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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
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Instrument Remote Control Application Framework

The Instrument Remote Control (IRC) architecture is a flexible, platform-independent application framework that is well suited for the control and monitoring of remote devices and sensors. IRC enables significant savings in development costs by utilizing extensible Markup Language (XML) descriptions to configure the framework for a specific application. The Instrument Markup Language (IML) is used to describe the commands used by an instrument, the data streams produced, the rules for formatting commands and parsing the data, and the method of communication. Often no custom code is needed to communicate with a new instrument or device. An IRC instance can advertise and publish a description about a device or subscribe to another device's description on a network. This simple capability of dynamically publishing and subscribing to interfaces enables a very flexible, self-adapting architecture for monitoring and control of complex instruments in diverse environments.

Ames, Troy↗
DOE OSTI2024

Equivariant, safe and sensitive — graph networks for new physics

This study introduces a novel Graph Neural Network (GNN) architecture that leverages infrared and collinear (IRC) safety and equivariance to enhance the analysis of collider data for Beyond the Standard Model (BSM) discoveries. By integrating equivariance in the rapidity-azimuth plane with IRC-safe principles, our model significantly reduces computational overhead while ensuring theoretical consistency in identifying BSM scenarios amidst Quantum Chromodynamics backgrounds. The proposed GNN architecture demonstrates superior performance in tagging semi-visible jets, highlighting its potential as a robust tool for advancing BSM search strategies at high-energy colliders.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

The information content of jet quenching and machine learning assisted observable design

Jets produced in high-energy heavy-ion collisions are modified compared to those in proton-proton collisions due to their interaction with the deconfined, strongly-coupled quark-gluon plasma (QGP). In this work, we employ machine learning techniques to identify important features that distinguish jets produced in heavy-ion collisions from jets produced in proton-proton collisions. We formulate the problem using binary classification and focus on leveraging machine learning in ways that inform theoretical calculations of jet modification: (i) we quantify the information content in terms of Infrared Collinear (IRC)-safety and in terms of hard vs. soft emissions, (ii) we identify optimally discriminating observables that are in principle calculable in perturbative QCD, and (iii) we assess the information loss due to the heavy-ion underlying event and background subtraction algorithms. We illustrate our methodology using Monte Carlo event generators, where we find that important information about jet quenching is contained not only in hard splittings but also in soft emissions and IRC-unsafe physics inside the jet. This information appears to be significantly reduced by the presence of the underlying event. We discuss the implications of this for the prospect of using jet quenching to extract properties of the QGP. Since the training labels are exactly known, this methodology can be used directly on experimental data without reliance on modeling. We outline a proposal for how such an experimental analysis can be carried out, and how it can guide future measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Ethanol-fueled metal supported solid oxide fuel cells with a high entropy alloy internal reforming catalyst

High-performance metal supported solid oxide fuel cells (MS-SOFC) with an integrated high entropy alloy (HEA) internal reforming catalyst (IRC) are demonstrated for transportation applications using ethanol and methanol as fuels. Addition of the HEA IRC dramatically improves cell performance and stability when using ethanol/water blend fuel. Absence of carbon deposition predicted by thermodynamic calculations is confirmed by Raman spectroscopy analysis of posttest anodes. Optimal catalyst processing (deposition technique, loading, firing temperature) and cell operation conditions (flow rates, temperature, fuel compositions) are explored. Infiltrated HEA reforming catalyst provides a highly porous structure and low catalyst loading (6 mg cm –2 ). The designed structure and catalysts achieve small mass transport resistances in the fuel electrode (26.2 s m –1 ) and oxygen electrode (41.6 s m –1 ). The best ethanol concentration (60:40 v% ethanol: water) provides 0.83 W cm –1 at 700 °C, without carbon deposition. The ethanol-fueled MS-SOFC is operated for 500 h, including five thermal cycles. As a result, cell evolution is similar to that reported previously for hydrogen fuel; nickel aggregation and chromia deposition were the major observed changes, and carbon formation can be avoided even after long-term operation.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2024

Energetic and Spectroscopic Properties of Astrophysically Relevant MgC 4 H Radicals Using High-Level Ab Initio Calculations

