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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Atmospheric transformation of multispectral remote sensor data

The author has identified the following significant results. The effects of earth's atmosphere were accounted for, and a simple algorithm, based upon a radiative transfer model, was developed to determine the radiance at earth's surface free of atmospheric effects. Acutal multispectral remote sensor data for Lake Erie and associated optical thickness data were used to demonstrate the effectiveness of the atmospheric transformation algorithm. The basic transformation was general in nature and could be applied to the large scale processing of multispectral aircraft or satellite remote sensor data.

Turner, R. E.↗
NASA NTRS1978

Extending reliability: Transformational tailoring of abstract mathematical software

Methods for automatically constructing concrete executable programs from an abstract prototype program by applying transformations based on theorems of matrix algebra and on algebraic properties of programming languages are described. These methods provide a user with highly efficient programs tailored to his environment while maintaining the advantages of high reliability and low cost associated with routines from the best mathematical software libraries. Also, the transformations which produce such programs represent a formal codification of rules for writing linear algebra programs.

Boyle, J. M.↗
NASA NTRS1979

Direct current transformer

A direct current transformer in which the primary consists of an elongated strip of superconductive material, across the ends of which is direct current potential is described. Parallel and closely spaced to the primary is positioned a transformer secondary consisting of a thin strip of magnetoresistive material.

Khanna, S. M.↗
NASA NTRS1978

Apparatus including a plurality of spaced transformers for locating short circuits in cables

A cable fault locator is described for sensing faults such as short circuits in power cables. The apparatus includes a plurality of current transformers strategically located along a cable. Trigger circuits are connected to each of the current transformers for placing a resistor in series with a resistive element responsive to an abnormally high current flowing through that portion of the cable. By measuring the voltage drop across the resistive element, the location of the fault can be determined.

Cason, R. L.↗
NASA NTRS1979

Description of a 2.3 kW power transformer for space applications

The principle features and special testing of a high voltage high power transformer designed and developed for space application are described. The transformer is operated in a series resonant inverter supplying beam power to a 30 cm mercury ion thruster. Electrical requirements include operation of 2.3 kW continuous power output, primary currents to 35 amps rms, and frequencies up to 20 kHz. High efficiency was obtained through detailed considerations of the tradeoffs available in core materials, wire selection, coil configurations and thermal control. A number of novel heat removal techniques are discussed which control the winding temperature using only the available conductive cooling.

Hansen, I.↗
NASA NTRS1979

System for automatically switching transformer coupled lines

A system is presented for automatically controlling transformer coupled alternating current electric lines. The secondary winding of each transformer is provided with a center tap. A switching circuit is connected to the center taps of a pair of secondary windings and includes a switch controller. An impedance is connected between the center taps of the opposite pair of secondary windings. The switching circuit has continuity when the AC lines are continuous and discontinuity with any disconnect of the AC lines. Normally open switching means are provided in at least one AC line. The switch controller automatically opens the switching means when the AC lines become separated.

Dwinell, W. S.↗
NASA NTRS1978

Principal component greenness transformation in multitemporal agricultural Landsat data

A data compression technique for multitemporal Landsat imagery which extracts phenological growth pattern information for agricultural crops is described. The principal component greenness transformation was applied to multitemporal agricultural Landsat data for information retrieval. The transformation was favorable for applications in agricultural Landsat data analysis because of its physical interpretability and its relation to the phenological growth of crops. It was also found that the first and second greenness eigenvector components define a temporal small-grain trajectory and nonsmall-grain trajectory, respectively.

Abotteen, R. A.↗
NASA NTRS1979

Description of A 2.3 kW power transformer for space applications

The paper describes the principal features and special testing of a high-frequency high-power low-specific-weight (0.57 kg/kW) 2.3-kW electronic power transformer developed for space applications. The transformer is operated in a series resonant inverter supplying beam power to a 30-cm mercury ion thruster. High efficiency (above 98.5%) is obtained through careful detailed design. A number of unique heat removal techniques are discussed which control the winding temperature using only the available conductive cooling.

Hansen, I.↗
NASA NTRS1978

A fast complex integer convolution using a hybrid transform

It is shown that the Winograd transform can be combined with a complex integer transform over the Galois field GF(q-squared) to yield a new algorithm for computing the discrete cyclic convolution of complex number points. By this means a fast method for accurately computing the cyclic convolution of a sequence of complex numbers for long convolution lengths can be obtained. This new hybrid algorithm requires fewer multiplications than previous algorithms.

Reed, I. S.↗
NASA NTRS1979

Velocity Fourier transform solution of a model collision operator

A simpler technique than those introduced by Lenard and Bernstein (1958), and Dougherty (1964) is employed to obtain the perturbed species density from a specified kinetic equation for a plasma in a given uniform magnetic field. The technique is a generalization of the velocity-Fourier transform method employed by Karpman (1967) for B sub 0 identical to zero, and relies on the fact that in transform space the model collision operator, used to obtain the kinetic equation for waves in a magnetized plasma, contains only first derivatives. The technique is illustrated by evaluating the perturbed density of an arbitrary species.

