Vibrational transfer functions for base excited systems
Computer program GD203 develops transfer functions to compute governing vibration environment for complex structures subjected to a base motion.
Ernst, C.↗
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Statistical energy methods Final report, 18 May 1969 - 18 May 1970
Statistical energy analysis for studying dynamic behavior of large, complex structures and acoustic spaces
Manning, J. E.↗
Snap dynamics
Computer program calculates normal vibration modes of complex structures elimating excessively large amounts of input data, run time, and core storage. Provision for accuracy improvement is also included.
Kiefling, L.↗
Rocket study of the X-ray background
The X-ray optical detection system flown on Aerobee 17.08 is described in detail, and the preliminary results of the 24 June 1971 flight are discussed. The optical design, fabrication and parabolic nature of the mirrors, effective aperture of mirror array, and X-ray detectors are considered. Preliminary analysis of data from the flight confirms the extended nature and complex structure of the X-ray source in Virgo. A core of X-ray emission is indicated which is approximately 0.5 deg in diameter and surrounded by an emitting region at least 2 deg across. The Virgo source spectrum is observed to have few low energy photons.
Fisher, P. C.↗
Synthesis of stiffness and mass matrices from experimental vibration modes.
With highly complex structures, it is sometimes desirable to derive a dynamic model of the system from experimental vibration data. This paper presents algorithms for synthesizing the mass and stiffness matrices from experimentally derived modal data in a way which preserves the physical significance of the individual mass and stiffness elements. The synthesizing procedures allow for the incorporation of other mass and stiffness data, whether empirical or based on the analyst's insight. The mass and stiffness matrices are derived for a cantilever beam example and are compared with those obtained using earlier techniques.
Ross, R. G., Jr.↗
Analysis of large-scale Martian topography variations. I - Data preparation from earth-based radar, earth-based CO2 spectroscopy, and Mariners 6 and 7 CO2 spectroscopy.
Using direct radar ranging of surface heights on Mars and spectrophotometric observations of absorptions produced by carbon dioxide molecules in the Martian atmosphere, data have been obtained on Martian topographical variations at spatial resolutions ranging from about 100 to 1000 km. These data have been studied and analyzed. As a result, a surface height contour map has been produced which clearly reveals a structural complex of blocks and basins whose distribution enhances the magnitude of low-degree surface harmonics. It is emphasized that Mars possesses unexpectedly pronounced topography which can have important geophysical consequences.
Wells, R. A.↗
Reduction of truncation errors in modal analysis
A condensation method and computer program are described for large discrete parameter vibration analysis of complex structures that greatly reduces truncation errors and provides accurate definition of modes in a selected frequency range. A dynamic transformation is obtained from the partitioned equations of motion that relates modes not explicitly in the condensed solution to the retained modes at a selected system frequency. The generalized mass and stiffness matrices, obtained with existing modal synthesis methods, are reduced using this transformation and solved. Revised solutions are then obtained using new transformations at the calculated eigenvalues and are also used to assess the accuracy of the results. Computations are made tractable by simplified forms of the transformation that result with various modal synthesis methods. Three examples using the dynamic transformation in conjunction with a General Electric stiffness coupling method and the method of Craig and Bampton indicate large reductions in truncation errors and demonstrate the method for sequential groups of modes.
Kuhar, E. J.↗
New laser technique for the identification of molecular transitions.
A laser technique is proposed which may be useful for the assignment of molecular spectra in the visible and infrared regions. The method is based on the resonant interaction of two monochromatic fields with a Doppler-broadened three-level system. Under the appropriate conditions the absorption line shape of one of the transitions shows a complex structure over a narrow section of the Doppler profile, and for sufficiently high laser power the line shape splits into a number of narrow peaks. Analysis of the resulting intensity pattern leads to unambiguous assignment of the angular momentum quantum numbers of the three levels involved. A simple set of rules is given to facilitate interpretation of spectra. The line shapes discussed are also relevant to monochromatic optical pumping of gases and unidirectional laser amplifiers.
Skribanowitz, N.↗
A dynamic transformation method for modal synthesis.
This paper presents a condensation method for large discrete parameter vibration analysis of complex structures that greatly reduces truncation errors and provides accurate definition of modes in a selected frequency range. A dynamic transformation is obtained from the partitioned equations of motion that relates modes not explicity in the condensed solution to the retained modes at a selected system frequency. The generalized mass and stiffness matrices, obtained with existing modal synthesis methods, are reduced using this transformation and solved. Revised solutions are then obtained using new transformations at the calculated eigenvalues and are also used to assess the accuracy of the results. If all the modes of interest have not been obtained, the results are used to select a new set of retained coordinates and a new transformation frequency, and the procedure is repeated for another group of modes.
Kuhar, E. J.↗
NASTRAN analysis of the 1/8-scale space shuttle dynamic model
The space shuttle configuration has more complex structural dynamic characteristics than previous launch vehicles primarily because of the high model density at low frequencies and the high degree of coupling between the lateral and longitudinal motions. An accurate analytical representation of these characteristics is a primary means for treating structural dynamics problems during the design phase of the shuttle program. The 1/8-scale model program was developed to explore the adequacy of available analytical modeling technology and to provide the means for investigating problems which are more readily treated experimentally. The basic objectives of the 1/8-scale model program are: (1) to provide early verification of analytical modeling procedures on a shuttle-like structure, (2) to demonstrate important vehicle dynamic characteristics of a typical shuttle design, (3) to disclose any previously unanticipated structural dynamic characteristics, and (4) to provide for development and demonstration of cost effective prototype testing procedures.
