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A Comparison of Analytical Approaches for Wellbore Heat Transmission in Layered Formations (open access)

A Comparison of Analytical Approaches for Wellbore Heat Transmission in Layered Formations

This report presents an analytical method for determining wellbore heat transmission during liquid or gas flow along the tubing. The mathematical model describes the heat transfer between the flowing fluid in the wellbore and in the surrounding formation as one whole physical system. The transient heat transfer equations in the two regions with coupling at the sandface are solved simultaneously. Non-homogeneous formations are treated which consist of several layers with different physical properties and arbitrary initial temperature distributions in the vertical direction. Closed form analytical solutions are obtained in real space and in Laplace space, which can be used to calculate the temperature distribution along the wellbore and in the formation, and to evaluate heat transfer rate and cumulative heat exchange between wellbore and formation. A more accurate formula is given for the widely-used transient heat conduction function f(t{sub D}) of thermal resistance. 14 refs., 12 figs., 1 tab.
Date: August 1, 1988
Creator: Wu, Yu-Shu
System: The UNT Digital Library
Recent studies related to head-end fuel processing at the Hanford PUREX plant (open access)

Recent studies related to head-end fuel processing at the Hanford PUREX plant

This report presents the results of studies addressing several problems in the head-end processing (decladding, metathesis, and core dissolution) of N Reactor fuel elements in the Hanford PUREX plant. These studies were conducted over 2 years: FY 1986 and FY 1987. The studies were divided into three major areas: 1) differences in head-end behavior of fuels having different histories, 2) suppression of /sup 106/Ru volatilization when the ammonia scrubber solution resulting from decladding is decontaminated by distillation prior to being discharged, and 3) suitability of flocculating agents for lowering the amount of transuranic (TRU) element-containing solids that accompany the decladding solution to waste. 16 refs., 43 figs.
Date: August 1, 1988
Creator: Swanson, J.L.
System: The UNT Digital Library
A manual for applying the allowable residual contamination level method for decommissioning facilities on the Hanford Site (open access)

A manual for applying the allowable residual contamination level method for decommissioning facilities on the Hanford Site

This report describes the modifications that have been made to enhance the original Allowable Residual Contamination Level (ARCL) method to make it more applicable to site-specific analyses. This version considers the mixture of radionuclides present at the time of site characterization, the elapsed time after decommissioning when exposure to people could occur, and includes a calculation of the upper confidence limit of the potential dose based on sampling statistics that are developed during the site characterization efforts. The upper confidence limit of potential exposure can now be used for comparison against applicable radiation dose limits (i.e., 25 mrem/yr at Hanford). The level of confidence can be selected by the user. A wide range of exposure scenarios were evaluated; the rationale used to select the most limiting scenarios is explained. The radiation dose factors used for the inhalation and ingestion pathways were also updated to correspond with the radiation dosimetry methods utilized in the International Commission of Radiological Protection Publications 26 and 30 (ICRP 1977; 1979a,b, 1980, 1981, 1982a,b). This simplifies the calculations, since ''effective whole body'' doses are now calculated, and also brings the dosimetry methods used in the ARCL method in conformance with the rationale used by DOE in …
Date: August 1, 1988
Creator: Napier, B. A.; Piepel, G. F.; Kennedy, W. E. & Schreckhise, R. G.
System: The UNT Digital Library
Modeling of the sawtooth instability in tokamaks using a current viscosity term (open access)

Modeling of the sawtooth instability in tokamaks using a current viscosity term

We propose a new method for modeling the sawtooth instability and other MHD activity in axisymmetric tokamak transport simulations. A hyper-resistivity (or current viscosity) term is included in the mean field Ohm's law to describe the effects of the three-dimensional fluctuating fields on the evolution of the inverse transform, q, characterizing the mean fields. This term has the effect of flattening the current profile, while dissipating energy and conserving helicity. A fully implicit MHD transport and 2-D toroidal equilibrium code has been developed to calculate the evolution in time of the q-profile and the current profile using this new term. The results of this code are compared to the Kadomtsev reconnection model in the circular cylindrical limit. 17 refs., 8 figs.
Date: August 1, 1988
Creator: Ward, D. J. & Jardin, S. C.
System: The UNT Digital Library
Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers (open access)

