Publications

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

The goal of the ExaWind project is to enable predictive simulations of wind farms composed of many MW-scale turbines situated in complex terrain. Predictive simulations will require computational fluid dynamics (CFD) simulations for which the mesh resolves the geometry of the turbines, and captures the rotation and large deflections of blades. Whereas such simulations for a single turbine are arguably petascale class, multi-turbine wind farm simulations will require exascale-class resources.

A previous report assesses our progress to date on the Eyes On the Ground project, and reviews lessons learned. In this report, we address the implications of those lessons in defining the most productive path forward for the remainder of the project. We propose two main concepts: Interactive Diagnosis and Model-Driven Assistance. Among these, the Model-Driven Assistance concept appears the most promising. The Model-Driven Assistance concept is based on an approximate but useful model of a facility, which provides a unified representation for storing, viewing, and analyzing data that is known about the facility. This representation provides value to both inspectors and IAEA headquarters, and facilitates communication between the two. The concept further includes a lightweight, portable field tool to aid the inspector in executing a variety of inspection tasks, including capture of images and 3-d scan data. We develop a detailed description of this concept, including its system components, functionality, and example use cases. The envisioned tool would provide value by reducing inspector cognitive load, streamlining inspection tasks, and facilitating communication between the inspector and teams at IAEA headquarters. We conclude by enumerating the top implementation priorities to pursue in the remaining limited time of the project. Approved for public release; further dissemination unlimited.

The goal of the Eyes On the Ground project is to develop tools to aid IAEA inspectors. Our original vision was to produce a tool that would take three-dimensional measurements of an unknown piece of equipment, construct a semantic representation of the measured object, and then use the resulting data to infer possible explanations of equipment function. We report our tests of a 3-d laser scanner to obtain 3-d point cloud data, and subsequent tests of software to convert the resulting point clouds into primitive geometric objects such as planes and cylinders. These tests successfully identified pipes of moderate diameter and planar surfaces, but also incurred significant noise. We also investigated the IAEA inspector task context, and learned that task constraints may present significant obstacles to using 3-d laser scanners. We further learned that equipment scale and enclosing cases may confound our original goal of equipment diagnosis. Meanwhile, we also surveyed the rapidly evolving field of 3-d measurement technology, and identified alternative sensor modalities that may prove more suitable for inspector use in a safeguards context. We conclude with a detailed discussion of lessons learned and the resulting implications for project goals. Approved for public release; further dissemination unlimited.

Abstract not provided.

Abstract not provided.

Sandia National Laboratories is charged with working on tough technical problems on behalf of the nation. As Sandia's sole discretionary research and development (R&D) program, Laboratory Directed Research and Development (LDRD) funds foundational, leading-edge R&D that nurtures and enhances core science and engineering capabilities, supports national security missions, and creates new capabilities. Sandia's LDRD program is an essential element of the Laboratories' purpose to provide "exceptional service in the national interest'

Abstract not provided.

Abstract not provided.

This document is a user's guide for capabilities that are not considered mature but are available in Sierra/SolidMechanics (Sierra/SM) for early adopters. The determination of maturity of a capability is determined by many aspects: having regression and verification level testing, documentation of functionality and syntax, and usability are such considerations. Capabilities in this document are lacking in one or many of these aspects.

Accurate and efficient constitutive modeling remains a cornerstone issues for solid mechanics analysis. Over the years, the LAME advanced material model library has grown to address this challenge by implement- ing models capable of describing material systems spanning soft polymers to stiff ceramics including both isotropic and anisotropic responses. Inelastic behaviors including (visco)plasticity, damage, and fracture have all incorporated for use in various analyses. This multitude of options and flexibility, however, comes at the cost of many capabilities, features, and responses and the ensuing complexity in the resulting imple- mentation. Therefore, to enhance confidence and enable the utilization of the LAME library in application, this effort seeks to document and verify the various models in the LAME library. Specifically, the broader strategy, organization, and interface of the library itself is first presented. The physical theory, numerical implementation, and user guide for a large set of models is then discussed. Importantly, a number of verifi- cation tests are performed with each model to not only have confidence in the model itself but also highlight some important response characteristics and features that may be of interest to end-users. Finally, in looking ahead to the future, approaches to add material models to this library and further expand the capabilities are presented.

This document covers Sierra/SolidMechanics capabilities specific to Goodyear use cases. Some information may be duplicated directly from the Sierra/SolidMechanics User's Guide but is reproduced here to provide context for Goodyear-specific options.

This is an addendum to the Sierra/SolidMechanics 4.48 User's Guide that documents additional capabilities available only in alternate versions of the Sierra/SolidMechanics (Sierra/SM) code. These alternate versions are enhanced to provide capabilities that are regulated under the U.S. Department of State's International Traffic in Arms Regulations (ITAR) export-control rules. The ITAR regulated codes are only distributed to entities that comply with the ITAR export-control requirements. The ITAR enhancements to Sierra/SM in- clude material models with an energy-dependent pressure response (appropriate for very large deformations and strain rates) and capabilities for blast modeling. Since this is an addendum to the standard Sierra/SM user's guide, please refer to that document first for general descriptions of code capability and use.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

This report supplements Joint Workplan on Filler Investigations for DPCs (SNL 2017) providing new and some corrected information for use in planning Phase 1 laboratory testing of slurry cements as possible DPC fillers. The scope description is to "Describe a complete laboratory testing program for filler composition, delivery, emplacement in surrogate canisters, and post-test examination. To the extent possible specify filler material and equipment sources." This report includes results from an independent expert review (Dr. Arun Wagh, retired from Argonne National Laboratory and contracted by Sandia) that helped to narrow the range of cement types for consideration, and to provide further guidance on mix variations to optimize injectability, durability, and other aspects of filler performance.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

The flight and unscheduled termination of a prototype solar powered hot air balloon are described. Impact speeds of the falling payload are estimated, and the cause of the unexpected release is discussed. Modifications to the flight system to reduce the chances of this failure mode are presented.

Lithium metal is considered the "holy grail" of next-generation battery anodes. However, severe parasitic reactions at the lithium-electrolyte interface deplete the liquid electrolyte and the uncontrolled formation of high surface area and dendritic lithium during cycling causes rapid capacity fading and battery failure. Engineering a dendrite-free lithium metal anode is therefore critical for the development of long-life batteries using lithium anodes. In this study, we deposit a conformal, organic/inorganic hybrid coating, for the first time, directly on lithium metal using molecular layer deposition (MLD) to alleviate these problems. This hybrid organic/inorganic film with high cross-linking structure can stabilize lithium against dendrite growth and minimize side reactions, as indicated by scanning electron microscopy. We discovered that the alucone coating yielded several times longer cycle life at high current rates compared to the uncoated lithium and achieved a steady Coulombic efficiency of 99.5%, demonstrating that the highly cross-linking structured material with great mechanical properties and good flexibility can effectively suppress dendrite formation. The protected Li was further evaluated in lithium-sulfur (Li-S) batteries with a high sulfur mass loading of ∼5 mg/cm2. After 140 cycles at a high current rate of ∼1 mA/cm2, alucone-coated Li-S batteries delivered a capacity of 657.7 mAh/g, 39.5% better than that of a bare lithium-sulfur battery. These findings suggest that flexible coating with high cross-linking structure by MLD is effective to enable lithium protection and offers a very promising avenue for improved performance in the real applications of Li-S batteries.

Sandia National Laboratories (SNL) and the Procter and Gamble Company (P&G), which eventually spun off The Duracell Company (Duracell) to Berkshire Hathaway, collaborated to develop a computational tool that predicts the in-use and manufacturing-process performance of consumer electrical energy storage devices. This computational tool was particularly useful in exploring the effects of material microstructure, device configuration/geometry, manufacturing and manufacturing defects on product performance.

