Language

3-D Force-balanced Magnetospheric Configurations (open access)

3-D Force-balanced Magnetospheric Configurations

The knowledge of plasma pressure is essential for many physics applications in the magnetosphere, such as computing magnetospheric currents and deriving magnetosphere-ionosphere coupling. A thorough knowledge of the 3-D pressure distribution has however eluded the community, as most in-situ pressure observations are either in the ionosphere or the equatorial region of the magnetosphere. With the assumption of pressure isotropy there have been attempts to obtain the pressure at different locations by either (a) mapping observed data (e.g., in the ionosphere) along the field lines of an empirical magnetospheric field model or (b) computing a pressure profile in the equatorial plane (in 2-D) or along the Sun-Earth axis (in 1-D) that is in force balance with the magnetic stresses of an empirical model. However, the pressure distributions obtained through these methods are not in force balance with the empirical magnetic field at all locations. In order to find a global 3-D plasma pressure distribution in force balance with the magnetospheric magnetic field, we have developed the MAG-3D code, that solves the 3-D force balance equation J x B = (upside-down delta) P computationally. Our calculation is performed in a flux coordinate system in which the magnetic field is expressed in terms …
Date: February 10, 2003
Creator: Zaharia, Sorin; Cheng, C. Z. & Maezawa, K.
Object Type: Report
System: The UNT Digital Library
The 10,000 Year Plan (open access)

The 10,000 Year Plan

Pallavi Pharkya thinks a lot about the future. Pharkya, a Ph.D. candidate in materials science and engineering, works in the area of corrosion science, predicting how materials will perform over extended periods of time. Her particular focus is a nickel-chromium-molybdenum alloy called C-22, a highly corrosion-resistant metal. Pharkya's aim is to help determine whether containers made from C-22 can be used to store high-energy nuclear waste--for 10,000 years and longer. Pharkya's work is part of a plan by the U.S. Department of Energy to consolidate the country's nuclear waste in a single proposed repository. The proposed repository is in Yucca Mountain located in a remote Nevada desert. Currently about 70,000 metric tons of spent nuclear fuel and high-level radioactive waste are divided between approximately 100 sites around the country. The undertaking, Pharkya emphasizes, is massive. To study just the corrosion aspects of the packaging, Case is collaborating with eight other universities, five national labs and Atomic Energy of Canada Limited. Even with so many players, the study will likely take several years to complete. Heading the entire group is Joe Payer, a professor of materials science and engineering at Case and Pharkya's mentor. ''I came here to have the opportunity …
Date: February 10, 2006
Creator: Srisaro, L.
Object Type: Article
System: The UNT Digital Library
THE 10,000 YEAR PLAN (open access)

THE 10,000 YEAR PLAN

Pharkya, a Ph.D. candidate in materials science and engineering, works in the area of corrosion science, predicting how materials will perform over extended periods of time. Her particular focus is a nickel-chromium-molybdenum alloy called C-22, a highly corrosion-resistant metal. Pharkya's aim is to help determine whether containers made from C-22 can be used to store high-energy nuclear waste--for 10,000 years and longer. Pharkya's work is part of a plan by the U.S. Department of Energy to consolidate the country's nuclear waste in a single proposed repository. The proposed repository is in Yucca Mountain located in a remote Nevada desert. Currently about 70,000 metric tons of spent nuclear fuel and high-level radioactive waste are divided between approximately 100 sites around the country. The undertaking, Pharkya emphasizes, is massive. To study just the corrosion aspects of the packaging, Case is collaborating with eight other universities, five national labs and Atomic Energy of Canada Limited. Even with so many players, the study will likely take several years to complete. Heading the entire group is Joe Payer, a professor of materials science and engineering at Case and Pharkya's mentor. ''I came here to have the opportunity to work with Dr. Payer, an expert in …
Date: February 10, 2006
Creator: Srisuro, L.
Object Type: Article
System: The UNT Digital Library
14-Inch Swing Check Valve Test (open access)

