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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Extreme Heterogeneity 2018 - Productive Computational Science in the Era of Extreme Heterogeneity: Report for DOE ASCR Workshop on Extreme Heterogeneity

The 2018 Basic Research Needs Workshop on Extreme Heterogeneity identified five Priority Research Directions for realizing the capabilities needed to address the challenges posed in this era of rapid technological change. This report captures the outcomes of that workshop. In the context of extreme heterogeneity, it defines basic research needs and opportunities in computer science research to develop smart and trainable operating and runtime systems, programming environments, and predictive tools that will make future systems easier to adapt to scientists’ computing needs and easier for facilities to deploy securely.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and wide angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. In conclusion, utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.

36 MATERIALS SCIENCE↗
DOE OSTI2018

ECCI based characterization of dislocation shear in polycrystalline arrays during heterogeneous deformation of commercially pure titanium

A new electron channeling contrast imaging (ECCI) based approach for the characterization of heterogeneous plastic deformation across multiple grains in a polycrystal is presented. The nature of the shear accommodation at grain boundaries has been assessed by evaluating the spatial distribution of dislocations and slip system activities near the boundaries and relating these observations to standard slip transfer criteria and the global state of stress. The direction of slip band propagation, and consequently the location of dislocation slip band nucleation, was determined by characterizing the slip band widths across individual grains. This assessment leads to a better understanding of the factors involved in polycrystalline deformation, including the grain boundary shear accommodation associated with both dislocation pile-ups and grain boundary dislocation nucleation. Because ECCI allows study of dislocation structures over large surface areas, and thus larger overall volumes than typically are accessible by other techniques, the overall approach allows the dislocation distribution across individual grains to be understood in terms of the broader polycrystalline constraints.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of chemical and physical heterogeneities on colloid-facilitated cesium transport

A set of column experiments was conducted to investigate the chemical and physical heterogeneity effect on colloid facilitated transport under slow pore velocity conditions. Pore velocities were kept below 100 cm d-1 for all experiments. Glass beads were packed into columns establishing four different conditions: 1) homogeneous, 2) mixed physical heterogeneity, 3) sequentially layered physical heterogeneity, and 4) chemical heterogeneity. The homogeneous column was packed with glass beads (diameter 500-600 µm), and physical heterogeneities were created by sequential layering or mixing two sizes of glass bead (500-600 µm and 300-400 µm). A chemical heterogeneity was created using 25% of the glass beads coated with hydrophobic molecules (1H-1H-2H-2H-perfluorooctyltrichlorosilane) mixed with 75% pristine glass beads (all 500-600 µm). Input solution with 0.5 mM CsI and 50 mg L-1 colloids (1-µm diameter SiO2) was pulsed into columns under saturated conditions. The physical heterogeneity in the packed glass beads retarded the transport of colloids compared to homogeneous (R = 25.0), but showed only slight differences between sequentially layered (R = 60.7) and mixed heterogeneity(R = 62.4). The column with the chemical, hydrophobic/hydrophilic, heterogeneity removed most of the colloids from the input solution. All column conditions stripped Cs from colloids onto the column matrix of packed glass beads.

Colloid-facilitated transport, cesium, physical he↗
DOE OSTI2017

Regime dependence of ice cloud heterogeneity – a convective life‐cycle effect?

