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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Voltage feed through apparatus having reduced partial discharge

A voltage feed-through apparatus, having reduced partial discharge, has an electrical conductor and an electrical terminal connected thereto. A semiconductor sleeve surrounds the conductor for reducing the electric field concentration at the metallic conductor surface and consequently reducing the partial discharge occurrences. An insulator sleeve encircles the semiconductor sleeve. A metallic sleeve surrounds a portion of the terminal. Another insulator is connected to the metallic sleeve and surrounds a portion of the insulator sleeve forming a space therebetween. Another metallic sleeve spaced from the first metallic sleeve surrounds a portion of the other insulator.

Peck, S. R.↗
NASA NTRS1979

A device for determining the intensity of partial sweating

An invention which can measure partial perspiration is disclosed. The partial perspiration is measured with a specially shaped device tightly fastened to the body but not touching the skin area being studied. A special grid is used to keep the moisture-absorbing agent from touching the skin.

Rayskiy, V. A.↗
NASA NTRS1980

A new method of measuring radio source parameters of a partially polarized distributed source from spacecraft observations

An experimental system is analyzed which is designed to determine the angular and polarization properties of low frequency radio sources from measurements made on a spinning spacecraft. The system has been optimized to provide high accuracies for sources at high as well as low elevation angles. Theoretical expressions are derived for the response of this system to a partially polarized point source. Integrations are then carried out to get the system response to a uniform circular distributed source. Data processing techniques are derived so that computer simulations can be carried out to investigate the accuracy of this technique. It is shown that using 24 measurements of a partially polarized source (with Q = U = V = 0.5), taken in one spacecraft rotation, the resulting rms errors in angular position are less than one degree and the errors in determining the Stokes parameters are generally 1-10% for a wide range of source elevations.

Manning, R.↗
NASA NTRS1981

Analysis of effect of flameholder characteristics on lean, premixed, partially vaporized fuel-air mixtures quality and nitrogen oxides emissions

An analysis was conducted of the effect of flameholding devices on the precombustion fuel-air characteristics and on oxides of nitrogen (NOx) emissions for combustion of premixed partially vaporized mixtures. The analysis includes the interrelationships of flameholder droplet collection efficiency, reatomization efficiency and blockage, and the initial droplet size distribution and accounts for the contribution of droplet combustion in partially vaporized mixtures to NOx emissions. Application of the analytical procedures is illustrated and parametric predictions of NOx emissions are presented.

Cooper, L. P.↗
NASA NTRS1980

Free fall - A partial unique motion environment

Conditions leading to the elicitation of motion sickness have been divided into two main categories: partial motion environments, in which head movements are required to elicit motion sickness, and complete motion environments, in which independent movements of the head are not required for the production of symptoms. It is postulated that, according to this categorization, free fall constitutes a partial motion environment. In support of this hypothesis evidence is reviewed from Skylab missions, experiments in parabolic flight, and ground-based studies.

Graybiel, A.↗
NASA NTRS1981

Melt segregation from partially molten source regions - The importance of melt density and source region size

An investigation is conducted regarding the changes expected in the density contrast between basic melts and peridotites with increasing pressure using the limited data available on the compressibilities of silicate melts and data on the densities of mantle minerals. It is concluded that since compressibilities of silicate melts are about an order of magnitude greater than those of mantle minerals, the density contrast between basic melts and mantle minerals must diminish significantly with increasing pressure. An earlier analysis regarding the migration of liquid in partially molten source regions conducted by Walker et al. (1978) is extended, giving particular attention to the influence of the diminished density contrast between melt and residual crystals with increasing source region depth and to the influence of source region size. This analysis leads to several generalizations concerning the factors influencing the depths at which magmas will segregate from their source regions and the degrees of partial melting that can be achieved in these source regions before melt segregation occurs.

Stolper, E.↗
NASA NTRS1981

An experimental study of the flow in a wing with a partial span drooped leading edge

The flow field produced by a low aspect ratio wing (AR = 3.0) with a partial span leading edge droop was investigated in a series of low speed wind tunnel tests (Reynolds number based on 17.8 cm chord = 560,000). Photographs were obtained of surface oil flow patterns over an angle of attack range of alpha = 0 to 29 deg. Flow field surveys of the partially stalled wing at alpha = 25 deg were completed using a hot-wire probe, a split-film probe and a Conrad probe. The flow field survey data was presented using a color video display. The data indicated regions of apparent reversed flow in the separation region behind the wing and indicated the general cross-sectional shape of the separated wake flow.