14-Inch Swing Check Valve Test

The check valve for the Hallam Power Reactor uses a knife-edge bearing for the flapper in place of the usual journal-type bearing. Mechanical cycling in sodium at 600 deg F was used to check operation of this bearing. A total of 309 mechanical cycles was completed with no apparent malfunctioning of the valve. Measured leskage rates were 0.46 gpm at 0.93 psig, 0.73 gpm at 3.4 psig. and 0.32 gpm at 5.9 psig. (M.C.G.)
Date: February 10, 1960
Creator: Cygan, R.
Object Type: Report
System: The UNT Digital Library
105-KW Sandfilter Backwash Pit sludge volume calculation (open access)

105-KW Sandfilter Backwash Pit sludge volume calculation

The volume of sludge contained in the 100-KW Sandfilter Backwash Pit (SFBWP) was calculated from depth measurements of the sludge, pit dimension measurements and analysis of video tape recordings taken by an underwater camera. The term sludge as used in this report is any combination of sand, sediment, or corrosion products visible in the SFBWP area. This work was performed to determine baseline volume for use in determination of quantities of uranium and plutonium deposited in the pit from sandfilter backwashes. The SFBWP has three areas where sludge is deposited: (1) the main pit floor, (2) the transfer channel floor, and (3) the surfaces and structures in the SFBWP. The depths of sludge and the uniformity of deposition varies significantly between these three areas. As a result, each of the areas was evaluated separately. The total volume of sludge determined was 3.75 M{sup 3} (132.2 ft{sup 3}).
Date: February 10, 1995
Creator: Dodd, E.N. Jr.
Object Type: Report
System: The UNT Digital Library
317/319 Phytoremediation site monitoring report - 2009 growing season : final report. (open access)

317/319 Phytoremediation site monitoring report - 2009 growing season : final report.

In 1999, Argonne National Laboratory (Argonne) designed and installed a series of engineered plantings consisting of a vegetative cover system and approximately 800 hybrid poplars and willows rooting at various predetermined depths. The plants were installed using various methods including Applied Natural Science's TreeWell{reg_sign} system. The goal of the installation was to protect downgradient surface and groundwater by intercepting the contaminated groundwater with the tree roots, removing moisture from the upgradient soil area, reducing water infiltration, preventing soil erosion, degrading and/or transpiring the residual volatile organic compounds (VOCs), and removing tritium from the subsoil and groundwater. This report presents the results of the monitoring activities conducted by Argonne's Energy Systems (ES) Division in the growing season of 2009. Monitoring of the planted trees began soon after the trees were installed in 1999 and has been conducted every summer since then. As the trees grew and consolidated their growth into the contaminated soil and groundwater, their exposure to the contaminants was progressively shown through tissue sampling. During the 2009 sampling campaign, VOC concentrations found in the French Drain area were in general consistent with or slightly lower than the 2008 results. Additionally, closely repeated, stand wide analyses showed contaminant fluctuations that …
Date: February 10, 2010
Creator: Negri, C .N.; Benda, P. L.; Gopalakrishnan, G. & Systems, Energy
Object Type: Report
System: The UNT Digital Library
2H Evaporator CP class instrumentation uncertainties evaluations (open access)

2H Evaporator CP class instrumentation uncertainties evaluations

The Evaporator Pot Temperature Instrumentations and the Steam Condensate Gamma Monitors are two instrumentation systems in the 2H Evaporator facilities that are classified as the critical protection. The temperature high alarm and interlock circuit and the temperature recorder circuit of the pot temperature instrumentation loop are described. From the gamma monitor loop, the high gamma alarm and interlock circuit, failure alarm and interlock circuit, cesium activity recorder circuit, and americium activity recorder circuit are described. (GHH)
Date: February 10, 1994
Creator: Hwang, E.
Object Type: Report
System: The UNT Digital Library
3D Imaging of Porous Media Using Laser Scanning Confocal Microscopy with Application to Microscale Transport Processes (open access)

