The twelve-year periodicities of the decametric radiation of Jupiter
Twelve year periodicities of Jupiter decametric radiation, noting correlation with Jupiter magnetic field rotation period
Carr, T. D.↗
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The stability of motion in a periodic cubic force field
Motion stability in periodic cubic force field, using nonliner differential equation integration with time periodic square wave function and Jacobian table
Bartlett, J. H.↗
Bifurcation limits for the existence of periodic orbits
Limiting bounds determination for existence of periodic orbits near known existing periodic orbit, presenting linear perturbation analysis
Pines, S.↗
Lunar gravity derived from long-period satellite motion, a proposed method
A method was devised to determine the spherical harmonic coefficients of the lunar gravity field. The method consists of a two-step data reduction and estimation process. Pseudo-Doppler data were generated simulating two different lunar orbits. The analysis included the perturbing effects of the L1 lunar gravity field, the earth, the sun, and solar radiation pressure. Orbit determinations were performed on these data and long-period orbital elements were obtained. The Kepler element rates from these solutions were used to recover L1 lunar gravity coefficients. Overall results of the experiment show that lunar gravity coefficients can be accurately determined and that the method is dynamically consistent with long-period perturbation theory.
Ferrari, A. J.↗
Second decrease in the period of the Vela Pulsar.
Preliminary analysis of the period discontinuities of the Vela Pulsar observed in 1969 and 1971. The fractional change in period for the 1971 discontinuity is -0.000002, slightly less than the magnitude of the previous change. The time span between the discontinuities is 2.50 plus or minus 0.03 yr; the uncertainty is determined by the time span between observations. It is pointed out that the Vela Pulsar could very well be as old as the supernova remnant Vela X (Shklovsky, 1970), which apparently surrounds the pulsar (Brandt et al., 1971).
Reichley, P. E.↗
Circadian periodicity of resistance to ionizing radiation in the pocket mouse.
Investigation of the response of pocket mice to Co 60 irradiation delivered at two times of day - namely, the predicted high and low points of the metabolic rate. The validity of torpor as an assay of the circadian period of body temperature in pocket mice and as a basis for selecting irradiation times is examined. A study is made of the mitotic activity in the pocket mouse intestinal epithelium as an example of a physiological rhythm which might influence radiation sensitivity. The results of tests in which pocket mice were exposed to ionizing radiation at two different times of day are cited. It is found that under the investigated conditions pocket mice irradiated during their metabolically active period (2330 hr) live significantly longer than those irradiated while their metabolic rate is low (0900 hr).
Lindberg, R. G.↗
Electromagnetic wave propagation and wave-vector diagram in space-time periodic media.
Analysis of TE and TM wave propagation in space-time periodic media such as dielectrics, isotropic plasmas and uniaxial plasmas. A numerical solution is obtained for media with sinusoidal periodicity. Wave-vector diagrams are plotted to facilitate studies of dipole radiation, wave propagation in waveguides and wave interactions with a half-space.
Elachi, C.↗
Critical current periodicity of Josephson junction interferometers.
Numerical calculation of the critical current through a Josephson junction interferometer, taking into consideration the effect of applied and self-induced magnetic fields on the junctions and in the interference loop. The periodicity of the interference pattern is shown to be less than the flux quantum. Quantitative results are given which illustrate the degree of deviation in periodicity from the flux quantum.
Stuehm, D. L.↗
Cerenkov and transition radiation in space-time periodic media.
The solution to the problem of determining the radiation emitted by a uniformly moving charged particle in a sinusoidally space-time periodic medium is obtained. The space-time periodicity can be considered as due to a strong pump wave and is expressed as a traveling-wave-type change in the dielectric constant or the plasma density. The solution covers also the limiting case of sinusoidally stratified media. The expression and spectrum of the radiated electromagnetic field are determined for different media: dielectric, isotropic and uniaxial plasma. Depending on the nature of the medium and the velocity of the particle, the radiated field is of the Cerenkov and/or transition type. The Brillouin diagram is used extensively in understanding and determining the nature, extent, and spectrum of the different modes of radiation, and a focusing effect is also studied.
Elachi, C.↗
An Exercise Prescription Intervention Program with Periodic Ergometric Grading
A long term exercise prescription type of physical conditioning program has been available to executive personnel of the NASA Manned Spacecraft Center for the past two years. Periodic ergometric testing with a heart rate controlled, automatically programmed, bicycle ergometer is used to follow the individual's progress and appropriately alter his exercise prescription from time to time. Such a program appears feasible, and acceptance is excellent, dropout rates small and periodic testing participation good. Subjects training diligently can maintain satisfactory levels of conditioning.
Owen, C. A.↗
Summary of Jovian latitude and rotation period observations from 1898 to 1970.
