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Advanced Measurement and Modeling Techniques for Improved SOFC Cathodes

Description: The goal of this project was to develop an improved understanding of factors governing performance and degradation of mixed-conducting SOFC cathodes. Two new diagnostic tools were developed to help achieve this goal: (1) microelectrode half-cells for improved isolation of cathode impedance on thin electrolytes, and (2) nonlinear electrochemical impedance spectroscopy (NLEIS), a variant of traditional impedance that allows workers to probe nonlinear rates as a function of frequency. After reporting on the development and efficacy of these tools, this document reports on the use of these and other tools to better understand performance and degradation of cathodes based on the mixed conductor La{sub 1-x}Sr{sub x}CoO{sub 3-{delta}} (LSC) on gadolinia or samaria-doped ceria (GDC or SDC). We describe the use of NLEIS to measure O{sub 2} exchange on thin-film LSC electrodes, and show that O{sub 2} exchange is most likely governed by dissociative adsorption. We also describe parametric studies of porous LSC electrodes using impedance and NLEIS. Our results suggest that O{sub 2} exchange and ion transport co-limit performance under most relevant conditions, but it is O{sub 2} exchange that is most sensitive to processing, and subject to the greatest degradation and sample-to-sample variation. We recommend further work that focuses on electrodes of well-defined or characterized geometry, and probes the details of surface structure, composition, and impurities. Parallel work on primarily electronic conductors (LSM) would also be of benefit to developers, and to improved understanding of surface vs. bulk diffusion.
Date: December 31, 2006
Creator: Adler, Stuart; Dunyushkina, L.; Huff, S.; Lu, Y. & Wilson, J.
Partner: UNT Libraries Government Documents Department

A Bloch-Torrey Equation for Diffusion in a Deforming Media

Description: Diffusion Tensor Magnetic Resonance Imaging (DTMRI)technique enables the measurement of diffusion parameters and therefore,informs on the structure of the biological tissue. This technique isapplied with success to the static organs such as brain. However, thediffusion measurement on the dynamically deformable organs such as thein-vivo heart is a complex problem that has however a great potential inthe measurement of cardiac health. In order to understand the behavior ofthe Magnetic Resonance (MR)signal in a deforming media, the Bloch-Torreyequation that leads the MR behavior is expressed in general curvilinearcoordinates. These coordinates enable to follow the heart geometry anddeformations through time. The equation is finally discretized andpresented in a numerical formulation using implicit methods, in order toget a stable scheme that can be applied to any smooth deformations.Diffusion process enables the link between the macroscopic behavior ofmolecules and themicroscopic structure in which they evolve. Themeasurement of diffusion in biological tissues is therefore of majorimportance in understanding the complex underlying structure that cannotbe studied directly. The Diffusion Tensor Magnetic ResonanceImaging(DTMRI) technique enables the measurement of diffusion parametersand therefore provides information on the structure of the biologicaltissue. This technique has been applied with success to static organssuch as the brain. However, diffusion measurement of dynamicallydeformable organs such as the in-vivo heart remains a complex problem,which holds great potential in determining cardiac health. In order tounderstand the behavior of the magnetic resonance (MR) signal in adeforming media, the Bloch-Torrey equation that defines the MR behavioris expressed in general curvilinear coordinates. These coordinates enableus to follow the heart geometry and deformations through time. Theequation is finally discretized and presented in a numerical formulationusing implicit methods in order to derive a stable scheme that can beapplied to any smooth deformations.
Date: December 29, 2006
Creator: Rohmer, Damien & Gullberg, Grant T.
Partner: UNT Libraries Government Documents Department

Simulation and Analysis of Large-Scale Compton Imaging Detectors

Description: We perform simulations of two types of large-scale Compton imaging detectors. The first type uses silicon and germanium detector crystals, and the second type uses silicon and CdZnTe (CZT) detector crystals. The simulations use realistic detector geometry and parameters. We analyze the performance of each type of detector, and we present results using receiver operating characteristics (ROC) curves.
Date: December 27, 2006
Creator: Manini, H A; Lange, D J & Wright, D M
Partner: UNT Libraries Government Documents Department