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers

Six alloys are being considered as possible materials for the fabrication of containers for the disposal of high-level radioactive waste. Three of these candidate materials are copper-based alloys: CDA 102 (oxygen-free copper), CDA 613 (Cu-7Al), and CDA 715 (Cu-30Ni). The other three are iron- to nickel-based austenitic materials: Types 304L and 316L stainless steels and Alloy 825. Radioactive waste will include spent-fuel assemblies from reactors as well as waste in borosilicate glass and will be sent to the prospective site at Yucca Mountain, Nevada, for disposal. The waste-package containers must maintain substantially complete containment for at least 300 yr and perhaps as long as 1000 yr. During the first 50 yr after emplacement, the containers must be retrievable from the disposal site. Shortly after emplacement of the containers in the repository, they will be exposed to high temperatures and high gamma radiation fields from the decay of high-level waste. This radiation will promote the radiolytic decomposition of moist air to hydrogen. This volume surveys the available data on the effects of hydrogen on the six candidate alloys for fabrication of the containers. For copper, the mechanism of hydrogen embrittlement is discussed, and the effects of hydrogen on the mechanical properties …
Date: August 1, 1988
Creator: Gdowski, G. E. & Bullen, D. B.
System: The UNT Digital Library
The production and characterization of mid-gap states in trans-polyacetylene (open access)

The production and characterization of mid-gap states in trans-polyacetylene

Photoinduced ir absorptions with much longer lifetimes and lower excitation energies than previously reported were observed after the photolysis of polyacetylene with upsilon > 5000 cm/sup -1/. These absorptions are similar to those previously reported to have millisecond lifetimes, and are attributed to charged bond-alternation defects. The persistent photoinduced absorptions could be depleted by photoexcitation of a transition with an absorption maximum near 4000 cm/sup -1/. Unpaired spins were observed to develop and be depleted at the same photolysis frequencies as the ir activity. These spins may be due to the charged defects. This would mean that the defects are charged polarons. The temperature required to dope polyacetylene chemically was measured for various dopants. This was taken to be a measure of the activation energy for the doping reaction. The activation energies were found to be much lower than predicted by stepwise reaction mechanisms. Photolysis with above-band-gap light did not alter the temperature required for reaction. The chemical stabilization of photoinduced defects does not occur at a perceptible rate at lower temperatures than the chemical doping reaction. 35 refs., 26 figs., 14 tabs.
Date: August 1, 1988
Creator: Hoener, C.F.
System: The UNT Digital Library
Evaluation of liquid-fed ceramic melter scale-up correlations (open access)

Evaluation of liquid-fed ceramic melter scale-up correlations

This study was conducted to determine the parameters governing factors of scale for liquid-fed ceramic melters (LFCMs) in order to design full-scale melters using smaller-scale melter data. Results of melter experiments conducted at Pacific Northwest Laboratory (PNL) and Savannah River Laboratory (SRL) are presented for two feed compositions and five different liquid-fed ceramic melters. The melter performance data including nominal feed rate and glass melt rate are correlated as a function of melter surface area. Comparisons are made between the actual melt rate data and melt rates predicted by a cold cap heat transfer model. The heat transfer model could be used in scale-up calculations, but insufficient data are available on the cold cap characteristics. Experiments specifically designed to determine heat transfer parameters are needed to further develop the model. 17 refs.
Date: August 1, 1988
Creator: Koegler, S.S. & Mitchell, S.J.
System: The UNT Digital Library
Computer-aided methods of determining thyristor thermal transients (open access)

Computer-aided methods of determining thyristor thermal transients

An accurate tracing of the thyristor thermal response is investigated. This paper offers several alternatives for thermal modeling and analysis by using an electrical circuit analog: topological method, convolution integral method, etc. These methods are adaptable to numerical solutions and well suited to the use of the digital computer. The thermal analysis of thyristors was performed for the 1000 MVA converter system at the Princeton Plasma Physics Laboratory. Transient thermal impedance curves for individual thyristors in a given cooling arrangement were known from measurements and from manufacturer's data. The analysis pertains to almost any loading case, and the results are obtained in a numerical or a graphical format. 6 refs., 9 figs.
Date: August 1, 1988
Creator: Lu, E. & Bronner, G.
System: The UNT Digital Library
Treatment option evaluation for liquid effluent secondary streams on the Hanford Site (open access)

