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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Using Remote Sensing to Assess of Growth and Distribution for Floating Invasive Plants and Growth Response Times to Altered Environments

Management of aquatic weeds in complex watersheds and river systems present many challenges to assessment, planning and implementation of management practices for aquatic invasive plants. The Delta Region Areawide Aquatic Weed Project (DRAAWP), a USDA (U. S. Dept. of Agriculture)-sponsored area-wide project, is working to enhance planning, decision-making and operational efficiency of invasive plant management in the California Sacramento-San Joaquin Delta. Satellite and airborne remote sensing are used to map area of plant coverage and estimate biomass density to aid operations and assess management impacts on plant communities. Modeling at local and watershed scales using the SWAT (Soil Water Assessment Tool) modeling tool provides insight into land-use effects on water quality. Environmental variability in the Delta occurs across a range of time scales from long-term climate and seasonal trends to short-term water flow mediated variations. Controlled environment growth studies have been conducted to quantify the growth response of invasive aquatic plants to water quality and other environmental factors. Response time for invasive species response are examined at time scales of weeks, day, and hours using a combination of study duration and growth assessment techniques to assess water quality, temperature (air and water), and light effects. These provide response parameters for plant growth models in response to environmental variation and interact with management and economic models associated with aquatic weed management. Plant growth models are to be informed by remote sensing and applied spatially across the Delta to balance location and type of aquatic plant, growth response to altered environments and phenology. Initial utilization of remote sensing tools developed for mapping of aquatic invasive plants improved operational efficiency in management practices. These assessment methods provide a comprehensive and quantitative view of aquatic invasive plant communities in the California Delta.

Floating↗
DOE OSTI2021

Intermediate Sr 2 Co 1.5 Fe 0.5 O 6-δ Tetragonal Structure between Perovskite and Brownmillerite as a Model Catalyst with Layered Oxygen Deficiency for Enhanced Electrochemical Water Oxidation

The generation of hydrogen in an environmentally benign way is highly essential to meet future energy demands. However, in the process of splitting water electrochemically, sluggish kinetics of the oxygen evolution reaction (OER) curtails its applicability, as it drags energy input. Herein, we synthesized SrCo-Fe-O oxides to optimize their OER activity by varying the Co/Fe ratio. Among them, Sr 2 Co 1.5 Fe 0.5 O 6-δ exhibited the best OER catalytic activity in the series, with an overpotential of 318 mV at 10 mA cm -2 and Tafel slope of 44.8 mV dec -1 . High-resolution neutron powder diffraction analysis identified an intermediate structure between the perovskite and brownmillerite, with alternating layers of disorderly orientated oxygen-deficient tetrahedra and fully stoichiometric octahedra. The unique stacking of tetrahedral and octahedral units facilitates desired interactions between the electrode surface and electrolyte. Theoretical calculations revealed that increased covalency of Co 3d and O 2p in Sr 2 Co 1.5 Fe 0.5 O 6-δ oxide is another primary contributor to its augmented water oxidation ability. As a model for developing catalysts with such an intermediate structure, the synergetic effect of oxygen vacancy and hybridization between Co 3d and O 2p assured the Sr 2 Co 1.5 Fe 0.5 O 6-δ oxide as a better catalyst for its enhanced OER activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

A radiative transfer model for remote sensing of laser induced fluorescence of phytoplankton in non-homogeneous turbid water

A radiative transfer computer model was developed to characterize the total flux of chlorophyll a fluoresced or backscattered photons when laser radiation is incident on turbid water that contains a non-homogeneous suspension of inorganic sediments and phytoplankton. The radiative transfer model is based on the Monte Carlo technique and assumes that: (1) the aquatic medium can be represented by a stratified concentration profile; and (2) that appropriate optical parameters can be defined for each layer. The model was designed to minimize the required computer resources and run time. Results are presented for an anacystis marinus culture.

