7,451 research outputs found
An Orbital Stability Study of the Proposed Companions of SW Lyncis
We have investigated the dynamical stability of the proposed companions
orbiting the Algol type short-period eclipsing binary SW Lyncis (Kim et al.
2010). The two candidate companions are of stellar to sub-stellar nature, and
were inferred from timing measurements of the system's primary and secondary
eclipses. We applied well-tested numerical techniques to accurately integrate
the orbits of the two companions and to test for chaotic dynamical behaviour.
We carried out the stability analysis within a systematic parameter survey
varying both the geometries and orientation of the orbits of the companions, as
well as their masses. In all our numerical integrations we found that the
proposed SW Lyn multi-body system is highly unstable on time-scales on the
order of 1000 years. Our results cast doubt on the interpretation that the
timing variations are caused by two companions. This work demonstrates that a
straightforward dynamical analysis can help to test whether a best-fit
companion-based model is a physically viable explanation for measured eclipse
timing variations. We conclude that dynamical considerations reveal that the
propsed SW Lyncis multi-body system most likely does not exist or the
companions have significantly different orbital properties as conjectured in
Kim et al. (2010).Comment: 9 pages, 6 figures, 2 tables. Submitted to and accepted by JASS --
Journal for Astronomy and Space Sciences (using JKAS LaTeX style file
Play it Again: Evolved Audio Effects and Synthesizer Programming
Automatic programming of sound synthesizers and audio devices to match a given, desired sound is examined and a Genetic Algorithm (GA) that functions independent of specific synthesis techniques is proposed. Most work in this area has focused on one synthesis model or synthesizer, designing the GA and tuning the operator parameters to obtain optimal results. The scope of such inquiries has been limited by available computing power, however current software (Ableton Live, herein) and commercially available hardware is shown to quickly find accurate solutions, promising a practical application for music creators. Both software synthesizers and audio effects processors are examined, showing a wide range of performance times (from seconds to hours) and solution accuracy, based on particularities of the target devices. Random oscillators, phase synchronizing, and filters over empty frequency ranges are identified as primary challenges for GA based optimization
Decoding sequential vs non-sequential two-photon double ionization of helium using nuclear recoil
Above 54.4 eV, two-photon double ionization of helium is dominated by a
sequential absorption process, producing characteristic behavior in the single
and triple differential cross sections. We show that the signature of this
process is visible in the nuclear recoil cross section, integrated over all
energy sharings of the ejected electrons, even below the threshold for the
sequential process. Since nuclear recoil momentum imaging does not require
coincident photoelectron measurement, the predicted images present a viable
target for future experiments with new short-pulse VUV and soft X-ray sources.Comment: 4 pages, 3 figure
A Detailed Investigation of the Proposed NN Serpentis Planetary System
The post-main sequence eclipsing binary NN Serpentis was recently announced
as the potential host of at least two massive planetary companions. In that
work, the authors put forward two potential architectures that fit the
observations of the eclipsing binary with almost identical precision. In this
work, we present the results of a dynamical investigation of the orbital
stability of both proposed system architectures, finding that they are only
stable for scenarios in which the planets are locked in mutual mean motion
resonance. In the discovery work, the authors artificially fixed the orbital
eccentricity of the more massive planet, NN Ser(AB) c, at 0. Here, we reanalyse
the observational data on NN Serpentis without this artificial constraint, and
derive a new orbital solution for the two proposed planets. We detail the
results of further dynamical simulations investigating the stability of our new
orbital solution, and find that allowing a small non-zero eccentricity for the
outer planet renders the system unstable. We conclude that, although the
original orbits proposed for the NN Serpentis planetary system prove
dynamically feasible, further observations of the system are vital in order to
better constrain the system's true architecture.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society; 5 figures, 2 table
The effectiveness of functional analysis and behavioral intervention for children who are multi-handicapped and exhibit challenging behaviors
The purpose of this study was to determine the effectiveness of functional analysis of challenging behaviors and behavioral intervention programs on children with multiple handicaps. It was hypothesized that there would be difference in the exhibition of challenging behaviors in children with multiple handicaps following administration of a functional analysis and a behavioral intervention plan. Ten challenging behaviors exhibited by seven children who are multi-handicapped were examined using the process of functional analysis (records review, Motivation Assessment Scale and Analog Setting/Environmental Manipulation) and behavioral intervention. The children ranged in age from five years, four months, to eight years, nine months. The behaviors exhibited included stereotype, self-injury, aggressive and food refusal behaviors. Baseline and post-intervention scores were obtained using the observational recording method of partial interval recording. The data was analyzed using the Wilcoxon Test for Paired Samples. The results of the testing indicated that there was a significance between the two sets of scores. Individual differences in the behaviors of children with multiple handicaps appear to be affected by factors such as the behavior itself, its maintaining variables and the resultant consequences of the behavior
Luncheon
Introductions: George Faenza, General Chairman
Speaker: Charles A. Horner, Commander in Chief, U.S. Space Comman
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