A ten-year summary of recent measurements of the latitudes of Jupiter's belts and the rotation periods of the various atmospheric currents is presented. Comparison of these measured values with earlier visual observations indicates that the latter are sufficiently accurate to provide a reliable and continuous record of latitudes since 1908 and rotation periods since 1898. A summary of the earlier observations is also given.
Reese, E. J.↗
The dynamic behavior of articulated pipes conveying fluid with periodic flow rate.
The plane motion of two rigid, straight articulated pipes conveying fluid is examined. In contrast to previous work, the flow rate is not taken as constant, but is allowed to have small periodic oscillations about a mean value, as would be expected in a pump-driven system. It is shown that in the presence of such disturbances, both parametric and combination resonances are possible. When the system can also admit loss of stability by static buckling or by flutter, it is found that the presence of small periodic disturbances constitutes a destabilizing effect. Floquet theory and converging infinite determinant expansions are used to illustrate a basic difference between systems which lose stability by divergence and those that lose stability by flutter. An algebraic criterion is obtained for the minimum amplitude of flow-rate oscillation required for the system to be affected by the presence of small disturbances.
Bohn, M. P.↗
Far field effects of weak spatially periodic inhomogeneities.
Small variations in the properties of an acoustic medium produce cumulative effects that significantly alter wave forms propagating over long distances. To investigate some aspects of these effects, without statistical models, the one-dimensional wave equation with a weak spatially periodic variation in the sound speed is treated. An approximation is developed valid for such weak inhomogeneities over large distances based upon the approximate treatment of a linear differential equation with a periodic coefficient. It is applied to the propagation of an initial step wave and identifies the dispersive nature of the medium which accounts for the cumulative effects.
Friedman, M. B.↗
Jupiter's decametric rotation period and the source-A emission beam
Determinations of the average decametric rotation period for the planet Jupiter are discussed. Mean rotation periods for a twelve year span are plotted as a function of the mean epochs. Two lesser peaks in the longitude histograms were resolved in addition to the main peak. The three peaks, which are believed to result from emission beams oriented in different directions relative to the corotating magnetic field of the planet, are designated Sources A, B, and C in decreasing order of prominence at frequencies in the vicinity of 18 MHz.
Carr, T. D.↗
Evaluation of wet tantalum capacitors after exposure to extended periods of ripple current, volume 1
The application of tantalum capacitors in the Viking Lander includes both dc voltage and ripple current electrical stress, high temperature during nonoperating times (sterilization), and high vibration and shock loads. The capacitors must survive these severe environments without any degradation if reliable performance is to be achieved. A test program was established to evaluate both wet-slug tantalum and wet-foil capacitors under conditions accurately duplicating actual Viking applications. Test results of the electrical performance characteristics during extended periods of ripple current, the characteristics of the internal silver migration as a function for extended periods of ripple current, and the existence of any memory characteristics are presented.
Watson, G. W.↗
A survey of possible missions to the periodic comets in the interval 1974 - 2010
Catalogs are developed to survey the mission possibilities for the short period comets. In the first the physical and pertinent orbital characteristics are given for 65 short period comets. The second catalog is one containing the predicted perihelia for each of the 65 comets between 1974 and 2010. Geometry is included to indicate feasibility of Earth-based observation and sighting within 100 days of perihelion. The comets are divided on the basis of size and activity into three groups from the data in the first catalog: primary, secondary and low interest. The perihelia are separated into two groups: satisfactory and not satisfactory on the basis of earth-comet distance.
Bender, D. F.↗
Micropulsation periods and the size of the magnetosphere
Using a set of 112 magnetopause locations selected from those obtained in recent years with the aid of Imp satellites on the dayside of the magnetosphere over 0600-1800 LT, extended results are presented on the problem of geomagnetic micropulsation periods in relation to magnetospheric parameters. These results include the finding that the two groups represented by micropulsation period ranges from 20 to 40 sec and from 40 to 80 sec, respectively, have a completely different dependence on the radial distance of the magnetopause from satellite experiments.
Patel, V. L.↗
Computer experiments on periodic systems identification using rotor blade transient flapping-torsion responses at high advance ratio
Computer experiments are described which used transient responses in flap-bending and torsion of a rotor blade at high advance ratio. It was found that a simple system identification method applying a linear sequential estimator also called equation of motion estimator, is suitable for this periodic system and can be used directly, if only the acceleration data are noise-polluted. In the case where noise is also present in the state-variable data, the direct application of the estimator gave poor results. However after prefiltering the data with a digital Graham filter having a cutoff frequency above the natural blade torsion frequency, the linear sequential estimator successfully recovered the parameters of the periodic coefficient analytical model.
Hohenemser, K. H.↗