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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

A momentum source model for wire-wrapped rod bundles—Concept, validation, and application

Large uncertainties still exist in the treatment of wire-spacers and drag models for momentum transfer in current lumped parameter models. Here, to improve the hydraulic modeling of wire-wrap spacers in a rod bundle, a three-dimensional momentum source model (MSM) has been developed to model the anisotropic flow without the need to resolve the geometric details of the wire-wraps. The MSM is examined for 7-pin and 37-pin bundles steady-state simulations using the commercial CFD code STAR-CCM+. The calculated steady-state inter-subchannel cross flow velocities match very well in comparisons between bare bundles with the MSM applied and the wire-wrapped bundles with explicit geometry. The validity of the model is further verified by mesh and parameter sensitivity studies. Furthermore, the MSM is applied to a 61-pin EBR-II experimental subassembly for both steady state and PLOF transient simulations. Reasonably accurate predictions of temperature, pressure, and fluid flow velocities have been achieved using the MSM for both steady-state and transient conditions. Significant computing resources are saved with the MSM since it can be used on a much coarser computational mesh.

42 ENGINEERING↗
DOE OSTI2023

Accelerated test protocols to predict service life and durability of solid oxide fuel cells

Reliable accelerated test protocols are needed for solid oxide fuel cell research to facilitate rapid learning on key durability issues, identify potential modes of failure expeditiously, and eventually predict the calendar lifetime of an electrochemical cell. In this work, solid oxide fuel cells operated at a constant current density were compared to cells undergoing accelerated measurements, which are composed of intermittent current injection to the cell. A general accelerated test profile was developed by cycling a solid oxide fuel cell from open circuit to a predetermined operating current density that is the same as the current density during a steady-state operation, to accelerate the local redox environment. The following parameters were studied: current density, operation temperature, moist level, sintering temperature, cycling current, cycling frequency, and operation time. Up to 1,320,000 cycles were generated in this work. The cell degradation was accelerated by nearly 10 times, suggesting the feasibility of using this protocol for acceleration test to predict life performance and durability of solid oxide fuel cells.

08 HYDROGEN↗
DOE OSTI2021

Review of heat transfer enhancement techniques in two-phase flows for highly efficient and sustainable cooling

We show that two-phase internal flow is ubiquitous to many systems due to its ability to transfer large amounts of heat effectively. Recent advances motivated by sustainability have pushed towards augmenting the heat transfer between the tube and the two-phase working fluid. Augmenting heat transfer in two-phase flows enables process intensification, and compactness leading to reduced cost and material consumption. This review investigates the effect of heat transfer enhancement techniques on different fluids including R134a, R407C, R22, etc … The techniques are categorized into passive and active and focus on durable enhancement methods which do not include surface structuring or coating. Passive techniques utilize geometrical and surface modifications to induce better mixing. Several passive techniques are analyzed including fins, inserts, and more. In analyzing these techniques, the effect of changing geometric parameters is studied, and the limitations are highlighted. Further, active techniques that enable heat transfer enhancement through applying power are also investigated. Electrohydrodynamic approaches are analyzed and compared to passive techniques. Additionally, the implications of heat exchange enhancement in the context of global energy are discussed. An energy analysis discretized by the use sector is conducted, with an emphasis on predicting the future potential for renewable and sustainable development. Moreover, although active approaches provide the highest heat transfer enhancement, due to implementation difficulties, passive techniques are more frequently adopted. The review ends with discussion of next-generation heat exchangers which will rely more on additive manufacturing due to its flexibility and reduced cost per part as the technology matures.

Nusselt number↗
DOE OSTI2016

Mechanisms of tramadol-related neurotoxicity in the rat: Does diazepam/tramadol combination play a worsening role in overdose?

