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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6

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NASA NTRS1985

Heat flow in eastern Egypt - The thermal signature of a continental breakup

It is noted that the Red Sea is a modern example of continental fragmentation and incipient ocean formation. A consistent pattern of high heat flow in the Red Sea margins and coastal zone, including Precambrian terrane up to at least 30 km from the Red Sea, has emerged from the existing data. It is noted that this pattern has important implications for the mode and mechanism of Red Sea opening. High heat flow in the Red Sea shelf requires either a high extension of the crust in this zone (probably with major basic magmatic activity) or young oceanic crust beneath this zone. High heat flow in the coastal thermal anomaly zone may be caused by lateral conduction from the offshore lithosphere and/or from high mantle heat flow. It is suggested that new oceanic crust and highly extended continental crust would be essentially indistinguishable with the available data in the Red Sea margins, and are for many purposes essentially identical.

Morgan, P.↗

NASA NTRS1988

Remote sensing of ocean color in the Arctic

The main objectives of the research are: to increase the understanding of biological production (and carbon fluxes) along the ice edge, in frontal regions, and in open water areas of the Arctic and the physical factors controlling that production through the use of satellite and aircraft remote sensing techniques; and to develop relationships between measured radiances from the Multichannel Aircraft Radiometer System (MARS) and the bio-optical properties of the water in the Arctic and adjacent seas. Several recent Coastal Zone Color Scanner (CZCS) studies in the Arctic have shown that, despite constraints imposed by cloud cover, satellite ocean color is a useful means of studying mesoscale physical and biological oceanographic phenomena at high latitudes. The imagery has provided detailed information on ice edge and frontal processes such as spring breakup and retreat of the ice edge, influence of ice on ice effects of stratification on phytoplankton production, river sediment transport, effects of spring runoff, water mass boundaries, circulation patterns, and eddy formation in Icelandic waters and in the Greenland, Barents, Norwegian, and Bering Seas.

Maynard, N. G.↗

NASA NTRS1990

The dense interstellar medium and the birthplaces of OB stars

A review is presented of Stromgren's research on the relationships among atomic, ionized, and molecular hydrogen in the Galaxy and the spatial distribution and kinematics of OB stars. Particular attention is given to the development of density-wave theory, the implication that the pattern of the formation of OB stars in a spiral galaxy should rotate at a constant angular speed, which differs generally from the mean material speed of the interstellar gas. Other theories involving the mechanical support of molecular clouds; triggered star formation; and the relationships among H2, H I, and H II are discussed.

Shu, Frank H.↗

NASA NTRS2002

Phase Synchronization and Desynchronization of Structural Response Induced by Turbulent and External Sound

Acoustic and turbulent boundary layer flow loadings over a flexible structure are used to study the spatial-temporal dynamics of the response of the structure. The stability of the spatial synchronization and desynchronization by an active external force is investigated with an array of coupled transducers on the structure. In the synchronous state, the structural phase is locked, which leads to the formation of spatial patterns while the amplitude peaks exhibit chaotic behaviors. Large amplitude, spatially symmetric loading is superimposed on broadband, but in the desynchronized state, the spectrum broadens and the phase space is lost. The resulting pattern bears a striking resemblance to phase turbulence. The transition is achieved by using a low power external actuator to trigger broadband behaviors from the knowledge of the external acoustic load inducing synchronization. The changes are made favorably and efficiently to alter the frequency distribution of power, not the total power level. Before synchronization effects are seen, the panel response to the turbulent boundary layer loading is discontinuously spatio-temporally correlated. The stability develops from different competing wavelengths; the spatial scale is significantly shorter than when forced with the superimposed external sound. When the external sound level decreases and the synchronized phases are lost, changes in the character of the spectra can be linked to the occurrence of spatial phase transition. These changes can develop broadband response. Synchronized responses of fuselage structure panels have been observed in subsonic and supersonic aircraft; results from two flights tests are discussed.

