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Results of model intercomparison : predicted vs. measured system performance

Stein, Joshua

This is a blind modeling study to illustrate the variability expected between PV performance model results. Objectives are to answer: (1) What is the modeling uncertainty; (2) Do certain models do better than others; (3) How can performance modeling be improved; and (4) What are the sources of uncertainty? Some preliminary conclusions are: (1) Large variation seen in model results; (2) Variation not entirely consistent across systems; (3) Uncertainty in assigning derates; (4) Discomfort when components are not included in database - Is there comfort when the components are in the database?; and (5) Residual analysis will help to uncover additional patterns in the models.

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A standardized approach to PV system performance model validation

Cameron, Christopher P.

PV performance models are used to predict how much energy a PV system will produce at a given location and subject to prescribed weather conditions. These models are commonly used by project developers to choose between module technologies and array designs (e.g., fixed tilt vs. tracking) for a given site or to choose between different geographic locations, and are used by the financial community to establish project viability. Available models can differ significantly in their underlying mathematical formulations and assumptions and in the options available to the analyst for setting up a simulation. Some models lack complete documentation and transparency, which can result in confusion on how to properly set up, run, and document a simulation. Furthermore, the quality and associated uncertainty of the available data upon which these models rely (e.g., irradiance, module parameters, etc.) is often quite variable and frequently undefined. For these reasons, many project developers and other industry users of these simulation tools have expressed concerns related to the confidence they place in PV performance model results. To address this problem, we propose a standardized method for the validation of PV system-level performance models and a set of guidelines for setting up these models and reporting results. This paper describes the basic elements for a standardized model validation process adapted especially for PV performance models, suggests a framework to implement the process, and presents an example of its application to a number of available PV performance models.

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Expanding the Trilinos developer community

Heroux, Michael A.

The Trilinos Project started approximately nine years ago as a small effort to enable research, development and ongoing support of small, related solver software efforts. The 'Tri' in Trilinos was intended to indicate the eventual three packages we planned to develop. In 2007 the project expanded its scope to include any package that was an enabling technology for technical computing. Presently the Trilinos repository contains over 55 packages covering a broad spectrum of reusable tools for constructing full-featured scalable scientific and engineering applications. Trilinos usage is now worldwide, and many applications have an explicit dependence on Trilinos for essential capabilities. Users come from other US laboratories, universities, industry and international research groups. Awareness and use of Trilinos is growing rapidly outside of Sandia. Members of the external research community are becoming more familiar with Trilinos, its design and collaborative nature. As a result, the Trilinos project is receiving an increasing number of requests from external community members who want to contribute to Trilinos as developers. To-date we have worked with external developers in an ad hoc fashion. Going forward, we want to develop a set of policies, procedures, tools and infrastructure to simplify interactions with external developers. As we go forward with multi-laboratory efforts such as CASL and X-Stack, and international projects such as IESP, we will need a more streamlined and explicit process for making external developers 'first-class citizens' in the Trilinos development community. This document is intended to frame the discussion for expanding the Trilinos community to all strategically important external members, while at the same time preserving Sandia's primary leadership role in the project.

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Use of a hybrid technology in a critical security system

Trujillo, David J.

Assigning an acceptable level of power reliability in a security system environment requires a methodical approach to design when considering the alternatives tied to the reliability and life of the system. The downtime for a piece of equipment, be it for failure, routine maintenance, replacement, or refurbishment or connection of new equipment is a major factor in determining the reliability of the overall system. In addition to these factors is the condition where the system is static or dynamic in its growth. Most highly reliable security power source systems are supplied by utility power with uninterruptable power source (UPS) and generator backup. The combination of UPS and generator backup with a reliable utility typically provides full compliance to security requirements. In the energy market and from government agencies, there is growing pressure to utilize alternative sources of energy other than fossil fuel to increase the number of local generating systems to reduce dependence on remote generating stations and cut down on carbon effects to the environment. There are also conditions where a security system may be limited on functionality due to lack of utility power in remote locations. One alternative energy source is a renewable energy hybrid system including a photovoltaic or solar system with battery bank and backup generator set. This is a viable source of energy in the residential and commercial markets where energy management schemes can be incorporated and systems are monitored and maintained regularly. But, the reliability of this source could be considered diminished when considering the security system environment where stringent uptime requirements are required.

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Discontinuous Galerkin finite element methods for gradient plasticity

Ostien, Jakob T.

In this report we apply discontinuous Galerkin finite element methods to the equations of an incompatibility based formulation of gradient plasticity. The presentation is motivated with a brief overview of the description of dislocations within a crystal lattice. A tensor representing a measure of the incompatibility with the lattice is used in the formulation of a gradient plasticity model. This model is cast in a variational formulation, and discontinuous Galerkin machinery is employed to implement the formulation into a finite element code. Finally numerical examples of the model are shown.

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Thermal modeling of carbon-epoxy laminates in fire environments

Dodd, Amanda B.

A thermal model is developed for the response of carbon-epoxy composite laminates in fire environments. The model is based on a porous media description that includes the effects of gas transport within the laminate along with swelling. Model comparisons are conducted against the data from Quintere et al. Simulations are conducted for both coupon level and intermediate scale one-sided heating tests. Comparisons of the heat release rate (HRR) as well as the final products (mass fractions, volume percentages, porosity, etc.) are conducted. Overall, the agreement between available the data and model is excellent considering the simplified approximations to account for flame heat flux. A sensitivity study using a newly developed swelling model shows the importance of accounting for laminate expansion for the prediction of burnout. Excellent agreement is observed between the model and data of the final product composition that includes porosity, mass fractions and volume expansion ratio.

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A life cycle cost analysis framework for geologic storage of hydrogen : a scenario analysis

Lord, Anna S.; Kobos, Peter; Borns, David J.