Verification Test Suite for Physics Simulation Codes

Description: The DOE/NNSA Advanced Simulation & Computing (ASC) Program directs the development, demonstration and deployment of physics simulation codes. The defensible utilization of these codes for high-consequence decisions requires rigorous verification and validation of the simulation software. The physics and engineering codes used at Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL), and Sandia National Laboratory (SNL) are arguably among the most complex utilized in computational science. Verification represents an important aspect of the development, assessment and application of simulation software for physics and engineering. The purpose of this note is to formally document the existing tri-laboratory suite of verification problems used by LANL, LLNL, and SNL, i.e., the Tri-Lab Verification Test Suite. Verification is often referred to as ensuring that ''the [discrete] equations are solved [numerically] correctly''. More precisely, verification develops evidence of mathematical consistency between continuum partial differential equations (PDEs) and their discrete analogues, and provides an approach by which to estimate discretization errors. There are two variants of verification: (1) code verification, which compares simulation results to known analytical solutions, and (2) calculation verification, which estimates convergence rates and discretization errors without knowledge of a known solution. Together, these verification analyses support defensible verification and validation (V&V) of physics and engineering codes that are used to simulate complex problems that do not possess analytical solutions. Discretization errors (e.g., spatial and temporal errors) are embedded in the numerical solutions of the PDEs that model the relevant governing equations. Quantifying discretization errors, which comprise only a portion of the total numerical simulation error, is possible through code and calculation verification. Code verification computes the absolute value of discretization errors relative to an exact solution of the governing equations. In contrast, calculation verification, which does not utilize a reference solution, combines an assessment of stable self-convergence and exact solution ...
Date: December 21, 2006
Creator: Brock, J S; Kamm, J R; Rider, W J; Brandon, S; Woodward, C; Knupp, P et al.
Partner: UNT Libraries Government Documents Department

Evaluating Cumulative Ecosystem Response to Restoration Projects in the Columbia River Estuary, Annual Report 2005

Description: This report is the second annual report of a six-year project to evaluate the cumulative effects of habitat restoration projects in the Columbia River Estuary, conducted by Pacific Northwest National Laboratory's Marine Sciences Laboratory, NOAA's National Marine Fisheries Service Pt. Adams Biological Field Station, and the Columbia River Estuary Study Taskforce for the US Army Corps of Engineers. In 2005, baseline data were collected on two restoration sites and two associated reference sites in the Columbia River estuary. The sites represent two habitat types of the estuary--brackish marsh and freshwater swamp--that have sustained substantial losses in area and that may play important roles for salmonids. Baseline data collected included vegetation and elevation surveys, above and below-ground biomass, water depth and temperature, nutrient flux, fish species composition, and channel geometry. Following baseline data collection, three kinds of restoration actions for hydrological reconnection were implemented in several locations on the sites: tidegate replacements (2) at Vera Slough, near the city of Astoria in Oregon State, and culvert replacements (2) and dike breaches (3) at Kandoll Farm in the Grays River watershed in Washington State. Limited post-restoration data were collected: photo points, nutrient flux, water depth and temperature, and channel cross-sections. In subsequent work, this and additional post-restoration data will be used in conjunction with data from other sites to estimate net effects of hydrological reconnection restoration projects throughout the estuary. This project is establishing methods for evaluating the effectiveness of individual projects and a framework for assessing estuary-wide cumulative effects including a protocol manual for monitoring restoration and reference sites.
Date: December 20, 2006
Creator: Diefenderfer, Heida L.; Thom, Ronald M.; Borde, Amy B.; Roegner, G. C.; Whiting, Allan H.; Johnson, Gary E. et al.
Partner: UNT Libraries Government Documents Department

New Dimensions for Wound Strings:The Modular Transform of Geometry to Topology

Description: We show, using a theorem of Milnor and Margulis, that string theory on compact negatively curved spaces grows new effective dimensions as the space shrinks, generalizing and contextualizing the results in [1]. Milnor's theorem relates negative sectional curvature on a compact Riemannian manifold to exponential growth of its fundamental group, which translates in string theory to a higher effective central charge arising from winding strings. This exponential density of winding modes is related by modular invariance to the infrared small perturbation spectrum. Using self-consistent approximations valid at large radius, we analyze this correspondence explicitly in a broad set of time-dependent solutions, finding precise agreement between the effective central charge and the corresponding infrared small perturbation spectrum. This indicates a basic relation between geometry, topology, and dimensionality in string theory.
Date: December 18, 2006
Creator: McGreevy, John; Silverstein, Eva & Starr, David
Partner: UNT Libraries Government Documents Department

Status report on high fidelity reactor simulation.

