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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Directional Solidification of a Binary Alloy into a Cellular Convective Flow: Localized Morphologies

A steady, two dimensional cellular convection modifies the morphological instability of a binary alloy that undergoes directional solidification. When the convection wavelength is far longer than that of the morphological cells, the behavior of the moving front is described by a slow, spatial-temporal dynamics obtained through a multiple-scale analysis. The resulting system has a "parametric-excitation" structure in space, with complex parameters characterizing the interactions between flow, solute diffusion, and rejection. The convection stabilizes two dimensional disturbances oriented with the flow, but destabilizes three dimensional disturbances in general. When the flow is weak, the morphological instability behaves incommensurably to the flow wavelength, but becomes quantized and forced to fit into the flow-box as the flow gets stronger. At large flow magnitudes the instability is localized, confined in narrow envelopes with cells traveling with the flow. In this case the solutions are discrete eigenstates in an unbounded space. Their stability boundary and asymptotics are obtained by the WKB analysis.

Chen, Y.- J.↗
NASA NTRS2006

"One-Stop Shopping" for Ocean Remote-Sensing and Model Data

OurOcean Portal 2.0 (http:// ourocean.jpl.nasa.gov) is a software system designed to enable users to easily gain access to ocean observation data, both remote-sensing and in-situ, configure and run an Ocean Model with observation data assimilated on a remote computer, and visualize both the observation data and the model outputs. At present, the observation data and models focus on the California coastal regions and Prince William Sound in Alaska. This system can be used to perform both real-time and retrospective analyses of remote-sensing data and model outputs. OurOcean Portal 2.0 incorporates state-of-the-art information technologies (IT) such as MySQL database, Java Web Server (Apache/Tomcat), Live Access Server (LAS), interactive graphics with Java Applet at the Client site and MatLab/GMT at the server site, and distributed computing. OurOcean currently serves over 20 real-time or historical ocean data products. The data are served in pre-generated plots or their native data format. For some of the datasets, users can choose different plotting parameters and produce customized graphics. OurOcean also serves 3D Ocean Model outputs generated by ROMS (Regional Ocean Model System) using LAS. The Live Access Server (LAS) software, developed by the Pacific Marine Environmental Laboratory (PMEL) of the National Oceanic and Atmospheric Administration (NOAA), is a configurable Web-server program designed to provide flexible access to geo-referenced scientific data. The model output can be views as plots in horizontal slices, depth profiles or time sequences, or can be downloaded as raw data in different data formats, such as NetCDF, ASCII, Binary, etc. The interactive visualization is provided by graphic software, Ferret, also developed by PMEL. In addition, OurOcean allows users with minimal computing resources to configure and run an Ocean Model with data assimilation on a remote computer. Users may select the forcing input, the data to be assimilated, the simulation period, and the output variables and submit the model to run on a backend parallel computer. When the run is complete, the output will be added to the LAS server for

Li, P. Peggy↗
NASA NTRS2015

A Coordinated X-Ray and Optical Campaign of the Nearest Massive Eclipsing Binary, Delta Orionis Aa. II. X-Ray Variability

We present time-resolved and phase-resolved variability studies of an extensive X-ray high-resolution spectral data set of the delta Ori Aa binary system. The four observations, obtained with Chandra ACIS (Advanced CCD Imaging Spectrometer) HETGS (High Energy Transmission Grating), have a total exposure time approximately equal to 479 kiloseconds and provide nearly complete binary phase coverage. Variability of the total X-ray flux in the range of 5-25 angstroms is confirmed, with a maximum amplitude of about plus or minus15 percent within a single approximately equal to125 kiloseconds observation. Periods of 4.76 and 2.04 days are found in the total X-ray flux, as well as an apparent overall increase in the flux level throughout the nine-day observational campaign. Using 40 kiloseconds contiguous spectra derived from the original observations, we investigate the variability of emission line parameters and ratios. Several emission lines are shown to be variable, including S (sub XV), Si (sub XIII), and Ne (sub IX). For the first time, variations of the X-ray emission line widths as a function of the binary phase are found in a binary system, with the smallest widths at phi = 0.0 when the secondary delta Ori Aa2 is at the inferior conjunction. Using 3D hydrodynamic modeling of the interacting winds, we relate the emission line width variability to the presence of a wind cavity created by a wind-wind collision, which is effectively void of embedded wind shocks and is carved out of the X-ray-producing primary wind, thus producing phase-locked X-ray variability.