Sandia National Laboratories (Sandia) and Cool Earth Solar, Inc. (CES) collaborated to evaluate and validate a new Concentrating Photovoltaic (CPV) technology for the utility-scale power market. Project goals included demonstration of CES's tracking and energy production mechanism and operation in a realworld configuration to validate and evaluate mechanical reliability, uptime, operations and maintenance, and energy production models. The test facility was located at Sandia California’s Livermore Valley Open Campus (LVOC). The collaboration allowed CES to quickly move from design concept to system prototype deployment in an operational environment, with approximately 17kW of engineering samples deployed. However, economic pressure from inexpensive flat panel photovoltaic modules caused a major contraction in the broader CPV market. CES was ultimately unable to overcome this economic pressure and discontinued efforts to develop their novel CPV product.

The goal of the DOE OE ESS Safety Roadmap1 is to foster confidence in the safety and reliability of energy storage systems. There are three interrelated objectives to support the realization of that goal: research, codes and standards and communication/coordination. The objective focused on codes and standards is: To apply research and development to support efforts that are focused on ensuring that codes and standards are available to enable the safe implementation of energy storage systems in a comprehensive, non-discriminatory and science-based manner. The following activities support that objective and realization of the goal: a. Review and assess codes and standards which affect the design, installation, and operation of ESS systems. b. Identify gaps in knowledge that require research and analysis that can serve as a basis for criteria in those codes and standards. c. Identify areas in codes and standards that are potentially in need of revision or enhancement and can benefit from activities conducted under research and development. d. Develop input for new or revisions to existing codes and standards through individual stakeholders, facilitated task forces, or through laboratory staff supporting these efforts. The purpose of this document is to support the above activities by providing information on current and upcoming efforts being conducted by U.S. standards developing organizations (SDOs) and other entities that are focused on energy storage system safety.

Lightweight complex metal hydrides are of interest for use as energy-dense on-board vehicular hydrogen stores. One material of particular interest, magnesium borohydride (Mg(BH₄)₂), has very high hydrogen capacity, at 14.9 wt.% H, but suffers from slow kinetics and the need for extreme conditions for both dehydrogenation and rehydrogenation from magnesium diboride (MgB₂). In order to establish methods to improve the kinetic properties of this system, a greater understanding of the nucleation and growth of various solid phases is essential.

This report evaluates the relative performance of two directional gamma-ray spectrometers and processing algorithms that are used to construct images and spatially resolved spectra. Polaris, which was developed by H3D Inc., uses 18 pixelated CZT crystals to construct gamma-ray images in either Compton camera(CC) or coded aperture (CA) mode. The other sensor that is referenced in this report incorporates a commercial high-purity germanium based imager, called GeGI, with a coded aperture mask and processing software developed by Oak Ridge National Laboratory (ORNL). H3D and the University of Michigan provided several algorithms that can be used to process data collected by Polaris in CC mode. This evaluation compares the performance of these algorithms with a Directional Unfolded Source Term (DUST) approach developed by Sandia National Laboratories (SNL). DUST differs from the other algorithms because its primary objective is synthesis of spatially-resolved gamma ray spectra as opposed to image reconstruction.

The Chemical Waste Landfill (CWL) at SNL/New Mexico (SNL/NM) is a remediated hazardous waste landfill that underwent closure. The CWL Post-Closure Care Permit (PCCP), which became effective June 2, 2011 and as modified, defines all post-closure requirements. This sixth CWL Annual Post-Closure Care Report documents all activities and results as required by the PCCP Attachment 1, Section 1.12.

Wind energy is quickly becoming a significant contributor to the United States' overall energy portfolio. Wind turbine blades pose a unique set of inspection challenges that span from very thick and attenuative spar cap structures to porous bond lines, varying core material and a multitude of manufacturing defects of interest. The need for viable, accurate nondestructive inspection (NDI) technology becomes more important as the cost per blade, and lost revenue from downtime, grows. To address this growing need, Sandia and SkySpecs collaborated to evaluate NDI methods that are suitable for integration on an autonomous drone inspection platform. A trade study of these NDI methods was performed, and thermography was selected as the primary technique for further evaluation. Based on the capabilities of SkySpecs' custom inspection drone, a miniature microbolometer IR camera was successfully selected and tested in a benchtop setting. After identifying key operating parameters for inspecting wind blade materials, hardware and software integration of the IR camera was performed, and Sandia and SkySpecs conducted initial field testing. Finally, recommendations for a path forward for drone-deployed thermography inspections were provided.

This catalog was created through the Grid Modernization Laboratory Consortium's (GMLC) Testing Network project. The GMLC is a strategic partnership between the Department of Energy (DOE) and its National Laboratories to bring together leading experts, technologies, and resources to collaborate on the goal of modernizing the nation's electric grid. The benefits of the GMLC include more efficient use of resources; shared networks; improving learning and preservation of knowledge; enhanced lab coordination and collaboration; and regional perspective and relationships with local stakeholders and industry.

This document introduces Sandia's quality assurance program and presents case studies illustrating how members of the workforce implement quality assurance as they perform work. Managers have a responsibility to ensure that work performed meets Sandia and customer expectations for delivering quality products and services consistently and predictably. Individuals are responsible for creating workflow processes and products that conform to corporate quality requirements.

The purpose of this study is to identify potential alternative uses for the LAC-owned BESS. One critical fact that must be considered in evaluating any profitable use of the BESS is the standby cost associated with keeping the NaS battery on-line, as it must be kept at 300 degrees Celsius at all times, regardless of whether it is being used or not. Standby for the NaS battery online requires approximately 80 MWh/month, costing approximately 28,000 dollars annually. Other relevant costs include a 22,000 dollar annual maintenance contract required for the NaS, and accounting for any losses due to inefficiencies during the operation of the battery. County operations personnel respond to all alarms and visit the BESS on a monthly basis to walk down the site. It estimated this cost approximately 10,000 dollars per year. The total cost of maintaining and keeping the NaS battery on-line for a year, then, is roughly 60,000 dollars.

There are two good reasons to attempt to build quantum bits (qubits) out of silicon. The first is the obvious foundation of classical microelectronics. Although silicon quantum computers would operate in a fundamentally different way from classical computers$-$for example, at cryogenic temperatures$-$still the level of development in material quality, crystal growth, and fabrication methodologies for silicon is unrivaled by any other material in the world. Leveraging even a small fraction of the worldwide investment in silicon for qubit development could potentially put silicon-based qubits far ahead of other solid-state alternatives. The second, less obvious reason for choosing silicon is the remarkably clean magnetic environment witnessed by spins in highly purified and isotopically enriched silicon material. Fortuitously, 95.3% of the naturally occurring isotopes of Si nuclei (²⁸Si and ³⁰Si) are spin-0. These nuclei therefore have a “closed shell” of nuclear moments, providing no external magnetic field whatsoever. Add to this the possibility of intrinsic silicon with part-per-billion chemical quality and the system is remarkably close to “vacuum” with respect to magnetic noise properties.

This report documents the completion of milestone STPM12-2 Kokkos User Support Infrastructure. The goal of this milestone was to develop and deploy an initial Kokkos support infrastructure, which facilitates communication and growth of the user community, adds a central place for user documentation and manages access to technical experts. Multiple possible support infrastructure venues were considered and a solution was put into place by Q1 of FY 18 consisting of (1) a Wiki programming guide, (2) github issues and projects for development planning and bug tracking and (3) a “Slack” channel for low latency support communications with the Kokkos user community. Furthermore, the desirability of a cloud based training infrastructure was recognized and put in place in order to support training events.

