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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Molecular organization in MAPLE-deposited conjugated polymer thin films and the implications for carrier transport characteristics

The morphological structure of poly(3-hexylthiophene) (P3HT) thin films deposited by both Matrix Assisted Pulsed Laser Evaporation (MAPLE) and solution spin-casting methods are investigated. We found that the MAPLE samples possessed a higher degree of disorder, with random orientations of polymer crystallites along the side-chain stacking, π-π stacking, and conjugated backbone directions. Furthermore, the average molecular orientations and relative degrees of crystallinity of MAPLE-deposited polymer films are insensitive to the chemistries of the substrates onto which they were deposited; this is in stark contrast to the films prepared by the conventional spin-casting technique. In spite of the seemingly unfavorable molecular orientations and the highly disordered morphologies, the in-plane charge carrier transport characteristics of the MAPLE samples are comparable to those of spin-cast samples, exhibiting similar transport activation energies (56 meV versus 54 meV) to those reported in the literature for high mobility polymers.

36 MATERIALS SCIENCE↗
DOE OSTI2012

IMPACT OF SYSTEMATICS ON SZ-OPTICAL SCALING RELATIONS

One of the central goals of multi-wavelength galaxy cluster cosmology is to unite all cluster observables to form a consistent understanding of cluster mass. Here, we study the impact of systematic effects from optical cluster catalogs on stacked Sunyaev-Zel'dovich (SZ) signals. We show that the optically predicted Y-decrement can vary by as much as 50% based on the current 2{sigma} systematic uncertainties in the observed mass-richness relationship. Miscentering and impurities will suppress the SZ signal compared to expectations for a clean and perfectly centered optical sample, but to a lesser degree. We show that the levels of these variations and suppression are dependent on the amount of systematics in the optical cluster catalogs. We also study X-ray luminosity-dependent sub-sampling of the optical catalog and find that it creates Malmquist bias, increasing the observed Y-decrement of the stacked signal. We show that the current Planck measurements of the Y-decrement around Sloan Digital Sky Survey optical clusters and their X-ray counterparts are consistent with expectations after accounting for the 1{sigma} optical systematic uncertainties using the Johnston mass-richness relation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Ambient pressure synthesis and characterization of layered honeycomb Li 2 PdO 3

Single-phase polycrystalline Li 2 PdO 3 has been synthesized at 640°C in oxygen for the first time under ambient pressure. X-ray and neutron diffraction analyses show that the sample possesses a monoclinic layered structure belonging to the C2/m space group. Rietveld refinements of neutron powder diffraction data indicate ~10% Li–Pd site exchange and DIFFaX modelling manifest ~2% stacking faults present within LiPd 2 layers. A band gap of ~2.23 eV was calculated for the golden Li 2 PdO 3 using absorbance measurements. Thermogravimetric analysis of the sample shows that Li 2 PdO 3 is stable up to 730°C under oxygen. Here a Curie tail is observed at low temperature magnetic measurements (T < 50K), yielding an effective moment of 0.038 μ B , possibly due to spin ½ impurities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

The dark matter haloes of HI selected galaxies

We present the neutral hydrogen mass (M HI) function (HIMF) and velocity width (w 50 ) function (HIWF) based on a sample of 7857 galaxies from the 40 per cent data release of the ALFALFA survey (α.40). The low mass (velocity width) end of the HIMF (HIWF) is dominated by the blue population of galaxies whereas the red population dominates the HIMF (HIWF) at the high mass (velocity width) end. We use a deconvolution method to estimate the HI rotational velocity (V rot ) functions (HIVF) from the HIWF for the total, red, and blue samples. The HIWF and HIVF for the red and blue samples are well separated at the knee of the function compared to their HIMFs. We then use recent stacking results from the ALFALFA survey to constrain the halo mass (M h ) function of HI-selected galaxies. This allows us to obtain various scaling relations between M HI –w 50 –V rot –M h , which we present. The M HI –M h relation has a steep slope ~2.10 at small masses and flattens to ~0.34 at masses larger than a transition halo mass, $\log _{10}(M_{\rm{ht}}h_{70}^2/M_{\odot })=10.62$. Our scaling relation is robust and consistent with a volume-limited sample of α.40. The M HI –M h relation is qualitatively similar to the M star –M h relation but the transition halo mass is smaller by ~1.4 dex compared to that of the M star –M h relation. Our results suggest that baryonic processes like heating and feedback in larger mass haloes suppress HI gas on a shorter time-scale compared to star formation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Theoretical study of time-resolved luminescence in semiconductors. I. Decay from the steady state

