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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Shock compaction heating and collisional processes in the production of type 3 ordinary chondrites: Lessons from the (nearly) unique L3 chondrite melt breccia Northwest Africa 8709

Abstract Northwest Africa (NWA) 8709 is a rare example of a type 3 ordinary chondrite melt breccia and provides critical information for the shock compaction histories of chondrites. An L3 protolith for NWA 8709 is inferred on the basis of oxygen isotope composition, elemental composition, diverse mineral chemistry, and overall texture. NWA 8709 is among the most strongly shocked type 3 chondrites known, and experienced complete melting of the matrix and partial melting of chondrules. Unmelted phases underwent FeO reduction and partial homogenization, with reduction possibly occurring by reaction of olivine and low‐Ca pyroxene with an S‐bearing gas that was produced by vaporization. Chondrules and metal grains became foliated by uniaxial compaction, and during compression, chondrules and fragments became attached to form larger clumps. This process, and possibly also melt incorporation into chondrules to cause “inflation,” may have contributed to anomalously large chondrule sizes in NWA 8709. The melt breccia character is attributed to strong shock affecting a porous precursor. Data‐model comparisons suggest that a precursor with 23% porosity that was impacted by a 3 km/s projectile could have produced the meteorite. The rarity of other type 3 ordinary chondrite melt breccias implies that the immediate precursors to such chondrites were lower in porosity than the NWA 8709 precursor, or experienced weaker shocks. Altogether, the data imply a predominantly “quiet” dynamical environment to form most type 3 ordinary chondrites, with compaction occurring in a series of relatively weak shock events.

Ruzicka, Alex M.↗
DOE OSTI2016

Sub-kiloparsec ALMA imaging of compact star-forming galaxies at z ∼ 2.5: revealing the formation of dense galactic cores in the progenitors of compact quiescent galaxies

We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm dust continuum maps of six massive, compact, dusty star-forming galaxies at z ∼ 2.5. These galaxies are selected for their small rest-frame optical sizes (r{sub e,F160W}∼1.6 kpc) and high stellar mass densities that suggest that they are direct progenitors of compact quiescent galaxies at z ∼ 2. The deep observations yield high far-infrared (FIR) luminosities of L{sub IR}=10{sup 12.3−12.8} L{sub ⊙} and star formation rates (SFRs) of SFR = 200–700 M {sub ⊙} yr{sup −1}, consistent with those of typical star-forming “main sequence” galaxies. The high spatial resolution (FWHM ∼ 0.″12–0.″18) ALMA and Hubble Space Telescope photometry are combined to construct deconvolved, mean radial profiles of their stellar mass and (UV+IR) SFR. We find that the dusty, nuclear IR–SFR overwhelmingly dominates the bolometric SFR up to r ∼ 5 kpc, by a factor of over 100× from the unobscured UV–SFR. Furthermore, the effective radius of the mean SFR profile (r{sub e,SFR}∼1 kpc) is ∼30% smaller than that of the stellar mass profile. The implied structural evolution, if such nuclear starburst last for the estimated gas depletion time of Δt = ±100 Myr, is a 4× increase of the stellar mass density within the central 1 kpc and a 1.6× decrease of the half-mass–radius. This structural evolution fully supports dissipation-driven, formation scenarios in which strong nuclear starbursts transform larger, star-forming progenitors into compact quiescent galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Application of X-ray computed tomography for the characterization of graphite morphology in compact-graphite iron

Highlights: • X-ray Tomography is a powerful technique for graphite morphology characterization. • 3D characterization reveals true nodularity and spatial connectivity of graphite. • Tri-modal distribution of SG suggests a multi-stage graphite nucleation process. - Abstract: In the present study, high-energy X-ray tomography technique was used to characterize the graphite morphology of compact graphite iron. The size, shape, spatial connectivity and structure of different graphite morphologies were examined in 3D using computer-aided image analysis. In addition, nodularity analysis was performed in 3D and the results are compared to the traditional 2D technique. It is found that the variation of nodularity within 2 × 2 × 1.2 mm{sup 3} of the sample can be as high as 20 (%) from 2D analysis and the averaged nodularity (2D) is higher than that from 3D analysis. The size distribution of spheroidal graphite shows a tri-modal distribution, which suggests a multi-step nucleation process during solidification.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Compact and multi-view solid state neutral particle analyzer arrays on National Spherical Torus Experiment-Upgrade

