SEARCH · Engineering Papers

Results for “visible spectrum”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7

All sources NASA NTRS DOE OSTI

DOE OSTI2022

Image Analysis for Rapid Assessment and Quality-Based Sorting of Corn Stover

Imaging in the visible spectrum is a low-cost tool that can be readily deployed for in-field or over-belt monitoring of biomass quality for bio-refining operations. Rapid image analysis coupled with innovative preprocessing may reduce the impacts of feedstock variability through identification of contaminants or other material attributes to guide selective sorting and quality management. Image analysis was employed to evaluate the quality of corn stover in red-green-blue (RGB) chromatic space. This study used controlled, bench-scale imaging as a proof-of-concept for rapid quality assessment of corn stover based on variations in material attributes, including chemical and physical attributes, that relate to biological degradation and soil contamination. Additionally, logistic regression-based classification algorithms were used to develop a method for biomass screening as a function of biological degradation or soil contamination. This study demonstrated the use of image analysis to extract features from RGB color space to investigate variations in critical material attributes from chemical composition of corn stover. Fourier transform infrared (FT-IR) suggested a correlation between red band intensity and biological degradation, while detailed surface texture analysis was found to distinguish among variations in ash. These insights offer promise for development of a rapid screening tool that could be deployed by farmers for in-field assessment of biomass quality or biorefinery operators for in-line sorting and process optimization.

09 BIOMASS FUELS↗

DOE OSTI2024

The Preclinical Validation of 405 nm Light Parasiticidal Efficacy on Leishmania donovani in Ex Vivo Platelets in a Rag2 -/- Mouse Model

Violet–blue light of 405 nm in the visible spectrum at a dose of 270 J/cm 2 alone has been shown to be an effective microbicidal tool for inactivating several bacteria, HIV-1, and Trypanosoma cruzi in ex vivo plasma and platelets. Unlike chemical- and ultraviolet (UV)-based pathogen inactivation methods for plasma and platelet safety, 405 nm light is shown to be less toxic to host cells at light doses that are microbicidal. In this report, we evaluated the parasiticidal activity of a 405 nm light treatment on platelets spiked with the Leishmania donovani parasite. Following the light treatment, parasite viability was observed to be near zero in both low- and high-titer-spiked platelets relative to controls. Furthermore, to test the residual infectivity after inactivation in vivo, the light-treated low-titer L. donovani-spiked platelets were evaluated in an immunodeficient Rag2 -/- mouse model and monitored for 9 weeks. The parasiticidal efficacy of 405 nm light was evident from the lack of a presence of parasites in the mice spleens. Parasiticidal activity was confirmed to be mediated through 405 nm light-induced reactive oxygen species (ROS), as quantitatively measured by a 2',7'-Dichlorodihydrofluorescein diacetate (H 2 DCFDA)-based assay. Overall, these results confirm the complete inactivation of L. donovani spiked in ex vivo platelets by 405 nm light treatment and exemplify the utility of the Rag2 -/- mouse infection model for the preclinical validation of the parasiticidal efficacy of 405 nm light and this light-based technology as a potential PRT for ex vivo platelets.

405 nm light↗

DOE OSTI2023

Optimizing cloud motion estimation on the edge with phase correlation and optical flow

Abstract. Phase correlation (PC) is a well-known method for estimating cloud motion vectors (CMVs) from infrared and visible spectrum images. Commonly, phase shift is computed in the small blocks of the images using the fast Fourier transform. In this study, we investigate the performance and the stability of the blockwise PC method by changing the block size, the frame interval, and combinations of red, green, and blue (RGB) channels from the total sky imager (TSI) at the United States Atmospheric Radiation Measurement user facility's Southern Great Plains site. We find that shorter frame intervals, followed by larger block sizes, are responsible for stable estimates of the CMV, as suggested by the higher autocorrelations. The choice of RGB channels has a limited effect on the quality of CMVs, and the red and the grayscale images are marginally more reliable than the other combinations during rapidly evolving low-level clouds. The stability of CMVs was tested at different image resolutions with an implementation of the optimized algorithm on the Sage cyberinfrastructure test bed. We find that doubling the frame rate outperforms quadrupling the image resolution in achieving CMV stability. The correlations of CMVs with the wind data are significant in the range of 0.38–0.59 with a 95 % confidence interval, despite the uncertainties and limitations of both datasets. A comparison of the PC method with constructed data and the optical flow method suggests that the post-processing of the vector field has a significant effect on the quality of the CMV. The raindrop-contaminated images can be identified by the rotation of the TSI mirror in the motion field. The results of this study are critical to optimizing algorithms for edge-computing sensor systems.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1969

Photodetachment of NO sub 2.

