4,914 research outputs found
Research on computational and display requirements for human control of space vehicle boosters. Part 1 - Theory and results Final report, 22 Jun. - 22 Oct. 1966
Computational and display requirements for man-computer guidance and control techniques for reusable manned spacecraf
Investigation of analytical methods for efficient partitioning of on-board processing functions for remote sensing applications
Risk decomposition and ring theory, lattice techniques and universal algebras, and unary functions are considered
Dynamic Formation of Metastable Intermediate State Patterns in Type-I Superconductors
Structure of the intermediate state in type-I superconducting lead (Pb) is
shown to be very sensitive to the ramp rate of an applied magnetic field. The
configurations of resulting static patterns depend sensitively on the shape of
the specimen. In particular, geometric barrier, present in the samples with
rectangular cross-section, plays an important role in determining the sharp
boundary between the phases of different topology. We propose that seemingly
laminar (stripe) pattern obtained as a result of the fast field ramp is simply
an imprint left behind by the fast-moving flux tubes. Our results confirm that
flux tube phase is topologically favorable.Comment: to be presented at LT-25 (Amsterdam, 2008
Full scale visualization of the wing tip vortices generated by a typical agricultural aircraft
The trajectories of the wing tip vortices of a typical agricultural aircraft were experimentally determined by flight test. A flow visualization method, similar to the vapor screen method used in wind tunnels, was used to obtain trajectory data for a range of flight speeds, airplane configurations, and wing loadings. Detailed measurements of the spanwise surface pressure distribution were made for all test points. Further, a powered 1/8 scale model of the aircraft was designed, built, and used to obtain tip vortex trajectory data under conditions similar to that of the full scale test. The effects of light wind on the vortices were demonstrated, and the interaction of the flap vortex and the tip vortex was clearly shown in photographs and plotted trajectory data
Equilibrium topology of the intermediate state in type-I superconductors of different shapes
High-resolution magneto-optical technique was used to analyze flux patterns
in the intermediate state of bulk Pb samples of various shapes - cones,
hemispheres and discs. Combined with the measurements of macroscopic
magnetization these results allowed studying the effect of bulk pinning and
geometric barrier on the equilibrium structure of the intermediate state.
Zero-bulk pinning discs and slabs show hysteretic behavior due to geometric
barrier that results in a topological hysteresis -- flux tubes on penetration
and lamellae on flux exit. (Hemi)spheres and cones do not have geometric
barrier and show no hysteresis with flux tubes dominating the intermediate
field region. It is concluded that flux tubes represent the equilibrium
topology of the intermediate state in reversible samples, whereas laminar
structure appears in samples with magnetic hysteresis (either bulk or
geometric). Real-time video is available in
http://www.cmpgroup.ameslab.gov/supermaglab/video/Pb.html
NOTE: the submitted images were severely downsampled due to Arxiv's
limitations of 1 Mb total size
Fiscal year 1981 US corn and soybeans pilot preliminary experiment plan, phase 1
A draft of the preliminary experiment plan for the foreign commodity production forecasting project fiscal year 1981 is presented. This draft plan includes: definition of the phase 1 and 2 U.S. pilot objectives; the proposed experiment design to evaluate crop calendar, area estimation, and area aggregation components for corn and soybean technologies using 1978/1979 crop-year data; a description of individual sensitivity evaluations of the baseline corn and soybean segment classification procedure; and technology and data assessment in support of the corn and soybean estimation technology for use in the U.S. central corn belt
TECHNICAL BASIS FOR DOE STANDARD 3013 EQUIVALENCY SUPPORTING REDUCED TEMPERATURE STABILIZATION OF OXALATE-DERIVED PLUTONIUM OXIDE PRODUCED BY THE HB-LINE FACILITY AT SAVANNAH RIVER SITE
