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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 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Consequences of Lattice Mismatch for Phase Equilibrium in Heterostructured Solids

Lattice mismatch - the difference in natural bond length between two species comprising a solid is a common occurrence in modern materials. Spatial patterns in certain nanocrystal heterostructures, for instance, are thought to be a result of elastic forces arising from lattice mismatch. However, the role of lattice mismatch in mediating the arrangement of atoms in such materials is incompletely understood. Here we consider a simple microscopic model for lattice mismatch, in which the difference in natural lengths between bonded atoms produces interactions mediated by elastic strain. Computer simulations reveal that the model exhibits rich phase behavior, including structures with periodic order and unusual coexistence scenarios. To explain this phase behavior, we derive an effective pairwise interaction potential between atoms, revealing preferred spatial arrangements of atoms driven by spatial variations in the interaction potential. We then develop a mean field theory based on this effective interaction which qualitatively captures observed transition to phases with modulated order. Finally, we explain the observed scenarios of coexistence between using a graphical construction, based on the realization that the free energy cost of phase separation in elastic systems grows with system size. Here, these results clarify the equilibrium effects of lattice mismatch in macroscopic solids and suggest a role for lattice mismatch in creating spatially heterogeneous compositions in nanoscale materials.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Greybox Thermal Parameter Identification of Electric Machine Stators

The parameters of electric machine thermal equivalent circuit networks are difficult to predict due to material and manufacturing uncertainties. In this paper, a Greybox system identification approach is used to identify parameters of electric machine stator lumped parameter thermal networks (LPTNs). LPTNs provide a low order, computationally efficient, dynamic model of temperatures at specific locations. Second and third order LPTN model structures are defined as state space equations with stator thermal parameters to be identified. To test the Greybox electric machine stator thermal system identification, five stator motorette prototypes were constructed with controlled variations in slot fill and slot liner thickness. The variation in the motorette thermal parameters and thermal time constants are detected using the Greybox identification. Special attention is given to the impact of sampling rate and Greybox data record length on parameter estimation accuracy.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2018

167-PFlops Deep Learning for Electron Microscopy: From Learning Physics to Atomic Manipulation

An artificial intelligence system called MENNDL, which used 25,200 Nvidia Volta GPUs on Oak Ridge National Laboratory’s Summit machine, automatically designed an optimal deep learning network in order to extract structural information from raw atomic-resolution microscopy data. In a few hours, MENNDL creates and evaluates millions of networks using a scalable, parallel, asynchronous genetic algorithm augmented with a support vector machine to automatically find a superior deep learning network topology and hyper-parameter set than a human expert can find in months. For the application of electron microscopy, the system furthers the goal of improving our understanding of the electron-beam-matter interactions and real-time image-based feedback, which enables a huge step beyond human capacity toward nanofabricating materials automatically. Finally, MENNDL has been scaled to the 4,200 available nodes of Summit achieving a measured 152.5 PFlops, with an estimated sustained performance of 167 PFlops when the entire machine is available.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Magnetic and Electronic Properties of Gd-Doped Topological Insulator Bi{sub 1.09}Gd{sub 0.06}Sb{sub 0.85}Te{sub 3}

The recent realization of quantum anomalous Hall effect and Majorana fermions observation enhance interest in magnetism investigation in topological insulators. In this work, the electronic and magnetic structure of the Gd-doped topological insulator Bi{sub 1.09}Gd{sub 0.06}Sb{sub 0.85}Te{sub 3} were systematically studied by means of angle-resolved photoemission spectroscopy, resonance photoemission spectroscopy (ResPES) and SQUID magnetometry. Resonant features related to the Gd density of states near the Fermi level are experimentally observed. Study of magnetic structure showed antiferromagnetic ordered bulk at low temperatures as well as presence of hysteresis loop at elevated temperatures. Finally, possible mechanism of magnetism and its relation to observed electronic features are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Surface Modification of Melamine-Formaldehyde (MF-R) Macroparticles in Complex Plasma

