Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “EVALUATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Evaluation of satellite Leaf Area Index in California vineyards for improving water use estimation

Remote sensing estimation of evapotranspiration (ET) directly quantifies plant water consumption and provides essential information for irrigation scheduling, which is a pressing need for California vineyards as extreme droughts become more frequent. Many ET models take satellite-derived Leaf Area Index (LAI) as a major input, but how uncertainties of LAI estimations propagate to ET and the partitioning between evaporation and transpiration is poorly understood. Here we assessed six satellite-based LAI estimation approaches using Landsat and Sentinel-2 images against ground measurements from four vineyards in California and evaluated ET sensitivity to LAI in the thermal-based two-source energy balance (TSEB) model. We found that radiative transfer modeling-based approaches predicted low to medium LAI well, but they significantly underestimated high LAI in highly clumped vine canopies (RMSE ~ 0.97 to 1.27). Cubist regression models trained with ground LAI measurements from all vineyards achieved high accuracy (RMSE ~ 0.3 to 0.48), but these empirical models did not generalize well between sites. Red edge bands and the related vegetation index (VI) from the Sentinel-2 satellite contain complementary information of LAI to VIs based on near-infrared and red bands. TSEB ET was more sensitive to positive LAI biases than negative ones. Positive LAI errors of 50% resulted in up to 50% changes in ET, while negative biases of 50% in LAI caused less than 10% deviations in ET. However, even when ET changes were minimal, negative LAI errors of 50% led to up to a 40% reduction in modeled transpiration, as soil evaporation and plant transpiration responded to LAI change divergently. These findings call for careful consideration of satellite LAI uncertainties for ET modeling, especially for the partitioning of water loss between vine and soil or cover crop for effective vineyard irrigation management.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

The effects of bias, drift, and trends in calculating anomalies for evaluating skill of seasonal-to-decadal initialized climate predictions

In initialized seasonal to decadal (S2D) predictions, model hindcasts rapidly drift away from the initial observed state and converge toward a preferred state characterized by systematic error, or bias. Bias and drift are among the greatest challenges facing initialized prediction today. Differences in trends between initial states and drifted states, combined with bias and drift, introduce complexities in calculating anomalies to assess skill of initialized predictions. We examine several methods of calculating anomalies using the Decadal Prediction Large Ensemble (DPLE) using the Community Earth System Model (CESM) initialized hindcasts and focus on Pacific and Atlantic SSTs to illustrate issues with anomaly calculations. Three methods of computing anomalies, one as differences from a long term model climatology, another as bias-adjusted differences from the previous 15 year average from observations, and a third as differences from the previous 15 year average from the model, are contrasted and each is shown to have limitations. For the first, trends in bias and drift introduce higher skill estimates earlier and later in the hindcast period due to the trends that contribute to skill. For the second, higher skill can be introduced in situations where low frequency variability in the observations is large compared to the hindcasts on timescales greater than 15 years, while lower skill can result if the predicted signal is small and the bias-correction itself produces a transition of SST anomalies to the opposite sign of those that are observed. The third method has somewhat lower skill compared to each of the others, but has less difficulties with not only the long term trends in the model climatology, but also with the unrealistic situational skill from using observations as a reference. However, the first 15 years of the hindcast period cannot be evaluated due to having to wait to accumulate the previous 15 year model climatology before the method can be applied. Here, the IPO transition in the 2014–2016 time frame from negative to positive (predicted by Meehl et al. in in Nat Commun, 10.1038/NCOMMS11718, 2016) did indeed verify using all three methods, though each provides somewhat different skill values as a result of the respective limitations. There is no clear best method, as all are roughly comparable, and each has its own set of limitations and caveats. However, all three methods show generally higher overall skill in the AMO region compared to the IPO region.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

A proximal trust-region method for nonsmooth optimization with inexact function and gradient evaluations

Many applications require minimizing the sum of smooth and nonsmooth functions. For example, basis pursuit denoising problems in data science require minimizing a measure of data misfit plus an $\ell^1$-regularizer. Similar problems arise in the optimal control of partial differential equations (PDEs) when sparsity of the control is desired. Here, we develop a novel trust-region method to minimize the sum of a smooth nonconvex function and a nonsmooth convex function. Our method is unique in that it permits and systematically controls the use of inexact objective function and derivative evaluations. When using a quadratic Taylor model for the trust-region subproblem, our algorithm is an inexact, matrix-free proximal Newton-type method that permits indefinite Hessians. We prove global convergence of our method in Hilbert space and demonstrate its efficacy on three examples from data science and PDE-constrained optimization.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Evaluating the regional risks to food availability and access from land-based climate policies in an Integrated Assessment Model

