A thickness-weighted average perspective of force balance in an idealized circumpolar current

DOE PAGES

Ringler, Todd Darwin; Saenz, Juan Antonio; Wolfram, Jr., Phillip Justin; ...

2016-11-22

The exact, three-dimensional thickness-weighted averaged (TWA) Boussinesq equations are used to diagnose eddy-mean flow interaction in an idealized circumpolar current (ICC). The force exerted by mesoscale eddies on the TWA velocity is expressed as the divergence of the Eliassen-Palm flux tensor. Consistent with previous findings, the analysis indicates that the dynamically relevant definition of the ocean surface layer is comprised of the set of buoyancy coordinates that ever reside at the ocean surface at a given horizontal position. The surface layer is found to be a physically distinct object with a diabatic- and force-balance that is largely isolated from themore » underlying adiabatic region in the interior. Within the ICC surface layer, the TWA meridional velocity is southward/northward in the top/bottom half, and has a value near zero at the bottom. In the top half of the surface layer, the zonal forces due to wind stress and meridional advection of potential vorticity act to accelerate the TWA zonal velocity; equilibrium is obtained by eddies decelerating the zonal flow via a downward flux of eastward momentum that increases with depth. In the bottom half of the surface layer, the accelerating force of the wind stress is balanced by the eddy force and meridional advection of potential vorticity. The bottom of the surface layer coincides with the location where the zonal eddy force, meridional advection of potential vorticity and zonal wind stress force are all zero. The net meridional transport, S f, within the surface layer is a small residual of its southward and northward TWA meridional flows. Furthermore, the mean meridional gradient of surface-layer buoyancy is advected by S f to balance the surface buoyancy fluxs.« less

Geoid Anomalies and Dynamic Topography from Time Dependent, Spherical Axisymmetric Mantle Convection

NASA Technical Reports Server (NTRS)

Kiefer, Walter S.; Kellogg, Louise H.

1998-01-01

Geoid anomalies and dynamic topography are two important diagnostics of mantle convection. We present geoid and topography results for several time-dependent convection models in spherical axisymmetric geometry for Rayleigh numbers between 10(exp 6) and 10(exp 7) with depth-dependent viscosity and mixtures of bottom and internal heating. The models are strongly chaotic, with boundary layer instabilities erupting out of both thermal boundary layers. In some instances, instabilities from one boundary layer influence the development of instabilities in the other boundary layer. Such coupling between events at the top and bottom of the mantle has been suggested to play a role in a mid-Cretaceous episode of enhanced volcanism in the Pacific. These boundary layer instabilities produce large temporal variations in the geoid anomalies and dynamic nd to the topography associated with the convection. The amplitudes of these fluctuations depend on the detailed model parameter,.% it of this but fluctuations of 30-50% relative to the time-averaged geoid and topography are common. The convective planform is strongly sensitive to the specific initial conditions. Convection cells with larger aspect ratio tend to have larger fractional fluctuations in their geoid and topography amplitudes, because boundary layer instabilities have more time to develop in long cells. In some instances, we observe low-amplitude topographic highs adjacent to the topographic lows produced by cold downwellings. We discuss applications of these results to several situations, including the temporal variability of m basis. hotspots such as Hawaii, the topography of subduction zone outer rises, and the topography of coronae on Venus.

The dynamics of femtosecond pulsed laser removal of 20 nm Ni films from an interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schrider, Keegan J.; Yalisove, Steven M.; Torralva, Ben

2015-09-21

The dynamics of femtosecond laser removal of 20 nm Ni films on glass substrates was studied using time-resolved pump-probe microscopy. 20 nm thin films exhibit removal at two distinct threshold fluences, removal of the top 7 nm of Ni above 0.14 J/cm{sup 2}, and removal of the entire 20 nm film above 0.36 J/cm{sup 2}. Previous work shows the top 7 nm is removed through liquid spallation, after irradiation the Ni melts and rapidly expands leading to tensile stress and cavitation within the Ni film. This work shows that above 0.36 J/cm{sup 2} the 20 nm film is removed in two distinct layers, 7 nm and 13 nm thick. The topmore » 7 nm layer reaches a speed 500% faster than the bottom 13 nm layer at the same absorbed fluence, 500–2000 m/s and 300–700 m/s in the fluence ranges studied. Significantly different velocities for the top 7 nm layer and bottom 13 nm layer indicate removal from an interface occurs by a different physical mechanism. The method of measuring film displacement from the development of Newton's rings was refined so it could be shown that the 13 nm layer separates from the substrate within 70 ps and accelerates to its final velocity within several hundred picoseconds. We propose that removal of the bottom 13 nm is consistent with heterogeneous nucleation and growth of vapor at the Ni-glass interface, but that the rapid separation and acceleration of the 13 nm layer from the Ni-glass interface requires consideration of exotic phases of Ni after excitation.« less

Piezoelectric Resonator with Two Layers

NASA Technical Reports Server (NTRS)

Stephanou, Philip J. (Inventor); Black, Justin P. (Inventor)

2013-01-01

A piezoelectric resonator device includes: a top electrode layer with a patterned structure, a top piezoelectric layer adjacent to the top layer, a middle metal layer adjacent to the top piezoelectric layer opposite the top layer, a bottom piezoelectric layer adjacent to the middle layer opposite the top piezoelectric layer, and a bottom electrode layer with a patterned structure and adjacent to the bottom piezoelectric layer opposite the middle layer. The top layer includes a first plurality of electrodes inter-digitated with a second plurality of electrodes. A first one of the electrodes in the top layer and a first one of the electrodes in the bottom layer are coupled to a first contact, and a second one of the electrodes in the top layer and a second one of the electrodes in the bottom layer are coupled to a second contact.

Distribution and transport of suspended particulate matter in Monterey Canyon, California

USGS Publications Warehouse

Xu, J. P.; Noble, M.; Eittreim, S.L.; Rosenfeld, L.K.; Schwing, F.B.; Pilskaln, C.H.

2002-01-01

From August 1993 to August 1994, six moorings that measure current, temperature, salinity, and water clarity were deployed along the axis of Monterey Canyon to study the circulation and transport of water and suspended particulate matter through the canyon system. The moorings occupied three sites that are morphologically different: a narrow transverse section (axis width 900 m) at 1450 m water depth, a wide transverse section at 2837 m, and a third site in the fan valley axis farther offshore at 3223 m that recorded for 3 yr. In addition, CTD/transmissometer casts were conducted within and near the Monterey Canyon during four cruises. Our data show a mainly biogenic, surface turbid layer, a limited intermediate nepheloid layer, and a bottom nepheloid layer. There is a consistent presence of a turbid layer within the canyon at a water depth of about 1500 m. Tidal flow dominates at all sites, but currents above the canyon rim and within the canyon appear to belong to two distinct dynamic systems. Bottom intensification of currents plays an important role in raising the near-bottom shear stress high enough that bottom sediments are often, if not always, resuspended. Mean flow pattern suggests a convergence zone between the narrow and wide site: the near-bed (100 m above bottom where the lowest current meter was located) mean transport is down-canyon at the 1450-m site, while the near-bottom transport at the 2837-m site is up-canyon, at a smaller magnitude. Transport at the 3223-m site is dominantly NNW, cross-canyon, with periods of up-canyon flow over 3 yr. A very high-turbidity event was recorded 100 m above the canyon bottom at the narrow site. The event started very abruptly and lasted more than a week. This event was not detected at either of the deeper sites. A canyon head flushing event is likely the cause. ?? 2002 Elsevier Science B.V. All rights reserved.

Effect of Mass Proportion of Municipal Solid Waste Incinerator Bottom Ash Layer to Municipal Solid Waste Layer on the Cu and Zn Discharge from Landfill.

PubMed

Kong, Qingna; Yao, Jun; Qiu, Zhanhong; Shen, Dongsheng

2016-01-01

Municipal solid waste incinerator (MSWI) bottom ash is often used as the protection layer for the geomembrane and intermediate layer in the landfill. In this study, three sets of simulated landfills with different mass proportion of MSWI bottom ash layer to municipal solid waste (MSW) layer were operated. Cu and Zn concentrations in the leachates and MSW were monitored to investigate the effect of MSWI bottom ash layer on the Cu and Zn discharge from the landfill. The results showed that the Zn discharge was dependent on the mass proportion of MSWI bottom ash layer. The pH of landfill was not notably increased when the mass proportion of MSWI bottom ash layer to MSW layer was 1 : 9, resulting in the enhancement of the Zn discharge. However, Zn discharge was mitigated when the mass proportion was 2 : 8, as the pH of landfill was notably promoted. The discharge of Cu was not dependent on the mass proportion, due to the great affinity of Cu to organic matter. Moreover, Cu and Zn contents of the sub-MSW layer increased due to the MSWI bottom ash layer. Therefore, the MSWI bottom ash layer can increase the potential environmental threat of the landfill.

Current structure of strongly nonlinear interfacial solitary waves

NASA Astrophysics Data System (ADS)

Semin, Sergey; Kurkina, Oxana; Kurkin, Andrey; Talipova, Tatiana; Pelinovsky, Efim; Churaev, Egor

2015-04-01

The characteristics of highly nonlinear solitary internal waves (solitons) in two-layer flow are computed within the fully nonlinear Navier-Stokes equations with use of numerical model of the Massachusetts Institute of Technology (MITgcm). The verification and adaptation of the model is based on the data from laboratory experiments [Carr & Davies, 2006]. The present paper also compares the results of our calculations with the computations performed in the framework of the fully nonlinear Bergen Ocean Model [Thiem et al, 2011]. The comparison of the computed soliton parameters with the predictions of the weakly nonlinear theory based on the Gardner equation is given. The occurrence of reverse flow in the bottom layer directly behind the soliton is confirmed in numerical simulations. The trajectories of Lagrangian particles in the internal soliton on the surface, on the interface and near the bottom are computed. The results demonstrated completely different trajectories at different depths of the model area. Thus, in the surface layer is observed the largest displacement of Lagrangian particles, which can be more than two and a half times larger than the characteristic width of the soliton. Located at the initial moment along the middle pycnocline fluid particles move along the elongated vertical loop at a distance of not more than one third of the width of the solitary wave. In the bottom layer of the fluid moves in the opposite direction of propagation of the internal wave, but under the influence of the reverse flow, when the bulk of the velocity field of the soliton ceases to influence the trajectory, it moves in the opposite direction. The magnitude of displacement of fluid particles in the bottom layer is not more than the half-width of the solitary wave. 1. Carr, M., and Davies, P.A. The motion of an internal solitary wave of depression over a fixed bottom boundary in a shallow, two-layer fluid. Phys. Fluids, 2006, vol. 18, No. 1, 1 - 10. 2. Thiem, O., Carr, M., Berntsen, J., and Davies, P.A. Numerical simulation of internal solitary wave-induced reverse flow and associated vortices in a shallow, two-layer fluid benthic boundary layer. Ocean Dynamics, 2011, vol. 61, No. 6, 857 - 872.

Effect of Mass Proportion of Municipal Solid Waste Incinerator Bottom Ash Layer to Municipal Solid Waste Layer on the Cu and Zn Discharge from Landfill

PubMed Central

Kong, Qingna; Qiu, Zhanhong; Shen, Dongsheng

2016-01-01

Municipal solid waste incinerator (MSWI) bottom ash is often used as the protection layer for the geomembrane and intermediate layer in the landfill. In this study, three sets of simulated landfills with different mass proportion of MSWI bottom ash layer to municipal solid waste (MSW) layer were operated. Cu and Zn concentrations in the leachates and MSW were monitored to investigate the effect of MSWI bottom ash layer on the Cu and Zn discharge from the landfill. The results showed that the Zn discharge was dependent on the mass proportion of MSWI bottom ash layer. The pH of landfill was not notably increased when the mass proportion of MSWI bottom ash layer to MSW layer was 1 : 9, resulting in the enhancement of the Zn discharge. However, Zn discharge was mitigated when the mass proportion was 2 : 8, as the pH of landfill was notably promoted. The discharge of Cu was not dependent on the mass proportion, due to the great affinity of Cu to organic matter. Moreover, Cu and Zn contents of the sub-MSW layer increased due to the MSWI bottom ash layer. Therefore, the MSWI bottom ash layer can increase the potential environmental threat of the landfill. PMID:28044139

Sediment dynamics in the Adriatic Sea investigated with coupled models

USGS Publications Warehouse

Sherwood, Christopher R.; Book, Jeffrey W.; Carniel, Sandro; Cavaleri, Luigi; Chiggiato, Jacopo; Das, Himangshu; Doyle, James D.; Harris, Courtney K.; Niedoroda, Alan W.; Perkins, Henry; Poulain, Pierre-Marie; Pullen, Julie; Reed, Christopher W.; Russo, Aniello; Sclavo, Mauro; Signell, Richard P.; Traykovski, Peter A.; Warner, John C.

2004-01-01

Several large research programs focused on the Adriatic Sea in winter 2002-2003, making it an exciting place for sediment dynamics modelers (Figure 1). Investigations of atmospheric forcing and oceanic response (including wave generation and propagation, water-mass formation, stratification, and circulation), suspended material, bottom boundary layer dynamics, bottom sediment, and small-scale stratigraphy were performed by European and North American researchers participating in several projects. The goal of EuroSTRATAFORM researchers is to improve our ability to understand and simulate the physical processes that deliver sediment to the marine environment and generate stratigraphic signatures. Scientists involved in the Po and Apennine Sediment Transport and Accumulation (PASTA) experiment benefited from other major research programs including ACE (Adriatic Circulation Experiment), DOLCE VITA (Dynamics of Localized Currents and Eddy Variability in the Adriatic), EACE (the Croatian East Adriatic Circulation Experiment project), WISE (West Istria Experiment), and ADRICOSM (Italian nowcasting and forecasting) studies.

Passive scalars chaotic dynamics induced by two vortices in a two-layer geophysical flow with shear and rotation

NASA Astrophysics Data System (ADS)

Ryzhov, Eugene

2015-11-01

Vortex motion in shear flows is of great interest from the point of view of nonlinear science, and also as an applied problem to predict the evolution of vortices in nature. Considering applications to the ocean and atmosphere, it is well-known that these media are significantly stratified. The simplest way to take stratification into account is to deal with a two-layer flow. In this case, vortices perturb the interface, and consequently, the perturbed interface transits the vortex influences from one layer to another. Our aim is to investigate the dynamics of two point vortices in an unbounded domain where a shear and rotation are imposed as the leading order influence from some generalized perturbation. The two vortices are arranged within the bottom layer, but an emphasis is on the upper-layer fluid particle motion. Point vortices induce singular velocity fields in the layer they belong to, however, in the other layers of a multi-layer flow, they induce regular velocity fields. The main feature is that singular velocity fields prohibit irregular dynamics in the vicinity of the singular points, but regular velocity fields, provided optimal conditions, permit irregular dynamics to extend almost in every point of the corresponding phase space.

Comparison of the key mechanisms leading to rollovers in Liquefied Natural Gas using Computational Fluid Dynamics

NASA Astrophysics Data System (ADS)

Hubert, Antoine; Dadonau, Maksim; Dembele, Siaka; Denissenko, Petr; Wen, Jennifer

2017-11-01

Growing demand for the LNG fosters growth of the number of production sites with varying composition and density. Combining different sources of LNG may result in a stably stratified system, in which heat and mass transfer between the layers is limited. Heating of the LNG due to wall thermal conductivity leads to formation of convection cells confined within the layers. While the upper layer can release the extra energy via preferential methane boil-off, the bottom layer cannot and hence becomes superheated. Gradual density equilibration reduces stratification and may eventually lead to a sudden mixing event called ``rollover'', accompanied by violent evaporation of the superheated LNG. Three phenomena are potentially responsible for density equilibration. The first is the growing difference in thermal expansion of the layers due to the reduced ability of the bottom layer to reject heat. The second is the penetration of the heated near-wall boundary layer into the upper layer. The third is the ``entrainment mixing'' occurring at the contact surface between the two layers. The present study uses CFD to compare these mechanisms. Boussinesq approximation and an extended version of the k- ɛ model is used. The code is validated by comparison with a large-scale LNG rollover experiment.

Microphytobenthos production potential and contribution to bottom layer oxygen dynamics on the inner Louisiana continental shelf

EPA Science Inventory

To investigate the relative importance of microphytobenthos (MPB) oxygen (O2) production on a river-dominated shelf, we made sediment core incubation measurements of MPB O2 production and sediment O2 consumption, and compared these to water-column measures of primary production ...

Weak wind-wave/tide interaction over fixed and moveable bottoms: a formulation and some preliminary results

NASA Astrophysics Data System (ADS)

Kagan, B. A.; Alvarez, O.; Izquierdo, A.

2005-05-01

The formulation of weak wind-wave/low-frequency current interaction is discussed comprehensively as applied to fixed- and moveable-bottom cases. It involves (1) a dependence of the drag coefficient on the ratio between wave and current bottom friction velocity amplitudes, (2) the resistance law for the oscillatory, rough, turbulent bottom boundary layer (BBL) which accounts for the usually neglected effects of rotation and the phase difference between the bottom stress and the friction-free current velocity, (3) the expression for the BBL depth in terms of the bottom Rossby number and (4) the bottom roughness predictor of Grant and Madsen (J. Geophys. Res., 87 (1982) 469) in the version of Tolman (J. Phys. Oceanogr., 24 (1994) 994). The formulation is implemented in the UCA (University of Cadiz) 2D nonlinear, high-resolution, hydrodynamic model and used to study the influence of wind-wave/tide interaction, bottom mobility and the improved flow-resistance description on the M 2 tidal dynamics of Cadiz Bay. The inclusion of either of the first two factors can cause the drag coefficient to increase significantly over its reference value. If the third factor is included, changes in the drag coefficient are quite moderate. This is because the effect of rotation is opposite in sign to the effect of phase difference, so that these effects taken together very nearly balance. The reason why bottom mobility has such an important influence on shallow-water tidal dynamics as wind-wave/tide interaction has, is the occurrence of the large irregular variations in the drag coefficient that accompany sediment motion.

Interplay between dewetting and layer inversion in poly(4-vinylpyridine)/polystyrene bilayers.

PubMed

Thickett, Stuart C; Harris, Andrew; Neto, Chiara

2010-10-19

We investigated the morphology and dynamics of the dewetting of metastable poly(4-vinylpyridine) (P4VP) thin films situated on top of polystyrene (PS) thin films as a function of the molecular weight and thickness of both films. We focused on the competition between the dewetting process, occurring as a result of unfavorable intermolecular interactions at the P4VP/PS interface, and layer inversion due to the lower surface energy of PS. By means of optical and atomic force microscopy (AFM), we observed how both the dynamics of the instability and the morphology of the emerging patterns depend on the ratio of the molecular weights of the polymer films. When the bottom PS layer was less viscous than the top P4VP layer (liquid-liquid dewetting), nucleated holes in the P4VP film typically stopped growing at long annealing times because of a combination of viscous dissipation in the bottom layer and partial layer inversion. Full layer inversion was achieved when the viscosity of the top P4VP layer was significantly greater (>10⁴) than the viscosity of the PS layer underneath, which is attributed to strongly different mobilities of the two layers. The density of holes produced by nucleation dewetting was observed for the first time to depend on the thickness of the top film as well as the polymer molecular weight. The final (completely dewetted) morphology of isolated droplets could be achieved only if the time frame of layer inversion was significantly slower than that of dewetting, which was characteristic of high-viscosity PS underlayers that allowed dewetting to fall into a liquid-solid regime. Assuming a simple reptation model for layer inversion occurring at the dewetting front, the observed surface morphologies could be predicted on the basis of the relative rates of dewetting and layer inversion.

Surface dynamics of micellar diblock copolymer films

NASA Astrophysics Data System (ADS)

Song, Sanghoon; Cha, Wonsuk; Kim, Hyunjung; Jiang, Zhang; Narayanan, Suresh

2011-03-01

We studied the structure and surface dynamics of poly(styrene)-b-poly(dimethylsiloxane) (PS-b-PDMS) diblock copolymer films with micellar PDMS surrounded by PS shells. By `in-situ' high resolution synchrotron x-ray reflectivity and diffuse scattering, we obtained exact thickness, electron density and surface tension. A segregation layer near the top surface was appeared with increasing temperature Surface dynamics were measured as a function of film thickness and temperature by x-ray photon correlation spectroscopy. The best fit to relaxation time constants as a function of in-plane wavevectors were analyzed with a theory based on capillary waves with hydrodynamics with bilayer model Finally the viscosities for the top segregated layer as well as for the bottom layer are obtained at given temperatures This work was supported by National Research Foundation of Korea (R15-2008-006-01001-0), Seoul Research and Business Development Program (10816), and Sogang University Research Grant (2010).

A nonlinear steady model for moist hydrostatic mountain waves

NASA Technical Reports Server (NTRS)

Barcilon, A.; Fitzjarrald, D.

1985-01-01

The dynamics of hydrostatic gravity waves generated by the passage of a steady, stably stratified, moist flow over a two-dimensional topography is considered. Coriolis effects are neglected. The cloud region is determined by the dynamics, and within that region the Brunt-Vaisala frequency takes on a value smaller than the outside value. In both the dry and cloudy regions the Brunt-Vaisala frequency is constant with height. The moist layer is considered to be either next to the mountain or at midlevels and to be deep enough so that an entire cloud forms in that layer. The nonlinearity in the flow and lower boundary affects the dynamics of these waves and wave drag. The latter is found to depend upon: (1) the location of the moist layer with respect to the ground, (2) the amount of moisture, (3) the degree of nonlinearity and (4) the departure from symmetry in the bottom topography.

Dynamic topography and gravity anomalies for fluid layers whose viscosity varies exponentially with depth

NASA Technical Reports Server (NTRS)

Revenaugh, Justin; Parsons, Barry

1987-01-01

Adopting the formalism of Parsons and Daly (1983), analytical integral equations (Green's function integrals) are derived which relate gravity anomalies and dynamic boundary topography with temperature as a function of wavenumber for a fluid layer whose viscosity varies exponentially with depth. In the earth, such a viscosity profile may be found in the asthenosphere, where the large thermal gradient leads to exponential decrease of viscosity with depth, the effects of a pressure increase being small in comparison. It is shown that, when viscosity varies rapidly, topography kernels for both the surface and bottom boundaries (and hence the gravity kernel) are strongly affected at all wavelengths.

Depinning and heterogeneous dynamics of colloidal crystal layers under shear flow

NASA Astrophysics Data System (ADS)

Gerloff, Sascha; Klapp, Sabine H. L.

2016-12-01

Using Brownian dynamics (BD) simulations and an analytical approach we investigate the shear-induced, nonequilibrium dynamics of dense colloidal suspensions confined to a narrow slit-pore. Focusing on situations where the colloids arrange in well-defined layers with solidlike in-plane structure, the confined films display complex, nonlinear behavior such as collective depinning and local transport via density excitations. These phenomena are reminiscent of colloidal monolayers driven over a periodic substrate potential. In order to deepen this connection, we present an effective model that maps the dynamics of the shear-driven colloidal layers to the motion of a single particle driven over an effective substrate potential. This model allows us to estimate the critical shear rate of the depinning transition based on the equilibrium configuration, revealing the impact of important parameters, such as the slit-pore width and the interaction strength. We then turn to heterogeneous systems where a layer of small colloids is sheared with respect to bottom layers of large particles. For these incommensurate systems we find that the particle transport is dominated by density excitations resembling the so-called "kink" solutions of the Frenkel-Kontorova (FK) model. In contrast to the FK model, however, the corresponding "antikinks" do not move.

Tunnel barrier schottky

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, Rongming; Cao, Yu; Li, Zijian

2018-02-20

A diode includes: a semiconductor substrate; a cathode metal layer contacting a bottom of the substrate; a semiconductor drift layer on the substrate; a graded aluminum gallium nitride (AlGaN) semiconductor barrier layer on the drift layer and having a larger bandgap than the drift layer, the barrier layer having a top surface and a bottom surface between the drift layer and the top surface, the barrier layer having an increasing aluminum composition from the bottom surface to the top surface; and an anode metal layer directly contacting the top surface of the barrier layer.

Migration of nitrate, nitrite, and ammonia through the municipal solid waste incinerator bottom ash layer in the simulated landfill.

PubMed

Yao, Jun; Chen, Luxi; Zhu, Huayue; Shen, Dongsheng; Qiu, Zhanhong

2017-04-01

Simulated landfill was operated for 508 days to investigate the effect of municipal solid waste incinerator (MSWI) bottom ash layer on the migration of nitrate, nitrite, and ammonia when it was used as the intermediate layer in the landfill. The result suggested that the MSWI bottom ash layer could capture the nitrate, nitrite, and ammonia from the leachate. The adsorption of the nitrate, nitrite, and ammonia on the MSWI bottom ash layer was saturated at the days 396, 34, and 97, respectively. Afterwards, the nitrogen species were desorbed from the MSWI bottom ash layer. Finally, the adsorption and desorption could reach the equilibrium. The amounts of adsorbed nitrate and nitrite on the MSWI bottom ash layer were 1685.09 and 7.48 mg, respectively, and the amount of the adsorbed and transformed ammonia was 13,773.19 mg, which was much higher than the desorbed. The water leaching test and synthetic precipitation leaching procedure (SPLP) results showed that the leachable nitrate, nitrite, and ammonia in the MSWI bottom ash were greatly increased after the landfill operation, suggesting that the adsorbed nitrogen could be finally leached out. Besides, the results also showed that MSWI bottom ash layer could affect the release of nitrate and ammonia at the initial stage of the landfill. However, it had little effect on the release of nitrite.

The Deep Meridional Overturning Circulation in the Indian Ocean Inferred from the GECCO Synthesis

NASA Astrophysics Data System (ADS)

Wang, W.; Koehl, A.; Stammer, D.

2012-04-01

The meridional overturning circulation in the Indian Ocean and its temporal variability in the GECCO ocean synthesis are being investigated. An analysis of the integrated circulation in different layers suggests that, on time average, 2.1 Sv enter the Indian Ocean in the bottom layer (>3200m) from the south and that 12.3 Sv leave the Indian Ocean in the upper and intermediate layers (<1500m), composed of the up-welled bottom layer inflow water, augmented by 9.6 Sv Indonesian Throughflow (ITF) water. The GECCO time-mean results differ significantly from those obtained by box inverse models, which, being based on individual hydrographic sections, are susceptible to aliasing. The GECCO solution has a large seasonal variation in its meridional overturning caused by the seasonal reversal of monsoon-related wind stress forcing. Associated seasonal variations of the deep meridional overturning range from -7 Sv in boreal winter to 3 Sv in summer. In addition, the upper and bottom transports across 34°S section show pronounced interannual variability with roughly biennial variations superimposed by strong anomalies during each La Niña phase as well as the ITF, which mainly affect the upper layer transports. On decadal and longer timescale, the meridional overturning variability as well as long-term trends differ before and after 1980. Notably, our analysis shows a rather stable trend for the period 1960-1979 and significant changes in the upper and bottom layer for the period 1980-2001. By means of a multivariate EOF analysis, the importance of Ekman dynamics as driving forces of the deep meridional overturning of the Indian Ocean on the interannual timescale is highlighted. The leading modes of the zonal and meridional wind stress favour a basin-wide meridional overturning mode via Ekman upwelling or downwelling mostly in the central and eastern Indian Ocean. Moreover, tropical zonal wind stress along the equator and alongshore wind stress off the Sumatra-Java coast contributes to evolution of IOD events.

Interior Pathways to Dissipation of Mesoscale Energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nadiga, Balasubramanya T.

This talk at Goethe University asks What Powers Overturning Circulation? How does Ocean Circulation Equilibrate? There is a HUGE reservoir of energy sitting in the interior ocean. Can fluid dynamic instabilities contribute to the mixing required to drive global overturning circulation? Study designed to eliminate distinguished horizontal surfaces such as bottom BL and surface layer

Predicting U.S. food demand in the 20th century: a new look at system dynamics

NASA Astrophysics Data System (ADS)

Moorthy, Mukund; Cellier, Francois E.; LaFrance, Jeffrey T.

1998-08-01

The paper describes a new methodology for predicting the behavior of macroeconomic variables. The approach is based on System Dynamics and Fuzzy Inductive Reasoning. A four- layer pseudo-hierarchical model is proposed. The bottom layer makes predications about population dynamics, age distributions among the populace, as well as demographics. The second layer makes predications about the general state of the economy, including such variables as inflation and unemployment. The third layer makes predictions about the demand for certain goods or services, such as milk products, used cars, mobile telephones, or internet services. The fourth and top layer makes predictions about the supply of such goods and services, both in terms of their prices. Each layer can be influenced by control variables the values of which are only determined at higher levels. In this sense, the model is not strictly hierarchical. For example, the demand for goods at level three depends on the prices of these goods, which are only determined at level four. Yet, the prices are themselves influenced by the expected demand. The methodology is exemplified by means of a macroeconomic model that makes predictions about US food demand during the 20th century.

Doubled heterogeneous crystal nucleation in sediments of hard sphere binary-mass mixtures

NASA Astrophysics Data System (ADS)

Löwen, Hartmut; Allahyarov, Elshad

2011-10-01

Crystallization during the sedimentation process of a binary colloidal hard spheres mixture is explored by Brownian dynamics computer simulations. The two species are different in buoyant mass but have the same interaction diameter. Starting from a completely mixed system in a finite container, gravity is suddenly turned on, and the crystallization process in the sample is monitored. If the Peclet numbers of the two species are both not too large, crystalline layers are formed at the bottom of the cell. The composition of lighter particles in the sedimented crystal is non-monotonic in the altitude: it is first increasing, then decreasing, and then increasing again. If one Peclet number is large and the other is small, we observe the occurrence of a doubled heterogeneous crystal nucleation process. First, crystalline layers are formed at the bottom container wall which are separated from an amorphous sediment. At the amorphous-fluid interface, a secondary crystal nucleation of layers is identified. This doubled heterogeneous nucleation can be verified in real-space experiments on colloidal mixtures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stefek, T.; Daugherty, W.; Estochen, E.

Compaction of lower layers in the fiberboard assembly has been observed in 9975 packages that contain elevated moisture. Lab testing has resulted in a better understanding of the relationship between the fiberboard moisture level and compaction of the lower fiberboard assembly, and the behavior of the fiberboard during transport. In laboratory tests of cane fiberboard, higher moisture content has been shown to correspond to higher total compaction, greater rate of compaction, and continued compaction over a longer period of time. In addition, laboratory tests have shown that the application of a dynamic load results in higher fiberboard compaction compared tomore » a static load. The test conditions and sample geometric/loading configurations were chosen to simulate the regulatory requirements for 9975 package input dynamic loading. Dynamic testing was conducted to acquire immediate and cumulative changes in geometric data for various moisture levels. Two sample sets have undergone a complete dynamic test regimen, one set for 27 weeks, and the second set for 47 weeks. The dynamic input, data acquisition, test effects on sample dynamic parameters, and results from this test program are summarized and compared to regulatory specifications for dynamic loading. Compaction of the bottom fiberboard layers due to the accumulation of moisture is one possible cause of an increase in the axial gap at the top of the package. The net compaction of the bottom layers will directly add to the axial gap. The moisture which caused this compaction migrated from the middle region of the fiberboard assembly (which is typically the hottest). This will cause the middle region to shrink axially, which will also contribute directly to the axial gap. Measurement of the axial gap provides a screening tool for identifying significant change in the fiberboard condition. The data in this report provide a basis to evaluate the impact of moisture and fiberboard compaction on 9975 package performance during storage at the Savannah River Site (SRS).« less

Multicore runup simulation by under water avalanche using two-layer 1D shallow water equations

NASA Astrophysics Data System (ADS)

Bagustara, B. A. R. H.; Simanjuntak, C. A.; Gunawan, P. H.

2018-03-01

The increasing of layers in shallow water equations (SWE) produces more dynamic model than the one-layer SWE model. The two-layer 1D SWE model has different density for each layer. This model becomes more dynamic and natural, for instance in the ocean, the density of water will decreasing from the bottom to the surface. Here, the source-centered hydro-static reconstruction (SCHR) numerical scheme will be used to approximate the solution of two-layer 1D SWE model, since this scheme is proved to satisfy the mathematical properties for shallow water equation. Additionally in this paper, the algorithm of SCHR is adapted to the multicore architecture. The simulation of runup by under water avalanche is elaborated here. The results show that the runup is depend on the ratio of density of each layers. Moreover by using grid sizes Nx = 8000, the speedup and efficiency by 2 threads are obtained 1.74779 times and 87.3896 % respectively. Nevertheless, by 4 threads the speedup and efficiency are obtained 2.93132 times and 73.2830 % respectively by similar number of grid sizes Nx = 8000.

Dynamics of internal waves on the Southeast Florida shelf: Implications for cross-shelf exchange and turbulent mixing on a barrier reef system

NASA Astrophysics Data System (ADS)

Davis, Kristen Alexis

The dynamics of internal waves shoaling on the Southeast Florida shelf and the resulting stratified turbulence in the shelf bottom boundary layer are investigated using observational studies completed during the summers of 2003-2005. This work is driven by a desire to understand the effects of internal wave-driven flow and the shoreward transport of cool, nutrient-rich water masses on cross-shelf exchange, vertical mixing, and mass transfer to benthic reef organisms. Shelf sea internal wave fields are typically highly variable and dominated by wind and tidal forces. However, this is not necessarily true for outer shelf regions or very narrow shelves where remote physical processes originating over the slope or deep ocean may exert a strong influence on the internal wave climate. During the summers of 2003 and 2004 observational studies were conducted to examine the effects of a western boundary current (the Florida Current), tides, and wind on the mean currents and internal wave field on the outer Southeast Florida shelf. We present evidence that suggests that the Florida Current plays as large a role in the determination of the high frequency internal wave field as tidal forces. These observations and analyses show that it is necessary to include the forcing from the Florida Current meanders and instabilities in order to predict accurately the episodic nature of the internal wave field on the Southeast Florida shelf. Deep ocean and continental shelf processes intersect at the shelf edge and influence the exchange of water masses and their associated characteristics including heat, nutrients, sediment, and larvae across the shelf. Thus, the dynamics of cross-shelf circulation have important consequences for organisms living on the shelf. In the second phase of this work, we investigate physical mechanisms controlling the exchange of water masses during the summer season across the Southeast Florida shelf. A time series of cross-shelf transport from May to August 2003 suggests that, during the summer months, instabilities in the Florida Current and nonlinear internal waves are the primary mechanisms driving cross-shelf transport on the outer shelf Surface tide, wind, and wave-driven transport were found to be small in comparison. Additionally, this data set highlights the importance of baroclinic processes to cross-shelf transport in this region. In the last phase of my research, I sought to investigate how boundary layer dynamics over a rough coral bed were modified by shoaling internal waves and to understand the implications for mixing and mass transfer to the bed. Results are presented from an observational study of the turbulent bottom boundary layer on the outer Southeast Florida shelf in July and August 2005. Turbulence in the reef bottom boundary layer is highly variable in time and is modified by near bed flow, shear, and stratification driven by shoaling internal waves. We examined turbulence in the bottom boundary layer during a typical internal wave event and found that in addition to the episodic onshore transport of cool, subthermocline water masses, with elevated nutrient concentrations, bottom-intensified currents from shoaling internal waves can increase turbulent dissipation and mixing in the reef bottom boundary layer. Additionally, we show that estimates of flux Richardson number, calculated directly from measurements of dissipation and buoyancy flux, support the dependence of R f on turbulent intensity, epsilon/nuN 2, a relationship that has only been previously shown in laboratory and numerical work. While the importance of surface gravity waves in generating turbulent mixing and controlling mass transfer on coral reefs has been well documented in the literature, this work represents the first time the appropriate field data have been collected for a detailed dynamic analysis of the physical effects and biological implications of internal waves on reef ecosystems. Results from these studies suggest that for reef communities exposed to continental shelf and slope processes, internal waves may play an important role in cross-shelf transport and mass transfer to benthic organisms and may be essential to modeling key biological processes, the connectivity of coral populations, or designing and managing marine reserves and fisheries.

Diel Vertical Dynamics of Gelatinous Zooplankton (Cnidaria, Ctenophora and Thaliacea) in a Subtropical Stratified Ecosystem (South Brazilian Bight)

PubMed Central

Nogueira Júnior, Miodeli; Brandini, Frederico Pereira; Codina, Juan Carlos Ugaz

2015-01-01

The diel vertical dynamics of gelatinous zooplankton in physically stratified conditions over the 100-m isobath (~110 km offshore) in the South Brazilian Bight (26°45’S; 47°33’W) and the relationship to hydrography and food availability were analyzed by sampling every six hours over two consecutive days. Zooplankton samples were taken in three depth strata, following the vertical structure of the water column, with cold waters between 17 and 13.1°C, influenced by the South Atlantic Central Water (SACW) in the lower layer (>70 m); warm (>20°C) Tropical Water in the upper 40 m; and an intermediate thermocline with a deep chlorophyll-a maximum layer (0.3–0.6 mg m-3). Two distinct general patterns were observed, emphasizing the role of (i) physical and (ii) biological processes: (i) a strong influence of the vertical stratification, with most zooplankton absent or little abundant in the lower layer. The influence of the cold SACW on the bottom layer apparently restricted the vertical occupation of most species, which typically inhabit epipelagic warm waters. Even among migratory species, only a few (Aglaura hemistoma, Abylopsis tetragona eudoxids, Beroe sp., Thalia democratica, Salpa fusiformis) crossed the thermocline and reached the bottom layer. (ii) A general tendency of partial migrations, with variable intensity depending on the different species and developmental stages; populations tended to be more widely distributed through the water column during daylight, and to become more aggregated in the upper layer during the night, which can be explained based on the idea of the “hunger-satiation hypothesis”, maximizing feeding and minimizing the chances of being predated. PMID:26637179

Diel Vertical Dynamics of Gelatinous Zooplankton (Cnidaria, Ctenophora and Thaliacea) in a Subtropical Stratified Ecosystem (South Brazilian Bight).

PubMed

Nogueira Júnior, Miodeli; Brandini, Frederico Pereira; Codina, Juan Carlos Ugaz

2015-01-01

The diel vertical dynamics of gelatinous zooplankton in physically stratified conditions over the 100-m isobath (~110 km offshore) in the South Brazilian Bight (26°45'S; 47°33'W) and the relationship to hydrography and food availability were analyzed by sampling every six hours over two consecutive days. Zooplankton samples were taken in three depth strata, following the vertical structure of the water column, with cold waters between 17 and 13.1°C, influenced by the South Atlantic Central Water (SACW) in the lower layer (>70 m); warm (>20°C) Tropical Water in the upper 40 m; and an intermediate thermocline with a deep chlorophyll-a maximum layer (0.3-0.6 mg m-3). Two distinct general patterns were observed, emphasizing the role of (i) physical and (ii) biological processes: (i) a strong influence of the vertical stratification, with most zooplankton absent or little abundant in the lower layer. The influence of the cold SACW on the bottom layer apparently restricted the vertical occupation of most species, which typically inhabit epipelagic warm waters. Even among migratory species, only a few (Aglaura hemistoma, Abylopsis tetragona eudoxids, Beroe sp., Thalia democratica, Salpa fusiformis) crossed the thermocline and reached the bottom layer. (ii) A general tendency of partial migrations, with variable intensity depending on the different species and developmental stages; populations tended to be more widely distributed through the water column during daylight, and to become more aggregated in the upper layer during the night, which can be explained based on the idea of the "hunger-satiation hypothesis", maximizing feeding and minimizing the chances of being predated.

a Numerical Study of Basic Coastal Upwelling Processes.

NASA Astrophysics Data System (ADS)

Li, Zhihong

Available from UMI in association with The British Library. Two-dimensional (2-D) and three-dimensional (3 -D) numerical models with a second order turbulence closure are developed for the study of coastal upwelling processes. A logarithmic coordinate system is introduced to obtain increased resolution in the regions near the surface and bottom where high velocity shear occurs and in the upwelling zone where its width is confined to the coast. In the experiments performed in the 2-D model an ocean initially at rest is driven by a spatially uniform alongshore wind-stress. There is a development of an offshore flow in the surface layer and an onshore flow below the surface layer. In the wind-stress direction there is a development of a coastal surface jet. The neglect of the alongshore pressure gradient leads to the intensification of the jet, and the concentration of the onshore flow in an over-developed Ekman layer yielding an unrealistic deepening of a bottom mixed layer. When bathymetric variations are introduced, some modifications in the dynamics of upwelling are observed. On the shelf region there is another upwelling zone and isotherms are interested with the bottom topography. When an alongshore pressure gradient is added externally into the model, the strength of the coastal jet decreases and a coastal undercurrent exists at greater depth. In addition the return onshore flow is largely independent of depth and the deepening of the bottom mixed layer disappears. In the experiments performed in the 3-D model a wind-stress with limited domain is used. Coastally trapped waves are generated and propagate along the coastline leading to a development of an alongshore pressure gradient, which has a significant effect on upwelling. The evolution of the alongshore flow, vertical velocity and the temperature is determined by both remote and local wind due to the propagation of waves. As the integration proceeds, the flow pattern becomes remarkably 3-dimensional. Finally the influence of bathymetric variations on upwelling processes is examined.

Predictions and Experimental Microstructural Characterization of High Strain Rate Failure Modes in Layered Aluminum Composites

NASA Astrophysics Data System (ADS)

Khanikar, Prasenjit

Different aluminum alloys can be combined, as composites, for tailored dynamic applications. Most investigations pertaining to metallic alloy layered composites, however, have been based on quasi-static approaches. The dynamic failure of layered metallic composites, therefore, needs to be characterized in terms of strength, toughness, and fracture response. A dislocation-density based crystalline plasticity formulation, finite-element techniques, rational crystallographic orientation relations and a new fracture methodology were used to predict the failure modes associated with the high strain rate behavior of aluminum layered composites. Two alloy layers, a high strength alloy, aluminum 2195, and an aluminum alloy 2139, with high toughness, were modeled with representative microstructures that included precipitates, dispersed particles, and different grain boundary (GB) distributions. The new fracture methodology, based on an overlap method and phantom nodes, is used with a fracture criteria specialized for fracture on different cleavage planes. One of the objectives of this investigation, therefore, was to determine the optimal arrangements of the 2139 and 2195 aluminum alloys for a metallic layered composite that would combine strength, toughness and fracture resistance for high strain-rate applications. Different layer arrangements were investigated for high strain-rate applications, and the optimal arrangement was with the high toughness 2139 layer on the bottom, which provided extensive shear strain localization, and the high strength 2195 layer on the top for high strength resistance. The layer thickness of the bottom high toughness layer also affected the bending behavior of the roll-boned interface and the potential delamination of the layers. Shear strain localization, dynamic cracking and delamination were the mutually competing failure mechanisms for the layered metallic composite, and control of these failure modes can be optimized for high strain-rate applications. The second major objective of this investigation was the use of recently developed dynamic fracture formulations to model and analyze the crack nucleation and propagation of aluminum layered composites subjected to high strain rate loading conditions and how microstructural effects, such as precipitates, dispersed particles, and GB orientations affect failure evolution. This dynamic fracture approach is used to investigate crack nucleation and crack growth as a function of the different microstructural characteristics of each alloy in layered composites with and without pre-existing cracks. The zigzag nature of the crack paths were mainly due to the microstructural features, such as precipitates and dispersed particles distributions and orientations ahead of the crack front, and it underscored the capabilities of the fracture methodology. The evolution of dislocation density and the formation of localized shear slip contributed to the blunting of the propagating crack. Extensive geometrical and thermal softening due to the localized plastic slip also affected crack path orientations and directions. These softening mechanisms resulted in the switching of cleavage planes, which affected crack path orientations. Interface delamination can also have an important role in the failure and toughening of the layered composites. Different scenarios of delamination were investigated, such as planar crack growth and crack penetration into the layers. The presence of brittle surface oxide platelets in the interface region also significantly influenced the interface delamination process. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Optical Microscopy (OM) characterization provided further physical insights and validation of the predictive capabilities. The inherent microstructural features of each alloy play a significant role in the dynamic fracture, shear strain localization, and interface delamination of the layered metallic composite. These microstructural features, such as precipitates, dispersed particles, and GB orientations and distributions can be optimized for desired behavior of metallic composites.

Hybrid Dye-Sensitized Solar Cells Consisting of Double Titania Layers for Harvesting Light with Wide Range of Wavelengths

NASA Astrophysics Data System (ADS)

Sadamasu, Kengo; Inoue, Takafumi; Ogomi, Yuhei; Pandey, Shyam S.; Hayase, Shuzi

2011-02-01

We report a hybrid dye-sensitized solar cell consisting of double titania layers (top and bottom layers) stained with two dyes. A top layer fabricated on a glass was mechanically pressed with a bottom layer fabricated on a glass cloth. The glass cloth acts as a supporter of a porous titania layer as well as a holder of electrolyte. The incident photon to current efficiency (IPCE) curve had two peaks corresponding to those of the two dyes, which demonstrates that electrons are collected from both the top and bottom layers.

Ultrasensitive displacement sensor based on tunable horn-shaped resonators

NASA Astrophysics Data System (ADS)

Tian, Ying; Wu, Jiong; Yu, Le; Yang, Helin; Huang, Xiaojun

2018-04-01

In this paper, we proposed a novel double-deck displacement sensor with a high linearity based on tunable horn-shaped resonators. The designed sensor included two substrate layers etched with copper metallization in various shapes. When the upper trip-type resonator layer has a relative displacement to the bottom horn-shaped resonator layer, the resonance frequency of the sensor is redshift. High sensitivity of the sensor is around 207.2 MHz mm-1 with 4 mm linear dynamic range. We fabricate the sample of the proposed displacement sensor, in addition the simulated results are verified by experiment. The proposed displacement sensor is appropriate for using MEMS technology in further miniaturization.

Trawling-induced daily sediment resuspension in the flank of a Mediterranean submarine canyon

NASA Astrophysics Data System (ADS)

Martín, Jacobo; Puig, Pere; Palanques, Albert; Ribó, Marta

2014-06-01

Commercial bottom trawling is one of the anthropogenic activities causing the biggest impact on the seafloor due to its recurrence and global distribution. In particular, trawling has been proposed as a major driver of sediment dynamics at depths below the reach of storm waves, but the issue is at present poorly documented with direct observations. This paper analyses changes in water turbidity in a tributary valley of the La Fonera (=Palamós) submarine canyon, whose flanks are routinely exploited by a local trawling fleet down to depths of 800 m. A string of turbidimeters was deployed at 980 m water depth inside the tributary for two consecutive years, 2010-2011. The second year, an ADCP profiled the currents 80 m above the seafloor. The results illustrate that near-bottom water turbidity at the study site is heavily dominated, both in its magnitude and temporal patterns, by trawling-induced sediment resuspension at the fishing ground. Resuspended sediments are channelised along the tributary in the form of sediment gravity flows, being recorded only during working days and working hours of the trawling fleet. These sediment gravity flows generate turbid plumes that extend to at least 100 m above the bottom, reaching suspended sediment concentrations up to 236 mg l-1 close to the seafloor (5 m above bottom). A few hours after the end of daily trawling activities, water turbidity progressively decreases but resuspended particles remain in suspension for several hours, developing bottom and intermediate nepheloid layers that reach background levels ˜2 mg l-1 before trawling activities resume. The presence of these nepheloid layers was recorded in a CTD+turbidimeter transect conducted across the fishing ground a few hours after the end of a working day. These results highlight that deep bottom trawling can effectively replace natural processes as the main driving force of sediment resuspension on continental slope regions and generate increased near-bottom water turbidity that propagates from fishing grounds to wider and deeper areas via sediment gravity flows and nepheloid layer development.

The Bottom Boundary Layer.

PubMed

Trowbridge, John H; Lentz, Steven J

2018-01-03

The oceanic bottom boundary layer extracts energy and momentum from the overlying flow, mediates the fate of near-bottom substances, and generates bedforms that retard the flow and affect benthic processes. The bottom boundary layer is forced by winds, waves, tides, and buoyancy and is influenced by surface waves, internal waves, and stratification by heat, salt, and suspended sediments. This review focuses on the coastal ocean. The main points are that (a) classical turbulence concepts and modern turbulence parameterizations provide accurate representations of the structure and turbulent fluxes under conditions in which the underlying assumptions hold, (b) modern sensors and analyses enable high-quality direct or near-direct measurements of the turbulent fluxes and dissipation rates, and (c) the remaining challenges include the interaction of waves and currents with the erodible seabed, the impact of layer-scale two- and three-dimensional instabilities, and the role of the bottom boundary layer in shelf-slope exchange.

The Bottom Boundary Layer

NASA Astrophysics Data System (ADS)

Trowbridge, John H.; Lentz, Steven J.

2018-01-01

The oceanic bottom boundary layer extracts energy and momentum from the overlying flow, mediates the fate of near-bottom substances, and generates bedforms that retard the flow and affect benthic processes. The bottom boundary layer is forced by winds, waves, tides, and buoyancy and is influenced by surface waves, internal waves, and stratification by heat, salt, and suspended sediments. This review focuses on the coastal ocean. The main points are that (a) classical turbulence concepts and modern turbulence parameterizations provide accurate representations of the structure and turbulent fluxes under conditions in which the underlying assumptions hold, (b) modern sensors and analyses enable high-quality direct or near-direct measurements of the turbulent fluxes and dissipation rates, and (c) the remaining challenges include the interaction of waves and currents with the erodible seabed, the impact of layer-scale two- and three-dimensional instabilities, and the role of the bottom boundary layer in shelf-slope exchange.

A numerical analysis of biogeochemical controls with physical modulation on hypoxia during summer in the Pearl River estuary

NASA Astrophysics Data System (ADS)

Wang, Bin; Hu, Jiatang; Li, Shiyu; Liu, Dehong

2017-06-01

A three-dimensional (3-D) physical-biogeochemical coupled model was applied to explore the mechanisms controlling the dissolved oxygen (DO) dynamics and bottom hypoxia during summer in the Pearl River estuary (PRE). By using the numerical oxygen tracers, we proposed a new method (namely the physical modulation method) to quantify the contributions of boundary conditions and each source and sink process occurring in local and adjacent waters to the DO conditions. A mass balance analysis of DO based on the physical modulation method indicated that the DO conditions at the bottom layer were mainly controlled by the source and sink processes, among which the sediment oxygen demand (SOD) at the water-sediment interface and the re-aeration at the air-sea interface were the two primary processes determining the spatial extent and duration of bottom hypoxia in the PRE. The SOD could cause a significant decrease in the bottom DO concentrations (averaged over July-August 2006) by over 4 mg L-1 on the shelf off the Modaomen sub-estuary, leading to the formation of a high-frequency zone of hypoxia (HFZ). However, the hypoxia that occurred in the HFZ was intermittent and distributed in a small area due to the combined effects of re-aeration and photosynthesis, which behaved as sources for DO and offset a portion of the DO consumed by SOD. The bottom DO concentrations to the west of the lower Lingdingyang Bay (i.e. the western shoal near Qi'ao Island) were also largely affected by high SOD, but there was no hypoxia occurring there because of the influence of re-aeration. Specifically, re-aeration could lead to an increase in the bottom DO concentrations by ˜ 4.8 mg L-1 to the west of the lower Lingdingyang Bay. The re-aeration led to a strong vertical DO gradient between the surface and the lower layers. As a result, the majority (˜ 89 %) of DO supplemented by re-aeration was transported to the lower layers through vertical diffusion and ˜ 28 % reached the bottom eventually. Additional numerical experiments showed that turning off re-aeration could lead to an expansion of the hypoxic area from 237 to 2203 km2 and result in persistent hypoxia (hypoxic frequency > 80 %) to the west of the lower Lingdingyang Bay. Compared to re-aeration and SOD, photosynthesis and water column respiration had relatively small impacts on the DO conditions; turning off these two processes increased the hypoxic area to 591 km2. In summary, our study explicitly elucidated the interactive impacts of physical and biogeochemical processes on the DO dynamics in the PRE, which is critical to understanding hypoxia in this shallow and river-dominated estuarine system.

Dynamics of thermal plumes in three-dimensional isoviscous thermal convection

NASA Astrophysics Data System (ADS)

Zhong, Shijie

2005-07-01

The dynamics of mantle plumes are important for understanding intraplate volcanism and heat transfer in the mantle. Using 3-D numerical models and scaling analyses, we investigated the controls of convective vigour or Ra (Rayleigh number) on the dynamics of thermal plumes in isoviscous and basal heating thermal convection. We examined the Ra dependence of plume number, plume spacing, plume vertical velocity and plume radius. We found that plume number does not increase monotonically with Ra. At relatively small Ra(<=106), plume number is insensitive to Ra. For 3 × 106<=Ra<= 3 × 107, plume number scales as Ra0.31 and plume spacing λ~Ra-0.16~δ1/2, where δ is the thickness of the thermal boundary layer. However, for larger Ra(~108) plume number and plume spacing again become insensitive to Ra. This indicates that the box depth poses a limit on plume spacing and plume number. We demonstrate from both scaling analyses and numerical experiments that the scaling exponents for plume number, n, heat flux, β, and average velocity on the bottom boundary, v, satisfy n= 4β- 2v. Our scaling analyses also suggest that vertical velocity in upwelling plumes Vup~Ra2(1-n+β/2)/3 and that plume radius Rup~Ra(β-1-n/2)/3, which differ from the scalings for the bottom boundary velocity and boundary layer thickness.

Critical Latitude in Tidal Dynamics Using the Kara Sea as an Example

NASA Astrophysics Data System (ADS)

Kagan, B. A.; Sofina, E. V.; Timofeev, A. A.

2018-03-01

It is well known that, within the linear nonviscous equations of tidal dynamics, the amplitudes of oscillations of the barotropic and baroclinic tidal velocity components unlimitedly increase when approaching the critical latitude. It is also known that the linear equations of tidal dynamics with a constant and specified vertical eddy viscosity indicate the occurrence of significant tidal velocity shears in the near-bottom layer, which are responsible for increasing the baroclinic tidal energy dissipation, the turbulent kinetic energy, and the thickness of the bottom boundary layer. The first circumstance—the growth of the amplitudes of oscillations of the barotropic and baroclinic tidal velocity components—is due to the elimination in the original equations of small terms, which are small everywhere except for the critical latitude zone. The second circumstance—the occurrence of significant tidal velocity shears—is due to the fact that internal tidal waves, which induce the dissipation of the baroclinic tidal energy and the diapycnal diffusion, are either not taken into account or described inadequately. It is suggested that diapycnal diffusion can lead to the degeneration (complete or partial) of tidal velocity shears, with all the ensuing consequences. The aforesaid is confirmed by simulation results obtained using the QUODDY-4 high-resolution three-dimensional finite-element hydrostatic model along the 66.25° E section, which passes in the Kara Sea across the critical latitude.

Ikaite crystal distribution in Arctic winter sea ice and implications for CO2 system dynamics

NASA Astrophysics Data System (ADS)

Rysgaard, S.; Søgaard, D. H.; Cooper, M.; Pućko, M.; Lennert, K.; Papakyriakou, T. N.; Wang, F.; Geilfus, N. X.; Glud, R. N.; Ehn, J.; McGinnnis, D. F.; Attard, K.; Sievers, J.; Deming, J. W.; Barber, D.

2012-12-01

The precipitation of ikaite (CaCO3·6H2O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikaite in unmelted ice and vertical profiles of ikaite abundance and concentration in sea ice for the crucial season of winter. Ice was examined from two locations: a 1 m thick land-fast ice site and a 0.3 m thick polynya site, both in the Young Sound area (74° N, 20° W) of NE Greenland. Ikaite crystals, ranging in size from a few µm to 700 µm were observed to concentrate in the interstices between the ice platelets in both granular and columnar sea ice. In vertical sea-ice profiles from both locations, ikaite concentration determined from image analysis, decreased with depth from surfaceice values of 700-900 µmol kg-1 ice (~ 25 × 106 crystals kg-1) to bottom-layer values of 100-200 µmol kg-1 ice (1-7 × 106 kg-1), all of which are much higher (4-10 times) than those reported in the few previous studies. Direct measurements of total alkalinity (TA) in surface layers fell within the same range as ikaite concentration whereas TA concentrations in bottom layers were twice as high. This depth-related discrepancy suggests interior ice processes where ikaite crystals form in surface sea ice layers and partly dissolved in bottom layers. From these findings and model calculations we relate sea ice formation and melt to observed pCO2 conditions in polar surface waters, and hence, the air-sea CO2 flux.

Probing the nanoscale with high-speed interferometry of an impacting drop

NASA Astrophysics Data System (ADS)

Thoroddsen, S. T.; Li, E. Q.; Vakarelski, I. U.; Langley, K.

2017-02-01

The simple phenomenon of a water drop falling onto a glass plate may seem like a trivial fluid mechanics problem. However, detailed imaging has shown that this process is highly complex and a small air-bubble is always entrapped under the drop when it makes contact with the solid. This bubble can interfere with the uniformity of spray coatings and degrade inkjet fabrication of displays etc. We will describe how we use high-speed interferometry at 5 million frames per second to understand the details of this process. As the impacting drop approaches the solid, the dynamics are characterized by a balance between the lubrication pressure in the thin air layer and the inertia of the bot-tom of the drop. This deforms the drop, forming a dimple at its bottom and making the drop touch the surface along a ring, thereby entrapping the air-layer, which is typically 1-3 μm thick. This air-layer can be highly compressed and the deceleration of the bottom of the drop can be as large as 300,000 g. We describe how the thickness evolution of the lubricating air-layer is extracted from following the interference fringes between frames. Two-color interferometry is also used to extract absolute layer thicknesses. Finally, we identify the effects of nanometric surface roughness on the first contact of the drop with the substrate. Here we need to resolve the 100 nm thickness changes occurring during 200 ns intervals, requiring these state of the art high-speed cameras. Surprisingly, we see a ring of micro-bubbles marking the first contact of the drop with the glass, only for microscope slides, which have a typical roughness of 20 nm, while such rings are absent for drop impacts onto molecularly smooth mica surfaces.

Vertical gas injection into liquid cross-stream beneath horizontal surfaces

NASA Astrophysics Data System (ADS)

Lee, In-Ho; Makiharju, Simo; Lee, Inwon; Perlin, Marc; Ceccio, Steve

2013-11-01

Skin friction drag reduction on flat bottomed ships and barges can be achieved by creating an air layer immediately beneath the horizontal surface. The simplest way of introducing the gas is through circular orifices; however the dynamics of gas injection into liquid cross-streams under horizontal surfaces is not well understood. Experiments were conducted to investigate the development of the gas topology following its vertical injection through a horizontal surface. The liquid cross-flow, orifice diameter and gas flow rate were varied to investigate the effect of different ratios of momentum fluxes. The testing was performed on a 4.3 m long and 0.73 m wide barge model with air injection through a hole in the transparent bottom hull. The incoming boundary layer was measured via a pitot tube. Downstream distance based Reynolds number at the injection location was 5 × 105 through 4 × 106 . To observe the flow topology, still images and video were recorded from above the model (i.e. through the transparent hull), from beneath the bottom facing upward, and from the side at an oblique angle. The transition point of the flow topology was determined and analyzed.

Effects of the bottom boundary condition in numerical investigations of dense water cascading on a slope

NASA Astrophysics Data System (ADS)

Berntsen, Jarle; Alendal, Guttorm; Avlesen, Helge; Thiem, Øyvind

2018-05-01

The flow of dense water along continental slopes is considered. There is a large literature on the topic based on observations and laboratory experiments. In addition, there are many analytical and numerical studies of dense water flows. In particular, there is a sequence of numerical investigations using the dynamics of overflow mixing and entrainment (DOME) setup. In these papers, the sensitivity of the solutions to numerical parameters such as grid size and numerical viscosity coefficients and to the choices of methods and models is investigated. In earlier DOME studies, three different bottom boundary conditions and a range of vertical grid sizes are applied. In other parts of the literature on numerical studies of oceanic gravity currents, there are statements that appear to contradict choices made on bottom boundary conditions in some of the DOME papers. In the present study, we therefore address the effects of the bottom boundary condition and vertical resolution in numerical investigations of dense water cascading on a slope. The main finding of the present paper is that it is feasible to capture the bottom Ekman layer dynamics adequately and cost efficiently by using a terrain-following model system using a quadratic drag law with a drag coefficient computed to give near-bottom velocity profiles in agreement with the logarithmic law of the wall. Many studies of dense water flows are performed with a quadratic bottom drag law and a constant drag coefficient. It is shown that when using this bottom boundary condition, Ekman drainage will not be adequately represented. In other studies of gravity flow, a no-slip bottom boundary condition is applied. With no-slip and a very fine resolution near the seabed, the solutions are essentially equal to the solutions obtained with a quadratic drag law and a drag coefficient computed to produce velocity profiles matching the logarithmic law of the wall. However, with coarser resolution near the seabed, there may be a substantial artificial blocking effect when using no-slip.

Spin currents and spin-orbit torques in ferromagnetic trilayers.

PubMed

Baek, Seung-Heon C; Amin, Vivek P; Oh, Young-Wan; Go, Gyungchoon; Lee, Seung-Jae; Lee, Geun-Hee; Kim, Kab-Jin; Stiles, M D; Park, Byong-Guk; Lee, Kyung-Jin

2018-06-01

Magnetic torques generated through spin-orbit coupling 1-8 promise energy-efficient spintronic devices. For applications, it is important that these torques switch films with perpendicular magnetizations without an external magnetic field 9-14 . One suggested approach 15 to enable such switching uses magnetic trilayers in which the torque on the top magnetic layer can be manipulated by changing the magnetization of the bottom layer. Spin currents generated in the bottom magnetic layer or its interfaces transit the spacer layer and exert a torque on the top magnetization. Here we demonstrate field-free switching in such structures and show that its dependence on the bottom-layer magnetization is not consistent with the anticipated bulk effects 15 . We describe a mechanism for spin-current generation 16,17 at the interface between the bottom layer and the spacer layer, which gives torques that are consistent with the measured magnetization dependence. This other-layer-generated spin-orbit torque is relevant to energy-efficient control of spintronic devices.

Evaluating wave-current interaction in an urban estuary and flooding implications for coastal communities

NASA Astrophysics Data System (ADS)

Cifuentes-Lorenzen, A.; O'Donnell, J.; Howard-Strobel, M. M.; Fake, T.; McCardell, G.

2016-12-01

Accurate hydrodynamic-wave coupled coastal circulation models aid the prediction of storm impacts, particularly in areas where data is absent, and can inform mitigation options. They are essential everywhere to account for the effects of climate change. Here, the Finite Volume Community Ocean Model (FVCOM) was used to estimate the residual circulation inside a small urban estuary, Long Island Sound, during three severe weather events of different magnitude (i.e. 1/5, 1/25 and 1/50 year events). The effect of including wave coupling using a log-layer bottom boundary and the bottom wave-current coupling, following the approach of Madsen (1994) on the simulated residual circulation was assessed. Significant differences in the solutions were constrained to the near surface (s>-0.3) region. No significant difference in the depth-averaged residual circulation was detected. When the Madsen (1994) bottom boundary layer model for wave-current interaction was employed, differences in residual circulation resulted. The bottom wave-current interaction also plays an important role in the wave dynamics. Significant wave heights along the northern Connecticut shoreline were enhanced by up to 15% when the bottom wave-current interaction was included in the simulations. The wave-induced bottom drag enhancement has a substantial effect on tides in the Sound, possibly because it is nearly resonant at semidiurnal frequencies. This wave-current interaction current leads to severe tidal dampening ( 40% amplitude reduction) at the Western end of the estuary in the modeled sea surface displacement. The potential magnitude of these effects means that wave current interaction should be included and carefully evaluated in models of estuaries that are useful.

Device for thermal transfer and power generation

DOEpatents

Weaver, Stanton Earl [Northville, NY; Arik, Mehmet [Niskayuna, NY

2011-04-19

A system is provided. The system includes a device that includes top and bottom thermally conductive substrates positioned opposite to one another, wherein a top surface of the bottom thermally conductive substrate is substantially atomically flat and a thermal blocking layer disposed between the top and bottom thermally conductive substrates. The device also includes top and bottom electrodes separated from one another between the top and bottom thermally conductive substrates to define a tunneling path, wherein the top electrode is disposed on the thermal blocking layer and the bottom electrode is disposed on the bottom thermally conductive substrate.

An Optimized Combined Wave and Current Bottom Boundary Layer Model for Arbitrary Bed Roughness

DTIC Science & Technology

2017-06-30

Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL), Flood and Storm Protection Division (HF), Coastal ...ER D C/ CH L TR -1 7- 11 Coastal Inlets Research Program An Optimized Combined Wave and Current Bottom Boundary Layer Model for...client/default. Coastal Inlets Research Program ERDC/CHL TR-17-11 June 2017 An Optimized Combined Wave and Current Bottom Boundary Layer Model

Thermal stability and specular reflection behaviour of CoNbZr-based bottom spin valves with nano-oxide layer

NASA Astrophysics Data System (ADS)

Kim, Jong Soo; Lee, Seong-Rae

2004-06-01

The thermal stability and specularity aspects of a CoNbZr-based bottom spin valve (SV) employing a nano-oxide layer (NOL) were investigated. The magnetoresistance (MR) ratio of the as-deposited CoNbZr-based bottom SV increased by 62% (from 6.3 to 10.2%) with incorporation of the NOL. The enhancement of the MR ratio was considered to be due to the specular effect ( increased from 0.722 to 1.363 cm) of the NOL. The MR ratio of a Ta-based bottom SV decreased by about 45% (from 6.9 to 3.8%) when the samples were annealed at 300 °C for 240 min. By contrast, the MR ratio of the CoNbZr-based bottom SV with NOL increase d by 14 % (from 10.2 to 11.7%). The root mean square roughness value of the CoNbZr layer (0.07 nm) was superior to that of the Ta layer (0.43 nm). Although Mn in IrMn diffused out to the surface through the active layers resulting in the formation of Mn oxide at the surface in the CoNbZr-based bottom SV, no trace of Mn was found in the active layers and no significant degradation occurred.

Numerical model for a watering plan to wash out organic matter from the municipal solid waste incinerator bottom ash layer in closed system disposal facilities.

PubMed

Ishii, Kazuei; Furuichi, Toru; Tanikawa, Noboru

2009-02-01

Bottom ash from municipal solid waste incineration (MSWI) is a main type of waste that is landfilled in Japan. The long-term elution of organic matter from the MSWI bottom ash layers is a concern because maintenance and operational costs of leachate treatment facilities are high. In closed system disposal facilities (CSDFs), which have a roof to prevent rainfall from infiltrating into the waste layers, water must be supplied artificially and its quantity can be controlled. However, the quantity of water needed and how to apply it (the intensity, period and frequency) have not been clearly defined. In order to discuss an effective watering plan, this study proposes a new washout model to clarify a fundamental mechanism of total organic carbon (TOC) elution behavior from MSWI bottom ash layers. The washout model considers three phases: solid, immobile water and mobile water. The parameters, including two mass transfer coefficients of the solid-immobile water phases and immobile-mobile water phases, were determined by one-dimensional column experiments for about 2 years. The intensity, period and frequency of watering and other factors were discussed based on a numerical analysis using the above parameters. As a result, our washout model explained adequately the elution behavior of TOC from the MSWI bottom ash layer before carbonation occurred (pH approximately 8.3). The determined parameters and numerical analysis suggested that there is a possibility that the minimum amount of water needed for washing out TOC per unit weight of MSWI bottom ash layer could be determined, which depends on the two mass transfer coefficients and the depth of the MSWI bottom ash layer. Knowledge about the fundamental mechanism of the elution behavior of TOC from the MSWI bottom ash layer before carbonation occurs, clarified by this study, will help an effective watering plan in CSDFs.

Effect of tethering on the surface dynamics of a thin polymer melt layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uğur, Gökçe; Akgun, Bulent; Jiang, Zhang

The surface height fluctuations of a layer of low molecular weight (2.2k) untethered perdeuterated polystyrene (dPS) chains adjacent to a densely grafted polystyrene brush are slowed dramatically. Due to the interpenetration of the brush with the layer of “untethered chains” a hydrodynamic continuum theory can only describe the fluctuations when the effective thickness of the film is taken to be that which remains above the swollen brush. Furthermore, the portion of the film of initially untethered chains that interpenetrates with the brush becomes so viscous as to effectively play the role of a rigid substrate. They provide a route formore » tailoring polymer layer surface properties such as wetting, adhesion and friction, since these hybrid samples contain a covalently tethered layer at the bottom, does not readily dewet, and are more robust than thin layers of untethered short chains on rigid substrates.« less

Effect of tethering on the surface dynamics of a thin polymer melt layer

DOE PAGES

Uğur, Gökçe; Akgun, Bulent; Jiang, Zhang; ...

2016-05-13

The surface height fluctuations of a layer of low molecular weight (2.2k) untethered perdeuterated polystyrene (dPS) chains adjacent to a densely grafted polystyrene brush are slowed dramatically. Due to the interpenetration of the brush with the layer of “untethered chains” a hydrodynamic continuum theory can only describe the fluctuations when the effective thickness of the film is taken to be that which remains above the swollen brush. Furthermore, the portion of the film of initially untethered chains that interpenetrates with the brush becomes so viscous as to effectively play the role of a rigid substrate. They provide a route formore » tailoring polymer layer surface properties such as wetting, adhesion and friction, since these hybrid samples contain a covalently tethered layer at the bottom, does not readily dewet, and are more robust than thin layers of untethered short chains on rigid substrates.« less

A Bottom-Up Approach to Understanding Protein Layer Formation at Solid-Liquid Interfaces

PubMed Central

Kastantin, Mark; Langdon, Blake B.; Schwartz, Daniel K.

2014-01-01

A common goal across different fields (e.g. separations, biosensors, biomaterials, pharmaceuticals) is to understand how protein behavior at solid-liquid interfaces is affected by environmental conditions. Temperature, pH, ionic strength, and the chemical and physical properties of the solid surface, among many factors, can control microscopic protein dynamics (e.g. adsorption, desorption, diffusion, aggregation) that contribute to macroscopic properties like time-dependent total protein surface coverage and protein structure. These relationships are typically studied through a top-down approach in which macroscopic observations are explained using analytical models that are based upon reasonable, but not universally true, simplifying assumptions about microscopic protein dynamics. Conclusions connecting microscopic dynamics to environmental factors can be heavily biased by potentially incorrect assumptions. In contrast, more complicated models avoid several of the common assumptions but require many parameters that have overlapping effects on predictions of macroscopic, average protein properties. Consequently, these models are poorly suited for the top-down approach. Because the sophistication incorporated into these models may ultimately prove essential to understanding interfacial protein behavior, this article proposes a bottom-up approach in which direct observations of microscopic protein dynamics specify parameters in complicated models, which then generate macroscopic predictions to compare with experiment. In this framework, single-molecule tracking has proven capable of making direct measurements of microscopic protein dynamics, but must be complemented by modeling to combine and extrapolate many independent microscopic observations to the macro-scale. The bottom-up approach is expected to better connect environmental factors to macroscopic protein behavior, thereby guiding rational choices that promote desirable protein behaviors. PMID:24484895

DOE Office of Scientific and Technical Information (OSTI.GOV)

Werne, Roger W.; Sampayan, Stephen; Harris, John Richardson

This patent document discloses high voltage switches that include one or more electrically floating conductor layers that are isolated from one another in the dielectric medium between the top and bottom switch electrodes. The presence of the one or more electrically floating conductor layers between the top and bottom switch electrodes allow the dielectric medium between the top and bottom switch electrodes to exhibit a higher breakdown voltage than the breakdown voltage when the one or more electrically floating conductor layers are not present between the top and bottom switch electrodes. This increased breakdown voltage in the presence of onemore » or more electrically floating conductor layers in a dielectric medium enables the switch to supply a higher voltage for various high voltage circuits and electric systems.« less

Resistive heater geometry and regeneration method for a diesel particulate filter

DOEpatents

Phelps, Amanda [Malibu, CA; Kirby, Kevin W [Calabasas Hills, CA; Gregoir, Daniel J [Thousand Oaks, CA

2011-10-25

One embodiment of the invention includes a diesel particulate filter comprising a first face and a second face; a bottom electrode layer formed over the first face of the diesel particulate filter; a middle resistive layer formed over a portion of the bottom electrode layer; and a top electrode layer formed over a portion of the middle resistive layer.

Vorticity and Vertical Motions Diagnosed from Satellite Deep-Layer Temperatures. Revised

NASA Technical Reports Server (NTRS)

Spencer, Roy W.; Lapenta, William M.; Robertson, Franklin R.

1994-01-01

Spatial fields of satellite-measured deep-layer temperatures are examined in the context of quasigeostrophic theory. It is found that midtropospheric geostrophic vorticity and quasigeostrophic vertical motions can be diagnosed from microwave temperature measurements of only two deep layers. The lower- ( 1000-400 hPa) and upper- (400-50 hPa) layer temperatures are estimated from limb-corrected TIROS-N Microwave Sounding Units (MSU) channel 2 and 3 data, spatial fields of which can be used to estimate the midtropospheric thermal wind and geostrophic vorticity fields. Together with Trenberth's simplification of the quasigeostrophic omega equation, these two quantities can be then used to estimate the geostrophic vorticity advection by the thermal wind, which is related to the quasigeostrophic vertical velocity in the midtroposphere. Critical to the technique is the observation that geostrophic vorticity fields calculated from the channel 3 temperature features are very similar to those calculated from traditional, 'bottom-up' integrated height fields from radiosonde data. This suggests a lack of cyclone-scale height features near the top of the channel 3 weighting function, making the channel 3 cyclone-scale 'thickness' features approximately the same as height features near the bottom of the weighting function. Thus, the MSU data provide observational validation of the LID (level of insignificant dynamics) assumption of Hirshberg and Fritsch.

Distinct bacterial assemblages reside at different depths in Arctic multiyear sea ice.

PubMed

Hatam, Ido; Charchuk, Rhianna; Lange, Benjamin; Beckers, Justin; Haas, Christian; Lanoil, Brian

2014-10-01

Bacterial communities in Arctic sea ice play an important role in the regulation of nutrient and energy dynamics in the Arctic Ocean. Sea ice has vertical gradients in temperature, brine salinity and volume, and light and UV levels. Multiyear ice (MYI) has at least two distinct ice layers: old fresh ice with limited permeability, and new saline ice, and may also include a surface melt pond layer. Here, we determine whether bacterial communities (1) differ with ice depth due to strong physical and chemical gradients, (2) are relatively homogenous within a layer, but differ between layers, or (3) do not vary with ice depth. Cores of MYI off northern Ellesmere Island, NU, Canada, were subsectioned in 30-cm intervals, and the bacterial assemblage structure was characterized using 16S rRNA gene pyrotag sequencing. Assemblages clustered into three distinct groups: top (0-30 cm); middle (30-150 cm); and bottom (150-236 cm). These layers correspond to the occurrence of refrozen melt pond ice, at least 2-year-old ice, and newly grown first-year ice at the bottom of the ice sheet, respectively. Thus, MYI houses multiple distinct bacterial assemblages, and in situ conditions appear to play a less important role in structuring microbial assemblages than the age or conditions of the ice at the time of formation. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

The deep meridional overturning circulation in the Indian Ocean inferred from the GECCO synthesis

NASA Astrophysics Data System (ADS)

Wang, Weiqiang; Köhl, Armin; Stammer, Detlef

2012-11-01

The deep time-varying meridional overturning circulation (MOC) in the Indian Ocean in the German “Estimating the Circulation and Climate of the Ocean” consortium efforts (GECCO) ocean synthesis is being investigated. An analysis of the integrated circulation suggests that, on time average, 2.1 Sv enter the Indian Ocean in the bottom layer (>3200 m) from the south and that 12.3 Sv leave the Indian Ocean in the upper and intermediate layers (<1500 m), composed of the up-welled bottom layer inflow water, augmented by 9.6 Sv Indonesian Throughflow (ITF) water. The GECCO time-mean results differ substantially from those obtained by inverse box models, which being based on individual hydrographic sections and due to the strong seasonal cycle are susceptible to aliasing. The GECCO solution shows a large seasonal variation in its deep MOC caused by the seasonal reversal of monsoon-related wind stress forcing. The associated seasonal variations of the deep MOC range from -7 Sv in boreal winter to 3 Sv in summer. In addition, the upper and bottom transports across the 34°S section show pronounced interannual variability with roughly biennial variations superimposed by strong anomalies during each La Niña phase as well as the ITF, which mainly affect the upper layer transports. On decadal and longer timescale, the meridional overturning variability as well as long-term trends differs before and after 1980. GECCO shows a stable trend for the period 1960-1979 and substantial changes in the upper and bottom layer for the period 1980-2001. By means of an extended EOF analysis, the importance of Ekman dynamics as driving forces of the deep MOC of the Indian Ocean on the interannual timescale is highlighted. The leading modes of the zonal and meridional wind stress favour a basin-wide meridional overturning mode via Ekman upwelling or downwelling mostly in the central and eastern Indian Ocean. Moreover, tropical zonal wind stress along the equator and alongshore wind stress off the Sumatra-Java coast contribute to the evolution of the Indian Ocean dipole (IOD) events.

Exact Solutions for Stationary and Unsteady Layered Convection of a Viscous Incompressible Fluid with the Specified Velocities at the Bottom

NASA Astrophysics Data System (ADS)

Prosviryakov, E. Yu; Spevak, L. F.

2017-06-01

The layered convective flow of a viscous incompressible fluid is considered with the specified velocities at the bottom of an infinite layer. A new exact stationary and nonstationary solution of the Oberbeck-Boussinesq system is presented. The account of fluid velocity at the bottom is characterized by the presence of two stagnant points, this being indicative of the nonmonotonic kinetic energy profile with two local extrema.

Ferromagnetic resonance investigation in as-prepared NiFe/FeMn/NiFe trilayer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, S. J.; Xu, K.; Yu, L. M.

