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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Athena: High-Performance Sparse Tensor Contraction Sequence on Heterogeneous Memory

Sparse tensor contraction sequence has been widely employed in many fields, such as chemistry and physics. However, how to efficiently implement the sequence faces multiple challenges, such as redundant computations and memory operations, massive memory consumption, and inefficient utilization of hardware. To address the above challenges, we introduce Athena, a high-performance framework for SpTC sequences. Athena introduces new data structures, leverages emerging Optane-based heterogeneous memory (HM) architecture, and stage parallelism. In particular, Athena introduces shared hash table-represented sparse accumulator to eliminate unnecessary input processing and data migration; Athena uses a novel data-semantic guided dynamic migration solution to make the best use of the Optane-based HM for high performance; Athena also co-runs execution phases with different characteristics to enable high hardware utilization. Evaluating with 12 datasets, we show that Athena brings 327-7362× speedup over the state-of-the-art SpTC algorithm. With the dynamic data placement guided by data semantics, Athena brings performance improvement on Optane-based HM over a state-of-the-art software-based data management solution, a hardware-based data management solution, and PMM-only by 1.58×, 1.82×, and 2.34× respectively.

Liu, Jiawen↗
DOE OSTI2018

On efficient Hessian computation using the edge pushing algorithm in Julia

Evaluating the Hessian matrix of second-order derivatives at a sequence of points can be costly when applying second-order methods for nonlinear optimization. In this work, we discuss our experiences implementing the recently proposed Edge Pushing (EP) method in Julia as an experimental replacement for the current colouring-based methods used by JuMP, an open-source algebraic modelling language. We propose an alternative data structure for sparse Hessians to avoid the use of hash tables and analyse the space and time complexity of EP method. In our benchmarks, we find that EP is very competitive in terms of both preprocessing time and Hessian evaluation time. As a result, we identify cases where EP closes the performance gap between JuMP's previous implementation and the implementation in AMPL, a commercial software package with similar functionality.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Analysis and Comparison of Different Metrics of DC-DC Converters to Determine Fuel Cell Stack Architectures in Heavy Duty Fuel Cell Vehicle Applications

This paper presents a comparative study of the DC-DC converters used in heavy-duty fuel cell electric vehicles for different input fuel cell stack configurations and voltages in terms of various important metrics including efficiency, cost, weight and power density. Contrary to conventional use of an interleaved boost topology, the analysis presented in this paper demonstrates that improved converter metrics can be achieved for an interleaved buck topology that uses a different input fuel cell stack. An insight to the optimal choice of number of interleaved phases for each metric is also presented. Results presented in the tables and plots convey the findings.

Mukherjee, Subho↗
DOE OSTI2014

Department of Energy's Biological and Environmental Research Strategic Data Roadmap for Earth System Science

Rapid advances in experimental, sensor, and computational technologies and techniques are driving exponential growth in the volume, acquisition rate, variety, and complexity of scientific data. This wealth of scientifically meaningful data has tremendous potential to lead to scientific discovery. However, to achieve scientific breakthroughs, these data must be exploitable—they must be analyzed effectively and efficiently and the results shared and communicated easily within the wider Department of Energy’s (DOE’s) Biological and Environmental Research (BER) Climate and Environmental Sciences Division (CESD) community. The explosion in data complexity and scale makes these tasks exceedingly difficult to achieve, particularly given that an increasing number of disciplines are working across techniques, integrating simulation and experimental or observational results (see Table 5 in Appendix 2). Consequently, we need new approaches to data management, analysis, and visualization that provide research teams with easy-to-use and scalable end-to-end solutions. These solutions must facilitate (and where feasible, automate and capture) every stage in the data lifecycle (shown in Figure 1), from collection to management, annotation, sharing, discovery, analysis, and visualization. In addition, the core functionalities are the same across climate science communities, but they require customization to adapt to specific needs and fit into research and analysis workflows. To this end, the mission of CESD’s Data and Informatics Program is to integrate all existing and future distributed CESD data holdings into a seamless and unified environment for the acceleration of Earth system science.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Metal-Metal Interactions in Heterobimetallic Complexes as a Strategy to Promote Multielectron Redox And Small Molecule Activation Processes