A compact and multi-view solid state neutral particle analyzer (SSNPA) diagnostic based on silicon photodiode arrays has been successfully tested on the National Spherical Torus Experiment-Upgrade. The SSNPA diagnostic provides spatially, temporally, and pitch-angle resolved measurements of fast-ion distribution by detecting fast neutral flux resulting from the charge exchange (CX) reactions. The system consists of three 16-channel subsystems: t-SSNPA viewing the plasma mid-radius and neutral beam (NB) line #2 tangentially, r-SSNPA viewing the plasma core and NB line #1 radially, and p-SSNPA with no intersection with any NB lines. Due to the setup geometry, the active CX signals of t-SSNPA and r-SSNPA are mainly sensitive to passing and trapped particles, respectively. In addition, both t-SSNPA and r-SSNPA utilize three vertically stacked arrays with different filter thicknesses to obtain coarse energy information. The experimental data show that all channels are operational. The signal to noise ratio is typically larger than 10, and the main noise is x-ray induced signal. The active and passive CX signals are clearly observed on t-SSNPA and r-SSNPA during NB modulation. The SSNPA data also indicate significant losses of passing particles during sawteeth, while trapped particles are weakly affected. Fluctuations up to 120 kHz have been observed on SSNPA, and they are strongly correlated with magnetohydrodynamics instabilities.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Dynamic compaction of nickel powder examined by x-ray phase contrast imaging

Understanding the shock response of porous, granular materials is important for many scientific applications. In this work, a propagation-based x-ray phase contrast imaging technique was used to examine the shock compaction response of Ni powder (particle size: 30 and 45 µm), encapsulated in PMMA cylinders, in situ and in real time. The propagating shock wave in the PMMA cylinder and the deformation of the Ni powder column were recorded, but the compaction wave in the Ni powder could not be observed due to insufficient penetration of x-ray photons through the sample. The overall shape of the deformed Ni column downstream of the PMMA shock looked qualitatively similar for both particle sizes: it deformed inward and then outward similar to a converging-diverging nozzle, followed by a ‘mushroom’-like structure at the impact face. A preliminary analysis of our data using shock-polar method provided insight into the observed shock and flow deflection angles at the PMMA/Ni interface, and permitted evaluation of the Ni powder EOS used in this work.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Learning compact physics‐aware delayed photocurrent models using dynamic mode decomposition

Abstract Radiation‐induced photocurrent in semiconductor devices can be simulated using complex physics‐based models, which are accurate, but computationally expensive. This presents a challenge for implementing device characteristics in high‐level circuit simulations where it is computationally infeasible to evaluate detailed models for multiple individual circuit elements. In this work we demonstrate a procedure for learning compact delayed photocurrent models that are efficient enough to implement in large‐scale circuit simulations, but remain faithful to the underlying physics. Our approach utilizes dynamic mode decomposition (DMD), a system identification technique for learning reduced‐order discrete‐time dynamical systems from time series data based on singular value decomposition. To obtain physics‐aware device models, we simulate the excess carrier density induced by radiation pulses by solving numerically the ambipolar diffusion equation, then use the simulated internal state as training data for the DMD algorithm. Our results show that the significantly reduced‐order delayed photocurrent models obtained via this method accurately approximate the dynamics of the internal excess carrier density—which can be used to calculate the induced current at the device boundaries—while remaining compact enough to incorporate into larger circuit simulations.

Hanson, Joshua↗
DOE OSTI2018

In situ grain fracture mechanics during uniaxial compaction of granular solids

Grain fracture and crushing are known to influence the macroscopic mechanical behavior of granular materials and be influenced by factors such as grain composition, morphology, and microstructure. In this paper, we investigate grain fracture and crushing by combining synchrotron x-ray computed tomography and three-dimensional x-ray diffraction to study two granular samples undergoing uniaxial compaction. Our measurements provide details of grain kinematics, contacts, average intra-granular stresses, inter-particle forces, and intra-grain crystal and fracture plane orientations. Our analyses elucidate the complex nature of fracture and crushing, showing that: (1) the average stress states of grains prior to fracture vary widely in their relation to global and local trends; (2) fractured grains experience inter-particle forces and stored energies that are statistically higher than intact grains prior to fracture; (3) fracture plane orientations are primarily controlled by average intra-granular stress and contact fabric rather than the orientation of the crystal lattice; (4) the creation of new surfaces during fracture accounts for a very small portion of the energy dissipated during compaction; (5) mixing brittle and ductile grain materials alters the grain-scale fracture response. The results highlight an application of combined x-ray measurements for non-destructive in situ analysis of granular solids and provide details about grain fracture that have important implications for theory and modeling.