A potentially attractive way to control nanoparticle assembly is to graft one or more polymers on the nanoparticle, to control the nanoparticle-nanoparticle interactions. When two immiscible polymers are grafted on the nanoparticle, they can microphase separate to form domains at the nanoparticle surface. Here, we computationally investigate the phase behavior of such binary mixed brush nanoparticles in solution, across a large and experimentally relevant parameter space. Specifically, we calculate the mean-field phase diagram, assuming uniform grafting of the two polymers, as a function of the nanoparticle size relative to the length of the grafted chains, the grafting density, the enthalpic repulsion between the grafted chains, and the solvent quality. We find a variety of phases including a Janus phase and phases with varying numbers of striped domains. Using a nonuniform, random distribution of grafting sites on the nanoparticle instead of the uniform distribution leads to the development of defects in the mixed brush structures. Introducing fluctuations as well leads to increasingly defective structures for the striped phases. However, we find that the simple Janus phase is preserved in all calculations, even with the introduction of nonuniform grafting and fluctuations. We conclude that the formation of the Janus phase is more realistic experimentally than is the formation of defect-free multivalent mixed brush nanoparticles.

This report introduces the concepts of Bayesian model selection, which provides a systematic means of calibrating and selecting an optimal model to represent a phenomenon. This has many potential applications, including for comparing constitutive models. The ideas described herein are applied to a model selection problem between different yield models for hardened steel under extreme loading conditions.

Nonequilibrium processes of small systems such as molecular machines are ubiquitous in biology, chemistry, and physics but are often challenging to comprehend. In the past two decades, several exact thermodynamic relations of nonequilibrium processes, collectively known as fluctuation theorems, have been discovered and provided critical insights. These fluctuation theorems are generalizations of the second law and can be unified by a differential fluctuation theorem. Here we perform the first experimental test of the differential fluctuation theorem using an optically levitated nanosphere in both underdamped and overdamped regimes and in both spatial and velocity spaces. We also test several theorems that can be obtained from it directly, including a generalized Jarzynski equality that is valid for arbitrary initial states, and the Hummer-Szabo relation. Our study experimentally verifies these fundamental theorems and initiates the experimental study of stochastic energetics with the instantaneous velocity measurement.

Quantum state tomography on a d-dimensional system demands resources that grow rapidly with d. They may be reduced by using model selection to tailor the number of parameters in the model (i.e., the size of the density matrix). Most model selection methods typically rely on a test statistic and a null theory that describes its behavior when two models are equally good. Here, we consider the loglikelihood ratio. Because of the positivity constraint ρ ≥ 0, quantum state space does not generally satisfy local asymptotic normality (LAN), meaning the classical null theory for the loglikelihood ratio (the Wilks theorem) should not be used. Thus, understanding and quantifying how positivity affects the null behavior of this test statistic is necessary for its use in model selection for state tomography. We define a new generalization of LAN, metric-projected LAN, show that quantum state space satisfies it, and derive a replacement for the Wilks theorem. In addition to enabling reliable model selection, our results shed more light on the qualitative effects of the positivity constraint on state tomography.

Increasingly, cyberspace is the battlefield of choice for twenty first century criminal activity and foreign conflict. This suggests that traditional modeling and simulation approaches have stalled in the information security domain. We propose a game theoretic model based on a multistage model of computer network exploitation (CNE) campaigns comprising reconnaissance, tooling, implant, lateral movement, exfiltration and cleanup stages. In each round of the game, the attacker chooses whether to proceed with the next stage of the campaign, nature decides whether the defender is cognizant of the campaign's progression, and the defender chooses to respond in an active or passive fashion. We propose a dynamic, asymmetric, complete-information, general-sum game to model CNE campaigns and techniques to estimate this game's parameters. Researchers can extend this work to other threat models, and practitioners can use this work for decision support.

Information security is a top priority in government and industry because high consequence cyber incidents continue with regularity. The blue teamers that protect cyber systems cannot stop or even know about all these incidents, so they must take measures to tolerate these incursions in addition to preventing and detecting them. We propose dynamically compartmentalizing subject networks into collaboration zones and limiting the communication between these zones. In this article, we demonstrate this technique's effect on the attacker and the defender for various parameter settings using discrete-time simulation. Based on our results, we conclude that dynamic cyber zone defense is a viable intrusion tolerance technique and should be considered for technology transfer.

A novel strategy for the versatile functionalization of the external surface of metal-organic frameworks (MOFs) has been developed based on the direct coordination of a phenolic-inspired lipid molecule DPGG (1,2-dipalmitoyl-sn-glycero-3-galloyl) with metal nodes/sites surrounding MOF surface. X-ray diffraction and Argon sorption analysis prove that the modified MOF particles retain their structural integrity and porosity after surface modification. Density functional theory calculations reveal that strong chelation strength between the metal sites and the galloyl head group of DPGG is the basic prerequisite for successful coating. Due to the pH-responsive nature of metal-phenol complexation, the modification process is reversible by simple washing in weak acidic water, showing an excellent regeneration ability for water-stable MOFs. Moreover, the colloidal stability of the modified MOFs in the nonpolar solvent allows them to be further organized into 2 dimensional MOF or MOF/polymer monolayers by evaporation-induced interfacial assembly conducted on an air/water interface. Lastly, the easy fusion of a second functional layer onto DPGG-modified MOF cores, enabled a series of MOF-based functional nanoarchitectures, such as MOFs encapsulated within hybrid supported lipid bilayers (so-called protocells), polyhedral core-shell structures, hybrid lipid-modified-plasmonic vesicles and multicomponent supraparticles with target functionalities, to be generated. for a wide range of applications.

We introduce a general model for a network of quantum sensors, and we use this model to consider the following question: When can entanglement between the sensors, and/or global measurements, enhance the precision with which the network can measure a set of unknown parameters? We rigorously answer this question by presenting precise theorems proving that for a broad class of problems there is, at most, a very limited intrinsic advantage to using entangled states or global measurements. Moreover, for many estimation problems separable states and local measurements are optimal, and can achieve the ultimate quantum limit on the estimation uncertainty. This immediately implies that there are broad conditions under which simultaneous estimation of multiple parameters cannot outperform individual, independent estimations. Our results apply to any situation in which spatially localized sensors are unitarily encoded with independent parameters, such as when estimating multiple linear or nonlinear optical phase shifts in quantum imaging, or when mapping out the spatial profile of an unknown magnetic field. We conclude by showing that entangling the sensors can enhance the estimation precision when the parameters of interest are global properties of the entire network.

Magnetoresistive random-access memory (MRAM) is poised to become a next-generation information storage device. Yet, many materials challenges remain unsolved before it can become a widely used memory storage solution. Among them, an urgent need is to identify a material system that is suitable for downscaling and is compatible with low-power logic applications. Self-assembled, vertically aligned La_2/3Sr_1/3MnO₃: ZnO nanocomposites, in which La_2/3Sr_1/3MnO₃ (LSMO) matrix and ZnO nanopillars form an intertwined structure with coincident-site-matched growth occurring between the LSMO and ZnO vertical interfaces, may offer new MRAM applications by combining their superior electric, magnetic ( B ), and optical properties. Here, in this Rapid Communication, we show the results of electrical current induced magnetic hysteresis in magnetoresistance measurements in these nanopillar composites. We observe that when the current level is low, for example, 1 µA, the magnetoresistance displays a linear, negative, nonhysteretic B field dependence. Surprisingly, when a large current is used, I > 10 µA, a hysteretic behavior is observed when the B field is swept in the up and down directions. This hysteresis weakens as the sample temperature is increased. Finally, a possible spin-valve mechanism related to this electrical current induced magnetic hysteresis is proposed and discussed.

