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Results for “concept drift”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Adaptive Learning for Concept Drift in Application Performance Modeling

Supervised learning is a promising approach for modeling the performance of applications running on large HPC systems. A key assumption in supervised learning is that the training and testing data are obtained under the same conditions. However, in production HPC systems these conditions might not hold because the conditions of the platform can change over time as a result of hardware degradation, hardware replacement, software upgrade, and configuration updates. These changes could alter the data distribution in a way that affects the accuracy of the predictive performance models and render them less useful; this phenomenon is referred to as concept drift. Ignoring concept drift can lead to suboptimal resource usage and decreased efficiency when those performance models are deployed for tuning and job scheduling in production systems. To address this issue, we propose a concept-drift-aware predictive modeling approach that comprises two components: (1) an online Bayesian changepoint detection method that can automatically identify the location of events that lead to concept drift in near-real time and (2) a moment-matching transformation inspired by transfer learning that converts the training data collected before the drift to be useful for retraining. We use application input/output performance data collected on Cori, a production supercomputing system at the National Energy Research Scientific Computing Center, to demonstrate the effectiveness of our approach. The results show that concept-drift-aware models obtain significant improvement in accuracy; the median absolute error of the best-performing Gaussian process regression improved by 58.8% when the proposed approaches were used.

adaptive learning↗
DOE OSTI2022

A Data Quality-Aware Framework to Reliably Forecast Photovoltaic Generation and Consumer Load for an Improved Resilience of Microgrids

Photovoltaic (PV) power and consumer load forecasting plays a critical role to ensure operational resilience of the electric grid. Most data-driven forecasting algorithms rely heavily on the continuous availability of good quality data for periodic training and validation. When deployed at the grid’s edge, prolonged disruptions to communications during extreme events degrade data quality. Factors such as missing observations, epistemic uncertainties, data drift, and concept drift are manifestations of data quality that impact the generalization of such field-deployed forecasting models. Currently, there exists no mechanism in the literature to dynamically switch between models under varying degrees of data quality as quantified by certain metrics for each factor highlighted above. This paper addresses this shortcoming by conceptually introducing a data qualityaware framework for reliable PV generation and consumer load forecasting. The framework’s design incorporates components of missing values, divergence tests, and continuous monitoring of generalization performance to detect changes in data quality caused by communications disruptions and trigger specific classes of forecasting models grouped under three use cases (UC1- UC3). As a first step towards validating this framework, real data collected from an actual field microgrid system is used to demonstrate the viability of the three use cases. Results show that the performance is the best in UC1 with an unadjusted R-square value of 0.954, followed by 0.939 for UC2 and 0.757 for UC3.

Sundararajan, Aditya↗
DOE OSTI2024

Evaluating Model Robustness for Defect Identification and Classification in a Composite Aerostructure Material

Aircraft structures are required to have a high level of quality to satisfy their need for light weight, efficient flight, and withstanding high loads over their lifespan. These aerostructures are typically made from a composite material due to their good tensile strength and resistance to compression. To ensure their structural integrity, the composite material requires inspection for common flaws such as porosity, delaminations, voids, foreign object debris, and other defects. Ultrasonic testing (UT) is a popular non-destructive inspection (NDI) technique used for effectively evaluating the composite material. Current inspection methods rely heavily on human experience and are extremely time consuming. Therefore, there is a need for the development of techniques to reduce the manual inspection time. This work compares the performance of different deep learning-based methods in the identification and classification of defects. Deep learning has shown great promise in numerous fields, and we show its effectiveness in the evaluation of the composite aerostructure material. The methods developed here are both highly reliable with a top recall value of 98.64% as well as extremely efficient requiring an average of 4 s during the inferencing stage to evaluate new composites. Lastly, we investigate model robustness to concept drift by measuring its performance over time.

36 MATERIALS SCIENCE↗
NASA NTRS2009

Drifting Recovery Base Concept for GEO Derelict Object Capture

Over 250 objects hover within 6 m/sec of perfect geostationary orbit. Over half of these objects lie within 0.1 m/sec of the GEO velocity. Such items have 62% of the total velocity required to achieve Earth gravitational escape. A conceptual architecture is proposed to clean this orbit area of derelict objects while providing a demonstration mission for many facets of future asteroid mining operations. These near-GEO objects average nearly 2000kg each, consisting of (typically functioning) power systems, batteries, and large quantities of components and raw aerospace-grade refined materials. Such a demonstration collection system could capture, collect and remove all GEO derelict objects in an international effort to create a depot of components and of aerospace-grade raw materials--with a total mass greater than that of the International Space Station--as a space scrap depot ready for transfer to lunar or Mars orbit, using only two heavy-lift launches and 2-3 years of on-orbit operations.