Treatment option evaluation for liquid effluent secondary streams on the Hanford Site

This study, conducted by the Pacific Northwest Laboratory (PNL) for Westinghouse Hanford Company (WHC), examines the range of secondary waste types and volumes likely to result from treatment of contaminated liquid effluents. Alternatives for treatment of these effluents were considered, taking into account the implementation of the ''best-available technology'' as assumed in current and ongoing engineering studies for treating the various liquid effluent waste streams. These treatment alternatives, and potential variations in the operating schedules for Hanford Site facilities generating contaminated liquid effluents, were evaluated to project an estimated range for the volume of each of the various secondary waste streams that are likely to be generated. The conclusions and recommendations were developed, based on these estimates. 23 refs., 34 figs., 16 tabs.
Date: August 1, 1988
Creator: Holter, G.M.; Triplett, M.B.; Fow, C.L. & White, M.K.
System: The UNT Digital Library
A database of PFT ventilation measurements (open access)

A database of PFT ventilation measurements

About five years ago, a method for measuring the ventilation flows of a building was developed at Brookhaven National Laboratory (BNL). This method is based on the use of a family of compounds known as perfluorocarbon tracers or PFTs. Since 1982, BNL has measured ventilation in more than 4000 homes, comprising about 100 separate research projects throughout the world. This measurement set is unique in that it is the only set of ventilation measurements that acknowledge and measure the multizone characteristics of residences. Other large measurement sets assume that a home can be treated as a single well-mixed zone. This report describes the creation of a database of approximately half of the PFT ventilation measurements made by BNL over the last five years. The PFT database is currently available for use on any IBM PC or Apple Macintosh based personal computer system. In addition to its utility in modeling indoor pollutant dispersion, this database may also be useful to those people studying energy conservation, thermal comfort and heating system design in residential buildings. 2 refs.
Date: August 1, 1988
Creator: D'Ottavio, T. W.; Goodrich, R. W.; Spandau, D. J. & Dietz, R. N.
System: The UNT Digital Library
A proposed method for reducing the sticking constant in muon catalyzed fusion (open access)

A proposed method for reducing the sticking constant in muon catalyzed fusion

We present a method of reducing the effective sticking coefficient involving reacceleration of the He..mu.. ion-by-ion cyclotron resonance. It is necessary to work with the target D--T in solid or liquid form, and the target has to be divided into many thin rods or pellets of order 100 microns in radius. The idea is to impose a magnetic field and a rotating electric field. A balance is achieved between drag in the rods or pellets and acceleration in the region between, so that the He..mu.. ion is held at a constant velocity until stripping occurs. Although stripping is greatly reduced, the idea is not practical as it stands because of the large alpha particle heat produced in the target. 2 refs., 3 figs., 2 tabs.
Date: August 1, 1988
Creator: Kulsrud, R.M.
System: The UNT Digital Library
Determination of physical and mechanical properties of copper-clad molybdenum sheet (open access)

Determination of physical and mechanical properties of copper-clad molybdenum sheet

Selected physical and mechanical properties of copper-clad molybdenum sheet have been determined. Among those properties determined were: room-temperature density, coefficient of thermal expansion in the temperature range {minus}43 to 800 C, specific heat between {minus}40 and +150 C, thermal conductivity from {minus}50 to +150 C, electrical resistivity in the same temperature range, magnetic susceptibility and modulus of elasticity both at room temperature. Materials with several different copper/molybdenum thickness ratios and composite thicknesses were evaluated.
Date: August 15, 1988
Creator: Grobner, P. J.
System: The UNT Digital Library
Investigation of processes to treat zinc-ferrite regeneration offgases in high temperature desulfurization of coal gases (open access)

Investigation of processes to treat zinc-ferrite regeneration offgases in high temperature desulfurization of coal gases

A bench-scale test program has been performed to evaluate the effect of critical operating variables on sulfur dioxide removal efficiency for two candidate throwaway'' desulfurization processes for treating zinc-ferrite reactor regeneration offgas. These two throwaway'' processes, dual-alkali wet scrubbing and spray dryer desulfurization, generate a gypsum waste sludge environmentally acceptable for disposal. They have seen extensive commercial application in flue gas desulfurization, but have not been evaluated for such high levels of removal efficiency and such high inlet sulfur dioxide concentrations as would be required for this application. 13 figs., 15 tabs.
Date: August 1, 1988
Creator: Woodland, L. R.
System: The UNT Digital Library
Interaction of impurity ions with a weakly non-Maxwellian simple hydrogenic plasma (open access)