3D Imaging of Porous Media Using Laser Scanning Confocal Microscopy with Application to Microscale Transport Processes

We present advances in the application of laser scanning confocal microscopy (LSCM) to image, reconstruct, and characterize statistically the microgeometry of porous geologic and engineering materials. We discuss technical and practical aspects of this imaging technique, including both its advantages and limitations. Confocal imaging can be used to optically section a material, with sub-micron resolution possible in the lateral and axial planes. The resultant volumetric image data, consisting of fluorescence intensities for typically {approximately}50 million voxels in XYZ space, can be used to reconstruct the three-dimensional structure of the two-phase medium. We present several examples of this application, including studying pore geometry in sandstone, characterizing brittle failure processes in low-porosity rock deformed under triaxial loading conditions in the laboratory, and analyzing the microstructure of porous ceramic insulations. We then describe approaches to extract statistical microgeometric descriptions from volumetric image data, and present results derived from confocal volumetric data sets. Finally, we develop the use of confocal image data to automatically generate a three-dimensional mesh for numerical pore-scale flow simulations.
Date: February 10, 1999
Creator: Fredrich, J.T.
Object Type: Article
System: The UNT Digital Library
Ability of the Confined Explosive Component Water Gap Test STANAG 4363 to Assess the Shock Sensitivity of MM-Scale Detonators (open access)

Ability of the Confined Explosive Component Water Gap Test STANAG 4363 to Assess the Shock Sensitivity of MM-Scale Detonators

The Explosive Component Water Gap Test (ECWGT) has been validated to assess the shock sensitivity of lead and booster components having a diameter larger than 5 mm. Several countries have investigated by experiments and numerical simulations the effect of confinement on the go/no go threshold for Pentaerythritol Tetranitrate (PETN) pellets having a height and diameter of 3 mm, confined by a steel annulus of wall thickness 1-3.5 mm. Confinement of the PETN by a steel annulus of the same height of the pellet with 1-mm wall thickness makes the component more sensitive (larger gap). As the wall thickness is increased to 2-mm, the gap increases a lesser amount, but when the wall thickness is increased to 3.5-mm a decrease in sensitivity is observed (smaller gap). This decrease of the water gap has been reproduced experimentally. Recent numerical simulations using Ignition and Growth model [1] for the PETN Pellet have reproduced the experimental results for the steel confinement up to 2 mm thick [2]. The presence of a stronger re-shock following the first input shock from the water and focusing on the axis have been identified in the pellet due to the steel confinement. The double shock configuration is well-known to …
Date: February 10, 2006
Creator: Lefrancois, A. S.; Roeske, F.; Benterou, J.; Tarver, C. M.; Lee, R. S. & Hannah, B.
Object Type: Report
System: The UNT Digital Library
Accelerating Atomic Orbital-based Electronic Structure Calculation via Pole Expansion plus Selected Inversion (open access)

Accelerating Atomic Orbital-based Electronic Structure Calculation via Pole Expansion plus Selected Inversion

We describe how to apply the recently developed pole expansion plus selected inversion (PEpSI) technique to Kohn-Sham density function theory (DFT) electronic structure calculations that are based on atomic orbital discretization. We give analytic expressions for evaluating charge density, total energy, Helmholtz free energy and atomic forces without using the eigenvalues and eigenvectors of the Kohn-Sham Hamiltonian. We also show how to update the chemical potential without using Kohn-Sham eigenvalues. The advantage of using PEpSI is that it has a much lower computational complexity than that associated with the matrix diagonalization procedure. We demonstrate the performance gain by comparing the timing of PEpSI with that of diagonalization on insulating and metallic nanotubes. For these quasi-1D systems, the complexity of PEpSI is linear with respect to the number of atoms. This linear scaling can be observed in our computational experiments when the number of atoms in a nanotube is larger than a few hundreds. Both the wall clock time and the memory requirement of PEpSI is modest. This makes it even possible to perform Kohn-Sham DFT calculations for 10,000-atom nanotubes on a single processor. We also show that the use of PEpSI does not lead to loss of accuracy required in …
Date: February 10, 2012
Creator: Lin, Lin; Chen, Mohan; Yang, Chao & He, Lixin
Object Type: Article
System: The UNT Digital Library
Adaptations of the Purge Water Management System for Long-Term Groundwater Monitoring at Savannah River Site, South Carolina (final) (open access)

