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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Argobots: A Lightweight Low-Level Threading and Tasking Framework

In the past few decades, a number of user-level threading and tasking models have been proposed in the literature to address the shortcomings of OS-level threads, primarily with respect to cost and flexibility. Current state-of-the-art user-level threading and tasking models, however, are either too specific to applications or architectures or are not as powerful or flexible. In this paper, we present Argobots, a lightweight, low-level threading and tasking framework that is designed as a portable and performant substrate for high-level programming models or runtime systems. Argobots offers a carefully designed execution model that balances generality of functionality with providing a rich set of controls to allow specialization by the user or high-level programming model. We describe the design, implementation, and optimization of Argobots and present integrations with three example high-level models: OpenMP, MPI, and co-located I/O service. Evaluations show that (1) Argobots outperforms existing generic threading runtimes; (2) our OpenMP runtime offers more efficient interoperability capabilities than production OpenMP runtimes do; (3) when MPI interoperates with Argobots instead of Pthreads, it enjoys reduced synchronization costs and better latency hiding capabilities; and (4) I/O service with Argobots reduces interference with co-located applications, achieving performance competitive with that of the Pthreads version.

Seo, Sangmin (ORCID:0000000295159836)↗
DOE OSTI2017

Melter feed viscosity during conversion to glass: Comparison between low-activity waste and high-level waste feeds

During nuclear waste vitrification, a melter feed (generally a slurry-like mixture of a nuclear waste and various glass forming and modifying additives) is charged into the melter where undissolved refractory constituents are suspended together with evolved gas bubbles from complex reactions. Knowledge of flow properties of various reacting melter feeds is necessary to understand their unique feed-to-glass conversion processes occurring within a floating layer of melter feed called a cold cap. The viscosity of two low-activity waste (LAW) melter feeds were studied during heating and correlated with volume fractions of undissolved solid phase and gas phase. In contrast to the high-level waste (HLW) melter feed, the effects of undissolved solid and gas phases play comparable roles and are required to represent the viscosity of LAW melter feeds. This study can help bring physical insights to feed viscosity of reacting melter feeds with different compositions and foaming behavior in nuclear waste vitrification.

Jin, Tongan↗
DOE OSTI2024

Reliability of Copper Inverse Opal Surfaces for Extreme-Heat-Flux Micro-Coolers in Low-Global-Warming-Potential Refrigerant R-1233zd Pool Boiling Experiments

This presentation provides a brief snapshot of the InterPACK paper InterPACK2023-113781. The paper explores copper inverse opal (CIO) surface reliability in pool boiling experiments in water and a new, low-global-warming-potential (GWP = 1) hydrofluoroolefin (HFO) refrigerant R-1233zd. The CIO-based structure is intended to develop enhanced two-phase heat transfer surfaces for extreme-heat-flux (approximately 1 kW/cm2) micro-coolers. In this study, a limited number of pool boiling experiments were performed using water and HFO-1233zd fluid, and the reliability of the CIO-based surfaces was evaluated. Critical heat flux (CHF) values in HFO-1233zd at 40 Degrees Celsius to 45 Degrees Celsius saturation temperatures and the corresponding saturation pressures were also measured. The CHF values with the refrigerant are significantly lower compared to those with water, but the refrigerant allows for a wider usable temperature range in the end application of the micro-coolers and is not limited to data centers with controlled ambient conditions. Reliability experiments with CIO surface samples - involving pool boiling with water on the CIO surfaces for approximately 48 hours and with HFO-1233zd for 144 hours - showed no structural degradation of the enhanced surface or any significant performance drop in heat transfer coefficients. The CIO surface samples in water were oxidized, most likely due to the presence of air in water and in the experimental vessel.

critical heat flux↗
DOE OSTI2014

Low sheet resistance titanium nitride films by low-temperature plasma-enhanced atomic layer deposition using design of experiments methodology

