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34,006 Matching Results
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LEEM investigations of clean surfaces driven by energetic ion beams
The original purpose of this award was to use low‐energy electron microscopy (LEEM) to explore the dynamics of surfaces of clean single crystal surfaces when driven by a beam of energetic ions. The goal was to understand the nanoscience of hyperthermal growth, surface erosion by sublimation and irradiation, operation of surface sinks in irradiated materials, diffusion on driven surfaces, and the creation of structural patterns. This project was based on a novel LEEM system constructed by C. P. Flynn, which provided real‐time imaging of surface dynamics by scattering low energy electrons. With the passing of Prof. Flynn in late 2011, this project was completed under a slightly different scope by constructing a low‐energy, inelastic electron scattering (�EELS�) instrument. Consistent with Flynn�s original objectives for his LEEM system, this device probes the dynamics of crystal surfaces. However the measurements are not carried out in real time, but instead are done in the frequency domain, through the energy lost from the probe electrons. The purpose of this device is to study the collective bosonic excitations in a variety of materials, including high temperature superconductors, topological insulators, carbon allotropes including (but not limited to) graphene, etc. The ultimate goal here is to identify …
Date:
April 24, 2013
Creator:
Abbamonte, Peter M.
Object Type:
Report
System:
The UNT Digital Library
Optical Mapping of Oak Ridge Research Reactor Experiment Tubes
Report issued by the Oak Ridge National Laboratory discussing optical mapping of experiment tubes. Descriptions of experiment equipment, and designs of the tubes are presented. This report includes tables, illustrations, and photographs.
Date:
April 1965
Creator:
Abbatiello, A. A.
Object Type:
Report
System:
The UNT Digital Library
The Low-Income Home Energy Assistance Program: How are State Allotments Determined?
This report discusses the Low-Income Home Energy Assistance Program (LIHEAP), which is a block grant program under which the federal government provides states annual grants to operate multi-component home energy assistance programs for needy households.
Date:
April 17, 2001
Creator:
Abbey, Craig W.
Object Type:
Report
System:
The UNT Digital Library
Experiments With an Airfoil Model on Which the Boundary Layers Are Controlled Without the Use of Supplementary Equipment
This report describes test made in the Variable Density Wind Tunnel of the NACA to determine the possibility of controlling the boundary layer on the upper surface of an airfoil by use of the low pressure existing near the leading edge. The low pressure was used to induce flow through slots in the upper surface of the wing. The tests showed that the angle of attack for maximum lift was increased at the expense of a reduction in the maximum lift coefficient and an increase in the drag coefficient.
Date:
April 1931
Creator:
Abbott, Ira H.
Object Type:
Report
System:
The UNT Digital Library
Comparison of a constraint directed search to a genetic algorithm in a scheduling application
Scheduling plutonium containers for blending is a time-intensive operation. Several constraints must be taken into account; including the number of containers in a dissolver run, the size of each dissolver run, and the size and target purity of the blended mixture formed from these runs. Two types of algorithms have been used to solve this problem: a constraint directed search and a genetic algorithm. This paper discusses the implementation of these two different approaches to the problem and the strengths and weaknesses of each algorithm.
Date:
April 1, 1993
Creator:
Abbott, L.
Object Type:
Article
System:
The UNT Digital Library
Toxic vapor cloud impacts from accidental releases of anhydrous ammonia and nitrogen dioxide at the ICPP NO{sub x} Abatement Facility
This report evaluates potential atmospheric and human health impacts that may result from accidental releases of anhydrous ammonia and nitrogen dioxide at the Idaho Chemical Processing Plant (ICPP) NO{sub x} Abatement Facility. Excess process gas releases are evaluated using a traditional Gaussian puff model. Dense two-phase aerosol releases from an 18,000 gallon liquefied ammonia storage tank and a 6,000 gallon tanker truck accident are evaluated using the refined vapor dispersion model, SLAB. The SLAB results are also compared to those using the neutral-buoyancy puff model. A SLAB sensitivity analysis is presented which examines various combinations of ambient temperatures and wind speeds in order to determine worst-case downwind air concentrations. The results from the storage tank releases indicated that potentially serious ammonia concentrations (greater than 1000 ppm) could result at downwind distances ranging from 150 meters (relief valve malfunction) to approximately 3 kilometers (catastrophic tank failure). The tank failure scenario produced concentrations that could be rapidly fatal (greater than 5000 ppm) out to 1.3 kilometers. Under worst-case meteorological dispersion conditions, recognized exposure limits (IDLH, TLV-STEL) were exceeded for very large distances (greater than 15 kilometers).