Winkelmann, A. E.↗
NASA NTRS1982

Refined Monte Carlo method for simulating angle-dependent partial frequency redistributions

A refined algorithm for generating emission frequencies from angle-dependent partial frequency redistribution functions R sub II and R sub III is described. The improved algorithm has as its basis a 'rejection' technique that, for absorption frequencies x less than 5, involves no approximations. The resulting procedure is found to be essential for effective studies of radiative transfer in optically thick or temperature varying media involving angle-dependent partial frequency redistributions.

Lee, J.-S.↗
NASA NTRS1982

Radiative transfer with partial frequency redistribution in inhomogeneous atmospheres - Application to the Jovian aurora

A direct finite difference numerical solution for the equation of radiative transfer by the Feautrier method is developed for use in planetary atmospheres. The procedure described here uses a plane-parallel atmosphere, and can treat partial frequency redistribution, inhomogeneity, external or internal sources, and various boundary conditions. Isotropic scattering is assumed, but in the case of no frequency redistribution, Rayleigh scattering can also be handled. A program utilizing this method is tested in a variety of situations against more powerful and elaborate methods. The case of the Lyman alpha aurora on Jupiter is then considered, where the effects of partial frequency redistribution are shown to be of great importance. New results for the detailed line profiles for Lyman alpha in the Jovian aurora are presented. The method is quite versatile, and should be especially useful in studying a wide range of problems related to auroral or dayglow emissions in planetary atmospheres.

Gladstone, G. R.↗
NASA NTRS1981

Coding tradeoffs for improved performance of FH/MFSK systems in partial band noise

Partial band noise jamming can severely degrade the performance of frequency-hopped, M-ary frequency-shift keyed communciation systems. This paper illustrates the tradeoffs between channel coding, diversity, and block orthogonal (MFSK) modulation as a means of overcoming the advantage of worst case, non-adaptive (as opposed to repeat-back) partial band jamming. For ease of computation, the analysis relies on exponentially tight error bounds, and is based on a noncoherent detection metric that requires jamming state information for each hop. A more robust, less complex receiver structure which eliminates the jamming knowledge requirement is shown to degrade performance less than 2-1/2 dB. The coding tradeoffs discussed in this report are exemplified in the design of a hypothetical 32 kb/s military frequency-hopped communication link.

Levitt, B. K.↗
NASA NTRS1982

Boundary-fitted coordinate systems for numerical solution of partial differential equations - A review

A comprehensive review of methods of numerically generating curvilinear coordinate systems with coordinate lines coincident with all boundary segments is given. Some general mathematical framework and error analysis common to such coordinate systems is also included. The general categories of generating systems are those based on conformal mapping, orthogonal systems, nearly orthogonal systems, systems produced as the solution of elliptic and hyperbolic partial differential equations, and systems generated algebraically by interpolation among the boundaries. Also covered are the control of coordinate line spacing by functions embedded in the partial differential operators of the generating system and by subsequent stretching transformation. Dynamically adaptive coordinate systems, coupled with the physical solution, and time-dependent systems that follow moving boundaries are treated. References reporting experience using such coordinate systems are reviewed as well as those covering the system development.

Thompson, J. F.↗
NASA NTRS1984

Transfer Function Bounds for Partial-unit-memory Convolutional Codes Based on Reduced State Diagram

The performance of a coding system consisting of a convolutional encoder and a Viterbi decoder is analytically found by the well-known transfer function bounding technique. For the partial-unit-memory byte-oriented convolutional encoder with m sub 0 binary memory cells and (k sub 0 m sub 0) inputs, a state diagram of 2(K) (sub 0) was for the transfer function bound. A reduced state diagram of (2 (m sub 0) +1) is used for easy evaluation of transfer function bounds for partial-unit-memory codes.

Lee, P. J.↗
NASA NTRS1984

Area estimation using multiyear designs and partial crop identification

Statistical procedures were developed for large area assessments using both satellite and conventional data. Crop acreages, other ground cover indices, and measures of change were the principal characteristics of interest. These characteristics are capable of being estimated from samples collected possibly from several sources at varying times, with different levels of identification. Multiyear analysis techniques were extended to include partially identified samples; the best current year sampling design corresponding to a given sampling history was determined; weights reflecting the precision or confidence in each observation were identified and utilized, and the variation in estimates incorporating partially identified samples were quantified.

