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Degraded reality: Using VR/AR to simulate visual impairments
The effects of eye disease cannot be depicted accurately using traditional media. Consequently, public understanding of eye disease is often poor. We present a VR/AR system for simulating common visual impairments, including disability glare, spatial distortions (Metamorphopsia), the selective blurring and filling-in of information across the visual field, and color vision deficits. Unlike most existing simulators, the simulations are informed by patients' self-reported symptoms, can be quantitatively manipulated to provide custom disease profiles, and support gaze-contingent presentation (i.e., when using a VR/AR headset that contains eye-tracking technology, such as the Fove0). Such a simulator could be used as a teaching/empathy aid, or as a tool for evaluating the accessibility of new products and environments
The design and development of a release mechanism for space shuttle life-science experiments
The design, development, and testing of a release mechanism for use in two life science experiments on the Spacelab 1, 4, and D1 missions is described. The mechanism is a self latching ball lock device actuated by a linear solenoid. An unusual feature is the tapering of the ball lock plunger to give it a near constant breakout force for release under a wide range of loads. The selection of the design, based on the design requirements, is discussed. A number of problems occurred during development and test, including problems caused by human factors that became apparent after initial delivery for crewtraining sessions. These problems and their solutions are described to assist in the design and testing of similar mechanisms
The effect of timing noise on targeted and narrow-band coherent searches for continuous gravitational waves from pulsars
Most searches for continuous gravitational-waves from pulsars use Taylor
expansions in the phase to model the spin-down of neutron stars. Studies of
pulsars demonstrate that their electromagnetic (EM) emissions suffer from
\emph{timing noise}, small deviations in the phase from Taylor expansion
models. How the mechanism producing EM emission is related to any continuous
gravitational-wave (CW) emission is unknown; if they either interact or are
locked in phase then the CW will also experience timing noise. Any disparity
between the signal and the search template used in matched filtering methods
will result in a loss of signal-to-noise ratio (SNR), referred to as
`mismatch'. In this work we assume the CW suffers a similar level of timing
noise to its EM counterpart. We inject and recover fake CW signals, which
include timing noise generated from observational data on the Crab pulsar.
Measuring the mismatch over durations of order months, the effect is
for the most part found to be small. This suggests recent so-called
`narrow-band' searches which placed upper limits on the signals from the Crab
and Vela pulsars will not be significantly affected. At a fixed observation
time, we find the mismatch depends upon the observation epoch. Considering the
averaged mismatch as a function of observation time, we find that it increases
as a power law with time, and so may become relevant in long baseline searches.Comment: 9 pages, 5 figure
Comparing models of the periodic variations in spin-down and beam-width for PSR B1828-11
We build a framework using tools from Bayesian data analysis to evaluate
models explaining the periodic variations in spin-down and beam-width of PSR
B1828-11. The available data consists of the time averaged spin-down rate,
which displays a distinctive double-peaked modulation, and measurements of the
beam-width. Two concepts exist in the literature that are capable of explaining
these variations; we formulate predictive models from these and quantitatively
compare them. The first concept is phenomenological and stipulates that the
magnetosphere undergoes periodic switching between two meta-stable states as
first suggested by Lyne et al. The second concept, precession, was first
considered as a candidate for the modulation of B1828-11 by Stairs et al.. We
quantitatively compare models built from these concepts using a Bayesian
odds-ratio. Because the phenomenological switching model itself was informed by
this data in the first place, it is difficult to specify appropriate
parameter-space priors that can be trusted for an unbiased model comparison.
Therefore we first perform a parameter estimation using the spin-down data, and
then use the resulting posterior distributions as priors for model comparison
on the beam-width data. We find that a precession model with a simple circular
Gaussian beam geometry fails to appropriately describe the data, while allowing
for a more general beam geometry provides a good fit to the data. The resulting
odds between the precession model (with a general beam geometry) and the
switching model are estimated as in favour of the precession
model.Comment: 20 pages, 15 figures; removed incorrect factor of (2\pi) from
equation (15), allowed for arbitrary braking index, and revised prior ranges;
overall conclusions unchange
Laser velocimeter applications to high-lift research
The application of the Lockheed-Georgia 2-D laser velocimeter (LV) burst-counter system to the flow field around a 2- and 3-element high-lift airfoil is discussed. The characteristic behavior of the confluent boundary layer (that is, the boundary layer existing downstream of a slot as it approaches and undergoes separation is evaluated. In this application, the LV represents all ideal instruments for nonintrusively probing into the narrow slots and cove areas characterizing mechanical high-lift systems. The work is being performed in the Lockheed-Georgia 10 x 30-inch low-speed test facility using a 9-inch (basic) chord section of the general aviation GAW-1 airfoil. The LV system employs a 4-W argon laser and operates in an off-axis, backscatter mode with a focus length of about 30 inches. Smoke is used as the seeding medium and is injected downstream of the model such that particle uniformity and size are constant upon completion of the tunnel circuit into the test area. The LV system is fully automated by utilizing a MAC-16 minicomputer for positioning, data acquisition, and preliminary data reduction
The economics of garbage collection
This paper argues that economic theory can improve our understanding of memory management. We introduce the allocation curve, as an analogue of the demand curve from microeconomics. An allocation curve for a program characterises how the amount of garbage collection activity required during its execution varies in relation to the heap size associated with that program. The standard treatment of microeconomic demand curves (shifts and elasticity) can be applied directly and intuitively to our new allocation curves. As an application of this new theory, we show how allocation elasticity can be used to control the heap growth rate for variable sized heaps in Jikes RVM
Sixty-GHz integrated RF head Final report
Integrated 60.8 GHz RF receiver and low noise IF preamplifier developmen
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