9,425 research outputs found
Development of a fault-tolerant microprocessor based computer system for space flight
A methodology for the design of a tightly coupled, highly reliable microprocessor based computer system is described. The concept of triple modular redundancy with sparing is used. The notion of synchronizing by using a single crystal oscillator is examined. The use of decoders to replace voters is also used. The decoders not only isolate the failed module but also allow error identification to be accomplished. Each module is to have its own RAM memory. The necessary circuitry to select a correct memory and the corresponding DMA controller was designed
Toroidal Vortices in Resistive Magnetohydrodynamic Equilibria
Resistive steady states in toroidal magnetohydrodynamics (MHD), where Ohm's
law must be taken into account, differ considerably from ideal ones. Only for
special (and probably unphysical) resistivity profiles can the Lorentz force,
in the static force-balance equation, be expressed as the gradient of a scalar
and thus cancel the gradient of a scalar pressure. In general, the Lorentz
force has a curl directed so as to generate toroidal vorticity. Here, we
calculate, for a collisional, highly viscous magnetofluid, the flows that are
required for an axisymmetric toroidal steady state, assuming uniform scalar
resistivity and viscosity. The flows originate from paired toroidal vortices
(in what might be called a ``double smoke ring'' configuration), and are
thought likely to be ubiquitous in the interior of toroidally driven
magnetofluids of this type. The existence of such vortices is conjectured to
characterize magnetofluids beyond the high-viscosity limit in which they are
readily calculable.Comment: 17 pages, 4 figure
Chow's theorem and universal holonomic quantum computation
A theorem from control theory relating the Lie algebra generated by vector
fields on a manifold to the controllability of the dynamical system is shown to
apply to Holonomic Quantum Computation. Conditions for deriving the holonomy
algebra are presented by taking covariant derivatives of the curvature
associated to a non-Abelian gauge connection. When applied to the Optical
Holonomic Computer, these conditions determine that the holonomy group of the
two-qubit interaction model contains . In particular, a
universal two-qubit logic gate is attainable for this model.Comment: 13 page
The influence of relatives on the efficiency and error rate of familial searching
We investigate the consequences of adopting the criteria used by the state of
California, as described by Myers et al. (2011), for conducting familial
searches. We carried out a simulation study of randomly generated profiles of
related and unrelated individuals with 13-locus CODIS genotypes and YFiler
Y-chromosome haplotypes, on which the Myers protocol for relative
identification was carried out. For Y-chromosome sharing first degree
relatives, the Myers protocol has a high probability (80 - 99%) of identifying
their relationship. For unrelated individuals, there is a low probability that
an unrelated person in the database will be identified as a first-degree
relative. For more distant Y-haplotype sharing relatives (half-siblings, first
cousins, half-first cousins or second cousins) there is a substantial
probability that the more distant relative will be incorrectly identified as a
first-degree relative. For example, there is a 3 - 18% probability that a first
cousin will be identified as a full sibling, with the probability depending on
the population background. Although the California familial search policy is
likely to identify a first degree relative if his profile is in the database,
and it poses little risk of falsely identifying an unrelated individual in a
database as a first-degree relative, there is a substantial risk of falsely
identifying a more distant Y-haplotype sharing relative in the database as a
first-degree relative, with the consequence that their immediate family may
become the target for further investigation. This risk falls disproportionately
on those ethnic groups that are currently overrepresented in state and federal
databases.Comment: main text: 19 pages, 4 tables, 2 figures supplemental text: 2 pages,
5 tables all together as single fil
Anisotropy in MHD turbulence due to a mean magnetic field
The development of anisotropy in an initially isotropic spectrum is studied numerically for two-dimensional magnetohydrodynamic turbulence. The anisotropy develops due to the combined effects of an externally imposed dc magnetic field and viscous and resistive dissipation at high wave numbers. The effect is most pronounced at high mechanical and magnetic Reynolds numbers. The anisotropy is greater at the higher wave numbers
Humanizing critical care
Sleep is important for human neurocognitive, emotional and physical health. Increasing evidence shows that the intensive care unit environment is disruptive to sleep patterns. Such disruption is unpleasant to patients, but mounting evidence suggests that it may also worsen outcome. However, improvements in the patient experience are readily obtained through simple measures such as the use of eyepads and earplugs. Early data suggest that such interventions are not only kind, but may impact on patient outcomes such as delirium rates
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