Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “beta”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Short term prediction of E greater than or equal to 10 MeV proton fluxes from solar flares

Both the anisotropic and isotropic diffusion theories can be used to extrapolate proton fluxes for E greater than or equal to 10 meV for over 50% of the particle events. The isotropic diffusion theory uses a diffusion coefficient: D = Mr sup beta. It was found that M and beta tended to be functions of flare position on the solar disk. A measurement of the interplanetary flux in near earth space gives a good indication of the polar cap fluxes. It was found that the 30 MHz absorption over the poles during a PCA is proportional to the square root of the integral proton flux E greater than or equal to 11 meV in interplanetary space, J = KA squared, with K = 8 plus or minus 2 and J in protons/sq cm-sec-ster.

Kuck, G. A.↗
NASA NTRS1972

A study of B6 stars

A study of the spectra of zeta Draconis (B6 III), beta Sextantis (B6 V), and alpha Leonis (B7 V), was made from high dispersion spectrograms which cover the spectral region 3100 A to 6700 A and from OAO 2 spectral scans covering the spectral region 1100 A to 3600 A. Profiles, equivalent widths and central intensities of many lines in the spectrum of zeta Draconis are presented, as well as for the major lines of beta Sextantis. Alpha Leonis rotates too rapidly for these measurements to be made from high resolution spectrograms. Flux envelopes for zeta Draconis and alpha Leonis, from 1100 A to 6050 A, were derived from published spectrum scans and from new scans obtained with OAO 2. Estimates of the radii and masses of these single stars are presented.

Underhill, A. B.↗
NASA NTRS1971

Current driven electrostatic and electromagnetic ion cyclotron instabilities

Growth rates and parameter dependences are calculated for the current driven instabilities of electrostatic (with finite-beta corrections) and electromagnetic ion cyclotron waves. For 0.25 (T sub e)/(T sub i) 2.5, ion cyclotron waves have large growth rates, while ion acoustic waves are still stable. In fusion devices, where electrostatic waves may be stable, electromagnetic ion cyclotron waves are unstable for beta sub i 0.001.

Forslund, D. W.↗
NASA NTRS1970

Laminar wave train structure of collisionless magnetic slow shocks

The laminar wave train structure of collisionless magnetic slow shocks is investigated using two fluid hydromagnetics with ion cyclotron radius dispersion. For shock strengths less than the maximally strong switch-off shock, in the shock leading edge dispersive steepening forms a magnetic field gradient, while in the downstream flow dispersive propagation forms a trailing wave train; dispersion scale lengths are the ion inertial length if beta is smaller than 1 and the ion cyclotron radius if beta is greater than 1. In the switch-off slow shock leading edge, dispersion only produced rotations of the magnetic field direction; the gradient of the magnetic field magnitude, and hence the shock steepening length, is determined solely by resistive diffusion. The switch-off shock structure consists of a long trailing of magnetic rotations which are gradually damped by resistivity.

Coroniti, F. V.↗
NASA NTRS1971

Ordinary-mode electromagnetic instability in colliding plasma streams.

The instability of the electromagnetic linearly polarized mode propagating perpendicularly to the magnetic field is studied for a system composed of two colliding plasma streams, in each of which the electrons and ions are streaming at the same velocity. Using linearized Vlasov-Maxwell equations and allowing for anisotropic temperatures, it is found that in the presence of streaming ions the instability can occur in very low-beta plasmas. The plasma is increasingly susceptible to the electromagnetic instability with increasing values of beta, streaming velocity, temperature ratio of parallel to perpendicular electrons, and temperature ratio of perpendicular electrons to perpendicular ions.

Lee, K. F.↗
NASA NTRS1971

Individual variation in circadian rhythms of sleep, EEG, temperature, and activity among monkeys - Implications for regulatory mechanisms.

Investigation of circadian rhythms in a number of variables related to sleep, EEG, temperature, and motor activity in rhesus monkeys on an LD 12:12 schedule. Circadian rhythms were found to appear in each of 15 variables investigated. Statistical procedures assessed the variables for evidence of common regulation in these aspects of their circadian rhythms: acrophase (timing), amplitude (extent of change), and level (24-hr mean value). Patterns appearing in the data suggested that the circadian rhythms of certain variables are regulated in common. The circadian modulation of activity in the beta and sigma frequency bands of the EEG was correlated with statistical significance in acrophase, level, and amplitude. The delta frequency band appeared to be under circadian rhythm regulation distinct from that of the other bands. The circadian rhythm of REM stage sleep was like that of beta activity in level and amplitude. The data indicate that REM stage may share some common regulation of circadian timing with both stage 3-4 sleep and with temperature. Generally, however, the circadian rhythm of temperature appeared to bear little relation to the circadian rhythms of motor activity, EEG, or sleep.

Crowley, T. J.↗
NASA NTRS1972

Magnetic-field anomalies in the lunar wake.

