Simulation model of erosion and deposition on a barchan dune

Erosion and deposition over a barchan dune near the Salton Sea, California, are modeled by bookkeeping the quantity of sand in saltation following streamlines of transport. Field observations of near surface wind velocity and direction plus supplemental measurements of the velocity distribution over a scale model of the dune are combined as input to Bagnold type sand transport formulas corrected for slope effects. A unidirectional wind is assumed. The resulting patterns of erosion and deposition compare closely with those observed in the field and those predicted by the assumption of equilibrium (downwind translation of the dune without change in size or geometry). Discrepancies between the simulated results and the observed or predicted erosional patterns appear to be largely due to natural fluctuations in the wind direction. The shape of barchan dunes is a function of grain size, velocity, degree of saturation of the oncoming flow, and the variability in the direction of the oncoming wind. The size of the barchans may be controlled by natural atmospheric scales, by the age of the dunes, or by the upwind roughness. The upwind roughness can be controlled by fixed elements or by sand in the saltation. In the latter case, dune scale is determined by grain size and wind velocity

Alaska Victimization Survey: 2011 Results for Bristol Bay

This is a handout of a Powerpoint slide presentation providing an overview of key results from the 2011 Alaska Victimization Survey for the Bristol Bay region, which was conducted from April to June 2011, with results released on October 12, 2011 in Dillingham. Findings include: * Over 50% of adult women in the Bristol Bay Region have experienced intimate partner violence, sexual violence or both, in their lifetime; * Nearly 15% have experienced intimate partner violence, sexual violence or both, in the past year; * 3 out of every 10 adult women in the Bristol Bay Region have experienced sexual violence in their lifetime; and * 4 out of every 10 have experienced intimate partner violence in their lifetime.Council on Domestic Violence and Sexual Assault, Alaska Department of Public SafetyAlaska Victimization Survey in Bristol Bay / Intimate Partner Violence Definitions / Intimate Partner Violence Estimates / Sexual Violence Definitions / Sexual Violence Estimates / Summary of Past Year Estimates / Summary of Lifetime Estimates / Lifetime Estimates / Important Limitations / A Special Thank You! / Contact

The interaction of unidirectional winds with an isolated barchan sand dune

Velocity profile measurements are determined on and around a barchan dune model inserted in the roughness layer on the tunnel floor. A theoretical investigation is made into the factors influencing the rate of sand flow around the dune. Flow visualization techniques are employed in the mapping of streamlines of flow on the dune's surface. Maps of erosion and deposition of sand are constructed for the barchan model, utilizing both flow visualization techniques and friction velocities calculated from the measured velocity profiles. The sediment budget found experimentally for the model is compared to predicted and observed results reported. The comparison shows fairly good agreement between the experimentally determined and predicted sediment budgets

Thin-film flow in helically wound rectangular channels with small torsion

Laminar gravity-driven thin-film flow down a helically-wound channel of rectangular cross-section with small torsion in which the fluid depth is small is considered. Neglecting the entrance and exit regions we obtain the steady-state solution that is independent of position along the axis of the channel, so that the flow, which comprises a primary flow in the direction of the axis of the channel and a secondary flow in the cross-sectional plane, depends only on position in the two-dimensional cross-section of the channel. A thin-film approximation yields explicit expressions for the fluid velocity and pressure in terms of the free-surface shape, the latter satisfying a non-linear ordinary differential equation that has a simple exact solution in the special case of a channel of rectangular cross-section. The predictions of the thin-film model are shown to be in good agreement with much more computationally intensive solutions of the small-helix-torsion Navier–Stokes equations. The present work has particular relevance to spiral particle separators used in the mineral-processing industry. The validity of an assumption commonly used in modelling flow in spiral separators, namely that the flow in the outer region of the separator cross-section is described by a free vortex, is shown to depend on the problem parameters

Probing anharmonic properties of nuclear surface vibration by heavy-ion fusion reactions

Describing fusion reactions between ^{16}O and ^{154}Dy and, between ^{16}O and ^{144}Sm by the $sd-$ and $sdf-$ interacting boson model, we show that heavy-ion fusion reactions are strongly affected by anharmonic properties of nuclear surface vibrations and nuclear shape, and thus provide a powerful method to study details of nuclear structure and dynamics.Comment: 8 pages, 5 figures, To be published in the Proceedings of the FUSION 97 Conference, South Durras, Australia, March 1997 (J. Phys. G