Bacon, John B.↗
DOE OSTI2022

A LArTPC with Vertical Drift for the DUNE Far Detector

The Far Detector of the Deep Underground Neutrino Experiment (DUNE) will be a large LArdetector located at a baseline of 1300 kilometers, 1.5 km deep underground. It is planned to bemade up of four modules, each with a total mass of 17 kt of LAr, at least the first two of which willconsist in Liquid Argon Time Projection Chambers (LArTPCs). To prove the feasibility of theLArTPC technology at the kiloton scale, the ProtoDUNE Single and Dual-Phase detectors wereconstructed and operated at the CERN Neutrino facility.This document describes the Vertical Drift detector concept, which is proposed to instrument thesecond DUNE module. It consists of a TPC where the electrons drift vertically, with a cathodesuspended at mid-height, towards anodes placed at the bottom and top of the detector. The anodeswould be made out of printed PCBs instead of wires, and the new disposition would allow the topreadout electronics to be accessible during the lifetime of the experiment. An enhanced photo-detection system is also proposed, with the photo-sensors placed on the cryostat walls and thecathode, but posing a challenge in terms of power and signal transmission. Studies are ongoingboth to overcome the technical challenges of this new design and to finalize the concept.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Experiments and Modeling to Support Field Test Design

Salt repositories continue to be a primary concept for disposal of heat-generating nuclear waste (HGNW). For the past several years, efforts have focused on the in-drift disposal concept (e.g. Hansen and Leigh 2011; Stauffer et al. 2013; Jordan et al. 2015a,b,c; Bourret et al. 2016; Hansen et al. 2016; Bourret et al. 2017; Johnson et al. 2017a,b; Kuhlman et al. 2017). Ongoing research efforts aim to improve understanding of the behavior of the salt backfill surrounding HGNW sources, the responses of drift walls to heat sources, and the chemistry and chemical evolution of brine in such environments.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2026

Uncertainty guided online ensemble for non-stationary data streams in fusion science

Machine Learning (ML) is poised to play a pivotal role in the development and operation of next-generation fusion devices. Fusion data shows non-stationary behavior with distribution drifts, resulted by both experimental evolution and machine wear-and-tear. ML models assume stationary distribution and fail to maintain performance when encountered with such non-stationary data streams. Online learning techniques have been leveraged in other domains, however it has been largely unexplored for fusion applications. In this paper, we investigate online learning for continuous adaptation to drifting data streams in the prediction of Toroidal Field (TF) coils deflection at the DIII-D fusion facility. We further address the short-term performance degradation inherent to standard online learning, which arises because ground truth is unavailable at prediction time. To mitigate this issue, we propose an uncertainty-guided online ensemble framework. The method leverages the Deep Gaussian Process Approximation (DGPA) for calibrated uncertainty estimation and uses these uncertainty measures to guide a meta-algorithm that aggregates predictions from learners trained over different historical horizons. Our results show that online learning reduces prediction error by 80% compared to a static model. The online ensemble and the proposed uncertainty-guided ensemble further reduce error by approximately 6%, and 10% respectively, relative to standard single-model online learning, while also providing calibrated uncertainty estimates to support operational decision-making.

