Development of Key Technologies for White Lighting Based on Light-Emitting Diodes (LEDs) (open access)

Development of Key Technologies for White Lighting Based on Light-Emitting Diodes (LEDs)

This program was organized to focus on materials development issues critical to the acceleration of solid-state lighting, and was split into three major thrust areas: (1) study of dislocation density reduction for GaN grown on sapphire using 'cantilever epitaxy', and the impact of dislocation density on the performance of state-of-the-art high-power LEDs; (2) the evaluation of in situ techniques for monitoring gas phase chemistry and the properties of GaN-based layers during metal-organic vapor phase epitaxy (MOCVD), and (3) feasibility for using semiconductor nanoparticles ('quantum dots') for the down-conversion of blue or ultraviolet light to generate white light. The program included a partnership between Lumileds Lighting (epitaxy and device fabrication for high power LEDs) and Sandia National Laboratories (cantilever epitaxy, gas phase chemistry, and quantum dot synthesis). Key findings included: (1) cantilever epitaxy can provide dislocation density reduction comparable to that of more complicated approaches, but all in one epitaxial growth step; however, further improvements are required to realize significant gains in LED performance at high drive currents, (2) in situ tools can provide detailed knowledge about gas phase chemistry, and can be used to monitor and control epitaxial layer composition and temperature to provide improved yields (e.g., a fivefold increase …
Date: March 31, 2004
Creator: Goetz, Werner; Imler, Bill; Kim, James; Kobayashi, Junko; Kim, Andrew; Krames, Mike et al.
Object Type: Report
System: The UNT Digital Library
Determination of critical length scales for corrosion processes using microelectroanalytical techniques. (open access)

Determination of critical length scales for corrosion processes using microelectroanalytical techniques.

A key factor in our ability to produce and predict the stability of metal-based macro- to nano-scale structures and devices is a fundamental understanding of the localized nature of corrosion. Corrosion processes where physical dimensions become critical in the degradation process include localized corrosion initiation in passivated metals, microgalvanic interactions in metal alloys, and localized corrosion in structurally complex materials like nanocrystalline metal films under atmospheric and inundated conditions. This project focuses on two areas of corrosion science where a fundamental understanding of processes occurring at critical dimensions is not currently available. Sandia will study the critical length scales necessary for passive film breakdown in the inundated aluminum (Al) system and the chemical processes and transport in ultra-thin water films relevant to the atmospheric corrosion of nanocrystalline tungsten (W) films. Techniques are required that provide spatial information without significantly perturbing or masking the underlying relationships. Al passive film breakdown is governed by the relationship between area of the film sampled and its defect structure. We will combine low current measurements with microelectrodes to study the size scale required to observe a single initiation event and record electrochemical breakdown events. The resulting quantitative measure of stability will be correlated with metal …
Date: March 1, 2004
Creator: Zavadil, Kevin Robert & Wall, Frederick Douglas
Object Type: Report
System: The UNT Digital Library
Tracing Geothermal Fluids (open access)

Tracing Geothermal Fluids

Geothermal water must be injected back into the reservoir after it has been used for power production. Injection is critical in maximizing the power production and lifetime of the reservoir. To use injectate effectively the direction and velocity of the injected water must be known or inferred. This information can be obtained by using chemical tracers to track the subsurface flow paths of the injected fluid. Tracers are chemical compounds that are added to the water as it is injected back into the reservoir. The hot production water is monitored for the presence of this tracer using the most sensitive analytic methods that are economically feasible. The amount and concentration pattern of the tracer revealed by this monitoring can be used to evaluate how effective the injection strategy is. However, the tracers must have properties that suite the environment that they will be used in. This requires careful consideration and testing of the tracer properties. In previous and parallel investigations we have developed tracers that are suitable from tracing liquid water. In this investigation, we developed tracers that can be used for steam and mixed water/steam environments. This work will improve the efficiency of injection management in geothermal fields, lowering …
Date: March 1, 2004
Creator: Adams, Michael C. & Nash, Greg
Object Type: Report
System: The UNT Digital Library
Characterizing two-phase flow relative permeabilities in chemicalflooding using a pore-scale network model (open access)

Characterizing two-phase flow relative permeabilities in chemicalflooding using a pore-scale network model

