 citations


Journal ArticleDOI
TL;DR: In this article, nonlinear wave propagation in inhomogeneous media is studied analytically in the model of the nonlinear Schrodinger equation and exact solutions in the form of multisolitons, accelerated in the nonuniform medium are obtained.
Abstract: Nonlinear wave propagation in inhomogeneous media is studied analytically in the model of the nonlinear Schrodinger equation Exact solutions in the form of multisolitons, accelerated in the nonuniform medium, are obtained (AIP)

382 citations



Journal ArticleDOI
TL;DR: In this article, a nonlinear, charged elementary excitation was predicted to occur for weakly pinned Fr''ohlich charge density wave condensates at low temperatures, and new, nonlinear elementary excitations were obtained for the weakly-pinned Fr ''ohlich condenser.
Abstract: New, nonlinear, charged elementary excitations are predicted to occur for weakly pinned Fr\"ohlich charge-density-wave condensates at low temperatures.

Journal ArticleDOI
TL;DR: In this article, the propagation of quasi-longitudinal waves along a slender magnetic tube in pressure equilibrium with the ambient medium is considered, and the velocity of such waves is expressed in terms of the Alven speed and the sound speed inside the tube.
Abstract: Motivated by the filamentary structure of solar magnetic fields, this paper considers the propagation of quasi-longitudinal waves along a slender magnetic tube in pressure equilibrium with the ambient medium. The velocity of such waves is expressed in terms of the Alven speed and the sound speed inside the tube. The divergence of a vertical magnetic tube in a stratified atmosphere introduces a critical frequency below which propagation is impossible.

Journal ArticleDOI
TL;DR: The Lagrangian and Hamiltonian for nonlinear gravity waves in a cylindrical basin are constructed in terms of the generalized co-ordinates of the free-surface displacement, {qn(t)} ≡ q, thereby reducing the continuum-mechanics problem to one in classical mechanics as discussed by the authors.
Abstract: The Lagrangian and Hamiltonian for nonlinear gravity waves in a cylindrical basin are constructed in terms of the generalized co-ordinates of the free-surface displacement, {qn(t)} ≡ q, thereby reducing the continuum-mechanics problem to one in classical mechanics. This requires a preliminary description, in terms of q, of the fluid motion beneath the free surface, which kinematical boundary-value problem is solved through a variational formulation and the truncation and inversion of an infinite matrix. The results are applied to weakly coupled oscillations, using the time-averaged Lagrangian, and to resonantly coupled oscillations, using Poincare's action—angle formulation. The general formulation provides for excitation through either horizontal or vertical translation of the basin and for dissipation. Detailed results are given for free and forced oscillations of two, resonantly coupled degrees of freedom.

Journal ArticleDOI
Akira Hasegawa1, Kunioki Mima1
TL;DR: In this article, an exact solitary Alfv\'en wave was found using kinetic theory, which has a long structure in the direction of an ambient magnetic field and a short structure with a size comparable to an ion gyroradius in the perpendicular direction.
Abstract: An exact solitary Alfv\'en wave is found using kinetic theory. The wave has a long structure in the direction of an ambient magnetic field and a short structure with a size comparable to an ion gyroradius in the perpendicular direction. It propagates in a direction oblique to the ambient magnetic field.


Journal ArticleDOI
TL;DR: Friedlander as discussed by the authors studied the theoretical theory of wave propagation in curved space-time, both for treatment of classical radiation and as a basis for the more recent developments in the subject of quantum fields on a manifold.
Abstract: F G Friedlander London: Cambridge University Press 1976 pp ix + 282 price £15 The continuing interest in general relativity has created the need for a book on the rigorous mathematical theory of wave propagation in curved space–time, both for treatment of classical radiation and as a basis for the more recent developments in the subject of quantum fields on a manifold. This book meets that demand by treating in the language of modern differential geometry and the theory of distributions some of the pioneering work on wave propagation due to Hadamard and Riesz.

Journal ArticleDOI
01 Jan 1976
TL;DR: In this paper, global existence, uniqueness and regularity of solutions and continuous dependence of solutions on varied initial data are established for the initial value problem for the coupled system of equations.
Abstract: Global existence, uniqueness and regularity of solutions and continuous dependence of solutions on varied initial data are established for the initial-value problem for the coupled system of equationsThis system has the same formal justification as a model for the two-way propagation of (one-dimensional) long waves of small but finite amplitude in an open channel of water of constant depth as other versions of the Boussinesq equations. A feature of the analysis is that bounds on the wave amplitude η are obtained which are valid for all time.