Date:
April 1, 1992
Creator:
Abbott, M. L.
Object Type:
Report
System:
The UNT Digital Library
Toxic vapor cloud impacts from accidental releases of anhydrous ammonia and nitrogen dioxide at the ICPP NO sub x Abatement Facility
This report evaluates potential atmospheric and human health impacts that may result from accidental releases of anhydrous ammonia and nitrogen dioxide at the Idaho Chemical Processing Plant (ICPP) NO{sub x} Abatement Facility. Excess process gas releases are evaluated using a traditional Gaussian puff model. Dense two-phase aerosol releases from an 18,000 gallon liquefied ammonia storage tank and a 6,000 gallon tanker truck accident are evaluated using the refined vapor dispersion model, SLAB. The SLAB results are also compared to those using the neutral-buoyancy puff model. A SLAB sensitivity analysis is presented which examines various combinations of ambient temperatures and wind speeds in order to determine worst-case downwind air concentrations. The results from the storage tank releases indicated that potentially serious ammonia concentrations (greater than 1000 ppm) could result at downwind distances ranging from 150 meters (relief valve malfunction) to approximately 3 kilometers (catastrophic tank failure). The tank failure scenario produced concentrations that could be rapidly fatal (greater than 5000 ppm) out to 1.3 kilometers. Under worst-case meteorological dispersion conditions, recognized exposure limits (IDLH, TLV-STEL) were exceeded for very large distances (greater than 15 kilometers).
Date:
April 1, 1992
Creator:
Abbott, M.L.
Object Type:
Report
System:
The UNT Digital Library
Radiological Dose Calculations for Fusion Facilities
This report summarizes the results and rationale for radiological dose calculations for the maximally exposed individual during fusion accident conditions. Early doses per unit activity (Sieverts per TeraBecquerel) are given for 535 magnetic fusion isotopes of interest for several release scenarios. These data can be used for accident assessment calculations to determine if the accident consequences exceed Nuclear Regulatory Commission and Department of Energy evaluation guides. A generalized yearly dose estimate for routine releases, based on 1 Terabecquerel unit releases per radionuclide, has also been performed using averaged site parameters and assumed populations. These routine release data are useful for assessing designs against US Environmental Protection Agency yearly release limits.
Date:
April 1, 2003
Creator:
Abbott, Michael L.; Cadwallader, Lee C. & Petti, David A.
Object Type:
Report
System:
The UNT Digital Library
An automated vacuum gauge calibration system
An automated system for calibrating vacuum gauges over the pressure range of 10{sup {minus}6} to 0.1 Pa was designed and constructed at the National Institute of Standards and Technology (NIST) for the Department of Energy (DOE) Primary Standards Laboratory at Sandia National Laboratories (SNL). Calculable pressures are generated by passing a known flow of gas through an orifice of known conductance. The orifice conductance is derived from dimensional measurements and accurate flows are generated using metal capillary leaks. The expanded uncertainty (k = 2) in the generated pressure is estimated to be between 1% and 4% over the calibration range. The design, calibration results. and component uncertainties will be discussed.
Date:
April 1, 1998
Creator:
Abbott, P. J. & Benner, M. S.