Maestrello, Lucio↗

NASA NTRS2011

Sensor for Direct Measurement of the Boundary Shear Stress in Fluid Flow

The formation of scour patterns at bridge piers is driven by the forces at the boundary of the water flow. In most experimental scour studies, indirect processes have been applied to estimate the shear and normal stress using measured velocity profiles. The estimations are based on theoretical models and associated assumptions. However, the turbulence flow fields and boundary layer in the pier-scour region are very complex. In addition, available turbulence models cannot account accurately for the bed roughness effect. Direct measurement of the boundary shear and normal stress and their fluctuations are attractive alternatives. However, this approach is a challenging one especially for high spatial resolution and high fidelity measurements. The authors designed and fabricated a prototype miniature shear stress sensor including an EDM machined floating plate and a high-resolution laser optical encoder. Tests were performed both in air as well as operation in water with controlled flow. The sensor sensitivity, stability and signal-to-noise level were measured and evaluated. The detailed test results and a discussion of future work will be presented in this paper.

sheer stress↗

NASA NTRS2012

Sensor for Boundary Shear Stress in Fluid Flow

The formation of scour patterns at bridge piers is driven by the forces at the boundary of the water flow. In most experimental scour studies, indirect processes have been applied to estimate the shear stress using measured velocity profiles. The estimations are based on theoretical models and associated assumptions. However, the turbulence flow fields and boundary layer in the pier-scour region are very complex and lead to low-fidelity results. In addition, available turbulence models cannot account accurately for the bed roughness effect. Direct measurement of the boundary shear stress, normal stress, and their fluctuations are attractive alternatives. However, most direct-measurement shear sensors are bulky in size or not compatible to fluid flow. A sensor has been developed that consists of a floating plate with folded beam support and an optical grid on the back, combined with a high-resolution optical position probe. The folded beam support makes the floating plate more flexible in the sensing direction within a small footprint, while maintaining high stiffness in the other directions. The floating plate converts the shear force to displacement, and the optical probe detects the plate s position with nanometer resolution by sensing the pattern of the diffraction field of the grid through a glass window. This configuration makes the sensor compatible with liquid flow applications.

Bao, Xiaoqi↗

NASA NTRS2011

Sensor for Direct Measurement of the Boundary Shear Stress in Fluid Flow

shear stress↗

NASA NTRS2003

A patterns catalog for RTSJ software designs

In this survey paper, we bring together current progress to date in identifying design patterns for use with the real-time specification for Java in a format consistent with contemporary patterns descriptions.

Java design patterns real-time Java↗

NASA NTRS2015

Re-Evaluation of HSE DATA in Light of High P-T Partitioning Data: Late Chondritic Addition to Inner Solar System Bodies Not Always Required for HSE

Studies of terrestrial peridotite and martian and achondritic meteorites have led to the conclusion that addition of chondritic material to growing planets or planetesimals, after core formation, occurred on Earth, Moon, Mars, asteroid 4 Vesta, and the parent body of the angritic meteorites. One study even proposed that this was a common process in the final stages of growth. These conclusions are based al-most entirely on the 8 highly siderophile elements (HSE; Re, Au, Pt, Pd, Rh, Ru, Ir, Os), which have been used to argue for late accretion of chondritic material to the Earth after core formation was complete. This idea was originally proposed because the D(metal/silicate) values for the HSE are very high (greater than 10,000), yet their concentration in the terrestrial mantle is too high to be consistent with such high Ds. The HSE in the terrestrial mantle also are present in chondritic relative abundances and hence require similar Ds if this was the result of core-mantle equilibration. The conclusion that late chondritic additions are required for all five of these bodies is based on the chondritic relative abundances of the HSE, as well as their elevated concentrations in the samples. An easy solution is to call upon addition of chondritic material to the mantle of each body, just after core formation; however, in practice this means similar additions of chondritic materials to each body just after core formation which ranges from approximately 4-5 Ma after T(sub 0) for 4 Vesta and the angrites, to 10-25 Ma for Mars, to 35 to 60 Ma for Moon and perhaps the Earth. Since the work of there has been a realization that high PT conditions can lower the partition coefficients of many siderophile elements, indicating that high PT conditions (magma ocean stage) can potentially explain elevated siderophile element abundances. However, detailed high PT partitioning data have been lacking for many of the HSE to evaluate whether such ideas are viable for all four bodies. Re-cent partitioning studies have covered P, T, fO2, and compositional ranges that allow values to be predicted at conditions relevant to these five inner solar system bodies. Because the D(HSE) metal/silicate are lowered substantially at higher PT conditions and natural com-positions (FeNi metallic liquids and peridotites) it is natural to re-examine the role of core formation on the HSE patterns in a variety of inner solar system bodies. Here I will discuss other processes (including high PT core formation for Mars, Moon and Earth) that can produce the observed HSE patterns, and demonstrate that there are viable hypotheses other than the "one size fits all" hypothesis of late chondritic additions.