Cloud condensate varies on scales smaller than those typically resolved by global weather and climate models. In order to accurately predict the radiative and microphysical process rates representative of the entire model grid box, the effect of the subgrid‐scale heterogeneity of cloud must be taken into account. In this study, observed ice water content retrieved from A‐Train satellite observations is used to explore how spatial ice condensate variability, characterized by the fractional standard deviation (FSD, the standard deviation divided by the mean), varies with cloud regime. FSD is generally lower for overcast cloud scenes, but an additional predictor based on convective activity is needed to capture the high FSD associated with more turbulent clouds and reproduce the observed latitudinal and height variations of FSD. Convective clouds that extend only a few kilometres above the freezing level are likely to be smaller at an earlier stage in their life cycle, and actively growing with a higher FSD. In contrast, more mature clouds reaching the tropopause are larger and generally have a lower variability and smaller FSD. To capture this life‐cycle effect, a new parametrization is tested which uses the ratio of a model's convectively detrained condensate to the existing cloud condensate mass as a proxy for the cloud's convective life stage to highlight areas with enhanced condensate variability. The parametrization is scale‐adaptive, situation‐dependent and captures seasonally varying global patterns and the zonal mean vertical structure of observed ice condensate variability well. Ground‐based observations obtained from five Atmospheric Radiation Measurement sites provide independent confirmation that the parametrization satisfactorily captures condensate variability in high‐altitude ice clouds.

Ahlgrimm, Maike↗
DOE OSTI2024

When and Where Lithium Plating Occurs, Its Correlation with Microstructure Heterogeneity, and the Mechanisms That Initiate and Self-Regulate Electrochemical Heterogeneity (A02-0444)

A microstructure scale electrochemical LIB model was used to investigate lithium plating onset, material non-uniform utilization, and in-plane heterogeneities for an NMC-graphite full cell. Model predicts active material particle surface roughness and size distribution (respectively, non-uniform curvature within and between particles) initiate in-plane heterogeneity, and that particle size heterogeneity at the separator interface controls the lithium plating preferential deposition ("Where"). These in-plane heterogeneities are then exacerbated by through-plane heterogeneities induced at fast charge as electrolyte depletion occurs and concentrates intercalation reaction near the anode-separator interface. Also, magnitude and occurrence of lithium plating is controlled by effective, or macroscale, microstructure parameters ("When"). As local states of charge start to diverge between nearby active material regions, overpotential differences induced by OCP difference kick in and contribute to reduce these SOC local heterogeneities. However, for staged materials such as graphite, with OCP profile alternating between plateaus and varying regions, this balancing mechanism is, respectively, inactive and active. This leads to a dynamic, non-monotonic, in-plane heterogeneity time evolution for state of charge and Faraday current density, for which their respective in-plane heterogeneity magnitude alternates. Such behavior has been modeled both for the whole electrode at the microstructure scale and at the particle scale. In-plane heterogeneities are usually considered to be detrimental, as they result in material non-uniform utilization (i.e., under and over stressed regions) and earlier degradations. However, this work provides a more granular approach as it discriminates between a harmful in-plane heterogeneity (non-uniform curvature) that triggers SOC in-plane heterogeneity, and a beneficial in-plane heterogeneity (Faraday current density) that contributes to reduce SOC in-plane heterogeneity. This work comprehensively explains the mechanisms that initiate, exacerbate, and regulate heterogeneity at the microstructure scale, while providing some design suggestions to reduce both in-plane and through-plane heterogeneities, as summarized in the graphical abstract.

ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

$\mathrm{RADICAL}$-Pilot and $\mathrm{PMIx}$/$\mathrm{PRRTE}$: Executing Heterogeneous Workloads at Large Scale on Partitioned $\mathrm{HPC}$ Resources

