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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Cloud cover from high-resolution scanner data - Detecting and allowing for partially filled fields of view

A new technique is presented for obtaining cloud cover and determining clear sky radiances using high-resolution IR scanner data. The technique, which can be automated, employs the spatial structure of the IR radiance field to identify radiances associated with fields of view that are either free of clouds or completely covered by clouds drawn from one or more distinct layers. The approach is particularly well-suited for determining clear sky radiances over oceans from which sea surface temperatures may be derived. In addition, for single-layered systems, the cloud cover fraction for a given region may be obtained from the clear sky radiance, the completely cloud-covered radiance, and the mean radiance for the region. For such systems the separation of completely covered from partially covered fields of view makes it possible to estimate the errors associated with commonly used threshold techniques for determining cloud cover.

Coakley, J. A., Jr.↗
NASA NTRS1984

Partial-Payload Support Structure

Partial-payload support structure (PPSS) is modular, bridge like structure supporting experiments weighing up to 2 tons. PPSS handles such experiments more economically than standard Spacelab pallet system.

Mitchell, R.↗
NASA NTRS1982

Numerical simulation of a conducting disk partially covered by an insulator interacting with a plasma

A numerical simulation has been made of the 'pinhole effect' which produces the characteristic 'S-shaped' current-voltage curve. A disk-shaped conducting probe immersed in a plasma is modeled using a particle-in-cell (PIC) code. A probe partially covered by a very thin insulating layer is considered, as well as a probe mounted on an insulating disk. The simulation uses a cylindrical particle mover and allows for a variable number of particles in the system. The simulation space grid uses three different mesh sizes, the coarsest being away from the probe and the finest near the probe, in order to accurately calculate the trajectories of the simulation particles contributing the current to the probe and to the surface charge density on the dielectric. The calculation of the electrostatic potential is done self-consistently using successive over-relaxation (SOR). Backscattering and secondary electron emission are included for the case of positive probe voltage.

Chaky, R. C.↗
NASA NTRS1983

Area estimation using multiyear designs and partial crop identification

Progress is reported for the following areas: (1) estimating the stratum's crop acreage proportion using the multiyear area estimation model; (2) assessment of multiyear sampling designs; and (3) development of statistical methodology for incorporating partially identified sample segments into crop area estimation.

Sielken, R. L., Jr.↗
NASA NTRS1982

LANDSAT-D data format control book. Volume 6, appendix A: Partially processed thematic mapper High Density Tape (HDT-AT)

One of the outputs of the data management system being developed to provide a variety of standard image products from the thematic mapper and the multispectral band scanners on LANDSAT 4, is the partially processed TM data (radiometric corrections applied and geometric correction matrices for two projections appended) which is recorded on a 28-track high density tape. Specifications are presented for the format of the recorded data as well as for the time code and the major and minor frames of the tape. Major frame types, formats, and field definitions are included.

Jai, A.↗
NASA NTRS1982

An approximation theory for nonlinear partial differential equations with applications to identification and control

Approximation results from linear semigroup theory are used to develop a general framework for convergence of approximation schemes in parameter estimation and optimal control problems for nonlinear partial differential equations. These ideas are used to establish theoretical convergence results for parameter identification using modal (eigenfunction) approximation techniques. Results from numerical investigations of these schemes for both hyperbolic and parabolic systems are given.

Banks, H. T.↗
NASA NTRS1982

A parameterized model for global insolation under partially cloudy skies

A simple and efficient parameterization of insolation under partially cloudy skies is discussed and compared with a set of exact radiative transfer results for clear skies, an empirical equation and observations. The parameterization is physically based and requires, as input variables, the ozone path length, precipitable water, Angstrom turbidity, surface air pressure and albedo, fractional cloud-cover and cloud thickness. Multiple reflection between the surface and the overlying atmosphere, and clouds are considered. The albedo of the earth-atmosphere system is also formulated and compared with a set of exact radiative transfer results. As compared to the exact radiative transfer results, the errors in the insolations are generally less than 1 percent, and in the albedo of the earth-atmosphere system less than 10 percent. The errors in the calculated insolations using climatological data are 2-3 percent when compared with many years averaged observations at Maudheim (Antarctica) and at Rockville (U.S.A.). A parametric equation for calculating directly the daily total insolation is also given.

Choudhury, B.↗
NASA NTRS1983

Imaging performance of annular apertures. IV - Apodization and point spread functions. V - Total and partial energy integral functions

Reference is made to a study by Tschunko (1979) in which it was discussed how apodization modifies the modulation transfer function for various central obstruction ratios. It is shown here how apodization, together with the central obstruction ratio, modifies the point spread function, which is the basic element for the comparison of imaging performance and for the derivation of energy integrals and other functions. At high apodization levels and lower central obstruction (less than 0.1), new extended radial zones are formed in the outer part of the central ring groups. These transmutation of the image functions are of more than theoretical interest, especially if the irradiance levels in the outer ring zones are to be compared to the background irradiance levels. Attention is then given to the energy distribution in point images generated by annular apertures apodized by various transmission functions. The total energy functions are derived; partial energy integrals are determined; and background irradiance functions are discussed.

Tschunko, H. F. A.↗
NASA NTRS1983

Environmental control and life support - Partially closed system will save big money

Although the NASA space station has not yet been completely defined, realistic estimates may be made of the environmental control and life support system requirements entailed by a crew of eight, a resupply interval of 90 days, an initial launch which includes expendables for the first resupply interval, 7.86 lb/day of water per person, etc. An appraisal of these requirements is presented which strongly suggests the utility of a partially closed life support system. Such a scheme would give the crew high quality water to drink, and recycle nonpotable water from hand washing, bathing, clothes and dish washing, and urinal flushing. The excess recovery process water is electrolyzed to provide metabolic and leakage oxygen. The crew would drink electrolysis water and atmospheric humidity control moisture-derived water.