Venable, D. D.↗
DOE OSTI2026

Optimizing Porous Transport Layer Porosity for Proton Exchange Membrane Water Electrolysis

An empirical model is presented that describes anode-side losses related to porous transport layer (PTL) morphology in proton exchange membrane water electrolysis (PEMWE). The model is based on an advanced voltage breakdown analysis that links various overpotentials to PTL morphology. Custom Ti PTLs, spanning uncommonly low porosities (22 - 31%), were fabricated and analyzed with X-ray CT to obtain pore and particle size distributions. Particle size distributions were consistent across samples with an average particle diameter of 12.0?..mu..m, whereas average pore diameters ranged from 6.0 to 7.0?..mu..m. The PTLs were tested in standard PEMWE cell assemblies with anode catalyst loadings of 0.1 mgIr cm-2 to obtain polarization curves, electrochemical impedance spectra, and augmented Tafel analysis. The PTL-dependent anode side losses were deconvoluted and assigned to excess utilization, concentration, ion transport resistance, and electrical contact resistance overpotentials. The data and model reveal an optimal 20 - 28% PTL porosity region where utilization and contact resistance overpotentials are minimized without triggering concentration and ion transport losses related to water deprivation. The optimal PTL porosity depends on the operating current density and is demonstrated at realistic PEMWE water flow rates to establish PTL design guidance for operation at scale.

08 HYDROGEN↗
NASA NTRS1990

Recurrence in truncated Boussinesq models for nonlinear waves in shallow water

The rapid spatial recurrence of weakly nonlinear and weakly dispersive progressive shallow-water waves is examined using a numerical integration technique on the discretized and truncated form of the Boussinesq equations. This study primarily examines recurrence in wave fields with Ursell number O(1) and characterizes the sensitivity of recurrence to initial spectral shape and number of allowed frequency modes. It is shown that the rapid spatial recurrence is not an inherent property of the considered Boussinesq systems for evolution distances of 10-50 wavelengths. The main result of the study is that highly truncated Boussinesq models of resonant shallow-water ocean surface gravity waves predict rapid multiple recurrence cycles, but that this is an artifact dependent on the number of allowed modes. For initial conditions consisting of essentially all energy concentrated in a single mode, damping of the recurrence cycles increases as the number of low-power background modes increases. When more than 32 modes are allowed, the recurrence behavior is relatively insensitive to the number of allowed modes.

Elgar, Steve↗
NASA NTRS2011

Water in Planetary and Cometary Atmospheres: H2O/HDO Transmittance and Fluorescence Models

We developed a modern methodology to retrieve water (H2O) and deuterated water (HDO) in planetary and cometary atmospheres, and constructed an accurate spectral database that combines theoretical and empirical results. On the basis of a greatly expanded set of spectroscopic parameters, we built a full non-resonance cascade fluorescence model and computed fluorescence efficiencies for H2O (500 million lines) and HDO (700 million lines). The new line list was also integrated into an advanced terrestrial radiative transfer code (LBLRTM) and adapted to the CO2 rich atmosphere of Mars, for which we adopted the complex Robert-Bonamy formalism for line shapes. We retrieved water and D/H in the atmospheres of Mars, comet C/2007 W1 (Boattini), and Earth by applying the new formalism to spectra obtained with the high-resolution spectrograph NIRSPEC/Keck II atop Mauna Kea (Hawaii). The new model accurately describes the complex morphology of the water bands and greatly increases the accuracy of the retrieved abundances (and the D/H ratio in water) with respect to previously available models. The new model provides improved agreement of predicted and measured intensities for many H2O lines already identified in comets, and it identifies several unassigned cometary emission lines as new emission lines of H2O. The improved spectral accuracy permits retrieval of more accurate rotational temperatures and production rates for cometary water.

