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At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

CARETS: A prototype regional environmental information system. Volume 13: Utility of CARETS products to local planners; an evaluation

The Metropolitan Washington Council of Governments (MWCOG) in cooperation with and under contract to the U.S. Geological Survey, conducted an evaluation of the utility of remote-sensor derived land use data produced by the USGS Central Atlantic Regional Ecological Test Site (CARETS) project. Investigators invited representatives of Washington, D.C. metropolitan area planning agencies to a workshop, introduced them to the CARETS products, and asked them to evaluate the products. In follow-up interviews, planners from 12 participating agencies reported general support for the fulI spectrum of CARETS products but gave more positive responses towards products with which they had some familiarity. Planners considered some products of limited utility because of (1) insufficient detail, (2) too small a scale, or (3) lack of technical capability to incorporate the information and products into the current planning process. Some planners expressed doubt about the application of CARETS products in most day-to-day planning activities , which involve specific rezoning requests or site development plans requiring highly localized data. The greatest potential of the CARETS products was in the identification of broad development patterns at the county or regional level. An appendix documents the results of an inventory of local government decisions relating to land use.

Land use planning↗
NASA NTRS1975

Radar backscatter properties of milo and soybeans

The radar backscatter from fields of milo and soybeans was measured with a ground based radar as a function of frequency (8-18 GHz), polarization (HH and VV) and angle of incidence (0 deg-70 deg) during the summer of 1974. Supporting ground truth was gathered contemporaneously with the backscatter data. At nadir sigma deg of milo correlated highly, r = 0.96, with soil moisture in the milo field at 8.6 GHz but decreased to a value of r = 0.78 at a frequency of 17.0 GHz. Correlation studies of the variations of sigma deg with soil moisture in the soybean fields were not possible due to a lack of a meaningful soil moisture dynamic range. At the larger angles of incidence, however, sigma deg of soybeans did appear to be dependent on precipitation. It is suggested this phenomenon was caused by the rain altering plant geometry. In general sigma deg of both milo and soybeans had a relatively small dynamic range at the higher angles of incidence and showed no significant dependence on the measured crop parameters.

Bush, T. F.↗
NASA NTRS1976

On the habitability of Mars: An approach to planetary ecosynthesis

The possibility of utilizing Mars as a habitat for terrestrial life, including man, is examined. Available data, assumptions, and speculations on the climate, physical state, and chemical inventory of Mars are reviewed and compared with the known requirements and environmental limits of terrestrial life. No fundamental, insuperable limitation of the ability of Mars to support a terrestrial ecology is identified. The lack of an oxygen-containing atmosphere would prevent the unaided habitation of Mars by man. The present strong ultraviolet surface irradiation is an additional major barrier. The creation of an adequate oxygen and ozone-containing atmosphere on Mars may be feasible through the use of photosynthetic organisms. The time needed to generate such an atmosphere, however, might be several millions of years. This period might be drastically reduced by the synthesis of novel, Mars-adapted, oxygen producing photosynthetic strains by techniques of genetic engineering, and modifying the present Martian climate by melting of the Martian polar caps and concomitant advective and greenhouse heating effects.

Averner, M. M.↗
NASA NTRS1976

Improvements in aircraft extraction programs

Flight data from an F-8 Corsair and a Cessna 172 was analyzed to demonstrate specific improvements in the LRC parameter extraction computer program. The Cramer-Rao bounds were shown to provide a satisfactory relative measure of goodness of parameter estimates. It was not used as an absolute measure due to an inherent uncertainty within a multiplicative factor, traced in turn to the uncertainty in the noise bandwidth in the statistical theory of parameter estimation. The measure was also derived on an entirely nonstatistical basis, yielding thereby also an interpretation of the significance of off-diagonal terms in the dispersion matrix. The distinction between coefficients as linear and non-linear was shown to be important in its implication to a recommended order of parameter iteration. Techniques of improving convergence generally, were developed, and tested out on flight data. In particular, an easily implemented modification incorporating a gradient search was shown to improve initial estimates and thus remove a common cause for lack of convergence.

Balakrishnan, A. V.↗
NASA NTRS1976

Detailed results of ASTP experiment MA-011

This experiment was developed in order to conduct engineering and operational tests of electrokinetic equipment in a micro-gravity environment. The experimental hardware in general functioned as planned and electrophoretic separations were obtained in space. The results indicated the development of satisfactory sample collection, return, and preservation techniques. The application of a near-zero zeta potential interior wall coating to the experimental columns, confirmation of biocompatibility of all appropriate hardware components, and use of a sterile operating environment provided a significant step forward in the development of a biological processing facility in space. A separation of a test of aldehyde-fixed rabbit, human, and horse red blood cells was obtained. Human kidney cells were separated into several components and viable cells returned to earth. The isotachophoretic separation of red cells was also demonstrated. Problems associated with the hardware led to a lack of success in the attempt to separate subpopulations of human lymphocytes.

