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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Integrating Commercial Off-The-Shelf (COTS) graphics and extended memory packages with CLIPS

This paper addresses the question of how to mix CLIPS with graphics and how to overcome PC's memory limitations by using the extended memory available in the computer. By adding graphics and extended memory capabilities, CLIPS can be converted into a complete and powerful system development tool, on the other most economical and popular computer platform. New models of PCs have amazing processing capabilities and graphic resolutions that cannot be ignored and should be used to the fullest of their resources. CLIPS is a powerful expert system development tool, but it cannot be complete without the support of a graphics package needed to create user interfaces and general purpose graphics, or without enough memory to handle large knowledge bases. Now, a well known limitation on the PC's is the usage of real memory which limits CLIPS to use only 640 Kb of real memory, but now that problem can be solved by developing a version of CLIPS that uses extended memory. The user has access of up to 16 MB of memory on 80286 based computers and, practically, all the available memory (4 GB) on computers that use the 80386 processor. So if we give CLIPS a self-configuring graphics package that will automatically detect the graphics hardware and pointing device present in the computer, and we add the availability of the extended memory that exists in the computer (with no special hardware needed), the user will be able to create more powerful systems at a fraction of the cost and on the most popular, portable, and economic platform available such as the PC platform.

Callegari, Andres C.↗
NASA NTRS2007

The Suzaku Observation of the Nucleus of the Radio Loud Active Galaxy Centaurus A: Constraints on Abundances in the Accreting Material

A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The hard X-rays are fit by two power laws, absorbed by columns of 1.5 and 7 x 10(exp 23) per square centimeter. The dual power-laws are consistent with previous suggestions that the powerlaw components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, or are consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature VAPEC model, plus a third power-law component to account for scattered nuclear emission, kpc-scale jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The width of the Fe Ka line yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. K-shell absorption edges due to Fe, Ca, and S are detected. Elemental abundances are constrained via the fluorescent lines strengths, absorption edge depths and the diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.l) of the circumnuclear material compared to that in the metal-poor outer halo suggests that the accreting material could not have originated in the outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

Markowitz, A.↗
NASA NTRS1995

The Linux operating system: An introduction

Linux is a Unix-like operating system for Intel 386/486/Pentium based IBM-PCs and compatibles. The kernel of this operating system was written from scratch by Linus Torvalds and, although copyrighted by the author, may be freely distributed. A world-wide group has collaborated in developing Linux on the Internet. Linux can run the powerful set of compilers and programming tools of the Free Software Foundation, and XFree86, a port of the X Window System from MIT. Most capabilities associated with high performance workstations, such as networking, shared file systems, electronic mail, TeX, LaTeX, etc. are freely available for Linux. It can thus transform cheap IBM-PC compatible machines into Unix workstations with considerable capabilities. The author explains how Linux may be obtained, installed and networked. He also describes some interesting applications for Linux that are freely available. The enormous consumer market for IBM-PC compatible machines continually drives down prices of CPU chips, memory, hard disks, CDROMs, etc. Linux can convert such machines into powerful workstations that can be used for teaching, research and software development. For professionals who use Unix based workstations at work, Linux permits virtually identical working environments on their personal home machines. For cost conscious educational institutions Linux can create world-class computing environments from cheap, easily maintained, PC clones. Finally, for university students, it provides an essentially cost-free path away from DOS into the world of Unix and X Windows.

Bokhari, Shahid H.↗
NASA NTRS1990

A statistical study of Pc 3-5 pulsations observed by the AMPTE/CCE magnetic fields experiment. I - Occurrence distributions

A classification system based on dynamic power spectra of AMPTE/CCE magnetic field data has been developed which allows semiquantitative specification of pulsation activity at all times. Fifteen months of 6.24-s AMPTE/CCE magnetic field data have been analyzed using this scheme to generate a comprehensive data base of all pulsation activity observed from L = 5 to L = 9 at all local times in the frequency range 0-80 mHz. The pulsation divide naturally into five basic categories: toroidal fundamental mode resonances, toroidal harmonic resonances, compressional low-frequency waves, radially polarized waves, and disturbed intervals. Additional distinctions among members of these classes are made to arrive at 14 categories which describe 95 percent of the pulsations observed. Normal spatial distributions in local time and L shell are determined for each category. Magnetic latitude distributions are determined for four coherent categories of activity.