Time-resolved luminescence (TRL) is a non-destructive, non-invasive, and contactless characterization method. We studied TRL decay on semiconductor layers and thin film homostructures after a steady state illumination by simulation with Synopsys TCAD{sup ®} and by analytical approximate solution of the appropriate equations. First, we show that the luminescence decay time in general equals the minority carrier lifetime only for a homogeneous and time-independent carrier lifetime. Then, we investigate the influence of photon recycling, injection level, charge carrier diffusion, defects in the bulk and at the surfaces, as well as space charge on the TRL decay separately by quasi one-dimensional simulations of semiconductor layers and semiconductor homostructures. We further study the influence of sample non-homogeneity as may be found in polycrystalline semiconductors. We show how carrier lifetime can be extracted from the TRL transients and how the samples can be characterized by excitation dependent measurements in the open circuit case. We can explain some effects found in luminescence experiments, like a decrease of the decay time with an increasing excitation, a maximum in the decay time due to saturated bulk-defects and curved luminescence transients due to high injections or sample inhomogeneities. Furthermore, we are focussing on the question, how single layers within a semiconductor stack can be characterized.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

An automated approach to the alignment of compound refractive lenses

Compound refractive lenses (CRLs) are established X-ray focusing optics, and are used to focus the beam or image the sample in many beamlines at X-ray facilities. While CRLs are quite established, the stack of single lens elements affords a very small numerical aperture because of the thick lens profile, making them far more difficult to align than classical optical lenses that obey the thin-lens approximation. This means that the alignment must be very precise and is highly sensitive to changes to the incident beam, often requiring regular readjustments. Some groups circumvent the full realignment procedure by using engineering controls ( e.g. mounting optics) that sacrifice some of the beam's focusing precision, i.e. spot size, or resolution. While these choices minimize setup time, there are clear disadvantages. This work presents a new automated approach to align CRLs using a simple alignment apparatus that is easy to adapt and install at different types of X-ray experiments or facilities. This approach builds on recent CRL modeling efforts, using an approach based on the Stochastic Nelder–Mead (SNM) simplex method. This method is outlined and its efficacy is demonstrated with numerical simulation that is tested in real experiments conducted at the Advanced Photon Source to confirm its performance with a synchrotron beam. This work provides an opportunity to automate key instrumentation at X-ray facilities.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1971

A High Volume Stack Sampler

The stack sampler described in this paper has been developed to overcome the difficulties of particulate sampling with presently available equipment. Its use on emissions from hog fuel fired boilers, back-fired incinerators, wigwam burners, asphalt plants, and seed cleaning cyclones is reported. The results indicate that the sampler is rapid and reliable in its use. It is relatively simple and inexpensive to operate. For most sources it should be considered over the more complicated and expensive sampling trains being used and specified.

Boubel, Richard W.↗
NASA NTRS2015

Global Precipitation Measurement Cold Season Precipitation Experiment (GCPEx): For Measurement Sake Let it Snow

As a component of the Earth's hydrologic cycle, and especially at higher latitudes,falling snow creates snow pack accumulation that in turn provides a large proportion of the fresh water resources required by many communities throughout the world. To assess the relationships between remotely sensed snow measurements with in situ measurements, a winter field project, termed the Global Precipitation Measurement (GPM) mission Cold Season Precipitation Experiment (GCPEx), was carried out in the winter of 2011-2012 in Ontario, Canada. Its goal was to provide information on the precipitation microphysics and processes associated with cold season precipitation to support GPM snowfall retrieval algorithms that make use of a dual-frequency precipitation radar and a passive microwave imager on board the GPM core satellite,and radiometers on constellation member satellites. Multi-parameter methods are required to be able to relate changes in the microphysical character of the snow to measureable parameters from which precipitation detection and estimation can be based. The data collection strategy was coordinated, stacked, high-altitude and in-situ cloud aircraft missions with three research aircraft sampling within a broader surface network of five ground sites taking in-situ and volumetric observations. During the field campaign 25 events were identified and classified according to their varied precipitation type, synoptic context, and precipitation amount. Herein, the GCPEx fieldcampaign is described and three illustrative cases detailed.