Mitigating greenhouse gas (GHG) emissions is necessary to reduce the overall negative climate change impacts on crop yields and agricultural production. However, certain mitigation measures may generate unintended consequences to food availability and food access due to both land use competition and economic burden of mitigation. Integrated assessment models (IAM) are generally used to evaluate these policies; however, currently these models may not capture the importance of income and food prices for hunger and overall economic wellbeing. Here, we implement a measure of food security that captures the nutritional and economic aspects as the total expenditures on staple foods divided by income and weighted by total caloric consumption in an IAM, the Global Change Analysis Model (GCAM4.0). We then project consumer prices and our measure of food security along the Shared Socioeconomic Pathways (SSPs). Sustained economic growth underpins increases in caloric consumption and lowering expenditures on staple foods. Strict conservation policies affect food accessibility in a larger number of developing countries, whereas the negative effects of pricing terrestrial emissions is more concentrated on the poor in Sub-Saharan Africa, by substantially replacing their cropland with forests and affecting the production of key staples.

Cui, Ryna↗
DOE OSTI2023

Additively manufactured polymer composites for heat exchanger applications: evaluation of critical thermophysical properties

Polymeric heat exchangers (PHXs) have been used in applications involving weight restrictions, chemical compatibility, and fouling issues. Additive manufacturing (AM) or 3D printing provide new solutions to previously inaccessible combinations of properties and geometries. There are some advancements in the PHXs by AM; however, the process and the properties of materials still need further investigation to improve the overall performance. In this study, additively manufactured polyethylene terephthalate glycol (PETG) composites reinforced with graphite and pitch-based carbon fibers were evaluated for their potential application as PHXs. The thermal conductivity, volumetric heat capacity, coefficient of thermal expansion, creep behavior, and long-term performance were studied in detail. Our results reveal that the composites have an anisotropic thermal conductivity. The thermal conductivity along the printing direction is higher than the layer building direction due to the shear-induced alignment of the fillers. The printed composites achieve good thermal stability with 80% lower CTE at room temperature than neat PETG. Creep tests suggest the creep and creep recovery were highly temperature-dependent, and the deformation can be recovered when the temperature is below glass transition. These results suggest additive manufactured composites be potentially used for heat exchanger applications at low temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Evaluation of two extraction chromatography resins for scandium and titanium separation for medical isotope production

Scandium-47 ( 47 Sc) can be used in nuclear medicine as a therapeutic-diagnostic, or "theragnostic," radioactive medical isotope for cancer detection and treatment. The 47 Sc isotope can be produced through the photonuclear reaction 48 Ti(γ,p) 47 Sc by irradiating enriched 48 Ti target material. The enriched target material necessary for production is costly; 48 TiO 2 costs ~ $\$$1550/g, and targets can be > 50 g ($\$$77,500) to produce medically relevant amounts of 47 Sc. In order to keep costs low, a highly efficient separation of scandium from bulk titanium is desired, along with efficient methods for recycling the target material. Here this research is focused on evaluating efficient methods for the separation of scandium from bulk quantities of titanium using commercially available diglycolamide-based and hydroxamate-based extraction chromatography resins (DGA resin and ZR resin, respectively). The sorption of 47 Sc and Ti on these resins were investigated at varying concentrations of HNO 3 , HCl, H 2 SO 4 , and HF to explore how they might be used in a large-scale production/processing setting.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2026

Evaluating ecosystem water use efficiency under drought stress: a case study of the Helan Mountain region, northwest China

