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At least 865 records · Page 48

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DOE OSTI2014

Accounting for baryonic effects in cosmic shear tomography: Determining a minimal set of nuisance parameters using PCA

Systematic uncertainties that have been subdominant in past large-scale structure (LSS) surveys are likely to exceed statistical uncertainties of current and future LSS data sets, potentially limiting the extraction of cosmological information. Here we present a general framework (PCA marginalization) to consistently incorporate systematic effects into a likelihood analysis. This technique naturally accounts for degeneracies between nuisance parameters and can substantially reduce the dimension of the parameter space that needs to be sampled. As a practical application, we apply PCA marginalization to account for baryonic physics as an uncertainty in cosmic shear tomography. Specifically, we use CosmoLike to run simulated likelihood analyses on three independent sets of numerical simulations, each covering a wide range of baryonic scenarios differing in cooling, star formation, and feedback mechanisms. We simulate a Stage III (Dark Energy Survey) and Stage IV (Large Synoptic Survey Telescope/Euclid) survey and find a substantial bias in cosmological constraints if baryonic physics is not accounted for. We then show that PCA marginalization (employing at most 3 to 4 nuisance parameters) removes this bias. Our study demonstrates that it is possible to obtain robust, precise constraints on the dark energy equation of state even in the presence of large levels of systematic uncertainty in astrophysical processes. We conclude that the PCA marginalization technique is a powerful, general tool for addressing many of the challenges facing the precision cosmology program.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Cache directory lookup reader set encoding for partial cache line speculation support

In a multiprocessor system, with conflict checking implemented in a directory lookup of a shared cache memory, a reader set encoding permits dynamic recordation of read accesses. The reader set encoding includes an indication of a portion of a line read, for instance by indicating boundaries of read accesses. Different encodings may apply to different types of speculative execution.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2016

Favorable Structural–Tectonic Settings and Characteristics of Globally Productive Arcs

There are currently 74 productive geothermal systems associated with volcanic centers (VCs) in arcs globally, including actively producing systems, past producing systems, and systems with successful flow tests. The total installed or tested capacity of these 74 geothermal systems is 7,605 MWe, ranging from 0.7 MWe each at Copahue, Chile and Barkhatnaya Sopka, Kamchatka to 795 MWe, Larderello, Italy, and averaging 90.5 MWe per system. These 74 productive VCs constitute 10% of 732 VCs distributed across more than a dozen major arcs around the world. The intra-arc (within-arc) tectonic setting is highly variable globally, ranging from extension to transtension, transpression, or compression. Furthermore, the shear strain associated with oblique plate convergence can be accommodated by either intra-arc or arc-marginal deformation. The structural-tectonic settings of these 74 productive VCs were characterized to add to a global catalog of parameters to help guide future exploration, development, and regional resource potential.

15 GEOTHERMAL ENERGY↗

DOE OSTI2016

Jacobi Set Computation

Jacobi Set Computation is a software to compute the Jacobi set of 2 piecewise linear scalar functions defined on a triangular mesh. This functionality is useful for analyzing multiple scalar fields simultaneously.

Bhatia, Harsh↗

DOE OSTI2019

A Tool for Evaluating Youth Engagement in an Informal STEM Setting: The WGG Observation Protocol

This paper discusses findings from the use of the Wise Guys and Gals (WGG) Observation of WGG Youth Protocol in a blended learning environment. The protocol was used to assess youth engagement when completing blended engineering design challenges at two Boys and Girls Clubs. WGG is a project funded through a grant from the National Science Foundation and which brings blended learning design challenges to middle school aged learners in informal STEM (science, technology, engineering, and mathematics) settings. This paper explores the feasibility of using the observation protocol to collect data about youth engagement, and the potential use of the protocol in other informal STEM settings.

