Publications

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It is well known that the spectrum of a signal can be calculated with a Discrete Fourier Transform (DFT), where best resolution is achieved by processing the entire data set. However, in some situations it is advantageous to use a staged approach, where data is first processed within subapertures, and the results are then combined and further processed to a final result. An artifact of this approach is the creation of grating lobes in the final response. The nature of the grating lobes, including their amplitude and spacing, is an artifact of window taper functions, subaperture offsets, and subaperture processing parameters. We assess these factors and exemplify their effects.

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The "location" of the radar is the reference location to which the radar measures range. This is typically the antenna's "phase center". However, the antenna's phase center is not generally obvious, and may not correspond to any seemingly obvious physical location, such as the focal point of a dish reflector. This report calculates the phase center of an offset-fed dish reflector antenna.

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Capabilities are developed, verified and validated to generate constitutive responses using material and geometric measurements with representative volume elements (RVE). The geometrically accurate RVEs are used for determining elastic properties and damage initiation and propagation analysis. Finite element modeling of the meso-structure over the distribution of characterizing measurements is automated and various boundary conditions are applied. Plain and harness weave composites are investigated. Continuum yarn damage, softening behavior and an elastic-plastic matrix are combined with known materials and geometries in order to estimate the macroscopic response as characterized by a set of orthotropic material parameters. Damage mechanics and coupling effects are investigated and macroscopic material models are demonstrated and discussed. Prediction of the elastic, damage, and failure behavior of woven composites will aid in macroscopic constitutive characterization for modeling and optimizing advanced composite systems.

The wireless communications channel is innately insecure due to the broadcast nature of the electromagnetic medium. Many techniques have been developed and implemented in order to combat insecurities and ensure the privacy of transmitted messages. Traditional methods include encrypting the data via cryptographic methods, hiding the data in the noise floor as in wideband communications, or nulling the signal in the spatial direction of the adversary using array processing techniques. This work analyzes the design of signaling constellations, i.e. modulation formats, to combat eavesdroppers from correctly decoding transmitted messages. It has been shown that in certain channel models the ability of an adversary to decode the transmitted messages can be degraded by a clever signaling constellation based on lattice theory. This work attempts to optimize certain lattice parameters in order to maximize the security of the data transmission. These techniques are of interest because they are orthogonal to, and can be used in conjunction with, traditional security techniques to create a more secure communication channel.

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Digital in-line holography is an optical technique which can be applied to measure the size, three-dimensional position, and three-component velocity of disperse particle fields. This work summarizes recent developments at Sandia National Laboratories focused on improvement in measurement accuracy, experimental validation, and applications to multiphase flows. New routines are presented which reduce the uncertainty in measured position along the optical axis to a fraction of the particle diameter. Furthermore, application to liquid atomization highlights the ability to measure complex, three-dimensional structures. Finally, investigation of particles traveling at near sonic conditions prove accuracy despite significant experimental noise due to shock-waves.

This report describes an FY13 effort to develop the latest version of the Sandia Cooler, a breakthrough technology for air-cooled heat exchangers that was developed at Sandia National Laboratories. The project was focused on fabrication, assembly and demonstration of ten prototype systems for the cooling of high power density electronics, specifically high performance desktop computers (CPUs). In addition, computational simulation and experimentation was carried out to fully understand the performance characteristics of each of the key design aspects. This work culminated in a parameter and scaling study that now provides a design framework, including a number of design and analysis tools, for Sandia Cooler development for applications beyond CPU cooling.

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In response to the challenges related to the increasing size and complexity of systems, organizations have recognized the need to integrate human considerations in the beginning stages of systems development. Human Systems Integration (HSI) seeks to accomplish this objective by incorporating human factors within systems engineering (SE) processes and methodologies, which is the focus of this paper. A representative set of HSI methods from multiple sources are organized, analyzed, and mapped to the systems engineering Vee-model. These methods are then consolidated and evaluated against the SE process and Models-Based Systems Engineering (MBSE) methodology to determine where and how they could integrate within systems development activities in the form of specific enhancements. Overall conclusions based on these evaluations are presented and future research areas are proposed.

