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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

On-Line Prediction of Resistant Force During Soil–Tool Interaction

For off-road vehicles such as excavators and wheel loaders, a large portion of energy is consumed to overcome the soil resistant force in the digging process. For optimal control of the digging tool, a high-fidelity model of the soil–tool interaction force is important to reduce energy consumption. Here, in this paper, an on-line soil resistant force prediction method is proposed. In this method, a hybrid model, which combines a physical model and a data-driven model, is used for the force prediction. In addition, the parameters of the hybrid model can be updated on-line based on real-time data. Comparisons with experimental data demonstrate that the proposed prediction method has an average error of around 12.7%.

42 ENGINEERING↗
DOE OSTI2020

Biophysical impacts of Earth greening largely controlled by aerodynamic resistance

Satellite observations show widespread increasing trends of leaf area index (LAI), known as the Earth greening. However, the biophysical impacts of this greening on land surface temperature (LST) remain unclear. Here, we quantify the biophysical impacts of Earth greening on LST from 2000 to 2014 and disentangle the contributions of different factors using a physically based attribution model. We find that 93% of the global vegetated area shows negative sensitivity of LST to LAI increase at the annual scale, especially for semiarid woody vegetation. Further considering the LAI trends (P ≤ 0.1), 30% of the global vegetated area is cooled by these trends and 5% is warmed. Aerodynamic resistance is the dominant factor in controlling Earth greening’s biophysical impacts: The increase in LAI produces a decrease in aerodynamic resistance, thereby favoring increased turbulent heat transfer between the land and the atmosphere, especially latent heat flux.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Large magnetoelectric resistance in the topological Dirac semimetal α-Sn

The spin-momentum locking of surface states in topological materials can produce a resistance that scales linearly with magnetic and electric fields. Such a bilinear magnetoelectric resistance (BMER) effect offers a new approach for information reading and field sensing applications, but the effects demonstrated so far are too weak or for low temperatures. This article reports the first observation of BMER effects in topological Dirac semimetals; the BMER responses were measured at room temperature and were substantially stronger than those reported previously. The experiments used topological Dirac semimetal α-Sn thin films grown on silicon substrates. The films showed BMER responses that are 10 6 times larger than previously measured at room temperature and are also larger than those previously obtained at low temperatures. These results represent a major advance toward realistic BMER applications. Significantly, the data also yield the first characterization of three-dimensional Fermi-level spin texture of topological surface states in α-Sn.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Thin film design of amorphous hafnium oxide nanocomposites enabling strong interfacial resistive switching uniformity

A design concept of phase-separated amorphous nanocomposite thin films is presented that realizes interfacial resistive switching (RS) in hafnium-oxide-based devices. The films are formed by incorporating an average of 7% Ba into hafnium oxide during pulsed laser deposition at temperatures ≤400°C. The added Ba prevents the films from crystallizing and leads to ~20-nm-thin films consisting of an amorphous HfO x host matrix interspersed with ~2-nm-wide, ~5-to-10-nm-pitch Ba-rich amorphous nanocolumns penetrating approximately two-thirds through the films. This restricts the RS to an interfacial Schottky-like energy barrier whose magnitude is tuned by ionic migration under an applied electric field. Resulting devices achieve stable cycle-to-cycle, device-to-device, and sample-to-sample reproducibility with a measured switching endurance of ≥10 4 cycles for a memory window ≥10 at switching voltages of ±2 V. Each device can be set to multiple intermediate resistance states, which enables synaptic spike-timing–dependent plasticity. The presented concept unlocks additional design variables for RS devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Maternal Broadly Neutralizing Antibodies Can Select for Neutralization-Resistant, Infant-Transmitted/Founder HIV Variants

