Correction for guessing in choice reaction time.
Correction for guessing in choice reaction time, giving additional results for Ollman choice reaction time performance model
Yellott, J. I., Jr.↗
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The Apollo docking system
Apollo docking system design considerations and preliminary models evaluation for best choice to meet requirements
Bloom, K. A.↗
The structure of shock wave in a gas consisting of ideally elastic, rigid spherical molecules
Principal approaches are examined to the theoretical study of the shock layer structure. The choice of a molecular model is discussed and three procedures are formulated. These include a numerical calculation method, solution of the kinetic relaxation equation, and solution of the Boltzmann equation.
Cheremisin, F. G.↗
New two-metric theory of gravity with prior geometry
A Lagrangian-based metric theory of gravity is developed with three adjustable constants and two tensor fields, one of which is a nondynamic 'flat space metric' eta. With a suitable cosmological model and a particular choice of the constants, the 'post-Newtonian limit' of the theory agrees, in the current epoch, with that of general relativity theory (GRT); consequently the theory is consistent with current gravitation experiments. Because of the role of eta, the gravitational 'constant' G is time-dependent and gravitational waves travel null geodesics of eta rather than the physical metric g. Gravitational waves possess six degrees of freedom. The general exact static spherically-symmetric solution is a four-parameter family. Future experimental tests of the theory are discussed.
Lightman, A. P.↗
Computer program for analysis of coupled-cavity traveling wave tubes
A flexible, accurate, large signal computer program was developed for the design of coupled cavity traveling wave tubes. The program is written in FORTRAN IV for an IBM 360/67 time sharing system. The beam is described by a disk model and the slow wave structure by a sequence of cavities, or cells. The computational approach is arranged so that each cavity may have geometrical or electrical parameters different from those of its neighbors. This allows the program user to simulate a tube of almost arbitrary complexity. Input and output couplers, severs, complicated velocity tapers, and other features peculiar to one or a few cavities may be modeled by a correct choice of input data. The beam-wave interaction is handled by an approach in which the radio frequency fields are expanded in solutions to the transverse magnetic wave equation. All significant space harmonics are retained. The program was used to perform a design study of the traveling-wave tube developed for the Communications Technology Satellite. Good agreement was obtained between the predictions of the program and the measured performance of the flight tube.
Connolly, D. J.↗
A contribution to computer analysis of coupled-cavity traveling wave tubes
A flexible accurate large-signal computer program has been developed for the design of coupled-cavity traveling wave tubes. The program is written for a TSS-360 time sharing system. The beam is described by a disk model and the slow wave structure by a sequence of cavities or cells. The computational approach is arranged so that each cavity may have different geometrical or electrical parameters than its neighbors. This allows the program user to simulate a tube of almost arbitrary complexity. Input and output couplers, severs, complicated velocity tapers, and other features peculiar to one or a few cavities may be modeled by a correct choice of input data. The beam-wave interaction is handled by a new approach in which the RF fields are expanded in solutions to the TM wave equation retaining all significant space harmonics. The program was used to perform a design study of the TWT developed for the CTS satellite. Good agreement was obtained between the predictions of the program and the measured performance of the flight tube. The internal check on power balance was satisfied within plus or minus 0.2 per cent of input beam power.
Connolly, D. J.↗
Basis for interpretation regarding the ages of the Serenitatis, Imbrium and Orientale events
One of the most important objectives of lunar study is to relate the lunar sample data to important lunar events. This paper utilizes as the basis of interpretation consideration of the following: (1) photogeologic data, (2) the choice of a cratering model, (3) estimates of temperature of impact ejecta and shock-induced heating, (4) petrologic data of lunar breccias and their thermal and shock history, and (5) meaningful age measurements. Both the author's interpretations and alternative views are discussed. The age of the Serenitatis event is not yet known. The interpreted age of the Imbrium event is between 3.90 and 3.84 Ga. The age of the Orientale event is 3.84 Ga.