Context Water use efficiency (WUE) is a fundamental ecological indicator links carbon assimilation and water loss in terrestrial ecosystems. Understanding its responses to drought stress is essential for adaptive ecosystem management, particularly in climate-sensitive mountain landscapes. Objectives This study aimed to investigate drought-driven variations in WUE across major vegetation types in the Helan Mountain region of Northwest China. Specifically, we sought to identify dominant ecological drivers of WUE variability and to disentangle their relative importance and causal pathways. Methods We quantified WUE using the Moderate Resolution Imaging Spectroradiometer (MODIS) products and the Drought Severity Index (DSI) data from 2001 to 2020. To examine WUE – drought relationships across contrasting vegetation types, we employed a spatially explicit analytical framework integrating Random Forest (RF) modeling, partial correlation analysis, and structural equation modeling (SEM). Results Regional WUE exhibited relatively stable interannual dynamics, yet pronounced spatial heterogeneity that was strongly modulated by drought conditions. Vegetation properties, particularly Leaf Area Index (LAI) and Normalized Difference Vegetation Index (NDVI), emerged as the dominant determinants of WUE, with NDVI alone explaining over 20% of its spatial variance in forest and grassland during non-drought periods. SEM analyses revealed that climate forcing influenced WUE mainly through indirect pathways mediated by soil moisture availability and vegetation structural dynamics, rather than through direct climatic controls. Among all regulating factors, LAI acted as the central control node governing ecosystem carbon–water coupling. In contrast, short-term climatic stress, especially atmospheric demand and drought duration, exerted weak or negative direct effects on WUE. Ecosystem-specific responses were observed, with croplands mainly regulated by soil water availability, whereas forests and grasslands showed more sensitive to atmospheric drought stress. Together, these results reveal a hierarchical control framework where soil–vegetation interactions mediate climate impacts on WUE, driving strong spatial heterogeneity in drought responses across mountain landscapes. Conclusions Our findings highlight the pivotal role of indirect drought effects mediated by vegetation and soil processes in shaping ecosystem WUE. The identified soil–vegetation–climate regulatory hierarchy provides mechanistic insight into landscape–scale drought sensitivity and supports integrated modeling approaches for evaluating ecosystem resilience and sustainable management in arid mountain regions.

China↗
DOE OSTI2019

Evaluating national hydrogen refueling infrastructure requirement and economic competitiveness of fuel cell electric long-haul trucks

This study explored the national hydrogen refueling infrastructure requirement along major United States (US) interstate highway corridors to support the deployment of fuel cell electric trucks (FCETs) for the national long-haul trucking fleet. Given the long-haul trucking shipment demand in 2025 projected by the Freight Analysis Framework, locations and capacities of hydrogen stations were identified for inter-zone freight flows, and the total daily refueling demand was estimated for intra-zone flows for each FAF zone. Based on the infrastructure deployment results, we conducted an economic feasibility analysis of FCETs by evaluating the total ownership cost. We found that when the FCET penetration is relatively high (e.g., 10% penetration), FCETs become more competitive in terms of fuel cost and idling cost and could be economic viable if the incremental vehicle cost is reduced to meet the near-term FCET technology cost targets and the liquefaction cost is reduced to an optimal case. We also observed that the station cost depends on regional factors, particularly regional demand, which is used to determine station capacity. Thus, one possible strategy for station roll-out is to have early investment in target regions where station costs are expected to be relatively low such as the Pacific and West South Central regions.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2019

Evaluation of genomic selection and marker-assisted selection in Miscanthus and energycane

Abstract Although energycane ( Saccharum spp. hybrids) is widely used as a source of lignocellulosic biomass for bioethanol, breeding this crop for disease resistance is challenging due to its narrow genetic base. Therefore, efforts are underway to introgress novel sources of genetic resistance from Miscanthus into energycane. Given that disease resistance in energycane could be either qualitative or quantitative in nature, careful examination of a wide variety of genomic-enabled breeding approaches will be crucial to the success of such an undertaking. Here we examined the efficiency of both genomic selection (GS) and marker-assisted selection (MAS) for traits simulated under different genetic architectures in F 1 and BC 1 populations of Miscanthus × Miscanthus and sugarcane × sugarcane crosses. We observed that the performance of MAS was comparable and sometimes superior to GS for traits simulated with four quantitative trait nucleotides (QTNs). In contrast, as the number of simulated QTN increased, all four GS models that were evaluated tended to outperform MAS, select more phenotypically optimal F 1 individuals, and accurately predict simulated trait values in subsequent BC 1 generations. We therefore conclude that GS is preferable to MAS for introgressing genetic sources of horizontal disease resistance from Miscanthus to energycane, while MAS remains a suitable option for introgressing vertical disease resistance.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Evaluating the contribution of plant metabolic pathways in the light to the ATP:NADPH demand using a meta-analysis of isotopically non-stationary metabolic flux analyses