Each year, >180,000 infants become infected via mother-to-child transmission (MTCT) of HIV despite the availability of effective maternal antiretroviral treatments, underlining the need for a maternal HIV vaccine. We characterized 224 maternal HIV envelope (Env)-specific IgG monoclonal antibodies (MAbs) from seven nontransmitting and transmitting HIV-infected U.S. and Malawian mothers and examined their neutralization activities against nontransmitted autologous circulating viruses and infant-transmitted founder (infant-T/F) viruses. Only a small subset of maternal viruses, 3 of 72 (4%), were weakly neutralized by maternal linear V3 epitope-specific IgG MAbs, whereas 6 out of 6 (100%) infant-T/F viruses were neutralization resistant to these V3-specific IgG MAbs. We also show that maternal-plasma broadly neutralizing antibody (bNAb) responses targeting the V3 glycan supersite in a transmitting woman may have selected for an N332 V3 glycan neutralization-resistant infant-T/F virus. These data have important implications for bNAb-eliciting vaccines and passively administered bNAbs in the setting of MTCT.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Campylobacter jejuni resistance to human milk involves the acyl carrier protein AcpP

Campylobacter jejuni is a common foodborne pathogen worldwide that is associated with high rates of morbidity and mortality among infants in low- to middle-income countries (LMICs). Human milk provides infants with an important source of nutrients and contains antimicrobial components for protection against infection. However, recent studies, including our own, have found significantly higher levels of Campylobacter in diarrheal stool samples collected from breastfed infants compared to non-breastfed infants in LMICs. We hypothesized that C. jejuni has unique strategies to resist the antimicrobial properties of human milk. Transcriptional profiling found human milk exposure induces genes associated with ribosomal function, iron acquisition, and amino acid utilization in C. jejuni strains 81–176 and 11168. However, unidentified proteinaceous components of human milk prevent bacterial growth. Evolving both C. jejuni isolates to survive in human milk resulted in mutations in genes encoding the acyl carrier protein (AcpP) and the major outer membrane porin (PorA). Introduction of the PorA/AcpP amino acid changes into the parental backgrounds followed by electron microscopy showed distinct membrane architectures, and the AcpP changes not only significantly improved growth in human milk, but also yielded cells surrounded with outer membrane vesicles. Analyses of the phospholipid and lipooligosaccharide (LOS) compositions suggest an imbalance in acyl chain distributions. For strain 11168, these changes protect both evolved and 11168ΔacpP G33R strains from bacteriophage infection and polymyxin killing. Taken together, this study provides insights into how C. jejuni may evolve to resist the bactericidal activity of human milk and flourish in the hostile environment of the gastrointestinal tract.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Study of the Crack Resistance of Microarc Oxidation Coatings after Laser Doping with Zirconium Oxide

In this paper we present the results of a study of crack resistance of a microarc oxidation coating (MAO) after laser doping with zirconium oxide. Crack resistance was determined by indentation with imprint imaging using atomic force microscopy. Laser doping with zirconium oxide was established to lead to a significant hardening of the MAO coating. The stress intensity factor increases by a factor of 2.7 while surface damage decreases by a factor of 2 compared with the initial MAO coating.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Deep 3D X-ray Lithography Based on High-Contrast Resist Layers

In classical X-ray lithography, the mask and resist layer are arranged perpendicular to the incident X-ray beam. Being absorbed in the resist layer, the X-ray beam induces a response in the form corresponding to its cross section. However, using a tilt and rotation of the mask/resist and sequential repeated exposures, it is possible to create three-dimensional forms that are accurate to within less than a micron. New approaches to the creation of 3D microstructures by deep X-ray lithography are described, which can ensure the formation of relatively large arrays.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Scalable Multiphysics Block Preconditioning for Low Mach Number Compressible Resistive MHD with Application to Magnetic Confinement Fusion

This study investigates multiphysics block preconditioners that are critical in devising scalable Newton–Krylov iterative solvers for longer time-scale fully implicit fluid plasma models. The specific model of interest is the visco-resistive, low Mach number, compressible magnetohydrodynamics (MHD) model. This model describes the dynamics of conducting fluids in the presence of electromagnetic fields and can be used to study aspects of astrophysical phenomena, important science and technology applications, and basic plasma physics. The specific application of interest that motivates this study is the macroscopic simulation of longer time-scale stability and disruptions of magnetic confinement fusion devices, specifically the ITER Tokamak. The computational solution of the governing balance equations for mass, momentum, heat transfer, and magnetic induction for resistive MHD systems can be extremely challenging. These difficulties arise from both the strong nonlinear, nonsymmetric coupling of fluid and electromagnetic phenomena as well as the significant range of time and length scales that the interactions of these physical mechanisms produce. To handle the range of time and spatial scales of interest, a fully implicit unstructured variational multiscale finite element formulation is employed. For the scalable solution of the Newton linearized systems, fully coupled block preconditioners are designed to leverage algebraic multigrid subsolves. In conclusion, results are presented for the strong and weak scaling of the method as well as the robustness of these techniques for a large range of Lundquist numbers.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