Poisoning with opioid analgesics including tramadol represents a challenge. Tramadol may induce respiratory depression, seizures and serotonin syndrome, possibly worsened when in combination to benzodiazepines. Our objectives were to investigate tramadol-related neurotoxicity, consequences of diazepam/tramadol combination, and mechanisms of drug-drug interactions in rats. Median lethal-doses were determined using Dixon–Bruce's up-and-down method. Sedation, seizures, electroencephalography and plethysmography parameters were studied. Concentrations of tramadol and its metabolites were measured using liquid-chromatography-high-resolution-mass-spectrometry. Plasma, platelet and brain monoamines were measured using liquid-chromatography coupled to fluorimetry. Median lethal-doses of tramadol and diazepam/tramadol combination did not significantly differ, although time-to-death was longer with combination (P = 0.04). Tramadol induced dose-dependent sedation (P < 0.05), early-onset seizures (P < 0.001) and increase in inspiratory (P < 0.01) and expiratory times (P < 0.05). The diazepam/tramadol combination abolished seizures but significantly enhanced sedation (P < 0.01) and respiratory depression (P < 0.05) by reducing tidal volume (P < 0.05) in addition to tramadol-related increase in respiratory times, suggesting a pharmacodynamic mechanism of interaction. Plasma M1 and M5 metabolites were mildly increased, contributing additionally to tramadol-related respiratory depression. Tramadol-induced early-onset increase in brain concentrations of serotonin and norepinephrine was not significantly altered by the diazepam/tramadol combination. Interestingly neither pretreatment with cyproheptadine (a serotonin-receptor antagonist) nor a benserazide/5-hydroxytryptophane combination (enhancing brain serotonin) reduced tramadol-induced seizures. Our study shows that diazepam/tramadol combination does not worsen tramadol-induced fatality risk but alters its toxicity pattern with enhanced respiratory depression but abolished seizures. Drug-drug interaction is mainly pharmacodynamic but increased plasma M1 and M5 metabolites may also contribute to enhancing respiratory depression. Tramadol-induced seizures are independent of brain serotonin. - Highlights: • Diazepam does not alter tramadol-induced median lethal dose but delays death onset. • Diazepam/tramadol combination worsens respiratory depression but prevents seizures. • Diazepam/tramadol-induced respiratory effects results from a pharmacodynamic drug-drug interaction. • Tramadol increases brain serotonin and norepinephrine that is not altered by diazepam. • Tramadol-induced seizures are independent of brain serotonin.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Application of Black Silicon for Nanostructure-Initiator Mass Spectrometry

Nanostructure-initiator mass spectrometry (NIMS) is a matrix-free desorption/ionization technique with high sensitivity for small molecules. Surface preparation has relied on hydrofluoric acid (HF) electrochemical etching which is undesirable given the significant safety controls required in this specialized process. Here in this study, we examine a conventional and widely used process for producing black silicon based on sulfur hexafluoride/oxygen (SF 6 /O 2 ) inductively coupled plasma (ICP) etching at cryogenic temperatures and we find it to be suitable for NIMS. A systematic study varying parameters in the plasma etching process was performed to understand the relationship of black silicon morphology and its sensitivity as a NIMS substrate. The results suggest that a combination of higher silicon temperature and oxygen flow rate gives rise to the formation of black silicon with fine pillar structures, whose aspect ratio are ~8.7 and depth are <1 μm resulting in higher NIMS sensitivity which is attributed to surface restructuring caused by their low melting point upon laser irradiation. Interestingly, we find selectivity of these black silicon substrates to different analytes depending on the etching parameters. Though, the sensitivity of the dry etching process is lower than the traditional "wet" electrochemical etching process, it is suitable for many applications and is prepared using conventional equipment without the use of HF.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Morphology Control of Self-Assembled Three-Phase Au-BaTiO 3 –ZnO Hybrid Metamaterial for Tunable Optical Properties

