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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 433 records · Page 24

The analysis of Gemini 7 EEG data by three different computer oriented methods

The problem in assessment of electroencephalograms has been the subject element in visual evaluations of such records as well as the need for extensive training (2 or 3 years) before suitable candidate is capable to perform this task. There have been variety of computer type analyses of EEG during the past ten years or more, and we are still searching for a reliable, inexpensive, online data processing procedure for this task. We are aware our Soviet colleagues are routinely using computer assessment of EEGs, using relatively inexpensive hardware. In our report we endeavor to show how four different assessment procedures (visual assessment, zero crossing technique, smoothing and peak counting technique, and Weibull Statistic) may be utilized, and indicate the advantages and disadvantages peculiar to each. We wish to point out that in the Gemini 7 EEG analog records supplied to the Henry Ford Hospital, Channel II (mid-line central to mid-line occipital electrodes) could not be assessed reliably after approximately 26 hours of flight. Channel I (left central to left occipital electrodes) provided the more assessable EEG up to approximately 54 hours of flight. These channels were compared during the first 26 hours of flight, and no significant difference was found by our various assessment procedures. We, therefore, have limited this report to the findings on the analyses of Channel I during its approximate 54 hours of flight.

Proctor, L. D.↗

Mixing of supersonic jets including the effects of supersonic jets including the effects of transverse pressure gradient using difference methods

The usual boundary-layer equations describing the steady-state mixing of parallel jets are supplemented by the momentum equation in the direction normal to the flow. This allows detailed computation of the flow field in the mixing region and simultaneous computation of the outer inviscid flow. An explicit and an implicit finite difference scheme have been developed and applied in several illustrative examples. The examples include mixing of planar and axisymmetric supersonic jets of different composition with both matched and unmatched static pressures. Numerical results were compared with available experimental data obtained for the unmatched pressure case.

Kurkov, A. P.↗

Computational efficiency achieved by time splitting of finite difference operators.

A technique is presented for computing multidimensional time-dependent flow fields that avoids much of the inefficiency typically found in finite difference calculations. The technique initially divides the flow field into regions, each containing a mesh of general quadrilateral cells chosen to provide spatial resolution of the local features of the flow. A finite difference operator of second order accuracy, consisting of a sequence of one-dimensional operators (each operating at near maximum Courant-Friedrich-Lewy number) is then constructed for each region. Numerical results illustrating the technique for inviscid flows about simple bodies that generate shock waves, embedded shock waves, and expansion fans are presented and compared with exact theory.

Maccormack, R. W.↗

An implicit finite-difference solution to the viscous shock layer, including the effects of radiation and strong blowing

An implicit finite-difference scheme is developed for the fully coupled solution of the viscous, radiating stagnation-streamline equations, including strong blowing. Solutions are presented for both air injection and injection of carbon-phenolic ablation products into air at conditions near the peak radiative heating point in an earth entry trajectory from interplanetary return missions. A detailed radiative-transport code that accounts for the important radiative exchange processes for gaseous mixtures in local thermodynamic and chemical equilibrium is utilized in the study. With minimum number of assumptions for the initially unknown parameters and profile distributions, convergent solutions to the full stagnation-line equations are rapidly obtained by a method of successive approximations. Damping of selected profiles is required to aid convergence of the solutions for massive blowing. It is shown that certain finite-difference approximations to the governing differential equations stabilize and improve the solutions. Detailed comparisons are made with the numerical results of previous investigations. Results of the present study indicate lower radiative heat fluxes at the wall for carbonphenolic ablation than previously predicted.

Garrett, L. B.↗

Application of finite difference techniques to noise propagation in jet engine ducts

A finite difference formulation is presented for wave propagation in a rectangular two-dimensional duct without steady flow. The difference technique, which should be useful in the study of acoustically treated inlet and exhausts ducts used in turbofan engines, can readily handle acoustical flow field complications such as axial variations in wall impedance and cross section area. In the numerical analysis, the continuous acoustic field is lumped into a series of grid points in which the pressure and velocity at each grid point are separated into real and imaginary terms. An example calculation is also presented for the sound attenuation in a two-dimensional straight soft-walled suppressor.

Baumeister, K. J.↗

Influence of atmosphere pathlengths for different bands

The author has identified the following significant results. Comparison of ERTS-1 imagery in three bands (MSS-4, 5, and 7) acquired over southwestern Kansas on 1 Dec. 72 reveals that low solar altitude has a pronounced different effect on apparent scene illumination in different bands.

Haralick, R. M.↗

Transformation between orbital parameters in different coordinate systems of the general relativistic Schwarzschild problem.

The relationships between the osculating orbital elements for a family of solutions of the general relativistic Schwarzschild problems are developed. These relationships provide a method for evaluating orbital elements in different Schwarzschild coordinate systems without the necessity of fitting to real data every time the system of coordinates is changed. The objectivity of different coordinate systems is discussed. Considerations of orbital motions favor the standard Schwarzschild metric, but the propagation of light signals is more objective in the metric of Painleve. Because the orbital motions usually dominate the representation of data, the standard Schwarzschild coordinates are the best objective choice for most applications.

