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  • Other Sources  (11,555)
  • NASA Technical Reports  (11,555)
  • FLUID MECHANICS AND HEAT TRANSFER  (3,947)
  • STRUCTURAL MECHANICS  (3,102)
  • INSTRUMENTATION AND PHOTOGRAPHY  (2,702)
  • SPACE RADIATION  (1,804)
  • 1985-1989  (7,027)
  • 1980-1984  (4,528)
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  • Other Sources  (11,555)
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  • NASA Technical Reports  (11,555)
Keywords
Years
Year
  • 1
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    Propagation and scattering of elastic waves in fiber-reinforced plates (1989)
    In:  CASI
    Details
    Publication Date: 2005-11-10
    Description: The objectives of this program are as follows: modelling of guided waves in fiber-reinforced plates in terms of different modes; and analysis of scattering by transverse cracks using modal representation. A hybrid numerical method combining the finite element representation of a region around the crack with the modal representation in the exterior region will be used in this program. Modes will be obtained using the through-the-thickness discretization of the displacement field.
    Keywords: STRUCTURAL MECHANICS
    Type: First Annual Symposium. Volume 1: Plenary Session; 15 p
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  • 2
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    Fluid management in space construction (1989)
    In:  CASI
    Details
    Publication Date: 2005-11-10
    Description: The low-g fluids management group with the Center for Space Construction is engaged in active research on the following topics: gauging; venting; controlling contamination; sloshing; transfer; acquisition; and two-phase flow. Our basic understanding of each of these topics at present is inadequate to design space structures optimally. A brief report is presented on each topic showing the present status, recent accomplishings by our group and our plans for future research. Reports are presented in graphic and outline form.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: First Annual Symposium. Volume 1: Plenary Session; 30 p
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  • 3
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    Proposed uses of laser light scattering instruments for polymerization studies (1989)
    In:  CASI
    Details
    Publication Date: 2006-06-11
    Description: Microgravity offers a unique environment for studying polymer diffusion and polymer polymerization reactions. The absence of convection currents, which are the major mode of mixing at the molecular level on Earth, are eliminated or reduced in the microgravity environment. More importantly, the prediction of unique copolymer composition development in microgravity allows controlled formation of new compositions of matter. The absence of mixing at the molecular level should produce unique short block copolymers available for the first time for comonomer compositions which normally lead to random or long block copolymer under good mixing. The investigation of fundamental polymer diffusion and polymer polymerization processes in microgravity is proposed. This effort will involve fundamental studies of monomer and polymer diffusion; their effects on initiation, propagation, and especially termination kinetics rate constant; and the accurate evaluation of copolymerization reactivity ratios in microgravity. The experimental design is presented for these studies along with an evaluation technique for in situ monitoring of polymer diffusion and polymerization kinetics.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Lewis Research Center, NASA Laser Light Scattering Advanced Technology Development Workshop, 1988; p 215-227
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  • 4
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    Light scattering instrumentation for micro gravity research (1989)
    In:  CASI
    Details
    Publication Date: 2006-06-11
    Description: The analysis of light scattered from an ensemble of particles has long been a preferred method for characterizing their physical properties. Instrumentation to perform the measurements which forms the basis for such analysis is available in many forms based upon a variety of different experimental techniques. A system is presented which is singularly applicable for making many types of measurements in a microgravity environment. The commercial version of this device, the DAWN-F, has been used in many labs throughout the world to perform analyses of particular importance for both research and production. Light scattering theory is reviewed and the structure and function of the system is described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Lewis Research Center, NASA Laser Light Scattering Advanced Technology Development Workshop, 1988; p 165-172
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  • 5
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    Photon counting modules using RCA silicon avalanche photodiodes (1989)
    In:  CASI
    Details
    Publication Date: 2006-06-11
    Description: Avalanche photodiodes (APD) are excellent small area, solid state detectors for photon counting. Performance possibilities include: photon detection efficiency in excess of 50 percent; wavelength response from 400 to 1000 nm; count rate to 10 (exp 7) counts per sec; afterpulsing at negligible levels; timing resolution better than 1 ns. Unfortunately, these performance levels are not simultaneously available in a single detector amplifier configuration. By considering theoretical performance predictions and previous and new measurements of APD performance, the anticipated performance of a range of proposed APD-based photon counting modules is derived.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Lewis Research Center, NASA Laser Light Scattering Advanced Technology Development Workshop, 1988; p 65-80
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  • 6
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    Miniature instrumentation for laser light scattering experiments (1989)
    In:  CASI
    Details
    Publication Date: 2006-06-11
    Description: Traditional optical systems for photon correlation spectroscopy and laser anemometry have relied upon physically large and fairly expensive lasers, bulk-optics such as lenses of a few inches diameter, large mechanical mounts and carefully selected, fragile and bulky photon counting photomultiplier detectors. In some cases, experimental fluid dynamics at a desired position in a flow, perhaps deep inside complex machinery, is physically impossible or very difficult. Similar problems exist with photon correlation spectroscopy, e.g., remote and heterodyne experiments. Various optical and electro optical components were investigated and characterized with the aim of replacing existing photon correlation laser spectroscopy and anemometry techniques in miniaturized form, and with significant cost reduction. Very recently, a range of miniature, modular light scattering systems were constructed from little solid state optical and electro optical components, and experimentally verified measurement performance comparable to standard lab photon correlation spectroscopy and laser anemometry equipment.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, Lewis Research Center, NASA Laser Light Scattering Advanced Technology Development Workshop, 1988; p 45-63
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  • 7
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    Critical transport parameters for porous media subjected to counterflow (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Experimental and theoretical studies have been conducted to determine critical parameters at the onset of nonlinear counterflow in He II below the lambda point of He-4. Critical temperature differences have been measured in porous media for zero net mass flow and for Darcy permeabilities in the order of magnitude range from 10 to the -10th to 10 to the -8th sq cm. The normalized critical temperature gradients, which covered the liquid temperature range of 1.5 K to the lambda temperature, are found to vary with T proportional to the ratio of the superfluid density to the normal fluid density. This liquid temperature dependence appears to be consistent with duct data which are limited at low temperature by a Reynolds number criterion.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Cryogenics (ISSN 0011-2275); 29; 498-502
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  • 8
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    Millimeter-wave sensor image enhancement (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Images from an airborne, scanning radiometer operating at a frequency of 98 GHz have been analyzed. The millimeter-wave images were obtained in 1985-1986 using the JPL millimeter-wave imaging sensor. The goal of this study was to enhance the information content of these images and make their interpretation easier. A visual-interpretative approach was used for information extraction from the images. This included application of nonlinear transform techniques for noise reduction and for color, contrast, and edge enhancement. Results of using the techniques on selected millimeter-wave images are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 9
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    The cosmic microwave background (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Recent observational and theoretical investigations of the cosmic microwave background radiation (CMBR) are reviewed. Particular attention is given to spectral distortions and CMBR temperature anisotropies at large, intermediate, and small angular scales. The implications of the observations for inflationary cosmological models with curvature fluctuation are explored, and it is shown that the limits determined for intermediate-scale CMBR anisotropy almost rule out a baryon-dominated cosmology.
    Keywords: SPACE RADIATION
    Type: New York Academy of Sciences, Annals (ISSN 0077-8923); 571; 44-61
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  • 10
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    Analysis of turbulence in shear flows using the stabilization principle (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An analysis is made based upon the concept that the velocity fluctuations, and therefore, the Reynolds stresses, driven by the instability of the original flow grow until a new stable state is approached. The Reynolds stresses incorporated into the Orr-Sommerfeld equation are coupled with the main flow such that all the imaginary parts of the complex eigenvalues vanish, i.e., the original instability is eliminated. Using this stabilization principle, it is possible to find the Reynolds stresses as well as the mean velocity for plane Poiseuille flow with the Reynolds number slightly higher than the critical.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Mathematical and Computer Modelling (ISSN 0895-7177); 12; 8, 19
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  • 11
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    Solution and sensitivity analysis of a complex transcendental eigenproblem with pairs of real eigenvalues (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper considers complex transcendental eigenvalue problems where one is interested in pairs of eigenvalues that are restricted to take real values only. Such eigenvalue problems arise in dynamic stability analysis of nonconservative physical systems, i.e., flutter analysis of aeroelastic systems. Some available solution methods are discussed and a new method is presented. Two computational approaches are described for analytical evaluation of the sensitivities of these eigenvalues when they are dependent on other parameters. The algorithms presented are illustrated through examples.
