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Testing and characterization of PV modules with integrated microinverters

Conference Record of the IEEE Photovoltaic Specialists Conference

Riley, Daniel; Stein, Joshua; Kratochvil, Jay A.

Photovoltaic (PV) modules with attached microinverters are becoming increasingly popular in PV systems, especially in the residential system market, as such systems offer several benefits not found in PV systems utilizing central inverters. PV modules with fully integrated microinverters are emerging to fill a similar market space. These 'AC modules' absorb solar energy and produce AC energy without allowing access to the intermediate DC bus. Existing test procedures and performance models designed for separate DC and AC components are unusable when the inverter is integrated into the module. Sandia National Laboratories is developing a new set of test procedures and performance model designed for AC modules. © 2013 IEEE.

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Simulated PV power plant variability: Impact of utility-imposed ramp limitations in Puerto Rico

Conference Record of the IEEE Photovoltaic Specialists Conference

Lave, Matthew; Kleissl, Jan; Ellis, Abraham; Mejia, Felipe

The variability of solar PV power plants has led to some utilities imposing ramp limitations. For example, the Puerto Rico Electric Power Authority (PREPA) includes a 10% of capacity per minute limit on ramp rates produced by PV power plants in its minimum technical requirements for photovoltaic generation projects. However, it is difficult to determine storage requirements to comply with ramp limitations for plants in the planning or construction phase since the variability of the plant output is not known. In this paper, we use the wavelet variability model (WVM) to upscale irradiance measured in Mayaguez, PR to simulate various sizes of PV power plants. The results show that ramps will often exceed 10%, even for the largest plants (60MW) that benefit the most from in-plant spatial smoothing, meaning significant amounts of storage will be needed to meet the PREPA requirement. The results from Puerto Rico are compared to sites in San Diego and Oahu, Hawaii. Significant differences are seen in the ramp rate distributions of the three locations, demonstrating the importance of performing location-specific simulations. © 2013 IEEE.

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Continuum simulation of hypersonic flows using the Quantum-Kinetic chemical reaction model

44th AIAA Thermophysics Conference

Wagnild, Ross M.; Gallis, Michael A.

The Quantum-Kinetic (Q-K) chemical reaction model is implemented in a Navier-Stokes solver, US3D, and tested on the Bow Shock UltraViolet flight experiments. The chemical reaction rates predicted by the Q-K model are compared to a commonly used Park model for flows in thermal non-equilibrium. The results show that in thermal equilibrium the reaction rates between these two models are comparable. The Q-K model predicts greater rates for some chemical reactions and lesser rates for other reactions in an five species air chemistry model. In thermal non-equilibrium, the Q-K model maintains comparable rates near thermal equilibrium, while avoiding issues of strong thermal non-equilibrium seen in the Park model. The application of the Q-K model to the Bow Shock UltraViolet flight experiments show that the model remains consistent with previous Navier-Stokes and DSMC computations over altitudes ranging from 53:5 km up to 87:5 km despite the enforcement of translational-rotational equilibrium. The commonly used Park model was unable to match this performance.

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Electrical simulations of series and parallel PV arc-faults

Conference Record of the IEEE Photovoltaic Specialists Conference

Flicker, Jack D.; Johnson, Jay

Arcing in PV systems has caused multiple residential and commercial rooftop fires. The National Electrical Code® (NEC) added section 690.11 to mitigate this danger by requiring arc-fault circuit interrupters (AFCI). Currently, the requirement is only for series arc-faults, but to fully protect PV installations from arc-fault-generated fires, parallel arc-faults must also be mitigated effectively. In order to de-energize a parallel arc-fault without module-level disconnects, the type of arc-fault must be identified so that proper action can be taken (e.g., opening the array for a series arc-fault and shorting for a parallel arc-fault). In this work, we investigate the electrical behavior of the PV system during series and parallel arc-faults to (a) understand the arcing power available from different faults, (b) identify electrical characteristics that differentiate the two fault types, and (c) determine the location of the fault based on current or voltage of the faulted array. This information can be used to improve arc-fault detector speed and functionality. © 2013 IEEE.

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Cost analysis for flat-plate concentrators employing microscale photovoltaic cells

Conference Record of the IEEE Photovoltaic Specialists Conference

Paap, Scott M.; Nelson, Jeffrey; Gupta, Vipin P.; Cruz-Campa, Jose L.; Okandan, Murat; Sweatt, W.C.; Jared, Bradley H.; Anderson, Benjamin J.; Nielson, Gregory N.; Tauke-Pedretti, Anna

Microsystems Enabled Photovoltaics (MEPV) is a relatively new field that uses microsystems tools and manufacturing techniques familiar to the semiconductor industry to produce microscale photovoltaic cells. The miniaturization of these PV cells creates new possibilities in system designs that may be able to achieve the US Department of Energy (DOE) price target of $1/Wp by 2020 for utility-scale electricity generation. In this article, we introduce analytical tools and techniques to estimate the costs associated with a concentrating photovoltaic system that uses microscale photovoltaic cells and miniaturized optics. The overall model comprises the component costs associated with the PV cells, concentrating optics, balance of systems, installation, and operation. Estimates include profit margin and are discussed in the context of current and projected prices for non-concentrating and concentrating photovoltaics. Our analysis indicates that cells with a width of between 100 and 300 μm will minimize the module costs of the initial design within the range of concentration ratios considered. To achieve the DOE price target of $1/Wp by 2020, module efficiencies over 35% will likely be necessary. © 2013 IEEE.

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Proton exchange membrane fuel cell systems for airplane auxiliary power

49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

Pratt, Joseph W.; Klebanoff, Leonard E.; Munoz-Ramos, Karina; Curgus, Dita B.; Schenkman, Benjamin L.

Deployed on a commercial airplane, proton exchange membrane (PEM) fuel cells may offer emissions reductions, thermal efficiency gains, and enable locating the power near the point of use. This work seeks to understand whether on-board fuel cell systems are technically feasible, and, if so, if they could offer a performance advantage for the airplane when using today’s off-the-shelf technology. Through hardware analysis and thermodynamic simulation, we found that an additional fuel cell system on a commercial airplane is technically feasible using current technology. Recovery and on-board use of the heat and water that is generated by the fuel cell is an important method to increase the benefit of such a system. Although the PEM fuel cell generates power more efficiently than the gas turbine generators currently used, when considering the effect of the fuel cell system on the airplane’s overall performance we found that an overall performance penalty (i.e., the airplane will burn more jet fuel) would result if using current technology for the fuel cell and hydrogen storage. Although applied to a Boeing 787-type airplane, the method presented is applicable to other airframes as well.

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Current status of the doe nuclear criticality safety program hands-on criticality safety training course at sandia

Topical Meeting Held by the ANS Nuclear Criticality Safety Division, NCSD 2013 - Criticality Safety in the Modern Era: Raising the Bar

Harms, Gary A.; Knief, Ronald A.; Miller, Allison D.; Ford, John T.