Recent attention in the chemical community has been focused on the energy efficient and environmentally benign conversion of abundant small molecules (CO 2 , H 2 O, etc.) to useful liquid fuels. This project addressed these goals by examining fundamental aspects of catalyst design to ultimately access small molecule activation processes under mild conditions. Specifically, Thomas and coworkers constructed heterobimetallic complexes that feature metal centers with vastly different electronic properties, dictated both by their respective positions on the periodic table and their coordination environment. Unlike homobimetallic complexes featuring identical or similar metals, the bonds between metals in early/late heterobimetallics are more polarized, with the more electron-rich late metal center donating electron density to the more electron-deficient early metal center. While metal-metal bonds pose an interesting strategy for storing redox equivalents and stabilizing reactive metal fragments, the polar character of metal-metal bonds in heterobimetallic complexes renders these molecules ideally poised to react with small molecule substrates via cleavage of energy-rich single and double bonds. This research project further explored such bond activation processes. In addition, metal-metal interactions were shown to dramatically affect redox potentials and promote multielectron redox activity, and it was demonstrated that metal-metal interactions provide a mechanism to tune redox potentials and access substrate reduction/activation at mild overpotentials. This research project provided a better fundamental understanding of how interactions between transition metals can be used as a strategy to promote and/or control chemical transformations related to the clean production of fuels. While this project focused on the study of homogeneous systems, the broad conclusions drawn from these investigations are applicable to heterogeneous catalysis as well, particularly to heterogeneous processes that occur at interfaces in multicomponent systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Application of New CERCLA Five-Year Review Guidance at Hanford - 16403

Under CERCLA, the implementation of remedial actions established in records of decision (ROD) are required to be reviewed every five years to evaluate their effectiveness in protecting human health and the environment. Past reviews have included evaluation of actions that were not implemented under existing RODs and, therefore, not subject to the requirement. While commendable for its transparency, discussing these out-of-scope actions created confusion and elicited comments that required time and effort to resolve. The fourth CERCLA Five Year Review (FYR) at the Hanford Site embraces the EPA guidance designed to streamline the process and focuses on the specific objectives of the review. This guidance and the training materials developed jointly by multiple federal agencies including EPA, DOE, DOD, and Department of the Interior (DOI), demonstrate a focused approach to the FYR process and offer real-world examples for streamlining this important document. This paper discusses the focused approach and process changes implemented at the Hanford Site that reduced the size and complexity of the document and provided the DOE, Richland Operations Office, with an efficient, effective template for preparing subsequent reviews. One key change was a thorough evaluation of what operable units were discussed and what operable units were not discussed in the five-year review. This process resulted in a reduction of 14 operable unit discussions. Additionally, extensive referencing of previously published CERCLA documents including closure reports and periodic groundwater monitoring reports minimized the amount of analytical data tables necessary to support the discussion. The Hanford five year review made good use of technology and provided internet links to existing documents where detailed information and voluminous analytical data reside. This eliminated the use of extensive data tables and summaries. The resulting five protectiveness determinations include: 1) 'Protective' which is used when there is sufficient data to conclude that the remedy is functioning as intended; 2) 'Protective in the short term' which is used when the data and/or documentation review raises issues that could affect future protectiveness; 3) 'Will be protective' which is used when the remedy under construction is anticipated to be protective on completion; 4) 'Protectiveness deferred' which is typically used when additional information is needed; and 5) 'Not protective' which is used when risks are not under control. Reviewing only on the appropriate operable units, and supporting the analysis of remedy performance with focused data, the resulting protectiveness determinations and overall effectiveness of the document were significantly improved. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Early-Late Heterobimetallic Complexes Linked by Phosphinoamide Ligands. Tuning Redox Potentials and Small Molecule Activation

