Steel refining possibilities in LF

NASA Astrophysics Data System (ADS)

Dumitru, M. G.; Ioana, A.; Constantin, N.; Ciobanu, F.; Pollifroni, M.

2018-01-01

This article presents the main possibilities for steel refining in Ladle Furnace (LF). These, are presented: steelmaking stages, steel refining through argon bottom stirring, online control of the bottom stirring, bottom stirring diagram during LF treatment of a heat, porous plug influence over the argon stirring, bottom stirring porous plug, analysis of porous plugs disposal on ladle bottom surface, bottom stirring simulation with ANSYS, bottom stirring simulation with Autodesk CFD.

Bottom-simulating reflector variability at the Costa Rica subduction zone and corresponding heat flow model

NASA Astrophysics Data System (ADS)

Cavanaugh, S.; Bangs, N. L.; Hornbach, M. J.; McIntosh, K. D.

2011-12-01

We use 3D seismic reflection data acquired in April - May 2011 by the R/V Marcus G. Langseth to extract heat flow information using the bottom-simulating reflector across the Costa Rica convergent margin. These data are part of the CRISP Project, which will image the Middle America subduction zone in 3D. The survey was conducted in an area approximately 55 x 11 km, to the northwest of the Osa Peninsula, Costa Rica. For the analysis presented here, 3D seismic data were processed with Paradigm Focus software through post-stack time migration. The bottom-simulating reflector (BSR)-a reverse polarity reflection indicating the base of the gas hydrate phase boundary-is imaged very clearly in two regions within the slope-cover sediments in the accretionary prism. In deep water environments, the BSR acts as a temperature gauge revealing subsurface temperatures across the margin. We predict BSR depth using a true 3D diffusive heat flow model combined with IODP drilling data and compare results with actual BSR depth observations to determine anomalies in heat flow. Uniform heat flow in the region should result in a deepening BSR downslope toward the trench, however our initial results indicate the BSR shoals near the trench to its shallowest level below sea floor of approximately 96 m below the sea floor, suggesting elevated heat flow towards the toe. Landward, the BSR deepens to about 333 m below the sea floor indicating lower heat flow. Both BSR segments display a trend of deepening landward from the trench, however the depth below the sea floor is greater overall for the landward segment than the segment near the toe. We suggest two regimes with differing heat flow exist across the margin that likely represent two separate fluid flow regimes - one from recently accreted sediments near the prism toe and the other through the older materials making up the prism.

The impact of floods and storms on the acoustic reflectivity of the inner continental shelf: A modeling assessment

USGS Publications Warehouse

Pratson, Lincoln F.; Hutton, E.W.H.; Kettner, A.J.; Syvitski, J.P.M.; Hill, P.S.; George, D.A.; Milligan, T.G.

2007-01-01

Flood deposition and storm reworking of sediments on the inner shelf can change the mixture of grain sizes on the seabed and thus its porosity, bulk density, bulk compressional velocity and reflectivity. Whether these changes are significant enough to be detectable by repeat sub-bottom sonar surveys, however, is uncertain. Here the question is addressed through numerical modeling. Episodic flooding of a large versus small river over the course of a century are modeled with HYDROTREND using the drainage basin characteristics of the Po and Pescara Rivers (respectively). A similarly long stochastic record of storms offshore of both rivers is simulated from the statistics of a long-term mooring recording of waves in the western Adriatic Sea. These time series are then input to the stratigraphic model SEDFLUX2D, which simulates flood deposition and storm reworking on the inner shelf beyond the river mouths. Finally, annual changes in seabed reflectivity across these shelf regions are computed from bulk densities output by SEDFLUX2D and compressional sound speeds computed from mean seafloor grain size using the analytical model of Buckingham [1997. Theory of acoustic attenuation, dispersion, and pulse propagation in unconsolidated granular materials including marine sediments. Journal of the Acoustical Society of America 102, 2579-2596; 1998. Theory of compressional and shear waves in fluidlike marine sediments. Journal of the Acoustical Society of America 103, 288-299; 2000. Wave propagation, stress relaxation, and grain-tograin shearing in saturated, unconsolidated marine sediments. Journal of the Acoustical Society of America 108, 2796-2815]. The modeling predicts reflectivities that change from 9 dB for muds farther offshore, values that agree with reflectivity measurements for these sediment types. On local scales of ???100 m, however, maximum changes in reflectivity are <0.5 dB. So are most annual changes in reflectivity over all water depths modeled (i.e., 0-35 m). Given that signal differences need to be ???2-3 dB to be resolved, the results suggest that grain-size induced changes in reflectivity caused by floods and storms will rarely be detectable by most current sub-bottom sonars. ?? 2006 Elsevier Ltd. All rights reserved.

Bottom-Interating Ocean Acoustics. Proceedings of a Conference held at SACLANTCEN on 9-13 June 1980.

DTIC Science & Technology

1980-07-15

scattering by John H. Hanrahan (M) 11 Some bottom-reflection loss anomalies near grazing and their effect on propagation in shallow water by Ole F. Hastrup (Q...SACLANTCEN CP-27 11 SOME BOTTOM-REFLECTION LOSS ANOMALIES NEAR GRAZING AND THEIR EFFECT ON PROPAGATION IN SHALLOW WATER by Ole F. Hastrup SACLANT ASW

Propagation modeling for sperm whale acoustic clicks in the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Sidorovskaia, Natalia A.; Udovydchenkov, Ilya A.; Rypina, Irina I.; Ioup, George E.; Ioup, Juliette W.; Caruthers, Jerald W.; Newcomb, Joal; Fisher, Robert

2004-05-01

Simulations of acoustic broadband (500-6000 Hz) pulse propagation in the northern Gulf of Mexico, based on environmental data collected as a part of the Littoral Acoustic Demonstration Center (LADC) experiments in the summers of 2001 and 2002, are presented. The results of the modeling support the hypothesis that consistent spectrogram interference patterns observed in the LADC marine mammal phonation data cannot be explained by the propagation effects for temporal analysis windows corresponding to the duration of an animal click, and may be due to a uniqueness of an individual animal phonation apparatus. The utilization of simulation data for the development of an animal tracking algorithm based on the acoustic recordings of a single bottom-moored hydrophone is discussed. The identification of the bottom and surface reflected clicks from the same animal is attempted. The critical ranges for listening to a deep-water forging animal by a surface receiving system are estimated. [Research supported by ONR.

Cybernetic group method of data handling (GMDH) statistical learning for hyperspectral remote sensing inverse problems in coastal ocean optics

NASA Astrophysics Data System (ADS)

Filippi, Anthony Matthew

For complex systems, sufficient a priori knowledge is often lacking about the mathematical or empirical relationship between cause and effect or between inputs and outputs of a given system. Automated machine learning may offer a useful solution in such cases. Coastal marine optical environments represent such a case, as the optical remote sensing inverse problem remains largely unsolved. A self-organizing, cybernetic mathematical modeling approach known as the group method of data handling (GMDH), a type of statistical learning network (SLN), was used to generate explicit spectral inversion models for optically shallow coastal waters. Optically shallow water light fields represent a particularly difficult challenge in oceanographic remote sensing. Several algorithm-input data treatment combinations were utilized in multiple experiments to automatically generate inverse solutions for various inherent optical property (IOP), bottom optical property (BOP), constituent concentration, and bottom depth estimations. The objective was to identify the optimal remote-sensing reflectance Rrs(lambda) inversion algorithm. The GMDH also has the potential of inductive discovery of physical hydro-optical laws. Simulated data were used to develop generalized, quasi-universal relationships. The Hydrolight numerical forward model, based on radiative transfer theory, was used to compute simulated above-water remote-sensing reflectance Rrs(lambda) psuedodata, matching the spectral channels and resolution of the experimental Naval Research Laboratory Ocean PHILLS (Portable Hyperspectral Imager for Low-Light Spectroscopy) sensor. The input-output pairs were for GMDH and artificial neural network (ANN) model development, the latter of which was used as a baseline, or control, algorithm. Both types of models were applied to in situ and aircraft data. Also, in situ spectroradiometer-derived Rrs(lambda) were used as input to an optimization-based inversion procedure. Target variables included bottom depth z b, chlorophyll a concentration [chl- a], spectral bottom irradiance reflectance Rb(lambda), and spectral total absorption a(lambda) and spectral total backscattering bb(lambda) coefficients. When applying the cybernetic and neural models to in situ HyperTSRB-derived Rrs, the difference in the means of the absolute error of the inversion estimates for zb was significant (alpha = 0.05). GMDH yielded significantly better zb than the ANN. The ANN model posted a mean absolute error (MAE) of 0.62214 m, compared with 0.55161 m for GMDH.

Orbiting Rainbows Simulation

NASA Image and Video Library

2015-04-22

This simulated image shows how a cloud of glitter in geostationary orbit would be illuminated and controlled by two laser beams. As the cloud orbits Earth, grains scatter the sun's light at different angles like many tiny prisms, similar to how rainbows are produced from light being dispersed by water droplets. That is why the project concept is called "Orbiting Rainbows." The cloud functions like a reflective surface, allowing the exoplanet (displayed in the bottom right) to be imaged. The orbit path is shown in the top right. On the bottom left, Earth's image is seen behind the cloud. To image an exoplanet, the cloud would need to have a diameter of nearly 98 feet (30 meters). This simulation confines the cloud to a 3.3 x 3.3 x 3.3 foot volume (1 x 1 x 1 meter volume) to simplify the computations. The elements of the orbiting telescope are not to scale. Orbiting Rainbows is currently in Phase II development through the NASA Innovative Advanced Concepts (NIAC) Program. It was one of five technology proposals chosen for continued study in 2014. In the current phase, Orbiting Rainbows researchers are conducting small-scale ground experiments to demonstrate how granular materials can be manipulated using lasers and simulations of how the imaging system would behave in orbit. http://photojournal.jpl.nasa.gov/catalog/PIA19318

Amplitude Variation of Bottom Simulating Reflection with Respect to Frequency - Transitional Base or Attenuation?

USGS Publications Warehouse

Lee, Myung W.

2007-01-01

The amplitude of a bottom simulating reflection (BSR), which occurs near the phase boundary between gas hydrate-bearing sediments and underlying gas-filled sediments, strongly depends on the frequency content of a seismic signal, as well as the impedance contrast across the phase boundary. A strong-amplitude BSR, detectable in a conventional seismic profile, is a good indicator of the presence of free gas beneath the phase boundary. However, the BSR as observed in low-frequency multichannel seismic data is generally difficult to identify in high-frequency, single-channel seismic data. To investigate the frequency dependence of BSR amplitudes, single-channel seismic data acquired with an air gun source at Blake Ridge, which is located off the shore of South Carolina, were analyzed in the frequency range of 10-240 Hz. The frequency-dependent impedance contrast caused by the velocity dispersion in partially gas saturated sediments is important to accurately analyze BSR amplitude. Analysis indicates that seismic attenuation of gas hydrate-bearing sediments, velocity dispersion, and a transitional base all contribute to the frequency-dependent BSR amplitude variation in the frequency range of 10-500 Hz. When velocity dispersion is incorporated into the BSR amplitude analysis, the frequency-dependent BSR amplitude at Blake Ridge can be explained with gas hydrate-bearing sediments having a quality factor of about 250 and a transitional base with a thickness of about 1 meter.

Grain size mapping in shallow rivers using spectral information: a lab spectroradiometry perspective

NASA Astrophysics Data System (ADS)

Niroumand-Jadidi, Milad; Vitti, Alfonso

2017-10-01

Every individual attribute of a riverine environment defines the overall spectral signature to be observed by an optical sensor. The spectral characteristic of riverbed is influenced not only by the type but also the roughness of substrates. Motivated by this assumption, potential of optical imagery for mapping grain size of shallow rivers (< 1 m deep) is examined in this research. The previous studies concerned with grain size mapping are all built upon the texture analysis of exposed bed material using very high resolution (i.e. cm resolution) imagery. However, the application of texturebased techniques is limited to very low altitude sensors (e.g. UAVs) to ensure the sufficient spatial resolution. Moreover, these techniques are applicable only in the presence of exposed substrates along the river channel. To address these drawbacks, this study examines the effectiveness of spectral information to make distinction among grain sizes for submerged substrates. Spectroscopic experiments are performed in controlled condition of a hydraulic lab. The spectra are collected over a water flume in a range of water depths and bottoms with several grain sizes. A spectral convolution is performed to match the spectra to WorldView-2 spectral bands. The material type of substrates is considered the same for all the experiments with only variable roughness/size of grains. The spectra observed over dry beds revealed that the brightness/reflectance increases with the grain size across all the spectral bands. Based on this finding, the above-water spectra over a river channel are simulated considering different grain sizes in the bottom. A water column correction method is then used to retrieve the bottom reflectances. Then the inferred bottom reflectances are clustered to segregate among grain sizes. The results indicate high potential of the spectral approach for clustering grain sizes (overall accuracy of 92%) which opens up some horizons for mapping this valuable attribute of rivers using remotely sensed data.

Modeling contamination of shallow unconfined aquifers through infiltration beds

USGS Publications Warehouse

Ostendorf, D.W.

1986-01-01

We model the transport of a simply reactive contaminant through an infiltration bed and underlying shallow, one-dimensional, unconfined aquifer with a plane, steeply sloping bottom in the assumed absence of dispersion and downgradient dilution. The effluent discharge and ambient groundwater flow under the infiltration beds are presumed to form a vertically mixed plume marked by an appreciable radial velocity component in the near field flow region. The near field analysis routes effluent contamination as a single linear reservoir whose output forms a source plane for the one-dimensional, far field flow region downgradient of the facility; the location and width of the source plane reflect the relative strengths of ambient flow and effluent discharge. We model far field contaminant transport, using an existing method of characteristics solution with frame speeds modified by recharge, bottom slope, and linear adsorption, and concentrations reflecting first-order reaction kinetics. The near and far field models simulate transport of synthetic detergents, chloride, total nitrogen, and boron in a contaminant plume at the Otis Air Force Base sewage treatment plant in Barnstable County, Massachusetts, with reasonable accuracy.

Overall evaluation of LANDSAT (ERTS) follow on imagery for cartographic application

NASA Technical Reports Server (NTRS)

Colvocoresses, A. P. (Principal Investigator)

1977-01-01

The author has identified the following significant results. LANDSAT imagery can be operationally applied to the revision of nautical charts. The imagery depicts shallow seas in a form that permits accurate planimetric image mapping of features to 20 meters of depth where the conditions of water clarity and bottom reflection are suitable. LANDSAT data also provide an excellent simulation of the earth's surface, for such applications as aeronautical charting and radar image correlation in aircraft and aircraft simulators. Radiometric enhancement, particularly edge enhancement, a technique only marginally successful with aerial photographs has proved to be high value when applied to LANDSAT data.

Deep seafloor arrivals in long range ocean acoustic propagation.

PubMed

Stephen, Ralph A; Bolmer, S Thompson; Udovydchenkov, Ilya A; Worcester, Peter F; Dzieciuch, Matthew A; Andrew, Rex K; Mercer, James A; Colosi, John A; Howe, Bruce M

2013-10-01

Ocean bottom seismometer observations at 5000 m depth during the long-range ocean acoustic propagation experiment in the North Pacific in 2004 show robust, coherent, late arrivals that are not readily explained by ocean acoustic propagation models. These "deep seafloor" arrivals are the largest amplitude arrivals on the vertical particle velocity channel for ranges from 500 to 3200 km. The travel times for six (of 16 observed) deep seafloor arrivals correspond to the sea surface reflection of an out-of-plane diffraction from a seamount that protrudes to about 4100 m depth and is about 18 km from the receivers. This out-of-plane bottom-diffracted surface-reflected energy is observed on the deep vertical line array about 35 dB below the peak amplitude arrivals and was previously misinterpreted as in-plane bottom-reflected surface-reflected energy. The structure of these arrivals from 500 to 3200 km range is remarkably robust. The bottom-diffracted surface-reflected mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor.

Parameterized code SHARM-3D for radiative transfer over inhomogeneous surfaces.

PubMed

Lyapustin, Alexei; Wang, Yujie

2005-12-10

The code SHARM-3D, developed for fast and accurate simulations of the monochromatic radiance at the top of the atmosphere over spatially variable surfaces with Lambertian or anisotropic reflectance, is described. The atmosphere is assumed to be laterally uniform across the image and to consist of two layers with aerosols contained in the bottom layer. The SHARM-3D code performs simultaneous calculations for all specified incidence-view geometries and multiple wavelengths in one run. The numerical efficiency of the current version of code is close to its potential limit and is achieved by means of two innovations. The first is the development of a comprehensive precomputed lookup table of the three-dimensional atmospheric optical transfer function for various atmospheric conditions. The second is the use of a linear kernel model of the land surface bidirectional reflectance factor (BRF) in our algorithm that has led to a fully parameterized solution in terms of the surface BRF parameters. The code is also able to model inland lakes and rivers. The water pixels are described with the Nakajima-Tanaka BRF model of wind-roughened water surface with a Lambertian offset, which is designed to model approximately the reflectance of suspended matter and of a shallow lake or river bottom.

Parameterized code SHARM-3D for radiative transfer over inhomogeneous surfaces

NASA Astrophysics Data System (ADS)

Lyapustin, Alexei; Wang, Yujie

2005-12-01

The code SHARM-3D, developed for fast and accurate simulations of the monochromatic radiance at the top of the atmosphere over spatially variable surfaces with Lambertian or anisotropic reflectance, is described. The atmosphere is assumed to be laterally uniform across the image and to consist of two layers with aerosols contained in the bottom layer. The SHARM-3D code performs simultaneous calculations for all specified incidence-view geometries and multiple wavelengths in one run. The numerical efficiency of the current version of code is close to its potential limit and is achieved by means of two innovations. The first is the development of a comprehensive precomputed lookup table of the three-dimensional atmospheric optical transfer function for various atmospheric conditions. The second is the use of a linear kernel model of the land surface bidirectional reflectance factor (BRF) in our algorithm that has led to a fully parameterized solution in terms of the surface BRF parameters. The code is also able to model inland lakes and rivers. The water pixels are described with the Nakajima-Tanaka BRF model of wind-roughened water surface with a Lambertian offset, which is designed to model approximately the reflectance of suspended matter and of a shallow lake or river bottom.

Determination of Acoustic Effects on Marine Mammals and Sea Turtles for the Hawaii-Southern California Training and Testing Environmental Impact Statement/Overseas Environmental Impact Statement

DTIC Science & Technology

2012-03-12

Acoustic Simulation System/Gaussian Ray Bundle (CASS/GRAB), Range-Dependent Acoustic Model (RAM), or Reflection and Refraction Multilayered Ocean / Ocean ...Multilayered Ocean / Ocean Bottoms with Shear Wave Effects RES Relative Environmental Suitability SEL Sound exposure level SOCAL Southern California SPL...the Office of Naval Research. The HSTT Study Area is comprised of established operating and warning areas across the north-central Pacific Ocean

Preliminary studies leading toward the development of a LIDAR bathymetry mapping instrument

NASA Astrophysics Data System (ADS)

Hill, John M.; Krenek, Brendan D.; Kunz, Terry D.; Krabill, William; Stetina, Fran

1993-02-01

The National Aeronautics and Space Administration (NASA) at Goddard Space Flight Center (GSFC) has developed a laser ranging device (LIDAR) which provides accurate and timely data of earth features. NASA/GSFC recently modified the sensor to include a scanning capability to produce LIDAR swaths. They have also integrated a Global Positioning System (GPS) and an Inertial Navigation System (INS) to accurately determine the absolute aircraft location and aircraft attitude (pitch, yaw, and roll), respectively. The sensor has been flown in research mode by NASA for many years. The LIDAR has been used in different configurations or modes to acquire such data as altimetry (topography), bathymetry (water depth), laser-induced fluorosensing (tracer dye movements, oil spills and oil thickness, chlorophyll and plant stress identification), forestry, and wetland discrimination studies. NASA and HARC are developing a commercial version of the instrument for topographic mapping applications. The next phase of the commercialization project will be to investigate other applications such as wetlands mapping and coastal bathymetry. In this paper we report on preliminary laboratory measurements to determine the feasibility of making accurate depth measurements in relatively shallow water (approximately 2 to 6 feet deep) using a LIDAR system. The LIDAR bathymetry measurements are relatively simple in theory. The water depth is determined by measuring the time interval between the water surface reflection and the bottom surface reflection signals. Depth is then calculated by dividing by the index of refraction of water. However, the measurements are somewhat complicated due to the convolution of the water surface return signal with the bottom surface return signal. Therefore in addition to the laboratory experiments, computer simulations of the data were made to show these convolution effects in the return pulse waveform due to: (1) water depth, and (2) changes in bottom surface reflectivity.

Preliminary Studies Leading Toward the Development of a LIDAR Bathymetry Mapping Instrument

NASA Technical Reports Server (NTRS)

Hill, John M.; Krenek, Brendan D.; Kunz, Terry D.; Krabill, William; Stetina, Fran

1993-01-01

The National Aeronautics and Space Administration (NASA) at Goddard Space Flight Center (GSFC) has developed a laser ranging device (LIDAR) which provides accurate and timely data of earth features. NASA/GSFC recently modified the sensor to include a scanning capability to produce LIDAR swaths. They have also integrated a Global Positioning System (GPS) and an Inertial Navigation System (INS) to accurately determine the absolute aircraft location and aircraft attitude (pitch, yaw, and roll), respectively. The sensor has been flown in research mode by NASA for many years. The LIDAR has been used in different configurations or modes to acquire such data as altimetry (topography), bathymetry (water depth), laser-induced fluorosensing (tracer dye movements, oil spills and oil thickness, chlorophyll and plant stress identification), forestry, and wetland discrimination studies. NASA and HARC are developing a commercial version of the instrument for topographic mapping applications. The next phase of the commercialization project will be to investigate other applications such as wetlands mapping and coastal bathymetry. In this paper we report on preliminary laboratory measurements to determine the feasibility of making accurate depth measurements in relatively shallow water (approximately 2 to 6 feet deep) using a LIDAR system. The LIDAR bathymetry measurements are relatively simple in theory. The water depth is determined by measuring the time interval between the water surface reflection and the bottom surface reflection signals. Depth is then calculated by dividing by the index of refraction of water. However, the measurements are somewhat complicated due to the convolution of the water surface return signal with the bottom surface return signal. Therefore in addition to the laboratory experiments, computer simulations of the data were made to show these convolution effects in the return pulse waveform due to: (1) water depth, and (2) changes in bottom surface reflectivity.

Analysis of thematic mapper simulator data acquired during winter season over Pearl River, Mississippi, test site

NASA Technical Reports Server (NTRS)

Anderson, J. E.; Kalcic, M. T. (Principal Investigator)

1982-01-01

Digital processed aircraft-acquired thematic mapping simulator (TMS) data collected during the winter season over a forested site in southern Mississippi are presented to investigate the utility of TMS data for use in forest inventories and monitoring. Analyses indicated that TMS data are capable of delineating the mixed forest land cover type to an accuracy of 92.5 % correct. The accuracies associated with river bottom forest and pine forest were 95.5 and 91.5 % correct. The accuracies associated with river bottom forest and pine forest were 95.5 and 91.5 % correct, respectively. The figures reflect the performance for products produced using the best subset of channels for each forest cover type. It was found that the choice of channels (subsets) has a significant effect on the accuracy of classification produced, and that the same channels are not the most desirable for all three forest types studied. Both supervised and unsupervised spectral signature development techniques are evaluated; the unsupervised methods proved unacceptable for the three forest types considered.

Remote sensing estimation of colored dissolved organic matter (CDOM) in optically shallow waters

NASA Astrophysics Data System (ADS)

Li, Jiwei; Yu, Qian; Tian, Yong Q.; Becker, Brian L.

2017-06-01

It is not well understood how bottom reflectance of optically shallow waters affects the algorithm performance of colored dissolved organic matters (CDOM) retrieval. This study proposes a new algorithm that considers bottom reflectance in estimating CDOM absorption from optically shallow inland or coastal waters. The field sampling was conducted during four research cruises within the Saginaw River, Kawkawlin River and Saginaw Bay of Lake Huron. A stratified field sampling campaign collected water samples, determined the depth at each sampling location and measured optical properties. The sampled CDOM absorption at 440 nm broadly ranged from 0.12 to 8.46 m-1. Field sample analysis revealed that bottom reflectance does significantly change water apparent optical properties. We developed a CDOM retrieval algorithm (Shallow water Bio-Optical Properties algorithm, SBOP) that effectively reduces uncertainty by considering bottom reflectance in shallow waters. By incorporating the bottom contribution in upwelling radiances, the SBOP algorithm was able to explain 74% of the variance of CDOM values (RMSE = 0.22 and R2 = 0.74). The bottom effect index (BEI) was introduced to efficiently separate optically shallow and optically deep waters. Based on the BEI, an adaptive approach was proposed that references the amount of bottom effect in order to identify the most suitable algorithm (optically shallow water algorithm [SBOP] or optically deep water algorithm [QAA-CDOM]) to improve CDOM estimation (RMSE = 0.22 and R2 = 0.81). Our results potentially help to advance the capability of remote sensing in monitoring carbon pools at the land-water interface.

Geoacoustic inversion with two source-receiver arrays in shallow water.

PubMed

Sukhovich, Alexey; Roux, Philippe; Wathelet, Marc

2010-08-01

A geoacoustic inversion scheme based on a double beamforming algorithm in shallow water is proposed and tested. Double beamforming allows identification of multi-reverberated eigenrays propagating between two vertical transducer arrays according to their emission and reception angles and arrival times. Analysis of eigenray intensities yields the bottom reflection coefficient as a function of angle of incidence. By fitting the experimental reflection coefficient with a theoretical prediction, values of the acoustic parameters of the waveguide bottom can be extracted. The procedure was initially tested in a small-scale tank experiment for a waveguide with a Plexiglas bottom. Inversion results for the speed of shear waves in Plexiglas are in good agreement with the table values. A similar analysis was applied to data collected during an at-sea experiment in shallow coastal waters of the Mediterranean. Bottom reflection coefficient was fitted with the theory in which bottom sediments are modeled as a multi-layered system. Retrieved bottom parameters are in quantitative agreement with those determined from a prior inversion scheme performed in the same area. The present study confirms the interest in processing source-receiver array data through the double beamforming algorithm, and indicates the potential for application of eigenray intensity analysis to geoacoustic inversion problems.

Differential Frequency Hopping (DFH) Modulation for Underwater Acoustic Communications and Networking

DTIC Science & Technology

2009-10-09

trains the coefficients c of a finite impulse response (FIR) filter by gradient descent. The coefficients at iteration k + 1 are computed with the update... absorption . Figure 9 shows the reflection loss as a function of grazing angle for this bottom model. Note that below 30◦ this bottom model predicts...less than 1 dB loss per ray bounce. 11 Figure 9: Jackson bottom reflection loss for sand at 15 kHz Absorption Loss The absorption loss in the medium was

The character and amplitude of ‘discontinuous’ bottom-simulating reflections in marine seismic data

DOE PAGES

Hillman, Jess I. T.; Cook, Ann E.; Sawyer, Derek E.; ...

2016-11-22

Bottom-simulating reflections (BSRs) identified in seismic data are well documented; and are commonly interpreted to indicate the presence of gas hydrates along continental margins, as well as to estimate regional volumes of gas hydrate. A BSR is defined as a reflection that sub-parallels the seafloor but is opposite in polarity and cross-cuts dipping sedimentary strata. BSRs form as a result of a strong negative acoustic impedance contrast. BSRs, however, are a diverse seismic phenomena that manifest in strikingly contrasting ways in different geological settings, and in different seismic data types. We investigate the characteristics of BSRs, using conventional and highmore » resolution, 2D and 3D seismic data sets in three locations: the Terrebonne and Orca Basins in the Gulf of Mexico, and Blake Ridge on the US Atlantic Margin. The acquisition geometry and frequency content of the seismic data significantly impact the resultant character of BSRs, as observed with depth and amplitude maps of the BSRs. Furthermore, our amplitude maps reinforce the concept that the BSR represents a zone, over which the transition from hydrate to free gas occurs, as opposed to the conventional model of the BSR occurring at a single interface. Our results show that a BSR can be mapped in three dimensions but it is not spatially continuous, at least not at the basin scale. Rather, a BSR manifests itself as a discontinuous, or patchy, reflection and only at local scales is it continuous. We suggest the discontinuous nature of BSRs is the result of variable saturation and distribution of free gas and hydrate, acquisition geometry and frequency content of the recorded seismic data. Lastly, the commonly accepted definition of a BSR should be broadened with careful consideration of these factors, to represent the uppermost extent of enhanced amplitude at the shallowest occurrence of free gas trapped by overlying hydrate-bearing sediments.« less

The character and amplitude of 'discontinuous' bottom-simulating reflections in marine seismic data

NASA Astrophysics Data System (ADS)

Hillman, Jess I. T.; Cook, Ann E.; Sawyer, Derek E.; Küçük, H. Mert; Goldberg, David S.

2017-02-01

Bottom-simulating reflections (BSRs) identified in seismic data are well documented; and are commonly interpreted to indicate the presence of gas hydrates along continental margins, as well as to estimate regional volumes of gas hydrate. A BSR is defined as a reflection that sub-parallels the seafloor but is opposite in polarity and cross-cuts dipping sedimentary strata. BSRs form as a result of a strong negative acoustic impedance contrast. BSRs, however, are a diverse seismic phenomena that manifest in strikingly contrasting ways in different geological settings, and in different seismic data types. We investigate the characteristics of BSRs, using conventional and high resolution, 2D and 3D seismic data sets in three locations: the Terrebonne and Orca Basins in the Gulf of Mexico, and Blake Ridge on the US Atlantic Margin. The acquisition geometry and frequency content of the seismic data significantly impact the resultant character of BSRs, as observed with depth and amplitude maps of the BSRs. Furthermore, our amplitude maps reinforce the concept that the BSR represents a zone, over which the transition from hydrate to free gas occurs, as opposed to the conventional model of the BSR occurring at a single interface. Our results show that a BSR can be mapped in three dimensions but it is not spatially continuous, at least not at the basin scale. Rather, a BSR manifests itself as a discontinuous, or patchy, reflection and only at local scales is it continuous. We suggest the discontinuous nature of BSRs is the result of variable saturation and distribution of free gas and hydrate, acquisition geometry and frequency content of the recorded seismic data. The commonly accepted definition of a BSR should be broadened with careful consideration of these factors, to represent the uppermost extent of enhanced amplitude at the shallowest occurrence of free gas trapped by overlying hydrate-bearing sediments.

The character and amplitude of ‘discontinuous’ bottom-simulating reflections in marine seismic data

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

Hillman, Jess I. T.; Cook, Ann E.; Sawyer, Derek E.

Bottom-simulating reflections (BSRs) identified in seismic data are well documented; and are commonly interpreted to indicate the presence of gas hydrates along continental margins, as well as to estimate regional volumes of gas hydrate. A BSR is defined as a reflection that sub-parallels the seafloor but is opposite in polarity and cross-cuts dipping sedimentary strata. BSRs form as a result of a strong negative acoustic impedance contrast. BSRs, however, are a diverse seismic phenomena that manifest in strikingly contrasting ways in different geological settings, and in different seismic data types. We investigate the characteristics of BSRs, using conventional and highmore » resolution, 2D and 3D seismic data sets in three locations: the Terrebonne and Orca Basins in the Gulf of Mexico, and Blake Ridge on the US Atlantic Margin. The acquisition geometry and frequency content of the seismic data significantly impact the resultant character of BSRs, as observed with depth and amplitude maps of the BSRs. Furthermore, our amplitude maps reinforce the concept that the BSR represents a zone, over which the transition from hydrate to free gas occurs, as opposed to the conventional model of the BSR occurring at a single interface. Our results show that a BSR can be mapped in three dimensions but it is not spatially continuous, at least not at the basin scale. Rather, a BSR manifests itself as a discontinuous, or patchy, reflection and only at local scales is it continuous. We suggest the discontinuous nature of BSRs is the result of variable saturation and distribution of free gas and hydrate, acquisition geometry and frequency content of the recorded seismic data. Lastly, the commonly accepted definition of a BSR should be broadened with careful consideration of these factors, to represent the uppermost extent of enhanced amplitude at the shallowest occurrence of free gas trapped by overlying hydrate-bearing sediments.« less

Textile inspired flexible metamaterial with negative refractive index

NASA Astrophysics Data System (ADS)

Burgnies, L.; Lheurette, É.; Lippens, D.

2015-04-01

This work introduces metallo-dielectric woven fabric as a metamaterial for phase-front manipulation. Dispersion diagram as well as effective medium parameters retrieved from reflection and transmission coefficients point out negative values of refractive index. By numerical simulations, it is evidenced that a pair of meandered metallic wires, arranged in a top to bottom configuration, can yield to a textile metamaterial with simultaneously negative permittivity and permeability. While the effective negative permittivity stems from the metallic grid arrangement, resonating current loop resulting from the top to bottom configuration of two meandered metallic wires in near proximity produces magnetic activity with negative permeability. By adjusting the distance between pairs of metallic wires, the electric plasma frequency can be shifted to overlap the magnetic resonance. Finally, it is shown that the woven metamaterial is insensitive to the incident angle up to around 60°.

Size-controllable nanopyramids photonic crystal selectively grown on p-GaN for enhanced light-extraction of light-emitting diodes.

PubMed

Du, Chengxiao; Wei, Tongbo; Zheng, Haiyang; Wang, Liancheng; Geng, Chong; Yan, Qingfeng; Wang, Junxi; Li, Jinmin

2013-10-21

Size-controllable p-GaN hexagonal nanopyramids (HnPs)-photonic crystal (PhC) structures were selectively grown on flat p-GaN layer for the elimination of total internal reflection of light-emitting diodes (LEDs). The LEDs with HnPs-PhC of 46.3% bottom fill factor (PhC lattice constant is 730 nm) showed an improved light output power by 99.9% at forward current of 350 mA compared to the reference LEDs with flat p-GaN layer. We confirmed the effect of HnPs-PhC with different bottom fill factors and the effect of nanopyramid-shaped and nanocolumn-shaped PhC on the light-extraction of LEDs was also investigated by using three-dimensional finite-difference time-domain simulations.

Passive bottom reflection-loss estimation using ship noise and a vertical line array.

PubMed

Muzi, Lanfranco; Siderius, Martin; Verlinden, Christopher M

2017-06-01

An existing technique for passive bottom-loss estimation from natural marine surface noise (generated by waves and wind) is adapted to use noise generated by ships. The original approach-based on beamforming of the noise field recorded by a vertical line array of hydrophones-is retained; however, additional processing is needed in order for the field generated by a passing ship to show features that are similar to those of the natural surface-noise field. A necessary requisite is that the ship position, relative to the array, varies over as wide a range of steering angles as possible, ideally passing directly over the array to ensure coverage of the steepest angles. The methodology is illustrated through simulation and applied to data from a field experiment conducted offshore of San Diego, CA in 2009.

Large Eddy Simulations of a Bottom Boundary Layer Under a Shallow Geostrophic Front

NASA Astrophysics Data System (ADS)

Bateman, S. P.; Simeonov, J.; Calantoni, J.

2017-12-01

The unstratified surf zone and the stratified shelf waters are often separated by dynamic fronts that can strongly impact the character of the Ekman bottom boundary layer. Here, we use large eddy simulations to study the turbulent bottom boundary layer associated with a geostrophic current on a stratified shelf of uniform depth. The simulations are initialized with a spatially uniform vertical shear that is in geostrophic balance with a pressure gradient due to a linear horizontal temperature variation. Superposed on the temperature front is a stable vertical temperature gradient. As turbulence develops near the bottom, the turbulence-induced mixing gradually erodes the initial uniform temperature stratification and a well-mixed layer grows in height until the turbulence becomes fully developed. The simulations provide the spatial distribution of the turbulent dissipation and the Reynolds stresses in the fully developed boundary layer. We vary the initial linear stratification and investigate its effect on the height of the bottom boundary layer and the turbulence statistics. The results are compared to previous models and simulations of stratified bottom Ekman layers.

Exit Presentation: Infrared Thermography on Graphite/Epoxy

NASA Technical Reports Server (NTRS)

Comeaux, Kayla

2010-01-01

This slide presentation reports on the internship project that was accomplished during the summer of 2010. The objectives of the project were to: (1) Simulate Flash Thermography on Graphite/Epoxy Flat Bottom hole Specimen and thin void specimens, (2) Obtain Flash Thermography data on Graphite/Epoxy flat bottom hole specimens, (3) Compare experimental results with simulation results, Compare Flat Bottom Hole Simulation with Thin Void Simulation to create a graph to determine size of IR Thermography detected defects

An analytical model for subsurface irradiance and remote sensing reflectance in deep and shallow case-2 waters.

PubMed

Albert, A; Mobley, C

2003-11-03

Subsurface remote sensing signals, represented by the irradiance re fl ectance and the remote sensing re fl ectance, were investigated. The present study is based on simulations with the radiative transfer program Hydrolight using optical properties of Lake Constance (German: Bodensee) based on in-situ measurements of the water constituents and the bottom characteristics. Analytical equations are derived for the irradiance re fl ectance and remote sensing re fl ectance for deep and shallow water applications. The input of the parameterization are the inherent optical properties of the water - absorption a(lambda) and backscattering bb(lambda). Additionally, the solar zenith angle thetas, the viewing angle thetav , and the surface wind speed u are considered. For shallow water applications the bottom albedo RB and the bottom depth zB are included into the parameterizations. The result is a complete set of analytical equations for the remote sensing signals R and Rrs in deep and shallow waters with an accuracy better than 4%. In addition, parameterizations of apparent optical properties were derived for the upward and downward diffuse attenuation coefficients Ku and Kd.

Absolute cavity pyrgeometer

DOEpatents

Reda, Ibrahim

2013-10-29

Implementations of the present disclosure involve an apparatus and method to measure the long-wave irradiance of the atmosphere or long-wave source. The apparatus may involve a thermopile, a concentrator and temperature controller. The incoming long-wave irradiance may be reflected from the concentrator to a thermopile receiver located at the bottom of the concentrator to receive the reflected long-wave irradiance. In addition, the thermopile may be thermally connected to a temperature controller to control the device temperature. Through use of the apparatus, the long-wave irradiance of the atmosphere may be calculated from several measurements provided by the apparatus. In addition, the apparatus may provide an international standard of pyrgeometers' calibration that is traceable back to the International System of Units (SI) rather than to a blackbody atmospheric simulator.

Top-down and bottom-up neurodynamic evidence in patients with tinnitus.

PubMed

Hong, Sung Kwang; Park, Sejik; Ahn, Min-Hee; Min, Byoung-Kyong

2016-12-01

Although a peripheral auditory (bottom-up) deficit is an essential prerequisite for the generation of tinnitus, central cognitive (top-down) impairment has also been shown to be an inherent neuropathological mechanism. Using an auditory oddball paradigm (for top-down analyses) and a passive listening paradigm (for bottom-up analyses) while recording electroencephalograms (EEGs), we investigated whether top-down or bottom-up components were more critical in the neuropathology of tinnitus, independent of peripheral hearing loss. We observed significantly reduced P300 amplitudes (reflecting fundamental cognitive processes such as attention) and evoked theta power (reflecting top-down regulation in memory systems) for target stimuli at the tinnitus frequency of patients with tinnitus but without hearing loss. The contingent negative variation (reflecting top-down expectation of a subsequent event prior to stimulation) and N100 (reflecting auditory bottom-up selective attention) were different between the healthy and patient groups. Interestingly, when tinnitus patients were divided into two subgroups based on their P300 amplitudes, their P170 and N200 components, and annoyance and distress indices to their tinnitus sound were different. EEG theta-band power and its Granger causal neurodynamic results consistently support a double dissociation of these two groups in both top-down and bottom-up tasks. Directed cortical connectivity corroborates that the tinnitus network involves the anterior cingulate and the parahippocampal areas, where higher-order top-down control is generated. Together, our observations provide neurophysiological and neurodynamic evidence revealing a differential engagement of top-down impairment along with deficits in bottom-up processing in patients with tinnitus but without hearing loss. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Multi-spectral Metasurface for Different Functional Control of Reflection Waves.

PubMed

Huang, Cheng; Pan, Wenbo; Ma, Xiaoliang; Luo, Xiangang

2016-03-22

Metasurface have recently generated much interest due to its strong manipulation of electromagnetic wave and its easy fabrication compared to bulky metamaterial. Here, we propose the design of a multi-spectral metasurface that can achieve beam deflection and broadband diffusion simultaneously at two different frequency bands. The metasurface is composed of two-layered metallic patterns backed by a metallic ground plane. The top-layer metasurface utilizes the cross-line structures with two different dimensions for producing 0 and π reflection phase response, while the bottom-layer metasurface is realized by a topological morphing of the I-shaped patterns for creating the gradient phase distribution. The whole metasurface is demonstrated to independently control the reflected waves to realize different functions at two bands when illuminated by a normal linear-polarized wave. Both simulation and experimental results show that the beam deflection is achieved at K-band with broadband diffusion at X-Ku band.

Multi-spectral Metasurface for Different Functional Control of Reflection Waves

PubMed Central

Huang, Cheng; Pan, Wenbo; Ma, Xiaoliang; Luo, Xiangang

2016-01-01

Metasurface have recently generated much interest due to its strong manipulation of electromagnetic wave and its easy fabrication compared to bulky metamaterial. Here, we propose the design of a multi-spectral metasurface that can achieve beam deflection and broadband diffusion simultaneously at two different frequency bands. The metasurface is composed of two-layered metallic patterns backed by a metallic ground plane. The top-layer metasurface utilizes the cross-line structures with two different dimensions for producing 0 and π reflection phase response, while the bottom-layer metasurface is realized by a topological morphing of the I-shaped patterns for creating the gradient phase distribution. The whole metasurface is demonstrated to independently control the reflected waves to realize different functions at two bands when illuminated by a normal linear-polarized wave. Both simulation and experimental results show that the beam deflection is achieved at K-band with broadband diffusion at X-Ku band. PMID:27001206

Bottom depth and type for shallow waters: Hyperspectral observations from a blimp

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

Lee, ZhongPing; Carder, K.; Steward, R.

1997-08-01

In a study of a blimp transect over Tampa Bay (Florida), hyperspectral upwelling radiance over the sand and seagrass bottoms was measured. These measurements were converted to hyperspectral remote-sensing reflectances. Using a shallow-water remote-sensing-reflectance model, in-water optical properties, bottom depths and bottom albedos were derived analytically and simultaneously by an optimization procedure. In the process, curvatures of sand and seagrass albedos were used. Also used was a model of absorption spectrum of phytoplankton pigments. The derived bottom depths were compared with bathymetry charts and found to agree well. This study suggests that a low-flying blimp is a useful platform formore » the study and mapping of coastal water environments. The optical model as well as the data-reduction procedure used are practical for the retrieval of shallow water optical properties.« less

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.

Measurement of ocean water optical properties and seafloor reflectance with scanning hydrographic operational airborne lidar survey (SHOALS): II. Practical results and comparison with independent data

NASA Astrophysics Data System (ADS)

Tuell, Grady H.; Feygels, Viktor; Kopilevich, Yuri; Weidemann, Alan D.; Cunningham, A. Grant; Mani, Reza; Podoba, Vladimir; Ramnath, Vinod; Park, J. Y.; Aitken, Jen

2005-08-01

Estimation of water column optical properties and seafloor reflectance (532 nm) is demonstrated using recent SHOALS data collected at Fort Lauderdale, Florida (November, 2003). To facilitate this work, the first radiometric calibrations of SHOALS were performed. These calibrations permit a direct normalization of recorded data by converting digitized counts at the output of the SHOALS receivers to input optical power. For estimation of environmental parameters, this normalization is required to compensate for the logarithmic compression of the signals and the finite frequency of the bandpass of the detector/amplifier. After normalization, the SHOALS data are used to estimate the backscattering coefficient, the beam attenuation coefficient, the single-scattering albedo, the VSF asymmetry, and seafloor reflectance by fitting simulated waveforms to actual waveforms measured by the SHOALS APD and PMT receivers. The resulting estimates of these water column optical properties are compared to in-situ measurements acquired at the time of the airborne data collections. Images of green laser bottom reflectance are also presented and compared to reflectance estimated from simultaneously acquired passive spectral data.

Limitations of quantitative analysis of deep crustal seismic reflection data: Examples from GLIMPCE

USGS Publications Warehouse

Lee, Myung W.; Hutchinson, Deborah R.

1992-01-01

Amplitude preservation in seismic reflection data can be obtained by a relative true amplitude (RTA) processing technique in which the relative strength of reflection amplitudes is preserved vertically as well as horizontally, after compensating for amplitude distortion by near-surface effects and propagation effects. Quantitative analysis of relative true amplitudes of the Great Lakes International Multidisciplinary Program on Crustal Evolution seismic data is hampered by large uncertainties in estimates of the water bottom reflection coefficient and the vertical amplitude correction and by inadequate noise suppression. Processing techniques such as deconvolution, F-K filtering, and migration significantly change the overall shape of amplitude curves and hence calculation of reflection coefficients and average reflectance. Thus lithological interpretation of deep crustal seismic data based on the absolute value of estimated reflection strength alone is meaningless. The relative strength of individual events, however, is preserved on curves generated at different stages in the processing. We suggest that qualitative comparisons of relative strength, if used carefully, provide a meaningful measure of variations in reflectivity. Simple theoretical models indicate that peg-leg multiples rather than water bottom multiples are the most severe source of noise contamination. These multiples are extremely difficult to remove when the water bottom reflection coefficient is large (>0.6), a condition that exists beneath parts of Lake Superior and most of Lake Huron.

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.

Sound Speed and Attenuation in Multiphase Media

DTIC Science & Technology

2008-09-20

Stoll [2] report shear wave speeds between 100 to 300 m/s for sandy sediments with porosities of 40-50%. Hastrup [12:121-127] reports empirical...by a factor of 64. The importance of shear wave conversion in bottom reflection has been treated by Hastrup [12] while the depth dependent...843, 1962 [12] O. F. Hastrup , Acoustic Bottom Reflectivity, Technical Report SR-115 SACLANT Undersea Research Centre, La Spezia, Italy, 1986. [13

Fate of internal waves on a shallow shelf

NASA Astrophysics Data System (ADS)

Davis, Kristen; Arthur, Robert; Reid, Emma; Decarlo, Thomas; Cohen, Anne

2017-11-01

Internal waves strongly influence the physical and chemical environment of coastal ecosystems worldwide. We report novel observations from a distributed temperature sensing (DTS) system that tracked the transformation of internal waves from the shelf break to the surf zone over a shelf-slope region of a coral atoll in the South China Sea. The spatially-continuous view of the near-bottom temperature field provided by the DTS offers a perspective of physical processes previously available only in laboratory settings or numerical models. These processes include internal wave reflection off a natural slope, shoreward transport of dense fluid within trapped cores, internal ``tide pools'' (dense water left behind after the retreat of an internal wave), and internal run-down (near-bottom, offshore-directed jets of water preceding a breaking internal wave). Analysis shows that the fate of internal waves on this shelf - whether they are transmitted into shallow waters or reflected back offshore - is mediated by local water column density and shear structure, with important implications for nearshore distributions of energy, heat, and nutrients. We acknowledge the US Army Research Laboratory DoD Supercomputing Resource Center for computer time on Excalibur, which was used for the numerical simulations in this work. Funding for field work supported by Academia Sinica and for K.D. and E.R. from NSF.

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.

Numerical modelling of GPR electromagnetic fields for locating burial sites

NASA Astrophysics Data System (ADS)

Carcione, José M.; Karczewski, Jerzy; Mazurkiewicz, Ewelina; Tadeusiewicz, Ryszard; Tomecka-Suchoń, Sylwia

2017-11-01

Ground-penetrating radar (GPR) is commonly used for locating burial sites. In this article, we acquired radargrams at a site where a domestic pig cadaver was buried. The measurements were conducted with the ProEx System GPR manufactured by the Swedish company Mala Geoscience with an antenna of 500MHz. The event corresponding to the pig can be clearly seen in the measurements. In order to improve the interpretation, the electromagnetic field is compared to numerical simulations computed with the pseudo-spectral Fourier method. A geological model has been defined on the basis of assumed electromagnetic properties (permittivity, conductivity and magnetic permeability). The results, when compared with the GPR measurements, show a dissimilar amplitude behaviour, with a stronger reflection event from the bottom of the pit. We have therefore performed another simulation by decreasing the electrical conductivity of the body very close to that of air. The comparison improved, showing more reflections, which could be an indication that the body contains air or has been degraded to a certain extent that the electrical resistivity has greatly increased.

Mediterranean Environmental Acoustic Data Catalog

DTIC Science & Technology

1975-05-01

kH.z. (C) SACLANT ASW Centre returned to the Tyrrhenian Sea to an area previously reported by Hastrup and Lallement to conduct extended tests uhich...were reported in 1962 by Hastrup . In these tests both explosive charges and an AN/SQS-26 sonar were used as sources, with a shallow suspended hydrophone...bottom at the point of reflection. The measured bottom reflection loss values in these tests agreed with the previously reported tests ( Hastrup and

Plate-Focusing Based on a Meta-Molecule of Dendritic Structure in the Visible Frequency.

PubMed

Cheng, Suna; An, Di; Chen, Huan; Zhao, Xiaopeng

2018-05-31

To study the potential application of metasurfaces in lens technology, we propose a dendritic meta-molecule surface (also referred to as a dendritic metasurface) and realize the focusing effect in the visible spectrum through simulations and experiments. Using asymmetric dendritic structures, this metasurface can achieve distinct broadband anomalous reflection and refraction. When the metasurface is rotated by 180° around the z axis, anomalous reflection and refraction in vertically incident optical waves are in opposite directions. Considering this feature, a metasurface is designed to achieve a prominent plate-focusing effect. Samples with a transmission peak of green light at 555 nm, yellow light at 580 nm, and red light at 650 nm were prepared using bottom-up electrochemical deposition, and the focus intensity of approximately 10% and focal length of almost 600 µm were experimentally demonstrated.

Validity of the semi-infinite tumor model in diffuse reflectance spectroscopy for epithelial cancer diagnosis: a Monte Carlo study

NASA Astrophysics Data System (ADS)

Zhu, Caigang; Liu, Quan

2011-08-01

The accurate understanding of optical properties of human tissues plays an important role in the optical diagnosis of early epithelial cancer. Many inverse models used to determine the optical properties of a tumor have assumed that the tumor was semi-infinite, which infers infinite width and length but finite thickness. However, this simplified assumption could lead to large errors for small tumor, especially at the early stages. We used a modified Monte Carlo code, which is able to simulate light transport in a layered tissue model with buried tumor-like targets, to investigate the validity of the semi-infinite tumor assumption in two common epithelial tissue models: a squamous cell carcinoma (SCC) tissue model and a basal cell carcinoma (BCC) tissue model. The SCC tissue model consisted of three layers, i.e. the top epithelium, the middle tumor and the bottom stroma. The BCC tissue model also consisted of three layers, i.e. the top epidermis, the middle tumor and the bottom dermis. Diffuse reflectance was simulated for two common fiber-optic probes. In one probe, both source and detector fibers were perpendicular to the tissue surface; while in the other, both fibers were tilted at 45 degrees relative to the normal axis of the tissue surface. It was demonstrated that the validity of the semi-infinite tumor model depends on both the fiber-optic probe configuration and the tumor dimensions. Two look-up tables, which relate the validity of the semi-infinite tumor model to the tumor width in terms of the source-detector separation, were derived to guide the selection of appropriate tumor models and fiber optic probe configuration for the optical diagnosis of early epithelial cancers.

Polarization-resolved simulations of multiple-order rainbows using realistic raindrop shapes

NASA Astrophysics Data System (ADS)

Haußmann, Alexander

2016-05-01

This paper presents selected results of a simulation study of the first five (primary-quinary) rainbow orders based on a realistic, size-dependent shape model for falling raindrops, taking into account that the drops' bottom part is flattened to higher degree than the dome-like top part. Moreover, broad drop size distributions are included in the simulations, as it is one goal of this paper to analyze, whether the predicted amplification and attenuation patterns for higher-order rainbows, as derived from previous simulations with monodisperse drop sizes, will still be pronounced under the conditions of natural rainfall. Secondly, deviations of the multiple rainbow orders' polarization state from the reference case of spherical drops are discussed. It is shown that each rainbow order may contain a small amount of circularly polarized light due to total internal reflections. Thirdly, it is investigated, how the conditions that generate twinned primary rainbows will affect the higher orders. For the simulations, geometric-optic ray tracing of the full Stokes vector as well as an approximate approach using appropriately shifted Debye series data is applied.

Analytical and numerical solution for wave reflection from a porous wave absorber

NASA Astrophysics Data System (ADS)

Magdalena, Ikha; Roque, Marian P.

2018-03-01

In this paper, wave reflection from a porous wave absorber is investigated theoretically and numerically. The equations that we used are based on shallow water type model. Modification of motion inside the absorber is by including linearized friction term in momentum equation and introducing a filtered velocity. Here, an analytical solution for wave reflection coefficient from a porous wave absorber over a flat bottom is derived. Numerically, we solve the equations using the finite volume method on a staggered grid. To validate our numerical model, comparison of the numerical reflection coefficient is made against the analytical solution. Further, we implement our numerical scheme to study the evolution of surface waves pass through a porous absorber over varied bottom topography.

Fidelity of Simulation for Pilot Training

DTIC Science & Technology

1980-12-01

is worthwhile emphasizing at this point that the study is focused on fidelity of simulators for pilot training. It does not consider simulation for...significantly higher cost than low fidelity. Motivation for 0~is study is to obtain background information on the effect of simulator fidel- ity on ...bottom of the diagram is the recom- mended approach. In practice, however, it is often the case that emphasis is placed on work in the bottom segment of

Fishing and bottom water temperature as drivers of change in maximum shell length in Atlantic surfclams (Spisula solidissima)

NASA Astrophysics Data System (ADS)

Munroe, D. M.; Narváez, D. A.; Hennen, D.; Jacobson, L.; Mann, R.; Hofmann, E. E.; Powell, E. N.; Klinck, J. M.

2016-03-01

Maximum shell length of Atlantic surfclams (Spisula solidissima) on the Middle Atlantic Bight (MAB) continental shelf, obtained from federal fishery survey data from 1982-present, has decreased by 15-20 mm. Two potential causes of this decreasing trend, fishery removal of large animals and stress due to warming bottom temperatures, were investigated using an individual-based model for post-settlement surfclams and a fifty-year hindcast of bottom water temperatures on the MAB. Simulations showed that fishing and/or warming bottom water temperature can cause decreases in maximum surfclam shell length (body size) equivalent to those observed in the fished stock. Independently, either localized fishing rates of 20% or sustained bottom temperatures that are 2 °C warmer than average conditions generate the observed decrease in maximum shell length. However, these independent conditions represent extremes and are not sustained in the MAB. The combined effects of fishing and warmer temperatures can generate simulated length decreases that are similar to observed decreases. Interannual variability in bottom water temperatures can also generate fluctuations in simulated shell length of up to 20 mm over a period of 10-15 years. If the change in maximum size is not genotypic, simulations also suggest that shell size composition of surfclam populations can recover if conditions change; however, that recovery could take a decade to become evident.

Distribution and Origin of Multiple Bottom Simulating Reflectors in the Danube Deep-Sea Fan, Black Sea

NASA Astrophysics Data System (ADS)

Zander, T.; Berndt, C.; Haeckel, M.; Klaucke, I.; Bialas, J.; Klaeschen, D.

2015-12-01

The sedimentary succession of the anoxic, deep Black Sea Basin is an ideal location for organic matter preservation and microbial methane generation. In the depth range of the gas hydrate stability zone (GHSZ) methane gas forms methane hydrates and presumably large accumulations of gas hydrate exist in porous sediments, such as those encountered on the Danube deep-sea fan. High-resolution P-Cable 3D seismic data reveals the character and distribution of up to four stacked bottom simulating reflectors (BSR) within the channel-levee systems of the Danube deep-sea fan. These anomalous BSRs were first described by Popescu et al. (2006). The geological processes that lead to multiple BSRs are still poorly understood. The theoretical base of the GHSZ calculated from regional temperature gradients and salinity data is in agreement with the shallowest BSR in the area. We have tested two hypotheses that may explain the formation of the lower BSRs. The first hypothesis is that the lower BSRs are formed by overpressure compartments. Large amounts of free gas below the BSRs are trapped in the pore space increasing the pressure above hydrostatic condition up to a level where gas hydrates are stable again. The second hypothesis is that the lower BSRs are linked to the growth of the Danube fan. Sediment deposits from the outer levee of the youngest channel cover the area hosting multiple BSRs. The youngest channel developed during the last sea level lowstand that is correlated with the Neo-Euxinian that started 23,000 yrs. BP. We propose that the rapid sediment loading during sea level lowstands is a key factor for the preservation of paleo-BSRs in the study area. References Popescu, I., De Batist, M., Lericolais, G., Nouzé, H., Poort, J., Panin, N., Versteeg, W., Gillet, H., 2006. Multiple bottom-simulating reflections in the Black Sea: Potential proxies of past climate conditions. Marine Geology 227, 163-176.

CONTRIBUTION OF VELOCITY VORTICES AND FAST SHOCK REFLECTION AND REFRACTION TO THE FORMATION OF EUV WAVES IN SOLAR ERUPTIONS

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

Wang, Hongjuan; Liu, Siqing; Gong, Jiancun

2015-06-01

We numerically study the detailed evolutionary features of the wave-like disturbance and its propagation in the eruption. This work is a follow-up to Wang et al., using significantly upgraded new simulations. We focus on the contribution of the velocity vortices and the fast shock reflection and refraction in the solar corona to the formation of the EUV waves. Following the loss of equilibrium in the coronal magnetic structure, the flux rope exhibits rapid motions and invokes the fast-mode shock at the front of the rope, which then produces a type II radio burst. The expansion of the fast shock, whichmore » is associated with outward motion, takes place in various directions, and the downward expansion shows the reflection and the refraction as a result of the non-uniform background plasma. The reflected component of the fast shock propagates upward and the refracted component propagates downward. As the refracted component reaches the boundary surface, a weak echo is excited. The Moreton wave is invoked as the fast shock touches the bottom boundary, so the Moreton wave lags the type II burst. A secondary echo occurs in the area where reflection of the fast shock encounters the slow-mode shock, and the nearby magnetic field lines are further distorted because of the interaction between the secondary echo and the velocity vortices. Our results indicate that the EUV wave may arise from various processes that are revealed in the new simulations.« less

Broadband moth-eye antireflection coatings on silicon

NASA Astrophysics Data System (ADS)

Sun, Chih-Hung; Jiang, Peng; Jiang, Bin

2008-02-01

We report a bioinspired templating technique for fabricating broadband antireflection coatings that mimic antireflective moth eyes. Wafer-scale, subwavelength-structured nipple arrays are directly patterned on silicon using spin-coated silica colloidal monolayers as etching masks. The templated gratings exhibit excellent broadband antireflection properties and the normal-incidence specular reflection matches with the theoretical prediction using a rigorous coupled-wave analysis (RCWA) model. We further demonstrate that two common simulation methods, RCWA and thin-film multilayer models, generate almost identical prediction for the templated nipple arrays. This simple bottom-up technique is compatible with standard microfabrication, promising for reducing the manufacturing cost of crystalline silicon solar cells.

Quantifying relative importance: Computing standardized effects in models with binary outcomes

USGS Publications Warehouse

Grace, James B.; Johnson, Darren; Lefcheck, Jonathan S.; Byrnes, Jarrett E.K.

2018-01-01

Results from simulation studies show that both the LT and OE methods of standardization support a similarly-broad range of coefficient comparisons. The LT method estimates effects that reflect underlying latent-linear propensities, while the OE method computes a linear approximation for the effects of predictors on binary responses. The contrast between assumptions for the two methods is reflected in persistently weaker standardized effects associated with OE standardization. Reliance on standard deviations for standardization (the traditional approach) is critically examined and shown to introduce substantial biases when predictors are non-Gaussian. The use of relevant ranges in place of standard deviations has the capacity to place LT and OE standardized coefficients on a more comparable scale. As ecologists address increasingly complex hypotheses, especially those that involve comparing the influences of different controlling factors (e.g., top-down versus bottom-up or biotic versus abiotic controls), comparable coefficients become a necessary component for evaluations.

Possible Significance of Early Paleozoic Fluctuations in Bottom Current Intensity, Northwest Iapetus Ocean

NASA Astrophysics Data System (ADS)

Lash, Gary G.

1986-06-01

Sedimentologic and geochemical characteristics of red and green deep water mudstone exposed in the central Appalachian orogen define climatically-induced fluctuations in bottom current intensity along the northwest flank of the Iapetus Ocean in Early and Middle Ordovician time. Red mudstone accumulated under the influence of moderate to vigorous bottom current velocities in oxygenated bottom water produced during climatically cool periods. Interbedded green mudstone accumulated at greater sedimentation rates, probably from turbidity currents, under the influence of reduced thermohaline circulation during global warming periods. The close association of green mudstone and carbonate turbidites of Early Ordovician (late Tremadocian to early Arenigian) age suggests that a major warming phase occurred at this time. Increasing temperatures reduced bottom current velocities and resulted in increased production of carbonate sediment and organic carbon on the carbonate platform of eastern North America. Much of the excess carbonate sediment and organic carbon was transported into deep water by turbidity currents. Although conclusive evidence is lacking, this eustatic event may reflect a climatic warming phase that followed the postulated glacio-eustatic Black Mountain event. Subsequent Middle Ordovician fluctuations in bottom current intensity recorded by thin red-green mudstone couplets probably reflect periodic growth and shrinkage of an ice cap rather than major glacial episodes.

Simulation of Voltage SET Operation in Phase-Change Random Access Memories with Heater Addition and Ring-Type Contactor for Low-Power Consumption by Finite Element Modeling

NASA Astrophysics Data System (ADS)

Gong, Yue-Feng; Song, Zhi-Tang; Ling, Yun; Liu, Yan; Li, Yi-Jin

2010-06-01

A three-dimensional finite element model for phase change random access memory is established to simulate electric, thermal and phase state distribution during (SET) operation. The model is applied to simulate the SET behaviors of the heater addition structure (HS) and the ring-type contact in the bottom electrode (RIB) structure. The simulation results indicate that the small bottom electrode contactor (BEC) is beneficial for heat efficiency and reliability in the HS cell, and the bottom electrode contactor with size Fx = 80 nm is a good choice for the RIB cell. Also shown is that the appropriate SET pulse time is 100 ns for the low power consumption and fast operation.

Can biophysical properties of submersed macrophytes be determined by remote sensing?

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

Malthus, T.J.; Ciraolo, G.; La Loggia, G.

1997-06-01

This paper details the development of a computationally efficient Monte Carlo simulation program to model photon transport through submersed plant canopies, with emphasis on Seagrass communities. The model incorporates three components: the transmission of photons through a water column of varying depth and turbidity; the interaction of photons within a submersed plant canopy of varying biomass; and interactions with the bottom substrate. The three components of the model are discussed. Simulations were performed based on measured parameters for Posidonia oceanica and compared to measured subsurface reflectance spectra made over comparable seagrass communities in Sicilian coastal waters. It is shown thatmore » the output is realistic. Further simulations are undertaken to investigate the effect of depth and turbidity of the overlying water column. Both sets of results indicate the rapid loss of canopy signal as depth increases and water column phytoplankton concentrations increase. The implications for the development of algorithms for the estimation of submersed canopy biophysical parameters are briefly discussed.« less

New light-shielding technique for shortening the baffle length of a star sensor

NASA Astrophysics Data System (ADS)

Kawano, Hiroyuki; Sato, Yukio; Mitani, Kenji; Kanai, Hiroshi; Hama, Kazumori

2002-10-01

We have developed a star sensor with a short baffle of 140 mm. Our baffle provides a Sun rejection angle of 35 degrees with stray light attenuation less than the intensity level of a visual magnitude of Mv = +5 for a wide field of view lens of 13x13 degrees. The application of a new light shielding technique taking advantage of total internal reflection phenomena enables us to reduce the baffle length to about three fourths that of the conventional two-stage baffle. We have introduced two ideas to make the baffle length shorter. The one is the application of a nearly half sphere convex lens as the first focusing lens. The bottom surface reflects the scattering rays with high incident angles of over 50 degrees by using the total internal reflection phenomena. The other is the painting of the surface of the baffle with not frosted but gloss black paint. The gloss black paint enables most of the specular reflection rays to go back to outer space without scattering. We confirm the baffle performance mentioned above by scattering ray tracing simulation and a light attenuation experiment in a darkroom on the ground.

AVO analysis of BSR to assess free gas within fine-grained sediments in the Shenhu area, South China Sea

NASA Astrophysics Data System (ADS)

Qian, Jin; Wang, Xiu-Juan; Wu, Shi-Guo; Wang, Zhen-zhen; Yang, Sheng-Xiong

2014-06-01

Gas hydrates have been identified from two-dimensional (2D) seismic data and logging data above bottom simulating reflector (BSR) during China's first gas hydrate drilling expedition in 2007. The multichannel reflection seismic data were processed to be preserved amplitudes for quantitatively analyzing amplitude variation with offset (AVO) at BSRs. Low P-wave velocity anomaly below BSR, coinciding with high amplitude reflections in 2D seismic data, indicates the presence of free gas. The absolute values of reflection coefficient versus incidence angles for BSR range from 0 to 0.12 at different CMPs near Site SH2. According to logging data and gas hydrate saturations estimated from resistivity of Site SH2, P-wave velocities calculated from effective media theory (EMT) fit the measured sonic velocities well and we choose EMT to calculate elastic velocities for AVO. The rock-physics modeling and AVO analysis were combined to quantitatively assess free gas saturations and distribution by the reflection coefficients variation of the BSRs in Shenhu area, South China Sea. AVO estimation indicates that free gas saturations immediately beneath BSRs may be about 0.2 % (uniform distribution) and up to about 10 % (patchy distribution) at Site SH2.

Investigation of Acoustic Vector Sensor Data Processing in the Presence of Highly Variable Bathymetry

DTIC Science & Technology

2014-06-01

shelf 10 region to the north of the canyon. The impact of this 3-dimensional (3D) variable bathymetry, which may be combined with the effects of...weaker arrivals at large negative angles, consistent with the earliest bottom reflections on the left. The impact of the bottom-path reflections from...nzout*(nrout+1)*ny))),’bof’); for ifr =1:64, for ir=1:nrout+1, for iy=1:ny, data=fread(fid3,2*nzout,’float32’); fwrite(fid,data

Double-use linear polarization convertor using hybrid metamaterial based on VO2 phase transition in the terahertz region

NASA Astrophysics Data System (ADS)

Zou, Huanling; Xiao, Zhongyin; Li, Wei; Li, Chuan

2018-04-01

A number of polarization convertors based on metamaterials(MMs) have been investigated recently, but no one has proposed a high-efficiency linear polarization transformer both in transmission and reflection modes. Here, a bilayered MM embedded with vanadium dioxide (VO2) composed of a pair of sloping gold patches, bottom hybrid layer and a dielectric spacer is proposed as a double-use linear polarization convertor. It has been demonstrated numerically that this device has advantages of switching between transmission polarization conversion and reflection polarization conversion based on the phase transition of the VO2 film in the terahertz (THz) regime and the polarization conversion ratios (PCR) in both cases are higher than 90% in wide bands. The simulated linear polarization transmission/reflection coefficients and the surface current distributions give insight into the mechanism of the linear polarization conversions. Moreover, the physical mechanism of polarization sensitivity of the designed structure is investigated by the distributions of electric field. The proposed double-use linear polarization convertor shows great prospects in polarization imaging, and polarized light communications.