A hands-on critical-experiment training class has been developed by the US DOE Nuclear Criticality Safety Program using the water-moderated pin-fueled critical experiments at Sandia National Laboratories. The class is offered as part of the NCSP training program for Nuclear Criticality Safety Engineers in a facility that allows attendance by both cleared and uncleared personnel. Laboratory exercises have been developed that demonstrate the effects of varying a number of the parameters that are considered important to criticality safety. Accompanying the experiments is a series of classroom presentations that emphasize the concepts that are demonstrated in the experiments.

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Copper ionic liquids: Tunable ligand and anion chemistries to control electrochemistry and deposition morphology

Journal of Electroanalytical Chemistry

Pratt, Harry D.; Ingersoll, David; Hudak, Nicholas S.; Mckenzie, Bonnie

A multi-technique investigation was performed on three copper-based ionic liquids to elucidate the influence of coordinating ligands and charge-balancing anions on the electrochemical properties of the materials. Galvanostatic cycling of Cu(OHCH2CH2NH2)6(BF 4)2 (Cu1) in 1-butyl-3-methyl-imidazolium hexafluorophosphate gave partially reversible plating of copper that was consistent with cyclic voltammetry data (collected using an ionic liquid-based reference electrode verified with measurements of ferrocene, cobaltocene, and lithium). Scanning electron microscopy also showed pitting in the copper-coated surface of the electrode that was consistent with the stripping wave observed by cyclic voltammetry. Potentiostatic deposition in neat Cu1 showed significant dendrite formation. The substitution of the OHCH2CH 2NH2 ligands of Cu1 with stronger coordinating NH(CH 2CH2OH)2 in Cu(NH(CH2CH 2OH)2)6(BF4)2 (Cu2) resulted in the complete suppression of both copper stripping and dendrite formation. Substitution of the BF4- anions of Cu2 with CF3SO3- in Cu(NH(CH2CH2OH)2)6(CF 3SO3)2 (Cu3) shifted the copper deposition 0.1 V more negative and produced slightly larger spherical particles (1.5 μm versus 5 μm). The results suggested that while the anion composition influenced particle size, and the metal-ligand bond strength helped control particle morphology, both factors affected the electrochemical properties including the plating and stripping of copper. © 2013 Elsevier B.V. All rights reserved.

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Ephemeral Biometrics: What are they and what do they solve?

Proceedings - International Carnahan Conference on Security Technology

Choi, Sung N.; Zage, David J.

For critical infrastructure facilities, mitigation techniques for insider threats are primarily non-technical in nature and rely heavily on policies/procedures. Traditional access control measures (access cards, biometrics, PIN numbers, etc.) are built on a philosophy of trust that enables those with appropriate permissions to access facilities without additional monitoring or restrictions. Systems based on these measures have three main limitations: 1) access is typically bound to a single authentication occurrence; 2) the authentication factors have little impact against human (insider) threats to security systems; and 3) many of the authentication systems inconvenience end-users. In order to mitigate the aforementioned deficiencies, we propose utilizing the concept of Ephemeral Biometrics to construct strong, persistent authentication protocols.

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Micro-Concentrators for a microsystems-enabled photovoltaic system

Optics InfoBase Conference Papers

Jared, Bradley H.; Saavedra, Michael P.; Anderson, Benjamin J.; Goeke, Ronald S.; Sweatt, W.C.; Nielson, Gregory N.; Okandan, Murat; Elisberg, Brenton

A 100X magnification, ±3° field of view micro-concentrating optical array has been developed with better than 90% transmission for a microsystems-enabled photovoltaic (MEPV) prototype module using 250 μm diameter multi-junction "stacked" PV cells. Renewable Energy and the Environment Congress. © 2013.

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Strategies for analyzing random vibration of jointed structures

Proceedings of the ASME Design Engineering Technical Conference

Segalman, Daniel J.; Starr, Michael; Guthrie, Michael

Development of mathematical models for built-up struc-tures, particularly those with many interfaces, is still primitive. This limitation is particularly evident when complex loads and load histories are considered, an example of which is random vibration. Two steps in simplifying this problem are explored here. First, the system response is approximated as that of the super-position of numerous decoupled modes, the coordinates of which evolve according to a constitutive model designed to capture the nonlinearity of the structure. Second, because among the cat-egories of load for which dynamic analysis on nonlinear struc-tures is particularly difficult is that of random loads and the re-sulting random vibration, and given the previous approximation, it is natural to apply the method of stochastic equivalent lin-earization to the governing equation of each mode. Both of these approximations are explored for the case where the nonlinear behavior of the interfaces is represented by a Masing-Prandtl-Ishlinskii-Iwan model employing a Palmov kernel. Copyright © 2013 by ASME.

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Electromechanical emulation of hydrokinetic generators for renewable energy research

OCEANS 2013 MTS/IEEE - San Diego: An Ocean in Common

Ruehl, Kelley M.; Jepsen, Richard A.; Roberts, Jesse D.; Glover, Steven F.; Horry, Michael L.

The pace of research and development efforts to integrate renewable power sources into modern electric utilities continues to increase. These efforts are motivated by a desire for cleaner, cheaper and more diverse sources of energy. As new analyses and controls approaches are developed to manage renewable sources and tie them into the grid, the need for these controls to be tested in hardware becomes paramount. In particular, hydrokinetic power is appealing due to its high energy density and superior forecastability; however, its development has lagged behind that of wind and solar due in part to the difficulty of acquiring hardware results on an integrated system. Thus, as an alternative to constructing an elaborate wave-tank or locating a power lab riverside, this paper presents a method based on electromechanical emulation of the energy source using a commercially available induction motor drive. Using an electromechanical emulator provides an option for universities and other laboratories to expand their research on hydrokinetics in a typical laboratory setting. © 2013 MTS.

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Kokkos: Enabling performance portability across manycore architectures

Proceedings - 2013 Extreme Scaling Workshop, XSW 2013

Edwards, Harold C.; Trott, Christian R.

The manycore revolution in computational hardware can be characterized by increasing thread counts, decreasing memory per thread, and architecture specific performance constraints for memory access patterns. High performance computing (HPC) on emerging many core architectures requires codes to exploit every opportunity for thread-level parallelism and satisfy conflicting performance constraints. We developed the Kokkos C++ library to provide scientific and engineering codes with a user accessible many core performance portable programming model. The two foundational abstractions of Kokkos are (1) dispatch work to a many core device for parallel execution and (2) manage multidimensional arrays with polymorphic layouts. The integration of these abstractions enables users' code to satisfy multiple architecture specific memory access pattern performance constraints without having to modify their source code. In this paper we describe the Kokkos abstractions, summarize its application programmer interface (API), and present performance results for a molecular dynamics computational kernel and finite element mini-application. © 2013 IEEE.

