23,970 research outputs found
Charged-Current Disappearance Measurements in the NuMI Off-Axis Beam
This article studies the potential of combining charged-current disappearance
measurements of \nu_{\mu} to \nu_{\tau} from MINOS and an off-axis beam. I find
that the error on \Delta m^2 from a 100 kt-yr off-axis measurement is a few
percent of itself. Further, I find little improvement to an off-axis
measurement by combining it with MINOS.Comment: Presented at NuFact'02. Four pages, three figure
The Detailed Chemical Abundance Patterns of M31 Globular Clusters
We present detailed chemical abundances for 20 elements in 30
globular clusters in M31. These results have been obtained using high
resolution (24,000) spectra of their integrated
light and analyzed using our original method. The globular clusters have
galactocentric radii between 2.5 kpc and 117 kpc, and therefore provide
abundance patterns for different phases of galaxy formation recorded in the
inner and outer halo of M31. We find that the clusters in our survey have a
range in metallicity of [Fe/H]. The inner halo clusters cover
this full range, while the outer halo globular clusters at R20 kpc have a
small range in abundance of [Fe/H]. We also measure abundances
of alpha, r- and s-process elements. These results constitute the first
abundance pattern constraints for old populations in M31 that are comparable to
those known for the Milky Way halo.Comment: XII International Symposium on Nuclei in the Cosmos August 5-12, 2012
Cairns, Australia. To appear in Proceedings of Scienc
Dissociation energy and long-range potential of diatomic molecules from vibrational spacings - The halogens
Dissociation energy and long-range potential of diatomic molecules from vibrational spacings, halogen
Shape resonances and rotationally predissociating levels - The atomic collision time delay functions and quasibound level properties of H2 /Chi /1 Sigma g plus//
Atomic collision time delay functions and quasibound level properties of ground state of molecular hydroge
Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques
We present abundances of globular clusters in the Milky Way and Fornax from
integrated light spectra. Our goal is to evaluate the consistency of the
integrated light analysis relative to standard abundance analysis for
individual stars in those same clusters. This sample includes an updated
analysis of 7 clusters from our previous publications and results for 5 new
clusters that expand the metallicity range over which our technique has been
tested. We find that the [Fe/H] measured from integrated light spectra agrees
to 0.1 dex for globular clusters with metallicities as high as
[Fe/H]=, but the abundances measured for more metal rich clusters may be
underestimated. In addition we systematically evaluate the accuracy of
abundance ratios, [X/Fe], for Na I, Mg I, Al I, Si I, Ca I, Ti I, Ti II, Sc II,
V I, Cr I, Mn I, Co I, Ni I, Cu I, Y II, Zr I, Ba II, La II, Nd II, and Eu II.
The elements for which the integrated light analysis gives results that are
most similar to analysis of individual stellar spectra are Fe I, Ca I, Si I, Ni
I, and Ba II. The elements that show the greatest differences include Mg I and
Zr I. Some elements show good agreement only over a limited range in
metallicity. More stellar abundance data in these clusters would enable more
complete evaluation of the integrated light results for other important
elements.Comment: Accepted for publication in ApJ, 37 pages, 13 tables, 29 figure
The Extrema-effect in Total Elastic Molecular Beam Scattering Cross Sections for Characterization of the Potential Well
Extrema effect in total elastic molecular beam scattering cross sections for characterization of potential wel
Deployable antenna demonstration project
Test program options are described for large lightweight deployable antennas for space communications, radar and radiometry systems
Dynamic autonomous intelligent control of an asteroid lander
One of the future flagship missions of the European Space Agency (ESA) is the asteroid sample return mission Marco-Polo. Although there have been a number of past missions to asteroids, a sample has never been successfully returned. The return of asteroid regolith to the Earth's surface introduces new technical challenges. This paper develops attitude control algorithms for the descent phase onto an asteroid in micro-gravity conditions and draws a comparison between the algorithms considered. Two studies are also performed regarding the Fault Detection Isolation and Recovery (FDIR) of the control laws considered. The potential of using Direct Adaptive Control (DAC) as a controller for the surface sampling process is also investigated. Use of a DAC controller incorporates increased levels of robustness by allowing realtime variation of control gains. This leads to better response to uncertainties encountered during missions
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