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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Zone plate-based extreme ultraviolet mask microscope with through-pellicle imaging capability

Mirror-based and zone plate-based imaging systems are being used in actinic extreme ultraviolet (EUV) reticle review tools. With regard to zone plates, a short working distance is advantageous in terms of the required spectral bandwidth, manufacturability, and potential throughput and imaging performance. Zone plates therefore typically have a short working distance. The industry has adopted the use of an EUV pellicle to protect the photomask. Imaging photomask through-pellicle requires a working distance larger than 2.5 mm. A zone-plate-based EUV mask microscope with a 3-mm working distance has been commissioned at beamline 11.3.2 of the Advanced Light Source. Through-pellicle imaging at an exposure time of 2 s is demonstrated. The instrument achieves an image contrast of 95% on large features on a photomask with a tantalum-based absorber. Imaging down to 45-nm half pitch (mask scale) is demonstrated. A NILS of 2.55 is achieved on 60-nm half-pitch (mask scale) lines and spaces. These results demonstrate that zone-plate-based imaging systems can meet the requirements of an actinic EUV mask review tool in terms of imaging performance and throughput in an instrument compatible with EUV pellicles.

Extreme ultraviolet↗
DOE OSTI2012

Field-Scale Assessment of Desiccation Implementation for Deep Vadose Zone Contaminants

Desiccation of the vadose zone has the potential to reduce the flux of contaminants to underlying groundwater by removing moisture and decreasing the aqueous-phase permeability of the desiccated zone. However, data to evaluate implementation of desiccation are needed to enable consideration of desiccation as a potential remedy. Implementation of desiccation was field tested by injecting dry nitrogen gas to a target treatment zone and monitoring the spatial and temporal progress of the drying process. Aqueous waste discharges to disposal cribs approximately 50 years ago distributed water and contaminants, including primarily technetium-99 and nitrate, within the 100-m deep vadose zone at the test site. A field test location was selected adjacent to one of the former disposal cribs. The test was conducted in a contaminated portion of the vadose zone dominated by fine sands with lenses of silt material. Desiccation reduced volumetric moisture content to as low as 0.01. The lateral and vertical distribution of drying from the injection well was influenced by the subsurface heterogeneity. However, over time, desiccation occurred in the initially wetter, lower permeability lenses.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2014

Scale-Up Information for Gas-Phase Ammonia Treatment of Uranium in the Vadose Zone at the Hanford Site Central Plateau

Uranium is present in the vadose zone at the Hanford Central Plateau and is of concern for protection of groundwater. The Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau identified gas-phase treatment and geochemical manipulation as potentially effective treatment approaches for uranium and technetium in the Hanford Central Plateau vadose zone. Based on laboratory evaluation, use of ammonia vapor was selected as the most promising uranium treatment candidate for further development and field testing. While laboratory tests have shown that ammonia treatment effectively reduces the mobility of uranium, additional information is needed to enable deployment of this technology for remediation. Of importance for field applications are aspects of the technology associated with effective distribution of ammonia to a targeted treatment zone, understanding the fate of injected ammonia and its impact on subsurface conditions, and identifying effective monitoring approaches. In addition, information is needed to select equipment and operational parameters for a field design. As part of development efforts for the ammonia technology for remediation of vadose zone uranium contamination, field scale-up issues were identified and have been addressed through a series of laboratory and modeling efforts. This report presents a conceptual description for field application of the ammonia treatment process, engineering calculations to support treatment design, ammonia transport information, field application monitoring approaches, and a discussion of processes affecting the fate of ammonia in the subsurface. The report compiles this information from previous publications and from recent research and development activities. The intent of this report is to provide technical information about these scale-up elements to support the design and operation of a field test for the ammonia treatment technology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Evaluating the Implications of Climate Projections on Heat Hardiness Zones for Green Infrastructure Planning