X-ray flux↗
NASA NTRS1995

Theory of the water vapor continuum and validations

A far-wing line shape theory based on the binary collision and quasistatic approximations that is applicable for both the low- and high-frequency wings of the vibration-rotational bands has been developed. This theory has been applied in order to calculate the frequency and temperature dependence of the continuous absorption coefficient for frequencies up to 10,000 cm(exp -1) for pure H2O and for H2O-N2 mixtures. The calculations were made assuming an interaction potential consisting of an isotropic Lennard-Jones part with two parameters that are consistent with values obtained from other data, and the leading long-range anisotropic part, together with the measured line strengths and transition frequencies. The results, obtained without the introduction of adjustable parameters, compare well with the existing laboratory data, both in magnitude and in temperature dependence. This leads us to the conclusion that the water continuum can be explained in terms of far-wing absorption. Current work in progress to extend the theory and to validate the theoretically calculated continuum will be discussed briefly.

Tipping, Richard H.↗
NASA NTRS1981

Theory of stellar coronae - An interpretation of X-ray emission from non-degenerate stellar sources

It is shown that the acoustic wave heating theory of stellar coronae explains neither Einstein Observatory coronae data nor previous UV and X-ray observations of the sun and other stars, on the evidence of data implying that magnetic fields, stellar rotation rates and convection zone parameters figure in the determination of coronal heating. Einstein Observatory results suggest that O-type star coronae are heated by the interaction of turbulent stellar winds with slowly-decaying primordial magnetic fields or by radiative instabilities in the flow. The apparent absence of coronae in Ap stars is due to the stability of atmospheres in which even weak convection is suppressed by the strong field. Dynamo action is implicated in some normal A-type stars and in F- and later-type dwarfs. Coronal characteristics of dMe and dM stars, close binaries, and K- and M-type giants are also considered.

Linsky, J. L.↗
NASA NTRS1983

User manual of the CATSS system (version 1.0) communication analysis tool for space station

The Communication Analysis Tool for the Space Station (CATSS) is a FORTRAN language software package capable of predicting the communications links performance for the Space Station (SS) communication and tracking (C & T) system. An interactive software package was currently developed to run on the DEC/VAX computers. The CATSS models and evaluates the various C & T links of the SS, which includes the modulation schemes such as Binary-Phase-Shift-Keying (BPSK), BPSK with Direct Sequence Spread Spectrum (PN/BPSK), and M-ary Frequency-Shift-Keying with Frequency Hopping (FH/MFSK). Optical Space Communication link is also included. CATSS is a C & T system engineering tool used to predict and analyze the system performance for different link environment. Identification of system weaknesses is achieved through evaluation of performance with varying system parameters. System tradeoff for different values of system parameters are made based on the performance prediction.

Tsang, C. S.↗
NASA NTRS1974

Binary stellar winds

Stellar winds from a binary star will interact with each other along a contact discontinuity. We discuss qualitatively the geometry of the flow and field resulting from this interaction in the simplest case where the stars and winds are identical. We consider the shape of the critical surface (defined as the surface where the flow speed is equal to the sound speed) as a function of stellar separation and the role of shock waves in the flow field. The effect of stellar spin and magnetic sectors on the field configuration is given. The relative roles of mass loss and magnetic torque in the evolution of orbital parameters are discussed.

Siscoe, G. L.↗
NASA NTRS1974

Binary stellar winds

Stellar winds from a binary star pair will interact with each other along a contact discontinuity. We discuss qualitatively the geometry of the flow and field resulting from this interaction in the simplest case where the stars and winds are identical. We consider the shape of the critical surface (defined as the surface where the flow speed is equal to the sound speed) as a function of stellar separation and the role of shock waves in the flow field. The effect of stellar spin and magnetic sectors on the field configuration is given. The relative roles of mass loss and magnetic torque in the evolution of orbital parameters is discussed.

