3,608 research outputs found
Sign Language Fingerspelling Classification from Depth and Color Images using a Deep Belief Network
Automatic sign language recognition is an open problem that has received a
lot of attention recently, not only because of its usefulness to signers, but
also due to the numerous applications a sign classifier can have. In this
article, we present a new feature extraction technique for hand pose
recognition using depth and intensity images captured from a Microsoft Kinect
sensor. We applied our technique to American Sign Language fingerspelling
classification using a Deep Belief Network, for which our feature extraction
technique is tailored. We evaluated our results on a multi-user data set with
two scenarios: one with all known users and one with an unseen user. We
achieved 99% recall and precision on the first, and 77% recall and 79%
precision on the second. Our method is also capable of real-time sign
classification and is adaptive to any environment or lightning intensity.Comment: Published in 2014 Canadian Conference on Computer and Robot Visio
The Implications of Gunn-Peterson Troughs in the HeII Lyman-alpha Forest
Many experts believe that the z ~ 3 HeII Ly-alpha forest will suffer from the
same saturation issues as the z ~ 6 HI Ly-alpha forest and, therefore, will not
be a sensitive probe of HeII reionization. However, there are several factors
that make HeII Ly-alpha absorption more sensitive than HI Ly-alpha. We show
that observations of HeII Ly-alpha and Ly-beta Gunn-Peterson troughs can
provide a relatively model-independent constraint on the volume-averaged HeII
fraction of x_HeII >~ 0.1. This bound derives from first using the most
underdense regions in the HeII forest to constrain the local HeII fraction and,
then, assuming photoionization equilibrium with the maximum allowed
photoionization rate to calculate the ionization state of nearby gas. It is
possible to evade this constraint by a factor of ~2, but only if the HeII were
reionized recently. We argue that HeII Ly-alpha Gunn-Peterson troughs observed
in the spectra of Q0302-003 and HE2347-4342 signify the presence of >~ 10
comoving Mpc patches in which x_HeII > 0.03. This is a factor of 20 improvement
over previous constraints from these spectra and 100 times stronger than the
tightest constraint on the HI volume-filling fraction from the z>6 HI Lyman
forest.Comment: 5 pages, 4 figures, includes some supplementary text not in ApJ
Letter versio
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