The interplanetary magnetic field is only slightly perturbed by the presence of the moon in the solar-wind flow. A statistical study of the umbral increases and penumbral decreases and increases was conducted with variation of the solar-wind plasma beta value, the distance from the moon and the selenographic longitude of the limb regions of the lunar surface in the solar-wind flow. All lunar-wake anomalies show a strong positive correlation with the plasma beta value, whereas only penumbral increases show a marked variation with distance from the moon. There is no clear correlation of occurrence of penumbral anomaly with selenographic longitude of the exposed lunar limb in the solar-wind flow.

Whang, Y. C.↗
NASA NTRS1972

Synthesis of data obtained at Jicamarca, Peru, during the September 11, 1969, eclipse.

Results of continuous measurements of electron temperatures, electron concentrations, and vertical plasma drift made at Jicamarca during the Sept. 11, 1969, solar eclipse and of control measurements made on Sept. 13, 1969. Synthesis of the observed electron concentrations was made, using a model that solved the time-dependent electron-ion continuity equations. Ions O(-), NO(+), O2(+), and N2(+) were treated. Physical and chemical processes pertinent to the F region were considered in a realistic way. At noon, 300 km above Jicamarca, the values q = 290 per cu cm per sec for the O(+) production rate, beta = 1.94 x 0.0001 per sec for the loss coefficient, and H = 59 km for the atomic oxygen scale height were obtained. All large-scale features observed in the F2 region were synthesized by the model. This synthesis was not sensitive to a simultaneous 30% reduction of q and beta.

Sterling, D. L.↗
NASA NTRS1972

Mercury's perihelion advance - Determination by radar.

Measurement of echo delays of radar signals transmitted from earth to Mercury, yielding an accurate value for the advance of the latter's perihelion position. Given that the sun's gravitational quadrupole moment is negligible, the result in terms of the Eddington-Robertson parameters is (2 + 2 gamma-beta)/3 approximately equal to 1.005 plus or minus 0.007, where gamma = beta = 1 in general relativity, and where 0.007 represents the statistical standard error. Inclusion of the probable contribution of systematic errors raises the uncertainty to about 0.02.

Shapiro, I. I.↗
NASA NTRS1972

Asymptotic theory of a slender rotating beam with end masses.

The method of matched asymptotic expansions is employed to solve the singular perturbation problem of the vibrations of a rotating beam of small flexural rigidity with concentrated end masses. The problem is complicated by the appearance of the eigenvalue in the boundary conditions. Eigenfunctions and eigenvalues are developed as power series in the perturbation parameter beta to the 1/2 power, and results are given for mode shapes and eigenvalues through terms of the order of beta.

Whitman, A. M.↗
NASA NTRS1972

Longitudinal waves in a perpendicular collisionless plasma shock. IV - Gradient B.

The consideration of elastic waves in a Vlasov plasma of unmagnetized ions and magnetized electrons undergoing E x B electron drift and gradient B drift, pursued in the earlier three parts, is brought to conclusion in this last part of the longitudinal wave study in a collisionless plasma shock. Detailed calculations of the effects of the beta sub e dimensionless parameter on the E x B electron drift instability are presented. It is shown that the range of propagation of the elastic waves about the perpendicular remains quite narrow, and that, for oblique propagation, the already narrow angular range of unstable waves is decreased by increases in the value of the beta sub e dimensionless parameter. Also, increases in wave number generally reduce the growth rate and the angular range of propagation.

Gary, S. P.↗
NASA NTRS1972

Energy loss of fast electrons and positrons in a plasma.

Calculation of the stopping power of a plasma for fast electrons and positrons. First the classical limit is considered where beta = v/c is much less than alpha is the fine structure constant. Then the nonrelativistic Born-approximation formulas are derived; this domain corresponds to alpha much less than beta much less than 1. Finally, the general case of relativistic electrons and positrons is treated; in the relativistic case the scattering cross sections of Moller (electron-electron) and Bhabha (positron-electron) are used in the calculation. In all three energy domains the problem is broken up into cases of small and large momentum transfers. For large q, scattering off individual plasma electrons is considered, while in the limit of very small q for the quantum-mechanical domain, excitation of quantized plasma oscillations contributes to dE/dx; in the classical limit for small q the polarizability of the plasma provides the effective cutoff. The formulas for the stopping power differ slightly from those for a heavy ion going through a plasma because there are exchange effects and the fast electrons and positrons can lose a large fraction of their energy in one scattering off a plasma electron.

Gould, R. J.↗
NASA NTRS1972

Observations of the stellar Mg II resonance doublet at 2795 and 2802 A.

Spectrophotometry of the Mg II resonance doublet at 2795.5 and 2802.7 A has been performed for five stars with a balloon-borne telescope and spectrometer. Spectral resolution attained was between 0.25 and 0.5 A. A description of the payload and flight operations is given. In beta Lyr the Mg II doublet displayed P Cygni characteristics, while in gamma Lyr the doublet was observed only in absorption. The star beta Cas shows broad overlapping Mg II absorption lines with possible weak emission at the line bottom. In alpha CMi, both components of the doublet are seen in emission at the bottom of the broad absorption feature. The Mg II doublet in alpha Ori is entirely in emission, with each component showing distinct self-reversal.

