10,953 research outputs found
The Feeling of Color: A Haptic Feedback Device for the Visually Disabled
Tapson J, Gurari N, Diaz J, et al. The Feeling of Color: A Haptic Feedback Device for the Visually Disabled. Presented at the Biomedical Circuits and Systems Conference (BIOCAS), Baltimore, MD.We describe a sensory augmentation system designed to provide the visually disabled with a sense of color. Our system consists of a glove with short-range optical color sensors mounted on its fingertips, and a torso-worn belt on which tactors (haptic feedback actuators) are mounted. Each fingertip sensor detects the observed objectpsilas color. This information is encoded to the tactor through vibrations in respective locations and varying modulations. Early results suggest that detection of primary colors is possible with near 100% accuracy and moderate latency, with a minimum amount of training
The Accuracy of Perturbative Master Equations
We consider open quantum systems with dynamics described by master equations
that have perturbative expansions in the system-environment interaction. We
show that, contrary to intuition, full-time solutions of order-2n accuracy
require an order-(2n+2) master equation. We give two examples of such
inaccuracies in the solutions to an order-2n master equation: order-2n
inaccuracies in the steady state of the system and order-2n positivity
violations, and we show how these arise in a specific example for which exact
solutions are available. This result has a wide-ranging impact on the validity
of coupling (or friction) sensitive results derived from second-order
convolutionless, Nakajima-Zwanzig, Redfield, and Born-Markov master equations.Comment: 6 pages, 0 figures; v2 updated references; v3 updated references,
extension to full-time and nonlocal regime
The Field White Dwarf Mass Distribution
We revisit the properties and astrophysical implications of the field white
dwarf mass distribution in preparation of Gaia applications. Our study is based
on the two samples with the best established completeness and most precise
atmospheric parameters, the volume-complete survey within 20 pc and the Sloan
Digital Sky Survey (SDSS) magnitude-limited sample. We explore the modelling of
the observed mass distributions with Monte Carlo simulations, but find that it
is difficult to constrain independently the initial mass function (IMF), the
initial-to-final-mass relation (IFMR), the stellar formation history (SFH), the
variation of the Galactic disk vertical scale height as a function of stellar
age, and binary evolution. Each of these input ingredients has a moderate
effect on the predicted mass distributions, and we must also take into account
biases owing to unidentified faint objects (20 pc sample), as well as unknown
masses for magnetic white dwarfs and spectroscopic calibration issues (SDSS
sample). Nevertheless, we find that fixed standard assumptions for the above
parameters result in predicted mean masses that are in good qualitative
agreement with the observed values. It suggests that derived masses for both
studied samples are consistent with our current knowledge of stellar and
Galactic evolution. Our simulations overpredict by 40-50% the number of massive
white dwarfs (M > 0.75 Msun) for both surveys, although we can not exclude a
Salpeter IMF when we account for all biases. Furthermore, we find no evidence
of a population of double white dwarf mergers in the observed mass
distributions.Comment: 15 pages, 16 figures, accepted for publication in MNRA
Supervised vs. Unsupervised Learning for Operator State Modeling in Unmanned Vehicle Settings
In this paper, we model operator states using hidden Markov models applied to human supervisory control behaviors. More specifically, we model the behavior of an operator of multiple heterogeneous unmanned vehicle systems. The hidden Markov model framework allows the inference of higher operator states from observable operator interaction with a computer interface. For example, a sequence of operator actions can be used to compute a probability distribution of possible operator states. Such models are capable of detecting deviations from expected operator behavior as learned by the model.The difficulty with parametric inference models such as hidden Markov models is that a large number of parameters must either be specified by hand or learned from example data.We compare the behavioral
models obtained with two different supervised learning techniques and an unsupervised hidden Markov model training technique. The results suggest that the best models of human supervisory control behavior are obtained through unsupervised learning. We conclude by presenting further extensions to this work.This research was supported by Boeing Phantom Works
Discovery, Isolation and Characterisation of Promoters from Perennial Ryegrass (\u3ci\u3eLolium Perenne\u3c/i\u3e)
The availability of a suite of promoters with a range of spatial, temporal and inducible expression patterns is of significant importance to enable targeted expression of genes of interest for molecular breeding of forage species. A range of resources and tools have been developed for promoter isolation and characterisation in perennial ryegrass (Lolium perenne L.) including genomic lambda and BAC libraries and a 15 K unigene microarray
The early X-ray afterglows of optically bright and dark Gamma-Ray Bursts
A systematical study on the early X-ray afterglows of both optically bright
and dark gamma-ray bursts (B-GRBs and D-GRBs) observed by Swift has been
presented. Our sample includes 25 GRBs. Among them 13 are B-GRBs and 12 are
D-GRBs. Our results show that the distributions of the X-ray afterglow fluxes
(), the gamma-ray fluxes (), and the ratio ()
for both the D-GRBs and B-GRBs are similar. The differences of these
distributions for the two kinds of GRBs should be statistical fluctuation.
These results indicate that the progenitors of the two kinds of GRBs are the
same population. Their total energy explosions are comparable. The suppression
of the optical emissions from D-GRBs should results from circumburst but not
their central engine.Comment: 10 pages, 3 figures, 1 table; accepted by ChJA
Method for fabricating a low stress x-ray mask using annealable amorphous refractory compounds
X‐ray masks have been fabricated by depositing a compressively stressed refractory material on a wafer, annealing to a zero stress state, and then forming the membrane. Amorphous TaSiN and TaSi alloys deposited with a magnetron sputter tool have been extensively characterized in terms of resistivity, composition, defectivity, surface roughness, and crystalline state. Optimization in terms of these parameters has resulted in base line selection of absorber films of the following compositions: Ta_(61)Si_(17)N_(21) and Ta_(75)Si_(23). The process is shown to be extendable to an entire class of amorphous annealable refractory materials. Careful studies of deposition and annealing conditions have resulted in a 4× reduction of image placement to the 30 nm maximum vector level. Finally, the importance of stress gradients is experimentally verified
Analytical model of non-Markovian decoherence in donor-based charge quantum bits
We develop an analytical model for describing the dynamics of a donor-based
charge quantum bit (qubit). As a result, the quantum decoherence of the qubit
is analytically obtained and shown to reveal non-Markovian features: The
decoherence rate varies with time and even attains negative values, generating
a non-exponential decay of the electronic coherence and a later recoherence.
The resulting coherence time is inversely proportional to the temperature, thus
leading to low decoherence below a material dependent characteristic
temperature.Comment: 19 pages, 3 figure
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