The U.S. Department of Energy has an interest in large scale hydrogen geostorage, which would offer substantial buffer capacity to meet possible disruptions in supply. Geostorage options being considered are salt caverns, depleted oil/gas reservoirs, aquifers and potentially hard rock cavrns. DOE has an interest in assessing the geological, geomechanical and economic viability for these types of hydrogen storage options. This study has developed an ecocomic analysis methodology to address costs entailed in developing and operating an underground geologic storage facility. This year the tool was updated specifically to (1) a version that is fully arrayed such that all four types of geologic storage options can be assessed at the same time, (2) incorporate specific scenarios illustrating the model's capability, and (3) incorporate more accurate model input assumptions for the wells and storage site modules. Drawing from the knowledge gained in the underground large scale geostorage options for natural gas and petroleum in the U.S. and from the potential to store relatively large volumes of CO{sub 2} in geological formations, the hydrogen storage assessment modeling will continue to build on these strengths while maintaining modeling transparency such that other modeling efforts may draw from this project.

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Potential underground risks associated with CAES

Bauer, Stephen J.

CAES in geologic media has been proposed to help 'firm' renewable energy sources (wind and solar) by providing a means to store energy when excess energy was available, and to provide an energy source during non-productive renewable energy time periods. Such a storage media may experience hourly (perhaps small) pressure swings. Salt caverns represent the only proven underground storage used for CAES, but not in a mode where renewable energy sources are supported. Reservoirs, both depleted natural gas and aquifers represent other potential underground storage vessels for CAES, however, neither has yet to be demonstrated as a functional/operational storage media for CAES.

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Characterization of the surface changes during the activation process of erbium/erbium oxide for hydrogen storage

Brumbach, Michael T.; Zavadil, Kevin R.; Snow, Clark S.; Ohlhausen, J.A.

Erbium is known to effectively load with hydrogen when held at high temperature in a hydrogen atmosphere. To make the storage of hydrogen kinetically feasible, a thermal activation step is required. Activation is a routine practice, but very little is known about the physical, chemical, and/or electronic processes that occur during Activation. This work presents in situ characterization of erbium Activation using variable energy photoelectron spectroscopy at various stages of the Activation process. Modification of the passive surface oxide plays a significant role in Activation. The chemical and electronic changes observed from core-level and valence band spectra will be discussed along with corroborating ion scattering spectroscopy measurements.

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High performance semantic factoring of giga-scale semantic graph databases

Goodman, Eric; Mackey, Greg E.

As semantic graph database technology grows to address components ranging from extant large triple stores to SPARQL endpoints over SQL-structured relational databases, it will become increasingly important to be able to bring high performance computational resources to bear on their analysis, interpretation, and visualization, especially with respect to their innate semantic structure. Our research group built a novel high performance hybrid system comprising computational capability for semantic graph database processing utilizing the large multithreaded architecture of the Cray XMT platform, conventional clusters, and large data stores. In this paper we describe that architecture, and present the results of our deploying that for the analysis of the Billion Triple dataset with respect to its semantic factors, including basic properties, connected components, namespace interaction, and typed paths.

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Premature ignition of a rocket motor

Moore, Darlene R.

During preparation for a rocket sled track (RST) event, there was an unexpected ignition of the zuni rocket motor (10/9/08). Three Sandia staff and a contractor were involved in the accident; the contractor was seriously injured and made full recovery. The data recorder battery energized the low energy initiator in the rocket.

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Foundations to the unified psycho-cognitive engine

Backus, George A.

This document outlines the key features of the SNL psychological engine. The engine is designed to be a generic presentation of cognitive entities interacting among themselves and with the external world. The engine combines the most accepted theories of behavioral psychology with those of behavioral economics to produce a unified simulation of human response from stimuli through executed behavior. The engine explicitly recognizes emotive and reasoned contributions to behavior and simulates the dynamics associated with cue processing, learning, and choice selection. Most importantly, the model parameterization can come from available media or survey information, as well subject-matter-expert information. The framework design allows the use of uncertainty quantification and sensitivity analysis to manage confidence in using the analysis results for intervention decisions.

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Split Hopkinson bar experiments of preloaded interfaces

Luk, Vincent K.

Preloads are routinely applied to stiffen structural members in many applications. However, the preloaded structural members have been observed to lose a significant portion of the imposed load due to internal relaxation mechanisms during impulsive impact events. This paper describes the design and initial experiments for a novel Hopkinson bar configuration designed to investigate the effect of preloads on the stress wave propagation across interfaces between the incident and transmission bars. Dynamic responses are measured by a variety of sensors, including accelerometers, strain gages, and a laser vibrometer. The transmissibility of a titanium incident bar is measured to establish the baseline frequency response between the input and the test interface. Wave transmission across an titanium-aluminum interface is also examined by analyzing the frequency response function, transmission efficiency, and transmissibility between the incident and transmitted waves. The presence of vacuum grease is shown to strongly influence the dynamic behavior of the system.

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XeF2 vapor phase silicon etch used in the fabrication of movable SOI structures

Shul, Randy J.; Bauer, Todd M.; Plut, Thomas A.; Sanchez, Carlos A.

Vapor phase XeF{sub 2} has been used in the fabrication of various types of devices including MEMS, resonators, RF switches, and micro-fluidics, and for wafer level packaging. In this presentation we demonstrate the use of XeF{sub 2} Si etch in conjunction with deep reactive ion etch (DRIE) to release single crystal Si structures on Silicon On Insulator (SOI) wafers. XeF{sub 2} vapor phase etching is conducive to the release of movable SOI structures due to the isotropy of the etch, the high etch selectivity to silicon dioxide (SiO{sub 2}) and fluorocarbon (FC) polymer etch masks, and the ability to undercut large structures at high rates. Also, since XeF{sub 2} etching is a vapor phase process, stiction problems often associated with wet chemical release processes are avoided. Monolithic single crystal Si features were fabricated by etching continuous trenches in the device layer of an SOI wafer using a DRIE process optimized to stop on the buried SiO{sub 2}. The buried SiO{sub 2} was then etched to handle Si using an anisotropic plasma etch process. The sidewalls of the device Si features were then protected with a conformal passivation layer of either FC polymer or SiO{sub 2}. FC polymer was deposited from C4F8 gas precursor in an inductively coupled plasma reactor, and SiO{sub 2} was deposited by plasma enhanced chemical vapor deposition (PECVD). A relatively high ion energy, directional reactive ion etch (RIE) plasma was used to remove the passivation film on surfaces normal to the direction of the ions while leaving the sidewall passivation intact. After the bottom of the trench was cleared to the underlying Si handle wafer, XeF{sub 2} was used to isotropically etch the handle Si, thus undercutting and releasing the features patterned in the device Si layer. The released device Si structures were not etched by the XeF{sub 2} due to protection from the top SiO{sub 2} mask, sidewall passivation, and the buried SiO{sub 2} layer. Optimization of the XeF{sub 2} process and the sidewall passivation layers will be discussed. The advantages of releasing SOI devices with XeF{sub 2} include avoiding stiction, maintaining the integrity of the buried SiO{sub 2}, and simplifying the fabrication flow for thermally actuated devices.

