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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 1,189 records · Page 66
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Near-Earth asteroid satellite spins under spin-orbit coupling

We develop a fourth-order numerical integrator to simulate the coupled spin and orbital motions of two rigid bodies having arbitrary mass distributions under the influence of their mutual gravitational potential. We simulate the dynamics of components in well-characterized binary and triple near-Earth asteroid systems and use surface of section plots to map the possible spin configurations of the satellites. For asynchronous satellites, the analysis reveals large regions of phase space where the spin state of the satellite is chaotic. For synchronous satellites, we show that libration amplitudes can reach detectable values even for moderately elongated shapes. The presence of chaotic regions in the phase space has important consequences for the evolution of binary asteroids. It may substantially increase spin synchronization timescales, explain the observed fraction of asychronous binaries, delay BYORP-type evolution, and extend the lifetime of binaries. The variations in spin rate due to large librations also affect the analysis and interpretation of light curve and radar observations.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2003

Implications of Martian North/South Polar Differences

Our first requirement was to create the specialized tools necessary to precisely co-locate at highest spatial resolution the rapidly growing MOC/NA and MOLA data sets in the polar regions. This meant promptly creating a very accurate Mars Polar GIs system (based on the commercial ArcView product) along with various other supporting routines. Later we extended its use to the THEMIS/VIS data. That customized GIS and integrated data system has enabled all of our polar research to date. We focused initially on a preliminary geological reconnaissance in the Ultimi Lobe region of the South Polar Layered Deposits, which also included the intended MPL landing site about which much remote sensing data and interpretations had been accumulated before the failed landing attempt on December 3, 1999. The most interesting findings from that effort were discoveries about the layering, faulting and contact relationships exposed along the bounding scarp. Those results were published in Icarus. We have had a priority interest in the cratering record of the polar layered deposits, starting with the first post-Viking survey based on MOLA shaded relief maps and crossing profiles. Those results, based primarily on craters < 1 km diameter, were published in JGR and showed that a portion of the SPLD exhibited a large crater population consistent with an exposure age of 30 million years or more. Those craters also exhibited remarkably low Depth to Diameter ratios, which Asmin Pathare, then at UCLA, subsequently interpreted as due to slow viscous flow in the ice-rich material composing the PLD. Our cratering study also recognized that the craters of less than 1 km diameter were many order of magnitudes too few compared to what the crater production function of the larger craters requires.

Murray, Bruce C.↗
NASA NTRS1989

Middle Atmosphere Program. Handbook for MAP, volume 28

Extended abstracts from the fourth workshop on the technical and scientific aspects of MST (mesosphere stratosphere troposphere) radar are presented. Individual sessions addressed the following topics: meteorological applications of MST and ST radars, networks, and campaigns; dynamics of the equatorial middle atmosphere; interpretation of radar returns from clear air; techniques for studying gravity waves and turbulence; intercomparison and calibration of wind and wave measurements at various frequencies; progress in existing and planned MST and ST radars; hardware design for MST and ST radars and boundary layer/lower troposphere profilers; signal processing; and data management.

Liu, C. H.↗
NASA NTRS2003

Medusae Fossae-Elysium Region, Mars: Depression in the HEND/Odyssey Map of Mars Epithermal Neutrons

The first data from the Gamma Ray Spectrometer (GRS) onboard Mars Odyssey spacecraft showed that the low neutron fluxes characterize both subpolar regions of Mars. The low neutron fluxes mean the presence of hydrogen-rich soils and have been interpreted as an indication on abundant water ice in these areas. The equatorial region of Mars (equatorward of approx. 50 deg) is characterized by higher fluxes of both epithermal (0.4 eV-100 keV, come from depth 1-2 m) and fast (3.4-7.3 MeV, come from depth 0.2-0.3 m) neutrons meaning that this area is mostly dry. The pattern of distribution of the neutron fluxes is in a good agreement with the theoretical predictions on the stability of ground ice on present Mars. The actual distribution of the ice, however, depends on variations of thermal inertia of soils and albedo of the surface. The flux of the epithermal neutrons detected by the HEND instrument, which is part of GRS, has two noticeable depressions in the equatorial region, one in Arabia Terra and another in the Medusae Fossae-Elysium region (MFER). Here we present the initial results of analysis of characteristics of the neutron fluxes and regional geological setting of the epithermal neutron depression in this area. The main goal of our study was to put some constraints on the time of the anomaly formation and to assess possible form of hydrogen (ground ice vs. chemically bound water) there.

