States

100 Area Columbia River sediment sampling (open access)

100 Area Columbia River sediment sampling

Forty-four sediment samples were collected from 28 locations in the Hanford Reach of the Columbia River to assess the presence of metals and man-made radionuclides in the near shore and shoreline settings of the Hanford Site. Three locations were sampled upriver of the Hanford Site plutonium production reactors. Twenty-two locations were sampled near the reactors. Three locations were sampled downstream of the reactors near the Hanford Townsite. Sediment was collected from depths of 0 to 6 in. and between 12 to 24 in. below the surface. Samples containing concentrations of metals exceeding the 95 % upper threshold limit values (DOE-RL 1993b) are considered contaminated. Contamination by arsenic, chromium, copper, lead, and zinc was found. Man-made radionuclides occur in all samples except four collected opposite the Hanford Townsite. Man-made radionuclide concentrations were generally less than 1 pCi/g.
Date: September 8, 1993
Creator: Weiss, S. G.
Object Type: Report
System: The UNT Digital Library
Additional evaluation of ``LDS Moldable`` for melter construction (open access)

Additional evaluation of ``LDS Moldable`` for melter construction

Use of ``LDS Moldable`` as a cushion material for future DWPF melters is deemed feasible, because it serves the purpose of reducing the stress in the steel shell to acceptable levels. The assessment is based on the design geometry of the DWPF melter currently undergoing testing.
Date: October 8, 1993
Creator: Yau, W. W. F.
Object Type: Report
System: The UNT Digital Library
Alternatives for sodium-potassium alloy treatment (open access)

Alternatives for sodium-potassium alloy treatment

Sodium-potassium alloy (NaK) is currently treated at the Y-12 Plant by open burning. Due to uncertainties with future permits for this process alternative treatment methods were investigated, revealing that two treatment processes are feasible. One process reacts the NaK with water in a highly concentrated molten caustic solution (sodium and potassium hydroxide). The final waste is a caustic that may be used elsewhere in the plant. This process has two safety concerns: Hot corrosive materials used throughout the process present handling difficulties and the process must be carefully controlled (temperature and water content) to avoid explosive NaK reactions. To avoid these problems a second process was developed that dissolves NaK in a mixture of propylene glycol and water at room temperature. While this process is safer, it generates more waste than the caustic process. The waste may possibly be used as a carbon food source in biological waste treatment operations at the Y-12 Plant. Experiments were conducted to demonstrate both processes, and they showed that both processes are feasible alternatives for NaK treatment. Process flow sheets with mass balances were generated for both processes and compared. While the caustic process generates less waste, the propylene glycol process is safer in …
Date: April 8, 1993
Creator: Takacs, T. J. & Johnson, M. E.
Object Type: Report
System: The UNT Digital Library
Bench-Scale Co-Processing (open access)

Bench-Scale Co-Processing

This topical report is the first for the UOP Bench-Scale Co-processing contract. The objective of this contract is to extend and optimize the UOP single-stage, slurry-catalyzed co-processing scheme. UOP co-processing uses a single-stage, slurry-catalyzed scheme in which petroleum vacuum resid and coal are simultaneously upgraded to a high-quality synthetic oil. A highly active, well-dispersed catalyst permits operations at moderate- and high-severity reaction conditions with minimum detrimental thermal reactions. In this process, finely ground coal, petroleum resid, and catalyst are mixed, combined with hydrogen, and then directed to a single-stage reactor, where the simultaneous upgrading of the petroleum resid and coal occurs. The reactor effluent is directed to a series of separators, where a hydrogen-rich gas is recovered and recycled back to the reactor inlet. The balance of the material is sent to a series of separators, where the light gasses, light oil, vacuum gas on (VGO), catalyst, unconverted coal, ash, and residues are recovered. The catalyst is recycled back to the reactor. The UOP co-processing scheme is designed to be integrated into a conventional petroleum refinery. the hydrocarbon products from the co-processing unit will be sent to the refinery for final upgrading to finished products. A major focus of this …
Date: November 8, 1993
Creator: Piasecki, C. A.; Gatsis, J. G. & Fullerton, H. E.
Object Type: Report
System: The UNT Digital Library
Calculated cross sections for production and destruction of some long-lived nuclides of importance in fusion energy applications (open access)

Calculated cross sections for production and destruction of some long-lived nuclides of importance in fusion energy applications

