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At least 253 records · Page 14

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NASA NTRS1983

Flow in a torsionally oscillating filled cylinder

The flow of a liquid in a completely filled cylinder undergoing torsional oscillations about its longitudinal symmetry axis was studied analytically and experimentally. The objective of the studies was to determine the efficacy of the torsional oscillations in mixing the confined liquid. Flow was found to be confined primarily to toroidal cells at the ends of the cylinder. Cell thickness was about equal to the cylinder radius. The use of baffles at the end walls was shown to enhance the mixing process.

Schafer, C. F.↗

NASA NTRS1982

A new brominated polymeric additive for flame retardant glass-filled polybutylene terephthalate

Attention is called to the undesirable effects (poor ultraviolet light stability and blooming) sometimes introduced by brominated flame retarders. A brominated polymeric additive (BPA) with little or none of these undesirable side effects is compared with decabromobiphenyl oxide (DBBPO). The additive bears the product name F-2300. It is found to be more easily dispersed than DBBPO. The F-2300 is as effective as the DBBPO in the oxygen index test. The improved efficiency of the F-2300 may be explained by its better dispersion in polybutylene terephthalate (PBT). Glass-filled PBT containing F-2300 is found to be more resistant to UV degradation than DBBPO-containing formulas. Formulations with F-2300 therefore have a longer useful outdoor life. F-2300 is a diglycidyl-type polymer containing 50 percent aromatically bound bromine. Its melting point is 112 C, and it is stable up to 372 C. It is pointed out that since its melts at a relatively low temperature, it can be introduced into the formulation as a large agglomerate and still be dispersed evenly throughout the polymer.

Nir, Z.↗

NASA NTRS1985

Vented Compression Molding of Granule-Filled Resins

Resins filled with granules formed to final size and shape in new process. New vented compression molding method takes less time than conventional method. Vacuum-bagging and machining stages eliminated. Part emerges from mold in final size and shape. Suitable for making variety of parts with simple shapes, vented compression molding takes less time and cost less than older processes.

Mccree, J. O.↗

NASA NTRS1985

Centrifugal Generator of Filled Spherical Shells

Centrifugal apparatus produces filled spherical shells for wide range of industrial and scientific applications. Rotating container has radially extending nozzle in which centrifugal force draws liquid shell material from container. Liquid shell material fed from outside container and automatically maintained at fixed level. Along axis of nozzle is tube that connects through rotating seal to source of gas or other filler material. Material-flow and rotation rates adjusted to change bubble size.

Wang, T. G.↗

NASA NTRS1985

Interaction of finite-amplitude sound with air-filled porous materials

The propagation of high intensity sound waves through an air-filled porus material was studied. The material is assumed: (1) to be rigid, incompressible, and homogeneous, and (2) to be adequately described by two properties: resistivity r and porosity. The resulting wave equation is still nonlinear, however, because of the u sgn(u) term in the resistivity. The equation is solved in the frequency domain as an infinite set of coupled inhomogeneous Helmholtz equations, one for each harmonic. An approximate but analytical solution leads to predictions of excess attenuation, saturation, and phase speed reduction for the fundamental component. A more general numerical solution is used to calculate the propagation curves for the higher harmonics. The u sgn(u) nonlinearity produces a cubic distortion pattern; when the input signal is a pure tone, only odd harmonic distortion products are generated.

Nelson, D. A.↗

NASA NTRS1985

Search for magnetic monopoles using proportional counters filled with helium gas

Slow magnetic monopoles in cosmic rays have been searched at sea level with the detector which consists of seven layers of proportional counters filled with a mixture of He + 20% CH4. The velocities and the energy losses of the incident particles are measured. The upper limit of flux for the monopoles in the velocity range of 1 x 0.001 Beta 4 x 0.001 is 2.78 x 10 to the minus 12th power square centimeters sr sec of 90% confidence level.

Cho, C.↗

NASA NTRS1984

Monopole excitation of vibrations in an infinite cylindrical elastic shell filled with fluid

The vibrations of a cylindrical elastic shell filled with fluid and excited by a monopole acoustic source are studied. The modal mobilities of the shell wall at the source plane are examined for different radial locations of the source. The distribution of vibrational energy between the shell and the fluid field is calculated at various axial locations along the shell and for different radial source locations. An interchange of energy of vibration between the shell and the fluid as the wave field propagates along the shell-fluid system is observed.

Fuller, C. R.↗

NASA NTRS1985

Fracto-emission from fiber-reinforced and particulate filled composites

Fracto-emission (FE) in the emission of particles and photons during and following crack propagation. The types of particles observed include electrons (EE), positive ions (PIE), photons (phE), and excited and ground state neutral emission (NE). In this paper work is presented on the characterization of the various FE components and measurements relating FE to the fracture events and material properties involved. FE characteristics measured include total emission, time dependence relative to crack propagation, species of neutral and ionic components, energy of charged species, and time correlations between pairs of FE components. Experiments on fracture of epoxy, single fibers, fiber/epoxy strands, particulate filled epoxy, and multi-ply fiber/epoxy systems will be presented.