Execution of heterogeneous workflows on high-performance computing (HPC) platforms present unprecedented resource management and execution coordination challenges for runtime systems. Task heterogeneity increases the complexity of resource and execution management, limiting the scalability and efficiency of workflow execution. Re-source partitioning and distribution of tasks execution over portioned re-sources promises to address those problems but we lack an experimental evaluation of its performance at scale. Here this paper provides a performance evaluation of the Process Management Interface for Exascale (PMIx) and its reference implementation PRRTE on the leadership-class HPC plat-form Summit, when integrated into a pilot-based runtime system called RADICAL-Pilot. We partition resources across multiple PRRTE Distributed Virtual Machine (DVM) environments, responsible for launching tasks via the PMIx interface. We experimentally measure the work-load execution performance in terms of task scheduling/launching rate and distribution of DVM task placement times, DVM startup and termination overheads on the Summit leadership-class HPC platform. Integrated solution with PMIx/PRRTE enables using an abstracted, standardized set of interfaces for orchestrating the launch process, dynamic process management and monitoring capabilities. It extends scaling capabilities allowing to overcome a limitation of other launching mechanisms (e.g., JSM/LSF). Explored different DVM setup configurations provide insights on DVM performance and a layout to leverage it. Our experimental results show that heterogeneous workload of 65,500 tasks on 2048 nodes, and partitioned across 32 DVMs, runs steady with resource utilization not lower than 52%. While having less concurrently executed tasks resource utilization is able to reach up to 85%, based on results of heterogeneous workload of 8200 tasks on 256 nodes and 2 DVMs.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Heterogeneous Nucleation and Growth of Barium Sulfate at Organic–Water Interfaces: Interplay between Surface Hydrophobicity and Ba 2+ Adsorption

Barium sulfate (BaSO4) is a common scale-forming mineral in natural and engineered systems, yet the rates and mechanisms of heterogeneous BaSO4 nucleation are not understood. To address these, we created idealized interfaces on which to study heterogeneous nucleation rates and mechanisms, which also are good models for organic–water interfaces: self-assembled thin films terminated with different functional groups (i.e., -COOH, -SH, or mixed -SH & COOH) coated on glass slides. BaSO4 precipitation on coatings from Barite-supersaturated solutions (saturation index, SI, = 1.1) was investigated using grazing-incidence small-angle X-ray scattering. After reaction for 1 h, a little amount of BaSO4 formed on hydrophilic bare and -COOH coated glasses. Meanwhile, BaSO4 nucleation was significantly promoted on hydrophobic -SH and mixed -SH & COOH coatings. This is because substrate hydrophobicity likely affected the interfacial energy and hence thermodynamic favorability of heterogeneous nucleation. The heterogeneous BaSO4 nucleation and growth kinetics were found to be affected by the amount of Ba2+ adsorption onto the substrate and incipient BaSO4 nuclei. The importance of Ba2+ adsorption was further corroborated by the finding that precipitation rate increased under [Ba2+]/[SO42–] concentration ratios >1. These observations suggest that thermodynamic favorability for nucleation is governed by substrate–water interfacial energy, while given favorable thermodynamics, the rate is governed by ion attachment to substrates and incipient nuclei.

barite↗
DOE OSTI2021

The Impact of Behind-the-Meter Heterogeneous Distributed Energy Resources on Distribution Grids

The increasing integration of distributed energy resources (DERs) on the electric grid brings new challenges and opportunities for utility grid operations. With the rapid deployment of DERs, there is emerging interest in integrating these controllable devices with utility operations at all levels for monitoring and management. To understand the challenges with increasing behind-the-meter (BTM) DERs and to identify the needs in deploying advanced controls, a comprehensive grid impact study is indispensable. This paper presents the analysis which help visualize the DER impact on the grid, identify the challenges and provides an insight into the new distribution management and control needs to enable reliable and resilient grid operations.

behind-the-meter↗
DOE OSTI2018

A Heterogeneity-Aware Task Scheduler for Spark

Big data processing systems such as Spark are employed in an increasing number of diverse applications-such as machine learning, graph computation, and scientific computing-each with dynamic and different resource needs. These applications increasingly run on heterogeneous hardware, e.g., with out-of-core accelerators. However, big data platforms do not factor in the multi-dimensional heterogeneity of applications and hardware. This leads to a fundamental mismatch between the application and hardware characteristics, and the resource scheduling adopted in big data platforms. For example, Hadoop and Spark consider only data locality when assigning tasks to nodes, and typically disregard the hardware capabilities and suitability to specific application requirements. In this paper, we present RUPAM, a heterogeneity-aware task scheduling system for big data platforms, which considers both task-level resource characteristics and underlying hardware characteristics, as well as preserves data locality. RUPAM adopts a simple yet effective heuristic to decide the dominant scheduling factor (e.g., CPU, memory, or I/O), given a task in a particular stage. Our experiments show that RUPAM is able to improve the performance of representative applications by up to 62.3% compared to the standard Spark scheduler.

