In/Si(111): Self-assembled one and two-dimensional electrongases (open access)

In/Si(111): Self-assembled one and two-dimensional electrongases

We present angle-resolved photoemission measurements forultrathin In films on Si(111). Depending on the coverage, this systemself-organizes into a metallic monolayer with either 4x1 or sqrt7 x sqrt3symmetry relative to the substrate. Electronically, they behave likeideal one- and two-dimensional electron gases (1DEG and 2DEG),respectively. The 4x1 system has atomic chains of In whose energy bandsdisperse only parallel to the chains, while for the sqrt7 x sqrt3 system,the dominant reciprocal space features (in both diffraction andbandstructure) resemble a pseudo-square lattice with only weakersecondary features relating to the sqrt7 x sqrt3 periodicity. In bothmaterials the electrons show coupling to the structure. The 1DEG couplesstrongly to phonons of momentum 2kF, leading to an 8x"2" Peierls-likeinsulating ground state. The 2DEG appears to be partially stabilized byelectron gap formation at the sqrt 7 x sqrt3 zone boundary.
Date: January 22, 2001
Creator: Rotenberg, Eli; Yeom, H. W.; Takeda, S.; Matsuda, I.; Horikoshi, K.; Schaefer, J. et al.
Object Type: Article
System: The UNT Digital Library
Optimization of the 8 GeV AP3-P1 Lattice for Antiproton Transfers (open access)

Optimization of the 8 GeV AP3-P1 Lattice for Antiproton Transfers

During 8 GeV antiproton transfers between the Accumulator to the Main Injector, the antiprotons must travel through four separate beam lines, AP3, AP1, P2, and P1. This note describes the optimization of a single lattice that describes these beam lines for 8 GeV antiproton transfers from the Accumulator to the Main Injector and 8 GeV proton transfers from the Main Injector to the Accumulator.
Date: January 22, 2001
Creator: McGinnis, Dave
Object Type: Report
System: The UNT Digital Library
FIRE HAZARDS ANALYSIS - BUSTED BUTTE (open access)

FIRE HAZARDS ANALYSIS - BUSTED BUTTE

The purpose of this fire hazards analysis (FHA) is to assess the risk from fire within individual fire areas at the Busted Butte Test Facility and to ascertain whether the DOE fire safety objectives are met. The objective, identified in DOE Order 420.1, Section 4.2, is to establish requirements for a comprehensive fire and related hazards protection program for facilities sufficient to minimize the potential for: (1) The occurrence of a fire related event. (2) A fire that causes an unacceptable on-site or off-site release of hazardous or radiological material that will threaten the health and safety of employees. (3) Vital DOE programs suffering unacceptable interruptions as a result of fire and related hazards. (4) Property losses from a fire and related events exceeding limits established by DOE. Critical process controls and safety class systems being damaged as a result of a fire and related events.
Date: January 22, 2001
Creator: Longwell, R.; Keifer, J. & Goodin, S.
Object Type: Report
System: The UNT Digital Library
Comparison of de-noising techniques for FIRST images (open access)

Comparison of de-noising techniques for FIRST images

Data obtained through scientific observations are often contaminated by noise and artifacts from various sources. As a result, a first step in mining these data is to isolate the signal of interest by minimizing the effects of the contaminations. Once the data has been cleaned or de-noised, data mining can proceed as usual. In this paper, we describe our work in denoising astronomical images from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. We are mining this survey to detect radio-emitting galaxies with a bent-double morphology. This task is made difficult by the noise in the images caused by the processing of the sensor data. We compare three different approaches to de-noising: thresholding of wavelet coefficients advocated in the statistical community, traditional Altering methods used in the image processing community, and a simple thresholding scheme proposed by FIRST astronomers. While each approach has its merits and pitfalls, we found that for our purpose, the simple thresholding scheme worked relatively well for the FIRST dataset.
Date: January 22, 2001
Creator: Fodor, I K & Kamath, C
Object Type: Article
System: The UNT Digital Library
3(omega) Power Balance Procedure on the NIF (open access)

