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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 1,711 records · Page 95
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Deep learning at the edge enables real-time streaming ptychographic imaging

Abstract Coherent imaging techniques provide an unparalleled multi-scale view of materials across scientific and technological fields, from structural materials to quantum devices, from integrated circuits to biological cells. Driven by the construction of brighter sources and high-rate detectors, coherent imaging methods like ptychography are poised to revolutionize nanoscale materials characterization. However, these advancements are accompanied by significant increase in data and compute needs, which precludes real-time imaging, feedback and decision-making capabilities with conventional approaches. Here, we demonstrate a workflow that leverages artificial intelligence at the edge and high-performance computing to enable real-time inversion on X-ray ptychography data streamed directly from a detector at up to 2 kHz. The proposed AI-enabled workflow eliminates the oversampling constraints, allowing low-dose imaging using orders of magnitude less data than required by traditional methods.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Hydrogen-induced degradation dynamics in silicon heterojunction solar cells via machine learning

Abstract Among silicon-based solar cells, heterojunction cells hold the world efficiency record. However, their market acceptance is hindered by an initial 0.5% per year degradation of their open circuit voltage which doubles the overall cell degradation rate. Here, we study the performance degradation of crystalline-Si/amorphous-Si:H heterojunction stacks. First, we experimentally measure the interface defect density over a year, the primary driver of the degradation. Second, we develop SolDeg, a multiscale, hierarchical simulator to analyze this degradation by combining Machine Learning, Molecular Dynamics, Density Functional Theory, and Nudged Elastic Band methods with analytical modeling. We discover that the chemical potential for mobile hydrogen develops a gradient, forcing the hydrogen to drift from the interface, leaving behind recombination-active defects. We find quantitative correspondence between the calculated and experimentally determined defect generation dynamics. Finally, we propose a reversed Si-density gradient architecture for the amorphous-Si:H layer that promises to reduce the initial open circuit voltage degradation from 0.5% per year to 0.1% per year.

14 SOLAR ENERGY↗
DOE OSTI2018

Pyrene hydrogel for promoting direct bioelectrochemistry: ATP-independent electroenzymatic reduction of N 2

Enzymatic bioelectrocatalysis often requires an artificial redox mediator to observe significant electron transfer rates. The use of such mediators can add a substantial overpotential and obfuscate the protein's native kinetics, which limits the voltage of a biofuel cell and alters the analytical performance of biosensors. Herein, we describe a material for facilitating direct electrochemical communication with redox proteins based on a novel pyrene-modified linear poly(ethyleneimine). This method was applied for promoting direct bioelectrocatalytic reduction of O 2 by laccase and, by immobilizing the catalytic subunit of nitrogenase (MoFe protein), to demonstrate the ATP-independent direct electroenzymatic reduction of N 2 to NH 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Rosette-scan video-rate atomic force microscopy: Trajectory patterning and control design

We introduce an analysis and a systematic design methodology for a novel nonraster scan method based on a rosette pattern and demonstrate its application in video-rate atomic force microscopy. This pattern is traced when the lateral axes of a parallel kinematic scanner are commanded to follow a combination of two sinusoids with identical amplitudes and different frequencies. We create an internal-model-based controller to enhance the tracking performance of this pattern and implement the scheme on a microelectromechanical system scanner. The conclusions reveal high-precision tracking of the rosette pattern in order to acquire time-lapsed atomic force microscope images at the rate of 10 frames/s.

42 ENGINEERING↗
DOE OSTI2019

Control of hydrogen content and fuel recycling for long pulse high performance plasma operation in EAST

