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Full-resolution two-color infrared detector

2021 IEEE Research and Applications of Photonics in Defense Conference, RAPID 2021

Anderson, Evan M.; Campbell, Deanna M.; Briscoe, Jayson; Coon, Wesley; Alford, Charles; Wood, Michael G.; Klem, John F.; Gamache, Phillip; Gunter, Mathew; Olesberg, Jonathon T.; Hawkins, Samuel D.; Rohwer, Lauren E.S.; Stephenson, Chad A.; Peters, David; Goldflam, Michael

We discuss thinned InAsSb resonant infrared detectors that are designed to enable high quantum efficiency by using interleaved nanoantennas to read out two wavelengths from each pixel simultaneously.

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TYPE Conference Presentation YEAR 2021
DOIOSTIScopus

A data-driven peridynamic continuum model for upscaling molecular dynamics

D'Elia, Marta; Silling, Stewart; Yu, Yue; You, Huaiqian

Nonlocal models, including peridynamics, often use integral operators that embed lengthscales in their definition. However, the integrands in these operators are difficult to define from the data that are typically available for a given physical system, such as laboratory mechanical property tests. In contrast, molecular dynamics (MD) does not require these integrands, but it suffers from computational limitations in the length and time scales it can address. To combine the strengths of both methods and to obtain a coarse-grained, homogenized continuum model that efficiently and accurately captures materials’ behavior, we propose a learning framework to extract, from MD data, an optimal Linear Peridynamic Solid (LPS) model as a surrogate for MD displacements. To maximize the accuracy of the learnt model we allow the peridynamic influence function to be partially negative, while preserving the well-posedness of the resulting model. To achieve this, we provide sufficient well-posedness conditions for discretized LPS models with sign-changing influence functions and develop a constrained optimization algorithm that minimizes the equation residual while enforcing such solvability conditions. This framework guarantees that the resulting model is mathematically well-posed, physically consistent, and that it generalizes well to settings that are different from the ones used during training. We illustrate the efficacy of the proposed approach with several numerical tests for single layer graphene. Our two-dimensional tests show the robustness of the proposed algorithm on validation data sets that include thermal noise, different domain shapes and external loadings, and discretizations substantially different from the ones used for training.

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TYPE Other Report YEAR 2021
DOIOSTI

Predicting large-scale pool fire dynamics using an unsteady flamelet- And large-eddy simulation-based model suite

Physics of Fluids

Domino, Stefan P.; Hewson, John C.; Knaus, Robert C.; Hansen, Michael A.

A low-Mach, unstructured, large-eddy-simulation-based, unsteady flamelet approach with a generalized heat loss combustion methodology (including soot generation and consumption mechanisms) is deployed to support a large-scale, quiescent, 5-m JP-8 pool fire validation study. The quiescent pool fire validation study deploys solution sensitivity procedures, i.e., the effect of mesh and time step refinement on capturing key fire dynamics such as fingering and puffing, as mesh resolutions approach O(1) cm. A novel design-order, discrete-ordinate-method discretization methodology is established by use of an analytical thermal/participating media radiation solution on both low-order hexahedral and tetrahedral mesh topologies in addition to quadratic hexahedral elements. The coupling between heat losses and the flamelet thermochemical state is achieved by augmenting the unsteady flamelet equation set with a heat loss source term. Soot and radiation source terms are determined using flamelet approaches for the full range of heat losses experienced in fire applications including radiative extinction. The proposed modeling and simulation paradigm are validated using pool surface radiative heat flux, maximum centerline temperature location, and puffing frequency data, all of which are predicted within 10% accuracy. Simulations demonstrate that under-resolved meshes predict an overly conservative radiative heat flux magnitude with improved comparisons as compared to a previously deployed hybrid Reynolds-averaged Navier-Stokes/eddy dissipation concept-based methodology.

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TYPE Journal Article YEAR 2021
DOIOSTIScopus

Randomized algorithms for generalized singular value decomposition with application to sensitivity analysis

Numerical Linear Algebra with Applications

Hart, Joseph L.; Van Bloemen Waanders, Bart; Saibaba, Arvind K.

The generalized singular value decomposition (GSVD) is a valuable tool that has many applications in computational science. However, computing the GSVD for large-scale problems is challenging. Motivated by applications in hyper-differential sensitivity analysis (HDSA), we propose new randomized algorithms for computing the GSVD which use randomized subspace iteration and weighted QR factorization. Detailed error analysis is given which provides insight into the accuracy of the algorithms and the choice of the algorithmic parameters. We demonstrate the performance of our algorithms on test matrices and a large-scale model problem where HDSA is used to study subsurface flow.

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TYPE Journal Article YEAR 2021
DOIOSTIScopus

PCalc User's Manual

Conley, Andrea C.; Downey, Nathan J.; Ballard, Sanford; Hipp, James R.; Hammond, Patrick; Davenport, Kathy; Begnaud, Michael E.

PCalc is a software tool that computes travel-time predictions, ray path geometry and model queries. This software has a rich set of features, including the ability to use custom 3D velocity models to compute predictions using a variety of geometries. The PCalc software is especially useful for research related to seismic monitoring applications.

