SEARCH · Search NASA

Results for “Yield Modeling”

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 253 records · Page 14

All sources NASA NTRS DOE OSTI

NASA NTRS1978

Ozone profiles and chemical loss rates in the tropical stratosphere deduced from backscatter ultraviolet measurements

Analysis of data obtained by the backscatter ultraviolet (BUV) experiment on the Atmosphere Explorer E satellite has provided equatorial ozone mixing ratio profiles for equinox and solstice conditions. The combination of these results with a pure oxygen chemical model yields the rate of odd oxygen loss due to the sum of the odd hydrogen, nitrogen, and chlorine cycles. Use of recent mid-latitude stratospheric measurements of HO(x), NO(x), and ClO(x) with the BUV data provides an independent calculation of the catalytic loss. Below 45 km the agreement between the two sets of loss rates is satisfactory. At higher altitudes the odd hydrogen cycle provides far more O(x) loss than can be tolerated by the BUV measurements if the photodissociation of O2 is the only source and has the currently accepted magnitude. The results suggest either a tropical HO(x) concentration smaller than is now believed or the presence of a very large source of odd oxygen in the upper stratosphere and lower mesosphere.

Frederick, J. E.↗

NASA NTRS1976

Design, processing, and testing of LSI arrays for space station

The applicability of a particular process for the fabrication of large scale integrated circuits is described. Test arrays were designed, built, and tested, and then utilized. A set of optimum dimensions for LSI arrays was generated. The arrays were applied to yield improvement through process innovation, and additional applications were suggested in the areas of yield prediction, yield modeling, and process reliability.

Ipri, A. C.↗

NASA NTRS1974

Evaluation of exercise-respiratory system modifications and integration schemes for physiological systems

Exercise subroutine modifications are implemented in an exercise-respiratory system model yielding improvement of system response to exercise forcings. A more physiologically desirable respiratory ventilation rate in addition to an improved regulation of arterial gas tensions and cerebral blood flow is observed. A respiratory frequency expression is proposed which would be appropriate as an interfacing element of the respiratory-pulsatile cardiovascular system. Presentation of a circulatory-respiratory system integration scheme along with its computer program listing is given. The integrated system responds to exercise stimulation for both nonstressed and stressed physiological states. Other integration possibilities are discussed with respect to the respiratory, pulsatile cardiovascular, thermoregulatory, and the long-term circulatory systems.

Gallagher, R. R.↗

NASA NTRS1978

Viking Orbiter observations of the Mars opposition effect

Viking television photography of two dust storms that occurred during the Viking extended mission are used to show that the enhancement of the opposition effect at short wavelengths reported during the 1967 and 1969 oppositions does not appear to be an atmospheric effect, as previously suggested. The brightness changes near 0 deg phase as seen by the Viking Orbiters during the June 15, 1977, dust storm are modeled, yielding first-order aerosol parameters that tend to suppress the opposition effect in violet light. It is proposed that the opposition-effect phenomenon, if real, might be characterized by assuming a surface covered with a particle microstructure of the same single-scattering albedo found for the June dust-storm aerosols, combined with a lunar phase function (macrostructure).

Thorpe, T. E.↗

NASA NTRS1978

An investigation into the role of plastic failure in crater modification

The mechanical stability of an impact crater is analyzed in this paper via a quasi-static, axisymmetric slip line theory of plasticity. The yield model incorporated is Mohr-Coulomb and a simplified rectangular profile is used for the transient cavity. The degree of stability (or instability) is described as a function of internal friction angle, depth/diameter ratio, and a dimensionless parameter. To match the observed slumping of large lunar craters the cohesion strength of the lunar surface material must be low (less than 20 bars) and the angle of internal friction must be less than 2 deg. It is not implausible that these failure strength characteristics are realized by freshly shocked rock.

Mckinnon, W. B.↗

NASA NTRS1979

Gravity model improvement using GEOS 3 /GEM 9 and 10/

Although errors in previous gravity models have produced large uncertainties in the orbital position of GEOS 3, significant improvement has been obtained with new geopotential solutions, Goddard Earth Model (GEM) 9 and 10. The GEM 9 and 10 solutions for the potential coefficients and station coordinates are presented along with a discussion of the new techniques employed. Also presented and discussed are solutions for three fundamental geodetic reference parameters, viz. the mean radius of the earth, the gravitational constant, and mean equatorial gravity. Evaluation of the gravity field is examined together with evaluation of GEM 9 and 10 for orbit determination accuracy. The major objectives of GEM 9 and 10 are achieved. GEOS 3 orbital accuracies from these models are about 1 m in their radial components for 5-day arc lengths. Both models yield significantly improved results over GEM solutions when compared to surface gravimetry, Skylab and GEOS 3 altimetry, and highly accurate BE-C (Beacon Explorer-C) laser ranges. The new values of the parameters discussed are given.