Control of fuel recycling and hydrogen content in the Experimental Advanced Superconducting Tokamak (EAST) using various methods is studied for high-power long pulse high confinement mode (H-mode) plasma operation. The results show that long duration first wall baking and discharge cleaning in EAST provides the necessary clean vacuum environment with a high ultimate vacuum of 3.6 × 10 -6 Pa and low outgassing rate of ~1.5 × 10 -4 Pa m 3 s -1 for plasma operation. In-vessel cryopumps are found to provide an efficient method for particle recycling control in the divertor region to decrease global recycling coefficient (R global ) from ~1.0 to ~0.8 during ohmic heating plasmas, and it provides a high particle exhausting rate of 10 20_ 10 21 D-atoms s -1 in high-power plasma operations. Long duration silicon coating is found to be more powerful than baking and discharge cleaning, which reduces the H/(H + D) ratio gradually to a value as low as 8%, and lithium coating is more effective and more efficient than silicon coating, to further reduce the H/(H + D) ratio to 3%. Real-time lithium powder injection is a novel method for recycling control, which reduces R global from 0.94 to 0.82 under lithium coating wall conditioning. By the combination and optimization of the above methods, H-mode plasmas with low hydrogen content and low fuel recycling have been achieved in EAST and have been extended gradually to 101 s in 2017. Recycling flux has even decreased gradually during 101 s H-mode plasmas due to increased first wall temperature and the resulting increased Li-II emission. These results provide valuable references on hydrogen content and fuel recycling control for long pulse H-mode plasmas of up to 400–1000 s with high-power heating in EAST and future fusion devices.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Evaluation of Advanced Phased-Array Techniques: Interim Results [Slides]

Report: “Evaluation of Advanced Phased-Array Techniques: Interim Results”, August 2023 ML23216A009, PNNL-34622 Results showed that detection rate drops as microstructures/materials become more complex Standard PA had the highest detection rates overall Detection rates in the CASS-CASS mockups were lowest overall FMC had the most accurate length sizing in the fine-grained WSS mockups. All methods struggled with length sizing in coarse-grained mockups SNR vs method depended on the specimen type SNR was consistently high with standard PA SNR was consistently the lowest with PWI FMC performed best on fine-grained WSS A lack of data received from some Round Robin participants resulted in low statistics for many of the analyses.

42 ENGINEERING↗
DOE OSTI2024

Evaluation of Advanced Phased-Array Techniques: Interim Results [Slides]

Report: “Evaluation of Advanced Phased-Array Techniques: Interim Results”, August 2023 ML23216A009, PNNL-34622 Results showed that detection rate drops as microstructures/materials become more complex Standard PA had the highest detection rates overall Detection rates in the CASS-CASS mockups were lowest overall FMC had the most accurate length sizing in the fine-grained WSS mockups. All methods struggled with length sizing in coarse-grained mockups SNR vs method depended on the specimen type SNR was consistently high with standard PA SNR was consistently the lowest with PWI FMC performed best on fine-grained WSS A lack of data received from some Round Robin participants resulted in low statistics for many of the analyses.

42 ENGINEERING↗
NASA NTRS1971

Dynamic testing of a single-degree-of-freedom strapdown gyroscope

Test methods and results are presented for the equivalent average input rate of a single-degree-of-freedom gyroscope operated both open loop and with a ternary-logic pulse-torque-to-balance loop during multiaxis angular oscillation. For the open-loop tests, good agreement was obtained with theoretical results. Two-axis testing was performed for oscillations about the Input-Output axes, the Input-Spin axes, and the Spin-Output axes. These tests run in the torque-to-balance mode revealed significant departures from open-loop results in the induced drift rate. An analysis is developed explaining much of the closed-loop data presented. Test data for the gryoscope in a ternary torque-to-balance loop with constant input rates is presented. The tests demonstrate that the instrument rate linearity does not change with interrogation frequency from 3,600 to 14,400 Hz if the torque coil is tuned to offer a resistive load to the current switch. Analysis cited shows that gyroscope lag compensation eliminates multiple pulsing and other equivalent forms of degraded resolution in a wide variety of quantizing loops. This result is test verified for the ternary delta-modulator loop.

Lory, C. B.↗
NASA NTRS1989

Multi-level bandwidth efficient block modulation codes

The multilevel technique is investigated for combining block coding and modulation. There are four parts. In the first part, a formulation is presented for signal sets on which modulation codes are to be constructed. Distance measures on a signal set are defined and their properties are developed. In the second part, a general formulation is presented for multilevel modulation codes in terms of component codes with appropriate Euclidean distances. The distance properties, Euclidean weight distribution and linear structure of multilevel modulation codes are investigated. In the third part, several specific methods for constructing multilevel block modulation codes with interdependency among component codes are proposed. Given a multilevel block modulation code C with no interdependency among the binary component codes, the proposed methods give a multilevel block modulation code C which has the same rate as C, a minimum squared Euclidean distance not less than that of code C, a trellis diagram with the same number of states as that of C and a smaller number of nearest neighbor codewords than that of C. In the last part, error performance of block modulation codes is analyzed for an AWGN channel based on soft-decision maximum likelihood decoding. Error probabilities of some specific codes are evaluated based on their Euclidean weight distributions and simulation results.