    Keywords: STRUCTURAL MECHANICS
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  • 12
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    On the reverse flow ceiling jet in pool fire-ventilation crossflow interactions in a simulated aircraft cabin interior (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The behavior of the reverse flow ceiling jet against the ventilation flow from 0.58 to 0.87 m/s was investigated in a 1/3 scale model of a wide body aircraft interior. For all tests, strong reverse-flow ceiling jets of hot gases were detected well upstream of the fire. Both thicknesses of the reverse-flow ceiling jet and the smoke layer increased with the fire-crossflow parameter. The thickness of the smoke layer where the smoke flows along the main flow below the reverse-flow ceiling jet was almost twice that of the reverse-flow ceiling jet. Detailed spatial and time-varying temperatures of the gas in the test section were measured, and velocity profiles were also measured using a temperature compensated hot film.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 13
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    Interactions in boundary-layer transition (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Certain theoretical studies of boundary-layer transition are described, based on high Reynolds numbers and with attention drawn to the various nonlinear interactions and scales present. The article concentrates in particular on theories for which the mean-flow profile is completely altered from its original state. Two- and three-dimensional flow theory and conjectures on turbulent-boundary-layer structures are included. Specific recent findings noted, and in qualitative agreement with experiments, are: nonlinear finite-time break-ups in unsteady interactive boundary layers; strong vortex/wave interactions; and prediction of turbulent boundary-layer displacement- and stress sublayer-thicknesses.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 14
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    Comparative study of high-resolution shock-capturing schemes for a real gas (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 27; 1332-134
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  • 15
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    Three-dimensional analysis of a postbuckled embedded delamination (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Delamination growth caused by local buckling of a delaminated group of plies was investigated. Delamination growth was assumed to be governed by the strain energy release rates, G(1), G(2) and G(3). The strain energy release rates were calculated using a geometrically nonlinear three-dimensional finite element analysis. The program is described and several checks of the analysis are discussed. Based on a limited parametric study, the following conclusions were reached: (1) the problem is definitely mixed mode (in some cases G(1) is larger than G(2), for other cases the opposite is true); (2) in general, there is a large gradient in the strain energy release rates along the delamination front; (3) the locations of maximum G(1) and G(2) depend on the delamination shape and the applied strain; (4) the mode 3 component was negligible for all cases considered; and (5) the analysis predicted that parts of the delamination would overlap. The results presented did not impose contact constraints to prevent overlapping. Further work is needed to determine the effects of allowing the overlapping.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composite Materials (ISSN 0021-9983); 23; 862-889
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  • 16
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    Application of multi-grid methods for solving the Navier-Stokes equations (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper presents the application of a class of multi-grid methods to the solution of the Navier-Stokes equations for two-dimensional laminar flow problems. The methods consists of combining the full approximation scheme-full multi-grid technique (FAS-FMG) with point-, line- or plane-relaxation routines for solving the Navier-Stokes equations in primitive variables. The performance of the multi-grid methods is compared to those of several single-grid methods. The results show that much faster convergence can be procured through the use of the multi-grid approach than through the various suggestions for improving single-grid methods. The importance of the choice of relaxation scheme for the multi-grid method is illustrated.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Institution of Mechanical Engineers, Proceedings, Part C - Journal of Mechanical Engineering Science (ISSN 0954-4062); 203; C4, 1; 255-265
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  • 17
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    A method for using a time interval counter to measure frequency stability (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is shown how a commercial time interval counter can be used to measure the relative stability of two signals that are offset in frequency and mixed down to a beat note of about 1 Hz. To avoid the dead-time problem, the counter is set up to read the time interval between each beat note upcrossing and the next pulse of a 10 Hz reference pulse train. The actual upcrossing times are recovered by a simple algorithm whose outputs can be used for computing residuals and Allan variance. A noise floor-test yielded a delta f-f Allan deviation of 1.3 times 10 to the minus 9th power/tau relative to the beat frequency.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (ISSN 0885-3010); 36; 478-480
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  • 18
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    Wave propagation in a thin cylinder that includes point masses (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The propagation of elastic waves of the type induced by impact are studied for a special class of cylinders. In this class are thin finite cylinders, for which Mindlin's equations are appropriate, on which point masses are attached. An approximation is derived valid for frequencies below cutoff of the lowest shear mode. An eigenfunction expansion is used to compute the transient response of the coupled system.
    Keywords: STRUCTURAL MECHANICS
    Type: Acoustical Society of America, Journal (ISSN 0001-4966); 85; 759-767
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  • 19
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    Adaptation of boundary elements to the dynamics of elastic solids (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The method of boundary elements is adapted to the dynamics of elastic axisymmetric solids. Three scalar potentials are used, each satisfying the Helmholtz equation and each represented by its own source distribution. The sources are distributed over a surface enclosing the solid boundary. Stress or displacement conditions on the boundary are realized by third-order derivatives of the potentials. Discrete ring elements on the source enclosure combine their influences at discrete ring elements on the solid boundary.
    Keywords: STRUCTURAL MECHANICS
    Type: Acoustical Society of America, Journal (ISSN 0001-4966); 85; 753-758
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  • 20
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    Distortion of homogeneous turbulence by axisymmetric strain and dilatation (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Rapid distortion theory is applied to study distortion of homogeneous turbulence subject to two different axisymmetric strain modes: the axisymmetric contraction (AC, nozzle-type flow), and the axisymmetric expansion (AE, diffuser-type flow). The paper explores the differences in effects of the two axisymmetric strain modes on the anisotropy of correlations and structures of turbulence; examines the effect of dilatation on the distortion of turbulence; and provides a theoretical background for turbulence model development. It is found that velocity and vorticity fluctuations are enhanced more efficiently by contraction than by expansion; contraction produces much higher anisotropy in velocity and vorticity than expansion; root-mean-square pressure is slightly reduced during contraction, whereas it increases rapidly during expansion; and vortical structures of rodlike shape develop in a contraction flow, while disklike structures develop in an expansion flow. A simple model that reflects the dependence of turbulence evolution on structural parameters such as the Reynolds-stress anisotropy and total strain is proposed, and is shown to outperform all other models for all cases examined, regardless of the mean strain rate.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids A (ISSN 0899-8213); 1; 1541-155
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  • 21
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    Calculation of structural dynamic forces and stresses using mode acceleration (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: While the standard mode acceleration formulation in structural dynamics has often been interpreted to suggest that the reason for improved convergence obtainable is that the dynamic correction factor is divided by the modal frequencies-squared, an alternative formulation is presented which clearly indicates that the only difference between mode acceleration and mode displacement data recovery is the addition of a static correction term. Attention is given to the advantages in numerical implementation associated with this alternative, as well as to an illustrative example.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 12; 760-762
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  • 22
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    Transition limits for water-droplet crystallization with the NASA Lewis icing nozzle (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Aircraft (ISSN 0021-8669); 26; 887
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  • 23
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    Experimental comparison of two hot-wire techniques in supersonic flow (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA Journal (ISSN 0001-1452); 27; 1074-108
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  • 24
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    Near-wall k-epsilon turbulence modeling (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 27; 1068-107
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  • 25
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    An improved correction algorithm for number density measurements made with the forward scattering spectrometer probe (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A correction factor to the number density measured by the Forward Scattering Spectrometer Probe (FSSP) which compensates for dead time and coincidence errors was determined by calculating the probabilities of, and the average number of particles in, the six possible types of dead time and coincidence events. These probabilities and averages were calculated by means of a probabilistic model based on Poisson statistics. A Monte Carlo computer simulation of the FSSP operation was also carried out and the number density correction factor was compared with the Monte Carlo data. For an actual number density of 2000/cu cm, it was found that the measured number density was of the order of 300/cu cm.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments (ISSN 0034-6748); 60; 1143-115
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  • 26
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    Computational aspects of sensitivity calculations in transient structural analysis (1989)
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    Publication Date: 2011-08-19
    Description: A key step in the application of formal automated design techniques to structures under transient loading is the calculation of sensitivities of response quantities to the design parameters. This paper considers response quantities to the design parameters. This paper considers structures with general forms of damping acted on by general transient loading and addresses issues of computational errors and computational efficiency. The equations of motion are reduced using the traditional basis of vibration modes and then integrated using a highly accurate, explicit integration technique. A critical point constraint formulation is used to place constraints on the magnitude of each response quantity as a function of time. Three different techniques for calculating sensitivities of the critical point constraints are presented. The first two are based on the straightforward application of the forward and central difference operators, respectively. The third is based on explicit differentiation of the equations of motion. Condition errors, finite difference truncation errors, and modal convergence errors for the three techniques are compared by applying them to a simple five-span-beam problem. Sensitivity results are presented for two different transient loading conditions and for both damped and undamped cases.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 32; 2, 19; 433-443
