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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Facile Dual-Protection Layer and Advanced Electrolyte Enhancing Performances of Cobalt-free/Nickel-rich Cathodes in Lithium-Ion Batteries

Despite cobalt (Co)-free/nickel (Ni)-rich layered oxides being considered as one of the promising cathode materials due to their high specific capacity, their highly reactive surface is one of the shortcomings that still hinder their practical usages in high-energy-density batteries. Herein, a polyimide/polyvinylpyrrolidone (PI/PVP, denoted as PP) coating layer is demonstrated as dual-protection for LiNi 0.96 Mg 0.02 Ti 0.02 O 2 (NMT) cathode material to suppress surface contamination against moisty air and to prevent unwanted side reactions between cathode and electrolyte during electrochemical cycling. The optimal PP-coated NMT (PP@NMT) preserves a clean surface without generation of lithium (Li) residues, structural degradation, and gas evolution after exposure to air with ~30% humidity for 2 weeks. Contrarily, the exposed bare NMT shows severe contamination, structural shrinkage due to Li loss, and increased gas release during charging. In addition, the exposed PP@NMT significantly enhances the electrochemical performance of graphite (Gr)||NMT cells by decreasing byproducts and maintaining structural stability. Moreover, the exposed PP@NMT achieves a high capacity retention of 86.7% after 500 cycles in Gr||NMT cells using an advanced localized high-concentration electrolyte. Furthermore, this work demonstrates a promising facile approach to the protection of Co-free/Ni-rich layered cathodes for their practical applications even after exposure to moisty air.

25 ENERGY STORAGE↗
DOE OSTI2025

Rotated-Droop Control for Enhanced Stability and Power Decoupling in Microgrids With Complex Line Impedances

Classical droop control in microgrids predominantly assumes inductive line impedance, which simplifies implementation but causes power coupling and steady-state errors in systems with resistive and inductive lines. This paper proposes a rotated-droop control strategy for grid-forming inverters that reformulates the power equations by incorporating the magnitude and angle of the line impedance within a rotated reference frame. This method enhances the decoupling of active and reactive power dynamics without increasing complexity or requiring communication links. A small-signal state-space model was created to capture the dynamic behavior of the system under varying impedance parameters, preserving the original droop gains by rotating the power control structure. This allows eigenvalue-based stability analysis and enhances damping and transient performance. Simulation and experimental results validated the improved power-sharing performance, faster response, and robustness of the proposed method under different impedance conditions. This approach maintains the decentralized structure of the conventional droop control while enabling greater adaptability and scalability, making it suitable for modern inverter-based microgrids with dynamic topologies.

Campo-Ossa, Daniel Dario [Univ. of Puerto Rico, Ag↗
DOE OSTI2020

Chiral algebra, localization, modularity, surface defects, and all that

We study the 2D vertex operator algebra (VOA) construction in 4D N = 2 superconformal field theories on S 3 × S 1 , focusing on both old puzzles and new observations. The VOA lives on a two-torus T 2 ⊂ S 3 × S 1 , it is 1 2 Z -graded, and this torus is equipped with the natural choice of spin structure (1,0) for the Z + 1 2 -graded operators, corresponding to the NS sector vacuum character. By analyzing the possible refinements of the Schur index that preserves the VOA, we find that it admits discrete deformations, which allows access to the remaining spin structures (1,1), (0,1), and (0,0), of which the latter two involve the inclusion of a particular surface defect. For Lagrangian theories, we perform the detailed analysis: we describe the natural supersymmetric background, perform localization, and derive the gauged symplectic boson action on a torus in any spin structure. In the absence of flavor fugacities, the 2D and 4D path integrals precisely match, including the Casimir factors. We further analyze the 2D theory: we identify its integration cycle and the two-point functions and interpret flavor holonomies as screening charges in the VOA. Next, we make some observations about modularity; the T-transformation acts on our four partition functions and lifts to a large diffeomorphism on S 3 × S 1 . More interestingly, we generalize the four partition functions on the torus to an infinite family labeled by both the spin structure and the integration cycle inside the complexified maximal torus of the gauge group. Members of this family transform into one another under the full modular group, and we confirm the recent observation that the S-transform of the Schur index in Lagrangian theories exhibits logarithmic behavior. Finally, we comment on how locally our background reproduces the Ω-background.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

A Survey on Privacy in Graph Neural Networks: Attacks, Preservation, and Applications