Chao, E. C. T.↗
On the size of the cometary tail magnetic field
Ershkovich's (1978) criticism of previous arguments in favor of magnetic fields of approximately 100 gammas in cometary plasma tails are shown to be unjustified. It is argued that the folding velocity of tail streamers indicates a substantial tail magnetic field and that much of Ershkovich's disagreement stems from the choice of completely different models for a comet's plasma tail. It is concluded that the use of growth rates or phase-velocity information obtained from a dispersion relation to interpret large-amplitude disturbances, such as those in comet tails, is categorically incorrect.
Mendis, D. A.↗
The dielectric properties of soil-water mixtures at microwave frequencies
Recent measurements on the dielectric constants of soil-water mixtures show the existence of two frequency regions in which the dielectric behavior of these mixtures was quite different. At the frequencies of 1.4 GHz to 5 GHz, there were strong evidences that the variations of the dielectric (epsilon) with water content (W) depended on soil type. While the real part of epsilon for sandy soils rose rapidly with the increase in W, epsilon for the high-clay content soils rose only slowly with W. As a consequence, epsilon was generally higher for the sandy soils than for the high-clay content soils at a given W. On the other hand, most of the measurements at frequencies 1 GHz indicated the increase of epsilon with W independent of soil types. At a given W, epsilon' (sandy soil) approximately equals epsilon (high-clay content soil) within the precision of the measurements. These observational features can be satisfactorily interpreted in terms of a simple dielectric relaxation model, with an appropriate choice of the mean relaxation frequency f(m) and the range of the activation energy (beta). It was found that smaller f(m) and larger beta were required for the high-clay content soils than the sandy soils in order to be consistent with the measured data.
Wang, J. R.↗
Radius and brightness temperature observations of Titan at centimeter wavelengths by the Very Large Array
Brightness and radius measurements of the surface of Titan at 6, 2, and 1.3 cm wavelengths obtained with the Very Large Array radio interferometer are presented. Combined results for the three wavelengths indicate that the radius is 2400 + or - 250 km, implying a density of 2.4 + or - 0.7 g/cu cm, and that the brightness temperature is 87 + or - 9 K. The surface temperature may be somewhat higher if the emissivity is less than unity. The new data do not permit a choice between an inversion model for the atmosphere of Titan that predicts a surface temperature of 78 K and a model with both a stratospheric temperature inversion and a modest greenhouse effect that would increase the surface temperature by 10-40 K.
Jaffe, W.↗
The Sun among stars. IV - Albedos of Uranus and Neptune and the solar color
Geometric albedos in 48 adjacent 50 A bands from 3250 to 5600 A have been derived from observations of Uranus and Neptune. The solar analog found in earlier papers (Hardorp 1978, 1980) was chosen for these reductions, so these albedos are more reliable systematically than earlier ones and allow a choice among the scattering models of Savage et al. (1980). Green methane bands are stronger on Neptune. Strong solar absorption lines are found to be partially filled in by Raman-scattering. Neglect of this effect caused Croft et al. (1972) to find a solar color that is too blue. It probably also affected the classification of G-type stars in the Michigan Spectral Catalogue as well as Garrison's (1979) interpretation of IUE observations.
Hardorp, J.↗
Energy state revisited
Kaiser (1944) has introduced the concept of 'resultant height' in connection with aircraft minimum-time climbs. Its use as a state variable in trajectory work is attractive because it is a 'slower' variable than either altitude or velocity. Kelley (1972, 1973) has made an attempt to synthesize 'slow' state variables in connection with singular-perturbation procedures. In the present investigation, attempts are made to synthesize both 'fast' and 'slow' variables for the minimum-time-to-climb problem along lines explored by Kelley. Attention is given to climb equations, energy-modeling simplifications, 'slow'-variable choice, 'fast'-variable-choice considerations, a singular-perturbation analysis, the choice of a 'fast' variable, and the climb-dash problem.
Kelley, H. J.↗
Energy state revisited
Kaiser (1944) has introduced the concept of "resultant height' in connection with aircraft minimum-time climbs. Its use as a state variable in trajectory work is attractive because it is a "slower' variable than either altitude or velocity. Kelley (1972, 1973) has made an attempt to synthesize "slow' state variables in connection with singular-perturbation procedures. In the present investigation, attempts are made to synthesize both "fast' and "slow' variables for the minimum-time-climb problem along lines explored by Kelley. Attention is given to climb equations, energy-modeling simplifications, "slow'-variable choice, "fast'-variable-choice considerations, a singular-perturbation analysis, the choise of a "fast' variable, and the climb-dash problem.