2007-06-01

NiFe/FeMn/NiFe trilayer prepared by dc magnetron sputtering was systematically investigated by ferromagnetic resonance technique (FMR) at room temperature. For NiFe/FeMn/NiFe trilayer, there are two distinct resonance peaks both in in-plane and out-of-plane FMR spectra, which are attributed to the two NiFe layers, respectively. The isotropic in-plane resonance field shift is negative for the bottom NiFe layer, while positive for the top NiFe layer. And, such phenomena result from the negative interfacial perpendicular anisotropy at the bottom NiFe/FeMn interface and positive interfacial perpendicular anisotropy at the top FeMn/NiFe interface. The linewidth of the bottom NiFe layer is larger than that ofmore » the top NiFe layer, which might be related to the greater exchange coupling at the bottom NiFe/FeMn interface.« less

Doped bottom-contact organic field-effect transistors

NASA Astrophysics Data System (ADS)

Liu, Shiyi; Billig, Paul; Al-Shadeedi, Akram; Kaphle, Vikash; Lüssem, Björn

2018-07-01

The influence of doping on doped bottom-gate bottom-contact organic field-effect transistors (OFETs) is discussed. It is shown that the inclusion of a doped layer at the dielectric/organic semiconductor layer leads to a significant reduction in the contact resistances and a fine control of the threshold voltage. Through varying the thickness of the doped layer, a linear shift of threshold voltage V T from ‑3.1 to ‑0.22 V is observed for increasing thickness of doped layer. Meanwhile, the contact resistance at the source and drain electrode is reduced from 138.8 MΩ at V GS = ‑10 V for 3 nm to 0.3 MΩ for 7 nm thick doped layers. Furthermore, an increase of charge mobility is observed for increasing thickness of doped layer. Overall, it is shown that doping can minimize injection barriers in bottom-contact OFETs with channel lengths in the micro-meter regime, which has the potential to increase the performance of this technology further.

Non-equilibrium steady-state distributions of colloids in a tilted periodic potential

NASA Astrophysics Data System (ADS)

Ma, Xiaoguang; Lai, Pik-Yin; Ackerson, Bruce; Tong, Penger

A two-layer colloidal system is constructed to study the effects of the external force F on the non-equilibrium steady-state (NESS) dynamics of the diffusing particles over a tilted periodic potential, in which detailed balance is broken due to the presence of a steady particle flux. The periodic potential is provided by the bottom layer colloidal spheres forming a fixed crystalline pattern on a glass substrate. The corrugated surface of the bottom colloidal crystal provides a gravitational potential field for the top layer diffusing particles. By tilting the sample with respect to gravity, a tangential component F is applied to the diffusing particles. The measured NESS probability density function Pss (x , y) of the particles is found to deviate from the equilibrium distribution depending on the driving or distance from equilibrium. The experimental results are compared with the exact solution of the 1D Smoluchowski equation and the numerical results of the 2D Smoluchowski equation. Moreover, from the obtained exact 1D solution, we develop an analytical method to accurately extract the 1D potential U0 (x) from the measured Pss (x) . Work supported in part by the Research Grants Council of Hong Kong SAR.

Fast Low-Current Spin-Orbit-Torque Switching of Magnetic Tunnel Junctions through Atomic Modifications of the Free-Layer Interfaces

NASA Astrophysics Data System (ADS)

Shi, Shengjie; Ou, Yongxi; Aradhya, S. V.; Ralph, D. C.; Buhrman, R. A.

2018-01-01

Future applications of spin-orbit torque will require new mechanisms to improve the efficiency of switching nanoscale magnetic tunnel junctions (MTJs), while also controlling the magnetic dynamics to achieve fast nanosecond-scale performance with low-write-error rates. Here, we demonstrate a strategy to simultaneously enhance the interfacial magnetic anisotropy energy and suppress interfacial spin-memory loss by introducing subatomic and monatomic layers of Hf at the top and bottom interfaces of the ferromagnetic free layer of an in-plane magnetized three-terminal MTJ device. When combined with a β -W spin Hall channel that generates spin-orbit torque, the cumulative effect is a switching current density of 5.4 ×106 A /cm2 .

Deep sediment resuspension and thick nepheloid layer generation by open-ocean convection

NASA Astrophysics Data System (ADS)

Durrieu de Madron, X.; Ramondenc, S.; Berline, L.; Houpert, L.; Bosse, A.; Martini, S.; Guidi, L.; Conan, P.; Curtil, C.; Delsaut, N.; Kunesch, S.; Ghiglione, J. F.; Marsaleix, P.; Pujo-Pay, M.; Séverin, T.; Testor, P.; Tamburini, C.

2017-03-01

The Gulf of Lions in the northwestern Mediterranean is one of the few sites around the world ocean exhibiting deep open-ocean convection. Based on 6 year long (2009-2015) time series from a mooring in the convection region, shipborne measurements from repeated cruises, from 2012 to 2015, and glider measurements, we report evidence of bottom thick nepheloid layer formation, which is coincident with deep sediment resuspension induced by bottom-reaching convection events. This bottom nepheloid layer, which presents a maximum thickness of more than 2000 m in the center of the convection region, probably results from the action of cyclonic eddies that are formed during the convection period and can persist within their core while they travel through the basin. The residence time of this bottom nepheloid layer appears to be less than a year. In situ measurements of suspended particle size further indicate that the bottom nepheloid layer is primarily composed of aggregates between 100 and 1000 µm in diameter, probably constituted of fine silts. Bottom-reaching open ocean convection, as well as deep dense shelf water cascading that occurred concurrently some years, lead to recurring deep sediments resuspension episodes. They are key mechanisms that control the concentration and characteristics of the suspended particulate matter in the basin, and in turn affect the bathypelagic biological activity.

Depth evolution of the Meirama pit lake, A Coruña, NW Spain

NASA Astrophysics Data System (ADS)

Delgado, Jordi; Juncosa-Rivera, Ricardo; Cereijo-Arango, José Luis; García-Morrondo, David; Muñoz-Ibáñez, Andrea; Grande-García, Elisa; Rodríguez-Cedrún, Borja

2016-04-01

The Meirama pit lake is a water mass in the process of controlled flooding that, by the end of December 2015, can be described as a steadily stratified meromictic system. The deepest portion of the lake (monimolimnion) is isolated regarding the annual mixing dynamics (December/January) of the upper water body (mixolimnion), for which the depth of mixing is restricted to a water column of 35-40 m thick. Due to the contrasting flooding history (access of groundwater at the beginning and mixed access of stream/groundwater (being dominant the stream water) the deepest portion of the lake is separated from the upper, non-mixed layer by a marked chemocline. Strictly speaking, the monimolimnion of a meromictic lake extends to the waters located beneath the mixed lake layer. In the case of the Meirama Lake the monimolimnion is internally stratified and made of two major water bodies. From hereafter the deep and upper monimolimnion will be identified as bottom and middle sections of the lake while the mixolimnion is referred to as the surface layer. The general characteristics and evolution of the Meirama Lake have been reported elsewhere. In this work we focus on a summary description of the chemical evolution of the monimolimnion of the lake based on data gathered between 2009 and 2015 from the still on-going monitoring survey. The chemical evolution of the monimolimnion of the lake differs significantly from that of the mixolimnion. In general, surface water is sensible to seasonal fluctuations due to weather conditions, rainfall and biogeochemical processes. The middle and bottom sections are not sensible, in general, to this effects and their evolution obeys to a number of internal processes. In the case of temperature we observe a nearly constant gradient increase (0.001 °C/day) in the middle and deep lake waters up to the beginning of 2012, where it remains constant. The rise in temperature is likely due to the heat provided by groundwater seepage whose temperature is above that of the lake water at the corresponding depth. Likewise, electrical conductance shows a similar constant-rate increasing rate (0.223 and 0.115 S/cm-day in the bottom and middle sections, respectively) whose origin we also associate with groundwater seepage. Based on a wide number of parameters (O2, Cl, SO4, NO3, NO2, NH4, Fe, Mn…) we observe that the monimolimnion of the lake, either in its bottom or middle layer is a rather dynamic (transient) geochemical system.

A Study of Baroclinic Instability Induced Convergence Near the Bottom Using Water Age Simulations

NASA Astrophysics Data System (ADS)

Zhang, Wenxia; Hetland, Robert D.

2018-03-01

Baroclinic instability of lateral density gradients gives way to lateral buoyancy transport, which often results in convergence of buoyancy transport. Along a sloping bottom, the induced convergence can force upward extension of bottom water. Eddy transport induced convergence at the bottom and the consequent suspended layers of bottom properties are investigated using a three-dimensional idealized model. Motivated by the distinct characteristics of intrusions over the Texas-Louisiana shelf, a series of configurations are performed with the purpose of identifying parameter impacts on the intensity of eddy transport. This study uses the "horizontal slope Burger number" as the predominant parameter; the parameter is functioned with SH=SRi-1/2=δ/Ri to identify formation of baroclinic instability, where S is the slope Burger number, δ is the slope parameter, and Ri is the Richardson number, previously shown to be the parameter that predicts the intensity of baroclinic instability on the shelf. Intrusion spreads into the interior abutting a layer that is characterized by degraded vertical stratification; a thickening in the bottom boundary layer colocates with the intrusion, which usually thins at either edge of the intrusion because of a density barrier in association with concentrated isopycnals. The intensity of convergence degrades and bottom tracer fluxes reduce linearly with increased SH on logarithmic scales, and the characteristics of bottom boundary layer behavior and the reversal in alongshore current tend to vanish.

Ultra-high current density thin-film Si diode

DOEpatents

Wang; Qi

2008-04-22

A combination of a thin-film .mu.c-Si and a-Si:H containing diode structure characterized by an ultra-high current density that exceeds 1000 A/cm.sup.2, comprising: a substrate; a bottom metal layer disposed on the substrate; an n-layer of .mu.c-Si deposited the bottom metal layer; an i-layer of .mu.c-Si deposited on the n-layer; a buffer layer of a-Si:H deposited on the i-layer, a p-layer of .mu.c-Si deposited on the buffer layer; and a top metal layer deposited on the p-layer.

Toward a Self-Consistent Dynamical Model of the NSSL

NASA Astrophysics Data System (ADS)

Matilsky, Loren

2018-01-01

The advent of helioseismology has revealed in detail the internal differential rotation profile of the Sun. In particular, the presence of two boundary layers, the tachocline at the bottom of the convection zone (CZ) and the Near Surface Shear Layer (NSSL) at the top of the CZ, has remained a mystery. These two boundary layers may have significant consequences for the internal dynamo that operates the Sun's magnetic field, and so understanding their dynamics is an important step in solar physics and in the theory of solar-like stellar structure in general. In this talk, we analyze three numerical models of hydrodynamic convection in rotating spherical shells with varying degrees of stratification in order to understand the dynamical balance of the solar near-surface shear layer (NSSL). We find that with sufficient stratification, a boundary layer with some characteristics of the NSSL develops at high latitudes, and it is maintained purely an inertial balance of torques in which the viscosity is negligible. An inward radial flux of angular momentum from the Reynold's stress (as has been predicted by theory) is balanced by the poleward latitudinal flux of angular momentum due to the meridional circulation. We analyze the similarities of the near surface shear in our models to that of the Sun, and find that the solar NSSL is most likely maintained by the inertial balance our simulations display at high latitudes, but with a modified upper boundary condition.

Optoelectrofluidic enhanced immunoreaction based on optically-induced dynamic AC electroosmosis.

PubMed

Han, Dongsik; Park, Je-Kyun

2016-04-07

We report a novel optoelectrofluidic immunoreaction system based on electroosmotic flow for enhancing antibody-analyte binding efficiency on a surface-based sensing system. Two conventional indium tin oxide glass slides are assembled to provide a reaction chamber for a tiny volume of sample droplet (∼5 μL), in which the top layer is employed as an antibody-immobilized substrate and the bottom layer acts as a photoconductive layer of an optoelectrofluidic device. Under the application of an AC voltage, an illuminated light pattern on the photoconductive layer causes strong counter-rotating vortices to transport analytes from the bulk solution to the vicinity of the assay spot on the glass substrate. This configuration overcomes the slow immunoreaction problem of a diffusion-based sensing system, resulting in the enhancement of binding efficiency via an optoelectrofluidic method. Furthermore, we investigate the effect of optically-induced dynamic AC electroosmotic flow on optoelectrofluidic enhancement for surface-based immunoreaction with a mathematical simulation study and real experiments using immunoglobulin G (IgG) and anti-IgG. As a result, dynamic light patterns provided better immunoreaction efficiency than static light patterns due to effective mass transport of the target analyte, resulting in an achievement of 2.18-fold enhancement under a growing circular light pattern compared to the passive mode.

Electrical characterization of anodic alumina substrate with via-in-pad structure

NASA Astrophysics Data System (ADS)

Kim, Moonjung

2013-10-01

An anodic alumina substrate has been developed as a package substrate for dynamic random access memory devices. Unlike the conventional package substrates commonly made by laminating an epoxy-based core and cladding with copper, this substrate is fabricated using aluminum anodization technology. The anodization process produces a thick aluminum oxide layer on the aluminum substrate to be used as a dielectric layer. Placing copper patterns on the anodic aluminum oxide layer forms a new substrate structure that consists of a layered structure of aluminum, anodic aluminum oxide, and copper. Using selective anodization in the fabrication process, a via structure connecting the top copper layer and bottom aluminum layer is demonstrated. Additionally, by putting vias directly in the bond and ball pads in the substrate design, the via-in-pad structure is applied in this work. These two-layer metal structures and via-in-pad arrangements make routing easier and thus provide more design flexibility. Additionally, this new package substrate has improved the power distribution network impedance given the characteristics of these structures.

21 CFR Appendix A to Part 74 - The Procedure for Determining Ether Soluble Material in D&C Red Nos. 6 and 7

Code of Federal Regulations, 2010 CFR

2010-04-01

... throughout method.) Allow the funnel to stand until the layers have separated. Transfer the bottom (aqueous) layer to a 500 mL separatory funnel, add 100 mL of ether, stopper and shake for one minute. When the layers have separated, drain off the bottom layer into a waste beaker. Pour the ether layer in the 500 mL...

Nepheloid Layers: Origin and Development In A Narrow Continental Shelf (nw Portugal)

NASA Astrophysics Data System (ADS)

Oliveira, A.; Vitorino, J.; Rodrigues, A.; Jouanneau, J. M.; Weber, O.; Dias, J. A.

A general hydrographic, nephelometric and sedimentological surveying of the NW Portuguese continental shelf and slope was undertaken, under winter and spring con- ditions in order to elaborate a conceptual model of suspended sediments (nepheloid layer) dynamics. Two major situations were found: 1) Spring/Summer - with northerly winds (upwelling) and low energetic wave regime that favour the deposition of sedi- ments. The northerly winds promote offshore transport in the surface nepheloid layer (SNL) and the establishment of a seasonal thermocline allow the expansion of the SNL to the west. The SNL can reach or even cross the shelf-break (50 km from coastline). Particulate organic carbon (POC) content in this layer highlights the higher contribution of biogenic particles (average concentration of 22%); 2) Winter, with southerly winds (downwelling) and high energetic wave regime that favour mid- shelf sediments resuspension and offshore transport in the bottom nepheloid layer (BNL). In the shelf-break the BNL detached to form intermediate nepheloid layers (INL). The SNL is restricted to the inner shelf. The effect of southerly winds gener- ates shoreward Ekman transport and detains the offshore westward extension of this layer even during high river run-off periods. The POC content indicates a dominance of litogenic particles in suspension (average concentration of 8%). Over the mid- and inner-shelf the dominant resuspension mechanism is associated with surface waves (Vitorino et al., 2002). Estimates based on wave measurements at mid-shelf (86m depth) suggested that, in winter, the wave shear velocity frequently exceeds 1 cm/s, assumed as the critical shear velocity for the resuspension of the fine grained sedi- ments (34m) of the bottom cover. Storm events, such as the one observed in November 1996 easily increase the wave shear velocities over 3 cm/s, leading to the increase of the BNL thickness (20-30m) (Vitorino et al., 2002; Oliveira et al., 2002). Low-frequency currents (periods longer than about 2 days) and internal waves can also lead to the resuspension of fine bottom sediments. Shelf morphology (outer shelf re- lieves and Porto submarine canyon) and sedimentary cover can also affect both spatial and vertical development of BNL.

SAR imaging and hydrodynamic analysis of ocean bottom topographic waves

NASA Astrophysics Data System (ADS)

Zheng, Quanan; Li, Li; Guo, Xiaogang; Ge, Yong; Zhu, Dayong; Li, Chunyan

2006-09-01

The satellite synthetic aperture radar (SAR) images display wave-like patterns of the ocean bottom topographic features at the south outlet of Taiwan Strait (TS). Field measurements indicate that the most TS water body is vertically stratified. However, SAR imaging models available were developed for homogeneous waters. Hence explaining SAR imaging mechanisms of bottom features in a stratified ocean is beyond the scope of those models. In order to explore these mechanisms and to determine the quantitative relations between the SAR imagery and the bottom features, a two-dimensional, three-layer ocean model with sinusoidal bottom topographic features is developed. Analytical solutions and inferences of the momentum equations of the ocean model lead to the following conditions. (1) In the lower layer, the topography-induced waves (topographic waves hereafter) exist in the form of stationary waves, which satisfy a lower boundary resonance condition σ = kC0, here σ is an angular frequency of the stationary waves, k is a wavenumber of bottom topographic corrugation, and C0 is a background current speed. (2) As internal waves, the topographic waves may propagate vertically to the upper layer with an unchanged wavenumber k, if a frequency relation N3 < σ < N2 is satisfied, here N2 and N3 are the Brunt-Wäisälä frequencies of middle layer and upper layer, respectively. (3) The topographic waves are extremely amplified if an upper layer resonance condition is satisfied. The SAR image of topographic waves is derived on the basis of current-modulated small wave spectra. The results indicate that the topographic waves on SAR images have the same wavelength of bottom topographic corrugation, and the imagery brightness peaks are either inphase or antiphase with respect to the topographic corrugation, depending on a sign of a coupling factor. These theoretical predictions are verified by field observations. The results of this study provide a physical basis for quantitative interpretation of SAR images of bottom topographic waves in the stratified ocean.

Distribution of Arctic and Pacific copepods and their habitat in the northern Bering Sea and Chukchi Sea

NASA Astrophysics Data System (ADS)

Sasaki, H.; Matsuno, K.; Fujiwara, A.; Onuka, M.; Yamaguchi, A.; Ueno, H.; Watanuki, Y.; Kikuchi, T.

2015-11-01

The advection of warm Pacific water and the reduction of sea-ice extent in the western Arctic Ocean may influence the abundance and distribution of copepods, i.e., a key component in food webs. To understand the factors affecting abundance of copepods in the northern Bering Sea and Chukchi Sea, we constructed habitat models explaining the spatial patterns of the large and small Arctic copepods and the Pacific copepods, separately, using generalized additive models. Copepods were sampled by NORPAC net. Vertical profiles of density, temperature and salinity in the seawater were measured using CTD, and concentration of chlorophyll a in seawater was measured with a fluorometer. The timing of sea-ice retreat was determined using the satellite image. To quantify the structure of water masses, the magnitude of pycnocline and averaged density, temperature and salinity in upper and bottom layers were scored along three axes using principal component analysis (PCA). The structures of water masses indexed by the scores of PCAs were selected as explanatory variables in the best models. Large Arctic copepods were abundant in the water mass with high salinity water in bottom layer or with cold/low salinity water in upper layer and cold/high salinity water in bottom layer, and small Arctic copepods were abundant in the water mass with warm/saline water in upper layer and cold/high salinity water in bottom layers, while Pacific copepods were abundant in the water mass with warm/saline in upper layer and cold/high salinity water in bottom layer. All copepod groups were abundant in areas with deeper depth. Although chlorophyll a in upper and bottom layers were selected as explanatory variables in the best models, apparent trends were not observed. All copepod groups were abundant where the sea-ice retreated at earlier timing. Our study might indicate potential positive effects of the reduction of sea-ice extent on the distribution of all groups of copepods in the Arctic Ocean.

Unconsolidated sediments at the bottom of Lake Vostok from seismic data

USGS Publications Warehouse

Filina, I.; Lukin, V.; Masolov, V.; Blankenship, D.

2007-01-01

Seismic soundings of Lake Vostok have been performed by the Polar Marine Geological Research Expedition in collaboration with the Russian Antarctic Expedition since the early 1990s. The seismograms recorded show at least two relatively closely spaced reflections associated with the lake bottom. These were initially interpreted as boundaries of a layer of unconsolidated sediments at the bottom of the lake. A more recent interpretation suggests that the observed reflections are side echoes from the rough lake bottom, and that there are no unconsolidated sediments at the bottom of the lake. The major goal of this paper is to reveal the nature of those reflections by testing three hypotheses of their origin. The results show that some of the reflections, but not all of them, are consistent with the hypothesis of a non-flat lake bottom along the source-receiver line (2D case). The reflections were also evaluated as side echoes from an adjacent sloping interface, but these tests implied unreasonably steep slopes (at least 8 degrees) at the lake bottom. The hypothesis that is the most compatible with seismic data is the presence of a widespread layer of unconsolidated sediments at the bottom of Lake Vostok. The modeling suggests the presence of a two hundred meter thick sedimentary layer with a seismic velocity of 1700 -1900 m/sec in the southern and middle parts of the lake. The sedimentary layer thickens in the northern basin to ~350 m

Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubbiotti, G., E-mail: gubbiotti@fisica.unipg.it; Tacchi, S.; Del Bianco, L.

2015-05-07

Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence ofmore » the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.« less

Shocks in oscillated granular layers

NASA Astrophysics Data System (ADS)

Bougie, J.; Moon, Sung Joon; Swift, J. B.; Swinney, Harry L.

2001-11-01

We study shock formation in vertically oscillated granular layers, where shock waves form with each collision between the layer and the bottom plate of the container. We use both three-dimensional numerical solutions of continuum equations developed by Jenkins and Richman (J.T. Jenkins and M.W. Richman, Arch. Rat. Mech. Anal. 87), 355 (1985) for smooth and nearly elastic hard spheres, and previously validated molecular dynamics (MD) simulations (C. Bizon, M.D. Shattuck, J.B. Swift, W.D. McCormick, and H.L. Swinney, Phys. Rev. Lett. 80), 57 (1998). Both methods capture the shock formation, and the two methods agree quantitatively for small dissipation. We also investigate the effect of inelasticity on shock formation, and use both smooth and rough hard-sphere MD simulations to investigate the effect of friction in this system.

Molten metal holder furnace and casting system incorporating the molten metal holder furnace

DOEpatents

Kinosz, Michael J.; Meyer, Thomas N.

2003-02-11

A bottom heated holder furnace (12) for containing a supply of molten metal includes a storage vessel (30) having sidewalls (32) and a bottom wall (34) defining a molten metal receiving chamber (36). A furnace insulating layer (42) lines the molten metal receiving chamber (36). A thermally conductive heat exchanger block (54) is located at the bottom of the molten metal receiving chamber (36) for heating the supply of molten metal. The heat exchanger block (54) includes a bottom face (65), side faces (66), and a top face (67). The heat exchanger block (54) includes a plurality of electrical heaters (70) extending therein and projecting outward from at least one of the faces of the heat exchanger block (54), and further extending through the furnace insulating layer (42) and one of the sidewalls (32) of the storage vessel (30) for connection to a source of electrical power. A sealing layer (50) covers the bottom face (65) and side faces (66) of the heat exchanger block (54) such that the heat exchanger block (54) is substantially separated from contact with the furnace insulating layer (42).

A photofunctional bottom-up bis(dipyrrinato)zinc(II) complex nanosheet

PubMed Central

Sakamoto, Ryota; Hoshiko, Ken; Liu, Qian; Yagi, Toshiki; Nagayama, Tatsuhiro; Kusaka, Shinpei; Tsuchiya, Mizuho; Kitagawa, Yasutaka; Wong, Wai-Yeung; Nishihara, Hiroshi

2015-01-01

Two-dimensional polymeric nanosheets have recently gained much attention, particularly top-down nanosheets such as graphene and metal chalcogenides originating from bulk-layered mother materials. Although molecule-based bottom-up nanosheets manufactured directly from molecular components can exhibit greater structural diversity than top-down nanosheets, the bottom-up nanosheets reported thus far lack useful functionalities. Here we show the design and synthesis of a bottom-up nanosheet featuring a photoactive bis(dipyrrinato)zinc(II) complex motif. A liquid/liquid interfacial synthesis between a three-way dipyrrin ligand and zinc(II) ions results in a multi-layer nanosheet, whereas an air/liquid interfacial reaction produces a single-layer or few-layer nanosheet with domain sizes of >10 μm on one side. The bis(dipyrrinato)zinc(II) metal complex nanosheet is easy to deposit on various substrates using the Langmuir–Schäfer process. The nanosheet deposited on a transparent SnO2 electrode functions as a photoanode in a photoelectric conversion system, and is thus the first photofunctional bottom-up nanosheet. PMID:25831973

Dynamics of Scroll Wave in a Three-Dimensional System with Changing Gradient.

PubMed

Yuan, Xiao-Ping; Chen, Jiang-Xing; Zhao, Ye-Hua; Liu, Gui-Quan; Ying, He-Ping

2016-01-01

The dynamics of a scroll wave in an excitable medium with gradient excitability is studied in detail. Three parameter regimes can be distinguished by the degree of gradient. For a small gradient, the system reaches a simple rotating synchronization. In this regime, the rigid rotating velocity of spiral waves is maximal in the layers with the highest filament twist. As the excitability gradient increases, the scroll wave evolutes into a meandering synchronous state. This transition is accompanied by a variation in twisting rate. Filament twisting may prevent the breakup of spiral waves in the bottom layers with a low excitability with which a spiral breaks in a 2D medium. When the gradient is large enough, the twisted filament breaks up, which results in a semi-turbulent state where the lower part is turbulent while the upper part contains a scroll wave with a low twisting filament.

Controls on Plume Spacing and Plume Population in 3-D High Rayleigh Number Thermal Convection

NASA Astrophysics Data System (ADS)

Zhong, S.

2004-12-01

Dynamics of mantle plumes are important for understanding intra-plate volcanism and heat transfer in the mantle. Using 3D numerical models and scaling analyses, we investigated the controls of convective vigor or Ra on the dynamics of thermal plumes in isoviscous and basal heating thermal convection. We examined Ra-dependence of plume population, plume spacing, plume vertical velocity, and plume radius. We found that plume population does not increase with Ra monotonically. At relatively small Ra (<106), plume population is insensitive to Ra. For 3x106

A Dynamical Downscaling study over the Great Lakes Region Using WRF-Lake: Historical Simulation

NASA Astrophysics Data System (ADS)

Xiao, C.; Lofgren, B. M.

2014-12-01

As the largest group of fresh water bodies on Earth, the Laurentian Great Lakes have significant influence on local and regional weather and climate through their unique physical features compared with the surrounding land. Due to the limited spatial resolution and computational efficiency of general circulation models (GCMs), the Great Lakes are geometrically ignored or idealized into several grid cells in GCMs. Thus, the nested regional climate modeling (RCM) technique, known as dynamical downscaling, serves as a feasible solution to fill the gap. The latest Weather Research and Forecasting model (WRF) is employed to dynamically downscale the historical simulation produced by the Geophysical Fluid Dynamics Laboratory-Coupled Model (GFDL-CM3) from 1970-2005. An updated lake scheme originated from the Community Land Model is implemented in the latest WRF version 3.6. It is a one-dimensional mass and energy balance scheme with 20-25 model layers, including up to 5 snow layers on the lake ice, 10 water layers, and 10 soil layers on the lake bottom. The lake scheme is used with actual lake points and lake depth. The preliminary results show that WRF-Lake model, with a fine horizontal resolution and realistic lake representation, provides significantly improved hydroclimates, in terms of lake surface temperature, annual cycle of precipitation, ice content, and lake-effect snowfall. Those improvements suggest that better resolution of the lakes and the mesoscale process of lake-atmosphere interaction are crucial to understanding the climate and climate change in the Great Lakes region.

Bi-layered nanocomposite bandages for controlling microbial infections and overproduction of matrix metalloproteinase activity.

PubMed

Anjana, J; Mohandas, Annapoorna; Seethalakshmy, S; Suresh, Maneesha K; Menon, Riju; Biswas, Raja; Jayakumar, R

2018-04-15

Chronic diabetic wounds is characterised by increased microbial contamination and overproduction of matrix metalloproteases that would degrade the extracellular matrix. A bi-layer bandage was developed, that promotes the inhibition of microbial infections and matrix metalloprotease (MMPs) activity. Bi-layer bandage containing benzalkonium chloride loaded gelatin nanoparticles (BZK GNPs) in chitosan-Hyaluronic acid (HA) as a bottom layer and sodium alendronate containing chitosan as top layer was developed. We hypothesized that the chitosan-gelatin top layer with sodium alendronate could inhibit the MMPs activity, whereas the chitosan-HA bottom layer with BZK GNPs (240±66nm) would enable the elimination of microbes. The porosity, swelling and degradation nature of the prepared Bi-layered bandage was studied. The bottom layer could degrade within 4days whereas the top layer remained upto 7days. The antimicrobial activity of the BZK NPs loaded bandage was determined using normal and clinical strains. Gelatin zymography shows that the proteolytic activity of MMP was inhibited by the bandage. Copyright © 2017 Elsevier B.V. All rights reserved.

An analytical model of capped turbulent oscillatory bottom boundary layers

NASA Astrophysics Data System (ADS)

Shimizu, Kenji

2010-03-01

An analytical model of capped turbulent oscillatory bottom boundary layers (BBLs) is proposed using eddy viscosity of a quadratic form. The common definition of friction velocity based on maximum bottom shear stress is found unsatisfactory for BBLs under rotating flows, and a possible extension based on turbulent kinetic energy balance is proposed. The model solutions show that the flow may slip at the top of the boundary layer due to capping by the water surface or stratification, reducing the bottom shear stress, and that the Earth's rotation induces current and bottom shear stress components perpendicular to the interior flow with a phase lag (or lead). Comparisons with field and numerical experiments indicate that the model predicts the essential characteristics of the velocity profiles, although the agreement is rather qualitative due to assumptions of quadratic eddy viscosity with time-independent friction velocity and a well-mixed boundary layer. On the other hand, the predicted linear friction coefficients, phase lead, and veering angle at the bottom agreed with available data with an error of 3%-10%, 5°-10°, and 5°-10°, respectively. As an application of the model, the friction coefficients are used to calculate e-folding decay distances of progressive internal waves with a semidiurnal frequency.

Bottom-boundary-layer measurements on the continental shelf off the Ebro River, Spain

USGS Publications Warehouse

Cacchione, D.A.; Drake, D.E.; Losada, M.A.; Medina, R.

1990-01-01

Measurements of currents, waves and light transmission obtained with an instrumented bottom tripod (GEOPROBE) were used in conjunction with a theoretical bottom-boundary-layer model for waves and currents to investigate sediment transport on the continental shelf south of the Ebro River Delta, Spain. The current data show that over a 48-day period during the fall of 1984, the average transport at 1 m above the seabed was alongshelf and slightly offshore toward the south-southwest at about 2 cm/s. A weak storm passed through the region during this period and caused elevated wave and current speeds near the bed. The bottom-boundary-layer model predicted correspondingly higher combined wave and current bottom shear velocities at this time, but the GEOPROBE optical data indicate that little to no resuspension occurred. This result suggests that the fine-grained bottom sediment, which has a clay component of 80%, behaves cohesively and is more difficult to resuspend than noncohesive materials of similar size. Model computations also indicate that noncohesive very fine sand in shallow water (20 m deep) was resuspended and transported mainly as bedload during this storm. Fine-grained materials in shallow water that are resuspended and transported as suspended load into deeper water probably account for the slight increase in sediment concentration at the GEOPROBE sensors during the waning stages of the storm. The bottom-boundary-layer data suggest that the belt of fine-grained bottom sediment that extends along the shelf toward the southwest is deposited during prolonged periods of low energy and southwestward bottom flow. This pattern is augmented by enhanced resuspension and transport toward the southwest during storms. ?? 1990.

The effect of annealing on the MR and exchange bias characteristics in dual spin valve with nano-oxide layer

NASA Astrophysics Data System (ADS)

Jang, S. H.; Kang, T.; Kim, H. J.; Kim, K. Y.

2002-02-01

We investigated magnetoresistance (MR) and exchange bias properties by annealing in the dual spin valve (SV) with nano-oxide layer (NOL). By analyzing effects of NOL in top and bottom pinned simple SVs, MR enhancement effect of NOL inserted in the bottom pinned layer was higher than that of NOL in the top pinned layer with annealing. By the enhanced specular scattering of electrons by NOL, the MR ratio of dual SV with NOL was increased to 15.5-15.9% with an annealing of 200-250°C. Exchange coupling constant Jex was improved rapidly as 0.13-0.16 erg/cm 2 by annealing in the bottom pinned layer, whereas the effect of annealing was not large in the top pinned layer with Jex of about 0.09-0.116 erg/cm 2.

The Structure of Microbial Community and Degradation of Diatoms in the Deep Near-Bottom Layer of Lake Baikal

PubMed Central

Zakharova, Yulia R.; Galachyants, Yuri P.; Kurilkina, Maria I.; Likhoshvay, Alexander V.; Petrova, Darya P.; Shishlyannikov, Sergey M.; Ravin, Nikolai V.; Mardanov, Andrey V.; Beletsky, Alexey V.; Likhoshway, Yelena V.

2013-01-01

Insight into the role of bacteria in degradation of diatoms is important for understanding the factors and components of silica turnover in aquatic ecosystems. Using microscopic methods, it has been shown that the degree of diatom preservation and the numbers of diatom-associated bacteria in the surface layer of bottom sediments decrease with depth; in the near-bottom water layer, the majority of bacteria are associated with diatom cells, being located either on the cell surface or within the cell. The structure of microbial community in the near-bottom water layer has been characterized by pyrosequencing of the 16S rRNA gene, which has revealed 149 208 unique sequences. According to the results of metagenomic analysis, the community is dominated by representatives of Proteobacteria (41.9%), Actinobacteria (16%); then follow Acidobacteria (6.9%), Cyanobacteria (5%), Bacteroidetes (4.7%), Firmicutes (2.8%), Nitrospira (1.6%), and Verrucomicrobia (1%); other phylotypes account for less than 1% each. For 18.7% of the sequences, taxonomic identification has been possible only to the Bacteria domain level. Many bacteria identified to the genus level have close relatives occurring in other aquatic ecosystems and soils. The metagenome of the bacterial community from the near-bottom water layer also contains 16S rRNA gene sequences found in previously isolated bacterial strains possessing hydrolytic enzyme activity. These data show that potential degraders of diatoms occur among the vast variety of microorganisms in the near-bottom water of Lake Baikal. PMID:23560063

Taking into Account Interelement Interference in X-Ray Fluorescence Analysis of Thin Two-Layer Ti/V Systems

NASA Astrophysics Data System (ADS)

Mashin, N. I.; Razuvaev, A. G.; Cherniaeva, E. A.; Gafarova, L. M.; Ershov, A. V.

2018-03-01

We propose a new method for determining the thickness of layers in x-ray fluorescence analysis of two-layer Ti/V systems, using easily fabricated standardized film layers obtained by sputter deposition of titanium on a polymer film substrate. We have calculated correction factors taking into account the level of attenuation for the intensity of the primary emission from the x-ray tube and the analytical line for the element of the bottom layer in the top layer, and the enhancement of the fluorescence intensity for the top layer by the emission of atoms in the bottom layer.

Strained layer Fabry-Perot device

DOEpatents

Brennan, Thomas M.; Fritz, Ian J.; Hammons, Burrell E.

1994-01-01

An asymmetric Fabry-Perot reflectance modulator (AFPM) consists of an active region between top and bottom mirrors, the bottom mirror being affixed to a substrate by a buffer layer. The active region comprises a strained-layer region having a bandgap and thickness chosen for resonance at the Fabry-Perot frequency. The mirrors are lattice matched to the active region, and the buffer layer is lattice matched to the mirror at the interface. The device operates at wavelengths of commercially available semiconductor lasers.

Stable isotope evidence for the Bottom Convective Layer homogeneity in the Black Sea

PubMed Central

2014-01-01

The Black Sea is the largest euxinic basin on the Earth. The anoxic zone consists of the upper part water mass stratified by density, and the lower water mass homogenized relative to density (depth >1750 m), named the Bottom Convective Layer. To assess homogeneity and possible exchange of matter across the upper and lower boundaries of the Bottom Convective Layer, new data on stable isotope composition of S, O and H were obtained. Samples were collected in August 2008 and March 2009 from two stations located in the eastern central part of the Black Sea. Distribution of δ18O and δD values of water for the entire water column did not vary seasonally. Appreciable differences were marked for δD value variation in the picnocline area (water depth 200-400 m) and in the BCL 5 m above the bottom that might be caused by penetration of intrusions with elevated portion of shelf modified Mediterranean Water. Observed linear relationship between δ18O (or δD) and salinity indicates that mixing water and salt occurs at the same time, and the deep water of the Black Sea has two end members: the high-salinity Mediterranean seawater and freshwater input. In the Bottom Convective Layer, the average δ34S (H2S) was -40.6 ± 0.5‰ and did not vary seasonally. At the bottom (depth > 2000 m), 34S depletion down to –41.0‰ was observed. Our δ34S (SO4) data are by 2-3‰ higher than those measured previously for the Bottom Convective Layer. Sulfate from the aerobic zone with δ34S (SO4) = +21‰ corresponds to ocean water sulfate and that has not been subjected to sulfate reduction. Average δ34S (SO4) values for depths > 1250 m were found to be +23.0 ± 0.2‰ (1σ). Sulfur isotope composition of sulfate does not change in the Bottom Convective Layer and on its upper and lower boundaries, and does not depend on the season of observation. PMID:24739078

The Role of Rough Topography in Mediating Impacts of Bottom Drag in Eddying Ocean Circulation Models.

PubMed

Trossman, David S; Arbic, Brian K; Straub, David N; Richman, James G; Chassignet, Eric P; Wallcraft, Alan J; Xu, Xiaobiao

2017-08-01

Motivated by the substantial sensitivity of eddies in two-layer quasi-geostrophic (QG) turbulence models to the strength of bottom drag, this study explores the sensitivity of eddies in more realistic ocean general circulation model (OGCM) simulations to bottom drag strength. The OGCM results are interpreted using previous results from horizontally homogeneous, two-layer, flat-bottom, f-plane, doubly periodic QG turbulence simulations and new results from two-layer β -plane QG turbulence simulations run in a basin geometry with both flat and rough bottoms. Baroclinicity in all of the simulations varies greatly with drag strength, with weak drag corresponding to more barotropic flow and strong drag corresponding to more baroclinic flow. The sensitivity of the baroclinicity in the QG basin simulations to bottom drag is considerably reduced, however, when rough topography is used in lieu of a flat bottom. Rough topography reduces the sensitivity of the eddy kinetic energy amplitude and horizontal length scales in the QG basin simulations to bottom drag to an even greater degree. The OGCM simulation behavior is qualitatively similar to that in the QG rough bottom basin simulations in that baroclinicity is more sensitive to bottom drag strength than are eddy amplitudes or horizontal length scales. Rough topography therefore appears to mediate the sensitivity of eddies in models to the strength of bottom drag. The sensitivity of eddies to parameterized topographic internal lee wave drag, which has recently been introduced into some OGCMs, is also briefly discussed. Wave drag acts like a strong bottom drag in that it increases the baroclinicity of the flow, without strongly affecting eddy horizontal length scales.

Depth investigation of rapid sand filters for drinking water production reveals strong stratification in nitrification biokinetic behavior.

PubMed

Tatari, K; Smets, B F; Albrechtsen, H-J

2016-09-15

The biokinetic behavior of NH4(+) removal was investigated at different depths of a rapid sand filter treating groundwater for drinking water preparation. Filter materials from the top, middle and bottom layers of a full-scale filter were exposed to various controlled NH4(+) loadings in a continuous-flow lab-scale assay. NH4(+) removal capacity, estimated from short term loading up-shifts, was at least 10 times higher in the top than in the middle and bottom filter layers, consistent with the stratification of Ammonium Oxidizing Bacteria (AOB). AOB density increased consistently with the NH4(+) removal rate, indicating their primarily role in nitrification under the imposed experimental conditions. The maximum AOB cell specific NH4(+) removal rate observed at the bottom was at least 3 times lower compared to the top and middle layers. Additionally, a significant up-shift capacity (4.6 and 3.5 times) was displayed from the top and middle layers, but not from the bottom layer at increased loading conditions. Hence, AOB with different physiological responses were active at the different depths. The biokinetic analysis predicted that despite the low NH4(+) removal capacity at the bottom layer, the entire filter is able to cope with a 4-fold instantaneous loading increase without compromising the effluent NH4(+). Ultimately, this filter up-shift capacity was limited by the density of AOB and their biokinetic behavior, both of which were strongly stratified. Copyright © 2016 Elsevier Ltd. All rights reserved.

Silicon micromachined broad band light source

NASA Technical Reports Server (NTRS)

George, Thomas (Inventor); Jones, Eric (Inventor); Tuma, Margaret L. (Inventor); Eastwood, Michael (Inventor); Hansler, Richard (Inventor)

2004-01-01

A micro electromechanical system (MEMS) broad band incandescent light source includes three layers: a top transmission window layer; a middle filament mount layer; and a bottom reflector layer. A tungsten filament with a spiral geometry is positioned over a hole in the middle layer. A portion of the broad band light from the heated filament is reflective off the bottom layer. Light from the filament and the reflected light of the filament are transmitted through the transmission window. The light source may operate at temperatures of 2500 K or above. The light source may be incorporated into an on board calibrator (OBC) for a spectrometer.

High-frequency internal waves and thick bottom mixed layers observed by gliders in the Gulf Stream

NASA Astrophysics Data System (ADS)

Todd, Robert E.

2017-06-01

Autonomous underwater gliders are conducting high-resolution surveys within the Gulf Stream along the U.S. East Coast. Glider surveys reveal two mechanisms by which energy is extracted from the Gulf Stream as it flows over the Blake Plateau, a portion of the outer continental shelf between Florida and North Carolina where bottom depths are less than 1000 m. Internal waves with vertical velocities exceeding 0.1 m s-1 and frequencies just below the local buoyancy frequency are routinely found over the Blake Plateau, particularly near the Charleston Bump, a prominent topographic feature. These waves are likely internal lee waves generated by the subinertial Gulf Stream flow over the irregular bathymetry of the outer continental shelf. Bottom mixed layers with O(100) m thickness are also frequently encountered; these thick bottom mixed layers likely form in the lee of topography due to enhanced turbulence generated by O(1) m s-1 near-bottom flows.

Confinement induced ordering in dewetting of ultra-thin polymer bilayers on nanopatterned substrates.

PubMed

Bhandaru, Nandini; Das, Anuja; Mukherjee, Rabibrata

2016-01-14

We report the dewetting of a thin bilayer of polystyrene (PS) and poly(methylmethacrylate) (PMMA) on a topographically patterned nonwettable substrate comprising an array of pillars, arranged in a square lattice. With a gradual increase in the concentration of the PMMA solution (Cn-PMMA), the morphology of the bottom layer changes to: (1) an aligned array of spin dewetted droplets arranged along substrate grooves at very low Cn-PMMA; (2) an interconnected network of threads surrounding each pillar at intermediate Cn-PMMA; and (3) a continuous bottom layer at higher Cn-PMMA. On the other hand the morphology of the PS top layer depends largely on the nature of the pre-existing bottom layer, in addition to Cn-PS. An ordered array of PMMA core-PS shell droplets forms right after spin coating when both Cn-PMMA and Cn-PS are very low. Bilayers with all other initial configurations evolve during thermal annealing, resulting in a variety of ordered structures. Unique morphologies realized include laterally coexisting structures of the two polymers confined within the substrate grooves due to initial rupture of the bottom layer on the substrate followed by a squeezing flow of the top layer; an array of core-shell and single polymer droplets arranged in an alternating order etc., to highlight a few. Such structures cannot be fabricated by any stand-alone lithography technique. On the other hand, in some cases the partially dewetted bottom layer imparts stability to an intact top PS layer against dewetting. Apart from ordering, under certain specific conditions significant miniaturization and downsizing of dewetted feature periodicity and dimension as compared to dewetting of a single layer on a flat substrate is observed. With the help of a morphology phase diagram we show that ordering is achieved over a wide combination of Cn-PMMA and Cn-PS, though the morphology and dewetting pathway differs significantly with variation in the thickness of the individual layers.

Two-layer anti-reflection strategies for implant applications

NASA Astrophysics Data System (ADS)

Guerrero, Douglas J.; Smith, Tamara; Kato, Masakazu; Kimura, Shigeo; Enomoto, Tomoyuki

2006-03-01

A two-layer bottom anti-reflective coating (BARC) concept in which a layer that develops slowly is coated on top of a bottom layer that develops more rapidly was demonstrated. Development rate control was achieved by selection of crosslinker amount and BARC curing conditions. A single-layer BARC was compared with the two-layer BARC concept. The single-layer BARC does not clear out of 200-nm deep vias. When the slower developing single-layer BARC was coated on top of the faster developing layer, the vias were cleared. Lithographic evaluation of the two-layer BARC concept shows the same resolution advantages as the single-layer system. Planarization properties of a two-layer BARC system are better than for a single-layer system, when comparing the same total nominal thicknesses.

A layered abduction model of perception: Integrating bottom-up and top-down processing in a multi-sense agent

NASA Technical Reports Server (NTRS)

Josephson, John R.

1989-01-01

A layered-abduction model of perception is presented which unifies bottom-up and top-down processing in a single logical and information-processing framework. The process of interpreting the input from each sense is broken down into discrete layers of interpretation, where at each layer a best explanation hypothesis is formed of the data presented by the layer or layers below, with the help of information available laterally and from above. The formation of this hypothesis is treated as a problem of abductive inference, similar to diagnosis and theory formation. Thus this model brings a knowledge-based problem-solving approach to the analysis of perception, treating perception as a kind of compiled cognition. The bottom-up passing of information from layer to layer defines channels of information flow, which separate and converge in a specific way for any specific sense modality. Multi-modal perception occurs where channels converge from more than one sense. This model has not yet been implemented, though it is based on systems which have been successful in medical and mechanical diagnosis and medical test interpretation.

Cyclotron Orbits of Composite Fermions in the Fractional Quantum Hall Regime

NASA Astrophysics Data System (ADS)

Jo, Insun; Deng, Hao; Liu, Yang; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Shayegan, M.

2018-01-01

We study a bilayer GaAs hole system that hosts two distinct many-body phases at low temperatures and high perpendicular magnetic fields. The higher-density (top) layer develops a Fermi sea of composite fermions (CFs) in its half-filled lowest Landau level, while the lower-density (bottom) layer forms a Wigner crystal (WC) as its filling becomes very small. Owing to the interlayer interaction, the CFs in the top layer feel the periodic Coulomb potential of the WC in the bottom layer. We measure the magnetoresistance of the top layer while changing the bottom-layer density. As the WC layer density increases, the resistance peaks separating the adjacent fractional quantum Hall states in the top layer change nonmonotonically and attain maximum values when the cyclotron orbit of the CFs encloses one WC lattice point. These features disappear at T =275 mK when the WC melts. The observation of such geometric resonance features is unprecedented and surprising as it implies that the CFs retain a well-defined cyclotron orbit and Fermi wave vector even deep in the fractional quantum Hall regime, far from half-filling.

Bottom-water observations in the Vema fracture zone

NASA Astrophysics Data System (ADS)

Eittreim, Stephen L.; Biscaye, Pierre E.; Jacobs, Stanley S.

1983-03-01

The Vema fracture zone trough, at 11°N between 41° and 45°E, is open to the west at the 5000-m level but is silled at the 4650-m level on the east where it intersects the axis of the Mid-Atlantic Ridge. The trough is filled with Antarctic Bottom Water (AABW) with a potential temperature of 1.32°C and salinity of 34.82 ppt. The bottom water is thermally well mixed in a nearly homogeneous layer about 700 m thick. The great thickness of this bottom layer, as compared with the bottom-water structure of the western Atlantic basin, may result from enhanced mixing induced by topographic constriction at the west end of the fracture zone trough. A benthic thermocline, with potential temperature gradients of about 1.2 mdeg m-1, is associated with an abrupt increase in turbidity with depth at about 1200 m above bottom. A transitional layer of more moderate temperature gradients, about 0.4 mdeg m-1, lies between the benthic thermocline above and the AABW below. The AABW layer whose depth-averaged suspended paniculate concentrations range from 8 to 19 μg L-1, is consistently higher in turbidity than the overlying waters. At the eastern end of the trough, 140 m below sill depth, very low northeastward current velocities, with maximums of 3 cm s-1, were recorded for an 11-day period.

Bottom-up and top-down controls on picoplankton in the East China Sea

NASA Astrophysics Data System (ADS)

Guo, C.; Liu, H.; Zheng, L.; Song, S.; Chen, B.; Huang, B.

2013-05-01

Dynamics of picoplankton population distribution in the East China Sea (ECS), a marginal sea in the western North Pacific Ocean, were studied during two "CHOICE-C" cruises in August 2009 (summer) and January 2010 (winter). Dilution experiments were conducted during the two cruises to investigate the growth and grazing among picophytoplantkon populations. Picoplankton accounted for an average of ~29% (2% to 88%) of community carbon biomass in the ECS on average, with lower percentages in plume region than in shelf and kuroshio regions. Averaged growth rates (μ) for Prochlorococcus (Pro), Synechococcus (Syn) and picoeukaryotes (peuk) were 0.36, 0.89, 0.90 d-1, respectively, in summer, and 0.46, 0.58, 0.56 d-1, respectively, in winter. Seawater salinity and nutrient availability exerted significant controls on picoplankton growth rate. Averaged grazing mortality (m) were 0.46, 0.63, 0.68 d-1 in summer, and 0.22, 0.32, 0.22 d-1 in winter for Pro, Syn and peuk respectively. The three populations demonstrated very different distribution patterns regionally and seasonally affected by both bottom-up and top-down controls. In summer, Pro, Syn and peuk were dominant in Kuroshio, transitional and plume regions respectively. Protist grazing consumed 84%, 78%, 73% and 45%, 47%, 57% of production for Pro, Syn and peuk in summer and winter respectively, suggesting more significant top-down controls in summer. In winter, all three populations tended to distribute in offshore regions, although the area of coverage was different (peuk > Syn > Pro). Bottom-up factors can explain as much as 91.5%, 82% and 81.2% of Pro, Syn and peuk abundance variance in winter, while only 59.1% and 43.7% for Pro and peuk in summer. Regionally, Yangtze River discharge plays a significant role in affecting the intensity of top-down control, indicated by significant and negative association between salinity and grazing mortality of all three populations and higher grazing mortality to growth rate ratio (m / μ) in plume region than Kuroshio region in summer. The gradient of bottom-up factors caused by Yangtze River input and Kuroshio warm current intrusion also exerted important influence on picoplankton abundance evidenced by the significant correlations. Vertically, picoplankton exhibited highest abundance at subsurface layer around 20 m thick in summer, while at surface in winter. Both growth rate and grazing mortality were higher at surface than at the deep chlorophyll maximum (DCM) layer. Our study first systematically described the bottom-up and top-down regulations of different picoplankton populations between contrasting seasons, different depths, and among different regions in the ECS, which provide insights for better understanding the population dynamics of picoplankton and trophic transfer in microbial food web in highly dynamic shelf ecosystems and in general.

Rapid Changes in Water Properties on a Shallow Reef in the Chesapeake Bay due to a Wind Driven Internal Seiche

NASA Astrophysics Data System (ADS)

Kilbourne, B.

2016-12-01

The Chesapeake Bay Interpretive Buoy System has collected oceanographic and meteorological observations in Chesapeake Bay from 2007 to the present. The relatively long and well resolved time series of wind, current, and salinity data provided by this array creates an opportunity to better understand the many finescale circulation pathways in Chesapeake Bay. The mean vertical structure of Chesapeake Bay is approximated by a three layer system: a well-mixed surface boundary layer from 1 to 8 m depth, a stratified transition layer from 8 to 15 m depth, and a well-mixed bottom boundary layer from 15 m to the bottom (typically < 30 m). The conditions in the surface and bottom boundary layers can be strikingly different with the bottom layer being saltier, lower in pH, and lower in dissolved oxygen than the surface layer. The Gooses Reef station of this array is located on `Gooses Reef', a shallow bar just 10 m in depth, dividing the Choptank River basin from the main channel of the Chesapeake Bay. This shallow bar provides habitat for oysters, a keystone species in the Chesapeake Bay, and is both commercially and ecologically critical to the region. These shallow habitats are threatened when anoxic (< 0.5 mg l-1 O2) conditions exist in the upper 10 m of the water column. The Gooses Reef station is unique in the array due to the addition of a bottom mounted sensor package; data from August 2012 show rapid changes in the salinity (11 to 17 PSU), dissolved oxygen (6 to 0.05 mg l-1) , and pH (8.3 to 7.7) at the bottom. Investigations of wind and current data before these rapid changes show along channel wind stress oscillations near the M2 tidal frequency. Current profiles from the buoy ADCP show low-frequency along-channel baroclinic oscillations. Observed currents appear to be an internal seiche, forced by resonance between the along-channel wind and diurnal tide. At the Gooses Reef bar, this internal seiche forced the bottom boundary layer up and over the bar, causing the sudden shift in water properties. These observations highlight the strong physical controls on local water conditions in the Chesapeake Bay and similar estuaries.

Characterization of a New Organosilicon Photoresist

NASA Astrophysics Data System (ADS)

Cunningham, Wells C.

1987-08-01

For a number of years, there has lo'ep. great interest in organometallic based photoresists for use as the top layer in multilevel resist schemes.-' In general, bilevel approaches to lithography are forced upon the industry as a means of planarizing topography for a subsequent patterning step. This pattern is initially defined by exposure and development of a thin top layer (0.3 to 0.5μm) over the thicker bottom layer (1.0 to 2.0μm). (See Figure 1). In a conventional bilevel approach, the chosen bottom layer is photoactive at a wavelength for which the top is relatively opaque. The top level acts as a portable conformable mask (PCM) for image transfer through the bottom layer after its exposure and wet development. By using a silicon containing photoresist on the top image transfer may be accomplished using an oxygen plasma instead of a second exposure and development. The PCM in this case acts as an etch mask by forming a silicon dioxide crust in the plasma which slows the etch rate of the top versus the bottom layer. A generic curve of etch rate of a photoresist versus percent silicon by weight is shown in Figure 2. The shape is similar over a wide range of organosilicon polymers.5,6

Radionuclides and mercury in the salt lakes of the Crimea

NASA Astrophysics Data System (ADS)

Mirzoyeva, Natalya; Gulina, Larisa; Gulin, Sergey; Plotitsina, Olga; Stetsuk, Alexandra; Arkhipova, Svetlana; Korkishko, Nina; Eremin, Oleg

2015-11-01

90Sr concentrations, resulting from the Chernobyl NPP accident, were determined in the salt lakes of the Crimea (Lakes Kiyatskoe, Kirleutskoe, Kizil-Yar, Bakalskoe and Donuzlav), together with the redistribution between the components of the ecosystems. The content of mercury in the waters of the studied reservoirs was also established. Vertical distributions of natural radionuclide activities (238U, 232Th, 226Ra, 210Pb, 40K) and anthropogenic 137Cs concentrations (as radiotracers) were determined in the bottom sediments of the Koyashskoe salt lake (located in the south-eastern Crimea) to evaluate the longterm dynamics and biogeochemical processes. Radiochemical and chemical analysis was undertaken and radiotracer and statistical methods were applied to the analytical data. The highest concentrations of 90Sr in the water of Lake Kiyatskoe (350.5 and 98.0 Bq/m3) and Lake Kirleutskoe (121.3 Bq/m3) were due to the discharge of the Dnieper water from the North-Crimean Canal. The high content of mercury in Lake Kiyatskoe (363.2 ng/L) and in seawater near Lake Kizil-Yar (364 ng/L) exceeded the maximum permissible concentration (3.5 times the maximum). Natural radionuclides provide the main contribution to the total radioactivity (artificial and natural combined) in the bottom sediments of Lake Koyashskoe. The significant concentration of 210Pb in the upper layer of bottom sediments of the lake indicates an active inflow of its parent radionuclide—gaseous 222Rn from the lower layers of the bottom sediment. The average sedimentation rates in Lake Koyashskoe, determined using 210Pb and 137Cs data, were 0.117 and 0.109 cm per year, respectively.

A Satellite-Based Lagrangian View on Phytoplankton Dynamics

NASA Astrophysics Data System (ADS)

Lehahn, Yoav; d'Ovidio, Francesco; Koren, Ilan

2018-01-01

The well-lit upper layer of the open ocean is a dynamical environment that hosts approximately half of global primary production. In the remote parts of this environment, distant from the coast and from the seabed, there is no obvious spatially fixed reference frame for describing the dynamics of the microscopic drifting organisms responsible for this immense production of organic matter—the phytoplankton. Thus, a natural perspective for studying phytoplankton dynamics is to follow the trajectories of water parcels in which the organisms are embedded. With the advent of satellite oceanography, this Lagrangian perspective has provided valuable information on different aspects of phytoplankton dynamics, including bloom initiation and termination, spatial distribution patterns, biodiversity, export of carbon to the deep ocean, and, more recently, bottom-up mechanisms that affect the distribution and behavior of higher-trophic-level organisms. Upcoming submesoscale-resolving satellite observations and swarms of autonomous platforms open the way to the integration of vertical dynamics into the Lagrangian view of phytoplankton dynamics.

A Satellite-Based Lagrangian View on Phytoplankton Dynamics.

PubMed

Lehahn, Yoav; d'Ovidio, Francesco; Koren, Ilan

2018-01-03

The well-lit upper layer of the open ocean is a dynamical environment that hosts approximately half of global primary production. In the remote parts of this environment, distant from the coast and from the seabed, there is no obvious spatially fixed reference frame for describing the dynamics of the microscopic drifting organisms responsible for this immense production of organic matter-the phytoplankton. Thus, a natural perspective for studying phytoplankton dynamics is to follow the trajectories of water parcels in which the organisms are embedded. With the advent of satellite oceanography, this Lagrangian perspective has provided valuable information on different aspects of phytoplankton dynamics, including bloom initiation and termination, spatial distribution patterns, biodiversity, export of carbon to the deep ocean, and, more recently, bottom-up mechanisms that affect the distribution and behavior of higher-trophic-level organisms. Upcoming submesoscale-resolving satellite observations and swarms of autonomous platforms open the way to the integration of vertical dynamics into the Lagrangian view of phytoplankton dynamics.

Re-initiation of bottom water formation in the East Sea (Japan Sea) in a warming world.

PubMed

Yoon, Seung-Tae; Chang, Kyung-Il; Nam, SungHyun; Rho, TaeKeun; Kang, Dong-Jin; Lee, Tongsup; Park, Kyung-Ae; Lobanov, Vyacheslav; Kaplunenko, Dmitry; Tishchenko, Pavel; Kim, Kyung-Ryul

2018-01-25

The East Sea (Japan Sea), a small marginal sea in the northwestern Pacific, is ventilated deeply down to the bottom and sensitive to changing surface conditions. Addressing the response of this marginal sea to the hydrological cycle and atmospheric forcing would be helpful for better understanding present and future environmental changes in oceans at the global and regional scales. Here, we present an analysis of observations revealing a slowdown of the long-term deepening in water boundaries associated with changes of water formation rate. Our results indicate that bottom (central) water formation has been enhanced (reduced) with more (less) oxygen supply to the bottom (central) layer since the 2000s. This paper presents a new projection that allows a three-layered deep structure, which retains bottom water, at least until 2040, contrasting previous results. This projection considers recent increase of slope convections mainly due to the salt supply via air-sea freshwater exchange and sea ice formation and decrease of open-ocean convections evidenced by reduced mixed layer depth in the northern East Sea, resulting in more bottom water and less central water formations. Such vigorous changes in water formation and ventilation provide certain implications on future climate changes.

Selective Activation of the Deep Layers of the Human Primary Visual Cortex by Top-Down Feedback.

PubMed

Kok, Peter; Bains, Lauren J; van Mourik, Tim; Norris, David G; de Lange, Floris P

2016-02-08

In addition to bottom-up input, the visual cortex receives large amounts of feedback from other cortical areas [1-3]. One compelling example of feedback activation of early visual neurons in the absence of bottom-up input occurs during the famous Kanizsa illusion, where a triangular shape is perceived, even in regions of the image where there is no bottom-up visual evidence for it. This illusion increases the firing activity of neurons in the primary visual cortex with a receptive field on the illusory contour [4]. Feedback signals are largely segregated from feedforward signals within each cortical area, with feedforward signals arriving in the middle layer, while top-down feedback avoids the middle layers and predominantly targets deep and superficial layers [1, 2, 5, 6]. Therefore, the feedback-mediated activity increase in V1 during the perception of illusory shapes should lead to a specific laminar activity profile that is distinct from the activity elicited by bottom-up stimulation. Here, we used fMRI at high field (7 T) to empirically test this hypothesis, by probing the cortical response to illusory figures in human V1 at different cortical depths [7-14]. We found that, whereas bottom-up stimulation activated all cortical layers, feedback activity induced by illusory figures led to a selective activation of the deep layers of V1. These results demonstrate the potential for non-invasive recordings of neural activity with laminar specificity in humans and elucidate the role of top-down signals during perceptual processing. Copyright © 2016 Elsevier Ltd. All rights reserved.

Plasmon resonance imaging apparatus having nano-lycurgus-cup arrays and methods of use

DOEpatents

Liu, Gang Logan; Gartia, Manas Ranjan; Hsiao, Austin Yin Kyai

2016-10-11

Apparatus and methods are disclosed that are configured to permit nanoplasmonic spectroscopy sensing in the form of colorimetric sensing. An example apparatus involves: (a) an array layer having a top surface and a bottom surface, wherein a plurality of nanoholes are defined in the top surface of the array layer, wherein the plurality of nanoholes each have at least one sidewall surface and a bottom surface, (b) a thin metal film disposed on the top surface of the array layer and on the bottom surface of each of the plurality of nanoholes, and (c) a plurality of nanoparticles disposed on the at least one sidewall surface of the plurality of nanoholes.

Sound Propagation in Shallow Water with an Inhomogeneous GAS-Saturated Bottom

NASA Astrophysics Data System (ADS)

Grigor'ev, V. A.; Petnikov, V. G.; Roslyakov, A. G.; Terekhina, Ya. E.

2018-05-01

We present the methods and results of numerical experiments studying the low-frequency sound propagation in one of the areas of the Arctic shelf with a randomly inhomogeneous gas-saturated bottom. The characteristics of the upper layer of bottom sedimentary rocks (sediments) used in calculations were obtained during a 3D seismic survey and trial drilling of the seafloor. We demonstrate the possibilities of substituting in numerical simulation a real bottom with a fluid homogeneous half-space where the effective value of the sound speed is equal to the average sound speed in the bottom, with averaging along the sound propagation path to a sediment depth of 0.6 wavelength in the bottom. An original technique is proposed for estimating the sound speed propagation in an upper inhomogeneous sediment layer. The technique is based on measurements of acoustic wave attenuation in water during waveguide propagation.

Experimental and theoretical modelling of sand-water-object interaction under nonlinear progressive waves

NASA Astrophysics Data System (ADS)

Testik, Firat Yener

An experimental and theoretical study has been conducted to obtain a fundamental understanding of the dynamics of the sand, water and a solid object interaction as progressive gravity waves impinge on a sloping beach. Aside from obvious scientific interest, this exceedingly complex physical problem is important for naval applications, related to the behavior of disk/cylindrical shaped objects (mines) in the coastal waters. To address this problem, it was divided into a set of simpler basic problems. To begin, nonlinear progressive waves were investigated experimentally in a wave tank for the case of a rigid (impermeable) sloping bottom. Parameterizations for wave characteristics were proposed and compared with the experiments. In parallel, a numerical wave tank model (NWT) was calibrated using experimental data from a single run, and wave field in the wave tank was simulated numerically for the selected experiments. Subsequently, a layer of sand was placed on the slope and bottom topography evolution processes (ripple and sandbar dynamics, bottom topography relaxation under variable wave forcing, etc.) were investigated experimentally. Models for those processes were developed and verified by experimental measurements. Flow over a circular cylinder placed horizontally on a plane wall was also studied. The far-flow field of the cylinder placed in the wave tank was investigated experimentally and numerical results from the NWT simulations were compared with the experimental data. In the mean time, the near-flow velocity/vorticity field around a short cylinder under steady and oscillatory flow was studied in a towing tank. Horseshoe vortex formation and periodic shedding were documented and explained. With the understanding gained through the aforementioned studies, dynamics and burial/scour around the bottom objects in the wave tank were studied. Possible scenarios on the behavior of the disk-shaped objects were identified and explained. Scour around 3D cylindrical objects was investigated. Different scour regimes were identified experimentally and explained theoretically. Proper physical parameterizations on the time evolution and equilibrium scour characteristics were proposed and verified experimentally.

The frequency-domain approach for apparent density mapping

NASA Astrophysics Data System (ADS)

Tong, T.; Guo, L.

2017-12-01

Apparent density mapping is a technique to estimate density distribution in the subsurface layer from the observed gravity data. It has been widely applied for geologic mapping, tectonic study and mineral exploration for decades. Apparent density mapping usually models the density layer as a collection of vertical, juxtaposed prisms in both horizontal directions, whose top and bottom surfaces are assumed to be horizontal or variable-depth, and then inverts or deconvolves the gravity anomalies to determine the density of each prism. Conventionally, the frequency-domain approach, which assumes that both top and bottom surfaces of the layer are horizontal, is usually utilized for fast density mapping. However, such assumption is not always valid in the real world, since either the top surface or the bottom surface may be variable-depth. Here, we presented a frequency-domain approach for apparent density mapping, which permits both the top and bottom surfaces of the layer to be variable-depth. We first derived the formula for forward calculation of gravity anomalies caused by the density layer, whose top and bottom surfaces are variable-depth, and the formula for inversion of gravity anomalies for the density distribution. Then we proposed the procedure for density mapping based on both the formulas of inversion and forward calculation. We tested the approach on the synthetic data, which verified its effectiveness. We also tested the approach on the real Bouguer gravity anomalies data from the central South China. The top surface was assumed to be flat and was on the sea level, and the bottom surface was considered as the Moho surface. The result presented the crustal density distribution, which was coinciding well with the basic tectonic features in the study area.

Co-fabrication of chitosan and epoxy photoresist to form microwell arrays with permeable hydrogel bottoms

PubMed Central

Ornoff, Douglas M.; Wang, Yuli; Proctor, Angela; Shah, Akash S.; Allbritton, Nancy L.

2015-01-01

Microfabrication technology offers the potential to create biological platforms with customizable patterns and surface chemistries, allowing precise control over the biochemical microenvironment to which a cell or group of cells is exposed. However, most microfabricated platforms grow cells on impermeable surfaces. This report describes the co-fabrication of a micropatterned epoxy photoresist film with a chitosan film to create a freestanding array of permeable, hydrogel-bottomed microwells. These films possess optical properties ideal for microscopy applications, and the chitosan layers are semi-permeable with a molecular exclusion of 9.9 ± 2.1 kDa. By seeding cells into the microwells, overlaying inert mineral oil, and supplying media via the bottom surface, this hybrid film permits cells to be physically isolated from one another but maintained in culture for at least 4 days. Arrays co-fabricated using these materials reduce both large-molecular-weight biochemical crosstalk between cells and mixing of different clonal populations, and will enable high-throughput studies of cellular heterogeneity with increased ability to customize dynamic interrogations compared to materials in currently available technologies. PMID:26447557

Numerical simulation of jet mixing concepts in Tank 241-SY-101

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trent, D.S.; Michener, T.E.

The episodic gas release events (GRES) that have characterized the behavior of Tank 241-SY-101 for the past several years are thought to result from gases generated by the waste material in it that become trapped in the layer of settled solids at the bottom of the tank. Several concepts for mitigating the GREs have been proposed. One concept involves mobilizing the solid particles with mixing jets. The rationale behind this idea is to prevent formation of a consolidated layer of settled solids at the bottom of the tank, thus inhibiting the accumulation of gas bubbles in this layer. Numerical simulationsmore » were conducted using the TEMPEST computer code to assess the viability and effectiveness of the proposed jet discharge concepts and operating parameters. Before these parametric studies were commenced, a series of turbulent jet studies were conducted that established the adequacy of the TEMPEST code for this application. Configurations studied for Tank 241-SY-101 include centrally located downward discharging jets, draft tubes, and horizontal jets that are either stationary or rotating. Parameter studies included varying the jet discharge velocity, jet diameter, discharge elevation, and material properties. A total of 18 simulations were conducted and are reported in this document. The effect of gas bubbles on the mixing dynamics was not included within the scope of this study.« less

On the role of infiltration and exfiltration in swash zone boundary layer dynamics

NASA Astrophysics Data System (ADS)

Pintado-Patiño, José Carlos; Torres-Freyermuth, Alec; Puleo, Jack A.; Pokrajac, Dubravka

2015-09-01

Boundary layer dynamics are investigated using a 2-D numerical model that solves the Volume-Averaged Reynolds-Averaged Navier-Stokes equations, with a VOF-tracking scheme and a k - ɛ turbulence closure. The model is validated with highly resolved data of dam break driven swash flows over gravel impermeable and permeable beds. The spatial gradients of the velocity, bed shear stress, and turbulence intensity terms are investigated with reference to bottom boundary layer (BL) dynamics. Numerical results show that the mean vorticity responds to flow divergence/convergence at the surface that result from accelerating/decelerating portions of the flow, bed shear stress, and sinking/injection of turbulence due to infiltration/exfiltration. Hence, the zero up-crossing of the vorticity is employed as a proxy of the BL thickness inside the shallow swash zone flows. During the uprush phase, the BL develops almost instantaneously with bore arrival and fluctuates below the surface due to flow instabilities and related horizontal straining. In contrast, during the backwash phase, the BL grows quasi-linearly with less influence of surface-induced forces. However, the infiltration produces a reduction of the maximum excursion and duration of the swash event. These effects have important implications for the BL development. The numerical results suggest that the BL growth rate deviates rapidly from a quasi-linear trend if the infiltration is dominant during the initial backwash phase and the flat plate boundary layer theory may no longer be applicable under these conditions.

Dynamics of particle export on the Northwest Atlantic margin

NASA Astrophysics Data System (ADS)

Hwang, Jeomshik; Manganini, Steven J.; Montluçon, Daniel B.; Eglinton, Timothy I.

2009-10-01

The Northwest Atlantic margin is characterized by high biological productivity in shelf and slope surface waters. In addition to carbon supply to underlying sediments, the persistent, intermediate depth nepheloid layers emanating from the continental shelves, and bottom nepheloid layers maintained by strong bottom currents associated with the southward flowing Deep Western Boundary Current (DWBC), provide conduits for export of organic carbon over the margin and/or to the interior ocean. As a part of a project to understand dynamics of particulate organic carbon (POC) cycling in this region, we examined the bulk and molecular properties of time-series sediment trap samples obtained at 968 m, 1976 m, and 2938 m depths from a bottom-tethered mooring on the New England slope (water depth, 2988 m). Frequent occurrences of higher fluxes in deep relative to shallower sediment traps and low Δ 14C values of sinking POC together provide strong evidence for significant lateral transport of aged organic matter over the margin. Comparison of biogeochemical properties such as aluminum concentration and flux, and iron concentration between samples intercepted at different depths shows that particles collected by the deepest trap had more complex sources than the shallower ones. These data also suggest that at least two modes of lateral transport exist over the New England margin. Based on radiocarbon mass balance, about 30% (±10%) of sinking POC in all sediment traps is estimated to be derived from lateral transport of resuspended sediment. A strong correlation between Δ 14C values and aluminum concentrations suggests that the aged organic matter is associated with lithogenic particles. Our results suggest that lateral transport of organic matter, particularly that resulting from sediment resuspension, should be considered in addition to vertical supply of organic matter derived from primary production, in order to understand carbon cycling and export over continental margins.

Observations of Antarctic Slope Current Transport and Dense Water Flow in the Northwestern Weddell Sea

NASA Astrophysics Data System (ADS)

Azaneu, M. V. C.; Heywood, K. J.; Queste, B. Y.; Thompson, A. F.

2016-02-01

In early 2012 the GENTOO project deployed three Seagliders in the northwest Weddell Sea, acquiring high temporal and spatial resolution measurements around Powell Basin for a period of 10 weeks. The Antarctic Slope Front and associated currents form a physical and dynamical barrier to the cross-slope exchange of properties, influencing local and global ocean dynamics. The Seaglider dataset comprises 1598 temperature and salinity profiles and is used to better understand cross-slope processes. From this dataset, 582 glider profiles with altimetric information at the east Antarctic Peninsula continental slope are used to investigate the properties and thickness of the dense bottom water spilling off the shelf. The dense water is identified mostly over the slope, between the 500 and 1000 m isobaths. The dense layer is thickest around ˜ 63.33 °S, along the 1000 m isobath, becoming thinner onshore and towards northern areas. We also evaluate with unprecedented resolution the along-stream velocity and potential vorticity fields along the 17 transects across the eastern Antarctic Peninsula shelf-break and the 4 transects that cross the South Orkney Islands plateau. Using an improved hydrodynamic flight model, we reference the geostrophic shear to the glider-derived depth-averaged currents corrected for tides. In the western Weddell Sea, the geostrophic velocities fields indicate the presence of a surprisingly weakened Antarctic Slope Current (ASC) around 63.5 °S, possibly indicative of high eddy activity in the area. ASC transport in this southernmost section is less than 0.2 Sv. In a more northerly section (˜ 63.1 °S), the ASC transport reaches 6 Sv. The transects west of the South Orkney Island indicate a northward flow, opposite to the previously assumed regime. The results also show intensified northward bottom flows close to the slope, which can be related to processes occurring in the bottom boundary layer. The potential vorticity fields are used to identify potential instability mechanisms contributing to the cross-slope exchange of water mass properties.

Particle dynamics in the Eastern Mediterranean Sea: A synthesis based on light transmission, PMC, and POC archives (1991 2001)

NASA Astrophysics Data System (ADS)

Karageorgis, Aristomenis P.; Gardner, Wilford D.; Georgopoulos, Dimitris; Mishonov, Alexey V.; Krasakopoulou, Evangelia; Anagnostou, Christos

2008-02-01

During the last two decades light transmission (LT) data have been collected routinely in the Eastern Mediterranean Sea, within the framework of several research projects. A procedure was developed to obtain beam attenuation coefficient due to particles ( cp) at 660-670 nm adjusted for variations in mid-depth 'clear' water and instrumental drifts. Data from 3146 stations occupied between 1991 and 2001 were converted to a common format for the analysis of particulate matter (PM) temporal and spatial distribution patterns. The data were separated into 'wet' (December-May) and 'dry' (June-November) periods. The horizontal distribution of beam cp at various depths revealed clearly higher values in the surface nepheloid layer (SNL) in the vicinity of river mouths during the 'wet' period, whilst the increase was negligible during the 'dry' period. In contrast, the bottom nepheloid layer (BNL; 1-10 m above bottom) appeared to be turbid throughout the year, particularly on the continental shelves receiving riverine discharge. This feature is attributed to resuspension and advection of recently deposited bottom sediments due to waves and currents. However, the Eastern Mediterranean as a whole is impoverished in PM in the water column, particularly at depths >200 m. The behavior of surface-water cp revealed a strong relationship to mesoscale dynamic features. Cyclonic eddies, which upwell nutrient-rich waters toward the surface, favor primary production, which was identified as elevated beam cp values. Beam cp was correlated with PM concentration (PMC) and particulate organic carbon (POC) concentration obtained by bottle sampling. Although there were regional differences in the correlations, no significant seasonal variations were observed. Two generic equations were generated that can be used for a first-order estimate of PMC and POC from historical LT measurements conducted in the area, provided that data are handled according to the proposed methodology.

Lattice-mismatched GaInP LED devices and methods of fabricating same

DOEpatents

Mascarenhas, Angelo; Steiner, Myles A; Bhusal, Lekhnath; Zhang, Yong

2014-10-21

A method (100) of fabricating an LED or the active regions of an LED and an LED (200). The method includes growing, depositing or otherwise providing a bottom cladding layer (208) of a selected semiconductor alloy with an adjusted bandgap provided by intentionally disordering the structure of the cladding layer (208). A first active layer (202) may be grown above the bottom cladding layer (208) wherein the first active layer (202) is fabricated of the same semiconductor alloy, with however, a partially ordered structure. The first active layer (202) will also be fabricated to include a selected n or p type doping. The method further includes growing a second active layer (204) above the first active layer (202) where the second active layer (204) Is fabricated from the same semiconductor alloy.

Dynamics of oxygen supply and consumption during mainstream large-scale composting in China.

PubMed

Zeng, Jianfei; Shen, Xiuli; Han, Lujia; Huang, Guangqun

2016-11-01

This study characterized some physicochemical and biological parameters to systematically evaluate the dynamics of oxygen supply and consumption during large-scale trough composting in China. The results showed that long active phases, low maximum temperatures, low organic matter losses and high pore methane concentrations were observed in different composting layers. Pore oxygen concentrations in the top, middle and bottom layers maintained <5vol.% for 40, 42 and 45days, respectively, which accounted for more than 89% of the whole period. After each mechanical turning, oxygen was consumed at a stable respiration rate to a concentration of 5vol.% in no more than 99min and remained anaerobic in the subsequent static condition. The daily percentage of time under aerobic condition was no more than 14% of a single day. Therefore, improving FAS, adjusting aeration interval or combining turning with forced aeration was suggested to provide sufficient oxygen during composting. Copyright © 2016 Elsevier Ltd. All rights reserved.

New insights on the propagation of the Near Inertial Waves (NIW) governing the bottom dynamic of the Western Ionian Sea (Eastern Mediterranean Sea).

NASA Astrophysics Data System (ADS)

Lo Bue, N.; Artale, V.; Marullo, S.; Marinaro, G.; Embriaco, D.; Favali, P.; Beranzoli, L.

