528 research outputs found
Power spectral measurements of clear-air turbulence to long wavelengths for altitudes up to 14,000 meters
Measurements of three components of clear air atmospheric turbulence were made with an airplane incorporating a special instrumentation system to provide accurate data resolution to wavelengths of approximately 12,500 m (40,000 ft). Flight samplings covered an altitude range from approximately 500 to 14,000 m (1500 to 46,000 ft) in various meteorological conditions. Individual autocorrelation functions and power spectra for the three turbulence components from 43 data runs taken primarily from mountain wave and jet stream encounters are presented. The flight location (Eastern or Western United States), date, time, run length, intensity level (standard deviation), and values of statistical degrees of freedom for each run are provided in tabular form. The data presented should provide adequate information for detailed meteorological correlations. Some time histories which contain predominant low frequency wave motion are also presented
Magnetic and Crystallographic Structure of Y₆Mn₂₃D₂₃
The magnetic behavior of Y6Mn23 is dramatically altered upon hydrogenation (or deuteration). In this study it has been found, by means of high-resolution powder diffraction and Rietveld refinement techniques, that the crystallographic structure is distorted from face-centered cubic (Fm3m) at 295 K to a primitive tetragonal structure at 4 K in which deuterium atoms are atomically ordered. Y6Mn23 is a ferromagnetic compound with Tc=486 K, and bulk magnetization of 13.2 Bf.u. (formula unit). After deuteration of Y6Mn23 to the composition Y6Mn23D23, low-temperature scattering data (T\u3c180 K) show that the b and f2 sites in the Fm3m structure are antiferromagnetic and the d and f1 sites have no spontaneous magnetic moment. © 1984 The American Physical Society
Temperature-induced reversal of magnetic interlayer exchange coupling
For epitaxial trilayers of the magnetic rare-earth metals Gd and Tb, exchange
coupled through a non-magnetic Y spacer layer, element-specific hysteresis
loops were recorded by the x-ray magneto-optical Kerr effect at the rare-earth
thresholds. This allowed us to quantitatively determine the strength of
interlayer exchange coupling (IEC). In addition to the expected oscillatory
behavior as a function of spacer-layer thickness , a temperature-induced
sign reversal of IEC was observed for constant , arising from
magnetization-dependent electron reflectivities at the magnetic interfaces.Comment: 4 pages, 4 figures; accepted version; minor changes and new Figs. 2
and 4 containing more dat
Mercury Toolset for Spatiotemporal Metadata
Mercury (http://mercury.ornl.gov) is a set of tools for federated harvesting, searching, and retrieving metadata, particularly spatiotemporal metadata. Version 3.0 of the Mercury toolset provides orders of magnitude improvements in search speed, support for additional metadata formats, integration with Google Maps for spatial queries, facetted type search, support for RSS (Really Simple Syndication) delivery of search results, and enhanced customization to meet the needs of the multiple projects that use Mercury. It provides a single portal to very quickly search for data and information contained in disparate data management systems, each of which may use different metadata formats. Mercury harvests metadata and key data from contributing project servers distributed around the world and builds a centralized index. The search interfaces then allow the users to perform a variety of fielded, spatial, and temporal searches across these metadata sources. This centralized repository of metadata with distributed data sources provides extremely fast search results to the user, while allowing data providers to advertise the availability of their data and maintain complete control and ownership of that data. Mercury periodically (typically daily) harvests metadata sources through a collection of interfaces and re-indexes these metadata to provide extremely rapid search capabilities, even over collections with tens of millions of metadata records. A number of both graphical and application interfaces have been constructed within Mercury, to enable both human users and other computer programs to perform queries. Mercury was also designed to support multiple different projects, so that the particular fields that can be queried and used with search filters are easy to configure for each different project
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Broadening Intellectual Diversity in Visualization Research Papers
Promoting a wider range of contribution types can facilitate healthy growth of the visualization community, while increasing the intellectual diversity of visualization research papers. In this article, we discuss the importance of contribution types and summarize contribution types that can be meaningful in visualization research. We also propose several concrete next steps we can and should take to ensure a successful launch of the contribution types
Annealing-Dependent Magnetic Depth Profile in Ga[1-x]Mn[x]As
We have studied the depth-dependent magnetic and structural properties of
as-grown and optimally annealed Ga[1-x]Mn[x]As films using polarized neutron
reflectometry. In addition to increasing total magnetization, the annealing
process was observed to produce a significantly more homogeneous distribution
of the magnetization. This difference in the films is attributed to the
redistribution of Mn at interstitial sites during the annealing process. Also,
we have seen evidence of significant magnetization depletion at the surface of
both as-grown and annealed films.Comment: 5 pages, 3 figure
Tricritical Point and the Doping Dependence of the Order of the Ferromagnetic Phase Transition of La1-xCaxMnO3
We report the doping dependence of the order of the ferromagnetic metal to
paramagnetic insulator phase transition in La1-xCaxMnO3. At x = 0.33,
magnetization and specific heat data show a first order transition, with an
entropy change (2.3 J/molK) accounted for by both volume expansion and the
discontinuity of M ~ 1.7 Bohr magnetons via the Clausius-Clapeyron equation. At
x = 0.4, the data show a continuous transition with tricritical point exponents
alpha = 0.48+/- 0.06, beta = 0.25+/- 0.03, gamma = 1.03+/- 0.05, and delta =
5.0 +/- 0.8. This tricritical point separates first order (x<0.4) from second
order (x>0.4) transitions.Comment: 14 pages, including 4 figures: i.e. 10 pages of text and 4 pages of
figures. to appear in Physical Review Letters (accepted
Observation of two time scales in the ferromagnetic manganite La(1-x)Ca(x)MnO(3), x = 0.3
We report new zero-field muon spin relaxation and neutron spin echo
measurements in ferromagnetic (FM) (La,Ca)MnO3 which taken together suggest two
spatially separated regions in close proximity possessing very different Mn-ion
spin dynamics. One region corresponds to an extended cluster which displays
'critical slowing down' near Tc and an increasing volume fraction below Tc. The
second region possesses more slowly fluctuating spins and a decreasing volume
fraction below Tc. These data are discussed in terms of the growth of small
polarons into overlapping regions of correlated spins below Tc, resulting in a
microscopically inhomogeneous FM transition.Comment: 10 pages, 3 figure
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