Siscoe, G. L.↗
NASA NTRS1992

Interaction of photons in a canopy of finite-dimensional leaves

Neutral particle interaction for photons traveling in media consisting of finite-dimensional scattering centers is investigated. A leaf canopy, a typical example of such media, is idealized as a binary medium consisting of gaps (voids) and regions with phytoelements (turbid phytomedium). The leaf canopy is represented by a combination of all possible open oriented spheres. The extinction coefficient at any phase-space location in a leaf canopy is the product of the extinction coefficient in the turbid phytomedium and the probability of absence gaps at that location. An expression for the differential scattering coefficient is derived using the same approach. The effect of canopy parameters and direction of photon travel on the extinction coefficient is illustrated by numerical examples.

Knyazikhin, Yuri V.↗
NASA NTRS1989

X-ray emission from O-type stars - Parameters which affect it

As a result of previous analyses of the X-ray fluxes of O-type stars, it has been established that, surprisingly, there is no correlation between X-ray flux and such basic parameters as M, R, v(rot), T(eff), mass accretion rate v(infinity), L(w) = mass accretion rate v(infinity), and wind energy. In this paper, other factors influencing the X-ray flux of the hottest stars are sought. As a result of the present analysis, it is found that stars embedded in dense clouds are often X-ray brighter, runaway stars are fainter in X-rays, massive binaries emit more X-rays than single stars, and radio-bright stars are also more active in X-rays. All these correlations lead to the conclusion that the stellar environment and the interaction of the stellar wind with circumstellar matter (possible remnants of protostellar clouds) play a dominant role in the production of the X-ray flux.

Chlebowski, T.↗
NASA NTRS2005

Virtual Machine Language

Virtual Machine Language (VML) is a mission-independent, reusable software system for programming for spacecraft operations. Features of VML include a rich set of data types, named functions, parameters, IF and WHILE control structures, polymorphism, and on-the-fly creation of spacecraft commands from calculated values. Spacecraft functions can be abstracted into named blocks that reside in files aboard the spacecraft. These named blocks accept parameters and execute in a repeatable fashion. The sizes of uplink products are minimized by the ability to call blocks that implement most of the command steps. This block approach also enables some autonomous operations aboard the spacecraft, such as aerobraking, telemetry conditional monitoring, and anomaly response, without developing autonomous flight software. Operators on the ground write blocks and command sequences in a concise, high-level, human-readable programming language (also called VML ). A compiler translates the human-readable blocks and command sequences into binary files (the operations products). The flight portion of VML interprets the uplinked binary files. The ground subsystem of VML also includes an interactive sequence- execution tool hosted on workstations, which runs sequences at several thousand times real-time speed, affords debugging, and generates reports. This tool enables iterative development of blocks and sequences within times of the order of seconds.

Grasso, Christopher↗
NASA NTRS1989

Fortran Program for X-Ray Photoelectron Spectroscopy Data Reformatting

A FORTRAN program has been written for use on an IBM PC/XT or AT or compatible microcomputer (personal computer, PC) that converts a column of ASCII-format numbers into a binary-format file suitable for interactive analysis on a Digital Equipment Corporation (DEC) computer running the VGS-5000 Enhanced Data Processing (EDP) software package. The incompatible floating-point number representations of the two computers were compared, and a subroutine was created to correctly store floating-point numbers on the IBM PC, which can be directly read by the DEC computer. Any file transfer protocol having provision for binary data can be used to transmit the resulting file from the PC to the DEC machine. The data file header required by the EDP programs for an x ray photoelectron spectrum is also written to the file. The user is prompted for the relevant experimental parameters, which are then properly coded into the format used internally by all of the VGS-5000 series EDP packages.