2017-12-01

The past general idea that the ocean-deep circulation is in quasi-stationary motion, has conditioned the observations of deep layers for a long time, excluding them from the majority of the surveys around the ocean world and influencing studies on the deep ocean processes. After the pioneering work of Munk (1966) highlighting the importance of bottom mixing processes, an underestimation of these issue has continued to persist for decades, due also to the difficulty to make reliable observations in the abyssal layers. The real awareness about the unsteady state of the abyssal layers has only risen recently and encourages us to wonder how the deep mechanisms can induce an internal instability and, consequently, affect the ocean circulation. The NIWs are characterized by a frequency near the inertial frequency f and can be generated by a variety of mechanisms, including wind, nonlinear interactions wave-shear flow and wave-topography, and geostrophic adjustments. NIWs represent one of the main high-frequency variabilities in the ocean, and they contain around half the kinetic energy observed in the oceans (Simmons et al. 2012) appearing as a prominent peak rising well above the Garrett & Munk (1975) continuum internal wave spectrum. As such, they upset the mixing processes in the upper ocean and they can interact strongly with mesoscale and sub-mesoscale motions. Likewise, NIWs likely affect the mixing of the deep ocean in ways that are just beginning to be understood. The analysis carried out on yearly time series collected by the bottom observatory SN1, the Western Ionian node of EMSO (European Multidisciplinary Seafloor and water column Observatory) Research Infrastructure, provides new important understanding on the role of the NIWs in the abyssal ocean. Also, this analysis is very useful to shed light on the possible mechanism that can trigger deep processes such as the abyssal vortex chains found by Rubino et al. (2012) in the Ionian abyssal plain of the Eastern Mediterranean (EM) basin. Finally, spectral analysis, including the Singular Spectrum Analysis (SSA) and Wavelet, allow us to explain how the NIWs can contributes to activate and increase the mixing in the bottom layers with significant impact on overall abyssal and deep circulation at local and regional scale (Mediterranean Sea).

Physics-based deformable organisms for medical image analysis

NASA Astrophysics Data System (ADS)

Hamarneh, Ghassan; McIntosh, Chris

2005-04-01

Previously, "Deformable organisms" were introduced as a novel paradigm for medical image analysis that uses artificial life modelling concepts. Deformable organisms were designed to complement the classical bottom-up deformable models methodologies (geometrical and physical layers), with top-down intelligent deformation control mechanisms (behavioral and cognitive layers). However, a true physical layer was absent and in order to complete medical image segmentation tasks, deformable organisms relied on pure geometry-based shape deformations guided by sensory data, prior structural knowledge, and expert-generated schedules of behaviors. In this paper we introduce the use of physics-based shape deformations within the deformable organisms framework yielding additional robustness by allowing intuitive real-time user guidance and interaction when necessary. We present the results of applying our physics-based deformable organisms, with an underlying dynamic spring-mass mesh model, to segmenting and labelling the corpus callosum in 2D midsagittal magnetic resonance images.

Subduction of a low-salinity water mass around the Xisha Islands in the South China Sea.

PubMed

Huang, Zhida; Zhuang, Wei; Liu, Hailong; Hu, Jianyu

2018-02-15

Based on three climatologically observed temperature and salinity datasets (i.e., GDEM-V3, SCSPOD14 and WOA13), this paper reports a low-salinity (~34.32) water mass in the subsurface-to-intermediate layer around the Xisha Islands in the South China Sea. This water mass mainly subducts from the surface layer into the intermediate layer, characterized by a relatively low potential vorticity tongue extending from the bottom of mixed layer to the thermocline, and accompanied by a thermocline ventilation in spring (especially in April). The potential dynamics are the joint effects of negative wind stress curl, and an anticyclonic eddy triggered by the inherent topographic effect of the Xisha Islands, reflecting that downward vertical motion dominates the subduction. Despite lacking of the homogenous temperature and density, the low-salinity water mass is to some extent similar to the classic mode water and can be regarded as a deformed mode water in the South China Sea.

Velocity and bottom-stress measurements in the bottom boundary layer, outer Norton Sound, Alaska.

USGS Publications Warehouse

Cacchione, D.A.; Drake, D.E.; Wiberg, P.

1982-01-01

We have used long-term measurements of near-bottom velocities at four heights above the sea floor in Norton Sound, Alaska, to compute hourly values of shear velocity u., roughness and bottom-drag coefficient. Maximum sediment resuspension and transport, predicted for periods when the computed value of u. exceeds a critical level, occur during peak tidal currents associated with spring tides. The fortnightly variation in u. is correlated with a distinct nepheloid layer that intensifies and thickens during spring tides and diminishes and thins during neap tides. The passage of a storm near the end of the experiment caused significantly higher u. values than those found during fair weather.-from Authros

Series interconnected photovoltaic cells and method for making same

DOEpatents

Albright, S.P.; Chamberlin, R.R.; Thompson, R.A.

1995-01-31

A novel photovoltaic module and method for constructing the same are disclosed. The module includes a plurality of photovoltaic cells formed on a substrate and laterally separated by interconnection regions. Each cell includes a bottom electrode, a photoactive layer and a top electrode layer. Adjacent cells are connected in electrical series by way of a conductive-buffer line. The buffer line is also useful in protecting the bottom electrode against severing during downstream layer cutting processes. 11 figs.

A modified gradient approach for the growth of low-density InAs quantum dot molecules by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Sharma, Nandlal; Reuter, Dirk

2017-11-01

Two vertically stacked quantum dots that are electronically coupled, so called quantum dot molecules, are of great interest for the realization of solid state building blocks for quantum communication networks. We present a modified gradient approach to realize InAs quantum dot molecules with a low areal density so that single quantum dot molecules can be optically addressed. The individual quantum dot layers were prepared by solid source molecular beam epitaxy depositing InAs on GaAs(100). The bottom quantum dot layer has been grown without substrate rotation resulting in an In-gradient across the surface, which translated into a density gradient with low quantum dot density in a certain region of the wafer. For the top quantum dot layer, separated from the bottom quantum dot layer by a 6 nm thick GaAs barrier, various InAs amounts were deposited without an In-gradient. In spite of the absence of an In-gradient, a pronounced density gradient is observed for the top quantum dots. Even for an In-amount slightly below the critical thickness for a single dot layer, a density gradient in the top quantum dot layer, which seems to reproduce the density gradient in the bottom layer, is observed. For more or less In, respectively, deviations from this behavior occur. We suggest that the obvious influence of the bottom quantum dot layer on the growth of the top quantum dots is due to the strain field induced by the buried dots.

Structural Response Prediction: Full-field, Dynamic Pressure and Displacement Measurements of a Panel Excited by Shock Boundary-layer Interaction

DTIC Science & Technology

2015-02-01

research cell14. The RC-19 facility is a continuous flow wind tunnel designed to study the mechanisms that govern the mixing and combustion process... angle of 39° from the tunnel bottom wall. The shock generator can translate 170 mm in the flow direction to allow for the shock wave to impinge from...approximate absolute pressure of 20.5 kPa. A series of “ wind -off” images for PSP were collected at that time. The tunnel was then started by setting the

Characteristics of the near-bottom suspended sediment field over the continental shelf off northern California based on optical attenuation measurements during STRESS and SMILE

NASA Astrophysics Data System (ADS)

Trowbridge, J. H.; Butman, B.; Limeburner, R.

1994-08-01

Time-series measurements of current velocity, optical attenuation and surface wave intensity obtained during the Sediment Transport Events on Shelves and Slopes (STRESS) experiments, combined with shipboard measurements of conductivity, temperature and optical attenuation obtained during the Shelf Mixed Layer Experiment (SMILE), provide a description of the sediment concentration field over the central and outer shelf off northern California. The questions addressed are: (1) existence and characteristics of bottom nepheloid layers and their relationship to bottom mixed layers; (2) characteristics of temporal fluctuations in sediment concentration and their relationship to waves and currents; (3) spatial scales over which suspended sediment concentrations vary horizontally; and (4) vertical distribution of suspended sediment.

Convection in an ideal gas at high Rayleigh numbers.

PubMed

Tilgner, A

2011-08-01

Numerical simulations of convection in a layer filled with ideal gas are presented. The control parameters are chosen such that there is a significant variation of density of the gas in going from the bottom to the top of the layer. The relations between the Rayleigh, Peclet, and Nusselt numbers depend on the density stratification. It is proposed to use a data reduction which accounts for the variable density by introducing into the scaling laws an effective density. The relevant density is the geometric mean of the maximum and minimum densities in the layer. A good fit to the data is then obtained with power laws with the same exponent as for fluids in the Boussinesq limit. Two relations connect the top and bottom boundary layers: The kinetic energy densities computed from free fall velocities are equal at the top and bottom, and the products of free fall velocities and maximum horizontal velocities are equal for both boundaries.

An analytical two-flow model to simulate the distribution of irradiance in coastal waters with a wind-roughed surface and bottom reflectance

NASA Astrophysics Data System (ADS)

Ma, Wei-Ming

1997-06-01

An analytical two-flow model is derived from the radiative transfer equation to simulate the distribution of irradiance in coastal waters with a wind-roughed surface and bottom reflectance. The model utilizes unique boundary conditions, including the surface slope of the downwelling and upwelling irradiance as well as the influence of wind and bottom reflectance on simulated surface reflectance. The developed model provides a simple mathematical concept for understanding the irradiant light flux and associated processes in coastal or fresh water as well as turbid estuarine waters. The model is applied to data from the Banana River and coastal Atlantic Ocean water off the east coast of central Florida, USA. The two-flow irradiance model is capable of simulating realistic above-surface reflectance signatures under wind-roughened air-water surface given realistic input parameters including a specular flux conversion coefficient, absorption coefficient, backscattering coefficient, atmospheric visibility, bottom reflectance, and water depth. The root-mean-squared error of the calculated above-surface reflectances is approximately 3% in the Banana River and is less than 15% in coastal Atlantic Ocean off the east of Florida. Result of the subsurface reflectance sensitivity analysis indicates that the specular conversion coefficient is the most sensitive parameter in the model, followed by the beam attenuation coefficient, absorption coefficient, water depth, backscattering coefficient, specular irradiance, diffuse irradiance, bottom reflectance, and wind speed. On the other hand, result of the above-surface reflectance sensitivity analysis indicates that the wind speed is the most important parameter, followed by bottom reflectance, attenuation coefficient, water depth, conversion coefficient, specular irradiance, downwelling irradiance, absorption coefficient, and backscattering coefficient. Model results depend on the accuracy of these parameters to a large degree and more important the water depth and value of the bottom reflectance. The results of this work indicates little change of subsurface or in-water reflectances, due to variations of wind speed and observation angle. Simulations of the wind effect on the total downwelling irradiance from the two- flow model indicates that the total downwelling irradiance just below a wind-roughened water surface increases to about 1% of the total downwelling irradiance on a calm water surface when the sun is near zenith and increases to about 3% when the sun is near the horizon. This analytically based model, solved or developed utilizing the unique boundary conditions, can be applied to remote sensing of oceanic upper mixed layer dynamics, plant canopies, primary production, and shallow water environments with different bottom type reflectances. Future applications may include determining effects of sediment resuspension of bottom sediments in the bottom boundary layer on remotely sensed data.

A new method for estimating the turbulent heat flux at the bottom of the daily mixed layer

NASA Technical Reports Server (NTRS)

Imawaki, Shiro; Niiler, Pearn P.; Gautier, Catherine H.; Knox, Robert A.; Halpern, David

1988-01-01

Temperature data in the mixed layer and net solar irradiance data at the sea surface are used to estimate the vertical turbulent heat flux at the bottom of the daily mixed layer. The method is applied to data obtained in the eastern tropical Pacific, where the daily cycle in the temperature field is confined to the upper 10-25 m. Equatorial turbulence measurements indicate that the turbulent heat flux is much greater during nighttime than daytime.

Crystal accumulation in the Hanford Waste Treatment Plant high level waste melter. Preliminary settling and resuspension testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fox, K. M.; Fowley, M. D.; Miller, D. H.

2016-05-01

The full-scale, room-temperature Hanford Tank Waste Treatment and Immobilization Plant (WTP) High-Level Waste (HLW) melter riser test system was successfully operated with silicone oil and magnetite particles at a loading of 0.1 vol %. Design and construction of the system and instrumentation, and the selection and preparation of simulant materials, are briefly reviewed. Three experiments were completed. A prototypic pour rate was maintained, based on the volumetric flow rate. Settling and accumulation of magnetite particles were observed at the bottom of the riser and along the bottom of the throat after each experiment. The height of the accumulated layer atmore » the bottom of the riser, after the first pouring experiment, approximated the expected level given the solids loading of 0.1 vol %. More detailed observations of particle resuspension and settling were made during and after the third pouring experiment. The accumulated layer of particles at the bottom of the riser appeared to be unaffected after a pouring cycle of approximately 15 minutes at the prototypic flow rate. The accumulated layer of particles along the bottom of the throat was somewhat reduced after the same pouring cycle. Review of the time-lapse recording showed that some of the settling particles flow from the riser into the throat. This may result in a thicker than expected settled layer in the throat.« less

Measurements in the bottom boundary layer on the Amazon subaqueous delta

USGS Publications Warehouse

Cacchione, D.A.; Drake, D.E.; Kayen, R.W.; Sternberg, R.W.; Kineke, G.C.; Tate, G.B.

1995-01-01

An instrumented bottom tripod (GEOPROBE) recorded flow and suspended sediment data in the bottom boundary layer above the lower foresets of the Amazon subaqueous delta in 65 m mean water depth in February, 1990. After about two weeks of operation the apparent seafloor at the tripod site rapidly elevated over a 14-hour period by about 44 cm. This sudden change, which was detected by an acoustic altimeter and which caused the loss of signals from the lowermost GEOPROBE current and optical sensors, is though to have been caused by the incursion of a dense bottom layer of fluid mud that migrated downslope from shallower sections of the foresets. The fluid-mud migration across the outer part of the foresets, if a repetitive and occasional process in this region, could be a major mechanism for episodic seaward growth of the delta. Current velocity profiles are used to estimate shear velocities, u*, and roughness lengths, zo, during the first two weeks of measurements. -from Authors

Fruit position within the canopy affects kernel lipid composition of hazelnuts.

PubMed

Pannico, Antonio; Cirillo, Chiara; Giaccone, Matteo; Scognamiglio, Pasquale; Romano, Raffaele; Caporaso, Nicola; Sacchi, Raffaele; Basile, Boris

2017-11-01

The aim of this research was to study the variability in kernel composition within the canopy of hazelnut trees. Kernel fresh and dry weight increased linearly with fruit height above the ground. Fat content decreased, while protein and ash content increased, from the bottom to the top layers of the canopy. The level of unsaturation of fatty acids decreased from the bottom to the top of the canopy. Thus, the kernels located in the bottom layers of the canopy appear to be more interesting from a nutritional point of view, but their lipids may be more exposed to oxidation. The content of different phytosterols increased progressively from bottom to top canopy layers. Most of these effects correlated with the pattern in light distribution inside the canopy. The results of this study indicate that fruit position within the canopy is an important factor in determining hazelnut kernel growth and composition. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Origins of Moiré Patterns in CVD-grown MoS2 Bilayer Structures at the Atomic Scales.

PubMed

Wang, Jin; Namburu, Raju; Dubey, Madan; Dongare, Avinash M

2018-06-21

The chemical vapor deposition (CVD)-grown two-dimensional molybdenum disulfide (MoS 2 ) structures comprise of flakes of few layers with different dimensions. The top layers are relatively smaller in size than the bottom layers, resulting in the formation of edges/steps across adjacent layers. The strain response of such few-layer terraced structures is therefore likely to be different from exfoliated few-layered structures with similar dimensions without any terraces. In this study, the strain response of CVD-grown few-layered MoS 2 terraced structures is investigated at the atomic scales using classic molecular dynamics (MD) simulations. MD simulations suggest that the strain relaxation of CVD-grown triangular terraced structures is observed in the vertical displacement of the atoms across the layers that results in the formation of Moiré patterns. The Moiré islands are observed to nucleate at the corners or edges of the few-layered structure and propagate inwards under both tensile and compressive strains. The nucleation of these islands is observed to happen at tensile strains of ~ 2% and at compressive strains of ~2.5%. The vertical displacements of the atoms and the dimensions of the Moiré islands predicted using the MD simulation are in excellent agreement with that observed experimentally.

Measurement and simulation of top- and bottom-illuminated solar-blind AlGaN metal-semiconductor-metal photodetectors with high external quantum efficiencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brendel, Moritz, E-mail: moritz.brendel@fbh-berlin.de; Helbling, Markus; Knigge, Andrea

2015-12-28

A comprehensive study on top- and bottom-illuminated Al{sub 0.5}Ga{sub 0.5}N/AlN metal-semiconductor-metal (MSM) photodetectors having different AlGaN absorber layer thickness is presented. The measured external quantum efficiency (EQE) shows pronounced threshold and saturation behavior as a function of applied bias voltage up to 50 V reaching about 50% for 0.1 μm and 67% for 0.5 μm thick absorber layers under bottom illumination. All experimental findings are in very good accordance with two-dimensional drift-diffusion modeling results. By taking into account macroscopic polarization effects in the hexagonal metal-polar +c-plane AlGaN/AlN heterostructures, new insights into the general device functionality of AlGaN-based MSM photodetectors are obtained. The observedmore » threshold/saturation behavior is caused by a bias-dependent extraction of photoexcited holes from the Al{sub 0.5}Ga{sub 0.5}N/AlN interface. While present under bottom illumination for any AlGaN layer thickness, under top illumination this mechanism influences the EQE-bias characteristics only for thin layers.« less

Abyssal Upwelling and Downwelling and the role of boundary layers

NASA Astrophysics Data System (ADS)

McDougall, T. J.; Ferrari, R. M.

2016-02-01

The bottom-intensified mixing activity arising from the interaction of internal tides with bottom topography implies that the dianeutral advection in the ocean interior is downwards, rather than upwards as is required by continuity. The upwelling of Bottom Water through density surfaces in the deep ocean is however possible because of the sloping nature of the sea floor. A budget study of the abyss (deeper than 2000m) will be described that shows that while the upwelling of Bottom Water might be 25 Sv, this is achieved by very strong upwelling in the bottom turbulent boundary layer (of thickness 50m) of 100 Sv and strong downwelling in the ocean interior of 75 Sv. This downwelling occurs within 10 degrees of longitude of the continental boundaries. This near-boundary confined strong upwelling and downwelling clearly has implications for the Stommel-Arons circulation.

Influence of nano-oxide layers on IrMn pinned bottom spin-valves at different positions

NASA Astrophysics Data System (ADS)

Qiu, J. J.; Li, K. B.; Luo, P.; Zheng, Y. K.; Wu, Y. H.

2004-05-01

The influence of nano-oxide layer (NOL) inserted at different positions on interlayer coupling (Hin), coercivity of free layer (Hcf), exchange bias (Hex) and MR ratio of IrMn pinned bottom type spin-valves (SV) were studied. Weak antiferromagnetic interlayer coupling was observed in NOL-added SV. The NOL inside pinned layer and after free layer can enhance the MR ratio remarkably. MR of SV with a structure Ta3/NiFe2/IrMn6/CoFe1/NOL/CoFe2.3/Cu2.2/CoFe2.3/AlO reached 18.2%. This is one of the best values ever reported for all-metal single spin-valves.

Global chaotization of fluid particle trajectories in a sheared two-layer two-vortex flow.

PubMed

Ryzhov, Evgeny A; Koshel, Konstantin V

2015-10-01

In a two-layer quasi-geostrophic approximation, we study the irregular dynamics of fluid particles arising due to two interacting point vortices embedded in a deformation flow consisting of shear and rotational components. The two vortices are arranged within the bottom layer, but an emphasis is on the upper-layer fluid particle motion. Vortices moving in one layer induce stirring of passive scalars in the other layer. This is of interest since point vortices induce singular velocity fields in the layer they belong to; however, in the other layer, they induce regular velocity fields that generally result in a change in passive particle stirring. If the vortices are located at stagnation points, there are three different types of the fluid flow. We examine how properties of each flow configuration are modified if the vortices are displaced from the stagnation points and thus circulate in the immediate vicinity of these points. To that end, an analysis of the steady-state configurations is presented with an emphasis on the frequencies of fluid particle oscillations about the elliptic stagnation points. Asymptotic relations for the vortex and fluid particle zero-oscillation frequencies are derived in the vicinity of the corresponding elliptic points. By comparing the frequencies of fluid particles with the ones of the vortices, relations between the parameters that lead to enhanced stirring of fluid particles are established. It is also demonstrated that, if the central critical point is elliptic, then the fluid particle trajectories in its immediate vicinity are mostly stable making it harder for the vortex perturbation to induce stirring. Change in the type of the central point to a hyperbolic one enhances drastically the size of the chaotic dynamics region. Conditions on the type of the central critical point also ensue from the derived asymptotic relations.

A preliminary study on puncture resistances of top and bottom layers of multi-layered needlepunched nonwoven geotextiles

NASA Astrophysics Data System (ADS)

Alan, G.; Tercan, M.

2017-10-01

Needlepunched nonwoven textiles are commonly used as geotextiles for various applications. Considering both environmental and economical benefits, utilization of recycled fibres in nonwoven geotextiles has become an attractive issue. Within this scope, the aim of this study is to evaluate the puncture resistance performances of top and bottom layers of multi-layered needle punched nonwovens made of recycled fibres to be used as membrane protective geotextiles by comparing them with those of made from polypropylene and polyester fibres. Puncture resistance results indicated that nonwovens made of recycled fibres demonstrated good performances at this preliminary stage.

The Sinking and Spreading of The Antarctic Deep Ice Shelf Water In The Ross Sea Studied By In Situ Observaions and Numerical Modeling

NASA Astrophysics Data System (ADS)

Rubino, A.; Budillon, G.; Pierini, S.; Spezie, G.

The sinking and spreading of the Deep Ice Shelf Water (DISW) in the Ross Sea are analyzed using in situ observations and the results of a nonlinear, reduced-gravity, frontal layered numerical "plume" model which is able to simulate the motion of a bottom-arrested current over realistic topography. The model is forced by prescribing the thickness of the DISW vein as well as its density structure at the southern model boundary. The ambient temperature and salinity are imposed using hydrographic data acquired by the Italian PNRA-CLIMA project. In the model water of the quiescent ambient ocean is allowed to entrain in the active deep layer due to a simple param- eterization of turbulent mixing. The importance of forcing the model with a realistic ambient density is demonstrated by carrying out a numerical simulation in which the bottom active layer is forced using an idealized ambient density. In a more realis- tic simulation the path and the density structure of the DISW vein flowing over the Challenger Basin are obtained and are found to be in good agreement with data. The evolution of the deep current beyond the continental shelf is also simulated. It provides useful information on the water flow and mixing in a region of the Ross Sea where the paucity of experimental data does not allow for a detailed description of the deep ocean dynamics.

Potential Mechanisms Underlying Intercortical Signal Regulation via Cholinergic Neuromodulators

PubMed Central

Whittington, Miles A.; Kopell, Nancy J.

2015-01-01

The dynamical behavior of the cortex is extremely complex, with different areas and even different layers of a cortical column displaying different temporal patterns. A major open question is how the signals from different layers and different brain regions are coordinated in a flexible manner to support function. Here, we considered interactions between primary auditory cortex and adjacent association cortex. Using a biophysically based model, we show how top-down signals in the beta and gamma regimes can interact with a bottom-up gamma rhythm to provide regulation of signals between the cortical areas and among layers. The flow of signals depends on cholinergic modulation: with only glutamatergic drive, we show that top-down gamma rhythms may block sensory signals. In the presence of cholinergic drive, top-down beta rhythms can lift this blockade and allow signals to flow reciprocally between primary sensory and parietal cortex. SIGNIFICANCE STATEMENT Flexible coordination of multiple cortical areas is critical for complex cognitive functions, but how this is accomplished is not understood. Using computational models, we studied the interactions between primary auditory cortex (A1) and association cortex (Par2). Our model is capable of replicating interaction patterns observed in vitro and the simulations predict that the coordination between top-down gamma and beta rhythms is central to the gating process regulating bottom-up sensory signaling projected from A1 to Par2 and that cholinergic modulation allows this coordination to occur. PMID:26558772

Warmer, deeper, and greener mixed layers in the North Atlantic subpolar gyre over the last 50 years.

PubMed

Martinez, Elodie; Raitsos, Dionysios E; Antoine, David

2016-02-01

Shifts in global climate resonate in plankton dynamics, biogeochemical cycles, and marine food webs. We studied these linkages in the North Atlantic subpolar gyre (NASG), which hosts extensive phytoplankton blooms. We show that phytoplankton abundance increased since the 1960s in parallel to a deepening of the mixed layer and a strengthening of winds and heat losses from the ocean, as driven by the low frequency of the North Atlantic Oscillation (NAO). In parallel to these bottom-up processes, the top-down control of phytoplankton by copepods decreased over the same time period in the western NASG, following sea surface temperature changes typical of the Atlantic Multi-decadal Oscillation (AMO). While previous studies have hypothesized that climate-driven warming would facilitate seasonal stratification of surface waters and long-term phytoplankton increase in subpolar regions, here we show that deeper mixed layers in the NASG can be warmer and host a higher phytoplankton biomass. These results emphasize that different modes of climate variability regulate bottom-up (NAO control) and top-down (AMO control) forcing on phytoplankton at decadal timescales. As a consequence, different relationships between phytoplankton, zooplankton, and their physical environment appear subject to the disparate temporal scale of the observations (seasonal, interannual, or decadal). The prediction of phytoplankton response to climate change should be built upon what is learnt from observations at the longest timescales. © 2015 John Wiley & Sons Ltd.

Series interconnected photovoltaic cells and method for making same

DOEpatents

Albright, Scot P.; Chamberlin, Rhodes R.; Thompson, Roger A.

1995-01-01

A novel photovoltaic module (10) and method for constructing the same are disclosed. The module (10) includes a plurality of photovoltaic cells (12) formed on a substrate (14) and laterally separated by interconnection regions (15). Each cell (12) includes a bottom electrode (16), a photoactive layer (18) and a top electrode layer (20). Adjacent cells (12) are connected in electrical series by way of a conductive-buffer line (22). The buffer line (22) is also useful in protecting the bottom electrode (16) against severing during downstream layer cutting processes.

Hydrodynamics of Bacterial Cooperation

NASA Astrophysics Data System (ADS)

Petroff, A.; Libchaber, A.

2012-12-01

Over the course of the last several decades, the study of microbial communities has identified countless examples of cooperation between microorganisms. Generally—as in the case of quorum sensing—cooperation is coordinated by a chemical signal that diffuses through the community. Less well understood is a second class of cooperation that is mediated through physical interactions between individuals. To better understand how the bacteria use hydrodynamics to manipulate their environment and coordinate their actions, we study the sulfur-oxidizing bacterium Thiovulum majus. These bacteria live in the diffusive boundary layer just above the muddy bottoms of ponds. As buried organic material decays, sulfide diffuses out of the mud. Oxygen from the pond diffuses into the boundary layer from above. These bacteria form communities—called veils— which are able to transport nutrients through the boundary layer faster than diffusion, thereby increasing their metabolic rate. In these communities, bacteria attach to surfaces and swim in place. As millions of bacteria beat their flagella, the community induces a macroscopic fluid flow, which mix the boundary layer. Here we present experimental observations and mathematical models that elucidate the hydrodynamics linking the behavior of an individual bacterium to the collective dynamics of the community. We begin by characterizing the flow of water around an individual bacterium swimming in place. We then discuss the flow of water and nutrients around a small number of individuals. Finally, we present observations and models detailing the macroscopic dynamics of a Thiovulum veil.

Die singulation method and package formed thereby

DOEpatents

Anderson, Robert C [Tucson, AZ; Shul, Randy J [Albuquerque, NM; Clews, Peggy J [Tijeras, NM; Baker, Michael S [Albuquerque, NM; De Boer, Maarten P [Albuquerque, NM

2012-08-07

A method is disclosed for singulating die from a substrate having a sacrificial layer and one or more device layers, with a retainer being formed in the device layer(s) and anchored to the substrate. Deep Reactive Ion Etching (DRIE) etching of a trench through the substrate from the bottom side defines a shape for each die. A handle wafer is then attached to the bottom side of the substrate, and the sacrificial layer is etched to singulate the die and to form a frame from the retainer and the substrate. The frame and handle wafer, which retain the singulated die in place, can be attached together with a clamp or a clip and to form a package for the singulated die. One or more stops can be formed from the device layer(s) to limit a sliding motion of the singulated die.

[Effects of mulching management on biomass of Phyllostachys praecox and soil fertility].

PubMed

Zhai, Wan Lu; Yang, Chuan Bao; Zhang, Xiao Ping; Gao, Gui Bin; Zhong, Zhe Ke

2018-04-01

We analyzed the dynamics of stand growth and soil nutrient availability during the degradation processes of Phyllostachys praecox plantation, taking the advantage of bamboo forest stands with different mulching ages (0, 3, 6, 9 and 12 a). The results showed the aboveground and belowground biomass of bamboo forest reached the maximum value when they were covered by three years, which was significantly increased by 14.6% and 146.6% compared with the control. The soil nutrient content was affected by the mulching age and soil layer. Soil nutrients gradually accumulated in upper layer. Soil organic carbon and total nitrogen content were increased with the increases of coverage years. The soil total phosphorus content at different soil layers showed a trend of decreasing first and then increasing. It was the lowest level in the surface layer (0-20 cm) and the bottom (40-60 cm) in 6 years, and the subsurface (20-40 cm) soil reached the lowest level in three years. The total potassium content kept increasing in 0-20 cm soil layer, but decreased during the first three years of mulching and then increased in 20-60 cm soil layer. The comprehensive index of soil fertility quality was greatly improved after nine years mulching, with fertility of subsurface soil being better than that of surface and bottom soils. There was no relationship between the soil fertility index and biomass of different organs in bamboo in the different mulching ages. In the subsurface, however, nitrogen content was negatively related to leaf biomass and potassium was negatively correlated with the biomass of leaves and whip roots. Our results indicated that excessive accumulation of soil nutrients seriously inhibited the propagation and biomass accumulation of P. praecox after long-term mulching management and a large amount of fertilizer, which further aggravated the degradation of bamboo plantation.

INDIVIDUAL TURBULENT CELL INTERACTION: BASIS FOR BOUNDARY LAYER ESTABLISHMENT

EPA Science Inventory

Boundary layers are important in determining the forces on objects in flowing fluids, mixing characteristics, and other phenomena. For example, benthic boundary layers are frequently active resuspension layers that determine bottom turbidity and transniissivity. Traditionally, bo...

Research on Hydrodynamic Interference Suppression of Bottom-Mounted Monitoring Platform with Fairing Structure

NASA Astrophysics Data System (ADS)

Wang, Zhen; Zheng, Yi; Mao, Yu-feng; Wang, Ya-zhou; Yu, Yan-ting; Liu, Hong-ning

2018-03-01

In the disturbance of unsteady flow field under the sea, the monitoring accuracy and precision of the bottom-mounted acoustic monitoring platform will decrease. In order to reduce the hydrodynamic interference, the platform wrapped with fairing structure and separated from the retrieval unit is described. The suppression effect evaluation based on the correlation theory of sound pressure and particle velocity for spherical wave in infinite homogeneous medium is proposed and the difference value between them is used to evaluate the hydrodynamic restraining performance of the bottom-mounted platform under far field condition. Through the sea test, it is indicated that the platform with sparse layers fairing structure (there are two layers for the fairing, in which the inside layer is 6-layers sparse metal net, and the outside layer is 1-layer polyester cloth, and then it takes sparse layers for short) has no attenuation in the sound pressure response to the sound source signal, but obvious suppression in the velocity response to the hydrodynamic noise. The effective frequency of the fairing structure is decreased below 10 Hz, and the noise magnitude is reduced by 10 dB. With the comparison of different fairing structures, it is concluded that the tighter fairing structure can enhance the performance of sound transmission and flow restraining.

Liquid/liquid interface layering of 1-butanol and [bmim]PF6 ionic liquid: a nonlinear vibrational spectroscopy and molecular dynamics simulation study.

PubMed

Iwahashi, Takashi; Ishiyama, Tatsuya; Sakai, Yasunari; Morita, Akihiro; Kim, Doseok; Ouchi, Yukio

2015-10-14

IR-visible sum-frequency generation (IV-SFG) vibrational spectroscopy and a molecular dynamics (MD) simulation were used to study the local layering order at the interface of 1-butanol-d9 and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6), a room-temperature ionic liquid (RTIL). The presence of a local non-polar layer at the interface of the two polar liquids was successfully demonstrated. In the SFG spectra of 1-butanol-d9, we observed significant reduction and enhancement in the strength of the CD3 symmetric stretching (r(+)) mode and the antisymmetric stretching (r(-)) mode peaks, respectively. The results can be well explained by the presence of an oppositely oriented quasi-bilayer structure of butanol molecules, where the bottom layer is strongly bound by hydrogen-bonding with the PF6(-) anion. MD simulations reveal that the hydrogen-bonding of butanol with the PF6(-) anion causes the preferential orientation of the butanols; the restriction on the rotational distribution of the terminal methyl group along their C3 axis enhances the r(-) mode. As for the [bmim](+) cations, the SFG spectra taken within the CH stretch region indicate that the butyl chain of [bmim](+) points away from the bulk RTIL phase to the butanol phase at the interface. Combining the SFG spectroscopy and MD simulation results, we propose an interfacial model structure of layering, in which the butyl chains of the butanol molecules form a non-polar interfacial layer with the butyl chains of the [bmim](+) cations at the interface.

Learning enhances the relative impact of top-down processing in the visual cortex

PubMed Central

Makino, Hiroshi; Komiyama, Takaki

2015-01-01

Theories have proposed that in sensory cortices learning can enhance top-down modulation by higher brain areas while reducing bottom-up sensory inputs. To address circuit mechanisms underlying this process, we examined the activity of layer 2/3 (L2/3) excitatory neurons in the mouse primary visual cortex (V1) as well as L4 neurons, the main bottom-up source, and long-range top-down projections from the retrosplenial cortex (RSC) during associative learning over days using chronic two-photon calcium imaging. During learning, L4 responses gradually weakened, while RSC inputs became stronger. Furthermore, L2/3 acquired a ramp-up response temporal profile with learning, coinciding with a similar change in RSC inputs. Learning also reduced the activity of somatostatin-expressing inhibitory neurons (SOM-INs) in V1 that could potentially gate top-down inputs. Finally, RSC inactivation or SOM-IN activation was sufficient to partially reverse the learning-induced changes in L2/3. Together, these results reveal a learning-dependent dynamic shift in the balance between bottom-up and top-down information streams and uncover a role of SOM-INs in controlling this process. PMID:26167904

Experimental study of a depth-encoding PET detector inserting horizontal-striped glass between crystal layers

NASA Astrophysics Data System (ADS)

Yang, J.; Kim, K. B.; Choi, Y.; Kang, J.

2018-04-01

A depth-encoding positron emission tomography (PET) detector inserting a horizontal-striped glass between pixilated scintillation crystal layers was developed and experimentally evaluated. The detector consists of 2-layers of 4×4 LYSO array arranged with a 3.37 mm pitch. Horizontal-striped glasses with 1×4 array with different thickness of 3, 4 and 5 mm were inserted between top- and bottom-crystal layers. Bottom surface of bottom-layer was optically coupled to a 4×4 GAPD array. Sixteen output signals from DOI-PET detector were multiplexed by modified resistive charge division (RCD) networks and multiplexed signals were fed into custom-made charge-sensitive preamplifiers. The four amplified signals were digitized and recorded by the custom-made DAQ system based on FPGA. The four digitized outputs were post-processed and converted to flood histograms for each interaction event. Experimental results revealed that all crystal pixels were clearly identified on the 2D flood histogram without overlapping. Patterns of the 2D flood histogram were constituted with arrangements of [bottom–top–bottom–top–\\ldots–top–bottom–top–bottom] crystal responses in X-direction. These could be achieved by employing horizontal-striped glass that controlled the extent of light dispersion towards the X-direction in crystal layers for generation of a different position mapping for each layer and the modified RCD network that controls degree of charge sharing in readout electronics for reduction of identification error. This study demonstrated the proposed DOI-PET detector can extract the 3D γ-ray interaction position without considerable performance degradation of PET detector from the 2D flood histogram.

Molecular Modeling of the Binding Structures in the Interlayer Adsorption of a Tetracycline Antibiotic by Smectite Clays

NASA Astrophysics Data System (ADS)

Aristilde, L.

2009-12-01

A controlling factor in the fate of antibiotics in the environment is their sequestration in soil particles including clay minerals. Of special interest is the interlayer adsorption by smectite clays, which has been shown to influence both the bioavailability and persistence of antibiotics in the soil environment. However, the interlayer structures of the bound antibiotics, essential to an accurate understanding of the adsorption mechanisms, are not well understood. Molecular simulations of oxytetracycline (OTC) with a model montmorillonite (MONT) clay were performed to gain insights into these structures for tetracycline antibiotics. Monte Carlo simulations were used for explorations of the clay layer spacing required for the adsorption of the antibiotic under different hydration states of the clay interlayer; these preliminary results were validated with previous X-ray diffraction patterns obtained following sorption experiments of OTC with MONT. Molecular dynamics relaxation simulations were performed subsequently in order to obtain geometry-optimized structures of the binding conformations of the intercalated antibiotic in the model MONT layers. This study contributes to a mechanistic understanding of the factors controlling the interlayer adsorption of the tetracycline antibiotics by the expandable smectite clay minerals. Figure 1. Optimized Monte Carlo simulation cell of OTC in the interlayer of MONT: perspective side view (top) and bottom view (bottom).

Soil Characterization and Site Response of Marine and Continental Environments

NASA Astrophysics Data System (ADS)

Contreras-Porras, R. S.; Huerta-Lopez, C. I.; Martinez-Cruzado, J. A.; Gaherty, J. B.; Collins, J. A.

2009-05-01

An in situ soil properties study was conducted to characterize both site and shallow layer sediments under marine and continental environments. Data from the SCoOBA (Sea of Cortez Ocean Bottom Array) seismic experiment and in land ambient vibration measurements on the urban areas of Tijuana, B. C., and Ensenada, B. C., Mexico were used in the analysis. The goal of this investigation is to identify and to analyze the effect of the physical/geotechnical properties of the ground on the site response upon seismic excitations in both marine and continental environments. The time series were earthquakes and background noise recorded within interval of 10/2005 to 10/2006 in the Gulf of California (GoC) with very-broadband Ocean Bottom Seismographs (OBS), and ambient vibration measurements collected during different time periods on Tijuana and Ensenada urban areas. The data processing and analysis was conducted by means of the H/V Spectral Ratios (HVSPR) of multi component data, the Random Decrement Method (RDM), and Blind Deconvolution (BD). This study presents ongoing results of a long term project to characterize the local site response of soil layers upon dynamic excitations using digital signal processing algorithms on time series, as well as the comparison between the results these methodologies are providing.

Wrinkling of solidifying polymeric coatings

NASA Astrophysics Data System (ADS)

Basu, Soumendra Kumar

2005-07-01

In coatings, wrinkles are viewed as defects or as desired features for low gloss, and texture. In either case, discovering the origin of wrinkles and the conditions that lead to their formation is important. This research examines what wrinkling requires and proposes a mechanism to explain the observations. All curing wrinkling coatings contain multi-functional reactants. Upon curing, all develop a depth-wise gradient in solidification that result in a cross-linked elastic skin atop a viscous bottom layer. It is hypothesized that compressive stress develops in the skin when liquid below diffuses up into the skin. High enough compressive stress buckles the skin to produce wrinkles. The hypothesis is substantiated by experimental and theoretical evidences. Effects of various application and compositional parameters on wrinkle size in a liquid-applied acrylic coating and a powder-applied epoxy coating were examined. All three components, namely resin, cross-linker and catalyst blocked with at least equimolar volatile blocker, proved to be required for wrinkling. The wrinkling phenomenon was modeled with a theory that accounts for gradient generation, cross-linking reaction and skinning; predictions compared well with observations. Two-layer non-curing coatings that have a stiff elastic layer atop a complaint elastic bottom layer wrinkled when the top layer is compressed. The top layer was compressed by either moisture absorption or differential thermal expansion. Experimental observations compared well with predictions from a theory based on force balance in multilayer systems subjected to differential contraction or expansion. A model based on the Flory-Rehner free energy of a constrained cross-linked gel was constructed that predicts the compressive stress generated in a coating when it absorbs solvent. Linear stability analysis predicts that when a compressed elastic layer is attached atop a viscous layer, it is always unstable to buckles whose wavelength exceeds a critical value; more cross-linking and poor solvent produce higher wavelength, lower amplitude wrinkles. When a compressed elastic layer is attached atop an elastic layer and subjected to more than a critical compressive stress, it is unstable to intermediate wavelengths of buckling; better solvent, higher ratio of bottom-to-top layer thickness, and lower bottom layer modulus produce higher wavelength, higher amplitude wrinkles.

Layered growth with bottom-spray granulation for spray deposition of drug.

PubMed

Er, Dawn Z L; Liew, Celine V; Heng, Paul W S

2009-07-30

The gap in scientific knowledge on bottom-spray fluidized bed granulation has emphasized the need for more studies in this area. This paper comparatively studied the applicability of a modified bottom-spray process and the conventional top-spray process for the spray deposition of a micronized drug during granulation. The differences in circulation pattern, mode of growth and resultant granule properties between the two processes were highlighted. The more ordered and consistent circulation pattern of particles in a bottom-spray fluidized bed was observed to give rise to layered granule growth. This resulted in better drug content uniformity among the granule batches and within a granule batch. The processes' sensitivities to wetting and feed material characteristics were also compared and found to differ markedly. Less robustness to differing process conditions was observed for the top-spray process. The resultant bottom-spray granules formed were observed to be less porous, more spherical and had good flow properties. The bottom-spray technique can thus be potentially applied for the spray deposition of drug during granulation and was observed to be a good alternative to the conventional technique for preparing granules.

Directional bottom roughness associated with waves, currents, and ripples

USGS Publications Warehouse

Sherwood, Christopher R.; Rosati, Julie D.; Wang, Ping; Roberts, Tiffany M.

2011-01-01

Roughness lengths are used in wave-current bottom boundary layer models to parameterize drag associated with grain roughness, the effect of saltating grains during sediment transport, and small-scale bottom topography (ripples and biogenic features). We made field measurements of flow parameters and recorded sonar images of ripples at the boundary of a sorted-bedform at ~12-m depth on the inner shelf for a range of wave and current conditions over two months. We compared estimates of apparent bottom roughness inferred from the flow measurements with bottom roughness calculated using ripple geometry and the Madsen (1994) one-dimensional (vertical) wave-current bottom boundary layer model. One result of these comparisons was that the model over predicted roughness of flow from the dormant large ripples when waves were small. We developed a correction to the ripple-roughness model that incorporates an apparent ripple wavelength related to the combined wave-current flow direction. This correction provides a slight improvement for low-wave conditions, but does not address several other differences between observations and the modeled roughness.

A Physical Mechanism for the Asymmetry in Top-Down and Bottom-Up Diffusion.

NASA Astrophysics Data System (ADS)

Wyngaard, J. C.

1987-04-01

Recent large-eddy simulations of the vertical diffusion of a passive, conservative scalar through the convective boundary layer (CBL) show strikingly different eddy diffusivity profiles in the `top-down' and `bottom-up' cases. These results indicate that for a given turbulent velocity field and associated scalar flux, the mean change in scalar mixing ratio across the CBL is several times larger if the flux originates at the top of the boundary layer (i.e., in top-down diffusion) rather than at the bottom. The large-eddy simulation (LES) data show that this asymmetry is due to a breakdown of the eddy-diffusion concept.A simple updraft-downdraft model of the CBL reveals a physical mechanism that could cause this unexpected behavior. The large, positive skewness of the convectively driven vertical velocity gives an appreciably higher probability of downdrafts than updrafts; this excess probability of downdrafts, interacting with the time changes of the mean mixing ratio caused by the nonstationarity of the bottom-up and top-down diffusion processes, decreases the equilibrium value of mean mixing-ratio jump across the mixed layer in the bottom-up case and increases it in the top-down case. The resulting diffusion asymmetry agrees qualitatively with that found through LES.

Characterization of PZT Capacitor Structures with Various Electrode Materials Processed In-Situ Using AN Automated, Rotating Elemental Target, Ion Beam Deposition System

NASA Astrophysics Data System (ADS)

Gifford, Kenneth Douglas

Ferroelectric thin film capacitor structures containing lead zirconate titanate (PZT) as the dielectric, with the chemical formula Pb(rm Zr_{x }Ti_{1-x})O_3, were synthesized in-situ with an automated ion beam sputter deposition system. Platinum (Pt), conductive ruthenium oxide (RuO_2), and two types of Pt-RuO_2 hybrid electrodes were used as the electrode materials. The capacitor structures are characterized in terms of microstructure and electrical characteristics. Reduction or elimination of non-ferroelectric phases, that nucleate during PZT processing on Pt/TiO _2/MgO and RuO_2/MgO substrates, is achieved by reducing the thickness of the individually deposited layers and by interposing a buffer layer (~100-200A) of PbTiO _3 (PT) between the bottom electrode and the PZT film. Capacitor structures containing a Pt electrode exhibit poor fatigue resistance, irregardless of the PZT microstructure or the use of a PT buffer layer. From these results, and results from similar capacitors synthesized with sol-gel and laser ablation, PZT-based capacitor structures containing Pt electrodes are considered to be unsuitable for use in memory devices. Using a PT buffer layer, in capacitor structures containing RuO_2 top and bottom electrodes and polycrystalline, highly (101) oriented PZT, reduces or eliminates the nucleation of zirconium-titanium oxide, non-ferroelectric species at the bottom electrode interface during processing. This results in good fatigue resistance up to ~2times10^ {10} switching cycles. DC leakage current density vs. time measurements follow the Curie-von Schweidler law, J(t) ~ t^ {rm -n}. Identification of the high electric field current conduction mechanism is inconclusive. The good fatigue resistance, low dc leakage current, and excellent retention, qualifies the use of these capacitor structures in non-volatile random access (NVRAM) and dynamic random access (DRAM) memory devices. Excellent fatigue resistance (10% loss in remanent polarization up to ~2times10^ {10} switching cycles), low dc leakage current, and excellent retention are observed in capacitor structures containing polycrystalline PZT (exhibiting dominant (001) and (100) XRD reflections), a Pt-RuO_2 hybrid bottom electrode (Type IA), and an RuO _2 top electrode. These results, and electrical characterization results on capacitors containing co-deposited Pt-RuO_2 hybrid electrodes (Type II), show potential for application of these capacitor structures in NVRAM and DRAM memory devices.

Experimental Study of the Morphology and Dynamics of Gas-Laden Layers Under the Anodes in an Air-Water Model of Aluminum Reduction Cells

NASA Astrophysics Data System (ADS)

Vékony, Klára; Kiss, László I.

2012-10-01

The bubble layer formed under an anode and the bubble-induced flow play a significant role in the aluminum electrolysis process. The bubbles covering the anode bottom reduce the efficient surface that can carry current. In our experiments, we filmed and studied the bubble layer under the anode in a real-size air-water electrolysis cell model. Three different flow regimes were found depending on the gas generation rate. The covering factor was found to be proportional to the gas generation rate and inversely proportional to the angle of inclination. A correlation between the average height of the entire bubble layer and the position under the anode was determined. From this correlation and the measured contact sizes, the volume of the accumulated gas was calculated. The sweeping effect of large bubbles was observed. Moreover, the small bubbles under the inner edge of the anode were observed to move backward as a result of the escape of huge gas pockets, which means large momentum transport occurs in the bath.

Migration and transformation of different phosphorus forms in rainfall runoff in bioretention system.

PubMed

Song, Yujia; Song, Shoufa

2018-06-04

Artificial bioretention system consisting of Ophiopogon japonicus infiltration medium was used to simulate an infiltration experiment of rainfall runoff. Continuous extraction method was used to detect contents of inorganic phosphorus (P) under exchangeable state (Ex-P) and aluminium phosphate (Al-P) and iron phosphate (Fe-P) at different depths (0, 5, 15 and 35 cm) of soil infiltration medium in bioretention system. Effluent total P (TP) concentration of the system was also monitored. Results indicated that the adsorption of inorganic P, Al-P and Fe-P by soil infiltration medium was implemented layer by layer from top to bottom and gradually weakened. Moreover, Ex-P was gradually transformed into Al-P and Fe-P, whereas Al-P was gradually transformed into Fe-P; thus, Ex-P content reduced layer by layer, whereas Al-P and Fe-P gradually accumulated. The TP removal rate in runoff rainwater by the system was more than 90%, where the TP that was not used by plants was under dynamic equilibrium in water-soil-root system/biological system.

Transient response of an active nonlinear sandwich piezolaminated plate

NASA Astrophysics Data System (ADS)

Oveisi, Atta; Nestorović, Tamara

2017-04-01

In this paper, the dynamic modelling and active vibration control of a piezolaminated plate with geometrical nonlinearities are investigated using a semi-analytical approach. For active vibration control purposes, the core orthotropic elastic layer is assumed to be perfectly bonded with two piezo-layers on its top and bottom surfaces which act as sensor and actuator, respectively. In the modelling procedure, the piezo-layers are assumed to be connected via a proportional derivative (PD) feedback control law. Hamilton's principle is employed to acquire the strong form of the dynamic equation in terms of additional higher order strain expressions by means of von Karman strain-displacement correlation. The obtained nonlinear partial differential equation (NPDE) is converted to a system of nonlinear ordinary differential equations (NODEs) by engaging Galerkin method and using the orthogonality of shape functions for the simply supported boundary conditions. Then, the resulting system of NODEs is solved numerically by employing the built-in Mathematica function, "NDSolve". Next, the vibration attenuation performance is evaluated and sensitivity of the closed-loop system is investigated for several control parameters and the external disturbance parameters. The proposed solution in open loop configuration is validated by finite element (FE) package ABAQUS both in the spatial domain and for the time-/frequency-dependent response.

Optimum concentration gradient of the electrocatalyst, Nafion® and poly(tetrafluoroethylene) in a membrane-electrode-assembly for enhanced performance of direct methanol fuel cells.

PubMed

Liu, Jing Hua; Jeon, Min Ku; Lee, Ki Rak; Woo, Seong Ihl

2010-12-14

A combinatorial library of membrane-electrode-assemblies (MEAs) which consisted of 27 different compositions was fabricated to optimize the multilayer structure of direct methanol fuel cells. Each spot consisted of three layers of ink and a gradient was generated by employing different concentrations of the three components (Pt catalyst, Nafion® and polytetrafluoroethylene (PTFE)) of each layer. For quick evaluation of the library, a high-throughput optical screening technique was employed for methanol electro-oxidation reaction (MOR) activity. The screening results revealed that gradient layers could lead to higher MOR activity than uniform layers. It was found that the MOR activity was higher when the concentrations of Pt catalyst and Nafion ionomer decreased downward from the top layer to the bottom layer. On the other hand, higher MOR activity was observed when PTFE concentration increased downward from the top to the bottom layer.

Tsunami process: From upper mantle to atmosphere

NASA Astrophysics Data System (ADS)

Ershov, S.; Mikhaylovskaya, I.; Novik, O.

Earthquakes in near sea regions and/or tsunamis are manifestations of powerful geodynamic processes beneath the Ocean floor (75 % of the Earth' surface). An effective monitoring of these large-scale processes is not possible without satellites as well as without understanding of physical nature of signals accompanying these processes, e.g. connection between parameters of a seismic excitation in ocean lithosphere and electromagnetic (EM) signals in atmosphere. Basing on the theory of elasticity, electrodynamics, fluid dynamics and geophysical data we formulate a nonlinear mathematical model of generation and propagation of seismo-EM signals in the basin of a marginal sea including transfer of seismic and EM energy from upper mantle to hydrosphere and EM emission into atmosphere up to ionosphere domain D. For a model basin approximately similar to the central part of the Sea of Japan, we calculate signals caused by moderate elastic displacements (EDs): the ampl of a few cm, the main freq. 0.01-10 Hz and duration up to 10 sec (by runs with different acceptable data) which are supposed to be arising at the moment t=0 at the bottom of the upper mantle layer M. The EM signal appears near the bottom of the conductive (0.02 S/m) layer M and reaches for the sea bottom by t=3.5 sec with the ampl. Of 50 pT. This signal propagate in sea water (4 S/m) rather slowly and seems to be "frozen": its front is located near the sea bottom and is replicating the bottom's configuration up to the moment (t=5.2 sec) of the seismic P wave (from M) arrival at the sea bottom. The EM field is generated in seismically disturbed sea water in presence of the geomagnetic field" a specific structure of a seismo-hydrodynamic flow, a spatial break of the diffusive magnetic field, joining of its contours, and other details of the seismo-hydro-EM tsunami process are shown to clear out the out the physical nature of its signals. By the moderate EDs (above), the magnetic signal (freq. 0.01-10 Hz, i.e. the same as the EDs' freq.) is of order of a few hundreds of pT at the ocean-atmosphere interface and of order of a few tens of hydrodynamic wave's amplitude far from the shore is too small (20 cm) and EM observations are needed to discover this threatening wave. The computed signals' characteristics are of orders observed. The recommendations for the EM monitoring (at a sea bottom, surface, and atmosphere) of seismic excitations in ocean lithosphere and tsunamis are given.

Constraints on Thermochemical Convection of the Mantle from Plume-related Observations

NASA Astrophysics Data System (ADS)

Zhong, S.

2005-05-01

Although geochemical observations have long suggested a layered mantle with more enriched mantle material in the bottom layer to provide a significant amount of heat to the top layer, the nature of such a layering remains unclear. An important observation that has been used to argue against the conventional layered mantle model (i.e., the layering at the 670 km depth) was the plume heat flux [Davies, 1999]. Plume heat flux is estimated as ~ 3.5 TW, or 10% of the surface heat flux [Davies, 1988; Sleep, 1990]. In this study, we demonstrate with 3-D spherical models of mantle convection with depth- and temperature-dependent viscosity that observed plume heat flux, plume excess temperature (<350°C), and upper mantle temperature (~ 1300°C) can pose important constraints on the layered mantle convection. We show that for a purely thermal convection model (i.e., a whole mantle convection), the observations of plume heat flux, plume excess temperature, and upper mantle temperature can be simultaneously explained only when internal heating rate is about 65%. For smaller internal heating rate, plume heat flux and plume excess temperature would be too large, and upper mantle temperature would be too small, compared with the observed. This suggests that for a whole mantle convection the CMB heat flux needs to be > 10 TW. For a core with no significant heat producing elements, such large CMB heat flux may lead to too rapid cooling of the core or a too young inner core. A layered mantle convection may help reduce the CMB heat flux. For layered convection models, we found that the top layer needs to be ~70% internally heated to explain the upper mantle temperature and plume-related observations, and this required internal heating ratio is insensitive to the layer thickness for the bottom layer (we used ~600 km and 1100 km thicknesses). This result suggests that heat generation rate for the bottom layer cannot be significantly larger (< a factor of 2) than that for the top layer. thus challenging the conventional geochemical inference for an significantly enriched bottom layer. However, this is more consistent with recent estimate of the MORB source composition that increases heat producing element concentration by a factor of three compared with the previously proposed.

Use of weathered and fresh bottom ash mix layers as a subbase in road constructions: environmental behavior enhancement by means of a retaining barrier.

PubMed

Del Valle-Zermeño, R; Chimenos, J M; Giró-Paloma, J; Formosa, J

2014-12-01

The presence of neoformed cement-like phases during the weathering of non-stabilized freshly quenched bottom ash favors the development of a bound pavement material with improved mechanical properties. Use of weathered and freshly quenched bottom ash mix layers placed one over the other allowed the retention of leached heavy metals and metalloids by means of a reactive percolation barrier. The addition of 50% of weathered bottom ash to the total subbase content diminished the release of toxic species to below environmental regulatory limits. The mechanisms of retention and the different processes and factors responsible of leaching strongly depended on the contaminant under concern as well as on the chemical and physical factors. Thus, the immediate reuse of freshly quenched bottom ash as a subbase material in road constructions is possible, as both the mechanical properties and long-term leachability are enhanced. Copyright © 2014 Elsevier Ltd. All rights reserved.

Observations of the R reflector and sediment interface reflection at the Shallow Water '06 Central Site.

PubMed

Choi, Jee Woong; Dahl, Peter H; Goff, John A

2008-09-01

Acoustic bottom-interacting measurements from the Shallow Water '06 experiment experiment (frequency range 1-20 kHz) are presented. These are co-located with coring and stratigraphic studies showing a thin (approximately 20 cm) higher sound speed layer overlaying a thicker (approximately 20 m) lower sound speed layer ending at a high-impedance reflector (R reflector). Reflections from the R reflector and analysis of the bottom reflection coefficient magnitude for the upper two sediment layers confirm both these features. Geoacoustic parameters are estimated, dispersion effects addressed, and forward modeling using the parabolic wave equation undertaken. The reflection coefficient measurements suggest a nonlinear attenuation law for the thin layer of sandy sediments.

A Water Model Study on Mixing Behavior of the Two-Layered Bath in Bottom Blown Copper Smelting Furnace

NASA Astrophysics Data System (ADS)

Shui, Lang; Cui, Zhixiang; Ma, Xiaodong; Jiang, Xu; Chen, Mao; Xiang, Yong; Zhao, Baojun

2018-05-01

The bottom-blown copper smelting furnace is a novel copper smelter developed in recent years. Many advantages of this furnace have been found, related to bath mixing behavior under its specific gas injection scheme. This study aims to use an oil-water double-phased laboratory-scale model to investigate the impact of industry-adjustable variables on bath mixing time, including lower layer thickness, gas flow rate, upper layer thickness and upper layer viscosity. Based on experimental results, an overall empirical relationship of mixing time in terms of these variables has been correlated, which provides the methodology for industry to optimize mass transfer in the furnace.

High Energy Benthic Boundary Layer Experiment (HEBBLE): Preliminary program plan and conceptual design

NASA Technical Reports Server (NTRS)

Frewing, K.

1980-01-01

Deep sea processes of flow-sediment interaction, particularly the role of high energy ocean bottom current events in forming the seafloor topography, transporting material, and mixing the bottom of the water column are examined. A series of observations at and near the sea bottom, in water depths of 4 to 5 km, in areas of the western North Atlantic where high energy current events occur, include site surveys and physical reconnaissance to identify suitable areas and positions, and one or more six month experiments to investigate temporal and spatial variations of high energy events within the boundary layer and their interaction with the seabed. Descriptions of proposed HEBBLE activities are included, with emphasis on technology transfer to the oceanographic community through design, fabrication, testing, and operation of an instrumented ocean bottom lander.

A Novel, Diazonium-Phenolic Resin Two-Layer Resist System Utilizing Photoinduced Interfacial Insolubilization

NASA Astrophysics Data System (ADS)

Uchino, Shou-ichi; Iwayanagi, Takao; Ueno, Takumi; Hashimoto, Michiaki; Nonogaki, Saburo

1987-08-01

This paper deals with a negative two-layer photoresist system utilizing a photoinduced insolubilization process at the interface. The bottom layer is a phenolic resin either with or without aromatic azide and the top layer is a photosensitive layer comprised of an aromatic diazonium compound and a water soluble polymer. Upon exposure to light, the diazo compound decomposes to cause insolubilization at the interface between the two layers. The system exhibits high contrast due to the combination of interfacial insolubilization and contrast enhancement by photobleaching of the diazonium compound. Patterns of 0.5 um lines and spaces are obtained using an i-line stepper and a resist system containing 4-diazo-N,N-dimethylaniline chloride zinc chloride in the top layer and 3-(4-azidostyry1)- 5,5-dimethyl- 2-cyclohexen-1-one in the bottom layer. Resists with varying spectral responses from mid-UV to g-line can be designed by selecting the kind of diazo compound used in the top layer.

Laser induced forward transfer of graphene

NASA Astrophysics Data System (ADS)

Smits, Edsger C. P.; Walter, Arnaud; de Leeuw, Dago M.; Asadi, Kamal

2017-10-01

Transfer of graphene and other two-dimensional materials is still a technical challenge. The 2D-materials are typically patterned after transfer, which leads to a major loss of material. Here, we present laser induced forward transfer of chemical vapor deposition grown graphene layers with well-defined shapes and geometries. The transfer is based on photo-decomposition of a triazene-based transfer layer that produces N2 gas, which propels a graphene layer from the donor to the acceptor substrate. The functionality of the graphene-metal junction was verified by realizing functional bottom contact bottom gate field-effect transistors.

The Coupled Boundary Layers and Air-Sea Transfer (CBLAST) Experiments at the Martha's Vineyard Coastal Observatory

NASA Astrophysics Data System (ADS)

Edson, J. B.

2001-12-01

The Woods Hole Oceanographic Institution (WHOI) completed the initial phase of the Martha's Vineyard Coastal Observatory (MVCO) in July of 2001. The MVCO is being using to monitor coastal atmospheric and oceanic processes. Specifically, the observatory is expected to: - Provide continuous long-term observations for climate studies. - Provide a reliable system and rugged sensors that allow opportunistic sampling of extreme events. - Provide a local climatology for intensive, short duration field campaigns. - Further facilitate regional studies of coastal processes by providing infrastructure that supports easy access to power and data. This talk provides an example of the last two objectives using the low wind component of the Office of Naval Research's (ONR) Coupled Boundary Layers and Air-Sea Transfer (CBLAST) program. CBLAST-LOW has been designed to investigate air-sea interaction and coupled atmospheric and oceanic boundary layer dynamics at low wind speeds where the dynamic processes are driven and/or strongly modulated by thermal forcing. This effort is being carried out by scientists at WHOI, NPS, NOAA, NRL, Rutgers, UW/APL, JH/APL, OSU, NCAR, and other institutions, and includes observational and modeling components. The MVCO is providing observations and infrastructure in support of several intensive operating periods in the summers of 2001, 2002, and possibly 2003. During these periods, the observational network around the observatory was and will be greatly expanded using traditional oceanographic moorings and bottom mounted instrumentation, innovative 2- and 3-D moored and drifting arrays, survey ships, AUVs, satellite remote sensing, and heavily instrumented aircraft. In addition, the MVCO cabled components will be extended out to the 20-m isobath where we plan to deploy a 35-m tower. The tower will be instrumented from 15-m above the ocean surface to the ocean bottom with instruments capable of directly measuring the momentum, heat, and radiative fluxes in the atmospheric, oceanic, and bottom boundary layers. This tower will be directly connected to shore via the existing node at the MVCO using an additional fiber-optic-power cable. All of these measurements will be combined to obtain direct measurements of vertical fluxes (transfer) of momentum, heat and mass across the coupled boundary layers (CBLs); to map the 3-D structure of the CBLs over a range of spatial and temporal scales; to identify the processes that drive the fluxes and CBL structure; to develop and evaluate parameterizations of the flux-producing processes; and to test the mean and variance budgets for momentum, heat, mass, and kinetic energy. These measurements will also be used to evaluate and improve mesoscale models, large eddy simulations (LES), and direct numerical simulations (DNS) that will, in-turn, provide nowcasts, forecasts, and simulations of these processes to help interpret the observations. >http://www.whoi.edu/science/AOPE/dept/CBLAST/lowwind.html

Reducing the contact resistance in bottom-contact-type organic field-effect transitors using an AgO x interface layer

NASA Astrophysics Data System (ADS)

Minagawa, Masahiro; Kim, Yeongin; Claus, Martin; Bao, Zhenan

2017-09-01

Bottom-contact organic field-effect transistors (OFETs) are prepared by inserting an AgO x layer between a pentacene layer and the source-drain electrodes. The contact resistance in the device is ˜8.1 kΩ·cm with an AgO x layer oxidized for 60 s but reaches 116.9 kΩ·cm with a non-oxidized Ag electrode. The drain current and mobility in the OFETs with the AgO x layer increase with the oxidization time and then gradually plateau, and this trend strongly depends on the work function of the Ag surface. Further, the hole injection is enhanced by the presence of Ag2O but inhibited by the presence of AgO.

Controlled metal-semiconductor sintering/alloying by one-directional reverse illumination

DOEpatents

Sopori, Bhushan L.

1993-01-01

Metal strips deposited on a top surface of a semiconductor substrate are sintered at one temperature simultaneously with alloying a metal layer on the bottom surface at a second, higher temperature. This simultaneous sintering of metal strips and alloying a metal layer on opposite surfaces of the substrate at different temperatures is accomplished by directing infrared radiation through the top surface to the interface of the bottom surface with the metal layer where the radiation is absorbed to create a primary hot zone with a temperature high enough to melt and alloy the metal layer with the bottom surface of the substrate. Secondary heat effects, including heat conducted through the substrate from the primary hot zone and heat created by infrared radiation reflected from the metal layer to the metal strips, as well as heat created from some primary absorption by the metal strips, combine to create secondary hot zones at the interfaces of the metal strips with the top surface of the substrate. These secondary hot zones are not as hot as the primary hot zone, but they are hot enough to sinter the metal strips to the substrate.

Improved electrical performance and bias stability of solution-processed active bilayer structure of indium zinc oxide based TFT.

PubMed

Seo, Jin-Suk; Bae, Byeong-Soo

2014-09-10

We fabricated active single- and bilayer structure thin film transistors (TFTs) with aluminum or gallium doped (IZO:Al or IZO:Ga) and undoped indium zinc oxide (IZO) thin film layers using an aqueous solution process. The electrical performance and bias stability of these active single- and bilayer structure TFTs were investigated and compared to reveal the effects of Al/Gal doping and bilayer structure. The single-layer structure IZO TFT shows a high mobility of 19 cm(2)/V · s with a poor positive bias stability (PBS) of ΔVT + 3.4 V. However, Al/Ga doped in IZO TFT reduced mobility to 8.5-9.9 cm(2)/V · s but improved PBS to ΔVT + 1.6-1.7 V due to the reduction of oxygen vacancy. Thus, it is found the bilayer structure TFTs with a combination of bottom- and top-layer compositions modify both the mobility and bias stability of the TFTs to be optimized. The bilayer structure TFT with an IZO:X bottom layer possess high mobility and an IZO bottom layer improves the PBS.

Near bottom velocity and suspended solids measurements in San Francisco Bay, California

USGS Publications Warehouse

Gartner, Jeffrey W.; Cheng, Ralph T.; Cacchione, David A.; Tate, George B.

1997-01-01

Ability to accurately measure long-term time-series of turbulent mean velocity distribution within the bottom boundary layer (BBL) in addition to suspended solids concentration (SSC) is critical to understanding complex processes controlling transport, resuspension, and deposition of suspended sediments in bays and estuaries. A suite of instruments, including broad band acoustic Doppler current profilers (BB-ADCPs), capable of making very high resolution measurement of velocity profiles in the BBL, was deployed in the shipping channel of South San Francisco Bay (South Bay), California in an investigation of sediment dynamics during March and April 1995. Results of field measurements provide information to calculate suspended solids flux (SSF) at the site. Calculations show striking patterns; residual SSF varies through the spring-neap tidal cycle. Significant differences from one spring tide to another are caused by differences in tidal current diurnal inequalities. Winds from significant storms establish residual circulation patterns that may affect magnitude of residual SSF more than increased tidal energy at spring tides.

Settling-driven gravitational instabilities associated with volcanic clouds: new insights from experimental investigations

NASA Astrophysics Data System (ADS)

Scollo, Simona; Bonadonna, Costanza; Manzella, Irene

2017-06-01

Downward propagating instabilities are often observed at the bottom of volcanic plumes and clouds. These instabilities generate fingers that enhance the sedimentation of fine ash. Despite their potential influence on tephra dispersal and deposition, their dynamics is not entirely understood, undermining the accuracy of volcanic ash transport and dispersal models. Here, we present new laboratory experiments that investigate the effects of particle size, composition and concentration on finger generation and dynamics. The experimental set-up consists of a Plexiglas tank equipped with a removable plastic sheet that separates two different layers. The lower layer is a solution of water and sugar, initially denser than the upper layer, which consists of water and particles. Particles in the experiments include glass beads as well as andesitic, rhyolitic and basaltic volcanic ash. During the experiments, we removed the horizontal plastic sheet separating the two fluids. Particles were illuminated with a laser and filmed with a HD camera; particle image velocimetry (PIV) is used to analyse finger dynamics. Results show that both the number and the downward advance speed of fingers increase with particle concentration in the upper layer, while finger speed increases with particle size but is independent of particle composition. An increase in particle concentration and turbulence is estimated to take place inside the fingers, which could promote aggregation in subaerial fallout events. Finally, finger number, finger speed and particle concentration were observed to decrease with time after the formation of fingers. A similar pattern could occur in volcanic clouds when the mass supply from the eruptive vent is reduced. Observed evolution of the experiments through time also indicates that there must be a threshold of fine ash concentration and mass eruption rate below which fingers do not form; this is also confirmed by field observations.

Eddy Effects in the General Circulation, Spanning Mean Currents, Mesoscale Eddies, and Topographic Generation, Including Submesoscale Nests

DTIC Science & Technology

2013-09-30

bottom form stress (pressure force) and bottom boundary layers – all the aspects associated with turbulent flows over steep topography in the presence of...filaments, and eddies; topographic current separation, form stress , and submesoscale vortex generation; Our work on isoneutral diffusion for tracers...Bump region, are due to the contribution of the bottom stress curl. Fig. 4 shows how the Gulf Stream path is directly linked to the Bottom Pressure

Self-oscillations in large storages of highly mineralized brines

NASA Astrophysics Data System (ADS)

Lyubimova, Tatyana; Lepikhin, Anatoly; Tsiberkin, Kirill; Parshakova, Yanina

2014-05-01

One of the stages of the production process at large enrichment plants is settling of aqueous solutions in large technological storages. The present work is devoted to the modeling of hydrodynamic regimes of large storage of highly mineralized brines. The density of brines in these objects depends not only on the content of dissolved macrocomponents, but also on the concentration of fine particulate matter. This leads to the need to consider the dynamics of the suspended sediment under significant density stratification, which greatly complicates the problem. Because of that it is important to develop hydrodynamical models of these objects. A peculiarity of these systems is the possibility of self-oscillatory regimes the mechanism of which is as follows. In warm sunny days, with high solar insolation, the heating of the sediments and bottom water takes place. The bottom water warming and the decrease of its density give rise to flow. The slurry particles composing the sediments are involved in the flow. The heated particles entrained by the flow transfer the heat to the surrounding liquid and increase the absorption of the solar radiation in the volume, which leads to equalization of temperature and convective flow damping. After the particle settling on the bottom the process is repeated. We study the stability of equilibrium of the horizontal liquid layer containing heavy insoluble particles in the presence of evaporation from the free surface and solar radiation absorption by insoluble particles. The time-dependent solution of heat transfer problem is obtained and used for estimate of time of instability onset. It is found that for the layer of saturated brines of potassium chloride of the thickness about 10 m the time for instability onset is about one hour. By using analytical estimates based on the empirical model of turbulence by Prandtl we confirmed the time for the onset of instability and obtained the estimates for the period of self-oscillations. Numerical simulation of the dynamics of suspended sediment in the storage is performed within the framework of two-dimensional unsteady approach taking into account the temperature jumps due to the water evaporation from the free surface and the radiation heating of the sediments. The dynamics of sediment in a rectangular cavity of the length 500 m and depth 10 m is considered. Initially, the water is assumed to be motionless and nonuniformly heated. The calculations show that in the first stage of the process the flows arise near the boundaries of the heated areas. Next, the large-scale vortices with the characteristic size equal to the depth of the storage are formed. The sediment located at the bottom sets into motion and only some portion of sediment located near the bottom remains motionless. Throughout several hours the mass fraction of the suspended particles in water increases, then the flow decays and the sedimentation of particles is observed. This work was supported by RFBR and Perm Region Government (grant 13-01-96040) and by President of Russian Federation (grant 4022.2014.1 for the support of Leading Scientific Schools).

Distribution of Arctic and Pacific copepods and their habitat in the northern Bering and Chukchi seas

NASA Astrophysics Data System (ADS)

Sasaki, Hiroko; Matsuno, Kohei; Fujiwara, Amane; Onuka, Misaki; Yamaguchi, Atsushi; Ueno, Hiromichi; Watanuki, Yutaka; Kikuchi, Takashi

2016-08-01

The advection of warm Pacific water and the reduction in sea ice in the western Arctic Ocean may influence the abundance and distribution of copepods, a key component of food webs. To quantify the factors affecting the abundance of copepods in the northern Bering and Chukchi seas, we constructed habitat models explaining the spatial patterns of large and small Arctic and Pacific copepods separately. Copepods were sampled using NORPAC (North Pacific Standard) nets. The structures of water masses indexed by principle component analysis scores, satellite-derived timing of sea ice retreat, bottom depth and chlorophyll a concentration were integrated into generalized additive models as explanatory variables. The adequate models for all copepods exhibited clear continuous relationships between the abundance of copepods and the indexed water masses. Large Arctic copepods were abundant at stations where the bottom layer was saline; however they were scarce at stations where warm fresh water formed the upper layer. Small Arctic copepods were abundant at stations where the upper layer was warm and saline and the bottom layer was cold and highly saline. In contrast, Pacific copepods were abundant at stations where the Pacific-origin water mass was predominant (i.e. a warm, saline upper layer and saline and a highly saline bottom layer). All copepod groups showed a positive relationship with early sea ice retreat. Early sea ice retreat has been reported to initiate spring blooms in open water, allowing copepods to utilize more food while maintaining their high activity in warm water without sea ice and cold water. This finding indicates that early sea ice retreat has positive effects on the abundance of all copepod groups in the northern Bering and Chukchi seas, suggesting a change from a pelagic-benthic-type ecosystem to a pelagic-pelagic type.

The impact of surface chemistry on the performance of localized solar-driven evaporation system

PubMed Central

Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-01-01

This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation. PMID:26337561

The impact of surface chemistry on the performance of localized solar-driven evaporation system.

PubMed

Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-09-04

This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation.

Cascaded Ga1-xAlxAs/GaAs solar cell with graded i-region

NASA Astrophysics Data System (ADS)

Mil'shtein, Sam; Halilov, Samed

2018-02-01

In current study we designed p-i-n junction with extended intrinsic layer, where linearly graded Alx Ga1-x As presents variable energy gap so needed for effective harvesting of sun radiation. The design realization involves two regions of compositional structure in the stacking direction. The top AlxGa1-xAs layer of 1 um total thickness has stoichiometric structure x=0.3-0.2d, where depth d runs from 0 to 1 um, topmost 200 nm of which is Be-doped. Bottom AlxGa1-xAs layer of 3 um total thickness has a variable composition of x=0.133-0.033d, d runs from 1 to 4 um, the very bottom of which with 10 nm thickness is Si-doped. On the top surface, there is a 50 nm layer of p+ doped GaAs as a spacer for growing AuGe/Ni anode electrode of 20% surface area, the bottom is coated with AuGe/Ni cathode electrode. The designed cell demonstrates 89% fill factor and 30% conversion efficiency without anti-reflection coating.

Structure of Subsurface Sediments in the Scan Basin (Scotia Sea)

NASA Astrophysics Data System (ADS)

Schreider, Al. A.; Schreider, A. A.; Sazhneva, A. E.; Galindo-Zaldivar, J.; Ruano, P.; Maldonado, A.; Martos-Martin, Y.; Lobo, F.

2018-01-01

The structure of sediments in the Scotia Sea is used as a basis for reconstructing the geological history of its bottom in the Late Quaternary. The Scan Basin is one of the main elements of the topography of the southern Scotia Sea. Its formation played a considerable role in the fragmentation of the continent, which included the Bruce and Discovery banks. The main parameters of the sediment layer in the Scan Basin have been reconstructed by the present time, but its top part has not been studied. In this work, we analyze the first data obtained on the R/V Gesperidas with the use of a TOPAS PS 18/40 high-resolution seismic profilograph in 2012. Three layers in the subsurface sediments on the bottom of the Scan Basin were specified for the first time. The mean periods of their deposition in the Late Quaternary were determined as 115000 years for the first, 76000 years for the second, and 59 000 years for the third layer from the surface of the bottom. The duration of the total accumulation period of the three layers is about 250000 years.

Shubnikov-de Haas oscillations of high mobility holes in monolayer and bilayer WSe2: spin-valley locking, effective mass, and inter-layer coupling

NASA Astrophysics Data System (ADS)

Fallahazad, Babak; Movva, Hema Chandra Prakash; Kim, Kyounghwan; Larentis, Stefano; Taniguchi, Takashi; Watanabe, Kenji; Banerjee, Sanjay K.; Tutuc, Emanuel

We study the magnetotransport properties of high mobility holes in monolayer and bilayer WSe2, measured in dual-gated samples with top and bottom hexagonal boron-nitride dielectrics, and using platinum bottom contacts. Thanks to the Pt high work-function combined with the a high hole density induced electrostatically by an applied top gate bias, the contacts remain ohmic down to low (1.5 K) temperatures. The samples display well defined Shubnikov-de Haas (SdH) oscillations, and quantum Hall states (QHS) in high magnetic fields. In both mono and bilayer WSe2, the SdH oscillations and the QHSs occur predominantly at even filling factors, evincing a two-fold Landau level degeneracy consistent with spin-valley locking. The Fourier transform analysis of the SdH oscillations in dual-gated bilayer WSe2 reveal the presence of two subbands, each localized in the top or the bottom layer, as well as negative compressibility. From the temperature dependence of the SdH oscillation amplitude we determine a hole effective mass of 0.45me for both mono and bilayer WSe2. The top and bottom layer densities can be independently tuned using the top and bottom gates, respectively, evincing a weak interlayer coupling. This work has been supported by NRI-SWAN and Intel corporation.

Evaporation characteristics of thin film liquid argon in nano-scale confinement: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Hasan, Mohammad Nasim; Shavik, Sheikh Mohammad; Rabbi, Kazi Fazle; Haque, Mominul

2016-07-01

Molecular dynamics simulation has been carried out to explore the evaporation characteristics of thin liquid argon film in nano-scale confinement. The present study has been conducted to realize the nano-scale physics of simultaneous evaporation and condensation inside a confined space for a three phase system with particular emphasis on the effect of surface wetting conditions. The simulation domain consisted of two parallel platinum plates; one at the top and another at the bottom. The fluid comprised of liquid argon film at the bottom plate and vapor argon in between liquid argon and upper plate of the domain. Considering hydrophilic and hydrophobic nature of top and bottom surfaces, two different cases have been investigated: (i) Case A: Both top and bottom surfaces are hydrophilic, (ii) Case B: both top and bottom surfaces are hydrophobic. For all cases, equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. Then the lower wall was set to four different temperatures such as 110 K, 120 K, 130 K and 140 K to perform non-equilibrium molecular dynamics (NEMD). The variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat fluxes normal to top and bottom walls were estimated and discussed to illuminate the effectiveness of heat transfer in both hydrophilic and hydrophobic confinement at various boundary temperatures of the bottom plate.

Tracing groundwater input into Lake Vanda, Wright Valley, Antarctica using major ions, stable isotopes and noble gas

NASA Astrophysics Data System (ADS)

Dowling, C. B.; Poreda, R. J.; Snyder, G. T.