Background: Green Infrastructure (GI) is widely being promoted as an adaptation strategy for urban flooding. Like urban flooding, tree species could be impacted by future climatic conditions. However, there have been limited studies on the implications of future climate on GI planning, mostly due to the lack of climate data at higher spatial resolutions. Objective: Here in this paper, we analyze the implications of climate projections on heat hardiness zones since this could impact the GI landscape in the coming years. This is an extension of our earlier work on evaluating impacts of climate projections on plant hardiness zones. Method: Using downscaled daily temperature data from ten Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models for the historical (1980-2005) and projected (2025-2050) periods, we analyzed future heat hardiness zones in the watershed bounding Knox County, TN. We analyzed the implications of these outputs for the current list of suggested native and non-native tree species selected for GI in the study area. Results: All the models suggest that a considerable part of the study area will move into the next warmer heat zone. While most trees remain suitable for GI, several are at the limit of their ideal heat zones. Conclusion: The insights from this study will help to guide the selection and placement of GI across the study area. Specifically, it should help green infrastructure planners design better mitigation and adaptation strategies to achieve higher returns on investments as more cities are now investing in GI projects.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Crossing Multiple Gray Zones in the Transition from Mesoscale to Microscale Simulation over Complex Terrain

This review paper explores the field of mesoscale to microscale modeling over complex terrain as it traverses multiple so-called gray zones. In an attempt to bridge the gap between previous large-scale and small-scale modeling efforts, atmospheric simulations are being run at an unprecedented range of resolutions. The gray zone is the range of grid resolutions where particular features are neither subgrid nor fully resolved, but rather are partially resolved. The definition of a gray zone depends strongly on the feature being represented and its relationship to the model resolution. This paper explores three gray zones relevant to simulations over complex terrain: turbulence, convection, and topography. Taken together, these may be referred to as the gray continuum. The focus is on horizontal grid resolutions from ∼10 km to ∼10 m. In each case, the challenges are presented together with recent progress in the literature. A common theme is to address cross-scale interaction and scale-awareness in parameterization schemes. How numerical models are designed to cross these gray zones is critical to complex terrain applications in numerical weather prediction, wind resource forecasting, and regional climate modeling, among others.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Vadose Zone Transport of Tritium and Nitrate under Ponded Water Conditions

Vadose zone transport of tritium and nitrate can be important considerations at radioactive waste sites, landfills, or areas with industrial impacts. These contaminants are of particular concern because they typically have a relatively higher mobility in the subsurface compared to other compounds. Here, we describe a semiarid site with tritium and nitrate contamination involving a manmade ponded water source above a thick unsaturated zone at Los Alamos National Laboratory in New Mexico, USA. This study demonstrates the value of vadose zone flow and transport modeling for the development of field investigation plans (i.e., identifying optimal borehole locations and depths for contaminant characterization), and how a combination of modeling with isotope and geochemical measurements can provide insight into how tritium and nitrate transport in the vadose zone in semiarid environments. Modeling results suggest that at this location, tritium transport is well predicted by classical multiphase theory. Our work expands the demonstrated usefulness of a standard tritium conceptual model to sites with ponded surface conditions and agrees with previous results where a standard model was able to explain the evolution of a tritium plume at an arid waste disposal site. In addition, depth-based analyses of δ 18 O and δ 2 H of pore waters helped confirm the extent of pond infiltration into the vadose zone, and the δ 15 N of nitrate showed that the contaminant release history of the site was different than originally assumed.

