Elastic Dispersion, Homogeneous Dispersive Media and an Application to Periodic Elastic Media

1978 ◽  
Vol 45 (2) ◽  
pp. 337-342
Author(s):  
G. N. Balanis
Keyword(s):  
Energy Loss ◽  
Wave Dispersion ◽  
Inhomogeneous Media ◽  
Dispersive Media ◽  
Elastic Media ◽  
The Media ◽  
Propagation Of Waves ◽  
The Waves

Wave dispersion that occurs without energy loss is examined and media capable of supporting waves with such dispersion are developed. The media are homogeneous and dispersive. The dispersion of the waves they generate shares many of the characteristics of the dispersion of waves propagating through inhomogeneities. Thus these media can be useful in modeling the propagation of waves in inhomogeneous media. An example supporting the utility of modeling applications is presented.

Attenuation of Harmonic Waves in Layered Media

1973 ◽  
Vol 40 (1) ◽  
pp. 155-160 ◽  
Author(s):  
R. M. Christensen
Keyword(s):  
Perturbation Method ◽  
Explicit Formula ◽  
Layered Media ◽  
Harmonic Waves ◽  
Elastic Media ◽  
Attenuation Effect ◽  
The Media ◽  
The Waves ◽  
Periodic Spacing ◽  
Layered Elastic Media

The effective attenuation of harmonic waves propagating through periodically layered elastic media is studied. The waves are taken to be propagating in the direction normal to that of the layering of the media, which has alternate layers of like material. The main restriction of the derivation is that the wavelength of the waves must be long compared with the periodic spacing of the layering. An explicit formula for the attenuation is derived by a perturbation method of analysis. The analysis reveals the basic cause of the attenuation effect in terms of the scattering properties of the medium. Specific examples are studied.

Kompressionswellen in einer isothermen Atmosphäre mit vertikalem Magnetfeld

1966 ◽  
Vol 21 (7) ◽  
pp. 1098-1106 ◽  
Author(s):  
R. Lust ◽  
M. Scholer
Keyword(s):  
Magnetic Field ◽  
Strong Influence ◽  
Vertical Direction ◽  
Time Dependent ◽  
Solar Chromosphere ◽  
Magnetohydrodynamic Equation ◽  
One Dimensional ◽  
Spatial Dimensions ◽  
Propagation Of Waves ◽  
The Waves

The propagation of waves in the solar atmosphere is investigated with respect to the problem of the chromospheric spiculae and of the heating of the solar chromosphere and corona. In particular the influence of external magnetic fields is considered. Waves of finite amplitudes are numerically calculated by solving the time-dependent magnetohydrodynamic equation for two spatial dimensions by assuming axial symmetry. For the case without a magnetic field the comparison between one dimensional and two dimensional treatment shows the strong influence of the radial propagation on the steepening of waves in the vertical direction. In the presence of a magnetic field it is shown that the propagation is strongly guided along the lines of force. The steepening of the waves along the field is much larger as compared to the case where no field is present.

scholarly journals Propagation of Surface Waves in Asphalt Pavements Generated by Different Load Impulse of Falling Weight Deflectometer

2019 ◽  
Vol 15 (1) ◽  
pp. 29-35
Author(s):  
Jozef Komačka ◽  
IIja Březina
Keyword(s):  
Surface Waves ◽  
Travel Time ◽  
Time History ◽  
Asphalt Pavements ◽  
Load Force ◽  
Falling Weight Deflectometer ◽  
Waves Propagation ◽  
Propagation Of Waves ◽  
Falling Weight ◽  
The Waves

Abstract The propagation of waves generated by load impulse of two FWD types was assessed using test outputs in the form of time history data. The calculated travel time of wave between the receiver in the centre of load and others receivers showed the contradiction with the theory as for the receivers up to 600 (900) mm from the centre of load. Therefore, data collected by the sensors positioned at the distance of 1200 and 1500 mm were used. The influence of load magnitude on the waves propagation was investigated via the different load force with approximately the same load time and vice versa. Expectations relating to the travel time of waves, depending on the differences of load impulse, were not met. The shorter travel time of waves was detected in the case of the lower frequencies. The use of load impulse magnitude as a possible explanation was not successful because opposite tendencies in travel time were noticed.

Propagation of Alfvén-gravitational waves in a stratified perfectly conducting flow with transverse magnetic field

1972 ◽  
Vol 54 (2) ◽  
pp. 209-215 ◽  
Author(s):  
N. Rudraiah ◽  
M. Venkatachalappa
Keyword(s):  
Magnetic Field ◽  
Gravitational Waves ◽  
Transverse Magnetic Field ◽  
Transverse Magnetic ◽  
Constant Coefficients ◽  
Downward Propagation ◽  
The Mean ◽  
Propagation Of Waves ◽  
The Waves ◽  
Vertical Height

Alfvén-gravitational waves are found to propagate in a Boussinesq, inviscid, adiabatic, perfectly conducting fluid in the presence of a uniform transverse magnetic field in which the mean horizontal velocity U is independent of vertical height z. The governing wave equation is a fourth-order ordinary differential equation with constant coefficients and is not singular when the Doppler-shifted frequency Ωd = 0, but is singular when the Alfvén frequency ΩA = 0.If Ω2d < Ω2A the waves are attenuated by a factor exp − [2ΩA(N2−Ω2d)½−Ω2d + Ω2A]z, which tends to zero as z → ∞. This attenuation is similar to the viscous attenuation of waves discussed by Hughes & Young (1966). The interpretation of upward and downward propagation of waves is given.