Geoacoustic inversion of a shallow fresh-water environment

NASA Astrophysics Data System (ADS)

Stotts, Steven A.; Knobles, David P.; Koch, Robert A.; Piper, James N.; Keller, Jason A.

2003-10-01

A recent experiment was conducted at The University of Texas/Applied Research Laboratories test station located at Lake Travis, Austin, TX. Implosive (light bulb), explosive (firecracker), and tonal sources were recorded on a dual receiver system located on the bottom next to a range-independent underwater river channel. Inversion results of the broadband time series obtained over ranges less than 1.5 km were used to predict measured transmission loss at several tonal frequencies in the band from 250-1000 Hz. The average water depth was approximately 38 m along the channel during the experiment. Sound speed profiles were calculated from recorded temperature readings measured as a function of depth. Implosive source spectrums were measured and used to evaluate a model/data correlation cost function in a simulated annealing algorithm. Comparisons of inversion results using both a normal mode and a ray-based plane wave reflection coefficient forward model [Stotts et al., J. Acoust. Soc. Am. (submitted)] are discussed. Predicted transmission loss based on the inversion results are compared to the measured transmission loss. Differences between fluid and elastic layer bottom models will also be presented.

The impact of bottom brightness on spectral reflectance of suspended sediments

USGS Publications Warehouse

Tolk, Brian L.; Han, L.; Rundquist, D. C.

2000-01-01

Two experiments were conducted outdoors to investigate how bottom brightness impacts the spectral response of a water column under varied suspended sediment concentrations. A white aluminum panel placed at the bottom of the tank was used as the bright bottom, and a flat-black tank liner served as the dark bottom. Sixteen levels of suspended sediment from 25 to 400 mg litre -1 were used in each experiment. Spectral data were collected using a Spectron SE-590 spectroradiometer. The major findings include the following: the bright bottom had the greatest impact at visible wavelengths; when suspended sediment concentrations exceeded 100 mg litre -1, the bright bottom response was found to be negligible; and, substrate brightness has minimal impact between 740 and 900 nm, suggesting that these wavelengths are best for measuring suspended sediment concentrations by means of remote sensing.

Shear wave modelling of high resolution OBS data in a gas hydrate environment in the Danube deep-sea fan, Black Sea

NASA Astrophysics Data System (ADS)

Dannowski, A.; Bialas, J.; Zander, T.; Klaeschen, D.

2016-12-01

The Danube deep-sea fan, with his ancient channel-levee systems, hosts multiple bottom-simulating reflections (BSRs) observed in high-resolution reflection seismic data, indicating the occurrence of gas hydrates and free gas. To image the distribution of submarine gas hydrates and the occurrence of free gas in a channel-levee system, high-resolution 2D and 3D multichannel seismic reflection data were collected and fifteen ocean bottom seismometers (OBS) were deployed. The OBS data in particular reveal information about seismic P- and S-wave velocities of the subsurface. They record wave fields of a wide range of incidence angles. Both, P- and S-wave traveltime modelling cover a depth down to 1.5 km below the seafloor; thus, providing seismic velocity information far below the BSR. The seismic P-wave velocities increase with depth from 1600 m/s beneath the seafloor up to 2400 m/s at 1.5 km depth. The frequencies of the S-waves are much lower than the P-wave reflection signals. This is characteristic for shear waves in unconsolidated sediments where the S-wave attenuation is high. However, they travel much slower than P-waves and thus, show a higher resolution. The first S-wave appears at 0.7 s after the direct wave. Some of the S-phases can be traced up to 3.5 km in offset to the station. The seismic S-wave velocities increase from 240 m/s beneath the seafloor up to 1100 m/s at a depth of 1.5 km below the seafloor. From these observations, the P-to-S ratio can be derived. The P-to-S ratio might help to estimate the thickness of the zones with gas hydrates and free gas, while there will be a limited capability to constrain their concentrations.

Fabrication and characterization of TiO2/SiO2 based Bragg reflectors for light trapping applications

NASA Astrophysics Data System (ADS)

Dubey, R. S.; Ganesan, V.

Distributed Bragg reflectors (DBRs) have received an intensive attention due to their increasing demand in optoelectronic and photonic devices. Such reflectors are capable to prohibit the light propagation within the specified wavelength range of interest. In this paper, we present the fabrication of TiO2/SiO2 stacks based Bragg reflectors by using a simple and in-expensive sol-gel spin coating technique. The prepared single-layer thin films of TiO2 and SiO2 onto glass substrates were characterized for their optical constants. By tuning the process parameters, one-seven DBR stacks of TiO2/SiO2 were prepared. The corresponding shift of the Bragg reflection peak was observed with the increased number of DBR stacks and as much as about 90% reflectance is observed from the 7DBR stacks. The experimentally measured reflectance was compared with the simulated one, which showed good in agreement. FESEM measurement has confirmed the formation of bright and dark strips of TiO2 and SiO2 films with their thicknesses 80 and 115 nm respectively. The simulation study was explored to a design of thin film silicon solar cell using 7DBR stacks. An enhancement in light absorption in the visible wavelength range is observed which coincides with the experimental result of the reflectance. The use of DBR at the bottom of the solar cell could felicitate the better light harvesting with the occurrence of Fabry-Perot resonances in the absorbing layer.

Direct Numerical Simulation of Oscillatory Flow Over a Wavy, Rough, and Permeable Bottom

NASA Astrophysics Data System (ADS)

Mazzuoli, Marco; Blondeaux, Paolo; Simeonov, Julian; Calantoni, Joseph

2018-03-01

The results of a direct numerical simulation of oscillatory flow over a wavy bottom composed of different layers of spherical particles are described. The amplitude of wavy bottom is much smaller in scale than typical bed forms such as sand ripples. The spherical particles are packed in such a way to reproduce a bottom profile observed during an experiment conducted in a laboratory flow tunnel with well-sorted coarse sand. The amplitude and period of the external forcing flow as well as the size of the particles are set equal to the experimental values and the computed velocity field is compared with the measured velocity profiles. The direct numerical simulation allows for the evaluation of quantities, which are difficult to measure in a laboratory experiment (e.g., vorticity, seepage flow velocity, and hydrodynamic force acting on sediment particles). In particular, attention is focused on the coherent vortex structures generated by the vorticity shed by both the spherical particles and the bottom waviness. Results show that the wavy bottom triggers transition to turbulence. Moreover, the forces acting on the spherical particles are computed to investigate the mechanisms through which they are possibly mobilized by the oscillatory flow. It was found that forces capable of mobilizing surface particles are strongly correlated with the particle position above the mean bed elevation and the passage of coherent vortices above them.

Bottom currents and sediment transport in Long Island Sound: A modeling study

USGS Publications Warehouse

Signell, R.P.; List, J.H.; Farris, A.S.

2000-01-01

A high resolution (300-400 m grid spacing), process oriented modeling study was undertaken to elucidate the physical processes affecting the characteristics and distribution of sea-floor sedimentary environments in Long Island Sound. Simulations using idealized forcing and high-resolution bathymetry were performed using a three-dimensional circulation model ECOM (Blumberg and Mellor, 1987) and a stationary shallow water wave model HISWA (Holthuijsen et al., 1989). The relative contributions of tide-, density-, wind- and wave-driven bottom currents are assessed and related to observed characteristics of the sea-floor environments, and simple bedload sediment transport simulations are performed. The fine grid spacing allows features with scales of several kilometers to be resolved. The simulations clearly show physical processes that affect the observed sea-floor characteristics at both regional and local scales. Simulations of near-bottom tidal currents reveal a strong gradient in the funnel-shaped eastern part of the Sound, which parallels an observed gradient in sedimentary environments from erosion or nondeposition, through bedload transport and sediment sorting, to fine-grained deposition. A simulation of estuarine flow driven by the along-axis gradient in salinity shows generally westward bottom currents of 2-4 cm/s that are locally enhanced to 6-8 cm/s along the axial depression of the Sound. Bottom wind-driven currents flow downwind along the shallow margins of the basin, but flow against the wind in the deeper regions. These bottom flows (in opposition to the wind) are strongest in the axial depression and add to the estuarine flow when winds are from the west. The combination of enhanced bottom currents due to both estuarine circulation and the prevailing westerly winds provide an explanation for the relatively coarse sediments found along parts of the axial depression. Climatological simulations of wave-driven bottom currents show that frequent high-energy events occur along the shallow margins of the Sound, explaining the occurrence of relatively coarse sediments in these regions. Bedload sediment transport calculations show that the estuarine circulation coupled with the oscillatory tidal currents result in a net westward transport of sand in much of the eastern Sound. Local departures from this regional westward trend occur around topographic and shoreline irregularities, and there is strong predicted convergence of bedload transport over most of the large, linear sand ridges in the eastern Sound, providing a mechanism which prevents their decay. The strong correlation between the near-bottom current intensity based on the model results and the sediment response, as indicated by the distribution of sedimentary environments, provides a framework for predicting the long-term effects of anthropogenic activities.

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.

Bottom Up Succession Planning Works Better.

ERIC Educational Resources Information Center

Stevens, Paul

The majority of current succession planning practices reflect the viewpoint of only a linear career direction for ambitious people. They are based on the premise that competent people have and want only one career direction--an upwardly mobile one. In today's work force, however, a "bottom-up" process works better in succession planning. This…

Multicomponent seismic methods for characterizing gas hydrate occurrences and systems in deep-water Gulf of Mexico

USGS Publications Warehouse

Haines, Seth S.; Lee, Myung W.; Collett, Timothy S.; Hardage, Bob A.

2011-01-01

In-situ characterization and quantification of natural gas hydrate occurrences remain critical research directions, whether for energy resource, drilling hazard, or climate-related studies. Marine multicomponent seismic data provide the full seismic wavefield including partial redundancy, and provide a promising set of approaches for gas hydrate characterization. Numerous authors have demonstrated the possibilities of multicomponent data at study sites around the world. We expand on this work by investigating the utility of very densely spaced (10’s of meters) multicomponent receivers (ocean-bottom cables, OBC, or ocean-bottom seismometers, OBS) for gas hydrate studies in the Gulf of Mexico and elsewhere. Advanced processing techniques provide high-resolution compressional-wave (PP) and converted shearwave (PS) reflection images of shallow stratigraphy, as well as P-wave and S-wave velocity estimates at each receiver position. Reflection impedance estimates can help constrain velocity and density, and thus gas hydrate saturation. Further constraint on velocity can be determined through identification of the critical angle and associated phase reversal in both PP and PS wideangle data. We demonstrate these concepts with examples from OBC data from the northeast Green Canyon area and numerically simulated OBS data that are based on properties of known gas hydrate occurrences in the southeast (deeper water) Green Canyon area. These multicomponent data capabilities can provide a wealth of characterization and quantification information that is difficult to obtain with other geophysical methods.

Model for the Interpretation of Hyperspectral Remote-Sensing Reflectance

NASA Technical Reports Server (NTRS)

Lee, Zhongping; Carder, Kendall L.; Hawes, Steve K.; Steward, Robert G.; Peacock, Thomas G.; Davis, Curtiss O.

1994-01-01

Remote-sensing reflectance is easier to interpret for the open ocean than for coastal regions because the optical signals are highly coupled to the phytoplankton (e.g., chlorophyll) concentrations. For estuarine or coastal waters, variable terrigenous colored dissolved organic matter (CDOM), suspended sediments, and bottom reflectance, all factors that do not covary with the pigment concentration, confound data interpretation. In this research, remote-sensing reflectance models are suggested for coastal waters, to which contributions that are due to bottom reflectance, CDOM fluorescence, and water Raman scattering are included. Through the use of two parameters to model the combination of the backscattering coefficient and the Q factor, excellent agreement was achieved between the measured and modeled remote-sensing reflectance for waters from the West Florida Shelf to the Mississippi River plume. These waters cover a range of chlorophyll of 0.2-40 mg/cu m and gelbstoff absorption at 440 nm from 0.02-0.4/m. Data with a spectral resolution of 10 nm or better, which is consistent with that provided by the airborne visible and infrared imaging spectrometer (AVIRIS) and spacecraft spectrometers, were used in the model evaluation.

Remote sensing of aerosol plumes: a semianalytical model

NASA Astrophysics Data System (ADS)

Alakian, Alexandre; Marion, Rodolphe; Briottet, Xavier

2008-04-01

A semianalytical model, named APOM (aerosol plume optical model) and predicting the radiative effects of aerosol plumes in the spectral range [0.4,2.5 μm], is presented in the case of nadir viewing. It is devoted to the analysis of plumes arising from single strong emission events (high optical depths) such as fires or industrial discharges. The scene is represented by a standard atmosphere (molecules and natural aerosols) on which a plume layer is added at the bottom. The estimated at-sensor reflectance depends on the atmosphere without plume, the solar zenith angle, the plume optical properties (optical depth, single-scattering albedo, and asymmetry parameter), the ground reflectance, and the wavelength. Its mathematical expression as well as its numerical coefficients are derived from MODTRAN4 radiative transfer simulations. The DISORT option is used with 16 fluxes to provide a sufficiently accurate calculation of multiple scattering effects that are important for dense smokes. Model accuracy is assessed by using a set of simulations performed in the case of biomass burning and industrial plumes. APOM proves to be accurate and robust for solar zenith angles between 0° and 60° whatever the sensor altitude, the standard atmosphere, for plume phase functions defined from urban and rural models, and for plume locations that extend from the ground to a height below 3 km. The modeling errors in the at-sensor reflectance are on average below 0.002. They can reach values of 0.01 but correspond to low relative errors then (below 3% on average). This model can be used for forward modeling (quick simulations of multi/hyperspectral images and help in sensor design) as well as for the retrieval of the plume optical properties from remotely sensed images.

Remote sensing of aerosol plumes: a semianalytical model.

PubMed

Alakian, Alexandre; Marion, Rodolphe; Briottet, Xavier

2008-04-10

A semianalytical model, named APOM (aerosol plume optical model) and predicting the radiative effects of aerosol plumes in the spectral range [0.4,2.5 microm], is presented in the case of nadir viewing. It is devoted to the analysis of plumes arising from single strong emission events (high optical depths) such as fires or industrial discharges. The scene is represented by a standard atmosphere (molecules and natural aerosols) on which a plume layer is added at the bottom. The estimated at-sensor reflectance depends on the atmosphere without plume, the solar zenith angle, the plume optical properties (optical depth, single-scattering albedo, and asymmetry parameter), the ground reflectance, and the wavelength. Its mathematical expression as well as its numerical coefficients are derived from MODTRAN4 radiative transfer simulations. The DISORT option is used with 16 fluxes to provide a sufficiently accurate calculation of multiple scattering effects that are important for dense smokes. Model accuracy is assessed by using a set of simulations performed in the case of biomass burning and industrial plumes. APOM proves to be accurate and robust for solar zenith angles between 0 degrees and 60 degrees whatever the sensor altitude, the standard atmosphere, for plume phase functions defined from urban and rural models, and for plume locations that extend from the ground to a height below 3 km. The modeling errors in the at-sensor reflectance are on average below 0.002. They can reach values of 0.01 but correspond to low relative errors then (below 3% on average). This model can be used for forward modeling (quick simulations of multi/hyperspectral images and help in sensor design) as well as for the retrieval of the plume optical properties from remotely sensed images.

Bottom water production variability in the Ross Sea slope during the Late Pleistocene-Holocene as revealed by benthic foraminifera and sediment geochemistry

NASA Astrophysics Data System (ADS)

Langone, Leonardo; Asioli, Alessandra; Tateo, Fabio; Giglio, Federico; Ridente, Domenico; Summa, Vito; Carraro, Anna; Luigia Giannossi, Maria; Piva, Andrea; Trincardi, Fabio

2010-05-01

The Antarctic area produces bottom waters that ventilate the vast majority of the deep basins in the rest of the world ocean. The rate of formation in the source area and the strength of these cold bottom waters are key factors affecting the Global Thermohaline Circulation during modern and past climate conditions. The western Ross Sea is considered a formation site for a particularly salty variety of AABW as well as an important area of off-shelf transfer of water as plumes entraining in Lower CDW and as rapid downhill cascades. The results here presented were obtained within the frame of the PNRA project 4.8. Among the goals of the project, the main is to detect a qualitative signal of possible changes in the rate of bottom water production during the Late Pleistocene-Holocene by integrating data on foraminifera assemblages with sediment geochemistry (bulk mineralogy, Total Organic Carbon, biogenic silica, C and N stable isotopes) and IRD. A gravity core was collected at 2377m water depth off Drygalski Basin on the slope adjacent the western continental shelf of the Ross Sea, along the pathway of bottom water spreading. The chronology is based on the best fitting of twelve control points selected among twenty-two 14C AMS datings performed on the bulk organic carbon and 210Pb excess data. The trend of the parameters allows the following observations: 1) two main intervals (15-10 and 7.5-6 cab kyr BP) mark a subsequent enhanced nutrient supply. Indeed, δ15N variations depend on the utilization degree of nitrates, in turn reflecting productivity/nutrient supply changes. The concurrent increase of OC and biogenic silica suggests an increase of the nutrient availability. As the Upper CDW is a water mass rich in nutrients we interpret these intervals as characterized by a higher efficiency in the Upper CDW upwelling; 2) around 7.5-7kyr BP (part of the Middle Holocene Climatic Optimum) the IRD content drops, suggesting the reduction of iceberg production or a change of the iceberg path. Within this general context, an oscillatory trend is present from 15 kyr BP to present time. Two hypotheses are proposed: a) minima in foraminifera concentrations reflect relatively stronger dissolution, weaker bottom currents (minima in dry density) and lower nutrient supply (lighter values of δ15N). These intervals may reflect a lower rate of bottom water formation; the intervals corresponding to maxima in foraminifers concentration should indicate better preservation, higher benthic productivity and/or better oxygenation at bottom, stronger bottom currents (maxima in dry density) and relatively higher nutrient supply reflecting a relatively higher rate of bottom water formation. b) alternatively, minima in foraminifers, corresponding to minima in %OC and to reversal of 14C (relative increase of older carbon), reflect dilution in the sediment because of rapid accumulation of fine sediment re-suspended at the shelf edge by the cascading currents. Therefore, the minima represent higher rate of bottom water formation. The comparison of the D/H ratio in ice-cores from the Ross Sea sector with the core AS05-10 record indicates that the foraminifers minima always correspond to colder condition. This scenario also correlates to the record reported in literature on the slope off Wilkes-Adelie Land. At last, a condensed/hiatus interval at ca. 3.5-4 kyr BP does not seems to mark a major change in the general pattern of our variables, apart from biogenic silica and sheets silicates showing an increase of the oscillation amplitude. Nevertheless, this feature is coeval to the base of the Neoglacial and it is time-equivalent to the beginning of major changes in the Antarctic environment.

Feasibility study for airborne fluorescence/reflectivity lidar bathymetry

NASA Astrophysics Data System (ADS)

Steinvall, Ove; Kautsky, Hans; Tulldahl, Michael; Wollner, Erika

2012-06-01

There is a demand from the authorities to have good maps of the coastal environment for their exploitation and preservation of the coastal areas. The goal for environmental mapping and monitoring is to differentiate between vegetation and non-vegetated bottoms and, if possible, to differentiate between species. Airborne lidar bathymetry is an interesting method for mapping shallow underwater habitats. In general, the maximum depth range for airborne laser exceeds the possible depth range for passive sensors. Today, operational lidar systems are able to capture the bottom (or vegetation) topography as well as estimations of the bottom reflectivity using e.g. reflected bottom pulse power. In this paper we study the possibilities and advantages for environmental mapping, if laser sensing would be further developed from single wavelength depth sounding systems to include multiple emission wavelengths and fluorescence receiver channels. Our results show that an airborne fluorescence lidar has several interesting features which might be useful in mapping underwater habitats. An example is the laser induced fluorescence giving rise to the emission spectrum which could be used for classification together with the elastic lidar signal. In the first part of our study, vegetation and substrate samples were collected and their spectral reflectance and fluorescence were subsequently measured in laboratory. A laser wavelength of 532 nm was used for excitation of the samples. The choice of 532 nm as excitation wavelength is motivated by the fact that this wavelength is commonly used in bathymetric laser scanners and that the excitation wavelengths are limited to the visual region as e.g. ultraviolet radiation is highly attenuated in water. The second part of our work consisted of theoretical performance calculations for a potential real system, and comparison of separability between species and substrate signatures using selected wavelength regions for fluorescence sensing.

Spatial bottom-up controls on fire likelihood vary across western North America

Treesearch

Sean A. Parks; Marc-Andre Parisien; Carol Miller

2012-01-01

The unique nature of landscapes has challenged our ability to make generalizations about the effects of bottom-up controls on fire regimes. For four geographically distinct fire-prone landscapes in western North America, we used a consistent simulation approach to quantify the influence of three key bottom-up factors, ignitions, fuels, and topography, on spatial...

High efficiency silicon solar cell based on asymmetric nanowire.

PubMed

Ko, Myung-Dong; Rim, Taiuk; Kim, Kihyun; Meyyappan, M; Baek, Chang-Ki

2015-07-08

Improving the efficiency of solar cells through novel materials and devices is critical to realize the full potential of solar energy to meet the growing worldwide energy demands. We present here a highly efficient radial p-n junction silicon solar cell using an asymmetric nanowire structure with a shorter bottom core diameter than at the top. A maximum short circuit current density of 27.5 mA/cm(2) and an efficiency of 7.53% were realized without anti-reflection coating. Changing the silicon nanowire (SiNW) structure from conventional symmetric to asymmetric nature improves the efficiency due to increased short circuit current density. From numerical simulation and measurement of the optical characteristics, the total reflection on the sidewalls is seen to increase the light trapping path and charge carrier generation in the radial junction of the asymmetric SiNW, yielding high external quantum efficiency and short circuit current density. The proposed asymmetric structure has great potential to effectively improve the efficiency of the SiNW solar cells.

Efficiency enhancement and angle-dependent color change in see-through organic photovoltaics using distributed Bragg reflectors

NASA Astrophysics Data System (ADS)

Dong, Wan Jae; Lo, Nhat-Truong; Jung, Gwan Ho; Ham, Juyoung; Lee, Jong-Lam

2016-03-01

A distributed Bragg reflector (DBR) is conducted as a bottom reflector in see-through organic photovoltaics (OPVs) with an active layer of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM). The DBR consists of alternative layers of the high- and low-refractive index materials of Ta2O5 (n = 2.16) and SiO2 (n = 1.46). The DBR selectively reflects the light within a specific wavelength region (490 nm-630 nm) where the absorbance of P3HT:PCBM is maximum. The see-through OPVs fabricated on DBR exhibit efficiency enhancement by 31% compared to the device without DBR. Additionally, the angle-dependent transmittance of DBR is analysed using optical simulation and verified by experimental results. As the incident angle of light increases, peak of reflectance shifts to shorter wavelength and the bandwidth gets narrower. This unique angle-dependent optical properties of DBR allows the facile color change of see-through OPVs.

Seabed Scattering from Low Frequency Reverberation Measurements

DTIC Science & Technology

2015-09-30

in bottom reflection loss can be compensated for by increasing (decreasing) the angu - lar index of bottom scattering.5 That is, there is an uncer...Mackenzie-Lambert40 were extended to more general angu - lar dependence as follows.6–8 When a plane wave with an in- tensity of IiðhÞ is incident upon unit

Pedagogical Perspectives and Practices Reflected in Metaphors of Learning and Digital Learning of ICT Leaders

ERIC Educational Resources Information Center

Blau, Ina; Grinberg, Ronen; Shamir-Inbal, Tamar

2018-01-01

This study examines the meaning attributed to the contribution of technology to pedagogical practices from the perspective of school ICT leaders. While previous studies use metaphors for bottom-up exploration, this study employs an innovative combination of bottom-up and top-down metaphor analysis based on two frameworks: (a) metaphors of general…

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.

Geographical distribution of shear wave anisotropy within marine sediments in the northwestern Pacific

NASA Astrophysics Data System (ADS)

Tonegawa, Takashi; Fukao, Yoshio; Fujie, Gou; Takemura, Shunsuke; Takahashi, Tsutomu; Kodaira, Shuichi

2015-12-01

In the northwestern Pacific, the elastic properties of marine sediments, including P-wave velocities ( Vp) and S wave velocities ( Vs), have recently been constrained by active seismic surveys. However, information on S anisotropy associated with the alignments of fractures and fabric remains elusive. To obtain such information, we used ambient noise records observed by ocean-bottom seismometers at 254 sites in the northwestern Pacific to calculate the auto-correlation functions for the S reflection retrieval from the top of the basement. For these S reflections, we measured differential travel times and polarized directions to reveal the potential geographical systematic distribution of S anisotropy. As a result, the observed differential times between fast and slow axes were at most 0.05 s. The fast polarization axes tend to align in the trench-parallel direction in the outer rise region. In particular, their directions changed systematically in accordance with the direction of the trench axis, which changes sharply across the junction of the Kuril and Japan trenches. We consider that a contributing factor for the obtained S anisotropy within marine sediments in the outer rise region is primarily aligned fractures due to the tensional stresses associated with the bending of the Pacific Plate. Moreover, numerical simulations conducted by using the three-dimensional (3D) finite difference method for isotropic and anisotropic media indicates that the successful extraction of S anisotropic information from the S reflection observed in this study is obtained from near-vertically propagating S waves due to extremely low Vs within marine sediments. In addition, we conducted an additional numerical simulation with a realistic velocity model to confirm whether S reflections below the basement can be extracted or not. The resultant auto-correlation function shows only S reflections from the top of the basement. It appears that such near-vertically propagating S waves obscure S reflections from interfaces below the basement.

Fin field effect transistor directionality impacts printing of implantation shapes

NASA Astrophysics Data System (ADS)

Wang, Xiren; Granik, Yuri

2018-01-01

In modern integrated circuit (IC) fabrication processes, the photoresist receives considerable illumination energy that is reflected by underlying topography during optical lithography of implantation layers. Bottom antireflective coating (BARC) is helpful to mitigate the reflection. Often, however, BARC is not used, because its removal is technically challenging, in addition to its relatively high economic cost. Furthermore, the advanced technology nodes, such as 14/10-nm nodes, have introduced fin field effect transistor (FinFET), which makes reflection from nonuniform silicon substrates exceptionally complicated. Therefore, modeling reflection from topography becomes obligatory to accurately predict printing of implantation shapes. Typically, FinFET is always fixed in one direction in realistic designs. However, the same implantation rectangle may be oriented in either horizontal or vertical direction. Then, there are two types of relations between the critical dimension (CD) and FinFET, namely a parallel-to and a perpendicular-to relation. We examine the fin directionality impact on CD. We found that this impact may be considerable in some cases. We use our in-house rigorous optical topography simulator to reveal underlining physical reasons. One of the major causes of the CD differences is that in the parallel orientation, the solid sidewalls of the fins conduct considerable light reflections unlike for the perpendicular orientation. This finding can aid the compact modeling in optical proximity correction of implantation masks.

Unmixing of spectral components affecting AVIRIS imagery of Tampa Bay

NASA Astrophysics Data System (ADS)

Carder, Kendall L.; Lee, Z. P.; Chen, Robert F.; Davis, Curtiss O.

1993-09-01

According to Kirk's as well as Morel and Gentili's Monte Carlo simulations, the popular simple expression, R approximately equals 0.33 bb/a, relating subsurface irradiance reflectance (R) to the ratio of the backscattering coefficient (bb) to absorption coefficient (a), is not valid for bb/a > 0.25. This means that it may no longer be valid for values of remote-sensing reflectance (above-surface ratio of water-leaving radiance to downwelling irradiance) where Rrs4/ > 0.01. Since there has been no simple Rrs expression developed for very turbid waters, we developed one based in part on Monte Carlo simulations and empirical adjustments to an Rrs model and applied it to rather turbid coastal waters near Tampa Bay to evaluate its utility for unmixing the optical components affecting the water- leaving radiance. With the high spectral (10 nm) and spatial (20 m2) resolution of Airborne Visible-InfraRed Imaging Spectrometer (AVIRIS) data, the water depth and bottom type were deduced using the model for shallow waters. This research demonstrates the necessity of further research to improve interpretations of scenes with highly variable turbid waters, and it emphasizes the utility of high spectral-resolution data as from AVIRIS for better understanding complicated coastal environments such as the west Florida shelf.

Numerical Analysis of Residual Stress and Distortion Use Finite Element Method on Inner Bottom Construction of Geomarin IV Survey Ship with Welding Sequence Variations

NASA Astrophysics Data System (ADS)

Syahroni, N.; Hartono, A. B. W.; Murtedjo, M.

2018-03-01

In the ship fabrication industry, welding is the most critical stage. If the quality of welding on ship fabrication is not good, then it will affect the strength and overall appearance of the structure. One of the factors that affect the quality of welding is residual stress and distortion. In this research welding simulation is performed on the inner bottom construction of Geomarin IV Ship Survey using shell element and has variation to welding sequence. In this study, welding simulations produced peak temperatures at 2490 K at variation 4. While the lowest peak temperature was produced by variation 2 with a temperature of 2339 K. After welding simulation, it continued simulating residual stresses and distortion. The smallest maximum tensile residual stress found in the inner bottom construction is 375.23 MPa, and the maximum tensile pressure is -20.18 MPa. The residual stress is obtained from variation 3. The distortion occurring in the inner bottom construction for X=720 mm is 4.2 mm and for X=-720 mm, the distortion is 4.92 mm. The distortion is obtained from the variation 3. Near the welding area, distortion value reaches its minimum point. This is because the stiffeners in the form of frames serves as anchoring.

Biological Response to the Dynamic Spectral-Polarized Underwater Light Field

DTIC Science & Technology

2010-01-01

organic in nature (e.g. detrital flocs) and not re-suspended bottom sediments. 5 (v) (Dierssen) Benthic reflectance from the seagrass Thalassia ...Laboratory measurements of polarized reflectance over the leaves of the seagrass Thalassia testudinum. 15 Fig 14. Noon time

Study on the criterion to determine the bottom deployment modes of a coilable mast

NASA Astrophysics Data System (ADS)

Ma, Haibo; Huang, Hai; Han, Jianbin; Zhang, Wei; Wang, Xinsheng

2017-12-01

A practical design criterion that allows the coilable mast bottom to deploy in local coil mode was proposed. The criterion was defined with initial bottom helical angle and obtained by bottom deformation analyses. Discretizing the longerons into short rods, analyses were conducted based on the cylinder assumption and Kirchhoff's kinetic analogy theory. Then, iterative calculations aiming at the bottom four rods were carried out. A critical bottom helical angle was obtained while the angle changing rate equaled to zero. The critical value was defined as a criterion for judgement of bottom deployment mode. Subsequently, micro-gravity deployment tests were carried out and bottom deployment simulations based on finite element method were developed. Through comparisons of bottom helical angles in critical state, the proposed criterion was evaluated and modified, that is, an initial bottom helical angle less than critical value with a design margin of -13.7% could ensure the mast bottom deploying in local coil mode, and further determine a successful local coil deployment of entire coilable mast.

Optimization of 248nm bottom anti-reflective coatings with thin film and high etch rate on real device

NASA Astrophysics Data System (ADS)

Kim, MyoungSoo; Kim, HakJoon; Shim, KewChan; Jeon, JeHa; Gil, MyungGoon; Song, YongWook; Enomoto, Tomoyuki; Sakaguchi, Takahiro; Nakajima, Yasuyuki

2005-05-01

A frequent problem encountered by photoresists during the manufacturing of semiconductor device is that activating radiation is reflected back into the photoresist by the substrate. So, it is necessary that the light reflection is reduced from the substrate. One approach to reduce the light reflection is the use of bottom anti-reflective coating (BARC) applied to the substrate beneath the photoresist layer. The BARC technology has been utilized for a few years to minimize the reflectivity. As the chip size is reduced to sub 100nm, the photoresist thickness has to decrease with the aspect ratio being less than 3.0. Therefore, new Organic BARC is strongly required which has the minimum reflectivity with thinner BARC thickness and higher etch selectivity toward resists. Hynix Semiconductor Inc., Nissan Chemical Industries, Ltd., and Brewer Science, Inc. have developed the advanced Organic BARC for achieving the above purpose. As a result, the suitable high performance 248nm Organic BARCs, NCA series, were achieved. Using CF4 gas as etchant, the plasma etch rate of NCA series is about 1.4 times higher than that of conventional 248nm resists. NCA series can be minimizing the substrate reflectivity at below 45nm BARC thickness. NCA series show the excellent litho performance and coating property on real device.

Reflective properties of melt ponds on sea ice

NASA Astrophysics Data System (ADS)

Malinka, Aleksey; Zege, Eleonora; Istomina, Larysa; Heygster, Georg; Spreen, Gunnar; Perovich, Donald; Polashenski, Chris

2018-06-01

Melt ponds occupy a large part of the Arctic sea ice in summer and strongly affect the radiative budget of the atmosphere-ice-ocean system. In this study, the melt pond reflectance is considered in the framework of radiative transfer theory. The melt pond is modeled as a plane-parallel layer of pure water upon a layer of sea ice (the pond bottom). We consider pond reflection as comprising Fresnel reflection by the water surface and multiple reflections between the pond surface and its bottom, which is assumed to be Lambertian. In order to give a description of how to find the pond bottom albedo, we investigate the inherent optical properties of sea ice. Using the Wentzel-Kramers-Brillouin approximation approach to light scattering by non-spherical particles (brine inclusions) and Mie solution for spherical particles (air bubbles), we conclude that the transport scattering coefficient in sea ice is a spectrally independent value. Then, within the two-stream approximation of the radiative transfer theory, we show that the under-pond ice spectral albedo is determined by two independent scalar values: the transport scattering coefficient and ice layer thickness. Given the pond depth and bottom albedo values, the bidirectional reflectance factor (BRF) and albedo of a pond can be calculated with analytical formulas. Thus, the main reflective properties of the melt pond, including their spectral dependence, are determined by only three independent parameters: pond depth z, ice layer thickness H, and transport scattering coefficient of ice σt.The effects of the incident conditions and the atmosphere state are examined. It is clearly shown that atmospheric correction is necessary even for in situ measurements. The atmospheric correction procedure has been used in the model verification. The optical model developed is verified with data from in situ measurements made during three field campaigns performed on landfast and pack ice in the Arctic. The measured pond albedo spectra were fitted with the modeled spectra by varying the pond parameters (z, H, and σt). The coincidence of the measured and fitted spectra demonstrates good performance of the model: it is able to reproduce the albedo spectrum in the visible range with RMSD that does not exceed 1.5 % for a wide variety of melt pond types observed in the Arctic.

Water Column Correction for Coral Reef Studies by Remote Sensing

PubMed Central

Zoffoli, Maria Laura; Frouin, Robert; Kampel, Milton

2014-01-01

Human activity and natural climate trends constitute a major threat to coral reefs worldwide. Models predict a significant reduction in reef spatial extension together with a decline in biodiversity in the relatively near future. In this context, monitoring programs to detect changes in reef ecosystems are essential. In recent years, coral reef mapping using remote sensing data has benefited from instruments with better resolution and computational advances in storage and processing capabilities. However, the water column represents an additional complexity when extracting information from submerged substrates by remote sensing that demands a correction of its effect. In this article, the basic concepts of bottom substrate remote sensing and water column interference are presented. A compendium of methodologies developed to reduce water column effects in coral ecosystems studied by remote sensing that include their salient features, advantages and drawbacks is provided. Finally, algorithms to retrieve the bottom reflectance are applied to simulated data and actual remote sensing imagery and their performance is compared. The available methods are not able to completely eliminate the water column effect, but they can minimize its influence. Choosing the best method depends on the marine environment, available input data and desired outcome or scientific application. PMID:25215941

Water column correction for coral reef studies by remote sensing.

PubMed

Zoffoli, Maria Laura; Frouin, Robert; Kampel, Milton

2014-09-11

Human activity and natural climate trends constitute a major threat to coral reefs worldwide. Models predict a significant reduction in reef spatial extension together with a decline in biodiversity in the relatively near future. In this context, monitoring programs to detect changes in reef ecosystems are essential. In recent years, coral reef mapping using remote sensing data has benefited from instruments with better resolution and computational advances in storage and processing capabilities. However, the water column represents an additional complexity when extracting information from submerged substrates by remote sensing that demands a correction of its effect. In this article, the basic concepts of bottom substrate remote sensing and water column interference are presented. A compendium of methodologies developed to reduce water column effects in coral ecosystems studied by remote sensing that include their salient features, advantages and drawbacks is provided. Finally, algorithms to retrieve the bottom reflectance are applied to simulated data and actual remote sensing imagery and their performance is compared. The available methods are not able to completely eliminate the water column effect, but they can minimize its influence. Choosing the best method depends on the marine environment, available input data and desired outcome or scientific application.

Seismic reflection profile of the Blake Ridge near sites 994, 995, and 997: Chapter 4

USGS Publications Warehouse

Dillon, William P.; Hutchinson, Deborah R.; Drury, Rebecca M.

1996-01-01

Seismic reflection profiles near Sites 994, 995, and 997 were collected with seismic sources that provide maximum resolution with adequate power to image the zone of gas hydrate stability and the region direction beneath it. The overall structure of the sediment drift deposit that constitutes the Blake Ridge consists of southwestward-dipping strata. These strata are approximately conformal to the seafloor on the southwest side of the ridge and are truncated by erosion on the northeast side. A bottom-simulating reflection (BSR) marks the velocity contrast between gas hydrate-bearing sediment and regions containing free gas beneath the zone of gas hydrate stability. The BSR is strong and continuous near the ridge crest but becomes discontinuous on the flanks, where concentration of gas is reduced and dipping strata pass through the level of the base o fgas hydrate stability or the strata are disrupted by faults. Seismic reflection amplitudes appear to be reduced in the region of gas hydrate formation compared to normal amplitudes. A faulted zone ~0.5-0.6 s thick parallels reflections from strata. We infer that this may represent a formerly gas hydrate-bearing zone that was faulted because of a breakdown of hydrate near its phase limit (at the base of the zone). Strong reflections at the top of the faulted zone are caused by free-gas acccumulation at Site 994. Similar strong reflections probably are caused by free-gas accumulations where the top of the faulted zone rises above the BSR, although this would require local free gas within the hydrate-stable zone.

Surface-geophysical characterization of ground-water systems of the Caloosahatchee River basin, southern Florida

USGS Publications Warehouse

Cunningham, Kevin J.; Locker, Stanley D.; Hine, Albert C.; Bukry, David; Barron, John A.; Guertin, Laura A.

2001-01-01

The Caloosahatchee River Basin, located in southwestern Florida, includes about 1,200 square miles of land. The Caloosahatchee River receives water from Lake Okeechobee, runoff from the watershed, and seepage from the underlying ground-water systems; the river loses water through drainage to the Gulf of Mexico and withdrawals for public-water supply and agricultural and natural needs. Water-use demands in the Caloosahatchee River Basin have increased dramatically, and the Caloosahatchee could be further stressed if river water is used to accommodate restoration of the Everglades. Water managers and planners need to know how much water will be used within the river basin and how much water is contributed by Lake Okeechobee, runoff, and ground water. In this study, marine seismic-reflection and ground-penetrating radar techniques were used as a means to evaluate the potential for flow between the river and ground-water systems. Seven test coreholes were drilled to calibrate lithostratigraphic units, their stratal geometries, and estimated hydraulic conductivities to surface-geophysical profiles. A continuous marine seismic-reflection survey was conducted over the entire length of the Caloosahatchee River and extending into San Carlos Bay. Lithostratigraphic units that intersect the river bottom and their characteristic stratal geometries were identified. Results show that subhorizontal reflections assigned to the Tamiami Formation intersect the river bottom between Moore Haven and about 9 miles westward. Oblique and sigmoidal progradational reflections assigned to the upper Peace River Formation probably crop out at the floor of the river in the Ortona area between the western side of Lake Hicpochee and La Belle. These reflections image a regional-scale progradational deltaic depositional system containing quartz sands with low to moderate estimated hydraulic conductivities. In an approximate 6-mile length of the river between La Belle and Franklin Lock, deeper karstic collapse structures are postulated. These structures influence the geometries of parallel reflections that intersect the river channel. Here, reflections assigned to the Buckingham Limestone Member of the Tamiami Formation (a confining unit) and reflections assigned to the clastic zone of the sandstone aquifer likely crop out at the river bottom. Beneath these shallow reflections, relatively higher amplitude parallel reflections of the carbonate zone of the sandstone aquifer are well displayed in the seismic-reflection profiles. In San Carlos Bay, oblique progradational reflections assigned to the upper Peace River Formation are shown beneath the bay. Almost everywhere beneath the river, a diffuse ground-water flow system is in contact with the channel bottom. Ground-penetrating radar profiles of an area about 2 miles north of the depositional axis of the deltaic depositional system in the Ortona area show that progradational clinoforms imaged on seismic reflection profiles in the Caloosahatchee River are present within about 17 feet of the ground surface. Ground-penetrating radar profiles show southward dipping, oblique progradational reflections assigned to the upper Peace River Formation that are terminated at their tops by a toplapping or erosional discontinuity. These clinoformal reflections image clean quartz sand that is probably characterized by moderate hydraulic conductivity. This sand could be mapped using ground-penetrating radar methods.

Thin film type 248-nm bottom antireflective coatings

NASA Astrophysics Data System (ADS)

Enomoto, Tomoyuki; Nakayama, Keisuke; Mizusawa, Kenichi; Nakajima, Yasuyuki; Yoon, Sangwoong; Kim, Yong-Hoon; Kim, Young-Ho; Chung, Hoesik; Chon, Sang Mun

2003-06-01

A frequent problem encountered by photoresists during the manufacturing of semiconductor device is that activating radiation is reflected back into the photoresist by the substrate. So, it is necessary that the light reflection is reduced from the substrate. One approach to reduce the light reflection is the use of bottom anti-reflective coating (BARC) applied to the substrate beneath the photoresist layer. The BARC technology has been utilized for a few years to minimize the reflectivity. As the chip size is reduced to sub 0.13-micron, the photoresist thickness has to decrease with the aspect ratio being less than 3.0. Therefore, new Organic BARC is strongly required which has the minimum reflectivity with thinner BARC thickness and higher etch selectivity towards resist. SAMSUNG Electronics has developed the advanced Organic BARC with Nissan Chemical Industries, Ltd. and Brewer Science, Inc. for achieving the above purpose. As a result, the suitable high performance SNAC2002 series KrF Organic BARCs were developed. Using CF4 gas as etchant, the plasma etch rate of SNAC2002 series is about 1.4 times higher than that of conventional KrF resists and 1.25 times higher than the existing product. The SNAC2002 series can minimize the substrate reflectivity at below 40nm BARC thickness, shows excellent litho performance and coating properties.

Use of remote-sensing reflectance to constrain a data assimilating marine biogeochemical model of the Great Barrier Reef

NASA Astrophysics Data System (ADS)

Jones, Emlyn M.; Baird, Mark E.; Mongin, Mathieu; Parslow, John; Skerratt, Jenny; Lovell, Jenny; Margvelashvili, Nugzar; Matear, Richard J.; Wild-Allen, Karen; Robson, Barbara; Rizwi, Farhan; Oke, Peter; King, Edward; Schroeder, Thomas; Steven, Andy; Taylor, John

2016-12-01

Skillful marine biogeochemical (BGC) models are required to understand a range of coastal and global phenomena such as changes in nitrogen and carbon cycles. The refinement of BGC models through the assimilation of variables calculated from observed in-water inherent optical properties (IOPs), such as phytoplankton absorption, is problematic. Empirically derived relationships between IOPs and variables such as chlorophyll-a concentration (Chl a), total suspended solids (TSS) and coloured dissolved organic matter (CDOM) have been shown to have errors that can exceed 100 % of the observed quantity. These errors are greatest in shallow coastal regions, such as the Great Barrier Reef (GBR), due to the additional signal from bottom reflectance. Rather than assimilate quantities calculated using IOP algorithms, this study demonstrates the advantages of assimilating quantities calculated directly from the less error-prone satellite remote-sensing reflectance (RSR). To assimilate the observed RSR, we use an in-water optical model to produce an equivalent simulated RSR and calculate the mismatch between the observed and simulated quantities to constrain the BGC model with a deterministic ensemble Kalman filter (DEnKF). The traditional assumption that simulated surface Chl a is equivalent to the remotely sensed OC3M estimate of Chl a resulted in a forecast error of approximately 75 %. We show this error can be halved by instead using simulated RSR to constrain the model via the assimilation system. When the analysis and forecast fields from the RSR-based assimilation system are compared with the non-assimilating model, a comparison against independent in situ observations of Chl a, TSS and dissolved inorganic nutrients (NO3, NH4 and DIP) showed that errors are reduced by up to 90 %. In all cases, the assimilation system improves the simulation compared to the non-assimilating model. Our approach allows for the incorporation of vast quantities of remote-sensing observations that have in the past been discarded due to shallow water and/or artefacts introduced by terrestrially derived TSS and CDOM or the lack of a calibrated regional IOP algorithm.

Far-field tsunami magnitude determined from ocean-bottom pressure gauge data around Japan

NASA Astrophysics Data System (ADS)

Baba, T.; Hirata, K.; Kaneda, Y.

2003-12-01

\\hspace*{3mm}Tsunami magnitude is the most fundamental parameter to scale tsunamigenic earthquakes. According to Abe (1979), the tsunami magnitude, Mt, is empirically related to the crest to trough amplitude, H, of the far-field tsunami wave in meters (Mt = logH + 9.1). Here we investigate the far-field tsunami magnitude using ocean-bottom pressure gauge data. The recent ocean-bottom pressure measurements provide more precise tsunami data with a high signal-to-noise ratio. \\hspace*{3mm}Japan Marine Science and Technology Center is monitoring ocean bottom pressure fluctuations using two submarine cables of depths of 1500 - 2400 m. These geophysical observatory systems are located off Cape Muroto, Southwest Japan, and off Hokkaido, Northern Japan. The ocean-bottom pressure data recorded with the Muroto and Hokkaido systems have been collected continuously since March, 1997 and October, 1999, respectively. \\hspace*{3mm}Over the period from March 1997 to June 2003, we have observed four far-field tsunami signals, generated by earthquakes, on ocean-bottom pressure records. These far-field tsunamis were generated by the 1998 Papua New Guinea eq. (Mw 7.0), 1999 Vanuatu eq. (Mw 7.2), 2001 Peru eq. (Mw 8.4) and 2002 Papua New Guinea eq. (Mw 7.6). Maximum amplitude of about 30 mm was recorded by the tsunami from the 2001 Peru earthquake. \\hspace*{3mm}Direct application of the Abe's empirical relation to ocean-bottom pressure gauge data underestimates tsunami magnitudes by about an order of magnitude. This is because the Abe's empirical relation was derived only from tsunami amplitudes with coastal tide gauges where tsunami is amplified by the shoaling of topography and the reflection at the coastline. However, these effects do not work for offshore tsunami in deep oceans. In general, amplification due to shoaling near the coastline is governed by the Green's Law, in which the tsunami amplitude is proportional to h-1/4, where h is the water depth. Wave amplitude also is doubled by reflection at the fixed edge (coastline). Hence, we introduce a water-depth term and a reflection coefficient of 2 in the original Abe_fs empirical relation to correct tsunami amplitude for open oceans and obtain Mt = log(2H/h-1/4) + 9.1, where h is the depth of the ocean bottom pressure gage. The modified empirical relation produces tsunami magnitudes close to those determined using tide gauges.

Information Extraction in Tomb Pit Using Hyperspectral Data

NASA Astrophysics Data System (ADS)

Yang, X.; Hou, M.; Lyu, S.; Ma, S.; Gao, Z.; Bai, S.; Gu, M.; Liu, Y.

2018-04-01

Hyperspectral data has characteristics of multiple bands and continuous, large amount of data, redundancy, and non-destructive. These characteristics make it possible to use hyperspectral data to study cultural relics. In this paper, the hyperspectral imaging technology is adopted to recognize the bottom images of an ancient tomb located in Shanxi province. There are many black remains on the bottom surface of the tomb, which are suspected to be some meaningful texts or paintings. Firstly, the hyperspectral data is preprocessing to get the reflectance of the region of interesting. For the convenient of compute and storage, the original reflectance value is multiplied by 10000. Secondly, this article uses three methods to extract the symbols at the bottom of the ancient tomb. Finally we tried to use morphology to connect the symbols and gave fifteen reference images. The results show that the extraction of information based on hyperspectral data can obtain a better visual experience, which is beneficial to the study of ancient tombs by researchers, and provides some references for archaeological research findings.

The effects of the bottom anti-reflective coating with different baked temperatures and thicknesses on nanoscale patterns

NASA Astrophysics Data System (ADS)

Zheng, Jie; Li, Ling; Chen, Weidong

2015-12-01

The bottom anti-reflective coating (BARC) material can enhance the resolution of the nanopatterns structures in laser interference lithography process. In this study, WIDE-B ARC material was investigated to confirm the reduction of the vertical standing wave which leads to defect of nanopatterns. And the critical dimension (CD) of 100 nm L/S patterns with and without the application of BARC material was fabricated by laser interference lithography technology. The compared results showed that BARC can effectively reduce CD swing and obtain more uniform nanopatterns. Meanwhile, we also verified the influence of cured temperature and film thickness of BARC on the uniformity of nanopatterns.

A comparative study of thermal characteristics of GaN-based VCSELs with three different typical structures

NASA Astrophysics Data System (ADS)

Mei, Yang; Xu, Rong-Bin; Xu, Huan; Ying, Lei-Ying; Zheng, Zhi-Wei; Zhang, Bao-Ping; Li, Mo; Zhang, Jian

2018-01-01

Thermal characteristics of GaN-based vertical cavity surface emitting lasers (VCSELs) with three typical structures were investigated both theoretically and experimentally. The simulation results based on a steady state quasi three-dimensional cylindrical model show that the thermal resistance (R th) is affected by cavity length, mesa size, as well as the bottom distributed Bragg reflector (DBR) size, and the detail further depends on different structures. Among different devices, GaN VCSEL with a hybrid cavity formed by one nitride bottom DBR and another dielectric top DBR is featured with lower R th, which is meanwhile affected strongly by the materials of the epitaxial bottom DBR. The main issues affecting the thermal dissipation in VCSELs with double dielectric DBRs are the bottom dielectric DBR and the dielectric current-confinement layer. To validate the simulation results, GaN-based VCSEL bonded on a copper plate was fabricated. R th of this device was measured and the results agreed well with the simulation. This work provides a better understanding of the thermal characteristics of GaN-based VCSELs and is useful in optimizing the structure design and improving the device performance.

Quick and Easy Measurements of the Inherent Optical Property of Water by Laser

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

Izadi, Dina; Hajiesmaeilbaigi, Fereshteh

2009-04-19

To generate realistic images of natural waters, one must consider in some detail the interaction of light with the water body. The reflectance and attenuation coefficient of the second harmonic of Nd:YAG laser light through distilled water and a sample of water from the Oman Sea were measured in a solid-state laser laboratory to estimate inherent optical properties of natural waters. These measurements determined the bottom conditions and the impurities of the water. The water's reflectivity varied depending on the angle of incidence, height of the laser from water surface, wavelength of laser light, radiant intensities, and depth of water.more » In these experiments laser light propagated through the water nonlinearly, and different reflectance showed different bottom slopes. The differences among various water samples were obtained taking into account the exponential equation in attenuation coefficient versus depth graphs.« less

Effect of bottom slope on the nonlinear triad interactions in shallow water

NASA Astrophysics Data System (ADS)

Chen, Hongzhou; Tang, Xiaocheng; Zhang, Ri; Gao, Junliang

2018-05-01

This paper aims at investigating the effect of bottom slope to the nonlinear triad interactions for irregular waves propagating in shallow water. The physical experiments are conducted in a wave flume with respect to the transformation of waves propagating on three bottom slopes ( β = 1/15, 1/30, and 1/45). Irregular waves with different type of breaking that are mechanically generated based on JONSWAP spectra are used for the test. The obviously different variations of spectra measured on each bottom reveal a crucial role of slope effect in the energy transfer between harmonics. The wavelet-based bispectrum were used to examine the bottom slope effect on the nonlinear triad interactions. Results show that the different bottom slopes which waves are propagated on will cause a significant discrepancy of triad interactions. Then, the discussions on the summed bicoherence which denote the distribution of phase coupling on each frequency further clarify the effect of bottom slope. Furthermore, the summed of the real and imaginary parts of bispectrum which could reflect the intensity of frequency components participating in the wave skewness and asymmetry were also investigated. Results indicate that the value of these parameters will increase as the bottom slope gets steeper.

Parameterization and sensitivity analyses of a radiative transfer model for remote sensing plant canopies

NASA Astrophysics Data System (ADS)

Hall, Carlton Raden

A major objective of remote sensing is determination of biochemical and biophysical characteristics of plant canopies utilizing high spectral resolution sensors. Canopy reflectance signatures are dependent on absorption and scattering processes of the leaf, canopy properties, and the ground beneath the canopy. This research investigates, through field and laboratory data collection, and computer model parameterization and simulations, the relationships between leaf optical properties, canopy biophysical features, and the nadir viewed above-canopy reflectance signature. Emphasis is placed on parameterization and application of an existing irradiance radiative transfer model developed for aquatic systems. Data and model analyses provide knowledge on the relative importance of leaves and canopy biophysical features in estimating the diffuse absorption a(lambda,m-1), diffuse backscatter b(lambda,m-1), beam attenuation alpha(lambda,m-1), and beam to diffuse conversion c(lambda,m-1 ) coefficients of the two-flow irradiance model. Data sets include field and laboratory measurements from three plant species, live oak (Quercus virginiana), Brazilian pepper (Schinus terebinthifolius) and grapefruit (Citrus paradisi) sampled on Cape Canaveral Air Force Station and Kennedy Space Center Florida in March and April of 1997. Features measured were depth h (m), projected foliage coverage PFC, leaf area index LAI, and zenith leaf angle. Optical measurements, collected with a Spectron SE 590 high sensitivity narrow bandwidth spectrograph, included above canopy reflectance, internal canopy transmittance and reflectance and bottom reflectance. Leaf samples were returned to laboratory where optical and physical and chemical measurements of leaf thickness, leaf area, leaf moisture and pigment content were made. A new term, the leaf volume correction index LVCI was developed and demonstrated in support of model coefficient parameterization. The LVCI is based on angle adjusted leaf thickness Ltadj, LAI, and h (m). Its function is to translate leaf level estimates of diffuse absorption and backscatter to the canopy scale allowing the leaf optical properties to directly influence above canopy estimates of reflectance. The model was successfully modified and parameterized to operate in a canopy scale and a leaf scale mode. Canopy scale model simulations produced the best results. Simulations based on leaf derived coefficients produced calculated above canopy reflectance errors of 15% to 18%. A comprehensive sensitivity analyses indicated the most important parameters were beam to diffuse conversion c(lambda, m-1), diffuse absorption a(lambda, m-1), diffuse backscatter b(lambda, m-1), h (m), Q, and direct and diffuse irradiance. Sources of error include the estimation procedure for the direct beam to diffuse conversion and attenuation coefficients and other field and laboratory measurement and analysis errors. Applications of the model include creation of synthetic reflectance data sets for remote sensing algorithm development, simulations of stress and drought on vegetation reflectance signatures, and the potential to estimate leaf moisture and chemical status.

Optical image modulation above the submarine bottom topography: a case study on the Taiwan Banks, China

NASA Astrophysics Data System (ADS)

Li, Yan; Hu, Jianyu; Li, Jing; Fu, Bin; Ma, Liming

2003-05-01

A possible mechanism to explain the correlation between submarine topography and the direct sunlight specially reflected from the sea surface with variable roughness caused by the bottom-current effect was suggested fifteen years ago by Henning et al. in International Journal of Remote Sensing, 9, 45-67, after comparing radar satellite image and Skylab satellite photograph of the North American east coast (Nantucket Shoals) with submarine relief features. A case study is carried out in the famous sand waves field located at the Taiwan banks of Taiwan Strait in August 1998. The TM images, either visible bands (TM1, TM2, TM3) or near infrared bands (TM4, TM5, TM7), shows submarine relief features for sand waves, with wavelength of 300 to 2000 meters, riding on the lager scale sand ridges and channel system. Sea truth data including 660 nm beam attenuation coefficient profiles were conducted in the same period. We compare signals of TM images, attenuation coefficient profiles, and sounding maps of the Taiwan Bands. The subsurface upwelling signals with contributions of the water column and the bottom, either estimated by single or quasi-single-scattering theory or revealed by the TM images after removing the contribution of direct sunlight reflected signals from sea surface, were too weak to distinguish the ridges and troughs of bedforms especially for red and near infrared bands. However, the direct sunlight specially reflected signals from the sea surface, approximately at same level in water-leaving reflectance not only for visible bands (TM1, TM2, TM3) but also for near infrared bands (TM4, TM5, TM7), was the major submarine bottom topography signals especially for those pixels towards the direction of the sun azimuth. Following a physical description for the lee waves appeared on free surface when the current flows round an underwater obstacle, the direct sunlight reflected signals related wave face slope, is dominated by the height and depth of sand waves and sand ridges, and current speed of the flows over those bedforms. The direct sunlight reflected signals from the sea surface could be regarded as a powerful tool to detect bedforms and other underwater obstacles.

Metasurface integrated high energy efficient and high linearly polarized InGaN/GaN light emitting diode.

PubMed

Wang, Miao; Xu, Fuyang; Lin, Yu; Cao, Bing; Chen, Linghua; Wang, Chinhua; Wang, Jianfeng; Xu, Ke

2017-07-06

We proposed and demonstrated an integrated high energy efficient and high linearly polarized InGaN/GaN green LED grown on (0001) oriented sapphire with combined metasurface polarizing converter and polarizer system. It is different from those conventional polarized light emissions generated with plasmonic metallic grating in which at least 50% high energy loss occurs inherently due to high reflection of the transverse electric (TE) component of an electric field. A reflecting metasurface, with a two dimensional elliptic metal cylinder array (EMCA) that functions as a half-wave plate, was integrated at the bottom of a LED such that the back-reflected TE component, that is otherwise lost by a dielectric/metal bi-layered wire grids (DMBiWG) polarizer on the top emitting surface of the LED, can be converted to desired transverse magnetic (TM) polarized emission after reflecting from the metasurface. This significantly enhances the polarized light emission efficiency. Experimental results show that extraction efficiency of the polarized emission can be increased by 40% on average in a wide angle of ±60° compared to that with the naked bottom of sapphire substrate, or 20% compared to reflecting Al film on the bottom of a sapphire substrate. An extinction ratio (ER) of average value 20 dB within an angle of ±60° can be simultaneously obtained directly from an InGaN/GaN LED. Our results show the possibility of simultaneously achieving a high degree of polarization and high polarization extraction efficiency at the integrated device level. This advances the field of GaN LED toward energy efficiency, multi-functional applications in illumination, display, medicine, and light manipulation.

Fire and climate variation in western North America from fire-scar and tree-ring networks

Treesearch

Donald A. Falk; E. K. Heyerdahl; P. M. Brown; T. W. Swetnam; E. K. Sutherland; Z. Gedalof; L. Yocom; T. J. Brown

2010-01-01

Fire regimes (i.e., the pattern, frequency and intensity of fire in a region) reflect a complex interplay of bottom-up and top-down controls (Lertzman et al., 1998; Mc Kenzie et al., in press). Bottom-up controls include local variations in topographic, fuel and weather factors at the time of a burn (e.g., fuel moisture and continuity, ignition density and local wind...

Simulation of sea surface wave influence on small target detection with airborne laser depth sounding.

PubMed

Tulldahl, H Michael; Steinvall, K Ove

2004-04-20

A theoretical model for simulation of airborne depth-sounding lidar is presented with the purpose of analyzing the influence from water surface waves on the ability to detect 1-m3 targets placed on the sea bottom. Although water clarity is the main limitation, sea surface waves can significantly affect the detectability. The detection probability for a target at a 9-m depth can be above 90% at 1-m/s wind and below 80% at 6-m/s wind for the same water clarity. The simulation model contains both numerical and analytical components. Simulated data are compared with measured data and give realistic results for bottom depths between 3 and 10 m.

Study of droplet flow in a T-shape microchannel with bottom wall fluctuation

NASA Astrophysics Data System (ADS)

Pang, Yan; Wang, Xiang; Liu, Zhaomiao

2018-03-01

Droplet generation in a T-shape microchannel, with a main channel width of 50 μm , side channel width of 25 μm, and height of 50 μm, is simulated to study the effects of the forced fluctuation of the bottom wall. The periodic fluctuations of the bottom wall are applied on the near junction part of the main channel in the T-shape microchannel. Effects of bottom wall's shape, fluctuation periods, and amplitudes on the droplet generation are covered in the research of this protocol. In the simulation, the average size is affected a little by the fluctuations, but significantly by the fixed shape of the deformed bottom wall, while the droplet size range is expanded by the fluctuations under most of the conditions. Droplet sizes are distributed in a periodic pattern with small amplitude along the relative time when the fluctuation is forced on the bottom wall near the T-junction, while the droplet emerging frequency is not varied by the fluctuation. The droplet velocity is varied by the bottom wall motion, especially under the shorter period and the larger amplitude. When the fluctuation period is similar to the droplet emerging period, the droplet size is as stable as the non-fluctuation case after a development stage at the beginning of flow, while the droplet velocity is varied by the moving wall with the scope up to 80% of the average velocity under the conditions of this investigation.

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.

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

The Bottom Line Threatens Professional Excellence All across America. The Editor Reflects.

ERIC Educational Resources Information Center

Erb, Tom

2002-01-01

Maintains that commercial pressures for profitability threaten best practice in fields such as broadcast journalism and history publishing. Asserts that similar pressures for improved student standardized achievement test scores force educational quality to be sacrificed to the demands of the marketplace. Contends that it is time to reflect on…

193-nm multilayer imaging systems

NASA Astrophysics Data System (ADS)

Meador, James D.; Holmes, Doug; DiMenna, William; Nagatkina, Mariya I.; Rich, Michael D.; Flaim, Tony D.; Bennett, Randy; Kobayashi, Ichiro

2003-06-01

This paper highlights the performance of new materials that have been developed for use in 193-nm trilayer microlithography. The products are embedded etch masking layers (EMLs) and bottom antireflective coatings (BARCs). Both coatings are spin applied from organic solvent(s) and then thermoset during a hot plate bake. The EMLs (middle layers) are imaging compatible with JSR, Sumitomo, and TOK 193-nm photoresists. Best-case trilayer film stacks have given 100-nm dense and semi-dense L/S. Plasma etching, selectivities and solution compatibility performance of the EMLs meet or exceed proposed product targets. In addition, the EMLs exhibit both solution and plasma etching properties that should lead to successful rework processes for photoresists. The multiplayer BARCs offer good thick film coating quality and contribute to excellent images when used in trilayer applications. Combining the EMLs, which are nearly optically transparent (k=0.04) at 193-nm, with the new trilayer BARCs results in outstanding Prolith simulated reflectance control. In one modeling example, reflectance is a flat line at 0.5% on five different substrates for BARC thicknesses between 300 and 700-nm.

Thin film and high-etch-rate type 248-nm bottom antireflective coatings

NASA Astrophysics Data System (ADS)

Enomoto, Tomoyuki; Takei, Satoshi; Kishioka, Takahiro; Hatanaka, Tadashi; Sakamoto, Rikimaru; Nakajima, Yasuyuki

2004-05-01

A frequent problem encountered by photoresists during the manufacturing of semiconductor device is that activating radiation is reflected back into the photoresist by the substrate. So, it is necessary that the light reflection is reduced from the substrate. One approach to reduce the light reflection is the use of bottom anti-reflective coating (BARC) applied to the substrate beneath the photoresist layer. The BARC technology has been utilized for a few years to minimize the reflectivity. As the chip size is reduced to sub 0.13 micron, the photoresist thickness has to decrease with the aspect ratio being less than 3.0. Therefore, new Organic BARC is strongly required which has the minimum reflectivity with thinner BARC thickness and higher etch selectivity toward resists. Nissan Chemical Industries, Ltd. and Brewer Science, Inc. have developed the advanced Organic BARC for achieving the above purpose. As a result, the suitable high performance NCA3000 series 248nm Organic BARCs were developed. Using CF4 gas as etchant, the plasma etch rate of NCA3000 series is about 1.4-1.6 times higher than that of conventional 248nm resists and 1.1-1.2 times higher than that of the existing product. The NCA3000 series can minimize the substrate reflectivity at below 45nm BARC thickness, shows excellent litho performance and coating properties.

Determination of thermal wave reflection coefficient to better estimate defect depth using pulsed thermography

NASA Astrophysics Data System (ADS)

Sirikham, Adisorn; Zhao, Yifan; Mehnen, Jörn

2017-11-01

Thermography is a promising method for detecting subsurface defects, but accurate measurement of defect depth is still a big challenge because thermographic signals are typically corrupted by imaging noise and affected by 3D heat conduction. Existing methods based on numerical models are susceptible to signal noise and methods based on analytical models require rigorous assumptions that usually cannot be satisfied in practical applications. This paper presents a new method to improve the measurement accuracy of subsurface defect depth through determining the thermal wave reflection coefficient directly from observed data that is usually assumed to be pre-known. This target is achieved through introducing a new heat transfer model that includes multiple physical parameters to better describe the observed thermal behaviour in pulsed thermographic inspection. Numerical simulations are used to evaluate the performance of the proposed method against four selected state-of-the-art methods. Results show that the accuracy of depth measurement has been improved up to 10% when noise level is high and thermal wave reflection coefficients is low. The feasibility of the proposed method in real data is also validated through a case study on characterising flat-bottom holes in carbon fibre reinforced polymer (CFRP) laminates which has a wide application in various sectors of industry.

Seasonal canopy reflectance patterns of wheat, sorghum, and soybean

NASA Technical Reports Server (NTRS)

Kanemasu, E. T.

1974-01-01

An investigation was conducted of canopy-reflectance patterns as a basis for the determination of surface conditions. Two fields each of wheat, sorghum, and soybeans were selected in a bottom land area. One field contained a dark-colored, silty clay loam and the other a light-colored, silt loam. The study suggests that the reflectance ratio of the 545- to 655-nm-wavelengths may be used as an indicator of crop growth.

Hyperspectral signatures and WorldView-3 imagery of Indian River Lagoon and Banana River Estuarine water and bottom types

NASA Astrophysics Data System (ADS)

Bostater, Charles R.; Oney, Taylor S.; Rotkiske, Tyler; Aziz, Samin; Morrisette, Charles; Callahan, Kelby; Mcallister, Devin

2017-10-01

Hyperspectral signatures and imagery collected during the spring and summer of 2017 and 2016 are presented. Ground sampling distances (GSD) and pixel sizes were sampled from just over a meter to less than 4.0 mm. A pushbroom hyperspectral imager was used to calculate bidirectional reflectance factor (BRF) signatures. Hyperspectral signatures of different water types and bottom habitats such as submerged seagrasses, drift algae and algal bloom waters were scanned using a high spectral and digital resolution solid state spectrograph. WorldView-3 satellite imagery with minimal water wave sun glint effects was used to demonstrate the ability to detect bottom features using a derivative reflectance spectroscopy approach with the 1.3 m GSD multispectral satellite channels centered at the solar induced fluorescence band. The hyperspectral remote sensing data collected from the Banana River and Indian River Lagoon watersheds represents previously unknown signatures to be used in satellite and airborne remote sensing of water in turbid waters along the US Atlantic Ocean coastal region and the Florida littoral zone.

