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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Coarsening of AA6013-T6 Precipitates During Sheet Warm Forming Applications

The use of warm forming for AA6xxx-T6 sheet is of interest to improve its formability; however, the effect warm forming may have on the coarsening of precipitates and the mechanical strength of these sheets has not been well studied. In this research, the coarsening behavior of AA6013-T6 precipitates has been explored, in the temperature range of 200-300 °C, and time of 30 s up to 50 h. Additionally, the effect of warm deformation on coarsening behavior was explored using: (1) simulated warm forming tests in a Gleeble thermo-mechanical simulator and (2) bi-axial warm deformation tests. Using a strong obstacle model to describe the yield strength (YS) evolution of the AA6013-T6 material, and a Lifshitz, Slyozov, and Wagner (LSW) particle coarsening law to describe the change in precipitate size with time, the coarsening kinetics were modeled for this alloy. The coarsening kinetics in the range of 220-300 °C followed a trend similar to that previously found for AA6111 for the 180-220 °C range. There was strong evidence that coarsening kinetics were not altered due to warm deformation above 220 °C. For warm forming between 200 and 220 °C, the YS of the AA6013-T6 material increased slightly, which could be attributed to strain hardening during warm deformation. Finally, a non-isothermal coarsening model was used to assess the potential reduction in the YS of AA6013-T6 for practical processing conditions related to auto-body manufacturing. The model calculations showed that 90% of the original AA6013-T6 YS could be maintained, for warm forming temperatures up to 280 °C, if the heating schedule used to get the part to the warm forming temperature was limited to 1 min.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Development of cast alumina-forming austenitic stainless steels

Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt. % are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt. % Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800 C - 850 C in H 2 O-, S-, and C- containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloy along with improved oxidation resistance typical of alumina-forming alloys. Lastly, challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Canonical forms for single-qutrit Clifford+T operators

We introduce canonical forms for single qutrit Clifford+T circuits and prove that every single-qutrit Clifford+T operator admits a unique such canonical form. We show that our canonical forms are T-optimal in the sense that among all the single-qutrit Clifford+T circuits implementing a given operator our canonical form uses the least number of T gates. Finally, we provide an algorithm which inputs the description of an operator (as a matrix or a circuit) and constructs the canonical form for this operator. The algorithm runs in time linear in the number of T gates. Our results provide a higher-dimensional generalization of prior work by Matsumoto and Amano who introduced similar canonical forms for single-qubit Clifford+T circuits.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Fracton phases via exotic higher-form symmetry-breaking

We study p-string condensation mechanisms for fracton phases from the viewpoint of higher-form symmetry, focusing on the examples of the X-cube model and the rank-two symmetric-tensor scalar charge theory. This work is motivated by questions of the relationship between fracton phases and continuum quantum field theories, and also provides general principles to describe p-string condensation independent of specific lattice model constructions. We give a perspective on higher-form symmetry in lattice models in terms of cellular homology. Applying this perspective to the coupled-layer construction of the X-cube model, we identify a foliated 1-form symmetry that is broken in the X-cube phase, but preserved in the phase of decoupled toric code layers. Similar considerations for the scalar charge theory lead to a framed 1-form symmetry. These symmetries are distinct from standard 1-form symmetries that arise, for instance, in relativistic quantum field theory. Here, we also give a general discussion on interpreting p-string condensation, and related constructions involving gauging of symmetry, in terms of higher-form symmetry.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Selection and properties of alternative forming fluids for TRISO fuel kernel production