GCPEx↗
DOE OSTI2026

Prospects for Astrobiology and Technosignature Searches with the Vera C. Rubin Observatory Legacy Survey of Space and Time

The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will map sources in multiband colour--variability space. We present a prototype coherence-based framework for astrobiology and technosignature searches, in which candidates are treated as structured departures from natural astrophysical manifolds rather than isolated photometric outliers. We illustrate the framework with three simulated cases: five Kuiper Belt Object (KBO) surface/activity states, a grid of 649 synthetic exoplanet spectra with vegetation-red-edge-like (VRE) perturbations, and 500 synthetic multiband light curves, each projected into LSST-like observable space and analysed through colour geometry, chromatic variability, and cross-band coherence. Key results include a full-colour Mahalanobis distance $D\approx5.1$ for the weak-coma KBO state (${\sim}5σ$ in the five-dimensional colour vector), an indicative VRE coherence threshold at $f_{\rm crit}\approx0.13$, and an idealised stacking forecast reaching $5σ$ under optimistic assumptions. We show, using a small Gaia~DR3 stellar sample, that stellar colour and photometric stability may inform the prioritisation of Galactic regions for applying such coherence diagnostics.

Kovačević, Andjelka B. [Belgrade U.] (ORCID:000000↗
DOE OSTI2014

Rapid determination of actinides in seawater samples

A new rapid method for the determination of actinides in seawater samples has been developed at the Savannah River National Laboratory. The actinides can be measured by alpha spectrometry or inductively-coupled plasma mass spectrometry. The new method employs novel pre-concentration steps to collect the actinide isotopes quickly from 80 L or more of seawater. Actinides are co-precipitated using an iron hydroxide co-precipitation step enhanced with Ti +3 reductant, followed by lanthanum fluoride co-precipitation. Stacked TEVA Resin and TRU Resin cartridges are used to rapidly separate Pu, U, and Np isotopes from seawater samples. TEVA Resin and DGA Resin were used to separate and measure Pu, Am and Cm isotopes in seawater volumes up to 80 L. This robust method is ideal for emergency seawater samples following a radiological incident. It can also be used, however, for the routine analysis of seawater samples for oceanographic studies to enhance efficiency and productivity. In contrast, many current methods to determine actinides in seawater can take 1–2 weeks and provide chemical yields of ~30–60 %. This new sample preparation method can be performed in 4–8 h with tracer yields of ~85–95 %. By employing a rapid, robust sample preparation method with high chemical yields, less seawater is needed to achieve lower or comparable detection limits for actinide isotopes with less time and effort.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2011

DIFFUSE Ly{alpha} EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES

Using a sample of 92 UV continuum-selected, spectroscopically identified galaxies with (z) = 2.65, all of which have been imaged in the Ly{alpha} line with extremely deep narrow-band imaging, we examine galaxy Ly{alpha} emission profiles to very faint surface brightness limits. The galaxy sample is representative of spectroscopic samples of Lyman break galaxies (LBGs) at similar redshifts in terms of apparent magnitude, UV luminosity, inferred extinction, and star formation rate and was assembled without regard to Ly{alpha} emission properties. Approximately 45% (55%) of the galaxy spectra have Ly{alpha} appearing in net absorption (emission), with {approx_equal} 20% satisfying commonly used criteria for the identification of 'Ly{alpha} emitters' (LAEs; W{sub 0}(Ly{alpha}) {>=} 20 A). We use extremely deep stacks of rest-UV continuum and continuum-subtracted Ly{alpha} images to show that all sub-samples exhibit diffuse Ly{alpha} emission to radii of at least 10'' ({approx}80 physical kpc). The characteristic exponential scale lengths for Ly{alpha} line emission exceed that of the {lambda}{sub 0} = 1220 A UV continuum light by factors of {approx}5-10. The surface brightness profiles of Ly{alpha} emission are strongly suppressed relative to the UV continuum light in the inner few kpc, by amounts that are tightly correlated with the galaxies' observed spectral morphology; however, all galaxy sub-subsamples, including that of galaxies for which Ly{alpha} appears in net absorption in the spectra, exhibit qualitatively similar diffuse Ly{alpha} emission halos. Accounting for the extended Ly{alpha} emission halos, which generally would not be detected in the slit spectra of individual objects or with typical narrow-band Ly{alpha} imaging, increases the total Ly{alpha} flux (and rest equivalent width W{sub 0}(Ly{alpha})) by an average factor of {approx}5, and by a much larger factor for the 80% of LBGs not classified as LAEs. We argue that most, if not all, of the observed Ly{alpha} emission in the diffuse halos originates in the galaxy H II regions but is scattered in our direction by H I gas in the galaxy's circum-galactic medium. The overall intensity of Ly{alpha} halos, but not the surface brightness distribution, is strongly correlated with the emission observed in the central {approx}1''-more luminous halos are observed for galaxies with stronger central Ly{alpha} emission. We show that whether or not a galaxy is classified as a giant 'Ly{alpha} blob' (LAB) depends sensitively on the Ly{alpha} surface brightness threshold reached by an observation. Accounting for diffuse Ly{alpha} halos, all LBGs would be LABs if surveys were sensitive to 10 times lower Ly{alpha} surface brightness thresholds; similarly, essentially all LBGs would qualify as LAEs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Testing the role of AGN on the star formation and metal enrichment of ‘twin galaxies’