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AstroTouch: A multi-touch digital desktop for astrodynamics

ITS 2013 - Proceedings of the 2013 ACM International Conference on Interactive Tabletops and Surfaces

Coram, Jamie L.; Iverson, John; Ackerman, Andrew

In this paper, we present the design, implementation, and preliminary evaluation of AstroTouch, a prototype desktop surface application to support analysis and visualization in the field of astrodynamics. We describe the fundamental characteristics of this complex scientific domain and discuss how these characteristics, combined with an assessment of current research surrounding multi-touch and the digital desktop, informed the design of our system. We detail the prototype implementation and present the results of an initial design critique conducted with domain experts. © 2013 ACM.

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How we successfully adapted agile for a research-heavy engineering software team

Proceedings - AGILE 2013

Lorber, Alfred; Mish, Kyran D.

In our development team at Sandia National Laboratories we have honed our Scrum processes to where we continually deliver high-performance engineering analysis software to our customers. We deliver despite non-ideal circumstances, including development work that can be categorized as exploratory research, regular use of part-time developers, team size that varies widely among Sprints, highly specialized technical skill sets and a broad range of deliverables. We believe our methodologies can be applied to many research-oriented environments such as those found in government laboratories, academic institutions and corporate research facilities. Our goal is to increase the adoption of Lean/Agile project management in these environments by sharing our experiences with those research-oriented development teams who are considering using Lean/Agile, or have started and are encountering problems. In this paper we discuss how we create and prioritize our product backlog, write our user stories, calculate our capacity, plan our Sprints, report our results and communicate our progress to customers. By providing guidance and evidence of success in these areas we hope to overcome real and perceived obstacles that may limit the adoption of Lean/Agile techniques in research-oriented development environments. © 2013 IEEE.

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Nano-ordering of donor-acceptor interactions using Metal-Organic Frameworks as scaffolds

ECS Transactions

Leong, Kirsty; Foster, Michael E.; Wong, Bryan M.; Spoerke, Erik D.; Gough, Dara; Deaton, Joseph C.; Allendorf, Mark

Metal-Organic Frameworks (MOFs) are nanoporous materials with tunable pore sizes that can accommodate and stabilize small molecules. Because of their long-range order and wellunderstood pore environment, the nano-confinement of donoracceptor materials within MOFs offers a new methodology for creating uniform phase-segregated donor-acceptor interfaces. Phase segregation and the photo-physical effects of confining α,ω-Dihexylsexithiophene (DH-6T) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in several MOFs and the potential role of the MOF in creating a nano-heterojunction for organic photovoltaics are discussed. We demonstrate infiltration of both molecules into MOF pores and use luminescence and absorption spectroscopies to characterize the MOF-guest energy transfer processes. Comparison with density functional theory allows us to determine the energetics and band alignment within the MOF. The results demonstrate the utility of MOFs as scaffolds for sub-nanoscale ordering of donor and acceptor species within a highly uniform environment, allowing both the interaction and separation distance to be much more controlled than in the classical bulk heterojunction. © The Electrochemical Society.

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Design of materials for solar-driven fuel production by metal-oxide thermochemical cycles

Electrochemical Society Interface

Miller, James E.; Mcdaniel, Anthony H.

Thermochemical cycles that divide the energetically unfavorable thermolysis of water or carbon dioxide into two or more reactions were used for solar driven fuel production. A large number of diverse metal oxides have been proposed for solar thermochemical fuel production (STFP) including stoichiometric compounds such as ferrites and other transition metal spinels. The design parameter is determined by a set of interacting factors, including reaction thermodynamics, target efficiency, and durability of reactor materials. Operating temperature window is determined by a set of interacting factors, including reaction thermodynamics, target efficiency, and durability of reactor materials. In the absence of kinetic data, however, it can be stated that achieving high average annual solar-to-fuel efficiencies (AASFE) requires that energy consumption of the reactions, and hence the reaction rates, be matched to the solar flux entering the system.

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Mixed addenda polyoxometalate "solutions" for stationary energy storage

Dalton Transactions

Pratt, Harry D.; Anderson, Travis M.

A series of redox flow batteries utilizing mixed addenda (vanadium and tungsten), phosphorus-based polyoxometalates (A-α-PV3W 9O406-, B-α-PV3W 9O406-, and P2V3W 15O629-) were prepared and tested. Cyclic voltammetry and bulk electrolysis experiments on the Keggin compounds (A-α-PV3W9O406- and B-α-PV3W9O406-) established that the vanadium centers of these compounds could be used as the positive electrode (PVIV3WVI9O 409-/PVV3WVI 9O406-), and the tungsten centers could be used as the negative electrode (PVIV3WVI 9O409-/PVIV3W V3WVI6O4012-) since these electrochemical processes are separated by about 1 V. The results showed that A-α-PV3W9O406- (where A indicates adjacent, corner-sharing vanadium atoms) had coulombic efficiencies (charge in divided by charge out) above 80%, while the coulombic efficiency of B-α-PV3W9O406- (where B indicates adjacent edge-sharing vanadium atoms) fluctuated between 50% and 70% during cycling. The electrochemical yield, a measurement of the actual charge or discharge observed in comparison with the theoretical charge, was between 40% and 50% for A-α-PV3W9O40 6-, and 31P NMR showed small amounts of PV 2W10O405- and PVW11O 404- formed with cycling. The electrochemical yield for B-α-PV3W9O406- decreased from 90% to around 60% due to precipitation of the compound on the electrode, but there were no decomposition products detected in the solution by 31P NMR, and infrared data on the electrode suggested that the cluster remained intact. Testing of P2V3W15O62 9- (Wells-Dawson structure) suggested higher charge density clusters were not as suitable as the Keggin structures for a redox flow battery due to the poor stability and inaccessibility of the highly reduced materials. © The Royal Society of Chemistry 2013.

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Results of critical experiments on water-moderated fully-reflected 6.90% enriched UO2 fuel pin arrays with a fuel-to-water volume ratio of 0.52

Topical Meeting Held by the ANS Nuclear Criticality Safety Division, NCSD 2013 - Criticality Safety in the Modern Era: Raising the Bar

Harms, Gary A.; Miller, Allison D.; Ford, John T.

The Seven Percent Critical Experiment (7uPCX) at Sandia National Laboratories was designed to provide benchmark criticality and reactor physics data for water-moderated pin-fueled nuclear reactor cores in the 5 to 10 percent enrichment range. Approach-to-critical experiments were performed on fifteen roughly cylindrical pure water-moderated and -reflected 7uPCX configurations with a fuel-to-water volume ratio of 0.52. Those configurations are described and the results of the measurements are reported in this paper.

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Safety Relief Valve cyclic failure analysis for use in discrete dynamic event trees

International Topical Meeting on Probabilistic Safety Assessment and Analysis 2013, PSA 2013

Denman, Matthew R.