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The energy-water nexus and the role of carbon capture and sequestration

Malczynski, Leonard A.; Kobos, Peter; Castillo, Cesar R.

There is growing evidence of human induced climate change. Various legislation has been introduced to cap carbon emissions. Fossil powered electric generation is responsible for over 30% of the U.S. emissions. Carbon Capture and Sequestration (CCS) technology is water and energy intensive. The project's objectives are: (1) Explore water consumption implications associated with full deployment of a Carbon Capture and Storage (CCS) future; (2) Identify vulnerable areas in which water resources may be too limited to enable full deployment of CCS technology; and (3) Implement project with the cooperation of the National Energy Technology Laboratory (NETL) and DOE Office of Policy and International Affairs. Thermoelectric consumption projected to increase by 3.7 BGD due to CCS by 2035, a doubling over 2004. This increase is equivalent to projected growth in consumption by all other sectors. Demand is not equally distributed across the U.S. 18.5% of this future demand is located in watershed prone to surface and groundwater stress. 30% of current and future demand is located in watersheds prone to drought stress.

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Nanocrystal-enabled solid state bonding

Holm, Elizabeth A.; Puskar, J.D.; Reece, Mark; Tikare, Veena

In this project, we performed a preliminary set of sintering experiments to examine nanocrystal-enabled diffusion bonding (NEDB) in Ag-on-Ag and Cu-on-Cu using Ag nanoparticles. The experimental test matrix included the effects of material system, temperature, pressure, and particle size. The nanoparticle compacts were bonded between plates using a customized hot press, tested in shear, and examined post mortem using microscopy techniques. NEDB was found to be a feasible mechanism for low-temperature, low-pressure, solid-state bonding of like materials, creating bonded interfaces that were able to support substantial loads. The maximum supported shear strength varied substantially within sample cohorts due to variation in bonded area; however, systematic variation with fabrication conditions was also observed. Mesoscale sintering simulations were performed in order to understand whether sintering models can aid in understanding the NEDB process. A pressure-assisted sintering model was incorporated into the SPPARKS kinetic Monte Carlo sintering code. Results reproduce most of the qualitative behavior observed in experiments, indicating that simulation can augment experiments during the development of the NEDB process. Because NEDB offers a promising route to low-temperature, low-pressure, solid-state bonding, we recommend further research and development with a goal of devising new NEDB bonding processes to support Sandia's customers.

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Structural simulations of nanomaterials self-assembled from ionic macrocycles

Van Swol, Frank B.

Recent research at Sandia has discovered a new class of organic binary ionic solids with tunable optical, electronic, and photochemical properties. These nanomaterials, consisting of a novel class of organic binary ionic solids, are currently being developed at Sandia for applications in batteries, supercapacitors, and solar energy technologies. They are composed of self-assembled oligomeric arrays of very large anions and large cations, but their crucial internal arrangement is thus far unknown. This report describes (a) the development of a relevant model of nonconvex particles decorated with ions interacting through short-ranged Yukawa potentials, and (b) the results of initial Monte Carlo simulations of the self-assembly binary ionic solids.

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Model electrode structures for studies of electrocatalyst degradation

Goeke, Ronald S.

Proton exchange membrane fuel cells are being extensively studied as power sources because of their technological advantages such as high energy efficiency and environmental friendliness. The most effective catalyst in these systems consists of nanoparticles of Pt or Pt-based alloys on carbon supports. Understanding the role of the nanoparticle size and structure on the catalytic activity and degradation is needed to optimize the fuel cell performance and reduce the noble metal loading. One of the more significant causes of fuel cell performance degradation is the cathode catalyst deactivation. There are four mechanisms considered relevant to the loss of electrochemically active surface area of Pt in the fuel cell electrodes that contribute to cathode catalyst degradation including: catalyst particle sintering such as Ostwald ripening, migration and coalescence, carbon corrosion and catalyst dissolution. Most approaches to study this catalyst degradation utilize membrane electrode assemblies (MEAs), which results in a complex system where it is difficult to deconvolute the effects of the metal nanoparticles. Our research addresses catalyst degradation by taking a fundamental approach to study electrocatalyst using model supports. Nanostructured particle arrays are engineered directly onto planar glassy carbon electrodes. These model electrocatalyst structures are applied to electrochemical activity measurements using a rotating disk electrode and surface characterization by scanning electron microscopy. Sample transfer between these measurement techniques enables examination of the same catalyst area before and after electrochemical cycling. This is useful to probe relationships between electrochemical activity and catalyst structure such as particle size and spacing. These model systems are applied to accelerated aging studies of activity degradation. We will present our work demonstrating the mechanistic aspects of catalyst degradation using this simplified geometric system. The active surface area loss observed in repeated cyclic voltammetry is explained through characterization and imaging of the same RDE electrode structures throughout the aging process.

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Cloud computing security

Claycomb, William R.; Urias, Vincent

Cloud computing is a paradigm rapidly being embraced by government and industry as a solution for cost-savings, scalability, and collaboration. While a multitude of applications and services are available commercially for cloud-based solutions, research in this area has yet to fully embrace the full spectrum of potential challenges facing cloud computing. This tutorial aims to provide researchers with a fundamental understanding of cloud computing, with the goals of identifying a broad range of potential research topics, and inspiring a new surge in research to address current issues. We will also discuss real implementations of research-oriented cloud computing systems for both academia and government, including configuration options, hardware issues, challenges, and solutions.

