4,133 research outputs found
Official Publications at Texas A&M University: A Case Study in Cataloging Archival Material
Institutional reorganization and staffing changes at Texas A&M University's Cushing Library, which houses the university's archives, made necessary the cataloging of a substantial number of publications produced by different university agencies and departments, publications which had previously been largely inaccessible. The authors designed and implemented a plan to catalog thousands of pamphlets, reports, newsletters, conference proceedings and other material; a project that resulted in increased exposure and usage. This article outlines the development and ongoing refinement of the project. Undertaken in a cooperative spirit aimed at creating an integrated catalog of information resources, this project illustrates ways in which local practices can be improved through the use of technology
Mechanical behaviour of additively manufactured lunar regolith simulant components
Additive manufacturing and its related techniques have frequently been put forward as a promising candidate for planetary in-situ manufacturing, from building life-sustaining habitats on the Moon to fabricating various replacements parts, aiming to support future extra-terrestrial human activity. This paper investigates the mechanical behaviour of lunar regolith simulant material components, which is a potential future space engineering material, manufactured by a laser-based powder bed fusion additive manufacturing system. The influence of laser energy input during processing was associated with the evolution of component porosity, measured via optical and scanning electron microscopy in combination with gas expansion pycnometry. The compressive strength performance and Vickers microhardness of the components were analysed and related back to the processing history and resultant microstructure of the lunar regolith simulant build material. Fabricated structures exhibited a relative porosity of 44 – 49% and densities ranging from 1.76 – 2.3 g cm-3 , with a maximum compressive strength of 4.2 ± 0.1 MPa and elastic modulus of 287.3 ± 6.6 MPa, the former is comparable to a typical masonry clay brick (3.5 MPa). The 2 AM parts also had an average hardness value of 657 ± 14 HV0.05/15, better than borosilicate glass (580 HV). This study has shed significant insight into realizing the potential of a laser-based powder bed fusion AM process to deliver functional engineering assets via in-situ and abundant material sources that can be potentially used for future engineering applications in aerospace and astronautics
A Human-Autonomy Teaming Approach for a Flight-Following Task
Managing aircraft is becoming more complex with increasingly sophisticated automation responsible for more flight tasks. With this increased complexity, it is becoming more difficult for operators to understand what the automation is doing and why. Human involvement with increasingly autonomous systems must adjust to allow for a more dynamic relationship involving cooperation and teamwork. As part of an ongoing project to develop a framework for human-autonomy teaming (HAT) in aviation, a part-task study was conducted to demonstrate, evaluate and refine proposed critical aspects of HAT. These features were built into an automated recommender system on a ground station available from previous studies. Participants performed a flight-following task once with the original ground station (i.e., No HAT condition) and once with the HAT features enabled (i.e., HAT condition). Behavioral and subjective measures were collected; subjective measures are presented here. Overall, participants preferred the ground station with HAT features enabled compared to the station without the HAT features. Participants reported that the HAT displays and automation were preferred for keeping up with operationally important issues. Additionally, participants reported that the HAT displays and automation provided enough situation awareness to complete the task and reduced workload relative to the No HAT baseline
Chandra localisation and optical/NIR follow-up of Galactic X-ray sources
We investigate a sample of eleven Galactic X-ray sources recently discovered
with INTEGRAL or RXTE with the goal of identifying their optical and/or
near-infrared (NIR) counterpart. For this purpose new Chandra positions of nine
objects are presented together with follow-up observations of all the targets
in the optical and NIR. For the four sources IGR J16194-2810, IGRJ 16479-4514,
IGR J16500-3307 and IGR J19308+530, the Chandra position confirms an existing
association with an optical/NIR object, while for two sources (XTE J1716-389
and 18490-0000) it rules out previously proposed counterparts indicating new
ones. In the case of IGR J17597-220, a counterpart is selected out of the
several possibilities proposed in the literature and we present the first
association with an optical/NIR source for J16293-4603 and XTE J1743-363.