2008-12-01

The McMurdo Dry Valleys (MDV), Antarctica, is the largest ice-free region on Antarctica. Lake Vanda, located in central Wright Valley, is the deepest lake among the MDV lakes. It has a relatively fresh water layer above 50 m with a hypersaline calcium-chloride brine below (50-72 m). The Onyx River is the only stream input into Lake Vanda. It flows westward from the coastal Lower Wright Glacier and discharges into Lake Vanda. Suggested by the published literature and this study, there has been and may still be groundwater input into Lake Vanda. Stable isotopes, major ions, and noble gas data from this study coupled with previously published data indicate that the bottom waters of Lake Vanda have had significant contributions from a deep groundwater system. The dissolved gas of the bottom waters of Lake Vanda display solubility concentrations rather than the Ar-enriched dissolved gas seen in the Taylor Valley lakes (such as Lake Bonney). The isotopic data indicate that the bottom calcium-chloride-brine of Lake Vanda has undergone very little evaporation. The calcium-chloride chemistry of the groundwater that discharges into Lake Vanda most likely results from the chemical weathering and dissolution of cryogenic evaporites (antarcticite and gypsum) within the glacial sediments of Wright Valley. The high calcium concentrations of the brine have caused gypsum to precipitate on the lake bottom. Our work also supports previous physical and chemical observations suggesting that the upper portion actively circulates and the hypersaline bottom layer does not. The helium and calcium chloride values are concentrated at the bottom, with a very narrow transition layer between it and the above fresh water. If the freshwater layer did not actively circulate, then diffusion over time would have caused the helium and calcium chloride to slowly permeate upwards through the water column.

Mg concentration profile and its control in the low temperature grown Mg-doped GaN epilayer

NASA Astrophysics Data System (ADS)

Liu, S. T.; Yang, J.; Zhao, D. G.; Jiang, D. S.; Liang, F.; Chen, P.; Zhu, J. J.; Liu, Z. S.; Liu, W.; Xing, Y.; Zhang, L. Q.; Wang, W. J.; Li, M.; Zhang, Y. T.; Du, G. T.

2018-01-01

In this work, the Cp2Mg flux and growth pressure influence to Mg doping concentration and depth profiles is studied. From the SIMS measurement we found that a transition layer exists at the bottom region of the layer in which the Mg doping concentration changes gradually. The thickness of transition layer decreases with the increases of Mg doping concentration. Through analysis, we found that this is caused by Ga memory effect which the Ga atoms stay residual in MOCVD system will react with Mg source, leading a transition layer formation and improve the growth rate. And the Ga memory effect can be well suppressed by increasing Mg doping concentration and growth pressure and thus get a steep Mg doping at the bottom region of p type layer.

Sources, behaviors and degradation of dissolved organic matter in the East China Sea

NASA Astrophysics Data System (ADS)

Chen, Yan; Yang, Gui-Peng; Liu, Li; Zhang, Peng-Yan; Leng, Wei-Song

2016-03-01

Concentrations of dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON) and its major compound classes-total hydrolysable amino acids (THAA) were measured at 4 cross-shelf transects of the East China Sea in July 2011. Surface concentrations of DOC, DIN, DON and THAA at the nearshore stations were mostly in excess of those found at the offshore sites, indicating either substantial autochthonous production or allochthonous inputs from the Changjiang River. The vertical distributions of DOC, DON and THAA showed similar trends with higher values in the surface layer, whereas the elevated concentrations of DIN were observed in the bottom layer. Major constituents of THAA presented in the study area were glycine, serine, alanine, glutamic acid, aspartic acid and valine. The mole percentages of neutral amino acids increased from surface water to bottom water, whereas acidic and hydroxy amino acids decreased with the water depth. Concentrations of DOC and THAA were negatively correlated to the ΔDIN values (the difference between the real concentration and theoretical concentration), respectively, indicating the coupling relation between dissolved organic matter (DOM) remineralization and nutrient regeneration in the water column. The C/N ratios in the water column exhibited different characteristics with elevated values appearing in the surface and bottom layers. Box and whisker plots showed that both degradation index (DI) values and THAA yields displayed a decreasing trend from the surface layer to the bottom layer, implying increasing degradation with the water depth. Our data revealed that glycine and alanine increased in relative abundance with decreasing DI, while tyrosine, valine, phenylalanine and isoleucine increased with increasing DI.

Twisting dirac fermions: circular dichroism in bilayer graphene

NASA Astrophysics Data System (ADS)

Suárez Morell, E.; Chico, Leonor; Brey, Luis

2017-09-01

Twisted bilayer graphene is a chiral system which has been recently shown to present circular dichroism. In this work we show that the origin of this optical activity is the rotation of the Dirac fermions’ helicities in the top and bottom layer. Starting from the Kubo formula, we obtain a compact expression for the Hall conductivity that takes into account the dephasing of the electromagnetic field between the top and bottom layers and gathers all the symmetries of the system. Our results are based in both a continuum and a tight-binding model, and they can be generalized to any two-dimensional Dirac material with a chiral stacking between layers.

Wind-induced flow velocity effects on nutrient concentrations at Eastern Bay of Lake Taihu, China.

PubMed

Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Jianwei; Gao, Xiaomeng; Wang, Wencai; Acharya, Kumud

2017-07-01

Shallow lakes are highly sensitive to respond internal nutrient loading due to wind-induced flow velocity effects. Wind-induced flow velocity effects on nutrient suspension were investigated at a long narrow bay of large shallow Lake Taihu, the third largest freshwater lake in China. Wind-induced reverse/compensation flow and consistent flow field probabilities at vertical column of the water were measured. The probabilities between the wind field and the flow velocities provided a strong correlation at the surface (80.6%) and the bottom (65.1%) layers of water profile. Vertical flow velocity profile analysis provided the evidence of delay response time to wind field at the bottom layer of lake water. Strong wind field generated by the west (W) and west-north-west (WNW) winds produced displaced water movements in opposite directions to the prevailing flow field. An exponential correlation was observed between the current velocities of the surface and the bottom layers while considering wind speed as a control factor. A linear model was developed to correlate the wind field-induced flow velocity impacts on nutrient concentration at the surface and bottom layers. Results showed that dominant wind directions (ENE, E, and ESE) had a maximum nutrient resuspension contribution (nutrient resuspension potential) of 34.7 and 43.6% at the surface and the bottom profile layers, respectively. Total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) average concentrations were 6.38, 1.5, and 0.03 mg/L during our field experiment at Eastern Bay of Lake Taihu. Overall, wind-induced low-to-moderate hydrodynamic disturbances contributed more in nutrient resuspension at Eastern Bay of Lake Taihu. The present study can be used to understand the linkage between wind-induced flow velocities and nutrient concentrations for shallow lakes (with uniform morphology and deep margins) water quality management and to develop further models.

Activity in the superior colliculus reflects dynamic interactions between voluntary and involuntary influences on orienting behaviour.

PubMed

Bell, Andrew H; Munoz, Douglas P

2008-10-01

Performance in a behavioural task can be influenced by both bottom-up and top-down processes such as stimulus modality and prior probability. Here, we exploited differences in behavioural strategy to explore the role of the intermediate and deep layers of the superior colliculus (dSC) in covert orienting. Two monkeys were trained on a predictive cued-saccade task in which the cue predicted the target's upcoming location with 80% validity. When the delay between cue and target onset was 250 ms, both monkeys showed faster responses to the uncued (Invalid) location. This was associated with a reduced target-aligned response in the dSC on Valid trials for both monkeys and is consistent with a bottom-up (i.e. involuntary) bias. When the delay was increased to 650 ms, one monkey continued to show faster responses to the Invalid location whereas the other monkey showed faster responses to the Valid location, consistent with a top-down (i.e. voluntary) bias. This latter behaviour was correlated with an increase in activity in dSC neurons preceding target onset that was absent in the other monkey. Thus, using the information provided by the cue shifted the emphasis towards top-down processing, while ignoring this information allowed bottom-up processing to continue to dominate. Regardless of the selected strategy, however, neurons in the dSC consistently reflected the current bias between the two processes, emphasizing its role in both the bottom-up and top-down control of orienting behaviour.

Tunneling-Magnetoresistance Ratio Comparison of MgO-Based Perpendicular-Magnetic-Tunneling-Junction Spin Valve Between Top and Bottom Co2Fe6B2 Free Layer Structure.

PubMed

Lee, Du-Yeong; Lee, Seung-Eun; Shim, Tae-Hun; Park, Jea-Gun

2016-12-01

For the perpendicular-magnetic-tunneling-junction (p-MTJ) spin valve with a nanoscale-thick bottom Co2Fe6B2 free layer ex situ annealed at 400 °C, which has been used as a common p-MTJ structure, the Pt atoms of the Pt buffer layer diffused into the MgO tunneling barrier. This transformed the MgO tunneling barrier from a body-centered cubic (b.c.c) crystallized layer into a mixture of b.c.c, face-centered cubic, and amorphous layers and rapidly decreased the tunneling-magnetoresistance (TMR) ratio. The p-MTJ spin valve with a nanoscale-thick top Co2Fe6B2 free layer could prevent the Pt atoms diffusing into the MgO tunneling barrier during ex situ annealing at 400 °C because of non-necessity of a Pt buffer layer, demonstrating the TMR ratio of ~143 %.

Anisotropic Turbulence Models for Acoustic Propagation Through the Neutral Atmospheric Surface Layer

DTIC Science & Technology

1998-02-01

and Brost (1984). †Specific means per unit mass. 2 Observations Top-Down Approach Bottom-Up Approach Equations for the energy spectra Equations for...R. A. Brost (1984): Top-down and bottom-up diffusion of a scalar in the convective boundary layer. J. Atmos. Sci., 41, 102–112. 62 Distribution 63...Agency Attn W21 Longbothum 9800 Savage Rd FT George G Meade MD 20755-6000 TACOM Attn AMSTA-TR-R E Shalis Mail Stop 263 Warren MI 48090 US Army

Implications for Crustal Structures and Heat Fluxes from Depth-to-the-Bottom of the Magnetic Source Estimates in West Antarctica, Amundsen Sea Sector

NASA Astrophysics Data System (ADS)

Dziadek, R.; Ferraccioli, F.; Gohl, K.; Spiegel, C.; Kaul, N. E.

2017-12-01

The West Antarctic Rift System is one of the least understood rift systems on earth, but displays a unique coupled relationship between tectonic processes and ice sheet dynamics. Geothermal heat flux (GHF) is a poorly constrained parameter in Antarctica and suspected to affect basal conditions of ice sheets, i.e., basal melting and subglacial hydrology. Thermomechanical models demonstrate the influential boundary condition of geothermal heat flux for (paleo) ice sheet stability. Young, continental rift systems are regions with significantly elevated geothermal heat flux (GHF), because the transient thermal perturbation to the lithosphere caused by rifting requires 100 Ma to reach long-term thermal equilibrium. We discuss airborne, high-resolution magnetic anomaly data from the Amundsen Sea Sector, to provide additional insight into deeper crustal structures related to the West Antarctic Rift System in the Amundsen/Bellingshausen sector. With the depth-to-the-bottom of the magnetic source (DBMS) estimates we reveal spatial changes at the bottom of the igneous crust and the thickness of the magnetic layer, which can be further incorporated into tectonic interpretations. The DBMS also marks an important temperature transition zone of approximately 580°C and therefore serves as a boundary condition for our numerical FEM thermal models in 2D and 3D.

Model test on partial expansion in stratified subsidence during foundation pit dewatering

NASA Astrophysics Data System (ADS)

Wang, Jianxiu; Deng, Yansheng; Ma, Ruiqiang; Liu, Xiaotian; Guo, Qingfeng; Liu, Shaoli; Shao, Yule; Wu, Linbo; Zhou, Jie; Yang, Tianliang; Wang, Hanmei; Huang, Xinlei

2018-02-01

Partial expansion was observed in stratified subsidence during foundation pit dewatering. However, the phenomenon was suspected to be an error because the compression of layers is known to occur when subsidence occurs. A slice of the subsidence cone induced by drawdown was selected as the prototype. Model tests were performed to investigate the phenomenon. The underlying confined aquifer was generated as a movable rigid plate with a hinge at one end. The overlying layers were simulated with remolded materials collected from a construction site. Model tests performed under the conceptual model indicated that partial expansion occurred in stratified settlements under coordination deformation and consolidation conditions. During foundation pit dewatering, rapid drawdown resulted in rapid subsidence in the dewatered confined aquifer. The rapidly subsiding confined aquifer top was the bottom deformation boundary of the overlying layers. Non-coordination deformation was observed at the top and bottom of the subsiding overlying layers. The subsidence of overlying layers was larger at the bottom than at the top. The layers expanded and became thicker. The phenomenon was verified using numerical simulation method based on finite difference method. Compared with numerical simulation results, the boundary effect of the physical tests was obvious in the observation point close to the movable endpoint. The tensile stress of the overlying soil layers induced by the underlying settlement of dewatered confined aquifer contributed to the expansion phenomenon. The partial expansion of overlying soil layers was defined as inversed rebound. The inversed rebound was induced by inversed coordination deformation. Compression was induced by the consolidation in the overlying soil layers because of drainage. Partial expansion occurred when the expansion exceeded the compression. Considering the inversed rebound, traditional layer-wise summation method for calculating subsidence should be revised and improved.

Photobleachable Diazonium Salt-Phenolic Resin Two-Layer Resist System

NASA Astrophysics Data System (ADS)

Uchino, Shou-ichi; Iwayanagi, Takao; Hashimoto, Michiaki

1988-01-01

This article describes a new negative two-layer photoresist system formed by a simple, successive spin-coating method. An aqueous acetic acid solution of diazonium salt and poly(N-vinylpyrrolidone) is deposited so as to contact a phenolic resin film spin-coated on a silicon wafer. The diazonium salt diffuses into the phenolic resin layer after standing for several minutes. The residual solution on the phenolic resin film doped with diazonium salt is spun to form the diazonium salt-poly(N-vinylpyrrolidone) top layer. This forms a uniform two-layer resist without phase separation or striation. Upon UV exposure, the diazonium salt in the top layer bleaches to act as a CEL dye, while the diazonium salt in the bottom layer decomposes to cause insolubilization. Half μm line-and-space patterns are obtained with an i-line stepper using 4-diazo-N,N-dimethylaniline chloride zinc chloride double salt as the diazonium salt and a cresol novolac resin for the bottom polymer layer. The resist formation processes, insolubilization mechanism, and the resolution capability of the new two-layer resist are discussed.

Mass-physical properties of surficial sediments on the Rhoˆne continental margin: implications for the nepheloid benthic layer

NASA Astrophysics Data System (ADS)

Chassefiere, Bernard

1990-09-01

Mass-physical properties of the surficial (upper 5 m) sediments on the Gulf of Lions continental margin were analysed, from more than 100 short (1 m) and longer (5 m) cores obtained during several cruises. Data include water content, unit weight, Atterberg limits (liquid limit, plastic limit, plasticity index), shear strength and compression index, and are used to determine: first, the mass property distribution, according to the main parameters influencing mass-physical properties; the relationships between these properties and the nepheloid layer on the shelf. The shoreline (lagoons) and inner shelf are characterized by low density and shear strength and high water content deposits, due to electrochemical flocculation of the sediment. The outer shelf is blanketed by higher density and shear strength and lower water content deposits generated by normal settling of suspended particles. On the inner shelf, during river peak discharges, a short-term thin bottom layer of "yogurt-like" [ FASS (1985) Geomarine Letters, 4, 147-152; FASS (1986) Continental Shelf Research, 6, 189-208] fluid-mud (unit weight lower than 1.3 mg m -3) is supplied, by a bottom nepheloid layer. During stormy periods, this "yogurt-like" layer (about 10 cm thick) partly disappears by resuspension of suspended particulate matter; this is advected, in the bottom nepheloid layer, over the shelf and the canyons within the upper slope.

Management of light absorption in extraordinary optical transmission based ultra-thin-film tandem solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mashooq, Kishwar; Talukder, Muhammad Anisuzzaman, E-mail: anis@eee.buet.ac.bd

2016-05-21

Although ultra-thin-film solar cells can be attractive in reducing the cost, they suffer from low absorption as the thickness of the active layer is usually much smaller than the wavelength of incident light. Different nano-photonic techniques, including plasmonic structures, are being explored to increase the light absorption in ultra-thin-film solar cells. More than one layer of active materials with different energy bandgaps can be used in tandem to increase the light absorption as well. However, due to different amount of light absorption in different active layers, photo-generated currents in different active layers will not be the same. The current mismatchmore » between the tandem layers makes them ineffective in increasing the efficiency. In this work, we investigate the light absorption properties of tandem solar cells with two ultra-thin active layers working as two subcells and a metal layer with periodically perforated holes in-between the two subcells. While the metal layer helps to overcome the current mismatch, the periodic holes increase the absorption of incident light by helping extraordinary optical transmission of the incident light from the top to the bottom subcell, and by coupling the incident light to plasmonic and photonic modes within ultra-thin active layers. We extensively study the effects of the geometry of holes in the intermediate metal layer on the light absorption properties of tandem solar cells with ultra-thin active layers. We also study how different metals in the intermediate layer affect the light absorption; how the geometry of holes in the intermediate layer affects the absorption when the active layer materials are changed; and how the intermediate metal layer affects the collection of photo-generated electron-hole pairs at the terminals. We find that in a solar cell with 6,6-phenyl C61-butyric acid methyl ester top subcell and copper indium gallium selenide bottom subcell, if the periodic holes in the metal layer are square or polygon, total absorption remains approximately the same. However, the total absorption suffers significantly if the holes are triangle. The transmission spectra of incident light into the bottom subcell, and hence the absorption, change significantly for square and circle holes if the active materials change to cadmium selenide (CdSe) and cadmium telluride (CdTe) in the top and bottom subcells, respectively. Although the intermediate metal layer may induce electron-hole pair recombination due to surface defects, the short-circuit current density of an ultra-thin plasmonic solar cell with an intermediate metal layer with two-dimensional hole array is >9% of that of a structure without the intermediate metal layer.« less

Bottom-up meets top-down: tailored raspberry-like Fe 3 O 4 –Pt nanocrystal superlattices

DOE PAGES

Qiu, Fen; Vervuurt, René H. J.; Verheijen, Marcel A.; ...

2018-01-01

Bottom up colloidal synthesis is combined with top down atomic layer deposition to achieve raspberry-like Pt-decorated Fe 3 O 4 nanoparticle superlattices with good metal–oxide–metal contact for photoelectrocatalysis.

Bottom-up meets top-down: tailored raspberry-like Fe 3 O 4 –Pt nanocrystal superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiu, Fen; Vervuurt, René H. J.; Verheijen, Marcel A.

Bottom up colloidal synthesis is combined with top down atomic layer deposition to achieve raspberry-like Pt-decorated Fe 3 O 4 nanoparticle superlattices with good metal–oxide–metal contact for photoelectrocatalysis.

Analysis of Tip Vortices Identified in the Instantaneous Wake of a Horizontal-Axis Model Wind Turbine Placed in a Turbulent Boundary Layer

NASA Astrophysics Data System (ADS)

Jain, Akash; Mehdi, Faraz; Sheng, Jian

2014-11-01

The near-wake field, a short region characterized by the physical specifications of a turbine, is of particular interest for flow-structure interactions responsible for asymmetric loadings, premature structural breakdown, noise generation etc. Helical tip vortices constitute a distinctive feature of this region and are dependent not only on the turbine geometry but also on the incoming flow profile. High-spatial resolution PIV measurements are made in the wake of a horizontal-axis model wind turbine embedded in a neutrally stratified turbulent boundary layer. The data is acquired over consecutive locations up to 10 diameters downstream of the turbine but the focus here is on the tip vortices identified in the instantaneous fields. Contrary to previous studies, both top and bottom tip vortices are clearly distinguishable in either ensemble fields or instantaneous realizations. The streamwise extent of these vortices stretches from the turbine till they merge into the expanding mid-span wake. The similarities and differences in the top and bottom tip vortices are explored through the evolution of their statistics. In particular, the distributions of the loci of vortex cores and their circulations are compared. The information will improve our understanding of near wake vortical dynamics, provide data for model validation, and aid in the devise of flow control strategies.

Improvement of resist profile roughness in bilayer resist process

NASA Astrophysics Data System (ADS)

Jeong, Chang-Young; Ryu, Sang-Wook; Park, Ki-Yeop; Lee, Won-Kyu; Lee, Seung-Woog; Lee, Dai-Hoon

2000-06-01

The bi-layer resist (BLR) process, which first accomplish imaging on a thin top layer and transfer it down to a thick organic layer, is one of newly emerging patterning techniques in silicon processing. In this work, we studied the lithographic performance of the BLR process adopting FK- SPTM (Fujifilm Olin Co.) as top layer material and various organic material as bottom layer. Generally, considerable advantages of planarization, reduced substrate reflection, improved process latitude, and of enhanced resolution are achieved. However, the resolution and the process latitude are highly affected by surface interaction between the top resist and the bottom material. Moreover, the BLR process has a sidewall roughness problem related to the material factors of the resist and the degraded aerial image contrast, which can affect the reliability of the device. We found that thermal curing treatment applied after development with the consideration of the glass transition temperature are very effective in reducing the line edge roughness. More smooth and steep patterning is achieved by the thermal treatment. The linewidth controllability is below 10 nm and the k1 value is reduced from 0.5 down to 0.32 in this process. The reactive ion etching adopting O2 gas demonstrated selectivity of the top resist over bottom material more than 15:1, together with residue-free and vertical wall profile.

Bottom friction. A practical approach to modelling coastal oceanography

NASA Astrophysics Data System (ADS)

Bolanos, Rodolfo; Jensen, Palle; Kofoed-Hansen, Henrik; Tornsfeldt Sørensen, Jacob

2017-04-01

Coastal processes imply the interaction of the atmosphere, the sea, the coastline and the bottom. The spatial gradients in this area are normally large, induced by orographic and bathymetric features. Although nowadays it is possible to obtain high-resolution bathymetry, the details of the seabed, e.g. sediment type, presence of biological material and living organisms are not available. Additionally, these properties as well as bathymetry can also be highly dynamic. These bottom characteristics are very important to describe the boundary layer of currents and waves and control to a large degree the dissipation of flows. The bottom friction is thus typically a calibration parameter in numerical modelling of coastal processes. In this work, we assess this process and put it into context of other physical processes uncertainties influencing wind-waves and currents in the coastal areas. A case study in the North Sea is used, particularly the west coast of Denmark, where water depth of less than 30 m cover a wide fringe along the coast, where several offshore wind farm developments are being carried out. We use the hydrodynamic model MIKE 21 HD and the spectral wave model MIKE 21 SW to simulate atmosphere and tidal induced flows and the wind wave generation and propagation. Both models represent state of the art and have been developed for flexible meshes, ideal for coastal oceanography as they can better represent coastlines and allow a variable spatial resolution within the domain. Sensitivity tests to bottom friction formulations are carried out into context of other processes (e.g. model forcing uncertainties, wind and wave interactions, wind drag coefficient). Additionally, a map of varying bottom properties is generated based on a literature survey to explore the impact of the spatial variability. Assessment of different approaches is made in order to establish a best practice regarding bottom friction and coastal oceanographic modelling. Its contribution is also assessed during storm conditions, where its most evident impact is expected as waves are affected by the bottom processes in larger areas, making bottom dissipation more efficient. We use available waves and current measurements in the North Sea (e.g. Ekofisk, Fino platforms and some other coastal stations at the west coast of Denmark) to quantify the importance of processes influencing waves and currents in the coastal zone and putting it in the context of the importance of bottom friction and other processes uncertainties.

Phreatomagmatic eruptions under the West Antarctic Ice Sheet: potential hazard for ice sheet stability

NASA Astrophysics Data System (ADS)

Iverson, N. A.; Dunbar, N. W.; Lieb-Lappen, R.; Kim, E. J.; Golden, E. J.; Obbard, R. W.

2014-12-01

Volcanic tephra layers have been seen in most ice cores in Antarctica. These tephra layers are deposited almost instantaneously across wide areas of ice sheets, creating horizons that can provide "pinning points" to adjust ice time scales that may otherwise be lacking detailed chronology. A combination of traditional particle morphology characterization by SEM with new non-destructive X-ray micro-computed tomography (Micro-CT) has been used to analyze selected coarse grained tephra in the West Antarctica Ice Sheet (WAIS) Divide WDC06A ice core. Micro-CT has the ability to image particles as small as 50µm in length (15µm resolution), quantifying both particle shape and size. The WDC06A contains hundreds of dusty layers of which 36 have so far been identified as primary tephra layers. Two of these tephra layers have been characterized as phreatomagmatic eruptions based on SEM imagery and are blocky and platy in nature, with rare magmatic particles. These layers are strikingly different in composition from the typical phonolitic and trachytic tephra produced from West Antarctic volcanoes. These two layers are coarser in grain size, with many particles (including feldspar crystals) exceeding 100µm in length. One tephra layer found at 3149.138m deep in the ice core is a coarse ~1mm thick basanitic tephra layer with a WDC06-7 ice core age of 45,381±2000yrs. The second layer is a ~1.3 cm thick zoned trachyandesite to trachydacite tephra found at 2569.205m deep with an ice core age 22,470±835yrs. Micro-CT analysis shows that WDC06A-3149.138 has normal grading with the largest particles at the bottom of the sample (~160μm). WDC06A-2569.205 has a bimodal distribution of particles with large particles at the top and bottom of the layer. These large particles are more spherical in shape at the base and become more irregular and finer grained higher in the layer, likely showing changes in eruption dynamics. The distinct chemistry as well as the blocky and large grain size of the two tephra lead us to believe that these eruptions are from volcanoes proximal to WAIS Divide and did not transport far because neither tephra was observed in the Byrd core (<100km away). It is likely that these tephra are sourced from volcanoes beneath the WAIS and have since been buried and if they were to erupt again, may contribute to ice sheet instability.

An Investigation on Low Velocity Impact Response of Multilayer Sandwich Composite Structures

PubMed Central

Jedari Salami, S.; Sadighi, M.; Shakeri, M.; Moeinfar, M.

2013-01-01

The effects of adding an extra layer within a sandwich panel and two different core types in top and bottom cores on low velocity impact loadings are studied experimentally in this paper. The panel includes polymer composite laminated sheets for faces and the internal laminated sheet called extra layer sheet, and two types of crushable foams are selected as the core material. Low velocity impact tests were carried out by drop hammer testing machine to the clamped multilayer sandwich panels with expanded polypropylene (EPP) and polyurethane rigid (PUR) in the top and bottom cores. Local displacement of the top core, contact force and deflection of the sandwich panel were obtained for different locations of the internal sheet; meanwhile the EPP and PUR were used in the top and bottom cores alternatively. It was found that the core material type has made significant role in improving the sandwich panel's behavior compared with the effect of extra layer location. PMID:24453804

Stratification Modelling of Key Bacterial Taxa Driven by Metabolic Dynamics in Meromictic Lakes.

PubMed

Zhu, Kaicheng; Lauro, Federico M; Su, Haibin

2018-06-22

In meromictic lakes, the water column is stratified into distinguishable steady layers with different physico-chemical properties. The bottom portion, known as monimolimnion, has been studied for the functional stratification of microbial populations. Recent experiments have reported the profiles of bacterial and nutrient spatial distributions, but quantitative understanding is invoked to unravel the underlying mechanism of maintaining the discrete spatial organization. Here a reaction-diffusion model is developed to highlight the spatial pattern coupled with the light-driven metabolism of bacteria, which is resilient to a wide range of dynamical correlation between bacterial and nutrient species at the molecular level. Particularly, exact analytical solutions of the system are presented together with numerical results, in a good agreement with measurements in Ace lake and Rogoznica lake. Furthermore, one quantitative prediction is reported here on the dynamics of the seasonal stratification patterns in Ace lake. The active role played by the bacterial metabolism at microscale clearly shapes the biogeochemistry landscape of lake-wide ecology at macroscale.

Effects of interfacial layer on characteristics of TiN/ZrO2 structures.

PubMed

Kim, Younsoo; Kang, Sang Yeol; Choi, Jae Hyoung; Lim, Jae Soon; Park, Min Young; Chung, Suk-Jin; Chung, Jaegwan; Lee, Hyung Ik; Kim, Ki Hong; Kyoung, Yong Koo; Heo, Sung; Yoo, Cha Young; Kang, Ho-Kyu

2011-09-01

To minimize the formation of unwanted interfacial layers, thin interfacial layer (ZrCN layer) was deposited between TiN bottom electrode and ZrO2 dielectric in TiN/ZrO2/TiN capacitor. Carbon and nitrogen were also involved in the layer because ZrCN layer was thermally deposited using TEMAZ without any reactant. Electrical characteristics of TiN/ZrO2/TiN capacitor were improved by insertion of ZrCN layer. The oxidation of TiN bottom electrode was largely inhibited at TiN/ZrCN/ZrO2 structure compared to TiN/ZrO2 structure. While the sheet resistance of TiN/ZrCN/ZrO2 structure was constantly sustained with increasing ZrO2 thickness, the large increase of sheet resistance was observed in TiN/ZrO2 structure after 6 nm ZrO2 deposition. When ZrO2 films were deposited on ZrCN layer, the deposition rate of ZrO2 also increased. It is believed that ZrCN layer acted both as a protection layer of TiN oxidation and a seed layer of ZrO2 growth.

Magnetoresistance enhancement in specular, bottom-pinned, Mn83Ir17 spin valves with nano-oxide layers

NASA Astrophysics Data System (ADS)

Veloso, A.; Freitas, P. P.; Wei, P.; Barradas, N. P.; Soares, J. C.; Almeida, B.; Sousa, J. B.

2000-08-01

Bottom-pinned Mn83Ir17 spin valves with enhanced specular scattering were fabricated, showing magnetoresistance (MR) values up to 13.6%, lower sheet resistance R□ and higher ΔR□. Two nano-oxide layers (NOL) are grown on both sides of the CoFe/Cu/CoFe spin valve structure by natural oxidation or remote plasma oxidation of the starting CoFe layer. Maximum MR enhancement is obtained after just 1 min plasma oxidation. Rutherford backscattering analysis shows that a 15±2 Å oxide layer grows at the expense of the initial (prior to oxidation) CoFe layer, with ˜12% reduction of the initial 40 Å CoFe thickness. X-ray reflectometry indicates that Kiessig fringes become better defined after NOL growth, indicating smoother inner interfaces, in agreement with the observed decrease of the spin valve ferromagnetic Néel coupling.

Stretchable Metamaterial Absorber Using Liquid Metal-Filled Polydimethylsiloxane (PDMS)

PubMed Central

Kim, Kyeongseob; Lee, Dongju; Eom, Seunghyun; Lim, Sungjoon

2016-01-01

A stretchable metamaterial absorber is proposed in this study. The stretchability was achieved by liquid metal and polydimethylsiloxane (PDMS). To inject liquid metal, microfluidic channels were fabricated using PDMS powers and microfluidic-channel frames, which were built using a three-dimensional printer. A top conductive pattern and ground plane were designed after considering the easy injection of liquid metal. The proposed metamaterial absorber comprises three layers of PDMS substrate. The top layer is for the top conductive pattern, and the bottom layer is for the meandered ground plane. Flat PDMS layers were inserted between the top and bottom PDMS layers. The measured absorptivity of the fabricated absorber was 97.8% at 18.5 GHz, and the absorption frequency increased from 18.5 to 18.65 GHz as the absorber was stretched from its original length (5.2 cm) to 6.4 cm. PMID:27077861

Ab initio study of friction of graphene flake on graphene/graphite or SiC surface

NASA Astrophysics Data System (ADS)

Gulseren, Oguz; Tayran, Ceren; Sayin, Ceren Sibel

Recently, the rich dynamics of graphene flake on graphite or SiC surfaces are revealed from atomic force microcopy experiments. The studies toward to the understanding of microscopic origin of friction are getting a lot of attention. Despite the several studies of these systems using molecular dynamics methods, density functional theory based investigations are limited because of the huge system sizes. In this study, we investigated the frictional force on graphene flake on graphite or SiC surfaces from pseudopotential planewave calculations based on density functional theory. In both cases, graphene flake (24 C) on graphite or SiC surface, bilayer flake is introduced by freezing the top layer as well as the bottom layer of the surface slab. After fixing the load with these frozen layers, we checked the relative motion of the flake over the surface. A minimum energy is reached when the flake is moved on graphene to attain AB stacking. We also conclude that edge reconstruction because of the finite size of the flake is very critical for frictional properties of the flake; therefore the saturation of dangling bonds with hydrogen is also addressed. Not only the symmetric configurations remaining parameter space is extensively studied. Supported by TUBITAK Project No: 114F162. This work is supported by TUBITAK Project No: 114F162.

Homogenization of one-dimensional draining through heterogeneous porous media including higher-order approximations

NASA Astrophysics Data System (ADS)

Anderson, Daniel M.; McLaughlin, Richard M.; Miller, Cass T.

2018-02-01

We examine a mathematical model of one-dimensional draining of a fluid through a periodically-layered porous medium. A porous medium, initially saturated with a fluid of a high density is assumed to drain out the bottom of the porous medium with a second lighter fluid replacing the draining fluid. We assume that the draining layer is sufficiently dense that the dynamics of the lighter fluid can be neglected with respect to the dynamics of the heavier draining fluid and that the height of the draining fluid, represented as a free boundary in the model, evolves in time. In this context, we neglect interfacial tension effects at the boundary between the two fluids. We show that this problem admits an exact solution. Our primary objective is to develop a homogenization theory in which we find not only leading-order, or effective, trends but also capture higher-order corrections to these effective draining rates. The approximate solution obtained by this homogenization theory is compared to the exact solution for two cases: (1) the permeability of the porous medium varies smoothly but rapidly and (2) the permeability varies as a piecewise constant function representing discrete layers of alternating high/low permeability. In both cases we are able to show that the corrections in the homogenization theory accurately predict the position of the free boundary moving through the porous medium.

A coupled physical-biological pelagic model of a shallow sill fjord

NASA Astrophysics Data System (ADS)

Aksnes, Dag L.; Lie, Ulf

1990-10-01

A vertically resolved model for the land-locked fjord Lindåspollene, western Norway is presented. Salinity, temperature, oxygen, nitrogen-nutrients, silicate, and two groups of phytoplankton and herbivores are represented as dynamic variables. From 'below' the model is driven by solar radiation, precipitation, wind and tidal exchange and from 'above' by herbivore mortality. Simulation results are presented and discussed together with actual observations from Lindåspollene. The main seasonal and vertical characteristics of the phytoplankton and herbivore dynamics seem to be well reflected by the model, and realistic seasonal patterns may be produced for several successive years. The most characteristic vertical features are the formation of a summer surface production maximum and a deep chlorophyll maximum. Furthermore, a herbivore biomass which develops in the surface layer divides into a shallow and a deep component during summer and becomes concentrated in the surface layer again in the autumn. The nutricline and the pycnocline develop independently of one another, with consequences for the supply of nutrients to the upper euphotic zone. The bottom-up control exerted by the meteorological forcing, especially the freshwater runoff, seems to be of paramount significance for the observed vertical structure and seasonality of the present fjord system.

Single-layer 1T‧-MoS2 under electron irradiation from ab initio molecular dynamics

NASA Astrophysics Data System (ADS)

Pizzochero, Michele; Yazyev, Oleg V.

2018-04-01

Irradiation with high-energy particles has recently emerged as an effective tool for tailoring the properties of two-dimensional transition metal dichalcogenides. In order to carry out an atomically-precise manipulation of the lattice, a detailed understanding of the beam-induced events occurring at the atomic scale is necessary. Here, we investigate the response of 1T' -MoS2 to the electron irradiation by ab initio molecular dynamics means. Our simulations suggest that an electron beam with energy smaller than 75 keV does not result in any knock-on damage. The displacement threshold energies are different for the two nonequivalent sulfur atoms in 1T' -MoS2 and strongly depend on whether the top or bottom chalcogen layer is considered. As a result, a careful tuning of the beam energy can promote the formation of ordered defects in the sample. We further discuss the effect of the electron irradiation in the neighborhood of a defective site, the mobility of the sulfur vacancies created and their tendency to aggregate. Overall, our work provides useful guidelines for the imaging and the defect engineering of 1T' -MoS2 using electron microscopy.

Current-induced switching in CoGa/L10 MnGa/(CoGa)/Pt structure with different thicknesses

NASA Astrophysics Data System (ADS)

Ranjbar, R.; Suzuki, K. Z.; Mizukami, S.

2018-06-01

In this paper, we present the results of our study into current-induced spin-orbit torque (SOT) switching in perpendicularly magnetized CoGa/MnGa/Pt trilayers with different thicknesses of MnGa and Pt. The SOT switching was observed for all films that undergo Joule heating. We also investigate SOT switching in the bottom (CoGa)/MnGa/top(CoGa/Pt) films with different top layers. Although both the bottom and top layers contribute to the SOT, the relative magnitudes of the switching current densities JC in the top and bottom layers indicate that the SOT is dominant in the top layer. The JC as a function of thickness is discussed in terms of the magnetic properties and resistivity. Experimental data suggested that the MnGa thickness dependence of JC may originate from the perpendicular magnetic anisotropy thickness product Kueff t value. On the other hand, JC as a function of the Pt thickness shows weak dependence. This may be attributed to the slight change of spin-Hall angle θSH value with different thicknesses of Pt, when we assumed that the SOT switching is primarily due to the spin-Hall effect.

Wound Tissue Can Utilize a Polymeric Template to Synthesize a Functional Extension of Skin

NASA Astrophysics Data System (ADS)

Yannas, I. V.; Burke, J. F.; Orgill, D. P.; Skrabut, E. M.

1982-01-01

Prompt and long-term closure of full-thickness skin wounds in guinea pigs and humans is achieved by applying a bilayer polymeric membrane. The membrane comprises a top layer of a silicone elastomer and a bottom layer of a porous cross-linked network of collagen and glycosaminoglycan. The bottom layer can be seeded with a small number of autologous basal cells before grafting. No immunosuppression is used and infection, exudation, and rejection are absent. Host tissue utilizes the sterile membrane as a culture medium to synthesize neoepidermal and neodermal tissue. A functional extension of skin over the entire wound area is formed in about 4 weeks.

Transitional boundary layer in low-Prandtl-number convection at high Rayleigh number

NASA Astrophysics Data System (ADS)

Schumacher, Joerg; Bandaru, Vinodh; Pandey, Ambrish; Scheel, Janet

2016-11-01

The boundary layer structure of the velocity and temperature fields in turbulent Rayleigh-Bénard flows in closed cylindrical cells of unit aspect ratio is revisited from a transitional and turbulent viscous boundary layer perspective. When the Rayleigh number is large enough the boundary layer dynamics at the bottom and top plates can be separated into an impact region of downwelling plumes, an ejection region of upwelling plumes and an interior region (away from side walls) that is dominated by a shear flow of varying orientation. This interior plate region is compared here to classical wall-bounded shear flows. The working fluid is liquid mercury or liquid gallium at a Prandtl number of Pr = 0 . 021 for a range of Rayleigh numbers of 3 ×105 <= Ra <= 4 ×108 . The momentum transfer response to these system parameters generates a fluid flow in the closed cell with a macroscopic flow Reynolds number that takes values in the range of 1 . 8 ×103 <= Re <= 4 . 6 ×104 . It is shown that particularly the viscous boundary layers for the largest Ra are highly transitional and obey some properties that are directly comparable to transitional channel flows at friction Reynolds numbers below 100. This work is supported by the Deutsche Forschungsgemeinschaft.

Development of a three-dimensional, regional, coupled wave, current, and sediment-transport model

USGS Publications Warehouse

Warner, J.C.; Sherwood, C.R.; Signell, R.P.; Harris, C.K.; Arango, H.G.

2008-01-01

We are developing a three-dimensional numerical model that implements algorithms for sediment transport and evolution of bottom morphology in the coastal-circulation model Regional Ocean Modeling System (ROMS v3.0), and provides a two-way link between ROMS and the wave model Simulating Waves in the Nearshore (SWAN) via the Model-Coupling Toolkit. The coupled model is applicable for fluvial, estuarine, shelf, and nearshore (surfzone) environments. Three-dimensional radiation-stress terms have been included in the momentum equations, along with effects of a surface wave roller model. The sediment-transport algorithms are implemented for an unlimited number of user-defined non-cohesive sediment classes. Each class has attributes of grain diameter, density, settling velocity, critical stress threshold for erosion, and erodibility constant. Suspended-sediment transport in the water column is computed with the same advection-diffusion algorithm used for all passive tracers and an additional algorithm for vertical settling that is not limited by the CFL criterion. Erosion and deposition are based on flux formulations. A multi-level bed framework tracks the distribution of every size class in each layer and stores bulk properties including layer thickness, porosity, and mass, allowing computation of bed morphology and stratigraphy. Also tracked are bed-surface properties including active-layer thickness, ripple geometry, and bed roughness. Bedload transport is calculated for mobile sediment classes in the top layer. Bottom-boundary layer submodels parameterize wave-current interactions that enhance bottom stresses and thereby facilitate sediment transport and increase bottom drag, creating a feedback to the circulation. The model is demonstrated in a series of simple test cases and a realistic application in Massachusetts Bay. 

49 CFR 393.122 - What are the rules for securing paper rolls?

Code of Federal Regulations, 2010 CFR

2010-10-01

... be loaded on a layer of paper rolls beneath unless the lower layer extends to the front of the vehicle. (2) Paper rolls in the second and subsequent layers must be prevented from forward, rearward or lateral movement by means as allowed for the bottom layer, or by use of a blocking roll from a lower layer...

Design high water clearances for highway pavements : [executive summary].

DOT National Transportation Integrated Search

2008-01-01

The majority of state roads in Florida are built using asphalt concrete surfaces. They are constructed in layers. The bottom layer consists of the native soil. The top layer is the surface course, or pavement. It is built upon one or more intermediat...

Impact of viscous boundary layers on the emission of lee-waves

NASA Astrophysics Data System (ADS)

Renaud, Antoine; Venaille, Antoine; Bouchet, Freddy

2017-04-01

Oceans large-scale structures such as jets and vortices can lose their energy into small-scale turbulence. Understanding the physical mechanisms underlying those energy transfers remains a major theoretical challenge. Here we propose an approach that shed new light on the role of bottom topography in this problem. At a linear level, one efficient way of extracting energy and momentum from the mean-flow above topography undulations is the radiation of lee-waves. The generated lee-waves are well described by inviscid theory which gives a prediction for the energy-loss rate at short time [1]. Using a quasi-linear approach we describe the feedback of waves on the mean-flow occurring mostly close to the bottom topography. This can thereafter impact the lee-waves radiation and thus modify the energy-loss rate for the mean-flow. In this work, we consider the Boussinesq equations with periodic boundary conditions in the zonal direction. Taking advantage of this idealized geometry, we apply zonally-symmetric wave-mean interaction theory [2,3]. The novelty of our work is to discuss the crucial role of dissipative effects, such as molecular or turbulent viscosities, together with the importance of the boundary conditions (free-slip vs no-slip). We provide explicite computations in the case of the free evolution of an initially barotropic flow above a sinusoidal topography with free-slip bottom boundary condition. We show how the existence of the boundary layer for the wave-field can enhance the streaming close to the topography. This leads to the emergence of boundary layer for the mean-flow impacting the energy-loss rate through lee-wave emissions. Our results are compared against direct numerical simulations using the MIT general circulation model and are found to be in good agreement. References [1] S.L. Smith, W.R. Young, Conversion of the Barotropic Tide, JPhysOcean 2002 [2] 0. Bühler, Waves and Mean Flows, second edition, Cambridge university press 2014 [3] J. Muraschko et al, On the application of WKB theory for the simulation of the weakly nonlinear dynamics of gravity waves, Q. J. R. Meteorol. Soc. 2013

The influence of nano-oxide layer on magnetostriction of sensing layer in bottom spin valves

NASA Astrophysics Data System (ADS)

Qiu, J. J.; Han, G. C.; Li, K. B.; Liu, Z. Y.; Zong, B. Y.; Wu, Y. H.

2006-05-01

The magnetostriction coefficient (λs) of ultrathin sputtered polycrystalline as-deposited and annealed Ta/Ni81Fe19(t)/Ta films was studied as a function of the thickness. λs and magnetoresistance (MR) of bottom-type spin valves (SVs) with nano-oxide layer (NOL) added in the pinned layer were investigated by using NiFe, Co90Fe10, and CoFe/NiFe/CoFe layers as free layer (FL), respectively. λs of SV with NOL increased slightly except that of CoFe FL. NOLs were added at different positions to study the effects of NOL on λs of CoFe FL. All λs of CoFe FL change from negative to positive and its absolute value also increases significantly with CoFeOx related NOL added below. Our λs and surface roughness results indicated that the structure of the film not the roughness dominates λs of ultrathin FL in SVs.

Bottom-up GGM algorithm for constructing multiple layered hierarchical gene regulatory networks

USDA-ARS?s Scientific Manuscript database

Multilayered hierarchical gene regulatory networks (ML-hGRNs) are very important for understanding genetics regulation of biological pathways. However, there are currently no computational algorithms available for directly building ML-hGRNs that regulate biological pathways. A bottom-up graphic Gaus...

Hydrochemistry of the Tumen River Estuary, Sea of Japan

NASA Astrophysics Data System (ADS)

Tishchenko, P. Ya.; Semkin, P. Yu.; Pavlova, G. Yu.; Tishchenko, P. P.; Lobanov, V. B.; Marjash, A. A.; Mikhailik, T. A.; Sagalaev, S. G.; Sergeev, A. F.; Tibenko, E. Yu.; Khodorenko, N. D.; Chichkin, R. V.; Shvetsova, M. G.; Shkirnikova, E. M.

2018-03-01

The hydrological and hydrochemical parameters of the Tumen River estuary were collected at 13 stations in May and October 2015. Vertical temperature, conductivity, dissolved oxygen, chlorophyll fluorescence, and turbidity profiles were obtained. Water was sampled from the surface and bottom layer. The water samples were analyzed for major ions, pH, salinity, concentrations of dissolved oxygen, major nutrients, dissolved organic carbon, humic matter, and δ18O and δD isotopes. This estuary is attributed to microtidal type with a flushing time of about 10 h. A phytoplakton bloom occurred in the top layer of the estuary. For surface horizons, the hydrochemical parameters show a linear correlation with salinity. In the bottom horizons, all these parameters, except for major ions and δ18O and δD isotopes, reveal substantial nonconservative behavior. The nonconservative behavior of the hydrochemical parameters in the bottom waters was mainly caused by degradation of the phytoplankton biomass at the water/sediment interface. Hypoxic conditions were established in the bottom waters of the estuary in May.

Integrated resonant tunneling diode based antenna

DOEpatents

Hietala, Vincent M.; Tiggers, Chris P.; Plut, Thomas A.

2000-01-01

An antenna comprising a plurality of negative resistance devices and a method for making same comprising employing a removable standoff layer to form the gap between the microstrip antenna metal and the bottom contact layer.

Characterization and migration of oil and solids in oily sludge during centrifugation.

PubMed

Wang, Jun; Han, Xu; Huang, Qunxing; Ma, Zengyi; Chi, Yong; Yan, Jianhua

2018-05-01

The migration behaviors of oil, water and solids in sludge during centrifugation were elaborated. Size distribution, surface topography and lypohydrophilic properties were studied in detail. The average size of solids was 61 μm in original sludge, 31 μm in upper layer and 235 μm in bottom layer. The result shows that solvent is essential to separate oil phase into molecular light and weight fractions during centrifugation. With solvent/oil ratio increases from 1:2, 1:1, 2:1 to 5:1, molecular weight in upper layer decreases from 1044, 1043, 1020 to 846 combined with that in bottom layer increases. A model was proposed to calculate the oil residue content in solid phases after sedimentation. The findings of this paper provide information for optimizing the oil recovery and clean treatment.

Heat transport and coupling modes in Rayleigh-Bénard convection occurring between two layers with largely different viscosities

NASA Astrophysics Data System (ADS)

Yoshida, Masaki; Iwamori, Hikaru; Hamano, Yozo; Suetsugu, Daisuke

2017-09-01

A high-resolution numerical simulation model in two-dimensional cylindrical geometry was used to discuss the heat transport and coupling modes in two-layer Rayleigh-Bénard convection with a high Rayleigh number (up to the order of 109), an infinite Prandtl number, and large viscosity contrasts (up to 10-3) between an outer, highly viscous layer (HVL) and an inner, low-viscosity layer (LVL). In addition to mechanical and thermal interaction across the HVL-LVL interface, which has been investigated by Yoshida and Hamano ["Numerical studies on the dynamics of two-layer Rayleigh-Bénard convection with an infinite Prandtl number and large viscosity contrasts," Phys. Fluids 28(11), 116601 (2016)], the spatiotemporal analysis in this study provides new insights into (1) heat transport over the entire system between the bottom of the LVL and the top of the HVL, in particular that associated with thermal plumes, and (2) the convection regime and coupling mode of the two layers, including the transition mechanism between the mechanical coupling mode at relatively low viscosity contrasts and the thermal coupling mode at higher viscosity contrasts. Although flow in the LVL is highly time-dependent, it shares the spatially opposite/same flow pattern synchronized to the nearly stationary upwelling and downwelling plumes in the HVL, corresponding to the mechanical/thermal coupling mode. In the transitional regime between the mechanical and thermal coupling modes, the LVL exhibits periodical switching between the two phases (i.e., the mechanical and thermal coupling phases) with a stagnant period. A detailed inspection revealed that the switching was initiated by the instability in the uppermost boundary layer of the LVL. These results suggest that convection in the highly viscous mantle of the Earth controls that of the extremely low-viscosity outer core in a top-down manner under the thermal coupling mode, which may support a scenario of top-down hemispherical dynamics proposed by the recent geochemical study.

Reduction of Leaching Impacts by Applying Biomass Bottom Ash and Recycled Mixed Aggregates in Structural Layers of Roads

PubMed Central

Cabrera, Manuel; Galvin, Adela P.; Agrela, Francisco; Beltran, Manuel G.; Ayuso, Jesus

2016-01-01

This research is focused on analyzing the environmental pollution potential of biomass bottom ashes as individual materials, as mixtures manufactured with biomass bottom ashes and granular construction aggregates, and these mixtures treated with cement. For the environmental assessment of all of the samples and materials mentioned, the following leaching procedures have been performed: the compliance batch test of UNE-EN 12457-3:2003 for aggregates and bottom ashes; the column test according to NEN 7343:1994 for the mixtures prepared in the laboratory; and the tank test by EA NEN 7375:2004 for analyzing the behavior of mixtures after their solidification/stabilization with 5% cement. After the discussion of the data, the reduction of the pollution load of the most hazardous biomass bottom ashes after their combination with different aggregates can be confirmed, which implies their possible application in civil infrastructures, such as filler embankments and road construction layers, without negatively impacting the environment. In addition, the positive effect of the stabilization/solidification of the cement-treated mixtures with a reduction of the heavy metals that were released at the highest levels, namely As, Hg Cr, Ni, Cu, Se and Mo, was proven. PMID:28773352

Two-phase convection in Ganymede's high-pressure ice layer - Implications for its geological evolution

NASA Astrophysics Data System (ADS)

Kalousová, Klára; Sotin, Christophe; Choblet, Gaël; Tobie, Gabriel; Grasset, Olivier

2018-01-01

Ganymede, the largest moon in the solar system, has a fully differentiated interior with a layer of high-pressure (HP) ice between its deep ocean and silicate mantle. In this paper, we study the dynamics of this layer using a numerical model of two-phase ice-water mixture in two-dimensional Cartesian geometry. While focusing on the generation of water at the silicate/HP ice interface and its upward migration towards the ocean, we investigate the effect of bottom heat flux, the layer thickness, and the HP ice viscosity and permeability. Our results suggest that melt can be generated at the silicate/HP ice interface for small layer thickness ( ≲ 200 km) and high values of heat flux ( ≳ 20 mW m-2) and viscosity ( ≳ 1015 Pa s). Once generated, the water is transported through the layer by the upwelling plumes. Depending on the vigor of convection, it stays liquid or it may freeze before melting again as the plume reaches the temperate (partially molten) layer at the boundary with the ocean. The thickness of this layer as well as the amount of melt that is extracted from it is controlled by the permeability of the HP ice. This process constitutes a means of transporting volatiles and salts that might have dissolved into the melt present at the silicate/HP ice interface. As the moon cools down, the HP ice layer becomes less permeable because the heat flux from the silicates decreases and the HP ice layer thickens.

GaN Micromechanical Resonators with Meshed Metal Bottom Electrode.

PubMed

Ansari, Azadeh; Liu, Che-Yu; Lin, Chien-Chung; Kuo, Hao-Chung; Ku, Pei-Cheng; Rais-Zadeh, Mina

2015-03-17

This work describes a novel architecture to realize high-performance gallium nitride (GaN) bulk acoustic wave (BAW) resonators. The method is based on the growth of a thick GaN layer on a metal electrode grid. The fabrication process starts with the growth of a thin GaN buffer layer on a Si (111) substrate. The GaN buffer layer is patterned and trenches are made and refilled with sputtered tungsten (W)/silicon dioxide (SiO₂) forming passivated metal electrode grids. GaN is then regrown, nucleating from the exposed GaN seed layer and coalescing to form a thick GaN device layer. A metal electrode can be deposited and patterned on top of the GaN layer. This method enables vertical piezoelectric actuation of the GaN layer using its largest piezoelectric coefficient ( d 33 ) for thickness-mode resonance. Having a bottom electrode also results in a higher coupling coefficient, useful for the implementation of acoustic filters. Growth of GaN on Si enables releasing the device from the frontside using isotropic xenon difluoride (XeF₂) etch and therefore eliminating the need for backside lithography and etching.

Nonstationary plasma-thermo-fluid dynamics and transition in processes of deep penetration laser beam-matter interaction

NASA Astrophysics Data System (ADS)

Golubev, Vladimir S.; Banishev, Alexander F.; Azharonok, V. V.; Zabelin, Alexandre M.

1994-09-01

A qualitative analysis of the role of some hydrodynamic flows and instabilities by the process of laser beam-metal sample deep penetration interaction is presented. The forces of vapor pressure, melt surface tension and thermocapillary forces can determined a number of oscillatory and nonstationary phenomena in keyhole and weld pool. Dynamics of keyhole formation in metal plates has been studied under laser beam pulse effect ((lambda) equals 1.06 micrometers ). Velocities of the keyhole bottom motion have been determined at 0.5 X 105 - 106 W/cm2 laser power densities. Oscillatory regime of plate break- down has been found out. Small-dimensional structures with d-(lambda) period was found on the frozen cavity walls, which, in our opinion, can contribute significantly to laser beam absorption. A new form of periodic structure on the frozen pattern being a helix-shaped modulation of the keyhole walls and bottom relief has been revealed. Temperature oscillations related to capillary oscillations in the melt layer were discovered in the cavity. Interaction of the CW CO2 laser beam and the matter by beam penetration into a moving metal sample has been studied. The pulsed and thermodynamic parameters of the surface plasma were investigated by optical and spectroscopic methods. The frequencies of plasma jets pulsations (in 10 - 105 Hz range) are related to possible melt surface instabilities of the keyhole.

Navigating in foldonia: Using accelerated molecular dynamics to explore stability, unfolding and self-healing of the β-solenoid structure formed by a silk-like polypeptide

PubMed Central

Zhao, Binwu

2017-01-01

The β roll molecules with sequence (GAGAGAGQ)10 stack via hydrogen bonding to form fibrils which have been themselves been used to make viral capsids of DNA strands, supramolecular nanotapes and pH-responsive gels. Accelerated molecular dynamics (aMD) simulations are used to investigate the unfolding of a stack of two β roll molecules, (GAGAGAGQ)10, to shed light on the folding mechanism by which silk-inspired polypeptides form fibrils and to identify the dominant forces that keep the silk-inspired polypeptide in a β roll configuration. Our study shows that a molecule in a stack of two β roll molecules unfolds in a step-wise fashion mainly from the C terminal. The bottom template is found to play an important role in stabilizing the β roll structure of the molecule on top by strengthening the hydrogen bonds in the layer that it contacts. Vertical hydrogen bonds within the β roll structure are considerably weaker than lateral hydrogen bonds, signifying the importance of lateral hydrogen bonds in stabilizing the β roll structure. Finally, an intermediate structure was found containing a β hairpin and an anti-parallel β sheet consisting of strands from the top and bottom molecules, revealing the self-healing ability of the β roll stack. PMID:28329017

Untold muddy tales: Paleoenvironmental dynamics of a ``barren'' mudrock succession from a shallow Permian epeiric sea

NASA Astrophysics Data System (ADS)

Simões, M. G.; Matos, S. A.; Warren, L. V.; Assine, M. L.; Riccomini, C.; Bondioli, J. G.

2016-11-01

During the late Paleozoic, the intracratonic Paraná Basin, Brazil, in central Gondwanaland, was covered by a huge (>1.600.000 km2), shallow and isolated epeiric sea. Within the Permian succession, oxygen-deficient facies are commonly recorded in the Mesosaurus-bearing Irati Formation (Cisuralian, Artinskian/Kungurian) and the overlaying Serra Alta Formation (Guadalupian, Wordian/Capitanian). Barren, dark-grey mudstones are the main facies preserved in this last unit, which has usually discouraged extensive and detailed stratigraphical and paleontological investigations. However, exhaustive sedimentological, taphonomic and paleontological surveys in those deposits reveal a dynamic and complex depositonal history. Based on sedimentary fabric, autochthonous to parautochthonous occurrences of shelly benthic invertebrates (bivalves) and the presence/absence of concretion-bearing and phosphate-rich layers, we report variations in the oxygen levels of bottom and pore waters, in bathymetry, sedimentation rates, and changes in benthic colonization. Our data indicate that the deposition of this "apparently barren" mudstone-dominated succession was driven by a complex interplay of variations in sedimentation rate and oxygen pulses tied to tectonic and climate changes. Three distinct populations or invertebrate paleocommunities were recorded, which were adapted to (a) normal background low-oxygen (dysoxic) conditions (i.e., minute infaunal suspension-feeding bivalves associated with the trace fossil Planolites), (b) chemically toxic (anoxic/extreme dysoxic) substrates, including gigantic burrowing bivalves (probable chemosymbiotic taxa), and (c) oxic/dysoxic substrates following short-term bottom disruptions.

In situ nitrification rates and activity of present nitrifiers in the bottom water layer of two Baltic coastal zones affected by different riverine nutrient loads

NASA Astrophysics Data System (ADS)

Bartl, I.; Münster Happel, E.; Riemann, L.; Voss, M.

2016-02-01

Baltic coastal zones are among the most eutrophied in the world receiving high loads of nitrogen from riverine inputs. However, not only the loads but also the internal dynamics in coastal zones might have positive feedback on eutrophication through efficient remineralisation of organic material in the bottom water. Therefore, we studied nitrification, which is a vital remineralisation process, near the seafloor along with the community of nitrifying microorganisms. We hypothesize that a high nutrient and organic matter load leads to elevated ammonium concentrations in coastal waters and thus stimulates nitrification rates and alters the nitrifying community. Here we present results from 3 cruises combining nitrification rate measurements by 15N-incubations with sequence-based analyses of present and active nitrifiers in the bottom water of two sites in the Baltic Sea receiving different nutrient loads. The first results from the Bonus projects COCOA and BLUEPRINT indicate an increase of nitrification rates with depth as well as distance from the river mouth. In situ rates in the bottom water of the nutrient rich Vistula plume range from 53 to 197 nmol L-1 d-1 and from 10 to 646 nmol L-1 d-1 during winter and summer, respectively. In the nutrient poor Öre estuary rates increased significantly by 11 nmol L-1 d-1 from the river mouth to the outermost station. The relationship between nitrification rates, nitrifiers and trophic state of the coastal zone shall be discussed.

Methods to induce perpendicular magnetic anisotropy in full-Heusler Co2FeSi thin layers in a magnetic tunnel junction structure

NASA Astrophysics Data System (ADS)

Shinohara, Koki; Suzuki, Takahiro; Takamura, Yota; Nakagawa, Shigeki

2018-05-01

In this study, to obtain perpendicular magnetic tunnel junctions (p-MTJs) using half-metallic ferromagnets (HMFs), several methods were developed to induce perpendicular magnetic anisotropy (PMA) in full-Heusler Co2FeSi (CFS) alloy thin layers in an MTJ multilayer composed of a layered CFS/MgO/CFS structure. Oxygen exposure at 2.0 Pa for 10 min after deposition of the bottom CFS layer was effective for obtaining PMA in the CFS layer. One of the reasons for the PMA is the formation of nearly ideal CFS/MgO interfaces due to oxygen exposure before the deposition of the MgO layer. The annealing process was effective for obtaining PMA in the top CFS layer capped with a Pd layer. PMA was clearly observed in the top CFS layer of a Cr(40 nm)/Pd(50 nm)/bottom CFS(0.6 nm)/MgO(2.0 nm)/top CFS(0.6 nm)/ Pd(10 nm) multilayer, where the top CFS and Pd thin films were deposited at RT and subsequently annealed at 300°C. In addition to the continuous layer growth of the films, the crystalline orientation alignment at the top CFS/Pd interface probably attributes to the origin of PMA at the top CFS layer.

Observations of near-bottom currents in Bornholm Basin, Slupsk Furrow and Gdansk Deep

NASA Astrophysics Data System (ADS)

Bulczak, A. I.; Rak, D.; Schmidt, B.; Beldowski, J.

2016-06-01

Dense bottom currents are responsible for transport of the salty inflow waters from the North Sea driving ventilation and renewal of Baltic deep waters. This study characterises dense currents in three deep locations of the Baltic Proper: Bornholm Basin (BB), Gdansk Basin (GB) and Slupsk Furrow (SF). These locations are of fundamental importance for the transport and pollution associated with chemical munitions deposited in BB and GB after 2nd World War. Of further importance the sub-basins are situated along the pathway of dense inflowing water.Current velocities were measured in the majority of the water column during regular cruises of r/v Oceania and r/v Baltica in 2001-2012 (38 cruises) by 307 kHz vessel mounted (VM), downlooking ADCP. Additionally, the high-resolution CTD and oxygen profiles were collected. Three moorings measured current velocity profiles in SF and GB over the summer 2012. In addition, temperature, salinity, oxygen and turbidity were measured at about 1 m above the bottom in GB. The results showed that mean current speed across the Baltic Proper was around 12 cm s-1 and the stronger flow was characteristic to the regions located above the sills, in the Bornholm and Slupsk Channels, reaching on average about 20 cm s-1. The results suggest that these regions are important for the inflow of saline waters into the eastern Baltic and are the areas of intense vertical mixing. The VM ADCP observations indicate that the average near-bottom flow across the basin can reach 35±6 cm s-1. The mooring observations also showed similar near-bottom flow velocities. However, they showed that the increased speed of the near-bottom layer occurred frequently in SF and GB during short time periods lasting for about few to several days or 10-20% of time. The observations showed that the bottom mixed layer occupies at least 10% of the water column and the turbulent mixing induced by near-bottom currents is likely to produce sediment resuspension and transport within the layer in all three sub-basins. The turbidity measurements, performed for 5-month-long time period over the summer 2012 in GB show that increased sediment resuspension is associated with a faster near-bottom flow.

Acoustic Profiling of Bottom Sediments in Large Oil Storage Tanks

NASA Astrophysics Data System (ADS)

Svet, V. D.; Tsysar', S. A.

2018-01-01

Characteristic features of acoustic profiling of bottom sediments in large oil storage tanks are considered. Basic acoustic parameters of crude oil and bottom sediments are presented. It is shown that, because of the presence of both transition layers in crude oil and strong reverberation effects in oil tanks, the volume of bottom sediments that is calculated from an acoustic surface image is generally overestimated. To reduce the error, additional post-processing of acoustic profilometry data is proposed in combination with additional measurements of viscosity and tank density distributions in vertical at several points of the tank.

Transient tidal eddy motion in the western Gulf of Maine, part 1: Primary structure

NASA Astrophysics Data System (ADS)

Brown, W. S.; Marques, G. M.

2013-07-01

High frequency radar-derived surface current maps of the Great South Channel (GSC) in the western Gulf of Maine in 2005 revealed clockwise (CW) and anticlockwise (ACW) eddy motion associated with the strong regional tidal currents. To better elucidate the kinematics and dynamics of these transient tidal eddy motions, an observational and modeling study was conducted during the weakly stratified conditions of winter 2008-2009. Our moored bottom pressure and ADCP current measurements in 13m depth were augmented by historical current measurements in about 30m in documenting the dominance of highly polarized M2 semidiurnal currents in our nearshore study region. The high-resolution finite element coastal ocean model (QUODDY) - forced by the five principal tidal constituents - produced maps depicting the formation and evolution of the CW and ACW eddy motions that regularly follow maximum ebb and flood flows, respectively. Observation versus model current comparison required that the model bottom current drag coefficient be set to at an unusually high Cd=0.01 - suggesting the importance of form drag in the study region. The observations and model results were consistent in diagnosing CW or ACW eddy motions that (a) form nearshore in the coastal boundary layer (CBL) for about 3h after the respective tidal current maxima and then (b) translate southeastward across the GSC along curved 50m isobath at speeds of about 25m/s. Observation-based and model-based momentum budget estimates were consistent in showing a first order forced semidiurnal standing tidal wave dynamics (like the adjacent Gulf of Maine) which was modulated by adverse pressure gradient/bottom stress forcing to generate the eddy motions. Observation-based estimates of terms in the transport vorticity budget showed that in the shallower Inner Zone subregion (average depth=23m) that the diffusion of nearshore vorticity was dominant in feeding the growth of eddy motion vorticity; while in the somewhat deeper Outer Zone subregion (33m) bottom current lateral shear and water column stretching/squashing was significant in modulating the eddy motion. We conclude that the transient eddy motions in the GSC region are phase eddies that accompany the change of tide across the GSC and are (1) generated by bottom stress gradients in the shallower nearshore - an issue which needs to be better understood for improved future forecasting.

Symmetric vibrations of a liquid in a vessel with a separator and an elastic bottom

NASA Astrophysics Data System (ADS)

Goncharov, D. A.; Pozhalostin, A. A.

2018-04-01

The paper considers the problem of small axisymmetric vibrations of an ideal fluid filling a vessel with rigid walls and an elastic bottom. The liquid is divided into two layers by an elastic septum. The elastic baffle and the vessel elastic bottom are modeled by elastic membranes. The Neumann boundary-value problem is posed for the fluid. The equations of motion of the membranes are integrated with boundary conditions.

A deep-sea sediment transport storm

NASA Astrophysics Data System (ADS)

Gross, Thomas F.; Williams, A. J.; Newell, A. R. M.

1988-02-01

Photographs taken of the sea bottom since the 1960s suggest that sediments at great depth may be actively resuspended and redistributed1. Further, it has been suspected that active resus-pension/transport may be required to maintain elevated concentrations of particles in deep-sea nepheloid layers. But currents with sufficient energy to erode the bottom, and to maintain the particles in suspension, have not been observed concurrently with large concentrations of particles in the deep nepheloid layer2-4. The high-energy benthic boundary-layer experiment (HEBBLE) was designed to test the hypothesis that bed modifications can result from local erosion and deposition as modelled by simple one-dimensional local forcing mechanics5. We observed several 'storms' of high kinetic energy and near-bed flow associated with large concentrations of suspended sediment during the year-long deployments of moored instruments at the HEBBLE study site. These observations, at 4,880 m off the Nova Scotian Rise in the north-west Atlantic, indicate that large episodic events may suspend bottom sediments in areas well removed from coastal and shelf sources.

Dynamics of a vertical-flow windrow vermicomposting system.

PubMed

Hanc, Ales; Castkova, Tereza; Kuzel, Stanislav; Cajthaml, Tomas

2017-11-01

Large-scale vermicomposting under outdoor conditions may differ from small-scale procedures in the laboratory. The present study evaluated changes in selected properties of a large-scale vertical-flow windrow vermicomposting system with continuous feeding with household biowaste. The windrow profile was divided into five layers of differing thickness and age after more than 12 months of vermicomposting. The top layer (0-30 cm, age <3 months) was characterised by partially decomposed organic matter with a high pH value and an elevated carbon/nitrogen (C/N) ratio. The earthworm biomass was 15 g kg -1 with a population density of 125 earthworms per kilogram predominantly found in clusters. The greatest amount of fungi (3.5 µg g -1 dw) and bacteria (62 µg g -1 dw) (expressed as phospholipid fatty acid analysis) was found in this layer. Thus, the top layer could be used for an additional cycle of windrow vermicomposting and for the preparation of aqueous extracts to protect plants against diseases. The lower layers (graduated by 30 cm and by 3 months of age) were mature as reflected by the low content of ammonia nitrogen, ratio of ammonia to nitrate nitrogen and dissolved organic carbon, and high ion-exchange capacity and its ratio to carbon. These layers were characterised by elevated values for electrical conductivity, total content of nutrients, available magnesium content, and a relatively large bacterial/fungal ratio. On the basis of the observed properties, the bottom layers were predetermined as effective fertilisers.

Static ferroelectric memory transistor having improved data retention

DOEpatents

Evans, Jr., Joseph T.; Warren, William L.; Tuttle, Bruce A.

1996-01-01

An improved ferroelectric FET structure in which the ferroelectric layer is doped to reduce retention loss. A ferroelectric FET according to the present invention includes a semiconductor layer having first and second contacts thereon, the first and second contacts being separated from one another. The ferroelectric FET also includes a bottom electrode and a ferroelectric layer which is sandwiched between the semiconductor layer and the bottom electrode. The ferroelectric layer is constructed from a perovskite structure of the chemical composition ABO.sub.3 wherein the B site comprises first and second elements and a dopant element that has an oxidation state greater than +4 in sufficient concentration to impede shifts in the resistance measured between the first and second contacts with time. The ferroelectric FET structure preferably comprises Pb in the A-site. The first and second elements are preferably Zr and Ti, respectively. The preferred B-site dopants are Niobium, Tantalum, and Tungsten at concentrations between 1% and 8%.

Impact of bimetal electrodes on dielectric properties of TiO2 and Al-doped TiO2 films.

PubMed

Kim, Seong Keun; Han, Sora; Jeon, Woojin; Yoon, Jung Ho; Han, Jeong Hwan; Lee, Woongkyu; Hwang, Cheol Seong

2012-09-26

Rutile structured Al-doped TiO(2) (ATO) and TiO(2) films were grown on bimetal electrodes (thin Ru/thick TiN, Pt, and Ir) for high-performance capacitors. The work function of the top Ru layer decreased on TiN and increased on Pt and Ir when it was thinner than ~2 nm, suggesting that the lower metal within the electrodes influences the work function of the very thin Ru layer. The use of the lower electrode with a high work function for bottom electrode eventually improves the leakage current properties of the capacitor at a very thin Ru top layer (≤2 nm) because of the increased Schottky barrier height at the interface between the dielectric and the bottom electrode. The thin Ru layer was necessary to achieve the rutile structured ATO and TiO(2) dielectric films.

Electrodeposition of platinum and silver into chemically modified microporous silicon electrodes

PubMed Central

2012-01-01

Electrodeposition of platinum and silver into hydrophobic and hydrophilic microporous silicon layers was investigated using chemically modified microporous silicon electrodes. Hydrophobic microporous silicon enhanced the electrodeposition of platinum in the porous layer. Meanwhile, hydrophilic one showed that platinum was hardly deposited within the porous layer, and a film of platinum on the top of the porous layer was observed. On the other hand, the electrodeposition of silver showed similar deposition behavior between these two chemically modified electrodes. It was also found that the electrodeposition of silver started at the pore opening and grew toward the pore bottom, while a uniform deposition from the pore bottom was observed in platinum electrodeposition. These electrodeposition behaviors are explained on the basis of the both effects, the difference in overpotential for metal deposition on silicon and on the deposited metal, and displacement deposition rate of metal. PMID:22720690

In situ measurement of radioactive contamination of bottom sediments.

PubMed

Zhukouski, A; Anshakou, O; Kutsen, S

2018-04-30

A gamma spectrometric method is presented for in situ radiation monitoring of bottom sediments with contaminated layer of unknown thickness to be determined. The method, based on the processing of experimental spectra using the results of their simulation by the Monte Carlo method, is proposed and tested in practice. A model for the transport of gamma radiation from deposited radionuclides 137 Cs and 134 Cs to a scintillation detection unit located on the upper surface of the contaminated layer of sediments is considered. The relationship between the effective radius of the contaminated site and the thickness of the layer has been studied. The thickness of the contaminated layer is determined by special analysis of experimental and thickness-dependent simulated spectra. The technique and algorithm developed are verified as a result of full-scale studies performed with the submersible gamma-spectrometer. Copyright © 2018 Elsevier Ltd. All rights reserved.

Laminated metal composite formed from low flow stress layers and high flow stress layers using flow constraining elements and making same

DOEpatents

Syn, C.K.; Lesuer, D.R.

1995-07-04

A laminated metal composite of low flow stress layers and high flow stress layers is described which is formed using flow constraining elements, preferably in the shape of rings, individually placed around each of the low flow stress layers while pressure is applied to the stack to bond the layers of the composite together, to thereby restrain the flow of the low flow stress layers from the stack during the bonding. The laminated metal composite of the invention is made by the steps of forming a stack of alternate layers of low flow stress layers and high flow stress layers with each layer of low flow stress material surrounded by an individual flow constraining element, such as a ring, and then applying pressure to the top and bottom surfaces of the resulting stack to bond the dissimilar layers together, for example, by compression rolling the stack. In a preferred embodiment, the individual flow constraining elements surrounding the layers of low flow stress material are formed of a material which may either be the same material as the material comprising the high flow stress layers, or have similar flow stress characteristics to the material comprising the high flow stress layers. Additional sacrificial layers may be added to the top and bottom of the stack to avoid damage to the stack during the bonding step; and these additional layers may then be removed after the bonding step. 5 figs.

Laminated metal composite formed from low flow stress layers and high flow stress layers using flow constraining elements and making same

DOEpatents

Syn, Chol K.; Lesuer, Donald R.

1995-01-01

A laminated metal composite of low flow stress layers and high flow stress layers is described which is formed using flow constraining elements, preferably in the shape of rings, individually placed around each of the low flow stress layers while pressure is applied to the stack to bond the layers of the composite together, to thereby restrain the flow of the low flow stress layers from the stack during the bonding. The laminated metal composite of the invention is made by the steps of forming a stack of alternate layers of low flow stress layers and high flow stress layers with each layer of low flow stress material surrounded by an individual flow constraining element, such as a ring, and then applying pressure to the top and bottom surfaces of the resulting stack to bond the dissimilar layers together, for example, by compression rolling the stack. In a preferred embodiment, the individual flow constraining elements surrounding the layers of low flow stress material are formed of a material which may either be the same material as the material comprising the high flow stress layers, or have similar flow stress characteristics to the material comprising the high flow stress layers. Additional sacrificial layers may be added to the top and bottom of the stack to avoid damage to the stack during the bonding step; and these additional layers may then be removed after the bonding step.

Dynamic ikaite production and dissolution in sea ice - control by temperature, salinity and pCO2 conditions

NASA Astrophysics Data System (ADS)

Rysgaard, S.; Wang, F.; Galley, R. J.; Grimm, R.; Lemes, M.; Geilfus, N.-X.; Chaulk, A.; Hare, A. A.; Crabeck, O.; Else, B. G. T.; Campbell, K.; Papakyriakou, T.; Sørensen, L. L.; Sievers, J.; Notz, D.

2013-12-01

Ikaite is a hydrous calcium carbonate mineral (CaCO3 · 6H2O). It is only found in a metastable state, and decomposes rapidly once removed from near-freezing water. Recently, ikaite crystals have been found in sea ice and it has been suggested that their precipitation may play an important role in air-sea CO2 exchange in ice-covered seas. Little is known, however, of the spatial and temporal dynamics of ikaite in sea ice. Here we present evidence for highly dynamic ikaite precipitation and dissolution in sea ice grown at an out-door pool of the Sea-ice Environmental Research Facility (SERF). During the experiment, ikaite precipitated in sea ice with temperatures below -3 °C, creating three distinct zones of ikaite concentrations: (1) a mm to cm thin surface layer containing frost flowers and brine skim with bulk concentrations of > 2000 μmol kg-1, (2) an internal layer with concentrations of 200-400 μmol kg-1 and (3) a~bottom layer with concentrations of < 100 μmol kg-1. Snowfall events caused the sea ice to warm, dissolving ikaite crystals under acidic conditions. Manual removal of the snow cover allowed the sea ice to cool and brine salinities to increase, resulting in rapid ikaite precipitation. The modeled (FREZCHEM) ikaite concentrations were in the same order of magnitude as observations and suggest that ikaite concentration in sea ice increase with decreasing temperatures. Thus, varying snow conditions may play a key role in ikaite precipitation and dissolution in sea ice. This will have implications for CO2 exchange with the atmosphere and ocean.

Temporal dynamics of ikaite in experimental sea ice

NASA Astrophysics Data System (ADS)

Rysgaard, S.; Wang, F.; Galley, R. J.; Grimm, R.; Notz, D.; Lemes, M.; Geilfus, N.-X.; Chaulk, A.; Hare, A. A.; Crabeck, O.; Else, B. G. T.; Campbell, K.; Sørensen, L. L.; Sievers, J.; Papakyriakou, T.

2014-08-01

Ikaite (CaCO3 · 6H2O) is a metastable phase of calcium carbonate that normally forms in a cold environment and/or under high pressure. Recently, ikaite crystals have been found in sea ice, and it has been suggested that their precipitation may play an important role in air-sea CO2 exchange in ice-covered seas. Little is known, however, of the spatial and temporal dynamics of ikaite in sea ice. Here we present evidence for highly dynamic ikaite precipitation and dissolution in sea ice grown at an outdoor pool of the Sea-ice Environmental Research Facility (SERF) in Manitoba, Canada. During the experiment, ikaite precipitated in sea ice when temperatures were below -4 °C, creating three distinct zones of ikaite concentrations: (1) a millimeter-to-centimeter-thin surface layer containing frost flowers and brine skim with bulk ikaite concentrations of >2000 μmol kg-1, (2) an internal layer with ikaite concentrations of 200-400 μmol kg-1, and (3) a bottom layer with ikaite concentrations of <100 μmol kg-1. Snowfall events caused the sea ice to warm and ikaite crystals to dissolve. Manual removal of the snow cover allowed the sea ice to cool and brine salinities to increase, resulting in rapid ikaite precipitation. The observed ikaite concentrations were on the same order of magnitude as modeled by FREZCHEM, which further supports the notion that ikaite concentration in sea ice increases with decreasing temperature. Thus, varying snow conditions may play a key role in ikaite precipitation and dissolution in sea ice. This could have a major implication for CO2 exchange with the atmosphere and ocean that has not been accounted for previously.

