13,007 research outputs found
Aluminum chlorine battery Quarterly report
High energy density battery based on aluminum and chlorine carbon electrode
The new Section 23 of DO160C/ED14C lightning testing of externally mounted electrical equipment
The new Section 23 is introduced which has only very recently been fully approved by the RTCA for incorporation into the first revision of DO160C/ED14C. Full threat lightning direct effects testing of equipment is entirely new to DO160, the only existing lightning testing is transient testing for LRU's (Line Replaceable Units) by pin or cable bundle injection methods, for equipment entirely contained within the airframe and assumed to be unaffected by direct effects. This testing required transients of very low amplitude compared with lightning itself, whereas the tests now to be described involve full threat lightning testing, that is using the previously established severe parameters of lightning appropriate to the Zone, such as 200 kA for Zone 1A as in AC20-136. Direct effects (i.e., damage) testing involves normally the lightning current arc attaching to the object under test (or very near to it) so submitting it to full potential for the electric, mechanical, thermal and shock damage which is caused by high current arcing. Since equipment for any part of the airframe require qualification, tests to demonstrate safety of equipment in fuel vapor regions of the airframe are also included
Comment on "Pulsar Velocities and Neutrino Oscillations"
In a recent Letter, Kusenko and Segre proposed a new mechanism to explain the
observed proper motions of pulsars. Their mechanism was based on the asymmetric
neutrino emission induced by neutrino oscillations in the protoneutron star
magnetic field. In this note I point out that their estimate of the asymmetry
in the neutrino emission is incorrect. A proper calculation shows that their
mechanism at least requires a magnetic field of 10**16 G in order to produce
the observed average pulsar velocity.Comment: 4 pages, RevTe
Summary of Discussion Question 4: Energy Expandability of a Linear Collider
We report on Discussion Question 4, in Sub-group 1 (`TeV-class') of the
Snowmass Working Group E3: `Experimental Approaches: Linear Colliders', which
addresses the energy expandability of a linear collider. We first synthesize
discussions of the energy reach of the hardware of the 500 GeV designs for
TESLA and NLC/JLC. Next, we review plans for increasing the energy to 800-1000
GeV. We then look at options for expanding the energies to 1500 GeV and sketch
the two-beam accelerator approach to achieving multi-TeV energies.Comment: Presented at Snowmass 2001 (6 pages, 2 figures
Theory for the Secondary Eclipse Fluxes, Spectra, Atmospheres, and Light Curves of Transiting Extrasolar Giant Planets
We have created a general methodology for calculating the
wavelength-dependent light curves of close-in extrasolar giant planets (EGPs)
as they traverse their orbits. Focussing on the transiting EGPs HD189733b,
TrES-1, and HD209458b, we calculate planet/star flux ratios during secondary
eclipse and compare them with the Spitzer data points obtained so far in the
mid-infrared. We introduce a simple parametrization for the redistribution of
heat to the planet's nightside, derive constraints on this parameter (P_n), and
provide a general set of predictions for planet/star contrast ratios as a
function of wavelength, model, and phase. Moreover, we calculate average
dayside and nightside atmospheric temperature/pressure profiles for each
transiting planet/P_n pair with which existing and anticipated Spitzer data can
be used to probe the atmospheric thermal structure of severely irradiated EGPs.
We find that the baseline models do a good job of fitting the current secondary
eclipse dataset, but that the Spitzer error bars are not yet small enough to
discriminate cleanly between all the various possibilities.Comment: 14 figures, 7 text pages (in two-column emulateapj format); Accepted
to the Ap.J. June 26, 2006; one cosmetic change made to astro-ph version
Should One Use the Ray-by-Ray Approximation in Core-Collapse Supernova Simulations?
We perform the first self-consistent, time-dependent, multi-group
calculations in two dimensions (2D) to address the consequences of using the
ray-by-ray+ transport simplification in core-collapse supernova simulations.