Considering the importance of magnesium-bearing hydrocarbon molecules (MgC n H; n = 2, 4, and 6) in the carbon-rich circumstellar envelopes (e.g., IRC+10216), a total of 28 constitutional isomers of MgC 4 H have been theoretically investigated using density functional theory (DFT) and coupled-cluster methods. The zero-point vibrational energy corrected relative energies at the ROCCSD(T)/cc-pCVTZ level of theory reveal that the linear isomer, 1-magnesapent-2,4-diyn-1-yl (1, 2 Σ + ), is the global minimum geometry on the MgC 4 H potential energy surface. The latter has been detected both in the laboratory and in the evolved carbon star, IRC+10216. The calculated spectroscopic data for 1 match well with the experimental observations (error ~ 0.78%) which validates our theoretical methodology. Plausible isomerization processes happening among different isomers are examined using DFT and coupled-cluster methods. CASPT2 calculations have been performed for a few isomers exhibiting multireference characteristics. The second most stable isomer, 1-ethynyl-1λ 3 -magnesacycloprop-2-ene-2,3-diyl (2, 2 A 1 , μ = 2.54 D), is 146 kJ mol –1 higher in energy than 1 and possibly the next promising candidate to be detected in the laboratory or in the interstellar medium in future.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

Luminosity functions for K giant stars derived from the two-micron sky survey.

Description of a method for determining either the space density or the luminosity function from star counts covering large areas of sky. Space density is assumed to vary only in the direction perpendicular to the galactic plane. The method extends that derived for use with the star counts in the Selected Areas by allowing for an integration over a wide and continuous range of galactic latitudes, and is therefore applicable to surveys where the number of stars per square degree is small but the area surveyed is an appreciable fraction of the sky. The catalog (IRC) produced from the 2-micron sky survey at Caltech is such a survey. Application of the method to a selection of IRC stars dominated by K giants shows that if these stars obey Oort's determination of their normalized space density perpendicular to the galactic plane than the dispersion of their 2.2-micron luminosity distribution must be large - i.e., on the order of plus or minus 1.0 min within a single spectral subtype. This result is in accord with conclusions recently set forth by Jung (1970).

Hughes, E. E., Jr.↗
NASA NTRS1974

BM Scorpii and a possible cluster of infrared sources

BM Sco and six other infrared sources near the cluster M6 were observed at infrared wavelengths. BM Sco has the flat free-free spectrum between 1.5 and 8 microns with a small silicate emission feature typical of the NML Tauri-type objects. IRC-30308 is also an infrared star of the NML Tauri type, and IRC-30312 has long wavelength radiation characteristic of the luminous M supergiants. The remaining four sources resemble reddened long-period variables. The presence of these infrared sources near M6 is not statistically significant and is not sufficient to associate them with the cluster.

Ney, E. P.↗
NASA NTRS1975

Very long baseline interferometric observations of OH/IR stars

Results are reported for spectral-line very long baseline interferometric observations of the following II OH/IR objects, which emit strong 1612-MHz OH maser radiation concentrated at two velocities: NML Cyg, R Aql, IRC+10011, IRC-10529, and OH 1837-05. The apparent angular sizes were obtained for NML Cyg and R Aql, and lower limits upon the apparent sizes were obtained for the other objects. The data for NML Cyg agree with previous size determinations and indicate that the low- and high-velocity components are separated by about 20 times their apparent size. The maser component of R Aql is calculated within a factor of two to be about 5 by 10 to the 14th power cm, although the emitting region can be significantly larger. A qualitative description is given for II OH/IR objects with late M-type Mira variable center stars and circumstellar dust shells of similar dimensions.

Reid, M. J.↗
NASA NTRS1980

Infrared heterodyne spectroscopy of circumstellar molecules

Ammonia has been detected in the circumstellar envelopes of IRC+10216, VY CMa, VX Sgr, and IRC+10420. A number of absorption lines of (N-14)H3 in the nu sub 2 vibration-rotation band around 28 THz (950 per cm) have been observed at a velocity resolution of 0.2 km/s. Typical linewidths are 1 to 4 km/s, and the details of the line profiles provide additional insights on the process of mass loss in these stars.