99 GENERAL AND MISCELLANEOUS↗

DOE OSTI2020

Setting operating points for circuits in an integrated circuit chip using an integrated voltage regulator power loss model

An apparatus includes an integrated circuit chip with a set of circuits having two or more subsets of circuits; an external voltage regulator separate from the integrated circuit chip; two or more integrated voltage regulators on the integrated circuit chip that each provide an input voltage to a respective subset of the circuits; and a controller. The controller determines, using an integrated voltage regulator power loss model, an electrical power loss for the integrated voltage regulators for a first combination of operating points for the subsets of the circuits. The controller then determines, based on the electrical power loss, a second combination of operating points for the subsets of the circuits that includes an adjustment to an operating point for at least one of the subsets of the circuits that compensates for an electrical power loss of the corresponding integrated voltage regulator. The controller sets an operating point of each of the subsets of the circuits based on the second combination of operating points.

42 ENGINEERING↗

DOE OSTI2020

Albedo Data Sets for Bifacial PV Systems: Preprint

For use by the PV and financial communities to better estimate the performance and to reduce the risk of bifacial PV systems, data sets of ground albedo and associated meteorological data were developed by using existing measurement network data and data contributed by the PV industry. The data sets include time-series data as well as summary information of tabular monthly and yearly data and plots of monthly and hourly albedo values. Complete information is presented in a user’s guide and data are available for download from NREL’s DuraMAT website.

41 EE - Solar Energy Technologies Office (EE-4S)↗

DOE OSTI2021

PRECISE™ PREconfiguring and Controlling Inverter SEt-points: A Solution for Easy Solar Integration

PRECISE™ is a software solution for preconfiguring solar inverter settings. It can be used by utilities and system operators to efficiently process new inverter applications at much less the time and effort, and with greater precision for settings that optimize stability and energy savings. PRECISE has received an R&D 100 award, and has been used to dramatically cut wait times and labor costs for new residential solar installations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2022

Adaptive Protective Relay Settings – A Vision to the Future

Adaptive relaying utilizes the continuously changing status of the power system as the basis for online adjustment of the power system relay settings. Fundamentally they are protection schemes that adjust settings and/or logic of operations based on the prevailing conditions of the system. These adjustments can include, but are not limited to, the logging of data for post-mortem analysis, communication throughout the system, as well as changing relay parameters. Adaptive relaying considers the fact that the status of a power system can change. These include system configuration changes, load effect, cold load pickup, end-of-line protection, transformer protection, and automatic reclosing. In this research, the author focus on the need for a secure, selective, and reliable system for adaptive overcurrent protection in T&D and Distributed Energy Systems. Various types of adaptive methods are presented and explained along with some pros and cons of each.

Mukherjee, Srijib↗

DOE OSTI2017

Human-Centered Exoskeleton: Upper Extremity Strength Augmentation in Occupational Settings - 17297

Robotic exoskeletons have a wide variety of applications ranging from rehabilitation to military combat to strength- and performance-augmentation in occupational settings. Currently, the high-cost, complexity, and bio-mechanical limitations prevent these devices from introduction into specialized applications where low-cost and practicality are essential. Here, an initial prototype of Robotic Exoskeleton for Upper Extremity Strength Augmentation is introduced. Expanding upon previous three generations of robotic arms for muscle retraining, the new generation emphasizes high fidelity, low-cost, and practical strength-augmentation with focus on enhancing performance by muscle fatigue reduction and injury prevention. Simplified set up and configurability of the system make it suitable for highly dynamic environments, where time and safety are vital. This prototype demonstrates the feasibility of low-cost and practical exoskeletons; however, further improvements and investigations are necessary to improve and validate its function. (authors)

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2015

Advanced simulation capability for environmental management, integrated tool-sets and simulator to enhance public communication - 15186