Dickinson, J. T.↗

NASA NTRS1987

Cotton-Fiber-Filled Rubber Insulation

Carbonization of fibers at high temperatures improves strength and erosion resistance. Cotton linters tested as replacement for asbestos filler currently used in rubber insulation in solid rocket motors. Cotton-filled rubber insulation has industrial uses; in some kinds of chemical- or metal-processing equipment, hoses, and protective clothing.

Anderson, Floyd A.↗

NASA NTRS1987

Distributed feedback modes in a partially filled ring cavity

The threshold longitudinal modes of a structure composed of a ring cavity partially filled with a distributed feedback (DFB) medium have been studied. An eigenvalue equation and dispersion relation for the propagation constant, threshold gain, and mode location are derived and numerically solved for a number of cases. It is shown that the incommensurate nature of the unfilled ring cavity eigenfrequencies and DFB eigenfrequencies can lead to an enhancement of the frequency selectivity of the distributed feedback laser. The analysis is extended to consider finite linewidth and dispersion.

Rabinovich, William S.↗

NASA NTRS1987

Mercurian crater-filling classes constrain the emplacement process of the intercrater plains material

The multivariate method for statistical analysis of crater-filling classes, as presently applied to craters of more than 10-km diameter on Mercury, is noted to be superior to current techniques due to the obviation of any amalgamation of data from regions with different histories in order to arrive at the pertinent counting statistics. In this application to the Mercury intercrater plains, the process responsible for emplacement is constrained to be one that leaves the crater class distribution unaltered from that observed on the densely cratered terrain. The analysis explicitly eliminates the viability of the pulse emplacement of volcanics or basin ejecta.

Woronow, Alex↗

NASA NTRS1987

Transient radiative cooling of a layer filled with solidifying drops

An analysis is carried out for radiative cooling of a plane layer initially filled with liquid drops that solidify and then continue to cool by loss of sensible heat. This is in connection with a proposed lightweight radiator system for heat dissipation in space. Hot liquid drops would be ejected and then cooled by direct exposure in space; they would then pass into a collector for reuse. The cooling analysis contains three transient zones. In the first, the drops cool by losing latent heat until the outermost drops become solid. Then the cooling continues by loss of both latent and sensible heat. A similarity behavior is eventually achieved in which the transient emittance of the layer depends only on the optical thickness.

Siegel, R.↗

NASA NTRS1988

Surface tension and bubble shapes in a partially filled rotating cylinder under low gravity

A computer algorithm is developed to simulate the profile of a free liquid surface for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry. The equilibrium shape of the free surface is governed by a balance of capillary, centrifugal, and gravity forces. The results can be used to determine the profile of a bubble at various rotating speeds under the gravity environments from low gravity, microgravity to zero-gravity. The present paper discusses the further extension of the study of the determination of bubble shape in a higher rotating speed container developed by Hung and Leslie.

Hung, R. J.↗

NASA NTRS1989

Optically controlled absorption modulator based on state filling of In(x)Ga(1-x)As/GaAs quantum wells

The first demonstration of an optically controlled absorption modulator based on state filling in a periodically doped In(x)Ga(1-x)As/GaAs multiple quantum well structure is reported. Differential absorption of approximately 10,000/cm is observed in the quantum wells of the test structure at saturation pump powers. Photoluminescence and time-resolved modulation measurements confirm the predicted behavior of carrier recombination and give a measure of enhanced carrier lifetime of approximately 1 ms. These initial results show the potential for developing these structures into optically addressed spatial light modulators.

Iannelli, J. M.↗

NASA NTRS1988

Quench gases for xenon- (and krypton-) filled proportional counters

Xenon-filled proportional counters are used extensively in astronomy, particularly in the hard X-ray region. The choice of quench gas can have a significant effect on the operating characteristics of the instrument although the data necessary to make the choice are not easily obtainable. Results which detail the performance obtained from both cylindrical and parallel field geometries for a wide variety of readily available, ultrahigh or research grade purity, quench gases are presented.

Ramsey, B. D.↗

NASA NTRS1990

Integrated Process For Insertion And Beatup Of Fill Yarns

Integrated apparatus and process devised for insertion and beatup of fill yarns during weaving of fabrics containing bias-oriented yarns. New technology supplants old shuttle method and modern water-jet method of insertion and conventional reed method of beatup. Intended for use in angle-ply or bias-direction weaving process.

Farley, Gary L.↗

NASA NTRS1989

Solidification by radiative cooling of a cylindrical region filled with drops

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.

Siegel, Robert↗

NASA NTRS1990

CFIE MM solution for TE and TM incidence on a 2-D conducting body with dielectric filled cavity

The problem of determining the scattering cross section of an arbitrarily shaped two-dimensional conducting body with an arbitrarily shaped dielectric-filled cavity is considered. The problem is solved using a method-of-moments (MM) solution for the combined field integral equations (CFIE). The particular form of the method of moments solution used has here uses a minimum number of expansion coefficients. Results are given for TE and TM incident waves.

Goggans, Paul M.↗