Anderson, B. J.↗
NASA NTRS1993

Approaches to solar cell design for pulsed laser power receivers

Using a laser to beam power from Earth to a photovoltaic receiver in space could be a technology with applications to many space missions. Extremely high average-power lasers would be required in a wavelength range of 700-1000 nm. However, high-power lasers inherently operate in a pulsed format. Existing solar cells are not well designed to respond to pulsed incident power. To better understand cell response to pulsed illumination at high intensity, the PC-1D finite-element computer model was used to analyze the response of solar cells to continuous and pulsed laser illumination. Over 50 percent efficiency was calculated for both InP and GaAs cells under steady-state illumination near the optimum wavelength. The time-dependent response of a high-efficiency GaAs concentrator cell to a laser pulse was modeled, and the effect of laser intensity, wavelength, and bias point was studied. Three main effects decrease the efficiency of a solar cell under pulsed laser illumination: series resistance, L-C 'ringing' with the output circuit, and current limiting due to the output inductance. The problems can be solved either by changing the pulse shape or designing a solar cell to accept the pulsed input. Cell design possibilities discussed are a high-efficiency, light-trapping silicon cell, and a monolithic, low-inductance GaAs cell.

Jain, Raj K.↗
NASA NTRS1998

Navier-Stokes Computations on Commodity Computers

In this paper we discuss and demonstrate the feasibility of solving high-fidelity, nonlinear computational fluid dynamics (CFD) problems of practical interest on commodity machines, namely Pentium Pro PC's. Such calculations have now become possible due to the progress in computational power and memory of the off-the-shelf commodity computers, along with the growth in bandwidth and communication speeds of networks. A widely used CFD code known as TLNS3D, which was developed originally on large shared memory computers was selected for this effort. This code has recently been ported to massively parallel processor (MPP) type machines, where natural partitioning along grid blocks is adopted in which one or more blocks are distributed to each of the available processors. In this paper, a similar approach is adapted to port this code to a cluster of Pentium Pro computers. The message passing among the processors is accomplished through the use of standard message passing interface (MPI) libraries. Scaling studies indicate fairly high level of parallelism on such clusters of commodity machines, thus making solutions to Navier-Stokes equations for practical problems more affordable.

Vatsa, Veer N.↗
NASA NTRS1984

Small-scale variations in the galactic magnetic field - The rotation measure structure function and birefringence in interstellar scintillations

The structure function of rotation measures of extragalactic sources and birefringence in interstellar scintillations are used to investigate variations in the interstellar magnetic field on length scales of about 0.01-100 pc and 10 to the 11th cm, respectively. Model structure functions are derived for the case of a power-law power spectrum of irregularities in the quantity (n(e)B), and an estimate for the structure function is computed for several regions of the sky using data on extragalactic sources. The results indicate an outer angular scale for rotation measure (RM) variations of not less than about 5 deg (a linear scale of about 9-90 pc at a distance of 0.1-1 kpc). There is also evidence for RM variations on angular scales as small as 1 arcmin, but it cannot be determined whether these are intrinsic to the source or caused by the interstellar medium. The effect of a random, Faraday-active medium on the diffraction of radio waves is derived, and an upper limit to the variations in n(e)B on a length scale of 10 to the 11th cm is obtained from available observations.