Water and sediment dynamics in the Red River mouth and adjacent coastal zone

NASA Astrophysics Data System (ADS)

van Maren, D. S.

2007-02-01

The coastline of the Red River Delta is characterized by alternating patterns of rapid accretion and severe erosion. The main branch of the Red River, the Ba Lat, is presently expanding seaward with a main depositional area several km downstream and offshore the Ba Lat River mouth. Sediment deposition rates are approximately 6 m in the past 50 years. Field measurements were done to determine the processes that regulate marine dispersal and deposition of sediment supplied by the Ba Lat. These measurements reveal that the waters surrounding the Ba Lat delta are strongly stratified with a pronounced southward-flowing surface layer. This southward-flowing surface layer is a coastal current which is generated by river plumes that flow into the coastal zone north of the Ba Lat. However, outflow of turbid river water is not continuous and most sediment enters the coastal zone when the alongshore surface velocities are low. As a consequence, most sediment settles from suspension close to the river mouth. In addition to the southward surface flow, the southward near-bottom currents are also stronger than northward currents. Contrasting with the residual flow near-surface, this southward flow component near-bottom is caused by tidal asymmetry. Because most sediment is supplied by the Ba Lat when wave heights are low, sediment is able to consolidate and therefore the long-term deposition is southward of, but still close to, the Ba Lat mouth.

Deep water characteristics and circulation in the South China Sea

NASA Astrophysics Data System (ADS)

Wang, Aimei; Du, Yan; Peng, Shiqiu; Liu, Kexiu; Huang, Rui Xin

2018-04-01

This study investigates the deep circulation in the South China Sea (SCS) using oceanographic observations combined with results from a bottom layer reduced gravity model. The SCS water, 2000 m below the surface, is quite different from that in the adjacent Pacific Ocean, and it is characterized by its low dissolved oxygen (DO), high temperature and low salinity. The horizontal distribution of deep water properties indicates a basin-scale cyclonic circulation driven by the Luzon overflow. The results of the bottom layer reduced gravity model are consistent with the existence of the cyclonic circulation in the deep SCS. The circulation is stronger at the northern/western boundary. After overflowing the sill of the Luzon Strait, the deep water moves broadly southwestward, constrained by the 3500 m isobath. The broadening of the southward flow is induced by the downwelling velocity in the interior of the deep basin. The main deep circulation bifurcates into two branches after the Zhongsha Islands. The southward branch continues flowing along the 3500 m isobath, and the eastward branch forms the sub-basin scale cyclonic circulation around the seamounts in the central deep SCS. The returning flow along the east boundary is fairly weak. The numerical experiments of the bottom layer reduced gravity model reveal the important roles of topography, bottom friction, and the upwelling/downwelling pattern in controlling the spatial structure, particularly the strong, deep western boundary current.

The Breakup of Temperature Inversions In Steep Valleys

NASA Astrophysics Data System (ADS)

Colette, A.; Street, R.

The purpose of this research is to model and provide a better understanding of tem- perature inversions breakup in steep valleys. The Advanced Regional Prediction Sys- tem (ARPS), a three-dimensional, compressible, and non-hydrostatic modeling tool developed by the Center for Analysis and Prediction of Storms at the University of Oklahoma was used. Many field studies indicate that the evolution of the convective and inversion layers are strongly dependant on the surrounding topography. In relatively open valleys, the convective boundary layer usually grows from the bottom of the valley while in steeper cases, the upslope morning winds affects the dynamic of the mixing layer resulting in the destruction of the inversion from its bottom and its top (see Whiteman 1980). ARPS allows one to perform accurate simulation of such situations. First, written in terrain following coordinates, it handles steep topographies; then its extensive radi- ation and surface flux packages provide a good treatment of land related processes. Moreover, ARPS accounts for the incidence angle of sunrays, differencing the ex- posed and non-exposed mountain slopes. However, it neglects the topographic shade which can delay the sunrise of a hour or more in steep valleys. A new subroutine described by Colette etal. 2002 is thus used to compute the projected shade on the surrounding topography. Simulations of temperature inversion breakup for various two-dimensional valleys are presented. The time scale of evolution of the mixing layer is in good agreement with field studies and, as expected, the convective boundary layer shows an asymmetry between east and west facing slopes. The different patterns of inversion breakup doc- umented by Whiteman are also reproduced. These simulations of idealized cases give a better understanding of inversion breakup in steep valleys. Our code is now being applied to a real case: the study of a peculiar wind, la Ora del Garda, caused by the interaction between a lake breeze and a valley wind in the Garda Valley (Northern Italy). Preliminary simulations will be presented. The support of AC by TotalFinaElf and RS by the Physical Meteorology Program of NSF and the VTMX Program of DoE is appreciated.

Benthic nepheloid layers in the Gulf of Maine and Alexandrium cyst inventories

PubMed Central

Pilskaln, C.H.; Hayashi, K.; Keafer, B.A.; Anderson, D.M.; McGillicuddy, D.J.

2014-01-01

Cysts residing in benthic nepheloid layers (BNLs) documented in the Gulf of Maine have been proposed as a possible source of inoculum for annual blooms of a toxic dinoflagellate in the region. Herein we present a spatially extensive data set of the distribution and thickness of benthic nepheloid layers in the Gulf of Maine and the abundance and inventories of suspended Alexandrium fundyense cysts within these near-bottom layers. BNLs are pervasive throughout the gulf and adjacent Bay of Fundy with maximum layer thicknesses of 50–60 m observed. Mean BNL thickness is 30 m in the eastern gulf and Bay of Fundy, and 20 m in the western gulf. Cyst densities in the near-bottom particle resuspension layers varied by three orders of magnitude across the gulf with maxima of 105 cysts m−3. An important interconnection of elevated BNL cyst densities is observed between the Bay of Fundy, the Maine Coastal Current and the south-central region of the gulf. BNL cyst inventories estimated for the eastern and western gulf are each on the order of 1015 cysts, whereas the BNL inventory in the Bay of Fundy is on the order of 1016 . Although BNL cyst inventories in the eastern and western gulf are 1–2 orders of magnitude smaller than the abundance of cysts in the upper 1 cm of sediment in those regions, BNL and sediment-bound cyst inventories are comparable in the Bay of Fundy. The existence of widespread BNLs containing substantial cyst inventories indicates that these near-bottom layers represent an important source of germinating A. fundyense cysts in the region. PMID:25419055

Benthic nepheloid layers in the Gulf of Maine and Alexandrium cyst inventories.

PubMed

Pilskaln, C H; Hayashi, K; Keafer, B A; Anderson, D M; McGillicuddy, D J

2014-05-01

Cysts residing in benthic nepheloid layers (BNLs) documented in the Gulf of Maine have been proposed as a possible source of inoculum for annual blooms of a toxic dinoflagellate in the region. Herein we present a spatially extensive data set of the distribution and thickness of benthic nepheloid layers in the Gulf of Maine and the abundance and inventories of suspended Alexandrium fundyense cysts within these near-bottom layers. BNLs are pervasive throughout the gulf and adjacent Bay of Fundy with maximum layer thicknesses of 50-60 m observed. Mean BNL thickness is 30 m in the eastern gulf and Bay of Fundy, and 20 m in the western gulf. Cyst densities in the near-bottom particle resuspension layers varied by three orders of magnitude across the gulf with maxima of 10 5 cysts m -3 . An important interconnection of elevated BNL cyst densities is observed between the Bay of Fundy, the Maine Coastal Current and the south-central region of the gulf. BNL cyst inventories estimated for the eastern and western gulf are each on the order of 10 15 cysts, whereas the BNL inventory in the Bay of Fundy is on the order of 10 16 . Although BNL cyst inventories in the eastern and western gulf are 1-2 orders of magnitude smaller than the abundance of cysts in the upper 1 cm of sediment in those regions, BNL and sediment-bound cyst inventories are comparable in the Bay of Fundy. The existence of widespread BNLs containing substantial cyst inventories indicates that these near-bottom layers represent an important source of germinating A. fundyense cysts in the region.

Formation of anomalous eutectic in Ni-Sn alloy by laser cladding

NASA Astrophysics Data System (ADS)

Wang, Zhitai; Lin, Xin; Cao, Yongqing; Liu, Fencheng; Huang, Weidong

2018-02-01

Ni-Sn anomalous eutectic is obtained by single track laser cladding with the scanning velocity from 1 mm/s to 10 mm/s using the Ni-32.5 wt.%Sn eutectic powders. The microstructure of the cladding layer and the grain orientations of anomalous eutectic were investigated. It is found that the microstructure is transformed from primary α-Ni dendrites and the interdendritic (α-Ni + Ni3Sn) eutectic at the bottom of the cladding layer to α-Ni and β-Ni3Sn anomalous eutectic at the top of the cladding layer, whether for single layer or multilayer laser cladding. The EBSD maps and pole figures indicate that the spatially structure of α-Ni phase is discontinuous and the Ni3Sn phase is continuous in anomalous eutectic. The transformation from epitaxial growth columnar at bottom of cladding layer to free nucleation equiaxed at the top occurs, i.e., the columnar to equiaxed transition (CET) at the top of cladding layer during laser cladding processing leads to the generation of anomalous eutectic.

Growth and characterization of low composition Ge, x in epi-Si1‑x Gex (x  ⩽  10%) active layer for fabrication of hydrogenated bottom solar cell

NASA Astrophysics Data System (ADS)

Ajmal Khan, M.; Sato, R.; Sawano, K.; Sichanugrist, P.; Lukianov, A.; Ishikawa, Y.

2018-05-01

Semiconducting epi-Si1‑x Ge x alloys have promising features as solar cell materials and may be equally important for some other semiconductor device applications. Variation of the germanium compositional, x in epi-Si1‑x Ge x , makes it possible to control the bandgap between 1.12 eV and 0.68 eV for application in bottom solar cells. A low proportion of Ge in SiGe alloy can be used for photovoltaic application in a bottom cell to complete the four-terminal tandem structure with wide bandgap materials. In this research, we aimed to use a low proportion of Ge—about 10%—in strained or relaxed c-Si1‑x Ge x /c-Si heterojunctions (HETs), with or without insertion of a Si buffer layer grown by molecular beam epitaxy, to investigate the influence of the relaxed or strained SiGe active layer on the performance of HET solar cells grown using the plasma enhanced chemical vapor deposition system. Thanks to the c-Si buffer layer at the hetero-interface, the efficiency of these SiGe based HET solar cells was improved from 2.3% to 3.5% (fully strained and with buffer layer). The Jsc was improved, from 8 mA cm‑2 to 15.46 mA cm‑2, which might be supported by strained c-Si buffer layer at the hetero-interface, by improving the crystalline quality.

Splitting of the neutral mechanical plane depends on the length of the multi-layer structure of flexible electronics.

PubMed

Li, Shuang; Su, Yewang; Li, Rui

2016-06-01

Multi-layer structures with soft (compliant) interlayers have been widely used in flexible electronics and photonics as an effective design for reducing interactions among the hard (stiff) layers and thus avoiding the premature failure of an entire device. The analytic model for bending of such a structure has not been well established due to its complex mechanical behaviour. Here, we present a rational analytic model, without any parameter fitting, to study the bending of a multi-layer structure on a cylinder, which is often regarded as an important approach to mechanical reliability testing of flexible electronics and photonics. For the first time, our model quantitatively reveals that, as the key for accurate strain control, the splitting of the neutral mechanical plane depends not only on the relative thickness of the middle layer, but also on the length-to-thickness ratio of the multi-layer structure. The model accurately captures the key quantities, including the axial strains in the top and bottom layers, the shear strain in the middle layer and the locations of the neutral mechanical planes of the top and bottom layers. The effects of the length of the multi-layer and the thickness of the middle layer are elaborated. This work is very useful for the design of multi-layer structure-based flexible electronics and photonics.

Splitting of the neutral mechanical plane depends on the length of the multi-layer structure of flexible electronics

PubMed Central

Li, Shuang; Li, Rui

2016-01-01

Multi-layer structures with soft (compliant) interlayers have been widely used in flexible electronics and photonics as an effective design for reducing interactions among the hard (stiff) layers and thus avoiding the premature failure of an entire device. The analytic model for bending of such a structure has not been well established due to its complex mechanical behaviour. Here, we present a rational analytic model, without any parameter fitting, to study the bending of a multi-layer structure on a cylinder, which is often regarded as an important approach to mechanical reliability testing of flexible electronics and photonics. For the first time, our model quantitatively reveals that, as the key for accurate strain control, the splitting of the neutral mechanical plane depends not only on the relative thickness of the middle layer, but also on the length-to-thickness ratio of the multi-layer structure. The model accurately captures the key quantities, including the axial strains in the top and bottom layers, the shear strain in the middle layer and the locations of the neutral mechanical planes of the top and bottom layers. The effects of the length of the multi-layer and the thickness of the middle layer are elaborated. This work is very useful for the design of multi-layer structure-based flexible electronics and photonics. PMID:27436977

Estimating Bottom Water Dissolved Oxygen in the Mississippi River Gulf Outlet and Gulf Intracoastal Waterway Resulting from Proposed Structures

DTIC Science & Technology

2008-09-01

used in the analysis. The analytical approach assumes steady-state, summer conditions applied to a continuously stirred tank reactor ( CSTR ). CSTR ...constituent due to the fully mixed CSTR assumption. Thus, there is no spatial dimensionality. The DO CSTR model is solved using a spreadsheet...For this study, the CSTR represents the bottom meter of water along the reach of the channel being assessed. A unit bottom layer thickness of 1 m

Pin fin compliant heat sink with enhanced flexibility

DOEpatents

Schultz, Mark D.

2018-04-10

Heat sinks and methods of using the same include a top and bottom plate, at least one of which has a plurality of pin contacts flexibly connected to one another, where the plurality of pin contacts have vertical and lateral flexibility with respect to one another; and pin slice layers, each having multiple pin slices, arranged vertically between the top and bottom plates such that the plurality of pin slices form substantially vertical pins connecting the top and bottom plates.

Estimating hydrodynamic roughness in a wave-dominated environment with a high-resolution acoustic Doppler profiler

USGS Publications Warehouse

Lacy, J.R.; Sherwood, C.R.; Wilson, D.J.; Chisholm, T.A.; Gelfenbaum, G.R.

2005-01-01

Hydrodynamic roughness is a critical parameter for characterizing bottom drag in boundary layers, and it varies both spatially and temporally due to variation in grain size, bedforms, and saltating sediment. In this paper we investigate temporal variability in hydrodynamic roughness using velocity profiles in the bottom boundary layer measured with a high-resolution acoustic Doppler profiler (PCADP). The data were collected on the ebb-tidal delta off Grays Harbor, Washington, in a mean water depth of 9 m. Significant wave height ranged from 0.5 to 3 m. Bottom roughness has rarely been determined from hydrodynamic measurements under conditions such as these, where energetic waves and medium-to-fine sand produce small bedforms. Friction velocity due to current u*c and apparent bottom roughness z0a were determined from the PCADP burst mean velocity profiles using the law of the wall. Bottom roughness kB was estimated by applying the Grant-Madsen model for wave-current interaction iteratively until the model u*c converged with values determined from the data. The resulting kB values ranged over 3 orders of magnitude (10-1 to 10-4 m) and varied inversely with wave orbital diameter. This range of kB influences predicted bottom shear stress considerably, suggesting that the use of time-varying bottom roughness could significantly improve the accuracy of sediment transport models. Bedform height was estimated from kB and is consistent with both ripple heights predicted by empirical models and bedforms in sonar images collected during the experiment. Copyright 2005 by the American Geophysical Union.

Understanding the interfacial behavior of lysozyme on Au (111) surfaces with multiscale simulations

NASA Astrophysics Data System (ADS)

Samieegohar, Mohammadreza; Ma, Heng; Sha, Feng; Jahan Sajib, Md Symon; Guerrero-García, G. Iván; Wei, Tao

2017-02-01

The understanding of the adsorption and interfacial behavior of proteins is crucial to the development of novel biosensors and biomaterials. By using bottom-up atomistic multiscale simulations, we study here the adsorption of lysozyme on Au(111) surfaces in an aqueous environment. Atomistic simulations are used to calculate the inhomogeneous polarization of the gold surface, which is induced by the protein adsorption, and by the presence of an interfacial layer of water molecules and monovalent salts. The corresponding potential of mean force between the protein and the gold surface including polarization effects is used in Langevin Dynamics simulations to study the time dependent behavior of proteins at finite concentration. These simulations display a rapid adsorption and formation of a first-layer of proteins at the interface. Proteins are initially adsorbed directly on the gold surface due to the strong protein-surface attractive interaction. A subsequent interfacial weak aggregation of proteins leading to multilayer build-up is also observed at long times.

Impacts of estuarine mixing on vertical dispersion of polycyclic aromatic hydrocarbons (PAHs) in a tide-dominated estuary.

PubMed

Liu, Feng; Hu, Shuai; Guo, Xiaojuan; Niu, Lixia; Cai, Huayang; Yang, Qingshu

2018-06-01

To examine the impacts of estuarine mixing on the dispersion of polycyclic aromatic hydrocarbons (PAHs), seasonal variations in the vertical distribution of dissolved PAHs in the Humen River mouth of the Pearl River Estuary, which is a tide-dominated estuary, were thoroughly examined. An analysis of the vertical distribution of the concentration, composition and sources of PAHs indicates enhanced mixing of PAHs in January relative to June, which is strongly related to seasonal variations in the magnitude of estuarine mixing. Furthermore, the vertical distribution of PAHs initially indicated an increase and then a decrease from the surface layer to the bottom layer. In general, estuarine mixing promotes the vertical dispersion of PAHs, causing a more even PAHs distribution, while salinity stratification can trap PAHs, resulting in higher PAHs concentrations. Our study indicates that salinity variability stimulates significant dynamic effects regarding the dispersion of PAHs within estuarine environments. Copyright © 2018 Elsevier Ltd. All rights reserved.

Internal Gravity Waves: Generation and Breaking Mechanisms by Laboratory Experiments

NASA Astrophysics Data System (ADS)

la Forgia, Giovanni; Adduce, Claudia; Falcini, Federico

2016-04-01

Internal gravity waves (IGWs), occurring within estuaries and the coastal oceans, are manifest as large amplitude undulations of the pycnocline. IGWs propagating horizontally in a two layer stratified fluid are studied. The breaking of an IGW of depression shoaling upon a uniformly sloping boundary is investigated experimentally. Breaking dynamics beneath the shoaling waves causes both mixing and wave-induced near-bottom vortices suspending and redistributing the bed material. Laboratory experiments are conducted in a Perspex tank through the standard lock-release method, following the technique described in Sutherland et al. (2013). Each experiment is analysed and the instantaneous pycnocline position is measured, in order to obtain both geometric and kinematic features of the IGW: amplitude, wavelength and celerity. IGWs main features depend on the geometrical parameters that define the initial experimental setting: the density difference between the layers, the total depth, the layers depth ratio, the aspect ratio, and the displacement between the pycnoclines. Relations between IGWs geometric and kinematic features and the initial setting parameters are analysed. The approach of the IGWs toward a uniform slope is investigated in the present experiments. Depending on wave and slope characteristics, different breaking and mixing processes are observed. Sediments are sprinkled on the slope to visualize boundary layer separation in order to analyze the suspension e redistribution mechanisms due to the wave breaking.

TANK 32 EVAPORATOR FEED PUMP TRANSFER ANALYSIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamburello, D; Richard Dimenna, R; Si Lee, S

2009-01-27

The transfer of liquid salt solution from Tank 32 to an evaporator is to be accomplished by activating the evaporator feed pump, with the supernate surface at a minimum height of approximately 74.4 inches above the sludge layer, while simultaneously turning on the downcomer with a flow rate of 110 gpm. Previously, activation of the evaporator feed pump was an isolated event without any other components running at the same time. An analysis of the dissolved solution transfer has been performed using computational fluid dynamics (CFD) methods to determine the amount of entrained sludge solids pumped out of the tankmore » toward the evaporator with the downcomer turned on. The analysis results shows that, for the minimum tank liquid level of 105 inches above the tank bottom (which corresponds to a liquid depth of 74.4 inches above the sludge layer), the evaporator feed pump will contain less than 0.1 wt% sludge solids in the discharge stream, which is an order of magnitude less than the 1.0 wt% undissolved solids (UDS) loading criteria to feed the evaporator. Lower liquid levels with respect to the sludge layer will result in higher amounts of sludge entrainment due to the increased plunging jet velocity from the downcomer disturbing the sludge layer.« less

Nanofiber based triple layer hydro-philic/-phobic membrane - a solution for pore wetting in membrane distillation

PubMed Central

Prince, J. A.; Rana, D.; Matsuura, T.; Ayyanar, N.; Shanmugasundaram, T. S.; Singh, G.

2014-01-01

The innovative design and synthesis of nanofiber based hydro-philic/phobic membranes with a thin hydro-phobic nanofiber layer on the top and a thin hydrophilic nanofiber layer on the bottom of the conventional casted micro-porous layer which opens up a solution for membrane pore wetting and improves the pure water flux in membrane distillation. PMID:25377488

Modeling sound propagation in a waveguide with a gas-saturated sedimentary layer

NASA Astrophysics Data System (ADS)

Yarina, M. V.

2017-11-01

There was developed an acoustic wave propagation model in a waveguide, where the bottom is represented as a gas-saturated layer. This study uses the ray theory because the investigation of shallow reservoirs with a gas-saturated bottom requires modeling the sound field on short distances. The theory takes into account the rays passing through a gas-saturated layer. The obtained model was used in order to define the distance and the depth of the receiving array (in a horizontal position) elements. The experiment was carried out in the Klyazma reservoir in 2014. In accordance with the peculiarities of the experiment (short distance between receiving array and radiator; irregular array of the radiated signal) there was designed an algorithm agreed with the processing environment in the time domain.

Experimental visualization of the cathode layer in AC surface dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Kim, Sang-You; Lho, Taihyeop; Chung, Kyu-Sun

2018-06-01

A narrow etched polyimide line at the bottom edge of a biased electrode (BE) and a non-etched dielectric surface near the biased electrode were observed in an atmospheric AC flexible surface dielectric barrier discharge of polyimide dielectric. These findings are attributed to the bombardment of positive oxygen ions on the bottom edge of the BE and the electron breakdown trajectory not contacting the polyimide surface following the electric field lines formed between the BE edge and the surface charge layer on the dielectric. The length of the non-etched dielectric surface during the first micro-discharge was observed as 22 μm. This occurred, regardless of three different operating durations, which is in good agreement with the length of the cathode layer according to Paschen's law.

Modeling of sedimentation and resuspension processes induced by intensive internal gravity waves in the coastal water systems with the use of the advection-diffusion equation for sediment concentration

NASA Astrophysics Data System (ADS)

Rouvinskaya, Ekaterina; Kurkin, Andrey; Kurkina, Oxana

2017-04-01

Intensive internal gravity waves influence bottom topography in the coastal zone. They induce substantial flows in the bottom layer that are essential for the formation of suspension and for the sediment transport. It is necessary to develop a mathematical model to predict the state of the seabed near the coastline to assess and ensure safety during the building and operation of the hydraulic engineering constructions. There are many models which are used to predict the impact of storm waves on the sediment transport processes. Such models for the impact of the tsunami waves are also actively developing. In recent years, the influence of intense internal waves on the sedimentation processes is also of a special interest. In this study we adapt one of such models, that is based on the advection-diffusion equation and allows to study processes of resuspension under the influence of internal gravity waves in the coastal zone, for solving the specific practical problems. During the numerical simulation precomputed velocity values are substituted in the advection - diffusion equation for sediment concentration at each time step and each node of the computational grid. Velocity values are obtained by the simulation of the internal waves' dynamics by using the IGW Research software package for numerical integration of fully nonlinear two-dimensional (vertical plane) system of equations of hydrodynamics of inviscid incompressible stratified fluid in the Boussinesq approximation bearing in mind the impact of barotropic tide. It is necessary to set the initial velocity and density distribution in the computational domain, bottom topography, as well as the value of the Coriolis parameter and, if necessary, the parameters of the tidal wave to carry out numerical calculations in the software package IGW Research. To initialize the background conditions of the numerical model we used data records obtained in the summer in the southern part of the shelf zone of Sakhalin Island from 1999 to 2003, provided by SakhNIRO, Russia. The process of assimilation of field data with numerical model is described in detail in our previous studies. It has been shown that process of suspension formation is quite intense for the investigated condition. Concentration of suspended particles significantly increases during the tide, especially on naturally uneven bottom relief as well as on the right boundary of the computational domain (near shoreline). Pronounced nepheloid layer is produced. Its thickness is about 5.6 m. At the phase of low tide, the process of suspension sediment production stops, and suspended particles are beginning to settle because of the small vertical velocities. Thickness of nepheloid layer is actively reduced. Obviously, this should lead to a change in the bottom relief. The presented results of research were obtained with the support of the Russian President's scholarship for young scientists and graduate students SP-2311.2016.5.

On sharp vorticity gradients in elongating baroclinic eddies and their stabilization with a solid-body rotation

NASA Astrophysics Data System (ADS)

Sutyrin, Georgi G.

2016-06-01

Wide compensated vortices are not able to remain circular in idealized two-layer models unless the ocean depth is assumed to be unrealistically large. Small perturbations on both cyclonic and anticyclonic eddies grow slower if a middle layer with uniform potential vorticity (PV) is added, owing to a weakening of the vertical coupling between the upper and lower layers and a reduction of the PV gradient in the deep layer. Numerical simulations show that the nonlinear development of the most unstable elliptical mode causes self-elongation of the upper vortex core and splitting of the deep PV anomaly into two corotating parts. The emerging tripolar flow pattern in the lower layer results in self-intensification of the fluid rotation in the water column around the vortex center. Further vortex evolution depends on the model parameters and initial conditions, which limits predictability owing to multiple equilibrium attractors existing in the dynamical system. The vortex core strips thin filaments, which roll up into submesoscale vortices to result in substantial mixing at the vortex periphery. Stirring and damping of vorticity by bottom friction are found to be essential for subsequent vortex stabilization. The development of sharp PV gradients leads to nearly solid-body rotation inside the vortex core and formation of transport barriers at the vortex periphery. These processes have important implications for understanding the longevity of real-ocean eddies.

Measurement of tidal and residual currents in the Strait of Hormuz

NASA Astrophysics Data System (ADS)

Azizpour, Jafar; Siadatmousavi, Seyed Mostafa; Chegini, Vahid

2016-09-01

Quantifying the current in the Strait of Hormuz (SH) is vital for understanding the circulation in the Persian Gulf. To measure the current in the strait, four subsurface moorings were deployed at four different stations close to SH from early November 2012 to the end of January 2013. Tidal current were dominant in the SH. The tides in the SH were complex partially standing waves and the dominant pattern varied from being primarily semi-diurnal to diurnal. The phase difference between tidal constituents of current and sea level elevation time series was used as an index to show the partially progressive wave pattern inside the study area. At mooring positions 3 and 4, located to the left of SH, the phase differences were close to 160° and 100°, respectively. It indicates partially progressive waves in opposite direction at these stations. K1 and M2 were the two main constituents at all stations inside the study area. At surface, the magnitude of semi-major axis of ellipses for M2 constituent was larger than corresponding value for K1 whereas at the bottom layer, the opposite pattern was observed. The M2 rotary coefficients at mooring 1 illustrated that current vector at the bottom layer rotated in opposite direction compared to current vectors at the middle and surface layers. The rotation was counterclockwise in the bottom layer, while it was clockwise in the surface and middle layers.

Tandem Solar Cells from Solution-Processed CdTe and PbS Quantum Dots Using a ZnTe–ZnO Tunnel Junction

DOE PAGES

Crisp, Ryan W.; Pach, Gregory F.; Kurley, J. Matthew; ...

2017-01-10

Here, we developed a monolithic CdTe-PbS tandem solar cell architecture in which both the CdTe and PbS absorber layers are solution-processed from nanocrystal inks. Due to their tunable nature, PbS quantum dots (QDs), with a controllable band gap between 0.4 and ~1.6 eV, are a promising candidate for a bottom absorber layer in tandem photovoltaics. In the detailed balance limit, the ideal configuration of a CdTe (E g = 1.5 eV)-PbS tandem structure assumes infinite thickness of the absorber layers and requires the PbS band gap to be 0.75 eV to theoretically achieve a power conversion efficiency (PCE) of 45%.more » But, modeling shows that by allowing the thickness of the CdTe layer to vary, a tandem with efficiency over 40% is achievable using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first step toward developing this technology, we explore CdTe-PbS tandem devices by developing a ZnTe-ZnO tunnel junction, which appropriately combines the two subcells in series. Furthermore, we examine the basic characteristics of the solar cells as a function of layer thickness and bottom-cell band gap and demonstrate open-circuit voltages in excess of 1.1 V with matched short circuit current density of 10 mA/cm 2 in prototype devices.« less

Tandem Solar Cells from Solution-Processed CdTe and PbS Quantum Dots Using a ZnTe-ZnO Tunnel Junction.

PubMed

Crisp, Ryan W; Pach, Gregory F; Kurley, J Matthew; France, Ryan M; Reese, Matthew O; Nanayakkara, Sanjini U; MacLeod, Bradley A; Talapin, Dmitri V; Beard, Matthew C; Luther, Joseph M

2017-02-08

We developed a monolithic CdTe-PbS tandem solar cell architecture in which both the CdTe and PbS absorber layers are solution-processed from nanocrystal inks. Due to their tunable nature, PbS quantum dots (QDs), with a controllable band gap between 0.4 and ∼1.6 eV, are a promising candidate for a bottom absorber layer in tandem photovoltaics. In the detailed balance limit, the ideal configuration of a CdTe (E g = 1.5 eV)-PbS tandem structure assumes infinite thickness of the absorber layers and requires the PbS band gap to be 0.75 eV to theoretically achieve a power conversion efficiency (PCE) of 45%. However, modeling shows that by allowing the thickness of the CdTe layer to vary, a tandem with efficiency over 40% is achievable using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first step toward developing this technology, we explore CdTe-PbS tandem devices by developing a ZnTe-ZnO tunnel junction, which appropriately combines the two subcells in series. We examine the basic characteristics of the solar cells as a function of layer thickness and bottom-cell band gap and demonstrate open-circuit voltages in excess of 1.1 V with matched short circuit current density of 10 mA/cm 2 in prototype devices.

Tuning the exchange bias in NiFe/Fe-oxide bilayers by way of different Fe-oxide based mixtures made with an ion-beam deposition technique.

PubMed

Lin, K W; Kol, P H; Guo, Z Y; Ouyang, H; van Lierop, J

2007-01-01

We have investigated the structural and magnetic properties of ion-beam deposited polycrystalline NiFe (25 nm)/Fe-oxide (35 nm) bilayers. A film prepared with an assist beam O2 to Ar gas ratio of 0% during deposition had a bottom layer that consisted of pure b.c.c. Fe (a = 2.87 A) whereas films prepared with 19%O2/Ar and 35%O2/Ar had either Fe3O4 (a = 8.47 angstroms) or alpha-Fe2O3 (a = 5.04 angstroms, c = 13.86 angstroms) bottom layers, respectively. Cross-sectional transmission electron microscopy revealed a smooth interface between the top nano-columnar NiFe and bottom nano-columnar Fe-oxide layer for all films. At room temperature, the observed coercivity (Hc approximately 25 Oe) for a film prepared with 19% O2/Ar indicates the existence of a magnetically hard ferrimagnetic Fe3O4 phase that is enhancing the plain NiFe (Hc approximately 2 Oe) by way of exchange coupling. A significant amount of exchange bias is observed below 50 K, and at 10 K the size of exchange bias hysteresis loops shift increases with increasing oxygen in the films. Furthermore, the strongest exchange coupling (H(ex) approximately 135 Oe at 10 K) is with alpha-Fe2O3 (35% O2/Ar) as the bottom film layer. This indicates that the pure antiferromagnetic phases work better than ferrimagnetic phases when in contact with ferromagnetic NiFe. H(ex) (T) is well described by an effective AF domain wall energy that creates an exchange field with a (1 - T/T(crit)) temperature dependence. Hc (T) exhibits three distinct regimes of constant temperature that may indicate the existence of different AF spin populations that couple to the FM layer at different temperatures.

Bottom boundary layer forced by finite amplitude long and short surface waves motions

NASA Astrophysics Data System (ADS)

Elsafty, H.; Lynett, P.

2018-04-01

A multiple-scale perturbation approach is implemented to solve the Navier-Stokes equations while including bottom boundary layer effects under a single wave and under two interacting waves. In this approach, fluid velocities and the pressure field are decomposed into two components: a potential component and a rotational component. In this study, the two components are exist throughout the entire water column and each is scaled with appropriate length and time scales. A one-way coupling between the two components is implemented. The potential component is assumed to be known analytically or numerically a prior, and the rotational component is forced by the potential component. Through order of magnitude analysis, it is found that the leading-order coupling between the two components occurs through the vertical convective acceleration. It is shown that this coupling plays an important role in the bottom boundary layer behavior. Its effect on the results is discussed for different wave-forcing conditions: purely harmonic forcing and impurely harmonic forcing. The approach is then applied to derive the governing equations for the bottom boundary layer developed under two interacting wave motions. Both motions-the shorter and the longer wave-are decomposed into two components, potential and rotational, as it is done in the single wave. Test cases are presented wherein two different wave forcings are simulated: (1) two periodic oscillatory motions and (2) short waves interacting with a solitary wave. The analysis of the two periodic motions indicates that nonlinear effects in the rotational solution may be significant even though nonlinear effects are negligible in the potential forcing. The local differences in the rotational velocity due to the nonlinear vertical convection coupling term are found to be on the order of 30% of the maximum boundary layer velocity for the cases simulated in this paper. This difference is expected to increase with the increase in wave nonlinearity.

A spatial-temporal system for dynamic cadastral management.

PubMed

Nan, Liu; Renyi, Liu; Guangliang, Zhu; Jiong, Xie

2006-03-01

A practical spatio-temporal database (STDB) technique for dynamic urban land management is presented. One of the STDB models, the expanded model of Base State with Amendments (BSA), is selected as the basis for developing the dynamic cadastral management technique. Two approaches, the Section Fast Indexing (SFI) and the Storage Factors of Variable Granularity (SFVG), are used to improve the efficiency of the BSA model. Both spatial graphic data and attribute data, through a succinct engine, are stored in standard relational database management systems (RDBMS) for the actual implementation of the BSA model. The spatio-temporal database is divided into three interdependent sub-databases: present DB, history DB and the procedures-tracing DB. The efficiency of database operation is improved by the database connection in the bottom layer of the Microsoft SQL Server. The spatio-temporal system can be provided at a low-cost while satisfying the basic needs of urban land management in China. The approaches presented in this paper may also be of significance to countries where land patterns change frequently or to agencies where financial resources are limited.

Water mass dynamics shape Ross Sea protist communities in mesopelagic and bathypelagic layers

NASA Astrophysics Data System (ADS)

Zoccarato, Luca; Pallavicini, Alberto; Cerino, Federica; Fonda Umani, Serena; Celussi, Mauro

2016-12-01

Deep-sea environments host the largest pool of microbes and represent the last largely unexplored and poorly known ecosystems on Earth. The Ross Sea is characterized by unique oceanographic dynamics and harbors several water masses deeply involved in cooling and ventilation of deep oceans. In this study the V9 region of the 18S rDNA was targeted and sequenced with the Ion Torrent high-throughput sequencing technology to unveil differences in protist communities (>2 μm) correlated with biogeochemical properties of the water masses. The analyzed samples were significantly different in terms of environmental parameters and community composition outlining significant structuring effects of temperature and salinity. Overall, Alveolata (especially Dinophyta), Stramenopiles and Excavata groups dominated mesopelagic and bathypelagic layers, and protist communities were shaped according to the biogeochemistry of the water masses (advection effect and mixing events). Newly-formed High Salinity Shelf Water (HSSW) was characterized by high relative abundance of phototrophic organisms that bloom at the surface during the austral summer. Oxygen-depleted Circumpolar Deep Water (CDW) showed higher abundance of Excavata, common bacterivores in deep water masses. At the shelf-break, Antarctic Bottom Water (AABW), formed by the entrainment of shelf waters in CDW, maintained the eukaryotic genetic signature typical of both parental water masses.

Manufacturing of PZT-nickel functionally graded piezoelectric ceramics

NASA Astrophysics Data System (ADS)

Rubio, Wilfredo M.; Silva, Emílio C. N.; Buiochi, Flávio

2012-05-01

A recent approach for designing and manufacturing piezoelectric ceramics consists of using the functionally graded materials (FGM) concept. In this work, nickel (Ni) is used to generate a new PZT-Ni graded ceramic and its dynamic behavior is experimentally explored. The PZT-Ni graded ceramic is manufactured by using the technique of Spark Plasma Sintering (SPS). The ceramic is graded from the top to the bottom surface (along 6 mm of thickness). Specifically, five layers of green powders are sintered: 100 wt% PZT-5A, 90 wt% PZT-5A and 10 wt% Ni, 80 wt% PZT-5A and 20 wt% Ni, 70 wt% PZT-5A and 30 wt% Ni, 60 wt% PZT-5A and 40 wt% Ni. Thus, Ni is used as a second phase, which is added to a PZT-5A matrix, changing its concentration. No manufacturing defects or cracks or exfoliated layers are observed. However, graphite diffusion is observed from the graphite die into the graded ceramic, which does not affect its performance; hence, the ceramic contains enough piezoelectric properties, which allows its polarization and dynamic characterization by determining the impedance curve of the PZT-Ni graded ceramic. The PZT-Ni graded ceramic vibrates at 1.04 MHz, 1.55 MHz and 2.07 MHz.

Detailed studies of aviation fuel flowability

NASA Technical Reports Server (NTRS)

Mehta, H. K.; Armstrong, R. S.

1985-01-01

Six Jet A fuels, with varying compositions, were tested for low temperature flowability in a 190-liter simulator tank that modeled a section of a wing tank of a wide-body commercial airplane. The insulated tank was chilled by circulating coolant through the upper and lower surfaces. Flow-ability was determined as a function of fuel temperature by holdup, the fraction of unflowable fuel remaining in the tank after otherwise complete withdrawal. In static tests with subfreezing tank conditions, hold up varied with temperature and fuel composition. However, a general correlation of two or three classes of fuel type was obtained by plotting holdup as a function of the difference between freezing point and boundary-layer temperature, measured 0.6 cm above the bottom tank surface. Dynamic conditions of vibrations and slosh or rate of fuel withdrawal had very minor effects on holdup. Tests with cooling schedules to represent extreme, cold-day flights showed, at most, slight holdup for any combination of fuel type or dynamic conditions. Tests that superimposed external fuel heating and recirculation during the cooldown period indicates reduced hold up by modification of the low-temperature boundary layer. Fuel heating was just as effective when initiated during the later times of the tests as when applied continuously.

Numerical study of sediment dynamics during hurricane Gustav

NASA Astrophysics Data System (ADS)

Zang, Zhengchen; Xue, Z. George; Bao, Shaowu; Chen, Qin; Walker, Nan D.; Haag, Alaric S.; Ge, Qian; Yao, Zhigang

2018-06-01

In this study, the coupled ocean-atmosphere-wave-and-sediment transport (COAWST) modeling system was employed to explore sediment dynamics in the northern Gulf of Mexico during hurricane Gustav in 2008. The performance of the model was evaluated quantitatively and qualitatively against in-situ and remote sensing measurements, respectively. After Gustav's landfall in coastal Louisiana, the maximum significant wave heights reached more than 8 m offshore and they decreased quickly as it moved toward the inner shelf, where the vertical stratification was largely destroyed. Alongshore currents were dominant westward on the eastern sector of the hurricane track, and offshoreward currents prevailed on the western sector. High suspended sediment concentrations (>1000 mg/l) were confined to the inner shelf at surface layers and the simulated high concentrations at the bottom layer extended to the 200 m isobaths. The stratification was restored one week after landfall, although not fully. The asymmetric hurricane winds induced stronger hydrodynamics in the eastern sector, which led to severe erosion. The calculated suspended sediment flux (SSF) was convergent to the hurricane center and the maximum SSF was simulated near the south and southeast of the Mississippi river delta. The averaged post-hurricane deposition over the Louisiana shelf was 4.0 cm, which was 3.2-26 times higher than the annual accumulation rate under normal weather conditions.

Implications for the crustal Architecture in West Antarctica revealed by the means of depth-to-the-bottom of the magnetic source (DBMS) mapping and 3D FEM geothermal heat flux models

NASA Astrophysics Data System (ADS)

Dziadek, Ricarda; Gohl, Karsten; Kaul, Norbert

2017-04-01

The West Antarctic Rift System (WARS) is one of the largest rift systems in the world, which displays unique coupled relationships between tectonic processes and ice sheet dynamics. Palaeo-ice streams have eroded troughs across the Amundsen Sea Embayment (ASE) that today route warm ocean deep water to the West Antarctic Ice Sheet (WAIS) grounding zone and reinforce dynamic ice sheet thinning. Rift basins, which cut across West Antarctica's landward-sloping shelves, promote ice sheet instability. Young, continental rift systems are regions with significantly elevated geothermal heat flux (GHF), because the transient thermal perturbation to the lithosphere caused by rifting requires 100 m.y. to reach long-term thermal equilibrium. The GHF in this region is, especially on small scales, poorly constrained and suspected to be heterogeneous as a reflection of the distribution of tectonic and volcanic activity along the complex branching geometry of the WARS, which reflects its multi-stage history and structural inheritance. We investigate the crustal architecture and the possible effects of rifting history from the WARS on the ASE ice sheet dynamics, by the use of depth-to-the-bottom of the magnetic source (DBMS) estimates. These are based on airborne-magnetic anomaly data and provide an additional insight into the deeper crustal properties. With the DBMS estimates we reveal spatial changes at the bottom of the igneous crust and the thickness of the magnetic layer, which can be further incorporated into tectonic interpretations. The DBMS also marks an important temperature transition zone of approximately 580°C and therefore serves as a boundary condition for our numerical FEM models in 2D and 3D. On balance, and by comparison to global values, we find average GHF of 90 mWm-2 with spatial variations due to crustal heterogeneities and volcanic activities. This estimate is 30% more than commonly used in ice sheet models in the ASE region.

Origin and history of the Charleston Bump - Geological formations, currents, bottom conditions, and their relationship to wreckfish habitats on the Blake Plateau

USGS Publications Warehouse

Popenoe, P.; Manheim, F.T.

2001-01-01

The Charleston Bump is a structural and topographic high on the northern Blake Plateau that overlies a seaward offset of the edge of continental crust. The feature causes the bottom to shoal and deflects the Gulf Stream offshore, causing an intensification of bottom currents. The area has been swept by strong currents since late Cretaceous time, but the strongest currents have occurred in the Neogene (last ???25 million years). Nondepositional conditions prevail at present, but erosion of the bottom is checked where the bottom is armored by a hard surficial layer of phosphorite pavement. The phosphorite pavements were formed by re-cementation of eroded residues of phosphorite-rich sediments of early-Neogene age. In some places there are multiple pavements separated by poorly lithified sediments. Submersible observations indicate that the south, or current-facing flank of the Charleston Bump has several deep (>100 m) scour depressions, the southern flanks of which form cliffs characterized by ledges and overhangs. In other areas discrete layers of older Paleogene rocks have been partly eroded away, leaving cliff-like steps of 5 m or more relief. Conglomeratic phosphorite pavement layers up to 1 m thick armor most of the bottom. Where breached by scour, these pavements form both low-relief ledges and rock piles. These features form a reef-like environment of caves and overhangs utilized by wreckfish Polyprion americanus and barrelfish Hyperoglyphe perciformis as shelter from the current and as staging areas to prey on passing schools of squid. Wreckfish and other large fish were often localized in rugged bottom habitat, including caves and other shelter areas. We observed wreckfish darting from shelters to feed on passing schools of squid. Present and past observations, are consistent with the concept that impingement of the Gulf Stream at the Charleston Bump compresses midwater fauna from much thicker water layers, providing food for a flourishing big-fish fauna. During our dives we noted currents often exceeding 1 knot, and ranging to 2.4 knots. Evidence of fossil, manganese-iron-encrusted megaripples suggest even greater current regimes in the past. Investigation of the site of an earlier report of possible freshwater discharge failed to find any evidence of a closed sinkhole or freshwater discharge. Rather, we concluded that the apparent loss of buoyancy experienced by the submarine was probably caused by downward-directed eddy currents generated by currents sweeping across the pavement/void interface of a more than 100-m high cliff 3 km south of the reported location.

The inner core thermodynamics of the tropical cyclone boundary layer

NASA Astrophysics Data System (ADS)

Williams, Gabriel J.

2016-10-01

Although considerable progress has been made in understanding the inner-core dynamics of the tropical cyclone boundary layer (TCBL), our knowledge of the inner-core thermodynamics of the TCBL remains limited. In this study, the inner-core budgets of potential temperature (θ), specific humidity ( q), and reversible equivalent potential temperature (θ _e) are examined using a high-resolution multilevel boundary layer model. The potential temperature budgets show that the heat energy is dominated by latent heat release in the eyewall, evaporative cooling along the outer edge of the eyewall, and upward surface fluxes of sensible and latent heat from the underlying warm ocean. It is shown that the vertical θ advection overcompensates the sum of radial advective warming from the boundary layer outflow jet and latent heating for the development of cooling in the eyewall within the TCBL. The moisture budgets show the dominant upward transport of moisture in the eyewall updrafts, partly by the boundary-layer outflow jet from the bottom eye region, so that the eyewall remains nearly saturated. The θ _e budgets reveal that the TCBL is maintained thermodynamically by the upward surface flux of higher-θ _e air from the underlying warm ocean, the radial transport of low-θ _e air from the outer regions of the TCBL, and the dry adiabatic cooling associated by eyewall updrafts. These results underscore the significance of vertical motion and the location of the boundary layer outflow jet in maintaining the inner core thermal structure of the TCBL.

46 CFR 164.009-15 - Test procedure.

Code of Federal Regulations, 2010 CFR

2010-10-01

... material, is less than 47 mm, the specimens prepared consist of layers of the sample. (3) If the sample is a composite material and has a height that is not 50 ±3mm, the layers of the specimen prepared are proportional in thickness to the layers of the sample. (4) The top and bottom faces of each specimen prepared...

Art across the Curriculum: Ellipse Clips

ERIC Educational Resources Information Center

Sartorius, Tara Cady

2011-01-01

This article discusses Al Souza's "Orlando City Maps," which was created not by adding colored ink to paper, but by cutting the printed paper away. Seven layers of pages are stacked upon one another and, except for the intact bottom layer, oval-shaped holes are cut through each page to reveal the layers below. When designing "Orlando City Maps,"…

An analysis of dynamical factors influencing 2013 giant jellyfish bloom near Qinhuangdao in the Bohai Sea, China∗

NASA Astrophysics Data System (ADS)

Wu, Lingjuan; Wang, Jia; Gao, Song; Zheng, Xiangrong; Huang, Rui

2017-02-01

The explosive growth of Nemopilema nomurai occurred near the coastal waters of Qinhuangdao in July 2013. However, it did not take place in 2012. In this paper, the dynamical factors of wind, ocean current and sea temperature on giant jellyfish bloom in 2013 is analyzed by a comprehensive investigation. The numerical experiments are based on a numerical trajectory model of the jellyfish particles, which are released into the waters from Feiyan Shoal to New Yellow River Mouth, where is speculated as the most likely remote source of Qinhuangdao jellyfish bloom. The results show that in surface layer the jellyfish drift is jointly driven by the surface wind and surface current. For example, in northeastern Bohai Bay, the giant jellyfish moved northwestward in surface layer with influence of the westward wind and current anomalies during the second half of May in 2013, then approached the south of Jingtang Port by early June, and accumulated near Qinhuangdao in early July. The 2012 scenario during the same period was quite different. The jellyfish particles influencing waters near Qinhuangdao decreased with depth and there was few (no) particles influencing Qinhuangdao in middle (bottom) layer because the anticyclonic residual circulation weakened with depth in Bohai Bay. Besides, in the potential source waters of jellyfish, sea temperature in 2012 was more suitable for jellyfish bloom than that in 2013 if there was adequate bait. Hence, the specified direction of wind and current pattern in the Bohai Sea in surface layer (especially in the northeastern Bohai Bay during the second half of May) was more important for jellyfish bloom near Qinhuangdao than the sea temperature in the potential source.

Identification And Survival Of Bacteriohopanepolyol In A Hot Spring Microbial Mat

NASA Technical Reports Server (NTRS)

Janke, Linda L.; Chang, Sherwood (Technical Monitor)

1995-01-01

The polar lipids of a hot spring microbial mat located in Yellowstone National Park were examined for the presence of bacteriohopanepolvols (BHP). BHP are a group of molecules consisting of a hopanoid (peotacyclic triterpene) linked via a n-alkyl polyhydroxylated chain to a variety of polar end groups. BHP have been isolated in varying amounts from phylogenetically diverse eubacterial groups including cyanobacteria, methanotrophs and the Rhodospirillaceae. The hopanoids are excellent biomarkers and have been detected in sedimentary rocks as old as 1.7 bya. In order to interpret the ancient organic record, it is important to understand the abundance, source and fate of such biomarker compounds in microbial mats. A 40 sq cm mat section was taken from a 52 to 55 C site in the effluent channel of Octopus Spring and was sampled vertically over approximately 16 mm. The first 5-6 mm was sectioned into a top green layer (310 mg dry weight) and several subjacent, deep orange layers (240 and 250 mg, respectively). The lower 10 mm of the mat was sectioned into two gelatinous orange layers containing a siliceous gritty material (260 and 440 mg) which increased with depth, and a bottom layer composed almost exclusively of siliceous sinter (4.1 g). The progressive decrease in total organic carbon from 45% in the top green layer to only 4% in the bottom layer reflects the observed increase in siliceous deposition. GC-MS analysis of the phospholipid and glycolipid fatty acids yielded predominantly saturated normal chain acids, n-15 to n-18, and iso-branched acids, i-15 to i-17. Small amounts of unsaturated fatty acids (16:1, two positional isomers of 18:1, and two cyclopropyl acids, C(sub 17) and C(sub 19)) were present mainly in the top layer. Esterified fatty acid which is a good index for intact cellular membrane, i.e. viable organisms, was highest in the top two layers (203 and 231 micro g/mg total lipid, respectively) and gradually decreased to 66 micro g/mg total lipid in the bottom layer. Small amounts of BHP were present in all six layers, however in this case, BHP was lowest in the top green and subjacent deep-orange layers (118 and 172 micro g/mg total lipid, respectively) and increased with depth reaching almost 400 micro g/mg in the bottom two layers. This data suggest that BHP are survivina the initial phase of mat degradation and may be preferentially enriched in any organic record of such thermal environments. The relatively low level of BHP in the top layer also suggests that cyanobacteria may not be the major source of BHP in this mat. Since Chloroflexus a major component of the deep-orange layer has been reported to lack BHP, this material may prove a valuable biomarker for some other mat inhabitant. Further isotopic characterization of this BHP should help resolve this finding.

Layer structure of the Venus daytime ionosphere from Venera-15,-16 radio occultation

NASA Astrophysics Data System (ADS)

Gavrik, Anatoly

Up to now more than five hundred radio occultation experiments had been carried out by different missions to research physical properties of the Venus ionosphere. The purpose of this report is to show new properties of the Venus daytime ionosphere reanalyzing Venera-15,-16 dual-frequency occultation data. The high coherence and stability of radio signals of Venera- 15,-16 at wave lengths 32 cm and 8 cm, along with the fact, that the refractive amplification at 32 cm in the ionosphere exceeds by factor 6 the refractive amplification at 13 cm used by others researches, have allowed to perform analysis of radiophysical parameters in the Venus ionosphere more accurate. Progress in the radiovision theory and up-to-date digital processing techniques have provided an opportunity to discover unknown layered structure of the Venus daytime ionosphere. We offer the new technique of the data analysis that allows us to separate influence of noise, ionosphere and atmosphere on the radio occultation results. We point out that significant gradient variations in the vertical distribution of the electron density are observed in the region of maximum electron density of the daytime ionosphere at altitudes of 150-175 km. That testifies layered structure of this part of the Venus ionosphere. The results of data analysis reveal the regular existence of the ionospheric layers in the bottom daytime ionosphere at altitudes from 80 up to 115 km. The bottom border of the ionosphere part can vary in the range of 80-100 km, and gradients of the electron density show strong variability. We detect the wave structure in the top atmosphere and in the bottom ionosphere at altitudes from 60 up to 115 km as well. It is difficult to obtain correct electron density in the region, where we have detected the new ionospheric layers. Relative errors of the electron density are greater than 100% at altitudes between 80 and 120 km. The bottom part of the ionosphere is more variable, than overlying area of the main maximum of the daytime ionosphere. It is difficult to explain such layered structures of the Venus daytime ionosphere by means of existing model of the photochemical equilibrium.

Two-layer displacement flow of miscible fluids with viscosity ratio: Experiments

NASA Astrophysics Data System (ADS)

Etrati, Ali; Alba, Kamran; Frigaard, Ian A.

2018-05-01

We investigate experimentally the density-unstable displacement flow of two miscible fluids along an inclined pipe. This means that the flow is from the top to bottom of the pipe (downwards), with the more dense fluid above the less dense. Whereas past studies have focused on iso-viscous displacements, here we consider viscosity ratios in the range 1/10-10. Our focus is on displacements where the degree of transverse mixing is low-moderate, and thus a two-layer, stratified flow is observed. A wide range of parameters is covered in order to observe the resulting flow regimes and to understand the effect of the viscosity contrast. The inclination of the pipe (β) is varied from near horizontal β = 85° to near vertical β = 10°. At each angle, the flow rate and viscosity ratio are varied at fixed density contrast. Flow regimes are mapped in the (Fr, Re cos β/Fr)-plane, delineated in terms of interfacial instability, front dynamics, and front velocity. Amongst the many observations, we find that viscosifying the less dense fluid tends to significantly destabilize the flow. Different instabilities develop at the interface and in the wall-layers.

Plankton assembly in an ultra-oligotrophic Antarctic lake over the summer transition from the ice-cover to ice-free period: A size spectra approach

NASA Astrophysics Data System (ADS)

Rochera, Carlos; Quesada, Antonio; Toro, Manuel; Rico, Eugenio; Camacho, Antonio

2017-03-01

Lakes from the Antarctic maritime region experience climate change as a main stressor capable of modifying their plankton community structure and function, essentially because summer temperatures are commonly over the freezing point and the lake's ice cap thaws. This study was conducted in such seasonally ice-covered lake (Lake Limnopolar, Byers Peninsula, Livingston Is., Antarctica), which exhibits a microbial dominated pelagic food web. An important feature is also the occurrence of benthic mosses (Drepanocladus longifolius) covering the lake bottom. Plankton dynamics were investigated during the ice-thawing transition to the summer maximum. Both bacterioplankton and viral-like particles were higher near the lake's bottom, suggesting a benthic support. When the lake was under dim conditions because of the snow-and-ice cover, autotrophic picoplankters dominated at deep layers. The taxa-specific photopigments indicated dominance of picocyanobacteria among them when the light availability was lower. By contrast, larger and less edible phytoplankton dominated at the onset of the ice melting. The plankton size spectra were fitted to the continuous model of Pareto distribution. Spectra evolved similarly at two sampled depths, in surface and near the bottom, with slopes increasing until mid-January. However, slopes were less steep (i.e., size classes more uniformly distributed) at the bottom, thus denoting a more efficient utilization of resources. These findings suggest that microbial loop pathways in the lake are efficiently channelized during some periods to the metazoan production (mainly the copepod Boeckella poppei). Our results point to that trophic interactions may still occur in these lakes despite environmental harshness. This results of interest in a framework of increasing temperatures that may reduce the climatic restrictions and therefore stimulate biotic interactions.

Temperature and heat flux scaling laws for isoviscous, infinite Prandtl number mixed heating convection

NASA Astrophysics Data System (ADS)

Vilella, Kenny; Deschamps, Frédéric

2018-07-01

Thermal evolution of terrestrial planets is controlled by heat transfer through their silicate mantles. A suitable framework for modelling this heat transport is a system including bottom heating (from the core) and internal heating, for example, generated by secular cooling or by the decay of radioactive isotopes. The mechanism of heat transfer depends on the physical properties of the system. In systems where convection is able to operate, two different regimes are possible depending on the relative amount of bottom and internal heating. For moderate internal heating rates, the system is composed of active hot upwellings and cold downwellings. For large internal heating rates, the bottom heat flux becomes negative and the system is only composed of active cold downwellings. Here, we build theoretical scaling laws for both convective regimes following the approach of Vilella & Kaminski (2017), which links the surface heat flux and the temperature jump across both the top and the bottom thermal boundary layer (TBL) to the Rayleigh number and the dimensionless internal heating rate. Theoretical predictions are then verified against numerical simulations performed in 2-D and 3-D Cartesiangeometry, and covering a large range of the parameter space. Our theoretical scaling laws are more successful in predicting the thermal structure of systems with large internal heating rates than that of systems with no or moderate internal heating. The differences between moderate and large internal heating rates are interpreted as differences in the mechanisms generating thermal instabilities. We identified three mechanisms: conductive growth of the TBL, instability impacting, and TBL erosion, the last two being present only for moderate internal heating rates, in which hot plumes are generated at the bottom of the system and are able to reach the surface. Finally, we apply our scaling laws to the evolution of the early Earth, proposing a new model for the cooling of the primordial magma ocean that reconciles geochemical observations and magma ocean dynamics.

Temperature and heat flux scaling laws for isoviscous, infinite Prandtl number mixed heating convection.

NASA Astrophysics Data System (ADS)

Vilella, Kenny; Deschamps, Frederic

2018-04-01

Thermal evolution of terrestrial planets is controlled by heat transfer through their silicate mantles. A suitable framework for modelling this heat transport is a system including bottom heating (from the core) and internal heating, e.g., generated by secular cooling or by the decay of radioactive isotopes. The mechanism of heat transfer depends on the physical properties of the system. In systems where convection is able to operate, two different regimes are possible depending on the relative amount of bottom and internal heating. For moderate internal heating rates, the system is composed of active hot upwellings and cold downwellings. For large internal heating rates, the bottom heat flux becomes negative and the system is only composed of active cold downwellings. Here, we build theoretical scaling laws for both convective regimes following the approach of Vilella & Kaminski (2017), which links the surface heat flux and the temperature jump across both the top and bottom thermal boundary layer (TBL) to the Rayleigh number and the dimensionless internal heating rate. Theoretical predictions are then verified against numerical simulations performed in 2D and 3D-Cartesian geometry, and covering a large range of the parameter space. Our theoretical scaling laws are more successful in predicting the thermal structure of systems with large internal heating rates than that of systems with no or moderate internal heating. The differences between moderate and large internal heating rates are interpreted as differences in the mechanisms generating thermal instabilities. We identified three mechanisms: conductive growth of the TBL, instability impacting, and TBL erosion, the last two being present only for moderate internal heating rates, in which hot plumes are generated at the bottom of the system and are able to reach the surface. Finally, we apply our scaling laws to the evolution of the early Earth, proposing a new model for the cooling of the primordial magma ocean that reconciles geochemical observations and magma ocean dynamics.

Investigating the importance of sediment resuspension in Alexandrium fundyense cyst population dynamics in the Gulf of Maine

USGS Publications Warehouse

Butman, Bradford; Aretxabaleta, Alfredo L.; Dickhudt, Patrick J.; Dalyander, P. Soupy; Sherwood, Christopher R.; Anderson, Donald M.; Keafer, Bruce A.; Signell, Richard P.

2014-01-01

Cysts of Alexandrium fundyense, a dinoflagellate that causes toxic algal blooms in the Gulf of Maine, spend the winter as dormant cells in the upper layer of bottom sediment or the bottom nepheloid layer and germinate in spring to initiate new blooms. Erosion measurements were made on sediment cores collected at seven stations in the Gulf of Maine in the autumn of 2011 to explore if resuspension (by waves and currents) could change the distribution of over-wintering cysts from patterns observed in the previous autumn; or if resuspension could contribute cysts to the water column during spring when cysts are viable. The mass of sediment eroded from the core surface at 0.4 Pa ranged from 0.05 kg m−2 near Grand Manan Island, to 0.35 kg m−2 in northern Wilkinson Basin. The depth of sediment eroded ranged from about 0.05 mm at a station with sandy sediment at 70 m water depth on the western Maine shelf, to about 1.2 mm in clayey–silt sediment at 250 m water depth in northern Wilkinson Basin. The sediment erodibility measurements were used in a sediment-transport model forced with modeled waves and currents for the period October 1, 2010 to May 31, 2011 to predict resuspension and bed erosion. The simulated spatial distribution and variation of bottom shear stress was controlled by the strength of the semi-diurnal tidal currents, which decrease from east to west along the Maine coast, and oscillatory wave-induced currents, which are strongest in shallow water. Simulations showed occasional sediment resuspension along the central and western Maine coast associated with storms, steady resuspension on the eastern Maine shelf and in the Bay of Fundy associated with tidal currents, no resuspension in northern Wilkinson Basin, and very small resuspension in western Jordan Basin. The sediment response in the model depended primarily on the profile of sediment erodibility, strength and time history of bottom stress, consolidation time scale, and the current in the water column. Based on analysis of wave data from offshore buoys from 1996 to 2012, the number of wave events inducing a bottom shear stress large enough to resuspend sediment at 80 m ranged from 0 to 2 in spring (April and May) and 0 to 10 in winter (October through March). Wave-induced resuspension is unlikely in water greater than about 100 m deep. The observations and model results suggest that a millimeter or so of sediment and associated cysts may be mobilized in both winter and spring, and that the frequency of resuspension will vary interannually. Depending on cyst concentration in the sediment and the vertical distribution in the water column, these events could result in a concentration in the water column of at least 104 cysts m−3. In some years, resuspension events could episodically introduce cysts into the water column in spring, where germination is likely to be facilitated at the time of bloom formation. An assessment of the quantitative effects of cyst resuspension on bloom dynamics in any particular year requires more detailed investigation.

Settlement statistics of a granular layer composed of polyhedral particles

NASA Astrophysics Data System (ADS)

Quezada, Juan Carlos; Saussine, Gilles; Breul, Pierre; Radjai, Farhang

2013-06-01

We use 3D contact dynamics simulations to investigate the mechanical equilibrium and settlement of a granular material composed of irregular polyhedral particles confined between two horizontal frictional planes. We show that, as a consequence of mobilized wall-particle friction force at the top and bottom boundaries, the transient deformation induced by a constant vertical load increment is controlled by the aspect ratio (thickness over width) of the packing as well as the stress ratio. The transient deformation declines considerably for increasingly smaller aspect ratios and grows with the stress ratio. From the simulation data for a large number of independent configurations, we find that sample-to-sample fluctuations of the deformation have a broad distribution and they scale with the average deformation.

Biquadratic coupling through nano-oxide layers in pinned layers of IrMn-based spin valves

NASA Astrophysics Data System (ADS)

Lai, Chih-Huang; Lu, K. H.

2003-05-01

We have investigated the coupling between top and bottom pinned layers through various nano-oxide layers (NOLs) in IrMn-based spin valves. The NOLs were formed by using oxygen-plasma oxidation or natural oxidation on 1 nm metallic layers. By inserting naturally oxidized Co-NOLs in the pinned layer, strong ferromagnetic coupling through NOLs and high specularity at the NOL interface were achieved. In contrast, when the plasma-oxidized Co-NOLs were inserted, ferromagnetic coupling through NOLs disappeared, plausibly due to the formation of nonferromagnetic oxides, which led to a low magnetoresistance (MR). Insertion of naturally oxidized Ni80Fe20-NOLs showed the same results as that of naturally oxidized Co-NOLs. On the other hand, biquadratic coupling between top and bottom pinned-Co90Fe10 layers was observed by inserting plasma-oxidized Ni80Fe20-NOLs. The highest MR was obtained when the field was applied along the direction perpendicular to the field-annealing direction. Similar biquadratic coupling was also found with naturally oxidized or plasma-oxidized Fe-NOLs. We suggest that the biquadratic coupling between pinned Co90Fe10 layers through NOLs results from the coupling between Fe (or Co90Fe10) and Fe+3 oxides

Role of the bottom sediments immediately beneath the lake water-groundwater interface in the transport and removal of cyanobacteria, cyanophage, and dissolved organic carbon during natural lake-bank filtration at a kettle pond subject to harmful algal blooms

NASA Astrophysics Data System (ADS)

Harvey, R. W.; Metge, D. W.; LeBlanc, D. R.; Underwood, J. C.; Aiken, G.; McCobb, T. D.; Jasperse, J.

2015-12-01

Bank filtration has proven to be a sustainable, cost-effective method of removing cyanobacteria and their harmful toxins from surface water during filtration through bottom and aquifer sediments. The biologically active layer of sediments immediately beneath the sediment-water interface (colmation layer) is believed to be particularly important in this process. An in situ experiment was conducted that involved assessing the transport behaviors of bromide (conservative tracer), Synechococcus sp. IU625 (cyanobacterium, 2.6 ± 0.2 µm), AS-1 (tailed cyanophages, 110 nm long), MS2 (coliphages, 26 nm diameter), and carboxylate-modified microspheres (1.7 µm diameter) introduced to the colmation layer using a bag-and-barrel (Lee-type) seepage meter. The constituents were monitored as they advected through the colmation layer and underlying aquifer sediments at Ashumet Pond in Cape Cod, MA, a mesotrophic kettle pond that recharges a portion of a sole-source, drinking water aquifer. Because the pond DOC includes the various cyanotoxins produced during harmful algal bloom senescence, the DOC and aforementioned colloids were tracked concomitantly. The tracer test constituents were monitored as they advected across the pond water-groundwater interface and through the underlying aquifer sediments under natural-gradient conditions past push-points samplers placed at ~30-cm intervals along a 1.2-m-long, diagonally downward flow path. More than 99% of the microspheres, IU625, MS2, AS-1, and ~42% of the pond DOC were removed in the colmation layer (upper 25 cm of poorly sorted bottom sediments) at two test locations characterized by dissimilar seepage rates (1.7 vs. 0.26 m d-1). Retention profiles in recovered core material indicated that >82% of the attached IU625 were in the top 3 cm of bottom sediments. The colmation layer was also responsible for rapid changes in the character of the DOC and was more effective (by 3 orders of magnitude) at removing microspheres than was the underlying 30-cm-long segment of sediment. A follow-up study conducted the following year at the same location demonstrated that removal of the top 5 cm of sediment resulted in a six-fold decrease in the efficiency of the near-surface bottom sediments for filtering out Synechococcus, cyanophage, and well-characterized microspheres.

A new instrument system to investigate sediment dynamics on continental shelves

USGS Publications Warehouse

Cacchione, D.A.; Drake, D.E.

1979-01-01

A new instrumented tripod, the GEOPROBE system, has been constructed and used to collect time-series data on physical and geological parameters that are important in bottom sediment dynamics on continental shelves. Simultaneous in situ digital recording of pressure, temperature, light scattering, and light transmission, in combination with current velocity profiles measured with a near-bottom vertical array of electromagnetic current meters, is used to correlate bottom shear generated by a variety of oceanic processes (waves, tides, mean flow, etc.) with incipient movement and resuspension of bottom sediment. A bottom camera system that is activated when current speeds exceed preset threshold values provides a unique method to identify initial sediment motion and bed form development. Data from a twenty day deployment of the GEOPROBE system in Norton Sound, Alaska, during the period September 24 - October 14, 1976 show that threshold conditions for sediment movement are commonly exceeded, even in calm weather periods, due to the additive effects of tidal currents, mean circulation, and surface waves. ?? 1979.

Diamond anvil cells using boron-doped diamond electrodes covered with undoped diamond insulating layer

NASA Astrophysics Data System (ADS)

Matsumoto, Ryo; Yamashita, Aichi; Hara, Hiroshi; Irifune, Tetsuo; Adachi, Shintaro; Takeya, Hiroyuki; Takano, Yoshihiko

2018-05-01

Diamond anvil cells using boron-doped metallic diamond electrodes covered with undoped diamond insulating layers have been developed for electrical transport measurements under high pressure. These designed diamonds were grown on a bottom diamond anvil via a nanofabrication process combining microwave plasma-assisted chemical vapor deposition and electron beam lithography. The resistance measurements of a high-quality FeSe superconducting single crystal under high pressure were successfully demonstrated by just putting the sample and gasket on the bottom diamond anvil directly. The superconducting transition temperature of the FeSe single crystal was increased to up to 43 K by applying uniaxial-like pressure.

The nepheloid bottom layer and water masses at the shelf break of the western Ross Sea

NASA Astrophysics Data System (ADS)

Capello, Marco; Budillon, Giorgio; Cutroneo, Laura; Tucci, Sergio

2009-06-01

In the austral summers of 2000/2001 and 2002/2003 the Italian CLIMA Project carried out two oceanographic cruises along the northwestern margin of the Ross Sea, where the Antarctic Bottom Water forms. Here there is an interaction between the water masses on the sea floor of the outer shelf and slope with a consequent evolution of benthic nepheloid layers and an increase in total particulate matter. We observed three different situations: (a) the presence of triads (bottom structures characterized by a concomitant jump in turbidity, temperature, and salinity data) and high re-suspension phenomena related to the presence of the Circumpolar Deep Water and its mixing with cold, salty shelf waters associated with gravity currents; (b) the absence of triads with high re-suspension, implying that when the gravity currents are no longer active the benthic nepheloid layer may persist until the suspended particles settle to the sea floor, suggesting that the turbidity data can be used to study recent gravity current events; and (c) the absence of turbidity and sediment re-suspension phenomena supports the theory that a steady situation had been re-established and the current interaction no longer occurred or had finished sometime before.

Case analyses and numerical simulation of soil thermal impacts on land surface energy budget based on an off-line land surface model

NASA Astrophysics Data System (ADS)

Guo, W. D.; Sun, S. F.; Qian, Y. F.

2002-05-01

The statistical relationship between soil thermal anomaly and short-term climate change is presented based on a typical case study. Furthermore, possible physical mechanisms behind the relationship are revealed through using an off-line land surface model with a reasonable soil thermal forcing at the bottom of the soil layer. In the first experiment, the given heat flux is 5 W m(-2) at the bottom of the soil layer (in depth of 6.3 m) for 3 months, while only a positive ground temperature anomaly of 0.06degreesC can be found compared to the control run. The anomaly, however, could reach 0.65degreesC if the soil thermal conductivity was one order of magnitude larger. It could be even as large as 0.81degreesC assuming the heat flux at bottom is 10 W m(-2). Meanwhile, an increase of about 10 W m(-2) was detected both for heat flux in soil and sensible heat on land surface, which is not neglectable to the short-term climate change. The results show that considerable response in land surface energy budget could be expected when the soil thermal forcing reaches a certain spatial-temporal scale. Therefore, land surface models should not ignore the upward heat flux from the bottom of the soil layer, Moreover, integration for a longer period of time and coupled land-atmosphere model are also necessary for the better understanding of this issues.

Magnetoconvection dynamics in a stratified layer. 1: Two-dimensional simulations and visualization

NASA Astrophysics Data System (ADS)

Lantz, Steven R.; Sudan, R. N.

1995-03-01

To gain insight in the problem of fluid convection below solar photosphere, time-dependent magnetohydrodynamic convection is studied by numerical simulation to the magneto-anelastic equations, a model appropiate for low Mach numbers. Numerical solutions to the equations are generated on a two-dimensional Cartesian mesh by a finite-difference, predictor-corrector algorithm. The thermodynamic properties of the fluid are held constant at the rigid, stress-free top and bottom boundaries of the computational box, while lateral boundaries are treated as periodic. In most runs the background polytropic fluid configuration is held fixed at Rayleigh number R = 5.44 times the critical value, Prandtl number P = 1.8, and aspect ratio a = 1, while the magnetic parameters are allowed to vary. The resulting dynamical behavior is shown to be strongly influenced by a horizontal magnetic field which is imposed at the bottom boundary. As the field strength increases from zero, an initially unsteady 'single-roll' state, featuring complex time dependence is replaced by a steady 'traveling-wave tilted state; then, an oscillatory or 'sloshing' state; then, a steady two-poll state with no tilting; and finally, a stationary state. Because the magnetic field is matched onto a potential field at the top boundary, it can penetrate into the nonconducting region above. By varying a magnetic diffusivity, the concentrations of weak magnetic fields at the top of these flows can be shown to be explainable in terms of an advection-diffusion balance.

On the origin of biological construction, with a focus on multicellularity.

PubMed

van Gestel, Jordi; Tarnita, Corina E

2017-10-17

Biology is marked by a hierarchical organization: all life consists of cells; in some cases, these cells assemble into groups, such as endosymbionts or multicellular organisms; in turn, multicellular organisms sometimes assemble into yet other groups, such as primate societies or ant colonies. The construction of new organizational layers results from hierarchical evolutionary transitions, in which biological units (e.g., cells) form groups that evolve into new units of biological organization (e.g., multicellular organisms). Despite considerable advances, there is no bottom-up, dynamical account of how, starting from the solitary ancestor, the first groups originate and subsequently evolve the organizing principles that qualify them as new units. Guided by six central questions, we propose an integrative bottom-up approach for studying the dynamics underlying hierarchical evolutionary transitions, which builds on and synthesizes existing knowledge. This approach highlights the crucial role of the ecology and development of the solitary ancestor in the emergence and subsequent evolution of groups, and it stresses the paramount importance of the life cycle: only by evaluating groups in the context of their life cycle can we unravel the evolutionary trajectory of hierarchical transitions. These insights also provide a starting point for understanding the types of subsequent organizational complexity. The central research questions outlined here naturally link existing research programs on biological construction (e.g., on cooperation, multilevel selection, self-organization, and development) and thereby help integrate knowledge stemming from diverse fields of biology.

Hydrogeomorphic controls on hyporheic and riparian transport in two headwater mountain streams during base flow recession

NASA Astrophysics Data System (ADS)

Ward, Adam S.; Schmadel, Noah M.; Wondzell, Steven M.; Harman, Ciaran; Gooseff, Michael N.; Singha, Kamini

2016-02-01

Solute transport along riparian and hyporheic flow paths is broadly expected to respond to dynamic hydrologic forcing by streams, aquifers, and hillslopes. However, direct observation of these dynamic responses is lacking, as is the relative control of geologic setting as a control on responses to dynamic hydrologic forcing. We conducted a series of four stream solute tracer injections through base flow recession in each of two watersheds with contrasting valley morphology in the H.J. Andrews Experimental Forest, monitoring tracer concentrations in the stream and in a network of shallow riparian wells in each watershed. We found hyporheic mean arrival time, temporal variance, and fraction of stream water in the bedrock-constrained valley bottom and near large roughness elements in the wider valley bottom were not variable with discharge, suggesting minimal control by hydrologic forcing. Conversely, we observed increases in mean arrival time and temporal variance and decreasing fraction stream water with decreasing discharge near the hillslopes in the wider valley bottom. This may indicate changes in stream discharge and valley bottom hydrology control transport in less constrained locations. We detail five hydrogeomorphic responses to base flow recession to explain observed spatial and temporal patterns in the interactions between streams and their valley bottoms. Models able to account for the transition from geologically dominated processes in the near-stream subsurface to hydrologically dominated processes near the hillslope will be required to predict solute transport and fate in valley bottoms of headwater mountain streams.

Complex layering of the Orange Mountain Basalt: New Jersey, USA

NASA Astrophysics Data System (ADS)

Puffer, John H.; Block, Karin A.; Steiner, Jeffrey C.; Laskowich, Chris

2018-06-01

The Orange Mountain Basalt of New Jersey is a Mesozoic formation consisting of three units: a single lower inflated sheet lobe about 70 m thick (OMB1), a middle pillow basalt about 10 to 20 m thick (OMB2), and an upper compound pahoehoe flow about 20 to 40 m thick (OMB3). The Orange Mountain Basalt is part of the Central Atlantic Magmatic Province. Quarry and road-cut exposures of OMB1 near Paterson, New Jersey, display some unusual layering that is the focus of this study. OMB1 exposures displays the typical upper crust, core, and basal crust layers of sheet lobes but throughout the Patterson area also display distinct light gray layers of microvesicular basalt mineralized with albite directly over the basal crust and under the upper crust. The lower microvesicular layer is associated with mega-vesicular diapirs. We propose that the upper and lower microvesicular layers were composed of viscous crust that was suddenly quenched before it could devolatilize immediately before the solidification of the core. During initial cooling, the bottom of the basal layer was mineralized with high concentrations of calcite and albite during a high-temperature hydrothermal event. Subsequent albitization, as well as zeolite, prehnite, and calcite precipitation events, occurred during burial and circulation of basin brine heated by recurring Palisades magmatism below the Orange Mountain Basalt. Some of the events experienced by the Orange Mountain Basalt are unusual and place constraints on the fluid dynamics of thick flood basalt flows in general. The late penetration of vesicular diapirs through the entire thickness of the flow interior constrains its viscosity and solidification history.

Scintillator assembly for alpha radiation detection and method of making the assembly

DOEpatents

McElhaney, Stephanie A.; Bauer, Martin L.; Chiles, Marion M.

1992-01-01

A scintillator assembly for use in the detection of alpha radiation includes a body of optically-transparent epoxy and an amount of phosphor particles embedded within the body adjacent one surface thereof. When making the body, the phosphor particles are mixed with the epoxy when in an uncured condition and permitted to settle to the bottom surface of a mold within which the epoxy/phosphor mixture is contained. When the mixture subsequently cures to form a hardened body, the one surface of the body which cured against the bottom surface of the mold is coated with a thin layer of opaque material for preventing ambient light form entering the body through the one surface. The layer of opaque material is thereafter coated with a layer of protective material to provide the assembly with a damage-resistant entrance window.