Thermophotovoltaics (TPV) is the process by which photons radiated from a thermal emitter are converted into electrical power via a photovoltaic cell. Selective thermal emitters that can survive at temperatures at or above ∼1000°C have the potential to greatly improve the efficiency of TPV energy conversion by restricting the emission of photons with energies below the photovoltaic (PV) cell bandgap energy. In this work, we demonstrated TPV energy conversion using a high-temperature selective emitter, dielectric filter, and 0.6 eV In0.68 Ga0.32 As photovoltaic cell. We fabricated a passivated platinum and alumina frequency-selective surface by conventional stepper lithography. To our knowledge, this is the first demonstration of TPV energy conversion using a metamaterial emitter. The emitter was heated to >1000°C, and converted electrical power was measured. After accounting for geometry, we demonstrated a thermal-to-electrical power conversion efficiency of 24.1 0.9% at 1055°C. We separately modeled our system consisting of a selective emitter, dielectric filter, and PV cell and found agreement with our measured efficiency and power to within 1%. Our results indicate that high-efficiency TPV generators are possible and are candidates for remote power generation, combined heat and power, and heat-scavenging applications.

Herein, we investigate the saturation limits of hydrogen on the (110) and (100) surfaces of tungsten via Density Functional Theory (DFT) and complement our findings with experimental measurements. We present a detailed study of the various stable configurations that hydrogen can adopt upon the surfaces at coverage ratios starting below 1.0, up to the point of their experimental coverage ratios, and beyond. We provide the many low-energy configurations that exist at all coverages along with the energy landscape they form. Our findings allow us to estimate that the saturation limit on each surface exists with one monolayer of hydrogen atoms adsorbed. In the case of (110) this corresponds to a coverage ratio of one hydrogen atom per tungsten atom, while in the case of (100) a full monolayer is present at a coverage ratio of 2.0 hydrogen atoms per tungsten atoms. Preliminary Low Energy Ion Scattering (LEIS) and Direct Recoil Spectroscopy (DRS) measurements complement this work on the W(110) surface. These results and some previously published measurements obtained on the W(100) surface confirm the findings obtained by DFT. In particular, the saturation limits on each surface, the preferred adsorption sites on both surfaces up to saturation, and the reconstruction of the bare and unsaturated (100) surface.

Irradiation-induced void swelling remains a major challenge to nuclear reactor operation. Swelling may take years to initiate and often results in rapid material property degradation once started. Alloy development for advanced nuclear systems will require rapid characterization of the swelling breakaway dose in new alloys, yet this capability does not yet exist. We demonstrate that transient grating spectroscopy (TGS) can detect void swelling in single crystal copper via changes in surface acoustic wave (SAW) velocity. Scanning transmission electron microscopy (STEM) links the TGS-observed changes with void swelling-induced microstructural evolution. These results are considered in the context of previous work to suggest that in situ TGS will be able to rapidly determine when new bulk materials begin void swelling, shortening alloy development and testing times.

For this study, cells based on nickel manganese cobalt oxide (NMC)/graphite electrodes, which contained polyvinylidene difluoride (PVDF) binders in the electrodes, were systematically charged to 100, 120, 140, 160, 180, and 250% state of charge (SOC). Characterization of the anodes by inductively-coupled-plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS), and high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) showed several extent-of-overcharge-dependent trends. The concentrations (by wt) of nickel, manganese, and cobalt in the negative electrode increased with SOC, but the metals remained in the same ratio as that of the positive. Electrolyte reaction products, such as LiF:LiPO₃, increased with overcharge, as expected. Three organic products were found by HPLC-ESI-MS. From an analysis of the mass spectra, two of these compounds seem to be organophosphates, which were formed by the reaction of polymerized electrolyte decomposition products and PF₃ or O=PF₃. Their concentration tended to reach a constant ratio. The third was seen at 250% SOC only.

The transfer Hamiltonian tunneling current is derived in a time-dependent density matrix formulation and is used to examine photon-assisted tunneling. Bardeen's tunneling expression arises as the result of first-order perturbation theory in a mean-field expansion of the density matrix. Photon-assisted tunneling from confined electromagnetic fields in the forbidden tunnel barrier region occurs due to time-varying polarization and wave-function overlap in the gap which leads to a nonzero tunneling current in asymmetric device structures, even in an unbiased state. The photon energy is seen to act as an effective temperature-dependent bias in a uniform barrier asymmetric tunneling example problem. Higher-order terms in the density matrix expansion give rise to multiphoton enhanced tunneling currents that can be considered an extension of nonlinear optics where the nonlinear conductance plays a similar role as the nonlinear susceptibilities in the continuity equations.

Defect formation in LiF, which is used as an observation window in ramp and shock experiments, has significant effects on its transmission properties. Given the extreme conditions of the experiments it is hard to measure the change in transmission directly. Using molecular dynamics, we estimate the change in conductivity as a function of the concentration of likely point and extended defects using a Green-Kubo technique with careful treatment of size effects. With this data, we form a model of the mean behavior and its estimated error; then, we use this model to predict the conductivity of a large sample of defective LiF resulting from a direct simulation of ramp compression as a demonstration of the accuracy of its predictions. Given estimates of defect densities in a LiF window used in an experiment, the model can be used to correct the observations of thermal energy through the window. In addition, the methodology we develop is extensible to modeling, with quantified uncertainty, the effects of a variety of defects on the thermal conductivity of solid materials.

Abstract not provided.

This report provides an overview of a workshop held on July 27-28, 2016 at Sandia National Laboratories in Albuquerque to itemize the DOE laboratory capabilties and provide a high level organization of those capabilties into a full evaluation framework for new computing paradigms that spans from fundamental breakthroughs in materials and devices to full system architectures and software environments.

By using multiple growth steps that separate the nucleation and growth processes, we show that nearly intrinsic InN single nanocrystals of high optical quality can be formed on patterned GaN nanowire arrays by molecular beam epitaxy. The InN nanostructures form into well-defined hexagonal prisms with pyramidal tops. Micro-photoluminescence (μ-PL) is carried out at low temperature (LT: 28.2 K) and room temperature (RT: 285 K) to gauge the relative material quality of the InN nanostructures. Nanopyramidal prisms grown using a three-step growth method are found to show superior quantum efficiency. Excitation and temperature dependent μ-PL demonstrates the very high quality and nearly intrinsic nature of the ordered InN nanostructure arrays.

A comparison of two fuels demonstrates how analysis of ˙OH and HO₂˙ formation kineticsviathe eigenvalues of a system of simplified kinetic equations can give mechanistic insights.

UiO-66 is a highly stable metal-organic framework (MOF) that has garnered interest for many adsorption applications. For small, nonpolar adsorbates, physisorption is dominated by weak Van der Waals interactions limiting the adsorption capacity. A common strategy to enhance the adsorption properties of isoreticular MOFs, such as UiO-66, is to add functional groups to the organic linker. Low and high pressure O2 isotherms were measured on UiO-66 MOFs functionalized with electron donating and withdrawing groups. It was found that the electron donating effects of -NH2, -OH, and -OCF3 groups enhance the uptake of O2. Interestingly, a significant enhancement in both the binding energy and adsorption capacity of O2 was observed for UiO-66-(OH)2-p, which has two -OH groups para from one another. Density functional theory (DFT) simulations were used to calculate the binding energy of oxygen to each MOF, which trended with the adsorption capacity and agreed well with the heats of adsorption calculated from the Toth model fit to multi-temperature isotherms. DFT simulations also determined the highest energy binding site to be on top of the electron π-cloud of the aromatic ring of the ligand, with a direct trend of the binding energy with low pressure adsorption capacity. Uniquely, DFT found that oxygen molecules adsorbed to UiO-66-(OH)2-p prefer to align parallel to the -OH groups on the aromatic ring. Similar effects for the electron donation of the functional groups were observed for the low pressure adsorption of N2, CH4, and CO2.