Description: This report presents the effort under way at Argonne National Laboratory toward a comprehensive, integrated computational tool intended mainly for the high-fidelity simulation of sodium-cooled fast reactors. The main activities carried out involved neutronics, thermal hydraulics, coupling strategies, software architecture, and high-performance computing. A new neutronics code, UNIC, is being developed. The first phase involves the application of a spherical harmonics method to a general, unstructured three-dimensional mesh. The method also has been interfaced with a method of characteristics. The spherical harmonics equations were implemented in a stand-alone code that was then used to solve several benchmark problems. For thermal hydraulics, a computational fluid dynamics code called Nek5000, developed in the Mathematics and Computer Science Division for coupled hydrodynamics and heat transfer, has been applied to a single-pin, periodic cell in the wire-wrap geometry typical of advanced burner reactors. Numerical strategies for multiphysics coupling have been considered and higher-accuracy efficient methods proposed to finely simulate coupled neutronic/thermal-hydraulic reactor transients. Initial steps have been taken in order to couple UNIC and Nek5000, and simplified problems have been defined and solved for testing. Furthermore, we have begun developing a lightweight computational framework, based in part on carefully selected open source tools, to nonobtrusively and efficiently integrate the individual physics modules into a unified simulation tool.
Date: December 11, 2006
Creator: Palmiotti, G.; Smith, M.; Rabiti, C.; Lewis, E.; Yang, W.; Leclere,M. et al.
Partner: UNT Libraries Government Documents Department

Conversion of Input Data between KENO and MCNP File Formats for Computer Criticality Assessments

Description: KENO is a Monte Carlo criticality code that is maintained by Oak Ridge National Laboratory (ORNL). KENO is included in the SCALE (Standardized Computer Analysis for Licensing Evaluation) package. KENO is often used because it was specifically designed for criticality calculations. Because KENO has convenient geometry input, including the treatment of lattice arrays of materials, it is frequently used for production calculations. Monte Carlo N-Particle (MCNP) is a Monte Carlo transport code maintained by Los Alamos National Laboratory (LANL). MCNP has a powerful 3D geometry package and an extensive cross section database. It is a general-purpose code and may be used for calculations involving shielding or medical facilities, for example, but can also be used for criticality calculations. MCNP is becoming increasingly more popular for performing production criticality calculations. Both codes have their own specific advantages. After a criticality calculation has been performed with one of the codes, it is often desirable (or may be a safety requirement) to repeat the calculation with the other code to compare the important parameters using a different geometry treatment and cross section database. This manual conversion of input files between the two codes is labor intensive. The industry needs the capability of converting geometry models between MCNP and KENO without a large investment in manpower. The proposed conversion package will aid the user in converting between the codes. It is not intended to be used as a “black box”. The resulting input file will need to be carefully inspected by criticality safety personnel to verify the intent of the calculation is preserved in the conversion. The purpose of this package is to help the criticality specialist in the conversion process by converting the geometry, materials, and pertinent data cards.
Date: November 30, 2006
Creator: Schwarz, Randolph A.; Carter, Leland L. & L., Schwarz Alysia
Partner: UNT Libraries Government Documents Department

TEM Studies of Carbon Coated LiFePO4 after Charge DischargeCycling

Description: Carbon coating has proven to be a successful approach toimprove the rate capability of LiFePO4 used in rechargeable Li-ionbatteries. Investigations of the microstructure of carbon coated LiFePO4after charge discharge cycling shows that the carbon surface layerremains intact over 100 cycles. We find micro cracks in the cycledmaterial that extend parallel to low indexed lattice planes. Ourobservations differ from observations made by other authors. However thedifferences between the orientations of crack surfaces in both studiescan be reconciled considering the location of weak bonds in the unit celland specimen geometry as well as elastic stress fields ofdislocation.
Date: November 30, 2006
Creator: Gabrisch, H.; Wilcox, J. & Doeff, M.
Partner: UNT Libraries Government Documents Department