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  • 27
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    Finite-element grid improvement by minimization of stiffness matrix trace (1989)
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    Publication Date: 2011-08-19
    Description: A new and simple method of finite-element grid improvement is presented. The objective is to improve the accuracy of the analysis. The procedure is based on a minimization of the trace of the stiffness matrix. For a broad class of problems this minimization is seen to be equivalent to minimizing the potential energy. The method is illustrated with the classical tapered bar problem examined earlier by Prager and Masur. Identical results are obtained.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 31; 6, 19; 891-896
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  • 28
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    Acoustic temperature profile measurement technique for large combustion chambers (1989)
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    Publication Date: 2011-08-19
    Description: Measurement of times of flight of sound waves can be used to determine temperatures in a gas. This paper describes a system, based on this principle, that is capable of giving the temperature profile in a nonisothermal gas volume, for example, prevalent in a large furnace. The apparatus is simple, rugged, accurate, and capable of being automated for process control applications. It is basically an acoustic waveguide where the outside temperature profile is transferred to a chosen gas contained inside the guide.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 111; 461-466
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  • 29
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    Ellipsometric method for the measurement of temperature and optical constants of incandescent transition metals (1989)
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    Publication Date: 2011-08-19
    Description: The development of a unique noncontact temperature measurement device utilizing rotating analyzer ellipsometry is described. The technique circumvents the necessity of spectral emissivity estimation by direct measurement concomitant with radiance brightness. Simultaneous determinations of dielectric constants and refractive indices allow changes in the physical and chemical state of a heated surface to be monitored. The results of optical property measurements at 633 nm as functions of temperature between 1000 and 2500 K for eight transition metals including Hf, Ir, Mo, Nb, Pd, Pt, Ta, and V are presented together with preliminary results of oxidation studies on iridium.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 28; 1885-189
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  • 30
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    Probabilistic structural analysis to quantify uncertainties associated with turbopump blades (1989)
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    Publication Date: 2011-08-19
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 27; 809-813
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  • 31
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    Numerical simulation of axisymmetric turbulent flow in combustors and diffusers (1989)
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    Publication Date: 2011-08-19
    Description: Numerical studies of turbulent flow in an axisymmetric 45-deg-expansion combustor and bifurcated diffuser are presented. The Navier-Stokes equations incorporating a k-epsilon model were solved in a nonorthogonal curvilinear coordinate system. A zonal-grid method, where the flow field was divided into several subsections, was developed. This approach permitted different computational schemes to be used in the various zones. In addition, grid generation was made a more simple task. Boundary overlap and interpolating techniques were used, and an adjustment of the flow variables was required to assure conservation of mass flux. Three finite-differencing methods (hybrid, quadratic upwind, and skew upwind) were used to represent the convection terms. Results were compared with existing experimental data. In general, good agreement between predicted and measured values was obtained.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Journal for Numerical Methods in Fluids (ISSN 0271-2091); 9; 167-183
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  • 32
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    Design of the polarimeter for the Solar Activity Measurements Experiments (SAMEX) vector magnetograph (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A design concept developed for a polarimeter on the vector magnetograph of the SAMEX satellite that would be very sensitive to solar vector magnetic fields is described. A description of the Poincare sphere is presented, along with the instrument scientific requirements, to provide an understanding of how the polarimeter design has been selected. It is shown that the design goal of a polarimetric sensitivity of 0.0001 can be achieved in the linear measurements using a hybrid analyzer. It is also noted that the systematic errors that produce linear crosstalk into the circular measurement will require the use of the redundant polarization measurements for in-flight calibrations and corrections of the data.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Engineering (ISSN 0091-3286); 28; 131-140
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    Nonlinear and snap-through responses of curved panels to intense acoustic excitation (1989)
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    Publication Date: 2011-08-19
    Description: Assuming a single-mode transverse displacement, a simple formula is derived for the transverse load-displacement relationship of a plate under in-plane compression. The formula is used to derive a simple analytical expression for the nonlinear dynamic response of postbuckled plates under sinusoidal or random excitation. The highly nonlinear motion of snap-through can be easily interpreted using the single-mode formula. Experimental results are obtained with buckled and cylindrical aluminum panels using discrete frequency and broadband excitation of mechanical and acoustic forces. Some important effects of the snap-through motion on the dynamic response of the postbuckled plates are described. Static tests were used to identify the deformation shape during snap-through.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Aircraft (ISSN 0021-8669); 26; 281-288
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    Effect of bond thickness on fracture and fatigue strength of adhesively bonded composite joints (1989)
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    Publication Date: 2011-08-19
    Description: An experimental investigation of composite to composite bonded joints was undertaken to study the effect of bond thickness on debond growth rate under cyclic loading and critical strain energy release rate under static loading. Double cantilever beam specimens of graphite/epoxy adherends bonded with EC 3445 were tested under mode I loading. A different behavior of fracture and fatigue strength was observed with variation of bondline thickness.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Adhesion and Adhesives (ISSN 0143-7496); 9; 33-37
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    Improved method of analyzing hot-wire measurements in supersonic turbulence (1989)
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    Publication Date: 2011-08-19
    Description: The present analysis method for hot-wire data in supersonic turbulence takes sound field effects into account and yields greater accuracy in its treatment of flow variable fluctuations than existing methods despite requiring only a moderately accurate estimate of static pressure fluctuations. The method demonstrates the way in which neglecting pressure fluctuations will affect hot-wire data analysis, as well as indicating the probable direction the errors will take.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA Journal (ISSN 0001-1452); 27; 115-117
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    False-color display of special sensor microwave/imager (SSM/I) data (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Displays of multifrequency passive microwave data from the Special Sensor Microwave/Imager (SSM/I) flying on the Defense Meteorological Satellite Program (DMSP) spacecraft are presented. Observed brightness temperatures at 85.5 GHz (vertical and horizontal polarizations) and 37 GHz (vertical polarization) are respectively used to 'drive' the red, green, and blue 'guns' of a color monitor. The resultant false-color images can be used to distinguish land from water, highlight precipitation processes and structure over both land and water, and detail variations in other surfaces such as deserts, snow cover, and sea ice. The observations at 85.5 GHz also add a previously unavailable frequency to the problem of rainfall estimation from space. Examples of mesoscale squall lines, tropical and extra-tropical storms, and larger-scale land and atmospheric features as 'viewed' by the SSM/I are shown.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: American Meteorological Society, Bulletin (ISSN 0003-0007); 70; 146-151
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    2CG013 - A monoenergetic source of cosmic rays? (1989)
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    Publication Date: 2011-08-19
    Description: Results from a Monte Carlo simulation of gamma-ray production under astrophysical conditions indicate that it is possible to produce gamma-ray spectra as hard as that of 2CG013+00 reported by COS-B using a monoenergetic beam of cosmic rays hitting a thin target material. It is suggested that the low mass X-ray binary GX13+1 might provide such a mechanism to produce the observed gamma-rays from the region.
    Keywords: SPACE RADIATION
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 208; 1-2,
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    Cyclotron scattering lines in gamma-ray burst spectra (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: If cyclotron scattering, rather than absorption, is responsible for the line features observed recently in two gamma-ray burst spectra (Murakami et al., 1988), then the second and higher harmonics are due to resonant scattering events that excite the electron to Landau levels above the ground state. Here, relativistic Compton scattering cross sections are used to estimate the expected ratio of third to second harmonics in the presence of Doppler broadening. At the field strength (1.7 TG) required to give first and second harmonics at 19 keV and 38 keV, there should be no detectable third harmonic in the spectrum.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 338; L21-L24
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    Limits to the radiative decays of neutrinos and axions from gamma-ray observations of SN 1987A (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Gamma-ray observations obtained by the SMM gamma-ray spectrometer in the energy range 4.1-6.4 MeV are used to provide limits on the possible radiative decay of neutrinos and axions emitted by SN 1987A. For branching ratio values for the radiative decay modes of less than about 0.0001, the present limits are more stringent than those based upon the photon flux from decaying relic neutrinos. The data are also used to set an axion mass limit.
    Keywords: SPACE RADIATION
    Type: Physical Review Letters (ISSN 0031-9007); 62; 509-512
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    Experimental limits on the radiative decay of SN 1987A neutrinos (1989)
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    Publication Date: 2011-08-19
    Description: SMM gamma-ray spectrometer data are examined to look for gamma-ray emission coincident with the about-10-s neutrino burst from SN 1987A. The absence of a detectable signal suggests that the energy radiated into MeV gamma rays by neutrino decay (or any other process) is less than 10 to the -10th of that in supernova neutrinos above 9 MeV. The results are used to set a direct limit on the lifetime of any massive neutrino type generated in the core collapse leading to SN 1987A.
