7,114 research outputs found
SATURN'S INNER SATELLITES: ORBITS, MASSES, AND THE CHAOTIC MOTION OF ATLAS FROM NEW CASSINI IMAGING OBSERVATIONS
We present numerically-derived orbits and mass estimates for the inner
Saturnian satellites, Atlas, Prometheus, Pandora, Janus and Epimetheus from a
fit to 2580 new Cassini ISS astrometric observations spanning February 2004 to
August 2013. The observations are provided in a supplementary table. We
estimate GM_ Atlas=0.384+/-0.001 x 10^(-3)km^3s^(-2), a value 13% smaller than
the previously published estimate but with an order of magnitude reduction in
the uncertainty. We also find GM_ Prometheus=10.677+/-0.006x10(-3)km^3s^(-2),
GM_Pandora=9.133+/-0.009x10^(-3)km^3s^(-2),
GM_Janus=126.51+/-0.03x10^(-3)km^3s^(-2) and
GM_Epimetheus=35.110+/-0.009x10^(-3)km^3s^(-2), consistent with previously
published values, but also with significant reductions in uncertainties. We
show that Atlas is currently librating in both the 54:53
co-rotation-eccentricity resonance (CER) and the 54:53 inner Lindblad (ILR)
resonance with Prometheus, making it the latest example of a coupled CER-ILR
system, in common with the Saturnian satellites Anthe, Aegaeon and Methone, and
possibly Neptune's ring arcs. We further demonstrate that Atlas's orbit is
chaotic, with a Lyapunov time of ~10 years, and show that its chaotic behaviour
is a direct consequence of the coupled resonant interaction with Prometheus,
rather than being an indirect effect of the known chaotic interaction between
Prometheus and Pandora. We provide an updated analysis of the second-order
resonant perturbations involving Prometheus, Pandora and Epimetheus based on
the new observations, showing that these resonant arguments are librating only
when Epimetheus is the innermost of the co-orbital pair, Janus and Epimetheus.
We also find evidence that the known chaotic changes in the orbits of
Prometheus and Pandora are not confined to times of apse anti-alignement.Comment: 23 pages, 16 figures. Accepted for publication in The Astronomical
Journal 23 September 2014 (corrected Fig. 11
Aperiodic tumbling of microrods advected in a microchannel flow
We report on an experimental investigation of the tumbling of microrods in
the shear flow of a microchannel (40 x 2.5 x 0.4 mm). The rods are 20 to 30
microns long and their diameters are of the order of 1 micron. Images of the
centre-of-mass motion and the orientational dynamics of the rods are recorded
using a microscope equipped with a CCD camera. A motorised microscope stage is
used to track individual rods as they move along the channel. Automated image
analysis determines the position and orientation of a tracked rods in each
video frame. We find different behaviours, depending on the particle shape, its
initial position, and orientation. First, we observe periodic as well as
aperiodic tumbling. Second, the data show that different tumbling trajectories
exhibit different sensitivities to external perturbations. These observations
can be explained by slight asymmetries of the rods. Third we observe that after
some time, initially periodic trajectories lose their phase. We attribute this
to drift of the centre of mass of the rod from one to another stream line of
the channel flow.Comment: 14 pages, 8 figures, as accepted for publicatio
Entropy in Image Analysis III
Image analysis can be applied to rich and assorted scenarios; therefore, the aim of this recent research field is not only to mimic the human vision system. Image analysis is the main methods that computers are using today, and there is body of knowledge that they will be able to manage in a totally unsupervised manner in future, thanks to their artificial intelligence. The articles published in the book clearly show such a future
Entropy in Image Analysis II
Image analysis is a fundamental task for any application where extracting information from images is required. The analysis requires highly sophisticated numerical and analytical methods, particularly for those applications in medicine, security, and other fields where the results of the processing consist of data of vital importance. This fact is evident from all the articles composing the Special Issue "Entropy in Image Analysis II", in which the authors used widely tested methods to verify their results. In the process of reading the present volume, the reader will appreciate the richness of their methods and applications, in particular for medical imaging and image security, and a remarkable cross-fertilization among the proposed research areas
Aerospace medicine and biology: A continuing bibliography with indexes (supplement 339)
This bibliography lists 105 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during July 1990. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance
Research on digital image watermark encryption based on hyperchaos
The digital watermarking technique embeds meaningful information into one or more watermark images hidden in one image, in which it is known as a secret carrier. It is difficult for a hacker to extract or remove any hidden watermark from an image, and especially to crack so called digital watermark. The combination of digital watermarking technique and traditional image encryption technique is able to greatly improve anti-hacking capability, which suggests it is a good method for keeping the integrity of the original image. The research works contained in this thesis include: (1)A literature review the hyperchaotic watermarking technique is relatively more advantageous, and becomes the main subject in this programme. (2)The theoretical foundation of watermarking technologies, including the human visual system (HVS), the colour space transform, discrete wavelet transform (DWT), the main watermark embedding algorithms, and the mainstream methods for improving watermark robustness and for evaluating watermark embedding performance. (3) The devised hyperchaotic scrambling technique it has been applied to colour image watermark that helps to improve the image encryption and anti-cracking capabilities. The experiments in this research prove the robustness and some other advantages of the invented technique. This thesis focuses on combining the chaotic scrambling and wavelet watermark embedding to achieve a hyperchaotic digital watermark to encrypt digital products, with the human visual system (HVS) and other factors taken into account. This research is of significant importance and has industrial application value
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