Wave propagation in magneto-electro-elastic multilayered plates with nonlocal effect

NASA Astrophysics Data System (ADS)

Chen, Jiangyi; Guo, Junhong; Pan, Ernian

2017-07-01

In this paper, analytical solutions for propagation of time-harmonic waves in three-dimensional, transversely isotropic, magnetoelectroelastic and multilayered plates with nonlocal effect are derived. We first convert the time-harmonic wave problem into a linear eigenvalue system, from which we obtain the general solutions of the extended displacements and stresses. The solutions are then employed to derive the propagator matrix which connects the field variables at the upper and lower interfaces of each layer. Making use of the continuity conditions of the physical quantities across the interface, the global propagator relation is assembled by propagating the solutions in each layer from the bottom to the top of the layered plate. From the global propagator matrix, the dispersion equation is obtained by imposing the traction-free boundary conditions on both the top and bottom surfaces of the layered plate. Dispersion curves and mode shapes in layered plates made of piezoelectric BaTiO3 and magnetostrictive CoFe2O4 materials are presented to show the influence of the nonlocal parameter, stacking sequence, as well as the orientation of incident wave on the time-harmonic field response.

Resistive Switching of Ta2O5-Based Self-Rectifying Vertical-Type Resistive Switching Memory

NASA Astrophysics Data System (ADS)

Ryu, Sungyeon; Kim, Seong Keun; Choi, Byung Joon

2018-01-01

To efficiently increase the capacity of resistive switching random-access memory (RRAM) while maintaining the same area, a vertical structure similar to a vertical NAND flash structure is needed. In addition, the sneak-path current through the half-selected neighboring memory cell should be mitigated by integrating a selector device with each RRAM cell. In this study, an integrated vertical-type RRAM cell and selector device was fabricated and characterized. Ta2O5 as the switching layer and TaOxNy as the selector layer were used to preliminarily study the feasibility of such an integrated device. To make the side contact of the bottom electrode with active layers, a thick Al2O3 insulating layer was placed between the Pt bottom electrode and the Ta2O5/TaOxNy stacks. Resistive switching phenomena were observed under relatively low currents (below 10 μA) in this vertical-type RRAM device. The TaOxNy layer acted as a nonlinear resistor with moderate nonlinearity. Its low-resistance-state and high-resistance-state were well retained up to 1000 s.

Energy dissipation in intercalated carbon nanotube forests with metal layers

USDA-ARS?s Scientific Manuscript database

Vertically aligned carbon nanotube (CNT) forests were synthesized to study their quasi-static mechanical properties in a layered configuration with metallization. The top and bottom surfaces of CNT forests were metalized with Ag, Fe, and In using paste, sputtering, and thermal evaporation, respectiv...

MEANS FOR SHIELDING AND COOLING REACTORS

DOEpatents

Wigner, E.P.; Ohlinger, L.A.; Young, G.J.; Weinberg, A.M.

1959-02-10

Reactors of the water-cooled type and a means for shielding such a rcactor to protect operating personnel from harmful radiation are discussed. In this reactor coolant tubes which contain the fissionable material extend vertically through a mass of moderator. Liquid coolant enters through the bottom of the coolant tubes and passes upwardly over the fissionable material. A shield tank is disposed over the top of the reactor and communicates through its bottom with the upper end of the coolant tubes. A hydrocarbon shielding fluid floats on the coolant within the shield tank. With this arrangements the upper face of the reactor can be opened to the atmosphere through the two superimposed liquid layers. A principal feature of the invention is that in the event radioactive fission products enter thc coolant stream. imposed layer of hydrocarbon reduces the intense radioactivity introduced into the layer over the reactors and permits removal of the offending fuel material by personnel shielded by the uncontaminated hydrocarbon layer.

The interplay between estuarine transport and biogeochemical processes in determining the nutrient conditions in bottom layers of non-tidal Gulf of Finland

NASA Astrophysics Data System (ADS)

Kõuts, Mariliis; Raudsepp, Urmas; Maljutenko, Ilja

2017-04-01

In coastal areas, especially estuaries, spatial distribution and seasonal cycling of chemical and biological variables is largely determined by local biogeochemical processes and water transport of different properties. In tidal estuaries, however, biogeochemical processes are affected by tides as frequent water exchange alters nutrient and oxygen concentrations. In wide and deep non-tidal estuary-type marginal seas spatial distribution and seasonal cycling are determined by the mixture of water transport and local biogeochemistry. The Baltic Sea is a stratified water basin where halocline divides the water column into two parts: upper layer, which is horizontally uniform in terms of distribution of chemical and biological parameters, and has clear seasonal cycle; and bottom part, where nutrient and oxygen dynamics is more complex. There water transport and sediment-water interface fluxes play a major role. Our prime focus is the Gulf of Finland in the Baltic Sea. It is a wide, non-tidal and stratified sub-basin known for its high nutrient concentrations and severe oxygen deficiency in summer. We modelled the Baltic Sea (including Gulf of Finland) using ERGOM, a biogeochemical model coupled with circulation model GETM. Seasonal cycling and water circulation were observed with a 40-year simulation from 1966 to 2006. Our results show that in shallow areas above halocline the seasonal cycle of phytoplankton, nutrients and oxygen concentrations is uniform in space. Water circulation does not create inhomogeneous distribution pattern of biogeochemical parameters and their seasonal cycle. The circulation in the Gulf of Finland is strongly modulated by the seasonality of estuarine transport. Below the halocline saline low-oxygen and nutrient-rich water is transported from the open Baltic Proper to the Gulf of Finland in spring and early summer. This results in the highest nutrient concentrations and the poorest oxygen conditions by the end of August. In the shallow area nutrients have high concentrations in March-April before the spring bloom of diatoms starts. Low oxygen and nutrient concentrations are observed at the end of August. There is a qualitative difference of nutrient dynamics between shallow and deep layers but quantification of the role of transport and local biogeochemical processes is still challenging.

Horizontal and Vertical Distributions of Transparent Exopolymer Particles (TEP) in the NW Mediterranean Sea Are Linked to Chlorophyll a and O2 Variability

PubMed Central

Ortega-Retuerta, Eva; Sala, Maria M.; Borrull, Encarna; Mestre, Mireia; Aparicio, Fran L.; Gallisai, Rachele; Antequera, Carolina; Marrasé, Cèlia; Peters, Francesc; Simó, Rafel; Gasol, Josep M.

2017-01-01

Transparent Exopolymer Particles (TEP) are relevant in particle and carbon fluxes in the ocean, and have economic impact in the desalination industry affecting reverse osmosis membrane fouling. However, general models of their occurrence and dynamics are not yet possible because of the poorly known co-variations with other physical and biological variables. Here, we describe TEP distributions in the NW Mediterranean Sea during late spring 2012, along perpendicular and parallel transects to the Catalan coast. The stations in the parallel transect were sampled at the surface, while the stations in the perpendicular transect were sampled from the surface to the bathypelagic, including the bottom nepheloid layers. We also followed the short-term TEP dynamics along a 2-day cycle in offshore waters. TEP concentrations in the area ranged from 4.9 to 122.8 and averaged 31.4 ± 12.0 μg XG eq L−1. The distribution of TEP measured in transects parallel to the Catalan Coast correlated those of chlorophyll a (Chla) in May but not in June, when higher TEP-values with respect to Chla were observed. TEP horizontal variability in epipelagic waters from the coast to the open sea also correlated to that of Chla, O2 (that we interpret as a proxy of primary production) and bacterial production (BP). In contrast, the TEP vertical distributions in epipelagic waters were uncoupled from those of Chla, as TEP maxima were located above the deep chlorophyll maxima. The vertical distribution of TEP in the epipelagic zone was correlated with O2 and BP, suggesting combined phytoplankton (through primary production) and bacterial (through carbon reprocessing) TEP sources. However, no clear temporal patterns arose during the 2-day cycle. In meso- and bathypelagic waters, where phytoplanktonic sources are minor, TEP concentrations (10.1 ± 4.3 μg XG eq l−1) were half those in the epipelagic, but we observed relative TEP increments coinciding with the presence of nepheloid layers. These TEP increases were not paralleled by increases in particulate organic carbon, indicating that TEP are likely to act as aggregating agents of the mostly inorganic particles present in these bottom nepheloid layers. PMID:28197126

Assessment of burned coal shale properties based on cyclic load

NASA Astrophysics Data System (ADS)

Grygierek, Marcin; Kalisz, Piotr; Pacześniowski, Krzysztof; Pytlik, Andrzej; Zięba, Magdalena

2018-04-01

Road surfaces that are subjected to cyclic loads generated by vehicle wheels must meet the requirements concerning the durability in the assumed period of use. The durability of the layered pavement construction systems depends on the value and frequency of the load as well as on the mechanical features of its individual layers. Layers of unbound, mechanically stabilized mixtures are a significant aspect of surfaces that are susceptible. Mixtures of this type can be applied both to the subgrade layers as well as to the bottom pavement layers, including the improved course. Considering the cyclic nature of the load on the surface of the entire system, mechanically stabilized layers are subject to continuous, but slow, densification during the period of use, which results in the formation of permanent deformations and so-called structural ruts. Post-mining waste is frequently used in road construction. which is the so-called burned shale that can be used for the bottom layers of the surface and layers of the improved subgrade (soil replacement). This material was the subject of the analysis. The evaluation was based mainly on the results of pilot studies covering cyclic loads of the layer/course made of the so-called red shale. The applied research method was aimed at preliminary assessment of its suitability for the assessment of the behaviour of the disintegrated medium under the conditions of test loads simulating the movement of vehicles.

Influence of substrates and rutile seed layers on the assembly of hydrothermally grown rutile TiO2 nanorod arrays

NASA Astrophysics Data System (ADS)

Kalb, Julian; Dorman, James A.; Folger, Alena; Gerigk, Melanie; Knittel, Vanessa; Plüisch, Claudia S.; Trepka, Bastian; Lehr, Daniela; Chua, Emily; Goodge, Berit H.; Wittemann, Alexander; Scheu, Christina; Polarz, Sebastian; Schmidt-Mende, Lukas

2018-07-01

Rutile TiO2 nanorod arrays (NRAs) are applicable in various prospective technologies. Hydrothermal methods present a simple technique to fabricate such NRAs. In this report, we present the fabrication of seed layers for the hydrothermal growth of rutile TiO2 nanorods via sputter deposition, electron-beam evaporation, and sol-gel method and study the influence of each on the growth behavior. To satisfy the requirements of numerous applications, p-type silicon, platinum, levitating carbon membranes, a template made of polystyrene spheres, and commercial fluorine tin oxide (FTO) were employed as substrates. We document the structural properties of the TiO2 seed layers and describe the relationship between the characteristics of the seed crystals, the growth evolution, and the appearance of as-grown nanorods. Various growth stages of rutile TiO2 nanorods are compared depending on whether they are grown on polycrystalline TiO2 or FTO seed layers. In both cases, a homogenous TiO2 bottom layer is formed at the seed layer/substrate interface, which is essential for electronic applications such as hybrid solar cells. Detached NRAs illustrate the effect of rutile FTO and TiO2 on the porosity of this bottom layer. Further details about the formation process of this layer are obtained from the growth on confined seed layers fabricated by electron-beam lithography.

Single-Band and Dual-Band Infrared Detectors

NASA Technical Reports Server (NTRS)

Ting, David Z. (Inventor); Gunapala, Sarath D. (Inventor); Soibel, Alexander (Inventor); Nguyen, Jean (Inventor); Khoshakhlagh, Arezou (Inventor)

2015-01-01

Bias-switchable dual-band infrared detectors and methods of manufacturing such detectors are provided. The infrared detectors are based on a back-to-back heterojunction diode design, where the detector structure consists of, sequentially, a top contact layer, a unipolar hole barrier layer, an absorber layer, a unipolar electron barrier, a second absorber, a second unipolar hole barrier, and a bottom contact layer. In addition, by substantially reducing the width of one of the absorber layers, a single-band infrared detector can also be formed.

Single-Band and Dual-Band Infrared Detectors

NASA Technical Reports Server (NTRS)

Ting, David Z. (Inventor); Gunapala, Sarath D. (Inventor); Soibel, Alexander (Inventor); Nguyen, Jean (Inventor); Khoshakhlagh, Arezou (Inventor)

2017-01-01

Bias-switchable dual-band infrared detectors and methods of manufacturing such detectors are provided. The infrared detectors are based on a back-to-back heterojunction diode design, where the detector structure consists of, sequentially, a top contact layer, a unipolar hole barrier layer, an absorber layer, a unipolar electron barrier, a second absorber, a second unipolar hole barrier, and a bottom contact layer. In addition, by substantially reducing the width of one of the absorber layers, a single-band infrared detector can also be formed.

Investigation of Primary Causes of Load-Related Cracking in Asphalt Concrete Pavement in North Carolina

NASA Astrophysics Data System (ADS)

Park, Hong Joon

This dissertation presents causes of cracking in asphalt concrete pavement in North Carolina through field investigation and laboratory experiments with field extracted material. North Carolina is experiencing higher than anticipated rates of fatigue cracking compared to other state. These higher than expected rates could be reflective of the national trends in mix design practice or could be caused by structural pavement failures. The problems associated with premature cracking in North Carolina pavements point to the need to evaluate the North Carolina Department of Transportation (NCDOT) mixes, processes, and measures to ensure that these factors properly balance the goals of preventing cracking and minimizing permanent deformation. Without solid data from in-service pavements, any conclusions regarding the causes of these failures might be pure conjecture. Accordingly, this research examines material properties through laboratory experiments using field-extracted materials and investigates in situ pavements and pavement structure. In order to assess condition of existing pavement, alligator cracking index (ACI) was developed. The asphalt content in the top layer that exhibits top-down cracking or bottom-up cracking has a proportional relationship to ACI values. The air void content in a bottom layer that exhibits top-down cracking or bottom-up cracking shows an inverse proportional relationship to ACI values. These observations reflect reasonable results. A comparison between ACI and asphalt film thickness values does not produce noteworthy findings, but somewhat reasonable results are evident once the range of comparison is narrowed down. Thicker film thicknesses show higher ACI values. From field core visual observations, road widening is identified as a major cause of longitudinal cracking. Regions with observed layer interface separation tend to have low ACI values. Through tensile strain simulation based on actual field conditions, it is observed that sites with observed bottom-up cracking have higher tensile strain levels at the bottom of the asphalt layer than sites with observed top-down cracking. Extracted binder fatigue test results indicate that binder properties between good and poor sections of a given site are not the result of differences in the binder properties. Hence, other mixture design factors are at work in controlling the site variability in terms of fatigue resistance.

Heinrich-type glacial surges in a low-order dynamical climate model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verbitsky, M.; Saltzman, B.

1994-07-01

Recent studies suggest the occurrence of sporadic episodes during which the ice streams that discharge ice sheets become enormously active, producing large numbers of icebergs (reflected in North Atlantic sea cores as {open_quotes}Heinrich events{close_quotes}) and possibly causing the partial collapse of the ice sheets. To simulate the mechanism of implied internal thermo-hydrodynamical instability in the context of a more general paleoclimate dynamics model (PDM), a new sliding-catastrophe function that can account for ice-sheet surges in terms of the thickness, density, viscosity, heat-capacity. and heat-conductivity of ice is introduced. Analysis suggests these events might be of three possible kinds: the firstmore » occurs in periods of glacial maximum when temperature conditions on the ice surface are extremely cold, but internal friction within bottom boundary layer is also at its maximum and is strong enough to melt ice and cause its surge. The second may happen during an interglacial, when the ice thickness is small but relatively warm climate conditions on the upper surface of ice can be easily advected with the flow of ice to the bottom where even a small additional heating due to friction may cause melting. The third and, perhaps, most interesting type is one that may occur during ice sheet growth: in this period particles of ice reaching the bottom {open_quotes}remember{close_quotes} the warm temperature conditions of the previous interglacial and additional heating due to increasing friction associated with the growing ice sheet may again cause melting. This third introduces the interesting possibility that earlier CO{sub 2} concentrations may be as important for the present-day climate as its current value. According to our model the climate system seems more vulnerable to surges during the penultimate interglacial period than in present one contributing to an explanation of the recent results of the Greenland Ice Core Project. 18 refs., 3 figs., 1 tab.« less

Why Do the Boreal Forest Ecosystems of Northwestern Europe Differ from Those of Western North America?

PubMed Central

Boonstra, Rudy; Andreassen, Harry P.; Boutin, Stan; Hušek, Jan; Ims, Rolf A.; Krebs, Charles J.; Skarpe, Christina; Wabakken, Petter

2016-01-01

Abstract The boreal forest is one of the largest terrestrial biomes on Earth. Conifers normally dominate the tree layer across the biome, but other aspects of ecosystem structure and dynamics vary geographically. The cause of the conspicuous differences in the understory vegetation and the herbivore–predator cycles between northwestern Europe and western North America presents an enigma. Ericaceous dwarf shrubs and 3– to 4-year vole–mustelid cycles characterize the European boreal forests, whereas tall deciduous shrubs and 10-year snowshoe hare–lynx cycles characterize the North American ones. We discuss plausible explanations for this difference and conclude that it is bottom-up: Winter climate is the key determinant of the dominant understory vegetation that then determines the herbivore–predator food-web interactions. The crucial unknown for the twenty-first century is how climate change and increasing instability will affect these forests, both with respect to the dynamics of individual plant and animal species and to their community interactions. PMID:28533563

Why Do the Boreal Forest Ecosystems of Northwestern Europe Differ from Those of Western North America?

PubMed

Boonstra, Rudy; Andreassen, Harry P; Boutin, Stan; Hušek, Jan; Ims, Rolf A; Krebs, Charles J; Skarpe, Christina; Wabakken, Petter

2016-09-01

The boreal forest is one of the largest terrestrial biomes on Earth. Conifers normally dominate the tree layer across the biome, but other aspects of ecosystem structure and dynamics vary geographically. The cause of the conspicuous differences in the understory vegetation and the herbivore-predator cycles between northwestern Europe and western North America presents an enigma. Ericaceous dwarf shrubs and 3- to 4-year vole-mustelid cycles characterize the European boreal forests, whereas tall deciduous shrubs and 10-year snowshoe hare-lynx cycles characterize the North American ones. We discuss plausible explanations for this difference and conclude that it is bottom-up: Winter climate is the key determinant of the dominant understory vegetation that then determines the herbivore-predator food-web interactions. The crucial unknown for the twenty-first century is how climate change and increasing instability will affect these forests, both with respect to the dynamics of individual plant and animal species and to their community interactions.

Measuring and Modeling the Growth Dynamics of Self-Catalyzed GaP Nanowire Arrays.

PubMed

Oehler, Fabrice; Cattoni, Andrea; Scaccabarozzi, Andrea; Patriarche, Gilles; Glas, Frank; Harmand, Jean-Christophe

2018-02-14

The bottom-up fabrication of regular nanowire (NW) arrays on a masked substrate is technologically relevant, but the growth dynamic is rather complex due to the superposition of severe shadowing effects that vary with array pitch, NW diameter, NW height, and growth duration. By inserting GaAsP marker layers at a regular time interval during the growth of a self-catalyzed GaP NW array, we are able to retrieve precisely the time evolution of the diameter and height of a single NW. We then propose a simple numerical scheme which fully computes shadowing effects at play in infinite arrays of NWs. By confronting the simulated and experimental results, we infer that re-emission of Ga from the mask is necessary to sustain the NW growth while Ga migration on the mask must be negligible. When compared to random cosine or random uniform re-emission from the mask, the simple case of specular reflection on the mask gives the most accurate account of the Ga balance during the growth.

A frictionally and hydraulically constrained model of the convectively driven mean flow in partially enclosed seas

NASA Astrophysics Data System (ADS)

Maxworthy, T.

1997-08-01

A simple three-layer model of the dynamics of partially enclosed seas, driven by a surface buoyancy flux, is presented. It contains two major elements, a hydraulic constraint at the exit contraction and friction in the interior of the main body of the sea; both together determine the vertical structure and magnitudes of the interior flow variables, i.e. velocity and density. Application of the model to the large-scale dynamics of the Red Sea gives results that are not in disagreement with observation once the model is applied, also, to predict the dense outflow from the Gulf of Suez. The latter appears to be the agent responsible for the formation of dense bottom water in this system. Also, the model is reasonably successful in predicting the density of the outflow from the Persian Gulf, and can be applied to any number of other examples of convectively driven flow in long, narrow channels, with or without sills and constrictions at their exits.

Personal care compounds in a reed bed sludge treatment system.

PubMed

Chen, Xijuan; Pauly, Udo; Rehfus, Stefan; Bester, Kai

2009-08-01

Sewage sludge (also referred to as biosolids) has long been used as fertilizer on agricultural land. The usage of sludge as fertilizer is controversial because of possible high concentration of xenobiotic compounds, heavy metals as well as pathogens. In this study, the fate of the xenobiotic compounds triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol), OTNE (1-(2,3,8,8-tetramethyl-1,2,3,4,5,6,7,8-octahydro-naphthalen-2-yl)ethan-1-one), HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(g)-2-benzopyran), HHCB-lactone, AHTN (7-acetyl-1,1,3,4,4,6 hexamethyl-1,2,3,4 tetrahydronaphthalene), and DEHP (bis(2-ethylhexyl)phthalate) in advanced biological treatment of sludge was determined. During 13months of field-incubation of the sludge in reed beds, the xenobiotic compounds were analysed. The bactericide triclosan was reduced to 60%, 45%, and 32% of its original concentration in the top, middle, and bottom layer. The fragrance OTNE was decreased to 42% in the top layer, 53% in the middle layer, and 70% in the bottom layer, respectively. For DEHP a reduction of 70%, 71%, and 40% was observed in the top, middle, and bottom layer, respectively. The polycyclic musk compounds HHCB, AHTN, and the primary metabolite of HHCB, i.e., HHCB-lactone showed no degradation in 13months during the experimental period in this installation. Tentative half-lives of degradation of triclosan, OTNE and DEHP were estimated to be 315-770d, 237-630d, and 289-578d, respectively.

Computational Study of Ventilation and Disease Spread in Poultry Houses

NASA Astrophysics Data System (ADS)

Cimbala, John; Pawar, Sourabh; Wheeler, Eileen; Lindberg, Darla

2006-11-01

The air flow in and around poultry houses has been studied numerically with the goal of determining disease spread characteristics and comparing ventilation schemes. A typical manure-belt layer egg production facility is considered. The continuity, momentum, and energy equations are solved for flow both inside and outside poultry houses using the commercial computational fluid dynamics (CFD) code FLUENT. Both simplified two-dimensional and fully three-dimensional geometries are modeled. The spread of virus particles is considered to be analogous to diffusion of a tracer contaminant gas, in this case ammonia. The effect of thermal plumes produced by the hens in the poultry house is also considered. Two ventilation schemes with opposite flow directions are compared. Contours of temperature and ammonia mass fraction for both cases are obtained and compared. The analysis shows that ventilation and air quality characteristics are much better for the case in which the air flow is from bottom to top (enhancing the thermal plume) instead of from top to bottom (fighting the thermal plume) as in most poultry houses. This has implications in air quality control in the event of epidemic outbreaks of avian flu or other infectious diseases.

The clouds of Venus. II - An investigation of the influence of coagulation on the observed droplet size distribution

NASA Technical Reports Server (NTRS)

Rossow, W. B.

1977-01-01

An approximate numerical technique is used to investigate the influence of coagulation, sedimentation and turbulent motions on the observed droplet size distribution in the upper layers of the Venus clouds. If the cloud mass mixing ratio is less than 0.000001 at 250 K or the eddy diffusivity throughout the cloud is greater than 1,000,000 sq cm per sec, then coagulation is unimportant. In this case, the observed droplet size distribution is the initial size distribution produced by the condensation of the droplets. It is found that all cloud models with droplet formation near the cloud top (e.g., a photochemical model) must produce the observed droplet size distribution by condensation without subsequent modification by coagulation. However, neither meteoritic or surface dust can supply sufficient nucleating particles to account for the observed droplet number density. If the cloud droplets are formed near the cloud bottom, the observed droplet size distribution can be produced solely by the interaction of coagulation and dynamics; all information about the initial size distribution is lost. If droplet formation occurs near the cloud bottom, the lower atmosphere of Venus is oxidizing rather than reducing.

Rational design of bottom blocks for development of ore deposits systems with caving of ore and enclosing rocks

NASA Astrophysics Data System (ADS)

Versilov, S. O.; Posylniy, Yu V.; Shurygin, D. N.; Tretyak, A. Ya

2017-10-01

The assessment of the geological conditions of development of existing ore deposits was made. For testing ore deposits in difficult mining and geological conditions, the authors proposed the system of development, accompanied by collapse of the mechanical ore with the use of feeders of active action that could be manufactured directly in the mine in accordance with the specific conditions of occurrence of minerals. The paper demonstrates the technology of manufacture of load-bearing structures of the feeder directly in the mine at the scene of the breaking of the first layer of ore, as well as the dynamics of the ore and the choice of parameters of concrete feeders. A new design of the bottom block was proposed, the idea of technical solution of which consists in the fact that it is offered to undergo the production of the smallest possible cross section, which is determined only by the dimensions of the conveyors to deliver ore. And before the explosion of fans of production wells, it is necessary to produce local collapse of the roof production to increase its height at the place of production of ore by blasting wellheads in two or three rows.

Circulation exchange patterns in Sinclair Inlet, Washington

USGS Publications Warehouse

Noble, Marlene A.; Rosenberger, Kurt J.; Paulson, Anthony J.; Gartner, Anne L.

2013-01-01

In 1994, the U.S. Geological Survey (USGS), in cooperation with the U.S. Navy, deployed three sets of moorings in Sinclair Inlet, which is a relatively small embayment on the western side of Puget Sound (fig. 1). This inlet is home to the Puget Sound Naval Shipyard. One purpose of the measurement program was to determine the transport pathways and fate of contaminants known to be present in Sinclair Inlet. Extensive descriptions of the program and the resultant information about contaminant pathways have been reported in Gartner and others (1998). This report primarily focused on the bottom boundary layer and the potential for resuspension and transport of sediments on the seabed in Sinclair Inlet as a result of tides and waves. Recently (2013), interest in transport pathways for suspended and dissolved materials in Sinclair Inlet has been rekindled. In particular, the USGS scientists in Washington and California have been asked to reexamine the datasets collected in the earlier study to refine not only our understanding of transport pathways through the inlet, but to determine how those transport pathways are affected by subtidal currents, local wind stress, and fresh water inputs. Because the prior study focused on the bottom boundary layer and not the water column, a reanalysis of the datasets could increase our understanding of the dynamic forces that drive transport within and through the inlet. However, the early datasets are limited in scope and a comprehensive understanding of these transport processes may require more extensive datasets or the development of a detailed numerical model of transport processes for the inlet, or both.

Early transformation of the Mediterranean Outflow Water (MOW) in the Gulf Of Cádiz, SW Iberian Peninsula: pathways, mixing and temporal variability.

NASA Astrophysics Data System (ADS)

Sánchez Leal, Ricardo F.; Sánchez Garrido, José Carlos; Jesús Bellanco Esteban, María; Ruiz Villarreal, Manuel; González-Pola Muñiz, César

2014-05-01

The inverse estuarine circulation through the strait of Gibraltar is responsible for the overflow of dense, saline MOW towards the Atlantic basin. Initially as a gravity undercurrent, the MOW entrains large amounts of the overlying Eastern North Atlantic Central Water to become a multi-layered, buoyant plume at depths of 800-1300 m past Cape St. Vincent. Much of the entrainment occurs within 100 km of the Strait over a highly abrupt topography. In this work we analyze a repeated series of high-resolution CTD-LADCP observations along a number of standard sections crossing the early MOW. These data show that from the Strait of Gibraltar, the bottom-trapped flow bifurcates in the vicinity of the topographic features, diverting or rejoining the main MOW path as a function of the orientation of channels and valleys. As it turns anticyclonically, the undercurrent exhibits a cross-axis geostrophic gradient, with the margin closer to the slope being in near-geostrophic balance whereas the distal band is largely ageostrophic due to the flow curvature. Mixing is steered by the interplay of tidal stirring, bottom roughness, shear instability and double diffusion along the MOW path. Data also shows that seasonal variability is mostly related to the fluctuations in the overlying layer rather than to MOW dynamics. This is a contribution to INGRES3 project (Mediterranean outflow at Gibraltar, its influence on deep Mediterranean water ventilation and first transformation and coupling with North-Atlantic central waters in the Gulf of Cádiz, CTM2010_21229)

How could a freshwater swamp produce a chemical signature characteristic of a saltmarsh?

USGS Publications Warehouse

McCloskey, Terrence; Smith, Christopher G.; Liu, Kam-biu; Marot, Marci E.; Haller, Christian

2018-01-01

Reduction–oxidation (redox) reaction conditions, which are of great importance for the soil chemistry of coastal marshes, can be temporally dynamic. We present a transect of cores from northwest Florida wherein radical postdepositional changes in the redox regime has created atypical geochemical profiles at the bottom of the sedimentary column. The stratigraphy is consistent along the transect, consisting of, from the bottom upward, carbonate bedrock, a gray clay, an organic mud section, a dense clay layer, and an upper organic mud unit representing the current saltwater marsh. However, the geochemical signature of the lower organic mud unit suggests pervasive redox reactions, although the interval has been identified as representing a freshwater marsh, an unlikely environment for such conditions. Analyses indicate that this discrepancy results from postdepositional diagenesis driven by millennial-scale environmental parameters. Rising sea level that led to the deposition of the capping clay layer, created anaerobic conditions in the freshwater swamp interval, and isolated it hydrologically from the rest of the sediment column. The subsequent infiltration of marine water into this organic material led to sulfate reduction, the buildup of H2S and FeS, and anoxic conditions. Continued sulfidation eventually resulted in euxinic conditions, as evidenced by elevated levels of Fe, S, and especially Mo, the diagnostic marker of euxinia. Because this chemical transformation occurred long after the original deposition the geochemical signature does not reflect soil chemistry at the time of deposition and cannot be used to infer syn-depositional environmental conditions, emphasizing the importance of recognizing diagenetic processes in paleoenvironmental studies.

A SiC LDMOS with electric field modulation by a step compound drift region

NASA Astrophysics Data System (ADS)

Bao, Meng-tian; Wang, Ying; Yu, Cheng-hao; Cao, Fei

2018-07-01

In this paper, we propose a SiC LDMOS structure with a step compound drift region (SC-LDMOS). The proposed device has a compound drift region which consists of an n-type top layer, a step p-type middle layer and an n-type bottom layer. The step p-type middle layer can introduce two new electric field peaks and uniform the distribution of the electric field in the n-type top layer, which can modulate the surface electric field and improve the breakdown voltage of the proposed structure. In addition, the n-type bottom layer is applied under the heavy doping p-type middle layer，which contributes to realize the charge balance. Furthermore, it can also increase the doping concentration of the n-type top layer, which can decrease the on resistance of the proposed device. As a simulated result, the proposed device obtain a high BV of 976 V and a low Rsp,on of 7.74 mΩ·cm2. Compared with the conventional single REUSRF LDMOS and triple RESURF LDMOS, BV of proposed device is enhanced by 42.5% and 14.7%, respectively and Rsp,on is reduced by 37.3% and 30.9%, respectively. Meanwhile, the switching delays of the proposed device are significantly shorter than the conventional triple RESURF LDMOS.

Biologically inspired multi-layered synthetic skin for tactile feedback in prosthetic limbs.

PubMed

Osborn, Luke; Nguyen, Harrison; Betthauser, Joseph; Kaliki, Rahul; Thakor, Nitish

2016-08-01

The human body offers a template for many state-of-the-art prosthetic devices and sensors. In this work, we present a novel, sensorized synthetic skin that mimics the natural multi-layered nature of mechanoreceptors found in healthy glabrous skin to provide tactile information. The multi-layered sensor is made up of flexible piezoresistive textiles that act as force sensitive resistors (FSRs) to convey tactile information, which are embedded within a silicone rubber to resemble the compliant nature of human skin. The top layer of the synthetic skin is capable of detecting small loads less than 5 N whereas the bottom sensing layer responds reliably to loads over 7 N. Finite element analysis (FEA) of a simplified human fingertip and the synthetic skin was performed. Results suggest similarities in behavior during loading. A natural tactile event is simulated by loading the synthetic skin on a prosthetic limb. Results show the sensors' ability to detect applied loads as well as the ability to simulate neural spiking activity based on the derivative and temporal differences of the sensor response. During the tactile loading, the top sensing layer responded 0.24 s faster than the bottom sensing layer. A synthetic biologically-inspired skin such as this will be useful for enhancing the functionality of prosthetic limbs through tactile feedback.

Arctic Ocean Model Intercomparison Using Sound Speed

NASA Astrophysics Data System (ADS)

Dukhovskoy, D. S.; Johnson, M. A.

2002-05-01

The monthly and annual means from three Arctic ocean - sea ice climate model simulations are compared for the period 1979-1997. Sound speed is used to integrate model outputs of temperature and salinity along a section between Barrow and Franz Josef Land. A statistical approach is used to test for differences among the three models for two basic data subsets. We integrated and then analyzed an upper layer between 2 m - 50 m, and also a deep layer from 500 m to the bottom. The deep layer is characterized by low time-variability. No high-frequency signals appear in the deep layer having been filtered out in the upper layer. There is no seasonal signal in the deep layer and the monthly means insignificantly oscillate about the long-period mean. For the deep ocean the long-period mean can be considered quasi-constant, at least within the 19 year period of our analysis. Thus we assumed that the deep ocean would be the best choice for comparing the means of the model outputs. The upper (mixed) layer was chosen to contrast the deep layer dynamics. There are distinct seasonal and interannual signals in the sound speed time series in this layer. The mixed layer is a major link in the ocean - air interaction mechanism. Thus, different mean states of the upper layer in the models might cause different responses in other components of the Arctic climate system. The upper layer also strongly reflects any differences in atmosphere forcing. To compare data from the three models we have used a one-way t-test for the population mean, the Wilcoxon one-sample signed-rank test (when the requirement of normality of tested data is violated), and one-way ANOVA method and F-test to verify our hypothesis that the model outputs have the same mean sound speed. The different statistical approaches have shown that all models have different mean characteristics of the deep and upper layers of the Arctic Ocean.

Assessing site formation and assemblage integrity through stone tool refitting at Gruta da Oliveira (Almonda karst system, Torres Novas, Portugal): A Middle Paleolithic case study

PubMed Central

Zilhão, João

2018-01-01

We use stone tool refitting to assess palimpsest formation and stratigraphic integrity in the basal units of the Gruta da Oliveira archeo-stratigraphic sequence, layers 15–27, which TL and U-series dating places in late Marine Isotope Stage (MIS) 5 or early MIS 4. As in most karst contexts, the formation of this succession involved multiple and complex phenomena, including subsidence, bioturbation, carnivore activity and runoff as agents of potential post-depositional disturbance. During phases of stabilization, such as represented by layers 15, 21 and 22, the excavated area was inhabited and refits corroborate that post-depositional displacement is negligible. Layers 23–25 and 16–19 correspond to subdivisions that slice thick geological units primarily formed of material derived from the cave’s entrance via slope dynamics. Refit links are consistent with rapid fill-up of the interstitial spaces found in the Karren-like bedrock (for layers 23–25), or left between large boulders after major roof-collapse events (for layers 16–19). Layers 26 (the “Mousterian Cone”) and 27 are a “bottom-of-hourglass” deposit underlying the main sedimentary body; the refits show that this deposit consists of material derived from layers 15–25 that gravitated through fissures open in the sedimentary column above. Layer 20, at the interface between two major stratigraphic ensembles, requires additional analysis. Throughout, we found significant vertical dispersion along the contact between sedimentary fill and cave wall. Given these findings, a preliminary analysis of technological change across the studied sequence organized the lithic assemblages into five ensembles: layer 15; layers 16–19; layer 20; layers 21–22; layers 23–25. The lower ensembles show higher percentages of flint and of the Levallois method. Uniquely at the site, the two upper ensembles feature bifaces and cleavers. PMID:29451892

Properties of perpendicular-anisotropy magnetic tunnel junctions fabricated over the bottom electrode contact

NASA Astrophysics Data System (ADS)

Miura, Sadahiko; Honjo, Hiroaki; Kinoshita, Keizo; Tokutome, Keiichi; Koike, Hiroaki; Ikeda, Shoji; Endoh, Tetsuo; Ohno, Hideo

2015-04-01

Perpendicular-anisotropy magnetic tunnel junctions (MTJs) were prepared on four substrate geometries, i.e., directly on the axis of the bottom electrode contact, directly off the axis of the bottom electrode contact, on the axis of the bottom electrode contact with a polished bottom electrode, and off the axis of the bottom electrode contact with a polished bottom electrode. Electrical shorts were observed for direct on-axis geometry at a certain extent, whereas there were no electrical shorts for the other three geometries. The MR ratio/σR, JC0, and thermal stability factor of the devices for polish on-axis geometry were almost the same as those for polish off-axis geometry. From TEM observations of the polish on-axis device, the interface between the bottom contact and the base electrode was determined to be rough, whereas the MgO barrier layer was determined to be smooth, indicating that the polish process was effective for smooth magnetic tunnel junction fabrication over the bottom contact. MTJs for polish on-axis geometry eliminated the base electrode resistance and increased the magnetoresistance ratio. This technology contributes to the higher density of spin transfer torque magnetic random access memory.

Bottom friction models for shallow water equations: Manning’s roughness coefficient and small-scale bottom heterogeneity

NASA Astrophysics Data System (ADS)

Dyakonova, Tatyana; Khoperskov, Alexander

2018-03-01

The correct description of the surface water dynamics in the model of shallow water requires accounting for friction. To simulate a channel flow in the Chezy model the constant Manning roughness coefficient is frequently used. The Manning coefficient nM is an integral parameter which accounts for a large number of physical factors determining the flow braking. We used computational simulations in a shallow water model to determine the relationship between the Manning coefficient and the parameters of small-scale perturbations of a bottom in a long channel. Comparing the transverse water velocity profiles in the channel obtained in the models with a perturbed bottom without bottom friction and with bottom friction on a smooth bottom, we constructed the dependence of nM on the amplitude and spatial scale of perturbation of the bottom relief.

On Suspended matter grain size in Baltic sea

NASA Astrophysics Data System (ADS)

Bubnova, Ekaterina; Sivkov, Vadim; Zubarevich, Victor

2016-04-01

Suspended matter grain size data were gathered during the 25th research vessel "Akademik Mstislav Keldysh" cruise (1991, September-October). Initial quantitative data were obtained with a use of the Coulter counter and subsequently modified into volume concentrations (mm3/l) for size intervals. More than 80 samples from 15 stations were analyzed (depth range 0-355 m). The main goal of research was to illustrate the spatial variability of suspended matter concentration and dispersion in Baltic Sea. The mutual feature of suspended matter grain size distribution is the logical rise of particle number along with descending of particle's size. Vertical variability of grain size distribution was defined by Baltic Sea hydrological structure, including upper mixed layer - from the surface to the thermocline - with 35 m thick, cold intermediate layer - from the thermocline to the halocline- and bottom layer, which lied under the halocline. Upper layer showed a rise in total suspended matter concentration (up to 0.6 mm3/l), while cold intermediate level consisted of far more clear water (up to 0.1 mm3/l). Such a difference is caused by the thermocline boarding role. Meanwhile, deep bottom water experienced surges in suspended matter concentration owing to the nepheloid layer presence and "liquid bottom" effect. Coastal waters appeared to have the highest amount of particles (up to 5.0 mm3/l). Suspended matter grain size distribution in the upper mixed layer revealed a peak of concentration at 7 μ, which can be due to autumn plankton bloom. Another feature in suspended matter grain size distribution appeared at the deep layer below halocline, where both O2 and H2S were observed and red/ox barrier is. The simultaneous presence of Fe and Mn (in solutions below red/ox barrier) and O2 leads to precipitation of oxyhydrates Fe and Mn and grain size distribution graph peaking at 4.5 μ.

Thermo-chemical extraction of fuel oil from waste lubricating grease.

PubMed

Pilusa, Tsietsi Jefrey; Muzenda, Edison; Shukla, Mukul

2013-06-01

This study investigated the recovery of oil from waste grease through the process of thermal degradation in an aqueous solution of potassium hydroxide (KOH) followed by solvent extraction. Waste high temperature metal bearing grease was dissolved in a 15 w/w% KOH solution at 80°C while being agitated at 2000 rpm using a shear action agitator for a period of 15 min. Two distinct layers were observed after 8 min of settling time. The top layer being of dark brown oil and the bottom layer was a heterogeneous mixture. The two layers were separated by decantation. The bottom layer was cooled down to 45°C followed by slow addition of toluene (C7H8) while agitating at 1200 rpm for 15 min to prevent solids settling and minimise rapid volatilisation of the organic compounds in the mixture. Two distinct layers were also formed, the top homogeneous mixture of light brown oil-toluene mixture and the bottom sludge layer. The solvent was recovered from the oil for re-use by fractional distillation of the homogenous mixture. It was observed that 15 w/w% potassium hydroxide solution can chemically degrade the soap matrix in the grease and extract up to 49 w/w% of the fuel oil when subjected to high shear stress at a temperature of 80°C. The 26 w/w% extraction of oil in the remaining sludge was obtained by solvent extraction process with mass ratios of sludge to solvent of 2:1. Solvent recovery of 88% by mass was obtained via fractional distillation method. The combined extraction processes brought an overall oil yield of 75 w/w% from the waste grease. The fuel oil obtained from this process has similar properties to paraffin oil and can be blended with other oils as an alternative energy source. Copyright © 2013 Elsevier Ltd. All rights reserved.

Convective instability of sludge storage under evaporation and solar radiation

NASA Astrophysics Data System (ADS)

Tsiberkin, Kirill; Tatyana, Lyubimova

2014-05-01

The sludge storages are an important part of production cycle at salt manufacturing, water supply, etc. A quality of water in the storage depends on mixing of pure water and settled sediment. One of the leading factors is thermal convection. There are two main mechanisms of the layer instability exist. First, it is instability of water due to evaporation from the free surface [1]. It cools the water from upside, increases the particles concentration and leads to the instability in the near-surface layer. Second, the sediment absorbs a solar radiation and heats the liquid from below making it unstable in the near-bottom area. We assume the initial state is the mechanical equilibrium. The water and sediment particles are motionless, the sediment forms a uniform sludge layer of thickness z0, there are no evaporation and heating by solar energy, and the temperature has a linear profile is determined by fixed upper and bottom temperatures of the layer. Taking into account the evaporation and solar radiation absorption, we obtain a non-stationary solution for the temperature using Fourier series method. The local temperature gradients increases rapidly with time, and local Rayleigh number can be estimated by thermal conduction length Lt: Raloc(z,t) = gβ(δT(z,t)/δz)L4t-/νΞ , Lt ~ √Ξt, (1) where g is gravity acceleration, β, ν and Ξ are thermal volume expansion coefficient, kinematic viscosity and thermal conductivity of the liquid, respectively. Raloc* reaches the critical value at finite time t* and water motion begins. The maximal power of solar radiation in visible band equals 230 Wt/m2 at the latitude of "Uralkalii" salt manufacturer (Berezniki, Perm Region, Russian Federation). We neglect IR and UV radiation because of its huge absorption by water [2]. The evaporation speed is found using results for shallow water reservoir [3] and meteorological data for Berezniki [4]. We get the t*~ 6 · 102 s (10 min) for the layer of 1 m depth and t*~ 2 · 103 s (40 min) for the layer of 10 m depth. Dynamic of the system is studied by the Galerkin-Kantorovich method. Using the follow basis along z-axis: wn = cosqnz - cotqnsinh qnz - cosh qnz + coth qnsinh qnz, tanqn = tanhqn, (2) tn = sinpnz, pn = π(2n - 1), n = 1,2,3 ..., 2 (3) we introduce an infinite family of low-mode approximations of the full model. We found the parameter deviations from initial state grow rapidly with Ra > 0 and oscillate with Ra < 0 at the lowest order. Here, Ra is defined by temperature difference between upper and bottom sides of the layer under pure evaporation. The lowest order model does not describe the system in full, because the unstable areas are localized within layer. The study was financially supported by the Russian Foundation for Basic Research (Grant 13-01-96040). [1] Berg J.C. Acrivos A., Boudart M. Advances in Chemical Engineering. Ed. by Drew T.B., Hoopes J.W. Vermeulen T. Academic Press, NY, 1966, V.6, pp. 61-124. [2] ASTM Standard G173-03, 2012, Standard Tables for Reference Solar Spectral Irradiances: Direct Normal and Hemispherical on 37° Tilted Surface, ASTM International, 2012. [3] Tanny J. et al. Evaporation from a small water reservoir: direct measurements and estimates. J. Hydrol., 2008, V.351, pp. 218-229. [4] Shklyaev V.A., Shklyaeva L.S. Climatic resources of Ural's Prikamye. Geographical Bull., Perm State University, 2006, V.2, pp. 76-89.

Exact solutions for layered thermocapillary convection of a viscous incompressible fluid with specified stresses on the bottom

NASA Astrophysics Data System (ADS)

Prosviryakov, E. Yu.; Spevak, L. F.

2017-12-01

A new exact solution of the Oberbeck-Boussinesq system is found. The Marangoni thermocapillary convection in an infinite fluid layer is described. It is demonstrated that the specification of tangential stresses at both boundaries of the layered velocity field is nonstationary. Velocities describe a superposition of unidirectional flows with an intermediate time interval when there are counterflows.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fakhri, M.; Theisen, M.; Behrendt, A.

Top gated metal-oxide thin-film transistors (TFTs) provide two benefits compared to their conventional bottom-gate counterparts: (i) The gate dielectric may concomitantly serve as encapsulation layer for the TFT channel. (ii) Damage of the dielectric due to high-energetic particles during channel deposition can be avoided. In our work, the top-gate dielectric is prepared by ozone based atomic layer deposition at low temperatures. For ultra-low gas permeation rates, we introduce nano-laminates of Al{sub 2}O{sub 3}/ZrO{sub 2} as dielectrics. The resulting TFTs show a superior environmental stability even at elevated temperatures. Their outstanding stability vs. bias stress is benchmarked against bottom-gate devices withmore » encapsulation.« less

A molybdenum disulfide/carbon nanotube heterogeneous complementary inverter.

PubMed

Huang, Jun; Somu, Sivasubramanian; Busnaina, Ahmed

2012-08-24

We report a simple, bottom-up/top-down approach for integrating drastically different nanoscale building blocks to form a heterogeneous complementary inverter circuit based on layered molybdenum disulfide and carbon nanotube (CNT) bundles. The fabricated CNT/MoS(2) inverter is composed of n-type molybdenum disulfide (MOS(2)) and p-type CNT transistors, with a high voltage gain of 1.3. The CNT channels are fabricated using directed assembly while the layered molybdenum disulfide channels are fabricated by mechanical exfoliation. This bottom-up fabrication approach for integrating various nanoscale elements with unique characteristics provides an alternative cost-effective methodology to complementary metal-oxide-semiconductors, laying the foundation for the realization of high performance logic circuits.

Anoxic monimolimnia: Nutrients devious feeders or bombs ready to explode?

NASA Astrophysics Data System (ADS)

Gianni, Areti; Zacharias, Ierotheos

2015-04-01

Coastal regions are under strong human influence and its environmental impact is reflected into their water quality. Oligotrophic estuaries and coastal systems have changed in mesotrophic and/or eutrophic, shown an increase in toxic algal blooms, hypoxic/anoxic events, and massive mortalities of many aquatic and benthic organisms. In strongly stratified and productive water basins, bottom water dissolved oxygen is depleted due to the excessive organic matter decomposition in these depths. Distribution and recycling of nutrients in their water column is inextricably dependent on oxygenation and redox conditions. Bottom water anoxia accelerates PO43-, NH4+ and H2S recycling and accumulation from organic matter decomposition. The anoxic, H2S, PO43- and NH4+ rich bottom water constitutes a toxic layer, threatening the balance of the entire ecosystem. In permanently stratified water basins, storm events could result in stratification destruction and water column total mixing. The turnover brings large amounts of H2S to the surface resulting in low levels of oxygen and massive fish kills. PO43- and NH4+ are released to the interface and surface waters promoting algal blooms. Μore organic matter is produced fueling anoxia. The arising question is, whether the balance of an anoxic water ecosystem is under the threat of its hypolimnetic nutrient and sulfide load, only in the case of storm events and water column total mixing. In polymictic water basins it is clear that the accumulated, in the bottom layer, nutrients will supply surface waters, after the pycnocline overturn. Besides this mechanism of basins' water quality degradation is nowadays recognized as one of the biggest obstacles in eutrophic environments management and restoration efforts. The role of internal load, in permanently stratified water basins, is not so clear. In the present study the impact of storm events on water column stability and bottom water anoxia of meromictic coastal basins, is investigated. The importance of internal load is emerged, presenting the disturbance on the main nutrients, dissolved oxygen, hydrogen sulfide and chlorophyll distribution, caused by the total water column mixing. Additionally, the relationship between temporal nutrients variations in surface layers, of permanent anoxic coastal basins with a) changes on the physicochemical characteristics of their water column, b) changes on the bottom water phosphorus and nitrogen concentration and c) their effect on the basin's primary productivity, is sought. In order to achieve the objectives of this study, two different sets of Aitoliko basin's (western Greece) data were used. The first one includes measurements of physicochemical parameters, nutrients, chlorophyll and hydrogen sulfide, four days after a storm event and the consequent anoxic crisis in Aitoliko basin on 4th of December 2008. The second one contains respective data obtained from a biennial (May 2006-May 2008) basin's monitoring. The changes in the physical, chemical and biological characteristics, of Aitoliko basin water column, after its total mixing, highlighted the importance of the accumulated nutrients and sulfides in the bottom layer. In addition, turned out that bottom layer can supply with nutrients the surface waters, even during periods of high water column stratification. Small scale, subtle, changes in physicochemical and hydrological basin's characteristics promoted this supply, affecting both quantitative and qualitative the ecosystem's primary productivity and shifting its quality character.

Diffusive boundary layers at the bottom of gaps and cracks

NASA Astrophysics Data System (ADS)

Etzold, Merlin A.; Landel, Julien R.; Dalziel, Stuart B.

2017-11-01

This work is motivated by the chemical decontamination of droplets of chemical warfare agents trapped in the gaps and cracks found in most man-made objects. We consider axial laminar flow within gaps with both straight and angled walls. We study the diffusive mass transfer from a source (e.g. a droplet surface) located at the bottom of the gap. This problem is similar to boundary layers and Graetz-type problems (heat transfer in pipe flow) with the added complication of a non-uniform lateral concentration profile due to the lateral variation of the velocity profile. We present 3D solutions for the diffusive boundary layer and demonstrate that a 2D mean-field model, for which we calculate series and similarity solutions, captures the essential physics. We demonstrate the immediate practical relevance of our findings by comparing decontamination of a droplet located in a gap and on an exposed surface.

Scintillator assembly for alpha radiation detection and method of making the assembly

DOEpatents

McElhaney, S.A.; Bauer, M.L.; Chiles, M.M.

1992-09-22

A scintillator assembly for use in the detection of alpha radiation includes a body of optically-transparent epoxy and an amount of phosphor particles embedded within the body adjacent one surface thereof. When making the body, the phosphor particles are mixed with the epoxy when in an uncured condition and permitted to settle to the bottom surface of a mold within which the epoxy/phosphor mixture is contained. When the mixture subsequently cures to form a hardened body, the one surface of the body which cured against the bottom surface of the mold is coated with a thin layer of opaque material for preventing ambient light form entering the body through the one surface. The layer of opaque material is thereafter coated with a layer of protective material to provide the assembly with a damage-resistant entrance window. 6 figs.

Stacking-dependent electronic property of trilayer graphene epitaxially grown on Ru(0001)

NASA Astrophysics Data System (ADS)

Que, Yande; Xiao, Wende; Chen, Hui; Wang, Dongfei; Du, Shixuan; Gao, Hong-Jun

2015-12-01

The growth, atomic structure, and electronic property of trilayer graphene (TLG) on Ru(0001) were studied by low temperature scanning tunneling microscopy and spectroscopy in combined with tight-binding approximation (TBA) calculations. TLG on Ru(0001) shows a flat surface with a hexagonal lattice due to the screening effect of the bottom two layers and the AB-stacking in the top two layers. The coexistence of AA- and AB-stacking in the bottom two layers leads to three different stacking orders of TLG, namely, ABA-, ABC-, and ABB-stacking. STS measurements combined with TBA calculations reveal that the density of states of TLG with ABC- and ABB-stacking is characterized by one and two sharp peaks near to the Fermi level, respectively, in contrast to the V-shaped feature of TLG with ABA-stacking. Our work demonstrates that TLG on Ru(0001) might be an ideal platform for exploring stacking-dependent electronic properties of graphene.

Bottom-gate poly-Si thin-film transistors by nickel silicide seed-induced lateral crystallization with self-aligned lightly doped layer

NASA Astrophysics Data System (ADS)

Lee, Sol Kyu; Seok, Ki Hwan; Chae, Hee Jae; Lee, Yong Hee; Han, Ji Su; Jo, Hyeon Ah; Joo, Seung Ki

2017-03-01

We report a novel method to reduce source and drain (S/D) resistances, and to form a lightly doped layer (LDL) of bottom-gate polycrystalline silicon (poly-Si) thin-film transistors (TFTs). For application in driving TFTs, which operate under high drain voltage condition, poly-Si TFTs are needed in order to attain reliability against hot-carriers as well as high field-effect mobility (μFE). With an additional doping on the p+ Si layer, sheet resistance on S/D was reduced by 37.5% and an LDL was introduced between the channel and drain. These results contributed to not only a lower leakage current and gate-induced drain leakage, but also high immunity of kink-effect and hot-carrier stress. Furthermore, the measured electrical characteristics exhibited a steep subthreshold slope of 190 mV/dec and high μFE of 263 cm2/Vs.

Resonant tunneling through discrete quantum states in stacked atomic-layered MoS2.

PubMed

Nguyen, Linh-Nam; Lan, Yann-Wen; Chen, Jyun-Hong; Chang, Tay-Rong; Zhong, Yuan-Liang; Jeng, Horng-Tay; Li, Lain-Jong; Chen, Chii-Dong

2014-05-14

Two-dimensional crystals can be assembled into three-dimensional stacks with atomic layer precision, which have already shown plenty of fascinating physical phenomena and been used for prototype vertical-field-effect-transistors.1,2 In this work, interlayer electron tunneling in stacked high-quality crystalline MoS2 films were investigated. A trilayered MoS2 film was sandwiched between top and bottom electrodes with an adjacent bottom gate, and the discrete energy levels in each layer could be tuned by bias and gate voltages. When the discrete energy levels aligned, a resonant tunneling peak appeared in the current-voltage characteristics. The peak position shifts linearly with perpendicular magnetic field, indicating formation of Landau levels. From this linear dependence, the effective mass and Fermi velocity are determined and are confirmed by electronic structure calculations. These fundamental parameters are useful for exploitation of its unique properties.

Nutrient Dynamics in the Northern South China Sea Shelf-sea (NoSoCS)

NASA Astrophysics Data System (ADS)

Wong, G. T.; Guo, X.

2011-12-01

The Northern South China Sea Shelf-sea (NoSoCS) is situated in the sub-tropics along the southern Chinese coast between the southern end of the Taiwan Strait and the Hainan Island. Samples were collected in four cross-shelf transects in summer, 2010 and two cross-shelf transects in winter, 2011 in this Shelf-sea. The shelf may be sub-divided into the inner shelf (<40 m, low water temperature, high chlorophyll concentration), the middle shelf (50-80 m), and the outer shelf (90-120 m, high water temperature, low nutrient and chlorophyll concentrations). The mixed layer depth and the top of the nutricline depth (at ~30 m in the summer and ~70 m in the winter) were shallower than the shelf break depth (~120 m) in both seasons. The relatively nutrient-rich upper nutricline water (>1 μM in NO3- and >0.1 μM in soluble reactive phosphate) stretched across the shelf at least to the middle shelf. Thus, vertical mixing, even to relatively shallow depths, on the shelf may supply nutrients to and play a critical role in determining the primary production in the mixed layer. At least three such processes were observed. Through the year, internal waves of various strengths generated at the Luzon Strait propagated westward along the bottom of the mixed layer and dissipated along the middle and outer shelf. The effects of these waves were especially conspicuous north of the Dongsha Atoll and their action enhances vertical mixing. In the summer, upwelling occurred in the inner/middle shelf off Dongshan in response to the along shore southwest monsoon and the topographic forcing by the ridge extending offshore from Dongshan to the Taiwan Bank. In the winter, surface cooling and the strong northeast monsoon led to complete overturn in the shelf. The maximum density, reaching 24.6, in the surface waters was found offshore in the inner and middle shelf. This density was equivalent to the density of the water at >100 m offshore. As a result, this dense water also appeared as a layer of bottom water that extended across the shelf to the shelf edge.

What Happens Where the Water and the Rock Touch in Small Space Bodies

NASA Astrophysics Data System (ADS)

Byrne, P. K.; Regensburger, P. V.; Klimczak, C.; Bohnenstiehl, D. R.; Dombard, A. J.; Hauck, S. A., II

2017-12-01

There are several small space bodies that go around bigger worlds that might have a layer of water under a layer of ice. Lots of study has been done to understand the outside ice layer of these small space bodies, because the ice can tells us important things about the big water layer under it. Some of these small space bodies are very interesting because the right things for life—water, hot rock, and food—might be at the bottom of the water layer, where it touches the top of the next layer down, which is made of rock. But it is very hard to understand what this rock at the bottom of the water is like, because we can't see it. So, we are imagining what this rock is like by thinking about what the rock is like under the water layer on our own world. If hot rock comes out of the rock layer through cracks under the water, the cold of the water makes the hot rock go very cold very fast, and it makes funny rolls as it does so. This might happen on some small space bodies that are hot enough on the inside to make hot rock. We know that on our own world the rock layer under the water is wet to as far down as cracks can go, so it makes sense that this is true for small space bodies, too. We did some thinking about numbers and found out that the cracks can go a few ten hundred steps into the rock layer on small space bodies, but for bigger (well, not quite so small) space bodies, the cracks can go at least tens of ten hundred steps into the rock layer. This means that water goes into the rock layer this much, too. But get this: some small bodies are not really that small—one of them is bigger than the first world from the Sun! And on a few of these big (small) bodies, the layer of water is so heavy that the bottom of that water is pushed together from all sides and turns into a type of hot ice. This means that, for these big (small) worlds, the water can't get into the rock layer through cracks (since there is a layer of hot ice in the way), and so these bodies are not such good places to think about where life might be.

Hydrodynamics of the Fluid Filtrate on Drilling-In

NASA Astrophysics Data System (ADS)

Abbasov, É. M.; Agaeva, N. A.

2014-01-01

The volume of the liquid penetrating into the formation after drilling-in has been determined on the basis of theoretical investigations. The dynamics of change in the bottom-hole pressure has been determined in this process. It has been shown that because of the water hammer, the bottom-hole pressure can be doubled in the presence of large fractures and pores closer to the well-bottom zone.

Ocean-Science Mission Needs: Real-Time AUV Data for Command, Control, and Model Inputs

NASA Technical Reports Server (NTRS)

Carder, Kendall L.; Costello, D. K.; Warrior, H.; Langebrake, L. C.; Hou, W.; Patten, J. T.; Kaltenbacher, E.

2001-01-01

Predictive models for tides, hydrodynamics, and bio-optical properties affecting the visibility and buoyancy of coastal waters are needed to evaluate the safety of personnel and equipment engaged in maritime operations under potentially hazardous conditions. Predicted currents can be markedly different for two-layer systems affected by terrestrial runoff than for well-mixed conditions because the layering decouples the surface and bottom Ekman layers and rectifies the current response to oscillatory upwelling-and downwelling-favorable winds. Standard ocean models (e.g. Princeton Ocean Model) require initial-and boundary data on the physical and optical properties of the multilayered water column to provide accurate simulations of heat budgets and circulation. Two observational systems are designed to measure vertically structured conditions on the West Florida Shelf (WFS): a tethered buoy network and an autonomous underwater vehicle (AUV) observational system. The AUV system is described with a focus on the observational systems that challenge or limit the communications command and control network for various types of measurement programs. These include vertical oscillatory missions on shelf transects to observe the optical and hydrographic properties of the water column, and bottom-following missions for measuring the bottom albedo. Models of light propagation, absorption, and conversion to heat as well as determination of the buoyancy terms for physical models require these measurements. High data rates associated with video bottom imagery are the most challenging for the real-time, command and control communications system, but they are met through a combination of loss-less and lossy data-compression methods, depending upon the data-rate of the radio links.

Reaching state-of-the art requirements for MIM capacitors with a single-layer anodic Al2O3 dielectric and imprinted electrodes

NASA Astrophysics Data System (ADS)

Hourdakis, Emmanouel; Nassiopoulou, Androula G.

2017-07-01

Metal-Insulator-Metal (MIM) capacitors with a high capacitance density and low non-linearity coefficient using a single-layer dielectric of barrier-type anodic alumina (Al2O3) and an imprinted bottom Al electrode are presented. Imprinting of the bottom electrode aimed at increasing the capacitor effective surface area by creating a three-dimensional MIM capacitor architecture. The bottom Al electrode was only partly nanopatterned so as to ensure low series resistance of the MIM capacitor. With a 3 nm thick anodic Al2O3 dielectric, the capacitor with the imprinted electrode showed a 280% increase in capacitance density compared to the flat electrode capacitor, reaching a value of 20.5 fF/μm2. On the other hand, with a 30 nm thick anodic Al2O3 layer, the capacitance density was 7.9 fF/μm2 and the non-linearity coefficient was as low as 196 ppm/V2. These values are very close to reaching all requirements of the last International Technology Roadmap for Semiconductors for MIM capacitors [ITRS, http://www.itrs2.net/2013-itrs.html for ITRS Roadmap (2013)], and they are achieved by a single-layer dielectric instead of the complicated dielectric stacks of the literature. The obtained results constitute a real progress compared to previously reported results by our group for MIM capacitors using imprinted electrodes.

An ocean circulation model in σS- z- σB hybrid coordinate and its validation

NASA Astrophysics Data System (ADS)

Zhuang, Zhanpeng; Yuan, Yeli; Yang, Guangbing

2018-02-01

A 3D, two-time-level, σS- z- σB hybrid-coordinate Marine Science and Numerical Modeling numerical ocean circulation model (HyMOM) is developed in this paper. In HyMOM, the σ coordinate is employed in the surface and bottom regions, and the z coordinate is used in the intermediate layers. This method can overcome problems with vanishing surface cells and minimize the unwanted deviation in representing bottom topography. The connection between the σ and z layers vertically includes an expanded "ghost" method and the linear interpolation. The governing equations in the σS- z- σB hybrid coordinate based on the complete Reynolds-averaged Navier-Stokes equations are derived in detail. The two-level time staggered and Eulerian forward and backward schemes, which are of second-order of accuracy, are adopted for the temporal difference in internal and external mode, respectively. The computation of the baroclinic gradient force is tested in an analytic test problem; the errors for two methods in HyMOM, which are relatively large only in the bottom layers, are obviously smaller than those in the pure σ and z models in almost all of the vertical layers. A quasi-global climatologic numerical experiment is constructed to test the simulation performance of HyMOM. With the monthly mean Levitus climatology data as reference, the HyMOM can improve the simulating accuracy compared with its pure z or σ coordinate implementation.

Implementation of Non-Destructive Evaluation and Process Monitoring in DLP-based Additive Manufacturing

NASA Astrophysics Data System (ADS)

Kovalenko, Iaroslav; Verron, Sylvain; Garan, Maryna; Šafka, Jiří; Moučka, Michal

2017-04-01

This article describes a method of in-situ process monitoring in the digital light processing (DLP) 3D printer. It is based on the continuous measurement of the adhesion force between printing surface and bottom of a liquid resin bath. This method is suitable only for the bottom-up DPL printers. Control system compares the force at the moment of unsticking of printed layer from the bottom of the tank, when it has the largest value in printing cycle, with theoretical value. Implementation of suggested algorithm can make detection of faults during the printing process possible.

[Characterization of Chromophoric dissolved organic matter (CDOM) in Zhoushan fishery using excitation-emission matrix spectroscopy (EEMs) and parallel factor analysis (PARAFAC)].

PubMed

Zhou, Qian-qian; Su, Rong-guo; Bai, Ying; Zhang, Chuan-song; Shi, Xiao-yong

2015-01-01

The composition, distribution characteristics and sources of chromophoric dissolved organic matter(CDOM) in Zhoushan Fishery in spring were evaluated by fluorescence excitation-emission matrix (EEM) combined with parallel factor analysis (EEMs-PARAFAC). Three humic-like components [C1 (330/420 nm)], C2 [(290) 365/440 nm] and C3 [(260) 370/490 nm)] and two protein-like components [C4(285/340 nm) and C5 (270/310 nm)] were identified by EEMs-PARAFAC. The horizontal distribution patterns of the five components were almost the same with only slight differences, showing decreasing trends with increasing distance from shore. In the surface and middle layers, the high value areas were located in the north of Hangzhou Bay estuary and the outlet of Xiazhimen channel, and the former's was higher in the surface layer while the latter's was higher in the middle layer. In the bottom layer, CDOM decreased gradiently from the inshore to offshore, with higher CDOM near Zhoushan Island. The distributions of fluorescence components showed an opposite trend with salinity, and no significant linear relationship with Chl-a concentration was found, which indicated that CDOM in the surface and middle layers were dominated by terrestrial input and human activities of Zhoushan Island and that of the bottom layer was attribute to human activities of Zhoushan Island. The vertical distribution of five fluorescent components along 30.5 degrees N transect showed a decreasing trend from the surface and middle layers to bottom layer with high values in inshore and offshore areas, which were correlated with the lower salinity and higher Chl-a concentration, respectively. On this transect, CDOM was mainly affected by Yangtze River input in coastal area but by bioactivities in offshore waters. Along the 30 degrees N transect, the vertical distribution patterns of CDOM were similar to those of 30.5 degrees N transect but there was a high value area in the bottom layer near the shore, attributing to the CDOM release from the marine sediment pore water to the water body because of physical force role like tidal, the underlying upwelling and so on. A strong correlation occurred between C1 and C3, C4, indicating that they had similar sources; a weak correlation was found between C1 and C2, C5, reflecting some differences among their sources. CDOM in Zhoushan Fishery in spring had low humification index (HIX) values, which reflected a low degree of humification, poor stability and a short resident time in the environment. For biological index (BIX), its higher values appeared in the offshore waters and the lower values occurred in the inshore area, reflecting a greater influence of human and biological activities, respectively.

Laboratory Experiments Modelling Sediment Transport by River Plumes

NASA Astrophysics Data System (ADS)

Sutherland, Bruce; Gingras, Murray; Knudson, Calla; Steverango, Luke; Surma, Chris

2016-11-01

Through lock-release laboratory experiments, the transport of particles by hypopycnal (surface) currents is examined as they flow into a uniform-density and a two-layer ambient fluid. In most cases the tank is tilted so that the current flows over a slope representing an idealization of a sediment-bearing river flowing into the ocean and passing over the continental shelf. When passing into a uniform-density ambient, the hypopycnal current slows and stops as particles rain out, carrying some of the light interstitial fluid with them. Rather than settling on the bottom, in many cases the descending particles accumulate to form a hyperpycnal (turbidity) current that flows downslope. This current then slows and stops as particles both rain out to the bottom and also rise again to the surface, carried upward by the light interstitial fluid. For a hypopycnal current flowing into a two-layer fluid, the current slows as particles rain out and accumulate at the interface of the two-layer ambient. Eventually these particles penetrate through the interface and settle to the bottom with no apparent formation of a hyperpycnal current. Analyses are performed to characterize the speed of the currents and stopping distances as they depend upon experiment parameters. Natural Sciences and Engineering Research Council.

Extreme bottom velocities induced by wind wave and currents in the Gulf of Gdańsk

NASA Astrophysics Data System (ADS)

Cieślikiewicz, Witold; Dudkowska, Aleksandra; Gic-Grusza, Gabriela; Jędrasik, Jan

2017-11-01

The principal goal of this study is to get some preliminary insights about the intensity of water movement generated by wind waves, and due to the currents in the bottom waters of Gulf of Gdańsk, during severe storms. The Gulf of Gdańsk is located in the southern Baltic Sea. This paper presents the results of analysis of wave and current-induced velocities during extreme wind conditions, which are determined based on long-term historical records. The bottom velocity fields originated from wind wave and wind currents, during analysed extreme wind events, are computed independently of each other. The long-term wind wave parameters for the Baltic Sea region are derived from the 44-year hindcast wave database generated in the framework of the project HIPOCAS funded by the European Union. The output from the numerical wave model WAM provides the boundary conditions for the model SWAN operating in high-resolution grid covering the area of the Gulf of Gdańsk. Wind current velocities are calculated with the M3D hydrodynamic model developed in the Institute of Oceanography of the University of Gdańsk based on the POM model. The three dimensional current fields together with trajectories of particle tracers spreading out of bottom boundary layer are modelled, and the calculated fields of bottom velocities are presented in the form of 2D maps. During northerly winds, causing in the Gulf of Gdańsk extreme waves and most significant wind-driven circulation, the wave-induced bottom velocities are greater than velocities due to currents. The current velocities in the bottom layer appeared to be smaller by an order of magnitude than the wave-induced bottom orbital velocities. Namely, during most severe northerly storms analysed, current bottom velocities ranged about 0.1-0.15 m/s, while the root mean square of wave-induced near-seabed velocities reached maximum values of up to 1.4 m/s in the southern part of Gulf of Gdańsk.

Modelling turbulent boundary layer flow over fractal-like multiscale terrain using large-eddy simulations and analytical tools.

PubMed

Yang, X I A; Meneveau, C

2017-04-13

In recent years, there has been growing interest in large-eddy simulation (LES) modelling of atmospheric boundary layers interacting with arrays of wind turbines on complex terrain. However, such terrain typically contains geometric features and roughness elements reaching down to small scales that typically cannot be resolved numerically. Thus subgrid-scale models for the unresolved features of the bottom roughness are needed for LES. Such knowledge is also required to model the effects of the ground surface 'underneath' a wind farm. Here we adapt a dynamic approach to determine subgrid-scale roughness parametrizations and apply it for the case of rough surfaces composed of cuboidal elements with broad size distributions, containing many scales. We first investigate the flow response to ground roughness of a few scales. LES with the dynamic roughness model which accounts for the drag of unresolved roughness is shown to provide resolution-independent results for the mean velocity distribution. Moreover, we develop an analytical roughness model that accounts for the sheltering effects of large-scale on small-scale roughness elements. Taking into account the shading effect, constraints from fundamental conservation laws, and assumptions of geometric self-similarity, the analytical roughness model is shown to provide analytical predictions that agree well with roughness parameters determined from LES.This article is part of the themed issue 'Wind energy in complex terrains'. © 2017 The Author(s).

Determination of the Mass Absorption Coefficient in Two-Layer Ti/V and V/Ti Thin Film Systems by the X-Ray Fluorescence Method

NASA Astrophysics Data System (ADS)

Mashin, N. I.; Chernyaeva, E. A.; Tumanova, A. N.; Gafarova, L. M.

2016-03-01

A new XRF procedure for the determination of the mass absorption coefficient in thin film Ti/V and V/Ti two-layer systems has been proposed. The procedure uses easy-to-make thin-film layers of sputtered titanium and vanadium on a polymer film substrate. Correction coefficients have been calculated that take into account attenuation of primary radiation of the X-ray tube, as well as attenuation of the spectral line of the bottom layer element in the top layer.

Observational Characteristics of the Tropopause Inversion Layer derived from CHAMP/GRACE Radio Occultations and MOZAIC Aircraft Data

NASA Astrophysics Data System (ADS)

Schmidt, T.; Cammas, J.; Heise, S.; Wickert, J.; Haser, A.

2010-12-01

In this study we discuss characteristics of the northern hemisphere (NH) midlatitude (40°N-60°N) tropopause inversion layer (TIL) based on two datasets. First, temperature measurements from GPS radio occultation data (CHAMP and GRACE) for the time interval 2001-2009 are used to exhibit seasonal properties of the TIL bottom height defined here as the height of the squared buoyancy frequency minimum N2 below the thermal tropopause, the TIL maximum height as the height of the N2 maximum above the tropopause and the TIL top height as the height of the temperature maximum above the tropopause. Mean values of the TIL bottom, TIL maximum and TIL top heights relative to the thermal tropopause for the NH midlatitudes are (-2.08±0.35) km, (0.52±0.10) km and (2.10±0.23) km, respectively. A seasonal cycle of the TIL bottom and TIL top height is observed with values closer to the thermal tropopause during summer. Secondly, high-resolution temperature and trace gas profile measurements onboard commercial aircrafts (MOZAIC program) from 2001-2008 for the NH midlatitude (40°N-60°N) region are used to characterize the TIL as a mixing layer around the tropopause. Mean TIL bottom, TIL maximum and TIL top heights based on the MOZAIC temperature (N2) measurements confirm the results from the GPS data, even though most of the MOZAIC profiles used here are available under cyclonic situations. Further, we demonstrate that the mixing ratio gradients of ozone (O3) and carbon monoxide (CO) are suitable parameters for characterizing the TIL structure. Using O3-CO correlations we also show that on average the highest mixing occurs in a layer less than 1 km above the thermal tropopause, i.e., within the TIL.

The fabrication of a double-layer atom chip with through silicon vias for an ultra-high-vacuum cell

NASA Astrophysics Data System (ADS)

Chuang, Ho-Chiao; Lin, Yun-Siang; Lin, Yu-Hsin; Huang, Chi-Sheng

2014-04-01

This study presents a double-layer atom chip that provides users with increased diversity in the design of the wire patterns and flexibility in the design of the magnetic field. It is more convenient for use in atomic physics experiments. A negative photoresist, SU-8, was used as the insulating layer between the upper and bottom copper wires. The electrical measurement results show that the upper and bottom wires with a width of 100 µm can sustain a 6 A current without burnout. Another focus of this study is the double-layer atom chips integrated with the through silicon via (TSV) technique, and anodically bonded to a Pyrex glass cell, which makes it a desired vacuum chamber for atomic physics experiments. Thus, the bonded glass cell not only significantly reduces the overall size of the ultra-high-vacuum (UHV) chamber but also conducts the high current from the backside to the front side of the atom chip via the TSV under UHV (9.5 × 10-10 Torr). The TSVs with a diameter of 70 µm were etched through by the inductively coupled plasma ion etching and filled by the bottom-up copper electroplating method. During the anodic bonding process, the electroplated copper wires and TSVs on atom chips also need to pass the examination of the required bonding temperature of 250 °C, under an applied voltage of 1000 V. Finally, the UHV test of the double-layer atom chips with TSVs at room temperature can be reached at 9.5 × 10-10 Torr, thus satisfying the requirements of atomic physics experiments under an UHV environment.

A difference in using atomic layer deposition or physical vapour deposition TiN as electrode material in metal-insulator-metal and metal-insulator-silicon capacitors.

PubMed

Groenland, A W; Wolters, R A M; Kovalgin, A Y; Schmitz, J

2011-09-01

In this work, metal-insulator-metal (MIM) and metal-insulator-silicon (MIS) capacitors are studied using titanium nitride (TiN) as the electrode material. The effect of structural defects on the electrical properties on MIS and MIM capacitors is studied for various electrode configurations. In the MIM capacitors the bottom electrode is a patterned 100 nm TiN layer (called BE type 1), deposited via sputtering, while MIS capacitors have a flat bottom electrode (called BE type 2-silicon substrate). A high quality 50-100 nm thick SiO2 layer, made by inductively-coupled plasma CVD at 150 degrees C, is deposited as a dielectric on top of both types of bottom electrodes. BE type 1 (MIM) capacitors have a varying from low to high concentration of structural defects in the SiO2 layer. BE type 2 (MIS) capacitors have a low concentration of structural defects and are used as a reference. Two sets of each capacitor design are fabricated with the TiN top electrode deposited either via physical vapour deposition (PVD, i.e., sputtering) or atomic layer deposition (ALD). The MIM and MIS capacitors are electrically characterized in terms of the leakage current at an electric field of 0.1 MV/cm (I leak) and for different structural defect concentrations. It is shown that the structural defects only show up in the electrical characteristics of BE type 1 capacitors with an ALD TiN-based top electrode. This is due to the excellent step coverage of the ALD process. This work clearly demonstrates the sensitivity to process-induced structural defects, when ALD is used as a step in process integration of conductors on insulation materials.

Resource-limited heterotrophic prokaryote production and its potential environmental impact associated with Mn nodule exploitation in the northeast equatorial pacific.

PubMed

Hyun, Jung-Ho

2006-08-01

Shipboard enrichment incubation experiments were performed to elucidate the limiting resources for heterotrophic prokaryotic production and to discuss the potential impact of bottom water and sediment discharges in relation to manganese (Mn) nodule exploitation on the heterotrophic prokaryotes in the oligotrophic northeast equatorial Pacific. Compared to an unamended control, the production of heterotrophic prokaryotes increased 25-fold in water samples supplemented with amino acids (i.e., organic carbon plus nitrogen), whereas the production increased five and two times, respectively, in samples supplemented with either glucose or ammonium alone. These results indicate that heterotrophic prokaryote production in the northeast equatorial Pacific was co-limited by the availability of dissolved organic carbon and inorganic nitrogen. In samples from the nutrient-depleted surface mixed layer (10-m depth), the addition of a slurry of bottom water and sediment doubled heterotrophic prokaryote production compared to an unamended control, whereas sonicating the slurry prior to addition quadrupled the production rate. However, little difference was observed between an unamended control and slurry-amended samples in the subsurface chlorophyll a (Chl a) maximum (SCM) layer. Thus, the impact of slurry discharge is more significant at the nutrient-depleted surface mixed layer than at the high-nutrient SCM layer. The greatly enhanced prokaryote production resulting from the addition of sonicated slurry further suggests that dissociated organic carbon may directly stimulate heterotrophic prokaryote production in the surface mixed layer. Overall, the results suggest that the surface discharge of bottom water and sediments during manganese nodule exploitation could have a significant environmental impact on the production of heterotrophic prokaryotes that are currently resource limited.