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Power and Energy have been identified as a first order challenge for future extreme scale high performance computing (HPC) systems. In practice the breakthroughs will need to be provided by the hardware vendors. But to make the best use of the solutions in an HPC environment, it will likely require periodic tuning by facility operators and software components. This document describes the actions and interactions needed to maximize power resources. It strives to cover the entire operational space in which an HPC system occupies. The descriptions are presented as formal use cases, as documented in the Unified Modeling Language Specification [1]. The document is intended to provide a common understanding to the HPC community of the necessary management and control capabilities. Assuming a common understanding can be achieved, the next step will be to develop a set of Application Programing Interfaces (APIs) to which hardware vendors and software developers could utilize to steer power consumption.

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People responding to high-consequence national-security situations need tools to help them make the right decision quickly. The dynamic, time-critical, and ever-changing nature of these situations, especially those involving an adversary, require models of decision support that can dynamically react as a situation unfolds and changes. Automated knowledge capture is a key part of creating individualized models of decision making in many situations because it has been demonstrated as a very robust way to populate computational models of cognition. However, existing automated knowledge capture techniques only populate a knowledge model with data prior to its use, after which the knowledge model is static and unchanging. In contrast, humans, including our national-security adversaries, continually learn, adapt, and create new knowledge as they make decisions and witness their effect. This artificial dichotomy between creation and use exists because the majority of automated knowledge capture techniques are based on traditional batch machine-learning and statistical algorithms. These algorithms are primarily designed to optimize the accuracy of their predictions and only secondarily, if at all, concerned with issues such as speed, memory use, or ability to be incrementally updated. Thus, when new data arrives, batch algorithms used for automated knowledge capture currently require significant recomputation, frequently from scratch, which makes them ill suited for use in dynamic, timecritical, high-consequence decision making environments. In this work we seek to explore and expand upon the capabilities of dynamic, incremental models that can adapt to an ever-changing feature space.

This document describes the form and use of three supplemental capabilities added to Goma during 1998 -- augmenting conditions, automatic continuation and linear stability analysis. Augmenting conditions allow the addition of constraints and auxiliary conditions which describe the relationship between unknowns, boundary conditions, material properties and post-processing extracted quantities. Automatic continuation refers to a family of algorithms (zeroth and first order here, single and multi-parameter) that allow tracking steady-state solution paths as material parameters or boundary conditions are varied. The stability analysis capability in Goma uses the method of small disturbances and superposition of normal modes to test the stability of a steady- state flow, i.e., it determines if the disturbance grows or decays in time.

The primary metric for the viability of these next generation nuclear power plants will be the cost of generated electricity. One important component in achieving these objectives is the development of power conversion technologies that maximize the electrical power output of these advanced reactors for a given thermal power. More efficient power conversion systems can directly reduce the cost of nuclear generated electricity and therefore advanced power conversion cycle research is an important area of investigation for the Generation IV Program. Brayton cycles using inert or other gas working fluids, have the potential to take advantage of the higher outlet temperature range of Generation IV systems and allow substantial increases in nuclear power conversion efficiency, and potentially reductions in power conversion system capital costs compared to the steam Rankine cycle used in current light water reactors. For the Very High Temperature Reactor (VHTR), Helium Brayton cycles which can operate in the 900 to 950 C range have been the focus of power conversion research. Previous Generation IV studies examined several options for He Brayton cycles that could increase efficiency with acceptable capital cost implications. At these high outlet temperatures, Interstage Heating and Cooling (IHC) was shown to provide significant efficiency improvement (a few to 12%) but required increased system complexity and therefore had potential for increased costs. These scoping studies identified the potential for increased efficiency, but a more detailed analysis of the turbomachinery and heat exchanger sizes and costs was needed to determine whether this approach could be cost effective. The purpose of this study is to examine the turbomachinery and heat exchanger implications of interstage heating and cooling configurations. In general, this analysis illustrates that these engineering considerations introduce new constraints to the design of IHC systems that may require different power conversion configurations to take advantage of the possible efficiency improvement. Very high efficiency gains can be achieved with the IHC approach, but this can require large low pressure turbomachinery or heat exchanger components, whose cost may mitigate the efficiency gain. One stage of interstage cooling is almost always cost effective, but careful optimization of system characteristics is needed for more complex configurations. This report summarizes the primary factors that must be considered in evaluating this approach to more efficient cycles, and the results of the engineering analysis performed to explore these options for Generation IV high temperature reactors.