Microstructural control in metal-dielectric hybrid metamaterials presents enormous opportunities in tailoring the physical properties including the magnetic and optical properties. In this paper, we demonstrate a strong tunability achieved in the microstructure of self-assembled ordered three-phase Au-BaTiO 3 –ZnO hybrid metamaterial along with its optical properties, grown by a pulsed laser deposition method. Varying the growth temperature, deposition frequency, and template thickness evolves the microstructure by tuning the Au and ZnO pillar geometry as well as the shape and size of the Au nanoparticles capping the ZnO nanowires. The three-phase hybrid metamaterials exhibit unique optical properties, including enhanced nonlinear optical properties, hyperbolic dispersion in the visible and near-infrared wavelength region, and tuned epsilon-near-zero (ENZ) wavelength upon varying the deposition parameters. This study suggests that the three-phase hybrid metamaterials present great potential in the microstructure and optical property tuning that can also be applied to other two-phase and three-phase nanocomposite systems.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Promising Method of Sm–Co Magnet Reprocessing in Alkali Chloride Melts

Developing new, efficient methods for samarium and cobalt recovery from scraps/rejects and swarf at Sm–Co magnet manufacturing sites during shaping and finishing is an important task in terms of meeting their growing demand. In this work, the reaction of oxygen with a solution of samarium and cobalt chlorides in a LiCl–KCl eutectic melt was studied at 400–600 °C to explore possible methods for the separation and recovery of samarium and cobalt from these waste products. The pyrochemical reaction resulted in the formation and precipitation of samarium oxychloride, while the cobalt remained in the melt in a soluble chloride form. The effect of temperature and the amount of oxygen passed through the melt (oxygen-to-samarium molar ratio) on the course of the reaction were studied. Kinetic parameters of the oxygen with samarium chloride reaction were determined.

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

Confusion-Driven Machine Learning of Structural Phases of a Flexible, Magnetic Stockmayer Polymer

We use a semisupervised, neural-network-based machine learning technique, the confusion method, to investigate structural transitions in magnetic polymers, which we model as chains of magnetic colloidal nanoparticles characterized by dipole–dipole and Lennard-Jones interactions. As input for the neural network, we use the particle positions and magnetic dipole moments of equilibrium polymer configurations, which we generate via replica-exchange Wang–Landau simulations. We demonstrate that by measuring the classification accuracy of neural networks, we can effectively identify transition points between multiple structural phases without any prior knowledge of their existence or location. We corroborate our findings by investigating relevant conventional order parameters. Our study furthermore examines previously unexplored low-temperature regions of the phase diagram, where we find new structural transitions between highly ordered helicoidal polymer configurations.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Catalight─An Open-Source Automated Photocatalytic Reactor Package Illustrated through Plasmonic Acetylene Hydrogenation

An open-source and modular Python package, Catalight, is developed and demonstrated to automate (photo)catalysis measurements. (Photo)catalysis experiments require studying several parameters to evaluate performance, including the temperature, gas flow rate and composition, illumination power, and spectral profile. Catalight orchestrates measurements over this complicated parameter space and systematically stores, analyzes, and visualizes the results. To showcase the capabilities of Catalight, we perform an automated apparent activation barrier measurement of acetylene hydrogenation over a plasmonic AuPd catalyst on an Al 2 O 3 support, simultaneously varying laser power, wavelength, and temperature in a multiday experiment controlled by a simple Python script. Our chemical results unexpectedly show an increased activation barrier upon light excitation, contrary to previous findings for other plasmonic reactions and catalysts. We show that the reaction rate order with respect to both acetylene and hydrogen remains unchanged upon illumination, suggesting that molecular surface coverage is not changed by light. By analyzing the inhomogeneity of the laser-induced heating, we attribute these results to a partial photothermal effect combined with a photochemical/hot electron-driven mechanism. In conclusion, our findings highlight the capabilities of a new experiment automation tool; explore the photocatalytic mechanism for an industrially relevant reaction; and identify systematic sources of error in canonical photocatalysis experimental procedures.

