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Appearance of Saturn's F ring azimuthal channels for the anti-alignment configuration between the ring and Prometheus
In this article we explore the aspect of the F ring with respect to the
anti-alignment configuration between the ring and Prometheus. We focus our
attention on the shape of the F ring's azimuthal channels which were first
reported by Porco et al. (2005) and numerically explored by Murray et al.
(2005), who found excellent agreement between Cassini's ISS reprojected images
and their numerical model via a direct comparison. We find that for
anti-alignment the channels are wider and go deeper inside the ring material.
From our numerical model we find a new feature, an island in the middle of
the channel. This island is made up of the particles that have been perturbed
the most by Prometheus and only appears when this satellite is close to
apoapsis. In addition, plots of the anti-alignment configuration for different
orbital stages of Prometheus are obtained and discussed here.Comment: Number of pages: 12, number of tables: 1, number of figures:
Eccentricity Excitation and Apsidal Resonance Capture in the Planetary System Upsilon Andromedae
The orbits of the outer two known planets orbiting Upsilon Andromedae are
remarkably eccentric. Planet C possesses an orbital eccentricity of e1 = 0.253.
For the more distant planet D, e2 = 0.308. Previous dynamical analyses strongly
suggest that the two orbits are nearly co-planar and are trapped in an apsidal
resonance in which the difference between their longitudes of periastron
undergoes a bounded oscillation about 0 degrees. Here we elucidate the origin
of these large eccentricities and of the apsidal alignment. Resonant
interactions between a remnant circumstellar disk of gas lying exterior to the
orbits of both planets can smoothly grow e2. Secular interactions between
planets D and C can siphon off the eccentricity of the former to grow that of
the latter. Externally amplifying e2 during the phase of the apsidal
oscillation when e2/e1 is smallest drives the oscillation amplitude towards
zero. Thus, the substantial eccentricity of planet C and the locking of orbital
apsides are both consequences of externally pumping the eccentricity of planet
D over timescales exceeding apsidal precession periods of order 1e4 yr. We
explain why the recently detected stellar companion to Upsilon Andromedae is
largely dynamically decoupled from the planetary system.Comment: accepted to Ap
A DISCUSSION PAPER ON CANADIAN WHEAT BOARD GOVERNANCE
Crop Production/Industries, Institutional and Behavioral Economics,
Behavior of Spherical Particles at Low Reynolds Numbers in a Fluctuating Translational Flow. Preliminary Experiments
The behavior of small spheres in non-steady translational flow
has been studied experimentally' for values of Reynolds nunber from 0
to 3000. The aim of the work was to improve our quantitative understanding
of particle transport in turbulent gaseous media, a process of
extreme importance in powerplants and energy transfer mechanisms.
Particles, subjected to strong sinusoidal oscillations parallel
to the direction of steady translation, were found to have changes in
average drag coefficient depending upon their translational Reynolds
number, the frequency and amplitude of the oscillations. When the
Reynolds number based on the sphere diameter was les s than 200,
the synunetric translational oscillation had negligible effect on the
aver age particle dr ago
For Reynolds numbers exceeding 300, the effective drag coefficient
was significantly increased in a particular frequency range. For
example, an increase in drag coefficient of 25 per cent was observed at
a Reynolds nwnber of 3000 when the amplitude of the oscillation was
2 per cent of the sphere diazneter and the disturbance frequency was approximately
the Strouhal frequency. The occurrence of the maximum
effect at frequencies between one and two times the Stroubal frequency
strongly suggests non-linear interaction between wake vortex shedding
and the oscillation in translational motions. Flow visualization studies
support this suggestion
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