The development of antimicrobial-resistant (AMR) bacteria poses a serious worldwide health concern. CRISPR-based antibacterials, however, are a novel and adaptable method for building an arsenal of antibacterials potentially capable of targeting any pathogenic bacteria.

Here, we introduce a meshless method for solving both continuous and discrete variational formulations of a volume constrained, nonlocal diffusion problem. We use the discrete solution to approximate the continuous solution. Our method is nonconforming and uses a localized Lagrange basis that is constructed out of radial basis functions. By verifying that certain inf-sup conditions hold, we demonstrate that both the continuous and discrete problems are well-posed, and also present numerical and theoretical results for the convergence behavior of the method. The stiffness matrix is assembled by a special quadrature routine unique to the localized basis. Combining the quadrature method with the localized basis produces a well-conditioned, symmetric matrix. This then is used to find the discretized solution.

Based on operations prescribed under the paradigm of complex transformation optics (CTO) [F. Teixeira and W. Chew, J. Electromagn. Waves Appl. 13, 665 (1999)JEWAE50920-507110.1163/156939399X01104; F. L. Teixeira and W. C. Chew, Int. J. Numer. Model. 13, 441 (2000)0894-337010.1002/1099-1204(200009/10)13:5%3C441::AID-JNM376%3E3.0.CO;2-J; H. Odabasi, F. L. Teixeira, and W. C. Chew, J. Opt. Soc. Am. B 28, 1317 (2011)JOBPDE0740-322410.1364/JOSAB.28.001317; B.-I. Popa and S. A. Cummer, Phys. Rev. A 84, 063837 (2011)PLRAAN1050-294710.1103/PhysRevA.84.063837], it was recently shown in [G. Castaldi, S. Savoia, V. Galdi, A. Alù, and N. Engheta, Phys. Rev. Lett. 110, 173901 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.173901] that a complex source point (CSP) can be mimicked by parity-time (PT) transformation media. Such coordinate transformation has a mirror symmetry for the imaginary part, and results in a balanced loss/gain metamaterial slab. A CSP produces a Gaussian beam and, consequently, a point source placed at the center of such a metamaterial slab produces a Gaussian beam propagating away from the slab. Here, we extend the CTO analysis to nonsymmetric complex coordinate transformations as put forth in [S. Savoia, G. Castaldi, and V. Galdi, J. Opt. 18, 044027 (2016)2040-897810.1088/2040-8978/18/4/044027] and verify that, by using simply a (homogeneous) doubly anisotropic gain-media metamaterial slab, one can still mimic a CSP and produce Gaussian beam. In addition, we show that a Gaussian-like beams can be produced by point sources placed outside the slab as well. By making use of the extra degrees of freedom (the real and imaginary parts of the coordinate transformation) provided by CTO, the near-zero requirement on the real part of the resulting constitutive parameters can be relaxed to facilitate potential realization of Gaussian-like beams. We illustrate how beam properties such as peak amplitude and waist location can be controlled by a proper choice of (complex-valued) CTO Jacobian elements. In particular, the beam waist location may be moved bidirectionally by allowing for negative entries in the Jacobian (equivalent to inducing negative refraction effects). These results are then interpreted in light of the ensuing CSP location.

We conduct a global sensitivity analysis (GSA) of the Energy Exascale Earth System Model (E3SM), land model (ELM) to calculate the sensitivity of five key carbon cycle outputs to 68 model parameters. This GSA is conducted by first constructing a Polynomial Chaos (PC) surrogate via new Weighted Iterative Bayesian Compressive Sensing (WIBCS) algorithm for adaptive basis growth leading to a sparse, high-dimensional PC surrogate with 3,000 model evaluations. The PC surrogate allows efficient extraction of GSA information leading to further dimensionality reduction. The GSA is performed at 96 FLUXNET sites covering multiple plant functional types (PFTs) and climate conditions. About 20 of the model parameters are identified as sensitive with the rest being relatively insensitive across all outputs and PFTs. These sensitivities are dependent on PFT, and are relatively consistent among sites within the same PFT. The five model outputs have a majority of their highly sensitive parameters in common. A common subset of sensitive parameters is also shared among PFTs, but some parameters are specific to certain types (e.g., deciduous phenology). The relative importance of these parameters shifts significantly among PFTs and with climatic variables such as mean annual temperature.

Marine renewable energy devices require mooring and foundation systems that suitable in terms of device operation and are also robust and cost effective. In the initial stages of mooring and foundation development a large number of possible configuration permutations exist. Filtering of unsuitable designs is possible using information specific to the deployment site (i.e. bathymetry, environmental conditions) and device (i.e. mooring and/or foundation system role and cable connection requirements). The identification of a final solution requires detailed analysis, which includes load cases based on extreme environmental statistics following certification guidance processes. Static and/or quasi-static modelling of the mooring and/or foundation system serves as an intermediate design filtering stage enabling dynamic time-domain analysis to be focused on a small number of potential configurations. Mooring and foundation design is therefore reliant on logical decision making throughout this stage-gate process. The open-source DTOcean (Optimal Design Tools for Ocean Energy Arrays) Tool includes a mooring and foundation module, which automates the configuration selection process for fixed and floating wave and tidal energy devices. As far as the authors are aware, this is one of the first tools to be developed for the purpose of identifying potential solutions during the initial stages of marine renewable energy design. While the mooring and foundation module does not replace a full design assessment, it provides in addition to suitable configuration solutions, assessments in terms of reliability, economics and environmental impact. This article provides insight into the solution identification approach used by the module and features the verification of both the mooring system calculations and the foundation design using commercial software. Several case studies are investigated: a floating wave energy converter and several anchoring systems. It is demonstrated that the mooring and foundation module is able to provide device and/or site developers with rapid mooring and foundation design solutions to appropriate design criteria.

The heterogeneity in mechanical fields introduced by microstructure plays a critical role in the localization of deformation. To resolve this incipient stage of failure, it is therefore necessary to incorporate microstructure with sufficient resolution. On the other hand, computational limitations make it infeasible to represent the microstructure in the entire domain at the component scale. In this study, the authors demonstrate the use of concurrent multiscale modeling to incorporate explicit, finely resolved microstructure in a critical region while resolving the smoother mechanical fields outside this region with a coarser discretization to limit computational cost. The microstructural physics is modeled with a high-fidelity model that incorporates anisotropic crystal elasticity and rate-dependent crystal plasticity to simulate the behavior of a stainless steel alloy. The component-scale material behavior is treated with a lower fidelity model incorporating isotropic linear elasticity and rate-independent J2 plasticity. The microstructural and component scale subdomains are modeled concurrently, with coupling via the Schwarz alternating method, which solves boundary-value problems in each subdomain separately and transfers solution information between subdomains via Dirichlet boundary conditions. In this study, the framework is applied to model incipient localization in tensile specimens during necking.

Unmanned aerial vehicles (UAV) are among the major growing technologies that have many beneficial applications, yet they can also pose a significant threat. Recently, several incidents occurred with UAVs violating privacy of the public and security of sensitive facilities, including several nuclear power plants in France. The threat of UAVs to the security of nuclear facilities is of great importance and is the focus of this work. This paper presents an overview of UAV technology and classification, as well as its applications and potential threats. We show several examples of recent security incidents involving UAVs in France, USA, and United Arab Emirates. Further, the potential threats to nuclear facilities and measures to prevent them are evaluated. The importance of measures for detection, delay, and response (neutralization) of UAVs at nuclear facilities are discussed. An overview of existing technologies along with their strength and weaknesses are shown. Finally, the results of a gap analysis in existing approaches and technologies is presented in the form of potential technological and procedural areas for research and development. Based on this analysis, directions for future work in the field can be devised and prioritized.

