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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Characteristics of the MSFC, PDS microdensitometer

The results of several parametric studies carried out on the Marshall Space Flight Center (MSFC) Photometric Data System PDS-10 microdensitometer are summarized for the purposes of documenting the operation and limitations of the system for inhouse research and to provide a bench mark for comparison with other microdensitometers. The results are grouped into four general areas. These are: (1) system overall stability to drift, (2) photometric linearity and noise, (3) reproducibility, and (4) scanning performance. Test data taken in order to evaluate the interdependency of scan speed, noise and position are included. Shown also are results of tests for system stability, reproducibility, stray light and PMT settling time.

Fountain, W. F.↗
NASA NTRS1983

Dynamical injections as the source of near geostationary quiet time particle spatial boundaries

The question whether the noon-dusk feature is a manifestation of the spatial structures that should arise from quasi-stationary convection is examined. The key consideration here is whether the energy dispersion of the feature can be explained. It is shown that the observed energy dispersion cannot be attributed to the standard stationary convection configurations, either perturbed or unperturbed. It is also demonstrated, using a detailed computer simulation, that the nighttime, double-spiral-shaped injection boundary (used previously to reproduce the fast changing nighttime features) is successful at reproducing the noon-dusk feature by allowing the particles to evolve for periods of 12 to 36 hours after the injection. It is stressed that the portion of the injection boundary responsible for the feature looks very different from the standard convection boundaries configuration. Conclusions are offered concerning the importance of quasi-stationary convection as the mechanism by which the near geostationary regions are populated.

Mauk, B. H.↗
NASA NTRS1984

Long-period classical Cepheids - Theory versus observation

New full amplitude models of classical Cepheids having periods longer than 13 days have been calculated, allowing the complete systematics of the observed light and velocity curves of classical Cepheids to be discussed in detail. Assuming that a normal evolutionary mass-luminosity relation is obeyed, the models reproduce such empirical phenomena as the full Hertzsprung progression of light and velocity curves and the gradual shift in phase of the Hertzsprung bump, together with the persistence in phase of the postmaximum shoulder on the light curve. Also reproduced are the retardation of maximum expansion velocity after maximum light, the correlation of light and velocity amplitudes, and the period-amplitude scatter diagram for both the light and the velocity amplitude. The average period predicted for a Cepheid light curve type is noted to be about 40 percent longer than that actually observed.

Carson, T. R.↗
NASA NTRS1985

Evaluation of results of cell electrophoresis experiments on space shuttle STS-3 including pre-flight and post-flight laboratory experiments

The objectives of the red blood cell experiments were to provide a visual check on the electrophoretic process and especially electroosmotic flow in space as well as to provide test separations of non-degradable standard particles for comparison with the separations of the three viable cell types studied on the Apollo-Soyuz Test Project. Determination of the maximum concentrations of cells that can be separated in column electrophore was a significant goal. Two of the eight columns were available for red cell experiments, so two concentrations of human and rabbit RBC mixtures were used. The objectives of another experiment were to evaluate the reproducibility of microgravity electrophoretic separation of living kidney cells, to separate cells with highly viability despite two freeze-thaw cycles, and to optimize the physical conditions of cell separation. Owing to the uncertain heterogeneity of the starting material, the experimental design does not assess resolution in microgravity, but improved separability was sought in comparison to density-gradient electrophoresis or continuous-flow electrophoresis. Efforts were made to increase cell yield and cell viability and to assess reproducibility directly.

Todd, P. W.↗
NASA NTRS1985

New analysis of nuclear interaction observed by Mt. Kanbara emulsion chamber experiment

To date the analysis of the air cascade family has been performed using a full Monte Carlo simulation. It is difficult to draw a definite conclusion about the interaction mechanism by using only this kind of simulation. On the other hand, attempts to reproduce the original gamma ray at the interaction point, for example decascading, have also been made. This method makes it possible to observe the interaction directly and to analyze the data from various angles. All of these methods, however, assume a constant ER in the cascade shower, where E is energy and R is the distance from the center of the cascade shower. It is impossible to reproduce the exact interaction height and energy by these methods. A relative method in separating one cascade shower from others is adopted. This method makes it possible to estimate the interaction height and energy by using information about the lateral spread of the cascade shower.

Nanjo, H.↗
NASA NTRS1984

The CN radical in diffuse interstellar clouds

A survey of 15 lines of sight for the CN B2Sigma(+) X2Sigma(+) interstellar absorption lines shows that the CN column density in diffuse interstellar clouds follows the relation log N(CN) is proportional to m log N(H2), where m is approximately equal to 3. This result is reproduced by a reaction network in which CN is produced primarily from C2 by the neutral-neutral reaction C2 + N yields CN + C, and photodissociation is the main destruction pathway for the neutral molecules CH, C2, and CN. The CN radical is the first molecular species observed in diffuse clouds that requires a neutral-neutral reaction for its formation in the gas phase. The network also reproduces the observed ratio N(CN)/N(H2).