Catalysts↗
DOE OSTI2026

Ion Transport in Charged Membranes: Linking Electric-Field-Driven Mechanisms to Pore Size via Perturbation Analysis

Ion-exchange membranes are a critical component in electrochemical systems. Nevertheless, the understanding and modeling of ion transport within these porous structures have been limited by particular complexity reductions, either ignoring the dimensionality of their porous network architecture or imposing geometric assumptions (i.e., overlapping double layers). Before addressing this morphology-transport gap, a framework that relates the driving forces of transport to the geometry of a single pore is required. In this work, our modeling domain consists of a two-dimensional single pore with charged walls, connecting two identical electrolyte reservoirs. Using the Poisson-Nernst-Planck equations and regular perturbation theory, we decouple the electric fields and analyze the driving forces of ion transport, specifically electromigration and induced electroosmosis within the pore. These processes are described as analytical functions of the interaction aspect ratio, ?, defined as the ratio of the pore radius to the Debye length. Using this parameter, our study (i) describes the interplay between electromigrative and electroosmotic mechanisms that set ionic conductivity, (ii) identifies a dimensionless group of intrinsic electrolyte properties that indicates the predominant driving force, and (iii) provides a qualitative, confinement-dependent perspective on selectivity in ion-conducting membranes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Complex Phase Transitions of Fully Rigid Sphere–Rod Amphiphiles Induced by Solvent Polarity in Dilute Solutions

Here we report complex macrophase and microphase transitions of rigid amphiphiles with spherical Keggin molecular clusters as the solvophilic block and rod-like rigid oligofluorene (OF) as the solvophobic block in mixed solvents of water and polar organic solvent. By properly adjusting the solvent polarity, the amphiphiles are found to respond accordingly by self-assembling into multilayered incomplete onion-like structures (10–25 vol % THF), single-layered vesicular structures (60 vol % THF), and an unexpected macrophase separation in the middle (40–50 vol % THF), which is due to the anomalous trends in Keggin solubility as a result of the nature of TBA + counterions. The rigidity of the OF block prevents the amphiphile from assembling by following the rule of packing parameters; instead, interdigitation among different rods leads to the formation of the solvophobic domain to achieve self-assembly. The incomplete onion structures are controlled by the interdigitation of rigid rods for the number of layers and the electrostatic interaction among Keggin head groups for the interlayer distance. When the degree of interdigitation becomes lower, the self-assembly process shows a trend that can be explained by the traditional rule of packing parameter. This study demonstrates the formation of different self-assembled structures by rigid amphiphiles and their transitions induced by solvent composition. The self-assembly (microphase separation) of rigid amphiphiles in a dilute solution could indeed represent a broad area containing complicated, uncharted rules.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Matrix Approach to Accelerate Spin-Up of CLM5

Numerical models have been developed to investigate and understand responses of biogeochemical cycle to global changes. Steady state, when a system is in dynamic equilibrium, is generally required to initialize these model simulations. However, the spin-up process that is used to achieve steady state pose a great burden to computational resources, limiting the efficiency of global modeling analysis on biogeochemical cycles. This study introduces a new Semi-Analytical Spin-Up (SASU) to tackle this grand challenge. We applied SASU to Community Land Model version 5 and examined its computational efficiency and accuracy. At the Brazil site, SASU is computationally 7 times more efficient than (or saved up to 86% computational cost in comparison with) the traditional native dynamics (ND) spin-up to reach the same steady state. Globally, SASU is computationally 8 times more efficient than the accelerated decomposition spin-up and 50 times more efficient than ND. In summary, SASU achieves the highest computational efficiency for spin-up on site and globally in comparison with other spin-up methods. It is generalizable to wide biogeochemical models and thus makes computationally costly studies (e.g., parameter perturbation ensemble analysis and data assimilation) possible for a better understanding of biogeochemical cycle under climate change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Machine learning surrogates for surface complexation model of uranium sorption to oxides

