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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Attention-Augmented Parametric Kernel Graph Neural Network (APKGNN) for Node Classification

We present a new graph neural network, the Attention-based Parametric-Kernel augmented Graph Neural Network (APKGNN), developed for node classification tasks. Despite extensive work on modeling multi-faceted relationships between connected nodes of a graph, the effect of attention on edge features mapped to relationships has not yet been analyzed through learning representation. This study derives such an attention vector by first calculating node features corresponding to endpoints of an edge and then aggregating these with extracted local intrinsic patches of a given graph to generate augmented local patch vectors. This process uses a parametric kernel based on Gaussian mixture models (GMMs) to embed local neighborhoods of the graph in local patches. The patch vectors then convolve with the above node features to produce an updated node representation. We show that this new learning representation (APKGNN) achieves higher node classification accuracy on tasks - both standard benchmarks (Cora, PubMed, Citeseer) and new experimental short text corpora where nodes correspond to text documents and words. This implementation of the GNN convolution layer outperforms state-of-the-art (SOTA) algorithms, achieving higher training, validation, and test accuracy by a significant margin on three standard benchmark data sets under both SOTA experimental settings and those for new testbeds.

Bose, Avishek↗
DOE OSTI2013

Task Time Tracker

This client-side web app tracks the amount of time spent on arbitrary tasks. It allosw the creation of an unlimited number of arbitrarily named tasks ans via simple interactions, tracks the amount of time spent working on the drfined tasks.

Cleary, G.↗
DOE OSTI2013

Task Time Tracker

This client-side web app tracks the amount of time spent on arbitrary tasks. It allosw the creation of an unlimited number of arbitrarily named tasks ans via simple interactions, tracks the amount of time spent working on the drfined tasks.

Cleary, G.↗
DOE OSTI2019

Power System Dynamic State Estimation: Motivations, Definitions, Methodologies and Future Work

This paper summarizes the technical activities of the Task Force on Power System Dynamic State and Parameter Estimation. This Task Force was established by the IEEE Working Group on State Estimation Algorithms to investigate the added benefits of dynamic state and parameter estimation for the enhancement of the reliability, security, and resilience of electric power systems. The motivations and engineering values of dynamic state estimation (DSE) are discussed in detail. Then, a set of potential applications that will rely on DSE is presented and discussed. Furthermore, a unified framework is proposed to clarify the important concepts related to DSE, forecasting-aided state estimation, tracking state estimation and static state estimation. An overview of the current progress in DSE and dynamic parameter estimation is provided. The paper also provides future research needs and directions for the power engineering community.

task force, dynamic state estimation, Parameter Es↗
DOE OSTI2016

Mercury concentrations in urine of amerindian populations near oil fields in the peruvian and ecuadorian amazon

Background: Mercury is a global contaminant with toxic, persistent effects on human health. Petroleum extraction is an important source of elemental mercury; little is known about human exposure levels near oil fields in the Amazon basin. Objectives: To characterize mercury levels in people living near oil production sites in the Peruvian and Ecuadorian Amazon, controlling for fish consumption, occupation, source of water and socio-demographic characteristics. Methods: Analyze mercury levels in urine samples using cold vapour atomic fluorescence spectrometry from 76 indigenous men and women in eight riverine communities situated near oil wells or pipelines. Subjects answered a questionnaire soliciting socio-demographic, occupational and dietary information. Data were analyzed using multiple linear regression modeling. Results: The mean value of U-Hg was 2.61 μg/g creatinine (95% CI: 2.14–3.08), with 7% of the sample recording values above the global background standard suggested by The World Health Organization (5 μg/g creatinine). Women who used water from a surface source had two and a half times the amount of mercury in their urine (mean=3.70 μg/g creatinine, 95% CI: 2.26–5.15) compared with women who used other water sources (mean =1.39 μg/g creatinine, 95% CI: 0.51–2.25). Men who were involved in an oil clean-up operation had twice as much mercury in their urine (mean =3.07 μg/g creatinine, 95% CI: 1.97–4.16) as did those who worked on other tasks (mean =1.56 μg/g creatinine, 95% CI: 1.48–2.65). Mercury levels were not associated with the number of fish meals per week. Conclusions: Indigenous peoples of the Peruvian and Ecuadorian Amazon living near oil production sites generally had urine mercury levels within the global background standard suggested by the World Health Organization. Increased levels of mercury in urine were detected for men involved in oil spill remediation and for women who relied on surface water for household needs. These findings signal the need for strict safety measures to limit the amount of oil entering the waterways in Andean Amazonia so as to protect the health of indigenous people. - Highlights: • 7% of participants had levels of inorganic mercury at or exceeding levels suggested by WHO (5 μg/g creatinine). • U-Hg levels were 2.5 times higher among women using surface water than those who drew on water from a well, spring or rain. • Men who had worked cleaning up an oil spill had more than twice the amount of mercury in their urine as men who did not.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Evaluation of Steam Cycle Upgrades to Improve the Competitiveness of U.S. Coal Power Plants (Final Scientific / Technical Report)