Sandia has developed an optical design for wearable binoculars utilizing freeform surfaces and switchable mirrors. The goals of the effort included a design lightweight enough to be worn by the user while providing a useful field of view and magnification as well as non-mechanical switching between normal and zoomed vision. Sandia's approach is a four mirror, off-axis system taking advantage of the weight savings and chromatic performance of a reflective system. The system incorporates an electrochromic mirror on the final surface before the eye allowing the user to switch between viewing modes. Results from a prototype of a monocular version with 6.6x magnification will be presented. The individual mirrors, including three off-axis aspheres and one true freeform, were fabricated using a diamond-turning based process. A slow-slide servo process was used for the freeform element. Surface roughness and form measurement of the freeform mirror will be presented as well as the expected impact on performance. The alignment and assembly procedure will be reviewed as well as the measured optical performance of the prototype. In parallel to the optical design work, development of an electrochromic mirror has provided a working device with faster switching than current state of the art. Switchable absorbers have been demonstrated with switching times less than 0.5 seconds. The deposition process and characterization of these devices will be presented. Finally, details of an updated optical design with additional freeform surfaces will be presented as well as plans for integrating the electrochromic mirror into the system. © 2013 SPIE.

Graph theoretic tools were used to identify and classify clusters of ions and solvent molecules in molecular dynamics simulations of lithium-ion battery electrolytes. Electrolytes composed of various concentrations of LiPF 6 dissolved in ethylene carbonate (EC), dimethylene carbonate (DMC), or a 1:1 EC/DMC mixture were simulated at multiple temperatures using classical molecular dynamics. Contrary to Nernst-Einstein theory but consistent with experiment, pure DMC systems had the greatest diffusivity but the lowest conductivity. This disagreement with Nernst-Einstein theory is explained by the observed clustering behavior, which found that systems with pure EC as a solvent formed ion clusters with nonzero charge, whereas systems with pure DMC as a solvent formed primarily neutral clusters. © 2013 American Chemical Society.

In lithium ion batteries, Li+ intercalation into electrodes is induced by applied voltages, which are in turn associated with free energy changes of Li+ transfer (ΔGt) between the solid and liquid phases. Using ab initio molecular dynamics (AIMD) and thermodynamic integration techniques, we compute ΔGt for the virtual transfer of a Li+ from a LiC6 anode slab, with pristine basal planes exposed, to liquid ethylene carbonate confined in a nanogap. The onset of delithiation, at ΔGt = 0, is found to occur on LiC6 anodes with negatively charged basal surfaces. These negative surface charges are evidently needed to retain Li+ inside the electrode and should affect passivation (“SEI”) film formation processes. Fast electrolyte decomposition is observed at even larger electron surface densities. By assigning the experimentally known voltage (0.1 V vs Li+/Li metal) to the predicted delithiation onset, an absolute potential scale is obtained. This enables voltage calibrations in simulation cells used in AIMD studies and paves the way for future prediction of voltage dependences in interfacial processes in batteries.

We demonstrate a new type of electrically tunable strong coupling between a planar metamaterial layer and an ultra-thin epsilon-near-zero layer made of a doped semiconductor. This can find novel applications in chip-scale infrared optoelectronic devices. © OSA 2013.

Modeling agent behaviors in complex task environments requires the agent to be sensitive to complex stimuli such as the positions and actions of varying numbers of other entities. Entity state updates may be received asynchronously rather than on a coordinated clock signal, so the world state must be estimated based on the most recent information available for each entity. The simulation environment is likely to be distributed across several computers over a network. This paper presents the Relational Blackboard (RBB), which is a framework developed to address these needs with clarity and efficiency. The purpose of this paper is to explain the concepts used to represent and process spatio-temporal data in the RBB framework so researchers in related areas can apply the concepts and software to their own problems of interest; detailed description of our own research will be found in other papers. The software is freely available under the BSD open-source license at http://rbb.sandia.gov.

A novel fast method to update the object texture of the triangular mesh hologram is proposed. The angular spectrum of the three-dimensional object represented in triangular meshes is calculated with various pre-defined spectrum shifts. These shifted angular spectrums are added with appropriate coefficients to synthesize the hologram with arbitrary texture on the three-dimensional object in an enhanced speed. © 2013 Optical Society of America.