Graph Neural Networks (GNNs) have gained significant attention owing to their ability to handle graph-structured data and the improvement in practical applications. However, many of these models prioritize high utility performance, such as accuracy, with a lack of privacy consideration, which is a major concern in modern society where privacy attacks are rampant. To address this issue, researchers have started to develop privacy-preserving GNNs. Despite this progress, there is a lack of a comprehensive overview of the attacks and the techniques for preserving privacy in the graph domain. In this survey, we aim to address this gap by summarizing the attacks on graph data according to the targeted information, categorizing the privacy preservation techniques in GNNs, and reviewing the datasets and applications that could be used for analyzing/solving privacy issues in GNNs. We also outline potential directions for future research in order to build better privacy-preserving GNNs.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Solvent Transport in Disordered and Dynamic Membrane Pores: Implications for Reverse Osmosis and Nanofiltration Membranes

Pressure-driven separations with nanoporous membranes, such as reverse osmosis and nanofiltration, play a vital role in addressing water scarcity and enabling resource recovery. Understanding water or solvent transport in membrane pores is essential for advancing membrane separation technologies. A key question in transport modeling is to establish a relationship between solvent permeability and membrane porous structure properties, such as porosity or pore size. The nano- and subnanometer pores in polymeric membranes such as reverse osmosis and nanofiltration membranes are highly tortuous and dynamically connected, which challenges the conventional methods of transport modeling. This study addresses this challenge by developing a theoretical framework to describe solvent transport through membranes with dynamic and disordered porous structure. Specifically, we propose a lattice model to describe the pore network, while preserving the viscous nature of solvent permeation. We further establish a relationship between solvent permeability and membrane porosity or pore size, which is validated by molecular dynamics simulations and experimental data. By integrating this relationship into the solution-friction model, we define pore connectivity and local friction coefficient to quantify the impact of pore structure on solvent permeability. Our analysis highlights the dominant influence of pore connectivity on the permeability of reverse osmosis and nanofiltration membranes, particularly when the pore size approaches the dimensions of solvent molecules. Overall, this study provides critical insights into water and solvent transport mechanisms in nanoporous membranes, opening the door for strategies to substantially enhance membrane performance.

membranes↗
DOE OSTI2025

A Probabilistic Reasoner Based on Bayes Risk for Damage Detection in Structural Systems

Structural health monitoring (SHM) systems are used to inform operation of structural systems subject to loads and environments that may affect their integrity. SHM systems rely on continuous monitoring of the structure to determine its health state. These systems are often coupled with a model of the deployed structure to determine the consequences of changes in the system by forecasting the response to future states. These models, which may be thought of as digital twins, need to be updated to reflect the latest state of the structural system. This work makes use of an uncertainty-aware machine learning model that enforces distance preservation of the original input space to determine deviations from the training data input space distributions. This workflow enables domain shift detection to determine whether damage is present in the structure. The uncertainty metrics generated by this network are then used in a Bayes risk framework to design an optimal damage detector given cost and risk considerations. The approach is demonstrated on a computational example with simulated damage.

Najera-Flores, David [ATA Engineering, Inc.]↗
DOE OSTI2024

Phenomenology of TMD parton distributions in Drell-Yan and 𝑍 0 boson production in a hadron structure oriented approach

We present a first practical implementation of a recently proposed hadron structure oriented (HSO) approach to transverse momentum dependent (TMD) phenomenology applied to Drell-Yan-like processes, including lepton pair production at moderate 𝑄 2 and 𝑍 0 boson production. We compare and contrast general features of our methodology with other common practices and emphasize aspects that we view as improvements. Separately, we discuss the importance of treatments that preserve various theoretical properties of the nonperturbative parts of TMD parametrizations for future applications that have the extraction of hadron structure as a primary goal. These include the HSO’s preservation of a basic TMD parton-model-like framework even while accounting for full TMD factorization and evolution, explicit preservation of the integral relationship between TMD and collinear parton density functions, and the ability to meaningfully compare different theoretical models of nonperturbative TMD parton distributions. In our examples, we show that there is significant sensitivity at moderate 𝑄 2 to both the form of the nonperturbative transverse momentum dependence and the parametrization of collinear parton densities. However, we also find that evolving to 𝑄 2 =𝑀$^2_𝑍$, without fitting, results in a satisfactory postdiction of existing data for 𝑍0 production, nearly independently of the modeling of nonperturbative transverse momentum behavior. We argue that this demonstrates that moderate 𝑄 measurements should be given greater weight than high 𝑄 measurements in extractions of nonperturbative transverse momentum dependence. We also obtain new extractions of the nonperturbative Collins-Soper kernel within the HSO approach. We discuss its features and compare with some earlier extractions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Robust Spectral Anomaly Detection in EELS Spectral Images via 3D Convolutional Variational Autoencoders