To understand interfacial interaction of a bi-material during an impact loading event, the dynamic friction coefficient is one of the key parameters that must be characterized and quantified. In this study, a new experimental method to determine the dynamic friction coefficient between two metals was developed by using a Kolsky tension bar and a custom-designed friction fixture. Polyvinylidene fluoride (PVDF) force sensors were used to measure the normal force applied to the friction tribo pairs and the friction force was measured with conventional Kolsky tension bar method. To evaluate the technique, the dynamic friction coefficient between 4340 steel and 7075-T6 aluminum was investigated at an impact speed of approximately 8 m/s. In addition, the dynamic friction coefficient of the tribo pairs with varied surface roughness was also investigated. The data suggest that higher surface roughness leads to higher friction coefficients at the same speed of 8 m/s.

The Kaiser effect is a stress memory phenomenon which has most often been demonstrated in rock using acoustic emissions. During cyclic loading–unloading–reloading, the acoustic emissions are near zero until the load exceeds the level of the previous load cycle. Researchers explore the Kaiser effect in rock using real-time noble gas release. Laboratory studies using real-time mass spectrometry measurements during deformation have quantified, to a degree, the types of gases released, degree, the types of gases released (Bauer et al. 2016a, b), their release rates and amounts during deformation, estimates of permeability created from pore structure modifications during deformation and the impact of mineral plasticity upon gas release. Its observed that noble gases contained in brittle crystalline rock are readily released during deformation.

The Hawaiian Electric Company intends to procure grid-scale Battery Energy Storage System (“BESS”) capacity. The purpose of this study is to determine whether providing contingency reserve or time-of-day shifting is of more benefit to the Oahu grid, and to better understand the relationship between BESS size and level of benefit. This is an independent study by Sandia, and is not being used to support the regulatory case for BESS capacity by Hawaiian Electric. The study team created a production cost model of the Oahu grid using data primarily from the Hawaiian Electric Company. The proposed BESS supplied contingency reserve in one set of runs and time-of-day shifting in another. Supplying contingency reserve led to larger savings than time-of-day energy shifting. Assuming a renewable reserve and a quick-start reserve, and $15/MMBtu for Low-Sulphur Fuel Oil, the 50-MW/25-MWh, 100-MW/50-MWh, and 150-MW/75-MWh systems supplying contingency reserve provided, respectively, savings of 9.6, 15.6, and 18.3 million USD over system year 2018. Over the range of fuel prices tested, these cost savings were found to be directly proportional to the cost of fuel. As the focus is the operational benefit of BESS capacity, the capacity value of the BESS was not included in benefit calculations.

Quantum state tomography on a d-dimensional system demands resources that grow rapidly with d. They may be reduced by using model selection to tailor the number of parameters in the model (i.e., the size of the density matrix). Most model selection methods typically rely on a test statistic and a null theory that describes its behavior when two models are equally good. Here, we consider the loglikelihood ratio. Because of the positivity constraint ρ ≥ 0, quantum state space does not generally satisfy local asymptotic normality (LAN), meaning the classical null theory for the loglikelihood ratio (the Wilks theorem) should not be used. Thus, understanding and quantifying how positivity affects the null behavior of this test statistic is necessary for its use in model selection for state tomography. We define a new generalization of LAN, metric-projected LAN, show that quantum state space satisfies it, and derive a replacement for the Wilks theorem. In addition to enabling reliable model selection, our results shed more light on the qualitative effects of the positivity constraint on state tomography.

We use molecular simulations to probe the local viscoelasticity of an entangled polymer melt by tracking the motion of embedded nonsticky nanoparticles (NPs). As in conventional microrheology, the generalized Stokes-Einstein relation is employed to extract an effective stress relaxation function GGSE(t) from the mean square displacement of NPs. GGSE(t) for different NP diameters d are compared with the stress relaxation function G(t) of a pure polymer melt. The deviation of GGSE(t) from G(t) reflects the incomplete coupling between NPs and the dynamic modes of the melt. For linear polymers, a plateau in GGSE(t) emerges as d exceeds the entanglement mesh size a and approaches the entanglement plateau in G(t) for a pure melt with increasing d. For ring polymers, as d increases towards the spanning size R of ring polymers, GGSE(t) approaches G(t) of the ring melt with no entanglement plateau.

The volumetric calibration of a plenoptic camera is explored to correct for inaccuracies due to real-world lens distortions and thin-lens assumptions in current processing methods. Two methods of volumetric calibration based on a polynomial mapping function that does not require knowledge of specific lens parameters are presented and compared to a calibration based on thin-lens assumptions. The first method, volumetric dewarping, is executed by creation of a volumetric representation of a scene using the thin-lens assumptions, which is then corrected in post-processing using a polynomial mapping function. The second method, direct light-field calibration, uses the polynomial mapping in creation of the initial volumetric representation to relate locations in object space directly to image sensor locations. The accuracy and feasibility of these methods is examined experimentally by capturing images of a known dot card at a variety of depths. Results suggest that use of a 3D polynomial mapping function provides a significant increase in reconstruction accuracy and that the achievable accuracy is similar using either polynomial-mapping-based method. Additionally, direct light-field calibration provides significant computational benefits by eliminating some intermediate processing steps found in other methods. Finally, the flexibility of this method is shown for a nonplanar calibration.

Abstract not provided.

Abstract not provided.

Abstract not provided.

We investigated the simplest alkylperoxy radical, CH3OO, formed by reacting photolytically generated CH3 radicals with O2, using the new combustion reactions followed by photoelectron photoion coincidence (CRF-PEPICO) apparatus at the Swiss Light Source. Modeling the experimental photoion mass-selected threshold photoelectron spectrum using Franck-Condon simulations including transitions to triplet and singlet cationic states yielded the adiabatic ionization energy of 10.265 ± 0.025 eV. Dissociative photoionization of CH3OO generates the CH3+ fragment ion at the appearance energy of 11.164 ± 0.010 eV. Combining these two values with ΔfH0K°(CH3) yields ΔfH0K°(CH3OO) = 22.06 ± 0.97 kJ mol-1, reducing the uncertainty of the previously determined value by a factor of 5. Statistical simulation of the CH3OO breakdown diagram provides a molecular thermometer of the free radical's internal temperature, which we measured to be 330 ± 30 K.

Abstract not provided.

Abstract not provided.

Digital inline holography (DIH) provides instantaneous three-dimensional (3D) measurements of diffracting objects; however, phase disturbances in the beam path can distort the imaging. In this Letter, a phase conjugate digital inline holography (PCDIH) configuration is proposed for removal of phase disturbances. Brillouin-enhanced four-wave mixing produces a phase conjugate signal that back propagates along the DIH beam path. The results demonstrate the removal of distortions caused by gas-phase shocks to recover 3D images of diffracting objects.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

The development of antimicrobial-resistant (AMR) bacteria poses a serious worldwide health concern. CRISPR-based antibacterials are a novel and adaptable method for building an arsenal of antibacterials potentially capable of targeting any pathogenic bacteria.

