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NASA NTRS2005

A Comparison of Geographic Information Systems, Complex Networks, and Other Models for Analyzing Transportation Network Topologies

This report reviews six classes of models that are used for studying transportation network topologies. The report is motivated by two main questions. First, what can the "new science" of complex networks (scale-free, small-world networks) contribute to our understanding of transport network structure, compared to more traditional methods? Second, how can geographic information systems (GIS) contribute to studying transport networks? The report defines terms that can be used to classify different kinds of models by their function, composition, mechanism, spatial and temporal dimensions, certainty, linearity, and resolution. Six broad classes of models for analyzing transport network topologies are then explored: GIS; static graph theory; complex networks; mathematical programming; simulation; and agent-based modeling. Each class of models is defined and classified according to the attributes introduced earlier. The paper identifies some typical types of research questions about network structure that have been addressed by each class of model in the literature.

Alexandrov, Natalia↗

NASA NTRS1977

Is osmium chemically fractionated in the moon

An investigation was conducted involving the determination of Os in 53 highland samples from the Apollo 14-17 missions. The Os/Ir ratio was found to remain essentially constant at 1.05 as Os and Ir abundances vary over four orders of magnitude. The Os-Au and the Os-Ni correlation in highland samples is presented in graphs. The graphs show that the majority of highland samples have Os/Au and Os/Ni ratios somewhat below the cosmic value. But there is no reason to attribute this trend to a loss of Os by local processes, because two other refractory siderophiles, Ir and Re, show exactly the same trend. Results on more than 150 analyzed highland samples show that meteoritic groups of low (Ir, Re, Os)/Au ratio are much more common at the Apollo landing sites than are groups of high ratio.

Hertogen, J.↗

NASA NTRS1988

H2 spectroscopy and a diurnally changing cloud on Jupiter

Spectroscopic observations of H2 in specific longitude regions of Jupiter as they rotate from limb to limb are reported. Data obtained in the 3-0 S(0) and S(1) lines using a CCD detector and a spectrograph with either echelle or plane gratings at the Cassegrain focus of the 24-inch telescope at Whipple Observatory during April-June 1983 are presented in extensive tables and graphs and analyzed in detail, modeling spatial and temporal variations at seven latitudes. An east-to-west increase in the equivalent line widths is attributed to the combined action of internal and solar heating of a convective layer, resulting in diurnal changes in the vertical cloud structure. It is inferred that the hydrogen observed is mainly in an equilibrium thermodynamic state, with small amounts of nonequilibrium hydrogen at high altitudes.

Cunningham, Cindy C.↗

NASA NTRS1986

Clay-mineraloid weathering products in Antarctic meteorites

The production of clay mineraloids (CMs) in the weathering of stony meteorites recovered in the Allan Hills and Elephant Moraine areas of Antarctica is investigated, applying electron microbeam analysis, pyrolysis/mass spectroscopy, X-ray diffractometry, and differential scanning calorimetry to whole-rock chips from two eucrites, two diogenites, and an H5 chondrite. The data are presented in tables, graphs, and photomicrographs and characterized in detail. Massive to incipient-vermicular CM formations with smectitelike or micalike compositions and indications of poor crystallization are observed and attributed to hydrocryogenic diagenesis (with little or no liquid water) on time scales of 10-1000 kyr. The need to take the compositional effects of weathering into account before attempting to reconstruct the preterrestrial histories of meteorites is stressed.

Gooding, James L.↗

NASA NTRS1989

Diffraction of impulsive sounds by a curved obstruction - A time-domain study

The diffraction of spark-discharge-produced sound waves produced by a half circular cylinder covered with absorbing material is investigated theoretically and experimentally. The test bench setup and the measurement instrumentation and procedure are described; the derivation of an analytical model on the basis of the matched asymptotic expansion theory of Pierce (1981) is outlined; and the results are compared in graphs. Good general agreement is obtained, except in the deep shadow of the obstacle, where the theory underpredicts the magnitude of the received pulse. This discrepancy is tentatively attributed to the creeping-wave mechanism described by Pierce.

Berthelot, Yves H.↗

NASA NTRS1986

Implications of the light curve of the A-type W UMa binary V566 Ophiuchi

Broadband (2585-3200-A) IUE photometric observations of V566 Oph obtained in three 8-h shifts on July 17-19, 1984 are reported and solved simultaneously with the ground-based optical observations of Bookmyer (1976). The observed light curves are fit to theoretical Roche-model light curves using the computer program described by Eaton (1986). The data and solutions are presented in tables and graphs, and the modifications required to match the solutions to data for 1965 (Bookmyer, 1969) and 1957 (Binnendjik, 1959) are considered. The lower-than-expected darkening observed is attributed to a reduced common-radiative-envelope temperature gradient, probably a result of circulation related to energy transfer between the components of V566 Oph.