Safety Relief Valves (SRVs) are an important component of the safety case for a Light Water Reactor (LWR). The number and types of SRVs in LWRs vary from plant to plant, but they generally operate to perform the same safety function. During accidents in which the coolant pressurizes beyond a predetermined set-point, the SRV will open, releasing coolant from the primary system and into the containment. Once enough coolant has been released to lower the coolant pressure, the SRV will reset. This cycle will continue until the SRV fails, in either a "Failed to Open (FTO)" or "Failed To Close (FTC)" mode. These failures can be caused either through cyclic loading or as a result of thermalinduced stresses from the coolant passing through the valve. SRV failures can be important, because an SRV that has FTC will cause a small "Loss of Cooling Accident", which depressurizes the primary system. Alternatively, SRVs that have FTO will allow system pressure to rise until it reaches the next SRV set-point. If the pressure is not reduced through the successful operation of other safety systems, either creep rupture elsewhere in the system, such as in the steam line, or high-pressure core damage may occur. While some SRV failure data is recorded in NUREG/CR-6928, the spread of the epistemic uncertainty distributions for FTO and FTC are wide. These large uncertainties may cause an analyst to be overconfident in the results of a severe accident simulation that uses only point-estimates calculations of FTO and FTC.

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Bubble masks for time-encoded imaging of fast neutrons

IEEE Nuclear Science Symposium Conference Record

Brennan, J.; Brubaker, E.; Steele, J.; Sweany, Melinda D.; Throckmorton, Daniel J.

Time-encoded imaging is an approach to directional radiation detection that is being developed at SNL with a focus on fast neutron directional detection. In this technique, a time modulation of a detected neutron signal is induced - typically, a moving mask that attenuates neutrons with a time structure that depends on the source position. An important challenge in time-encoded imaging is to develop high-resolution two-dimensional imaging capabilities; building a mechanically moving high-resolution mask presents challenges both theoretical and technical. We have investigated an alternative to mechanical masks that replaces the solid mask with a liquid such as mineral oil. Instead of fixed blocks of solid material that move in predefined patterns, the oil is contained in tubing structures, and carefully introduced air gaps - bubbles - propagate through the tubing, generating moving patterns of oil mask elements and air apertures. Compared to current moving-mask techniques, the bubble mask is simple, since mechanical motion is replaced by gravity-driven bubble propagation; it is flexible, since arbitrary bubble patterns can be generated by a software-controlled valve actuator; and it is potentially high performance, since the tubing and bubble size can be tuned for high-resolution imaging requirements. We have built and tested various single-tube mask elements, and will present results on bubble introduction and propagation for different tube sizes and cross-sectional shapes; real-time bubble position tracking; neutron source imaging tests; and reconstruction techniques demonstrated on simple test data as well as a simulated full detector system. © 2013 IEEE.

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Benchmark experiments in water-moderated fully-reflected 6.90% enriched UO2 fuel rod lattices with a fuel-to-water volume ratio of 0.52

Transactions of the American Nuclear Society

Harms, Gary A.; Miller, Allison D.; Ford, John T.

A second set of experiments in the Seven Percent Critical Experiment (7uPCX) has been completed. Additionally, an evaluation of the experiments as criticality safety benchmark experiments has been performed. The Reviews of the benchmark evaluation have been completed. This evaluation will be published in the 2013 edition of the International Handbook of Evaluated Criticality Benchmark Experiments as LEU-COMP-THERM-078 (LCT078). This presentation is a brief tour of these experiments.

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Scalable matrix computations on large scale-free graphs using 2D graph partitioning

International Conference for High Performance Computing, Networking, Storage and Analysis, SC

Boman, Erik G.; Devine, Karen; Rajamanickam, Sivasankaran

Scalable parallel computing is essential for processing large scale-free (power-law) graphs. The distribution of data across processes becomes important on distributed-memory computers with thousands of cores. It has been shown that two dimensional layouts (edge partitioning) can have significant advantages over traditional one-dimensional layouts. However, simple 2D block distribution does not use the structure of the graph, and more advanced 2D partitioning methods are too expensive for large graphs. We propose a new two-dimensional partitioning algorithm that combines graph partitioning with 2D block distribution. The computational cost of the algorithm is essentially the same as 1D graph partitioning. We study the performance of sparse matrix-vector multiplication (SpMV) for scale-free graphs from the web and social networks using several different partitioners and both 1D and 2D data layouts. We show that SpMV run time is reduced by exploiting the graph's structure. Contrary to popular belief, we observe that current graph and hypergraph partitioners often yield relatively good partitions on scale-free graphs. We demonstrate that our new 2D partitioning method consistently outperforms the other methods considered, for both SpMV and an eigensolver, on matrices with up to 1.6 billion nonzeros using up to 16,384 cores. Copyright 2013 ACM.

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An exploration of accuracy and convergence of the degenerate uniform strain hexahedral element (a solution to the unmeshed void in an all-hexahedral mesh)

ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)

Shelton, Timothy R.; Crane, Nathan K.; Cox, James

The uniform strain hexahedral element mesh has long been a work horse for getting accurate and convergent answers in high deformation solid mechanics analyses. Obtaining an allhexahedral mesh can be a difficult and time consuming process thus limiting the element's use in design phase computations. Unconstrained paving and plastering offers a technique to get an all-hexahedral mesh automatically but still can leave un-meshable voids [1] . While degenerated forms of the uniform strain hexahedral element such as the wedge have been used sparingly, they have garnered limited general acceptance. We present a more exhaustive numerical exploration of the degenerated hexes with the hope of encouraging their use to resolve the un-meshable voids. The results of patch tests are used to numerically demonstrate linear completeness of the degenerate elements. A manufactured solution analysis is then used to show optimal convergence rates for meshes containing degenerate elements. Additionally, applications to a torsion rod and high velocity impact are used to highlight the accuracy and applicability of degenerates for solving more complex problems. Copyright © 2013 by ASME.

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A robust Approach to QMU, Validation, and Conservative Prediction

Segalman, Daniel J.; Bauman, Lara E.

A systematic approach to defining margin in a manner that incorporates statistical information and accommodates data uncertainty, but does not require assumptions about specific forms of the tails of distributions is developed. This approach extends to calculations underlying validation assessment and quantitatively conservative predictions.

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Electrical and thermal finite element modeling of arc faults in photovoltaic bypass diodes

World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conferen

Johnson, Jay; Bower, Ward I.; Quintana, Michael A.

Arc faults in photovoltaic (PV) modules have caused multiple rooftop fires. The arc generates a high-temperature plasma that ignites surrounding materials and subsequently spreads the fire to the building structure. While there are many possible locations in PV systems and PV modules where arcs could initiate, bypass diodes have been suspected of triggering arc faults in some modules. In order to understand the electrical and thermal phenomena associated with these events, a finite element model of a busbar and diode was created. Thermoelectrical simulations found Joule and internal diode heating from normal operation would not normally cause bypass diode or solder failures. However, if corrosion increased the contact resistance in the solder connection between the busbar and the diode leads, enough voltage potential would be established to arc across micron-scale electrode gaps. Lastly, an analytical arc radiation model based on observed data was employed to predicted polymer ignition times. The model predicted polymer materials in the adjacent area of the diode and junction box ignite in less than 0.1 seconds.

