On the distorted-wave Magnus approximation in nonreactive molecular collision.
Distorted wave Magnus /DWM/ approximation for nonreactive molecular collisions, noting applicability in inelastic transition probabilities computation
Levine, R. D.↗
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A computer method for the determination of rational functions
Computer method for determination of rational functions using sums of exponential approximations
Lee, S. Y.↗
Chebyshev polynomial expansion of Bose- Einstein functions of orders 1 to 10.
Chebyshev series approximations for Bose- Einstein functions of orders one to ten, noting computability of Fermi-Dirac functions and polylogarithms
Devine, C. J.↗
A multiple-beam spherical reflector antenna
A spherical reflector with multiple feeds is considered for application in communications satellite systems. Data are presented which show that spherical reflectors possessing relatively high gain (40 db) and very small phase path error are feasible. A design of a spherical reflector utilizing corrugated horn feeds is considered. Radiation patterns are computed using the physical-optics technique. The designed antenna is approximately 60 lambda in diameter. Calculations performed for this antenna with three beams indicate that each beam has a gain of about 42 db, a beamwidth of 1.4 deg, and sidelobes that can be expected to be at least 28 db down. These results indicate that the feature of low sidelobes makes the spherical reflector a consideration for a multiple-beam communications satellite antenna.
Woo, R.↗
A comparison of land-use determinations using data from ERTS-1 and high altitude aircraft
A manual interpretation of ERTS-1 MSS system corrected imagery has been performed on a study area within the Houston Area Test Site to classify land use using the Level 1 categories proposed by the Department of the Interior. The two types of imagery used included: (1) black and white transparencies of each band enlarged to a scale of approximately 1:250,000 and (2) color transparencies composited from the computer compatible tapes using the film recorder on a multispectral data analysis station. The results of this interpretation have been compared with the 1970 land use inventory of HATS which was compiled using color ektachrome imagery from high altitude aircraft (scale 1:120,000). Urban data from the same scene was also analyzed using a computer-aided (clustering) technique. The resulting clusters, representing areas of similar content, were compared with existing land use patterns in Houston. A technique was developed to correlate the spectral clusters to specific urban features on aircraft imagery by the location of specific, high contrast objects in particular resolution elements. It was concluded that ERTS-1 data could be used to develop Level 1 and many Level 2 land use categories for regional inventories and perhaps to some degree on a local level.
Lundelius, M. A.↗
The particle resonance in spiral galaxies - Nonlinear effects.
A theory is developed to account for the nonlinear effects, near the particle resonance, found by numerical integration. There are four equilibrium points in the rotating frame of reference: two of them unstable, at the minima of potential (L1, L2), and two stable, at the maxima of potential (L4, L5). Many particles are trapped in librating orbits around L4, L5. Using the lowest-order terms of a 'third integral' of motion near L4, L5, the behavior of the trapped orbits is determined, and the approximate theoretical results are compared with the orbits found numerically by computer. An estimate of the trapped mass is given. It amounts to about 30% of the total mass between 9 and 11 kpc when the particle resonance is at r sub s = 10 kpc and the maximum force due to the spiral is 4% of the axisymmetric force. Some effects due to these mass concentrations are found numerically and theoretically.
Contopoulos, G.↗
Coronal magnetic structure at a solar sector boundary
The persistent large-scale coronal magnetic structure associated with a sector boundary appears to consist of a magnetic arcade loop structure extending from one solar polar region to the other in approximately the North-South direction. This structure was inferred from computer coronal magnetic field maps for days on which a stable magnetic sector boundary was near central meridian, based on an interplanetary sector boundary observed to recur during much of 1968 and 1969.
Wilcox, J. M.↗
Coronal magnetic structure at a solar sector boundary
A persistent large-scale coronal magnetic structure associated with a sector boundary is shown to consist probably of a magnetic arcade loop structure extending from one solar polar region to the other in approximately the north-south direction. This structure was inferred from computed coronal magnetic field maps for days on which a stable magnetic sector boundary was near the central meridian, based on an interplanetary sector boundary observed to recur during much of 1968 and 1969.
Wilcox, J. M.↗
Elastodynamic response of hollow balls
Review of the underlying fundamentals, the performance procedure, and the results of an elastodynamic stress and deformation analysis of hollow balls aimed at providing a clear definition of parametric influences for the development of hollow ball bearing technology. A simplified model is used as a first approximation, and contact stress distributions are obtained with the aid of computer programming and processing.
Ling, F. F.↗
Neural pulse frequency modulation of an exponentially correlated Gaussian process
The effect of NPFM (Neural Pulse Frequency Modulation) on a stationary Gaussian input, namely an exponentially correlated Gaussian input, is investigated with special emphasis on the determination of the average number of pulses in unit time, known also as the average frequency of pulse occurrence. For some classes of stationary input processes where the formulation of the appropriate multidimensional Markov diffusion model of the input-plus-NPFM system is possible, the average impulse frequency may be obtained by a generalization of the approach adopted. The results are approximate and numerical, but are in close agreement with Monte Carlo computer simulation results.
