Radiative mean life measurements using low energy beam-foil excitation
Radiative mean life measurements by low energy beam foil excitation, considering branching ratio of transition probabilities equal to unity
Chupp, E. L.↗
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Mean lives of excited levels in O I-O VI
Ion beam-foil produced oxygen spectra in wavelength range between 450 and 2200 A, determining mean radiative lives of O I - O VI excitation levels
Berry, H. G.↗
Estimation of the mean of a discrete parameter, covariance stationary, stochastic process in rotation sampling
Discrete parameter covariance stationary stochastic process in rotation sampling, deriving minimum variance unbiased linear population mean estimator by constrained optimization procedure
Nishikawa, K.↗
Investigation of the utility of mean square approximation systems and in system response predictions
A method is presented for estimating the variability of a system's natural frequencies arising from the variability of the system's parameters. The only information required to obtain the estimates is the member variability, in the form of second order properties, and the natural frequencies and mode shapes of the mean system. Several examples are worked out in detail to illustrate how the method is applied.
Bogdanoff, J. L.↗
Analytical and experimental investigation of circulation control by means of a turbulent Coanda jet
An analytical and experimental investigation of circulation control on a circular cylinder by means of tangential blowing (Coanda effect) is presented. The analytical method developed has also been used to estimate the blowing coefficients required for achieving potential flow on airfoils with flaps. The analysis is presented for conditions for which the flow in the boundary layer ahead of the jet exit is turbulent. The turbulent boundary layer and the jet layer on the upper surface, and the turbulent boundary layer on the lower surface are computed by a multi-strip integral method. The region of integration is between the correponding transition and separation points on each surface. Longitudinal curvature effects, which give rise to a radial pressure gradient across the jet layer and to an additional adverse tangential pressure gradient just upstream of the separation point, are included in the jet layer analysis in an approximate manner. The longitudinal curvature effect is found to have a pronounced influence on the separation of the jet layer.
Levinsky, E. S.↗
Energy levels and mean lives of Cl II to Cl VII.
Investigation of the spectra of chlorine between 500 and 2800 A using the beam-foil technique. Over 200 multiplets have been observed, many of which had not been reported earlier. A number of such transitions could be classified, and several new term values are proposed for Cl IV, Cl V, Cl VI , and Cl VII. Mean lives of various excited levels were measured for Cl II to Cl VII. The results are compared with theoretical calculations and other measurements in appropriate isoelectronic systems.
Bashkin, S.↗
Calibration of a laboratory spectrophotometer for specular light by means of stacked glass plates.
Stacked glass plates have been used to calibrate a laboratory spectrophotometer, over the spectral range 0.5-2.5 microns, for specular light. The uncalibrated instrument was characterized by systematic errors when used to measure the reflectance and transmittance of stacked glass plates. Calibration included first, a determination of the reflectance of a standard composed of barium sulfate paint deposited on an aluminum plate; second, the approximation of the reflectance and transmittance residuals between observed and computed values by means of cubic equations; and, finally, the removal of the systematic errors by a computer. The instrument, after calibration, was accurate to 1% when used to measure the reflectance and transmittance of stacked glass plates.
Allen, W. A.↗
Mean and fluctuating velocity contours and acoustic characteristics of subsonic and supersonic jets.
Mean and fluctuating velocity contours were determined for a convergent nozzle from surveys with impact pressure and piezoelectric pressure gauge probes, at Mach numbers of 0.6 to 1.4. For supersonic Mach numbers of 1.2 and 1.4, the length of the supersonic region increased as the square of the Mach number, and the peak pressure fluctuations occurred close to the sonic velocity contour. For subsonic Mach numbers of 0.6 to 1.0, the peak pressure fluctuations occurred in a toroidal region located approximately 4 to 6 diameters from the nozzle. The normalized sound power spectra for subsonic Mach numbers were similar, and for supersonic Mach numbers the power spectra shifted to the higher frequencies.
Nagamatsu, H. T.↗
Simplified method for measuring mean opacities and effective absorption coefficients.
Use of wide bandwidths and a number of path lengths to obtain mean opacities and effective absorption coefficients. This method is applicable if the temperatures and pressures at which these qualities are desired can be duplicated experimentally. Additional restrictions are that the gas in the experiments must be essentially isothermal, homogeneous, nonscattering, and in local thermodynamic equilibrium. The method is most advantageous in shock tube experiments and experiments utilizing a pulsed arc of cylindrical symmetry viewed axially.
Patch, R. W.↗
Mean lifetimes and equilibrium abundances in the fast CN cycle.
It is shown that the production of small nitrogen to carbon ratios is possible, in contrast to the equilibrium production in the ordinary CN cycle. Associated with such a production are high ratios of C-13/C-12 and of N-15/N-14. The final ratios depend on the conditions under which cessation of hydrogen burning occurs under astrophysical circumstances. A table showing proton capture mean lifetimes of CN nuclei is provided together with tables of the equilibrium abundances in a fast CN cycle. The ratios of final abundances of nitrogen to carbon as functions of temperature are also presented.