A dynamic pore-scale network model is presented for investigating the effects of interfacial tension and oil-water viscosity on relative permeability during chemical flooding. This model takes into account both viscous and capillary forces in analyzing the impact of chemical properties on flow behavior or displacement configuration, as opposed to the conventional or invasion percolation algorithm which incorporates capillary pressure only. The study results indicate that both water and oil relative-permeability curves are dependent strongly on interfacial tension as well as an oil-water viscosity ratio. In particular, water and oil relative-permeability curves are both found to shift upward as interfacial tension is reduced, and they both tend to become linear versus saturation once interfacial tension is at low values. In addition, the oil-water viscosity ratio appears to have only a small effect under conditions of high interfacial tension. When the interfacial tension is low, however, water relative permeability decreases more rapidly (with the increase in the aqueous-phase viscosity) than oil relative permeability. The breakthrough saturation of the aqueous phase during chemical flooding tends to decrease with the reduction of interfacial tension and may also be affected by the oil-water viscosity ratio.
Date: March 15, 2004
Creator: Liu, Qingjie; Shen, Pingping & Wu, Yu-Shu
Object Type: Report
System: The UNT Digital Library
The Tiffany Unit N2 - ECBM Pilot: A Reservoir Modeling Study (open access)

The Tiffany Unit N2 - ECBM Pilot: A Reservoir Modeling Study

In October, 2000, the U.S. Department of Energy, through contractor Advanced Resources International, launched a multi-year government-industry R&D collaboration called the Coal-Seq project. The Coal-Seq project is investigating the feasibility of CO{sub 2} sequestration in deep, unmineable coalseams, by performing detailed reservoir studies of two enhanced coalbed methane recovery (ECBM) field projects in the San Juan basin. The two sites are the Allison Unit, operated by Burlington Resources, and into which CO{sub 2} is being injected, and the Tiffany Unit, operating by BP America, into which N{sub 2} is being injected (the interest in understanding the N{sub 2}-ECBM process has important implications for CO{sub 2} sequestration via flue-gas injection). The purposes of the field studies are to understand the reservoir mechanisms of CO{sub 2} and N{sub 2} injection into coalseams, demonstrate the practical effectiveness of the ECBM and sequestration processes, demonstrate an engineering capability to model them, and to evaluate sequestration economics. In support of these efforts, laboratory and theoretical studies are also being performed to understand and model multi-component isotherm behavior, and coal permeability changes due to swelling with CO{sub 2} injection. This report describes the results of an important component of the overall project, the Tiffany Unit reservoir …
Date: March 31, 2004
Creator: Reeves, Scott & Oudinot, Anne
Object Type: Report
System: The UNT Digital Library
Failure Forewarning in NPP Equipment NERI2000-109 Final Project Report (open access)

Failure Forewarning in NPP Equipment NERI2000-109 Final Project Report

The objective of this project is forewarning of machine failures in critical equipment at next-generation nuclear power plants (NPP). Test data were provided by two collaborating institutions: Duke Engineering and Services (first project year), and the Pennsylvania State University (Applied Research Laboratory) during the second and third project years. New nonlinear methods were developed and applied successfully to extract forewarning trends from process-indicative, time-serial data for timely, condition-based maintenance. Anticipation of failures in critical equipment at next-generation NPP will improve the scheduling of maintenance activities to minimize safety concerns, unscheduled non-productive downtime, and collateral damage due to unexpected failures. This approach provides significant economic benefit, and is expected to improve public acceptance of nuclear power. The approach is a multi-tiered, model-independent, and data-driven analysis that uses ORNL's novel nonlinear method to extract forewarning of machine failures from appropriate data. The first tier of the analysis provides a robust choice for the process-indicative data. The second tier rejects data of inadequate quality. The third tier removes signal artifacts that would otherwise confound the analysis, while retaining the relevant nonlinear dynamics. The fourth tier converts the artifact-filtered time-serial data into a geometric representation, that is then transformed to a discrete distribution function …
Date: March 26, 2004
Creator: Hively, LM
Object Type: Report
System: The UNT Digital Library
Design and testing of a control strategy for a large naturallyventilated office building (open access)

Design and testing of a control strategy for a large naturallyventilated office building