Increasing the competitiveness of the existing pulverized-coal utility fleet in the United States may be achieved by decreasing heat rate, via increases in steam cycle efficiency through upgraded steam temperatures and use of latest technology available in steam turbine and blading design. The average net plant efficiency of the US coal-fired fleet is approximately 33% (HHV). Plant efficiency increases to approximately 41.4% (HHV) at 1,350°F (732°C) steam temperature. However, achieving these Advanced Ultra-Super Critical (AUSC) steam conditions requires the use of advanced high-temperature materials. While there has been a significant amount of DOE-funded materials R&D, most of the related design work has focused on new (greenfield) units, rather than on opportunities to retrofit this advanced technology to the existing utility fleet. If technology, based upon the advanced materials required for AUSC steam conditions, may be applied to the existing fleet, using an economically viable retrofit, a higher capacity factor can be expected as a result of the increased plant competitiveness. The Electric Power Research Institute (EPRI) was awarded a project by the US Department of Energy to examine the technical and economic feasibility of a series of steam cycle upgrades to the two most prevalent types of U.S. coal power plants: 2,400 psig (16.6 MPa) subcritical and 3,500 psig (24.1 MPa) supercritical pulverized coal units. The nine upgrade options that were originally being considered included increasing the main and reheat steam temperatures from 1,000°F (538°C) to 1,100°, 1,200°, and 1,350°F (593°C, 649°C, and 732°C) while holding the steam pressures constant at their original design values, and cases where just the main steam or reheat steam temperatures were increased. The objective was to minimize the modifications required to the existing power plant while still providing a significant improvement in heat rate. The upgrade options assumed that the boiler enclosure envelope remained unchanged from each base case, and that all applicable OEM design guidelines for normal commercial units were imposed. For the highest temperature supercritical case, an option of using a low-pressure molten salt loop to transfer heat from the furnace to the steam was examined. The first major task of the work scope was designed to examine the technical feasibility of various upgrade options, while the subsequent work determined economic viability of the technically feasible upgrade options. Prior to evaluating the effect of these increased temperatures, a “base case” model of a subcritical and supercritical PC boiler was created, which was used for comparative purposes. Upgrade options were evaluated at full-load, part-load and dynamic transient conditions. Once the technical feasibility of each upgrade option was evaluated, the economic value of the heat rate improvement of each feasible option was determined by detailed modeling of unit dispatch in several regional power markets. The dispatch model was used to estimate the amount of revenue from power sales the upgraded unit would receive in comparison to a non-upgraded version of the same power plant. As a parallel task to the dispatch analysis, the capital cost of implementing the upgrades was estimated. The capital cost estimates were then compared to the increased revenue estimated by the dispatch modeling to determine the economic attractiveness of each upgrade option. Several upgrade options were determined to be technically feasible. The net present value (NPV) of the costs for steam cycle upgrades considered in this study ranged from approximately $\$$111 to $\$$130 million. The economic modeling results show that the unit dispatch changes resulting from steam cycle upgrades are relatively small, due largely to heat rate (and operating cost) changes being relatively small. Additionally, the cost of each upgrade exceeds the net revenue increases associated with the upgrade case. Note that the breakeven values are higher for subcritical retrofits, but the capital costs for the subcritical upgrades are also slightly higher. In typical new pulverized coal plants, fuel accounts for approximately 25% of the cost of electricity (COE), while capital costs represent around 50% of the COE. Therefore, in order to improve the heat rate by 4% one can only afford to increase the capital cost by 2%, at the same cost of electricity. The conclusion of this study is that without a cost for emitting CO 2 , it will be difficult to pay for significant efficiency improvements on plants firing low cost coals.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2012