We consider underwater multi-modal wireless sensor networks (UWSNs) suitable for applications on submarine surveillance and monitoring, where nodes offload data to a mobile autonomous underwater vehicle (AUV) via optical technology, and coordinate using acoustic communication. Sensed data are associated with a value, decaying in time. In this scenario, we address the problem of finding the path of the AUV so that the Value of Information (VoI) of the data delivered to a sink on the surface is maximized. We define a Greedy and Adaptive AUV Path-finding (GAAP) heuristic that drives the AUV to collect data from nodes depending on the VoI of their data. For benchmarking the performance of AUV path-finding heuristics, we define an integer linear programming (ILP) formulation that accurately models the considered scenario, deriving a path that drives the AUV to collect and deliver data with the maximum VoI. In our experiments GAAP consistently delivers more than 80 percent of the theoretical maximum VoI determined by the ILP model. We also compare the performance of GAAP with that of other strategies for driving the AUV among sensing nodes, namely, random paths, TSP-based paths and a 'lawn mower'-like strategy. Our results show that GAAP always outperforms every other heuristic in terms of delivered VoI, also obtaining higher energy efficiency.

Silsesquioxane nanoparticles are composed of repetitive organosilica fragments in their frameworks and are now recognized to have outstanding functional fertility. Depending on the organosilane and the synthetic pathways, silsesquioxane NPs can be pendant, bridged, dense or porous. Recently the diverse functionalities of mesoporous silsesquioxane nanoparticles have been exploited for the sake of drug-related biomedicine. Fine-tuning the silsesquioxane nanoparticles characteristics allow not only a superior retention capacity of therapeutics without the need of any further modification, but also a controlled release through various environmentally-stimulated triggers. Furthermore, the main focus of the present review is to highlight the different types of silsesquioxane nanoparticles and their exceptional features focused on controlled delivery of drugs, proteins, antibodies and DNA through pH, redox or light stimuli.

The size, temporal and spatial shape, and energy content of a laser pulse for the pre-heat phase of magneto-inertial fusion affect the ability to penetrate the window of the laser-entrance-hole and to heat the fuel behind it. High laser intensities and dense targets are subject to laser-plasma-instabilities (LPI), which can lead to an effective loss of pre-heat energy or to pronounced heating of areas that should stay unexposed. While this problem has been the subject of many studies over the last decades, the investigated parameters were typically geared towards traditional laser driven Inertial Confinement Fusion (ICF) with densities either at 10% and above or at 1% and below the laser's critical density, electron temperatures of 3-5 keV, and laser powers near (or in excess of) 1 × 1015 W/cm2. In contrast, Magnetized Liner Inertial Fusion (MagLIF) [Slutz et al., Phys. Plasmas 17, 056303 (2010) and Slutz and Vesey, Phys. Rev. Lett. 108, 025003 (2012)] currently operates at 5% of the laser's critical density using much thicker windows (1.5-3.5 μm) than the sub-micron thick windows of traditional ICF hohlraum targets. This article describes the Pecos target area at Sandia National Laboratories using the Z-Beamlet Laser Facility [Rambo et al., Appl. Opt. 44(12), 2421 (2005)] as a platform to study laser induced pre-heat for magneto-inertial fusion targets, and the related progress for Sandia's MagLIF program. Forward and backward scattered light were measured and minimized at larger spatial scales with lower densities, temperatures, and powers compared to LPI studies available in literature.

Could combining quantum computing and machine learning with Moore's law produce a true 'rebooted computer'? This article posits that a three-technology hybrid-computing approach might yield sufficiently improved answers to a broad class of problems such that energy efficiency will no longer be the dominant concern.

Soot formation in pyrolyzing sprays of n-dodecane is visualized and quantified in a high-pressure, high-temperature, constant-volume spray chamber at 38 bar, 76 bar, and 114 bar. Sprays of n-dodecane are injected at 500 bar from a single-hole, 186-µm orifice diameter fuel injector. We quantify the temporal evolution of the soot optical thickness and the total soot mass formed in the pyrolyzing sprays using a high-speed extinction imaging diagnostic. The vessel ambient temperature and pressure are varied independently to identify the soot onset temperature for n-dodecane pyrolysis. Linear extrapolation of the maximum soot formation rates as a function of ambient temperature reveals a soot onset temperature near 1450 K. The onset temperature determined here for n-dodecane is within 50 K of those previously measured along the centerline of atmospheric pressure coflow diffusion flames for smaller alkane fuels.

We study several natural instances of the geometric hitting set problem for input consisting of sets of line segments (and rays, lines) having a small number of distinct slopes. These problems model path monitoring (e.g., on road networks) using the fewest sensors (the “hitting points”). We give approximation algorithms for cases including (i) lines of 3 slopes in the plane, (ii) vertical lines and horizontal segments, (iii) pairs of horizontal/vertical segments. We give hardness and hardness of approximation results for these problems. We prove that the hitting set problem for vertical lines and horizontal rays is polynomially solvable.

Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 is a π-stacked layered metal-organic framework material with extended π-conjugation that is analogous to graphene. Published experimental results indicate that the material is semiconducting, but all theoretical studies to date predict the bulk material to be metallic. Given that previous experimental work was carried out on specimens containing complex nanocrystalline microstructures and the tendency for internal interfaces to introduce transport barriers, we apply DFT to investigate the influence of internal interface defects on the electronic structure of Ni3(HITP)2. The results show that interface defects can introduce a transport barrier by breaking the π-conjugation and/or decreasing the dispersion of the electronic bands near the Fermi level. We demonstrate that the presence of defects can open a small gap, in the range of 15-200 meV, which is consistent with the experimentally inferred hopping barrier.

The laminar flame speed sl is an important reference quantity for characterising and modelling combustion. Experimental measurements of laminar flame speed require the residence time of the fuel/air mixture (τf) to be shorter than the autoignition delay time (τ). This presents a considerable challenge for conditions where autoignition occurs rapidly, such as in compression ignition engines. As a result, experimental measurements in typical compression ignition engine conditions do not exist. Simulations of freely propagating premixed flames, where the burning velocity is found as an eigenvalue of the solution, are also not well posed in such conditions, since the mixture ahead of the flame can autoignite, leading to the so called “cold boundary problem”. Here, a numerical method for estimating a reference flame speed, sR, is proposed that is valid for laminar flame propagation at autoignitive conditions. Two isomer fuels are considered to test this method: ethanol, which in the considered conditions is a single-stage ignition fuel; and dimethyl ether, which has a temperature-dependent single- or two-stage ignition and a negative temperature coefficient regime for τ. Calculations are performed for the flame position in a one-dimensional computational domain with inflow-outflow boundary conditions, as a function of the inlet velocity UI and for stoichiometric fuel–air premixtures. The response of the flame position, LF, to UI shows distinct stabilisation regimes. For single-stage ignition fuels, at low UI the flame speed exceeds UI and the flame becomes attached to the inlet. Above a critical UI value, the flame detaches from the inlet and Lf becomes extremely sensitive to UI until, for sufficiently high UI, the sensitivity decreases and Lf corresponds to the location expected from a purely autoignition stabilised flame. The transition from the attached to the autoignition regimes has a corresponding peak dLf/dUI value which is proposed to be a unique reference flame speed sR for single-stage ignition fuels. For two-stage ignition fuels, there is an additional stable regime where a high-temperature flame propagates into a pool of combustion intermediates generated by the first stage of autoignition. This results in two peaks in dLf/dUI and therefore two reference flame speed values. The lower value corresponds to the definition of sR for single-stage ignition fuels, while the higher value exists only for two-stage ignition fuels and corresponds to a high temperature flame propagating into the first stage of autoignition and is denoted sR′. A transport budget analysis for low- and high-temperature radical species is also performed, which confirms that the flame structures at UI=sR and UI=sR′ do indeed correspond to premixed flames (deflagrations), as opposed to spontaneous ignition fronts which do not have a unique propagation speed.

