Science.gov

Sample records for boundary current final

  1. The Arctic Circumpolar Boundary Current

    NASA Astrophysics Data System (ADS)

    Aksenov, Yevgeny; Ivanov, Vladimir V.; Nurser, A. J. George; Bacon, Sheldon; Polyakov, Igor V.; Coward, Andrew C.; Naveira-Garabato, Alberto C.; Beszczynska-Moeller, Agnieszka

    2011-09-01

    We present high-resolution simulations and observational data as evidence of a fast current flowing along the shelf break of the Siberian and Alaskan shelves in the Arctic Ocean. Thus far, the Arctic Circumpolar Boundary Current (ACBC) has been seen as comprising two branches: the Fram Strait and Barents Sea Branches (FSB and BSB, respectively). Here we describe a new third branch, the Arctic Shelf Break Branch (ASBB). We show that the forcing mechanism for the ASBB is a combination of buoyancy loss and non-local wind, creating high pressure upstream in the Barents Sea. The potential vorticity influx through the St. Anna Trough dictates the cyclonic direction of flow of the ASBB, which is the most energetic large-scale circulation structure in the Arctic Ocean. It plays a substantial role in transporting Arctic halocline waters and exhibits a robust seasonal cycle with a summer minimum and winter maximum. The simulations show the continuity of the FSB all the way around the Arctic shelves and the uninterrupted ASBB between the St. Anna Trough and the western Fram Strait. The BSB flows continuously along the Siberian shelf as far as the Chukchi Plateau, where it partly diverges from the continental slope into the ocean interior. The Alaskan Shelf break Current (ASC) is the analog of the ASBB in the Canadian Arctic. The ASC is forced by the local winds and high upstream pressure in Bering Strait, caused by the drop in sea surface height between the Pacific and Arctic Oceans.

  2. Deep boundary current disintegration in Drake Passage

    NASA Astrophysics Data System (ADS)

    Brearley, J. Alexander; Sheen, Katy L.; Naveira Garabato, Alberto C.; Smeed, David A.; Speer, Kevin G.; Thurnherr, Andreas M.; Meredith, Michael P.; Waterman, Stephanie

    2014-01-01

    The fate of a deep boundary current that originates in the Southeast Pacific and flows southward along the continental slope of South America is elucidated. The current transports poorly ventilated water of low salinity (a type of Pacific Deep Water, PDW), into Drake Passage. East of Drake Passage, the boundary current breaks into fresh anticyclonic eddies, nine examples of which were observed in mooring data from December 2009 to March 2012. The observed eddies appear to originate mainly from a topographic separation point close to 60°W, have typical diameters of 20-60 km and accompanying Rossby numbers of 0.1-0.3. These features are likely to be responsible for transporting PDW meridionally across the Antarctic Circumpolar Current, explaining the near homogenization of Circumpolar Deep Water properties downstream of Drake Passage. This mechanism of boundary current breakdown may constitute an important process in the Southern Ocean overturning circulation.

  3. Regional Wave Climates along Eastern Boundary Currents

    NASA Astrophysics Data System (ADS)

    Semedo, Alvaro; Soares, Pedro

    2016-04-01

    Two types of wind-generated gravity waves coexist at the ocean surface: wind sea and swell. Wind sea waves are waves under growing process. These young growing waves receive energy from the overlaying wind and are strongly coupled to the local wind field. Waves that propagate away from their generation area and no longer receive energy input from the local wind are called swell. Swell waves can travel long distances across entire ocean basins. A qualitative study of the ocean waves from a locally vs. remotely generation perspective is important, since the air sea interaction processes is strongly modulated by waves and vary accordingly to the prevalence of wind sea or swell waves in the area. A detailed climatology of wind sea and swell waves along eastern boundary currents (EBC; California Current, Canary Current, in the Northern Hemisphere, and Humboldt Current, Benguela Current, and Western Australia Current, in the Southern Hemisphere), based on the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis will be presented. The wind regime along EBC varies significantly from winter to summer. The high summer wind speeds along EBC generate higher locally generated wind sea waves, whereas lower winter wind speeds in these areas, along with stronger winter extratropical storms far away, lead to a predominance of swell waves there. In summer, the coast parallel winds also interact with coastal headlands, increasing the wind speed through a process called "expansion fan", which leads to an increase in the height of locally generated waves downwind of capes and points. Hence the spatial patterns of the wind sea or swell regional wave fields are shown to be different from the open ocean along EBC, due to coastal geometry and fetch dimensions. Swell waves will be shown to be considerably more prevalent and to carry more energy in winter along EBC, while in summer locally generated wind sea waves are either more comparable to swell waves or

  4. Free boundary skin current MHD (magnetohydrodynamic) equilibria

    SciTech Connect

    Reusch, M.F.

    1988-02-01

    Function theoretic methods in the complex plane are used to develop simple parametric hodograph formulae which generate sharp boundary equilibria of arbitrary shape. The related method of Gorenflo and Merkel is discussed. A numerical technique for the construction of solutions, based on one of the methods is presented. A study is made of the bifurcations of an equilibrium of general form. 28 refs., 9 figs.

  5. Boundary Waves on the Ice Surface Created by Currents

    NASA Astrophysics Data System (ADS)

    Naito, K.; Izumi, N.; Yokokawa, M.; Yamada, T.; de Lima, A. C.

    2013-12-01

    The formation of periodic boundary waves, e.g. antidunes and cyclic steps (Parker & Izumi 2000) has been known to be caused by instabilities between flow and bed (e.g. Engelund 1970), and are observed not only on river beds or ocean floors but also on ice surfaces, such as the surface of glaciers and underside of river ice (Carey 1966). In addition, owing to recent advancements of remote sensing technology, it has been found that the surfaces of the polar ice caps on Mars as well as on the Earth have step-like formations (Smith & Holt 2010) which are assumed to be boundary waves, because they are generated perpendicularly to the direction of the currents. These currents acting on the polar ice caps are density airflow, i.e. katabatic wind (Howard et al 2000). The comprehension of the formation process of the Martian polar ice caps may reveal climate changes which have occurred on Mars. Although the formation of boundary waves on river beds or ocean floors has been studied by a number of researchers, there are few works on their formation on ice surfaces. Yokokawa et al (2013) suggested that the temperature distribution of the ambient air, fluid and ice is a factor which determines the direction of migration of boundary waves formed on ice surfaces through their experiments. In this study, we propose a mathematical model in order to describe the formation process of the boundary waves and the direction of their migration. We consider that a liquid is flowing through a flume filled with a flat ice layer on the bottom. The flow is assumed to be turbulent and its temperature is assumed to merge with the ambient temperature at the flow surface and with the melting point of ice at the bottom (ice surface). The ice surface evolution is dependent on the unbalance between the interfacial heat flux of the liquid and ice, and we employ the Reynolds-averaged Navier-Stokes equation, the continuity equation, heat transfer equations for the liquid and ice, and a heat balance

  6. The Coastal Boundary Layer of the Yucatan Current

    NASA Astrophysics Data System (ADS)

    Coronado, C.; Candela, J.

    2009-04-01

    High-resolution measurements of the Yucatan Current, one of the most intense western-boundary currents in the World at these latitudes, were performed by CICESE as part of its CANEK project to understand the mechanisms that transfer properties across the shelf slope. Eight shallow water and moored acoustic Doppler current profilers (ADCPs) were deployed along a transect southeast of the shallow fringing reef lagoon of Puerto Morelos, through the narrow continental shelf and down the slope of the Yucatan Channel. The dataset spans 22 months, starting in May 2006, and includes full water column current profiles. Currents were found more variable over the shelf break than on the shelf or the slope. The mean current strongly follows the bathymetry everywhere and particularly on the slope. Currents were highly depth-independent in the upper 100 m, accounting for more than 80% of the eddy kinetic energy (EKE) in this layer. The analysis suggest that the transition between deep and shallow water current regimes is driven by the coupling of the lateral boundary layer imposed by the shelf-break, and the shallow surface and bottom boundary layers originated by wind stress, tidal currents, and wind wave bottom stress.

  7. The current structure of stratified tidal planetary boundary layer flow

    SciTech Connect

    Myrhaug, D.; Slaattelid, O.H.

    1995-12-31

    The paper presents the bottom shear stress and velocity profiles in stratified tidal planetary boundary layer flow by using similarity theory. For a given seabed roughness length, free stream current velocity components, frequency of tidal oscillation, Coriolis parameter and stratification parameter the maximum bottom shear stress is determined for flow conditions in the rough, smooth and transitional smooth-to-rough turbulent regime. Further, the direction of the bottom shear stress and the velocity profiles are given. Comparison is made with data from field measurements of time-independent as well as tidal planetary boundary layer flow for neutral conditions, and the agreement between the predictions and the data is generally good. Further, an example of application for stable stratification is given, and qualitatively the predictions show, as expected, that the bottom shear stress and the thickness of the boundary layer become smaller for stable than for neutral stratification. Other features of the tidal planetary boundary layer flow are also discussed.

  8. Pacific western boundary currents and their roles in climate.

    PubMed

    Hu, Dunxin; Wu, Lixin; Cai, Wenju; Gupta, Alex Sen; Ganachaud, Alexandre; Qiu, Bo; Gordon, Arnold L; Lin, Xiaopei; Chen, Zhaohui; Hu, Shijian; Wang, Guojian; Wang, Qingye; Sprintall, Janet; Qu, Tangdong; Kashino, Yuji; Wang, Fan; Kessler, William S

    2015-06-18

    Pacific Ocean western boundary currents and the interlinked equatorial Pacific circulation system were among the first currents of these types to be explored by pioneering oceanographers. The widely accepted but poorly quantified importance of these currents-in processes such as the El Niño/Southern Oscillation, the Pacific Decadal Oscillation and the Indonesian Throughflow-has triggered renewed interest. Ongoing efforts are seeking to understand the heat and mass balances of the equatorial Pacific, and possible changes associated with greenhouse-gas-induced climate change. Only a concerted international effort will close the observational, theoretical and technical gaps currently limiting a robust answer to these elusive questions. PMID:26085269

  9. Pacific western boundary currents and their roles in climate

    NASA Astrophysics Data System (ADS)

    Hu, Dunxin; Wu, Lixin; Cai, Wenju; Gupta, Alex Sen; Ganachaud, Alexandre; Qiu, Bo; Gordon, Arnold L.; Lin, Xiaopei; Chen, Zhaohui; Hu, Shijian; Wang, Guojian; Wang, Qingye; Sprintall, Janet; Qu, Tangdong; Kashino, Yuji; Wang, Fan; Kessler, William S.

    2015-06-01

    Pacific Ocean western boundary currents and the interlinked equatorial Pacific circulation system were among the first currents of these types to be explored by pioneering oceanographers. The widely accepted but poorly quantified importance of these currents--in processes such as the El Niño/Southern Oscillation, the Pacific Decadal Oscillation and the Indonesian Throughflow--has triggered renewed interest. Ongoing efforts are seeking to understand the heat and mass balances of the equatorial Pacific, and possible changes associated with greenhouse-gas-induced climate change. Only a concerted international effort will close the observational, theoretical and technical gaps currently limiting a robust answer to these elusive questions.

  10. Carbon transport in the bottom boundary layer. Final report

    SciTech Connect

    Agrawal, Y.C.

    1998-10-05

    This report summarizes the activities and findings from a field experiment devised to estimate the rates and mechanisms of transport of carbon across the continental shelves. The specific site chosen for the experiment was the mid-Atlantic Bight, a region off the North Carolina coast. The experiment involved a large contingent of scientists from many institutions. The specific component of the program was the transport of carbon in the bottom boundary layer. The postulate mechanisms of transport of carbon in the bottom boundary layer are: resuspension and advection, downward deposition, and accumulation. The high turbulence levels in the bottom boundary layer require the understanding of the coupling between turbulence and bottom sediments. The specific issues addressed in the work reported here were: (a) What is the sediment response to forcing by currents and waves? (b) What is the turbulence climate in the bottom boundary layer at this site? and (c) What is the rate at which settling leads to carbon sequestering in bottom sediments at offshore sites?

  11. A western boundary current east of New Caledonia: Observed characteristics

    NASA Astrophysics Data System (ADS)

    Gasparin, Florent; Ganachaud, Alexandre; Maes, Christophe

    2011-09-01

    Waters from the South Equatorial Current (SEC), the northern branch of the South Pacific subtropical gyre, are a major supply of heat to the equatorial warm pool, and have an important contribution to climate variability and ENSO which motivated the Southwest Pacific Ocean and Climate Experiment (SPICE, CLIVAR/WCRP). Initially a broad westward current extending from the equator to 30°S, the SEC splits upon arriving at the major islands and archipelagoes of Fiji (18°S, 180°E), Vanuatu (16°S, 168°E), and New Caledonia (22°S, 165°E), resulting in a complex system of western boundary currents and zonal jets that feed the Coral and Solomon Seas. We focus here on the formation of one specific jet feeding the Coral Sea, the North Caledonian Jet (NCJ). Using a combination of recent oceanographic cruises, we describe the ocean circulation to the northeast of New Caledonia, where the SEC forms a western boundary current that ultimately becomes the NCJ. This current, which we document for the first time and propose to refer to as the East Caledonian Current (ECC), has its core located 10-100 km off the east coast of New Caledonia, and extends vertically to at least 1000 m depth. Water mass properties show continuous westward transports through the ECC, from the SEC to the NCJ in both the South Pacific Tropical Waters in the thermocline and Antarctic Intermediate Waters near 700 m depth. The ECC extends about 100 km horizontally; its average 0-1000 m transport was estimated at 14.5±3 Sv off the north tip of the New Caledonian reef, with a maximum of 20 Sv in May 2010. South of that the upstream branch of the ECC east of the Loyalty is close to 8 Sv suggesting an important additional contribution from central Pacific waters carried by the SEC at 16°S and diverted to our region through the western boundary current system east of Vanuatu.

  12. The Deep Western Boundary Current: tracers and velocities

    NASA Astrophysics Data System (ADS)

    Rhein, Monika

    1994-02-01

    In the Deep Western Boundary Current (DWBC) mean velocities obtained by the F11/F12 dating method are far smaller (1-2 cm s -1) than direct velocity measurements (5-20 cm s -1). To resolve this discrepancy, a simple box model is presented that uses the ideas of PICKARTet al. (1989, Physical Oceanography, 19, 940-951) to parametrize turbulent diffusion of the current with its surroundings. In contrast to previous models, however, the boundary conditions include all water masses forming the lower part of the DWBC (Denmark Strait Overflow Water, Iceland Scotland Overflow Water and Northeast Atlantic Water). The model-derived mean velocity of the DWBC leads to tracer concentrations that have to fit the observed F11 and F12 distributions, the F11/F12 ratios, and the tritium distributions. Moreover, the model area is extended from south of the Faroe bank along the continental margin of the American continent to 10°S. The model assumes uniform velocity and uniform turbulent mixing along the flow path of the DWBC, and enhanced turbulent mixing in the vicinity of the current compared to the ocean's interior allows the surrounding waters, which remain motionless, to accumulate tracers. The highest mean velocity of the DWBC, which results in model F12, F11, and 3H distributions as well as F11/F12 ratios, compatible to measurements of these tracers along the western boundary, are 4.8 cm s -1. Variations in the composition of the DWBC as well as changes in the time history of the source water masses do not increase the range of the model velocities.

  13. Three dimensional boundary element solutions for eddy current nondestructive evaluation

    NASA Astrophysics Data System (ADS)

    Yang, Ming; Song, Jiming; Nakagawa, Norio

    2014-02-01

    The boundary integral equations (BIE) method is a numerical computational method of solving linear partial differential equations which have been formulated as integral equations. It can be applied in many areas of engineering and science including fluid mechanics, acoustics, electromagnetics, and fracture mechanics. The eddy current problem is formulated by the BIE and discretized into matrix equations by the method of moments (MoM) or the boundary element method (BEM). The three dimensional arbitrarily shaped objects are described by a number of triangular patches. The Stratton-Chu formulation is specialized for the conductive medium. The equivalent electric and magnetic surface currents are expanded in terms of Rao-Wilton-Glisson (RWG) vector basis function while the normal component of magnetic field is expanded in terms of the pulse basis function. Also, a low frequency approximation is applied in the external medium. Additionally, we introduce Auld's impedance formulas to calculate impedance variation. There are very good agreements between numerical results and those from theory and/or experiments for a finite cross-section above a wedge.

  14. Plasma Transport at the Magnetospheric Flank Boundary. Final report

    SciTech Connect

    Otto, Antonius

    2012-04-23

    Progress is highlighted in these areas: 1. Model of magnetic reconnection induced by three-dimensional Kelvin Helmholtz (KH) modes at the magnetospheric flank boundary; 2. Quantitative evaluation of mass transport from the magnetosheath onto closed geomagnetic field for northward IMF; 3. Comparison of mass transfer by cusp reconnection and Flank Kelvin Helmholtz modes; 4. Entropy constraint and plasma transport in the magnetotail - a new mechanism for current sheet thinning; 5. Test particle model for mass transport onto closed geomagnetic field for northward IMF; 6. Influence of density asymmetry and magnetic shear on (a) the linear and nonlinear growth of 3D Kelvin Helmholtz (KH) modes, and (b) three-dimensional KH mediated mass transport; 7. Examination of entropy and plasma transport in the magnetotail; 8. Entropy change and plasma transport by KH mediated reconnection - mixing and heating of plasma; 9. Entropy and plasma transport in the magnetotail - tail reconnection; and, 10. Wave coupling at the magnetospheric boundary and generation of kinetic Alfven waves.

  15. Production regimes in four eastern boundary current systems

    NASA Technical Reports Server (NTRS)

    Carr, M. E.; Kearns, E. J.

    2003-01-01

    High productivity (maxima 3 g C m(sup -2)day(sup -1)) of the Eastern Boundary Currents (EBCs), i.e. the California, Peru-Humboldt, Canary and Benguela Currents, is driven by a combination of local forcing and large-scale circulation. The characteristics of the deep water brought to the surface by upwelling favorable winds depend on the large-scale circulation patterns. Here we use a new hydrographic and nutrient climatology together with satellite measurements ofthe wind vector, sea-surface temperature (SST), chlorophyll concentration, and primary production modeled from ocean color to quantify the meridional and seasonal patterns of upwelling dynamics and biological response. The unprecedented combination of data sets allows us to describe objectively the variability for small regions within each current and to characterize the governing factors for biological production. The temporal and spatial environmental variability was due in most regions to large-scale circulation, alone or in combination with offshore transport (local forcing). The observed meridional and seasonal patterns of biomass and primary production were most highlycorrelated to components representing large-scale circulation. The biomass sustained by a given nutrient concentration in the Atlantic EBCs was twice as large as that of the Pacific EBCs. This apparent greater efficiency may be due toavailability of iron, physical retention, or differences in planktonic community structure.

  16. Reversal process of the South China Sea western boundary current in autumn 2011

    NASA Astrophysics Data System (ADS)

    Zhang, Zhixin; Guo, Jingsong; Guo, Binghuo

    2016-05-01

    Using merged sea level anomaly and absolute geostrophic velocity products from satellite altimetry and Argos drifter data, we analyzed the reversal process of the South China Sea (SCS) western boundary current (SCSwbc) from a summer to winter pattern in 2011 and important oceanic phenomena during this process. Results show that the outbreak time of the northeast monsoon over the southern SCS lagged that over the northern SCS by about 1 month. During the SCS monsoon reversal period, the SCSwbc reversed rapidly into the winter pattern at the Guangdong continental slope in late September. Subsequently, the southward Vietnam coastal boundary current strengthened. However, the northward Natuna Current maintained a summer state until mid-October. Thus, the balance between the southward and northward currents was lost when they met, their junction moved gradually southward. However, a loop current formed southeast of Vietnam because the main stream of the Vietnam Offshore Current (VOC) remained near its original latitude. Meanwhile, the VOC and associated dipole circulation system strengthened. After mid-October, the northward Natuna Current began to weaken, the loop current finally shed, becoming a cool ring. The VOC and its associated dipole sub-basin circulation system also weakened gradually until it disappeared.

  17. Reversal process of the South China Sea western boundary current in autumn 2011

    NASA Astrophysics Data System (ADS)

    Zhang, Zhixin; Guo, Jingsong; Guo, Binghuo

    2015-10-01

    Using merged sea level anomaly and absolute geostrophic velocity products from satellite altimetry and Argos drifter data, we analyzed the reversal process of the South China Sea (SCS) western boundary current (SCSwbc) from a summer to winter pattern in 2011 and important oceanic phenomena during this process. Results show that the outbreak time of the northeast monsoon over the southern SCS lagged that over the northern SCS by about 1 month. During the SCS monsoon reversal period, the SCSwbc reversed rapidly into the winter pattern at the Guangdong continental slope in late September. Subsequently, the southward Vietnam coastal boundary current strengthened. However, the northward Natuna Current maintained a summer state until mid-October. Thus, the balance between the southward and northward currents was lost when they met, their junction moved gradually southward. However, a loop current formed southeast of Vietnam because the main stream of the Vietnam Offshore Current (VOC) remained near its original latitude. Meanwhile, the VOC and associated dipole circulation system strengthened. After mid- October, the northward Natuna Current began to weaken, the loop current finally shed, becoming a cool ring. The VOC and its associated dipole sub-basin circulation system also weakened gradually until it disappeared.

  18. Intensified Diapycnal Mixing in the Midlatitude Western Boundary Currents

    NASA Astrophysics Data System (ADS)

    Jing, Zhao; Wu, Lixin

    2014-12-01

    The wind work on oceanic near-inertial motions is suggested to play an important role in furnishing the diapycnal mixing in the deep ocean which affects the uptake of heat and carbon by the ocean as well as climate changes. However, it remains a puzzle where and through which route the near-inertial energy penetrates into the deep ocean. Using the measurements collected in the Kuroshio extension region during January 2005, we demonstrate that the diapycnal mixing in the thermocline and deep ocean is tightly related to the shear variance of wind-generated near-inertial internal waves with the diapycnal diffusivity 6 × 10-5 m2s-1 almost an order stronger than that observed in the circulation gyre. It is estimated that 45%-62% of the local near-inertial wind work 4.5 × 10-3 Wm-2 radiates into the thermocline and deep ocean and accounts for 42%-58% of the energy required to furnish mixing there. The elevated mixing is suggested to be maintained by the energetic near-inertial wind work and strong eddy activities causing enhanced downward near-inertial energy flux than earlier findings. The western boundary current turns out to be a key region for the penetration of near-inertial energy into the deep ocean and a hotspot for the diapycnal mixing in winter.

  19. Equatorial to Mid-Latitude Connections in Eastern Boundary Currents

    NASA Astrophysics Data System (ADS)

    Strub, T.

    2002-12-01

    Over twenty years ago, Enfield and Allen (1980, J. Phys. Oceaogr., 10, 557-578) used tide-gauge sea level height data to show the connection between the equator and the mid-latitude coastal ocean in the eastern Pacific. Careful selection of tide gauges and quality control of the data allowed both seasonal and interannual time scales to be examined over a period of 24 years. Today, 10 years of TOPEX/POSEIDON altimeter data allow us to re-examine the seasonal and non-seasonal connections between the equator and higher latitudes in the eastern boundary currents (EBC's) along the coasts of the Pacific and Atlantic Oceans. We present the seasonal progressions in both basins and hemispheres, showing the low-to-high latitude development of the seasonal cycle and also the offshore propagation of annual Rossby waves. This brings out several general tendencies: 1) The signals are stronger in the Northern Hemisphere basins, due to the fact that the ITCZ is located north of the equator in both basins; 2) The signals are stronger in the NE Pacific than in any of the other basins; and 3) There is an annual signal of high sea surface height that propagates down both Southern Hemisphere EBC's in austral spring (September-November) as the SW trade winds weaken along the equator and the equatorial cold tongue collapses. This last feature is somewhat like an annual "El Ni¤o" effect and acts to suppress the onset of wind driven upwelling in the Peru-Chile and Benguela Current Systems.

  20. Current issues in atmospheric change. Final report

    SciTech Connect

    Not Available

    1987-01-01

    In response to questions about the effects of long-term, global-scale changes in the atmosphere raised in congressional hearings, a group of leading experts held a two-day workshop to survey the state of current knowledge about atmospheric changes and their implications. The review focuses on the sources, concentrations, and changes of those gases most directly linked to human activities, i.e., carbon dioxide, ozone, and the chlorofluorocarbons; the direct physical effects of changes in trace gases; and the impacts of rising concentrations of trace gases. The review discusses the uncertainties associated with the knowledge of current trends and possible future changes, including ozone trends and the Antarctic ozone hole, and the impacts of rising concentrations of trace gases.

  1. Lower Atmospheric Boundary Layer Experiment (LABLE) Final Campaign Report

    SciTech Connect

    Klein, P; Bonin, TA; Newman, JF; Turner, DD; Chilson, P; Blumberg, WG; Mishra, S; Wainwright, CE; Carney, M; Jacobsen, EP; Wharton, S

    2015-11-01

    The Lower Atmospheric Boundary Layer Experiment (LABLE) included two measurement campaigns conducted at the Atmospheric Radiation Measurement (ARM) Southern Great Plains site in Oklahoma during 2012 and 2013. LABLE was designed as a multi-phase, low-cost collaboration among the University of Oklahoma, the National Severe Storms Laboratory, Lawrence Livermore National Laboratory, and the ARM program. A unique aspect was the role of graduate students in LABLE. They served as principal investigators and took the lead in designing and conducting experiments using different sampling strategies to best resolve boundary-layer phenomena.

  2. Mesoscale Coupled Ocean-Atmosphere Feedbacks in Boundary Current Systems

    NASA Astrophysics Data System (ADS)

    Putrasahan, Dian Ariyani

    The focus of this dissertation is on studying ocean-atmosphere (OA) interactions in the Humboldt Current System (HCS) and Kuroshio Extension (KE) region using satellite observations and the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model. Within SCOAR, a new technique is introduced by implementing an interactive 2-D spatial smoother within the SST-flux coupler to remove the mesoscale SST field felt by the atmosphere. This procedure allows large-scale SST coupling to be preserved while extinguishing the mesoscale eddy impacts on the atmospheric boundary layer (ABL). This technique provides insights to spatial-scale dependence of OA coupling, and the impact of mesoscale features on both the ABL and the surface ocean. For the HCS, the use of downscaled forcing from SCOAR, as compared to NCEP Reanalysis 2, proves to be more appropriate in quantifying wind-driven upwelling indices along the coast of Peru and Chile. The difference in their wind stress distribution has significant impact on the wind-driven upwelling processes and total upwelling transport along the coast. Although upwelling induced by coastal Ekman transport dominates the wind-driven upwelling along coastal areas, Ekman pumping can account for 30% of the wind-driven upwelling in several coastal locations. Control SCOAR shows significant SST-wind stress coupling during fall and winter, while Smoothed SCOAR shows insignificant coupling throughout, indicating the important role of ocean mesoscale eddies on air-sea coupling in HCS. The SST-wind stress coupling however, did not produce any rectified response on the ocean eddies. Coupling between SST, wind speed and latent heat flux is insignificant on large-scale coupling and full coupling mode. On the other hand, coupling between these three variables are significant on the mesoscale for most of the model run, which suggests that mesoscale SST affects latent heat through direct flux anomalies as well as indirectly through stability changes on the

  3. Carbon transport in the bottom boundary layer. Final report

    SciTech Connect

    Lohrenz, S.E.; Asper, V.L.

    1997-09-01

    The authors objective was to characterize distributions of chloropigment fluorescence in relation to physical processes in the benthic boundary layer in support of the Department of Energy (DOE) Ocean Margins Program`s (OMP) goal of quantifying carbon transport across the continental shelf. Their approach involved participation in the Ocean Margins Program (OMP) field experiment on the continental shelf off Cape Hatteras by conducting multi-sensor fluorescence measurements of photosynthetic pigments. Specific tasks included (1) pre- and post-deployment calibration of multiple fluorescence sensors in conjunction with Woods Hole personnel; (2) collection and analysis of photosynthetic pigment concentrations and total particulate carbon in water column samples to aid in interpretation of the fluorescence time-series during the field experiment; (3) collaboration in the analysis and interpretation of 1994 and 1996 time-series data in support of efforts to quantify pigment and particulate organic carbon transport on the continental shelf off Cape Hatteras. This third component included analysis of data obtained with a multi-sensor fiber-optic fluorometer in the benthic boundary layer of the inner shelf off Cape Hatteras during summer 1994.

  4. 78 FR 56650 - Boundary Description and Final Map for Roaring Wild and Scenic River, Mount Hood National Forest...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-13

    ... Forest Service Boundary Description and Final Map for Roaring Wild and Scenic River, Mount Hood National... transmitting the final boundary description and map of the Roaring Wild and Scenic River to Congress. DATES... Stat. 906 as amended; 16 U.S.C. 1274), the detailed boundary descriptions and final maps were...

  5. The influence of vortex pinning and grain boundary structure on critical currents across grain boundaries in YBa{sub 2}Cu{sub 3}O{sub x}.

    SciTech Connect

    Miller, D. J.

    1998-10-27

    We have used studies of single grain boundaries in YBCO thin films and bulk bicrystals to study the influence of vortex pinning along a grain boundary on dissipation. The critical current density for transport across grain boundaries in thin films is typically more than an order of magnitude larger than that measured for transport across grain boundaries in bulk samples. For low disorientation angles, the difference in critical current density within the grains that form the boundary can contribute to the substantial differences in current density measured across the boundary. However, substantial differences exist in the critical current density across boundaries in thin film compared to bulk bicrystals even in the higher angle regime in which grain boundary dissipation dominates. The differences in critical current density in this regime can be understood on the basis of vortex pinning along the boundary.

  6. Remote sensing of ocean current boundary layer. [Loop Current in Gulf of Mexico

    NASA Technical Reports Server (NTRS)

    Maul, G. A. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. A time series of the Loop Current in the Gulf of Mexico, covering an annual cycle of growth, spreading, and decay, has been obtained in synchronization with ERTS-1. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed either by color or sea state effects associated with the cyclonic boundary. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation. Several spectra of upwelling diffuse light are computed as a function of the concentration of particles and yellow substance. These calculations compare favorably with experimental measurements and show that the ratio of channels method gives ambiguous interpretative results. These results are used to discuss features in images where surface measurements were obtained and are extended to tentative explanation in others.

  7. Bottom boundary layer measurements in OMP. Final report

    SciTech Connect

    Gross, T.F.; Williams, A.J.

    1998-11-01

    The main role of the Benthic Acoustic Stress Sensor (BASS) tripods within the Ocean Margins Program experiments was to detect and quantify organic carbon rich particle transport off the shelf. This requires measures of the turbulent boundary layer flow and bed stress, the physical forcing of the particle transport, as well as the concentration and type of particles which are being transported. The BASS tripods were deployed at sites 17 and 26. Data from site 26 were recovered spanning three periods: Feb. 2--April 6, May 13--June 27, June 28--Aug. 18. Site 17 was occupied Feb. 12--april 11. The BASS tripods were arrayed with five BASS sensors measuring detailed velocity parameters within four meters of the seabed. Velocity time series indicate a usually weak tidal flow which produces small bed stress by itself. On the occasions when a strong flow, probably the Gulf Stream, crosses the area, the bed shear stress increases dramatically to as much as 10 dyne cm{sup {minus}2}. This is competent to move unconsolidated sediments in the area. Other instruments from the tripods include: two conductivity/temperature sensor pairs, five WetStar fluorometers, thermistors, transmissometer, optical backscatterence sensors and a pressure sensor.

  8. Surface capillary currents: Rediscovery of fluid-structure interaction by forced evolving boundary theory

    NASA Astrophysics Data System (ADS)

    Wang, Chunbai; Mitra, Ambar K.

    2016-01-01

    Any boundary surface evolving in viscous fluid is driven with surface capillary currents. By step function defined for the fluid-structure interface, surface currents are found near a flat wall in a logarithmic form. The general flat-plate boundary layer is demonstrated through the interface kinematics. The dynamics analysis elucidates the relationship of the surface currents with the adhering region as well as the no-slip boundary condition. The wall skin friction coefficient, displacement thickness, and the logarithmic velocity-defect law of the smooth flat-plate boundary-layer flow are derived with the advent of the forced evolving boundary method. This fundamental theory has wide applications in applied science and engineering.

  9. How to interpret current-voltage relationships of blocking grain boundaries in oxygen ionic conductors.

    PubMed

    Kim, Seong K; Khodorov, Sergey; Chen, Chien-Ting; Kim, Sangtae; Lubomirsky, Igor

    2013-06-14

    A new model based on a linear diffusion equation is proposed to explain the current-voltage characteristics of blocking grain boundaries in Y-doped CeO2 in particular. One can also expect that the model can be applicable to the ionic conductors with blocking grain boundaries, in general. The model considers an infinitely long chain of identical grains separated by grain boundaries, which are treated as regions in which depletion layers of mobile ions are formed due to trapping of immobile charges that do not depend on the applied voltage as well as temperature. The model assumes that (1) the grain boundaries do not represent physical blocking layers, which implies that if there is a second phase at the grain boundaries, then it is too thin to impede ion diffusion and (2) the ions follow Boltzmann distribution throughout the materials. Despite its simplicity, the model successfully reproduces the "power law": current proportional to voltage power n and illustrated with the experimental example of Y-doped ceria. The model also correctly predicts that the product nT, where T is the temperature in K, is constant and is proportional to the grain boundary potential as long as the charge at the grain boundaries remains trapped. The latter allows its direct determination from the current-voltage characteristics and promises considerable simplification in the analysis of the electrical characteristics of the grain boundaries with respect to the models currently in use. PMID:23640401

  10. Phase boundary of spin-polarized-current state of electrons in bilayer graphene

    NASA Astrophysics Data System (ADS)

    Yan, Xin-Zhong; Ma, Yinfeng; Ting, C. S.

    2016-06-01

    Using a four-band Hamiltonian, we study the phase boundary of spin-polarized-current state (SPCS) of interacting electrons in bilayer graphene. The model of spin-polarized-current state has previously been shown to resolve a number of experimental puzzles in bilayer graphene. The phase boundaries of the SPCS with and without the external voltage between the two layers are obtained in this work. An unusual phase boundary where there are two transition temperatures for a given carrier concentration is found at finite external voltage. The physics of this phenomenon is explained.

  11. 78 FR 56650 - Boundary Description and Final Map for Sandy Wild and Scenic River, Upper Portion, Mount Hood...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-13

    ... Forest Service Boundary Description and Final Map for Sandy Wild and Scenic River, Upper Portion, Mount..., is transmitting the final boundary description and map of the Sandy Wild and Scenic River, Upper... descriptions and final maps were forwarded on August 21, 2013. ADDRESSES: Documents may be viewed at...

  12. A high-latitude, low-latitude boundary layer model of the convection current system

    SciTech Connect

    Siscoe, G.L. ); Lotko, W.; Sonnerup, B.U.O. )

    1991-03-01

    Observations suggest that both the high- and low-latitude boundary layers contribute to magnetospheric convection, and that their contributions are linked. In the interpretation pursued here, the high-latitude boundary layer (HBL) generates the voltage while the low-latitude boundary layer (LBL) generates the current for the part of the convection electric circuit that closes through the ionosphere. This paper gives a model that joins the high- and low-latitude boundary layers consistently with the ionospheric Ohm's law. It describes an electric circuit linking both boundary layers, the region 1 Birkeland currents, and the ionospheric Pedersen closure currents. The model works by using the convection electric field that the ionosphere receives from the HBL to determine two boundary conditions to the equations that govern viscous LBL-ionosphere coupling. The result provides the needed self-consistent coupling between the two boundary layers and fully specifies the solution for the viscous LBL-ionosphere coupling equations. The solution shows that in providing the current required by the ionospheric Ohm's law, the LBL needs only a tenth of the voltage that spans the HBL. The solution also gives the latitude profiles of the ionospheric electric field, parallel currents, and parallel potential. It predicts that the plasma in the inner part of the LBL moves sunward instead of antisunward and that, as the transpolar potential decreases below about 40 kV, reverse polarity (region 0) currents appear at the poleward border of the region 1 currents. A possible problem with the model is its prediction of a thin boundary layer ({approximately}1000 km), whereas thicknesses inferred from satellite data tend to be greater.

  13. Observations of the magnetopause current layer: Cases with no boundary layer and tests of recent models

    NASA Technical Reports Server (NTRS)

    Eastman, Timothy E.

    1995-01-01

    Evidence for the probable existence of magnetospheric boundary layers was first presented by Hones, et al. (1972), based on VELA satellite plasma observations (no magnetic field measurements were obtained). This magnetotail boundary layer is now known to be the tailward extension of the high-latitude boundary layer or plasma mantle (first uniquely identified using HEOS 2 plasma and field observations by Rosenbauer et al., 1975) and the low-latitude boundary layer (first uniquely identified using IMP 6 plasma and field observations by Eastman et al., 1976). The magnetospheric boundary layer is the region of magnetosheath-like plasma located Earthward of, but generally contiguous with the magnetopause. This boundary layer is typically identified by comparing low-energy (less than 10 keV) ion spectra across the magnetopause. Low-energy electron measurements are also useful for identifying the boundary layer because the shocked solar wind or magnetosheath has a characteristic spectral signature for electrons as well. However, there are magnetopause crossings where low-energy electrons might suggest a depletion layer outside the magnetopause even though the traditional field-rotation signature indicates that this same region is a boundary layer Earthward of the current layer. Our analyses avoided crossings which exhibit such ambiguities. Pristine magnetopause crossings are magnetopause crossings for which the current layer is well defined and for which there is no adjoining magnetospheric boundary layer as defined above. Although most magnetopause models to date apply to such crossings, few comparisons between such theory and observations of pristine magnetopause crossings have been made because most crossings have an associated magnetospheric boundary layer which significantly affects the applicable boundary conditions for the magnetopause current layer. Furthermore, almost no observational studies of magnetopause microstructure have been done even though key

  14. Observed bottom boundary layer transport and uplift on the continental shelf adjacent to a western boundary current

    NASA Astrophysics Data System (ADS)

    Schaeffer, A.; Roughan, M.; Wood, J. E.

    2014-08-01

    Western boundary currents strongly influence the dynamics on the adjacent continental shelf and in particular the cross-shelf transport and uplift through the bottom boundary layer. Four years of moored in situ observations on the narrow southeastern Australian shelf (in water depths of between 65 and 140 m) were used to investigate bottom cross-shelf transport, both upstream (30°S) and downstream (34°S) of the separation zone of the East Australian Current (EAC). Bottom transport was estimated and assessed against Ekman theory, showing consistent results for a number of different formulations of the boundary layer thickness. Net bottom cross-shelf transport was onshore at all locations. Ekman theory indicates that up to 64% of the transport variability is driven by the along-shelf bottom stress. Onshore transport in the bottom boundary layer was more intense and frequent upstream than downstream, occurring 64% of the time at 30°S. Wind-driven surface Ekman transport estimates did not balance the bottom cross-shelf flow. At both locations, strong variability was found in bottom water transport at periods of approximately 90-100 days. This corresponds with periodicity in EAC fluctuations and eddy shedding as evidenced from altimeter observations, highlighting the EAC as a driver of variability in the continental shelf waters. Ocean glider and HF radar observations were used to identify the bio-physical response to an EAC encroachment event, resulting in a strong onshore bottom flow, the uplift of cold slope water, and elevated coastal chlorophyll concentrations.

  15. Depairing current density through a low-angle grain boundary in a superconducting film

    NASA Astrophysics Data System (ADS)

    Xue, Feng; Zhang, Zhaoxia; Zeng, Jun; Gou, Xiaofan

    2016-05-01

    In this paper, the effect of a grain boundary (GB) on the depairing current density of a high-temperature superconducting film is investigated. The modified effective free energy is proposed by considering the interaction of the superconducting condensate with the deformation of the superconductor due to the dislocations which constitute a grain boundary. After the elastic strain field of the dislocation is obtained, we analyzed the depress effect of the GB on the depairing current density of a superconducting film. The results are qualitatively agreement with the classic exponential relationship with the misorientation angles of the critical current density of high-temperature superconductors.

  16. Direct measurement of potential steps at grain boundaries in the presence of current flow

    SciTech Connect

    Kirtley, J.R.; Washburn, S.; Brady, M.J.

    1988-04-11

    We have used a new technique to measure simultaneously the surface topography and surface potential of current-carrying polycrystalline Au/sub 60/Pd/sub 40/ thin films using a scanning tunneling microscope. The variations of the gradients of the surface potential from a macroscopically constant value which are associated with scattering from grain boundaries in these films are observed. We find that the local potential changes abruptly at the boundaries between the grains.

  17. Comparison of DMSP and SECS region-1 and region-2 ionospheric current boundary

    NASA Astrophysics Data System (ADS)

    Weygand, J. M.; Wing, S.

    2016-06-01

    The region-1 and region-2 boundary has traditionally been identified using data from a single spacecraft crossing the auroral region and measuring the large scale changes in the cross track magnetic field. With data from the AUTUMN, CANMOS, CARISMA, GIMA, DTU MGS, MACCS, McMAC, STEP, THEMIS, and USGS ground magnetometer arrays we applied a state-of-art technique based on spherical elementary current system (SECS) method developed by Amm and Viljanen (1999) in order to calculate maps of region-1 and region-2 current system over the North American and Greenland auroral region. Spherical elementary current (SEC) amplitude (proxy for vertical currents) maps can be inferred at 10 s temporal resolution, ~1.5° geographic latitude (Glat), and 3.5° geographic longitude (Glon) spatial resolution. We compare the location of the region-1 and region-2 boundary obtained by the DMSP spacecraft with the region-1 and region-2 boundary observed in the SEC current amplitudes. We find that the boundaries typically agree within 0.2°±1.3°. These results indicate that the location of the region-1 and region-2 boundary can reasonably be determined from ground magnetometer data. The SECS maps represent a value-added product from the magnetometer database and can be used for contextual interpretation in conjunction with other missions as well as help with our understanding of magnetosphere-ionosphere coupling mechanisms using the ground arrays and the magnetospheric spacecraft data.

  18. Effects of the current boundary conditions at the plasma-gun gap on density in SSPX

    NASA Astrophysics Data System (ADS)

    Kolesnikov, Roman; Lodestro, L. L.; Meyer, W. H.

    2012-10-01

    The Sustained Spheromak Physics Experiment (SSPX) was a toroidal magnetic-confinement device without toroidal magnetic-field coils or a central transformer but which generated core-plasma currents by dynamo processes driven by coaxial plasma-gun injection into a flux-conserving vessel. Record electron temperatures in a spheromak (Te˜500eV) were achieved, and final results of the SSPX program were reported in [1]. Plasma density, which depended strongly on wall conditions, was an important parameter in SSPX. It was observed that density rises with Igun and that confinement improved as the density was lowered. Shortly after the last experiments, a new feature was added to the Corsica code's solver used to reconstruct SSPX equilibria. Motivated by n=0 fields observed in NIMROD simulations of SSPX, an insulating boundary condition was implemented at the plasma-gun gap. Using this option we will perform new reconstructions of SSPX equilibria and look for correlations between the location of the separatrix (which moves up the gun wall and onto the insulating gap as Igun increases) and plasma density and magnetic-flux amplification [2].[4pt] [1] H. S. McLean, APS, DPP, Dallas, TX, 2008.[0pt] [2] E. B. Hooper et al., Nucl. Fusion 47, 1064 (2007).

  19. Twin engineering for high critical current densities and twin boundary energy measurement in melt processed YBCO

    NASA Astrophysics Data System (ADS)

    Mei, Linfeng

    It has been proven that twin boundaries in YBa2Cu 3O7-delta (YBCO) are effective flux pinning centers. By increasing the twin density of a YBCO sample, it is possible to achieve a high critical current density (Jc). In this work, twin engineering for high critical current densities and strong flux pinning has been achieved in melt processed YBCO by increasing the annealing temperature up to 680°C. When the isothermal oxygenation temperature increases from 450°C to 680°C, the average twin boundary spacing of the samples decreases significantly, and its critical current density and flux pinning force are greatly increased. The prerequisites for twin boundary engineering for high critical current densities and strong flux pinning are also pointed out. For the first time, temperature dependent twin boundary energies (gammatw's) of melt processed YBCO are measured by the twin spacing method and the twin tip or shape method, and the geometrical factor alpha in the twin spacing method is estimated. As expected, the twin boundary energy of YBCO decreases with increasing temperature. In addition, the correlation between Jc and the concentrations of Y2BaCuO5 (211) and Samarium (Sm) in the melt-textured growth (MTG) YBCO has been studied, as well as the distributions of 211 and Sm in the MTG YBCO pellets. All our results can be applied towards microstructure tailoring for a high Jc and strong flux pinning in YBCO, especially in bulk YBCO samples.

  20. Exact asymptotics of the current in boundary-driven dissipative quantum chains in large external fields.

    PubMed

    Lenarčič, Zala; Prosen, Tomaž

    2015-03-01

    A boundary-driven quantum master equation for a general inhomogeneous (nonintegrable) anisotropic Heisenberg spin-1/2 chain, or an equivalent nearest neighbor interacting spinless fermion chain, is considered in the presence of a strong external field f. We present an exact closed form expression for large f asymptotics of the current in the presence of a pure incoherent source and sink dissipation at the boundaries. In application, we demonstrate an arbitrary large current rectification in the presence of the interaction. PMID:25871030

  1. Theory of beam induced current characterization of grain boundaries in polycrystalline solar cells

    NASA Astrophysics Data System (ADS)

    Donolato, C.

    1983-03-01

    A theoretical analysis is given of the induced current profiles at grain boundaries in polycrystalline solar cells, as obtained by light or electron beam excitation. The area A and the variance sigma-squared of the contrast profile of a grain boundary are calculated for realistic generations as functions of the interface recombination velocity v(s) and the minority carrier diffusion length L. A new graphical procedure is proposed which allows the simultaneous determination of v(s) and L from the measured values of A and sigma. The evaluation of an experimental electron beam-induced current profile illustrates the applicability of the theory.

  2. Theoretical model and experimental investigation of current density boundary condition for welding arc study

    NASA Astrophysics Data System (ADS)

    Boutaghane, A.; Bouhadef, K.; Valensi, F.; Pellerin, S.; Benkedda, Y.

    2011-04-01

    This paper presents results of theoretical and experimental investigation of the welding arc in Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW) processes. A theoretical model consisting in simultaneous resolution of the set of conservation equations for mass, momentum, energy and current, Ohm's law and Maxwell equation is used to predict temperatures and current density distribution in argon welding arcs. A current density profile had to be assumed over the surface of the cathode as a boundary condition in order to make the theoretical calculations possible. In stationary GTAW process, this assumption leads to fair agreement with experimental results reported in literature with maximum arc temperatures of ~21 000 K. In contrast to the GTAW process, in GMAW process, the electrode is consumable and non-thermionic, and a realistic boundary condition of the current density is lacking. For establishing this crucial boundary condition which is the current density in the anode melting electrode, an original method is setup to enable the current density to be determined experimentally. High-speed camera (3000 images/s) is used to get geometrical dimensions of the welding wire used as anode. The total area of the melting anode covered by the arc plasma being determined, the current density at the anode surface can be calculated. For a 330 A arc, the current density at the melting anode surface is found to be of 5 × 107 A m-2 for a 1.2 mm diameter welding electrode.

  3. Transport and bottom boundary layerobservations of the North Atlantic Deep Western Boundary Current at the Blake Outer Ridge

    NASA Astrophysics Data System (ADS)

    Stahr, Frederick R.; Sanford, Thomas B.

    1999-01-01

    The North Atlantic Deep Western Boundary Current (DWBC) was surveyed at the Blake Outer Ridge over 14 days in July and August 1992 to determine its volume transport and to investigate its bottom boundary layer (BBL). This site was chosen because previous investigations showed the DWBC to be strong and bottom-intensified on the ridge's flanks and to have a thick BBL. The primary instrument used was the Absolute Velocity Profiler, a free-falling velocity and conductivity-temperature-depth device. In two sections across the width of the DWBC, volume transports of 17±1 Sv and 18±1 Sv were measured for all water flowing equatorward below a potential temperature of 6°C (1 Sv=1×10 6 m 3 s -1). Transport values were derived using both absolute velocities and AVP-referenced geostrophic velocities and were the same within experimental uncertainty. Good agreement was found between our results and historical ones when both were similarly bounded and referenced. Although this was a short-term survey, the mean of a 9-day time series of absolute velocity profiles was the same as the means of year-long current-meter records at three depths in the same location. A turbulent planetary BBL was found everywhere under the current. The thickness of the bottom mixed layer (BML), where concentrations of density, nutrients, and suspended sediments were vertically uniform, was asymmetrical across the current and up to 5 times thicker than the BBL. There was no velocity shear above the BBL within the thicker BMLs, and the across-slope density gradient was very small. The extra-thick BML is perhaps maintained by a combination of processes, including turbulence, downwelling Ekman transport, a weak up-slope return flow above the BBL, and buoyant convection from the BBL into the BML. The frictional bottom stress was mostly balanced by a down-stream change in the current's external potential energy evidenced by a drop in the velocity core of the current.

  4. Critical-current diffraction patterns of grain-boundary Josephson weak links

    SciTech Connect

    Peterson, R.L.; Ekin, J.W. )

    1990-11-01

    We discuss the diffraction patterns and other characteristics of the critical current as a function of magnetic field in grain-boundary Josephson barriers. Diffraction patterns occur not just for {ital SIS} junctions but for all types of Josephson links, including {ital SNS} junctions, which may be present at grain boundaries in high-{Tc} superconductors. We discuss the generality of the Airy diffraction pattern, which is expected to characterize grain-boundary barriers in bulk material more accurately than the Fraunhofer pattern. The transport critical-current density in many bulk, granular high-{ital T}{sub {ital c}} superconductors has a power-law dependence on very low magnetic fields, characteristic of averaged diffraction patterns, and cannot be fitted by an exponential magnetic-field dependence, which may result from the material properties of the barriers.

  5. Sources and transport of the Deep Western Boundary Current East of the Kerguelen Plateau

    NASA Astrophysics Data System (ADS)

    Donohue, Kathleen A.; Hufford, Gwyneth E.; McCartney, Michael S.

    East of the Kerguelen Plateau, a deep western boundary current in the Australian-Antarctic Basin brings cold dense waters north from the margins of Antarctica. Geostrophic velocities referenced to acoustic Doppler current profiler data, both shipboard and lowered, suggest the flow is unidirectional throughout the water column with estimated northwestward transport below potential temperature 1°C of 28 ± 7 × 106 m³s-1 and 49 ± 9 × 106 m³s-1 respectively. Hydrographie and acoustic Doppler current profiler data show that the deep boundary current is supplied by northward flow emerging from the confluence of westward flow along the Antarctic continental slope and eastward flow of Weddell Basin waters through the Princess Elizabeth Trough to the south of the Kerguelen Plateau.

  6. TOPOLOGICAL MATTER. Observation of chiral currents at the magnetic domain boundary of a topological insulator.

    PubMed

    Wang, Y H; Kirtley, J R; Katmis, F; Jarillo-Herrero, P; Moodera, J S; Moler, K A

    2015-08-28

    A magnetic domain boundary on the surface of a three-dimensional topological insulator is predicted to host a chiral edge state, but direct demonstration is challenging. We used a scanning superconducting quantum interference device to show that current in a magnetized topological insulator heterostructure (EuS/Bi2Se3) flows at the edge when the Fermi level is gate-tuned to the surface band gap. We further induced micrometer-scale magnetic structures on the heterostructure and detected a chiral edge current at the magnetic domain boundary. The chirality of the current was determined by magnetization of the surrounding domain, and its magnitude by the local chemical potential rather than the applied current. Such magnetic structures provide a platform for detecting topological magnetoelectric effects and may enable progress in quantum information processing and spintronics. PMID:26272905

  7. Seasonal to interannual variability of the Pacific water boundary current in the Beaufort Sea

    NASA Astrophysics Data System (ADS)

    Brugler, Eric T.; Pickart, Robert S.; Moore, G. W. K.; Roberts, Steven; Weingartner, Thomas J.; Statscewich, Hank

    2014-09-01

    Between 2002 and 2011 a single mooring was maintained at the core of the Pacific water boundary current in the Beaufort Sea, approximately 150 km east of Pt. Barrow, Alaska. Using velocity and hydrographic data from six year-long deployments, we examine the variability of the current on seasonal to interannual timescales. The seasonal signal is characterized by enhanced values of volume, heat, and freshwater transport during the summer months associated with the presence of two summertime Pacific water masses, Alaskan Coastal Water and Chukchi Summer Water. Strikingly, over the decade the volume transport of the current has decreased by more than 80%, with comparable reductions in the heat and freshwater transports, despite the fact that the flow through Bering Strait has increased over this time period. The largest changes in the boundary current have occurred in the summer months. Using atmospheric reanalysis fields and weather station data, we demonstrate that an increase in summer easterly winds along the Beaufort slope is the primary cause for the reduction in transport. The stronger winds are due to an intensification of the summer Beaufort High and deepening of the summer Aleutian Low. Using additional mooring and shipboard data in conjunction with satellite fields, we investigate the implications of the reduction in transport of the boundary current. We argue that a significant portion of the mass and heat passing through Bering Strait in recent years has been advected out of Barrow Canyon into the interior Canada Basin - rather than entering the boundary current in the Beaufort Sea - where it is responsible for a significant portion of the increased sea ice melt in the basin.

  8. Interannual variability of South Equatorial Current bifurcation and western boundary currents along the Madagascar coast

    NASA Astrophysics Data System (ADS)

    Yamagami, Y.; Tozuka, T.

    2015-12-01

    The South Equatorial Current (SEC) in the southern Indian Ocean bifurcates at the east coast of Madagascar into the Northeast and Southeast Madagascar Currents (NEMC and SEMC, respectively). In observational and reanalysis data, interannual variations of the NEMC and SEMC transports are strongly correlated with those of the SEC transport, rather than those of the SEC bifurcation latitude (SBL). Their dynamical mechanisms are then examined based on the Time-Dependent Island Rule for the first time. It is shown that interannual anomalies of the SBL as well as the NEMC and SEMC transports are predominantly a response to the anomalous inflow from the ocean interior that is determined by the meridional interior transport. This, in turn, is a result of westward propagating Rossby waves induced by wind stress curl anomalies mainly in 60°E-90°E. The above mechanism is contrasted with that of the seasonal variation, where the local transport driven by wind stress around the island plays a role. Furthermore, the interannual variations of the SBL and the NEMC and SEMC transports are significantly correlated with the Niño 3.4 index with 5-15 months lag. It is suggested that diabatic heating anomalies associated with the El Niño/Southern Oscillation (ENSO) along with a local process in the southeastern Indian Ocean may generate wind stress curl anomalies over the southern Indian Ocean.

  9. Grain boundary dependency of nonlinear current-voltage characteristics in Pr and Co Doped ZnO Bicrystals

    NASA Astrophysics Data System (ADS)

    Sato, Yukio; Oba, Fumiyasu; Yodogawa, Masatada; Yamamoto, Takahisa; Ikuhara, Yuichi

    2004-02-01

    Pr and Co doped ZnO bicrystals with various types of grain boundaries were fabricated to investigate their current-voltage characteristics. In addition, their grain boundary structures and chemical compositions were investigated using high-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy. It was found that all the boundaries are atomically joined, but have some precipitates of Pr6O11. Co dopants are distributed over the grain interiors and boundaries, while Pr dopants segregate at the fabricated grain boundaries except for a highly coherent Σ1 boundary. The Σ1 boundary with no Pr segregation shows an almost Ohmic characteristic, and coincidence-site lattice and random boundaries with clear Pr segregations show nonlinear characteristics. The change in the nonlinearity is attributed to the difference of the Pr concentration that is associated with the grain boundary structure.

  10. Edge plasma and current profile diagnostic development. Final report

    SciTech Connect

    McChesney, J.M.

    1997-05-01

    This is the final report covering the research conducted under DOE Grant No. DE-FG03-92ER54150 entitled ``Edge Plasma and Current Profile Diagnostic Development.`` It is intended to summarize the investigation and will go into somewhat more detail regarding the aims, techniques, and results of the project research than the standard technical progress reports submitted previously. During the course of this work the authors developed and implemented an atomic beam-based diagnostic technique for investigating edge plasma density behavior on the TEXT Tokamak. The project required the modification of the existing 100 keV TEXT lithium beam to operate at 20--30 keV and the addition of a new 20 detector chain to collect the fluorescence emissions. The modifications were completed and experimental density profiles were unfolded using a new inversion technique.

  11. Enhanced current transport at grain boundaries in high-T(c) superconductors.

    PubMed

    Klie, R F; Buban, J P; Varela, M; Franceschetti, A; Jooss, C; Zhu, Y; Browning, N D; Pantelides, S T; Pennycook, S J

    2005-05-26

    Large-scale applications of high-transition-temperature (high-T(c)) superconductors, such as their use in superconducting cables, are impeded by the fact that polycrystalline materials (the only practical option) support significantly lower current densities than single crystals. The superconducting critical current density (J(c)) across a grain boundary drops exponentially if the misorientation angle exceeds 2 degrees -7 degrees. Grain texturing reduces the average misorientation angle, but problems persist. Adding impurities (such as Ca in YBa2Cu3O7-delta; YBCO) leads to increased J(c) (refs 9, 10), which is generally attributed to excess holes introduced by Ca2+ substituting for Y3+ (ref. 11). However, a comprehensive physical model for the role of grain boundaries and Ca doping has remained elusive. Here we report calculations, imaging and spectroscopy at the atomic scale that demonstrate that in poly-crystalline YBCO, highly strained grain-boundary regions contain excess O vacancies, which reduce the local hole concentration. The Ca impurities indeed substitute for Y, but in grain-boundary regions under compression and tension they also replace Ba and Cu, relieving strain and suppressing O-vacancy formation. Our results demonstrate that the ionic radii are more important than their electronic valences for enhancing J(c). PMID:15917804

  12. The Effects of Grain Boundaries on the Current Transport Properties in YBCO-Coated Conductors

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Xia, Yudong; Xue, Yan; Zhang, Fei; Tao, Bowan; Xiong, Jie

    2015-10-01

    We report a detailed study of the grain orientations and grain boundary (GB) networks in Y2O3 films grown on Ni-5 at.%W substrates. Electron back scatter diffraction (EBSD) exhibited different GB misorientation angle distributions, strongly decided by Y2O3 films with different textures. The subsequent yttria-stabilized zirconia (YSZ) barrier and CeO2 cap layer were deposited on Y2O3 layers by radio frequency sputtering, and YBa2Cu3O7-δ (YBCO) films were deposited by pulsed laser deposition. For explicating the effects of the grain boundaries on the current carry capacity of YBCO films, a percolation model was proposed to calculate the critical current density ( J c) which depended on different GB misorientation angle distributions. The significantly higher J c for the sample with sharper texture is believed to be attributed to improved GB misorientation angle distributions.

  13. The Effects of Grain Boundaries on the Current Transport Properties in YBCO-Coated Conductors.

    PubMed

    Yang, Chao; Xia, Yudong; Xue, Yan; Zhang, Fei; Tao, Bowan; Xiong, Jie

    2015-12-01

    We report a detailed study of the grain orientations and grain boundary (GB) networks in Y2O3 films grown on Ni-5 at.%W substrates. Electron back scatter diffraction (EBSD) exhibited different GB misorientation angle distributions, strongly decided by Y2O3 films with different textures. The subsequent yttria-stabilized zirconia (YSZ) barrier and CeO2 cap layer were deposited on Y2O3 layers by radio frequency sputtering, and YBa2Cu3O7-δ (YBCO) films were deposited by pulsed laser deposition. For explicating the effects of the grain boundaries on the current carry capacity of YBCO films, a percolation model was proposed to calculate the critical current density (J c) which depended on different GB misorientation angle distributions. The significantly higher J c for the sample with sharper texture is believed to be attributed to improved GB misorientation angle distributions. PMID:26497731

  14. A High-Lift Building Block Flow: Turbulent Boundary Layer Relaminarization A Final Report

    NASA Technical Reports Server (NTRS)

    Bourassa, Corey; Thomas, Flint O.; Nelson, Robert C.

    2000-01-01

    Experimental evidence exists which suggests turbulent boundary layer relaminarization may play an important role in the inverse Reynolds number effect in high-lift systems. An experimental investigation of turbulent boundary layer relaminarization has been undertaken at the University of Notre Dame's Hessert Center for Aerospace Research in cooperation with NASA Dryden Flight Research Center. A wind tunnel facility has been constructed at the Hessert Center and relaminarization achieved. Preliminary evidence suggests the current predictive tools available are inadequate at determining the onset of relaminarization. In addition, an in-flight relaminarization experiment for the NASA Dryden FTF-II has been designed to explore relaminarization at Mach and Reynolds numbers more typical of commercial high-lift systems.

  15. Transforming the representation of the boundary layer and low clouds for high-resolution regional climate modeling: Final report

    SciTech Connect

    Huang, Hsin-Yuan; Hall, Alex

    2013-07-24

    Stratocumulus and shallow cumulus clouds in subtropical oceanic regions (e.g., Southeast Pacific) cover thousands of square kilometers and play a key role in regulating global climate (e.g., Klein and Hartmann, 1993). Numerical modeling is an essential tool to study these clouds in regional and global systems, but the current generation of climate and weather models has difficulties in representing them in a realistic way (e.g., Siebesma et al., 2004; Stevens et al., 2007; Teixeira et al., 2011). While numerical models resolve the large-scale flow, subgrid-scale parameterizations are needed to estimate small-scale properties (e.g. boundary layer turbulence and convection, clouds, radiation), which have significant influence on the resolved scale due to the complex nonlinear nature of the atmosphere. To represent the contribution of these fine-scale processes to the resolved scale, climate models use various parameterizations, which are the main pieces in the model that contribute to the low clouds dynamics and therefore are the major sources of errors or approximations in their representation. In this project, we aim to 1) improve our understanding of the physical processes in thermal circulation and cloud formation, 2) examine the performance and sensitivity of various parameterizations in the regional weather model (Weather Research and Forecasting model; WRF), and 3) develop, implement, and evaluate the advanced boundary layer parameterization in the regional model to better represent stratocumulus, shallow cumulus, and their transition. Thus, this project includes three major corresponding studies. We find that the mean diurnal cycle is sensitive to model domain in ways that reveal the existence of different contributions originating from the Southeast Pacific land-masses. The experiments suggest that diurnal variations in circulations and thermal structures over this region are influenced by convection over the Peruvian sector of the Andes cordillera, while

  16. Decadal covariability of the Deep Western Boundary Current and the Atlantic meridional overturning circulation

    NASA Astrophysics Data System (ADS)

    Mielke, Charlotte; Gary, Stefan; Baehr, Johanna

    2015-04-01

    We investigate the decadal variability of the North Atlantic Deep Western Boundary Current (DWBC), its meridional coherence and relation to the Atlantic meridional overturning circulation (AMOC) in a high-resolution ocean model. The modeled DWBC is defined after a comparison of model results of both scalar quantities and integrated transports to observations, and its mean and the structure of its temporal variability correspond well to observations. We find that the DWBC exhibits multidecadal variability, which is mostly coherent between 26°N and 53°N, and is closely related to the negative integrated wind stress curl at the western boundary, particularly in the subtropical gyre. This implies that the DWBC and the AMOC show opposing behavior if the western boundary and basin interior wind stress curl anomalies are of opposite sign. The relation is thus non-stationary. Our results suggest that - on decadal timescales - both the AMOC and the DWBC at one latitude are representative of the variability of the same quantity over a wide range of adjacent latitudes. However, observations of the DWBC can only be used as a proxy for the AMOC variability if the boundary and basin-wide wind stress curl are in phase. This indicates that observations of the DWBC cannot easily be used as a shortcut to obtain an estimate of the decadal AMOC variability.

  17. Western boundary currents regulated by interaction between ocean eddies and the atmosphere.

    PubMed

    Ma, Xiaohui; Jing, Zhao; Chang, Ping; Liu, Xue; Montuoro, Raffaele; Small, R Justin; Bryan, Frank O; Greatbatch, Richard J; Brandt, Peter; Wu, Dexing; Lin, Xiaopei; Wu, Lixin

    2016-07-28

    Current climate models systematically underestimate the strength of oceanic fronts associated with strong western boundary currents, such as the Kuroshio and Gulf Stream Extensions, and have difficulty simulating their positions at the mid-latitude ocean's western boundaries. Even with an enhanced grid resolution to resolve ocean mesoscale eddies-energetic circulations with horizontal scales of about a hundred kilometres that strongly interact with the fronts and currents-the bias problem can still persist; to improve climate models we need a better understanding of the dynamics governing these oceanic frontal regimes. Yet prevailing theories about the western boundary fronts are based on ocean internal dynamics without taking into consideration the intense air-sea feedbacks in these oceanic frontal regions. Here, by focusing on the Kuroshio Extension Jet east of Japan as the direct continuation of the Kuroshio, we show that feedback between ocean mesoscale eddies and the atmosphere (OME-A) is fundamental to the dynamics and control of these energetic currents. Suppressing OME-A feedback in eddy-resolving coupled climate model simulations results in a 20-40 per cent weakening in the Kuroshio Extension Jet. This is because OME-A feedback dominates eddy potential energy destruction, which dissipates more than 70 per cent of the eddy potential energy extracted from the Kuroshio Extension Jet. The absence of OME-A feedback inevitably leads to a reduction in eddy potential energy production in order to balance the energy budget, which results in a weakened mean current. The finding has important implications for improving climate models' representation of major oceanic fronts, which are essential components in the simulation and prediction of extratropical storms and other extreme events, as well as in the projection of the effect on these events of climate change. PMID:27466126

  18. Effects of the boundary geometry on the edge current in the two dimensional topological insulator

    NASA Astrophysics Data System (ADS)

    Doh, Hyeonjin; Choi, Hyoung Joon

    2015-03-01

    We study the effects of the boundary shape on the edge transport of the two dimensional topological insulator described by Kane-Mele model. The edge state is robust against all time-reversal invariant defects. However, when we consider an arbitrary sample, the edge is not straight and consists of various types of boundaries. Actually, the transport property of the edge-state in the Kane-Mele model depends on the boundary type of the edge such as zigzag and armchair edges. Therefore, the edge-transport can be affected by a corner connecting two different types of edges. Here, we investigate the energy spectrum of the various shapes of finite-size honeycomb lattice with corners along the edge. We also calculate the transport properties on the edges by applying an artificial gauge field which drives a persistent current along the edges. Although the corner of the edge seems a geometrical defects and is expected to have a little effect on the transport, our results show that the geometrical defects strongly affect the edge current depending on the corner types. This work was supported by NRF of Korea (Grant No. 2011-0018306) and KISTI supercomputing center (Project No. KSC-2013-C3-062).

