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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

On the reality of the Venus winds

The article presents a rebuttal of Young's (1975) view that the 140 m/sec horizontal wind at 45 km reported by Venera 8 is anomalous or spurious. Some errors are discussed and the largest contribution is attributed to descent probe measurements designed to find the true probe descent rate. Young's suggestion of error in in situ measurement of winds due to selection of a reference speed and to unrecognized oscillator drift is scrutinized. Evidence is seen for a wide band of variable high-grade retrograde horizontal winds girdling Venus at the equator. Mariner 10 evidence (UV photographs) is taken into account. The band of winds at 45 km is seen to extend well beyond the top of the visible cloud, and an upper turbulent region is attributed to vertical convection currents carried along by high-speed horizontal winds.

Ainsworth, J. E.↗
NASA NTRS1994

The validation by measurement theory of proposed object-oriented software metrics

Moving software development into the engineering arena requires controllability, and to control a process, it must be measurable. Measuring the process does no good if the product is not also measured, i.e., being the best at producing an inferior product does not define a quality process. Also, not every number extracted from software development is a valid measurement. A valid measurement only results when we are able to verify that the number is representative of the attribute that we wish to measure. Many proposed software metrics are used by practitioners without these metrics ever having been validated, leading to costly but often useless calculations. Several researchers have bemoaned the lack of scientific precision in much of the published software measurement work and have called for validation of software metrics by measurement theory. This dissertation applies measurement theory to validate fifty proposed object-oriented software metrics (Li and Henry, 1993; Chidamber and Kemerrer, 1994; Lorenz and Kidd, 1994).

Neal, Ralph D.↗
NASA NTRS1995

The Validation by Measurement Theory of Proposed Object-Oriented Software Metrics

Moving software development into the engineering arena requires controllability, and to control a process, it must be measurable. Measuring the process does no good if the product is not also measured, i.e., being the best at producing an inferior product does not define a quality process. Also, not every number extracted from software development is a valid measurement. A valid measurement only results when we are able to verify that the number is representative of the attribute that we wish to measure. Many proposed software metrics are used by practitioners without these metrics ever having been validated, leading to costly but often useless calculations. Several researchers have bemoaned the lack of scientific precision in much of the published software measurement work and have called for validation of software metrics by measurement theory. This dissertation applies measurement theory to validate fifty proposed object-oriented software metrics.

Neal, Ralph D.↗
NASA NTRS1996

The Validation by Measurement Theory of Proposed Object-Oriented Software Metrics

Moving software development into the engineering arena requires controllability, and to control a process, it must be measurable. Measuring the process does no good if the product is not also measured, i.e., being the best at producing an inferior product does not define a quality process. Also, not every number extracted from software development is a valid measurement. A valid measurement only results when we are able to verify that the number is representative of the attribute that we wish to measure. Many proposed software metrics are used by practitioners without these metrics ever having been validated, leading to costly but often useless calculations. Several researchers have bemoaned the lack of scientific precision in much of the published software measurement work and have called for validation of software metrics by measurement theory. This dissertation applies measurement theory to validate fifty proposed object-oriented software metrics.

Neal, Ralph D.↗
DOE OSTI2021

Non-destructive quantification of anaerobic gut fungi and methanogens in co-culture reveals increased fungal growth rate and changes in metabolic flux relative to mono-culture

