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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Strength and ductility of additively manufactured 316L stainless steel: Impact of neutron irradiation and data variability

Here, this article presents the mechanical properties of additively manufactured (AM) 316L stainless steel processed via the laser powder bed fusion (LPBF) method, focusing on the effects of neutron irradiation on mechanical properties and the variability in strength and ductility data. The rapid melting-solidification process and multiple heating-cooling cycles inherent in LPBF typically result in a fine, metastable microstructure with significant local variability. AM 316L builds of varying thicknesses were fabricated, and SS-J3 miniature tensile specimens were machined from six different locations. These specimens were irradiated with fast neutrons to doses of 2 and 10 dpa at target temperatures of 300 °C and 600 °C. Post-irradiation tensile tests were conducted at room temperature, 300 °C, and 600 °C. Compared to conventional 316L stainless steel, AM 316L exhibited higher initial strength but lower ductility. Irradiation at 300 °C caused significant hardening and prompt necking at yield, with limited uniform ductility, although embrittlement was not observed up to 10 dpa. While neutron irradiation, particularly at 600 °C, increased the variability in strength and ductility data, no clear dependence of mechanical properties on build thickness or sampling location was found—contrary to the conventional perception that AM materials may exhibit high property variability. Furthermore, we observed that the variability in property data for LPBF-processed 316L was relatively low compared to that of wrought 316L stainless steel. This reduced variability in AM 316L steel may be attributed to its highly metastable, stress-containing microstructure, which is discussed in the context of general tensile property variations.

Additively manufactured 316L stainless steel↗
DOE OSTI2018

Standardized protocols and procedures can precisely and accurately quantify non-structural carbohydrates

Non-structural carbohydrates (NSCs), the stored products of photosynthesis, building blocks for growth, and fuel for respiration, are central to plant metabolism, but their measurement is challenging. Differences in methods and procedures among laboratories can cause results to vary widely, limiting our ability to integrate and generalize patterns in plant C balance among studies. A recent assessment found that NSC concentrations measured for a common set of samples can vary by an order of magnitude, but sources for this variability were unclear. We measured a common set of nine plant material types, and two synthetic samples with known NSC concentrations, using a common protocol for sugar extraction and starch digestion, and three different sugar quantification methods (ion chromatography, enzyme, acid) in six laboratories. We also tested how sample handling, extraction solvent, and centralizing parts of the procedure in one laboratory affected results. NSC concentrations measured for synthetic samples were within about 11.5% of known values for all three methods. However, differences among quantification methods were the largest source of variation in NSC measurements for natural plant samples because the three methods quantify different NSCs. The enzyme method quantified only glucose, fructose, and sucrose, with ion chromatography we additionally quantified galactose, while the acid method quantified a large range of mono- and oligosaccharides. For some natural samples, acid method quantification doubled sugar relative to the other methods, demonstrating that trees allocate C to a range of sugar molecules. Sample handling had little effect on measurements, while ethanol sugar extraction improved accuracy over water extraction. Our results demonstrate that reasonable accuracy of NSC measurements can be achieved when different methods are used, as long as protocols are robust and standardized. Thus, we provide detailed protocols for the extraction, digestion and quantification of NSCs in plant samples, which should improve the comparability of NSC measurements among laboratories.

Landhäusser, Simon M.↗
DOE OSTI2023

A Stochastic Covariance Shrinkage Approach in Ensemble Transform Kalman Filtering

The Ensemble Kalman Filters (EnKF) employ a Monte-Carlo approach to represent covariance information, and are affected by sampling errors in operational settings where the number of model realizations is much smaller than the model state dimension. To alleviate the effects of these errors EnKF relies on model-specific heuristics such as covariance localization, which takes advantage of the spatial locality of correlations among the model variables. This work proposes an approach to alleviate sampling errors that utilizes a locally averaged-in-time dynamics of the model, described in terms of a climatological covariance of the dynamical system. We use this covariance as the target matrix in covariance shrinkage methods, and develop a stochastic covariance shrinkage approach where synthetic ensemble members are drawn to enrich both the ensemble subspace and the ensemble transformation. We additionally provide for a way in which this methodology can be localized similar to the state-of-the-art LETKF method, and that for a certain model setup, our methodology significantly outperforms it.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1983