Abstract The safety assessments of the geological storage of spent nuclear fuel require understanding the underground radionuclide mobility in case of a leakage from multi-barrier canisters. Uranium, the most common radionuclide in non-reprocessed spent nuclear fuels, is immobile in reduced form (U(IV) and highly mobile in an oxidized state (U(VI)). The latter form is considered one of the most dangerous environmental threats in the safety assessments of spent nuclear fuel repositories. The sorption of uranium to mineral surfaces surrounding the repository limits their mobility. We quantify uranium sorption using surface complexation models (SCMs). Unfortunately, numerical SCM solvers often encounter convergence problems due to the complex nature of convoluted equations and correlations between model parameters. This study explored two machine learning surrogates for the 2-pK Triple Layer Model of uranium retention by oxide surfaces if released as U(IV) in the oxidizing conditions: random forest regressor and deep neural networks. Our surrogate models, particularly DNN, accurately reproduce SCM model predictions at a fraction of the computational cost without any convergence issues. The safety assessment of spent fuel repositories, specifically the migration of leaked radioactive waste, will benefit from having ultrafast AI/ML surrogates for the computationally expensive sorption models that can be easily incorporated into larger-scale contaminant migration models. One such model is presented here.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

BEYONDPLANCK IV. On end-to-end simulations in CMB analysis — Bayesian versus frequentist statistics

End-to-end simulations play a key role in the analysis of any high-sensitivity cosmic microwave background (CMB) experiment, providing high-fidelity systematic error propagation capabilities that are unmatched by any other means. In this paper, we address an important issue regarding such simulations, namely, how to define the inputs in terms of sky model and instrument parameters. These may either be taken as a constrained realization derived from the data or as a random realization independent from the data. We refer to these as posterior and prior simulations, respectively. We show that the two options lead to significantly different correlation structures, as prior simulations (contrary to posterior simulations) effectively include cosmic variance, but they exclude realization-specific correlations from non-linear degeneracies. Consequently, they quantify fundamentally different types of uncertainties. We argue that as a result, they also have different and complementary scientific uses, even if this dichotomy is not absolute. In particular, posterior simulations are in general more convenient for parameter estimation studies, while prior simulations are generally more convenient for model testing. Before BEYONDPLANCK, most pipelines used a mix of constrained and random inputs and applied the same hybrid simulations for all applications, even though the statistical justification for this is not always evident. BEYONDPLANCK represents the first end-to-end CMB simulation framework that is able to generate both types of simulations and these new capabilities have brought this topic to the forefront. The BEYONDPLANCK posterior simulations and their uses are described extensively in a suite of companion papers. In this work, we consider one important applications of the corresponding prior simulations, namely, code validation. Specifically, we generated a set of one-year LFI 30 GHz prior simulations with known inputs and we used these to validate the core low-level BEYONDPLANCK algorithms dealing with gain estimation, correlated noise estimation, and mapmaking.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Candidate strongly lensed type Ia supernovae in the Zwicky Transient Facility archive

Gravitationally lensed type Ia supernovae (glSNe Ia) are unique astronomical tools that can be used to study cosmological parameters, distributions of dark matter, the astrophysics of the supernovae, and the intervening lensing galaxies themselves. A small number of highly magnified glSNe Ia have been discovered by ground-based telescopes such as the Zwicky Transient Facility (ZTF), but simulations predict that a fainter, undetected population may also exist. We present a systematic search for glSNe Ia in the ZTF archive of alerts distributed from June 1 2019 to September 1 2022. Using the AMPEL platform, we developed a pipeline that distinguishes candidate glSNe Ia from other variable sources. Initial cuts were applied to the ZTF alert photometry (with constraints on the peak absolute magnitude and the distance to a catalogue-matched galaxy, as examples) before forced photometry was obtained for the remaining candidates. Additional cuts were applied to refine the candidates based on their light curve colours, lens galaxy colours, and the resulting parameters from fits to the SALT2 SN Ia template. The candidates were also cross-matched with the DESI spectroscopic catalogue. Seven transients were identified that passed all the cuts and had an associated galaxy DESI redshift, which we present as glSN Ia candidates. Although superluminous supernovae (SLSNe) cannot be fully rejected as contaminants, two events, ZTF19abpjicm and ZTF22aahmovu, are significantly different from typical SLSNe and their light curves can be modelled as two-image glSN Ia systems. From this two-image modelling, we estimate time delays of 22 ± 3 and 34 ± 1 days for the two events, respectively, which suggests that we have uncovered a population of glSNe Ia with longer time delays. The pipeline is efficient and sensitive enough to parse full alert streams. It is currently being applied to the live ZTF alert stream to identify and follow-up future candidates while active. This pipeline could be the foundation for glSNe Ia searches in future surveys, such as the Rubin Observatory Legacy Survey of Space and Time.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Space- and time-resolved characterization of nanosecond time scale discharge at pressurized gas