  19. Ecological importance of the Southern Boundary of the Antarctic Circumpolar Current

    NASA Astrophysics Data System (ADS)

    Tynan, Cynthia T.

    1998-04-01

    The Southern Ocean surrounds the Antarctic continent and supports one of the most productive marine ecosystems. Migratory and endemic species of whales, seals and birds benefit from the high biomass of their principal prey, krill (Euphausia superba) and cephalopods, in this area. Most species of baleen whales and male sperm whales in the Southern Hemisphere migrate between low-latitude breeding grounds in winter and highly productive Antarctic feeding grounds in summer. Here I show the importance of the southernmost reaches of the strongest ocean current, the Antarctic Circumpolar Current (ACC), to a complex and predictable food web of the Southern Ocean. The circumpolar distributions of blue, fin and humpback whales from spring to midsummer trace the non-uniform high-latitude penetration of shoaled, nutrient-rich Upper Circumpolar Deep Water, which is carried eastward by the ACC. The poleward extent of this water mass delineates the Southern Boundary of the ACC and corresponds not only to the circumpolar distributions of baleen whales, but also to distributions of krill and to regions of high, seasonally averaged, phytoplankton biomass. Sperm whales, which feed on cephalopods, also congregate in highest densities near the Southern Boundary. The association of primary production, Krill, and whales with the Southern Boundary, suggests that it provides predictably productive foraging for many species, and is of critical importance to the function of the Southern Ocean ecosystem.

  20. Gliders Measure Western Boundary Current Transport from the South Pacific to the Equator

    NASA Astrophysics Data System (ADS)

    Davis, R. E.; Kessler, W. S.; Sherman, J. T.

    2011-12-01

    Since 2007, the Consortium on the Ocean's Role in Climate (CORC) has used repeated glider transects across the southern Solomon Sea to measure the previously nearly unsampled mass and heat transport from the South Pacific to the equatorial zone. Mean transport is dominated by the New Guinea Coastal Undercurrent (NGCUC). This low-latitude western boundary current is a major element of the shallow meridional overturning circulation, returning water from the subtropical South Pacific to the Equatorial Undercurrent (EUC) where it upwells. We find the mean NGCUC to be a jet less than 100 km wide, centered near 300 m depth, with equatorward velocities reaching 35 cm/s and salinity anomalies on isopycnals up to 0.05. Weaker poleward flow is found near the surface in the eastern basin. Equatorward transport above 700 m is typically 20 Sv, but nearly vanished during two La Niñas and reached 25 Sv during an El Niño. Within these events the seasonal cycle cannot yet be defined. Transport variability is strongest outside the boundary current and appears to consist of two independently moving layers with a boundary near 250 m. ENSO variability is predominantly in the upper layer. The relation of Solomon Sea mass and heat transport with ENSO indicators will be discussed The ability to initiate and maintain measurements that support such quantitative analyses with a small effort in a remote site far from research institutions demonstrates that gliders can be a productive part of the global ocean observing system.

  1. Observation of chiral currents at the magnetic domain boundary of a topological insulator

    NASA Astrophysics Data System (ADS)

    Wang, Yihua

    2015-03-01

    The broken time-reversal symmetry (TRS) states on the surface of a three-dimensional topological insulator (3D-TI) promise many exotic quantum phenomena. Breaking TRS opens a band gap on the surface Dirac cone and transforms the metallic surface into a Chern insulator. The TRS-broken surface states coupled to a superconductor are predicted to lead to Majorana fermions, which are the fundamental ingredients of topological quantum computation. Just as the surface Dirac cone is a signature of the non-trivial topological bulk band structure of a time-reversal invariant 3D-TI, bulk-boundary correspondence dictates that the TRS-broken surface states with a nonzero Chern number is manifested by a gapless chiral edge state (CES) at the domain boundary. In the special case where the domain boundary is the edge of the sample surface, CES along the edge leads to a quantized anomalous Hall conductance, which was recently measured in a magnetically doped 3D-TI. More generally, a magnetic domain boundary on the surface of TI hosts a CES, which is yet to be directly demonstrated because any local change of conductivity due to the CES does not affect conductance globally. Here we use a scanning superconducting quantum interference device (SQUID) to show that in a uniformly magnetized topological insulator - ferromagnetic insulator (TI-FMI) heterostructure current flows at the edge of the surface of the topological insulator when the Fermi level is gate-tuned to the surface band gap. We further induce micron-scale magnetic structures using the field coil of the SQUID and show that there emerges a chiral edge current at the magnetic domain boundary. In both cases the magnitude of the chiral edge current depends on the chemical potential rather than the applied current. Such magnetic nano-structures, which can be readily created on a TI in an arbitrary geometry, provide a versatile platform for detecting topological magnetoelectric effects and may allow the engineering of

  2. Current Pattern Change in the Fram Strait at the Pliocene/Pleistocene Boundary

    NASA Astrophysics Data System (ADS)

    Gebhardt, C.; Geissler, W. H.; Matthiessen, J. J.; Jokat, W.

    2014-12-01

    Thick packages of drift-type sediments were identified in the northwestern and central part of the Fram Strait, mainly along the western Yermak Plateau flank, but also in the central, flat part of the Fram Strait. A large-scale field of sediment waves was found north of 80.5°, along the Yermak Plateau rise. This field separates two drift bodies, a deeper one towards west and a shallower one towards east. The drift bodies were deposited by bottom currents, most likely by the northbound Yermak Branch of the West Spitsbergen Current, but an influence of a southbound current on the westren drift body cannot be ruled out. Within the drift bodies and even more pronounced withing the sediment waves, a stratigraphic boundary is clearly visible. It separates a lower package of waves migrating upslope at a low angle of ~5° from an upper package with significantly increased wave crest migration at ~16.5°. Using the seismic network, this stratigraphic boundary could be tracked to ODP Leg 151, Site 911, where it corresponds to the lithostratigraphic boundary between units IA and IB dated to 2.7 Ma. The increase in wave-crest migration angle points at a shift towards higher sedimentation rates at 2.7 Ma. This corresponds to the intensification of the Northern Hemisphere glaciation with a major expansion of the Scandinavian, northern Barents Sea, North American and Greenland ice sheets. The Barents Shelf that was subaerially exposed and the expansion of the northern Barents Sea ice sheet (as well as Svalbard) are the likely sources for enhanced erosion and fluvial input along the pathway of the West Spitsbergen Current, resulting in higher sedimentation rates in the Fram Strait.

  3. Turbulent boundary layers under irregular waves and currents: Experiments and the equivalent-wave concept

    NASA Astrophysics Data System (ADS)

    Yuan, Jing

    2016-04-01

    A full-scale experimental study of turbulent boundary layer flows under irregular waves and currents is conducted with the primary objective to investigate the equivalent-wave concept by Madsen (1994). Irregular oscillatory flows following the bottom-velocity spectrum under realistic surface irregular waves are produced over two fixed rough bottoms in an oscillatory water tunnel, and flow velocities are measured using a Particle Image Velocimetry. The root-mean-square (RMS) value and representative phase lead of wave velocities have vertical variations very similar to those of the first-harmonic velocity of periodic wave boundary layers, e.g., the RMS wave velocity follows a logarithmic distribution controlled by the physical bottom roughness in the very near-bottom region. The RMS wave bottom shear stress and the associated representative phase lead can be accurately predicted using the equivalent-wave approach. The spectra of wave bottom shear stress and boundary layer velocity are found to be proportional to the spectrum of free-stream velocity. Currents in the presence of irregular waves exhibit the classic two-log-profile structure with the lower log-profile controlled by the physical bottom roughness and the upper log-profile controlled by a much larger apparent roughness. Replacing the irregular waves by their equivalent sinusoidal waves virtually makes no difference for the coexisting currents. These observations, together with the excellent agreement between measurements and model predictions, suggest that the equivalent-wave representation adequately characterizes the basic wave-current interaction under irregular waves.

  4. Western boundary currents regulated by interaction between ocean eddies and the atmosphere

    NASA Astrophysics Data System (ADS)

    Ma, Xiaohui; Jing, Zhao; Chang, Ping; Liu, Xue; Montuoro, Raffaele; Small, R. Justin; Bryan, Frank O.; Greatbatch, Richard J.; Brandt, Peter; Wu, Dexing; Lin, Xiaopei; Wu, Lixin

    2016-07-01

    Current climate models systematically underestimate the strength of oceanic fronts associated with strong western boundary currents, such as the Kuroshio and Gulf Stream Extensions, and have difficulty simulating their positions at the mid-latitude ocean’s western boundaries. Even with an enhanced grid resolution to resolve ocean mesoscale eddies—energetic circulations with horizontal scales of about a hundred kilometres that strongly interact with the fronts and currents—the bias problem can still persist; to improve climate models we need a better understanding of the dynamics governing these oceanic frontal regimes. Yet prevailing theories about the western boundary fronts are based on ocean internal dynamics without taking into consideration the intense air–sea feedbacks in these oceanic frontal regions. Here, by focusing on the Kuroshio Extension Jet east of Japan as the direct continuation of the Kuroshio, we show that feedback between ocean mesoscale eddies and the atmosphere (OME-A) is fundamental to the dynamics and control of these energetic currents. Suppressing OME-A feedback in eddy-resolving coupled climate model simulations results in a 20–40 per cent weakening in the Kuroshio Extension Jet. This is because OME-A feedback dominates eddy potential energy destruction, which dissipates more than 70 per cent of the eddy potential energy extracted from the Kuroshio Extension Jet. The absence of OME-A feedback inevitably leads to a reduction in eddy potential energy production in order to balance the energy budget, which results in a weakened mean current. The finding has important implications for improving climate models’ representation of major oceanic fronts, which are essential components in the simulation and prediction of extratropical storms and other extreme events, as well as in the projection of the effect on these events of climate change.

  5. On the Structure of the Ice-Shelf-Ocean Boundary Layer and Current

    NASA Astrophysics Data System (ADS)

    Jenkins, A.

    2015-12-01

    Ocean-forced basal melting has been implicated in the widespread thinning of Antarctic ice shelves that has been causally linked with acceleration in the outflow of grounded ice. What determines the distribution and rates of basal melting and freezing beneath an ice shelf and how these respond to changes in the ocean temperature or circulation are therefore key questions. Recent years have seen major progress in our ability to observe basal melting and the ocean conditions that drive it, but data on the latter remain sparse, limiting our understanding of the key processes of ice-ocean heat transfer. In particular, we have no observations of current profiles through the buoyancy- and frictionally-controlled flows along the ice shelf base that drive mixing through the ice-ocean boundary layer. This presentation represents an attempt to address this gap in our knowledge through the application of a very simple model of such boundary flows that considers only the spatial dimension perpendicular to the boundary. Results indicate that for the purely buoyancy-driven flow two possible regimes exist: a weakly-stratified, geostrophic cross-slope current with an embedded Ekman layer; or a strongly-stratified upslope jet with weak cross-slope flow. The latter regime, while well-known to students of katabatic winds, has no analogue in the ocean, and is most appropriate when the ice-ocean interface is very steep. For the gentle slopes typical of ice shelves the buoyant Ekman regime provides some useful insight. When combined with a background flow a range of possible near-ice current profiles emerges as a result of arrest or enhancement of the upslope Ekman transport. Furthermore a simple expression for the upslope transport can be formed that is analogous to that for the wind-forced surface Ekman layer, with the curvature of the ice shelf base replacing the wind-stress curl in driving Ekman pumping to and from the geostrophic flow.

  6. Magnetopause boundary layer. Final report, 19 February 1987-18 May 1990

    SciTech Connect

    Sonnerup, B.U.; Lotko, W.

    1990-06-29

    Theoretical models have been developed to describe the structure of, and dynamical processes in the magnetopause current layer and the adjoining low latitude boundary layer (LLBL), including coupling of the latter to the dayside auroral ionosphere. Also a pilot study has been performed to demonstrate how information about magnetopause and boundary layer structure can be extracted from in-situ measurements of magnetic fields and plasma velocities. (1) Simple two-dimensional dynamic models of the LLBL and other shear flows have been developed and used to study the decay of shear layers, and the breakup of driven unstable shear flows, such as the LLBL, into quasisteady vortex rows similar to those observed in the post-noon auroral-zone ionosphere, or into turbulence. A steady-state viscous LLBL model has also generated in which the magnetic field deformation caused by the currents is included in a self consistent manner. (2) A viscous-resistive model of magnetic field annihilation at the magnetopause has been developed which allows for plasma flow along the reconnection line. (3) The structure of resistive and resistive dispersive MHD intermediate shocks has been determined and their possible role as part of the magnetopause structure assessed. (4) Certain geometric and dynamic properties of the magnetopause/LLBL have been extracted from AMPTE/IRM data with special emphasis on magnetic-field reconnection and flux transfer events.

  7. The Boundary Layer Character of Tidal Currents in the Eastern Irish Sea

    NASA Astrophysics Data System (ADS)

    Elliott, A. J.

    2002-09-01

    The vertical profile of the tidal currents observed by a ship borne ADCP at a site in the eastern Irish Sea where the water depth is 50 m was logarithmic with height above the bed in the lower 50-60% of the water column except for periods of about 1 h either side of slack water. The maximum height of the boundary layer reached 40 m during the flood tide. The shearing stress, determined by the method of Bowden et al. (1959), showed a tendency to be uniform with height in the lower half of the water column while the eddy viscosity increased linearly away from the bed, scaling on κu*z where u* is the friction velocity. Both of these features are characteristic of the logarithmic profile region of a boundary layer flow. Estimates of zo, the roughness length, and CD, the bottom drag coefficient, were around 10-3 m and 2·4×10-3, consistent with the known character of the bed. The scatter in the derived boundary layer parameters was reduced significantly by averaging the data within 30-min intervals which suggests the presence of tidal eddies having periods comparable to the 5-min sampling period of the ADCP. Short period fluctuations in the flow were coherent over the lower 20 m of the water column and propagated vertically away from the bed.

  8. Australian Sphingidae – DNA Barcodes Challenge Current Species Boundaries and Distributions

    PubMed Central

    Rougerie, Rodolphe; Kitching, Ian J.; Haxaire, Jean; Miller, Scott E.; Hausmann, Axel; Hebert, Paul D. N.

    2014-01-01

    Main Objective We examine the extent of taxonomic and biogeographical uncertainty in a well-studied group of Australian Lepidoptera, the hawkmoths (Sphingidae). Methods We analysed the diversity of Australian sphingids through the comparative analysis of their DNA barcodes, supplemented by morphological re-examinations and sequence information from a nuclear marker in selected cases. The results from the analysis of Australian sphingids were placed in a broader context by including conspecifics and closely related taxa from outside Australia to test taxonomic boundaries. Results Our results led to the discovery of six new species in Australia, one case of erroneously synonymized species, and three cases of synonymy. As a result, we establish the occurrence of 75 species of hawkmoths on the continent. The analysis of records from outside Australia also challenges the validity of current taxonomic boundaries in as many as 18 species, including Agrius convolvuli (Linnaeus, 1758), a common species that has gained adoption as a model system. Our work has revealed a higher level of endemism than previously recognized. Most (90%) Australian sphingids are endemic to the continent (45%) or to Australia, the Pacific Islands and the Papuan and Wallacean regions (45%). Only seven species (10%) have ranges that extend beyond this major biogeographical boundary toward SE Asia and other regions of the Old World. Main Conclusions This study has established that overlooked cryptic diversity and inaccurate species delineation produced significant misconceptions concerning diversity and distribution patterns in a group of insects that is considered well known taxonomically. Because DNA barcoding represents a straightforward way to test taxonomic boundaries, its implementation can improve the accuracy of primary diversity data in biogeography and conservation studies. PMID:24987846

  9. Magnetohydrodynamic Stability of Free-Boundary Quasi-Axisymmetric Stellarator Equilibria with Finite Bootstrap Current

    SciTech Connect

    Coope, Wilfred Anthony; Ferrando i Margalet, Sergi; Allfrey, Simon J.; Kisslinger, Johann; Wobig, Horst F.G.; Narushima, Yoshiro; Okamura, Shoichi; Suzuki, Chihiro; Watanabe, Kiyomasa Y.; Yamazaki, Kozo; Isaev, Maxim Yu

    2004-09-15

    The impact of the bootstrap current is investigated on the equilibrium properties of a two-period quasi-axisymmetric stellarator reactor with free boundary and on the corresponding ideal magnetohydrodynamic stability properties. Although the magnetic field strength B spectrum is dominated by a m/n = 1/0 component, the discrete filamentary coils trigger some small-amplitude symmetry-breaking components that can disturb the quasi-symmetry of B. Finite {beta} causes the plasma column to shift outward in the absence of bootstrap current. With a self-consistent bootstrap current in the 1/{nu} regime, the plasma becomes more elongated and more distorted in the horizontally elongated up-down symmetric cross section. At {beta} (approximately equal to) 3.25%, the plasma can be restored to its near-vacuum shape with the application of a vertical field with coil currents 20% of those of the modular coils, but at the expense of a significant mirror component in the B-field spectrum. The bootstrap current causes the rotational transform {iota} profile to increase above the critical resonant value ({iota}{sub c} = 1/2 for {beta} {>=}1.1%) and combines with the Pfirsch-Schlueter current to destabilize a m/n = 2/1 external kink mode for {beta} {>=}1.8%.

  10. The Effect of Local Wind Along an Eastern Boundary Current on the Local Wave Pattern: The Canary Current Case

    NASA Astrophysics Data System (ADS)

    Semedo, Alvaro

    2015-04-01

    There are two types of waves at the ocean surface. During the generation and growing processes, they are designated as wind sea; as waves propagate away from their generation area, they are called swell. Swell waves travel long distances across the globe with little attenuation For this reason the wave field does not necessarily reflect the local wind field characteristics. Since swell propagates long distances, across entire ocean basins, in the open ocean the wave field is, most of the times, the result of contributions from waves with different frequencies and directions, reflecting different origins and ages. The qualitative analysis of ocean surface waves has been the focus of several recent studies, from the wave climate to the air-sea interaction community. The reason for this interest lies mostly in the fact that waves have an impact on the lower atmosphere, and that the air-sea coupling is different depending on the wave regime. Waves modulate the exchange of momentum, heat, and mass across the air-sea interface, and this modulation is different and dependent on the prevalence of one type of waves: wind sea or swell. For fully developed seas the coupling between the ocean-surface and the overlaying atmosphere can be seen as quasi-perfect, in a sense that the momentum transfer and energy dissipation at the ocean surface are in equilibrium. This can only occur in special areas of the Ocean, like marginal or enclosed seas, with limited fetch, or in Open Ocean, in areas with strong and persistent wind speed with little or no variation in direction. The wind pattern along eastern boundary currents, in the summer, is equator-ward and coast parallel, due to the presence of a semi-permanente high pressure system off-shore, in the ocean, and to a thermal low in-land. The resulting coast parallel winds are the geostrophically adjusted response to this synoptic pattern that drives upwelling along EBC, due to the Eknam transport offshore, sharpening the thermal and

  11. Seasonal variability of alongshore winds and sea surface temperature fronts in Eastern Boundary Current Systems

    NASA Astrophysics Data System (ADS)

    Wang, Yuntao; Castelao, Renato M.; Yuan, Yeping

    2015-03-01

    Seven years of satellite observations (2003-2009) are used to describe variability in sea surface temperature (SST) fronts and in the alongshore component of ocean winds, and to investigate their relations in four Eastern Boundary Current Systems (EBCS). The general patterns of SST frontal activity are remarkably similar in all EBCS, with high frontal probabilities along the coast decreasing with distance from the coastline. Results from empirical orthogonal function decompositions reveal that the seasonal evolution of SST fronts and wind stress are significantly correlated, with intensified upwelling favorable winds associated with an increase in frontal probabilities. An offshore migration of the region of high frontal activity is observed during the period of upwelling favorable alongshore wind stress in EBCS. In all regions, the seasonal variability of frontal activity and wind stress is stronger at mid than at low latitudes. The width of the region of high frontal activity is relatively broader in the California and Benguela Current Systems, and narrower in the Canary and Humboldt Current Systems. The width of the band of high frontal activity may be influenced by multiple factors, including wind forcing, flow topography interactions, and mesoscale dynamics. While seasonal variability in frontal activity in the California Current System acts to reinforce or weaken the average pattern, they are substantially different in the Canary Current System, where there is little overlap in the areas characterized by persistent and seasonally varying front activity.

  12. Eddy Surface properties and propagation at Southern Hemisphere western boundary current systems

    NASA Astrophysics Data System (ADS)

    Pilo, G. S.; Mata, M. M.; Azevedo, J. L. L.

    2015-02-01

    Oceanic eddies occur in all world oceans, but are more energetic when associated to western boundary currents (WBC) systems. In these regions, eddies play an important role on mixing and energy exchange. Therefore, it is important to quantify and qualify eddies occurring within these systems. Previous studies performed eddy censuses in Southern Hemisphere WBC systems. However, important aspects of local eddy population are still unknown. Main questions to be answered relate to eddies' spatial distribution, propagation and lifetime within each system. Here, we use a global eddy dataset to qualify eddies based on their surface characteristics at the Agulhas Current (AC), the Brazil Current (BC) and the East Australian Current (EAC) Systems. We show that eddy propagation within each system is highly forced by the local mean flow and bathymetry. In the AC System, eddy polarity dictates its propagation distance. BC system eddies do not propagate beyond the Argentine Basin, and are advected by the local ocean circulation. EAC System eddies from both polarities cross south of Tasmania, but only anticyclonics reach the Great Australian Bight. Eddies in all systems and from both polarities presented a geographical segregation according to size. Large eddies occur along the Agulhas Retroflection, the Agulhas Return Current, the Brazil-Malvinas Confluence and the Coral Sea. Small eddies occur in the systems southernmost domains. Understanding eddies' propagation helps to establish monitoring programs, and to better understand how these features would affect local mixing.

  13. Atomistic studies of grain boundaries and heterophase interfaces in alloys and compounds. Final report, July 1987-August 1998

    SciTech Connect

    Vitek, Vaclav

    1998-08-01

    The overarching goal of the research supported by this grant was investigation of the structure and properties of interfaces in multicomponent systems by atomistic modeling. Initially, the research was devoted to studies of segregation to grain boundaries in binary disordered alloys. The next step was then studies of the structure and properties of grain boundaries in ordered compounds, specifically Ni3Al and NiAl, and grain boundary segregation in these compounds in the case of off-stoichiometry. Finally, the structure of Nb/sapphire interfaces, in particular the core configurations of the misfit dislocations, was studied.

  14. Air-sea boundary layer dynamics in the presence of mesoscale surface currents

    NASA Astrophysics Data System (ADS)

    Rooth, Claes; Xie, Lian

    1992-09-01

    In the presence of surface currents, a shear stress at the air-sea interface is induced by the surface currents. In the case of a unidirectional current, a quadratic stress law leads to a stress curl proportional to and opposing the surface current vorticity even with a uniform wind. This causes a spindown effect on the surface vorticity field at a rate proportional to the wind speed. In the steady state, or in slowly varying processes which can be treated as parametrically developing quasi-steady states, the surface-layer potential vorticity modulation causes upwelling and downwelling patterns associated with the surface-current vorticity. These effects are analyzed for an idealized jet current, and for a physical situation characteristic of a Gulf Stream boundary ring along the Florida Keys, where the induced transport patterns may be important for onshore transport of fish and spiny lobster larvae, as well as for onshore transport to the Florida Keys of general flotsam transported past them by the Gulf Stream. The spindown time scale (t*) for a 1.5-layer system is H/( ρ'cdVa) for a surface jet on the deformation radius scale (where H is the thickness of the surface layer, Va the surface wind speed, ρ' the air to water density ratio and cd the surface drag coefficient) and increases for large horizontal scales in proportion to the current width squared. For a typical wind speed of 5 m/s and a density normalized drag coefficient ρ'cd= 2 × 10-6, t* is on the order of 1 month for a 30-m surface layer. In the more general case of a stratified interior water column, the vorticity spindown directly affects only the potential vorticity of the surface layer and generally leads to subsurface velocity and vorticity maxima for mesoscale eddies and jets.

  15. Current-Driven Filament Instabilities in Relativistic Plasmas. Final report

    SciTech Connect

    Ren, Chuang

    2013-02-13

    This grant has supported a study of some fundamental problems in current- and flow-driven instabilities in plasmas and their applications in inertial confinement fusion (ICF) and astrophysics. It addressed current-driven instabilities and their roles in fast ignition, and flow-driven instabilities and their applications in astrophysics.

  16. Structure and variability of the boundary current in the Eurasian Basin of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Pnyushkov, Andrey V.; Polyakov, Igor V.; Ivanov, Vladimir V.; Aksenov, Yevgeny; Coward, Andrew C.; Janout, Markus; Rabe, Benjamin

    2015-07-01

    The Arctic Circumpolar Boundary Current (ACBC) transports a vast amount of mass and heat around cyclonic gyres of the deep basins, acting as a narrow, topographically-controlled flow, confined to the continental margins. Current observations during 2002-2011 at seven moorings along the major Atlantic Water (AW) pathway, complemented by an extensive collection of measured temperatures and salinities as well as results of state-of-the-art numerical modeling, have been used to examine the spatial structure and temporal variability of the ACBC within the Eurasian Basin (EB). These observations and modeling results suggest a gradual, six-fold decrease of boundary current speed (from 24 to 4 cm/s) on the route between Fram Strait and the Lomonosov Ridge, accompanied by a transformation of the vertical flow structure from mainly barotropic in Fram Strait to baroclinic between the area north of Spitsbergen and the central Laptev Sea continental slope. The relative role of density-driven currents in maintaining AW circulation increases with the progression of the ACBC eastward from Fram Strait, so that baroclinic ACBC forcing dominates over the barotropic in the eastern EB. Mooring records have revealed that waters within the AW and the cold halocline layers circulate in roughly the same direction in the eastern EB. The seasonal signal, meanwhile, is the most powerful mode of variability in the EB, contributing up to ~70% of the total variability in currents (resolved by moorings records) within the eastern EB. Seasonal signal amplitudes for current speed and AW temperature both decrease with the eastward progression of AW flow from source regions, and demonstrate strong interannual modulation. In the 2000s, the state of the EB (e.g., circulation pattern, thermohaline conditions, and freshwater balance) experienced remarkable changes. Results showing anomalous circulation patterns for an extended period of 30 months in 2008-2010 for the eastern EB, and a two-core AW

  17. Enthalpy and Momentum Fluxes During Hurricane Earl over the North Atlantic Western Boundary Current System

    NASA Astrophysics Data System (ADS)

    Shay, L. K.; Jaimes, B.; Uhlhorn, E.

    2013-05-01

    The North Atlantic Western Boundary Current System consists of several energetic currents such as the Antilles Current, Caribbean Current, Yucatan Current, Loop Current, Florida Current, and Gulf Stream. These currents often support a rich eddy field along strong frontal regimes where thermal gradients change over distances of O(10) km. These warm oceanic regimes force the marine atmospheric boundary layer (ABL) at differing temporal scales which impact the wind stress and air-sea fluxes. The impact of these oceanic regimes on the evolution of the ABL in tropical cyclones (TC) and on rapid TC intensity fluctuations remains an important research question, where forecasts of TC intensity are typically inaccurate. This problem is relevant to recent hurricanes Earl (2010), Irene (2011), and Sandy (2012) that moved over the Gulf Stream. Using Global Positioning System Sondes deployed from several research flights in hurricane Earl (2010) from NASA and NOAA aircraft, satellite products, ocean buoys and drifters, this study estimates enthalpy and momentum fluxes, as well as the ocean heat loss, during Earl's rapid intensity changes (category 4 hurricane) over the Antilles Current and Gulf Stream. In an environment of weak wind shear, Earl experienced rapid intensification (40 kt in 24 hrs) over warm waters of the Antilles Current where the oceanic heat content was high (>100 kJ cm-2). This intensification was temporarily halted by increased wind shear and an eyewall replacement cycle. Subsequently, Earl experienced a second intensification, attaining its maximum intensity of 125 kt over warm waters where the Antilles Current and Gulf Stream merge. Earl then rapidly weakened as it moved in less favorable atmospheric environment and over cooler shelf waters on the western flank of the Gulf Stream. Reduced sea surface temperature (SST) cooling of less than 2°C occurred over the Antilles Current during Earl's rapid intensification, while SST cooling of 4°C occurred during

  18. Current state and prospects of researches on the control of turbulent boundary layer by air blowing

    NASA Astrophysics Data System (ADS)

    Kornilov, V. I.

    2015-07-01

    The paper presents the analytical review of the current state of the investigations and development trends on the problem of turbulent friction and aerodynamic drag reduction in simple model configurations, which is among key ones in modern aeromechanics. Under consideration is the modern fast progressing method of the turbulent flow control by air- and other gases (micro)blowing through a permeable surface, which is utilized in incompressible and compressible turbulent boundary layers. Several computational results to understand the essential flow physics are also included. The problem of simulation of the flow over a perforated wall where some ambiguities, in particular, at the permeable/impermeable boundary being still remained is discussed. Special attention is paid to the analysis of most important experimental and numerical results obtained with the air blowing through a finely-perforated surface, analysis of the physical peculiarities and regularities of the flow with the blowing, probability to describe the properties of such a flow within simple approach frameworks, evaluation of the efficiency of this control method, as well as the trends and opportunities of this method progress in view of state-of-the-art achievements. Although this technology has a penalty for developing the effective turbulent-flow control method, some modifications of the air blowing are an attractive alternative for real applications.

  19. The change features of the west boundary bifurcation line of the North Equatorial Current in the Pacific

    NASA Astrophysics Data System (ADS)

    Guo, Junru; Liu, Yulong; Song, Jun; Bao, Xianwen; Li, Yan; Chen, Shaoyang; Yang, Jinkun

    2015-12-01

    The equatorial Current in the North Pacific (NEC) is an upper layer westward ocean current, which flows to the west boundary of the ocean, east of the Philippines, and bifurcates into the northerly Kuroshio and the main body of the southerly Mindanao current. Thus, NEC is both the south branch of the Subtropical Circulation and the north branch of the Tropical Circulation. The junction of the two branches extends to the west boundary to connect the bifurcation points forming the bifurcation line. The position of the North Pacific Equatorial Current bifurcation line of the surface determines the exchange between and the distribution of subtropical and tropical circulations, thus affecting the local or global climate. A new identification method to track the line and the bifurcation channel was used in this study, focusing on the climatological characteristics of the western boundary of the North Equatorial Current bifurcation line. The long-term average NEC west boundary bifurcation line shifts northwards with depth. In terms of seasonal variation, the average position of the western boundary of the bifurcation line is southernmost in June and northernmost in December, while in terms of interannual variation, from spring to winter in the years when ENSO is developing, the position of the west boundary bifurcation line of NEC is relatively to the north (south) in EI Niño (La Niña) years as compared to normal years.

  20. A Final Approach Trajectory Model for Current Operations

    NASA Technical Reports Server (NTRS)

    Gong, Chester; Sadovsky, Alexander

    2010-01-01

    Predicting accurate trajectories with limited intent information is a challenge faced by air traffic management decision support tools in operation today. One such tool is the FAA's Terminal Proximity Alert system which is intended to assist controllers in maintaining safe separation of arrival aircraft during final approach. In an effort to improve the performance of such tools, two final approach trajectory models are proposed; one based on polynomial interpolation, the other on the Fourier transform. These models were tested against actual traffic data and used to study effects of the key final approach trajectory modeling parameters of wind, aircraft type, and weight class, on trajectory prediction accuracy. Using only the limited intent data available to today's ATM system, both the polynomial interpolation and Fourier transform models showed improved trajectory prediction accuracy over a baseline dead reckoning model. Analysis of actual arrival traffic showed that this improved trajectory prediction accuracy leads to improved inter-arrival separation prediction accuracy for longer look ahead times. The difference in mean inter-arrival separation prediction error between the Fourier transform and dead reckoning models was 0.2 nmi for a look ahead time of 120 sec, a 33 percent improvement, with a corresponding 32 percent improvement in standard deviation.

  1. The velocity and mixing time scale of the Arctic Ocean Boundary Current estimated with transient tracers

    NASA Astrophysics Data System (ADS)

    Mauldin, A.; Schlosser, P.; Newton, R.; Smethie, W. M.; Bayer, R.; Rhein, M.; Jones, E. Peter

    2010-08-01

    The Arctic Ocean Boundary Current (AOBC) is a persistent, large-scale feature of Arctic circulation that transports water of Atlantic origin around the Eurasian and Canadian Basins. Despite its importance as a link between North Atlantic sea surface temperature and the heat budget of the Arctic Ocean, elements of the pathways of the AOBC are still not well understood. Here we use transient tracer data collected during the 1990s at 22 locations to calculate the velocity and mixing time scale of the AOBC. The apparent spreading velocity derived from correlating 3H-3He ages in the Barents Sea branch water (BSBW) with the distance from its entry point at the Santa Anna Trough is 0.9 cm s-1. To correct this apparent velocity for the effects of mixing along the pathway, the AOBC is modeled as a leaky pipe, and 3H-3He and chlorofluorocarbon data are used to calculate the parameters of its transit time distribution function. The modeled velocity of the AOBC is 2.5 ± 0.5 cm s-1, and the time scale for mixing of waters between the core of the boundary current and the adjacent water masses is 5-10 years. These results imply that the advective time for transport around the perimeter of the Arctic Ocean from the Santa Anna Trough to the southern Canada Basin (approximately 6000 km) is 7.5 years, and the amplitude of a temperature anomaly or salinity anomaly in BSBW should decrease by 50%-75% along this path.

  2. Orbital obliquity cycles recorded in Kuroshio Current region, eastern Asia, around Plio-Pleistocene boundary

    NASA Astrophysics Data System (ADS)

    Iwatani, Hokuto; Kondo, Yasuo; Irizuki, Toshiaki; Iwai, Masao; Ikehara, Minoru

    2016-05-01

    Global climate underwent a period of significant cooling at the Plio-Pleistocene Transition (∼2.6 Ma). The influence of this change on the Kuroshio Current region in the Pacific Ocean, off eastern Asia, is not well known. In this study, we clarify temporal changes in the paleoenvironment under the influence of the Kuroshio Current during the late Pliocene and early Pleistocene using high-resolution faunal proxy records of fossil Ostracoda (Crustacea). The study unit is the Ananai Formation in the southeastern region of Shikoku, southwest Japan. The modern analog technique (MAT) is employed for the quantitative estimation of paleo-bottom water temperatures (PBWTs) and paleo-water depth (PWD) during the deposition of the formation. Ostracode MAT results show PBWT fluctuations during warmest and coldest months, with values of 16°C-20 °C and 12°C-16 °C, respectively, and a PWD of 70-140 m, reflecting sea-level oscillations. Moreover, the PBWT in the coldest month is 3 °C-4 °C lower than present-day water temperatures at the same shallow water depths. Temporal changes in these paleoenvironmental variables based on MAT are in good agreement with global oxygen isotope records. Orbital obliquity cycles with 41-kyr periodicity are recorded for the first time in an onshore section in the Kuroshio Current region at the Plio-Pleistocene boundary interval.

  3. New observations of eddies and boundary currents in the Red Sea

    NASA Astrophysics Data System (ADS)

    Bower, Amy S.; Swift, Stephen A.; Churchill, James H.; McCorkle, Daniel C.; Abualnaja, Yasser; Limeburner, Richard; Zhai, Ping

    2013-04-01

    Physical oceanographic studies of the Red Sea have often focused on the large-scale overturning circulation, in which water entering the sea from the Gulf of Aden becomes cooler, saltier and more dense as it flows northward, due mainly to strong evaporation (~2 m/y), and then flows back southward and exits the sea as a dense overflow through Bab al Mandeb. Less attention has been focused on the details of the horizontal circulation, in large part due to the dearth of high-resolution observations of the three-dimensional structure of water properties and currents. Two high-resolution hydrographic and current surveys were recently carried out in the eastern Red Sea, in March 2010 and September-October 2011. Of particular note are the continuous measurements of current velocity, taken along the cruise tracks from the sea surface to 600 m with a hull-mounted Acoustic Doppler Current Profiler, which revealed the presence and structure of several basin-scale eddies and eastern boundary currents. In March 2010, a strong, 200-km diameter anticyclonic eddy was found centered near 23oN, with peak azimuthal velocities of nearly 1 m/s, a transport of 6-7 Sv and eddy currents extending to ~400 m depth. The eddy's core was in solid body rotation, with six-day rotation period and a relative vorticity of 0.5f (i.e., 1/2 the local Coriolis parameter). Surface drifters deployed in the eddy core remained trapped for their entire lifetimes (up to 5 months). An eddy was observed several times previously in this location-20 years of satellite-derived altimetric measurements of sea level anomaly indicate that it is a quasi-permanent feature of the Red Sea circulation and that there is an annual cycle in its strength. This may be linked to the annual cycle in buoyancy forcing and the strength of the cyclonic circulation in the northern Red Sea. In September 2011, cross-basin transects in the southern Red Sea (17-19oN) revealed a layer of relatively cold, fresh, low-oxygen, high

  4. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Ross, R.; Levy, R.; Makeig, D.

    1987-03-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  5. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.R.; Curtiss, E.R.; Heitzman, J.; LePoer, B.A.; Levy, R.J.

    1985-10-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  6. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Ross, R.; LePoer, B.; Levy, R.; Curtiss, E.

    1987-08-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  7. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Curtiss, E.; Heitzman, J.; LePoer, B.; Levy, R.

    1985-09-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  8. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.R.; Curtiss, E.R.; Heitzman, J.; LePoer, B.A.; Levy, R.J.

    1986-01-01

    This bibliography provides selective annotations of open source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  9. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.R.; Levy, R.J.; Heitzman, J.; LePoer, B.; Ross, R.

    1986-11-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  10. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.R.; Curtiss, E.R.; Heitzman, J.; LePoer, B.A.; Levy, R.J.

    1985-12-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  11. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.R.; Curtiss, E.R.; Heitzman, J.; LePoer, B.A.; Levy, R.J.

    1985-07-01

    This bibliography procides selective annotations of open-source material on two current issues: nuclear developments in South Asia and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  12. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.R.; Levy, R.J.; Heitzman, J.; Ross, R.; Curtiss, E.

    1987-01-01

    This bibliography provides selective annotations of open source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  13. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.R.; Curtiss, E.R.; Hietzman, J.; LePoer, B.A.; Levy, R.J.

    1985-11-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  14. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Ross, R.R.; Blood, P.; Curtiss, E.; Heitzman, J.; LePoer, B.

    1986-05-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  15. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Heitzman, J.; Levy, R.; Ross, R.; Curtiss, E.

    1986-12-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  16. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Curtiss, E.; Heitzman, J.; LePoer, B.; Levy, R.

    1985-08-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  17. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Heitzman, J.; Levy, R.; Ross, R.; Curtiss, E.

    1986-03-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  18. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Heitzman, J.; Levy, R.; Ross, R.; Curtiss, E.

    1986-04-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  19. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Makeig, D.C.; Heitzman, J.; Ross, R.; Curtiss, E.

    1986-10-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  20. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Curtiss, E.; Heitzman, J.; LePoer, B.; Levy, R.

    1987-02-01

    This bibliography provides selective annotations of open source material on two current issues: nuclear developments in South Asia and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  1. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Heitzman, J.; Levy, R.; Levy, R.; Ross, R.

    1986-09-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  2. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Heitzman, J.; Levy, R.; Ross, R.; Curtiss, E.

    1986-06-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  3. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Curtiss, E.; Heitzman, J.; LePoer, B.; Levy, R.

    1987-09-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  4. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Curtiss, E.; Heitzman, J.; LePoer, B.; Levy, R.

    1986-02-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  5. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Heitzman, J.; Levy, R.; Ross, R.; Curtiss, E.

    1986-07-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  6. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Heitzman, J.; Levy, R.; Curtiss, E.; LaPoer, B.

    1987-12-01

    This bibliography provides selective annotations of open source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  7. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Ross, R.; Makeig, D.; LePoer, B.; Heitzman, J.; Levy, R.

    1988-03-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  8. Selective, annotated bibliography on current south Asian issues. Final report

    SciTech Connect

    Blood, P.; Heitzman, J.; Levy, R.; Ross, R.; Curtiss, E.

    1988-08-01

    This bibliography provides selective annotations of open-source material on two current issues: nuclear developments in South Asia, and tactics and organization of Afghan resistance groups. The monthly bibliography incorporates serials and monographs arranged alphabetically by author and title within each section.

  9. Lower hybrid current drive for edge current density modification in DIII-D: Final status report

    SciTech Connect

    Fenstermacher, M.E.; Porkolab, M.

    1993-08-04

    Application of Lower Hybrid (LH) Current Drive (CD) in the DIII-D tokamak has been studied at LLNL, off and on, for several years. The latest effort began in February 1992 in response to a letter from ASDEX indicating that the 2.45 GHz, 3 MW system there was available to be used on another device. An initial assessment of the possible uses for such a system on DIII-D was made and documented in September 1992. Multiple meetings with GA personnel and members of the LH community nationwide have occurred since that time. The work continued through the submission of the 1995 Field Work Proposals in March 1993 and was then put on hold due to budget limitations. The purpose of this document is to record the status of the work in such a way that it could fairly easily be restarted at a future date. This document will take the form of a collection of Appendices giving both background and the latest results from the FY 1993 work, connected by brief descriptive text. Section 2 will describe the final workshop on LHCD in DIII-D held at GA in February 1993. This was an open meeting with attendees from GA, LLNL, MIT and PPPL. Summary documents from the meeting and subsequent papers describing the results will be included in Appendices. Section 3 will describe the status of work on the use of low frequency (2.45 GHZ) LH power and Parametric Decay Instabilities (PDI) for the special case of high dielectric in the edge regions of the DIII-D plasma. This was one of the critical issues identified at the workshop. Other potential issues for LHCD in the DIII-D scenarios are: (1) damping of the waves on fast ions from neutral beam injection, (2) runaway electrons in the low density edge plasma, (3) the validity of the WKB approximation used in the ray-tracing models in the steep edge density gradients.

  10. Features and variability of the South China Sea western boundary current from 1992 to 2011

    NASA Astrophysics Data System (ADS)

    Quan, Qi; Xue, Huijie; Qin, Huiling; Zeng, Xuezhi; Peng, Shiqiu

    2016-04-01

    Different from the traditional definition of the South China Sea western boundary current (SCSWBC), in this paper, only the southwestward and southward currents along the northern and western slopes in the SCS, which are closely associated with the basin-wide wind stress curl, are defined as the SCSWBC, while the flows on the southwestern shelf driven directly by the local wind stress are regarded as part of the shelf circulation. Using a new reanalysis dataset of the SCS in conjunction with the in situ and remote sensing data, the main features and variability of the SCSWBC from 1992 to 2011 were studied. Dictated by the prevailing monsoonal winds and in- and outflows, the SCSWBC in winter extended the full length of the western slope and reached its maximum intensity off the southeast coast of Vietnam, while in summer the main body of the SCSWBC was limited to the northern half of the western slope and merged with the northward coastal current to form the Vietnam Offshore Current (VOC) at about 12° N. Moreover, the respective seasonal patterns of the SCSWBC showed pronounced interannual variations in its structure, including the axis, the width, and the maximum depth. The strength of the SCSWBC, with the transport of -11.8 ± 3.5 Sv in winter and -3.0 ± 1.6 Sv in summer off the central coast of Vietnam, also varied significantly from year to year. It was demonstrated that the monsoonal forcing over the SCS, the interannual variability of which was closely associated with El Niño events, played an important role in modulating the interannual variability of the SCSWBC, whereas the influence from the upper-layer Luzon Strait transport was secondary.

  11. Features and variability of the South China Sea western boundary current from 1992 to 2011

    NASA Astrophysics Data System (ADS)

    Quan, Qi; Xue, Huijie; Qin, Huiling; Zeng, Xuezhi; Peng, Shiqiu

    2016-07-01

    Different from the traditional definition of the South China Sea western boundary current (SCSWBC), in this paper, only the southwestward and southward currents along the northern and western slopes in the SCS, which are closely associated with the basin-wide wind stress curl, are defined as the SCSWBC, while the flows on the southwestern shelf driven directly by the local wind stress are regarded as part of the shelf circulation. Using a new reanalysis dataset of the SCS in conjunction with the in situ and remote sensing data, the main features and variability of the SCSWBC from 1992 to 2011 were studied. Dictated by the prevailing monsoonal winds and in- and outflows, the SCSWBC in winter extended the full length of the western slope and reached its maximum intensity off the southeast coast of Vietnam, while in summer the main body of the SCSWBC was limited to the northern half of the western slope and merged with the northward coastal current to form the Vietnam Offshore Current (VOC) at about 12° N. Moreover, the respective seasonal patterns of the SCSWBC showed pronounced interannual variations in its structure, including the axis, the width, and the maximum depth. The strength of the SCSWBC, with the transport of -11.8 ± 3.5 Sv in winter and -3.0 ± 1.6 Sv in summer off the central coast of Vietnam, also varied significantly from year to year. It was demonstrated that the monsoonal forcing over the SCS, the interannual variability of which was closely associated with El Niño events, played an important role in modulating the interannual variability of the SCSWBC, whereas the influence from the upper-layer Luzon Strait transport was secondary.

  12. Eddy surface properties and propagation at Southern Hemisphere western boundary current systems

    NASA Astrophysics Data System (ADS)

    Pilo, G. S.; Mata, M. M.; Azevedo, J. L. L.

    2015-08-01

    Oceanic eddies exist throughout the world oceans, but are more energetic when associated with western boundary currents (WBC) systems. In these regions, eddies play an important role in mixing and energy exchange. Therefore, it is important to quantify and qualify eddies associated with these systems. This is particularly true for the Southern Hemisphere WBC system where only few eddy censuses have been performed to date. In these systems, important aspects of the local eddy population are still unknown, like their spatial distribution and propagation patterns. Moreover, the understanding of these patterns helps to establish monitoring programs and to gain insight in how eddies would affect local mixing. Here, we use a global eddy data set to qualify eddies based on their surface characteristics in the Agulhas Current (AC), the Brazil Current (BC) and the East Australian Current (EAC) systems. The analyses reveal that eddy propagation within each system is highly forced by the local mean flow and bathymetry. Large values of eddy amplitude and temporal variability are associated with the BC and EAC retroflections, while small values occur in the centre of the Argentine Basin and in the Tasman Sea. In the AC system, eddy polarity dictates the propagation distance. BC system eddies do not propagate beyond the Argentine Basin, and are advected by the local ocean circulation. EAC system eddies from both polarities cross south of Tasmania but only the anticyclonic ones reach the Great Australian Bight. For all three WBC systems, both cyclonic and anticyclonic eddies present a geographical segregation according to radius size and amplitude. Regions of high eddy kinetic energy are associated with the eddies' mean amplitudes, and not with their densities.

  13. Bifurcation boundary conditions for current programmed PWM DC-DC converters at light loading

    NASA Astrophysics Data System (ADS)

    Fang, Chung-Chieh

    2012-10-01

    Three types of bifurcations (instabilities) in the PWM DC-DC converter at light loading under current mode control in continuous-conduction mode (CCM) or discontinuous-conduction mode (DCM) are analysed: saddle-node bifurcation (SNB) in CCM or DCM, border-collision bifurcation during the CCM-DCM transition, and period-doubling bifurcation in CCM. Different bifurcations occur in some particular loading ranges. Bifurcation boundary conditions separating stable regions from unstable regions in the parametric space are derived. A new methodology to analyse the SNB in the buck converter based on the peak inductor current is proposed. The same methodology is applied to analyse the other types of bifurcations and converters. In the buck converter, multiple stable/unstable CCM/DCM steady-state solutions may coexist. Possibility of multiple solutions deserves careful study, because an ignored solution may merge with a desired stable solution and make both disappear. Understanding of SNB can explain some sudden disappearances or jumps of steady-state solutions observed in switching converters.

  14. Nonlinear Gulf Stream Interaction with the Deep Western Boundary Current System: Observations and a Numerical Simulation

    NASA Technical Reports Server (NTRS)

    Dietrich, David E.; Mehra, Avichal; Haney, Robert L.; Bowman, Malcolm J.; Tseng, Yu-Heng

    2003-01-01

    Gulf Stream (GS) separation near its observed Cape Hatteras (CH) separation location, and its ensuing path and dynamics, is a challenging ocean modeling problem. If a model GS separates much farther north than CH, then northward GS meanders, which pinch off warm core eddies (rings), are not possible or are strongly constrained by the Grand Banks shelfbreak. Cold core rings pinch off the southward GS meanders. The rings are often re-absorbed by the GS. The important warm core rings enhance heat exchange and, especially, affect the northern GS branch after GS bifurcation near the New England Seamount Chain. This northern branch gains heat by contact with the southern branch water upstream of bifurcation, and warms the Arctic Ocean and northern seas, thus playing a major role in ice dynamics, thermohaline circulation and possible global climate warming. These rings transport heat northward between the separated GS and shelf slope/Deep Western Boundary Current system (DWBC). This region has nearly level time mean isopycnals. The eddy heat transport convergence/divergence enhances the shelfbreak and GS front intensities and thus also increases watermass transformation. The fronts are maintained by warm advection by the Florida Current and cool advection by the DWBC. Thus, the GS interaction with the DWBC through the intermediate eddy field is climatologically important.

  15. Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) Final Campaign Report

    SciTech Connect

    Wood, R.

    2016-01-01

    The extensive coverage of low clouds over the subtropical eastern oceans greatly impacts the current climate. In addition, the response of low clouds to changes in atmospheric greenhouse gases and aerosols is a major source of uncertainty, which thwarts accurate prediction of future climate change. Low clouds are poorly simulated in climate models, partly due to inadequate long-term simultaneous observations of their macrophysical and microphysical structure, radiative effects, and associated aerosol distribution in regions where their impact is greatest. The thickness and extent of subtropical low clouds is dependent on tight couplings between surface fluxes of heat and moisture, radiative cooling, boundary layer turbulence, and precipitation (much of which evaporates before reaching the ocean surface and is closely connected to the abundance of cloud condensation nuclei). These couplings have been documented as a result of past field programs and model studies. However, extensive research is still required to achieve a quantitative understanding sufficient for developing parameterizations, which adequately predict aerosol indirect effects and low cloud response to climate perturbations. This is especially true of the interactions between clouds, aerosol, and precipitation. These processes take place in an ever-changing synoptic environment that can confound interpretation of short time period observations.

  16. Combined effect of rheology and confining boundaries on spreading of gravity currents in porous media

    NASA Astrophysics Data System (ADS)

    Longo, Sandro; Ciriello, Valentina; Chiapponi, Luca; Di Federico, Vittorio

    2015-05-01

    inclination, and the constant thickness profile depends only on n. Theoretical results are validated by comparison with experiments (i) in horizontal and inclined channels with triangular or semicircular cross-section, (ii) with different shear-thinning fluids, and (iii) for constant volume and constant flux conditions. The experimental results show good agreement with theoretical predictions in the long-time regime. Our analysis demonstrates that self-similar solutions are able to capture the essential long-term behaviour of gravity currents in porous media, accounting for diverse effects such as non-Newtonian rheology, presence of boundaries, and channel inclination. This provides a relatively simple framework for sensitivity analysis, and a convenient benchmark for numerical studies.

  17. Final Technical Report: Grain Boundary Complexions and Transitions in Doped Silicon

    SciTech Connect

    Jian Luo

    2012-10-15

    This four-year research project has advanced the fundamental knowledge of grain boundary (GB) complexions (i.e., "two-dimensional interfacial phases") and associated GB "phase" transitions in several grounds. First, a bilayer interfacial phase, which had been directly observed by microscopy only in complex ceramic systems in prior studies, has been identified in simpler systems such as Au-doped Si and Bi-doped Ni in this study, where the interpretations of the their formation mechanisms and microscopic images are less equivocal. Second, convincing evidence for the existence of a first-order GB transition from a nominally "clean" GB to a bilayer adsorption interfacial phase has been revealed for Au-doped Si; the confirmation of the first-order nature of interfacial transitions at GBs, which was rare in prior studies, is scientifically significant and technologically important. Third, the bilayer interfacial phase discovered in Bi-doped Ni has been found to be the cause of the mysterious liquid metal embrittlement phenomenon in this system; the exact atomic level mechanism of this phenomenon has puzzled the materials and physics communities for over a century. Finally, significant advancements have been made to establish phenomenological thermodynamic models for GB complexions and transitions. Since GB complexions can control the transport, mechanical and physical properties of a broad range of metallic and ceramic materials, the fundamental knowledge generated by this project can have broad impacts on materials design in general. In this regard, understanding and controlling GB phase behaviors (complexions and transitions) can be an important component for the "Materials Genome" project.

  18. Role of Detuning in the Final Stage of Subharmonic Mode Transition in Boundary Layers

    NASA Technical Reports Server (NTRS)

    Corke, Thomas C.

    2007-01-01

    This work involves mechanisms for transition to turbulence in a Blasius boundary layer through resonant interactions between a plane Tollmien-Schlichting Wave and pairs of oblique waves with equal-but-opposite wave angles. When the frequency of the TS wave is exactly twice that of the oblique waves, we have a "tuned" subharmonic resonance. This leads to the enhanced growth of the oblique modes. Following this, other nonlinear interactions lead to the growth of other 3-D modes which are harmonically based, along with a 3-D mean flow distortion. In the final stage of this process, a gradual spectral filling occurs which we have traced to the growth of fundamental and subharmonic side-band modes. To simulate this with controlled inputs, we introduced the oblique wave pairs at the same conditions, but shifted the frequency of the plane TS mode (by as much as 12 percent) so that it was not exactly twice that of the 3-D modes. These "detuned" conditions also lead to the enhanced growth of the oblique modes, as well as discrete side-band modes which come about through sum and difference interactions. Other interactions quickly lead to a broad band of discrete modes. Of particular importance is the lowest difference frequency which produces a low frequency modulation similar to what has been seen in past experiments with natural 3-D mode input. Cross-bispectral analysis of time series allows us to trace the origin and development of the different modes. Following these leads to a scenario which we believe is more relevant to conditions of "natural" transitions, where low amplitude background disturbances either lead to the gradual detuning of exact fundamental/subharmonic resonance, or in which 3-D mode resonance is detuned from the onset. The results contrast the two conditions, and document the propensity of the 2-D/3-D mode interactions to become detuned.

  19. Eddy-current steam generator data analysis performance. Final report

    SciTech Connect

    Harris, D.H.

    1993-06-01

    This study assessed the accuracy of eddy current, bobbin coil data analysis of steam generator tubes conducted under the structure of the PWR Steam Generator Examination Guidelines, Individual and team performance measures were obtained from independent analyses of data from 1619 locations in a sample of 199 steam generator tubes. The 92 reportable indications contained in the tube sample, including 64 repairable indications, were attributable to: wear at anti-vibration bars, intergranular attack/stress-corrosion cracking (IGA/SCC) within tube sheet crevice regions, primary-water stress-corrosion cracking (PWSCC) at tube roll transitions, or thinning at cold-leg tube supports. Analyses were conducted by 20 analysts, four each from five vendors of eddy current steam generator examination services. In accordance with the guidelines, site orientation was provided with plant-specific guidelines; preanalysis practice was completed on plant-specific data; analysts were qualified by performance testing; and independent primary-secondary analyses were conducted with resolution of discrepancies (team analyses). Measures of analysis performance included percentages of indications correctly reported, percentages of false reports, and relative operating characteristic (ROC) curves. ROC curves presented comprehensive pictures of analysis accuracy generalizable beyond the specific conditions of this study. They also provided single-value measures of analysis accuracy. Conclusions and recommendations were provided relative to analysis accuracy, effect of primary-secondary analyses, analyses of tube sheet crevice regions, establishment of reporting criteria, improvement of examination guidelines, and needed research.

  20. Constructing Integrable High-pressure Full-current Free-boundary Stellarator Magnetohydrodynamic Equilibrium Solutions

    SciTech Connect

    S.R. Hudson; D.A. Monticello; A.H. Reiman; D.J. Strickler; S.P. Hirshman; L-P. Ku; E. Lazarus; A. Brooks; M.C. Zarnstorff; A.H. Boozer; G-Y. Fu; and G.H. Neilson

    2003-09-15

    For the (non-axisymmetric) stellarator class of plasma confinement devices to be feasible candidates for fusion power stations it is essential that, to a good approximation, the magnetic field lines lie on nested flux surfaces; however, the inherent lack of a continuous symmetry implies that magnetic islands responsible for breaking the smooth topology of the flux surfaces are guaranteed to exist. Thus, the suppression of magnetic islands is a critical issue for stellarator design, particularly for small aspect ratio devices. Pfirsch-Schluter currents, diamagnetic currents, and resonant coil fields contribute to the formation of magnetic islands, and the challenge is to design the plasma and coils such that these effects cancel. Magnetic islands in free-boundary high-pressure full-current stellarator magnetohydrodynamic equilibria are suppressed using a procedure based on the Princeton Iterative Equilibrium Solver [Reiman and Greenside, Comp. Phys. Comm. 43 (1986) 157] which iterate s the equilibrium equations to obtain the plasma equilibrium. At each iteration, changes to a Fourier representation of the coil geometry are made to cancel resonant fields produced by the plasma. The changes are constrained to preserve certain measures of engineering acceptability and to preserve the stability of ideal kink modes. As the iterations continue, the coil geometry and the plasma simultaneously converge to an equilibrium in which the island content is negligible, the plasma is stable to ideal kink modes, and the coils satisfy engineering constraints. The method is applied to a candidate plasma and coil design for the National Compact Stellarator Experiment [Reiman, et al., Phys. Plasmas 8 (May 2001) 2083].

  1. Upwelling processes along a western boundary current in the Abrolhos-Campos region of Brazil

    NASA Astrophysics Data System (ADS)

    Aguiar, A. L.; Cirano, M.; Pereira, J.; Marta-Almeida, M.

    2014-08-01

    Upwelling events observed from the years 2003 to 2011 were analyzed. Our focus was on the Abrolhos-Campos region (ACR, 15°S-23°S), which is located along the Brazilian Margin and influenced by a western boundary current, the Brazil Current (BC). Satellite sea surface temperature, National Centers for Environmental Prediction (NCEP) and Global Forecast System (GFS) wind data were used to complement the results of a high-resolution regional oceanic model to investigate the occurrence of and the mechanisms responsible for intense upwelling events in this region. These events were more frequent from 20°S to 23°S. Over 90% of the identified upwelling events were influenced by favorable wind stress. Surface Ekman transport was found to be more important for the region from Prado (17°S) to Marataízes (21°S), whereas upward Ekman pumping played a more important role from 22°S to 23°S. Current-driven upwelling processes associated with the location of the BC as well as its velocity and meso-scale activity were also analyzed. The results showed that these mechanisms are highly influenced by the local topography. Topographic effects exerted via the acceleration of the BC are more obvious in the southern ACR, while in the Prado region, BC cyclonic meanders tend to be more relevant. Moreover, eddy-driven upwelling increases in the southward direction after the passage of the Vitória-Trindade Ridge (20°S), an important submarine chain, which acts to constrain and modulate the southward flow of the BC.

  2. Conductance and persistent current in quasi-one-dimensional systems with grain boundaries: Effects of the strongly reflecting and columnar grains

    NASA Astrophysics Data System (ADS)

    Feilhauer, J.; Moško, M.

    2011-08-01

    We study mesoscopic transport in the quasi-one-dimensional wires and rings made of a two-dimensional conductor of width W and length L≫W. Our aim is to compare an impurity-free conductor with grain boundaries with a grain-free conductor with impurity disorder. A single grain boundary is modeled as a set of the two-dimensional δ-function-like barriers positioned equidistantly on a straight line and disorder is emulated by a large number of such straight lines, intersecting the conductor with random orientation in random positions. The impurity disorder is modeled by the two-dimensional δ barriers with the randomly chosen positions and signs. The electron transmission through the wires is calculated by the scattering-matrix method, and the Landauer conductance is obtained. Moreover, we calculate the persistent current in the rings threaded by magnetic flux: We incorporate into the scattering-matrix method the flux-dependent cyclic boundary conditions and we introduce a trick allowing us to study the persistent currents in rings of almost realistic size. We mainly focus on the numerical results for L much larger than the electron mean-free path, when the transport is diffusive. If the grain boundaries are weakly reflecting, the systems with grain boundaries show the same (mean) conductance and the same (typical) persistent current as the systems with impurities, and the results also agree with the single-particle theories treating disorder as a white-noise-like potential. If the grain boundaries are strongly reflecting, the rings with the grain boundaries show the typical persistent currents about three times larger than the white-noise-based theory, thus resembling the experimental data of Jariwala [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.86.1594 86, 1594 (2001)]. Finally, we extend our study to the three-dimensional wires/rings with columnar grains. Due to the columnar shape of the grains, the resulting persistent current exceeds the white

  3. Field-aligned current signatures in the near-tail region. I - ISEE observations in the plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Ohtani, S.; Kokubun, S.; Elphic, R. C.; Russell, C. T.

    1988-01-01

    Field-aligned currents in the near-tail region are examined using ISEE magnetometer data. Two substorms (the 1054 UT and the 1436 UT substorms on March 22, 1979) were examined, demonstrating the consistency of the current polarity and intensity with observations at lower altitudes, which suggests that field-aligned currents in the plasma sheet boundary layer are parts of the large-scale current system, the region-1 system. An examination of the steplike changes of the magnetic field direction, which correspond to the spacecraft crossing of a net field-aligned current, showed that the field-aligned currents in the plasma sheet boundary layer have the same polarity as the region-1 system.

  4. Relative impact of seasonal and oceanographic drivers on surface chlorophyll a along a Western Boundary Current

    NASA Astrophysics Data System (ADS)

    Everett, Jason D.; Baird, Mark E.; Roughan, Moninya; Suthers, Iain M.; Doblin, Martina A.

    2014-01-01

    Strengthening Western Boundary Currents (WBCs) advect warm, low nutrient waters into temperate latitudes, displacing more productive waters. WBCs also influence phytoplankton distribution and growth through current-induced upwelling, mesoscale eddy intrusion and seasonal changes in strength and poleward penetration. Here we examine dynamics of chlorophyll a (Chl. a) in the western Pacific Ocean, a region strongly influenced by the East Australian Current (EAC). We interpreted a spatial and temporal analysis of satellite-derived surface Chl. a, using a hydrodynamic model, a wind-reanalysis product and an altimetry-derived eddy-census. Our analysis revealed regions of persistently elevated surface Chl. a along the continental shelf and showed that different processes have a dominant effect in different locations. In the northern and central zones, upwelling events tend to regulate surface Chl. a patterns, with peaks in phytoplankton biomass corresponding to two known upwelling locations south of Cape Byron (28.5°S) and Smoky Cape (31°S). Within the central EAC separation zone, positive surface Chl. a anomalies occurred 65% of the time when both wind-stress (τw) and bottom-stress (τB) were upwelling-favourable, and only 17% of the time when both were downwelling-favourable. The interaction of wind and the EAC was a critical driver of surface Chl. a dynamics, with upwelling-favourable τW resulting in a 70% increase in surface Chl. a at some locations, when compared to downwelling-favourable τW . In the southern zone, surface Chl. a was driven by a strong seasonal cycle, with phytoplankton biomass increasing up to 152% annually each spring. The Stockton Bight region (32.25-33.25°S) contained ⩾20% of the total shelf Chl. a on 27% of occasions due to its location downstream of upwelling locations, wide shelf area and reduced surface velocities. This region is analogous to productive fisheries regions in the Aghulus Current (Natal Bight) and Kuroshio Current

  5. Intensification and poleward shift of subtropical western boundary currents under global warming

    NASA Astrophysics Data System (ADS)

    Yang, Hu; Lohmann, Gerrit; Wei, Wei; Dima, Mihai; Liu, Jiping

    2015-04-01

    Dynamic changes of subtropical western boundary currents (WBCs) are investigated based on three types of independent data sets. These include reconstructed and reanalysis products, satellite/blended observations and climate models output from the fifth phase of the Climate Model Intercomparison Project (CMIP5). Consistent increasing of sea surface temperature (SST) and ocean surface heat loss are found over the mid-latitude expansions of WBCs. Furthermore, the upper 100 m ocean water velocity are increasing in the same direction as the background WBCs, demonstrating that WBCs are strengthening. In addition, the positions of WBCs induced sharp SST fronts and intensive ocean heat loss are migrating towards the poles, suggesting that the routes of WBCs are shifting poleward. According to the ensemble projections from the CMIP5 models, the WBCs (except the Gulf Stream) will continue strengthening and shifting poleward if carbon dioxide levels keep rising in this century. The significant dynamic changes of WBCs are affected by an intensified and poleward shift of near-surface ocean zonal winds, which are attributed to positive annular modes-like trends, particularly over the Southern Hemisphere.

  6. The impact of open boundary forcing on forecasting the East Australian Current using ensemble data assimilation

    NASA Astrophysics Data System (ADS)

    Sandery, Paul A.; Sakov, Pavel; Majewski, Leon

    2014-12-01

    We investigate the performance of an eddy resolving regional ocean forecasting system of the East Australian Current (EAC) for both ensemble optimal interpolation (EnOI) and ensemble Kalman filter (EnKF) with a focus on open boundary model nesting solutions. The performance of nesting into a global re-analysis; nesting into the system's own analysis; and nesting into a free model is quantified in terms of forecast innovation error. Nesting in the global reanalysis is found to yield the best results. This is closely followed by the system that nests inside its own analysis, which seems to represent a viable practical option in the absence of a suitable analysis to nest within. Nesting into a global reanalysis without data assimilation and nesting into an unconstrained model were both found to be unable to constrain the mesoscale circulation at all times. We also find that for a specific interior area of the domain where the EAC separation takes place, there is a mixture of results for all the systems investigated here and that, whilst the application of EnKF generates the best results overall, there are still times when not even this method is able to constrain the circulation in this region with the available observations.

  7. Mixed layer depth variability in the tropical boundary of the California Current, 1997-2007

    NASA Astrophysics Data System (ADS)

    Jeronimo, Gilberto; Gomez-Valdes, Jose

    2010-05-01

    The variability of the mixed layer depth (MLD) is examined over a decade (1997-2007) for the tropical boundary of the California Current (24-32°N), using conductivity-temperature-depth observations collected by quarterly survey cruises. Results indicate that salinity gradients control MLD rather than temperature gradients. The mean state of the upper ocean indicates that contours of constant MLD are parallel to the coast, with mixed layer thickness decreasing toward the coastal zone. The deepest (˜70 m) thickness is reached in January and the shallowest (˜15 m) occurs in July. The warmer conditions (summer) are reproduced for a simple thermal energy equation. The rest of the seasons are reproduced for a one-dimensional momentum balance for the upper ocean, which includes Ekman dynamics and stratification. This comparison indicates that the variability of MLD is mainly due to wind-driven phenomena except during the heating period. In particular, seasonal and interannual variability of the MLD are correlated with offshore Ekman transport. An abrupt MLD change occurs between January 1998 and January 2000 associated with the strong El Niño-La Niña cycle shift that occurred in this period.

