28,783 research outputs found
Effect of contrast on the perception of direction of a moving pattern
A series of experiments examining the effect of contrast on the perception of moving plaids was performed to test the hypothesis that the human visual system determines the direction of a moving plaid in a two-staged process: decomposition into component motion followed by application of the intersection-of-contraints rule. Although there is recent evidence that the first tenet of the hypothesis is correct, i.e., that plaid motion is initially decomposed into the motion of the individual grating components, the nature of the second-stage combination rule has not yet been established. It was found that when the gratings within the plaid are of different contrast the preceived direction is not predicted by the intersection-of-constraints rule. There is a strong (up to 20 deg) bias in the direction of the higher-constrast grating. A revised model, which incorporates a contrast-dependent weighting of perceived grating speed as observed for one-dimensional patterns, can quantitatively predict most of the results. The results are then discussed in the context of various models of human visual motion processing and of physiological responses of neurons in the primate visual system
RANDOM MATRIX THEORY APPROACH TO THE INTENSITY DISTRIBUTIONS OF WAVES PROPAGATING IN A RANDOM MEDIUM
Statistical properties of coherent radiation propagating in a quasi - 1D
random media is studied in the framework of random matrix theory. Distribution
functions for the total transmission coefficient and the angular transmission
coefficient are obtained.Comment: 8 pages, latex, no figures. Submitted to Phys.Rev.
Relaxation time of the topological T1 process in a two-dimensional foam
The elementary topological T1 process in a two-dimensional foam corresponds
to the "flip" of one soap film with respect to the geometrical constraints.
From a mechanical point of view, this T1 process is an elementary relaxation
process through which the entire structure of an out-of-equilibrium foam
evolves. The dynamics of this elementary relaxation process has been poorly
investigated and is generally neglected during simulations of foams. We study
both experimentally and theoretically the T1 dynamics in a dry two-dimensional
foam. We show that the dynamics is controlled by the surface viscoelastic
properties of the soap films (surface shear plus dilatational viscosity, ms+k,
and Gibbs elasticity e), and is independent of the shear viscosity of the bulk
liquid. Moreover, our approach illustrates that the dynamics of T1 relaxation
process provides a convenient tool for measuring the surface rheological
properties: we obtained e = 32+/-8 mN/m and ms+k = 1.3+/-0.7 mPa.m.s for SDS,
and e = 65+/-12 mN/m and ms+k = 31+/-12 mPa.m.s for BSA, in good agreement with
values reported in the literature
Quantum coherence in a ferromagnetic metal: time-dependent conductance fluctuations
Quantum coherence of electrons in ferromagnetic metals is difficult to assess
experimentally. We report the first measurements of time-dependent universal
conductance fluctuations in ferromagnetic metal (NiFe)
nanostructures as a function of temperature and magnetic field strength and
orientation. We find that the cooperon contribution to this quantum correction
is suppressed, and that domain wall motion can be a source of
coherence-enhanced conductance fluctuations. The fluctuations are more strongly
temperature dependent than those in normal metals, hinting that an unusual
dephasing mechanism may be at work.Comment: 5 pages, 4 figure
A simple portable somomicrometer, March - July 1966
Portable sonomicrometer for measuring heart dimension
An analysis of pilot error-related aircraft accidents
A multidisciplinary team approach to pilot error-related U.S. air carrier jet aircraft accident investigation records successfully reclaimed hidden human error information not shown in statistical studies. New analytic techniques were developed and applied to the data to discover and identify multiple elements of commonality and shared characteristics within this group of accidents. Three techniques of analysis were used: Critical element analysis, which demonstrated the importance of a subjective qualitative approach to raw accident data and surfaced information heretofore unavailable. Cluster analysis, which was an exploratory research tool that will lead to increased understanding and improved organization of facts, the discovery of new meaning in large data sets, and the generation of explanatory hypotheses. Pattern recognition, by which accidents can be categorized by pattern conformity after critical element identification by cluster analysis
Landauer Conductance of Luttinger Liquids with Leads
We show that the dc conductance of a quantum wire containing a Luttinger
liquid and attached to non-interacting leads is given by per spin
orientation, regardless of the interactions in the wire. This explains the
recent observations of the absence of conductance renormalization in long
high-mobility wires by Tarucha, Honda and Saku (Solid State
Communications {\bf 94}, 413 (1995)).Comment: 4 two-column pages, RevTeX + 1 uuencoded figure
NASA research in supersonic propulsion: A decade of progress
A second generation, economically viable, and environmentally acceptable supersonic aircraft is reviewed. Engine selection, testbed experiments, and noise reduction research are described
Optimizing Clinical and Cost Outcomes for Patients on Enteral Nutrition Support for Treatment of Exocrine Pancreatic Insufficiency: Proceedings from an expert advisory board meeting
Nanoengineered Curie Temperature in Laterally-Patterned Ferromagnetic Semiconductor Heterostructures
We demonstrate the manipulation of the Curie temperature of buried layers of
the ferromagnetic semiconductor (Ga,Mn)As using nanolithography to enhance the
effect of annealing. Patterning the GaAs-capped ferromagnetic layers into
nanowires exposes free surfaces at the sidewalls of the patterned (Ga,Mn)As
layers and thus allows the removal of Mn interstitials using annealing. This
leads to an enhanced Curie temperature and reduced resistivity compared to
unpatterned samples. For a fixed annealing time, the enhancement of the Curie
temperature is larger for narrower nanowires.Comment: Submitted to Applied Physics Letters (minor corrections
- …