7,494 research outputs found
Early Air Force Flight Test Center (AFFTC) experience with Peripheral Vision Horizon Displays (PVHD)
Three separate Air Force Flight Test Center (AFFTC) tests were conducted in 1980 and 1981 on two models of the peripheral vision horizon displays (PVHD) (Malcolm Horizon). A fixed base simulator test was conducted with twenty test pilot subjects using the Flight Simulator Demonstration Model which incorporated a Helium Neon laser as the light bar medium. Two separate flight tests were conducted by the Test Pilot School classes 80A and 80B in a Twin Otter commuter aircraft using the Stage A Model PVHD. The Xenon lighted A Model was tested in its original configuration by class 80A. Class 80B used a modified configuration which incorporated an AFFTC designed and manufactured hood. With the hood, the PVHD projected a thinner, distinct light bar. Only a few general remarks concerning the tests and unrestricted, overall conclusions reached by the author are presented. The conclusions of all three AFFTC evaluations of the PVHD concept were that it has not yet been adequately evaluated. There seems to be a significant learning curve associated with the PVHD and the project pilots for Test Pilot School Class 80B only got a good start on the learning curve. A lengthy learning curve for the PVHD should be anticipated in view of the training period required for the attitude display indicator (ADI). This does seem to point out that the PVHD, in its present form, is simply not as compelling as the natural horizon. It can also be concluded that any attempt at a valid evaluation of the PVHD concept can be done only under instrument meteorological conditions (IMC) or validly simulated IMC conditions. The knee in the learning curve, however, may be reached without full IMC, although it may take much longer to reach
The assessment of pain in older people
Pain is under-recognised and under-treated in older people. It is a subjective, personal experience, only known to the person who suffers. The assessment of pain is particularly challenging in the presence of severe cognitive impairment, communication difficulties or language and cultural barriers. These guidelines set out the key components of assessing pain in older people, together with a variety of practical scales that may be used with different groups, including those with varying levels of cognitive or communication impairment. The purpose is to provide professionals with a set of practical skills to assess pain as the first step towards its effective management. The guidance has implications for all healthcare and social care staff and can be applied in all settings, including the older personās own home, in care homes, and in hospital
Transport anomalies in a simplified model for a heavy electron quantum critical point
We discuss the transport anomalies associated with the development of heavy
electrons out of a neutral spin fluid using the large-N treatment of the
Kondo-Heisenberg lattice model. At the phase transition in this model the spin
excitations suddenly acquire charge. The Higgs process by which this takes
place causes the constraint gauge field to loosely ``lock'' together with the
external, electromagnetic gauge field. From this perspective, the heavy fermion
phase is a Meissner phase in which the field representing the difference
between the electromagnetic and constraint gauge field, is excluded from the
material. We show that at the transition into the heavy fermion phase, both the
linear and the Hall conductivity jump together. However, the Drude weight of
the heavy electron fluid does not jump at the quantum critical point, but
instead grows linearly with the distance from the quantum critical point,
forming a kind of ``gossamer'' Fermi-liquid.Comment: 15 pages, 3 figures. Small change in references in v
Discontinuous Molecular Dynamics for Rigid Bodies: Applications
Event-driven molecular dynamics simulations are carried out on two rigid body
systems which differ in the symmetry of their molecular mass distributions.
First, simulations of methane in which the molecules interact via discontinuous
potentials are compared with simulations in which the molecules interact
through standard continuous Lennard-Jones potentials. It is shown that under
similar conditions of temperature and pressure, the rigid discontinuous
molecular dynamics method reproduces the essential dynamical and structural
features found in continuous-potential simulations at both gas and liquid
densities. Moreover, the discontinuous molecular dynamics approach is
demonstrated to be between 2 to 100 times more efficient than the standard
molecular dynamics method depending on the specific conditions of the
simulation. The rigid discontinuous molecular dynamics method is also applied
to a discontinuous-potential model of a liquid composed of rigid benzene
molecules, and equilibrium and dynamical properties are shown to be in
qualitative agreement with more detailed continuous-potential models of
benzene. Qualitative differences in the dynamics of the two models are related
to the relatively crude treatment of variations in the repulsive interactions
as one benzene molecule rotates by another.Comment: 14 pages, double column revte
Interaction Correction of Conductivity Near a Ferromagnetic Quantum Critical Point
We calculate the temperature dependence of conductivity due to interaction
correction for a disordered itinerant electron system close to a ferromagnetic
quantum critical point which occurs due to a spin density wave instability. In
the quantum critical regime, the crossover between diffusive and ballistic
transport occurs at a temperature ,
where is the parameter associated with the Landau damping of the spin
fluctuations, is the impurity scattering time, and is the Fermi
energy. For a generic choice of parameters, is few orders of
magnitude smaller than the usual crossover scale . In the ballistic
quantum critical regime, the conductivity has a temperature
dependence, where is the dimensionality of the system. In the diffusive
quantum critical regime we get dependence in three dimensions, and
dependence in two dimensions. Away from the quantum critical regime
we recover the standard results for a good metal.Comment: 15 pages, 8 figure
Quantum Cluster Variables via Serre Polynomials
For skew-symmetric acyclic quantum cluster algebras, we express the quantum
-polynomials and the quantum cluster monomials in terms of Serre polynomials
of quiver Grassmannians of rigid modules. As byproducts, we obtain the
existence of counting polynomials for these varieties and the positivity
conjecture with respect to acyclic seeds. These results complete previous work
by Caldero and Reineke and confirm a recent conjecture by Rupel.Comment: minor corrections, reference added, example 4.3 added, 38 page
The Oxidation State of Iron in Silicate Minerals from the Matrices of CO Carbonaceous Chondrites
No abstract available
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