Here, we explore the effect of AGN activity on the star formation history of galaxies by analysing the stellar population properties of 10 pairs of nearby twin galaxies – selected as being visually similar except for the presence of an AGN. The selection of such twin samples represents a method to study AGN feedback, as recently proposed by del Moral Castro et al. We use integral field unit (IFU) data from CALIFA, stacked within three fixed apertures. AGN galaxies in a twin pair suggest more evolved stellar populations than their non-AGN counterpart 90 per cent of the time, regardless of aperture size. A comparison with a large sample from SDSS confirms that most twins are representative of the general population, but in each twin the differences between twin members is significant. A set of targeted line strengths reveal the AGN member of a twin pair is older and more metal-rich than the non-AGN galaxy, suggesting AGN galaxies in our sample may either have an earlier formation time or follow a different star formation and chemical enrichment history. These results are discussed within two simple, contrasting hypotheses for the role played by AGN in galaxy evolution, which can be tested in the future at a greater detail with the use of larger data sets.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

CONCURRENT SUPERMASSIVE BLACK HOLE AND GALAXY GROWTH: LINKING ENVIRONMENT AND NUCLEAR ACTIVITY IN z = 2.23 H{alpha} EMITTERS

We present results from a Almost-Equal-To 100 ks Chandra observation of the 2QZ Cluster 1004+00 structure at z = 2.23 (hereafter 2QZ Clus). 2QZ Clus was originally identified as an overdensity of four optically-selected QSOs at z = 2.23 within a 15 Multiplication-Sign 15 arcmin{sup 2} region. Narrow-band imaging in the near-IR (within the K band) revealed that the structure contains an additional overdensity of 22 z = 2.23 H{alpha}-emitting galaxies (HAEs), resulting in 23 unique z = 2.23 HAEs/QSOs (22 within the Chandra field of view). Our Chandra observations reveal that three HAEs in addition to the four QSOs harbor powerfully accreting supermassive black holes (SMBHs), with 2-10 keV luminosities of Almost-Equal-To (8-60) Multiplication-Sign 10{sup 43} erg s{sup -1} and X-ray spectral slopes consistent with unobscured active galactic nucleus (AGN). Using a large comparison sample of 210 z = 2.23 HAEs in the Chandra-COSMOS field (C-COSMOS), we find suggestive evidence that the AGN fraction increases with local HAE galaxy density. The 2QZ Clus HAEs reside in a moderately overdense environment (a factor of Almost-Equal-To 2 times over the field), and after excluding optically-selected QSOs, we find that the AGN fraction is a factor of Almost-Equal-To 3.5{sup +3.8}{sub -2.2} times higher than C-COSMOS HAEs in similar environments. Using stacking analyses of the Chandra data and Herschel SPIRE observations at 250 {mu}m, we respectively estimate mean SMBH accretion rates ( M-dot{sub BH}) and star formation rates (SFRs) for the 2QZ Clus and C-COSMOS samples. We find that the mean 2QZ Clus HAE stacked X-ray luminosity is QSO-like (L{sub 2-10{sub keV}} Almost-Equal-To [6-10] Multiplication-Sign 10{sup 43} erg s{sup -1}), and the implied M-dot{sub BH}/SFR Almost-Equal-To (1.6-3.2) Multiplication-Sign 10{sup -3} is broadly consistent with the local M{sub BH}/M{sub *} relation and z Almost-Equal-To 2 X-ray selected AGN. In contrast, the C-COSMOS HAEs are on average an order of magnitude less X-ray luminous and have M-dot{sub BH}/SFR Almost-Equal-To (0.2-0.4) Multiplication-Sign 10{sup -3}, somewhat lower than the local M{sub BH}/M{sub *} relation, but comparable to that found for z Almost-Equal-To 1-2 star-forming galaxies with similar mean X-ray luminosities. We estimate that a periodic QSO phase with duty cycle Almost-Equal-To 2%-8% would be sufficient to bring star-forming galaxies onto the local M{sub BH}/M{sub *} relation. This duty cycle is broadly consistent with the observed C-COSMOS HAE AGN fraction ( Almost-Equal-To 0.4%-2.3%) for powerful AGN with L{sub X} {approx}> 10{sup 44} erg s{sup -1}. Future observations of 2QZ Clus will be needed to identify key factors responsible for driving the mutual growth of the SMBHs and galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Comparison of Stack Measurement Data from R&D Facilities to Regulatory Criteria. A Case Study from PNNL