Interaction of impurity ions with a weakly non-Maxwellian simple hydrogenic plasma

The average acceleration of an ensemble of ''test particles'' in a plasma is called the ''dynamical friction''; the average rate at which their velocity vectors spread out in velocity space is expressed in a velocity-space diffusion-rate tensor. These quantities are derived for impurity ions interacting with a weakly non-Maxwellian simple hydrogenic plasma. The distribution functions for the plasma ions and electrons are written explicitly. 5 refs., 3 figs.
Date: August 1, 1988
Creator: Terry, W.K.
System: The UNT Digital Library
PISCES and ALT-II: Juelich PSI papers (open access)

PISCES and ALT-II: Juelich PSI papers

This publication comprises papers from the PISCES and ALT-II Programs at UCLA which were presented at the International Plasma Surface Interactions Meeting held in Juelich, FRG, on May 2-6, 1988. A list of publications from the PISCES and ALT-II contained in this report are: Deuterium pumping and erosion behavior of selected graphite materials under high flux plasma bombardment in PISCES; Erosion and redeposition behavior of selected NET-candidate materials under high-flux hydrogen, deuterium plasma bombardment in PISCES; Presheath profiles in simulated tokamak edge plasmas; Boundary asymmetries and plasma flow to the ALT-II toroidal belt pump limiter; ALT-II toroidal belt pump limiter performance in TEXTOR; and An in-situ spectroscopic erosion yield measurement with applications to sputtering and surface morphology alterations.
Date: August 1, 1988
Creator: Conn, R. W.; Hirooka, Y.; LaBombard, B.; Moyer, R.; Goebel, D. M.; Leung, W. K. et al.
System: The UNT Digital Library
Three-dimensional plasma equilibrium near a separatrix (open access)

Three-dimensional plasma equilibrium near a separatrix

The limiting behavior of a general three-dimensional MHD equilibrium near a separatrix is calculated explicitly. No expansions in ..beta.. or assumptions about island widths are made. Implications of the results for the numerical calculation of such equilibria, are discussed, as well as for issues concerning the existence of three-dimensional MHD equilibria. 16 refs., 2 figs.
Date: August 1, 1988
Creator: Reiman, A. H.; Pomphrey, N. & Boozer, A. H.
System: The UNT Digital Library
Neoclassical tearing modes in a tokamak (open access)

Neoclassical tearing modes in a tokamak

Linear tearing instability is studied in the banana collisionality regime in tokamak geometry. Neoclassical effects produce significant modifications of Ohm's law and the vorticity equation so that the growth rate of tearing modes driven by ..delta..' is dramatically reduced compared to the usual resistive MHD value. Consequences of this result, regarding the presence of pressure-gradient-driven neoclassical resistive interchange instabilities and the evolution of magnetic islands in the Rutherford regime, are discussed. 10 refs.
Date: August 1, 1988
Creator: Hahm, T.S.
System: The UNT Digital Library
A survey of geothermal process heat applications in Guatemala: An engineering survey (open access)

A survey of geothermal process heat applications in Guatemala: An engineering survey

This study investigates how process heat from Guatemala's geothermal energy resources can be developed to reduce Guatemala's costly importation of oil, create new employment by encouraging new industry, and reduce fuel costs for existing industry. This investigation was funded by the US Agency for International Development and carried out jointly by the Guatemalan Government and the Los Alamos National Laboratory. Two sites, Amatitlan and Zunil, are being developed geothermally. Amatitlan is in the better industrial area but Zunil's geothermal development is more advanced. The industry around Zunil is almost exclusively agricultural and the development of an agricultural processing plant (freezing, dehydration, and cold storage) using geothermal heat is recommended. Similar developments throughout the volcanic zones of Guatemala are possible. Later, when the field at Amatitlan has been further developed, an industrial park can be planned. Potential Amatitlan applications are the final stage of salt refining, a thermal power plant, hospital/hotel heating and cooling, steam curing of concrete blocks, production of alcohol from sugar cane, and production of polyethylene from ethanol. Other special developments such as water pumping for the city of Guatemala and the use of moderate-temperature geothermal fluids for localized power production are also possible. 12 refs., 13 figs., …
Date: August 1, 1988
Creator: Altseimer, J.H. & Edeskuty, F.J.
System: The UNT Digital Library
Passive seismic monitoring of hydraulic fracture experiments at the Multiwell Experiment site (open access)