The Whipple bumper is a space shield designed to protect a space station from the most hazardous orbital space debris environment. A series of numerical simulations has been performed using the multi-dimensional hydrodynamics code CTH to estimate the effectiveness of the thin Whipple bumper design. These simulations are performed for impact velocities of ~ 10 km/s which are now accessible by experiments using the Sandia hypervelocity launcher facility. For a ~ 10 km/s impact by a 0.7 gm aluminum flier plate, the experimental results indicate that the debris cloud resulting upon impact of the bumper shield by the flier plate, completely penetrates the sub-structure. The CTH simulations also predict complete penetration by the subsequent debris cloud.

A rezone stencil for ALE shock calculations has been developed based on a stabilized variant of the serendipity element. This rezone stencil is compared to the Winslow rezone stencil. Unlike the Winslow stencil, which equalizes element volumes as well as node angles, the serendipity stencil equalizes node angles only. This may be advantageous for calculations involving strong density gradients such as those associated with shock compression.

Hydrocode simulations constitute an important tool at Sandia National Laboratories and elsewhere for analyzing complex two- and three-dimensional systems. However, current vector supercomputers do not provide a growth path to enable fast, routine, and cost-effective simulations of large problems. Future, massively-parallel computers will provide a solution. Sandia has already developed simplified versions of the production hydrocode CTH for the Connection Machine and the nCUBE massively-parallel supercomputers. The parallel versions solve problems in two-dimensional, multi-fluid, shock-wave physics. Code development strategy, coding methodology, visualization techniques and performance results for this work are described.

Computational and analytical investigations have been performed for laser-driven flyer plate experiments and compared with data. These have resulted in a more fundamental understanding of the physical processes in the laser absorption, and acceleration of the flyers by the expansion of laser produced plasma. The analytical work describes the dependences of final foil velocity, while the computational simulations permit a detailed look at energy coupling and foil acceleration issues.

Because of complications associated with temperature heterogeneities in shocked metal powders, time-resolved radiation pyrometer measurements of shock temperatures in powders with particle sizes greater than a few tens of microns cannot be made under normal laboratory conditions with uniaxial loading durations limited to about one microsecond. Fortunately, for highly porous, reactive powders, the difference between shock and postshock temperature is negligible. For loading conditions similar to those that have yielded reaction products in recovery experiments, there is no evidence of any chemical reaction in a coarse (-325 mesh) nickel/aluminum powder mixture within the first 6 μs of shock arrival, based on constraints on postshock temperatures provided by thermal radiation measurements. This result is in contrast to that for a micron-sized nickel/aluminum mixture, for which there is evidence of significant reaction on a time scale of 100 ns under similar shock loading conditions.

Time-encoded imaging (TEI) is a new approach to directional detection of energetic radiation that produces images by inducing a time-dependent modulation of detected particles. TEI-based detectors use single-scatter events and have a low channel count, reducing complexity and cost while maintaining high efficiency with respect to other radiation imaging techniques such as double-scatter or coded aperture imaging. The scalability of TEI systems makes them a very promising detector class for weak source detection. Extension of the technique to high-resolution imaging is also under study. With a prototype time-encoding detector, we demonstrated detection of a neutron source at 60 m with neutron output equivalent to an IAEA significant quantity of WGPu. We have since designed and built a full-scale detector based on the time-encoding concept. We will present results from characterization of very large liquid scintillator cells, including pulse shape discrimination, as well as from studies of the detector system performance in weak source detection scenarios. © 2013 SPIE.

Time-encoded imaging (TEI) is a new approach to directional detection of energetic radiation that produces images by inducing a time-dependent modulation of detected particles. TEI-based detectors use single-scatter events and have a low channel count, reducing complexity and cost while maintaining high efficiency with respect to other radiation imaging techniques such as double-scatter or coded aperture imaging. The scalability of TEI systems makes them a very promising detector class for weak source detection. Extension of the technique to high-resolution imaging is also under study. With a prototype time-encoding detector, we demonstrated detection of a neutron source at 60 m with neutron output equivalent to an IAEA significant quantity of WGPu. We have since designed and built a full-scale detector based on the time-encoding concept. We will present results from characterization of very large liquid scintillator cells, including pulse shape discrimination, as well as from studies of the detector system performance in weak source detection scenarios. © 2013 SPIE.

