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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
NASA NTRS1982

Image Analysis for Facility Siting: a Comparison of Lowand High-altitude Image Interpretability for Land Use/land Cover Mapping

For two test sites in Pennsylvania the interpretability of commercially acquired low-altitude and existing high-altitude aerial photography are documented in terms of time, costs, and accuracy for Anderson Level II land use/land cover mapping. Information extracted from the imagery is to be used in the evaluation process for siting energy facilities. Land use/land cover maps were drawn at 1:24,000 scale using commercially flown color infrared photography obtained from the United States Geological Surveys' EROS Data Center. Detailed accuracy assessment of the maps generated by manual image analysis was accomplished employing a stratified unaligned adequate class representation. Both 'area-weighted' and 'by-class' accuracies were documented and field-verified. A discrepancy map was also drawn to illustrate differences in classifications between the two map scales. Results show that the 1:24,000 scale map set was more accurate (99% to 94% area-weighted) than the 1:62,500 scale set, especially when sampled by class (96% to 66%). The 1:24,000 scale maps were also more time-consuming and costly to produce, due mainly to higher image acquisition costs.

Borella, H. M.↗
NASA NTRS1983

Quantitative comparisons of radar image, scatterometer, and surface roughness data from Pisgah Crater, CA

The relationships between radar image brightness and backscatter coefficient, between the backscatter coefficient and surface roughness, and between surface roughness and geology, must be established in order to satisfy criteria for the quantitative use of radar images. Attention is presently given to the merits of calibrated radar images and scatterometers as sources of the backscatter coefficient, theories that yield the coefficient on the basis of known surface roughness (and vice versa), and the geologic interpretation of surface roughness and backscatter signatures. These considerations are discussed in the case of the Pisgah Crater and lava field in the Mojave Desert of California.

Farr, T. G.↗
NASA NTRS1988

Comparison of Shuttle Imaging Radar-B ocean wave image spectra with linear model predictions based on aircraft measurements

During October 1984, coincident Shuttle Imaging Radar-B synthetic aperture radar (SAR) imagery and wave measurements from airborne instrumentation were acquired. The two-dimensional wave spectrum was measured by both a radar ocean-wave spectrometer and a surface-contour radar aboard the aircraft. In this paper, two-dimensional SAR image intensity variance spectra are compared with these independent measures of ocean wave spectra to verify previously proposed models of the relationship between such SAR image spectra and ocean wave spectra. The results illustrate both the functional relationship between SAR image spectra and ocean wave spectra and the limitations imposed on the imaging of short-wavelength, azimuth-traveling waves.

Monaldo, Frank M.↗
NASA NTRS1998

Auroral Boundaries: Comparison Between UV Images, In Situ Precipitation, and Groundbased Optical Observations

The location of poleward and equatorward boundaries are used as diagnostics of substorm phase and energy storage in the magnetosphere. Boundaries are estimated from groundbased observations (all sky imagers, meridian scanning photometers, and magnetometers), from in situ particle observations, and from spacebased global auroral observations. Each observational technique has relative advantages. Based on recent studies, different observing techniques can give differing boundary locations. Understanding any differences in the boundaries from each observing technique is important when using the data as a diagnostic for the magnetosphere. In this study, FUV auroral images from the POLAR Ultraviolet Imager are used to estimate auroral boundaries. These boundaries are then compared with similar boundaries derived from DMSP in situ particle precipitation observations and from groundbased meridian scanning photometers. The goal is to see how well the boundaries from these three dissimilar observations correlate, to estimate dependences on instrumental capabilities, i.e. imager resolution, and to serve as a potential first step to derive an algorithm for finding oval boundaries from groundbased optical data.

Germany, G. A.↗
NASA NTRS1998

Auroral Boundaries: Comparison Between UV Images, In Situ Precipitation, and Groundbased Optical Observations

The location of poleward and equatorward boundaries are used as diagnostics of substorm phase and energy storage in the magnetosphere. Boundaries are estimated from groundbased observations (all sky imagers, meridian scanning photometers, and magnetometers), from in situ particle observations, and from spacebased global auroral observations. Each observational technique has relative advantages. However, recent studies suggest caution when comparing boundaries derived from different methods. in the study, FUV auroral images from the POLAR Ultraviolet Imager are used to estimate auroral boundaries. These boundaries are then compared with similar boundaries derived from DMSP in situ particle precipitation observations and from groundbased meridian scanning photometers. The goal is to see how well the boundaries from these three dissimilar observations correlate, to estimate dependencies on instrumental capabilities, i.e. imager resolution, and to serve as a potential first step to derive an algorithm for finding oval boundaries from groundbased optical data.