The strategic and economic impacts of high performance computing (HPC) systems, over the last several decades, have enabled dramatic improvements in manufacturing, design, development, and research, across almost every sector of the U.S. economy, including genetic analysis for agriculture and medicine, oil exploration, electronics, aircraft, and automotive design, and of course national defense technologies. HPC has repeatedly compounded reductions in time-to-solution and time-to-market in each of these areas. In recognition of these strategic and economic impacts, the Department of Energy (DOE) created the Exascale Computing Project (ECP) as a broad-based technology project focusing on simultaneously co-evolving high-performance computing architecture, system software, and application software. While many details of the exascale architectures are undefined, communicating the form and direction of this co-evolution of advances, in each of these three components, across the project, presents a need for a common language through which these advances can be shared. In this document we present a series of abstract representations designed to allow application developers to focus on the aspects of the machine that are important or relevant to performance and code structure. These abstract machine models (AMMs) describe the proposed architectures at the component and system level and are intended as communication aids between application developers and hardware architects during the co-design process. In addition to providing a common language for communication, the constraints of protecting the intellectual property of ECP’s vendor partners requires that the architectural advances be presented in an abstract sense, rather than exposing the specifics of an individual vendor’s designs, while still providing enough detail such that application developers will be able to reason about the performance trade-offs in the design space of their applications.

This SWMU and AOC Annual Long-Term Monitoring and Maintenance (LTMM) Report for Calendar Year 2017 (Annual LTMM Report) details the measures performed for 21 Solid Waste Management Units (SWMUs) and Areas of Concern (AOCs) at Sandia National Laboratories/New Mexico (SNL/NM) in accordance with the requirements of the “Long-Term Monitoring and Maintenance [LTMM] Plan for SWMUs and AOCs Granted Corrective Action Complete with Controls” in Attachment M of the Resource Conservation and Recovery Act Facility Operating Permit (Permit), which took effect February 26, 2015. This Annual LTMM Report does not present the measures for SWMU 76, Mixed Waste Landfill (MWL), as the applicable MWL reporting adheres to the approved MWL LTMM Plan, Section 4.8.1 and requires a separate annual report which will be submitted to the New Mexico Environment Department by June 30, 2018. Measures at these SWMUs and AOCs include surveillance of site conditions and maintenance of institutional controls. Conditions requiring maintenance or repair activities were identified at three of the inspected SWMUs and AOCs (SWMUs 45, 46, and 87) during the Permit-required annual site inspections. One SWMU identification sign located at SWMU 46 and two identification signs located at SWMU 87 were replaced due to weathered lettering. Evidence of erosion was observed at SWMU 45 during the annual site inspection; erosion controls will be implemented as needed to prevent the inadvertent exposure of hazardous wastes or hazardous waste constituents. SWMU 45 is located on the sloped border of Tijeras Arroyo south of Technical Area-IV. The erosion controls planned for the Tijeras Arroyo Escarpment will address not only SWMU 45, but also SWMUs 46 and 229 as a best management practice. SNL/NM personnel plan to complete this work in calendar year 2018. The status and progress of this project will be reported in the 2018 Annual SWMUs and AOCs Annual LTMM Report for Calendar Year 2018 to be submitted to the New Mexico Environment Department on March 31, 2019, as required by the Permit. Based upon the inspections performed and site conditions observed, the administrative and physical institutional controls in place at the SWMUs and AOCs are effectively providing continued protection of human health and the environment.

The run-out phenomenon was observed in Ag-Cu-Zr active braze joints made between the alumina ceramic and Kovar™ base material. Run-out introduces a significant yield loss by generating functional and/or cosmetic defects in brazements. A prior study identified a correlation between run-out and the aluminum (Al) released by the reduction/oxidation and the latter’s reaction with the Kovar™ base material. A study was undertaken to understand the fundamental principles of run-out by examining the interface reaction between Ag-xAl filler metals (x=2, 5, and 10 wt.%) and Kovar™ base material. Sessile drop samples were fabricated using brazing temperatures of 965°C or 995°C and times of 5 min or 20 min. The correlation was made between the degree of wetting-and-spreading by the sessile drops and the run-out phenomenon. Wetting-and-spreading increased with Al content (x) of the Ag-xAl filler metal, but was largely insensitive to the brazing process parameters. The increased Al concentration resulted in higher Al contents of the (Fe, Ni, Co)_xAl_y reaction layer. Run-out was predicted when the filler metal has a locally-elevated, Al content exceeding 2 – 5 wt.%. Lastly, several mitigation strategies were proposed, based upon these findings.

A controlled between-groups experiment was conducted to demonstrate the value of human factors for process design. Most evidence to convey the benefits of human factors is derived from reactive studies of existing flawed systems designed with little or no human factors involvement. Controlled experiments conducted explicitly to demonstrate the benefits of human factors have been scarce since the 1990s. Further, most previous research focused on product or interface design as opposed to process design. The present study was designed to fill these research gaps. Toward that end, 24 Sandia National Laboratories employees completed a simple visual inspection task simulating receipt inspection. The experimental group process was designed to conform to human factors and visual inspection principles, whereas the control group process was designed without consideration of such principles. Results indicated the experimental group exhibited superior performance accuracy, lower workload, and more favorable usability ratings as compared to the control group. Given the differences observed in the simple task used in the present study, the author concluded that incorporating human factors should have even greater benefits for complex products and processes. The study provides evidence to help human factors practitioners revitalize the critical message regarding the benefits of human factors involvement for a new generation of designers.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Using internal investment funds within Sandia National Laboratories’ (SNL) Division 6000, JUBA was a collaborative exercise between SNL Orgs. 6533 & 6913 (later 8863) to demonstrate simultaneous flights of tethered balloons and UAS on the North Slope of Alaska. JUBA UAS and tethered balloon flights were conducted within the Restricted Airspace associated with the ARM AMF3 site at Oliktok Point, Alaska. The Restricted Airspace occupies a 2 nautical mile radius around Oliktok Point. JUBA was conducted at the Sandia Arctic Site, which is approximately 2 km east-southeast of the AMF3. JUBA activities occurred from 08/08/17 – 08/10/17. Atmospheric measurements from tethered balloons can occur for a long duration, but offer limited spatial variation. Measurements from UAS could offer increased spatial variability.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Ever tighter fuel economy standards and concerns about energy security motivate efforts to improve engine efficiency and to develop alternative fuels. This project contributes to the science base needed by industry to develop highly efficient direct injection spark ignition (DISI) engines that also beneficially exploit the different properties of alternative fuels. Here, the emphasis is on lean operation, which can provide higher efficiencies than traditional non-dilute stoichiometric operation. Since lean operation can lead to issues with ignition stability, slow flame propagation and low combustion efficiency, the focus is on techniques that can overcome these challenges. Specifically, fuel stratification is used to ensure ignition and completeness of combustion but this technique has soot and NOx emissions challenges. For ultra-lean well-mixed operation, turbulent deflagration can be combined with controlled end-gas autoignition to render mixed-mode combustion for sufficiently fast heat release. However, such mixed-mode combustion requires very stable inflammation, motivating studies on the effects of near-spark flow and turbulence, and the use of small amounts of fuel stratification near the spark plug.

Improved engine efficiency is required to comply with future fuel economy standards. Alternative fuels have the potential to enable more efficient engines while addressing concerns about energy security. This project contributes to the science base needed by industry to develop highly efficient direct injection spark igniton (DISI) engines that also beneficially exploit the different properties of alternative fuels. Here, the emphasis is on quantifying autoignition behavior for a range of spark-ignited engine conditions, including directly injected boosted conditions. The efficiency of stoichiometrically operated spark ignition engines is often limited by fuel-oxidizer end-gas autoignition, which can result in engine knock. A fuel’s knock resistance is assessed empirically by the Research Octane Number (RON) and Motor Octane Number (MON) tests. By clarifying how these two tests relate to the autoignition behavior of conventional and alternative fuel formulations, fuel design guidelines for enhanced engine efficiency can be developed.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.