3(omega) Power Balance Procedure on the NIF

This document defines the detailed NIF full system shot procedure to obtain 8% power balance as specified by the SDR002 3.2.1.04. Because the 48 quads of the NIF will be set up over a period of five years, obtaining power balance will naturally be accomplished in two steps. First, as each quad is brought online, the four laser beams within each quad will be tuned by setting the PABTS splitter ratios so that each beam will give the same laser power on target during low energy square pulse shots. During the quad activation period all of the technical tools and procedures will be developed that are needed for attaining full laser power balance. After the initial settings of the 48 PABTS, if no other tuning is done the overall NIF power balance is expected to be about <15%. In the second step, an iteration procedure with approximately 18 full laser system shots will be needed to obtain 8% power balance by tuning out the remaining systematic differences among the quads to an acceptable small difference of 2% rms (at 3{omega}). This rms difference is smaller than the expected variation of the injection energy or the amplifier gain, and is also …
Date: January 22, 2001
Creator: Glenzer, S.; Jones, O.; Speck, D. R.; Munro, D.; Lerche, R.; Salmon, T. et al.
Object Type: Report
System: The UNT Digital Library
Improving development planning in a natural gas storage field through simulation-optimization uncertainty analyses (open access)

Improving development planning in a natural gas storage field through simulation-optimization uncertainty analyses

This is the second of two papers describing the application of simulation-optimization methods to a gas storage field development planning problem. The first paper began by giving a detailed description of the field and earlier efforts to model the effects of selected field development options on the field's productivity. It then outlined the basic steps required to apply a combination of artificial neural networks (ANNs) and the genetic algorithm (GA) to explore a much larger universe of field development planning options. Familiarity with the contents of the first paper is a prerequisite for understanding the material presented in this second paper. The optimized solutions to the planning problem presented in the first paper were based on a deterministic, ''best guess'' view of the field's reservoir properties. However, practical field development planning dictates that at least some of the uncertainties associated with these properties be taken into account. This second paper describes procedures and presents results showing how the ANN-GA approach to optimization can be extended to accommodate three sources of uncertainty pertinent to the field being studied: (1) Alternative hypotheses regarding the permeabilities in a key region of the field; (2) Uncertainty regarding the likely success of remediating existing wells; …
Date: January 22, 2001
Creator: Johnson, V M
Object Type: Report
System: The UNT Digital Library
Nuclear Criticality Safety Bounding Analysis for the In-Tank Precipitation (ITP) Process (open access)

Nuclear Criticality Safety Bounding Analysis for the In-Tank Precipitation (ITP) Process

This report focuses solely on the accumulation of uranium and plutonium during In-Tank Precipitation process (ITP) processing and precipitate storage. The concentration of uranium and plutonium from solution into the smaller volume of precipitate represents a possible concern for criticality.
Date: January 22, 2001
Creator: Chandler, M.C.
Object Type: Report
System: The UNT Digital Library
Message passing vs. shared address space on a cluster of SMPs (open access)

Message passing vs. shared address space on a cluster of SMPs

The emergence of scalable computer architectures using clusters of PCs or PC-SMPs with commodity networking has made them attractive platforms for high-end scientific computing. Currently, message passing (MP) and shared address space (SAS) are the two leading programming paradigms for these systems. MP has been standardized with MPI, and is the most common and mature parallel programming approach. However, MP code development can be extremely difficult, especially for irregularly structured computations. SAS offers substantial ease of programming, but may suffer from performance limitations due to poor spatial locality and high protocol overhead. In this paper, they compare the performance of and programming effort required for six applications under both programming models on a 32-CPU PC-SMP cluster. Our application suite consists of codes that typically do not exhibit scalable performance under shared-memory programming due to their high communication-to-computation ratios and complex communication patterns. Results indicate that SAS can achieve about half the parallel efficiency of MPI for most of the applications; however, on certain classes of problems, SAS performance is competitive with MPI.
Date: January 22, 2001
Creator: Shan, Hongzhang; Singh, Jaswinder Pal; Oliker, Leonid & Biswas, Rupak
Object Type: Article
System: The UNT Digital Library
Model-Based Reliability Analysis (open access)

