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Investigating the Intelligibility of a Computer Vision System for Blind Users
Computer vision systems to help blind usersare becoming increasingly common yet often these systems are not intelligible. Our work investigates the intelligibility of a wearable computer vision system to help blind users locate and identify people in their vicinity. Providing a continuous stream of information, this system allows us to explore intelligibility through interaction and instructions, going beyond studies of intelligibility that focus on explaining a decision a computer vision system might make. In a study with 13 blind users, we explored whether varying instructions (either basic or enhanced) about how the system worked would change blind users’ experience of the system. We found offering a more detailed set of instructions did not affect how successful users were using the system nor their perceived workload. We did, however, find evidence of significant differences in what they knew about the system, and they employed different, and potentially more effective, use strategies. Our findings have important implications for researchers and designers of computer vision systemsfor blind users, as well more general implications for understanding what it means to make interactive computer vision systems intelligible
Edge Magnetoplasmons in Quantum Hall Line Junction Systems
A quantum Hall line junction system consists of a one-dimensional Luttinger
liquid (LL) and two chiral channels that allow density waves incident upon and
reflected by the LL to be measured separately. We demonstrate that interactions
in a quantum Hall line junction system can be probed by studying edge
magnetoplasmon absorption spectra and their polarization dependences. Strong
interactions in the junction lead to collective modes that are isolated in
either Luttinger liquid or contact subsystems.Comment: 4 pages, 3 figures, submitted to Phys. Rev. B Rapid Communicatio
Line junction in a quantum Hall system with two filling fractions
We present a microscopic model for a line junction formed by counter or
co-propagating single mode quantum Hall edges corresponding to different
filling factors. The ends of the line junction can be described by two possible
current splitting matrices which are dictated by the conditions of both lack of
dissipation and the existence of a linear relation between the bosonic fields.
Tunneling between the two edges of the line junction then leads to a
microscopic understanding of a phenomenological description of line junctions
introduced some time ago. The effect of density-density interactions between
the two edges is considered, and renormalization group ideas are used to study
how the tunneling parameter changes with the length scale. This leads to a
power law variation of the conductance of the line junction with the
temperature. Depending on the strength of the interactions the line junction
can exhibit two quite different behaviors. Our results can be tested in bent
quantum Hall systems fabricated recently.Comment: 9 pages including 4 figure
\u3ci\u3eAmbystoma maculatum\u3c/i\u3e (Spotted Salamander) Occurrence
Natural History Notes: Ambystoma maculatum is a wide ranging mole salamander found from Nova Scotia and southern Ontario through Georgia and eastern Texas (Conant and Collins 1998)
Experiments on the Fermi to Tomonaga-Luttinger liquid transition in quasi-1D systems
We present experimental results on the tunneling into the edge of a two
dimensional electron gas (2DEG) obtained with GaAs/AlGaAs cleaved edge
overgrown structures. The electronic properties of the edge of these systems
can be described by a one-dimensional chiral Tomonaga-Luttinger liquid when the
filling factor of the 2DEG is very small. Here we focus on the region where the
Tomonaga-Luttinger liquid breaks down to form a standard Fermi liquid close to
and show that we recover a universal curve, which describes all
existing data.Comment: 5 pages, localisation 2002, conference proceeding
Real rank boundaries and loci of forms
In this article we study forbidden loci and typical ranks of forms with
respect to the embeddings of given by the line
bundles . We introduce the Ranestad-Schreyer locus corresponding to
supports of non-reduced apolar schemes. We show that, in those cases, this is
contained in the forbidden locus. Furthermore, for these embeddings, we give a
component of the real rank boundary, the hypersurface dividing the minimal
typical rank from higher ones. These results generalize to a class of
embeddings of . Finally, in connection with real
rank boundaries, we give a new interpretation of the
hyperdeterminant.Comment: 17 p
Smoothing a Rock by Chipping
We investigate an idealized model for the size reduction and smoothing of a
polygonal rock due to repeated chipping at corners. Each chip is sufficiently
small so that only a single corner and a fraction of its two adjacent sides are
cut from the object in a single chipping event. After many chips have been cut
away, the resulting shape of the rock is generally anisotropic, with facet
lengths and corner angles distributed over a broad range. Although a
well-defined shape is quickly reached for each realization, there are large
fluctuations between realizations.Comment: 7 pages, 10 figures, 2-column revtex4 format; version 2: final
published form in PRE; contains minor changes in response to referee comment
Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells
A doping series of AlAs (001) quantum wells with Si delta-modulation doping
on both sides reveals different dark and post-illumination saturation
densities, as well as temperature dependent photoconductivity. The lower dark
two-dimensional electron density saturation is explained assuming deep binding
energy of Delta_DK = 65.2 meV for Si-donors in the dark. Persistent
photoconductivity (PPC) is observed upon illumination, with higher saturation
density indicating shallow post-illumination donor binding energy. The
photoconductivity is thermally activated, with 4 K illumination requiring
post-illumination annealing to T = 30 K to saturate the PPC. Dark and
post-illumination doping efficiencies are reported.Comment: The values of binding energy changed from previous versions because
of a better understanding for the dielectric permittivity. Also, the Gamma -
X donor states are better explaine
Fermi liquid to Luttinger liquid transition at the edge of a two-dimensional electron gas
We present experimental results on the tunneling into the edge of a two
dimensional electron gas (2DEG) obtained with a GaAs/AlGaAs cleaved edge
overgrown structure in a strong perpendicular magnetic field. While the 2DEG
exhibits typical fractional quantum Hall features of a very high mobility
sample, we observe the onset of a non-linear current-voltage characteristic in
the vicinity of nu=1. For filling factor nu<1 the system is consistent with a
non-Fermi liquid behavior, such as a Luttinger liquid, whereas for nu>1 we
observe an Ohmic tunneling resistance between the edge and a three dimensional
contact, typical for a Fermi liquid. Hence, at the edge, there is a transition
from a Luttinger liquid to a Fermi liquid. Finally, we show that the Luttinger
liquid exponent at a given filling factor is not universal but depends on
sample parameters.Comment: 4 pages, 4 figure
Nanometer-scale sharpness in corner-overgrown heterostructures
A corner-overgrown GaAs/AlGaAs heterostructure is investigated with
transmission and scanning transmission electron microscopy, demonstrating
self-limiting growth of an extremely sharp corner profile of 3.5 nm width. In
the AlGaAs layers we observe self-ordered diagonal stripes, precipitating
exactly at the corner, which are regions of increased Al content measured by an
XEDS analysis. A quantitative model for self-limited growth is adapted to the
present case of faceted MBE growth, and the corner sharpness is discussed in
relation to quantum confined structures. We note that MBE corner overgrowth
maintains nm-sharpness even after microns of growth, allowing the realization
of corner-shaped nanostructures.Comment: 4 pages, 3 figure
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