International Linear Collider Physics and Detectors (2011 Status Report)

The studies of physics and detectors for the International Linear Collider are an important parallel element to the effort for the ILC Technical Design Report. The studies comprise the physics opportunities, detector requirements, and detector development to achieve the challenging high performance demanded by the physics, as well as integration of detectors into the accelerator. The current phase of this effort began with a call for Letters of Intent (LOIs) in 2007 and will lead to the submission of Detailed Baseline Design (DBD) report together with the ILC Technical Design Report at the end of 2012. Here we summarise the current status of this process, review what it has accomplished and identify the work that still needs to be completed. This report, titled International Linear Collider Physics and Detectors: 2011 Status Report, does just this. This report begins with a discussion of the outstanding issues in physics that motivate the construction of the ILC. It describes the organisation of the LOI process, the validation of the LOIs by the International Detector Advisory Group, and the results of R&D carried out to support the detector designs. The details of the concept detectors have already been published in the LOIs, which were completed in 2009. This report will, in a complementary way, describe the status of the detector R&D for each individual detector component and the status of the physics simulation infrastructure that has been built for the detector design process. Much of this work is carried out in cooperation between the two detector concept groups. This report describes the five common task groups and two working groups that have organised these cooperative activities. Many members of the detector concept groups and the common task groups have contributed to this report. Many more people have carried out the actual work that is reviewed. The complete list of members of each detector concept group can be found from the author lists of the published LOIs. The members of the ILC physics and detector organisation are listed at the end of this document. As we are now nearing the completion of the DBD phase, we are also entering a new stage of our preparation process. The experiments at the Large Hadron Collider at CERN, Switzerland, are accumulating data and are extending our knowledge of the physics of the teraelectronvolt energy scale. The LHC results may confirm the standard model of electroweak symmetry breaking or they may deliver something completely new. In either case, we believe, the ILC will be critical to resolve the questions that the LHC programme will bring forward. In any scenario, we will need very high-quality detectors and excellent technical and simulation capabilities. This report describes the status of our work in pursuit of that goal.

Brau, James E.↗
DOE OSTI2021

New Insights into Structural Evolution of LiNiO 2 Revealed by Operando Neutron Diffraction

LiNiO 2 (LNO) represents the end member in the compositional space of the LiNi 1-x-y Mn x Co y O 2 (as x and y approach zero) cathode system. Despite its high theoretical specific capacity (275 mAh/g), LNO suffers from phase transitions with large volume change and unfavorable reactions upon electrochemical cycling, which restricts its practical use in the application of lithium-ion batteries. While the contributing factor to the structural instability is commonly linked to the undesired volume collapse associated with the H2-H3 phase transition, detailed analysis of structural evolution following the entire route of phase transitions (H1-M-H2-H3) in real time under battery operating conditions remains a challenging task. In this work, we employ operando neutron diffraction to study the structural changes (crystal lattice, Li/Ni–O bond length, O–Ni–O bond angles, and LiO 2 /NiO 2 layer thickness) of LNO cathode in a home-built Li x NiO 2 || graphite full cell during Li + de-/intercalation. In particular, the anomalous increase(decrease) of Ni–O(Li–O) bond length at high SOC (>~85 %) in the H3 phase is discussed in the context of O 2- (2p)→Ni 4+ (3d) negative charge transfer.

25 ENERGY STORAGE↗
DOE OSTI2019

Macrocycle-Directed Construction of Tetrahedral Anion-pi Receptors for Nesting Anions with Complementary Geometry

The unprecedented tetrahedral anion-? receptors have been successfully constructed by a macrocycle-directed approach. The use of large macrocycle precursors bearing four reaction sites enabled kinetic-favored cross-linking pathway and afforded otherwise-inaccessible tetrahedral cages in considerable yields. Crystal structure suggested that the tetrahedral cages have an enclosed three-dimensional cavity surrounded by four electron-deficient triazine faces in a tetrahedral array. The complementary accommodation of a series of tetrahedral and relevant anions including BF4-, ClO4-, H2PO4-, HSO4-, SO42- and PF6- has been observed by ESI-MS. Two complex crystal structures with ClO4- and PF6- demonstrated the anion was nicely encapsulated within the tetrahedral cavity through up to quadruple cooperative anion-? interactions by an excellent shape and size match. The favored complexation energies were established by DFT calculation and further confirmed by negative ion photoelectron spectroscopy study.

