Publications

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Photoacoustic Sounds from Meteors

Sandia journal manuscript; Not yet accepted for publication

Spalding, Richard; Tencer, John T.; Sweatt, W.C.; Foulk, James W.; Boslough, Mark; Gonzales, Gigi

High-speed photometric observations of meteor fireballs have shown that they often produce high-amplitude light oscillations with frequency components in the kHz range, and in some cases exhibit strong millisecond flares. We built a light source with similar characteristics and illuminated various materials in the laboratory, generating audible sounds. Models suggest that light oscillations and pulses can radiatively heat dielectric materials, which in turn conductively heats the surrounding air on millisecond timescales. The sound waves can be heard if the illuminated material is sufficiently close to the observer’s ears. The mechanism described herein may explain many reports of meteors that appear to be audible while they are concurrently visible in the sky and too far away for sound to have propagated to the observer. This photoacoustic (PA) explanation provides an alternative to electrophonic (EP) sounds hypothesized to arise from electromagnetic coupling of plasma oscillation in the meteor wake to natural antennas in the vicinity of an observer.

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TYPE Journal Article YEAR 2015
OSTI

The 2014 Sandia Nonlinear Mechanics and Dynamics Summer Research Institute

Brake, M.R.W.; Reuss, Pascal; Schwingshackl, Christoph W.; Salles, Loic; Negus, Michaela; Peebles, Diane; Mayes, Randall L.; Bilbao-Ludena, Juan-Carlos; Bonney, Matthew S.; Catalfamo, Simone; Gastaldi, Chiara; Gross, Johann; Lacayo, Robert M.; Robertson, Brett A.; Smith, Scott; Swacek, Christian; Tiedemann, Merten

A collaborative research institute was organized and held at Sandia Albuquerque for a period of six weeks. This research institute brought together researchers from around the world to work collaboratively on a set of research projects. These research projects included: developing experimental guidelines for studying variability and repeatability of nonlinear structures; decoupling aleatoric and epistemic uncertainty in measurements to improve dynamic predictions; a numerical round robin to assess the performance of five different numerical codes for modeling systems with strong nonlinearities; and an assessment of experimentally derived and numerically derived reduced order models. In addition to the technical collaborations, the institute also included a series of seminars given by both Sandians and external experts, as well as a series of tours and field trips to local places of scientific and engineering importance. This report details both the technical research and the programmatic organization of the 2014 Sandia Nonlinear Mechanics and Dynamics Summer Research Institute.

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TYPE SAND Report YEAR 2015
DOIOSTI

Dominion. A game exploring information exploitation

Hobbs, Jacob; Estrada, Trilce

FlipIt is a game theoretic framework published in 2012[1] to investigate optimal strategies for managing security resources in response to Advanced Persistent Threats. It is a two-player game wherein a resource is controlled by exactly one player at any time. A player may move at any time to capture the resource, incurring a move cost, and is informed of the last time their opponent has moved only upon completing their move. Thus, moves may be wasted and takeover is considered \stealthy", with regard to the other player. The game is played for an unlimited period of time, and the goal of each player is to maximize the amount of time they are in control of the resource minus their total move cost, normalized by the current length of play. Marten Van Dijk and others[1] provided an analysis of various player strategies and proved optimal results for certain subclasses of players. We extend their work by providing a reformulation of the original game, wherein the optimal player strategies can be solved exactly, rather than only for certain subclasses. We call this reformulation Dominion, and place it within a broader framework of stealthy move games. We de ne Dominion to occur over a nite time scale (from 0 to 1), and give each player a certain number of moves to make within the time frame. Their expected score in this new scenario is the expected amount of time they have control, and the point of the game is to dominate as much of the unit interval as possible. We show how Dominion can be treated as a two player, simultaneous, constant sum, unit square game, where the gradient of the bene t curves for the players are linear and possibly discontinuous. We derive Nash equilibria for a basic version of Dominion, and then further explore the roles of information asymmetry in its variants. We extend these results to FlipIt and other cyber security applications.

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TYPE Thesis or Dissertation YEAR 2015
OSTI

CCC7-119 Reactive Molecular Dynamics Simulations of Hot Spot Growth in Shocked Energetic Materials

Thompson, A.P.