A computational study of liposome logic: towards cellular computing from the bottom up

PubMed Central

Smaldon, James; Romero-Campero, Francisco J.; Fernández Trillo, Francisco; Gheorghe, Marian; Alexander, Cameron

2010-01-01

In this paper we propose a new bottom-up approach to cellular computing, in which computational chemical processes are encapsulated within liposomes. This “liposome logic” approach (also called vesicle computing) makes use of supra-molecular chemistry constructs, e.g. protocells, chells, etc. as minimal cellular platforms to which logical functionality can be added. Modeling and simulations feature prominently in “top-down” synthetic biology, particularly in the specification, design and implementation of logic circuits through bacterial genome reengineering. The second contribution in this paper is the demonstration of a novel set of tools for the specification, modelling and analysis of “bottom-up” liposome logic. In particular, simulation and modelling techniques are used to analyse some example liposome logic designs, ranging from relatively simple NOT gates and NAND gates to SR-Latches, D Flip-Flops all the way to 3 bit ripple counters. The approach we propose consists of specifying, by means of P systems, gene regulatory network-like systems operating inside proto-membranes. This P systems specification can be automatically translated and executed through a multiscaled pipeline composed of dissipative particle dynamics (DPD) simulator and Gillespie’s stochastic simulation algorithm (SSA). Finally, model selection and analysis can be performed through a model checking phase. This is the first paper we are aware of that brings to bear formal specifications, DPD, SSA and model checking to the problem of modeling target computational functionality in protocells. Potential chemical routes for the laboratory implementation of these simulations are also discussed thus for the first time suggesting a potentially realistic physiochemical implementation for membrane computing from the bottom-up. PMID:21886681

Experimental investigation on circumferential and axial temperature gradient over fuel channel under LOCA

NASA Astrophysics Data System (ADS)

Yadav, Ashwini Kumar; kumar, Ravi; Gupta, Akhilesh; Chatterjee, Barun; Mukhopadhyay, Deb; Lele, H. G.

2014-06-01

In a nuclear reactor temperature rises drastically in fuel channels under loss of coolant accident due to failure of primary heat transportation system. Present investigation has been carried out to capture circumferential and axial temperature gradients during fully and partially voiding conditions in a fuel channel using 19 pin fuel element simulator. A series of experiments were carried out by supplying power to outer, middle and center rods of 19 pin fuel simulator in ratio of 1.4:1.1:1. The temperature at upper periphery of pressure tube (PT) was slightly higher than at bottom due to increase in local equivalent thermal conductivity from top to bottom of PT. To simulate fully voided conditions PT was pressurized at 2.0 MPa pressure with 17.5 kW power injection. Ballooning initiated from center and then propagates towards the ends and hence axial temperature difference has been observed along the length of PT. For asymmetric heating, upper eight rods of fuel simulator were activated and temperature difference up-to 250 °C has been observed from top to bottom periphery of PT. Such situation creates steep circumferential temperature gradient over PT and could lead to breaching of PT under high pressure.

Numerical simulation and optimization of casting process for complex pump

NASA Astrophysics Data System (ADS)

Liu, Xueqin; Dong, Anping; Wang, Donghong; Lu, Yanling; Zhu, Guoliang

2017-09-01

The complex shape of the casting pump body has large complicated structure and uniform wall thickness, which easy give rise to casting defects. The numerical simulation software ProCAST is used to simulate the initial top gating process, after analysis of the material and structure characteristics of the high-pressure pump. The filling process was overall smooth, not there the water shortage phenomenon. But the circular shrinkage defects appear at the bottom of casting during solidification process. Then, the casting parameters were optimized and adding cold iron in the bottom. The shrinkage weight was reduced from 0.00167g to 0.0005g. The porosity volume was reduced from 1.39cm3 to 0.41cm3. The optimization scheme is simulated and actual experimented. The defect has been significantly improved.

Influence of aerosol estimation on coastal water products retrieved from HICO images

NASA Astrophysics Data System (ADS)

Patterson, Karen W.; Lamela, Gia

2011-06-01

The Hyperspectral Imager for the Coastal Ocean (HICO) is a hyperspectral sensor which was launched to the International Space Station in September 2009. The Naval Research Laboratory (NRL) has been developing the Coastal Water Signatures Toolkit (CWST) to estimate water depth, bottom type and water column constituents such as chlorophyll, suspended sediments and chromophoric dissolved organic matter from hyperspectral imagery. The CWST uses a look-up table approach, comparing remote sensing reflectance spectra observed in an image to a database of modeled spectra for pre-determined water column constituents, depth and bottom type. In order to successfully use this approach, the remote sensing reflectances must be accurate which implies accurately correcting for the atmospheric contribution to the HICO top of the atmosphere radiances. One tool the NRL is using to atmospherically correct HICO imagery is Correction of Coastal Ocean Atmospheres (COCOA), which is based on Tafkaa 6S. One of the user input parameters to COCOA is aerosol optical depth or aerosol visibility, which can vary rapidly over short distances in coastal waters. Changes to the aerosol thickness results in changes to the magnitude of the remote sensing reflectances. As such, the CWST retrievals for water constituents, depth and bottom type can be expected to vary in like fashion. This work is an illustration of the variability in CWST retrievals due to inaccurate aerosol thickness estimation during atmospheric correction of HICO images.

Low-Frequency Shallow Water Acoustics (20 to 500 Hz),

DTIC Science & Technology

1986-05-01

developed by Hastrup 49 and the results are shown in Figure V-1. See also Table 11-4. 20- 16.m ./ \\ 12. Fig. V-I. SILT Computed reflection loss...33-39. APL-UW 8606 91 UNIVERSITY OF WASHINGTON • APPLIED PHYSICS LABORATORY 49. O.F. Hastrup , "Some bottom-reflection loss anomalies near grazing and

Perovskite/c-Si tandem solar cell with inverted nanopyramids: realizing high efficiency by controllable light trapping

PubMed Central

Shi, Dai; Zeng, Yang; Shen, Wenzhong

2015-01-01

Perovskite/c-Si tandem solar cells (TSCs) have become a promising candidate in recent years for achieving efficiency over 30%. Although general analysis has shown very high upper limits for such TSCs, it remains largely unclear what specific optical structures could best approach these limits. Here we propose the combination of perovskite/c-Si tandem structure with inverted nanopyramid morphology as a practical way of achieving efficiency above 31% based on realistic solar cell parameters. By full-field simulation, we have shown that an ultra-low surface reflectance can be achieved by tuning the pyramid geometry within the range of experimental feasibility. More importantly, we have demonstrated that the index-guided modes can be excited within the top cell layer by introducing a TCO interlayer that prevents coupling of guided light energy into the bottom cell. This light trapping scheme has shown superior performance over the Bragg stack intermediate reflector utilized in previous micropyramid-based TSCs. Finally, by controlling the coupling between the top and bottom cell through the thickness of the interlayer, current generation within the tandem can be optimized for both two- and four-terminal configurations, yielding efficiencies of 31.9% and 32.0%, respectively. These results have provided useful guidelines for the fabrication of perovskite/c-Si TSCs. PMID:26566176

Perovskite/c-Si tandem solar cell with inverted nanopyramids: realizing high efficiency by controllable light trapping.

PubMed

Shi, Dai; Zeng, Yang; Shen, Wenzhong

2015-11-13

Perovskite/c-Si tandem solar cells (TSCs) have become a promising candidate in recent years for achieving efficiency over 30%. Although general analysis has shown very high upper limits for such TSCs, it remains largely unclear what specific optical structures could best approach these limits. Here we propose the combination of perovskite/c-Si tandem structure with inverted nanopyramid morphology as a practical way of achieving efficiency above 31% based on realistic solar cell parameters. By full-field simulation, we have shown that an ultra-low surface reflectance can be achieved by tuning the pyramid geometry within the range of experimental feasibility. More importantly, we have demonstrated that the index-guided modes can be excited within the top cell layer by introducing a TCO interlayer that prevents coupling of guided light energy into the bottom cell. This light trapping scheme has shown superior performance over the Bragg stack intermediate reflector utilized in previous micropyramid-based TSCs. Finally, by controlling the coupling between the top and bottom cell through the thickness of the interlayer, current generation within the tandem can be optimized for both two- and four-terminal configurations, yielding efficiencies of 31.9% and 32.0%, respectively. These results have provided useful guidelines for the fabrication of perovskite/c-Si TSCs.

Inversion of ocean-bottom seismometer (OBS) waveforms for oceanic crust structure: a synthetic study

NASA Astrophysics Data System (ADS)

Li, Xueyan; Wang, Yanbin; Chen, Yongshun John

2016-08-01

The waveform inversion method is applied—using synthetic ocean-bottom seismometer (OBS) data—to study oceanic crust structure. A niching genetic algorithm (NGA) is used to implement the inversion for the thickness and P-wave velocity of each layer, and to update the model by minimizing the objective function, which consists of the misfit and cross-correlation of observed and synthetic waveforms. The influence of specific NGA method parameters is discussed, and suitable values are presented. The NGA method works well for various observation systems, such as those with irregular and sparse distribution of receivers as well as single receiver systems. A strategy is proposed to accelerate the convergence rate by a factor of five with no increase in computational complexity; this is achieved using a first inversion with several generations to impose a restriction on the preset range of each parameter and then conducting a second inversion with the new range. Despite the successes of this method, its usage is limited. A shallow water layer is not favored because the direct wave in water will suppress the useful reflection signals from the crust. A more precise calculation of the air-gun source signal should be considered in order to better simulate waveforms generated in realistic situations; further studies are required to investigate this issue.

Imaging Reservoir Siltation and Quaternary Stratigraphy Beneath the Mactaquac Headpond by Acoustic and Ground Penetrating Radar Sub-bottom Imaging

NASA Astrophysics Data System (ADS)

Grace, M.; Butler, K. E.; Peter, S.; Yamazaki, G.; Haralampides, K.

2016-12-01

The Mactaquac Hydroelectric Generating Station, located on the Saint John River in New Brunswick, Canada, is approaching the end of its life due to deterioration of the concrete structures. As part of an aquatic ecosystem study, designed to support a decision on the future of the dam, sediment in the headpond, extending 80 km upriver, is being examined. The focus of this sub-study lies in (i) mapping the thickness of sediments that have accumulated since inundation in 1968, and (ii) imaging the deeper glacial and post-glacial stratigraphy. Acoustic sub-bottom profiling surveys were completed during 2014 and 2015. An initial 3.5 kHz chirp sonar survey proved ineffective, lacking in both resolution and depth of the penetration. A follow-up survey employing a boomer-based "Seistec" sediment profiler provided better results, resolving sediment layers as thin as 12 cm, and yielding coherent reflections from the deeper Quaternary sediments. Post-inundation sediments in the lowermost 25 km of the headpond, between the dam and Bear Island, are interpreted to average 26 cm in thickness with the thickest deposits (up to 65 cm) in deep water areas overlying the pre-inundation riverbed west of Snowshoe Island, and south and east of Bear Island. A recent coring program confirmed the presence of silty sediment and showed good correlation with the Seistec thickness estimates. In the 15 km stretch upriver of Bear Island to Nackawic, the presence of gas in the uppermost sediments severely limits sub-bottom penetration and our ability to interpret sediment thicknesses. Profiles acquired in the uppermost 40 km reach of the headpond, extending to Woodstock, show a strong, positive water bottom reflection and little to no sub-bottom penetration, indicating the absence of soft post-inundation sediment. Deeper reflections observed within 5 km of the dam reveal a buried channel cut into glacial till, extending up to 20 m below the water bottom. Channel fill includes a finely laminated unit interpreted to be glaciolacustrine clay-silt and a possible esker - similar to stratigraphy found 20 - 30 km downriver at Fredericton. Future plans include a small scale survey in late summer, 2016 to evaluate the suitability of waterborne ground penetrating radar (GPR) profiling as an alternative to acoustic profiling in areas of gas-charged sediment.

Understanding deviations in lithographic patterns near interfaces: Characterization of bottom anti-reflective coatings (BARC) and the BARC resist interface

NASA Astrophysics Data System (ADS)

Lenhart, Joseph L.; Fischer, Daniel; Sambasivan, Sharadha; Lin, Eric K.; Wu, Wen-Li; Guerrero, Douglas J.; Wang, Yubao; Puligadda, Rama

2007-02-01

Interactions between a bottom anti-reflective coating (BARC) and a photoresist can critically impact lithographic patterns. For example, a lithographic pattern can shrink or spread near a BARC interface, a process called undercutting or footing respectively, due to incompatibility between the two materials. Experiments were conducted on two industrial BARC coatings in an effort to determine the impact of BARC surface chemistry on the footing and undercutting phenomena. The BARC coatings were characterized by near edge X-ray absorption fine structure (NEXAFS), contact angle measurements, and neutron and X-ray reflectivity. Contact angle measurement using a variety of fluids showed that the fluid contact angles were independent of the type of BARC coating or the BARC processing temperature. NEXAFS measurements showed that the surface chemistry of each BARC was also independent of the processing temperature. These results suggest that acid-base interactions at the BARC-resist interface are not the cause of the footing-undercutting phenomena encountered in lithographic patterns.

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.

Some Approaches to the Analysis and Interpretation of Wide-Angle Bottom Loss Data.

DTIC Science & Technology

1982-02-15

1979; Hastrup , 1969). This is described by the equation I ( ) = A( ) x where I(w)z impulse response estimate, A(w) = bottom interacting signal, S(w...quite significant subbottom reflectivity structure ( Hastrup , 1970; Herstein et al, 1979; Santaniello et al, 1979; Chapman, 1980; Tyce et al, 1980...Use of Windows for Harmonic Analysis with the Discrete Fourier Transform," Proo. IEEE 66, 51. 186 Hastrup , 0. F., 1970. "Digital Analysis of Acoustic

Three-dimensional numerical modeling of bottom-diffracted surface-reflected arrivals in the North Pacific

NASA Astrophysics Data System (ADS)

Stephen, R. A.; Udovydchenkov, I. A.; Bolmer, T.; Komatitsch, D.; Tromp, J.; Casarotti, E.; Xie, Z.; Worcester, P. F.

2015-12-01

Bottom-diffracted surface-reflected (BDSR) arrivals were first identified in the 2004 Long-range Ocean Acoustic Propagation Experiment (Stephen et al, 2013, JASA, v.134, p.3307-3317). The BDSR mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor. At depths greater than the conjugate depth ambient noise and PE- predicted arrivals are sufficiently quiet that BDSR paths, scattered from small seamounts, can be the largest amplitude arrivals observed. The Ocean Bottom Seismometer Augmentation in the North Pacific (OBSANP) Experiment in June-July 2013 was designed to further define the characteristics of the BDSRs and to understand the conditions under which BDSRs are excited and propagate. An example of BDSR arrivals is shown on the record section in the figure. Other arrivals are the direct water wave and first and second multiples. The reciprocal of the BDSR mechanism also plays a role in T-phase excitation. To further understand the BDSR mechanism, the SPECFEM3D code was extended to handle high-frequency, deep water bottom scattering problems with actual bathymetry and a typical sound speed profile in the water column. The model size is 38km x 27km x 6.5km. The source is centered at 10Hz with a 5Hz bandwidth. Work supported by NSF and ONR.

Field measurements of the spectral response of natural waters

NASA Technical Reports Server (NTRS)

Bartolucci, L. A.; Robinson, B. F.; Silva, L. F.

1977-01-01

The spectral response (air-water interface reflectance and water-volume scattering) of turbid river water (99 mg/liter suspended solids) and relatively clear lake water (10 mg/liter suspended solids) was measured in situ with a field spectroradiometer. The influence of the river bottom on the spectral response of the water also was determined by using a modified Secchi disc approach. The results indicated that turbid river water had a higher spectral response than clear lake water (about 6 percent) in the red (0.6-0.7 micron) and near-infrared (0.7-0.9 micron) portions of the spectrum. Also, the reflectance characteristics of the river bottom did not influence the spectral response of the turbid river water when the water was deeper than 30 cm

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.

Southern Ocean bottom water characteristics in CMIP5 models

NASA Astrophysics Data System (ADS)

Heuzé, CéLine; Heywood, Karen J.; Stevens, David P.; Ridley, Jeff K.

2013-04-01

Southern Ocean deep water properties and formation processes in climate models are indicative of their capability to simulate future climate, heat and carbon uptake, and sea level rise. Southern Ocean temperature and density averaged over 1986-2005 from 15 CMIP5 (Coupled Model Intercomparison Project Phase 5) climate models are compared with an observed climatology, focusing on bottom water. Bottom properties are reasonably accurate for half the models. Ten models create dense water on the Antarctic shelf, but it mixes with lighter water and is not exported as bottom water as in reality. Instead, most models create deep water by open ocean deep convection, a process occurring rarely in reality. Models with extensive deep convection are those with strong seasonality in sea ice. Optimum bottom properties occur in models with deep convection in the Weddell and Ross Gyres. Bottom Water formation processes are poorly represented in ocean models and are a key challenge for improving climate predictions.

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.

Laboratory and field measurements of upwelled radiance and reflectance spectra of suspended James River sediments near Hopewell, Virginia

NASA Technical Reports Server (NTRS)

Whilock, C. H.; Witte, W. G.; Gurganus, E. A.; Usry, J. W.

1978-01-01

Spectral reflectance characteristics of suspended Bermuda Hundred and Bailey Bay bottom sediments taken from the Hopewell, Va., area were measured in the laboratory for water mixture total suspended solids concentrations between 4 and 173 parts per million. Field spectral reflectance measurements were made of the James River waters near Bermuda Hundred on two occasions. The results of these tests indicate that both Bermuda Hundred and Bailey Bay suspended sediments produce their strongest reflectance in the green and red regions of the spectrum.

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.

Optical analysis of down-conversion OLEDs

NASA Astrophysics Data System (ADS)

Krummacher, Benjamin; Klein, Markus; von Malm, Norwin; Winnacker, Albrecht

2008-02-01

Phosphor down-conversion of blue organic light-emitting diodes (OLEDs) is one approach to generate white light, which offers the possibility of easy color tuning, a simple device architecture and color stability over lifetime. In this article previous work on down-conversion devices in the field of organic solid state lighting is briefly reviewed. Further, bottom emitting down-conversion OLEDs are studied from an optical point of view. Therefore the physical processes occurring in the down-conversion layer are translated into a model which is implemented in a ray tracing simulation. By comparing its predictions to experimental results the model is confirmed. For the experiments a blue-emitting polymer OLED (PLED) panel optically coupled to a series of down-conversion layers is used. Based on results obtained from ray tracing simulation some of the implications of the model for the performance of down-conversion OLEDs are discussed. In particular it is analysed how the effective reflectance of the underlying blue OLED and the particle size distribution of the phosphor powder embedded in the matrix of the down-conversion layer influence extraction efficiency.

Highly doped InP as a low loss plasmonic material for mid-IR region.

PubMed

Panah, M E Aryaee; Takayama, O; Morozov, S V; Kudryavtsev, K E; Semenova, E S; Lavrinenko, A V

2016-12-12

We study plasmonic properties of highly doped InP in the mid-infrared (IR) range. InP was grown by metal-organic vapor phase epitaxy (MOVPE) with the growth conditions optimized to achieve high free electron concentrations by doping with silicon. The permittivity of the grown material was found by fitting the calculated infrared reflectance spectra to the measured ones. The retrieved permittivity was then used to simulate surface plasmon polaritons (SPPs) propagation on flat and structured surfaces, and the simulation results were verified in direct experiments. SPPs at the top and bottom interfaces of the grown epilayer were excited by the prism coupling. A high-index Ge hemispherical prism provides efficient coupling conditions of SPPs on flat surfaces and facilitates acquiring their dispersion diagrams. We observed diffraction into symmetry-prohibited diffraction orders stimulated by the excitation of surface plasmon-polaritons in a periodically structured epilayer. Characterization shows good agreement between the theory and experimental results and confirms that highly doped InP is an effective plasmonic material aiming it for applications in the mid-IR wavelength range.

Simulation of Blast Loading on an Ultrastructurally-based Computational Model of the Ocular Lens

DTIC Science & Technology

2013-10-01

gradient components in the axial ( F22 ) and radial (F11) directions. One can observe the very large deformation (approaching 800%) and 5 Figure 5...and (bottom left) show deformation gradient in axial ( F22 ) and radial (F11) directions. (bottom right) normalized force versus displacement curve for

Three-dimensional modelling for assessment of far-field impact of tidal stream turbine: A case study at the Anglesey Coast, Wales, UK

NASA Astrophysics Data System (ADS)

Li, Xiaorong; Li, Ming; Wolf, Judith

2017-04-01

As a response to worldwide climate change, clean non-carbon renewable energy resources have been gaining significant attention. Among a range of renewable alternatives, tidal stream energy is considered very promising; due to its consistent predictability and availability. To investigate impacts of tidal stream devices on their surroundings, prototype experiments involving small scale laboratory studies have been implemented. Computational Flow Dynamics (CFD) modelling is also commonly applied to study turbine behaviours. However, these studies focus on impacts of the turbine in the near-field scale. As a result, in order to study and predict the far-field impacts caused by the operation of turbines, large scale 2D and 3D numerical oceanography models have been used, with routines added to reflect the impacts of turbines. In comparison to 2D models, 3D models are advantageous in providing complete prediction of vertical flow structures and hence mixing in the wake of a turbine. This research aims to deliver a thorough 3D tidal stream turbine simulation system, by considering major coastal processes, i.e. current, waves and sediment transport, based on a 3D wave-current-sediment fully coupled numerical oceanography model — the Unstructured Grid Finite Volume Community Ocean Model (FVCOM). The energy extraction of turbines is simulated by adding a body force to the momentum equations. Across the water depth, the coefficient related to the additional body force is given different values according to the turbine configuration and operation to reflect the vertical variation of the turbine's impacts on the passing flow. Three turbulence perturbation terms are added to the turbulence closure to simulate the turbine-induced turbulence generation, dissipation and interference for the turbulence length-scale. Impacts of turbine operation on surface waves are also considered by modification of wave energy flux across the device. A thorough validation study is carried out in which the developed model is tested; based on a combination of laboratory measured data and CFD simulated results. The developed turbine simulation system is then applied to the Anglesey coast, North Wales, UK for a case study. The validation study suggests that the developed turbine simulation system is able to accurately simulate both hydrodynamics and wave dynamics in the turbine wake. The case study with 18 turbines (diameter is 15 m) modelled individually in the waterway between the north-west Anglesey and the Skerries reveals impacts of the turbine farm on free surface elevation, flow field, turbulence kinetic energy (TKE), surface waves, bottom shear stress and suspended sediment transport. The wake is observable up to 4.5 km downstream of the device farm. Flow near the bed in the wake is accelerated, leading to enhanced bottom shear stress. The device farm has a strong influence on TKE and hence the vertical mixing of suspended sediment in the wake. Further, the eastwards directed residual sediment transport along the north coast of Anglesey is found to be weakened by the turbine farm.

A probabilistic model for analysing the effect of performance levels on visual behaviour patterns of young sailors in simulated navigation.

PubMed

Manzanares, Aarón; Menayo, Ruperto; Segado, Francisco; Salmerón, Diego; Cano, Juan Antonio

2015-01-01

The visual behaviour is a determining factor in sailing due to the influence of the environmental conditions. The aim of this research was to determine the visual behaviour pattern in sailors with different practice time in one star race, applying a probabilistic model based on Markov chains. The sample of this study consisted of 20 sailors, distributed in two groups, top ranking (n = 10) and bottom ranking (n = 10), all of them competed in the Optimist Class. An automated system of measurement, which integrates the VSail-Trainer sail simulator and the Eye Tracking System(TM) was used. The variables under consideration were the sequence of fixations and the fixation recurrence time performed on each location by the sailors. The event consisted of one of simulated regatta start, with stable conditions of wind, competitor and sea. Results show that top ranking sailors perform a low recurrence time on relevant locations and higher on irrelevant locations while bottom ranking sailors make a low recurrence time in most of the locations. The visual pattern performed by bottom ranking sailors is focused around two visual pivots, which does not happen in the top ranking sailor's pattern. In conclusion, the Markov chains analysis has allowed knowing the visual behaviour pattern of the top and bottom ranking sailors and its comparison.

A New Global Anthropogenic SO2 Emission Inventory for the Last Decade: A Mosaic of Satellite-derived and Bottom-up Emissions

NASA Astrophysics Data System (ADS)

Liu, F.; Joiner, J.; Choi, S.; Krotkov, N. A.; Li, C.; Fioletov, V. E.; McLinden, C. A.

2017-12-01

Sulfur dioxide (SO2) measurements from the Ozone Monitoring Instrument (OMI) satellite sensor have been used to detect emissions from large point sources using an innovative estimation technique. Emissions from about 500 sources have been quantified individually based on OMI observations, accounting for about a half of total reported anthropogenic SO2 emissions. We developed a new emission inventory, OMI-HTAP, by combining these OMI-based emission estimates and the conventional bottom-up inventory. OMI-HTAP includes OMI-based estimates for over 400 point sources and is gap-filled with the emission grid map of the latest available global bottom-up emission inventory (HTAP v2.2) for the rest of sources. We have evaluated the OMI-HTAP inventory by performing simulations with the Goddard Earth Observing System version 5 (GEOS-5) model. The GEOS-5 simulated SO2 concentrations driven by both the HTAP and the OMI-HTAP inventory were compared against in-situ and satellite measurements. Results show that the OMI-HTAP inventory improves the model agreement with observations, in particular over the US, India and the Middle East. Additionally, simulations with the OMI-HTAP inventory capture the major trends of anthropogenic SO2 emissions over the world and highlight the influence of missing sources in the bottom-up inventory.

A quick method for AlCu interconnect electromigration performance predicting and monitoring

NASA Astrophysics Data System (ADS)

Zhang, Wenjie; Yi, Leeward; Tao, Kai; Ma, Yue; Chang, Pingyi; Mao, Duli; Wu, Jin; Zou, S. C.

2006-05-01

The film properties and microstructures of (bottom)Si/SiO2/Ti(top) and (bottom)Si/SiO2/Ti/TiN/AlCu(top) stacks deposited by different processes were characterized. The resistivities of thin Ti films and the reflectivities of AlCu alloy films were found to correlate with the microstructure as well as the mean time to failure (MTTF) in the electromigration (EM) test. A quick-turn monitor for AlCu interconnect reliability in the semiconductor manufacturing industry was established.

Ultra-low loss fully-etched grating couplers for perfectly vertical coupling compatible with DUV lithography tools

NASA Astrophysics Data System (ADS)

Dabos, G.; Pleros, N.; Tsiokos, D.

2016-03-01

Hybrid integration of VCSELs onto silicon-on-insulator (SOI) substrates has emerged as an attractive approach for bridging the gap between cost-effective and energy-efficient directly modulated laser sources and silicon-based PICs by leveraging flip-chip (FC) bonding techniques and silicon grating couplers (GCs). In this context, silicon GCs, should comply with the process requirements imposed by the complimentary-metal-oxide-semiconductor manufacturing tools addressing in parallel the challenges originating from the perfectly vertical incidence. Firstly, fully etched GCs compatible with deep-ultraviolet lithography tools offering high coupling efficiencies are imperatively needed to maintain low fabrication cost. Secondly, GC's tolerance to VCSEL bonding misalignment errors is a prerequisite for practical deployment. Finally, a major challenge originating from the perfectly vertical coupling scheme is the minimization of the direct back-reflection to the VCSEL's outgoing facet which may destabilize its operation. Motivated from the above challenges, we used numerical simulation tools to design an ultra-low loss, bidirectional VCSEL-to-SOI optical coupling scheme for either TE or TM polarization, based on low-cost fully etched GCs with a Si-layer of 340 nm without employing bottom reflectors or optimizing the buried-oxide layer. Comprehensive 2D Finite-Difference-Time- Domain simulations have been performed. The reported GC layout remains fully compatible with the back-end-of-line (BEOL) stack associated with the 3D integration technology exploiting all the inter-metal-dielectric (IMD) layers of the CMOS fab. Simulation results predicted for the first time in fully etched structures a coupling efficiency of as low as -0.87 dB at 1548 nm and -1.47 dB at 1560 nm with a minimum direct back-reflection of -27.4 dB and -14.2 dB for TE and TM polarization, respectively.

Evaluation of Space-Based Constraints on Global Nitrogen Oxide Emissions with Regional Aircraft Measurements over and Downwind of Eastern North America

NASA Technical Reports Server (NTRS)

Martin, Randall V.; Sioris, Christopher E.; Chance, Kelly; Ryerson, Thomas B.; Flocke, Frank M.; Bertram, Timothy H.; Wooldridge, Paul J.; Cohen, Ronald C.; Neuman, J. Andy; Swanson, Aaron

2006-01-01

We retrieve tropospheric nitrogen dioxide (NO 2) columns for May 2004 to April 2005 from the SCIAMACHY satellite instrument to derive top-down emissions of nitrogen oxides (NO(x) = NO + NO2) via inverse modeling with a global chemical transport model (GEOS-Chem). Simulated NO 2 vertical profiles used in the retrieval are evaluated with airborne measurements over and downwind of North America (ICARTT); a northern midlatitude lightning source of 1.6 Tg N/yr minimizes bias in the retrieval. Retrieved NO2 columns are validated (r2 = 0.60, slope = 0.82) with coincident airborne in situ measurements. The top-down emissions are combined with a priori information from a bottom-up emission inventory with error weighting to achieve an improved a posteriori estimate of the global distribution of surface NOx emissions. Our a posteriori NOx emission inventory for land surface NOx emissions (46.1 Tg N/yr) is 22% larger than the GEIA-based a priori bottom-up inventory for 1998, a difference that reflects rising anthropogenic emissions, especially from East Asia A posteriori NOx emissions for East Asia (9.8 Tg N/yr) exceed those from other continents. The a posteriori inventory improves the GEOS-Chem simulation of NOx, peroxyacetylnitrate, and nitric acid with respect to airborne in situ measurements over and downwind of New York City. The a posteriori is 7% larger than the EDGAR 3.2FT2000 global inventory, 3% larger than the NEI99 inventory for the United States, and 68% larger than a regional inventory for 2000 for eastern Asia. SCIAMACHY NO2 columns over the North Atlantic show a weak plume from lightning NO(x).

Attenuating reaches and the regional flood response of an urbanizing drainage basin

NASA Astrophysics Data System (ADS)

Turner-Gillespie, Daniel F.; Smith, James A.; Bates, Paul D.

The Charlotte, North Carolina metropolitan area has experienced extensive urban and suburban growth and sharply increasing trends in the magnitude and frequency of flooding. The hydraulics and hydrology of flood response in the region are examined through a combination of numerical modeling studies and diagnostic analyses of paired discharge observations from upstream-downstream gaging stations. The regional flood response is shown to strongly reflect urbanization effects, which increase flood peaks and decrease response times, and geologically controlled attenuating reaches, which decrease flood peaks and increase lag times. Attenuating reaches are characterized by systematic changes in valley bottom geometry and longitudinal profile. The morphology of the fluvial system is controlled by the bedrock geology, with pronounced changes occurring at or near contacts between intrusive igneous and metamorphic rocks. Analyses of wave celerity and flood peak attenuation over a range of discharge values for an 8.3 km valley bottom section of Little Sugar Creek are consistent with Knight and Shiono's characterization of the variation of flood wave velocity from in-channel conditions to valley bottom full conditions. The cumulative effect of variation in longitudinal profile, expansions and contractions of the valley bottom, floodplain roughness and sub-basin flood response is investigated using a two-dimensional, depth-averaged, finite element hydrodynamic model coupled with a distributed hydrologic model. For a 10.1 km stream reach of Briar Creek, with drainage area ranging from 13 km 2 at the upstream end of the reach to 49 km 2 at the downstream end, it is shown that flood response reflects a complex interplay of hydrologic and hydraulic processes on hillslopes and valley bottoms.

Sublake geologic structure from high-resolution seismic-reflection data from four sinkhole lakes in the Lake Wales Ridge, Central Florida

USGS Publications Warehouse

Tihansky, A.B.; Arthur, J.D.; DeWitt, D.W.

1996-01-01

Seismic-reflection profiles from Lake Wales, Blue Lake, Lake Letta, and Lake Apthorp located along the Lake Wales Ridge in central Florida provide local detail within the regional hydrogeologic framework as described by litho- and hydrostratigraphic cross sections. Lakes located with the mantled karst region have long been considered to be sinkhole lakes, originating from subsidence activity. High-resolution seismic- reflection data confirm this origin for these four lakes. The geologic framework of the Lake Wales Ridge has proven to be a suitable geologic setting for continuous high-resolution seismic-reflection profiling in lakes; however, the nature of the lake-bottom sediments largely controls the quality of the seismic data. In lakes with significant organic-rich bottom deposits, interpretable record was limited to areas where organic deposits were minimal. In lakes with clean, sandy bottoms, the seismic-reflection methods were highly successful in obtaining data that can be correlated with sublake subsidence features. These techniques are useful in examining sublake geology and providing a better understanding of how confining units are affected by subsidence in a region where their continuity is of significant importance to local lake hydrology. Although local geologic control around each lake generally corresponds to the regional geologic framework, local deviations from regional geologic trends occur in sublake areas affected by subsidence activity. Each of the four lakes examined represents a unique set of geologic controls and provides some degree of structural evidence of subsidence activity. Sublake geologic structures identified include: (1) marginal lake sediments dipping into bathymetric lows, (2) lateral discontinuity of confining units including sags and breaches, (3) the disruption and reworking of overlying unconsolidated siliciclastic sediments as they subside into the underlying irregular limestone surface, and (4) sublake regions where confining units appear to remain intact and unaffected by nearby subsidence activity. Each lake likely is underlain by several piping features rather than one large subsidence feature.

Bottom water production variability in the Ross Sea slope during the Late-Pleistocene-Holocene as revealed by benthic foraminifera and sediment geochemistry

NASA Astrophysics Data System (ADS)

Asioli, A.; Langone, L.; Tateo, F.; Giannossi, M. L.; Giglio, F.; Summa, V.; Piva, A.; Ridente, D.; Trincardi, F.

2009-04-01

The Antarctic area produces bottom waters that ventilate the vast majority of the deep basins in the rest of the world ocean. The rate of formation in the source area and the strength of these cold bottom waters affect their flow toward the equator and are key factors affecting the Global Thermohaline Circulation during modern and past climate conditions. We present the results of a multidisciplinary study carried out on a core collected in 2377m of water depth on the slope off the Drygalski Basin (Ross Sea), along the modern path of the bottom waters. The goal of this research is to detect a qualitative signal of possible changes in the rate of bottom water production during the Late Pleistocene-Holocene by integrating micropaleontological and geochemical proxies. The micropaleontological signal is represented by the quantitative and qualitative variations of the agglutinated benthic foraminifera assemblages, while the amount of TOC, nitrogen, δ13C, δ15N, biogenic silica, CaCO3 in the sediment, along with the bulk rock mineralogy, provide information on the paleoproductivity and allow reconstruction of changes in the paleocirculation. The chronology is supported by 14C AMS datings on organic matter. Although this study is still in progress, the results obtained allow the following observations: 1) the Holocene sequence includes a major turnover around 8-8.5 calib kyr BP, leading to reduced nutrient utilization, probably reflecting an increased nutrient supply induced by an enhanced Upper Circumpolar Deep Water upwelling; 2) within this general context, the total concentration of benthic foraminifera preserved in the fossil component records millennial scale cycles of variable amplitude after 8.5 calib kyr BP and to present time. This oscillatory trend is paralleled by other parameters, such as the magnetic susceptibility, the dry density, the sheet silicates and the δ15N; 3) minima in foraminifera concentration reflect relatively increased dissolution, weaker bottom currents (minima in dry density=higher amount of fine fraction), and lower nutrient supply; maxima in foraminifera concentration indicate better preservation, higher benthic productivity and/or better oxygenation at bottom, stronger bottom currents (maxima in dry density) and relatively higher nutrient supply; 4) these cycles are interpreted to reflect a relatively higher (maxima in forams concentration) or lower (minima in forams concentration) rate of bottom water formation; 5) between 8.5 and 6 kyr BP the amplitude of these cycles (and particularly those with increased rates of bottom water formation) is higher than the subsequent ones. We equate this interval with the early part of the Middle Holocene Climatic Optimum of the literature; 6) the condensed/hiatus interval centred at ca. 3.5-4 kyr BP does not seem to mark a major change in the general pattern. Nevertheless, this feature is time-equivalent to a major change in the circulation pattern in other Antarctic regions, such as the Antarctic Peninsula. This major change consists in oscillations between two contrasting circulation modes dominated respectively by: a) Upper Circumpolar Deep Water and b) shelf-water formation. This major change can therefore be ascribed to the southward migration of the Intertropical Convergence Zone vs. ENSO prevalence, respectively.

Container for heat treating materials in microwave ovens

DOEpatents

Holcombe, Cressie E.; Dykes, Norman L.; Kimrey, Jr., Harold D.; Mills, James E.

1989-01-01

The efficiency of a microwave oven of a conventional two-source configuration and energy level is increased by providing the oven with a container for housing a refractory material to be treated. The container is formed of top and bottom walls transparent to microwaves while the sidewalls, in a circular configuration, are formed of a nonmetallic material opaque to microwave radiation reflecting the radiation penetrating the top and bottom walls radially inwardly into the center of the container wherein a casket of heat-insulating material is provided for housing the material to be heat treated. The reflection of the microwave radiation from the sidewalls increases the concentration of the microwaves upon the material being heat treated while the casket retains the heat to permit the heating of the material to a substantially higher temperature than achieveable in the oven without the container.

Initiation of Detonation in Multiple Shock-Compressed Liquid Explosives

NASA Astrophysics Data System (ADS)

Yoshinaka, A. C.; Zhang, F.; Petel, O. E.; Higgins, A. J.

2006-07-01

Initiation and resulting propagation of detonation via multiple shock reverberations between two high impedance plates has been investigated in amine-sensitized nitromethane. Experiments were designed so that the first reflected shock strength was below the critical value for initiation found previously. Luminosity combined with a distinct pressure hump indicated onset of reaction and successful initiation after double or triple shock reflection off the bottom plate. Final temperature estimates for double or triple shock reflection immediately before initiation lie between 700-720 K, consistent with those found previously for both incident and singly reflected shock initiation.

An Improved Heat Budget Estimation Including Bottom Effects for General Ocean Circulation Models

NASA Technical Reports Server (NTRS)

Carder, Kendall; Warrior, Hari; Otis, Daniel; Chen, R. F.

2001-01-01

This paper studies the effects of the underwater light field on heat-budget calculations of general ocean circulation models for shallow waters. The presence of a bottom significantly alters the estimated heat budget in shallow waters, which affects the corresponding thermal stratification and hence modifies the circulation. Based on the data collected during the COBOP field experiment near the Bahamas, we have used a one-dimensional turbulence closure model to show the influence of the bottom reflection and absorption on the sea surface temperature field. The water depth has an almost one-to-one correlation with the temperature rise. Effects of varying the bottom albedo by replacing the sea grass bed with a coral sand bottom, also has an appreciable effect on the heat budget of the shallow regions. We believe that the differences in the heat budget for the shallow areas will have an influence on the local circulation processes and especially on the evaporative and long-wave heat losses for these areas. The ultimate effects on humidity and cloudiness of the region are expected to be significant as well.

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.

Impact of Gas Hydrate and Related Fluid Seepage on Submarine Slope Failures along the Margins of the Ulleung Basin, East Sea (Japan Sea)

NASA Astrophysics Data System (ADS)

Horozal, S.; Bahk, J. J.; Urgeles, R.; Kim, G. Y.; Cukur, D.; Lee, G. H.; Lee, S. H.; Kim, S. P.; Ryu, B. J.; Kim, J. H.

2016-12-01

The Ulleung Basin is a back-arc basin that is known to retain gas hydrate reservoirs in the East (Japan) Sea. The basin contains large volumes of mass-transport deposits (MTDs) due to submarine slope failures along its margins since the Neogene. In this study, seismic indicators of gas hydrate and associated gas and fluid flow were re-compiled on a regional multi-channel seismic reflection data. The gas hydrate occurrence zone (GHOZ) is defined by the BSR (bottom-simulating reflector) distribution. It is more pronounced along the southwestern slope with a minimum depth of 100 mbsf (meters below seafloor) at 295 mbsl (meter below sea level) on the southern, while its thickness is the greatest (250 mbsf) at the southwestern margin. Flow and seepage structures reflected on the seismic data as columnar acoustic-blanking zones varying in width and height (up to hundreds of meters) were classified into: (a) buried seismic chimneys (BSC), (b) chimneys with a mound (SCM), and (c) chimneys with a depression (SCD) on the seafloor. Pockmarks which are not associated with seismic chimneys, reflection anomalies (i.e., enhanced reflections below the BSR and hyperbolic reflections), and SCD are predominant features in the western margin, while the BSR, BSC and SCM are densely distributed in the south-southwestern margin. Present-day gas hydrate stability zone (GHSZ) is calculated using in-situ bottom-water temperature and geothermal gradient measurements (ranging between 0-17.5 oC and 25-200 oC/km, respectively) and multibeam bathymetry data. The GHSZ thickness exceeds 190 m, and the upslope limit of GHSZ ranges between about 180 and 260 mbsl. This depth range is in the proximity of the uppermost depths of landslide scars ( 190 mbsl) which are common features on the slopes along with glide planes, slides/slumps and MTDs. Overall, the base of GHSZ (BGHSZ) and the BSR depths are well-correlated in the basin. However, the BSR depths are typically greater (up to 50 m) than the BGHSZ depths on the slopes suggesting that the GHOZ is not stable. A close correlation exists between the spatial distributions of the landslides, and indicators of gas hydrate and gas/fluid flow and the GHSZ. This may imply that excess pore-pressure caused by dissociation/dissolution of gas hydrates could have played a role on slope failures.

When everything is not everywhere but species evolve: an alternative method to model adaptive properties of marine ecosystems

PubMed Central

Sauterey, Boris; Ward, Ben A.; Follows, Michael J.; Bowler, Chris; Claessen, David

2015-01-01

The functional and taxonomic biogeography of marine microbial systems reflects the current state of an evolving system. Current models of marine microbial systems and biogeochemical cycles do not reflect this fundamental organizing principle. Here, we investigate the evolutionary adaptive potential of marine microbial systems under environmental change and introduce explicit Darwinian adaptation into an ocean modelling framework, simulating evolving phytoplankton communities in space and time. To this end, we adopt tools from adaptive dynamics theory, evaluating the fitness of invading mutants over annual timescales, replacing the resident if a fitter mutant arises. Using the evolutionary framework, we examine how community assembly, specifically the emergence of phytoplankton cell size diversity, reflects the combined effects of bottom-up and top-down controls. When compared with a species-selection approach, based on the paradigm that “Everything is everywhere, but the environment selects”, we show that (i) the selected optimal trait values are similar; (ii) the patterns emerging from the adaptive model are more robust, but (iii) the two methods lead to different predictions in terms of emergent diversity. We demonstrate that explicitly evolutionary approaches to modelling marine microbial populations and functionality are feasible and practical in time-varying, space-resolving settings and provide a new tool for exploring evolutionary interactions on a range of timescales in the ocean. PMID:25852217

When everything is not everywhere but species evolve: an alternative method to model adaptive properties of marine ecosystems.

PubMed

Sauterey, Boris; Ward, Ben A; Follows, Michael J; Bowler, Chris; Claessen, David

2015-01-01

The functional and taxonomic biogeography of marine microbial systems reflects the current state of an evolving system. Current models of marine microbial systems and biogeochemical cycles do not reflect this fundamental organizing principle. Here, we investigate the evolutionary adaptive potential of marine microbial systems under environmental change and introduce explicit Darwinian adaptation into an ocean modelling framework, simulating evolving phytoplankton communities in space and time. To this end, we adopt tools from adaptive dynamics theory, evaluating the fitness of invading mutants over annual timescales, replacing the resident if a fitter mutant arises. Using the evolutionary framework, we examine how community assembly, specifically the emergence of phytoplankton cell size diversity, reflects the combined effects of bottom-up and top-down controls. When compared with a species-selection approach, based on the paradigm that "Everything is everywhere, but the environment selects", we show that (i) the selected optimal trait values are similar; (ii) the patterns emerging from the adaptive model are more robust, but (iii) the two methods lead to different predictions in terms of emergent diversity. We demonstrate that explicitly evolutionary approaches to modelling marine microbial populations and functionality are feasible and practical in time-varying, space-resolving settings and provide a new tool for exploring evolutionary interactions on a range of timescales in the ocean.

Numerical simulation of spatter formation during fiber laser welding of 5083 aluminum alloy at full penetration condition

NASA Astrophysics Data System (ADS)

Wu, Dongsheng; Hua, Xueming; Huang, Lijin; Zhao, Jiang

2018-03-01

The droplet escape condition in laser welding is established in this paper. A three-dimensional numerical model is developed to study the weld pool convection and spatter formation at full penetration during the fiber laser welding of 5083 aluminum alloy. It is found that when laser power is 9 kW, the bottom of the keyhole is dynamically opened and closed. When the bottom of the keyhole is closed, the molten metal at the bottom of the back keyhole wall flows upwards along the fusion line. When the bottom of the keyhole is opened, few spatters can be seen around the keyhole at the top surface, two flow patterns exists in the rear part of the keyhole: a portion of molten metal flows upwards along the fusion line, other portion of molten metal flows to the bottom of the keyhole, which promote the spatter formation at the bottom of the keyhole rear wall.

The effect of pits of different sizes on ultrasonic shear wave signals

NASA Astrophysics Data System (ADS)

Howard, Richard; Cegla, Frederic

2018-04-01

The use of 0-degree shear waves in NDE and SHM has become more commonplace as the disadvantage of coupling has been eliminated by permanent sensor installations or the use of non-contact transducers, such as EMATs. While the effect of rough surfaces and flat bottom holes on shear waves has been studied in depth, the effect of more complex geometries, such as pitting, has not. In this work, 3D finite element simulations are used to explore the reflection and scattering characteristics of shear bulk waves from pits. Specifically, three scenarios have been investigated, the effect on shear waves of: a sloped backwall; pitting directly under the transducer; and the effect of pits with variable pit position. High speed GPU finite element models enabled a wide range of pit radii and positions to be modeled. Hemispherical pits were used throughout. Key findings of the study are that the anisotropic effects that are clearly visible on sloped reflecting surfaces can also be measured on pits that are located not directly below the center of a shear wave transducer. These anisotropic effects are due to the nature of shear wave polarization. This can potentially be used for better defect characterization purposes.

Black Hills

Atmospheric Science Data Center

2014-05-15

... 2004. The color-coded maps (along the bottom) provide a quantitative measurement of the sunlight reflected from these surfaces, and the ... MD. The MISR data were obtained from the NASA Langley Research Center Atmospheric Science Data Center in Hampton, VA. Image ...

Process effects resulting from an increased BARC thickness

NASA Astrophysics Data System (ADS)

Eakin, Ronald J.; Detweiler, Shangting F.; Stagaman, Gregory J.; Tesauro, Mark R.; Spak, Mark A.; Dammel, Ralph R.

1997-07-01

Process improvements attributed to the use of bottom anti- reflective coatings (B.A.R.C.s) are well documented. As our experience with these materials improves, so does our understanding of additional optimization. Recent supplier experiments suggest an increase in the thickness of AZR BARLiTM (bottom anti-reflective layer i-line) solution to reduce photoresist swing curve ratios. Also, changes in thin film stack on common substrates can adversely affect the degree of photoresist reflective notching. It is therefore of extreme importance to determine optimum thickness(es) of a B.A.R.C. material to ensure maximum process potential. We document several process effects in the conversion of a SRAM test device (0.38 - 0.45 micrometers) from a 650 angstrom to a 2000 angstrom BARLiTM film thickness using conventional i-line photolithography. Critical dimension (CD) uniformity and depth of focus (DOF) are evaluated. Defect density between the two processes are compared before and after etch employing optical metrology and electrical test structures. Sensitivity of overlay as a function of BARLiTM film thickness is investigated as well.

A Bottom-Up Engineered Broadband Optical Nanoabsorber for Radiometry and Energy Harnessing Applications

NASA Technical Reports Server (NTRS)

Kaul, Anupama B.; Coles, James B.; Megerian, Krikor G.; Eastwood, Michael; Green, Robert O.; Bandaru, Prabhakar R.

2013-01-01

Optical absorbers based on vertically aligned multi-walled carbon nanotubes (MWCNTs), synthesized using electric-field assisted growth, are described here that show an ultra-low reflectance, 100X lower compared to Au-black from wavelength lamba approximately 350 nm - 2.5 micron. A bi-metallic Co/Ti layer was shown to catalyze a high site density of MWCNTs on metallic substrates and the optical properties of the absorbers were engineered by controlling the bottom-up synthesis conditions using dc plasma-enhanced chemical vapor deposition (PECVD). Reflectance measurements on the MWCNT absorbers after heating them in air to 400deg showed negligible changes in reflectance which was still low, approximately 0.022 % at lamba approximately 2 micron. In contrast, the percolated structure of the reference Au-black samples collapsed completely after heating, causing the optical response to degrade at temperatures as low as 200deg. The high optical absorption efficiency of the MWCNT absorbers, synthesized on metallic substrates, over a broad spectral range, coupled with their thermal ruggedness, suggests they have promise in solar energy harnessing applications, as well as thermal detectors for radiometry.

Tidal-flow, circulation, and flushing characteristics of Kings Bay, Citrus County, Florida

USGS Publications Warehouse

Hammett, K.M.; Goodwin, C.R.; Sanders, G.L.

1996-01-01

Kings Bay is an estuary on the gulf coast of peninsular Florida with a surface area of less than one square mile. It is a unique estuarine system with no significant inflowing rivers or streams. As much as 99 percent of the freshwater entering the bay originates from multiple spring vents at the bottom of the estuary. The circulation and flushing characteristics of Kings Bay were evaluated by applying SIMSYS2D, a two-dimensional numerical model. Field data were used to calibrate and verify the model. Lagrangian particle simulations were used to determine the circulation characteristics for three hydrologic conditions: low inflow, typical inflow, and low inflow with reduced friction from aquatic vegetation. Spring discharge transported the particles from Kings Bay through Crystal River and out of the model domain. Tidal effects added an oscillatory component to the particle paths. The mean particle residence time was 59 hours for low inflow with reduced friction; therefore, particle residence time is affected more by spring discharge than by bottom friction. Circulation patterns were virtually identical for the three simulated hydroloigc conditions. Simulated particles introduced in the southern part of Kings Bay traveled along the eastern side of Buzzard Island before entering Crystal River and existing the model domain. The flushing characteristics of Kings Bay for the three hydrodynamic conditions were determined by simulating the injection of conservative dye constituents. The average concentration of dye initially injected in Kings Bay decreased asymptotically because of spring discharge, and the tide caused some oscillation in the average dye concentration. Ninety-five percent of the injected dye exited Kings Bay and Crystal River with 94 hours for low inflow, 71 hours for typical inflow, and 94 hours for low inflow with reduced bottom friction. Simulation results indicate that all of the open waters of Kings Bay are flushed by the spring discharge. Reduced bottom friction has little effect on flushing.

Influence of additional heat exchanger block on directional solidification system for growing multi-crystalline silicon ingot - A simulation investigation

NASA Astrophysics Data System (ADS)

Nagarajan, S. G.; Srinivasan, M.; Aravinth, K.; Ramasamy, P.

2018-04-01

Transient simulation has been carried out for analyzing the heat transfer properties of Directional Solidification (DS) furnace. The simulation results revealed that the additional heat exchanger block under the bottom insulation on the DS furnace has enhanced the control of solidification of the silicon melt. Controlled Heat extraction rate during the solidification of silicon melt is requisite for growing good quality ingots which has been achieved by the additional heat exchanger block. As an additional heat exchanger block, the water circulating plate has been placed under the bottom insulation. The heat flux analysis of DS system and the temperature distribution studies of grown ingot confirm that the established additional heat exchanger block on the DS system gives additional benefit to the mc-Si ingot.

Wave-Current Conditions and Navigation Safety at an Inlet Entrance

DTIC Science & Technology

2015-06-26

effects of physical processes. Wave simulations with refraction, shoaling, and breaking provide estimates of wave-related parameters of interest to...summer and winter months and to better understand the cause- effect relationship between navigability conditions at Tillamook Inlet and characteristics of...the Coriolis force, wind stress, wave stress, bottom stress, vegetation flow drag, bottom friction, wave roller, and turbulent diffusion. Governing

The Role of Bottom-Up Processing in Perceptual Categorization by 3- to 4-Month-Old Infants: Simulations and Data

ERIC Educational Resources Information Center

French, Robert M.; Mareschal, Denis; Mermillod, Martial; Quinn, Paul C.

2004-01-01

Disentangling bottom-up and top-down processing in adult category learning is notoriously difficult. Studying category learning in infancy provides a simple way of exploring category learning while minimizing the contribution of top-down information. Three- to 4-month-old infants presented with cat or dog images will form a perceptual category…

Quenching behavior of molten pool with different strategies – A review

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

Shrikant,, E-mail: 2014rmt9018@mnit.ac.in; Pandel, U.; Duchaniya, R. K.

After the major severe accident in nuclear reactor, there has been lot of concerns regarding long term core melt stabilization following a severe accident in nuclear reactors. Numerous strategies have been though for quenching and stabilization of core melt like top flooding, bottom flooding, indirect cooling, etc. However, the effectiveness of these schemes is yet to be determined properly, for which, lot of experiments are needed. Several experiments have been performed for coolability of melt pool under bottom flooding as well as for indirect cooling. Besides these tests are very scattered because they involve different simulants material initial temperatures andmore » masses of melt, which makes it very complex to judge the effectiveness of a particular technique and advantage over the other. In this review paper, a study has been carried on different cooling techniques of simulant materials with same mass. Three techniques have been compared here and the results are discussed. Under top flooding technique it took several hours to cool the melt under without decay heat condition. In bottom flooding technique was found to be the best technique among in indirect cooling technique, top flooded technique, and bottom flooded technique.« less

Maritime NOx Emissions Over Chinese Seas Derived From Satellite Observations

NASA Astrophysics Data System (ADS)

Ding, J.; van der A, R. J.; Mijling, B.; Jalkanen, J.-P.; Johansson, L.; Levelt, P. F.

2018-02-01

By applying an inversion algorithm to NOx satellite observations from Ozone Monitoring Instrument, monthly NOx emissions for a 10 year period (2007 to 2016) over Chinese seas are presented for the first time. No effective regulations on NOx emissions have been implemented for ships in China, which is reflected in the trend analysis of maritime emissions. The maritime emissions display a continuous increase rate of about 20% per year until 2012 and slow down to 3% after that. The seasonal cycle of shipping emissions has regional variations, but all regions show lower emissions during winter. Simulations by an atmospheric chemistry transport model show a notable influence of maritime emissions on air pollution over coastal areas, especially in summer. The satellite-derived spatial distribution and the magnitude of maritime emissions over Chinese seas are in good agreement with bottom-up studies based on the Automatic Identification System of ships.

Infrared photocurrent management in monolithic perovskite/silicon heterojunction tandem solar cells by using a nanocrystalline silicon oxide interlayer.

PubMed

Mazzarella, Luana; Werth, Matteo; Jäger, Klaus; Jošt, Marko; Korte, Lars; Albrecht, Steve; Schlatmann, Rutger; Stannowski, Bernd

2018-05-14

We performed optical simulations using hydrogenated nanocrystalline silicon oxide (nc-SiO x :H) as n-doped interlayer in monolithic perovskite/c-Si heterojunction tandem solar cells. Depending on the adjustable value of its refractive index (2.0 - 2.7) and thickness, nc-SiO x :H allows to optically manage the infrared light absorption in the c-Si bottom cell minimizing reflection losses. We give guidelines for nc-SiO x :H optimization in tandem devices in combination with a systematic investigation of the effect of the surface morphology (flat or textured) on the photocurrent density. For full-flat and rear textured devices, we found matched photocurrents higher than 19 and 20 mA/cm 2 , respectively, using a 90 nm nc-SiO x :H interlayer with a refractive index of 2.7.

Observations of gas hydrates in marine sediments, offshore northern California

USGS Publications Warehouse

Brooks, J.M.; Field, M.E.; Kennicutt, M.C.

1991-01-01

Biogenic gas hydrates were recovered in shallow cores (< 6 m deep) from the Eel River basin in offshore northern California between 40??38??? and 40??56???N. The gas hydrates contained primarily methane (??13C = -57.6 to -69.1???) and occurred as dispersed crystals, small (2-20 mm) nodules, and layered bands within the sediment. These hydrates, recovered in sediment at water depths between 510 and 642 m, coincide nearly, but not exactly, with areas showing bottom-simulating reflectors (BSRs) on seismic-reflection records. This study confirms indirect geophysical and geologic observations that gas hydrates are present north of the Mendocino Fracture Zone in sediment of the Eel River basin but probably are absent to the south in the Point Arena basin. This discovery extends the confirmed sites of gas hydrates in the eastern Pacific region beyond the Peruvian and Central American margins to the northern California margin. ?? 1991.

Evaluation of NOx emissions from U.S. wildfires occurring during August-October 2006 using WRF-Chem model simulations and satellite observations

NASA Astrophysics Data System (ADS)

Kim, S.; Brioude, J.; Hilboll, A.; Richter, A.; Gleason, J. F.; Burrows, J. P.; Ryerson, T. B.; Peischl, J. W.; Holloway, J.; Lee, S.; Frost, G. J.; McKeen, S. A.; Trainer, M.

2009-12-01

During August-October 2006, there were many fire events in the U.S., including a month-long fire in Los Padres National Forest in California and numerous fires in the southeastern U.S. The OMI instrument onboard NASA's Aura satellite, the MODIS instrument on NASA's Terra satellite, and instruments on the NOAA GOES satellites clearly detected fire plumes during this period, opening the possibility of using trace gas and aerosol measurements from satellites to improve bottom-up emission estimates from wildfires. WRF-Chem model simulations of U.S. air quality without bottom-up fire emissions underestimated satellite-observed nitrogen dioxide columns substantially over fire-impacted regions during this time period. In this presentation, nitrogen dioxide columns simulated from the model including the wildfire emissions will be compared with the satellite retrievals and uncertainties in the bottom-up fire NOx emissions will be discussed. In addition, the sensitivities of satellite retrievals to aerosols resulting from these fires will be shown. The satellite NO2 columns will also be tested with aircraft observations made over the Texas region during September-October 2006 as part of the TexAQS/GoMACCS field campaign.

Bottom Backscatter from Trapped Bubbles

DTIC Science & Technology

1993-07-30

work included studies of a Blot model for acoustic transmission and reflection, originally developed by Stern, Bedford, and Millwater . 2 Also included...This model was originally developed by Stem, Bedford, and Millwater 7 and later modified to treat gassy sediments. This was done by varying the... Millwater , "Wave Reflection from a Sediment Layer with Depth-Dependent Properties,’ J. Acoust. Soc. Am. 77(5), 1781-1788 (1985). 3. L. M

Polarization radiation in the planetary atmosphere delimited by a heterogeneous diffusely reflecting surface

NASA Technical Reports Server (NTRS)

Strelkov, S. A.; Sushkevich, T. A.

1983-01-01

Spatial frequency characteristics (SFC) and the scattering functions were studied in the two cases of a uniform horizontal layer with absolutely black bottom, and an isolated layer. The mathematical model for these examples describes the horizontal heterogeneities in a light field with regard to radiation polarization in a three dimensional planar atmosphere, delimited by a heterogeneous surface with diffuse reflection. The perturbation method was used to obtain vector transfer equations which correspond to the linear and nonlinear systems of polarization radiation transfer. The boundary value tasks for the vector transfer equation that is a parametric set and one dimensional are satisfied by the SFC of the nonlinear system, and are expressed through the SFC of linear approximation. As a consequence of the developed theory, formulas were obtained for analytical calculation of albedo in solving the task of dissemination of polarization radiation in the planetary atmosphere with uniform Lambert bottom.

A container for heat treating materials in microwave ovens

DOEpatents

Holcombe, C.E.; Dykes, N.L.; Kimrey, H.D. Jr.; Mills, J.E.

1988-01-26

The efficiency of a microwave oven of a conventional two-source configuration and energy level is increased by providing the oven with a container for housing a refractory material to be treated. The container is formed to top and bottom walls transparent to microwaves while the sidewalls, in a circular configuration, are formed of a nonmetallic material opaque to microwave radiation for reflecting the radiation penetrating the top and bottom walls radially inwardly into the center of the container wherein a casket of heat-insulating material is provided for housing the material to be heat treated. The reflection of the microwave radiation from the sidewalls increases the concentration of the microwaves upon the material being heat treated while the concentration of the microwaves upon the material being heat treated while the casket retains the heat to permit the heating of the material to a substantially higher temperature than achievable in the oven without the container.

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.

Bottom RedOx Model (BROM v.1.1): a coupled benthic-pelagic model for simulation of water and sediment biogeochemistry

NASA Astrophysics Data System (ADS)

Yakushev, Evgeniy V.; Protsenko, Elizaveta A.; Bruggeman, Jorn; Wallhead, Philip; Pakhomova, Svetlana V.; Yakubov, Shamil Kh.; Bellerby, Richard G. J.; Couture, Raoul-Marie

2017-02-01

Interactions between seawater and benthic systems play an important role in global biogeochemical cycling. Benthic fluxes of some chemical elements (e.g., C, N, P, O, Si, Fe, Mn, S) alter the redox state and marine carbonate system (i.e., pH and carbonate saturation state), which in turn modulate the functioning of benthic and pelagic ecosystems. The redox state of the near-bottom layer in many regions can change with time, responding to the supply of organic matter, physical regime, and coastal discharge. We developed a model (BROM) to represent key biogeochemical processes in the water and sediments and to simulate changes occurring in the bottom boundary layer. BROM consists of a transport module (BROM-transport) and several biogeochemical modules that are fully compatible with the Framework for the Aquatic Biogeochemical Models, allowing independent coupling to hydrophysical models in 1-D, 2-D, or 3-D. We demonstrate that BROM is capable of simulating the seasonality in production and mineralization of organic matter as well as the mixing that leads to variations in redox conditions. BROM can be used for analyzing and interpreting data on sediment-water exchange, and for simulating the consequences of forcings such as climate change, external nutrient loading, ocean acidification, carbon storage leakage, and point-source metal pollution.

The Influence of a Sandy Substrate, Seagrass, or Highly Turbid Water on Albedo and Surface Heat Flux

NASA Astrophysics Data System (ADS)

Fogarty, M. C.; Fewings, M. R.; Paget, A. C.; Dierssen, H. M.

2018-01-01

Sea-surface albedo is a combination of surface-reflected and water-leaving irradiance, but water-leaving irradiance typically contributes less than 15% of the total albedo in open-ocean conditions. In coastal systems, however, the bottom substrate or suspended particulate matter can increase the amount of backscattered light, thereby increasing albedo and decreasing net shortwave surface heat flux. Here a sensitivity analysis using observations and models predicts the effect of light scattering on albedo and the net shortwave heat flux for three test cases: a bright sand bottom, a seagrass canopy, and turbid water. After scaling to the full solar shortwave spectrum, daytime average albedo for the test cases is up to 0.20 and exceeds the value of 0.05 predicted using a commonly applied parameterization. Daytime net shortwave heat flux into the water is significantly reduced, particularly for waters with bright sediments, dense horizontal seagrass canopies < 0.25 m from the sea surface, or highly turbid waters with suspended particulate matter concentration ≥ 50 g m-3. Observations of a more vertical seagrass canopy within 0.2 and 1 m of the surface indicate the increase in albedo compared to the common parameterization is negligible. Therefore, we suggest that the commonly applied albedo lookup table can be used in coastal heat flux estimates in water as shallow as 1 m unless the bottom substrate is highly reflective or the water is highly turbid. Our model results provide guidance to researchers who need to determine albedo in highly reflective or highly turbid conditions but have no direct observations.

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.

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.

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.

Quantum simulation from the bottom up: the case of rebits

NASA Astrophysics Data System (ADS)

Enshan Koh, Dax; Yuezhen Niu, Murphy; Yoder, Theodore J.

2018-05-01

Typically, quantum mechanics is thought of as a linear theory with unitary evolution governed by the Schrödinger equation. While this is technically true and useful for a physicist, with regards to computation it is an unfortunately narrow point of view. Just as a classical computer can simulate highly nonlinear functions of classical states, so too can the more general quantum computer simulate nonlinear evolutions of quantum states. We detail one particular simulation of nonlinearity on a quantum computer, showing how the entire class of -unitary evolutions (on n qubits) can be simulated using a unitary, real-amplitude quantum computer (consisting of n  +  1 qubits in total). These operators can be represented as the sum of a linear and antilinear operator, and add an intriguing new set of nonlinear quantum gates to the toolbox of the quantum algorithm designer. Furthermore, a subgroup of these nonlinear evolutions, called the -Cliffords, can be efficiently classically simulated, by making use of the fact that Clifford operators can simulate non-Clifford (in fact, non-linear) operators. This perspective of using the physical operators that we have to simulate non-physical ones that we do not is what we call bottom-up simulation, and we give some examples of its broader implications.

Investigating the use of Active Crop Canopy Sensors for Soybean Management in Field Research and Production

NASA Astrophysics Data System (ADS)

Miller, Joshua Jay

Approximately one-third of soybean yield gain is a result of improved agronomic practices, which includes disease and insect management. Treatments containing fungicide, insecticide, biological, and nutrient components were evaluated in Nebraska soybean fields during 2013 through 2015 to determine effects on soybean yield and profitability. The greatest yield (4.83 Mg ha -1, p=0.019) was achieved with a complete seed and pod set treatment, but resulted in the second lowest calculated net return (US151 ha -1, p=0.019) after accounting for fixed and variable costs at a soybean market price of US0.367 kg-1. The most profitable treatment was the fungicide seed treatment followed by no pod set treatment (US$241 ha-1, p=0.019). The use of pod set treatments in the absence of significant disease and insect pressure was not profitable in most instances. Crop canopy reflectance was measured several times throughout the season during 2014 and 2015 to evaluate normalized difference red edge (NDRE) index to predict soybean productivity. The NDRE values were used to calculate a cumulative reflectance value through the R6 growth stage, defined as area under the reflectance progress curve (AURPC). The AURPC values and seed yield were classified as top 25%, middle 50%, or bottom 25% by location. Multinomial regression determined that bottom AURPC values correctly predicted bottom yield 52.5% of the time (p=0.033), but ranged from 46.7 to 86.2% by location. Misclassifications by incorrectly identifying a bottom yield within the top AURPC ranged from 0.0% to 16.7% by location. The AURPC offers a novel method to delineate management zones in soybean production fields. Soybean canopy reflectance was also evaluated for the relationship between NDRE and soybean response to soybean cyst nematode (SCN; Heterodera glycines Ichinohe) infection. SCN-resistant and -susceptible varieties were planted in SCN-infested and non-infested sites during 2015 and 2016. Susceptible varieties yielded more than the resistant varieties at the non-infested sites by 245 kg ha-1 (p=0.004), and resistant varieties yielded more than the susceptible varieties at the SCN-infested sites by 340 kg ha -1 (p=0.0021). Measured NDRE values at R4 and R5 were different between resistant and susceptible varieties, but were not correlated with yield.