Such a dimensional reduction is employed by many researchers to facilitate
their resource-intensive calculations. Our new code (F{\sc{ornax}}) implements
multi-D transport, and can, by zeroing out transverse flux terms, emulate the
ray-by-ray+ scheme. Using the same microphysics, initial models, resolution,
and code, we compare the results of simulating 12-, 15-, 20-, and
25-M progenitor models using these two transport methods. Our
findings call into question the wisdom of the pervasive use of the ray-by-ray+
approach. Employing it leads to maximum post-bounce/pre-explosion shock radii
that are almost universally larger by tens of kilometers than those derived
using the more accurate scheme, typically leaving the post-bounce matter less
bound and artificially more "explodable." In fact, for our 25-M
progenitor, the ray-by-ray+ model explodes, while the corresponding multi-D
transport model does not. Therefore, in two dimensions the combination of
ray-by-ray+ with the axial sloshing hydrodynamics that is a feature of 2D
supernova dynamics can result in quantitatively, and perhaps qualitatively,
incorrect results.Comment: Updated and revised text; 13 pages; 13 figures; Accepted to Ap.
Probing the galactic halo with ROSAT
We discuss the current status of ROSAT shadowing observations designed to search for emission from million degree gas in the halo of the Milky Way galaxy. Preliminary results indicate that million degree halo gas is observed in the 1/4 keV band in some directions, most notably toward the Draco cloud at (l,b) = (92 deg, +38 deg), but that the halo emission is patchy and highly anisotropic. Our current understanding of this halo emission is based on a small handful of observations which have been analyzed to date. Many more observations are currently being analyzed or are scheduled for observation within the next year, and we expect our understanding of this component of the galactic halo to improve dramatically in the near future
Dimension as a Key to the Neutrino Mechanism of Core-Collapse Supernova Explosions
We explore the dependence on spatial dimension of the viability of the
neutrino heating mechanism of core-collapse supernova explosions. We find that
the tendency to explode is a monotonically increasing function of dimension,
with 3D requiring 4050\% lower driving neutrino luminosity than 1D and
1525\% lower driving neutrino luminosity than 2D. Moreover, we find
that the delay to explosion for a given neutrino luminosity is always shorter
in 3D than 2D, sometimes by many hundreds of milliseconds. The magnitude of
this dimensional effect is much larger than the purported magnitude of a
variety of other effects, such as nuclear burning, inelastic scattering, or
general relativity, which are sometimes invoked to bridge the gap between the
current ambiguous and uncertain theoretical situation and the fact of robust
supernova explosions. Since real supernovae occur in three dimensions, our
finding may be an important step towards unraveling one of the most problematic
puzzles in stellar astrophysics. In addition, even though in 3D we do see
pre-explosion instabilities and blast asymmetries, unlike the situation in 2D,
we do not see an obvious axially-symmetric dipolar shock oscillation. Rather,
the free energy available to power instabilites seems to be shared by more and
more degrees of freedom as the dimension increases. Hence, the strong dipolar
axisymmetry seen in 2D and previously identified as a fundamental
characteristic of the shock hydrodynamics may not survive in 3D as a prominent
feature.Comment: Accepted to ApJ July 7th, Replaced with accepted versio
Mentoring in acute stroke : evaluation of an information provision strategy for stroke survivors and carers
University of Technology, Sydney. Faculty of Nursing, Midwifery and Health.Stroke survivors and their carers face a multitude of challenges. Literature suggests the need for new approaches to address an identified lack in the provision of information following discharge from hospital. This exploratory study evaluates the effects of a program using stroke survivors and their carers (defined as mentors) to provide information on available services and resources to current stroke in-patients and their carers in an acute setting. Mentoring has been successfully used in breast cancer, ischaemic heart disease and traumatic brain injury but an extensive literature search has found no evidence of evaluation of this form of intervention in acute stroke.
Using Fourth Generation Evaluation and mixed methods, data was collected from three stakeholder groups. Semi structured interviews were conducted with the inpatients and carers at 48hrs and 4 weeks post meeting the mentors. Data was transcribed and thematically analysed and the primary themes identified were: there is life after stroke, providing hope and understanding, and easing the burden of stroke. Focus groups (4) conducted with the mentors (3) and members of the Acute Stroke Team (1) were used to identify claims, concerns and issues. Mentors identified that the experience was beneficial for them and that they gained personal growth from the experience. The Acute Stroke Team identified positive aspects of the program and provided valuable input into the development of an agenda for future programs. This research confirms that mentoring can provide positive benefits for stroke survivors and their carers
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