The phenomenon of ultra-fast electrical gas breakdown was investigated. Nanosecond high-voltage pulses with durations of 1 and 5 ns and amplitudes of 100 and 200 kV, respectively, were used to study the parameters of the discharge in a pressured (1-7) x 10{sup 5} Pa air-filled gap. The development of the discharge and the plasma propagation velocity was examined using optical fast frame imaging. The generation of runaway electrons in the breakdown process was confirmed by electron imaging and time-resolved x-ray diagnostics. Runaway electron beam energy distribution was obtained for a 1 ns duration high-voltage pulse. The origin and the role of runaway electrons in the discharge initiation are also discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Two-pion exchange currents in photodisintegration of the deuteron

Chiral effective field theory (ChEFT) is a modern framework to analyze the properties of few-nucleon systems at low energies. It is based on the most general effective Lagrangian for pions and nucleons consistent with the chiral symmetry of QCD. For energies below the pion-production threshold it is possible to eliminate the pionic degrees of freedom and derive nuclear potentials and nuclear current operators solely in terms of the nucleonic degrees of freedom. This is very important because, despite a lot of experience gained in the past, the consistency between two-nucleon forces, many-nucleon forces and the corresponding current operators has not been achieved yet. In this presentation we consider the recently derived long-range two-pion exchange (TPE) contributions to the nuclear current operator which appear at next-to leading order of the chiral expansion. These operators do not contain any free parameters. We study their role in the deuteron photodisintegration reaction and compare our predictions with experimental data from Refs [3]. The bound and scattering states are calculated using five different chiral N2LO nucleon-nucleon (NN) potentials which allows to estimate the theoretical uncertainty at a given order in the chiral expansion. For some observables the results are very close to the reference predictions based on the AV18 NN potential and the current operator (partly) consistent with this force.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Time-dependent 2-D modeling of edge plasma transport with high intermittency due to blobs

The results on time-dependent 2-D fluid modeling of edge plasmas with non-diffusive intermittent transport across the magnetic field (termed cross-field) based on the novel macro-blob approach are presented. The capability of this approach to simulate the long temporal evolution ({approx}0.1 s) of the background plasma and simultaneously the fast spatiotemporal dynamics of blobs ({approx}10{sup -4} s) is demonstrated. An analysis of a periodic sequence of many macro-blobs (PSMB) is given showing that the resulting plasma attains a dynamic equilibrium. Plasma properties in the dynamic equilibrium are discussed. In PSMB modeling, the effect of macro-blob generation frequency on edge plasma parameters is studied. Comparison between PSMB modeling and experimental profile data is given. The calculations are performed for the same plasma discharge using two different models for anomalous cross-field transport: time-average convection and PSMB. Parametric analysis of edge plasma variation with transport coefficients in these models is presented. The capability of the models to accurately simulate enhanced transport due to blobs is compared. Impurity dynamics in edge plasma with macro-blobs is also studied showing strong impact of macro-blob on profiles of impurity charge states caused by enhanced outward transport of high-charge states and simultaneous inward transport of low-charge states towards the core. Macro-blobs cause enhancement of sputtering rates, increase radiation and impurity concentration in plasma, and change erosion/deposition patterns.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