58,825 research outputs found
Multi-axis manual controllers: A state-of-the-art report
A literature search was carried out to examine the feasibility of a six degree of freedom hand controller. Factors addressed included related areas, approaches to manual control, applications of manual controllers, and selected studies of the human neuromuscular system. Results are presented
Design and development of a six degree of freedom hand controller
The design objectives of a six degree of freedom manual controller are discussed with emphasis on a space environment. Details covered include problems associated with a zero-g environment, the need to accommodate both 'shirt sleeve' and space suited astronauts, the combination of both manipulator operation and spacecraft flight control in a single device, and to accommodate restraints in space. A variable configuration device designed as a development tool in which rotational axes can be moved relative to one another, is described and its limitations discussed. Two additional devices were developed for concept testing. Each device combines the need for good quality with its ability achieve a wide range of adjustments
The relationship of dementia prevalence in older adults with intellectual disability (ID) to age and severity of ID
Background: Previous research has shown that adults with intellectual disability (ID) may be more at risk of developing dementia in old age than expected. However, the effect of age and ID severity on dementia prevalence rates has never been reported. We investigated the predictions that older adults with ID should have high prevalence rates of dementia that differ between ID severity groups and that the age-associated risk should be shifted to a younger age relative to the general population.
Method: A two-staged epidemiological survey of 281 adults with ID without Down syndrome (DS) aged >60 years; participants who screened positive with a memory task, informant-reported change in function or with the Dementia Questionnaire for Persons with Mental Retardation (DMR) underwent a detailed assessment. Diagnoses were made by psychiatrists according to international criteria. Prevalence rates were compared with UK prevalence and European consensus rates using standardized morbidity ratios (SMRs).
Results: Dementia was more common in this population (prevalence of 18.3%, SMR 2.77 in those aged >65 years). Prevalence rates did not differ between mild, moderate and severe ID groups. Age was a strong risk factor and was not influenced by sex or ID severity. As predicted, SMRs were higher for younger age groups compared to older age groups, indicating a relative shift in age-associated risk.
Conclusions: Criteria-defined dementia is 2ā3 times more common in the ID population, with a shift in risk to younger age groups compared to the general population
Six degree of freedom manual controls study report
The feasibility of using degree of freedom manual controls in space in an on orbit environment was determined. Several six degree of freedom controls were tested in a laboratory environment, and replica controls were used to control robot arms. The selection of six degrees of freedom as a design goal was based on the fact that six degrees are sufficient to define the location and orientation of a rigid body in space
Saturated laser fluorescence in turbulent sooting flames at high pressure
The primary objective was to develop a quantitative, single pulse, laser-saturated fluorescence (LSF) technique for measurement of radical species concentrations in practical flames. The species of immediate interest was the hydroxyl radical. Measurements were made in both turbulent premixed diffusion flames at pressures between 1 and 20 atm. Interferences from Mie scattering were assessed by doping with particles or by controlling soot loading through variation of equivalence ratio and fuel type. The efficacy of the LSF method at high pressure was addressed by comparing fluorescence and adsorption measurements in a premixed, laminar flat flame at 1-20 atm. Signal-averaging over many laser shots is sufficient to determine the local concentration of radical species in laminar flames. However, for turbulent flames, single pulse measurements are more appropriate since a statistically significant number of laser pulses is needed to determine the probability function (PDF). PDFs can be analyzed to give true average properties and true local kinetics in turbulent, chemically reactive flows
Improving CMB non-Gaussianity estimators using tracers of local structure
Local non-Gaussianity causes correlations between large scale perturbation
modes and the small scale power. The large-scale CMB signal has contributions
from the integrated Sachs Wolfe (ISW) effect, which does not correlate with the
small scale power. If this ISW contribution can be removed, the sensitivity to
local non-Gaussianity is improved. Gravitational lensing and galaxy counts can
be used to trace the ISW contribution; in particular we show that the CMB
lensing potential is highly correlated with the ISW signal. We construct a
nearly-optimal estimator for the local non-Gaussianity parameter \fnl and
investigate to what extent we can use this to decrease the variance on
{\fnl}. We show that the variance can be decreased by up to at Planck
sensitivity using galaxy counts. CMB lensing is a good bias-independent ISW
tracer for future more sensitive observations, though the fractional decrease
in variance is small if good polarization data is also available.Comment: 8 pages, 3 figures. Comments welcom
Maximization of capacity and p-norms for some product channels
It is conjectured that the Holevo capacity of a product channel \Omega
\otimes \Phi is achieved when product states are used as input. Amosov, Holevo
and Werner have also conjectured that the maximal p-norm of a product channel
is achieved with product input states. In this paper we establish both of these
conjectures in the case that \Omega is arbitrary and \Phi is a CQ or QC channel
(as defined by Holevo). We also establish the Amosov, Holevo and Werner
conjecture when \Omega is arbitrary and either \Phi is a qubit channel and p=2,
or \Phi is a unital qubit channel and p is integer. Our proofs involve a new
conjecture for the norm of an output state of the half-noisy channel I \otimes
\Phi, when \Phi is a qubit channel. We show that this conjecture in some cases
also implies additivity of the Holevo capacity
Axion-like-particle decay in strong electromagnetic backgrounds
The decay of a massive pseudoscalar, scalar and U(1) boson into an
electron-positron pair in the presence of strong electromagnetic backgrounds is
calculated. Of particular interest is the constant-crossed-field limit,
relevant for experiments that aim to measure high-energy axion-like-particle
conversion into electron-positron pairs in a magnetic field. The total
probability depends on the quantum nonlinearity parameter - a product of field
and lightfront momentum invariants. Depending on the seed particle mass,
different decay regimes are identified. In the below-threshold case, we find
the probability depends on a non-perturbative tunnelling exponent depending on
the quantum parameter and the particle mass. In the above-threshold case, we
find that when the quantum parameter is varied linearly, the probability
oscillates nonlinearly around the spontaneous decay probability. A strong-field
limit is identified in which the threshold is found to disappear. In modelling
the fall-off of a quasi-constant-crossed magnetic field, we calculate
probabilities beyond the constant limit and investigate when the decay
probability can be regarded as locally constant.Comment: 22 pages, 7 figure
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