The surface modification of melamine-formaldehyde (MF-R) macroparticles (4.12 ± 0.09 μm in diameter) in dc glow discharges in neon, argon, and an argon–oxygen mixture (90% Ar, 10% O{sub 2}) was studied experimentally. The macroparticles were treated in the discharge plasma for 10, 20, 40, and 60 min. The macroparticles were placed in ordered plasma–dust structures and then extracted from them. The results of atomic force microscopy of the surface profile are presented. Quantitative data on destruction of the surface layer and aspects of its modification are discussed. The amount of substance removed from the particle surface for the exposure time was calculated using the fractal analysis method.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Subnanometer Spatial Resolution Chemical Imaging

We develop submolecular-resolution spectroscopic imaging in the visible, near-visible, and vibrational infrared ranges. These scanning tunneling microscopes (STMs) are used for chemical imaging in order to measure structure, function, and spectroscopy simultaneously. By combining these measurements we will develop enabling tools to elucidate the nanoscale rules of function at the ultimate limits of miniaturization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Vertical Axis Wind Turbine (VAWT) with Thermoplastic Composite Blades

Rising concerns about global climate change, planet pollution and increasing use of energy have accelerated wider utilization of renewable energy sources. A recent trend in energy system development is decentralization of power generation systems. The opportunity for individuals or organizations to generate electricity locally decreases losses and part of the electricity price caused by the long-distance power transmission. Vertical axis wind turbines (VAWTs) cannot compete with traditional horizontal axis wind turbines (HAWTs) on the basis of aerodynamic performance or maximum power output generated for a given footprint. However, their ability to perform at a wide range of wind speeds, indifference to wind direction, simplicity of fabrication, transportability and maintainability make them ideal candidates for decentralized installations in urban and residential areas. The project team including Steelhead Composites (SHC), Colorado State University (CSU), National Renewable Energy Laboratory (NREL) and Arkema Inc. designed and fabricated a VAWT rotor assembly with thermoplastic composite blades using novel infusion and fabrication techniques. This full-scale VAWT rotor assembly was designed for a rated power output of 0.5-1 kW, as estimated through analytical computational fluid dynamics (CFD) methods. Those CFD simulations were combined with structural finite element analysis (FEA) to optimize the shape and composite layup of the wind blades. Much of the emphasis of this program was to characterize the recyclable thermoplastic material and composite structural design, in order to take full advantage of the material properties of such composites. Additionally, this project examined the potential of thermoplastic resin systems to transform the way VAWT rotor assemblies are joined both in the factory in in the field, by utilizing thermally welded joints to minimize field failure. The infused composite blades manufactured during this program are an excellent example of these benefits made possible by the Arkema thermoplastic resin system. This prototype blade manufacturing also provided the groundwork to inform decisions for larger scale manufacturing techniques applicable to a commercialization strategy. There is specific commercial interest for small scale VAWT’s that are competitively priced, perform to expectations, and have environmentally conscious end-of-life characteristics. Economic analysis was also conducted to compare designs and material usage, providing an estimated levelized cost of energy (LCOE) for the VAWT. The next steps for commercialization would include testing of the rotor assembly to verify predicted performance, specification of the balance of plant components (generator, inverter, etc.), and identification of a manufacturing partner with capability to scale-up production. This program has showed the potential for a commercially viable product through detailed analysis, material characterization and prototype fabrication.

17 WIND ENERGY↗
DOE OSTI2024

Universality of Collective Density Fluctuations in Liquids at and away from Equilibrium – An Integrated Neutron Scattering, Theoretical, and Computational Study (Final Technical Report)

Liquids, ubiquitous on earth, are prototypical disordered condensed matter. As the mediate phase between non-structured gases and ordered solids, liquids p ossess intriguing complexities that are absent on either extreme counter phase, especially when they are driven away from equilibrium. Despite decades of studies, the physics of liquids still keeps surprising us and challenges our understanding of condensed matter, emergent phenomena, and complex systems. Among the many interesting properties, the nature of collective dynamics in liquids remains elusive because of both the presence of strong interactions and the absence of translational invariance. This project studied the universal features of collective density fluctuations (or collective modes), which include both phonon-like excitations and collective relaxations, in the Q-dependent generalized hydrodynamic regime in liquids and liquid-like matter both at and away from equilibrium. We performed systematic studies of the fast collective dynamics (including both phonon-like excitations and collective relaxations) of four classes of liquids characterized by different fragilities and interactions using synergistically integrated coherent neutron scattering experiments (Inelastic Neutron Scattering (INS), Quasi-Elastic Neutron Scattering (QENS), and Neutron Spin Echo (NSE)), a ViscoElastic Hydrodynamics theory we have been developing, andMolecular Dynamics (MD) simulations and our analysis package LiquidLib. The transformative knowledge of the collective dynamics in liquids is important to understand and ultimately control the transport of mass, energy, and charge in liquids, both at and away from thermal equilibrium, which may will likely impact a wide range of disciplines.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Acoustic-based monitoring and machine learning of component status for microreactor applications