Simonetti, J. H.↗
NASA NTRS2003

Discovery of an Obscured Supernova in Arp 299

The galaxy merger Arp 299, at a distance of 40 Mpc, is one of the most extensively studied interacting starburst galaxies known. It has been the site of 4 known supernovae (SNe) since 1990. Arp 299 contains a number of strong radio and infrared condensations, with the strongest starburst occurring in 'Source A,' in the nuclear region of the eastern galaxy. Source A has an inferred supernova rate of 0.5-0.7/yr, and its star formation peaked 6-8 Myr ago. Our recent observations identify a new radio-loud SN in Source A, which occurred sometime between April 2002 and February 2003. We imaged Arp 299 at milliarcsecond resolution at two epochs, in April 2002 and February 2003, using the Very Long Baseline Array and (at the first epoch) the Green Bank Telescope. In 2002, four compact radio sources were found in Source A at 2.3 GHz, with flux densities ranging from 0.3 to 1.7 mJy. In 2003, 8.4 GEz images revealed a new 3 mJy source, as well as the four objects detected a year earlier. The new radio SN is more than 1000 times more powerful than the galactic supernova remnant Cassiopeia A and is located located only 12 milliarcseconds (2.5 pc projected) from the strongest source seen in 2002. Milliarcsecond radio imaging is the only technique that could have detected this supernova, since it is embedded within an 80 mJy VLA source and buried in gas and dust (Av 15-25 mag). We suggest that both the new supernova and its nearest neighbor are occurring within a super star cluster, perhaps a newly formed globular cluster akin to those seen in a number of nearby galaxies and particularly galaxy mergers. If so, we are observing this cluster just as its massive stars have begun to explode into a very dense surrounding medium. The likelihood that most supernovae in such a medium will be radio-loud implies that future VLBI imaging over a number of years could lead to a direct measurement of the supernova rate in the Source A starburst, placing powerful constraints on models of present-day star formation processes.

Neff, Susan↗
DOE OSTI2025

Levelized cost and carbon intensity of solar hydrogen production via water splitting using a scalable and intrinsically safe photocatalytic Z-scheme raceway system

Generating hydrogen from local energy resources such as solar or wind would unlock a low-carbon energy carrier that could be used to reduce greenhouse gas emissions in sectors such as industry and transportation. Yet, the allocation of new or existing power generation solely to hydrogen production remains contentious due to disputes regarding emissions accounting. Photocatalytic (PC) hydrogen production technologies offer a unique solution, as hydrogen is produced directly from solar energy and water, without the need for electricity generation. However, cost projections for all photocatalytic designs to date have suggested that they are not cost competitive compared to conventional electrolysis systems manufactured at scale. Herein, we offer the first illustrative benchmark of cost and carbon intensity of hydrogen produced in a type 2 “Z-scheme” photocatalytic reactor design, which employs suspended semiconducting nanoconductor particles organized into two stacked volumes in a raceway design. The “Z-scheme” system utilizes two separate photoabsorber particles, tuned to drive either the hydrogen evolution reaction or the oxygen evolution reaction individually, connected via a reversible, charge transfer redox couple in solution. Furthermore, the results suggest a highly competitive and scalable technology, that justifies further experimental validation and prototyping in the field.

Carbon↗
NASA NTRS1993

A Novel Method for Characterization of Superconductors: Physical Measurements and Modeling of Thin Films

A method for characterization of granular superconducting thin films has been developed which encompasses both the morphological state of the sample and its fabrication process parameters. The broad scope of this technique is due to the synergism between experimental measurements and their interpretation using numerical simulation. Two novel technologies form the substance of this system: the magnetically modulated resistance method for characterizing superconductors; and a powerful new computer peripheral, the Parallel Information Processor card, which provides enhanced computing capability for PC computers. This enhancement allows PC computers to operate at speeds approaching that of supercomputers. This makes atomic scale simulations possible on low cost machines. The present development of this system involves the integration of these two technologies using mesoscale simulations of thin film growth. A future stage of development will incorporate atomic scale modeling.

Kim, B. F.↗
NASA NTRS1994

The radio emission from the ultraluminous far-infrared galaxy NGC 6240

We present new radio observations of the 'prototypical' ultraluminous far-infrared galaxy NGC 6240, obtained using the Very Large Array (VLA) at lambda = 20 cm in B-configuration and at lambda = 3.6 cm in A-configuration. These data, along with those from four previous VLA observations, are used to perform a comprehensive study of the radio emission from NGC 6240. Approximately 70% (approximately 3 x 10(exp 23) W/Hz) of the total radio power at 20 cm originates from the nuclear region (approximately less than 1.5 kpc), of which half is emitted by two unresolved (R approximately less than 36 pc) cores and half by a diffuse component. The radio spectrum of the nuclear emission is relatively flat (alpha approximately equals 0.6; S(sub nu) proportional to nu(exp -alpha). The supernova rate required to power the diffuse component is consistent with that predicted by the stellar evolution models of Rieke et al. (1985). If the radio emission from the two compact cores is powered by supernova remnants, then either the remnants overlap and form hot bubbles in the cores, or they are very young (approximately less than 100 yr.) Nearly all of the remaining 30% of the total radio power comes from an 'armlike' region extending westward from the nuclear region. The western arm emission has a steep spectrum (alpha approximately equals 1.0), suggestive of aging effects from synchrotron or inverse-Compton losses, and is not correlated with starlight; we suggest that it is synchrotron emission from a shell of material driven by a galactic superwind. Inverse Compton scattering of far-infrared photons in the radio sources is expected to produce an X-ray flux of approximately 2 - 6 x 10(exp -14) ergs/s/sq cm in the 2 - 10 keV band. No significant radio emission is detected from or near the possible ultramassive 'dark core'.

