3,164 research outputs found
The Application of Feedback in Measurement
Instrument errors, error reduction, and elements of measurements for measurement systems with feedback instrumentatio
An investigation of environmental factors associated with the current and proposed jetty systems at Belle Pass, Louisiana
The history of the existing jetty system at Belle Pass was investigated to determine its past effect on the littoral currents and beach erosion. Present flow patterns and erosion rates were also studied, along with the prevailing recession rates of local beaches not influenced by the jetty system. Aerial photographs and maps were used in conjunction with periodic hydraulic measurements, ground observations, and physical measurements of beach erosion. A scale model was constructed to further the study of flow patterns and velocities. It is shown that the existing jetty has not adversely affected the coastline in the area; erosive processes have been retarded by the jetty and its companion groin. Future erosion patterns are predicted, and projected effects of the proposed jetty system are given
Capacitive pressure transducer system
Closed loop capacitive pressure transducer with extended frequency response for very low pressure measurement
Spontaneous dressed-state polarization in the strong driving regime of cavity QED
We utilize high-bandwidth phase quadrature homodyne measurement of the light
transmitted through a Fabry-Perot cavity, driven strongly and on resonance, to
detect excess phase noise induced by a single intracavity atom. We analyze the
correlation properties and driving-strength dependence of the atom-induced
phase noise to establish that it corresponds to the long-predicted phenomenon
of spontaneous dressed-state polarization. Our experiment thus provides a
demonstration of cavity quantum electrodynamics in the strong driving regime,
in which one atom interacts strongly with a many-photon cavity field to produce
novel quantum stochastic behavior.Comment: 4 pages, 4 color figure
Polarization rotation via a monoclinic phase in the piezoelectric 92%PbZn1/3Nb2/3O3-8%PbTiO3
The origin of ultrahigh piezoelectricity in the relaxor ferroelectric
PbZn1/3Nb2/3O3-PbTiO3 was studied with an electric field applied along the
[001] direction. The zero-field rhombohedral R phase starts to follow the
direct polarization path to tetragonal symmetry via an intermediate monoclinic
M phase, but then jumps irreversibly to an alternate path involving a different
type of monoclinic distortion. Details of the structure and domain
configuration of this novel phase are described. This result suggests that
there is a nearby R-M phase boundary as found in the Pb(Ti,Zr)O3 system.Comment: REVTeX file. 4 pages. New version after referees' comment
Dual-band infrared imaging applications: locating buried minefields, mapping sea ice and inspecting aging aircraft
We discuss the use of dual-band infrared (DBIR) imaging for three quantitative NDE applications: locating buried surrogate mines, mapping sea ice thicknesses and inspecting subsurface flaws in aging aircraft parts. Our system of DBIR imaging offers a unique combination of thermal resolution, detectability, and interpretability. Pioneered at Lawrence Livermore Laboratory, it resolves 0.2 °C differences in surface temperatures needed to identify buried mine sites and distinguish them from surface features. It produces both surface temperature and emissivity-ratio images of sea ice, needed to accurately map ice thicknesses (e.g., by first removing clutter due to snow and surface roughness effects). The DBIR imaging technique depicts subsurface flaws in composite patches and lap joints of aircraft, thus providing a needed tool for aging aircraft inspections
Genetic Correlations in Mutation Processes
We study the role of phylogenetic trees on correlations in mutation
processes. Generally, correlations decay exponentially with the generation
number. We find that two distinct regimes of behavior exist. For mutation rates
smaller than a critical rate, the underlying tree morphology is almost
irrelevant, while mutation rates higher than this critical rate lead to strong
tree-dependent correlations. We show analytically that identical critical
behavior underlies all multiple point correlations. This behavior generally
characterizes branching processes undergoing mutation.Comment: revtex, 8 pages, 2 fig
Anomalities in the Analysis of Calibrated Data
This study examines effects of calibration errors on model assumptions and
data--analytic tools in direct calibration assays. These effects encompass
induced dependencies, inflated variances, and heteroscedasticity among the
calibrated measurements, whose distributions arise as mixtures. These anomalies
adversely affect conventional inferences, to include the inconsistency of
sample means; the underestimation of measurement variance; and the
distributions of sample means, sample variances, and Student's t as mixtures.
Inferences in comparative experiments remain largely intact, although error
mean squares continue to underestimate the measurement variances. These
anomalies are masked in practice, as conventional diagnostics cannot discern
irregularities induced through calibration. Case studies illustrate the
principal issues
Reorientation of Spin Density Waves in Cr(001) Films induced by Fe(001) Cap Layers
Proximity effects of 20 \AA thin Fe layers on the spin density waves (SDWs)
in epitaxial Cr(001) films are revealed by neutron scattering. Unlike in bulk
Cr we observe a SDW with its wave vector Q pointing along only one {100}
direction which depends dramatically on the film thickness t_{Cr}. For t_{Cr} <
250 \AA the SDW propagates out-of-plane with the spins in the film plane. For
t_{Cr} > 1000 \AA the SDW propagates in the film plane with the spins
out-of-plane perpendicular to the in-plane Fe moments. This reorientation
transition is explained by frustration effects in the antiferromagnetic
interaction between Fe and Cr across the Fe/Cr interface due to steps at the
interface.Comment: 4 pages (RevTeX), 3 figures (EPS
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