The U.S. Department of Energy (US DOE) Office of Environmental Management (EM), Office of Soil and Groundwater Remediation, is supporting multi-laboratory development of the Advanced Simulation Capability for Environmental Management (ASCEM). ASCEM is an open source and modular computing framework that incorporates new advances and tools for predicting contaminant fate and transport in natural and engineered systems. ASCEM facilitates transparent, efficient and integrated approaches to modeling and site characterization, and provides robust and standardized assessments of performance and risk for EM cleanup and closure activities. Site subsurface simulation modeling and performance assessments are complex and involve sensitivity evaluations and uncertainty quantification to better understand the risks at a site. The ASCEM tool-set was designed in close collaboration with the sites and other potential end-users (both the public and regulators) to allow better communication and understanding of these complex modeling efforts. ASCEM's integrated tool-sets provide a user interface and tools for managing work-flows, including conceptual model development, management of data and metadata for model input, sensitivity analysis, model calibration and uncertainty analysis, model execution on diverse computational platforms, and processing of model output, including visualization. The hierarchical and modular design of ASCEM HPC simulator Amanzi easily lends itself to translating this conceptual model of a site into a numerical model that can easily be spatially and temporally discretized to run on the HPC simulator. Together this integrated work-flow allows for a seamless and integrated analysis tracking all provenance information and modeling uncertainties. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2015

Enhancing performance assessments using the ASCEM tool-set - 15222

The Office of Soil and Groundwater Remediation within the U.S. Department of Energy's Office of Environmental Management (EM) is supporting development of the Advanced Simulation Capability for Environmental Management (ASCEM). ASCEM is an open source and modular computing framework that incorporates new advances and tools for predicting contaminant fate and transport in natural and engineered systems. ASCEM integrates modeling tools into a common work-flow that facilitates integrated approaches to modeling and site characterization, and enables robust and standardized assessments of performance and risk for EM cleanup and closure activities. The ASCEM project includes collaboration with end users engaged in performance assessments and subsurface simulation. Two working groups are engaged in performance assessment activities at the Hanford Site and Savannah River Site (SRS). The Hanford Site working group is focused on evaluating an alternative conceptual model that includes fine-scale heterogeneities. The baseline conceptual model for the performance assessment includes the large-scale stratigraphy at the site. The working group is applying the ASCEM tool-set to develop and evaluate alternative conceptual models and evaluate the effect of heterogeneities on long-term transport under rainfall-driven conditions. Because the heterogeneous models require long compute times due to increased model complexity, the simulations are implemented on a high-performance computing platform to reduce simulation times. The ASCEM Akuna work-flow enables efficient organization, simulation execution, and processing and visualization of results. Current performance assessments for waste tank closure at the SRS are limited to two-dimensional axi-symmetric representations. The SRS working group is collaborating with the site contractor to address technical review issues by resolving fine-scale tank features and simulating three-dimensional flow with Richards equation for selected closure scenarios using the ASCEM simulator, Amanzi. The Akuna tool-set is being applied to support model setup, sensitivity analysis, uncertainty quantification, and visualization. Both of the ASCEM working groups are addressing issues that cannot readily be evaluated with the existing tools. In these efforts, ASCEM is being used to provide technical underpinnings for ongoing performance assessments. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2015

Incorporating climate and regional setting into realistic-efficacious end states for contaminated sites - 15386

Data from former uranium milling and processing sites in the arid western United States (US) exemplify a conceptual model in which climate and geomorphology, and the associated geochemical and hydrological conditions, control the fate and transport of contaminants. In arid settings, shallow groundwater is transferred to the vadose zone and atmosphere via evaporation, transpiration and seepage. During these transfers, dissolved constituents accumulate in the vadose zone near the capillary fringe and around the roots of phreatophyte plants. In areas where the water table is shallow, minerals will also accumulate at the surface as a result of capillarity and evaporation. Two western-semiarid former milling sites, Tuba City AZ and Riverton WY, represent deep and shallow water table cases, respectively. At Tuba City, hydrological and geochemical factors limit the size of the groundwater plume and reduce the potential for contaminated water to crop at the locally significant Moenkopi Wash. At both sites, minerals that have formed in the groundwater and vadose zone in the near-field and mid-field areas will sustain elevated groundwater concentrations of anthropogenic contaminants, such as sulfate and uranium, for an extended time frame. The presence of secondary source mineral accumulations in the vadose zone in the mid-field area at Riverton is significant because episodic flooding occurs at this site. The contaminant distributions and plume dynamics observed at arid sites contrast with sites in the eastern US with stronger hydrologic driving forces and weaker evaporative processes. In both arid and non-arid settings, long term contaminant behaviors and concomitant exposure, risk and remediation time frames are controlled by regional conditions and climate and by local modifying factors. As a result, incorporating these conditions and factors into environmental management decisions provides new opportunities to develop more robust, sustainable and technically-defensible end states. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2018