Chemical emissions from research and development (R&D) activities are difficult to estimate because of the large number of chemicals used and the potential for continual changes in processes. In this case study, stack measurements taken from R&D facilities at Pacific Northwest National Laboratory (PNNL) were examined, including extreme worst-case emissions estimates and alternate analyses using a Monte Carlo method that takes into account the full distribution of sampling results. The results from these analyses were then compared to emissions estimated from chemical inventories. Results showed that downwind ambient air concentrations calculated from the stack measurement data were below acceptable source impact levels (ASILs) for almost all compounds, even under extreme worst-case analyses. However, for compounds with averaging periods of a year, the unrealistic but simplifying extreme worst-case analysis often resulted in exceedances of lower level regulatory criteria used to determine modeling requirements or to define trivial releases. Compounds with 24-hour averaging periods were nearly all several orders of magnitude below all, including the trivial release, criteria. The alternate analysis supplied a more realistic basis of comparison and an ability to explore effects under different operational modes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Composition-dependence of 316 austenitic stainless steel deformation and aging properties for high-temperature applications - 18696

The present article is part of a broader effort aimed at assessing the possibility of tailoring the plasticity of austenitic stainless steels for structural applications in nuclear reactors. Three annealed heats of 316 stainless steel with large differences in stacking fault energy, carbon content, and ferrite content were used to study deformation and aging behaviors. Deformation of samples was investigated at room temperature by conventional tensile testing and at 350 deg. C by in situ neutron diffraction tensile testing. Aging was studied after 15 h at 750 deg. C through X ray diffraction and nano-indentation. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2016

Three-dimensional FIB/EBSD characterization of irradiated HfAl{sub 3}-Al composite

A thermal neutron-absorbing composite comprised of 28.4 vol.% HfAl{sub 3} intermetallic particles in an Al matrix, developed for use in a conduction-cooled thermal neutron filter, will enable fast flux irradiation of materials and fuels in an existing pressurized water test reactor. In this paper, an EBSD-FIB characterization approach is used to observe the microstructural changes of the HfAl{sub 3}-Al composite in response to simulated long-term neutron irradiation. Using a focused ion beam (FIB), the sample was fabricated to 25 μm x 25 μm x 20 μm and mounted on a transmission electron microscopy (TEM) grid. A series of operations were carried out repeatedly on the sample's top surface to prepare it for scanning electron microscopy (SEM). First, a ∼ 100-nm layer was removed by high voltage FIB milling. Then, several cleaning passes were performed on the newly exposed surface using low voltage FIB milling to improve the SEM image quality. The surface was then scanned by Electron Backscattering Diffraction (EBSD) to obtain a two-dimensional image. After 50 to 100 two-dimensional images were collected, the images were stacked to reconstruct a three-dimensional model using DREAM.3D software. Two such reconstructed three dimensional models were obtained from samples of the original and post-irradiation HfAl{sub 3}-Al composite, from which the most significant microstructural change caused by neutron irradiation appears to be the size reduction of both HfAl{sub 3} and Al grains. Possible causes include thermal expansion and related thermal strain from thermal neutron capture. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Influence of scan pattern and geometry on the microstructure and soft-magnetic performance of additively manufactured Fe-Si

The influence of geometry and scan pattern on the microstructure evolution and magnetic performance of additively manufactured Fe-3Si components was investigated. To reduce eddy current losses, novel geometries were designed and built and the microstructure and properties of these samples were characterized. The laser scan pattern was shown to strongly influence both the as-built grain structure and strength of the crystallographic texture, resulting in measurable changes in the as-built magnetic performance. In thin wall samples, heat treatment resulted in an increase in the maximum relative magnetic permeability and decrease in power losses in most samples, consistent with grain growth. However, decreases in the spacing between thin walls to increase the stacking factor of the cross-section was shown to result in unwanted electrical shorting between walls and an increase in eddy current losses. Compared to simple parallel plate construction and a mesh structure, a novel cross-section design based on the Hilbert space filling curve was found to produce the lowest power losses. The mechanisms behind these results were explored using a combination of heat conduction and electromagnetic simulations, providing a route for future component and process optimization.

36 MATERIALS SCIENCE↗