In this review we discuss recent research on driving self assembly of magnetic particle suspensions subjected to alternating magnetic fields. The variety of structures and effects that can be induced in such systems is remarkably broad due to the large number of variables involved. The alternating field can be uniaxial, biaxial or triaxial, the particles can be spherical or anisometric, and the suspension can be dispersed throughout a volume or confined to a soft interface. In the simplest case the field drives the static or quasi-static assembly of unusual particle structures, such as sheets, networks and open-cell foams. More complex, emergent collective behaviors evolve in systems that can follow the time-dependent field vector. In these cases energy is continuously injected into the system and striking °ow patterns and structures can arise. In fluid volumes these include the formation of advection and vortex lattices. At air-liquid and liquid-liquid interfaces striking dynamic particle assemblies emerge due to the particle-mediated coupling of the applied field to surface excitations. These out-of-equilibrium interface assemblies exhibit a number of remarkable phenomena, including self-propulsion and surface mixing. In addition to discussing various methods of driven self assembly in magnetic suspensions, some of the remarkable properties of these novel materials are described.

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This report summarizes the first year’s effort on the Enceladus project, under which Sandia was asked to evaluate the potential advantages of adiabatic quantum computing for analyzing large data sets in the near future, 5-to-10 years from now. We were not specifically evaluating the machine being sold by D-Wave Systems, Inc; we were asked to anticipate what future adiabatic quantum computers might be able to achieve. While realizing that the greatest potential anticipated from quantum computation is still far into the future, a special purpose quantum computing capability, Adiabatic Quantum Optimization (AQO), is under active development and is maturing relatively rapidly; indeed, D-Wave Systems Inc. already offers an AQO device based on superconducting flux qubits. The AQO architecture solves a particular class of problem, namely unconstrained quadratic Boolean optimization. Problems in this class include many interesting and important instances. Because of this, further investigation is warranted into the range of applicability of this class of problem for addressing challenges of analyzing big data sets and the effectiveness of AQO devices to perform specific analyses on big data. Further, it is of interest to also consider the potential effectiveness of anticipated special purpose adiabatic quantum computers (AQCs), in general, for accelerating the analysis of big data sets. The objective of the present investigation is an evaluation of the potential of AQC to benefit analysis of big data problems in the next five to ten years, with our main focus being on AQO because of its relative maturity. We are not specifically assessing the efficacy of the D-Wave computing systems, though we do hope to perform some experimental calculations on that device in the sequel to this project, at least to provide some data to compare with our theoretical estimates.

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The subject of this work is the development of models for the numerical simulation of matter, momentum, and energy balance in heterogeneous materials. These are materials that consist of multiple phases or species or that are structured on some (perhaps many) scale(s). By computational mechanics we mean to refer generally to the standard type of modeling that is done at the level of macroscopic balance laws (mass, momentum, energy). We will refer to the flow or flux of these quantities in a generalized sense as transport. At issue here are the forms of the governing equations in these complex materials which are potentially strongly inhomogeneous below some correlation length scale and are yet homogeneous on larger length scales. The question then becomes one of how to model this behavior and what are the proper multi-scale equations to capture the transport mechanisms across scales. To address this we look to the area of generalized stochastic process that underlie the transport processes in homogeneous materials. The archetypal example being the relationship between a random walk or Brownian motion stochastic processes and the associated Fokker-Planck or diffusion equation. Here we are interested in how this classical setting changes when inhomogeneities or correlations in structure are introduced into the problem. Aspects of non-classical behavior need to be addressed, such as non-Fickian behavior of the mean-squared-displacement (MSD) and non-Gaussian behavior of the underlying probability distribution of jumps. We present an experimental technique and apparatus built to investigate some of these issues. We also discuss diffusive processes in inhomogeneous systems, and the role of the chemical potential in diffusion of hard spheres is considered. Also, the relevance to liquid metal solutions is considered. Finally we present an example of how inhomogeneities in material microstructure introduce fluctuations at the meso-scale for a thermal conduction problem. These fluctuations due to random microstructures also provide a means of characterizing the aleatory uncertainty in material properties at the mesoscale.

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Increasing energy costs, the dependence on foreign oil supplies, and environmental concerns have emphasized the need to produce sustainable renewable fuels and chemicals. The strategy for producing next-generation biofuels must include efficient processes for biomass conversion to liquid fuels and the fuels must be compatible with current and future engines. Unfortunately, biofuel development generally takes place without any consideration of combustion characteristics, and combustion scientists typically measure biofuels properties without any feedback to the production design. We seek to optimize the fuel/engine system by bringing combustion performance, specifically for advanced next-generation engines, into the development of novel biosynthetic fuel pathways. Here we report an innovative coupling of combustion chemistry, from fundamentals to engine measurements, to the optimization of fuel production using metabolic engineering. We have established the necessary connections among the fundamental chemistry, engine science, and synthetic biology for fuel production, building a powerful framework for co-development of engines and biofuels.