A sampling system for estimating the cultivation of wheat (Triticum aestivum L) from LANDSAT data

Using digitally processed MSS/LANDSAT data as auxiliary variable, a methodology to estimate wheat (Triticum aestivum L) area by means of sampling techniques was developed. To perform this research, aerial photographs covering 720 sq km in Cruz Alta test site at the NW of Rio Grande do Sul State, were visually analyzed. LANDSAT digital data were analyzed using non-supervised and supervised classification algorithms; as post-processing the classification was submitted to spatial filtering. To estimate wheat area, the regression estimation method was applied and different sample sizes and various sampling units (10, 20, 30, 40 and 60 sq km) were tested. Based on the four decision criteria established for this research, it was concluded that: (1) as the size of sampling units decreased the percentage of sampled area required to obtain similar estimation performance also decreased; (2) the lowest percentage of the area sampled for wheat estimation with relatively high precision and accuracy through regression estimation was 90% using 10 sq km s the sampling unit; and (3) wheat area estimation by direct expansion (using only aerial photographs) was less precise and accurate when compared to those obtained by means of regression estimation.

Parada, N. D. J.↗
NASA NTRS1990

Broad-band properties of the CfA Seyfert galaxies. III - Ultraviolet variability

A total of 657 archived IUE spectra are used to study the UV variability properties of six members of the CfA Seyfert I galaxy sample. All show strong evidence for continuum and line variations and a tendency for less luminous objects to be more strongly variable. Most objects show a clear correlation at zero lag between UV spectral index and luminosity, evidence that the variable component is an accretion disk around a black hole which is systematically smaller in less luminous sources. No correlation is seen between the continuum luminosity and equivalent width of the C IV, Mg II, and semiforbidden C III emission lines when the entire sample is examined, but a clear anticorrelation is present when only repeated observations of individual objects are considered. This is due to a combination of light-travel time effects in the broad-line region and the nonlinear responses of lines to continuum fluctuations.

Edelson, R. A.↗
DOE OSTI2018

Subnanogram proteomics: Impact of LC column selection, MS instrumentation and data analysis strategy on proteome coverage for trace samples

One of the greatest challenges for mass spectrometry (MS)-based proteomics is the limited ability to analyze small samples. Here we investigate the relative contributions of liquid chromatography (LC), MS instrumentation and data analysis methods with the aim of improving proteome coverage for sample sizes ranging from 0.5 ng to 50 ng. We show that the LC separations utilizing 30-µm-i.d. columns increase signal intensity by >3-fold relative to those using 75-µm-i.d. columns, leading to 32% increase in peptide identifications. The Orbitrap Fusion Lumos mass spectrometer significantly boosted both sensitivity and sequencing speed relative to earlier generation Orbitraps (e.g., LTQ-Orbitrap), leading to a ~3× increase in peptide identifications and 1.7× increase in identified protein groups for 2 ng tryptic digests of bacterial lysate. The Match Between Runs algorithm of open-source MaxQuant software further increased proteome coverage by ~ 95% for 0.5 ng samples and by ~42% for 2 ng samples. The present platform is capable of identifying >3000 protein groups from tryptic digestion of cell lysates equivalent to 50 HeLa cells and 100 THP-1 cells (~10 ng total proteins), respectively, and >950 proteins from subnanogram bacterial and archaeal cell lysates. The present ultrasensitive LC-MS platform is expected to enable deep proteome coverage for subnanogram samples, including single mammalian cells.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2024

The variability structure function of the highest luminosity quasars on short time-scales