42 ENGINEERING↗
DOE OSTI2016

Robust and compact entanglement generation from diode-laser-pumped four-wave mixing

Four-wave-mixing processes are now routinely used to demonstrate multi-spatial-mode Einstein-Podolsky-Rosen entanglement and intensity difference squeezing. Diode-laser-pumped four-wave mixing processes have recently been shown to provide an affordable, compact, and stable source for intensity difference squeezing, but it was unknown if excess phase noise present in power amplifier pump configurations would be an impediment to achieving quadrature entanglement. Here, we demonstrate the operating regimes under which these systems are capable of producing entanglement and under which excess phase noise produced by the amplifier contaminates the output state. We show that Einstein-Podolsky-Rosen entanglement in two mode squeezed states can be generated by a four-wave-mixing source deriving both the pump field and the local oscillators from a tapered-amplifier diode-laser. This robust continuous variable entanglement source is highly scalable and amenable to miniaturization, making it a critical step toward the development of integrated quantum sensors and scalable quantum information processors, such as spatial comb cluster states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Electric and Hydraulic Propel Torque Modulation for a Compact Track Loader With the Hybrid Hydraulic Electric Architecture (HHEA)

Abstract The Hybrid Hydraulic Electric Architecture (HHEA) has previously been proposed for off-highway vehicles to reap the efficiency and controllability benefits of electrification without needing very large electric motors. This is achieved with the use of a set of selectable common pressure rails to transmit the majority of power and small electric motors to modulate that power. Previous work has shown significant energy savings for the work circuits of a variety of machines. In this paper, the energy saving potential of HHEA for the propel circuit of a compact track loader is studied. The ports of the track hydraulic motors are selectably connected to the common pressure rails, and instead of using the electric assist motors to buck/boost pressure, as in HHEA for linear actuators, small electric assist motors are used to add/subtract torque directly. The interplay between the torque limits of the electric motors and the ability of the hydraulic motor to vary displacements is studied, along with the effect these factors have on energy saving potential. It is found that the ability to vary the displacement of the hydraulic motor allows for: more efficient electric motor operating conditions, reduced electric torque requirement, and reduced pressure rail switching events. All three of these advantages can be achieved at once using variable displacements; but trade-offs exist between these advantages (i.e. improved efficiency can be achieved at the expense of a larger electric torque requirement). Overall, the HHEA can reduce energy consumption by ∼ 36% compared to the stock machine, depending on the hydraulic motor’s ability to vary displacements, and assuming the electric motor torque is limited to 20% of that required in a direct electrification scheme.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2016

Compact binary merger rates: Comparison with LIGO/Virgo upper limits

We compare evolutionary predictions of double compact object merger rate densities with initial and forthcoming LIGO/Virgo upper limits. We find that: (i) Due to the cosmological reach of advanced detectors, current conversion methods of population synthesis predictions into merger rate densities are insufficient. (ii) Our optimistic models are a factor of 18 below the initial LIGO/Virgo upper limits for BH–BH systems, indicating that a modest increase in observational sensitivity (by a factor of ∼2.5) may bring the first detections or first gravitational wave constraints on binary evolution. (iii) Stellar-origin massive BH–BH mergers should dominate event rates in advanced LIGO/Virgo and can be detected out to redshift z ≃ 2 with templates including inspiral, merger, and ringdown. Normal stars (<150 M{sub ⊙}) can produce such mergers with total redshifted mass up to M{sub tot,z}≃400 M{sub ⊙}. (iv) High black hole (BH) natal kicks can severely limit the formation of massive BH–BH systems (both in isolated binary and in dynamical dense cluster evolution), and thus would eliminate detection of these systems even at full advanced LIGO/Virgo sensitivity. We find that low and high BH natal kicks are allowed by current observational electromagnetic constraints. (v) The majority of our models yield detections of all types of mergers (NS–NS, BH–NS, BH–BH) with advanced detectors. Numerous massive BH–BH merger detections will indicate small (if any) natal kicks for massive BHs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Impact of Conformality and Crystallinity for Ultrathin 4 nm Compact TiO 2 Layers in Perovskite Solar Cells