Guy, W. W.↗
NASA NTRS1983

The partial phase of the eclipse of epsilon Aurigae

Ultraviolet spectra of the peculiar eclipsing binary Epsilon Aurigae (FO Ia + ?) were obtained with the International Ultraviolet Explorer at pre-eclipse and ingress partial phases. The results show a wavelength dependence of the eclipse in contrast to the grayness (non-wavelength dependence) of the eclipse observed in visible light. From the current results, incorporating previous observations, it is suggested that: (1) the obscuration of the light of the F supergiant by the disk proposed by Huang (1965) is the result of electron scattering in visible light; (2) the increase in the eclipse depths toward shorter wavelengths observed in the ultraviolet is caused by dust; and (3) the temperature of the disk is in the range from 1000 to 2000 K.

Chapman, R. D.↗
NASA NTRS1983

Period doubling and chaos in partial differential equations for thermosolutal convection

Numerical experiments on two-dimensional thermosolutal convection reveal a transition from periodic oscillations to chaos through a sequence of period-doubling bifurcations. Within the chaotic region there are narrow periodic windows. This is the first example of period-doubling in solutions of partial differential equations. A truncated model indicates that this behavior is associated with heteroclinic explosions.

Moore, D. R.↗
NASA NTRS1982

Numerical grid generation; Proceedings of the Symposium on Numerical Generation of Curvilinear Coordinate Systems and Their Use in the Numerical Solution of Partial Differential Equations, Nashville, TN, April 13-16, 1982

General curvilinear coordinate systems are considered along with the error induced by coordinate systems, basic differential models for coordinate generation, elliptic grid generation, conformal grid generation, algebraic grid generation, orthogonal grid generation, patched coordinate systems, and solid mechanics applications of boundary fitted coordinate systems. Attention is given to coordinate system control and adaptive meshes, the application of body conforming curvilinear grids for finite difference solution of external flow, the use of solution adaptive grids in solving partial differential equations, adaptive gridding for finite difference solutions to heat and mass transfer problems, and the application of curvilinear coordinate generation techniques to the computation of internal flows. Other topics explored are related to the solution of nonlinear water wave problems using boundary-fitted coordinate systems, the numerical modeling of estuarine hydrodynamics on a boundary-fitted coordinate system, and conformal grid generation for multielement airfoils.

Thompson, J. F.↗
NASA NTRS1982

The use of solution adaptive grids in solving partial differential equations

The grid point distribution used in solving a partial differential equation using a numerical method has a substantial influence on the quality of the solution. An adaptive grid which adjusts as the solution changes provides the best results when the number of grid points available for use during the calculation is fixed. Basic concepts used in generating and applying adaptive grids are reviewed in this paper, and examples illustrating applications of these concepts are presented.

Anderson, D. A.↗
NASA NTRS1982

Grid generation by elliptic partial differential equations for a tri-element Augmentor-Wing airfoil

Two efforts to numerically simulate the flow about the Augmentor-Wing airfoil in the cruise configuration using the GRAPE elliptic partial differential equation grid generator algorithm are discussed. The Augmentor-Wing consists of a main airfoil with a slotted trailing edge for blowing and two smaller airfoils shrouding the blowing jet. The airfoil and the algorithm are described, and the application of GRAPE to an unsteady viscous flow simulation and a transonic full-potential approach is considered. The procedure involves dividing a complicated flow region into an arbitrary number of zones and ensuring continuity of grid lines, their slopes, and their point distributions across the zonal boundaries. The method for distributing the body-surface grid points is discussed.

Sorenson, R. L.↗
NASA NTRS1982

Marching grid generation using parabolic partial differential equations

The feasibility of using parabolic partial differential equations for grid generation is examined. Source terms in the form of a linear interpolation between the current grid and the outer boundary are used in generating a grid for a two-dimensional airfoil flow. Grid generation equations are derived by assuming that grid spacings are locally nonuniform on the computational domain. The grid spacing control method is described in detail, and the local orthogonality of the grid lines is discussed. An O-mesh and an H-mesh generated by the described method are shown.

Nakamura, S.↗
NASA NTRS1983

Explicit finite difference predictor and convex corrector with applications to hyperbolic partial differential equations

An explicit finite difference scheme consisting of a predictor and a corrector has been developed and applied to solve some hyperbolic partial differential equations (PDEs). The corrector is a convex-type function which is applied at each time level and at each mesh point. It consists of a parameter which may be estimated such that for larger time steps the algorithm should remain stable and generate a fast speed of convergence to the steady-state solution. Some examples have been given.

Dey, C.↗
NASA NTRS1983

Evaporation from a partially wet forest canopy

The results of experimental studies of water storage in a Sitka-spruce canopy are presented and analyzed in terms of model simulations of evaporation. Wet-branch cantilever deflection was measured along with meteorological data on three days in August, 1976, to determine the relationship of canopy evaporation to wind speed and (hence) aerodynamic resistance. Two versions of a simple unilayer model of sensible and latent heat transport from a partially wet canopy were tested in the data analysis: model F1 forbids the exchange of heat between wet and dry foliage surfaces; model F2 assumes that this exchange is highly efficient. Model F1 is found to give results consistent with the rainfall-interception model of Rutter et al. (1971, 1975, 1977), but model F2 gives results which are more plausible and correspond to the multilayer simulations of Sellers and Lockwood (1981) and the experimental findings of Hancock and Crowther (1979). It is inferred that the role of eddy diffusivity for water vapor is enhanced relative to momentum transport, and that the similarity hypothesis used in conventional models may fail in the near vicinity of a forest canopy.

Hancock, N. H.↗