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AbstractAbstract

[en] The modulational instability of surface waves in magnetohydrodynamics is calculated in such a manner that a correct description of the role of the tangential magnetic field in the nonlinear stability characteristics of the surface waves is given. The governing boundary-value problem for the wave motions is formulated and solved. The resulting nonlinear Schroedinger equation shows clearly that the vacuum magnetic field has a completely stabilizing effect on the surface waves

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Zeitschrift fuer Angewandte Mathematik und Mechanik; ISSN 0044-2267; ; CODEN ZAMMA; v. 68(9); p. 456-458

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[en] The problem of generating fluctuation magnetic fields for a uniform, isotropic and spatially unbounded flow was examined. The random velocity field was assumed to be mirror symmetric and have a short correlation time. A study was made of the evolution of the correlation function of the magnetic field in a wide range of Reynolds numbers, especially for Reynolds numbers less than the critical value. An equation is derived for the correlation function of the magnetic field. The self-excitation of the field at Reynolds numbers above the critical value was modeled along with the behavior of the magnetic energy in the subcritical regime. An unbounded medium with a uniform velocity distribution was the object of study

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Translated from Magn. Gidrodin.; 23: No. 3, 3-7(Jul-Sep 1987). Cover-to-cover translation of Magnitnaya Gidrodinamika (USSR).

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[en] In this paper, the effect of buoyancy force on the parallel flows bounded above by a rigid permeable plate which may be moving or stationary and below, by a permeable bed has been investigated. To discuss the solution, the flow region is divided into two zones. In Zone 1, the flow is laminar and is governed by the Navier-Stokes equations from the impermeable upper rigid plate to the permeable bed. In Zone 2, the flow is governed by the Darcy law in the permeable bed below the nominal surface. The expressions for velocity and temperature distributions. Slip velocity, slip temperature, mass flow rate and the rates of heat transfer coefficients are obtained. The effects of magnetic porous, slip and buoyancy parameters and Biot number on the above physical quantities are investigated. The thickness of the boundary layer in Zone 2 has been evaluated. (author)

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9 refs., 6 figures.

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[en] The study deals with phenomenological and theoretical models in order to explain the existence of cosmic magnetic fields. Following aspects are considered: non-linear recursions, the theory of chaotic motions, turbulence, convection, the turbulent dynamo theory and magnetohydrodynamics. In the frame of these model assumptions it is tried to explain the causes of the solar activity cycle and the geomagnetic field

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Struktur aus dem Chaos: Magnetfelder kosmischer Objekte

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[en] An attempt has been made to study the problem of free convection hydromagnetic flow of an elastico-viscous fluid past a porous vertical plate in a rotating frame of reference taking ohmic and viscous dissipations into account in the presence of Hall current. The nature of velocity profile shows the existence of multiple boundary layers. Their 'thickness' is seen to decrease with increasing values of Ekman, Hartman and Prandtl numbers and Hall parameter. The graphical study reveals that the increasing values of Hall parameter and Ekman number (for a fixed large value of Hall parameter) exert opposite influence on the flow. (author). 11 refs., 2 tables

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[en] The unsteady two-dimensional laminar flow of an electrically conducting viscous fluid past an impulsively started infinite porous plate in the presence of a transverse magnetic field has been discussed. The suction velocity, normal to the plate, is constant and is directed towards it. Expression for velocity and skin-friction are derived in the non-dimensional forms for two different case : (1) exponentially increasing small perturbation, and (2) exponentially decreasing small perturbation. It has been observed that velocity of the flow field increases with the velocity of the plate when it moves in the direction of the fluid flow. But when the plate moves in the direction opposite to that of the flow, there is a reverse type flow near the wall. The skin-friction is greater when the plate moves in the opposite direction of the flow than it is, when the plate is moving in the direction of the flow. (author). 9 refs

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Journal of Scientific Research (Bhopal); CODEN JSRED; v. 9(2-3); p. 89-93

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[en] An investigation is made into the propagation of long nonlinear weakly nonone-dimensional internal waves in an incompressible stratified fluid of infinite depth in the presence of a horizontal magnetic field. It is shown that such waves are described by an equation representing the extension of the Benjamin-Ono equation to the weakly nonone-dimensional case. The equation obtained differs from that obtained by M.J. Ablowitz et al., which is attributable to the anisotropy of the medium resulting from the presence of a magnetic field. The stability of a soliton with respect to flexural perturbations is investigated. A particular case of the variation of the density with height at constant Alfven velocity is examined in detail

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Translated from Izv. Akad. Nauk SSSR, Mekh. Zhidk. Gaza; 22: No. 6, 65-72(Nov-Dec 1987). Cover-to-cover translation of Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza (USSR).

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[en] Starting from a simple energy level structure, a model is proposed for the kinetics of thermal annihilation of paramagnetic centers induced in yttria-stabilized zirconia. Previous experimental works show very different activation energies and frequency factors from sample to sample. An explanation is given taking into account the distribution of oxygen vacancy defects: the paramagnetic center annihilation depends on the number of charged oxygen vacancies and on their thermally activated rearrangement. (author). 10 refs.; 2 figs

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[en] The axial penetration of an azimuthal magnetic field into a short-duration hollow cylindrical plasma is studied. When the process is so fast that the ion motion is small and the plasma dissipative resistivity, electron inertia, and pressure are small, the evolution of the magnetic field is governed by the Hall field. When the radial current flows inward, the magnetic field penetrates in the form of a Hall-induced shock wave with a narrow current channel. When outward, the magnetic field does not penetrate the plasma. Moreover, in the latter case the magnetic field is expelled from an initially magnetized plasma. The increase and decrease of the magnetic field intensity in the cylindrical plasma are shown to result naturally from the frozen-in law

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[en] The substantial forces available through the use of magnetohydrodynamics (MHD) find diverse uses in the field of metallurgy. This paper describes three of these: two of which have undergone benchscale development and one of which awaits development of the requisite critical field strength capabilities in high-temperature superconductors. All three devices depend upon a very simple concept. When a current-carrying conductor is crossed by a magnetic field, an MHD body force (the Lorenz force) is exerted on that conductor. Two of the three devices discussed utilize the application of that force to molten metals. The third device utilizes the force as a magnetic pressure against a solid metallic surface

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Anon; 231 p; 1990; p. 114; IEEE Service Center; Piscataway, NJ (USA); 17. IEEE international conference on plasma science (ICOPS 17); Oakland, CA (USA); 21-23 May 1990; CONF-900585--; IEEE Service Center, 445 Hoes Ln., Piscataway, NJ 08854 (USA)

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