Evaluation of three-dimensional virtual perception of garments

NASA Astrophysics Data System (ADS)

Aydoğdu, G.; Yeşilpinar, S.; Erdem, D.

2017-10-01

In recent years, three-dimensional design, dressing and simulation programs came into prominence in the textile industry. By these programs, the need to produce clothing samples for every design in design process has been eliminated. Clothing fit, design, pattern, fabric and accessory details and fabric drape features can be evaluated easily. Also, body size of virtual mannequin can be adjusted so more realistic simulations can be created. Moreover, three-dimensional virtual garment images created by these programs can be used while presenting the product to end-user instead of two-dimensional photograph images. In this study, a survey was carried out to investigate the visual perception of consumers. The survey was conducted for three different garment types, separately. Questions about gender, profession etc. was asked to the participants and expected them to compare real samples and artworks or three-dimensional virtual images of garments. When survey results were analyzed statistically, it is seen that demographic situation of participants does not affect visual perception and three-dimensional virtual garment images reflect the real sample characteristics better than artworks for each garment type. Also, it is reported that there is no perception difference depending on garment type between t-shirt, sweatshirt and tracksuit bottom.

Acoustic Propagation Studies For Sperm Whale Phonation Analysis During LADC Experiments

NASA Astrophysics Data System (ADS)

Sidorovskaia, Natalia A.; Ioup, George E.; Ioup, Juliette W.; Caruthers, Jerald W.

2004-11-01

The Littoral Acoustic Demonstration Center (LADC) conducted a series of passive acoustic experiments in the Northern Gulf of Mexico and the Ligurian Sea in 2001 and 2002. Environmental and acoustic moorings were deployed in areas of large concentrations of marine mammals (mainly, sperm whales). Recordings and analysis of whale phonations are among the objectives of the project. Each mooring had a single autonomously recording hydrophone (Environmental Acoustic Recording System (EARS)) obtained from the U.S. Naval Oceanographic Office after modification to record signals up to 5,859 Hz in the Gulf of Mexico and up to 12,500 Hz in the Ligurian Sea. Self-recording environmental sensors, attached to the moorings, and concurrent environmental ship surveys provided the environmental data for the experiments. The results of acoustic simulations of long-range propagation of the broad-band (500-6,000 Hz) phonation pulses from a hypothetical whale location to the recording hydrophone in the experimental environments are presented. The utilization of the simulation results for an interpretation of the spectral features observed in whale clicks and for the development of tracking algorithms from single hydrophone recordings based on the identification of direct and surface and bottom reflected arrivals are discussed. [Research supported by ONR.

Design of dual-diameter nanoholes for efficient solar-light harvesting

PubMed Central

2014-01-01

A dual-diameter nanohole (DNH) photovoltaic system is proposed, where a top (bottom) layer with large (small) nanoholes is used to improve the absorption for the short-wavelength (long-wavelength) solar incidence, leading to a broadband light absorption enhancement. Through three-dimensional finite-element simulation, the core device parameters, including the lattice constant, nanohole diameters, and nanohole depths, are engineered in order to realize the best light-matter coupling between nanostructured silicon and solar spectrum. The designed bare DNH system exhibits an outstanding absorption capability with a photocurrent density (under perfect internal quantum process) predicted to be 27.93 mA/cm2, which is 17.39%, 26.17%, and over 100% higher than the best single-nanohole (SNH) system, SNH system with an identical Si volume, and equivalent planar configuration, respectively. Considering the fabrication feasibility, a modified DNH system with an anti-reflection coating and back silver reflector is examined by simulating both optical absorption and carrier transport in a coupled way in frequency and three-dimensional spatial domains, achieving a light-conversion efficiency of 13.72%. PACS 85.60.-q; Optoelectronic device; 84.60.Jt; Photovoltaic conversion PMID:25258605

Collection, processing, and interpretation of ground-penetrating radar data to determine sediment thickness at selected locations in Deep Creek Lake, Garrett County, Maryland, 2007

USGS Publications Warehouse

Banks, William S.L.; Johnson, Carole D.

2011-01-01

This investigation focused on selected regions of the study area, particularly in the coves where sediment accumulations were presumed to be thickest. GPR was the most useful tool for interpreting sediment thickness, especially in these shallow coves. The radar profiles were interpreted for two surfaces of interest-the water bottom, which was defined as the "2007 horizon," and the interface between Lake sediments and the original Lake bottom, which was defined as the "1925 horizon"-corresponding to the year the Lake was impounded. The ground-penetrating radar data were interpreted on the basis of characteristics of the reflectors. The sediments that had accumulated in the impounded Lake were characterized by laminated, parallel reflections, whereas the subsurface below the original Lake bottom was characterized by more discontinuous and chaotic reflections, often with diffractions indicating cobbles or boulders. The reflectors were picked manually along the water bottom and along the interface between the Lake sediments and the pre-Lake sediments. A simple graphic approach was used to convert traveltimes to depth through water and depth through saturated sediments using velocities of the soundwaves through the water and the saturated sediments. Nineteen cross sections were processed and interpreted in 9 coves around Deep Creek Lake, and the difference between the 2007 horizon and the 1925 horizon was examined. In most areas, GPR data indicate a layer of sediment between 1 and 7 feet thick. When multiple cross sections from a single cove were compared, the cross sections indicated that sediment thickness decreased toward the center of the Lake.

Patchiness of phytoplankton and primary production in Liaodong Bay, China.

PubMed

Pei, Shaofeng; Laws, Edward A; Zhang, Haibo; Ye, Siyuan; Yuan, Hongming; Liu, Haiyue

2017-01-01

A comprehensive study of water quality, phytoplankton biomass, and photosynthetic rates in Liaodong Bay, China, during June and July of 2013 revealed two large patches of high biomass and production with dimensions on the order of 10 km. Nutrient concentrations were above growth-rate-saturating concentrations throughout the bay, with the possible exception of phosphate at some stations. The presence of the patches therefore appeared to reflect the distribution of water temperature and variation of light penetration restricted by water turbidity. There was no patch of high phytoplankton biomass or production in a third, linear patch of water with characteristics suitable for rapid phytoplankton growth; the absence of a bloom in that patch likely reflected the fact that the width of the patch was less than the critical size required to overcome losses of phytoplankton to turbulent diffusion. The bottom waters of virtually all of the eastern half of the bay were below the depth of the mixed layer, and the lowest bottom water oxygen concentrations, 3-5 mg L-1, were found in that part of the bay. The water column in much of the remainder of the bay was within the mixed layer, and oxygen concentrations in both surface and bottom waters exceeded 5 mg L-1.

Patchiness of phytoplankton and primary production in Liaodong Bay, China

PubMed Central

Laws, Edward A.; Zhang, Haibo; Ye, Siyuan; Yuan, Hongming; Liu, Haiyue

2017-01-01

A comprehensive study of water quality, phytoplankton biomass, and photosynthetic rates in Liaodong Bay, China, during June and July of 2013 revealed two large patches of high biomass and production with dimensions on the order of 10 km. Nutrient concentrations were above growth-rate-saturating concentrations throughout the bay, with the possible exception of phosphate at some stations. The presence of the patches therefore appeared to reflect the distribution of water temperature and variation of light penetration restricted by water turbidity. There was no patch of high phytoplankton biomass or production in a third, linear patch of water with characteristics suitable for rapid phytoplankton growth; the absence of a bloom in that patch likely reflected the fact that the width of the patch was less than the critical size required to overcome losses of phytoplankton to turbulent diffusion. The bottom waters of virtually all of the eastern half of the bay were below the depth of the mixed layer, and the lowest bottom water oxygen concentrations, 3–5 mg L–1, were found in that part of the bay. The water column in much of the remainder of the bay was within the mixed layer, and oxygen concentrations in both surface and bottom waters exceeded 5 mg L–1. PMID:28235070

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.

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.

Estimates of Crustal Transmission Losses Using MLM Array Processing.

DTIC Science & Technology

1982-07-01

boundary with a half space below, and with some form of reflection characteristic and/or loss mechanism. If acoustic energy , upon encountering the bottom...sea-sediment interface would probably be sufficient. However, sound energy does penetrate beneath the sea -2- floor and is both reflected and refracted...back to the water. In an active acoustical experiment, especially at longer ranges, a significant amount of tne received energy may come from waves

Climate-induced warming of lakes can be either amplified or suppressed by trends in water clarity

USGS Publications Warehouse

Rose, Kevin C.; Winslow, Luke A.; Read, Jordan S.; Hansen, Gretchen J. A.

2016-01-01

Climate change is rapidly warming aquatic ecosystems including lakes and reservoirs. However, variability in lake characteristics can modulate how lakes respond to climate. Water clarity is especially important both because it influences the depth range over which heat is absorbed, and because it is changing in many lakes. Here, we show that simulated long-term water clarity trends influence how both surface and bottom water temperatures of lakes and reservoirs respond to climate change. Clarity changes can either amplify or suppress climate-induced warming, depending on lake depth and the direction of clarity change. Using a process-based model to simulate 1894 north temperate lakes from 1979 to 2012, we show that a scenario of decreasing clarity at a conservative yet widely observed rate of 0.92% yr−1 warmed surface waters and cooled bottom waters at rates comparable in magnitude to climate-induced warming. For lakes deeper than 6.5 m, decreasing clarity was sufficient to fully offset the effects of climate-induced warming on median whole-lake mean temperatures. Conversely, a scenario increasing clarity at the same rate cooled surface waters and warmed bottom waters relative to baseline warming rates. Furthermore, in 43% of lakes, increasing clarity more than doubled baseline bottom temperature warming rates. Long-term empirical observations of water temperature in lakes with and without clarity trends support these simulation results. Together, these results demonstrate that water clarity trends may be as important as rising air temperatures in determining how waterbodies respond to climate change.

Transportable and vibration-free full-field low-coherent quantitative phase microscope

NASA Astrophysics Data System (ADS)

Yamauchi, Toyohiko; Yamada, Hidenao; Goto, Kentaro; Matsui, Hisayuki; Yasuhiko, Osamu; Ueda, Yukio

2018-02-01

We developed a transportable Linnik-type full-field low-coherent quantitative phase microscope that is able to compensate for optical path length (OPL) disturbance due to environmental mechanical noises. Though two-beam interferometers such as Linnik ones suffer from unstable OPL difference, we overcame this problem with a mechanical feedback system based on digital signal-processing that controls the OPL difference in sub-nanometer resolution precisely with a feedback bandwidth of 4 kHz. The developed setup has a footprint of 200 mm by 200 mm, a height of 500 mm, and a weight of 4.5 kilograms. In the transmission imaging mode, cells were cultured on a reflection-enhanced glass-bottom dish, and we obtained interference images sequentially while performing stepwise quarter-wavelength phase-shifting. Real-time image processing, including retrieval of the unwrapped phase from interference images and its background correction, along with the acquisition of interference images, was performed on a laptop computer. Emulation of the phase contrast (PhC) images and the differential interference contrast (DIC) images was also performed in real time. Moreover, our setup was applied for full-field cell membrane imaging in the reflection mode, where the cells were cultured on an anti-reflection (AR)-coated glass-bottom dish. The phase and intensity of the light reflected by the membrane revealed the outer shape of the cells independent of the refractive index. In this paper, we show imaging results on cultured cells in both transmission and reflection modes.

Simulation of forced convection in a channel with nanofluid by the lattice Boltzmann method

PubMed Central

2013-01-01

This paper presents a numerical study of the thermal performance of fins mounted on the bottom wall of a horizontal channel and cooled with either pure water or an Al2O3-water nanofluid. The bottom wall of the channel is heated at a constant temperature and cooled by mixed convection of laminar flow at a relatively low temperature. The results of the numerical simulation indicate that the heat transfer rate of fins is significantly affected by the Reynolds number (Re) and the thermal conductivity of the fins. The influence of the solid volume fraction on the increase of heat transfer is more noticeable at higher values of the Re. PMID:23594696

Building Intercultural Competency in the Language Immersion Montessori Classroom

ERIC Educational Resources Information Center

Carver-Akers, Kateri

2013-01-01

In her article entitled, "Theoretical Reflections: Intercultural Framework / Model" Darla Deardorff provides the Pyramid Model of Cultural Competency. At the bottom of the pyramid she places three "Requisite Attitudes," which support the remaining three blocks above ("Knowledge & Comprehension/Skills,"…

Gas hydrate exploration of Porangahau Ridge, East Coast, North Island, New Zealand

NASA Astrophysics Data System (ADS)

Pecher, I. A.; Henrys, S. A.; Crutchley, G.; Toulmin, S.; Gorman, A. R.; Wood, W. T.; Kukowski, N.; Greinert, J.; Faure, K.; Coffin, R. B.

2007-12-01

During June and July 2006 the R/V Tangaroa collected high-resolution seismic profiles, EM 300 swath bathymetry, 3.5 sub-bottom, as well as water column echosounder data across Porangahau Ridge east of the North Island. Piston cores were recovered for pore water chemistry, microbiology, and paleoceanographic analyses. We also acquired heatflow data, CTDs, and seawater samples for water-column chemistry. The seismic data show amplitude anomalies beneath the ridge. The anomalies develop along a prominent N-S fault-propagation anticline. We analyzed reflection coefficients and conclude that the anomalies are most likely caused by free gas within the regional gas hydrate stability field as defined by the depth of bottom simulating reflections. We suggest that local warming associated with fluid expulsion through faults keeps the temperature at the anomalies outside of the gas hydrate stability field. Based on the seismic amplitudes, we predict at least ~7% of the pore space to be saturated with gas if gas is evenly distributed. Gas saturation is predicted to be almost 70% for "patchy'' gas distribution. For the pressure-temperature conditions beneath the ridge, gas at a saturation of 7% would form gas hydrate at a saturation of ~10% of pore space. Should the localized heat flow anomaly weaken, e.g., because of sealing of the faults, the ridge could become an area with significant hydrate deposits. We speculate that the Porangahau Ridge constitutes a gas hydrate "sweet spot" in the process of formation. Pore water chemistry shows a shoaling of the base of the sulfate reduction zone across this feature, indicative of elevated methane flux through the hydrate stability field. There is a distinct thermal anomaly across the Porangahau Ridge, albeit with a complex signature. On the other hand, there are no indications of methane expulsion into the water column, neither in the echosounder records nor in the water chemistry profiles from CTDs.

Nannofossils in upper quaternary bottom sediments of back-arc basins in the southwestern Pacific

NASA Astrophysics Data System (ADS)

Dmitrenko, O. B.

2015-05-01

The analysis of calcareous nannoplankton assemblages in bottom sediments sampled during Cruise 21 of the R/V Akademik Mstislav Keldysh in three areas located in back-arc basins of the southwestern Pacific (western Woodlark in the Solomon Sea, Manus in the Bismarck Sea, Central Lau) reveal that they belong to the Emiliania huxleyi Acme Zone, the most detailed one in the Gartner's scale of 1977. The content of coccoliths and their taxonomic composition indicate warm subtropical-tropical conditions. Long cores demonstrate a decrease in species diversity reflecting the transition from the cold late Pleistocene to the Holocene. The changes in species diversity and presence/absence of thermophilic representatives indicate transformation of depositional environments with unstable conditions in the water column and bottom layer, seismic activity, and widely developed processes of sediment redistribution and reworking.

Numerical Simulation of the Vortex-Induced Vibration of A Curved Flexible Riser in Shear Flow

NASA Astrophysics Data System (ADS)

Zhu, Hong-jun; Lin, Peng-zhi

2018-06-01

A series of fully three-dimensional (3D) numerical simulations of flow past a free-to-oscillate curved flexible riser in shear flow were conducted at Reynolds number of 185-1015. The numerical results obtained by the two-way fluid-structure interaction (FSI) simulations are in good agreement with the experimental results reported in the earlier study. It is further found that the frequency transition is out of phase not only in the inline (IL) and crossflow (CF) directions but also along the span direction. The mode competition leads to the non-zero nodes of the rootmean- square (RMS) amplitude and the relatively chaotic trajectories. The fluid-structure interaction is to some extent reflected by the transverse velocity of the ambient fluid, which reaches the maximum value when the riser reaches the equilibrium position. Moreover, the local maximum transverse velocities occur at the peak CF amplitudes, and the values are relatively large when the vibration is in the resonance regions. The 3D vortex columns are shed nearly parallel to the axis of the curved flexible riser. As the local Reynolds number increases from 0 at the bottom of the riser to the maximum value at the top, the wake undergoes a transition from a two-dimensional structure to a 3D one. More irregular small-scale vortices appeared at the wake region of the riser, undergoing large amplitude responses.

Parameters on reconstructions of geohistory, thermal history, and hydrocarbon generation history in a sedimentary basin

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

Cao, S.; Lerche, I.

1988-01-01

Geological processes related to petroleum generation, migration, and accumulation are very complicated in terms of time and variables involved, and are very difficult to simulate by laboratory experiments. For this reason, many mathematic/computer models have been developed to simulate these geological processes based on geological, geophysical, and geochemical principles. Unfortunately, none of these models can exactly simulate these processes because of the assumptions and simplifications made in these models and the errors in the input for the models. The sensitivity analysis is a comprehensive examination on how geological, geophysical, and geochemical parameters affect the reconstructions of geohistory, thermal history, andmore » hydrocarbon generation history. In this study, a one-dimensional fluid flow/compaction model has been used to run the sensitivity analysis. The authors will show the effects of some commonly used parameters such as depth, age, lithology, porosity, permeability, unconformity (time and eroded thickness), temperature at sediment surface, bottom hole temperature, present day heat flow, thermal gradient, thermal conductivity and kerogen type, and content on the evolutions of formation thickness, porosity, permeability, pressure with time and depth, heat flow with time, temperature with time and depth, vitrinite reflectance (R/sub 0/) and TTI with time and depth, oil window in terms of time and depth, and amount of hydrocarbon generated with time and depth.« less

Efficient Optical Logic, Interconnections and Processing Using Quantum Confined Structures

DTIC Science & Technology

1991-05-01

No bis I With bias Ra ( b ’ OotI o lNo bias Use Il) felectro-refraicc n to phase-s’:t A- X I 3 Wavelength 3 Figure II-1. Efficient modulation in a...operation. The top (bottom) mirror of an AFP structure has an amplitude reflection coefficient of rt( b ) and power reflectivity of RT( B )=Ir0)12, viewed...and ( b ) for the case of a=O and a=ln(rb/rt), respectively. Adding (1) and (2), we obtain the total amplitude reflection rto as: -13- I Ii/V aoabl

Geoacoustic models of Coastal Bottom Strata at Jeongdongjin in the Korean continental margin of the East Sea

NASA Astrophysics Data System (ADS)

Ryang, Woo Hun; Han, Jooyoung

2017-04-01

Geoacoustic models provide submarine environmental data to predict sound transmission through submarine bottom layers of sedimentary strata and acoustic basement. This study reconstructed four geoacoustic models for sediments of 50 m thick at the Jeongdongjin area in the western continental margin of the East Sea. Bottom models were based on about 1100 line-km data of the high-resolution air-gun seismic and subbottom profiles (SBP) with sediment cores. The 4 piston cores were analyzed for reconstruction of the bottom and geoacoustic models in the study area, together with 2 long cores in the adjacent area. P-wave speed in the core sediment was measured by the pulse transmission technique, and the resonance frequency of piezoelectric transducers was maintained at 1 MHz. Measurements of 42 P-wave speeds and 41 attenuations were fulfilled in three core sediments. For actual modeling, the P-wave speeds of the models were compensated to in situ depth below the sea floor using the Hamilton method. These geoacoustic models of coastal bottom strata will be used for geoacoustic and underwater acoustic experiments reflecting vertical and lateral variability of geoacoustic properties in the Jeongdongjin area of the East Sea. Keywords: geoacosutic model, bottom model, P-wave speed, Jeongdongjin, East Sea Acknowledgements: This research was supported by the research grants from the Agency of Defense Development (UD140003DD and UE140033DD).

Evaluation of multi-resolution satellite sensors for assessing water quality and bottom depth of Lake Garda.

PubMed

Giardino, Claudia; Bresciani, Mariano; Cazzaniga, Ilaria; Schenk, Karin; Rieger, Patrizia; Braga, Federica; Matta, Erica; Brando, Vittorio E

2014-12-15

In this study we evaluate the capabilities of three satellite sensors for assessing water composition and bottom depth in Lake Garda, Italy. A consistent physics-based processing chain was applied to Moderate Resolution Imaging Spectroradiometer (MODIS), Landsat-8 Operational Land Imager (OLI) and RapidEye. Images gathered on 10 June 2014 were corrected for the atmospheric effects with the 6SV code. The computed remote sensing reflectance (Rrs) from MODIS and OLI were converted into water quality parameters by adopting a spectral inversion procedure based on a bio-optical model calibrated with optical properties of the lake. The same spectral inversion procedure was applied to RapidEye and to OLI data to map bottom depth. In situ measurements of Rrs and of concentrations of water quality parameters collected in five locations were used to evaluate the models. The bottom depth maps from OLI and RapidEye showed similar gradients up to 7 m (r = 0.72). The results indicate that: (1) the spatial and radiometric resolutions of OLI enabled mapping water constituents and bottom properties; (2) MODIS was appropriate for assessing water quality in the pelagic areas at a coarser spatial resolution; and (3) RapidEye had the capability to retrieve bottom depth at high spatial resolution. Future work should evaluate the performance of the three sensors in different bio-optical conditions.

ERPs Differentially Reflect Automatic and Deliberate Processing of the Functional Manipulability of Objects

PubMed Central

Madan, Christopher R.; Chen, Yvonne Y.; Singhal, Anthony

2016-01-01

It is known that the functional properties of an object can interact with perceptual, cognitive, and motor processes. Previously we have found that a between-subjects manipulation of judgment instructions resulted in different manipulability-related memory biases in an incidental memory test. To better understand this effect we recorded electroencephalography (EEG) while participants made judgments about images of objects that were either high or low in functional manipulability (e.g., hammer vs. ladder). Using a between-subjects design, participants judged whether they had seen the object recently (Personal Experience), or could manipulate the object using their hand (Functionality). We focused on the P300 and slow-wave event-related potentials (ERPs) as reflections of attentional allocation. In both groups, we observed higher P300 and slow wave amplitudes for high-manipulability objects at electrodes Pz and C3. As P300 is thought to reflect bottom-up attentional processes, this may suggest that the processing of high-manipulability objects recruited more attentional resources. Additionally, the P300 effect was greater in the Functionality group. A more complex pattern was observed at electrode C3 during slow wave: processing the high-manipulability objects in the Functionality instruction evoked a more positive slow wave than in the other three conditions, likely related to motor simulation processes. These data provide neural evidence that effects of manipulability on stimulus processing are further mediated by automatic vs. deliberate motor-related processing. PMID:27536224

MODFLOW-NWT – Robust handling of dry cells using a Newton Formulation of MODFLOW-2005

USGS Publications Warehouse

Hunt, Randal J.; Feinstein, Daniel T.

2012-01-01

The first versions of the widely used groundwater flow model MODFLOW (McDonald and Harbaugh 1988) had a sure but inflexible way of handling unconfined finite-difference aquifer cells where the water table dropped below the bottom of the cell—these "dry cells" were turned inactive for the remainder of the simulation. Problems with this formulation were easily seen, including the potential for inadvertent loss of simulated recharge in the model (Doherty 2001; Painter et al. 2008), and rippling of dry cells through the solution that unacceptably changed the groundwater flow system (Juckem et al. 2006). Moreover, solving problems of the natural world often required the ability to reactivate dry cells when the water table rose above the cell bottom. This seemingly simple desire resulted in a two-decade attempt to include the simulation flexibility while avoiding numerical instability.

Bivalve grazing can shape phytoplankton communities

USGS Publications Warehouse

Lucas, Lisa; Cloern, James E.; Thompson, Janet K.; Stacey, Mark T.; Koseff, Jeffrey K.

2016-01-01

The ability of bivalve filter feeders to limit phytoplankton biomass in shallow waters is well-documented, but the role of bivalves in shaping phytoplankton communities is not. The coupled effect of bivalve grazing at the sediment-water interface and sinking of phytoplankton cells to that bottom filtration zone could influence the relative biomass of sinking (diatoms) and non-sinking phytoplankton. Simulations with a pseudo-2D numerical model showed that benthic filter feeding can interact with sinking to alter diatom:non-diatom ratios. Cases with the smallest proportion of diatom biomass were those with the fastest sinking speeds and strongest bivalve grazing rates. Hydrodynamics modulated the coupled sinking-grazing influence on phytoplankton communities. For example, in simulations with persistent stratification, the non-sinking forms accumulated in the surface layer away from bottom grazers while the sinking forms dropped out of the surface layer toward bottom grazers. Tidal-scale stratification also influenced vertical gradients of the two groups in opposite ways. The model was applied to Suisun Bay, a low-salinity habitat of the San Francisco Bay system that was transformed by the introduction of the exotic clam Potamocorbula amurensis. Simulation results for this Bay were similar to (but more muted than) those for generic habitats, indicating that P. amurensis grazing could have caused a disproportionate loss of diatoms after its introduction. Our model simulations suggest bivalve grazing affects both phytoplankton biomass and community composition in shallow waters. We view these results as hypotheses to be tested with experiments and more complex modeling approaches.

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.

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

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.

[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

SWIM: A Semi-Analytical Ocean Color Inversion Algorithm for Optically Shallow Waters

NASA Technical Reports Server (NTRS)

McKinna, Lachlan I. W.; Werdell, P. Jeremy; Fearns, Peter R. C. S.; Weeks, Scarla J.; Reichstetter, Martina; Franz, Bryan A.; Shea, Donald M.; Feldman, Gene C.

2014-01-01

Ocean color remote sensing provides synoptic-scale, near-daily observations of marine inherent optical properties (IOPs). Whilst contemporary ocean color algorithms are known to perform well in deep oceanic waters, they have difficulty operating in optically clear, shallow marine environments where light reflected from the seafloor contributes to the water-leaving radiance. The effect of benthic reflectance in optically shallow waters is known to adversely affect algorithms developed for optically deep waters [1, 2]. Whilst adapted versions of optically deep ocean color algorithms have been applied to optically shallow regions with reasonable success [3], there is presently no approach that directly corrects for bottom reflectance using existing knowledge of bathymetry and benthic albedo.To address the issue of optically shallow waters, we have developed a semi-analytical ocean color inversion algorithm: the Shallow Water Inversion Model (SWIM). SWIM uses existing bathymetry and a derived benthic albedo map to correct for bottom reflectance using the semi-analytical model of Lee et al [4]. The algorithm was incorporated into the NASA Ocean Biology Processing Groups L2GEN program and tested in optically shallow waters of the Great Barrier Reef, Australia. In-lieu of readily available in situ matchup data, we present a comparison between SWIM and two contemporary ocean color algorithms, the Generalized Inherent Optical Property Algorithm (GIOP) and the Quasi-Analytical Algorithm (QAA).

Analysis of Academic and Non-Academic Outcomes from a Bottom-up Comprehensive School Reform in the Absence of Student Level Data through Simulation Methods: A Mixed Methods Case Study

ERIC Educational Resources Information Center

Sondergeld, Toni A.

2009-01-01

This dissertation examines the efficacy of a bottom-up comprehensive school reform (CSR) program by evaluating its impact on student achievement, attendance, and behavior outcomes through an explanatory mixed methods design. The CSR program (Gear Up) was implemented in an urban junior high school over the course of seven years allowing for…

Theory of tailorable optical response of two-dimensional arrays of plasmonic nanoparticles at dielectric interfaces.

PubMed

Sikdar, Debabrata; Kornyshev, Alexei A

2016-09-22

Two-dimensional arrays of plasmonic nanoparticles at interfaces are promising candidates for novel optical metamaterials. Such systems materialise from 'top-down' patterning or 'bottom-up' self-assembly of nanoparticles at liquid/liquid or liquid/solid interfaces. Here, we present a comprehensive analysis of an extended effective quasi-static four-layer-stack model for the description of plasmon-resonance-enhanced optical responses of such systems. We investigate in detail the effects of the size of nanoparticles, average interparticle separation, dielectric constants of the media constituting the interface, and the nanoparticle position relative to the interface. Interesting interplays of these different factors are explored first for normally incident light. For off-normal incidence, the strong effects of the polarisation of light are found at large incident angles, which allows to dynamically tune the reflectance spectra. All the predictions of the theory are tested against full-wave simulations, proving this simplistic model to be adequate within the quasi-static limit. The model takes seconds to calculate the system's optical response and makes it easy to unravel the effect of each system parameter. This helps rapid rationalization of experimental data and understanding of the optical signals from these novel 'metamaterials', optimised for light reflection or harvesting.

Validation of Individual-Based Markov-Like Stochastic Process Model of Insect Behavior and a “Virtual Farm” Concept for Enhancement of Site-Specific IPM

PubMed Central

Lux, Slawomir A.; Wnuk, Andrzej; Vogt, Heidrun; Belien, Tim; Spornberger, Andreas; Studnicki, Marcin

2016-01-01

The paper reports application of a Markov-like stochastic process agent-based model and a “virtual farm” concept for enhancement of site-specific Integrated Pest Management. Conceptually, the model represents a “bottom-up ethological” approach and emulates behavior of the “primary IPM actors”—large cohorts of individual insects—within seasonally changing mosaics of spatiotemporally complex faming landscape, under the challenge of the local IPM actions. Algorithms of the proprietary PESTonFARM model were adjusted to reflect behavior and ecology of R. cerasi. Model parametrization was based on compiled published information about R. cerasi and the results of auxiliary on-farm experiments. The experiments were conducted on sweet cherry farms located in Austria, Germany, and Belgium. For each farm, a customized model-module was prepared, reflecting its spatiotemporal features. Historical data about pest monitoring, IPM treatments and fruit infestation were used to specify the model assumptions and calibrate it further. Finally, for each of the farms, virtual IPM experiments were simulated and the model-generated results were compared with the results of the real experiments conducted on the same farms. Implications of the findings for broader applicability of the model and the “virtual farm” approach—were discussed. PMID:27602000

Validation of Individual-Based Markov-Like Stochastic Process Model of Insect Behavior and a "Virtual Farm" Concept for Enhancement of Site-Specific IPM.

PubMed

Lux, Slawomir A; Wnuk, Andrzej; Vogt, Heidrun; Belien, Tim; Spornberger, Andreas; Studnicki, Marcin

2016-01-01

The paper reports application of a Markov-like stochastic process agent-based model and a "virtual farm" concept for enhancement of site-specific Integrated Pest Management. Conceptually, the model represents a "bottom-up ethological" approach and emulates behavior of the "primary IPM actors"-large cohorts of individual insects-within seasonally changing mosaics of spatiotemporally complex faming landscape, under the challenge of the local IPM actions. Algorithms of the proprietary PESTonFARM model were adjusted to reflect behavior and ecology of R. cerasi. Model parametrization was based on compiled published information about R. cerasi and the results of auxiliary on-farm experiments. The experiments were conducted on sweet cherry farms located in Austria, Germany, and Belgium. For each farm, a customized model-module was prepared, reflecting its spatiotemporal features. Historical data about pest monitoring, IPM treatments and fruit infestation were used to specify the model assumptions and calibrate it further. Finally, for each of the farms, virtual IPM experiments were simulated and the model-generated results were compared with the results of the real experiments conducted on the same farms. Implications of the findings for broader applicability of the model and the "virtual farm" approach-were discussed.

Tsunami simulation method initiated from waveforms observed by ocean bottom pressure sensors for real-time tsunami forecast; Applied for 2011 Tohoku Tsunami

NASA Astrophysics Data System (ADS)

Tanioka, Yuichiro

2017-04-01

After tsunami disaster due to the 2011 Tohoku-oki great earthquake, improvement of the tsunami forecast has been an urgent issue in Japan. National Institute of Disaster Prevention is installing a cable network system of earthquake and tsunami observation (S-NET) at the ocean bottom along the Japan and Kurile trench. This cable system includes 125 pressure sensors (tsunami meters) which are separated by 30 km. Along the Nankai trough, JAMSTEC already installed and operated the cable network system of seismometers and pressure sensors (DONET and DONET2). Those systems are the most dense observation network systems on top of source areas of great underthrust earthquakes in the world. Real-time tsunami forecast has depended on estimation of earthquake parameters, such as epicenter, depth, and magnitude of earthquakes. Recently, tsunami forecast method has been developed using the estimation of tsunami source from tsunami waveforms observed at the ocean bottom pressure sensors. However, when we have many pressure sensors separated by 30km on top of the source area, we do not need to estimate the tsunami source or earthquake source to compute tsunami. Instead, we can initiate a tsunami simulation from those dense tsunami observed data. Observed tsunami height differences with a time interval at the ocean bottom pressure sensors separated by 30 km were used to estimate tsunami height distribution at a particular time. In our new method, tsunami numerical simulation was initiated from those estimated tsunami height distribution. In this paper, the above method is improved and applied for the tsunami generated by the 2011 Tohoku-oki great earthquake. Tsunami source model of the 2011 Tohoku-oki great earthquake estimated using observed tsunami waveforms, coseimic deformation observed by GPS and ocean bottom sensors by Gusman et al. (2012) is used in this study. The ocean surface deformation is computed from the source model and used as an initial condition of tsunami simulation. By assuming that this computed tsunami is a real tsunami and observed at ocean bottom sensors, new tsunami simulation is carried out using the above method. The station distribution (each station is separated by 15 min., about 30 km) observed tsunami waveforms which were actually computed from the source model. Tsunami height distributions are estimated from the above method at 40, 80, and 120 seconds after the origin time of the earthquake. The Near-field Tsunami Inundation forecast method (Gusman et al. 2014) was used to estimate the tsunami inundation along the Sanriku coast. The result shows that the observed tsunami inundation was well explained by those estimated inundation. This also shows that it takes about 10 minutes to estimate the tsunami inundation from the origin time of the earthquake. This new method developed in this paper is very effective for a real-time tsunami forecast.

Oligocene to Holocene sediment drifts and bottom currents on the slope of Gabon continental margin (west Africa). Consequences for sedimentation and southeast Atlantic upwelling

NASA Astrophysics Data System (ADS)

Séranne, Michel; Nzé Abeigne, César-Rostand

1999-10-01

Seismic reflection profiles on the slope of the south Gabon continental margin display furrows 2 km wide and some 200 m deep, that develop normal to the margin in 500-1500 m water depth. Furrows are characterised by an aggradation/progradation pattern which leads to margin-parallel, northwestward migration of their axes through time. These structures, previously interpreted as turbidity current channels, display the distinctive seismic image and internal organisation of sediment drifts, constructed by the activity of bottom currents. Sediment drifts were initiated above a major Oligocene unconformity, and they developed within a Oligocene to Present megasequence of general progradation of the margin, whilst they are markedly absent from the underlying Late Cretaceous-Eocene aggradation megasequence. The presence of upslope migrating sediment waves, and the northwest migration of the sediment drifts indicate deposition by bottom current flowing upslope, under the influence of the Coriolis force. Such landwards-directed bottom currents on the slope probably represent coastal upwelling, which has been active along the west Africa margin throughout the Neogene.

Salient region detection by fusing bottom-up and top-down features extracted from a single image.

PubMed

Tian, Huawei; Fang, Yuming; Zhao, Yao; Lin, Weisi; Ni, Rongrong; Zhu, Zhenfeng

2014-10-01

Recently, some global contrast-based salient region detection models have been proposed based on only the low-level feature of color. It is necessary to consider both color and orientation features to overcome their limitations, and thus improve the performance of salient region detection for images with low-contrast in color and high-contrast in orientation. In addition, the existing fusion methods for different feature maps, like the simple averaging method and the selective method, are not effective sufficiently. To overcome these limitations of existing salient region detection models, we propose a novel salient region model based on the bottom-up and top-down mechanisms: the color contrast and orientation contrast are adopted to calculate the bottom-up feature maps, while the top-down cue of depth-from-focus from the same single image is used to guide the generation of final salient regions, since depth-from-focus reflects the photographer's preference and knowledge of the task. A more general and effective fusion method is designed to combine the bottom-up feature maps. According to the degree-of-scattering and eccentricities of feature maps, the proposed fusion method can assign adaptive weights to different feature maps to reflect the confidence level of each feature map. The depth-from-focus of the image as a significant top-down feature for visual attention in the image is used to guide the salient regions during the fusion process; with its aid, the proposed fusion method can filter out the background and highlight salient regions for the image. Experimental results show that the proposed model outperforms the state-of-the-art models on three public available data sets.

Stress testing hydrologic models using bottom-up climate change assessment

NASA Astrophysics Data System (ADS)

Stephens, C.; Johnson, F.; Marshall, L. A.

2017-12-01

Bottom-up climate change assessment is a promising approach for understanding the vulnerability of a system to potential future changes. The technique has been utilised successfully in risk-based assessments of future flood severity and infrastructure vulnerability. We find that it is also an ideal tool for assessing hydrologic model performance in a changing climate. In this study, we applied bottom-up climate change to compare the performance of two different hydrologic models (an event-based and a continuous model) under increasingly severe climate change scenarios. This allowed us to diagnose likely sources of future prediction error in the two models. The climate change scenarios were based on projections for southern Australia, which indicate drier average conditions with increased extreme rainfall intensities. We found that the key weakness in using the event-based model to simulate drier future scenarios was the model's inability to dynamically account for changing antecedent conditions. This led to increased variability in model performance relative to the continuous model, which automatically accounts for the wetness of a catchment through dynamic simulation of water storages. When considering more intense future rainfall events, representation of antecedent conditions became less important than assumptions around (non)linearity in catchment response. The linear continuous model we applied may underestimate flood risk in a future climate with greater extreme rainfall intensity. In contrast with the recommendations of previous studies, this indicates that continuous simulation is not necessarily the key to robust flood modelling under climate change. By applying bottom-up climate change assessment, we were able to understand systematic changes in relative model performance under changing conditions and deduce likely sources of prediction error in the two models.

Bounding the error on bottom estimation for multi-angle swath bathymetry sonar

NASA Astrophysics Data System (ADS)

Mullins, Geoff K.; Bird, John S.

2005-04-01

With the recent introduction of multi-angle swath bathymetry (MASB) sonar to the commercial marketplace (e.g., Benthos Inc., C3D sonar, 2004), additions must be made to the current sonar lexicon. The correct interpretation of measurements made with MASB sonar, which uses filled transducer arrays to compute angle-of-arrival information (AOA) from backscattered signal, is essential not only for mapping, but for applications such as statistical bottom classification. In this paper it is shown that aside from uncorrelated channel to channel noise, there exists a tradeoff between effects that govern the error bounds on bottom estimation for surfaces having shallow grazing angle and surfaces distributed along a radial arc centered at the transducer. In the first case, as the bottom aligns with the radial direction to the receiver, footprint shift and shallow grazing angle effects dominate the uncertainty in physical bottom position (surface aligns along a single AOA). Alternatively, if signal from a radial arc arrives, a single AOA is usually estimated (not necessarily at the average location of the surface). Through theoretical treatment, simulation, and field measurements, the aforementioned factors affecting MASB bottom mapping are examined. [Work supported by NSERC.

Experimental and Numerical Investigations of Applying Tip-bottomed Tool for Bending Advanced Ultra-high Strength Steel Sheet

NASA Astrophysics Data System (ADS)

Mitsomwang, Pusit; Borrisutthekul, Rattana; Klaiw-awoot, Ken; Pattalung, Aran

2017-09-01

This research was carried out aiming to investigate the application of a tip-bottomed tool for bending an advanced ultra-high strength steel sheet. The V-die bending experiment of a dual phase steel (DP980) sheet which had a thickness of 1.6 mm was executed using a conventional bending and a tip-bottomed punches. Experimental results revealed that the springback of the bent worksheet in the case of the tip-bottomed punch was less than that of the conventional punch case. To further discuss bending characteristics, a finite element (FE) model was developed and used to simulate the bending of the worksheet. From the FE analysis, it was found that the application of the tip-bottomed punch contributed the plastic deformation to occur at the bending region. Consequently, the springback of the worksheet reduced. In addition, the width of the punch tip was found to affect the deformation at the bending region and determined the springback of the bent worksheet. Moreover, the use of the tip-bottomed punch resulted in the apparent increase of the surface hardness of the bent worksheet, compared to the bending with the conventional punch.

Re-construction of action awareness depends on an internal model of action-outcome timing.

PubMed

Stenner, Max-Philipp; Bauer, Markus; Machts, Judith; Heinze, Hans-Jochen; Haggard, Patrick; Dolan, Raymond J

2014-04-01

The subjective time of an instrumental action is shifted towards its outcome. This temporal binding effect is partially retrospective, i.e., occurs upon outcome perception. Retrospective binding is thought to reflect post-hoc inference on agency based on sensory evidence of the action - outcome association. However, many previous binding paradigms cannot exclude the possibility that retrospective binding results from bottom-up interference of sensory outcome processing with action awareness and is functionally unrelated to the processing of the action - outcome association. Here, we keep bottom-up interference constant and use a contextual manipulation instead. We demonstrate a shift of subjective action time by its outcome in a context of variable outcome timing. Crucially, this shift is absent when there is no such variability. Thus, retrospective action binding reflects a context-dependent, model-based phenomenon. Such top-down re-construction of action awareness seems to bias agency attribution when outcome predictability is low. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Re-construction of action awareness depends on an internal model of action-outcome timing

PubMed Central

Stenner, Max-Philipp; Bauer, Markus; Machts, Judith; Heinze, Hans-Jochen; Haggard, Patrick; Dolan, Raymond J.

2014-01-01

The subjective time of an instrumental action is shifted towards its outcome. This temporal binding effect is partially retrospective, i.e., occurs upon outcome perception. Retrospective binding is thought to reflect post-hoc inference on agency based on sensory evidence of the action – outcome association. However, many previous binding paradigms cannot exclude the possibility that retrospective binding results from bottom-up interference of sensory outcome processing with action awareness and is functionally unrelated to the processing of the action – outcome association. Here, we keep bottom-up interference constant and use a contextual manipulation instead. We demonstrate a shift of subjective action time by its outcome in a context of variable outcome timing. Crucially, this shift is absent when there is no such variability. Thus, retrospective action binding reflects a context-dependent, model-based phenomenon. Such top-down re-construction of action awareness seems to bias agency attribution when outcome predictability is low. PMID:24555983

Using ocean bottom pressure from the gravity recovery and climate experiment (GRACE) to estimate transport variability in the southern Indian Ocean

NASA Astrophysics Data System (ADS)

Makowski, Jessica K.; Chambers, Don P.; Bonin, Jennifer A.

2015-06-01

Previous studies have suggested that ocean bottom pressure (OBP) from the Gravity Recovery and Climate Experiment (GRACE) can be used to measure the depth-averaged, or barotropic, transport variability of the Antarctic Circumpolar Current (ACC). Here, we use GRACE OBP observations to calculate transport variability in a region of the southern Indian Ocean encompassing the major fronts of the ACC. We use a statistical analysis of a simulated GRACE-like data set to determine the uncertainty of the estimated transport for the 2003.0-2013.0 time period. We find that when the transport is averaged over 60° of longitude, the uncertainty (one standard error) is close to 1 Sv (1 Sv = 106 m3 s-1) for low-pass filtered transport, which is significantly smaller than the signal and lower than previous studies have found. The interannual variability is correlated with the Southern Annual mode (SAM) (0.61), but more highly correlated with circumpolar zonally averaged winds between 45°S and 65°S (0.88). GRACE transport reflects significant changes in transport between 2007 and 2009 that is observed in the zonal wind variations but not in the SAM index. We also find a statistically significant trend in transport (-1.0 ± 0.4 Sv yr-1, 90% confidence) that is correlated with a local deceleration in zonal winds related to an asymmetry in the SAM on multidecadal periods.

A comparison of waveform processing algorithms for single-wavelength LiDAR bathymetry

NASA Astrophysics Data System (ADS)

Wang, Chisheng; Li, Qingquan; Liu, Yanxiong; Wu, Guofeng; Liu, Peng; Ding, Xiaoli

2015-03-01

Due to the low-cost and lightweight units, single-wavelength LiDAR bathymetric systems are an ideal option for shallow-water (<12 m) bathymetry. However, one disadvantage of such systems is the lack of near-infrared and Raman channels, which results in difficulties in extracting the water surface. Therefore, the choice of a suitable waveform processing method is extremely important to guarantee the accuracy of the bathymetric retrieval. In this paper, we test six algorithms for single-wavelength bathymetric waveform processing, i.e. peak detection (PD), the average square difference function (ASDF), Gaussian decomposition (GD), quadrilateral fitting (QF), Richardson-Lucy deconvolution (RLD), and Wiener filter deconvolution (WD). To date, most of these algorithms have previously only been applied in topographic LiDAR waveforms captured over land. A simulated dataset and an Optech Aquarius dataset were used to assess the algorithms, with the focus being on their capability of extracting the depth and the bottom response. The influences of a number of water and equipment parameters were also investigated by the use of a Monte Carlo method. The results showed that the RLD method had a superior performance in terms of a high detection rate and low errors in the retrieved depth and magnitude. The attenuation coefficient, noise level, water depth, and bottom reflectance had significant influences on the measurement error of the retrieved depth, while the effects of scan angle and water surface roughness were not so obvious.

An inherent-optical-property-centered approach to correct the angular effects in water-leaving radiance.

PubMed

Lee, Zhong Ping; Du, Keping; Voss, Kenneth J; Zibordi, Giuseppe; Lubac, Bertrand; Arnone, Robert; Weidemann, Alan

2011-07-01

Remote-sensing reflectance (R(rs)), which is defined as the ratio of water-leaving radiance (L(w)) to downwelling irradiance just above the surface (E(d)(0⁺)), varies with both water constituents (including bottom properties of optically-shallow waters) and angular geometry. L(w) is commonly measured in the field or by satellite sensors at convenient angles, while E(d)(0⁺) can be measured in the field or estimated based on atmospheric properties. To isolate the variations of R(rs) (or L(w)) resulting from a change of water constituents, the angular effects of R(rs) (or L(w)) need to be removed. This is also a necessity for the calibration and validation of satellite ocean color measurements. To reach this objective, for optically-deep waters where bottom contribution is negligible, we present a system centered on water's inherent optical properties (IOPs). It can be used to derive IOPs from angular R_rs and offers an alternative to the system centered on the concentration of chlorophyll. This system is applicable to oceanic and coastal waters as well as to multiband and hyperspectral sensors. This IOP-centered system is applied to both numerically simulated data and in situ measurements to test and evaluate its performance. The good results obtained suggest that the system can be applied to angular R(rs) to retrieve IOPs and to remove the angular variation of R(rs).

Extraordinary optical transmission in nanopatterned ultrathin metal films without holes

DOE PAGES

Peer, Akshit; Biswas, Rana

2016-02-01

In this study, we experimentally and theoretically demonstrate that a continuous gold film on a periodically textured substrate exhibits extraordinary optical transmission, even though no holes were etched in the film. Our film synthesis started by nanoimprinting a periodic array of nanocups with a period of ~750 nm on a polystyrene film over a glass substrate. A thin non-conformal gold film was sputter-deposited on the polystyrene by angle-directed deposition. The gold film was continuous with spatial thickness variation, the film being thinnest at the bottom of the nanocup. Measurements revealed an extraordinary transmission peak at a wavelength just smaller thanmore » the period, with an enhancement of ~2.5 compared to the classically expected value. Scattering matrix simulations model well the transmission and reflectance measurements when an ultrathin gold layer (~5 nm), smaller than the skin depth is retained at the bottom of the nanocups. Electric field intensities are enhanced by >100 within the nanocup, and ~40 in the ultrathin gold layer causing transmission through it. We show a wavelength red-shift of ~30 nm in the extraordinary transmission peak when the nanocups are coated with a thin film of a few nanometers, which can be utilized for biosensing. The continuous corrugated metal films are far simpler structures to observe extraordinary transmission, circumventing the difficult process of etching the metal film. Such continuous metal films with ultrathin regions are simple platforms for non-linear optics, plasmonics, and biological and chemical sensing.« less

Complementary Metal-Oxide-Silicon (CMOS)-Memristor Hybrid Nanoelectronics for Advanced Encryption Standard (AES) Encryption

DTIC Science & Technology

2016-04-01

with Al top electrodes and Cu bottom electrodes. ................... 9 Figure 4. SPICE netlist structure...memory elements play a part in logic gate. 4.4.2 Simulation SPICE Simulation Program for Integrated Circuits Emphasis ( SPICE ) is a general-purpose...analog circuit simulator that was developed at the Electronics Research Laboratory of the University of California, Berkeley [6]. In 1975, SPICE

Southern Ocean Bottom Water Characteristics in CMIP5 Models

NASA Astrophysics Data System (ADS)

Heuzé, Céline; Heywood, Karen; Stevens, David; Ridley, Jeff

2013-04-01

The depiction of Southern Ocean deep water properties and formation processes in climate models is an indicator of their capability to simulate future climate, heat and carbon uptake, and sea level rise. Southern Ocean potential temperature and density averaged over 1986-2005 from fifteen CMIP5 climate models are compared with an observed climatology, focusing on bottom water properties. The mean bottom properties are reasonably accurate for half of the models, but the other half may not yet have approached an equilibrium state. Eleven models create dense water on the Antarctic shelf, but it does not spill off and propagate northwards, alternatively mixing rapidly with less dense water. Instead most models create deep water by open ocean deep convection. Models with large deep convection areas are those with a strong seasonal cycle in sea ice. The most accurate bottom properties occur in models hosting deep convection in the Weddell and Ross gyres.

Instrumenting free-swimming dolphins echolocating in open water.

PubMed

Martin, Stephen W; Phillips, Michael; Bauer, Eric J; Moore, Patrick W; Houser, Dorian S

2005-04-01

Dolphins within the Navy Marine Mammal Program use echolocation to effectively locate underwater mines. They currently outperform manmade systems at similar tasks, particularly in cluttered environments and on buried targets. In hopes of improving manmade mine-hunting sonar systems, two instrumentation packages were developed to monitor free-swimming dolphin motion and echolocation during open-water target detection tasks. The biosonar measurement tool (BMT) is carried by a dolphin and monitors underwater position and attitude while simultaneously recording echolocation clicks and returning echoes through high-gain binaural receivers. The instrumented mine simulator (IMS) is a modified bottom target that monitors echolocation signals arriving at the target during ensonification. Dolphin subjects were trained to carry the BMT in open-bay bottom-object target searches in which the IMS could serve as a bottom object. The instrumentation provides detailed data that reveal hereto-unavailable information on the search strategies of free-swimming dolphins conducting open-water, bottom-object search tasks with echolocation.

Application of Numerical Simulation for the Analysis of the Processes of Rotary Ultrasonic Drilling

NASA Astrophysics Data System (ADS)

Naď, Milan; Čičmancová, Lenka; Hajdu, Štefan

2016-12-01

Rotary ultrasonic machining (RUM) is a hybrid process that combines diamond grinding with ultrasonic machining. It is most suitable to machine hard brittle materials such as ceramics and composites. Due to its excellent machining performance, RUM is very often applied for drilling of hard machinable materials. In the final phase of drilling, the edge deterioration of the drilled hole can occur, which results in a phenomenon called edge chipping. During hole drilling, a change in the thickness of the bottom of the drilled hole occurs. Consequently, the bottom of the hole as a plate structure is exposed to the transfer through the resonance state. This resonance state can be considered as one of the important aspects leading to edge chipping. Effects of changes in the bottom thickness and as well as the fillet radius between the wall and bottom of the borehole on the stress-strain states during RUM are analyzed.

Instrumenting free-swimming dolphins echolocating in open water

NASA Astrophysics Data System (ADS)

Martin, Stephen W.; Phillips, Michael; Bauer, Eric J.; Moore, Patrick W.; Houser, Dorian S.

2005-04-01

Dolphins within the Navy Marine Mammal Program use echolocation to effectively locate underwater mines. They currently outperform manmade systems at similar tasks, particularly in cluttered environments and on buried targets. In hopes of improving manmade mine-hunting sonar systems, two instrumentation packages were developed to monitor free-swimming dolphin motion and echolocation during open-water target detection tasks. The biosonar measurement tool (BMT) is carried by a dolphin and monitors underwater position and attitude while simultaneously recording echolocation clicks and returning echoes through high-gain binaural receivers. The instrumented mine simulator (IMS) is a modified bottom target that monitors echolocation signals arriving at the target during ensonification. Dolphin subjects were trained to carry the BMT in open-bay bottom-object target searches in which the IMS could serve as a bottom object. The instrumentation provides detailed data that reveal hereto-unavailable information on the search strategies of free-swimming dolphins conducting open-water, bottom-object search tasks with echolocation. .

Application of Sub-Bottom Profiler to Study Riverbed Structure and Sediment Density

NASA Astrophysics Data System (ADS)

Rui, Wang; Changzheng, Li; Xiaofei, Yan

2018-03-01

In this pater, we present a study on the riverbed structure and sediment density in-situ test by using sub-bottom profiler. Compared with traditional direct observation methods, the sub-bottom profiler method based on sonar technology is non-contact, low-disturbance and high-efficient. We finish the investigation of several sections in Sanmenxia and Xiaolangdi reservoirs, which located on the main channel of lower reaches of Yellow River. Collected data show a detailed layered structure of the riverbed sediment which believed caused by sedimentary processes in different periods. Further more, we analyse the reflection coefficient of water-sediment interface and inverse the sediment density data from the raw wave record. The inversion method is based on the effective density fluid model and Kozeny-Carman formula. The comparison of the inversion results and sample tests shows that the in-situ test is reliable and useable.

Analysis of coal seam thickness and seismic wave amplitude: A wedge model

NASA Astrophysics Data System (ADS)

Zou, Guangui; Xu, Zhiliang; Peng, Suping; Fan, Feng

2018-01-01

Coal seam thickness is of great significance in mining coal resources. The focus of this study is to determine the relationship between coal seam thickness and seismic wave amplitude, and the factors influencing this relationship. We used a wedge model to analyze this relationship and its influencing factors. The results show that wave interference from the top and bottom interfaces is the primary reason for the linear relationship between seismic wave amplitude and wedge thickness, when the thickness of the wedge is less than one quarter of the wavelength. This relationship is influenced by the dominant frequency, reflection coefficients from the top and bottom boundaries, depth, thickness, and angle of the wedge. However, when the lateral shift between the reflected waves is smaller than the radius of the first Fresnel zone, the wedge angle and change in lithology at the top and bottom layers are considered to have little effect on the amplitude of the interference wave. The difference in the dominant frequency of seismic waves can be reduced by filtering, and the linear relationship between amplitude and coal thickness can be improved. Field data from Sihe coal mine was analyzed, and the error was found to be within 4% of the predicted seismic wave amplitude. The above conclusions could help predict the thickness of coal seam by seismic amplitude.

Validation of normalized pulse volume in the outer ear as a simple measure of sympathetic activity using warm and cold pressor tests: towards applications in ambulatory monitoring.

PubMed

Lee, Jihyoung; Matsumura, Kenta; Yamakoshi, Takehiro; Rolfe, Peter; Tanaka, Naoto; Kim, Kyungho; Yamakoshi, Ken-ichi

2013-03-01

Normalized pulse volume (NPV) derived from the ear has the potential to be a practical index for monitoring daily life stress. However, ear NPV has not yet been validated. Therefore, we compared NPV derived from an index finger using transmission photoplethysmography as a reference, with NPV derived from a middle finger and four sites of the ear using reflection photoplethysmography during baseline and while performing cold and warm water immersion in ten young and six middle-aged subjects. The results showed that logarithmically-transformed NPV (lnNPV) during cold water immersion as compared with baseline values was significantly lower, only at the index finger, the middle finger and the bottom of the ear-canal. Furthermore, lnNPV reactivities (ΔlnNPV; the difference between baseline and test values) from an index finger were significantly related to ΔlnNPV from the middle finger and the bottom of the ear-canal (young: r = 0.90 and 0.62, middle-aged: r = 0.80 and 0.58, respectively). In conclusion, these findings show that reflection and transmission photoplethysmography are comparable methods to derive NPV in accordance with our theoretical prediction. NPV derived from the bottom of the ear-canal is a valid approach, which could be useful for evaluating daily life stress.

Regional Geology of the Southern Lake Erie (Ohio) Bottom: A Seismic Reflection and Vibracore Study.

DTIC Science & Technology

1982-12-01

identify by block number) Geomorphology Sand resources Seismic reflection Lake Erie Sediments Vibracores Ohio 20. ABST’RACT (Cotfme -n 9e~re .ft if...postglacial deposit thicknesses range from 0 to 22 meters and like the till, the postglacial sediment thickens lakeward. The tills were first deposited on an...ihen Data Entered) PREFACE This report is one of three reports which describe results of the Inner Continental Shelf Sediment and Structure (ICONS

The crustal structure in the transition zone between the western and eastern Barents Sea

NASA Astrophysics Data System (ADS)

Shulgin, Alexey; Mjelde, Rolf; Faleide, Jan Inge; Høy, Tore; Flueh, Ernst; Thybo, Hans

2018-04-01

We present a crustal-scale seismic profile in the Barents Sea based on new data. Wide-angle seismic data were recorded along a 600 km long profile at 38 ocean bottom seismometer and 52 onshore station locations. The modeling uses the joint refraction/reflection tomography approach where co-located multi-channel seismic reflection data constrain the sedimentary structure. Further, forward gravity modeling is based on the seismic model. We also calculate net regional erosion based on the calculated shallow velocity structure.

Experimental Investigation and Computer Modeling of Optical Switching in Distributed Bragg Reflector and Vertical Cavity Surface Emitting Laser Structures.

DTIC Science & Technology

1995-12-01

of a Molecular Beam Epitaxy (MBE) system prior to growing a Vertical Cavity Surface Emitting Laser ( VCSEL ). VCSEL bistability is discussed later in...addition, optical bistability 1 in the reflectivity of a DBR, as well as in the lasing power, wavelength, and beam divergence of a lasing VCSEL are...Spectral Reflectivity of AlGaAs/AlAs VCSEL Top DBR Mirror Cavity Bottom DBR Mirror Substrate Output Beam Resonance Pump Minimum Stop Band Figure 2. VCSEL

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

Geographic variability in elevation and topographic constraints on the distribution of native and nonnative trout in the Great Basin

USGS Publications Warehouse

Warren, Dana R.; Dunham, Jason B.; Hockman-Wert, David

2014-01-01

Understanding local and geographic factors influencing species distributions is a prerequisite for conservation planning. Our objective in this study was to model local and geographic variability in elevations occupied by native and nonnative trout in the northwestern Great Basin, USA. To this end, we analyzed a large existing data set of trout presence (5,156 observations) to evaluate two fundamental factors influencing occupied elevations: climate-related gradients in geography and local constraints imposed by topography. We applied quantile regression to model upstream and downstream distribution elevation limits for each trout species commonly found in the region (two native and two nonnative species). With these models in hand, we simulated an upstream shift in elevation limits of trout distributions to evaluate potential consequences of habitat loss. Downstream elevation limits were inversely associated with latitude, reflecting regional gradients in temperature. Upstream limits were positively related to maximum stream elevation as expected. Downstream elevation limits were constrained topographically by valley bottom elevations in northern streams but not in southern streams, where limits began well above valley bottoms. Elevation limits were similar among species. Upstream shifts in elevation limits for trout would lead to more habitat loss in the north than in the south, a result attributable to differences in topography. Because downstream distributions of trout in the north extend into valley bottoms with reduced topographic relief, trout in more northerly latitudes are more likely to experience habitat loss associated with an upstream shift in lower elevation limits. By applying quantile regression to relatively simple information (species presence, elevation, geography, topography), we were able to identify elevation limits for trout in the Great Basin and explore the effects of potential shifts in these limits that could occur in response to changing climate conditions that alter streams directly (e.g., through changes in temperature and precipitation) or indirectly (e.g., through changing water use).

Chemical evolution of the Salton Sea, California: Nutrient and selenium dynamics

USGS Publications Warehouse

Schroeder, R.A.; Orem, W.H.; Kharaka, Y.K.

2002-01-01

The Salton Sea is a 1000-km2 terminal lake located in the desert area of southeastern California. This saline (???44 000 mg l-1 dissolved solids) lake started as fresh water in 1905-07 by accidental flooding of the Colorado River, and it is maintained by agricultural runoff of irrigation water diverted from the Colorado River. The Salton Sea and surrounding wetlands have recently acquired substantial ecological importance because of the death of large numbers of birds and fish, and the establishment of a program to restore the health of the Sea. In this report, we present new data on the salinity and concentration of selected chemicals in the Salton Sea water, porewater and sediments, emphasizing the constituents of concern: nutrients (N and P), Se and salinity. Chemical profiles from a Salton Sea core estimated to have a sedimentation rate of 2.3 mm yr-1 show increasing concentrations of OC, N, and P in younger sediment that are believed to reflect increasing eutrophication of the lake. Porewater profiles from two locations in the Sea show that diffusion from bottom sediment is only a minor source of nutrients to the overlying water as compared to irrigation water inputs. Although loss of N and Se by microbial-mediated volatilization is possible, comparison of selected element concentrations in river inputs and water and sediments from the Salton Sea indicates that most of the N (from fertilizer) and virtually all of the Se (delivered in irrigation water from the Colorado River) discharged to the Sea still reside within its bottom sediment. Laboratory simulation on mixtures of sediment and water from the Salton Sea suggest that sediment is a potential source of N and Se to the water column under aerobic conditions. Hence, it is important that any engineered changes made to the Salton Sea for remediation or for transfer of water out of the basin do not result in remobilization of nutrients and Se from the bottom sediment into the overlying water.

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

Assessing suitability of multispectral satellites for mapping benthic macroalgal cover in turbid coastal waters by means of model simulations

NASA Astrophysics Data System (ADS)

Kutser, Tiit; Vahtmäe, Ele; Martin, Georg

2006-04-01

One of the objectives of monitoring benthic algal cover is to observe short- and long-term changes in species distribution and structure of coastal benthic habitats as indicators of ecological state. Mapping benthic algal cover with conventional methods (diving) provides great accuracy and high resolution, yet is very expensive and is limited by the time and manpower necessary. We measured reflectance spectra of three indicator species for the Baltic Sea: Cladophora glomerata (green macroalgae), Furcellaria lumbricalis (red macroalgae), and Fucus vesiculosus (brown macroalgae) and used a bio-optical model in an attempt to estimate whether these algae are separable from each other and sandy bottom or deep water by means of satellite remote sensing. Our modelling results indicate that to some extent it is possible to map the studied species with multispectral satellite sensors in turbid waters. However, the depths where the macroalgae can be detected are often shallower than the maximum depths where the studied species usually grow. In waters deeper than just a few meters, the differences between the studied bottom types are seen only in band 2 (green) of the multispectral sensors under investigation. It means that multispectral sensors are capable of detecting difference in brightness only in one band which is insufficient for recognition of different bottom types in waters where no or few in situ data are available. Configuration of MERIS spectral bands allows the recognition of red, green and brown macroalgae based on their spectral signatures provided the algal belts are wider than MERIS spatial resolution. Commercial stock of F. lumbricalis in West-Estonian Archipelago covers area where MERIS 300 m spatial resolution is adequate. However, strong attenuation of light in the water column and signal to noise ratio of the sensor do not allow mapping of Furcellaria down to maximum depths where it occurs.

Baseline seismic survey for the 2nd offshore methane hydrate production test in the Eastern Nankai Trough

NASA Astrophysics Data System (ADS)

Teranishi, Y.; Inamori, T.; Kobayashi, T.; Fujii, T.; Saeki, T.; Takahashi, H.; Kobayashi, F.

2017-12-01

JOGMEC carries out seismic monitoring surveys before and after the 2nd offshore methane hydrate (MH) production test in the Eastern Nankai Trough and evaluates MH dissociation behavior from the time-lapse seismic response. In 2016, JOGMEC deployed Ocean Bottom Cable (OBC) system provided by OCC in the Daini Atsumi Knoll with water depths of 900-1100 m. The main challenge of the seismic survey was to optimize the cable layout for ensuring an effective time-lapse seismic detectability while overcoming the following two issues: 1. OBC receiver lines were limited to only two lines. It was predicted that the imaging of shallow reflectors would suffer from lack of continuity and resolution due to this limitation of receiver lines. 2. The seafloor and shallow sedimentary layers including monitoring target are dipping to the Northwest direction. It was predicted that the refection points would laterally shift to up-dip direction (Southeast direction). In order to understand the impact of the issues above, the seismic survey was designed with elastic wave field simulation. The reflection seismic survey for baseline data was conducted in August 2016. A total of 70 receiver stations distributed along one cable were deployed successfully and a total of 9952 shots were fired. After the baseline seismic survey, the hydrophone and geophone vertical component datasets were processed as outlined below: designaturing, denoising, surface consistent deconvolution and surface consistent amplitude correction. High-frequency imaging with Reverse Time Migration (RTM) was introduced to these data sets. Improvements in imaging from the RTM are remarkable compared to the Kirchhoff migration and the existing Pre-stack time migration with 3D marine surface seismic data obtained and processed in 2002, especially in the following parts. The MH concentrated zone which has complex structures. Below the Bottom Simulating Reflector (BSR) which is present as a impedance-contrast boundary

Observations and simulations of the bottom nepheloid layer in the Lafourche Trough, Louisiana Continental Shelf

NASA Astrophysics Data System (ADS)

Jolliff, J.; Jarosz, E.; Penko, A.; Smith, T.

2017-12-01

The "Lafourche Trough" is a mud/silt -dominated, elongate seafloor depression located between transgressive sandy shoals approximately 50 km south of Cocodrie, Louisiana. These irregular bathymetric features are relicts of the abandoned Lafourche delta complex that still have an impact upon coupled sediment-hydrodynamic processes occurring today. Repeated optical and physical oceanographic surveys conducted during the spring of 2015 and winter 2017 reveal persistent bottom nepheloid layers (BNLs) characterized by extreme optical turbidity (beam attenuation 10 m-1, 532 nm). The manifestation and persistence of cohesive sediment BNLs in this area appears to result from a complex interplay between tidal currents, bathymetry, and frontal dynamics along the edge of the Mississippi River plume. Numerical experiments were performed using the Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS), an integrated air-sea-wave operational forecasting tool, that includes a simplified numerical sediment resuspension and transport scheme in order to simulate the nepheloid layer observations through the trough. The model results suggest that the wave-current bottom boundary layer is a critical factor in BNL development, and thusly, without wave model integration into COAMPS the system struggles to replicate the observations. Future modeling work will need to explore the potential suppression of physical mixing due to density perturbations along the BNL to fluid mud continuum within the bottom boundary layer.

Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module

DTIC Science & Technology

2015-02-01

executed with SolidWorks Flow Simulation , a computational fluid-dynamics code. The graph in Fig. 2 shows the timing and amplitudes of power pulses...defined a convective flow of air perpendicular to the bottom surface of the mounting plate, with a velocity of 10 ft/s. The thermal simulations were...Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module by Gregory K Ovrebo ARL-TR-7210

Tsujal Marine Survey: Crustal Characterization of the Rivera Plate-Jalisco Block Boundary and its Implications for Seismic and Tsunami Hazard Assessment

NASA Astrophysics Data System (ADS)

Bartolome, R.; Danobeitia, J.; Barba, D. C., Sr.; Nunez-Cornu, F. J.; Cameselle, A. L.; Estrada, F.; Prada, M.; Bandy, W. L.

2014-12-01

During the spring of 2014, a team of Spanish and Mexican scientists explored the western margin of Mexico in the frame of the TSUJAL project. The two main objectives were to characterize the nature and structure of the lithosphere and to identify potential sources triggering earthquakes and tsunamis at the contact between Rivera plate-Jalisco block with the North American Plate. With these purposes a set of marine geophysical data were acquired aboard the RRS James Cook. This work is focus in the southern part of the TSUJAL survey, where we obtain seismic images from the oceanic domain up to the continental shelf. Thus, more than 800 km of MCS data, divided in 7 profiles, have been acquired with a 6km long streamer and using an air-gun sources ranging from 5800 c.i. to 3540 c.i. Furthermore, a wide-angle seismic profile of 190 km length was recorded in 16 OBS deployed perpendicular to the coast of Manzanillo. Gravity and magnetic, multibeam bathymetry and sub-bottom profiler data were recorded simultaneously with seismic data in the offshore area. Preliminary stacked MCS seismic sections reveal the crustal structure in the different domains of the Mexican margin. The contact between the Rivera and NA Plates is observed as a strong reflection at 6 s two way travel time (TWTT), in a parallel offshore profile (TS01), south of Manzanillo. This contact is also identified in a perpendicular profile, TS02, along a section of more than 100 km in length crossing the Rivera transform zone, and the plate boundary between Cocos and Rivera Plates. Northwards, offshore Pto. Vallarta, the MCS data reveals high amplitude reflections at around 7-8.5 s TWTT, roughly 2.5-3.5 s TWTT below the seafloor, that conspicuously define the subduction plane (TS06b). These strong reflections which we interpret as the Moho discontinuity define the starting bending of subduction of Rivera Plate. Another clear pattern observed within the first second of the MCS data shows evidences of a bottom simulating reflector (BSR) along the continental margin, particularly strong offshore Pto. Vallarta. The integration of all these acquired geophysical information will allow obtaining a comprehensive image of the lithosphere that will be valuable for the seismic and tsunamigenic hazard assessment.

Sound Speed and Attenuation in Multiphase Media

DTIC Science & Technology

2012-03-15

wave speeds between 100 to 300 m/s for sandy sediments with porosities of 40-50%. Hastrup [21:121-127] reports empirical relationships that 12...4, pp. 689-692, 1955. [20] R.D. Stoll, Sediment Acoustics, Springer-Verlag, New York, 1989. [21] O. F. Hastrup , Acoustic Bottom Reflectivity

A nonreflecting upper boundary condition for anelastic nonhydrostatic mesoscale gravity-wave models

NASA Technical Reports Server (NTRS)

Kim, Young-Joon; Kar, Sajal K.; Arakawa, Akio

1993-01-01

A sponge layer is formulated to prevent spurious reflection of vertically propagating quasi-stationary gravity waves at the upper boundary of a two-dimensional numerical anelastic nonhydrostatic model. The sponge layer includes damping of both Newtonian-cooling type and Rayleigh-friction type, whose coefficients are determined in such a way that the reflectivity of wave energy at the bottom of the layer is zero. Unlike the formulations in earlier studies, our formulation includes the effects of vertical discretization, vertical mean density variation, and nonhydrostaticity. This sponge formulation is found effective in suppressing false downward reflection of waves for various types of quasi-stationary forcing.

A Wide Band Absorbing Material Design Using Band-Pass Frequency Selective Surface

NASA Astrophysics Data System (ADS)

Xu, Yonggang; Xu, Qiang; Liu, Ting; Zheng, Dianliang; Zhou, Li

2018-03-01

Based on the high frequency advantage characteristics of the Fe based absorbing coating, a method for designing the structure of broadband absorbing structure by using frequency selective surface (FSS) is proposed. According to the transmission and reflection characteristic of the different size FSS structure, the frequency variation characteristic was simulated. Secondly, the genetic algorithm was used to optimize the high frequency broadband absorbing materials, including the single and double magnetic layer material. Finally, the absorbing characteristics in iron layer were analyzed as the band pass FSS structure was embedded, the results showed that the band-pass FSS had the influence on widening the absorbing frequency. As the FSS was set as the bottom layer, it was effective to achieve the good absorbing property in low frequency and the high frequency absorbing performance was not weakened, because the band-pass FSS led the low frequency absorption and the high frequency shielding effect. The results of this paper are of guiding significance for designing and manufacturing the broadband absorbing materials.

Ultrahigh-Resolution 3-Dimensional Seismic Imaging of Seeps from the Continental Slope of the Northern Gulf of Mexico: Subsurface, Seafloor and Into the Water Column

NASA Astrophysics Data System (ADS)

Brookshire, B. N., Jr.; Mattox, B. A.; Parish, A. E.; Burks, A. G.

2016-02-01

Utilizing recently advanced ultrahigh-resolution 3-dimensional (UHR3D) seismic tools we have imaged the seafloor geomorphology and associated subsurface aspects of seep related expulsion features along the continental slope of the northern Gulf of Mexico with unprecedented clarity and continuity. Over an area of approximately 400 km2, over 50 discrete features were identified and three general seafloor geomorphologies indicative of seep activity including mounds, depressions and bathymetrically complex features were quantitatively characterized. Moreover, areas of high seafloor reflectivity indicative of mineralization and areas of coherent seismic amplitude anomalies in the near-seafloor water column indicative of active gas expulsion were identified. In association with these features, shallow source gas accumulations and migration pathways based on salt related stratigraphic uplift and faulting were imaged. Shallow, bottom simulating reflectors (BSRs) interpreted to be free gas trapped under near seafloor gas hydrate accumulations were very clearly imaged.

A Fluid Pulse on the Hikurangi Subduction Margin: Evidence From a Heat Flux Transect Across the Upper Limit of Gas Hydrate Stability

NASA Astrophysics Data System (ADS)

Pecher, I. A.; Villinger, H.; Kaul, N.; Crutchley, G. J.; Mountjoy, J. J.; Huhn, K.; Kukowski, N.; Henrys, S. A.; Rose, P. S.; Coffin, R. B.

2017-12-01

A transect of seafloor heat probe measurements on the Hikurangi Margin shows a significant increase of thermal gradients upslope of the updip limit of gas hydrate stability at the seafloor. We interpret these anomalously high thermal gradients as evidence for a fluid pulse leading to advective heat flux, while endothermic cooling from gas hydrate dissociation depresses temperatures in the hydrate stability field. Previous studies predict a seamount on the subducting Pacific Plate to cause significant overpressure beneath our study area, which may be the source of the fluid pulse. Double-bottom simulating reflections are present in our study area and likely caused by uplift based on gas hydrate phase boundary considerations, although we cannot exclude a thermogenic origin. We suggest that uplift may be associated with the leading edge of the subducting seamount. Our results provide further evidence for the transient nature of fluid expulsion in subduction zones.

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.

Wave trapping by dual porous barriers near a wall in the presence of bottom undulation

NASA Astrophysics Data System (ADS)

Kaligatla, R. B.; Manisha; Sahoo, T.

2017-09-01

Trapping of oblique surface gravity waves by dual porous barriers near a wall is studied in the presence of step type varying bottom bed that is connected on both sides by water of uniform depths. The porous barriers are assumed to be fixed at a certain distance in front of a vertical rigid wall. Using linear water wave theory and Darcy's law for flow past porous structure, the physical problem is converted into a boundary value problem. Using eigenfunction expansion in the uniform bottom bed region and modified mild-slope equation in the varying bottom bed region, the mathematical problem is handled for solution. Moreover, certain jump conditions are used to account for mass conservation at slope discontinuities in the bottom bed profile. To understand the effect of dual porous barriers in creating tranquility zone and minimum load on the sea wall, reflection coefficient, wave forces acting on the barrier and the wall, and surface wave elevation are computed and analyzed for different values of depth ratio, porous-effect parameter, incident wave angle, gap between the barriers and wall and slope length of undulated bottom. The study reveals that with moderate porosity and suitable gap between barriers and sea wall, using dual barriers an effective wave trapping system can be developed which will exert less wave force on the barriers and the rigid wall. The proposed wave trapping system is likely to be of immense help for protecting various facilities/ infrastructures in coastal environment.

Source Rupture Models and Tsunami Simulations of Destructive October 28, 2012 Queen Charlotte Islands, British Columbia (Mw: 7.8) and September 16, 2015 Illapel, Chile (Mw: 8.3) Earthquakes

NASA Astrophysics Data System (ADS)

Taymaz, Tuncay; Yolsal-Çevikbilen, Seda; Ulutaş, Ergin

2016-04-01

The finite-fault source rupture models and numerical simulations of tsunami waves generated by 28 October 2012 Queen Charlotte Islands (Mw: 7.8), and 16 September 2015 Illapel-Chile (Mw: 8.3) earthquakes are presented. These subduction zone earthquakes have reverse faulting mechanisms with small amount of strike-slip components which clearly reflect the characteristics of convergence zones. The finite-fault slip models of the 2012 Queen Charlotte and 2015 Chile earthquakes are estimated from a back-projection method that uses teleseismic P- waveforms to integrate the direct P-phase with reflected phases from structural discontinuities near the source. Non-uniform rupture models of the fault plane, which are obtained from the finite fault modeling, are used in order to describe the vertical displacement on seabed. In general, the vertical displacement of water surface was considered to be the same as ocean bottom displacement, and it is assumed to be responsible for the initial water surface deformation gives rise to occurrence of tsunami waves. In this study, it was calculated by using the elastic dislocation algorithm. The results of numerical tsunami simulations are compared with tide gauges and Deep-ocean Assessment and Reporting of Tsunami (DART) buoy records. De-tiding, de-trending, low-pass and high-pass filters were applied to detect tsunami waves in deep ocean sensors and tide gauge records. As an example, the observed records and results of simulations showed that the 2012 Queen Charlotte Islands earthquake generated about 1 meter tsunami-waves in Maui and Hilo (Hawaii), 5 hours and 30 minutes after the earthquake. Furthermore, the calculated amplitudes and time series of the tsunami waves of the recent 2015 Illapel (Chile) earthquake are exhibiting good agreement with the records of tide and DART gauges except at stations Valparaiso and Pichidangui (Chile). This project is supported by The Scientific and Technological Research Council of Turkey (TUBITAK Project No: CAYDAG-114Y066).

A Generic Mesh Data Structure with Parallel Applications

ERIC Educational Resources Information Center

Cochran, William Kenneth, Jr.

2009-01-01

High performance, massively-parallel multi-physics simulations are built on efficient mesh data structures. Most data structures are designed from the bottom up, focusing on the implementation of linear algebra routines. In this thesis, we explore a top-down approach to design, evaluating the various needs of many aspects of simulation, not just…

Macro Scale Independently Homogenized Subcells for Modeling Braided Composites

NASA Technical Reports Server (NTRS)

Blinzler, Brina J.; Goldberg, Robert K.; Binienda, Wieslaw K.

2012-01-01

An analytical method has been developed to analyze the impact response of triaxially braided carbon fiber composites, including the penetration velocity and impact damage patterns. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. Currently, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. To determine the stiffness and strength properties required for the constitutive model, a top-down approach for determining the strength properties is merged with a bottom-up approach for determining the stiffness properties. The top-down portion uses global strengths obtained from macro-scale coupon level testing to characterize the material strengths for each subcell. The bottom-up portion uses micro-scale fiber and matrix stiffness properties to characterize the material stiffness for each subcell. Simulations of quasi-static coupon level tests for several representative composites are conducted along with impact simulations.

An RC-1 organic Rankine bottoming cycle for an adiabatic diesel engine

NASA Technical Reports Server (NTRS)

Dinanno, L. R.; Dibella, F. A.; Koplow, M. D.

1983-01-01

A system analysis and preliminary design were conducted for an organic Rankine-cycle system to bottom the high-temperature waste heat of an adiabatic diesel engine. The bottoming cycle is a compact package that includes a cylindrical air cooled condenser regenerator module and other unique features. The bottoming cycle output is 56 horsepower at design point conditions when compounding the reference 317 horsepower turbocharged diesel engine with a resulting brake specific fuel consumption of 0.268 lb/hp-hr for the compound engine. The bottoming cycle when applied to a turbocompound diesel delivers a compound engine brake specific fuel consumption of 0.258 lb/hp-hr. This system for heavy duty transport applications uses the organic working fluid RC-1, which is a mixture of 60 mole percent pentafluorobenzene and 40 mole percent hexafluorobenzene. The thermal stability of the RC-1 organic fluid was tested in a dynamic fluid test loop that simulates the operation of Rankine-cycle. More than 1600 hours of operation were completed with results showing that the RC-1 is thermally stable up to 900 F.

Simulation of Pressure-swing Distillation for Separation of Ethyl Acetate-Ethanol-Water

NASA Astrophysics Data System (ADS)

Yang, Jing; Zhou, Menglin; Wang, Yujie; Zhang, Xi; Wu, Gang

2017-12-01

In the light of the azeotrope of ethyl acetate-ethanol-water, a process of pressure-swing distillation is proposed. The separation process is simulated by Aspen Plus, and the effects of theoretical stage number, reflux ratio and feed stage about the pressure-swing distillation are optimized. Some better process parameters are as follows: for ethyl acetate refining tower, the pressure is 500.0 kPa, theoretical stage number is 16, reflux ratio is 0.6, feed stage is 5; for crude ethanol tower, the pressure is 101.3 kPa, theoretical stage number is 15, reflux ratio is 0.3, feed stage is 4; for ethanol tower, the pressure is 101.3 kPa, theoretical stage number is 25, reflux ratio is 1.2, feed stage is 10. The mass fraction of ethyl acetate in the bottom of the ethyl acetate refining tower reaches 0.9990, the mass fraction of ethanol in the top of the ethanol tower tower reaches 0.9017, the mass fraction of water in the bottom of the ethanol tower tower reaches 0.9622, and there is also no ethyl acetate in the bottom of the ethanol tower. With laboratory tests, experimental results are in good agreement with the simulation results, which indicates that the separation of ethyl acetate ethanol water can be realized by the pressure-swing distillation separation process. Moreover, it has certain practical significance to industrial practice.

Defect printability of alternating phase-shift mask: a critical comparison of simulation and experiment

NASA Astrophysics Data System (ADS)

Ozawa, Ken; Komizo, Tooru; Kikuchi, Koji; Ohnuma, Hidetoshi; Kawahira, Hiroichi

2002-07-01

An alternative phase shift mask (alt-PSM) is a promising device for extending optical lithography to finer design rules. There have been few reports, however, on the mask's ability to identify phase defects. We report here an alt-PSM of a dual-trench type for KrF exposure, with programmed quartz defects used to evaluate defect printability by measuring aerial images with a Zeiss MSM100 measuring system. The experimental results are simulated using the TEMPEST program. First, a critical comparison of the simulation and the experiment is conducted. The actual measured topography of quartz defects are used in the simulation. Moreover, a general simulation study on defect printability using an alt-PSM for ArF exposure is conducted. The defect dimensions, which produce critical CD errors are determined by simulation that takes into account the full 3-dimensional structure of phase defects as well as a simplified structure. The critical dimensions of an isolated defect identified by the alt-PSM of a single-trench type for ArF exposure are 240 nm in bottom diameter and 50 degrees in height (phase) for the cylindrical shape and 240 nm in bottom diameter and 90 degrees in height (phase) for the rotating trapezoidal shape, where the CD error limit is +/- 5%.

Storm-driven sediment transport in Massachusetts Bay

USGS Publications Warehouse

Warner, J.C.; Butman, B.; Dalyander, P.S.

2008-01-01

Massachusetts Bay is a semi-enclosed embayment in the western Gulf of Maine about 50 km wide and 100 km long. Bottom sediment resuspension is controlled predominately by storm-induced surface waves and transport by the tidal- and wind-driven circulation. Because the Bay is open to the northeast, winds from the northeast ('Northeasters') generate the largest surface waves and are thus the most effective in resuspending sediments. The three-dimensional oceanographic circulation model Regional Ocean Modeling System (ROMS) is used to explore the resuspension, transport, and deposition of sediment caused by Northeasters. The model transports multiple sediment classes and tracks the evolution of a multilevel sediment bed. The surficial sediment characteristics of the bed are coupled to one of several bottom-boundary layer modules that calculate enhanced bottom roughness due to wave-current interaction. The wave field is calculated from the model Simulating WAves Nearshore (SWAN). Two idealized simulations were carried out to explore the effects of Northeasters on the transport and fate of sediments. In one simulation, an initially spatially uniform bed of mixed sediments exposed to a series of Northeasters evolved to a pattern similar to the existing surficial sediment distribution. A second set of simulations explored sediment-transport pathways caused by storms with winds from the northeast quadrant by simulating release of sediment at selected locations. Storms with winds from the north cause transport southward along the western shore of Massachusetts Bay, while storms with winds from the east and southeast drive northerly nearshore flow. The simulations show that Northeasters can effectively transport sediments from Boston Harbor and the area offshore of the harbor to the southeast into Cape Cod Bay and offshore into Stellwagen Basin. This transport pattern is consistent with Boston Harbor as the source of silver found in the surficial sediments of Cape Cod Bay and Stellwagen Basin.

Approaches to quantifying long-term continental shelf sediment transport with an example from the Northern California STRESS mid-shelf site

NASA Astrophysics Data System (ADS)

Harris, Courtney K.; Wiberg, Patricia L.

1997-09-01

Modeling shelf sediment transport rates and bed reworking depths is problematic when the wave and current forcing conditions are not precisely known, as is usually the case when long-term sedimentation patterns are of interest. Two approaches to modeling sediment transport under such circumstances are considered. The first relies on measured or simulated time series of flow conditions to drive model calculations. The second approach uses as model input probability distribution functions of bottom boundary layer flow conditions developed from wave and current measurements. Sediment transport rates, frequency of bed resuspension by waves and currents, and bed reworking calculated using the two methods are compared at the mid-shelf STRESS (Sediment TRansport on Shelves and Slopes) site on the northern California continental shelf. Current, wave and resuspension measurements at the site are used to generate model inputs and test model results. An 11-year record of bottom wave orbital velocity, calculated from surface wave spectra measured by the National Data Buoy Center (NDBC) Buoy 46013 and verified against bottom tripod measurements, is used to characterize the frequency and duration of wave-driven transport events and to estimate the joint probability distribution of wave orbital velocity and period. A 109-day record of hourly current measurements 10 m above bottom is used to estimate the probability distribution of bottom boundary layer current velocity at this site and to develop an auto-regressive model to simulate current velocities for times when direct measurements of currents are not available. Frequency of transport, the maximum volume of suspended sediment, and average flux calculated using measured wave and simulated current time series agree well with values calculated using measured time series. A probabilistic approach is more amenable to calculations over time scales longer than existing wave records, but it tends to underestimate net transport because it does not capture the episodic nature of transport events. Both methods enable estimates to be made of the uncertainty in transport quantities that arise from an incomplete knowledge of the specific timing of wave and current conditions. 1997 Elsevier Science Ltd

North Atlantic Coast Comprehensive Study (NACCS) Coastal Storm Model Simulations: Waves and Water Levels

DTIC Science & Technology

2015-08-01

published in the NGA’s DNCs, with distinct values assigned to areas of sand, gravel, clay , etc. ERDC/CHL TR-15-14 94 6.5.2 Lateral eddy viscosity As with...6.5.1 Manning’s n bottom friction coefficient ................................................................... 93 6.5.2 Lateral eddy viscosity ...this study include (1) Manning’s n bottom friction coefficient, (2) lateral eddy viscosity , (3) land cover effects on winds (also referred to as

Bi-Directional Reflectance Measurements of the Ocean Bottom

DTIC Science & Technology

2001-09-30

waters”, 1998, Limnol. and Ocean., 43: 1198 - 1206. K J. Voss, W. M. Balch, K. A. Kilpatrick, "Scattering and attenuation properties of Emiliania ... huxleyi cells and their detached coccoliths", 1998, Limnol. and Ocean., 43: 870-876. J. S. Bartlett, K. J. Voss, S. Sathyendranath, and A. Vodacek

Estimation of Nitrogen Vertical Distribution by Bi-Directional Canopy Reflectance in Winter Wheat

PubMed Central

Huang, Wenjiang; Yang, Qinying; Pu, Ruiliang; Yang, Shaoyuan

2014-01-01

Timely measurement of vertical foliage nitrogen distribution is critical for increasing crop yield and reducing environmental impact. In this study, a novel method with partial least square regression (PLSR) and vegetation indices was developed to determine optimal models for extracting vertical foliage nitrogen distribution of winter wheat by using bi-directional reflectance distribution function (BRDF) data. The BRDF data were collected from ground-based hyperspectral reflectance measurements recorded at the Xiaotangshan Precision Agriculture Experimental Base in 2003, 2004 and 2007. The view zenith angles (1) at nadir, 40° and 50°; (2) at nadir, 30° and 40°; and (3) at nadir, 20° and 30° were selected as optical view angles to estimate foliage nitrogen density (FND) at an upper, middle and bottom layer, respectively. For each layer, three optimal PLSR analysis models with FND as a dependent variable and two vegetation indices (nitrogen reflectance index (NRI), normalized pigment chlorophyll index (NPCI) or a combination of NRI and NPCI) at corresponding angles as explanatory variables were established. The experimental results from an independent model verification demonstrated that the PLSR analysis models with the combination of NRI and NPCI as the explanatory variables were the most accurate in estimating FND for each layer. The coefficients of determination (R2) of this model between upper layer-, middle layer- and bottom layer-derived and laboratory-measured foliage nitrogen density were 0.7335, 0.7336, 0.6746, respectively. PMID:25353983

Predictive models of turbidity and water depth in the Doñana marshes using Landsat TM and ETM+ images.

PubMed

Bustamante, Javier; Pacios, Fernando; Díaz-Delgado, Ricardo; Aragonés, David

2009-05-01

We have used Landsat-5 TM and Landsat-7 ETM+ images together with simultaneous ground-truth data at sample points in the Doñana marshes to predict water turbidity and depth from band reflectance using Generalized Additive Models. We have point samples for 12 different dates simultaneous with 7 Landsat-5 and 5 Landsat-7 overpasses. The best model for water turbidity in the marsh explained 38% of variance in ground-truth data and included as predictors band 3 (630-690 nm), band 5 (1550-1750 nm) and the ratio between bands 1 (450-520 nm) and 4 (760-900 nm). Water turbidity is easier to predict for water bodies like the Guadalquivir River and artificial ponds that are deep and not affected by bottom soil reflectance and aquatic vegetation. For the latter, a simple model using band 3 reflectance explains 78.6% of the variance. Water depth is easier to predict than turbidity. The best model for water depth in the marsh explains 78% of the variance and includes as predictors band 1, band 5, the ratio between band 2 (520-600 nm) and band 4, and bottom soil reflectance in band 4 in September, when the marsh is dry. The water turbidity and water depth models have been developed in order to reconstruct historical changes in Doñana wetlands during the last 30 years using the Landsat satellite images time series.

Estimation of nitrogen vertical distribution by bi-directional canopy reflectance in winter wheat.

PubMed

Huang, Wenjiang; Yang, Qinying; Pu, Ruiliang; Yang, Shaoyuan

2014-10-28

Timely measurement of vertical foliage nitrogen distribution is critical for increasing crop yield and reducing environmental impact. In this study, a novel method with partial least square regression (PLSR) and vegetation indices was developed to determine optimal models for extracting vertical foliage nitrogen distribution of winter wheat by using bi-directional reflectance distribution function (BRDF) data. The BRDF data were collected from ground-based hyperspectral reflectance measurements recorded at the Xiaotangshan Precision Agriculture Experimental Base in 2003, 2004 and 2007. The view zenith angles (1) at nadir, 40° and 50°; (2) at nadir, 30° and 40°; and (3) at nadir, 20° and 30° were selected as optical view angles to estimate foliage nitrogen density (FND) at an upper, middle and bottom layer, respectively. For each layer, three optimal PLSR analysis models with FND as a dependent variable and two vegetation indices (nitrogen reflectance index (NRI), normalized pigment chlorophyll index (NPCI) or a combination of NRI and NPCI) at corresponding angles as explanatory variables were established. The experimental results from an independent model verification demonstrated that the PLSR analysis models with the combination of NRI and NPCI as the explanatory variables were the most accurate in estimating FND for each layer. The coefficients of determination (R2) of this model between upper layer-, middle layer- and bottom layer-derived and laboratory-measured foliage nitrogen density were 0.7335, 0.7336, 0.6746, respectively.

LAGRANGIAN MODELING OF A SUSPENDED-SEDIMENT PULSE.

USGS Publications Warehouse

Schoellhamer, David H.

1987-01-01

The one-dimensional Lagrangian Transport Model (LTM) has been applied in a quasi two-dimensional manner to simulate the transport of a slug injection of microbeads in steady experimental flows. A stationary bed segment was positioned below each parcel location to simulate temporary storage of beads on the bottom of the flume. Only one degree of freedom was available for all three bead simulations. The results show the versatility of the LTM and the ability of the LTM to accurately simulate transport of fine suspended sediment.

Sensitivity analysis of 1-D dynamical model for basin analysis

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

Cao, S.

1987-01-01

Geological processes related to petroleum generation, migration and accumulation are very complicated in terms of time and variables involved, and it is very difficult to simulate these processes by laboratory experiments. For this reasons, many mathematic/computer models have been developed to simulate these geological processes based on geological, geophysical and geochemical principles. The sensitivity analysis in this study is a comprehensive examination on how geological, geophysical and geochemical parameters influence the reconstructions of geohistory, thermal history and hydrocarbon generation history using the 1-D fluid flow/compaction model developed in the Basin Modeling Group at the University of South Carolina. This studymore » shows the effects of some commonly used parameter such as depth, age, lithology, porosity, permeability, unconformity (eroded thickness and erosion time), temperature at sediment surface, bottom hole temperature, present day heat flow, thermal gradient, thermal conductivity and kerogen type and content on the evolutions of formation thickness, porosity, permeability, pressure with time and depth, heat flow with time, temperature with time and depth, vitrinite reflectance (Ro) and TTI with time and depth, and oil window in terms of time and depth, amount of hydrocarbons generated with time and depth. Lithology, present day heat flow and thermal conductivity are the most sensitive parameters in the reconstruction of temperature history.« less

Event-Related Potentials of Bottom-Up and Top-Down Processing of Emotional Faces

PubMed Central

Moradi, Afsane; Mehrinejad, Seyed Abolghasem; Ghadiri, Mohammad; Rezaei, Farzin

2017-01-01

Introduction: Emotional stimulus is processed automatically in a bottom-up way or can be processed voluntarily in a top-down way. Imaging studies have indicated that bottom-up and top-down processing are mediated through different neural systems. However, temporal differentiation of top-down versus bottom-up processing of facial emotional expressions has remained to be clarified. The present study aimed to explore the time course of these processes as indexed by the emotion-specific P100 and late positive potential (LPP) event-related potential (ERP) components in a group of healthy women. Methods: Fourteen female students of Alzahra University, Tehran, Iran aged 18–30 years, voluntarily participated in the study. The subjects completed 2 overt and covert emotional tasks during ERP acquisition. Results: The results indicated that fearful expressions significantly produced greater P100 amplitude compared to other expressions. Moreover, the P100 findings showed an interaction between emotion and processing conditions. Further analysis indicated that within the overt condition, fearful expressions elicited more P100 amplitude compared to other emotional expressions. Also, overt conditions created significantly more LPP latencies and amplitudes compared to covert conditions. Conclusion: Based on the results, early perceptual processing of fearful face expressions is enhanced in top-down way compared to bottom-up way. It also suggests that P100 may reflect an attentional bias toward fearful emotions. However, no such differentiation was observed within later processing stages of face expressions, as indexed by the ERP LPP component, in a top-down versus bottom-up way. Overall, this study provides a basis for further exploring of bottom-up and top-down processes underlying emotion and may be typically helpful for investigating the temporal characteristics associated with impaired emotional processing in psychiatric disorders. PMID:28446947

Simulation of air velocity in a vertical perforated air distributor

NASA Astrophysics Data System (ADS)

Ngu, T. N. W.; Chu, C. M.; Janaun, J. A.

2016-06-01

Perforated pipes are utilized to divide a fluid flow into several smaller streams. Uniform flow distribution requirement is of great concern in engineering applications because it has significant influence on the performance of fluidic devices. For industrial applications, it is crucial to provide a uniform velocity distribution through orifices. In this research, flow distribution patterns of a closed-end multiple outlet pipe standing vertically for air delivery in the horizontal direction was simulated. Computational Fluid Dynamics (CFD), a tool of research for enhancing and understanding design was used as the simulator and the drawing software SolidWorks was used for geometry setup. The main purpose of this work is to establish the influence of size of orifices, intervals between outlets, and the length of tube in order to attain uniformity of exit flows through a multi outlet perforated tube. However, due to the gravitational effect, the compactness of paddy increases gradually from top to bottom of dryer, uniform flow pattern was aimed for top orifices and larger flow for bottom orifices.

Tsunami Simulation Method Assimilating Ocean Bottom Pressure Data Near a Tsunami Source Region

NASA Astrophysics Data System (ADS)

Tanioka, Yuichiro

2018-02-01

A new method was developed to reproduce the tsunami height distribution in and around the source area, at a certain time, from a large number of ocean bottom pressure sensors, without information on an earthquake source. A dense cabled observation network called S-NET, which consists of 150 ocean bottom pressure sensors, was installed recently along a wide portion of the seafloor off Kanto, Tohoku, and Hokkaido in Japan. However, in the source area, the ocean bottom pressure sensors cannot observe directly an initial ocean surface displacement. Therefore, we developed the new method. The method was tested and functioned well for a synthetic tsunami from a simple rectangular fault with an ocean bottom pressure sensor network using 10 arc-min, or 20 km, intervals. For a test case that is more realistic, ocean bottom pressure sensors with 15 arc-min intervals along the north-south direction and sensors with 30 arc-min intervals along the east-west direction were used. In the test case, the method also functioned well enough to reproduce the tsunami height field in general. These results indicated that the method could be used for tsunami early warning by estimating the tsunami height field just after a great earthquake without the need for earthquake source information.

Vertical Cable Seismic Survey for SMS exploration

NASA Astrophysics Data System (ADS)

Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hotoshi; Mizohata, Shigeharu

2014-05-01

The Vertical Cable Seismic (VCS) survey is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by sea-surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. Because the VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed it for the SMS survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We have been developing the VCS survey system, including not only data acquisition hardware but data processing and analysis technique. We carried out several VCS surveys combining with surface towed source, deep towed source and ocean bottom source. The water depths of these surveys are from 100m up to 2100 m. Through these experiments, our VCS data acquisition system has been also completed. But the data processing techniques are still on the way. One of the most critical issues is the positioning in the water. The uncertainty in the positions of the source and of the hydrophones in water degraded the quality of subsurface image. GPS navigation system is available on sea surface, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging. We have developed a new approach to determine the positions in water using the travel time data from the source to VCS hydrophones. In 2013, we have carried out the second VCS survey using the surface-towed high-voltage sparker and ocean bottom source in the Izena Cauldron, which is one of the most promising SMS areas around Japan. The positions of ocean bottom source estimated by this method are consistent with the VCS field records. The VCS data with the sparker have been processed with 3D PSTM. It gives the very high resolution 3D volume deeper than two hundred meters. Our VCS system has been demonstrated as a promising survey tool for the SMS exploration.

Geophysical Inversion with Adaptive Array Processing of Ambient Noise

NASA Astrophysics Data System (ADS)

Traer, James

2011-12-01

Land-based seismic observations of microseisms generated during Tropical Storms Ernesto and Florence are dominated by signals in the 0.15--0.5Hz band. Data from seafloor hydrophones in shallow water (70m depth, 130 km off the New Jersey coast) show dominant signals in the gravity-wave frequency band, 0.02--0.18Hz and low amplitudes from 0.18--0.3Hz, suggesting significant opposing wave components necessary for DF microseism generation were negligible at the site. Both storms produced similar spectra, despite differing sizes, suggesting near-coastal shallow water as the dominant region for observed microseism generation. A mathematical explanation for a sign-inversion induced to the passive fathometer response by minimum variance distortionless response (MVDR) beamforming is presented. This shows that, in the region containing the bottom reflection, the MVDR fathometer response is identical to that obtained with conventional processing multiplied by a negative factor. A model is presented for the complete passive fathometer response to ocean surface noise, interfering discrete noise sources, and locally uncorrelated noise in an ideal waveguide. The leading order term of the ocean surface noise produces the cross-correlation of vertical multipaths and yields the depth of sub-bottom reflectors. Discrete noise incident on the array via multipaths give multiple peaks in the fathometer response. These peaks may obscure the sub-bottom reflections but can be attenuated with use of Minimum Variance Distortionless Response (MVDR) steering vectors. A theory is presented for the Signal-to-Noise-Ratio (SNR) for the seabed reflection peak in the passive fathometer response as a function of seabed depth, seabed reflection coefficient, averaging time, bandwidth and spatial directivity of the noise field. The passive fathometer algorithm was applied to data from two drifting array experiments in the Mediterranean, Boundary 2003 and 2004, with 0.34s of averaging time. In the 2004 experiment, the response showed the array depth varied periodically with an amplitude of 1 m and a period of 7 s consistent with wave driven motion of the array. This introduced a destructive interference which prevents the SNR growing with averaging time, unless the motion is removed by use of a peak tracker.

Linked hydro-thermo-chemo-microbiological processes within a cool hydrothermal circulation system in 18-24 M.y. old seafloor of the Cocos Plate

NASA Astrophysics Data System (ADS)

Fisher, A. T.; Wheat, C. G.; Lauer, R. M.; Villinger, H. W.; McManus, J.; Orcutt, B.

2017-12-01

We present results from surveys and studies of ridge-flank hydrothermal circulation in part of the Cocos Plate. Fluids flowing into and out of the crust in an area >104 km2 extract most of the lithospheric heat. Water moves in and out of the crust through a few mid-plate seamounts, which penetrate low-permeability sediments, and water flows laterally across tens of kilometers between seamounts. This kind of fluid circulation is common globally, extracting 20-25% of Earth's geothermal heat, but focused fluid discharge from these systems has not previously been found or sampled. Sites of discharge from this cool hydrothermal system (CHS) were found and sampled on Dorado Outcrop, a small volcanic edifice on 23 M.y. old seafloor, using deep-submergence vehicles. Seafloor measurements show that Dorado Outcrop is a local site of elevated geothermal heat flux, and temperatures recorded during outcrop surveys show a pattern of small bottom-water temperature anomalies (≤0.04°C, mainly above the central and southern part of the outcrop). Direct measurements of shimmering fluids discharging from patches of bare rock on Dorado Outcrop indicate temperatures up to 10.5°C warmer than bottom water, whereas heat flux and reflection seismic data show regional reaction temperatures in basement of 15-20 °C. Heat budget calculations and coupled fluid-heat simulations of regional circulation indicate that the net discharge from Dorado Outcrop is on the order of 1,000-5,000 L/s, and direct observations show that spring discharge rates vary with time, likely being modulated by ocean tides. Samples of Dorado Outcrop fluids have concentrations that are indistinguishable from bottom seawater for many major ions, but concentrations of minor and trace elements differ significantly, especially Mo, V, Rb, U, phosphate, Li, and silicate. In addition, CHS fluids discharging from Dorado Outcrop have about 50% of the dissolved oxygen (DO) found in bottom seawater, showing that DO is consumed as it flows through the crust. Analytical calculations show that diffusion alone, into overlying sediments, cannot explain the observed DO concentrations; we therefore infer that biotic and abiotic reactions within the volcanic crust consume oxygen.

Seismic Evidence for Fluid/Gas Beneath the Mentawai Fore-Arc Basin, Central Sumatra

NASA Astrophysics Data System (ADS)

Huot, Gabriel; Singh, Satish C.

2018-02-01

Since 2004, there have been three great interplate earthquakes (Mw > 8.0) offshore Sumatra. In addition to rupturing the megathrust, these earthquakes might also have ruptured the backthrusts that bound the Andaman Islands to the Mentawai Islands toward the forearc basins. Here we apply a combination of traveltime tomography and seismic full waveform inversion to an ultralong offset seismic reflection profile from the Mentawai forearc basin, in the region of the 2007 Mw 8.4 Bengkulu earthquake. We perform a waveform inversion of far-offset data followed by a waveform inversion of near-offset data using the starting model derived from the traveltime tomography. Our results show the presence of a large, low-velocity anomaly above the backthrust. The seismic reflection image indicates that this low-velocity anomaly lies either within highly compacted sediments from the accretionary wedge or within highly deformed sediments from the forearc basin. The porosity estimation, using the effective medium theory, suggests that a small amount of gas (from 2 to 13%) or a significant amount of fluid (from 17 to 40%) could generate this low-velocity zone. The presence of fluids and the observation of bottom simulating reflector below a push-up ridge might be associated with mud diapirism. The fluids could originate locally from the dewatering of the sediments from the accretionary wedge or forearc basin. The high reflectivity of the backthrust in this region might also indicate deeper fluid origin, either from underplated sediments on the subduction interface or from the serpentinized mantle wedge.

InxAl1-xN chiral nanorods mimicking the polarization features of scarab beetles

NASA Astrophysics Data System (ADS)

Magnusson, R.; Birch, J.; Hsiao, C.-L.; Sandström, P.; Arwin, H.; Järrendahl, K.

2015-03-01

The scarab beetle Cetonia aurata is known to reflect light with brilliant colors and a high degree of circular polarization. Both color and polarization effects originate from the beetles exoskeleton and have been attributed to a Bragg reflection of the incident light due to a twisted laminar structure. Our strategy for mimicking the optical properties of the Cetonia aurata was therefore to design and fabricate transparent, chiral films. A series of films with tailored transparent structures of helicoidal InxAl1-xN nanorods were grown on sapphire substrates using UHV magnetron sputtering. The value of x is tailored to gradually decrease from one side to the other in each nanorod normal to its growth direction. This introduces an in-plane anisotropy with different refractive indices in the direction of the gradient and perpendicular to it. By rotating the sample during film growth the in-plane optical axis will be rotated from bottom to top and thereby creating a chiral film. Based on Muellermatrix ellipsometry, optical modeling has been done suggesting that both the exoskeleton of Cetonia aurata and our artificial material can be modeled by an anisotropic film made up of a stack of thin layers, each one with its in-plane optical axis slightly rotated with respect to the previous layer. Simulations based on the optical modeling were used to investigate how pitch and thickness of the film together with the optical properties of the constitutive materials affects the width and spectral position of the Bragg reflection band.

A Systematic Review of Agent-Based Modelling and Simulation Applications in the Higher Education Domain

ERIC Educational Resources Information Center

Gu, X.; Blackmore, K. L.

2015-01-01

This paper presents the results of a systematic review of agent-based modelling and simulation (ABMS) applications in the higher education (HE) domain. Agent-based modelling is a "bottom-up" modelling paradigm in which system-level behaviour (macro) is modelled through the behaviour of individual local-level agent interactions (micro).…

Numerical simulation of multi-directional random wave transformation in a yacht port

NASA Astrophysics Data System (ADS)

Ji, Qiaoling; Dong, Sheng; Zhao, Xizeng; Zhang, Guowei

2012-09-01

This paper extends a prediction model for multi-directional random wave transformation based on an energy balance equation by Mase with the consideration of wave shoaling, refraction, diffraction, reflection and breaking. This numerical model is improved by 1) introducing Wen's frequency spectrum and Mitsuyasu's directional function, which are more suitable to the coastal area of China; 2) considering energy dissipation caused by bottom friction, which ensures more accurate results for large-scale and shallow water areas; 3) taking into account a non-linear dispersion relation. Predictions using the extended wave model are carried out to study the feasibility of constructing the Ai Hua yacht port in Qingdao, China, with a comparison between two port layouts in design. Wave fields inside the port for different incident wave directions, water levels and return periods are simulated, and then two kinds of parameters are calculated to evaluate the wave conditions for the two layouts. Analyses show that Layout I is better than Layout II. Calculation results also show that the harbor will be calm for different wave directions under the design water level. On the contrary, the wave conditions do not wholly meet the requirements of a yacht port for ship berthing under the extreme water level. For safety consideration, the elevation of the breakwater might need to be properly increased to prevent wave overtopping under such water level. The extended numerical simulation model may provide an effective approach to computing wave heights in a harbor.

[Simulation on remediation of benzene contaminated groundwater by air sparging].

PubMed

Fan, Yan-Ling; Jiang, Lin; Zhang, Dan; Zhong, Mao-Sheng; Jia, Xiao-Yang

2012-11-01

Air sparging (AS) is one of the in situ remedial technologies which are used in groundwater remediation for pollutions with volatile organic compounds (VOCs). At present, the field design of air sparging system was mainly based on experience due to the lack of field data. In order to obtain rational design parameters, the TMVOC module in the Petrasim software package, combined with field test results on a coking plant in Beijing, is used to optimize the design parameters and simulate the remediation process. The pilot test showed that the optimal injection rate was 23.2 m3 x h(-1), while the optimal radius of influence (ROI) was 5 m. The simulation results revealed that the pressure response simulated by the model matched well with the field test results, which indicated a good representation of the simulation. The optimization results indicated that the optimal injection location was at the bottom of the aquifer. Furthermore, simulated at the optimized injection location, the optimal injection rate was 20 m3 x h(-1), which was in accordance with the field test result. Besides, 3 m was the optimal ROI, less than the field test results, and the main reason was that field test reflected the flow behavior at the upper space of groundwater and unsaturated area, in which the width of flow increased rapidly, and became bigger than the actual one. With the above optimized operation parameters, in addition to the hydro-geological parameters measured on site, the model simulation result revealed that 90 days were needed to remediate the benzene from 371 000 microg x L(-1) to 1 microg x L(-1) for the site, and that the opeation model in which the injection wells were progressively turned off once the groundwater around them was "clean" was better than the one in which all the wells were kept operating throughout the remediation process.

Long-term simulation of vertical transport process and its impact on bottom DO in Chesapeake Bay

NASA Astrophysics Data System (ADS)

Du, J.; Shen, J.

2016-02-01

Hypoxia in coastal waters is a widespread phenomenon that appears to have been growing globally for at least 60 years. The fact that physical transport processes and biological processes are equally important in determining the bottom DO in Chesapeake Bay is commonly agreed. However, the quantitative impact of physical transport processes is rarely documented. In this study, we use a timescale, vertical exchange time (VET), to quantify the impact of all physical processes that might have on the bottom DO. Simulation of VET from 1985 to 2012 is conducted and the monthly observed DO data along the deep channel in the Bay's main stem is collected. A conceptual bottom DO budget model is applied, using the VET to quantify the physical condition and net oxygen consumption rate to quantify biological activities. The DO budget model results show that the interannual variations of physical conditions accounts for 88.8% of the interannual variations of observed DO. The high similarity between the VET spatial pattern and the observed DO suggests that physical processes play a key role in regulating the DO condition. Model results also show that long-term VET has a slight increase in summer, but no statistically significant trend is found. Correlations among southerly wind strength, North Atlantic Oscillation index, and VET demonstrate that the physical condition in the Chesapeake Bay is highly controlled by the large-scale climate variation. The relationship is most significant during the summer, when the southerly wind dominates throughout the Chesapeake Bay.

Lapped substrate for enhanced backsurface reflectivity in a thermophotovoltaic energy conversion system

DOEpatents

Baldasaro, Paul F; Brown, Edward J; Charache, Greg W; DePoy, David M

2000-01-01

A method for fabricating a thermophotovoltaic energy conversion cell including a thin semiconductor wafer substrate (10) having a thickness (.beta.) calculated to decrease the free carrier absorption on a heavily doped substrate; wherein the top surface of the semiconductor wafer substrate is provided with a thermophotovoltaic device (11), a metallized grid (12) and optionally an antireflective (AR) overcoating; and, the bottom surface (10') of the semiconductor wafer substrate (10) is provided with a highly reflecting coating which may comprise a metal coating (14) or a combined dielectric/metal coating (17).

Lapped substrate for enhanced backsurface reflectivity in a thermophotovoltaic energy conversion system

DOEpatents

Baldasaro, Paul F; Brown, Edward J; Charache, Greg W; DePoy, David M

2000-09-05

A method for fabricating a thermophotovoltaic energy conversion cell including a thin semiconductor wafer substrate (10) having a thickness (.beta.) calculated to decrease the free carrier absorption on a heavily doped substrate; wherein the top surface of the semiconductor wafer substrate is provided with a thermophotovoltaic device (11), a metallized grid (12) and optionally an antireflective (AR) overcoating; and, the bottom surface (10') of the semiconductor wafer substrate (10) is provided with a highly reflecting coating which may comprise a metal coating (14) or a combined dielectric/metal coating (17).

Optical roughness BRDF model for reverse Monte Carlo simulation of real material thermal radiation transfer.

PubMed

Su, Peiran; Eri, Qitai; Wang, Qiang

2014-04-10

Optical roughness was introduced into the bidirectional reflectance distribution function (BRDF) model to simulate the reflectance characteristics of thermal radiation. The optical roughness BRDF model stemmed from the influence of surface roughness and wavelength on the ray reflectance calculation. This model was adopted to simulate real metal emissivity. The reverse Monte Carlo method was used to display the distribution of reflectance rays. The numerical simulations showed that the optical roughness BRDF model can calculate the wavelength effect on emissivity and simulate the real metal emissivity variance with incidence angles.

Comparison of entrainment in constant volume and constant flux dense currents over sloping bottoms

NASA Astrophysics Data System (ADS)

Bhaganagar, K.; Nayamatullah, M.; Cenedese, C.

2014-12-01

Three dimensional high resolution large eddy simulations (LES) are employed to simulate lock-exchange and constant flux dense flows over inclined surface with the aim of investigating, visualizing and describing the turbulent structure and the evolution of bottom-propagating compositional density current at the channel bottom. The understanding of dynamics of density current is largely determined by the amount of interfacial mixing or entrainment between the ambient and dense fluids. No previous experimental or numerical studies have been done to estimate entrainment in classical lock-exchange system. The differences in entrainment between the lock-exchange and constant flux are explored. Comparing the results of flat bed with inclined surface results, flow exhibits significant differences near the leading edge or nose of the front of the density currents due to inclination of surface. Further, the instabilities are remarkably enhanced resulting Kelvin-Helmholtz and lobe-cleft type of instabilities arises much earlier in time. In this study, a brief analysis of entrainment on lock-exchange density current is presented using different bed slopes and a set of reduced gravity values (g'). We relate the entrainment value with different flow parameters such as Froude number (Fr) and Reynolds number (Re).

Alpha power increases in right parietal cortex reflects focused internal attention

PubMed Central

Benedek, Mathias; Schickel, Rainer J.; Jauk, Emanuel; Fink, Andreas; Neubauer, Aljoscha C.

2014-01-01

This study investigated the functional significance of EEG alpha power increases, a finding that is consistently observed in various memory tasks and specifically during divergent thinking. It was previously shown that alpha power is increased when tasks are performed in mind—e.g., when bottom-up processing is prevented. This study aimed to examine the effect of task-immanent differences in bottom-up processing demands by comparing two divergent thinking tasks, one intrinsically relying on bottom-up processing (sensory-intake task) and one that is not (sensory-independence task). In both tasks, stimuli were masked in half of the trials to establish conditions of higher and lower internal processing demands. In line with the hypotheses, internal processing affected performance and led to increases in alpha power only in the sensory-intake task, whereas the sensory-independence task showed high levels of task-related alpha power in both conditions. Interestingly, conditions involving focused internal attention showed a clear lateralization with higher alpha power in parietal regions of the right hemisphere. Considering evidence from fMRI studies, right-parietal alpha power increases may correspond to a deactivation of the right temporoparietal junction, reflecting an inhibition of the ventral attention network. Inhibition of this region is thought to prevent reorienting to irrelevant stimulation during goal-driven, top-down behavior, which may serve the executive function of task shielding during demanding cognitive tasks such as idea generation and mental imagery. PMID:24561034

Identification of bedforms in lower cook inlet, Alaska

USGS Publications Warehouse

Bouma, A.H.; Rappeport, M.L.; Orlando, R.C.; Hampton, M.A.

1980-01-01

The seafloor of the central part of lower Cook Inlet, Alaska, is characterized by the presence of different sizes and types of bedforms. The bedforms in the sandy sediments include straight-crested to sinuous to lunate ripples, small, medium, and large sand waves, sand ridges, sand ribbons, and sand patches. In addition, rocky and pebbly seafloor has been identified. The water depth ranges from 25 to 120 m, and surface currents average 3.8 kt (2 m/s). Bottom currents have been measured at as much as 42 cm/s at 1 m above bottom. Underwater television observations have shown that the rate of sand transport is lower than expected because small amounts of clay and organic matter appear to inhibit remobilization. Only during the last 1 to 2 h of ebb and flood stages of spring tides, and during storms, does significant transport occur. Comparison of data from high-resolution seismic profiling systems, side-scan sonar, bottom television and camera, and bottom sampling shows that bottom and bedform interpretations based solely on sonographs can be in error. Measuring the length of 'acoustic shadows' on sonographs to obtain bedform heights gives dimensions that are too large by factors of 3-7. Bottom television investigations revealed that the troughs between small sand waves are flat and carpeted by shell fragments. Such coarse material has a high acoustic reflectance that is not related to slope or height and can lead to false interpretations on bedform dimensions. Our observations have shown that small sand waves commonly superimposed on larger ones are slightly higher than those present on flat hard bottom but are still less than calculated from acoustic shadows. Where the bottom is rather smooth or contains elevations small enough to be masked by bathymetric 'noise' caused by the pitching of the vessel, sonographs typically show either small sand waves, sand ribbons, sand patches, rocks, or smooth bottom. The smooth-bottom category can vary widely from ripples to gravelly or shelly or to small rocks with biological overgrowth as verified by television observations. Our observations have clearly demonstrated the need for an integrated multi-scale observation and sampling program in order to classify the bottom characteristics and to provide quantitative data for transport calculations. ?? 1980.

Dissociable Effects of Aging and Mild Cognitive Impairment on Bottom-Up Audiovisual Integration.

PubMed

Festa, Elena K; Katz, Andrew P; Ott, Brian R; Tremont, Geoffrey; Heindel, William C

2017-01-01

Effective audiovisual sensory integration involves dynamic changes in functional connectivity between superior temporal sulcus and primary sensory areas. This study examined whether disrupted connectivity in early Alzheimer's disease (AD) produces impaired audiovisual integration under conditions requiring greater corticocortical interactions. Audiovisual speech integration was examined in healthy young adult controls (YC), healthy elderly controls (EC), and patients with amnestic mild cognitive impairment (MCI) using McGurk-type stimuli (providing either congruent or incongruent audiovisual speech information) under conditions differing in the strength of bottom-up support and the degree of top-down lexical asymmetry. All groups accurately identified auditory speech under congruent audiovisual conditions, and displayed high levels of visual bias under strong bottom-up incongruent conditions. Under weak bottom-up incongruent conditions, however, EC and amnestic MCI groups displayed opposite patterns of performance, with enhanced visual bias in the EC group and reduced visual bias in the MCI group relative to the YC group. Moreover, there was no overlap between the EC and MCI groups in individual visual bias scores reflecting the change in audiovisual integration from the strong to the weak stimulus conditions. Top-down lexicality influences on visual biasing were observed only in the MCI patients under weaker bottom-up conditions. Results support a deficit in bottom-up audiovisual integration in early AD attributable to disruptions in corticocortical connectivity. Given that this deficit is not simply an exacerbation of changes associated with healthy aging, tests of audiovisual speech integration may serve as sensitive and specific markers of the earliest cognitive change associated with AD.

Radiometry simulation within the end-to-end simulation tool SENSOR

NASA Astrophysics Data System (ADS)

Wiest, Lorenz; Boerner, Anko

2001-02-01

12 An end-to-end simulation is a valuable tool for sensor system design, development, optimization, testing, and calibration. This contribution describes the radiometry module of the end-to-end simulation tool SENSOR. It features MODTRAN 4.0-based look up tables in conjunction with a cache-based multilinear interpolation algorithm to speed up radiometry calculations. It employs a linear reflectance parameterization to reduce look up table size, considers effects due to the topology of a digital elevation model (surface slope, sky view factor) and uses a reflectance class feature map to assign Lambertian and BRDF reflectance properties to the digital elevation model. The overall consistency of the radiometry part is demonstrated by good agreement between ATCOR 4-retrieved reflectance spectra of a simulated digital image cube and the original reflectance spectra used to simulate this image data cube.

Sound absorption coefficient of coal bottom ash concrete for railway application

NASA Astrophysics Data System (ADS)

Ramzi Hannan, N. I. R.; Shahidan, S.; Maarof, Z.; Ali, N.; Abdullah, S. R.; Ibrahim, M. H. Wan

2017-11-01

A porous concrete able to reduce the sound wave that pass through it. When a sound waves strike a material, a portion of the sound energy was reflected back and another portion of the sound energy was absorbed by the material while the rest was transmitted. The larger portion of the sound wave being absorbed, the lower the noise level able to be lowered. This study is to investigate the sound absorption coefficient of coal bottom ash (CBA) concrete compared to the sound absorption coefficient of normal concrete by carried out the impedance tube test. Hence, this paper presents the result of the impedance tube test of the CBA concrete and normal concrete.

Measuring Zonal Transport Variability of the Antarctic Circumpolar Current Using GRACE Ocean Bottom Pressure

NASA Astrophysics Data System (ADS)

Makowski, J.; Chambers, D. P.; Bonin, J. A.

2012-12-01

Previous studies have suggested that ocean bottom pressure (OBP) can be used to measure the transport variability of the Antarctic Circumpolar Current (ACC). Using OBP data from the JPL ECCO model and the Gravity Recovery and Climate Experiment (GRACE), we examine the zonal transport variability of the ACC integrated between the major fronts between 2003-2010. The JPL ECCO data are used to determine average front positions for the time period studies, as well as where transport is mainly zonal. Statistical analysis will be conducted to determine the uncertainty of the GRACE observations using a simulated data set. We will also begin looking at low frequency changes and how coherent transport variability is from region to region of the ACC. Correlations with bottom pressure south of the ACC and the average basin transports will also be calculated to determine the probability of using bottom pressure south of the ACC as a means for describing the ACC dynamics and transport.

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.

Evaluating visibility of age spot and freckle based on simulated spectral reflectance distribution and facial color image

NASA Astrophysics Data System (ADS)

Hirose, Misa; Toyota, Saori; Tsumura, Norimichi

2018-02-01

In this research, we evaluate the visibility of age spot and freckle with changing the blood volume based on simulated spectral reflectance distribution and the actual facial color images, and compare these results. First, we generate three types of spatial distribution of age spot and freckle in patch-like images based on the simulated spectral reflectance. The spectral reflectance is simulated using Monte Carlo simulation of light transport in multi-layered tissue. Next, we reconstruct the facial color image with changing the blood volume. We acquire the concentration distribution of melanin, hemoglobin and shading components by applying the independent component analysis on a facial color image. We reproduce images using the obtained melanin and shading concentration and the changed hemoglobin concentration. Finally, we evaluate the visibility of pigmentations using simulated spectral reflectance distribution and facial color images. In the result of simulated spectral reflectance distribution, we found that the visibility became lower as the blood volume increases. However, we can see that a specific blood volume reduces the visibility of the actual pigmentations from the result of the facial color images.

Nursing students' perceptions of learning after high fidelity simulation: Effects of a Three-step Post-simulation Reflection Model.

PubMed

Lestander, Örjan; Lehto, Niklas; Engström, Åsa

2016-05-01

High-fidelity simulation (HFS) has become a bridge between theoretical knowledge and practical skills. A safe and realistic environment is commonly used in nursing education to improve cognitive, affective and psychomotor abilities. Debriefing following a simulation experience provides opportunities for students to analyze and begin to reflect upon their decisions, actions and results. The nursing literature highlights the need to promote the concept of reflective practice and to assist students in reflection, and research indicates the need to refine and develop debriefing strategies, which is the focus of the current paper. To explore the value of reflections after HFS by investigating nursing students' perceptions of their learning when a Three-step Post-simulation Reflection Model is used. A qualitative descriptive research approach was applied. A Three-step Post-simulation Reflection Model that combined written and verbal reflections was used after an HFS experience in a second-year course in the Bachelor Program in Nursing at Luleå University of Technology, Sweden. Reflective texts written before and after a verbal group reflection were subjected to qualitative content analysis. The main theme in the first written reflections was identified as "Starting to act as a nurse", with the following categories: feeling stressed, inadequate and inexperienced; developing an awareness of the importance of never compromising patient safety; planning the work and prioritizing; and beginning to understand and implement nursing knowledge. The main theme in the second written reflections was identified to be "Maturing in the profession", with the following categories: appreciating colleagues, good communication and thoughtfulness; gaining increased self-awareness and confidence; and beginning to understand the profession. The Three-step Post-simulation Reflection Model fostered an appreciation of clear and effective communication. Having time for thoughtfulness and reflection promotes self-awareness and a better understanding of both the nursing profession and patient safety. The progress demonstrated in the depth of the themes in the written reflections indicates that repeated reflections stimulate and enhance student learning. The findings point towards the potential effectiveness of alternate methods of reflections. Copyright © 2016 Elsevier Ltd. All rights reserved.

Measurement of the Solar Absorptance and Thermal Emittance of Lunar Simulants

NASA Technical Reports Server (NTRS)

Gaier, James R.; Street, Kenneth W.; Gutafson, Robert J.

2010-01-01

The first comparative study of the reflectance spectra of lunar simulants is presented. All of the simulants except one had a wavelength-dependant reflectivity ( ( )) near 0.10 over the wavelength range of 8 to 25 m, so they are highly emitting at room temperature and lower. The 300 K emittance ( ) of all the lunar simulants except one ranged from 0.884 to 0.906. The 300 K of JSC Mars-1 simulant was 0.927. There was considerably more variation in the lunar simulant reflectance in the solar spectral range (250 to 2500 nm) than in the thermal infrared. Larger particle size simulants reflected much less than those with smaller particle size. As expected, the lunar highlands simulants were more reflective in this wavelength range than the lunar mare simulants. The integrated solar absorptance ( ) of the simulants ranged from 0.413 to 0.817 for those with smaller particles, and 0.669 to 0.906 for those with larger particles. Although spectral differences were observed, the for the simulants appears to be similar to that of lunar soils (0.65 to 0.88). These data are now available to be used in modeling the effects of dust on thermal control surfaces.

Measurement of the Solar Absorptance and Thermal Emittance of Lunar Simulants

NASA Technical Reports Server (NTRS)

Gaier, James R.; Street, Kenneth W.; Gustafson, Robert J.

2010-01-01

The first comparative study of the reflectance spectra of lunar simulants is presented. All of the simulants except one had a wavelength-dependent reflectivity, rho(lambda), near 0.10 over the wavelength range of 8 to 25 microns, so they are highly emitting at room temperature and lower. The 300 K emittance, epsilon, of all the lunar simulants except one ranged from 0.884 to 0.906. The 300 K epsilon of JSC Mars-1 simulant was 0.927. There was considerably more variation in the lunar simulant reflectance in the solar spectral range (250 to 2500 nm) than in the thermal infrared. Larger particle size simulants reflected much less than those with smaller particle size. As expected, the lunar highlands simulants were more reflective in this wavelength range than the lunar mare simulants. The alpha of the simulants ranged from 0.413 to 0.817 for those with smaller particles and 0.669 to 0.906 for large particles. Although spectral differences were observed, the total integrated alpha for the simulants appears to be similar to that of lunar soils (0.65 to 0.88). These data are now available to be used in modeling the effects of dust on thermal control surfaces.

Modeling biogenic gas bubbles formation and migration in coarse sand

NASA Astrophysics Data System (ADS)

Ye, S.

2011-12-01

Shujun Ye Department of Hydrosciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China; sjye@nju.edu.cn Brent E. Sleep Department of Civil Engineering, University of Toronto, Toronto, ON, M5S 1A4 CANADA; sleep@ecf.utoronto.ca Methane gas generation in porous media was investigated in an anaerobic two-dimensional sand-filled cell. Inoculation of the lower portion of the cell with a methanogenic culture and addition of methanol to the bottom of the cell led to biomass growth and formation of a gas phase. The formation, migration, distribution and saturation of gases in the cell were visualized by the charge-coupled device (CCD) camera. Gas generated at the bottom of the cell in the biologically active zone moved upwards in discrete fingers, so that gas phase saturations (gas-filled fraction of void space) in the biologically active zone at the bottom of the cell did not exceed 40-50%, while gas accumulation at the top of the cell produced gas phase saturations as high as 80%. Macroscopic invasion percolation (MIP) at near pore scale[Glass, et al., 2001; Kueper and McWhorter, 1992]was used to model gas bubbles growth in porous media. The nonwetting phase migration pathway can be yielded directly by MIP. MIP was adopted to simulate the expansion, fragmentation, and mobilization of gas clusters in the cell. The production of gas, and gas phash saturations were simulated by a continuum model - compositional simulator (COMPSIM) [Sleep and Sykes, 1993]. So a combination of a continuum model and a MIP model was used to simulate the formation, fragmentation and migration of biogenic gas bubbles. Key words: biogenic gas; two dimensional; porous media; MIP; COMPSIM

Characteristics of Wind Generated Waves in the Delaware Estuary

NASA Astrophysics Data System (ADS)

Chen, J. L.; Ralston, D. K.; Geyer, W. R.; Chant, R. J.; Sommerfield, C. K.

2016-02-01

Coastal marshes provide important services for human uses such as fishery industry, recreation, ports and marine operations. Bombay Hook Wildlife Refuge, located along the western shore of the Delaware Estuary, has experienced substantial loss of salt marsh in recent decades. To evaluate the importance of different mechanisms which cause observed shoreline retreat, wave gauges were deployed along the dredged navigation channel and shoreline in the Delaware Estuary. A coupled wave and circulation modeling system (SWAN/ROMS) based on the most recent bathymetry (last updated 2013) is validated with waves observed during both calm and energetic conditions in November 2015. Simulation results based on different model parameterizations of whitecapping, bottom friction and the wind input source are compared. The tendency of observed wave steepness is more similar to a revised whitecapping source term [Westhuysen, 2007] than the default in SWAN model. Both model results and field data show that the generation/dissipation of waves in the Delaware estuary is determined by the local wind speed and channel depth. Whitecapping-induced energy dissipation is dominant in the channel, while dissipation due to bottom friction and depth-induced breaking become important on lateral shoals. To characterize the effects of wind fetch on waves in estuaries more generally, simulations with an idealized domain and varying wind conditions are compared and the results are expressed in terms of non-dimensional parameters. The simulations based on a 10m-depth uniform idealized channel show that the dissipation of waves is mainly controlled by whitecapping in all wind conditions. Under strong wind conditions (wind speed >10m/s) the effect of bottom friction becomes important so the simulated wave heights are no longer linearly correlated with wind speed.

Budget Cuts and Educational Quality

ERIC Educational Resources Information Center

Capaldi, Elizabeth D.

2011-01-01

Public universities are not for-profit businesses with an easy-to-understand bottom line: their financial reports are not designed to convey information to the public fully or to reflect all the costs of teaching and research. Financial reports do track every dollar in accordance with the accounting rules required by auditors, but they do not…

Environmental Acoustical Modelling at Supreme Allied Commander, Atlantic, Anti-Submarine Warfare Research Center (SACLANTCEN),

DTIC Science & Technology

1979-11-01

the RAIBAC computer model. Journal Acoustical Society America 59, 1976: 31-38. 13. HASTRUP , O.F. Reflection of plane waves from a solid multilayered...damping bottom, SACLANTCEN TR-50. La Spezia, Italy, SACLANT ASW Research Centre, 1966. [AD 479 4371 14. HASTRUP , O.F. Impulse response of a layered

Contribution à l'étude d'une partie du bassin d'Essaouira (Maroc) par sismique réflexionContribution to part of the Essaouira Basin (Morocco) by seismic reflection

NASA Astrophysics Data System (ADS)

Jaffal, Mohammed; Kchikach, Azzouz; Lefort, Jean-Pierre; Hanich, Lahoucine

A large number of seismic reflection lines and boreholes have been carried out in the Essaouira Basin by the oil industry. The present study concentrates on the reinterpretation of these data in the restricted area of Khemis Meskala, in order to better characterise the structure of the Cretaceous aquiferous system. The reflector corresponding to the bottom of the Vraconian formation has been identified on the different seismic sections. This horizon, which marks the base of the aquiferous system, was first digitised on time migration sections and then converted to depth sections using a suitable linear velocity law. The isobath map of the bottom of the Vraconian resulting from this study images the 3D geometrical structure of this horizon and shows that it is slightly folded in domes and basins. This document will be useful for rationalising the future hydrogeological researches that will be undertaken in the Khemis Meskala area. To cite this article: M. Jaffal et al., C. R. Geoscience 334 (2002) 229-234.

Laboratory upwelled radiance and reflectance spectra of Kerr reservoir sediment waters

NASA Technical Reports Server (NTRS)

Witte, W. G.; Whitlock, C. H.; Morris, W. D.; Gurganus, E. A.

1982-01-01

Reflectance, chromaticity, and several other physical and chemical properties were measured for various water mixtures of bottom sediments taken from two sites at Kerr Reservoir, Virginia. Mixture concentrations ranged from 5 to 1000 ppm by weight of total suspended solids (TSS) in filtered deionized tap water. The two sets of radiance and reflectance spectra obtained were similar in shape and magnitude for comparable values of TSS. Upwelled reflectance was observed to be a nonlinear function of TSS with the degree of curvature a function of wavelength. Sediment from the downstream site contained a greater amount of particulate organic carbon than from the upstream site. No strong conclusions can be made regarding the effects of this difference on the radiance and reflectance spectra. Near-infrared wavelengths appear useful for measuring highly turbid water with concentrations up to 1000 ppm or more. Chromaticity characteristics do not appear useful for monitoring sediment loads above 150 ppm.

Passively Q-switched side pumped monolithic ring laser

NASA Technical Reports Server (NTRS)

Li, Steven X. (Inventor)

2012-01-01

Disclosed herein are systems and methods for generating a side-pumped passively Q-switched non-planar ring oscillator. The method introduces a laser into a cavity of a crystal, the cavity having a round-trip path formed by a reflection at a dielectrically coated front surface, a first internal reflection at a first side surface of the crystal at a non-orthogonal angle with the front, a second internal reflection at a top surface of the crystal, and a third internal reflection at a second side surface of the crystal at a non-orthogonal angle with the front. The method side pumps the laser at the top or bottom surface with a side pump diode array beam and generates an output laser emanating at a location on the front surface. The design can include additional internal reflections to increase interaction with the side pump. Waste heat may be removed by mounting the crystal to a heatsink.