Adaptations of the Purge Water Management System for Long-Term Groundwater Monitoring at Savannah River Site, South Carolina (final)

To monitor the groundwater contamination and the effectiveness of remedial actions, over a thousand monitoring wells are in active operation (i.e., require quarterly or semi-annual sampling) at SRS. Most wells are expected to continue in operation for another 20 to 40 more years. Required sample volumes can range from a less than a liter to 10 liters. To support the long-term groundwater monitoring requirements of these wells, SRS actively seeks technologies that can maximize data acquisition and minimize costs. To meet this end, SRS has implemented the Purge Water Management System (PWMS). The key attributes of this system lie in its ability to reduce or eliminate the generation of purged groundwater, which is costly in terms of the time and management.
Date: February 10, 2004
Creator: Schiefer, E
Object Type: Article
System: The UNT Digital Library
Advanced fuel cells for transportation applications. Final report (open access)

Advanced fuel cells for transportation applications. Final report

This Research and Development (R and D) contract was directed at developing an advanced technology compressor/expander for supplying compressed air to Proton Exchange Membrane (PEM) fuel cells in transportation applications. The objective of this project was to develop a low-cost high-efficiency long-life lubrication-free integrated compressor/expander utilizing scroll technology. The goal of this compressor/expander was to be capable of providing compressed air over the flow and pressure ranges required for the operation of 50 kW PEM fuel cells in transportation applications. The desired ranges of flow, pressure, and other performance parameters were outlined in a set of guidelines provided by DOE. The project consisted of the design, fabrication, and test of a prototype compressor/expander module. The scroll CEM development program summarized in this report has been very successful, demonstrating that scroll technology is a leading candidate for automotive fuel cell compressor/expanders. The objectives of the program are: develop an integrated scroll CEM; demonstrate efficiency and capacity goals; demonstrate manufacturability and cost goals; and evaluate operating envelope. In summary, while the scroll CEM program did not demonstrate a level of performance as high as the DOE guidelines in all cases, it did meet the overriding objectives of the program. A fully-integrated, low-cost …
Date: February 10, 1998
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Aerodynamic, structural, and trajectory analysis of ASTRID-1 vehicle (open access)

Aerodynamic, structural, and trajectory analysis of ASTRID-1 vehicle

The Johns Hopkins University/Applied Physics Laboratory, JHU/API, in support of Lawrence Livermore National Laboratory, LLNL, is conducting aerodynamic, trajectory, and structural analysis of the Advanced Single Stage Technology Rapid Insertion Demonstration (ASTRID) vehicle, being launched out of Vandenberg Air Force Base (VAFB) in February 1994. The launch is designated ASTRID-1 and is the first in a series of three that will be launched out of VAFB. Launch dates for the next two flights have not been identified, but they are scheduled for the 1994-1995 time frame. The primary goal of the ASTRID-1 flight is to test the LLNL light weight thrust on demand bi-propellant pumped divert propulsion system. The system is employed as the main thrusters for the ASTRID-1 vehicle and uses hydrazine as the mono-propellant. The major conclusions are: (1) The vehicle is very stable throughout flight (stability margin = 17 to 24 inches); (2) The aerodynamic frequency and the roll rate are such that pitch-roll interactions will be small; (3) The high stability margin combined with the high launcher elevation angle makes the vehicle flight path highly sensitive to perturbations during the initial phase of flight, i.e., during the first second of flight after leaving the rail; (4) …
Date: February 10, 1994
Creator: Glover, L. S.; Iwaskiw, A. P.; Oursler, M. A.; Perini, L. L. & Schaefer, E. D.
Object Type: Report
System: The UNT Digital Library
Algae Tile Data: 2004-2007, BPA-51; Preliminary Report, October 28, 2008. (open access)

Algae Tile Data: 2004-2007, BPA-51; Preliminary Report, October 28, 2008.