Journal ArticleDOI
TL;DR: In this paper, a large collisionless quiescent plasma source is developed for investigating the phase and amplitude distribution of antenna-launched whistler waves in a specified parameter regime relating wave frequency to electron cyclotron frequency.
Abstract: A large collisionless quiescent plasma source is developed for investigating the phase and amplitude distribution of antenna-launched whistler waves in a specified parameter regime relating wave frequency to electron cyclotron frequency. Wave dispersion is studied both by interferometer techniques with monochromatic waves and by propagation of short phase-coherent wave bursts. The wave damping mechanism is examined by propagating perfectly ducted whistler waves. The dispersion of single frequency waves and wave packets is demonstrated. Trough ducting for wave frequency to electron cyclotron frequency ratio greater than 1/2 is verified, and new eigenmodes in nonuniform plasmas at ratio values less than 1/2 are observed. It is shown that geometric effects due to ray divergence and wave refraction dominate over collisional damping.

Journal ArticleDOI
TL;DR: The most prevalent microscale fluctuations appeared to be large-amplitude Alfven waves with small but non-zero fluctuations in the magnetic field intensity as mentioned in this paper, and these waves are present about 40% of the time and are predominantly propagating away from the sun.
Abstract: Analysis of IMP 1 (Explorer 43) plasma and magnetic field fluctuations on a scale of one hour revealed that linearly and circularly polarized Alfven waves are rarely present in the solar wind at 1 AU. The most prevalent microscale fluctuations appeared to be large-amplitude Alfven waves with small but non-zero fluctuations in the magnetic field intensity. These waves are present about 40% of the time and are predominantly propagating away from the sun.

Journal ArticleDOI
TL;DR: In this article, the principal part of a high-frequency pulse, the part governed by frequencies closest to the pulse carrier frequency, is studied, and the most significant theoretical results on one-dimensional pulse propagation, using all three approaches are described.
Abstract: The propagation of pulsed wave fields in a homogeneous medium or in a homogeneous line with known dispersion law and damping can be regarded from the ray, wave, and energy points of view. The review describes the most significant theoretical results on one-dimensional pulse propagation, using all three approaches. Greatest attention is paid to the principal part of a high-frequency pulse, the part governed by frequencies closest to the pulse carrier frequency. Paradoxes pertaining to superluminal and negative "group velocities" are resolved, and questions connected with amplification or attenuation of waves in wave beams and active media are discussed.

Journal ArticleDOI
TL;DR: In this paper, the propagation of magnetic flux pulses along the insulating barrier of a long Josephson junction is investigated both theoretically and experimentally, and the theoretical study includes applications of both (i) the recently developed "inverse−scattering−transform method" (ISTM) to the corresponding sine−Gordon equation in characteristic (light cone) coordinates and (ii) Whitham's method (WM) of averaged Lagrangian analysis to the sine • Gordon equation in laboratory coordinates.
Abstract: The propagation of magnetic flux pulses along the insulating barrier of a long Josephson junction is investigated both theoretically and experimentally. The theoretical study includes applications of both (i) the recently developed ’’inverse‐scattering‐transform method’’ (ISTM) to the corresponding sine‐Gordon equation in characteristic (light cone) coordinates and (ii) Whitham’s method (WM) of averaged Lagrangian analysis to the sine‐Gordon equation in laboratory coordinates. As the number of solitons (flux quanta) in the pulse becomes large, the ISTM becomes numerically unwieldy while WM becomes more accurate; thus these two analytical tools are complementary. WM has the advantage of being readily modified to account for small dissipative effects. Our experimental observations of magnetic‐flux propagation were entirely restricted to the ’’large‐amplitude limit’’ in which the average of the ac Josephson current is effectively zero. In this limit, WM indicates pulse propagation with linear dissipation. Th...

Journal ArticleDOI
TL;DR: In this paper, a periodic structure formed by selectively etching the surface of an epitaxial yttrium iron garnet (YIG) film is reported, and insertion loss data obtained in the 2-4 GHz range from a structure comprising 20 grooves each 1 μm deep and 30 μm wide, and each separated by 120 μm, formed in a 9-μm-thick YIG film are in good agreement with theory based on repetitively mismatched transmission lines.
Abstract: Magnetostatic wave propagation at microwave frequencies through a periodic structure formed by selectively etching the surface of an epitaxial yttrium iron garnet (YIG) film is reported. Experimental insertion loss data obtained in the 2–4‐GHz range from a structure comprising 20 grooves each 1 μm deep and 30 μm wide, and each separated by 120 μm, formed in a 9‐μm‐thick YIG film are in good agreement with theory based on repetitively mismatched transmission lines.

Journal ArticleDOI
TL;DR: The basic equations relating the five independent second-order elastic stiffness constants (fourth-rank tensor) to the ultrasonic wave speeds in a hexagonal medium are derived, with special emphasis on determining the microtextural symmetry of human cortical bone.