Abel, Phillip B.↗
NASA NTRS2011

The Kepler Light Curves of V1504 Cygni and V344 Lyrae: A Study of the Outburst Properties

We examine the Kepler light curves of V1504 Cyg and V344 Lyr, encompassing approximately 460 d at 1 min cadence. During this span each system exhibited approximately 40 outbursts, including four superoutbursts. We find that, in both systems, the normal outbursts lying between two superoutbursts increase in duration by a factor approximately 1.2 - 1.7, and then reset to a small value after the following superoutburst. In V344 Lyr the trend of quiescent intervals between normal outbursts is to increase to a local maximum about half way through the supercycle the interval from one superoutburst to the next - and then to decrease back to a small value by the time of the next superoutburst, whereas for V1504 Cyg the quiescent intervals are relatively constant during the supercycle. Both of these trends are inconsistent with the Osaki's thermal-tidal model, which robustly predicts a secular increase in the quiescent intervals between normal outbursts during a supercycle. Also, most of the normal outbursts have an asymmetric, fast-rise/slower-decline shape, which would be consistent with outbursts triggered at large radii. The exponential rate of decay of the plateau phase of the superoutbursts is 8 d mag(sup -1) for approximately 1504 Cyg and 12 d mag(sup -1) for V344 Lyr. This time scale gives a direct measure of the VISCOUS time scale III the outer accretion disk given the expectation that the entire disk is in the hot, viscous state during superoutburst. The resulting constraint on the Shakura-Sunyaev parameter, alpha(sub hot) approximately equal to 0.1, is consistent with the value inferred from the fast dwarf nova decays. By looking at the slow decay rate for superoutbursts, which occur in systems below the period gap, in combination with the slow decay rate in one long outburst above the period gap (in U Gem), we infer a steep dependence of the decay rate on orbital period for long outbursts. We argue that this relation implies a steep dependence of alpha(sub cold) on orbital period, which may be consistent with recent findings of Patterson, and is consistent with tidal torquing as being the dominant angular momentum transport mechanism in quiescent disks in interacting binary systems.

Cannizzo, John K.↗
NASA NTRS1989

Optical pattern recognition; Proceedings of the Meeting, Los Angeles, CA, Jan. 17, 18, 1989

Papers on optical pattern recognition are presented, covering topics such as the estimation of satellite pose and motion parameters using a neural net tracker, associative memory, optical implmentation of programmable neural networks, optoelectronic neural networks, dynamic autoassociative neural memory, heteroassociative memory, bilinear pattern recognition processors, optical processing of optical correlation plane data, and a synthetic discriminant function-based nonlinear optical correlator. Other topics include an interactive optical-digital image processor, geometric transformations for video compression and human teleoperator display, quasiconformal remapping for compensation of human visual field defects, hybrid vision for automated spacecraft landing, advanced symbolic and inference optical correlation filters, and a rotationally invariant holographic tracking system. Additional topics include the detection of rotational and scale-varying objects with a programmable joint transform correlator, a single spatial light modulator binary nonlinear optical correlator, optical joint transform correlation, linear phase coefficient composite filters, and binary phase-only filters.

Liu, Hua-Kuang↗
NASA NTRSDate not supplied

Modeling of Multicomponent Trace Contaminant Adsorption on Activated Carbon

Modeling of multicomponent trace contaminant adsorption on activated carbon for spacecraft life support applications presents challenges due to the very low contaminant concentrations in cabin air coupled with very strong adsorption of heavier components such as cyclic polydimethylsiloxanes. Both gas-phase and solid-phase micropore mass transfer resistances can be important, and competitive interactions between adsorbed components can result in behavior such as roll-up where lighter components displaced by heavier components have a higher concentration at the outlet than at the inlet. This paper describes the further development of a dynamic trace contaminant adsorption model based on Ideal Adsorbed Solution Theory (IAST). Alternative 1-dimensional and 2-dimensional versions of the model are described with different mass transfer resistance and driving force assumptions. Optimization of solution methods for speed and stability is also described. Mass balance equations are scaled to provide sensitivity over the wide range of component concentrations in cabin air. Model parameters are estimated from isotherm and breakthrough test data on single adsorbate and binary adsorbate systems. Multicomponent results are compared against predictions of a heritage model used extensively by NASA for trace contaminant control system (TCCS) carbon bed sizing. Finally, efforts to implement the model in a second software platform for wider access are described.