Ultrafast Coherent Diffractive Imaging at FLASH

Description: Using the FLASH facility we have demonstrated high-resolution coherent diffractive imaging with single soft-X-ray free-electron laser pulses [1]. The intense focused FEL pulse gives a high resolution low-noise coherent diffraction pattern of an object before that object turns into a plasma and explodes. Our experiments are an important milestone in the development of single-particle diffractive imaging with future X-ray free-electron lasers [2, 3]. Our apparatus provides a new and unique tool at FLASH to perform imaging of biological specimens beyond conventional radiation damage resolution limits [2, 4] and to acquire images of ultrafast processes initiated by an FEL pulse or other laser pulse. Coherent diffractive imaging is an ideal method for high-resolution ultrafast imaging with an FEL. Since no optical element is required, the method can in principle be scaled to atomic resolution with short enough wavelength. Spatial and temporal coherence are necessary to ensure that the scattered light waves from all positions across the sample are correlated when they interfere at the detector, giving rise to a coherent diffraction pattern that can be phased and inverted to give a high-resolution image of the sample. In contrast to crystals, where scattering from the many unit cells constructively interfere to give Bragg spots, the coherent diffraction pattern of a non-periodic object is continuous. Such a coherent diffraction pattern contains as much as twice the information content of the pattern of its crystallized periodic counterpart--exactly the amount of information needed to solve the phase problem and deterministically invert the pattern to yield an image of the object [5, 6]. The computer algorithm that performs this function replaces the analogue computations of a lens: summing the complex-valued amplitudes of scattered waves to form an image at a particular plane. Our experimental geometry is shown in Fig. 1. We focus a coherent X-ray pulse ...
Date: November 29, 2006
Creator: Chapman, H N
Partner: UNT Libraries Government Documents Department

Time-varying Reeb Graphs: A Topological Framework Supporting the Analysis of Continuous Time-varying Data

Description: I present time-varying Reeb graphs as a topological framework to support the analysis of continuous time-varying data. Such data is captured in many studies, including computational fluid dynamics, oceanography, medical imaging, and climate modeling, by measuring physical processes over time, or by modeling and simulating them on a computer. Analysis tools are applied to these data sets by scientists and engineers who seek to understand the underlying physical processes. A popular tool for analyzing scientific datasets is level sets, which are the points in space with a fixed data value s. Displaying level sets allows the user to study their geometry, their topological features such as connected components, handles, and voids, and to study the evolution of these features for varying s. For static data, the Reeb graph encodes the evolution of topological features and compactly represents topological information of all level sets. The Reeb graph essentially contracts each level set component to a point. It can be computed efficiently, and it has several uses: as a succinct summary of the data, as an interface to select meaningful level sets, as a data structure to accelerate level set extraction, and as a guide to remove noise. I extend these uses of Reeb graphs to time-varying data. I characterize the changes to Reeb graphs over time, and develop an algorithm that can maintain a Reeb graph data structure by tracking these changes over time. I store this sequence of Reeb graphs compactly, and call it a time-varying Reeb graph. I augment the time-varying Reeb graph with information that records the topology of level sets of all level values at all times, that maintains the correspondence of level set components over time, and that accelerates the extraction of level sets for a chosen level value and time. Scientific data sampled in space-time ...
Date: November 28, 2006
Creator: Mascarenhas, A
Partner: UNT Libraries Government Documents Department

Impedance Analysis of Electrochemical NOx Sensor Using a Au/Yttria-Stabilized Zirconia (YSZ)/Au cell