Federman, S. R.↗
NASA NTRS1986

Oxygen index: An approximate value for the evaluation of combustion characteristics

The oxygen index has gained international recognition for the determination of combustion characteristics of plastic material. The amounts of oxygen and nitrogen were more accurately determined for existing test equipment in order to specify the oxygen index as precisely and as reproducible as possible. Parameters are outlined such as the size of the ignition flame, ignition of test pieces, test piece sizes and test temperature. The minimum oxygen index was determined by the dimension and duration of the fire. The results are sufficiently accurate for factory operating conditions and are also reproducible.

Zartmann, I.↗
NASA NTRS1986

The accretion disk limit cycle mechanism in GK Persei

The accretion disk thermal instability (limit cycle) mechanism for dwarf novalike outbursts is applied to the old nova GK Per in order to find values of the input parameters which reproduce the observed outbursts and to constrain the physics associated with the disk and the mass transfer process. It is found that models in which the dimensionless viscosity parameter has the value of 0.003 in the cold phase and 0.015 in the hot phase reproduce the observed spacing and duration of the eruptions. The calculated light curves at V and 1750 A are close to those observed during recent eruptions of GK Per if the interstellar reddening E(B-V) to this system is roughly 0.3.

Cannizzo, J. K.↗
NASA NTRS1986

Thunderstorm cloud top dynamics as inferred from satellite observations and a cloud top parcel model

Thunderstorm top temperature-height structure and temperature-height conversion relations in the convective overshooting top region are examined using data from GOES IR, AVHRR, and aircraft overflights, and GOES stereoscopic observations. Using a Lagrangian one-dimensional cloud parcel model applied in the overshooting region, three classes of storm tops are described and the causes of their unique temperature-height structures are explored. Although the parcel model used does not fully reproduce the three-dimensional structure and dynamics of an evolving thunderstorm top, it is shown to crudely reproduce the parcel dynamics of updraft core parcels. The locations of cold points, high points, warm points, and the magnitude of cold-high offsets compare favorably between the model and the satellite observations.

Adler, Robert F.↗
NASA NTRS1987

Core formation in the shergottite parent body and comparison with the earth

Abundances of elements in shergottite, nakhlite, and Chassigny meteorites which originated on a single planet, the shergottite parent body (SPB), were examined with the aim of elucidating the chemical conditions of metal separation and core formation in the SPB and of testing present models of planetary core formation. Using partition coefficients and the SPB mantle composition determined in earlier studies, the abundances of Ag, Au, Co, Ga, Mo, Ni, P, Re, S, and W were modeled, with free parameters being oxygen fugacity, proportion of solid metal formed, proportion of metallic liquid formed, and proportion of silicate that is molten. It is shown that the abundances of all elements (except Mo) could be reproduced using models with these four free parameters. In contrast to the SPB, an equivalent model used to predict element abundances in the earth's mantle was shown by Jones and Drake (1986) to be inadequate; there is at present no hypothesis capable of quantitatively reproducing the elemental abundances of the earth's mantle. The contrast suggests that these two terrestrial planets (assuming that the SPB is Mars) may have accreted or differentiated differently.

Treiman, Allan H.↗
NASA NTRS1987

Chemistry of the global troposphere - Fluorocarbons as tracers of air motion

Winds and convective mixing from a general circulation model of the atmosphere have been applied in a chemical tracer model (CTM) to simulate the global distribution and temporal variability of chlorofluorocarbons (CFCs). The seasonal cycle in moist convection, with maximum activity over continents in summer, leads to an annual cycle in the surface concentration of CFCs. Emissions are retained in the lowest levels of the atmosphere during winter, and surface concentrations peak near sources. In this season, CFCs from European sources are carried by low-level winds into the Arctic. During summer, vertical exchange is more efficient, and pollutants are transported more rapidly to the middle atmosphere. Consequently, concentrations of CFCs during summer are relatively low near the surface and elevated in the middle troposphere. Time series analysis of data from Adrigole, Ireland, indicates that the model accurately simulates long-range transport of air pollution. The model reproduces global distributions and trends for CFC-11 and CFC-12 observed by the ALE experiment; however, subgrid diffusion must be introduced into the model in order to reproduce the observed interhemispheric gradient. Interhemispheric exchange occurs mainly in the upper tropical troposphere, producing a profile which increases with altitude in the Southern Hemisphere, in agreement with observations. The distribution of CFCs is such that it is necessary to apply important corrections to observations at surface stations in order to derive global distributions.