First-Principles Modeling of the Repassivation of Corrosion Resistant Alloys: Part I. O and Cl Adsorption Energy

To understand the mechanism of repassivation, a key process that controls the performance of corrosion resistant alloys (CRAs), it is useful to obtain some fundamental parameters that describe the atomistic processes. Oxygen and chlorine adsorption energies were systematically calculated with density functional theory for Ni-22Cr alloys with seven different solute elements: Co, Cu, Fe, Mn, Mo, Ru and W. All elements other than Cu enhance both O and Cl adsorption to alloy surfaces. Cr has the strongest effect among these elements. Surface configurations that give stronger O adsorption also tend to give stronger Cl adsorption. While this makes it difficult to differentiate the effect of these solute elements on the oxidation/repassivation tendency of alloys, these fundamental properties provide the foundation for higher scale models that could be used to study the oxidation process during corrosion and potentially inform the design of CRAs. Bader charge analysis reveals a strong relationship between the adatom adsorption energy and the Bader charges of both O and Cl adatom. In conclusion, the work function of alloy surfaces is increased by O while decreased by Cl, suggesting that Cl adsorption can have an intrinsic negative impact on corrosion resistance by decreasing the barrier to electron transfer.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Communication—Reduction of DC Resistance of Ni-Rich Lithium Transition Metal Oxide Cathode by Atomic Layer Deposition

A coating using Atomic layer deposition (ALD) of Al 2 O 3 was applied to Ni-rich lithium transition metal oxide cathode material. This ALD coating reduces the DC resistance (DCR) and increases the cycling performance of the Ni-rich cathode. Additionally, the reduced DCR comes from decreased solid electrolyte interphase (SEI) resistance on the anode, which is attributed to reduced transition metal deposition. This is due to the ALD coating preventing the direct contact between the cathode and the electrolyte, and therefore inhibits transition metal dissolution. This study suggests the promise of using ALD coating to reduce the DCR of Ni-rich cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2023

Temperature-Dependent Sheet and Contact Resistivity Measurements on Ag and Ag-Ni Circuit Pastes

The metal circuits and brazes used in electronic, energy conversion, and/or energy storage devices often have difficulty wetting and adhering to ceramic and/or ceramic-passivated metal substrates. Here, a novel Particle Interlayer Directed Wetting and Spreading (PIDWAS) technique is demonstrated that utilizes screen printing, the low wetting angle of silver on nickel, and the high work of adhesion between nickel and various ceramics to produce well-adhered, self-assembled silver patterns on ceramic and/or stainless-steel substrates not normally wet by silver. The resulting Ag-Ni circuits have higher sapphire adhesion strengths (up to 30 MPa on sapphire), higher densities (>97% on sapphire), and similar high-temperature electronic resistivities to those made using commercially-available Heraeus C8710 or DAD-87 silver circuit pastes. Similarly, Ag-Ni brazes between a variety of ceramic and/or stainless-steel substrates have better microstructural stability with rapid thermal cycling, reduction-oxidation cycling, and dual atmosphere isothermal aging than conventional Ag-CuO brazes. In addition, the residual Ni in these Ag-Ni circuits and brazes can be used to chemically getter surface segregated Al, ensuring low contact resistances on a variety of chromia- and/or alumina-passivated stainless steels. Reference: [1] Hu G, Zhou Q, Bhatlawande A, Park J, Termuhlen R, Ma Y, Bieler TR, Yu HC, Qi Y, Hogan T & Nicholas JD. Patterned Nickel Interlayers for Enhanced Silver Wetting, Spreading and Adhesion on Ceramic Substrates. Scripta Materialia, 2021; 196, 113767. 10.1016/j.scriptamat.2021.113767 [2] Park J, Phongpreecha T, Nicholas JD & Qi Y. Enhanced Liquid Metal Wetting on Oxide Surfaces via Patterned Particles. Acta Materialia, 2020; 199, 551-560. 10.1016/j.actamat.2020.08.037

Bhatlawande, Aishwarya↗
DOE OSTI2020

Are Supercells Resistant to Entrainment because of Their Rotation?