A design of experiments methodology was used to optimize the sheet resistance of titanium nitride (TiN) films produced by plasma-enhanced atomic layer deposition (PE-ALD) using a tetrakis(dimethylamino)titanium precursor in a N{sub 2}/H{sub 2} plasma at low temperature (250 °C). At fixed chamber pressure (300 mTorr) and plasma power (300 W), the plasma duration and N{sub 2} flow rate were the most significant factors. The lowest sheet resistance values (163 Ω/sq. for a 20 nm TiN film) were obtained using plasma durations ∼40 s, N{sub 2} flow rates >60 standard cubic centimeters per minute, and purge times ∼60 s. Time of flight secondary ion mass spectroscopy data revealed reduced levels of carbon contaminants in the TiN films with lowest sheet resistance (163 Ω/sq.), compared to films with higher sheet resistance (400–600 Ω/sq.) while transmission electron microscopy data showed a higher density of nanocrystallites in the low-resistance films. Further significant reductions in sheet resistance, from 163 Ω/sq. to 70 Ω/sq. for a 20 nm TiN film (corresponding resistivity ∼145 μΩ·cm), were achieved by addition of a postcycle Ar/N{sub 2} plasma step in the PE-ALD process.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Low Voltage, Low Power Organic Light Emitting Transistors for AMOLED Displays

Low voltage, low power dissipation, high aperture ratio organic light emitting transistors are demonstrated. The high level of performance is enabled by a carbon nanotube source electrode that permits integration of the drive transistor and the organic light emitting diode into an efficient single stacked device. Given the demonstrated performance, this technology could break the technical logjam holding back widespread deployment of active matrix organic light emitting displays at flat panel screen sizes.

McCarthy, M. A.↗
DOE OSTI2016

Formation of the low-resistivity compound Cu{sub 3}Ge by low-temperature treatment in an atomic hydrogen flux

The systematic features of the formation of the low-resistivity compound Cu{sub 3}Ge by low-temperature treatment of a Cu/Ge two-layer system in an atomic hydrogen flux are studied. The Cu/Ge two-layer system is deposited onto an i-GaAs substrate. Treatment of the Cu/Ge/i-GaAs system, in which the layer thicknesses are, correspondingly, 122 and 78 nm, in atomic hydrogen with a flux density of 10{sup 15} at cm{sup 2} s{sup –1} for 2.5–10 min at room temperature induces the interdiffusion of Cu and Ge, with the formation of a polycrystalline film containing the stoichiometric Cu{sub 3}Ge phase. The film consists of vertically oriented grains 100–150 nm in size and exhibits a minimum resistivity of 4.5 µΩ cm. Variations in the time of treatment of the Cu/Ge/i-GaAs samples in atomic hydrogen affect the Cu and Ge depth distribution, the phase composition of the films, and their resistivity. Experimental observation of the synthesis of the Cu{sub 3}Ge compound at room temperature suggests that treatment in atomic hydrogen has a stimulating effect on both the diffusion of Cu and Ge and the chemical reaction of Cu{sub 3}Ge-compound formation. These processes can be activated by the energy released upon the recombination of hydrogen atoms adsorbed at the surface of the Cu/Ge/i-GaAs sample.

36 MATERIALS SCIENCE↗
DOE OSTI2026

ObstacleSense: Low-Power Neuromorphic Vision for Corridor Obstacle Awareness in Low-Level ADAS

The automotive industry’s pursuit of Level 5 autonomy is constrained by substantial perception-compute power requirements, often reaching 1, 000 + watts in full autonomy stacks. Reducing this energy burden requires rethinking perception not only at the high-end autonomy level, but also at the foundational Advanced Driver Assistance Systems (ADAS) level where low-power, safety-critical sensing can have broad impact. Neuromorphic vision provides a promising starting point: HD Dynamic Vision Sensors (DVS) can operate below 100 mW at the sensor level by reporting only asynchronous brightness changes. However, low-power sensing alone is insufficient if downstream perception reintroduces dense, energy-intensive computation. In particular, many event-driven object-detection pipelines still rely on CNN backbones, while purely spiking alternatives often trade away accuracy or ignore deployment constraints. We introduce ObstacleSense, a highly compact, CNN-free hybrid ANN–SNN framework for Level 0–1 forward-corridor obstacle awareness. Instead of performing full-scene object detection with a convolutional feature backbone, ObstacleSense targets the safety-critical question of whether the ego corridor is occupied and how far the nearest obstacle is. The architecture combines polarity-conditioned event encoding, lightweight temporal spiking dynamics, axial spatial mixing, and coarse-to-fine range estimation within a regular fixed-grid compute pattern. This design avoids the dense CNN backbone commonly used in event-based detection while maintaining a small state footprint suitable for eventual small-FPGA deployment. Before hardware mapping, we evaluate the software implementation using a model-side power proxy derived from MACs, weight and activation traffic, and spiking state updates under shared FP16 assumptions. On simulated CARLA event corpora, the deployment-oriented model achieves 0.9464 objectness F1, 0.9978 grid-level mAP, and 0.8987 m distance Mean Absolute Error at an estimated 1.92 mW proxy cost, while maintaining performance on unseen generalization test sequences.