Ivanov, M. A.↗
DOE OSTI2022

Three-dimensional mapping of mineral in intact shark centra with energy dispersive x-ray diffraction

The centra of shark vertebrae consist of cartilage mineralized by a bioapatite similar to bone's carbonated hy-droxyapatite, and, without a repair mechanism analogous to remodeling in bone, these structures still survive millions of cycles of high-strain loading. The main structures of the centrum are an hourglass-shaped double cone and the intermedialia which supports the cones. Little is known about the nanostructure of shark centra, spe-cifically the relationship between bioapatite and cartilage fibers, and this study uses energy dispersive diffraction (EDD) with polychromatic synchrotron x-radiation to study the spatial organization of the mineral phase and its crystallographic texture. The unique energy-sensitive detector array at beamline 6-BM-B, the Advanced Photon Source, enables EDD to quantify the texture within each sampling volume with one exposure while constructing 3D maps via specimen translation across the sampling volume. Herein this study maps a centrum from two shark orders, a carcharhiniform and a lamniform, with different intermedialia structures. In the blue shark (Prionace glauca, Carcharhiniformes), the bioapatite's c-axes are oriented laterally within the centrum's cone walls but axially within the wide wedges of the intermedialia; the former is interpreted to resist lateral deformation, the latter to support axial loads. In the shortfin mako (Isurus oxyrinchus, Lamniformes), there is some tendency for c-axis variation with position, but the situation is unclear because one dimension of the sampling volume is consid-erably larger than the thickness and spacing of the intermedialia's radially-oriented lamellae. Because elastic modulus in collagen plus bioapatite mineralized tissues varies significantly with both volume fraction of bio-apatite and crystallographic texture, the present 3D EDD-derived maps should inform future 3D numerical models of shark centra under applied load.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

PDR MODEL MAPPING OF OBSCURED H{sub 2} EMISSION AND THE LINE-OF-SIGHT STRUCTURE OF M17-SW

We observed H{sub 2} line emission with Spitzer-IRS toward M17-SW and modeled the data with our photon-dominated region (PDR) code. Derived gas density values of up to few times 10{sup 7} cm{sup -3} indicate that H{sub 2} emission originates in high-density clumps. We discover that the PDR code can be utilized to map the amount of intervening extinction obscuring the H{sub 2} emission layers, and thus we obtain the radial profile of A{sub V} relative to the central ionizing cluster NGC 6618. The extinction has a positive radial gradient, varying between 15-47 mag over the projected distance of 0.9-2.5 pc from the primary ionizer, CEN 1. These high extinction values are in good agreement with previous studies of A{sub V} toward stellar targets in M17-SW. The ratio of data to PDR model values is used to infer the global line-of-sight structure of the PDR surface, which is revealed to resemble a concave surface relative to NGC 6618. Such a configuration confirms that this PDR can be described as a bowl-shaped boundary of the central H II region in M17. The derived structure and physical conditions are important for interpreting the fine-structure and rotational line emission from the PDR.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Interacting boson model from energy density functionals: {gamma}-softness and the related topics

A comprehensive way of deriving the Hamiltonian of the interacting boson model (IBM) is described. Based on the fact that the multi-nucleon induced surface deformation in finite nucleus is simulated by effective boson degrees of freedom, the potential energy surface calculated with self-consistent mean-field method employing a given energy density functional (EDF) is mapped onto the IBM analog, and thereby the excitation spectra and transition rates with good symmetry quantum numbers are calculated. Recent applications of the proposed approach are reported: (i) an alternative robust interpretation of the {gamma}-soft nuclei and (ii) shape coexistence in lead isotopes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Visualization of the operational space of edge-localized modes through low-dimensional embedding of probability distributions

Information visualization aimed at facilitating human perception is an important tool for the interpretation of experiments on the basis of complex multidimensional data characterizing the operational space of fusion devices. This work describes a method for visualizing the operational space on a two-dimensional map and applies it to the discrimination of type I and type III edge-localized modes (ELMs) from a series of carbon-wall ELMy discharges at JET. The approach accounts for stochastic uncertainties that play an important role in fusion data sets, by modeling measurements with probability distributions in a metric space. The method is aimed at contributing to physical understanding of ELMs as well as their control. Furthermore, it is a general method that can be applied to the modeling of various other plasma phenomena as well.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