ABSTRACT The stochastic photometric variability of quasars is known to follow a random-walk phenomenology on emission time-scales of months to years. Some high-cadence rest-frame optical monitoring in the past has hinted at a suppression of variability amplitudes on shorter time-scales of a few days or weeks, opening the question of what drives the suppression and how it might scale with quasar properties. Here, we study a few thousand of the highest luminosity quasars in the sky, mostly in the luminosity range of $L_{\rm bol}$$=[46.4, 47.3]$ and redshift range of $z=[0.7, 2.4]$. We use a data set from the NASA/Asteroid Terrestrial-impact Last Alert System facility with nightly cadence, weather permitting, which has been used before to quantify strong regularity in longer term rest-frame-UV variability. As we focus on a careful treatment of short time-scales across the sample, we find that a linear function is sufficient to describe the UV variability structure function. Although the result can not rule out the existence of breaks in some groups completely, a simpler model is usually favoured under this circumstance. In conclusion, the data are consistent with a single-slope random walk across rest-frame time-scales of $\Delta t=[10, 250]$ d.

Tang, Ji-Jia (ORCID:0000000218600886)↗
NASA NTRS2006

Exploring the Connection Between Sampling Problems in Bayesian Inference and Statistical Mechanics

The Bayesian and statistical mechanical communities often share the same objective in their work - estimating and integrating probability distribution functions (pdfs) describing stochastic systems, models or processes. Frequently, these pdfs are complex functions of random variables exhibiting multiple, well separated local minima. Conventional strategies for sampling such pdfs are inefficient, sometimes leading to an apparent non-ergodic behavior. Several recently developed techniques for handling this problem have been successfully applied in statistical mechanics. In the multicanonical and Wang-Landau Monte Carlo (MC) methods, the correct pdfs are recovered from uniform sampling of the parameter space by iteratively establishing proper weighting factors connecting these distributions. Trivial generalizations allow for sampling from any chosen pdf. The closely related transition matrix method relies on estimating transition probabilities between different states. All these methods proved to generate estimates of pdfs with high statistical accuracy. In another MC technique, parallel tempering, several random walks, each corresponding to a different value of a parameter (e.g. "temperature"), are generated and occasionally exchanged using the Metropolis criterion. This method can be considered as a statistically correct version of simulated annealing. An alternative approach is to represent the set of independent variables as a Hamiltonian system. Considerab!e progress has been made in understanding how to ensure that the system obeys the equipartition theorem or, equivalently, that coupling between the variables is correctly described. Then a host of techniques developed for dynamical systems can be used. Among them, probably the most powerful is the Adaptive Biasing Force method, in which thermodynamic integration and biased sampling are combined to yield very efficient estimates of pdfs. The third class of methods deals with transitions between states described by rate constants. These problems are isomorphic with chemical kinetics problems. Recently, several efficient techniques for this purpose have been developed based on the approach originally proposed by Gillespie. Although the utility of the techniques mentioned above for Bayesian problems has not been determined, further research along these lines is warranted

Pohorille, Andrew↗
DOE OSTI2022

Impact of specimen preparation method on photovoltaic backsheet degradation during accelerated aging test

In this study, we highlight some important factors in the specimen preparation methods for evaluating photovoltaic backsheet properties after accelerated aging. Two different sequences are considered: Method (I) cut-then-age: cut into 1-cm wide strips and then expose to stress, and Method (II) age-then-cut: expose a larger sheet to stress and then cut into 1-cm widths for mechanical property measurements. We also compare the effect of three cutting methods, (a) tensile specimen punch, (b) paper cutter, and (c) fresh razor blade. Several commercial backsheets were evaluated, with stress exposures including (a) pressure cooker test (PCT), (b) dry ultraviolet (UV) radiation exposure, and (c) UV combined damp heat tests. Fourier transform infrared spectrometer (FTIR) and intrinsic viscosity (IV) were used to analyze the materials on unstressed materials and samples exposed to PCT. The results show that both the cutting method and the time of cutting have an impact on the backsheet mechanical properties. Additionally, under UV exposure, Method II, age-then-cut, generally resulted in a higher average value, with more variation than Method I; however, if the side strips from Method II were excluded, the variation dropped to the same level. This is because the specimens at the sides of the sheet get additional damage from UV light from the exposed sides of the sample. In contrast to UV exposure, PCT specimens prepared by Method II result in lower average values and higher variability. This is attributed to embrittlement through the bulk of the sample where the cutting of embrittled specimens appears to result in more edge defects which can then initiate a break at smaller strains. The data suggest that for UV exposures, the specimens should be cut after aging and the exposed side specimens discarded, and that for PCT exposures, the specimens should be cut before the exposure.