Colbert, Edward J. M.↗
DOE OSTI2023

A Search for Technosignatures Around 11,680 Stars with the Green Bank Telescope at 1.15–1.73 GHz

We conducted a search for narrowband radio signals over four observing sessions in 2020–2023 with the $L$-band receiver (1.15–1.73 GHz) of the 100 m diameter Green Bank Telescope. We pointed the telescope in the directions of 62 TESS Objects of Interest, capturing radio emissions from a total of ~11,680 stars and planetary systems in the ~9' beam of the telescope. All detections were either automatically rejected or visually inspected and confirmed to be of anthropogenic nature. We also quantified the end-to-end efficiency of radio SETI pipelines with a signal injection and recovery analysis. The UCLA SETI pipeline recovers 94.0% of the injected signals over the usable frequency range of the receiver and 98.7% of the injections when regions of dense radio frequency interference are excluded. In another pipeline that uses incoherent sums of 51 consecutive spectra, the recovery rate is ~15 times smaller at ~6%. The pipeline efficiency affects calculations of transmitter prevalence and SETI search volume. Accordingly, we developed an improved Drake figure of merit and a formalism to place upper limits on transmitter prevalence that take the pipeline efficiency and transmitter duty cycle into account. Based on our observations, we can state at the 95% confidence level that fewer than 6.6% of stars within 100 pc host a transmitter that is continuously transmitting a narrowband signal with an equivalent isotropic radiated power (EIRP) > 10 13 W. For stars within 20,000 ly, the fraction of stars with detectable transmitters (EIRP > 5 × 10 16 W) is at most 3 × 10 -4 . Finally, we showed that the UCLA SETI pipeline natively detects the signals detected with AI techniques by Ma et al.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1982

On the origin of the 1 keV diffuse X-ray background

Soft X-ray sky survey data for high galactic latitudes are used to constrain simple geometric models for the source of the diffuse X-ray background at 1 keV. The intensity maps show two extended and enhanced features, in Eridanus and in the direction of the galactic center, with a relatively uniform sky away from these features and an observed degree of isotropy consistent with a model in which the 0.5-1.2 keV background consists of an isotropic extragalactic component and a thick disk galactic component. A temperature of 2-3 million K and an emission pressure of 0.004 per cm to the 6th pc are derived for the galactic component from an assumed spectrum of 11E to the -1.4 power photons/sq cm s sr keV. While consistent with the data, a local, isotropically distributed source model is shown to pose physical difficulties.

Nousek, J. A.↗
NASA NTRS1989

Electronically Variable Pressure Regulator (EVPR)

A new programmable electronically variable pressure regulator (EVPR) concept accurately controls the local outlet or remote system pressure. It uses an integral pulse width modulated rare earth permanent magnet motor operating in response to redundant pressure transducer feedback signals. The EVPR is a simple single stage device that does not use dynamic seals or pilot valving. Conversion of partial revolution motor torque to poppet lifting force is accomplished by pure flexure action to avoid using bearings. The flexure drive (called the ROTAX) has a variable lead to minimize motor weight and power consumption. Breadboard tests were completed successfully on two critical design elements of the EVPR: the ROTAX and the motor. The ROTAX cable system was tested for 250,000 cycles without failure. The breadboard motor met the basic design requirements including the design torque and power consumption. Prototype parts were fabricated, and testing of the prototype EVPR has started. It is PC computer controlled to facilitate programming, data acquisition and analysis. A lightweight dedicated microprocessor is planned for the flightweight EVPR.

