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  1. Structural biology in the age of X-ray free-electron lasers and exascale computing

    Mous, Sandra; Poitevin, Frédéric; Hunter, Mark; ... - Current Opinion in Structural Biology
    Serial femtosecond X-ray crystallography has emerged as a powerful method for investigating biomolecular structure and dynamics. With the new generation of X-ray free-electron lasers, which generate ultrabright X-ray pulses at megahertz repetition rates, we can now rapidly probe ultrafast conformational changes and charge movement in biomolecules. Over the last year, another innovation has been the deployment of Frontier, the world's first exascale supercomputer. Synergizing extremely high repetition rate X-ray light sources and exascale computing has the potential to accelerate discovery in biomolecular sciences. Here we outline our perspective on each of these remarkable innovations individually, and the opportunities and challengesmore » in yoking them within an integrated research infrastructure.« less

  2. Phase change electrolytes for combined electrochemical and thermal energy storage

    Brechtl, Jamieson; Ullman, Andrew; Li, Kai; ... - Energy Reports
    Inorganic salt-based phase change materials (PCMs) form the basis of next-generation thermal energy storage technologies that store and release energy at temperatures relevant for regulating energy usage in residential environments. Here, we detail a rational approach for designing a multifunctional electrolyte that stores latent heat using polymer-stabilized sodium sulfate and sodium thiosulfate mixture. This formulated PCM also allows rapid sodium ion transport in both the solid and liquid states. This PCM composite electrolyte was prepared by blending the components at elevated temperatures, forming a viscous liquid that can serve as a gel-electrolyte for Na-ion batteries. The addition of sodium boratemore » as a nucleating agent resulted in a PCM composite electrolyte with fusion enthalpy (120 J/g) and a phase transition centered around 25.0 °C with 11 °C supercooling. This PCM electrolyte showed excellent thermal cycling stability (>10 cycles) that also maintains high ionic conductivity (>10 mS cm–1). We show that the electrolyte enables Na ion cycling of the dual anode/cathode material, Na2VTi(PO4)3. These properties make this composite electrolyte a promising material for multifunctional energy storage devices.« less

  3. Skyrmion lattice in centrosymmetric magnets with local Dzyaloshinsky–Moriya interaction

    Lin, Shi-Zeng - Materials Today Quantum
    It is common for the local inversion symmetry to break in crystals, even though the whole crystal has global inversion symmetry. This local inversion symmetry breaking allows for a local Dzyaloshinsky–Moriya interaction (DMI) in magnetic crystals. Here we show that the local DMI can stabilize a skyrmion as a metastable excitation or as a skyrmion crystal in equilibrium. We consider the crystal structure with layered structure as an example, where local inversion is violated in each layer but a global inversion center exists in the middle of the two layers. These skyrmions come in pairs that are related by inversionmore » symmetry. The two skyrmions with opposite helicity in a pair form a bound state. We study the properties of a skyrmion pair in the ferromagnetic background and determine the equilibrium phase diagram, where a robust lattice of skyrmion pairs is stabilized. Our results point to a new direction to search for the skyrmion lattice in centrosymmetric magnets.« less

  4. Normally closed thermally activated irreversible solid state erbium hydrides switches

    Abere, Michael; Gallegos, Richard; Moorman, Matthew; ... - Micro and Nano Engineering
    A thermally driven, micrometer-scale switch technology has been created that utilizes the ErH3/Er2O3 materials system. The technology is comprised of novel thin film switches, interconnects, on-board micro-scale heaters for passive thermal environment sensing, and on-board micro-scale heaters for individualized switch actuation. Switches undergo a thermodynamically stable reduction/oxidation reaction leading to a multi-decade (>11 orders) change in resistance. The resistance contrast remains after cooling to room temperature, making them suitable as thermal fuses. An activation energy of 290 kJ/mol was calculated for the switch reaction, and a thermos-kinetic model was employed to determine switch times of 120 ms at 560 °Cmore » with the potential to scale to 1 ms at 680 °C.« less

