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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Chemical-specific Parameters Dataset

The chemical-specific parameters dataset is searchable for physicochemical information for multiple chemicals simultaneously. After selecting chemicals of interest and the desired parameters, the RAIS will generate a table containing the values, chosen according to an established hierarchy. Results can be downloaded in Excel format. Over 40 parameters are available, including melting point, boiling point, density, density, vapor pressure, water solubility, and Henry’s Law constants. Thirteen primary sources are used to populate the dataset of chemical-specific parameters. These values should be used in cancer risk and noncancer hazard assessments for the calculation of preliminary remediation goals (PRGs), hazard characterization, and transport modeling. Users can select up to 1000 chemicals per query. The dataset supports environmental risk assessments, regulatory decision-making, and environmental planning with tools for benchmarking against risk-based standards. This structured approach ensures a robust evaluation of environmental risks tailored to regulatory needs.

Dolislager, Fred [Oak Ridge National Laboratory (O↗
NASA NTRS1986

The effect of leaf size on the microwave backscattering by corn

Attema and Ulaby (1978) proposed the cloud model to predict the microwave backscattering properties of vegetation. This paper describes a modification in which the biophysical properties and microwave properties of vegetation are related at the level of the individual scatterer (e.g., the leaf or the stalk) rather than at the level of the aggregated canopy (e.g., the green leaf area index). Assuming that the extinction cross section of an average leaf was proportional to its water content, that a power law relationship existed between the backscattering cross section of an average green corn leaf and its area, and that the backscattering coefficient of the surface was a linear function of its volumetric soil moisture content, it is found that the explicit inclusion of the effects of corn leaf size in the model led to an excellent fit between the observed and predicted backscattering coefficients. Also, an excellent power law relationship existed between the backscattering cross section of a corn leaf and its area.

Paris, J. F.↗
NASA NTRS1989

Marine stratocumulus structure

Thirty-three Landsat TM scenes of California stratocumulus cloud fields were acquired as part of the FIRE Marine Stratocumulus Intensive Field Observations in July 1987. They exhibit a wide variety of stratocumulus structures. Analysis has so far focused upon the July 7 scene, in which aircraft from NASA, NCAR, and the British Meteorological Office repeatedly gathered data across a stratocumulus-fair weather cumulus transition. The aircraft soundings validate the cloud base temperature threshold determined by spatial coherence analysis of the TM thermal band. Brightness variations in the stratocumulus region exhibit a -5/3 power-law decrease of the wavenumber spectra for scales larger than the cloud thickness, about 200 m, changing to a -3 power at smaller scales. Observations by an upward-looking three-channel microwave radiometer on San Nicolas Island also show the -5/3 power-law in total integrated liquid water, suggesting that the largest-scale TM brightness variations are primarily due to variations in the liquid water. The Kolmogorov 5/3 power suggests that for some purposes liquid water in turbulent stratocumulus clouds may be treated as a passive scalar, simply reflecting variations in vertical velocity. This may be tested using the velocities measured by the aircraft.

Cahalan, Robert F.↗
NASA NTRS1992

Emissivity of terrestrial materials in the 8-14 microns atmospheric window

Remotely sensed infrared radiance emitted by a surface is a function both of its kinetic temperature and its spectral emissivity. Consequently, assumptions are usually made about the emissivity of earth surface materials to allow their temperatures to be determined, or vice versa. To increase the accuracy of these assumptions, the directional hemispherical spectral reflectance of a wide range of natural earth surface materials has been measured and is summarized here. These include igneous, metamorphic, and sedimentary rocks, desert varnish, soils, vegetation, water, and ice. Kirchhoff's Law can be used to predict directional spectral emissivity from these data.

Salisbury, John W.↗
NASA NTRS1994

Mantle devolatilization and rheology in the framework of planetary evolution

We investigate the thermal history of an Earth-like planet with the help of a parameterized mantle convection model including the volatile exchange between mantle and surface reservoirs. The weakening of mantle silicates by dissolved volatiles is described by a functional relationship between creep rate and water fugacity. We use flow law parameters of diffusion creep in olivine under dry and wet conditions. The mantle degassing rate is considered as directly proportional to the seafloor spreading rate, which is also dependent on the mantle heat flow. To calculate the spreading rate, we assume that the heat flow under the mid-ocean ridges is double the average mantle heat flow. The rate of regassing also depends on the seafloor spreading rate as well as on other factors like the efficiency of volatile recycling through island arc volcanism. Both mechanisms (de- and regassing) are coupled self-consistently with the help of the parameterized convection model under implementation of a temperature and volatile-content-dependent mantle viscosity.

