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Phase Equilibria Modification by Electric Fields
This project has been focused on equilibrium and transport properties of gas-liquid, liquid-liquid, and solid-liquid systems under electric fields. The objective was to intensify separations methods that are used or can be used to process liquid waste or contaminated groundwater within DOE sites. Examples of processes that have been investigated are distillation (gas-liquid), extraction (liquid-liquid), and sorption (solid-liquid). Effects of electric fields on phase equilibria and interfacial transport have been investigated. So far, this project was directed at basic research on a broadly crosscutting concept. The results advocate continuation of this research in two directions, with the objective to solve problems related to solvent extraction of tank waste and groundwater treatment.
Date:
December 31, 2000
Creator:
Tsouris, Costas
Object Type:
Report
System:
The UNT Digital Library
Photocatalytic and Chemical Oxidation of Organic Compounds in Supercritical Carbon Dioxide
The goal of the proposed research is to develop new chemistry for the removal of organic contaminants from supercritical carbon dioxide. This has application in processes used for continuous cleaning and extraction of parts and waste materials. Cleaning and extraction using supercritical carbon dioxide (scCO2) can be applied to the solution of a wide range of environmental and pollution prevention problems in the DOE complex. The objectives at the outset of the project were to: (1) determine if photocatalytic or other clean oxidation chemistry can be applied to the removal of organic or inorganic contaminants that are introduced into supercritical carbon dioxide during its use as an extraction and cleaning medium. The target will be contaminants left in solution after the bulk of solutes have been separated from the fluid phase by changing pressure and/or temperature (but not evaporating the CO2). This is applicable to development of efficient separations and will strengthen pollution prevention strategies that eliminate hazardous solvents and cleaning agents. (2) explore the use of supercritical carbon dioxide as a solvent for the photocatalytic oxidation of organic compounds and to compare it to other types of oxidation chemistry. This will add to the fundamental understanding of photocatalytic oxidation …
Date:
December 31, 2000
Creator:
Blake, Daniel M.
Object Type:
Report
System:
The UNT Digital Library
Physics of DNAPL Migration and Remediation in the Presence of Heterogeneities
Spilled solvents have created pervasive groundwater contamination problems across the DOE complex because of their ubiquitous use, their toxicity and persistence in the environment, combined with the difficulty of recovering them from the subsurface. Because organic solvents are more dense than water and immiscible with water, they are commonly referred to as DNAPLs (dense nonaqueous phase liquids). They migrate below the water table downward and laterally under the influence of gravity, capillary, and viscous forces. Variations in media texture that the DNAPLs encounter as they migrate can have a profound influence on the migration path. This interplay between textural heterogeneities and driving forces complicates the migration of the DNAPLs and therefore it is not straightforward to predict the locations in the aquifer at which the spilled DNAPLs may ultimately reside. Uncertainties in the region of solvent contamination translate into higher remediation costs as the remedial system must be designed in light of these uncertainties. In an effort to clean up spilled DNAPLs, several remediation approaches are currently under development. Chemically enhanced solubilization, alcohol displacement, in situ oxidation, and air sparging are among the most promising. Many of these techniques have already undergone preliminary field demonstrations. However, results from such field …
Date:
December 31, 2000
Creator:
Conrad, Stephen & Glass, Robert
Object Type:
Report
System:
The UNT Digital Library
Plant Rhizosphere Effects on Metal Mobilization and Transport
The myriad of human activities including strategic and energy development at various DOE installations have resulted in the contamination of soils and waterways that can seriously threaten human and ecosystem health. Development of efficacious and economical remediation technologies is needed to ameliorate these immensely costly problems. Bioremediation (both plant and microbe-based) has promising potential to meet this demand but still requires advances in fundamental knowledge. For bioremediation of heavy metals, the three-way interaction of plant root, microbial community, and soil organic matter (SOM) in the rhizosphere is critically important for long-term sustainability but often underconsidered. Particularly urgent is the need to understand processes that lead to metal ion stabilization in soils, which is crucial to all of the goals of bioremediation: removal, stabilization, and transformation. We have developed the tools for probing the chemistry of plant rhizosphere and generated information regarding the role of root exudation and metabolism for metal mobilization and sequestration.
Date:
December 31, 2000
Creator:
Fan, Teresa W.-M; Higashi, Richard M. & Crowley, David E.