Journal ArticleDOI
TL;DR: In this article, self-similar solutions are presented for the equatorial propagation of axisymmetric, piston-driven magnetohydrodynamic shocks into an inhomogeneous ideal gas permeated by a current-free azimuthal magnetic field.
Abstract: Self‐similar solutions are presented for the equatorial propagation of axisymmetric, piston‐driven magnetohydrodynamic shocks into an inhomogeneous ideal gas permeated by a current‐free azimuthal magnetic field. Several regimes of magnetically dominated flow near the piston are possible, depending on the ambient density distribution of the unshocked gas. The strong hydrodynamic and magnetic gradients which permeate this flow indicate the need for a more refined treatment which will include the effects of diffusion due to dissipative phenomena. Global features of the flow are discussed and illustrated by numerical solutions. The use of reductive properties of the equations to simplify the problem in several special cases is indicated. Implications regarding the propagation of disturbances in stellar atmospheres are considered.

Journal ArticleDOI
TL;DR: In this paper, a microwave probe was developed based on the principle of the cavity shift method for diagnosing local density perturbations in a magnetized plasma in the presence of large-amplitude RF signals and nonuniform anisotropic electron distributions.
Abstract: Experiments performed in a pulsed afterglow plasma column with specified parameters revealed a filamentation instability of a large-amplitude whistler wave launched from antennas which produce a diverging energy flow in the linear regime. The difficult problem of diagnosing local density perturbations in a magnetized plasma in the presence of large-amplitude RF signals and nonuniform anisotropic electron distributions is discussed. Since Langmuir probes are too unreliable under these conditions, a microwave probe is developed based on the principle of the cavity shift method. The temporal and spatial evolution of the duct formation and wave propagation are shown. The role of the observed electron heating in the filamentation process is examined. The observed self-focusing process appears to be the result of the reinforcing interaction between the wave-induced density depression and the density-induced wave refraction. Interesting applications are noted.

Journal ArticleDOI
TL;DR: In this article, it is suggested that the large-scale brightness distribution can be most simply described in terms of a pattern with zonal wavenumber of unity which extends between about + and - 50 deg latitude and which progresses around the planet in about 4.2 days, and the observed Y pattern could be produced by the superposition of a Rossby-Haurwitz wave dominant at middle latitudes and a Kelvin wave dominant near the equator.
Abstract: Detailed descriptions and interpretations are provided for phenomena seen in the UV markings on Venus during the Mariner 10 encounter with that planet. The phenomena include the dark horizontal Y, circumequatorial belts, bowlike waves, the subsolar disturbance, midlatitude spiral streaks, the polar ring, and the polar region. Interpreting some of these phenomena in terms of physical processes that are familiar in earth's atmosphere, it is proposed that the large-scale brightness distribution can be most simply described in terms of a pattern with zonal wavenumber of unity which extends between about + and - 50 deg latitude and which progresses around the planet in about 4.2 days. The large-scale UV markings are interpreted as a wave phenomenon, and it is shown how the observed Y pattern could be produced by the superposition of a Rossby-Haurwitz wave dominant at middle latitudes and a Kelvin wave dominant near the equator. It is suggested that the bowlike waves may be true bow waves formed by the interaction of the rapid supercritical zonal flow with internal gravity waves of lower horizontal phase speeds generated by the subsolar disturbance.

Journal ArticleDOI
TL;DR: In this article, a detailed analysis of the slow-wave propagation on Schottky-contact microstrip lines (SCMLs) is presented, including the effect of metallic losses.
Abstract: Schottky-contact microstrip lines (SCML) are a special type of transmission line on the semiconducting substrate: the metallic-strip conductor is specially selected to form a rectifying metal-semiconductor transition while the ground plane exhibits an ohmic metallization. Thus the cross section of SCML is similar to that of a Schottky-barrier diode. The resulting voltage-dependent capacitance per unit length causes the nonlinear behavior of such lines. In this paper a detailed analysis of the, slow-wave propagation on SCML is presented, including the effect of metallic losses. Formulas for the propagation constant and characteristic impedance are derived and an equivalent circuit is presented. Conditions for slow-mode behavior are given, particularly taking into account the influence of imperfect conductors and defining the range of many interesting applications. Experimental results performed on Si-SCML are compared with theory.

Journal ArticleDOI
TL;DR: The dispersion of higher modes of surface waves over a region covered by an array of stations can be measured by applying a frequency-wavenumber transform to segments of the signals in these stations, centered at a number of group-velocities as discussed by the authors.
Abstract: The dispersion of higher modes of surface waves over a region covered by an array of stations can be measured by applying a frequency-wavenumber transform to segments of the signals in these stations, centered at a number of group-velocities. Thus, at a fixed period, modes appear as separate maxima in a display of the power spectrum on a phase-velocity vs. group velocity plane.

Journal ArticleDOI
TL;DR: In this article, conditions for the break-up of a finite amplitude Alfven wave into upper and lower sideband waves and a longitudinal disturbance are derived, which can occur over a much wider range of conditions than the decay instability.
Abstract: Conditions are derived for the break‐up of a finite amplitude Alfven wave into upper and lower sideband waves and a longitudinal disturbance. This instability can occur over a much wider range of conditions than the decay instability. The longitudinal disturbance is only nonoscillatory when dissipation is neglected.