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Ultrafast 25 keV backlighting for experiments on Z

Geissel, Matthias; Atherton, B.; Pitts, Todd A.; Schollmeier, Marius; Headley, Daniel I.; Kimmel, Mark; Rambo, Patrick K.; Robertson, G.K.; Sefkow, Adam B.; Schwarz, Jens; Speas, Christopher S.

To extend the backlighting capabilities for Sandia's Z-Accelerator, Z-Petawatt, a laser which can provide laser pulses of 500 fs length and up to 120 J (100TW target area) or up to 450 J (Z/Petawatt target area) has been built over the last years. The main mission of this facility focuses on the generation of high energy X-rays, such as tin K{alpha} at 25 keV in ultra-short bursts. Achieving 25 keV radiographs with decent resolution and contrast required addressing multiple problems such as blocking of hot electrons, minimization of the source, development of suitable filters, and optimization of laser intensity. Due to the violent environment inside of Z, an additional very challenging task is finding massive debris and radiation protection measures without losing the functionality of the backlighting system. We will present the first experiments on 25 keV backlighting including an analysis of image quality and X-ray efficiency.

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The theory of diversity and redundancy in information system security : LDRD final report

Mayo, Jackson R.; Armstrong, Robert C.; Allan, Benjamin A.; Walker, Andrea M.

The goal of this research was to explore first principles associated with mixing of diverse implementations in a redundant fashion to increase the security and/or reliability of information systems. Inspired by basic results in computer science on the undecidable behavior of programs and by previous work on fault tolerance in hardware and software, we have investigated the problem and solution space for addressing potentially unknown and unknowable vulnerabilities via ensembles of implementations. We have obtained theoretical results on the degree of security and reliability benefits from particular diverse system designs, and mapped promising approaches for generating and measuring diversity. We have also empirically studied some vulnerabilities in common implementations of the Linux operating system and demonstrated the potential for diversity to mitigate these vulnerabilities. Our results provide foundational insights for further research on diversity and redundancy approaches for information systems.

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Measurements of radiative material properties for astrophysical plasmas

Bailey, James E.

The new generation of z-pinch, laser, and XFEL facilities opens the possibility to produce astrophysically-relevant laboratory plasmas with energy densities beyond what was previously possible. Furthermore, macroscopic plasmas with uniform conditions can now be created, enabling more accurate determination of the material properties. This presentation will provide an overview of our research at the Z facility investigating stellar interior opacities, AGN warm-absorber photoionized plasmas, and white dwarf photospheres. Atomic physics in plasmas heavily influence these topics. Stellar opacities are an essential ingredient of stellar models and they affect what we know about the structure and evolution of stars. Opacity models have become highly sophisticated, but laboratory tests have not been done at the conditions existing inside stars. Our research is presently focused on measuring Fe at conditions relevant to the base of the solar convection zone, where the electron temperature and density are believed to be 190 eV and 9 x 10{sup 22} e/cc, respectively. The second project is aimed at testing atomic kinetics models for photoionized plasmas. Photoionization is an important process in many astrophysical plasmas and the spectral signatures are routinely used to infer astrophysical object's characteristics. However, the spectral synthesis models at the heart of these interpretations have been the subject of very limited experimental tests. Our current research examines photoionization of neon plasma subjected to radiation flux similar to the warm absorber that surrounds active galactic nuclei. The third project is a recent initiative aimed at producing a white dwarf photosphere in the laboratory. Emergent spectra from the photosphere are used to infer the star's effective temperature and surface gravity. The results depend on knowledge of H, He, and C spectral line profiles under conditions where complex physics such as quasi-molecule formation may be important. These profiles have been studied in past experiments, but puzzles emerging from recent white dwarf analysis have raised questions about the accuracy of the line profile models. Proof-of-principle data has been acquired that indicates radiation-heated quiescent plasmas can be produced with {approx} 1 eV temperature and 10{sup 17}-10{sup 19} e/cc densities, in an {approx} 20cm{sup 3} volume. Such plasmas would provide a valuable platform for investigating numerous line profile questions.

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Doppler effects on 3-D non-LTE radiation transport and emission spectra

Hansen, Stephanie B.; Jones, Brent M.; Ampleford, David J.; Bailey, James E.; Rochau, G.A.; Coverdale, Christine A.; Jennings, Christopher A.; Cuneo, Michael E.

Spatially and temporally resolved X-ray emission lines contain information about temperatures, densities, velocities, and the gradients in a plasma. Extracting this information from optically thick lines emitted from complex ions in dynamic, three-dimensional, non-LTE plasmas requires self-consistent accounting for both non-LTE atomic physics and non-local radiative transfer. We present a brief description of a hybrid-structure spectroscopic atomic model coupled to an iterative tabular on-the-spot treatment of radiative transfer that can be applied to plasmas of arbitrary material composition, conditions, and geometries. The effects of Doppler line shifts on the self-consistent radiative transfer within the plasma and the emergent emission and absorption spectra are included in the model. Sample calculations for a two-level atom in a uniform cylindrical plasma are given, showing reasonable agreement with more sophisticated transport models and illustrating the potential complexity - or richness - of radially resolved emission lines from an imploding cylindrical plasma. Also presented is a comparison of modeled L- and K-shell spectra to temporally and radially resolved emission data from a Cu:Ni plasma. Finally, some shortcomings of the model and possible paths for improvement are discussed.

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Aerosol cluster impact and break-up : model and implementation

Lechman, Jeremy B.

In this report a model for simulating aerosol cluster impact with rigid walls is presented. The model is based on JKR adhesion theory and is implemented as an enhancement to the granular (DEM) package within the LAMMPS code. The theory behind the model is outlined and preliminary results are shown. Modeling the interactions of small particles is relevant to a number of applications (e.g., soils, powders, colloidal suspensions, etc.). Modeling the behavior of aerosol particles during agglomeration and cluster dynamics upon impact with a wall is of particular interest. In this report we describe preliminary efforts to develop and implement physical models for aerosol particle interactions. Future work will consist of deploying these models to simulate aerosol cluster behavior upon impact with a rigid wall for the purpose of developing relationships for impact speed and probability of stick/bounce/break-up as well as to assess the distribution of cluster sizes if break-up occurs. These relationships will be developed consistent with the need for inputs into system-level codes. Section 2 gives background and details on the physical model as well as implementations issues. Section 3 presents some preliminary results which lead to discussion in Section 4 of future plans.