Model-Based Reliability Analysis

Modeling, in conjunction with testing, is a rich source of insight. Model parameters are easily controlled and monitoring can be done unobtrusively. The ability to inject faults without otherwise affecting performance is particularly critical. Many iterations can be done quickly with a model while varying parameters and conditions based on a small number of validation tests. The objective of Model-Based Reliability Analysis (MBRA) is to identify ways to capitalize on the insights gained from modeling to make both qualitative and quantitative statements about product reliability. MBRA will be developed and exercised in the realm of weapon system development and maintenance, where the challenges of severe environmental requirements, limited production quantities, and use of one-shot devices can make testing prohibitively expensive. However, the general principles will also be applicable to other product types.
Date: January 22, 2001
Creator: Bierbaum, Rene L.; Brown, Thomas d. & Kerschen, Thomas J.
Object Type: Article
System: The UNT Digital Library
Exploring the microscopic origin of exchange bias with photo-electron emission microscopy (PEEM) (open access)

Exploring the microscopic origin of exchange bias with photo-electron emission microscopy (PEEM)

It is well known that magnetic exchange coupling across the ferromagnet--antiferromagnet interface results in a unidirectional magnetic anisotropy of the ferromagnetic layer, called exchange bias. Despite large experimental and theoretical efforts, the origin of exchange bias is still controversial, mainly because detection of the interfacial magnetic structure is difficult. We have applied photoelectron emission microscopy (PEEM) on several ferromagnet - antiferromagnet thin-film structures and microscopically imaged the ferromagnetic and the antiferromagnetic structure with high spatial resolution. Taking advantage of the surface sensitivity and elemental specificity of PEEM, the magnetic configuration and critical properties such as the Neel temperature were determined on LaFeO{sub 3} and NiO thin films and single crystals. On samples coated with a ferromagnetic layer, we microscopically observe exchange coupling across the interface, causing a clear correspondence of the domain structures in the adjacent ferromagnet and antiferromagnet. Field dependent measurements reveal a strong uniaxial anisotropy in individual ferromagnetic domains. A local exchange bias was observed even in not explicitly field-annealed samples, caused by interfacial uncompensated magnetic spins. These experiments provide highly desired information on the relative orientation of electron spins at the interface between ferromagnets and antiferromagnets.
Date: January 22, 2001
Creator: Scholl, A.; Nolting, F.; Stohr, J.; Regan, T.; Luning, J.; Seo, J.W. et al.
Object Type: Article
System: The UNT Digital Library
Experimental Facilities Division/User Program Division technical progress report 1999-2000. (open access)

Experimental Facilities Division/User Program Division technical progress report 1999-2000.

In October 1999, the two divisions of the Advanced Photon Source (APS), the Accelerator Systems Division (ASD) and the Experimental Facilities Division (XFD), were reorganized into four divisions (see high-level APS organizational chart, Fig. 1.1). In addition to ASD and XFD, two new divisions were created, the APS Operations Division (AOD), to oversee APS operations, and the User Program Division (UPD), to serve the APS user community by developing and maintaining the highest quality user technical and administration support. Previous XFD Progress Reports (ANL/APS/TB-30 and ANL/APS/TB-34) covered a much broader base, including APS user administrative support and what was previously XFD operations (front ends, interlocks, etc.) This Progress Report summarizes the main scientific and technical activities of XFD, and the technical support, research and development (R and D) activities of UPD from October 1998 through November 2000. The report is divided into four major sections, (1) Introduction, (2) SRI-CAT Beamlines, Technical Developments, and Scientific Applications, (3) User Technical Support, and (4) Major Plans for the Future. Sections 2 and 3 describe the technical activities and research accomplishments of the XFD and UPD personnel in supporting the synchrotron radiation instrumentation (SRI) collaborative access team (CAT) and the general APS user community. …
Date: January 22, 2001
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Wind Turbine Wake Measurements in the Operating Region of a Tail Vain (open access)

Wind Turbine Wake Measurements in the Operating Region of a Tail Vain

In conjunction with the National Renewable Energy Laboratory's (NREL's) Unsteady Aerodynamics Experiment (UAE) at NASA Ames, we measured the wake of an upwind 10-meter (m) diameter wind turbine in the typical region of a tail vane. The experiment was performed in a 24.4-by-36.6-m wind tunnel. We placed two sonic anemometers 0.58 rotor diameters downwind of the rotor at hub height. One was positioned nominally behind the nacelle at 9% radius and the second was placed 2-m outboard at 49% radius. The tunnel wind speed was varied from 5 to 25 meters per second (m/s) and the turbine rotor speed was held at 72 revolutions per minute (rpm). We varied yaw from 0{degree} to 60{degree}. The data showed unsteadiness in the wake due to the nacelle wake. Also, the unsteadiness increased with the onset of blade stall. The axial induction factor in the wake showed that the turbine was operating within the windmill brake state of actuator disk momentum theory. Little variation in unsteadiness was shown under yawed conditions. We also discovered that lateral velocity behind the nacelle was negative and would result in an unfurling normal force on a tail vane. The vertical velocity was shown to change sign under …
Date: January 22, 2001
Creator: Larwood, S.
Object Type: Article
System: The UNT Digital Library
Facility Effluent Monitoring Plan for Pacific Northwest National Laboratory Balance-of-Plant Facilities (open access)