Description: An electrochemical cell employing a YSZ electrolyte and two Au electrodes was utilized as a model system for investigating the mechanisms responsible for impedance metric NO{sub x} (NO and NO{sub 2}) sensing. The cell consists of two dense Au electrodes on top of a porous/dense YSZ bilayer structure (with the additional porous layer present only under the Au electrodes). Both electrodes were co-located on the same side of the cell, resulting in an in-plane geometry for the current path. The porous YSZ appears to extend the triple phase boundary and allows for enhanced NO{sub x} sensing performance, although the exact role of the porous layer is not completely understood. Impedance data were obtained over the frequency range of 0.1 Hz to 1 MHz, and over a range of oxygen (2 to 18.9%) and NO{sub x} (10 to 100 ppm) concentrations, and temperatures (600 to 700 C). Data were fit with an equivalent circuit, and the values of the circuit elements were obtained for different concentrations and temperatures. Changes in a single low-frequency arc were found to correlate with concentration changes, and to be temperature dependent. In the absence of NO{sub x}, the effect of O{sub 2} on the low-frequency resistance could be described by a power law, and the temperature dependence described by a single apparent activation energy at all O{sub 2} concentrations. When both O{sub 2} and NO{sub x} were present, however, the power law exponent varied as a function of both temperature and concentration, and the apparent activation energy also showed dual dependence. Adsorption mechanisms are discussed as possibilities for the rate-limiting steps.
Date: November 20, 2006
Creator: Woo, L Y; Martin, L P; Glass, R S & Gorte, R J
Partner: UNT Libraries Government Documents Department

Calculation of Photoneutrons from Varian Clinac Accelerators and Their Transmissions in Materials

Description: Monte Carlo calculations of the giant-dipole-resonance photoneutrons (GRN) around the Varian Clinac 2100C/2300C medical accelerator heads (10-20 MV modes) were made using the coupled EGS4-MORSE code. The actual head materials and geometries were simulated in great detail using the Combinatorial Geometry facility of MORSE. The neutron production (i.e., sites and yields) was calculated with EGS4 and, then, the neutron transport in the accelerator head was done with MORSE. Both the evaporation and direct neutron components of the GRN were considered by incorporating the EVAP4 code and an empirical algorithm, respectively, into MORSE. With the calculated neutron spectra around the head as source terms, MCNP4a was used to estimate the corresponding dose equivalent transmission (considering both the neutron attenuation and the build-up of captured gamma rays) in several different types of concrete. The calculated results of the absolute neutron fluence and spectra around the heads, as well as the transmission curves, are presented and discussed.
Date: November 13, 2006
Creator: Liu, J.C.; Kase, K.R.; Mao, X.S.; Nelson, W.R.; Kleck, J.H.; Johnson, S. et al.
Partner: UNT Libraries Government Documents Department

Quantum Monte-Carlo Study of Electron Correlation in Heterostructure Quantum Dots

Description: The goal of this project is to study electron correlation in a confined geometry (quantum dots) within the two-dimensional quantum well in the sandwiches of two semiconductor materials. For these systems one is able to tune the electronic properties by controlling the size and the electron number, creating tremendous potential for novel applications. Much effort in this emerging field has been devoted to producing entangled states that are required for quantum information processing. At the same time, new physical phenomena have emerged from these artificial structures. Adding electrons to a quantum dot is more complicated than filling up discrete energy levels due to electron correlation. Therefore, our project is focusing on employing the state-of-the-art quantum Monte Carlo methods to study the electron-electron interaction. A close examination of the breakdown of Hund's rules and electron localization has been conducted in our simulations. The results are summarized in this report.
Date: November 12, 2006
Creator: Chou, Mei-Yin
Partner: UNT Libraries Government Documents Department

Monte Carlo Particle Transport Capability for Inertial Confinement Fusion Applications

Description: A time-dependent massively-parallel Monte Carlo particle transport calculational module (ParticleMC) for inertial confinement fusion (ICF) applications is described. The ParticleMC package is designed with the long-term goal of transporting neutrons, charged particles, and gamma rays created during the simulation of ICF targets and surrounding materials, although currently the package treats neutrons and gamma rays. Neutrons created during thermonuclear burn provide a source of neutrons to the ParticleMC package. Other user-defined sources of particles are also available. The module is used within the context of a hydrodynamics client code, and the particle tracking is performed on the same computational mesh as used in the broader simulation. The module uses domain-decomposition and the MPI message passing interface to achieve parallel scaling for large numbers of computational cells. The Doppler effects of bulk hydrodynamic motion and the thermal effects due to the high temperatures encountered in ICF plasmas are directly included in the simulation. Numerical results for a three-dimensional benchmark test problem are presented in 3D XYZ geometry as a verification of the basic transport capability. In the full paper, additional numerical results including a prototype ICF simulation will be presented.
Date: November 6, 2006
Creator: Brantley, P S & Stuart, L M
Partner: UNT Libraries Government Documents Department