Current Very High Temperature Reactor (VHTR) designs incorporate TRi-structural ISOtropic (TRISO) fuel, which consists of a spherical fissile fuel kernel surrounded by layers of pyrolytic carbon and silicon carbide. An internal sol-gel process forms the fuel kernel using wet chemistry to produce uranium oxyhydroxide gel spheres by dropping a cold precursor solution into a hot column of trichloroethylene (TCE). Over time, gelation byproducts inhibit complete gelation, and the TCE must be purified or discarded. The resulting TCE waste stream contains both radioactive and hazardous materials and is thus considered a mixed hazardous waste. Changing the forming fluid to a non-hazardous alternative could greatly improve the economics of TRISO fuel kernel production. Selection criteria for a replacement forming fluid narrowed a list of ~10,800 chemicals to yield ten potential replacement forming fluids: 1-bromododecane, 1- bromotetradecane, 1-bromoundecane, 1-chlorooctadecane, 1-chlorotetradecane, 1-iododecane, 1-iodododecane, 1-iodohexadecane, 1-iodooctadecane, and squalane. The density, viscosity, and surface tension for each potential replacement forming fluid were measured as a function of temperature between 25 °C and 80 °C. Calculated settling velocities and heat transfer rates give an overall column height approximation. 1-bromotetradecane, 1-chlorooctadecane, and 1-iodododecane show the greatest promise as replacements, and future tests will verify their ability to form satisfactory fuel kernels.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2013

Synthesis and characterization of two crystallographic forms of Ag{sub 0.79}VS{sub 2}

A previously unreported compound, Ag{sub 0.79}VS{sub 2}, has been synthesized; its structure and elementary properties are reported. Ag{sub 0.79}VS{sub 2} crystallizes in two forms, designated as the α and β, related to the 1s-InTaS{sub 2} structure. Single crystal x-ray diffraction shows the α form to have a single layer hexagonal structure with a unit cell of 3.213(3) Å×7.809(6) Å, consisting of layers of edge-shared VS{sub 6} triangular prisms separated by layers of Ag. The β form is similar but has an a{sub o}√((3)) supercell in the basal plane, yielding a unit cell of 5.573(5) Å×7.822(6) Å. Both forms have disordered and displaced silver in the basal plane, but the β form has partial ordering of its silver sublattice and in-plane vanadium trimers. Resistivity measurements show metallic temperature dependence with an unusual hysteresis between 210 K and 130 K. Magnetic susceptibility measurements show Pauli Paramagnetic behavior. The Seebeck coefficient at 300 K is 42 µV/K. - Graphical abstract: Red=Vanadium, Gray=Silver, Yellow=Sulfur. Top left is α-Ag{sub 0.79}VS{sub 2} in the 1s-InTaS{sub 2} structure type. Top right: 2a×2b projection down the c-axis with displacement ellipsoids (50% probability) of atoms drawn to illustrate the split silver model. Bottom left is β-Ag{sub 0.79}VS{sub 2} having the a{sub o}√((3)) supercell. Bottom right: projection along the c-axis, displacement ellipsoids of atoms drawn. - Highlights: • Two crystallographic forms of Ag{sub 0.79}VS{sub 2}, designated α and β, are reported. • They are found to crystallize in the 1s-InTaS{sub 2} structure type. • β-Ag{sub 0.79}VS{sub 2} has partial ordering of the Ag sublattice and vanadium trimers. • Ag{sub 0.79}VS{sub 2} shows Pauli Paramagnetic behavior, a Seebeck coefficient of 42 µV/K at 300 K. • Ag{sub 0.79}VS{sub 2} shows metallic resistivity with an unusual hysteresis between 210 K and 130 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Improved the microstructures and properties of M3:2 high-speed steel by spray forming and niobium alloying

The microstructures and properties of spray formed (SF) high-speed steels (HSSs) with or without niobium (Nb) addition were studied. Particular emphasis was placed on the effect of Nb on the solidification microstructures, decomposition of M{sub 2}C carbides, thermal stability and mechanical properties. The results show that spray forming can refine the cell size of eutectic carbides due to the rapid cooling effect during atomization. With Nb addition, further refinement of the eutectic carbides and primary austenite grains are obtained. Moreover, the Nb addition can accelerate the decomposition of M{sub 2}C carbides and increase the thermal stability of high-speed steel, and also can improve the hardness and bending strength with slightly decrease the impact toughness. The high-speed steel made by spray forming and Nb alloying can give a better tool performance compared with powder metallurgy M3:2 and commercial AISI M2 high-speed steels. - Highlights: • Spray forming can effectively refine the microstructure of M3:2 steel. • Niobium accelerates the decomposition of M{sub 2}C carbides. • Niobium increases the hardness and bending strength of spray formed M3:2 steel. • Spray-formed niobium-containing M3:2 steel has the best tool performance.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Novel bacterial clade reveals origin of form I Rubisco