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Radar Antenna Pointing for Optimized Signal to Noise Ratio

Doerry, Armin W.

The Signal-to-Noise Ratio (SNR) of a radar echo signal will vary across a range swath, due to spherical wavefront spreading, atmospheric attenuation, and antenna beam illumination. The antenna beam illumination will depend on antenna pointing. Calculations of geometry are complicated by the curved earth, and atmospheric refraction. This report investigates optimizing antenna pointing to maximize the minimum SNR across the range swath.

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A case study of a residential photovoltaic system with microinverters

World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conferen

Ho, Clifford K.

This paper presents a case study of a 3 kW photovoltaic system with Enphase microinverters. A brief introduction to microinverters and central inverters is first presented, followed by an overview of the installation, features, operation, monitoring, and costs of the system. The monthly and annual energy production during the first three years is presented and compared against modeled results using the System Advisor Model. Various factors that have impacted the performance (e.g., shading, weather, temperature, wind, tilt, orientation) are discussed, and the performance of the system is compared against a simulated optimized system. The optimal sizing of microinverters is also discussed to explain why the power rating of the microinverter may be less than the power rating of the module to achieve maximum energy production.

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Improvement and validation of a transient model to predict photovoltaic module temperature

World Renewable Energy Forum Wref 2012 Including World Renewable Energy Congress Xii and Colorado Renewable Energy Society Cres Annual Conferen

Luketa-Hanlin, Amanda; Stein, Joshua

Module temperature is modeled using a transient heat-flow model. Module temperature predicted in this fashion is important in the calculation of cell temperature, a vital input in performance modeling. Parameters important to the model are tested for sensitivity, and optimized to a single day of measured module temperature using simultaneous non-linear least squares regression. These optimized parameters are then tested for accuracy using a year's worth of data for one location. The results obtained from this analysis are compared with modeled data from a different site, as well as to results obtained using a steadystate model. We find that the transient model best captures the variability in module temperature, and that the transient model works best when calibrated for a specific location.

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The variability index: A new and novel metric for quantifying irradiance and pv output variability

World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conferen

Stein, Joshua; Hansen, Clifford; Reno, Matthew J.

Variability of photovoltaic (PV) power output is a potential concern to utilities because it can lead to voltage changes on the distribution system and have other adverse impacts on power quality unless additional equipment is added or operational practices are changed to mitigate these effects. This paper develops and evaluates a simple yet novel approach for quantifying irradiance variability over various timescales. The approach involves comparison between measured irradiance and a reference, clear sky irradiance, determined from a model. Conceptually, the "Variability Index" is the ratio of the "length" of the measured irradiance plotted against time divided by the "length" of the reference clear sky irradiance signal. Adjustments are proposed that correct for different measurement intervals. By evaluating the variability index at several sites, we show how annual and monthly distributions of this metric can help to classify sites and periods of time when variability is significant. Copyright © (2012) by American Solar Energy Society.

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Improvement and validation of a transient model to predict photovoltaic module temperature

World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conferen

Luketa-Hanlin, Amanda; Stein, Joshua

Module temperature is modeled using a transient heat-flow model. Module temperature predicted in this fashion is important in the calculation of cell temperature, a vital input in performance modeling. Parameters important to the model are tested for sensitivity, and optimized to a single day of measured module temperature using simultaneous non-linear least squares regression. These optimized parameters are then tested for accuracy using a year's worth of data for one location. The results obtained from this analysis are compared with modeled data from a different site, as well as to results obtained using a steadystate model. We find that the transient model best captures the variability in module temperature, and that the transient model works best when calibrated for a specific location.

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Computational model of miniature pulsating heat pipes

Givler, Richard C.; Martinez, Mario J.

The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heat pipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heat pipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.

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Security by Design Handbook

Snell, Mark K.; Jaeger, Calvin D.; Jordan, Sabina E.; Scharmer, Carol

This document is a draft Security-by-Design (SeBD) handbook produced to support the Work Plan of the Nuclear Security Summit to share best practices for nuclear security in new facility design. The Work Plan calls on States to “encourage nuclear operators and architect/engineering firms to take into account and incorporate, where appropriate, effective measures of physical protection and security culture into the planning, construction, and operation of civilian nuclear facilities and provide technical assistance, upon request, to other States in doing so.” The materials for this document were generated primarily as part of a bilateral project to produce a SeBD handbook as a collaboration between the Japan Atomic Energy Agency (JAEA) Nuclear Nonproliferation Science and Technology Center and Sandia National Laboratories (SNL), which represented the US Department Energy (DOE) National Nuclear Security Administration (NNSA) under a Project Action Sheet PAS-PP04. Input was also derived based on tours of the Savannah River Site (SRS) and Japan Nuclear Fuel Limited (JNFL) Rokkasho Mixed Oxide Fuel fabrication facilities and associated project lessons-learned. For the purposes of the handbook, SeBD will be described as the system-level incorporation of the physical protection system (PPS) into a new nuclear power plant or nuclear facility resulting in a PPS design that minimizes the risk of malicious acts leading to nuclear material theft; nuclear material sabotage; and facility sabotage as much as possible through features inherent in (or intrinsic to) the design of the facility. A four-element strategy is presented to achieve a robust, durable, and responsive security system.

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Report on Project Action Sheet PP05 task 3 between the U.S. Department of Energy and the Republic of Korea Ministry of Education, Science, and Technology (MEST)

Snell, Mark K.

This report documents the results of Task 3 of Project Action Sheet PP05 between the United States Department of Energy (DOE) and the Republic of Korea (ROK) Ministry of Education, Science, and Technology (MEST) for Support with Review of an ROK Risk Evaluation Process. This task was to have Sandia National Laboratories collaborate with the Korea Institute of Nuclear Nonproliferation and Control (KINAC) on several activities concerning how to determine the Probability of Neutralization, PN, and the Probability of System Effectiveness, PE, to include: providing descriptions on how combat simulations are used to determine PN and PE; comparisons of the strengths and weaknesses of two neutralization models (the Neutralization.xls spreadsheet model versus the Brief Adversary Threat-Loss Estimator (BATLE) software); and demonstrating how computer simulations can be used to determine PN. Note that the computer simulation used for the demonstration was the Scenario Toolkit And Generation Environment (STAGE) simulation, which is a stand-alone synthetic tactical simulation sold by Presagis Canada Incorporated. The demonstration is provided in a separate Audio Video Interleave (.AVI) file.

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Phase Conjugation of High Energy Lasers

Valley, Michael T.; Atherton, B.