Plio-Pleistocene Depositional Sequences of the Southwestern Louisiana Continental Shelf and Slope: Geologic Framework, Sedimentary Facies and Hydrocarbon Distribution

The Plio-Pleistocene hydrocarbon fairway of offshore Louisiana is restricted to the outer continental shelf and upper continental slope where a thick wedge of nearshore and deep marine sediments was deposited. Electric logs, paleontological reports, and seismic profiles form the basis for (1) dividing the wedge of Plio-Pleistocene strata into eight genetic sequences, (2) establishing the structural framework, (3) determining the timing of deformation, and (4) mapping the principal depositional systems of the West Cameron and western Garden Banks areas during the past five million years. Sedimentary facies and structural styles in this part of the basin are highly variable owing to contemporaneous sea-level fluctuations, salt migration, and shifting sites of deltaic, shelf, and slope sedimentation. The resulting complex geologic history of this part of the basin directly controlled the generation, migration, and entrapment of hydrocarbons. The early Pliocene was a period of continental platform inundation and deposition of a thick succession of marine mudstones. About 3 Ma, this monotonous accumulation of deep-water mudstone was interrupted by deposition of sand-rich submarine channels and fans associated with a lowering of sea level. These lowstand deposits extended at least 55 mi (90 km) basinward of the paleomargin. Overlying Pleistocene sediments were deposited mainly by prograding mud-rich fluvial-deltaic systems of moderate size. These rivers and shelf-edge deltas constructed a broad continental platform that buried the submarine fans and prograded the shelf margin approximately 70 mi (110 km) basinward. During this rapid outbuilding, slumping and other gravity-driven mass transport processes removed sand-rich delta-front sediments from unstable shelf margins and redeposited them on the continental slope.Bureau of Economic Geolog

Plio-Pleistocene Depositional Sequences of the Southwestern Louisiana Continental Shelf and Slope: Geologic Framework, Sedimentary Facies and Hydrocarbon Distribution

The Plio-Pleistocene hydrocarbon fairway of offshore Louisiana is restricted to the outer continental shelf and upper continental slope where a thick wedge of nearshore and deep marine sediments was deposited. Electric logs, paleontological reports, and seismic profiles form the basis for (1) dividing the wedge of Plio-Pleistocene strata into eight genetic sequences, (2) establishing the structural framework, (3) determining the timing of deformation, and (4) mapping the principal depositional systems of the West Cameron and western Garden Banks areas during the past five million years. Sedimentary facies and structural styles in this part of the Gulf Coast basin are highly variable owing to contemporaneous sea-level fluctuations, salt migration, and shifting sites of deltaic, shelf, and slope sedimentation. The resulting complex geologic history of this part of the basin was interpreted to determine what controlled the generation, migration, and entrapment of hydrocarbons. The early Pliocene was a period of continental platform inundation and deposition of a thick succession of marine mudstones. About 3 million years ago, this monotonous accumulation of deep-water mudstone was interrupted by deposition of sand-rich submarine channels and fans associated with a lowering of sea level. These lowstand deposits extended at least 55 miles (90 km) basinward of the paleomargin. Overlying Pleistocene sediments were deposited mainly by prograding mud-rich fluvial-deltaic systems of moderate size. These rivers and shelf-edge deltas constructed a broad continental platform that buried the submarine fans and prograded the shelf margin approximately 70 miles (110 km) basinward. During this rapid outbuilding, slumping and other gravity-driven mass transport processes removed sand-rich delta-front sediments from unstable shelf margins and redeposited them on the continental slope.Bureau of Economic Geolog

Global Optical Control of a Quantum Spin Chain

Quantum processors which combine the long decoherence times of spin qubits together with fast optical manipulation of excitons have recently been the subject of several proposals. I show here that arbitrary single- and entangling two-qubit gates can be performed in a chain of perpetually coupled spin qubits solely by using laser pulses to excite higher lying states. It is also demonstrated that universal quantum computing is possible even if these pulses are applied {\it globally} to a chain; by employing a repeating pattern of four distinct qubit units the need for individual qubit addressing is removed. Some current experimental qubit systems would lend themselves to implementing this idea.Comment: 5 pages, 3 figure