Eaton, Joel A.↗

NASA NTRS1985

Laboratory simulation of meteoritic noble gases. I - Sorption of xenon on carbon: Trapping experiments

The sorption of Xe-127 at 5 x 10 to the -7th atm onto carbon black, pyrolyzed polyvinylidene chloride, and pyrolyzed acridine at 100-1000 C for 5 min-240 h is measured experimentally by gamma spectrometry. The results are presented in tables and graphs and characterized in detail. The tightly bound Xe remaining in the samples after 4000 min pumping at temperatures above 100 C is found to comprise two components: a low-temperature component attributed to physisorption within an atomic-scale labyrinth of micropores, and a high-temperature component due to volume diffusion. The implications for the trapping of noble gases near grain surfaces of amorphous carbon in meteorites are considered.

Wacker, J. F.↗

NASA NTRS1983

Space station needs, attributes and architectural options: Mission requirements

Various mission requirements for the proposed space station are examined. Subjects include modelling methodology, science applications, commercial opportunities, operations analysis, integrated mission requirements, and the role of man in space station functions and activities. The information is presented through the use of graphs.

Source record↗

NASA NTRS1984

Magnetic cristobalite (?) - A possible new magnetic phase produced by the thermal decomposition of nontronite

The effect of heat treatment for 1 h or more at 900-1000 C on the magnetic properties of nontronite, an iron-rich smectite clay thought to be an important component of Martian regolith, is investigated experimentally, extending the findings of Moskowitz and Hargraves (1982). The results are presented in graphs and tables and discussed. A phase with Curie temperature 200-220 C, remanent coercivity greater than 800 mT, and a type-2 room-temperature-coercivity response to thermomagnetic cycling is observed and attributed to an iron-substituted cristobalite which may form by topotactic growth from a smectite precursor.

Moskowitz, B. M.↗

NASA NTRS1983

The role of spatial, spectral and radiometric resolution on information content

The results of a factorial experiment to evaluate the effects of spatial, spectral, and radiometric resolution on training-data spectral separability and classification accuracy are reported. Aircraft scanner data from five flightlines at 19.8 km over California including croplands, rangeland, forest, water, and urban areas were systematically degraded over a range approximately from Landsat MSS to Thematic Mapper specifications. Reference data were collected on the ground and from aerial photography. The degradations, training-site delineation, data-analysis procedures, and accuracy-assessment techniques are described; the results are presented in tables and graphs and discussed. It is found that while accuracy was increased by higher spectral resolution in 70 percent of the cases and uniformly by increased radiometric resolution, it was decreased by higher spatial resolution. This phenomenon is attributed to classification methods.

Buis, J. S.↗

NASA NTRS1986

Brightness asymmetry in comet Kopff

Observations of comet Kopff, obtained at 350-650 nm with resolution 1.15 nm using an IDS spectrograph on the 2.7-m telescope at McDonald Observatory during the 1983 apparition, are reported, summarizing the results of Cochran (1985). The data are presented in tables and graphs and analyzed using two models: the one-dimensional nonequilibrium-chemistry code developed by Cochran (1982 and 1985) for comet Stephan-Oterma, or the simpler model of Haser (1957). A brightness asymmetry in comet Kopff is attributed to preperihelion gas excess and postperihelion gas depletion.

Cochran, A. L.↗

NASA NTRS1987

Surface brightness profiles of 10 comets

CCD photometric observations of the comae of 10 comets, obtained at the 4-m and 2.1-m telescopes at KPNO during 1985-1986 using filters centered at 700.5, 650.0, or 546.0 nm, are reported. The data are presented in extensive tables and graphs and characterized in detail. The radial surface brightness profiles are shown to be steeper than predicted by an idealized spherically symmetric steady-state comet model, the steepness increasing with the projected distance from the nucleus. These profiles are attributed, on the basis of Monte Carlo simulations, to imperfect coupling between the sublimated gas and the optically dominant grains of the coma.

Jewitt, D. C.↗

NASA NTRS2007

A Longitudinal Analysis of the Causal Factors in Major Maritime Accidents in the USA and Canada (1996-2006)

Accident reports provide important insights into the causes and contributory factors leading to particular adverse events. In contrast, this paper provides an analysis that extends across the findings presented over ten years investigations into maritime accidents by both the US National Transportation Safety Board (NTSB) and Canadian Transportation Safety Board (TSB). The purpose of the study was to assess the comparative frequency of a range of causal factors in the reporting of adverse events. In order to communicate our findings, we introduce J-H graphs as a means of representing the proportion of causes and contributory factors associated with human error, equipment failure and other high level classifications in longitudinal studies of accident reports. Our results suggest the proportion of causal and contributory factors attributable to direct human error may be very much smaller than has been suggested elsewhere in the human factors literature. In contrast, more attention should be paid to wider systemic issues, including the managerial and regulatory context of maritime operations.

