Showing papers by "Sandia National Laboratories published in 2023"
TL;DR: In this paper , the authors proposed a novel method to scale MagLIF loads to higher peak currents based on similarity scaling and attempts to preserve much of the physics regimes already known or being studied on today's Z pulsed-power driver.
Abstract: Magnetized liner inertial fusion (MagLIF) is a magneto-inertial-fusion (MIF) concept, which is presently being studied on the Z pulsed power facility. The MagLIF platform has achieved interesting plasma conditions at stagnation and produced significant fusion yields in the laboratory. Given the relative success of MagLIF, there is a strong interest to scale the platform to higher peak currents. However, scaling MagLIF is not entirely straightforward due to the large dimensionality of the experimental input parameter space and the numerous physical processes involved in MIF implosions. In this work, we propose a novel method to scale MagLIF loads to higher currents. Our method is based on similarity (or similitude) scaling and attempts to preserve much of the physics regimes already known or being studied on today's Z pulsed-power driver. By avoiding significant deviations into unexplored and/or less well-understood regimes, the risk of unexpected outcomes on future scaled-up experiments is reduced. Using arguments based on similarity scaling, we derive the scaling rules for the experimental input parameters characterizing a MagLIF load (as functions of the characteristic current driving the implosion). We then test the estimated scaling laws for various metrics measuring performance against results of 2D radiation–magneto-hydrodynamic hydra simulations. Agreement is found between the scaling theory and the simulation results.
4 citations
TL;DR: Gomez et al. as discussed by the authors developed a simplified analytical model that identifies the main physical processes at play during a MagLIF implosion and provided estimates of such parameters using typical fielded or experimentally observed quantities.
Abstract: Magneto-inertial fusion concepts, such as the magnetized liner inertial fusion (MagLIF) platform [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)], constitute an alternative path for achieving ignition and significant fusion yields in the laboratory. The space of experimental input parameters defining a MagLIF load is highly multi-dimensional, and the implosion itself is a complex event involving many physical processes. In the first paper of this series, we develop a simplified analytical model that identifies the main physical processes at play during a MagLIF implosion. Using non-dimensional analysis, we determine the most important dimensionless parameters characterizing MagLIF implosions and provide estimates of such parameters using typical fielded or experimentally observed quantities for MagLIF. We then show that MagLIF loads can be “incompletely” similarity scaled, meaning that the experimental input parameters of MagLIF can be varied such that many (but not all) of the dimensionless quantities are conserved. Based on similarity-scaling arguments, we can explore the parameter space of MagLIF loads and estimate the performance of the scaled loads. In the follow-up papers of this series, we test the similarity-scaling theory for MagLIF loads against simulations for two different scaling “vectors,” which include current scaling and rise-time scaling.
4 citations
TL;DR: In this article , the effect of various dopants on catalytic performance can be attributed to crystalline phase, specific surface area and electronic interaction involved in NaBH 4 hydrolysis.
2 citations
TL;DR: Tao et al. as mentioned in this paper examined the initiation, propagation and structure of oblique detonation waves in stoichiometric H2-air mixtures through numerical simulations with and without nonthermal reactivity on a two-dimensional adaptive grid.
2 citations
TL;DR: In this article , the authors provide approaches to separately measure the numerical errors arising from different error sources, and demonstrate the effectiveness of these approaches for cases with and without coding errors for both cases.
1 citations
TL;DR: In this article , a general method for optimizing the configuration of an experimental diagnostic to minimize uncertainty and bias in inferred quantities from experimental data is presented, which relies on Bayesian inference to sample the posterior using a physical model of the experiment and instrument.