The design for the new Federal Building for San Franciscoincludes an office tower that is to be naturally ventilated. Each flooris designed to be cross-ventilated, through upper windows that arecontrolled by the building management system (BMS). Users have controlover lower windows, which can be as much as 50 percent of the totalopenable area. There are significant differences in the performance andthe control of the windward and leeward sides of the building, andseparate monitoring and control strategies are determined for each side.The performance and control of the building has been designed and testedusing a modified version of EnergyPlus. Results from studies withEnergyPlus and CFD are used in designing the control strategy. EnergyPluswas extended to model a simplified version of the airflow patterndetermined using CFD. Wind-driven cross-ventilation produces a main jetthrough the upper openings of the building, across the ceiling from thewindward to the leeward side. Below this jet, the occupied regions aresubject to a recirculating air flow. Results show that temperatureswithin the building are predicted to be satisfactory, provided a suitablecontrol strategy is implemented uses night cooling in periods of hotweather. The control strategy has 10 window opening modes. EnergyPlus wasextended to simulate the effects of these modes, and to assess …
Date: March 16, 2004
Creator: Carrilho da Graca, Guilherme; Linden, Paul F. & Haves, Philip
Object Type: Article
System: The UNT Digital Library
Synthesis of 6-acrylamido-4-(2-[18F]fluoroanilino)quinazoline: Aprospective irreversible EGFR binding probe (open access)

Synthesis of 6-acrylamido-4-(2-[18F]fluoroanilino)quinazoline: Aprospective irreversible EGFR binding probe

Acrylamido-quinazolines substituted at the 6-position bindirreversibly to the intracellular ATP binding domain of the epidermalgrowth factor receptor (EGFR). A general route was developed forpreparing 6-substituted-4-anilinoquinazolines from [18F]fluoroanilinesfor evaluation as EGFR targeting agents with PET. By a cyclizationreaction, 2-[18F]fluoroaniline was reacted withN'-(2-cyano-4-nitrophenyl)-N,N-dimethylimidoformamide to produce6-nitro-4-(2-[18F]fluoroanilino)quinazoline in 27.5 percentdecay-corrected radiochemical yield. Acid mediated tin chloride reductionof the nitro group was achieved in 5 min (80 percent conversion) andsubsequent acylation with acrylic acid gave6-acrylamido-4-(2-[18F]fluoroanilino)quinazoline in 8.5 percentdecay-corrected radiochemical yield, from starting fluoride, in less than2 hours.
Date: March 30, 2004
Creator: Vasdev, Neil; Dorff, Peter N.; Gibbs, Andrew R.; Nandanan,Erathodiyil; Reid, Leanne M.; O'Neil, James P. et al.
Object Type: Article
System: The UNT Digital Library
A second order accurate embedded boundary method for the wave equation with Dirichlet data (open access)

A second order accurate embedded boundary method for the wave equation with Dirichlet data

The accuracy of Cartesian embedded boundary methods for the second order wave equation in general two-dimensional domains subject to Dirichlet boundary conditions is analyzed. Based on the analysis, we develop a numerical method where both the solution and its gradient are second order accurate. We avoid the small-cell stiffness problem without sacrificing the second order accuracy by adding a small artificial term to the Dirichlet boundary condition. Long-time stability of the method is obtained by adding a small fourth order dissipative term. Several numerical examples are provided to demonstrate the accuracy and stability of the method. The method is also used to solve the two-dimensional TM{sub z} problem for Maxwell's equations posed as a second order wave equation for the electric field coupled to ordinary differential equations for the magnetic field.
Date: March 2, 2004
Creator: Kreiss, H O & Petersson, N A
Object Type: Article
System: The UNT Digital Library
Deformation behavior of ion-irradiated polyimide (open access)

Deformation behavior of ion-irradiated polyimide

None
Date: March 15, 2004
Creator: Kucheyev, S O; Felter, T E; Anthamatten, M & Bradby, J E
Object Type: Article
System: The UNT Digital Library
Strategy application, observability, and the choice combinator. (open access)

Strategy application, observability, and the choice combinator.

