6,795 research outputs found
Study to determine potential flight applications and human factors design guidelines for voice recognition and synthesis systems
A study was conducted to determine potential commercial aircraft flight deck applications and implementation guidelines for voice recognition and synthesis. At first, a survey of voice recognition and synthesis technology was undertaken to develop a working knowledge base. Then, numerous potential aircraft and simulator flight deck voice applications were identified and each proposed application was rated on a number of criteria in order to achieve an overall payoff rating. The potential voice recognition applications fell into five general categories: programming, interrogation, data entry, switch and mode selection, and continuous/time-critical action control. The ratings of the first three categories showed the most promise of being beneficial to flight deck operations. Possible applications of voice synthesis systems were categorized as automatic or pilot selectable and many were rated as being potentially beneficial. In addition, voice system implementation guidelines and pertinent performance criteria are proposed. Finally, the findings of this study are compared with those made in a recent NASA study of a 1995 transport concept
On numerically accurate finite element
A general criterion for testing a mesh with topologically similar repeat units is given, and the analysis shows that only a few conventional element types and arrangements are, or can be made suitable for computations in the fully plastic range. Further, a new variational principle, which can easily and simply be incorporated into an existing finite element program, is presented. This allows accurate computations to be made even for element designs that would not normally be suitable. Numerical results are given for three plane strain problems, namely pure bending of a beam, a thick-walled tube under pressure, and a deep double edge cracked tensile specimen. The effects of various element designs and of the new variational procedure are illustrated. Elastic-plastic computation at finite strain are discussed
A Preliminary Study of Solar Powered Aircraft and Associated Power Trains
The feasibility of regeneratively powered solar high altitude powered platform (HAPP) remotely piloted vehicles was assessed. Those technologies which must be pursued to make long duration solar HAPPs feasible are recommended. A methodology which involved characterization and parametric analysis of roughly two dozen variables to determine vehicles capable of fulfilling the primary mission are defined. One of these vehicles was then conceptually designed. Variations of each major design parameter were investigated along with state-of-the-art changes in power train component capabilities. The midlatitude mission studied would be attainable by a solar HAPP if fuel cell, electrolyzer and photovoltaic technologies are pursued. Vehicles will be very large and have very lightweight structures in order to attain the combinations of altitude and duration required by the primary mission
Superconducting pairing of interacting electrons: implications from the two-impurity Anderson model
We study the non-local superconducting pairing of two interacting Anderson
impurities, which has an instability near the quantum critical point from the
competition between the Kondo effect and an antiferromagnetic inter-impurity
spin exchange interaction. As revealed by the dynamics over the whole energy
range, the superconducting pairing fluctuations acquire considerable strength
from an energy scale much higher than the characteristic spin fluctuation scale
while the low energy behaviors follow those of the staggered spin
susceptibility. We argue that the glue to the superconducting pairing is not
the spin fluctuations, but rather the effective Coulomb interaction. On the
other hand, critical spin fluctuations in the vicinity of quantum criticality
are also crucial to a superconducting pairing instability, by preventing a
Fermi liquid fixed point being reached to keep the superconducting pairing
fluctuations finite at low energies. A superconducting order, to reduce the
accumulated entropy carried by the critical degrees of freedom, may arise
favorably from this instability.Comment: 6 pages, 2 figure
Urban wind power and the private sector : community benefits, social acceptance and public engagement
Given the ambitious government targets for renewable energy generation in the UK, there has been a push by government and industry towards various types and scales of Renewable Energy Technologies (RETs). This paper explores the implications of commercial urban wind projects for local communities, drawing on a case study of proposals by ASDA to construct wind turbines in two semi-urban locations in the UK. The paper argues that community responses to the proposals were complex and varied and could not adequately be encapsulated by 'nimby' (not in my back yard) assignations. It concludes that while ASDA followed a process of consulting local people, this process highlighted the problems of the 'business as usual' approach to public engagement employed by ASDA, and assumptions made about public acceptance of RETs
Angular dependence of the magnetization of isotropic superconductors: which is the vortex direction?
We present studies of the dc magnetization of thin platelike samples of the
isotropic type II superconductor PbTl(10%), as a function of the angle between
the normal to the sample and the applied magnetic field . We determine
the magnetization vector by measuring the components both parallel
and normal to in a SQUID magnetometer, and we further decompose it in
its reversible and irreversible contributions. The behavior of the reversible
magnetization is well understood in terms of minimization of the free energy
taking into account geometrical effects. In the mixed state at low fields, the
dominant effect is the line energy gained by shortening the vortices, thus the
flux lines are almost normal to the sample surface. Due to the geometrical
constrain, the irreversible magnetization remains locked to the
sample normal over a wide range of fields and orientations, as already known.
We show that in order to undestand the angle and field dependence of the
modulus of , which is a measure of the vortex pinning, and to
correctly extract the field dependent critical current density, the knowledge
of the modulus and orientation of the induction field is required.Comment: 11 pages, 6 figure
Vortex lattice for a holographic superconductor
We investigate the vortex lattice solution in a (2+1)-dimensional holographic
model of superconductors constructed from a charged scalar condensate. The
solution is obtained perturbatively near the second-order phase transition and
is a holographic realization of the Abrikosov lattice. Below a critical value
of magnetic field, the solution has a lower free energy than the normal state.
Both the free energy density and the superconducting current are expressed by
nonlocal functions, but they reduce to the expressions in the Ginzburg-Landau
(GL) theory at long wavelength. As a result, a triangular lattice becomes the
most favorable solution thermodynamically as in the GL theory of type II
superconductors.Comment: v2: minor changes, references added; 11 pages, 2 figures: version to
appear in PR
A feasibility study: California Department of Forestry and Fire Protection utilization of infrared technologies for wildland fire suppression and management
NASA's JPL has completed a feasibility study using infrared technologies for wildland fire suppression and management. The study surveyed user needs, examined available technologies, matched the user needs with technologies, and defined an integrated infrared wildland fire mapping concept system configuration. System component trade-offs were presented for evaluation in the concept system configuration. The economic benefits of using infrared technologies in fire suppression and management were examined. Follow-on concept system configuration development and implementation were proposed
Holographic Superconductors with Ho\v{r}ava-Lifshitz Black Holes
We discuss the phase transition of planar black holes in Ho\v{r}ava-Lifshitz
gravity by introducing a Maxwell field and a complex scalar field. We calculate
the condensates of the charged operators in the dual CFTs when the mass square
of the complex scalar filed is and , respectively. We
compute the electrical conductivity of the \hl superconductor in the probe
approximation. In particular, it is found that there exists a spike in the
conductivity for the case of the operator with scaling dimension one. These
results are quite similar to those in the case of Schwarzschild-AdS black
holes, which demonstrates that the holographic superconductivity is a robust
phenomenon associated with asymptotic AdS black holes.Comment: 12 pages, 7 figures,refs adde
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