Johnson-Scott, Zac [ORNL]↗
DOE OSTI2011

High‐Resolution Numerical Simulation and Analysis of Mach ReflectionStructures in Detonation Waves in Low‐Pressure H 2 –O 2 –Ar Mixtures: A Summary of Results Obtained with the Adaptive Mesh Refinement Framework AMROC

Numerical simulation can be key to the understanding of the multidimensional nature of transient detonation waves. However, the accurate approximation of realistic detonations is demanding as a wide range of scales needs to be resolved. This paper describes a successful solution strategy that utilizes logically rectangular dynamically adaptive meshes. The hydrodynamic transport scheme and the treatment of the nonequilibrium reaction terms are sketched. A ghost fluid approach is integrated into the method to allow for embedded geometrically complex boundaries. Large‐scale parallel simulations of unstable detonation structures of Chapman‐Jouguet detonations in low‐pressure hydrogen‐oxygen‐argon mixtures demonstrate the efficiency of the described techniques in practice. In particular, computations of regular cellular structures in two and three space dimensions and their development under transient conditions, that is, under diffraction and for propagation through bends are presented. Some of the observed patterns are classified by shock polar analysis, and a diagram of the transition boundaries between possible Mach reflection structures is constructed.

Deiterding, Ralf↗
DOE OSTI2013

Real-time Molecular Study of Bystander Effects of Low dose Low LET radiation Using Living Cell Imaging and Nanoparticale Optics

In this study two novel approaches are proposed to investigate precisely the low dose low LET radiation damage and its effect on bystander cells in real time. First, a flow shear model system, which would provide us a near in vivo situation where endothelial cells in the presence of extra cellular matrix experiencing continuous flow shear stress, will be used. Endothelial cells on matri-gel (simulated extra cellular matrix) will be subjected to physiological flow shear (that occurs in normal blood vessels). Second, a unique tool (Single nano particle/single live cell/single molecule microscopy and spectroscopy; Figure A) will be used to track the molecular trafficking by single live cell imaging. Single molecule chemical microscopy allows one to single out and study rare events that otherwise might be lost in assembled average measurement, and monitor many target single molecules simultaneously in real-time. Multi color single novel metal nanoparticle probes allow one to prepare multicolor probes (Figure B) to monitor many single components (events) simultaneously and perform multi-complex analysis in real-time. These nano-particles resist to photo bleaching and hence serve as probes for unlimited timeframe of analysis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Low-Carbon City Policy Databook: 72 Policy Recommendations for Chinese Cities from the Benchmarking and Energy Savings Tool for Low Carbon Cities

This report is designed to help city authorities evaluate and prioritize more than 70 different policy strategies that can reduce their city’s energy use and carbon-based greenhouse gas emissions of carbon dioxide (CO 2 ) and methane (CH 4 ). Local government officials, researchers, and planners can utilize the report to identify policies most relevant to local circumstances and to develop a low carbon city action plan that can be implemented in phases, over a multi-year timeframe. The policies cover nine city sectors: industry, public and commercial buildings, residential buildings, transportation, power and heat, street lighting, water & wastewater, solid waste, and urban green space. See Table 1 for a listing of the policies. Recognizing the prominence of urban industry in the energy and carbon inventories of Chinese cities, this report includes low carbon city policies for the industrial sector. The policies gathered here have proven effective in multiple locations around the world and have the potential to achieve future energy and carbon savings in Chinese cities.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2017

A Novel Hybrid Reformer-Electrolyzer-Purifier (REP) for Distributed Production of Low-Cost, Low Greenhouse Gas Hydrogen

FuelCell Energy with support from the Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) has investigated the production of low-cost, low CO2 hydrogen using a molten carbonate fuel cell operating as an electrolyzer. We confirmed the feasibility of the technology by testing a large-scale short stack. Economic analysis was done with the assistance of the National Fuel Cell Center at the University of California, Irvine and we found the technology to be attractive, especially for distributed hydrogen. We explored the performance under various operating parameters and developed an accurate model for further analysis and development calculations. We achieved the expected results, meeting all program goals. We identified additional uses of the technology such as for CO2 capture, power storage, and power load leveling.