Facility Effluent Monitoring Plan for Pacific Northwest National Laboratory Balance-of-Plant Facilities

The Pacific Northwest National Laboratory (Pacific Northwest) operates a number of Research and Development facilities for the U.S. Department of Energy (DOE) on the Hanford Site. According to DOE Order 5400.1, a written environmental monitoring plan is required for each site, facility, or process that uses, generates, releases, or manages significant pollutants or hazardous materials. Facility Effluent Monitoring Plans (FEMPs) have been developed on the Hanford Site to document the facility effluent monitoring portion of the Environmental Monitoring Plan (DOE 2000) for the Hanford Site. Three of Pacific Northwest's R and D facilities, the 325, 331, and 3720 Buildings, are considered major emission points for radionuclide air sampling; thus, individual FEMPs have been developed for these facilities. Because no definition of ''significant'' is provided in DOE Order 5400.1 or the accompanying regulatory guide DOE/EH?0173T, this FEMP was developed to describe monitoring requirements in the DO E-owned, Pacific Northwest-operated facilities that do not have individual FEMPs. These facilities are referred to as Balance-of-Plant (BOP) facilities.
Date: January 22, 2001
Creator: Ballinger, Marcel Y & Shields, Keith D
Object Type: Report
System: The UNT Digital Library
Tenth Workshop on Crystalline Silicon Solar Cell Materials and Processes: A Summary of Discussion Sessions (open access)

Tenth Workshop on Crystalline Silicon Solar Cell Materials and Processes: A Summary of Discussion Sessions

The 10th Workshop on Silicon Solar Cell Materials and Processes was held in Copper Mountain, Colorado, on August 13-16, 2000. The workshop was attended by 85 scientists and engineers from 15 international photovoltaic (PV) companies and 24 research institutions. Review and poster presentations were augmented by discussion sessions to address the recent progress and critical issues in meeting the goals for Si in the PV Industry Roadmap. The theme of the workshop was Si Photovoltaics: 10 Years of Progress and Opportunities for the Future. Two special sessions were held: Advanced Metallization and Interconnections - covering recent advances in solar cell metallization, printed contacts and interconnections, and addressing new metallization schemes for low-cost cell interconnections; and Characterization Methods - addressing the growing need for process monitoring techniques in the PV industry. The following major issues emerged from the discussion sessions: (1) Mechanical breakage in the P V industry involves a large fraction, about 5%-10%, of the wafers. (2) The current use of Al screen-printed back-contacts appears to be incompatible with the PV Industry Roadmap requirements. (3) The PV manufacturers who use hydrogen passivation should incorporate the plasma-enhanced chemical vapor deposited (PECVD) nitride for antireflection coating and hydrogenation. (4) There is an …
Date: January 22, 2001
Creator: Tan, T.; Swanson, D.; Sinton, R. & Sopori, B.
Object Type: Article
System: The UNT Digital Library
Increased Oil Recovery from Mature Oil Fields Using Gelled Polymer Treatments (open access)

Increased Oil Recovery from Mature Oil Fields Using Gelled Polymer Treatments

This report describes the progress of the first year of a three-year research program. This program is aimed at reducing barriers to the widespread use of gelled polymer treatments by (1) developing methods to predict gel behavior during placement in matrix rock and fractures, (2) determining the persistence of permeability reduction after gel placement, and (3) developing methods to design production well treatments to control water production.
Date: January 22, 2001
Creator: Willhite, G.P.; Green, D.W. & McCool, C.S.
Object Type: Report
System: The UNT Digital Library
Specific PVMaT R and D in CdTe Product Manufacturing; Phase II Annual Subcontract Technical Report; May 1999--September 2000 (open access)

Specific PVMaT R and D in CdTe Product Manufacturing; Phase II Annual Subcontract Technical Report; May 1999--September 2000