Abstract Balancing the ATP: NADPH demand from plant metabolism with supply from photosynthesis is essential for preventing photodamage and operating efficiently, so understanding its drivers is important for integrating metabolism with the light reactions of photosynthesis and for bioengineering efforts that may radically change this demand. It is often assumed that the C3 cycle and photorespiration consume the largest amount of ATP and reductant in illuminated leaves and as a result mostly determine the ATP: NADPH demand. However, the quantitative extent to which other energy consuming metabolic processes contribute in large ways to overall ATP: NADPH demand remains unknown. Here, we used the metabolic flux networks of numerous recently published isotopically non-stationary metabolic flux analyses (INST-MFA) to evaluate flux through the C3 cycle, photorespiration, the oxidative pentose phosphate pathway, the tricarboxylic acid cycle, and starch/sucrose synthesis and characterize broad trends in the demand of energy across different pathways and compartments as well as in the overall ATP:NADPH demand. These data sets include a variety of species including Arabidopsis thaliana , Nicotiana tabacum , and Camelina sativa as well as varying environmental factors including high/low light, day length, and photorespiratory levels. Examining these datasets in aggregate reveals that ultimately the bulk of the energy flux occurred in the C3 cycle and photorespiration, however, the energy demand from these pathways did not determine the ATP: NADPH demand alone. Instead, a notable contribution was revealed from starch and sucrose synthesis which might counterbalance photorespiratory demand and result in fewer adjustments in mechanisms which balance the ATP deficit.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Evaluation of pre-training large language models on leadership-class supercomputers

Large language models (LLMs) have arisen rapidly to the center stage of artificial intelligence as the foundation models applicable to many downstream learning tasks. However, how to effectively build, train, and serve such models for many high-stake and first-principle-based scientific use cases are both of great interests and of great challenges. Moreover, pre-training LLMs with billions or even trillions of parameters can be prohibitively expensive not just for academic institutions, but also for well-funded industrial and government labs. Furthermore, the energy cost and the environmental impact of developing LLMs must be kept in mind. Here, in this work, we conduct a first-of-its-kind performance analysis to understand the time and energy cost of pre-training LLMs on the Department of Energy (DOE)’s leadership-class supercomputers. Employing state-of-the-art distributed training techniques, we evaluate the computational performance of various parallelization approaches at scale for a range of model sizes, and establish a projection model for the cost of full training. Our findings provide baseline results, best practices, and heuristics for pre-training such large models that should be valuable to HPC community at large. We also offer insights and optimization strategies for using the first exascale computing system, Frontier, to train models of the size of GPT-3 and beyond.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Performance evaluations of signed and unsigned noisy approximate quantum Fourier arithmetic

The Quantum Fourier Transform (QFT) grants competitive advantages, especially in resource usage and circuit approximation, for performing arithmetic operations on quantum computers, and offers a potential route toward a numerical quantum-computational paradigm. In this paper, we utilize efficient techniques to implement QFT-based integer addition and multiplications. These operations are fundamental to various quantum applications including Shor’s algorithm, weighted-sum optimization problems in data processing and machine learning, and quantum algorithms requiring inner products. We carry out performance evaluations of these implementations based on IBM’s superconducting-qubit architecture using different compatible noise models. We isolate the sensitivity of the component quantum circuits on both one-/two-qubit gate error rates, and the number of the arithmetic operands’ superposed integer states. We analyze performance and identify the most effective approximation depths for unsigned quantum addition and quantum multiplication within the given context. We then perform a similar analysis of signed addition and compare to the unsigned results. We observe significant dependency of the optimal approximation depth on the degree of machine noise and the number of superposed states in certain performance regimes. Finally, we elaborate on the algorithmic challenges—relevant to signed, unsigned, modular and non-modular versions—that could also be applied to current implementations of QFT-based subtraction, division, exponentiation, and their potential tensor extensions. Here, we analyze the performance trends in our results and speculate on possible future developments within this computational paradigm.

