13,429 research outputs found
Application of an On-machine Gage for Diameter Measurements
This paper describes the design analysis and application of a laser based gage made specifically for measuring parts on the machine tool to a high accuracy. The tri-beam gage uses three beams of light to measure the local curvature of the part in a manner similar to a V-block gage. The properties of this design include: calibration that is independent of the machine tool scales, non-contact damage free operation, low cost of the gage, and the ability to measure parts in motion
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Not going it alone: social integration and tenancy sustainability for formerly homeless substance users
This article draws on findings from a study of a specialised tenancy support service for homeless substance users in a Midlands city, and contributes to debates about what makes solutions to homelessness sustainable. Two approaches to tenancy support are examined: first, a resettlement model based on risk management; and second, a restorative model which prioritises support that enables people to rebuild their lives in a more holistic sense. Conclusions point to a need for a broader training for tenancy support workers and a funding level that enables them to stay with their clients long enough to facilitate this fuller restoration
Development of Moire machine vision
Three dimensional perception is essential to the development of versatile robotics systems in order to handle complex manufacturing tasks in future factories and in providing high accuracy measurements needed in flexible manufacturing and quality control. A program is described which will develop the potential of Moire techniques to provide this capability in vision systems and automated measurements, and demonstrate artificial intelligence (AI) techniques to take advantage of the strengths of Moire sensing. Moire techniques provide a means of optically manipulating the complex visual data in a three dimensional scene into a form which can be easily and quickly analyzed by computers. This type of optical data manipulation provides high productivity through integrated automation, producing a high quality product while reducing computer and mechanical manipulation requirements and thereby the cost and time of production. This nondestructive evaluation is developed to be able to make full field range measurement and three dimensional scene analysis
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Service users as peer research interviewers: why bother?
Drawing on two studies completed within the social housing sector, this chapter asks if there are advantages to peer interviewing, whereby those currently or recently receiving services interview their peers as part of a research project. Contribution is made to the broader methodological debate of how service users should be involved in research about their lives. Along with contributions from a peer interviewer, we examine the benefits to peer interviewers themselves, and whether there are any positive differences for the people being interviewed. This chapter argues that there are clear methodological advantages to peer interviewing as it can lend vital insights from rapport with those often regarded as âhardest to reachâ. The chapter also discusses peer interviewing in terms of strategic risk and limitations, as well as practical and ethical considerations. Ways of developing peer research in general are also suggested
High-Altitude Particle Acceleration and Radiation in Pulsar Slot Gaps
We explore the pulsar slot gap electrodynamics up to very high altitudes,
where for most relatively rapidly rotating pulsars both the standard
small-angle approximation and the assumption that the magnetic field lines are
ideal stream lines break down. We address the importance of the electrodynamic
conditions at the slot gap boundaries and the occurrence of a steady-state
drift of charged particles across the slot gap field lines at very high
altitudes. These boundary conditions and the deviation of particle trajectories
from stream lines determine the asymptotic behavior of the scalar potential at
all radii from the polar cap to near the light cylinder. As a result, we
demonstrate that the steady-state accelerating electric field must approach a
small and constant value at high altitude above the polar cap. This parallel
electric field is capable of maintaining electrons moving with high Lorentz
factors (a few times 10^7) and emitting curvature gamma-ray photons up to
nearly the light cylinder. By numerical simulations, we show that primary
electrons accelerating from the polar cap surface to high altitude in the slot
gap along the outer edge of the open field region will form caustic emission
patterns on the trailing dipole field lines. Acceleration and emission in such
an extended slot gap may form the physical basis of a model that can
successfully reproduce some pulsar high-energy light curves.Comment: 26 pages, 2 figures, to appear in the Astrophysical Journal, May 10,
200
Photon Splitting in Magnetar Models of Soft Gamma Repeaters
The recent association of soft gamma repeaters (SGRs) with counterparts in
other wavebands has sparked much interest in these sources. One of the recent
models for these objects is that they originate in the environs of neutron
stars with fields much stronger than the quantum critical field
\teq{B_{cr}=4.413\times 10^{13}} Gauss. Near such neutron stars, dubbed
magnetars, the exotic quantum process of magnetic photon splitting becomes
prolific. Its principal effect is to degrade photon energies and thereby soften
gamma-ray spectra from neutron stars; it has recently been suggested that
splitting may be responsible for limiting the hardness of emission in SGRs, if
these sources originate in neutron stars with supercritical surface fields.
Seed photons in supercritical fields efficiently generate soft gamma-ray
spectra, typical of repeaters. In this paper, the influence of the curved
dipole field geometry of a neutron star magnetosphere on the photon splitting
rate is investigated. The dependence of the attenuation length on the location
and angular direction of the seed photons is explored.Comment: 5 pages including 3 encapsulated figures, as a compressed, uuencoded,
Postscript file. To appear in Proc. of the 1995 La Jolla workshop ``High
Velocity Neutron Stars and Gamma-Ray Bursts'' eds. Rothschild, R. et al.,
AIP, New Yor
A Photon Splitting Cascade Model of Soft Gamma-Ray Repeaters
The spectra of soft gamma-ray repeaters (SGRs), with the exception of the
March 5, 1979 main burst, are characterized by high-energy cutoffs around 30
keV and low-energy turnovers that are much steeper than a Wien spectrum. Baring
(1995) found that the spectra of cascades due to photon splitting in a very
strong, homogeneous magnetic field can soften spectra and produce good fits to
the soft spectra of SGRs. Magnetic field strengths somewhat above the QED
critical field strength , where
G, is required to produce cutoffs at 30-40 keV. We have improved upon this
model by computing Monte Carlo photon splitting cascade spectra in a neutron
star dipole magnetic field, including effects of curved space-time in a
Schwarzschild metric. We investigate spectra produced by photons emitted at
different locations and observer angles. We find that the general results of
Baring hold for surface emission throughout most of the magnetosphere, but that
emission in equatorial regions can best reproduce the constancy of SGR spectra
observed from different bursts.Comment: 5 pages in LATEX using REVTEX aipbook.sty + 4 figures (uuencoded,
compressed postscript), to appear in the proceedings of the Third Huntsville
Workshop on Gamma-Ray Bursts, eds. C. Kouveliotou, M. S. Briggs and G. J.
Fishman (New York, AIP
A New Class of Radio Quiet Pulsars
The complete absence of radio pulsars with periods exceeding a few seconds
has lead to the popular notion of the existence of a high death line. In
the standard picture, beyond this boundary, pulsars with low spin rates cannot
accelerate particles above the stellar surface to high enough energies to
initiated pair cascades through curvature radiation, and the pair creation
needed for radio emission is strongly suppressed. In this paper we postulate
the existence of another pulsar ``death line,'' corresponding to high magnetic
fields in the upper portion of the -- diagram, a domain where
few radio pulsars are observed. The origin of this high boundary, which
occurs when becomes comparable to or exceeds Gauss, is again due
to the suppression of magnetic pair creation , but in this
instance, primarily because of ineffective competition with the exotic QED
process of magnetic photon splitting. This paper describes the origin, shape
and position of the new ``death line,'' above which pulsars are expected to be
radio quiet, but perhaps still X-ray and -ray bright.Comment: 5 pages, including 1 eps figure, to appear in Proc. 4th Compton
Symposium, (1997) ed. Dermer, C. D. & Kurfess, J. D. (AIP, New York
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