  8. The low-latitude boundary layer at mid-altitiudes: Relation to large-scale Birkeland currents

    SciTech Connect

    Woch, J.; Yamauchi, M.; Lundin, R. ); Potemra, T.A.; Zanetti, L.J. )

    1993-10-22

    In this work the authors seek to test a projected relationship between the low latitude boundary layer (LLBL) and field aligned currents (FAC), or Birkeland currents. They use the procedure developed by Woch and Lundin for identifying LLBL boundaries. They look for correlations between properties of the FAC and properties of the LLBL. Their results show that in most cases the FAC observed are totally inside the region which exhibits LLBL plasma precipitation. The authors argue that within the biases to their data because of its source, and relative sensitivities, their conclusions support earlier work which argues for the LLBL acting as a source region for FAC features.

  9. Western Maryland Power Plant Siting Study: discussion of licensing issues and site boundary considerations at three candidate sites. Final report

    SciTech Connect

    Klauda, R.J.; Portner, E.M.

    1984-10-01

    This document is one of a series of technical reports prepared for the Western Maryland Power Plant Siting Study. Selected licensing issues for the three remaining candidate sites are discussed and related to site boundary considerations. None of the four licensing issues evaluated (noise, fugitive dust, solid waste disposal, point source water discharges) would eliminate any of the three candidate sites from the comparison study. All three sites could likely comply with the air quality standards applicable to fugitive dust emissions. Compliance could be periodically complicated by levels of airborne coal dust at WP-26 during high wind episodes. Noise and fugitive dust level predictions suggested that the original site boundaries could be further refined. Final site boundaries will not be established until after the preferred site is selected.

  10. Characterising primary productivity measurements across a dynamic western boundary current region

    NASA Astrophysics Data System (ADS)

    Everett, Jason D.; Doblin, Martina A.

    2015-06-01

    Determining the magnitude of primary production (PP) in a changing ocean is a major research challenge. Thousands of estimates of marine PP exist globally, but there remain significant gaps in data availability, particularly in the Southern Hemisphere. In situ PP estimates are generally single-point measurements and therefore we rely on satellite models of PP in order to scale up over time and space. To reduce the uncertainty around the model output, these models need to be assessed against in situ measurements before use. This study examined the vertically-integrated productivity in four water-masses associated with the East Australian Current (EAC), the major western boundary current (WBC) of the South Pacific. We calculated vertically integrated PP from shipboard 14C PP estimates and then compared them to estimates from four commonly used satellite models (ESQRT, VGPM, VGPM-Eppley, VGPM-Kameda) to assess their utility for this region. Vertical profiles of the water-column show each water-mass had distinct temperature-salinity signatures. The depth of the fluorescence-maximum (fmax) increased from onshore (river plume) to offshore (EAC) as light penetration increased. Depth integrated PP was highest in river plumes (792±181 mg C m-2 d-1) followed by the EAC (534±116 mg C m-2 d-1), continental shelf (140±47 mg C m-2 d-1) and cyclonic eddy waters (121±4 mg C m-2 d-1). Surface carbon assimilation efficiency was greatest in the EAC (301±145 mg C (mg Chl-a)-1 d-1) compared to other water masses. All satellite primary production models tested underestimated EAC PP and overestimated continental shelf PP. The ESQRT model had the highest skill and lowest bias of the tested models, providing the best first-order estimates of PP on the continental shelf, including at a coastal time-series station, Port Hacking, which showed considerable inter-annual variability (155-2957 mg C m-2 d-1). This work provides the first estimates of depth integrated PP associated with the

  11. Effects of grain size and grain boundary on critical current density of high T(sub c) superconducting oxides

    NASA Technical Reports Server (NTRS)

    Zhao, Y.; Zhang, Q. R.; Zhang, H.

    1990-01-01

    By means of adding impurity elements in high T sub c oxides, the effects were studied of grain size and grain boundary on the critical current density of the following systems: YBa2Cu3O(7-y) and Bi-Pr-Sr-Ca-Cu-O. In order to only change the microstructure instead of the superconductivity of the grains in the samples, the impurity elements were added into the systems in terms of the methods like this: (1) substituting Y with the lanthanide except Pr, Ce, and Tb in YBa2Cu3O(7-y) system to finning down grains in the samples, therefore, the effect can be investigated of the grain size on the critical current density of 1:2:3 compounds; (2) mixing the high T sub c oxides with the metal elements, such as Ag, according to the composition of (high T sub c oxide)1-xAgx to metallize the grain boundaries in the samples, studying the effect of the electric conductivity of the grain boundaries on the critical current density; (3) adding SiO2, PbO2, and SnO2 into the high T sub c oxide to form impurity phases in the grain boundaries, trying to find out the effects of the impurity phases or metalloid grain boundaries on the critical current density of the high T sub c superconductors. The experimental results indicate that in the case of of the presence of the metalloid grain boundaries finning down grains fails to enhance the j sub c, but restrains it strongly, the granular high T sub c superconductors with the small size grains coupled weakly is always the low j sub c system.

  12. Observed and simulated variability of the Atlantic meridional overturning circulation and the deep western boundary current

    NASA Astrophysics Data System (ADS)

    Mielke, Charlotte; Frajka-Williams, Eleanor; Gary, Stefan; Shimizu, Kenji; Toole, John; Baehr, Johanna

    2014-05-01

    Despite the importance of Atlantic meridional overturnig circulation (AMOC) for the climate of Africa, America and Europe, continuous AMOC observations are at present restricted to two latitudes, and are available for less than ten years. We therefore investigate whether the AMOC's variability can be inferred from measurements of the deep western boundary current (DWBC), which are already available at several locations. To that end, we jointly analyze the available 26°N RAPID and the 41°N Argo-based AMOC estimates with RAPID and line W (40°N) DWBC estimates. We also compare them to a 60-year simulation with a high-resolution NCEP-forced ocean model. The DWBC and its layers are defined dynamically in the model based on a comparison of temperature-versus-salinity data in model and observations and the time-dependent velocity field. On the timescales where observations are available, the model is able to reproduce the variability of the DWBC and its individual layers at both locations. Our preliminary analysis of the observational data and model results suggests that different mechanisms dominate the DWBC's variability at different timescales. On sub-seasonal to seasonal timescales, the DWBC is mostly barotropic, and its variability is linked to local processes. Thus, the DWBC has a well-defined seasonal cycle which is opposite to the seasonal cycle of the non-Ekman component of the AMOC seasonal cycle. On interannual timescales, there is no obvious relation between AMOC and DWBC. However, on decadal timescales, our analysis indicates covariability between AMOC and DWBC. We conclude that although caution should be exercised on interannual timescales, the DWBC might be used as a proxy for long-term AMOC trends and possibly modulations of the AMOC's seasonal cycle.

  13. PLASMOID RELEASES IN THE HELIOSPHERIC CURRENT SHEET AND ASSOCIATED CORONAL HOLE BOUNDARY LAYER EVOLUTION

    SciTech Connect

    Foullon, C.; Lavraud, B.; Opitz, A.; Sauvaud, J.-A.; Luhmann, J. G.; Farrugia, C. J.; Simunac, K. D. C.; Galvin, A. B.; Kucharek, H.; Popecki, M.; Retino, A.; Wardle, N. C.; Owen, C. J.

    2011-08-10

    As the heliospheric current sheet (HCS) is corotating past STEREO-B, near-Earth spacecraft ACE, Wind and Cluster, and STEREO-A over more than three days between 2008 January 10 and 14, we observe various sections of (near-pressure-balanced) flux-rope- and magnetic-island-type plasmoids in the associated heliospheric plasma sheet (HPS). The plasmoids can qualify as slow interplanetary coronal mass ejections and are relatively low proton beta (<0.5) structures, with small length scales (an order of magnitude lower than typical magnetic cloud values) and low magnetic field strengths (2-8 nT). One of them, in particular, detected at STEREO-B, corresponds to the first reported evidence of a detached plasmoid in the HPS. The in situ signatures near Earth are associated with a long-decay X-ray flare and a slow small-scale streamer ejecta, observed remotely with white-light coronagraphs aboard STEREO-B and SOHO and tracked by triangulation. Before the arrival of the HPS, a coronal hole boundary layer (CHBL) is detected in situ. The multi-spacecraft observations indicate a CHBL stream corotating with the HCS but with a decreasing speed distribution suggestive of a localized or transient nature. While we may reasonably assume that an interaction between ejecta and CHBL provides the source of momentum for the slow ejecta's acceleration, the outstanding composition properties of the CHBL near Earth provide here circumstantial evidence that this interaction or possibly an earlier one, taking place during streamer swelling when the ejecta rises slowly, results in additional mixing processes.

  14. Direct imaging of enhanced current collection on grain boundaries of Cu(In,Ga)Se{sub 2} solar cells

    SciTech Connect

    Kim, JunHo; Kim, SeongYeon; Jiang, Chun-Sheng; Ramanathan, Kannan; Al-Jassim, Mowafak M.

    2014-02-10

    We report on direct imaging of current collection by performing conductive atomic force microscopy (C-AFM) measurement on a complete Cu(In,Ga)Se{sub 2} solar cell. The localized current was imaged by milling away the top conductive layer of the device by repeated C-AFM scans. The result exhibits enhanced photocurrent collection on grain boundaries (GBs) of CIGS films, consistent with the argument for electric-field-assisted carrier collection on the GBs.

  15. Seasonal variability in the Deep Western Boundary Current around the Eastern tip of Brazil

    NASA Astrophysics Data System (ADS)

    Rhein, Monika; Stramma, Lothar

    2005-08-01

    The spreading of recently ventilated North Atlantic Deep Water (NADW) from the formation region to the equatorial Atlantic occurs mainly in the Deep Western Boundary Current (DWBC). When crossing the equator between 44°W and 35°W, the DWBC is split in two velocity cores through a chain of seamounts around the Atoll das Rocas at 3.5°S. Further eastward the DWBC contributes to the zonally oriented equatorial current system. The circulation of the NADW in the crucial region around the eastern tip of Brazil is examined using 8 CTD and Chlorofluorocarbon (CFC) sections along 35°W and along 5°S, respectively, taken mainly in spring and fall in the years 1990-2002. As expected from the short direct flow path between the two sections, the CFC concentrations in the upper NADW (1400-2200 m) were similar at 35°W and 5°S during boreal autumn. In spring, however, a significant downstream CFC decrease was observed. If one attributes the decrease solely to the older age of water further downstream, the CFC concentration age difference between 35°W and 5°S in May 2002 would be 3-5 years. We interpret the aging to be caused by an eastward detour of the flow with the deep equatorial circulation before reaching 5°S in spring. Another conspicuous anomaly was found in the middle NADW (2200-3400 m) with downstream decreasing salinities in boreal spring, but not in autumn. This variability might also be caused by differences in the deep equatorial circulation, but in contrast to the uNADW, one cannot exclude enhanced mixing with water of South Atlantic origin in spring to be the cause of that variability. No seasonal difference was observed in the hydrography or the CFC concentrations for the lower NADW. The weaker CFC decrease along the equator compared with that in the DWBC downstream of 35°W, and the topographic features along the downstream path, point to a predominantly eastward flow of the deep lNADW core. The lNADW CFC core is no longer observed at 11°S. Repeated

  16. Variations of the deep western boundary current in Wake Island Passage

    NASA Astrophysics Data System (ADS)

    Kawabe, Masaki; Yanagimoto, Daigo; Kitagawa, Shoji; Kuroda, Yoshifumi

    2005-07-01

    Two moorings were deployed at 168°30'E (Sta. WPW) and 169°30'E (WPE) on 18°20'N in Wake Island Passage (WIP) to measure the velocity of the eastern branch of the deep western boundary current (DWBC) in the North Pacific. We obtained hourly velocity data from eight current meters located at depths of 3020, 4020, 5020, and 5120 m (near-bottom) at WPW and 2000, 4000, 5000, and 5300 m (near-bottom) at WPE, and analyzed daily mean velocity data for 374 days from 10 February 1999 to 18 February 2000. The velocity of the DWBC and its variations are large near the ocean floor, at depths of 5000 m and more. The DWBC at WPE increases exponentially with depth, with the near-bottom mean velocity being 3.5 cm s -1, whereas the DWBC at WPW is almost uniform at the bottom layer with the mean velocity being 1.9 cm s -1. The direction of the DWBC in WIP is dominant between 15 and 55°T with a mean of approximately 35°T. This orientation is due to the direction of the bottom topography around 5000-m depth. The velocity and its variations decay markedly at 4000 m, indicating the characteristics of the eastern branch current of the DWBC, which is formed primarily by the portion of the DWBC below 4500 m. A peculiar property is that the velocity and its variations of the DWBC are much less in the western part (WPW) than in the eastern part (WPE) of WIP. The presence of several seamounts may decrease the velocity and modify the structure of the DWBC in the western half of WIP. On the other hand, the eastern half of WIP is deep and has no significant seamounts, which may enable the DWBC to flow smoothly there. The volume transport of the DWBC in WIP is estimated to be 3.6±1.3 Sv (10 6 m 3 s -1) northward on average, with a range of -5.3-14.8 Sv, although the uncertainty of the mean value must be larger than 1.3 Sv because of the estimation from just two moorings. The mean volume transport of the eastern branch current of the DWBC is found to be a little more than 3.6 Sv by adding the

  17. Seismotectonics of plate boundaries. Final report, 1 November 1973-30 June 1981

    SciTech Connect

    Berger, J.; Brune, J.N.; Goodkind, J.; Wyatt, F.; Agnew, D.C.; Beaumont, C.

    1981-06-01

    Research on the seismotectonics of plate boundaries is summarized. Instrumental development and an observational program designed to study various aspects of the seismotectonics of southern California and the northern Gulf of California are described. A unique superconducting gravimeter was further developed and supported under this program for deployment and operation at several sites. Work on Earth tides is also discussed.

  18. Final Report for Time Domain Boundary Element and Hybrid Finite Element Simulation for Maxwell's Equations

    SciTech Connect

    Pingenot, J; Jandhyala, V

    2007-03-01

    This report summarizes the work performed for Lawrence Livermore National Laboratory (LLNL) at the University of Washington between September 2004 and May 2006. This project studied fast solvers and stability for time domain integral equations (TDIE), especially as applied to radiating boundary for a massively parallel FEM solver.

  19. The Gulf Stream pathway and the impacts of the eddy-driven abyssal circulation and the Deep Western Boundary Current

    NASA Astrophysics Data System (ADS)

    Hurlburt, Harley E.; Hogan, Patrick J.

    2008-08-01

    A hydrodynamic model of the subtropical Atlantic basin and the Intra-Americas Sea (9-47°N) is used to investigate the dynamics of Gulf Stream separation from the western boundary at Cape Hatteras and its mean pathway to the Grand Banks. The model has five isopycnal Lagrangian layers in the vertical and allows realistic boundary geometry, bathymetry, wind forcing, and a meridional overturning circulation (MOC), the latter specified via ports in the northern and southern boundaries. The northward upper ocean branch of the MOC (14 Sv) was always included but the southward Deep Western Boundary Current (DWBC) was excluded in some simulations, allowing investigation of the impacts of the DWBC and the eddy-driven mean abyssal circulation on Gulf Stream separation from the western boundary. The result is resolution dependent with the DWBC playing a crucial role in Gulf Stream separation at 1/16° resolution but with the eddy-driven abyssal circulation alone sufficient to obtain accurate separation at 1/32° resolution and a realistic pathway from Cape Hatteras to the Grand Banks with minimal DWBC impact except southeast of the Grand Banks. The separation from the western boundary is particularly sensitive to the strength of the eddy-driven abyssal circulation. Farther to the east, between 68°W and the Grand Banks, all of the 1/16° and 1/32° simulations with realistic topography (with or without a DWBC) gave similar generally realistic mean pathways with clear impacts of the topographically constrained eddy-driven abyssal circulation versus very unrealistic Gulf Stream pathways between Cape Hatteras and the Grand Banks from otherwise identical simulations run with a flat bottom, in reduced-gravity mode, or with 1/8° resolution and realistic topography. The model is realistic enough to allow detailed model-data comparisons and a detailed investigation of Gulf Stream dynamics. The corresponding linear solution with a Sverdrup interior and Munk viscous western boundary

  20. Dynamics of the Leeuwin Current: Part 2. Impacts of mixing, friction, and advection on a buoyancy-driven eastern boundary current over a shelf

    NASA Astrophysics Data System (ADS)

    Benthuysen, Jessica; Furue, Ryo; McCreary, Julian P.; Bindoff, Nathaniel L.; Phillips, Helen E.

    2014-03-01

    The boundary currents over the Western Australian continental shelf and slope consist of the poleward flowing Leeuwin Current (LC) and the equatorward flowing Leeuwin Undercurrent (LUC). Key properties of the LC are its poleward strengthening, deepening to the south, and shelfbreak intensification. The alongshore flow reverses direction below about 300 m, forming the LUC at greater depths. To investigate the processes that cause these features, we obtain solutions to an idealized, regional ocean model of the South Indian Ocean. Solutions are forced by relaxing surface density to a prescribed, meridionally varying density profile ρ*(y) with a timescale of δt. In addition, vertical diffusion is intensified near the ocean surface. This diffusion establishes the minimum thickness over which density is well-mixed. We define this thickness as the “upper layer”. Solutions are obtained with and without a continental shelf and slope off Western Australia and for a range of values of δt and mixing parameters. Within this upper layer, there is a meridional density gradient that balances a near-surface, eastward geostrophic flow. The eastward current downwells near the eastern boundary, leading to westward flow at depth. The upper layer's meridional structure and zonal currents crucially depend on coastal processes, including the presence of topography near the eastern boundary. Kelvin waves inhibit the upper layer from deepening at the coast. Rossby waves propagate the coastal density structure offshore, hence modifying the interior currents. A comparison of the solutions with or without a continental shelf and slope demonstrate that topographic trapping of Rossby waves is a necessary process for maintaining realistic eastern boundary current speeds. Significant poleward speeds occur only onshore of where the upper layer intersects the slope, that is, at a grounding line. Its poleward transport increases when surface-enhanced vertical mixing is applied over a greater

  1. The Plate Boundary Observatory: Current status and plans for the next five years

    NASA Astrophysics Data System (ADS)

    Mattioli, G. S.; Feaux, K.; Meertens, C. M.; Mencin, D.; Miller, M.

    2013-12-01

    UNAVCO currently operates and maintains the NSF-funded Plate Boundary Observatory (PBO), which is the geodetic facility of EarthScope. PBO was designed and built from 2003 to 2008 with $100M investment from the NSF Major Research Equipment and Facilities Construction (MREFC) Program. UNAVCO operated and maintained PBO under a Cooperative Agreement (CA) with NSF from 2008 to 2013 and will continue PBO O&M for the next five years as part of the new Geodesy Advancing Geosciences and EarthScope (GAGE) Facility. PBO is largest continuous GPS and borehole geophysical network in the Americas, with 1100 continuous Global Positioning System (cGPS) sites, including several with multiple monuments, 79 boreholes, with 75 tensor strainmeters, 78 short-period, 3-component seismometers, and pore pressure sensors at 23 sites. PBO also includes 26 tiltmeters deployed at volcanoes in Alaska, Mt St Helens, and Yellowstone caldera and 6 long-baseline laser strainmeters. Surface meteorological sensors are collocated at 154 GPS sites. UNAVCO provides high-rate (1 Hz), low-latency (<1 s) GPS data streams (RT-GPS) from 382 stations in PBO. UNAVCO has delivered over 62 Tb of geodetic data to the EarthScope community since its PBO's inception in 2004. Over the past year, data return for the cGPS component of PBO is 98%, well above the data return metric of 85% set by the NSF, a result of efforts to upgrade power systems and communications infrastructure. In addition, PBO has set the standard for the design, construction, and operation of other multi-hazard networks across the Americas, including COCONet in the Caribbean region and TLALOCNet in Mexico. Funding to support ongoing PBO O&M has declined from FY2012 CA levels under the new GAGE Facility. The implications for data return and data quality metrics as well as replacement of aging PBO GPS instruments with GNSS-compatible systems are as yet unknown. A process to assess the cost of specific PBO components, data rates, enhanced

  2. Poleward displacement of coastal upwelling-favorable winds in the ocean's eastern boundary currents through the 21st century

    NASA Astrophysics Data System (ADS)

    Rykaczewski, Ryan R.; Dunne, John P.; Sydeman, William J.; García-Reyes, Marisol; Black, Bryan A.; Bograd, Steven J.

    2015-08-01

    Upwelling is critical to the biological production, acidification, and deoxygenation of the ocean's major eastern boundary current ecosystems. A leading conceptual hypothesis projects that the winds that induce coastal upwelling will intensify in response to increased land-sea temperature differences associated with anthropogenic global warming. We examine this hypothesis using an ensemble of coupled, ocean-atmosphere models and find limited evidence for intensification of upwelling-favorable winds or atmospheric pressure gradients in response to increasing land-sea temperature differences. However, our analyses reveal consistent latitudinal and seasonal dependencies of projected changes in wind intensity associated with poleward migration of major atmospheric high-pressure cells. Summertime winds near poleward boundaries of climatological upwelling zones are projected to intensify, while winds near equatorward boundaries are projected to weaken. Developing a better understanding of future changes in upwelling winds is essential to identifying portions of the oceans susceptible to increased hypoxia, ocean acidification, and eutrophication under climate change.

  3. A QR accelerated volume-to-surface boundary condition for finite element solution of eddy current problems

    SciTech Connect

    White, D; Fasenfest, B; Rieben, R; Stowell, M

    2006-09-08

    We are concerned with the solution of time-dependent electromagnetic eddy current problems using a finite element formulation on three-dimensional unstructured meshes. We allow for multiple conducting regions, and our goal is to develop an efficient computational method that does not require a computational mesh of the air/vacuum regions. This requires a sophisticated global boundary condition specifying the total fields on the conductor boundaries. We propose a Biot-Savart law based volume-to-surface boundary condition to meet this requirement. This Biot-Savart approach is demonstrated to be very accurate. In addition, this approach can be accelerated via a low-rank QR approximation of the discretized Biot-Savart law.

  4. Global Simulations of the March 17, 2013 Storm: Importance of Boundary Conditions in Reproducing Ring Current Observations

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Jordanova, V.; Larsen, B.; Claudepierre, S. G.; Welling, D. T.; Skoug, R. M.; Kletzing, C.

    2013-12-01

    As modeling capabilities become increasingly available for the study of inner magnetospheric dynamics, the models' boundary conditions remain a crucial controlling factor in reproducing observations. In this study, we use the kinetic Ring current-Atmosphere Interaction Model (RAM) two-way coupled with the global MHD model BATS-R-US to study the evolution of the ring current and its feedback to the ionospheric electrodynamics during the March 17, 2013 storm. The MHD code solves fluid quantities and provides the inner magnetosphere code with plasma sheet plasma, which is the primary source for the development of the ring current. In this study, we examine the effect of different boundary conditions in specifying the plasma sheet plasma source on reproducing observations of the inner magnetospheric/subauroral region, such as in-situ observations (e.g., flux, magnetic fields, and electric fields) from Van Allen Probes (RBSP), field-aligned currents from AMPERE, and global convection maps from SuperDARN. These different boundary settings include a Maxwellian distribution assumption with MHD single-fluid temperature and density, a Kappa distribution assumption with MHD single-fluid temperature and density, and a bi-Maxwellian distribution with anisotropic pressures passed from the MHD code. Results indicate that a Kappa distribution at the boundary of RAM leads to a better ring current flux prediction than that with a Maxwellian distribution assumption, as well as a more realistic spatial distribution of ion anisotropy, which is important in driving electromagnetic ion cyclotron waves. The anisotropic pressure coupling between the kinetic code and the MHD code with a bi-Maxwellian function significantly improves the agreement with observations, especially the Dst index prediction.

  5. Laboratory studies of the effects of interrupted, sloping topography on intermediate depth boundary currents in linearly stratified fluids

    NASA Astrophysics Data System (ADS)

    Folkard, Andrew M.; Davies, Peter A.

    2001-05-01

    Laboratory experiments are described which provide insight into the interaction of intermediate depth boundary currents (IDBCs) with interrupted sloping topography. Specifically, they contribute to the debate over meddy formation on the Iberian continental slope. The experiments were performed in a rectilinear rotating tank filled initially with a linearly-stratified fluid. A false bottom sloped away from the side-wall along which the current flowed, and was interrupted by a gap of variable length. The effects of varying gap length and rotation rate on the boundary current were observed. In the first of two sets of experiments, the current flowed above the slope, along the vertical sidewall. In the second, the current flowed along the sloping bottom. In the former, current nose speed was consistent with geostrophic predictions, but decreased in the presence of a gap in the topography. Kelvin wave radiation is postulated as a reason for this. The IDBCs exhibited vortical lateral intrusions at values of the Burger number Bu=(N 0/Ω) 2 at which counterpart flat-bottom studies had been stable, implying that the sloping topography had a de-stabilising effect. Energy measurements and qualitative observations suggest the intrusions were due to mixed barotropic/baroclinic instabilities, the latter dominating at higher rotation rates. In the second configuration, four distinct flows were observed, distinguished by the deformation radius:gap width ratio RD/ G∗. For a range of values of RD/ G∗, attached eddies formed at the upstream end of the gap. They remained at this position, unlike those in similar studies of surface boundary currents ( Klinger, 1993). Their persistence and ability to move downstream - salient factors for meddy - formation were greater for a finite gap size than a permanent change from sloping to flat bottom.

  6. Linear and nonlinear dynamic analysis by boundary element method. Ph.D. Thesis, 1986 Final Report

    NASA Technical Reports Server (NTRS)

    Ahmad, Shahid

    1991-01-01

    An advanced implementation of the direct boundary element method (BEM) applicable to free-vibration, periodic (steady-state) vibration and linear and nonlinear transient dynamic problems involving two and three-dimensional isotropic solids of arbitrary shape is presented. Interior, exterior, and half-space problems can all be solved by the present formulation. For the free-vibration analysis, a new real variable BEM formulation is presented which solves the free-vibration problem in the form of algebraic equations (formed from the static kernels) and needs only surface discretization. In the area of time-domain transient analysis, the BEM is well suited because it gives an implicit formulation. Although the integral formulations are elegant, because of the complexity of the formulation it has never been implemented in exact form. In the present work, linear and nonlinear time domain transient analysis for three-dimensional solids has been implemented in a general and complete manner. The formulation and implementation of the nonlinear, transient, dynamic analysis presented here is the first ever in the field of boundary element analysis. Almost all the existing formulation of BEM in dynamics use the constant variation of the variables in space and time which is very unrealistic for engineering problems and, in some cases, it leads to unacceptably inaccurate results. In the present work, linear and quadratic isoparametric boundary elements are used for discretization of geometry and functional variations in space. In addition, higher order variations in time are used. These methods of analysis are applicable to piecewise-homogeneous materials, such that not only problems of the layered media and the soil-structure interaction can be analyzed but also a large problem can be solved by the usual sub-structuring technique. The analyses have been incorporated in a versatile, general-purpose computer program. Some numerical problems are solved and, through comparisons

  7. Remote sensing of ocean currents. [detection of current boundary in Gulf of Mexico through changes in sea state or ocean color

    NASA Technical Reports Server (NTRS)

    Maul, G. A. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Fourteen field experiments in support of the NOAA investigation of ocean color boundary determination using ERTS-1 data have been conducted since June 1972. The boundary between coastal waters and the Loop Current has been detected by ERTS-1 as a result of sea state changes as well as color differences. Computer enchancement of MSS data are revealing many features not shown in the NDPF product. Analysis of the 24 channel MSS data shows that a thermal IR channel is required on an ERTS MSS to distinguish between atmospheric and sea state effects. Cloud cover analysis suggests the need for daily coverage of this type sensor for routinely useful oceanographic applications.

  8. Analysis of the photodiode boundary layer transition indicator. LDRD final report

    SciTech Connect

    Kuntz, D.W.; Wilken, A.C.; Payne, J.L.

    1994-06-01

    The photodiode transition indicator is a device which has been successfully used to determine the onset of boundary layer transition on numerous hypersonic flight vehicles. The exact source of the electromagnetic radiation detected by the photodiode at transition was not understood. In some cases early saturation of the device occurred, and the device failed to detect transition. Analyses have been performed to determine the source of the radiation producing the photodiode signal. The results of these analyses indicate that the most likely source of the radiation is blackbody emission from the heatshield material bordering the quartz window of the device. Good agreement between flight data and calculations based on this radiation source has been obtained. Analyses also indicate that the most probable source of the radiation causing early saturation is blackbody radiation from carbon particles which break away from the nosetip during the ablation process.

  9. Sea turtle distribution along the boundary of the Gulf Stream current off eastern Florida

    USGS Publications Warehouse

    Hoffman, W.; Fritts, T.H.

    1982-01-01

    Aerial surveys, out to 222 km off the east coast of central Florida during August 1980, revealed that marine turtles were distributed in a narrow zone west of the Gulf Stream. Of 255 loggerhead turtles, Caretta caretta, only three were observed east of the western boundary of the Gulf Stream. Radiometric thermometry revealed that the waters occupied by most Caretta were markedly cooler than the nearby waters of the Gulf Stream. Of 18 leatherback turtles, Dermochelys coriacea, all were seen west of the Gulf Stream in waters less than 70 m in depth. Marine turtles off eastern Florida are confined seasonally to nearshore waters west of the Gulf Stream. The records of Dermochelys in nearshore waters are in contrast with a deep water oceanic ecology often hypothesized for this species.

  10. Critical current density behaviors across a grain boundary inclined to current with different angles in YBa2Cu3O7‑δ bicrystal junctions

    NASA Astrophysics Data System (ADS)

    Tao, Hua; Wei-Wei, Xu; Zheng-Ming, Ji; Da-Yuan, Guo; Qing-Yun, Wang; Xiang-Rong, Ma; Rui-Yu, Liang

    2016-06-01

    The critical current density behaviors across a bicrystal grain boundary (GB) inclined to the current direction with different angles in YBa2Cu3O7‑δ bicrystal junctions in magnetic fields are investigated. There are two main reasons for the difference in critical current density in junctions at different GB inclined angles in the same magnetic field: (i) the GB plane area determines the current carrying cross section; (ii) the vortex motion dynamics at the GB affects the critical current value when the vortex starts to move along the GB by Lorentz force. Furthermore, the vortex motion in a bicrystal GB is studied by investigating transverse (Hall) and longitudinal current–voltage characteristics (I–V xx and I–V xy ). It is found that the I–V xx curve diverges from linearity at a high driving current, while the I–V xy curve keeps nearly linear, which indicates the vortices inside the GB break out of the GB by Lorentz force. Project supported by the National Natural Science Foundation of China (Grant Nos. 61501222, 61371036, and 61571219) and the School Scientific Research Fund of Nanjing Institute of Technology, China (Grant Nos. YKJ201418).

  11. Transient, small-scale field-aligned currents in the plasma sheet boundary layer during storm time substorms

    NASA Astrophysics Data System (ADS)

    Nakamura, R.; Sergeev, V. A.; Baumjohann, W.; Plaschke, F.; Magnes, W.; Fischer, D.; Varsani, A.; Schmid, D.; Nakamura, T. K. M.; Russell, C. T.; Strangeway, R. J.; Leinweber, H. K.; Le, G.; Bromund, K. R.; Pollock, C. J.; Giles, B. L.; Dorelli, J. C.; Gershman, D. J.; Paterson, W.; Avanov, L. A.; Fuselier, S. A.; Genestreti, K.; Burch, J. L.; Torbert, R. B.; Chutter, M.; Argall, M. R.; Anderson, B. J.; Lindqvist, P.-A.; Marklund, G. T.; Khotyaintsev, Y. V.; Mauk, B. H.; Cohen, I. J.; Baker, D. N.; Jaynes, A. N.; Ergun, R. E.; Singer, H. J.; Slavin, J. A.; Kepko, E. L.; Moore, T. E.; Lavraud, B.; Coffey, V.; Saito, Y.

    2016-05-01

    We report on field-aligned current observations by the four Magnetospheric Multiscale (MMS) spacecraft near the plasma sheet boundary layer (PSBL) during two major substorms on 23 June 2015. Small-scale field-aligned currents were found embedded in fluctuating PSBL flux tubes near the separatrix region. We resolve, for the first time, short-lived earthward (downward) intense field-aligned current sheets with thicknesses of a few tens of kilometers, which are well below the ion scale, on flux tubes moving equatorward/earthward during outward plasma sheet expansion. They coincide with upward field-aligned electron beams with energies of a few hundred eV. These electrons are most likely due to acceleration associated with a reconnection jet or high-energy ion beam-produced disturbances. The observations highlight coupling of multiscale processes in PSBL as a consequence of magnetotail reconnection.

  12. Immersed boundary Eulerian-Lagrangian 3D simulation of pyroclastic density currents: numerical scheme and experimental validation

    NASA Astrophysics Data System (ADS)

    Doronzo, Domenico Maria; de Tullio, Marco; Pascazio, Giuseppe; Dellino, Pierfrancesco

    2010-05-01

    Pyroclastic density currents are ground hugging, hot, gas-particle flows representing the most hazardous events of explosive volcanism. Their impact on structures is a function of dynamic pressure, which expresses the lateral load that such currents exert over buildings. In this paper we show how analog experiments can be matched with numerical simulations for capturing the essential physics of the multiphase flow. We used an immersed boundary scheme for the mesh generation, which helped in reconstructing the steep velocity and particle concentration gradients near the ground surface. Results show that the calculated values of dynamic pressure agree reasonably with the experimental measurements. These outcomes encourage future application of our method for the assessment of the impact of pyroclastic density currents at the natural scale.

  13. Mooring-Based Observations of Boundary Current in the Nansen Basin of the Arctic Ocean: Vertical Structure and Variability

    NASA Astrophysics Data System (ADS)

    Pnyushkov, A.; Polyakov, I.

    2010-12-01

    The pan-Arctic Boundary Current (BC) provides the largest input of water, heat, and salt into the Polar Basins. Recent mooring-based observations at several locations along the continental slope of the Arctic Ocean’s Eurasian Basin showed a transformation of the BC from a mostly barotropic flow in Fram Strait to a jet-like baroclinic current northeast of Svalbard, and the reemergence of the barotropic structure of the flow further along in the eastern Eurasian Basin. The speed maximum of the baroclinic jet-like BC segment coincides with the Atlantic Water core at an intermediate depth (~200-370 m). Strongly amplified current events with corresponding changes in T and S are associated with eddies which are an integral part of the BC. Vertical velocity shear of tidal/inertial oscillations is an important contributor to mixing in the BC region. This new information is critically important to understand the ocean's role in the arctic climate system.

  14. Critical current from dynamical boundary instability for fully frustrated Josephson junction arrays

    NASA Astrophysics Data System (ADS)

    Kim, Beom Jun; Minnhagen, Petter

    2000-03-01

    We investigate numerically the critical current of two-dimensional fully frustrated arrays of resistively shunted Josephson junctions at zero temperature. It is shown that a domino-type mechanism is responsible for the existence of a critical current lower than the one predicted from the translationally invariant flux lattice. This domino mechanism is demonstrated for uniform-current injection as well as for various busbar conditions. It is also found that inhomogeneities close to the contacts make it harder for the domino propagation to start, which increases the critical current towards the value based on the translational invariance. This domino-type vortex motion can be observed in experiments as voltage pulses propagating from the contacts through the array.

  15. Near-surface Density Currents Observed in the Southeast Pacific Stratocumulus-topped Marine Boundary Layer

    SciTech Connect

    Wilbanks, Matt C.; Yuter, S. E.; de Szoeke, S.; Brewer, W. A.; Miller, Matthew A.; Hall, Andrew M.; Burleyson, Casey D.

    2015-09-01

    Density currents (i.e. cold pools or outflows) beneath marine stratocumulus clouds are characterized using a 30-d data set of ship-based observations obtained during the 2008 Variability of American Monsoon Systems (VAMOS) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) in the southeast Pacific. An objective method identifies 71 density current fronts using an air density criterion and isolates each density current’s core (peak density) and tail (dissipating) zone. Compared to front and core zones, most density current tails exhibited weaker density gradients and wind anomalies elongated about the axis of the mean wind. The mean cloud-level advection relative to the surface layer wind (1.9 m s-1) nearly matches the mean density current propagation speed (1.8 m s-1). The similarity in speeds allows drizzle cells to deposit tails in their wakes. Based on high-resolution scanning Doppler lidar data, prefrontal updrafts had a mean intensity of 0.91 m s-1, reached an average altitude of 800 m, and were often surmounted by low-lying shelf clouds not connected to the overlying stratocumulus cloud. Nearly 90% of density currents were identified when C-band radar estimated 30-km diameter areal average rain rates exceeded 1 mm d-1. Rather than peaking when rain rates are highest overnight, density current occurrence peaks between 0600 and 0800 local solar time when enhanced local drizzle co-occurs with shallow subcloud dry and stable layers. The dry layers may contribute to density current formation by enhancing subcloud evaporation of drizzle. Density currents preferentially occur in regions of open cells but also occur in regions of closed cells.

  16. Fidelity susceptibility and conductivity of the current in one-dimensional lattice models with open or periodic boundary conditions

    NASA Astrophysics Data System (ADS)

    Greschner, S.; Kolezhuk, A. K.; Vekua, T.

    2013-11-01

    We study, both numerically and analytically, the finite-size scaling of the fidelity susceptibility χJ with respect to the charge or spin current in one-dimensional lattice models and relate it to the low-frequency behavior of the corresponding conductivity. It is shown that in gapless systems with open boundary conditions the leading dependence on the system size L stems from the singular part of the conductivity and is quadratic, with a universal form χJ=[7ζ(3)/2π4]KL2, where K is the Luttinger liquid parameter and ζ(x) is the Riemann ζ function. In contrast to that for periodic boundary conditions the leading system size dependence is directly connected to the regular part of the conductivity and is subquadratic, χJ∝Lγ, where the K-dependent exponent γ is equal to 1 in most situations (as a side effect, this relation provides an alternative way to study the low-frequency behavior of the regular part of the conductivity). For open boundary conditions, we also study another current-related quantity, the fidelity susceptibility to the lattice tilt χP, and show that it scales as the quartic power of the system size, χP=[31ζ(5)/8π6](KL4/u2), where u is the sound velocity. Thus, the ratio L2χJ/χP directly measures the sound velocity in open chains. The behavior of the current fidelity susceptibility in gapped phases is discussed, particularly in the topologically ordered Haldane state.

  17. A linear diffusion model for ion current across blocking grain boundaries in oxygen-ion and proton conductors.

    PubMed

    Kim, Seong K; Khodorov, Sergey; Lubomirsky, Igor; Kim, Sangtae

    2014-07-28

    We demonstrate the applicability of the linear diffusion model recently proposed for the current-voltage, Igb-Ugb, characteristics of blocking grain boundaries in solid electrolytes to various oxygen-ion and proton conductors: the model precisely reproduces the Igb-Ugb characteristics of La-, Sm-, Gd-, and Y-doped ceria as well as Y-doped barium zirconate to provide accurate explanations to the "power law" behavior of the Igb-Ugb relationship, i.e. Igb ∝ Ugb(n), experimentally observed. The model also predicts that the grain-boundary potential, Ψgb, in doped ceria weakly depends on temperature, if the trapped charge remains constant, and that the value of Ψgb can be determined from the value of the power n. Furthermore, the model provides a plausible explanation for the increase in the Ψgb with temperature observed for the proton conductor in which the concentration of the charge carrier decreases with temperature. Hence, it is evident that the linear diffusion model is robust and applicable to grain boundaries in a large variety of practically important solid electrolytes. PMID:24930884

  18. Sediment-current interactions at Valcour Island, Lake Champlain--A case of helical flow in the bottom boundary layer

    SciTech Connect

    Manley, P.L.; Manley, T.O. . Geology Dept.)

    1993-03-01

    Sediment furrows have been documented in diverse environments. In all cases they are morphologically similar exhibiting long, linear parallel troughs oriented with the dominant bottom current direction. The similar nature of their morphology suggests that they form as a result of a long-term interaction between the sediment surface and bottom current flow. Thus furrows are maintained in regions where bottom currents are sufficiently stable in direction and of high flow rates. Previous studies suggest that furrow formation is controlled by secondary circulation within the bottom boundary layer which localize erosion at flow convergence on the bed. Once established, the furrow field and flow reinforce this secondary circulation pattern. Thus the trough continues to exist by the resuspension of finer grained sediment and abrasion by coarser debris concentrated within the trough. Sediment furrows were documented by side-scan sonar surveys near the long-term current meter mooring east of Valcour Island. The furrows are located in 63 m of water. Their widths range from 4 to 8 m while inter-furrow spacing varies from 10 to 30 m. Grain size of surface bottom sediments ranged from silty mud (5.48[phi]) near the mooring site to very fine sand (3.4[phi]) in the south end of the survey area. The furrow orientations are consistent with the typical north-south flow observed within this region. Although still under investigation, it appears that the bottom moored current meter at Valcour Island (during the summer months of 1991) documented the secondary flow pattern within the bottom boundary layer.

  19. Statistics of the field-aligned currents at the high-latitude energetic electron boundaries in the nightside: Cluster observation

    NASA Astrophysics Data System (ADS)

    Ren, Jie; Zong, Q. G.; Zhou, X. Z.; Zhang, Hui; Fu, S. Y.; Wang, Y. F.; Liu, Yong C.-M.

    2016-03-01

    Magnetic field disturbances with a clear bipolar signature are frequently observed when the Cluster spacecraft fleet passes through both southern and northern high-latitude energetic electron boundaries at the nightside magnetosphere. The dominant variation of the bipolar signature is in the azimuthal direction of the local mean field-aligned coordinate, indicating a field-aligned current. From 2001 to 2008, we have examined 110 events with the magnetic field and energetic electron measurements. The main results can be summarized as follows: (1) The density and thickness of the field-aligned current, calculated under the assumption of the one-dimensional sheet, are in order of tens of nA/m2 and hundreds of kilometers, respectively. (2) Currents flowing into and away from the ionosphere tend to be observed in the postmidnight and premidnight sector, respectively, which have the same polarity as the region 1 current system. (3) These currents mainly distribute in the 60°-75° magnetic latitude region after mapping to the ionosphere. We also find that the current density and corresponding magnetic field variation are positively correlated with the Kp index and solar wind pressure, but almost independent of the AE index.

  20. Growth of a deep-water, predatory fish is influenced by the productivity of a boundary current system

    PubMed Central

    Nguyen, Hoang Minh; Rountrey, Adam N.; Meeuwig, Jessica J.; Coulson, Peter G.; Feng, Ming; Newman, Stephen J.; Waite, Anya M.; Wakefield, Corey B.; Meekan, Mark G.

    2015-01-01

    The effects of climate change on predatory fishes in deep shelf areas are difficult to predict because complex processes may govern food availability and temperature at depth. We characterised the net impact of recent environmental changes on hapuku (Polyprion oxygeneios), an apex predator found in continental slope habitats (>200 m depth) by using dendrochronology techniques to develop a multi-decadal record of growth from otoliths. Fish were sampled off temperate south-western Australia, a region strongly influenced by the Leeuwin Current, a poleward-flowing, eastern boundary current. The common variance among individual growth records was relatively low (3.4%), but the otolith chronology was positively correlated (r = 0.61, p < 0.02) with sea level at Fremantle, a proxy for the strength of the Leeuwin Current. The Leeuwin Current influences the primary productivity of shelf ecosystems, with a strong current favouring growth in hapuku. Leeuwin Current strength is predicted to decline under climate change models and this study provides evidence that associated productivity changes may flow through to higher trophic levels even in deep water habitats. PMID:25761975

  1. Growth of a deep-water, predatory fish is influenced by the productivity of a boundary current system

    NASA Astrophysics Data System (ADS)

    Nguyen, Hoang Minh; Rountrey, Adam N.; Meeuwig, Jessica J.; Coulson, Peter G.; Feng, Ming; Newman, Stephen J.; Waite, Anya M.; Wakefield, Corey B.; Meekan, Mark G.

    2015-03-01

    The effects of climate change on predatory fishes in deep shelf areas are difficult to predict because complex processes may govern food availability and temperature at depth. We characterised the net impact of recent environmental changes on hapuku (Polyprion oxygeneios), an apex predator found in continental slope habitats (>200 m depth) by using dendrochronology techniques to develop a multi-decadal record of growth from otoliths. Fish were sampled off temperate south-western Australia, a region strongly influenced by the Leeuwin Current, a poleward-flowing, eastern boundary current. The common variance among individual growth records was relatively low (3.4%), but the otolith chronology was positively correlated (r = 0.61, p < 0.02) with sea level at Fremantle, a proxy for the strength of the Leeuwin Current. The Leeuwin Current influences the primary productivity of shelf ecosystems, with a strong current favouring growth in hapuku. Leeuwin Current strength is predicted to decline under climate change models and this study provides evidence that associated productivity changes may flow through to higher trophic levels even in deep water habitats.

  2. Growth of a deep-water, predatory fish is influenced by the productivity of a boundary current system.

    PubMed

    Nguyen, Hoang Minh; Rountrey, Adam N; Meeuwig, Jessica J; Coulson, Peter G; Feng, Ming; Newman, Stephen J; Waite, Anya M; Wakefield, Corey B; Meekan, Mark G

    2015-01-01

    The effects of climate change on predatory fishes in deep shelf areas are difficult to predict because complex processes may govern food availability and temperature at depth. We characterised the net impact of recent environmental changes on hapuku (Polyprion oxygeneios), an apex predator found in continental slope habitats (>200 m depth) by using dendrochronology techniques to develop a multi-decadal record of growth from otoliths. Fish were sampled off temperate south-western Australia, a region strongly influenced by the Leeuwin Current, a poleward-flowing, eastern boundary current. The common variance among individual growth records was relatively low (3.4%), but the otolith chronology was positively correlated (r = 0.61, p < 0.02) with sea level at Fremantle, a proxy for the strength of the Leeuwin Current. The Leeuwin Current influences the primary productivity of shelf ecosystems, with a strong current favouring growth in hapuku. Leeuwin Current strength is predicted to decline under climate change models and this study provides evidence that associated productivity changes may flow through to higher trophic levels even in deep water habitats. PMID:25761975

  3. Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Frank, L. A.; Huang, C. Y.

    1988-01-01

    Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.

  4. Invigorating ocean boundary current systems around Australia during 1979-2014: As simulated in a near-global eddy-resolving ocean model

    NASA Astrophysics Data System (ADS)

    Feng, Ming; Zhang, Xuebin; Oke, Peter; Monselesan, Didier; Chamberlain, Matthew; Matear, Richard; Schiller, Andreas

    2016-05-01

    Ocean boundary currents, transporting water masses and marine biota along the coastlines, are important for regional climate and marine ecosystem functions. In this study, we review the dominant multi-decadal trends of ocean boundary currents around Australia. Using an eddy-resolving global ocean circulation model, this study has revealed that the major ocean boundary current systems around Australia, the East Australian Current (EAC), the Indonesian Throughflow (ITF), the Leeuwin Current, the South Australian Current and the Flinders Current, have strengthened during 1979-2014, consistent with existing observations. Eddy energetics in the EAC, the ITF/South Equatorial Current in the southeast Indian Ocean, and the Leeuwin Current have also enhanced during the same period. The multi-decadal strengthening of the ocean boundary current systems are primarily driven by large scale wind patterns associated with the dominant modes of climate variability and change - the phase shift of the Inter-decadal Pacific Oscillation/Pacific Decadal Oscillation strengthens the ITF and the Leeuwin Current/South Australian Current; and the poleward shift and strengthening of surface winds in the subtropical gyres reinforce the EAC and the Flinders Current. The invigorating ocean boundary current systems have induced extreme oceanographic conditions along the Australian coastlines in recent years, including the poleward shift of marine ecosystems off the east coast of Australia and the consecutive Ningaloo Niño - marine heatwave events off the west coast during 2011-2013. Understanding long-term trends and decadal variations of the ocean boundary currents is crucial to project future changes of the coastal marine systems under the influence of human-induced greenhouse gas forcing.

  5. Zooplankton abundance, biovolume and size spectra at western boundary currents in the subtropical North Pacific during winter 2012

    NASA Astrophysics Data System (ADS)

    Dai, Luping; Li, Chaolun; Yang, Guang; Sun, Xiaoxia

    2016-03-01

    Horizontal changes in mesozooplankton abundance, biovolume and size spectra at western boundary currents in the subtropical North Pacific during winter 2012 were evaluated by ZooScan measurement on samples collected by net towing from 23 stations. Zooplankton abundance and biovolume ranged from 35.1 to 456.8 ind. m- 3 and 4.3 to 231.7 mm3 m- 3, respectively. Copepoda were the most dominant species, followed by Chaetognatha and Tunicata. According to the Bray-Curtis cluster analysis based on biovolume of zooplankton size classes of each taxonomic group at intervals of 1 (log2 mm3 ind.- 1) between - 6 and 12 and considering the effect of regional factors, zooplankton communities were classified into four groups, which basically coincided with the geographical patterns of different currents: the North Equatorial Current (NEC), the North Equatorial Counter Current (NECC), the Kuroshio Current (KC), and the Mindanao Eddy (ME), respectively. The largest and lowest biovolumes were observed in the NECC region and the NEC region, respectively, and both were dominated by the 0.3 to 1 mm equivalent spherical diameter (ESD) size class, while the ME region was dominant by the 1 to 2 mm ESD size class. The slopes of the normalized biovolume size spectra for each group were slightly lower than - 1 (range from - 0.85 to - 0.92), which indicates that zooplankton communities in the study area were characterized by low productivity and high energy transfer efficiency.

  6. Multiscale wind cycles and current pulses at the Black Sea eastern boundary

    NASA Astrophysics Data System (ADS)

    Melnikov, Vasiliy; Moskalenko, Lidija; Piotoukh, Vladimir; Zatsepin, Andrey

    2015-04-01

    The goal of the research is to examine meteorological descriptive elements, sea-water properties, regional hydrodynamics and energy conversion fluxes in order to study sea responses to the local and far-field weather system. The Black Sea is situated in the chain of internal basins between the North Atlantic and Central Asia deserts in the marginal interaction zone and, accordingly, is under the influence of the Azores and Siberian anticyclones, Arctic cold-air surges and subtropical desert belt to the south. The analysis is based on the data of modern oceanographic measuring network "Hydro-physical Polygon" of the Institute of oceanology, using contact and remote sensing methods, weather stations around the Black Sea coasts, including long-term (1938-2014) measurements at the Gelendzhik weather station. Various satellite and Reanalysis databases are used. Currently, there are three long-time measuring moored stations (each contains ADCP and thermistor chain) and scanning profiling system "Akvalog". Hydrological sections and field surveys using towed ADCP and CTD are performed on a regular basis. The data are accumulated in the coastal archive which allows calibration of satellite measurements and testing results of numerical modeling. Data processing includes data sets preparation, editing, time series statistical calculations using histograms, progressive vector diagrams, traditional Fourier spectral analysis including auto- and cross spectra, auto and mutual wavelet diagrams, moving spectrograms, vector data methods using rotary components, spectral invariants, empirical modes, hodograph and pre-specified spectrum representations on the basis of stochastic models with imposed dynamical assumptions. Due to the intermittent nature of the time rows, spectral representation is misleading, often. In order to identify the individual evolving dynamical phenomenon, typical background (seasonal) three-dimensional structures of the hydrological field, as well as

  7. Current Sheet Boundaries in MHD Turbulence and in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean; Mason, Joanne

    2011-10-01

    Current sheets inside of plasmas are characterized by strong changes in the magnetic field direction. We study this property of current sheets by measuring the angular change of the magnetic field direction across fixed spatial increments throughout the plasma domain. Using data from turbulent MHD simulations, we find that the probability distribution of angular change obeys an exponential law, with a scaling that is largely independent of the choice of spatial increment. In the first case, reduced MHD is used with a strong guide field (δb/B0 = 1 / 5), and the scaling is approximately fit by exp(- θ / 6 . 5). In the second case, full MHD is used with a weak guide field, and the fit is exp(- θ / 21 . 7). It is proposed that the difference in scaling parameters between the two regimes is due to the strength of the background magnetic field. This may explain the observations of spacecraft in the solar wind, which found two distinct populations of magnetic discontinuities with different exponential distributions of angular change in magnetic field, e.g. Borovsky (2008) and Miao et al. (2011).

  8. Final Report Experimental Study of Impulsive Reconnection in a Current Carrying Magnetic Arcade

    SciTech Connect

    Craig, Darren

    2011-10-27

    The Wheaton Impulsive Reconnection Experiment (WIRX) is a new experiment now underway at Wheaton College for the study of magnetic reconnection. The experiment is composed of two parallel electrodes, linked by a magnetic arcade that is generated by a coil surrounding the electrodes. Current is driven along the arcade from one electrode to another. When enough current is driven, the arcade is expected to disrupt or segment by reconnection allowing a study of 3D reconnection. This report is the final report for a three year grant period.

  9. Observed evidence of the anomalous South China Sea western boundary current during the summers of 2010 and 2011

    NASA Astrophysics Data System (ADS)

    Shu, Yeqiang; Xue, Huijie; Wang, Dongxiao; Xie, Qiang; Chen, Ju; Li, Jian; Chen, Rongyu; He, Yunkai; Li, Daning

    2016-02-01

    Seven years of directly measured current data from a mooring in the Xisha area of the South China Sea (SCS), together with shipboard ADCP and satellite data, have shown the western boundary current (WBC) anomaly and its vertical structure during the summers of 2010 and 2011. The observed WBC presented obvious year-to-year variability, especially in the summer. Overall, the summer mean velocity at the mooring site over 7-year (2007-2013) was northeastward. The moored ADCP showed that the northeastward velocity was particularly strong in the summer of 2010, but the increase was confined in the upper 120 m. In contrast, the northeastward current disappeared throughout the observed depth range (from 50 to 450 m) in the summer of 2011. Even at the deepest observed position, the monthly velocity anomalies reached 14 cm s-1 westward and 12 cm s-1 southward in the zonal and meridional directions, respectively. Both the Vietnam offshore current (VOC) and double gyres in the western SCS disappeared and the southern anticyclonic gyre expanded to strengthened the northward WBC in the summer of 2010. However, in summer of 2011, the VOC intensified, and the northern cyclonic gyre enlarged with its northern edge reaching 18°N, slightly north of mooring site, which weakened the northeastward WBC. The observed SCS circulation anomalies during 2010 and 2011 were mainly induced by the basin-scale wind field anomalies associated with the 2009/2010 El Niño and 2010/2011 La Niña.

  10. Control of plasma properties in a short direct-current glow discharge with active boundaries

    NASA Astrophysics Data System (ADS)

    Adams, S. F.; Demidov, V. I.; Bogdanov, E. A.; Koepke, M. E.; Kudryavtsev, A. A.; Kurlyandskaya, I. P.

    2016-02-01

    To demonstrate controlling electron/metastable density ratio and electron temperature by applying negative voltages to the active (conducting) discharge wall in a low-pressure plasma with nonlocal electron energy distribution function, modeling has been performed in a short (lacking the positive-column region) direct-current glow discharge with a cold cathode. The applied negative voltage can modify the trapping of the low-energy part of the energetic electrons that are emitted from the cathode sheath and that arise from the atomic and molecular processes in the plasma within the device volume. These electrons are responsible for heating the slow, thermal electrons, while production of slow electrons (ions) and metastable atoms is mostly due to the energetic electrons with higher energies. Increasing electron temperature results in increasing decay rate of slow, thermal electrons (ions), while decay rate of metastable atoms and production rates of slow electrons (ions) and metastable atoms practically are unchanged. The result is in the variation of electron/metastable density ratio and electron temperature with the variation of the wall negative voltage.

  11. Direct measurements of HOx radicals in the marine boundary layer: testing the current tropospheric chemistry mechanism.

    PubMed

    Kanaya, Yugo; Akimoto, Hajime

    2002-01-01

    OH and HO(2) radicals, atmospheric detergents, and the reservoir thereof, play central roles in tropospheric chemistry. In spite of their importance, we had no choice but to trust their concentrations predicted by modeling studies based on known chemical processes. However, recent direct measurements of these radicals have enabled us to test and revise our knowledge of the processes by comparing the predicted and observed values of the radical concentrations. We developed a laser-induced fluorescence (LIF) instrument and successfully observed OH and HO(2) at three remote islands of Japan (Oki Island, Okinawa Island, and Rishiri Island). At Okinawa Island, the observed daytime level of HO(2) agreed closely with the model estimates, suggesting that the photochemistry at Okinawa is well described by the current chemistry mechanism. At Rishiri Island, in contrast, the observed daytime level of HO(2) was consistently much lower than the calculated values. We proposed that iodine chemistry, usually not incorporated into the mechanism, is at least partly responsible for the discrepancy in the results. At night, HO(2) was detected at levels greater than 1 pptv at all three islands, suggesting the presence of processes in the dark that produce radicals. We showed that ozone reactions with unsaturated hydrocarbons, including monoterpenes, could significantly contribute to radical production. PMID:12112871

  12. Investigations on residual strains and the cathodoluminescence and electron beam induced current signal of grain boundaries in silicon

    SciTech Connect

    Nacke, M.; Allardt, M.; Hieckmann, E.; Weber, J.; Chekhonin, P.; Skrotzki, W.

    2014-04-28

    Cathodoluminescence (CL) and electron beam induced current (EBIC) measurements were used to investigate the optical behavior and electrical activity of grain boundaries (GBs) in coarsely grained silicon. Electron backscatter diffraction (EBSD) was applied for a comprehensive characterization of the structural properties of the high angle and low angle GBs (HAGBs and LAGBs) in the sample. It was found that not only the EBIC but also the panchromatic (pan) CL contrast of Σ3 HAGBs strongly depends on the hkl-type of the boundary plane. At room temperature coherent Σ3 GBs exhibit no significant contrast in the CL or EBIC images, whereas at low temperatures the pan-CL contrast is strong. For incoherent Σ3 GBs, a strong pan-CL and EBIC contrast was observed in the entire temperature range. Only on a LAGB (misorientation angle 4.5°) CL investigations at low temperatures revealed a line with peak position at about (0.82 ± 0.01) eV, usually related to the dislocation associated D1 transition. Cross-correlation EBSD was applied to analyze the strain fields of Σ3 HAGBs as well as of the LAGB. All the components of the local strain tensors were quantitatively determined. The relationship between the extension of the strain field at the LAGB and the spatial D1 intensity distribution is discussed.

  13. Temperature-dependent recombination velocity analysis on artificial small angle grain boundaries using electron beam induced current method

    NASA Astrophysics Data System (ADS)

    Kojima, Takuto; Tachibana, Tomihisa; Ohshita, Yoshio; Prakash, Ronit R.; Sekiguchi, Takashi; Yamaguchi, Masafumi

    2016-02-01

    The details of the process of carrier recombination via the Shockley-Read-Hall (SRH) defect level, at the grain boundaries of multicrystalline silicon, were investigated. For this, the temperature-dependent recombination velocities, as determined by experiments, were analyzed by the application of an electron beam induced current method. For the model, the misorientation angles at the grain boundaries were defined using a multi-seed casting-growth method. The results of our experiments indicated different temperature behaviors at low and high temperatures. These can be explained by controlling the process anticipated by the SRH model, that is, the process whereby minority carriers (electrons) are captured at lower temperatures, followed by the reemission of the carriers before recombination with Arrhenius behavior at higher temperatures. The minority capture process appeared to conform to the power law T-α temperature behavior. Thus, there are two candidate electron capture mechanisms, namely, cascade phonon emission capture for shallow centers and excitonic-Auger capture for deep centers. The activation energy for the reemission of carriers was around 0.1 eV. These findings regarding the temperature dependence are essentially independent of the misorientation angles, suggesting a common defect level and recombination mechanism. The difference in the recombination velocities can be regarded as being derived from the difference in the density at the defect level.

  14. Spatial, seasonal and vertical distributions of currently-used pesticides in the marine boundary layer of the North Sea

    NASA Astrophysics Data System (ADS)

    Mai, Carolin; Theobald, Norbert; Lammel, Gerhard; Hühnerfuss, Heinrich

    2013-08-01

    Pesticides are transported beyond source regions and reach coastal waters and shelf seas. 23 representatives of six chemical classes of currently-used pesticides (CUPs) were simultaneously quantified in the marine boundary layer and the surface seawater of the German Bight and the central North Sea in 2009 and 2010.Terbuthylazine, metolachlor, metazachlor, pendimethalin and trifluralin exhibited the highest concentrations, seasonally highly variable. Advection of contaminated air from land and subsequent atmospheric deposition was shown to contribute to surface seawater contamination significantly, in particular in regions beyond riverine input and during the main seasons of application in agriculture. Deposition was most significant for the seasonal and spatial distributions of pendimethalin and trifluralin. Atrazine and simazine levels in the air are lower than 1-2 decades ago.

  15. The dynamics and energetics of midlatitude western boundary currents: A comparison of the Kuroshio Extension and the Gulf Stream

    NASA Technical Reports Server (NTRS)

    Mitchell, James L.; Hallock, Z. R.; Hurlburt, H. E.; Johnson, D. R.; Kindle, J. C.; Teague, W. J.; Thompson, J. D.; Schmitz, W. J.

    1991-01-01

    We will use TOPEX/POSEIDON altimetry in combination with ongoing and planned efforts, including data from the European Remote Sensing satellite (ERS-1), in situ measurements designed specifically to complement satellite altimetry, and assimilation of these several data types into eddy-resolving numerical models in order to understand the dynamics and energetics of midlatitude western boundary currents (specifically, the Gulf Stream and the Kuroshio Extension). A better understanding of the recirculation of midlatitude gyres can best be undertaken in the format of such regional, eddy-resolving experiments. Such regional programs will enhance and be enhanced by the larger scale circulation studies of the World Ocean Circulation Experiment (WOCE) as well as by global-scale eddy-resolving models that we will develop prior to the TOPEX/POSEIDON mission. This effort includes participation on the TOPEDX/POSEIDON Science Team.

  16. Key Signatures in the Barotropic Vorticity Budget within Ocean Western Boundary Currents : Understanding the Gulf Stream Pathway

    NASA Astrophysics Data System (ADS)

    Schoonover, J. A.; Dewar, W. K.; Wienders, N.; Gula, J.; McWilliams, J. C.; Molemaker, M. J.; Bates, S. C.; Danabasoglu, G.

    2014-12-01

    A suite of ocean simulations are conducted at resolutions of 1 degree down to 1/36 degree using the MIT General Circulation Model, Regional Ocean Modeling System, and the Community Earth Systems Model. The 1 degree simulations in the CESM exhibit warm sea surface temperature biases (upwards of 8 C) from the Mid-Atlantic Bight through the Gulf of Maine. In a coupled climate simulation the bias can lead to misplaced heat fluxes which drastically reduce the fidelity of the climate simulation. These observed errors are typical of coarsely resolved ocean simulations and are directly linked to the improper location of the Gulf Stream. Thus, determing a the cause of this error requires a detailed study of a more well-behaved numerical Gulf Stream. 1/12 degree and 1/36 degree simulations show an improvement in the modelled Gulf Stream when compared with observations. All of the simulations show an agreement in the leading balance in the barotropic vorticity budget within the Gulf Stream, dominantly between planetary vorticity advection and bottom pressure torques. This suggests that this inviscid balance is not the only requirement for proper Gulf Stream pathway, since this signature appears in the poorly separating scenario. However, it is shown that the free surface and baroclinic contributions to the bottom pressure torque largely cancel where the modelled Gulf Stream separates. This compensation is necessary for the transport and the upper layer Gulf Stream to cross the edge of the continental shelf. Scaling arguments owe this cancellation to the relative strength between the Gulf Stream and Deep Western Boundary Current. Hence, weak shear may not allow for the appropriate compensation to allow the transport to cross at Cape Hatteras where the bathymetric gradients are upwards of 20%. It is supposed that the sea surface temperature bias is directly caused by the weak vertical shear between the Gulf Stream and Deep Western Boundary Current which disallows decoupling

  17. Dramatic Weakening of the Pacific Water Boundary Current in the Beaufort Sea during the First Decade of the 2000s.

    NASA Astrophysics Data System (ADS)

    Pickart, R. S.; Brugler, E.; Moore, K.; Roberts, S.; Weingartner, T.; Statscewich, H.

    2014-12-01

    Pacific-origin water has profound impacts on the physical state andecosystem of the Western Arctic Ocean. The cold winter waterventilates the upper halocline and supplies nutrients that fuelprimary productivity, while the warm summer waters melt sea ice andsupply freshwater to the Beaufort Gyre. Here we use mooring datacollected as part of the Arctic Observing Network (AON) to examine theinterannual trends in the current over the period 2002-2011.Strikingly, the volume transport of the current has decreased by morethan 80%, despite the fact that the flow through Bering Strait hasincreased over this time period. The largest changes have occurred inthe summer months. Using atmospheric reanalysis fields and weatherstation data, we demonstrate that an increase in summer easterly windsis the primary cause for the reduction in transport, which is largelydictated by the behavior of the two atmospheric centers of action, theBeaufort High and Aleutian Low. Using additional mooring and shipboarddata, together with satellite fields, we argue that a significantportion of the mass and heat passing through Bering Strait in recentyears has been advected out of Barrow Canyon into the interior CanadaBasin - rather than entering the boundary current in the Beaufort Sea- where it is responsible for a significant portion of the increasedsea ice melt in the basin.

  18. Dual-bridge inverters: A new approach to bearing currents and conducted EMI. Final report

    SciTech Connect

    1998-04-01

    The purpose of this research report is to present a dual-bridge inverter approach to eliminating the motor common-mode voltage and resulting bearing and leakage currents and conducted electromagnetic interference (EMI). The report reviews first the existing technologies in solving the problems concerning the application of adjustable speed drives. The theoretical analysis is then given for the operation of the novel dual-bridge inverter which is controlled to generate balanced excitation of the induction motor under pulse-width modulation (PWM) operation mode. Finally, simulation and experimental results are presented to verify this concept.

  19. Current Lead System of the SuperKEKB Final Focus SC Magnet Cryostats

    NASA Astrophysics Data System (ADS)

    Zong, Z. G.; Ohuchi, N.; Tsuchiya, K.; Arimoto, Y.; Higashi, N.; Yamaoka, H.; Kondou, Y.; Kawai, M.