Righter, K.↗

NASA NTRS1991

Modeling of jet-induced geyser formation in a reduced gravity environment

Flow patterns predicted by a computational model of jet-induced geyser formation in a reduced gravity environment are presented and comparison is made to patterns predicted by experimentally based correlations. The configuration studied is an idealization of a forthcoming flight experiment to examine cryogenic propellant management issues. A transitional version of the ECLIPSE code used as a computational tool for the analyses is described. It is shown that computationally predicted flow patterns are in qualitative agreement with the correlation-based predictions, and some details of the predicted flow fields are given.

Wendl, M. C.↗

NASA NTRS1991

Phosphates in pallasite meteorites as probes of mantle processes in small planetary bodies

Trace element analyses of the phosphates minerals in stony-iron pallasite meteorites are used here to investigate the magmatic history of the silicate portions of pallasites. In Eagle Station and seven other pallasites, the phosphates have relatively low concentrations of REEs and are strongly enriched in heavy relative to light REE. These patterns are consistent with formation of phosphate by subsolidus reactions between metal and silicate, in which phosphate inherits the REE pattern of olivine. In Springwater and Santa Rosalia, calcium-rich phosphates have higher concentrations of REE, are enriched in light relative to heavy REE, and have negative europium anomalies. These patterns are consistent with crystallization of phosphate from a europium-depleted chondritic liquid. This is unlikely to have happened near the base of the differentiating parent-body mantle; it suggests that some pallasites may come from regions of their parent bodies much nearer the surface than the core-mantle boundary.

Davis, Andrew M.↗

NASA NTRS1980

Thunderstorm-environment interactions determined with three-dimensional trajectories

Diagnostically determined three dimensional trajectories were used to reveal some of the scale interaction processes that occur between convective storms and their environment. Data from NASA's fourth Atmospheric Variability Experiment are analyzed. Two intense squall lines and numerous reports of severe weather occurred during the period. Convective storm systems with good temporal and spatial continuity are shown to be related to the development and movement of short wave circulation systems aloft that propagate eastward within a zonal mid tropospheric wind pattern. These short wave systems are found to produce the potential instability and dynamic triggering needed for thunderstorm formation. The environmental flow patterns, relative to convective storm systems, are shown to produce large upward air parcel movements in excess of 50 mb/3h in the immediate vicinity of the storms. The air undergoing strong lifting originates as potentially unstable low level air traveling into the storm environment from southern and southwestern directions. The thermo and hydrodynamical processes that lead to changes in atmospheric structure before, during, and after convective storm formation are described using total time derivatives of pressure or net vertical displacement, potential temperature, and vector wind calculated by following air parcels.

Wilson, G. S.↗

NASA NTRS1986

Onset of surface-tension-driven Benard convection

An experimental investigation of the onset of convection in shallow fluid layers heated uniformly from below and cooled from above by an air layer has been made. If the depth of the silicone layer is smaller than 2 mm the onset of convection takes place in two stages. There is first a weak pattern, which is characterized by its appearance at ever smaller temperature gradients as the depth of the fluid is decreased. When the temperature difference across the fluid is increased a second strong pattern forms near the predicted critical Marangoni number. The cells in this pattern are hexagonal and seem to be what one has always referred to as Benard cells. The temperature gradient at which this pattern appears increases with decreased depth. The heat transfer through the fluid has been measured. The critical temperature gradient for the formation of the hexagonal pattern has been determined from the break of the heat transfer curve.

Koschmieder, E. L.↗

NASA NTRS2024

Alaska Ecological Conservation: Using NASA Earth Observations to Identify Recent Changes in River Ice Phenology and Its Impacts on Caribou Migration