The rapid rise in power conversion efficiencies of lead-based perovskite solar cells (PSCs) has established their promise, motivating scale-up and commercialization. As a thin film solar cell, interfacial properties are key to the performance of PSCs; there is a need to further understand which properties are important to control. Here, the impact of the compact TiO 2 (com-TiO 2 ) film properties on the performance of mesoporous PSCs is studied. Com-TiO 2 layers are fabricated by spray pyrolysis as well as by atomic layer deposition (ALD), using ALD as a proof-of-concept method to achieve highly conformal films of precisely controlled thickness. The com-TiO 2 layers’ conformality and surface roughness are examined by microscopy techniques; their relative crystallinity is studied by grazing-incidence X-ray diffraction with a synchrotron source and an in situ annealing chamber; and completed devices are analyzed by J–V and impedance spectroscopy techniques. The results show that an ultraconformal comTiO 2 layer can be thinned to 4 nm and match the performance of a ≈50 nm spray-pyrolysis TiO 2 layer. This work concludes that film conformality is the primary consideration for creating a high-performing com-TiO 2 layer, overriding any effects of flm crystallinity—a fnding that can guide fabrication choices for the scale-up of PSCs.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Modeling the AC Power Flow Equations with Optimally Compact Neural Networks: Application to Unit Commitment

Nonlinear power flow constraints render a variety of power system optimization problems computationally intractable. Emerging research shows, however, that the nonlinear AC power flow equations can be successfully modeled using neural networks. These neural networks can be exactly transformed into mixed integer linear programs and embedded inside challenging optimization problems, thus replacing nonlinearities that are intractable for many applications with tractable piecewise linear approximations. Such approaches, though, suffer from an explosion of the number of binary variables needed to represent the neural network. Accordingly, this paper develops a technique for training an "optimally compact'' neural network, i.e., one that can represent the power flow equations with a sufficiently high degree of accuracy while still maintaining a tractable number of binary variables. We demonstrate the use of this neural network as an approximator of the nonlinear power flow equations by embedding it in the AC unit commitment problem, transforming the problem from a mixed integer nonlinear program into a more manageable mixed integer linear program. We use the 14-, 57-, and 89-bus networks as test cases and compare the AC-feasibility of commitment decisions resulting from the neural network, DC, and linearized power flow approximations. Our results show that the neural network model outperforms both the DC and linearized power flow approximations when embedded in the unit commitment problem. The neural network formulation most often selects a feasible unit commitment schedule, and furthermore, it only s

AC power flow↗
DOE OSTI2016

Compact spherical neutron polarimeter using high-T{sub c} YBCO films

We describe a simple, compact device for spherical neutron polarimetry measurements at small neutron scattering angles. The device consists of a sample chamber with very low (<0.01 G) magnetic field flanked by regions within which the neutron polarization can be manipulated in a controlled manner. This allows any selected initial and final polarization direction of the neutrons to be obtained. We have constructed a prototype device using high-T{sub c} superconducting films and mu-metal to isolate regions with different magnetic fields and tested device performance in transmission geometry. Finite-element methods were used to simulate the device’s field profile and these have been verified by experiment using a small solenoid as a test sample. Measurements are reported using both monochromatic and polychromatic neutron sources. The results show that the device is capable of extracting sample information and distinguishing small angular variations of the sample magnetic field. As a more realistic test, we present results on the characterization of a 10 μm thick Permalloy film in zero magnetic field, as well as its response to an external magnetic field.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

A compact cryogenic pump

A centrifugal cryogenic pump has been designed at Argonne National Laboratory to circulate liquid nitrogen (LN2) in a closed circuit allowing the recovery of excess fluid. The pump can circulate LN2 at rates of 2-10 L/min, into a head of 0.5-3 m. Over four years of laboratory use the pump has proven capable of operating continuously for 50-100 days without maintenance.

Centrifugal pump↗