Multi-Grained Level of Detail for Rendering Complex Meshes Using a Hierarchical Seamless Texture Atlas

Description: Previous algorithms for view-dependent level of detail provide local mesh refinements either at the finest granularity or at a fixed, coarse granularity. The former provides triangle-level adaptation, often at the expense of heavy CPU usage and low triangle rendering throughput; the latter improves CPU usage and rendering throughput by operating on groups of triangles. We present a new multiresolution hierarchy and associated algorithms that provide adaptive granularity. This multi-grained hierarchy allows independent control of the number of hierarchy nodes processed on the CPU and the number of triangles to be rendered on the GPU. We employ a seamless texture atlas style of geometry image as a GPU-friendly data organization, enabling efficient rendering and GPU-based stitching of patch borders. We demonstrate our approach on both large triangle meshes and terrains with up to billions of vertices.
Date: November 6, 2006
Creator: Niski, K; Purnomo, B & Cohen, J
Partner: UNT Libraries Government Documents Department

Coherent Control of Optically Generated and Detected Picosecond Surface Acoustic Phonons

Description: Coherent control of elementary optical excitations is a key issue in ultrafast materials science. Manipulation of electronic and vibronic excitations in solids as well as chemical and biological systems on ultrafast time scales has attracted a great deal of attention recently. In semiconductors, coherent control of vibronic excitations has been demonstrated for bulk acoustic and optical phonons generated in superlattice structures. The bandwidth of these approaches is typically fully utilized by employing a 1-D geometry where the laser spot size is much larger than the superlattice repeat length. In this presentation we demonstrate coherent control of optically generated picosecond surface acoustic waves using sub-optical wavelength absorption gratings. The generation and detection characteristics of two material systems are investigated (aluminum absorption gratings on Si and GaAs substrates).
Date: November 1, 2006
Creator: Hurley, David H.
Partner: UNT Libraries Government Documents Department

GBL-2D Version 1.0: a 2D geometry boolean library.

Description: This report describes version 1.0 of GBL-2D, a geometric Boolean library for 2D objects. The library is written in C++ and consists of a set of classes and routines. The classes primarily represent geometric data and relationships. Classes are provided for 2D points, lines, arcs, edge uses, loops, surfaces and mask sets. The routines contain algorithms for geometric Boolean operations and utility functions. Routines are provided that incorporate the Boolean operations: Union(OR), XOR, Intersection and Difference. A variety of additional analytical geometry routines and routines for importing and exporting the data in various file formats are also provided. The GBL-2D library was originally developed as a geometric modeling engine for use with a separate software tool, called SummitView [1], that manipulates the 2D mask sets created by designers of Micro-Electro-Mechanical Systems (MEMS). However, many other practical applications for this type of software can be envisioned because the need to perform 2D Boolean operations can arise in many contexts.
Date: November 1, 2006
Creator: McBride, Cory L. (Elemental Technologies, American Fort, UT); Schmidt, Rodney Cannon; Yarberry, Victor R. & Meyers, Ray J. (Elemental Technologies, American Fort, UT)
Partner: UNT Libraries Government Documents Department

Geologic technical assessment of the Stratton Ridge salt dome, Texas, for potential expansion of the U.S. strategic petroleum reserve.

Description: The Stratton Ridge salt dome is a large salt diapir located only some ten miles from the currently active Strategic Petroleum Reserve Site at Bryan Mound, Texas. The dome is approximately 15 miles south-southwest of Houston. The Stratton Ridge salt dome has been intensively developed, in the desirable central portions, with caverns for both brine production and product storage. This geologic technical assessment indicates that the Stratton Ridge salt dome may be considered a viable, if less-than-desirable, candidate site for potential expansion of the Strategic Petroleum Reserve (SPR). Past development of underground caverns significantly limits the potential options for use by the SPR. The current conceptual design layout of proposed caverns for such an expansion facility is based upon a decades-old model of salt geometry, and it is unacceptable, according to this reinterpretation of salt dome geology. The easternmost set of conceptual caverns are located within a 300-ft buffer zone of a very major boundary shear zone, fault, or other structural feature of indeterminate origin. This structure transects the salt stock and subdivides it into an shallow western part and a deeper eastern part. In places, the distance from this structural boundary to the design-basis caverns is as little as 150 ft. A 300-ft distance from this boundary is likely to be the minimum acceptable stand-off, from both a geologic and a regulatory perspective. Repositioning of the proposed cavern field is possible, as sufficient currently undeveloped salt acreage appears to be available. However, such reconfiguration would be subject to limitations related to land-parcel boundaries and other existing infrastructure and topographic constraints. More broadly speaking, the past history of cavern operations at the Stratton Ridge salt dome indicates that operation of potential SPR expansion caverns at this site may be difficult, and correspondingly expensive. Although detailed information is difficult to come ...
Date: November 1, 2006
Creator: Rautman, Christopher Arthur; Snider, Anna C. & Looff, Karl M. (Geologic Consultant, Lovelady, TX)
Partner: UNT Libraries Government Documents Department