  5. Physics-informed machine learning with optimization-based guarantees: Applications to AC power flow

    Jalving, Jordan; Eydenberg, Michael; Blakely, Logan; ... - International Journal of Electrical Power and Energy Systems
    This manuscript presents a complete framework for the development and verification of physics-informed neural networks with application to the alternating-current power flow (ACPF) equations. Physics-informed neural networks (PINN)s have received considerable interest within power systems communities for their ability to harness underlying physical equations to produce simple neural network architectures that achieve high accuracy using limited training data. The methodology developed in this work builds on existing methods and explores new important aspects around the implementation of PINNs including: (i) obtaining operationally relevant training data, (ii) efficiently training PINNs and using pruning techniques to reduce their complexity, and (iii) globallymore » verifying the worst-case predictions given known physical constraints. Here, the methodology is applied to the IEEE-14 and 118 bus systems where PINNs show substantially improved accuracy in a data-limited setting and attain better guarantees with respect to worst-case predictions.« less

  6. Effect of additive and subtractive sequence on the distortion of cone-shaped part during hybrid direct energy deposition

    Madireddy, Guru; Feldhausen, Thomas; Kannan, Rangasayee; ... - Journal of Manufacturing Processes
    Hybrid manufacturing combines additive manufacturing (AM) and subtractive manufacturing processes to achieve simultaneous benefits. Unlike traditional AM, it allows for interleaved subtractive steps, enhancing machining tool access for parts with high aspect ratios. However, optimizing the printing sequence remains as an area of exploration. In this study with two conical shapes, one exhibited a geometrical mismatch at the interface between two printing sections, while the other did not. 3D laser scanning, finite element simulation, and methodical analysis were used to understand this issue. Printing support structure before machining improved dimensional accuracy, with 0.5 mm reduction in distortion achieved, corresponding tomore » 50 % of the final wall thickness. However, the absence of a feedback mechanism to track wall distortion after the additive process resulted in non-uniform wall thickness with a constant depth of cut during the machining operation. This research highlights the importance of process sequencing in hybrid manufacturing for achieving desired geometry.« less

  7. Assessment of Transmission-level Fault Impacts on 3-phase and 1-phase Distribution IBR Operation

    Xiao, Qi; Woo, Jongha; Song, Lidong; ...
    The widespread deployment of inverter-based resources (IBRs) renders distribution systems susceptible to transmission-level faults. This paper presents a comprehensive analysis of the impact of transmission-level faults on 3-phase and 1-phase distribution IBR operation. To evaluate distributed IBR tripping across various phases and locations on a distribution feeder, we conduct simulations of both symmetrical and unsymmetrical transmission faults at progressively greater electrical distances on a real-time transmission and distribution (T&D) co-simulation platform. The IBR power-to-load ratios (PLRs) at 50%, 100%, and 300% are considered to emulate low, medium, and high IBR conditions. Our results indicate that, while 1-phase and 2-phase faultsmore » typically trigger fewer IBR trips when compared to 3-phase faults, a significant power imbalance arises from the tripping of 1-phase IBRs on the affected phases. The imbalance can result in significant power quality problems and unintended equipment tripping. It may be necessary to design fault-ride-through mechanisms specifically tailored to 1-phase IBRs to help mitigate the power imbalances caused by unbalanced faults.« less

  8. Estimating geographic variation of infection fatality ratios during epidemics

    Ladau, Joshua; Brodie, Eoin; Falco, Nicola; ... - Infectious Disease Modelling
    Objectives: We propose a framework for estimating geographic variability in total numbers of infections and infection fatality ratios (IFR; the number of deaths caused by an infection per 1,000 infected people) when estimates of geographic variability in disease burden are limited by the availability and quality of data during an epidemic. Methods: We develop a noncentral hypergeometric framework that accounts for differential probability of positive tests and reflects the fact that symptomatic people are more likely to seek testing. We demonstrate the robustness, accuracy, and precision of this framework, and apply it to the United States (U.S.) COVID-19 pandemic tomore » estimate county-level SARS-CoV-2 IFRs. Results: The estimators for the numbers of infections and IFRs showed high accuracy and precision; for instance, when applied to simulated validation data sets, across counties, Pearson correlation coefficients between estimator means and true values were 0.996 and 0.928, respectively, and they showed strong robustness to model misspecification. Applying the county-level estimators to the real, unsimulated COVID-19 data spanning April 1, 2020 to September 30, 2020 from across the U.S., we found that IFRs varied from 0 to 44.69, with a standard deviation of 3.55 and a median of 2.14. Conclusions: The proposed estimation framework can be used to identify geographic variation in IFRs across settings.« less