58 GEOSCIENCES↗
DOE OSTI2017

Chaotic Zones around Rotating Small Bodies

Small bodies of the solar system, like asteroids, trans-Neptunian objects, cometary nuclei, and planetary satellites, with diameters smaller than 1000 km usually have irregular shapes, often resembling dumb-bells or contact binaries. The spinning of such a gravitating dumb-bell creates around it a zone of chaotic orbits. We determine its extent analytically and numerically. We find that the chaotic zone swells significantly if the rotation rate is decreased; in particular, the zone swells more than twice if the rotation rate is decreased 10 times with respect to the “centrifugal breakup” threshold. We illustrate the properties of the chaotic orbital zones in examples of the global orbital dynamics about asteroid 243 Ida (which has a moon, Dactyl, orbiting near the edge of the chaotic zone) and asteroid 25143 Itokawa.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Estimating the Impact of Vadose Zone Sources on Groundwater to Support Performance Assessment of Soil Vapor Extraction

Soil vapor extraction (SVE) is a prevalent remediation approach for volatile contaminants in the vadose zone. To support selection of an appropriate endpoint for the SVE remedy, an evaluation is needed to determine whether vadose zone contamination has been diminished sufficiently to protect groundwater. When vapor-phase transport is an important component of the overall contaminant fate and transport from a vadose zone source, the contaminant concentration expected in groundwater is controlled by a limited set of parameters, including specific site dimensions, vadose zone properties, and source characteristics. An approach was developed for estimating the contaminant concentration in groundwater resulting from a contaminant source in the vadose zone based on pre-modeling contaminant transport for a matrix of parameter value combinations covering a range of potential site conditions. An interpolation and scaling process are then applied to estimate groundwater impact for site-specific conditions.

58 GEOSCIENCES↗
DOE OSTI2019

The Decarburization Kinetics of Metal Droplets in Emulsion Zone

Abstract:: A mathematical model has been developed to predict the decarburization rate within individual droplets in the emulsion zone. All the chronological events pertaining to the life cycle of a metal droplet in the emulsion zone like oxygen supply (from slag), external and internal decarburization have been modeled dynamically and validated against experimental data available in open literature. The bloating behavior of metal droplets in the emulsion was represented theoretically by incorporating an escape function dependent on internal CO gas generation. The model is able to predict the onset of bloating and the residence time of metal droplets in the emulsion zone. The residence time of droplet containing 2.6 wt pct C and 0.007 wt pct S is in the range of 10 to 13 seconds. The contribution of decarburization rate in the emulsion zone to the overall decarburization rate is studied using the industrial data reported by Cicutti et al. The model predicts 5 to 75 pct of total decarburization takes place in the emulsion zone. It is found that the extent of decarburization of a metal droplet depends on its initial carbon content rather than its oxygen content for slag containing FeO greater than 10 wt pct.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Deep Vadose Zone Contaminant Flux Evaluation at the Hanford BY-Cribs Site using Forward and Imposed Concentration Modeling Approaches

For sites with vadose zone contamination, the nature and extent of groundwater contaminant plumes are related to the flux into groundwater. In thick vadose zones at arid sites, transport is likely relative slow, complicating direct measurement of contaminant flux. A predictive numerical analysis was applied to estimate contaminant flux to groundwater at the Hanford BY Cribs site. The site received large amounts of waste water in the 1950’s, containing contaminants such as technicium-99 and nitrate. Recently, large increases in groundwater concentrations have been observed in site groundwater wells and, for potential remediation purposes, the assumption that the changes are the result of increased vadose zone fluxes into groundwater needed to be evaluated. The analysis approach uses forward simulations, tracking contaminants during and after disposal, and imposed concentration (IC) simulations, where concentrations, derived from electrical conductivity data obtained in 2007, are imposed on the flow field. A total of three IC methods, relating electrical conductivity to nitrate concentrations, are developed and tested. The numerical analysis shows that the forward simulations predict high fluxes during and directly after disposal, with decreasing trends starting not later than 1970. Although the IC simulations show differences in the nitrate vadose zone mass imposed in 2007 compared to forward simulations, the IC simulations also show declining nitrate fluxes over time. The predicted fluxes of the forward and IC simulations after 2007 are in reasonable agreement. Given the declining nature of the contaminant fluxes, it can be concluded that the observed concentration increases in the groundwater below the BY Cribs site cannot be explained as resulting from an increase in contaminant flux from the vadose zone. An alternative explanation, based on the observed decrease in aquifer thickness below the site, is presented.