Abstract: We present a general method for optimizing the configuration of an experimental diagnostic to minimize uncertainty and bias in inferred quantities from experimental data. The method relies on Bayesian inference to sample the posterior using a physical model of the experiment and instrument. The mean squared error (MSE) of posterior samples relative to true values obtained from a high fidelity model (HFM) across multiple configurations is used as the optimization metric. The method is demonstrated on a common problem in dense plasma research, the use of radiation detectors to estimate physical properties of the plasma. We optimize a set of filtered photoconducting diamond detectors to minimize the MSE in the inferred X-ray spectrum, from which we can derive quantities like the electron temperature. In the optimization we self-consistently account for uncertainties in the instrument response with appropriate prior probabilities. We also develop a penalty term, acting as a soft constraint on the optimization, to produce results that avoid negative instrumental effects. We show results of the optimization and compare with two other reference instrument configurations to demonstrate the improvement. The MSE with respect to the total inferred X-ray spectrum is reduced by more than an order of magnitude using our optimized configuration compared with the two reference cases. We also extract multiple other quantities from the inference and compare with the HFM, showing an overall improvement in multiple inferred quantities like the electron temperature, the peak in the X-ray spectrum and the total radiated energy.
1 citations
TL;DR: In this paper , the Baer and Nunziato model is extended to N-phases by incorporating deformation mechanics using the deformation gradient with a full stress tensor.
1 citations
TL;DR: In this paper , the authors present a novel intrusion detection and response approach for DER systems, called SOAR4DER, that ingests data from multiple Intrusion Detection Systems (IDSs) to quickly block attacks and revert DER system to known good states.
Abstract: Monitoring data and control functionality presented by interoperable photovoltaic (PV) inverters and other Distributed Energy Resources (DER) can be used to improve site maintenance, prognostics, and grid operations. Unfortunately, DER communications present attack vectors which could lead to power systems impacts. Since adversary capabilities continually improve, avoiding catastrophic consequences requires intelligent intrusion detection and remediation systems that consider both physical and cyber features. New Security Orchestration, Automation, and Response (SOAR) technologies are equipping cyber-defenders with new capabilities to autonomously respond to network and host-based system alerts, threat hunting results, and cyber intelligence data streams. In this Chapter, we present a novel SOAR approach for DER systems, called SOAR4DER, that ingests data from multiple Intrusion Detection Systems (IDSs) to quickly block attacks and revert DER systems to known good states. Our implementation used a collection of IDS technologies on a Bump-in-the-Wire (BITW) device which incorporated physical and cyber data to detect abnormal and potential malicious behaviors. Multiple SOAR playbooks then used the IDS data streams to automatically defend the system. Laboratory testing of the SOAR4DER system showed detection and response times under 30 s for all adversary reconnaissance operations, denial-of-service attacks, malicious Modbus commands, brute force logins, and machine-in-the-middle attacks.
1 citations
TL;DR: In this article , a researcher accidentally contacted, and discharged, a capacitor in an X-ray diffraction instrument during diagnostic activities, and the discharge path had occurred hand-to-hand across the heart, a serious injury may have been possible.
TL;DR: In this paper , the authors present a more intuitive visualization by projecting structural data into virtual reality (VR) for PZT perovskites using CAD2VR and the new CrystalVR plugin.
Abstract: Pb–Zr–Ti–O (PZT) perovskites span a large solid-solution range and have found widespread use due to their piezoelectric and ferroelectric properties that also span a large range. Crystal structure analysis via Rietveld refinement facilitates materials analysis via the extraction of the structural parameters. These parameters, often obtained as a function of an additional dimension (e.g., pressure), can help to diagnose materials response within a use environment. Often referred to as “ in-situ ” studies, these experiments provide an abundance of data. Viewing structural changes due to applied pressure conditions can give much-needed insight into materials performance. However, challenges exist for viewing/presenting results when the details are inherently three-dimensional (3D) in nature. For PZT perovskites, the use of polyhedra (e.g., Zr/Ti–O 6 octahedra) to view bonding/connectivity is beneficial; however, the visualization of the octahedra behavior with pressure dependence is less easily demonstrated due to the complexity of the added pressure dimension. We present a more intuitive visualization by projecting structural data into virtual reality (VR). We employ previously published structural data for Pb 0.99 (Zr 0.95 Ti 0.05 ) 0.98 Nb 0.02 O 3 as an exemplar for VR visualization of the PZT R3c crystal structure between ambient and 0.62 GPa pressure. This is accomplished via our in-house CAD2VR™ software platform and the new CrystalVR plugin. The use of the VR environment enables a more intuitive viewing experience, while enabling on-the-fly evaluation of crystal data, to form a detailed and comprehensive understanding of in-situ datasets. Discussion of methodology and tools for viewing are given, along with how recording results in video form can enable the viewing experience.