Betz, A. L.↗
NASA NTRS1981

The abundance and excitation of the carbon chains in interstellar molecular clouds

Emission lines from the carbon chains HC3N, HC5N, HC7N and HC9N were observed at 3 mm, 7 mm, and 1.4 cm in a number of dark clouds, Orion A and IRC(plus)10216. Non-LTE models were constructed to describe excitation and column densities. Component models for the Taurus dark cloud TMC-1 suggested that relative molecular abundances do not vary substantially along the cloud ridge, whereas the H2 density does by a factor of three. Data available for other dark clouds showed that the decrease in abundance with length from one carbon chain to the next is nearly constant, being close to 2.3. The decline in carbon chain abundance with length is steeper in Orion KL than in dark clouds by a factor of approximately four. Abundance ratios derived for the carbon star IRC(plus)10216 are uncertain, due to difficulties in modeling excitation rates in this environment.

Bujarrabal, V.↗
NASA NTRS1984

Multiple circumstellar shells and radiation pressure on grains in the outflows from late-type giants

It is pointed out that mass loss from red giants and supergiants is sometimes as high as 0.0001 solar mass per year. This mass loss represents a major source of new interstellar matter. The present investigation is concerned with the phenomena involved in stellar mass loss, taking into account a comparison of currently available observations with plausible models. The case of the extended circumstellar envelope around IRC +10216 is considered. In observations about mass loss from circumstellar shells, it is sometimes found that the P Cygni profiles are split into two or more sharp, distinct components. The question is considered whether such narrow separate components can be understood in terms of the radiation pressure model. A grain growth model is discussed along with outflow velocity, radiation pressure, and mass loss rates. The models are compared with observations from Alpha Orionis, Mira, and IRC +10216. It is concluded that a hybrid model for the mass loss from some late-type stars seems appropriate. Under certain conditions, outflow speeds of 10 to 20 km/s can be understood.

Jura, M.↗
NASA NTRS1985

Submillimeter observations of evolved stars

Broadband submillimeter observations of thermal emission from several evolved stars have been obtained using the United Kingdom Infrared Telescope on Mauna Kea, Hawaii. The observations were carried out at an effective wavelength of 400 microns in order to estimate the mass loss rates in dust from the stars. Direct estimates of mass loss rates are in the range 10 to the -9th to 10 to the -6th solar mass/yr. Analysis of the spectrum of IRC + 10216 confirmed previous estimates of dust grain emissivity in the range 10-1000 microns. The infrared properties of IRC + 10216 are found to be similar to the carbon rich object CRL 3068. No systematic difference was found between the dust masses of carbon rich and oxygen rich envelopes. The largest mass loss rates in dust were obtained for the bipolar objects OH 231.8 + 4.2 CRL 2688, CRL 618, and NGC 7027. It is suggested that the ratios of gas to dust, and the slopes of the far infrared to submillimeter wavelength continua of these stars objects are probably representative of amorphous rather than crystalline grains.

Sopka, R. J.↗
NASA NTRS1985

The infrared characteristics of circumstellar silicate grains

A theoretical study of the infrared emission from circumstellar shells around late-type giants is made, with the aim of deriving the infrared characteristics of the silicate grains condensing in these shells. A large grid of models has been compared with observations of optically visible Miras, IRC sources and OH/IR stars. From fitting the observed relation between the color temperature and the strength of the 10-micron feature, it is concluded that the ratio of the 3.5 to 10-micron absorption efficiencies of the dust is about 0.25, a factor of 2 less than a previous determination. Detailed modeling of the 2 to 13-micron spectrum of OH 26.5 + 0.6, IRC + 10011 and R Cas yielded a similar ratio. These detailed models also show that the shape of the 10-micron feature, particularly around 8 and 13 microns, varies from source to source. The derived 10-micron feature is narrower for larger dust column densities. These observed differences in the intrinsic shape of the 10-micron feature are not due to differences in size of the condensing particles. Probably they are related to structural or compositional differences in the condensing silicates.