Oostrom, Martinus↗
DOE OSTI2023

Stochastic scheduling for commercial building cooling systems: considering uncertainty in zone temperature prediction

Here, this paper presents the first attempt to address the uncertainty in zone temperature prediction with stochastic optimization. The uncertain zone temperature is a process uncertainty and has not been considered in the existing stochastic optimization for building control. To fill this gap, we proposed a novel formulation of stochastic optimization to handle process uncertainty in building control. Specifically, we first examined the accuracy of a typical linear model for predicting zone temperature. We then formulated the scheduling of the building cooling system as a stochastic optimization problem over a 24-hour look-ahead period to minimize the electricity cost of the studied building cooling system. After that, we applied the proposed stochastic load scheduling (SLS) to a direct expansion (DX) cooling system that serves a medium office building. Through simulation with a detailed building energy simulation software, EnergyPlus, we evaluated the operational cost and the thermal comfort compared with a deterministic load scheduling. The operation cost of scheduling was found to vary with the level of zone temperature prediction uncertainty. The proposed SLS can mitigate the impacts of uncertain zone temperature predictions on both operational cost and thermal comfort. The evaluation results indicate that the proposed SLS works better when the uncertainty level is more significant.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Validation of an inverse model of zone air heat balance

Our work introduces the validation method and results of an inverse model of zone air heat balance. The inverse model, implemented in EnergyPlus and published in a previous article [1], calculates highly uncertain model parameters such as internal thermal mass and infiltration airflow by inversely solving the zone air heat balance equation using the easy-to-measure zone air temperature data. The paper provides technical details of validation from the experiments using LBNL's Facility for Low Energy eXperiment in Buildings (FLEXLAB) that measures zone air temperature under the controlled experiment of two levels of internal mass and four levels of infiltration airflow. The simulation results of the zone infiltration airflow and internal thermal mass from the inverse model agree well with the measured data from the FLEXLAB experiments. The validated inverse model in EnergyPlus can be utilized to enhance the energy modeling of existing buildings that enables energy performance assessments for energy efficiency improvements.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Persistence of uranium groundwater plumes: Contrasting mechanisms at two DOE sites in the groundwater-river interaction zone

We examine subsurface uranium (U) plumes at two U.S. Department of Energy sites that are located near large river systems and that are influenced by groundwater-river hydrologic interaction. Following surface excavation of contaminated materials, both sites were projected to naturally flush remnant uranium contamination to levels below regulatory limits (e.g., 30 µg/L or 0.126 µmol/L; U.S. EPA drinking water standard), with 10 years projected for the Hanford 300 Area (Columbia River) and 12 years for the Rifle site (Colorado River). The rate of observed uranium decrease was much lower than expected at both sites. While uncertainty remains, a comparison of current understanding suggests that the two sites have common, but also different mechanisms controlling plume persistence. At the Hanford 300 A, the persistent source is adsorbed U(VI) in the vadose zone that is released to the aquifer during spring water table excursions. The release of U(VI) from the vadose zone and its transport within the oxic, coarse-textured aquifer sediments is dominated by kinetically-limited surface complexation. Modeling implies that annual plume discharge volumes to the Columbia River are small (< one pore volume). At the Rifle site, slow oxidation of naturally reduced, contaminant U(IV) in the saturated zone and a continuous influx of U(VI) from natural, up-gradient sources influences plume persistence. Rate-limited mass transfer and surface complexation also control U(VI) migration velocity in the sub-oxic Rifle groundwater. Flux of U(VI) from the vadose zone at the Rifle site may be locally important, but it is not the dominant process that sustains the plume. A wide range in microbiologic functional diversity exists at both sites. Strains of Geobacter and other metal reducing bacteria are present at low natural abundance that are capable of enzymatic U(VI) reduction in localized zones of accumulated detrital organic carbon or after organic carbon amendment. Major differences between the sites include the geochemical nature of residual, contaminant U; the rates of current kinetic processes (both biotic and abiotic) influencing U(VI) solid-liquid distribution; the presence of detrital organic matter and the resulting spatial heterogeneity in microbially-driven redox properties; and the magnitude of groundwater hydrologic dynamics controlled by river-stage fluctuations, geologic structures, and aquifer hydraulic properties. The comparative analysis of these sites provides important guidance to the characterization, understanding, modeling, and remediation of groundwater contaminant plumes influenced by surface water interaction that are common world-wide.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2013