Lin, Shu↗
NASA NTRS2006

Insitu Calibration of Quartz Crystal Microbalances

Computer models that predict the rate at which molecular contamination will deposit on optical surfaces typically use outgassing source terms, measured with quartz crystal microbalances, as a basis for the prediction. The American Society of Testing and Materials, Standard Test Method for Contamination Outgassing Characteristics of Spacecraft Materials (Method E-1559), is probably the best know technique used by the aerospace community to measure the outgassing rates or source terms of materials. A simple method for the insitu calibration of quartz crystal microbalances, based on the heat of enthalphy of Adipic Acid, has been developed and demonstrated by the Marshall Space Flight Center, Environmental Effects Group. The calibration has been demonstrated over a sample temperature range of 25 to 66 degrees Celsius and deposition rates of 7 x 10 (exp -11) grams/cm(sup 2)-s and greater, for several measurement system configurations. This calibration technique is fully compatible with the American Society for Testing and Materials, Method E-1559, as well as other methodology. The calibration requires no modification of outgassing facilities employing an effusion cell and does not degrade the performance or function of typical vacuum systems.

Albyn, Keith↗
NASA NTRS2012

Indirect M-MRAC for Systems with Time Varying Parameters and Bounded Disturbances

The paper presents a prediction-identification model based adaptive control method for uncertain systems with time varying parameters in the presence of bounded external disturbances. The method guarantees desired tracking performance for the system s state and input signals. This is achieved by feeding back the state prediction error to the identification model. It is shown that the desired closed-loop properties are obtained with fast adaptation when the error feedback gain is selected proportional to the square root of the adaptation rate. The theoretical findings are confirmed via a simulation example.

Stepanyan, Vahram↗
NASA NTRS2015

The Structural Heat Intercept-Insulation-Vibration Evaluation Rig (SHIVER)

NASA is currently investigating methods to reduce the boil-off rate on large cryogenic upper stages. Two such methods to reduce the total heat load on existing upper stages are vapor cooling of the cryogenic tank support structure and integration of thick multilayer insulation systems to the upper stage of a launch vehicle. Previous efforts have flown a 2-layer MLI blanket and shown an improved thermal performance, and other efforts have ground-tested blankets up to 70 layers thick on tanks with diameters between 2 3 meters. However, thick multilayer insulation installation and testing in both thermal and structural modes has not been completed on a large scale tank. Similarly, multiple vapor cooled shields are common place on science payload helium dewars; however, minimal effort has gone into intercepting heat on large structural surfaces associated with rocket stages. A majority of the vapor cooling effort focuses on metallic cylinders called skirts, which are the most common structural components for launch vehicles. In order to provide test data for comparison with analytical models, a representative test tank is currently being designed to include skirt structural systems with integral vapor cooling. The tank is 4 m in diameter and 6.8 m tall to contain 5000 kg of liquid hydrogen. A multilayer insulation system will be designed to insulate the tank and structure while being installed in a representative manner that can be extended to tanks up to 10 meters in diameter. In order to prove that the insulation system and vapor cooling attachment methods are structurally sound, acoustic testing will also be performed on the system. The test tank with insulation and vapor cooled shield installed will be tested thermally in the B2 test facility at NASAs Plumbrook Station both before and after being vibration tested at Plumbrooks Space Power Facility.

Cryogenic Fluid Management↗
NASA NTRS2017

Structural Heat Intercept, Insulation, and Vibration Evaluation Rig (SHIIVER)

