共查询到20条相似文献，搜索用时 26 毫秒
1.
P. S. Deshwal 《Pure and Applied Geophysics》1971,88(1):12-28
Summary The problem of diffraction of compressional waves incident obliquely on a barrier of finite height fixed at a boundary between a liquid layer and a solid halfspace has been studied. The problem has been solved by employing the Wiener-Hopf technique. The displacement potential in the liquid layer has been obtained in terms of Fourier integrals, whose evalutation along an appropriate contour yields the transmitted, reflected and diffracted waves. Approximate values of the amplitudes of the waves reflected in the solid medium have also been found. 相似文献
2.
The magnetic field generated by an acoustic wave from a nonstationary point source in an infinite marine medium has been considered.
The spatial-temporal structure of the induced field has been studied in a quasistatic approximation and taking into account
self-induction. The magnetic field in the transient and stationary regimes has been considered. 相似文献
3.
Summary The propagation of disturbances has been studied in a layered media, comprising a liquid and a general linear substance, subject to a body force and permeated by an initial magnetic field acting normal to the plane of the contact. The effect of the body force due to some internal source has been considered in the problem and a set of results has been obtained under two possible extreme variants of the boundary conditions in the form of integral forms, which can be computed to visualize the displacement—time and displacement—depth variations, both in the presence and absence of the body force. The effect of body force on the substance has been, as a sample case, illustrated in the graphs. The stress-strain relation of the general linear substance and the electromagnetic equations of Maxwell have been used in working out the problem. 相似文献
4.
Bani Pramanik 《Pure and Applied Geophysics》1972,93(1):60-67
Summary In this note displacement of a thin perfectly conducting viscoelastic plate of Reiss type in contact with vacuum on both sides and in a uniform magnetic field has been discussed. The plate has been assumed to be acted on by an impulsive load. Solutions have been obtained for small and large values of time. Results have also been discussed for some particular cases. 相似文献
5.
P. S. Deshwal 《Pure and Applied Geophysics》1971,85(1):107-124
Summary The problem of diffraction of compressional waves by a rigid barrier of finite height fixed in a liquid half space has been studied. Wiener-Hopf technique forms the basis of the methods used to solve the problem. Exact solutions have been obtained in terms of Fourier integrals whose evaluation along an appropriate contour gives the transmitted, reflected and diffracted waves. The diffracted waves decay rapidly away from the barrier. 相似文献
6.
S. N. Chatterjee 《Pure and Applied Geophysics》1971,86(1):69-79
Summary Propagation of Rayleigh waves in a layer lying over a heterogeneous incompressible half space has been studied. The dispersion equations have been derived and displacements due to an infinite line source have also been investigated. 相似文献
7.
P. S. Deshwal 《Pure and Applied Geophysics》1971,91(1):14-33
Summary The problem of diffraction of compressional waves striking obliquely at a rigid barrier fixed in the surface of a liquid layer lying over a solid halfspace has been studied. Exact values for the amplitudes of the waves reflected in the solid halfspace have been obtained. The method of solution is based on the Wiener-Hopf technique. 相似文献
8.
Charged particle motion in magnetoactive plasma with an axially symmetric electrostatic field has been studied. It has been indicated that a difference between drift velocities of electrons and ions leads to a magnetic field disturbance. The equations for stationary magnetic field disturbances stretched along the magnetic field, which can be magnetic ducts for propagation of whistlers, have been obtained. The possibility of formation of such ducts by electrostatic fields from thunderstorm sources, penetrating into the ionosphere, has been estimated. 相似文献
9.
M. Yu. Reshetnyak 《Geomagnetism and Aeronomy》2010,50(2):263-273
The successive development of thermal convection in a rotating spherical shell heated from below has been studied. It has
been indicated that the convection properties strongly differ within and outside a Taylor cylinder. The distributions of the
kinetic energy, helicity, temperature, and differential rotation in these regions are presented. The consequences for the
geodynamo theory and interpretation of geomagnetic observations are considered. 相似文献
10.
The present paper investigates the effect of voids on the propagation of surface waves in a homogeneous micropolar elastic
solid medium which contains a distribution of vacuous pores (voids). The general theory for surface wave propagation in micropolar
elastic media containing voids has been presented. Particular cases of surface waves (Rayleigh’s, Love’s and Stoneley’s) in
micropolar media which contain vacuous pores have been deduced from the above general theory. Discussions have been made in
each case to highlight the effect of voids and micropolar character of the material medium separately. Their joint effect
has also been studied in details. Modulation of Rayleigh wave velocity has been studied numerically. It is observed that Love
waves are not affected by the presence of voids. 相似文献
11.
Scattering of antiplane shear waves (SH) in two dimensions by surface and near-surface defects in a homogeneous, isotropic elastic semi-infinite medium has been studied. Attention has been focused here in the range of medium to long wavelengths. A combined finite element and analytical technique has been used to study the problems of scattering by semi-circular and triangular canyons. The results for the former case are compared with the known exact solution and those for the latter case are compared with some available approximate solutions. Finally a problem of multiple scattering by a triangular canyon and a nearby circular tunnel is studied. Numerical results are presented showing the effects of multiple scattering and different angles of incidence. These results are of interest in earthquake engineering. 相似文献
12.