Bernstein, M.↗
Recognition of the geologic framework of porphyry deposits on ERTS-1 imagery
The author has identified the following significant results. Three major tectonic provinces have been mapped by geologic photointerpretation of ERTS-1 imagery over the Ok Tedi test site. These areas can be characterized as follows: (1) A broad area of low relief and mature topography suggesting a history of relative tectonic stability. (2) A narrow belt of moderate to high relief, broad open folds and prominent linear features. The Mount Fubilan-type porphyry copper deposits and recent volcanic effusive centers occur in this province. (3) A heterogeneous zone of high relief and high drainage density suggestive of relative structural complexity.
Wilson, J. C.↗
Using the NASTRAN Thermal Analyzer to simulate a flight scientific instrument package
The NASTRAN Thermal Analyzer has proven to be a unique and useful tool for thermal analyses involving large and complex structures where small, thermally induced deformations are critical. Among its major advantages are direct grid point-to-grid point compatibility with large structural models; plots of the model that may be generated for both conduction and boundary elements; versatility of applying transient thermal loads especially to repeat orbital cycles; on-line printer plotting of temperatures and rate of temperature changes as a function of time; and direct matrix input to solve linear differential equations on-line. These features provide a flexibility far beyond that available in most finite-difference thermal analysis computer programs.
Lee, H.-P.↗
Fabrication of composite fan blades using PMR A-type polyimide resin and graphite fiber reinforcement
PMR polyimides are safe, easy to handle, can be processed with relatively wide process controls, and offer excellent mechanical properties, with thermo-oxidative stability. Procedures, staging and cure schedules fully dense, crackfree, dimensionally controlled, complex structure: high tip speed fan blades 1.27 cm (0.5 in) thick.
Winters, W. E.↗
Meter-wavelength VLBI. I - Cassiopeia A
Very-long-baseline interferometric observations of the supernova remnant Cassiopeia A, at 74 MHz with a 12,000-wavelength baseline and at 111 MHz with a 18,500-wavelength baseline, are reported. The fringe amplitudes are strongly varying on a time scale of about 15 to 30 minutes, which is attributed to much the same complex structure as that observed at higher frequencies, plus one other compact source. Due to the poor (u, nu)-plane coverage, the location of the extra source can not be isolated unambiguously, but possibilities are suggested. The source must lie outside the supernova remnant shell, possibly associated with a concentration of emission north of the shell, or lying outside the gap in the northeastern side of the shell. The flux and spectral index deduced for the compact source depend on the assumed size, with a range of 100 Jy and 500 Jy at 74 MHz. If the source is associated with the supernova explosion, it must have been traveling at least 5000 km/sec.
Hutton, L. K.↗
The X-ray morphology of the Perseus cluster of galaxies
Results are reported for a sounding-rocket measurement of the spatial distribution of the X-ray flux from the Perseus cluster of galaxies in the range from 0.5 to 4.5 keV. Two scans (N-S and E-W) were made along the line of galaxies extending from NGC 1275 to IC 310. A flux maximum is observed which is coincident with the location of NGC 1275, but the X-ray distribution is shown to exclude just a point source. More broadening is detected in the E-W direction, and a comparison with other X-ray and optical data indicates a complex structure for the cluster. A three-component model is proposed in which the total X-ray luminosity of the cluster may be a combination of contributions from a central point source (NGC 1275), a condensed disk-like region oriented edge-on along the line of galaxies, and a more symmetric region extending out to at least 1 deg.
Wolff, R. S.↗
Effects of convection electric field on the distribution of ring current type protons
The topology of the boundaries of penetration (or, inversely, the boundaries of the forbidden regions) of 90-deg pitch-angle equatorial protons with energies less than 100 keV are explored for an equatorial convection E-field which is directed in general from dawn to dusk. Due to the dependence of drift path on energy (or magnetic moment), complex structural features are expected in the proton energy spectra detected by satellites since the penetration distance of a proton is not a monotonically increasing or decreasing function of energy. During a storm when the convection E is enhanced, model calculations predict elongations of the forbidden regions analogous to tail extensions of the plasmasphere. Following a reduction in the convection field, spiral-structured forbidden regions can occur. Structural features inherent to large-scale convection field changes may be seen in the nose-like proton spectrograms observed near dusk by instrumentation on Explorer 45. These nose events are modelled by using an electric field model developed originally by Volland (1973). The strength of the field is related to the Kp index through night-time equatorial plasmapause measurements.
Grebowsky, J. M.↗
A high-resolution map of the W3 region at far-infrared wavelengths
The area in the vicinity of the H II region W3 is mapped at an effective wavelength of 69 microns with high angular resolution (1 min) using the 102-cm balloon-borne telescope. The main continuum source, W3, shows a partially resolved complex structure with a FWHM size of 1.8 min. The radio sources W3(OH) and G133.8 + 1.4 are also observed as well as three faint sources not associated with known radio emission.
Fazio, G. G.↗
Disintegration phenomena in Comet West
Two peculiarities of Comet West, the multiple splitting of the nucleus as seen in telescope observations and the complex structure of the dust tail, are discussed. A method of analysis based on the premise that the observed rate of separation of a fragment from the principal nucleus is determined by the difference in effective solar attraction acting on the bodies is applied to investigate the motion of the four fragments that separated from the nucleus of Comet West. The predicted motion of the fragments is in good agreement with available observations. It is suggested that the 'synchronic' bands of the dust tail consist of tiny fragments from relatively large particles that burst after release from the comet. The unusual orientation of these bands and their high surface brightness relative to the diffuse tail are explained by a sudden increase in the particle acceleration and in the total scattering surface as the result of the disintegration of the larger particles.
Sekanina, Z.↗