Franck, S.↗
DOE OSTI2021

Mechanisms of water oxidation on heterogeneous catalyst surfaces

Water oxidation, an essential step in photosynthesis, has attracted intense research attention. Understanding the reaction pathways at the electrocatalyst/water interface is of great importance for the development of water oxidation catalysts. How the water is oxidized on the electrocatalyst surface by the positive charges is still an open question. This review summarizes current advances in studies on surface chemistry within the context of water oxidation, including the intermediates, reaction mechanisms, and their influences on the reaction kinetics. The Tafel analyses of some electrocatalysts and the rate-laws relative to charge consumption rates are also presented. Moreover, how the multiple charge transfer relies on the intermediate coverage and the accumulated charge numbers is outlined. Finally, the intermediates and rate-determining steps on some water oxidation catalysts are discussed based on density functional theories.

14 SOLAR ENERGY↗
NASA NTRS1975

Degree of interdependence among atmospheric optical thicknesses in spectral bands between 0.36-2.4 micron

The degree of dependence among the atmospheric optical thicknesses that are measured in nonselective absorption bands is studied. The observations were made previously in many spectral bands within the range 0.36-2.4 micron from near sea level in two continents where urban and industrial pollutions were weak. The sample covariance matrices and corresponding eigenvalues and eigenvectors are computed. The two highest eigenvalues account for 90% of the total variance in 10 spectral bands within the range 0.4-1.6 micron. The linear regression of the optical thickness on the total precipitable water vapor is computed to determine the attenuation coefficient that is associated with water vapor. This coefficient shows a rapid power-law decrease with wavelength in the visible spectrum and indicates that numerous water particles of radius 0.03-0.06 micron cause the attenuation.

Fraser, R. S.↗
DOE OSTI2020

Thermal Stability of a Eutectic Mixture of Bis(2,2-dinitropropyl) Acetal and Formal: Part C. Kinetic Compensation Effect

Here, the aging behavior of a eutectic mixture of bis(2,2-dinitropropyl) acetal and formal [called NP here] has been studied in various atmospheres [dry (air or nitrogen) versus wet] at temperatures 70 °C and below. The properties of aged samples were analyzed using Fourier transform infrared (FTIR) spectroscopy, Karl Fischer (KF) titration, liquid chromatography/mass spectrometry (LC/MS), and thermogravimetric analysis (TGA) over a period of three years. The results indicate that at aging temperatures up to 55 °C, the initial rates of water production from nitrous acid (HONO) formation and decomposition into the water, NO, and NO 2 follows a 1st order rate law and the rate constants follow an Arrhenius law as a function of temperature. The activation energies and pre-factors for water and volatiles production yield a single linear kinetic compensation plot, suggesting a common degradation pathway between NP and the various combinations of its constituents. Within a narrow temperature range, around 55 °C, a trace amount of water in NP stabilizes its properties by preventing HONO elimination. When the aging temperature is substantially higher than 55 °C, the nature of the degradation mechanism changes. It is suspected that the degradation products of NO x , water, and HNO 3 serve as catalysts to auto-catalyze (kinetics beyond the 1st order) and further degrade NP. The effect of headspace volume on this auto-catalytic process will be discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Enhancement of reactive oxygen species production by ultra-short electron pulses

The development of laser-driven accelerators-on-chip has provided an opportunity to miniaturize devices for electron radiotherapy delivery. Laser-driven accelerators produce highly time-compressed electron pulses, on the 100 fs to 1 ps scale. This delivers electrons at high peak power yet low average beam current compared with conventional delivery devices, which generate pulses of approximately 3 µs. The biophysical effects of this time structure, however, are unclear. Here, we use a Monte Carlo simulation approach to explore the effects of the electron beam time structure on the production of reactive oxygen species (ROS) in water. Our results show a power law increase in the generation of hydroxyl ions per deposited electron with decreasing pulse length over the pulse length range of 10 µs to 100 fs. Similar trends were observed for hydrogen peroxide, superoxide, hydroperoxyl, hydronium and solvated electrons. In practical terms, this indicates a fourfold increase in the efficiency of free radical production for sub-picosecond pulses, relative to that of conventional microsecond pulses, for the same number of deposited electrons.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1981

Thermodynamic and transport properties of air/water mixtures

Subroutine WETAIR calculates properties at nearly 1,500 K and 4,500 atmospheres. Necessary inputs are assigned values of combinations of density, pressure, temperature, and entropy. Interpolation of property tables obtains dry air and water (steam) properties, and simple mixing laws calculate properties of air/water mixture. WETAIR is used to test gas turbine engines and components operating in relatively humid air. Program is written in SFTRAN and FORTRAN.