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Shock compression of liquid helium and helium-hydrogen mixtures : development of a cryogenic capability for shock compression of liquid helium on Z, final report for LDRD Project 141536

Hanson, David L.; Lopez, Andrew J.; Shelton, K.P.; Knudson, Marcus D.

This final report on SNL/NM LDRD Project 141536 summarizes progress made toward the development of a cryogenic capability to generate liquid helium (LHe) samples for high accuracy equation-of-state (EOS) measurements on the Z current drive. Accurate data on He properties at Mbar pressures are critical to understanding giant planetary interiors and for validating first principles density functional simulations, but it is difficult to condense LHe samples at very low temperatures (<3.5 K) for experimental studies on gas guns, magnetic and explosive compression devices, and lasers. We have developed a conceptual design for a cryogenic LHe sample system to generate quiescent superfluid LHe samples at 1.5-1.8 K. This cryogenic system adapts the basic elements of a continuously operating, self-regulating {sup 4}He evaporation refrigerator to the constraints of shock compression experiments on Z. To minimize heat load, the sample holder is surrounded by a double layer of thermal radiation shields cooled with LHe to 5 K. Delivery of LHe to the pumped-He evaporator bath is controlled by a flow impedance. The LHe sample holder assembly features modular components and simplified fabrication techniques to reduce cost and complexity to levels required of an expendable device. Prototypes have been fabricated, assembled, and instrumented for initial testing.

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OVIS 3.2 user's guide

Brandt, James M.; Gentile, Ann C.; Houf, Catherine A.; Mayo, Jackson R.; Pebay, Philippe P.; Roe, Diana C.; Thompson, David; Wong, Matthew H.

This document describes how to obtain, install, use, and enjoy a better life with OVIS version 3.2. The OVIS project targets scalable, real-time analysis of very large data sets. We characterize the behaviors of elements and aggregations of elements (e.g., across space and time) in data sets in order to detect meaningful conditions and anomalous behaviors. We are particularly interested in determining anomalous behaviors that can be used as advance indicators of significant events of which notification can be made or upon which action can be taken or invoked. The OVIS open source tool (BSD license) is available for download at ovis.ca.sandia.gov. While we intend for it to support a variety of application domains, the OVIS tool was initially developed for, and continues to be primarily tuned for, the investigation of High Performance Compute (HPC) cluster system health. In this application it is intended to be both a system administrator tool for monitoring and a system engineer tool for exploring the system state in depth. OVIS 3.2 provides a variety of statistical tools for examining the behavior of elements in a cluster (e.g., nodes, racks) and associated resources (e.g., storage appliances and network switches). It provides an interactive 3-D physical view in which the cluster elements can be colored by raw or derived element values (e.g., temperatures, memory errors). The visual display allows the user to easily determine abnormal or outlier behaviors. Additionally, it provides search capabilities for certain scheduler logs. The OVIS capabilities were designed to be highly interactive - for example, the job search may drive an analysis which in turn may drive the user generation of a derived value which would then be examined on the physical display. The OVIS project envisions the capabilities of its tools applied to compute cluster monitoring. In the future, integration with the scheduler or resource manager will be included in a release to enable intelligent resource utilization. For example, nodes that are deemed less healthy (i.e., nodes that exhibit outlier behavior with respect to some set of variables shown to be correlated with future failure) can be discovered and assigned to shorter duration or less important jobs. Further, HPC applications with fault-tolerant capabilities would respond to changes in resource health and other OVIS notifications as needed, rather than undertaking preventative measures (e.g. checkpointing) at regular intervals unnecessarily.

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Metal fires and their implications for advanced reactors

Hewson, John C.; Nowlen, Steven P.; Figueroa Faria, Victor G.; Blanchat, Thomas K.; Olivier, Tara J.

This report details the primary results of the Laboratory Directed Research and Development project (LDRD 08-0857) Metal Fires and Their Implications for Advance Reactors. Advanced reactors may employ liquid metal coolants, typically sodium, because of their many desirable qualities. This project addressed some of the significant challenges associated with the use of liquid metal coolants, primary among these being the extremely rapid oxidation (combustion) that occurs at the high operating temperatures in reactors. The project has identified a number of areas for which gaps existed in knowledge pertinent to reactor safety analyses. Experimental and analysis capabilities were developed in these areas to varying degrees. In conjunction with team participation in a DOE gap analysis panel, focus was on the oxidation of spilled sodium on thermally massive surfaces. These are spills onto surfaces that substantially cool the sodium during the oxidation process, and they are relevant because standard risk mitigation procedures seek to move spill environments into this regime through rapid draining of spilled sodium. While the spilled sodium is not quenched, the burning mode is different in that there is a transition to a smoldering mode that has not been comprehensively described previously. Prior work has described spilled sodium as a pool fire, but there is a crucial, experimentally-observed transition to a smoldering mode of oxidation. A series of experimental measurements have comprehensively described the thermal evolution of this type of sodium fire for the first time. A new physics-based model has been developed that also predicts the thermal evolution of this type of sodium fire for the first time. The model introduces smoldering oxidation through porous oxide layers to go beyond traditional pool fire analyses that have been carried out previously in order to predict experimentally observed trends. Combined, these developments add significantly to the safety analysis capabilities of the advanced-reactor community for directly relevant scenarios. Beyond the focus on the thermally-interacting and smoldering sodium pool fires, experimental and analysis capabilities for sodium spray fires have also been developed in this project.