Abstract Background Quantification of individual species in microbial co-cultures and consortia is critical to understanding and designing communities with prescribed functions. However, it is difficult to physically separate species or measure species-specific attributes in most multi-species systems. Anaerobic gut fungi (AGF) (Neocallimastigomycetes) are native to the rumen of large herbivores, where they exist as minority members among a wealth of prokaryotes. AGF have significant biotechnological potential owing to their diverse repertoire of potent lignocellulose-degrading carbohydrate-active enzymes (CAZymes), which indirectly bolsters activity of other rumen microbes through metabolic exchange. While decades of literature suggest that polysaccharide degradation and AGF growth are accelerated in co-culture with prokaryotes, particularly methanogens, methods have not been available to measure concentrations of individual species in co-culture. New methods to disentangle the contributions of AGF and rumen prokaryotes are sorely needed to calculate AGF growth rates and metabolic fluxes to prove this hypothesis and understand its causality for predictable co-culture design. Results We present a simple, microplate-based method to measure AGF and methanogen concentrations in co-culture based on fluorescence and absorbance spectroscopies. Using samples of < 2% of the co-culture volume, we demonstrate significant increases in AGF growth rate and xylan and glucose degradation rates in co-culture with methanogens relative to mono-culture. Further, we calculate significant differences in AGF metabolic fluxes in co-culture relative to mono-culture, namely increased flux through the energy-generating hydrogenosome organelle. While calculated fluxes highlight uncertainties in AGF primary metabolism that preclude definitive explanations for this shift, our method will enable steady-state fluxomic experiments to probe AGF metabolism in greater detail. Conclusions The method we present to measure AGF and methanogen concentrations enables direct growth measurements and calculation of metabolic fluxes in co-culture. These metrics are critical to develop a quantitative understanding of interwoven rumen metabolism, as well as the impact of co-culture on polysaccharide degradation and metabolite production. The framework presented here can inspire new methods to probe systems beyond AGF and methanogens. Simple modifications to the method will likely extend its utility to co-cultures with more than two organisms or those grown on solid substrates to facilitate the design and deployment of microbial communities for bioproduction and beyond.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1991

Infrared spectroscopic measurements of the vertical column abundance of sulfur hexafluoride, SF6, from the ground

The solar observations involved in the present monitoring evaluation were made at two facilities, using Fourier-transform spectrometers achieving spectral resolutions of 0.005/cm and signal-to-rms noise ratios for individual scans from near 500 to near 1000. The monthly mean total vertical-column abundances of SF6 above both facilities are reported for time intervals from June 1986 to June 1990 and from March 1981 to June 1990. It is found that the vertical-column abundances increased at mean rates of 6.9 +/- 2.8 pct above one station and 6.6 +/- 7.2 pct above the other. Since all the results were retrieved using the same spectroscopic parameters and similar nonlinear least-squares curve-fitting algorithms validated through intercomparison exercises, the large error reported for the second station is attributed to a larger measurement uncertainty due to stronger H2O and C2O interferences, and a greater variability during each month.

Zander, R.↗
DOE OSTI2025

Geographic source attribution of honey by strontium isotope analyses: Latvia and India measurements compared to model predictions in a feasibility study

Strontium isotope ratios ( 87 Sr/ 86 Sr) can be used to determine the geographic origin of agricultural products. Here, in this study, we measured the 87 Sr/ 86 Sr of honey samples from Richland, WA, USA, Latvia, and India, and compared the results to published 87 Sr/ 86 Sr from surrounding areas and values predicted based upon a random forest isoscape model (Bataille et al., 2020). While the 87 Sr/ 86 Sr of the honey samples compared well with previously published data, the model did not accurately predict the 87 Sr/ 86 Sr of the honey samples, demonstrating that further refinement of the model would be beneficial. Because Sr cycling in terrestrial ecosystems is complex, the 87 Sr/ 86 Sr of honey is likely to reflect several sources (e.g., nectar, surface water, dust) and may change over time. In order to accurately predict the 87 Sr/ 86 Sr of honey, models must consider local geology, ecology, and bee behavior. Additional research examining how Sr is incorporated into honey is needed to inform models.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Benchmark study of the DTU OWC chamber with both two-way and one-way absorption

This paper reports on a benchmark study based on small-scale (1:50) measurements of a single, oscillating water column chamber mounted sideways in a long flume. The geometry of the OWC chamber is extracted from a barge-like, attenuator-type floating concept “KNSwing” with 40 chambers targeted for deployment in the Danish part of the North Sea. In addition to traditional two-way energy extraction we also consider one-way energy extraction with passive venting and compare chamber response, pressures and total absorbed energy between the two methods. A blind study was established for the numerical modeling, with participants applying several implementations of weakly nonlinear potential flow theory and commercial Navier–Stokes solvers (CFD). Both compressible and incompressible models were used for the air phase. Potential flow calculations predict more energy absorption near the chamber resonance for one-way absorption than for two-way absorption, but the opposite is found from the experimental measurements. This outcome is mainly attributed to energy losses in the experimental passive valve system, but this conclusion must be confirmed by better experimental measurements. Modeling the one-way valve in CFD proved to be very challenging and only one team was able to provide results which were generally closer to the experiments. The study illustrates the challenges associated with both numerical and experimental analysis of OWC chambers. Air compressibility effects were not found to be important at this scale, even with the large volume of additional air used for the one-way case.