Kondo, Y.↗
NASA NTRS1972

Gaseous hydrogen-induced cracking of Ti-5Al-2.5Sn.

Study of the kinetics of hydrogen-induced cracking in the Ti-5Al-2.5Sn titanium alloy, which has a structure of acicular alpha platelets in a beta matrix. The crack-growth rate at low stress-intensity levels was found to be exponentially dependent on stress intensity but essentially independent of temperature. The crack-growth rate at intermediate stress-intensity levels was found to be independent of stress intensity but dependent on temperature in such a way that crack-growth rate was controlled by a thermally activated mechanism having an activation energy of 5500 cal/mole and varied as the square root of the hydrogen pressure. The crack-growth rate at stress-intensity levels very near the fracture toughness is presumed to be independent of environment. The results are interpreted to suggest that crack growth at high stress intensities is controlled by normal, bulk failure mechanisms such as void coalescence and the like. At intermediate stress-intensity levels the transport of hydrogen to some interaction site along the alpha-beta boundary is the rate-controlling mechanism. The crack-growth behavior at low stress intensities suggests that the hydrogen interacts at this site to produce a strain-induced hydride which, in turn, induces crack growth by restricting plastic flow at the crack tip.

Williams, D. P.↗
NASA NTRS1972

Instability of ring current protons beyond the plasmapause during injection events.

The stability of ring current protons with an injection spectrum modeled by a loss cone distribution function is examined for typical ring current parameters. It is found that a quasi-electrostatic ion loss cone mode can be excited with frequencies just below and growth rates of the order of 0.01 times the ion plasma frequency. The instability is strongest in the moderate beta about equal to 1, low-density region just outside the plasmapause; for the beta much greater than 1 auroral regions and the high-density plasmasphere the mode is nearly stable. For the same ring current parameters the electromagnetic ion cyclotron wave is almost nonconvectively unstable, with growth rates of the order of 0.1 times the ion cyclotron frequency. The combination of the two unstable modes results in a large quasi-linear diffusion coefficient throughout most of the proton velocity space. Unless it is maintained by rapid inward convection, the ring current injection anisotropy will be reduced by diffusion toward the loss cone on time scales short in comparison to the minimum precipitation lifetime.

Coroniti, F. V.↗
NASA NTRS1972

On the mass-luminosity relation.

The results of a least-squares study of the mass-luminosity relation for eclipsing and visual binary stars consisting of main sequence components are presented. Two methods are discussed. First, the values of the coefficients A and B in the relation log M = A + BM sub BOL are determined. Then a technique which permits the determination of alpha and beta in the relation M = alpha L beta, when only the sum of the masses, and not the individual masses of each component, is known. The results and a comparison of the two methods are discussed. It is found that the following mass-luminosity relation represents the observational data satisfactorily: log M = 0.504 - 0.103 M sub BOL, -8 less than or equal to M sub BOL less than or equal to +10.5. A discussion of the data and of the possibility that separate mass-luminosity relations may exist for visual and eclipsing binaries is given. The possibility that more than one mass-luminosity relation is required in the range -8 less than or equal to M sub BOL less than or equal to +13 is also discussed.

Mccluskey, G. E., Jr.↗
NASA NTRS1972

Resistance of soil microorganisms to starvation.

Most groups of soil microorganisms died when exposed to prolonged starvation in a carbon-free solution, but the relative abundance of Bacillus and actinomycetes increased with time. Certain nonspore-forming bacteria also persisted. The ability of individual soil isolates to endure starvation in solution was not correlated with their glycogen content or rate of endogenous respiration. However, cells of the resistant populations were rich in poly-beta-hydroxybutyrate, whereas the starvation-susceptible bacteria generally contained little of this substance. Poly-beta-hydroxybutyrate was used rapidly in cells deprived of exogenous sources of carbon.

Chen, M.↗
NASA NTRS1972

A radar image of Venus.

Radar scans of Venus have yielded a brightness map of a large portion of the surface. The bright area in the south (alpha) and the twin such areas in the north (beta and delta) were first discovered by spectral analysis of radar echos. When range-gating is also applied, their shapes are revealed, and they are seen to be roundish and about 1000 km across. Although radar brightness can be the result of either intrinsic reflectivity or surface roughness, polarization studies show these features to be rough (to the scale of the wavelength, 12.5 cm). Dark, circular areas can also be seen, many with bright central spots. The dark areas are probably smooth. The blurring of the equatorial strip is an artifact of the range-Doppler geometry; all resolution disappears at the equator. Another artifact of the method is the 'ghost', in the south, of the images of beta and delta. Such ghosts appear only at the eastern and western extremes of the map.

Goldstein, R. M.↗