Germany, G. A.↗
NASA NTRSDate not supplied

Comparison of Multispectral Imaging and Traditional Fundoscopy in the Detection of Terrestrial Retinal and Optic Nerve Pathologies like those Encountered During and/or Immediately Following Long-Duration Spaceflight

INTRODUCTION: The purpose of this investigation was to evaluate if MultiColor Imaging (MCI) can replace color fundus photography (CFP) as a diagnostic screening tool during spaceflight. MCI significantly reduces crew time (approx. 115 minutes/session, 36 hours/year) by eliminating nominal on-orbit fundoscopy sessions, while also providing the option to capture a larger field of view (55 vs. 35). METHODS: A comprehensive PubMed literature search was conducted using the following key words: multicolor, multispectral, imaging, retina, choroid, optic nerve, optic disc, and papilledema. Publications were filtered based on optic nerve and chorioretinal pathologies matching those seen during or immediately after spaceflight: optic disc edema (ODE), cotton wool spots (CWS), retinal hemorrhage, pigment epithelial detachment (PED), and serous chorioretinopathy (SCR). In a separate effort, 44 multicolor images (30 abnormal) of terrestrial patients were graded and compared to corresponding color fundus images acquired at the Doheny Eye Centers and UCLA. RESULTS: The search identified 340 articles; 9 describing MCI in relevant pathologies, 6 comparing MCI to CFP. MCI is superior in detecting CWS (1 paper), PED (2 papers), retinal hemorrhages (2 papers), and choroidal folds (1 paper), and can better delineate extent or boundaries of subretinal fluid and identify areas of RPE damage in SCR (2 papers). On MCI, ODE was described as a hyperreflective ring with a green shift and indistinct disc margins, with equaldetectability as using CFP (3 papers). Grading at Doheny Eye Institute confirmed these findings. DISCUSSION: MCI can effectively detect all retinal and optic nerve findings detectable by CFP during and immediately post-spaceflight and represents a suitable replacement as an on-orbit diagnostic screening tool. Additionally, by eliminating the nominal on-orbit fundoscopy sessions, dozens of crew hours are spared per year by utilizing MCI.

Jorge Nagel↗
NASA NTRS1999

Polar/Tide Observations of Field Aligned O(+) Flows at 5000 km Altitude over the Auroral Regions in Comparison to UVI Auroral Images

Measurements of thermal O(+) ion parameters from the Thermal Ion Dynamics Experiment (TIDE) on POLAR obtained near 5000 km altitude are compared with auroral images from the Ultra Violet Imager (UVI), for southern perigee passes. Ion parameters, including parallel velocity, density, and flux are combined with simultaneous auroral images to investigate relationships between their properties and the structure and brightness of the auroral forms. Results indicate field aligned upflowing O(+) ions over bright auroral regions and downward flows over dark regions. These and other relationships will be presented for several POLAR passes when both ion measurements and auroral images are observed under favorable conditions for comparison.

Stevenson, Benjamin Adam↗
DOE OSTI2022

Intrinsic Halide Immiscibility in 2D Mixed-Halide Ruddlesden–Popper Perovskites

Halide alloying of 3D and 2D Ruddlesden–Popper lead halide perovskites (RPPs) allows their bandgaps to be fine-tuned for optoelectronic applications. Many studies of mixed-halide RPPs assume that halide mixing yields homogeneous alloys like in 3D lead halide perovskites, with halide segregation only occurring under perturbations like light or heat. Here we carefully investigate the mixed I/Br phases in solution grown microplates of three representative n = 1 and n = 2 RPP phases to reveal heterogeneous halide microscale domains – even in absence of photoinduced phase separation. Such halide immiscibility is revealed by X-ray diffraction and heterogeneity is confirmed by secondary ion mass spectrometry (SIMS) imaging, however, comparison with photoluminescence (PL) imaging results show how PL information alone can falsely imply homogeneous alloy formation in heterogeneous RPPs. Finally, we then demonstrate the use of spectral imaging as an alternative high-throughput tool for accurate halide phase characterization in mixed-halide RPPs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2015