Kevin E Lange↗
NASA NTRS1988

Companions to peculiar red giants: HR 363 and HR 1105

Recent IUE observations of two Tc-deficient S-type peculiar red giants that are also spectroscopic binaries, HR 363 and HR 1105 are reported. A 675 min SWP exposure of HR 363 shows emission lines of O I 1304 and Si II 1812 and a trace of continuum. Compared to the M giants, the far UV flux may be relatively larger, indicating a possible contribution from a white dwarf companion, but no high temperature emission lines are seen to indicate that this is an interacting system where mass-transfer recently occurred. However, HR 1105 appears to have a highly variable UV companion. In 1982, no UV flux was discerned for this system, but by 1986 C IV was strong, increasing by a factor of 3 in 1987 with prominent lines of Si III, C III, O III, Si IV, and N V. Using orbital parameters, these observations are consistent with high activity occuring when the side of the S-star primary illuminated by the companion faces the Earth, but since the IUE data were taken over 3 orbits, a secular change in the UV component cannot be excluded.

Ake, Thomas B., III↗
NASA NTRS2011

Imaging with HST the Time Evolution of Eta Carinae's Colliding Winds

We report new HST/STIS observations that map the high-ionization forbidden line emission in the inner arcsecond of Eta Car, the first that fully image the extended wind-wind interaction region of the massive colliding wind binary. These observations were obtained after the 2009.0 periastron at orbital phases 0.084, 0.163, and 0.323 of the 5.54-year spectroscopic cycle. We analyze the variations in brightness and morphology of the emission, and find that blue-shifted emission (-400 to -200 km/s is symmetric and elongated along the northeast-southwest axis, while the red-shifted emission (+ 100 to +200 km/s) is asymmetric and extends to the north-northwest. Comparison to synthetic images generated from a 3-D dynamical model strengthens the 3-D orbital orientation found by Madura et al. (2011), with an inclination i approx. 138deg, argument of periapsis omega approx. 270deg, and an orbital axis that is aligned at the same PA on the sky as the symmetry axis of the Homunculus, 312deg. We discuss the potential that these and future mappings have for constraining the stellar parameters of the companion star and the long-term variability of the system.

Gull, Theodore R.↗
NASA NTRS1993

Discovery of Orbital Decay in SMC X-1

We report on the results of three observations of the binary X-ray pulsar SMC X-1 with the Ginga satellite. Timing analyses of the 0.71 s X-ray pulsations yield Doppler delay curves which, in turn, enable the most accurate determination of the SMC X-1 orbital parameters available to date. Epochs of phase zero for the 3.9 day orbit were determined for 1987 May, 1988 August, and 1989 August with accuracies of 13, 0.6, and 3 s, respectively. These epochs are combined with two previous determinations of the orbital epoch to yield the rate of change in the orbital period dot-P(orb)/P(orb) = ( 3.36 +/- 0.02) x 10(exp -6) yr(exp -1). An interpretation of the orbital decay is made in the context of tidal evolution, with consideration of the influence of the increasing moment of inertia of the companion star due to its nuclear evolution. We find that, while the orbital decay is probably driven by tidal interactions, the asynchronism between the orbit and the rotation of the companion star is most likely maintained by the evolutionary expansion of the companion star (Sk 160) rather than via the Darwin instability. In this case Sk 160 is likely to be in the hydrogen shell burning phase of its evolution. Finally, a discussion is presented of the relation among the time scales for stellar evolution (less than 10(exp 7) yr), orbital decay (3 x 10(exp 5) yr), and neutron-star spin-up in the SMC X-1 system (2000 yr). In particular, we present the result of a self-consistent calculation for the histories of the spin of the neutron star and the mass transfer in this system. A plausible case can be made for the spin-up time scale being directly related to the lifetime of the luminous X-ray phase which will end in a common-envelope phase within a time of less than approx. 10(exp 4) yr.

Levine, A.↗