01 Jan 2023
TL;DR: In this article , the authors summarize a few of the recent research efforts addressing uncertainty quantification aspects of homogenized properties using CPFEM in a big picture context, including UQ also plays a crucial role in verification and validation for both ICMEIntegrated Computational Materials Engineering (ICME) and ML models, it is important to include UQ in the picture.
Abstract: The structure-property linkage is one of the two most important relationships in materials science besides the process-structure linkage, especially for metals and polycrystalline alloys. The stochastic nature of microstructures begs for a robust approach to reliably address the linkage. As such, uncertainty quantificationUncertainty quantification (UQ) plays an important role in this regard and cannot be ignored. To probe the structure-property linkage, many multi-scale integrated computational materials engineeringIntegrated Computational Materials Engineering (ICME) (ICME) tools have been proposed and developed over the last decade to accelerate the material design process in the spirit of Material Genome Initiative (MGI), notably crystal plasticity finite element modelCrystal Plasticity Finite Element Model (CPFEM) (CPFEM) and phase-field simulations. Machine learningMachine learning (ML) methods, including deep learning and physics-informed/-constrained approaches, can also be conveniently applied to approximate the computationally expensive ICMEIntegrated Computational Materials Engineering (ICME) models, allowing one to efficiently navigate in both structure and property spaces effortlessly. Since UQ also plays a crucial role in verification and validation for both ICMEIntegrated Computational Materials Engineering (ICME) and ML models, it is important to include UQ in the picture. In this paper, we summarize a few of our recent research efforts addressing UQ aspects of homogenized properties using CPFEMCrystal Plasticity Finite Element Model (CPFEM) in a big picture context.
01 Jan 2023
21 Mar 2023
TL;DR: In this paper , the authors used a large number of soil organic carbon (SOC) field observations (n = 54,000), geospatial datasets of environmental factors, and two machine learning approaches (Random Forest (RF) and Generalized Additive Modeling (GAM)) to identify dominant environmental controllers of global and biome-specific SOC stocks, and derive functional relationships between environmental controllers and SOC stocks.
Abstract: Abstract. Representing soil organic carbon (SOC) dynamics in Earth system models (ESMs) is a key source of uncertainty in predicting carbon climate feedbacks. Machine learning models can help identify dominant environmental controllers and their functional relationships with SOC stocks. The resulting knowledge can be implemented in ESMs to reduce uncertainty and better predict SOC dynamics over space and time. In this study, we used a large number of SOC field observations (n = 54,000), geospatial datasets of environmental factors (n = 46), and two machine learning approaches (Random Forest (RF) and Generalized Additive Modeling (GAM)) to: (1) identify dominant environmental controllers of global and biome-specific SOC stocks, (2) derive functional relationships between environmental controllers and SOC stocks, and (3) compare the identified environmental controllers and predictive relationships with those in Coupled Model Intercomparison Project phase six (CMIP6) models. Our results showed that diurnal temperature, drought index, cation exchange capacity, and precipitation were important observed environmental controllers of SOC stocks. RF model predictions of global-scale SOC stocks were relatively accurate (R2 = 0.61, RMSE = 0.46 kg m−2). In contrast, precipitation, temperature, and net primary productivity explained > 96 % of ESM-modeled SOC stock variability. We also found very different functional relationships between environmental factors and SOC stocks in observations and ESMs. SOC predictions in ESMs may be improved significantly by including additional environmental controls (e.g., cation exchange capacity) and representing the functional relationships of environmental controllers consistent with observations.
01 Jan 2023
TL;DR: In this paper , the authors present a logarithmic model that can predict installed cost conditional on energy capacity, power capacity, AC or DC coupling with distributed generation, customer sector, and local wages for electricians.
23 Jan 2023
TL;DR: In this paper , high-resolution electron backscatter diffraction (HREBSD) was used to measure distortions on the thinned surface of a microelectronic device and the distortions were then related to the stresses in the metallic layers through elastic simulations.