Moreover, optical/NIR observations are reported for XTE J1710-281 and IGR
J17254-3257: we investigate the counterpart to the X-ray sources based on their
XMM-Newton positions. We discuss the nature of each system considering its
optical/NIR and X-ray properties.Comment: 15 pages,14 figures. Accepted for publication on MNRA
'It's a film' : medium specificity as textual gesture in Red road and The unloved
British cinema has long been intertwined with television. The
buzzwords of the transition to digital media, 'convergence' and
'multi-platform delivery', have particular histories in the British
context which can be grasped only through an understanding of the
cultural, historical and institutional peculiarities of the British film
and television industries. Central to this understanding must be two
comparisons: first, the relative stability of television in the duopoly
period (at its core, the licence-funded BBC) in contrast to the repeated
boom and bust of the many different financial/industrial combinations
which have comprised the film industry; and second, the cultural and
historical connotations of 'film' and 'television'. All readers of this
journal will be familiar – possibly over-familiar – with the notion that
'British cinema is alive and well and living on television'. At the end of
the first decade of the twenty-first century, when 'the end of medium
specificity' is much trumpeted, it might be useful to return to the
historical imbrication of British film and television, to explore both
the possibility that medium specificity may be more nationally specific
than much contemporary theorisation suggests, and to consider some
of the relationships between film and television manifest at a textual
level in two recent films, Red Road (2006) and The Unloved (2009)
Quantum Hair on Black Holes
A black hole may carry quantum numbers that are {\it not} associated with
massless gauge fields, contrary to the spirit of the ``no-hair'' theorems. We
describe in detail two different types of black hole hair that decay
exponentially at long range. The first type is associated with discrete gauge
charge and the screening is due to the Higgs mechanism. The second type is
associated with color magnetic charge, and the screening is due to color
confinement. In both cases, we perform semi-classical calculations of the
effect of the hair on local observables outside the horizon, and on black hole
thermodynamics. These effects are generated by virtual cosmic strings, or
virtual electric flux tubes, that sweep around the event horizon. The effects
of discrete gauge charge are non-perturbative in , but the effects of
color magnetic charge become -independent in a suitable limit. We
present an alternative treatment of discrete gauge charge using dual variables,
and examine the possibility of black hole hair associated with discrete {\it
global} symmetry. We draw the distinction between {\it primary} hair, which
endows a black hole with new quantum numbers, and {\it secondary} hair, which
does not, and we point out some varieties of secondary hair that occur in the
standard model of particle physics.Comment: (100 pages
The X-ray luminous cluster underlying the bright radio-quiet quasar H1821+643
We present a Chandra observation of the only low redshift, z=0.299, galaxy
cluster to contain a highly luminous radio-quiet quasar, H1821+643. By
simulating the quasar PSF, we subtract the quasar contribution from the cluster
core and determine the physical properties of the cluster gas down to 3 arcsec
(15 kpc) from the point source. The temperature of the cluster gas decreases
from 9.0\pm0.5 keV down to 1.3\pm0.2 keV in the centre, with a short central
radiative cooling time of 1.0\pm0.1 Gyr, typical of a strong cool-core cluster.
The X-ray morphology in the central 100 kpc shows extended spurs of emission
from the core, a small radio cavity and a weak shock or cold front forming a
semi-circular edge at 15 arcsec radius. The quasar bolometric luminosity was
estimated to be 2 x 10^{47} erg per sec, requiring a mass accretion rate of 40
Msolar per yr, which corresponds to half the Eddington accretion rate. We
explore possible accretion mechanisms for this object and determine that Bondi
accretion, when boosted by Compton cooling of the accretion material, could
provide a significant source of the fuel for this outburst. We consider
H1821+643 in the context of a unified AGN accretion model and, by comparing
H1821+643 with a sample of galaxy clusters, we show that the quasar has not
significantly affected the large-scale cluster gas properties.Comment: 20 pages, 19 figures, accepted by MNRA
Causes of variation in BCG vaccine efficacy: examining evidence from the BCG REVAC cluster randomized trial to explore the masking and the blocking hypotheses.
BCG protection varies and in some places (nearest the equator) is low or absent. Understanding this variation can inform the efforts to develop new vaccines against tuberculosis. Two main hypotheses are used to explain this variation: under masking, new vaccines are unlikely to increase protection; under blocking new vaccines have a greater potential to be effective when BCG is not. We conducted a cluster randomized trial to explored the masking and blocking hypotheses by studying BCG vaccine efficacy of neonatal vaccination and when administered for the first or a second (revaccination) time at school age in two sites (Manaus close and Salvador further south from the equator). Seven hundred and sixty three state schools were matched on socio economic characteristics of the neighborhood and 239,934 children were randomized to vaccine (BCG vaccination at school age) or control group. Protection by first BCG vaccination at school age was high in Salvador (34%, 95% CI 7-53%, p=0.017) but low in Manaus (8%, 95% CI t0 39-40%, p=0.686). For revaccination at school age, protection was modest in Salvador (19%, 95% CI 3-33%, p=0.022) and absent in Manaus (1%, 95% CI to 27-23%, p=0.932). Vaccine efficacy for neonatal vaccination was similar in Salvador (40%, 95% CI 22-54%, p<0.001) and Manaus (36%, 95% CI 11-53%, p=0.008). Variation in BCG efficacy was marked when vaccine was given at school age but absent at birth, which points towards blocking as the dominant mechanism. New tuberculosis vaccines that overcome or by pass this blocking effect could confer protection in situations where BCG is not protective
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