Luo, Jian↗
DOE OSTI2018

Resolving environmental effects of wind energy

Concerns for potential wildlife impacts resulting from land-based and offshore wind energy have created challenges for wind project development. Research is not always adequately supported, results are neither always readily accessible nor are they satisfactorily disseminated, and so decisions are often made based on the best available information, which may be missing key findings. The potential for high impacts to avian and bat species and marine mammals have been used by wind project opponents to stop, downsize, or severely delay project development. The global nature of the wind industry - combined with the understanding that many affected species cross-national boundaries, and in many cases migrate between continents - also points to the need to collaborate on an international level. The International Energy Agency (IEA) Wind Technology Collaborative Programs facilitates coordination on key research issues. IEA Wind Task 34 - WREN: Working Together to Resolve Environmental Effects of Wind Energy-is a collaborative forum to share lessons gained from field research and modeling, including management methods, wildlife monitoring methods, best practices, study results, and successful approaches to mitigating impacts and addressing the cumulative effects of wind energy on wildlife.

17 WIND ENERGY↗
DOE OSTI2019

Approach to Defect-Free Lifetime and High Electron Density in CdTe

Achieving simultaneously high carrier density and lifetime is crucial to II-VI semiconductor-based applications such as photovoltaics and infrared detectors; yet, it is a challenging task. In this work, high purity CdTe single crystals doped with indium (In) were grown by vertical Bridgman melt growth under carefully controlled stoichiometry. Two-photon excitation time-resolved photoluminescence was employed to measure bulk recombination lifetime by eliminating surface recombination effects. By adjusting stoichiometry with post growth annealing, high-net free carrier density approaching 10 18 cm -3 was attained simultaneously with lifetime approaching the radiative limit by suppressing non-radiative recombination centers.

14 SOLAR ENERGY↗
DOE OSTI2019

Study of Thermomechanical Behavior of Zirconium-0.3 Tin Alloy

Zirconium-based alloys are used in the manufacturing of nuclear fuel tubes. These tubes need to be clad with zirconium-tin (Zr-0.3 wt.% Sn) alloy to enhance the lives of tubes. Manufacturing of such clad tubes is a challenging task, due to work hardening and dynamic softening phenomenon. In this study, hot deformation behavior of Zr-0.3Sn alloy is investigated at different temperatures and strain rates. It is found that fully recrystallized microstructure can be obtained by working at around 900 °C and high strain rate of 10 s{sup −1}. Further, constitutive equations are developed for the entire domain of deformation range and fitted into standard FEM-based simulation model for extrusion. The simulation results are validated with experimental data. The difference in flow stresses values obtained from numerical and experimental methods was around 14%.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Analyzing the impact of design factors on solar module thermomechanical durability using interpretable machine learning techniques

Solar modules in utility-scale systems are expected to maintain decades of lifetime to rival conventional energy sources. However, cyclic thermomechanical loading often degrades their long-term performance, highlighting the importance of effective design to mitigate thermal expansion mismatches between module materials. Given the complex composition of solar modules, isolating the impact of individual components on overall durability remains a challenging task. In this work, we analyze a comprehensive data set that comprises bill-of-materials (BOM) and thermal cycling power loss from 251 distinct module designs to identify the predominant design factors and their impacts on the thermomechanical durability of modules. The methodology of our analysis combines machine learning modeling (random forest) and Shapley additive explanation (SHAP) to correlate design factors with power loss and interpret the model’s decision-making. The interpretation reveals that silicon type (monocrystalline or polycrystalline), encapsulant thickness, busbar numbers, and wafer thickness predominantly influence the degradation. With lower power loss of around 0.6% on average in the SHAP analysis, monocrystalline cells present better durability than polycrystalline cells. This finding is further substantiated by statistical testing on our raw data set. The SHAP analysis also demonstrates that while thicker encapsulants lead to reduced power loss, further increasing their thickness over around 0.6 to 0.7 mm does not yield additional benefits, particularly for the front side one. In addition, other important BOM features such as the number of busbars are analyzed. This study provides a blueprint for utilizing explainable machine learning techniques in a complex material system and can potentially guide future research on optimizing the design of solar modules.