14 SOLAR ENERGY↗
NASA NTRS1992

Cryogenic leak testing of tube fittings/valves

A high pressure and variable temperature cryogenic leak testing system was conceived and designed in order to conduct leakage testing of pipe fittings/valves in liquid hydrogen supply lines of the Space Shuttle. The system can create a continuous testing environment of variable temperature, 5.5 to about 300 K, and variable pressure, 0.01 to about 70 x 10 exp 5 Pa, with a large sample space, 90 mm diameter x 228 mm length, and at low operating cost. In terms of cryogenic leak testing the system has a special capability for extensive applications. The system comprised a variable temperature cryostat, a high pressure sample chamber, a vacuum pumping station, gas flow control system, pressure and temperature control systems, and leak detecting and measuring systems. A general discussion of cryogenic leak testing methods is also presented.

Jia, L. X.↗
DOE OSTI2018

Magnetic and Transport Properties of Bi{sub 0.5−x}Pr{sub x}Ca{sub 0.5}MnO{sub 3}(0.0 ≤ x ≤ 0.50) Manganites

In this work, the effect of Pr doping at the Bi site on the critical behavior and magnetocaloric and transport properties of Bi{sub 0.5−x}Pr{sub x}Ca{sub 0.5}MnO{sub 3} (0.0 ≤ x ≤ 0.50) manganite synthesized by sol–gel method is reported. An increase in Curie temperature (T{sub C}) with an increase in Pr content is observed. The samples with x = 0.0–0.40 show first-order phase transition whereas the sample with x = 0.50 shows second-order phase transition near T{sub C}. The estimated values of critical exponents β = 0.75 and γ = 0.82 for the sample with x = 0.50 do not fall into any universality class. The sample with x = 0.50 shows maximum magnetic entropy change (|ΔS{sub m}| = (1.22 J kg{sup −1} K{sup −1}) at T{sub C} in an applied magnetic field of 40 kOe, which is associated with magnetocaloric effect (MCE). All the samples show semiconducting behavior and also follow Mott’s variable range hopping (VRH) model below the charge ordering temperature (T{sub CO}). The changes in magnetic and transport properties are correlated with the changes in the structural parameters of the samples. The results are discussed in view of the effect of Pr doping on the 6s{sup 2} lone pair character of Bi{sup 3+} ions and disorder in the samples.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Oxidation Temperature-Dependent Electrochemical Doping of WO 3 Deposited via Atomic Layer Deposition

Silicon-based photoelectrochemical devices show promise for the performance of light-driven CO 2 reduction but suffer from instability under photoelectrochemical conditions relevant to CO 2 reduction. Coating silicon electrodes with thin layers of metal oxides has shown promise to passivate unstable silicon surfaces, and many different metal oxides can be deposited on silicon using various techniques. In this study, we investigate the fundamental photoelectrochemical performance of WO 3 -coated silicon photoelectrodes, which were generated by oxidation of W-metal films deposited via atomic layer deposition on both degenerately doped (nSi + ) and low-doped (pSi) silicon. Two different oxidation temperatures were investigated (400 and 600 °C), and it was found that the monoclinic phase of WO 3 predominates at both temperatures but that more grain boundaries are present in the 600 °C film. From X-ray photoelectron spectroscopy, the stoichiometry of both films was found to be 1:3 W:O, and low electron energy loss experiments indicate band gaps of 3.0 and 3.1 eV for 400 and 600 °C films, respectively. Cyclic voltammetry experiments showed that the electron transfer kinetics increased after continued redox cycling, particularly for the material produced at 400 °C. X-ray photoelectron spectra suggest that the observed increase in electrode conductivity is due to the formation of oxygen vacancies in the film. Electrochemical impedance spectroscopy indicated that charge transport through the films was impacted by the grain boundaries that formed during oxidation of the film. Photoelectrochemical studies on pSi/WO 3 electrodes were highly variable, only producing a photocurrent and photovoltage with some samples. Our best sample, formed at 400 °C, produced a photovoltage of 180 mV, which is lower than what has previously been reported for WO 3 -coated silicon (500 mV). We hypothesize that the variability in photoelectrochemical experiments arose from a roughened WSiO x interface that is generated during film preparation. WO 3 shows promise as a metal oxide coating for silicon, but our results suggest that formation of a high-quality interface between Si and WO 3 is vital for best performance.