Just prior to the beginning of Phase II of the PVMaT project Solar Cells, Inc, (SCI) and True North Partners of Scottsdale, AZ, formed a joint venture partnership name First Solar, LLC. By the end of 1999, this event resulted in the construction of a new major manufacturing plant for photovoltaic modules, based on cadmium telluride, located in Perrysburg, a suburb of Toledo, Ohio. This plant was designed to be capable of producing PV modules at a rate of 100 MW per year within about three years. Significantly, a new semiconductor coating system, the heat of the production line, has already shown the capability of the 100 MW per year rate. These events have led to the expansion of the effort on the PVMaT project that included the former SCI team in Toledo, Ohio, a new team of engineering subcontractor, Product Search, Inc., and, later, a new laser team from First Solar, both from Scottsdale, Arizona. These three teams joined in a collaborative effort on Tasks 4: Manufacturing Line Improvements, on Task 5: Product Readiness, and on Task Environmental, Health, and Safety Issues. One Task 4 goal was to address the technical issues of the failed UL 1703 qualification testing …
Date: January 22, 2001
Creator: McMaster, A.
Object Type: Report
System: The UNT Digital Library
CIS-Type PV Device Fabrication by Novel Techniques; Phase II Subcontract Report 1 July 1999--31 June 2000 (open access)

CIS-Type PV Device Fabrication by Novel Techniques; Phase II Subcontract Report 1 July 1999--31 June 2000

The R and D program at ISET is centered on development of a novel, dispersion-based route to the deposition of precursor thin films that are converted to CIS-type absorbers through high temperature reactions at or close to atmospheric pressure. The goal of the current research program at ISET is to bring a non-vacuum processing route for CIS closer to commercialization by improving the device efficiency through an increase in absorber bandgap. The basic processing approach involves first synthesizing a powder containing the oxides of copper, indium and gallium. A dispersion (ink) is prepared from the starting powder by mechanical milling or sonication. This ink is then deposited onto the glass/moly substrate as a thin precursor (3-4 {micro}m) and converted to a metallic alloy film by reaction in a hydrogen atmosphere. Controlled synthesis of starting powders and proper reduction results in reasonably smooth, metallic precursor films similar to those produced by sputtering or evaporation. From this point the processing is similar to that in the other two-stage techniques, with the metallic film being reacted in H2Se to form the final photovoltaic absorber, followed by CdS and TCO deposition.
Date: January 22, 2001
Creator: Fisher, M. L. & Kapur, V. K.
Object Type: Report
System: The UNT Digital Library
Advanced Characterization of Fractured Reservoirs in Carbonate Rocks: The Michigan Basin (open access)

Advanced Characterization of Fractured Reservoirs in Carbonate Rocks: The Michigan Basin

The main objective of this project is for a university-industry consortium to develop a comprehensive model for fracture carbonate reservoirs based on the ''data cube'' concept using the Michigan Basin as a prototype. This project combined traditional historical data with 2D and 3D seismic data as well as data from modern logging tools in a novel way to produce a new methodology for characterizing fractured reservoirs in carbonate rocks. Advanced visualization software was used to fuse the data and to image it on a variety of scales, ranging from basin-scale to well-scales.
Date: January 22, 2001
Creator: Wood, J.R. & Harrison, W.B.
Object Type: Report
System: The UNT Digital Library
Proceeding of Workshop on Photo-Injector for Energy Recovery Linac (open access)

Proceeding of Workshop on Photo-Injector for Energy Recovery Linac

Workshop on Photo-injectors for Energy Recovery Linac was held at National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory (BNL) on January 22 and 23, 2001. Fifty people attended the workshop; they came from three countries, representing universities, industries and national laboratories. This is the first workshop ever held on photo-injectors for CW operation, and for the first time, both DC and RF photo-injectors were discussed at the workshop. Workshop covered almost all major issues of photo-injectors, photocathode, laser system, vacuum, DC, 433 MHz/B-factory cavities based RF gun, 1.3 GHz RF gun and beam instrumentation. High quantum efficiency and long live time photocathode is the issue discussed during the workshop. Four working group leaders have done great jobs summarizing the workshop discussion, and identifying the major issues for future R and D.
Date: January 22, 2001
Creator: Wang, X. J.
Object Type: Report
System: The UNT Digital Library