8,769 research outputs found
Safety management of a complex R and D ground operating system
A perspective on safety program management was developed for a complex R&D operating system, such as the NASA-Lewis Research Center. Using a systems approach, hazardous operations are subjected to third-party reviews by designated-area safety committees and are maintained under safety permit controls. To insure personnel alertness, emergency containment forces and employees are trained in dry-run emergency simulation exercises. The keys to real safety effectiveness are top management support and visibility of residual risks
Global gyrokinetic simulations of ITG turbulence in the configuration space of the Wendelstein 7-X stellarator
We study the effect of turbulent transport in different magnetic
configurations of the Weldenstein 7-X stellarator. In particular, we performed
direct numerical simulations with the global gyrokinetic code GENE-3D, modeling
the behavior of Ion Temperature Gradient turbulence in the Standard,
High-Mirror, and Low-Mirror configurations of W7-X. We found that the
Low-Mirror configuration produces more transport than both the High-Mirror and
the Standard configurations. By comparison with radially local simulations, we
have demonstrated the importance of performing global nonlinear simulations to
predict the turbulent fluxes quantitatively
Homothetic Wyman Spacetimes
The time-dependent, spherically symmetric, Wyman sector of the Unified Field
Theory is shown to be equivalent to a self-gravitating scalar field with a
positive-definite, repulsive self-interaction potential. A homothetic symmetry
is imposed on the fundamental tensor, and the resulting autonomous system is
numerically integrated. Near the critical point (between the collapsing and
non-collapsing spacetimes) the system displays an approximately periodic
alternation between collapsing and dispersive epochs.Comment: 15 pages with 6 figures; requires amsart, amssymb, amsmath, graphicx;
formatted for publication in Int. J. Mod. Phys.
Vortex spectrum in superfluid turbulence: interpretation of a recent experiment
We discuss a recent experiment in which the spectrum of the vortex line
density fluctuations has been measured in superfluid turbulence. The observed
frequency dependence of the spectrum, , disagrees with classical
vorticity spectra if, following the literature, the vortex line density is
interpreted as a measure of the vorticity or enstrophy. We argue that the
disagrement is solved if the vortex line density field is decomposed into a
polarised field (which carries most of the energy) and an isotropic field
(which is responsible for the spectrum).Comment: Submitted for publication
http://crtbt.grenoble.cnrs.fr/helio/GROUP/infa.html
http://www.mas.ncl.ac.uk/~ncfb
Quantification of finite-temperature effects on adsorption geometries of -conjugated molecules
The adsorption structure of the molecular switch azobenzene on Ag(111) is
investigated by a combination of normal incidence x-ray standing waves and
dispersion-corrected density functional theory. The inclusion of non-local
collective substrate response (screening) in the dispersion correction improves
the description of dense monolayers of azobenzene, which exhibit a substantial
torsion of the molecule. Nevertheless, for a quantitative agreement with
experiment explicit consideration of the effect of vibrational mode
anharmonicity on the adsorption geometry is crucial.Comment: 12 pages, 3 figure
Linking Classical and Quantum Key Agreement: Is There "Bound Information"?
After carrying out a protocol for quantum key agreement over a noisy quantum
channel, the parties Alice and Bob must process the raw key in order to end up
with identical keys about which the adversary has virtually no information. In
principle, both classical and quantum protocols can be used for this
processing. It is a natural question which type of protocols is more powerful.
We prove for general states but under the assumption of incoherent
eavesdropping that Alice and Bob share some so-called intrinsic information in
their classical random variables, resulting from optimal measurements, if and
only if the parties' quantum systems are entangled. In addition, we provide
evidence that the potentials of classical and of quantum protocols are equal in
every situation. Consequently, many techniques and results from quantum
information theory directly apply to problems in classical information theory,
and vice versa. For instance, it was previously believed that two parties can
carry out unconditionally secure key agreement as long as they share some
intrinsic information in the adversary's view. The analysis of this purely
classical problem from the quantum information-theoretic viewpoint shows that
this is true in the binary case, but false in general. More explicitly, bound
entanglement, i.e., entanglement that cannot be purified by any quantum
protocol, has a classical counterpart. This "bound intrinsic information"
cannot be distilled to a secret key by any classical protocol. As another
application we propose a measure for entanglement based on classical
information-theoretic quantities.Comment: Accepted for Crypto 2000. 17 page
Linearisation Instabilities of the Massive Nonsymmetric Gravitational Theory
The massive nonsymmetric gravitational theory is shown to posses a
linearisation instability at purely GR field configurations, disallowing the
use of the linear approximation in these situations. It is also shown that
arbitrarily small antisymmetric sector Cauchy data leads to singular evolution
unless an ad hoc condition is imposed on the initial data hypersurface.Comment: 14 pages, IOP style for submission to CQG. Minor changes and
additional background material adde
ESC CardioMed
Reprinted with permission from: Eur Heart J. 2018; 19: 959–961Reprinted with permission from: Eur Heart J. 2018; 19: 959–96
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