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This report explores how error-correction data generated by a Reed-Solomon code may be used as a mechanism to apply changes to an existing installed codebase. Using the Reed-Solomon code to generate error-correction data for a changed or updated codebase will allow the error-correction data to be applied to an existing codebase to both validate and introduce changes or updates from some upstream source to the existing installed codebase.

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A series of design studies are performed to investigate the effects of advanced core materials and a new core material strategy on blade weight and performance for large blades using the Sandia 100-meter blade designs as a starting point. The initial core material design studies were based on the SNL100-01 100- meter carbon spar design. Advanced core material with improved performance to weight was investigated with the goal to reduce core material content in the design and reduce blade weight. A secondary element of the core study was to evaluate the suitability of core materials from natural, regrowable sources such as balsa and recyclable foam materials. The new core strategy for the SNL100-02 design resulted in a design mass of 59 tons, which is a 20% reduction from the most recent SNL100-01 carbon spar design and over 48% reduction from the initial SNL100-00 all-glass baseline blade. This document provides a description of the final SNL100-02 design, includes a description of the major design modifications, and summarizes the pertinent blade design information. This document is also intended to be a companion document to the distribution of the NuMAD blade model files for SNL100-02 that are made publicly available.

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The high penetration of utility interconnected photovoltaic (PV) systems is causing heightened concern over the effect that variable renewable generation will have on the electrical power system (EPS). These concerns have initiated the need to amend the utility interconnection standard to allow advanced inverter control functionalities that provide: (1) reactive power control for voltage support, (2) real power control for frequency support and (3) better tolerance of grid disturbances. These capabilities are aimed at minimizing the negative impact distributed PV systems may have on EPS voltage and frequency. Unfortunately, these advanced control functions may interfere with island detection schemes, and further development of advanced inverter functions requires a study of the effect of advanced functions on the efficacy of antiislanding schemes employed in industry. This report summarizes the analytical, simulation and experimental work to study interactions between advanced inverter functions and anti-islanding schemes being employed in distributed PV systems.

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Thermal degradation of a high temperature epoxy network is studied in terms glass transition temperature (Tg) reduction over a temperature window encompassing the Tg of the network. The Tg is shown to decrease as the network is thermally aged at elevated temperatures in air and in argon. The duration of the aging experiments is extended to long time such that the absolute Tg reduction approaches a long time reduction plateau. Degradation is dominated by non-oxidative pyrolysis with a small contribution from diffusion limited thermal oxidative degradation at the surface. A time-temperature superposition is constructed from the extent of Tg reduction of samples aged in air and the thermal shift factors are shown to have Arrhenius scaling behavior. An activation energy is extracted that agrees with previous activation energy measurements derived from other property measurements of the same network aged under similar conditions. The agreement of the activation energy with past results shows that Tg reduction is controlled by the same degradation mechanism and may be used as an observable for lifetime estimates when thermal degradation is pyrolytic in nature. The extent of Tg reduction is modeled with an autocatalytic rate expression and compared to previous property measurements to show the difference in sensitivity of observable material properties on degradation. © 2013 Elsevier Ltd. All rights reserved.

We present a new extended finite element method with algebraic constraints (XFEM-AC) for recovering weakly discontinuous solutions across internal element interfaces. If necessary, cut elements are further partitioned by a local secondary cut into body-fitting subelements. Each resulting subelement contributes an enrichment of the parent element. The enriched solutions are then tied using algebraic constraints, which enforce C0 continuity across both cuts. These constraints impose equivalence of the enriched and body-fitted finite element solutions, and are the key differentiating feature of the XFEM-AC. In so doing, a stable mixed formulation is obtained without having to explicitly construct a compatible Lagrange multiplier space and prove a formal inf-sup condition. Likewise, convergence of the XFEM-AC solution follows from its equivalence to the interface-fitted finite element solution. This relationship is further exploited to improve the numerical solution of the resulting XFEM-AC linear system. Examples are shown demonstrating the new approach for both steady-state and transient diffusion problems. © 2013 Elsevier B.V.