Comparison of the magnitude and phase of the reflection coefficient from a smooth water/sand interface with elastic and poroelastic models

NASA Astrophysics Data System (ADS)

Isakson, Marcia; Camin, H. John; Canepa, Gaetano

2005-04-01

The reflection coefficient from a sand/water interface is an important parameter in modeling the acoustics of littoral environments. Many models have been advanced to describe the influence of the sediment parameters and interface roughness parameters on the reflection coefficient. In this study, the magnitude and phase of the reflection coefficient from 30 to 160 kHz is measured in a bistatic experiment on a smoothed water/sand interface at grazing angles from 5 to 75 degrees. The measured complex reflection coefficient is compared with the fluid model, the elastic model and poro-elastic models. Effects of rough surface scattering are investigated using the Bottom Response from Inhomogeneities and Surface using Small Slope Approximation (BoRIS-SSA). Spherical wave effects are modeled using plane wave decomposition. Models are considered for their ability to predict the measured results using realistic parameters. [Work supported by ONR, Ocean Acoustics.

Simulation With Debriefing and Guided Reflective Journaling to Stimulate Critical Thinking in Prelicensure Baccalaureate Degree Nursing Students.

PubMed

Padden-Denmead, Mary L; Scaffidi, Rose M; Kerley, Regina M; Farside, Amy Lee

2016-11-01

Simulation and guided reflective journaling have been identified as effective teaching and learning methods to develop critical thinking (CT) and clinical reasoning skills in nursing students. A descriptive correlational design was used to determine the relationship between CT and level of reflection using the Holistic Critical Thinking Skills Rubric (HCTSR) and the level of reflection on action assessment (LORAA), respectively, to evaluate 23 baccalaureate student-guided reflective journal entries after a simulation exercise with guided debriefing and after two subsequent clinical experiences. A statistically significant positive relationship (p < .01) was found between mean HCTSR and LORAA scores on all three journal entries, but no relationship to CT during simulation or on standardized test scores. The results also indicated support for use of the guided reflection after significant learning experiences. The LORAA and the HCTSR are effective measures of level of reflection and CT to evaluate learning from simulation and clinical experiences. [J Nurs Educ. 2016;55(11):645-650.]. Copyright 2016, SLACK Incorporated.

Vision-based gait impairment analysis for aided diagnosis.

PubMed

Ortells, Javier; Herrero-Ezquerro, María Trinidad; Mollineda, Ramón A

2018-02-12

Gait is a firsthand reflection of health condition. This belief has inspired recent research efforts to automate the analysis of pathological gait, in order to assist physicians in decision-making. However, most of these efforts rely on gait descriptions which are difficult to understand by humans, or on sensing technologies hardly available in ambulatory services. This paper proposes a number of semantic and normalized gait features computed from a single video acquired by a low-cost sensor. Far from being conventional spatio-temporal descriptors, features are aimed at quantifying gait impairment, such as gait asymmetry from several perspectives or falling risk. They were designed to be invariant to frame rate and image size, allowing cross-platform comparisons. Experiments were formulated in terms of two databases. A well-known general-purpose gait dataset is used to establish normal references for features, while a new database, introduced in this work, provides samples under eight different walking styles: one normal and seven impaired patterns. A number of statistical studies were carried out to prove the sensitivity of features at measuring the expected pathologies, providing enough evidence about their accuracy. Graphical Abstract Graphical abstract reflecting main contributions of the manuscript: at the top, a robust, semantic and easy-to-interpret feature set to describe impaired gait patterns; at the bottom, a new dataset consisting of video-recordings of a number of volunteers simulating different patterns of pathological gait, where features were statistically assessed.

An integrative top-down and bottom-up qualitative model construction framework for exploration of biochemical systems.

PubMed

Wu, Zujian; Pang, Wei; Coghill, George M

Computational modelling of biochemical systems based on top-down and bottom-up approaches has been well studied over the last decade. In this research, after illustrating how to generate atomic components by a set of given reactants and two user pre-defined component patterns, we propose an integrative top-down and bottom-up modelling approach for stepwise qualitative exploration of interactions among reactants in biochemical systems. Evolution strategy is applied to the top-down modelling approach to compose models, and simulated annealing is employed in the bottom-up modelling approach to explore potential interactions based on models constructed from the top-down modelling process. Both the top-down and bottom-up approaches support stepwise modular addition or subtraction for the model evolution. Experimental results indicate that our modelling approach is feasible to learn the relationships among biochemical reactants qualitatively. In addition, hidden reactants of the target biochemical system can be obtained by generating complex reactants in corresponding composed models. Moreover, qualitatively learned models with inferred reactants and alternative topologies can be used for further web-lab experimental investigations by biologists of interest, which may result in a better understanding of the system.

Turbidity distribution in the Atlantic Ocean

USGS Publications Warehouse

Eittreim, S.; Thorndike, E.M.; Sullivan, L.

1976-01-01

The regional coverage of Lamont nephelometer data in the North and South Atlantic can be used to map seawater turbidity at all depths. At the level of the clearest water, in the mid-depth regions, the turbidity distribution primarily reflects the pattern of productivity in the surface waters. This suggests that the 'background' turbidity level in the oceans is largely a function of biogenic fallout. The bottom waters of the western Atlantic generally exhibit large increases in turbidity. The most intense benthic nepheloid layers are in the southwestern Argentine basin and northern North American basin; the lowest bottom water turbidity in the western Atlantic is in the equatorial regions. Both the Argentine and North American basin bottom waters appear to derive their high turbidity largely from local resuspension of terrigenous input in these basins. In contrast to the west, the eastern Atlantic basins show very low turbidities with the exception of three regions: the Mediterranean outflow area, the Cape basin, and the West European basin. ?? 1976.

Bottom-up and top-down computations in word- and face-selective cortex

PubMed Central

Kay, Kendrick N; Yeatman, Jason D

2017-01-01

The ability to read a page of text or recognize a person's face depends on category-selective visual regions in ventral temporal cortex (VTC). To understand how these regions mediate word and face recognition, it is necessary to characterize how stimuli are represented and how this representation is used in the execution of a cognitive task. Here, we show that the response of a category-selective region in VTC can be computed as the degree to which the low-level properties of the stimulus match a category template. Moreover, we show that during execution of a task, the bottom-up representation is scaled by the intraparietal sulcus (IPS), and that the level of IPS engagement reflects the cognitive demands of the task. These results provide an account of neural processing in VTC in the form of a model that addresses both bottom-up and top-down effects and quantitatively predicts VTC responses. DOI: http://dx.doi.org/10.7554/eLife.22341.001 PMID:28226243

Numerical simulations of the stratified oceanic bottom boundary layer

NASA Astrophysics Data System (ADS)

Taylor, John R.

Numerical simulations are used to consider several problems relevant to the turbulent oceanic bottom boundary layer. In the first study, stratified open channel flow is considered with thermal boundary conditions chosen to approximate a shallow sea. Specifically, a constant heat flux is applied at the free surface and the lower wall is assumed to be adiabatic. When the surface heat flux is strong, turbulent upwellings of low speed fluid from near the lower wall are inhibited by the stable stratification. Subsequent studies consider a stratified bottom Ekman layer over a non-sloping lower wall. The influence of the free surface is removed by using an open boundary condition at the top of the computational domain. Particular attention is paid to the influence of the outer layer stratification on the boundary layer structure. When the density field is initialized with a linear profile, a turbulent mixed layer forms near the wall, which is separated from the outer layer by a strongly stable pycnocline. It is found that the bottom stress is not strongly affected by the outer layer stratification. However, stratification reduces turbulent transport to the outer layer and strongly limits the boundary layer height. The mean shear at the top of the boundary layer is enhanced when the outer layer is stratified, and this shear is strong enough to cause intermittent instabilities above the pycnocline. Turbulence-generated internal gravity waves are observed in the outer layer with a relatively narrow frequency range. An explanation for frequency content of these waves is proposed, starting with an observed broad-banded turbulent spectrum and invoking linear viscous decay to explain the preferential damping of low and high frequency waves. During the course of this work, an open-source computational fluid dynamics code has been developed with a number of advanced features including scalar advection, subgrid-scale models for large-eddy simulation, and distributed memory parallelism.

Design of teleoperation system with a force-reflecting real-time simulator

NASA Technical Reports Server (NTRS)

Hirata, Mitsunori; Sato, Yuichi; Nagashima, Fumio; Maruyama, Tsugito

1994-01-01

We developed a force-reflecting teleoperation system that uses a real-time graphic simulator. This system eliminates the effects of communication time delays in remote robot manipulation. The simulator provides the operator with predictive display and feedback of computed contact forces through a six-degree of freedom (6-DOF) master arm on a real-time basis. With this system, peg-in-hole tasks involving round-trip communication time delays of up to a few seconds were performed at three support levels: a real image alone, a predictive display with a real image, and a real-time graphic simulator with computed-contact-force reflection and a predictive display. The experimental results indicate the best teleoperation efficiency was achieved by using the force-reflecting simulator with two images. The shortest work time, lowest sensor maximum, and a 100 percent success rate were obtained. These results demonstrate the effectiveness of simulated-force-reflecting teleoperation efficiency.

Indirect effects of predators control herbivore richness and abundance in a benthic eelgrass (Zostera marina) mesograzer community.

PubMed

Amundrud, Sarah L; Srivastava, Diane S; O'Connor, Mary I

2015-07-01

Herbivore communities can be sensitive to changes in predator pressure (top-down effects) and resource availability (bottom-up effects) in a wide range of systems. However, it remains unclear whether such top-down and bottom-up effects reflect direct impacts of predators and/or resources on herbivores, or are indirect, reflecting altered interactions among herbivore species. We quantified direct and indirect effects of bottom-up and top-down processes on an eelgrass (Zostera marina) herbivore assemblage. In a field experiment, we factorially manipulated water column nutrients (with Osmocote(™) slow-release fertilizer) and predation pressure (with predator exclusion cages) and measured the effects on herbivore abundance, richness and beta diversity. We examined likely mechanisms of community responses by statistically exploring the response of individual herbivore species to trophic manipulations. Predators increased herbivore richness and total abundance, in both cases through indirect shifts in community composition. Increases in richness occurred through predator suppression of common gammarid amphipod species (Monocorophium acherusicum and Photis brevipes), permitting the inclusion of rarer gammarid species (Aoroides columbiae and Pontogeneia rostrata). Increased total herbivore abundance reflected increased abundance of a caprellid amphipod species (Caprella sp.), concurrent with declines in the abundance of other common species. Furthermore, predators decreased beta diversity by decreasing variability in Caprella sp. abundance among habitat patches. Osmocote(™) fertilization increased nutrient concentrations locally, but nutrients dissipated to background levels within 3 m of the fertilizer. Nutrient addition weakly affected the herbivore assemblage, not affecting richness and increasing total abundance by increasing one herbivore species (Caprella sp.). Nutrient addition did not affect beta diversity. We demonstrated that assemblage-level effects of trophic manipulations on community structure are the result of distinct and often indirect responses of herbivore species. These results underscore the importance of understanding herbivore-herbivore interactions in a system commonly subjected to both eutrophication and overfishing. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

A Decade Remote Sensing River Bathymetry with the Experimental Advanced Airborne Research LiDAR

NASA Astrophysics Data System (ADS)

Kinzel, P. J.; Legleiter, C. J.; Nelson, J. M.; Skinner, K.

2012-12-01

Since 2002, the first generation of the Experimental Advanced Airborne Research LiDAR (EAARL-A) sensor has been deployed for mapping rivers and streams. We present and summarize the results of comparisons between ground truth surveys and bathymetry collected by the EAARL-A sensor in a suite of rivers across the United States. These comparisons include reaches on the Platte River (NE), Boise and Deadwood Rivers (ID), Blue and Colorado Rivers (CO), Klamath and Trinity Rivers (CA), and the Shenandoah River (VA). In addition to diverse channel morphologies (braided, single thread, and meandering) these rivers possess a variety of substrates (sand, gravel, and bedrock) and a wide range of optical characteristics which influence the attenuation and scattering of laser energy through the water column. Root mean square errors between ground truth elevations and those measured by the EAARL-A ranged from 0.15-m in rivers with relatively low turbidity and highly reflective sandy bottoms to over 0.5-m in turbid rivers with less reflective substrates. Mapping accuracy with the EAARL-A has proved challenging in pools where bottom returns are either absent in waveforms or are of such low intensity that they are treated as noise by waveform processing algorithms. Resolving bathymetry in shallow depths where near surface and bottom returns are typically convolved also presents difficulties for waveform processing routines. The results of these evaluations provide an empirical framework to discuss the capabilities and limitations of the EAARL-A sensor as well as previous generations of post-processing software for extracting bathymetry from complex waveforms. These experiences and field studies not only provide benchmarks for the evaluation of the next generation of bathymetric LiDARs for use in river mapping, but also highlight the importance of developing and standardizing more rigorous methods to characterize substrate reflectance and in-situ optical properties at study sites. They also point out the continued necessity of ground truth data for algorithm refinement and survey verification.

Importance of large-scale bathymetry features on 2011 Tohoku tsunami waveforms through comparison of simulations with the spatially dense ALBACORE OBS array data

NASA Astrophysics Data System (ADS)

Kohler, M. D.; Lynett, P. J.; Legg, M. R.; Weeraratne, D. S.

2012-12-01

In March 2011, a deployment of ocean bottom seismometers (OBSs) off the coast of Southern California recorded the tsunami resulting from the Mw=9.0 Tohoku, Japan earthquake with very high spatial resolution. The ALBACORE (Asthenosphere and Lithosphere Broadband Architecture from the California Offshore Region Experiment) OBS array spanned a region that was 150 km north-south by 400 km east-west, extending into deep open ocean west of the Patton escarpment. In that array, 22 stations with a spacing of 75 km had differential pressure gauges (DPGs) that recorded water pressure waveform data continuously at 50 samples/second. The DPG tsunami records across the entire array show multiple large-amplitude, coherent phases arriving one hour to more than 36 hours after the initial tsunami phase. To determine the source of the large-amplitude coherent phases, gravity ocean wave propagation calculations were carried out for the Pacific Ocean. Simulated pressure waveforms were compared with data for the ALBACORE stations, as well as for the NOAA DART buoys. The linear, non-dispersive shallow-water simulations include bottom frictional effects, and use the USGS NEIC Tohoku slip model and ETOPO2 (two-minute spatial resolution) bathymetry. The predicted travel times of the initial arrivals are found to be less than 1% different from the observed travel times in the southern California ALBACORE DPG data. In order to gauge the effects of large-scale features in Pacific Ocean bathymetry, several large-scale features were individually removed, and simulations were carried out for the modified bathymetry. The removed features include the Emperor Seamount chain, Hawaiian Islands, Oceania, French Polynesia, and the South American coastline. The results show that the removal of these features has an effect on the arrival time of the phases that depends on the feature proximity to the direct path, but their removal does not have a significant effect on the frequency content or phase amplitudes of the waves. The direct paths recorded in Southern California indicate that the tsunami wave did not interfere with distant above-water features such as the Aleutians, but was diffracted around Point Conception in the California coastline and around southern California islands. It is more likely that the scattered phases are the result of wave reflections off the western Japan coastline, or interactions with local structures such as the central-southern California coastline, plateaus beneath the Channel Islands, and the Patton Escarpment.

Modern sedimentary environments in Boston Harbor, Massachusetts

USGS Publications Warehouse

Knebel, H.J.; Rendigs, R. R.; Bothner, Michael H.

1991-01-01

Analyses of sidescan-sonar records supplemented by available bathymetric, sedimentary, subbottom, and bottom-current data reveal the distributions of the following three categories of sedimentary environments within the glaciated, topographically complex Boston Harbor estuary in Massachusetts. 1) Environments of erosion appear on the sonographs either as patterns with isolated strong reflections or as uniform patterns of strong reflectivity. These patterns define outcrops of bedrock or till and coarse lag deposits that are being scoured and winnowed by tidal- and wave-induced currents. Erosional areas are located primarily along mainland and insular shores, within large channels that have strong tidal currents, atop submerged ridges and knolls, and across much of the harbor entrance. 2) Environments of deposition are depicted on the sidescan-sonar records as smooth, featureless surfaces that have low to moderate reflectivity. Depositional environments are found predominantly over shallow subtidal flats and in broad bathymetric lows where tidal currents are weak. Sediments within depositional areas are organic-rich sandy and clayey silts that are accumulating at rates ranging from 0.01 to 0.11 g/cm 2 /yr or 4000 to 46,100 metric tons/yr. The cumulative mass of modern mud in harbor depocenters is 24.3 million metric tons. 3) Environments of sediment reworking constitute areas affected by a combination of erosional and depositional processes. They are characterized on the sonographs by mosaics of light and dark patches produced by relatively subtle and gradational changes in reflectivity. Reworked sediments have diverse grain sizes that overlap and are transitional between those of the other two sedimentary environments, and they are indicative of highly variable bottom currents.

Age Differences in Hospital Mortality for Acute Myocardial Infarction: Implications for Hospital Profiling.

PubMed

Dharmarajan, Kumar; McNamara, Robert L; Wang, Yongfei; Masoudi, Frederick A; Ross, Joseph S; Spatz, Erica E; Desai, Nihar R; de Lemos, James A; Fonarow, Gregg C; Heidenreich, Paul A; Bhatt, Deepak L; Bernheim, Susannah M; Slattery, Lara E; Khan, Yosef M; Curtis, Jeptha P

2017-10-17

Publicly reported hospital risk-standardized mortality rates (RSMRs) for acute myocardial infarction (AMI) are calculated for Medicare beneficiaries. Outcomes for older patients with AMI may not reflect general outcomes. To examine the relationship between hospital 30-day RSMRs for older patients (aged ≥65 years) and those for younger patients (aged 18 to 64 years) and all patients (aged ≥18 years) with AMI. Retrospective cohort study. 986 hospitals in the ACTION (Acute Coronary Treatment and Intervention Outcomes Network) Registry-Get With the Guidelines. Adults hospitalized for AMI from 1 October 2010 to 30 September 2014. Hospital 30-day RSMRs were calculated for older, younger, and all patients using an electronic health record measure of AMI mortality endorsed by the National Quality Forum. Hospitals were ranked by their 30-day RSMRs for these 3 age groups, and agreement in rankings was plotted. The correlation in hospital AMI achievement scores for each age group was also calculated using the Hospital Value-Based Purchasing (HVBP) Program method computed with the electronic health record measure. 267 763 and 276 031 AMI hospitalizations among older and younger patients, respectively, were identified. Median hospital 30-day RSMRs were 9.4%, 3.0%, and 6.2% for older, younger, and all patients, respectively. Most top- and bottom-performing hospitals for older patients were neither top nor bottom performers for younger patients. In contrast, most top and bottom performers for older patients were also top and bottom performers for all patients. Similarly, HVBP achievement scores for older patients correlated weakly with those for younger patients (R = 0.30) and strongly with those for all patients (R = 0.92). Minority of U.S. hospitals. Hospital mortality rankings for older patients with AMI inconsistently reflect rankings for younger patients. Incorporation of younger patients into assessment of hospital outcomes would permit further examination of the presence and effect of age-related quality differences. American College of Cardiology.

Decoupled choice-driven and stimulus-related activity in parietal neurons may be misrepresented by choice probabilities.

PubMed

Zaidel, Adam; DeAngelis, Gregory C; Angelaki, Dora E

2017-09-28

Trial-by-trial correlations between neural responses and choices (choice probabilities) are often interpreted to reflect a causal contribution of neurons to task performance. However, choice probabilities may arise from top-down, rather than bottom-up, signals. We isolated distinct sensory and decision contributions to single-unit activity recorded from the dorsal medial superior temporal (MSTd) and ventral intraparietal (VIP) areas of monkeys during perception of self-motion. Superficially, neurons in both areas show similar tuning curves during task performance. However, tuning in MSTd neurons primarily reflects sensory inputs, whereas choice-related signals dominate tuning in VIP neurons. Importantly, the choice-related activity of VIP neurons is not predictable from their stimulus tuning, and these factors are often confounded in choice probability measurements. This finding was confirmed in a subset of neurons for which stimulus tuning was measured during passive fixation. Our findings reveal decoupled stimulus and choice signals in the VIP area, and challenge our understanding of choice signals in the brain.Choice-related signals in neuronal activity may reflect bottom-up sensory processes, top-down decision-related influences, or a combination of the two. Here the authors report that choice-related activity in VIP neurons is not predictable from their stimulus tuning, and that dominant choice signals can bias the standard metric of choice preference (choice probability).

Controls on the global distribution of contourite drifts: Insights from an eddy-resolving ocean model

NASA Astrophysics Data System (ADS)

Thran, Amanda C.; Dutkiewicz, Adriana; Spence, Paul; Müller, R. Dietmar

2018-05-01

Contourite drifts are anomalously high sediment accumulations that form due to reworking by bottom currents. Due to the lack of a comprehensive contourite database, the link between vigorous bottom water activity and drift occurrence has yet to be demonstrated on a global scale. Using an eddy-resolving ocean model and a new georeferenced database of 267 contourites, we show that the global distribution of modern contourite drifts strongly depends on the configuration of the world's most powerful bottom currents, many of which are associated with global meridional overturning circulation. Bathymetric obstacles frequently modify flow direction and intensity, imposing additional finer-scale control on drift occurrence. Mean bottom current speed over contourite-covered areas is only slightly higher (2.2 cm/s) than the rest of the global ocean (1.1 cm/s), falling below proposed thresholds deemed necessary to re-suspend and redistribute sediments (10-15 cm/s). However, currents fluctuate more frequently and intensely over areas with drifts, highlighting the role of intermittent, high-energy bottom current events in sediment erosion, transport, and subsequent drift accumulation. We identify eddies as a major driver of these bottom current fluctuations, and we find that simulated bottom eddy kinetic energy is over three times higher in contourite-covered areas in comparison to the rest of the ocean. Our work supports previous hypotheses which suggest that contourite deposition predominantly occurs due to repeated acute events as opposed to continuous reworking under average-intensity background flow conditions. This suggests that the contourite record should be interpreted in terms of a bottom current's susceptibility to experiencing periodic, high-speed current events. Our results also highlight the potential role of upper ocean dynamics in contourite sedimentation through its direct influence on deep eddy circulation.

Radiative transfer simulations of the two-dimensional ocean glint reflectance and determination of the sea surface roughness.

PubMed

Lin, Zhenyi; Li, Wei; Gatebe, Charles; Poudyal, Rajesh; Stamnes, Knut

2016-02-20

An optimized discrete-ordinate radiative transfer model (DISORT3) with a pseudo-two-dimensional bidirectional reflectance distribution function (BRDF) is used to simulate and validate ocean glint reflectances at an infrared wavelength (1036 nm) by matching model results with a complete set of BRDF measurements obtained from the NASA cloud absorption radiometer (CAR) deployed on an aircraft. The surface roughness is then obtained through a retrieval algorithm and is used to extend the simulation into the visible spectral range where diffuse reflectance becomes important. In general, the simulated reflectances and surface roughness information are in good agreement with the measurements, and the diffuse reflectance in the visible, ignored in current glint algorithms, is shown to be important. The successful implementation of this new treatment of ocean glint reflectance and surface roughness in DISORT3 will help improve glint correction algorithms in current and future ocean color remote sensing applications.

Radiative Transfer Simulations of the Two-Dimensional Ocean Glint Reflectance and Determination of the Sea Surface Roughness

NASA Technical Reports Server (NTRS)

Lin, Zhenyi; Li, Wei; Gatebe, Charles; Poudyal, Rajesh; Stamnes, Knut

2016-01-01

An optimized discrete-ordinate radiative transfer model (DISORT3) with a pseudo-two-dimensional bidirectional reflectance distribution function (BRDF) is used to simulate and validate ocean glint reflectances at an infrared wavelength (1036 nm) by matching model results with a complete set of BRDF measurements obtained from the NASA cloud absorption radiometer (CAR) deployed on an aircraft. The surface roughness is then obtained through a retrieval algorithm and is used to extend the simulation into the visible spectral range where diffuse reflectance becomes important. In general, the simulated reflectances and surface roughness information are in good agreement with the measurements, and the diffuse reflectance in the visible, ignored in current glint algorithms, is shown to be important. The successful implementation of this new treatment of ocean glint reflectance and surface roughness in DISORT3 will help improve glint correction algorithms in current and future ocean color remote sensing applications.

Simulation of laser beam reflection at the sea surface

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2011-05-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for both the calculation of images of SWIR (short wave infrared) imaging sensor and for determination of total detected power of reflected laser light for a bistatic configuration of laser source and receiver at different atmospheric conditions. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. The propagation model for water waves is applied for sea surface animation. To predict the view of a camera in the spectral band SWIR the sea surface radiance must be calculated. This is done by considering the emitted sea surface radiance and the reflected sky radiance, calculated by MODTRAN. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled in the SWIR band considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). This BRDF model considers the statistical slope statistics of waves and accounts for slope-shadowing of waves that especially occurs at flat incident angles of the laser beam and near horizontal detection angles of reflected irradiance at rough seas. Simulation results are presented showing the variation of the detected laser power dependent on the geometric configuration of laser, sensor and wind characteristics.

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.

The (Inter)disciplinarity of Media Studies: Pedagogical Challenges and Opportunities From the Perspective of Teaching Staff

ERIC Educational Resources Information Center

Iqani, Mehita; Feigenbaum, Anna

2015-01-01

In a series of Teaching Exchange (TE) staff development workshops aimed at exploring prospective, bottom-up quality assurance in media studies in the United Kingdom, interdisciplinarity arose as a key topic. This article reflects on teaching staff's views expressed in the TE workshops around interdisciplinarity in relation to their experiences in…

Roughness Perception during the Rubber Hand Illusion

ERIC Educational Resources Information Center

Schutz-Bosbach, Simone; Tausche, Peggy; Weiss, Carmen

2009-01-01

Watching a rubber hand being stroked by a paintbrush while feeling identical stroking of one's own occluded hand can create a compelling illusion that the seen hand becomes part of one's own body. It has been suggested that this so-called rubber hand illusion (RHI) does not simply reflect a bottom-up multisensory integration process but that the…

Conditions for the emergence of life on the early Earth: summary and reflections

PubMed Central

Jortner, Joshua

2006-01-01

This review attempts to situate the emergence of life on the early Earth within the scientific issues of the operational and mechanistic description of life, the conditions and constraints of prebiotic chemistry, together with bottom-up molecular fabrication and biomolecular nanofabrication and top-down miniaturization approaches to the origin of terrestrial life. PMID:17008225

Near-bottom circulation and dispersion of sediment containing Alexandrium fundyense cysts in the Gulf of Maine during 2010-2011

USGS Publications Warehouse

Aretxabaleta, Alfredo L.; Butman, Bradford; Signell, Richard P.; Dalyander, P. Soupy; Sherwood, Christopher R.; Sheremet, Vitalii A.; McGillicuddy, Dennis J.

2014-01-01

The life cycle of Alexandrium fundyense in the Gulf of Maine includes a dormant cyst stage that spends the winter predominantly in the bottom sediment. Wave-current bottom stress caused by storms and tides induces resuspension of cyst-containing sediment during winter and spring. Resuspended sediment could be transported by water flow to different locations in the Gulf and the redistribution of sediment containing A. fundyense cysts could alter the spatial and temporal manifestation of its spring bloom. The present study evaluates model near-bottom flow during storms, when sediment resuspension and redistribution are most likely to occur, between October and May when A. fundyense cells are predominantly in cyst form. Simulated water column sediment (mud) concentrations from representative locations of the Gulf are used to initialize particle tracking simulations for the period October 2010–May 2011. Particles are tracked in full three-dimensional model solutions including a sinking velocity characteristic of cyst and aggregated mud settling (0.1 mm s−1). Although most of the material was redeposited near the source areas, small percentages of total resuspended sediment from some locations in the western (~4%) and eastern (2%) Maine shelf and the Bay of Fundy (1%) traveled distances longer than 100 km before resettling. The redistribution changed seasonally and was sensitive to the prescribed sinking rate. Estimates of the amount of cysts redistributed with the sediment were small compared to the inventory of cysts in the upper few centimeters of sediment but could potentially have more relevance immediately after deposition.

Simulation of laser beam reflection at the sea surface modeling and validation

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2013-06-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for the pre-calculation of images for cameras operating in different spectral wavebands (visible, short wave infrared) for a bistatic configuration of laser source and receiver for different atmospheric conditions. In the visible waveband the calculated detected total power of reflected laser light from a 660nm laser source is compared with data collected in a field trial. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser beam reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the view of a camera the sea surface radiance must be calculated for the specific waveband. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). Validation of simulation results is prerequisite before applying the computer simulation to maritime laser applications. For validation purposes data (images and meteorological data) were selected from field measurements, using a 660nm cw-laser diode to produce laser beam reflection at the water surface and recording images by a TV camera. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam.

Simulated nuclear reactor fuel assembly

DOEpatents

Berta, V.T.

1993-04-06

An apparatus for electrically simulating a nuclear reactor fuel assembly. It includes a heater assembly having a top end and a bottom end and a plurality of concentric heater tubes having electrical circuitry connected to a power source, and radially spaced from each other. An outer target tube and an inner target tube is concentric with the heater tubes and with each other, and the outer target tube surrounds and is radially spaced from the heater tubes. The inner target tube is surrounded by and radially spaced from the heater tubes and outer target tube. The top of the assembly is generally open to allow for the electrical power connection to the heater tubes, and the bottom of the assembly includes means for completing the electrical circuitry in the heater tubes to provide electrical resistance heating to simulate the power profile in a nuclear reactor. The embedded conductor elements in each heater tube is split into two halves for a substantial portion of its length and provided with electrical isolation such that each half of the conductor is joined at one end and is not joined at the other end.

[Development of a microenvironment test chamber for airborne microbe research].

PubMed

Zhan, Ningbo; Chen, Feng; Du, Yaohua; Cheng, Zhi; Li, Chenyu; Wu, Jinlong; Wu, Taihu

2017-10-01

One of the most important environmental cleanliness indicators is airborne microbe. However, the particularity of clean operating environment and controlled experimental environment often leads to the limitation of the airborne microbe research. This paper designed and implemented a microenvironment test chamber for airborne microbe research in normal test conditions. Numerical simulation by Fluent showed that airborne microbes were evenly dispersed in the upper part of test chamber, and had a bottom-up concentration growth distribution. According to the simulation results, the verification experiment was carried out by selecting 5 sampling points in different space positions in the test chamber. Experimental results showed that average particle concentrations of all sampling points reached 10 7 counts/m 3 after 5 minutes' distributing of Staphylococcus aureus , and all sampling points showed the accordant mapping of concentration distribution. The concentration of airborne microbe in the upper chamber was slightly higher than that in the middle chamber, and that was also slightly higher than that in the bottom chamber. It is consistent with the results of numerical simulation, and it proves that the system can be well used for airborne microbe research.

Combined top-down and bottom-up climate change impact assessment for the hydrological system in the Vu Gia- Thu Bon River Basin.

PubMed

Tra, Tran Van; Thinh, Nguyen Xuan; Greiving, Stefan

2018-07-15

Vu Gia- Thu Bon (VGTB) River Basin, located in the Central Coastal zone of Viet Nam currently faces water shortage. Climate change is expected to exacerbate the challenge. Therefore, there is a need to study the impacts of climate change on water shortage in the river basin. The study adopts a combined top-down and bottom-up climate change impact assessment to address the impacts of climate change on water shortage in the VGTB River Basin. A MIKE BASIN water balance model for the river basin was established to simulate the response of the hydrological system. Simulations were performed through parametrically varying temperature and precipitation to determine the vulnerability space of water shortage. General Circulation Models (GCMs) were then utilized to provide climate projections for the river basin. The output from GCMs was then mapped onto the vulnerability space determined earlier. In total, 9 out of 55 water demand nodes in the simulation are expected to face problematic conditions as future climate changes. Copyright © 2018 Elsevier B.V. All rights reserved.

Simulated nuclear reactor fuel assembly

DOEpatents

Berta, Victor T.

1993-01-01

An apparatus for electrically simulating a nuclear reactor fuel assembly. It includes a heater assembly having a top end and a bottom end and a plurality of concentric heater tubes having electrical circuitry connected to a power source, and radially spaced from each other. An outer target tube and an inner target tube is concentric with the heater tubes and with each other, and the outer target tube surrounds and is radially spaced from the heater tubes. The inner target tube is surrounded by and radially spaced from the heater tubes and outer target tube. The top of the assembly is generally open to allow for the electrical power connection to the heater tubes, and the bottom of the assembly includes means for completing the electrical circuitry in the heater tubes to provide electrical resistance heating to simulate the power profile in a nuclear reactor. The embedded conductor elements in each heater tube is split into two halves for a substantial portion of its length and provided with electrical isolation such that each half of the conductor is joined at one end and is not joined at the other end.

Optimizing Fukushima Emissions Through Pattern Matching and Genetic Algorithms

NASA Astrophysics Data System (ADS)

Lucas, D. D.; Simpson, M. D.; Philip, C. S.; Baskett, R.

2017-12-01

Hazardous conditions during the Fukushima Daiichi nuclear power plant (NPP) accident hindered direct observations of the emissions of radioactive materials into the atmosphere. A wide range of emissions are estimated from bottom-up studies using reactor inventories and top-down approaches based on inverse modeling. We present a new inverse modeling estimate of cesium-137 emitted from the Fukushima NPP. Our estimate considers weather uncertainty through a large ensemble of Weather Research and Forecasting model simulations and uses the FLEXPART atmospheric dispersion model to transport and deposit cesium. The simulations are constrained by observations of the spatial distribution of cumulative cesium deposited on the surface of Japan through April 2, 2012. Multiple spatial metrics are used to quantify differences between observed and simulated deposition patterns. In order to match the observed pattern, we use a multi-objective genetic algorithm to optimize the time-varying emissions. We find that large differences with published bottom-up estimates are required to explain the observations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Scalar field configurations supported by charged compact reflecting stars in a curved spacetime

NASA Astrophysics Data System (ADS)

Peng, Yan

2018-05-01

We study the system of static scalar fields coupled to charged compact reflecting stars through both analytical and numerical methods. We enclose the star in a box and our solutions are related to cases without box boundaries when putting the box far away from the star. We provide bottom and upper bounds for the radius of the scalar hairy compact reflecting star. We obtain numerical scalar hairy star solutions satisfying boundary conditions and find that the radius of the hairy star in a box is continuous in a range, which is very different from cases without box boundaries where the radius is discrete in the range. We also examine effects of the star charge and mass on the largest radius.

Formation of localized sand patterns downstream from a vertical cylinder under steady flows: Experimental and theoretical study.

PubMed

Auzerais, Anthony; Jarno, Armelle; Ezersky, Alexander; Marin, François

2016-11-01

The generation of localized, spatially periodic patterns on a sandy bottom is experimentally and theoretically studied. Tests are performed in a hydrodynamic flume where patterns are produced downstream from a vertical cylinder under a steady current. It is found that patterns appear as a result of a subcritical instability of the water-sand bottom interface. A dependence of the area shape occupied by the patterns on the flow velocity and the cylinder diameter is investigated. It is shown that the patterns' characteristics can be explained using the Swift-Hohenberg equation. Numerical simulations point out that for a correct description of the patterns, an additional term which takes into account the impact of vortices on the sandy bottom in the wake of a cylinder must be added in the Swift-Hohenberg equation.

Bottom-up heating method for producing polyethylene lunar concrete in lunar environment

NASA Astrophysics Data System (ADS)

Lee, Jaeho; Ann, Ki Yong; Lee, Tai Sik; Mitikie, Bahiru Bewket

2018-07-01

The Apollo Program launched numerous missions to the Moon, Earth's nearest and only natural satellite. NASA is now planning new Moon missions as a first step toward human exploration of Mars and other planets. However, the Moon has an extreme environment for humans. In-situ resource utilization (ISRU) construction must be used on the Moon to build habitable structures. Previous studies on polymeric lunar concrete investigated top-down heating for stabilizing the surface. This study investigates bottom-up heating with manufacturing temperatures as low as 200 °C in a vacuum chamber that simulates the lunar environment. A maximum compressive strength of 5.7 MPa is attained; this is suitable for constructing habitable structures. Furthermore, the bottom-up heating approach achieves solidification two times faster than does the top-down heating approach.

Study on installation of the submersible mixer

NASA Astrophysics Data System (ADS)

Tian, F.; Shi, W. D.; He, X. H.; Jiang, H.; Xu, Y. H.

2013-12-01

Study on installation of the submersible mixer for sewage treatment has been limited. In this article, large-scale computational fluid dynamics software FLUENT6.3 was adopted. ICEM software was used to build an unstructured grid of sewage treatment pool. After that, the sewage treatment pool was numerically simulated by dynamic coordinate system technology and RNG k-ε turbulent model and PIOS algorithm. Agitation pools on four different installation location cases were simulated respectively, and the external characteristic of the submersible mixer and the velocity cloud of the axial section were respectively comparatively analyzed. The best stirring effect can be reached by the installation location of case C, which is near the bottom of the pool 600 mm and blade distance the bottom at least for 200 mm wide and wide edge and narrow edge distance by 4:3. The conclusion can guide the engineering practice.

Energy dependence of the spatial distribution of inelastically scattered electrons in backscatter electron diffraction

NASA Astrophysics Data System (ADS)

Ram, Farangis; De Graef, Marc

2018-04-01

In an electron backscatter diffraction pattern (EBSP), the angular distribution of backscattered electrons (BSEs) depends on their energy. Monte Carlo modeling of their depth and energy distributions suggests that the highest energy BSEs are more likely to hit the bottom of the detector than the top. In this paper, we examine experimental EBSPs to validate the modeled angular BSE distribution. To that end, the Kikuchi bandlet method is employed to measure the width of Kikuchi bands in both modeled and measured EBSPs. The results show that in an EBSP obtained with a 15 keV primary probe, the width of a Kikuchi band varies by about 0 .4∘ from the bottom of the EBSD detector to its top. The same is true for a simulated pattern that is composed of BSEs with 5 keV to 15 keV energies, which validates the Monte Carlo simulations.

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.

Santa Claus, Ga./Ind.

NASA Image and Video Library

2002-12-23

The towns of Santa Claus, Ga., (top) and Santa Claus, Ind. (bottom), are shown in these two images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra satellite. They are the only two Santa Claus towns in the United States with post offices and zip codes, although there are 11 towns with this name in the United States. Santa Claus, Ga. is located in Toombs County, and has a population of 237. Santa Claus, Ind. is located in Spencer County, and has a population of 2,041. Its name was accepted by the United States Postal Service in 1856. The images were acquired on July 3, 2000 (top) and June 16, 2001 (bottom), respectively. http://photojournal.jpl.nasa.gov/catalog/PIA03891

Some effects of sublethal concentrations of sodium arsenite on bluegills and the aquatic environment

USGS Publications Warehouse

Gilderhus, P.A.

1966-01-01

Bluegills were exposed to sodium arsenite at various concentrations and treatment frequencies in outdoor pools. The effects of the treatments on the fish and invertebrates in the pools were assessed. Applications totaling 4.0 ppm or more of NaAsO2 during the experiment were reflected in reduced survival and growth of the fish, with immature fish being affected to a greater degree than adults. Some pathological changes were observed in adults. Substantial residues of arsenic were found in the water, bottom soil, and throughout the organs and flesh of the bluegills at the termination of the experiment. Bottom fauna and plankton populations were reduced or inhibited in several pools with the highest concentrations of the herbicide.

Near-bottom suspended matter concentration on the Continental Shelf during storms: estimates based on in situ observations of light transmission and a particle size dependent transmissometer calibration

USGS Publications Warehouse

Moody, J.A.; Butman, B.; Bothner, Michael H.

1987-01-01

A laboratory calibration of Sea Tech and Montedoro-Whitney beam transmissometers shows a linear relation between light attenuation coefficient (cp) and suspended matter concentration (SMC) for natural sediments and for glass beads. However the proportionality constant between cp and SMC depends on the particle diameter and particle type. Thus, to measure SMC, observations of light attenuation must be used with a time-variable calibration when suspended particle characteristics change with time. Because of this variable calibration, time series of light attenuation alone may not directly reflect SMC and must be interpreted with care.The near-bottom concentration of suspended matter during winter storms on the U.S. East Coast Continental Shelf is estimated from light transmission measurements made 2 m above the bottom and from the size distribution of suspended material collected simultaneously in sediment traps 3 m above the bottom. The average concentrations during six storms between December 1979 and February 1980 in the Middle Atlantic Bight ranged from 2 to 4 mg l1 (maximum concentration of 7 mg l1) and 8 to 12 mg l1 (maximum concentration of 22 mg l1) on the south flank of Georges Bank.

Effect of the 6PBT stirrer eccentricity and off-bottom clearance on mixing of pseudoplastic fluid in a stirred tank

NASA Astrophysics Data System (ADS)

Luan, Deyu; Zhang, Shengfeng; Wei, Xing; Duan, Zhenya

The aim of this work is to investigate the effect of the shaft eccentricity on the flow field and mixing characteristics in a stirred tank with the novel stirrer composed of perturbed six-bent-bladed turbine (6PBT). The difference between coaxial and eccentric agitations is studied using computational fluid dynamics (CFD) simulations combined with standard k-ε turbulent equations, that offer a complete image of the three-dimensional flow field. In order to determine the capability of CFD to forecast the mixing process, particle image velocimetry (PIV), which provide an accurate representation of the time-averaged velocity, was used to measure fluid velocity. The test liquid used was 1.25% (wt) xanthan gum solution, a pseudoplastic fluid with a yield stress. The comparison of the experimental and simulated mean flow fields has demonstrated that calculations based on Reynolds-averaged Navier-Stokes equations are suitable for obtaining accurate results. The effects of the shaft eccentricity and the stirrer off-bottom distance on the flow model, mixing time and mixing efficiency were extensively analyzed. It is observed that the microstructure of the flow field has a significant effect on the tracer mixing process. The eccentric agitation can lead to the flow model change and the non-symmetric flow structure, which would possess an obvious superiority of mixing behavior. Moreover, the mixing rate and mixing efficiency are dependent on the shaft eccentricity and the stirrer off-bottom distance, showing the corresponding increase of the eccentricity with the off-bottom distance. The efficient mixing process of pseudoplastic fluid stirred by 6PBT impeller is obtained with the considerably low mixing energy per unit volume when the stirrer off-bottom distance, C, is T/3 and the eccentricity, e, is 0.2. The research results provide valuable references for the improvement of pseudoplastic fluid agitation technology.

Laboratory measurements of physical, chemical, and optical characteristics of Lake Chicot sediment waters

NASA Technical Reports Server (NTRS)

Witte, W. G.; Whitlock, C. H.; Usry, J. W.; Morris, W. D.; Gurganus, E. A.

1981-01-01

Reflectance, chromaticity, diffuse attenuation, beam attenuation, and several other physical and chemical properties were measured for various water mixtures of lake bottom sediment. Mixture concentrations range from 5 ppm to 700 ppm by weight of total suspended solids in filtered deionized tap water. Upwelled reflectance is a nonlinear function of remote sensing wave lengths. Near-infrared wavelengths are useful for monitoring highly turbid waters with sediment concentrations above 100 ppm. It is found that both visible and near infrared wavelengths, beam attenuation correlates well with total suspended solids ranging over two orders of magnitude.

Recording and processing procedures for multi-channel seismic-reflection data collected in the western Ross Sea, Antarctica

USGS Publications Warehouse

Dadisman, Shawn V.; Ryan, Holly F.; Mann, Dennis M.

1987-01-01

During 1984, over 2300 km of multichannel seismic-reflection data were recorded by the U.S. Geological Survey in the western Ross Sea and Iselin Bank regions.  A temporary loss and sinking of the streamer led to increasing the streamer tow depth to 20 m, which resulted in some attenuation of frequencies in the 30-50 Hz range but no significant difference in resolution of the stacked data.  Severe water bottom multiples were encountered and removed by dip-filtering, weighted stacking, and severe post-NMO muting.

The photochemical reflectance index from directional cornfield reflectances: Observations and simulations

USDA-ARS?s Scientific Manuscript database

The two-layer Markov chain Analytical Canopy Reflectance Model (ACRM) was linked with in situ hyperspectral leaf optical properties to simulate the Photochemical Reflectance Index (PRI) for a corn crop canopy at three different growth stages. This is an extended study after a successful demonstratio...

Seismic character of gas hydrates on the Southeastern U.S. continental margin

USGS Publications Warehouse

Lee, M.W.; Hutchinson, D.R.; Agena, W.F.; Dillon, William P.; Miller, J.J.; Swift, B.A.

1994-01-01

Gas hydrates are stable at relatively low temperature and high pressure conditions; thus large amounts of hydrates can exist in sediments within the upper several hundred meters below the sea floor. The existence of gas hydrates has been recognized and mapped mostly on the basis of high amplitude Bottom Simulating Reflections (BSRs) which indicate only that an acoustic contrast exists at the lower boundary of the region of gas hydrate stability. Other factors such as amplitude blanking and change in reflection characteristics in sediments where a BSR would be expected, which have not been investigated in detail, are also associated with hydrated sediments and potentially disclose more information about the nature of hydratecemented sediments and the amount of hydrate present. Our research effort has focused on a detailed analysis of multichannel seismic profiles in terms of reflection character, inferred distribution of free gas underneath the BSR, estimation of elastic parameters, and spatial variation of blanking. This study indicates that continuous-looking BSRs in seismic profiles are highly segmented in detail and that the free gas underneath the hydrated sediment probably occurs as patches of gas-filled sediment having variable thickness. We also present an elastic model for various types of sediments based on seismic inversion results. The BSR from sediments of high ratio of shear to compressional velocity, estimated as about 0.52, encased in sediments whose ratios are less than 0.35 is consistent with the interpretation of gasfilled sediments underneath hydrated sediments. This model contrasts with recent results in which the BSR is explained by increased concentrations of hydrate near the base of the hydrate stability field and no underlying free gas is required. 

Fluctuation-dissipation relations for motions of center of mass in driven granular fluids under gravity.

PubMed

Wakou, Jun'ichi; Isobe, Masaharu

2012-06-01

We investigated the validity of fluctuation-dissipation relations in the nonequilibrium stationary state of fluidized granular media under gravity by two independent approaches, based on theory and numerical simulations. A phenomenological Langevin-type theory describing the fluctuation of center of mass height, which was originally constructed for a one-dimensional granular gas on a vibrating bottom plate, was generalized to any dimensionality, even for the case in which the vibrating bottom plate is replaced by a thermal wall. The theory predicts a fluctuation-dissipation relation known to be satisfied at equilibrium, with a modification that replaces the equilibrium temperature by an effective temperature defined by the center of mass kinetic energy. To test the validity of the fluctuation-dissipation relation, we performed extensive and accurate event-driven molecular dynamics simulations for the model system with a thermal wall at the bottom. The power spectrum and response function of the center of mass height were measured and closely compared with theoretical predictions. It is shown that the fluctuation-dissipation relation for the granular system is satisfied, especially in the high-frequency (short time) region, for a wide range of system parameters. Finally, we describe the relationship between systematic deviations in the low-frequency (long time) region and the time scales of the driven granular system.

Impact of Satellite Remote Sensing Data on Simulations of ...

EPA Pesticide Factsheets

We estimated surface salinity flux and solar penetration from satellite data, and performed model simulations to examine the impact of including the satellite estimates on temperature, salinity, and dissolved oxygen distributions on the Louisiana continental shelf (LCS) near the annual hypoxic zone. Rainfall data from the Tropical Rainfall Measurement Mission (TRMM) were used for the salinity flux, and the diffuse attenuation coefficient (Kd) from Moderate Resolution Imaging Spectroradiometer (MODIS) were used for solar penetration. Improvements in the model results in comparison with in situ observations occurred when the two types of satellite data were included. Without inclusion of the satellite-derived surface salinity flux, realistic monthly variability in the model salinity fields was observed, but important inter-annual variability wasmissed. Without inclusion of the satellite-derived light attenuation, model bottom water temperatures were too high nearshore due to excessive penetration of solar irradiance. In general, these salinity and temperature errors led to model stratification that was too weak, and the model failed to capture observed spatial and temporal variability in water-column vertical stratification. Inclusion of the satellite data improved temperature and salinity predictions and the vertical stratification was strengthened, which improved prediction of bottom-water dissolved oxygen. The model-predicted area of bottom-water hypoxia on the

Application of homomorphic signal processing to stress wave factor analysis

NASA Technical Reports Server (NTRS)

Karagulle, H.; Williams, J. H., Jr.; Lee, S. S.

1985-01-01

The stress wave factor (SWF) signal, which is the output of an ultrasonic testing system where the transmitting and receiving transducers are coupled to the same face of the test structure, is analyzed in the frequency domain. The SWF signal generated in an isotropic elastic plate is modelled as the superposition of successive reflections. The reflection which is generated by the stress waves which travel p times as a longitudinal (P) wave and s times as a shear (S) wave through the plate while reflecting back and forth between the bottom and top faces of the plate is designated as the reflection with p, s. Short-time portions of the SWF signal are considered for obtaining spectral information on individual reflections. If the significant reflections are not overlapped, the short-time Fourier analysis is used. A summary of the elevant points of homomorphic signal processing, which is also called cepstrum analysis, is given. Homomorphic signal processing is applied to short-time SWF signals to obtain estimates of the log spectra of individual reflections for cases in which the reflections are overlapped. Two typical SWF signals generated in aluminum plates (overlapping and non-overlapping reflections) are analyzed.

Process solutions for reducing PR residue over non-planar wafer

NASA Astrophysics Data System (ADS)

Lin, C. H.; Huang, C. H.; Yang, Elvis; Yang, T. H.; Chen, K. C.; Lu, Chih-Yuan

2011-03-01

SAS (Self-Aligned Source) process has been widely adopted on manufacturing NOR Flash devices. To form the SAS structure, the compromise between small space patterning and sufficiently removing photo resist residue in topographical substrate has been a critical challenge as the device scaling down. In this study, photo simulation, layout optimization, resist processing and tri-layer materials were evaluated to form defect-free and highly extendible SAS structure for NOR Flash devices. Photo simulation suggested more coherent light source allowed the incident light to reach the trench bottom that facilitates the removal of photo resist. Mask bias also benefited the process latitude extension for residue-free SAS printing. In the photo resist processing, both lowering the SB (Soft Bake) and raising PEB (Post-Exposure Bake) temperature of photo resist were helpful to broaden the process window but the final pattern profile was not good enough. Thermal flow for pos-exposure pattern shrinkage achieved small CD (Critical Dimension) patterning with residue-free, however the materials loading effect is another issue to be addressed at memory array boundary. Tri-layer scheme demonstrated good results in terms of free from residue, better substrate reflectivity control, enabling smaller space printing to loosen overlay specification and minimizing the poly gate clipping defect. It was finally proposed to combine with etch effort to from the SAS structure. Besides it is also promising to extend to even smaller technology nodes.

Frequency Domain Response at Pacific Coast Harbors to Major Tsunamis of 2005-2011

NASA Astrophysics Data System (ADS)

Xing, Xiuying; Kou, Zhiqing; Huang, Ziyi; Lee, Jiin-Jen

2013-06-01

Tsunamis waves caused by submarine earthquake or landslide might contain large wave energy, which could cause significant human loss and property damage locally as well as in distant region. The response of three harbors located at the Pacific coast (i.e. Crescent City Harbor, Los Angeles/Long Beach Port, and San Diego Harbor) to six well-known tsunamis events generated (both near-field and far-field) between 2005 and 2011 are examined and simulated using a hybrid finite element numerical model in frequency domain. The model incorporated the effects of wave refraction, wave diffraction, partial wave reflection from boundaries, entrance and bottom energy dissipation. It can be applied to harbor regions with arbitrary shapes and variable water depth. The computed resonant periods or modes of oscillation for three harbors are in good agreement with the energy spectral analysis of the time series of water surface elevations recorded at tide gauge stations inside three harbors during the six tsunamis events. The computed wave induced currents based on the present model are also in qualitative agreement with some of the reported eye-witness accounts absence of reliable current data. The simulated results show that each harbor responded differently and significantly amplified certain wave period(s) of incident wave trains according to the shape, topography, characteristic dimensions and water depth of the harbor basins.

Use of Airborne Hyperspectral Data in the Simulation of Satellite Images

NASA Astrophysics Data System (ADS)

de Miguel, Eduardo; Jimenez, Marcos; Ruiz, Elena; Salido, Elena; Gutierrez de la Camara, Oscar

2016-08-01

The simulation of future images is part of the development phase of most Earth Observation missions. This simulation uses frequently as starting point images acquired from airborne instruments. These instruments provide the required flexibility in acquisition parameters (time, date, illumination and observation geometry...) and high spectral and spatial resolution, well above the target values (as required by simulation tools). However, there are a number of important problems hampering the use of airborne imagery. One of these problems is that observation zenith angles (OZA), are far from those that the misisons to be simulated would use.We examine this problem by evaluating the difference in ground reflectance estimated from airborne images for different observation/illumination geometries. Next, we analyze a solution for simulation purposes, in which a Bi- directional Reflectance Distribution Function (BRDF) model is attached to an image of the isotropic surface reflectance. The results obtained confirm the need for reflectance anisotropy correction when using airborne images for creating a reflectance map for simulation purposes. But this correction should not be used without providing the corresponding estimation of BRDF, in the form of model parameters, to the simulation teams.

The K1 internal tide simulated by a 1/10° OGCM

NASA Astrophysics Data System (ADS)

Li, Zhuhua; von Storch, Jin-Song; Müller, Malte

2017-05-01

This paper quantifies the K1 internal tide simulated by the 1/10° STORMTIDE model, which simultaneously resolves the eddying general circulation and tides. An evident feature of the K1 internal tide is the critical latitude φc at 30°, which in the STORMTIDE model is characterized by variations from a high energy level equatorward of 30° to a low energy level poleward of 30°. This critical latitude separates the internal tide dynamics into bottom-trapped (at latitudes |φ| > |φc|) and freely propagating (at |φ| < |φc|) motions, respectively. Both types of motions are examined. The bottom-trapping process reveals a gradual vertical decrease of wave energy away from the bottom. The vertical scale, over which the wave energy decrease occurs, is smaller in shallow than in deep water regions. For the freely propagating K1 internal tides, the STORMTIDE model is able to simulate the first three low modes, with the wavelengths ranging from 200-400 km, 100-200 km, to 60-120 km. These wavelength distributions reveal not only a zonal asymmetry but also a poleward increase up to φc, in particular in the Pacific. Such distributions indicate the impact of stratification N and the Coriolis frequency f on the wavelengths. The large wavelength gradient near φc is caused by the wavelength increase from finite values at subcritical latitudes to infinity at φc. Compared to the M2 internal tide, the lower K1 tidal frequency leads to a stronger role of f, hence a weaker effect of N, for the K1 internal tide.

Numerical simulations: Toward the design of 27.6% efficient four-terminal semi-transparent perovskite/SiC passivated rear contact silicon tandem solar cell

NASA Astrophysics Data System (ADS)

Pandey, Rahul; Chaujar, Rishu

2016-12-01

In this work, a novel four-terminal perovskite/SiC-based rear contact silicon tandem solar cell device has been proposed and simulated to achieve 27.6% power conversion efficiency (PCE) under single AM1.5 illumination. 20.9% efficient semitransparent perovskite top subcell has been used for perovskite/silicon tandem architecture. The tandem structure of perovskite-silicon solar cells is a promising method to achieve efficient solar energy conversion at low cost. In the four-terminal tandem configuration, the cells are connected independently and hence avoids the need for current matching between top and bottom subcell, thus giving greater design flexibility. The simulation analysis shows, PCE of 27.6% and 22.4% with 300 μm and 10 μm thick rear contact Si bottom subcell, respectively. This is a substantial improvement comparing to transparent perovskite solar cell and c-Si solar cell operated individually. The impact of perovskite layer thickness, monomolecular, bimolecular, and trimolecular recombination have also been obtained on the performance of perovskite top subcell. Reported PCEs of 27.6% and 22.4% are 1.25 times and 1.42 times higher as compared to experimentally available efficiencies of 22.1% and 15.7% in 300 μm and 10 μm thick stand-alone silicon solar cell devices, respectively. The presence of SiC significantly suppressed the interface recombination in bottom silicon subcell. Detailed realistic technology computer aided design (TCAD) analysis has been performed to predict the behaviour of the device.

Evidence for faulting related to dissociation of gas hydrate and release of methane off the southeastern United States

USGS Publications Warehouse

Dillon, William P.; Danforth, W.W.; Hutchinson, D.R.; Drury, R.M.; Taylor, M.H.; Booth, J.S.

1998-01-01

This paper is part of the special publication Gas hydrates: relevance to world margin stability and climatic change (eds J.P. Henriet and J. Mienert). An irregular, faulted, collapse depression about 38 x 18 km in extent is located on the crest of the Blake Ridge offshore from the south- eastern United States. Faults disrupt the sea floor and terminate or sole out about 40-500 m below the sea floor at the base of the gas hydrate stable zone, which is identified from the location of the bottom simulating reflection (BSR). Normal faults are common but reverse faults and folds also are widespread. Folds commonly convert upward into faults. Sediment diapirs and deposits of sediments that were erupted onto the sea floor are also present. Sea-floor depressions at faults may represent locations of liquid/gas vents. The collapse was probably caused by overpressures and by the decoupling of the overlying sediments by gassy muds that existed just beneath the zone of gas hydrate stability.

Evaluation of fine soil moisture data from the IFloodS (NASA GPM) Ground Validation campaign using a fully-distributed ecohydrological model

NASA Astrophysics Data System (ADS)

Bastola, S.; Dialynas, Y. G.; Arnone, E.; Bras, R. L.

2014-12-01

The spatial variability of soil, vegetation, topography, and precipitation controls hydrological processes, consequently resulting in high spatio-temporal variability of most of the hydrological variables, such as soil moisture. Limitation in existing measuring system to characterize this spatial variability, and its importance in various application have resulted in a need of reconciling spatially distributed soil moisture evolution model and corresponding measurements. Fully distributed ecohydrological model simulates soil moisture at high resolution soil moisture. This is relevant for range of environmental studies e.g., flood forecasting. They can also be used to evaluate the value of space born soil moisture data, by assimilating them into hydrological models. In this study, fine resolution soil moisture data simulated by a physically-based distributed hydrological model, tRIBS-VEGGIE, is compared with soil moisture data collected during the field campaign in Turkey river basin, Iowa. The soil moisture series at the 2 and 4 inch depth exhibited a more rapid response to rainfall as compared to bottom 8 and 20 inch ones. The spatial variability in two distinct land surfaces of Turkey River, IA, reflects the control of vegetation, topography and soil texture in the characterization of spatial variability. The comparison of observed and simulated soil moisture at various depth showed that model was able to capture the dynamics of soil moisture at a number of gauging stations. Discrepancies are large in some of the gauging stations, which are characterized by rugged terrain and represented, in the model, through large computational units.

Turbulence-enhanced bottom melting of a horizontal glacier--lake interface

NASA Astrophysics Data System (ADS)

Keitzl, T.; Mellado, J. P.; Notz, D.

2014-12-01

We use laboratory tank experiments and direct numerical simulations to investigate the meltrates of a horizontal bottom glacier--lake interface as a function of lake temperature. Existing parameterisations of such meltrates are usually based on empirical fits to field observations. To understand the meltrates of an ice--water interface more systematically we study an idealised system in terms of its temperature-driven buoyancy forcing. In such systems, the meltrate can be expressed analytically for a stable stratification. Here we investigate the unstable case and present how the meltrate depends on the lake temperature when the water beneath the ice is overturning and turbulent. We use laboratory tank experiments and direct numerical simulations to study an idealised ice--water boundary. The laboratory tank experiments provide robust observation-based mean-temperature profiles. The numerical simulations provide the full three-dimensional structure of the turbulent flow down to scales not accessible in the laboratory, with a minimum 0.2mm gridspacing. Our laboratory mean-temperature profiles agree well with the numerical simulations and lend credibility to our numerical setup. The structure of the turbulent flow in our simulations is well described by two self-similar subregions, a diffusion-dominated inner layer close to the ice and a turbulence-dominated outer layer far from the ice. We provide an explicit expression for the parameterisation of the meltrate of a horizontal glacier--lake interface as a function of lake temperature.

Experimental study on the effect of shape of bolt and nut on fatigue strength for bolted joint

NASA Astrophysics Data System (ADS)

Matsunari, T.; Oda, K.; Tsutsumi, N.; Yakushiji, T.; Noda, N. A.; Sano, Y.

2018-06-01

In this study, the effect of curvature radius of the thread bottom and the pitch difference between of M16 bolt and nut on fatigue strength for bolted joint is considered experimentally. The M16 bolt-nut specimens having the two kinds of thread bottom radii and the pitch differences are prepared. The S-N curves for bolted specimens with different thread shapes are obtained by the stress-controlled fatigue test (stress ratio R>0). The experimental results are compared and discussed in terms of stress analysis. The finite element method is used to make a simulation of the fatigue experiment and the mean stress and stress amplitude at each thread bottom of bolt are analysed. It is found that the initiation and propagation of crack are changed by introducing the pitch difference of α=15 μm from the crack observation in cross section of the bolt specimens after the experiment. Furthermore, the fatigue life can be extended by increasing curvature radius of thread bottom and introducing the pitch difference.

The effect of bottom friction on tidal dipolar vortices and the associated transport

NASA Astrophysics Data System (ADS)

Duran-Matute, Matias; Kamp, Leon; van Heijst, Gertjan

2016-11-01

Tidal dipolar vortices can be formed in a semi-enclosed basin as the tides flow in and out through an inlet. If they are strong enough to overcome the opposing tidal currents, these vortices can travel away from the inlet due to their self-propelling mechanism, and hence, act as an efficient transport agent for suspended material. We present results of two-dimensional numerical simulations of the flow through an idealized tidal inlet, with either a linear or a nonlinear parameterization of the bottom friction. We then quantify the effect of the bottom friction on the propagation of the dipolar vortex and on its ability as a transport agent by computing the flushing and residence times of passive particles. Bottom friction is detrimental to the ability of tidal dipolar vortices to propagate and hinders transport away from the inlet. The magnitude of this effect is related to the relative duration of the tidal period as compared to the typical decay time scale of the vortex dipole. This research is funded by NWO (the Netherlands) through the VENI Grant 863.13.022.

Electrowetting-driven solar indoor lighting (e-SIL): an optofluidic approach towards sustainable buildings.

PubMed

Thio, Si Kuan; Jiang, Dongyue; Park, Sung-Yong

2018-06-12

Optofluidics is an emerging research field that combines the two disciplines of microfluidics and optics. By using microfluidic technologies for light control, optofluidic devices can offer several advantages over solid-type optical components, including optical-grade smoothness at the fluidic interface and a high degree of optical tunability without bulky and complex mechanical moving parts. These features have made optofluidic devices more versatile and reconfigurable to improve their optical performances. In this paper, we present a novel optofluidic sunlight manipulation technology for solar indoor lighting using the electrowetting principle. Rooftop sunlight is collected by a solar concentrator and guided to individual rooms along an optical fiber (waveguide) on the bottom of which tunable liquid prisms are linearly integrated. In the light-off mode, electrowetting controls the apex angle of the prisms to be φ = 0°. Under this condition, incoming sunlight experiences total internal reflection and thus keeps propagating along the optical fiber without leaking to the prism bottom for indoor lighting. In contrast, when liquid prisms are controlled to have the angle at φ > 0°, incoming sunlight is partially transmitted to the bottom surface of the arrayed prisms to contribute to interior illumination. Simulation studies validate that our electrowetting-driven solar indoor lighting (e-SIL) system is capable of variably tuning the lighting power from 0% to 98.6% of the input solar power by controlling the prism angle and varying the refractive index of prism materials. For experimental studies, we fabricated an array of 5 prisms filled with silicone oil and water. Using a fiber illuminator as a white light source that includes visible light with various incident angles, we have demonstrated two important lighting functions, (1) light on/off and (2) illumination power control. Lighting performance can be further enhanced by lowering the aspect ratio of the prism as well as increasing the number of prisms. The e-SIL technology based on tunable liquid prisms offers a new approach towards sustainable buildings that are able to reduce their electricity usage as well as provide a healthy and comfortable indoor environment under illumination of natural sunlight.

Chemical evolution of the Salton Sea, California: nutrient and selenium dynamics

USGS Publications Warehouse

Schroeder, Roy A.; Orem, William H.; Kharaka, Yousif K.

2002-01-01

The Salton Sea is a 1000-km2 terminal lake located in the desert area of southeastern California. This saline (∼44 000 mg l−1 dissolved solids) lake started as fresh water in 1905–07 by accidental flooding of the Colorado River, and it is maintained by agricultural runoff of irrigation water diverted from the Colorado River. The Salton Sea and surrounding wetlands have recently acquired substantial ecological importance because of the death of large numbers of birds and fish, and the establishment of a program to restore the health of the Sea. In this report, we present new data on the salinity and concentration of selected chemicals in the Salton Sea water, porewater and sediments, emphasizing the constituents of concern: nutrients (N and P), Se and salinity. Chemical profiles from a Salton Sea core estimated to have a sedimentation rate of 2.3 mm yr−1 show increasing concentrations of OC, N, and P in younger sediment that are believed to reflect increasing eutrophication of the lake. Porewater profiles from two locations in the Sea show that diffusion from bottom sediment is only a minor source of nutrients to the overlying water as compared to irrigation water inputs. Although loss of N and Se by microbial-mediated volatilization is possible, comparison of selected element concentrations in river inputs and water and sediments from the Salton Sea indicates that most of the N (from fertilizer) and virtually all of the Se (delivered in irrigation water from the Colorado River) discharged to the Sea still reside within its bottom sediment. Laboratory simulation on mixtures of sediment and water from the Salton Sea suggest that sediment is a potential source of N and Se to the water column under aerobic conditions. Hence, it is important that any engineered changes made to the Salton Sea for remediation or for transfer of water out of the basin do not result in remobilization of nutrients and Se from the bottom sediment into the overlying water.

Everything you wanted to know about VAMPs but were afraid to ask

NASA Astrophysics Data System (ADS)

Martin, K. M.; Stern, R. J.; Barth, G. A.; Wood, W. T.; Scholl, D. W.; Scheirer, D. S.

2017-12-01

Velocity-AMPlitude anomalies (VAMPs) are distinctive seismic reflection features attributed to regions of fluid upflow in sedimentary basins. The largely Cenozoic, flat-lying sediments of the Aleutian Basin have many VAMPs and make a natural laboratory to without complicating factors such as faults or folds. VAMPs were first identified in the Bering Sea in 1978 and have since been found in several other basins where stratigraphic reflections are almost perfectly parallel across hundreds of kilometers. VAMPs are high amplitude anomalies disrupting these smooth reflectors at depths consistent with the base of the gas Hydrate Stability Zone (HSZ). Below these "bright" areas are "push-downs" of the flat reflectors, increasing in downward deflection with depth, in a column often visible to basement. This downward deflection is consistent with presence of methane gas, while high amplitudes near the HSZ are consistent with build-up of hydrate that traps the gas below. Analysis of multi-channel seismic reflection data acquired by RV Marcus G. Langseth in 2011 reveals VAMPs as radially symmetric features. Methane flowing up a roughly circular conduit is slowed by hydrate build up in the pore space of the HSZ and spreads outward, creating more hydrate. Over time, amplitude anomalies spread outward and thicken into a shape resembling a pointy mushroom (caps as wide as 5 km, conduits thinner than 300 meters). Using available seismic reflection data for the Aleutian Basin, we mapped VAMPs, top of basement, and a Bottom Simulating Reflector (BSR) at the base of the HSZ. The widely distributed BSR indicates gas is present in and migrating through sediments outside of VAMP conduits. Thus some portions of the system host diffuse upward flow of fluids in addition to the VAMPs generated by focused flow. The BSR depth gives constraints on the magnitude and variation of basin heat flow. The BSR amplitudes show how areas of diffuse fluid upwelling interact with the VAMP system.