High-Temperature High-Power Packaging Techniques for HEV Traction Applications

Description: A key issue associated with the wider adoption of hybrid-electric vehicles (HEV) and plug in hybrid-electric vehicles (PHEV) is the implementation of the power electronic systems that are required in these products. One of the primary industry goals is the reduction in the price of these vehicles relative to the cost of traditional gasoline powered vehicles. Today these systems, such as the Prius, utilize one coolant loop for the engine at approximately 100 C coolant temperatures, and a second coolant loop for the inverter at 65 C. One way in which significant cost reduction of these systems could be achieved is through the use of a single coolant loop for both the power electronics as well as the internal combustion engine (ICE). This change in coolant temperature significantly increases the junction temperatures of the devices and creates a number of challenges for both device fabrication and the assembly of these devices into inverters and converters for HEV and PHEV applications. Traditional power modules and the state-of-the-art inverters in the current HEV products, are based on chip and wire assembly and direct bond copper (DBC) on ceramic substrates. While a shift to silicon carbide (SiC) devices from silicon (Si) devices would allow the higher operating temperatures required for a single coolant loop, it also creates a number of challenges for the assembly of these devices into power inverters. While this traditional packaging technology can be extended to higher temperatures, the key issues are the substrate material and conductor stability, die bonding material, wire bonds, and bond metallurgy reliability as well as encapsulation materials that are stable at high operating temperatures. The larger temperature differential during power cycling, which would be created by higher coolant temperatures, places tremendous stress on traditional aluminum wire bonds that are used to interconnect power devices. Selection ...
Date: November 1, 2006
Creator: Elshabini, Aicha & Barlow, Fred D.
Partner: UNT Libraries Government Documents Department

LENS repair and modification of metal NW components:materials and applications guide.

Description: Laser Engineered Net Shaping{trademark} (LENS{reg_sign}) is a unique, layer additive, metal manufacturing technique that offers the ability to create fully dense metal features and components directly from a computer solid model. LENS offers opportunities to repair and modify components by adding features to existing geometry, refilling holes, repairing weld lips, and many other potential applications. The material deposited has good mechanical properties with strengths typically slightly higher that wrought material due to grain refinement from a quickly cooling weld pool. The result is a material with properties similar to cold worked material, but without the loss in ductility traditionally seen with such treatments. Furthermore, 304L LENS material exhibits good corrosion resistance and hydrogen compatibility. This report gives a background of the LENS process including materials analysis addressing the requirements of a number of different applications. Suggestions are given to aid both the product engineer and the process engineer in the successful utilization of LENS for their applications. The results of testing on interface strength, machinability, weldability, corrosion resistance, geometric effects, heat treatment, and repair strategy testing are all included. Finally, the qualification of the LENS process is briefly discussed to give the user confidence in selecting LENS as the process of choice for high rigor applications. The testing showed LENS components to have capability in repair/modification applications requiring complex castings (W80-3 D-Bottle bracket), thin wall parts requiring metal to be rebuilt onto the part (W87 Firing Set Housing and Y-12 Test Rings), the filling of counterbores for use in reservoir reclamation welding (SRNL hydrogen compatibility study) and the repair of surface defects on pressure vessels (SRNL gas bottle repair). The material is machinable, as testing has shown that LENS deposited material machines similar to that of welded metal. Tool wear is slightly higher in LENS material than in wrought material, ...
Date: November 1, 2006
Creator: Smugeresky, John E. (Sandia National Laboratories, Livermore, CA); Gill, David Dennis; Oberhaus, Jason (BWXT Y-12); Adams, Thad (Savannah River National Laboratory) & VanCamp, Chad (Kansas City Plant)
Partner: UNT Libraries Government Documents Department