Abstract: NASA is currently investigating methods to reduce the boil-off rate on large cryogenic upper stages. Two such methods to reduce the total heat load on existing upper stages are vapor cooling of the cryogenic tank support structure and integration of thick multilayer insulation systems to the upper stage of a launch vehicle. Previous efforts have flown a 2-layer MLI blanket and shown an improved thermal performance, and other efforts have ground-tested blankets up to 70 layers thick on tanks with diameters between 2 3 meters. However, thick multilayer insulation installation and testing in both thermal and structural modes has not been completed on a large scale tank. Similarly, multiple vapor cooled shields are common place on science payload helium dewars; however, minimal effort has gone into using boil-off to intercept heat on large structural surfaces associated with rocket stages. A majority of the vapor cooling effort focuses on metallic cylinders called skirts, which are the most common structural components for launch vehicles. In order to provide test data for comparison with analytical models, a 4 meter diameter test tank and assembly is currently being designed to include skirt structural systems with integral vapor cooling. In order to give a more representative result for actual applications, the technologies will be designed for an 8.4 m and scaled down to a 4 meter tank. In order to prove that the insulation system and vapor cooling attachment methods are structurally sound, acoustic testing will also be performed on the system. The test tank with insulation and vapor cooled shield installed will be tested thermally in the B2 test facility at NASAs Plum Brook Station both before and after being vibration tested at Plum Brooks Space Power Facility.

Johnson, Wesley↗
NASA NTRS2023

Investigating Abrasion Effects of Lunar Simulant Grain Sizes on Candidate Spacesuit Fabric

Lunar dust is identified as one of the most significant challenges during the Apollo exploration missions due to its extremely abrasive and electrostatic characteristics. As NASA and the space industry prepare for the upcoming Artemis missions, researching and testing with lunar simulant is quintessential to understanding the effects of lunar dust on the systems and equipment that will be deployed on the lunar surface. Testing will also provide paths that lead to developing technologies and cleaning tools that could be used for dust mitigation. Additionally, it is expected that any hardware that will be exposed to the dusty environment should undergo rigorous testing to ensure it will maintain long-term performance and operate on the lunar surface. For this study, exterior spacesuit fabric was observed. Abrasion is one of the main concerns of lunar dust exposure for spacesuit fabric. Three different abrasion methods were chosen: a rotary tumbler, the Martindale method, and Accelerotor. These abrasion methods were tested on coated and uncoated spacesuit material, Orthofabric, to understand the abrasion rates of sieved lunar simulant and investigate if the addition of ceramic coating mitigated dust abrasion. To summarize, the testing results provided that larger grains are more abrasive than smaller grains, and the selected ceramic coatings did not minimize abrasion during the controlled abrasion tests. It is important to note that the selected ceramic coatings were not designed or intended to provide protection from the abrasive lunar environment. It is recommended to select additional ceramic coatings with an elevated TRL of 5 or greater for testing with Orthofabric and lunar simulant. As an additional note, contact angle measurements were not accounted for in coating selection and should be a factor when selecting adhesion resistant coatings for lunar dust.

grain size↗
NASA NTRSDate not supplied

Fluid & Thermal Analysis of a Manifold Microchannel Heat Sink

A three-dimensional (3-D) numerical model has been developed to study the fluid flow and heat transfer through a manifold-microchannel (MMC) heat sink, a microfluidic cooling system designed as a heat dissipation solution for compact, high-powered electronic systems. An MMC consists of a 3-D manifold structure that distributes working fluid through alternating inlet and outlet manifold channels that guide the fluid to and from the microchannels, shortening the flow length and thereby, reducing the pressure drop across the system. Wide bandgap semiconductors such as silicon carbide (SiC) are increasingly utilized due to their ability to enable smaller electronic devices and components to operate more efficiently at higher frequencies. These semiconductors can greatly benefit from the MMC, which can extract all the heat produced by compact, high-powered electronics, enabling them to achieve optimal performance. The MMC also utilizes an embedded cooling approach which allows for fabrication directly within SiC-based electronics, resulting in significant mass and weight savings and lower thermal resistance than conventional heat sink designs. This paper outlines the methods used to conduct fluid and thermal analysis of different MMC configurations for flow parameters such as flow rate and inlet flow conditions. This study involves both steady state and transient thermal analysis as a gradually increasing heat flux is applied to the system over time, which is representative of the heat dissipation from the electronics over a given period. Results from the analysis show that the MMC is capable of effectively dissipating heat flux of ~100 W/cm2 while maintaining considerably low pressure drop (< 1 kPa) and thermal resistance (< 1 K/W) for certain single-phase working fluids.