comets↗
NASA NTRS1980

Studies of H2O on beta-AgI surfaces - An effective pair potential model

The adsorption of a water molecule on surfaces of beta-AgI, the hexagonal crystal believed to be primarily responsible for the ice-nucleating properties of AgI, is studied on the basis of an effective pair potential model. The water molecule is represented by a rigid point charge ST-2 model and the AgI substrate by an array of point atoms, and maximal binding energy surfaces and optimal H2O configurations are generated for the water molecule adsorbed on the rigid and unrelaxed basal and prism faces. Modeling of H2O adsorption above a two-layer ledge, an iodine vacancy and an H2O molecule trapped in the vacancy indicates that H2O adsorption is favored at interstitial sites where no substrate atoms lie directly below. The prism face is found to attract the water molecule more strongly and provide larger energy barriers to surface diffusion than basal face sites, with the ideal basal faces providing hexagonal patterns of adsorption sites for the H2O with preferred dipole moments aligned.

Hale, B. N.↗
DOE OSTI2023

An ensemble of 48 physically perturbed model estimates of the 1/8° terrestrial water budget over the conterminous United States, 1980–2015

Terrestrial water budget (TWB) data over large domains are of high interest for various hydrological applications. Spatiotemporally continuous and physically consistent estimations of TWB rely on land surface models (LSMs). As an augmentation of the operational North American Land Data Assimilation System Phase 2 (NLDAS-2) four-LSM ensemble, this paper describes a dataset simulated from an ensemble of 48 physics configurations of the Noah LSM with multi-physics options (Noah-MP). The 48 Noah-MP physics configurations are selected to give a representative cross-section of commonly used LSMs for parameterizing runoff, atmospheric surface layer turbulence, soil moisture limitation on photosynthesis, and stomatal conductance. The dataset spans from 1980 to 2015 over the conterminous United States (CONUS) at a monthly temporal resolution and a 1/8° spatial resolution. The dataset variables include total evapotranspiration and its constituents (canopy evaporation, soil evaporation, and transpiration), runoff (the surface and subsurface components), as well as terrestrial water storage (snow water equivalent, four-layer soil water content from the surface down to 2 m, and the groundwater storage anomaly). The dataset is available at https://doi.org/10.5281/zenodo.7109816. Evaluations carried out in this study and previous investigations show that the ensemble per forms well in reproducing the observed terrestrial water storage, snow water equivalent, soil moisture, and runoff. Noah-MP complements the NLDAS models well, and adding Noah-MP consistently improves the NLDAS es timations of the above variables in most areas of CONUS. Besides, the perturbed-physics ensemble facilitates the identification of model deficiencies. The parameterizations of shallow snow, spatially varying groundwater dynamics, and near-surface atmospheric turbulence should be improved in future model versions.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1981

Improvements in lake volume predictions using Landsat data

A cumulative error in the water balance budget for Lake Okeechobee produces a one million acre-foot discrepancy in the predicted water volume over a 4-year period. The major source of error appears to be complex shoreline marshes that comprise 20 percent of the lake surface. The water balance budget model presently treats these marshes as open water. Using Landsat data, the vegetation in the lake's littoral zone was classified multispectrally to provide a data base for determining water budget information. First, the acreage of a given plant species in the littoral zone was obtained with satellite data. Second, the surface area occupied by plants (which therefore could not be considered open water) was used to adjust the vegetation acreage giving an effective water surface. Based on this information, more detailed representations of evapotranspiration and total water surface (and hence total lake volume) could be provided to the water balance budget computation.

Gervin, J. C.↗
NASA NTRS1989

Photochemical stability of CO2 in the Martian atmosphere - Reevaluation of the eddy diffusion coefficient and the role of water vapor

Theoretical models of CO2 photodissociation in the atmosphere of Mars are developed and analyzed, with a focus on the conditions prevailing during the Mariner 6/7 experiments. The aeronomy of Martian CO2 is reviewed; the atomic O distribution in the upper atmosphere is characterized; the construction of the basic model is described; and simulation results are presented in extensive tables and graphs and discussed in detail. The vertical eddy-diffusion coefficient corresponding to the estimated upper-atmosphere O density (1-2 percent at 135 km) is found to be about 5 x 10 to the 7th sq cm/sec, and HO(x) is found to play a significant role in catalyzing the recombination of CO and O to form CO2. The reasons why the model overpredicts the production of HO(x) and hence of CO2 are explored.