Object Type:
Article
System:
The UNT Digital Library
Flywheel energy storage using superconducting magnetic bearings
Storage of electrical energy on a utility scale is currently not practicable for most utilities, preventing the full utilization of existing base-load capacity. A potential solution to this problem is Flywheel Energy Storage (FES), made possible by technological developments in high-temperature superconducting materials. Commonwealth Research Corporation (CRC), the research arm of Commonwealth Edison Company, and Argonne National Laboratory are implementing a demonstration project to advance the state of the art in high temperature superconductor (HTS) bearing performance and the overall demonstration of efficient Flywheel Energy Storage. Currently, electricity must be used simultaneously with its generation as electrical energy storage is not available for most utilities. Existing storage methods either are dependent on special geography, are too expensive, or are too inefficient. Without energy storage, electric utilities, such as Commonwealth Edison Company, are forced to cycle base load power plants to meet load swings in hourly customer demand. Demand can change by as much as 30% over a 12-hour period and result in significant costs to utilities as power plant output is adjusted to meet these changes. HTS FES systems can reduce demand-based power plant cycling by storing unused nighttime capacity until it is needed to meet daytime demand.
Date:
April 1, 1994
Creator:
Abboud, R. G.; Uherka, K.; Hull, J. & Mulcahy, T.
Object Type:
Article
System:
The UNT Digital Library
Multiphoton physics with x-rays: Two photon K-shell ionization of chlorine
A calculation of the two X-ray K-shell photoionization cross section of chlorine will be presented and the feasibility of an experiment will be discussed.
Date:
April 1, 1993
Creator:
Abdallah, J.; Collins, L. A.; Csanak, G.; Kyrala, G. A. & Schappert, G. T.
Object Type:
Article
System:
The UNT Digital Library
Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes
The diffuse galactic {gamma}-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess {gamma}-ray emission {ge}1 GeV relative to diffuse galactic {gamma}-ray emission models consistent with directly measured CR spectra (the so-called 'EGRET GeV excess'). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse {gamma}-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10{sup o} {le} |b| {le} 20{sup o}. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic {gamma}-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.
Date:
April 11, 2012
Creator:
Abdo, A. A.; Ackermann, M.; Ajello, M.; Anderson, B.; Atwood, W. B.; Axelsson, M. et al.
Object Type:
Article
System:
The UNT Digital Library
Fermi LAT Observations of LS I +61 303: First Detection of an Orbital Modulation in GeV Gamma Rays
This Letter presents the first results from the observations of LS I +61{sup o}303 using Large Area Telescope data from the Fermi Gamma-Ray Space Telescope between 2008 August and 2009 March. Our results indicate variability that is consistent with the binary period, with the emission being modulated at 26.6 {+-} 0.5 days. This constitutes the first detection of orbital periodicity in high-energy gamma rays (20 MeV-100 GeV, HE). The light curve is characterized by a broad peak after periastron, as well as a smaller peak just before apastron. The spectrum is best represented by a power law with an exponential cutoff, yielding an overall flux above 100 MeV of 0.82 {+-} 0.03(stat) {+-} 0.07(syst) 10{sup -6} ph cm{sup -2} s{sup -1}, with a cutoff at 6.3 {+-} 1.1(stat) {+-} 0.4(syst) GeV and photon index {Gamma} = 2.21 {+-} 0.04(stat) {+-} 0.06(syst). There is no significant spectral change with orbital phase. The phase of maximum emission, close to periastron, hints at inverse Compton scattering as the main radiation mechanism. However, previous very high-energy gamma ray (>100 GeV, VHE) observations by MAGIC and VERITAS show peak emission close to apastron. This and the energy cutoff seen with Fermi suggest that the link …
Date:
April 2, 2012
Creator:
Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwood, W. B.; Axelsson, M.; Baldini, L. et al.
Object Type:
Article
System:
The UNT Digital Library
Important aspects of radiation shielding for fusion reactor tokamaks
Radiation shielding is a key subsystem in tokamak reactors. Design of this shield must evolve from economic and technological trade-off studies that account for the strong interrelations among the various components of the reactor system. These trade-offs are examined for the bulk shield on the inner side of the torus and for the special shields of major penetrations. Results derived are applicable for a large class of tokamak-type reactors.