  9. The Impact of Cement Plant Air Ingress on Membrane-Based CO2 Capture Retrofit Cost

    Hughes, Sydney; Cvetic, Patricia; Newby, Richard; ... - Carbon Capture Science & Technology
    The industrial sector is responsible for a significant portion of global CO2 emissions. Since some industrial CO2 emissions cannot be avoided, carbon capture and storage has a critical role to play in industrial decarbonization. The objective of this study is to highlight the impact of false air ingress—a standard cement production process occurrence that dilutes kiln CO2 emissions—on utilizing membrane-based capture for cement plant decarbonization. Correlations for ideal countercurrent membrane separation and a compression and purification unit (CPU) model are integrated to estimate the performance of a two-stage membrane system with CPU; membrane parameters are varied, with permeance ranging frommore » 1,000 to 10,000 GPU and CO2:N2 selectivity ranging from 25 to 200. The range of permeance and selectivity values evaluated in this study reflects current commercially available membranes through future stretch performance of yet to be developed membranes. By evaluating this large range of material performance, this study can be used by material developers to inform which performance parameters offer the greatest potential for overall cost reductions based on the study assumptions. The capital and operating costs and the resulting cost of CO2 captured (COC) are estimated. A conventional solvent-based capture system with costs derived on a similar basis is presented for comparison. The results indicate that for the two-stage configuration presented, (1) increasing CO2:N2 selectivity from 25 to 60 can significantly reduce cost, but further improving selectivity, or increasing permeance beyond 1,000 GPU, has only incremental impact; (2) the COC for membrane-based capture systems can be comparable to solvent-based capture systems when the impact of false air ingress into the emissions stream is neglected; and (3) when false air ingress is included, while the COC for solvent-based systems is incrementally affected, the COC for membrane-based capture systems is significantly impacted, rising by 64–111%. Cement plants have typically been characterized with flue gas CO2 concentrations higher than those of coal- or natural gas-fired power plants, which in idealized scenarios provides a higher driving force for membrane separation; however, the substantial false air ingress typically diluting kiln emissions reverses this advantage, leading to higher-than-expected costs. It is recommended that future research and development and techno-economic analyses of membrane-based capture from cement plants address the impact of false air ingress on system design.« less

  10. Future of hydrogen in the U.S. energy sector: MARKAL modeling results

    Victor, Nadejda; Nichols, Christopher - Applications in Energy and Combustion Science
    Hydrogen is an attractive energy carrier which could play a role in decarbonizing process heat, power or transport applications. Though the U.S. already produces about 10 million metric tons of H2 (over 1 quadrillion BTUs or 1 % of the U.S. primary energy consumption), production technologies primarily use fossil fuels that release CO2, and the deployment of other, cleaner H2 production technologies is still in the very early stages in the U.S. This study explores (1) the level of current U.S. hydrogen production and demand, (2) the importance of hydrogen to accelerate a net-zero CO2 future, and (3) the challengesmore » that must be overcome to make hydrogen an important part of the U.S. energy system. The study discusses four scenarios and hydrogen production has been shown to increase in the future, but this growth is not enough to establish a hydrogen economy. In this study, the characteristics of hydrogen technologies and their deployments in the long-term future are investigated using energy system model MARKAL. The effects of strong carbon constraints do not cause higher hydrogen demand but show a decrease in comparison to the business-as-usual scenario. Further, according to our modeling results, hydrogen grows only as a fuel for hard-to-decarbonize heavy-duty vehicles and is less competitive than other decarbonization solutions in the U.S. Without improvements in reducing the cost of electrolysis and increasing the performance of near-zero carbon technologies for hydrogen production, hydrogen will remain a niche player in the U.S. energy system in the long-term future. This article provides the reader with a comprehensive understanding of the role of hydrogen in the U.S. energy system, thereby explaining the long-term future projections.« less
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