Multiple files containing 2004 through 2007 Tile Chlorophyll data for the Kootenai River sites designated as: KR1, KR2, KR3, KR4 (Downriver) and KR6, KR7, KR9, KR9.1, KR10, KR11, KR12, KR13, KR14 (Upriver) were received by SCS. For a complete description of the sites covered, please refer to http://ktoi.scsnetw.com. To maintain consistency with the previous SCS algae reports, all analyses were carried out separately for the Upriver and Downriver categories, as defined in the aforementioned paragraph. The Upriver designation, however, now includes three additional sites, KR11, KR12, and the nutrient addition site, KR9.1. Summary statistics and information on the four responses, chlorophyll a, chlorophyll a Accrual Rate, Total Chlorophyll, and Total Chlorophyll Accrual Rate are presented in Print Out 2. Computations were carried out separately for each river position (Upriver and Downriver) and year. For example, the Downriver position in 2004 showed an average Chlorophyll a level of 25.5 mg with a standard deviation of 21.4 and minimum and maximum values of 3.1 and 196 mg, respectively. The Upriver data in 2004 showed a lower overall average chlorophyll a level at 2.23 mg with a lower standard deviation (3.6) and minimum and maximum values of (0.13 and 28.7, respectively). A more …
Date: February 10, 2009
Creator: Holderman, Charles
Object Type: Report
System: The UNT Digital Library
Analysis of Devonian Black Shales in Kentucky for Potential Carbon Dioxide Sequestration and Enhanced Natural Gas Production Quarterly Report: July-Septmeber 2002 (open access)

Analysis of Devonian Black Shales in Kentucky for Potential Carbon Dioxide Sequestration and Enhanced Natural Gas Production Quarterly Report: July-Septmeber 2002

Proposed carbon management technologies include geologic sequestration of CO{sub 2}. A possible, but untested, strategy is to inject CO{sub 2} into organic-rich shales of Devonian age. Devonian black shales underlie approximately two-thirds of Kentucky and are generally thicker and deeper in the Illinois and Appalachian Basin portions of Kentucky. The Devonian black shales serve as both the source and trap for large quantities of natural gas; total gas in place for the shales in Kentucky is estimated to be between 63 and 112 trillion cubic feet. Most of this natural gas is adsorbed on clay and kerogen surfaces, analogous to the way methane is stored in coal beds. In coals, it has been demonstrated that CO{sub 2} is preferentially adsorbed, displacing methane at a ratio of two to one. Black shales may similarly desorb methane in the presence of CO{sub 2}. If black shales similarly desorb methane in the presence of CO{sub 2}, the shales may be an excellent sink for CO{sub 2} with the added benefit of serving to enhance natural gas production. The concept that black, organic-rich Devonian shales could serve as a significant geologic sink for CO{sub 2} is the subject this research. To accomplish this investigation, …
Date: February 10, 2003
Creator: Nuttall, Brandon C.
Object Type: Report
System: The UNT Digital Library
Analysis of production line motor failure. CRADA final report for CRADA number Y-1293-0215 (open access)

Analysis of production line motor failure. CRADA final report for CRADA number Y-1293-0215