Shimazaki, Tatsuo↗
NASA NTRS1935

Tank tests of a model of a flying-boat hull with a fluted bottom

A 1/5-scale model of a flying-boat hull having flutes in the bottom both forward and aft of the step (NACA model 19) was tested to determine its water performance. The model was also tested after the successive removal of the flutes on the afterbody and forebody. The results from these tests are compared with those from tests of a model of the hull of the Navy PN-8 flying boat and it is concluded that the fluted-bottom model and its modifications are inferior to the model of the PN-8.

Dawson, John R↗
NASA NTRS1997

Ground-Based GPS Sensing of Azimuthal Variations in Precipitable Water Vapor

Current models for troposphere delay employed by GPS software packages map the total zenith delay to the line-of-sight delay of the individual satellite-receiver link under the assumption of azimuthal homogeneity. This could be a poor approximation for many sites, in particular, those located at an ocean front or next to a mountain range. We have modified the GIPSY-OASIS II software package to include a simple non-symmetric mapping function (MacMillan, 1995) which introduces two new parameters.

azimuthal homogeneity zenith troposphere delay↗
NASA NTRS2015

Scale Model Acoustic Test Validation of IOP-SS Water Prediction using Loci-STREAM-VoF

The Scale Model Acoustic Test (SMAT) is a 5% scale test of the Space Launch System (SLS), which is currently being designed at Marshall Space Flight Center (MSFC). SMAT consists of a 5% scale representation of the ignition overpressure sound-suppression system (IOP-SS) that is being tested to quantify the water flow and induced air entrainment in and around the mobile launcher exhaust hole. This data will be compared with computational fluid dynamics (CFD) simulations using the newly developed Loci-STREAM Volume of Fluid (VoF) methods. Compressible and incompressible VoF methods have been formulated, and are currently being used to simulate the water flow of SMAT IOP-SS. The test data will be used to qualitatively and quantitatively assess and validate the VoF methods.

Nielsen, Tanner↗
NASA NTRS2009

NASA Workmanship Hot Topics: Water Soluble Flux and ESD Charge Device Model

This slide presentation reviews two topics of interest to NASA Workmanship: (1) Water Soluble Flux (WSF) and Electrostatic Discharge (ESD) safety. In the first topic, WSF, the presentation reviews voiding and the importance of cleanliness in using WSF for welding and soldering operations. The second topic reviews the NASA-HDBK-8739.21 for Human Body Model, and Machine Model safety methods, and challenges associated with the Charged Device Model (CDM)

Plante, Jeannette F.↗
NASA NTRS2014

Hybrid Wing Body Model Identification Using Forced-Oscillation Water Tunnel Data

Static and dynamic testing of the NASA 0.7 percent scale Hybrid Wing Body (HWB) configuration was conducted in the Rolling Hills Research Corporation water tunnel to investigate aerodynamic behavior over a large range of angle-of-attack and to develop models that can predict aircraft response in nonlinear unsteady flight regimes. This paper reports primarily on the longitudinal axis results. Flow visualization tests were also performed. These tests provide additional static data and new dynamic data that complement tests conducted at NASA Langley 14- by 22-Foot Subsonic Tunnel. HWB was developed to support the NASA Environmentally Responsible Aviation Project goals of lower noise, emissions, and fuel burn. This study also supports the NASA Aviation Safety Program efforts to model and control advanced transport configurations in loss-of-control conditions.