Recent attention in the chemical community has been focused on the energy efficient and environmentally benign conversion of abundant small molecules (CO 2 , H 2 O, etc.) to useful liquid fuels. This project addresses these goals by examining fundamental aspects of catalyst design to ultimately access small molecule activation processes under mild conditions. Specifically, Thomas and coworkers have targetted heterobimetallic complexes that feature metal centers with vastly different electronic properties, dictated both by their respective positions on the periodic table and their coordination environment. Unlike homobimetallic complexes featuring identical or similar metals, the bonds between metals in early/late heterobimetallics are more polarized, with the more electron-rich late metal center donating electron density to the more electron-deficient early metal center. While metal-metal bonds pose an interesting strategy for storing redox equivalents and stabilizing reactive metal fragments, the polar character of metal-metal bonds in heterobimetallic complexes renders these molecules ideally poised to react with small molecule substrates via cleavage of energy-rich single and double bonds. In addition, metal-metal interactions have been shown to dramatically affect redox potentials and promote multielectron redox activity, suggesting that metal-metal interactions may provide a mechanism to tune redox potentials and access substrate reduction/activation at mild overpotentials. This research project has provided a better fundamental understanding of how interactions between transition metals can be used as a strategy to promote and/or control chemical transformations related to the clean production of fuels. While this project focused on the study of homogeneous systems, it is anticipated that the broad conclusions drawn from these investigations will be applicable to heterogeneous catalysis as well, particularly on heterogeneous processes that occur at interfaces in multicomponent systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

RES-E-NEXT: Next Generation of RES-E Policy Instruments

The rapid deployment of renewable sources of electricity (RES-E) is transforming power systems globally. This trend is likely to continue with large increases in investment and deployment of RES-E capacity over the coming decades. Several countries now have penetration levels of variable RES-E generation (i.e., wind and solar) in excess of 15% of their annual electricity generation; and many jurisdictions (e.g., Spain, Portugal, Ireland, Germany, and Denmark; and, in the United States, Colorado) have experienced instantaneous penetration levels of more than 50% variable generation.1 These penetration levels of variable RES-E have prompted many jurisdictions to begin modifying practices that evolved in an era of readily dispatchable, centralised power systems. Providing insights for the transition to high levels of variable RES-E generation is the focus of this document, which is the final report of the RES-E-NEXT project commissioned by the International Energy Agency’s implementing agreement on Renewable Energy Technology Deployment (IEA-RETD). It presents a comprehensive assessment of issues that will shape power system evolution during the transition to high levels of variable RES-E generation. While policy will be a central tool to sustain the growth of RES-E capacity and to enable power system transitions, the scope of the report extends beyond policy considerations to include the related domains of regulation, power market design, and system operation protocols. This broad scope is in recognition that a changing resource mix with greater penetration levels of variable RES-E has broad implications for grid operations, wholesale and retail power markets, and infrastructure needs. The next decade will be a critical transition period for power system stakeholders, as global deployment of RES-E capacity (and especially variable RES-E capacity) continues to scale-up in many regions of the world. To address increased penetration levels of RES-E in power systems and the new challenges that could emerge, coordinated portfolios of policies, market designs, regulations, and operational protocols are essential. The goal for policymakers is to facilitate investment in RES-E technologies and to enable efficient and reliable system operation, costeffective service delivery, and continued public acceptance. Although the factors that impact the speed and scale of RES-E deployment manifest uniquely in each power system, in the transition to high shares of variable RES-E this report identifies four critical domains and the changing drivers that will shape next-generation policy for each. These domains are introduced in Table I, and comprise the major sections of this report.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

Modularization of EDGE Workflows Using Nextflow: Improving the Efficiency and Maintainability of Bioinformatics Software

