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At least 865 records · Page 48

Vortex breakdown simulation

A vortex breakdown was simulated by the vortex filament method, and detailed figures are presented based on the results. Deformations of the vortex filaments showed clear and large swelling at a particular axial station which implied the presence of a recirculation bubble at that station. The tendency for two breakdowns to occur experimentally was confirmed by the simulation, and the jet flow inside the bubble was well simulated. The particle paths spiralled with expansion, and the streamlines took spiral forms at the breakdown with expansion.

Nakamura, Y.↗

A numerical study of forced lithospheric thinning

Subsolidus lithospheric thinning by mantle plumes may be involved in the creation of swells, hotspots, and rifts. Among the major questions concerning this process are the timescale on which it occurs and the structure of the plumes. The lithosphere is known to have been substantially thinned in 10 Ma or less. Current studies are focused on the lithospheric thinning by time-dependent plumes hypothesized to have large temperature differences across them.

Schubert, G.↗

Waves across the ocean

The predictions of linear surface wave theory (S = 1/2A sq rt L and S = 1/2A squared P, where S is speed, A is a proportionality constant, L is wavelength, and P is period) are discussed in connection with the remote measurement of swell, i.e., long ocean waves. Particular attention is given to the Scripps experiments and to the APL experiment involving Seasat microwave remote sensing. It is noted that these measurements have yielded an exceptionally clear field verification of the theory, indicating the fidelity of ocean remote sensors.

Irvine, D. E.↗

Performance of 12Ah aerospace nickel-cadmium cells of design variable groups

The design variable program of NASA is a systematic approach to evaluate the performance of 12Ah aerospace nickel-cadmium cells of 9 important cell designs. These cells were life cycled in a Low-Earth Orbit (LEO) regime for 3 to 4 years. Representative cells taken from the design variable groups after different cycling periods have been examined. The results show that: (1) positive swelling and carbonate content in the electrolyte increases as a function of the number of cycles, (2) electrolyte distribution follows the order NEG greater than POS greater than SEP, 3) control and no PQ groups outperformed the rest of the groups and (4) the polypropylene group shows very heavy cadmium migration and poor performance.

Vasanth, K. L.↗

Spatial variations of ocean wave directional spectra from the Seasat synthetic aperture radar

Seasat synthetic aperture radar ocean wave spectra for a 900-km pass are analyzed and interpreted in the context of both their probable generation sources and their surface current and bathymetric modifiers. Systematic vector wavenumber variations of several times the standard error of determination (about 1.5 percent in magnitude and 0.9 deg in direction) occur along the entire 900-km pass. The large-scale spatial variation of a 200-m swell system can be accurately accounted for as a result of dispersion from a distant storm. The more local variations are qualitatively well correlated in position with known currents and bathymetry but show systematic biases that appear partly due to an environmentally dependent instrument transfer function in the regions of high current and highest sea state. There is also substantial evidence that a large angular deviation in the center of the pass is the result of a mesoscale eddy just to the east.

Beal, R. C.↗

Controlling Growth Rates of Protein Samples

Apparatus enables control of humidity in chamber to control rates of growth of crystalline samples of protein. Size of drop of solution from which protein is grown made larger or smaller by condensation or evaporation of water. Situated between desiccant and water source, drop of protein solution shrinks or swells, according to which valve operator opens. Growing protein crystal viewed through polarizing film. Readily adapted to automation.

Herrmann, Frederick T.↗

Production of large-particle-size monodisperse latexes

The research program achieved two objectives: (1) it has refined and extended the experimental techniques for preparing monodisperse latexes in quantity on the ground up to a particle diameter of 10 microns; and (2) it has demonstrated that a microgravity environment can be used to grow monodisperse latexes to larger sizes, where the limitations in size have yet to be defined. The experimental development of the monodisperse latex reactor (MLR) and the seeded emulsion polymerizations carried out in the laboratory prototype of the flight hardware, as a function of the operational parameters is discussed. The emphasis is directed towards the measurement, interpretation, and modeling of the kinetics of seeded emulsion polymerization and successive seeded emulsion polymerization. The recipe development of seeded emulsion polymerization as a function of particle size is discussed. The equilibrium swelling of latex particles with monomers was investigated both theoretically and experimentally. Extensive studies are reported on both the type and concentration of initiators, surfactants, and inhibitors, which eventually led to the development of the flight recipes. The experimental results of the flight experiments are discussed, as well as the experimental development of inhibition of seeded emulsion polymerization in terms of time of inhibition and the effect of inhibitors on the kinetics of polymerization.

Vanderhoff, J. W.↗

Analysis of 12 AH aerospace nickel-cadmium cells from the design variable program

The Design Variable Program of NASA/GSFC provided a systematic approach to evaluate the performance of 12 Ampere-Hour Nickel-Cadmium cells of different designs. Design Variables tested in this program included teflonated negative plates, silver treated negative plates, lightly loaded negative plates, positive plates with no cadmium treatment, plate design of 1968 utilizing old and new processing techniques and electrochemically impregnated positive plates. These cells were life cycled in a Low-Earth Orbit (LEO) regime for 3 to 4 years. Representative cells taken from the Design Variable Program were examined via chemical, electrochemical and surface analyses. The results indicate the following: (1) positive swelling and carbonate content in the electrolyte increase as a function of number of cycles; (2) electrolyte distribution follows a general order NEG greater than POS greater than SEP; (3) control and No PQ groups outperformed the rest of the groups; and (4) the polyproylene group exhibited heavy cadmium migration and poor performance.