AI↗
DOE OSTI2024

KOMPASS-II: Compaction of Crushed salt for Safe Containment – Phase 2

Long-term stable sealing elements are a basic component in the safety concept for a possible repository for heat-emitting radioactive waste in rock salt. The sealing elements will be part of the closure concept for drifts and shafts. They will be made from a welldefinied crushed salt in employ a specific manufacturing process. The use of crushed salt as geotechnical barrier as required by the German Site Selection Act from 2017 /STA 17/ represents a paradigm change in the safety function of crushed salt, since this material was formerly only considered as stabilizing backfill for the host rock. The demonstration of the long-term stability and impermeability of crushed salt is crucial for its use as a geotechnical barrier. The KOMPASS-II project, is a follow-up of the KOMPASS-I project and continues the work with focus on improving the understanding of the thermal-hydraulic-mechanical (THM) coupled processes in crushed salt compaction with the objective to enhance the scientific competence for using crushed salt for the long-term isolation of high-level nuclear waste within rock salt repositories. The project strives for an adequate characterization of the compaction process and the essential influencing parameters, as well as a robust and reliable long-term prognosis using validated constitutive models. For this purpose, experimental studies on long-term compaction tests are combined with microstructural investigations and numerical modeling. The long-term compaction tests in this project focused on the effect of mean stress, deviatoric stress and temperature on the compaction behavior of crushed salt. A laboratory benchmark was performed identifying a variability in compaction behavior. Microstructural investigations were executed with the objective to characterize the influence of pre-compaction procedure, humidity content and grain size/grain size distribution on the overall compaction process of crushed salt with respect to the deformation mechanisms. The created database was used for benchmark calculations aiming for improvement and optimization of a large number of constitutive models available for crushed salt. The models were calibrated, and the improvement process was made visible applying the virtual demonstrator.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1980

A Lagrangian mean theory of wave, mean-flow interaction with applications to nonacceleration and its breakdown

A review is given of new Lagrangian mean theory of wave transport. Attention is focused on the so-called 'nonacceleration' theorem, and it is shown that such a theorem arises naturally in the Lagrangian mean framework. Also discussed is a simple example of the Stokes drift, a concept which is central to nonacceleration. The Lagrangian mean theory substantially simplifies and unifies the understanding of wave driving in cases where nonacceleration is violated because of wave transience and dissipation. Moreover, the theory has given new insights in one particular case, that of Rossby gravity wave, mean-flow interaction. These insights have successfully explained some hitherto unresolved paradoxes in the theory of the quasi-biennial oscillation of zonal wind in the equatorial stratosphere. Some brief remarks are also made concerning some of the outstanding difficulties of the theory in need of future investigation.

Dunkerton, T.↗
NASA NTRS2011

The Parable of the Boiled Safety Professional

Common and unique issues contribute to system failures. This paper touches on the concept of drift to failure as a cautionary message. Managers and leaders, design team members, fabricators and assemblers, analysis and assurance personnel, and others associated with operating and maintaining systems, need to pay attention to identify the manifestation of individual and collective behaviors that might indicate slips in rigor or focus or decisions that might eat away at safety margins as our system drifts to failure. Corrections to drift made during design and development phases may efficiently prevent or mitigate drift problems occurring in the operational phase.

Shivers, Charles H.↗
DOE OSTI2023

RF Power Estimates for LAMP Drift-Tube Linac

The LANSCE Modernization Project (LAMP) concept includes a drift-tube proton linac (DTL) from 3 MeV to 100 MeV consisting of 6 tanks. This technical note provides estimates of RF power required for the LAMP DTL tanks using DTLfish modeling.

43 PARTICLE ACCELERATORS↗
NASA NTRS1972

Nighttime sporadic-E.

At night, internal atmospheric gravity waves are able to induce drift instabilities in the ionospheric plasma. Nighttime constant height type sporadic-E(Esc) may then be explained as an effect due to the combined effect of ionization movement due to the wind shear mechanism and due to the cross-field gradient drifts. This combined concept provides a qualitative explanation of the rocket observed nighttime electron density profiles, of the speeds of the Esc irregularities and of the variations of Esc with latitude and electric field strength.-

Beer, T.↗
NASA NTRS1985

Mechanical obstacles to the movement of continent-bearing plates

Selected geophysical problems associated with the concept of continental drift as an incidental corollary of plate movement are discussed. The problems include the absence of a suitable plate-driving mechanism for plates with continental leading edges, the absence of the low-velocity zone under shields, and continental roots of 400 to 700 km depths. It is shown that if continental drift occurs, it must use mechanisms not now understood, or that it may not occur at all, plate movement being confined to ocean basins.

Lowman, P. D., Jr.↗
NASA NTRS2008

Analysis and Design of Launch Vehicle Flight Control Systems

This paper describes the fundamental principles of launch vehicle flight control analysis and design. In particular, the classical concept of "drift-minimum" and "load-minimum" control principles is re-examined and its performance and stability robustness with respect to modeling uncertainties and a gimbal angle constraint is discussed. It is shown that an additional feedback of angle-of-attack or lateral acceleration can significantly improve the overall performance and robustness, especially in the presence of unexpected large wind disturbance. Non-minimum-phase structural filtering of "unstably interacting" bending modes of large flexible launch vehicles is also shown to be effective and robust.

Wie, Bong↗