    To energize the SuperKEKB final focus superconducting (SC) magnets, 110 current leads in total will be equipped in the two service cryostats. For the SC quadrupoles and solenoids, 22 leads are the conventional vapor cooled type and the others for the SC correction coils employ an HTS section at the cold ends. The qualification program on the leads is being carried out at KEK as the cryogenic acceptance test prior to installation. This paper presents the thermal and electrical results of the cryogenic tests.

  20. Characterization of extrinsic grain-boundary dislocations and grain-boundary dislocation sources by transmission electron microscopy. Final report, June 1, 1979-May 31, 1981

    SciTech Connect

    Murr, L E

    1981-06-01

    The microstructures attendant to specific peak strains along the strain axis of the stress-strain diagram for type 304 stainless steel and nickel have been examined and compared by transmission electron microscopy from epsilon = 0.05% to 55% in the former and from epsilon = 0.05% to 35% in the latter. The onset of flow is characterized by the emission of dislocations from grain boundary ledge source which form emission profiles resembling dislocation pileups in the stainless steel, and a random distribution of dislocations with evidence for very short emission profiles near the grain boundaries in nickel. At the engineering yield point (0.2%) every grain in the stainless steel shows evidence for dislocation emission profiles, while in the nickel every grain contains some dislocations distributed within the grain interior.

  1. Current good manufacturing practices, quality control procedures, quality factors, notification requirements, and records and reports, for infant formula. Final rule.

    PubMed

    2014-06-10

    The Food and Drug Administration (FDA or we) is issuing a final rule that adopts, with some modifications, the interim final rule (IFR) entitled "Current Good Manufacturing Practices, Quality Control Procedures, Quality Factors, Notification Requirements, and Records and Reports, for Infant Formula'' (February 10, 2014). This final rule affirms the IFR's changes to FDA's regulations and provides additional modifications and clarifications. The final rule also responds to certain comments submitted in response to the request for comments in the IFR. PMID:24922980

  2. Effective probe response calculation using impedance boundary condition in eddy current NDE problems with massive conducting regions present

    SciTech Connect

    Badics, Z.; Matsumoto, Y.; Aoki, K.; Nakayasu, F.

    1996-05-01

    A 3-D finite element scheme is described for calculating probe responses in eddy current NDE problems if massive conducting regions with small penetration depth are in the vicinity of the host specimen. These problems are related to the eddy current inspection of the tube support plate or tube sheet zones in PWR steam generator tubing. Recently, an efficient finite element scheme has been introduced to calculate the probe responses outside these zones. As a sequel to that work, the authors extend here the technique for the tube support plate and the tube sheet zones. They use impedance boundary conditions (IBC) on the surface of the massive conductors and evaluate the probe responses due to these components by performing an integral over these IBC surfaces, thereby ensuring the same accuracy as in the previous work for the flaw signals. Benchmark problems--models of tube support plate zones with defects--have been measured and analyzed. The calculated probe responses show good agreement with the experimental data.

  3. Experimental study of nonlinear interaction of plasma flow with charged thin current sheets: 1. Boundary structure and motion

    NASA Astrophysics Data System (ADS)

    Amata, E.; Savin, S.; André, M.; Dunlop, M.; Khotyaintsev, Y.; Marcucci, M. F.; Fazakerley, A.; Bogdanova, Y. V.; Décréau, P. M. E.; Rauch, J. L.; Trotignon, J. G.; Skalsky, A.; Romanov, S.; Buechner, J.; Blecki, J.; Rème, H.

    2006-08-01

    We study plasma transport at a thin magnetopause (MP), described hereafter as a thin current sheet (TCS), observed by Cluster at the southern cusp on 13 February 2001 around 20:01 UT. The Cluster observations generally agree with the predictions of the Gas Dynamic Convection Field (GDCF) model in the magnetosheath (MSH) up to the MSH boundary layer, where significant differences are seen. We find for the MP a normal roughly along the GSE x-axis, which implies a clear departure from the local average MP normal, a ~90 km thickness and an outward speed of 35 km/s. Two populations are identified in the MSH boundary layer: the first one roughly perpendicular to the MSH magnetic field, which we interpret as the "incident" MSH plasma, the second one mostly parallel to B. Just after the MP crossing a velocity jet is observed with a peak speed of 240 km/s, perpendicular to B, with MA=3 and β>10 (peak value 23). The magnetic field clock angle rotates by 70° across the MP. Ex is the main electric field component on both sides of the MP, displaying a bipolar signature, positive on the MSH side and negative on the opposite side, corresponding to a ~300 V electric potential jump across the TCS. The E×B velocity generally coincides with the perpendicular velocity measured by CIS; however, in the speed jet a difference between the two is observed, which suggests the need for an extra flow source. We propose that the MP TCS can act locally as an obstacle for low-energy ions (<350 eV), being transparent for ions with larger gyroradius. As a result, the penetration of plasma by finite gyroradius is considered as a possible source for the jet. The role of reconnection is briefly discussed. The electrodynamics of the TCS along with mass and momentum transfer across it are further discussed in the companion paper by Savin et al. (2006).

  4. EPA REGION 6 NPL SITE BOUNDARIES

    EPA Science Inventory

    This dataset includes boundaries for sites on the EPA's National Priority List (NPL) as of 05/01/2005, although boundaries for all sites are not included. The field "Status" provides a description of each site's current status, i.e. Proposed, Final, Deleted, o...

  5. Two-Equation Low-Reynolds-Number Turbulence Modeling of Transitional Boundary Layer Flows Characteristic of Gas Turbine Blades. Ph.D. Thesis. Final Contractor Report

    NASA Technical Reports Server (NTRS)

    Schmidt, Rodney C.; Patankar, Suhas V.

    1988-01-01

    The use of low Reynolds number (LRN) forms of the k-epsilon turbulence model in predicting transitional boundary layer flow characteristic of gas turbine blades is developed. The research presented consists of: (1) an evaluation of two existing models; (2) the development of a modification to current LRN models; and (3) the extensive testing of the proposed model against experimental data. The prediction characteristics and capabilities of the Jones-Launder (1972) and Lam-Bremhorst (1981) LRN k-epsilon models are evaluated with respect to the prediction of transition on flat plates. Next, the mechanism by which the models simulate transition is considered and the need for additional constraints is discussed. Finally, the transition predictions of a new model are compared with a wide range of different experiments, including transitional flows with free-stream turbulence under conditions of flat plate constant velocity, flat plate constant acceleration, flat plate but strongly variable acceleration, and flow around turbine blade test cascades. In general, calculational procedure yields good agreement with most of the experiments.

  6. Low-Frequency Variability of the Western Boundary Currents at the Gappy Western Pacific Using a Shallow-Water Equation Model : Basic Bifurcation Diagram

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Dijkstra, H. A.; Yuan, D.

    2014-12-01

    For a long time, observations have indicated that the Kuroshio displays multiple steady states (loop, leap or direct intrusion) at Luzon Strait. Similarly, Low-latitude western boundary currents of the Pacific - Mindanao Current and South Equatorial Current also show some bimodal behavior (intrusion or choke) east of the Sulawesi Sea. It is still not well known whether these low frequency variabilities arise from external forcing or internal mechanism. In this paper we explore how temporal variability arises through successive bifurcations of the wind-driven circulation as lateral friction is decreased in a 1.5-layer shallow-water equation models with real continental geometry boundary of the western Pacific. Multiple equilibria of the intrusion of the western boundary currents are found. The origin of these equilibria is investigated by determining the structure of steady solutions by using continuation techniques. In both single-gyre model (analog to the Kuroshio at Luzon Strait)and double-gyre model (analog to the Mindanao Current and South equatorial Current at the source region of the Indonesian Throughflow), the western boundary currents become unstable as the lateral friction decreases. These solutions subsequently destabilize to two sets of barotropic oscillatory modes, introducing an annual and monthly time scale.

  7. Identifications of the polar cap boundary and the auroral belt in the high altitude magnetosphere: A model for field aligned currents

    NASA Technical Reports Server (NTRS)

    Sugiura, M.

    1974-01-01

    Using the OGO-5 fluxgate magnetometer data, the polar cap boundary is identified in the high altitude magnetosphere by a sudden transition from a dipolar field to a more tail like configuration. The basic pattern of the magnetic field variations observed during the satellite's traversal of the auroral belt is presented. This pattern shows the existence of a field aligned current layer on the equator side of the polar cap boundary. Currents flow in the opposite directions in the two field aligned current layers. The current directions in these layers as observed by OGO-5 in the high-altitude magnetosphere are the same as those observed at low altitudes by the polar orbiting TRIAD satellite. The magnetic field in the region where the lower latitude field aligned current layer is situated is essentially meridional. Thus the equatorial current closure of this current system must be via the equatorial current sheet. The two field aligned current systems, one at the polar cap boundary and the other on the low latitude side of the auroral belt, are coupled through the Pedersen current in the ionosphere.

  8. Links Between the Deep Western Boundary Current, Labrador Sea Water Formation and Export, and the Meridional Overturning Circulation

    NASA Astrophysics Data System (ADS)

    Myers, Paul G.; Kulan, Nilgun

    2010-05-01

    Based on an isopyncal analysis of historical data, 3-year overlapping triad fields of objectively analysed temperature and salinity are produced for the Labrador Sea, covering 1949-1999. These fields are then used to spectrally nudge an eddy-permitting ocean general circulation model of the sub-polar gyre, otherwise forced by inter annually varying surface forcing based upon the Coordinated Ocean Reference Experiment (CORE). High frequency output from the reanalysis is used to examine Labrador Sea Water formation and its export. A number of different apprpoaches are used to estimate Labrador Sea Water formation, including an instanteous kinematic approach to calculate the annual rate of water mass subduction at a given density range. Historical transports are computed along sections at 53 and 56N for several different water masses for comparison with recent observations, showing a decline in the stength of the deep western boundary current with time. The variability of the strength of the meridional overturning circulation (MOC) from the reanalysis is also examined in both depth and density space. Linkages between MOC variability and water mass formation variability is considered.

  9. Temperature signature of high latitude Atlantic boundary currents revealed by marine mammal-borne sensor and Argo data

    NASA Astrophysics Data System (ADS)

    Grist, Jeremy P.; Josey, Simon A.; Boehme, Lars; Meredith, Michael P.; Davidson, Fraser J. M.; Stenson, Garry B.; Hammill, Mike O.

    2011-08-01

    Results from the development and analysis of a novel temperature dataset for the high latitude North-West Atlantic are presented. The new 1° gridded dataset (“ATLAS”) has been produced from about 13,000 Argo and 48,000 marine mammal (hooded seal, harp seal, grey seal and beluga) profiles spanning 2004-8. These data sources are highly complementary as marine mammals greatly enhance shelf region coverage where Argo floats are absent. ATLAS reveals distinctive boundary current related temperature minima in the Labrador Sea (-1.1°C) and at the east Greenland coast (1.8°C), largely absent in the widely-used Levitus'09 and EN3v2a datasets. The ATLAS 0-500 m average temperature is lower than Levitus'09 and EN3v2a by up to 3°C locally. Differences are strongest from 0-300 m and persist at reduced amplitude from 300-500 m. Our results clearly reveal the value of marine mammal-borne sensors for a reliable description of the North-West Atlantic at a time of rapid change.

  10. Prototyping global Earth System Models at high resolution: Representation of climate, ecosystems, and acidification in Eastern Boundary Currents

    NASA Astrophysics Data System (ADS)

    Dunne, J. P.; John, J. G.; Stock, C. A.

    2013-12-01

    The world's major Eastern Boundary Currents (EBC) such as the California Current Large Marine Ecosystem (CCLME) are critically important areas for global fisheries. Computational limitations have divided past EBC modeling into two types: high resolution regional approaches that resolve the strong meso-scale structures involved, and coarse global approaches that represent the large scale context for EBCs, but only crudely resolve only the largest scales of their manifestation. These latter global studies have illustrated the complex mechanisms involved in the climate change and acidification response in these regions, with the CCLME response dominated not by local adjustments but large scale reorganization of ocean circulation through remote forcing of water-mass supply pathways. While qualitatively illustrating the limitations of regional high resolution studies in long term projection, these studies lack the ability to robustly quantify change because of the inability of these models to represent the baseline meso-scale structures of EBCs. In the present work, we compare current generation coarse resolution (one degree) and a prototype next generation high resolution (1/10 degree) Earth System Models (ESMs) from NOAA's Geophysical Fluid Dynamics Laboratory in representing the four major EBCs. We review the long-known temperature biases that the coarse models suffer in being unable to represent the timing and intensity of upwelling-favorable winds, along with lack of representation of the observed high chlorophyll and biological productivity resulting from this upwelling. In promising contrast, we show that the high resolution prototype is capable of representing not only the overall meso-scale structure in physical and biogeochemical fields, but also the appropriate offshore extent of temperature anomalies and other EBC characteristics. Results for chlorophyll were mixed; while high resolution chlorophyll in EBCs were strongly enhanced over the coarse resolution

  11. Calibration of Nitrogen Stable Isotopes and N-dynamics in a Western Boundary Current System (Brazil) during the Holocene

    NASA Astrophysics Data System (ADS)

    Albuquerque, A. L.; Fontana, L.

    2015-12-01

    This research documents changes in relative nitrate utilization and sources based on δ15N of nitrate and sinking particles in an oligotrophic Western Boundary to improve the efficience of the δ15N to provide an understanding of the N-dynamic during the Holocene from sediment records. The Continental Shelf of Southeastern Brazil is dominated by the oligotrophic Brazil Current, whose instabilities promote an untypical western boundary upwelling of South Atlantic Central Water (SACW) and consequently increases of primary productivity. The inorganic nitrogen concentration and the δ15N­nitrate and δ15N of sinking particles was characterized for each water masses present on the shelf (SACW, Tropical Water and Coastal Water). Cross­shelf gradients of nitrogen concentration and stable isotopes were observed. The SACW showed δ15N­nitrate signature around 5­6‰ characterizing the inner and mid­shelf conditions, where the input of new nitrate from upwelling is rapidly used by organisms in the euphotic zone without any fractionation. On the other hands, the dominance of N­ limited TW on the outer shelf provided a δ15N­nitrate and δ15N­sinking particles signals (­2.0 to 3.0‰) lower than the SACW average indicating N­fixation as a dominant source of nitrogen. The δ15N fractionation during upwelling events are also identified, but in smaller scale. The information of preliminary δ15N results from Holocene sediment record along a cross-shelf gradient showed values ranging from 3 to 8 ‰. In general, the tendency of low values recorded in middle Holocene indicates low availability of N during these low productivity stages. These results agreed pretty well with the δ13C records. In contrast, during late Holocene the values were heavy, probably indicating another processes (e.g. complete use of N-pool), which are still under investigation in association with another proxies (e.g. degraded pigments, opal, CaCO3).

  12. Low-frequency variability of Western Boundary Currents in the turbulent ocean: intrinsic modes and atmospheric forcing

    NASA Astrophysics Data System (ADS)

    Sérazin, Guillaume; Penduff, Thierry; Terray, Laurent; Grégorio, Sandy; Barnier, Bernard; Molines, Jean-Marc

    2015-04-01

    Ocean-atmosphere heat fluxes are particularly strong in Western Boundary Current (WBC) regions where SST front variations influence basin-scale climate variability. Observed low-frequency fluctuations in latitude and strength of these oceanic jets are classically thought to be essentially atmospherically-driven by wind stress curl variability via the oceanic Rossby wave adjustment. Yet academic eddy-resolving process-oriented models with double-gyre configurations have revealed that an idealized WBC may exhibit low-frequency intrinsic fluctuations without low-frequency external forcing (e.g. Berloff et al., 2007, Dijkstra and Ghil, 2005, etc). Experiments with eddying Ocean General Circulation Models (OGCMs) have also shown that the amount of low-frequency Sea Level Anomaly (SLA) variability is largely intrinsic in WBCs (Penduff et al. 2011; Sérazin et al 2014) and that the frontal-scale (<10°) pattern of the Kuroshio Extension (KE) variability is similar to intrinsic modes (Taguchi et al. 2010). Based on a pair of atmospherically-forced 1/12° OGCM experiments that simulate with accuracy either the intrinsic variability (seasonally-forced) or the observed total variability (forced with the full range of atmospheric timescales), Empirical Orthogonal Function analysis is performed on zonally-averaged SLA fields of four main WBCs (e.g. Gulf Stream, Kuroshio Extension, Agulhas Current and East Australian Current). The first two modes of the KE and GS exhibit a similar spatial structure that is shaped by oceanic intrinsic processes. The frequency content is however different between the intrinsic and total Principal Components, the former containing a wide range of timescales similar to a red noise and the latter being more autocorrelated at interannual-to-decadal timescales. These modes are compared with those obtained from the 20 years of altimetry observation and relationships with low-frequency westward propagative features in the respective oceanic basin are

  13. Current status of final design and R&D for ITER blanket shield blocks in Korea

    NASA Astrophysics Data System (ADS)

    Ha, M. S.; Kim, S. W.; Jung, H. C.; Hwang, H. S.; Heo, Y. G.; Kim, D. H.; Ahn, H. J.; Lee, H. G.; Jung, K. J.

    2015-07-01

    them and to optimize the cooling channels. The SB #8 FSP was manufactured and tested in accordance with the pre-qualification program based on the preliminary design, and related R&D activities were implemented to resolve the fabrication issues. This paper provides the current status of the final design and relevant R&D activities of the blanket SB.

  14. Influence of point defects on grain boundary diffusion in oxides. Final technical report, July 1, 1990--June 30, 1993

    SciTech Connect

    Stubican, V.S.

    1993-11-01

    Grain boundary diffusion coefficients of {sup 57}Co and {sup 59}Co in polycrys. NiO, NiO bicrystal, and polycrys. Fe{sub 3}O{sub 4} were determined at various oxygen pressures at 750 C. For NiO, the low oxygen pressure region (<10{sup {minus}10} MPa) displayed constant grain boundary diffusion coefficients as the oxygen pressure decreased, indicating an extrinsic region in which the impurity-induced defects dominated the intrinsic defects. At greater oxygen pressures, the intrinsic defects (Ni vacancies) dominated the extrinsic defects, causing the diffusion to increase with pressure. For Fe{sub 3}O{sub 4}, at low oxygen pressures (<10{sup {minus}16} MPa), the grain boundary diffusion coefficient increased when the pressure decreased, owing to interstitial type diffusion; at >10{sup {minus}15} MPa, the diffusion increased with pressure, owing to vacancy type diffusion. D{sub gb} of Co ions in Fe{sub 3}O{sub 4} is proportional to pO{sub 2}{sup {minus}2/3} in the low pressure region and to pO{sub 2}{sup 2/3} in the high pressure region, indicating similar mechanisms in the grain boundary diffusion and volume diffusion. Ratio of D{sub gb}/D was about 10{sup 3}.

  15. Boundary-layer cumulus over heterogeneous landscapes: A subgrid GCM parameterization. Final report, December 1991--November 1995

    SciTech Connect

    Stull, R.B.; Tripoli, G.

    1996-01-08

    The authors developed single-column parameterizations for subgrid boundary-layer cumulus clouds. These give cloud onset time, cloud coverage, and ensemble distributions of cloud-base altitudes, cloud-top altitudes, cloud thickness, and the characteristics of cloudy and clear updrafts. They tested and refined the parameterizations against archived data from Spring and Summer 1994 and 1995 intensive operation periods (IOPs) at the Southern Great Plains (SGP) ARM CART site near Lamont, Oklahoma. The authors also found that: cloud-base altitudes are not uniform over a heterogeneous surface; tops of some cumulus clouds can be below the base-altitudes of other cumulus clouds; there is an overlap region near cloud base where clear and cloudy updrafts exist simultaneously; and the lognormal distribution of cloud sizes scales to the JFD of surface layer air and to the shape of the temperature profile above the boundary layer.

  16. Low Reynold's number boundary layers in a disturbed environment. Ph.D. Thesis - August, 1985 - Final Report

    NASA Technical Reports Server (NTRS)

    Paik, D. K.; Reshotko, E.

    1986-01-01

    Studies of flat plate boundary layer development were made in a low speed wind tunnel at turbulence levels from 2%to 7%. Only transitional and turbulent flows were observed in the range 280 Re sub theta 700. The mean turbulent velocity profiles display law-of-the-wall behavior but have negligible wake component. The u' disturbance profiles compare well with those of other experiments, the peak value of u'/u sub tau being about 2.5. The effect of free-stream turbulence level on turbulent skin friction can be nicely correlated with those of other investigations on a plot of u sub e/u sub tau versus Re sub theta. A discussion on the u' spectra for the transitional boundary-layers is presented.

  17. Joint Effects of Boundary Currents, Thermohaline Intrusions and Gyre Circulation on the Recent Warming of Atlantic Water in the Canada Basin: 1993-2007

    NASA Astrophysics Data System (ADS)

    McLaughlin, F.; Carmack, E.; Zimmermann, S.; Shimada, K.; Itoh, M.; Williams, B.

    2008-12-01

    The 1990-91 influx Atlantic water, both anomalously warm and in greater volume than in the past, enveloped the Chukchi Borderland in the western Canada Basin by 2002 and has spread across the southeastern Canada Basin by 2007. Warmer, younger (more ventilated) and less dense Fram Strait Branch waters have displaced colder, older and denser ambient waters, increasing the temperature of the Fram Strait Branch core from a fifty-year or more mean of ~0.45 oC to ~0.7 oC. Physical and geochemical data collected from 1993-2007 show that the two main transport mechanisms are the boundary current and thermohaline intrusions, established by large thermal gradients. The boundary current operates in a cyclonic direction whereas the thermohaline intrusions operate in an anticyclonic direction due to the background of the Beaufort Gyre. The boundary current, a fully-pan Arctic structure, has slowed considerably in the Canada Basin, with effective speeds of ~ 0.5 cm/sec, similar to the effective spreading rate of the thermohaline intrusions (~0.3 cm/s). Our data also shows that the influence of the Beaufort Gyre on circulation extends into and perhaps deeper than the FSB of the Atlantic layer. The thermohaline intrusions show signs of dissipation near the Northwind Ridge in 2007 suggesting that, in the absence of similar influxes in the future, they would disappear from the Canada Basin with time.

  18. Coupled Climate Model Simulations of Large-scale Eastern Boundary Current Forcing During the Mid-Holocene and Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Diffenbaugh, N. S.

    2005-12-01

    We analyze coupled atmosphere-ocean general circulation model (GCM) output from the IPCC Fourth Assessment and the Paleoclimate Modelling Intercomparison Project. We focus on three time periods: the 20th century, 6 ka and 21 ka. The coupled GCMs capture the basic late-20th century seasonal structure of large-scale sea level pressure and wind forcing in the four major eastern boundary current regions (California, Canary, Humbolt and Benguela). There are moderate biases in the simulation of late-20th century inter-annual variability of large-scale sea level pressure and wind forcing, and substantial biases in the simulation of late-20th century mean monthly coastal winds. The coupled models show large changes in the magnitude of mean sea level pressure forcing in the 21 ka simulations and smaller changes in the 6 ka simulations. However, the magnitude of changes in inter-annual variability of sea level pressure forcing is similar in the 21 ka and 6 ka simulations. These and related analyses will aid in the evaluation of existing hypotheses of the response of eastern boundary currents to changes in external climate forcing. They will also help to create new testable hypotheses of eastern boundary current response and, in conjunction with proxy records, allow for a more sophisticated understanding of the mechanisms that shaped the late-Quaternary evolution of these important upwelling systems.

  19. Boundaries, kinetic properties, and final domain structure of plane discrete uniform Poisson-Voronoi tessellations with von Neumann neighborhoods

    NASA Astrophysics Data System (ADS)

    Korobov, A.

    2009-03-01

    Discrete random tessellations appear not infrequently in describing nucleation and growth transformations. Generally, several non-Euclidean metrics are possible in this case. Previously [A. Korobov, Phys. Rev. B 76, 085430 (2007)] continual analogs of such tessellations have been studied. Here one of the simplest discrete varieties of the Kolmogorov-Johnson-Mehl-Avrami model, namely, the model with von Neumann neighborhoods, has been examined per se, i.e., without continualization. The tessellation is uniform in the sense that domain boundaries consist of tiles. Similarities and distinctions between discrete and continual models are discussed.

  20. Scaling and modeling of three-dimensional, end-wall, turbulent boundary layers. Ph.D. Thesis - Final Report

    NASA Technical Reports Server (NTRS)

    Goldberg, U. C.; Reshotko, E.

    1984-01-01

    The method of matched asymptotic expansion was employed to identify the various subregions in three dimensional, turbomachinery end wall turbulent boundary layers, and to determine the proper scaling of these regions. The two parts of the b.l. investigated are the 3D pressure driven part over the endwall, and the 3D part located at the blade/end wall juncture. Models are proposed for the 3d law of the wall and law of the wake. These models and the data of van den Berg and Elsenaar and of Mueller are compared and show good agreement between models and experiments.

  1. Application of taxonomy theory, Volume 1: Computing a Hopf bifurcation-related segment of the feasibility boundary. Final report

    SciTech Connect

    Zaborszky, J.; Venkatasubramanian, V.

    1995-10-01

    Taxonomy Theory is the first precise comprehensive theory for large power system dynamics modeled in any detail. The motivation for this project is to show that it can be used, practically, for analyzing a disturbance that actually occurred on a large system, which affected a sizable portion of the Midwest with supercritical Hopf type oscillations. This event is well documented and studied. The report first summarizes Taxonomy Theory with an engineering flavor. Then various computational approaches are sighted and analyzed for desirability to use with Taxonomy Theory. Then working equations are developed for computing a segment of the feasibility boundary that bounds the region of (operating) parameters throughout which the operating point can be moved without losing stability. Then experimental software incorporating large EPRI software packages PSAPAC is developed. After a summary of the events during the subject disturbance, numerous large scale computations, up to 7600 buses, are reported. These results are reduced into graphical and tabular forms, which then are analyzed and discussed. The report is divided into two volumes. This volume illustrates the use of the Taxonomy Theory for computing the feasibility boundary and presents evidence that the event indeed led to a Hopf type oscillation on the system. Furthermore it proves that the Feasibility Theory can indeed be used for practical computation work with very large systems. Volume 2, a separate volume, will show that the disturbance has led to a supercritical (that is stable oscillation) Hopf bifurcation.

  2. MMS observations of small-scale field-aligned currents in the plasma sheet boundary layer during storm-time substorms

    NASA Astrophysics Data System (ADS)

    Nakamura, Rumi

    2016-04-01

    During major substorms at 0315 and 0505 UT on June 23 2015, the four MMS spacecraft, located near the center of the current wedge, enabled us to resolve detailed properties of the field-aligned currents in the plasma sheet boundary layer during its thinning and expansion. In particular, during the expansion of the plasma sheet, transient small-scale field-aligned currents were detected near the large-scale separatrix region. In this study we analyze their temporal and spatial evolution based on multi-point measurements of fields and plasma. We found ion-scale downward field-aligned currents, which are well correlated with the field-aligned upward electron beams. These upward electrons are most likely accelerated between the ionosphere and the spacecraft, and are associated with the intensified reconnection jets that cause the expansion of the plasma sheet.

  3. Influence of shallowness, bank inclination and bank roughness on the variability of flow patterns and boundary shear stress due to secondary currents in straight open-channels

    NASA Astrophysics Data System (ADS)

    Blanckaert, K.; Duarte, A.; Schleiss, A. J.

    2010-09-01

    Boundary shear stress and flow variability due to its interaction with main flow and secondary currents were investigated under conditions that extend previous research on trapezoidal channels. Secondary currents that scale with the flow depth were found over the entire width in all experiments. These findings contradict the widespread perception that secondary currents die out at a distance of 2.5 times the flow depth from the bank, a perception which is largely based on experiments with smooth boundaries. The reported results indicate that a stable pattern of secondary currents over the entire channel width can only be sustained over a fixed horizontal bed if the bed's roughness is sufficient to provide the required transverse oscillations in the turbulent shear stresses. Contrary to laboratory flumes, alluvial river bed always provide sufficient roughness. The required external forcing of this hydrodynamic instability mechanism is provided by the turbulence-generated near-bank secondary currents. The pattern of near-bank secondary currents depends on the inclination and the roughness of the bank. In all configurations, secondary currents result in a reduction of the bed shear stress in the vicinity of the bank and a heterogeneous bank shear stress that reaches a maximum close to the toe of the bank. Moreover, these currents cause transverse variability of 10-15% for the streamwise velocities and 0.2 u*2-0.3 u* 2 for the bed shear stress. These variations are insufficient to provide the flow variability required in river restoration projects, but nevertheless must be accounted for in the design of stable channels.

  4. Low frequency RF current drive. Final report, January 1, 1988--May 31, 1997

    SciTech Connect

    Hershkowitz, N.

    1999-05-01

    This report starts with a summary of research done on the Phaedrus Tandom Mirror concept and how this research led to the design and construction of the Phaedrus-T Tokamak. Next it gives a more detailed description of the results from the last four years of research, which include the following areas: (1) first experimental demonstration of AWCD (Alfven Wave Current Drive); (2) current drive location and loop voltage response; (3) trapping and current drive efficiency; and (4) reflectometry.

  5. Benefit-cost analysis of DOE's Current Federal Program to increase hydrothermal resource utilization. Final report

    SciTech Connect

    Not Available

    1981-12-10

    The impact of DOE's Current Federal Program on the commercialization of hydrothermal resources between 1980 and 2000 is analyzed. The hydrothermal resources of the United States and the types of DOE activities used to stimulate the development of these resources for both electric power and direct heat use are described briefly. The No Federal Program and the Current Federal Program are then described in terms of funding levels and the resultant market penetration estimates through 2000. These market penetration estimates are also compared to other geothermal utilization forecasts. The direct benefits of the Current Federal Program are next presented for electric power and direct heat use applications. An analysis of the external impacts associated with the additional hydrothermal resource development resulting from the Current Federal Program is also provided. Included are environmental effects, national security/balance-of-payments improvements, socioeconomic impacts and materials requirements. A summary of the analysis integrating the direct benefits, external impacts and DOE program costs concludes the report.

  6. NIST measurement services: Calibration service for current transformers. Special pub. (Final)

    SciTech Connect

    Ramboz, J.D.; Petersons, O.

    1991-06-01

    A calibration service at the National Institute of Standards and Technology (NIST) for laboratory-quality current transformers is described. The service provides measurements of the current ratio and the phase angle between the secondary and primary currents. In the Report of Calibration or Test, the measured ratio is reported as the product of the marked (nominal) ratio and the ratio correction factor. The measured phase angle is reported directly in milliradians (mrad) and is positive if the secondary current leads the primary. The range of primary-to-secondary current ratios that can be measured with the equipment at NIST extends from 0.25 A:5 A to 12000 A:5 A. The maximum current at the present time is about 20000 A. Estimates of calibration uncertainties, including their sources, are given and quality control procedures are described. For routine calibrations, uncertainties of + or - 0.01% for the ratio and + or - 0.1 mrad for the phase angle are quoted. However, lower uncertainties--to + or - 0.0005% or 5 parts per million (ppm) for ratio and + or - 0.005 mrad or 5 microrads for phase angle--are possible under the provisions of Special Tests.

  7. Novel free-boundary equilibrium and transport solver with theory-based models and its validation against ASDEX Upgrade current ramp scenarios

    NASA Astrophysics Data System (ADS)

    Fable, E.; Angioni, C.; Casson, F. J.; Told, D.; Ivanov, A. A.; Jenko, F.; McDermott, R. M.; Medvedev, S. Yu; Pereverzev, G. V.; Ryter, F.; Treutterer, W.; Viezzer, E.; the ASDEX Upgrade Team

    2013-12-01

    Tokamak scenario development requires an understanding of the properties that determine the kinetic profiles in non-steady plasma phases and of the self-consistent evolution of the magnetic equilibrium. Current ramps are of particular interest since many transport-relevant parameters explore a large range of values and their impact on transport mechanisms has to be assessed. To this purpose, a novel full-discharge modelling tool has been developed, which couples the transport code ASTRA (Pereverzev et al 1991 IPP Report 5/42) and the free boundary equilibrium code SPIDER (Ivanov et al 2005 32nd EPS Conf. on Plasma Physics vol 29C (ECA) P-5.063 and http://epsppd.epfl.ch/Tarragona/pdf/P5_063.pdf), utilizing a specifically designed coupling scheme. The current ramp-up phase can be accurately and reliably simulated using this scheme, where a plasma shape, position and current controller is applied, which mimics the one of ASDEX Upgrade. Transport of energy is provided by theory-based models (e.g. TGLF (Staebler et al 2007 Phys. Plasmas 14 055909)). A recipe based on edge-relevant parameters (Scott 2000 Phys. Plasmas 7 1845) is proposed to resolve the low current phase of the current ramps, where the impact of the safety factor on micro-instabilities could make quasi-linear approaches questionable in the plasma outer region. Current ramp scenarios, selected from ASDEX Upgrade discharges, are then simulated to validate both the coupling with the free-boundary evolution and the prediction of profiles. Analysis of the underlying transport mechanisms is presented, to clarify the possible physics origin of the observed L-mode empirical energy confinement scaling. The role of toroidal micro-instabilities (ITG, TEM) and of non-linear effects is discussed.

  8. SUPPLEMENTARY COMPARISON: Final report EURAMET.EM-S30 on EURAMET Project 1081: Supplementary comparison of measurements of current transformers

    NASA Astrophysics Data System (ADS)

    Dimitrov, Emil; Kumanova, Ginka; Styblíková, Renata; Draxler, Karel; Dierikx, Erik

    2010-01-01

    The supplementary comparison was carried out between CMI, Czech Republic and BIM, NCM Bulgaria in the field of current transformer ratio measurements. The current errors and phase displacement of the traveling standards, current transformers: Tettex 4720, CLA 2.2, CLA 2.2, CLA 3.2, CLB 10, I 523 were determined at 50 Hz, 5 VA burden at unity power factor at ratios: primary (4000, 2000, 1000, 500, 100, 5, 1 and 0.5) A/secondary 5 A. Both participants used their own standard measurement method. The obtained results show good agreement for all of the current ratio error measurements (except for the measurements at 2 kA) and for the current phase displacement measurements (the agreement on several measurement points is marginal). The aim of the comparison was to demonstrate the improvement and extension of the calibration and measurement capabilities (CMCs) of BIM in this working field and to support the improved CMCs in Appendix C of the CIPM Mutual Recognition Arrangement (MRA). Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

  9. A TECHNICAL ASSESSMENT OF THE CURRENT WATER POLICY BOUNDARY AT U.S. DEPARTMENT OF ENERGY, PADUCAH GASEOUS DIFFUSION PLANT, PADUCAH, KENTUCKY

    SciTech Connect

    2012-12-13

    In 1988, groundwater contaminated with trichloroethene (TCE) and technetium-99 (Tc-99) was identified in samples collected from residential water wells withdrawing groundwater from the Regional Gravel Aquifer (RGA) north of the Paducah Gaseous Diffusion Plant (PGDP) facility. In response, the U.S. Department of Energy (DOE) provided temporary drinking water supplies to approximately 100 potentially affected residents by initially supplying bottled water, water tanks, and water-treatment systems, and then by extending municipal water lines, all at no cost, to those persons whose wells could be affected by contaminated groundwater. The Water Policy boundary was established in 1993. In the Policy, DOE agreed to pay the reasonable monthly cost of water for homes and businesses and, in exchange, many of the land owners signed license agreements committing to cease using the groundwater via rural water wells. In 2012, DOE requested that Oak Ridge Associated Universities (ORAU), managing contractor of Oak Ridge Institute for Science and Education (ORISE), provide an independent assessment of the quality and quantity of the existing groundwater monitoring data and determine if there is sufficient information to support a modification to the boundary of the current Water Policy. As a result of the assessment, ORAU concludes that sufficient groundwater monitoring data exists to determine that a shrinkage and/or shift of the plume(s) responsible for the initial development of this policy has occurred. Specifically, there is compelling evidence that the TCE plume is undergoing shrinkage due to natural attenuation and associated degradation. The plume shrinkage (and migration) has also been augmented in local areas where large volumes of groundwater were recovered by pump-and treat remedial systems along the eastern and western boundaries of the Northwest Plume, and in other areas where pump-and-treat systems have been deployed by DOE to remove source contaminants. The

  10. Definition of sanitary boundaries to prevent ISAv spread between salmon farms in southern Chile based on numerical simulations of currents

    NASA Astrophysics Data System (ADS)

    Olivares, Gonzalo; Sepúlveda, H. H.; Yannicelli, B.

    2015-06-01

    The infectious Salmon Anemia virus (ISAv) is a pathogen that mainly affects the Atlantic Salmon (Salmo salar). It was detected in Norway in 1984 and in June 2007 appeared in Chile, producing a drop of more than 30% in the country's production level. It is expected that with certain regularity, outbreaks will continue to appear in Chile without the need of reintroducing the virus from foreign countries. We present a numerical study of the influence of winds and tides in the dispersion of lagrangian particles to simulate the transport of ISAv in the Aysen region, in southern Chile. This study combines the use of numerical models of the ocean and atmosphere, lagrangian tracking and biological aspects of ISAv infections. As in previous results, a wider dispersion of ISAv was observed during spring tides. Temporal changes in wind significantly modified the transport of viral particles from an infected center. Under similar forcing conditions, the areas of risk associated to culture sites separated by a few kilometers could be very different. Our main results remark the importance of the use of a detailed knowledge of hydrographic and atmospheric circulation in the definition of boundaries for sanitary management areas. We suggest that a methodology similar to the one presented in this study should be considered to define sanitary strategies to minimize the occurrence of native outbreaks of ISAv.

  11. Forecasting Performance in Organizations: An Application of Current-Value Human Resources Accounting. Final Report.

    ERIC Educational Resources Information Center

    Pecorella, Patricia A.; And Others

    A methodology to describe current-value human resources accounting (HRA) was developed to aid management in decision making and provide information about the effects of organizational policies and practices on the value of the organizations' human resources. A two-phase activity was designed to investigate the nature of the relationship between…

  12. Remote field eddy current detection of stress-corrosion cracks. Final report

    SciTech Connect

    Nestleroth, J.B.

    1990-02-01

    The feasibility of detecting stress-corrosion cracks (SSC) using the Remote Field Eddy Current (RFEC) technique was demonstrated. The RFEC technique interrogates the entire thickness of the pipe and is applicable for in-line inspection. If it can be shown that the RFEC technique is effective in detecting SSC, then the technique is an ideal method for detecting the defects of interest. A defect detection model is proposed for explaining the mechanism for crack detection. For axially oriented, closed cracks, such as SCC, the conventional defect detection model proved to be too simplistic and not applicable. Therefore, a new detection mode that examines the flow of circumferential eddy currents was developed based on experimental results. This model, though not rigorous, provides a general understanding of the applicability of the RFEC technique for finding SSC. The data from the cracks and various artificial defects is presented in three formats: isometric projections, pseudocolor images and line-of-sight data. Though only two cracks were found, the experimental results correlate well with the circumferential eddy current theory. A theoretical analysis of the effects of motion on the output signal of the receiver is presented. This analysis indicates that inspection speed of simple implementations may be limited to a few miles per hour. Remote field eddy current inspection has excellent potential for inspection of gas transmission lines for detecting stress corrosion cracks that should be further developed.

  13. A feature-based eddy-current imaging system for personal computers: Final report

    SciTech Connect

    Elmo, P.M.; Shankar, R.

    1989-03-01

    Imaging eddy current nondestructive evaluation (NDE) data on low-cost, field-deployable personal computer (PC) systems is now possible. This report describes the modification of a previously developed feature-based ultrasonic (UT) testing system for automatic eddy current (EC) inspection. This EC system was applied to flat plate and circular geometries. The PC system manipulates the eddy current probe around the part to be inspected; acquires multi-frequency, dual-channel digital data and displays images of an operator-selected channel; and utilizes advanced signal processing software to generate and display impedance-plane trajectories for all frequencies. Laboratory experiments using this eddy current test system on flaw calibration standards, induced intergranular-stress-corrosion-cracking (IGSCC) in retaining ring material coupons, and induced cracks in full size retaining rings have demonstrated the system's capability to detect surface damage. Future efforts will incorporate other problem-relevant signal processing algorithms to aid in detecting and characterizing surface-damage, such as pitting and cracking. 6 refs., 20 figs.

  14. Are current sheets the boundary of fluxtubes in the solar wind? -- A study from multiple spacecraft observation

    NASA Astrophysics Data System (ADS)

    Li, G.; Arnold, L.; Miao, B.; Yan, Y.

    2011-12-01

    G. Li (1,2), L. Arnold (1), B. Miao (3) and Y. Yan (4) (1) Department of Physics, University of Alabama in Huntsville Huntsville, AL, 35899 (2) CSPAR, University of Alabama in Huntsville Huntsville, AL, 35899 (3) School of Earth and Space Sciences, University of Science and Technology of CHINA, Hefei, China (4) Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Science, Beijing 100012, China Current sheets is a common structure in the solar wind and is a significant source of solar wind MHD turbulence intermittency. The origin of these structure is presently unknown. Non-linear interactions of the solar wind MHD turbulence can spontaneously generate these structures. On the other hand, there are proposals that these structures may represent relic structures having solar origins. Using a technique developed in [1], we examine current sheets in the solar wind from multiple spacecraft. We identify the "single-peak" and "double-peak" events in the solar wind and discuss possible scenarios for these events and its implication of the origin of the current sheets. [1] Li, G., "Identify current-sheet-like structures in the solar wind", ApJL 672, L65, 2008.

  15. A description of eddy-mean flow feedbacks in equatorial and boundary current systems of the South Indian Ocean

    NASA Astrophysics Data System (ADS)

    Aguiar-González, Borja; Ponsoni, Leandro; Maas, Leo R. M.; Ridderinkhof, Herman; van Aken, Hendrik

    2015-04-01

    While many observational and modeling efforts have addressed eddy-mean flow interactions acting over nearly idealized zonal jets, little is know about whether findings in those studies can be extended to current systems with different configurations in the real ocean. This topic is of special interest for ocean-climate models where eddy interactions with the mean flow may be unresolved, demanding further insight on the mechanism by which the eddy field and the mean circulation should feed back in a realistic representation of future climate change scenarios. Following this motivation, we investigate local exchange of momentum and kinetic energy operating in a variety of eddy-mean flow systems of the South Indian Ocean (SIO). To this aim we use 21 years (1993-2013) of newly processed satellite altimetry observations, and adopt a definition of the mean flow as a seasonally-dependent temporal mean where the eddy field encompasses the daily instantaneous deviation from the altimeter-derived velocities. This approach allows time-varying feedbacks to evolve throughout the year. We find that the eddy field feeds back on the mean circulation, contributing importantly to the overall seasonal strengthening and weakening of all current systems involved in the tropical and subtropical gyre of the SIO. Although significant contributions to the momentum and energy balances were also obtained along the Agulhas (Return) Current and the Antarctic Circumpolar Current (ACC), they exhibit a weak/absent seasonal cycle, suggesting that the strength of these dynamical processes is mostly persistent throughout the year. Spatial distribution of the eddy kinetic energy conversion rates and the convergence of horizontal eddy momentum fluxes indicate that over regions where the eddy field draws energy from the mean flow through barotropic instabilities, the current is importantly decelerated by alongstream eddy forces on its upstream side, while further downstream the situation reverses with

  16. Recirculation acceleration of high current relativistic electron beams--a feasibility study. Final report

    SciTech Connect

    Wilson, M.

    1981-06-01

    One of the advanced accelerator concepts under study at NBS involves multiplying the energy gained by a long-pulse, high current relativistic electron beam by directing the beam several times through the same induction accelerator during the time of one voltage pulse. Should this concept of the recirculation acceleration of intense electron beams be proven feasible, the savings in cost, size, and weight of a high current accelerator would be considerable. Energy gain by recirculation acceleration through a small-scale proof-of principle facility has been demonstrated at NBS. The study employs a 750A, 750keV electron beam pulse, 2 microsec long, generated by a linear induction accelerator of unique design which was also developed at NBS.

  17. Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska final report

    SciTech Connect

    Wright, Bruce Albert

    2014-05-07

    The Aleutian Pribilof Islands Association was awarded a U.S. Department of Energy Tribal Energy Program grant (DE-EE0005624) for the Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska (Project). The goal of the Project was to perform a feasibility study to determine if a tidal energy project would be a viable means to generate electricity and heat to meet long-term fossil fuel use reduction goals, specifically to produce at least 30% of the electrical and heating needs of the tribally-owned buildings in False Pass. The Project Team included the Aleut Region organizations comprised of the Aleutian Pribilof Island Association (APIA), and Aleutian Pribilof Island Community Development Association (APICDA); the University of Alaska Anchorage, ORPC Alaska a wholly-owned subsidiary of Ocean Renewable Power Company (ORPC), City of False Pass, Benthic GeoScience, and the National Renewable Energy Laboratory (NREL). The following Project objectives were completed: collected existing bathymetric, tidal, and ocean current data to develop a basic model of current circulation at False Pass, measured current velocities at two sites for a full lunar cycle to establish the viability of the current resource, collected data on transmission infrastructure, electrical loads, and electrical generation at False Pass, performed economic analysis based on current costs of energy and amount of energy anticipated from and costs associated with the tidal energy project conceptual design and scoped environmental issues. Utilizing circulation modeling, the Project Team identified two target sites with strong potential for robust tidal energy resources in Isanotski Strait and another nearer the City of False Pass. In addition, the Project Team completed a survey of the electrical infrastructure, which identified likely sites of interconnection and clarified required transmission distances from the tidal energy resources. Based on resource and electrical data

  18. R & D on Very-High-Current Superconducting Proton Linac, Final Report

    SciTech Connect

    Ben-Zvi, Ilan

    2013-03-31

    The aim of this R&D project was to develop a superconducting cavity for a very-­ high-current proton accelerator. The particular application motivating the proposal was a LHC upgrade called the Superconducting Proton Linac, or SPL. Under the grant awarded to Stony Brook University the cavity was designed, a prototype copper cavity, followed by the niobium cavity, were built. A new set of HOM dampers was developed. The cavity has outstanding RF performance parameters – low surface fields, low power loss and all HOMs are fully damped. In fact, it is a “universal cavity” in the sense that it is suited for the acceleration of high-­current protons and well as high current electrons. Its damping of HOM modes is so good that it can see service in a multi-pass linac or an Energy Recovery Linac in addition to the easier service in a single-pass linac. Extensive measurements were made on the cavities and couplers, with the exception of the cold test of the niobium cavity. At the time of this report the cavity has been chemically processed and is ready for vertical testing which will be carried out shortly.

  19. The spatial extent of the Deep Western Boundary Current into the Bounty Trough: new evidence from parasound sub-bottom profiling

    NASA Astrophysics Data System (ADS)

    Horn, Michael; Uenzelmann-Neben, Gabriele

    2016-04-01

    Deep currents such as the Pacific Deep Western Boundary Current (DWBC) are strengthened periodically in Milankovitch cycles. We studied periodic fluctuations in seismic reflection pattern and reflection amplitude in order to detect cycles in the sedimentary layers of Bounty Trough and bounty fan, east of New Zealand. There, the occurrence of the obliquity frequency is caused only by the DWBC. Therefore, it provides direct evidence for the spatial extent of the DWBC. We can confirm the extent of the DWBC west of the outer sill, previously only inferred via erosional features at the outer sill. Further, our data allow an estimation of the extent of the DWBC into the Bounty Trough, limiting the DWBC presence to east of 178.15°E. Using the presented method a larger dataset will allow a chronological and areal mapping of sedimentation processes and hence provide information on glacial/interglacial cycles.

  20. The spatial extent of the Deep Western Boundary Current into the Bounty Trough: new evidence from parasound sub-bottom profiling

    NASA Astrophysics Data System (ADS)

    Horn, Michael; Uenzelmann-Neben, Gabriele

    2016-06-01

    Deep currents such as the Pacific Deep Western Boundary Current (DWBC) are strengthened periodically in Milankovitch cycles. We studied periodic fluctuations in seismic reflection pattern and reflection amplitude in order to detect cycles in the sedimentary layers of Bounty Trough and bounty fan, east of New Zealand. There, the occurrence of the obliquity frequency is caused only by the DWBC. Therefore, it provides direct evidence for the spatial extent of the DWBC. We can confirm the extent of the DWBC west of the outer sill, previously only inferred via erosional features at the outer sill. Further, our data allow an estimation of the extent of the DWBC into the Bounty Trough, limiting the DWBC presence to east of 178.15°E. Using the presented method a larger dataset will allow a chronological and areal mapping of sedimentation processes and hence provide information on glacial/interglacial cycles.

  1. Beat wave current drive experiment on the Davis Diverted Tokamak (DDT). Final report

    SciTech Connect

    Hwang, D.Q.; Horton, R.D.; Rogers, J.H. |

    1993-12-31

    The beatwave current drive experiment is summarized. The first phase of the experiment was the construction of the microwave sources and the diagnostics needed to demonstrate the beat wave effects, i.e. the measurement of the electrostatic plasma wave produced by the beating of two high intensity electromagnetic waves. In order to keep the cost of the experiments to a minimum, a low density filament plasma source (10{sup 8}) to (10{sup 10} particles cm{sup {minus}3}) was employed and the magnetic field in the toroidal plasma was produced by a dc power supply.

  2. Utilization of low-quality natural gas: A current assessment. Final report

    SciTech Connect

    Acheson, W.P.; Hackworth, J.H.; Kasper, S.; McIlvried, H.G.

    1993-01-01

    The objective of this report is to evaluate the low quality natural gas (LQNG) resource base, current utilization of LQNG, and environmental issues relative to its use, to review processes for upgrading LQNG to pipeline quality, and to make recommendations of research needs to improve the potential for LQNG utilization. LQNG is gas from any reservoir which contains amounts of nonhydrocarbon gases sufficient to lower the heating value or other properties of the gas below commercial, pipeline standards. For the purposes of this study, LQNG is defined as natural gas that contains more than 2% carbon dioxide, more than 4% nitrogen, or more than 4% combined CO{sub 2} plus N{sub 2}. The other contaminant of concern is hydrogen sulfide. A minor contaminant in some natural gases is helium, but this inert gas usually presents no problems.

  3. Analysis of environmental constraints on expanding reserves in current and future reservoirs in wetlands. Final report

    SciTech Connect

    Harder, B.J.

    1995-03-01

    Louisiana wetlands require careful management to allow exploitation of non-renewable resources without destroying renewable resources. Current regulatory requirements have been moderately successful in meeting this goal by restricting development in wetland habitats. Continuing public emphasis on reducing environmental impacts of resource development is causing regulators to reassess their regulations and operators to rethink their compliance strategies. We examined the regulatory system and found that reducing the number of applications required by going to a single application process and having a coherent map of the steps required for operations in wetland areas would reduce regulatory burdens. Incremental changes can be made to regulations to allow one agency to be the lead for wetland permitting at minimal cost to operators. Operators need cost effective means of access that will reduce environmental impacts, decrease permitting time, and limit future liability. Regulators and industry must partner to develop incentive based regulations that can provide significant environmental impact reduction for minimal economic cost. In addition regulators need forecasts of future E&P trends to estimate the impact of future regulations. To determine future activity we attempted to survey potential operators when this approach was unsuccessful we created two econometric models of north and south Louisiana relating drilling activity, success ratio, and price to predict future wetland activity. Results of the econometric models indicate that environmental regulations have a small but statistically significant effect on drilling operations in wetland areas of Louisiana. We examined current wetland practices and evaluated those practices comparing environmental versus economic costs and created a method for ranking the practices.

  4. Characterization of Final State Interaction Strength in Plastic Scintillator by Muon-Neutrino Charged Current Charged Pion Production

    SciTech Connect

    Eberly, Brandon M.

    2014-01-01

    Precise knowledge of neutrino-nucleus interactions is increasingly important as neutrino oscillation measurements transition into the systematics-limited era. In addition to modifying the initial interaction, the nuclear medium can scatter and absorb the interaction by-products through final state interactions, changing the types and kinematic distributions of particles seen by the detector. Recent neutrino pion production data from MiniBooNE is inconsistent with the final state interaction strength predicted by models and theoretical calculations, and some models fit best to the MiniBooNE data only after removing final state interactions entirely. This thesis presents a measurement of dσ/dTπ and dσ/dθπ for muon-neutrino charged current charged pion production in the MINER A scintillator tracker. MINER A is a neutrino-nucleus scattering experiment installed in the few-GeV NuMI beam line at Fermilab. The analysis is limited to neutrino energies between 1.5-10 GeV. Dependence on invariant hadronic mass W is studied through two versions of the analysis that impose the limits W < 1.4 GeV and W < 1.8 GeV. The lower limit on W increases compatibility with the MiniBooNE pion data. The shapes of the differential cross sections, which depend strongly on the nature of final state interactions, are compared to Monte Carlo and theoretical predictions. It is shown that the measurements presented in this thesis favor models that contain final state interactions. Additionally, a variety of neutrino-nucleus interaction models are shown to successfully reproduce the thesis measurements, while simultaneously failing to describe the shape of the MiniBooNE data.

  5. RF current drive antenna. Final report, August 15, 1993--August 14, 1995

    SciTech Connect

    Probert, P.H.

    1995-09-01

    This work represents an attempt to solve a fundamental problem with all coupling devices in tokamaks intended to launch waves in the ion cyclotron range of frequencies (ICRF), that of excessive voltage levels on the launcher and its feed lines. These voltages can lead to impurity problems in the plasma, and they determine the maximum power that can be coupled to the plasma, since it is when arcs caused by this voltage frequently occur that the power must be reduced. The approach taken is to consider an antenna which is composed of many smaller units, each operating at much lower voltages, stacked on end to provide the equivalent functionality of a conventional launcher. The work described herein involved designing, building, and operating such a launcher in the Phaedrus-T tokamak. The results showed that the antenna worked as expected, reducing the voltage dramatically, while still functioning property, and producing fewer impurity problems and no arcing. A design extrapolating the principles of this idea to reactor-sized tokamaks such as ITER was developed. In addition, a novel decoupling scheme was developed in order to adapt this antenna idea to low frequency current drive schemes.

  6. Thermal plasma waste remediation technology: Historical perspective and current trends. Final report

    SciTech Connect

    Counts, D.A.; Sartwell, B.D.; Peterson, S.H.; Kirkland, R.; Kolak, N.P.

    1999-01-29

    The idea of utilizing thermal plasma technology for waste processing goes back to the mid-1970`s during the energy crisis. Since then, more interest has been shown by universities, industry, and government in developing thermal plasma waste processing technology for hazardous and non-hazardous waste treatment. Much of the development has occurred outside of the United States, most significantly in Japan and France, while the market growth for thermal plasma waste treatment technology has remained slow in the United States. Despite the slow expansion of the market in the United States, since the early 1990`s there has been an increase in interest in utilizing thermal plasma technology for environmental remediation and treatment in lieu of the more historical methods of incineration and landfilling. Currently within the Department of Defense there are several demonstration projects underway, and details of some of these projects are provided. Prior to these efforts by the U.S. Government, the State of New York had investigated the use of thermal plasma technology for treating PCB contaminated solvent wastes from the Love Canal cleanup. As interest continues to expand in the application of thermal plasma technology for waste treatment and remediation, more and more personnel are becoming involved with treatment, regulation, monitoring, and commercial operations and many have little understanding of this emerging technology. To address these needs, this report will describe: (1) characteristics of plasmas; (2) methods for generating sustained thermal plasmas; (3) types of thermal plasma sources for waste processing; (4) the development of thermal plasma waste treatment systems; and (5) Department of Defense plasma arc waste treatment demonstration projects.

  7. Spatial and seasonal patterns of fine-scale to mesoscale upper ocean dynamics in an Eastern Boundary Current System

    NASA Astrophysics Data System (ADS)

    Grados, Daniel; Bertrand, Arnaud; Colas, François; Echevin, Vincent; Chaigneau, Alexis; Gutiérrez, Dimitri; Vargas, Gary; Fablet, Ronan

    2016-03-01

    The physical forcing of the ocean surface includes a variety of energetic processes, ranging from internal wave (IW) to submesoscale and mesoscale, associated with characteristic horizontal scales. While the description of mesoscale ocean dynamics has greatly benefited from the availability of satellite data, observations of finer scale patterns remain scarce. Recent studies showed that the vertical displacements of the oxycline depth, which separates the well-mixed oxygenated surface layer from the less oxygenated deeper ocean, estimated by acoustics, provide a robust proxy of isopycnal displacements over a wide range of horizontal scales. Using a high-resolution and wide-range acoustic data set in the Northern Humboldt Current System (NHCS) off Peru, the spatial and temporal patterns of fine-scale-to-mesoscale upper ocean dynamics are investigated. The spectral content of oxycline/pycnocline profiles presents patterns characteristic of turbulent flows, from the mesoscale to the fine scale, and an energization at the IW scale (2 km-200 m). On the basis of a typology performed on 35,000 structures we characterized six classes of physical structures according to their shape and scale range. The analysis reveals the existence of distinct features for the fine-scale range below ∼2-3 km, and clearly indicates the existence of intense IW and submesoscale activity over the entire NHCS region. Structures at scales smaller than ∼2 km were more numerous and energetic in spring than in summer. Their spatiotemporal variability supports the interpretation that these processes likely relate to IW generation by interactions between tidal flows, stratification and the continental slope. Given the impact of the physical forcing on the biogeochemical and ecological dynamics in EBUS, these processes should be further considered in future ecosystem studies based on observations and models. The intensification of upper ocean stratification resulting from climate change makes such

  8. SOLE SOURCE AQUIFER BOUNDARY DATA

    EPA Science Inventory

    There are 7 polygons representing 6 individual sole source aquifer boundaries and one streamflow source area in California, Arizona, and Nevada. Various efforts were combined to create the final product, which represents the Federal Register boundary description. Sole source aqu...

  9. Investigation of blown boundary layers with an improved wall jet system. Ph.D. Thesis. Final Technical Report, 1 Jul. 1978 - Dec. 1979; [to prevent turbulent boundary layer separation

    NASA Technical Reports Server (NTRS)

    Saripalli, K. R.; Simpson, R. L.

    1979-01-01

    The behavior of two dimensional incompressible turbulent wall jets submerged in a boundary layer when they are used to prevent boundary layer separation on plane surfaces is investigated. The experimental set-up and instrumentation are described. Experimental results of zero pressure gradient flow and adverse pressure gradient flow are presented. Conclusions are given and discussed.

  10. Final Scientific/Technical Report for "Role of Electron Kinetic Effects on the Macroscopic Structure and Evolution of Collisionless Reconnection in Simulations with Open Boundary Conditions"

    SciTech Connect

    Scudder, Jack

    2011-02-04

    The final years of this grant have been dedicated to diagnosing the observable properties of Collisionless Magnetic Reconnection (CMR) as disclosed by the open boundary condition PIC simulations developed under this grant. Particular attention has focussed on identifying the Electron Diffusion Region (EDR), the short scale domain where the process is thought to be enabled. The critical issue has been the need for experimental closure for CMR that is widely invoked in astrophysics, but has actually rather little direct, incontrovertible evidence for its involvement. This difficulty arises because CMR is about topology change of the magnetic field - a concept that is not conducive to single, or even few point correlations as are beginning to be possible with spacecraft armada, like Cluster or the planned Magnetospheric Multi-Scale (MMS) mission to be launched in 2014. Alternate formulations about the time rate of magnetic flux inventoried by a moving observer, reformulate the needed evidence in terms of the curl of various weak vector fields, such as E+UexB, that is zero in ideal MHD. To sense E+UexB from space measurements is already a heroic task. The curl of such a small vector field is outside the domain of the possible.

  11. Diet of sardine ( Sardinops sagax) in the northern Humboldt Current system and comparison with the diets of clupeoids in this and other eastern boundary upwelling systems

    NASA Astrophysics Data System (ADS)

    Espinoza, Pepe; Bertrand, Arnaud; van der Lingen, Carl D.; Garrido, Susana; Rojas de Mendiola, Blanca

    2009-12-01

    Sardines are one of the main small pelagic fish resources in eastern boundary upwelling systems (EBUS) where they play an important ecological role both as a predator of plankton and as prey of top predators. Sardine trophodynamics have been relatively well studied in three of the EBUS (the Benguela, California and Canary upwelling systems) but not in the Humboldt Current system. In this paper we describe the diet of sardine Sardinops sagax in the northern Humboldt Current system (NHCS) off Peru, using an analytical method which assesses relative dietary importance in terms of estimated prey carbon content. We assessed sardine diet by examining a total of 555 stomachs collected during six surveys conducted off Peru during the period 1996-1998, and compare our results with the diet of anchoveta Engraulis ringens off Peru and with the diets of sardines from the southern Benguela (also S. sagax) and the northern Canary ( Sardina pilchardus) upwelling systems. The diet of sardine off Peru is based primarily on zooplankton, similar to that observed for anchoveta but with several important differences. Firstly, sardine feed on smaller zooplankton than do anchoveta, with sardine diet consisting of smaller copepods and fewer euphausiids than anchoveta diet. Secondly, whilst phytoplankton represents <2% of sardine dietary carbon, this fraction is dominated by dinoflagellates, whereas diatoms are the dominant phytoplankton consumed by anchoveta. Hence, trophic competition between sardine and anchovy in the northern Humboldt Current system is minimized by their partitioning of the zooplankton food resource based on prey size, as has been reported in other systems. Whereas sardine in the NHCS feed on smaller zooplankton than do anchovy in that system, sardine in the NHCS forage on larger prey and obtain a substantial portion of their dietary carbon from euphausiids compared to sardine from the northern Canary and southern Benguela Current systems.

  12. Analysis of the electron-beam-induced current of a polycrystalline p-n junction when the diffusion lengths of the material on either side of a grain boundary differ

    NASA Technical Reports Server (NTRS)

    Von Roos, O.; Luke, K. L.

    1984-01-01

    The short circuit current generated by the electron beam of a scanning electron microscope in p-n junctions is reduced by enhanced recombination at grain boundaries in polycrystalline material. Frequently, grain boundaries separate the semiconductor into regions possessing different minority carrier life times. This markedly affects the short circuit current I(sc) as a function of scanning distance from the grain boundary. It will be shown theoretically that (1) the minimum of the I(sc) in crossing the grain boundary with the scanning electron beam is shifted away from the grain boundary toward the region with smaller life time (shorter diffusion length), (2) the magnitude of the minimum differs markedly from those calculated under the assumption of equal diffusion lengths on either side of the grain boundary, and (3) the minimum disappears altogether for small surface recombination velocities (s less than 10,000 cm/s). These effects become negligible, however, for large recombination velocities s at grain boundaries. For p-type silicon this happens for s not less than 100,000 cm/s.

  13. Boundary issues

    NASA Astrophysics Data System (ADS)

    Townsend, Alan R.; Porder, Stephen

    2011-03-01

    -centric boundary (Filippelli 2008, Handoh and Lenton 2003). However, human alteration of the P cycle has multiple potential boundaries (figure 1), including P-driven freshwater eutrophication (Smith and Schindler 2009), the potential for world P supply to place an ultimate limit on food production (Smil 2000, Childers et al 2011), and depletion of soil P stocks in some world regions (MacDonald et al 2011). Carpenter and Bennett revisit the P boundary from the freshwater eutrophication perspective. Given the extraordinary variation in freshwater ecosystems across the globe, this is a challenging task, but the authors strengthen their analysis by using three different boundaries with relevance to eutrophication, along with two water quality targets and a range of estimates of P flow to the sea. In doing so, they make a compelling case that if freshwater eutrophication is indeed a Rubicon, we have already crossed it. Importantly, Carpenter and Bennett go beyond the calculation of new boundaries to make broader points about humanity's relationship with the P cycle. Disruptions of both the P and N cycles are mostly about our need for food (Galloway et al 2008, Cordell et al 2009), but unlike N, P supplies are finite and irreplaceable. Environmental concerns aside, we can fix all the N2 from the atmosphere we want—but deplete our economically viable P reserves and we're in trouble. Figure 1 Figure 1. Human alteration of the global P cycle has multiple possible boundaries. These include the environmental risks posed by freshwater eutrophication and marine anoxic events, and the food security risks that come from depletion of soil P stocks in some world regions, as well as finite global supplies of high-value mineral P reserves. Photo credits beyond authors: upper left, Shelby Riskin; upper right, Pedro Sanchez. In effect, Carpenter and Bennett argue that among P's multiple boundaries, the one for freshwaters is less forgiving of our current activities (but no less important) than is

  14. Intermediate water links to Deep Western Boundary Current variability in the subtropical NW Atlantic during marine isotope stages 5 and 4

    NASA Astrophysics Data System (ADS)

    Evans, H. K.; Hall, I. R.; Bianchi, G. G.; Oppo, D. W.

    2007-09-01

    Records from Ocean Drilling Program Sites 1057 and 1059 (2584 m and 2985 m water depth, respectively) have been used to reconstruct the behavior of the Deep Western Boundary Current (DWBC) on the Blake Outer Ridge (BOR) from 130 to 60 kyr B.P. (marine isotope stage (MIS) 5 and the 5/4 transition). Site 1057 lies within Labrador Sea Water (LSW) but close to the present-day boundary with Lower North Atlantic Deep Water (LNADW), while Site 1059 lies within LNADW. High-resolution sortable silt mean (?) grain size and benthic δ13C records were obtained, and changes in the DWBC intensity and spatial variability were inferred. Comparisons are made with similar proxy records generated for the Holocene from equivalent depth cores on the BOR. During MIS 5e, ? evidence at Site 1057 suggests slower relative flow speeds consistent with a weakening and a possible shoaling of the LSW-sourced shallower limb of the DWBC that occupies these depths today. In contrast, the paleocurrent record from the deeper site suggests that the fast flowing deep core of the DWBC was located close to its modern depth below 3500 m. During this interval the benthic δ13C suggests little chemical stratification of the water column and the presence of a near-uniform LNADW-dominated water mass. After ˜111 kyr B.P. the ? record at Site 1057 increases to reach values similar to Site 1059 for the rest of MIS 5. The strengthening of flow speeds at the shallow site may correspond to the initiation of Glacial North Atlantic Intermediate Water formation also suggested by a divergence in the benthic δ13C records with Site 1057 values increasing to ˜1.2‰. Coupled suborbital oscillations in DWBC flow variability and paleohydrography persisted throughout MIS 5. Comparison of these data with planktonic δ18O records from the sites and alkenone-derived sea surface temperature (SST) estimates from the nearby Bermuda Rise suggest a hitherto unrecognized degree of linkage between oscillations in subtropical North

  15. Biogeography of the Oceans: a Review of Development of Knowledge of Currents, Fronts and Regional Boundaries from Sailing Ships in the Sixteenth Century to Satellite Remote Sensing

    NASA Astrophysics Data System (ADS)

    Priede, Imants G.