EDGE is a bioinformatics platform developed in 2016 by researchers at Los Alamos National Laboratory (LANL) to facilitate the analysis of next-generation sequencing data by researchers with varying levels of experience in bioinformatics (Li et al., 2017). Users with single-end, paired-end or long-read sequencing data can provide their reads as input to EDGE and select the combination of workflows to run that are most useful for their research (e.g., quality control of reads, genome assembly, or the taxonomic classification of input reads). Table 1 summarizes the modules available in EDGE. EDGE is available as a web platform at https://edgebioinformatics.org, as installable source code maintained on GitHub under a GPLv3 license, and as a publicly hosted Docker image.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Ultra Barrier Topsheet Film for Flexible Photovoltaics with 3M Company

In this DOE sponsored program, 3M achieved the critical UBT features to enable durable flexible high efficiency modules to be produced by a range of customers who have now certified the 3M UBT and are actively developing said flexible modules. The specific objectives and accomplishments of the work under this program were; Scale-up the current Generation-1 UBT from 12” width, as made on 3M’s pilot line, to 1+meter width full-scale manufacturing, while maintaining baseline performance metrics (see table below); This objective was fully met; Validate service life of Generation-1 UBT for the 25+ year lifetime demanded by the photovoltaic market; Aggressive testing revealed potential failure modes in the Gen 1 UBT. Deficiencies were identified and corrective action taken in the Gen 2 UBT; Develop a Generation-2 UBT on the pilot line, targeting improved performance relative to baseline, including higher %T (percent transmission), lower water vapor transmission rate (WVTR) with targets based on what the technology needs for 25 year lifetime, proven lifetime of 25 years in solar module construction in the field, and lower cost; Testing of UBT Gen 2 under a wide range of conditions presented in this report failed to reveal any failure mode. Therefore UBT Gen 2 is known to be highly durable. 3M will continue to test towards statistically validating a 25 year lifetime under 3M funding; Transfer Generation-2 UBT from the pilot line to the full-scale manufacturing line within three years; and This objective was fully met.

14 SOLAR ENERGY↗
DOE OSTI2026

2025 Annual INMM Graph and Tables for High Purity Germanium Detector Normalization Presentation

The data set includes gamma spectroscopy peak data for measurements taken with two different high purity germanium detectors using a mixed nuclide source and a U-235 fuel rod. There are a total of 5 specific energy peaks that were analyzed for the mixed nuclide source stemming from Am-241, Cd-109, Cs-137, and Co-60. There are a total of 3 specific energy peaks that were analyzed for the U-235 fuel rod. The data set includes the calculations and results from using a linear correction factor, absolute efficiency curve, and relative efficiency curve to compare the net peaks counts from two different detectors.

Drumm, Natalie Daphne [Sandia National Laboratorie↗
DOE OSTI2014

Efficacy of fixed filtration for rapid kVp-switching dual energy x-ray systems

Purpose: Dose efficiency of dual kVp imaging can be improved if the two beams are filtered to remove photons in the common part of their spectra, thereby increasing spectral separation. While there are a number of advantages to rapid kVp-switching for dual energy, it may not be feasible to have two different filters for the two spectra. Therefore, the authors are interested in whether a fixed added filter can improve the dose efficiency of kVp-switching dual energy x-ray systems. Methods: The authors hypothesized that a K-edge filter would provide the energy selectivity needed to remove overlap of the spectra and hence increase the precision of material separation at constant dose. Preliminary simulations were done using calcium and water basis materials and 80 and 140 kVp x-ray spectra. Precision of the decomposition was evaluated based on the propagation of the Poisson noise through the decomposition function. Considering availability and cost, the authors chose a commercial Gd{sub 2}O{sub 2}S screen as the filter for their experimental validation. Experiments were conducted on a table-top system using a phantom with various thicknesses of acrylic and copper and 70 and 125 kVp x-ray spectra. The authors kept the phantom exposure roughly constant with and without filtration by adjusting the tube current. The filtered and unfiltered raw data of both low and high energy were decomposed into basis material and the variance of the decomposition for each thickness pair was calculated. To evaluate the filtration performance, the authors measured the ratio of material decomposition variance with and without filtration. Results: Simulation results show that the ideal filter material depends on the object composition and thickness, and ranges across the lanthanide series, with higher atomic number filters being preferred for more attenuating objects. Variance reduction increases with filter thickness, and substantial reductions (40%) can be achieved with a 2× loss in intensity. The authors’ experimental results validate the simulations, yet were overall slightly worse than expectation. For large objects, conventional (non-K-edge) beam hardening filters perform well. Conclusions: This study demonstrates the potential of fixed K-edge filtration to improve the dose efficiency and material decomposition precision for rapid kVp-switching dual energy systems.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

