6,398 research outputs found
Reliability analysis of semi-automatic train door systems in service on today's rolling stock of the SNCB
This article analyses the reliability of semi-automatic train door systems that are in use on today’s rolling stock of the SNCB. For the analysis several databases of the SNCB concerning both operation and maintenance were thoroughly screened. These databases are briefly explained and scaling factors are applied to compare the performance of different series of rolling stock relative to each other. Conclusions are made out of the available data
Tight Noise Thresholds for Quantum Computation with Perfect Stabilizer Operations
We study how much noise can be tolerated by a universal gate set before it
loses its quantum-computational power. Specifically we look at circuits with
perfect stabilizer operations in addition to imperfect non-stabilizer gates. We
prove that for all unitary single-qubit gates there exists a tight depolarizing
noise threshold that determines whether the gate enables universal quantum
computation or if the gate can be simulated by a mixture of Clifford gates.
This exact threshold is determined by the Clifford polytope spanned by the 24
single-qubit Clifford gates. The result is in contrast to the situation wherein
non-stabilizer qubit states are used; the thresholds in that case are not
currently known to be tight.Comment: 4 pages, 2 figure
Elastic wave propagation in confined granular systems
We present numerical simulations of acoustic wave propagation in confined
granular systems consisting of particles interacting with the three-dimensional
Hertz-Mindlin force law. The response to a short mechanical excitation on one
side of the system is found to be a propagating coherent wavefront followed by
random oscillations made of multiply scattered waves. We find that the coherent
wavefront is insensitive to details of the packing: force chains do not play an
important role in determining this wavefront. The coherent wave propagates
linearly in time, and its amplitude and width depend as a power law on
distance, while its velocity is roughly compatible with the predictions of
macroscopic elasticity. As there is at present no theory for the broadening and
decay of the coherent wave, we numerically and analytically study
pulse-propagation in a one-dimensional chain of identical elastic balls. The
results for the broadening and decay exponents of this system differ
significantly from those of the random packings. In all our simulations, the
speed of the coherent wavefront scales with pressure as ; we compare
this result with experimental data on various granular systems where deviations
from the behavior are seen. We briefly discuss the eigenmodes of the
system and effects of damping are investigated as well.Comment: 20 pages, 12 figures; changes throughout text, especially Section V.
Critical scaling in linear response of frictionless granular packings near jamming
We study the origin of the scaling behavior in frictionless granular media
above the jamming transition by analyzing their linear response. The response
to local forcing is non-self-averaging and fluctuates over a length scale that
diverges at the jamming transition. The response to global forcing becomes
increasingly non-affine near the jamming transition. This is due to the
proximity of floppy modes, the influence of which we characterize by the local
linear response. We show that the local response also governs the anomalous
scaling of elastic constants and contact number.Comment: 4 pages, 3 figures. v2: Added new results; removed part of
discussion; changed Fig.
Associations between the measures of physical function, risk of falls and the quality of life in haemodialysis patients : a cross-sectional study
Background Impaired physical function due to muscle weakness and exercise intolerance reduces the ability to perform activities of daily living in patients with end-stage kidney disease, and by consequence, Health-Related Quality of Life (HRQoL). Furthermore, the risk of falls is an aggregate of physical function and, therefore, could be associated with HRQoL as well. The present study examined the associations between objective and subjective measures of physical function, risk of falls and HRQoL in haemodialysis patients. Methods This cross-sectional multicentre study included patients on maintenance haemodialysis. Physical function (quadriceps force, handgrip force, Sit-to-Stand, and six-minute walking test), the risk of falls (Tinetti, FICSIT-4, and dialysis fall index) and HRQoL (PROMIS-29 and EQ-5D-3 L) were measured and analysed descriptively, by general linear models and logistic regression. Results Of the 113 haemodialysis patients (mean age 67.5 +/- 16.1, 57.5% male) enrolled, a majority had impaired quadriceps force (86.7%) and six-minute walking test (92%), and an increased risk of falls (73.5%). Whereas muscle strength and exercise capacity were associated with global HRQoL (R-2 = 0.32) and the risk of falls, the risk of falls itself was related to psycho-social domains (R-2 = 0.11) such as depression and social participation, rather than to the physical domains of HRQoL. Objective measures of physical function were not associated with subjective fatigue, nor with subjective appreciation of health status. Conclusions More than muscle strength, lack of coordination and balance as witnessed by the risk of falls contribute to social isolation and HRQoL of haemodialysis patients. Mental fatigue was less common than expected, whereas, subjective and objective physical function were decreased
Emerging Hepatitis E viruses from swine in Europe
Hepatitis E virus (HEV) is endemic in much of the developing world. Infections in humans can resulte of acute hepatitis and especially in pregnant women the infection may cause serious complications. The most important route of transmission is faecal-orally, and HEV disease outbreaks are often associated with contaminated drinking water or poor hygienic conditions
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