The mathematical model of the magnetic field of the partial ring current has been proposed. This current is considered as a pair of spatial current circuits in the Northern and Southern hemispheres, either of which includes two ring zones, in the geomagnetic equator plane and ionosphere, and two zones of the field-aligned current, flowing along the geomagnetic dipole field lines and joining ring fragments of the circuit. The model parameters are: colatitude of the eastward electrojet, longitudinal shift relative to the Sun-Earth axis, circuit half-angle, and the total current flowing in the circuit. The Biot-Savart-Laplace law has been used to calculate the magnetic field of the current circuit. The magnetic field of the partial ring current has been calculated under the conditions typical of a strong magnetic storm. The technique for calculating the partial ring current intensity, using the Asym-H geomagnetic index, has been proposed. 相似文献
13.
S. Basu Mallik 《Pure and Applied Geophysics》1969,76(1):87-91
Summary The problem of disturbances in a visco-elastic medium due to Maxwell in contact with a liquid medium — both being perfectly conductive — has been investigated when an impulsive force acts along the plane of the contact. The electro-magnetic equations of Maxwell, equation of elasticity and the stress-strain relations of the material have been used in the investigation. 相似文献
14.
Ultra low frequency (ULF) wave activity in the high-latitude ionosphere has been observed by a high frequency (HF) Doppler sounder located at Tromsø, Norway (69.71°N, 19.2°E geographic coordinates). A statistical study of the occurrence of these waves has been undertaken from data collected between 1979 and 1984. The diurnal, seasonal, solar cycle and geomagnetic activity variations in occurrence have been investigated. The findings demonstrate that the ability of the sounder to detect ULF wave signatures maximises at the equinoxes and that there is a peak in occurrence in the morning sector. The occurrence rate is fairly insensitive to changes associated with the solar cycle but increases with the level of geomagnetic activity. As a result, it has been possible to characterise the way in which prevailing ionospheric and magnetospheric conditions affect such observations of ULF waves. 相似文献
15.
S. Ghoshal 《Pure and Applied Geophysics》1969,73(1):90-92
Summary In this note the waves in a viscous fluid rotating on a sphere has been studied. The solution contains unknown constants which may be evaluated in particular cases applying the boundary conditions. 相似文献
16.
17.
A three-layer elastic-gravitational fault displacement model using dislocation theory has been developed and used to examine the effect of layering of earth elastic moduli on surface and subsurface displacement fields for a vertical strike-slip fault. The model has been used to examine the effect of depth variation of elastic properties at coseismic and postseismic time scales. For pure strike-slip motion the effect of gravity on coseismic and postseismic horizontal deformation is negligible. For coseismic deformation the model predicts that (for constant Poisson's ratio) an increase in elastic moduli with depth attenuates the displacements within the upper layers with respect to displacement distribution for a uniform half-space, while an inclusion of a soft layer between the top layer and lower half-space amplifies upper layer displacements. The effect of variation in Poisson's ratio on surface and subsurface displacements has also been examined.The effect of postseismic stress relaxation on surface and subsurface displacements for a three-layer model has been calculated and compared with that of a uniformly relaxed half-space model. Layer 1 is assumed to correspond to the upper crust, layer 2 the lower crust and layer 3 the upper mantle. The effect of postseismic stress relaxation within a uniform half-space and within just the lower crust and upper mantle has been examined. Stress relaxation within the whole half-space decreases the amplitude and shortens the wavelength of displacements, while stress relaxation within the lower two layers increases the amplitude and broadens the wavelength of displacements. The difference between uniform and layered postseismic relaxation is particularly pronounced at the base of the crust.Coseismic and postseismic normal and volumetric strains for a vertical strike-slip fault have also been examined. For a uniformly relaxed half-space model, an increase in normal strains is shown with respect to the coseismic elastic solution, whereas the postseismic volumetric strain is effectively zero. For a three-layer model with stress relaxation in the lower layers only, the normal and volumetric strains within the top elastic layer resemble coseismic strains, while in the lower layers which suffer a rigidity decrease, the postseismic volumetric strain is effectively zero. 相似文献
18.
B. Yadava 《Pure and Applied Geophysics》1970,78(1):78-85
Summary The transform calculus has been applied to investigate the disturbances in a composite piezoelectric media traversed by a magnetic field. 相似文献
19.
M. Rahman 《Advances in water resources》1983,6(1):44-53
The tidal propagation in a rectangular basin of an estuary has been studied in this paper. The dynamic response of the tidal current and elevation inside the basin has been obtained using the concept of Kelvin waves and spectrum of Poincare waves. In this study, we have found that initial tidal elevations are amplified near the closed end of the basin or at the tidal barrier site. 相似文献
20.
P. Roy 《Pure and Applied Geophysics》1970,82(1):29-33
Summary The propagation of longitudinal disturbances in a viscoelastic solid of Reiss type subjected to a magnetic field has been obtained in the present note. 相似文献