Abstract A 3D Convolutional Variational Autoencoder (3D‐CVAE) is introduced for automated anomaly detection in electron energy‐loss spectroscopy spectrum imaging (EELS‐SI) data. This approach leverages the full 3D structure of EELS‐SI data to detect subtle spectral anomalies while preserving both spatial and spectral correlations across the datacube. By employing cross‐entropy loss and training on bulk spectra, the model learns to reconstruct bulk features characteristic of the defect‐free material. In exploring methods for anomaly detection, both the 3D‐CVAE approach and principal component analysis (PCA) are evaluated, testing their performance using FeL‐edge ΔEpeak shifts designed to simulate material defects. These results show that 3D‐CVAE achieves superior anomaly detection and maintains consistent performance across various shift magnitudes. The method demonstrates clear bimodal separation between bulk and anomalous spectra, enabling reliable classification. Further analysis verifies that lower‐dimensional representations are robust to anomalies in the data. While performance advantages over PCA diminish with decreasing anomaly concentration, our method maintains high reconstruction quality even in challenging, noise‐dominated spectral regions. This approach provides a robust framework for unsupervised automated detection of spectral anomalies in EELS‐SI data, particularly valuable for analyzing complex material systems.

Chemistry↗
DOE OSTI2020

High Voltage Mg-Ion Battery Cathode via a Solid Solution Cr–Mn Spinel Oxide

We discuss how lattice Mg 2+ in a tailored solid solution spinel, MgCrMnO 4 , is electrochemically utilized at high Mn-redox potentials in a nonaqueous electrolyte. Complementary evidence from experimental and theoretical analyses supports bulk Mg 2+ (de)intercalation throughout the designed oxide frame where strong electrostatic interaction between Mg 2+ and O 2- exists. Mg/Mn antisite inversion in the spinel is lowered to similar to 10% via postannealing at 350 degrees C to further improve Mg 2+ mobility. Spinel lattice is preserved upon removal of Mg 2+ without any phase transformations, denoting structural stability at the charged state at a high potential similar to 3.0 V (vs Mg/Mel. Clear remagnesiation upon first discharge, harvesting up to similar to 180 Wh/kg at 60 degrees C is shown. In the remagnesiated state, insertion of Mg 2+ into interstitial sites in the spinel is detected, possibly resulting in partial reversibility which needs to be addressed for structural stability. The observations constitute a first clear path to the development of a practical high voltage Mg-ion cathode using a spinel oxide.

25 ENERGY STORAGE↗
DOE OSTI2024

Infrared Imaging Using Thermally Stable HgTe/CdS Nanocrystals

Transferring nanocrystals (NCs) from the laboratory environment toward practical applications has raised new challenges. HgTe appears as the most spectrally tunable infrared colloidal platform. Its low-temperature synthesis reduces the growth energy cost yet also favors sintering. Once coupled to a read-out circuit, the Joule effect aggregates the particles, leading to a poorly defined optical edge and large dark current. Here, in this study, we demonstrate that CdS shells bring the expected thermal stability (no redshift upon annealing, reduced tendency to form amalgams, and preservation of photoconduction after an atomic layer deposition process). The electronic structure of these confined particles is unveiled using k.p self-consistent simulations showing a significant exciton binding energy of ~ 200 meV. After shelling, the material displays a p-type behavior that favors the generation of photoconductive gain. The latter is then used to increase the external quantum efficiency of an infrared imager, which now reaches 40% while presenting long-term stability.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

High Capacity for Mg 2+ Deintercalation in Spinel Vanadium Oxide Nanocrystals

Nonaqueous Mg batteries can theoretically reach high energy density with cost-effective materials, yet no such device to date has performance competitive with Li-ion technologies. A major barrier is the need for oxide cathodes that combine high capacity and voltage. Very few oxides have shown intrinsic ability for Mg 2+ intercalation in electrolytes with acceptably low content of H2O. Herein, we demonstrate that nanocrystals of MgV 2 O 4 can reach high capacity for Mg 2+ deintercalation with a mechanism that preserves their spinel framework, validated through measurements with different chemical and structural sensitivity. The structural stability contrasts with other phases where reaching high capacity required distortions that introduce undesirable mechanical strain. The favorable properties of the oxide allowed cycling in a full cell with Mg metal. This work reveals new insights into the viability of multivalent intercalation in oxides, meeting a milestone toward the feasibility of high-voltage batteries with either Mg metal or Mg-ion anodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Eocene-Oligocene Metamorphism, Fluid Flow and Deformation in the Ruby Mountains-East Humboldt Range Metamorphic Core Complex