This report provides a description and assessment of recent efforts to couple acoustic-based experimental measurements and characterization with machine learning models in order to enhance structural health monitoring capabilities for nuclear microreactors. With resilient embedded sensors in development by others supported by programs funded by the US Department of Energy’s Office of Nuclear Energy, the work described herein builds upon ongoing efforts to improve non-destructive testing technology that relates measured acoustic signatures to component stresses and/or structural defects, using a combination of new experimental measurements and machine learning architectures. The experimental procedure remained similar to that developed for the previous year’s demonstration of damage detection by the authors, with the same damaged sample tested under similar applied stress conditions. Notably, a new mounting fixture was designed and implemented to improve measurement consistency and a more sophisticated laser Doppler vibrometer was employed to make high-fidelity vibration measurements. Two nominally identical sets of training data were collected for each experimental setup to better understand the repeatability of the experiment and to better test the generality of trained neural network models. Additionally, we obtained new high-quality 3D mode shapes of the damaged test article at various stress and excitation levels, providing greater insights into the physical response of the sample during testing. Previously, we demonstrated that a machine learning model based on a convolutional neural network can predict structural details of an artificially introduced interface (intact, rough cut, smooth cut), and the applied torque level. In this study, we have transitioned to graph-based neural network architectures to better develop and test a flexible framework that is more suitable to being transferred away from controlled benchtop experiments and into more applied settings where less-structured data inputs may be expected. In general, performance testing of a graph neural network on frequency-domain representations of the data indicates strong and consistent identification of test conditions for datasets recorded on damaged components. With goals of predicting damage location and other changing experimental conditions using limited datasets, predictive models using a graph neural network architecture correctly predicted the applied torque level with an accuracy of 85% using only a single measurement point and predicted within one torque level in 95% of test windows. Predictions of damage location had limited success due to the symmetry and minimal number of the damage scenarios presented during model training. Results were ambiguous as to whether the model could detect the location of the artificial damage, or if it was instead learning the location of a given measurement point on the part and subsequently detecting which points were closest to the location of the damage. This finding will be factored into upcoming planned work on damaged graphite components, where new experimental tests with a larger number and variety of damage scenarios are expected to provide improved validation of recent developments in monitoring methodology.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2021

Out-of-Plane Sulfur Distortions in the Bi4O4S3 Superconductor

The local atomic structure of the non-magnetic layered superconductor Bi4O4S3 was investigated using neutron diffraction and pair density function (PDF) analysis. Although on average, the crystal structure is well ordered, evidence for local, out–of–plane sulfur distortions is provided, which may act as a conduit for charge transfer from the SO4 blocks into the superconducting BiS2 planes. In contrast with LaO1−xFxBiS2, no sulfur distortions were detected in the planes, which indicates that charge density wave fluctuations are not supported in Bi4O4S3.

Philip, Sharon S. (ORCID:000000031055718X)↗
NASA NTRS1973

Shuttle cryogenic supply system optimization study. Volume 5A-1: Users manual for math models

The Integrated Math Model for Cryogenic Systems is a flexible, broadly applicable systems parametric analysis tool. The program will effectively accommodate systems of considerable complexity involving large numbers of performance dependent variables such as are found in the individual and integrated cryogen systems. Basically, the program logic structure pursues an orderly progression path through any given system in much the same fashion as is employed for manual systems analysis. The system configuration schematic is converted to an alpha-numeric formatted configuration data table input starting with the cryogen consumer and identifying all components, such as lines, fittings, and valves, each in its proper order and ending with the cryogen supply source assembly. Then, for each of the constituent component assemblies, such as gas generators, turbo machinery, heat exchangers, and accumulators, the performance requirements are assembled in input data tabulations. Systems operating constraints and duty cycle definitions are further added as input data coded to the configuration operating sequence.