SU-F-P-18: Development of the Technical Training System for Patient Set-Up Considering Rotational Correction in the Virtual Environment Using Three-Dimensional Computer Graphic Engine

Purpose: Patient set-up skills in radiotherapy treatment room have a great influence on treatment effect for image guided radiotherapy. In this study, we have developed the training system for improving practical set-up skills considering rotational correction in the virtual environment away from the pressure of actual treatment room by using three-dimensional computer graphic (3DCG) engine. Methods: The treatment room for external beam radiotherapy was reproduced in the virtual environment by using 3DCG engine (Unity). The viewpoints to perform patient set-up in the virtual treatment room were arranged in both sides of the virtual operable treatment couch to assume actual performance by two clinical staffs. The position errors to mechanical isocenter considering alignment between skin marker and laser on the virtual patient model were displayed by utilizing numerical values expressed in SI units and the directions of arrow marks. The rotational errors calculated with a point on the virtual body axis as the center of each rotation axis for the virtual environment were corrected by adjusting rotational position of the body phantom wound the belt with gyroscope preparing on table in a real space. These rotational errors were evaluated by describing vector outer product operations and trigonometric functions in the script for patient set-up technique. Results: The viewpoints in the virtual environment allowed individual user to visually recognize the position discrepancy to mechanical isocenter until eliminating the positional errors of several millimeters. The rotational errors between the two points calculated with the center point could be efficiently corrected to display the minimum technique mathematically by utilizing the script. Conclusion: By utilizing the script to correct the rotational errors as well as accurate positional recognition for patient set-up technique, the training system developed for improving patient set-up skills enabled individual user to indicate efficient positional correction methods easily.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Interlinked tuples in coordination namespace

A system and method for supporting tuple record interlinking in one or more tuple space/coordinated namespace (CNS) extended memory storage systems. A system-wide CNS provides for efficient storing and communicating of data generated by local processes running at the nodes, and coordinated to generate a union/intersection of multiple CNS where tuple records are interlinked in multiple CNS hashtables, and/or share tuple data between two sets of processes that are part of different CNSs. Local node processes further generate multi-key tuples where two or more tuple records are interlinked within the same CNS hash table, thereby permitting a look up of the tuple data by either tuple name/keys. A CNS controller further provides a tuple iterator for a key-value storage in a CNS system that adds more links between tuples enables creation of iterator structures such as linked list or trees etc. of “different” tuples in a tuple database.

Jacob, Philip↗
DOE OSTI2026

One-Step Relativistic Driven Similarity Renormalization Group Multireference Perturbation Theory

We present an efficient implementation of a one-step relativistic second-order multireference perturbation theory based on the multireference driven similarity renormalization group (MR-DSRG) using the exact two-component (X2C) Hamiltonian, which we denote X2C-DSRG-MRPT2. We show that the X2C-DSRG-MRPT2 method can accurately capture spin–orbit coupling (SOC) effects in the electronic structure of strongly correlated systems containing elements across the periodic table. We further demonstrate that the X2C-DSRG-MRPT2 method, through its variational treatment of SOC effects, can yield spin–orbit splittings with mean absolute percentage errors consistently below 7% with respect to experimental values for systems containing up to sixth row elements. With its modest computational scaling (fourth power in system size for the perturbative step) and high accuracy, X2C-DSRG-MRPT2 provides a promising avenue for the routine treatment of relativistic effects in strongly correlated molecular systems.