Microstructure characterization of the stir zone of submerged friction stir processed aluminum alloy 2219

Aluminum alloy 2219-T6 was friction stir processed using a novel submerged processing technique to facilitate cooling. Processing was conducted at a constant tool traverse speed of 200 mm/min and spindle rotation speeds in the range from 600 to 800 rpm. The microstructural characteristics of the base metal and processed zone, including grain structure and precipitation behavior, were studied using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness maps were constructed on polished cross sections of as-processed samples. The effect of tool rotation speed on the microstructure and hardness of the stir zone was investigated. The average grain size of the stir zone was much smaller than that of the base metal, but the hardness was also lower due to the formation of equilibrium θ precipitates from the base metal θ′ precipitates. Stir zone hardness was found to decrease with increasing rotation speed (heat input). The effect of processing conditions on strength (hardness) was rationalized based on the competition between grain refinement strengthening and softening due to precipitate overaging. - Highlights: • SZ grain size (∼ 1 μm) is reduced by over one order of magnitude relative to the BM. • Hardness in the SZ is lower than that of the precipitation strengthened BM. • Metastable θ′ in the base metal transforms to equilibrium θ in the stir zone. • Softening in the SZ results from a decrease of precipitation strengthening.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Li-atoms-induced structure changes of Guinier–Preston–Bagaryatsky zones in AlCuLiMg alloys

Guinier–Preston–Bagaryatsky (GPB) zones are the well-known strengthening precipitates of AlCuMg alloys formed upon thermal ageing. Here we report that when formed in AlCuLiMg alloys the GPB zones can change significantly in morphology and structure. It is shown that though they do still consist of Al, Cu and Mg elements fundamentally, the GPB zones in AlCuLiMg alloys have a rather different structure due to a featured Li-segregation at their interfaces with the matrix and possible Li-replacement of partial Mg atoms in the structure. As such the Li-containing GPB zones often develop from one-dimensional to quasi-two-dimensional precipitates. - Highlights: • We observe Guinier–Preston–Bagaryatsky zone variants in AlCuLiMg alloys. • We obtain atomic-resolution images of the precipitates and model their structures. • Li-atoms play a key role in modifying the structure of these precipitate variants.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Lattice rotations in precipitate free zones in an Al-Mg-Si alloy

Highlights: • Recovery processes in precipitate free zones differ from those in grain interiors. • Most precipitate free zones contain few dislocations, after deformation. • Deformation can induce large misorientations in precipitate free zones. • Some deformed precipitate free zones contain nanoscale grains. - Abstract: Scanning precession electron diffraction and automated crystal orientation mapping in a transmission electron microscope (TEM) have been applied to quantitatively study the crystal orientation of precipitate free zones (PFZs) of four GB regions in an AA6060 alloy in peak aged condition (temper T6) after uniaxial compression to 20% engineering strain. The PFZ width in the alloy was found to be w = 170 ± 40 nm. The results show that some PFZs develop significant misorientations relative to their parent grain, and represent, to the best knowledge of the authors, the first quantitative evidence of this. This misorientation may either be constant inside a particular PFZ, making it appear like a band or a very elongated subgrain, or be partitioned in discrete regions with a diameter comparable to the PFZ width, making the former PFZ into a collection of small grains. The band-like PFZ observed in this work had a misorientation relative to its parent grain of ≈ 7°, while the grain-like PFZ had grains with misorientations between ≈ 12° and ≈ 20° relative to its parent grain. The other PFZs that were observed had only limited misorientations relative to their parent grains, and had either dislocations perpendicular to the GB plane or a dislocation wall at the transition region. A general TEM study of the material at various engineering strains was also conducted and suggests that grain-like PFZs are more frequent for larger strains, indicating that the different PFZ features are likely due to different strain localisation in individual PFZs. This localisation is expected to be influenced by the orientation of the loading axis relative to crystal orientations and GB planes. It is also suggested that the different PFZ features engender different work hardening rates and possibly affect nucleation of intergranular fracture. The results support previous studies on the microstructure evolution of PFZs in age-hardenable aluminium alloys during deformation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Characterization of multi-regime reaction zones in a piloted inhomogeneous jet flame with local extinction

