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  • Wave propagation
  • Springer  (10)
  • Elsevier  (2)
  • Cambridge Univ. Press  (1)
  • 1995-1999  (8)
  • 1980-1984  (5)
  • 1925-1929
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 47 (1996), S. 906-914 
    ISSN: 1420-9039
    Keywords: Wave propagation ; cylindrical anisotropy ; SH-wave ; exact solution ; transient response ; wave pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract Propagation of a transient SH-wave in a cylindrically anisotropic elastic solid is considered and an exact closed form solution for a special class of anisotropy is obtained. This is a case where a square root of the shear rigidity ratio is an integer. In this case we find an interesting wave pattern. However, the singularity at the wave front is of the same order as the one in the isotropic solid.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 148 (1996), S. 155-173 
    ISSN: 1420-9136
    Keywords: Wave propagation ; synthetic seismograms ; heterogeneous media ; one-return approximation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract When reverberations between heterogeneities or resonance scattering can be neglected but accumulated effects of forward scattering are strong, the Born approximation is not valid but the De Wolf approximation can be applied in such cases. In this paper, renormalized MFSB (multiple-forescattering single-backscattering) equations and the dual-domain expression for scalar, acoustic and elastic waves are derived by a unified approach. Two versions of the one-return method (using MFSB approximation) are given: One is the wide-angle dual-domain formulation (thin-slab approximation); the other is the screen approximation. In the screen approximation, which involves a small-angle approximation for the wave-medium interaction, it can be seen clearly that the forward scattered, or transmitted waves are mainly controlled by velocity perturbations; while the backscattered or reflected waves, by impedance perturbations. The validity of the method and the wide-angle capability of the dual-domain implementation are demonstrated by numerical examples. Reflection coefficients of a plane interface derived from numerical simulations by the wide-angle method match the theoretical curves well up to critical angles. For the reflections of a low-velocity slab, the agreement between theory and synthetics only starts to deteriorate for angles greater than 70°. The accuracy of the wide-angle version of the method could be further improved by optimizing the wave-number filtering for the forward propagation and shrinking the step length along the propagation direction.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Meccanica 30 (1995), S. 341-357 
    ISSN: 1572-9648
    Keywords: Balance equations ; Wave propagation ; Continua with Microstructure ; Continuum mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Sommario Si ricavano le equazioni di moto per i materiali granulari dilatanti da un principio variazionale Hamiltoniano di tipo locale nel caso conservativo. Si studia la propagazione delle onde non lineari in una regione di stato costante per mezzo di un approccio asintotico già rivelatosi utile nello studio della propagazione di onde nei liquidi con bolle e nelle miscele di fluidi. Quando si supponga che i granuli siano incomprimibili, si dimostra che il materiale si comporta come un continuo con microstruttura latente.
    Notes: Abstract The equations of motion for dilatant granular material are obtained from a Hamiltonian variational principle of local type in the conservative case. The propagation of nonlinear waves in a region with uniform state is studied by means of an asymptotic approach that has already appeared useful in an investigation on wave propagation in bubbly liquids and in fluid mixtures. When the grains are assumed to be incompressible, it is shown that the material behaves as a continuum with latent microstructure.
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  • 4
    ISSN: 1572-9648
    Keywords: Wave propagation ; Poroelasticity ; Unsaturated media ; Transform methods ; Solid mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In this paper, it is demonstrated how a direct stiffness method for wavepropagation in multilayered saturated poroelastic media, based on integraltransform techniques, can be modified to account for a small amount of gasin the pores. Unsaturated media with small gas fractions can be treatedusing Smeulders‘ extension of Biot‘s poroelastic theory. The effect of thepresence of gas bubbles on the fluid bulk modulus and the dispersioncharacteristics of a water-saturated sand of Mol is demonstrated. Thedirect stiffness method is illustrated with a numerical example wheretransient wave propagation in a dry, saturated and unsaturated halfspaceis considered.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Meccanica 32 (1997), S. 231-239 
    ISSN: 1572-9648
    Keywords: Magnetoelastic interaction ; Wave propagation ; Concentrated forces ; Transform method ; Solid mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In this paper the generation of harmonic waves in an elastic magneticmaterial, which is a perfect conductor of electricity, isconsidered. It has been assumed that an infinite body is subjected tothe action of an initially constant magnetic fieldH = (H,0,0) and in the plane ax+by=0 acts a source ofdistortion. It has been shown that this source may produce bothtransverse and longitudinal waves and each of them consists of two parts,which propagate with different speeds. The amplitudes and speeds in dependence on theangle between the direction of wave propagation and the magnetic fieldintensity H have been discussed.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Annales geophysicae 16 (1998), S. 914-920 
    ISSN: 0992-7689
    Keywords: Ionosphere-magnetosphere interactions ; Wave propagation ; MHD waves and instabilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract As a continuation of our earlier paper, we consider here the case of the excitation of standing Alfvén waves by a source of the type of sudden impulse. It is shown that, following excitation by such a source, a given magnetic shell will exhibit oscillations with a variable frequency which increases from the shell’s poloidal to toroidal frequency. Simultaneously, the oscillations will also switch over from poloidally (radially) to toroidally (azimuthally) polarized. With a reasonably large attenuation, only the start of this process, the stage of poloidal oscillations, will be observed in the ionosphere.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Annales geophysicae 16 (1998), S. 900-913 
    ISSN: 0992-7689
    Keywords: Ionosphere-magnetosphere interaction ; Wave propagation ; Magnetospheric physics ; MHD waves and instabilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In the framework of an axisymmetric magnetospheric model, we have constructed a theory for broad-band standing Alfvén waves with large azimuthal wave number m ≫ 1 excited by a stochastic source. External currents in the ionosphere are taken as the oscillation source. The source with statistical properties of –white noise” is considered at length. It is shown that such a source drives oscillations which also have the –white noise” properties. The spectrum of such oscillations for each harmonic of standing Alfvén waves has two maxima: near the poloidal and toroidal eigenfre-quencies of the magnetic shell of the observation. In the case of a small attenuation in the ionosphere the maximum near the toroidal frequency is dominated, and the oscillations are nearly toroidally polarized. With a large attenuation, a maximum is dominant near the poloidal frequency, and the oscillations are nearly poloidally polarized.