The Oak Ridge National Laboratory (ORNL) was approached by a Food Products Manufacturer (FPM) to investigate the rapid failure of motors in a manufacturing facility. It was reported that some motors or their bearings were being replaced after as little as four months of service. The deciding symptom for replacement was always high motor vibration. To protect against unscheduled downtime in the middle of a process run, the FPM`s maintenance team removes a motor from service when its vibration level reaches a conservative threshold of approximately 0.4 inches per second. In their experience, motors left in service after reaching this vibration threshold can fail at any time within the time span of the next process run causing significant losses of raw material and production capacity. A peculiar finding of vibration level trend analysis was that at least one motor exhibited cyclic variations with 24-hour periodicity. The vibration level reached a maximum at about 4:00 a.m., ramped down during the day, and then rose again during the night. Another peculiarity was that most of the vibration energy in the affected motors was at the 120 Hz frequency. Since this is twice the 60 Hz line frequency the FPM suspected the vibration …
Date: February 10, 1995
Creator: Kueck, J. & Talbott, C.
Object Type: Report
System: The UNT Digital Library
Analysis of the Third H-Reactor Core Load (open access)

Analysis of the Third H-Reactor Core Load

None
Date: February 10, 1964
Creator: Ringle, R. P.
Object Type: Report
System: The UNT Digital Library
Analyzing industrial furnace efficiency using comparative visualization in a virtual reality environment. (open access)

Analyzing industrial furnace efficiency using comparative visualization in a virtual reality environment.

We describe an interactive toolkit used to perform comparative analysis of two or more data sets arising from numerical simulations. Several techniques have been incorporated into this toolkit, including (1) successive visualization of individual data sets, (2) data comparison techniques such as computation and visualization of the differences between data sets, and (3) image comparison methods such as scalar field height profiles plotted in a common coordinate system. We describe each technique in detail and show example usage in an industrial application aimed at designing an efficient, low-NOX burner for industrial furnaces. Critical insights are obtained by interactively adjusted color maps, data culling, and data manipulation. New paradigms for scaling small values in the data comparison technique are described. The display device used for this application was the CAVE virtual reality theater, and we describe the user interface to the visualization toolkit and the benefits of immersive 3D visualization for comparative analysis.
Date: February 10, 1999
Creator: Freitag, L. & Urness, T.
Object Type: Article
System: The UNT Digital Library
Architectural Surety Applications for Building Response to Dynamic Loads (open access)

Architectural Surety Applications for Building Response to Dynamic Loads

This paper provides a summary introduction to the emerging area of Architectural Surety{trademark} applications for buildings and infrastructures that are subjected to dynamic loads from blast and naturally occurring events. This technology area has been under investigation to assist with the definition of risks associated with dynamic loads and to provide guidance for determining the required upgrading and retrofitting techniques suggested for reducing building and infrastructure vulnerabilities to such dynamic forces. This unique approach involves the application of risk management techniques for solving problems of the as-built environment through the application of security, safety, and reliability principles developed in the nuclear weapons programs of the United States Department of Energy (DOE) and through the protective structures programs of the German Ministry of Defense (MOD). The changing responsibilities of engineering design professionals are addressed in light of the increased public awareness of structural and facility systems' vulnerabilities to malevolent, normal, and abnormal environment conditions. Brief discussions are also presented on (1) the need to understand how dynamic pressures are affected by the structural failures they cause, (2) the need to determine cladding effects on columns, walls, and slabs, and (3) the need to establish effective standoff distance for perimeter barriers. A …
Date: February 10, 1999
Creator: Matalucci, R.V. & Mayrhofer, C.
Object Type: Article
System: The UNT Digital Library
Argonne National Laboratory - West's approach to filter characterization. (open access)

Argonne National Laboratory - West's approach to filter characterization.