Reinicke, R. H.↗
NASA NTRS2000

NGC 1614: A Laboratory for Starburst Evolution

The modest extinction and reasonably face-on viewing geometry make the luminous infrared galaxy NGC 1614 an ideal laboratory for study of a powerful starburst. HST/NICMOS observations show: (1) deep CO stellar absorption, tracing a starburst nucleus about 45 pc in diameter; (2) surrounded by an approx. 600 pc diameter ring of supergiant H II regions revealed in Pa-alpha line emission; (3) lying within a molecular ring indicated by its extinction shadow in H - K; and (4) all at the center of a disturbed spiral galaxy. The luminosities of the giant H II regions in the ring axe extremely high, an order of magnitude brighter than 30 Doradus; very luminous H II regions, comparable with 30 Dor, are also found in the spiral arms of the galaxy. Luminous stellar clusters surround the nucleus and lie in the spiral arms, similar to clusters observed in other infrared luminous and ultraluminous galaxies. The star forming activity may have been initiated by a merger between a disk galaxy and a companion satellite, whose nucleus appears in projection about 300 pc to the NE of the nucleus of the primary galaxy. The relation of deep stellar CO bands to surrounding ionized gas ring to molecular gas indicates that the luminous starburst started in the nucleus and is propagating outward into the surrounding molecular ring. This hypothesis is supported by evolutionary starburst modeling that shows that the properties of NGC 1614 can be fitted with two short-lived bursts of star formation separated by 5 Myr (and by inference by a variety of models with a similar duration of star formation). The total dynamical mass of the starburst region of 1.3 x 10(exp 9) solar masses is mostly accounted for by the old pre-starburst stellar population. Although our starburst models use a modified Salpeter initial mass function (turning over near one solar mass), the tight mass budget suggests that the IMF may contain relatively more 10 - 30 solar masses stars and fewer low mass stars than the Salpeter function. The dynamical mass is nearly four times smaller than the mass of molecular gas estimated from the standard ratio of (C-12)O (1 - 0) to H2. A number of arguments place the mass of gas in the starburst region at approx. 25% of the dynamical mass, nominally about 1/15 and with an upper limit of 1/10 of the amount estimated from (C-12)O and the standard ratio.

Alonso-Herrero, A.↗
NASA NTRS1995

On M31's Double Nucleus

The recent HST discovery of a double nucleus in M31 brings into prominence the question how long, a second core can survive within the nuclear regions of a galaxy. Physical conditions in the nuclear regions of a typical galaxy help a second core survive, so it can orbit for a long time. possibly for thousands of orbits. Given the nearly uniform mass density in a core, tidal forces within a core radius are compressive in all directions and help the core survive the buffeting it takes as it orbits near the center of the galaxy. We use numerical experiments to illustrate these physical principles. Our method allows the full power of the experiments to be concentrated on the nuclear regions. Spatial resolution of about 0.2 pc comfortably resolves detail within the 1.4 parsec core radius of the second, but brighter core (P1) in M31. We use these physical principles to discuss M31's double nucleus, but they apply to other galaxies as well. and in other astronomical situations such as dumbbell galaxies. galaxies orbiting near the center of a galaxy cluster, and subclustering in galaxy clusters. The experiments also illustrate that galaxy encounters and merging are quite sensitive to external tidal forces, such as those produced by the gravitational potential in a group or cluster of galaxies.

Miller, R. H.↗
NASA NTRS1987

Ground-based 1- to 32-microns observations of ARP 220: Evidence for a dust-embedded AGN?

New observations of the 10 and 20 micron size of the emission region in Arp 220 are presented. Also given are ground based photometry from 1 to 32 micron including measurements of the strength of the silicate feature at 10 micron. The results show that the 20 micron size of Arp is smaller than 1.5 arcsec (500 pc); comparison of IRAS and ground based observations show that IRAS 12 micron flux measured with a large arcmin beam is the same as that seen from the ground with a 3 arcsec aperture. At 10 micron a deep silicate absorption feature is seen that corresponds to a visual extinction of about 50 mag. These results suggest that a very significant portion of the 10 to the 12th power L sub 0 infrared luminosity from Arp 220 comes from a region less than or of the order of 500 pc in diameter. When these results are combined with recent measurement of a broad Brackett alpha line by DePoy and an unresolved 2.2 micron source by Neugebauer, Matthews and Scoville, a very attractive possibility for the primary luminosity source Arp 220 is a dust embedded compact Seyfert type nucleus.

Becklin, E. E.↗