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  • 8
    ISSN: 1432-2048
    Keywords: Biological oscillations ; Oscillations (Physarum) ; Phase gradients ; Physarum ; Wave propagation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plasmodia ofPhysarum polycephalum were analyzed with the aid of cinematography and the infrared reflection technique for characterization of the phase behavior of their oscillating contraction activity, with special emphasis placed on the effects of temperature gradients. In response to temperature gradients, phase gradients were documented cinematographically as well as by infrared registration. A quantitative evaluation of the cinematographically recorded phenomena was carried out with the aid of streak photography. The phase gradient is directed across the region of the temperature gradient with a delay in phase toward the colder side. The correspondingly generated waves are as short as 1 mm and are propagated toward the colder region. A comparison of these waves with the known “flickering” phenomena in cinematographic films reveals a common nature of both.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical biology 18 (1983), S. 53-67 
    ISSN: 1432-1416
    Keywords: Wave propagation ; Arteries ; Atherosclerosis ; Blood flow ; Navier-Stokes equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A theoretical analysis for the problem of wave propagation in arteries is presented. Blood is treated as a Newtonian, viscous incompressible fluid. On the basis of information derived from experimental investigations on the mechanical properties of wall tissues, the arterial wall is considered to be nonlinearly viscoelastic and orthotropic. The analysis is carried out for a cylindrical artery, under the purview of membrane theory, by taking account the effect of initial stresses. The motion of the wall and that of the fluid are assumed to be axisymmetric. Particular emphasis has been paid to the propagation of small amplitude harmonic waves whose wavelength is large compared to the radius of the vessel. By employing the equations of motion of the fluid and those for the wall, together with the equations of continuity, a frequency equation is derived by exploiting the conditions of continuity of the velocity of the arterial wall and that of blood on the endosteal surface of the wall. In order to illustrate the validity of the derived analytical expressions a quantitative analysis is made for the variations of the phase velocities as well as the transmission coefficient with frequency corresponding to different transmural pressures which relate to different initial stresses. Computational results indicate that phase velocities increase with the increase of transmural pressures.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Nonlinear dynamics 13 (1997), S. 243-257 
    ISSN: 1573-269X
    Keywords: Wave propagation ; submerged cable ; structural dynamics ; fluid/structure interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This study focuses on the relative importance of two sources of nonlinearities affecting submerged cable response. The first of these is the added fluid damping offered by the surrounding medium while the second is the geometric stiffening offered by the cable through finite extensions of its centerline. The contribution of each nonlinear effect, taken separately and in tandem, is evaluated herein through the study of structural waves that form in the (out-of-plane) direction normal to the cable equilibrium plane. Numerical solutions are pursued herein using a finite difference algorithm which is brought to bear on two nonlinear cable/fluid models including: (1)~a nonlinear submerged cable model in which hydrodynamic drag is the sole nonlinear mechanism (referred to herein as the 'nonlinear drag model'); and (2)~a nonlinear submerged cable model in which hydrodynamic drag and geometric stiffening are both active nonlinear mechanisms (the 'nonlinear elastic-drag model'). Numerical solutions for propagating cable waves are developed for the case of a long suspension subjected to a concentrated harmonic excitation source. Conclusions are subsequently drawn regarding the spatial decay of the resulting out-of-plane waves and the dynamic cable tension induced by these waves. The effect of these two nonlinear mechanisms is further explored through the analysis of two additional, linear models: (3)~a simple linear taut string model without drag (the 'simple model'); and (4)~a linear taut string model with linear drag (the 'linear drag model'). The results of all models are critically compared and the range of validity of the linear/cable fluid models are assessed.
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  • 11
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    Elsevier
    In:  Amsterdam, 253 pp., Elsevier, vol. 10, no. 1, pp. 1-40, (ISBN: 3-540-23712-7)
    Publication Date: 1983
    Keywords: Textbook of geophysics ; Acoustics ; Seismics (controlled source seismology) ; Waves ; Wave propagation
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  • 12
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    Elsevier
    In:  Amsterdam, Elsevier
    Publication Date: 1980
    Keywords: Seismology ; Seismics (controlled source seismology) ; Wave propagation ; Waves ; Textbook of geophysics
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  • 13
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    Cambridge Univ. Press
    In:  Cambridge, Cambridge Univ. Press, vol. 2, no. XVI:, pp. 1-14, (ISBN: 0-691-05010-4)
    Publication Date: 1980
    Keywords: Waves ; Elasticity ; Source ; Wave propagation ; Seismology ; Textbook of geophysics
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