In metals, as grain size is reduced below 100nm, conventional dislocation plasticity is suppressed resulting in improvements in strength, hardness, and wears resistance. Existing and emerging components use fine grained metals for these beneficial attributes. However, these benefits can be lost in service if the grains undergo growth during the component’s lifespan. While grain growth is traditionally viewed as a purely thermal process that requires elevated temperature exposure, recent evidence shows that some metals, especially those with nanocrystalline grain structure, can undergo grain growth even at room temperature or below due to mechanical loading. This report has been assembled to survey the key concepts regarding how mechanical loads can drive grain coarsening at room temperature and below. Topics outlined include the atomic level mechanisms that facilitate grain growth, grain boundary mobility, and the impact of boundary structure, loading scheme, and temperature.

Small-scale supercritical CO2 demonstration loops are successful at identifying the important technical issues that one must face in order to scale up to larger power levels. The Sandia National Laboratories supercritical CO2 Brayton cycle test loops are identifying technical needs to scale the technology to commercial power levels such as 10 MWe. The small size of the Sandia 1 MWth loop has demonstration of the split flow loop efficiency and effectiveness of the Printed Circuit Heat Exchangers (PCHXs) leading to the design of a fully recuperated, split flow, supercritical CO2 Brayton cycle demonstration system. However, there were many problems that were encountered, such as high rotational speeds in the units. Additionally, the turbomachinery in the test loops need to identify issues concerning the bearings, seals, thermal boundaries, and motor controller problems in order to be proved a reliable power source in the 300 kWe range. Although these issues were anticipated in smaller demonstration units, commercially scaled hardware would eliminate these problems caused by high rotational speeds at small scale. The economic viability and development of the future scalable 10 MWe solely depends on the interest of DOE and private industry. The Intellectual Property collected by Sandia proves that the ~10 MWe supercritical CO2 power conversion loop to be very beneficial when coupled to a 20 MWth heat source (either solar, geothermal, fossil, or nuclear). This paper will identify a commercialization plan, as well as, a roadmap from the simple 1 MWth supercritical CO2 development loop to a power producing 10 MWe supercritical CO2 Brayton loop.

This report provides an overview of information, prior studies, and analyses relevant to the development of functional and operational requirements for electrochemical testing of batteries and energy storage devices carried out by Sandia Organization 2546, Advanced Power Sources R&D. Electrochemical operations for this group are scheduled to transition from Sandia Building 894 to a new Building located in Sandia TA-II referred to as Building 1012. This report also provides background on select design considerations and identifies the Safety Goals, Stakeholder Objectives, and Design Objectives required by the Sandia Design Team to develop the Performance Criteria necessary to the design of Building 1012. This document recognizes the Architecture-Engineering (A-E) Team as the primary design entity. Where safety considerations are identified, suggestions are provided to provide context for the corresponding operational requirement(s).

From 17-21 June 2013, Sandia National Laboratories, Technical Area-V (SNL TA-V) represented the United States Department of Energy/National Nuclear Security Administration (DOE/NNSA) at the International Atomic Energy Agency (IAEA) Training Workshop (T3-TR-45486). This report gives a breakdown of the IAEA regulatory structure for those unfamiliar, and the lessons learned and observations that apply to SNL TA-V that were obtained from the workshop. The Safety Report Series, IAEA workshop final report, and SNL TA-V presentation are included as attachments.

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Trapped atomic ions are a leading physical system for quantum information processing. However, scalability and operational fidelity remain limiting technical issues often associated with optical qubit control. One promising approach is to develop on-chip microwave electronic control of ion qubits based on the atomic hyperfine interaction. This project developed expertise and capabilities at Sandia toward on-chip electronic qubit control in a scalable architecture. The project developed a foundation of laboratory capabilities, including trapping the ¹⁷¹Yb⁺ hyperfine ion qubit and developing an experimental microwave coherent control capability. Additionally, the project investigated the integration of microwave device elements with surface ion traps utilizing Sandia’s state-of-the-art MEMS microfabrication processing. This effort culminated in a device design for a multi-purpose ion trap experimental platform for investigating on-chip microwave qubit control, laying the groundwork for further funded R&D to develop on-chip microwave qubit control in an architecture that is suitable to engineering development.

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