Murphy, Patrick C.↗
NASA NTRS1997

Evaluation of Tropospheric Water Vapor Simulations from the Atmospheric Model Intercomparison Project

Simulations of humidity from 28 general circulation models for the period 1979-88 from the Atmospheric Model Intercomparison Project are compared with observations from radiosondes over North America and the globe and with satellite microwave observations over the Pacific basin. The simulations of decadal mean values of precipitable water (W) integrated over each of these regions tend to be less moist than the real atmosphere in all three cases; the median model values are approximately 5% less than the observed values. The spread among the simulations is larger over regions of high terrain, which suggests that differences in methods of resolving topographic features are important. The mean elevation of the North American continent is substantially higher in the models than is observed, which may contribute to the overall dry bias of the models over that area. The authors do not find a clear association between the mean topography of a model and its mean W simulation, however, which suggests that the bias over land is not purely a matter of orography. The seasonal cycle of W is reasonably well simulated by the models, although over North America they have a tendency to become moister more quickly in the spring than is observed. The interannual component of the variability of W is not well captured by the models over North America. Globally, the simulated W values show a signal correlated with the Southern Oscillation index but the observations do not. This discrepancy may be related to deficiencies in the radiosonde network, which does not sample the tropical ocean regions well. Overall, the interannual variability of W, as well as its climatology and mean seasonal cycle, are better described by the median of the 28 simulations than by individual members of the ensemble. Tests to learn whether simulated precipitable water, evaporation, and precipitation values may be related to aspects of model formulation yield few clear signals, although the authors find, for example, a tendency for the few models that predict boundary layer depth to have large values of evaporation and precipitation. Controlled experiments, in which aspects of model architecture are systematically varied within individual models, may be necessary to elucidate whether and how model characteristics influence simulations.

Gaffen, Dian J.↗
NASA NTRS1991

A model of the formation of high-salinity shelf water on polar continental shelves

This study presents a model of the flow and salinity fields forced by sea-surface salinity flux and wind stress curl and examines the processes that create High-Salinity Shelf Water (HSSW). To investigate the relative effects of wind stress and buoyancy forcing in HSSW production, the polynya freezing rate in the model is varied from 0.0 to 0.30 m/d, and the Ekman pumping derived from the wind stress curl is varied independently from 0.0 to 1.8 x 10 exp 6 m/s. The Ekman pumping was found to control the magnitude of the circulation, while the polynya freezing rate controlled the extent of salinization in the shelf water. The flux of HSSW increases linearly with increasing Ekman pumping above 0.3 x 10 exp -6 m/s. The modeled flux of HSSW and the flux of derived Botttom Water for the present estimates of the forcings (a peak freezing rate of 0.10 m/d and Ekman pumping of 0.2 x 10 exp -6 m/s) agree with the fluxes inferred from physical and chemical observations in the deep Weddel Sea by oceanographic field programs.

Grumbine, Robert W.↗
DOE OSTI2025

Thermodynamic modeling of countercurrent chemical looping reverse water gas shift process for redox material screening

The reverse water gas shift (RWGS) reaction is a key pathway for CO 2 utilization, particularly within Power-to-X process chains aimed at sustainable fuel and chemical production. Countercurrent chemical looping (CL-RWGS) using non-stoichiometric oxides can overcome equilibrium limitations of conventional RWGS reactors, enabling significantly higher CO 2 conversions. However, modeling the limiting performance of such systems is challenging due to their multiphase nature and coupled spatial and temporal variation in chemical composition. In this work, we present a discretized batch equilibrium model that simulates CL-RWGS reactors as a series of localized equilibrium exchanges between gas and solid elements. The model is numerically stable, computationally efficient, and free of kinetic source terms, making it well-suited for parametric studies and system-level integration. It is validated against established convection–diffusion models and shown to predict reasonable upper bounds on experimental results. Application of the model to a range of oxygen carrier materials identifies cerium–zirconium solid solutions, particularly Ce 0.80 Zr 0.20 O 2 , as a promising class offering superior oxygen storage characteristics compared to state-of-the-art La 0.6 Sr 0.4 FeO 3 . This framework provides a robust platform for materials screening, reactor sizing, and performance optimization in chemical looping systems. The model implementation is available as open-source software to support further research and development.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