Knowledge of the production and destruction of long-lived species via neutrons, photons, and charged-particles is required in many fusion energy applications, such as reactor first-wall and blanket design, radioactive waste management, etc. Here we describe our calculational results for the production, via the (n,2n) reaction, of the following long-lived species: {sup 150}Eu(t{sub 1/2} = 36 y), {sup 152}Eu(t{sub 1/2} = 13 y), and {sup 192m2}Ir(t{sub 1/2} = 241 y). Some comments on calculations that we`ve made for destruction reactions of these species are also included.
Date: July 8, 1993
Creator: Gardner, M. A. & Gardner, D. G.
Object Type: Article
System: The UNT Digital Library
Cathode strip chamber interface with support structure for SSC GEM detector muon subsystem (open access)

Cathode strip chamber interface with support structure for SSC GEM detector muon subsystem

Structural design and analysis and other practical engineering considerations indicate that the 3-point, kinematic chamber support concept in the GEM Technical Design Report should be replaced by a 4-point, {open_quotes}partial{close_quotes} kinematic support design. Detector physics performance may increase due to a resulting decreased mass in the secondary support structure.
Date: December 8, 1993
Creator: Belser, F. C.; Clements, J. W.; Holdener, F. R.; Horvath, J. A.; Pratuch, S. M.; Wuest, C. R. et al.
Object Type: Report
System: The UNT Digital Library
Corrosion-resistant iridium-platinum anode material for high polarization application in corrosive acids (open access)

Corrosion-resistant iridium-platinum anode material for high polarization application in corrosive acids

The present invention relates to highly corrosion resistant components for use in an electrochemical cell. Specifically, these components are resistant to corrosion under very extreme conditions such as exposure to aqua regia in the presence of a constant current density of 100mA/m{sup 2}. The components are comprised of an iridium-platinum alloy that comprises less than 30% iridium. In a preferred embodiment of the present invention, the iridium-platinum alloy comprises 15-20% iridium. In another preferred embodiment of the present invention, the iridium-platinum alloy is deposited on the surface of an electrochemical cell component by magnetron sputtering. The present invention also relates to a method for conducting an electrochemical reaction in the presence of highly corrosive acids under a high degree of polarization wherein the electrochemical cell comprises a component, preferably the anode, containing an iridium-platinum alloy that comprises less than 30% iridium.
Date: September 8, 1993
Creator: Farmer, J.; Summers, L. & Lewis, P.
Object Type: Patent
System: The UNT Digital Library
Design of an electromagnetic accelerator for turbulent hydrodynamic mix studies (open access)

Design of an electromagnetic accelerator for turbulent hydrodynamic mix studies

An electromagnetic accelerator in the form of a linear electric motor (LEM) has been designed to achieve controlled acceleration profiles of a carriage containing hydrodynamically unstable fluids for the investigation of the development of turbulent mix. The Rayleigh- Taylor instability is investigated by accelerating two dissimilar density fluids using the LEM to achieve a wide variety of acceleration and deceleration profiles. The acceleration profiles are achieved by independent control of rail and augmentation currents. A variety of acceleration-time profiles are possible including: (1) constant, (2) impulsive and (3) shaped. The LEM and support structure are a robust design in order to withstand high loads with deflections and to mitigate operational vibration. Vibration of the carriage during acceleration could create artifacts in the data which would interfere with the intended study of the Rayleigh-Taylor instability. The design allows clear access for diagnostic techniques such as laser induced fluorescence radiography, shadowgraphs and particle imaging velocimetry. Electromagnetic modeling codes were used to optimize the rail and augmentation coil positions within the support structure framework. Results of contemporary studies for non-arcing sliding contact of solid armatures are used for the design of the driving armature and the dynamic electromagnetic braking system. A 0. 6MJ …
Date: December 8, 1993
Creator: Susoeff, A. R.; Hawke, R. S.; Morrison, J. J.; Dimonte, G. & Remington, B. A.
Object Type: Article
System: The UNT Digital Library
Development of a catalyst for conversion of syngas-derived materials to isobutylene. Quarterly report No. 7, October 1, 1992--December 31, 1992 (open access)

Development of a catalyst for conversion of syngas-derived materials to isobutylene. Quarterly report No. 7, October 1, 1992--December 31, 1992