In many strategic systems, the choice combinator provides a powerful mechanism for controlling the application of rules and strategies to terms. The ability of the choice combinator to exercise control over rewriting is based on the premise that the success and failure of strategy application can be observed. In this paper we present a higher-order strategic framework with the ability to dynamically construct strategies containing the choice combinator. To this framework, a combinator called hide is introduced that prevents the successful application of a strategy from being observed by the choice combinator. We then explore the impact of this new combinator on a real-world problem involving a restricted implementation of the Java Virtual Machine.
Date: March 1, 2004
Creator: Winter, Victor Lono (University of Nebraska at Omaha)
Object Type: Report
System: The UNT Digital Library
China's sustainable energy future: Scenarios of energy and carbonemissions (Summary) (open access)

China's sustainable energy future: Scenarios of energy and carbonemissions (Summary)

China has ambitious goals for economic development, and mustfind ways to power the achievement of those goals that are bothenvironmentally and socially sustainable. Integration into the globaleconomy presents opportunities for technological improvement and accessto energy resources. China also has options for innovative policies andmeasures that could significantly alter the way energy is acquired andused. These opportunities andoptions, along with long-term social,demographic, and economic trends, will shape China s future energysystem, and consequently its contribution to emissions of greenhousegases, particularly carbon dioxide (CO2). In this study, entitled China sSustainable Energy Future: Scenarios of Energy and Carbon Emissions, theEnergy Research Institute (ERI), an independent analytic organizationunder China's Na tional Development and Reform Commission (NDRC), soughtto explore in detail how China could achieve the goals of the TenthFive-Year Plan and its longer term aims through a sustainable developmentstrategy. China's ability to forge a sustainable energy path has globalconsequences. China's annual emissions of greenhouse gases comprisenearly half of those from developing countries, and 12 percent of globalemissions. Most of China's greenhouse gas emissions are in the form ofCO2, 87 percent of which came from energy use in 2000. In that year,China's carbon emissions from energy use and cement production were 760million metric tons (Mt-C), …
Date: March 10, 2004
Creator: Zhou, Dadi; Levine, Mark; Dai, Yande; Yu, Cong; Guo, Yuan; Sinton, Jonathan E. et al.
Object Type: Report
System: The UNT Digital Library
INTERNATIONAL COLLABORATION ON CO2 SEQUESTRATION (open access)

INTERNATIONAL COLLABORATION ON CO2 SEQUESTRATION

After the permit to conduct a field experiment in Norway was revoked on August 22, 2002, we started executing our contingency plan to conduct a cruise at the Loihi Seamount in Hawaii in December 2002. After a few intense months of preparation, the cruise took place on December 3-13, 2002. In total, eight dives were made with the Pisces V submarine. The primary goal of the experiment was to assess the effect of CO{sub 2} on marine organisms. Studies were done using scavenger traps, as well as collecting water samples and surveying the natural CO{sub 2} plume at the Loihi Seamount. This report documents the experiment in more detail as summarized by the various participants. The data was still being analyzed at the end of this reporting period, so no results are reported here. Both papers and a video on the experiment are being prepared. Some related modeling work is presented in an Appendix in the form of a paper submitted to the Journal of Marine Environmental Engineering. The main goal of our work during this reporting period (August 23, 2002-August 23, 2003) was to conduct an experimental cruise at the Loihi Seamount in the Hawaiian Islands. The work included …
Date: March 1, 2004
Creator: Herzog, Howard J. & Adams, E. Eric
Object Type: Report
System: The UNT Digital Library
Final-part metrology for LIGA springs, Build Group 1. (open access)

Final-part metrology for LIGA springs, Build Group 1.

The LIGA spring is a recently designed part for defense program applications. The Sandia California LIGA team has produced an initial group build of these nickel alloy parts. These are distinctive in having a macroscopic lateral size of about 1 cm, while requiring microscopic dimensional precision on the order of a few micrometers. LIGA technology capabilities at Sandia are able to manufacture such precise structures. While certain aspects of the LIGA process and its production capabilities have been dimensionally characterized in the past, [1-6] the present work is exclusive in defining a set of methods and techniques to inspect and measure final LIGA nickel alloy parts in large prototype quantities. One hundred percent inspection, meaning that every single LIGA part produced needs to be measured, ensures quality control and customer satisfaction in this prototype production run. After a general visual inspection of the parts and an x-ray check for voids, high precision dimensional metrology tools are employed. The acquired data is analyzed using both in house and commercially available software. Examples of measurements illustrating these new metrology capabilities are presented throughout the report. These examples furthermore emphasize that thorough inspection of every final part is not only essential to characterize …
Date: March 1, 2004
Creator: Aigeldinger, Georg; Skala, Dawn M.; Ceremuga, Joseph T. & Mills, Bernice E.
Object Type: Report
System: The UNT Digital Library
Development of laser diagnostics for in situ measurements of entrained particles in recovery boilers. (open access)

Development of laser diagnostics for in situ measurements of entrained particles in recovery boilers.