Interface and thickness tuning for blade coated small-molecule organic light-emitting diodes with high power efficiency

NASA Astrophysics Data System (ADS)

Chang, Yu-Fan; Chiu, Yu-Chian; Chang, Hao-Wen; Wang, Yi-Siang; Shih, Yi-Lun; Wu, Chih-Hao; Liu, Yi-Lun; Lin, Yu-Sheng; Meng, Hsin-Fei; Chi, Yun; Huang, Heh-Lung; Tseng, Mei-Rurng; Lin, Hao-Wu; Zan, Hsiao-Wen; Horng, Sheng-Fu; Juang, Jenh-Yih

2013-09-01

We developed a general method based on fluorescence microscopy to characterize the interface dissolution in multi-layer organic light-emitting diodes (OLEDs) by blade coating. A sharp bi-layer edge was created before blade coating, with the bottom layer being insoluble and top layer soluble. After blade coating, fluorescence images showed that the edge of the top layer shifted when the layer dissolved completely, whereas the bottom layer's edge remained in place as a positioning mark. The dissolution depth was determined to be 15-20 nm when the emissive-layer host of 2,6-bis (3-(9H-carbazol-9-yl)phenyl) pyridine (26DCzPPy) was coated on the hole-transport layer of N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine(NPB), which was consistent with a sudden drop in efficiency of orange OLEDs with layer thickness below 20 nm. Thus, the layer thickness of OLEDs was optimized to stay more than 20 nm for blade coating. For a two-color white OLED with the structure TCTA/26DCzPPy:PO-01-TB:FIrpic/TPBI, efficiency was 24 cd/A and 8.5 lm/W at 1000 cd/m2. For a three-color white OLED with Os(fptz)2(dhpm) added as the emitter, the efficiency was 12.3 cd/A and 3.7 lm/W at 1000 cd/m2. For a green device with the structure TCTA/26DCzPPy:Ir(mppy)3/TPBI, the efficiency was 41.9 cd/A and 23.4 lm/W at 1000 cd/m2.

Amorphous indium-gallium-zinc-oxide thin-film transistors using organic-inorganic hybrid films deposited by low-temperature plasma-enhanced chemical vapor deposition for all dielectric layers

NASA Astrophysics Data System (ADS)

Hsu, Chao-Jui; Chang, Ching-Hsiang; Chang, Kuei-Ming; Wu, Chung-Chih

2017-01-01

We investigated the deposition of high-performance organic-inorganic hybrid dielectric films by low-temperature (close to room temperature) inductively coupled plasma chemical vapor deposition (ICP-CVD) with hexamethyldisiloxane (HMDSO)/O2 precursor gas. The hybrid films exhibited low leakage currents and high breakdown fields, suitable for thin-film transistor (TFT) applications. They were successfully integrated into the gate insulator, the etch-stop layer, and the passivation layer for bottom-gate staggered amorphous In-Ga-Zn-O (a-IGZO) TFTs having the etch-stop configuration. With the double-active-layer configuration having a buffer a-IGZO back-channel layer grown in oxygen-rich atmosphere for better immunity against plasma damage, the etch-stop-type bottom-gate staggered a-IGZO TFTs with good TFT characteristics were successfully demonstrated. The TFTs showed good field-effect mobility (μFE), threshold voltage (V th), subthreshold swing (SS), and on/off ratio (I on/off) of 7.5 cm2 V-1 s-1, 2.38 V, 0.38 V/decade, and 2.2 × 108, respectively, manifesting their usefulness for a-IGZO TFTs.

Micro-electro-mechanically switchable near infrared complementary metamaterial absorber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pitchappa, Prakash; Pei Ho, Chong; Institute of Microelectronics

2014-05-19

We experimentally demonstrate a micro-electro-mechanically switchable near infrared complementary metamaterial absorber by integrating the metamaterial layer to be the out of plane movable microactuator. The metamaterial layer is electrostatically actuated by applying voltage across the suspended complementary metamaterial layer and the stationary bottom metallic reflector. Thus, the effective spacing between the metamaterial layer and bottom metal reflector is varied as a function of applied voltage. With the reduction of effective spacing between the metamaterial and reflector layers, a strong spectral blue shift in the peak absorption wavelength can be achieved. With spacing change of 300 nm, the spectral shift of 0.7 μmmore » in peak absorption wavelength was obtained for near infrared spectral region. The electro-optic switching performance of the device was characterized, and a striking switching contrast of 1500% was achieved at 2.1 μm. The reported micro-electro-mechanically tunable complementary metamaterial absorber device can potentially enable a wide range of high performance electro-optical devices, such as continuously tunable filters, modulators, and electro-optic switches that form the key components to facilitate future photonic circuit applications.« less

Crystal Identification in Dual-Layer-Offset DOI-PET Detectors Using Stratified Peak Tracking Based on SVD and Mean-Shift Algorithm

NASA Astrophysics Data System (ADS)

Wei, Qingyang; Dai, Tiantian; Ma, Tianyu; Liu, Yaqiang; Gu, Yu

2016-10-01

An Anger-logic based pixelated PET detector block requires a crystal position map (CPM) to assign the position of each detected event to a most probable crystal index. Accurate assignments are crucial to PET imaging performance. In this paper, we present a novel automatic approach to generate the CPMs for dual-layer offset (DLO) PET detectors using a stratified peak tracking method. In which, the top and bottom layers are distinguished by their intensity difference and the peaks of the top and bottom layers are tracked based on a singular value decomposition (SVD) and mean-shift algorithm in succession. The CPM is created by classifying each pixel to its nearest peak and assigning the pixel with the crystal index of that peak. A Matlab-based graphical user interface program was developed including the automatic algorithm and a manual interaction procedure. The algorithm was tested for three DLO PET detector blocks. Results show that the proposed method exhibits good performance as well as robustness for all the three blocks. Compared to the existing methods, our approach can directly distinguish the layer and crystal indices using the information of intensity and offset grid pattern.

The role of thin MgO(100) epilayer for polarized charge injection into top-emitting OLED

NASA Astrophysics Data System (ADS)

Kim, Tae Hee; Jong Lee, Nyun; Bae, Yu Jeong; Cho, Hyunduck; Lee, Changhee; Ito, Eisuke

2012-02-01

A new top-emitting OLED (TOLED) structure, which is formed on an Si(100) substrate and an epitaxial MgO(100)/Fe(100)/MgO(100) bottom electrode, was investigated. Our TOLED design included a semi-transparent cathode Al, a stack of conventional organic electroluminescent layers (α-NPD/Alq3/LiF) and a thin Cu-Phthalocyanine (CuPc) film to enhance the hole injection into the luminescent layers. At room temperature (RT), magnetoluminescence of ˜5 % was observed in low magnetic field up to 1 Tesla , which is obviously larger than that of the OLEDs with epitaxial and polycrystalline Fe anodes without MgO(100) covering layer. Our results indicate that the magnetic field effect on the electroluminescence could be strongly related to the magnetic properties of bottom electrode, more precisely the interfacial properties between CuPc layer and the anode. Therefore, we focused on understanding interface electronic states and energy alignment by using x-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy. Our results showed that the use of appropriate oxide layers could represent a new interface engineering technique for improving reliability and functionality in organic semiconductor devices.

Thin-layer heap bioleaching of copper flotation tailings containing high levels of fine grains and microbial community succession analysis

NASA Astrophysics Data System (ADS)

Hao, Xiao-dong; Liang, Yi-li; Yin, Hua-qun; Liu, Hong-wei; Zeng, Wei-min; Liu, Xue-duan

2017-04-01

Thin-layer heap bioleaching of copper flotation tailings containing high levels of fine grains was carried out by mixed cultures on a small scale over a period of 210 d. Lump ores as a framework were loaded at the bottom of the ore heap. The overall copper leaching rates of tailings and lump ores were 57.10wt% and 65.52wt%, respectively. The dynamic shifts of microbial community structures about attached microorganisms were determined using the Illumina MiSeq sequencing platform based on 16S rRNA amplification strategy. The results indicated that chemolithotrophic genera Acidithiobacillus and Leptospirillum were always detected and dominated the microbial community in the initial and middle stages of the heap bioleaching process; both genera might be responsible for improving the copper extraction. However, Thermogymnomonas and Ferroplasma increased gradually in the final stage. Moreover, the effects of various physicochemical parameters and microbial community shifts on the leaching efficiency were further investigated and these associations provided some important clues for facilitating the effective application of bioleaching.

Water in Inhomogeneous Nanoconfinement: Coexistence of Multilayered Liquid and Transition to Ice Nanoribbons.

PubMed

Qiu, Hu; Zeng, Xiao Cheng; Guo, Wanlin

2015-10-27

Phase behavior and the associated phase transition of water within inhomogeneous nanoconfinement are investigated using molecular dynamics simulations. The nanoconfinement is constructed by a flat bottom plate and a convex top plate. At 300 K, the confined water can be viewed as a coexistence of monolayer, bilayer, and trilayer liquid domains to accommodate the inhomogeneous confinement. With increasing liquid density, the confined water with uneven layers transforms separately into two-dimensional ice crystals with unchanged layer number and rhombic in-plane symmetry for oxygen atoms. The monolayer water undergoes the transition first into a puckered ice nanoribbon, and the bilayer water transforms into a rhombic ice nanoribbon next, followed by the transition of trilayer water into a trilayer ice nanoribbon. The sequential localized liquid-to-solid transition within the inhomogeneous confinement can also be achieved by gradually decreasing the temperature at low liquid densities. These findings of phase behaviors of water under the inhomogeneous nanoconfinement not only extend the phase diagram of confined water but also have implications for realistic nanofluidic systems and microporous materials.

Dynamics of Crust Dissolution and Gas Release in Tank 241-SY-101

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rassat, Scot D.; Stewart, Charles W.; Wells, Beric E.

2000-01-24

Due primarily to an increase in floating crust thickness, the waste level in Tank 241-SY-101 has grown appreciably and the flammable gas volume stored in the crust has become a potential hazard. To remediate gas retention in the crust and the potential for buoyant displacement gas releases from the nonconvective layer at the bottom of the tank, SY-101 will be diluted to dissolve a large fraction of the solids that allow the waste to retain gas. The plan is to transfer some waste out and back-dilute with water in several steps. In this work, mechanisms and rates of waste solidsmore » dissolution and gas releases are evaluated theoretically and experimentally. Particular emphasis is given to crust dissolution processes and associated gas releases, although dissolution and gas release from the mixed-slurry and nonconvective layers are also considered. The release of hydrogen gas to the tank domespace is modeled for a number of scenarios. Under the tank conditions expected at the time of back-dilution, no plausible continuous or sudden gas release scenarios resulting in flammable hydrogen concentrations were identified.« less

Shear wave velocity and attenuation in the upper layer of ocean bottoms from long-range acoustic field measurements.

PubMed

Zhou, Ji-Xun; Zhang, Xue-Zhen

2012-12-01

Several physics-based seabed geoacoustic models (including the Biot theory) predict that compressional wave attenuation α(2) in sandy marine sediments approximately follows quadratic frequency dependence at low frequencies, i.e., α(2)≈kf(n) (dB/m), n=2. A recent paper on broadband geoacoustic inversions from low frequency (LF) field measurements, made at 20 locations around the world, has indicated that the frequency exponent of the effective sound attenuation n≈1.80 in a frequency band of 50-1000 Hz [Zhou et al., J. Acoust. Soc. Am. 125, 2847-2866 (2009)]. Carey and Pierce hypothesize that the discrepancy is due to the inversion models' neglect of shear wave effects [J. Acoust. Soc. Am. 124, EL271-EL277 (2008)]. The broadband geoacoustic inversions assume that the seabottom is an equivalent fluid and sound waves interact with the bottom at small grazing angles. The shear wave velocity and attenuation in the upper layer of ocean bottoms are estimated from the LF field-inverted effective bottom attenuations using a near-grazing bottom reflection expression for the equivalent fluid model, derived by Zhang and Tindle [J. Acoust. Soc. Am. 98, 3391-3396 (1995)]. The resultant shear wave velocity and attenuation are consistent with the SAX99 measurement at 25 Hz and 1000 Hz. The results are helpful for the analysis of shear wave effects on long-range sound propagation in shallow water.

Denitrification potential in relation to lithology in five headwater riparian zones.

PubMed

Hill, Alan R; Vidon, Philippe G F; Langat, Jackson

2004-01-01

The influence of riparian zone lithology on nitrate dynamics is poorly understood. We investigated vertical variations in potential denitrification activity in relation to the lithology and stratigraphy of five headwater riparian zones on glacial till and outwash landscapes in southern Ontario, Canada. Conductive coarse sand and gravel layers occurred in four of the five riparian areas. These layers were thin and did not extend to the field-riparian perimeter in some riparian zones, which limited their role as conduits for ground water flow. We found widespread organic-rich layers at depths ranging from 40 to 300 cm that resulted from natural floodplain processes and the burial of surface soils by rapid valley-bottom sedimentation after European settlement. The organic matter content of these layers varied considerably from 2 to 5% (relic channel deposit) to 5 to 21% (buried soils) and 30 to 62% (buried peat). Denitrification potential (DNP) was measured by the acetylene block method in sediment slurries amended with nitrate. The highest DNP rates were usually found in the top 0- to 15-cm surface soil layer in all riparian zones. However, a steep decline in DNP with depth was often absent and high DNP activity occurred in the deep organic-rich layers. Water table variations in 2000-2002 indicated that ground water only interacted frequently with riparian surface soils between late March and May, whereas subsurface organic layers that sustain considerable DNP were below the water table for most of the year. These results suggest that riparian zones with organic deposits at depth may effectively remove nitrate from ground water even when the water table does not interact with organic-rich surface soil horizons.

Elevated [CO2] mitigates the effect of surface drought by stimulating root growth to access sub-soil water.

PubMed

Uddin, Shihab; Löw, Markus; Parvin, Shahnaj; Fitzgerald, Glenn J; Tausz-Posch, Sabine; Armstrong, Roger; O'Leary, Garry; Tausz, Michael

2018-01-01

Through stimulation of root growth, increasing atmospheric CO2 concentration ([CO2]) may facilitate access of crops to sub-soil water, which could potentially prolong physiological activity in dryland environments, particularly because crops are more water use efficient under elevated [CO2] (e[CO2]). This study investigated the effect of drought in shallow soil versus sub-soil on agronomic and physiological responses of wheat to e[CO2] in a glasshouse experiment. Wheat (Triticum aestivum L. cv. Yitpi) was grown in split-columns with the top (0-30 cm) and bottom (31-60 cm; 'sub-soil') soil layer hydraulically separated by a wax-coated, root-penetrable layer under ambient [CO2] (a[CO2], ∼400 μmol mol-1) or e[CO2] (∼700 μmol mol-1) [CO2]. Drought was imposed from stem-elongation in either the top or bottom soil layer or both by withholding 33% of the irrigation, resulting in four water treatments (WW, WD, DW, DD; D = drought, W = well-watered, letters denote water treatment in top and bottom soil layer, respectively). Leaf gas exchange was measured weekly from stem-elongation until anthesis. Above-and belowground biomass, grain yield and yield components were evaluated at three developmental stages (stem-elongation, anthesis and maturity). Compared with a[CO2], net assimilation rate was higher and stomatal conductance was lower under e[CO2], resulting in greater intrinsic water use efficiency. Elevated [CO2] stimulated both above- and belowground biomass as well as grain yield, however, this stimulation was greater under well-watered (WW) than drought (DD) throughout the whole soil profile. Imposition of drought in either or both soil layers decreased aboveground biomass and grain yield under both [CO2] compared to the well-watered treatment. However, the greatest 'CO2 fertilisation effect' was observed when drought was imposed in the top soil layer only (DW), and this was associated with e[CO2]-stimulation of root growth especially in the well-watered bottom layer. We suggest that stimulation of belowground biomass under e[CO2] will allow better access to sub-soil water during grain filling period, when additional water is converted into additional yield with high efficiency in Mediterranean-type dryland agro-ecosystems. If sufficient water is available in the sub-soil, e[CO2] may help mitigating the effect of drying surface soil.

Suspended Alexandrium spp. hypnozygote cysts in the Gulf of Maine

NASA Astrophysics Data System (ADS)

Kirn, Sarah L.; Townsend, David W.; Pettigrew, Neal R.

2005-09-01

The life cycle of dinoflagellates of the genus Alexandrium includes sexual reproduction followed by the formation of a dormant hypnozygote cyst, which serves as a resting stage. Negatively buoyant cysts purportedly fall to the benthos where they undergo a mandatory period of quiescence. Previous reports of cysts in the surficial sediments of the Gulf of Maine, where Alexandrium blooms are well documented, show a broad distribution of cysts, with highest concentrations generally in sediments below 100 m depth. We report here an exploration of cysts suspended in the water column, where they would be better positioned to inoculate springtime Alexandrium populations. During cruises in February, April, and June of 2000, water samples were collected at depths just off the bottom (within 5 m), at the top of the bottom nepheloid layer, and near the surface (1 m) and examined for cyst concentrations. Suspended cysts were found throughout the Gulf of Maine and westernmost Bay of Fundy. Planktonic cyst densities were generally greater in near-bottom and top of the bottom nepheloid layer samples than in near-surface water samples; densities were of the order of 10 2 cysts m -3 in surface waters, and 10 2-10 3 cysts m -3 at near-bottom depths. Temporally, they were most abundant in February and least abundant in April. Reports by earlier workers of cysts in the underlying sediments were on the order of 10 3 cysts cm -3. We present calculations that demonstrate the likelihood of cyst resuspension from bottom sediments forced by swell and tidal currents, and propose that such resuspended cysts are important in inoculating the seasonal bloom. We estimate that suspended cysts may contribute significantly to the annual vegetative cell population in the Gulf of Maine.

Bottom water circulation in Cascadia Basin

NASA Astrophysics Data System (ADS)

Hautala, Susan L.; Paul Johnson, H.; Hammond, Douglas E.

2009-10-01

A combination of beta spiral and minimum length inverse methods, along with a compilation of historical and recent high-resolution CTD data, are used to produce a quantitative estimate of the subthermocline circulation in Cascadia Basin. Flow in the North Pacific Deep Water, from 900-1900 m, is characterized by a basin-scale anticyclonic gyre. Below 2000 m, two water masses are present within the basin interior, distinguished by different potential temperature-salinity lines. These water masses, referred to as Cascadia Basin Bottom Water (CBBW) and Cascadia Basin Deep Water (CBDW), are separated by a transition zone at about 2400 m depth. Below the depth where it freely communicates with the broader North Pacific, Cascadia Basin is renewed by northward flow through deep gaps in the Blanco Fracture Zone that feeds the lower limb of a vertical circulation cell within the CBBW. Lower CBBW gradually warms and returns to the south at lighter density. Isopycnal layer renewal times, based on combined lateral and diapycnal advective fluxes, increase upwards from the bottom. The densest layer, existing in the southeast quadrant of the basin below ˜2850 m, has an advective flushing time of 0.6 years. The total volume flushing time for the entire CBBW is 2.4 years, corresponding to an average water parcel residence time of 4.7 years. Geothermal heating at the Cascadia Basin seafloor produces a characteristic bottom-intensified temperature anomaly and plays an important role in the conversion of cold bottom water to lighter density within the CBBW. Although covering only about 0.05% of the global seafloor, the combined effects of bottom heat flux and diapycnal mixing within Cascadia Basin provide about 2-3% of the total required global input to the upward branch of the global thermohaline circulation.

19. EMPTY SEDIMENTATION TANKS. TOP LAYER OF WATER FLOWS OVER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

19. EMPTY SEDIMENTATION TANKS. TOP LAYER OF WATER FLOWS OVER TRIANGULATED CHANNELS AND OUT THE RAISED DUCTS TO FILTRATION PLANT. MOVEABLE BOARDS ON BOTTOM ASSIST IN REMOVING SLUDGE. VIEW LOOKING NORTHEAST. FILTER CONTROL BUILDING AT REAR. - F. E. Weymouth Filtration Plant, 700 North Moreno Avenue, La Verne, Los Angeles County, CA

Bottom Penetration at Shallow Grazing Angles II

DTIC Science & Technology

1992-06-19

Millwater , "Wave Reflection from a Sediment Layer with Depth-Dependent Properties," J. Acoust. Soc. Am. 77, 1781- 1788 (1985). 35 8. N. P. Chotiros, ’High...Acoust. Soc. Am. 8B1 S131 (1990). 12. M. Stern, A. Bedford, and H. R. Millwater , "Wave Reflection from a Sediment Layer with Depth-Dependent

An experimental assessment of resistance reduction and wake modification of a kvlcc model by using outer-layer vertical blades

NASA Astrophysics Data System (ADS)

An, Nam Hyun; Ryu, Sang Hoon; Chun, Ho Hwan; Lee, Inwon

2014-03-01

In this study, an experimental investigation has been made of the applicability of outer-layer vertical blades to real ship model. After first devised by Hutchins and Choi (2003), the outer-layer vertical blades demonstrated its effectiveness in reducing total drag of flat plate (Park et al., 2011) with maximum drag reduction of 9.6%. With a view to assessing the effect in the flow around a ship, the arrays of outer-layer vertical blades have been installed onto the side bottom and flat bottom of a 300k KVLCC model. A series of towing tank test has been carried out to investigate resistance (CTM) reduction efficiency and improvement of stern wake distribution with varying geometric parameters of the blades array. The installation of vertical blades led to the CTM reduction of 2.15~2.76% near the service speed. The nominal wake fraction was affected marginally by the blades array and the axial velocity distribution tended to be more uniform by the blades array.

Enhanced Carrier Collection from CdS Passivated Grains in Solution-Processed Cu2ZnSn(S,Se)4 Solar Cells.

PubMed

Werner, Melanie; Keller, Debora; Haass, Stefan G; Gretener, Christina; Bissig, Benjamin; Fuchs, Peter; La Mattina, Fabio; Erni, Rolf; Romanyuk, Yaroslav E; Tiwari, Ayodhya N

2015-06-10

Solution processing of Cu2ZnSn(S,Se)4 (CZTSSe)-kesterite solar cells is attractive because of easy manufacturing using readily available metal salts. The solution-processed CZTSSe absorbers, however, often suffer from poor morphology with a bilayer structure, exhibiting a dense top crust and a porous bottom layer, albeit yielding efficiencies of over 10%. To understand whether the cell performance is limited by this porous layer, a systematic compositional study using (scanning) transmission electron microscopy ((S)TEM) and energy-dispersive X-ray spectroscopy of the dimethyl sulfoxide processed CZTSSe absorbers is presented. TEM investigation revealed a thin layer of CdS that is formed around the small CZTSSe grains in the porous bottom layer during the chemical bath deposition step. This CdS passivation is found to be beneficial for the cell performance as it increases the carrier collection and facilitates the electron transport. Electron-beam-induced current measurements reveal an enhanced carrier collection for this buried region as compared to reference cells with evaporated CdS.

Rapid electrostatics-assisted layer-by-layer assembly of near-infrared-active colloidal photonic crystals.

PubMed

Askar, Khalid; Leo, Sin-Yen; Xu, Can; Liu, Danielle; Jiang, Peng

2016-11-15

Here we report a rapid and scalable bottom-up technique for layer-by-layer (LBL) assembling near-infrared-active colloidal photonic crystals consisting of large (⩾1μm) silica microspheres. By combining a new electrostatics-assisted colloidal transferring approach with spontaneous colloidal crystallization at an air/water interface, we have demonstrated that the crystal transfer speed of traditional Langmuir-Blodgett-based colloidal assembly technologies can be enhanced by nearly 2 orders of magnitude. Importantly, the crystalline quality of the resultant photonic crystals is not compromised by this rapid colloidal assembly approach. They exhibit thickness-dependent near-infrared stop bands and well-defined Fabry-Perot fringes in the specular transmission and reflection spectra, which match well with the theoretical calculations using a scalar-wave approximation model and Fabry-Perot analysis. This simple yet scalable bottom-up technology can significantly improve the throughput in assembling large-area, multilayer colloidal crystals, which are of great technological importance in a variety of optical and non-optical applications ranging from all-optical integrated circuits to tissue engineering. Copyright © 2016 Elsevier Inc. All rights reserved.

Varieties of submesoscale dynamics in the south-west Pacific.

NASA Astrophysics Data System (ADS)

Srinivasan, K.; Renault, L.; McWilliams, J. C.

2016-02-01

The large-scale circulation in the topographically complex south-west Pacific region con-sists of an equatorward western boundary current along the coast of Papua New Guinea andwestern Solomon sea, the equatorial currents to the north and east of the Solomon islands,and the multiple jet-like zonal currents generated by the numerous islands to the south in theCoral Sea. Employing a hierarchy of nested, realistic ocean modeling experiments in ROMS,with horizontal resolutions as fine as 500m, we examine the dynamics of submesoscales inthis region. We construct spatial maps of statistics of the surface divergence (δ), vortic-ity (ζ)), buoyancy gradient (∇b) and the frontogenetic tendency (Tadv ), to identify areas ofactive submesoscales and their seasonal variability. More specifically, such areas are charac-terized by high variance of δ, ζ, ∇b and Tadv and a corresponding high negative skewnessin surface divergence, since frontogenesis is a downwelling-dominant physical process. Suchareas include sites in and around the Solomon Sea, with eddy generation through separa-tion of bottom-drag generated shear layers, the Coral Sea open ocean mixed-layer submesoscale `soup'generated through baroclinic instability and frontogenesis, and lastly, Equatorial fronts thatwe believe are hitherto unobserved and thought to be largely absent on theoretical groundsrequiring the presence of background rotation in frontogenesis. While the Coral Sea subme-soscale soup peaks in the (Southern hemisphere) winter, Equatorial frontal activity showsa summer-spring maximum. The dynamics of frontogenesis is particularly complex in theSolomon Sea where topographically generated eddies interact with mixed-layer buoyancygradients, that are in turn controlled by interplay of the warm equatorial currents to thenorth, the cooler Coral sea intrusions from the south and rather significantly, the strongand highly seasonal rainfall patterns and the corresponding freshwater input. A concomi-tant analysis of the energy inter-conversion between eddy and mean potential and kineticenergies is used to supplement the statistical results.

[Estimating Winter Wheat Nitrogen Vertical Distribution Based on Bidirectional Canopy Reflected Spectrum].

PubMed

Yang, Shao-yuan; Huang, Wen-jiang; Liang, Dong; Uang, Lin-sheng; Yang, Gui-jun; Zhang, Gui-jan; Cai, Shu-Hong

2015-07-01

The vertical distribution of crop nitrogen is increased with plant height, timely and non-damaging measurement of crop nitrogen vertical distribution is critical for the crop production and quality, improving fertilizer utilization and reducing environmental impact. The objective of this study was to discuss the method of estimating winter wheat nitrogen vertical distribution by exploring bidirectional reflectance distribution function (BRDF) data using partial least square (PLS) algorithm. The canopy reflectance at nadir, +/-50 degrees and +/- 60 degrees; at nadir, +/- 30 degrees and +/- 40 degrees; and at nadir, +/- 20 degrees and +/- 30 degrees were selected to estimate foliage nitrogen density (FND) at upper layer, middle layer and bottom layer, respectively. Three PLS analysis models with FND as the dependent variable and vegetation indices at corresponding angles as the explicative variables were. established. The impact of soil reflectance and the canopy non-photosynthetic materials, was minimized by seven kinds of modifying vegetation indices with the ratio R700/R670. The estimated accuracy is significant raised at upper layer, middle layer and bottom layer in modeling experiment. Independent model verification selected the best three vegetation indices for further research. The research result showed that the modified Green normalized difference vegetation index (GNDVI) shows better performance than other vegetation indices at each layer, which means modified GNDVI could be used in estimating winter wheat nitrogen vertical distribution

Layer-by-Layer Templated Assembly of Silica at the Nanoscale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hinestrosa, Juan Pablo; Sutton, Jonathan E.; Allison, David P.

2013-01-29

Bioinspired bottom-up assembly and layer-by-layer (LbL) construction of inorganic materials from lithographically defined organic templates enables the fabrication of nanostructured systems under mild temperature and pH conditions. Such processes open the door to low-impact manufacturing and facile recycling of hybrid materials for energy, biology, and information technologies. Here, templated LbL assembly of silica was achieved using a combination of electron beam lithography, chemical lift-off, and aqueous solution chemistry. Nanopatterns of lines, honeycomb-lattices, and dot arrays were defined in polymer resist using electron beam lithography. Following development, exposed areas of silicon were functionalized with a vapor deposited amine-silane monolayer. Silicic acidmore » solutions of varying pH and salt content were reacted with the patterned organic amine-functional templates. Vapor treatment and solution reaction could be repeated, allowing LbL deposition. Conditions for the silicic acid deposition had a strong effect on thickness of each layer, and the morphology of the amorphous silica formed. Defects in the arrays of silica nanostructures were minor and do not affect the overall organization of the layers. In conclusion, the bioinspired method described here facilitates the bottom-up assembly of inorganic nanostructures defined in three dimensions and provides a path, via LbL processing, for the construction of layered hybrid materials under mild conditions.« less

Fibre laser cutting stainless steel: Fluid dynamics and cut front morphology

NASA Astrophysics Data System (ADS)

Pocorni, Jetro; Powell, John; Deichsel, Eckard; Frostevarg, Jan; Kaplan, Alexander F. H.

2017-01-01

In this paper the morphology of the laser cut front generated by fibre lasers was investigated by observation of the 'frozen' cut front, additionally high speed imaging (HSI) was employed to study the fluid dynamics on the cut front while cutting. During laser cutting the morphology and flow properties of the melt film on the cut front affect cut quality parameters such as cut edge roughness and dross (residual melt attached to the bottom of the cut edge). HSI observation of melt flow down a laser cutting front using standard cutting parameters is experimentally problematic because the cut front is narrow and surrounded by the kerf walls. To compensate for this, artificial parameters are usually chosen to obtain wide cut fronts which are unrepresentative of the actual industrial process. This paper presents a new experimental cutting geometry which permits HSI of the laser cut front using standard, commercial parameters. These results suggest that the cut front produced when cutting medium section (10 mm thick) stainless steel with a fibre laser and a nitrogen assist gas is covered in humps which themselves are covered by a thin layer of liquid. HSI observation and theoretical analysis reveal that under these conditions the humps move down the cut front at an average speed of approximately 0.4 m/s while the covering liquid flows at an average speed of approximately 1.1 m/s, with an average melt depth at the bottom of the cut zone of approximately 0.17 mm.

A model experiment of liquefaction and fluid transport: quantifying the effect of permeability discontinuity

NASA Astrophysics Data System (ADS)

Yasuda, N.; Sumita, I.

2013-12-01

Model experiments of liquefaction of a water-saturated sand (quick sand) is commonly conducted in class and in public. Various phenomena caused by liquefaction are reproduced within a closed bottle containing push-pins (Nohguchi, 2004). Experiments for tilted and layered case have also been conducted (Peacock, 2006). However quantitative measurements of liquid transport in these experiments have rarely been made. Here we show that such measurements are possible by analyzing the video images taken during such experiments. In addition, we show that a simple physical model is capable of explaining the time scales needed to expel the interstitial liquid. An experimental cell (cross section 22.0 mm x 99.4 mm, height 107.6 mm) is filled with a granular matter and water. The lower 33.0 mm consists of a two-layered granular medium, the upper layer consists of fine particles and the lower layer consists of coarse particles, with particle sizes of 0.05 mm and 0.2 mm, respectively. Since permeability depends on the square of the particle size, the upper layer becomes a low-permeability layer. We liquefy the cell by an impulsive vibration and study how the liquid migrates afterwards. We also vary the particle size combinations (upper layer: 0.05-0.15 mm, lower layer: 0.15-0.6 mm) and the thickness ratio of the 2 layers, and study how the time scale of the liquid migration depends on these changeable parameters. In a two-layered medium, we find that the pore water which originated from the bottom layer temporary accumulates at the interface of the two layers, and then ascends through the upper layer in the form of horizontal sheet or vertical channels. We find that these two different discharge styles are controlled by the permeability ratio of the two layers. We study the temporal change of the thicknesses of the two layers and find that there are three stages; 1: the slope of the upper surface is leveled by the impulse, 2: the pore water is discharged from the bottom layer and accumulates at the interface, after which it migrates upwards, 3: water discharge ends, and particles settle. We measured the relaxation time needed for the discharge and compaction to end. Because low-permeability layer inhibits pore water from rising, longer time is needed for a two-layer case compared to the one-layer case. When the particle size of the upper layer is about 1/3 or smaller than that of the lower layer, relaxation time becomes independent of the bottom particle size. We modeled the relaxation time by introducing the effective permeability of two-layered medium, and find that it explains the measurements well. References Nohguchi, Y., 2004, ICTAM04 Proceedings, Warsaw, Poland. Peacock, D. C. P., 2006, J. Geosci.Ed, 54, 550

Evaluation of Sloped Bottom Tuned Liquid Damper for Reduction of Seismic Response of Tall Buildings

NASA Astrophysics Data System (ADS)

Patil, G. R.; Singh, K. D.

2016-12-01

Due to migration of people to urban area, high land costs and use of light weight materials modern buildings tend to be taller, lighter and flexible. These buildings possess low damping. This increases the possibility of failure during earthquake ground motion and also affect the serviceability during wind vibrations. Out of many available techniques today, to reduce the response of structure under dynamic loading, Tuned Liquid Damper (TLD) is a recent technique to mitigate seismic response. However TLD has been used to mitigate the wind induced structural vibrations. Flat bottom TLD gives energy back to the structure after event of dynamic loading and it is termed as beating. Beating affects the performance of TLD. Study attempts to analyze the effectiveness of sloped bottom TLD for reducing seismic vibrations of structure. Concept of equivalent flat bottom LD has been used to analyze sloped bottom TLD. Finite element method (EM) is used to model the structure and the liquid in the TLD. MATLAB code is developed to study the response of structure, the liquid sloshing in the tank and the coupled fluid-structure interaction. A ten storey two bay RC frame is analyzed for few inputs of ground motion. A sinusoidal ground motion corresponding to resonance condition with fundamental frequency of frame is analyzed. In the analysis the inherent damping of structure is not considered. Observations from the study shows that sloped bottom TLD uses less amount of liquid than flat bottom TLD. Also observed that efficiency of sloped bottom TLD can be improved if it is properly tuned.

Great differences in the critical erosion threshold between surface and subsurface sediments: A field investigation of an intertidal mudflat, Jiangsu, China

NASA Astrophysics Data System (ADS)

Shi, Benwei; Wang, Ya Ping; Wang, Li Hua; Li, Peng; Gao, Jianhua; Xing, Fei; Chen, Jing Dong

2018-06-01

Understanding of bottom sediment erodibility is necessary for the sustainable management and protection of coastlines, and is of great importance for numerical models of sediment dynamics and transport. To investigate the dependence of sediment erodibility on degree of consolidation, we measured turbidity, waves, tidal currents, intratidal bed-level changes, and sediment properties on an exposed macrotidal mudflat during a series of tidal cycles. We estimated the water content of surface sediments (in the uppermost 2 cm of sediment) and sub-surface sediments (at 2 cm below the sediment surface). Bed shear stress values due to currents (τc), waves (τw), and combined current-wave action (τcw) were calculated using a hydrodynamic model. In this study, we estimate the critical shear stress for erosion using two approaches and both of them give similar results. We found that the critical shear stress for erosion (τce) was 0.17-0.18 N/m2 in the uppermost 0-2 cm of sediment and 0.29 N/m2 in sub-surface sediment layers (depth, 2 cm), as determined by time series of τcw values and intratidal bed-level changes, and values of τce, obtained using the water content of bottom sediments, were 0.16 N/m2 in the uppermost 2 cm and 0.28 N/m2 in the sub-surface (depth, 2 cm) sediment. These results indicate that the value of τce for sub-surface sediments (depth, 2 cm) is much greater than that for the uppermost sediments (depth, 0-2 cm), and that the τce value is mainly related to the water content, which is determined by the extent of consolidation. Our results have implications for improving the predictive accuracy of models of sediment transport and morphological evolution, by introducing variable τce values for corresponding sediment layers, and can also provide a mechanistic understanding of bottom sediment erodibility at different sediment depths on intertidal mudflats, as related to differences in the consolidation time.

Evaluation of processes occurring in the bottom nepheloid layer (BNL) of an eastern Mediterranean area using 234Th/238U disequilibria.

PubMed

Evangeliou, Nikolaos; Florou, Heleny

2013-09-01

Particle-reactive radionuclide (234)Th and its ratios with the conservative (238)U were used to trace the marine processes occurring over short timescales in the bottom nepheloid layer (BNL) of seven stations in the Saronikos Gulf and the Elefsis Bay (Greece) during three seasons (summer 2008, autumn 2008 and winter 2009). Summer was considered as a steady season where low physical processes occur and stratification is well established, autumn as a commutative period and winter as period of extensive trawling and physical activities. The obtained ratio profiles showed excess of (234)Th relative to (238)U in the BNL of the sampling area during summer, caused by the dissolved fraction of (234)Th. During autumn, the situation was different with large (234)Th deficit throughout the water column leading to large export fluxes of particles from the water column. Finally, during winter the ratios showed that predominant phenomenon in the area was likely resuspension of bottom sediments. The resuspension signature was additionally evaluated by total suspended matter (TSM) inventories in the BNL. Despite the intense resuspension, small scavenging of dissolved (234)Th was recorded in the BNL resulting in high residence times of dissolved (234)Th. A 1 order of magnitude difference between dissolved and particulate (234)Th residence times was observed indicating that scavenging from dissolved to particulate (234)Th could be highly variable and, as a result, the Saronikos Gulf is a highly dynamic environment, in terms of temporal and spatial particle uptake and removal. Comparing these values to literature ones consistent results were obtained. The possibility of sediment resuspension in the BNL during winter was amplified by the bloom of phytoplankton resulting in even decreased residence times of particulate (234)Th (average values). In contrast, the respective residence times of the dissolved fraction of (234)Th in the BNL were higher showing a maximum in winter at the stations where resuspension concluded. Nevertheless, (234)Th cycling in the area is not controlled by TSM, probably due to the presence of colloids, which could play an essential role in (234)Th scavenging.

A high-sensitivity fiber-optic evanescent wave sensor with a three-layer structure composed of Canada balsam doped with GeO2.

PubMed

Zhong, Nianbing; Zhao, Mingfu; Zhong, Lianchao; Liao, Qiang; Zhu, Xun; Luo, Binbin; Li, Yishan

2016-11-15

In this paper, we present a high-sensitivity polymer fiber-optic evanescent wave (FOEW) sensor with a three-layer structure that includes bottom, inter-, and surface layers in the sensing region. The bottom layer and inter-layer are POFs composed of standard cladding and the core of the plastic optical fiber, and the surface layer is made of dilute Canada balsam in xylene doped with GeO2. We examine the morphology of the doped GeO2, the refractive index and composition of the surface layer and the surface luminous properties of the sensing region. We investigate the effects of the content and morphology of the GeO2 particles on the sensitivity of the FOEW sensors by using glucose solutions. In addition, we examine the response of sensors incubated with staphylococcal protein A plus mouse IgG isotype to goat anti-mouse IgG solutions. Results indicate very good sensitivity of the three-layer FOEW sensor, which showed a 3.91-fold improvement in the detection of the target antibody relative to a conventional sensor with a core-cladding structure, and the novel sensor showed a lower limit of detection of 0.2ng/l and a response time around 320s. The application of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, biomedical and biochemical analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Multi-layer carbon-based coatings for field emission

DOEpatents

Sullivan, John P.; Friedmann, Thomas A.

1998-01-01

A multi-layer resistive carbon film field emitter device for cold cathode field emission applications. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced.

Optimized capping layers for EUV multilayers

DOEpatents

Bajt, Sasa [Livermore, CA; Folta, James A [Livermore, CA; Spiller, Eberhard A [Livermore, CA

2004-08-24

A new capping multilayer structure for EUV-reflective Mo/Si multilayers consists of two layers: A top layer that protects the multilayer structure from the environment and a bottom layer that acts as a diffusion barrier between the top layer and the structure beneath. One embodiment combines a first layer of Ru with a second layer of B.sub.4 C. Another embodiment combines a first layer of Ru with a second layer of Mo. These embodiments have the additional advantage that the reflectivity is also enhanced. Ru has the best oxidation resistance of all materials investigated so far. B.sub.4 C is an excellent barrier against silicide formation while the silicide layer formed at the Si boundary is well controlled.

When Art Moves the Eyes: A Behavioral and Eye-Tracking Study

PubMed Central

Massaro, Davide; Savazzi, Federica; Di Dio, Cinzia; Freedberg, David; Gallese, Vittorio; Gilli, Gabriella; Marchetti, Antonella

2012-01-01

The aim of this study was to investigate, using eye-tracking technique, the influence of bottom-up and top-down processes on visual behavior while subjects, naïve to art criticism, were presented with representational paintings. Forty-two subjects viewed color and black and white paintings (Color) categorized as dynamic or static (Dynamism) (bottom-up processes). Half of the images represented natural environments and half human subjects (Content); all stimuli were displayed under aesthetic and movement judgment conditions (Task) (top-down processes). Results on gazing behavior showed that content-related top-down processes prevailed over low-level visually-driven bottom-up processes when a human subject is represented in the painting. On the contrary, bottom-up processes, mediated by low-level visual features, particularly affected gazing behavior when looking at nature-content images. We discuss our results proposing a reconsideration of the definition of content-related top-down processes in accordance with the concept of embodied simulation in art perception. PMID:22624007

When art moves the eyes: a behavioral and eye-tracking study.

PubMed

Massaro, Davide; Savazzi, Federica; Di Dio, Cinzia; Freedberg, David; Gallese, Vittorio; Gilli, Gabriella; Marchetti, Antonella

2012-01-01

The aim of this study was to investigate, using eye-tracking technique, the influence of bottom-up and top-down processes on visual behavior while subjects, naïve to art criticism, were presented with representational paintings. Forty-two subjects viewed color and black and white paintings (Color) categorized as dynamic or static (Dynamism) (bottom-up processes). Half of the images represented natural environments and half human subjects (Content); all stimuli were displayed under aesthetic and movement judgment conditions (Task) (top-down processes). Results on gazing behavior showed that content-related top-down processes prevailed over low-level visually-driven bottom-up processes when a human subject is represented in the painting. On the contrary, bottom-up processes, mediated by low-level visual features, particularly affected gazing behavior when looking at nature-content images. We discuss our results proposing a reconsideration of the definition of content-related top-down processes in accordance with the concept of embodied simulation in art perception.

Near-bottom energy cascade from subinertial flows to ocean mixing in the northeastern South China Sea

NASA Astrophysics Data System (ADS)

Zhang, Y.; Liu, Z.; Zhao, Y.; Wang, W.; Li, J.; Xu, J.

2013-12-01

The motions with different scales in the bottom boundary layer are potentially important in controlling the water mass transportation. Many physical processes are involved in transferring energy from mesoscale to small-scale motions. Recent studies suggest that subinertial flows should be taken into account in the parameterization of deep-ocean mixing besides topography and tidal forcing. Here, we present the current velocity data obtained from 2 moored downward-looking ADCPs (Acoustic Doppler Current Profiler) and 1 RCM (Recording Current Meter) moored near the bottom boundary layer at a water depth of about 2000 m in the northeastern South China Sea from 2012 to 2013. Specifically, they include an ADCP 1200 kHz deployed at 30 m, an ADCP 300 kHz deployed at 110 m, and a RCM deployed at 40 m above the seafloor. Subinertial flows were calculated from the moored current velocity data by low-pass filtering with a cutoff frequency of 0.3 cycles per day (the local inertial period is about 35 hours). The horizontal subinertial flows were quite strong with average values of 2-5 cm/s. The strong downward vertical velocity with average values of 1-2 cm/s was observed during times of weak subinertial flows. The vertical propagation during both the times of weak and strong subinertial flows can also be shown by vector spectra of horizontal near-inertial current velocity. Turbulent kinetic energy production rate estimated indirectly with the variances of ADCP velocities will be compared with the subinertial kinetic energy to detect the processes of energy cascade from mesoscale motions to small-scale oscillations. The results presented in this study can provide an observational evidence for such energy cascade near the bottom boundary layer in the deep South China Sea.

Observational characteristics of the tropopause inversion layer derived from CHAMP/GRACE radio occultations and MOZAIC aircraft data

NASA Astrophysics Data System (ADS)

Schmidt, T.; Cammas, J.-P.; Smit, H. G. J.; Heise, S.; Wickert, J.; Haser, A.

2010-12-01

In this study we discuss characteristics of the Northern Hemisphere (NH) midlatitude (40°N-60°N) tropopause inversion layer (TIL) based on two data sets. First, temperature measurements from GPS radio occultation data (CHAMP and GRACE) for the time interval 2001-2009 are used to exhibit seasonal properties of the TIL bottom height defined here as the height of the squared buoyancy frequency minimum N2 below the thermal tropopause, the TIL maximum height as the height of the N2 maximum above the tropopause, and the TIL top height as the height of the temperature maximum above the tropopause. Mean values of the TIL bottom, TIL maximum, and TIL top heights relative to the thermal tropopause for the NH midlatitudes are (-2.08 ± 0.35) km, (0.52 ± 0.10) km and (2.10 ± 0.23) km, respectively. A seasonal cycle of the TIL bottom and TIL top height is observed with values closer to the thermal tropopause during summer. Secondly, high-resolution temperature and trace gas profile measurements on board commercial aircrafts (Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program) from 2001-2008 for the NH midlatitude (40°N-60°N) region are used to characterize the TIL as a mixing layer around the tropopause. Mean TIL bottom, TIL maximum, and TIL top heights based on the MOZAIC temperature (N2) measurements confirm the results from the GPS data, even though most of the MOZAIC profiles used here are available under cyclonic situations. Further, we demonstrate that the mixing ratio gradients of ozone (O3) and carbon monoxide (CO) are suitable parameters for characterizing the TIL structure.

Dynamic relationship between ocean bottom pressure and bathymetry around northern part of Hikurangi

NASA Astrophysics Data System (ADS)

Muramoto, T.; Inazu, D.; Ito, Y.; Hino, R.; Suzuki, S.

2017-12-01

In recent years, observation using ocean bottom pressure recorders for the purpose of the evaluation of sea floor crustal deformation is in great vogue. The observation network set up for the observation of sea floor is densely spaced compared with the instrument network for the observation of ocean. Therefore, it has the characteristic that it can observe phenomena on a local scale. In this study, by using these in situ data, we discuss ocean phenomena on a local scale. In this study, we use a high-resolution ocean model (Inazu Ocean Model) driven by surface air pressure and surface wind vector published by the Japan Meteorological Agency. We perform a hindcast experiment for ocean bottom pressure anomaly from April 2013 to June 2017. Then, we compare these results with in situ data. In this study, we use observed pressure records which were recorded by autonomous type instrument spanning a period from April 2013 to June 2017 off the coast of North Island in New Zealand. Consequently, we found this model can simulate not only the amplitude but also phase of non-tidal oceanic variation of East Cape Current (ECC) off the coast of North Island of New Zealand. Then, we calculate cross-correlation coefficient between the data at the OBP sites. We revealed that the ocean bottom pressure shows different behavior on the west side from the east side of edge of the continental shelf. This result implies that the submarine slope induces a dynamic effect and contributes to the seasonal variation of ocean bottom pressure. In addition, we calculate the velocity of the surface current in this area using our model, and consider the relationship between it and ocean bottom pressure variation. Taken together, we can say that the barotropic flow in the direction of south-west extends to the bottom of the sea in this area. Therefore, the existence of local cross-isobath currents is suggested. Our result indicates bathymetry has dynamic effect to ocean circulation on local scale and at the same time the surface ocean circulation contributes to ocean bottom pressure considerably.

Optimum Design of ARC-less InGaP/GaAs DJ Solar Cell with Hetero Tunnel Junction

NASA Astrophysics Data System (ADS)

Abbasian, Sobhan; Sabbaghi-Nadooshan, Reza

2018-07-01

The operation of hetero In0.49Ga0.51P-Al0.7Ga0.3As tunnel diodes has been evaluated, and an approach for optimizing the back surface field (BSF) layer of a InGaP/GaAs dual-junction (DJ) solar cell developed. The results show that the hetero In0.49Ga0.51P-Al0.7Ga0.3As tunnel diode transferred more electrons and holes and showed less recombination between the top and bottom cells with increased efficiency ( η) in the InGaP/GaAs DJ solar cell. To achieve higher open-circuit voltage ( V oc), GaAs semiconductor was investigated to match with Al0.52In0.48P with bandgap of 2.4 eV, and replacement of the bottom cell in the InGaP/GaAs DJ solar cell with such an Al0.52In0.48P-GaAs heterojunction increased the photogeneration in this region. In the next step, addition of a BSF layer to the top cell required two BSF layers in the bottom cell to optimize the short-circuit current ( J sc) and η. The thickness and doping of the BSF layers were increased to obtain the highest η for the cell. The proposed structure was then compared with previous works. The proposed structure yielded V oc = 2.46 V, J sc = 30 mA/cm2, fill factor (FF) = 88.61%, and η = 65.51% under AM1.5 (1 sun) illumination.

Design of a backlighting structure for very large-area luminaries

NASA Astrophysics Data System (ADS)

Carraro, L.; Mäyrä, A.; Simonetta, M.; Benetti, G.; Tramonte, A.; Benedetti, M.; Randone, E. M.; Ylisaukko-Oja, A.; Keränen, K.; Facchinetti, T.; Giuliani, G.

2017-02-01

A novel approach for RGB semiconductor LED-based backlighting system is developed to satisfy the requirements of the Project LUMENTILE funded by the European Commission, whose scope is to develop a luminous electronic tile that is foreseen to be manufactured in millions of square meters each year. This unconventionally large-area surface of uniform, high-brightness illumination requires a specific optical design to keep a low production cost, while maintaining high optical extraction efficiency and a reduced thickness of the structure, as imposed by architectural design constraints. The proposed solution is based on a light-guiding layer to be illuminated by LEDs in edge configuration, or in a planar arrangement. The light guiding slab is finished with a reflective top interface and a diffusive or reflective bottom interface/layer. Patterning is used for both the top interface (punctual removal of reflection and generation of a light scattering centers) and for the bottom layer (using dark/bright printed pattern). Computer-based optimization algorithms based on ray-tracing are used to find optimal solutions in terms of uniformity of illumination of the top surface and overall light extraction efficiency. Through a closed-loop optimization process, that assesses the illumination uniformity of the top surface, the algorithm generates the desired optimized top and bottom patterns, depending on the number of LED sources used, their geometry, and the thickness of the guiding layer. Specific low-cost technologies to realize the patterning are discussed, with the goal of keeping the production cost of these very large-area luminaries below the value of 100$/sqm.

The benthoneuston of the Black Sea: Composition and environmental factors influencing its nocturnal dynamic

NASA Astrophysics Data System (ADS)

Vereshchaka, Alexander L.; Anokhina, Ludmila L.

2017-05-01

Plankton fauna nocturnally migrating from the sea-floor or near-bottom layer to the uppermost surface layer (benthoneuston) links benthic, benthopelagic, pelagic, and neustonic realms. We conducted five intervals of sampling (every 1-2 h during five nights) synchronously in the neustal (surface to 10-cm depth layer) and in the water column below to examine which taxa concentrate in the neustal, and under which circumstances they do so. We tested the following environmental factors: sea-floor biotope type, temperature, time after sunset, time to midnight, moon phase, and moon altitude. Of the 77 taxa recorded, about half (41) were found in the neustal. Among these, less than half (16) of the taxa showed a quantified attraction (by L-index) to the neustal and may be called the true benthoneuston. In contrast to the benthopelagic zone, where the contribution of the characteristic benthopelagic fauna exceeded 50%, the neustal was not dominated by a specific benthoneuston fauna. Nocturnal dynamics of the benthoneuston was mainly controlled by the proximity of the twilight time, then by the sea-floor biotope type and time to midnight. Neustonic taxa were more affected by moon illumination (moon phase and moon altitude) than those in the water column below. The benthoneuston in the studied area was represented by either juveniles or reproducing adults. This component of plankton communities is thus temporary and seasonal, at least in the temperate Black Sea. In the "high" summer-autumn season, contribution of benthoneuston to the coastal plankton communities is significant, whilst in winter this contribution may be negligible. The next step in the understanding of the role of benthoneuston should be associated with tropical areas where seasonal changes in reproduction are less distinctive and this group may represent an important permanent component of coastal communities.

A chemical perspective of day and night tropical (10°N-15°N) mesospheric inversion layers

NASA Astrophysics Data System (ADS)

Ramesh, K.; Sridharan, S.; Raghunath, K.; Rao, S. Vijaya Bhaskara

2017-03-01

The various occurrence characteristics of day and night tropical (10°N-15°N, 60°E-90°E) mesospheric inversion layers (MILs) are studied by using TIMED Sounding of the Atmosphere using Broadband Emission Radiometry satellite data products of kinetic temperature; volume mixing ratios of O, H, and O3; volume emission rates of O2 (1Δ) and OH (1.6 µm channel), and chemical heating rates due to seven dominant exothermic reactions among H, O, O2, O3, OH, HO2, and CO2 cooling rates for the year 2011. Although both dynamics and chemistry play important roles, the present study mainly focuses on the chemical processes involved in the formation of day and night MILs. It is found that the upper level height of daytime (nighttime) MIL descends (ascends) from 88 km ( 80 km) in winter to 72 km ( 90 km) in summer. The day and night inversion amplitudes are correlated with total chemical heating rates and CO2 cooling rates, and they show semi annual variation with larger (smaller) values during equinoxes (solstices). The daytime (nighttime) inversion layers are predominantly due to the exothermic reaction, R5: O + O + M → O2 + M and R6: O + O2 + M → O3 + M (R3: H + O3 → OH + O2). In addition, the CO2 causes large cooling at the top and small heating at the bottom levels of both day and night MILs. In the absence of dynamical effects, the chemical heating and CO2 cooling jointly contribute for the occurrence of day and night MILs.

Observed and modeled mesoscale variability near the Gulf Stream and Kuroshio Extension

NASA Astrophysics Data System (ADS)

Schmitz, William J.; Holland, William R.

1986-08-01

Our earliest intercomparisons between western North Atlantic data and eddy-resolving two-layer quasi-geostrophic symmetric-double-gyre steady wind-forced numerical model results focused on the amplitudes and largest horizontal scales in patterns of eddy kinetic energy, primarily abyssal. Here, intercomparisons are extended to recent eight-layer model runs and new data which allow expansion of the investigation to the Kuroshio Extension and throughout much of the water column. Two numerical experiments are shown to have realistic zonal, vertical, and temporal eddy scales in the vicinity of the Kuroshio Extension in one case and the Gulf Stream in the other. Model zonal mean speeds are larger than observed, but vertical shears are in general agreement with the data. A longitudinal displacement between the maximum intensity in surface and abyssal eddy fields as observed for the North Atlantic is not found in the model results. The numerical simulations examined are highly idealized, notably with respect to basin shape, topography, wind-forcing, and of course dissipation. Therefore the zero-order agreement between modeled and observed basic characteristics of mid-latitude jets and their associated eddy fields suggests that such properties are predominantly determined by the physical mechanisms which dominate the models, where the fluctuations are the result of instability processes. The comparatively high vertical resolution of the model is needed to compare with new higher-resolution data as well as for dynamical reasons, although the precise number of layers required either kinematically or dynamically (or numerically) has not been determined; we estimate four to six when no attempt is made to account for bottom- or near-surface-intensified phenomena.

Role of ground ice dynamics and ecological feedbacks in recent ice wedge degradation and stabilization

USGS Publications Warehouse

Mark Torre Jorgenson,; Mikhail Kanevskiy,; Yuri Shur,; Natalia Moskalenko,; Dana Brown,; Wickland, Kimberly P.; Striegl, Robert G.; Koch, Joshua C.

2015-01-01

Ground ice is abundant in the upper permafrost throughout the Arctic and fundamentally affects terrain responses to climate warming. Ice wedges, which form near the surface and are the dominant type of massive ice in the Arctic, are particularly vulnerable to warming. Yet processes controlling ice wedge degradation and stabilization are poorly understood. Here we quantified ice wedge volume and degradation rates, compared ground ice characteristics and thermal regimes across a sequence of five degradation and stabilization stages and evaluated biophysical feedbacks controlling permafrost stability near Prudhoe Bay, Alaska. Mean ice wedge volume in the top 3 m of permafrost was 21%. Imagery from 1949 to 2012 showed thermokarst extent (area of water-filled troughs) was relatively small from 1949 (0.9%) to 1988 (1.5%), abruptly increased by 2004 (6.3%) and increased slightly by 2012 (7.5%). Mean annual surface temperatures varied by 4.9°C among degradation and stabilization stages and by 9.9°C from polygon center to deep lake bottom. Mean thicknesses of the active layer, ice-poor transient layer, ice-rich intermediate layer, thermokarst cave ice, and wedge ice varied substantially among stages. In early stages, thaw settlement caused water to impound in thermokarst troughs, creating positive feedbacks that increased net radiation, soil heat flux, and soil temperatures. Plant growth and organic matter accumulation in the degraded troughs provided negative feedbacks that allowed ground ice to aggrade and heave the surface, thus reducing surface water depth and soil temperatures in later stages. The ground ice dynamics and ecological feedbacks greatly complicate efforts to assess permafrost responses to climate change.

Role of ground ice dynamics and ecological feedbacks in recent ice wedge degradation and stabilization

NASA Astrophysics Data System (ADS)

Jorgenson, M. T.; Kanevskiy, M.; Shur, Y.; Moskalenko, N.; Brown, D. R. N.; Wickland, K.; Striegl, R.; Koch, J.

2015-11-01

Ground ice is abundant in the upper permafrost throughout the Arctic and fundamentally affects terrain responses to climate warming. Ice wedges, which form near the surface and are the dominant type of massive ice in the Arctic, are particularly vulnerable to warming. Yet processes controlling ice wedge degradation and stabilization are poorly understood. Here we quantified ice wedge volume and degradation rates, compared ground ice characteristics and thermal regimes across a sequence of five degradation and stabilization stages and evaluated biophysical feedbacks controlling permafrost stability near Prudhoe Bay, Alaska. Mean ice wedge volume in the top 3 m of permafrost was 21%. Imagery from 1949 to 2012 showed thermokarst extent (area of water-filled troughs) was relatively small from 1949 (0.9%) to 1988 (1.5%), abruptly increased by 2004 (6.3%) and increased slightly by 2012 (7.5%). Mean annual surface temperatures varied by 4.9°C among degradation and stabilization stages and by 9.9°C from polygon center to deep lake bottom. Mean thicknesses of the active layer, ice-poor transient layer, ice-rich intermediate layer, thermokarst cave ice, and wedge ice varied substantially among stages. In early stages, thaw settlement caused water to impound in thermokarst troughs, creating positive feedbacks that increased net radiation, soil heat flux, and soil temperatures. Plant growth and organic matter accumulation in the degraded troughs provided negative feedbacks that allowed ground ice to aggrade and heave the surface, thus reducing surface water depth and soil temperatures in later stages. The ground ice dynamics and ecological feedbacks greatly complicate efforts to assess permafrost responses to climate change.

Biotronics

DTIC Science & Technology

2012-11-01

BLOCKING LAYER IN ORGANIC LIGHT EMITTING DIODES ............................70 2.3.1 Materials Used for the Fabrication of BioLEDs...optical losses. Using a lower molecular weight DNA-based biopolymer as the top and bottom cladding layers in an NLO polymer EO modulator, we were able...application, these new biopolymer -based materials have been used for many types of electronic and photonic applications. Even with growing research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubin, H.; Bemporad, G.A.

The advanced solar pond (ASP) is characterized by having two thermal layers. The homogeneous thermal layer is adjacent to the pond bottom. On top of this layer a stratified thermal layer is located. One of the major advantages of the solar pond (SP) stems from its capability to store large quantities of thermal energy. In cases of excessive needs for thermal energy, the flow of the thermal layers may be subject to turbulent flow conditions. In this paper the effect of such conditions on transport phenomena in the ASP is analyzed. The analysis indicates that whereas the homogeneous thermal layermore » flows turbulently, the stratified thermal layer may be subject to laminar flow.« less

Achieving Campus Sustainability: Top-Down, Bottom-Up, or Neither?

ERIC Educational Resources Information Center

Brinkhurst, Marena; Rose, Peter; Maurice, Gillian; Ackerman, Josef Daniel

2011-01-01

Purpose: The dynamics of organizational change related to environmental sustainability on university campuses are examined in this article. Whereas case studies of campus sustainability efforts tend to classify leadership as either "top-down" or "bottom-up", this classification neglects consideration of the leadership roles of…

Experimental and Numerical Investigation of Internal Gravity Waves Excited by Turbulent Penetrative Convection in Water Around Its Density Maximum

NASA Astrophysics Data System (ADS)

Perrard, Stéphane; Le Bars, Michaël; Le Gal, Patrice

This study is devoted to the experimental and numerical analysis of the excitation of gravity waves by turbulent convection. This situation is representative of many geophysical or astrophysical systems such as the convective bottom layer of the atmosphere that radiates internal waves in the stratosphere, or the interaction between the convective and the radiative zones in stars. In our experiments, we use water as a working fluid as it possesses the remarkable property of having a maximum density at 4 °C. Therefore, when establishing on a water layer a temperature gradient between 0 °C at the bottom and room temperature at the top, a turbulent convective region appears spontaneously under a stably stratified zone. In these conditions, gravity waves are excited by the convective fluid motions penetrating the stratified layer. Although this type of flow, called penetrative convection, has already been described, we present here the first velocity field measurement of wave emission and propagation. We show in particular that an intermediate layer that we call the buffer layer emerges between the convective and the stratified zones. In this buffer layer, the angle of propagation of the waves varies with the altitude since it is slaved to the Brunt-Väisälä frequency which evolves rapidly between the convective and the stratified layer. A minimum angle is reached at the end of the buffer layer. Then we observe that an angle of propagation is selected when the waves travel through the stratified layer. We expect this process of wave selection to take place in natural situations.

Structure and properties of small molecule-polymer blend semiconductors for organic thin film transistors.

PubMed

Kang, Jihoon; Shin, Nayool; Jang, Do Young; Prabhu, Vivek M; Yoon, Do Y

2008-09-17

A comprehensive structural and electrical characterization of solution-processed blend films of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) semiconductor and poly(alpha-methylstyrene) (PalphaMS) insulator was performed to understand and optimize the blend semiconductor films, which are very attractive as the active layer in solution-processed organic thin-film transistors (OTFTs). Our study, based on careful measurements of specular neutron reflectivity and grazing-incidence X-ray diffraction, showed that the blends with a low molecular-mass PalphaMS exhibited a strong segregation of TIPS-pentacene only at the air interface, but surprisingly the blends with a high molecular-mass PalphaMS showed a strong segregation of TIPS-pentacene at both air and bottom substrate interfaces with high crystallinity and desired orientation. This finding led to the preparation of a TIPS-pentacene/PalphaMS blend active layer with superior performance characteristics (field-effect mobility, on/off ratio, and threshold voltage) over those of neat TIPS-pentacene, as well as the solution-processability of technologically attractive bottom-gate/bottom-contact OTFT devices.

Contribution of topographically generated submesoscale turbulence to Southern Ocean overturning

NASA Astrophysics Data System (ADS)

Ruan, Xiaozhou; Thompson, Andrew F.; Flexas, Mar M.; Sprintall, Janet

2017-11-01

The ocean's global overturning circulation regulates the transport and storage of heat, carbon and nutrients. Upwelling across the Southern Ocean's Antarctic Circumpolar Current and into the mixed layer, coupled to water mass modification by surface buoyancy forcing, has been highlighted as a key process in the closure of the overturning circulation. Here, using twelve high-resolution hydrographic sections in southern Drake Passage, collected with autonomous ocean gliders, we show that Circumpolar Deep Water originating from the North Atlantic, known as Lower Circumpolar Deep Water, intersects sloping topography in narrow and strong boundary currents. Observations of strong lateral buoyancy gradients, enhanced bottom turbulence, thick bottom mixed layers and modified water masses are consistent with growing evidence that topographically generated submesoscale flows over continental slopes enhance near-bottom mixing, and that cross-density upwelling occurs preferentially over sloping topography. Interactions between narrow frontal currents and topography occur elsewhere along the path of the Antarctic Circumpolar Current, which leads us to propose that such interactions contribute significantly to the closure of the overturning in the Southern Ocean.

Paradigm shift from self-assembly to commanded assembly of functional materials: recent examples in porphyrin/fullerene supramolecular systems

NASA Astrophysics Data System (ADS)

Li, Mao; Ishihara, Shinsuke; Ji, Qingmin; Akada, Misaho; Hill, Jonathan P.; Ariga, Katsuhiko

2012-10-01

Current nanotechnology based on top-down nanofabrication may encounter a variety of drawbacks in the near future so that development of alternative methods, including the so-called bottom-up approach, has attracted considerable attention. However, the bottom-up strategy, which often relies on spontaneous self-assembly, might be inefficient in the development of the requisite functional materials and systems. Therefore, assembly processes controlled by external stimuli might be a plausible strategy for the development of bottom-up nanotechnology. In this review, we demonstrate a paradigm shift from self-assembly to commanded assembly by describing several examples of assemblies of typical functional molecules, i.e. porphyrins and fullerenes. In the first section, we describe recent progress in the design and study of self-assembled and co-assembled supramolecular architectures of porphyrins and fullerenes. Then, we show examples of assembly induced by external stimuli. We emphasize the paradigm shift from self-assembly to commanded assembly by describing the recently developed electrochemical-coupling layer-by-layer (ECC-LbL) methodology.

Observations on Cretaceous abyssal hills in the northeast Pacific

USGS Publications Warehouse

Eittreim, S.L.; Piper, D.Z.; Chezar, H.; Jones, D.R.; Kaneps, A.

1984-01-01

An abyssal hills area of 50 ?? 60 km in the northeast Pacific was studied using bottom transponder navigation, closely spaced survey lines, and long-traverse oblique photography. The block-faulted north-south hills are bounded by scarps, commonly with 40?? slopes. On these steep scarps sedimentation is inhibited and pillow basalts often crop out. An ash layer of high acoustic reflectivity at about 7 m subbottom depth blankets the area. This ash occurs in multiple beds altered to phillipsite and is highly consolidated. A 24 m.y. age for the ash is based on ichthyolith dates from samples in the overlying sediments. Acoustically transparent Neogene sediments above the ash are thickest in trough bottoms and are absent or thin on steep slopes. These Neogene sediments are composed of pale-brown pelagic clays of illite, quartz, smectite, chlorite and kaolinite. Dark-brown pelagic clays, rich in smectite and amorphous iron oxides, underlie the Neogene surficial sediments. Manganese nodules cover the bottom in varying percentages. The nodules are most abundant near basement outcrops and where the subbottom ash layer is absent. ?? 1984.

Waves plus currents at a right angle: The rippled bed case

NASA Astrophysics Data System (ADS)

Faraci, C.; Foti, E.; Musumeci, R. E.

2008-07-01

The present paper deals with wave plus current flow over a fixed rippled bed. More precisely, modifications of the current profiles due to the superimposition of orthogonal cylindrical waves have been investigated experimentally. Since the experimental setup permitted only the wave dominated regime to be investigated (i.e., the regime where orbital velocity is larger than current velocity), also a numerical k-ɛ turbulence closure model has been developed in order to study a wider range of parameters, thus including the current dominated regime (i.e., where current velocity is larger than wave orbital one). In both cases a different response with respect to the flat bed case has been found. Indeed, in the flat bed case laminar wave boundary layers in a wave dominated regime induce a decrease in bottom shear stresses, while the presence of a rippled bed behaves as a macroroughness, which causes the wave boundary layer to become turbulent and therefore the current velocity near the bottom to be smaller than the one in the case of current only, with a consequent increase in the current bottom roughness.

Two-level magnetovariational measurements for the determination of underground resistivity distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patella, D.; Siniscalchi, A.

1994-07-01

The authors investigate, from a theoretical point of view, the possibility of performing marine two-level magnetovariational measurements. An apparent resistivity function is defined and calculated after solving the differential equation governing the behavior of the natural magnetic field variations inside a one-dimensional earth. In order to generalize the problem, a frequency-dependent resistivity is assumed to characterize the layers and the distortions caused by the polarization effects are carefully analyzed. The computation of three-layer amplitude and phase diagrams for the apparent resistivity function shows that, in the case of an intermediate polarizable layer, sandwiched between a non-dispersive overburden and substratum, themore » H-type sequence results are the most affected by the dispersion phenomenon as it occurs in magnetotellurics. Finally they consider the problem of the sensitivity of the method, since, in practice, it requires top and bottom sensors separated by a vertical finite distance. It is found that in the higher-frequency range, due to the strong attenuation of the relative components of the field, the depth of the bottom sensor must be small enough to guarantee detectable signals, well above the full-scale resolution of the acquisition system. Conversely, in the lower-frequency range such a depth must be large enough to allow the difference between the top and bottom signals to be above the same recording sensitivity threshold.« less

Inverted, Organic WORM Device Based on PEDOT:PSS with Very Low Turn-On Voltage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nawrocki, Robert A.; Galiger, Erin M.; Ostrowski, David P.

An organic Write-Once-Read-Many (WORM) device based on poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) as the active layer was fabricated with an inverted architecture. Insertion of an ultrathin layer of poly(methylmethacrylate) (PMMA) between the bottom electrode and the PEDOT:PSS resulted in a systematic and substantial decrease in turn-on voltage, from 7.0 V to less than 1.0 V. An optimal thickness of the PMMA layer was found to yield the lowest consistent turn-on voltage of ~0.8 V, with 0.5 V being the lowest value of all fabricated devices. The switching mechanism was attributed to filamentary doping of the PEDOT:PSS. Insertion of the PMMA acted tomore » protect the underlying ZnO from being etched by the acidic PEDOT:PSS as well as to improve its wetting properties. Moreover, devices were demonstrated on both ITO and aluminum bottom electrodes, with aluminum yielding the highest ON/OFF ratios in the study. Owing to their inverted architecture, the devices demonstrated good stability, and the retention time of the ON-state was determined to be greater than twenty months while stored in air for devices with ITO bottom electrodes. Blade-coating was demonstrated as a viable processing technique for applications requiring rapid or large-area manufacturing in addition to deposition via spin-coating.« less

Pathways of basal meltwater from Antarctic ice shelves: A model study

NASA Astrophysics Data System (ADS)

Kusahara, Kazuya; Hasumi, Hiroyasu

2014-09-01

We investigate spreading pathways of basal meltwater released from all Antarctic ice shelves using a circumpolar coupled ice shelf-sea ice-ocean model that reproduces major features of the Southern Ocean circulation, including the Antarctic Circumpolar Current (ACC). Several independent virtual tracers are used to identify detailed pathways of basal meltwaters. The spreading pathways of the meltwater tracers depend on formation sites, because the meltwaters are transported by local ambient ocean circulation. Meltwaters from ice shelves in the Weddell and Amundsen-Bellingshausen Seas in surface/subsurface layers are effectively advected to lower latitudes with the ACC. Although a large portion of the basal meltwaters is present in surface and subsurface layers, a part of the basal meltwaters penetrates into the bottom layer through active dense water formation along the Antarctic coastal margins. The signals at the seafloor extend along the topography, showing a horizontal distribution similar to the observed spreading of Antarctic Bottom Water. Meltwaters originating from ice shelves in the Weddell and Ross Seas and in the Indian sector significantly contribute to the bottom signals. A series of numerical experiments in which thermodynamic interaction between the ice shelf and ocean is neglected regionally demonstrates that the basal meltwater of each ice shelf impacts sea ice and/or ocean thermohaline circulation in the Southern Ocean. This article was corrected on 10 OCT 2014. See the end of the full text for details.

Experimenting with mixing and layered convection in phono-trachytic magmas: Implications on reservoir dynamics

NASA Astrophysics Data System (ADS)

de Campos, C. P.; Civetta, L.; Dingwell, D. B.; Perugini, D.; Petrelli, M.; Fehr, T. K.

2006-12-01

Abundant geochemical and volcanological data on the Campanian Ignimbrite, (>200 km3, 39 ka) Phlegrean Fields, Italy, support the existence of a layered magmatic reservoir, which evolved via 1) replenishment of the chamber with trachytic magma and 2) short-term pre-eruptive mixing between new trachytic and phono- trachytic resident magmas. We have initiated an experimental program in order to constrain the dynamics of such mingling/mixing events. We used melted natural products from these two magmas of sub-equal but distinct composition, which are thought to have been involved in the origin of this magmatic system as end-members (phono-trachyte = end- member A and trachyte = end-member B). The two were then stirred together and sampled by experiment termination as a time series, ranging from 1-hour up to 1-week. Stirring under constant low flow velocity (0.5 rotations per minute) generated at first homogenization and mixing of the starting compositions. Then separate convection cells and compositional layering for major and minor elements emerged. Calculated density distributions along sections from the experimental glasses, after decoupling, are very similar to density distributions in aqueous systems under double-diffusive convection. In order to test double- diffusive decoupled convection in this system, we performed 87Sr/86Sr-isotopic and Sr- LA-ICP-MS- measurements, using the 25-hour experimental glasses. The effective chemical separation of different convection cells has been confirmed with clearly distinct isotopic signatures for both bottom and top cells. Comparison with natural samples from the Campanian Ignimbrite strengthens the importance of the role of a double-diffusive similar convection as a major differentiation process leading to layering in this system. Our results support the effectiveness of a DDC-driven fractionation for moderately high-silica magmas under high near-liquidus temperatures, before the onset of fractional crystallization.

Assessment of pseudo-bilayer structures in the heterogate germanium electron-hole bilayer tunnel field-effect transistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padilla, J. L., E-mail: jose.padilladelatorre@epfl.ch; Alper, C.; Ionescu, A. M.

2015-06-29

We investigate the effect of pseudo-bilayer configurations at low operating voltages (≤0.5 V) in the heterogate germanium electron-hole bilayer tunnel field-effect transistor (HG-EHBTFET) compared to the traditional bilayer structures of EHBTFETs arising from semiclassical simulations where the inversion layers for electrons and holes featured very symmetric profiles with similar concentration levels at the ON-state. Pseudo-bilayer layouts are attained by inducing a certain asymmetry between the top and the bottom gates so that even though the hole inversion layer is formed at the bottom of the channel, the top gate voltage remains below the required value to trigger the formation of themore » inversion layer for electrons. Resulting benefits from this setup are improved electrostatic control on the channel, enhanced gate-to-gate efficiency, and higher I{sub ON} levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures.« less

Sequence control of phase separation and dewetting in PS/PVME blend thin films by changing molecular weight of PS.

PubMed

Xia, Tian; Qin, Yaping; Huang, Yajiang; Huang, Ting; Xu, Jianhui; Li, Youbing

2016-11-28

The morphology evolution mechanism of polystyrene (PS)/poly (vinyl methyl ether) (PVME) blend thin films with different PS molecular weights (M w ) was studied. It was found that the morphology evolution was closely related to the molecular weight asymmetry between PS and PVME. In the film where M w (PS) ≈ M w (PVME), dewetting happened at the interface between the bottom layer and substrate after SD phase separation. While in the film where M w (PS) > M w (PVME), dewetting happened at the interface between the middle PS/PVME blend layer and bottom PVME layer near the substrate prior to phase separation. The different sequences of phase separation and dewetting and different interface for dewetting occurrence were studied by regarding the competitive effects of viscoelasticity contrast between polymer components and preferential wetting between PVME and the substrate. The viscoelastic nature of the PS component played a crucial role in the sequence of phase separation and dewetting.

Stacking-dependent electronic property of trilayer graphene epitaxially grown on Ru(0001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Que, Yande; Xiao, Wende, E-mail: wdxiao@iphy.ac.cn, E-mail: hjgao@iphy.ac.cn; Chen, Hui

The growth, atomic structure, and electronic property of trilayer graphene (TLG) on Ru(0001) were studied by low temperature scanning tunneling microscopy and spectroscopy in combined with tight-binding approximation (TBA) calculations. TLG on Ru(0001) shows a flat surface with a hexagonal lattice due to the screening effect of the bottom two layers and the AB-stacking in the top two layers. The coexistence of AA- and AB-stacking in the bottom two layers leads to three different stacking orders of TLG, namely, ABA-, ABC-, and ABB-stacking. STS measurements combined with TBA calculations reveal that the density of states of TLG with ABC- andmore » ABB-stacking is characterized by one and two sharp peaks near to the Fermi level, respectively, in contrast to the V-shaped feature of TLG with ABA-stacking. Our work demonstrates that TLG on Ru(0001) might be an ideal platform for exploring stacking-dependent electronic properties of graphene.« less

Reduction of bonding resistance of two-terminal III-V/Si tandem solar cells fabricated using smart-stack technology

NASA Astrophysics Data System (ADS)

Baba, Masaaki; Makita, Kikuo; Mizuno, Hidenori; Takato, Hidetaka; Sugaya, Takeyoshi; Yamada, Noboru

2017-12-01

This paper describes a method that remarkably reduces the bonding resistance of mechanically stacked two-terminal GaAs/Si and InGaP/Si tandem solar cells, where the top and bottom cells are bonded using a Pd nanoparticle array. A transparent conductive oxide (TCO) layer, which partially covers the surface of the Si bottom cell below the electrodes of the III-V top cell, significantly enhances the fill factor (FF) and cell conversion efficiency. The partial TCO layer reduces the bonding resistance and thus, increases the FF and efficiency of InGaP/Si by factors of 1.20 and 1.11, respectively. Eventually, the efficiency exceeds 15%. Minimizing the optical losses at the bonding interfaces of the TCO layer is important in the fabrication of high-efficiency solar cells. To help facilitate this, the optical losses in the tandem solar cells are thoroughly characterized through optical simulations and experimental verifications.

Electrical in-situ characterisation of interface stabilised organic thin-film transistors

PubMed Central

Striedinger, Bernd; Fian, Alexander; Petritz, Andreas; Lassnig, Roman; Winkler, Adolf; Stadlober, Barbara

2015-01-01

We report on the electrical in-situ characterisation of organic thin film transistors under high vacuum conditions. Model devices in a bottom-gate/bottom-contact (coplanar) configuration are electrically characterised in-situ, monolayer by monolayer (ML), while the organic semiconductor (OSC) is evaporated by organic molecular beam epitaxy (OMBE). Thermal SiO2 with an optional polymer interface stabilisation layer serves as the gate dielectric and pentacene is chosen as the organic semiconductor. The evolution of transistor parameters is studied on a bi-layer dielectric of a 150 nm of SiO2 and 20 nm of poly((±)endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, diphenylester) (PNDPE) and compared to the behaviour on a pure SiO2 dielectric. The thin layer of PNDPE, which is an intrinsically photo-patternable organic dielectric, shows an excellent stabilisation performance, significantly reducing the calculated interface trap density at the OSC/dielectric interface up to two orders of magnitude, and thus remarkably improving the transistor performance. PMID:26457122

Numerical study of compressible magnetoconvection with an open transitional boundary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanami, H.; Tajima, T.