Johnson, C. W.↗

NASA NTRS1991

Absolute extinction and the influence of environment - Dark cloud sight lines toward VCT 10, 30, and Walker 67

The range of validity of the average absolute extinction law (AAEL) proposed by Cardelli et al. (1988 and 1989) is investigated, combining published visible and NIR data with IUE UV observations for three lines of sight through dense dark cloud environments with high values of total-to-selective extinction. The characteristics of the data sets and the reduction and parameterization methods applied are described in detail, and the results are presented in extensive tables and graphs. Good agreement with the AAEL is demonstrated for wavelengths from 3.4 microns to 250 nm, but significant deviations are found at shorter wavelengths (where previous studies of lines of sight through bright nebulosity found good agreement with the AAEL). These differences are attributed to the effects of coatings on small-bump and FUV grains.

Cardelli, Jason A.↗

NASA NTRS1986

Rare earth element patterns in Archean high-grade metasediments and their tectonic significance

REE data on metasedimentary rocks from two different types of high-grade Archean terrains are presented and analyzed. The value of REEs as indicators of crustal evolution is explained; the three geologic settings (in North America, Southern Africa, and Australia) from which the samples were obtained are described; and the data are presented in extensive tables and graphs and discussed in terms of metamorphic effects, the role of accessory phases, provenance, and tectonic implications (recycling, the previous extent of high-grade terrains, and a model of Archean crustal growth). The diversity of REE patterns in shallow-shelf metasediments is attributed to local provenance, while the Eu-depleted post-Archean patterns are associated with K-rich plutons from small, stable early Archean terrains.

Taylor, Stuart Ross↗

NASA NTRS1987

Shock effects and argon loss in samples of the Leedey L6 chondrite experimentally shocked to 29-70 GPa pressures

The recovery of polished 600-micron-thick 7-mm-diameter disk samples and powder samples of the Leedey L6 chondrite from 29-70-GPa experimental shocks is investigated experimentally under vacuum conditions, with a focus on the possible direct shock loss of radiogenic Ar. The results of petrographic examination of the shocked samples and Ar isotope measurements are presented in tables, graphs, and micrographs and characterized in detail. The principal damage mechanisms are identified as mechanical disaggregation and increasing cataclasis, with little melting. The degassing of radiogenic Ar is found to be relatively modest and to increase with shock pressure and sample porosity; it is attributed to a combination of mechanical grain disruption and feldspar melting. It is inferred that Ar loss in naturally shocked materials (especially those showing few signs of melting) probably occurs during extended exposure to high temperatures during impact formation.

Bogard, Donald↗

NASA NTRS1990

The stabilization of electrolytes for rechargeable lithium batteries

Recent experimental studies of Li secondary cells are reviewed, focusing on (1) the novel anion lithium trifluoromethanesulfonyl imide (LTI) and (2) the use of KO2 and KOH additives to stabilize the electrolyte. Sample data are presented in tables and graphs and briefly characterized. The charging limits of LTI were found to compare favorably with those of LiAsFe6/THF and 2-MeTHF. Significant improvements were also obtained with the additives, but the results were erratic, with 2-3-fold variations among identical preparations. These differences are tentatively attributed to Li-film inhomogeneities and reactions of O2(-) with the solvent and impurities, especially in the cathode pores.

Dominey, L. A.↗

NASA NTRS1985

Shock associated noise of inverted-profile coannular jets. II - Condition for minimum noise. III - Shock structure and noise characteristic

The generation of noise by the shock-turbulence interaction with shock cells in an inverted-profile coannular jet with nozzle exit velocity aligned with the jet axis is investigated analytically, interpreting the optical measurements of Tanna et al. (1985). The noise-intensity minimum at slightly supersonic primary-flow velocities is related to the weakness of the primary-stream shock-cell structure and the lack of such a pattern in the outer fan stream. The discrepancies between this finding and those of Dosanjh et al. (1977 and 1978) are attributed to nozzle design, the definition of minimum noise, and different interpretative approaches. A first-order shock-cell model is then developed to derive formulas for the peak frequencies and the scaling of noise intensity. The results of computations using these formulas are presented in graphs and found to be in good agreement with the experimental data.

Tam, C. K. W.↗