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Adaptive multi-index collocation for uncertainty quantification and sensitivity analysis

Jakeman, John D.; Eldred, Michael S.; Geraci, G.; Gorodetsky, A.

In this paper, we present an adaptive algorithm to construct response surface approximations of high-fidelity models using a hierarchy of lower fidelity models. Our algorithm is based on multiindex stochastic collocation and automatically balances physical discretization error and response surface error to construct an approximation of model outputs. This surrogate can be used for uncertainty quantification (UQ) and sensitivity analysis (SA) at a fraction of the cost of a purely high-fidelity approach. We demonstrate the effectiveness of our algorithm on a canonical test problem from the UQ literature and a complex multi-physics model that simulates the performance of an integrated nozzle for an unmanned aerospace vehicle. We find that when the input-output response is sufficiently smooth our algorithm produces approximations that can be up to orders of magnitude more accurate than single fidelity approximations for a fixed computational budget.

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TYPE Other Report YEAR 2019
DOIOSTI

Multi-Level Memory Algorithmics for Large, Sparse Problems

Berry, Jonathan W.; Butcher, Neil; Catalyurek, Umit; Kogge, Peter; Lin, Paul; Olivier, Stephen L.; Phillips, Cynthia A.; Rajamanickam, Sivasankaran R.; Slota, George M.; Voskuilen, Gwendolyn R.; Yasar, Abdurrahman; Young, Jeffrey G.

In this report, we abstract eleven papers published during the project and describe preliminary unpublished results that warrant follow-up work. The topic is multi-level memory algorithmics, or how to effectively use multiple layers of main memory. Modern compute nodes all have this feature in some form.

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TYPE SAND Report YEAR 2019
DOIOSTI

Sandia National Laboratories (FY19 Progress Report)

Aguirre, Brandon A.; Martin, William J.; Neville, Steven M.

The Energetic Neutrons campaign led by Sandia National Laboratories (SNL) had a successful year testing electronic devices under 14 MeV neutron irradiation at OMEGA. During FY19 SNL employees were trained to take over new responsibilities while visiting LLE, continued collaborating with external organizations and generated knowledge that supports SNL's National Security mission.

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TYPE Other Report YEAR 2019
DOIOSTI

Fast and Robust Linear Solvers based on Hierarchical Matrices (LDRD Final Report)

Boman, Erik G.; Darve, Eric; Lehoucq, Richard B.; Rajamanickam, Sivasankaran R.; Tuminaro, Raymond S.; Yamazaki, Ichitaro Y.

This report is the final report for the LDRD project "Fast and Robust Linear Solvers using Hierarchical Matrices". The project was a success. We developed two novel algorithms for solving sparse linear systems. We demonstrated their effectiveness on ill-conditioned linear systems from ice sheet simulations. We showed that in many cases, we can obtain near-linear scaling. We believe this approach has strong potential for difficult linear systems and should be considered for other Sandia and DOE applications. We also report on some related research activities in dense solvers and randomized linear algebra.

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TYPE Other Report YEAR 2019
DOIOSTI

Red Storm Case Study

Dodge, Haley D.

Sandia and Cray Inc. co-developed Red Storm, a distributed memory, massively paralleled highperformance supercomputer modeled on ASCI Redl, to run computer codes used for conducting materials science simulations for national security. Supercomputers have some of the fastest highperformance systems available and are used primarily for scientific and engineering work requiring exceedingly high-speed computations. Unlike conventional computers, supercomputers have large storage capacity; more than one central processing unit to rapidly retrieve stored data and program instructions; and input/output capability.

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TYPE Other Report YEAR 2019
DOIOSTI

Fine-Grained Analysis of Communication Similarity between Real and Proxy Applications

Proceedings of PMBS 2019: Performance Modeling, Benchmarking and Simulation of High Performance Computer Systems - Held in conjunction with SC 2019: The International Conference for High Performance Computing, Networking, Storage and Analysis

Aaziz, Omar R.; Vaughan, Courtenay T.; Cook, Jonathan E.; Cook, Jeanine C.; Kuehn, Jeffery; Richards, David

In this work we investigate the dynamic communication behavior of parent and proxy applications, and investigate whether or not the dynamic communication behavior of the proxy matches that of its respective parent application. The idea of proxy applications is that they should match their parent well, and should exercise the hardware and perform similarly, so that from them lessons can be learned about how the HPC system and the application can best be utilized. We show here that some proxy/parent pairs do not need the extra detail of dynamic behavior analysis, while others can benefit from it, and through this we also identified a parent/proxy mismatch and improved the proxy application.

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TYPE Conference Poster YEAR 2019
OSTIScopus

Integrated Safety Management System Description

Mowrer, Jared M.

Personnel at Sandia National Laboratories (hereinafter referred to as Sandia) comply with United States Department of Energy (DOE) Policy 450.4A, Chg 1, Integrated Safety Management Policy, and implement an Integrated Safety Management System (ISMS) to ensure safe operations. Safety is integrated into management and work practices at all levels so missions are accomplished while protecting Members of the Workforce, the public, and the environment. As a result, safety is effectively integrated into all facets of work planning and execution. Thus the management of safety functions becomes an integral part of mission accomplishment and meets the requirements outlined in the DOE Acquisition Regulation (DEAR) 970.5223-1, Integration of Environment, 4/.01, and Health into Work Planning and Execution, clause incorporated by reference into the Prime Contract.

