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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 6 (1996), S. 334-347 
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism leading to the observed coexistence of gaps and narrow ringlets in the planetary rings is found. It is based upon the quasi-stationary radial drift of the matter under action of two forces in the disk plane: the Coriolis force and the Reynolds stresses. To an accuracy of the factor of 2 the first force coincides with the Lorentz force, therefore the radial drift in rings is similar to the gradient drift of plasma in the magnetic field. The second force is produced by the wave generated by the nearby satellite in the resonance position. In inertial systems, the second force alone causes a matter flow in its direction, called acoustic streaming. Since the radial drift is caused by nonlinear time-averaged force of high-frequency harmonic interactions in the wave, it exists in the wave propagation zone: from the birth place of the wave—the resonance position, up to the reflection point of the wave, where its group velocity vanishes. Our estimations show that the size of the density wave propagation zone corresponding to the density wave which had been formerly generated the 2:1 orbital resonance with Mimas is consistent with the width of the Cassini Division. In our case the nature of the radial drift is such that first of all it clears out the farthest from the resonance position; later, the closer areas also get affected by the drift. The zone closest to the resonance position itself is the last to be involved in the process. The matter carried away by the drift is partially accumulated near the resonance position forming a narrow dense ringlet. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1562-6873
    Keywords: spiral galaxies ; Fourier analysis of line-of-sight velocities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Our main goal is to investigate the effects of data incompleteness on the results of Fourier analysis of line-of-sight velocity fields in the disks of spiral galaxies. We have carried out a number of numerical experiments, first with an artificially created simple velocity field and then with the velocity fields of two real galaxies, which qualitatively differ in data filling: NGC 157 and NGC 3631 with good and bad data filling, respectively. The field of purely circular velocities is chosen as the simplest artificial velocity field, because the circular velocities of spiral galaxies are much high than the residual (noncircular) velocities. Superimposing a “mask” simulating blank spots (holes) in the map of observational data on this artificial field has no effect on the results of Fourier analysis of this simplest field. A similar result is obtained for real galaxies with good data filling of the observed velocity fields. Superimposing arbitrarily shaped masks on the observed velocity field of NGC 157 in such a way that the field was filled by a mere 50% (at each radius) could not change appreciably the radial variations of large-scale Fourier harmonics. The situation qualitatively changes in attempting to fill the holes in the observed velocity field of NGC 3631 in some way. When missing velocities are artificially introduced by using the simplest model of purely circular gas rotation, the amplitudes and phases of the principal Fourier harmonics are distorted. In particular, a substantial distortion of the third harmonic also causes an increase in the error when determining the corotation radius from data of the filled field. When the filling of the velocity field is increased by degrading the spatial resolution, the amplitudes of most harmonics decrease throughout the entire disk region; as a result, their radial variations are smoothed out and the behavior of harmonic phases in the range of moderately high initial amplitudes can be distorted. An abnormal enhancement of the highest Fourier harmonics in the regions of low filling of the initial field is also possible. At the same time, despite the above distortions, the corotation radius determined from the smoothed fields matches that for the initial velocity fields.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 103 (1984), S. 137-142 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In article by Morozov and Fridman (1984) the general equation of motion of an elastic thread in an external gravitational field was formulated and also instability of an elastic thread rotating around a gravitating center was established. On this basis, in the present article we show that the classical model of a hypothetical continous ice ring around Saturn, proposed by Laplace and Maxwell, was incorrectly interpreted by them. Specifically, supposing the ring to be infinitely hard and firm, they came to the conclusion that it will fall on the planet's surface. However, in reality such a ring would be destroyed due to internal stresses under displacements which are three orders of magnitude smaller than the distance between the ring and the planet. We also note that accounting for this effect is important under discussions of cosmogonical models. In conclusion, estimates are given which show that the steel ring (thread) revolving the Earth and rotating around it at the distance of 200 km from the surface would be torn, due to its instability before it falls on the Earth. Meanwhile, for threads of firm aluminium fusions the opposite picture is to be expected. It is noted that the instabilities indicated may be stabilized by using follow-up (‘cybernetic’) systems with power plants.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Atomic energy 46 (1979), S. 256-258 
    ISSN: 1573-8205
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied mechanics and technical physics 8 (1967), S. 92-93 
    ISSN: 1573-8620
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics 39 (1996), S. 252-271 
    ISSN: 1573-8191
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A closed system of two-dimensional equations describing the dynamics of rotating, gravitating gas disks is derived. It is an integrodifferential system for barotropic disks and a differential system for polytropic disks. For both barotropic and polytropic disks, these equations differ both from the dynamical equations used in the literature for astrophysical disks and from the traditional equations of two-dimensional hydrodynamics. The sufficient conditions under which the dynamics of a disk can be described in a two-dimensional formulation are obtained. The first condition reflects the thin-disk approximation. The second condition imposes a limit on the characteristic times of processes studied in a two-dimensional formulation. In most cases this condition limits the characteristic frequency of a process to the disk's rotational frequency.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics 8 (1972), S. 338-343 
    ISSN: 1573-8191
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied mechanics and technical physics 10 (1969), S. 333-341 
    ISSN: 1573-8620
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The stability of a rotating dust cylinder against perturbations located in the plane perpendicular to the axis of rotation is investigated. It is shown that a homogeneous rotating cylinder containing a weak inhomogeneity is stable against such perturbations. A weakly inhomogeneous cylinder with opposite streams of equal density is unstable for thel=2 mode in the case of a perturbation of the form∼ei(lϕ−ωt), when the density increases radially. The instability of a system consisting of a homogeneous rotating dust cylinder in a hot homogeneous medium is determined. It is shown that the maximum growth rate corresponds tol = 2 when the density of a cold cylinder is not negligible in comparison with the density of the medium. In the opposite case, the maximum growth rate shifts toward l=3. An attempt is made to associate the existence of the maximum growth rate for l=2 with the presence of two spiral arms in most galaxies. It is shown that, when the longitudinal temperature is high enough, a rotating cylinder which is bounded in the radial direction is stable against arbitrary perturbations.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Strength of materials 7 (1975), S. 996-1000 
    ISSN: 1573-9325
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions 1. The scale effect is substantial for graphite, and the relationship can be described by Bolotin's formula. 2. The type of state of stress influences the parameters of the strength-distribution curves, especially on the left flank. 3. There are marked changes in the limiting surfaces corresponding to different volumes of deformed material and different failure probabilities in this graphite. 4. A strength criterion to be applied in calculations on components should be based on tests on specimens comparable in size with the component. We are indebted to A. A. Lebedev for valuable comments on the formulation and analysis.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Strength of materials 12 (1980), S. 346-348 
    ISSN: 1573-9325
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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