Prather, Michael↗
NASA NTRS1988

Stand For Infrared Multiple-Internal-Reflection Mount

Infrared MIR spectra more reproducible, and MIR crystal suffers less damage. Technique prevents lateral movement between elements in multiple-internal-reflection (MIR) cell during assembly. Reproducibility of infrared MIR spectra relies on ability to maintain condition of crystal, which is MIR element, and to control contact between crystal and sample. Cell used in infrared spectroscopy.

Long, Edward R., Jr.↗
NASA NTRS1986

A new type of lamp and reflector for I.R. simulation

The lamps and reflectors used for infrared radiation simulation tests at ESTEC did not allow researchers to predict the intensity needed for test conditions with the desired accuracy. This was due to poor reproducibility of the polar diagrams, the unknown contribution of the radiation in the long wavelength range in vacuum, imperfections in the quartz bulbs, and misalignment of the lamp in the reflector. When using a 1000 W coiled spiral quartz lamp with a diffuse reflector, these shortcomings are overcome. Due to the good reproducibility, an overall accuracy within plus or minus 2 percent should be obtained.

Saenger, G.↗
NASA NTRS1988

Core-core and core-valence correlation

The effect of (1s) core correlation on properties and energy separations was analyzed using full configuration-interaction (FCI) calculations. The Be 1 S - 1 P, the C 3 P - 5 S and CH+ 1 Sigma + or - 1 Pi separations, and CH+ spectroscopic constants, dipole moment and 1 Sigma + - 1 Pi transition dipole moment were studied. The results of the FCI calculations are compared to those obtained using approximate methods. In addition, the generation of atomic natural orbital (ANO) basis sets, as a method for contracting a primitive basis set for both valence and core correlation, is discussed. When both core-core and core-valence correlation are included in the calculation, no suitable truncated CI approach consistently reproduces the FCI, and contraction of the basis set is very difficult. If the (nearly constant) core-core correlation is eliminated, and only the core-valence correlation is included, CASSCF/MRCI approached reproduce the FCI results and basis set contraction is significantly easier.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1988

Image-gathering system design for information and fidelity

Image gathering and processing are assessed in terms of information and fidelity, and the relationship between these two figures of merit is examined. It is assumed that the system is linear and isoplanatic and that the signal and noise amplitudes are Gaussian, wide-sense stationary, and statistically independent. Within these constraints, it is found that the combined process of image gathering and reconstruction (which is intended to reproduce the output of the image-gathering system) behaves as optical, or photographic, image formation in that the informationally optimized design of the image-gathering system ordinarily does not maximize the fidelity of the reconstructed image. The combined process of image gathering and restoration (which is intended to reproduce the input of the image-gathering system) behaves more as a communication channel in that the informationally optimized design of the image-gathering system tends to maximize the fidelity of optimally restored representations of the input.

Huck, Friedrich O.↗
NASA NTRS1988

Preparation of multistage zone-refined materials for thermochemical standards

This paper describes the steps of a two-step zone purification procedure for completed minicells filled with ultrahigh-purity succinonitrile (SCN) in which the CNS is under its own vapor pressure. The solid-liquid equilibrium, as determined by melting and freezing point measurements, is therefore considered to be a realization of the triple-point. The freezing-point plateaus measured at a variety of bath temperatures demonstrated both the fundamental reproducibility of the measurement for a given sample and the lack of dependence of that measurement on the bath temperature which controls the freezing rate. The measurement reproducibility and the sample consistency indicate that the method described is indeed suitable for the preparation of pure material which can be used for the purposes of thermistor and thermometer calibration at 58.0796 + or - 0.0015 C.

Rubinstein, E.↗
NASA NTRS1989

Toward an image compression algorithm for the high-resolution electronic still camera

Taking pictures with a camera that uses a digital recording medium instead of film has the advantage of recording and transmitting images without the use of a darkroom or a courier. However, high-resolution images contain an enormous amount of information and strain data-storage systems. Image compression will allow multiple images to be stored in the High-Resolution Electronic Still Camera. The camera is under development at Johnson Space Center. Fidelity of the reproduced image and compression speed are of tantamount importance. Lossless compression algorithms are fast and faithfully reproduce the image, but their compression ratios will be unacceptably low due to noise in the front end of the camera. Future efforts will include exploring methods that will reduce the noise in the image and increase the compression ratio.

Nerheim, Rosalee↗
NASA NTRS1988

A model of auroral potential structures based on Dynamics Explorer plasma data

Dynamics Explorer 1 hot plasma data are used to investigate three major features of the mid-altitude auroral electron distribution -- the hole, the bump (at large pitch angles), and the loss cone. The results of a computer simulation show that these features can be approximately reproduced by a model involving an initial plasma sheet electron distribution and two potential drop regions that are widely separated in altitude. The observed distributions could not be reproduced, even qualitatively, by any of a wide range of distributed potential drops involving parallel electric fields at the point of observation.

Burch, J. L.↗