This research investigates a hypothesis posed by previous authors, which argues that the helical nature of the flow in supercell updrafts makes them more resistant to entrainment than nonsupercellular updrafts because of the suppressed turbulence in purely helical flows. It was further supposed that this entrainment resistance contributes to the steadiness and longevity of supercell updrafts. A series of idealized large-eddy simulations were run to address this idea, wherein the deep-layer shear and hodograph shape were varied, resulting in supercells in the strongly sheared runs, nonsupercells in the weakly sheared runs, and variations in the percentage of streamwise vorticity in updrafts among runs. Fourier energy spectrum analyses show well-developed inertial subranges in all simulations, which suggests that the percentages of streamwise and crosswise vorticity have little effect on turbulence in convective environments. Additional analyses find little evidence of updraft-scale centrifugally stable flow within updrafts, which has also been hypothesized to limit horizontal mass flux across supercell updrafts. Results suggest that supercells do have smaller fractional entrainment rates than nonsupercells, but these differences are consistent with theoretical dependencies of entrainment on updraft width, and with supercells being wider than nonsupercells. Thus, while supercells do experience reduced fractional entrainment rates and entrainment-driven dilution, this advantage is primarily attributable to increased supercell updraft width relative to ordinary convection, and has little to do with updraft helicity and rotation.

Peters, John M.↗
DOE OSTI2020

The crystal structure of a Polerovirus exoribonuclease-resistant RNA shows how diverse sequences are integrated into a conserved fold

Exoribonuclease-resistant RNAs (xrRNAs) are discrete elements that block the progression of 5' to 3' exoribonucleases using specifically folded RNA structures. A recently discovered class of xrRNA is widespread in several genera of plant-infecting viruses, within both noncoding and protein-coding subgenomic RNAs. The structure of one such xrRNA from a dianthovirus revealed three-dimensional details of the resistant fold but did not answer all questions regarding the conservation and diversity of this xrRNA class. Here, we present the crystal structure of a representative polerovirus xrRNA that contains sequence elements that diverge from the previously solved structure. This new structure rationalizes previously unexplained sequence conservation patterns and shows interactions not present in the first structure. Together, the structures of these xrRNAs from dianthovirus and polerovirus genera support the idea that these plant virus xrRNAs fold through a defined pathway that includes a programmed intermediate conformation. This work deepens our knowledge of the structure-function relationship of xrRNAs and shows how evolution can craft similar RNA folds from divergent sequences.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Dataset for "Resistance of Boron Nitride Nanotubes to Radiation-Induced Oxidation" as published in The Journal of Physical Chemistry C

We present unprecedented results on the damage thresholds and pathways for boron nitride nanotubes (BNNT) under the influence of energetic electrons in an oxidative gas environment, using an environmental aberration-corrected electron microscope over a range of oxygen pressures. We observe a damage cascade process that resists damage until a higher electron dose, compared with carbon nanotubes, initiating at defect-free BNNT sidewalls and proceeding through the conversion from crystalline nanotubes to amorphous boron nitride (BN), resisting oxidation throughout. We compare with prior results on the oxidation of carbon nanotubes and present a model that attributes the onset of damage in both cases to a physisorbed oxygen layer that reduces the threshold for damage onset. Surprisingly, increased temperatures offer protection against damage, as do electron dose rates that significantly exceed the oxygen dose rates, and our model attributes both effects to a physisorbed oxygen population.

