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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Verification of the principle of equivalence for massive bodies

Analysis of 1389 measurements, accumulated between 1970 and 1974, of echo delays of laser signals transmitted from earth and reflected from cube corners on the moon shows gravitational binding energy to contribute equally to earth's inertial and passive gravitational masses to within the estimated uncertainty of 1.5%. The corresponding restriction on the Eddington-Robertson parameters is 4(beta) - gamma 3 = -0.001 plus or minus 0.015. Combination with other results, as if independent, yields values for beta and gamma in accord with general relativity.

Shapiro, I. I.↗
NASA NTRS1977

On the equivalence of polynomial GCD and squarefree factorization problems

It is shown that a closer reexamination of Yun's 1976 paper reveals the reducibility of SQFR to GCD. The natural question that follows is whether GCD is reducible to SQFR. That is answered affirmatively and the derivation actually suggests an algorithm for computing GCD's when input polynomials are already represented by their SQFR form.

Yun, D. Y. Y.↗
NASA NTRS1979

Equivalence of airborne and ground-acquired wheat canopy temperatures

The relationship between airborne and ground-based measurements of soil and crop canopy temperatures is investigated for a partial crop canopy. Daily ground-based measurements using a wide-field-of-view radiometer oriented towards the nadir at a height of 1.5 m and airborne thermal imagery at two-week intervals were obtained throughout the entire growing season of a stand of wheat. When corrected for atmospheric effects, the airborne measurements were found to be virtually identical to ground-based measurements, with a regression line slope of 0.985, a standard deviation of 1.8 C and a correlation coefficient of 0.97.

Millard, J. P.↗
NASA NTRS1981

Converting a digital filter to its analog equivalent

Two complementary methods for conversion are direct conversion method and inverse of Tustin's method. Required accuracy of filter is achieved using best-matched technique. Both require only direct computations and are simpler and more efficient than conventional iterative systems or methods requiring "ad hoc" filter parameter adjustment.

Lee, J. F. L.↗
NASA NTRS1980

Equivalent source modeling of the main field using Magsat data

A graphic software package was developed to plot the dipole positions for a particular model on a world map. An arrow is drawn at each dipole in the direction of the horizontal magnetization vector, with length proportional to the horizontal magnitude. A contouring package represents the radical component of the magnetization vector. Based on quiet Magsat data, several dipole models were derived. These are being verified against each other and against MGST (6/80) data set as to goodness of fit and stability of solution. The spatial power spectra computed from spherical harmonic expansions of the dipole models is being analyzed relative to crustal and core content. The power spectra for one of the dipole models and a spherical harmonic model based on Magsat data through degree and order 23 is presented.

Source record↗
NASA NTRS1981

Equivalent source modeling of the main field using Magsat data

Magsat dipole solution models were obtained with both 32 deg and 21 deg resolution based on a data set extending over 4 months. Time dependence was modeled using first time derivatives for the dipole magnetization vector components. This doubles the n total number of parameters in the solution. The solutions displayed a very slow convergence in time derivatives although at each iteration the conversion of the dipole parameters to spherical harmonic coefficients showed close agreement with the MGST (12/80) spherical harmonic model to degree 13 in the constant terms and 8 in the secular variation terms. The program error in the option to simultaneously estimate observatory anomaly biases was found and corrected. A 32 deg resolution dipole model was generated using the selected magnetic observatory data from 1960-1977 used in the GSFC (9/80) spherical harmonic model.

Source record↗
NASA NTRS1981

Equivalent source modeling of the main field using MAGSAT data

Modeling and software development of the main field using MAGSAT data is discussed. The cause of the apparent bulge in the power spectrum of Dipole model no. 4 was investigated by simulation with POGO crustal anomaly field model. Results for cases with and without noise, and the spectra of selected reslts are given. It is indicated that the beginning of the bump in the spectrum of Dipole no. 4 is due to crustal influence, while the departure of the spectrum from that of MGST (12/80-2) around expansion order 17 is due to the resolution limits of the Dipole density.

Source record↗
NASA NTRS1982

The equivalent angle-of-attack method for estimating the nonlinear aerodynamic characteristics of missile wings and control surfaces

A method has been developed for estimating the nonlinear aerodynamic characteristics of missile wing and control surfaces. The method is based on the following assumption: if a fin on a body has the same normal-force coefficient as a wing alone composed of two of the same fins joined together at their root chords, then the other force and moment coefficients of the fin and the wing alone are the same including the nonlinearities. The method can be used for deflected fins at arbitrary bank angles and at high angles of attack. In the paper, a full derivation of the method is given, its accuracy demonstrated and its use in extending missile data bases is shown.

Hemsch, M. J.↗
NASA NTRS1982

The damage equivalence of electrons, protons, and gamma rays in MOS devices

The results of laboratory tests to determine the radiation damage effects induced on MOS devices from Co-60, electron, and proton radiation are reported. The tests are performed to establish the relationship between the Co-60 gamma rays and the level of damage to the MOS devices in regards to different damages which can be expected with the electron and particle bombardments experienced in space applications. CMOS devices were exposed to the Co-60 gamma rays, 1 MeV electrons, and 1 MeV protons while operating at 3, 10, and 15 V. The test data indicated that the Co-60 source was reliable for an initial evaluation of the electron damages up to 2 MeV charge. A correction factor was devised for transferring the Co-60 measurements to proton damages, independent of bias and transistor types, for any orbit or environment.

Brucker, G. J.↗
NASA NTRS1984

An on-line equivalent system identification scheme for adaptive control

A prime obstacle to the widespread use of adaptive control is the degradation of performance and possible instability resulting from the presence of unmodeled dynamics. The approach taken is to explicitly include the unstructured model uncertainty in the output error identification algorithm. The order of the compensator is successively increased by including identified modes. During this model building stage, heuristic rules are used to test for convergence prior to designing compensators. Additionally, the recursive identification algorithm as extended to multi-input, multi-output systems. Enhancements were also made to reduce the computational burden of an algorithm for obtaining minimal state space realizations from the inexact, multivariate transfer functions which result from the identification process. A number of potential adaptive control applications for this approach are illustrated using computer simulations. Results indicated that when speed of adaptation and plant stability are not critical, the proposed schemes converge to enhance system performance.

Sliwa, S. M.↗
NASA NTRS1983

The strong equivalence principle and its violation

Theoretical and observational aspects of an SEP violation are discussed. A two-times theory is presented as a possible framework to handle an SEP violation, and tests performed to check the compatibility of such violation with a host of data ranging from nucleosynthesis to geophysics are summarized. Also discussed are the dynamical equations needed to analyze radar ranging data to reveal an SEP violation and in particular the method employed by Shapiro and Reasenberg (1976).

Canuto, V. M.↗