14 SOLAR ENERGY↗
DOE OSTI2020

Coupled confined phase behavior and transport of methane in slit nanopores

The proximity of the order of magnitude molecular mean free path and pore sizes in nanopores leads to remarkable interactions between molecules and walls. In such systems, the thermodynamic property and the transport behavior of fluids deviate from those at bulk conditions. Molecular dynamics (MD) simulation may be used to investigate the effects of confinement on fluid physics in nanosize pores. However, translating these subscale observations into a larger scale of interest remains a challenging task. In this work, we propose a modified extension of Peng-Robinson equation of state (PR-EOS) motivated and guided by MD simulation results. The shift of critical properties, i.e., pressure and temperature, are evaluated independently. A temperature dependent parameter is introduced to account for the existence of capillary pressure in the two-phase region. Here, this formulation is capable of capturing the shift in critical properties as well as density phase diagrams under various confinement scenarios. We incorporate the proposed EOS in the lattice Boltzmann method (LBM) to study coupled confined phase behavior and transport of methane in nano-size slit pores. Adsorptive strength is determined such that the resulting density ratio matches that from MD simulation. Results indicate that the use of the proposed EOS leads to smaller fluid velocities compared to PR-EOS. This effect is due to stronger interactions between fluid particles under confinement. Also, results show that transport characteristics are impacted by the pressure of the system: in systems with a relatively low pressure, transport seems to be dominated by Knudsen diffusion; however, at a higher pressure, the contribution from viscous flow increases as the pore widens while the influence of Knudsen and surface diffusion diminishes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

SPH with dynamical smoothing length adjustment based on the local flow kinematics

Due to the Lagrangian nature of Smoothed Particle Hydrodynamics (SPH), the adaptive resolution remains a challenging task. In this work, we first analyse the influence of the simulation parameters and the smoothing length on solution accuracy, in particular in high strain regions. Based on this analysis we develop a novel approach to dynamically adjust the kernel range for each SPH particle separately, accounting for the local flow kinematics. We use the Okubo–Weiss parameter that distinguishes the strain and vorticity dominated regions in the flow domain. The proposed development is relatively simple and implies only a moderate computational overhead. We validate the modified SPH algorithm for a selection of two-dimensional test cases: the Taylor–Green flow, the vortex spin-down, the lid-driven cavity and the dam-break flow against a sharp-edged obstacle. The simulation results show good agreement with the reference data and improvement of the long-term accuracy for unsteady flows. For the lid-driven cavity case, the proposed dynamical adjustment remedies the problem of tensile instability (particle clustering).

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

A dosimetric study of small photon fields using polymer gel and Gafchromic EBT films

The use of small field sizes is increasingly becoming important in radiotherapy particularly since the introduction of stereotactic radiosurgery and intensity-modulated radiation therapy techniques. The reliable measurement of delivered dose from such fields with conventional dosimeters, such as ionization chambers, is a challenging task. In this work, methacrylic and ascorbic acid in gelatin initiated by copper polymer gel dosimeters are employed to measure dose in 3 dimensions. Field sizes of 5 × 5 mm{sup 2}, 10 × 10 mm{sup 2}, 20 × 20 mm{sup 2}, and 30 × 30 mm{sup 2} are investigated for a 6-MV x-rays. The results show an agreement with Gafchromic film, with some variation in measured doses near the edge of the fields, where the film data decrease more rapidly than the other methods. Dose penumbra widths obtained with gel dosimeters and Gafchormic film were generally in agreement with each other. The results of this work indicate that polymer gel dosimetry could be invaluable for the quantification of the 3-dimensional dose distribution in small field size.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2025

Linking structural and rheological memory in disordered soft materials

Linking the macroscopic flow properties and nanoscopic structure is a fundamental challenge to understanding, predicting, and designing disordered soft materials. Under small stresses, these materials are soft solids, while larger loads can lead to yielding and the acquisition of plastic strain, which adds complexity to the task. In this work, we connect the transient structure and rheological memory of a colloidal gel under cyclic shearing across a range of amplitudes via a generalized memory function using rheo-X-ray photon correlation spectroscopy (rheo-XPCS). Our rheo-XPCS data show that the nanometer scale aggregate-level structure recorrelates whenever the change in recoverable strain over some interval is zero. The macroscopic recoverable strain is therefore a measure of the nano-scale structural memory. We further show that yielding in disordered colloidal materials is strongly heterogeneous and that memories of prior deformation can exist even after the material has been subjected to flow.

Kamani, Krutarth M. [Univ. of Illinois at Urbana-C↗