As part of the U.S. Department of Energy (DOE) Office of Industrial Technologies (OIT) Industries of the Future (IOF) Forest Products research program, two different laser diagnostic techniques have been implemented in pulp mill recovery boilers to provide important information on entrained particles. One technique, based on single-particle scattering of a low-power, continuous-wave (cw) laser source, measures the velocity, concentration, and size distribution of particles within the furnace flow, over a predetermined range of particle sizes. For application to recovery boilers, this technique was designed to measure the range of particle sizes known as intermediate size particles (ISPs), roughly from 2-100 {micro}m in diameter. The other diagnostic technique, known as laser-induced breakdown spectroscopy (LIBS), uses a pulsed, high-power laser beam to create a localized plasma spark in the flow, allowing the measurement of the elemental composition of the entrained particles. This technique is most sensitive for particles less than 10 {micro}m in diameter. Implementing these laser diagnostic techniques in recovery boilers proved to be challenging. For the particle scattering measurement, the use of a narrow aperture for measurement of the forward scattered light was postulated and later confirmed to be effective in minimizing background signals associated with the dense sodium …
Date: March 1, 2004
Creator: Holve, Donald J. (Process Metrix LLC, San Ramon, CA) & Shaddix, Christopher R.
Object Type: Report
System: The UNT Digital Library
The interfacial bioscience grand challenge. (open access)

The interfacial bioscience grand challenge.

This report is broken down into the following 3 sections: (1) Chemical Cross-linking and Mass Spectrometry Applied to Determination of Protein Structure and Dynamics; (2) Computational Modeling of Membrane Protein Structure and Dynamics; and (3) Studies of Toxin-Membrane Interactions using Single Molecule Biophysical Methods.
Date: March 1, 2004
Creator: Lane, Pamela; Stevens, Mark Jackson; Jacobsen, Richard B.; Hong, Joohee; Ayson, Marites J.; Crozier, Paul Stewart et al.
Object Type: Report
System: The UNT Digital Library
Soot properties and species measurements in a two-meter diameter JP-8 pool fire : 2003 test series. (open access)

Soot properties and species measurements in a two-meter diameter JP-8 pool fire : 2003 test series.

A tunable diode laser absorption spectroscopy probe was used to measure in situ soot properties and species concentrations in a two-meter diameter JP-8 pool fire. Thirty-five tests were performed at the Lurance Canyon Burn Site operated by Sandia in Albuquerque, New Mexico. The axial profile of the fire was characterized with a series of tests with the probe located on the centerline at heights ranging from 0.5 m to 2.0 m in 0.25 m increments. The radial profile of the fire was characterized with a series of tests with the probe 1.0 m above the fuel surface at radial positions ranging from 0.0 m to 0.6 m, in 0.1 m increments. Experiments were also performed with variation of the air flow into the facility. Soot concentration was determined using a light extinction measurement based on the transmission of a solid-state red laser (635 nm) through the 3.7 cm long probe volume. Soot temperature and a second estimate of soot concentration were measured using two-color optical pyrometry at 850 nm and 1000 nm. The effective data rate for these measurements was 10 kHz. Finally, tunable diode laser absorption spectroscopy was used to estimate the concentrations of water vapor, acetylene, and methane. …
Date: March 1, 2004
Creator: Shaddix, Christopher R. & Murphy, Jeffrey J.
Object Type: Report
System: The UNT Digital Library
DVD Based Integrated Electronic Pulser (open access)

DVD Based Integrated Electronic Pulser

The DVD based integrated pulser combines the storage capacity and simplicity of DVD technology with commonly available electronic components to build a relatively inexpensive yet highly capable testing instrument. DVD technology has matured to the mass consumer level and has found widespread acceptance in many scientific, industrial, and consumers sectors. Coupling the removable media and relatively large data capacity with a simple electronic readout allows this device to be easy to build, export and authenticate. Since there are few parts and the heart of the device is a mass consumer item the duplication cost is very low.
Date: March 30, 2004
Creator: Hughes, Michael A.; Kouzes, Richard T.; Morris, Scott J.; Pitts, W. K.; Pratt, Rick M. & Robinson, Eric E.
Object Type: Report
System: The UNT Digital Library
Towards quantum information processing with impurity spins insilicon (open access)