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TYPE Other Report YEAR 2019
DOIOSTI

Hβ and Hγ Absorption-line Profile Inconsistencies in Laboratory Experiments Performed at White Dwarf Photosphere Conditions

The Astrophysical Journal (Online)

Schaeuble, Marc-Andre S.; Nagayama, Taisuke N.; Bailey, James E.; Gomez, T.A.; Laros, James H.; Winget, D.E.

The spectroscopic method relies on hydrogen Balmer absorption lines to infer white dwarf (WD) masses. These masses depend on the choice of atmosphere model, hydrogen atomic line shape calculation, and which Balmer series members are included in the spectral fit. In addition to those variables, spectroscopic masses disagree with those derived using other methods. In this article, we present laboratory experiments aimed at investigating the main component of the spectroscopic method: hydrogen line shape calculations. These experiments use X-rays from Sandia National Laboratories' Z-machine to create a uniform ~15 cm3 hydrogen plasma and a ~4 eV backlighter that enables recording high-quality absorption spectra. The large plasma, volumetric X-ray heating that fosters plasma uniformity, and the ability to collect absorption spectra at WD photosphere conditions are improvements over past laboratory experiments. Analysis of the experimental absorption spectra reveals that electron density (${n}_{{\rm{e}}}$) values derived from the Hγ line are ~34% ± 7.3% lower than from Hβ. Two potential systematic errors that may contribute to this difference were investigated. A detailed evaluation of self-emission and plasma gradients shows that these phenomena are unlikely to produce any measurable Hβ–Hγ ${n}_{{\rm{e}}}$ difference. WD masses inferred with the spectroscopic method are proportional to the photosphere density. Hence, the measured Hβ–Hγ ${n}_{{\rm{e}}}$ difference is qualitatively consistent with the trend that WD masses inferred from their Hβ line are higher than that resulting from the analysis of Hβ and Hγ. This evidence may suggest that current hydrogen line shape calculations are not sufficiently accurate to capture the intricacies of the Balmer series.

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TYPE Journal Article YEAR 2019
DOIOSTI

Elucidation of Host-Pathogen Interactions via Dual RNA-Seq Analysis to Support Development of Countermeasures Against the Intracellular Bacterial Pathogen Burkholderia pseudomallei

Branda, Steven B.; Wang, Pei-Li; Labauve, Annette; Sinha, Anupama S.; Poorey, Kunal N.; Williams, Kelly P.; Michailidis, George; Schoeniger, Joseph S.; Mageeney, Catherine M.; Courtney, Colleen M.; El-Etr, Sahar; Franco, Magda; Lao, Victoria; D'Haeseleer, Patrik; Pena, Jose; Segelke, Brent

Abstract not provided.

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TYPE Conference Poster YEAR 2019
OSTI

A summary of the Advanced WEC Dynamics and Control project

Coe, Ryan G.; Bacelli, Giorgio B.

This report serves as a comprehensive summary of the work completed by the "Advanced WEC Dynamics and Controls projecr during the period of 2013-2019. This project was first envisioned to simply consider the question of designing a controller for wave energy converters (WECs), without a complete recognition of the broader considerations that such a task must necessarily examine. This document describes both the evolution of the project scope and the key findings produced. The basic goal of the project has been to deliver tractable methodologies and work flows that WEC designers can use to improve the performance of their machines. Engineering solutions, which may offer 80% of the impact, but require 20% of the effort compared to a perfect result (which may be many years of development down the road) were preferred. With this doctrine, the work of the project often involved translating existing methods that have been successfully developed and applied for other fields, into the application area of wave energy.

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TYPE SAND Report YEAR 2019
DOIOSTI

Optimization of Adjustable Drivetrain Assistance Mechanisms for Efficient Robotic Bipeds

Spencer, Steven; Mazumdar, Anirban; Buerger, Stephen B.; Pratt, Jerry; Bertrand, Sylvain

Legged robots promise radical mobility for challenging environments, but must be made more energy efficient to be practical. Historically, legged robot design has required efficiency to be traded against versatility. Much energy is lost in actuators and transmissions because few actuation systems are capable of operating efficiently across the wide range of operating conditions (e.g. different joint speeds and torques) required for legged locomotion. We describe a drivetrain topology that overcomes many of these limitations. Our approach combines high-torque electromagnetic motors and low-loss transmissions with a tailored and adjustable set of joint-specific passive mechanisms called support elements, which modulate the energy flow between motors and joints to minimize the electrical energy consumed. We present an optimization-based design method that draws on available bipedal gait data to select optimal support element configurations and parameters. Simple adjustments may be made to support elements at certain joints to enable a wide variety of locomotion with high efficiency. We present results, specific to the 3D humanoid bipedal STEPPR robot, in which support elements are co-optimized across a library of several gaits, converging on a set of designs that predict an average reduction of electrical energy of more than 50% across a set of 15 gaits, with energy savings reaching as much as 85% for some gaits. Concepts were prototyped and tested on a bench testbed, validating the predicted energy savings. Support elements were implemented on STEPPR, and energy savings of more than 35% were demonstrated.

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TYPE SAND Report YEAR 2019
DOIOSTI
Results 18201–18400 of 96,771
Results 18201–18400 of 96,771