Kelley, H. J.↗
Computational problems on composite grids
Most currently used algorithms for the numerical solution of the partial differential equations encountered in fluid flow problems can be implemented on composite grid systems. Finite volume formulations are easier to derive on composite grids, and may in principle be derived for partial differential equations of all types. Except when using Alternating Difference Implicit-type schemes, the overlapping of grids is an alternative to the more common grid construction procedure where grid lines continue smoothly from one subregion to the next. In the solution of model problems, the correct choice of an interpolation formula has been found able to reduce errors by a factor of two.
Mastin, C. W.↗
Evolution of the luminosity function of extragalactic objects
A nonparametric procedure for determining the evolution of the luminosity function (LF) of extragalactic objects is described. The following steps are required: (1) selection of complete samples with known observational selection effects, (2) choice of a cosmological model, (3) statistical analysis of the sample and determination of the evolution of the luminosity function, and (4) the use of the luminosity function for the determination of the formation rate and the physical evolution of the objects. When the present technique is applied to a sample of optically selected quasars with redshifts less than two, it is shown that the LF evolves more strongly for higher luminosities, indicating a larger quasar activity at earlier epochs and a more rapid evolution of the objects during their higher luminosity phases.
Petrosian, V.↗
A simplified orthotropic formulation of the viscoplasticity theory based on overstress
An orthotropic, small strain viscoplasticity theory based on overstress is presented. In each preferred direction the stress is composed of time (rate) independent (or plastic) and viscous (or rate dependent) contributions. Tension-compression asymmetry can depend on direction and is included in the model. Upon a proper choice of a material constant one preferred direction can exhibit linear elastic response while the other two deform in a viscoplastic manner.
Sutcu, M.↗
Transient nucleation induction time from the birth-death equations
For the set of finite-difference equations of Becker-Doering an exact formula for the induction time, which is expressed in terms of rapidly convergent sums, is presented. The form of the result is particularly amenable for analytical study, and the latter is carried out to obtain approximations of the exact expression in a rigorous manner and to assess its sensitivity to the choice of the nucleation model. The induction time is found to be governed by two main nucleation parameters, the normalized barrier height, and the number of molecules in the critical cluster. The ratio of these two parameters provides an assessment of the importance of discreteness effects. The exact expression is studied in both the continuous and the asymptotic limits. The accuracy of the Zeldovich equation, which is produced in the continuous limit, is discussed for several nucleation models.
Shneidman, Vitaly A.↗
ROSAT PSPC observations of NGC 4636: Interaction with Virgo gas ?
ROSAT Position Sensitive Proportional Counter (PSPC) observations of NGC 4636 have provided a deep image of the galaxy and its surroundings, which reveal the presence of emission well outside the optical galaxy. The source emission is measured out to r approximately 18 min, where the instrument support structure prevents us at this time from following it farther out. The nature of this emission is not fully understood, but could be evidence that the Virgo cluster gas extends as far out as this galaxy (greater than 3 Mpc from M87). Spectral analysis of the X-ray emission suggests a relatively cool (kT approximately 0.5 to 0.9 keV) interstellar medium, with temperatures increasing with radius. However, the detailed properties of the interstellar gas cannot be unambiguously determined with the present data, since the results we obtain depend strongly on the choice of the spectral model. Comparison of the spectral distributions in concentric annuli clearly indicates significant differences with radius, which can be parameterized as a general increase of the temperature. For low cosmic abundance models, kT varies from approximately 0.55 keV in the inner 1 min to approximately 0.8 keV at r approximately 6 to 8 min. Outside 8 min the average temperature is higher than in the inner region (kT approximately 0.8 to 1.2 keV) and the low-energy absorption is significantly lower. For 100% cosmic abundance and galactic line-of-sight absorption, multi-temperature fits are required, suggesting the possibility that the interstellar medi um is inhomogeneous.
Trinchieri, G.↗