The main goal of this contract is to develop a catalyst and technology that will produce iC{sub 4}= directly from coal-derived syngas and that is capable of utilizing a lower (0.5 to 1.0) H{sub 2}:CO ratio. The research will identify and optimize the key catalyst and process characteristics that give improved performance for CO conversion by a non-Fischer-Tropsch process. This report, which is the seventh quarterly report covers the testing of various ZrO{sub 2}-based catalyst systems designed to examine the effects of catalyst preparation and process variables, especially low calcination temperature and mild reaction conditions (low temperatures, low pressure and low space velocity). Testing of solvent-extracted sol-gel ZrO{sub 2} catalysts indicate a decrease in isobutene yield. Lowering the reaction temperature, pressure and space velocity resulted in a small improvement in isobutene yield. Three extended runs demonstrated reasonable catalyst stability. In view of the generally poor isobutene yields, the emphasis in this project will shift to isoalcohol production.
Date: September 8, 1993
Creator: Gajda, G.J.
Object Type: Report
System: The UNT Digital Library
Direct aromatization of methane; Quarterly technical progress report No. 4, July 1, 1993--September 30, 1993 (open access)

Direct aromatization of methane; Quarterly technical progress report No. 4, July 1, 1993--September 30, 1993

The pyrolysis of methane in the absence of a quench was studied at temperatures between 900 and 1050{degrees}C and methane flows of 80--200 Scc/min. At 1050{degrees}C and a methane flow rate of 100 Scc/minute, methane conversion ranged between 15--19% with the major products being benzene, acetylene, and ethylene. The benzene molar selectivity was ca. 50%, corresponding to molar yield of ca. 7.5--10%. The reaction resulted in the formation of visible amounts of solid carbon, particularly at 1050{degrees}C. The resulting solid consisted partly of carbon and partly of a yellowish tar-like material which was soluble in toluene and contained various heavy hydrocarbons and polyring aromatics.
Date: October 8, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Human genome sequencing with direct x-ray holographic imaging (open access)

Human genome sequencing with direct x-ray holographic imaging

Direct holographic imaging of biological materials is widely applicable to the study of the structure, properties and action of genetic material. This particular application involves the sequencing of the human genome where prospective genomic imaging technology is composed of three subtechnologies, name an x-ray holographic camera, suitable chemistry and enzymology for the preparation of tagged DNA samples, and the illuminator in the form of an x-ray laser. We report appropriate x-ray camera, embodied by the instrument developed by MCR, is available and that suitable chemical and enzymatic procedures exist for the preparation of the necessary tagged DNA strands. Concerning the future development of the x-ray illuminator. We find that a practical small scale x-ray light source is indeed feasible. This outcome requires the use of unconventional physical processes in order to achieve the necessary power-compression in the amplifying medium. The understanding of these new physical mechanisms is developing rapidly. Importantly, although the x-ray source does not currently exist, the understanding of these new physical mechanisms is developing rapidly and the research has established the basic scaling laws that will determine the properties of the x-ray illuminator. When this x-ray source becomes available, an extremely rapid and cost effective instrument for …
Date: June 8, 1993
Creator: Rhodes, C.K.
Object Type: Report
System: The UNT Digital Library
Human genome sequencing with direct x-ray holographic imaging. Final report (open access)

Human genome sequencing with direct x-ray holographic imaging. Final report

Direct holographic imaging of biological materials is widely applicable to the study of the structure, properties and action of genetic material. This particular application involves the sequencing of the human genome where prospective genomic imaging technology is composed of three subtechnologies, name an x-ray holographic camera, suitable chemistry and enzymology for the preparation of tagged DNA samples, and the illuminator in the form of an x-ray laser. We report appropriate x-ray camera, embodied by the instrument developed by MCR, is available and that suitable chemical and enzymatic procedures exist for the preparation of the necessary tagged DNA strands. Concerning the future development of the x-ray illuminator. We find that a practical small scale x-ray light source is indeed feasible. This outcome requires the use of unconventional physical processes in order to achieve the necessary power-compression in the amplifying medium. The understanding of these new physical mechanisms is developing rapidly. Importantly, although the x-ray source does not currently exist, the understanding of these new physical mechanisms is developing rapidly and the research has established the basic scaling laws that will determine the properties of the x-ray illuminator. When this x-ray source becomes available, an extremely rapid and cost effective instrument for …
Date: June 8, 1993
Creator: Rhodes, C. K.
Object Type: Report
System: The UNT Digital Library
INEL cold test pit demonstration of improvements in information derived from non-intrusive geophysical methods over buried waste sites. Phase 1, Final report (open access)