Towards quantum information processing with impurity spins insilicon

The finding of algorithms for factoring and data base search that promise substantially increased computational power, as well as the expectation for efficient simulation of quantum systems have spawned an intense interest in the realization of quantum information processors [1]. Solid state implementations of quantum computers scaled to >1000 quantum bits ('qubits') promise to revolutionize information technology, but requirements with regard to sources of decoherence in solid state environments are sobering. Here, we briefly review basic approaches to impurity spin based qubits and present progress in our effort to form prototype qubit test structures. Since Kane's bold silicon based spin qubit proposal was first published in 1998 [2], several groups have taken up the challenge of fabricating elementary building blocks [3-5], and several exciting variations of single donor qubit schemes have emerged [6]. Single donor atoms, e. g. {sup 31}P, are 'natural quantum dots' in a silicon matrix, and the spins of electrons and nuclei of individual donor atoms are attractive two level systems for encoding of quantum information. The coupling to the solid state environment is weak, so that decoherence times are long (hours for nuclear spins, and {approx}60 ms for electron spins of isolated P atoms in silicon …
Date: March 1, 2004
Creator: Schenkel, T.; Liddle, J. A.; Bokor, J.; Rangelow, I. W.; Park, S. J. & Persaud, A.
Object Type: Article
System: The UNT Digital Library
Measurement of the Ratio of Branching Fractions Br(Bs -> Ds- pi+)/Br(B -> D- pi+) at CDF-II (open access)

Measurement of the Ratio of Branching Fractions Br(Bs -> Ds- pi+)/Br(B -> D- pi+) at CDF-II

The measurement of B{sub s}{sup 0} mixing is one of the flagship analyses for the Run II B physics program. The sensitivity of the measurement to the frequency of B{sub s}{sup 0} oscillations strongly depends on the number of reconstructed B{sub s}{sup 0} mesons. They present the measurement of the ratio of branching fractions Br(B{sub s}{sup 0} {yields} D{sub s}{sup -}{pi}{sup +})/Br(B{sup 0} {yields} D{sup -}{pi}{sup +}), which directly influences the number of B{sub s}{sup 0} events available for the measurement of B{sub s}{sup 0} mixing at CDF-II. They analyze 115 pb{sup -1} of data collected with the CDF-II detector in p{bar p} collisions at {radical}s = 1.96 TeV using a novel displaced track trigger. They reconstruct 78 {+-} 11 B{sub s}{sup 0} {yields} D{sub s}{sup -}{pi}{sup +} decays at 1153 {+-} 45 B{sup 0} {yields} D{sup -}{pi}{sup +} decays with good signal to background ratio. This is the world's largest sample of fully reconstructed B{sub s}{sup 0} {yields} D{sub s}{sup -}{pi}{sup +} decays. They find the ratio of production fractions multiplied by the ratio of branching fractions to be: f{sub s}/f{sub d} {center_dot} Br(B{sub s}{sup 0} {yields} D{sub s}{sup -}{pi}{sup +})/Br(B{sup 0} {yields} D{sup -}{pi}{sup +}) = 0.325 {+-} …
Date: March 1, 2004
Creator: Furic, Ivan Kresimir
Object Type: Thesis or Dissertation
System: The UNT Digital Library
EXAFS Measurements of Laser-Shocked V and Ti and Crystal Phase Transformation in Ti (open access)

EXAFS Measurements of Laser-Shocked V and Ti and Crystal Phase Transformation in Ti

Extended X-Ray Absorption Fine Structure (EXAFS), using a laser-imploded target as a source, can yield the properties of laser-shocked metals on a nanosecond time scale. EXAFS measurements of vanadium shocked to {approx}0.4 Mbar yield the compression and temperature in good agreement with hydrodynamic simulations and shock-speed measurements. In laser-shocked titanium at the same pressure, the EXAFS modulation damping is much higher than warranted by the predicted temperature increase. This is shown to be due to the {alpha}-Ti to {omega}-Ti crystal-phase transformation, known to occur below {approx}0.1 Mbar for slower shock waves. The dynamics of material response to shock loading has been extensively studied in the past [1]. The goal of those studies has been to understand the shock-induced deformation and structural changes at the microscopic level [2]. Laser-generated shocks can be employed to broaden these studies to higher pressures ({approx}1 Mbar) and strain rates ({approx} 10{sup 7}-10{sup 8} s{sup -1}). Recently, laser-shocked materials have been studied with in-situ x-ray diffraction [3,4]. The goal of this work is to examine the use of in-situ EXAFS [5] as a complementary characterization of laser-shocked metals. EXAFS is the modulation in the x-ray absorption above the K edge (or L edge) due to the …
Date: March 10, 2004
Creator: Yaakobi, B.; Meyerhofer, D. D.; Boehly, T. R.; Rehr, J. J.; Remington, B. A.; Allen, P. G. et al.
Object Type: Article
System: The UNT Digital Library
Synthesis of Novel Extended Phases of Molecular Solids at High Pressures and Temperatures (open access)