    2014-06-01

    The development of knowledge of global biogeography of the oceans from sixteenthcentury European voyages of exploration to present-day use of satellite remote sensing is reviewed in three parts; the pre-satellite era (1513-1977), the satellite era leading to a first global synthesis (1978-1998), and more recent studies since 1998. The Gulf Stream was first identified as a strong open-ocean feature in 1513 and by the eighteenth century, regular transatlantic voyages by sailing ships had established the general patterns of winds and circulation, enabling optimisation of passage times. Differences in water temperature, water colour and species of animals were recognised as important cues for navigation. Systematic collection of information from ships' logs enabled Maury (The Physical Geography of the Sea Harper and Bros. New York 1855) to produce a chart of prevailing winds across the entire world's oceans, and by the early twentieth century the global surface ocean circulation that defines the major biogeographic regions was well-known. This information was further supplemented by data from large-scale plankton surveys. The launch of the Coastal Zone Color Scanner, specifically designed to study living marine resources on board the Nimbus 7 polar orbiting satellite in 1978, marked the advent of the satellite era. Over subsequent decades, correlation of satellite-derived sea surface temperature and chlorophyll data with in situ measurements enabled Longhurst (Ecological Geography of the Sea. Academic Press, New York 1998) to divide the global ocean into 51 ecological provinces with Polar, Westerly Wind, Trade Wind and Coastal Biomes clearly recognisable from earlier subdivisions of the oceans. Satellite imagery with semi-synoptic images of large areas of the oceans greatly aided definition of boundaries between provinces. However, ocean boundaries are dynamic, varying from season to season and year to year

  16. Boundary Crossing and Boundary Objects

    ERIC Educational Resources Information Center

    Akkerman, Sanne F.; Bakker, Arthur

    2011-01-01

    Diversity and mobility in education and work present a paramount challenge that needs better conceptualization in educational theory. This challenge has been addressed by educational scholars with the notion of "boundaries", particularly by the concepts of "boundary crossing" and "boundary objects". Although studies on boundary crossing and…

  17. Physics of magnetospheric boundary layers

    NASA Technical Reports Server (NTRS)

    Cairns, I. H.

    1993-01-01

    The central ideas of this grant are that the magnetospheric boundary layers link disparate regions of the magnetosphere together, and the global behavior of the magnetosphere can be understood only by understanding the linking mechanisms. Accordingly the present grant includes simultaneous research on the global, meso-, and micro-scale physics of the magnetosphere and its boundary layers. These boundary layers include the bow shock, magnetosheath, the plasma sheet boundary layer, and the ionosphere. Analytic, numerical and simulation projects have been performed on these subjects, as well as comparison of theoretical results with observational data. Very good progress has been made, with four papers published or in press and two additional papers submitted for publication during the six month period 1 June - 30 November 1993. At least two projects are currently being written up. In addition, members of the group have given papers at scientific meetings. The further structure of this report is as follows: section two contains brief accounts of research completed during the last six months, while section three describes the research projects intended for the grant's final period.

  18. Nutrient uplift in a cyclonic eddy increases diversity, primary productivity and iron demand of microbial communities relative to a western boundary current.

    PubMed

    Doblin, Martina A; Petrou, Katherina; Sinutok, Sutinee; Seymour, Justin R; Messer, Lauren F; Brown, Mark V; Norman, Louiza; Everett, Jason D; McInnes, Allison S; Ralph, Peter J; Thompson, Peter A; Hassler, Christel S

    2016-01-01

    The intensification of western boundary currents in the global ocean will potentially influence meso-scale eddy generation, and redistribute microbes and their associated ecological and biogeochemical functions. To understand eddy-induced changes in microbial community composition as well as how they control growth, we targeted the East Australian Current (EAC) region to sample microbes in a cyclonic (cold-core) eddy (CCE) and the adjacent EAC. Phototrophic and diazotrophic microbes were more diverse (2-10 times greater Shannon index) in the CCE relative to the EAC, and the cell size distribution in the CCE was dominated (67%) by larger micro-plankton [Formula: see text], as opposed to pico- and nano-sized cells in the EAC. Nutrient addition experiments determined that nitrogen was the principal nutrient limiting growth in the EAC, while iron was a secondary limiting nutrient in the CCE. Among the diazotrophic community, heterotrophic NifH gene sequences dominated in the EAC and were attributable to members of the gamma-, beta-, and delta-proteobacteria, while the CCE contained both phototrophic and heterotrophic diazotrophs, including Trichodesmium, UCYN-A and gamma-proteobacteria. Daily sampling of incubation bottles following nutrient amendment captured a cascade of effects at the cellular, population and community level, indicating taxon-specific differences in the speed of response of microbes to nutrient supply. Nitrogen addition to the CCE community increased picoeukaryote chlorophyll a quotas within 24 h, suggesting that nutrient uplift by eddies causes a 'greening' effect as well as an increase in phytoplankton biomass. After three days in both the EAC and CCE, diatoms increased in abundance with macronutrient (N, P, Si) and iron amendment, whereas haptophytes and phototrophic dinoflagellates declined. Our results indicate that cyclonic eddies increase delivery of nitrogen to the upper ocean to potentially mitigate the negative consequences of increased

  19. Nutrient uplift in a cyclonic eddy increases diversity, primary productivity and iron demand of microbial communities relative to a western boundary current

    PubMed Central

    Petrou, Katherina; Sinutok, Sutinee; Seymour, Justin R.; Messer, Lauren F.; Brown, Mark V.; Norman, Louiza; Everett, Jason D.; McInnes, Allison S.; Ralph, Peter J.; Thompson, Peter A.; Hassler, Christel S.

    2016-01-01

    The intensification of western boundary currents in the global ocean will potentially influence meso-scale eddy generation, and redistribute microbes and their associated ecological and biogeochemical functions. To understand eddy-induced changes in microbial community composition as well as how they control growth, we targeted the East Australian Current (EAC) region to sample microbes in a cyclonic (cold-core) eddy (CCE) and the adjacent EAC. Phototrophic and diazotrophic microbes were more diverse (2–10 times greater Shannon index) in the CCE relative to the EAC, and the cell size distribution in the CCE was dominated (67%) by larger micro-plankton \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$(\\geq 20\\lrm{\\mu }\\mathrm{m})$\\end{document}≥20μm, as opposed to pico- and nano-sized cells in the EAC. Nutrient addition experiments determined that nitrogen was the principal nutrient limiting growth in the EAC, while iron was a secondary limiting nutrient in the CCE. Among the diazotrophic community, heterotrophic NifH gene sequences dominated in the EAC and were attributable to members of the gamma-, beta-, and delta-proteobacteria, while the CCE contained both phototrophic and heterotrophic diazotrophs, including Trichodesmium, UCYN-A and gamma-proteobacteria. Daily sampling of incubation bottles following nutrient amendment captured a cascade of effects at the cellular, population and community level, indicating taxon-specific differences in the speed of response of microbes to nutrient supply. Nitrogen addition to the CCE community increased picoeukaryote chlorophyll a quotas within 24 h, suggesting that nutrient uplift by eddies causes a ‘greening’ effect as well as an increase in phytoplankton biomass. After three days in both the EAC and CCE, diatoms

  20. Studies of microstructure/critical current density relationships for grain boundaries in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} bicrystals

    SciTech Connect

    Babcock, S.E.; Cai, Xue-Yu; Larbalestier, D.C.; Shin, D.H.; Zhang, Na; Gao, Yufei; Merkle, K.L.; Kaiser, D.L.; Zhang, Hong

    1992-11-01

    Results of coupled electromagnetic and microstructural studies of bicrystalline YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} specimens are described from a microstructural perspective. High-spatial-resolution transmission electron microscopy techniques (imaging and energy dispersive x-ray microanalysis) are used to probe the structure and composition of the grain boundaries. All of the boundaries studied possess microstructural features that are consistent with their specific electromagnetic character.

  1. Fundamental studies of grain boundary passivation in polycrystalline silicon with application to improved photovoltaic devices. A final research report covering work completed from February-December 1979

    SciTech Connect

    Seager, C.H.; Ginley, D.S.

    1980-02-01

    Several aspects of the electrical properties of silicon grain boundaries have been studied. The temperature dependence of the zero-bias conductance and capacitance of single boundaries has been measured and shown to be in good agreement with a simple double depletion layer/thermal emission (DDL/TE) model developed to predict the transport properties of such structures. In addition, it has been shown that deconvolution of the I-V properties of some boundaries via a deconvolution scheme suggested by Pike and Seager yields effective one-electron densities of trapping states which are in good agreement with estimates obtained by low temperature electron emission measurements. Experiments have also been performed which indicate that diffusion of atomic hydrogen into silicon grain boundaries greatly reduces this density of trapping states. In properly prepared, large grained polycrystalline samples all measurable traces of grain boundary potential barriers can be removed to substantial penetration depths after several hours exposure to a hydrogen plasma at elevated temperatures. Initial experiments on prototype polysilicon solar cells have shown that this passivation process can improve AM1 efficiencies. In order to more fully understand and develop this process for improving practical multigrained cells, several device research efforts with other DOE/SERI funded contractors have been initiated.

  2. Boundary issues

    NASA Astrophysics Data System (ADS)

    Townsend, Alan R.; Porder, Stephen

    2011-03-01

    -centric boundary (Filippelli 2008, Handoh and Lenton 2003). However, human alteration of the P cycle has multiple potential boundaries (figure 1), including P-driven freshwater eutrophication (Smith and Schindler 2009), the potential for world P supply to place an ultimate limit on food production (Smil 2000, Childers et al 2011), and depletion of soil P stocks in some world regions (MacDonald et al 2011). Carpenter and Bennett revisit the P boundary from the freshwater eutrophication perspective. Given the extraordinary variation in freshwater ecosystems across the globe, this is a challenging task, but the authors strengthen their analysis by using three different boundaries with relevance to eutrophication, along with two water quality targets and a range of estimates of P flow to the sea. In doing so, they make a compelling case that if freshwater eutrophication is indeed a Rubicon, we have already crossed it. Importantly, Carpenter and Bennett go beyond the calculation of new boundaries to make broader points about humanity's relationship with the P cycle. Disruptions of both the P and N cycles are mostly about our need for food (Galloway et al 2008, Cordell et al 2009), but unlike N, P supplies are finite and irreplaceable. Environmental concerns aside, we can fix all the N2 from the atmosphere we want—but deplete our economically viable P reserves and we're in trouble. Figure 1 Figure 1. Human alteration of the global P cycle has multiple possible boundaries. These include the environmental risks posed by freshwater eutrophication and marine anoxic events, and the food security risks that come from depletion of soil P stocks in some world regions, as well as finite global supplies of high-value mineral P reserves. Photo credits beyond authors: upper left, Shelby Riskin; upper right, Pedro Sanchez. In effect, Carpenter and Bennett argue that among P's multiple boundaries, the one for freshwaters is less forgiving of our current activities (but no less important) than is

  3. Coastal flooding and storm protection program; field verification program. Mathematical modeling of three-dimensional coastal currents and sediment dispersion: model development and application. Final report

    SciTech Connect

    Sheng, Y.P.

    1983-09-01

    A comprehensive model of Coastal currents and sediment dispersion has been formulated and applied to the Mississippi Sound and adjacent continental shelf waters. The study combines mathematical modeling of various hydrodynamic and sedimentary processes with laboratory and field experiments. Of primary importance is the development of an efficient and comprehensive three-dimensional, finite-difference model of coastal, estuarine, and lake currents (CELC3D). The model resolves currents driven by tide, wind, and density gradient. It has been applied to the Mississippi Sound, and results agree well with measured surface displacements and currents during two episodes. Rates of entrainment and deposition of the Mississippi Sound sediments have been studied in a laboratory flume. Effects of (1) bottom shear stress, (2) bed properties, (3) salinity of water, and (4) sediment type on the erodability of sediments have been examined. Results of the laboratory study have been incorporated into the bottom boundary conditions for a three-dimensional sediment dispersion model. Gravitational settling and particle size distribution of the Mississippi Sound sediments were also studied in laboratories. Bottom boundary layer dynamics and wave effect on sediment dispersion have been studied by means of a turbulent transport model and a wave model. Model simulations of sediment dispersion in the Mississippi Sound agree well available data from ship surveys.

  4. Ground boundaries

    SciTech Connect

    Balluffi, R.W.; Bristowe, P.D.

    1990-01-01

    The present document is a progress report describing the work accomplished on the study of grain boundaries in Ag, Au, Ni, Si, and Ge. Research was focused on the following four major efforts: study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; grain boundary migration; short-circuit diffusion along grain boundaries; and development of Thin-Film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals. 10 refs., 1 fig.

  5. Assessment of Alternative Student and Delivery Systems: Assessment of the Current Delivery System. Supplement I to the Final Report.

    ERIC Educational Resources Information Center

    Advanced Technology, Inc., Reston, VA.

    The effects of the current student financial aid delivery system on five major participant groups are examined: federal government, states/guarantee agencies, postsecondary institutions, lenders and secondary markets, and applicants and families. Attention is directed to effects of the current system, including: administrative costs, fund…

  6. Advanced development of the boundary element method for elastic and inelastic thermal stress analysis. Ph.D. Thesis, 1987 Final Report

    NASA Technical Reports Server (NTRS)

    Henry, Donald P., Jr.

    1991-01-01

    The focus of this dissertation is on advanced development of the boundary element method for elastic and inelastic thermal stress analysis. New formulations for the treatment of body forces and nonlinear effects are derived. These formulations, which are based on particular integral theory, eliminate the need for volume integrals or extra surface integrals to account for these effects. The formulations are presented for axisymmetric, two and three dimensional analysis. Also in this dissertation, two dimensional and axisymmetric formulations for elastic and inelastic, inhomogeneous stress analysis are introduced. The derivatives account for inhomogeneities due to spatially dependent material parameters, and thermally induced inhomogeneities. The nonlinear formulation of the present work are based on an incremental initial stress approach. Two inelastic solutions algorithms are implemented: an iterative; and a variable stiffness type approach. The Von Mises yield criterion with variable hardening and the associated flow rules are adopted in these algorithms. All formulations are implemented in a general purpose, multi-region computer code with the capability of local definition of boundary conditions. Quadratic, isoparametric shape functions are used to model the geometry and field variables of the boundary (and domain) of the problem. The multi-region implementation permits a body to be modeled in substructured parts, thus dramatically reducing the cost of analysis. Furthermore, it allows a body consisting of regions of different (homogeneous) material to be studied. To test the program, results obtained for simple test cases are checked against their analytic solutions. Thereafter, a range of problems of practical interest are analyzed. In addition to displacement and traction loads, problems with body forces due to self-weight, centrifugal, and thermal loads are considered.

  7. Burial, remineralization and utilization of organic matter at the sea floor under a strong western boundary current. Final report, May 1, 1992--April 30, 1995

    SciTech Connect

    Jahnke, R.A.

    1995-08-24

    The overall goals of this project were to quantify the rates of organic carbon export from the southern mid-Atlantic Bight and to quantify the rates at which carbon is exchanged between the inorganic and organic pools within the bottom sediments. This information is necessary to constrain the role of the oceans in the control of carbon dioxide released to the atmosphere in association with energy production. During this project, in situ benthic flux chamber incubations have been performed at six sites on the continental slope and rise adjacent to Cape Hatteras. Based on the analysis of the time-series samples recovered during each experiment, the sea floor exchange rates of the major biogenic elements, oxygen, carbon, nitrogen, phosphorus and silicon were calculated. From the estimated benthic flux rates and the ancillary pore water and sediment analyses, the deposition, remineralization and burial rates of organic carbon to the sea floor in this area was evaluated. This information has been incorporated into regional and global assessments of organic carbon fluxes to the deep sea.

  8. Experimental and theoretical investigation of three-dimensional turbulent boundary layers and turbulence characteristics inside an axial flow inducer passage. Final Report. Ph.D. Thesis, Jun. 1971

    NASA Technical Reports Server (NTRS)

    Anand, A. K.; Lakshminarayana, B.

    1977-01-01

    Analytical and experimental investigations of the characteristics of three dimensional turbulent boundary layers in a rotating helical passage of an inducer rotor are reported. Expressions are developed for the velocity profiles in the inner layer, where the viscous effects dominate, in the outer layer, where the viscous effects are small, and in the interference layer, where the end walls influence the flow. The prediction of boundary layer growth is based on the momentum integral technique. The equations derived are general enough to be valid for all turbomachinery rotors with arbitrary pressure gradients. The experimental investigations are carried out in a flat plate inducer 3 feet in diameter. The mean velocity profiles, turbulence intensities and shear stresses, wall shear stress, and limiting streamline angles are measured at various radial and chordwise locations by using rotating probes. The measurements are in general agreement with the predictions. The radial flows are well represented by an expression which includes the effect of stagger angle and radial pressure gradient. The radial flows in the rotor channel are higher than those on a single blade. The collateral region exists only very near the blade surface. The radial component of turbulence intensity is higher than the streamwise component because of the effect of rotation.

  9. Currents induced in a human being for electromagnetic fields 10 kHz-50 MHz. Final report

    SciTech Connect

    Gandhi, O.P.

    1988-01-15

    The two tasks undertaken during the period of this project are: 1. Development of a high-resolution thermal model of the human leg and its use to estimate the temperature distribution as a result of the induced high current densities at radio frequencies. 2. Development of a high-resolution, anatomically-realistic, inhomogeneous model of man and its use to calculate the SAR and induced current distributions for frequencies to 100 MHz. It was previously shown that vertically polarized incident plane waves are capable of inducing fairly significant r-f currents in a free-standing human being. Foot currents were found to be proportional to the frequency of incident radiation for the frequency band 0-40 Mega Hz with values as high as 12.7 milli A/(V/m) measured for adult human volunteers at 40 MHz. Recognizing that the induced current is divided equally between the two legs on its way to the ground underneath, fairly high current densities result in the various cross sections of the leg with concommitant high rates of energy deposition (SAR). In particular, due to the predominantly bony nature of the ankle cross section forcing the RF current to flow in an effective 9.5-cm/sup 2/ cross section of the high-conductivity tissues, very high current densities (J) and the resulting SARs are set up. These SARs are almost two orders of magnitude larger than the metabolic rates of the tissues and considerably in excess of the ANSI guideline of 8 W/kg for any 1 g of tissue.

  10. Boundary Layer

    NASA Technical Reports Server (NTRS)

    Loitsianskii. L. G.

    1956-01-01

    The fundamental, practically the most important branch of the modern mechanics of a viscous fluid or a gas, is that branch which concerns itself with the study of the boundary layer. The presence of a boundary layer accounts for the origin of the resistance and lift force, the breakdown of the smooth flow about bodies, and other phenomena that are associated with the motion of a body in a real fluid. The concept of boundary layer was clearly formulated by the founder of aerodynamics, N. E. Joukowsky, in his well-known work "On the Form of Ships" published as early as 1890. In his book "Theoretical Foundations of Air Navigation," Joukowsky gave an account of the most important properties of the boundary layer and pointed out the part played by it in the production of the resistance of bodies to motion. The fundamental differential equations of the motion of a fluid in a laminar boundary layer were given by Prandtl in 1904; the first solutions of these equations date from 1907 to 1910. As regards the turbulent boundary layer, there does not exist even to this day any rigorous formulation of this problem because there is no closed system of equations for the turbulent motion of a fluid. Soviet scientists have done much toward developing a general theory of the boundary layer, and in that branch of the theory which is of greatest practical importance at the present time, namely the study of the boundary layer at large velocities of the body in a compressed gas, the efforts of the scientists of our country have borne fruit in the creation of a new theory which leaves far behind all that has been done previously in this direction. We shall herein enumerate the most important results by Soviet scientists in the development of the theory of the boundary layer.

  11. Grain boundaries

    SciTech Connect

    Balluffi, R.W.; Bristowe, P.D.

    1991-01-01

    The present document is a progress report describing the work accomplished to date during the second year of our four-year grant (February 15, 1990--February 14, 1994) to study grain boundaries. The research was focused on the following three major efforts: Study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; study of short-circuit diffusion along grain boundaries; and development of a Thin-film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  12. Corrosion protection of Arctic offshore structures: Final report. [Effects of temperature and salinity on required cathodic protection current

    SciTech Connect

    Sackinger, W.M.; Rogers, J.C.; Feyk, C.; Theuveny, B.

    1985-10-01

    Results are presented for a research program on corrosion prevention for Arctic offshore structures which are in contact with sea ice for a significant portion of the year. The electrical method most adaptable for structure protection involves the injection of impressed current from several remote anodes buried just beneath the sea floor. The electrical resistivity of annual sea ice as a function of temperature and salinity is presented. Details of the interface layers formed between sea ice and steel in the presence of current injection are shown. A computer program was developed to enable the calculation of protective current density into the structure, in the presence of ice rubble and ridges around the structure. The program and the results of an example calculation are given for a caisson- retained island structure. 81 refs., 103 figs., 3 tabs.

  13. Testing an e2v CCD230-42 sensor for dark current performance at ambient temperatures - Final Paper

    SciTech Connect

    Dungee, Ryan

    2015-08-20

    The design of the Guidance Focus and Alignment (GFA) system for the Dark Energy Spectroscopic Instrument (DESI) project calls for a set of charge-coupled devices (CCDs) which operate at ambient temperature. Here we assess the performance of these CCDs under such conditions. Data was collected from –21°C to 28°C and used to determine the effect of temperature on the effectiveness of dark current subtraction. Comparing the dark current uncertainty to our expected signal has shown that the DESI design specifications will be met without need for significant changes.

  14. Current collection from the space plasma through defects in high voltage solar array insulation. Ph.D. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Stillwell, R. P.

    1983-01-01

    For spacecraft operation in the near Earth environment, solar cell arrays constitute the major source of reliable long term power. Optimization of mass and power efficiency results in a general requirement for high voltage solar arrays. The space plasma environment, though, can result in large currents being collected by exposed solar cells. The solution of a protective covering of transparent insulation is not a complete solution, inasmuch as defects in the insulation result in anomalously large currents being collected through the defects. Tests simulating the electron collection from small defects in an insulation have shown that there are two major collection modes. The first mode involves current enhancement by means of a surface phenomenon involving the surrounding insulator. In the second mode the current collection is enhanced by vaporization and ionization of the insulators materials, in addition to the surface enhancement of the first mode. A model for the electron collection is the surface enhanced collection mode was developed. The model relates the secondary electron emission yield to the electron collection. It correctly predicts the qualitative effects of hole size, sample temperature and roughening of sample surface. The theory was also shown to predict electron collection within a factor of two for the polymers teflon and polyimide.

  15. Assessment of Alternative Student Aid Delivery Systems: Specification of the Current System. Supplement II to the Final Report.

    ERIC Educational Resources Information Center

    Advanced Technology, Inc., Reston, VA.

    Specifications of the current student financial aid system, with attention to the Pell Grant, Guaranteed Student Loan (GSL), and campus-based programs, are provided. The methodology used to develop the specifications is also described. The campus-based programs include the Supplemental Educational Opportunity Grant Program, the College Work Study…

  16. Final Report Providing the Design for Low-Cost Wireless Current Transducer and Electric Power Sensor Prototype

    SciTech Connect

    Kintner-Meyer, Michael CW; Burghard, Brion J.; Reid, Larry D.

    2005-01-31

    This report describes the design and development of a wireless current transducer and electric power sensor prototype. The report includes annotated schematics of the power sensor circuitry and the printed circuit board. The application program used to illustrate the functionality of the wireless sensors is described in this document as well.

  17. Review and Evaluation of Current Training Programs Found in Various Mining Environments. Final Report. Volume I, Summary.

    ERIC Educational Resources Information Center

    Adkins, John; And Others

    A project was designed to produce a broad description of current mining training programs and to evaluate their effectiveness with respect to reducing mine injuries. The research strategy was built on the ranking of mines according to the effectiveness of their training with an effective training effort being defined as that training which is…

  18. Review and Evaluation of Current Training Programs Found in Various Mining Environments. Final Report. Volume II, Analysis and Recommendations.

    ERIC Educational Resources Information Center

    Adkins, John; And Others

    A project was designed to produce a broad description of current mining training programs and to evaluate their effectiveness with respect to reducing mine injuries. Aggregate training and injury data were used to evaluate the overall training effort at 300 mines as well as specific efforts in 12 categories of training course objectives. From such…

  19. The development of an ultralow frequency eddy current instrument for the detection and sizing of stress corrosion cracks: Final report

    SciTech Connect

    Hayford, D.T.

    1988-05-04

    Eddy current testing has received only limited application to ferrous materials because the high permeability of the material in combination with the normally high frequency of the eddy current instrument results in a very small depth of penetration of the eddy currents into the material. The objectives of this research program were threefold. The first goal was to develop an eddy current instrument with frequencies low enough to penetrate pipeline steel. The second was to use the new instrument to develop techniques for locating stress-corrosion cracks (SCC) on coated pipelines without requiring the removal of the coating. Our last goal was to develop methods of characterizing SCC, i.e., determining the lengths and depths of the defects. We accomplished two out of these three goals; we were able to build the instrument and use it to detect SCC in pipelines. Simple defect characterization algorithms (measuring defect length and depth) have been more difficult to develop. At present we can estimate the depth of ''long'' defects (relative to the coil diameter) but have problems with shorter ones. 24 figs.

  20. Ultrahigh-current-density metal-ion implantation and diamondlike-hydrocarbon films for tribological applications; Final report

    SciTech Connect

    Wilbur, P.J.

    1993-09-01

    The metal-ion-implantation system used to implant metals into substrates are described. The metal vapor required for operation is supplied by drawing sufficient electron current from the plasma discharge to an anode-potential crucible so a solid, pure metal placed in the crucible will be heated to the point of vaporization. The ion-producing, plasma discharge is initiated within a graphite-ion-source body, which operates at high temperature, by using an argon flow that is turned off once the metal vapor is present. Extraction of ion beams several cm in diameter at current densities ranging to several hundred {mu}A/cm{sup 2} on a target 50 cm downstream of the ion source have been demonstrated using Mg, Ag, Cr, Cu, Si, Ti, V, B and Zr. These metals were implanted into over 100 substrates (discs, pins, flats, wires). A model describing thermal stresses induced in materials (e.g. ceramic plates) during high-current-density implantation is presented. Tribological and microstructural characteristics of iron and 304-stainless-steel samples implanted with Ti or B are examined. Diamondlike-hydrocarbon coatings were applied to steel surfaces and found to exhibit good tribological performance.

  1. Development of a two-beam high-current ion accelerator based on Doppler effect. Final report (1994)

    SciTech Connect

    Ivanov, B.I.; Yegorov, A.M.

    1995-03-01

    This Final Report presents the results of work accomplished in accordance with the Scope of Work to the Purchase Order No 4596310. The amount of works includes the following items: 1. Start of the manufacture of the Experimental Accelerating Stand (EAS)-the section for proton acceleration from 5 MeV to 8 MeV, in which RF fields are excited by an electron beam at the anomalous Doppler effect. 2. Theoretical investigation and computer simulation of field excitation and ion acceleration in the EAS. Under item 1, the EAS manufacturing is begun. To present time, a pedestal for the EAS and a stainless steel vacuum chamber for RF resonator are made (length of the chamber is about 180 cm, diameter is about 40 cm). Besides, parts of the EAS resonator with the acceleration structure are manufactured, and its assembly is begun. Under item 2, it is realized three works: calculation of increment and frequency shift of the EAS resonator excited by electron beam, calculation of the solenoid for creation of magnetic field with required spatial distribution, and theoretical investigation and computer simulation of ion acceleration in the EAS. 14 figs., 16 refs.

  2. Combustion of pulverized coal in counter-current flow. [Final report], December 7, 1988--April 30, 1991

    SciTech Connect

    Timnat, Y.M.; Goldman, Y.

    1991-12-31

    In this report we describe the results obtained with two prototypes of pulverized coal combustors operating in counter-current flow, one at atmospheric pressure, the other at higher pressure and compare them to the predictions of a theoretical-numerical model, we have developed. The first prototype treats a vertical configuration, eight times larger than the one treated before (Hazanov et al. 1985), while in the second a horizontal arrangement with a smaller volume is studied. Attention was focused on particle trajectories, burnout, angle of injection, ash separation by rotational motion, effects of initial particle size and temperature, impingement velocity and the effect of gravity. Main development activity was directed to achieving stable and reliable coal burning in the combustors.

  3. (abstract) Experimental and Modeling Studies of the Exchange Current at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kikkert, S.

    1993-01-01

    The microscopic mechanism of the alkali ion-electron recombination reaction at the three phase boundary zone formed by a porous metal electrode in the alkali vapor on the surface of an alkali beta'-alumina solid electrolyte (BASE) ceramic has been studied by comparison of the expected rates for the three simplest reaction mechanisms with known temperature dependent rate data; and the physical parameters of typical porous metal electrode/BASE/alkali metal vapor reaction zones. The three simplest reactions are tunneling of electrons from the alkali coated electrode to a surface bound alkali metal ion; emission of an electron from the electrode with subsequent capture by a surface bound alkali metal ion; and thermal emission of an alkali cation from the BASE and its capture on the porous metal electrode surface where it may recombine with an electron. Only the first reaction adequately accounts for both the high observed rate and its temperature dependence. New results include crude modeling of simple, one step, three phase, solid/solid/gas electrochemical reaction.

  4. SUPPLEMENTARY COMPARISON: Final report EUROMET.EM-S11 on EUROMET Projects 473 and 612: Comparison of the measurement of current transformers (CTs)

    NASA Astrophysics Data System (ADS)

    Harmon, Stuart; Henderson, Lesley

    2009-01-01

    The Euromet comparison entitled 'Comparison of the measurement of current transformers' was carried out over two projects with NPL as pilot laboratory and thirteen other participating European National Measurement Institutes (NMI). Current transformer measurements made by the participating NMIs support a large number of measurements made in the electrical generation, supply and distribution industries in their own countries. They also support many transformer manufacturers who rely on national standards as a source of traceability. The current (ratio) errors and phase displacement of each ratio of the uncompensated current transformer transfer standard were determined at a defined frequency, burden and power factor, using each participant's standard measuring method and equipment. The results supplied by each participant generally show good agreement but with a few exceptions over the whole range of measured values. Deviations from the comparison reference value were mostly within the quoted uncertainties, but again with a few exceptions. A summary of outlying results compared to laboratories' declared Calibration and Measurement Capabilities (CMC) is given in the conclusion. In several cases participants have been making current transformer measurements with new measurement systems and techniques, and in one case for the first time; therefore a large amount of experience in the measurement and interpretation of results has been obtained from this comparison. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

  5. Modeling the response of the California Current system to global greenhouse warming. Final report to the National Institute for Global Environmental Change (August 1993)

    SciTech Connect

    Pares-Sierra, A.; Somerville, R.C.J.

    1993-12-31

    This is the final report for the project ``Modeling the Response of the California Current System to Global Greenhouse Warming,`` supported 1990 and 1991 by NIGEC. The scientists involved are Dr. Richard C.J. Somerville and Alejandro Paries-Sierra of Scripps Institution of Oceanography, UCSD. A copy of papers submitted to the Journal of Physical Oceanography, and Geofisica Internacional that were supported in part or whole by WEST-GEC, as well as a summary of a talk delivered at the XX General Assembly of the IUGG, Vienna (1991) are appended to this report. The objective of the research was to improve the understanding of the response of the California Current system to the large-scale anomalous forcing thought to be associated with greenhouse warming. The authors viewed this as a necessary initial step in the study of the California climate response to global change.

  6. Current plate boundary deformation of the Afar rift from a 3-D velocity field inversion of InSAR and GPS

    NASA Astrophysics Data System (ADS)

    Pagli, Carolina; Wang, Hua; Wright, Tim J.; Calais, Eric; Lewi, Elias

    2014-11-01

    Extension, faulting, and magmatism are the main controls on the magnitude and localization of strain at mid-ocean ridges. However, the temporal and spatial patterns of such processes are not clear since the strain distribution has not been resolved in the past at sufficient spatial resolution and over extended areas. Interferometric synthetic aperture radar (InSAR) and GPS data with unprecedented resolution are now available to us from the Afar rift of Ethiopia. Here we use a velocity field method to combine InSAR and GPS to form the first high-resolution continuous three-dimensional velocity field of Afar. We study an area that is 500 km wide and 700 km long, covering three branches of the Afar continental rift and their triple junctions. Our velocity field shows that plate spreading is currently achieved in Afar in contrasting modes. A transient postdiking deformation is focused at the Dabbahu rift segment, while in central Afar, spreading is distributed over several overlapping segments and southern Afar exhibits an interdiking deformation pattern focused at the Asal-Ghoubbet segment. We find that current spreading rates at Dabbahu, following the 2005-2010 intrusions, are up to 110 mm/yr, 6 times larger than the long-term plate divergence. A segment-centered uplift of up to 80 mm/yr also occurs, indicating that magma flow is still a primary mechanism of deformation during postdiking. On the other hand, no vertical displacements are currently observed in central and southern Afar, suggesting lack of significant magmatic activity at shallow levels.

  7. Final report on RMO comparison SIM.EM-S10: High value resistance comparison with two-terminal cryogenic current comparators

    NASA Astrophysics Data System (ADS)

    Bierzychudek, Marcos E.; Elmquist, Randolph; Hernández, Felipe

    2014-01-01

    This work presents a supplementary comparison of high value resistance standards performed during 2012 and January 2013, following the guidelines presented in a document about measurement comparisons in the CIPM MRA. The purpose of this task was to compare the high resistance cryogenic current comparator scaling of the participating institutes: National Institute of Standards and Technology, USA (NIST), Centro Nacional de Metrología, Mexico (CENAM) and Instituto Nacional de Tecnología Industrial, Argentina (INTI), all of which are members of the Sistema Interamericano de Metrología (SIM) Regional Metrology Organization. All the measurements of this comparison were performed with two-terminal cryogenic current comparators (CCC). Degrees of equivalence of the participating institutes relative to the comparison reference values are given in the report for the measured resistance values. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by SIM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  8. Albedo Boundary

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-510, 11 October 2003

    The sharp, nearly straight line that runs diagonally across the center of this April 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is an albedo boundary. Albedois a term that refers to reflectance of sunlight. A surface with a low albedo is one that appears dark because it reflects less light than a high albedo (bright) surface. On Mars, albedo boundaries occur between two materials of differing texture, particle size, or composition, or some combination of these three factors. The boundary shown here is remarkable because it is so sharp and straight. This is caused by wind. Most likely, the entire surface was once covered with the lower-albedo (darker) material that is now seen in the upper half of the image. At some later time, wind stripped away this darker material from the surfaces in the lower half of the image. The difference in albedo here might be related to composition, and possibly particle size. This picture is located near the southwest rim of Schiaparelli Basin at 5.5oS, 345.9oW. The picture covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the left.

  9. Chemical Speciation of Sulfur in Marine Cloud Droplets and Particles: Analysis of Individual Particles from Marine Boundary Layer over the California Current

    SciTech Connect

    William R. Wiley Environmental Sciences Laboratory, Pacific Northwest National Laboratory; Gilles, Mary K; Hopkins, Rebecca J.; Desyaterik, Yury; Tivanski, Alexei V.; Zaveri, Rahul A.; Berkowitz, Carl M.; Tyliszczak, Tolek; Gilles, Mary K.; Laskin, Alexander

    2008-03-12

    Detailed chemical speciation of the dry residue particles from individual cloud droplets and interstitial aerosol collected during the Marine Stratus Experiment (MASE) was performed using a combination of complementary microanalysis techniques. Techniques include computer controlled scanning electron microscopy with energy dispersed analysis of X-rays (CCSEM/EDX), time-of-flight secondary ionization mass spectrometry (TOF-SIMS), and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Samples were collected at the ground site located in Point Reyes National Seashore, approximately 1 km from the coast. This manuscript focuses on the analysis of individual particles sampled from air masses that originated over the open ocean and then passed through the area of the California current located along the northern California coast. Based on composition, morphology, and chemical bonding information, two externally mixed, distinct classes of sulfur containing particles were identified: chemically modified (aged) sea salt particles and secondary formed sulfate particles. The results indicate substantial heterogeneous replacement of chloride by methanesulfonate (CH3SO3-) and non-sea salt sulfate (nss-SO42-) in sea-salt particles with characteristic ratios of nss-S/Na>0.10 and CH3SO3-/nss-SO42->0.6.

  10. The atmospheric boundary layer

    SciTech Connect

    Garratt, J.R.

    1992-01-01

    This book is aimed at researchers in the atmospheric and associated sciences who require a moderately advanced text on the Atmospheric Boundary Layer (ABL) in which the many links between turbulence, air-surface transfer, boundary-layer structure and dynamics, and numerical modeling are discussed and elaborated upon. Chapter 1 serves as an introduction, with Chapters 2 and 3 dealing with the development of mean and turbulence equations, and the many scaling laws and theories that are the cornerstone of any serious ABL treatment. Modelling of the ABL is crucially dependent for its realism on the surface boundary conditions, and Chapters 4 and 5 deal with aerodynamic and energy considerations, with attention to both dry and wet land surfaces and the sea. The structure of the clear-sky, thermally stratified ABL is treated in Chapter 6, including the convective and stable cases over homogeneous land, the marine ABL and the internal boundary layer at the coastline. Chapter 7 then extends the discussion to the cloudy ABL. This is seen as particularly relevant since the extensive stratocumulus regions over the sub-tropical oceans and stratus regions over the Arctic are now identified as key players in the climate system. Finally, Chapters 8 and 9 bring much of the book's material together in a discussion of appropriate ABL and surface parameterization schemes for the general circulation models of the atmosphere that are being used for climate simulation.

  11. Chemical Speciation of Sulfur in Marine Cloud Droplets and Particles: Analysis of Individual Particles from the Marine Boundary Layer Over the California Current

    SciTech Connect

    Hopkins, Rebecca J; Desyaterik, Yury; Tivanski, Alexei V; Zaveri, Rahul A; Berkowitz, Carl M; Tyliszczak, T; Gilles, Marry K; Laskin, Alexander

    2008-02-27

    Detailed chemical speciation of the dry residue particles from individual cloud droplets and interstitial aerosol collected during the Marine Stratus Experiment (MASE) was performed using a complementary combination of microanalysis techniques. Techniques include computer controlled scanning electron microscopy with energy dispersed analysis of X-rays (CCSEM/EDX), time-of-flight secondary ionization mass spectrometry (TOFSIMS), and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Samples were collected at the ground site located in Point Reyes National Seashore, approximately 1 km from the coast. This manuscript focuses on the analysis of individual particles sampled from an air mass that originated over the open ocean and then passed through the area of the California current located along the northern California coast. Based on composition, morphology, and chemical bonding information, two externally mixed, distinct classes of sulfur containing particles were identified: chemically modified (aged) sea salt particles and secondary formed sulfate particles. The results indicate substantial heterogeneous replacement of chloride by methanesulfonate (CH3SO3-) and non-sea salt sulfate (nss-SO42-) in sea-salt particles with the characteristic ratios of CH3SO3-/nss-SO42-> 0.6. Although this value seems too high for a mid-latitude site, our model calculations suggest that high CH3SO3-/nss-SO42- ratios are expected during the early stages of dimethyl sulfide (DMS) oxidation when CH3SO3H forms more rapidly than H2SO4.

  12. Evidence for composition variations and impurity segregation at grain boundaries in high current-density polycrystalline K- and Co-doped BaFe{sub 2}As{sub 2} superconductors

    SciTech Connect

    Kim, Yoon-Jun; Weiss, Jeremy D.; Hellstrom, Eric E.; Larbalestier, David C.; Seidman, David N.

    2014-10-20

    Some polycrystalline forms of the K- and Co-doped BaFe{sub 2}As{sub 2} and SrFe{sub 2}As{sub 2} superconductors now have a critical current density (J{sub c}) within a factor of ∼5 of that required for real applications, even though it is known that some grain boundaries (GBs) block current, thus, raising the question of whether this blocking is intrinsic or extrinsically limited by artefacts amenable to improvement by better processing. Herein, we utilize atom-probe tomography (APT) to study the grain and GB composition in high J{sub c} K- and Co-doped BaFe{sub 2}As{sub 2} polycrystals. We find that all GBs studied show significant compositional variations on the scale of a few coherence lengths (ξ), as well as strong segregation of oxygen impurities, which we believe are largely introduced in the starting materials. Importantly, these findings demonstrate that APT enables quantitative analysis of the highest J{sub c} K-doped BaFe{sub 2}As{sub 2} samples, where analytical transmission electron microscopy (TEM) fails because of the great reactivity of thin TEM samples. The observations of major chemical perturbations at GBs make us cautiously optimistic that there is a large extrinsic component to the GB current blocking, which will be ameliorated by better processing, for which APT will likely be a crucial instrument.

  13. Dimension of fractal basin boundaries

    SciTech Connect

    Park, B.S.

    1988-01-01

    In many dynamical systems, multiple attractors coexist for certain parameter ranges. The set of initial conditions that asymptotically approach each attractor is its basin of attraction. These basins can be intertwined on arbitrary small scales. Basin boundary can be either smooth or fractal. Dynamical systems that have fractal basin boundary show final state sensitivity of the initial conditions. A measure of this sensitivity (uncertainty exponent {alpha}) is related to the dimension of the basin boundary d = D - {alpha}, where D is the dimension of the phase space and d is the dimension of the basin boundary. At metamorphosis values of the parameter, there might happen a conversion from smooth to fractal basin boundary (smooth-fractal metamorphosis) or a conversion from fractal to another fractal basin boundary characteristically different from the previous fractal one (fractal-fractal metamorphosis). The dimension changes continuously with the parameter except at the metamorphosis values where the dimension of the basin boundary jumps discontinuously. We chose the Henon map and the forced damped pendulum to investigate this. Scaling of the basin volumes near the metamorphosis values of the parameter is also being studied for the Henon map. Observations are explained analytically by using low dimensional model map.

  14. Final Report

    SciTech Connect

    Gurney, Kevin R

    2015-01-12

    This document constitutes the final report under DOE grant DE-FG-08ER64649. The organization of this document is as follows: first, I will review the original scope of the proposed research. Second, I will present the current draft of a paper nearing submission to Nature Climate Change on the initial results of this funded effort. Finally, I will present the last phase of the research under this grant which has supported a Ph.D. student. To that end, I will present the graduate student’s proposed research, a portion of which is completed and reflected in the paper nearing submission. This final work phase will be completed in the next 12 months. This final workphase will likely result in 1-2 additional publications and we consider the results (as exemplified by the current paper) high quality. The continuing results will acknowledge the funding provided by DOE grant DE-FG-08ER64649.

  15. Boundary dynamics in landscapes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Landscapes consist of a mosaic of distinct vegetation types and their intervening boundaries with distinct characteristics. Boundaries can exist along abrupt environmental gradients or along gradual changes that are reinforced by feedback mechanisms between plants and soil properties. Boundaries can...

  16. Event boundaries and anaphoric reference.

    PubMed

    Thompson, Alexis N; Radvansky, Gabriel A

    2016-06-01

    The current study explored the finding that parsing a narrative into separate events impairs anaphor resolution. According to the Event Horizon Model, when a narrative event boundary is encountered, a new event model is created. Information associated with the prior event model is removed from working memory. So long as the event model containing the anaphor referent is currently being processed, this information should still be available when there is no narrative event boundary, even if reading has been disrupted by a working-memory-clearing distractor task. In those cases, readers may reactivate their prior event model, and anaphor resolution would not be affected. Alternatively, comprehension may not be as event oriented as this account suggests. Instead, any disruption of the contents of working memory during comprehension, event related or not, may be sufficient to disrupt anaphor resolution. In this case, reading comprehension would be more strongly guided by other, more basic language processing mechanisms and the event structure of the described events would play a more minor role. In the current experiments, participants were given stories to read in which we included, between the anaphor and its referent, either the presence of a narrative event boundary (Experiment 1) or a narrative event boundary along with a working-memory-clearing distractor task (Experiment 2). The results showed that anaphor resolution was affected by narrative event boundaries but not by a working-memory-clearing distractor task. This is interpreted as being consistent with the Event Horizon Model of event cognition. PMID:26452376

  17. Representation of Clear and Cloudy Boundary Layers in Climate Models. Chapter 14

    NASA Technical Reports Server (NTRS)

    Randall, D. A.; Shao, Q.; Branson, M.

    1997-01-01

    The atmospheric general circulation models which are being used as components of climate models rely on their boundary layer parameterizations to produce realistic simulations of the surface turbulent fluxes of sensible heat. moisture. and momentum: of the boundary-layer depth over which these fluxes converge: of boundary layer cloudiness: and of the interactions of the boundary layer with the deep convective clouds that grow upwards from it. Two current atmospheric general circulation models are used as examples to show how these requirements are being addressed: these are version 3 of the Community Climate Model. which has been developed at the U.S. National Center for Atmospheric Research. and the Colorado State University atmospheric general circulation model. The formulations and results of both models are discussed. Finally, areas for future research are suggested.

  18. A Survey of Measurements and Measuring Techniques in Rapidly Distorted Compressible Turbulent Boundary Layers

    NASA Technical Reports Server (NTRS)

    Fernholz, H. H.; Finley, P. J.; Dussauge, J. P.; Smits, A. J.; Reshotko, E. (Editor)

    1989-01-01

    A wide range of recent work on compressible turbulent boundary layers is described. Special attention was paid to flows with rapid changes in pressure including flows with shock waves, curved walls, and expansions. The application of rapid distortion theory to flows transversing expansion and shock waves is reviewed. This is followed by an account of experiments aimed at elucidating the large scale structures present in supersonic boundary layers. The current status of laser-Doppler and hot-wire anemometry in supersonic flow is discussed, and a new interferometric technique for the determination of wall-stress is described. The use of small pressure transducers to deduce information about the structure of zero pressure-gradient and severely perturbed boundary layers is investigated. Finally, there is an extension of the data presentation of AGARDographs 223, 253 and 263 to cover rapidly distorted boundary layers.

  19. Physics of magnetospheric boundary layers

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    1995-01-01

    This final report was concerned with the ideas that: (1) magnetospheric boundary layers link disparate regions of the magnetosphere-solar wind system together; and (2) global behavior of the magnetosphere can be understood only by understanding its internal linking mechanisms and those with the solar wind. The research project involved simultaneous research on the global-, meso-, and micro-scale physics of the magnetosphere and its boundary layers, which included the bow shock, the magnetosheath, the plasma sheet boundary layer, and the ionosphere. Analytic, numerical, and simulation projects were performed on these subjects, as well as comparisons of theoretical results with observational data. Other related activity included in the research included: (1) prediction of geomagnetic activity; (2) global MHD (magnetohydrodynamic) simulations; (3) Alfven resonance heating; and (4) Critical Ionization Velocity (CIV) effect. In the appendixes are list of personnel involved, list of papers published; and reprints or photocopies of papers produced for this report.

  20. The Role of Grain Boundary Energy on Grain Boundary Complexion Transitions

    SciTech Connect

    Bojarski, Stephanie A.; Rohrer, Gregory S.

    2014-09-01

    Grain boundary complexions are distinct equilibrium structures and compositions of a grain boundary and complexion transformations are transition from a metastable to an equilibrium complexion at a specific thermodynamic and geometric conditions. Previous work indicates that, in the case of doped alumina, a complexion transition that increased the mobility of transformed boundaries and resulted in abnormal grain growth also caused a decrease in the mean relative grain boundary energy as well as an increase in the anisotropy of the grain boundary character distribution (GBCD). The current work will investigate the hypothesis that the rates of complexion transitions that result in abnormal grain growth (AGG) depend on grain boundary character and energy. Furthermore, the current work expands upon this understanding and tests the hypothesis that it is possible to control when and where a complexion transition occurs by controlling the local grain boundary energy distribution.

  1. Law of 22 April 2005 on patients' rights and the end of life in France: setting the boundaries of euthanasia, with regard to current legislation in other European countries.

    PubMed

    Clin, Bénédicte; Ophélie, Ferrant

    2010-10-01

    The term 'euthanasia' is not clearly defined. Euthanasia is evoked in many aspects of terminal care: interruption of curative treatment at the end of life, palliative care or the act of deliberately provoking death through compassion. A law on 'patients' rights and the end of life', promulgated in France on 22 April 2005, led to changes in the French Code of Public Health. In this work, we have first outlined the key provisions of this law and the changes it has brought, then we have compared current legislation on the subject throughout Europe, where a rapid overview of current practice in terminal patient care revealed four different types of legislation: the first authorizes euthanasia (in the sense of provoking death, if this choice is medically justified), the second legalizes 'assisted suicide', the third, which is sometimes referred to as 'passive euthanasia', consists of the non-administration of life-sustaining treatment and, finally, the fourth prohibits euthanasia in any form whatsoever. In the last section, we have attempted to clarify the as yet indistinct notion of 'euthanasia' in order to determine whether the conception of terminal care in the Law of 22 April 2005 was consistent with that put forward by the philosopher Francis Bacon, who claimed that, 'The physician's role is to relieve pain, not only when such relief can lead to healing, but also when it can proffer a calm and trouble-free death, thus putting an end to the suffering and the agony of death' (modern adaptation of the original quote). PMID:21539283

  2. Discovering the Role of Grain Boundary Complexions in Materials

    SciTech Connect

    Harmer, Martin P.

    2015-03-19

    Grain boundaries are inherently an area of disorder in polycrystalline materials which define the transport and various other material properties. The relationship between the interfacial chemistry, structure and the material properties is not well understood. Among the various taxonomies for grain boundaries, Grain Boundary Complexion is a relatively new conceptual scheme that relates the structure and kinetic properties of grain boundaries. In this classification scheme, grain boundaries are considered to be distinct three dimensional (the thickness being considerably smaller as compared to the other two dimensions but nonetheless discernible) equilibrium thermodynamic phases abutted between two crystalline phases. The stability and structure of these interfacial phases are dictated by various thermodynamic variables such as temperature, stress (pressure), interfacial chemistry (chemical potential) and most importantly by the energies of the adjoining crystal surfaces. These phases are only stable within the constraint of the adjoining grains. Although these interfacial phases are not stable in bulk form, they can transform from one complexion to another as a function of various thermodynamic variables analogous to the behavior of bulk phases. Examples of different complexions have been reported in various publications. However, a systematic investigation exploring the existence of grain boundary complexions in material systems other than alumina remains to be done. Although the role of interfacial chemistry on grain boundary complexions in alumina has been addressed, a clear understanding of the underlying thermodynamics governing complexion formation is lacking. Finally, the effects of grain boundary complexions in bulk material properties are widely unknown. Factors above urge a thorough exploration of grain boundary complexions in a range of different materials systems The purpose of the current program is to verify the existence of grain boundary complexion

  3. Computer-Assisted Instruction for Severely Handicapped Persons: A Program Based on Stimulus Control Research Modifying Current Software and Hardware. November 1, 1988-April 1, 1990. Final Report.

    ERIC Educational Resources Information Center

    Karsh, Kathryn G.

    This final report describes activities of a federally funded project which developed an educational computer-assisted instructional program for persons with severe disabilities. A preliminary review of the literature identified specific inadequacies of most software for this population, such as: too few examples of a task or concept thus limiting…

  4. Baseline and verification tests of the electric vehicle associates' current fare station wagon. Final test report, March 27, 1980-November 6, 1981

    SciTech Connect

    Dowgiallo, E.J. Jr.; Chapman, R.D.

    1983-01-01

    The EVA Current Fare Wagon was manufactured by Electric Vehicle Associates, Incorporated (EVA) of Cleveland, Ohio. It is now available from Lectra Motors Corp. of Las Vegas, Nevada. The vehicle was tested under the direction of MERADCOM from 27 March 1980 to 6 November 1981. The tests are part of a Department of Energy project to assess advances in electric vehicle design. This report presents the performance test results on the EVA Current Fare Wagon. The EVA Current Fare Wagon is a 1980 Ford Fairmont station wagon which has been converted to an electric vehicle. The propulsion system is made up of a Cableform controller, a series-wound 30-hp Reliance Electric Motor, and 22 6-V lead-acid batteries. The Current Fare Wagon is also equipped with regenerative braking. Further details of the vehicle are given in the Vehicle Summary Data Sheet, Appendix A. The results of this testing are given in Table 1.

  5. On supersymmetry, boundary actions and brane charges

    NASA Astrophysics Data System (ADS)

    Di Pietro, Lorenzo; Klinghoffer, Nizan; Shamir, Itamar

    2016-02-01

    Supersymmetry transformations change the Lagrangian [InlineMediaObject not available: see fulltext.] into a total derivative [InlineMediaObject not available: see fulltext.]. On manifolds with boundaries the total derivative term is an obstruction to preserving supersymmetry. Such total derivative terms can be canceled by a boundary action without specifying boundary conditions, but only for a subalgebra of supersymmetry. We study compensating boundary actions for {N}=1 supersymmetry in 4d, and show that they are determined independently of the details of the theory and of the boundary conditions. Two distinct classes of boundary actions exist, which correspond to preserving either a linear combination of supercharges of opposite chirality (called A-type) or supercharges of opposite chirality independently (B-type). The first option preserves a subalgebra isomorphic to {N}=1 in 3d, while the second preserves only a 2d subgroup of the Lorentz symmetry and a subalgebra isomorphic to {N}=(0,2) in 2d. These subalgebras are in one to one correspondence with half-BPS objects: the A-type corresponds to domain walls while the B-type corresponds to strings. We show that integrating the full current algebra and taking into account boundary contributions leads to an energy-momentum tensor which contains the boundary terms. The boundary terms come from the domain wall and string currents in the two respective cases.

  6. NATIONAL FOREST BOUNDARIES

    EPA Science Inventory

    This dataset contains National Forest boundaries for the lower 48 states, including Puerto Rico. Alaska is maintained separately. This dataset includes administrative unit boundaries, derived primarily from the GSTC SOC data system, comprised of Cartographic Feature Files (CFFs...

  7. Carrier mobility of highly transparent conductive Al-doped ZnO polycrystalline films deposited by radio-frequency, direct-current, and radio-frequency-superimposed direct-current magnetron sputtering: Grain boundary effect and scattering in the grain bulk

    NASA Astrophysics Data System (ADS)

    Nomoto, Junichi; Makino, Hisao; Yamamoto, Tetsuya

    2015-01-01

    The effects of using radio-frequency (RF)-superimposed direct-current (DC) magnetron sputtering deposition on the structural, electrical, and optical properties of aluminum-doped ZnO (AZO)-based highly transparent conducting oxide films have been examined. AZO films were deposited on heated non-alkaline glass substrates (200 °C) using ZnO:Al2O3 (2 wt. % Al2O3) ceramic oxide targets with the total power varied from 150 to 300 W, and at various RF to DC power ratios, AZO films deposited by a mixed approach with the RF to the total power ratio of 0.14 showed the lowest resistivity of 2.47 × 10-4 Ω cm with the highest carrier concentration of 6.88 × 1020 cm-3 and the highest Hall mobility (μH) of 36.8 cm2/Vs together with the maximum value of an average transmittance in the visible spectral range from 400 to 700 nm. From the analysis of optical data based on the simple Drude model combined with the Tauc-Lorentz model and the results of Hall effect measurements, the optical mobility (μopt) was determined. A comparison of μopt with μH clarified the effects of the mixed approach not only on the reduction of the grain boundary contribution to the carrier transport but also on retaining high carrier mobility of in-grains for the AZO films.

  8. Edge plasma boundary layer generated by kink modes in tokamaks

    SciTech Connect

    Zakharov, Leonid E.

    2011-06-15

    This paper describes the structure of the electric current generated by external wall touching and free boundary kink modes at the plasma edge using the ideally conducting plasma model. Both kinds of modes generate {delta}-functional surface current at the plasma edge. Free boundary kink modes also perturb the core plasma current, which in the plasma edge compensates the difference between the {delta}-functional surface currents of free boundary and wall touching kink modes. In addition, the resolution of an apparent paradox with the pressure balance across the plasma boundary in the presence of the surface currents is provided.

  9. Edge plasma boundary layer generated by kink modes in tokamaks

    NASA Astrophysics Data System (ADS)

    Zakharov, Leonid E.

    2011-06-01

    This paper describes the structure of the electric current generated by external wall touching and free boundary kink modes at the plasma edge using the ideally conducting plasma model. Both kinds of modes generate δ-functional surface current at the plasma edge. Free boundary kink modes also perturb the core plasma current, which in the plasma edge compensates the difference between the δ-functional surface currents of free boundary and wall touching kink modes. In addition, the resolution of an apparent paradox with the pressure balance across the plasma boundary in the presence of the surface currents is provided.

  10. Numerical Boundary Condition Procedures

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Topics include numerical procedures for treating inflow and outflow boundaries, steady and unsteady discontinuous surfaces, far field boundaries, and multiblock grids. In addition, the effects of numerical boundary approximations on stability, accuracy, and convergence rate of the numerical solution are discussed.

  11. On boundary superalgebras

    SciTech Connect

    Doikou, Anastasia

    2010-04-15

    We examine the symmetry breaking of superalgebras due to the presence of appropriate integrable boundary conditions. We investigate the boundary breaking symmetry associated with both reflection algebras and twisted super-Yangians. We extract the generators of the resulting boundary symmetry as well as we provide explicit expressions of the associated Casimir operators.

  12. Measurement of density and temperature in a hypersonic turbulent boundary layer using the electron beam fluorescence technique. Ph.D. Thesis. Final Report, 1 Oct. 1969 - 1 Sep. 1972

    NASA Technical Reports Server (NTRS)

    Mcronald, A. D.

    1975-01-01

    Mean density and temperature fluctuations were measured across the turbulent, cooled-wall boundary layer in a continuous hypersonic (Mach 9.4) wind tunnel in air, using the nitrogen fluorescence excited by a 50 kV electron beam. Data were taken at three values of the tunnel stagnation pressure, the corresponding free stream densities being equivalent to 1.2, 4.0, and 7.4 torr at room temperature, and the boundary layer thicknesses about 4.0, 4.5, and 6.0 inches. The mean temperature and density profiles were similar to those previously determined in the same facility by conventional probes (static and pitot pressure, total temperature). A static pressure variation of about 50% across the boundary layer was found, the shape of the variation changing somewhat for the three stagnation pressure levels. The quadrupole model for rotational temperature spectra gave closer agreement with the free stream isentropic level (approximately 44 K) than the dipole model.

  13. 78 FR 14318 - Final Flood Hazard Determinations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-05

    ... (SFHA) boundaries or zone designations, or regulatory floodways on the Flood Insurance Rate Maps (FIRMs... SECURITY Federal Emergency Management Agency Final Flood Hazard Determinations AGENCY: Federal Emergency Management Agency, DHS. ACTION: Final Notice. SUMMARY: Flood hazard determinations, which may...

  14. The relationship between grain boundary structure, defect mobility, and grain boundary sink efficiency

    SciTech Connect

    Uberuaga, Blas Pedro; Vernon, Louis J.; Martinez, Enrique; Voter, Arthur F.

    2015-03-13

    Nanocrystalline materials have received great attention due to their potential for improved functionality and have been proposed for extreme environments where the interfaces are expected to promote radiation tolerance. However, the precise role of the interfaces in modifying defect behavior is unclear. Using long-time simulations methods, we determine the mobility of defects and defect clusters at grain boundaries in Cu. We find that mobilities vary significantly with boundary structure and cluster size, with larger clusters exhibiting reduced mobility, and that interface sink efficiency depends on the kinetics of defects within the interface via the in-boundary annihilation rate of defects. Thus, sink efficiency is a strong function of defect mobility, which depends on boundary structure, a property that evolves with time. Further, defect mobility at boundaries can be slower than in the bulk, which has general implications for the properties of polycrystalline materials. Finally, we correlate defect energetics with the volumes of atomic sites at the boundary.

  15. The relationship between grain boundary structure, defect mobility, and grain boundary sink efficiency

    PubMed Central

    Uberuaga, Blas Pedro; Vernon, Louis J.; Martinez, Enrique; Voter, Arthur F.

    2015-01-01

    Nanocrystalline materials have received great attention due to their potential for improved functionality and have been proposed for extreme environments where the interfaces are expected to promote radiation tolerance. However, the precise role of the interfaces in modifying defect behavior is unclear. Using long-time simulations methods, we determine the mobility of defects and defect clusters at grain boundaries in Cu. We find that mobilities vary significantly with boundary structure and cluster size, with larger clusters exhibiting reduced mobility, and that interface sink efficiency depends on the kinetics of defects within the interface via the in-boundary annihilation rate of defects. Thus, sink efficiency is a strong function of defect mobility, which depends on boundary structure, a property that evolves with time. Further, defect mobility at boundaries can be slower than in the bulk, which has general implications for the properties of polycrystalline materials. Finally, we correlate defect energetics with the volumes of atomic sites at the boundary. PMID:25766999

  16. A measurement of the muon neutrino charged current quasielastic-like cross section on a hydrocarbon target and final state interaction effects

    SciTech Connect

    Walton, Tammy

    2014-01-01

    Presented is the analysis of the μ charged-current quasielastic-like interaction with a polystyrene (CH or hydrocarbon) target in the MINER A experiment, which was exposed to a neutrino beam that peaked at 3.5 GeV.

  17. Future Performance Trend Indicators: A Current Value Approach to Human Resources Accounting. Report I. Internal Consistencies and Relationships to Performance By Site. Final Report.

    ERIC Educational Resources Information Center

    Pecorella, Patricia A.; Bowers, David G.

    Analyses preparatory to construction of a suitable file for generating a system of future performance trend indicators are described. Such a system falls into the category of a current value approach to human resources accounting. It requires that there be a substantial body of data which: (1) uses the work group or unit, not the individual, as…

  18. Preliminary Structural Design Conceptualization for Composite Rotor for Verdant Power Water Current: Cooperative Research and Development Final Report, CRADA Number CRD-08-296

    SciTech Connect

    Hughes, S.

    2011-02-01

    The primary thrust of the CRADA will be to develop a new rotor design that will allow higher current flows (>4m/s), greater swept area (6-11m), and in the process, will maximize performance and energy capture.

  19. On Boundary Stimulation and Optimal Boundary Control of the Bidomain Equations

    PubMed Central

    Nagaiah, Chamakuri; Kunisch, Karl; Plank, Gernot

    2014-01-01

    The bidomain equations with Neumann boundary stimulation and optimal control of these stimuli are investigated. First an analytical framework for boundary control is provided. Then a parallel finite element based algorithm is devised and its efficiency is demonstrated not only for the direct problem but also for the optimal control problem. The computations realize a model configuration corresponding to optimal boundary defibrillation of a reentry phenomenon by applying current density stimuli. PMID:23856647

  20. Integrable Boundary for Quad-Graph Systems: Three-Dimensional Boundary Consistency

    NASA Astrophysics Data System (ADS)

    Caudrelier, Vincent; Crampé, Nicolas; Zhang, Qi Cheng

    2014-02-01

    We propose the notion of integrable boundary in the context of discrete integrable systems on quad-graphs. The equation characterizing the boundary must satisfy a compatibility equation with the one characterizing the bulk that we called the three-dimensional (3D) boundary consistency. In comparison to the usual 3D consistency condition which is linked to a cube, our 3D boundary consistency condition lives on a half of a rhombic dodecahedron. The We provide a list of integrable boundaries associated to each quad-graph equation of the classification obtained by Adler, Bobenko and Suris. Then, the use of the term ''integrable boundary'' is justified by the facts that there are Bäcklund transformations and a zero curvature representation for systems with boundary satisfying our condition. We discuss the three-leg form of boundary equations, obtain associated discrete Toda-type models with boundary and recover previous results as particular cases. Finally, the connection between the 3D boundary consistency and the set-theoretical reflection equation is established.

  1. The significance of gender boundaries in preadolescence: contemporary correlates and antecedents of boundary violation and maintenance.

    PubMed

    Sroufe, L A; Bennett, C; Englund, M; Urban, J; Shulman, S

    1993-04-01

    Previous research has established the importance of gender boundaries as a normative aspect of development in middle childhood. Here, the nature and importance of gender boundaries as an individual differences construct was explored. Ratings of gender boundary violation and gender boundary maintenance were made of 47 10-11-year-old children participating in a series of summer day camps. These ratings were supported by videotape-based behavior codings of gender boundary violating behaviors and by live observations of sheer number of associations with members of the opposite gender. In addition, considerable external validation of these individual differences was obtained. Children low on gender boundary violation and (especially) children high on boundary maintenance were independently judged by camp counselors to be socially competent. They also were found to be higher on a friendship variable, based on observation. Those who violated boundaries were especially unpopular with peers, based on a child interview. Finally, boundary violation and maintenance were related to attachment history and to early measures of parent-child generational boundary distortions. PMID:8477628

  2. Grain boundary diffusion in olivine (Invited)

    NASA Astrophysics Data System (ADS)

    Marquardt, K.; Dohmen, R.

    2013-12-01

    . Grain boundary diffusion perpendicular to the dislocation lines of the small angle grain boundaries proved to be about an order of magnitude faster than volume diffusion, whereas diffusion in high angle grain boundaries is several orders of magnitude faster. We will discuss the variation of element diffusion rates with grain boundary orientation and the temperature- and/or time-induced transition from one diffusion regime to the next regime. This is done using time series experiments and two-dimensional grain boundary diffusion simulations. Finally, we will debate the differences between our data and other data sets that result from different experimental setups, conditions and analyses.

  3. Coordinated radar and satellite studies of ionospheric currents in the auroral zone and polar cap. Final report, 1 September 1982-31 December 1985

    SciTech Connect

    Tsunoda, R.T.; Smith, A.Q.; Kelly, J.D.; Robinson, R.M.

    1985-12-01

    The objective is to provide real time surveillance of short term predictions in the electrodynamic state of the ionosphere and magnetosphere. The desired approach is to obtain all necessary environmental information by remote sensing or by in situ sampling from satellites; the necessary quantities include electric fields, ionospheric conductivities, and field-aligned currents. Recently, a DMSP (Defense Meteorological Satellite Program) satellite has been launched from (Flight 7) equipped with a triaxial fluxgate magnetometer. To qualify this type of instrument for participation in the above objective, an investigation was invested to field aligned currents estimated from two different approaches: using magnetometer measurements made from the DMSP-F7 satellite and using ionospheric measurements made by the Sondrestrom incoherent scatter radar. Three events are analyzed when near-simultaneous measurements were made by both instruments during satellite passes over the radar. Varying degrees of correlation were found in the derived field-aligned currents. In all three cases, the gross features measured by the two methods were similar. The differences are discussed in terms of measurement error, analysis approximation, and geophysical uncertainties.