Date:
April 30, 1977
Creator:
Abdou, M. A.
Object Type:
Article
System:
The UNT Digital Library
INTOR Impurity Control and First Wall System
The highlights of the recent INTOR effort on examining the key issues of the impurity control/first wall system are summarized. The emphasis of the work was an integrated study of the edge-region physics, plasma-wall interaction, materials, engineering and magnetic considerations associated with the poloidal divertor and pump limiter. The development of limiter and divertor collector plate designs with an acceptable lifetime was a major part of the work.
Date:
April 1, 1983
Creator:
Abdou, M. A.
Object Type:
Report
System:
The UNT Digital Library
Chamber and target technology development for inertial fusion energy
Fusion chambers and high pulse-rate target systems for inertial fusion energy (IFE) must: regenerate chamber conditions suitable for target injection, laser propagation, and ignition at rates of 5 to 10 Hz; extract fusion energy at temperatures high enough for efficient conversion to electricity; breed tritium and fuel targets with minimum tritium inventory; manufacture targets at low cost; inject those targets with sufficient accuracy for high energy gain; assure adequate lifetime of the chamber and beam interface (final optics); minimize radioactive waste levels and annual volumes; and minimize radiation releases under normal operating and accident conditions. The primary goal of the US IFE program over the next four years (Phase I) is to develop the basis for a Proof-of-Performance-level driver and target chamber called the Integrated Research Experiment (IRE). The IRE will explore beam transport and focusing through prototypical chamber environment and will intercept surrogate targets at high pulse rep-rate. The IRE will not have enough driver energy to ignite targets, and it will be a non-nuclear facility. IRE options are being developed for both heavy ion and laser driven IFE. Fig. 1 shows that Phase I is prerequisite to an IRE, and the IRE plus NIF (Phase II) is prerequisite …
Date:
April 7, 1999
Creator:
Abdou, M.; Besenbruch, G.; Duke, J.; Forman, L.; Goodin, D.; Gulec, K. et al.
Object Type:
Report
System:
The UNT Digital Library
Pattern of Thermal Fluctuations in a Recovery Boiler Floor
The floor of a black liquor recovey boiler at a mill in central Canada has experienced cracking and delamination of the composite tubing near the spout wall and deformation of the floor panels that is most severe in the vicinity of the spout wall. One possible explanation for the observed damage is impacts of salt cake falling from the convective section onto the floor. In order to determine if such impacts do occur, strain gauges and thermocouples were installed on the boiler floor in areas where cracking and deformation were most frequent. The data obtained from these instruments indicate that brief, sudden temperature fluctuations do occur, and changes in the strain experienced by the affected tube occur simultaneously. These fluctuations appear to occur less often along the spout wall and more frequently with increasing distance from the wall. The frequency of these temperature fluctuations is insufficient for thermal fatigue to be the sole cause of the cracking observed on the tubes, but the data are consistent with what might be expected from pieces of falling salt cake.
Date:
April 25, 1999
Creator:
Abdullah, Z.; Gorog, J. P.; Keiser, J. R.; Meyers, L. E. & Swindeman, R. W.
Object Type:
Article
System:
The UNT Digital Library
Results from Sage
The Russian-American Gallium Solar Neutrino Experiment (SAGE) is described. Beginning in September 1992, SAGE II data were taken with 55 tons of Ga and with significantly reduced backgrounds. The solar neutrino flux measured by 31 extractions through October 1993 is presented. The result of 69 {+-} 10 +5/{minus}7 SNU is to be compared with a Standard Solar Model prediction of 132 SNU.
Date:
April 1, 1996
Creator:
Abdurashitov, J. N.; Gavrin, V. N. & Girin, S. V.