Passive seismic monitoring of hydraulic fracture experiments at the Multiwell Experiment site

Redesign of hardware, software, and data-reduction techniques associated with the Sandia National Laboratories' Borehole Seismic System (BSS) have made possible better estimates of hydraulic fracture geometry at the Multiwell Experiment (MWX) site. The redesigned system now incorporates four geophones per axis and provides up to 112 dB of downhole gain, for 100 times the sensitivity of the original system. Improved signal-to-noise ratios, extended frequency response and increased digitization rates have made possible the acquisition and processing of data which were previously inaccessible. A maximum likelihood event location scheme, which incorporates an algorithm based on the use of spherical statistics, is used to compute the location of microseismic events and error estimates for these locations. Accuracy estimates for the redesigned system, based on the ability to locate perforation shots, indicates a 25 ft (7.6 m) uncertainty in the location of individual microseismic events using data from two BSS receivers. This resulted in a high level of confidence in determination of the azimuth of the November 1, 1986, hydraulic fracture in the Fluvial B sandstone. A reasonable determination of the azimuth, propped wing length and height for the September 23, 1987, hydraulic fracture in the Fluvial E sandstone was possible using data …
Date: August 1, 1988
Creator: Thorne, B.J. & Morris, H.E.
System: The UNT Digital Library
Inhaled /sup 239/PuO/sub 2/ and/or total-body gamma radiation: Early mortality and morbidity in rats and dogs (open access)

Inhaled /sup 239/PuO/sub 2/ and/or total-body gamma radiation: Early mortality and morbidity in rats and dogs

Rats and beagle dogs were given doses of /sup 60/Co gamma radiation and/or body burdens of /sup 239/PuO/sub 2/ within lethal ranges in an experiment to determine and compare morbidity and mortality responses of both species within 1 year after exposure. Radiation-induced morbidity was assessed by measuring changes in body weights, hematologic parameters, and pulmonary-function parameters. Gamma radiation caused transient morbidity, reflected by immediately depressed blood cell concentrations and by long-term loss of body weight and diminished pulmonary function in animals of both species that survived the acute gamma radiation syndrome. Inhaled plutonium caused a loss of body weight and diminished pulmonary function in both species, but its only effect on blood cell concentrations was lymphocytopenia in dogs. Combined gamma irradiation and plutonium lung burdens were synergistic, in that animals receiving both radiation insults had higher morbidity and mortality rates than would be predicted based on the effect of either kind of radiation alone. Plutonium lung burdens enhanced the effect of gamma radiation in rats within the first 30 days of exposure, and gamma radiation enhanced the long-term effect of plutonium lung burdens in both species. Rats were less sensitive to both kinds of radiation, whether administered alone or in …
Date: August 1, 1988
Creator: Filipy, R. E.; Decker, J. R.; Lai, Y. L.; Lauhala, K. E.; Buschbom, R. L.; Hiastala, M. P. et al.
System: The UNT Digital Library
Steam generator group project: Task 13 final report: Nondestructive examination validation (open access)

Steam generator group project: Task 13 final report: Nondestructive examination validation

The Steam Generator Group Project (SGGP) was a multi-task effort using the retired-from-service Surry 2A pressurized water reactor steam generator as a test bed to investigate the reliability and effectiveness of in-service nondestructive eddy current (EC) inspection equipment and procedures. The information developed provided the technical basis for recommendations for improved in- service inspection and tube plugging criteria of steam generators. This report describes the results and analysis from Task 13--NDE Validation. The primary objective of Task 13 was to validate the EC inspection to detect and size tube defects. Additional objectives were to assess the nature and severity of tube degradation from all regions of the generator and to measure the remaining integrity of degraded specimens by burst testing. More than 550 specimens were removed from the generator and included in the validation studies. The bases for selecting the specimens and the methods and procedures used for specimen removal from the generator are reported. Results from metallurgical examinations of these specimens are presented and discussed. These examinations include visual inspection of all specimens to locate and identify tube degradation, metallographic examination of selected specimens to establish defect severity and burst testing of selected specimens to establish the remaining integrity …
Date: August 1, 1988
Creator: Bradley, E. R.; Doctor, P. G.; Ferris, R. H. & Buchanan, J. A.
System: The UNT Digital Library
Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers (open access)