Charge transfer↗
DOE OSTI2018

A study of Ni/La-Al 2 O 3 catalysts: A competitive system for CO 2 methanation

Ni/La-γ-Al 2 O 3 samples containing 13.6 wt.% Ni and a variable amount of lanthana (0, 4, 14 and 37 wt.%) were prepared by incipient wetness impregnation, using silica-free γ-Al 2 O 3 support. The materials were characterized, as such or after reaction, with XRD, H 2 -TPR, IR, UV–vis-NIR, XPS and FE-SEM techniques. They were tested as catalysts for CO 2 methanation at atmospheric pressure at GHSV 55000 h –1 . The reaction is under kinetic control at T < 650–673 K, while the product mixture is under thermodynamic control above this temperature range. Lanthanum addition strongly increases the activity of Ni/γ-Al 2 O 3 for CO 2 methanation. Methane selectivity is increased to nearly 100% at low temperatures (T < 650 K). The CO 2 methanation reaction on La-doped Ni/γ-Al 2 O 3 occurs with similar activation energies (80 kJ/mol), and with slightly higher reaction order for hydrogen and lower reaction order for CO 2 than those observed for undoped Ni/γ-Al 2 O 3 . Lanthanum acts as a promoter because of the stronger basicity of the lanthana-alumina support allowing stronger adsorption of CO 2 as surface carbonates that can be act as “reactant reservoirs”. Finally, the Ni/La-alumina catalysts studied here are similarly effective as Ru/alumina catalysts for the selective CO 2 methanation at low temperature and atmospheric pressure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Spatial and temporal characterization of municipal solid waste based on resource recovery pathways

This study presents a two-year, quarterly assessment of MSW across four source sectors (residential, schools, restaurants, and grocery stores) from sixteen sites across five U.S. states. MSW was manually sorted into 27 categories and aggregated into pathway fractions: high-moisture (HM) organics, low-moisture (LM) organics, recyclable (RC) materials, and residuals for disposal. Organics represented 89 % of the MSW stream. The largest fraction was HM organics consisting of food waste (31 %) and yard waste (3 %), with large coefficient of variations (CV), 79 and 278 %, respectively, reflecting high seasonal and site variability that varied significantly (p < 0.01) across sampling periods. The HM fraction showed properties favorable for anaerobic digestion, with moisture content ranging from 56 to 95 % and volatile solids ranges of 86-95 %. In contrast, the LM and RC fractions remained more stable (plastics CV = 41 %; paper CV = 53 %) with heating values up to 26.9 MJ/kg across sources, reflecting suitability for gasification. Microstructural analysis revealed less porosity in residential waste sampled at the landfill, which can influence preprocessing efficiency and microbial accessibility. Pathway informed allocations showed that 35 % of MSW is suitable for anaerobic digestion, 36 % for gasification, and 18 % for recycling, leaving 11 % requiring landfill disposal. These results provide quantitative evidence to determine feedstock allocation, waste-to-energy system design, and the development of data-driven sustainability and resource recovery strategies within a circular bioeconomy.