In this study, gradient free regime identification (GFRI) is applied to 1D Raman/Rayleigh/LIF measurements of temperature and major species from the intermediate velocity case of the Sydney piloted inhomogeneous jet flame series to better understand the structure of reaction zones and the downstream evolution of multi-regime characteristics. The GFRI approach allows local reaction zones to be detected and characterized as premixed, dominantly premixed, multi-regime, dominantly non-premixed, or non-premixed flame structures, based on flame markers (mixture fraction, chemical mode, and heat release rate) derived from the experimental data. The statistics of chemical mode zero-crossings, which mark premixed reaction zones, and the relative populations of flame structures are shown to be sensitive to the state of mixing in the near field of the flame and to the level of local extinction farther downstream. Multi-regime structures, where premixed and non-premixed reaction zones occur in close proximity and both contribute to overall heat release, account for nearly half the total population at streamwise locations within the first several jet diameters. There is a rapid transition within the near field whereby the relative population of non-premixed and dominantly non-premixed structures grows from 0.05 to nearly 0.5, and the population of premixed and dominantly premixed structures decreases correspondingly as fluid entering the reaction zone becomes progressively fuel-rich. Local extinction and re-ignition bring a resurgence in premixed-type structures, many of which occur at fuel-lean conditions. There are also modest populations of multi-regime structures, having chemical mode zero-crossings at lean conditions, which would not exist in a fully burning jet flame.

42 ENGINEERING↗
DOE OSTI2023

The effects of mixed-species root zones on the resistance of soil bacteria and fungi to long-term experimental and natural reductions in soil moisture

Mixed forest stands tend to be more resistant to drought than species-specific stands partially due to complementarity in root ecology and physiology. For this work, we asked whether complementary differences in the drought resistance of soil microbiomes might contribute to this phenomenon. We experimented on the effects of reduced soil moisture on bacterial and fungal community composition in species-specific (single species) and mixed-species root zones of Norway spruce and European beech forests in a 5-year-old throughfall-exclusion experiment and across seasonal (spring-summer-fall) and latitudinal moisture gradients. Bacteria were most responsive to changes in soil moisture, especially members of Rhizobiales, while fungi were largely unaffected, including ectomycorrhizal fungi (EMF). Community resistance was higher in spruce relative to beech root zones, corresponding with the proportions of drought-favored (more in spruce) and drought-sensitive bacterial taxa (more in beech). The spruce soil microbiome also exhibited greater resistance to seasonal changes between spring (wettest) and fall (driest). Mixed-species root zones contained a hybrid of beech- and spruce-associated microbiomes. Several bacterial populations exhibited either enhanced resistance or greater susceptibility to drought in mixed root zones. Overall, patterns in the relative abundances of soil bacteria closely tracked moisture in seasonal and latitudinal precipitation gradients and were more predictive of soil water content than other environmental variables. We conclude that complementary differences in the drought resistance of soil microbiomes can occur and the likeliest form of complementarity in mixed-root zones coincides with the enrichment of drought-tolerant bacteria associated with spruce and the sustenance of EMF by beech.

54 ENVIRONMENTAL SCIENCES↗