Vasanth, Kunigahalli L.↗

New predictions methods for composites hygrothermal behavior

The methodology in this paper allows prediction of the thermal expansion and swelling of a composite material to temperature and moisture variations which typically occur in a launch environment. It is demonstrated that constitutive equations for moisture absorption and moisture-induced dimensional changes can be obtained with an internal variable method which is rooted in the theory of irreversible thermodynamics. Realism is injected into the model through the concept of free volume.

Hiel, C. C.↗

Compression of oceanic lithosphere - An analysis of intraplate deformation in the Central Indian Basin

The development of intraplate structure in the Central Indian Basin is examined using models in which deformation is due to flexural buckling and the hydrodynamic growth of instabilities. Comparison of the models reveal that in a strong viscous lithosphere, deformation of the layer occurs by flexural folding at a wavelength which corresponds to the flexural buckling theory; in a lithosphere of intermediate strength, the layer deforms by folding characterized by thickening which localizes beneath topographic heights; and in a relatively weak lithosphere, the layer incurs an even greater amount of localized thickening and deforms in the symmetric or pinch-and-swell mode by inverse boudinage. It is noted that the models in which the layer folds either flexurally or with periodic thickening correspond with observed depth distribution of seismicity in the Central Indian Basin and with experimental rock rheological data.

Zuber, Maria T.↗

The formation of small scale granularities in latex particles

A series of latices were synthesized using emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonic acid. The final latex particles display an internal granular structure which can be ascribed to the primary particles present in the early stages of particle growth. In these systems, the primary particles appear to have maintained their integrity during the swelling and growth stage.

Zukoski, C. F.↗

Heat Exchanger For Rotating Modular Structures

Heat exchanger transfers heat from one structure to another while accommodating rotary motion of structures. Flat-panel heat exchanger passes heat from fluid in middle panel to fluid in outer panels. Diaphragm-like outer panels swell to conform to surfaces of middle panel, ensuring thermal contact. Rotary fluid coupling provides connection for both supply fluid and return fluid. Flexible hoses carrying fluid to and from coupling accommodate tilt of one structure with respect to other. Adapted to transfer of fluids and heat across joints of machine tools and robot arms and to flow of coolant through portable electronic equipment.

Clark, William E.↗

Radar Detects Ocean Surface Currents

Interferometric system uses reflections from ripples. Experimental airborne interferometric synthetic-aperture radar system measures line-of-sight component of velocity of ripples on surface of ocean. With help of suitable assumptions about relationships among ripples, larger waves or swells on which they occur, and overall movement of water, component of velocity of underlying surface current perpendicular to path of airplane deduced.

Goldstein, R. M.↗

Physical processes in the growth of the continental crust

Major mechanisms of crustal addition are volcanism and plutonism at plate boundaries and within plate interiors. One approach to deciding if island arc magmatism dominated ancient crustal growth is to assess the rate at which the process has operated in the recent past. The localized addition rates were found to be comparable to present day global rates. One physical observable that was used to constrain models of crustal growth is sea level. A simple physical model was developed to explore the consequences of constant freeboard (the height of the continents above sea level). Global geoid and sea floor topography data were used to identify and study oceanic plateaus and swells that have either continental crustal roots or anomalously thick ocean crusts.

Schubert, G.↗

Large-scale topography of Io - Implications for internal structure and heat transfer

Recent stereographic methods have been applied to Voyager 1 images in order to determine the shape and large-scale topography of Io. The best triaxial figure of semiaxes of 1830.0, 1818.7, and 1815.3 kilometers is consistent with a differentiated satellite in hydrostatic equilibrium. It is suggested that many of the broad topographic swells and basins noted may be due to isostatic responses to thermal changes in the lithosphere-asthenosphere system. Results support the picture of increasing heat flow converting the basal lithosphere into a lower-density asthenosphere, resulting in isostatic uplift. It is shown that lithospheric thicknesses ranging from 5-100 km may results in elevation variations of up to 1 km.

Gaskell, Robert W.↗

Polymeric Electrolytic Hygrometer For Harsh Environments

Design of polymeric electrolytic hygrometer improved to meet need for reliable measurements of relative humidity in harsh environments of pulpmills and papermills. Redesigned sensor head features shorter, more-rigidly-held sensing element, less vulnerable than previous version to swell and loss of electrical contact. Useful for control of batch dryers in food and pharmaceutical industries.

Lawson, Daniel D.↗

Modelling the SIR-B image response to partially coherent seas

A mathematical model of transient seas modulated by coherent swells is developed as a Rayleigh-Poisson random process subject to deterministic correlations of scattering sites, as they appear in a time window defined by a SAR's range-Doppler measurements of the surface coordinates. This model of SAR response to sea surface dynamics is discussed as a Fourier domain predictor/corrector of a dynamic motion blur.

Tilley, D. G.↗

Directional measurement of short ocean waves with stereophotography

Stereophotographs of the sea surface, acquired during the Tower Ocean Wave and Radar Dependence experiment are analyzed to yield directional wave height spectra of short surface waves in the 6-80-cm range. The omnidirectional wave height spectra are found to deviate from the k exp -4 distribution, where k is the wave number. The stereo data processing errors are found to be within + or - 5 percent. The omnidirectional spectra yield 514 deg of freedom for 30-cm-long waves. The directional distribution of short waves is processed with a directional resolution of 30 deg, so as to yield 72 deg of freedom for 30-cm-long waves. The directional distributions show peaks that are aligned with the wind and swell directions. It is found that dynamically relevant measurements can be obtained with stereophotography, after removal of the mean surface associated with long waves.

Shemdin, Omar H.↗