Hydrogeologic Setting and Groundwater Contaminant Conceptual Model, Los Alamos National Laboratory - 18681

Our understanding of the complex hydrogeologic setting at Los Alamos National Laboratory (LANL) has evolved significantly over the previous decade. The semi-arid, high-desert setting consists of generally dry drainages in canyons that head either in uplands to the west of the Laboratory or on the high mountain-front plateau where the Laboratory is spread across approximately 40 square miles. Some canyon drainages have spatially limited reaches with perennial surface water from natural runoff and spring sources and/or from permitted effluent sources. The Rio Grande rift basin-fill stratigraphy includes primary volcanic deposits from pyroclastic eruptions and intermediate composition lava flows, and fluvial and alluvial fan deposits. Highly complex and spatially variable stratigraphy governs the occurrences of three groundwater zones: shallow 'alluvial groundwater', deep perched groundwater, and a thick 'regional' aquifer that is the water supply for the community of Los Alamos and the Laboratory. The current understanding of the hydrogeologic framework was greatly expanded as part of a site hydrogeologic characterization program completed in 2005. Higher resolution information exists in area where more detailed groundwater characterization has been conducted to support specific project objectives. A conceptual model for occurrences of contaminants in each of the three groundwater zones is governed by four factors: contaminant solubility/mobility, the mass of historical release, presence of a continuous hydraulic driver, and 'breakthrough' geology, defined as geology conducive to infiltration of shallow groundwater to deeper groundwater zones. The Laboratory's operations were historically somewhat spatially partitioned. Most of the radionuclide work (and historical releases) was conducted in the northern portion of the Laboratory, high explosives work has taken place exclusively in the southwestern portion, and treated sanitary effluent was released at a limited number of outfalls. Historical material disposal areas (MDAs) are dispersed throughout the Laboratory, and active MDAs are all located on a single dry mesa at the eastern part of the Laboratory. Evidence exists of transport of anthropogenic constituents to the regional aquifer. However, years of groundwater characterization have identified only two cases for which all the key factors were present and a complete contaminant pathway to the regional aquifer has resulted in contamination at levels above an applicable standard. Hexavalent chromium contamination associated with historical use as a corrosion inhibitor in a power plant is present beneath Mortandad Canyon, and RDX contamination associated with high-explosives machining is present beneath Canon de Valle. Each of those project areas have refined conceptual and numerical models that address contaminant migration pathways, spatial extent of perched-intermediate groundwater, mass balance, and fate and transport within the regional aquifer. No known contamination is present in the regional aquifer associated with MDAs, and interestingly, much of the Laboratory's groundwater background dataset is from wells located beneath active MDAs. A comprehensive groundwater monitoring program is in place to track the evolution of chromium and RDX contamination, and to identify any other constituents that may be attributable to historical LANL operations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

The Challenges of Air Monitoring at a Soil Remediation Project in a Suburban Setting - 20448

Air monitoring during soil excavation at a chemically and radiologically impacted site in a suburban setting presents unique challenges. Site activities were conducted in a manner that minimized the release of airborne particulates of concern, principally radionuclides of concern (ROC). Dust and air monitoring were performed to ensure the public was not being exposed to the soil contaminants. The project team collected representative air and dust data while being mindful to not impose on the lives of residents in the area. Due to the close proximity to the public, there was a high level of oversight from the client and regulatory agencies. The challenges involved with air sampling at this soil remediation site located in a suburban setting included the number of contaminants, the ranges of risks and hazards presented by the contaminants and the method of remediation, the concerns of the regulators and the public, and the perception of risk from the public. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