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Synthesis and electrical analysis of nano-crystalline barium titanate nanocomposites for use in high-energy density applications

Diantonio, Christopher; Monson, Todd; Winter, Michael R.; Roesler, Alexander; Chavez, Thomas P.; Yang, Pin

Ceramic based nanocomposites have recently demonstrated the ability to provide enhanced permittivity, increased dielectric breakdown strength, and reduced electromechanical strain making them potential materials systems for high energy density applications. A systematic characterization and optimization of barium titanate and PLZT based nanoparticle composites employing a glass or polymer matrix to yield a high energy density component will be presented. This work will present the systematic characterization and optimization of barium titanate and lead lanthanum zirconate titanate nanoparticle based ceramics. The nanoparticles have been synthesized using solution and pH-based synthesis processing routes and employed to fabricate polycrystalline ceramic and nanocomposite based components. The dielectric/ferroelectric properties of these various components have been gauged by impedance analysis and electromechanical response and will be discussed.

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Measured and predicted temperature profiles along MEMS bridges at pressures from 0.05 to 625 torr

Phinney, Leslie; Serrano, Justin R.; Piekos, Edward S.; Torczynski, John R.; Gallis, Michael A.; Gorby, Allen D.

We will present experimental and computational investigations of the thermal performance of microelectromechanical systems (MEMS) as a function of the surrounding gas pressure. Lowering the pressure in MEMS packages reduces gas damping, providing increased sensitivity for certain MEMS sensors; however, such packaging also dramatically affects their thermal performance since energy transfer to the environment is substantially reduced. High-spatial-resolution Raman thermometry was used to measure the temperature profiles on electrically heated, polycrystalline silicon bridges that are nominally 10 microns wide, 2.25 microns thick, 12 microns above the substrate, and either 200 or 400 microns long in nitrogen atmospheres with pressures ranging from 0.05 to 625 Torr. Finite element modeling of the thermal behavior of the MEMS bridges is performed and compared to the experimental results. Noncontinuum gas effects are incorporated into the continuum finite element model by imposing temperature discontinuities at gas-solid interfaces that are determined from noncontinuum simulations. The experimental and simulation results indicate that at pressures below 0.5 Torr the gas-phase heat transfer is negligible compared to heat conduction through the thermal actuator legs. As the pressure increases above 0.5 Torr, the gas-phase heat transfer becomes more significant. At ambient pressures, gas-phase heat transfer drastically impacts the thermal performance. The measured and simulated temperature profiles are in qualitative agreement in the present study. Quantitative agreement between experimental and simulated temperature profiles requires accurate knowledge of temperature-dependent thermophysical properties, the device geometry, and the thermal accommodation coefficient.

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Determination of thermal accommodation coefficients from heat transfer measurements between parallel plates

Trott, Wayne M.; Torczynski, John R.; Gallis, Michael A.; Rader, Daniel J.; Castaeda, Jaime N.

Thermal accommodation coefficients have been derived for a variety of gas-surface combinations using an experimental apparatus developed to measure the pressure dependence of the conductive heat flux between parallel plates at unequal temperature separated by a gas-filled gap. The heat flux is inferred from temperature-difference measurements across the plates in a configuration where the plate temperatures are set with two carefully controlled thermal baths. Temperature-controlled shrouds provide for environmental isolation of the opposing test plates. Since the measured temperature differences in these experiments are very small (typically 0.3 C or less over the entire pressure range), high-precision thermistors are used to acquire the requisite temperature data. High-precision components have also been utilized on the other control and measurement subsystems in this apparatus, including system pressure, gas flow rate, plate alignment, and plate positions. The apparatus also includes the capability for in situ plasma cleaning of the installed test plates. Measured heat-flux results are used in a formula based on Direct Simulation Monte Carlo (DSMC) code calculations to determine the thermal accommodation coefficients. Thermal accommodation coefficients have been determined for three different gases (argon, nitrogen, helium) in contact with various surfaces. Materials include metals and alloys such as aluminum, gold, platinum, and 304 stainless steel. A number of materials important to fabrication of Micro Electro Mechanical Systems (MEMS) devices have also been examined. For most surfaces, coefficient values are near 0.95, 0.85, and 0.45 for argon, nitrogen, and helium, respectively. Only slight differences in accommodation as a function of surface roughness have been seen. Surface contamination appears to have a more significant effect: argon plasma treatment has been observed to reduce thermal accommodation by as much as 0.10 for helium. Mixtures of argon and helium have also been examined, and the results have been compared to DSMC simulations incorporating thermal-accommodation values from single-species experiments.

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Aqueous synthesis and electrical properties of nano-crystalline PLZT capacitors

Diantonio, Christopher; Monson, Todd; Chavez, Thomas P.; Stevens, Tyler E.; Roesler, Alexander; Huber, Dale L.

Devices with nano-crystalline microstructures have been shown to possess improved electrical properties. Further advantages include lower processing temperatures; however, device fabrication from nano-particles poses several challenges. This presentation describes a novel aqueous synthesis technique to produce large batch sizes with minimal waste. The precipitate is readily converted at less than 550 C to a phase pure, nano-crystalline Pb{sub 0.88} La{sub 0.12}(Zr{sub 0.70} Ti{sub 0.30}){sub 0.97} O{sub 3} powder. Complications and solutions to sample fabrication from nano-powders are discussed, including the use of glass sintering aids to improve density and further lower sintering temperatures. Finally, electrical properties are presented to demonstrate the potential benefits of nano-crystalline capacitors.

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Applying insights from repository safety assessments to evaluating impacts of partitioning and transmutation

Swift, Peter

Published analyses of geologic repositories indicate potential for excellent long-term performance for a range of disposal concepts. Estimates of peak dose may be dominated by different radionuclides in different disposal concepts. Thermal loading issues can be addressed by design and operational choices. Impact of waste form lifetime on estimates of peak dose varies for different disposal concepts.

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Understanding and predicting soot generation in turbulent non-premixed jet flames

Shaddix, Christopher R.; Zhang, Jiayao; Oefelein, Joseph; Pickett, Lyle M.