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers

Three copper-based alloys and three iron- to nickel-based austenitic alloys are being considered as possible materials for fabrication of containers for disposal of high-level radioactive waste. This waste will include spent fuel assemblies from reactors as well as high-level waste in borosilicate glass and will be sent to the prospective site at Yucca Mountain, Nevada, for disposal. The containers must maintain substantially complete containment for at least 300 yr and perhaps as long as 1000 yr. During the first 50 yr after emplacement, they must be retrievable from the disposal site. Shortly after the containers are emplaced in the repository, they will be exposed to high temperatures and high gamma radiation fields from the decay of the high-level waste. This volume surveys the available data on oxidation and corrosion of the iron- to nickel-based austenitic materials (Types 304L and 316L stainless steels and Alloy 825) and the copper-based alloy materials (CDA 102 (oxygen-free copper), CDA 613 (Cu-7Al), and CDA 715 (Cu-30Ni)), which are the present candidates for fabrication of the containers. Studies that provided a large amount of data are highlighted, and those areas in which little data exists are identified. Examples of successful applications of these materials are given. …
Date: August 1, 1988
Creator: Gdowski, G. E. & Bullen, D. B.
System: The UNT Digital Library
Inhalation reproductive toxicology studies: Sperm morphology study of n-hexane in B6C3F1 mice: Final report (open access)

Inhalation reproductive toxicology studies: Sperm morphology study of n-hexane in B6C3F1 mice: Final report

The straight-chain hydrocarbon, n-hexane, is a volatile, ubiquitous solvent routinely used in industrial environments. Although myelinated nerve tissue is the primary target organ of hexane, the testes have also been identified as being sensitive to hexacarbon exposure. The objective of this study was to evaluate the epididymal sperm morphology of male B6D3F1 mice 5 weeks after exposure to 0, 200, 1000, or 5000 ppM n-hexane, 20 h/day for 5 consecutive days. Two concurrent positive control groups of animals were injected intraperitoneally with either 200 or 250 mg/kg ethyl methanesulfonate, a known mutagen, once each day for 5 consecutive days. The mice were weighed just prior to the first day of exposure and at weekly intervals until sacrifice. During the fifth post-exposure week the animals were killed and examined for gross lesions of the reproductive tract and suspensions of the epididymal sperm were prepared for morphological evaluations. The appearance and behavior of the mice were unremarkable throughout the experiment and there were no deaths. No evidence of lesions in any organ was noted at sacrifice. Mean body weights of male mice exposed to n-hexane were not significantly different from those for the 0-ppM animals at any time during the study. Analyses …
Date: August 1, 1988
Creator: Mast, T. J.; Hackett, P. L.; Decker, J. R.; Westerberg, R. B.; Sasser, L. B.; McClanahan, B. J. et al.
System: The UNT Digital Library
Hanford radiological protection support services annual report for 1987 (open access)

Hanford radiological protection support services annual report for 1987

This report documents the performance of certain radiological protection sitewide services during calendar year (CY) 1987 by Pacific Northwest Laboratory in support of the US Department of Energy-Richland Operations Office (DOE-RL) and contractor activities on the Hanford Site. The routine program for each service is discussed along with any significant program changes and tasks, investigations, and studies performed in support of each program. Other related activities such as publications, presentations, and memberships on standards or industry committees are also discussed. The programs covered provide services in the areas of: external dosimetry, internal dosimetry, in vivo measurements, instrument calibration and evaluation, calibration of radiation sources traceable to the National Bureau of Standards, and radiological records. 21 refs., 10 figs., 12 tabs.
Date: August 1, 1988
Creator: Lyon, M.; Fix, J. J.; Kenoyer, J. L.; Leonowich, J. A.; Palmer, H. E. & Sula, M. J.
System: The UNT Digital Library