INEL cold test pit demonstration of improvements in information derived from non-intrusive geophysical methods over buried waste sites. Phase 1, Final report

The objectives of this research project were to lay the foundation for further improvement in the use of geophysical methods for detection of buried wastes, and to increase the information content derived from surveys. Also, an important goal was to move from mere detection to characterization of buried wastes. The technical approach to achieve these objectives consisted of: (1) Collect a data set of high spatial density; (2) Acquire data with multiple sensors and integrate the interpretations inferred from the various sensors; (3) Test a simplified time domain electromagnetic system; and (4) Develop imaging and display formats of geophysical data readily understood by environmental scientists and engineers. The breadth of application of this work is far reaching. Not only are uncontrolled waste pits and trenches, abandoned underground storage tanks, and pipelines found throughout most US DOE facilities, but also at military installations and industrial facilities. Moreover, controlled land disposal sites may contain ``hot spots`` where drums and hazardous material may have been buried. The technologies addressed by the R&D will benefit all of these activities.
Date: September 8, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Insect community structure and function in Upper Three Runs, Savannah River Site, South Carolina (open access)

Insect community structure and function in Upper Three Runs, Savannah River Site, South Carolina

A project to document the insect species in the upper reaches of Upper Three Runs at the Savannah River site was recently completed. This research was supported by the US Department of Energy under the National Environmental Research Park Program. The work was performed by the Department of Entomology at Clemson University in clemson, SC, by John C. Morse (principal investigator), William R. English and their colleagues. The major output from this study was the dissertation of Dr. William R. English entitled ``Ecosystem Dynamics of a South Carolina Sandhills Stream.`` He investigated selected environmental resources and determined their dynamics and the dynamics of the aquatic invertebrate community structure in response to them.
Date: July 8, 1993
Creator: Morse, J. C.; English, W. R. & Looney, B. B.
Object Type: Report
System: The UNT Digital Library
Inspection of selected intelligence and special access program work-for-others projects (open access)

Inspection of selected intelligence and special access program work-for-others projects

At the request of the former Secretary, an inspection of six classified intelligence and special access program work-for-others projects was conducted. The purpose of this inspection was to evaluate managements, effectiveness regarding these work-for-others projects and included tests for financial integrity and adherence to applicable laws and regulations. Details of the inspection are provided in this report.
Date: October 8, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Investigation of the relative abundance of heavy versus light nuclei in primary cosmic rays using underground muon bundles (open access)

Investigation of the relative abundance of heavy versus light nuclei in primary cosmic rays using underground muon bundles

We study multiple muon events (muon bundles) recorded underground at a depth of 2090 mwe. To penetrate to this depth, the muons must have energies above 0.8 TeV at the Earth`s surface; the primary cosmic ray nuclei which give rise to the observed muon bundles have energies at incidence upon the upper atmosphere of 10 to 10{sup 5}TeV. The events are detected using the Soudan 2 experiment`s fine grained tracking calorimeter which is surrounded by a 14 m {times}10 m {times} 31 m proportional tube array (the ``active shield``). Muon bundles which have at least one muon traversing the calorimeter, are reconstructed using tracks in the calorimeter together with hit patterns in the proportional tube shield. All ionization pulses are required to be coincident within 3 microseconds. A goal of this study is to investigate the relative nuclear abundances in the primary cosmic radiation around the ``knee`` region (10{sup 3} {minus} 10{sup 4} TeV) of the incident energy spectrum. Four models for the nuclear composition of cosmic rays are considered: The Linsley model, the Constant Mass Composition model (CMC), the Maryland model and the Proton-poor model. A Monte Carlo which incorporates one model at a time is used to simulate …
Date: June 8, 1993
Creator: Sundaralingam, N.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Knob manager (KM) operators guide (open access)

Knob manager (KM) operators guide

KM, Knob Manager, is a tool which enables the user to use the SUNDIALS knob box to adjust the settings of the control system. The followings are some features of KM: dynamic knob assignments with the user friendly interface; user-defined gain for individual knob; graphical displays for operating range and status of each process variable is assigned; backup and restore one or multiple process variable; save current settings to a file and recall the settings from that file in future.
Date: October 8, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Measurement of chemical emissions under the influence of low-NO{sub x} combustion modifications. Final report (open access)

Measurement of chemical emissions under the influence of low-NO{sub x} combustion modifications. Final report