Source record↗
NASA NTRS1974

A study of X-ray emission from galactic and extragalactic sources with emphasis on soft and ultra-soft wavelengths

A Black Brant VC rocket was used to scan the Coma and Virgo clusters in order to measure structure in the X-ray sources. The rocket also made measurements of soft X-ray spectra, soft X-ray background flux during a 50 deg scan of the sky, soft X-rays from De Voucoulers 50, set limits to the energy dependence of soft X-ray background spectra, and the flux of solar 584 A radiation resonantly scattered by interstellar He flowing through the solar system.

Bowyer, C. S.↗
NASA NTRS1975

On the lattice dynamics of metallic hydrogen and other Coulomb systems

Numerical results for the phonon spectra of metallic hydrogen and other Coulomb systems in cubic lattices are presented. In second order in the electron-ion interaction, the behavior of the dielectric function of the interacting electron gas for arguments around the seond Fermi harmonic leads to drastic Kohn anomalies and even to imaginary phonon frequencies. Third-order band-structure corrections are also calculated. Properties of self-consistent phonons and the validity of the adiabatic approximation are discussed.

Beck, H.↗
NASA NTRS1979

Optimized multisectioned acoustic liners

A critical examination is presented of the use of optimized axially segmented acoustic liners to increase the attenuation of a liner. New calculations show that segmenting is most efficient at high frequencies with relatively long duct lengths where the attenuation is low for both uniform and segmented liners. Statistical considerations indicate little advantage in using optimized liners with more than two segments while the bandwidth of an optimized two-segment liner is shown to be nearly equal to that of a uniform liner. Multielement liner calculations show a large degradation in performance due to changes in assumed input modal structure. Finally, in order to substantiate previous and future analytical results, in-house (finite difference) and contractor (mode matching) programs are used to generate theoretical attenuations for a number of liner configurations for liners in a rectangular duct with no mean flow. Overall, the use of optimized multisectioned liners (sometimes called phased liners) fails to offer sufficient advantage over a uniform liner to warrant their use except in low frequency single mode application.

Baumeister, K. J.↗
NASA NTRS1980

Defect structure of EFG silicon ribbon

The defect structure of EFG ribbons was studied using EBIC, TEM and HVEM. By imaging the same areas in EBIC and HVEM, a direct correlation between the crystallographic nature of defects and their electrical properties was obtained. (1) Partial dislocations at coherent twin boundaries may or may not be electrically active. Since no microprecipitates were observed at these dislocations it is likely that the different electrical activity is a consequence of the different dislocation core structures. (2) 2nd order twin joins were observed which followed the same direction as the coherent first order twins normally associated with EFG ribbons. These 2nd order twin joins are in all cases strongly electrically active. EFG ribbons contain high concentrations of carbon. Since no evidence of precipitation was found with TEM it is suggested that the carbon may be incorporated into the higher order twin boundaries now known to exist in EFG ribbons.

Strunk, H.↗
NASA NTRS1984

Fine Structure of Solar Acoustic Oscillations Due to Rotation

The nature of the fine structure of high order, low degree five minute period solar oscillations following from various postulated forms of spherical rotation is predicted. The first and second order effects of rotation are included.

Goode, P. R.↗
NASA NTRS1985

Laboratory and astronomical detection of the deuterated ethynyl radical CCD

Two rotational transitions of CCD, N = 1-2 at 144 GHz and 2-3 at 216 GHz, were detected in a laboratory glow discharge through deuterated acetylene and helium, after which one, N = 2-1, was detected toward the rich molecular cloud behind the Orion Nebula. The 144 GHz transition is a well-resolved spin doublet split by 55 MHz, the components of which contain hyperfine structure of the order of 1 MHz, so far only partially resolved. From observations toward two positions in Orion, at and near the Kleinmann-Low nebula, the column density of CCD is determined to be 1.8 x 10 to the 13th/sq cm and the isotopic ratio CCD/CCH = 0.05. CCD was not detected at two positions in TMC-1.

Vrtilek, J. M.↗