    Keywords: SPACE RADIATION
    Type: Physical Review Letters (ISSN 0031-9007); 62; 505-508
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    Postdispersion system for astronomical observations with Fourier transform spectrometers in the thermal infrared (1989)
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    Publication Date: 2011-08-19
    Description: A postdispersion system for astronomical observations with Fourier transform spectrometers in the thermal infrared has been developed which improves the sensitivity of radiation noise limited observations by reducing the spectral range incident on the detector. Special attention is given to the first-generation blocked impurity band detector. Planetary, solar, and stellar observations are reported.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 28; 139-145
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    The cosmic-ray antiproton spectrum from dark matter annihilation and its astrophysical implications - A new look (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The spectrum of antiprotons from dark matter annihilation are calculated using the Lund Monte Carlo program, and simple analytic expressions for the spectrum and low-energy antiproton/proton ratio are derived. Comparing the results with recent upper limits on low energy antiprotons, it is concluded that the reported 4-13 GeV antiproton flux cannot be accounted for by dark matter annihilation. The new upper limits do not provide useful constraints on dark matter particles. They restrict the annihilation rate and imply that annihilation gamma ray and e(+) fluxes would be far below the fluxes produced by cosmic-ray collisions. It may be possible to look for a dark matter halo annihilation signal at antiprotons energies below 0.5 GeV, where the flux from cosmic-ray collisions is expected to be negligible.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal (ISSN 0004-637X); 336; L51-L54
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  • 43
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    The autocorrelation properties of fluctuations in the cosmic X-ray background (1989)
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    Publication Date: 2011-08-19
    Description: The HEAO 1 A-2 all-sky survey data have been analyzed to investigate the autocorrelation function of the surface brightness fluctuations of the extragalactic 2-10 keV X-ray background on angular scales ranging from 3 to 27 deg. The derived upper limits are compatible with optical estimates of the spatial correlation function of Abell's clusters and set interesting constraints on possible AGN clustering.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal (ISSN 0004-637X); 336; L47-L50
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  • 44
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    Geometric bias and time coincidence in 3-dimensional laser Doppler velocimeter systems (1989)
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    Publication Date: 2011-08-19
    Description: The measurement by a three-dimensional laser Doppler velocimeter of a turbulent flow has been numerically simulated. Errors associated with the probe volume geometry and the coincidence time window concept are revealed. One type of error occurs for high system data rates when multiple particles lead to system realizations. Another error occurs associated with a geometric bias discovered in the present study. This three-dimensional ldv geometric bias exists even for single-particle realizations and regardless of the system data rate. A technique for the elimination of the geometric bias is presented.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Experiments in Fluids (ISSN 0723-4864); 7; 1, 19
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    Nuclear cross sections for estimating secondary radiations produced in spacecraft (1989)
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    Publication Date: 2011-08-19
    Description: The physical theory underlying calculations of nuclear absorption and fragmentation cross sections and EM dissociation cross sections is reviewed; typical results are presented in graphs; and the adequacy of the experimental data bases for each type of cross section are discussed. The emphasis is on computations applicable to the estimation of secondary radiation in shielded spacecraft.
    Keywords: SPACE RADIATION
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    Computer processing of tunable diode laser spectra (1989)
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    Publication Date: 2011-08-19
    Description: A computer-controlled tunable diode laser spectrometer and spectral analysis software are described. The three-channel system records simultaneously the transmission of a subject gas, a temperature-stabilized etalon, and a calibration gas. The software routines are applied to diode laser spectra of HNO3 and NO2 to illustrate the procedures adopted for conversion of raw spectral data to useful transmission and harmonic spectra. Extraction of line positions, absorption intensities, collisional broadening coefficients, and gas concentrations from recorded spectra is also described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Spectroscopy (ISSN 0003-7028); 43; 834-839
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    A high-speed GaAs MESFET optical controller (1989)
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    Publication Date: 2011-08-19
    Description: Optical interconnects are being considered for control signal distribution in phased array antennas. A packaged hybrid GaAs optical controller with a 1:16 demultiplexed output that is suitable for this application is described. The controller, which was fabricated using enhancement/depletion mode MESFET technology, operates at demultiplexer-limited input data rates up to 305 Mb/s and requires less than 200 microW optical input power.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Photonics Technology Letters (ISSN 1041-1135); 1; 389-391
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    PC based graphic display real-time particle beam uniformity (1989)
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    Publication Date: 2011-08-19
    Description: A technique has been developed to support the study of the effects of cosmic rays on integrated circuits. The system is designed to determine the particle distribution across the surface of an integrated circuit accurately while the circuit is bombarded by a particle beam. The system uses photomultiplier tubes, an octal discriminator, a computer-controlled NIM quad counter, and an IBM PC. It provides real-time operator feedback for fast beam tuning and monitors momentary fluctuations in the particle beam. The hardware, software, and system performance are described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); 36; 1738-174
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    Applications of ground-based radiometric observations of millimeter wave radiation (1989)
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    Publication Date: 2011-08-19
    Description: A three-channel transportable radiometer that operates at 20.6, 31.65, and 90.0 GHz has been developed. The design of the radiometer is described and the results of various experimental applications of the radiometer are presented. The experiments include a comparison of brightness temperature measurements at various frequencies with the water vapor absorption models of Waters (1976) and Lieve (1989). Measurements of absorption ratios for cloud attenuation are given and the radiometer measurements are compared with oxygen absorption calculated using the Rasenkranz (1988) model.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: (ISSN 0002-6557); 58; 467-474
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    Passive millimeter-wave imaging - A tool for remote sensing (1989)
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    Publication Date: 2011-08-19
    Description: This paper describes a program of airborne radiometric imaging at 90 GHz and 140 GHz. Using high sensitivity (below 1 K) and high angular resolution (0.5-1.0 degree), high quality images have been made. The following measurements are discussed: cloud and fog penetration at 90 GHz, discrimination between agricultural and urban areas, discrimination between different vegetation types, detection of vehicles on roads, detection and classification of airports and airplanes, ship detection and quantitative oil spill sensing. The application of information enhancement techniques with automatic and real time application aspects is also described, and results of applied techniques for contrast and contour enhancement are shown.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: (ISSN 0002-6557); 58; 457-465
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    Analytical and finite element solutions of some problems using a viscoplastic model (1989)
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    Publication Date: 2011-08-19
    Description: The feasibility of using a viscoplastic model developed by Robinson to perform a nonlinear structural analysis was investigated. The paper presents analytical solutions for three classical problems: (1) a pressurized thick-walled cylinder, (2) a thin rotating disk, and (3) a pressurized thick-walled sphere. The analytical expressions derived for the stress and the strain rates for these components are general in nature as they consider both the mechanical and thermal loadings to be time-dependent. A computer program VISTAN (VIscoplastic STructural ANalyzer) was developed to obtain the stress and strain distributions. The finite element solutions for these problems are also presented. The numerical results pertaining to isothermal loading conditions are provided. The results obtained demonstrate the feasibility of using the viscoplastic model developed by Robinson to perform nonlinear structural analyses.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 33; 4, 19
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    Numerical simulation of thermocapillary bubble migration under microgravity for large Reynolds and Marangoni numbers (1989)
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    Publication Date: 2011-08-19
    Description: A numerical procedure in which the Navier-Stokes equations are discretized using tightly coupled discretizations of pressure derivatives and continuity equations is used here to extend the range of known terminal velocities of gaseous bubbles in liquids well beyond that in previous investigations. Computations performed for Reynolds numbers up to 2000 and Marangoni numbers up to 1000 show only a modest variation of the scaled bubble velocity between 0.16 and 0.5. The bubble velocity is influenced more by the Marangoni number than by the Reynolds number.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Numerical Heat Transfer, Part A: Applications (ISSN 1040-7782); 16; 2, Se
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    Numerical analysis of natural convection in liquid droplets by phase change (1989)
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    Publication Date: 2011-08-19
    Description: A numerical analysis is performed on thermocapillary buoyancy convection induced by phase change in a liquid droplet. A finite-difference code is developed using an alternating-direction implicit (ADI) scheme. The intercoupling relation between thermocapillary force, buoyancy force, fluid property, heat transfer, and phase change, along with their effects on the induced flow patterns, are disclosed. The flow is classified into three types: thermocapillary, buoyancy, and combined convection. Among the three mechanisms, the combined convection simulates the experimental observations quite well, and the basic mechanism of the observed convection inside evaporating sessile drops is thus identified. It is disclosed that evaporation initiates unstable convection, while condensation always brings about a stable density distribution which eventually damps out all fluid disturbances. Another numerical model is presented to study the effect of boundary recession due to evaporation, and the 'peeling-off' effect (the removal of the surface layer of fluid by evaporation) is shown to be relevant.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Numerical Heat Transfer, Part A: Applications (ISSN 1040-7782); 16; 2, Se
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    Effects of anisotropic heat conduction on solidification (1989)
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    Publication Date: 2011-08-19
    Description: Two-dimensional solidification influenced by anisotropic heat conduction has been considered. The interfacial energy balance was derived to account for the heat transfer in one direction (x or y) depending on the temperature gradient in both the x and y directions. A parametric study was made to determine the effects of the Stefan number, aspect ratio, initial superheat, and thermal conductivity ratios on the solidification rate. Because of the imposed boundary conditions, the interface became skewed and sometimes was not a straight line between the interface position at the upper and lower adiabatic walls (spatially nonlinear along the height). This skewness depends on the thermal conductivity ratio k(yy)/k(yx). The nonlinearity of the interface is influenced by the solidification rate, aspect ratio, and k(yy/k(yx).