Metamorphic core complexes are ubiquitous in collapsed orogens globally and play a primary role in crustal exhumation. Here, we investigate the metamorphic history of the Ruby Mountains-East Humboldt Range metamorphic core complex, Nevada, using petrochronology to understand how magmatism, metamorphism and deformation interact to modulate crustal rheology, and the timing of exhumation within the Sevier orogenic belt. Field study, microstructural analysis, thermobarometry and laser ablation split-stream monazite, titanite and allanite petrochronology of the mylonitic footwall were integrated to elucidate the pressure-temperature-time (P-T-t) evolution. Major-, trace-element and quartz-in-garnet thermobarometry show peak metamorphism occurred at 5.5–6 kbar and 600–650°C across the study area. Monazite and titanite U-(Th)-Pb petrochronology constrain this episode of metamorphism to 88–81 Ma with the structurally deepest samples yielding dates down to ca. 71 Ma. The preservation of peak metamorphic mineral assemblages indicates these rocks remained at near-peak temperature conditions into the Cenozoic. Cenozoic metamorphism occurred during a punctuated episode contemporaneous with the Great Basin ignimbrite flare up. All samples show a distinct 39–37 Ma population of monazite, titanite and allanite dates that correlate with the emplacement of quartz diorite and gabbro intrusions throughout the footwall. Accessory phases contain zoning textures in backscattered electron images that are consistent with fluid-mediated dissolution-reprecipitation reactions. The U-(Th)-Pb analyses from these zones yield 39–27 Ma dates interpreted as the timing of fluid flow. The results of this study elucidate the integrated importance of magmatism, melting and fluid flow in driving the coupled evolution of Late Cretaceous metamorphism within the Sevier hinterland and the subsequent Cenozoic metamorphic core complex development that exhumed the middle crust.

58 GEOSCIENCES↗
DOE OSTI2021

Pressure-induced excimer formation and fluorescence enhancement of an anthracene derivative

Excimer materials have been widely studied and have generated significant interest for their applications in many optoelectronic devices. However, a thorough investigation of the entire process involved in excimer formation, enhancement, and annihilation in solid materials is still lacking. Here we designed a crystal based on an anthracene derivative with dissociative, molecular-ordered dimer assembly, and studied the formation and evolution of an anthracene excimer as a function of pressure. During the initial stage of pressurization, the fluorescence intensity arising from anthracene monomers gradually decreases. Therefore, with continued compression, the two anthracene units become increasingly closer allowing strong intermolecular π–π interactions to develop that lead to excimer formation at 3.5 GPa, accompanied with a phase transition. The fluorescence intensity then keeps increasing with pressure and reaches its maximum at 5.6 GPa due to the strengthening of the excimer and the increased structural defects. Meanwhile the fluorescence color shows a continuous redshift, which initially results from conformation planarization and then excimer evolution. After releasing pressure back to ambient conditions, the structural changes in the sample are reversible, while the fluorescence signal preserves some high-pressure features due to the partial retention of the π–π interactions between the anthracene dimers. This study reveals the evolution of an excimer and its intrinsic photophysical properties, and provides guidance for future research on pressure-sensitive fluorescent devices.

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

Six-dimensional matching of intense beam with linear accelerating structure

Beam matching is a common technique that is routinely employed in accelerator design with the aim of minimizing beam losses and preservation of beam brightness. Despite being widely used, a full theoretical understanding of beam matching in 6D remains elusive. In this work, we present an analytical treatment of 6D beam matching of a high-intensity beam onto an RF structure. We begin our analysis within the framework of a linear model, and apply the averaging method to a set of 3D beam envelope equations. Accordingly, we obtain a matched solution that is comprised of smoothed envelopes and periodic terms, describing envelope oscillations with the period of the focusing structure. We then consider the nonlinear regime, where the beam size is comparable with the separatrix size. Stating with a Hamiltonian analysis in 6D phase space, we attain a self-consistent beam profile and show that it is significantly different from the commonly used ellipsoidal shape. Subsequently, we analyze the special case of an equilibrium with equal space charge depression between all degrees of freedom. Comparison of beam dynamics for equipartitioned, equal space charge depression, and equal emittances beams is given. Finally, we present experimental results on beam matching in the LANSCE linac.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Structure and composition of natural ferrihydrite nano-colloids in anoxic groundwater