Abstract: Abstract Delayed failure due to stress voiding is a concern with some aging microelectronics, as these voids can grow large enough to cause an open circuit. Local measurements of stress in the metallic layers are crucial to understanding and predicting this failure, but such measurements are complicated by the fact that exposing the aluminum conducting lines will relieve most of their stress. In this study, we instead mechanically thin the device substrate and measure distortions on the thinned surface using high resolution electron backscatter diffraction (HREBSD). These measurements are then related to the stresses in the metallic layers through elastic simulations. This study found that in legacy components that had no obvious voids, the stresses were comparable to the theoretical stresses at the time of manufacture (≈300 MPa). Distortion fields in the substrate were also determined around known voids, which may be directly compared to stress voiding models. The technique presented here for stress determination, HREBSD coupled with finite element analysis to infer subsurface stresses, is a valuable tool for assessing failure in layered microelectronics devices.
07 Jun 2023
TL;DR: Triaxial magnetic fields of even modest strength are a powerful and flexible means of controlling magnetic soft matter as mentioned in this paper , and they can be used to create fully optimized isometric or anisometric particle composites that have high magnetic permeability, thermal conductivity, magnetoresistance and magnetostriction, as well as minimal gas permeability and strain-sensitive electrical conductivity.
Abstract: Triaxial magnetic fields of even modest strength are a powerful and flexible means of controlling magnetic soft matter. If the continuous phase is a polymerizing resin, triaxial fields can be used to create fully optimized isometric or anisometric particle composites that have high magnetic permeability, thermal conductivity, magnetoresistance and magnetostriction, as well as minimal gas permeability and strain-sensitive electrical conductivity. Applications for such materials include sensors, actuators, heat spreaders, electromagnetic shielding and so forth. If the continuous phase is a liquid, vigorous fluid vorticity can be stimulated such that the vorticity vector itself can be either stationary or can undergo a limitless variety of complex, 3D orbits that stimulate a variety of biomimetic dynamics in a magnetic fluid suspended in an immiscible liquid. Finally, in suspensions of magnetic flakes it is possible to create advection lattices with a controllable lattice spacing, and even vortex lattices of remarkable regularity. These various fields of research will be described in this chapter to inspire others to pursue this research direction.
04 Mar 2023
TL;DR: In this article , the error present between a fine, solid element mesh and a reduced order spring beam model was quantified, with the aim of finding the best balance of a low computational cost and high accuracy analysis.
Abstract: Springs play important roles in many mechanisms, including critical safety components employed by Sandia National Laboratories. Due to the nature of these safety component applications, serious concerns arise if their springs become damaged or unhook from their posts. Finite element analysis (FEA) is one technique employed to ensure such adverse scenarios do not occur. Ideally, a very fine spring mesh would be used to make the simulation as accurate as possible with respect to mesh convergence. While this method does yield the best results, it is also the most time consuming and therefore most computationally expensive process. In some situations, reduced order models (ROMs) can be adopted to lower this cost at the expense of some accuracy. This study quantifies the error present between a fine, solid element mesh and a reduced order spring beam model, with the aim of finding the best balance of a low computational cost and high accuracy analysis. Two types of analyses were performed, a quasi-static displacement-controlled pull and a haversine shock. The first used implicit methods to examine basic properties as the elastic limit of the spring material was reached. This analysis was also used to study the convergence and residual tolerance of the models. The second used explicit dynamics methods to investigate spring dynamics and stress/strain properties, as well as examine the impact of the chosen friction coefficient. Both the implicit displacement-controlled pull test and explicit haversine shock test showed good similarities between the hexahedral and beam meshes. The results were especially favorable when comparing reaction force and stress trends and maximums. However, the EQPS results were not quite as favorable. This could be due to differences in how the shear stress is calculated in both models, and future studies will need to investigate the exact causes. The data indicates that the beam model may be less likely to correctly predict spring failure, defined as inappropriate application of tension and/or compressive forces to a larger assembly. Additionally, this study was able to quantify the computational cost advantage of using a reduced order model beam mesh. In the transverse haversine shock case, the hexahedral mesh took over three days with 228 processors to solve, compared to under 10 hours for the ROM using just a single processor. Depending on the required use case for the results, using the beam mesh will significantly improve the speed of work flows, especially when integrated into larger safety component models. However, appropriate use of the ROM should carefully balance these optimized run times with its reduction in accuracy, especially when examining spring failure and outputting variables such as equivalent plastic strain. Current investigations are broadening the scope of this work to include a validation study comparing the beam ROM to physical testing data.