Effect of low-NO{sub x} firing. There was no clear-cut effect on the emission of trace metals or acid gases. The data give marginal evidence for a decreased emission of Cr(VI), which would be a favorable change but is not certain by any means. The effect on aldehydes and ketones cannot be stated because of the loss of samples for baseline conditions; no credible data on these compounds were obtained for baseline conditions. The change in volatile organics appeared to be a reduction in emissions, whereas that for semi-volatiles seemed to be an increase. Inasmuch as low-NO{sub x} firing is sometimes accompanied by large increases in the amount of unburned carbon in the ash, the result for semi-volatiles is more in line with expectation. Effect of the hot-side ESP. As indicated above, the hot-side ESP lowered trace-element emissions to the range roughly from 1 to 5% of the levels found in the inlet gas stream. Not surprisingly, the hot-side ESP had no measurable influence on the emissions of SO{sub x}, HF, and HCl. Quite surprisingly, on the other hand, the ESP seemed to suppress the emission of certain organic substances. Suppression of the emission of formaldehyde is particularly difficult to explain. …
Date: October 8, 1993
Creator: Dismukes, E. B.
Object Type: Report
System: The UNT Digital Library
Nondestructive method and apparatus for imaging grains in curved surfaces of polycrystalline articles (open access)

Nondestructive method and apparatus for imaging grains in curved surfaces of polycrystalline articles

A nondestructive method, and associated apparatus, are provided for determining the grain flow of the grains in a convex curved, textured polycrystalline surface. The convex, curved surface of a polycrystalline article is aligned in a horizontal x-ray diffractometer and a monochromatic, converging x-ray beam is directed onto the curved surface of the polycrystalline article so that the converging x-ray beam is diffracted by crystallographic planes of the grains in the polycrystalline article. The diffracted x-ray beam is caused to pass through a set of horizontal, parallel slits to limit the height of the beam and thereafter. The linear intensity of the diffracted x-ray is measured, suing a linear position sensitive proportional counter, as a function of position in a direction orthogonal to the counter so as to generate two dimensional data. An image of the grains in the curved surface of the polycrystalline article is provided based on the two-dimensional data.
Date: September 8, 1993
Creator: Carpenter, D.A.
Object Type: Patent
System: The UNT Digital Library
Nuclear Spectroscopic Studies (open access)

Nuclear Spectroscopic Studies

The Nuclear Physics group at the University of Tennessee, Knoxville is involved in several aspects of heavy-ion physics including both nuclear structure and reaction mechanisms. While our main emphasis is on experimental problems involving heavy-ion accelerators, we have maintained a strong collaboration with several theorists in order to best pursue the physics of our measurements. During the last year we have led several experiments at the Holifield Heavy Ion Research Facility and participated in others at Argonne National Laboratory. Also, we continue to be very active in the collaboration to study ultra-relativistic heavy ion physics utilizing the SPS accelerator at CERN in Geneva, Switzerland and in a RHIC detector R D project. Our experimental work is in four broad areas: (1) the structure of nuclei at high angular momentum, (2) heavy-ion induced transfer reactions, (3) the structure of nuclei far from stability, and (4) ultra-relativistic heavy-ion physics. The results of studies in these particular areas will be described in this document in sections IIA, IIB, IIC, and IID, respectively. Areas (1), (3), and (4) concentrate on the structure of nuclear matter in extreme conditions of rotational motion, imbalance of neutrons and protons, or very high temperature and density. Area (2) …
Date: February 8, 1993
Creator: Bingham, C. R.; Guidry, M. W.; Riedinger, L. L. & Sorensen, S. P.
Object Type: Report
System: The UNT Digital Library
Nuclear spectroscopic studies. Progress report (open access)

Nuclear spectroscopic studies. Progress report

The Nuclear Physics group at the University of Tennessee, Knoxville is involved in several aspects of heavy-ion physics including both nuclear structure and reaction mechanisms. While our main emphasis is on experimental problems involving heavy-ion accelerators, we have maintained a strong collaboration with several theorists in order to best pursue the physics of our measurements. During the last year we have led several experiments at the Holifield Heavy Ion Research Facility and participated in others at Argonne National Laboratory. Also, we continue to be very active in the collaboration to study ultra-relativistic heavy ion physics utilizing the SPS accelerator at CERN in Geneva, Switzerland and in a RHIC detector R&D project. Our experimental work is in four broad areas: (1) the structure of nuclei at high angular momentum, (2) heavy-ion induced transfer reactions, (3) the structure of nuclei far from stability, and (4) ultra-relativistic heavy-ion physics. The results of studies in these particular areas will be described in this document in sections IIA, IIB, IIC, and IID, respectively. Areas (1), (3), and (4) concentrate on the structure of nuclear matter in extreme conditions of rotational motion, imbalance of neutrons and protons, or very high temperature and density. Area (2) pursues …
Date: February 8, 1993
Creator: Bingham, C. R.; Guidry, M. W.; Riedinger, L. L. & Sorensen, S. P.
Object Type: Report
System: The UNT Digital Library
Plans for building the largest thin solenoid ever (open access)