16 TIDAL AND WAVE POWER↗
DOE OSTI2024

Flow reversal benchmark of a one-sided heated narrow rectangular channel with CATHARE and RELAP5

Flow reversal in narrow coolant channels can be a crucial phenomenon for the safety of research reactors with a downward nominal flow direction. During a loss of forced flow accident, the downward flow stagnates briefly before transitioning into an upward natural circulation flow. The fuel may be damaged if dryout occurs and threshold fuel and/or cladding temperatures are exceeded. A comprehensive study is provided for flow reversal in narrow rectangular channels by examining experimental data and conducting software model analyses. The literature on flow reversal was reviewed, and selected experimental datasets were used to benchmark against CATHARE and RELAP5 models and also compare the code calculations with each other. The experimental data comes from flow reversal tests conducted with a narrow rectangular channel with one-sided heating. The results were compared with experimental data for successful flow reversal tests and predicted dryout power for dryout conditions. Also, the study examined the effects of the pump coastdown period, inlet liquid temperature, system pressure, and localized pressure drops. The experimental results showed that shorter coastdown periods, reduced pressure drops, and lower coolant inlet temperatures increased the dryout power. However, the system pressure did not noticeably affect the results. The simulation results showed that both CATHARE and RELAP5 agreed with experimental data, capturing the trends of the experimental results. Slight differences between each code calculation, as well as the predicted and measured dryout powers, were attributed to experimental uncertainties and the modeling of physical phenomena such as wall nucleation, interfacial heat transfer, drag coefficients, and critical heat flux. Overall, this study provides an understanding of flow reversal and the prediction capabilities of thermal-hydraulics software models. In conclusion, a future study of the flow reversal benchmark of a narrow rectangular channel with two-sided heating may provide additional valuable insights.

CATHARE↗
DOE OSTI2025

Oxygen vacancy-induced ferroelectric effect in (111) strontium titanate single crystals controls photoelectrochemical water oxidation

Ferroelectric materials, such as tetragonal BaTiO 3 , have a permanent electric polarization that can be controlled with an external electric field, however, a ferroelectric polarization in cubic SrTiO 3 is forbidden by the higher symmetry of the lattice. Here we demonstrate that hydrogen annealed SrTiO 3−x single crystals can be polarized electrically, and that the polarization controls the activity for photoelectrochemical water oxidation, a pathway to solar hydrogen fuel. Specifically, it is observed that the anodic water oxidation photocurrent increases from 0.99 to 2.22 mA cm −2 at 1.23 V RHE (60 mW cm −2 , UV illumination) or decreases to 0.50 mA cm −2 after electric polarization of hydrogen-annealed (111) SrTiO 3−x single crystals in forward or reverse direction. The polarization also modifies the surface photovoltage signal of the material and its flat band potential, based on Mott–Schottky measurements. These observations are attributed to the formation of an electric dipole at the (111) SrTiO 3−x surface, which alters the potential drop across the depletion layer at the solid–liquid junction, and with it the electron transfer barrier. Density functional theory calculations confirm that an electric dipole can result from the movement of oxygen vacancies between the surface or sub-surface layers of SrTiO 3−x . The filling of these surface oxygen vacancies is the probable cause for the observed disappearance of the electric polarization after 24 h storage in air and 48 h in argon. Overall, this work establishes a new surface-based ferroelectric effect in SrTiO 3−x and its use for solar energy conversion during photoelectrochemical water oxidation. Because oxygen vacancy defects are common, similar electric polarization effects are to be expected in other metal oxides.

Assavachin, Samutr [University of California, Davi↗
DOE OSTI2026

Resilience Metrics Framework for Solar Photovoltaics

This presentation was given at the Photovoltaic Specialist Conference (PVSC) 54 in New Orleans, Louisiana. Photovoltaic (PV) systems are routinely exposed to extreme weather, including wind and hail storms. Historically, most systems have proven to be resilient to such events, but some storms have damaged PV systems, leading to physical and financial loss. Storm hardening measures and specific system attributes can reduce this risk. This work introduces a set of resilience metrics and a framework for quantifying, comparing, and predicting PV system resilience. The framework is divided into two parts: 1) predictive, attribute metrics based on site and component characteristics, and 2) impact metrics that assess post-storm performance. Metrics are weighted and aggregated, producing hazard-specific resilience scores. We derive damage functions from storm-impacted PV systems, establishing a baseline against which post-storm performance can be compared. This damage was widely variable across hail and wind intensities, and field hail damage was less than predicted by laboratory tests, suggesting that system features - in addition to storm conditions - influence damage likelihood. Finally, the metrics framework is demonstrated using three case studies of storm damaged PV systems. Although additional data are needed to create attribute specific damage functions and establish metric weights, this study presents a methodology for evaluating PV resilience and contributes new damage functions to the literature.