  4. A boundary layer model for magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Rostoker, Gordon; Eastman, Tim

    1987-01-01

    An alternative framework for understanding magnetospheric substorm activity is presented. It is argued that observations of magnetic field and plasma flow variations in the magnetotail can be explained in terms of the passage of the plasma sheet boundary layer over the satellite detecting the tail signatures. It is shown that field-aligned currents and particle acceleration processes on magnetic field lines threading the ionospheric Harang discontinuity lead to the distinctive particle and field signatures observed in the magnetotail during substorms. It is demonstrated that edge effects of field-aligned currents associated with the westward traveling surge can lead to the negative B(z) perturbations observed in the tail that are presently attributed to observations made on the anti-earthward side of a near-earth neutral line. Finally, it is shown that the model can provide a physical explanation of both the driven system and the loading-unloading system whose combined effects provide the observed substorm perturbation pattern in the magnetosphere and ionosphere.

  5. The Structure of Grain Boundaries in Strontium Titanate: Theory, Simulation, and Electron Microscopy

    NASA Astrophysics Data System (ADS)

    von Alfthan, Sebastian; Benedek, Nicole A.; Chen, Lin; Chua, Alvin; Cockayne, David; Dudeck, Karleen J.; Elsässer, Christian; Finnis, Michael W.; Koch, Christoph T.; Rahmati, Behnaz; Rühle, Manfred; Shih, Shao-Ju; Sutton, Adrian P.

    2010-08-01

    We review a combination of theoretical and experimental techniques that have been applied to the study of grain boundaries in SrTiO3, with particular attention to Σ3 and ( 100 )-oriented grain boundaries. Electron microscopy, which includes high-resolution transmission and high-angle annular dark-field methods, is discussed, with successful applications to mapping atomic columns and testing theoretical models. Then, we compare and contrast different techniques of electron holography that may be used to map electrostatic potentials. Problems with the current methods of interpretation in holography and impedance spectroscopy are highlighted in an attempt to reconcile their respective estimates of electrostatic potentials at grain boundaries. Then, standard theoretical tools for the atomistic simulation of boundary structures are critically reviewed, which include classical potentials and density functional theory. A promising genetic algorithm for discovering low-energy grain boundary structures is described and tested. Finally, the synergy of experiment, theory, and simulation that is required to understand boundaries is demonstrated, and we identify major challenges to understanding multicomponent systems.

  6. Incorporation of the planetary boundary layer in atmospheric models

    NASA Technical Reports Server (NTRS)

    Moeng, Chin-Hoh; Wyngaard, John; Pielke, Roger; Krueger, Steve

    1993-01-01

    The topics discussed include the following: perspectives on planetary boundary layer (PBL) measurements; current problems of PBL parameterization in mesoscale models; and convective cloud-PBL interactions.

  7. 78 FR 35960 - Minor Boundary Revision at Mojave National Preserve

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-14

    ... National Park Service Minor Boundary Revision at Mojave National Preserve AGENCY: National Park Service....S.C. 460l- 9(c)(1), the boundary of Mojave National Preserve is modified to include 7.12 acres of..., California, immediately adjacent to the current northern boundary of Mojave National Preserve. ] Notice...

  8. Boundary-Layer & health

    NASA Astrophysics Data System (ADS)

    Costigliola, V.

    2010-09-01

    It has long been known that specific atmospheric processes, such as weather and longer-term climatic fluctuations, affect human health. The biometeorological literature refers to this relationship as meteorotropism, defined as a change in an organism that is correlated with a change in atmospheric conditions. Plenty of (patho)physiological functions are affected by those conditions - like the respiratory diseases - and currently it is difficult to put any limits for pathologies developed in reply. Nowadays the importance of atmospheric boundary layer and health is increasingly recognised. A number of epidemiologic studies have reported associations between ambient concentrations of air pollution, specifically particulate pollution, and adverse health effects, even at the relatively low concentrations of pollution found. Since 1995 there have been over twenty-one studies from four continents that have explicitly examined the association between ambient air pollutant mixes and daily mortality. Statistically significant and positive associations have been reported in data from various locations around the world, all with varying air pollutant concentrations, weather conditions, population characteristics and public health policies. Particular role has been given to atmospheric boundary layer processes, the impact of which for specific patient-cohort is, however, not well understood till now. Assessing and monitoring air quality are thus fundamental to improve Europe's welfare. One of current projects run by the "European Medical Association" - PASODOBLE will develop and demonstrate user-driven downstream information services for the regional and local air quality sectors by combining space-based and in-situ data with models in 4 thematic service lines: - Health community support for hospitals, pharmacies, doctors and people at risk - Public information for regions, cities, tourist industry and sporting event organizers - Compliance monitoring support on particulate

  9. Final results on the Jurassic-Cretaceous boundary in the Gresten Klippenbelt (Austria): Macro-, micro-, nannofossils, isotopes, geochemistry, susceptibility, gamma-log and palaeomagnetic data as environmental proxies of the early Penninic Ocean history

    NASA Astrophysics Data System (ADS)

    Lukeneder, A.; Halásová, E.; Kroh, A.; Mayrhofer, S.; Pruner, P.; Reháková, D.; Schnabl, P.; Sprovieri, M.

    2009-04-01

    Jurassic to Lower Cretaceous pelagic sediments are well known to form a major element of the northernmost tectonic units of the Gresten Klippenbelt (Lower Austria). The Penninic Ocean was a side tract of the Central Atlantic Oceanic System intercalated between the European and the Austroalpine plates. Its opening started during the Mid Jurrasic, as rifting of the of the oceanic crust between the European and the Austroalpine plates. The turnover of the deposition on the European shelf (Helvetic Zone) from deep-water siliciclastics into pelagic carbonates is correlated with the deepening of this newly arising ocean. Within the Gresten Klippenbelt Unit, this transition is reflected by the lithostratigraphic boundary between the Tithonian marl-limestone succession and the Berriasian limestones of the Blassenstein Formation. This boundary is well exposed in a newly discovered site at Nutzhof, in the heart of Lower Austria (Kroh and Lukeneder 2009, Lukeneder 2009, Pruner, Schnabl, and Lukeneder 2009, Reháková, Halásová and Lukeneder 2009). Biostratigraphy. According to microfossil (calcareous dinoflagellates, calpionellids) and palaeomagnetic data, the association indicates that the cephalopod-bearing beds of the Nutzhof section belong to the Carpistomiosphaera tithonica-Zone of the Early Tithonian up to the Calpionella Zone of the Middle Berriasian. This interval corresponds to the ammonoid zones from the Early Tithonian Hybonoticeras hybonotum-Zone up to the Middle Berriasian Subthurmannia occitanica-Zone. Ammonoids. Late Jurassic to Early Cretaceous ammonoids were collected at the Nutzhof locality in the eastern part of the Gresten Klippenbelt in Lower Austria. The cephalopod fauna from the Blassenstein Formation, correlated with micro- and nannofossil data from the marly unit and the limestone unit, indicates Early Tithonian to Middle Berriasian age (Hybonoticeras hybonotum Zone up to the Subthurmannia occitanica Zone). According to the correlation of the fossil

  10. Theory and Fluid Simulations of Boundary Plasma Fluctuations

    SciTech Connect

    Cohen, R H; LaBombard, B; LoDestro, L L; Rognlien, T D; Ryutov, D D; Terry, J L; Umansky, M V; Xu, X Q; Zweben, S

    2007-01-09

    Theoretical and computational investigations are presented of boundary plasma microturbulence that take into account important effects of the geometry of diverted tokamaks--in particular, the effect of x-point magnetic shear and the termination of field lines on divertor plates. We first generalize our previous 'heuristic boundary condition' which describes, in a lumped model, the closure of currents in the vicinity of the x-point region to encompass three current-closure mechanisms. We then use this boundary condition to derive the dispersion relation for low-beta flute-like modes in the divertor-leg region under the combined drives of curvature, sheath impedance, and divertor tilt effects. The results indicate the possibility of strongly growing instabilities, driven by sheath boundary conditions, and localized in either the private or common flux region of the divertor leg depending on the radial tilt of divertor plates. We re-visit the issue of x-point effects on blobs, examining the transition from blobs terminated by x-point shear to blobs that extend over both the main SOL and divertor legs. We find that, for a main-SOL blob, this transition occurs without a free-acceleration period as previously thought, with x-point termination conditions applying until the blob has expanded to reach the divertor plate. We also derive propagation speeds for divertor-leg blobs. Finally, we present fluid simulations of the C-Mod tokamak from the BOUT edge fluid turbulence code, which show main-SOL blob structures with similar spatial characteristics to those observed in the experiment, and also simulations which illustrate the possibility of fluctuations confined to divertor legs.

  11. Boundary lubrication: Revisited

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1982-01-01

    A review of the various lubrication regimes, with particular, emphasis on boundary lubrication, is presented. The types of wear debris and extent of surface damage is illustrated for each regime. The role of boundary surface films along with their modes of formation and important physical properties are discussed. In addition, the effects of various operating parameters on friction and wear in the boundary lubrication regime are considered.

  12. Thermal stress imposed by prototype bilayer and current ground crew chemical defense ensembles: a limited laboratory comparison. Final report, 30 June 1986-1 January 1987

    SciTech Connect

    Krock, L.P.; Navalta, R.; Myhre, L.G.

    1988-07-01

    An open bilayer ground-crew chemical defense ensemble (CDE) was proposed to reduce the thermal burden during vapor-only exposure periods. This study compared the thermal-stress profile of the proposed ensemble to that produced by the currently employed closed CDE. Four subjects, alternating ensembles on separate days, walked on a treadmill in an environmental chamber at 5.3 km/h (3.3 mph) and 2% grade (an energy expenditure of 350 kcal/h) for alternating work/rest to achieve significant recovery. Mean total sweat production was lower (1.38 vs. 2.50 liters) and percent sweat evaporation greater (65.7% vs. 30.0%) in the prototype ensemble than in the CDE. The prototype ensemble provided greater heat dissipation and allowed more-efficient sweat evaporation which had the double benefit of reducing heat storage and limiting dehydration.

  13. Jupiter's deep magnetotail boundary layer

    NASA Astrophysics Data System (ADS)

    Nicolaou, G.; McComas, D. J.; Bagenal, F.; Elliott, H. A.; Ebert, R. W.

    2015-06-01

    In 2007 the New Horizons (NH) spacecraft flew by Jupiter for a gravity assist en route to Pluto. After closest approach on day of year (DOY) 58, 2007, NH followed a tailward trajectory that provided a unique opportunity to explore the deep jovian magnetotail and the surrounding magnetosheath. After DOY 132, 16 magnetopause crossings were observed between 1654 and 2429 Jupiter radii (Rj) along the dusk flank tailward of the planet. In some cases the crossings were identified as rapid transitions from the magnetotail to the magnetosheath and vice versa. In other cases a boundary layer was observed just inside the magnetopause. Solar Wind Around Pluto (SWAP) is an instrument on board NH that obtained spectra of low energy ions during the flyby period. We use a forward model including the SWAP instrument response to derive plasma parameters (density, temperature and velocity) which best reproduce the observations. We also vary the plasma parameters in our model in order to fit the observations more accurately on occasions where the measurements exhibit significant variability. We compare the properties of the plasma in the boundary layer with those of the magnetosheath plasma derived in our earlier work. We attempt to estimate the magnetic field in the boundary layer assuming pressure balance between it and the magnetosheath. Finally, we investigate several possible scenarios to assess if magnetopause movement and structure could cause the variations seen in the data.

  14. How good is the impedance boundary condition?

    NASA Technical Reports Server (NTRS)

    Lee, Shung-Wu; Gee, W.

    1987-01-01

    The impedance boundary condition (IBC) is often used in scattering problems involving material-coated conducting bodies. It is shown that for some commonly encountered coating configurations, the value of the impedance varies significantly as functions of the incident angle and polarization. Hence, the use of IBC in a rigorously formulated problem may affect the accuracy of the final solution.

  15. NATIONAL PARK BOUNDARIES

    EPA Science Inventory

    The National Park Service has produced a data base of boundaries for its National Parks. A copy of this data was downloaded from the National Parks Service ftp site by Region 10. These digital boundaries represent the best guess and data that could be collected in a short time....

  16. The Atmospheric Boundary Layer

    ERIC Educational Resources Information Center

    Tennekes, Hendrik

    1974-01-01

    Discusses some important parameters of the boundary layer and effects of turbulence on the circulation and energy dissipation of the atmosphere. Indicates that boundary-layer research plays an important role in long-term forecasting and the study of air-pollution meteorology. (CC)

  17. Review of the current status of reverse electrodialysis systems for salinity power systems using a stratified saturated solar pond. Final report. Report No. 220280

    SciTech Connect

    Not Available

    1980-02-22

    The overall objective of this study was to develop and place in operation a small salinity power heat engine of 100-watt capacity consisting of a saturated solar pond (SSP) coupled to a reverse electrodialysis (RED) membrane stack. The objectives of the contract were: (1) to demonstrate that a SSP can be used for unmixing of a mixed brine into a dilute and a concentrated brine stream, (2) to demonstrate that a RED stack can generate electrical power, and (3) to generate the necessary experimental data on the RED-SSP system which can be used to assess the potential of such a system for economical energy generation. The results of findings on the current status of ion-exchange membranes and RED stacks is summarized. It is shown that the electrical resistance of the present-day membranes, which are produced for electrodialysis and not reverse electrodialysis, and the solution compartments are very high. This causes the power density of present-day RED stacks, in terms of watts per unit membrane area, to be very low. This factor combined with the high cost of present-day membranes results in very high costs for the RED stack. Furthermore, present-day membranes as well as adhesives for membrane assemblies cannot operate at about 80/sup 0/C for any reasonable length of time without severe deterioration in performance. The areas that require development work include: (1) development of cheap ion-exchange membranes with low electrical resistance and high permselectivity; (2) development of very thin solution compartments; (3) development of RED stacks which can operate at high temperatures; and (4) laboratory testing of small RED stacks to investigate the effect of temperature on stack performance and the fouling of RED membranes with time, have been identified. (WHK)

  18. Sensitivity to volcanic field boundary

    NASA Astrophysics Data System (ADS)

    Runge, Melody; Bebbington, Mark; Cronin, Shane; Lindsay, Jan; Rashad Moufti, Mohammed

    2016-04-01

    Volcanic hazard analyses are desirable where there is potential for future volcanic activity to affect a proximal population. This is frequently the case for volcanic fields (regions of distributed volcanism) where low eruption rates, fertile soil, and attractive landscapes draw populations to live close by. Forecasting future activity in volcanic fields almost invariably uses spatial or spatio-temporal point processes with model selection and development based on exploratory analyses of previous eruption data. For identifiability reasons, spatio-temporal processes, and practically also spatial processes, the definition of a spatial region is required to which volcanism is confined. However, due to the complex and predominantly unknown sub-surface processes driving volcanic eruptions, definition of a region based solely on geological information is currently impossible. Thus, the current approach is to fit a shape to the known previous eruption sites. The class of boundary shape is an unavoidable subjective decision taken by the forecaster that is often overlooked during subsequent analysis of results. This study shows the substantial effect that this choice may have on even the simplest exploratory methods for hazard forecasting, illustrated using four commonly used exploratory statistical methods and two very different regions: the Auckland Volcanic Field, New Zealand, and Harrat Rahat, Kingdom of Saudi Arabia. For Harrat Rahat, sensitivity of results to boundary definition is substantial. For the Auckland Volcanic Field, the range of options resulted in similar shapes, nevertheless, some of the statistical tests still showed substantial variation in results. This work highlights the fact that when carrying out any hazard analysis on volcanic fields, it is vital to specify how the volcanic field boundary has been defined, assess the sensitivity of boundary choice, and to carry these assumptions and related uncertainties through to estimates of future activity and

  19. Isogeometric Boundary Element analysis with elasto-plastic inclusions. Part 1: Plane problems

    NASA Astrophysics Data System (ADS)

    Beer, Gernot; Marussig, Benjamin; Zechner, Jürgen; Dünser, Christian; Fries, Thomas-Peter

    2016-08-01

    In this work a novel approach is presented for the isogeometric Boundary Element analysis of domains that contain inclusions with different elastic properties than the ones used for computing the fundamental solutions. In addition the inclusion may exhibit inelastic material behavior. In this paper only plane stress/strain problems are considered. In our approach the geometry of the inclusion is described using NURBS basis functions. The advantage over currently used methods is that no discretization into cells is required in order to evaluate the arising volume integrals. The other difference to current approaches is that Kernels of lower singularity are used in the domain term. The implementation is verified on simple finite and infinite domain examples with various boundary conditions. Finally a practical application in geomechanics is presented.

  20. Burst vortex/boundary layer interaction

    NASA Technical Reports Server (NTRS)

    Bradshaw, P.; Naaseri, M.

    1988-01-01

    Several configurations of delta wing vortex generator and boundary layer test plate were tested, and two final ones selected. Sample measurements and flow visualizations in the candidate configurations, together with more detailed measurements in one of the two final arrangements, which were selected so that a pure vortex bursts repeatably and then interacts, in as simple fashion as possible, with a simple turbulent boundary layer, are included. It is concluded that different intensities of bursting or breakdown, like different strengths of shock wave or hydraulic jump, can be produced by minor changes of configuration. The weaker breakdowns do not produce flow reversal. The initial measurements were done with a fairly weak, but repeatable, breakdown. Basic measurements on the second final arrangement, with a stronger breakdown, are in progress.

  1. Identifying chemicals that are planetary boundary threats.

    PubMed

    MacLeod, Matthew; Breitholtz, Magnus; Cousins, Ian T; de Wit, Cynthia A; Persson, Linn M; Rudén, Christina; McLachlan, Michael S

    2014-10-01

    Rockström et al. proposed a set of planetary boundaries that delimit a "safe operating space for humanity". Many of the planetary boundaries that have so far been identified are determined by chemical agents. Other chemical pollution-related planetary boundaries likely exist, but are currently unknown. A chemical poses an unknown planetary boundary threat if it simultaneously fulfills three conditions: (1) it has an unknown disruptive effect on a vital Earth system process; (2) the disruptive effect is not discovered until it is a problem at the global scale, and (3) the effect is not readily reversible. In this paper, we outline scenarios in which chemicals could fulfill each of the three conditions, then use the scenarios as the basis to define chemical profiles that fit each scenario. The chemical profiles are defined in terms of the nature of the effect of the chemical and the nature of exposure of the environment to the chemical. Prioritization of chemicals in commerce against some of the profiles appears feasible, but there are considerable uncertainties and scientific challenges that must be addressed. Most challenging is prioritizing chemicals for their potential to have a currently unknown effect on a vital Earth system process. We conclude that the most effective strategy currently available to identify chemicals that are planetary boundary threats is prioritization against profiles defined in terms of environmental exposure combined with monitoring and study of the biogeochemical processes that underlie vital Earth system processes to identify currently unknown disruptive effects. PMID:25181298

  2. Immersed Boundary Methods for High-Resolution Simulation of Atmospheric Boundary-Layer Flow Over Complex Terrain

    SciTech Connect

    Lundquist, K A

    2010-05-12

    Mesoscale models, such as the Weather Research and Forecasting (WRF) model, are increasingly used for high resolution simulations, particularly in complex terrain, but errors associated with terrain-following coordinates degrade the accuracy of the solution. Use of an alternative Cartesian gridding technique, known as an immersed boundary method (IBM), alleviates coordinate transformation errors and eliminates restrictions on terrain slope which currently limit mesoscale models to slowly varying terrain. In this dissertation, an immersed boundary method is developed for use in numerical weather prediction. Use of the method facilitates explicit resolution of complex terrain, even urban terrain, in the WRF mesoscale model. First, the errors that arise in the WRF model when complex terrain is present are presented. This is accomplished using a scalar advection test case, and comparing the numerical solution to the analytical solution. Results are presented for different orders of advection schemes, grid resolutions and aspect ratios, as well as various degrees of terrain slope. For comparison, results from the same simulation are presented using the IBM. Both two-dimensional and three-dimensional immersed boundary methods are then described, along with details that are specific to the implementation of IBM in the WRF code. Our IBM is capable of imposing both Dirichlet and Neumann boundary conditions. Additionally, a method for coupling atmospheric physics parameterizations at the immersed boundary is presented, making IB methods much more functional in the context of numerical weather prediction models. The two-dimensional IB method is verified through comparisons of solutions for gentle terrain slopes when using IBM and terrain-following grids. The canonical case of flow over a Witch of Agnesi hill provides validation of the basic no-slip and zero gradient boundary conditions. Specified diurnal heating in a valley, producing anabatic winds, is used to validate the

  3. Immersed boundary methods for high-resolution simulation of atmospheric boundary-layer flow over complex terrain

    NASA Astrophysics Data System (ADS)

    Lundquist, Katherine Ann

    Mesoscale models, such as the Weather Research and Forecasting (WRF) model, are increasingly used for high resolution simulations, particularly in complex terrain, but errors associated with terrain-following coordinates degrade the accuracy of the solution. Use of an alternative Cartesian gridding technique, known as an immersed boundary method (IBM), alleviates coordinate transformation errors and eliminates restrictions on terrain slope which currently limit mesoscale models to slowly varying terrain. In this dissertation, an immersed boundary method is developed for use in numerical weather prediction. Use of the method facilitates explicit resolution of complex terrain, even urban terrain, in the WRF mesoscale model. First, the errors that arise in the WRF model when complex terrain is present are presented. This is accomplished using a scalar advection test case, and comparing the numerical solution to the analytical solution. Results are presented for different orders of advection schemes, grid resolutions and aspect ratios, as well as various degrees of terrain slope. For comparison, results from the same simulation are presented using the IBM. Both two-dimensional and three-dimensional immersed boundary methods are then described, along with details that are specific to the implementation of IBM in the WRF code. Our IBM is capable of imposing both Dirichlet and Neumann boundary conditions. Additionally, a method for coupling atmospheric physics parameterizations at the immersed boundary is presented, making IB methods much more functional in the context of numerical weather prediction models. The two-dimensional IB method is verified through comparisons of solutions for gentle terrain slopes when using IBM and terrain-following grids. The canonical case of flow over a Witch of Agnesi hill provides validation of the basic no-slip and zero gradient boundary conditions. Specified diurnal heating in a valley, producing anabatic winds, is used to validate the

  4. Topographically generated internal waves and boundary layer instabilities

    NASA Astrophysics Data System (ADS)

    Soontiens, Nancy; Stastna, Marek; Waite, Michael L.

    2015-08-01

    Flow over topography has been shown to generate finite amplitude internal waves upstream, over the topography and downstream. Such waves can interact with the viscous bottom boundary layer to produce vigorous instabilities. However, the strength and size of such instabilities depends on whether viscosity significantly modifies the wave generation process, which is usually treated using inviscid theory in the literature. In this work, we contrast cases in which boundary layer separation profoundly alters the wave generation process and cases for which the generated internal waves largely match inviscid theory. All results are generated using a numerical model that simulates stratified flow over topography. Several issues with using a wave-based Reynolds number to describe boundary layer properties are discussed by comparing simulations with modifications to the domain depth, background velocity, and viscosity. For hill-like topography, three-dimensional aspects of the instabilities are also discussed. Decreasing the Reynolds number by a factor of four (by increasing the viscosity), while leaving the primary two-dimensional instabilities largely unchanged, drastically affects their three-dimensionalization. Several cases at the laboratory scale with a depth of 1 m are examined in both two and three dimensions and a subset of the cases is scaled up to a field scale 10-m deep fluid while maintaining similar values for the background current and viscosity. At this scale, increasing the viscosity by an order of magnitude does not significantly change the wave properties but does alter the wave's interaction with the bottom boundary layer through the bottom shear stress. Finally, two subcritical cases for which disturbances are able to propagate upstream showcase a set of instabilities forming on the upstream slope of the elevated topography. The time scale over which these instabilities develop is related to but distinct from the advective time scale of the waves. At a

  5. Boundary detection via dynamic programming

    NASA Astrophysics Data System (ADS)

    Udupa, Jayaram K.; Samarasekera, Supun; Barrett, William A.

    1992-09-01

    This paper reports a new method for detecting optimal boundaries in multidimensional scene data via dynamic programming (DP). In its current form the algorithm detects 2-D contours on slices and differs from other reported DP-based algorithms in an essential way in that it allows freedom in 2-D for finding optimal contour paths (as opposed to a single degree of freedom in the published methods). The method is being successfully used in segmenting object boundaries in a variety of medical applications including orbital volume from CT images (for craniofacial surgical planning), segmenting bone in MR images for kinematic analysis of the joints of the foot, segmenting the surface of the brain from the inner surface of the cranial vault, segmenting pituitary gland tumor for following the effect of a drug on the tumor, segmenting the boundaries of the heart in MR images, and segmenting the olfactory bulb for verifying hypotheses related to the size of this bulb in certain disease states.

  6. Grain boundary migration: Atomistic simulation studies

    NASA Astrophysics Data System (ADS)

    Upmanyu, Moneesh

    shuffling of groups of atoms. The atomic population and frequency of the shuffles depend on the boundary structure and temperature. The atomic-level details also reveal the origin of frequent non-steady-state effects observed during boundary migration, i.e. the phenomenon of vacancy generation and emission from the boundaries. The excess boundary volume ejected into the bulk during the reduction in area of the grain boundaries manifests itself as vacancy/void generation events, which introduce transients in the otherwise steady-state migration process. Simulations of migration of individual triple junctions show that significant deviations occur between the dynamic and static dihedral angles, in the case of special, (low Sigma) tri-crystallographies. This implies that triple junctions have finite mobilities, and they impose a significant drag on the grain boundaries. Triple junction drag is also found to have a strong directional dependence. Finally, the simulations of simple circular grains prove that boundaries rotate to low energy misorientations. Grain rotation can potentially serve as an additional dynamic effect during microstructural evolution. Both triple junction drag and grain rotation are observed to have strong size dependence, implying their importance during nano-structural evolution of ultra-fine-grain-sized materials.

  7. Arc Flash Boundary Calculations Using Computer Software Tools

    SciTech Connect

    Gibbs, M.D.

    2005-01-07

    Arc Flash Protection boundary calculations have become easier to perform with the availability of personal computer software. These programs incorporate arc flash protection boundary formulas for different voltage and current levels, calculate the bolted fault current at each bus, and use built in time-current coordination curves to determine the clearing time of protective devices in the system. Results of the arc flash protection boundary calculations can be presented in several different forms--as an annotation to the one-line diagram, as a table of arc flash protection boundary distances, and as printed placards to be attached to the appropriate equipment. Basic arc flash protection boundary principles are presented in this paper along with several helpful suggestions for performing arc flash protection boundary calculations.

  8. MBTS Boundary Conditions in Continuous Systems

    NASA Astrophysics Data System (ADS)

    Benesh, G. A.; Haydock, Roger

    2015-03-01

    Boundary conditions imposed on a local system that is joined to a larger substrate system often introduce unphysical reflections that affect eigenstate energies, densities of states, and charge densities. These problems are common in both atomic cluster and surface slab calculations. Solutions of the Schrodinger equation for the physical system do not possess such reflections; these wave functions carry current smoothly across the (artificial) boundary between the local system and the underlying medium. Previously, Haydock and Nex derived a non-reflecting boundary condition for discrete systems [Phys. Rev. B 75, 205121 (2006)]. Solutions satisfying this maximal breaking of time-reversal symmetry (MBTS) boundary condition carry current away from the boundary at a maximal rate--in much the same way as the exact wave functions for the physical system. The MBTS boundary condition has proved useful in discrete systems for constructing densities of states and other distributions from moments or continued fractions. The MBTS approach has now been extended to studies employing continuous spatial wave functions, including surface slab calculations and model systems. Results are compared with free slab calculations, embedding calculations, and experiment.

  9. Improving Boundary Conditions for Electronic Structure Calculations

    NASA Astrophysics Data System (ADS)

    Benesh, G. A.; Haydock, Roger

    Boundary conditions imposed on a local system joined to a much larger substrate system routinely introduce unphysical reflections that affect the calculation of electronic properties such as energies, charge densities, and densities of states. These problems persist in atomic cluster, slab, and supercell calculations alike. However, wave functions in real, physical systems do not reflect at artificial boundaries. Instead, they carry current smoothly across the surface separating the local system from the underlying medium. Haydock and Nex have derived a non-reflecting boundary condition that works well for discrete systems [Phys. Rev. B 75, 205121 (2006)]. Solutions satisfying their maximal breaking of time-reversal symmetry (MBTS) boundary condition carry current away from the boundary at a maximal rate--in much the same way as exact wave functions in physical systems. The MBTS approach has now been extended to studies employing continuous basis functions. In model systems, MBTS boundary conditions work well for calculating wave functions, eigenenergies, and densities of states. Results are reported for an Al(001) surface. Comparisons are made with slab calculations, embedding calculations, and experiment.

  10. Multireflection boundary conditions for lattice Boltzmann models.

    PubMed

    Ginzburg, Irina; d'Humières, Dominique

    2003-12-01

    We present a general framework for several previously introduced boundary conditions for lattice Boltzmann models, such as the bounce-back rule and the linear and quadratic interpolations. The objectives are twofold: first to give theoretical tools to study the existing link-type boundary conditions and their corresponding accuracy; second to design boundary conditions for general flows which are third-order kinetic accurate. Using these new boundary conditions, Couette and Poiseuille flows are exact solutions of the lattice Boltzmann models for a Reynolds number Re=0 (Stokes limit) for arbitrary inclination with the lattice directions. Numerical comparisons are given for Stokes flows in periodic arrays of spheres and cylinders, linear periodic array of cylinders between moving plates, and for Navier-Stokes flows in periodic arrays of cylinders for Re<200. These results show a significant improvement of the overall accuracy when using the linear interpolations instead of the bounce-back reflection (up to an order of magnitude on the hydrodynamics fields). Further improvement is achieved with the new multireflection boundary conditions, reaching a level of accuracy close to the quasianalytical reference solutions, even for rather modest grid resolutions and few points in the narrowest channels. More important, the pressure and velocity fields in the vicinity of the obstacles are much smoother with multireflection than with the other boundary conditions. Finally the good stability of these schemes is highlighted by some simulations of moving obstacles: a cylinder between flat walls and a sphere in a cylinder. PMID:14754343

  11. Psychodynamic Perspective on Therapeutic Boundaries

    PubMed Central

    Bridges, Nancy A.

    1999-01-01

    Discussion of boundaries in therapeutic work most often focuses on boundary maintenance, risk management factors, and boundary violations. The psychodynamic meaning and clinical management of boundaries in therapeutic relationships remains a neglected area of discourse. Clinical vignettes will illustrate a psychodynamic, developmental-relational perspective using boundary dilemmas to deepen and advance the therapeutic process. This article contributes to the dialogue about the process of making meaning and constructing therapeutically useful and creative boundaries that further the psychotherapeutic process. PMID:10523432

  12. 78 FR 60309 - Minor Boundary Revision at Rocky Mountain National Park

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-01

    ... National Park Service Minor Boundary Revision at Rocky Mountain National Park AGENCY: National Park Service, Interior. ACTION: Notification of Boundary Revision. SUMMARY: The boundary of Rocky Mountain National Park... Larimer County, Colorado, immediately adjacent to the current eastern boundary of Rocky Mountain...

  13. Late Permian high-Mg andesite and basalt association from northern Liaoning, North China: Insights into the final closure of the Paleo-Asian ocean and the orogen-craton boundary

    NASA Astrophysics Data System (ADS)

    Yuan, Lingling; Zhang, Xiaohui; Xue, Fuhong; Lu, Yinghuai; Zong, Keqing

    2016-08-01

    High-Mg andesites (HMAs) and related basalts constitute a volumetrically minor, but genetically important occurrence along most convergent plate margins of various ages on Earth. The details of their petrogenesis can contain critical information for resolving essential geodynamic and crustal evolutionary issues. This zircon U-Pb dating and geochemical study documents the late Permian metamorphosed high-Mg basaltic to andesitic suite from Kaiyuan of northern Liaoning, North China. These rocks feature SiO2 contents ranging from 48.7 to 63.2 wt.%, high Mg# values of 63-75, an enrichment in large-ion lithophile elements (LILE), and depletion in high field strength elements (HFSE). They possess whole-rock initial 87Sr/86Sr ratios of 0.70417-0.70457, εNd(t) values from - 0.4 to 5.0, and εHf(t) values from 5.1 to 11, as well as zircon εHf(t) values from - 9.4 to 0.4. These features indicate that their petrogenesis most likely involved precursory metasomatism of mantle peridotites by melts from subduction-related sediments, and subsequent partial melting. With a depleted mantle source and possible tectonic link to post-subduction slab break-off, the Kaiyuan suite could present a spatial reference not only for defining the demarcation line between the North China craton (NCC) and the Central Asian Orogenic belt (CAOB) in the region, but also for tracing the final location of the cryptic suturing zone of the Paleo-Asian Ocean. Synthesizing the suite with coeval igneous episodes as well as concomitant metamorphic events along the Solonker-Xra Moron-Changchun zone leads to the characterization of the eventual closure of the Paleo-Asian Ocean within a double-sided subduction system during late Permian-Early Triassic.

  14. Tuberculosis: a disease without boundaries.

    PubMed

    Fogel, Nicole

    2015-09-01

    Tuberculosis (TB) is an airborne disease caused by Mycobacterium tuberculosis (MTB) that usually affects the lungs leading to severe coughing, fever, and chest pains. Although current research in the past four years has provided valuable insight into TB transmission, diagnosis, and treatment, much remains to be discovered to effectively decrease the incidence of and eventually eradicate TB. The disease still puts a strain on public health, being only second to HIV/AIDS in causing high mortality rates. This review will highlight the history of TB as well as provide an overview of the current literature on epidemiology, pathogenesis and the immune response, treatment, and control of TB. In this race to combat a disease that knows no boundaries, it is necessary to have a conceptual and clear understanding of TB overall with the hope of providing better treatment through novel and collaborative research and public health efforts. PMID:26198113

  15. Boundary Layer Heights from CALIOP

    NASA Astrophysics Data System (ADS)

    Kuehn, R.; Ackerman, S. A.; Holz, R.; Roubert, L.

    2012-12-01

    This work is focused on the development of a planetary boundary layer (PBL) height retrieval algorithm for CALIOP and validation studies. Our current approach uses a wavelet covariance transform analysis technique to find the top of the boundary layer. We use the methodology similar to that found in Davis et. al. 2000, ours has been developed to work with the lower SNR data provided by CALIOP, and is intended to work autonomously. Concurrently developed with the CALIOP algorithm we will show results from a PBL height retrieval algorithm from profiles of potential temperature, these are derived from Aircraft Meteorological DAta Relay (AMDAR) observations. Results from 5 years of collocated AMDAR - CALIOP retrievals near O'Hare airport demonstrate good agreement between the CALIOP - AMDAR retrievals. In addition, because we are able to make daily retrievals from the AMDAR measurements, we are able to observe the seasonal and annual variation in the PBL height at airports that have sufficient instrumented-aircraft traffic. Also, a comparison has been done between the CALIOP retrievals and the NASA Langley airborne High Spectral Resolution Lidar (HSRL) PBL height retrievals acquired during the GoMACCS experiment. Results of this comparison, like the AMDAR comparison are favorable. Our current work also involves the analysis and verification of the CALIOP PBL height retrieval from the 6 year CALIOP global data set. Results from this analysis will also be presented.

  16. Measurement of double-differential muon neutrino charged-current interactions on C8 H8 without pions in the final state using the T2K off-axis beam

    NASA Astrophysics Data System (ADS)

    Abe, K.; Andreopoulos, C.; Antonova, M.; Aoki, S.; Ariga, A.; Assylbekov, S.; Autiero, D.; Barbi, M.; Barker, G. J.; Barr, G.; Bartet-Friburg, P.; Batkiewicz, M.; Berardi, V.; Berkman, S.; Bhadra, S.; Blondel, A.; Bolognesi, S.; Bordoni, S.; Boyd, S. B.; Brailsford, D.; Bravar, A.; Bronner, C.; Buizza Avanzini, M.; Calland, R. G.; Cao, S.; Caravaca Rodríguez, J.; Cartwright, S. L.; Castillo, R.; Catanesi, M. G.; Cervera, A.; Cherdack, D.; Chikuma, N.; Christodoulou, G.; Clifton, A.; Coleman, J.; Collazuol, G.; Cremonesi, L.; Dabrowska, A.; De Rosa, G.; Dealtry, T.; Denner, P. F.; Dennis, S. R.; Densham, C.; Dewhurst, D.; Di Lodovico, F.; Di Luise, S.; Dolan, S.; Drapier, O.; Duffy, K. E.; Dumarchez, J.; Dytman, S.; Dziewiecki, M.; Emery-Schrenk, S.; Ereditato, A.; Feusels, T.; Finch, A. J.; Fiorentini, G. A.; Friend, M.; Fujii, Y.; Fukuda, D.; Fukuda, Y.; Furmanski, A. P.; Galymov, V.; Garcia, A.; Giffin, S. G.; Giganti, C.; Gizzarelli, F.; Gonin, M.; Grant, N.; Hadley, D. R.; Haegel, L.; Haigh, M. D.; Hamilton, P.; Hansen, D.; Hara, T.; Hartz, M.; Hasegawa, T.; Hastings, N. C.; Hayashino, T.; Hayato, Y.; Helmer, R. L.; Hierholzer, M.; Hillairet, A.; Himmel, A.; Hiraki, T.; Hirota, S.; Hogan, M.; Holeczek, J.; Horikawa, S.; Hosomi, F.; Huang, K.; Ichikawa, A. K.; Ieki, K.; Ikeda, M.; Imber, J.; Insler, J.; Intonti, R. A.; Irvine, T. J.; Ishida, T.; Ishii, T.; Iwai, E.; Iwamoto, K.; Izmaylov, A.; Jacob, A.; Jamieson, B.; Jiang, M.; Johnson, S.; Jo, J. H.; Jonsson, P.; Jung, C. K.; Kabirnezhad, M.; Kaboth, A. C.; Kajita, T.; Kakuno, H.; Kameda, J.; Karlen, D.; Karpikov, I.; Katori, T.; Kearns, E.; Khabibullin, M.; Khotjantsev, A.; Kielczewska, D.; Kikawa, T.; Kim, H.; Kim, J.; King, S.; Kisiel, J.; Knight, A.; Knox, A.; Kobayashi, T.; Koch, L.; Koga, T.; Konaka, A.; Kondo, K.; Kopylov, A.; Kormos, L. L.; Korzenev, A.; Koshio, Y.; Kropp, W.; Kudenko, Y.; Kurjata, R.; Kutter, T.; Lagoda, J.; Lamont, I.; Larkin, E.; Lasorak, P.; Laveder, M.; Lawe, M.; Lazos, M.; Lindner, T.; Liptak, Z. J.; Litchfield, R. P.; Li, X.; Longhin, A.; Lopez, J. P.; Ludovici, L.; Lu, X.; Magaletti, L.; Mahn, K.; Malek, M.; Manly, S.; Marino, A. D.; Marteau, J.; Martin, J. F.; Martins, P.; Martynenko, S.; Maruyama, T.; Matveev, V.; Mavrokoridis, K.; Ma, W. Y.; Mazzucato, E.; McCarthy, M.; McCauley, N.; McFarland, K. S.; McGrew, C.; Mefodiev, A.; Mezzetto, M.; Mijakowski, P.; Minamino, A.; Mineev, O.; Mine, S.; Missert, A.; Miura, M.; Moriyama, S.; Mueller, Th. A.; Murphy, S.; Myslik, J.; Nakadaira, T.; Nakahata, M.; Nakamura, K. G.; Nakamura, K.; Nakamura, K. D.; Nakayama, S.; Nakaya, T.; Nakayoshi, K.; Nantais, C.; Nielsen, C.; Nirkko, M.; Nishikawa, K.; Nishimura, Y.; Nowak, J.; O'Keeffe, H. M.; Ohta, R.; Okumura, K.; Okusawa, T.; Oryszczak, W.; Oser, S. M.; Ovsyannikova, T.; Owen, R. A.; Oyama, Y.; Palladino, V.; Palomino, J. L.; Paolone, V.; Patel, N. D.; Pavin, M.; Payne, D.; Perkin, J. D.; Petrov, Y.; Pickard, L.; Pickering, L.; Pinzon Guerra, E. S.; Pistillo, C.; Popov, B.; Posiadala-Zezula, M.; Poutissou, J.-M.; Poutissou, R.; Przewlocki, P.; Quilain, B.; Radicioni, E.; Ratoff, P. N.; Ravonel, M.; Rayner, M. A. M.; Redij, A.; Reinherz-Aronis, E.; Riccio, C.; Rojas, P.; Rondio, E.; Roth, S.; Rubbia, A.; Rychter, A.; Sacco, R.; Sakashita, K.; Sánchez, F.; Sato, F.; Scantamburlo, E.; Scholberg, K.; Schoppmann, S.; Schwehr, J.; Scott, M.; Seiya, Y.; Sekiguchi, T.; Sekiya, H.; Sgalaberna, D.; Shah, R.; Shaikhiev, A.; Shaker, F.; Shaw, D.; Shiozawa, M.; Shirahige, T.; Short, S.; Smy, M.; Sobczyk, J. T.; Sorel, M.; Southwell, L.; Stamoulis, P.; Steinmann, J.; Stewart, T.; Suda, Y.; Suvorov, S.; Suzuki, A.; Suzuki, K.; Suzuki, S. Y.; Suzuki, Y.; Tacik, R.; Tada, M.; Takahashi, S.; Takeda, A.; Takeuchi, Y.; Tanaka, H. K.; Tanaka, H. A.; Terhorst, D.; Terri, R.; Thakore, T.; Thompson, L. F.; Tobayama, S.; Toki, W.; Tomura, T.; Touramanis, C.; Tsukamoto, T.; Tzanov, M.; Uchida, Y.; Vacheret, A.; Vagins, M.; Vallari, Z.; Vasseur, G.; Wachala, T.; Wakamatsu, K.; Walter, C. W.; Wark, D.; Warzycha, W.; Wascko, M. O.; Weber, A.; Wendell, R.; Wilkes, R. J.; Wilking, M. J.; Wilkinson, C.; Wilson, J. R.; Wilson, R. J.; Yamada, Y.; Yamamoto, K.; Yamamoto, M.; Yanagisawa, C.; Yano, T.; Yen, S.; Yershov, N.; Yokoyama, M.; Yoshida, K.; Yuan, T.; Yu, M.; Zalewska, A.; Zalipska, J.; Zambelli, L.; Zaremba, K.; Ziembicki, M.; Zimmerman, E. D.; Zito, M.; Żmuda, J.; T2K Collaboration

    2016-06-01

    We report the measurement of muon neutrino charged-current interactions on carbon without pions in the final state at the T2K beam energy using 5.734 ×1020 protons on target. For the first time the measurement is reported as a flux-integrated, double-differential cross section in muon kinematic variables (cos θμ, pμ), without correcting for events where a pion is produced and then absorbed by final state interactions. Two analyses are performed with different selections, background evaluations and cross-section extraction methods to demonstrate the robustness of the results against biases due to model-dependent assumptions. The measurements compare favorably with recent models which include nucleon-nucleon correlations but, given the present precision, the measurement does not distinguish among the available models. The data also agree with Monte Carlo simulations which use effective parameters that are tuned to external data to describe the nuclear effects. The total cross section in the full phase space is σ =(0.417 ±0.047 (syst ) ±0.005 (stat ) )×10-38 cm2 nucleon-1 and the cross section integrated in the region of phase space with largest efficiency and best signal-over-background ratio (cos θμ>0.6 and pμ>200 MeV ) is σ =(0.202 ±0.036 (syst ) ±0.003 (stat ) )×10-38 cm2 nucleon-1 .

  17. The coordination of boundary tones and its interaction with prominence.

    PubMed

    Katsika, Argyro; Krivokapić, Jelena; Mooshammer, Christine; Tiede, Mark; Goldstein, Louis

    2014-05-01

    This study investigates the coordination of boundary tones as a function of stress and pitch accent. Boundary tone coordination has not been experimentally investigated previously, and the effect of prominence on this coordination, and whether it is lexical (stress-driven) or phrasal (pitch accent-driven) in nature is unclear. We assess these issues using a variety of syntactic constructions to elicit different boundary tones in an Electromagnetic Articulography (EMA) study of Greek. The results indicate that the onset of boundary tones co-occurs with the articulatory target of the final vowel. This timing is further modified by stress, but not by pitch accent: boundary tones are initiated earlier in words with non-final stress than in words with final stress regardless of accentual status. Visual data inspection reveals that phrase-final words are followed by acoustic pauses during which specific articulatory postures occur. Additional analyses show that these postures reach their achievement point at a stable temporal distance from boundary tone onsets regardless of stress position. Based on these results and parallel findings on boundary lengthening reported elsewhere, a novel approach to prosody is proposed within the context of Articulatory Phonology: rather than seeing prosodic (lexical and phrasal) events as independent entities, a set of coordination relations between them is suggested. The implications of this account for prosodic architecture are discussed. PMID:25300341

  18. Immersed boundary method for the MHD flows of liquid metals

    NASA Astrophysics Data System (ADS)

    Grigoriadis, D. G. E.; Kassinos, S. C.; Votyakov, E. V.

    2009-02-01

    Wall-bounded magnetohydrodynamic (MHD hereafter) flows are of great theoretical and practical interest. Even for laminar cases, MHD simulations are associated with very high computational cost due to the resolution requirements for the Hartmann and side layers developing in the presence of solid obstacles. In the presence of turbulence, these difficulties are further compounded. Thus, MHD simulations in complex geometries are currently a challenge. The immersed boundary (IB hereafter) method is a reliable numerical tool for efficient hydrodynamic field simulations in arbitrarily geometries, but it has not yet been extended for MHD simulations. The present study forms the first attempt to apply the IB methodology for the computation of both the hydrodynamic and MHD fields. A consistent numerical methodology is presented that is appropriate for efficient 3D MHD simulations in geometrically complicated domains using cartesian flow solvers. For that purpose, a projection scheme for the electric current density is presented, based on an electric potential correction algorithm. A suitable forcing scheme for electric density currents in the vicinity of non-conducting immersed surfaces is also proposed. The proposed methodology has been first extensively tested for Hartmann layers in fully-developed and developing channel and duct flows at Hartmann numbers Ha=500-2000. In order to demonstrate the potential of the method, the three-dimensional MHD flow around a circular cylinder at Reynolds number Re=200 is also presented. The effects of grid resolution and variable arrangement on the simulation accuracy and consistency were examined. When compared with existing numerical or analytic solutions, excellent agreement was found for all the cases considered. The proposed projection and forcing schemes for current densities were found capable of satisfying the charge conservation law in the presence of immersed non-conducting boundaries. Finally, we show how the proposed

  19. Free boundary, high beta equilibrium in a large aspect ratio tokamak with nearly circular plasma boundary

    SciTech Connect

    Qin, H.; Reiman, A.

    1996-09-25

    An analytic solution is obtained for free-boundary, high-beta equilibria in large aspect ratio tokamaks with a nearly circular plasma boundary. In the absence of surface currents at the plasma-vacuum interface, the free-boundary equilibrium solution introduces constraints arising from the need to couple to an external vacuum field which is physically realizable with a reasonable set of external field coils. This places a strong constraint on the pressure profiles that are consistent with a given boundary shape at high {epsilon}{beta}{sub p}. The equilibrium solution also provides information on the flux surface topology. The plasma is bounded by a separatrix. Increasing the plasma pressure at fixed total current causes the plasma aperture to decrease in a manner that is described.

  20. A Broad Approach to Abrupt Boundaries: Looking Beyond the Boundary at Soil Attributes within and Across Tropical Vegetation Types

    PubMed Central

    Warman, Laura; Bradford, Matt G.; Moles, Angela T.

    2013-01-01

    Most research on boundaries between vegetation types emphasizes the contrasts and similarities between conditions on either side of a boundary, but does not compare boundary to non-boundary vegetation. That is, most previous studies lack suitable controls, and may therefore overlook underlying aspects of landscape variability at a regional scale and underestimate the effects that the vegetation itself has on the soil. We compared 25 soil chemistry variables in rainforest, sclerophyll vegetation and across rainforest-sclerophyll boundaries in north-eastern Queensland, Australia. Like previous studies, we did find some contrasts in soil chemistry across vegetation boundaries. However we did not find greater variation in chemical parameters across boundary transects than in transects set in either rainforest or woodland. We also found that soil on both sides of the boundary is more similar to “rainforest soil” than to “woodland soil”. Transects in wet sclerophyll forests with increasing degrees of rainforest invasion showed that as rainforest invades wet sclerophyll forest, the soil beneath wet sclerophyll forest becomes increasingly similar to rainforest soil. Our results have implications for understanding regional vegetation dynamics. Considering soil-vegetation feedbacks and the differences between soil at boundaries and in non-boundary sites may hold clues to some of the processes that occur across and between vegetation types in a wide range of ecosystems. Finally, we suggest that including appropriate controls should become standard practice for studies of vegetation boundaries and edge effects worldwide. PMID:23593312

  1. Boundary layer receptivity and control

    NASA Technical Reports Server (NTRS)

    Hill, D. C.

    1993-01-01

    -dimensional motions of a non-parallel boundary layer was developed. The method makes use of the same computationally efficient formulation that makes the PSE currently so appealing. In the area of flow control, adjoint systems offer a powerful insight into the effect of control forces. One of the simplest control strategies for boundary layers involves the application of localized mean wall suction.

  2. Turbulent boundary layers over nonstationary plane boundaries

    NASA Technical Reports Server (NTRS)

    Roper, A. T.

    1976-01-01

    Methods of predicting integral parameters and skin-friction coefficients of turbulent boundary layers developing over moving-ground-planes are evaluated using test information from three different wind tunnel facilities at the NASA Langley Research Center. These data include test information from the VSTOL tunnel which is presented for the first time. The three methods evaluated were: (1) relative integral parameter method, (2) relative power law method, and (3) modified law of the wall method. Methods (1) and (2) can be used to predict moving-ground-plane shape factors with an expected accuracy of + or - 10%. They may also be used to predict moving-ground-plane displacement and momentum thicknesses with lower expected accuracy. This decrease in accuracy can be traced to the failure of approximations upon which these methods are based to prove universal when compared with VSTOL tunnel test results.

  3. Probabilistic boundary element method

    NASA Technical Reports Server (NTRS)

    Cruse, T. A.; Raveendra, S. T.

    1989-01-01

    The purpose of the Probabilistic Structural Analysis Method (PSAM) project is to develop structural analysis capabilities for the design analysis of advanced space propulsion system hardware. The boundary element method (BEM) is used as the basis of the Probabilistic Advanced Analysis Methods (PADAM) which is discussed. The probabilistic BEM code (PBEM) is used to obtain the structural response and sensitivity results to a set of random variables. As such, PBEM performs analogous to other structural analysis codes such as finite elements in the PSAM system. For linear problems, unlike the finite element method (FEM), the BEM governing equations are written at the boundary of the body only, thus, the method eliminates the need to model the volume of the body. However, for general body force problems, a direct condensation of the governing equations to the boundary of the body is not possible and therefore volume modeling is generally required.

  4. Boundary layer simulator improvement

    NASA Technical Reports Server (NTRS)

    Praharaj, Sarat C.; Schmitz, Craig P.; Nouri, Joseph A.

    1989-01-01

    Boundary Layer Integral Matrix Procedure (BLIMPJ) has been identified by the propulsion community as the rigorous boundary layer program in connection with the existing JANNAF reference programs. The improvements made to BLIMPJ and described herein have potential applications in the design of the future Orbit Transfer Vehicle engines. The turbulence model is validated to include the effects of wall roughness and a way is devised to treat multiple smooth-rough surfaces. A prediction of relaminarization regions is examined as is the combined effects of wall cooling and surface roughness on relaminarization. A turbulence model to represent the effects of constant condensed phase loading is given. A procedure is described for thrust decrement calculation in thick boundary layers by coupling the T-D Kinetics Program and BLIMPJ and a way is provided for thrust loss optimization. Potential experimental studies in rocket nozzles are identified along with the required instrumentation to provide accurate measurements in support of the presented new analytical models.

  5. Road boundary detection

    NASA Technical Reports Server (NTRS)

    Sowers, J.; Mehrotra, R.; Sethi, I. K.

    1989-01-01

    A method for extracting road boundaries using the monochrome image of a visual road scene is presented. The statistical information regarding the intensity levels present in the image along with some geometrical constraints concerning the road are the basics of this approach. Results and advantages of this technique compared to others are discussed. The major advantages of this technique, when compared to others, are its ability to process the image in only one pass, to limit the area searched in the image using only knowledge concerning the road geometry and previous boundary information, and dynamically adjust for inconsistencies in the located boundary information, all of which helps to increase the efficacy of this technique.

  6. USACE DIVISION AND DISTRICT BOUNDARIES

    EPA Science Inventory

    The USACE Division and District Boundary data contains the delination of Corps Division and District boundaries. District and Division Boundaries are based on the US political and watershed boundaries. In the mid 1990's, WES created the file by digitizing the 1984 Civil Wor...

  7. Extending the Boundaries of College Reading Programs.

    ERIC Educational Resources Information Center

    Jeremiah, Milford A.

    The current uniform content of college reading programs can be expanded to include insights from other disciplines, specifically those areas of instruction which pertain to the neuropsychological mechanisms governing behavior, especially language behavior. There are several reasons for expanding the boundaries of college reading programs to…

  8. Algorithms for Discovery of Multiple Markov Boundaries

    PubMed Central

    Statnikov, Alexander; Lytkin, Nikita I.; Lemeire, Jan; Aliferis, Constantin F.

    2013-01-01

    Algorithms for Markov boundary discovery from data constitute an important recent development in machine learning, primarily because they offer a principled solution to the variable/feature selection problem and give insight on local causal structure. Over the last decade many sound algorithms have been proposed to identify a single Markov boundary of the response variable. Even though faithful distributions and, more broadly, distributions that satisfy the intersection property always have a single Markov boundary, other distributions/data sets may have multiple Markov boundaries of the response variable. The latter distributions/data sets are common in practical data-analytic applications, and there are several reasons why it is important to induce multiple Markov boundaries from such data. However, there are currently no sound and efficient algorithms that can accomplish this task. This paper describes a family of algorithms TIE* that can discover all Markov boundaries in a distribution. The broad applicability as well as efficiency of the new algorithmic family is demonstrated in an extensive benchmarking study that involved comparison with 26 state-of-the-art algorithms/variants in 15 data sets from a diversity of application domains. PMID:25285052

  9. Ferroelectric translational antiphase boundaries in nonpolar materials

    PubMed Central

    Wei, Xian-Kui; Tagantsev, Alexander K.; Kvasov, Alexander; Roleder, Krystian; Jia, Chun-Lin; Setter, Nava

    2014-01-01

    Ferroelectric materials are heavily used in electro-mechanics and electronics. Inside the ferroelectric, domain walls separate regions in which the spontaneous polarization is differently oriented. Properties of ferroelectric domain walls can differ from those of the domains themselves, leading to new exploitable phenomena. Even more exciting is that a non-ferroelectric material may have domain boundaries that are ferroelectric. Many materials possess translational antiphase boundaries. Such boundaries could be interesting entities to carry information if they were ferroelectric. Here we show first that antiphase boundaries in antiferroelectrics may possess ferroelectricity. We then identify these boundaries in the classical antiferroelectric lead zirconate and evidence their polarity by electron microscopy using negative spherical-aberration imaging technique. Ab initio modelling confirms the polar bi-stable nature of the walls. Ferroelectric antiphase boundaries could make high-density non-volatile memory; in comparison with the magnetic domain wall memory, they do not require current for operation and are an order of magnitude thinner. PMID:24398704

  10. Edge Plasma Boundary Layer Generated By Kink Modes in Tokamaks

    SciTech Connect

    L.E. Zakharov

    2010-11-22

    This paper describes the structure of the electric current generated by external kink modes at the plasma edge using the ideally conducting plasma model. It is found that the edge current layer is created by both wall touching and free boundary kink modes. Near marginal stability, the total edge current has a universal expression as a result of partial compensation of the δ-functional surface current by the bulk current at the edge. The resolution of an apparent paradox with the pressure balance across the plasma boundary in the presence of the surface currents is provided.

  11. Boundary Layer Cloudiness Parameterizations Using ARM Observations

    SciTech Connect

    Bruce Albrecht

    2004-09-15

    This study used DOE ARM data and facilities to: (1) study macroscopic properties of continental stratus clouds at SGP and the factors controlling these properties, (2) develop a scientific basis for understanding the processes responsible for the formation of boundary layer clouds using ARM observations in conjunction with simple parametric models and LES, and (3) evaluate cumulus cloud characteristics retrieved from the MMCR operating at TWP-Nauru. In addition we have used high resolution 94 GHz observations of boundary layer clouds and precipitation to: (1) develop techniques for using high temporal resolution Doppler velocities to study large-eddy circulations and turbulence in boundary layer clouds and estimate the limitations of using current and past MMCR data for boundary layer cloud studies, (2) evaluate the capability and limitations of the current MMCR data for estimating reflectivity, vertical velocities, and spectral under low- signal-to-noise conditions associated with weak no n-precipitating clouds, (3) develop possible sampling modes for the new MMCR processors to allow for adequate sampling of boundary layer clouds, and (4) retrieve updraft and downdraft structures under precipitating conditions.

  12. The Kinematics of Turbulent Boundary Layer Structure

    NASA Technical Reports Server (NTRS)

    Robinson, Stephen Kern

    1991-01-01

    The long history of research into the internal structure of turbulent boundary layers has not provided a unified picture of the physics responsible for turbulence production and dissipation. The goals of the present research are to: (1) define the current state of boundary layer structure knowledge; and (2) utilize direct numerical simulation results to help close the unresolved issues identified in part A and to unify the fragmented knowledge of various coherent motions into a consistent kinematic model of boundary layer structure. The results of the current study show that all classes of coherent motion in the low Reynolds number turbulent boundary layer may be related to vortical structures, but that no single form of vortex is representative of the wide variety of vortical structures observed. In particular, ejection and sweep motions, as well as entrainment from the free-streem are shown to have strong spatial and temporal relationships with vortical structures. Disturbances of vortex size, location, and intensity show that quasi-streamwise vortices dominate the buffer region, while transverse vortices and vortical arches dominate the wake region. Both types of vortical structure are common in the log region. The interrelationships between the various structures and the population distributions of vortices are combined into a conceptual kinematic model for the boundary layer. Aspects of vortical structure dynamics are also postulated, based on time-sequence animations of the numerically simulated flow.

  13. SEMICONDUCTOR PHYSICS: Tunnelling piezoresistive effect of grain boundary in polysilicon nano-films

    NASA Astrophysics Data System (ADS)

    Rongyan, Chuai; Bin, Liu; Xiaowei, Liu; Xianlong, Sun; Changzhi, Shi; Lijian, Yang

    2010-03-01

    The experiment results indicate that the gauge factor of highly boron doped polysilicon nanofilm is bigger than that of monocrystalline silicon with the same doping concentration, and increases with the grain size decreasing. To apply the unique properties reasonably in the fabrication of piezoresistive devices, it was expounded based on the analysis of energy band structure that the properties were caused by the tunnel current which varies with the strain change forming a tunnelling piezoresistive effect. Finally, a calculation method of piezoresistance coefficients around grain boundaries was presented, and then the experiment results of polysilicon nanofilms were explained theoretically.

  14. 2D Turbulence with Complicated Boundaries

    NASA Astrophysics Data System (ADS)

    Roullet, G.; McWilliams, J. C.

    2014-12-01

    We examine the consequences of lateral viscous boundary layers on the 2D turbulence that arises in domains with complicated boundaries (headlands, bays etc). The study is carried out numerically with LES. The numerics are carefully designed to ensure all global conservation laws, proper boundary conditions and a minimal range of dissipation scales. The turbulence dramatically differs from the classical bi-periodic case. Boundary layer separations lead to creation of many small vortices and act as a continuing energy source exciting the inverse cascade of energy throughout the domain. The detachments are very intermittent in time. In free decay, the final state depends on the effective numerical resolution: laminar with a single dominant vortex for low Re and turbulent with many vortices for large enough Re. After very long time, the turbulent end-state exhibits a striking tendency for the emergence of shielded vortices which then interact almost elastically. In the forced case, the boundary layers allow the turbulence to reach a statistical steady state without any artificial hypo-viscosity or other large-scale dissipation. Implications are discussed for the oceanic mesoscale and submesoscale turbulence.

  15. Boundary-Layer-Ingesting Inlet Flow Control

    NASA Technical Reports Server (NTRS)

    Owens, Lewis R.; Allan, Brian G.; Gorton, Susan A.

    2008-01-01

    An experimental study was conducted to provide the first demonstration of an active flow control system for a flush-mounted inlet with significant boundary-layer-ingestion in transonic flow conditions. The effectiveness of the flow control in reducing the circumferential distortion at the engine fan-face location was assessed using a 2.5%-scale model of a boundary-layer-ingesting offset diffusing inlet. The inlet was flush mounted to the tunnel wall and ingested a large boundary layer with a boundary-layer-to-inlet height ratio of 35%. Different jet distribution patterns and jet mass flow rates were used in the inlet to control distortion. A vane configuration was also tested. Finally a hybrid vane/jet configuration was tested leveraging strengths of both types of devices. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow rates through the duct and the flow control actuators. The distortion and pressure recovery were measured at the aerodynamic interface plane. The data show that control jets and vanes reduce circumferential distortion to acceptable levels. The point-design vane configuration produced higher distortion levels at off-design settings. The hybrid vane/jet flow control configuration reduced the off-design distortion levels to acceptable ones and used less than 0.5% of the inlet mass flow to supply the jets.

  16. CBED and LACBED: characterization of antiphase boundaries.

    PubMed

    Morniroli, J P; Nó, M L; Rodríguez, P P; San Juan, J; Jezierska, E; Michel, N; Poulat, S; Priester, L

    2003-12-01

    Convergent-beam electron diffraction (CBED) and large-angle convergent-beam electron diffraction (LACBED) techniques are well adapted to the characterization of several types of crystal defects. In fact, dislocations, grain boundaries and stacking faults have already been successfully characterized with these methods. In the present paper, we describe the CBED and LACBED characterization of another type of crystal defect showing a special interest in materials science: antiphase boundaries (APBs). The first part of the paper is devoted to the determination of the effects of antiphase boundaries on CBED and LACBED patterns that could be expected from a theoretical point of view. It indicates that the superlattice excess lines present on these patterns are split into two lines with equal intensity when the incident beam is located on an APB. In the second part, we experimentally test these theoretical predictions on a specimen showing two different known types of antiphase boundaries. In a third part we indicate how these methods could be used to identify unknown APBs in a specimen. Finally, the advantages and disadvantages of both methods for the characterization of antiphase boundaries are discussed. PMID:14609639

  17. Free-boundary magnetohydrodynamic equilibria with flow

    SciTech Connect

    Schmitt, R. F.; Park, G. Y.; Guazzotto, L.; Strauss, H.; Chang, C.-S.

    2011-02-15

    The finite-element M3D code [W. Park et al., Phys. Plasmas 6, 1796 (1999)] has been modified to include a free-boundary equilibrium solver with arbitrary toroidal and poloidal flows. With this modification, the M3D code now has the capability to self-consistently model two essential ingredients necessary for equilibrium calculations in the edge region, namely, free-boundary and arbitrary flow. As a free-boundary code, M3D includes the separatrix and scrape-off layer regions in the equilibrium calculation. Poloidal flows in the subsonic, supersonic, and transonic regimes can be calculated with the new version of the M3D code. Calculation results show that the presence of equilibrium flows, in particular those next to the plasma boundary, can considerably influence the position of the X-point and magnetic separatrix shape/location and hence the position of the strike point on the divertor plates. Moreover, it is shown that poloidal flow is not a rigid-body rotation, with the fastest flows occurring on the inboard side of the plasma. A numerical confirmation of the ''de Laval nozzle'' model of Betti and Freidberg [R. Betti and J. P. Freidberg, Phys. Plasmas 7, 2439 (2000)] for free-boundary equilibrium calculations is obtained, with the formation of the predicted discontinuities between regions of subsonic and supersonic flows (with respect to the poloidal sound speed). Finally, a detailed comparison between isentropic and isothermal equilibria is presented, showing qualitative analogies and quantitative differences.

  18. RCRA TSD BOUNDARIES

    EPA Science Inventory

    This is a shapefile of RCRA Treatment, Storage, and Disposal facility boundaries developed by PRC Environmental Management, Inc (PRC) per a Work Assignment from the U.S. EPA under the Resource Conservation and Recovery Act (RCRA) Enforcement, Permitting, and Assistance (REPA) Con...

  19. 2000 CENSUS BLOCK BOUNDARIES

    EPA Science Inventory

    This data set is a polygon shapefile of the boundaries of Census Blocks in New England derived from U.S. Census Bureau 2000 TIGER/Line data. Numerous attributes pertaining to population are included. TIGER, TIGER/Line, and Census TIGER are registered trademarks of the Bureau o...

  20. Saturn's Magnetospheric Boundaries

    NASA Astrophysics Data System (ADS)

    Kurth, W. S.; Gurnett, D. A.; Hospodarsky, G. B.; Dougherty, M. K.; Arridge, C. S.; Achilleos, N. A.; Andre, N.; Crary, F. J.; McAndrews, H. J.; Szego, K.; Rymer, A. M.; Krimigis, S. M.; Mitchell, D. G.; Krupp, N.; Hamilton, D. C.; Hansen, K. C.

    2005-12-01

    Cassini has now been in orbit at Saturn for more than a year, making more than 12 passes through Saturn's magnetosphere. While the apoapses of these orbits have so far remained clustered near dawn and the inclinations have been mostly below about 20 degrees, progress has been made in mapping and understanding various magnetospheric boundaries. For example, initial modeling of the bow shock and magnetopause by Hendricks et al. [GRL, 32, 2005] suggest the magnetosphere is somewhat more inflated than thought from Pioneer- and Voyager-based models. Of perhaps even more interest are internal boundaries within the magnetosphere. These boundaries separate various magnetospheric regions and are less rigorously defined than the external boundaries. In fact, a number of authors have identified different regions based on particular sets of measurements; we review some of these and attempt to integrate these into a scheme of general utility, realizing that ongoing work on interpretation of existing observations and high inclination orbits to come will likely modify any such scheme we may devise this early in Cassini's tour.