Object Type:
Report
System:
The UNT Digital Library
Anode Sheath Switching in a Carbon Nanotube Arc Plasma
The anode ablation rate is investigated as a function of anode diameter for a carbon nanotube arc plasma. It is found that anomalously high ablation occurs for small anode diameters. This result is explained by the formation of a positive anode sheath. The increased ablation rate due to this positive anode sheath could imply greater production rate for carbon nanotubes.
Date:
April 8, 2008
Creator:
Abe Fetterman, Yevgeny Raitses, and Michael Keidar
Object Type:
Report
System:
The UNT Digital Library
Electrostatic design of the barrel CRID (Cherenkov Ring Imaging Detector) and associated measurements
We report on the electrostatic design and related measurements of the barrel Cherenkov Ring Imaging Detector for the Stanford Large Detector experiment at the Stanford Linear Accelerator Center Linear Collider. We include test results of photon feedback in TMAE-laden gas, distortion measurements in the drift boxes and corona measurements. 13 refs., 21 figs.
Date:
April 1, 1990
Creator:
Abe, K.; Hasegawa, K.; Suekane, F.; Yuta, H. (Tohoku Univ., Sendai (Japan). Dept. of Physics); Antilogus, P.; Aston, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Influence of access hole parameters on neutron moisture probe readings
Computing soil moisture content with a neutron probe requires use of a calibration curve that considers the thermal neutron capture cross section of the hole liner as well as the hole diameter. The influence of steel, polyvinyl chloride, and aluminum casings that fit 0.051 to 0.102-hole diameters was determined by comparison with neutron probe readings in uncased holes of corresponding diameters. Eccentricity of probe location was considered a potentially significant variable. The relationship between hole diameter and count rate also was investigated. The experiment was run in disturbed Bandelier tuff with an average dry density of 1.2 g . cm/sup -3/ and moisture content of 1.3 to 35.5% by volume. The casing material and hole diameter influenced the probe readings significantly, whereas eccentric location of the probe did not. Regression analyses showed an almost perfect inverse linear correlation between hole diameter and count rate.
Date:
April 1978
Creator:
Abeele, Willy V.
Object Type:
Report
System:
The UNT Digital Library
Electric Transmission: Approaches for Energizing a Sagging Industry
This report discusses factors that have contributed to the lack of new transmission capacity and some of the resulting issues. This report reviews approaches being taken to address the lack of investment in transmission infrastructure and transmission congestion.
Date:
April 27, 2007
Creator:
Abel, Amy
Object Type:
Report
System:
The UNT Digital Library
Electric Utility Regulatory Reform: Issues for the 109th Congress
This report discusses regulation issues affecting electricity today. Comprehensive electricity legislation may involve several components: Public Utility Holding Company Act (PUHCA) reform, PURPA's requirement that utilities purchase power from qualifying facilities (QFs), and reliability.
Date:
April 21, 2005
Creator:
Abel, Amy
Object Type:
Report
System:
The UNT Digital Library
Electricity: The Road Toward Restructuring
The Public Utility Holding Company Act of 1935 (PUHCA) and the Federal Power Act (FPA) were enacted to eliminate unfair practices and other abuses by electricity and gas holding companies by requiring federal control and regulation of interstate public utility holding companies. Comprehensive energy legislation has passed the House and Senate. The House passed H.R. 6 on April 11, 2003. On July 31, 2003, the Senate suspended debate on S. 14, inserted the text of H.R. 4 (107th Congress) as a substitute, and passed H.R. 6. A conference agreement was reached November 17, 2003, and passed by the House the next day. H.R. 6 includes an electricity title that would, in part, repeal PUHCA, would prospectively repeal the mandatory purchase requirement under PURPA, and would create an electric reliability organization. On June 15, 2004, H.R. 4503, a comprehensive energy policy bill, passed the House.
Date:
April 8, 2003
Creator:
Abel, Amy & Parker, Larry
Object Type:
Report
System:
The UNT Digital Library