14 SOLAR ENERGY↗
NASA NTRS1978

Passive microwave studies of snowpack properties

Microwave brightness temperatures were measured for the snowpacks at Walden and Steamboat Springs, Colorado during 1976 and 1977 aircraft experiments. Variations in measured brightness temperatures are attributed to snow grain and crystal sizes, liquid water content, and snowpack temperature. Results demonstrate that shorter wavelength radiation is scattered more strongly than longer wavelength radiation.

Hall, D. K.↗
NASA NTRS1980

Earth survey applications division: Research leading to the effective use of space technology in applications relating to the Earth's surface and interior

Accomplishments and future plans are described for the following areas: (1) geology - geobotanical indicators and geopotential data; (2) modeling magnetic fields; (3) modeling the structure, composition, and evolution of the Earth's crust; (4) global and regional motions of the Earth's crust and earthquake occurrence; (5) modeling geopotential from satellite tracking data; (6) modeling the Earth's gravity field; (7) global Earth dynamics; (8) sea surface topography, ocean dynamics; and geophysical interpretation; (9) land cover and land use; (10) physical and remote sensing attributes important in detecting, measuring, and monitoring agricultural crops; (11) prelaunch studies using LANDSAT D; (12) the multispectral linear array; (13) the aircraft linear array pushbroom radiometer; and (14) the spaceborne laser ranging system.

Carpenter, L.↗
NASA NTRS1982

Potential of multisensor data and strategies for data acquisition and analysis

Registration and simultaneous analysis of multisensor images is useful because the multiple data sets can be compressed through image processing techniques to facilitate interpretation. This also allows integration of other spatial data sets. Techniques being developed to analyze multisensor images involve comparison of image data with a library of attributes based on physical properties measured by each sensor. This results in the ability to characterize geologic units based on their similarity to the library attributes, as well as discriminate among them. Several studies can provide information on ways to optimize multisensor remote sensing. Continued analyses of the Death Valley and San Rafael Swell data sets can provide insight into tradeoffs in spectral and spatial resolutions of the various sensors used to obtain the coregistered data sets. These include imagery from LANDSAT, SEASAT, HCMM, SIR-A, 11-channel VIS-NIR, thermal inertia images, and aircraft L- and X-band radar.

Evans, D.↗
NASA NTRS1984

Determining forest canopy characteristics using airborne laser data

A study is reported in which a profiling laser system flown at relatively low altitudes over a forested area was used to measure various forest canopy attributes, including tree heights. An analysis of the data obtained indicates that canopy closure is most strongly related to the penetration capability of the laser pulse, with the pulses attenuated more quickly in a dense canopy. Laser estimates of the average tree heights differ by less than 1 m from the photogrammetrically acquired values. It is concluded that the laser system is suitable for remotely sensing the vertical forest canopy profile. Elements of this profile are linearly related to crown closure and can be used to assess tree height.

Nelson, R.↗
NASA NTRS1985

Laboratory simulation of meteoritic noble gases. II - Sorption of xenon on carbon: Etching and heating experiments

The release of trapped Xe from amorphous-C phases of meteorites is simulated experimentally by HNO3 etching of carbon-black and pyrolyzed polyvinylidene chloride samples exposed to Xe-127 for 0.5-240 h at 100-1000 C and then degassed for 9 h or more at the same temperatures, as reported by Wacker et al. (1985). The results are presented in tables and graphs and characterized in detail. Samples exposed at 100-200 C are found to lose most of their Xe after etching to a depth of only about 20 pm, while those exposed at 800-1000 C exhibit a second more tightly bound component extending to a depth of 3 nm, indicative of diffusion of Xe during exposure and resembling planetary Xe. The higher noble-gas concentrations measured in meteorites are attributed to rate-controlled Xe uptake over a long period in the solar nebula.

Zadnik, M. G.↗