Georgevic, R. M.↗

Contribution to the acoustic study of theater auditoriums transformable for different types of productions

The auditorium of the Bucharest National Theater has been equipped with devices permitting it to be transformed into three functional types of rooms for different types of productions. In view of the purpose of the room (spoken theater) and the volume of the room (3,000-3,600 cu m 3) the optimum reverberation time is 0.95 sec at a frequency of 1,000 Hz. By applying the different types of acoustic treatment, a reverberation time ranging from 0.96 to 1.06 sec was obtained. The problem of flutter echoes in the arena was solved by applying semispherical bodies to the fixed ceiling. The level of noise transmitted to the auditorium was reduced down to the Cz25 curve.

Belea, R.↗

A finite difference method for the solution of the transonic flow around harmonically oscillating wings

A finite difference method for the solution of the transonic flow about a harmonically oscillating wing is presented. The partial differential equation for the unsteady transonic flow was linearized by dividing the flow into separate steady and unsteady perturbation velocity potentials and by assuming small amplitudes of harmonic oscillation. The resulting linear differential equation is of mixed type, being elliptic or hyperbolic whereever the steady flow equation is elliptic or hyperbolic. Central differences were used for all derivatives except at supersonic points where backward differencing was used for the streamwise direction. Detailed formulas and procedures are described in sufficient detail for programming on high speed computers. To test the method, the problem of the oscillating flap on a NACA 64A006 airfoil was programmed. The numerical procedure was found to be stable and convergent even in regions of local supersonic flow with shocks.

Ehlers, E. F.↗

Application of finite difference techniques to noise propagation in jet engine ducts

A finite difference formulation is presented for wave propagation in a rectangular two-dimensional duct without steady flow. The difference technique, which should be used in the study of acoustically treated inlet and exhausts ducts used in turbofan engines, can readily handle acoustical flow field complications such as axial variations in wall impedance and cross-section area. In the numerical analysis, the continuous acoustic field is lumped into a series of grid points in which the pressure and velocity at each grid point are separated into real and imaginary terms. An example calculation is also presented for the sound attenuation in a two-dimensional straight soft-walled suppressor.

Baumeister, K. J.↗

Differences in the spectra of cosmic ray nuclear species below approximately 5 GeV/nuc

Extension of previous measurements made at high energies, which show clear evidence for energy-dependent changes in cosmic ray composition, to lower energies. The new data point to the fact that these spectral differences extend over the entire energy band from a few hundred MeV/nucleon to several tens of GeV/nucleon. The details of these composition variations are examined by studying in a systematic way the variations of the ratios of secondary to primary and different groups of primary cosmic ray nuclei.

Webber, W. R.↗

Wave propagation in a random medium - A complete set of the moment equations with different wavenumbers

The propagation of waves in a random medium is studied in the 'quasi-optics' and the 'Markov random process' approximations. Under these assumptions, a Fokker-Planck equation satisfied by the characteristic functional of the random wave field is derived. A complete set of moment equations with different transverse coordinates and different wave numbers is then obtained from the Fokker-Planck equation of the characteristic functional. The application of those results to the pulse smearing of the pulsar signal and the frequency correlation function of the wave intensity in interstellar scintillation is briefly discussed.

Lee, L. C.↗

Determination of astronomical refraction near the horizon in different seasons of the year

The results are presented of astronomical refraction measurements for zenith distances of 80-90 degrees performed in different seasons with a two inch universal instrument. The differences between observed and calculated refraction were found to exhibit seasonal variations, and the results were compared with data of atmospheric aerologic soundings. The great departures in observed refraction from that calculated with the Pulkovo tables were ascribed to temperature gradient changes within the ground kilometer layer of atmosphere.

Vasilenko, N. A.↗

A study of three finite-difference schemes and their role in asynoptic meteorological data assimilation

An investigation was conducted concerning the response of various finite-difference schemes to the insertion of unweighted data. A simple barotropic model was employed as a forecast model. The Mintz-Arakawa two-level general circulation model was used as a source of data. The schemes tested include a Shuman scheme employing centered time differences and 9-point spatial smoothing. Two other schemes investigated were a Matsuno-TASU scheme and a semiimplicit scheme similar to one proposed by McPherson (1971).

Halberstam, I.↗

Seasonal vegetation differences from ERTS imagery

Knowledge of the times when crop and forest vegetation experience seasonally related changes in development is important in understanding growth and yield relationships. This article describes how densitometry of earth resources technology satellite (ERTS-1) multispectral scanner (MSS) imagery can be used to identify such phenological events. Adjustments for instrument calibration, aperture size, gray-scale differences between overpasses, and normalization of changing solar elevation are considered in detail. Seasonal vegetation differences can be identified by densitometry of band 5 (0.6-0.7 microns) and band 7 (0.8-1.1 microns) MSS imagery. Band-to-band ratios of the densities depicted the changes more graphically than the individual band readings.

Ashley, M. D.↗