Synthesis of Novel Extended Phases of Molecular Solids at High Pressures and Temperatures

This study is for in-situ investigation of chemical bonding and molecular structure of low z-elements and simple molecular solids at high pressures and temperatures using 3rd-generation synchrotron x-ray diffraction. To understand the contribution of the empty d-electron orbital of Mg in relation to the formation of molecular solids like MgO, which is one of the important Earth lower mantle materials and MgB{sub 2}, which has recently been the focus of intense superconducting material research, we have performed double-sided laser heating experiments using a diamond anvil cell (DAC). Understanding the structural stability and the formation of the above Mg-compounds requires studying Mg itself as well as the relevant compounds. BL10XU at the Spring-8 was used to study phase stability and make accurate equation of state (EOS) determinations of Mg coupled with external heating and the double-sided laser heating technique. Monochromatic x-ray at 30 keV (0.4135 {angstrom}) was focused to about 40 {micro}m at the sample and the diffracted x-ray were recorded using a high-resolution image plate (3000 x 3000 pixels with a 0.1 mm resolution per pixel). EOS parameters for hcp and bcc Mg were determined by fitting to a Birch-Murnaghan equation. An isothermal compression of Mg at 300 K up …
Date: March 30, 2004
Creator: Yoo, C; Evans, W & Cynn, H
Object Type: Report
System: The UNT Digital Library
The 1997/98 El Nino: A Test for Climate Models (open access)

The 1997/98 El Nino: A Test for Climate Models

Version 3 of the Hadley Centre Atmospheric Model (HadAM3) has been used to demonstrate one means of comparing a general circulation model with observations for a specific climate perturbation, namely the strong 1997/98 El Nino. This event was characterized by the collapse of the tropical Pacific's Walker circulation, caused by the lack of a zonal sea surface temperature gradient during the El Nino. Relative to normal years, cloud altitudes were lower in the western portion of the Pacific and higher in the eastern portion. HadAM3 likewise produced the observed collapse of the Walker circulation, and it did a reasonable job of reproducing the west/east cloud structure changes. This illustrates that the 1997/98 El Nino serves as a useful means of testing cloud-climate interactions in climate models.
Date: March 5, 2004
Creator: Lu, R; Dong, B; Cess, R D & Potter, G L
Object Type: Article
System: The UNT Digital Library
Seismic Response Prediction of Nupec's Field Model Tests of Npp Structures With Adjacent Building Effect. (open access)

Seismic Response Prediction of Nupec's Field Model Tests of Npp Structures With Adjacent Building Effect.

As part of a verification test program for seismic analysis computer codes for Nuclear Power Plant (NPP) structures, the Nuclear Power Engineering Corporation (NUPEC) of Japan has conducted a series of field model tests to address the dynamic cross interaction (DCI) effect on the seismic response of NPP structures built in close proximity to each other. The program provided field data to study the methodologies commonly associated with seismic analyses considering the DCI effect. As part of a collaborative program between the United States and Japan on seismic issues related to NPP applications, the U.S. Nuclear Regulatory Commission sponsored a program at Brookhaven National Laboratory (BNL) to perform independent seismic analyses which applied common analysis procedures to predict the building response to recorded earthquake events for the test models with DCI effect. In this study, two large-scale DCI test model configurations were analyzed: (1) twin reactor buildings in close proximity and (2) adjacent reactor and turbine buildings. This paper describes the NUPEC DCI test models, the BNL analysis using the SASSI 2000 program, and comparisons between the BNL analysis results and recorded field responses. To account for large variability in the soil properties, the conventional approach of computing seismic responses …
Date: March 4, 2004
Creator: Xu, J.; Hofmayer, C. & Ali, S.
Object Type: Article
System: The UNT Digital Library