Computational models↗
DOE OSTI2021

Evaluation of engineered sorbents for the sorption of mercury from contaminated bank soils: a column study

Abstract As a global environmental pollutant, mercury (Hg) threatens our water resources and presents a substantial risk to human health. The rate and extent of immobilization of Hg 2+ (hereafter, Hg) on engineered sorbents (Thiol-SAMMS®, pine biochar, SediMite™, Organoclay™ PM-199, and quartz sand as a control) was evaluated using flow-through column experiments. The effectiveness of the sorbents was based on (1) the percentage of Hg removed in relation to the total amount of Hg passing the sorbent column, and (2) the rate of Hg uptake compared to the nonreactive tracer bromide (Br − ). All sorbents removed Hg to a certain extent, but none of the sorbents removed all the Hg introduced to the columns. Thiol-SAMMS showed the highest mean percentage of Hg removed (87% ± 2.9%), followed by Organoclay PM-199 (71% ± 0.4%), pine biochar (57% ± 22.3%), SediMite (61% ± 0.8%), and the control quartz sand (11% ± 5.6%). Thiol-SAMMS was the only sorbent to exhibit retardation of Hg in comparison to the conservative tracer Br − . For the remaining sorbents, Br − along with low concentrations of Hg were eluted within the first 3 pore volumes, indicating limited retardation of Hg. Overall, removal of Hg by sorbents was substantial, suggesting that sorbents might be suitable for deployment in contaminated environments. High concentrations of DOM leaching from the soil columns likely influenced the speciation of Hg and inhibited sorption to the sorbents. Incomplete removal of Hg by any sorbent suggests that additional optimization is needed to increase efficiency.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Quantitative Evaluations of Surface Cleanliness in IF Steel Slabs at Unsteady Casting

Macro-inclusions in the surface layer of slabs are mainly responsible for the sliver defects in IF steel sheets. In the present work, macro-inclusions in six kinds of unsteady cast IF steel slabs involving four unsteady states (casting start, ladle change, nozzle change and casting end) in one casting sequence were quantitatively characterized using an automatic inclusion analyzer with a total detection area of 238,048 mm{sup 2}. The cleanliness of corresponding normal slabs was also evaluated as the benchmark study, and the number density (ND) of inclusions > 50 µm was used to describe the surface slab cleanliness. Generally, alumina-based and mold powder inclusions were detected, and the former type was further subdivided into alumina clusters, alumina associated with bubbles, refractory-related alumina, Al-Ti complex oxides and CaO-Al{sub 2}O{sub 3}-MgO. Several large-sized alumina-based inclusions were detected in the normal slabs with an average ND of 0.31 N/cm{sup 2}, although they had very low total oxygen (TO) contents (10~13 ppm). No mold powder inclusions were found in normal slabs. For all the unsteady slabs, alumina-based and mold powder inclusions were both observed, and the percentage of the former kind was ≥ 90 pct. The average density of macro-inclusions for the first slab was 1.621 N/cm{sup 2}, whose cleanliness was much worse than any of the other unsteady slabs. The first slab should be downgraded. For the second slab, the ND of macro-inclusions was 0.385 N/cm{sup 2}, which was still larger than the normal slabs because of the lasting effect of the re-oxidation. For the penultimate, cap-off and SEN changed slabs, the density of macro-inclusions fluctuated from 0.25~0.35 N/cm{sup 2}, which was close to the average level of normal slabs. However, mold flux-originated inclusions were frequently observed in these slabs because of flow pattern variations due to the casting speed change. In terms of the slab during the ladle change process, mold powder inclusions were frequently detected even though the casting speed remained constant. A mold powder entrapment mechanism was proposed, which showed the entrapment occurred owing to the flow pattern change induced by forming/dropping of SEN clogs due to re-oxidation by FeO in the ladle slag and tundish steel temperature variations during the ladle change practice. The severity of powder entrapment and re-oxidation was also given for different kinds of unsteady slabs, which provides a direct guide to treating these slabs in the steel plant.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The Dissolution of Fe in HCl from the Ilmenite Concentrate; Evaluating the Effect of Operating Parameters and Mutual Interactions