Each fall, caribou (Rangifer tarandus) in the Western Arctic Herd migrate hundreds of kilometers across northwestern Alaska to acquire seasonal resources and reach wintering grounds. Various rivers intersect migration paths, and caribou can only cross over open water or high-ice extents but are unable to cross rivers in stages of partial freezing. Recent temperature increases in Alaska can alter the timing and duration of ice formation periods, impeding migratory patterns. The Massachusetts NASA DEVELOP team partnered with the National Park Service in Alaska to detect river ice onset dates and formation periods using Landsat 8 Operational Land Imager and Landsat 9 Operational Land Imager-2, Sentinel-1 C-band Synthetic Aperture Radar and Sentinel-2A/B MultiSpectral Instrument imagery in Google Earth Engine. This feasibility analysis measured ice coverage using the Normalized Difference Infrared Index, Relative Difference River Ice, and Vertical-Vertical/Vertical-Horizontal backscatter values based on the spectral and surface characteristics of rivers. The team produced annual freezing timelines, time series plots, and maps at three river stretches to analyze river ice phenology changes. Radar imagery assessed ice coverage more accurately, while optical imagery better identified ice onset dates. Meanwhile indices were unable to robustly establish ice formation thresholds across the study period. These study results can help the National Park Service to better evaluate spatiotemporal migratory shifts and contextualize recent regional caribou declines.

river phenology↗

NASA NTRS2005

By Different Cellular Mechanisms, Lymphatic Vessels Sprout by Endothelial Cell Recruitment Whereas Blood Vessels Grow by Vascular Expansion

The development of effective vascular therapies requires the understanding of all modes of vessel formation contributing to vasculogenesis, angiogenesis (here termed hemangiogenesis) and lymphangiogenesis. We show that lymphangiogenesis proceeds by blind-ended vessel sprouting via recruitment of isolated endothelial progenitor cells to the tips of growing vessels, whereas hemangiogenesis occurs by non-sprouting vessel expansion from the capillary network, during middevelopment in the quail chorioallantoic membrane (CAM). Blood vessels expanded out of capillaries that displayed transient expression of alpha smooth muscle actin (alphaSMA), accompanied by mural recruitment of migratory progenitor cells expressing SMA. Lymphatics and blood vessels were identified by confocal/fluorescence microscopy of vascular endothelial growth factor (VEGF) receptors VEGFR-1 and VEGFR-2, alphaSMA (expressed on CAM blood vessels but not on lymphatics), homeobox transcription factor Prox-1 (specific to CAM lymphatic endothelium), and the quail hematopoetic/vascular marker, QH-1. Expression of VEGFR-1 was highly restricted to blood vessels (primarily capillaries). VEGFR-2 was expressed intensely in isolated hematopoietic cells, lymphatic vessels and moderately in blood vessels. Prox-1 was absent from endothelial progenitor cells prior to lymphatic recruitment. Although vascular endothelial growth factor-165 (VEGF(sub 165)) is a key regulator of numerous cellular processes in hemangiogenesis and vasculogenesis, the role of VEGF(sub 165) in lymphangiogenesis is less clear. Exogenous VEGF(sub 165) increased blood vessel density without changing endogenous modes of vascular/lymphatic vessel formation or marker expression patterns. However, VEGF(sub 165) did increase the frequency of blood vascular anastomoses and strongly induced the antimaturational dissociation of lymphatics from blood vessels, with frequent formation of homogeneous lymphatic networks.

Parsons-Wingerter, Patricia↗

NASA NTRS1993

Selective formation of porous silicon

A pattern of porous silicon is produced in the surface of a silicon substrate by forming a pattern of crystal defects in said surface, preferably by applying an ion milling beam through openings in a photoresist layer to the surface, and then exposing said surface to a stain etchant, such as HF:HNO3:H20. The defected crystal will preferentially etch to form a pattern of porous silicon. When the amorphous content of the porous silicon exceeds 70 percent, the porous silicon pattern emits visible light at room temperature.

Fathauer, Jones↗

NASA NTRS1993

Selective formation of porous silicon

A pattern of porous silicon is produced in the surface of a silicon substrate by forming a pattern of crystal defects in said surface, preferably by applying an ion milling beam through openings in a photoresist layer to the surface, and then exposing said surface to a stain etchant, such as HF:HNO3:H2O. The defected crystal will preferentially etch to form a pattern of porous silicon. When the amorphous content of the porous silicon exceeds 70 percent, the porous silicon pattern emits visible light at room temperature.

Fathauer, Robert W.↗

NASA NTRS1973

Expansion pattern of helium-enriched shells associated with solar flares

The dependence of the thickness of the helium-enriched shell on the longitudinal position of the parent flares is considered along with the large-scale configuration of the expanding shell in interplanetary space. It is found that shock waves, magnetic bottles, and helium-enriched shells appear to expand eastwards of the meridian plane which crosses the flare region. It seems that the formation of the observed pattern of the shells is influenced by the interplanetary magnetic field between the sun and the earth.

Sakurai, K.↗