Fe-rich mobile colloids play vital yet poorly understood roles in the biogeochemical cycling of Fe in groundwater by influencing organic matter (OM) preservation and fluxes of Fe, OM, and other essential (micro-)nutrients. Yet, few studies have provided molecular detail on the structures and compositions of Fe-rich mobile colloids and factors controlling their persistence in natural groundwater. Here, we provide comprehensive new information on the sizes, molecular structures, and compositions of Fe-rich mobile colloids that accounted for up to 72% of aqueous Fe in anoxic groundwater from a redox-active floodplain. The mobile colloids are multi-phase assemblages consisting of Si-coated ferrihydrite nanoparticles and Fe(II)-OM complexes. Ferrihydrite nanoparticles persisted under both oxic and anoxic/sulfidic conditions, which we attribute to passivation by Si and OM. These findings suggest that mobile Fe-rich colloids generated in floodplains can persist during transport through redox-variable soils and could be discharged to surface waters. These results shed new light on their potential to transport Fe, OM, and nutrients across terrestrial-aquatic interfaces.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Structure and evolution of photosystem I in the early-branching cyanobacterium Anthocerotibacter panamensis

Thylakoid-free cyanobacteria are thought to preserve ancestral traits of early-evolving organisms capable of oxygenic photosynthesis. However, and until recently, photosynthesis studies in thylakoid-free cyanobacteria were only possible in the model strain Gloeobacter violaceus , limiting our understanding of photosynthesis evolution. Here, we report the isolation, biochemical characterization, cryo-EM structure, and phylogenetic analysis of photosystem I (PSI) from a recently discovered thylakoid-free cyanobacterium, Anthocerotibacter panamensis , a distant relative of the genus Gloeobacter . We find that A. panamensis PSI exhibits a distinct carotenoid composition and has one conserved low-energy chlorophyll site, which was lost in G. violaceus . Furthermore, PSI in thylakoid-free cyanobacteria has changed at the sequence level to a degree comparable to that of other strains, yet its subunit composition and oligomeric form might be identical to that of the most recent common ancestor of cyanobacteria. This study therefore provides a glimpse into the ancient evolution of photosynthesis.

Jiang, Han-Wei (ORCID:0000000234008698)↗
DOE OSTI2021

Persistent arsenate–iron( iii ) oxyhydroxide–organic matter nanoaggregates observed in coal

Understanding how natural nanoaggregates of iron (Fe) and organic matter (OM), currently identified in organic rich soil or peat, interact with metals and metalloids is environmentally significant. Here, coal is also organic-rich and exemplifies anoxic sedimentary environments with Fe usually as pyrite and not oxides. Here, we analyze the local structure of Fe (6880–21 700 mg kg –1 ) and As (45–5680 mg kg –1 ) in representative Guizhou coal samples using X-ray absorption near-edge structure and extended X-ray absorption fine structure (XANES and EXAFS) to illustrate how Fe(III) and As(V) are preserved in coal formed from reduced, organic-rich precursors. Arsenic XANES indicates that >80% of As exists as As(V) with <14% of As associated with sulfides in 5 Guizhou coal samples, confirming published but unexplained results. An As–Fe shell at 3.25–3.29 Å in the As EXAFS suggests that this As(V) is adsorbed on Fe(III) oxyhydroxides as evidenced by Fe EXAFS in these coal samples. Significantly, lower Fe–Fe coordination numbers (CN) of 0.6–1.1 relative to those in 2-line ferrihydrite (CN = 1.6) and goethite (CN = 2.1) suggest that these Fe(III) oxyhydroxides are likely Fe–OM nanoaggregates protected by OM encapsulation and adsorption of arsenate. Such structurally stabilized composites of As(V)–Fe(III)–OM may be more widely distributed and allow oxidized As and Fe to persist in other organic-rich, reducing environments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

A Data Deposition Platform for Sharing Nuclear Magnetic Resonance Data

Nuclear magnetic resonance (NMR) data are rarely deposited in open databases, leading to loss of critical scientific knowledge. Existing data reporting methods (images, tables, lists of values) contain less information than raw data, and are poorly standardized. Together, these issues limit FAIR (findable, accessible, interoperable, reusable) access to these data, which in turn creates barriers for compound dereplication and the development of new data-driven discovery tools. Existing NMR databases are either not designed for natural products data, or employ complex deposition interfaces that disincentivize deposition. Journals, including the Journal of Natural Products (JNP), are now requiring data submission as part of the publication process, creating the need for a streamlined, user-friendly mechanism to deposit and distribute NMR data. Recently, our team reported the development of the Natural Products Magnetic Resonance Database (NP-MRD; www.np-mrd.org). Here in this paper we present a new data deposition platform for the NP-MRD project that is designed to enable users to deposit NMR data for published or submitted manuscripts in under five minutes. This platform includes a suite of automated data extraction and standardization tools, together with a simple-to-use web-based interface and detailed error reporting to simplify the data deposition process and is available at www.np-mrd.org/submissions.

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