Retinal Image Quality Assessment for Spaceflight-Induced Vision Impairment Study

Long-term exposure to space microgravity poses significant risks for visual impairment. Evidence suggests such vision changes are linked to cephalad fluid shifts, prompting a need to directly quantify microgravity-induced retinal vascular changes. The quality of retinal images used for such vascular remodeling analysis, however, is dependent on imaging methodology. For our exploratory study, we hypothesized that retinal images captured using fluorescein imaging methodologies would be of higher quality in comparison to images captured without fluorescein. A semi-automated image quality assessment was developed using Vessel Generation Analysis (VESGEN) software and MATLAB® image analysis toolboxes. An analysis of ten images found that the fluorescein imaging modality provided a 36% increase in overall image quality (two-tailed p=0.089) in comparison to nonfluorescein imaging techniques.

retina↗
DOE OSTI2023

Complete Performance Comparison Between the Optimized Image Construction Algorithm (U-MBIR) and the Existing Reconstruction Algorithm for Detecting Defects and Damage in Concrete

Reinforced concrete (RC) is a composite material subjected to mechanical, thermal, and chemical loads throughout its service life. Because of these external stressors and the susceptibility of RC structural members to shrinkage and microcracking, the material degrades throughout its life cycle. This deterioration can lead to a decrease in member capacity and, ultimately, poses a threat to the structural integrity. Thus, it is crucial that the damage caused by aging and degradation be monitored and assessed at regular intervals throughout the material’s service life. Since coring of the material is typically not feasible for in-service structural systems, non-destructive evaluation (NDE) methodologies are used to assess remaining structural capacity. NDE methods enable surface and subsurface examination without damaging or degrading the medium. Moreover, RC is a critical component of nuclear power plants; thus, its safety and reliability must be thoroughly examined throughout the life cycle of the structural system. Ultrasonic measurements have been an industry standard for both surface and subsurface inspections. To this end, Oak Ridge National Laboratory (ORNL) has researched and developed advanced image reconstruction algorithms to capture internal damage. The results and discussion presented herein summarize the current state of the ultrasonic model–based iterative reconstruction (U-MBIR) algorithm developed at ORNL. More specifically, this report presents a comparison between reconstruction images produced via a widely employed ultrasonic NDE technique—the synthetic aperture focusing technique (SAFT)—and the ORNL-developed U-MBIR algorithm. These NDE methodologies are demonstrated using ultrasonic data collected from four concrete specimens. Overall, the U-MBIR algorithm eliminates artifacts and noise that are typically present within the SAFT reconstructions, and it shows defects and anomalies more clearly than the SAFT images. In conclusion, this algorithm is suitable for identifying concrete defects, although more improvements and optimization could be done to better define internal defects.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Theoretical Model Images and Spectra for Comparison with HESSI and Microwave Observations of Solar Flares

We have computed bremsstrahlung and gyrosynchrotron images and spectra from a model flare loop. Electrons with a power-law energy distribution are continuously injected at the top of a semi-circular magnetic loop. The Fokker-Planck equation is integrated to obtain the steady-state electron distribution throughout the loop. Coulomb scattering and energy losses and magnetic mirroring are included in the model. The resulting electron distributions are used to compute the radiative emissions. Sample images and spectra are presented. We are developing these models for the interpretation of the High Energy Solar Spectroscopic Imager (HESSI) x-ray/gamma ray data and coordinated microwave observations. The Fokker-Planck and radiation codes are available on the Web at http://hesperia.gsfc.nasa.gov/hessi/modelware.htm This work is supported in part by the NASA Sun-Earth Connection Program.

Fisher, Richard R.↗
NASA NTRS1991

Automated extraction of pressure ridges from SAR images of sea ice - Comparison with surface truth

The authors estimate the characteristics of ridges and leads in sea ice from SAR (synthetic aperture radar) images. Such estimates are based on the hypothesis that bright filamentary features in SAR sea ice images correspond with pressure ridges. A data set collected in the Greenland Sea in 1987 allows this hypothesis to be evaluated for X-band SAR images. A preliminary analysis of data collected from SAR images and ice elevation (from a laser altimeter) is presented. It is found that SAR image brightness and ice elevation are clearly related. However, the correlation, using the data and techniques applied, is not strong.