Plans for building the largest thin solenoid ever

The superconducting solenoid magnet for the GEM detector poses unusual fabrication and handling challenges because of its extraordinary size. It will be more than 30% larger in diameter than the largest existing particle detector coils. Each of the two coil elements that compose the air-core solenoid, will be about 19 meters in diameter and 15 meters long. Major components weighing as much as 1500 Mg must be transported and manipulated at the Interaction Region 5 (IR5) fabrication site of the SSC Laboratory as the magnets are fabricated. Because of their large size, the magnets will be fabricated, assembled and tested at special purpose facilities at the IR5 site. The site-use plan must accommodate the fabrication of other detector components and the assembly of large flux shaping iron structures in a timely manner to allow subsequent testing and detector assembly. Each cold mass will be composed of twelve 45-Mg coil windings that are joined prior to assembly into the 19-m diam annular cryostat.
Date: September 8, 1993
Creator: Heim, J.; Bowers, J. & Deis, G.
Object Type: Article
System: The UNT Digital Library
Proposed first-generation WSQ bit allocation procedure (open access)

Proposed first-generation WSQ bit allocation procedure

The Wavelet/Scalar Quantization (WSQ) gray-scale fingerprint image compression algorithm involves a symmetric wavelet transform (SWT) image decomposition followed by uniform scalar quantization of each subband. The algorithm is adaptive insofar as the bin widths for the scalar quantizers are image-specific and are included in the compressed image format. Since the decoder requires only the actual bin width values -- but not the method by which they were computed -- the standard allows for future refinements of the WSQ algorithm by improving the method used to select the scalar quantizer bin widths. This report proposes a bit allocation procedure for use with the first-generation WSQ encoder. In previous work a specific formula is provided for the relative sizes of the scalar quantizer bin widths in terms of the variances of the SWT subbands. An explicit specification for the constant of proportionality, q, that determines the absolute bin widths was not given. The actual compression ratio produced by the WSQ algorithm will generally vary from image to image depending on the amount of coding gain obtained by the run-length and Huffman coding, stages of the algorithm, but testing performed by the FBI established that WSQ compression produces archival quality images at compression …
Date: September 8, 1993
Creator: Bradley, J. N. & Brislawn, C. M.
Object Type: Article
System: The UNT Digital Library
Recent studies of short-range order in alloys: The Cowley theory revisited (open access)

Recent studies of short-range order in alloys: The Cowley theory revisited

We present comparisons of various statistical theories for effective pair interactions (EPI) in alloys. We then evaluate these EPI`s using the Cowley theory, the Krivoglaz-Clapp-Moss (KCM) approximation, the {gamma}-expansion method (GEM) of Tokar, Masanskii and coworkers, and the exact inverse Monte Carlo (IMC) method, introduced by Gerold and Kern. Via a series of model calculations on a hypothetical bcc alloy with a single nearest-neighbor interaction we show that the Cowley theory is successful in evaluating the EPI`s in more dilute alloys but tends to overestimate the magnitude of the nearest neighbor energy at higher concentrations, whereas the KCM expression becomes increasingly inaccurate at lower concentrations. In general, however, the approximate mean field theories are most accurate at higher concentrations and higher temperatures. Recent studies of short-range order in single crystals are discussed in which these EPI`s have been evaluated using the IMC, KCM, GEM and Cowley theories. Examples include the bcc alloy Fe{sub 0.53}Cr{sub 0.47} and the fcc alloys Cu{sub 3} Au, CU{sub 0.69}Zn{sub 0.31} and Ni{sub 0.89}BgCr{sub 0.11}. In all cases the approximate expressions do quite well, especially the GEM.
Date: February 8, 1993
Creator: Reinhard, L. & Moss, S. C.
Object Type: Article
System: The UNT Digital Library