CRITICAL CURVES AND CAUSTICS OF TRIPLE-LENS MODELS

Among the 25 planetary systems detected up to now by gravitational microlensing, there are two cases of a star with two planets, and two cases of a binary star with a planet. Other, yet undetected types of triple lenses include triple stars or stars with a planet with a moon. The analysis and interpretation of such events is hindered by the lack of understanding of essential characteristics of triple lenses, such as their critical curves and caustics. We present here analytical and numerical methods for mapping the critical-curve topology and caustic cusp number in the parameter space of n-point-mass lenses. We apply the methods to the analysis of four symmetric triple-lens models, and obtain altogether 9 different critical-curve topologies and 32 caustic structures. While these results include various generic types, they represent just a subset of all possible triple-lens critical curves and caustics. Using the analyzed models, we demonstrate interesting features of triple lenses that do not occur in two-point-mass lenses. We show an example of a lens that cannot be described by the Chang–Refsdal model in the wide limit. In the close limit we demonstrate unusual structures of primary and secondary caustic loops, and explain the conditions for their occurrence. In the planetary limit we find that the presence of a planet may lead to a whole sequence of additional caustic metamorphoses. We show that a pair of planets may change the structure of the primary caustic even when placed far from their resonant position at the Einstein radius.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE MAGNETIZED ENVIRONMENT OF THE W3(H{sub 2}O) PROTOSTARS

We present the first interferometric polarization map of the W3(OH) massive star-forming region observed with the Submillimeter Array (SMA) at 878 {mu}m with an angular resolution of 1.''5 (about 3 Multiplication-Sign 10{sup 3} AU). Polarization is detected in the W3(H{sub 2}O) hot core, an extended emission structure in the northwest of W3(H{sub 2}O), and part of the W3(OH) ultracompact H II region. The W3(H{sub 2}O) hot core is known to be associated with a synchrotron jet along the east-west direction. In this core, the inferred magnetic field orientation is well aligned with the synchrotron jet and close to the plane of sky. Using the Chandrasekhar-Fermi method with the observed dispersion in polarization angle, we estimate a plane-of-sky magnetic field strength of 17.0 mG. Combined with water maser Zeeman measurements, the total magnetic field strength is estimated to be 17.1 mG, comparable to the field strength estimated from the synchrotron model. The magnetic field energy dominates over turbulence in this core. In addition, the depolarization effect is discerned in both SMA and James Clerk Maxwell Telescope measurements. Despite the great difference in angular resolutions and map extents, the polarization percentage shows a similar power-law dependence with the beam averaged column density. We suggest that the column density may be an important factor to consider when interpreting the depolarization effect.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1982

Investigating tectonic and bathymetric features of the Indian Ocean using MAGSAT magnetic anomaly data

An equivalent source anomaly map and a map of the relative magnetization for the investigation region were produced. Gravimetry, bathymetry, and MAGSAT anomaly maps were contoured in pseudocolor displays. Finally, an autoregressive spectrum estimation technique was verified with synthetic data and shown to be capable of resolving exponential power spectra using small samples of data. Interpretations were made regarding the relationship between MAGSAT data spectra and crustal anomaly spectra.

Sailor, R. V.↗
NASA NTRS1985

Improving the geological interpretation of magnetic and gravity satellite anomalies

Current limitations in the quantitative interpretation of satellite-elevation geopotential field data and magnetic anomaly data were investigated along with techniques to overcome them. A major result was the preparation of an improved scalar magnetic anomaly map of South America and adjacent marine areas directly from the original MAGSAT data. In addition, comparisons of South American and Euro-African data show a strong correlation of anomalies along the Atlantic rifted margins of the continents.

Hinze, W. J.↗
NASA NTRS1985

Viscous remanent magnetization model for the Broken Ridge satellite magnetic anomaly

An equivalent source model solution of the satellite magnetic field over Australia obtained by Mayhew et al. (1980) showed that the satellite anomalies could be related to geological features in Australia. When the processing and selection of the Magsat data over the Australian region had progressed to the point where interpretation procedures could be initiated, it was decided to start by attempting to model the Broken Ridge satellite anomaly, which represents one of the very few relatively isolated anomalies in the Magsat maps, with an unambiguous source region. Attention is given to details concerning the Broken Ridge satellite magnetic anomaly, the modeling method used, the Broken Ridge models, modeling results, and characteristics of magnetization.