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TYPE SAND Report YEAR 2021
DOIOSTI

Uncoupling Electrokinetic Flow Solutions

Mathematical Geosciences

Kuhlman, Kristopher L.; Malama, Bwalya

The continuum-scale electrokinetic porous-media flow and excess charge redistribution equations are uncoupled using eigenvalue decomposition. The uncoupling results in a pair of independent diffusion equations for “intermediate” potentials subject to modified material properties and boundary conditions. The fluid pressure and electrostatic potential are then found by recombining the solutions to the two intermediate uncoupled problems in a matrix-vector multiplication. Expressions for the material properties or source terms in the intermediate uncoupled problem may require extended precision or careful rewriting to avoid numerical cancellation, but the solutions themselves can typically be computed in double precision. The approach works with analytical or gridded numerical solutions and is illustrated through two examples. The solution for flow to a pumping well is manipulated to predict streaming potential and electroosmosis, and a periodic one-dimensional analytical solution is derived and used to predict electroosmosis and streaming potential in a laboratory flow cell subjected to low frequency alternating current and pressure excitation. The examples illustrate the utility of the eigenvalue decoupling approach, repurposing existing analytical solutions or numerical models and leveraging solutions that are simpler to derive for coupled physics.

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TYPE Journal Article YEAR 2021
DOIOSTIScopus

Programmatic Advantages of Linear Equivalent Seismic Models

Preston, Leiph; Eliassi, Mehdi; Poppeliers, Christian

Underground explosions nonlinearly deform the surrounding earth material and can interact with the free surface to produce spall. However, at typical seismological observation distances the seismic wavefield can be accurately modeled using linear approximations. Although nonlinear algorithms can accurately simulate very near field ground motions, they are computationally expensive and potentially unnecessary for far field wave simulations. Conversely, linearized seismic wave propagation codes are orders of magnitude faster computationally and can accurately simulate the wavefield out to typical observational distances. Thus, devising a means of approximating a nonlinear source in terms of a linear equivalent source would be advantageous both for scenario modeling and for interpretation of seismic source models that are based on linear, far-field approximations. This allows fast linear seismic modeling that still incorporates many features of the nonlinear source mechanics built into the simulation results so that one can have many of the advantages of both types of simulations without the computational cost of the nonlinear computation. In this report we first show the computational advantage of using linear equivalent models, and then discuss how the near-source (within the nonlinear wavefield regime) environment affects linear source equivalents and how well we can fit seismic wavefields derived from nonlinear sources.

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TYPE SAND Report YEAR 2021
DOIOSTI

IPv6 Tunneling and Translation Technologies Pilot

Ferris, Jason E.; Radcliffe, Aaron C.

Based on the latest DOE (Department of Energy) milestones, Sandia needs to convert to IPv6 (Internet Protocol version 6)-only networks over the next 5 years. Our original IPv6 migration plan did not include migrating to IPv6-only networks at any point within the next 10 years, so it must necessarily change. To be successful in this endeavor, we need to evaluate technologies that will enable us to deploy IPv6-only networks early without creating system stability or security issues. We have set up a test environment using technology representative of our production network where we configured and evaluated industry standard translation technologies and techniques. Based on our results, bidirectional translation between IPv4 (Internet Protocol version 4) and IPv6 is achievable with our current equipment, but due to the complexity of the configuration, may not scale well to our production environment.

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TYPE SAND Report YEAR 2021
DOIOSTI

Energy Efficient Computing R&D Roadmap Outline for Automated Vehicles

Aitken, Rob; Nakahira, Yorie; Strachan, John P.; Bresniker, Kirk; Young, Ian; Li, Zhiyong; Klebanoff, Leonard E.; Burchard, Carrie; Kumar, Suhas; Marinella, Matthew; Severa, William M.; Talin, Albert A.; Vineyard, Craig M.; Mailhiot, Christian; Dick, Robert; Lu, Wei; Mogill, Jace

Automated vehicles (AV) hold great promise for improving safety, as well as reducing congestion and emissions. In order to make automated vehicles commercially viable, a reliable and highperformance vehicle-based computing platform that meets ever-increasing computational demands will be key. Given the state of existing digital computing technology, designers will face significant challenges in meeting the needs of highly automated vehicles without exceeding thermal constraints or consuming a large portion of the energy available on vehicles, thus reducing range between charges or refills. The accompanying increases in energy for AV use will place increased demand on energy production and distribution infrastructure, which also motivates increasing computational energy efficiency.

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TYPE Other Report YEAR 2021
DOIOSTI

Global System Reduction Order Modeling for Localized Feature Inclusion

Journal of Vibration and Acoustics

Brink, Adam R.; Quinn, D.D.

The development of reduced-order models remains an active research area, despite advances in computational resources. The present work develops a novel order-reduction approach that is designed to incorporate isolated regions that contain, for example, nonlinearitites or accumulating damage. The approach is designed to use global modes of the overall system response, which are then naturally coupled to the response in the isolated region of interest. Two examples are provided to demonstrate both the accuracy and the computational efficiency of the proposed approach. The performance of this approach is compared to the exact response corresponding to a finite element simulation for the chosen problems. In addition, the accuracy and computational efficiency are shown relative to a standard Galerkin reduction based on the linear normal modes. It is found that the proposed reduction offer computational efficiency comparable to a Galerkin reduction, but more accurately represents the response of the system when both are compared to the finite element simulation.

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TYPE Journal Article YEAR 2021
DOIOSTIScopus
Results 10801–10900 of 99,299
Results 10801–10900 of 99,299