Schutte, W.↗
NASA NTRS1986

Spectral characteristics of dust in carbon rich objects

Some carbon-rich objects exhibit a strong broad emission feature beginning at lambda is approximately 24 microns and extending to lambda is greater than 30 microns. A 20 to 65 microm spectrum of the carbon star IRC+10216 and 30 to 50 micron spectra of three carbon-rich planetary nebulae, IC 418, NGC 6572, and BD+30 degrees 3639 are presented. The strong emission feature around 30 microns is seen clearly in IRC+10216, IC 418, and NGC 6572. The role of silicon carbides and magnesium sulfur particles in this feature is discussed.

Silverberg, R. F.↗
NASA NTRS1986

Studies of interstellar vibrationally-excited molecules

Several molecules thus far have been detected in the ISM in vibrationally-excited states, including H2, SiO, HC3N, and CH3CN. In order for vibrational-excitation to occur, these species must be present in unusually hot and dense gas and/or where strong infrared radiation is present. In order to do a more thorough investigation of vibrational excitation in the interstellar medium (ISM), studies were done of several mm-wave transitions originating in excited vibrational modes of HCN, an abundant interstellar molecule. Vibrationally-excited HCN was recently detected toward Orion-KL and IRC+10216, using a 12 meter antenna. The J=3-2 rotational transitions were detected in the molecule's lowest vibrational state, the bending mode, which is split into two separate levels, due to l-type doubling. This bending mode lies 1025K above ground state, with an Einstein A coefficient of 3.6/s. The J=3-2 line mode of HCN, which lies 2050K above ground state, was also observed toward IRC+10216, and subsequently in Orion-KL. Further measurements of vibrationally-excited HCN were done using a 14 meter telescope, which include the observations of the (0,1,0) and (0,2,0) modes towards Orion-KL, via their J=3-2 transitions at 265-267 GHz. The spectrum of the J=3-2 line in Orion taken with the 14 meter telescope, is shown, along with a map, which indicates that emission from vibrationally-excited HCN arises from a region probably smaller than the 14 meter telescope's 20 arcsec beam.

Ziurys, L. M.↗
NASA NTRS1986

Detections of C-13-substituted C3H2 in astronomical sources

The more abundant C-13-substituted variant of the new interstellar ring molecule, C3H2, has been detected in TMC-1 and Sgr B2, and a tentative detection has been made in IRC + 10216. The fractional abundance relative to H2 is 1-2 x 10 to the -8th in TMC-1, a value similar to that of HCN. In Sgr B2, the C-12 species shows a self-absorbed profile and the relative abundance of C3H2 is about an order of magnitude less than in TMC-1. In IRC + 10216, the fractional abundance of C3H2 is an order of magnitude greater than that in TMC-1.

Madden, Suzanne C.↗
NASA NTRS1987

New CO and HCN sources associated with IRAS carbon stars

Emission of CO and HCN was detected in 22 out of a sample of 53 IRAS sources classified as unidentified carbon-rich objects. The sample was selected according to the presence of the silicon carbide feature as revealed by low-resolution spectra. The molecular line widths indicate that the CO and HCN emission arises from the circumstellar envelopes of very highly evolved stars undergoing mass loss. The visible stars tend to be deficient in CO as compared with unidentified sources. Most the detected CO and HCN IRAS stars are distinct and thick-shelled objects, but their infrared and CO luminosities are similar to those of IRC + 102156 AFGL and IRC-CO evolved stars. The 12 micron flux seems to be a good indicator of the distance, hence a guide for molecular searches.

NGUYEN-Q-RIEU↗
NASA NTRS1987

Photochemistry and molecular ions in carbon-rich circumstellar envelopes

An earlier theory of ionization of C-rich circumstellar envelopes based on the photochemical model is extended to include the temperature dependence of ion-molecule reactions with polar molecules, particularly HCN, and line self-shielding of CO dissociating radiation. The results are applied to the abundances of HCO(+) and HNC in C-rich circumstellar envelopes. With standard parameters for IRC + 10216, the model is found to be consistent with the new upper limit to the antenna temperature of the J = 1-0 line of HCO(+) obtained with the IRAM 30-m telescope. The photochemical model provides a natural explanation of the relatively large ratio of HCN to HNC observed for C-rich circumstellar envelopes, and good agreement is obtained for the H(C-13)N/HNC antenna temperature ratio measured for IRC + 10216.

Glassgold, A. E.↗