Lerch, F. J.↗

NASA NTRS1979

Trailing-edge flows at high Reynolds number

An investigation of trailing-edge flows at high Reynolds number and subsonic Mach numbers is presented. Symmetric and asymmetric trailing-edge flows are studied, each flow having pressure gradient regions upstream of the trailing edge similar to an airfoil. Measurements include model surface pressures, mean velocity, turbulent shear stress, and turbulent kinetic energy profiles in the trailing-edge and near-wake regions. Comparisons of the symmetric data with numerical solutions of boundary layer as well as Navier-Stokes equations employing two different turbulence models show increasing effects on viscous interactions as the Mach number increases. Both turbulence models yielded solutions of the mean flow of comparable quality. The experimental results of the asymmetric case are discussed.

Viswanath, P. R.↗

NASA NTRS1979

Accuracy and performance of LACIE yield estimates in major wheat producing regions of the world

The LACIE yield models developed, implemented, and tested during the three phases of the experiment represent the first generation of models designed for the large-scale prediction of wheat production. The models are capable of supporting the stated project goal of being within 10 percent of the actual wheat production 90 percent of the time. The limitations of the models are inherent in their nature. The temporal resolution limits their ability to handle the erratic weather occurring in critical situations. The relatively large spatial resolution of the individual models limits the capture of localized but important episodic events.

Phinney, D. E.↗

NASA NTRS1980

Measurements of the H2 4-0 quadrupole bands of Uranus and Neptune

It is found that the equivalent widths of the lines of the 4-0 H2 quadrupole band on Uranus and Neptune are substantially smaller than the values found by some previous observers. An analysis of the results based on a range of atmospheric models yields H2 abundances of 240 + or - 60 km-amagats for Uranus and greater than approximately 200 km amagats for Neptune.

Smith, W. H.↗

NASA NTRS1981

The albedo of snow for partially cloudy skies

The albedo of snow is defined as the ratio of reflected to incident solar energy, and it is an important parameter in the earth's radiation budget analysis and in the study of snowpack's thermal conditions. An approximate model for calculating the incident spectral flux for partially cloudy skies is presented. The input parameters for the calculation are atmospheric precipitable water, turbidity, ozone content, surface pressure, the optical thickness of clouds, and the grain size of snow crystals. The spectral snow reflectance model considers both specular surface reflection and volumetric multiple scattering. The surface reflection is calculated by using a crystal-shape-dependent bidirectional reflectance distribution function; the volumetric multiple scattering is calculated by using a crystal-size-dependent approximate solution in the radiative transfer equation. The model yields spectral and integrated solar flux and snow reflectance as a function of solar elevation and fractional cloud-cover. The illustrative insolation and albedo values were obtained from spectral reflectance and incident flux for representative parameters of Antarctic coastal regions. A simple relationship between grain size and the overcast albedo was obtained. For a set of grain size and shape, the albedo as a function of solar elevation and fractional cloud cover was tabulated.

Choudhury, B. J.↗

NASA NTRS1980

Flight test experience using advanced airborne equipment in a time-based metered traffic environment

A series of test flights have demonstrated that time-based metering guidance and control was acceptable to pilots and air traffic controllers. The descent algorithm of the technique, with good representation of aircraft performance and wind modeling, yielded arrival time accuracy within 12 sec. It is expected that this will represent significant fuel savings (1) through a reduction of the time error dispersions at the metering fix for the entire fleet, and (2) for individual aircraft as well, through the presentation of guidance for a fuel-efficient descent. Air traffic controller workloads were also reduced, in keeping with the reduction of required communications resulting from the transfer of navigation responsibilities to pilots. A second series of test flights demonstrated that an existing flight management system could be modified to operate in the new mode.