Catto, P. J.↗
NASA NTRS1981

28-Channel rotary transformer

Transformer transmits power and digital data across rotating interface. Array has many parallel data channels, each with potential l megabaud data rate. Ferrite-cored transformers are spaced along rotor; airgap between them reduces crosstalk.

Mclyman, W. T.↗
NASA NTRS1981

An approximation for inverse Laplace transforms

Programmable calculator runs simple finite-series approximation for Laplace transform inversions. Utilizing family of orthonormal functions, approximation is used for wide range of transforms, including those encountered in feedback control problems. Method works well as long as F(t) decays to zero as it approaches infinity and so is appliable to most physical systems.

Lear, W. M.↗
NASA NTRS1980

Heat storage in alloy transformations

Heats of transformation of eutectic alloys were measured for many binary and ternary systems by differential scanning calorimetry and thermal analysis. Only the relatively cheap and plentiful elements Mg, Al, Si, P, Ca, Cu, Zn were considered. A method for measuring volume change during transformation was developed using x-ray absorption in a confined sample. Thermal expansion coefficients of both solid and liquid states of aluminum and of its eutectics with copper and with silicon also were determined. Preliminary evaluation of containment materials lead to the selection of silicon carbide as the initial material for study. Possible applications of alloy PCMs for heat storage in conventional and solar central power stations, small solar receivers and industrial furnace operations are under consideration.

Birchenall, C. E.↗
NASA NTRS1980

Heat storage in alloy transformations

The feasibility of using metal alloys as thermal energy storage media was investigated. The elements selected as candidate media were limited to aluminum, copper, magnesium, silicon, zinc, calcium, and phosphorus on the basis of low cost and latent heat of transformation. Several new eutectic alloys and ternary intermetallic phases were determined. A new method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation. The method and apparatus are discussed and the experimental results are presented for aluminum and two aluminum-eutectic alloys. Candidate materials were evaluated to determine suitable materials for containment of the metal alloys. Graphite was used to contain the alloys during the volume change measurements. Silicon carbide was identified as a promising containment material and surface-coated iron alloys were also evaluated. System considerations that are pertinent if alloy eutectics are used as thermal energy storage media are discussed. Potential applications to solar receivers and industrial furnaces are illustrated schematically.

Birchenall, C. E.↗
NASA NTRS1982

Rotary Transformer Seals Power In

Rotary transformer originally developed for spacecraft transfers electrical power from stationary primary winding to rotating secondary without sliding contacts and very little leakage of electromagnetic radiation. Transformer has two stationary primary windings connected in parallel. Secondary, mounted on a shaft that extends out of housing, rotates between two windings of primary. Shaft of secondary is composed of electrically conducting inner and outer parts separated by an insulator. Electrical contact is made from secondary winding, through shaft, to external leads.

Studer, P. A.↗
NASA NTRS1980

Three dimensional spline-generated coordinate transformations for grids around wing-body configurations

A direct algebraic method was developed and applied to generate three dimensional grids around wing-body configurations. The method used is a generalized transfinite interpolation method which generates the desired coordinate transformation using geometric data only on the boundaries of the domain of interest. The geometric data that can be specified includes not only coordinates on the boundaries but also out-of-surface parametric derivatives that give a very precise control over the transformation in the vicinity of the surface. In addition to this, the method gives good control over the stretching of the mesh between different boundaries.

Eriksson, L. E.↗
NASA NTRS1980

An analytical transformation technique for generating uniformly spaced computational mesh

An analytical transformation method which can map arbitrary physical coordinate grid distribution into desired computational coordinate with uniform grid distribution is derived. The transformation function and its higher derivatives are differentiable. Salient features include; (1) precise control of grid sizes; (2) more than one location of clustered grids; (3) exact positioning of particular computational nodes in the physical plane; and (4) ensuring several patches of uniformly spaced grids in the physical plane for the higher accuracies (such as at the boundaries), etc., while keeping the variation of grid spacing continuous to avoid numerical instability.

Oh, Y. H.↗
NASA NTRS1980

Rapid correlation analysis in a group of motions and homogeneous scale transforms of the plane (M(2)xR sub +)

A method is proposed for picking out a given image, in a plane, irrespective of translations, rotations, and homogeneous scale transforms of the plane. The correlation integral is calculated, using the method of abstract harmonic analysis. In this case, and also for groups of translations, it is possible to carry out the calculations using the rapid Fourier transform. The latter fact makes it possible to substantially reduce the number of computer operations for calculating the correlation integral, as compared with direct methods.

Tkhabisimov, D. K.↗