Like other DOE facilities, ANL-W uses a variety of nuclear grade, industrial grade, or furnace-type particulate filters to control airborne radioactivity and hazardous contaminants in radiological containment structures or processes. As designed, these filters entrain and ultimately concentrate contaminants in the media. Toxic metal contaminants include cadmium, chromium, lead; and mercury present in sufficient concentrations to exhibit the hazardous waste characteristic of toxicity as defined in 40 CFR 261.24. Radionuclide contaminants deposited in the media may at times accumulate in sufficient quantity to classify the filter as transuranic or remote-handled waste. Upon their removal from the ventilation system, these particulate filters become wastes, which must be characterized to determine their hazardous and radioactive classifications. A well defined filter characterization process is essential for the proper/consistent waste characterization and minimization and for maintaining personnel radiological exposures as-low-as-reasonably-achievable (ALARA) (1,2). ANL-W has developed an approach to filter sampling and characterization to meet these needs. The ANL-W filter sampling and characterization process is designed to ensure representative sampling and/or process knowledge is utilized in characterizing the filters. The data obtained through sampling and/or process knowledge is used to show compliance with the Resource Conservation and Recovery Act (3) and Treatment/Storage/Disposal Facility Waste Acceptance …
Date: February 10, 1999
Creator: Miller, T. A.
Object Type: Article
System: The UNT Digital Library
ARROW (Version 2) Commercial Software Validation and Configuration Control (open access)

ARROW (Version 2) Commercial Software Validation and Configuration Control

ARROW (Version 2), a compressible flow piping network modeling and analysis computer program from Applied Flow Technology, was installed for use at the U.S. Department of Energy Hanford Site near Richland, Washington.
Date: February 10, 2000
Creator: HEARD, F.J.
Object Type: Report
System: The UNT Digital Library
[Aspects of photoionization of impurities and electron transfer in ionic crystals] (open access)

[Aspects of photoionization of impurities and electron transfer in ionic crystals]

Spectral evidence was found for photoionization in spectra of Eu[sup 2+] and Sm[sup 3+] in BaF[sub 2]; Ce[sup 3+] was also studied in BaF[sub 2], CaF[sub 2], and SrF[sub 2]. Two-photon spectroscopy of forbidden transitions (zero-phonon lines) was extended from NaF: Cu[sup +] to Mn[sup 4+] in Cs[sub 2]GeF[sub 6] and to MgO:Ni[sup 2+].
Date: February 10, 1993
Creator: McClure, D.S.
Object Type: Report
System: The UNT Digital Library
[Aspects of photoionization of impurities and electron transfer in ionic crystals]. Final report, [September 1984--September 1991] (open access)

[Aspects of photoionization of impurities and electron transfer in ionic crystals]. Final report, [September 1984--September 1991]

Spectral evidence was found for photoionization in spectra of Eu{sup 2+} and Sm{sup 3+} in BaF{sub 2}; Ce{sup 3+} was also studied in BaF{sub 2}, CaF{sub 2}, and SrF{sub 2}. Two-photon spectroscopy of forbidden transitions (zero-phonon lines) was extended from NaF: Cu{sup +} to Mn{sup 4+} in Cs{sub 2}GeF{sub 6} and to MgO:Ni{sup 2+}.
Date: February 10, 1993
Creator: McClure, D. S.
Object Type: Report
System: The UNT Digital Library
Asymmetric perfectly matched layer for the absorption of waves (open access)

Asymmetric perfectly matched layer for the absorption of waves

The Perfectly Matched Layer (PML) has become a standard for comparison in the techniques that have been developed to close the system of Maxwell equations (more generally wave equations) when simulating an open system. The original Berenger PML formulation relies on a split version of Maxwell equations with numerical electric and magnetic conductivities. They present here an extension of this formulation which introduces counterparts of the electric and magnetic conductivities affecting the term which is spatially differentiated in the equations. they phase velocity along each direction is also multiplied by an additional coefficient. They show that, under certain constraints on the additional numerical coefficients, this ''medium'' does not generate any reflection at any angle and any frequency and is then a Perfectly Matched Layer. Technically it is a super-set of Berenger's PML to which it reduces for a specific set of parameters and like it, it is anisotropic. However, unlike the PML, it introduces some asymmetry in the absorption rate and is therefore labeled an APML for Asymmetric Perfectly Matched Layer. They present here the numerical considerations that have led them to introduce such a medium as well as its theory. Several finite-different numerical implementations are derived (in one, two …
Date: February 10, 2002
Creator: Vay, Jean-Luc
Object Type: Article
System: The UNT Digital Library