In this report we explore claims that phase conjugation of high energy lasers by stimulated Brillouin scattering (SBS) can compensate optical aberrations associated with severely distorted laser amplifier media and aberrations induced by the atmosphere. The SBS media tested was a gas cell pressurized up to 300 psi with SF6 or Xe or both. The laser was a 10 Hz, 3J, Q-switched Nd:YAG with 25 ns wide pulses. Atmospheric aberrations were created with space heaters, helium jets and phase plates designed with a Kolmogorov turbulence spectrum characterized by a Fried parameter, ro, ranging from 0.6 – 6.0 mm. Phase conjugate tests in the laboratory were conducted without amplification. For the strongest aberrations, D/ro ~ 20, created by combining the space heaters with the phase plate, the Strehl ratio was degraded by a factor of ~50. Phase conjugation in SF6 restored the peak focusable intensity to about 30% of the original laser. Phase conjugate tests at the outdoor laser range were conducted with laser amplifiers providing gain in combination with the SBS cell. A large 600,000 BTU kerosene space heater was used to create turbulence along the beam path. An atmospheric structure factor of Cn2 = 5x10-13 m2/3 caused the illumination beam to expand to a diameter 250mm and overfill the receiver. The phase conjugate amplified return could successfully be targeted back onto glints 5mm in diameter. Use of a lenslet arrays to lower the peak focusable intensity in the SBS cell failed to produce a useful phase conjugate beam; The Strehl ratio was degraded with multiple random lobes instead of a single focus. I will review literature results which show how multiple beams can be coherently combined by SBS when a confocal reflecting geometry is used to focus the laser in the SBS cell.

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Areas for US-India Civilian Nuclear Cooperation to Prevent/Mitigate Radiological Events

Forden, Geoffrey

Over the decades, India and the United States have had very little formal collaboration on nuclear issues. Partly this was because neither country needed collaboration to make progress in the nuclear field. But it was also due, in part, to the concerns both countries had about the other's intentions. Now that the U.S.-India Deal on nuclear collaboration has been signed and the Hyde Act passed in the United States, it is possible to recognize that both countries can benefit from such nuclear collaboration, especially if it starts with issues important to both countries that do not touch on strategic systems. Fortunately, there are many noncontroversial areas for collaboration. This study, funded by the U.S. State Department, has identified a number of areas in the prevention of and response to radiological incidents where such collaboration could take place.

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Considerations of human intrusion in U.S. programs for deep geologic disposal of radioactive waste

Swift, Peter

Regulations in the United States that govern the permanent disposal of spent nuclear fuel and high-level radioactive waste in deep geologic repositories require the explicit consideration of hypothetical future human intrusions that disrupt the waste. Specific regulatory requirements regarding the consideration of human intrusion differ in the two sets of regulations currently in effect in the United States; one defined by the Environmental Protection Agency's 40 Code of Federal Regulations part 197, applied only to the formerly proposed geologic repository at Yucca Mountain, Nevada, and the other defined by the Environmental Protection Agencys 40 Code of Federal Regulations part 191, applied to the Waste Isolation Pilot Plant in New Mexico and potentially applicable to any repository for spent nuclear fuel and high-level radioactive waste in the United States other than the proposed repository at Yucca Mountain. This report reviews the regulatory requirements relevant to human intrusion and the approaches taken by the Department of Energy to demonstrating compliance with those requirements.

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Guiding Optimal Biofuels: A Comparative Analysis of the Biochemical Production of Ethanol and Fatty Acid Ethyl Esters from Switchgrass

Paap, Scott M.; West, Todd H.; Manley, Dawn K.; Dibble, Dean C.; Simmons, Blake

In the current study, processes to produce either ethanol or a representative fatty acid ethyl ester (FAEE) via the fermentation of sugars liberated from lignocellulosic materials pretreated in acid or alkaline environments are analyzed in terms of economic and environmental metrics. Simplified process models are introduced and employed to estimate process performance, and Monte Carlo analyses were carried out to identify key sources of uncertainty and variability. We find that the near-term performance of processes to produce FAEE is significantly worse than that of ethanol production processes for all metrics considered, primarily due to poor fermentation yields and higher electricity demands for aerobic fermentation. In the longer term, the reduced cost and energy requirements of FAEE separation processes will be at least partially offset by inherent limitations in the relevant metabolic pathways that constrain the maximum yield potential of FAEE from biomass-derived sugars.

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Formation of Algae Growth Constitutive Relations for Improved Algae Modeling

Gharagozloo, Patricia E.

This SAND report summarizes research conducted as a part of a two year Laboratory Directed Research and Development (LDRD) project to improve our abilities to model algal cultivation. Algae-based biofuels have generated much excitement due to their potentially large oil yield from relatively small land use and without interfering with the food or water supply. Algae mitigate atmospheric CO2 through metabolism. Efficient production of algal biofuels could reduce dependence on foreign oil by providing a domestic renewable energy source. Important factors controlling algal productivity include temperature, nutrient concentrations, salinity, pH, and the light-to-biomass conversion rate. Computational models allow for inexpensive predictions of algae growth kinetics in these non-ideal conditions for various bioreactor sizes and geometries without the need for multiple expensive measurement setups. However, these models need to be calibrated for each algal strain. In this work, we conduct a parametric study of key marine algae strains and apply the findings to a computational model.

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Elucidating the Role of Interfacial Materials Properties in Microfluidic Packages

Edwards, Thayne L.

The purpose of this work was to discover a method to investigate the properties of interfaces as described by a numerical physical model. The model used was adopted from literature and applied to a commercially available multiphysics software package. By doing this the internal properties of simple structures could be elucidated and then readily applied to more complex structures such as valves and pumps in laminate microfluidic structures. A numerical finite element multi-scale model of a cohesive interface comprised of heterogeneous material properties was used to elucidate irreversible damage from applied strain energy. An unknown internal state variable was applied to characterize the damage process. Using a constrained blister test, this unknown internal state variable could be determined for an adherend/adhesive/adherend body. This is particularly interesting for laminate systems with microfluidic and microstructures contained within the body. A laminate structure was designed and fabricated that could accommodate a variety of binary systems joined using nearly any technique such as adhesive, welding (solvent, laser, ultrasonic, RF, etc.), or thermal. The adhesive method was the most successful and easy to implement but also one of the more difficult to understand, especially over long periods of time. Welding methods are meant to achieve a bond that is similar to bulk properties and so are easier to predict. However, methods of welding often produce defects in the bonds.. Examples of the test structures used to elucidate the internal properties of the model were shown and demonstrated. The real life examples used this research to improve upon current designs and aided in creating complex structures for sensor and other applications.

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Vessel Cold-Ironing Using a Barge Mounted PEM Fuel Cell: Project Scoping and Feasibility

Pratt, Joseph W.; Harris, Aaron P.