Rubisco sustains the biosphere through the fixation of CO 2 into biomass. In plants and cyanobacteria, form I Rubisco is structurally comprised of large and small subunits, whereas all other Rubisco forms lack small subunits. The rise of the form I complex through the innovation of small subunits represents a key, yet poorly understood, transition in Rubisco's evolution. Here, through metagenomic analyses, we discovered a previously uncharacterized clade sister to form I Rubisco that evolved without small subunits. This clade diverged before the evolution of cyanobacteria and the origin of the small subunit; thus, it provides a unique reference point to advance our understanding of form I Rubisco evolution. Structural and kinetic data presented here reveal how a proto-form I Rubisco assembled and functioned without the structural stability imparted from small subunits. Our findings provide insight into a key evolutionary transition of the most abundant enzyme on Earth and the predominant entry point for nearly all global organic carbon.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

The Proton Form Factor Ratio Measurements at Jefferson Lab

The ratio of the proton form factors, G{sub Ep}/G{sub Mp}, has been measured from Q{sup 2} of 0.5 GeV{sup 2} to 8.5 GeV{sup 2}, at the Jefferson Laboratory, using the polarization transfer method. This ratio is extracted directly from the measured ratio of the transverse and longitudinal polarization components of the recoiling proton in elastic electron-proton scattering. The discovery that the proton form factor ratio measured in these experiments decreases approximately linearly with four-momentum transfer, Q{sup 2}, for values above ~1 GeV{sup 2}, is one of the most significant results to come out of JLab. These results have had a large impact on progress in hadronic physics; and have required a significant rethinking of nucleon structure. The increasingly common use of the double-polarization technique to measure the nucleon form factors, in the last 15 years, has resulted in a dramatic improvement of the quality of all four nucleon electromagnetic form factors, G{sub Ep}, G{sub Mp}, G{sub En} and G{sub Mn}. There is an approved experiment at JLab, GEP(V), to continue the ratio measurements to 12 GeV{sup 2}. A dedicated experimental setup, the Super Bigbite Spectrometer (SBS), will be built for this purpose. It will be equipped with a focal plane polarimeter to measure the polarization of the recoil protons. The scattered electrons will be detected in an electromagnetic calorimeter. In this presentation, I will review the status of the proton elastic electromagnetic form factors and discuss a number of theoretical approaches to describe nucleon form factors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

The effect of tooling design parameters on web-warping in the flexible roll forming of UHSS

To reduce weight and improve passenger safety there is an increased need in the automotive industry to use Ultra High Strength Steels (UHSS) for structural and crash components. However, the application of UHSS is restricted by their limited formability and the difficulty of forming them in conventional processes. An alternative method of manufacturing structural auto body parts from UHSS is the flexible roll forming process which can accommodate materials with high strength and limited ductility in the production of complex and weight-optimised components. However, one major concern in the flexible roll forming is web-warping, which is the height deviation of the profile web area. This paper investigates, using a numerical model, the effect on web-warping with respect to various forming methods. The results demonstrate that different forming methods lead to different amount of web-warping in terms of forming the product with identical geometry.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Simulation of root forms using cellular automata model

This research aims to produce a simulation program for root forms using cellular automata model. Stephen Wolfram in his book entitled “A New Kind of Science” discusses the formation rules based on the statistical analysis. In accordance with Stephen Wolfram’s investigation, the research will develop a basic idea of computer program using Delphi 7 programming language. To best of our knowledge, there is no previous research developing a simulation describing root forms using the cellular automata model compared to the natural root form with the presence of stone addition as the disturbance. The result shows that (1) the simulation used four rules comparing results of the program towards the natural photographs and each rule had shown different root forms; (2) the stone disturbances prevent the root growth and the multiplication of root forms had been successfully modeled. Therefore, this research had added some stones, which have size of 120 cells placed randomly in the soil. Like in nature, stones cannot be penetrated by plant roots. The result showed that it is very likely to further develop the program of simulating root forms by 50 variations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Extending the accuracy of the SNAP interatomic potential form