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Numerical Heat Transfer, Part A: Applications (ISSN 1040-7782); 15; 2, 19; 181-195
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    Practical application of HgI2 detectors to a space-flight scanning electron microscope (1989)
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    Publication Date: 2011-08-19
    Description: Mercuric iodide X-ray detectors have been undergoing tests in a prototype scanning electron microscope system being developed for unmanned space flight. The detector program addresses the issues of geometric configuration in the SEM, compact packaging that includes separate thermoelectric coolers for the detector and FET, X-ray transparent hermetic encapsulation and electrical contacts, and a clean vacuum environment.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Nuclear Instruments and Methods in Physics Research, Section A - Accelerators, Spectrometers, Detectors, and Associated Equipment (ISSN 0168-9002); 283; 348-351
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    A multiple-time-scale turbulence model based on variable partitioning of the turbulent kinetic energy spectrum (1989)
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    Publication Date: 2011-08-19
    Description: A multiple-time-scale turbulence model of a single point closure and a simplified split-spectrum method is presented. In the model, the effect of the ratio of the production rate to the dissipation rate on eddy viscosity is modeled by use of the multiple-time-scales and a variable partitioning of the turbulent kinetic energy spectrum. The concept of a variable partitioning of the turbulent kinetic energy spectrum and the rest of the model details are based on the previously reported algebraic stress turbulence model. Example problems considered include: a fully developed channel flow, a plane jet exhausting into a moving stream, a wall jet flow, and a weakly coupled wake-boundary layer interaction flow. The computational results compared favorably with those obtained by using the algebraic stress turbulence model as well as experimental data. The present turbulence model, as well as the algebraic stress turbulence model, yielded significantly improved computational results for the complex turbulent boundary layer flows, such as the wall jet flow and the wake boundary layer interaction flow, compared with available computational results obtained by using the standard kappa-epsilon turbulence model.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Numerical Heat Transfer, Part B: Fundamentals (ISSN 1040-7790); 16; 2, 19; 193-211
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    Bearing-bypass loading in composite joints - Testing and stress analysis (1989)
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    Publication Date: 2011-08-19
    Description: A combined experimental and analytical study of bearing and bypass loading on single-fastener specimens of a 16-ply, quasi-isotropic T300/5208 graphite/epoxy laminate with a centrally located hole is reported. The specimens were loaded in either tension or compression, and onset damage, ultimate strengths, and corresponding failure modes were determined. The tension data showed the expected linear interaction for combined bearing-bypass loading with damage developing in the net-section tension mode. However, the bearing-onset strengths showed an unexpected interaction of the bearing and compressive bypass loads in which the latter reduced the bearing-onset strength. A linear finite element analysis showed that bearing-bypass loading had a marked influence on the bolt-hole contact which in turn had a significant effect on local stresses.
    Keywords: STRUCTURAL MECHANICS
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    Finite element large-amplitude free and forced vibrations of rectangular thin composite plates (1989)
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    Publication Date: 2011-08-19
    Description: A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite rectangular thin plates. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite rectangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, different boundary conditions, aspect ratios, lamination angles and number of plies are presented. The finite element results are compared with available approximate continuum solutions.
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    Some aspects of transient cooling of a radiating rectangular medium (1989)
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    Publication Date: 2011-08-19
    Description: The emission from a gray radiating medium is analyzed for transient cooling in surroundings at a low temperature. The medium is rectangular with no variations in the direction normal to the cross section. The integral equation for the transient temperature distribution is solved numerically using a two-dimensional Gaussian integration subroutine. The emissive ability for a rectangle at uniform temperature is compared with that for transient cooling where the temperature distribution of the region has reached a fully developed shape, as shown by a separation of variables solution. The two solutions provide the upper and lower bounds for the emittance of a rectangle during transient cooling. The emittances for various aspect ratios are presented as a function of the mean length of the rectangle and are compared with results for a plane layer and a cylinder.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Journal of Heat and Mass Transfer (ISSN 0017-9310); 32; 1955-196
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    Transport-related phenomena for clusters of drops (1989)
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    Publication Date: 2011-08-19
    Description: Calculations for n-decane drops evaporating in a spherical cluster surrounded by unvitiated ambient air at atmospheric pressure were performed using two previously proposed cluster models. Both cluster models predict that turbulent transport effects are more important in the case of small clusters. This is due to the smaller volume to surface ratio and thus to the greater transport of hot unvitiated gas to the drops in order to promote evaporation. The results obtained are compared with those of two turbulent models for each one of the 'trapping factors' and similarity models.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Journal of Heat and Mass Transfer (ISSN 0017-9310); 32; 2000-200
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    Strain-energy release rate analysis of plates with postbuckled delaminations (1989)
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    Publication Date: 2011-08-19
    Description: The objectives are to present the derivation of the new virtual crack closure technique, evaluate the accuracy of the technique, and finally to present the results of a limited parametric study of laminates with a postbuckled delamination. Although the new virtual crack closure technique is general, only homogeneous, isotropic laminates were analyzed. This was to eliminate the variation of flexural stiffness with orientation, which occurs even for quasi-isotropic laminates. This made it easier to identify the effect of geometrical parameters on G. The new virtual crack closure technique is derived. Then the specimen configurations are described. Next, the stress analyses is discussed. Finally, the virtual crack closure technique is evaluated and then used to calculate the distribution of G along the delamination front of several laminates with a postbuckled delamination.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composite Materials (ISSN 0021-9983); 23; 714-734
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    Nonlinear evolution of interacting oblique waves on two-dimensional shear layers (1989)
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    Publication Date: 2011-08-19
    Description: The effects of critical layer nonlinearity are considered on spatially growing oblique instability waves on nominally two-dimensional shear layers between parallel streams. The analysis shows that three-dimensional effects cause nonlinearity to occur at much smaller amplitudes than it does in two-dimensional flows. The nonlinear instability wave amplitude is determined by an integro-differential equation with cubic type nonlinearity. The numerical solutions to this equation are worked out and discussed in some detail. The numerical solutions always end in a singularity at a finite downstream distance.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 207; 97-120
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    Nonlinear evolution of oblique waves on compressible shear layers (1989)
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    Publication Date: 2011-08-19
    Description: The effects of critical-layer nonlinearity on spatially growing oblique instability waves on compressible shear layers between two parallel streams are considered. The analysis shows that mean temperature nonuniformities cause nonlinearity to occur at much smaller amplitudes than it does when the flow is isothermal. The nonlinear instability wave growth rate effects are described by an integrodifferential equation which bears some resemblance to the Landau equation, in that it involves a cubic-type nonlinearity. The numerical solutions to this equation are worked out and discussed in some detail. Inviscid solutions always end in a singularity at a finite downstream distance, but viscosity can eliminate this singularity for certain parameter ranges.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 207; 73-96
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    Turbulence spectrum of strongly conductive temperature field in a rapidly stirred fluid (1989)
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    Publication Date: 2011-08-19
    Description: A simulation is performed of a passive scalar field convected by a rapidly fluctuating velocity field whose correlation time approaches zero. By using a code proposed in a previous study (Chasnov et al., 1988), the turbulence spectrum of the passive temperature field in the conductive subrange is determined. A theoretical model is proposed which explains the result obtained by representing the transfer of scalar variance by an eddy conductivity, whose correlation time is limited by the correlation time of the velocity field.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids A (ISSN 0899-8213); 1; 1698-170
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    Experimental shock-wave interference heating on a cylinder at Mach 6 and 8 (1989)
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    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 27; 1557-156
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  • 66
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    Finite element implementation of Robinson's unified viscoplastic model and its application to some uniaxial and multiaxial problems (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A description of the finite element implementation of Robinson's unified viscoplastic model into the General Purpose Finite Element Program (MARC) is presented. To demonstrate its application, the implementation is applied to some uniaxial and multiaxial problems. A comparison of the results for the multiaxial problem of a thick internally pressurized cylinder, obtained using the finite element implementation and an analytical solution, is also presented. The excellent agreement obtained confirms the correct finite element implementation of Robinson's model.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Computations (ISSN 0264-4401); 6; 237-247
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    Connection forces in deformable multibody dynamics (1989)
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    Publication Date: 2011-08-19
    Description: In the dynamic formulation of holonomic and nonholonomic systems based on D'Alembert-Lagrange equation, the forces of constraints are maintained in the dynamic equations by introducing auxiliary variables, called Lagrange multipliers. This approach introduces a set of generalized reaction forces associated with the system generalized coordinates. Different sets of variables can be used as generalized coordinates and accordingly, the generalized reactions associated with these generalized coordinates may not be the actual reaction forces at the joints. In rigid body dynamics, the generalized reaction forces and the actual reaction forces at the joints represent equipollent systems of forces since they produce the same total forces and moments at and about any point on the rigid body. This is not, however, the case in deformable body analyses wherein the generalized reaction forces depend on the system generalized reference and elastic coordinates. In this paper, a method for determining the actual reaction forces at the joints from the generalized reaction forces in deformable multibody systems is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 33; 1, 19; 307-318