The HB-Line (HBL) facility at the Savannah River Site (SRS) is designed to produce high-purity plutonium dioxide (PuO{sub 2}) which is suitable for future use in production of Mixed Oxide (MOX) fuel. The MOX Fuel Fabrication Facility (MFFF) requires PuO{sub 2} feed to be packaged per the U.S. Department of Energy (DOE) Standard 3013 (DOE-STD-3013) to comply with the facility's safety basis. The stabilization conditions imposed by DOE-STD-3013 for PuO{sub 2} (i.e., 950 C for 2 hours) preclude use of the HBL PuO{sub 2} in direct fuel fabrication and reduce the value of the HBL product as MFFF feedstock. Consequently, HBL initiated a technical evaluation to define acceptable operating conditions for production of high-purity PuO{sub 2} that fulfills the DOE-STD-3013 criteria for safe storage. The purpose of this document is to demonstrate that within the defined operating conditions, the HBL process will be equivalent for meeting the requirements of the DOE-STD-3013 stabilization process for plutonium-bearing materials from the DOE complex. The proposed 3013 equivalency reduces the prescribed stabilization temperature for high-purity PuO{sub 2} from oxalate precipitation processes from 950 C to 640 C and places a limit of 60% on the relative humidity (RH) at the lowest material temperature. The equivalency is limited to material produced using the HBL established flow sheet, for example, nitric acid anion exchange and Pu(IV) direct strike oxalate precipitation with stabilization at a minimum temperature of 640 C for four hours (h). The product purity must meet the MFFF acceptance criteria of 23,600 {micro}g/g Pu (i.e., 2.1 wt %) total impurities and chloride content less than 250 {micro}g/g of Pu. All other stabilization and packaging criteria identified by DOE-STD-3013-2012 or earlier revisions of the standard apply. Based on the evaluation of test data discussed in this document, the expert judgment of the authors supports packaging the HBL product under a 3013 equivalency. Under the defined process conditions and associated material specifications, the high-purity PuO{sub 2} produced in HBL presents no unique safety concerns for packaging or storage in the 3013 required configuration. The PuO{sub 2} produced using the HBL flow sheet conditions will have a higher specific surface area (SSA) than PuO{sub 2} stabilized at 950 C and, consequently, under identical conditions will adsorb more water from the atmosphere. The greatest challenge to HBL operators will be controlling moisture content below 0.5 wt %. However, even at the 0.5 wt % moisture limit, the maximum acceptable pressure of a stoichiometric mixture of hydrogen and oxygen in the 3013 container is greater than the maximum possible pressure for the HBL PuO{sub 2} product
Topological Hysteresis in the Intermediate State of Type-I Superconductors
Magneto-optical imaging of thick stress-free lead samples reveals two
distinct topologies of the intermediate state. Flux tubes are formed upon
magnetic field penetration (closed topology) and laminar patterns appear upon
flux exit (open topology). Two-dimensional distributions of shielding currents
were obtained by applying an efficient inversion scheme. Quantitative analysis
of the magnetic induction distribution and correlation with magnetization
measurements indicate that observed topological differences between the two
phases are responsible for experimentally observable magnetic hysteresis.Comment: 4 pages, RevTex
The Cost of Increasing Adoption of Beneficial Nutrient-Management Practices
We estimate the cost of offsets tied to reductions in the use of nitrogen on U.S. cornfields under the proposed American Clean Energy and Security Act.offsets, nitrogen, corn, Agricultural and Food Policy, Crop Production/Industries, Environmental Economics and Policy,
Confinement of knotted polymers in a slit
We investigate the effect of knot type on the properties of a ring polymer
confined to a slit. For relatively wide slits, the more complex the knot, the
more the force exerted by the polymer on the walls is decreased compared to an
unknotted polymer of the same length. For more narrow slits the opposite is
true. The crossover between these two regimes is, to first order, at smaller
slit width for more complex knots. However, knot topology can affect these
trends in subtle ways. Besides the force exerted by the polymers, we also study
other quantities such as the monomer-density distribution across the slit and
the anisotropic radius of gyration.Comment: 9 pages, 6 figures, submitted for publicatio
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