The Spectral Neighbor Analysis Potential (SNAP) is a classical interatomic potential that expresses the energy of each atom as a linear function of selected bispectrum components of the neighbor atoms. An extension of the SNAP form is proposed that includes quadratic terms in the bispectrum components. The extension is shown to provide a large increase in accuracy relative to the linear form, while incurring only a modest increase in computational cost. The mathematical structure of the quadratic SNAP form is similar to the embedded atom method (EAM), with the SNAP bispectrum components serving as counterparts to the two-body density functions in EAM. It is also argued that the quadratic SNAP form is a special case of an artificial neural network (ANN). The effectiveness of the new form is demonstrated using an extensive set of training data for tantalum structures. Similarly to ANN potentials, the quadratic SNAP form requires substantially more training data in order to prevent overfitting, as measured by cross-validation analysis.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Environmental influences on autocollimator-based angle and form metrology

Deflectometric profilometers are indispensable tools for the precision form measurement of beam-shaping optics of synchrotrons and x-ray free electron lasers. They are used in metrology labs for x-ray optics worldwide and are crucial for providing measurement accuracy dictated by the form tolerances for modern state-of-the-art x-ray optics. Deflectometric profilometers use surface slope (angle) to assess form, and they utilize commercial autocollimators for the contactless slope measurement. In this contribution, we discuss the influences of environmental parameters, such as temperature and air pressure, including their gradients, on high-accuracy metrology with autocollimators in profilometers. They can cause substantial systematic errors in form measurement, especially in the case of large and strongly curved optical surfaces of high dynamic range. Relative angle and form measuring errors of the order of 10 -4 are to be expected. We characterize environmental influences by extended theoretical and experimental investigations and derive strategies for correcting them. Additionally, we report on the possibility to minimize the contributions of some errors by the application of sophisticated experimental arrangements and methods. We aim at approaching fundamental limits in autocollimator-based slope and form metrology.

47 OTHER INSTRUMENTATION↗
DOE OSTI2012

THE SCHMIDT-KENNICUTT LAW OF MATCHED-AGE STAR-FORMING REGIONS; Pa{alpha} OBSERVATIONS OF THE EARLY-PHASE INTERACTING GALAXY TAFFY I

In order to test a recent hypothesis that the dispersion in the Schmidt-Kennicutt law arises from variations in the evolutionary stage of star-forming molecular clouds, we compared molecular gas and recent star formation in an early-phase merger galaxy pair, Taffy I (UGC 12915/UGC 12914, VV 254) which went through a direct collision 20 Myr ago and whose star-forming regions are expected to have similar ages. Narrowband Pa{alpha} image is obtained using the ANIR near-infrared camera on the mini-TAO 1 m telescope. The image enables us to derive accurate star formation rates within the galaxy directly. The total star formation rate, 22.2 M{sub Sun} yr{sup -1}, was found to be much higher than previous estimates. Ages of individual star-forming blobs estimated from equivalent widths indicate that most star-forming regions are {approx}7 Myr old, except for a giant H II region at the bridge which is much younger. Comparison between star formation rates and molecular gas masses for the regions with the same age exhibits a surprisingly tight correlation, a slope of unity, and star formation efficiencies comparable to those of starburst galaxies. These results suggest that Taffy I has just evolved into a starburst system after the collision, and the star-forming sites are at a similar stage in their evolution from natal molecular clouds except for the bridge region. The tight Schmidt-Kennicutt law supports the scenario that dispersion in the star formation law is in large part due to differences in evolutionary stage of star-forming regions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Nature of Hα selected galaxies at z > 2. I. Main-sequence and dusty star-forming galaxies