09 BIOMASS FUELS↗
DOE OSTI2020

Structural and Thermoelectric Properties of Black Arsenic–Phosphorus

Here, we report the structural and temperature dependent transport properties of As x P 1-x (x = 0, 0.2, 0.5, 0.83, 1) alloys. It is observed that black phosphorous (BP)-related phonon modes in the alloy samples are red-shifted with increasing arsenic concentration, while black arsenic-related modes in these samples are blue-shifted with increasing phosphorus concertation. As the arsenic concentration, x increases from 0 to 1, the 4-probe resistance of the As x P 1-x alloys is found to decrease by more than 3 orders of magnitude. The transport studies reveal that samples with the highest arsenic concentration (x = 1 and 0.83) show metallic behavior in the temperature dependence of resistance with a small thermopower at room temperature with an anomalous temperature dependence. In contrast, the samples with high phosphorus concentration (x = 0, 0.2, and 0.5) show very large thermopower values at room temperature reaching a value as high as 803 μV/k for x = 0.2. The temperature dependence of the thermopower of these samples can be well described by the variable range hopping (VRH) mechanism in two-dimensions (2-d), S ~ T 1/3 . Similarly, their 4-probe resistance (R) values can be fitted with 2-d VRH mechanism, R ~ exp(T -1/3 ).

36 MATERIALS SCIENCE↗
DOE OSTI2016

Development of a multi-lane X-ray mirror providing variable beam sizes

Grazing incidence mirrors are used on most X-ray synchrotron beamlines to focus, collimate or suppress harmonics. Increasingly beamline users are demanding variable beam shapes and sizes at the sample position. We have now developed a new concept to rapidly vary the beam size and shape of a focused X-ray beam. The surface of an elliptically figured mirror is divided into a number of laterally separated lanes, each of which is given an additional longitudinal height profile calculated to shape the X-ray beam to a top-hat profile in the focal plane. We have now fabricated two prototype mirrors and present the results of metrology tests and measurements made with one of the mirrors focusing the X-rays on a synchrotron beamline. We envisage that such mirrors could be widely applied to rapid beam-size switching on many synchrotron beamlines.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Hiding in plain sight: The prevalence and impact of trions and Fermi polarons in transient absorption spectroscopy experiments of 2D semiconductors

Transient absorption (TA) spectroscopy is one of the most popular experimental methods to measure the excited state lifetimes and charge carrier recombination mechanisms in two dimensional (2D) semiconductors. This fundamental information is essential for designing and optimizing the next generation of ultrathin and lightweight 2D semiconductor-based optoelectronic devices. However, the interpretation of TA spectroscopy data varies across the community. The community lacks a unifying physical explanation for how and why experimental variables such as incident light intensity, sample-substrate interactions, and/or applied bias affect TA spectral data. This Perspective (1) compares the physical chemistry TA literature to nanomaterial physics literature from a historical perspective, (2) reviews multiple physical explanations that the TA community developed to explain spectral features and experimental trends, (3) provides a unifying explanation for how and why trions—and, more generally, Fermi polarons—contribute to TA spectra, and (4) quantifies the extent to which various physical interpretations and data analysis procedures yield different timescales and mechanisms for the same set of experimental results. We highlight the importance of considering trions/Fermi polarons in TA measurements and their implications for advancing our understanding of 2D material properties.

2D materials↗
DOE OSTI2020

Online Optimization for Networked Distributed Energy Resources With Time-Coupling Constraints

This paper proposes a Lyapunov optimization-based online distributed (LOOD) algorithmic framework for active distribution networks (ADNs) with numerous photovoltaic inverters and inverter air conditionings (IACs). In the proposed scheme, ADNs can track an active power setpoint reference at the substation in response to transmission-level requests while concurrently minimizing the social utility loss and ensuring the security of voltages. Conventional distributed optimization methods are rarely feasible to track the optimal solutions in fast variable environments using a fine-grained sampling interval where the underlying optimization problem evolves with the iterations of the algorithms. In contrast, based on the framework of online convex optimization (OCO), the developed approach uses a distributed algebraic update to compute the next round decisions relying on the current feedback of measurements. Notably, the time-coupling constraints of IACs are decoupled for online implementation with Lyapunov optimization technique. An incentive scheme is tailored to coordinate the customer-owned assets in lieu of the direct control from network operators. Optimality and convergency are characterized analytically. Finally, we corroborate the proposed method on a modified version of 33-node test feeder. Benchmark tests show that the proposed method is computationally and economically efficient, and outperforming existing algorithms.

active distribution networks↗