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  • 68
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    Electron tunnel sensor technology (1989)
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    Publication Date: 2011-08-19
    Description: The recent development of Scanning Tunneling Microscopy technology allows the application of electron tunneling to position detectors for the first time. The vacuum tunnel junction is one of the most sensitive position detection mechanisms available. It is also compact, simple, and requires little power. A prototype accelerometer based on electron tunneling, and other sensor applications of this promising new technology are described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: British Interplanetary Society, Journal (ISSN 0007-084X); 42; 474-477
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  • 69
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    Stability of Long's vortex at large flow force (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Long's self-similar vortex is known to have two solutions for each supercritical value of the flow force. Each of those solutions is shown to have a double structure if the flow force is large. The inertial instabilities of one of those large-flow-force limit solutions are investigated, showing that they are related to the instabilities of the Bickley jet in one regime. However, the swirl in the vortex becomes important for long waves, very strongly modifying the sinuous and varicose, Bickley modes. The asymptotic results obtained agree well with the numerical solutions for the sinuous mode, but not for the varicose mode, the difficulty in the latter case being apparently due to mode jumping.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 206; 405-432
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  • 70
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    Time-dependent viscous incompressible Navier-Stokes equations - The finite difference Galerkin formulation and streamfunction algorithms (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Numerical techniques are developed to solve the Navier-Stokes equations for unsteady incompressible flow. The extension of the finite-difference Galerkin (FDG) method of Stephens et al. (1984) to the continuous-time case in two or three space dimensions is explained, and the numerical implementation of the method is discussed with particular attention to the staggered-MAC-grid primitive-variable discretization, the application of discrete mass balance to avoid problems inherent in FDG schemes, the direct interpretation of the FDG expansion variables as a discrete streamfunction, and a mass-balance approach to two-dimensional problems with throughflow or obstacles. Numerical results are presented graphically for the evolution of asymptotic steady flow in a driven cavity at Reynolds number 400, 1000, or 3200; good agreement with published experimental data is demonstrated, with accurate predictions of secondary-vortex formation from wall bubble recirculations at Reynolds number 1000.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Computational Physics (ISSN 0021-9991); 84; 207-241
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  • 71
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    An improved boundary force method for analysing cracked anisotropic materials (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Boundary Force Method (BFM), a form of indirect boundary element method, is used to analyze composite laminates with cracks. The BFM uses the orthotropic elasticity solution for a concentrated horizontal and vertical force and a moment applied at a point in a cracked, infinite sheet as the fundamental solution. The necessary stress functions for this fundamental solution were formulated using the complex variables theory of orthotropic elasticity. The current method is an improvement over a previous method using only forces and no moment. The improved method was verified by comparing it to accepted solutions for a finite-width, center-crack specimen subjected to uniaxial tension. Four graphite/epoxy laminates were used: (0 + or - 45/90)sub s, (0), (+ or - 45)sub s, and (+ or - 30)sub s. The BFM results agreed well with accepted solutions. Convergence studies showed that with the addition of the moment in the fundamental solution, the number of boundary elements required for a converged solution was significantly reduced. Parametric studies were done for two configurations for which no orthotropic solutions are currently available; a single edge crack and an inclined single edge crack.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics (ISSN 0013-7944); 34; 2, 19; 347-357
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  • 72
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    Two-component phase-averaged turbulence statistics downstream of a rotating spoked-wheel wake generator (1989)
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    Publication Date: 2011-08-19
    Description: Flow-field measurements of unsteady turbulent flow downstream of a rotating spoked-wheel wake generator were performed in a short-duration light-piston tunnel, and the instantaneous-velocity data were phase averaged based on a signal synchronized with the bar-passing frequency. Mean axial velocities were found to agree well with those obtained from measurements behind a stationary cylinder and to be independent of both Reynolds and bar-passing Strouhal numbers. Reynolds stresses were found to be consistent with related cylinder-wake measurements, but were significantly higher than corresponding measurements obtained in large-scale research turbomachines. Phase-averaged triple velocity correlations were calculated from the digital velocity records, revealing the sign and the magnitude of skewness in the velocity probability density distributions for the two components.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME, Transactions, Journal of Turbomachinery (ISSN 0889-504X); 111; 475-482
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  • 73
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    Experimental limit on low energy antiprotons in the cosmic radiation (1989)
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    Publication Date: 2011-08-19
    Description: Results are reported from the Low Energy Antiproton Experiment (LEAP), a balloon-borne instrument which was flown in August, 1987. No evidence of antiproton fluxes is found in the kinetic energy range of 120 MeV to 360 MeV, at the top of the atmosphere. The 90-percent is found confidence upper limit on the antiproton/proton ratio in this energy range is 3.5 x 10 to the -5th. In particular, this new experiment places an upper limit on the flux almost an order of magnitude below the reported flux of Buffington et al. (1981).
    Keywords: SPACE RADIATION
    Type: Advances in Space Research (ISSN 0273-1177); 9; 12, 1
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    Direct measurement of the composition and spectra of cosmic rays above 1 TeV/amu from JACEE (1989)
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    Publication Date: 2011-08-19
    Description: Direct measurements on cosmic ray protons through iron above about 1 TeV/amu have been performed in a series of balloon-borne experiments with emulsion chambers. The measured energy spectra of protons and helium are power laws with exponents of 2.77 + or - 0.09 and 2.72 + or - 0.11 in the energy range 5 to 500 TeV and 2 to 50 TeV/amu, respectively. The proton spectrum shows no evidence of the steepening near 2 TeV which was reported by other experiments. Helium has a slightly higher intensity compared to extrapolations from lower energy measurements. The heavier elements, carbon to sulfur, show a small tendency for intensity enhancement in the relative abundance obove 10 TeV/amu.
    Keywords: SPACE RADIATION
    Type: Advances in Space Research (ISSN 0273-1177); 9; 12, 1; 45-54
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    Bifurcation structure and the Eckhaus instability (1989)
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    Publication Date: 2011-08-19
    Description: The bifurcation diagram corresponding to the Eckhaus stability curve has been constructed for the one-dimensional Swift-Hohenberg equation in a finite domain. Finite-amplitude solutions with particular spatial wavelength recover linear stability, as predicted by the Eckhaus curve, after a sequence of secondary bifurcations from the branch of solutions with this wavelength. No connectivity between the primary-solution branches is admissible if the stability predicted by this bifurcation diagram is to correspond to the prediction of the Eckhaus analysis. The Eckhaus curve does not exist if nonlinear couplings destroy this pattern. This is demonstrated by analysis of a coupled pair of Swift-Hohenberg equations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physical Review Letters (ISSN 0031-9007); 63; 2048-205
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    Edge effects and delamination failures (1989)
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    Publication Date: 2011-08-19
    Description: The fundamental relationship between the morphology of a composite laminate and the resulting free edge effects is explored and related to delamination failures. Cross-ply, angle-ply, and quasi-isotropic laminates are discussed in detail. It is shown that the local mismatch in elastic properties of adjacent layers and the global stacking sequence of a laminate both have a significant influence on the interlaminar stresses and delamination failures.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Strain Analysis for Engineering Design (ISSN 0309-3247); 24; 245-252
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    Inverse heat transfer analysis of Bridgman crystal growth (1989)
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    Publication Date: 2011-08-19
    Description: The effects of asymmetry in furnace temperature profile and pulling velocity on the crystal interface shape are demonstrated while neglecting the latent heat of solidification. It is seen that the furnace temperature profile may be varied in order to influence the shape of the melt-crystal interface. An exact thermal analysis is then performed on the Bridgman technique by including the latent heat of solidification as a source term. The exact temperature field required for yielding a flat melt-crystal interface is obtained. The earlier observation regarding the influence of furnace temperature profile on the interface shape is confirmed and a criterion for achieving a flat interface is obtained. Various furnace temperature profiles are selected and their corresponding melt-crystal interface results are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Journal of Heat and Mass Transfer (ISSN 0017-9310); 32; 1741-175
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    An electron tunneling sensor (1989)
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    Publication Date: 2011-08-19
    Description: New methods have been developed to implement position sensors based on electron tunneling. The electron tunneling methods enable position to be detected with sub-Angstrom resolution using a compact mechanical structure and simple electronic control elements. A prototype accelerometer is the first sensor based on these principles; it shows reliable operation with a noise-limited sensitivity and a bandwidth of approximately 3 kHz. Based on these results, it is expected that tunnel sensors optimized for many applications will enable an entirely new class of sensors to be developed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Sensors and Actuators (ISSN 0250-6874); 19; 201-210
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    Tailoring of composite links for optimal damped elasto-dynamic performance (1989)
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    Publication Date: 2011-08-19
    Description: A method is developed for the optimal design of composite links based on dynamic performance criteria directly related to structural modal damping and dynamic stiffness. An integrated mechanics theory correlates structural composite damping to the parameters of basic composite material systems, laminate parameters, link shape, and modal deformations. The inclusion of modal properties allows the selective minimization of vibrations associated with specific modes. Ply angles and fiber volumes are tailored to obtain optimal combinations of damping and stiffness. Applications to simple composite links indicate wide margins for trade-offs and illustrate the importance of various design variables to the optimal design.