Vesecky, J. F.↗
NASA NTRS1987

Radio studies of large scale structures of the Sun's corona and transient activity

The use of meter-decimeter wavelength imaging observations for four different kinds of studies of solar coronal activity is discussed. (1) Large scale structure of the upper corona; daily imaging observations permit comparison of radio images with white light images from space and ground observation, generation of synoptic charts similar to white light coronagraph synoptic charts, and comparison of radio brightness enhancements and deficiencies with bright coronal streamers and coronal holes. (2) Relative positions of type III burst sources and coronal streamers as observed by Solwind experiment on the P-78-1 satellite and by the HAO C/P experiment aboard the SMM; infer the paths of type III emitting electrons in dense coronal streamers, and from multifrequency observations derive electron density distributions above active regions near the limb. (3) Non-flare associated type II/type IV bursts associated with coronal streamer disruption events; such type IV sources have a rather slow velocity (approx = to or less than 100 km/s) CMEs. (4) Meter-decimeter microbursts; these are short duration (2-10 sec) weak-type III-like bursts, produced at the fundamental plasma frequency by plasma radiation processes which have important differences from the standard mechanisms used to explain the strong type III bursts.

Kundu, Mukul R.↗
NASA NTRS1994

Comparison of the lossy image data compressions for the MESUR Pathfinder and for the Huygens Titan Probe

The commercial JPEG standard complies well with the specific requirements of exploratory space missions. Therefore, JPEG has been chosen to be the baseline for a series of spaceborne image data compressions (e.g. MARS94-HRSC, -WAOSS, HUYGENS-DISR, MESUR-IMP). One S/W-implementation (IMP) and one H/W-implementation (DISR) of image data compression are presented. Details of the modifications applied to standard JPEG are outlined. Finally, a performance comparison of the two implementations is given.

Rueffer, P.↗
NASA NTRSDate not supplied

Comparisons Between NO PLIF Imaging and CFD Simulations of Mixing Flowfields for High-Speed Fuel Injectors

The current work compares experimentally and computationally obtained nitric oxide (NO) planar laser-induced fluorescence (PLIF) images of the mixing flowfields for three types of high-speed fuel injectors: a strut, a ramp, and a rectangular flushwall. These injection devices, which exhibited promising mixing performance at lower flight Mach numbers, are currently being studied as a part of the Enhanced Injection and Mixing Project (EIMP) at the NASA Langley Research Center. The EIMP aims to investigate scramjet fuel injection and mixing physics, and improve the understanding of underlying physical processes relevant to flight Mach numbers greater than eight. In the experiments conducted in the NASA Langley Arc-Heated Scramjet Test Facility (AHSTF), the injectors are placed downstream of a Mach 6 facility nozzle, which simulates the high Mach number air flow at the entrance of a scramjet combustor. Helium is used as an inert substitute for hydrogen fuel. Both schlieren and PLIF techniques are applied to obtain mixing flowfield flow visualizations. The experimental PLIF is obtained by using a UV laser sheet to interrogate a plane of the flow by exciting fluorescence from the NO molecules that are present in the AHSTF air. Consequently, the absence of signal in the resulting PLIF images is an indication of pure helium (fuel). The computational PLIF is obtained by applying a fluorescence model for NO to the results of the Reynolds-averaged simulations (RAS) of the mixing flowfield carried out using the VULCAN-CFD solver. This approach is required because the PLIF signal is a nonlinear function of not only NO concentration, but also pressure, temperature, and the flow velocity. This complexity allows additional flow features to be identified and compared with those obtained from the computational fluid dynamics (CFD) simulations, however, such comparisons are only semiquantitative. Three-dimensional image reconstruction, similar to that used in magnetic resonance imaging, is also used to obtain images in the streamwise and spanwise planes from select cross-stream PLIF plane data. Synthetic schlieren is also computed from the RAS data. Good agreement between the experimental and computational results provides increased confidence in the CFD simulations for investigations of injector performance.

PLIF↗