A barge-mounted hydrogen-fueled proton exchange membrane (PEM) fuel cell system has the potential to reduce emissions and fossil fuel use of maritime vessels in and around ports. This study determines the technical feasibility of this concept and examines specific options on the U.S. West Coast for deployment practicality and potential for commercialization.The conceptual design of the system is found to be straightforward and technically feasible in several configurations corresponding to various power levels and run times.The most technically viable and commercially attractive deployment options were found to be powering container ships at berth at the Port of Tacoma and/or Seattle, powering tugs at anchorage near the Port of Oakland, and powering refrigerated containers on-board Hawaiian inter-island transport barges. Other attractive demonstration options were found at the Port of Seattle, the Suisun Bay Reserve Fleet, the California Maritime Academy, and an excursion vessel on the Ohio River.

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Analysis of Dose Consequences Arising from the Release of Spent Nuclear Fuel from Dry Storage Casks

Durbin, S.; Morrow, Charles

The resulting dose consequences from releases of spent nuclear fuel (SNF) residing in a dry storage casks are examined parametrically. The dose consequences are characterized by developing dose versus distance curves using simplified bounding assumptions. The dispersion calculations are performed using the MELCOR Accident Consequence Code System (MACCS2) code. Constant weather and generic system parameters were chosen to ensure that the results in this report are comparable with each other and to determine the relative impact on dose of each variable. Actual analyses of site releases would need to accommodate local weather and geographic data. These calculations assume a range of fuel burnups, release fractions (RFs), three exposure scenarios (2 hrs and evacuate, 2 hrs and shelter, and 24 hrs exposure), two meteorological conditions (D-4 and F-2), and three release heights (ground level – 1 meter (m), 10 m, and 100 m). This information was developed to support a policy paper being developed by U.S. Nuclear Regulatory Commission (NRC) staff on an independent spent fuel storage installation (ISFSI) and monitored retrievable storage installation (MRS) security rulemaking.

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Time series power flow analysis for distribution connected PV generation

Ellis, Abraham; Quiroz, Jimmy E.; Reno, Matthew J.; Broderick, Robert J.

Distributed photovoltaic (PV) projects must go through an interconnection study process before connecting to the distribution grid. These studies are intended to identify the likely impacts and mitigation alternatives. In the majority of the cases, system impacts can be ruled out or mitigation can be identified without an involved study, through a screening process or a simple supplemental review study. For some proposed projects, expensive and time-consuming interconnection studies are required. The challenges to performing the studies are twofold. First, every study scenario is potentially unique, as the studies are often highly specific to the amount of PV generation capacity that varies greatly from feeder to feeder and is often unevenly distributed along the same feeder. This can cause location-specific impacts and mitigations. The second challenge is the inherent variability in PV power output which can interact with feeder operation in complex ways, by affecting the operation of voltage regulation and protection devices. The typical simulation tools and methods in use today for distribution system planning are often not adequate to accurately assess these potential impacts. This report demonstrates how quasi-static time series (QSTS) simulation and high time-resolution data can be used to assess the potential impacts in a more comprehensive manner. The QSTS simulations are applied to a set of sample feeders with high PV deployment to illustrate the usefulness of the approach. The report describes methods that can help determine how PV affects distribution system operations. The simulation results are focused on enhancing the understanding of the underlying technical issues. The examples also highlight the steps needed to perform QSTS simulation and describe the data needed to drive the simulations. The goal of this report is to make the methodology of time series power flow analysis readily accessible to utilities and others responsible for evaluating potential PV impacts.

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Caltech campus executive LDRD

Shepodd, Timothy J.

The environment most brain systems of humans and other animals are almost constantly confronted with is complex and continuously changing, with each time step updating a potentially bewildering set of opportunities and demands for action. Far from the controlled, discrete trials used in most neuro- and psychological investigations, behavior outside the lab at Caltech is a seamless and continuous process of monitoring (and error correction) of ongoing action, and of evaluating persistence in the current activity with respect to opportunities to switch tasks as alternatives become available. Prior work on frontopolar and prefrontal task switching, use tasks within the same modality (View a stream of symbols on a screen and perform certain response mappings depending on task rules). However, in these task switches the effector is constant: only the mapping of visual symbols to the specific button changes. In this task, the subjects are choosing what kinds of future action decisions they want to perform, where they can control either which body part will act, or which direction they will orient an instructed body action. An effector choice task presents a single target and the subject selects which effector to use to reach the target (eye or hand). While the techniques available for humans can be less spatially resolved compared to non-human primate neural data, they do allow for experimentation on multiple brain areas with relative ease. Thus, we address a broader network of areas involved in motor decisions. We aim to resolve a current dispute regarding the specific functional roles of brain areas that are often co-activated in studies of decision tasks, dorsal premotor cortex(PMd) and posterior parietal cortex(PPC). In one model, the PPC distinctly drives intentions for action selection, whereas PMd stimulation results in complex multi-joint movements without any awareness of, nor subjective feeling of, willing the elicited movement, thus seems to merely help execute the chosen action.

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Genetic engineering of cyanobacteria as biodiesel feedstock

Ruffing, Anne R.; Jones, Howland D.T.

Algal biofuels are a renewable energy source with the potential to replace conventional petroleum-based fuels, while simultaneously reducing greenhouse gas emissions. The economic feasibility of commercial algal fuel production, however, is limited by low productivity of the natural algal strains. The project described in this SAND report addresses this low algal productivity by genetically engineering cyanobacteria (i.e. blue-green algae) to produce free fatty acids as fuel precursors. The engineered strains were characterized using Sandias unique imaging capabilities along with cutting-edge RNA-seq technology. These tools are applied to identify additional genetic targets for improving fuel production in cyanobacteria. This proof-of-concept study demonstrates successful fuel production from engineered cyanobacteria, identifies potential limitations, and investigates several strategies to overcome these limitations. This project was funded from FY10-FY13 through the President Harry S. Truman Fellowship in National Security Science and Engineering, a program sponsored by the LDRD office at Sandia National Laboratories.

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First Application of Geospatial Semantic Graphs to SAR Image Data (LDRD Final Report)

Mclendon, William; Brost, Randolph

Modeling geospatial information with semantic graphs enables search for sites of interest based on relationships between features, without requiring strong a priori models of feature shape or other intrinsic properties. Geospatial semantic graphs can be constructed from raw sensor data with suitable preprocessing to obtain a discretized representation. This report describes initial work toward extending geospatial semantic graphs to include temporal information, and initial results applying semantic graph techniques to SAR image data. We describe an efficient graph structure that includes geospatial and temporal information, which is designed to support simultaneous spatial and temporal search queries. We also report a preliminary implementation of feature recognition, semantic graph modeling, and graph search based on input SAR data. The report concludes with lessons learned and suggestions for future improvements.

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Exomerge user's manual :

Kostka, Timothy D.

Exomerge is a lightweight Python module for reading, manipulating and writing data within ExodusII files. It is built upon a Python wrapper around the ExodusII API functions. This module, the Python wrapper, and the ExodusII libraries are available as part of the standard SIERRA installation.