Morello, S. A.↗

NASA NTRS1981

On the significance of including the thermal motion of ions in determining the ion distribution behind a satellite

A comparative investigation concerning the spatial distribution of ions in the wake of small bodies was conducted using the theoretical wake models of Call (1969) and Parker (1976). Results for bodies with radius/ambient Debye length ratios of 2 and 5, with an electron temperature equal to the ambient electron temperature, and for the ionic Mach numbers S = 2, 4, 6, 8 are presented. Since the main physical difference between the models is in the consideration of the thermal motion of ions (Parker) versus ignoring this component (Call), a comparison between the models yields the quantitative significance of this component in determining the distribution of ions in the wake of artificial satellites. The application of this result to future experiments to be conducted on board the Spacelab and for any other large space platform in the area of space plasma physics is mentioned.

Samir, U.↗

NASA NTRS1981

Titan's atmosphere - Temperature and dynamics

In the lower atmosphere of Titan IR brightness temperatures exhibit meridional contrast less than approximately 3 K. Seasonal variations are absent because of the large radiative time constant. In the upper stratosphere meridional contrasts are approximately 20 K, consistent with 100 m/s cyclostrophic zonal winds, and the radiative time constant is short, implying a large seasonal variation in the temperature and wind field. The absence of longitudinal thermal structure implies that zonally symmetric flows effect the meridional transport of heat. A simple model yields meridional velocities approximately 0.04 cm/s and vertical eddy viscosities approximately 1,000 sq cm/s in the lower troposphere, and meridional velocities approximately 5 cm/s in the upper stratosphere.

Flasar, F. M.↗

NASA NTRS1981

An evaluation of the spatial resolution of soil moisture information

Rainfall-amount patterns in the central regions of the U.S. were assessed. The spatial scales of surface features and their corresponding microwave responses in the mid western U.S. were investigated. The usefulness for U.S. government agencies of soil moisture information at scales of 10 km and 1 km. was ascertained. From an investigation of 494 storms, it was found that the rainfall resulting from the passage of most types of storms produces patterns which can be resolved on a 10 km scale. The land features causing the greatest problem in the sensing of soil moisture over large agricultural areas with a radiometer are bodies of water. Over the mid-western portions of the U.S., water occupies less than 2% of the total area, the consequently, the water bodies will not have a significant impact on the mapping of soil moisture. Over most of the areas, measurements at a 10-km resolution would adequately define the distribution of soil moisture. Crop yield models and hydrological models would give improved results if soil moisture information at scales of 10 km was available.

Hardy, K. R.↗

NASA NTRS1981

AgRISTARS: Agriculture and resources inventory surveys through aerospace remote sensing

The major objectives and FY 1980 accomplishments are described of a long term program designed to determine the usefulness, cost, and extent to which aerospace remote sensing data can be integrated into existing or future USDA systems to improve the objectivity, reliability, timeliness, and adequacy of information. A general overview, the primary and participating agencies, and the technical highlights of each of the following projects are presented: early warning/crop condition assessment; foreign commodity production forecasting; yield model development; supporting research; soil moisture; domestic crops and land cover; renewable resources inventory; and conservation and pollution.

Source record↗

NASA NTRS1982

PKS 2155-304 - Relativistically beamed synchrotron radiation from a BL Lacertae object

The previously reported variability by a factor of two in less than a day is confirmed for the newly discovered BL Lac object PKS 2155-304, by means of the HEAO 1 A-2 experiment's medium- and high-energy detectors. An interpretation of the overall spectrum from radio through X-rays in terms of a synchrotron self-Compton model yields a good description of the data if relativistic beaming is allowed for. The presence of jets is inferred without their direct observation through consideration of the spectrum, combined with an estimate of the size of the source.

Urry, C. M.↗

NASA NTRS1981

Neutron star models

The current state of neutron star structure calculations is reviewed. Uncertainties in the equation of state for matter at and above nuclear density remain. The role of the delta resonance, pion condensates, and quark matter is reviewed. It is found that recent models yield stable neutron star masses which are consistent with observational estimates.

Canuto, V.↗

NASA NTRS1982

Stagnation point heat transfer augmentation due to free stream turbulence

A model has been proposed for the momentum eddy diffusivity induced by free stream turbulence intensity and integral length scale. The eddy diffusivity model is applied to the stagnation point of a cylinder situated in a uniform crossflow in the presence of free stream turbulence. A numerical solution of the governing momentum and energy equations with the proposed eddy diffusivity model yielded results for the skin friction coefficient and the Nusselt number. The numerical predictions of the present work are compared with experimental data and the agreement between the two is seen to be very good.

Gorla, R. S. R.↗