Hutchinson, C. E.↗
The use of the LANDSAT data collection system and imagery in reservoir management and operation
The author has identified the following significant results. An increase in the data collection system's (DCS) ability to function in the flood control mission with no additional manpower was demonstrated during the storms which struck New England during April and May of 1975 and August 1976. It was found that for this watershed, creditable flood hydrographs could be generated from DCS data. It was concluded that an ideal DCS for reservoir regulation would draw features from LANDSAT and GOES. MSS grayscale computer printout and a USGS topographic map were compared, yielding an optimum computer classification map of the wetland areas of the Merrimack River estuary. A classification accuracy of 75% was obtained for the wetlands unit, taking into account the misclassified and the unclassified pixels. The MSS band 7 grayscale printouts of the Franklin Falls reservoir showed good agreement to USGS topographic maps in total area of water depicted at the low water reservoir stage and at the maximum inundation level. Preliminary analysis of the LANDSAT digital data using the GISS computer algorithms showed that the radiance of snow cover/vegetation varied from approximately 20 mW/sq cm sr in nonvegetated areas to less than 4 mW/sq cm sr for densely covered forested area.
Cooper, S.↗
Evaluation of MOSTAS computer code for predicting dynamic loads in two bladed wind turbines
Calculated dynamic blade loads were compared with measured loads over a range of yaw stiffnesses of the DOE/NASA Mod-O wind turbine to evaluate the performance of two versions of the MOSTAS computer code. The first version uses a time-averaged coefficient approximation in conjunction with a multi-blade coordinate transformation for two bladed rotors to solve the equations of motion by standard eigenanalysis. The second version accounts for periodic coefficients while solving the equations by a time history integration. A hypothetical three-degree of freedom dynamic model was investigated. The exact equations of motion of this model were solved using the Floquet-Lipunov method. The equations with time-averaged coefficients were solved by standard eigenanalysis.
Kaza, K. R. V.↗
Evaluation of MOSTAS computer code for predicting dynamic loads in two-bladed wind turbines
Calculated dynamic blade loads are compared with measured loads over a range of yaw stiffnesses of the DOE/NASA Mod-0 wind turbine to evaluate the performance of two versions of the MOSTAS computer code. The first version uses a time-averaged coefficient approximation in conjunction with a multiblade coordinate transformation for two-bladed rotors to solve the equations of motion by standard eigenanalysis. The results obtained with this approximate analysis do not agree with dynamic blade load amplifications at or close to resonance conditions. The results of the second version, which accounts for periodic coefficients while solving the equations by a time history integration, compare well with the measured data.
Kaza, K. R. V.↗
A new payload integration method
This paper introduces a new payload integration method. The system equations of motion are derived in terms of interface-restrained booster and payload modes. These system equations are directly integrated, avoiding the solution of an expensive eigenvalue problem. A modified Newmark-Chan-Beta numerical scheme is used to perform this integration. Due to the unique form of the system equations it is possible to achieve significant savings. A similar savings is feasible for the computation of the internal loads. This new approach does not involve approximations. Although completely general, the presented technique is most effective when the number of interface degrees of freedom is relatively small. Both determinate and indeterminate interfaces are allowed.
Engels, R. C.↗
Some prospects for the future of computational fluid dynamics
For the oncoming decade it is anticipated that new generations of high-capacity and high-speed computers will appear and that some of them will be dedicated to fluid dynamics applications. An attempt is made here to examine the potential for a new generation of numerical techniques that will accompany the computer advances. Possibilities for improvement in solution techniques, grid adaptations, turbulence approximations, language constructions, and general code robustness are considered.
Lomax, H.↗
Effect of atmospheric scattering and surface reflection on upwelling solar radiation
A study is presented of the solar radiation transfer in the complete earth-atmosphere system, and numerical results are compared with satellite data obtained during the Earth Radiation Budget Experiment on Nimbus 6, in August, 1975. Emphasis is placed on the upwelling radiance distribution at the top of the atmosphere, assumed to be at 50 km. The numerical technique is based on the finite difference method, which includes azimuth and spectral variations for the entire solar wavelength range. Detailed solar properties, atmospheric physical properties, and optical properties are used. However, since the property descriptions are based on a trade-off between accuracy and computational realities, aerosol and cloud optical properties are treated with simple approximations. The radiative transfer model is in good agreement with the satellite radiance observations. The method provides a valuable tool in analyzing satellite- and ground-based radiation budget measurements and in designing instrumentation.
Suttles, J. T.↗
Layered synthetic microstructures as Bragg diffractors for X rays and extreme ultraviolet - Theory and predicted performance
The theory of X-ray diffraction by periodic structures is applied to the layered synthetic microstructures (LSMs) made possible by recent developments in thin film technology, and approximate formulas for estimating their performance are presented. A more complete computation scheme based on optical multilayer theory is also described, and it is shown that the diffracting properties may be tailored to specific applications by adjusting the refractive indices and thicknesses of the component layers. The theory may be modified to take account of imperfections in the LMS structure, and the properties of nonperiodic structures thereby computed. Structures with high integrated reflectivity constructed according to the methods defined have potential application in many areas of X-ray or EUV research and instrumentation.
Underwood, J. H.↗
Comparisons of free-flight experimental and predicted heating rates for the Space Shuttle
Experimental windward-ray heating rates measured during entry of the first Space Shuttle Orbiter mission are compared with predicted rates based on engineering and detailed equilibrium-air analyses. The experimental heating rates were reduced from temperature-time histories which are available only for the trajectory period after blackout which corresponds to a freestream Mach number and altitude of approximately 11.0 and 53 km, respectively. The experimental heating rates are computed for two measured emissivity data sets. The differences in the experimental heating rates based on the two emissivity data sets are sufficiently large that different interpretations of the STS-1 aerothermal environment may be inferred.
Zoby, E. V.↗