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Installation of five new hydrogeologic groundwater monitoring wells

Catechis, Christopher S.

There are two sites comprised of several parcels of land within the Kirtland Military Reservation, Bernalillo County, New Mexico. Site A is located within T 9N, R 4E, Section 13 and Site B is located within T 9N, R 4E, Section 36. The purpose of this EBS is to document the nature, magnitude, and extent of any environmental contamination of the property; identify potential environmental contamination liabilities associated with the property; develop sufficient information to assess the health and safety risks; and ensure adequate protection for human health and the environment related to a specific property.

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Stimulation of vigorous rotational flows and novel flow patterns using triaxial magnetic fields

Soft Matter

Solis, Kyle J.; Martin, James E.

We have discovered that new flow patterns can be created by applying a dc field to the ac biaxial fields that are used to induce isothermal magnetic advection (IMA). IMA is a recently discovered fluid flow phenomenon that occurs in suspensions of magnetic platelets subjected to particular time-dependent, uniform, biaxial magnetic fields. IMA is characterized by the formation of emergent flow patterns called advection lattices. We find that a dc field can disrupt the antiparallel flow symmetry of the advection lattice and give rise to qualitatively new flow patterns, including vigorous rotational flows and a highly regular diamond lattice. The rotational flows are very robust and may have applications to heat transfer. The diamond lattice is an intriguing and challenging example of emergent dynamics. Both of these effects occur when the dc field is applied orthogonal to the plane of the biaxial field. © The Royal Society of Chemistry 2012.

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Shock tube investigation of quasi-steady drag in shock-particle interactions

Physics of Fluids

Beresh, Steven J.; Kearney, Sean P.; Pruett, Brian; Wright, Elton K.

A reassessment of historical drag coefficient data for spherical particles accelerated in shock-induced flows has motivated new shock tube experiments of particle response to the passage of a normal shock wave. Particle drag coefficients were measured by tracking the trajectories of 1-mm spheres in the flow induced by incident shocks at Mach numbers 1.68, 1.93, and 2.04. The necessary data accuracy is obtained by accounting for the shock tube wall boundary layer growth and avoiding interactions between multiple particles. Similar to past experiments, the current data clearly show that as the Mach number increases, the drag coefficient increases substantially. This increase significantly exceeds the drag predicted by incompressible standard drag models, but a recently developed compressible drag correlation returns values quite close to the current measurements. Recent theoretical work and low particle accelerations indicate that unsteadiness should not be expected to contribute to the drag increase over the relatively long time scales of the experiments. These observations suggest that elevated particle drag coefficients are a quasi-steady phenomenon attributed to increased compressibility rather than true flow unsteadiness. © 2012 American Institute of Physics.

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A frequency selective surface with integrated limiter for receiver protection

IEEE Antennas and Propagation Society, AP-S International Symposium (Digest)

Scott, Sean; Nordquist, Christopher D.; Cich, Michael J.; Jordan, Tyler S.; Rodenbeck, Christopher T.

The design and simulation of a frequency selective surface (FSS) with integrated limiter for receiver-protection are presented. The FSS operates as normal until a certain power threshold is reached, at which point the temperature increase triggers a dramatic resistance change across the element, and the insertion loss changes from 0.2 dB to 20 dB. The limiting action is completely passive and automatically reversible. By placing the limiter outside of the system, no portion of the front-end risks damage from high-power signals, a level of protection not offered in conventional limiters. Finally, the design is compatible with standard lithography processes, requires no diodes, ferrites, or additional components, and can potentially be integrated on flexible substrates. © 2012 IEEE.

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Used fuel disposition campaign - Objectives, mission, plans and current activities

Materials Research Society Symposium Proceedings

Mcmahon, Kevin A.; Swift, Peter; Sorenson, Ken B.

The safe management and disposition of used nuclear fuel and/or high level nuclear waste is a fundamental aspect of the nuclear fuel cycle. The United States currently utilizes a once-through fuel cycle where used nuclear fuel is stored on-site in either wet pools or in dry storage systems with ultimate disposal in a deep mined geologic repository envisioned. However, a decision not to use the proposed Yucca Mountain Repository will result in longer interim storage at reactor sites than previously planned. In addition, alternatives to the once-through fuel cycle are being considered and a variety of options are being explored under the U.S. Department of Energy's Fuel Cycle Technologies Program. These two factors lead to the need to develop a credible strategy for managing radioactive wastes from any future nuclear fuel cycle in order to provide acceptable disposition pathways for all wastes regardless of transmutation system technology, fuel reprocessing scheme(s), and/or the selected fuel cycle. These disposition paths will involve both the storing of radioactive material for some period of time and the ultimate disposal of radioactive waste. To address the challenges associated with waste management, the DOE Office of Nuclear Energy established the Used Fuel Disposition Campaign in the summer of 2009. The mission of the Used Fuel Disposition Campaign is to identify alternatives and conduct scientific research and technology development to enable storage, transportation, and disposal of used nuclear fuel and wastes generated by existing and future nuclear fuel cycles. The near-and long-term objectives of the Fuel Cycle Technologies Program and its' Used Fuel Disposition Campaign are presented. © 2012 Materials Research Society.

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Preliminary performance assessment for deep borehole disposal of high-level radioactive waste

Materials Research Society Symposium Proceedings

Swift, Peter; Arnold, Bill W.; Brady, Patrick V.; Freeze, Geoffrey; Hadgu, Teklu; Lee, Joon H.

Deep boreholes have been proposed for many decades as an option for permanent disposal of high-level radioactive waste and spent nuclear fuel. Disposal concepts are straightforward, and generally call for drilling boreholes to a depth of four to five kilometers (or more) into crystalline basement rocks. Waste is placed in the lower portion of the hole, and the upper several kilometers of the hole are sealed to provide effective isolation from the biosphere. The potential for excellent long-term performance has been recognized in many previous studies. This paper reports updated results of what is believed to be the first quantitative analysis of releases from a hypothetical disposal borehole repository using the same performance assessment methodology applied to mined geologic repositories for high-level radioactive waste. Analyses begin with a preliminary consideration of a comprehensive list of potentially relevant features, events, and processes (FEPs) and the identification of those FEPs that appear to be most likely to affect long-term performance in deep boreholes. The release pathway selected for preliminary performance assessment modeling is thermally-driven flow and radionuclide transport upwards from the emplacement zone through the borehole seals or the surrounding annulus of disturbed rock. Estimated radionuclide releases from deep borehole disposal of spent nuclear fuel, and the annual radiation doses to hypothetical future humans associated with those releases, are extremely small, indicating that deep boreholes may be a viable alternative to mined repositories for disposal of both high-level radioactive waste and spent nuclear fuel. © 2012 Materials Research Society.

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Results 60201–60400 of 99,299