4. TOPSIDE VIEW FROM UPPER DECK LOOKING DOWN INTO TANK ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. TOPSIDE VIEW FROM UPPER DECK LOOKING DOWN INTO TANK WITH SHUTTLE CARGO BAY MOCK-UP AT BOTTOM OF 40 FOOT TANK. - Marshall Space Flight Center, Neutral Buoyancy Simulator Facility, Rideout Road, Huntsville, Madison County, AL

5. TOPSIDE VIEW FROM UPPER DECK LOOKING DOWN INTO TANK ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. TOPSIDE VIEW FROM UPPER DECK LOOKING DOWN INTO TANK WITH SHUTTLE CARGO BAY MOCK-UP AT BOTTOM OF 40 FOOT TANK. - Marshall Space Flight Center, Neutral Buoyancy Simulator Facility, Rideout Road, Huntsville, Madison County, AL

A novel method for quantitative geosteering using azimuthal gamma-ray logging.

PubMed

Yuan, Chao; Zhou, Cancan; Zhang, Feng; Hu, Song; Li, Chaoliu

2015-02-01

A novel method for quantitative geosteering by using azimuthal gamma-ray logging is proposed. Real-time up and bottom gamma-ray logs when a logging tool travels through a boundary surface with different relative dip angles are simulated with the Monte Carlo method. Study results show that response points of up and bottom gamma-ray logs when the logging tool moves towards a highly radioactive formation can be used to predict the relative dip angle, and then the distance from the drilling bit to the boundary surface is calculated. Copyright © 2014 Elsevier Ltd. All rights reserved.

Designs of infrared nonpolarizing beam splitters with a Ag layer in a glass cube.

PubMed

Shi, Jin Hui; Wang, Zheng Ping

2008-05-10

A novel design of a nonpolarizing beam splitter with a Ag layer in a cube was proposed and optimized, based on the needle optimization. The digital simulations of the reflectance and reflection-induced retardance were presented. The simulation results showed that both the amplitude and the phase characteristics of the nonpolarizing beam splitter could realize the design targets. The difference between the simulated and the target reflectance of 50% is less than 0.4% and the simulated and the reflection-induced retardance is less than 0.62 degrees in the 1260 -1360 nm range for both p and s components.

Variations in water clarity and bottom albedo in Florida Bay from 1985 to 1997

USGS Publications Warehouse

Stumpf, R.P.; Frayer, M.L.; Durako, M.J.; Brock, J.C.

1999-01-01

Following extensive seagrass die-offs of the late 1980s and early 1990s, Florida Bay reportedly had significant declines in water clarity due to turbidity and algal blooms. Scant information exists on the extent of the decline, as this bay was not investigated for water quality concerns before the die-offs and limited areas were sampled after the primary die-off. We use imagery from the Advanced Very High Resolution Radiometer (AVHRR) to examine water clarity in Florida Bay for the period 1985 to 1997. The AVHRR provides data on nominal water reflectance and estimated fight attenuation, which are used here to describe turbidity conditions in the bay on a seasonal basis. In situ observations on changes in seagrass abundance within the bay, combined with the satellite data, provide additional insights into losses of seagrass. The imagery shows an extensive region to the west of Florida Bay having increased reflectance and fight attenuation in both winter and summer beginning in winter of 1988. These increases are consistent with a change from dense seagrass to sparse or negligible cover. Approximately 200 km2 of these offshore seagrasses may have been lost during the primary die-off (1988 through 1991), significantly more than in the bay. The imagery shows the distribution and timing of increased turbidity that followed the die-offs in the northwestern regions of the bay, exemplified in Rankin Lake and Johnson Key Basin, and indicates that about 200 km2 of dense seagrass may have been lost or severely degraded within the bay from the start of the die-off. The decline in water clarity has continued in the northwestern bay since 1991. The area west of the Everglades National Park boundaries has shown decreases in both winter turbidity and summer reflectances, suggestive of partial seagrass recovery. Areas of low reflectance associated with a major Syringodium filiforme seagrass meadow north of Marathon (Vaca Key, in the Florida Keys) appear to have expanded westward toward Big Pine Key, indicating changes in the bottom cover from before the die-off. The southern and eastern sections of the Bay have not shown significant changes in water clarity or bottom albedo throughout the entire time period.

[A Method to Reconstruct Surface Reflectance Spectrum from Multispectral Image Based on Canopy Radiation Transfer Model].

PubMed

Zhao, Yong-guang; Ma, Ling-ling; Li, Chuan-rong; Zhu, Xiao-hua; Tang, Ling-li

2015-07-01

Due to the lack of enough spectral bands for multi-spectral sensor, it is difficult to reconstruct surface retlectance spectrum from finite spectral information acquired by multi-spectral instrument. Here, taking into full account of the heterogeneity of pixel from remote sensing image, a method is proposed to simulate hyperspectral data from multispectral data based on canopy radiation transfer model. This method first assumes the mixed pixels contain two types of land cover, i.e., vegetation and soil. The sensitive parameters of Soil-Leaf-Canopy (SLC) model and a soil ratio factor were retrieved from multi-spectral data based on Look-Up Table (LUT) technology. Then, by combined with a soil ratio factor, all the parameters were input into the SLC model to simulate the surface reflectance spectrum from 400 to 2 400 nm. Taking Landsat Enhanced Thematic Mapper Plus (ETM+) image as reference image, the surface reflectance spectrum was simulated. The simulated reflectance spectrum revealed different feature information of different surface types. To test the performance of this method, the simulated reflectance spectrum was convolved with the Landsat ETM + spectral response curves and Moderate Resolution Imaging Spectrometer (MODIS) spectral response curves to obtain the simulated Landsat ETM+ and MODIS image. Finally, the simulated Landsat ETM+ and MODIS images were compared with the observed Landsat ETM+ and MODIS images. The results generally showed high correction coefficients (Landsat: 0.90-0.99, MODIS: 0.74-0.85) between most simulated bands and observed bands and indicated that the simulated reflectance spectrum was well simulated and reliable.

High performance of treated and washed MSWI bottom ash granulates as natural aggregate replacement within earth-moist concrete.

PubMed

Keulen, A; van Zomeren, A; Harpe, P; Aarnink, W; Simons, H A E; Brouwers, H J H

2016-03-01

Municipal solid waste incineration bottom ash was treated with specially designed dry and wet treatment processes, obtaining high quality bottom ash granulate fractions (BGF) suitable for up to 100% replacement of natural gravel in concrete. The wet treatment (using only water for separating and washing) significantly lowers the leaching of e.g. chloride and sulfate, heavy metals (antimony, molybdenum and copper) and dissolved organic carbon (DOC). Two potential bottom ash granulate fractions, both in compliance with the standard EN 12620 (aggregates for concrete), were added into earth-moist concrete mixtures. The fresh and hardened concrete physical performances (e.g. workability, strength and freeze-thaw) of high strength concrete mixtures were maintained or improved compared with the reference mixtures, even after replacing up to 100% of the initial natural gravel. Final element leaching of monolithic and crushed granular state BGF containing concretes, showed no differences with the gravel references. Leaching of all mixtures did not exceed the limit values set by the Dutch Soil Quality Degree. In addition, multiple-life-phase emission (pH static test) for the critical elements of input bottom ash, bottom ash granulate (BGF) and crushed BGF containing concrete were assessed. Simulation pH lowering or potential carbonation processes indicated that metal (antimony, barium, chrome and copper) and sulfate element leaching behavior are mainly pH dominated and controlled, although differ in mechanism and related mineral abundance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Microgravity

NASA Image and Video Library

1998-11-04

Computer simulation of atmospheric flow corresponds well to imges taken during the second Geophysical Fluid Flow Cell (BFFC) mission. The top shows a view from the pole, while the bottom shows a view from the equator. Red corresponds to hot fluid rising while blue shows cold fluid falling. This simulation was developed by Anil Deane of the University of Maryland, College Park and Paul Fischer of Argorne National Laboratory. Credit: NASA/Goddard Space Flight Center

Large-Eddy Simulation in Planetary Boundary-Layer Research

NASA Technical Reports Server (NTRS)

Wyngaard, J. C.

1985-01-01

The structure and dynamics of the convective boundary layer are discussed. The vertical transport of a conservative, passive scalar was simulated. Also studied were the statistics by top-down and bottom-up scalar fields. Substantial differences were found between them due, presumably, to the asymmetry in the convective boundary layer. A generalization of mixed-layer scaling was developed which allows one to include the effects of top-down diffusion.

In-flight and simulated aircraft fuel temperature measurements

NASA Technical Reports Server (NTRS)

Svehla, Roger A.

1990-01-01

Fuel tank measurements from ten flights of an L1011 commercial aircraft are reported for the first time. The flights were conducted from 1981 to 1983. A thermocouple rake was installed in an inboard wing tank and another in an outboard tank. During the test periods of either 2 or 5 hr, at altitudes of 10,700 m (35,000 ft) or higher, either the inboard or the outboard tank remained full. Fuel temperature profiles generally developed in the expected manner. The bulk fuel was mixed by natural convection to a nearly uniform temperature, especially in the outboard tank, and a gradient existed at the bottom conduction zone. The data indicated that when full, the upper surface of the inboard tank was wetted and the outboard tank was unwetted. Companion NASA Lewis Research Center tests were conducted in a 0.20 cubic meter (52 gal) tank simulator of the outboard tank, chilled on the top and bottom, and insulated on the sides. Even though the simulator tank had no internal components corresponding to the wing tank, temperatures agreed with the flight measurements for wetted upper surface conditions, but not for unwetted conditions. It was concluded that if boundary conditions are carefully controlled, simulators are a useful way of evaluating actual flight temperatures.

Certainties and Uncertainties in CFD Prediction of the End of the Vortex Behaviour in Centrifugal Separators

NASA Astrophysics Data System (ADS)

Pisarev, Gleb I.; Hoffmann, Alex C.

2011-09-01

This paper compares CFD simulations of the `end of the vortex' (EoV) behaviour in centrifugal separators with experiment. The EoV was studied in `swirl tubes', cylindrical cyclone separators with swirl vanes. We refer to the EoV as the phenomenon whereby the core of the vortex does not reach the bottom of the separator, but deviates from the swirl tube axis and attaches to the wall, where it rotates at some level above the bottom. The crucial parameters governing the EoV are geometrical, specifically the ratio of the separator length to its diameter (L/D), and operational, specifically the fluid flowrate. Swirl tubes with varying body lengths have been studied experimentally and numerically. CFD simulations were carried out using the commercial package Star-CD. The 3-D Navier-Stokes equations were solved using the finite volume method based on the SIMPLE pressure-correction algorithm and the LES turbulence model. The vortex behaviour was very similar between the experiments and the numerical simulations, this agreement being both qualitative and quantitative. However, there were some cases where the CFD predictions showed only qualitative agreement with experiments, with some of the parameter-values delimiting given types of flows being somewhat different between experiment and simulations.

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).

Quantum spill-out in few-nanometer metal gaps: Effect on gap plasmons and reflectance from ultrasharp groove arrays

NASA Astrophysics Data System (ADS)

Skjølstrup, Enok J. H.; Søndergaard, Thomas; Pedersen, Thomas G.

2018-03-01

Plasmons in ultranarrow metal gaps are highly sensitive to the electron density profile at the metal surfaces. Using a quantum mechanical approach and assuming local response, we study the effects of electron spill-out on gap plasmons and reflectance from ultrasharp metal grooves. We demonstrate that the mode index of ultranarrow gap plasmons converges to the bulk refractive index in the limit of vanishing gap and, thereby, rectify the unphysical divergence found in classical models. Surprisingly, spill-out also significantly increases the plasmonic absorption for few-nanometer gaps and lowers the reflectance from arrays of ultrasharp metal grooves. These findings are explained in terms of enhanced gap plasmon absorption taking place inside the gap 1-2 Å from the walls and delocalization near the groove bottom. Reflectance calculations taking spill-out into account are shown to be in much better agreement with measurements compared with classical models.

Language with Character: A Stratified Corpus Comparison of Individual Differences in E-Mail Communication

ERIC Educational Resources Information Center

Oberlander, Jon; Gill, Alastair J.

2006-01-01

To what extent does the wording and syntactic form of people's writing reflect their personalities? Using a bottom-up stratified corpus comparison, rather than the top-down content analysis techniques that have been used before, we examine a corpus of e-mail messages elicited from individuals of known personality, as measured by the Eysenck…

"What Works" in Education and Social Welfare? A Mapping of the "Evidence Discourse" and Reflections upon Consequences for Professionals

ERIC Educational Resources Information Center

Krejsler, John B.

2013-01-01

Drawing on Foucauldian genealogy, the article maps major sources and trajectories of the evidence discourse. This enables scrutiny of the current struggle about "evidence" for "What Works" in education and social welfare. Evidence discourse is identified as emerging from the medical field as a bottom-up professional strategy.…

Modeling and Analysis of Target Echo and Clutter in Range-Dependent Bistatic Environments: FY12 Annual Report for ONR

DTIC Science & Technology

2012-09-30

interface since it includes the phase. The effects of a low-speed resonant layer have been noticed before in regard to propagation. Hastrup [Has80... Hastrup . Some bottom-reflection loss anomalies near grazing and their effect on propagation in shallow water. In W. A. Kuperman and F. B. Jensen, editors

Clinical Ethics Support for Healthcare Personnel: An Integrative Literature Review.

PubMed

Rasoal, Dara; Skovdahl, Kirsti; Gifford, Mervyn; Kihlgren, Annica

2017-12-01

This study describes which clinical ethics approaches are available to support healthcare personnel in clinical practice in terms of their construction, functions and goals. Healthcare personnel frequently face ethically difficult situations in the course of their work and these issues cover a wide range of areas from prenatal care to end-of-life care. Although various forms of clinical ethics support have been developed, to our knowledge there is a lack of review studies describing which ethics support approaches are available, how they are constructed and their goals in supporting healthcare personnel in clinical practice. This study engages in an integrative literature review. We searched for peer-reviewed academic articles written in English between 2000 and 2016 using specific Mesh terms and manual keywords in CINAHL, MEDLINE and Psych INFO databases. In total, 54 articles worldwide described clinical ethics support approaches that include clinical ethics consultation, clinical ethics committees, moral case deliberation, ethics rounds, ethics discussion groups, and ethics reflection groups. Clinical ethics consultation and clinical ethics committees have various roles and functions in different countries. They can provide healthcare personnel with advice and recommendations regarding the best course of action. Moral case deliberation, ethics rounds, ethics discussion groups and ethics reflection groups support the idea that group reflection increases insight into ethical issues. Clinical ethics support in the form of a "bottom-up" perspective might give healthcare personnel opportunities to think and reflect more than a "top-down" perspective. A "bottom-up" approach leaves the healthcare personnel with the moral responsibility for their choice of action in clinical practice, while a "top-down" approach risks removing such moral responsibility.

Seasonal pathways of organic matter within the Avilés submarine canyon: Food web implications

NASA Astrophysics Data System (ADS)

Romero-Romero, Sonia; Molina-Ramírez, Axayacatl; Höfer, Juan; Duineveld, Gerard; Rumín-Caparrós, Aitor; Sanchez-Vidal, Anna; Canals, Miquel; Acuña, José Luis

2016-11-01

The transport and fate of organic matter (OM) sources within the Avilés submarine canyon (Cantabrian Sea, Southern Bay of Biscay) were studied using carbon and nitrogen stable isotope ratios. The isotopic composition of settling particles and deep bottom sediments closely resembled that of surface particulate OM, and there were no marked differences in the isotopic composition of settling particles inside and outside of the AC. This indicates that the Avilés Canyon (AC) receives inputs of sinking OM mostly from the upper water column and less through advective near-bottom down-canyon transport. Sinking OM fluxes are of marine and terrestrial origin in proportions which vary seasonally. Analysis of δ13C in the canyon fauna indicates a dependence on OM mainly produced by marine phytoplankton. A tight coupling of isotopic signatures between pelagic organisms and benthic suspension feeders reflects an active biological vertical transport of OM from the surface to the deep-sea. The food web presented seasonal variations in the trophic niche width and the amplitude of the primary carbon sources, reflecting seasonality in the availability of fresh particulate OM. Those seasonal changes are larger for benthic organisms of lower trophic levels.

Wave equation datuming applied to marine OBS data and to land high resolution seismic profiling

NASA Astrophysics Data System (ADS)

Barison, Erika; Brancatelli, Giuseppe; Nicolich, Rinaldo; Accaino, Flavio; Giustiniani, Michela; Tinivella, Umberta

2011-03-01

One key step in seismic data processing flows is the computation of static corrections, which relocate shots and receivers at the same datum plane and remove near surface weathering effects. We applied a standard static correction and a wave equation datuming and compared the obtained results in two case studies: 1) a sparse ocean bottom seismometers dataset for deep crustal prospecting; 2) a high resolution land reflection dataset for hydrogeological investigation. In both cases, a detailed velocity field, obtained by tomographic inversion of the first breaks, was adopted to relocate shots and receivers to the datum plane. The results emphasize the importance of wave equation datuming to properly handle complex near surface conditions. In the first dataset, the deployed ocean bottom seismometers were relocated to the sea level (shot positions) and a standard processing sequence was subsequently applied to the output. In the second dataset, the application of wave equation datuming allowed us to remove the coherent noise, such as ground roll, and to improve the image quality with respect to the application of static correction. The comparison of the two approaches evidences that the main reflecting markers are better resolved when the wave equation datuming procedure is adopted.

Platforms for hyperspectral imaging, in-situ optical and acoustical imaging in urbanized regions

NASA Astrophysics Data System (ADS)

Bostater, Charles R.; Oney, Taylor

2016-10-01

Hyperspectral measurements of the water surface of urban coastal waters are presented. Oblique bidirectional reflectance factor imagery was acquired made in a turbid coastal sub estuary of the Indian River Lagoon, Florida and along coastal surf zone waters of the nearby Atlantic Ocean. Imagery was also collected using a pushbroom hyperspectral imager mounted on a fixed platform with a calibrated circular mechatronic rotation stage. Oblique imagery of the shoreline and subsurface features clearly shows subsurface bottom features and rip current features within the surf zone water column. In-situ hyperspectral optical signatures were acquired from a vessel as a function of depth to determine the attenuation spectrum in Palm Bay. A unique stationary platform methodology to acquire subsurface acoustic images showing the presence of moving bottom boundary nephelometric layers passing through the acoustic fan beam. The acoustic fan beam imagery indicated the presence of oscillatory subsurface waves in the urbanized coastal estuary. Hyperspectral imaging using the fixed platform techniques are being used to collect hyperspectral bidirectional reflectance factor (BRF) measurements from locations at buildings and bridges in order to provide new opportunities to advance our scientific understanding of aquatic environments in urbanized regions.

Monte Carlo simulation of reflection spectra of random multilayer media strongly scattering and absorbing light

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

Meglinskii, I V

2001-12-31

The reflection spectra of a multilayer random medium - the human skin - strongly scattering and absorbing light are numerically simulated. The propagation of light in the medium and the absorption spectra are simulated by the stochastic Monte Carlo method, which combines schemes for calculations of real photon trajectories and the statistical weight method. The model takes into account the inhomogeneous spatial distribution of blood vessels, water, and melanin, the degree of blood oxygenation, and the hematocrit index. The attenuation of the incident radiation caused by reflection and refraction at Fresnel boundaries of layers inside the medium is also considered.more » The simulated reflection spectra are compared with the experimental reflection spectra of the human skin. It is shown that a set of parameters that was used to describe the optical properties of skin layers and their possible variations, despite being far from complete, is nevertheless sufficient for the simulation of the reflection spectra of the human skin and their quantitative analysis. (laser applications and other topics in quantum electronics)« less

Temporal Variability of Observed and Simulated Hyperspectral Earth Reflectance

NASA Technical Reports Server (NTRS)

Roberts, Yolanda; Pilewskie, Peter; Kindel, Bruce; Feldman, Daniel; Collins, William D.

2012-01-01

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a climate observation system designed to study Earth's climate variability with unprecedented absolute radiometric accuracy and SI traceability. Observation System Simulation Experiments (OSSEs) were developed using GCM output and MODTRAN to simulate CLARREO reflectance measurements during the 21st century as a design tool for the CLARREO hyperspectral shortwave imager. With OSSE simulations of hyperspectral reflectance, Feldman et al. [2011a,b] found that shortwave reflectance is able to detect changes in climate variables during the 21st century and improve time-to-detection compared to broadband measurements. The OSSE has been a powerful tool in the design of the CLARREO imager and for understanding the effect of climate change on the spectral variability of reflectance, but it is important to evaluate how well the OSSE simulates the Earth's present-day spectral variability. For this evaluation we have used hyperspectral reflectance measurements from the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), a shortwave spectrometer that was operational between March 2002 and April 2012. To study the spectral variability of SCIAMACHY-measured and OSSE-simulated reflectance, we used principal component analysis (PCA), a spectral decomposition technique that identifies dominant modes of variability in a multivariate data set. Using quantitative comparisons of the OSSE and SCIAMACHY PCs, we have quantified how well the OSSE captures the spectral variability of Earth?s climate system at the beginning of the 21st century relative to SCIAMACHY measurements. These results showed that the OSSE and SCIAMACHY data sets share over 99% of their total variance in 2004. Using the PCs and the temporally distributed reflectance spectra projected onto the PCs (PC scores), we can study the temporal variability of the observed and simulated reflectance spectra. Multivariate time series analysis of the PC scores using techniques such as Singular Spectrum Analysis (SSA) and Multichannel SSA will provide information about the temporal variability of the dominant variables. Quantitative comparison techniques can evaluate how well the OSSE reproduces the temporal variability observed by SCIAMACHY spectral reflectance measurements during the first decade of the 21st century. PCA of OSSE-simulated reflectance can also be used to study how the dominant spectral variables change on centennial scales for forced and unforced climate change scenarios. To have confidence in OSSE predictions of the spectral variability of hyperspectral reflectance, it is first necessary for us to evaluate the degree to which the OSSE simulations are able to reproduce the Earth?s present-day spectral variability.

Modeling of Mixing Behavior in a Combined Blowing Steelmaking Converter with a Filter-Based Euler-Lagrange Model

NASA Astrophysics Data System (ADS)

Li, Mingming; Li, Lin; Li, Qiang; Zou, Zongshu

2018-05-01

A filter-based Euler-Lagrange multiphase flow model is used to study the mixing behavior in a combined blowing steelmaking converter. The Euler-based volume of fluid approach is employed to simulate the top blowing, while the Lagrange-based discrete phase model that embeds the local volume change of rising bubbles for the bottom blowing. A filter-based turbulence method based on the local meshing resolution is proposed aiming to improve the modeling of turbulent eddy viscosities. The model validity is verified through comparison with physical experiments in terms of mixing curves and mixing times. The effects of the bottom gas flow rate on bath flow and mixing behavior are investigated and the inherent reasons for the mixing result are clarified in terms of the characteristics of bottom-blowing plumes, the interaction between plumes and top-blowing jets, and the change of bath flow structure.

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.

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.

Hydrographic charting from Landsat satellite - A comparison with aircraft imagery

NASA Technical Reports Server (NTRS)

Middleton, E. M.; Barker, J. L.

1976-01-01

The relative capabilities of two remote-sensing systems in measuring depth and, consequently, bottom contours in sandy-bottomed and sediment-laden coastal waters were determined quantitatively. The Multispectral Scanner (MSS), orbited on the Landsat-2 satellite, and the Ocean Color Scanner (OCS), flown on U-2 aircraft, were used for this evaluation. Analysis of imagery taken simultaneously indicates a potential for hydrographic charting of marine coastal and shallow shelf areas, even when water turbidity is a factor. Several of the eight optical channels examined on the OCS were found to be sensitive to depth or depth-related information. The greatest sensitivity was in OCS-4 (0.544 plus or minus 0.012 micron) from which contours corresponding to depths up to 12 m were determined. The sharpness of these contours and their spatial stability through time suggests that upwelling radiance is a measure of bottom reflectance and not of water turbidity. The two visible channels on Landsat's MSS were less sensitive in the discrimination of contours, with depths up to 8 m in the high-gain mode (3 X) determined in MSS-4 (0.5 to 0.6 micron).

Hydrographic charting from LANDSAT Satellite: A comparison with aircraft imagery

NASA Technical Reports Server (NTRS)

Middleton, E. M.; Barker, J. L.

1976-01-01

The relative capabilities of two remote-sensing systems in measuring depth and, consequently, bottom contours in sandy-bottomed and sediment-laden coastal waters were determined quantitatively. The multispectral scanner (MSS), orbited on the LANDSAT-2 Satellite, and the ocean color scanner (OCS), flown on U-2 aircraft, were used. Analysis of imagery taken simultaneously indicates a potential for hydrographic charting of marine coastal and shallow shelf areas, even when water turbidity is a factor. Several of the eight optical channels examined on the OCS were found to be sensitive to depth or depth-related information. The greatest sensitivity was in OCS-4(0.544 + or - 0.012 microns) from which contours corresponding to depths up to 12m were determined. The sharpness of these contours and their spatial stability through time suggests that upwelling radiance is a measure of bottom reflectance and not of water turbidity. The two visible channels on LANDSAT's MSS were less sensitive in the discrimination of contours, with depths up to 8m in the high-gain mode (3x) determined in MSS-4(0.5 to 0.6 microns).

Characterization of shallow ocean sediments using the airborne electromagnetic method

NASA Technical Reports Server (NTRS)

Won, I. J.; Smits, K.

1986-01-01

Experimental airborne electromagnetic (AEM) survey data collected in Cape Cod Bay are used to derive continuous profiles of water depth, electrical depth, water conductivity, and bottom sediment conductivity. Through a few well-known empirical relationships, the conductivities are used, in turn, to derive density, porosity, sound speed, and acoustic reflectivity of the ocean bottom. A commercially available Dighem III AEM system was used for the survey without any significant modification. The helicopter-borne system operated at 385 and 7200 Hz; both were in a horizontal coplanar configuration. The interpreted profiles show good agreement with available ground truth data. Where no such data are available, the results appear to be very reasonable. Compared with the shipborne electrode array method, the AEM method can determine the necessary parameters at a much higher speed with a better lateral resolution over a wide range of water depths from 0 to perhaps 100 m. The bottom sediment conductivity that can be measured by the AEM method is closely related to physical properties of sediments, such as porosity, density, sound speed, and, indirectly, sediment types that might carry broad implications for various offshore activities.

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.

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.

Uranium Stable Isotopes: A Proxy For Productivity Or Ocean Oxygenation?

NASA Astrophysics Data System (ADS)

Severmann, S.

2015-12-01

Uranium elemental abundances in sediments have traditionally been used to reconstruct primary productivity and carbon flux in the ocean. 238U/235U isotope compositions, in contrast, are currently understood to reflect the extent of bottom water anoxia in the ocean. A review of our current understanding of authigenic U enrichment mechanism into reducing sediments suggests that a revision of this interpretation is warranted. Specifically, the current interpretation of U isotope effects in suboxic vs. anoxic deposits has not taken into account the well-documented linear relationship with organic C burial rates. Although organic C rain rates (i.e., surface productivity) and bottom water oxygenation are clearly related, distinction between these two environmental controls is conceptually important as it relates to the mechanism of enhanced C burial and ultimately the strength of the biological pump. Here we will review new and existing data to test the hypothesis that the isotope composition of authigenic U in reducing sediments are best described by their relationship with parameters related to organic carbon delivery and burial, rather than bottom water oxygen concentration.

P-Wave and S-Wave Velocity Structure of Submarine Landslide Associated With Gas Hydrate Layer on Frontal Ridge of Northern Cascadia Margin

NASA Astrophysics Data System (ADS)

He, T.; Lu, H.; Yelisetti, S.; Spence, G.

2015-12-01

The submarine landslide associated with gas hydrate is a potential risk for environment and engineering projects, and thus from long time ago it has been a hot topic of hydrate research. The study target is Slipstream submarine landslide, one of the slope failures observed on the frontal ridges of the Northern Cascadia accretionary margin off Vancouver Island. The previous studies indicated a possible connection between this submarine landslide feature and gas hydrate, whose occurrence is indicated by a prominent bottom-simulating reflector (BSR), at a depth of ~265-275 m beneath the seafloor (mbsf). The OBS (Ocean Bottom Seismometer) data collected during SeaJade (Seafloor Earthquake Array - Japan Canada Cascadia Experiment) project were used to derive the subseafloor velocity structure for both P- and S-wave using travel times picked from refraction and reflection events. The P-wave velocity structure above the BSR showed anomalous high velocities of about 2.0 km/s at shallow depths of 100 mbsf, closely matching the estimated depth of the glide plane (100 ± 10 m). Forward modelling of S-waves was carried out using the data from the OBS horizontal components. The S-wave velocities, interpreted in conjunction with the P-wave results, provide the key constraints on the gas hydrate distribution within the pores. The hydrate distribution in the pores is important for determining concentrations, and also for determining the frame strength which is critical for controlling slope stability of steep frontal ridges. The increase in S-wave velocity suggests that the hydrate is distributed as part of the load-bearing matrix to increase the rigidity of the sediment.

Design and development of next-generation bottom anti-reflective coatings for 45nm process with hyper NA lithography

NASA Astrophysics Data System (ADS)

Nakajima, Makoto; Sakaguchi, Takahiro; Hashimoto, Keisuke; Sakamoto, Rikimaru; Kishioka, Takahiro; Takei, Satoshi; Enomoto, Tomoyuki; Nakajima, Yasuyuki

2006-03-01

Integrated circuit manufacturers are consistently seeking to minimize device feature dimensions in order to reduce chip size and increase integration level. Feature sizes on chips are achieved sub 65nm with the advanced 193nm microlithography process. R&D activities of 45nm process have been started so far, and 193nm lithography is used for this technology. The key parameters for this lithography process are NA of exposure tool, resolution capability of resist, and reflectivity control with bottom anti-reflective coating (BARC). In the point of etching process, single-layer resist process can't be applied because resist thickness is too thin for getting suitable aspect ratio. Therefore, it is necessary to design novel BARC system and develop hard mask materials having high etching selectivity. This system and these materials can be used for 45nm generation lithography. Nissan Chemical Industries, Ltd. and Brewer Science, Inc. have been designed and developed the advanced BARCs for the above propose. In order to satisfy our target, we have developed novel BARC and hard mask materials. We investigated the multi-layer resist process stacked 4 layers (resist / thin BARC / silicon-contained BARC (Si-ARC) / spin on carbon hard mask (SOC)) (4 layers process). 4 layers process showed the excellent lithographic performance and pattern transfer performance. In this paper, we will discuss the detail of our approach and materials for 4 layers process.

Responses to atmospheric CO2 concentrations in crop simulation models: a review of current simple and semicomplex representations and options for model development.

PubMed

Vanuytrecht, Eline; Thorburn, Peter J

2017-05-01

Elevated atmospheric CO 2 concentrations ([CO 2 ]) cause direct changes in crop physiological processes (e.g. photosynthesis and stomatal conductance). To represent these CO 2 responses, commonly used crop simulation models have been amended, using simple and semicomplex representations of the processes involved. Yet, there is no standard approach to and often poor documentation of these developments. This study used a bottom-up approach (starting with the APSIM framework as case study) to evaluate modelled responses in a consortium of commonly used crop models and illuminate whether variation in responses reflects true uncertainty in our understanding compared to arbitrary choices of model developers. Diversity in simulated CO 2 responses and limited validation were common among models, both within the APSIM framework and more generally. Whereas production responses show some consistency up to moderately high [CO 2 ] (around 700 ppm), transpiration and stomatal responses vary more widely in nature and magnitude (e.g. a decrease in stomatal conductance varying between 35% and 90% among models was found for [CO 2 ] doubling to 700 ppm). Most notably, nitrogen responses were found to be included in few crop models despite being commonly observed and critical for the simulation of photosynthetic acclimation, crop nutritional quality and carbon allocation. We suggest harmonization and consideration of more mechanistic concepts in particular subroutines, for example, for the simulation of N dynamics, as a way to improve our predictive understanding of CO 2 responses and capture secondary processes. Intercomparison studies could assist in this aim, provided that they go beyond simple output comparison and explicitly identify the representations and assumptions that are causal for intermodel differences. Additionally, validation and proper documentation of the representation of CO 2 responses within models should be prioritized. © 2017 John Wiley & Sons Ltd.

3-D Voxel FEM Simulation of Seismic Wave Propagation in a Land-Sea Structure with Topography

NASA Astrophysics Data System (ADS)

Ikegami, Y.; Koketsu, K.

2003-12-01

We have already developed the voxel FEM (finite element method) code to simulate seismic wave propagation in a land structure with surface topography (Koketsu, Fujiwara and Ikegami, 2003). Although the conventional FEM often requires much larger memory, longer computation time and farther complicated mesh generation than the Finite Difference Method (FDM), this code consumes a similar amount of memory to FDM and spends only 1.4 times longer computation time thanks to the simplicity of voxels (hexahedron elements). The voxel FEM was successfully applied to inland earthquakes, but most earthquakes in a subduction zone occur beneath a sea, so that a simulation in a land-sea structure should be essential for waveform modeling and strong motion prediction there. We now introduce a domain of fluid elements into the model and formulate displacements in the elements using the Lagrange method. Sea-bottom motions are simulated for the simple land-sea models of Okamoto and Takenaka (1999). The simulation results agree well with their reflectivity and FDM seismograms. In order to enhance numerical stability, not only a variable mesh but also an adaptive time step is introduced. We can now choose the optimal time steps everywhere in the model based the Courant condition. This doubly variable formulation may result in inefficient parallel computing. The wave velocity in a shallow part is lower than that in a deeper part. Therefore, if the model is divided into horizontal slices and they are assigned to CPUs, a shallow slice will consist of only small elements. This can cause unbalanced loads on the CPUs. Accordingly, the model is divided into vertical slices in this study. They also reduce inter-processor communication, because a vertical cross section is usually smaller than a horizontal one. In addition, we will consider higher-order FEM formulation compatible to the fourth-order FDM. We will also present numerical examples to demonstrate the effects of a sea and surface topography on seismic waves and ground motions.

Three-dimensional Stochastic Estimation of Porosity Distribution: Benefits of Using Ground-penetrating Radar Velocity Tomograms in Simulated-annealing-based or Bayesian Sequential Simulation Approaches

DTIC Science & Technology

2012-05-30

annealing-based or Bayesian sequential simulation approaches B. Dafflon1,2 and W. Barrash1 Received 13 May 2011; revised 12 March 2012; accepted 17 April 2012...the withheld porosity log are also withheld for this estimation process. For both cases we do this for two wells having locally variable stratigraphy ...borehole location is given at the bottom of each log comparison panel. For comparison with stratigraphy at the BHRS, contacts between Units 1 to 4

Methane Hydrate Concentrations at GC955 and WR313 Drilling Sites in the Gulf of Mexico Determined from Seismic Prestack Waveform Inversion

NASA Astrophysics Data System (ADS)

Fortin, W.; Goldberg, D.; Küçük, H. M.

2016-12-01

Gas hydrates are naturally occurring compounds, which, at a molecular scale, are lattice structures of ice embedded with various gas molecules in the lattice voids. Volumetric estimates of associated hydrocarbons vary greatly due to the difficulty in remotely estimating hydrate concentrations in marine sediments but embedded hydrocarbon stores are thought to represent a significant portion of global deposits. The unstable nature of methane hydrates has been linked to submarine landslides and the subsequent release of large quantities of methane can accelerate global climate change. Understanding the details of gas hydrate systems is important for potential economic production and assessing natural hazards risks. Seismic reflection techniques are uniquely capable of detecting gas hydrates. Often, hydrate layers appear as bottom simulating reflectors (BSRs); however, BSRs are not present everywhere gas hydrates are known to occur. Using recently reprocessed prestack time migrated data and prestack waveform inversion (PWI) techniques, we produce velocity models at high vertical and horizontal resolution in order to investigate the presence of gas hydrates in the Gulf of Mexico. Coupling our PWI results with known velocity-property relationships and data from nearby well controls, we determine the viability of recently collected high-resolution seismic data and outline small-scale heterogeneities at GC955 and WR313. We outline where PWI techniques are capable of identifying gas hydrates in seismic reflection data where BSRs are not present.

Asynchronous warming and δ18O evolution of deep Atlantic water masses during the last deglaciation

NASA Astrophysics Data System (ADS)

Zhang, J.; Liu, Z.; Brady, E. C.; Oppo, D.; Clark, P. U.; Jahn, A.; Marcott, S. A.; Lindsay, K. T.

2017-12-01

The large-scale reorganization of deep-ocean circulation in the Atlantic involving changes in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) played a critical role in regulating hemispheric and global climate during the last deglaciation. However, changes in the relative contributions of NADW and AABW and their properties are poorly constrained by marine records, including δ18O of benthic foraminiferal calcite (δ18Oc). Here we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and δ18O evolution. Model results suggest that in response to North Atlantic freshwater forcing during the early phase of the last deglaciation, NADW nearly collapses while AABW mildly weakens. Rather than reflecting changes in NADW or AABW properties due to freshwater input as suggested previously, the observed phasing difference of deep δ18Oc likely reflects early warming of the deep northern North Atlantic by 1.4°C while deep Southern Ocean temperature remains largely unchanged. We propose a thermodynamic mechanism to explain the early warming in the North Atlantic, featuring a strong mid-depth warming and enhanced downward heat flux via vertical mixing. Our results emphasize that the way ocean circulation affects heat, a dynamic tracer, is considerably different than how it affects passive tracers like δ18O, and call for caution when inferring water mass changes from δ18Oc records while assuming uniform changes in deep temperatures.

Asynchronous warming and δ18O evolution of deep Atlantic water masses during the last deglaciation

NASA Astrophysics Data System (ADS)

Zhang, Jiaxu; Liu, Zhengyu; Brady, Esther C.; Oppo, Delia W.; Clark, Peter U.; Jahn, Alexandra; Marcott, Shaun A.; Lindsay, Keith

2017-10-01

The large-scale reorganization of deep ocean circulation in the Atlantic involving changes in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) played a critical role in regulating hemispheric and global climate during the last deglaciation. However, changes in the relative contributions of NADW and AABW and their properties are poorly constrained by marine records, including δ18O of benthic foraminiferal calcite (δ18Oc). Here, we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and δ18O evolution. Model results suggest that, in response to North Atlantic freshwater forcing during the early phase of the last deglaciation, NADW nearly collapses, while AABW mildly weakens. Rather than reflecting changes in NADW or AABW properties caused by freshwater input as suggested previously, the observed phasing difference of deep δ18Oc likely reflects early warming of the deep northern North Atlantic by ˜1.4 °C, while deep Southern Ocean temperature remains largely unchanged. We propose a thermodynamic mechanism to explain the early warming in the North Atlantic, featuring a strong middepth warming and enhanced downward heat flux via vertical mixing. Our results emphasize that the way that ocean circulation affects heat, a dynamic tracer, is considerably different from how it affects passive tracers, like δ18O, and call for caution when inferring water mass changes from δ18Oc records while assuming uniform changes in deep temperatures.

TiO2 with controlled nanoring/nanotube hierarchical structure: Multiabsorption oscillating peaks and photoelectrochemical properties

NASA Astrophysics Data System (ADS)

Sang, Lixia; Zhao, Yangbo; Niu, Youchen; Bai, Guangmei

2018-02-01

TiO2 with Nanoring/Nanotube (R/T) hierarchical structure can be prepared by tuning the oxidation time and oxidation voltage in the second step anodization. The resulting multiabsorption oscillating peaks in the visible light region present a strong dependence on the tube length which are derived from the interference of light reflected from the top nanorings and the bottom Ti substrate, and the optical path length in TiO2 R/T hierarchical structure can be estimated as about 2 μm. The tube length of the as-prepared TiO2 photoelectrode affects greatly its saturation photocurrent density, and the different tube-wall thickness can change the photocurrent-saturation potential. Under simulated AM 1.5 irradiation (100 mW/cm2), TiO2 R/T hierarchical structure with tube diameters of 20-40 nm and tube length of about 1.5 μm shows higher photocurrent density and hydrogen production rate at the bias of 0 V (vs. Ag/AgCl). The results from the IPCE plots and I-t curves verify that TiO2 R/T hierarchical structure can exhibit the visible light activity, which is more related to the absorption induced by the defects rather than oscillating peaks. Based on the unique multiple light reflection in TiO2 R/T hierarchical structure, surface treatment will pave a way for the better utilization of oscillating peaks in the visible light region.

The correlation of sedimentation processes and land use through remote sensing: The case study of the Jequia Lagoon, Alagoas, Brazil

NASA Astrophysics Data System (ADS)

Ferreira Gomes, Heliene

This study is focused on mapping the correlation between the land-cover change, sedimentation processes and the spectral radiance patterns along the Jequia estuary using field observations and reference information, laboratory spectral reflectance measurements and LANDSAT Thematic Mapper (TM) data. The Jequia estuary comprises the lagoon and its surrounding and a tidal channel to the Atlantic Ocean. It is inserted in Tertiary and Quaternary deposits covered mainly by sugar-cane crops and rare remains of the moist tropical forest. Bottom sediments along the lagoon were sampled and used to analyze their grain size distribution and mineral content by X-ray diffraction. Those samples were also used in an experiment where several sediment concentrations were simulated and their spectra's reflectance was determined. Silt is the predominating grain size within the lagoon. Quartz and kaolinite are the main minerals present within the silt and clay grain size fractions. Aerial photographs, satellite quick-look recorded in 1989 and a LANDSAT TM digital image recorded in 1990, were analyzed. The satellite data were analyzed through the photo-interpretation and quantitative approaches. Eight land-use units were mapped based on the aerial photographs and six land-use units were defined from the quick-look image. Despite the different scales within the data, we recognized that the most significant change in land-cover from 1968 to 1990 was the clearing of almost 100% of the moist tropical forest and its replacement by sugarcane crops. Overall, the digital results (0,48 to 0,82 mum) using standard classifiers indicate three water classes for the lagoon and ten land-use classes for the land surrounding the lagoon. The laboratory reflectance experimentation for suspended sediments demonstrates an overall increase of reflectance with increasing wavelength range for low and high concentrations. The reflectance for high sediment concentration shows a distinctive increase close to the TM4 range (0,82 mum). Although the correlation between the results was not precisely assessed, the results within this study demonstrate that any multidisciplinary approach is significantly facilitated using remote sensing techniques.

Field Spectroscopy And Spectral Analysis Of Caribbean Scleractinian Reef Corals And Related Benthic Biota

NASA Astrophysics Data System (ADS)

Torres-Perez, J. L.; Guild, L. S.; Armstrong, R.; Corredor, J. E.; Polanco, R.; Zuluaga-Montero, A. B.

2013-05-01

Coral reefs are highly heterogenic ecosystems with a plethora of photosynthetic organisms forming most of the benthic communities. Usually coral reef benthos is a composite of reef corals, different groups of algae, seagrasses, sandy bottoms, dead rubble, and even mangrove forests living in a relatively small area. The remote characterization of these important tropical ecosystems represents a challenge to scientists, particularly due to the similarity of the spectral signatures among some of these components. As such, we examined the similarities and differences between nine Scleractinian Caribbean shallow-water reef corals' spectral reflectance curves. Samples were also collected from each species for pigment analysis using High Performance Liquid Chromatography (HPLC). Reflectance curves were obtained with the aid of a GER-1500 hand-held field spectroradiometer enclosed in an underwater housing. Our findings showed that even though most of the pigmentation was directly related to the relationship of corals with their symbiotic dinoflagellates (zooxanthellae), the presence of other endolithic photosynthetic organisms can also contribute to the light absorption of corals and, hence, the reflectance spectra of each species. Also, the relative contribution of chlorophylls vs. carotenes or xanthophylls depends on the coral species with some species relying more on Chlorophyll a and other species relying on Chlorophyl c2 and Peridinin with a small Chlorophyll a component. Pigments associated with the xanthophyll cycle of dinoflagellates (Diadinoxanthin and Diatoxanthin) were detected in most species. Pigments typical of endolithic organisms such as Zeaxanthin, Fucoxanthin, Violaxanthin and Siphonaxanthin were also detected in some coral species. The influence of major pigments on the reflectance curve was evidenced with a 2nd derivative analysis. This could be used to discriminate among most species. Further, an analysis of the integration of the area under the reflectance curve in the photosynthetically active radiation (PAR; 400-700nm) yielded an inverse relationship with the total pigment concentration with an up to 97% confidence level. Corals were distinguished from seagrasses and other benthic components based on their reflectance and differences in curve inflection peaks. Special care needs to be taken when characterizing sandy bottoms as they are influenced by the presence of photosynthetic microbiota as reflected in their reflectance curves. The use of this integration is proposed as a novel non-invasive method to predict pigment changes in reef corals aimed to monitor their health in the present climate change scenario.

Long-term temperature monitoring at the biological community site on the Nankai accretionary prism off Kii Peninsula

NASA Astrophysics Data System (ADS)

Goto, S.; Hamamoto, H.; Yamano, M.; Kinoshita, M.; Ashi, J.

2008-12-01

Nankai subduction zone off Kii Peninsula is one of the most intensively surveyed areas for studies on the seismogenic zone. Multichannel seismic reflection surveys carried out in this area revealed the existence of splay faults that branched from the subduction zone plate boundary [Park et al., 2002]. Along the splay faults, reversal of reflection polarity was observed, indicating elevated pore fluid pressure along the faults. Cold seepages with biological communities were discovered along a seafloor outcrop of one of the splay faults through submersible observations. Long-term temperature monitoring at a biological community site along the outcrop revealed high heat flow carried by upward fluid flow (>180 mW/m2) [Goto et al., 2003]. Toki et al. [2004] estimated upward fluid flow rates of 40-200 cm/yr from chloride distribution of interstitial water extracted from sediments in and around biological community sites along the outcrop. These observation results suggest upward fluid flow along the splay fault. In order to investigate hydrological nature of the splay fault, we conducted long-term temperature monitoring again in the same cold seepage site where Goto et al. [2003] carried out long-term temperature monitoring. In this presentation, we present results of the temperature monitoring and estimate heat flow carried by upward fluid flow from the temperature records. In this long-term temperature monitoring, we used stand-alone heat flow meter (SAHF), a probe-type sediment temperature recorder. Two SAHFs (SAHF-3 and SAHF-4) were used in this study. SAHF-4 was inserted into a bacterial mat, within several meters of which the previous long-term temperature monitoring was conducted. SAHF-3 was penetrated into ordinary sediment near the bacterial mat. The sub-bottom temperature records were obtained for 8 months. The subsurface temperatures oscillated reflecting bottom- water temperature variation (BTV). For sub-bottom temperatures measured with SAHF-3 (outside of the bacterial mat), we found that the effects of the BTV propagated into sediment by conduction only. By correcting the effect of the BTV, conductive heat flow estimated is higher than 100 mW/m2. Sub-bottom temperatures measured within bacterial mat (SAHF-4) except for the topmost sensor could be explained by a conduction model. The heat flow estimated based on the conduction model is similar to that measured with SAHF-3. The temperature of the topmost sensor is slightly higher than that expected from the conduction model. To explain the high temperature, upward fluid flow at a rate of 10-7 m/s order is needed. Heat flow carried by the upward fluid flow is higher than that estimated by Goto et al. [2003]. Heat flow value expected from the distribution of heat flow around this area is 70-80 mW/m2. The high heat flow values inside and outside the bacterial mat estimated in the present and previous studies may reflect upward fluid flow along the splay fault.

Model simulations of dense bottom currents in the Western Baltic Sea

NASA Astrophysics Data System (ADS)

Burchard, Hans; Janssen, Frank; Bolding, Karsten; Umlauf, Lars; Rennau, Hannes

2009-01-01

Only recently, medium intensity inflow events into the Baltic Sea have gained more awareness because of their potential to ventilate intermediate layers in the Southern Baltic Sea basins. With the present high-resolution model study of the Western Baltic Sea a first attempt is made to obtain model based realistic estimates of turbulent mixing in this area where dense bottom currents resulting from medium intensity inflow events are weakened by turbulent entrainment. The numerical model simulation which is carried out using the General Estuarine Transport Model (GETM) during nine months in 2003 and 2004 is first validated by means of three automatic stations at the Drogden and Darss Sills and in the Arkona Sea. In order to obtain good agreement between observations and model results, the 0.5×0.5 nautical mile bathymetry had to be adjusted in order to account for the fact that even at that scale many relevant topographic features are not resolved. Current velocity, salinity and turbulence observations during a medium intensity inflow event through the Øresund are then compared to the model results. Given the general problems of point to point comparisons between observations and model simulations, the agreement is fairly good with the characteristic features of the inflow event well represented by the model simulations. Two different bulk measures for mixing activity are then introduced, the vertically integrated decay of salinity variance, which is equal to the production of micro-scale salinity variance, and the vertically integrated turbulent salt flux, which is related to an increase of potential energy due to vertical mixing of stably stratified flow. Both measures give qualitatively similar results and identify the Drogden and Darss Sills as well as the Bornholm Channel as mixing hot spots. Further regions of strong mixing are the dense bottom current pathways from these sills into the Arkona Sea, areas around Kriegers Flak (a shoal in the western Arkona Sea) and north-west of the island of Rügen.

Measuring third year undergraduate nursing students' reflective thinking skills and critical reflection self-efficacy following high fidelity simulation: A pilot study.

PubMed

Tutticci, Naomi; Lewis, Peter A; Coyer, Fiona

2016-05-01

Critical reflection underpins critical thinking, a highly desirable generic nursing graduate capability. To improve the likelihood of critical thinking transferring to clinical practice, reflective thinking needs to be measured within the learning space of simulation. This study was divided into two phases to address the reliability and validity measures of previously untested surveys. Phase One data was collected from individuals (n = 6) using a 'think aloud' approach and an expert panel to review content validity, and verbatim comment analysis was undertaken. The Reflective Thinking Instrument and Critical Reflection Self-Efficacy Visual Analogue Scale items were contextualised to simulation. The expert review confirmed these instruments exhibited content validity. Phase Two data was collected through an online survey (n = 58). Cronbach's alpha measured internal consistency and was demonstrated by all subscales and the Instrument as a whole (.849). There was a small to medium positive correlation between critical reflection self-efficacy and general self-efficacy (r = .324, n = 56, p = .048). Participant responses were positive regarding the simulation experience. The research findings demonstrated that the Reflective Thinking and Simulation Satisfaction survey is reliable. Further development of this survey to establish validity is recommended to make it viable. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of Natural (Storm) and Anthropogenic (Trawl) Resuspension the Sediment Transport on the Gulf of Lion's Shelf (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Ferre, B.; Durrieu de Madron, X.; Estournel, C.; Ulses, C.; Le Corre, G.

2006-12-01

Modern sediment deposits on continental margins form a vast reservoir of particulate matter that is regularly affected by resuspension processes. On shelves with strong fishing activity, resuspension by bottom trawling processes can modify the scale of natural disturbance by waves and currents. Recent field data shows that the impact of bottom trawls on the resuspension of the fine sediments per unit surface is comparable with that of the largest storms. We assessed the impact of both natural and anthropogenic processes on the dispersal of river-borne particles and shelf sediments on the Gulf of Lion's Shelf. Realistic numerical simulations of resuspension and transport forced by currents and waves or by a fleet of bottom trawlers were developed. Simulations were conducted for a 16-month period to characterize the seasonal variability. The sediment dynamics takes into account bed armoring, ripple geometry and the cohesive and non-cohesive characteristics of the sediment. Essential but uncertain parameters (clay content, erosion fluxes and critical shear stress for cohesive sediment) were set with existing data. Resuspension by waves and currents is controlled by the shear stress, whereas resuspension by the bottom trawler fleet is controlled by its density and distribution. Natural resuspension by waves and currents mostly occurs during short winter episodes, and is concentrated on the inner-shelf. Trawling-induced resuspension, in contrast, occurs regularly throughout the year and is concentrated on the outer shelf. The total annual net resuspension by trawls (8×106 T y-1 is four orders of magnitude lower than the resuspension induced by waves and currents (4×1010 T y-1. However, because trawled regions are located on the outer shelf, closer to the continental slope, export of fine sediment resuspended by trawls (0.6×106 T y-1 is only one order of magnitude lower than export associated with natural resuspension (8×106 T y-1. A simulation combining both resuspension processes reveals a decrease of about 10% in resuspension and export rates, compared with the sum of each individual process.

Fusion reactor pumped laser

DOEpatents

Jassby, D.L.

1987-09-04

A nuclear pumped laser capable of producing long pulses of very high power laser radiation is provided. A toroidal fusion reactor provides energetic neutrons which are slowed down by a moderator. The moderated neutrons are converted to energetic particles capable of pumping a lasing medium. The lasing medium is housed in an annular cell surrounding the reactor. The cell includes an annular reflecting mirror at the bottom and an annular output window at the top. A neutron reflector is disposed around the cell to reflect escaping neutrons back into the cell. The laser radiation from the annular window is focused onto a beam compactor which generates a single coherent output laser beam. 10 figs.

Fusion reactor pumped laser

DOEpatents

Jassby, Daniel L.

1988-01-01

A nuclear pumped laser capable of producing long pulses of very high power laser radiation is provided. A toroidal fusion reactor provides energetic neutrons which are slowed down by a moderator. The moderated neutrons are converted to energetic particles capable of pumping a lasing medium. The lasing medium is housed in an annular cell surrounding the reactor. The cell includes an annular reflecting mirror at the bottom and an annular output window at the top. A neutron reflector is disposed around the cell to reflect escaping neutrons back into the cell. The laser radiation from the annular window is focused onto a beam compactor which generates a single coherent output laser beam.

MODELING NITROGEN-CARBON CYCLING AND OXYGEN CONSUMPTION IN BOTTOM SEDIMENTS

EPA Science Inventory

A model framework is presented for simulating nitrogen and carbon cycling at the sediment–water interface, and predicting oxygen consumption by oxidation reactions inside the sediments. Based on conservation of mass and invoking simplifying assumptions, a coupled system of diffus...

CLARREO shortwave observing system simulation experiments of the twenty-first century: Simulator design and implementation

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

Feldman, D.R.; Algieri, C.A.; Ong, J.R.

2011-04-01

Projected changes in the Earth system will likely be manifested in changes in reflected solar radiation. This paper introduces an operational Observational System Simulation Experiment (OSSE) to calculate the signals of future climate forcings and feedbacks in top-of-atmosphere reflectance spectra. The OSSE combines simulations from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report for the NCAR Community Climate System Model (CCSM) with the MODTRAN radiative transfer code to calculate reflectance spectra for simulations of current and future climatic conditions over the 21st century. The OSSE produces narrowband reflectances and broadband fluxes, the latter of which have been extensivelymore » validated against archived CCSM results. The shortwave reflectance spectra contain atmospheric features including signals from water vapor, liquid and ice clouds, and aerosols. The spectra are also strongly influenced by the surface bidirectional reflectance properties of predicted snow and sea ice and the climatological seasonal cycles of vegetation. By comparing and contrasting simulated reflectance spectra based on emissions scenarios with increasing projected and fixed present-day greenhouse gas and aerosol concentrations, we find that prescribed forcings from increases in anthropogenic sulfate and carbonaceous aerosols are detectable and are spatially confined to lower latitudes. Also, changes in the intertropical convergence zone and poleward shifts in the subsidence zones and the storm tracks are all detectable along with large changes in snow cover and sea ice fraction. These findings suggest that the proposed NASA Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission to measure shortwave reflectance spectra may help elucidate climate forcings, responses, and feedbacks.« less

Age-related decline in bottom-up processing and selective attention in the very old.

PubMed

Zhuravleva, Tatyana Y; Alperin, Brittany R; Haring, Anna E; Rentz, Dorene M; Holcomb, Philip J; Daffner, Kirk R

2014-06-01

Previous research demonstrating age-related deficits in selective attention have not included old-old adults, an increasingly important group to study. The current investigation compared event-related potentials in 15 young-old (65-79 years old) and 23 old-old (80-99 years old) subjects during a color-selective attention task. Subjects responded to target letters in a specified color (Attend) while ignoring letters in a different color (Ignore) under both low and high loads. There were no group differences in visual acuity, accuracy, reaction time, or latency of early event-related potential components. The old-old group showed a disruption in bottom-up processing, indexed by a substantially diminished posterior N1 (smaller amplitude). They also demonstrated markedly decreased modulation of bottom-up processing based on selected visual features, indexed by the posterior selection negativity (SN), with similar attenuation under both loads. In contrast, there were no group differences in frontally mediated attentional selection, measured by the anterior selection positivity (SP). There was a robust inverse relationship between the size of the SN and SP (the smaller the SN, the larger the SP), which may represent an anteriorly supported compensatory mechanism. In the absence of a decline in top-down modulation indexed by the SP, the diminished SN may reflect age-related degradation of early bottom-up visual processing in old-old adults.

Benthic foraminiferal trace metal uptake: a field calibration from the Arabia Sea Oxygen Minimum Zone

NASA Astrophysics Data System (ADS)

Koho, K. A.; Reichart, G.-J.

2012-04-01

The Arabian Sea Oxygen Minimum Zone (OMZ) is sustained by high surface water productivity and relatively weak mid-depth water column ventilation. High primary productivity drives high respiration rates in the water column, causing severe oxygen depletion between ±150-1400 m water depths, with the oxygen concentrations falling below 2 μM in the core of the OMZ. Living (rose Bengal stained) benthic foraminifera were collected at 10-stations, covering a large bottom water oxygen concentration gradient from the Murray Ridge. This sub-marine ridge is located in the open marine environment of the Arabian Sea and thus not affected by large gradients in surface water productivity such as encountered at the continental margins. Since these sites thus receive similar organic fluxes, but are bathed in bottom waters with contrasting oxygen concentrations, pore water profiles mainly reflect bottom water oxygenation. The study sites represent a natural laboratory to investigate the impact of bottom water chemistry on trace metal incorporation in benthic foraminifera. Trace metal analyses by laser ablation ICP-MS allows detailed single chamber measurements of trace metal content, which can be related to in situ pore water geochemistry. Focus of this study is on redox sensitive trace metal (e.g. Mn, U) incorporation into foraminiferal test calcite in relation to pore water oxygen and carbonate chemistry.

A three-dimensional numerical simulation of cell behavior in a flow chamber based on fluid-solid interaction.

PubMed

Bai, Long; Cui, Yuhong; Zhang, Yixia; Zhao, Na

2014-01-01

The mechanical behavior of blood cells in the vessels has a close relationship with the physical characteristics of the blood and the cells. In this paper, a numerical simulation method was proposed to understand a single-blood cell's behavior in the vessels based on fluid-solid interaction method, which was conducted under adaptive time step and fixed time step, respectively. The main programme was C++ codes, which called FLUENT and ANSYS software, and UDF and APDL acted as a messenger to connect FLUENT and ANSYS for exchanging data. The computing results show: (1) the blood cell moved towards the bottom of the flow chamber in the beginning due to the influence of gravity, then it began to jump up when reached a certain height rather than touching the bottom. It could move downwards again after jump up, the blood cell could keep this way of moving like dancing continuously in the vessels; (2) the blood cell was rolling and deforming all the time; the rotation had oscillatory changes and the deformation became conspicuously when the blood cell was dancing. This new simulation method and results can be widely used in the researches of cytology, blood, cells, etc.

The effects of sub-ice-shelf melting on dense shelf water formation and export in idealized simulations of Antarctic margins

NASA Astrophysics Data System (ADS)

Marques, Gustavo; Stern, Alon; Harrison, Matthew; Sergienko, Olga; Hallberg, Robert

2017-04-01

Dense shelf water (DSW) is formed in coastal polynyas around Antarctica as a result of intense cooling and brine rejection. A fraction of this water reaches ice shelves cavities and is modified due to interactions with sub-ice-shelf melt water. This modified water mass contributes to the formation of Antarctic Bottom Water, and consequently, influences the large-scale ocean circulation. Here, we investigate the role of sub-ice-shelf melting in the formation and export of DSW using idealized simulations with an isopycnal ocean model (MOM6) coupled with a sea ice model (SIS2) and a thermodynamic active ice shelf. A set of experiments is conducted with variable horizontal grid resolutions (0.5, 1.0 and 2.0 km), ice shelf geometries and atmospheric forcing. In all simulations DSW is spontaneously formed in coastal polynyas due to the combined effect of the imposed atmospheric forcing and the ocean state. Our results show that sub-ice-shelf melting can significantly change the rate of dense shelf water outflows, highlighting the importance of this process to correctly represent bottom water formation.

Observations and simulations of specularly reflected He++ at Earth's quasiperpendicular bow shock

NASA Astrophysics Data System (ADS)

Broll, J. M.; Fuselier, S. A.; Trattner, K. J.; Anderson, B. J.; Burch, J. L.; Giles, B. L.

2016-12-01

Specular reflection of protons at Earth's quasiperpendicular bow shock is an important process for supercritical shock dissipation. Previous studies have found evidence of He++ specular reflection from reduced particle distributions downstream from the shock, but confirmation of the process for heavier ions in the shock foot was not possible due to time resolution constraints. We present He++ distributions, observed by MMS in a quasiperpendicular bow shock crossing, that are consistent with specularly reflected He++. We also investigate the He++ dynamics with test-particle simulations in a simulated shock based on this crossing and we conduct wave analysis to determine what processes lead to separate gyrotropization timescales for the transmitted and reflected populations.

XFEL OSCILLATOR SIMULATION INCLUDING ANGLE-DEPENDENT CRYSTAL REFLECTIVITY

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

Fawley, William; Lindberg, Ryan; Kim, K-J

The oscillator package within the GINGER FEL simulation code has now been extended to include angle-dependent reflectivity properties of Bragg crystals. Previously, the package was modified to include frequencydependent reflectivity in order to model x-ray FEL oscillators from start-up from shot noise through to saturation. We present a summary of the algorithms used for modeling the crystal reflectivity and radiation propagation outside the undulator, discussing various numerical issues relevant to the domain of high Fresnel number and efficient Hankel transforms. We give some sample XFEL-O simulation results obtained with the angle-dependent reflectivity model, with particular attention directed to the longitudinalmore » and transverse coherence of the radiation output.« less

Modelization of highly nonlinear waves in coastal regions

NASA Astrophysics Data System (ADS)

Gouin, Maïté; Ducrozet, Guillaume; Ferrant, Pierre

2015-04-01

The proposed work deals with the development of a highly non-linear model for water wave propagation in coastal regions. The accurate modelization of surface gravity waves is of major interest in ocean engineering, especially in the field of marine renewable energy. These marine structures are intended to be settled in coastal regions where the effect of variable bathymetry may be significant on local wave conditions. This study presents a numerical model for the wave propagation with complex bathymetry. It is based on High-Order Spectral (HOS) method, initially limited to the propagation of non-linear wave fields over flat bottom. Such a model has been developed and validated at the LHEEA Lab. (Ecole Centrale Nantes) over the past few years and the current developments will enlarge its application range. This new numerical model will keep the interesting numerical properties of the original pseudo-spectral approach (convergence, efficiency with the use of FFTs, …) and enable the possibility to propagate highly non-linear wave fields over long time and large distance. Different validations will be provided in addition to the presentation of the method. At first, Bragg reflection will be studied with the proposed approach. If the Bragg condition is satisfied, the reflected wave generated by a sinusoidal bottom patch should be amplified as a result of resonant quadratic interactions between incident wave and bottom. Comparisons will be provided with experiments and reference solutions. Then, the method will be used to consider the transformation of a non-linear monochromatic wave as it propagates up and over a submerged bar. As the waves travel up the front slope of the bar, it steepens and high harmonics are generated due to non-linear interactions. Comparisons with experimental data will be provided. The different test cases will assess the accuracy and efficiency of the method proposed.

Cueing cognitive flexibility: Item-specific learning of switch readiness.

PubMed

Chiu, Yu-Chin; Egner, Tobias

2017-12-01

The rich behavioral repertoire of the human species derives from our ability to flexibly reconfigure processing strategies (task sets) in response to changing requirements. This updating of task sets is effortful, as reflected by longer response times when switching a task than repeating it (switch costs). However, some recent data suggest that switch costs can be reduced by cueing switch readiness bottom-up, by associating particular stimuli with frequent switch requirements. This type of "stimulus-control (S-C) learning" would be highly adaptive, as it combines the speed of automatic (bottom-up) processing with the flexibility and generalizability of controlled (top-down) processing. However, it is unclear whether S-C learning of switch readiness is truly possible, and what the underlying mechanisms are. Here we address these questions by pairing specific stimuli with a need to update task-sets either frequently or rarely. In all 3 experiments, we observe robust item-specific switch probability (ISSP) effects as revealed by smaller switch costs for frequent switch items than for rare switch items. By including a neutral condition, we also show that the ISSP effect is primarily driven by S-C learning reducing switch costs in frequent switch items. Furthermore, by employing 3 tasks in Experiment 3, we establish that the ISSP effect reflects an enhancement of general switch readiness, rather than of the readiness to switch to a specific alternate task. These results firmly establish that switch readiness is malleable by item-specific S-C learning processes, documenting that a generalizable state of cognitive flexibility can be primed by a bottom-up stimulus. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Variability in the mechanisms controlling Southern Ocean phytoplankton bloom phenology in an ocean model and satellite observations

NASA Astrophysics Data System (ADS)

Rohr, Tyler; Long, Matthew C.; Kavanaugh, Maria T.; Lindsay, Keith; Doney, Scott C.

2017-05-01

A coupled global numerical simulation (conducted with the Community Earth System Model) is used in conjunction with satellite remote sensing observations to examine the role of top-down (grazing pressure) and bottom-up (light, nutrients) controls on marine phytoplankton bloom dynamics in the Southern Ocean. Phytoplankton seasonal phenology is evaluated in the context of the recently proposed "disturbance-recovery" hypothesis relative to more traditional, exclusively "bottom-up" frameworks. All blooms occur when phytoplankton division rates exceed loss rates to permit sustained net population growth; however, the nature of this decoupling period varies regionally in Community Earth System Model. Regional case studies illustrate how unique pathways allow blooms to emerge despite very poor division rates or very strong grazing rates. In the Subantarctic, southeast Pacific small spring blooms initiate early cooccurring with deep mixing and low division rates, consistent with the disturbance-recovery hypothesis. Similar systematics are present in the Subantarctic, southwest Atlantic during the spring but are eclipsed by a subsequent, larger summer bloom that is coincident with shallow mixing and the annual maximum in division rates, consistent with a bottom-up, light limited framework. In the model simulation, increased iron stress prevents a similar summer bloom in the southeast Pacific. In the simulated Antarctic zone (70°S-65°S) seasonal sea ice acts as a dominant phytoplankton-zooplankton decoupling agent, triggering a delayed but substantial bloom as ice recedes. Satellite ocean color remote sensing and ocean physical reanalysis products do not precisely match model-predicted phenology, but observed patterns do indicate regional variability in mechanism across the Atlantic and Pacific.