We present the results from our narrow-band imaging surveys of Hα emitters (HAEs) at z = 2.2 and z = 2.5 in the Subaru/XMM-Newton Deep survey Field with near-infrared camera MOIRCS on the Subaru Telescope. We have constructed a clean sample of 63 star-forming galaxies at z = 2.2 and 46 at z = 2.5. For 12 (or ∼92%) out of 13 HAEs at z = 2.2, their Hα emission lines have been successfully detected by the spectroscopy. While about 42% of the red, massive HAEs with M {sub *} > 10{sup 10.8} M {sub ☉} contain active galactic nuclei (AGNs), most of the blue, less massive ones are likely to be star-forming galaxies. This suggests that the AGN may play an important role in galaxy evolution at the late stage of truncation. For the HAEs excluding possible AGNs, we estimate the gas-phase metallicities on the basis of [N II]/Hα ratios, and find that the metallicities of the Hα selected galaxies at z = 2.2 are lower than those of local star-forming galaxies at fixed stellar mass, as shown by previous studies. Moreover, we present and discuss the so-called main sequence of star-forming galaxies at z > 2 based on our unique sample of HAEs. By correlating the level of dust extinction with the location on the main sequence, we find that there are two kinds/modes of dusty star-forming galaxies: starbursting galaxies and metal-rich normal star-forming galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Properties of cyclotron lines in a line-forming region injected by an anisotropic continuum in accreting X-ray pulsars

I examine the characteristics of profiles of cyclotron lines formed by the superposition of a number of lines formed at a number of altitudes in line-forming regions illuminated by anisotropic injections in an accretion column, which formed around the polar cap of Roche-lobe-type accretion-powered X-ray pulsars. In the present paper, I consider the line-forming region near the walls of a cylindrical geometry illuminated from the inside of the cylinder. I also examine how the direction of the peak of a beam pattern affects the profiles of cyclotron lines. I found that the width and depth of the line in a phase-averaged spectrum provide information concerning the direction of a beam. I demonstrate that the cyclotron line has a pure absorption in the phase-averaged spectrum regardless of the height of the cylinder, which is expected to change with luminosity. On the other hand, in phase-resolved spectra, an emission-like feature can be formed in the phase with lower intensity in a short cylinder, which is expected at L∼10{sup 36} erg s{sup −1}, while a pure absorption feature tends to appear in all phases due to the superposition of a large number of lines in a tall cylinder, which is expected at L≳10{sup 37} erg s{sup −1}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Dynamics of three-form dark energy with dark matter couplings

Three-form field can give rise to viable cosmological scenarios of dark energy with potentially observable signatures distinct from standard single scalar field models. In this study, the background dynamics of three-form cosmology are investigated. Our analysis suggests that the potential of three-form field should be runaway. We also investigate the possibility to solve the coincidence problem by using the coupling of three-form field to dark matter. Four types of coupling form are examined and we find that the coupling of the form Q = (6){sup 1/2}Γ( X-dot +3HX)/κ provides the possibility to solve the coincidence problem.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

$B\to Kl^+l^-$ decay form factors from three-flavor lattice QCD

We compute the form factors for the B → Kl + l - semileptonic decay process in lattice QCD using gauge-field ensembles with 2+1 flavors of sea quark, generated by the MILC Collaboration. The ensembles span lattice spacings from 0.12 to 0.045 fm and have multiple sea-quark masses to help control the chiral extrapolation. The asqtad improved staggered action is used for the light valence and sea quarks, and the clover action with the Fermilab interpretation is used for the heavy b quark. We present results for the form factors f+(q 2 ), f 0 (q 2 ), and f T (q 2 ), where q 2 is the momentum transfer, together with a comprehensive examination of systematic errors. Lattice QCD determines the form factors for a limited range of q 2 , and we use the model-independent z expansion to cover the whole kinematically allowed range. We present our final form-factor results as coefficients of the z expansion and the correlations between them, where the errors on the coefficients include statistical and all systematic uncertainties. Lastly, we use this complete description of the form factors to test QCD predictions of the form factors at high and low q 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