Seaman, G. V. F.↗
NASA NTRS1976

Development of techniques for processing metal-metal oxide systems

Techniques for producing model metal-metal oxide systems for the purpose of evaluating the results of processing such systems in the low-gravity environment afforded by a drop tower facility are described. Because of the lack of success in producing suitable materials samples and techniques for processing in the 3.5 seconds available, the program was discontinued.

Johnson, P. C.↗
NASA NTRS1976

Discharge stabilization studies of CO laser gas mixtures in quasi-steady supersonic flow

Experiments were conducted to study the applicability of a double discharge stabilization scheme in conditions appropriate for high energy CO lasers in supersonic flows. A Ludwieg tube impulse flow facility and a ballasted capacitor bank provided essentially steady flow and discharge conditions (d.c.) for times longer than ten electrode length-flow transit times. Steady, arc-free, volume discharges were produced in a Mach 3 test cavity using an auxiliary discharge to stabilize the main discharge in N2 and He/CO mixture. A signigicant result is the lack of observed plasma E/N changes in response to auxiliary discharge current changes. Also, where glow discharges were obtained, the energy loading achieved was very much less than the threshold level required for laser operation.

Srinivasan, G.↗
NASA NTRS1977

Measurements of far-ultraviolet photographs from skylab 4 and Apollo 6

Over 700 far UV photos were obtained with the S201 electrographic camera on Skylab 4 (27 Nov. 1973 - 28 Jan. 1974) and from the Apollo-16 lunar site (21 - 23 Apr. 1972). The Lyman-alpha geocorona was found to fit R. R. Meier's model, and the tropical airglow belts were measured quantitatively. The history of Comet Kohoutek's Ly-alpha halo (and lack of an oxygen halo) was followed from 32 days before to 13 days after perihelion passage, and fitted to a model of hydrogen production from the comet. Far UV emissions from the Large Magellanic Cloud were also measured quantitatively and compared with ground-based measurements of stellar associations and nebulae. Computer programs were developed to contour the densities measured by microphotometer on the original film and to locate and sum density-volumes in each starlike image. In addition, thousands of stars were identified and their far UV flux measured in two band-passes (1050 - 1600 A, 1250 - 1600 A).

Page, T.↗
NASA NTRS1975

Microwave properties of ice from The Great Lakes

The increasing use of radar systems as remote sensors of ice thickness has revealed a lack of basic data on the microwave properties of fresh-water ice. A program, in which the complex dielectric constant was measured for a series of ice samples taken from the Great Lakes, is described. The measurements were taken at temperatures of -5, -10, and -15 C. It is noted that the ice has considerable internal layered structure, and the effects of the layering are examined. Values of 3.0 to 3.2 are reported for the real part of the dielectric constant, with an error bar of + or - 0.01.

Vickers, R. S.↗
NASA NTRS1977

An automated consultant for MACSYMA

A consultant is necessary whenever on is faced with a problem solving situation in a domain one does not fully understand. The lack of knowledge may be incidental, as it is when the domain or device is fairly simple but time constraints make it impossible for the user to learn all that is necessary. Computer systems like MACSYMA in which the level of commands is so close to the level of the task environment that the user is apt to confuse a simply defined procedure (like COEFF) with its mathematical counterpart (here coefficient) that it at best approximates. A computer program is described which has the capability of conversing with its user in English about a difficulty he has encountered, and providing information tailored to his need. The MACSYMA Advisor is a program distinct from MACSYMA with its own separate data base and expertise. For convenience the program can be called directly from MACSYMA and can access the user's data structures contained therein. The Advisor described here deals only with the "straightline" or nested use of MACSYMA commands and not loops or user-defined functions. The implementation of the Advisor relies heavily on an explict, internal "model" of the user's state of knowledge, his goals, and his "plan" for achieving them.

Genesereth, M. R.↗
NASA NTRS1977

Potentially improved glasses from space environment

The benefits of processing glasses in a low-gravity space environment are examined. Containerless processing, the absence of gravity driven convection, and lack of sedimentation are seen as potential advantages. Potential applications include the formation of glass-ceramics with a high content of active elements for ferromagnetic devices, the production of ultrapure chalcogenide glasses for laser windows and IR fiber optics, and improved glass products for use in optical systems and laser fusion targets.

Nichols, R.↗
NASA NTRS1976

Meter-wavelength VLBI. IV - Temporal and spatial scattering of the Crab Nebula pulsar's radiation

The spatial and temporal phenomena observed in the Crab Nebula pulsar's radiation are reviewed, with emphasis on the recent VLBI observations of the apparent angular size and the ratio of pulsing to total power. Three models for scattering (single thin screen, two screen, and extended medium) are discussed and shown to be deficient, under the usual assumption of a uniform scattering medium, in explaining the observed combination of temporal and angular broadening. A new model is proposed, in which the temporal broadening is dominated by scattering in the small filament which lies in the nebula in front of the pulsar, while the extended interstellar medium causes the angular broadening. This model explains the otherwise discordant angular and temporal effects and also the lack of an apparent source-size expansion with pulse phase.