Two-phase Flow Regime Transition Study using Level-Set Method

In Boiling Water Reactors (BWRs) the coolant exiting the core often has void fractions as high as 50%, resulting in high gas volume fraction two-phase flow regimes, such as annular or churn-turbulent flow. As the coolant boils along the subchannels it will experience flow regime transitions from bubbly to slug, slug to churn, and, finally, churn to annular. While these transition points are known to occur as a higher void develops along the flow path, the driving physics of the transition phenomenon is not well understood. Currently, experiment based correlations are the most reliable method for predicting where in the core the flow regime transitions will occur. However, experimentally, it's ever difficult to observe the details of the two-phase flow at prototypical pressures/temperatures, or, as with high fidelity experiments, the conditions differ from those in a reactor. Being able to predict these flow regime transitions is critical to safe and efficient reactor operations as well as maintaining fuel rod integrity by avoiding dryout. The characterization of flow regimes has been extensively studied, producing a wide set of flow regime maps based on characteristic parameters such as vapor and liquid superficial velocity, time dependent pressure drop, interfacial area density, etc. While these studies are useful in predicting the flow regime for certain geometry and flow conditions, they do not provide a universal predictive capability for any geometry under any conditions. Additionally, it is difficult to achieve reactor realistic pressure and temperature conditions in experiments. Direct Numerical Simulation (DNS) coupled with Interface Tracking Methods (ITMs) becomes advantageous in this case because the simulations are not limited by the material properties or to the real world conditions. DNS allows for analysis of flows that would be impossible to achieve, or observe in detail, experimentally. The finite element based DNS code, PHASTA (parallel, hierarchic, higher-order accurate, adaptive, stabilized transient analysis flow solver), used in this work utilizes the level set ITM and has been previously shown to properly resolve bubbly, slug, and annular flows, but not transitions between the two-phase flow regimes. The present work uses PHASTA to analyze flow in a pipe for various void fractions and superficial velocities. Flow regime transitions were induced to demonstrate the transient behavior of this phenomenon. With the unique advanced analysis capabilities developed in PHASTA that allow for individual bubble tracking, it becomes possible to extract new localized information about the flow behavior that is currently not attainable from experiments. The potential of this capability is to uncover the underlying physics of the flow regime transition phenomenon. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2024

Federated Machine Learning-Based Anomaly Detection System for Synchrophasor Network Using Heterogeneous Data Sets: Preprint

Synchrophasor technology is widely deployed in the energy management system to monitor the grid health at micro level and perform necessary corrective actions in real time; however, integrated phasor devices and data aggregators are exposed to several cybersecurity threats. This paper proposes a federated ML(FML)-based ADS to detect several data integrity attacks in the synchrophasor network. The proposed approach integrates the horizontal FML technique and consists of substation-based local models and a control center-based global model. The proposed methodology includes training local models using heterogeneous data sets that include network and grid information and updating the global model through multiple iterations by sharing model gradients. Finally, the trained global model is applied to identify cyberattacks, normal operation, and physical events. To validate the proof of concept, we used synthetic data sets generated by Mississippi State University and Oak Ridge National Laboratory for training and testing the classification models using the National Renewable Energy Laboratory's high performance computing resources. Our experimental results, computed through several performance measures, reveal that the proposed approach shows consistent performance during the binary, three-class, and multiclass classifications while ensuring privacy of synchrophasor data.

anomaly detection system↗

DOE OSTI2025

A hereditary integral, transient network approach to modeling permanent set and viscoelastic response in polymers

An efficient numerical framework is presented for modeling viscoelasticity and permanent set of polymers. It is based on the hereditary integral form of transient network theory, in which polymer chains belong to distinct networks each with different natural equilibrium states. Chains continually detach from previously formed networks and reattach to new networks in a state of zero stress. The free energy of these networks is given in terms of the deformation gradient relative to the configuration at which the network was born . A decomposition of the kernel for various free energies allows for a recurrence relationship to be established, bypassing the need to integrate over all time history. The technique is established for both highly compressible and nearly incompressible materials through the use of neo-Hookean, Blatz–Ko, Yeoh, and Ogden-Hill material models. Multiple examples are presented showing the ability to handle rate-dependent response and residual strains under complex loading histories.

Finite element method↗