15 May 2023
TL;DR: In this paper , the authors reported the detection of a rare earth-grazing fireball that was observed by casual witnesses and all-sky cameras across Europe on 22 September 2020.
Abstract: The Earth’s atmosphere is continuously bombarded by extraterrestrial objects (generally referred to as meteoroids) of various sizes and velocities (11.2–72.5 km/s). Such high kinetic energy interactions with exponentially increasing higher density atmosphere result in a visual phenomenon known as a meteor. Optically very bright events, or fireballs, are typically produced by objects larger than about 10 cm in diameter. A rare class of fireballs are earthgrazers which enter the atmosphere at an extremely shallow angle. Depending on their size and velocity, some earthgrazers return to space after a relatively short hypersonic flight through the upper regions of the atmosphere. Due to a variety of factors, including the lack of dedicated observational resources, there are only a handful of documented observations of earthgrazing fireballs in the last 50 years. Nevertheless, this category of extraterrestrial objects is of significant interest to the scientific community for a range of practical reasons, such as the analogous relationship with artificial platforms capable of reaching the boundary of the outer atmosphere. In general, typical fireballs are capable of generating shockwaves that can decay to very low frequency acoustic waves, also known as infrasound. Theoretically, the resulting shockwaves and subsequent infrasound from earthgrazers should have distinct signatures. In principle, fireballs can serve as natural laboratories for testing regional and global infrasound monitoring capabilities and provide an important leverage towards improving high-altitude source detection, characterization and geolocation efforts. Infrasound signatures from earthgrazers should further enhance our understanding of infrasonic signals generated in the upper atmopshere. We report infrasound detection of a rare earthgrazing fireball that was observed by casual witnesses and all-sky cameras across Europe on 22 September 2020. It entered at 03:53:40 UTC over northern Europe, and its luminous path extended from Germany to the UK. Despite the high-altitude trajectory (~100 km), the earthgrazer generated a pressure wave that reached the ground at low frequencies detectable by infrasonic instruments. Three infrasound stations of the Royal Netherlands Meteorological Institute (KNMI) network detected the signal. The airwave swept one of the arrays at a particularly high trace velocity (>1 km/s), indicative of a near-vertical arrival angle from a high-altitude cylindrical line source. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA000352.
01 Jan 2023
24 Apr 2023
TL;DR: In this article , the authors apply density functional theory calculations to examine four criteria of oxidative stability (oxidation potential, hydrogen removal energies, and initial reactivity on two types of oxide facets) using four different solvent/additive molecules (ethylene carbonate, fluoroethylenecarbonate, 1,3-dioxolane, and dimethyl ether).
Abstract: Oxidative instability of the liquid electrolyte at or near battery cathode oxide surfaces has significant detrimental effects on batteries. Organic solvent molecules are often the fuel and precursors of such degradation processes, releasing electrons and protons that react with cathode oxides and electrolyte anions. These reactions contribute to cathode–electrolyte interphase (CEI) film formation, transition-metal ion dissolution, and phase transformation of the surface regions of the cathode. Here we apply density functional theory calculations to examine four criteria of oxidative stability (oxidation potential, hydrogen removal energies, and initial reactivity on two types of oxide facets) using four different solvent/additive molecules (ethylene carbonate, fluoroethylene carbonate, 1,3-dioxolane, and dimethyl ether). The ranking of molecular stability differs with each criterion. Surprisingly, the all-oxygen-terminated basal planes of layered oxides exhibit lower reaction barriers than spinel surface facets with exposed transition-metal cations, especially for ether solvents; the calculations also suggest basal planes contribute to the dissolution of transition-metal ions. The structure–degradation relation complexity underscores the challenge of understanding the function of the CEI but also offers a guide to future degradation-mitigation strategies including facet engineering. Our predictions and models help establish a framework for future studies relevant to high-voltage conditions.