This report documents the results of a project funded by DoD's Strategic Environmental Research and Development Program (SERDP) on the science behind development of predictive models for soot emission from gas turbine engines. Measurements of soot formation were performed in laminar flat premixed flames and turbulent non-premixed jet flames at 1 atm pressure and in turbulent liquid spray flames under representative conditions for takeoff in a gas turbine engine. The laminar flames and open jet flames used both ethylene and a prevaporized JP-8 surrogate fuel composed of n-dodecane and m-xylene. The pressurized turbulent jet flame measurements used the JP-8 surrogate fuel and compared its combustion and sooting characteristics to a world-average JP-8 fuel sample. The pressurized jet flame measurements demonstrated that the surrogate was representative of JP-8, with a somewhat higher tendency to soot formation. The premixed flame measurements revealed that flame temperature has a strong impact on the rate of soot nucleation and particle coagulation, but little sensitivity in the overall trends was found with different fuels. An extensive array of non-intrusive optical and laser-based measurements was performed in turbulent non-premixed jet flames established on specially designed piloted burners. Soot concentration data was collected throughout the flames, together with instantaneous images showing the relationship between soot and the OH radical and soot and PAH. A detailed chemical kinetic mechanism for ethylene combustion, including fuel-rich chemistry and benzene formation steps, was compiled, validated, and reduced. The reduced ethylene mechanism was incorporated into a high-fidelity LES code, together with a moment-based soot model and models for thermal radiation, to evaluate the ability of the chemistry and soot models to predict soot formation in the jet diffusion flame. The LES results highlight the importance of including an optically-thick radiation model to accurately predict gas temperatures and thus soot formation rates. When including such a radiation model, the LES model predicts mean soot concentrations within 30% in the ethylene jet flame.

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Practical issues and applications for vacuum and hermetic microsystems packaging

Fang, Lu; Chu, Dahwey; Ewsuk, Kevin G.

Microsystems packaging involves physically placing and electrically interconnecting a microelectronic device in a package that protects it from and interfaces it with the outside world. When the device requires a hermetic or controlled microenvironment, it is typically sealed within a cavity in the package. Sealing involves placing and attaching a lid, typically by welding, brazing, or soldering. Materials selection (e.g., the epoxy die attach), and process control (e.g., the epoxy curing temperature and time) are critical for reproducible and reliable microsystems packaging. This paper will review some hermetic and controlled microenvironment packaging at Sandia Labs, and will discuss materials, processes, and equipment used to package environmentally sensitive microelectronics (e.g., MEMS and sensors).

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Use of nanofiltration to reduce cooling tower water consumption

Altman, Susan J.

Nanofiltration (NF) can effectively treat cooling-tower water to reduce water consumption and maximize water usage efficiency of thermoelectric power plants. A pilot is being run to verify theoretical calculations. A side stream of water from a 900 gpm cooling tower is being treated by NF with the permeate returning to the cooling tower and the concentrate being discharged. The membrane efficiency is as high as over 50%. Salt rejection ranges from 77-97% with higher rejection for divalent ions. The pilot has demonstrated a reduction of makeup water of almost 20% and a reduction of discharge of over 50%.

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Value of storage with increased renewable penetration

Roach, Jesse D.

The problem statement for this project is: (1) Renewable energy portfolio standards - (a) high penetration of intermittent and variable renewable generation on the grid, (b) utilities constrained by NERC Control Performance Standards, (c) requires additional resources to match generation with load; and (2) mitigation of impacts with energy storage - at what level of renewable penetration does energy storage become an attractive value proposition. Use a simplified, yet robust dispatch model that: (a) incorporates New Mexico Balance Area load and wind generation data, (b) distributes the load among a suite of generators, (c) quantifies increased generation costs with increased penetration of intermittent and variable renewable generation - fuel, startup, shut down, ramping, standby, etc., (d) tracks and quantifies NERC pentalties and violations, and (e) quantifies storage costs. Dispatch model has been constructed and it: (a) accurately distributes a load among a suite of generators, (b) quantifies duty cycle metrics for each of the generators - cumulative energy production, ramping and non ramping duration, spinning reserves, number of start-ups, and shut down durations, etc., (c) quantifies energy exchanges - cumulative exchanges, duration, and number of exchanges, (d) tracks ACE violations.

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Photovoltaic self-assembly

Lavin, Judith M.; Stewart, Constantine A.; Kemp, Richard

This late-start LDRD was focused on the application of chemical principles of self-assembly on the ordering and placement of photovoltaic cells in a module. The drive for this chemical-based self-assembly stems from the escalating prices in the 'pick-and-place' technology currently used in the MEMS industries as the size of chips decreases. The chemical self-assembly principles are well-known on a molecular scale in other material science systems but to date had not been applied to the assembly of cells in a photovoltaic array or module. We explored several types of chemical-based self-assembly techniques, including gold-thiol interactions, liquid polymer binding, and hydrophobic-hydrophilic interactions designed to array both Si and GaAs PV chips onto a substrate. Additional research was focused on the modification of PV cells in an effort to gain control over the facial directionality of the cells in a solvent-based environment. Despite being a small footprint research project worked on for only a short time, the technical results and scientific accomplishments were significant and could prove to be enabling technology in the disruptive advancement of the microelectronic photovoltaics industry.

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Control systems field equipment forensics : what happened to my PLC and how do I fix it?

Parks, Raymond C.

The outline for the presentation is: (1) Advance preparation - (a) Think about attacks before they happen, (b) Configuration Management, (c) Backups, (d) Off-site storage, (e) Design and build for resiliency, (f) Training operators to detect attack; (2) Detection - (a) How do I know I've been attacked, (b) The front-line detection system - operators; (3) Triage - (a) Working through the attack, (b) Law enforcement or business continuity, (c) Deciding what to fix first; (4) Field Equipment Forensics - (a) Engineering Workstation, (b) Projects/Configurations/Programs; and (5) Conclusion and Discussion. Red teaming works for supply chain - Finds the worst attacks across multiple dimensions, Shows where to best expend resources to reduce risk, and Provides positive control of potentially negative activities.

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Staubli TX-90XL robot qualification at the LLIHE

Covert, Timothy T.