08 HYDROGEN↗
DOE OSTI2017

Development of ITM Oxygen Technology for Low-cost and Low-emission Gasification and Other Industrial Applications

Air Products carried out a scope of work under DOE Award No. DE-FE0012065 “Development of ITM Oxygen Technology for Low-cost and Low-emission Gasification and Other Industrial Applications” with subcontractors Ceramatec, Penn State, and WorleyParsons. The scope of work under this award was aimed at furthering the development of the Ion Transport Membrane (ITM) Oxygen production process toward a demonstration-scale facility known as the Oxygen Development Facility (ODF). Specific activities will help to enable design and construction of the ODF through advancement of a number of challenging technical elements that are required to manage risk in the initial deployment of ITM technology. Major objectives of the work included developing ITM Oxygen ceramic membrane materials with improved performance and reliability, optimizing ceramic module geometry and fabrication methods, testing module performance, trialing the improved fabrication process at commercial scale in the Ceramic Membrane Module Fabrication Facility (CerFab), and advancing engineering development of the ITM oxygen production process, including vessel design and contaminant control measures to prepare for deployment of the ODF. The comprehensive report that follows details the team’s work, which includes several notable accomplishments: 1) compressive creep, a likely limiter of ceramic module lifetime in service, was demonstrated to be retarded by an order of magnitude by changes in material formulation, module joining dimensions, and internal wafer geometry; 2) two promising new materials were shown to be superior to the incumbent ITM material in a key material parameter related to oxygen flux; 3) module degradation mechanisms were identified following operation in large pilot-scale equipment; 4) options for utilizing ITM in a coal-to-liquids (CTL) facility to enable liquids production with carbon capture were identified and studied; and 5) the benefits of potential improvements to the technology were assessed for their cost impact on ITM Oxygen applications to clean power, fuels, and other applications.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2015

Development of ITM Oxygen Technology for Low-cost and Low-emission Gasification and Other Industrial Applications

Air Products carried out a scope of work under DOE Award No. DE-FE0012065 “Development of ITM Oxygen Technology for Low-cost and Low-emission Gasification and Other Industrial Applications” with subcontractors Ceramatec, Penn State, and WorleyParsons. The scope of work under this award was aimed at furthering the development of the Ion Transport Membrane (ITM) Oxygen production process toward a demonstration-scale facility known as the Oxygen Development Facility (ODF). Specific activities will help to enable design and construction of the ODF through advancement of a number of challenging technical elements that are required to manage risk in the initial deployment of ITM technology. Major objectives of the work included developing ITM Oxygen ceramic membrane materials with improved performance and reliability, optimizing ceramic module geometry and fabrication methods, testing module performance, trialing the improved fabrication process at commercial scale in the Ceramic Membrane Module Fabrication Facility (CerFab), and advancing engineering development of the ITM oxygen production process, including vessel design and contaminant control measures to prepare for deployment of the ODF. The comprehensive report that follows details the team’s work, which includes several notable accomplishments: 1) compressive creep, a likely limiter of ceramic module lifetime in service, was demonstrated to be retarded by an order of magnitude by changes in material formulation, module joining dimensions, and internal wafer geometry; 2) two promising new materials were shown to be superior to the incumbent ITM material in a key material parameter related to oxygen flux; 3) module degradation mechanisms were identified following operation in large pilot-scale equipment; 4) options for utilizing ITM in a coal-to-liquids (CTL) facility to enable liquids production with carbon capture were identified and studied; and 5) the benefits of potential improvements to the technology were assessed for their cost impact on ITM Oxygen applications to clean power, fuels, and other applications.

42 ENGINEERING↗