Adsorption↗
DOE OSTI2020

Origin and effect of film sub-stoichiometry on ultraviolet, ns-laser damage resistance of hafnia single layers

Understanding the origin of laser damage-prone precursors in high index materials such as hafnia holds the key to the development of laser damage-resistant multilayer dielectric coated optics for high power and energy laser systems. In this study, we investigate the source of sub-stoichiometry, a potent laser damage precursor, in hafnia films produced by an ion beam sputtering (IBS) deposition method and the effect of such defects on the film performance upon ns ultraviolet (UV) laser (8 ns, 355 nm) exposure. Chemical analysis of data obtained via Rutherford backscattering spectroscopy (RBS) suggests that hafnia films deposited at two different planetary locations from the same deposition run exhibit anisotropic and location-dependent stoichiometries. While the oxygen-to-hafnium ratio is at the stoichiometric value of 2 for the hafnia film at the edge location, the ratio is significantly deviated and is 1.7 for that deposited at the planetary center. The sub-stoichiometric hafnia films display a much lower 1-on-1 damage onset at 1.6 ± 0.2 J/cm 2 compared to 2.3 ± 0.2 J/cm 2 in a stoichiometric film. The low damage performance films also have an over three times higher damage density at fluences above initiation. Coupled with Monte Carlo simulations, we reveal that sub-stoichiometry is primarily attributed to preferential removal of oxygen during film deposition by the bombardment of energetic reflected argon neutrals. The resulting oxygen deficiencies create the sub-bandgap states which facilitate the strong laser energy coupling and reduce the resistance to laser-induced damage in the hafnia single layer films.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Linking resource availability to pantropical forest canopy resistance and resilience to cyclone disturbance

Statement of purpose: Tropical cyclones are intensifying and occurring at higher latitudes in recent decades, but the mechanisms underpinning the resistance (ability to withstand disturbance-induced change) and resilience (pace of return to pre-disturbance reference values) of tropical forests to cyclones remains largely unexplored at the pantropical scale. We conducted a meta-analysis to investigate the role of soil resource availability (i.e., total soil phosphorus concentration) in mediating site-level forest canopy resistance and resilience to cyclones pan-tropically. We evaluated cyclone-induced and post-cyclone litterfall mass (g/m2/day), phosphorus (P) and nitrogen (N) fluxes (mg/m2/day), as well as concentrations (mg/g) across 73 case studies in Australia, Guadeloupe, Hawaii, Mexico, Puerto Rico, and Taiwan. The dataset zip file includes three data and two metadata files: - The compiled Litterfall Mass Flux data from tropical forests across the globe prior to and after varying tropical cyclone disturbances are provided in Litterfall_Mass.csv. This data file also includes site location, geographical characteristics, elevation, soil phosphorus concentration, geology, and several variables related to each tropical cyclone disturbance. - The compiled Litterfall Nitrogen and Phosphorus Flux data from tropical forests across the globe prior to and after varying tropical cyclone disturbances are provided in Litterfall_Nutrients.csv. This data file also includes site location, geographical characteristics, elevation, soil phosphorus concentration, geology, and several variables related to each tropical cyclone disturbance. - Tropical cyclone track data compiled from HURDAT2 and IBTrACS databases and used as input in the HURRECON model (https://github.com/hurrecon-model/HurreconR) to generate wind data is provided in hurdat2-1851-2019-052520.txt. - The metadata file (Metadata_Meta-analysis_Litterfall-Mass.pdf) has the complete information on each variable included in the Litterfall_Mass.csv dataset, the data sources, and data processing information. - The metadata file (Metadata_Meta-analysis_Litterfall-Nutrients.pdf) has the complete information on each variable included in the Litterfall_Nutrients.csv dataset, the data sources, and data processing information.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Resistance to fracture in the glassy solid electrolyte Lipon

We report on the mechanical behavior of a solid Li-ion conductor, lithium phosphorous oxynitride (Lipon), for solid-state batteries. In particular, the purpose of this investigation was to quantify the resistance to cracking (fracture toughness) of this material by nanoindentation. We observed surprising ductility and the ability to recover in Lipon. We were unsuccessful in inducing cracks in Lipon and observed accommodation of stress via pile-up and densification rather than by cracking at various strain rates. Simulations demonstrate that both deformation and densification depend on the alkali content. Densification appears to be recoverable at room temperature. We discuss the findings in comparison with nanoindentation-induced cracking in other inorganic solid electrolyte materials and provide possible explanations for high resistance of Lipon to Li filament propagation.

36 MATERIALS SCIENCE↗