The Light Initiated High Explosive (LIHE) Facility uses a robotic arm to spray explosive material onto test items for impulse tests. In 2007, the decision was made to replace the existing PUMA 760 robot with the Staubli TX-90XL. A qualification plan was developed and implemented to verify the safe operating conditions and failure modes of the new system. The robot satisfied the safety requirements established in the qualification plan. A performance issue described in this report remains unresolved at the time of this publication. The final readiness review concluded the qualification of this robot at the LIHE facility.

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Toward robust scalable algebraic multigrid solvers

Tuminaro, Raymond S.; Siefert, Christopher; Hu, Jonathan J.; Gaidamour, Jeremie

This talk highlights some multigrid challenges that arise from several application areas including structural dynamics, fluid flow, and electromagnetics. A general framework is presented to help introduce and understand algebraic multigrid methods based on energy minimization concepts. Connections between algebraic multigrid prolongators and finite element basis functions are made to explored. It is shown how the general algebraic multigrid framework allows one to adapt multigrid ideas to a number of different situations. Examples are given corresponding to linear elasticity and specifically in the solution of linear systems associated with extended finite elements for fracture problems.

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Option study of an orthogonal X-ray radiography axis for pRad at LANSCE area C, Los Alamos

Oliver, Bryan V.; Leckbee, Joshua

We report on an option study of two potential x-ray systems for orthogonal radiography at Area C in the LANSCE facility at Los Alamos National Laboratory. The systems assessed are expected to be near equivalent systems to the presently existing Cygnus capability at the Nevada Test Site. Nominal dose and radiographic resolution of 4 rad (measured at one meter) and 1 mm spot are desired. Both a system study and qualitative design are presented as well as estimated cost and schedule. Each x-ray system analyzed is designed to drive a rod-pinch electron beam diode capable of producing the nominal dose and spot.

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Drying/self-assembly of nanoparticle suspensions

Grest, Gary S.; Cheng, Shengfeng; Lechman, Jeremy B.; Plimpton, Steven J.

The most feasible way to disperse particles in a bulk material or control their packing at a substrate is through fluidization in a carrier that can be processed with well-known techniques such as spin, drip and spray coating, fiber drawing, and casting. The next stage in the processing is often solidification involving drying by solvent evaporation. While there has been significant progress in the past few years in developing discrete element numerical methods to model dense nanoparticle dispersion/suspension rheology which properly treat the hydrodynamic interactions of the solvent, these methods cannot at present account for the volume reduction of the suspension due to solvent evaporation. As part of LDRD project FY-101285 we have developed and implemented methods in the current suite of discrete element methods to remove solvent particles and volume, and hence solvent mass from the liquid/vapor interface of a suspension to account for volume reduction (solvent drying) effects. To validate the methods large scale molecular dynamics simulations have been carried out to follow the evaporation process at the microscopic scale.

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Measurements of prompt radiation induced conductivity of Kapton

Hartman, Elmer F.; Zarick, Thomas A.; Sheridan, Timothy J.

We performed measurements of the prompt radiation induced conductivity in thin samples of Kapton (polyimide) at the Little Mountain Medusa LINAC facility in Ogden, UT. Three mil samples were irradiated with a 0.5 {mu}s pulse of 20 MeV electrons, yielding dose rates of 1E9 to 1E10 rad/s. We applied variable potentials up to 2 kV across the samples and measured the prompt conduction current. Analysis rendered prompt conductivity coefficients between 6E-17 and 2E-16 mhos/m per rad/s, depending on the dose rate and the pulse width.

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Heat treatment and processing effects on precious metal electrical contact alloys

Robino, Charles V.; Reece, Mark; Kilgo, Alice C.

The effects of heat treatment parameters were examined in complex electrical contact alloys containing Pd-Ag-Cu-Au-Pt. These alloys (Paliney tradename, Deringer-Ney Inc., Bloomfield, CT) are strengthened by precipitation reactions. During processing such as glass-to-metal joining in hermetic connectors, if the cooling rate is too slow, discontinuous precipitation (DP) of lamellar 2nd phases can spoil the strengthening effect. Two different solutionizing temperatures were employed and the effects of cooling rates between 6 C/min and >200 C/min were studied. Novel metallographic techniques were developed to reveal the microstructure of these corrosion resistant alloys and quantitative image analysis (QIA) was used to determine the amount of 2nd phase precipitates. Vickers and Knoop microhardness testing was performed to determine the effects of heat treatment parameters on mechanical properties.

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Statistical criteria for characterizing irradiance time series

Hansen, Clifford; Stein, Joshua; Ellis, Abraham

We propose and examine several statistical criteria for characterizing time series of solar irradiance. Time series of irradiance are used in analyses that seek to quantify the performance of photovoltaic (PV) power systems over time. Time series of irradiance are either measured or are simulated using models. Simulations of irradiance are often calibrated to or generated from statistics for observed irradiance and simulations are validated by comparing the simulation output to the observed irradiance. Criteria used in this comparison should derive from the context of the analyses in which the simulated irradiance is to be used. We examine three statistics that characterize time series and their use as criteria for comparing time series. We demonstrate these statistics using observed irradiance data recorded in August 2007 in Las Vegas, Nevada, and in June 2009 in Albuquerque, New Mexico.

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Waste IPSC : Thermal-Hydrologic-Chemical-Mechanical (THCM) modeling and simulation

Arguello, Jose G.; Wang, Yifeng

Waste IPSC Objective is to develop an integrated suite of high performance computing capabilities to simulate radionuclide movement through the engineered components and geosphere of a radioactive waste storage or disposal system: (1) with robust thermal-hydrologic-chemical-mechanical (THCM) coupling; (2) for a range of disposal system alternatives (concepts, waste form types, engineered designs, geologic settings); (3) for long time scales and associated large uncertainties; (4) at multiple model fidelities (sub-continuum, high-fidelity continuum, PA); and (5) in accordance with V&V and software quality requirements. THCM Modeling collaborates with: (1) Other Waste IPSC activities: Sub-Continuum Processes (and FMM), Frameworks and Infrastructure (and VU, ECT, and CT); (2) Waste Form Campaign; (3) Used Fuel Disposition (UFD) Campaign; and (4) ASCEM.

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Results 71201–71400 of 99,299
Results 71201–71400 of 99,299