Sielken, R. L., Jr.↗
NASA NTRS1985

Film cooling on a convex wall: Heat transfer and hydrodynamic measurements for full and partial coverage

Turbine-blade cooling is an important issue for high-efficiency turbine engines, and discrete-hole injection is widely used as a cooling method. In the present study, detailed measurements were made of the heat transfer and hydrodynamics of a film-cooled flow on a convex wall, both for full and partial coverage. Two important parameters were altered: the blowing ratio, m, and the number of rows of injection holes. Three values of m were tested: m = 0.2, 0.4, and 0.6. In the blown region, m = 0.4 results in the lowest Stanton numbers of the three blowing ratios tested. This indicates that the value of m = 0.4 is near optimum on the convex wall from the point of view of cooling effect by injection. In the recovery region, Stanton numbers gradually approach the no injection values. Although the heat-transfer behavior during recovery from injection looks relatively complicated, the behavior of Stanton number can be explained in terms of two mechanisms: recovery from the thermal effect of injection and recovery from the turbulence augmentation. This interpretation of the data is supported by the hydrodynamic and temperture-profile measurements. For partial blowing cases, the data follow the full-coverage values inside the blown region. In the unblown region, both in the curved and in the flat plate, the effect of the number of blown rows is clearly seen. Hydrodynamic boundary-layer profiles were measured with the aid of a triple hot-water probe. Three mean-velocity components and six turbulence quantities were simultaneously measured, and inside the blown region strong three-dimensionality was observed.

Furuhama, K.↗
NASA NTRS1985

Small, two-stage, partial-admission turbine

The Rocketdyne Orbital Transfer Vehicle (OTV) cryogenic, rocket engine system, high pressure, liquid hydrogen turbopump was designed with a two-stage, partial-admission axial turbine. The turbine is basically two single-stage, partial-admission, subsonic impulse stages designed so the kinetic energy leaving the first-stage rotor is discharged directly into the second-stage nozzle at nominal operation to minimize staging losses. Very little data were available in the literature for this type of turbine design. Therefore, it was decided to test a full-size model of the turbine design using ambient-temperature gaseous nitrogen as the working fluid. The tester design features a variable orientation second-stage nozzle to determine the optimum circumferential location for highest performance. The tester also features the capability to vary the nozzle arcs of admission and incorporates quartz windows to study the flowfield upstream of the second-stage nozzle using a laser velocimeter. The test operations will probe the efficiency and flow characteristics for three arcs of admission and the effects of second-stage nozzle circumferential orientations over wide ranges of speed and pressure ratios as well as the interstage pressure distributions.

Sutton, R. F.↗
NASA NTRS1985

Strategies for FH/MFSK signaling with diversity in worst-case partial-band noise

Optimum diversity and worst-case partial-band noise jamming conditions have been derived for noncoherent energy detection of frequency-hopped (FH) M-ary frequency-shift keyed (MFSK) signals using a soft-chip decision suboptimum linear combining metric with perfect jamming-state side information. However, the assumption implicit in previous publications is that the error is first maximized over the jammer's partial-band duty factor for arbitrary diversity, and the result is then minimized over the amount of diversity. This paper shows that if the order of optimization is reversed, different conditions and performance are produced; that is, the previous solution is not a saddlepoint. This introduces some game-theoretic considerations for the communicator and the jammer, the risks and advantages of which are explored.

Levitt, B. K.↗
NASA NTRS1986

Analytic computation of energy derivatives - Relationships among partial derivatives of a variationally determined function

Formulas are presented relating Taylor series expansion coefficients of three functions of several variables, the energy of the trial wave function (W), the energy computed using the optimized variational wave function (E), and the response function (lambda), under certain conditions. Partial derivatives of lambda are obtained through solution of a recursive system of linear equations, and solution through order n yields derivatives of E through order 2n + 1, extending Puley's application of Wigner's 2n + 1 rule to partial derivatives in couple perturbation theory. An examination of numerical accuracy shows that the usual two-term second derivative formula is less stable than an alternative four-term formula, and that previous claims that energy derivatives are stationary properties of the wave function are fallacious. The results have application to quantum theoretical methods for the computation of derivative properties such as infrared frequencies and intensities.

King, H. F.↗