  1. 75 FR 50745 - Boundary Establishment for the Black National Wild and Scenic River; Ottawa National Forest...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-17

    ... Forest Service Boundary Establishment for the Black National Wild and Scenic River; Ottawa National..., is transmitting the final boundary of the Black National Wild and Scenic River to Congress. ] FOR... INFORMATION: The Black Wild and Scenic River boundary is available for review at the following offices:...

  2. 77 FR 18997 - Boundary Establishment for the Presque Isle National Wild and Scenic River, Ottawa National...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-29

    ...; ] DEPARTMENT OF AGRICULTURE Forest Service Boundary Establishment for the Presque Isle National Wild and Scenic... Service, Washington Office, is transmitting the final boundary of the Presque Isle National Wild and...-1330, ext. 342. SUPPLEMENTARY INFORMATION: The Presque Isle Wild and Scenic River boundary is...

  3. 77 FR 21522 - Boundary Establishment for the Allegheny National Wild and Scenic River, Allegheny National...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-10

    ...; ] DEPARTMENT OF AGRICULTURE Forest Service Boundary Establishment for the Allegheny National Wild and Scenic... Act, the USDA Forest Service, Washington Office, is transmitting the final boundary of the Allegheny... phone (814) 728-6239. SUPPLEMENTARY INFORMATION: The Allegheny Wild and Scenic River boundary...

  4. Accretion disk boundary layers in cataclysmic variables. 1: Optically thick boundary layers

    NASA Technical Reports Server (NTRS)

    Popham, Robert; Narayan, Ramesh

    1995-01-01

    We develop numerical models of accretions disks in cataclysmic variables (CVs), including and emphasizing the boundary layer region where the accretion disk meets the accreting white dwarf. We confine ourselves to solutions where the boundary layer region is vertically optically thick, and find that these solutions share several common features. The angular and radial velocities of the accreting material drop rapidly in a dynamical boundary layer, which has a radial width approximately 1%-3% of the white dwarf radius. The energy dissipated in this region diffuses through the inner part of the disk and is radiated from the disk surface in a thermal boundary layer, which has a radial width comparable to the disk thickness, approximately 5%-15% of the white dwarf radius. We examine the dependence of the boundary layer structure on the mass accretion rate, the white dwarf mass and rotation rate, and the viscosity parameter alpha. We delineate the boundary between optically thick and optically thin boundary layer solutions as a function of these parameters and suggest that by means of a careful comparison with observations it may be possible to estimate alpha in CVs. We derive an expression for the total boundary layer luminosities as a function of the parameters and show that it agrees well with the luminosites of our numerical solutions. Finally, we calcuate simple blackbody continuum spectra of the boundary layer and disk emission for our solutions and compare these to soft X-ray, EUV, and He II emission-line observations of CVs. We show that, through such comparisons, it may be possible to determine the rotation rates of the accreting stars in CVs, and perhaps also the white dwarf masses and the accretion rates. The spectra are quite insensitive to alpha, so the uncertainty in this parameter does not affect such comparisons.

  5. Computation of grain boundary stiffness and mobility from boundary fluctuations.

    SciTech Connect

    Hoyt, Jeffrey John; Foiles, Stephen Martin

    2005-06-01

    Grain boundary stiffness and mobility determine the kinetics of curvature-driven grain growth. Here the stiffness and mobility are computed using an analysis of fluctuations in the grain boundary position during molecular dynamics simulations. This work represents the first determination of grain boundary stiffness for a realistic three-dimensional system. The results indicate that the boundary stiffness for a given boundary plane has a strong dependence on the direction of the boundary distortion. The mobility deduced is comparable with that determined in previous computer simulation studies. The advantages and limitations of the fluctuation approach are discussed.

  6. On the theory of laminar boundary layers involving separation

    NASA Technical Reports Server (NTRS)

    Von Karman, TH; Millikan, C

    1934-01-01

    This paper presents a mathematical discussion of the laminar boundary layer, which was developed with a view of facilitating the investigation of those boundary layers in particular for which the phenomenon of separation occurs. The treatment starts with a slight modification of the form of the boundary layer equation first published by Von Mises. Two approximate solutions of this equation are found, one of which is exact at the outer edge of the boundary layer while the other is exact at the wall. The final solution is obtained by joining these two solutions at the inflection points of the velocity profiles. The final solution is given in terms of a series of universal functions for a fairly broad class of potential velocity distributions outside of the boundary layer. Detailed calculations of the boundary layer characteristics are worked out for the case in which the potential velocity is a linear function of the distance from the upstream stagnation point. Finally, the complete separation point characteristics are determined for the boundary layer associated with a potential velocity distribution made up of two linear functions of the distance from the stagnation point. It appears that extensions of the detailed calculations to more complex potential flows can be fairly easily carried out by using the explicit formulae given in the paper. (author)

  7. Uranus evolution models with simple thermal boundary layers

    NASA Astrophysics Data System (ADS)

    Nettelmann, N.; Wang, K.; Fortney, J. J.; Hamel, S.; Yellamilli, S.; Bethkenhagen, M.; Redmer, R.

    2016-09-01

    The strikingly low luminosity of Uranus (Teff ≃ Teq) constitutes a long-standing challenge to our understanding of Ice Giant planets. Here we present the first Uranus structure and evolution models that are constructed to agree with both the observed low luminosity and the gravity field data. Our models make use of modern ab initio equations of state at high pressures for the icy components water, methane, and ammonia. Proceeding step by step, we confirm that adiabatic models yield cooling times that are too long, even when uncertainties in the ice:rock ratio (I:R) are taken into account. We then argue that the transition between the ice/rock-rich interior and the H/He-rich outer envelope should be stably stratified. Therefore, we introduce a simple thermal boundary and adjust it to reproduce the low luminosity. Due to this thermal boundary, the deep interior of the Uranus models are up to 2-3 warmer than adiabatic models, necessitating the presence of rocks in the deep interior with a possible I:R of 1 × solar. Finally, we allow for an equilibrium evolution (Teff ≃ Teq) that begun prior to the present day, which would therefore no longer require the current era to be a "special time" in Uranus' evolution. In this scenario, the thermal boundary leads to more rapid cooling of the outer envelope. When Teff ≃ Teq is reached, a shallow, subadiabatic zone in the atmosphere begins to develop. Its depth is adjusted to meet the luminosity constraint. This work provides a simple foundation for future Ice Giant structure and evolution models, that can be improved by properly treating the heat and particle fluxes in the diffusive zones.

  8. Infrared Imaging of Boundary Layer Transition Flight Experiments

    NASA Technical Reports Server (NTRS)

    Berry, Scott A.; Horvath, Thomas J., Jr.; Schwartz, Richard; Ross, Martin; Anderson, Brian; Campbell, Charles H.

    2008-01-01

    The Hypersonic Thermodynamic Infrared Measurement (HYTHIRM) project is presently focused on near term support to the Shuttle program through the development of an infrared imaging capability of sufficient spatial and temporal resolution to augment existing on-board Orbiter instrumentation. Significant progress has been made with the identification and inventory of relevant existing optical imaging assets and the development, maturation, and validation of simulation and modeling tools for assessment and mission planning purposes, which were intended to lead to the best strategies and assets for successful acquisition of quantitative global surface temperature data on the Shuttle during entry. However, there are longer-term goals of providing global infrared imaging support to other flight projects as well. A status of HYTHIRM from the perspective of how two NASA-sponsored boundary layer transition flight experiments could benefit by infrared measurements is provided. Those two flight projects are the Hypersonic Boundary layer Transition (HyBoLT) flight experiment and the Shuttle Boundary Layer Transition Flight Experiment (BLT FE), which are both intended for reducing uncertainties associated with the extrapolation of wind tunnel derived transition correlations for flight application. Thus, the criticality of obtaining high quality flight data along with the impact it would provide to the Shuttle program damage assessment process are discussed. Two recent wind tunnel efforts that were intended as risk mitigation in terms of quantifying the transition process and resulting turbulent wedge locations are briefly reviewed. Progress is being made towards finalizing an imaging strategy in support of the Shuttle BLT FE, however there are no plans currently to image HyBoLT.

  9. Identification of DNA double strand breaks at chromosome boundaries along the track of particle irradiation.

    PubMed

    Niimi, Atsuko; Yamauchi, Motohiro; Limsirichaikul, Siripan; Sekine, Ryota; Oike, Takahiro; Sato, Hiro; Suzuki, Keiji; Held, Kathryn D; Nakano, Takashi; Shibata, Atsushi

    2016-08-01

    Chromosomal translocations arise from misrejoining of DNA double strand breaks (DSBs) between loci located on two chromosomes. One current model suggests that spatial proximity of potential chromosomal translocation partners influences translocation probability. Ionizing radiation (IR) is a potent inducer of translocations. Accumulating evidence demonstrates that particle irradiation more frequently causes translocations compared with X-ray irradiation. This observation has led to the hypothesis that the high frequency of translocations after particle irradiation may be due to the formation of DSBs at chromosome boundaries along the particle track, because such DSBs can be misrejoined between distinct chromosomes. In this study, we simultaneously visualized the site of IR-induced DSBs and chromosome position by combining Immunofluorescence and fluorescence in situ hybridization. Importantly, the frequency of γH2AX foci at the chromosome boundary of chromosome 1 after carbon-ion irradiation was >4-fold higher than that after X-ray irradiation. This observation is consistent with the idea that particle irradiation generates DSBs at the boundaries of two chromosomes along the track. Further, we showed that resolution of γH2AX foci at chromosome boundaries is prevented by inhibition of DNA-PKcs activity, indicating that the DSB repair is NHEJ-dependent. Finally, we found that γH2AX foci at chromosome boundaries after carbon-ion irradiation contain DSBs undergoing DNA-end resection, which promotes repair utilizing microhomology mediated end-joining during translocation. Taken together, our study suggests that the frequency of DSB formation at chromosome boundaries is associated with the incidence of chromosomal translocations, supporting the notion that the spatial proximity between breaks is an important factor in translocation formation. © 2016 Wiley Periodicals, Inc. PMID:27113385

  10. A VERSATILE SHARP INTERFACE IMMERSED BOUNDARY METHOD FOR INCOMPRESSIBLE FLOWS WITH COMPLEX BOUNDARIES

    PubMed Central

    Mittal, R.; Dong, H.; Bozkurttas, M.; Najjar, F.M.; Vargas, A.; von Loebbecke, A.

    2010-01-01

    A sharp interface immersed boundary method for simulating incompressible viscous flow past three-dimensional immersed bodies is described. The method employs a multi-dimensional ghost-cell methodology to satisfy the boundary conditions on the immersed boundary and the method is designed to handle highly complex three-dimensional, stationary, moving and/or deforming bodies. The complex immersed surfaces are represented by grids consisting of unstructured triangular elements; while the flow is computed on non-uniform Cartesian grids. The paper describes the salient features of the methodology with special emphasis on the immersed boundary treatment for stationary and moving boundaries. Simulations of a number of canonical two- and three-dimensional flows are used to verify the accuracy and fidelity of the solver over a range of Reynolds numbers. Flow past suddenly accelerated bodies are used to validate the solver for moving boundary problems. Finally two cases inspired from biology with highly complex three-dimensional bodies are simulated in order to demonstrate the versatility of the method. PMID:20216919

  11. The relationship between grain boundary structure, defect mobility, and grain boundary sink efficiency

    DOE PAGESBeta

    Uberuaga, Blas Pedro; Vernon, Louis J.; Martinez, Enrique; Voter, Arthur F.

    2015-03-13

    Nanocrystalline materials have received great attention due to their potential for improved functionality and have been proposed for extreme environments where the interfaces are expected to promote radiation tolerance. However, the precise role of the interfaces in modifying defect behavior is unclear. Using long-time simulations methods, we determine the mobility of defects and defect clusters at grain boundaries in Cu. We find that mobilities vary significantly with boundary structure and cluster size, with larger clusters exhibiting reduced mobility, and that interface sink efficiency depends on the kinetics of defects within the interface via the in-boundary annihilation rate of defects. Thus,more » sink efficiency is a strong function of defect mobility, which depends on boundary structure, a property that evolves with time. Further, defect mobility at boundaries can be slower than in the bulk, which has general implications for the properties of polycrystalline materials. Finally, we correlate defect energetics with the volumes of atomic sites at the boundary.« less

  12. Boundary layer simulator improvement

    NASA Technical Reports Server (NTRS)

    Praharaj, S. C.; Schmitz, C.; Frost, C.; Engel, C. D.; Fuller, C. E.; Bender, R. L.; Pond, J.

    1984-01-01

    High chamber pressure expander cycles proposed for orbit transfer vehicles depend primarily on the heat energy transmitted from the combustion products through the thrust wall chamber wall. The heat transfer to the nozzle wall is affected by such variables as wall roughness, relamarization, and the presence of particles in the flow. Motor performance loss for these nozzles with thick boundary layers is inaccurate using the existing procedure coded BLIMPJ. Modifications and innovations to the code are examined. Updated routines are listed.

  13. Boundary transfer matrices and boundary quantum KZ equations

    SciTech Connect

    Vlaar, Bart

    2015-07-15

    A simple relation between inhomogeneous transfer matrices and boundary quantum Knizhnik-Zamolodchikov (KZ) equations is exhibited for quantum integrable systems with reflecting boundary conditions, analogous to an observation by Gaudin for periodic systems. Thus, the boundary quantum KZ equations receive a new motivation. We also derive the commutativity of Sklyanin’s boundary transfer matrices by merely imposing appropriate reflection equations, in particular without using the conditions of crossing symmetry and unitarity of the R-matrix.

  14. Carbon transport in the bottom boundary layer. Final report

    SciTech Connect

    Walsh, I.D.

    1998-11-01

    The central goal of DOE`s Ocean Margin Program (OMP) has been to determine whether continental shelves are quantitatively significant in removing carbon dioxide from the atmosphere and isolating it via burial in sediments or exporting it to the open ocean. The purpose of this research was to recover and process samples from two sediment traps deployed on the continental slope in conjunction with the OMP physical oceanography mooring program.

  15. A Model for Axial Magnetic Bearings Including Eddy Currents

    NASA Technical Reports Server (NTRS)

    Kucera, Ladislav; Ahrens, Markus

    1996-01-01

    This paper presents an analytical method of modelling eddy currents inside axial bearings. The problem is solved by dividing an axial bearing into elementary geometric forms, solving the Maxwell equations for these simplified geometries, defining boundary conditions and combining the geometries. The final result is an analytical solution for the flux, from which the impedance and the force of an axial bearing can be derived. Several impedance measurements have shown that the analytical solution can fit the measured data with a precision of approximately 5%.

  16. Cell boundary fault detection system

    DOEpatents

    Archer, Charles Jens; Pinnow, Kurt Walter; Ratterman, Joseph D.; Smith, Brian Edward

    2009-05-05

    A method determines a nodal fault along the boundary, or face, of a computing cell. Nodes on adjacent cell boundaries communicate with each other, and the communications are analyzed to determine if a node or connection is faulty.

  17. Boundary terms for causal sets

    NASA Astrophysics Data System (ADS)

    Buck, Michel; Dowker, Fay; Jubb, Ian; Surya, Sumati

    2015-10-01

    We propose a family of boundary terms for the action of a causal set with a spacelike boundary. We show that in the continuum limit one recovers the Gibbons-Hawking-York boundary term in the mean. We also calculate the continuum limit of the mean causal set action for an Alexandrov interval in flat spacetime. We find that it is equal to the volume of the codimension-2 intersection of the two light-cone boundaries of the interval.

  18. The study of surface wetting, nanobubbles and boundary slip with an applied voltage: A review

    PubMed Central

    Pan, Yunlu; Zhao, Xuezeng

    2014-01-01

    Summary The drag of fluid flow at the solid–liquid interface in the micro/nanoscale is an important issue in micro/nanofluidic systems. Drag depends on the surface wetting, nanobubbles, surface charge and boundary slip. Some researchers have focused on the relationship between these interface properties. In this review, the influence of an applied voltage on the surface wettability, nanobubbles, surface charge density and slip length are discussed. The contact angle (CA) and contact angle hysteresis (CAH) of a droplet of deionized (DI) water on a hydrophobic polystyrene (PS) surface were measured with applied direct current (DC) and alternating current (AC) voltages. The nanobubbles in DI water and three kinds of saline solution on a PS surface were imaged when a voltage was applied. The influence of the surface charge density on the nanobubbles was analyzed. Then the slip length and the electrostatic force on the probe were measured on an octadecyltrichlorosilane (OTS) surface with applied voltage. The influence of the surface charge on the boundary slip and drag of fluid flow has been discussed. Finally, the influence of the applied voltage on the surface wetting, nanobubbles, surface charge, boundary slip and the drag of liquid flow are summarized. With a smaller surface charge density which could be achieved by applying a voltage on the surface, larger and fewer nanobubbles, a larger slip length and a smaller drag of liquid flow could be found. PMID:25161839

  19. The study of surface wetting, nanobubbles and boundary slip with an applied voltage: A review.

    PubMed

    Pan, Yunlu; Bhushan, Bharat; Zhao, Xuezeng

    2014-01-01

    The drag of fluid flow at the solid-liquid interface in the micro/nanoscale is an important issue in micro/nanofluidic systems. Drag depends on the surface wetting, nanobubbles, surface charge and boundary slip. Some researchers have focused on the relationship between these interface properties. In this review, the influence of an applied voltage on the surface wettability, nanobubbles, surface charge density and slip length are discussed. The contact angle (CA) and contact angle hysteresis (CAH) of a droplet of deionized (DI) water on a hydrophobic polystyrene (PS) surface were measured with applied direct current (DC) and alternating current (AC) voltages. The nanobubbles in DI water and three kinds of saline solution on a PS surface were imaged when a voltage was applied. The influence of the surface charge density on the nanobubbles was analyzed. Then the slip length and the electrostatic force on the probe were measured on an octadecyltrichlorosilane (OTS) surface with applied voltage. The influence of the surface charge on the boundary slip and drag of fluid flow has been discussed. Finally, the influence of the applied voltage on the surface wetting, nanobubbles, surface charge, boundary slip and the drag of liquid flow are summarized. With a smaller surface charge density which could be achieved by applying a voltage on the surface, larger and fewer nanobubbles, a larger slip length and a smaller drag of liquid flow could be found. PMID:25161839

  20. Derivation and implementation of the boundary integral formula for the convective acoustic wave equation in time domain.

    PubMed

    Lee, Yong Woo; Lee, Duck Joo

    2014-12-01

    Kirchhoff's formula for the convective wave equation is derived using the generalized function theory. The generalized convective wave equation for a stationary surface is obtained, and the integral formulation, the convective Kirchhoff's formula, is derived. The formula has a similar form to the classical Kirchhoff's formula, but an additional term appears due to a moving medium effect. For convenience, the additional term is manipulated to a final form as the classical Kirchhoff's formula. The frequency domain boundary integral can be obtained from the current time domain boundary integral form. The derived formula is verified by comparison with the analytic solution of source in the uniform flow. The formula is also utilized as a boundary integral equation. Time domain boundary element method (BEM) analysis using the boundary integral equation is conducted, and the results show good agreement with the analytical solution. The formula derived here can be useful for sound radiation and scattering by arbitrary bodies in a moving medium in the time domain. PMID:25480045

  1. Destiny of earthward streaming plasma in the plasmasheet boundary layer

    NASA Technical Reports Server (NTRS)

    Green, J. L.; Horwitz, J. L.

    1986-01-01

    The dynamics of the earth's magnetotail have been investigated, and it has become clear that the plasmasheet boundary layer field lines map into the Region I Field-Aligned Currents (FAC) of the auroral zone. It is pointed out that the role of earthward streaming ions in the plasmasheet boundary layer may be of fundamental importance in the understanding of magnetotail dynamics, auroral zone physics, and especially for ionospheric-magnetospheric interactions. The present paper has the objective to evaluate propagation characteristics for the earthward streaming ions observed in the plasmasheet boundary layer. An investigation is conducted of the propagation characteristics of protons in the plasmasheet boundary layer using independent single particle dynamics, and conclusions are discussed. The density of earthward streaming ions found in the plasmasheet boundary layer should include the ring current as well as the auroral zone precipitaiton and inner plasmasheet regions of the magnetosphere.

  2. Textured boundaries and their effects on ciliary locomotion

    NASA Astrophysics Data System (ADS)

    Jana, Saikat; Yang, Sung; Jung, Sunghwan

    2011-03-01

    Many microorganisms in nature propel themselves by creating coordinated motion of the cilia and often interact with each other through hydrodynamic interactions. We study the behavior of these organisms near boundaries of different topography and rationalize the hydrodynamic effects involved. Various geometries like wavy, rough or solid walls are simulated using micro fabrication and their effects on the locomotory traits are observed. Finally a comprehensive discussion on the effect of different boundaries on the swimming characteristics of the organism is presented.

  3. Interaction of a synthetic jet with a flat plate boundary layer

    NASA Astrophysics Data System (ADS)

    Rampunggoon, Prakit

    The interaction of a 2-dimensional modeled synthetic jet with a flat plate boundary layer is investigated numerically using an incompressible Navier-Stokes solver. A simple, two-dimensional synthetic jet configuration along with a flat plate, laminar Blasius boundary layer was used in the current study. The oscillating diaphragm of the actuator is modeled in a realistic manner as a moving boundary in an effort to accurately compute the flow inside the jet cavity. The primary focus of the current study is on describing the dynamics of the synthetic jet in the presence of external crossflow. However, in addition, simulations of the jet with quiescent external flow have also been performed. A systematic framework was put forth for characterizing the jet that consists of computing the various moments of the velocity profile along with an integral measure of the profile skewness. A comprehensive parametric study has been carried out where the diaphragm amplitude, external flow Reynolds number, boundary layer thickness, and slot dimensions are varied; and the scaling of the jet characteristics with parameters is examined. The simulations also allow us to extract some interesting flow physics associated with the vortex dynamics of the jet and to elucidate the effect of external cross flow on jet development. In addition, a low-dimensional model for jet velocity profile is proposed and tested. Finally, the so-called "virtual aero-shaping" effect of synthetic jets is examined and the current simulations indicate a simple scaling of this effect with the dynamical characteristics of the jet and external crossflow.

  4. Advantageous grain boundaries in iron pnictide superconductors

    PubMed Central

    Katase, Takayoshi; Ishimaru, Yoshihiro; Tsukamoto, Akira; Hiramatsu, Hidenori; Kamiya, Toshio; Tanabe, Keiichi; Hosono, Hideo

    2011-01-01

    High critical temperature superconductors have zero power consumption and could be used to produce ideal electric power lines. The principal obstacle in fabricating superconducting wires and tapes is grain boundaries—the misalignment of crystalline orientations at grain boundaries, which is unavoidable for polycrystals, largely deteriorates critical current density. Here we report that high critical temperature iron pnictide superconductors have advantages over cuprates with respect to these grain boundary issues. The transport properties through well-defined bicrystal grain boundary junctions with various misorientation angles (θGB) were systematically investigated for cobalt-doped BaFe2As2 (BaFe2As2:Co) epitaxial films fabricated on bicrystal substrates. The critical current density through bicrystal grain boundary (JcBGB) remained high (>1 MA cm−2) and nearly constant up to a critical angle θc of ∼9°, which is substantially larger than the θc of ∼5° for YBa2Cu3O7–δ. Even at θGB>θc, the decay of JcBGB was much slower than that of YBa2Cu3O7–δ. PMID:21811238

  5. Orbiter Boundary Layer Transition Prediction Tool Enhancements

    NASA Technical Reports Server (NTRS)

    Berry, Scott A.; King, Rudolph A.; Kegerise, Michael A.; Wood, William A.; McGinley, Catherine B.; Berger, Karen T.; Anderson, Brian P.

    2010-01-01

    Updates to an analytic tool developed for Shuttle support to predict the onset of boundary layer transition resulting from thermal protection system damage or repair are presented. The boundary layer transition tool is part of a suite of tools that analyze the local aerothermodynamic environment to enable informed disposition of damage for making recommendations to fly as is or to repair. Using mission specific trajectory information and details of each d agmea site or repair, the expected time (and thus Mach number) of transition onset is predicted to help define proper environments for use in subsequent thermal and stress analysis of the thermal protection system and structure. The boundary layer transition criteria utilized within the tool were updated based on new local boundary layer properties obtained from high fidelity computational solutions. Also, new ground-based measurements were obtained to allow for a wider parametric variation with both protuberances and cavities and then the resulting correlations were calibrated against updated flight data. The end result is to provide correlations that allow increased confidence with the resulting transition predictions. Recently, a new approach was adopted to remove conservatism in terms of sustained turbulence along the wing leading edge. Finally, some of the newer flight data are also discussed in terms of how these results reflect back on the updated correlations.

  6. Physics of Boundaries and their Interactions in Space Plasmas

    NASA Technical Reports Server (NTRS)

    Omidi, Nojan; Karimabadi, Homayoun; Krauss-Varban, Dietmar

    1997-01-01

    This report describes the work done by SciberNet, Inc. during the month of October. We are working on the further refinement of the model used in our large-scale hybrid simulations of the magnetopause. Specifically, we are experimenting with several ways of modeling the effects of cold magnetospheric ions into our simulations. In addition, we are preparing two presentations for the upcoming Fall AGU highlighting the results of these simulations. We have also made progress in our development of a new kinetic linear code which we are using to study the linear properties of the Kelvin-Helmholtz instability at the magnetopause. We have extended the code from the electrostatic limit to the fully electromagnetic regime and are currently in the process of debugging and testing the code. Finally, we have made several test runs with our 2-D hybrid code for the magnetopause. The inflow-outflow boundary conditions are working properly. However, there are issues related to the setup and evolution of the original equilibrium that we are still trying to resolve. Finally, we are preparing several presentations for the upcoming Fall AGU.

  7. Open Heisenberg chain under boundary fields: A magnonic logic gate

    NASA Astrophysics Data System (ADS)

    Landi, Gabriel T.; Karevski, Dragi

    2015-05-01

    We study the spin transport in the quantum Heisenberg spin chain subject to boundary magnetic fields and driven out of equilibrium by Lindblad dissipators. An exact solution is given in terms of matrix product states, which allows us to calculate exactly the spin current for any chain size. It is found that the system undergoes a discontinuous spin-valve-like quantum phase transition from ballistic to subdiffusive spin current, depending on the value of the boundary fields. Thus, the chain behaves as an extremely sensitive magnonic logic gate operating with the boundary fields as the base element.

  8. Boundaries and Boundary Marks - Substantive Cultural Heritage of Extensive Importance

    NASA Astrophysics Data System (ADS)

    Waldhaeusl, P.; Koenig, H.; Mansberger, R.

    2015-08-01

    The Austrian Society for surveying and Geoinformation (ASG) has proposed to submit "Boundaries and Boundary Marks" for the UNESCO World Heritage title. It was time that boundaries, borders and limits of all types as well as ownership rights would find the proper attention in the global public. Landmarks symbolize the real property and the associated rights and obligations, in a figurative sense, the property generally and all legal limits. A democratic state of law is impossible at today's population density without a functioning land administration system with surveying and jurisdiction. As monumental World Heritage representatives of the geodetic artwork "Boundaries and Boundary Marks" are specifically proposed: remaining monuments of the original cadastral geodetic network, the first pan-Austrian surveying headquarters in Vienna, and a specific selection of outstanding boundary monuments. Landmarks are monuments to the boundaries which separate rights and obligations, but also connect the neighbors peacefully after written agreement. "And cursed be he who does not respect the boundaries" you wrote already 3000 years ago. Boundaries and Boundary Marks are a real thing; they all belong to the tangible or material heritage of human history. In this context also the intangible heritage is discussed. This refers to oral tradition and expressions, performing arts; social practices, rituals and festive events; as well as to knowledge and practices handling nature and the universe. "Boundaries and Boundary Marks" do not belong to it, but clearly to the material cultural world heritage. "Boundary and Boundary Marks" is proposed to be listed according to the criteria (ii),(iv),(vi).

  9. Open boundary molecular dynamics

    NASA Astrophysics Data System (ADS)

    Delgado-Buscalioni, R.; Sablić, J.; Praprotnik, M.

    2015-09-01

    This contribution analyzes several strategies and combination of methodologies to perform molecular dynamic simulations in open systems. Here, the term open indicates that the total system has boundaries where transfer of mass, momentum and energy can take place. This formalism, which we call Open Boundary Molecular Dynamics (OBMD), can act as interface of different schemes, such as Adaptive Resolution Scheme (AdResS) and Hybrid continuum-particle dynamics to link atomistic, coarse-grained (CG) and continuum (Eulerian) fluid dynamics in the general framework of fluctuating Navier-Stokes equations. The core domain of the simulation box is solved using all-atom descriptions. The CG layer introduced using AdResS is located at the outer part of the open box to make feasible the insertion of large molecules into the system. Communications between the molecular system and the outer world are carried out in the outer layers, called buffers. These coupling preserve momentum and mass conservation laws and can thus be linked with Eulerian hydro- dynamic solvers. In its simpler form, OBMD allows, however, to impose a local pressure tensor and a heat flux across the system's boundaries. For a one component molecular system, the external normal pressure and temperature determine the external chemical potential and thus the independent parameters of a grand-canonical ensemble simulation. Extended ensembles under non-equilibrium stationary states can also be simulated as well as time dependent forcings (e.g. oscillatory rheology). To illustrate the robustness of the combined OBMD-AdResS method, we present simulations of star-polymer melts at equilibrium and in sheared flow.

  10. Local and social facets of planetary boundaries: right to nutrients

    NASA Astrophysics Data System (ADS)

    Kahiluoto, Helena; Kuisma, Miia; Kuokkanen, Anna; Mikkilä, Mirja; Linnanen, Lassi

    2015-10-01

    Anthropogenic nutrient flows exceed the planetary boundaries. The boundaries and the current excesses vary spatially. Such variations have both an ecological and a social facet. We explored the spatial variation using a bottom-up approach. The local critical boundaries were determined through the current or accumulated flow of the preceding five years before the planetary boundary criteria were met. Finland and Ethiopia served as cases with contrasting ecology and wealth. The variation in excess depends on historical global inequities in the access to nutrients. Globally, the accumulated use per capita is 2300 kg reactive nitrogen (Nr) and 200 kg phosphorus (P). For Finland, the accumulated use per capita is 3400 kg Nr and 690 kg P, whereas for Ethiopia, it is 26 kg Nr and 12 kg P. The critical N boundary in Finland is currently exceeded by 40 kg cap-1 a-1 and the accumulated excess is 65 kg cap-1 a-1, while the global current excess is 24 kg cap-1 a-1 and there is space in Ethiopia to increase even the accumulated flow. The critical P boundary is exceeded in Finland and (although less so) in Ethiopia, but for contrary reasons: (1) the excessive past inflow to the agrifood system in Finland and (2) the excessive outflow from the agrifood system triggered by deficits in inflow and waste management in Ethiopia. The critical boundaries set by Finnish marine systems are lower and those set by freshwaters are higher than the planetary boundaries downscaled per capita. The shift to dominance of internal loading in watercourses represents a tipping point. We conclude that food security within the safe boundaries requires global redistribution of nutrients in residues, soils and sediments and of rights to use nutrients. Bottom-up assessments reveal local dynamics that shed new light on the relevant boundary criteria and on estimates and remedies.

  11. BOUndary Plasma Turbulence

    Energy Science and Technology Software Center (ESTSC)

    2008-01-25

    BOUT is a parallelized 3D nonlocal electromagnetic turbulence code. The principal calculations are the boundary plasma turbulence in a realistic magnetic geometry. BOUT uses fluid Braginskii equations for plasma vorticity, density, electron and ion temperature and Parallel mementum. With sources added in the core-edge region and sinks in the scrape-off-layer (SOL), BOUT follows the self-consistent profile evolution together with turbulence. BOUT also includes coupling to a magnetohyfrodynamic equlibrium (EFIT package) and a two-dimensional hydrodynamic edgemore » transport model (UEDGE package).« less

  12. Space Boundary Tool (SBT)

    Energy Science and Technology Software Center (ESTSC)

    2012-07-01

    SBT is an application that automatically calculates thermal zone boundaries suitable for input to the EnergyPlus simulation engine from building element and space geometry defined in IFC. SBT has multiple components. There is a general computational core, a DLL for reading and writing IFC files, and a GUI front end. The GUI also has the capability to create ready-to-simulate IDF files for EnergyPlus. Hardware req: PC; Operating Syst/Version: MSVC++2010; Type of files: source code; Documentation:more » User Manual (Electronic).« less

  13. Boundary layer equations and symmetry analysis of a Carreau fluid

    NASA Astrophysics Data System (ADS)

    Dolapci, Ihsan Timuçin

    2016-06-01

    In this paper, boundary layer equations of the Carreau fluid have been examined. Lie group theory is applied to the governing equations and symmetries of the equations are determined. The non-linear partial differential equations and their boundary conditions are transformed into a system of ordinary differential equations using the similarity transformations obtained from the symmetries. The system of ordinary differential equations are numerically solved for the boundary layer conditions. Finally, effects of non-Newtonian parameters on the solutions are investigated in detail.

  14. Boundary anomalies and correlation functions

    NASA Astrophysics Data System (ADS)

    Huang, Kuo-Wei

    2016-08-01

    It was shown recently that boundary terms of conformal anomalies recover the universal contribution to the entanglement entropy and also play an important role in the boundary monotonicity theorem of odd-dimensional quantum field theories. Motivated by these results, we investigate relationships between boundary anomalies and the stress tensor correlation functions in conformal field theories. In particular, we focus on how the conformal Ward identity and the renormalization group equation are modified by boundary central charges. Renormalized stress tensors induced by boundary Weyl invariants are also discussed, with examples in spherical and cylindrical geometries.

  15. The Hale solar sector boundary

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.; Wilcox, J. M.

    1976-01-01

    A Hale solar-sector boundary is defined as that half (northern hemisphere or southern hemisphere) of a sector boundary in which the change of sector-magnetic-field polarity is the same as the change of polarity from a preceding spot to a following spot. Above a Hale sector boundary the green corona has maximum brightness, while above a non-Hale boundary the green corona has a minimum brightness. The Hale portion of a photospheric sector boundary tends to have maximum magnetic-field strength, while the non-Hale portion has minimum field strength.

  16. The Hale solar sector boundary

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.; Wilcox, J. M.

    1976-01-01

    A Hale solar sector boundary is defined as the half (Northern Hemisphere or Southern Hemisphere) of a sector boundary in which the change of sector magnetic field polarity is the same as the change of polarity from a preceding spot to a following spot. Above a Hale sector boundary the green corona has maximum brightness, while above a non-Hale boundary the green corona has a minimum brightness. The Hale portion of a photospheric sector boundary tends to have maximum magnetic field strength, while the non-Hale portion has minimum field strength.

  17. A classification of ecological boundaries

    USGS Publications Warehouse

    Strayer, D.L.; Power, M.E.; Fagan, W.F.; Pickett, S.T.A.; Belnap, J.

    2003-01-01

    Ecologists use the term boundary to refer to a wide range of real and conceptual structures. Because imprecise terminology may impede the search for general patterns and theories about ecological boundaries, we present a classification of the attributes of ecological boundaries to aid in communication and theory development. Ecological boundaries may differ in their origin and maintenance, their spatial structure, their function, and their temporal dynamics. A classification system based on these attributes should help ecologists determine whether boundaries are truly comparable. This system can be applied when comparing empirical studies, comparing theories, and testing theoretical predictions against empirical results.

  18. Addressing therapeutic boundaries in social networking.

    PubMed

    Ginory, Almari; Sabatier, Laura Mayol; Eth, Spencer

    2012-01-01

    Facebook is the leading social networking website, with over 500 million users. Prior studies have shown an increasing number of housestaff accessing the site. While Facebook can be used to foster camaraderie, it can also create difficulties in the doctor-patient relationship, especially when boundaries are crossed. This study explored the prevalence of such boundary crossings and offers recommendations for training. An anonymous voluntary survey regarding Facebook use was distributed to current psychiatry residents through the American Psychiatric Association (APA) listserv. Of the 182 respondents, 95.7% had current Facebook profiles, and 9.7% had received friend requests from patients. In addition, 18.7% admitted to viewing patient profiles on Facebook. There is a substantial utilization of Facebook among psychiatric residents as compared with prior studies. Specific guidance regarding social media websites and the potential for ethical difficulties should be offered to trainees. PMID:22397540

  19. Nuclear Power Plant Containment Pressure Boundary Research

    SciTech Connect

    Cherry, J.L.; Chokshi, N.C.; Costello, J.F.; Ellingwood, B.R.; Naus, D.J.

    1999-09-15

    Research to address aging of the containment pressure boundary in light-water reactor plants is summarized. This research is aimed at understanding the significant factors relating occurrence of corrosion, efficacy of inspection, and structural capacity reduction of steel containment and liners of concrete containment. This understanding will lead to improvements in risk-informed regulatory decision making. Containment pressure boundary components are described and potential aging factors identified. Quantitative tools for condition assessments of aging structures to maintain an acceptable level of reliability over the service life of the plant are discussed. Finally, the impact of aging (i.e., loss of shell thickness due to corrosion) on steel containment fragility for a pressurized water reactor ice-condenser plant is presented.

  20. Current sensor

    DOEpatents

    Yakymyshyn, Christopher Paul; Brubaker, Michael Allen; Yakymyshyn, Pamela Jane

    2007-01-16

    A current sensor is described that uses a plurality of magnetic field sensors positioned around a current carrying conductor. The sensor can be hinged to allow clamping to a conductor. The current sensor provides high measurement accuracy for both DC and AC currents, and is substantially immune to the effects of temperature, conductor position, nearby current carrying conductors and aging.

  1. Grain Boundaries In Thin Film Organic Semiconductors

    NASA Astrophysics Data System (ADS)

    Bougher, Cortney; Huston, Shawn; Lees, Eitan; Ward, Jeremy; Obaid, Abdul; Loth, Marsha; Anthony, John; Jurchescu, Oana; Conrad, Brad

    2012-02-01

    We utilize conductive atomic force microscopy (C-AFM) and tunneling atomic force microscopy (TUNA) to characterize dynamics of electronic transport across fluorinated triethylsilylethynyl anthradithiophene (diF-TES ADT) grain boundaries. The crystallization of diF-TES ADT grown on SiO2 will be discussed and related to comparable molecules. The resulting voltage drop between individual crystals as a function of dopants will be discussed in terms of charge transport models and compared to current device work.

  2. Current focusing and steering

    PubMed Central

    Bonham, Ben H.; Litvak, Leonid M.

    2008-01-01

    Current steering and current focusing are stimulation techniques designed to increase the number of distinct perceptual channels available to cochlear implant (CI) users by adjusting currents applied simultaneously to multiple CI electrodes. Previous studies exploring current steering and current focusing stimulation strategies are reviewed, including results of research using computational models, animal neurophysiology, and human psychophysics. Preliminary results of additional neurophysiological and human psychophysical studies are presented that demonstrate the success of current steering strategies in stimulating auditory nerve regions lying between physical CI electrodes, as well as current focusing strategies that excite regions narrower than those stimulated using monopolar configurations. These results are interpreted in the context of perception and speech reception by CI users. Disparities between results of physiological and psychophysical studies are discussed. The differences in stimulation used for physiological and psychophysical studies are hypothesized to contribute to these disparities. Finally, application of current steering and focusing strategies to other types of auditory prostheses is also discussed. PMID:18501539

  3. Helical currents in metallic Rashba strips

    NASA Astrophysics Data System (ADS)

    Hamad, Ignacio J.; Gazza, Claudio J.; Riera, José A.

    2016-05-01

    We study the texture of helical currents in metallic planar strips in the presence of Rashba spin-orbit coupling (RSOC) on the lattice at zero temperature. In the noninteracting case and in the absence of external electromagnetic sources, we determine, by exact numerical diagonalization of the single-particle Hamiltonian, the distribution across the strip section of these Rashba helical currents (RHC) as well as their sign oscillation, as a function of the RSOC strength, strip width, electron filling, and strip boundary conditions. Then, we study the effects of charge currents introduced into the system by an Aharonov-Bohm flux for the case of rings or by a voltage bias in the case of open strips. The former setup is studied by variational Monte Carlo, and the latter by the time-dependent density-matrix renormalization-group technique. Particularly for strips formed by two, three, and four coupled chains, we show how these RHC vary in the presence of such induced charge current, and how their differences between spin-up and spin-down electron currents on each chain help to explain the distribution across the strip of charge currents, both of the spin-conserving and the spin-flipping types. We also predict the appearance of polarized charge currents on each chain. Finally, we show that these Rashba helical currents and their derived features remain in the presence of an on-site Hubbard repulsion as long as the system remains metallic, at quarter filling, and even at half filling where a Mott-Hubbard metal-insulator transition occurs for large Hubbard repulsion.

  4. A boundary term for the gravitational action with null boundaries

    NASA Astrophysics Data System (ADS)

    Parattu, Krishnamohan; Chakraborty, Sumanta; Majhi, Bibhas Ranjan; Padmanabhan, T.

    2016-07-01

    Constructing a well-posed variational principle is a non-trivial issue in general relativity. For spacelike and timelike boundaries, one knows that the addition of the Gibbons-Hawking-York (GHY) counter-term will make the variational principle well-defined. This result, however, does not directly generalize to null boundaries on which the 3-metric becomes degenerate. In this work, we address the following question: What is the counter-term that may be added on a null boundary to make the variational principle well-defined? We propose the boundary integral of 2 √{-g} ( Θ +κ ) as an appropriate counter-term for a null boundary. We also conduct a preliminary analysis of the variations of the metric on the null boundary and conclude that isolating the degrees of freedom that may be fixed for a well-posed variational principle requires a deeper investigation.

  5. Information theoretic SAR boundary detection with user interaction

    NASA Astrophysics Data System (ADS)

    Demirkesen, Can; Leloǧlu, Uǧur M.

    2015-10-01

    Detection of region boundaries is a very challenging task especially in the presence of noise or speckle as in synthetic aperture radar images. In this work, we propose a user interaction based boundary detection technique which makes use of B-splines and well-known powerful tools of information theory such as the Kullback-Leibler divergence (KLD) and Bhattacharyya distance. The proposed architecture consists of the following four main steps: (1) The user selects points inside and outside of a region. (2) Profiles that link these inside and outside points are extracted. (3) Boundary points that lie on the profile are located. (4) Finally, the B-splines that provide both elasticity and smoothness are used connect boundary points together to obtain an accurate estimate of the actual boundary. Existing work related to this approach are extended in several axes. First the use of multiple points both inside and outside of a region made possible to obtain a few times more boundary points. A tracking stage is proposed to put the boundary points in the right order and at the same time eliminate some of them that are erroneously detected as boundary points as well. Experiments were conducted using simulated and real SAR images.

  6. Final Report

    SciTech Connect

    DeTar, Carleton

    2012-12-10

    This document constitutes the Final Report for award DE-FC02-06ER41446 as required by the Office of Science. It summarizes accomplishments and provides copies of scientific publications with significant contribution from this award.

  7. Eocene-Oligocene boundary problems, west coast, North America

    SciTech Connect

    Armentrout, J.M.

    1983-03-01

    Correlation of the international Eocene-Oligocene boundary with the provincial biostratigraphic framework of the northeast Pacific margin has been and continues to be controversial. The controversy centers about historical nomenclature and correlations, and current correlations based on planktonic fossil group. The Geological Society of America's C.E. Weaver Committee published the first interdisciplinary correlation chart for the Cenozoic rocks of the western United States in 1944. The committee placed the Eocene-Oligocene boundary at the base of the Keasey Molluscan Stage and Refugian Benthic Foraminiferal Stage. The most useful provincial boundaries of Late Eocene to Oligocene age are the Narizian-Refugian and Refugian-Zemorrian Benthic Foraminiferal Stage boundaries. Reevaluation of the Refugian Stage has recently been completed. The stage boundaries have been correlated to the international geologic time scale using planktonic microfossils. Planktonic assemblages are rare in samples from above and below the Refugian-Zemorrian Benthic Foraminiferal Stage boundary. In California this boundary is commonly at an unconformity or without superposition of diagnostic faunas. In southwestern Washington the Refugian-Zemorrian boundary occurs in continuously deposited and foraminiferally rich sections. Radiometric calibration of the provincial boundaries is not yet possible. Whole rock potassium-argon and fission track dates are available but both have very large error bars or lack adequate biostratigraphic control to be useful. Fossiliferous stratigraphic sections have rocks with sufficient remanent magnetism for magnetostratigraphic studies but to date only reconnaissance data are available.

  8. 76 FR 38684 - Minor Boundary Revision at Virgin Islands National Park

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ... National Park Service Minor Boundary Revision at Virgin Islands National Park AGENCY: National Park Service....S.C. 4601- 9(c)(1), the boundary of the Virgin Islands National Park is modified to include an... the Island of St. John, immediately adjacent to the current boundary of the Virgin Islands...

  9. 76 FR 29264 - Minor Boundary Revision at Rocky Mountain National Park

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-20

    ... National Park Service Minor Boundary Revision at Rocky Mountain National Park AGENCY: National Park Service....S.C. 4601-9(c)(1), the boundary of Rocky Mountain National Park is modified to include an additional... in Grand County, Colorado, immediately adjacent to the current western boundary of Rocky...

  10. Rossby rip currents

    NASA Astrophysics Data System (ADS)

    Marshall, David P.; Vogel, Bendix; Zhai, Xiaoming

    2013-08-01

    Oceanic Rossby waves and eddies flux energy and fluid westward, the latter through the Stokes drift or bolus transport. While the wave energy is largely dissipated at the western boundary, mass conservation requires that the fluid be returned offshore through Rossby rip currents. The form and magnitude of these rip currents are investigated through linear Rossby wave theory, a nonlinear numerical model, and analysis of sea surface height satellite observations. The net eastward volume transport by Rossby rip currents over the global ocean is estimated to be of order 10 Sv (1 Sv ≡106 m3 s-1). In an eddying ocean, both the westward Stokes drift and eastward rip currents can assume the form of banded quasi-zonal jets.

  11. Boundary layer transition studies

    NASA Technical Reports Server (NTRS)

    Watmuff, Jonathan H.

    1995-01-01

    A small-scale wind tunnel previously used for turbulent boundary layer experiments was modified for two sets of boundary layer transition studies. The first study concerns a laminar separation/turbulent reattachment. The pressure gradient and unit Reynolds number are the same as the fully turbulent flow of Spalart and Watmuff. Without the trip wire, a laminar layer asymptotes to a Falkner & Skan similarity solution in the FPG. Application of the APG causes the layer to separate and a highly turbulent and approximately 2D mean flow reattachment occurs downstream. In an effort to gain some physical insight into the flow processes a small impulsive disturbance was introduced at the C(sub p) minimum. The facility is totally automated and phase-averaged data are measured on a point-by-point basis using unprecedently large grids. The evolution of the disturbance has been tracked all the way into the reattachment region and beyond into the fully turbulent boundary layer. At first, the amplitude decays exponentially with streamwise distance in the APG region, where the layer remains attached, i.e. the layer is viscously stable. After separation, the rate of decay slows, and a point of minimum amplitude is reached where the contours of the wave packet exhibit dispersive characteristics. From this point, exponential growth of the amplitude of the disturbance is observed in the detached shear layer, i.e. the dominant instability mechanism is inviscid. A group of large-scale 3D vortex loops emerges in the vicinity of the reattachment. Remarkably, the second loop retains its identify far downstream in the turbulent boundary layer. The results provide a level of detail usually associated with CFD. Substantial modifications were made to the facility for the second study concerning disturbances generated by Suction Holes for laminar flow Control (LFC). The test section incorporates suction through interchangeable porous test surfaces. Detailed studies have been made using isolated

  12. Dynamic multiple thresholding breast boundary detection algorithm for mammograms

    SciTech Connect

    Wu, Yi-Ta; Zhou Chuan; Chan, Heang-Ping; Paramagul, Chintana; Hadjiiski, Lubomir M.; Daly, Caroline Plowden; Douglas, Julie A.; Zhang Yiheng; Sahiner, Berkman; Shi Jiazheng; Wei Jun

    2010-01-15

    Purpose: Automated detection of breast boundary is one of the fundamental steps for computer-aided analysis of mammograms. In this study, the authors developed a new dynamic multiple thresholding based breast boundary (MTBB) detection method for digitized mammograms. Methods: A large data set of 716 screen-film mammograms (442 CC view and 274 MLO view) obtained from consecutive cases of an Institutional Review Board approved project were used. An experienced breast radiologist manually traced the breast boundary on each digitized image using a graphical interface to provide a reference standard. The initial breast boundary (MTBB-Initial) was obtained by dynamically adapting the threshold to the gray level range in local regions of the breast periphery. The initial breast boundary was then refined by using gradient information from horizontal and vertical Sobel filtering to obtain the final breast boundary (MTBB-Final). The accuracy of the breast boundary detection algorithm was evaluated by comparison with the reference standard using three performance metrics: The Hausdorff distance (HDist), the average minimum Euclidean distance (AMinDist), and the area overlap measure (AOM). Results: In comparison with the authors' previously developed gradient-based breast boundary (GBB) algorithm, it was found that 68%, 85%, and 94% of images had HDist errors less than 6 pixels (4.8 mm) for GBB, MTBB-Initial, and MTBB-Final, respectively. 89%, 90%, and 96% of images had AMinDist errors less than 1.5 pixels (1.2 mm) for GBB, MTBB-Initial, and MTBB-Final, respectively. 96%, 98%, and 99% of images had AOM values larger than 0.9 for GBB, MTBB-Initial, and MTBB-Final, respectively. The improvement by the MTBB-Final method was statistically significant for all the evaluation measures by the Wilcoxon signed rank test (p<0.0001). Conclusions: The MTBB approach that combined dynamic multiple thresholding and gradient information provided better performance than the breast boundary

  13. Methods for determining the height of the atmospheric boundary layer

    SciTech Connect

    Sugiyama, Gayle; Nasstrom, John S.

    1999-02-01

    The Atmospheric Release Advisory Capability (ARAC) is an operational emergency response program which provides real-time dose assessments of airborne pollutant releases. This report reviews methodologies for determining the height of the atmospheric boundary layer (ABL), which were investigated for use in the next generation of ARAC diagnostic and dispersion models. The ABL height, hABL, is an essential parameter in atmospheric dispersion modeling, controlling the extent of the vertical mixing of pollutants near the surface. Although eventually instrumentation (radiosonde, lidar, sodar, etc.) may provide accurate means for determining hABL, at present the availability of such data is too limited to provide a general capability for ARAC. The current operational ARAC diagnostic models use a fixed value of hABL for any given time. ARAC's new models support a horizontally-varying atmospheric boundary layer height, which is used to generate meteorological (mean wind, temperature, etc.) and turbulence fields. The purpose of the present work is to develop methods to derive the ABL height for all atmospheric stability regimes. One of our key requirements is to provide approaches which are applicable to routinely available data, which may be of limited temporal and spatial resolution. The final objective is to generate a consistent set of meteorological and turbulence or eddy diffusivity fields to drive the new ARAC dispersion model. A number of alternative definitions of the atmospheric boundary layer exist, leading to different approaches to deriving hABL. The definitions are based on either the turbulence characteristics of the atmosphere or the vertical structure of one or more meteorological variables. Most diagnostic analyses determine hABL from profiles of temperature or occasionally wind. A class of methods of considerable current interest are based on Richardson number criteria. Prognostic methods calculate the

  14. Boundary work in knowledge teams.

    PubMed

    Faraj, Samer; Yan, Aimin

    2009-05-01

    The purpose of this article is to promote an open systems perspective on team research. The authors develop a model of team boundary activities: boundary spanning, buffering, and reinforcement. The model examines the relationship between these boundary activities and team performance, the moderating effects of organizational contextual factors, and the mediating effect of team psychological safety on the boundary work-performance relationship. These relationships were empirically tested with data collected from 64 software development teams. Boundary spanning, buffering, and boundary reinforcement were found to relate to team performance and psychological safety. Both relationships are moderated by the team's task uncertainty and resource scarcity. The implications of the findings are offered for future research and practice. PMID:19450002

  15. Boundary terms of conformal anomaly

    NASA Astrophysics Data System (ADS)

    Solodukhin, Sergey N.

    2016-01-01

    We analyze the structure of the boundary terms in the conformal anomaly integrated over a manifold with boundaries. We suggest that the anomalies of type B, polynomial in the Weyl tensor, are accompanied with the respective boundary terms of the Gibbons-Hawking type. Their form is dictated by the requirement that they produce a variation which compensates the normal derivatives of the metric variation on the boundary in order to have a well-defined variational procedure. This suggestion agrees with recent findings in four dimensions for free fields of various spins. We generalize this consideration to six dimensions and derive explicitly the respective boundary terms. We point out that the integrated conformal anomaly in odd dimensions is non-vanishing due to the boundary terms. These terms are specified in three and five dimensions.

  16. Modeling the urban boundary layer

    NASA Technical Reports Server (NTRS)

    Bergstrom, R. W., Jr.

    1976-01-01

    A summary and evaluation is given of the Workshop on Modeling the Urban Boundary Layer; held in Las Vegas on May 5, 1975. Edited summaries from each of the session chairpersons are also given. The sessions were: (1) formulation and solution techniques, (2) K-theory versus higher order closure, (3) surface heat and moisture balance, (4) initialization and boundary problems, (5) nocturnal boundary layer, and (6) verification of models.

  17. FINAL REPORT

    SciTech Connect

    Lettenmaier, Dennis

    2012-05-26

    We proposed to extend Maurer’s data sets through at least 2005 (to include extreme drought years in the Colorado basin). We updated and verified the forcings for tmin, tmax, and precipitation over the Colorado River basin at 1/8-deg spatial resolution through November 2008, with the potential to alter the resolution as needed (we subsequently extended the Maurer et al data set over the entire continental U.S. at 1/16 degree spatial resolution; see Livneh et al., 2013). We proposed to use either MODIS-based land cover data for recent years, or modification of the existing fixed seasonal cycle used in VIC (based on University of Maryland land cover data) to represent interannual variations in vegetation characteristics such as leaf area index (LAI) particularly in drought years. We assessed model performance with respect to evapotranspiration estimation through comparison of the model predictions with ground observations and in experiments that use time-varying and fixed seasonal LAI cycles (based on University of Maryland land cover data) in a test region of northwestern Mexico where the ground ET observations from eddy covariance tower sites are available for the period from 2001 to 2008 (Tang et al., 2011). We also proposed to implement statistical downscaling with an adjustment to constrain precipitation changes at the GCM level. These simulations were performed, using 20 IPCC AR4 GCMs over the Colorado River basin with two global emissions scenarios, and are reported in Vano et al., 2014. Task 2: Coupled model implementation We proposed to implement the “standard” climate version of WRF, as used by collaborator Ruby Leung in NARCCAP simulations (see Section 5.4), and perform tests to assure that model output for runs equivalent to NARCCAP Phase 1 (reanalysis boundary conditions) are consistent. We proposed do test sensitivity to higher spatial resolution. We made a run of 11 years’ length with the “standard” version of WRF, forced by NCEP/DOE with

  18. EIDOSCOPE: particle acceleration at plasma boundaries

    NASA Astrophysics Data System (ADS)

    Vaivads, A.; Andersson, G.; Bale, S. D.; Cully, C. M.; De Keyser, J.; Fujimoto, M.; Grahn, S.; Haaland, S.; Ji, H.; Khotyaintsev, Yu. V.; Lazarian, A.; Lavraud, B.; Mann, I. R.; Nakamura, R.; Nakamura, T. K. M.; Narita, Y.; Retinò, A.; Sahraoui, F.; Schekochihin, A.; Schwartz, S. J.; Shinohara, I.; Sorriso-Valvo, L.

    2012-04-01

    We describe the mission concept of how ESA can make a major contribution to the Japanese Canadian multi-spacecraft mission SCOPE by adding one cost-effective spacecraft EIDO (Electron and Ion Dynamics Observatory), which has a comprehensive and optimized plasma payload to address the physics of particle acceleration. The combined mission EIDOSCOPE will distinguish amongst and quantify the governing processes of particle acceleration at several important plasma boundaries and their associated boundary layers: collisionless shocks, plasma jet fronts, thin current sheets and turbulent boundary layers. Particle acceleration and associated cross-scale coupling is one of the key outstanding topics to be addressed in the Plasma Universe. The very important science questions that only the combined EIDOSCOPE mission will be able to tackle are: 1) Quantitatively, what are the processes and efficiencies with which both electrons and ions are selectively injected and subsequently accelerated by collisionless shocks? 2) How does small-scale electron and ion acceleration at jet fronts due to kinetic processes couple simultaneously to large scale acceleration due to fluid (MHD) mechanisms? 3) How does multi-scale coupling govern acceleration mechanisms at electron, ion and fluid scales in thin current sheets? 4) How do particle acceleration processes inside turbulent boundary layers depend on turbulence properties at ion/electron scales? EIDO particle instruments are capable of resolving full 3D particle distribution functions in both thermal and suprathermal regimes and at high enough temporal resolution to resolve the relevant scales even in very dynamic plasma processes. The EIDO spin axis is designed to be sun-pointing, allowing EIDO to carry out the most sensitive electric field measurements ever accomplished in the outer magnetosphere. Combined with a nearby SCOPE Far Daughter satellite, EIDO will form a second pair (in addition to SCOPE Mother-Near Daughter) of closely

  19. Magnetospheric plasma regions and boundaries

    NASA Technical Reports Server (NTRS)

    Heikkila, W. J.

    1975-01-01

    The boundaries of the various regions of the magnetospheric plasma are considered, taking into account the bow shock, the magnetopause, the outer boundary of the plasma sheet, the inner boundary of the plasma sheet, and the trapping boundary for energetic particles. Attention is given to the steady state, or quasi-steady state, to substorm effects in which temporal changes are important, and to primary auroral processes. A description is presented of the high latitude lobes of the magnetotail. The characteristics of magnetic field topology associated with interconnected interplanetary and geomagnetic field lines are illustrated with the aid of a graph.

  20. Symbolic Boundary Work in Schools: Demarcating and Denying Ethnic Boundaries

    ERIC Educational Resources Information Center

    Tabib-Calif, Yosepha; Lomsky-Feder, Edna

    2014-01-01

    This article examines the symbolic boundary work that is carried out at a school whose student population is heterogeneous in terms of ethnicity and class. Based on ethnography, the article demonstrates how the school's staff seeks to neutralize ethnic boundaries and their accompanying discourse, while the pupils try to bring ethnic…

  1. 76 FR 14897 - Boundary Establishment for the Yellow Dog National Wild and Scenic River, Ottawa National Forest...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-18

    ... Forest Service Boundary Establishment for the Yellow Dog National Wild and Scenic River, Ottawa National..., Washington Office, is transmitting the final boundary of the Yellow Dog National Wild and Scenic River to.... SUPPLEMENTARY INFORMATION: The Yellow Dog Wild and Scenic River boundary is available for review at...

  2. Kink modes and surface currents associated with vertical displacement events

    NASA Astrophysics Data System (ADS)

    Manickam, Janardhan; Boozer, Allen; Gerhardt, Stefan

    2012-08-01

    The fast termination phase of a vertical displacement event (VDE) in a tokamak is modeled as a sequence of shrinking equilibria, where the core current profile remains constant so that the safety-factor at the axis, qaxis, remains fixed and the qedge systematically decreases. At some point, the n = 1 kink mode is destabilized. Kink modes distort the magnetic field lines outside the plasma, and surface currents are required to nullify the normal component of the B-field at the plasma boundary and maintain equilibrium at finite pressure. If the plasma touches a conductor, the current can be transferred to the conductor, and may be measurable by the halo current monitors. This report describes a practical method to model the plasma as it evolves during a VDE, and determine the surface currents, needed to maintain equilibrium. The main results are that the onset conditions for the disruption are that the growth-rate of the n = 1 kink exceeds half the Alfven time and the associated surface current needed to maintain equilibrium exceeds one half of the core plasma current. This occurs when qedge drops below a low integer, usually 2. Application to NSTX provides favorable comparison with non-axisymmetric halo-current measurements. The model is also applied to ITER and shows that the 2/1 mode is projected to be the most likely cause of the final disruption.

  3. Dependence of Boundary Layer Mixing On Lateral Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Straub, D.

    Ocean circulation models often show strong mixing in association with lateral bound- ary layers. Such mixing is generally considered to be artifactual rather than real. Fur- thermore, the severity of the problem is boundary condition dependent. For example, an inconsistency between geostrophy and insulating boundary conditions on tempera- ture and salinity cause many modelers to opt for the no slip, rather than slip boundary condtion on the tangential component of momentum. As modellers increasingly move into the eddy revealing regime, biharmonic, rather than harmonic dissipative operators are likely to become more common. Biharmonic operators, however, require specifi- cation of additional boundary conditions. For example, there are several `natural ex- tensions' to each of the slip and no slip conditions. Here, these various possiblities are considered in the context of a simple model. Particular attention is payed to how mixing (and the associated overturning cell) is affected by the choice of boundary condition.

  4. A Model Study of the Strong and Weak Wind, Stably Stratified Nocturnal Boundary Layer: Influence of Gentle Slopes

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, S. G.; Freedman, Frank; Sharan, Maithili; Krishna, T. V. B. P. S. Rama

    2005-10-01

    With the exception of intermittency and waves, a brief review of the observed and modeled mean structure of the nocturnal boundary layer (NBL) is presented. The effect of gentle slopes on strong and weak wind NBL was investigated here using a one-dimensional model, with a simple correction term to account for the slope effects, identical to the one used by Brost and Wyngaard (1978). The study indicates that the wind profiles, temperature profiles and surface layer turbulence characteristics are extremely sensitive to the imposed geostrophic wind when small slopes are present especially for light winds. This is due to the complex interaction between the buoyancy driven slope flow and the imposed geostrophic wind that in turn influence the shear generation of turbulence. Finally, the current issues in the modeling of weak wind boundary layer are discussed.

  5. Azeotropic distillation in a middle vessel batch column. 2: Nonlinear separation boundaries

    SciTech Connect

    Cheong, W.; Barton, P.I.

    1999-04-01

    On the basis of the analytical tools developed for the middle vessel column (MVC) operated under limiting conditions, analysis of the qualitative dynamics of the MVC in separating an azeotropic mixture is extended to the more realistic case in which the separation boundaries are nonlinear. The differences between batch stripper pot composition boundaries and batch rectifier pot composition being able to cross these pot composition boundaries. On the basis of these insights, operating procedures are developed in which ternary azeotropic mixtures of acetone, benzene, and chloroform can be separated into their constituent pure components, a separation not achievable with either the batch stripper or the batch rectifier. The operating procedures suggested for separating the ternary azeotropic mixture of acetone, benzene, and chloroform in the MVC are then shown to be the time analogues of sequences of continuous distillation columns that achieve the same separation. On the basis of this space-time analogy, further analogies are developed between the MVC and a continuous column, and it is postulated that many complex separations currently achieved with sequences of continuous columns can also be achieved with a single MVC. Thus, the MVC represents the ultimate multipurpose solvent recovery technology, as it can handle, in a batch multipurpose mode. separations that will otherwise require a dedicated continuous distillation sequence. Finally, the characteristics of perfect MVC batch entrainers, which allow the complete separation of any azeotrope into its constituent pure components in a single MVC, are discussed.

  6. Boundary effects in entanglement entropy

    NASA Astrophysics Data System (ADS)

    Berthiere, Clément; Solodukhin, Sergey N.

    2016-09-01

    We present a number of explicit calculations of Renyi and entanglement entropies in situations where the entangling surface intersects the boundary of d-dimensional Minkowski spacetime. When the boundary is a single plane we compute the contribution to the entropy due to this intersection, first in the case of the Neumann and Dirichlet boundary conditions, and then in the case of a generic Robin type boundary condition. The flow in the boundary coupling between the Neumann and Dirichlet phases is analyzed in arbitrary dimension d and is shown to be monotonic, the peculiarity of d = 3 case is noted. We argue that the translational symmetry along the entangling surface is broken due the presence of the boundary which reveals that the entanglement is not homogeneous. In order to characterize this quantitatively, we introduce a density of entanglement entropy and compute it explicitly. This quantity clearly indicates that the entanglement is maximal near the boundary. We then consider the situation where the boundary is composed of two parallel planes at a finite separation and compute the entanglement entropy as well as its density in this case. The complete contribution to entanglement entropy due to the boundaries is shown not to depend on the distance between the planes and is simply twice the entropy in the case of single plane boundary. Additionally, we find how the area law, the part in the entropy proportional to the area of entire entangling surface, depends on the size of the separation between the two boundaries. The latter is shown to appear in the UV finite part of the entropy.

  7. Physics of Boundaries and their Interactions in Space Plasmas

    NASA Technical Reports Server (NTRS)

    Omidi, Nojan; Karimabadi, Homayoun; Krauss-Varban, Dietmar

    1998-01-01

    This final report describes a brief summary of our accomplishments during the complete contract period. Traditionally, due to computational limitations, it has been impossible to obtain a global view of the magnetosphere on ion time and spatial scales. As a result, kinetic simulations have concentrated on the local structure of different magnetospheric discontinuities and boundaries. However, due to the emergence of low cost desktop superconductors, as well as by taking full advantage of latest advances in data mining and visualization technology, we were able to bypass our planned (proposed) regional simulations and proceed to large-scale 3-D and 2-D global hybrid simulations of the magnetosphere. As a result, although we are only finishing the second year of the proposed activity, much of the original scientific objectives have been surpassed and new avenues of investigation have been opened. Such simulations have led us to possible explanations of some long-standing issues in magnetospheric physics. They have also enabled us to make a number of important discoveries/predictions, which need to be looked for in satellite data. Examples include: (1) the finding that the bow shock can become unstable to the Kelvin-Helmholtz (KH;) (2) the discovery of a mechanism for intermittent reconnection due to ion physics which may be relevant to the explanation of the recurrence rate of flux transfer events (FTEs;) and (3) the finding that the current sheet in the near-Earth magnetotail region can become unstable to KH with detectable, unique ionospheric signatures. Further, we demonstrated a viable mechanism for the onset of reconnection at the magnetopause, examined the detailed structure of the boundary layer incorporating curvature effects, and provided an explanation for the large core fields observed within FTEs as well as flux ropes in the magnetotail.

