1,721,011 research outputs found
Teoremi di unicità della magnetoidrodinamica in domini illimitati
No full textThe Author establishes two solution uniqueness theorems for the problem of homogeneous, incompressible, perfect, electrically conducting fluid motion around a fixed, electrically conducting solid body. In the first theorem displacemt current is disregarded, in the other one this current is considered. The proof is obtained by using the "weight function method" adopted by G. P. Galdi and S. Rionero in an analogous uniqueness theorem for viscous magnetofluids. © 1979 Università degli Studi di Ferrara
Onde di discontinuità di ogni ordine in una miscela di due solidi elastici
No full textIn this paper the Author studies the propagation of discontinuity waves of order r (r=O or through an anisotropic mixture of two linear homogeneous elastic solids, each having the same constant temperature. By using the method of Nariboli, it is proved that under suitable hypotheses there exist six possible real formal speeds of propagation of the wave front. Moreover the growth equations of the discontinuities along the rays are established and integrated. The speeds of propagation and the evolution law are the same as those of the waves of order 1 ([1])
Su un caso di esistenza e su uno di esistenza e unicità della soluzione di un problema della magnetoidrodinamica stazionaria
No full textThis paper deals with some questions of classical solution existence and uniqueness for the problem of the steady flow of an homogeneous, incompressible, perfect, electrically conducting fluid past a dielectric and discharged obstacle in which a magnetic dipole is situated. More precisely, in the first place the non-existence of solutions of the above mentioned problem is proved for fluids of finite conductivity, if rather restrictive conditions are placed on behavior of the kinetic and magnetic fields at infinity. In the next place an existence and uniqueness theorem is established for perfectly conducting fluids. © 1979 Università degli Studi di Ferrara
Teoremi di unicità per domini illimitati nella dinamica dei solidi elastici, termo e magnetoelastici
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Effetti di risonanza nell’interazione fra radio-onde in un plasma magnetoattivo
No full textSome resonance effects are studied occurring in nonlinear interaction of a «strong» radio wave of cyclic frequency ω1 with another «weaker» radio wave of cyclic frequency ω2 in magnetoplasma (ionosphere). More precisely, it is shown that, besides the well-known phenomena of cross and self-modulation, in particular conditions, there is a large increase in the strength of the «sideband» waves associated with the interacting waves and of «strong» wave harmonics of cyclic frequency 3ω1. © 1978 Università degli Studi di Ferrara
Spatial energy decay estimate in dynamical problems for a micropolar viscoelastic solid
No full textThis paper concerns some estimes of the energy for a micropolar viscoelastic solid in dynamical problems. First, under the assumptions that the solid occupies a semi-infinite cylinder and that the boundary values vanish only on the base, we estimate for any fixed t > 0, in terms of initial and boundary data, the energy of the portions of the solid at distance greater than z from the base and its norm in L^1(0, t). Finally these results are extended to more general domains under the hypothesis that the initial and boundary data have a bounded support. In our analysis we make use of a Maximal Free Energy which allows us to impose very mild restrictions on the relaxation functions
Decay and other estimates for a semi-infinite magnetoelastic cylinder: Saint-Venant's principle
No full textAn analogue of well known Toupin's version of Saint-Venant's principle is proved for a semi-infinite magnetoelastic cylinder under very mild assumptions on the asymptotic behaviour of the Dirichlet integral of the magnetic field anf of the elastic energy.
With regard to the elastic fields, we assign on the base either the stress or the displacement vector while we assume that the lateral surface is either traction free or held fixed at zero displacement. We make use of the first Korn inequality and we estimate the total energy of the conductor in terms of the data for all the problems considered
Discontinuity waves through a thermoviscoelastic solid of integral type
No full textIn this paper we investigate the propagation of discontinuity waves of order N > 1 through a homogeneous linear anisotropic thermo-viscoelastic solid whose heat flux vector depends upon the past history of the temperature gradient. We show that the normal speeds of propagation are independent of the order of the wave. Our analysis is simplified in the case of generalized longitudinal and transverse waves. For these waves we get also the evolution law of the discontinuities (which is the same for any N >= 1) along the rays associated with the wave front. © 1991
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