Hamiltonians↗
DOE OSTI2026

CO2 Handling & Electrolyzer Efficiency Scaling Evaluator

CHEESE is an interactive dashboard tool for estimating the performance and material requirements of carbon dioxide electrolysis systems. It helps users evaluate how electrode area, current density, product selectivity, gas flow, cell voltage, and the number of cells in a stack affect system operation. The dashboard provides simple and advanced modes so it can be used for both quick estimates and more detailed engineering analysis. Users can estimate product output, carbon dioxide use, electrical power, electrode area, gas and liquid flow rates, energy efficiency, material cost per test, and the effect of scaling from a single cell to a multi cell stack. It also includes tools for examining carbon balance, equipment durability, component replacement, and changes in performance over time. This is intended to help both academia and industry researchers who are either getting into CO2 electrolysis on lab-scale or are trying to establish a larger footprint. CHEESE presents results through tables, charts, and simplified cell and stack diagrams. It is intended to support research planning, experimental design, comparison of operating conditions, and early stage scale up studies.

Prajapati, Aditya [Lawrence Livermore National Lab↗
DOE OSTI2016

Metamodeling of Droplet Activation for Global Climate Models

The nucleation of cloud droplets from the ambient aerosol is a critical physical process that must be resolved for global models to faithfully predict aerosol–cloud interactions and aerosol indirect effects on climate. To better represent droplet nucleation from a complex, multimodal, and multicomponent aerosol population within the context of a global model, a new metamodeling framework is applied to derive an efficient and accurate activation parameterization. The framework applies polynomial chaos expansion to a detailed parcel model in order to derive an emulator that maps thermodynamic and aerosol parameters to the supersaturation maximum achieved in an adiabatically ascending parcel and can be used to diagnose droplet number from a single lognormal aerosol mode. The emulator requires much less computational time to build, store, and evaluate than a high-dimensional lookup table. Compared to large sample sets from the detailed parcel model, the relative error in the predicted supersaturation maximum and activated droplet number computed with the best emulator is and (one standard deviation), respectively. On average, the emulators constructed here are as accurate and between 10 and 17 times faster than a leading physically based activation parameterization. Because the underlying parcel model being emulated resolves size-dependent droplet growth factors, the emulator captures kinetic limitations on activation. Furthermore, the results discussed in this work suggest that this metamodeling framework can be extended to accurately account for the detailed activation of a complex aerosol population in an arbitrary coupled global aerosol–climate model.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Oak Ridge National Laboratory DOE Site Sustainability Plan (SSP) with FY 2013 Performance Data

Oak Ridge National Laboratory (ORNL) is both the largest science and energy laboratory of the US Department of Energy (DOE) and one of the oldest national laboratories still operating at its original site. These characteristics provide the Sustainable Campus Initiative (SCI) both a unique opportunity and a unique challenge to integrate sustainability into facilities and activities. As outlined in this report, SCI is leveraging the outcomes of ORNL’s DOE-sponsored research and development programs to maximize the efficient use of energy and natural resources across ORNL. Wherever possible, ORNL is integrating technical innovations into new and existing facilities, systems, and processes with a widespread approach to achieving Executive Order 13514. ORNL continues to pursue and deploy innovative solutions and initiatives to advance regional, national, and worldwide sustainability and continues to transform its culture and engage employees in supporting sustainability at work, at home, and in the community. Table 1 summarizes ORNL's FY 2013 performance and planned actions to attain future goals. ORNL has achieved numerous successes during FY 2013, which are described in detail throughout this document.

Nichols, Teresa A.↗