Fessler, T. E.↗
NASA NTRS1982

Numerical study of terrain-induced mesoscale motions in a mixed layer

Numerical integrations using a potential enstrophy-conserving scheme are presented for the flow within a mixed layer over hilly terrain using the hydrostatic shallow-water equations with a quadratic drag law. The mesoscale area treated is 150 km on a side; cyclic lateral boundary conditions are used. It is found that for the idealized conditions treated (no surface heating, no entrainment and no pressure adjustments aloft), the topography quickly induces a steady state flow pattern by means of surface friction. Unsteadiness does not occur unless a surface-friction Reynolds number is greater than approximately 100. Effects of varying the Rossby number, Froude number and terrain-height parameter are examined.

Han, Y.-J.↗
DOE OSTI2021

Quantifying the anomalous water absorption behavior of cement mortar in view of its physical sensitivity to water

The one-dimensional water absorption into cement-based materials, possibly the simplest case of unsaturated water flow playing a fundamental role in predicting mass transport and durability, is still far from being completely understood due to several puzzling anomalies. Considering the water sensitivity of C-S-H gels (swell upon wetting and contract upon drying), a modified Richards equation (MRE) is proposed to quantify the anomalous water absorption into cement-based materials of changing porosity. Consistent experimental tests on a cement mortar and calculations indicate that the MRE with time-decaying water permeability can quantitatively capture the long-term absorption with two linear stages and a nonlinear transition stage between them. The water sensitivity is validated to be responsible for the anomalous deviation of water absorption from the classical square root of time law. It also partially contributes to the anomalous dependence of sorptivity on the temperature-dependent surface tension and viscosity of water and many organic liquids.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Water under hydrophobic confinement: entropy and diffusion

The properties of liquid water are known to change drastically in confined geometries. A most interesting and intriguing phenomenon is that the diffusion of water is found to be strongly enhanced by the proximity of a hydrophobic confining wall relative to the bulk diffusion. We report a molecular dynamics simulation using a classical water model investigating the water diffusion near a non-interacting smooth confining wall, which is assumed to imitate a hydrophobic surface, revealing a pronounced diffusion enhancement within several water layers adjacent to the wall. We present evidence that the observed diffusion enhancement can be accounted for, with a quantitative accuracy, using the universal scaling law for liquid diffusion that relates the diffusion rate to the excess entropy. These results show that the scaling law, which has so far only been used for the description of the diffusion in simple liquids, can successfully describe the diffusion in water. It is shown that the law can be used for the analysis of water dynamics under nanoscale hydrophobic confinement, which is currently a subject of intense research activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2006

Slow Crack Growth and Fracture Toughness of Sapphire for the International Space Station Fluids and Combustion Facility

The fracture toughness, inert flexural strength, and slow crack growth parameters of the r- and a-planes of sapphire grown by the Heat Exchange Method were measured to qualify sapphire for structural use in the International Space Station. The fracture toughness in dry nitrogen, K(sub Ipb), was 2.31 +/- 0.12 MPa(square root of)m and 2.47 +/- 0.15 MPa(squre root of)m for the a- and r-planes, respectively. Fracture toughness measured in water via the operational procedure in ASTM C1421 was significantly lower, K(sub Ivb) = 1.95+/- 0.03 MPa(square root of)m, 1.94 +/- 0.07 and 1.77 +/- 0.13 MPa(square root of)m for the a- , m- and r-planes, respectively. The mean inert flexural strength in dry nitrogen was 1085 +/- 127 MPa for the r-plane and 1255 +/- 547 MPa for the a-plane. The power law slow crack growth exponent for testing in water was n = 21 +/- 4 for the r-plane and n (greater than or equal to) 31 for the a-plane. The power law slow crack growth coefficient was A = 2.81 x 10(exp -14) m/s x (MPa(squre root of)m)/n for the r-plane and A (approx. equals)2.06 x 10(exp -15) m/s x (MPa(square root of)m)/n for the a-plane. The r- and a-planes of sapphire are relatively susceptible to stress corrosion induced slow crack growth in water. However, failure occurs by competing modes of slow crack growth at long failure times and twinning for short failure time and inert environments. Slow crack growth testing needs to be performed at low failure stress levels and long failure times so that twinning does not affect the results. Some difficulty was encountered in measuring the slow crack growth parameters for the a-plane due to a short finish (i.e., insufficient material removal for elimination of the damage generated in the early grinding stages). A consistent preparation method that increases the Weibull modulus of sapphire test specimens and components is needed. This would impart higher component reliability, even if higher Weibull modulus is gained at the sacrifice of absolute strength of the component. The current specification frequently used for the preparation of sapphire test specimens and components (e.g., a "60/40" scratch-dig finish) is inadequate to avoid a short finish.