01 Jan 2023
TL;DR: In this paper , the authors identified common and inexpensive lab reagents that confer increased aerosol survivability on phi6 and other phages and suggested that soluble protein is a key protective component in nebulizing medium.
Abstract: We have identified common and inexpensive lab reagents that confer increased aerosol survivability on phi6 and other phages. Our results suggest that soluble protein is a key protective component in nebulizing medium.
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TL;DR: The Offshore Wind ENergy Simulator (OWENS) as mentioned in this paper is a simulation tool specifically designed for VAWT designs, and it has been used for modeling the aerodynamic properties of VAWTs.
Abstract: Vertical-axis wind turbines (VAWTs) offer some unique advantages over traditional designs, particularly for floating offshore and certain distributed wind applications. However, the modeling capabilities that exist for VAWT designs greatly lags those for the traditional horizontal-axis wind turbines (HAWTs). Differences between vertical and horizontal turbines necessitates several key additions in modeling, including the aerodynamic model, as well as solving a fundamentally different structural mesh. The Offshore Wind ENergy Simulator (OWENS) is specifically formulated to fulfill these requirements. This paper presents validation cases of this tool for modal, centrifugal, gravitational, startup, normal operation, and shutdown analyses. The aeroelastic validation is performed with increasing complexity from analytical test cases to an experimental VAWT. Validation data are taken from the Sandia National Laboratories 34 meter research turbine. The results of the validation cases are presented and examined.
TL;DR: In this paper , a direct numerical simulation (DNS) campaign is deployed for a series of confined downward oriented, non-isothermal turbulent impinging jet configurations, showing the effect of density disparity on flow characteristics such as core collapse, radial mixing of momentum and energy, nearwall stagnation behavior, wall-jet profiles, and large-scale vortical structures.
TL;DR: In this paper , a reflected shock tunnel capable of generating hypersonic environments at realistic flight enthalpies has been constructed at Sandia National Laboratory in New Mexico, USA, using an existing free-piston driver and shock tube coupled to a conical nozzle.
Abstract: A new reflected shock tunnel capable of generating hypersonic environments at realistic flight enthalpies has been commissioned at Sandia. The tunnel uses an existing free-piston driver and shock tube coupled to a conical nozzle to accelerate the flow to approximately Mach 9. The facility design process is outlined and compared to other ground test facilities. A representative flight-enthalpy condition is designed using an in-house state-to-state solver and piston dynamics model and evaluated using quasi-1D modeling with the University of Queensland L1d code. This condition is demonstrated using canonical models and a calibration rake. A 25-cm core flow with 4.6-MJ/kg total enthalpy is achieved over an approximately 1-ms test time. The condition was refined using analysis and a heavier piston, leading to an increase in test time. A novel high-speed molecular tagging velocimetry method is applied using in situ nitric oxide to measure the freestream velocity of approximately 3016 m/s. Companion simulation data show good agreement in exit velocity, pitot pressure, and core flow size.
01 Jan 2023
27 Mar 2023
TL;DR: The Altmetric Attention Score as discussed by the authors is a quantitative measure of the attention that a research article has received online, and it is calculated by using the number of articles citing this article, calculated by Crossref and updated daily.
Abstract: ADVERTISEMENT RETURN TO ISSUEEditorialNEXTWhen It Comes to Safety, Do Not Rush to CriticizeMary Beth MulcahyMary Beth MulcahyMore by Mary Beth Mulcahyhttps://orcid.org/0000-0002-3060-9189Cite this: ACS Chem. Health Saf. 2023, 30, 2, 29–30Publication Date (Web):March 27, 2023Publication History Received6 March 2023Published online27 March 2023Published inissue 27 March 2023https://doi.org/10.1021/acs.chas.3c00024Copyright © 2023 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views729Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (840 KB) Get e-AlertscloseSUBJECTS:Anions,Elimination reactions,Safety Get e-Alerts