The purpose of this work is to understand how defects control initiation in energetic materials used in stockpile components; Sequoia gives us the core-count to run very large-scale simulations of up to 10 million atoms and; Using an OpenMP threaded implementation of the ReaxFF package in LAMMPS, we have been able to get good parallel efficiency running on 16k nodes of Sequoia, with 1 hardware thread per core.

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TYPE Other Report YEAR 2015
DOIOSTI

Ensuring a Viable Future for the Weapons Laboratories

Exchange Monitor

Buican, Ileana G.

As recognized by the Mies-Augustine report (A New Foundation for the Nuclear Enterprise, Report of the Congressional Advisory Panel on the Governance of the Nuclear Security Enterprise, Nov. 2014), any consideration of governance must begin with an understanding of mission. At first glance, the mission of these three laboratories seems obvious: We are national security laboratories with the core mission being our support of nuclear deterrence. This is certainly true. However, there are nuances here that I believe are very important to consider. Furthermore, I suspect that, if I were to ask you what a “national security laboratory” means, I would get a wide variety of answers.

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TYPE Journal Article YEAR 2015
OSTI

An Elastic Plastic Contact Model with Strain Hardening for the LAMMPS Granular Package

Kuhr, Bryan; Brake, M.R.W.; Lechman, Jeremy B.

The following details the implementation of an analytical elastic plastic contact model with strain hardening for normal im pacts into the LAMMPS granular package. The model assumes that, upon impact, the co llision has a period of elastic loading followed by a period of mixed elastic plas tic loading, with contributions to each mechanism estimated by a hyperbolic seca nt weight function. This function is implemented in the LAMMPS source code as the pair style gran/ep/history. Preliminary tests, simulating the pouring of pure nickel spheres, showed the elastic/plastic model took 1.66x as long as similar runs using gran/hertz/history.

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TYPE SAND Report YEAR 2015
DOIOSTI

Laboratory Building

Herrera, Joshua M.

This report is an analysis of the means of egress and life safety requirements for the laboratory building. The building is located at Sandia National Laboratories (SNL) in Albuquerque, NM. The report includes a prescriptive-based analysis as well as a performance-based analysis. Following the analysis are appendices which contain maps of the laboratory building used throughout the analysis. The top of all the maps is assumed to be north.

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TYPE Other Report YEAR 2015
DOIOSTI

Parameter Estimation for Single Diode Models of Photovoltaic Modules

Hansen, Clifford

Many popular models for photovoltaic system performance employ a single diode model to compute the I - V curve for a module or string of modules at given irradiance and temperature conditions. A single diode model requires a number of parameters to be estimated from measured I - V curves. Many available parameter estimation methods use only short circuit, o pen circuit and maximum power points for a single I - V curve at standard test conditions together with temperature coefficients determined separately for individual cells. In contrast, module testing frequently records I - V curves over a wide range of irradi ance and temperature conditions which, when available , should also be used to parameterize the performance model. We present a parameter estimation method that makes use of a fu ll range of available I - V curves. We verify the accuracy of the method by recov ering known parameter values from simulated I - V curves . We validate the method by estimating model parameters for a module using outdoor test data and predicting the outdoor performance of the module.

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TYPE SAND Report YEAR 2015
DOIOSTI

Sandia_HighTemperatureComponentEvaluation_2015

Cashion, Avery T.

The objective of this project is to perform independent evaluation of high temperature components to determine their suitability for use in high temperature geothermal tools. Development of high temperature components has been increasing rapidly due to demand from the high temperature oil and gas exploration and aerospace industries. Many of these new components are at the late prototype or first production stage of development and could benefit from third party evaluation of functionality and lifetime at elevated temperatures. In addition to independent testing of new components, this project recognizes that there is a paucity of commercial-off-the-shelf COTS components rated for geothermal temperatures. As such, high-temperature circuit designers often must dedicate considerable time and resources to determine if a component exists that they may be able to knead performance out of to meet their requirements. This project aids tool developers by characterization of select COTS component performances beyond published temperature specifications. The process for selecting components includes public announcements of project intent (e.g., FedBizOps), direct discussions with candidate manufacturers,and coordination with other DOE funded programs.

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TYPE Other Report YEAR 2015
DOIOSTI
Results 49201–49300 of 99,299
Results 49201–49300 of 99,299