Anomalous ion beam scattering by shear Kelvin—Helmholtz wave interactions

1978 ◽  
Vol 20 (3) ◽  
pp. 351-364 ◽  
Author(s):  
J. P. Hauck ◽  
Gregory Benford
Keyword(s):  
Magnetic Field ◽  
Energy Loss ◽  
Beam Energy ◽  
Ion Beam ◽  
Theoretical Estimate ◽  
Stopping Power ◽  
Wave Interactions ◽  
Beam Scattering ◽  
Fast Ion ◽  
The Waves

We inject a fast ion beam across a magnetic field, through a cylindrical 5 cm diameter plasma. Shear Kelvin–Helmholtz waves, already present in the plasma, are considerably amplified. The ion beam is rapidly slowed and scattered. The observed stopping power exceeds the classical power by over two orders of magnitude. A simple theoretical estimate, ascribing beam energy loss to driving of the waves, agrees qualitatively with observations.

scholarly journals Propagation of high frequency waves in the quiet solar atmosphere

2008 ◽  
pp. 87-99 ◽  
Author(s):  
A. Andic
Keyword(s):  
Solar Atmosphere ◽  
High Frequency ◽  
Low Frequency ◽  
Magnetic Structures ◽  
Partial Heating ◽  
Fabry Perot ◽  
High Frequency Waves ◽  
Propagation Of Waves ◽  
The Waves ◽  
Low Frequency Waves

High-frequency waves (5 mHz to 20 mHz) have previously been suggested as a source of energy accounting for partial heating of the quiet solar atmosphere. The dynamics of previously detected high-frequency waves is analyzed here. Image sequences were taken by using the German Vacuum Tower Telescope (VTT), Observatorio del Teide, Izana, Tenerife, with a Fabry-Perot spectrometer. The data were speckle reduced and analyzed with wavelets. Wavelet phase-difference analysis was performed to determine whether the waves propagate. We observed the propagation of waves in the frequency range 10 mHz to 13 mHz. We also observed propagation of low-frequency waves in the ranges where they are thought to be evanescent in the regions where magnetic structures are present.

Finite differences on minimal grids

Geophysics ◽  
1994 ◽  
Vol 59 (9) ◽  
pp. 1435-1443 ◽  
Author(s):  
Sophie‐Adélade Magnier ◽  
Peter Mora ◽  
Albert Tarantola
Keyword(s):  
Finite Difference ◽  
Conventional Method ◽  
Finite Differences ◽  
Quantitative Estimation ◽  
Second Order ◽  
Finite Difference Approximation ◽  
Difference Approximation ◽  
Elastic Media ◽  
Numerical Tests ◽  
Propagation Of Waves

Conventional approximations to space derivatives by finite differences use orthogonal grids. To compute second‐order space derivatives in a given direction, two points are used. Thus, 2N points are required in a space of dimension N; however, a centered finite‐difference approximation to a second‐order derivative may be obtained using only three points in 2-D (the vertices of a triangle), four points in 3-D (the vertices of a tetrahedron), and in general, N + 1 points in a space of dimension N. A grid using N + 1 points to compute derivatives is called minimal. The use of minimal grids does not introduce any complication in programming and suppresses some artifacts of the nonminimal grids. For instance, the well‐known decoupling between different subgrids for isotropic elastic media does not happen when using minimal grids because all the components of a given tensor (e.g., displacement or stress) are known at the same points. Some numerical tests in 2-D show that the propagation of waves is as accurate as when performed with conventional grids. Although this method may have less intrinsic anisotropies than the conventional method, no attempt has yet been made to obtain a quantitative estimation.

Analysis of Energy Loss in Superconducting Waveguides

2016 ◽  
pp. 71-83 ◽  
Author(s):  
Kim Ho Yeap ◽  
Kee Choon Yeong ◽  
Choy Yoong Tham ◽  
Humaira Nisar
Keyword(s):  
Energy Loss ◽  
Propagation Constant ◽  
Complex Conductivity ◽  
Characteristic Equations ◽  
Propagation Of Waves

In this chapter, the characteristics of the propagation of waves in superconducting waveguides are investigated. To compute the propagation constant, the complex conductivity of the superconductor is incorporated into the set of characteristic equations which describes the propagation constant of waves in the waveguide. An important outcome from this analysis is that superconducting waveguides are shown to behave like a lossless waveguide, exhibiting literally lossless behaviour at frequencies above the cutoff and below the gap frequency. Above the gap frequency, however, the waveguide loses its superconductivity, giving attenuation which increases in correspond to frequencies. The result suggests strongly that superconducting waveguides can be applied in receiver systems to minimize the loss of propagating signals.

A note on the computation of Rayleigh wave dispersion curves for layered elastic media

1964 ◽  
Vol 54 (3) ◽  
pp. 1013-1019
Author(s):  
J. H. Rosenbaum
Keyword(s):  
Rayleigh Wave ◽  
Wave Dispersion ◽  
Dispersion Curves ◽  
Elastic Media ◽  
Significant Figures ◽  
Rayleigh Wave Dispersion ◽  
Layered Elastic Media

Abstract In the computation of Rayleigh wave dispersion curves for layered elastic media, difficulties arise which take the form of a loss of significant figures and which can be ascribed to the fact that the motion in one section of the medium is weakly or only partly coupled to the motion in another section. These difficulties can be effectively removed if account is taken of such decoupling effects.

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