1990-08-01

We study by computer simulation nonlinear evolution of magnetoconvection in a system with a dynamical open boundary between the convection region and corona of the sun. We study a model in which the fluid is subject to the vertical gravitation, magnetohydrodynamics (MHD), and high stratification, through an MHD code with the MacCormack-Donner cell hybrid scheme in order to well represent convective phenomena. Initially the vertical fluid flux penetrates from the convectively unstable zone at the bottom into the upper diffuse atmosphere. As the instability develops, the magnetic fields are twisted by the convection motion and the folding magnetic fields ismore » observed. When the magnetic pressure is comparable to the thermal pressure in the upper layer of convective zone, strong flux expulsion from the convective cell interior toward the cell boundary appears. Under appropriate conditions our simulation exhibits no shock formation incurred by the fluid convected to the photosphere, in contrast to earlier works with box boundaries. The magnetic field patterns observed are those of concentrated magnetic flux tubes, accumulation of dynamo flux near the bottom boundary, pinched flux near the downdraft region, and the surface movement of magnetic flux toward the downdraft region. Many of these computationally observed features are reminiscent of solar observations of the fluid and magnetic structures of their motions.« less

3D LDV Measurements in Oscillatory Boundary Layers

NASA Astrophysics Data System (ADS)

Mier, J. M.; Garcia, M. H.

2012-12-01

The oscillatory boundary layer represents a particular case of unsteady wall-bounded flows in which fluid particles follow a periodic sinusoidal motion. Unlike steady boundary layer flows, the oscillatory flow regime and bed roughness character change in time along the period for every cycle, a characteristic that introduces a high degree of complexity in the analysis of these flows. Governing equations can be derived from the general Navier-Stokes equations for the motion of fluids, from which the exact solution for the laminar oscillatory boundary layer is obtained (also known as the 2nd Stokes problem). No exact solution exists for the turbulent case, thus, understanding of the main flow characteristics comes from experimental work. Several researchers have reported experimental work in oscillatory boundary layers since the 1960's; however, larger scale facilities and the development of newer measurement techniques with improved temporal and spatial resolution in recent years provides a unique opportunity to achieve a better understanding about this type of flows. Several experiments were performed in the Large Oscillatory Water and Sediment Tunnel (LOWST) facility at the Ven Te Chow Hydrosystems Laboratory, for a range of Reynolds wave numbers between 6x10^4 < Rew < 6x10^6 over a flat and smooth bottom. A 3D Laser Doppler Velocimetry (LDV) system was used to measure instantaneous flow velocities with a temporal resolution up to ~ 1,000 Hz. It was mounted on a 3-axis traverse with a spatial resolution of 0.01 mm in all three directions. The closest point to the bottom was measured at z = 0.2 mm (z+ ≈ 4), which allowed to capture boundary layer features with great detail. In order to achieve true 3D measurements, 2 probes were used on a perpendicular configuration, such that u and w components were measured from a probe on the side of the flume and v component was measured from a probe pointing down through and access window on top of the flume. The top probe was submerged in a water container, such that the focal length remained constant and coincidence in the measurement volume for all 3 components was maintained when traversing the probes along the measurement profiles. Results show the existence of high turbulence levels inside the boundary layer up to about 30 mm away from the bottom. The streamwise component u shows greater intensities closer to the bottom and ahead of the freestream velocity maximum. On the contrary, the vertical component w shows smaller values of turbulent intensity, located higher up in the profile and lagging with respect to the freestream velocity maximum. Meanwhile, the spanwise component v shows similar intensities than w, happening in phase with it, but distributed all along the boundary layer, overlapping the areas of greater intensity of u and w. In addition, wall shear stress and other turbulent magnitudes related to the boundary layer were analyzed from the experimental results obtained through this research.

Preferential growth and enhanced dielectric properties of Ba0.7Sr0.3TiO3 thin films with preannealed Pt bottom electrode

NASA Astrophysics Data System (ADS)

Zhu, Xiaohong; Defaÿ, Emmanuel; Aïd, Marc; Ren, Yinjuan; Zhang, Caiyun; Zhu, Jiliang; Zhu, Jianguo; Xiao, Dingquan

2013-03-01

Ba0.7Sr0.3TiO3 (BST) thin films, about 100 nm in thickness, were prepared on unannealed and 700 °C-preannealed Pt bottom electrodes by the ion beam sputtering and post-deposition annealing method. It was found that the preannealed Pt layer has a more compact structure, making it not only a bottom electrode but also a good template for high-quality BST thin film growth. The BST films deposited on preannealed Pt bottom electrodes showed (0 0 l)-preferred orientation, dense and uniform microstructure with no intermediate phase formed at the film/electrode interface, and thus enhanced dielectric properties. As a result, the typical relative dielectric constant and tunability (under a dc electric field of 1 MV cm-1) reach 180 and 50.1%, respectively, for the BST thin films with preannealed Pt bottom electrodes, which are significantly higher than those (166 and 41.3%, respectively) for the BST thin films deposited on unannealed Pt bottom electrodes.

Nucleation sites of Ge nanoislands grown on pit-patterned Si substrate prepared by electron-beam lithography

NASA Astrophysics Data System (ADS)

Smagina, Zh. V.; Zinovyev, V. A.; Rudin, S. A.; Novikov, P. L.; Rodyakina, E. E.; Dvurechenskii, A. V.

2018-04-01

Regular pit-patterned Si(001) substrates were prepared by electron-beam lithography followed by plasma chemical etching. The geometry of the pits was controlled by varying the etching conditions and the electron-beam exposure duration. It was shown that the location of three-dimensional (3D) Ge nanoislands subsequently grown on the pit-patterned Si substrates depends on the shape of the pit bottom. In the case of pits having a sharp bottom, 3D Ge islands nucleate inside the pits. For pits with a wide flat bottom, the 3D Ge island nucleation takes place at the pit periphery. This effect is attributed to the strain relaxation depending not only on the initial pit shape, but also on its evolution during the Ge wetting layer deposition. It was shown by Monte Carlo simulations that in the case of a pit with a pointed bottom, the relaxation is most effective inside the pit, while for a pit with a wide bottom, the most relaxed area migrates during Ge deposition from the pit bottom to its edges, where 3D Ge islands nucleate.

Remote sensing of Earth terrain

NASA Technical Reports Server (NTRS)

Kong, Jin AU

1987-01-01

Earth terrain covers were modeled as random media characterized by different dielectric constants and correlation functions. In order to model sea ice with brine inclusions and vegetation with row structures, the random medium is assumed to be anisotropic. A three layer model is used to simulate a vegetation field or a snow covered ice field with the top layer being snow or leaves, the middle layer being ice or trunks, and the bottom layer being sea water or ground. The strong fluctuation theory with the distorted Born approximation is applied to the solution of the radar backscattering coefficients.

Peclet number analysis of cross-flow in porous gas diffusion layer of polymer electrolyte membrane fuel cell (PEMFC).

PubMed

Suresh, P V; Jayanti, Sreenivas

2016-10-01

Adoption of hydrogen economy by means of using hydrogen fuel cells is one possible solution for energy crisis and climate change issues. Polymer electrolyte membrane (PEM) fuel cell, which is an important type of fuel cells, suffers from the problem of water management. Cross-flow is induced in some flow field designs to enhance the water removal. The presence of cross-flow in the serpentine and interdigitated flow fields makes them more effective in proper distribution of the reactants on the reaction layer and evacuation of water from the reaction layer than diffusion-based conventional parallel flow fields. However, too much of cross-flow leads to flow maldistribution in the channels, higher pressure drop, and membrane dehydration. In this study, an attempt has been made to quantify the amount of cross-flow required for effective distribution of reactants and removal of water in the gas diffusion layer. Unit cells containing two adjacent channels with gas diffusion layer (GDL) and catalyst layer at the bottom have been considered for the parallel, interdigitated, and serpentine flow patterns. Computational fluid dynamics-based simulations are carried out to study the reactant transport in under-the-rib area with cross-flow in the GDL. A new criterion based on the Peclet number is presented as a quantitative measure of cross-flow in the GDL. The study shows that a cross-flow Peclet number of the order of 2 is required for effective removal of water from the GDL. Estimates show that this much of cross-flow is not usually produced in the U-bends of Serpentine flow fields, making these areas prone to flooding.

Benthic cyanobacterial mats in the high arctic: multi-layer structure and fluorescence responses to osmotic stress.

PubMed

Lionard, Marie; Péquin, Bérangère; Lovejoy, Connie; Vincent, Warwick F

2012-01-01

Cyanobacterial mats are often a major biological component of extreme aquatic ecosystems, and in polar lakes and streams they may account for the dominant fraction of total ecosystem biomass and productivity. In this study we examined the vertical structure and physiology of Arctic microbial mats relative to the question of how these communities may respond to ongoing environmental change. The mats were sampled from Ward Hunt Lake (83°5.297'N, 74°9.985'W) at the northern coast of Arctic Canada, and were composed of three visibly distinct layers. Microsensor profiling showed that there were strong gradients in oxygen within each layer, with an overall decrease from 100% saturation at the mat surface to 0%, at the bottom, accompanied by an increase of 0.6 pH units down the profile. Gene clone libraries (16S rRNA) revealed the presence of Oscillatorian sequences throughout the mat, while Nostoc related species dominated the two upper layers, and Nostocales and Synechococcales sequences were common in the bottom layer. High performance liquid chromatography analyses showed a parallel gradient in pigments, from high concentrations of UV-screening scytonemin in the upper layer to increasing zeaxanthin and myxoxanthin in the bottom layer, and an overall shift from photoprotective to photosynthetic carotenoids down the profile. Climate change is likely to be accompanied by lake level fluctuations and evaporative concentration of salts, and thus increased osmotic stress of the littoral mat communities. To assess the cellular capacity to tolerate increasing osmolarity on physiology and cell membrane integrity, mat sections were exposed to a gradient of increasing salinities, and PAM measurements of in vivo chlorophyll fluorescence were made to assess changes in maximum quantum yield. The results showed that the mats were tolerant of up to a 46-fold increase in salinity. These features imply that cyanobacterial mats are resilient to ongoing climate change, and that in the absence of major biological perturbations, these vertically structured communities will continue to be a prominent feature of polar aquatic ecosystems.

Subduction at upper ocean fronts by baroclinic instability

NASA Astrophysics Data System (ADS)

Verma, Vicky; Pham, Hieu T.; Radhakrishnan, Anand; Sarkar, Sutanu

2017-11-01

Large eddy simulations of upper ocean fronts that are initially in geostrophic balance show that the linear and subsequent nonlinear evolution of baroclinic intability are effective in restratifying the front. During the growth of baroclinic instability, the front develops thin regions with enhanced vertical vorticity, i.e., vorticity filaments. Moreover, the vorticity filaments organize into submesoscale eddies. The subsequent frontal dynamics is dominated by the vorticity filaments and the submesoscale eddies. Diagnosis of the horizontal force balance reveals that the regions occupied by these coherent structures have significantly large imbalance, and are characterized by large vertical velocity. High density fluid from the heavier side of the front is subducted by the vertical velocity to the bottom of the mixed layer. The process of subduction is illustrated by Lagrangian tracking of fluid particles released at a fixed depth.

Modeling of electron-specimen interaction in scanning electron microscope for e-beam metrology and inspection: challenges and perspectives

NASA Astrophysics Data System (ADS)

Suzuki, Makoto; Kameda, Toshimasa; Doi, Ayumi; Borisov, Sergey; Babin, Sergey

2018-03-01

The interpretation of scanning electron microscopy (SEM) images of the latest semiconductor devices is not intuitive and requires comparison with computed images based on theoretical modeling and simulations. For quantitative image prediction and geometrical reconstruction of the specimen structure, the accuracy of the physical model is essential. In this paper, we review the current models of electron-solid interaction and discuss their accuracy. We perform the comparison of the simulated results with our experiments of SEM overlay of under-layer, grain imaging of copper interconnect, and hole bottom visualization by angular selective detectors, and show that our model well reproduces the experimental results. Remaining issues for quantitative simulation are also discussed, including the accuracy of the charge dynamics, treatment of beam skirt, and explosive increase in computing time.

Fans on Crater Rims

NASA Image and Video Library

2016-12-14

Gas under pressure will choose an easy escape route. In this image, the terrain is covered with a seasonal layer of dry ice. The weak spots, for gas sublimating from the bottom of the seasonal ice layer to escape, appear to be around craters, where the surface was broken and pulverized by an impact. Fans of surface material deposited on top of the seasonal ice layer show where the escape vents are. http://photojournal.jpl.nasa.gov/catalog/PIA21271

Mobile Bay river plume mixing in the inner shelf

NASA Astrophysics Data System (ADS)

Parra, S. M.; Book, J. W.; Warner, S. J.; Moum, J.

2017-12-01

The microtidal region (0.5 m spring tides) of the inner shelf outside Mobile Bay presented a complex circulation pattern driven by the pulsed river discharge and winds. Currents, salinity, temperature, and turbulence profiles were measured for up to three weeks in April 2016 at six moorings outside Mobile Bay. Currents varied between locations and with depth. During neap and spring tides the currents were reliably >0.4 and <0.4 m/s, respectively. The outflow from Mobile Bay generated a complex density circulation, where two to three layers were normally present. Multiple density layers included a thicker brackish middle layer (5-10 m thickness), and a salty bottom layer (5-10 m thickness), with a thin ( 1-3 m) freshwater surface layer found intermittently. The multilayer currents were strongest at neap tides (>0.5 m/s) and toward deeper waters, concurrent with the strongest stratification. The possible flow drivers considered include tides, winds, inertial oscillations, waves, and stratification. Turbulent kinetic energy production and dissipation were calculated with multiple methods using data from bottom-mounted, upward-looking acoustic Doppler current profilers sampling at 1 Hz, and using data from line-moored chi-pod turbulent temperature microstructure instruments sampling at 100 Hz. This work explores different forcing mechanisms involved in modulating the circulation and turbulence in a multi-layered pulsed-river inner shelf region in the Gulf of Mexico.

Application of the top specified boundary layer (TSBL) approximation to initial characterization of an inland aquifer mineralization: 2. Seepage of saltwater through semi-confining layers

USGS Publications Warehouse

Rubin, H.; Buddemeier, R.W.

1998-01-01

This paper presents a generalized basic study that addresses practical needs for an understanding of the major mechanisms involved in the mineralization of groundwater in the Great Bend Prairie aquifer in south- central Kansas. This Quaternary alluvial aquifer and associated surface waters are subject to contamination by saltwater, which in some areas seeps from the deeper Permian bedrock formation into the overlying freshwater aquifer through semiconfining layers. A simplified conceptual model is adopted. It incorporates the freshwater aquifer whose bottom is comprised of a semiconfining layer through which a hydrologically minor but geochemically important saline water discharge seeps into the aquifer. A hierarchy of approximate approaches is considered to analyze the mineralization processes taking place in the aquifer. The recently developed top specified boundary layer (TSBL) approach is very convenient to use for the initial characterization of these processes, and is further adapted to characterization of head-driven seepage through semi-confining layers. TSBL calculations indicate that the seeping saline water may create two distinct new zones in the aquifer: (1) a completely saline zone (CSZ) adjacent to the semiconfining bottom of the aquifer, and (2) a transition zone (TZ) which develops between the CSZ and the freshwater zone. Some possible scenarios associated with the various mineralization patterns are analyzed and discussed.

Optimizing pentacene thin-film transistor performance: Temperature and surface condition induced layer growth modification.

PubMed

Lassnig, R; Hollerer, M; Striedinger, B; Fian, A; Stadlober, B; Winkler, A

2015-11-01

In this work we present in situ electrical and surface analytical, as well as ex situ atomic force microscopy (AFM) studies on temperature and surface condition induced pentacene layer growth modifications, leading to the selection of optimized deposition conditions and entailing performance improvements. We prepared p ++ -silicon/silicon dioxide bottom-gate, gold bottom-contact transistor samples and evaluated the pentacene layer growth for three different surface conditions (sputtered, sputtered + carbon and unsputtered + carbon) at sample temperatures during deposition of 200 K, 300 K and 350 K. The AFM investigations focused on the gold contacts, the silicon dioxide channel region and the highly critical transition area. Evaluations of coverage dependent saturation mobilities, threshold voltages and corresponding AFM analysis were able to confirm that the first 3-4 full monolayers contribute to the majority of charge transport within the channel region. At high temperatures and on sputtered surfaces uniform layer formation in the contact-channel transition area is limited by dewetting, leading to the formation of trenches and the partial development of double layer islands within the channel region instead of full wetting layers. By combining the advantages of an initial high temperature deposition (well-ordered islands in the channel) and a subsequent low temperature deposition (continuous film formation for low contact resistance) we were able to prepare very thin (8 ML) pentacene transistors of comparably high mobility.

Optimizing pentacene thin-film transistor performance: Temperature and surface condition induced layer growth modification

PubMed Central

Lassnig, R.; Hollerer, M.; Striedinger, B.; Fian, A.; Stadlober, B.; Winkler, A.

2015-01-01

In this work we present in situ electrical and surface analytical, as well as ex situ atomic force microscopy (AFM) studies on temperature and surface condition induced pentacene layer growth modifications, leading to the selection of optimized deposition conditions and entailing performance improvements. We prepared p++-silicon/silicon dioxide bottom-gate, gold bottom-contact transistor samples and evaluated the pentacene layer growth for three different surface conditions (sputtered, sputtered + carbon and unsputtered + carbon) at sample temperatures during deposition of 200 K, 300 K and 350 K. The AFM investigations focused on the gold contacts, the silicon dioxide channel region and the highly critical transition area. Evaluations of coverage dependent saturation mobilities, threshold voltages and corresponding AFM analysis were able to confirm that the first 3–4 full monolayers contribute to the majority of charge transport within the channel region. At high temperatures and on sputtered surfaces uniform layer formation in the contact–channel transition area is limited by dewetting, leading to the formation of trenches and the partial development of double layer islands within the channel region instead of full wetting layers. By combining the advantages of an initial high temperature deposition (well-ordered islands in the channel) and a subsequent low temperature deposition (continuous film formation for low contact resistance) we were able to prepare very thin (8 ML) pentacene transistors of comparably high mobility. PMID:26543442

Convection in three dimensions with surface plates - Generation of toroidal flow

NASA Technical Reports Server (NTRS)

Gable, Carl W.; O'Connell, Richard J.; Travis, Bryan J.

1991-01-01

This work presents numerical calculations of mantle convection that incorporate some of the basic observational constraints imposed by plate tectonics. The model is three-dimensional and includes surface plates; it allows plate velocity to change dynamically according to the forces which result from convection. It is shown that plates are an effective means of introducing a toroidal component into the flow field. After initial transients the plate motion is nearly parallel to transform faults and in the direction that tends to minimize the toroidal flow field. The toroidal field decays with depth from its value at the surface; the poloidal field is relatively constant throughout the layer but falls off slightly at the top and bottom boundaries. Layered viscosity increasing with depth causes the toroidal field to decay more rapidly, effectively confining it to the upper, low-viscosity layer. The effect of viscosity layering on the poloidal field is relatively small, which is attributed to its generation by temperature variations distributed throughout the system. The generation of toroidal flow by surface plates would seem to account for the observed nearly equal energy of toroidal and poloidal fields of plate motions on the earth. A low-viscosity region in the upper mantle will cause the toroidal flow to decay significantly before reaching the lower mantle. The resulting concentration of toroidal flow in the upper mantle may result in more thorough mixing there and account for some of the geochemical and isotopic differences proposed to exist between the upper and lower mantles.

Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

USGS Publications Warehouse

Hansen, C.J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

2013-01-01

Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

Use of co-combustion bottom ash to design an acoustic absorbing material for highway noise barriers.

PubMed

Arenas, Celia; Leiva, Carlos; Vilches, Luis F; Cifuentes, Héctor

2013-11-01

The present study aims to determine and evaluate the applicability of a new product consisting of coal bottom ash mixed with Portland cement in the application of highway noise barriers. In order to effectively recycle the bottom ash, the influence of the grain particle size of bottom ash, the thickness of the panel and the combination of different layers with various particle sizes have been studied, as well as some environmental properties including leachability (EN-12457-4, NEN-7345) and radioactivity tests. Based on the obtained results, the acoustic properties of the final composite material were similar or even better than those found in porous concrete used for the same application. According to this study, the material produced presented no environmental risk. Copyright © 2013 Elsevier Ltd. All rights reserved.

Anti-Fouling Double-Skinned Forward Osmosis Membrane with Zwitterionic Brush for Oily Wastewater Treatment.

PubMed

Ong, Chi Siang; Al-Anzi, Bader; Lau, Woei Jye; Goh, Pei Sean; Lai, Gwo Sung; Ismail, Ahmad Fauzi; Ong, Yue Seong

2017-07-31

Despite its attractive features for energy saving separation, the performance of forward osmosis (FO) has been restricted by internal concentration polarization and fast fouling propensity that occur in the membrane sublayer. These problems have significantly affected the membrane performance when treating highly contaminated oily wastewater. In this study, a novel double-skinned FO membrane with excellent anti-fouling properties has been developed for emulsified oil-water treatment. The double-skinned FO membrane comprises a fully porous sublayer sandwiched between a highly dense polyamide (PA) layer for salt rejection and a fairly loose dense bottom zwitterionic layer for emulsified oil particle removal. The top dense PA layer was synthesized via interfacial polymerization meanwhile the bottom layer was made up of a zwitterionic polyelectrolyte brush - (poly(3-(N-2-methacryloxyethyl-N,N-dimethyl) ammonatopropanesultone), abbreviated as PMAPS layer. The resultant double-skinned membrane exhibited a high water flux of 13.7 ± 0.3 L/m 2 .h and reverse salt transport of 1.6 ± 0.2 g/m 2 .h under FO mode using 2 M NaCl as the draw solution and emulsified oily solution as the feed. The double-skinned membrane outperforms the single-skinned membrane with much lower fouling propensity for emulsified oil-water separation.

1/12-scale physical modeling experiments in support of tank 241-SY- 101 hydrogen mitigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fort, J.A.; Bamberger, J.A.; Bates, J.M.

1993-01-01

Hanford tank 241-SY-101 is a 75-ft-dia double-shell tank that contains approximately 1.1 M gal of radioactive fuel reprocessing waste. Core samples have shown that the tank contents are separated into two main layers, a article laden supernatant liquid at the top of the tank and a more dense slurry on the bottom. Two additional layers may be present, one being a potentially thick sludge lying beneath the slurry at the bottom of the tank and the other being the crust that has formed on the surface of the supernatant liquid. The supernatant is more commonly referred to as the convectivemore » layer and the slurry as the non-convective layer. Accumulation of gas (partly hydrogen) in the non-convective layer is suspected to be the key mechanism behind the gas burp phenomena, and several mitigation schemes are being developed to encourage a more uniform gas release rate (Benegas 1992). To support the full-scale hydraulic mitigation test, scaled experiments were performed to satisfy two objectives: 1. provide an experimental database for numerical- model validation; 2. establish operating parameter values required to mobilize the settled solids and maintain the solids in suspension.« less

1/12-scale physical modeling experiments in support of tank 241-SY- 101 hydrogen mitigation. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fort, J.A.; Bamberger, J.A.; Bates, J.M.

1993-01-01

Hanford tank 241-SY-101 is a 75-ft-dia double-shell tank that contains approximately 1.1 M gal of radioactive fuel reprocessing waste. Core samples have shown that the tank contents are separated into two main layers, a article laden supernatant liquid at the top of the tank and a more dense slurry on the bottom. Two additional layers may be present, one being a potentially thick sludge lying beneath the slurry at the bottom of the tank and the other being the crust that has formed on the surface of the supernatant liquid. The supernatant is more commonly referred to as the convectivemore » layer and the slurry as the non-convective layer. Accumulation of gas (partly hydrogen) in the non-convective layer is suspected to be the key mechanism behind the gas burp phenomena, and several mitigation schemes are being developed to encourage a more uniform gas release rate (Benegas 1992). To support the full-scale hydraulic mitigation test, scaled experiments were performed to satisfy two objectives: 1. provide an experimental database for numerical- model validation; 2. establish operating parameter values required to mobilize the settled solids and maintain the solids in suspension.« less

A simplified fourwall interference assessment procedure for airfoil data obtained in the Langley 0.3-meter transonic cryogenic tunnel

NASA Technical Reports Server (NTRS)

Murthy, A. V.

1987-01-01

A simplified fourwall interference assessment method has been described, and a computer program developed to facilitate correction of the airfoil data obtained in the Langley 0.3-m Transonic Cryogenic Tunnel (TCT). The procedure adopted is to first apply a blockage correction due to sidewall boundary-layer effects by various methods. The sidewall boundary-layer corrected data are then used to calculate the top and bottom wall interference effects by the method of Capallier, Chevallier and Bouinol, using the measured wall pressure distribution and the model force coefficients. The interference corrections obtained by the present method have been compared with other methods and found to give good agreement for the experimental data obtained in the TCT with slotted top and bottom walls.

Determination of the electrostatic potential distribution in Pt/Fe:SrTiO3/Nb:SrTiO3 thin-film structures by electron holography

NASA Astrophysics Data System (ADS)

Marchewka, Astrid; Cooper, David; Lenser, Christian; Menzel, Stephan; Du, Hongchu; Dittmann, Regina; Dunin-Borkowski, Rafal E.; Waser, Rainer

2014-11-01

We determined the electrostatic potential distribution in pristine Pt/Fe:SrTiO3/Nb:SrTiO3 structures by electron holography experiments, revealing the existence of a depletion layer extending into the Nb-doped bottom electrode. Simulations of potential profiles in metal-insulator-metal structures were conducted assuming different types and distributions of dopants. It is found that the presence of acceptor-type dopant concentrations at the Fe:SrTiO3/Nb:SrTiO3 interface with a donor-doped insulating layer provides a good match to the measured profile. Such acceptor-type interface concentrations may be associated with Sr vacancies on the Nb:SrTiO3 side of the bottom interface.

Determination of the electrostatic potential distribution in Pt/Fe:SrTiO₃/Nb:SrTiO₃ thin-film structures by electron holography.

PubMed

Marchewka, Astrid; Cooper, David; Lenser, Christian; Menzel, Stephan; Du, Hongchu; Dittmann, Regina; Dunin-Borkowski, Rafal E; Waser, Rainer

2014-11-10

We determined the electrostatic potential distribution in pristine Pt/Fe:SrTiO3/Nb:SrTiO3 structures by electron holography experiments, revealing the existence of a depletion layer extending into the Nb-doped bottom electrode. Simulations of potential profiles in metal-insulator-metal structures were conducted assuming different types and distributions of dopants. It is found that the presence of acceptor-type dopant concentrations at the Fe:SrTiO3/Nb:SrTiO3 interface with a donor-doped insulating layer provides a good match to the measured profile. Such acceptor-type interface concentrations may be associated with Sr vacancies on the Nb:SrTiO3 side of the bottom interface.

Combined Inkjet Printing and Infrared Sintering of Silver Nanoparticles using a Swathe-by-Swathe and Layer-by-Layer Approach for 3-Dimensional Structures.

PubMed

Vaithilingam, Jayasheelan; Simonelli, Marco; Saleh, Ehab; Senin, Nicola; Wildman, Ricky D; Hague, Richard J M; Leach, Richard K; Tuck, Christopher J

2017-02-22

Despite the advancement of additive manufacturing (AM)/3-dimensional (3D) printing, single-step fabrication of multifunctional parts using AM is limited. With the view of enabling multifunctional AM (MFAM), in this study, sintering of metal nanoparticles was performed to obtain conductivity for continuous line inkjet printing of electronics. This was achieved using a bespoke three-dimensional (3D) inkjet-printing machine, JETx, capable of printing a range of materials and utilizing different post processing procedures to print multilayered 3D structures in a single manufacturing step. Multiple layers of silver were printed from an ink containing silver nanoparticles (AgNPs) and infrared sintered using a swathe-by-swathe (SS) and layer-by-layer sintering (LS) regime. The differences in the heat profile for the SS and LS was observed to influence the coalescence of the AgNPs. Void percentage of both SS and LS samples was higher toward the top layer than the bottom layer due to relatively less IR exposure in the top than the bottom. The results depicted a homogeneous microstructure for LS of AgNPs and showed less deformation compared to the SS. Electrical resistivity of the LS tracks (13.6 ± 1 μΩ cm) was lower than the SS tracks (22.5 ± 1 μΩ cm). This study recommends the use of LS method to sinter the AgNPs to obtain a conductive track in 25% less time than SS method for MFAM.

Persistent and energetic bottom-trapped topographic Rossby waves observed in the southern South China Sea.

PubMed

Shu, Yeqiang; Xue, Huijie; Wang, Dongxiao; Chai, Fei; Xie, Qiang; Cai, Shuqun; Chen, Rongyu; Chen, Ju; Li, Jian; He, Yunkai

2016-04-14

Energetic fluctuations with periods of 9-14 days below a depth of 1400 m were observed in the southern South China Sea (SCS) from 5 years of direct measurements. We interpreted such fluctuations as topographic Rossby waves (TRWs) because they obey the dispersion relation. The TRWs persisted from May 24, 2009 to August 23, 2013, and their bottom current speed with a maximum of ~10 cm/s was one order of magnitude greater than the mean current and comparable to the tidal currents near the bottom. The bottom-trapped TRWs had an approximate trapping depth of 325 m and reference wavelength of ~82 km, which were likely excited by eddies above. Upper layer current speed that peaked approximately every 2 months could offer the energy sources for the persistent TRWs in the southern SCS. Energetic bottom-trapped TRWs may have a comparable role in deep circulation to tides in areas with complex topography.

Persistent and energetic bottom-trapped topographic Rossby waves observed in the southern South China Sea

PubMed Central

Shu, Yeqiang; Xue, Huijie; Wang, Dongxiao; Chai, Fei; Xie, Qiang; Cai, Shuqun; Chen, Rongyu; Chen, Ju; Li, Jian; He, Yunkai

2016-01-01

Energetic fluctuations with periods of 9–14 days below a depth of 1400 m were observed in the southern South China Sea (SCS) from 5 years of direct measurements. We interpreted such fluctuations as topographic Rossby waves (TRWs) because they obey the dispersion relation. The TRWs persisted from May 24, 2009 to August 23, 2013, and their bottom current speed with a maximum of ~10 cm/s was one order of magnitude greater than the mean current and comparable to the tidal currents near the bottom. The bottom-trapped TRWs had an approximate trapping depth of 325 m and reference wavelength of ~82 km, which were likely excited by eddies above. Upper layer current speed that peaked approximately every 2 months could offer the energy sources for the persistent TRWs in the southern SCS. Energetic bottom-trapped TRWs may have a comparable role in deep circulation to tides in areas with complex topography. PMID:27075644

Enhancement of electron injection in inverted bottom-emitting organic light-emitting diodes using Al/LiF compound thin film

NASA Astrophysics Data System (ADS)

Nie, Qu-yang; Zhang, Fang-hui

2018-05-01

The inverted bottom-emitting organic light-emitting devices (IBOLEDs) were prepared, with the structure of ITO/Al ( x nm)/LiF (1 nm)/Bphen (40 nm)/CBP: GIr1 (14%):R-4b (2%) (10 nm)/BCP (3 nm)/CBP:GIr1 (14%):R-4b (2%) (20 nm)/TCTA (10 nm)/NPB (40 nm)/MoO3 (40 nm)/Al (100 nm), where the thickness of electron injection layer Al ( x) are 0 nm, 2 nm, 3 nm, 4 nm and 5 nm, respectively. In this paper, the electron injection condition and luminance properties of inverted devices were investigated by changing the thickness of Al layer in Al/LiF compound thin film. It turns out that the introduction of Al layer can improve electron injection of the devices dramatically. Furthermore, the device exerts lower driving voltage and higher current efficiency when the thickness of electron injection Al layer is 3 nm. For example, the current efficiency of the device with 3-nm-thick Al layer reaches 19.75 cd·A-1 when driving voltage is 7 V, which is 1.24, 1.17 and 17.03 times larger than those of the devices with 2 nm, 4 nm and 5 nm Al layer, respectively. The device property reaches up to the level of corresponding conventional device. In addition, all inverted devices with electron injection Al layer show superior stability of color coordinate due to the adoption of co-evaporation emitting layer and BCP spacer-layer, and the color coordinate of the inverted device with 3-nm-thick Al layer only changes from (0.580 6, 0.405 6) to (0.532 8, 0.436 3) when driving voltage increases from 6 V to 10 V.

Multi-layer carbon-based coatings for field emission

DOEpatents

Sullivan, J.P.; Friedmann, T.A.

1998-10-13

A multi-layer resistive carbon film field emitter device for cold cathode field emission applications is disclosed. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. 8 figs.

Asymptotic Representation for the Eigenvalues of a Non-selfadjoint Operator Governing the Dynamics of an Energy Harvesting Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shubov, Marianna A., E-mail: marianna.shubov@gmail.com

2016-06-15

We consider a well known model of a piezoelectric energy harvester. The harvester is designed as a beam with a piezoceramic layer attached to its top face (unimorph configuration). A pair of thin perfectly conductive electrodes is covering the top and the bottom faces of the piezoceramic layer. These electrodes are connected to a resistive load. The model is governed by a system consisting of two equations. The first of them is the equation of the Euler–Bernoulli model for the transverse vibrations of the beam and the second one represents the Kirchhoff’s law for the electric circuit. Both equations aremore » coupled due to the direct and converse piezoelectric effects. The boundary conditions for the beam equations are of clamped-free type. We represent the system as a single operator evolution equation in a Hilbert space. The dynamics generator of this system is a non-selfadjoint operator with compact resolvent. Our main result is an explicit asymptotic formula for the eigenvalues of this generator, i.e., we perform the modal analysis for electrically loaded (not short-circuit) system. We show that the spectrum splits into an infinite sequence of stable eigenvalues that approaches a vertical line in the left half plane and possibly of a finite number of unstable eigenvalues. This paper is the first in a series of three works. In the second one we will prove that the generalized eigenvectors of the dynamics generator form a Riesz basis (and, moreover, a Bari basis) in the energy space. In the third paper we will apply the results of the first two to control problems for this model.« less

Sediment transport and fluid mud layer formation in the macro-tidal Chikugo river estuary during a fortnightly tidal cycle

NASA Astrophysics Data System (ADS)

Azhikodan, Gubash; Yokoyama, Katsuhide

2018-03-01

The erosion and deposition dynamics of fine sediment in a highly turbid estuarine channel were successfully surveyed during the period from August 29 to September 12, 2009 using an echo sounder in combination with a high-resolution acoustic Doppler current profiler. Field measurements were conducted focusing on the tide driven dynamics of suspended sediment concentration (SSC), and fluid mud at the upstream of the macrotidal Chikugo river estuary during semidiurnal and fortnightly tidal cycles. Morphological evolution was observed especially during the spring tide over a period of two weeks. The elevation of the channel bed was stable during neap tide, but it underwent fluctuations when the spring tide occurred owing to the increase in the velocity and shear stress. Two days of time lag were observed between the maximum SSC and peak tidal flow, which resulted in the asymmetry between neap-to-spring and spring-to-neap transitions. During the spring tide, a hysteresis loop was observed between shear stress and SSC, and its direction was different during flood and ebb tides. Although both fine sediments and flocs were dominant during flood tides, only fine sediments were noticed during ebb tides. Hence, the net elevation change in the bed was positive, and sedimentation took place during the semilunar tidal cycle. Finally, a bed of consolidated mud was deposited on the initial bed, and the height of the channel bed increased by 0.9 m during the two-week period. The observed hysteretic effect between shear stress and SSC during the spring tides, and the asymmetrical neap-spring-neap tidal cycle influenced the near-bed sediment dynamics of the channel, and led to the formation of a fluid mud layer at the bottom of the river.

Improvement of Self-Heating of Indium Gallium Zinc Aluminum Oxide Thin-Film Transistors Using Al2O3 Barrier Layer

NASA Astrophysics Data System (ADS)

Jian, Li-Yi; Lee, Hsin-Ying; Lin, Yung-Hao; Lee, Ching-Ting

2018-02-01

To study the self-heating effect, aluminum oxide (Al2O3) barrier layers of various thicknesses have been inserted between the channel layer and insulator layer in bottom-gate-type indium gallium zinc aluminum oxide (IGZAO) thin-film transistors (TFTs). Each IGZAO channel layer was deposited on indium tin oxide (ITO)-coated glass substrate by using a magnetron radiofrequency cosputtering system with dual targets composed of indium gallium zinc oxide (IGZO) and Al. The 3 s orbital of Al cation provided an extra transport pathway and widened the conduction-band bottom, thus increasing the electron mobility of the IGZAO films. The Al-O bonds were able to sustain the oxygen stability of the IGZAO films. The self-heating behavior of the resulting IGZAO TFTs was studied by Hall measurements on the IGZAO films as well as the electrical performance of the IGZAO TFTs with Al2O3 barrier layers of various thicknesses at different temperatures. IGZAO TFTs with 50-nm-thick Al2O3 barrier layer were stressed by positive gate bias stress (PGBS, at gate-source voltage V GS = 5 V and drain-source voltage V DS = 0 V); at V GS = 5 V and V DS = 10 V, the threshold voltage shifts were 0.04 V and 0.2 V, respectively, much smaller than for the other IGZAO TFTs without Al2O3 barrier layer, which shifted by 0.2 V and 1.0 V when stressed under the same conditions.

Amplitude various angles (AVA) phenomena in thin layer reservoir: Case study of various reservoirs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nurhandoko, Bagus Endar B., E-mail: bagusnur@bdg.centrin.net.id, E-mail: bagusnur@rock-fluid.com; Rock Fluid Imaging Lab., Bandung; Susilowati, E-mail: bagusnur@bdg.centrin.net.id, E-mail: bagusnur@rock-fluid.com

2015-04-16

Amplitude various offset is widely used in petroleum exploration as well as in petroleum development field. Generally, phenomenon of amplitude in various angles assumes reservoir’s layer is quite thick. It also means that the wave is assumed as a very high frequency. But, in natural condition, the seismic wave is band limited and has quite low frequency. Therefore, topic about amplitude various angles in thin layer reservoir as well as low frequency assumption is important to be considered. Thin layer reservoir means the thickness of reservoir is about or less than quarter of wavelength. In this paper, I studied aboutmore » the reflection phenomena in elastic wave which considering interference from thin layer reservoir and transmission wave. I applied Zoeppritz equation for modeling reflected wave of top reservoir, reflected wave of bottom reservoir, and also transmission elastic wave of reservoir. Results show that the phenomena of AVA in thin layer reservoir are frequency dependent. Thin layer reservoir causes interference between reflected wave of top reservoir and reflected wave of bottom reservoir. These phenomena are frequently neglected, however, in real practices. Even though, the impact of inattention in interference phenomena caused by thin layer in AVA may cause inaccurate reservoir characterization. The relation between classes of AVA reservoir and reservoir’s character are different when effect of ones in thin reservoir and ones in thick reservoir are compared. In this paper, I present some AVA phenomena including its cross plot in various thin reservoir types based on some rock physics data of Indonesia.« less

Numerical and Experimental Investigation of Multiple Shock Wave/Turbulent Boundary Layer Interactions in a Rectangular Duct

DTIC Science & Technology

1988-01-06

the bottom % kall followin,, the interaction. At 6Wuh = 0.35 the shock train would not stay attached to a single wall long enough for the surface...Interaction of a Shock Wave with a Laminar Boundary Layer," Lecture Notes in Physics, Vol. 8, Springer-Verlag, 1971 , pp. 151-163. 51 MacCormack, R. W

Near-Bottom Turbulence and Sediment Resuspension Induced by Nonlinear Internal Waves

DTIC Science & Technology

2011-09-30

boundary layer (BBL) turbulence and particulate resuspension leading to benthic nepheloid layer ( BNL ) formation. OBJECTIVES The specific...identify mechanisms for the capturing of nearbed particles by the BBL-turbulence and their transport/deposition into BNLs . • Analyze field...resuspended particle distributions under NLIWs, a reliable proxy of BNLs , can be used to quantify the transmission or backscatter of optical/acoustic

Controlled porous pattern of anodic aluminum oxide by foils laminate approach.

PubMed

Wang, Gou-Jen; Peng, Chi-Sheng

2006-04-01

A novel, much simpler, and low-cost method to fabricate the porous pattern of the anodic aluminum oxide (AAO) based on the aluminum foils laminate approach was carried out. During our experiments, it was found that the pores of the AAO on the upper foil grew bi-directionally from both the top and the bottom surfaces. Experimental results further indicate that the upward porous pattern of the upper foil is determined by the surface structure of the bottom surface of the upper foil. The porous pattern of AAO can be controlled by a pre-made pattern on the bottom surface. Furthermore, no Aluminum (Al) layer removing process is required in this novel laminate method.

Particle Mass in Deep-Water Benthic Nepheloid Layers: a Global Synthesis

NASA Astrophysics Data System (ADS)

Mishonov, A. V.; Gardner, W. D.; Richardson, M. J.

2016-12-01

The mass of particles in benthic nepheloid layers in the deep ocean is mapped using profiles of beam attenuation coefficient obtained with transmissometers interfaced with CTDs during WOCE, SAVE, JGOFS, CLIVAR-Repeat Hydrography, and other programs during the last four decades using data from over 8000 profiles from >70 cruises. We map the maximum concentration of particle mass near the seafloor and integrate the particle mass throughout the benthic nepheloid layer. In the Atlantic Ocean particle mass is greater in areas where eddy kinetic energy is high in overlying waters. Areas of high bottom particle concentrations and integrated benthic nepheloid layer particle loads include the western North Atlantic beneath the Gulf Stream meanders and eddies, Argentine Basin, parts of the Southern Ocean and areas around South Africa. Particle concentrations are low in most of the Pacific and tropical and subtropical Atlantic away from margins. This synthesis is useful for GEOTRACES and other global programs where knowing particle distribution is critical for understanding trace metal absorption, sediment-water exchange and near-bottom processes. Additionally, our synthesis provides baseline data to identify where mining of metal-rich nodules and metal sulfides on the seafloor may impact the benthic environment.

Ligand-Asymmetric Janus Quantum Dots for Efficient Blue-Quantum Dot Light-Emitting Diodes.

PubMed

Cho, Ikjun; Jung, Heeyoung; Jeong, Byeong Guk; Hahm, Donghyo; Chang, Jun Hyuk; Lee, Taesoo; Char, Kookheon; Lee, Doh C; Lim, Jaehoon; Lee, Changhee; Cho, Jinhan; Bae, Wan Ki

2018-06-19

We present ligand-asymmetric Janus quantum dots (QDs) to improve the device performance of quantum dot light-emitting diodes (QLEDs). Specifically, we devise blue QLEDs incorporating blue QDs with asymmetrically modified ligands, in which the bottom ligand of QDs in contact with ZnO electron-transport layer serves as a robust adhesive layer and an effective electron-blocking layer and the top ligand ensures uniform deposition of organic hole transport layers with enhanced hole injection properties. Suppressed electron overflow by the bottom ligand and stimulated hole injection enabled by the top ligand contribute synergistically to boost the balance of charge injection in blue QDs and therefore the device performance of blue QLEDs. As an ultimate achievement, the blue QLED adopting ligand-asymmetric QDs displays 2-fold enhancement in peak external quantum efficiency (EQE = 3.23%) compared to the case of QDs with native ligands (oleic acid) (peak EQE = 1.49%). The present study demonstrates an integrated strategy to control over the charge injection properties into QDs via ligand engineering that enables enhancement of the device performance of blue QLEDs and thus promises successful realization of white light-emitting devices using QDs.

Looking into 'London'

NASA Technical Reports Server (NTRS)

2004-01-01

This mosaic image from the microscopic imager on the Mars Exploration Rover Opportunity shows the rock abrasion tool target, 'London.' The image was taken by the Mars Exploration Rover Opportunity on its 149th sol on Mars (June 24, 2004). Scientists 'read' the geology of the image from bottom to top, with the youngest material pictured at the bottom of the image and the oldest material in the layers pictured at the top. Millimeter-scale layers run horizontally across the exposed surface, with two sliced sphere-like objects, or 'blueberries' on the upper left and upper right sides of the impression. This material is similar to the evaporative material found in 'Eagle Crater.' However, the intense review of these layers in Endurance Crater is, in essence, deepening the water story authored by ancient Mars.

In Eagle Crater, the effects of water were traced down a matter of centimeters. Endurance Crater's depth has allowed the tracing of water's telltale marks up to meters. Another process that significantly affects martian terrain is muddying the water story a bit. Although it is clear that the layers in Endurance were affected by water, it is also evident that Aeolian, or wind, processes have contributed to the makeup of the crater.

Inorganic and organic nitrogen uptake by phytoplankton and heterotrophic bacteria in the stratified Mid-Atlantic Bight

NASA Astrophysics Data System (ADS)

Bradley, Paul B.; Sanderson, Marta P.; Frischer, Marc E.; Brofft, Jennifer; Booth, Melissa G.; Kerkhof, Lee J.; Bronk, Deborah A.

2010-08-01

Little is known about the relative importance of inorganic and organic nitrogen (N) sources in fueling production of phytoplankton versus heterotrophic bacteria on the continental shelf. This issue was addressed during two diel experiments conducted in the Mid-Atlantic Bight at the Long-term Ecosystem Observatory, LEO-15, off southern New Jersey. Uptake of 15N-labeled ammonium (NH 4+), nitrate (NO 3-), and nitrite (NO 2-), and dual-labeled ( 15N and 13C) urea and dissolved free amino acids was measured in water taken from the surface and bottom mixed layers approximately every 4 h over two 24 h periods in July 2002. Two methods were used to quantify 15N uptake rates: (1) traditional filtration into various phytoplankton and bacterial size classes, and (2) flow cytometric (FCM) sorting of autotrophic cells based on the presence of chlorophyll autofluorescence. Due to a strong pycnocline, the nutrient composition was quite distinct between the surface and bottom mixed layers. Dissolved organic N (DON) comprised >99% of the total dissolved N (TDN) pool in surface waters, whereas the bottom-water TDN pool was roughly divided between NH 4+, NO 3-, and DON. Urea was the dominant N form used by all fractions at the surface, and although phytoplankton >3 μm was responsible for most of the urea uptake, bacterial use was detected using stable isotopes and also suggested by ureC sequence analysis. The majority of ureC sequences recovered from the 0.2-0.8 μm fraction belonged to members of the Alphaproteobacteria (46%), whereas those of the 0.8-3.0 μm size class consisted primarily of Cyanobacteria (70%). In contrast to the surface, N uptake in the bottom layer was dominated by NH 4+. The bacterial fraction was responsible for 20-49% of the size-fractionated NH 4+ and NO 3- uptake in surface samples and 36-93% at the bottom. These results suggest that organic N, such as urea, is a viable source of N nutrition to phytoplankton forced to compete with heterotrophic bacteria for limited inorganic N.

Crystal accumulation in the Hanford Waste Treatment Plant high level waste melter: Summary of FY2016 experiements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fox, K.; Fowley, M.; Miller, D.

2016-12-01

Five experiments were completed with the full-scale, room temperature Hanford Waste Treatment and Immobilization Plant (WTP) high-level waste (HLW) melter riser test system to observe particle flow and settling in support of a crystal tolerant approach to melter operation. A prototypic pour rate was maintained based on the volumetric flow rate. Accumulation of particles was observed at the bottom of the riser and along the bottom of the throat after each experiment. Measurements of the accumulated layer thicknesses showed that the settled particles at the bottom of the riser did not vary in thickness during pouring cycles or idle periods.more » Some of the settled particles at the bottom of the throat were re-suspended during subsequent pouring cycles, and settled back to approximately the same thickness after each idle period. The cause of the consistency of the accumulated layer thicknesses is not year clear, but was hypothesized to be related to particle flow back to the feed tank. Additional experiments reinforced the observation of particle flow along a considerable portion of the throat during idle periods. Limitations of the system are noted in this report and may be addressed via future modifications. Follow-on experiments will be designed to evaluate the impact of pouring rate on particle re-suspension, the influence of feed tank agitation on particle accumulation, and the effect of changes in air lance positioning on the accumulation and re-suspension of particles at the bottom of the riser. A method for sampling the accumulated particles will be developed to support particle size distribution analyses. Thicker accumulated layers will be intentionally formed via direct addition of particles to select areas of the system to better understand the ability to continue pouring and re-suspend particles. Results from the room temperature system will be correlated with observations and data from the Research Scale Melter (RSM) at Pacific Northwest National Laboratory, and coordinated with modeling efforts underway at Idaho National Laboratory.« less

Latest Data on Thermohaline Structure and Circulation of the Dying Aral Sea

NASA Astrophysics Data System (ADS)

Izhitsky, Alexander; Zavialov, Peter

2010-05-01

The results of the latest expedition of the Shirshov Institute to the Aral Sea are reported. The survey encompassed 15 field days in August, 2009. An interdisciplinary oceanographic study in the western basin of the sea was conducted during the expedition. Vertical profiles of temperature, salinity and fluorescence were obtained using a CTD profiler at 8 stations across the western basin. Two mooring stations equipped with current meters, one at the surface and one in the bottom layer at each station, as well as pressure gauges at the bottom, were deployed for 5 days in the deepest portion of the western basin. One of the stations was installed at the western slope of the basin, while the other one was positioned at the eastern slope. A portable automatic meteorological station, continuously recording the variability of wind and principal meteorological parameters, was installed near the mooring sites. The vertical structure of the themohaline fields exhibited a 3-layered pattern, with local salinity maxima in the upper mixed layer and at the bottom. The intermediate layer was characterized by a core of minimum salinity and temperature, also accompanied by maximum fluorescence. Such a pattern indicates that the signature of the denser, saltier water originating from the eastern basin is still evident, even though the eastern basin itself dried up almost completely during the summer of 2009. The surface salinity was around 136 ppt, which constituted a notable increase for about 20 ppt since the summer of 2008. Over the same period, sea level decreased by 164 cm since the summer of 2008. Analysis of the current measurements data along with the meteorological data records demonstrated that the mean basin-scale surface circulation of the Large Aral Sea is likely to have remained anticyclonic, whilst the near-bottom circulation appears to be cyclonic. The current velocity and level anomalies responded energetically to winds. Correlation analysis of the velocity series versus the wind stress allowed to quantify the response of the system to the wind forcing.

AFRRI (Armed Forces Radiobiology Research Institute) Reports, July, August and September 1987.

DTIC Science & Technology

1987-11-01

mononuclear cell layer obtained after Percol isolation contained approximately 90% mono- cytes as assessed by esterase staining. In most experiments...forming cell) were assayed using the double layer agar technique basically as described by Hagan et al. (22). The culture medium was double strength CMRL...trypticase soy broth, 20 g/ml L-asparagine. and penicillin-streptomycin. In the bottom layer of 35 mm plastic Petri dishes was 1 ml of a 1:1 mixture of culture

Development and Evaluation of a New Spectral Planetary Boundary-Layer Architecture for the MM5

DTIC Science & Technology

1998-08-07

I’m grateful to Dr. George Young for his suggestion to use the Bulk-Richardson technique for diagnosis of boundary-layer depth during convection, and...simulation (LES) (Wyngaard and Brost 1984). However, these profiles are not generally representative of all conditions. They are instead prescribed for...Wyngaard, J. C, and R. A. Brost , 1984: Top-down and bottom diffusion of a scalar in the convective boundary layer. J. Atmos. Sei., 44, 102-112. Zeman

Noise-tolerant inverse analysis models for nondestructive evaluation of transportation infrastructure systems using neural networks

NASA Astrophysics Data System (ADS)

Ceylan, Halil; Gopalakrishnan, Kasthurirangan; Birkan Bayrak, Mustafa; Guclu, Alper

2013-09-01

The need to rapidly and cost-effectively evaluate the present condition of pavement infrastructure is a critical issue concerning the deterioration of ageing transportation infrastructure all around the world. Nondestructive testing (NDT) and evaluation methods are well-suited for characterising materials and determining structural integrity of pavement systems. The falling weight deflectometer (FWD) is a NDT equipment used to assess the structural condition of highway and airfield pavement systems and to determine the moduli of pavement layers. This involves static or dynamic inverse analysis (referred to as backcalculation) of FWD deflection profiles in the pavement surface under a simulated truck load. The main objective of this study was to employ biologically inspired computational systems to develop robust pavement layer moduli backcalculation algorithms that can tolerate noise or inaccuracies in the FWD deflection data collected in the field. Artificial neural systems, also known as artificial neural networks (ANNs), are valuable computational intelligence tools that are increasingly being used to solve resource-intensive complex engineering problems. Unlike the linear elastic layered theory commonly used in pavement layer backcalculation, non-linear unbound aggregate base and subgrade soil response models were used in an axisymmetric finite element structural analysis programme to generate synthetic database for training and testing the ANN models. In order to develop more robust networks that can tolerate the noisy or inaccurate pavement deflection patterns in the NDT data, several network architectures were trained with varying levels of noise in them. The trained ANN models were capable of rapidly predicting the pavement layer moduli and critical pavement responses (tensile strains at the bottom of the asphalt concrete layer, compressive strains on top of the subgrade layer and the deviator stresses on top of the subgrade layer), and also pavement surface deflections with very low average errors comparable with those obtained directly from the finite element analyses.

ZrO2 Layer Thickness Dependent Electrical and Dielectric Properties of BST/ZrO2/BST Multilayer Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahoo, S. K.; Misra, D.; Agrawal, D. C.

2011-01-01

Recently, high K materials play an important role in microelectronic devices such as capacitors, memory devices, and microwave devices. Now a days ferroelectric barium strontium titanate [Ba{sub x}Sr{sub 1-x}TiO{sub 3}, (BST)] thin film is being actively investigated for applications in dynamic random access memories (DRAM), field effect transistor (FET), and tunable devices because of its properties such as high dielectric constant, low leakage current, low dielectric loss, and high dielectric breakdown strength. Several approaches have been used to optimize the dielectric and electrical properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found thatmore » inserting a ZrO{sub 2} layer in between two BST layers results in a significant reduction in dielectric constant, loss tangent, and leakage current in the multilayer thin films. Also it is shown that the properties of multilayer structure are found to depend strongly on the sublayer thicknesses. In this work the effect of ZrO{sub 2} layer thickness on the dielectric, ferroelectric as well as electrical properties of BST/ZrO{sub 2}/BST multilayer structure is studied. The multilayer Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3}/ZrO{sub 2}/Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} film is deposited by a sol-gel process on the platinized Si substrate. The thickness of the middle ZrO{sub 2} layer is varied while keeping the top and bottom BST layer thickness as fixed. It is observed that the dielectric constant, dielectric loss tangent, and leakage current of the multilayer films reduce with the increase of ZrO{sub 2} layer thickness and hence suitable for memory device applications. The ferroelectric properties of the multilayer film also decrease with the ZrO{sub 2} layer thickness.« less

Impact of Land Model Depth on Long Term Climate Variability and Change.

NASA Astrophysics Data System (ADS)

Gonzalez-Rouco, J. F.; García-Bustamante, E.; Hagemann, S.; Lorentz, S.; Jungclaus, J.; de Vrese, P.; Melo, C.; Navarro, J.; Steinert, N.

2017-12-01

The available evidence indicates that the simulation of subsurface thermodynamics in current General Circulation Models (GCMs) is not accurate enough due to the land-surface model imposing a zero heat flux boundary condition that is too close to the surface. Shallow land model components distort the amplitude and phase of the heat propagation in the subsurface with implications for energy storage and land-air interactions. Off line land surface model experiments forced with GCM climate change simulations and comparison with borehole temperature profiles indicate there is a large reduction of the energy storage of the soil using the typical shallow land models included in most GCMs. However, the impact of increasing the depth of the soil model in `on-line' GCM simulations of climate variability or climate change has not yet been systematically explored. The JSBACH land surface model has been used in stand alone mode, driven by outputs of the MPIESM to assess the impacts of progressively increasing the depth of the soil model. In a first stage, preindustrial control simulations are developed increasing the lower depth of the zero flux bottom boundary condition placed for temperature at the base of the fifth model layer (9.83 m) down to 294.6 m (layer 9), thus allowing for the bottom layers to reach equilibrium. Starting from piControl conditions, historical and scenario simulations have been performed since 1850 yr. The impact of increasing depths on the subsurface layer temperatures is analysed as well as the amounts of energy involved. This is done also considering permafrost processes (freezing and thawing). An evaluation on the influence of deepening the bottom boundary on the simulation of low frequency variability and temperature trends is provided.

Vertical Structure of Ice Cloud Layers From CloudSat and CALIPSO Measurements and Comparison to NICAM Simulations

NASA Technical Reports Server (NTRS)

Ham, Seung-Hee; Sohn, Byung-Ju; Kato, Seiji; Satoh, Masaki

2013-01-01

The shape of the vertical profile of ice cloud layers is examined using 4 months of CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) global measurements taken on January, April, July, and October 2007. Ice clouds are selected using temperature profiles when the cloud base is located above the 253K temperature level. The obtained ice water content (IWC), effective radius, or extinction coefficient profiles are normalized by their layer mean values and are expressed in the normalized vertical coordinate, which is defined as 0 and 1 at the cloud base and top heights, respectively. Both CloudSat and CALIPSO observations show that the maximum in the IWC and extinction profiles shifts toward the cloud bottom, as the cloud depth increases. In addition, clouds with a base reaching the surface in a high-latitude region show that the maximum peak of the IWC and extinction profiles occurs near the surface, which is presumably due to snow precipitation. CloudSat measurements show that the seasonal difference in normalized cloud vertical profiles is not significant, whereas the normalized cloud vertical profile significantly varies depending on the cloud type and the presence of precipitation. It is further examined if the 7 day Nonhydrostatic Icosahedral Atmospheric Model (NICAM) simulation results from 25 December 2006 to 1 January 2007 generate similar cloud profile shapes. NICAM IWC profiles also show maximum peaks near the cloud bottom for thick cloud layers and maximum peaks at the cloud bottom for low-level clouds near the surface. It is inferred that oversized snow particles in the NICAM cloud scheme produce a more vertically inhomogeneous IWC profile than observations due to quick sedimentation.

Nutrition and parturition date effects on elk: potential implications for research and management.

Treesearch

John G. Cook; Bruce K. Johnson; Rachel C. Cook; Robert A. Riggs; Tim DelCurto; Larry D. Bryant; Larry L. Irwin

2004-01-01

Understanding and managing those mechanisms that affect population dynamics comprise, perhaps, the most fundamental aspect of wildlife management (Caughley 1977). Biologists generally categorize these mechanisms as either top-down (predator-driven) or bottom-up (habitat- or animal-density driven). Bottom-up influences involve imbalances between increasing animal...

Responses of water environment to tidal flat reduction in Xiangshan Bay: Part II locally re-suspended sediment dynamics

NASA Astrophysics Data System (ADS)

Li, Li; Guan, Weibing; He, Zhiguo; Yao, Yanming; Xia, Yuezhang

2017-11-01

Xiangshan Bay is a semi-enclosed bay in China, in which tidal flats have been substantially reclaimed to support the development of local economies and society over previous decades. The loss of tidal flats has led to changes of tides and locally suspended sediment in the bay. The effects of tidal flat reduction on locally suspended sediment dynamics was investigated using a numerical model forced by tidal data and calibrated by observed tidal elevation and currents. The model satisfactorily reproduces observed water levels, currents, and suspended sediment concentration in the estuary, and therefore is subsequently applied to analyze the impact of tidal flat reclamation on locally suspended sediment transport. After the loss of the tidal flats from 1963 to 2010, the suspended sediment concentrations (SSC) at the bottom boundary layer were reduced/increased in the outer bay/tidal flat areas due to weakened tidal currents. In the inner bay, the SSC values near the bottom level increased from 1963 to 2003 due to the narrowed bathymetry, and then decreased from 2003 to 2010 because of the reduced tidal prism. The model scenarios suggest that: (1) a reduction of tidal flat areas appears to be the main factor for enhancing the transport of sediments up-estuary, due to the increased Eulerian velocity and tidal pumping; (2) A reduction of tidal flat areas impacts on spatial and temporal SSC distribution: reducing the SSC values in the water areas due to the reduced current; and (3) a tidal flat reduction influences the net sediment fluxes: lessening the erosion and inducing higher/lower landward/seaward sediment transportation.

Experimental studies of rotating exchange flow

NASA Astrophysics Data System (ADS)

Rabe, B.; Smeed, D. A.; Dalziel, S. B.; Lane-Serff, G. F.

2007-02-01

Ocean basins are connected by straits and passages, geometrically limiting important heat and salt exchanges which in turn influence the global thermohaline circulation and climate. Such exchange can be modeled in an idealized way by taking into consideration the density-driven two-layer flow along a strait under the influence of rotation. We use a laboratory model of a lock exchange between two reservoirs of different density through a flat-bottom channel with a horizontal narrows, set up on two different platforms: a 1 m diameter turntable, where density interface position was measured by dye attenuation, and the 14 m diameter turntable at Coriolis/LEGI (Grenoble, France), where correlation imaging velocimetry, a particle imaging technique, allowed us to obtain for the first time detailed measurements of the velocity fields in these flows. The influence of rotation is studied by varying a parameter, Bu, a type of Burger number given by the ratio of the Rossby radius to the channel width at the narrows. In addition, a two-layer version of the Miami Isopycnic Coordinate Model (MICOM) is used, to study the cases with low Burger number. Results from experiments by Dalziel [1988. Two-layer hydraulics: maximal exchange flows. Ph.D. Thesis, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, see also ] are also included for comparison. Time-mean exchange fluxes for any Bu are in close agreement with the inviscid zero-potential vorticity theory of Dalziel [1990. Rotating two-layer sill flows. In: Pratt, L.J. (Ed.), The Physical Oceanography of Sea Straits. Kluwer Academic, Dordrecht, pp. 343-371] and Whitehead et al. [1974. Rotating hydraulics of strait and sill flows. Geophysical Fluid Dynamics 6, 101-125], who found that fluxes for Bu>1 mainly vary with channel width, similar to non-rotating flow, but for Bu<1 are only limited by the Rossby radius. We also show theoretically that non-zero-potential vorticity results in only a small increase in the predicted exchange flux around Bu˜1. The flow characteristics are found to be very different for small and large Burger numbers: for Bu>1 a steady, two-layer flow was observed that persisted across the channel at the narrows with only some across-channel variation. The distribution of the Froude number is found to give some evidence for hydraulic control in a manner similar to that of non-rotating flows under the influence of bottom drag. Flow for Bu<0.5 does not appear to reach a steady state but instead is characterized by an unsteady, meandering current and several eddies in the strait. Similar instabilities also occur in wide oceanic straits, where several mechanisms, such as barotropic and baroclinic instability, have been proposed and could also be one cause of time variability in our experiments. Both the laboratory experiments and the MICOM results suggest that in the presence of bottom drag or side wall friction some features of the flow, such as the location of the channel crossing, become sensitive to the initial conditions. These effects differ in flows with Bu>1 and Bu<1.

A comparison of the uniaxial deformation of copper and nickel (1 1 19) surfaces: a molecular dynamics study

PubMed Central

Pukšič, Nuša; Jenko, Monika; Godec, Matjaž; McGuiness, Paul J.

2017-01-01

While a lot is known about the deformation of metallic surfaces from experiments, elasticity theory and simulations, this investigation represents the first molecular-dynamics-based simulation of uniaxial deformation for the vicinal surfaces in a comparison of copper and nickel. These vicinal surfaces are composed of terraces divided by equidistant, mono-atomic steps. The periodicity of vicinals makes them good candidates for the study of the surface steps’ influences on surface dynamics. The simulations of tensile and compressive uniaxial deformations were performed for the (1 1 19) vicinal surfaces. Since the steps on the surfaces serve as stress concentrators, the first defects were expected to nucleate here. In the case of copper, this was found to be the case. In the case of nickel, however, dislocations nucleated beneath the near-surface layer affected by the displacement field generated by the steps. Slip was hindered at the surface step by the vortex in the displacement field. The differences in the deformation mechanisms for the Ni(1 1 19) and Cu(1 1 19) surfaces can be linked to the differences in their displacement fields. This could lead to novel bottom-up approaches to the nanostructuring of surfaces using strain. PMID:28169377

Modeling the formation of the quench product in municipal solid waste incineration (MSWI) bottom ash.

PubMed

Inkaew, Kanawut; Saffarzadeh, Amirhomayoun; Shimaoka, Takayuki

2016-06-01

This study investigated changes in bottom ash morphology and mineralogy under lab-scale quenching conditions. The main purpose was to clarify the mechanisms behind the formation of the quench product/layer around bottom ash particles. In the experiments, the unquenched bottom ashes were heated to 300°C for 1h, and were quenched by warm water (65°C) with different simulated conditions. After having filtered and dried, the ashes were analyzed by a combination of methodologies namely, particle size distribution analysis, intact particle and thin-section observation, X-ray diffractometry, and scanning electron microscope with energy dispersive X-ray spectroscopy. The results indicated that after quenching, the morphology and mineralogy of the bottom ash changed significantly. The freshly quenched bottom ash was dominated by a quench product that was characterized by amorphous and microcrystalline calcium-silicate-hydrate (CSH) phases. This product also enclosed tiny minerals, glasses, ceramics, metals, and organic materials. The dominant mineral phases produced by quenching process and detected by XRD were calcite, Friedel's salt, hydrocalumite and portlandite. The formation of quench product was controlled by the fine fraction of the bottom ash (particle size <0.425mm). From the observations, a conceptual model of the ash-water reactions and formation of the quench product in the bottom ash was proposed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Deep-sea macroplankton distribution (at 400 to 2300 m) in the northwestern Mediterranean in relation to environmental factors

NASA Astrophysics Data System (ADS)

Cartes, J. E.; Fanelli, E.; López-Pérez, C.; Lebrato, M.

2013-03-01

Changes in the composition and biomass distribution of deep-living zooplankton over wide gradients of depth (400-2300 m) and longitude (~ 180 km) have been analyzed in the Balearic Basin (western Mediterranean), seeking the environmental variables responsible for these changes. Zooplankton tends to aggregate at different levels of the water column (forming Deep Scattering Layers, DSL) and in the Benthic Boundary Layer (BBL). Macrozooplankton biomass and composition were analyzed along a transect performed in July 2010 in midwater (between ~ 350 and 450 m) and near the bottom (at ~ 5-200 mab), over soundings of 450-2263 m, including the top of Valencia Seamount (at ~ 40° 25' N-02° 42' E, 1076 m). Zooplankton changed significantly in composition at the mesoscale (~ 180 km) in both the DSL and the BBL. Siphonophores and calanoid copepods were the most dominant deep zooplankton taxa, calanoids reaching higher abundance in the BBL (1761-5177 individuals/1000 m3) than in the DSL (1568-1743 individuals/1000 m3). There was a significant increase in near-bottom zooplankton biomass over the middle slope, at 1000-1300 m, linked to an increase in scyphozoans and siphonophores (Lensia spp. and Abylopsis tetragona) with peaks of 1.5-2.0 gWW/1000 m3. The peak of near-bottom zooplankton at 1000-1300 m coincided with the lowest temperatures (13.08 °C) and maximum O2 concentration (4.40 ml/l) near the bottom and below 1000 m with higher records in near-bottom turbidity. Gelatinous zooplankton are the main prey in the diet of the demersal fish Alepocephalus rostratus in the western Mediterranean, fish responsible for the peak of megafauna biomass reported at around 1200-1400 m in the deep Mediterranean and at similar depths in other oceanic areas (e.g. the NW Atlantic). We suggest that deep-sea environmental conditions can govern peaks of near-bottom zooplankton, as well as influence the structure of the demersal fish community.

Experiment on large scale plume interaction with a stratified gas environment resembling the thermal activity of a autocatalytic recombiner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mignot, G.; Kapulla, R.; Paladino, D.

Computational Fluid Dynamics codes (CFD) are increasingly being used to simulate containment conditions after various transient accident scenarios. Consequently, the reliability of such codes must be tested against experimental data. Such validation experiments related to gas mixing and hydrogen transport within containment compartments addressing the effect of heat source are presented in this paper. The experiments were conducted in the large-scale thermal-hydraulics PANDA facility located at the Paul-Scherrer-Inst. (PSI) in Switzerland, in the frame of the OECD/SETH-2 project. A 10 kW electric heater simulating the thermal activity of the autocatalytic recombiner was activated at full power in a containment vesselmore » at the top of which a thick helium layer is initially present. The hot plume interacts with the bottom of the helium layer which is slowly eroded until complete break up at 1350 s. After final erosion of the layer a strong temperature and concentration gradient is maintained in the vessel below the heater inlet as well as in the adjacent vessel below the interconnecting pipe. A detailed characterization of the operating heater suggests the presence of cold gas ingress at the outlet that affects the flow in the chimney. This can be of concern if present in a real PAR unit. (authors)« less

Liquid-crystal microlens array with swing and adjusting focus and constructed by dual patterned ITO-electrodes

NASA Astrophysics Data System (ADS)

Dai, Wanwan; Xie, Xingwang; Li, Dapeng; Han, Xinjie; Liu, Zhonglun; Wei, Dong; Xin, Zhaowei; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

Under the condition of existing intense turbulence, the object's wavefront may be severely distorted. So, the wavefront sensors based on the traditional microlens array (MLA) with a fixed focal length can not be used to measure the wavefront effectively. In order to obtain a larger measurement range and higher measurement accuracy, we propose a liquid-crystal microlens array (LCMLA) with needed ability of swing focus over the focal plane and further adjusting focal length, which is constructed by a dual patterned ITO electrodes. The main structure of the LCMLA is divided into two layers, which are made of glass substrate with ITO transparent electrodes. The top layer of each liquid-crystal microlens consists of four rectangular electrodes, and the bottom layer is a circular electrode. In common optical measurements performed, the operations are carried out such as adding the same signal voltage over four electrodes of each microlens to adjust the focal length of the lens cell and adding a signal voltage with different RMS amplitude to adjust the focus position on the focal plane. Experiments show that the LCMLA developed by us demonstrate a desired focal length adjustable function and dynamic swing ability, so as to indicate that the method can be used not only to measure wavefront but also correct the wavefront with strong distortion.

Perforation patterned electrical interconnects

DOEpatents

Frey, Jonathan

2014-01-28

This disclosure describes systems and methods for increasing the usable surface area of electrical contacts within a device, such as a thin film solid state device, through the implementation of electrically conductive interconnects. Embodiments described herein include the use of a plurality of electrically conductive interconnects that penetrate through a top contact layer, through one or more multiple layers, and into a bottom contact layer. The plurality of conductive interconnects may form horizontal and vertical cross-sectional patterns. The use of lasers to form the plurality of electrically conductive interconnects from reflowed layer material further aids in the manufacturing process of a device.

Sediment size fractionation and focusing in the equatorial Pacific: Effect on 230Th normalization and paleoflux measurements

NASA Astrophysics Data System (ADS)

Lyle, Mitchell; Marcantonio, Franco; Moore, Willard S.; Murray, Richard W.; Huh, Chih-An; Finney, Bruce P.; Murray, David W.; Mix, Alan C.

2014-07-01

We use flux, dissolution, and excess 230Th data from the Joint Global Ocean Flux Study and Manganese Nodule Project equatorial Pacific study Site C to assess the extent of sediment focusing in the equatorial Pacific. Measured mass accumulation rates (MAR) from sediment cores were compared to reconstructed MAR by multiplying the particulate rain caught in sediment traps by the 230Th focusing factor and subtracting measured dissolution. CaCO3 MAR is severely overestimated when the 230Th focusing factor correction is large but is estimated correctly when the focusing factor is small. In contrast, Al fluxes in the sediment fine fraction are well matched when the focusing correction is used. Since CaCO3 is primarily a coarse sediment component, we propose that there is significant sorting of fine and coarse sediments during lateral sediment transport by weak currents. Because CaCO3 does not move with 230Th, normalization typically overcorrects the CaCO3 MAR; and because CaCO3 is 80% of the total sediment, 230Th normalization overestimates lateral sediment flux. Fluxes of 230Th in particulate rain caught in sediment traps agree with the water column production-sorption model, except within 500 m of the bottom. Near the bottom, 230Th flux measurements are as much as 3 times higher than model predictions. There is also evidence for lateral near-bottom 230Th transport in the bottom nepheloid layer since 230Th fluxes caught by near-bottom sediment traps are higher than predicted by resuspension of surface sediments alone. Resuspension and nepheloid layer transport under weak currents need to be better understood in order to use 230Th within a quantitative model of lateral sediment transport.

Effects of elastic bed on hydrodynamic forces for a submerged sphere in an ocean of finite depth

NASA Astrophysics Data System (ADS)

Mohapatra, Smrutiranjan

2017-08-01

In this paper, we consider a hydroelastic model to examine the radiation of waves by a submerged sphere for both heave and sway motions in a single-layer fluid flowing over an infinitely extended elastic bottom surface in an ocean of finite depth. The elastic bottom is modeled as a thin elastic plate and is based on the Euler-Bernoulli beam equation. The effect of the presence of surface tension at the free-surface is neglected. In such situation, there exist two modes of time-harmonic waves: the one with a lower wavenumber (surface mode) propagates along the free-surface and the other with higher wavenumber (flexural mode) propagates along the elastic bottom surface. Based on the small amplitude wave theory and by using the multipole expansion method, we find the particular solution for the problem of wave radiation by a submerged sphere of finite depth. Furthermore, this method eliminates the need to use large and cumbersome numerical packages for the solution of such problem and leads to an infinite system of linear algebraic equations which are easily solved numerically by any standard technique. The added-mass and damping coefficients for both heave and sway motions are derived and plotted for different submersion depths of the sphere and flexural rigidity of the elastic bottom surface. It is observed that, whenever the sphere nearer to the elastic bed, the added-mass move toward to a constant value of 1, which is approximately twice of the value of added-mass of a moving sphere in a single-layer fluid flowing over a rigid and flat bottom surface.

Distribution of Different Biogeographical Tintinnids in Yellow Sea and Bohai Sea

NASA Astrophysics Data System (ADS)

Chen, Xue; Li, Haibo; Zhao, Yuan; Zhao, Li; Dong, Yi; Zhang, Wuchang; Xiao, Tian

2018-04-01

There were different biogeographical tintinnids in the oceans. Knowledge of their distribution pattern and mixing was important to the understanding of ecosystem functions. Yellow Sea (YS) and Bohai Sea (BS) were semi-enclosed seas influenced by warm water intrusion and YS cold bottom water. The occurrence of tintinnids in YS and BS during two cruises (summer and winter) were investigated to find out: i) whether warm-water tintinnids appeared in YS and BS; ii) whether boreal tintinnids appeared in high summer; iii) the core area of neritic tintinnids and iv) how these different biogeographical tintinnids mixed. Our results showed that tintinnid community was dominated by neritic tintinnid. We confirmed the occurrence of warm-water tintinnids in summer and winter. In summer, they intruded into BS and mainly distributed in the upper 20 m where Yellow Sea Surface Warm Water (YSSWW) developed. In winter, they were limited in the surface water of central deep region (bottom depth >50 m) of YS where were affected by Yellow Sea Warm Water (YSWW). Boreal tintinnids occurred in YS in high summer (August) and in winter, while they were not observed in BS. In summer, the highest abundance of boreal tintinnids occurred in Yellow Sea Bottom Cold Water, indicating the presence of an oversummering stock. In winter, they were concentrated in the north of YSWW. Vertically, neritic tintinnids abundance was high in the bottom layers. Horizontally, high neritic tintinnids abundance in bottom layers occurred along the 50 m isobath coinciding with the position of front systems. Front systems were the core distribution area of neritic tintinnids. High abundance areas of warm-water and boreal tintinnids were clearly separated vertically in summer, and horizontally in winter. High abundance of neritic tintinnids rarely overlapped with that of warm-water or boreal tintinnids.

Nested large-eddy simulations of nighttime shear-instability waves and transient warming in a steep valley

NASA Astrophysics Data System (ADS)

Zhou, Bowen; Chow, Fotini

2012-11-01

This numerical study investigates the nighttime flow dynamics in a steep valley. The Owens Valley in California is highly complex, and represents a challenging terrain for large-eddy simulations (LES). To ensure a faithful representation of the nighttime atmospheric boundary layer (ABL), realistic external boundary conditions are provided through grid nesting. The model obtains initial and lateral boundary conditions from reanalysis data, and bottom boundary conditions from a land-surface model. We demonstrate the ability to extend a mesoscale model to LES resolutions through a systematic grid-nesting framework, achieving accurate simulations of the stable ABL over complex terrain. Nighttime cold-air flow was channeled through a gap on the valley sidewall. The resulting katabatic current induced a cross-valley flow. Directional shear against the down-valley flow in the lower layers of the valley led to breaking Kelvin-Helmholtz waves at the interface, which is captured only on the LES grid. Later that night, the flow transitioned from down-slope to down-valley near the western sidewall, leading to a transient warming episode. Simulation results are verified against field observations and reveal good spatial and temporal precision. Supported by NSF grant ATM-0645784.

A Layered Past: the Transformation and Development of Legacy Sediments as Alluvial Soils

NASA Astrophysics Data System (ADS)

Wade, A.; Richter, D. D., Jr.

2017-12-01

Legacy sediments are a widespread consequence of post-colonial upland erosion in the United States. Although these deposits are ubiquitous in valley bottoms of the southeastern Piedmont, mature hardwood forests and collapsed stream banks mask their occurrence. While these deposits have been studied for their fluvial dynamics and water quality impacts, they have received less attention in regards to soil structure and formation. In this study, we characterized legacy sediment mineraology, composition and structure to understand how pedogenic processes are overprinting sediment layering in a 40-hectare Piedmont floodplain. To constrain the timing of deposition, we used Pb-210 and C-14 dating on buried charcoal and tree stumps. Our results show that in 100 years of forest regeneration, vegetation and oscillating floodplain conditions have driven these eroded sediment deposits to evolve as soil profiles both in structure and composition. These textural and nutrient gradients have ramifications for the subsurface flow of nutrients through the floodplain. Given the estimated millennia it will take to erode legacy sediment from Piedmont floodplains, it is important to think of these deposits as new stable environments on their own trajectory of soil evolution.