Selective HCl dissolution of ilmenite components for obtaining Ti or titanium dioxide (TiO{sub 2}) has been highly recognized due to its advantages, greater environmental friendliness, and simplicity, compared to H{sub 2}SO{sub 4} and Cl{sub 2} methods. The effect of numerous parameters has been studied with the one-factor-at-a-time method. The present study aimed to evaluate the effect of key operation parameters, such as acid-to-solid ratio (A/S: 5 to 20 mL/g), reaction temperature (T: 70 °C to 100 °C), and acid concentration (A pct: 15 to 30 wt pct), on the dissolution of Fe in HCl solution with the minimum Ti losses to the leachate from its abundant, domestic, and low-cost mineral source (Kahnooj ilmenite concentrate) using central composite design–response surface methodology. After 90 minutes of leaching, the Ti/Fe (pct) in terms of dissolved amounts was selected as the process assessment response function. Based on the conducted experimental and statistical analysis, increasing the levels of parameters in the studied domain leads to an increase in Ti/Fe (pct), in the order of A pct > T > A/S. Two statistically significant mutual interactions between A/S-T and T-A pct, with 95 pct confidence level, were revealed for the first time in this study. The optimization strategy was set to the minimization of Ti/Fe (pct) by considering the objective of study and the selected response function. The A/S, T, and A pct were determined to be 5 mL/g, 70 °C, and 15 pct, respectively, for maximum impurity dissolution and minimum Ti loss to the leachate.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Cyclic Thermal Oxidation Evaluation to Improve Ti6Al4V Surface in Applications as Biomaterial

Thermal oxidation treatments are widely used to modify titanium surfaces. Thermally oxidized titanium alloys are used as biomaterials due to their better surface properties, such as corrosion resistance. However, the use of cyclic thermal treatment for this purpose has not yet been reported. This paper’s objective was to compare roughness, microhardness and corrosion resistance after cyclic and conventional isothermal heat treatments in a Ti6Al4V alloy. The heat treatments were performed over a period of 24 h with a maximum temperature of 650 °C, and cyclic conditions were executed from 200 to 400 °C for 48 cycles, each lasting 0.5 h. After the thermal treatments, roughness was measured through profilometer and atomic force microscopy, Vickers microhardness was evaluated, and polarization corrosion tests were performed in simulated body fluid. All treatments increased surface roughness, microhardness and corrosion resistance at 500 mV above open-circuit potential in polarization tests, compared to the material without oxidation. These results are associated with rutile formation, observed through XRD analysis. Although the isothermal and cyclic treatments presented similar behaviors, the 650-200 °C cyclic heat treatment provided an intermediate roughness and produced a slightly better corrosion resistance, demonstrating that cyclic thermal treatments are a viable alternative for improving titanium alloy surface properties.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Evaluating the Discharge Performance of Heat-Treated Al-Sb Alloys for Al-Air Batteries

In this work, the combined effects of heat treatment and Sb addition on the discharge performance of Al-Sb alloys as anode for Al-air batteries have been evaluated experimentally. The results indicate that heat treatment decreases the electrochemical and discharge activities of Al-Sb alloys. Heat-treated Al-Sb alloys at 550 °C for 3 h show an improved anode performance. The Al-0.02Sb alloy exhibits a high discharge capacity and anodic efficiency of 2758 Ah kg{sup −1} and 92.6%, respectively. Further prolonging the heat treatment time results in a decrease in anode performance. Microstructure characterization indicates that such negative effect is due to the higher-temperature and prolonged heat treatment to bring out significant grain growth and coarsening of Al-Sb precipitates. The corresponding corrosion behaviors are also discussed in detail.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Comparative Evaluation of Creep-Rupture Behavior of P9 Steel Plate and Thick Section Tubeplate Forging

In the present investigation, creep-rupture behavior of P9 steel in two different product forms of 20-mm plate and 300-mm-thick tubeplate forging has been studied at 793 and 873 K. It has been found that steady-state creep rate and rupture life followed power law dependence on applied stress at low and high stress regimes for both forms of products. At high stress regime, P9 steel plate exhibited better creep strength with respect to tubeplate forging in terms of lower creep rate and higher rupture life at 793 and 873 K. On contrary, both product forms exhibited similar creep rate and rupture behavior in the low stress regime at 873 K. Difference in creep ductility has been found to be insignificant in both product forms. Irrespective of test conditions and product forms, fracture appearance remained transgranular ductile characterized by dimples. The comparative evaluation of creep-rupture properties of both product forms has also been described in terms of creep rate-rupture life relationships of Monkman–Grant type, creep damage tolerance and tertiary creep characteristics at 793 and 873 K.

36 MATERIALS SCIENCE↗