Photodetachment of electrons from nitrogen dioxide ions by light in violet portion of visible spectrum, noting wavelength dependence

Warneck, P.↗

NASA NTRS1970

Mass motion in the solar chromosphere

Solar chromosphere mass motion, studying macroturbulence influences on visible spectrum lines high resolution profiles from rocket spectrograms

Jones, R. A.↗

NASA NTRS1971

NOAA's hydrology studies under the Earth Resources Survey Program

Results are presented of investigations of soil moisture, snow cover, and lake temperatures carried out with the support of the Earth Resources Survey Program. Objectives of these studies were: (1) Obtain more data with a multifrequency microwave system so that the range of soil moisture amounts and types can be extended. (2) Establish instrument and data specifications for microwave sensing of soil moisture from satellites and aircraft. (3) Refine the procedures for mapping snow cover that have been developed using satellite and aircraft remote sensor data in the visible spectrum. (4) Evaluation of satellite and aircraft infrared observations for determining their information content with respect to snow cover, ice cover, and water temperature over large lakes.

Mcclain, E. P.↗

NASA NTRS1971

Opacity of tungsten-seeded hydrogen to 2500 K and 115 atmospheres.

Experimental investigation and measurement of the radiant heat attenuation of an aerosol which may serve as a gas core nuclear-rocket propellant. The experiment uses a tungsten-hydrogen aerosol heated to temperatures as high as 2500 K under pressures up to 115 atmospheres. The hydrogen aerosol is produced by dispersion of submicron-sized particles of tungsten in hydrogen gas. A narrow beam of broad spectrum (visible and ultraviolet) light is passed through it with the attenuation being measured as a function of wavelength. Other aerosol characteristics examined include the nature and extent of chemical reactions between the seed material and the hydrogen and the degree of dispersion of the seed material obtained before and after heating. Chemical equilibrium calculations and vapor pressure data for the refractory metals indicate that tungsten is a prime candidate for the seed material in the gas core nuclear rocket.

Williams, J. R.↗

NASA NTRS1971

X-ray spectroscopy of solar active regions and flares.

Review of some recent contributions of X-ray spectroscopy to knowledge about solar active regions and flares. As an example of the importance of X-ray spectroscopy, it is pointed out that, while there are no emission lines from highly ionized silicon in the visible spectrum, the XUV spectrum has emission lines from SiIX through SiXIV. Jordan's (1969) calculations of ionization equilibria for silicon and iron are illustrated by diagrams and discussed. The observation of SiXIV gives evidence for regions having electron temperatures from 5 to 20 million deg. The ability to record the corona against the disk of the sun has enabled Van Speybroeck et al. (1970) to identify many bright diffuse X-ray emitting regions with remnants of old active regions of the type giving rise to unipolar magnetic regions. The physical characteristics of the hot coronal plasma associated with chromospheric flares are outlined on the basis of current observations.

Neupert, W. M.↗

NASA NTRS1972

Reflecting ablating heat shields for planetary entry.

Heat shielding for planetary entry probes of future Jovian and Venusian missions will encounter heating levels well beyond those previously experienced. These entries are typically dominated by radiative heating from the shock layer. This paper demonstrates the potential of reflecting this incident radiation diffusely from an ablating material. This technique contrasts with the absorption experienced by char-forming or graphitic ablators. Two dielectric materials, Teflon (polytetra-fluoroethylene) and boron nitride, are examined for their ablative performance, including reflection, in a combined convective- and radiative-heating environment. For Teflon, at the conditions obtained, superimposition of radiative heating upon a convective stream causes no additional increase in surface recession over the convective only results. For boron nitride, an excellent room-temperature reflector in the visible spectrum, a decrease in reflectivity from 90 to 55 percent is experienced when the surface undergoes sublimation at high temperatures. The process of reflection in each of these materials is described in terms of backscattering from crystals. The significance of a sizable reflection as a mode of energy accommodation is demonstrated for Venusian entries as a potential reduction in mass loss due to ablation.

Peterson, D. L.↗

NASA NTRS1972

Changes of multispectral soil patterns with increasing crop canopy

Multispectral data and automatic data processing were used to map surface soil patterns and to follow the changes in multispectral radiation from a field of maize (Zea mays L.) during a period from seeding to maturity. Panchromatic aerial photography was obtained in early May 1970 and multispectral scanner missions were flown on May 6, June 30, August 11 and September 5, 1970 to obtain energy measurements in 13 wavelength bands. The orange portion of the visible spectrum was used in analyzing the May and June data to cluster relative radiance of the soils into eight different radiance levels. The reflective infrared spectral band was used in analyzing the August and September data to cluster maize into different spectral categories. The computer-produced soil patterns had a striking similarity to the soil pattern of the aerial photograph. These patterns became less distinct as the maize canopy increased.

Kristof, S. J.↗

NASA NTRS1973

Visible infrared spin-scan radiometer

The visible infrared spin-scal radiometer (VISSR) may be considered as a camera system capable of simultaneously providing both visible and infrared earth and cloud cover pictures every 20 minutes from the geostationary synchronous meteorological satellite (SMS). With a 0.9-kilometer resolution in the visible spectrum and a 9-kilometer resolution in the IR spectrum, the VISSR/SMS SYSTEM makes its possible to study atmospheric dynamics through 24-hour continuous observation of cloud altitudes, patterns, motion, and temperature distributions.