    Keywords: STRUCTURAL MECHANICS
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    Particle background effects for Hubble Space Telescope (HST) and the Lyman Far Ultraviolet Spectroscopic Explorer (1989)
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    Publication Date: 2011-08-19
    Description: Requirements on orbital background counting rates are described for the UV and visible detectors on the planned second generation instrument Space Telescope Imaging Spectrograph (STIS) and for the proposed Lyman Far Ultraviolet Spectroscopic Explorer. Expected background rates and shielding requirements are analyzed for detector types in both instruments for low earth orbits, and for high orbits in the case of Lyman.
    Keywords: SPACE RADIATION
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    The HEAO 3 background - Spectrum observed by a large germanium spectrometer in low earth orbit (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Gamma-ray background spectra, obtained in the energy range from 45 keV to 10 MeV with the cooled high-resolution Ge spectrometer on the HEAO-3 satellite over a 50-day period in 1979-1980 are reported and analyzed. The instrument design and performance characteristics are reviewed; the data-analysis procedures are outlined; about 130 background lines are listed in a table with energies, count rates, and tentative identifications; and the spectra are presented graphically and discussed in detail.
    Keywords: SPACE RADIATION
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    Approximate angular distribution and spectra for geomagnetically trapped protons in low-earth orbit (1989)
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    Publication Date: 2011-08-19
    Description: The highly anisotropic nature of the radiation in the low-earth orbit has been ignored for most spacecraft shielding calculations made to date because the standard environmental models describe the omnidirectional flux only, because the varying attitude of the spacecraft in the environment is assumed to average out the effect and because of the added complexity of the calculation. The Space Station is planned to be stabilized with respect to the velocity vector and local vertical. Thus it will pass through the South Atlantic Anomaly where most of the radiation flux is encountered in much the same attitude on each pass. Any calculation including a complex shielding geometry should thus consider the angular distributuon of the incident radiation. An approximate trapped proton angular distribution is presented which includes both the 'pan caked' distribution relative to the magnetic field direction and the east-west effect which is energy dependent. This distribution is then used with a planar shielding geometry to obtain an estimate of the effect of the anisotropy on radiation dose rates in spacecraft.
    Keywords: SPACE RADIATION
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    Charged particle radiation exposure of geocentric satellites (1989)
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    Publication Date: 2011-08-19
    Description: The near-earth radiation environment is characterized, summarizing published data on trapped and transient charged particles and their potential effects on hardware systems and the crews of manned missions. Topics examined include the role of the magnetosphere, the five radiation domains, cyclic and sporadic variations in the radiation environment, the potential effect of a high-altitude nuclear explosion, NASA empirical models for predicting trapped proton and electron fluxes, and the South Atlantic anomaly and the estimation of flux-free periods. Consideration is given to solar cosmic rays and heavy ions, Galactic cosmic rays, geomagnetic shielding, secondary radiation, the design of shielding systems, variables affecting dose evaluations, and ionizing-radiation doses. Extensive diagrams, graphs, and tables of numerical data are provided.
    Keywords: SPACE RADIATION
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    Solidification by radiative cooling of a cylindrical region filled with drops (1989)
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    Publication Date: 2011-08-19
    Description: Transient cooling by radiation is analyzed for a cylindrical region filled with axially flowing streams of drops that are becoming solidified. This is of interest for the dissipation of waste heat from orbiting power system in space. The drops absorb, emit, and scatter radiation, and the surroundings are at a lower uniform temperature. The radiative properties are assumed gray, and the scattering is isotropic. The radiating region is a two-phase mixture that remains at the melting temperature of the drops. Its temperature uniformity maintains a high emissive power as energy is lost. This is an advantage over a sensible heat radiator in which the temperature decreases, thereby reducing the emissive power. The results provide the axial length that remains two-phase and the fraction of energy dissipated within this length in which the emissive power has not decreased because of sensible cooling. It is also shown how the radial distribution of the axial velocity of the drops can be modified to increase this energy fraction.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 3; 340-344
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    Assessment of two-temperature kinetic model for ionizing air (1989)
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    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 3; 233-244
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    Spectral multi-domain for large-scale fluid dynamic simulations (1989)
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    Publication Date: 2011-08-19
    Description: A number of successful applications of a spectral collocation method extended by a multi-domain patching technique are shown. The multi-domain technique can be used to improve resolution for problems with widely disparate scales, and to reduce the ill-conditioning of the spectral operators for problems in which a large number of points are required for distributed resolution. A new nonreflecting outflow boundary treatment for unsteady transition-to-turbulence simulations is also presented, which relies on the multi-domain technique. The role of multi-domain in improving the efficiency of such calculations is discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Applied Numerical Mathematics (ISSN 0168-9274); 6; 123-139
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    Spectral element simulations of laminar and turbulent flows in complex geometries (1989)
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    Publication Date: 2011-08-19
    Description: Spectral element methods are high-order weighted residual techniques based on spectral expansions of variables and geometry for the Navier-Stokes (NS) and transport equations. Here, practical aspects of these methods and their efficient implementation are examined, and several examples of flows in truly complex geometries are presented. The spectral element discretization for NS equations is introduced, and the convergence of the method is addressed. An efficient data management scheme is discussed in the context of parallel processing computations. The method is validated by comparing the spectral element solutions with the exact eigensolutions for the Orr-Sommerfeld equations in two and three dimensions. Computer-aided flow visualizations are presented for an impulsive flow past a sharp edge wedge. Three-dimensional states of channel flow disrupted by an array of cylindrical eddy promoters are studied, and the results of a direct simulation of the turbulent flow in a plane channel are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Applied Numerical Mathematics (ISSN 0168-9274); 6; 85-105
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  • 88
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    Comparison of full 3-D, thin-film 3-D, and thin-film plate analyses of a postbuckled embedded delamination (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Local buckling can cause large interlaminar stresses along the delamination front, which can lead to delamination growth. This paper examines several methods of calculating strain-energy release rates, which are often used to predict delamination growth. The thin-film plate analysis, which was least expensive, calculated the total strain-energy release rate G(T) quite accurately. However, the stress field along the delamination front is highly mixed-mode and has no fixed ratio of G(I) to G(II). Since plate analysis can only calculate G(T), it would not be useful for accurate predictions of delamination growth if mode mix is important.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composites Technology and Research (ISSN 0885-6804); 11; 154-157
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    Calibration of the Forward Scattering Spectrometer Probe used on the ER-2 during the Airborne Antarctic Ozone Experiment (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Particle Measuring Systems (PMS) Forwared Scattering Spectrometer Probe (FSSP-100) which was flown on the ER-2 during the Airborne Antarctic Ozone Experiment for the measurement of particles in polar stratospheric clouds has been evaluated and calibrated. The sample volume of the probe per 10-s sampling period increases from 257 cu cm for 1-micron particles to 412 for 15-micron particles, but there is substantial uncertainty in this value. Limitations in the measurements from this instrument and possible corrections are discussed. The uncertainty in the total particle mass measured by the probe may be as large as + or - 100 percent. Recommendations are given for the processing of data from the FSSP used in this project.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 16475-16
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  • 90
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    Defect stream function, law-of-the-wall/wake method for turbulent boundary layers (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 27; 1707-171
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    South Pole studies of the anisotropy of the cosmic background radiation at one degree (1989)
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    Publication Date: 2011-08-24
    Description: A system is developed for making measurements of spatial fluctuations in the Cosmic Microwave Background at the 3-mm wavelength, on an angular scale of .5 to 5 degrees. The system includes a telescope with a Gaussian beam with an FWHM of 20 to 50 arcmin, an SIS coherent receiver operating around 90 GHz, and for balloon flights, a pointing system capable of 1 arc-minute RMS stabilization. Results are reported from ground-based measurements made from the South Pole station during December, 1988.