  8. Physics of Boundaries and their Interactions in Space Plasmas

    NASA Technical Reports Server (NTRS)

    Omidi, Nojan; Karimabadi, Homayoun; Krauss-Varban, Dietmar

    1998-01-01

    This final report describes a brief summary of our accomplishments during the complete contract period. Traditionally, due to computational limitations, it has been impossible to obtain a global view of the magnetosphere on ion time and spatial scales. As a result, kinetic-simulations have concentrated on the local structure of different magnetospheric discontinuities and boundaries. However, due to the emergence of low cost supercomputers, as well as by taking full advantage of latest advances in data mining and visualization technology, we were able to bypass our planned (proposed) regional simulations and proceed to large-scale 3-D and 2-D global hybrid simulations of the magnetosphere. As a result, although we are only finishing the second year of the proposed activity, much of the original scientific objectives have been surpassed and new avenues of investigation have been opened. Such simulations have led us to possible explanations of some long-standing issues in magnetospheric physics. They have also enables us to make a number of important discoveries predictions, which need to be looked for in satellite data. Examples include the finding that the bow shock can become unstable to the Kelvin-Helmholtz (KH), (2) the discovery of a mechanism for intermittent reconnection due to ion physics which may be relevant to the explanation of the recurrence rate of flux transfer events (FTEs), and (3) this finding that the current sheet in the near-Earth magnetotail region can become unstable to KH with detectable, unique ionospheric signatures. Further, we demonstrated a viable mechanism for the onset of reconnection at the magnetopause, examined the detailed structure of the boundary layer incorporating curvature effects, and provided an explanation for the large core fields observed within FTEs as well as flux ropes in the magnetotail.

  9. Compositional space boundaries for organic compounds.

    PubMed

    Lobodin, Vladislav V; Marshall, Alan G; Hsu, Chang Samuel

    2012-04-01

    An upper elemental compositional boundary for fossil hydrocarbons has previously been established as double-bond equivalents (i.e., DBE = rings plus double bonds) not exceeding 90% of the number of carbons. For heteroatom-containing fossil compounds, the 90% rule still applies if each N atom is counted as a C atom. The 90% rule eliminates more than 10% of the possible elemental compositions at a given mass for fossil database molecules. However, some synthetic compounds can fall outside the upper boundary defined for naturally occurring compounds. Their inclusion defines an "absolute" upper boundary as DBE (rings plus double bonds to carbon) equal to carbon number plus one, and applies to all organic compounds including fullerenes and other molecules containing no hydrogen. Finally, the DBE definition can fail for molecules with particular atomic valences. Therefore, we also present a generalized DBE definition that includes atomic valence to enable calculation of the correct total number of rings, double bonds, and triple bonds for heteroatom-containing compounds. PMID:22376063

  10. Plasmastatic models of galathea traps with magnetically transparent boundaries

    NASA Astrophysics Data System (ADS)

    Brushlinskii, K. V.; Goldich, A. S.

    2014-08-01

    Mathematical models and results of calculation of plasma equilibrium in a circular cylinder with three helical or straight imbedded current-carrying conductors (i.e., in a straightened analog of a toroidal Galathea trap) are presented. The equilibrium is described in the framework of two-dimensional boundary value problems with plane and helical analogs of the Grad-Shafranov equation for the scalar magnetic flux function. Problems with first-kind boundary conditions corresponding to a magnetically transparent boundary of the cylinder and problems with second-kind boundary conditions and a given value of the electric current flowing in plasma (in addition to those flowing in the conductors) are considered. Deformations of magnetoplasma configurations in the cylinder for different formulations of the above-specified problems are investigated numerically.

  11. Defining Neighborhood Boundaries for Social Measurement: Advancing Social Work Research

    ERIC Educational Resources Information Center

    Foster, Kirk A.; Hipp, J. Aaron

    2011-01-01

    Much of the current neighborhood-based research uses variables aggregated on administrative boundaries such as zip codes, census tracts, and block groups. However, other methods using current technological advances in geographic sciences may broaden our ability to explore the spatial concentration of neighborhood factors affecting individuals and…

  12. Further studies of unsteady boundary layers with flow reversal

    NASA Technical Reports Server (NTRS)

    Nash, J. F.

    1976-01-01

    One set of calculations was performed using the first order, time dependent turbulent boundary layer equations, and extended earlier work by Nash and Patel to a wider range of flows. Another set of calculations was performed for laminar flow using the time dependent Navier-Stokes equations. The results of the calculations confirm previous conclusions concerning the existence of a regime of unseparated flow, containing an embedded region of reversal, which is accessible to first order boundary layer theory. However, certain doubts are cast on the precise nature of the events which accompany the eventual breakdown of the theory due to singularity onset. The earlier view that the singularity appears as the final event in a sequence involving rapid thickening of the boundary layer and the formation of a localized region of steep gradients is called into question by the present results. It appears that singularity onset is not necessarily preceded by rapid boundary layer thickening, or even necessarily produces immediate thickening.

  13. Final Words

    ERIC Educational Resources Information Center

    Bers, Trudy

    2012-01-01

    This final chapter provides observations about institutional research in community colleges derived from the preceding chapters and the issue editors' own experiences. Taken as a whole, the chapters in this issue, as well as the editors' experiences, suggest several observations about institutional research in community colleges. These include the…

  14. Redefinition of the Meramecian/Chesterian boundary (Mississippian)

    SciTech Connect

    Maples, C.G.; Waters, J.A.

    1987-07-01

    The Meramecian/Chesterian (Mississippi) boundary in the type area is currently defined as the highest occurrence of the crinoid Platycrinites penicillus and the lowest occurrence of the crinoid genera Agassizocrinus and Talarocrinus. Because these taxa have not been reported outside eastern North America, attempts have been made to use conodonts and Foraminifera to extend the Meramecian/Chesterian boundary outside the type area. Unfortunately, changes in conodont and foraminiferal assemblages do not coincide with the currently defined Meramecian/Chesterian boundary, and use of these fossil groups does not allow exact placement of the boundary outside of eastern North America. The authors suggest that the Meramecian/Chesterian boundary be redefined as the boundary between Foraminiferal Zones 15 and 16i of the Mamet scheme, irrespective of the occurrence of Platycrinites penicillus. This change in definition places the Ste. Genevieve Limestone (Genevievian Stage) in the lowermost part of the Chesterian Series, with which it is biotically and sedimentologically more allied than with the underlying St. Louis Limestone. This change provides a sound biostratigraphic base for correlating the Meramecian/Chesterian boundary outside of the type area. Foraminifera, conodonts, brachiopods, and corals all show significant changes at or slightly below the St. Louis/Ste. Genevieve contact rather than at the Genevievian/Chesterian contact. 52 references.

  15. Pushing the boundaries

    NASA Astrophysics Data System (ADS)

    Durrani, Matin

    2011-09-01

    Over a cup of green tea at the headquarters of the Institute for High Energy Physics (IHEP) in Beijing, Hesheng Chen, who has been its director since 1998, takes me through a list of the institute's many current and planned research facilities.

  16. Expansive Learning across Workplace Boundaries

    ERIC Educational Resources Information Center

    Kerosuo, Hannele; Toiviainen, Hanna

    2011-01-01

    The article analyses a collaborative effort of learning across workplace boundaries in a regional learning network of South Savo, Finland. The focus is on the "Forum of In-house Development" in the network. Our objective is to highlight a dialectical approach to boundaries that draws from the ideas of cultural-historical activity theory. Expansive…

  17. Cell boundary fault detection system

    DOEpatents

    Archer, Charles Jens; Pinnow, Kurt Walter; Ratterman, Joseph D.; Smith, Brian Edward

    2011-04-19

    An apparatus and program product determine a nodal fault along the boundary, or face, of a computing cell. Nodes on adjacent cell boundaries communicate with each other, and the communications are analyzed to determine if a node or connection is faulty.

  18. Maxwell-Chern-Simons theory with a boundary

    NASA Astrophysics Data System (ADS)

    Blasi, A.; Maggiore, N.; Magnoli, N.; Storace, S.

    2010-08-01

    The Maxwell-Chern-Simons (MCS) theory with a planar boundary is considered. The boundary is introduced according to Symanzik's basic principles of locality and separability. A method of investigation is proposed, which, avoiding the straight computation of correlators, is appealing for situations where the computation of propagators, modified by the boundary, becomes quite complex. For the MCS theory, the outcome is that a unique solution exists, in the form of chiral conserved currents, satisfying a Kač-Moody algebra, whose central charge does not depend on the Maxwell term.

  19. Further Improvements to Nozzle Boundary Layer Calculations in BLIMPJ

    NASA Technical Reports Server (NTRS)

    Praharaj, S. C.; Gross, Klaus W.

    1989-01-01

    Further improvements made to advance the current Boundary Layer Integral Matrix Procedure - Version J (BLIMPJ) containing previously modeled simplified calculation methods by accounting for condensed phase, thick boundary layer and free stream turbulence effects are discussed. The condensed phase effects were included through species composition effect considered via input to the code and through particle damping effect considered via a turbulence model. The thrust loss calculation procedure for thick boundary layer effects was improved and the optimization of net thrust with respect to nozzle length was performed. The effects of free stream turbulence were approximately modeled in the turbulence model.

  20. Structure of turbulence in three-dimensional boundary layers

    NASA Technical Reports Server (NTRS)

    Subramanian, Chelakara S.

    1993-01-01

    This report provides an overview of the three dimensional turbulent boundary layer concepts and of the currently available experimental information for their turbulence modeling. It is found that more reliable turbulence data, especially of the Reynolds stress transport terms, is needed to improve the existing modeling capabilities. An experiment is proposed to study the three dimensional boundary layer formed by a 'sink flow' in a fully developed two dimensional turbulent boundary layer. Also, the mean and turbulence field measurement procedure using a three component laser Doppler velocimeter is described.

  1. Paint and Click: Unified Interactions for Image Boundaries

    SciTech Connect

    Summa, B.; Gooch, A. A.; Scorzelli, G.; Pascucci, V.

    2015-06-22

    Image boundaries are a fundamental component of many interactive digital photography techniques, enabling applications such as segmentation, panoramas, and seamless image composition. Interactions for image boundaries often rely on two complementary but separate approaches: editing via painting or clicking constraints. In this work, we provide a novel, unified approach for interactive editing of pairwise image boundaries that combines the ease of painting with the direct control of constraints. Rather than a sequential coupling, this new formulation allows full use of both interactions simultaneously, giving users unprecedented flexibility for fast boundary editing. To enable this new approach, we provide technical advancements. In particular, we detail a reformulation of image boundaries as a problem of finding cycles, expanding and correcting limitations of the previous work. Our new formulation provides boundary solutions for painted regions with performance on par with state-of-the-art specialized, paint-only techniques. In addition, we provide instantaneous exploration of the boundary solution space with user constraints. Finally, we provide examples of common graphics applications impacted by our new approach.

  2. Integrating seismological and tectonic studies to constrain lithospheric evolution at complex plate boundaries

    NASA Astrophysics Data System (ADS)

    Hayes, Gavin Peter

    The relative motion of tectonic plates across their boundaries generates deformation in the surrounding lithosphere. How this deformation is expressed reflects both present-day plate configurations and how plate boundaries evolve. To understand the behavior of plate boundaries, we must study how they have developed. The advances made in seismology over the past fifty years---both in observation and application---provide tools ideal for such analysis. Here, I use these tools to investigate the tectonic evolution of complex plate boundaries. I focus on two areas that have experienced geologically recent plate tectonic variations---the Mendocino triple junction in northern California, and the Australia:Pacific plate boundary south of New Zealand. In northern California, the northward migration of the Mendocino triple junction over the past ˜10Ma has driven a synchronous pattern of thickening and thinning of North American crust. In studying this deformation I find major thinning is localized to a narrow region of crust in the Redwood Valley area. This thinning is accompanied by a steeply dipping Moho (>15°), and by high Poisson's Ratio's in the lower crust, characteristic of layers of melt. These melts may link to shallow (˜10km) dike injections that drive a migrating sequence of seismicity in the shallow crust near Lake Pillsbury. The limited data sets available led me to develop new tools in receiver function and crustal velocity ratio analyses that significantly improve our ability to resolve spatial changes in crustal properties. The application of these techniques forms a second major aspect of this thesis. Finally, I analyze the deformation of Australian lithosphere adjacent to the plate boundary south of New Zealand. I perform earthquake relocations on the distribution of intra- and inter-plate seismicity, and combined with plate reconstructions since the late Oligocene show that deformation occurs over a ˜150km wide area west of the current plate boundary

  3. Evaluating the Importance of Outflow Velocity at the MHD Inner Boundary

    NASA Astrophysics Data System (ADS)

    Welling, D. T.; Liemohn, M. W.; Toth, G.; Glocer, A.

    2013-12-01

    Including an ionospheric source of magnetospheric plasma in global magnetohydrodynamic models (MHD) is an exercise in setting inner boundary mass density and radial velocity. Recently, in order to account for the complex processes that accelerate plasmas up from ionospheric altitudes to MHD inner boundary altitudes (typically 2.5 to 3 Earth Radii), empirical and first-principles-based models have been developed to set inner boundary conditions in a dynamic and activity-dependent manner. However, such measures are not necessary to achieve outflowing fluences of the order observed by various spacecraft. Spatially and temporally constant boundary conditions, even with zero radial velocity, have been shown to produce dynamic outflow patterns and supply the bulk of magnetospheric plasma. Noteworthy of this approach is the inherent assumption that no acceleration has occurred between the ionosphere and the inner boundary, that is, the ionosphere is simply a mass reservoir. This assumption is contrary to our understanding of the magnetosphere-ionosphere system, yet the net result - outflowing heavy and light ions that populate the rest of geospace - is similar to that when a more realistic outflow specification is applied. The implication is that radial velocity matters little when supplying outflow to global MHD models. This paper investigates the importance of radial velocity at the inner boundary of MHD codes in driving ionospheric outflows into the greater domain. Multi-fluid BATS-R-US is used to simulate an idealized storm, first using zero radial velocity at the inner boundary, then non-zero constant values, and finally with spatially and temporally dynamic values driven by the Polar Wind Outflow Model (PWOM), which sets radial velocity and number density based on physics-based modeling of gap region populations. The results, in terms of total fluence, spatial outflowing flux patterns, and overall magnetospheric response, are compared to investigate how the

  4. Reconstruction of multiple cracks from experimental electrostatic boundary measurements

    NASA Technical Reports Server (NTRS)

    Bryan, Kurt; Liepa, Valdis; Vogelius, Michael

    1993-01-01

    An algorithm for recovering a collection of linear cracks in a homogeneous electrical conductor from boundary measurements of voltages induced by specified current fluxes is described. The technique is a variation of Newton's method and is based on taking weighted averages of the boundary data. An apparatus that was constructed specifically for generating laboratory data on which to test the algorithm is also described. The algorithm is applied to a number of different test cases and the results are discussed.

  5. Entanglement and boundary critical phenomena

    SciTech Connect

    Zhou Huanqiang; Barthel, Thomas; Schollwoeck, Ulrich; Fjaerestad, John Ove

    2006-11-15

    We investigate boundary critical phenomena from a quantum-information perspective. Bipartite entanglement in the ground state of one-dimensional quantum systems is quantified using the Renyi entropy S{sub {alpha}}, which includes the von Neumann entropy ({alpha}{yields}1) and the single-copy entanglement ({alpha}{yields}{infinity}) as special cases. We identify the contribution of the boundaries to the Renyi entropy, and show that there is an entanglement loss along boundary renormalization group (RG) flows. This property, which is intimately related to the Affleck-Ludwig g theorem, is a consequence of majorization relations between the spectra of the reduced density matrix along the boundary RG flows. We also point out that the bulk contribution to the single-copy entanglement is half of that to the von Neumann entropy, whereas the boundary contribution is the same.

  6. Grain boundary chemistry and heat treatment effects on the ductile-to-brittle transition behavior of vanadium alloys

    NASA Astrophysics Data System (ADS)

    Kurtz, R. J.; Hamilton, M. L.; Li, H.

    1998-10-01

    The ductile-to-brittle transition (DBTT) behavior of vanadium alloys currently being developed for fusion power systems is sensitive to thermo-mechanical processing variables and history. Factors which contribute to this sensitivity are (1) pickup of interstitial impurities such as oxygen, nitrogen and carbon during heat treatments and elevated temperature forming operations, (2) the final grain size achieved, (3) removal of impurities from solid solution due to precipitation reactions, and (4) segregation of impurities to grain boundaries. Previous work on a V-5Cr-5Ti (Heat No. 832394) alloy suggested that sulfur segregation or precipitation during final mill annealing may play a role in determining DBTT behavior. The effect of heat treatment on grain boundary chemistry and Charpy impact behavior was investigated using a production-scale heat of V-4Cr-4Ti (Heat No. 832665). Specimens were examined with Auger electron spectroscopy to characterize grain boundary microchemistry for correlation with Charpy impact test results obtained from one-third size specimens.

  7. Grain boundaries in CdTe thin film solar cells: a review

    NASA Astrophysics Data System (ADS)

    Major, Jonathan D.

    2016-09-01

    The current state of knowledge on the impact of grain boundaries in CdTe solar cells is reviewed with emphasis being placed on working cell structures. The role of the chemical composition of grain boundaries as well as growth processes are discussed, along with characterisation techniques such as electron beam induced current and cathodoluminescence, which are capable of extracting information on a level of resolution comparable to the size of the grain boundaries. Work which attempts to relate grain boundaries to device efficiency is also assessed and gaps in the current knowledge are highlighted.

  8. Final Project Report

    SciTech Connect

    Small, R. Justin; Bryan, Frank; Tribbia, Joseph; Park, Sungsu; Dennis, John; Saravanan, R.; Schneider, Niklas; Kwon, Young-Oh

    2015-06-01

    Most climate models are currently run with grid spacings of around 100km, which, with today’s computing power, allows for long (up to 1000 year) simulations, or ensembles of simulations to explore climate change and variability. However this grid spacing does not resolve important components of the weather/climate system such as atmospheric fronts and mesoscale systems, and ocean boundary currents and eddies. The overall aim of this project has been to look at the effect of these small-scale features on the weather/climate system using a suite of high and low resolution climate models, idealized models and observations. This project was only possible due to the highly scalable aspect of the CAM Spectral Element dynamical core, and the significant resources allocated at Yellowstone and NERSC for which we are grateful.

  9. Final Report

    SciTech Connect

    R. Paul Drake

    2001-11-30

    This final report describes work involving 22 investigators from 11 institutions to explore the dynamics present in supernova explosions by means of experiments on the Omega laser. The specific experiments emphasized involved the unstable expansion of a spherical capsule and the coupling of perturbations at a first interface to a second interface by means of a strong shock. Both effects are present in supernovae. The experiments were performed at Omega and the computer simulations were undertaken at several institutions. B139

  10. Final Report

    SciTech Connect

    Marchant, Gary E.

    2013-04-23

    This is the final report of a two year project entitled "Governing Nanotechnology Risks and Benefits in the Transition to Regulation: Innovative Public and Private Approaches." This project examined the role of new governance or "soft law" mechanisms such as codes of conduct, voluntary programs and partnership agreements to manage the risks of emerging technologies such as nanotechnology. A series of published or in publication papers and book chapters are attached.

  11. Experimental and theoretical studies of a high temperature cesium-barium tacitron, with application to low voltage-high current inversion. Final report, April 1, 1993--February 28, 1994

    SciTech Connect

    Murray, C.S.; El-Genk, M.S.

    1994-02-01

    A low voltage/high current switch refer-red as ``Cs-Ba tacitron`` is studied for use as a dc to ac inverter in high temperature and/or ionizing radiation environments. The operational characteristics of the Cs-Ba tacitron as a switch were investigated experimentally in three modes: (a) breakdown mode, (b) I-V mode, and (c) current modulation mode. Operation parameters measured include switching frequencies up to 20 kHz, hold-off voltages up to 200 V, current densities in excess of 15 A/CM{sup 2}, switch power density of 1 kW/cm{sup 2}, and a switching efficiency in excess of 90 % at collector voltages greater than 30 V. Also, if the discharge current is circuit limited to a value below the maximum thermal emission current density, the voltage drop is constant and below 3 V.

  12. An Evaluation of Boundary Conditions for Modeling Urban Boundary Layers

    SciTech Connect

    Calhoun, R.J.; Chan, S.T.; Lee, R.L.

    2000-05-18

    Numerical modeling of the urban boundary layer is complicated by the need to describe airflow patterns outside of the computational domain. These patterns have an impact on how successfully the simulation is able to model the turbulence associated with the urban boundary layer. This talk presents experiments with the model boundary conditions for simulations that were done to support two Department of Energy observational programs involving the Salt Lake City basin. The Chemical/Biological Non-proliferation Program (CBNP) is concerned with the effects of buildings on influencing dispersion patterns in urban environments. The Vertical Transport and Mixing Program (VTMX) investigating mixing mechanisms in the stable boundary layer and how they are influenced by the channeling caused by drainage flows or by obstacles such as building complexes. Both of these programs are investigating the turbulent mixing caused by building complexes and other urban obstacles.

  13. Effect of Insolation Boundary Conditions on Type B Package Internal Temperatures

    SciTech Connect

    Hovingh, J; Shah, VL

    2002-05-30

    The prescription of the initial conditions and the final conditions for a thermal accident for Type B packages are different for differing regulations. This paper presents an analytical method for estimating the effect of the boundary conditions on post-fire peak internal package temperatures. Results are given for several boundary conditions for a Type B drum-type package.

  14. 76 FR 62038 - Boundary Establishment for North Fork Crooked National Wild and Scenic River, Ochoco National...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-06

    ... Forest Service Boundary Establishment for North Fork Crooked National Wild and Scenic River, Ochoco National Forest, Crook County, Oregon AGENCY: Forest Service, USDA. ACTION: Notice of availability. SUMMARY..., Washington Office, is transmitting the final boundary of the North Fork Crooked National Wild and...

  15. Physics of Boundaries and their Interactions in Space Plasmas

    NASA Technical Reports Server (NTRS)

    Omidi, Nojan; Karimabadi, Homayoun; Krauss-Varban, Dietmar

    1997-01-01

    This report describes the work done by SciberNet, Inc. during the month of August. We have resolved the issues associated with the implementation of the dipole field in our large scale hybrid simulations of the magnetopause. We have setup several runs and will spend the next several months analyzing the data. The results will be presented at the Fall AGU. We are also continuing our analysis of the 3-D simulations of thin current sheets at the magnetopause, paying special attention to the conditions under which Kelvin-Helmholtz would lead to sizable perturbations of the magnetopause. In a related study, we are in the process of developing a new kinetic linear code that would for the first time enable us to examine the linear properties of the Kelvin-Helmholtz instability in the fully kinetic regime. Finally, we are continuing our code development to include inflow-outflow boundary conditions in our 2-D and 3-D hybrid codes. We are also comparing the different methods of code parallelization in order to extend the limits of our calculations.

  16. Boundary Layer Protuberance Simulations in Channel Nozzle Arc Jet

    NASA Technical Reports Server (NTRS)

    Larin, M. E.; Campbell, C. H.; Pulsonetti, M. V.

    2009-01-01

    Various protuberance heights and shapes were modeled in the channel nozzle of the NASA Johnson Space Center Atmospheric Reentry Materials and Strictures Facility with the Data- Parallel Line Relaxation computational fluid dynamics code. The heating on the protuberance was compared to baseline (no protuberance) heating at a single fixed arc jet condition in order to obtain heating augmentation factors that will be used for flight traceability in the Boundary Layer Transition Flight Experiment on Space Shuttle Orbiter flights STS-119 (completed) and STS-128 (future flight). The arc jet simulations were performed in conjunction with the actual ground tests performed on the flight version (selected height and shape) of the protuberance. Thearc jet simulations for the final (flight version) protuberance included non-uniform inflow conditions beginning at the channel nozzle throat. The 2D inflow condition was modeled based on the current best practices methodology and used variable enthalpy and mass flow rate across the throat. Channel walls were modeled as fully catalytic isothermal surfaces, while the test section (consisting of Reaction Cured Glass tiles) was modeled as a partially catalytic radiative equilibrium wall. The results of the protuberance and baseline simulations were compared to the applicable ground test results. In addition, the obtained heating augmentation factors were compared to the factors derived from the STS-119 flight data. The effects of the protuberance shock on the opposite channel wall were also investigated.

  17. Lamellar diblock copolymer grain boundary morphology. 1. Twist boundary characterization

    SciTech Connect

    Gido, S.P.; Gunther, J.; Thomas, E.L. . Dept. of Materials Science and Engineering); Hoffman, D. . Dept. of Mathematics and Statistics)

    1993-08-16

    Grain boundary morphologies in poly(styrene-b-butadiene) lamellar diblock copolymers were characterized using transmission electron microscopy (TEM). Two types of twist grain boundaries were observed in which microphase separation of the two blocks was maintained in the grain boundary region by intermaterial dividing surfaces that approximate classically known minimal surfaces. The geometry of these interfaces was demonstrated by comparing experimental TEM images with ray tracing computer simulations of the model surfaces as the projection direction was systematically varied in both the experimental and simulated images. The two morphologies observed were found to have intermaterial dividing surfaces that approximate either Scherk's first (doubly periodic) surface or a section of the right helicoid. The helicoid section boundary was observed at low twist angles, less than or equal to about 15. The Scherk surface family of boundary morphologies, which consists of a doubly periodic array of saddle surfaces, was found over the entire twist range from 0 to 90[degree]. As the twist angle approaches 0[degree] the Scherk surface grain boundary morphology is transformed into a single screw dislocation that has an intermaterial dividing surface with the geometry of a single helicoid. Direct TEM imaging of the detailed core structure of this screw dislocation is presented. These images demonstrate that in the lamellar diblock copolymer the screw dislocation core is nonsingular. This nonsingular core structure represents a radical departure from the singular core structures observed in classical studies of dislocations in atomic crystals.

  18. Brain response to prosodic boundary cues depends on boundary position

    PubMed Central

    Holzgrefe, Julia; Wellmann, Caroline; Petrone, Caterina; Truckenbrodt, Hubert; Höhle, Barbara; Wartenburger, Isabell

    2013-01-01

    Prosodic information is crucial for spoken language comprehension and especially for syntactic parsing, because prosodic cues guide the hearer's syntactic analysis. The time course and mechanisms of this interplay of prosody and syntax are not yet well-understood. In particular, there is an ongoing debate whether local prosodic cues are taken into account automatically or whether they are processed in relation to the global prosodic context in which they appear. The present study explores whether the perception of a prosodic boundary is affected by its position within an utterance. In an event-related potential (ERP) study we tested if the brain response evoked by the prosodic boundary differs when the boundary occurs early in a list of three names connected by conjunctions (i.e., after the first name) as compared to later in the utterance (i.e., after the second name). A closure positive shift (CPS)—marking the processing of a prosodic phrase boundary—was elicited for stimuli with a late boundary, but not for stimuli with an early boundary. This result is further evidence for an immediate integration of prosodic information into the parsing of an utterance. In addition, it shows that the processing of prosodic boundary cues depends on the previously processed information from the preceding prosodic context. PMID:23882234

  19. Generation of Boundary Manikin Anthropometry

    NASA Technical Reports Server (NTRS)

    Young, Karen S.; Margerum, Sarah; Barr, Abbe; Ferrer, Mike A.; Rajulu, Sudhakar

    2008-01-01

    The purpose of this study was to develop 3D digital boundary manikins that are representative of the anthropometry of a unique population. These digital manikins can be used by designers to verify and validate that the components of the spacesuit design satisfy the requirements specified in the Human Systems Integration Requirements (HSIR) document. Currently, the HSIR requires the suit to accommodate the 1st percentile American female to the 99th percentile American male. The manikin anthropometry was derived using two methods: Principal Component Analysis (PCA) and Whole Body Posture Based Analysis (WBPBA). PCA is a statistical method for reducing a multidimensional data set by using eigenvectors and eigenvalues. The goal is to create a reduced data set that encapsulates the majority of the variation in the population. WBPBA is a multivariate analytical approach that was developed by the Anthropometry and Biomechanics Facility (ABF) to identify the extremes of the population for a given body posture. WBPBA is a simulation-based method that finds extremes in a population based on anthropometry and posture whereas PCA is based solely on anthropometry. Both methods yield a list of subjects and their anthropometry from the target population; PCA resulted in 20 female and 22 male subjects anthropometry and WBPBA resulted in 7 subjects' anthropometry representing the extreme subjects in the target population. The subjects anthropometry is then used to 'morph' a baseline digital scan of a person with the same body type to create a 3D digital model that can be used as a tool for designers, the details of which will be discussed in subsequent papers.

  20. ThreaDom: extracting protein domain boundary information from multiple threading alignments

    PubMed Central

    Xue, Zhidong; Xu, Dong; Wang, Yan; Zhang, Yang

    2013-01-01

    Motivation: Protein domains are subunits that can fold and evolve independently. Identification of domain boundary locations is often the first step in protein folding and function annotations. Most of the current methods deduce domain boundaries by sequence-based analysis, which has low accuracy. There is no efficient method for predicting discontinuous domains that consist of segments from separated sequence regions. As template-based methods are most efficient for protein 3D structure modeling, combining multiple threading alignment information should increase the accuracy and reliability of computational domain predictions. Result: We developed a new protein domain predictor, ThreaDom, which deduces domain boundary locations based on multiple threading alignments. The core of the method development is the derivation of a domain conservation score that combines information from template domain structures and terminal and internal alignment gaps. Tested on 630 non-redundant sequences, without using homologous templates, ThreaDom generates correct single- and multi-domain classifications in 81% of cases, where 78% have the domain linker assigned within ±20 residues. In a second test on 486 proteins with discontinuous domains, ThreaDom achieves an average precision 84% and recall 65% in domain boundary prediction. Finally, ThreaDom was examined on 56 targets from CASP8 and had a domain overlap rate 73, 87 and 85% with the target for Free Modeling, Hard multiple-domain and discontinuous domain proteins, respectively, which are significantly higher than most domain predictors in the CASP8. Similar results were achieved on the targets from the most recently CASP9 and CASP10 experiments. Availability: http://zhanglab.ccmb.med.umich.edu/ThreaDom/. Contact: zhng@umich.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:23812990

  1. Final Report

    SciTech Connect

    R Paul Drake

    2004-01-12

    OAK-B135 This is the final report from the project Hydrodynamics by High-Energy-Density Plasma Flow and Hydrodynamics and Radiation Hydrodynamics with Astrophysical Applications. This project supported a group at the University of Michigan in the invention, design, performance, and analysis of experiments using high-energy-density research facilities. The experiments explored compressible nonlinear hydrodynamics, in particular at decelerating interfaces, and the radiation hydrodynamics of strong shock waves. It has application to supernovae, astrophysical jets, shock-cloud interactions, and radiative shock waves.

  2. Solid Inflammability Boundary at Low Speed (SIBAL)

    NASA Technical Reports Server (NTRS)

    Tien, James S.; Sacksteder, Kurt R.; Ferkul, Paul V.; Bedir, Hasan; Shih, Hsin-Yi; Greenberg, Paul S.; Pettegrew, Richard D.; Piltch, Nancy; Frate, David

    1997-01-01

    This research program is concerned with the effect of low speed flow on the spreading and extinction processes of flames over solid fuels. We are particularly interested in the flammability boundary and the near-limit flame behavior in a microgravity environment. Primary attention is given to flame propagation in concurrent flow - the more hazardous situation from the point of view of fire safety. Both theoretical modeling and experimental research are in progress. This project passed the Science Concept Review (SCR) in 1996. As a result, the experiment continues on the flight definition path, and is currently scheduled to be performed in the Space Station Fluids and Combustion Facility (FCF).

  3. Rotating fermions inside a cylindrical boundary

    NASA Astrophysics Data System (ADS)

    Ambruş, Victor E.; Winstanley, Elizabeth

    2016-05-01

    We study a quantum fermion field inside a cylinder in Minkowski space-time. On the surface of the cylinder, the fermion field satisfies either spectral or MIT bag boundary conditions. We define rigidly-rotating quantum states in both cases, assuming that the radius of the cylinder is sufficiently small that the speed-of-light surface is excluded from the space-time. With this assumption, we calculate rigidly-rotating thermal expectation values of the fermion condensate, neutrino charge current and stress-energy tensor relative to the bounded vacuum state. These rigidly-rotating thermal expectation values are finite everywhere inside and on the surface of the cylinder, and their detailed properties depend on the choice of boundary conditions. We also compute the Casimir divergence of the expectation values of these quantities in the bounded vacuum state relative to the unbounded Minkowski vacuum. We find that the rate of divergence of the Casimir expectation values depends on the conditions imposed on the boundary.

  4. Remote sensing of ocean currents

    NASA Technical Reports Server (NTRS)

    Maul, G. A. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Monthly field experiments in support of the NOAA investigation of ocean color boundary determination using ERTS-1 data have been conducted since June 1972. The boundary between coastal waters and the Loop Current has been detected by ERTS-1 as a result of sea state changes as well as color differences. Ocean information is contained in all 24 channels of the Bendix MSS flown on the C-130 in June 1972; this includes UV, visible, reflected IR, and emitted IR. Computer enhancement of MSS data is revealing many features not shown in the NDPF product.

  5. Boundary Layer Control on Airfoils.

    ERIC Educational Resources Information Center

    Gerhab, George; Eastlake, Charles

    1991-01-01

    A phenomena, boundary layer control (BLC), produced when visualizing the fluidlike flow of air is described. The use of BLC in modifying aerodynamic characteristics of airfoils, race cars, and boats is discussed. (KR)

  6. FINAL REPORT

    SciTech Connect

    Kanai S. Shah

    2003-08-07

    Current and next generation experiments in nuclear and particle physics require detectors with high spatial resolution, fast response, and accurate energy information. In many nuclear physics experiments, existing detector technology is the limiting factor. The proposed project aims to investigate a promising detector concept that will have wide applicability in particle physics and many other applications.

  7. Pyramidal inversion domain boundaries revisited

    SciTech Connect

    Remmele, T.; Albrecht, M.; Irmscher, K.; Fornari, R.; Strassburg, M.

    2011-10-03

    The structure of pyramidal inversion domain boundaries in GaN:Mg was investigated by aberration corrected transmission electron microscopy. The analysis shows the upper (0001) boundary to consist of a single Mg layer inserted between polarity inverted GaN layers in an abcab stacking. The Mg bound in these defects is at least one order of magnitude lower than the chemical Mg concentration. Temperature dependent Hall effect measurements show that up to 27% of the Mg acceptors is electrically compensated.

  8. Changing the Structure Boundary Geometry

    SciTech Connect

    Karasev, Viktor; Dzlieva, Elena; Ivanov, Artyom

    2008-09-07

    Analysis of previously obtained results shows that hexagonal crystal lattice is the dominant type of ordering, in particular, in striated glow discharges. We explore the possibility for changing the dust distribution in horizontal cross sections of relatively highly ordered structures in a glow-discharge. Presuming that boundary geometry can affect dust distribution, we used cylindrical coolers held at 0 deg. C and placed against a striation containing a structure, to change the geometry of its outer boundary. By varying the number of coolers, their positions, and their separations from the tube wall, azimuthally asymmetric thermophoretic forces can be used to form polygonal boundaries and vary the angles between their segments (in a horizontal cross section). The corner in the structure's boundary of 60 deg. stimulates formation of hexagonal cells. The structure between the supported parallel boundaries is also characterized by stable hexagonal ordering. We found that a single linear boundary segment does not give rise to any sizable domain, but generates a lattice extending from the boundary (without edge defects). A square lattice can be formed by setting the angle equal to 90 deg. . However, angles of 45 deg. and 135 deg. turned out easier to form. Square lattice was created by forming a near-135 deg. corner with four coolers. It was noted that no grain ordering is observed in the region adjacent to corners of angles smaller than 30 deg. , which do not promote ordering into cells of any shape. Thus, manipulation of a structure boundary can be used to change dust distribution, create structures free of the ubiquitous edge defects that destroy orientation order, and probably change the crystal lattice type.

  9. Removing Boundary Layer by Suction

    NASA Technical Reports Server (NTRS)

    Ackeret, J

    1927-01-01

    Through the utilization of the "Magnus effect" on the Flettner rotor ship, the attention of the public has been directed to the underlying physical principle. It has been found that the Prandtl boundary-layer theory furnishes a satisfactory explanation of the observed phenomena. The present article deals with the prevention of this separation or detachment of the flow by drawing the boundary layer into the inside of a body through a slot or slots in its surface.

  10. Thermal boundaries analysis program document

    NASA Technical Reports Server (NTRS)

    Evans, M. E.

    1975-01-01

    The digital program TBAP has been developed to provide thermal boundaries in the DD/M-relative velocity (D-V), dynamic pressure-relative velocity (q-V), and altitude-relative velocity (h-V) planes. These thermal boundaries are used to design and/or analyze shuttle orbiter entry trajectories. The TBAP has been used extensively in supporting the Flight Performance Branch of NASA in evaluating candidate trajectories for the thermal protection system design trajectory.

  11. Boundary development in the field of international nutrition science.

    PubMed

    Centrone Stefani, Monique; Humphries, Debbie L

    2014-03-01

    Using a sociological approach that elaborates on key observations of institutional entrepreneurs in international nutrition, this paper explores institutional boundaries and boundary work in international nutrition. Sociological concepts of "boundary making" and "situated knowledge" are applied to the boundaries between the nutrition sciences and lay nutrition knowledge in nutrition intervention. These concepts allow an analysis of how nutrition science creates boundaries between its field and other sciences and between nutrition as a science and other nutrition practices, providing additional perspective on current challenges in global food security and malnutrition. Analysis of boundary processes in international nutrition can also illuminate the development of "implementation" or "delivery science" in the field of international nutrition as it attempts to strengthen effectiveness of global efforts to reduce malnutrition. Although some risk taking in the academic world is rewarded, the analysis indicates that there are underlying processes that may inhibit full partnership with local people in the course of intervention work that builds scientific nutrition knowledge. As nutrition science becomes increasingly central to development, the boundaries that are reinforced by digging in heels over the implementation of programs with little local input or softened by inviting local stakeholders to publicly consider the problems in global nutrition together are important to consider in helping to create directions that favor viable solutions. PMID:24618761

  12. Boundary-layer receptivity and laminar-flow airfoil design

    NASA Technical Reports Server (NTRS)

    Kerschen, Edward J.

    1987-01-01

    Boundary-layer receptivity examines the way in which external disturbances generate instability waves in boundary layers. Receptivity theory is complementary to stability theory, which studies the evolution of disturbances that are already present in the boundary layer. A transition prediction method which combines receptivity with linear stability theory would directly account for the influence of free-stream disturbances and also consider the characteristics of the boundary layer upstream of the neutral stability point. The current e sup N transition prediction methods require empirical correlations for the influence of environmental disturbances, and totally ignore the boundary layer characteristics upstream of the neutral stability point. The regions where boundary-layer receptivity occurs can be separated into two classes, one near the leading edges and the other at the downstream points where the boundary layer undergoes rapid streamwise adjustments. Analyses were developed for both types of regions, and parametric studies which examine the relative importance of different mechanisms were carried out. The work presented here has focused on the low Mach number case. Extensions to high subsonic and supersonic conditions are presently underway.

  13. Boundary Development in the Field of International Nutrition Science12

    PubMed Central

    Centrone Stefani, Monique; Humphries, Debbie L.

    2014-01-01

    Using a sociological approach that elaborates on key observations of institutional entrepreneurs in international nutrition, this paper explores institutional boundaries and boundary work in international nutrition. Sociological concepts of “boundary making” and “situated knowledge” are applied to the boundaries between the nutrition sciences and lay nutrition knowledge in nutrition intervention. These concepts allow an analysis of how nutrition science creates boundaries between its field and other sciences and between nutrition as a science and other nutrition practices, providing additional perspective on current challenges in global food security and malnutrition. Analysis of boundary processes in international nutrition can also illuminate the development of “implementation” or “delivery science” in the field of international nutrition as it attempts to strengthen effectiveness of global efforts to reduce malnutrition. Although some risk taking in the academic world is rewarded, the analysis indicates that there are underlying processes that may inhibit full partnership with local people in the course of intervention work that builds scientific nutrition knowledge. As nutrition science becomes increasingly central to development, the boundaries that are reinforced by digging in heels over the implementation of programs with little local input or softened by inviting local stakeholders to publicly consider the problems in global nutrition together are important to consider in helping to create directions that favor viable solutions. PMID:24618761

  14. Imaging grain boundary scattering of graphene in real space

    NASA Astrophysics Data System (ADS)

    Ji, Shuai-Hua; Hannon, James B.; Tromp, Ruud M.; Subbiah, Chockalingam; Pasupathy, Abhay; Heinz, Tony F.; Ross, Frances M.

    2012-02-01

    Graphene grain boundaries are unavoidable defects in most growth methods, in particular chemical vapor deposition and thermal decomposition on the SiC(0001) surface. How electrons are scattered by those grain boundaries has not been experimentally demonstrated at the nanoscale. Here we report atomic-scale images of grain boundary scattering measured by scanning tunneling potentiometry (STP). Monolayer graphene sheets were synthesized on the SiC(0001) surface by thermal decomposition in a background of disilane, using low energy electron microscopy to monitor the graphene thickness during its formation. High resolution scanning tunneling microscopy (STM) reveals graphene grain boundaries and various grain orientations, and STP shows variations in voltage across grains and terraces as current flows across the graphene layer. We have identified two types of grain boundary. One shows a trench structure in STM images; potential mapping shows prominent potential drops. These boundaries between grains appear to be weak links and the dominant scattering locations. The other type of boundary shows a continuous lattice between the grains, with periodic dislocations accommodating the grain misorientation. Potential mapping indicates much weaker scattering despite the grain misorientation. We will discuss transport in polycrystalline graphene based on these measurements.

  15. Grain-boundary migration in KCl bicrystals

    NASA Technical Reports Server (NTRS)

    Gibbon, C. F.

    1968-01-01

    Boundary migration in melt-grown bicrystals of KCl containing pure twist boundaries was investigated. The experiments involve the use of bicrystal specimens in the shape of right-triangular prisms with the boundary parallel to one side.

  16. Boundary Condition for Modeling Semiconductor Nanostructures

    NASA Technical Reports Server (NTRS)

    Lee, Seungwon; Oyafuso, Fabiano; von Allmen, Paul; Klimeck, Gerhard

    2006-01-01

    A recently proposed boundary condition for atomistic computational modeling of semiconductor nanostructures (particularly, quantum dots) is an improved alternative to two prior such boundary conditions. As explained, this boundary condition helps to reduce the amount of computation while maintaining accuracy.

  17. Boundary element analysis of post-tensioned slabs

    NASA Astrophysics Data System (ADS)

    Rashed, Youssef F.

    2015-06-01

    In this paper, the boundary element method is applied to carry out the structural analysis of post-tensioned flat slabs. The shear-deformable plate-bending model is employed. The effect of the pre-stressing cables is taken into account via the equivalent load method. The formulation is automated using a computer program, which uses quadratic boundary elements. Verification samples are presented, and finally a practical application is analyzed where results are compared against those obtained from the finite element method. The proposed method is efficient in terms of computer storage and processing time as well as the ease in data input and modifications.

  18. Exploring the planetary boundary for chemical pollution.

    PubMed

    Diamond, Miriam L; de Wit, Cynthia A; Molander, Sverker; Scheringer, Martin; Backhaus, Thomas; Lohmann, Rainer; Arvidsson, Rickard; Bergman, Åke; Hauschild, Michael; Holoubek, Ivan; Persson, Linn; Suzuki, Noriyuki; Vighi, Marco; Zetzsch, Cornelius

    2015-05-01

    Rockström et al. (2009a, 2009b) have warned that humanity must reduce anthropogenic impacts defined by nine planetary boundaries if "unacceptable global change" is to be avoided. Chemical pollution was identified as one of those boundaries for which continued impacts could erode the resilience of ecosystems and humanity. The central concept of the planetary boundary (or boundaries) for chemical pollution (PBCP or PBCPs) is that the Earth has a finite assimilative capacity for chemical pollution, which includes persistent, as well as readily degradable chemicals released at local to regional scales, which in aggregate threaten ecosystem and human viability. The PBCP allows humanity to explicitly address the increasingly global aspects of chemical pollution throughout a chemical's life cycle and the need for a global response of internationally coordinated control measures. We submit that sufficient evidence shows stresses on ecosystem and human health at local to global scales, suggesting that conditions are transgressing the safe operating space delimited by a PBCP. As such, current local to global pollution control measures are insufficient. However, while the PBCP is an important conceptual step forward, at this point single or multiple PBCPs are challenging to operationalize due to the extremely large number of commercial chemicals or mixtures of chemicals that cause myriad adverse effects to innumerable species and ecosystems, and the complex linkages between emissions, environmental concentrations, exposures and adverse effects. As well, the normative nature of a PBCP presents challenges of negotiating pollution limits amongst societal groups with differing viewpoints. Thus, a combination of approaches is recommended as follows: develop indicators of chemical pollution, for both control and response variables, that will aid in quantifying a PBCP(s) and gauging progress towards reducing chemical pollution; develop new technologies and technical and social

  19. Current limiters

    SciTech Connect

    Loescher, D.H.; Noren, K.

    1996-09-01

    The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.

  20. Coupling of magnetopause-boundary layer to the polar ionosphere

    NASA Technical Reports Server (NTRS)

    Wei, C. Q.; Lee, L. C.

    1993-01-01

    The plasma dynamics in the low-latitude boundary layer and its coupling to the polar ionosphere under boundary conditions at the magnetopause are investigated. In the presence of a driven plasma flow along the magnetopause, the Kelvin-Helmholtz instability can develop, leading to the formation and growth of plasma vortices in the boundary layer. The finite ionospheric conductivity leads to the decay of these vortices. The competing effect of the formation and decay of vortices leads to the formation of strong vortices only in a limited region. Several enhanced field-aligned power density regions associated with the boundary layer vortices and the upward field-aligned current (FAC) filaments can be found along the postnoon auroral oval. These enhanced field-aligned power density regions may account for the observed auroral bright spots.

  1. Large discrete resistance jump at grain boundary in copper nanowire

    SciTech Connect

    Li, An-Ping; Kim, Tae Hwan; Zhang, Xiaoguang; Nicholson, Don M; Evans III, Boyd Mccutchen; Kulkarni, Nagraj S; Kenik, Edward A; Radhakrishnan, Balasubramaniam

    2010-01-01

    Copper is the current interconnect metal of choice in integrated circuits. As interconnect dimensions decrease, the resistivity of copper increases dramatically because of electron scattering from surfaces, impurities, and grain boundaries (GBs), and threatens to stymie continued device scaling. Lacking direct measurements of individual scattering sources, understanding of the relative importance of these scattering mechanisms has largely been relied on semi-empirical modeling. Here we present the first attempt to measure and calculate individual GB resistances in copper nanowires with a one-to-one correspondence to the GB structure. Four-probe scanning tunneling microscope measurements show discrete resistance jumps across high-angle random GBs and negligibly small resistances across coincidence boundaries. The latter is substantiated by first-principles calculations, while the former is consistent with the prediction of an intrinsic high resistance for random boundaries from a free-electron boundary scattering model. Such a big difference between these GBs provides vital information for nanoscale interconnect technology.

  2. Desert bird associations with broad-scale boundary length: Applications in avian conservation

    USGS Publications Warehouse

    Gutzwiller, K.J.; Barrow, W.C., Jr.

    2008-01-01

    1. Current understanding regarding the effects of boundaries on bird communities has originated largely from studies of forest-non-forest boundaries in mesic systems. To assess whether broad-scale boundary length can affect bird community structure in deserts, and to identify patterns and predictors of species' associations useful in avian conservation, we studied relations between birds and boundary-length variables in Chihuahuan Desert landscapes. Operationally, a boundary was the border between two adjoining land covers, and broad-scale boundary length was the total length of such borders in a large area. 2. Within 2-km radius areas, we measured six boundary-length variables. We analysed bird-boundary relations for 26 species, tested for assemblage-level patterns in species' associations with boundary-length variables, and assessed whether body size, dispersal ability and cowbird-host status were correlates of these associations. 3. The abundances or occurrences of a significant majority of species were associated with boundary-length variables, and similar numbers of species were related positively and negatively to boundary-length variables. 4. Disproportionately small numbers of species were correlated with total boundary length, land-cover boundary length and shrubland-grassland boundary length (variables responsible for large proportions of boundary length). Disproportionately large numbers of species were correlated with roadside boundary length and riparian vegetation-grassland boundary length (variables responsible for small proportions of boundary length). Roadside boundary length was associated (positively and negatively) with the most species. 5. Species' associations with boundary-length variables were not correlated with body size, dispersal ability or cowbird-host status. 6. Synthesis and applications. For the species we studied, conservationists can use the regressions we report as working models to anticipate influences of boundary-length changes

  3. Reconnection properties in collisionless plasma with open boundary conditions

    SciTech Connect

    Sun, H. E.; Ma, Z. W.; Huang, J.

    2014-07-15

    Collisionless magnetic reconnection in a Harris current sheet with different initial thicknesses is investigated using a 21/2 -D Darwin particle-in-cell simulation with the magnetosonic open boundary condition. It is found that the thicknesses of the ion dissipation region and the reconnection current sheet, when the reconnection rate E{sub r} reaches its first peak, are independent of the initial thickness of the current sheet; while the peak reconnection rate depends on it. The peak reconnection rate increases with decrease of the current sheet thickness as E{sub r}∼a{sup −1/2}, where a is the initial current sheet half-thickness.

  4. Squirmer dynamics near a boundary.

    PubMed

    Ishimoto, Kenta; Gaffney, Eamonn A

    2013-12-01

    The boundary behavior of axisymmetric microswimming squirmers is theoretically explored within an inertialess Newtonian fluid for a no-slip interface and also a free surface in the small capillary number limit, preventing leading-order surface deformation. Such squirmers are commonly presented as abridged models of ciliates, colonial algae, and Janus particles and we investigate the case of low-mode axisymmetric tangential surface deformations with, in addition, the consideration of a rotlet dipole to represent torque-motor swimmers such as flagellated bacteria. The resulting boundary dynamics reduces to a phase plane in the angle of attack and distance from the boundary, with a simplifying time-reversal duality. Stable swimming adjacent to a no-slip boundary is demonstrated via the presence of stable fixed points and, more generally, all types of fixed points as well as stable and unstable limit cycles occur adjacent to a no-slip boundary with variations in the tangential deformations. Nonetheless, there are constraints on swimmer behavior-for instance, swimmers characterized as pushers are never observed to exhibit stable limit cycles. All such generalities for no-slip boundaries are consistent with observations and more geometrically faithful simulations to date, suggesting the tangential squirmer is a relatively simple framework to enable predications and classifications for the complexities associated with axisymmetric boundary swimming. However, in the presence of a free surface, with asymptotically small capillary number, and thus negligible leading-order surface deformation, no stable surface swimming is predicted across the parameter space considered. While this is in contrast to experimental observations, for example, the free-surface accumulation of sterlet sperm, extensive surfactants are present, most likely invalidating the low capillary number assumption. In turn, this suggests the necessity of surface deformation for stable free-surface three

  5. Tidal Boundary Conditions in SEAWAT

    USGS Publications Warehouse

    Mulligan, Ann E.; Langevin, Christian; Post, Vincent E.A.

    2011-01-01

    SEAWAT, a U.S. Geological Survey groundwater flow and transport code, is increasingly used to model the effects of tidal motion on coastal aquifers. Different options are available to simulate tidal boundaries but no guidelines exist nor have comparisons been made to identify the most effective approach. We test seven methods to simulate a sloping beach and a tidal flat. The ocean is represented in one of the three ways: directly using a high hydraulic conductivity (high-K) zone and indirect simulation via specified head boundaries using either the General Head Boundary (GHB) or the new Periodic Boundary Condition (PBC) package. All beach models simulate similar water fluxes across the upland boundary and across the sediment-water interface although the ratio of intertidal to subtidal flow is different at low tide. Simulating a seepage face results in larger intertidal fluxes and influences near-shore heads and salinity. Major differences in flow occur in the tidal flat simulations. Because SEAWAT does not simulate unsaturated flow the water table only rises via flow through the saturated zone. This results in delayed propagation of the rising tidal signal inland. Inundation of the tidal flat is delayed as is flow into the aquifer across the flat. This is severe in the high-K and PBC models but mild in the GHB models. Results indicate that any of the tidal boundary options are fine if the ocean-aquifer interface is steep. However, as the slope of that interface decreases, the high-K and PBC approaches perform poorly and the GHB boundary is preferable.

  6. Cassini multi-instrument assessment of Saturn's polar cap boundary

    NASA Astrophysics Data System (ADS)

    Jinks, S. L.; Bunce, E. J.; Cowley, S. W. H.; Provan, G.; Yeoman, T. K.; Arridge, C. S.; Dougherty, M. K.; Gurnett, D. A.; Krupp, N.; Kurth, W. S.; Mitchell, D. G.; Morooka, M.; Wahlund, J.-E.

    2014-10-01

    We present the first systematic investigation of the polar cap boundary in Saturn's high-latitude magnetosphere through a multi-instrument assessment of various Cassini in situ data sets gathered between 2006 and 2009. We identify 48 polar cap crossings where the polar cap boundary can be clearly observed in the step in upper cutoff of auroral hiss emissions from the plasma wave data, a sudden increase in electron density, an anisotropy of energetic electrons along the magnetic field, and an increase in incidence of higher-energy electrons from the low-energy electron spectrometer measurements as we move equatorward from the pole. We determine the average level of coincidence of the polar cap boundary identified in the various in situ data sets to be 0.34° ± 0.05° colatitude. The average location of the boundary in the southern (northern) hemisphere is found to be at 15.6° (13.3°) colatitude. In both hemispheres we identify a consistent equatorward offset between the poleward edge of the auroral upward directed field-aligned current region of ~1.5-1.8° colatitude to the corresponding polar cap boundary. We identify atypical observations in the boundary region, including observations of approximately hourly periodicities in the auroral hiss emissions close to the pole. We suggest that the position of the southern polar cap boundary is somewhat ordered by the southern planetary period oscillation phase but that it cannot account for the boundary's full latitudinal variability. We find no clear evidence of any ordering of the northern polar cap boundary location with the northern planetary period magnetic field oscillation phase.

  7. Our Children's Education: A Time for Reform. Conference Presentations from a Regional Conference on the Current Education System, Policy Alternatives for Quality, Finance and Educational Programming to Improve Education. Final Report and Close Out Recommendation Memorandum.

    ERIC Educational Resources Information Center

    Foundation for Oregon Research and Education, Portland.

    Following a brief welcoming statement by Gwen Ericcsen, Executive Director of the Foundation for Oregon Research and Education (FORE), conference papers address a wide range of issues on the current challenges of educational reform. Among these issues are the hard choices brought about by the changing economics of education, and the value of…

  8. Towards Arbitrary Accuracy Inviscid Surface Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Dyson, Rodger W.; Hixon, Ray

    2002-01-01

    Inviscid nonlinear surface boundary conditions are currently limited to third order accuracy in time for non-moving surfaces and actually reduce to first order in time when the surfaces move. For steady-state calculations it may be possible to achieve higher accuracy in space, but high accuracy in time is required for efficient simulation of multiscale unsteady phenomena. A surprisingly simple technique is shown here that can be used to correct the normal pressure derivatives of the flow at a surface on a Cartesian grid so that arbitrarily high order time accuracy is achieved in idealized cases. This work demonstrates that nonlinear high order time accuracy at a solid surface is possible and desirable, but it also shows that the current practice of only correcting the pressure is inadequate.

  9. Antimatter Production at a Potential Boundary

    NASA Technical Reports Server (NTRS)

    LaPointe, Michael R.; Reddy, Dhanireddy (Technical Monitor)

    2001-01-01

    Current antiproton production techniques rely on high-energy collisions between beam particles and target nuclei to produce particle and antiparticle pairs, but inherently low production and capture efficiencies render these techniques impractical for the cost-effective production of antimatter for space propulsion and other commercial applications. Based on Dirac's theory of the vacuum field, a new antimatter production concept is proposed in which particle-antiparticle pairs are created at the boundary of a steep potential step formed by the suppression of the local vacuum fields. Current antimatter production techniques are reviewed, followed by a description of Dirac's relativistic quantum theory of the vacuum state and corresponding solutions for particle tunneling and reflection from a potential barrier. The use of the Casimir effect to suppress local vacuum fields is presented as a possible technique for generating the sharp potential gradients required for particle-antiparticle pair creation.

  10. 78 FR 48884 - Final Flood Hazard Determinations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-12

    ...Flood hazard determinations, which may include additions or modifications of Base Flood Elevations (BFEs), base flood depths, Special Flood Hazard Area (SFHA) boundaries or zone designations, or regulatory floodways on the Flood Insurance Rate Maps (FIRMs) and where applicable, in the supporting Flood Insurance Study (FIS) reports have been made final for the communities listed in the table......

  11. Boundary Layer Transition Flight Experiment Overview

    NASA Technical Reports Server (NTRS)

    Berger, Karen T.; Anderson, Brian P.; Campbell, Charles H.; Garske, Michael T.; Saucedo, Luis A.; Kinder, Gerald R.; Micklos, Ann M.

    2011-01-01

    In support of the Boundary Layer Transition Flight Experiment (BLT FE) Project, a manufactured protuberance tile was installed on the port wing of Space Shuttle Orbiter Discovery for STS-119, STS-128, STS-131 and STS-133 as well as Space Shuttle Endeavour for STS-134. Additional instrumentation was installed in order to obtain more spatially resolved measurements downstream of the protuberance. This paper provides an overview of the BLT FE Project with emphasis on the STS-131 and STS-133 results. A high-level overview of the in-situ flight data is presented, along with a summary of the comparisons between pre- and post-flight analysis predictions and flight data. Comparisons show that empirically correlated predictions for boundary layer transition onset time closely match the flight data, while predicted surface temperatures were significantly higher than observed flight temperatures. A thermocouple anomaly observed on a number of the missions is discussed as are a number of the mitigation actions that will be taken on the final flight, STS-134, including potential alterations of the flight trajectory and changes to the flight instrumentation.

  12. Boundary-integral simulations of containerless solidification

    NASA Astrophysics Data System (ADS)

    Ajaev, Vladimir S.; Davis, Stephen H.

    2003-05-01

    We carry out boundary-integral simulations of a two-dimensional liquid droplet surrounded by air and solidified from a cool point on the boundary. There are three interfaces in the problem: solid-liquid, air-liquid, and air-solid. All three evolve in time in such a way that certain tri-junction conditions must be satisfied. Our numerical method describes the quasi-steady evolution of the interfaces in the limit of zero surface energy on the solidification front. A new iterative technique is developed to describe the interface evolution when mass and total energy are conserved and the local tri-junction conditions are satisfied at every instant in time. A method is also developed for efficient numerical integration over the interfaces by taking advantage of analytical formulas for Green's functions. We start the simulations by studying the case of equal densities of the solid and liquid. This allows us to verify the numerical method and obtain some estimates of the speed of the solidification front. Solid-liquid interface flattening is observed at the intermediate stages of solidification. When the densities of the two phases are different, elongated solidified particles are observed when the solid density is smaller than the liquid density. At the final stages of solidification, a corner is formed in agreement with observations in related experiments.

  13. Sound Radiation from a Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Laufer, J.

    1961-01-01

    If the restriction of incompressibility in the turbulence problem is relaxed, the phenomenon of energy radiation in the form of sound from the turbulent zone arises. In order to calculate this radiated energy, it is shown that new statistical quantities, such as time-space correlation tensors, have to be known within the turbulent zone in addition to the conventional quantities. For the particular case of the turbulent boundary layer, indications are that the intensity of radiation becomes significant only in supersonic flows. Under these conditions, the recent work of Phillips is examined together with some experimental findings of the author. It is shown that the qualitative features of the radiation field (intensity, directionality) as predicted by the theory are consistent with the measurements; however, even for the highest Mach number flow, some of the assumptions of the asymptotic theory are not yet satisfied in the experiments. Finally, the question of turbulence damping due to radiation is discussed, with the result that in the Mach number range covered by the experiments, the energy lost from the boundary layer due to radiation is a small percentage of the work done by the wall shearing stresses.

  14. Thermal Boundary Conductance: A Materials Science Perspective

    NASA Astrophysics Data System (ADS)

    Monachon, Christian; Weber, Ludger; Dames, Chris

    2016-07-01

    The thermal boundary conductance (TBC) of materials pairs in atomically intimate contact is reviewed as a practical guide for materials scientists. First, analytical and computational models of TBC are reviewed. Five measurement methods are then compared in terms of their sensitivity to TBC: the 3ω method, frequency- and time-domain thermoreflectance, the cut-bar method, and a composite effective thermal conductivity method. The heart of the review surveys 30 years of TBC measurements around room temperature, highlighting the materials science factors experimentally proven to influence TBC. These factors include the bulk dispersion relations, acoustic contrast, and interfacial chemistry and bonding. The measured TBCs are compared across a wide range of materials systems by using the maximum transmission limit, which with an attenuated transmission coefficient proves to be a good guideline for most clean, strongly bonded interfaces. Finally, opportunities for future research are discussed.

  15. The coordination of boundary tones and its interaction with prominence1

    PubMed Central

    Katsika, Argyro; Krivokapić, Jelena; Mooshammer, Christine; Tiede, Mark; Goldstein, Louis

    2014-01-01

    This study investigates the coordination of boundary tones as a function of stress and pitch accent. Boundary tone coordination has not been experimentally investigated previously, and the effect of prominence on this coordination, and whether it is lexical (stress-driven) or phrasal (pitch accent-driven) in nature is unclear. We assess these issues using a variety of syntactic constructions to elicit different boundary tones in an Electromagnetic Articulography (EMA) study of Greek. The results indicate that the onset of boundary tones co-occurs with the articulatory target of the final vowel. This timing is further modified by stress, but not by pitch accent: boundary tones are initiated earlier in words with non-final stress than in words with final stress regardless of accentual status. Visual data inspection reveals that phrase-final words are followed by acoustic pauses during which specific articulatory postures occur. Additional analyses show that these postures reach their achievement point at a stable temporal distance from boundary tone onsets regardless of stress position. Based on these results and parallel findings on boundary lengthening reported elsewhere, a novel approach to prosody is proposed within the context of Articulatory Phonology: rather than seeing prosodic (lexical and phrasal) events as independent entities, a set of coordination relations between them is suggested. The implications of this account for prosodic architecture are discussed. PMID:25300341

  16. Effective surface and boundary conditions for heterogeneous surfaces with mixed boundary conditions

    NASA Astrophysics Data System (ADS)

    Guo, Jianwei; Veran-Tissoires, Stéphanie; Quintard, Michel

    2016-01-01

    To deal with multi-scale problems involving transport from a heterogeneous and rough surface characterized by a mixed boundary condition, an effective surface theory is developed, which replaces the original surface by a homogeneous and smooth surface with specific boundary conditions. A typical example corresponds to a laminar flow over a soluble salt medium which contains insoluble material. To develop the concept of effective surface, a multi-domain decomposition approach is applied. In this framework, velocity and concentration at micro-scale are estimated with an asymptotic expansion of deviation terms with respect to macro-scale velocity and concentration fields. Closure problems for the deviations are obtained and used to define the effective surface position and the related boundary conditions. The evolution of some effective properties and the impact of surface geometry, Péclet, Schmidt and Damköhler numbers are investigated. Finally, comparisons are made between the numerical results obtained with the effective models and those from direct numerical simulations with the original rough surface, for two kinds of configurations.

  17. Undulatory microswimming near solid boundaries

    NASA Astrophysics Data System (ADS)

    Schulman, R. D.; Backholm, M.; Ryu, W. S.; Dalnoki-Veress, K.

    2014-10-01

    The hydrodynamic forces involved in the undulatory microswimming of the model organism C. elegans are studied in proximity to solid boundaries. Using a micropipette deflection technique, we attain direct and time-resolved force measurements of the viscous forces acting on the worm near a single planar boundary as well as confined between two planar boundaries. We observe a monotonic increase in the lateral and propulsive forces with increasing proximity to the solid interface. We determine normal and tangential drag coefficients for the worm, and find these to increase with confinement. The measured drag coefficients are compared to existing theoretical models. The ratio of normal to tangential drag coefficients is found to assume a constant value of 1.5 ± 0.1(5) at all distances from a single boundary, but increases significantly as the worm is confined between two boundaries. In response to the increased drag due to confinement, we observe a gait modulation of the nematode, which is primarily characterized by a decrease in the swimming amplitude.

  18. Detecting dynamical boundaries from kinematic data in biomechanics

    PubMed Central

    Ross, Shane D.; Tanaka, Martin L.; Senatore, Carmine

    2010-01-01

    Ridges in the state space distribution of finite-time Lyapunov exponents can be used to locate dynamical boundaries. We describe a method for obtaining dynamical boundaries using only trajectories reconstructed from time series, expanding on the current approach which requires a vector field in the phase space. We analyze problems in musculoskeletal biomechanics, considered as exemplars of a class of experimental systems that contain separatrix features. Particular focus is given to postural control and balance, considering both models and experimental data. Our success in determining the boundary between recovery and failure in human balance activities suggests this approach will provide new robust stability measures, as well as measures of fall risk, that currently are not available and may have benefits for the analysis and prevention of low back pain and falls leading to injury, both of which affect a significant portion of the population. PMID:20370297

  19. Detecting dynamical boundaries from kinematic data in biomechanics

    NASA Astrophysics Data System (ADS)

    Ross, Shane D.; Tanaka, Martin L.; Senatore, Carmine

    2010-03-01

    Ridges in the state space distribution of finite-time Lyapunov exponents can be used to locate dynamical boundaries. We describe a method for obtaining dynamical boundaries using only trajectories reconstructed from time series, expanding on the current approach which requires a vector field in the phase space. We analyze problems in musculoskeletal biomechanics, considered as exemplars of a class of experimental systems that contain separatrix features. Particular focus is given to postural control and balance, considering both models and experimental data. Our success in determining the boundary between recovery and failure in human balance activities suggests this approach will provide new robust stability measures, as well as measures of fall risk, that currently are not available and may have benefits for the analysis and prevention of low back pain and falls leading to injury, both of which affect a significant portion of the population.

  20. A poroelastic immersed boundary method with applications to cell biology

    NASA Astrophysics Data System (ADS)

    Strychalski, Wanda; Copos, Calina A.; Lewis, Owen L.; Guy, Robert D.

    2015-02-01

    The immersed boundary method is a widely used mixed Eulerian/Lagrangian framework for simulating the motion of elastic structures immersed in viscous fluids. In the traditional immersed boundary method, the fluid and structure move with the same velocity field. In this work, a model based on the immersed boundary method is presented for simulating poroelastic media in which the fluid permeates a porous, elastic structure of small volume fraction that moves with its own velocity field. Two distinct methods for calculating elastic stresses are presented and compared. The methods are validated on a radially symmetric test problem by comparing with a finite difference solution of the classical equations of poroelasticity. Finally, two applications of the modeling framework to cell biology are provided: cellular blebbing and cell crawling. It is shown that in both examples, poroelastic effects are necessary to explain the relevant mechanics.