Salem, Jonathan A.↗
DOE OSTI2020

Dissolution of Fluoride Salts in Hanford Tank Waste

The Direct Feed High-Level Waste (DFHLW) strategy seeks to bypass the Hanford Waste Treatment and Immobilization Plant Pretreatment Facility while retaining some processing functions to maximize waste feed loading and minimize high-level waste (HLW) waste volume. The DFHLW flowsheet needs leaching, washing, and solids concentration operations either in new or existing tanks. The effectiveness and efficiency of sludge washing has a substantial impact on DST space, mission duration, and the evaporation and low-activity waste (LAW) treatment operations required by these large wash-water additions. One target species requiring washing is fluoride. The HLW glass composition limits for fluorine drive operations to dissolve fluoride-bearing salts into the LAW fraction and thereby maximize waste loading in HLW glass. The fluoride in many high-level wastes at Hanford is predominantly in the form of fluoride-salt precipitates: villiaumite (NaF), kogarkoite (Na 3 FSO 4 ), and natrophosphate (Na 7 F(PO 4 ) 2 ·19H 2 O). Fluoride produces melter off-gas that creates corrosion risk in the off-gas system piping, while the sulfate and phosphate in the fluoride double salts kogarkoite and natrophosphate can be detrimental to glass waste loading. Fluoride salts are sparingly soluble, with solubilities ranging from approximately 40 to 130 kg per kL of pure water, and the dissolution kinetics of the three fluoride salts are not well known. Unexpected delays in a tank dissolution process could be encountered as a result of the lack of information about dissolution rates. In addition, if the double salts show transient non-stoichiometric dissolution of fluoride versus phosphate or sulfate, unexpectedly high concentrations of one of these other constituents could be produced. Washington River Protection Solutions authorized Pacific Northwest National Laboratory to collect the available data for fluoride salt dissolution rate, provide a scoping estimate of dissolution time if possible, and identify gaps in the understanding and predictive capability for estimating dissolution time. Open literature and Hanford reports were reviewed to document, understand, and (where possible) evaluate limitations on fluoride salt equilibria and dissolution kinetics, including both mass transport and surface reaction rate. Scoping estimates of dissolution time were made for mass-transfer-controlled dissolution of spherical particles of fluoride salts suspended in liquid. This is not the only potential governing mechanism; dissolution could be substantially slower if the surface reaction rate (the rate of release of ions from the surface) is the controlling mechanism. When the minimum amount of water for complete dissolution is used and the slip velocity between the liquid and suspended particles is less than or equal to the terminal settling velocity, the estimated mass-transfer rates allow 0.1 mm particles of fluoride salt to dissolve in minutes at 25 °C in water containing no other dissolved salts. Much larger solids, such as the 6-mm chunks that have been seen in heels, could take a few hours to more than a week to dissolve. The actual dissolution times will depend strongly on the actual slip velocity, the extent of particle suspension, constraint by surface reaction rates, the ratio of solvent to solid, and the presence of common ions that shift the solubility equilibria to restrict dissolution of fluoride salts.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1993

Flow of ices in the Ammonia-Water System

We have fabricated in the laboratory and subsequently deformed crystalline hydrates and partial melts of the water-rich end of the NH3-H2O system, with the aim of improving our understanding of physical processes occurring in icy moons of the outer solar system. Deformation experiments were carried out at constant strain rate. The range of experimental variables are given. Phase relationships in the NH3-H2O system indicate that water ice and ammonia dihydrate, NH3-2H2O, are the stable phases under our experiment conditions. X-ray diffraction of our samples usually revealed these as the dominant phases, but we have also observed an amorphous phase (in unpressurized samples only) and occasionally significant ammonia monohydrate, NH3-H2O. The onset of partial melting at the peritectic temperature at about 176 K appeared as a sharp transition in strength observed in samples of x(sub NH3) = 0.05 and 0.01, the effect of melt was less pronounced. For any given water ice + dihydrate alloy in the subsolidus region, we observed one rheological law over the entire temperature range from 175 K to about 140 K. Below 140 K, a shear instability similar to that occurring in pure water ice under the same conditions limited our ability to measure ductile flow. The rheological laws for the several alloys vary systematically from that of pure ice to that of dihydrate. Pure dihydrate is about 4 orders of magnitude less viscous than water ice just below the peritectic temperature, but because of a very pronounced temperature dependence in dihydrate (100 kJ/mol versus 43 kJ/mol for water ice) the viscosity of dihydrate equals or exceeds that of water ice at T less than 140 K. The large variation in viscosity of dihydrate with relatively small changes in temperature may be helpful in explaining the rich variety of tectonic and volcanic features seen on the surfaces of icy moons in the outer solar system.

Durham, W. B.↗