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.

Marine Geophysical Investigation of Selected Sites in Bridgeport Harbor, Connecticut, 2006

USGS Publications Warehouse

Johnson, Carole D.; White, Eric A.

2007-01-01

A marine geophysical investigation was conducted in 2006 to help characterize the bottom and subbottom materials and extent of bedrock in selected areas of Bridgeport Harbor, Connecticut. The data will be used by the U.S. Army Corps of Engineers in the design of confined aquatic disposal (CAD) cells within the harbor to facilitate dredging of the harbor. Three water-based geophysical methods were used to evaluate the geometry and composition of subsurface materials: (1) continuous seismic profiling (CSP) methods provide the depth to water bottom, and when sufficient signal penetration can be achieved, delineate the depth to bedrock and subbottom materials; (2) continuous resistivity profiling (CRP) methods were used to define the electrical properties of the shallow subbottom, and to possibly determine the distribution of conductive materials, such as clay, and resistive materials, such as sand and bedrock; (3) and magnetometer data were used to identify conductive anomalies of anthropogenic sources, such as cables and metallic debris. All data points were located using global positioning systems (GPS), and the GPS data were used for real-time navigation. The results of the CRP, CSP, and magnetometer data are consistent with the conceptual site model of a bedrock channel incised beneath the present day harbor. The channel appears to follow a north-northwest to south-southeast trend and is parallel to the Pequannock River. The seismic record and boring data indicate that under the channel, the depth to bedrock is as much as 42.7 meters (m) below mean low-low water (MLLW) in the dredged part of the harbor. The bedrock channel becomes shallower towards the shore, where bedrock outcrops have been mapped at land surface. CSP and CRP data were able to provide a discontinuous, but reasonable, trace from the channel toward the west under the proposed southwestern CAD cell. The data indicate a high amount of relief on the bedrock surface, as well as along the water bottom. Under the southwestern CAD cell, the sediments are only marginally thick enough for a CAD cell, at about 8 to 15 m in depth. Some of the profiles show small diffractions in the unconsolidated sediments, but no large-scale boulders or boulder fields were identified. No bedrock reflectors were imaged under the southeastern CAD cell, where core logs indicate the rock is as much as 30 m below MLLW. The chirp frequency, tuned transducer, and boomer-plate CSP surveys were adversely affected by a highly reflective water bottom causing strong multiples in the seismic record and very limited depths of penetration. These multiples are attributed to entrapped gas (methane) in the sediments or to very hard bottom conditions. In a limited number of places, the bedrock surface was observed in the CSP record, creating a discontinuous and sporadic image of the bedrock surface. These interpretations generally matched core data at FP-03-10 and FB-06-1. Use of two analog CSP systems, the boomer plate and tuned transducer, did not overcome the reflections off the water bottom and did not improve the depth of penetration. In general, the CRP profiles were used to corroborate the results of the CSP profiles. Relatively resistive zones associated with the locations of seismic reflections were interpreted as bedrock. The shape of the bedrock surface generally was similar in the CRP and CSP profiles. Evaluation of the CRP profiles indicated that the inversions were adversely affected where the depth and (or) ionic concentration of the water column varied. Consequently, the CRP profiles were broken into short intervals that extended just over the area of interest, where the depth to water bottom was fairly constant. Over these short profiles, efforts were made to evaluate the resistivity of the very shallow sediments to determine if there were any large contrasts in the resistivity of the sediments that might indicate differences in the shallow subbottom materials. No conclusions abo

Ecosystem Predictions with Approximate vs. Exact Light Fields

DTIC Science & Technology

2009-03-27

and optically shallow waters for which bottom reflectance can substantially increase the irradiance available for photosynthesis and water heating...primary productivity, heating of water, and photochemical reactions. When modeling photosynthesis , which depends on the number of photons oabsorbed, it...irradiance, W m nm , to quantum units,-2 -1 photons s m nm .-1 -2 -1 A wavelength-integrated measure of the total light available for photosynthesis

Trade-Offs between the Top-Down and Bottom-Up School Education Management Models: The Implementation of School Development Planning in Western China

ERIC Educational Resources Information Center

Zhu, Zhiyong

2008-01-01

In the 1990s, numerous primary and secondary schools in China began experimental exploration and research on the implementation of school development planning (SDP). However, there has been a lack of self-criticism and reflection on the actual implementation situations and changes in SDP's concepts in the participating schools. This study assessed…

The Presence and Characterization of Antarctic Bottom Water Located Between the Mid-Atlantic Ridge and the Rio Grande Rise

NASA Astrophysics Data System (ADS)

Miller, R. H.; Reece, R.; Estep, J.; Christeson, G. L.; Acquisto, T. M.

2016-12-01

Circumpolar waters of widely varying properties enter South Atlantic Ocean circulation, interleaving their properties. Antarctic bottom water (ABW) flows northward into the South Atlantic at the eastern edge of the South American continent and around the Rio Grande Rise (RGR), a large aseismic ocean ridge in the deep water off the coast of Brazil. The majority of ABW transport occurs below depths of 3500 m, so very little is lost at the top of the RGR. In early 2016, the CREST (Crustal Reflectivity Experiment Southern Transect) expedition acquired multichannel seismic (MCS) and ocean bottom seismometer (OBS) datasets along a crustal segment in the South Atlantic, stretching from the Mid Atlantic Ridge (MAR) west to the RGR. During OBS recovery, a communications problem occurred in which the OBS received the transducer pulse from the ship, but the ship did not receive the OBS return pulse. The nine shallowest instruments, closest to the MAR, did not experience this problem, but all remaining instruments did. All instruments were extensively tested in the water column and in the lab and exhibited no malfunctions. We hypothesize that a deepwater layer of differing physical properties, located nearer the OBS than the boat, dispersed the return pulse resulting in the break in communications. ABW is a good candidate for a potential cold deepwater body in this region. We will examine multi-beam bathymetry returns and seismic reflection data for indications of reflections in the deepwater column. If observations support the presence of cold deepwater, we will fully characterize its properties and boundaries and determine if the characteristics match that of ABW. This study will characterize the behavior and nature of potential cold deepwater currents east of the Rio Grande Rise in an attempt to verify the presence of ABW. Information regarding the effects of differential water layering on acoustic communication with seafloor instruments could benefit future deployments to affected regions. Additionally, more insight into deep water ocean circulation could provide critical information for modeling with implications for chemical and heat exchange as well as ocean-climate interaction.

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

Renewed circulation scheme of the Baltic Sea - based on the 40-year simulation with GETM.

NASA Astrophysics Data System (ADS)

Maljutenko, Ilja; Raudsepp, Urmas

2015-04-01

The general circulation of the Baltic Sea has been characterized as cyclonic in all sub-basins based on numerous measurements and model simulations. From the long-term hydrodynamical simulation our model results have verified the general cyclonic circulation in the Baltic Proper and in the Gulf of Bothnia, but the Gulf of Finland and the Gulf of Riga have shown tendency to anticyclonic circulation. We have applied the General Estuarine Transport Model ( GETM ) for the period of 1966 - 2006 with a 1 nautical mile horizontal resolution and density adaptive bottom following vertical coordinates to make it possible to simulate horizontal and vertical density gradients with better precision. The atmospheric forcing from dynamically downscaled ERA40-HIRLAM and parametrized lateral boundary conditions are applied. Model simulation show close agreement with measurements conducted in the main monitoring stations in the BS during the simulation period. The geostrophic adjustment of density driven currents along with the upward salinity flux due to entrainment could explain the anticyclonic circulation and strong coastal current. Mean vertical velocities show that upward and downward movements are forming closed vertical circulation loops along the bottom slope of the Baltic Proper and the Gulf of Bothnia. The model has also reproduced patchy vertical movement across the BS with some distinctive areas of upward advective fluxes in the GoF along the thalweg. The distinctive areas of deepwater upwelling are also evident in the Gdansk Basin, western Gotland Basin, northern Gotland Basin and in the northen part of the Bothnia Sea.

Quasi-periodic Oscillations in Flares and Coronal Mass Ejections Associated with Magnetic Reconnection

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

Takahashi, Takuya; Shibata, Kazunari; Qiu, Jiong, E-mail: takahasi@kusastro.kyoto-u.ac.jp

We propose a mechanism for quasi-periodic oscillations of both coronal mass ejections (CMEs) and flare loops as related to magnetic reconnection in eruptive solar flares. We perform two-dimensional numerical MHD simulations of magnetic flux rope eruption, with three different values of the global Lundquist number. In the low Lundquist number run, no oscillatory behavior is found. In the moderate Lundquist number run, on the other hand, quasi-periodic oscillations are excited both at the bottom of the flux rope and at the flare loop top. In the high Lundquist number run, quasi-periodic oscillations are also excited; in the meanwhile, the dynamicsmore » become turbulent owing to the formation of multiple plasmoids in the reconnection current sheet. In high and moderate Lundquist number runs, thin reconnection jets collide with the flux rope bottom or flare loop top and dig them deeply. Steep oblique shocks are formed as termination shocks where reconnection jets are bent (rather than decelerated) in the horizontal direction, resulting in supersonic backflows. The structure becomes unstable, and quasi-periodic oscillations of supersonic backflows appear at locally confined high-beta regions at both the flux rope bottom and flare loop top. We compare the observational characteristics of quasi-periodic oscillations in erupting flux ropes, post-CME current sheets, flare ribbons, and light curves with corresponding dynamical structures found in our simulation.« less

Numerical study on inter-tidal transports in coastal seas

NASA Astrophysics Data System (ADS)

Mao, Xinyan; Jiang, Wensheng; Zhang, Ping; Feng, Shizuo

2016-06-01

Inter-tidal (subtidal) transport processes in coastal sea depend on the residual motion, turbulent dispersion and relevant sources/sinks. In Feng et al. (2008), an updated Lagrangian inter-tidal transport equation, as well as new concept of Lagrangian inter-tidal concentration (LIC), has been proposed for a general nonlinear shallow water system. In the present study, the LIC is numerically applied for the first time to passive tracers in idealized settings and salinity in the Bohai Sea, China. Circulation and tracer motion in the three idealized model seas with different topography or coastline, termed as `flat-bottom', `stairs' and `cape' case, respectively, are simulated. The dependence of the LIC on initial tidal phase suggests that the nonlinearities in the stairs and cape cases are stronger than that in the flat-bottom case. Therefore, the `flat-bottom' case still meets the convectively weakly nonlinear condition. For the Bohai Sea, the simulation results show that most parts of it still meet the weakly nonlinear condition. However, the dependence of the LIS (Lagrangian inter-tidal salinity) on initial tidal phase is significant around the southern headland of the Liaodong Peninsula and near the mouth of the Yellow River. The nonlinearity in the former region is mainly related to the complicated coastlines, and that in the latter region is due to the presence of the estuarine salinity front.

Quasi-periodic Oscillations in Flares and Coronal Mass Ejections Associated with Magnetic Reconnection

NASA Astrophysics Data System (ADS)

Takahashi, Takuya; Qiu, Jiong; Shibata, Kazunari

2017-10-01

We propose a mechanism for quasi-periodic oscillations of both coronal mass ejections (CMEs) and flare loops as related to magnetic reconnection in eruptive solar flares. We perform two-dimensional numerical MHD simulations of magnetic flux rope eruption, with three different values of the global Lundquist number. In the low Lundquist number run, no oscillatory behavior is found. In the moderate Lundquist number run, on the other hand, quasi-periodic oscillations are excited both at the bottom of the flux rope and at the flare loop top. In the high Lundquist number run, quasi-periodic oscillations are also excited; in the meanwhile, the dynamics become turbulent owing to the formation of multiple plasmoids in the reconnection current sheet. In high and moderate Lundquist number runs, thin reconnection jets collide with the flux rope bottom or flare loop top and dig them deeply. Steep oblique shocks are formed as termination shocks where reconnection jets are bent (rather than decelerated) in the horizontal direction, resulting in supersonic backflows. The structure becomes unstable, and quasi-periodic oscillations of supersonic backflows appear at locally confined high-beta regions at both the flux rope bottom and flare loop top. We compare the observational characteristics of quasi-periodic oscillations in erupting flux ropes, post-CME current sheets, flare ribbons, and light curves with corresponding dynamical structures found in our simulation.

Geometric and boundary element method simulations of acoustic reflections from rough, finite, or non-planar surfaces

NASA Astrophysics Data System (ADS)

Rathsam, Jonathan

This dissertation seeks to advance the current state of computer-based sound field simulations for room acoustics. The first part of the dissertation assesses the reliability of geometric sound-field simulations, which are approximate in nature. The second part of the dissertation uses the rigorous boundary element method (BEM) to learn more about reflections from finite reflectors: planar and non-planar. Acoustical designers commonly use geometric simulations to predict sound fields quickly. Geometric simulation of reflections from rough surfaces is still under refinement. The first project in this dissertation investigates the scattering coefficient, which quantifies the degree of diffuse reflection from rough surfaces. The main result is that predicted reverberation time varies inversely with scattering coefficient if the sound field is nondiffuse. Additional results include a flow chart that enables acoustical designers to gauge how sensitive predicted results are to their choice of scattering coefficient. Geometric acoustics is a high-frequency approximation to wave acoustics. At low frequencies, more pronounced wave phenomena cause deviations between real-world values and geometric predictions. Acoustical designers encounter the limits of geometric acoustics in particular when simulating the low frequency response from finite suspended reflector panels. This dissertation uses the rigorous BEM to develop an improved low-frequency radiation model for smooth, finite reflectors. The improved low frequency model is suggested in two forms for implementation in geometric models. Although BEM simulations require more computation time than geometric simulations, BEM results are highly accurate. The final section of this dissertation uses the BEM to investigate the sound field around non-planar reflectors. The author has added convex edges rounded away from the source side of finite, smooth reflectors to minimize coloration of reflections caused by interference from boundary waves. Although the coloration could not be fully eliminated, the convex edge increases the sound energy reflected into previously nonspecular zones. This excess reflected energy is marginally audible using a standard of 20 dB below direct sound energy. The convex-edged panel is recommended for use when designers want to extend reflected energy spatially beyond the specular reflection zone of a planar panel.

Reconstructing in-vivo reflectance spectrum of pigmented skin lesion by Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Wang, Shuang; He, Qingli; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

2012-03-01

In dermatology applications, diffuse reflectance spectroscopy has been extensively investigated as a promising tool for the noninvasive method to distinguish melanoma from benign pigmented skin lesion (nevus), which is concentrated with the skin chromophores like melanin and hemoglobin. We carried out a theoretical study to examine melanin distribution in human skin tissue and establish a practical optical model for further pigmented skin investigation. The theoretical simulation was using junctional nevus as an example. A multiple layer skin optical model was developed on established anatomy structures of skin, the published optical parameters of different skin layers, blood and melanin. Monte Carlo simulation was used to model the interaction between excitation light and skin tissue and rebuild the diffuse reflectance process from skin tissue. A testified methodology was adopted to determine melanin contents in human skin based on in vivo diffuse reflectance spectra. The rebuild diffuse reflectance spectra were investigated by adding melanin into different layers of the theoretical model. One of in vivo reflectance spectra from Junctional nevi and their surrounding normal skin was studied by compare the ratio between nevus and normal skin tissue in both the experimental and simulated diffuse reflectance spectra. The simulation result showed a good agreement with our clinical measurements, which indicated that our research method, including the spectral ratio method, skin optical model and modifying the melanin content in the model, could be applied in further theoretical simulation of pigmented skin lesions.

A three dimensional Dirichlet-to-Neumann map for surface waves over topography

NASA Astrophysics Data System (ADS)

Nachbin, Andre; Andrade, David

2016-11-01

We consider three dimensional surface water waves in the potential theory regime. The bottom topography can have a quite general profile. In the case of linear waves the Dirichlet-to-Neumann operator is formulated in a matrix decomposition form. Computational simulations illustrate the performance of the method. Two dimensional periodic bottom variations are considered in both the Bragg resonance regime as well as the rapidly varying (homogenized) regime. In the three-dimensional case we use the Luneburg lens-shaped submerged mound, which promotes the focusing of the underlying rays. FAPERJ Cientistas do Nosso Estado Grant 102917/2011 and ANP/PRH-32.

Plant operation planning and scheduling

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

Jammar, R.J.

When properly designed, planning and scheduling can actually add millions of dollars per year to the bottom line. Planning and scheduling is a continuum of decisions starting with crude selection and ending with establishing short-term targets for crude processing and blending. It also includes maintaining optimization and operation simulation models. It is thought that conservatively, a refinery may save from $5 million to $10 million a year if it pays more attention to the processes behind proper planning and scheduling. Of course, the amount of savings can reach staggering proportions for companies now at the bottom of the Solomon Associatesmore » Inc. refinery performance ranking.« less

Improvement of fluorescence intensity of nitrogen vacancy centers in self-formed diamond microstructures

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

Furuyama, S.; Yaita, J.; Kondo, M.

2015-10-19

We present umbrella-shaped diamond microstructures with metal mirrors at the bottom in order to improve the amount of collected photons from nitrogen vacancy centers. The metal mirrors at the bottom are self-aligned to the umbrella-shaped diamond microstructures which are selectively grown through holes created on a metal mask. By the finite-difference time-domain simulations, we found that the umbrella-shaped microstructures, which have an effect similar to solid immersion lens, could collect photons more efficiently than bulk or pillar-shaped microstructures. Improvement of the fluorescence intensity by factors of from 3 to 5 is shown experimentally.

The Effect of Barotropic and Baroclinic Tides on Coastal Stratification and Mixing

NASA Astrophysics Data System (ADS)

Suanda, S. H.; Feddersen, F.; Kumar, N.

2017-12-01

The effects of barotropic and baroclinic tides on subtidal stratification and vertical mixing are examined with high-resolution, three-dimensional numerical simulations of the Central Californian coastal upwelling region. A base simulation with realistic atmospheric and regional-scale boundary forcing but no tides (NT) is compared to two simulations with the addition of predominantly barotropic local tides (LT) and with combined barotropic and remotely generated, baroclinic tides (WT) with ≈ 100 W m-1 onshore baroclinic energy flux. During a 10 day period of coastal upwelling when the domain volume-averaged temperature is similar in all three simulations, LT has little difference in subtidal temperature and stratification compared to NT. In contrast, the addition of remote baroclinic tides (WT) reduces the subtidal continental shelf stratification up to 50% relative to NT. Idealized simulations to isolate barotropic and baroclinic effects demonstrate that within a parameter space of typical U.S. West Coast continental shelf slopes, barotropic tidal currents, incident energy flux, and subtidal stratification, the dissipating baroclinic tide destroys stratification an order of magnitude faster than barotropic tides. In WT, the modeled vertical temperature diffusivity at the top (base) of the bottom (surface) boundary layer is increased up to 20 times relative to NT. Therefore, the width of the inner-shelf (region of surface and bottom boundary layer overlap) is increased approximately 4 times relative to NT. The change in stratification due to dissipating baroclinic tides is comparable to the magnitude of the observed seasonal cycle of stratification.

Quantitative 3D model of light transmittance through translucent rocks applied to the hypolithic microbial community.

PubMed

Jolitz, Rebecca D; McKay, Christopher P

2013-07-01

In extreme desert environments, photosynthetic microorganisms often live on the buried undersides of translucent rocks. Computing the light level reaching these locations requires 3D modeling of a finite rock. We report on Monte Carlo calculations of skylight and sunlight transmission through a partially buried flat cylindrical rock using one billion photons per simulation. Transmitted light level drops inversely with increasing rock opacity, as expected for purely scattering media. For a half-buried rock with an extinction coefficient of 0.1 cm(-1) (opacity of 0.2), transmission at the bottom is 64 % for sunlight at a solar zenith angle of 60° and 82 % for skylight. Transmitted light level increases slowly with increasing scattering asymmetry factor of the rock independent of illumination or depth buried. Transmitted sunlight at zenith through a thick half-buried rock (opacity of 0.6) is six times brighter at the bottom than the subsurface sides. Skylight transmits equally to the subsurface sides and bottom. When the sun is not straight overhead, the sunward side of the rock is brighter than the underside of the rock. Compared to the sunlight transmitted to the bottom, transmitted sunlight inclined at 60° is 24 times brighter at the subsurface side towards the sun and 14 times brighter at the subsurface side 70° away from the sun. Transmitted sunlight emitted from zenith and skylight is uniformly bright at the bottom regardless of how deeply the rock is buried. Sunlight not at zenith transmits preferentially to the sunward bottom edge depending on the depth the rock is buried.

Near-shore talik development beneath shallow water in expanding thermokarst lakes, Old Crow Flats, Yukon

NASA Astrophysics Data System (ADS)

Roy-Leveillee, Pascale; Burn, Christopher R.

2017-05-01

It is generally assumed that permafrost is preserved beneath shallow lakes and ponds in the Western North American Arctic where water depth is less than about two thirds of the late-winter lake ice thickness. Here we present field observations of talik development beneath water as shallow as 0.2 m despite a lake ice thickness of 1.5 m, in Old Crow Flats (OCF), YT. Conditions leading to the initiation and development of taliks beneath shallow water were investigated with field measurements of shore erosion rates, bathymetry, ice thickness, snow accumulation, and lake bottom temperature near the shores of two expanding lakes in OCF. The sensitivity of talik development to variations in lake bottom thermal regime was then investigated numerically. Where ice reached the lake bottom, talik development was controlled by the ratio of freezing degree days to thawing degree days at the lake bottom (FDDlb/TDDlb). In some cases, spatial variations in on-ice snow depth had a minimal effect on annual mean lake bottom temperature (Tlb) but caused sufficient variations in FDDlb/TDDlb to influence talik development. Where Tlb was close to but greater than 0°C simulations indicated that the thermal offset allowed permafrost aggradation to occur under certain conditions, resulting in irregular near-shore talik geometries. The results highlight the sensitivity of permafrost to small changes in lake bottom thermal conditions where the water column freezes through in early winter and indicate the occurrence of permafrost degradation beneath very shallow water in the near-shore zone of Arctic ponds and lakes.

Bottom currents and sediment waves on a shallow carbonate shelf, Northern Carnarvon Basin, Australia

NASA Astrophysics Data System (ADS)

Belde, Johannes; Reuning, Lars; Back, Stefan

2017-04-01

The modern seafloor of the Australian Northwest Shelf between Exmouth and Dampier was analyzed for large scale sedimentary bedforms on 3D seismic reflection data. The Carnarvon MegaSurvey of Petroleum Geo-Services (PGS), a merged dataset of multiple industrial 3D seismic reflection surveys with a total size of 49,717 km2, offers an extensive view of the continental shelf, slope and rise of the Northern Carnarvon Basin. Over the shelf two fields of large scale sediment waves were observed in water depths between 55-130 m, where the seafloor may be influenced by different processes including internal waves, tides and storms. Based on the dimensions and orientations of the sediment waves the dominant direction and approximate strength of local bottom currents could be estimated. Information on local sediment grain-size distribution was provided by the auSEABED database allowing a classification of the observed sediment waves into sand- or mudwaves. The first sediment wave field is positioned northwest of the Montebello Islands where the shelf is comparatively narrow and local sediment is mainly sand-sized. It most likely formed by increased bottom currents induced by the diversion of tidal flows around the islands. The second sediment wave field is located north of the Serrurier and Bessieres Islands within a local seafloor depression. Local sediments are poorly sorted, containing significant amounts of mud and gravel in addition to the mainly sand-sized grains. The coarser sediment fraction could have been reworked to sandwaves by cyclone-induced bottom currents. Alternatively, the finer sediment fraction could form mudwaves shaped by less energetic along-slope oriented currents in the topographic depression. The sediment waves consist partially of carbonate grains such as ooids and peloids that formed in shallow water during initial stages of the post glacial sea-level rise. These stranded carbonate grains thus formed in a different environment than the sediment waves in which they were redeposited. In fossil examples of similar high-energy ramp systems this possible out-of-equilibrium relationship between grains and bedforms has to be taken into account for the interpretation of the depositional environment.

Simulated BRDF based on measured surface topography of metal

NASA Astrophysics Data System (ADS)

Yang, Haiyue; Haist, Tobias; Gronle, Marc; Osten, Wolfgang

2017-06-01

The radiative reflective properties of a calibration standard rough surface were simulated by ray tracing and the Finite-difference time-domain (FDTD) method. The simulation results have been used to compute the reflectance distribution functions (BRDF) of metal surfaces and have been compared with experimental measurements. The experimental and simulated results are in good agreement.

Derivation of scaled surface reflectances from AVIRIS data

NASA Technical Reports Server (NTRS)

Gao, Bo-Cai; Heidebrecht, Kathleen B.; Goetz, Alexander F. H.

1993-01-01

A method for retrieving 'scaled surface reflectances' assuming horizontal surfaces having Lambertian reflectances from spectral data collected by Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) is presented here. In this method, the integrated water vapor amount on a pixel by pixel basis is derived from the 0.94 micron and 1.14 micron water vapor absorption features. The transmission spectra of H2O, CO2, O3, N2O, CO, CH4, and O2 in the 0.4-2.5 micron region are simulated. The scattering effect due to atmospheric molecules and aerosols is modeled with the 5S computer code. The AVIRIS radiances are divided by solar irradiances above the atmosphere to obtain the apparent reflectances. The scaled surface reflectances are derived from the apparent reflectances using the simulated atmospheric gaseous transmittances and the simulated molecular and aerosol scattering data. The scaled surface reflectances differ from the real surface reflectances by a multiplicative factor. In order to convert the scaled surface reflectances into real surface reflectances, the slopes and aspects of the surfaces must be known.

Value of Collaboration With Standardized Patients and Patient Facilitators in Enhancing Reflection During the Process of Building a Simulation.

PubMed

Stanley, Claire; Lindsay, Sally; Parker, Kathryn; Kawamura, Anne; Samad Zubairi, Mohammad

2018-05-09

We previously reported that experienced clinicians find the process of collectively building and participating in simulations provide (1) a unique reflective opportunity; (2) a venue to identify different perspectives through discussion and action in a group; and (3) a safe environment for learning. No studies have assessed the value of collaborating with standardized patients (SPs) and patient facilitators (PFs) in the process. In this work, we describe this collaboration in building a simulation and the key elements that facilitate reflection. Three simulation scenarios surrounding communication were built by teams of clinicians, a PF, and SPs. Six build sessions were audio recorded, transcribed, and thematically analyzed through an iterative process to (1) describe the steps of building a simulation scenario and (2) identify the key elements involved in the collaboration. The five main steps to build a simulation scenario were (1) storytelling and reflection; (2) defining objectives and brainstorming ideas; (3) building a stem and creating a template; (4) refining the scenario with feedback from SPs; and (5) mock run-throughs with follow-up discussion. During these steps, the PF shared personal insights, challenging participants to reflect deeper to better understand and consider the patient's perspective. The SPs provided unique outside perspective to the group. In addition, the interaction between the SPs and the PF helped refine character roles. A collaborative approach incorporating feedback from PFs and SPs to create a simulation scenario is a valuable method to enhance reflective practice for clinicians.

Documentation of Computer Program INFIL3.0 - A Distributed-Parameter Watershed Model to Estimate Net Infiltration Below the Root Zone

USGS Publications Warehouse

,

2008-01-01

This report documents the computer program INFIL3.0, which is a grid-based, distributed-parameter, deterministic water-balance watershed model that calculates the temporal and spatial distribution of daily net infiltration of water across the lower boundary of the root zone. The bottom of the root zone is the estimated maximum depth below ground surface affected by evapotranspiration. In many field applications, net infiltration below the bottom of the root zone can be assumed to equal net recharge to an underlying water-table aquifer. The daily water balance simulated by INFIL3.0 includes precipitation as either rain or snow; snowfall accumulation, sublimation, and snowmelt; infiltration into the root zone; evapotranspiration from the root zone; drainage and water-content redistribution within the root-zone profile; surface-water runoff from, and run-on to, adjacent grid cells; and net infiltration across the bottom of the root zone. The water-balance model uses daily climate records of precipitation and air temperature and a spatially distributed representation of drainage-basin characteristics defined by topography, geology, soils, and vegetation to simulate daily net infiltration at all locations, including stream channels with intermittent streamflow in response to runoff from rain and snowmelt. The model does not simulate streamflow originating as ground-water discharge. Drainage-basin characteristics are represented in the model by a set of spatially distributed input variables uniquely assigned to each grid cell of a model grid. The report provides a description of the conceptual model of net infiltration on which the INFIL3.0 computer code is based and a detailed discussion of the methods by which INFIL3.0 simulates the net-infiltration process. The report also includes instructions for preparing input files necessary for an INFIL3.0 simulation, a description of the output files that are created as part of an INFIL3.0 simulation, and a sample problem that illustrates application of the code to a field setting. Brief descriptions of the main program routine and of each of the modules and subroutines of the INFIL3.0 code, as well as definitions of the variables used in each subroutine, are provided in an appendix.

Gag grouper larvae pathways on the West Florida Shelf

NASA Astrophysics Data System (ADS)

Weisberg, Robert H.; Zheng, Lianyuan; Peebles, Ernst

2014-10-01

A numerical circulation model, quantitatively assessed against in situ observations, is used to describe the circulation on the West Florida Continental Shelf during spring 2007 when pre-settlement gag (Mycteroperca microlepis) were present in the surf zone near Tampa Bay, Florida. The pre-settlement fish were found to be isotopically distinct from settled juveniles in the area, which is consistent with recent arrival at near shore nursery habitats from offshore spawning grounds. Simulated particle trajectories are employed to test hypotheses relating to either a surface or a near-bottom route of across-shelf transport. The surface-route hypothesis is rejected, whereas the bottom-route hypothesis is found to be consistent with the location of pre-settlement fish and their co-occurrence with macroalgae of offshore, hard-bottom origin. We conclude that gag larvae are transported to the near shore via the bottom Ekman layer and that such transport is facilitated by remote forcing associated with Gulf of Mexico Loop Current interactions with the shelf slope near the Dry Tortugas. Being that such remote forcing occurs inter-annually and not always in phase with the preferred spawning months (late winter through early spring), gag recruitment success should similarly vary with year and location.

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

Configuration Management, Capacity Planning Decision Support, Modeling and Simulation

DTIC Science & Technology

1988-12-01

flow includes both top-down and bottom-up requirements. The flow also includes hardware, software and transfer acquisition, installation, operation ... management and upgrade as required. Satisfaction of a users needs and requirements is a difficult and detailed process. The key assumptions at this

The Influence of Physical Forcing on Bottom-water Dissolved Oxygen within the Caloosahatchee River Estuary, FL

EPA Science Inventory

Environmental Fluid Dynamic Code (EFDC), a numerical estuarine and coastal ocean circulation hydrodynamic model, was used to simulate the distribution of dissolved oxygen (DO), salinity, temperature, nutrients (nitrogen and phosphorus), and chlorophyll a in the Caloosahatchee Riv...

Heat flow bounds over the Cascadia margin derived from bottom simulating reflectors and implications for thermal models of subduction

NASA Astrophysics Data System (ADS)

Phrampus, Benjamin J.; Harris, Robert N.; Tréhu, Anne M.

2017-09-01

Understanding the thermal structure of the Cascadia subduction zone is important for understanding megathrust earthquake processes and seismogenic potential. Currently our understanding of the thermal structure of Cascadia is limited by a lack of high spatial resolution heat flow data and by poor understanding of thermal processes such as hydrothermal fluid circulation in the subducting basement, sediment thickening and dewatering, and frictional heat generation on the plate boundary. Here, using a data set of publically available seismic lines combined with new interpretations of bottom simulating reflector (BSR) distributions, we derive heat flow estimates across the Cascadia margin. Thermal models that account for hydrothermal circulation predict BSR-derived heat flow bounds better than purely conductive models, but still over-predict surface heat flows. We show that when the thermal effects of in-situ sedimentation and of sediment thickening and dewatering due to accretion are included, models with hydrothermal circulation become consistent with our BSR-derived heat flow bounds.

Enhanced Photon Extraction from a Nanowire Quantum Dot Using a Bottom-Up Photonic Shell

NASA Astrophysics Data System (ADS)

Jeannin, Mathieu; Cremel, Thibault; Häyrynen, Teppo; Gregersen, Niels; Bellet-Amalric, Edith; Nogues, Gilles; Kheng, Kuntheak

2017-11-01

Semiconductor nanowires offer the possibility to grow high-quality quantum-dot heterostructures, and, in particular, CdSe quantum dots inserted in ZnSe nanowires have demonstrated the ability to emit single photons up to room temperature. In this paper, we demonstrate a bottom-up approach to fabricate a photonic fiberlike structure around such nanowire quantum dots by depositing an oxide shell using atomic-layer deposition. Simulations suggest that the intensity collected in our NA =0.6 microscope objective can be increased by a factor 7 with respect to the bare nanowire case. Combining microphotoluminescence, decay time measurements, and numerical simulations, we obtain a fourfold increase in the collected photoluminescence from the quantum dot. We show that this improvement is due to an increase of the quantum-dot emission rate and a redirection of the emitted light. Our ex situ fabrication technique allows a precise and reproducible fabrication on a large scale. Its improved extraction efficiency is compared to state-of-the-art top-down devices.

[A study of magnetic shielding design for a magnetic resonance imaging linac system].

PubMed

Zhang, Zheshun; Chen, Wenjing; Qiu, Yang; Zhu, Jianming

2017-12-01

One of the main technical challenges when integrating magnetic resonance imaging (MRI) systems with medical linear accelerator is the strong interference of fringe magnetic fields from the MRI system with the electron beams of linear accelerator, making the linear accelerator not to work properly. In order to minimize the interference of magnetic fields, a magnetic shielding cylinder with an open structure made of high permeability materials is designed. ANSYS Maxwell was used to simulate Helmholtz coil which generate uniform magnetic field instead of the fringe magnetic fields which affect accelerator gun. The parameters of shielding tube, such as permeability, radius, length, side thickness, bottom thickness and fringe magnetic fields strength are simulated, and the data is processed by MATLAB to compare the shielding performance. This article gives out a list of magnetic shielding effectiveness with different side thickness and bottom thickness under the optimal radius and length, which showes that this design can meet the shielding requirement for the MRI-linear accelerator system.

Free energy, precision and learning: the role of cholinergic neuromodulation

PubMed Central

Moran, Rosalyn J.; Campo, Pablo; Symmonds, Mkael; Stephan, Klaas E.; Dolan, Raymond J.; Friston, Karl J.

2014-01-01

Acetylcholine (ACh) is a neuromodulatory transmitter implicated in perception and learning under uncertainty. This study combined computational simulations and pharmaco-electroencephalography in humans, to test a formulation of perceptual inference based upon the free energy principle. This formulation suggests that acetylcholine enhances the precision of bottom-up synaptic transmission in cortical hierarchies by optimising the gain of supragranular pyramidal cells. Simulations of a mismatch negativity paradigm predicted a rapid trial-by-trial suppression of evoked sensory prediction error (PE) responses that is attenuated by cholinergic neuromodulation. We confirmed this prediction empirically with a placebo-controlled study of cholinesterase inhibition. Furthermore – using dynamic causal modelling – we found that drug-induced differences in PE responses could be explained by gain modulation in supragranular pyramidal cells in primary sensory cortex. This suggests that acetylcholine adaptively enhances sensory precision by boosting bottom-up signalling when stimuli are predictable, enabling the brain to respond optimally under different levels of environmental uncertainty. PMID:23658161

Seismic analysis of offshore wind turbines on bottom-fixed support structures.

PubMed

Alati, Natale; Failla, Giuseppe; Arena, Felice

2015-02-28

This study investigates the seismic response of a horizontal axis wind turbine on two bottom-fixed support structures for transitional water depths (30-60 m), a tripod and a jacket, both resting on pile foundations. Fully coupled, nonlinear time-domain simulations on full system models are carried out under combined wind-wave-earthquake loadings, for different load cases, considering fixed and flexible foundation models. It is shown that earthquake loading may cause a significant increase of stress resultant demands, even for moderate peak ground accelerations, and that fully coupled nonlinear time-domain simulations on full system models are essential to capture relevant information on the moment demand in the rotor blades, which cannot be predicted by analyses on simplified models allowed by existing standards. A comparison with some typical design load cases substantiates the need for an accurate seismic assessment in sites at risk from earthquakes. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

The fast-ice growth and freezing of the bottom in the Braganzavagen Gulf (Van Mijenfjorden, Svalbard)

NASA Astrophysics Data System (ADS)

Bogorodsky, Petr; Marchenko, Aleksey; Pnyushkov, Andrey; Filchuk, Kirill; Morozov, Yevgenii; Ryzhov, Ivan

2017-04-01

The results of oceanographic and sea ice studies in the shallow Braganzavågen Gulf (Van Mijenfjorden, Svalbard) in March 2016 are presented. These studies are a continuation of observational efforts initiated by UNIS (Svalbard, Norway) in 2014. 2016 field campaign includes instrumental measurements of snow and ice properties in the fjord (e.g., ice thicknesses, temperatures, and salinities), as well as high-resolution CTD measurements within the under-ice water column. Collected observations were accompanied by freezing simulations of adjacent water and bottom ground layers performed with a one-dimensional thermodynamic model (Bogorodskii and Pnyushkov, 2015). The model uses two methods to reproduce phase transition areas - a "classic" (frontal) method for the fast ice, and transition in the continuous media (mushy zone) for the bottom sediments. Meteorological observations during the winter 2015-16 at Sveagruva (northwest coast) were used in these simulations as the atmospheric forcing. Numerical experiments were carried out for the initial salinity of 35 psu and 2 m water depth. The simulations start with the beginning of water freezing determined by a steady air temperature transition through the freezing point. The start of freezing was also verified by comparison with sea ice charts available for the Van Mijenfjorden for the period of simulations. Model simulations showed that the growth of sea ice in shallow (<1 m) areas of the basin significantly increases water salinity in the under-ice layer. For instance, at a 0.5 m depth the salinity in the under ice water layer exceeds 160 psu, which corresponds to the freezing temperature below -9C. In fact, the water salinity does not reach high values because of the horizontal mixing. However, available hydrological observations showed relatively small (0.2-0.5 m) amplitudes of tides - the major contributor to the horizontal exchange in this area. These small amplitudes likely suggest small advective salt fluxes induced by tides, and thus their little effect on the rate of ice formation at seasonal time scales. As expected, substantial water cooling in the under-ice layer leads to freezing of the bottom ground, mostly evident in areas with small depths. For example, during the cold season this freezing may be as large as 1 m at a fjord part with typical depths of 0.5 m. In general, the model shows a relativity good agreement with direct observations of fast ice properties. However, due to uncertainty in the thermodynamic properties of the ground, the quantitative description of the heat transfer processes in this layer is still incomplete and required additional clarification in the specially targeted field experiments.

Emergency Simulation Drill

NASA Image and Video Library

2013-12-04

ISS038-E-011716 (4 Dec. 2013) --- The Expedition 38 crew members participate in an emergency simulation drill with participation from flight controllers on the ground. During the exercise, the crew practiced emergency communication and procedures in response to a predetermined scenario such as pressure leak. Pictured in the International Space Station?s Destiny laboratory are Russian cosmonaut Oleg Kotov (left), commander; NASA astronaut Michael Hopkins (bottom), Japan Aerospace Exploration Agency astronaut Koichi Wakata (center) and Russian cosmonaut Sergey Ryazanskiy, all flight engineers.

Flash Infrared Thermography Contrast Data Analysis Technique

NASA Technical Reports Server (NTRS)

Koshti, Ajay

2014-01-01

This paper provides information on an IR Contrast technique that involves extracting normalized contrast versus time evolutions from the flash thermography inspection infrared video data. The analysis calculates thermal measurement features from the contrast evolution. In addition, simulation of the contrast evolution is achieved through calibration on measured contrast evolutions from many flat-bottom holes in the subject material. The measurement features and the contrast simulation are used to evaluate flash thermography data in order to characterize delamination-like anomalies. The thermal measurement features relate to the anomaly characteristics. The contrast evolution simulation is matched to the measured contrast evolution over an anomaly to provide an assessment of the anomaly depth and width which correspond to the depth and diameter of the equivalent flat-bottom hole (EFBH) similar to that used as input to the simulation. A similar analysis, in terms of diameter and depth of an equivalent uniform gap (EUG) providing a best match with the measured contrast evolution, is also provided. An edge detection technique called the half-max is used to measure width and length of the anomaly. Results of the half-max width and the EFBH/EUG diameter are compared to evaluate the anomaly. The information provided here is geared towards explaining the IR Contrast technique. Results from a limited amount of validation data on reinforced carbon-carbon (RCC) hardware are included in this paper.

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.

Evaluation of bottom-up and downscaled emission inventories for Paris and consequences for estimating urban air pollution increments

NASA Astrophysics Data System (ADS)

Timmermans, R.; Denier van der Gon, H.; Segers, A.; Honore, C.; Perrussel, O.; Builtjes, P.; Schaap, M.

2012-04-01

Since a major part of the Earth's population lives in cities, it is of great importance to correctly characterise the air pollution levels over these urban areas. Many studies in the past have already been dedicated to this subject and have determined so-called urban increments: the impact of large cities on the air pollution levels. The impact of large cities on air pollution levels usually is determined with models driven by so-called downscaled emission inventories. In these inventories official country total emissions are gridded using information on for example population density and location of industries and roads. The question is how accurate are the downscaled inventories over cities or large urban areas. Within the EU FP 7 project MEGAPOLI project a new emission inventory has been produced including refined local emission data for two European megacities (Paris, London) and two urban conglomerations (the Po valley, Italy and the Rhine-Ruhr region, Germany) based on a bottom-up approach. The inventory has comparable national totals but remarkable difference at the city scale. Such a bottom up inventory is thought to be more accurate as it contains local knowledge. Within this study we compared modelled nitrogen dioxide (NO2) and particulate matter (PM) concentrations from the LOTOS-EUROS chemistry transport model driven by a conventional downscaled emission inventory (TNO-MACC inventory) with the concentrations from the same model driven by the new MEGAPOLI 'bottom-up' emission inventory focusing on the Paris region. Model predictions for Paris significantly improve using the new Megapoli inventory. Both the emissions as well as the simulated average concentrations of PM over urban sites in Paris are much lower due to the different spatial distribution of the anthropogenic emissions. The difference for the nearby rural stations is small implicating that also the urban increment for PM simulated using the bottom-up emission inventory is much smaller than for the downscaled emission inventory. Urban increments for PM calculated with downscaled emissions, as is common practice, might therefore be overestimated. This finding is likely to apply to other European Megacities as well.

Evaluation of Cloud-Resolving Model Intercomparison Simulations Using TWP-ICE Observations: Precipitation and Cloud Structure

NASA Technical Reports Server (NTRS)

Varble, Adam; Fridlind, Ann M.; Zipser, Edward J.; Ackerman, Andrew S.; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; McFarlane, Sally A.; Pinty, Jean-Pierre; Shipway, Ben

2011-01-01

The Tropical Warm Pool.International Cloud Experiment (TWP ]ICE) provided extensive observational data sets designed to initialize, force, and constrain atmospheric model simulations. In this first of a two ]part study, precipitation and cloud structures within nine cloud ]resolving model simulations are compared with scanning radar reflectivity and satellite infrared brightness temperature observations during an active monsoon period from 19 to 25 January 2006. Seven of nine simulations overestimate convective area by 20% or more leading to general overestimation of convective rainfall. This is balanced by underestimation of stratiform rainfall by 5% to 50% despite overestimation of stratiform area by up to 65% because of a preponderance of very low stratiform rain rates in all simulations. All simulations fail to reproduce observed radar reflectivity distributions above the melting level in convective regions and throughout the troposphere in stratiform regions. Observed precipitation ]sized ice reaches higher altitudes than simulated precipitation ]sized ice despite some simulations that predict lower than observed top ]of ]atmosphere infrared brightness temperatures. For the simulations that overestimate radar reflectivity aloft, graupel is the cause with one ]moment microphysics schemes whereas snow is the cause with two ]moment microphysics schemes. Differences in simulated radar reflectivity are more highly correlated with differences in mass mean melted diameter (Dm) than differences in ice water content. Dm is largely dependent on the mass ]dimension relationship and gamma size distribution parameters such as size intercept (N0) and shape parameter (m). Having variable density, variable N0, or m greater than zero produces radar reflectivities closest to those observed.

Replication of Optical Microstructures of Papilio palinurus through Biomimicry

NASA Astrophysics Data System (ADS)

Srinivasarao, Mohan; Crne, Matija; Sharma, Vivek; Blair, John; Park, Jung Ok; Summers, Christopher J.

2009-03-01

The coloration of animals in nature is sometimes based on their structure rather than pigments. Structural coloration based on diffraction, multilayer reflection, cholesteric analogues or photonic crystal-like structures is pervasive especially in the world of insects. The color of Papilio palinurus results from microbowl lined with a multilayer of air and chitin. The green color is the result of color mixing of the yellow light reflecting from the bottom of the bowl and the blue light reflecting from the sides of the bowl. We have used breath figure templated assembly as the starting point to mimic the structure of Papilio palinurus. We were able to produce microbowls which were then coated with a multilayer of alternating titanium oxide and aluminum oxide. The resulting structure exhibits the same color mixing as the original butterfly structure does.

Earth observation

NASA Image and Video Library

2014-09-06

ISS040-E-124198 (6 Sept. 2014) --- Puget Sound is partly reflecting the sun in this detailed image taken by an Expedition 40 crew member on the International Space Station. Patterns of boat wakes are prominent in the sun’s partial reflection zone. The difference between the boat wakes in this view relates to the speed of the boat and the particular patterns (of several) that happen to be captured in the specific light reflection angles at the time the image was taken. The land areas show parts of Seattle. The darkest areas with rectangular grids are suburbs richly covered with trees. The broadly gray zones of the central city (bottom center) are brighter where structures are lower, as in the harbor zone (Harbor Island), and darker where the shadows of high-rise buildings downtown cast black shadows. Interstate Highway 5 bisects downtown.

Detecting grouting quality of tendon ducts using the impact-echo method

NASA Astrophysics Data System (ADS)

Qu, Guangzhen; Sun, Min; Zhou, Guangli

2018-06-01

The performance, durability and safety of prestressed concrete bridge were directly affected by the compaction of prestressed pipe. However, the pipe was hidden in the beam, and its grouting density was difficult to detect. The paper had modified three different status of gouting quality through making test model. After that, the impact-Echo method was adopted to detect the grouting quality of tendon ducts, the study was sunmmarized as follow. If the reflect time of slab bottom and nominal thickness of slab increased, the degree of density will increase; testing from half-hole of web, the reflect time and nominal thickness of slab was biggest. At the same time, the reflect time of compacted and uncompacted tendon ducts were mainly. At last, the method was verified by the engineering project, which provided reference value.

Simulation of a polarized laser beam reflected at the sea surface: modeling and validation

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric

2015-05-01

A 3-D simulation of the polarization-dependent reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation considers polarized or unpolarized laser sources and calculates the polarization states upon reflection at the sea surface. It is suitable for the radiance calculation of the scene in different spectral wavebands (e.g. near-infrared, SWIR, etc.) not including the camera degradations. The simulation also considers a bistatic configuration of laser source and receiver as well as different atmospheric conditions. In the SWIR, the detected total power of reflected laser light is compared with data collected in a field trial. Our computer simulation combines the 3-D simulation of a maritime scene (open sea/clear sky) with the simulation of polarized or unpolarized laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the input of a camera equipped with a linear polarizer, the polarized sea surface radiance must be calculated for the specific waveband. The s- and p-polarization states are calculated for the emitted sea surface radiance and the specularly reflected sky radiance to determine the total polarized sea surface radiance of each component. The states of polarization and the radiance of laser light specularly reflected at the wind-roughened sea surface are calculated by considering the s- and p- components of the electric field of laser light with respect to the specular plane of incidence. This is done by using the formalism of their coherence matrices according to E. Wolf [1]. Additionally, an analytical statistical sea surface BRDF (bidirectional reflectance distribution function) is considered for the reflection of laser light radiances. Validation of the simulation results is required to ensure model credibility and applicability to maritime laser applications. For validation purposes, field measurement data (images and meteorological data) was analyzed. An infrared laser, with or without a mounted polarizer, produced laser beam reflection at the water surface and images were recorded by a camera equipped with a polarizer with horizontal or vertical alignment. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam and different alignment for the laser polarizers (vertical/horizontal/without) and the camera (vertical/horizontal).

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.

Comparison of PARASOL Observations with Polarized Reflectances Simulated Using Different Ice Habit Mixtures

NASA Technical Reports Server (NTRS)

Cole, Benjamin H.; Yang, Ping; Baum, Bryan A.; Riedi, Jerome; Labonnote, Laurent C.; Thieuleux, Francois; Platnick, Steven

2012-01-01

Insufficient knowledge of the habit distribution and the degree of surface roughness of ice crystals within ice clouds is a source of uncertainty in the forward light scattering and radiative transfer simulations required in downstream applications involving these clouds. The widely used MODerate Resolution Imaging Spectroradiometer (MODIS) Collection 5 ice microphysical model assumes a mixture of various ice crystal shapes with smooth-facets except aggregates of columns for which a moderately rough condition is assumed. When compared with PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) polarized reflection data, simulations of polarized reflectance using smooth particles show a poor fit to the measurements, whereas very rough-faceted particles provide an improved fit to the polarized reflectance. In this study a new microphysical model based on a mixture of 9 different ice crystal habits with severely roughened facets is developed. Simulated polarized reflectance using the new ice habit distribution is calculated using a vector adding-doubling radiative transfer model, and the simulations closely agree with the polarized reflectance observed by PARASOL. The new general habit mixture is also tested using a spherical albedo differences analysis, and surface roughening is found to improve the consistency of multi-angular observations. It is suggested that an ice model incorporating an ensemble of different habits with severely roughened surfaces would potentially be an adequate choice for global ice cloud retrievals.

Instability of bottom-water redox conditions during accumulation of Quaternary sediment in the Japan Sea

USGS Publications Warehouse

Piper, D.Z.; Isaacs, C.M.

1996-01-01

The concentrations of Cd, Cr, Cu, Mo, Ni, Sb, U, V, and Zn were measured in early Quaternary sediment (1.32 to 1.08 Ma) from the Oki Ridge in the Japan Sea. The elements were partitioned between a detrital fraction, composed of terrigenous and volcaniclastic aluminosilicate debris, and a marine fraction, composed of biogenic and hydrogenous debris derived from seawater. The most important factors controlling minor-element accumulation rates in the marine fraction were (1) primary productivity in the photic zone, which largely controlled the flux of particulate organic-matter-bound minor elements settling through the water column and onto the seafloor, and (2) bottom-water redox, which determined the suite of elements that accumulated directly from seawater. This marine fraction of minor elements on Oki Ridge recorded six periods of high minor-element abundance. Assuming a constant bulk sediment accumulation rate, each period lasted roughly 5,000 to 10,000 years with a 41,000-year cycle. Accumulation rates of individual elements such as Cd, Mo, and U suggest sulfate-reducing conditions were established in the bottom water during the 10,000-year periods; accumulation rates of Cr and V during the intervening periods are indicative of less reducing, denitrifying conditions. Interelement ratios, for example, Cu:Mo, V:Cr, and Sb:Mo, further reflect bottom-water instability, such that bottom-water redox actually varied from sulfate reducing to denitrifying during the periods of highest minor-element accumulation rates; it varied from denitrifying to oxidizing during the intervening periods. Sediment lithology supports these interpretations of the minor-element distributions; the sediment is finely laminated for several of the periods represented by Cd, Mo, and U maxima and weakly laminated to bioturbated for the intervening periods. The geochemistry of this sediment demonstrates the unambiguous signal of Mo, principally, but of several other minor elements as well in recording sulfate-reducing conditions in bottom water. The forcing function that altered their accumulation, that is, that altered primary productivity and bottom water redox conditions, is problematic. Currently held opinion suggests that O2 depletion was most strongly developed during glacial advances. Low sea level during such times is interpreted to have enhanced primary productivity and restricted bottom-water advection.

Neural correlates of context-dependent feature conjunction learning in visual search tasks.

PubMed

Reavis, Eric A; Frank, Sebastian M; Greenlee, Mark W; Tse, Peter U

2016-06-01

Many perceptual learning experiments show that repeated exposure to a basic visual feature such as a specific orientation or spatial frequency can modify perception of that feature, and that those perceptual changes are associated with changes in neural tuning early in visual processing. Such perceptual learning effects thus exert a bottom-up influence on subsequent stimulus processing, independent of task-demands or endogenous influences (e.g., volitional attention). However, it is unclear whether such bottom-up changes in perception can occur as more complex stimuli such as conjunctions of visual features are learned. It is not known whether changes in the efficiency with which people learn to process feature conjunctions in a task (e.g., visual search) reflect true bottom-up perceptual learning versus top-down, task-related learning (e.g., learning better control of endogenous attention). Here we show that feature conjunction learning in visual search leads to bottom-up changes in stimulus processing. First, using fMRI, we demonstrate that conjunction learning in visual search has a distinct neural signature: an increase in target-evoked activity relative to distractor-evoked activity (i.e., a relative increase in target salience). Second, we demonstrate that after learning, this neural signature is still evident even when participants passively view learned stimuli while performing an unrelated, attention-demanding task. This suggests that conjunction learning results in altered bottom-up perceptual processing of the learned conjunction stimuli (i.e., a perceptual change independent of the task). We further show that the acquired change in target-evoked activity is contextually dependent on the presence of distractors, suggesting that search array Gestalts are learned. Hum Brain Mapp 37:2319-2330, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Geochemistry of the Black Sea during the last 15 kyr: A protracted evolution of its hydrography and ecology

USGS Publications Warehouse

Piper, David Z.

2016-01-01

The Black Sea is a 2200 m deep anoxic, marine sea connected to the Mediterranean Sea via the Dardanelles Strait, Marmara Sea, and the 3 km wide, 35 m deep Bosphorus Strait. The biogeochemistry of sediment from the Anatolia slope has recorded changes to the hydrography leading up to and following the input of Mediterranean water at ~9.4 ka (103 years B.P.), when global sea level rose to the level of the Bosphorus sill and high-salinity water from the Mediterranean began to spill into the then brackish lake. The water initially mixed little with the lake water but cascaded to the bottom where it remained essentially isolated for ~1.6 kyr, the time required to fill the basin from the bottom up at its present input rate. The accumulation of Mo in the seafloor sediments, a proxy of bottom-water anoxia, increased sharply at ~8.6 ka, when bacterial respiration in the bottom water advanced to SO42− reduction by the oxidation of organic detritus that settled out of the photic zone. Its accumulation remained elevated to ~5.6 ka, when it decreased 60%, only to again increase slightly at ~2.0 ka. The accumulation of Corg, a proxy of primary productivity, increased threefold to fourfold at ~7.8 ka, when upward mixing of the high-salinity bottom water replaced the then thin veneer of the brackish photic zone in less than 50 years. From that time onward, the accumulation of Corg, Mo, and additional trace metals has reflected the hydrography of the basin and Bosphorus Strait, controlled largely by climate.

Large area compatible broadband superabsorber surfaces in the VIS-NIR spectrum utilizing metal-insulator-metal stack and plasmonic nanoparticles.

PubMed

Dereshgi, Sina Abedini; Okyay, Ali Kemal

2016-08-08

Plasmonically enhanced absorbing structures have been emerging as strong candidates for photovoltaic (PV) devices. We investigate metal-insulator-metal (MIM) structures that are suitable for tuning spectral absorption properties by modifying layer thicknesses. We have utilized gold and silver nanoparticles to form the top metal (M) region, obtained by dewetting process compatible with large area processes. For the middle (I) and bottom (M) layers, different dielectric materials and metals are investigated. Optimum MIM designs are discussed. We experimentally demonstrate less than 10 percent reflection for most of the visible (VIS) and near infrared (NIR) spectrum. In such stacks, computational analysis shows that the bottom metal is responsible for large portion of absorption with a peak of 80 percent at 1000 nm wavelength for chromium case.

Russian Activities in Space Photovoltaic Power Modules with Concentrators

NASA Technical Reports Server (NTRS)

Andreev, Vyacheslav M.; Rumyantsev, Valeri D.

2004-01-01

Space concentrator modules with point-and line-focus Fresnel lenses and with reflective parabolic troughs have been developed recently at Ioffe Physico-Technical Institute. PV receivers for these modules are based: on the single junction LPE and MOCVD AlGaAs/GaAs solar cells characterized by AM0 efficiencies of 23.5 - 24% at 20 - 50 suns and 24 - 24.75 at 50 - 200 suns; on the mechanically stacked tandem AlGaAs/GaAs-GaSb cells with efficiency of 27 - 28 at 20 - 100 suns. MOCVD AlGaAs/GaAs cells with internal Bragg reflector have shown a higher radiation resistance as compared to a traditional structure. Monolithic two-terminal tandems AlGaAs (top)-GaAs (bottom) for space application and GaSb (top) - InGaAsSb (bottom) for TRV application are under development as well.

Joint Estimation of Source Range and Depth Using a Bottom-Deployed Vertical Line Array in Deep Water

PubMed Central

Li, Hui; Yang, Kunde; Duan, Rui; Lei, Zhixiong

2017-01-01

This paper presents a joint estimation method of source range and depth using a bottom-deployed vertical line array (VLA). The method utilizes the information on the arrival angle of direct (D) path in space domain and the interference characteristic of D and surface-reflected (SR) paths in frequency domain. The former is related to a ray tracing technique to backpropagate the rays and produces an ambiguity surface of source range. The latter utilizes Lloyd’s mirror principle to obtain an ambiguity surface of source depth. The acoustic transmission duct is the well-known reliable acoustic path (RAP). The ambiguity surface of the combined estimation is a dimensionless ad hoc function. Numerical efficiency and experimental verification show that the proposed method is a good candidate for initial coarse estimation of source position. PMID:28590442

Velocity-intermittency structure for wake flow of the pitched single wind turbine under different inflow conditions

NASA Astrophysics Data System (ADS)

Crist, Ryan; Cal, Raul Bayoan; Ali, Naseem; Rockel, Stanislav; Peinke, Joachim; Hoelling, Michael

2017-11-01

The velocity-intermittency quadrant method is used to characterize the flow structure of the wake flow in the boundary layer of a wind turbine array. Multifractal framework presents the intermittency as a pointwise Hölder exponent. A 3×3 wind turbine array tested experimentally provided a velocity signal at a 21×9 downstream location, measured via hot-wire anemometry. The results show a negative correlation between the velocity and the intermittency at the hub height and bottom tip, whereas the top tip regions show a positive correlation. Sweep and ejection based on the velocity and intermittency are dominant downstream from the rotor. The pointwise results reflect large-scale organization of the flow and velocity-intermittency events corresponding to a foreshortened recirculation region near the hub height and the bottom tip.

The anomalous amplification of M2 tide in the Taiwan Strait

NASA Astrophysics Data System (ADS)

Jan, Sen; Chern, Ching-Sheng; Wang, Joe; Chao, Shenn-Yu

2004-04-01

The complex tidal wave propagation pattern in the Taiwan Strait invites parochialism. Along the eastern (Taiwan) boundary of the strait, the anomalous amplification of M2 tide in the middle often led to the parochial view that two tidal waves coming from both ends of the strait collide in the middle, creating wave resonance. Along the western (China) boundary, one sees a southward progressive tidal wave and hence no wave collision. To reconcile, we examine a few solutions of a numerical tidal model below. Both realistic bottom bathymetry and idealized bottom topographies are used to identify dominant mechanism leading to the complex tidal wave propagation. Our process of elimination identifies the wave reflection of southward propagating tidal wave by the deep trench in the southern strait as the true cause responsible for the complex wave propagation pattern.

Arctic Deep Water Ferromanganese-Oxide Deposits Reflect the Unique Characteristics of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Hein, James R.; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe J.; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah R.; Till, Claire P.

2017-11-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, and HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits. The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ˜15 Myr ago.

Variations in freshwater pathways from the Arctic Ocean into the North Atlantic Ocean

NASA Astrophysics Data System (ADS)

Wang, Zeliang; Hamilton, James; Su, Jie

2017-06-01

Understanding the mechanisms that drive exchanges between the Arctic Ocean and adjacent oceans is critical to building our knowledge of how the Arctic is reacting to a warming climate, and how potential changes in Arctic Ocean freshwater export may impact the AMOC (Atlantic Meridional Overturning Circulation). Here, freshwater pathways from the Arctic Ocean to the North Atlantic are investigated using a 1 degree global model. An EOF analysis of modeled sea surface height (SSH) demonstrates that while the second mode accounts for only 15% of the variability, the associated geostrophic currents are strongly correlated with freshwater exports through CAA (Canadian Arctic Archipelago; r = 0.75), Nares Strait (r = 0.77) and Fram Strait (r = -0.60). Separation of sea level into contributing parts allows us to show that the EOF1 is primarily a barotropic mode reflecting variability in bottom pressure equivalent sea level, while the EOF2 mode reflects changes in steric height in the Arctic Basin. This second mode is linked to momentum wind driven surface current, and dominates the Arctic Ocean freshwater exports. Both the Arctic Oscillation and Arctic Dipole atmospheric indices are shown to be linked to Arctic Ocean freshwater exports, with the forcing associated with the Arctic Dipole reflecting the out-of-phase relationship between transports through the CAA and those through Fram Strait. Finally, observed freshwater transport variation through the CAA is found to be strongly correlated with tide gauge data from the Beaufort Sea coast (r = 0.81), and with the EOF2 mode of GRACE bottom pressure data (r = 0.85) on inter-annual timescales.

Arctic deep-water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean

USGS Publications Warehouse

Hein, James; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah; Till, Claire P.

2017-01-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits.The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ∼15 Myr ago.

MFP-REA Follow-Up 2002-2005

DTIC Science & Technology

2007-03-01

Sabel, ir. C.A.M. van Moll, Datum TNO Defensie en Veiligheid TNO Defensie en Veiligheid maart 2007 Auteur (s) Programmatitel Projecttitel prof. dr. D.G...parameters by means of bottom reflection loss data derived from ambient noise. Matched field inversion is an application of inverse theory . Addressing... theory . Because inverse theory estimates the best fitting model, the uncertainty of this estimate should be specified. These topics are not investigated

Fabrication of trough-shaped solar collectors

DOEpatents

Schertz, William W.

1978-01-01

There is provided a radiant energy concentration and collection device formed of a one-piece thin-walled plastic substrate including a plurality of nonimaging troughs with certain metallized surfaces of the substrate serving as reflective side walls for each trough. The one-piece plastic substrate is provided with a seating surface at the bottom of each trough which conforms to the shape of an energy receiver to be seated therein.

Application of Biot Theory to the Study of Acoustic Reflection from Sediments

DTIC Science & Technology

1992-09-08

of bottom loss at all frequencies. To predict propagation loss, a multipath expansion propagation model [15] was used. The sound velocity profile in...public release; distribution unlimited. 13. AISTRACT (Maximum 200 wovov Wave Propagation in fluid-saturated poroelastic media may be described using...of grazing angle and frequency is compared against the more common fluid-fluid and fluid-solid interface models . Finally, shallow water propagation

Model for the Formation and Evolution of Sand Ridges on the Continental Shelf

DTIC Science & Technology

1992-10-01

difficulties of conducting laboratory experiments involving liquid/sediment media (such as leveling the sediment bed after each trial, extracting gas...reflected component, the 54 55 bottom velocities to lowest order are Uob = uo+ 32’.uoxr = E’= 1 Cja(X, y)e(•k’x-W’t) + c.c. (3.3) Vob = VO + 02 2 h(3 Vb2 To

Lake Mohave Geophysical Survey 2002: GIS Data Release

USGS Publications Warehouse

Cross, VeeAnn A.; Foster, David S.; Twichell, David C.

2005-01-01

This CD-ROM contains sidescan-sonar imagery, sub-bottom reflection profiles, and an interpretive map derived from these data. These data were collected in Lake Mohave, a reservoir behind the Davis Dam and below the Hoover Dam on the Colorado River. These data are veiwable within an Environmental system Research Institute, Inc. (ESRI) Geographic Information system (GIS) ArcView 3.2 project file stored on this CD-ROM

Long time-series of turbid coastal water using AVHRR: An example from Florida Bay, USA

USGS Publications Warehouse

Stumpf, R.P.; Frayer, M.L.

1997-01-01

The AVHRR can provide information on the reflectance of turbid case II water, permitting examination of large estuaries and plumes from major rivers. The AVHRR has been onboard several NOAA satellites, with afternoon overpasses since 1981, offering a long time-series to examine changes in coastal water. We are using AVHRR data starting in December 1989, to examine water clarity in Florida Bay, which has undergone a decline since the late 1980's. The processing involves obtaining a nominal reflectance for red light with standard corrections including those for Rayleigh and aerosol path radiances. Established relationships between reflectance and the water properties being measured in the Bay provide estimates of diffuse attenuation and light limitation for phytoplankton and seagrass productivity studies. Processing also includes monthly averages of reflectance and attenuation. The AVHRR data set describes spatial and temporal patterns, including resuspension of bottom sediments in the winter, and changes in water clarity. The AVHRR also indicates that Florida Bay has much higher reflectivity relative to attenuation than other southeastern US estuaries. ??2005 Copyright SPIE - The International Society for Optical Engineering.

Long time-series of turbid coastal water using AVHRR: an example from Florida Bay, USA

NASA Astrophysics Data System (ADS)

Stumpf, Richard P.; Frayer, M. L.

1997-02-01

The AVHRR can provide information on the reflectance of turbid case II water, permitting examination of large estuaries and plumes from major rivers. The AVHRR has been onboard several NOAA satellites, with afternoon overpasses since 1981, offering a long time-series to examine changes in coastal water. We are using AVHRR data starting in December 1989, to examine water clarity in Florida Bay, which has undergone a decline since the late 1980's. The processing involves obtaining a nominal reflectance for red light with standard corrections including those for Rayleigh and aerosol path radiances. Established relationships between reflectance and the water properties being measured in the Bay provide estimates of diffuse attenuation and light limitation for phytoplankton and seagrass productivity studies. Processing also includes monthly averages of reflectance and attenuation. The AVHRR data set describes spatial and temporal patterns, including resuspension of bottom sediments in the winter, and changes in water clarity. The AVHRR also indicates that Florida Bay has much higher reflectivity relative to attenuation than other southeastern US estuaries.

Decision making, impulse control and loss of willpower to resist drugs: a neurocognitive perspective.

PubMed

Bechara, Antoine

2005-11-01

Here I argue that addicted people become unable to make drug-use choices on the basis of long-term outcome, and I propose a neural framework that explains this myopia for future consequences. I suggest that addiction is the product of an imbalance between two separate, but interacting, neural systems that control decision making: an impulsive, amygdala system for signaling pain or pleasure of immediate prospects, and a reflective, prefrontal cortex system for signaling pain or pleasure of future prospects. After an individual learns social rules, the reflective system controls the impulsive system via several mechanisms. However, this control is not absolute; hyperactivity within the impulsive system can override the reflective system. I propose that drugs can trigger bottom-up, involuntary signals originating from the amygdala that modulate, bias or even hijack the goal-driven cognitive resources that are needed for the normal operation of the reflective system and for exercising the willpower to resist drugs.