manifold microchannel↗
NASA NTRSDate not supplied

Fluid & Thermal Analysis of a Manifold Microchannel Heat Sink

A three-dimensional (3-D) numerical model has been developed to study the fluid flow and heat transfer through a manifold-microchannel (MMC) heat sink, a microfluidic cooling system designed as a heat dissipation solution for compact, high-powered electronic systems. An MMC consists of a 3-D manifold structure that distributes working fluid through alternating inlet and outlet manifold channels that guide the fluid to and from the microchannels, shortening the flow length and thereby, reducing the pressure drop across the system. Wide bandgap semiconductors such as silicon carbide (SiC) are increasingly utilized due to their ability to enable smaller electronic devices and components to operate more efficiently at higher frequencies. These semiconductors can greatly benefit from the MMC, which can extract all the heat produced by compact, high-powered electronics, enabling them to achieve optimal performance. The MMC also utilizes an embedded cooling approach which allows for fabrication directly within SiC-based electronics, resulting in significant mass and weight savings and lower thermal resistance than conventional heat sink designs. This paper outlines the methods used to conduct fluid and thermal analysis of different MMC configurations for flow parameters such as flow rate and inlet flow conditions. This study involves both steady state and transient thermal analysis as a gradually increasing heat flux is applied to the system over time, which is representative of the heat dissipation from the electronics over a given period. Results from the analysis show that the MMC is capable of effectively dissipating heat flux of ~100 W/cm2 while maintaining considerably low pressure drop (< 1 kPa) and thermal resistance (< 1 K/W) for certain single-phase working fluids.

manifold microchannel↗
NASA NTRS2026

Fatigue Life of Flow-Formed Aluminum 2195 and 6061 Alloys

The successful design and fabrication of metallic cryotanks for commercial aviation applications require lightweight, durable materials capable of withstanding high pressures and cryogenic temperatures through tens of thousands of thermomechanical refueling cycles. Flow forming is an advanced manufacturing technique that offers high-rate production and scalability for fabricating integrally stiffened cylinders suitable for cryotank applications. This work establishes the durability of flow-formed aluminum alloys by characterizing their fatigue life performance under conditions that mimic cryotank refueling cycles. Residual stresses in flow-formed aluminum-lithium (Al-Li) 2195-T6 cylinders were assessed using the contour method and found to be minimal. Fatigue life testing was conducted on flow-formed Al-Li 2195-T6 at room temperature and cryogenic temperatures (-321°F [-196°C]), with wrought Al-Li 2195-T6 serving as a baseline for comparison. Results showed that flow-formed materials exhibited fatigue performance comparable to or better than wrought materials, with no statistically significant differences observed between different specimen orientations relative to processing directions. Fractography revealed reduced delaminations in the flow-formed Al-Li 2195 samples as compared to wrought, indicating potential improvement to the microstructure that could result in improved service properties. Texture analysis using electron backscattered diffraction (EBSD) indicated recrystallization during heat treatment, potentially contributing to reduced delamination susceptibility. These findings demonstrating flow-formed material durability coupled with the high manufacturing efficiency of flow forming, makes flow forming an attractive process to produce aircraft cryotanks.

EBF3↗
DOE OSTI2019

Summary: Verification of the ENDF/B-VII.1 and VIII.0 AMPX 1597-group Libraries for Advanced Reactor Analysis

The SCALE/AMPX multigroup (MG) cross section processing procedure has been updated to minimize reactivity differences for various advanced thermal and fast reactor designs, as observed for the current MG libraries, resulting in excellent agreement between the calculations with the new MG libraries and the continuous-energy reference calculations. The SCALE MG calculations are widely applied to thermal spectrum light-water reactor systems, as well as fast spectrum metallic systems. Due to growing interest from industry and regulators in applying SCALE for the design of fast spectrum reactors—both sodium and molten salt—it was desirable to review and improve the SCALE/AMPX procedure for unresolved resonance self-shielded data and high-energy neutron spectra. The data were improved by generating MG unresolved resonance data based on the analytic probability table method with the narrow resonance approximation and by using very fine and intermediate group structures that are typical for fast system analysis. This study focused on verifying the improved SCALE/AMPX MG cross section processing procedure and the new AMPX 1597-group library with the ENDF/B-VII.1 and VIII.0 evaluated nuclear data. The verification was made by performing reaction rate analysis and benchmark calculations for various thermal and fast reactor systems. Results indicate that the improved SCALE/AMPX MG cross section processing and libraries provide excellent results for advanced reactor analysis.

Kim, Kang Seog↗