Computer Science↗
DOE OSTI2023

Middleware for a Heterogeneous CAV Fleet

This paper introduces CAN to ROS, a model-based code generation tool used in development, testing, and deployment of a heterogeneous fleet of vehicles with robotic sensing in ROS. Code generation supports two main features: (1) self-configuration for deployment in a heterogeneous vehicle fleet, and (2) quick iteration for testing and development of reading vehicle sensors and robotic control. This tool features the ability to detect the vehicle it is in and regenerate and rebuild itself at runtime to provide the proper two-way bridge between ROS and the sensed on-board vehicle sensor network. Code generation relies on a per-model defined JSON to map a CAN database (DBC) to the desired ROS topic names and message types. The live ROS publishing of CAN messages allows for instant feedback, and the code regeneration allows for adjustments in DBC or vehicle JSON to iteratively hone in on new vehicle signals. Generated ROS nodes are written in C++ for runtime use in lightweight embedded computers. This has been tested in vehicles from three different Original Equipment Manufacturers (OEMs), and can be extended to support a wide array of vehicles. By using a unifying ROS specification, a heterogeneous set of vehicles can be unified into a fleet with abstracted model-specific details; this opens the door for developing cross-model software applications for vehicle control, connected vehicle applications, or fleet monitoring systems.

42 ENGINEERING↗
DOE OSTI2022

Enhanced delivery of engineered Fe-Mn binary oxides in heterogeneous porous media for efficient arsenic stabilization

Heterogeneity in sediment and aquifer is universal, resulting in preferential flows of injected materials in the high permeability regions and forming flow by-passed zones in the low permeability regions during in-situ subsurface remediation. This adverse effect can considerably delay the completion of remedial operations and significantly increase the cost. Column experiments were designed and conducted to study the transport of starch- and starch-xanthan gum modified Fe-Mn binary oxide particles (SFM and SXFM) in saturated heterogeneous porous media and to reveal the particles’ arsenic (As) stabilization performance. Fine-in-Coarse (FIC) and Coarse-in-Fine (CIF) patterns of heterogeneous packings were set up in the columns. Testing results demonstrated that starch-xanthan gum dual treatment on Fe-Mn binary oxides successfully improved the particles’ migration capability in heterogeneous porous media and their distribution uniformity attributed to the profound shear thinning behavior of xanthan gum solution. The addition of xanthan gum to the system increased the viscosity and shear thinning property of SXFM suspension, making it a better candidate for delivery. Both SFM and SXFM stabilized As in heterogeneously packed sediment collected from a contaminated site, with SXFM showing better stabilization performance than SFM. The stabilization effects of SXFM were 90.7-97.0%, compared to 82.0-95.2% of SFM.

Yan, Xiulan↗
DOE OSTI2025

Well-defined Pt(0) heterogeneous hydrosilylation catalysts supported by a surface bound phosphenium

Single atom, low valent transition metals are important for heterogeneous catalysis but are challenging to generate and stabilize in a well-defined manner. Herein, we explored the functionalization of silica with well-defined N-heterocyclic phosphenium (NHP) ions to heterogenize low-valent metals. The surface electro-statically bound [NHP] + coordinate to Pt(0) precursors resulting in well-defined, chemisorbed [(NHP)Pt(0)L n ] + sites. The resulting materials catalyze the hydrosilylation of alkynes and exhibit activities and selectivities that rival the current industry standard homogeneous catalysts. The catalysts leach Pt limiting their recyclability; however, recycling studies support that the high regioselectivities arise from heterogeneous sites and Pt particles do not form on the surface. Here we suspect that this phosphenium-based immobilization strategy will result in stable, tunable, low valent heterogeneous transition metal catalysts in a wider array of catalytic reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