Vandenberg, N. R.↗
NASA NTRS1976

High-silica /greater than 60%/ lunar glasses in an Apollo 14 soil sample - Evidence for silicic lunar volcanism

The major-element compositions of 93 low-specific-gravity (less than 2.60) high-silica (greater than 60%) glass particles from a sample of lunar fines (14259,20) were determined by electron microprobe analyses. The size, shape, abundance, mineralogy, and major-element composition of more than 60% of the high-silica glasses is consistent with their being fragments of interstitial glass from mare basalts. However, one group of 30 glasses with between 72% and 78% SiO2 and an average of approximately 2.6% FeO can be distinguished from other high-silica glasses both chemically and petrographically. Glass particles with this composition do not contain crystalline inclusions and are fairly homogeneous not only within a single particle but also from particle to particle. The chemistry and petrology of these glasses suggest that they are not fragments of interstitial glass or shock-melted particles from a 'granitic' source rock. Rather, the homogeneity and lack of crystalline inclusions suggest that this group of high-silica glasses was the product of lunar acidic volcanism.

Glass, B. P.↗
NASA NTRS1976

Observation of a north-south anisotropy of atmospheric radiation at balloon altitudes

Measurements have been made of an azimuthal asymmetry of atmospheric radiation at balloon altitudes and mid-latitudes. The measured asymmetry is 6% peak to peak in the north-south direction at energies above 500 keV. A lack of east-west asymmetry indicates that the arrival direction of the atmospheric radiation is highly decoupled from that of the primary radiation. Present models of secondary atmospheric radiation production and transport do not quantitatively agree with the observations.

Fishman, G. J.↗
NASA NTRS1977

Galilean satellites - Anomalous temperatures disputed

Anomalous averaged infrared brightness temperatures of the Galilean satellites of Jupiter reported by Gross (1975) are rejected as falsely conceived and lacking physical reality. It is argued that the calculations of equilibrium temperatures should be corrected, whereupon predictions would be in satisfactory agreement with observations, in conformity with the radiometric method of determining the diameters of asteroids and satellites. The IR irradiance and the related disk-averaged brightness temperature for the spectral band are recommended as more relevant. Attention is drawn to some interesting discrepancies between calculated and observed temperatures of the Jovian satellites which merit further investigation.

Morrison, D.↗
NASA NTRS1977

The direct observation of solidification as a function of gravity level

A saturated solution of NH4Cl was solidified on earth at 1 g and in a suborbital rocket flight at .00001 g. In the 1 g experiments, macrosegregation caused by the gravitational acceleration was marked. Nucleation started at the cold walls after which dendrites and dendritic debris were swept into the center of the cuvette by convective fluid flow. Secondary dendrite arms were oriented toward the cold wall. When solidified in low g, only four nuclei grew to form the complete casting. There were no free floating crystals or visible dendrite remelting. The lack of fluid flow allowed symmetrical dendrite growth into the fluid.

Johnston, M. H.↗
NASA NTRS1977

Use of human engineering standards in design

Results are presented for a research study intended to assess the impact of present human engineering standards on product design. The approach consisted of three basic steps: a comparison of two display panels to determine if, in fact, products designed to the same standards are truly standardized; a review of two existing standards to determine how well their information can be used to solve design problems; and a survey of human factors specialists to assess their opinions about standards. It is shown that standards have less than the desired influence on product design. This is evidenced by a lack of standardization between hardware designed under common standards, by deficiencies within the standards that detract from their usefulness and encourage users to ignore them, and by the respondents of the survey who consider standards less valuable than other reference sources for design implementation. Recommendations aimed at enhancing the use of standards are set forth.

Rogers, J. G.↗
NASA NTRS1976

Quasi-three-dimensional laminar boundary-layer separations in supersonic flow

A numerical algorithm is presented for solving laminar, steady, supersonic interacting boundary-layer flows for quasi-three-dimensional configurations. The interaction problem is treated as a boundary-value problem and a salient feature of the scheme is the direct implementation of the downstream boundary condition. Solutions are presented for axisymmetric and swept (yawed) compression ramps for both adiabatic and heat transfer conditions over a Mach number range of 2-6. The results are in good agreement with experimental data and existing theories for axisymmetric cases. For the swept (yawed) configurations, lack of experimental data makes a direct comparison impossible, but the present solutions are found to be in qualitative agreement with earlier studies. In addition it is shown that the trends obtained here for the sweep effects are well predicted by a simple extension of the two-dimensional asymptotic theory.

Vatsa, V. N.↗