Detailed Structure of the X-Ray Jet in 4C 19.44 (=PKS1354+195)

Description: We investigate the variations of the magnetic field, Doppler factor, and relativistic particle density along the jet of a quasar at z=0.72. We chose 4C 19.44 for this study because of its length and straight morphology. The 18 arcsec length of the jet provides many independent resolution elements in the Chandra X-ray image. The straightness suggests that geometry factors, although uncertain, are almost constant along the jet. We assume the X-ray emission is from inverse Compton scattering of the cosmic microwave background. With the aid of assumptions about jet alignment, equipartition between magnetic-field and relativistic-particle energy, and filling factors, we find that the jet is in bulk relativistic motion with a Doppler factor {approx} 6 at an angle no more than 10{sup o} to the line of sight over deprojected distances {approx} 150-600 kpc from the quasar, and with a magnetic field {approx} 10 {micro}Gauss.
Date: October 31, 2006
Creator: Schwartz, Daniel A.; Harris, D.E.; Landt, H.; Siemiginowska, A.; Observ., /Smithsonian Astrophys.; Perlman, E.S. et al.
Partner: UNT Libraries Government Documents Department

Fracture Dissolution of Carbonate Rock: An Innovative Process for Gas Storage

Description: The goal of the project is to develop and assess the feasibility and economic viability of an innovative concept that may lead to commercialization of new gas-storage capacity near major markets. The investigation involves a new approach to developing underground gas storage in carbonate rock, which is present near major markets in many areas of the United States. Because of the lack of conventional gas storage and the projected growth in demand for storage capacity, many of these areas are likely to experience shortfalls in gas deliverability. Since depleted gas reservoirs and salt formations are nearly non-existent in many areas, alternatives to conventional methods of gas storage are required. The need for improved methods of gas storage, particularly for ways to meet peak demand, is increasing. Gas-market conditions are driving the need for higher deliverability and more flexibility in injection/withdrawal cycling. In order to meet these needs, the project involves an innovative approach to developing underground storage capacity by creating caverns in carbonate rock formations by acid dissolution. The basic concept of the acid-dissolution method is to drill to depth, fracture the carbonate rock layer as needed, and then create a cavern using an aqueous acid to dissolve the carbonate rock. Assessing feasibility of the acid-dissolution method included a regional geologic investigation. Data were compiled and analyzed from carbonate formations in six states: Indiana, Ohio, Kentucky, West Virginia, Pennsylvania, and New York. To analyze the requirements for creating storage volume, the following aspects of the dissolution process were examined: weight and volume of rock to be dissolved; gas storage pressure, temperature, and volume at depth; rock solubility; and acid costs. Hydrochloric acid was determined to be the best acid to use because of low cost, high acid solubility, fast reaction rates with carbonate rock, and highly soluble products (calcium chloride) ...
Date: October 31, 2006
Creator: Castle, James W.; Falta, Ronald W.; Bruce, David; Murdoch, Larry; Brame, Scott E. & Brooks, Donald
Partner: UNT Libraries Government Documents Department

Geometrically induced metastability and holography

Description: We construct metastable configurations of branes and anti-branes wrapping 2-spheres inside local Calabi-Yau manifolds and study their large N duals. These duals are Calabi-Yau manifolds in which the wrapped 2-spheres have been replaced by 3-spheres with flux through them, and supersymmetry is spontaneously broken. The geometry of the non-supersymmetric vacuum is exactly calculable to all orders of the't Hooft parameter, and to the leading order in 1/N. The computation utilizes the same matrix model techniques that were used in the supersymmetric context. This provides a novel mechanism for breaking supersymmetry in the context of flux compactifications.
Date: October 23, 2006
Creator: Aganagic, Mina; Aganagic, Mina; Beem, Christopher; Seo, Jihye & Vafa, Cumrun
Partner: UNT Libraries Government Documents Department