Caughlan, G. R.↗
The turbulent mean-flow, Reynolds-stress, and heat flux equations in mass-averaged dependent variables
The time-dependent, turbulent mean-flow, Reynolds stress, and heat flux equations in mass-averaged dependent variables are presented. These equations are given in conservative form for both generalized orthogonal and axisymmetric coordinates. For the case of small viscosity and thermal conductivity fluctuations, these equations are considerably simpler than the general Reynolds system of dependent variables for a compressible fluid and permit a more direct extension of low speed turbulence modeling to computer codes describing high speed turbulence fields.
Rubesin, M. W.↗
Evaluation of errors in prior mean and variance in the estimation of integrated circuit failure rates using Bayesian methods
The critical point of any Bayesian analysis concerns the choice and quantification of the prior information. The effects of prior data on a Bayesian analysis are studied. Comparisons of the maximum likelihood estimator, the Bayesian estimator, and the known failure rate are presented. The results of the many simulated trails are then analyzed to show the region of criticality for prior information being supplied to the Bayesian estimator. In particular, effects of prior mean and variance are determined as a function of the amount of test data available.
Fletcher, B. C.↗
Wave-mean flow interactions in the upper atmosphere
The nature of internal gravity waves is described with special emphasis on their ability to transport energy and momentum. The conditions under which these fluxes interact with the mean state of the atmosphere are described and the results are applied to various problems of the upper atmosphere, including the quasi-biennial oscillation, the heat budget of the thermosphere, the general circulation of the mesosphere, turbulence in the mesosphere, and the 4-day circulation of the Venusian atmosphere.
Lindzen, R. S.↗
Mean flow and turbulence measurements in a Mach 5 shear layer.
Hot-wire study of turbulent mixing in the near field of a Mach 5 jet with extension of the results into the hypersonic range. Mean and fluctuating measurement data are given for the free shear layer of the 10.6-cm diameter jet which was contained in a 61-by-61 cm vacuum chamber and exhausted into a diffuser 44 cm downstream of the jet exit. An auxiliary air supply was used to equalize the static pressures in the chamber and the nozzle. The nozzle wall boundary layer was turbulent at the jet exit, providing measurement data at higher Reynolds numbers, which are also included.
Morrisette, E. L.↗
Wave-mean flow interactions in the upper atmosphere.
The nature of internal gravity waves is described with special emphasis on their ability to transport energy and momentum. The conditions under which these fluxes interact with the mean state of the atmosphere are described, and the results are applied to various problems of the upper atmosphere, including the quasi-biennial oscillation, the heat budget of the thermosphere, the general circulation of the mesosphere, turbulence in the mesosphere, and even the '4-day' circulation of the Venusian stratosphere. It is the implied purpose of this paper to convey some of the thinking that has gone on about the role of gravity waves in the large-scale circulation of the upper atmosphere.
Lindzen, R. S.↗
Acoustic propagation in ducts with varying cross sections and sheared mean flow.
An analysis is presented of the wave propagation and attenuation in two-dimensional ducts with slowly varying cross sections which carry sheared mean flow. A uniformly valid asymptotic expansion of the acoustic waves is obtained in terms of the maximum slope of the wall by using the method of multiple scales. The result is a first-order differential equation describing the amplitude variation with the axial distance. This equation is used to evaluate the effects of variations of the duct cross section and growing boundary layers on the different acoustic modes.
Nayfeh, A. H.↗
Investigation of laser dynamics, modulation and control by means of intra-cavity time varying perturbation
Work continued on a number of projects aimed at the generation of tunable visible, infrared, and ultraviolet light; and on the control of this light by means of novel mode-locking and modulation techniques. Progress is summarized for the following projects: (1) the transient modelocking of the Nd:YAG laser and application of short optical pulses; (2) studies of the sodium-xenon excimer laser; (3) development of techniques for vacuum ultraviolet holography; and (4) studies of multiple photon pumped xenon and argon excimer lasers.
Harris, S. E.↗
Testing and evaluation of the LES-6 pulsed plasma thruster by means of a torsion pendulum system
Performance characteristics of the LES-6 pulsed plasma thruster over a range of input conditions were investigated by means of a torsion pendulum system. Parameters of particular interest included the impulse bit and time average thrust (and their repeatability), specific impulse, mass ablated per discharge, specific thrust, energy per unit area, efficiency, and variation of performance with ignition command rate. Intermittency of the thruster as affected by input energy and igniter resistance were also investigated. Comparative experimental data correlation with the data presented. The results of these tests indicate that the LES-6 thruster, with some identifiable design improvements, represents an attractive reaction control thruster for attitude contol applications on long-life spacecraft requiring small metered impulse bits for precise pointing control of science instruments.
Hamidian, J. P.↗