    Keywords: SPACE RADIATION
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    Longwave spectral dependence of emission from warm dust clouds (1989)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Observations of the continuum emission from warm dust clouds at 230 GHz, or 1300 microns, enables the determination of the frequency dependence of the optically thin longwave emission. Integrating the emission over the solid angle of the clouds gives a flux independent of the beam size and of the internal temperature structure of the clouds. The frequency resolving power of 64 allows the correction of these fluxes for the contribution of free-free emission from nearby H II regions at a price of reduced sensitivity. These observations were combined with similar observations made by others in the submillimeter and far infrared regimes to determine the continuum spectra of the dust clouds. Mean characteristics were determined for these clouds, fitting the spectra with simple transfer equations. Results are briefly discussed.
    Keywords: SPACE RADIATION
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 201-202
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    Infrared emission from ultracompact H II regions (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Models of circumstellar dust shells around ultracompact (UC) H II regions were constructed that accurately fit the observed IR flux distributions. The models assume spherically symmetric dust shells illuminated by stars whose bolometric luminosity is inferred from the integrated FIR flux densities. Assuming ionization by a single zero age main sequence (ZAMS) star, the relations of Panagia were used to infer the stellar radius and effective temperature for a given luminosity. The grain mixture in the dust shell consists of bare graphite and silicate grains with the optical properties of Draine and Lee and the size distribution of Mathis et al. The computer code of Wolfire et al was used to solve the radiative transfer equations through a spherical dust shell. The model provides monochromatic luminosities, dust temperatures, and opacities through the shell. Aside from the stellar and dust properties, the only other input parameters to the model are the distance to the shell, the form of its density distribution, and its outer radius. Predictions of the model are compared with observations of a typical UC H II region and the run of dust temperature with radius and the optical depth with frequency are discussed.
    Keywords: SPACE RADIATION
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 195
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  • 94
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    The compact far infrared emission from the young stellar object IRAS 16293-2422 (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: High resolution far IR observations at 50 and 100 microns were made of the young stellar object (YSO), IRAS 16293-2422. The observations are part of a systematic high resolution study of nearby YSO's. The purpose is to obtain resolution in the far IR comparable to that at other wavelengths. Until recently, the high resolution that has been available in the far IR has been from either IRAS (angular resolution of approx 4 min) or the KAO using standard FIR photometry (approx 35 sec). With scanning techniques, it is possible to obtain 10 sec resolution on bright sources. Such a resolution is necessary to better determine the physical conditions of the YSO, and to compare with model of star formation. In order to better constrain the models for the source, the YSO was observed at both 50 and 100 microns on several flights in 1988 April from the KAO. Estimates are presented of the size both along the major and minor axis of the disk, as well as estimates of the dust temperature and 100 micron opacity for the YSO.
    Keywords: SPACE RADIATION
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 191-192
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  • 95
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    The 3.3 micron emission feature: Map of the galactic disk, 10 deg less than 1 less than 35 deg, - 6 deg less than b less than 6 deg (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The 3.3 micron aromatic feature has been detected in the diffuse galactic emission with the AROME balloon-borne instrument. The results are presented in the form of an map of the 3.3 micron feature's intensity. The AROME instrument consists in a Cassegrain telescope with wobbling secondary mirrors and a liquid/solid nitrogen cooled photometer. The instrumental output is modified by the impulse response of the system. So the galactic surface brightness was restored in Fourier space by an inverse optimal filtering. The map of the feature's intensity is presented for a region of galactic coordinates. All the known H II giant molecular cloud complexes are visible in the 3.3 micron feature emission showing a good correlation with the infrared dust emission.
    Keywords: SPACE RADIATION
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 129-130
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  • 96
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    IR emission and UV extinction in two open clusters (1989)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Recent models of interstellar extinction have shown the importance of understanding both the UV and IR properties of interstellar dust grains. IRAS data have shown variations in 60 and 100 micron emissions presumably due to the presence of IR cirrus, while recent observations in the UV by Fitzpatrick and Massa have identified components in the UV extinction curve which vary in different star regions. A Draine and Anderson model connects these results by proposing that different size variations in interstellar grains would cause distinct changes in both the IR emission and the UV extinction. In order to test this model it is necessary to make observations in well defined locations away from peculiar extinction regions. In the infrared this means looking away from the galactic plane so as to limit non-local sources of IR radiation. Two open clusters that are out of the galactic plane and which contain a number of late B and early A stars suitable for UV extinction studies, and whose IRAS data show variations in the 60/100 micron ratio were studied. Based on the Drain and Anderson model, variations were expected in their UV extinction curves that correlate with the IR cirrus emission.
    Keywords: SPACE RADIATION
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 131
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  • 97
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    Spectral structure near the 11.3 micron emission feature (1989)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: If the 11.3 micron emission feature seen in the spectra of many planetary nebulae, H II regions, and reflection nebulae is attributable to polycyclic aromatic hydrocarbons (PAHs), then additional features should be present between 11.3 and 13.0 microns. Moderate resolution spectra of NGC 7027, HD 44179, BD+30 deg 3639, and IRAS 21282+5050 are presented which show evidence for new emission features centered near 12.0 and 12.7 microns. These are consistent with an origin from PAHs and can be used to constrain the molecular structure of the family of PAHs responsible for the infrared features. There is an indication that coronene-like PAHs contribute far more to the emission from NGC 7027 than to the emission from HD 44179. The observed asymmetric profile of the 11.3 micron band in all the spectra is consistent with the slight anharmonicity expected in the C-H out-of-plane bending mode in PAHs. A series of repeating features between 10 and 11 microns in the spectrum of HD 44179 suggests a simple hydride larger than 2 atoms is present in the gas phase in this object.
    Keywords: SPACE RADIATION
    Type: Interstellar Dust: Contributed Papers; p 11
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  • 98
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    A new facility to study three dimensional viscous flow and rotor-stator interaction in turbines (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A description of the Axial Flow Turbine Research Facility (AFTRF) being built at the Turbomachinery Laboratory of the Pennsylvania State University is presented. The purpose of the research to be performed in this facility is to obtain a better understanding of the rotor/stator interaction, three dimensional viscous flow field in nozzle and rotor blade passages, spanwise mixing and losses in these blade rows, transport of wake through rotor passage, and unsteady aerodynamics and heat transfer of rotor blade row. The experimental results will directly feed and support the analytical and the computational tool development. This large scale low speed facility is heavily instrumented with pressure and temperature probes and has provision for flow visualization and laser Doppler anemometer measurement. The facility design permits extensive use of the high frequency response instrumentation on the stationary vanes and more importantly on the rotating blades. Furthermore it facilitates detailed nozzle wake, rotor wake, and boundary layer surveys. The large size of the rig also has the advantage of operating at Reynolds numbers representative of the engine environment.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Structural Integrity and Durability of Reusable Space Propulsion Systems; p 223-236
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  • 99
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    Overview of aerothermodynamic loads definition study (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Over the years, NASA has been conducting the Advanced Earth-to-Orbit (AETO) Propulsion Technology Program to provide the knowledge, understanding, and design methodology that will allow the development of advanced Earth-to-orbit propulsion systems with high performance, extended service life, automated operations, and diagnostics for in-flight health monitoring. The objective of the Aerothermodynamic Loads Definition Study is to develop methods to more accurately predict the operating environment in AETO propulsion systems, such as the Space Shuttle Main Engine (SSME) powerhead. The approach taken consists of 2 parts: to modify, apply, and disseminate existing computational fluid dynamics tools in response to current needs and to develop new technology that will enable more accurate computation of the time averaged and unsteady aerothermodynamic loads in the SSME powerhead. The software tools are detailed. Significant progress was made in the area of turbomachinery, where there is an overlap between the AETO efforts and research in the aeronautical gas turbine field.
    Keywords: STRUCTURAL MECHANICS
    Type: Structural Integrity and Durability of Reusable Space Propulsion Systems; p 209-214
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  • 100
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    Probabilistic boundary element method (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The purpose of the Probabilistic Structural Analysis Method (PSAM) project is to develop structural analysis capabilities for the design analysis of advanced space propulsion system hardware. The boundary element method (BEM) is used as the basis of the Probabilistic Advanced Analysis Methods (PADAM) which is discussed. The probabilistic BEM code (PBEM) is used to obtain the structural response and sensitivity results to a set of random variables. As such, PBEM performs analogous to other structural analysis codes such as finite elements in the PSAM system. For linear problems, unlike the finite element method (FEM), the BEM governing equations are written at the boundary of the body only, thus, the method eliminates the need to model the volume of the body. However, for general body force problems, a direct condensation of the governing equations to the boundary of the body is not possible and therefore volume modeling is generally required.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center, Structural Integrity and Durability of Reusable Space Propulsion Systems; p 153-158
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