Johnson, B. D.↗
NASA NTRS1987

Fluvial valleys on Martian volcanoes

Channels and valleys were known on the Martian volcanoes since their discovery by the Mariner 9 mission. Their analysis has generally centered on interpretation of possible origins by fluvial, lava, or viscous flows. The possible fluvial dissection of Martian volcanoes has received scant attention in comparison to that afforded outflow, runoff, and fretted channels. Photointerpretative, mapping, and morphometric studies of three Martian volcanoes were initiated: Ceraunius Tholus, Hecate Tholus, and Alba Patera. Preliminary morphometric results indicate that, for these three volcanoes, valley junction angles increase with decreasing slope. Drainage densities are quite variable, apparently reflecting complex interactions in the landscape-forming factors described. Ages of the Martian volcanoes were recently reinterpreted. This refined dating provides a time sequence in which to evaluate the degradational forms. An anomaly has appeared from the initial study: fluvial valleys seem to be present on some Martian volcanoes, but not on others of the same age. Volcanic surfaces characterized only by high permeability lava flows may have persisted without fluvial dissection.

Baker, Victor R.↗
NASA NTRS1988

Software development without languages

Automatic programming generally involves the construction of a formal specification; i.e., one which allows unambiguous interpretation by tools for the subsequent production of the corresponding software. Previous practical efforts in this direction have focused on the serious problems of: (1) designing the optimum specification language; and (2) mapping (translating or compiling) from this specification language to the program itself. The approach proposed bypasses the above problems. It postulates that the specification proper should be an intermediate form, with the sole function of containing information sufficient to facilitate construction of programs and also of matching documentation. Thus, the means of forming the intermediary becomes a human factors task rather than a linguistic one; human users will read documents generated from the specification, rather than the specification itself.

Osborne, Haywood S.↗
NASA NTRS1989

Multifrequency survey of the intergalactic cloud in the M96 group

The intergalactic cloud of neutral hydrogen in the M96 group are examined for signs of emission over a wide range of frequencies, from radio waves to X rays. Past or present stellar activity in the gas might have been expected to produce detectable visual infrared, CO, OH, or radio recombination-line emission. None was detected. The limits are used to study physical conditions in the intergalactic gas. In particular, B and V band limits on starlight and IRAS limits on the presence of dust strongly constrain the presence of stars or stellar by-products. However, given the uncertainties about physical conditions in the intergalactic environment, it is difficult to rule out entirely the presence of stellar-processed materials. Results of neutral hydrogen mapping from a large-scale survey of the intergalactic cloud and surrounding region are also presented. These observations confirm that the gas is confined to a large ringlike structure. The simplest interpretation remains that the intergalactic gas in Leo is primordial.

Schneider, Stephen E.↗
NASA NTRS1999

Investigating Galactic Structure with COBE/DIRBE and Simulation

In this work I applied the current version of the SKY model of the point source sky to the interpretation of the diffuse all-sky emission observed by COBE/DIRBE (Cosmic Background Explorer Satellite/Diffuse Infrared Background Experiment). The goal was to refine the SKY model using the all-sky DIRBE maps of the Galaxy, in order that a search could be made for an isotropic cosmic background."Faint Source Model" [FSM] was constructed to remove Galactic fore ground stars from the ZSMA products. The FSM mimics SKY version 1 but it was inadequate to seek cosmic background emission because of the sizeable residual emission in the ZSMA products after this starlight subtraction. At this point I can only support that such models are currently inadequate to reveal a cosmic background. Even SKY5 yields the same disappointing result.

Cohen, Martin↗
NASA NTRS1995

Statistical properties of DNA sequences

We review evidence supporting the idea that the DNA sequence in genes containing non-coding regions is correlated, and that the correlation is remarkably long range--indeed, nucleotides thousands of base pairs distant are correlated. We do not find such a long-range correlation in the coding regions of the gene. We resolve the problem of the "non-stationarity" feature of the sequence of base pairs by applying a new algorithm called detrended fluctuation analysis (DFA). We address the claim of Voss that there is no difference in the statistical properties of coding and non-coding regions of DNA by systematically applying the DFA algorithm, as well as standard FFT analysis, to every DNA sequence (33301 coding and 29453 non-coding) in the entire GenBank database. Finally, we describe briefly some recent work showing that the non-coding sequences have certain statistical features in common with natural and artificial languages. Specifically, we adapt to DNA the Zipf approach to analyzing linguistic texts. These statistical properties of non-coding sequences support the possibility that non-coding regions of DNA may carry biological information.

Non-NASA Center↗