Phenix, J. E.↗

NASA NTRS1973

Stratospheric aerosol layer detection.

The earth's daytime horizon was scanned on several occasions between 1963 and 1968. The limb was observed at six wavelengths in the ultraviolet and visible spectrum with a narrow field of view instrument on the X-15 aircraft. The inversion of such horizon observations to yield atmospheric density and the concentrations of ozone and aerosol extinctions is discussed. The most significant features of the X-15 data are effects attributed to stratospheric aerosols. Observations of both the 20-km aerosol layer and a layer at approximately 50 km are inferred from the data. Both layers apparently possess considerable variability. It is pointed out that the existence of substantial aerosol concentrations above 30 km is an important limitation of the nadir technique of determining ozone concentrations in which the earth's radiance is observed at ultraviolet wavelengths from a satellite.

Cunnold, D. M.↗

NASA NTRS1973

Measuring earth-to-space contrast transmittance from ground stations.

Inherent object and background radiance, beam transmittance through the atmosphere, and sky radiance are all measurable from a ground station. It is shown how, in the visible spectrum, the sky radiance and beam transmittance may be used to compute the path radiance for orbital downward paths of sight. Thus, the components for calculating apparent radiance, apparent contrast, and the contrast transmittance from earth to space are measurable from a ground station. Four in-flight experiments were conducted to obtain measurements of contrast transmittance for comparison with measurements made simultaneously at ground stations. The in-flight and ground-based measurements are in good agreement.

Gordon, J. I.↗

NASA NTRS1973

Fabrication and properties of gallium phosphide variable colour displays

The unique properties of single-junction gallium phosphide devices incorporating both red and green radiative recombination centers were investigated in application to the fabrication of monolithic 5 x 7 displays capable of displaying symbolic and alphanumeric information in a multicolor format. A number of potentially suitable material preparation techniques were evaluated in terms of both material properties and device performance. Optimum results were obtained for double liquid-phase-epitaxial process in which an open-tube dipping technique was used for n-layer growth and a sealed tipping procedure for subsequent p-layer growth. It was demonstrated that to prepare devices exhibiting a satisfactory range of dominant wavelengths which can be perceived as distinct emission colors extending from the red through green region of the visible spectrum involves a compromise between the material properties necessary for efficient red emission and those considered optimum for efficient green emission.

Effer, D.↗

NASA NTRS1974

A new device for acquiring ground truth on the absorption of light by turbid waters

The author has identified the following significant results. A new device, called a Spectral Attenuation Board, has been designed and tested, which enables ERTS-1 sea truth collection teams to monitor the attenuation depths of three colors continuously, as the board is being towed behind a boat. The device consists of a 1.2 x 1.2 meter flat board held below the surface of the water at a fixed angle to the surface of the water. A camera mounted above the water takes photographs of the board. The resulting film image is analyzed by a micro-densitometer trace along the descending portion of the board. This yields information on the rate of attenuation of light penetrating the water column and the Secchi depth. Red and green stripes were painted on the white board to approximate band 4 and band 5 of the ERTS MSS so that information on the rate of light absorption by the water column of light in these regions of the visible spectrum could be concurrently measured. It was found that information from a red, green, and white stripe may serve to fingerprint the composition of the water mass. A number of these devices, when automated, could also be distributed over a large region to provide a cheap method of obtaining valuable satellite ground truth data at present time intervals.

Klemas, V.↗

NASA NTRS1974

Automated life-detection experiments for the Viking mission to Mars

As part of the Viking mission to Mars in 1975, an automated set of instruments is being built to test for the presence of metabolizing organisms on that planet. Three separate modules are combined in this instrument so that samples of the Martian surface can be subjected to a broad array of experimental conditions so as to measure biological activity. The first, the Pyrolytic Release Module, will expose surface samples to a mixture of C-14O and C-14O2 in the presence of Martian atmosphere and a light source that simulates the Martian visible spectrum. The assay system is designed to determine the extent of assimilation of CO or CO2 into organic compounds. The Gas Exchange Module will incubate surface samples in a humidified CO2 atmosphere. At specified times, portions of the incubation atmosphere will be analyzed by gas chromatography to detect the release or uptake of CO2 and several additional gases. The Label Release Module will incubate surface samples with a dilute aqueous solution of simple radioactive organic substrates in Martian atmosphere, and the gas phase will be monitored continuously for the release of labeled CO2.

Klein, H. P.↗

NASA NTRS1975

Multiple scattering in planetary atmospheres

Methods for solving radiative transfer problems within the extended visible spectrum in planetary atmospheres are reviewed for use by the nonspecialist. Emphasis is placed on rapid, approximate procedures for the determination of such quantities as the plane and spherical (Bond) albedo, surface illumination, absorbed energy, limb darkening, phase curve, and spectra. Precise numerical methods and analytical results are also discussed. Recent approaches to such complications as atmospheric inhomogeneity and reflection from a porous regolith are described briefly.

Irvine, W. M.↗

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.↗