Object Type:
Report
System:
The UNT Digital Library
Plutonium Speciation, Solubilization,And Migration in soils
The DOE is currently conducting cleanup activities at its nuclear weapons development sites, many of which have accumulated plutonium (Pu) in soils for 50 years. To properly control Pu migration within Federal areas and onto public lands, to better evaluate the public risk, and to design effective remediation strategies, a fundamental understanding of Pu speciation and environmental transport is needed. Our goal is to use characterization, mobility, thermodynamic, and mineral-interaction data to develop better models of radionuclide transport and risk assessment which will enable the development of science-based decontamination strategies. In addition, if direct characterization of Pu in samples from a contaminated site reveal that the Pu is predominantly in an exceedingly low soluble, low mobility form, then acceptable, reasonable limits for site remediation and closure can be set in a directly defensible manner. Our overarching research approach has the following three interrelated facets: characterization of Pu in samples from a contaminated site; fundamental study of environmentally-relevant Pu species; and thermodynamic geochemical modeling of PU speciation and mobility. This approach differs from those of most other projects funded at a similar level because of its very broad scope and the range of specific methods and techniques used in the research. …
Date:
December 31, 2000
Creator:
Neu, Mary P.
Object Type:
Report
System:
The UNT Digital Library
Polk County Enterprise (Livingston, Tex.), Vol. 118, No. 104, Ed. 1 Sunday, December 31, 2000
Semi-weekly newspaper from Livingston, Texas that includes local, state and national news along with advertising.
Date:
December 31, 2000
Creator:
White, Barbara
Object Type:
Newspaper
System:
The Portal to Texas History
Pressure dependence of defect emissions and the appearance of pressure-induced deep centers in chalcopyrite alloys AgxCu1-xGaS2
We present the pressure dependence of the defect emissions in the chalcopyrite alloy semiconductor Ag{sub x}Cu{sub 1-x}GaS{sub 2} for values of the alloy concentration x varying between 0 and 1. A large variation in the pressure coefficients of the different defect emissions with x was found. In one alloy concentration x=0.25 deep levels were found to appear under pressure. Plausible explanations of our results have been proposed.
Date:
December 31, 2000
Creator:
Choi, In-Hwan & Yu, Peter Y.
Object Type:
Article
System:
The UNT Digital Library
Pressure dependence of Raman modes in the chalcopyrite quaternary alloy AgxCu1-xGaS2
Raman scattering in the chalcopyrite quaternary alloy Ag{sub x}Cu{sub 1-x}GaS{sub 2} has been studied under high pressure (up to 7 GPa) and at low temperature (50 K) using a diamond anvil high pressure cell for alloy concentrations x=1, 0.75, 0.5, 0.25 and 0. This has allowed us to determine the dependence of their zone-center phonon modes on both pressure and alloy concentration. The resultant phonon pressure coefficients are helpful in understanding the nature of the phonon modes in these chalcopyrites.
Date:
December 31, 2000
Creator:
Choi, In-Hwan & Yu, Peter Y.
Object Type:
Article
System:
The UNT Digital Library
RADIATION EFFECTS IN NUCLEAR WASTE MATERIALS
The objective of this research was to develop fundamental understanding and predictive models of radiation effects in glasses and ceramics at the atomic, microscopic, and macroscopic levels, as well as an understanding of the effects of these radiation-induced solid-state changes on dissolution kinetics (i.e., radionuclide release). The research performed during the duration of this project has addressed many of the scientific issues identified in the reports of two DOE panels [1,2], particularly those related to radiation effects on the structure of glasses and ceramics. The research approach taken by this project integrated experimental studies and computer simulations to develop comprehensive fundamental understanding and capabilities for predictive modeling of radiation effects and dissolution kinetics in both glasses and ceramics designed for the stabilization and immobilization of high-level tank waste (HLW), plutonium residues and scraps, surplus weapons plutonium, other actinides, and other highly radioactive waste streams. Such fundamental understanding is necessary in the development of predictive models because all experimental irradiation studies on nuclear waste materials are ''accelerated tests'' that add a great deal of uncertainty to predicted behavior because the damage rates are orders of magnitude higher than the actual damage rates expected in nuclear waste materials. Degradation and dissolution processes …
Date:
December 31, 2000
Creator:
Weber, William J.
Object Type:
Report
System:
The UNT Digital Library
Real-Time Broad Spectrum Characterization of Hazardous Mixed Waste by Membrane Introduction Mass Spectrometry
The goal of this project was to expand the range of chemical species that may be detected by membrane introduction mass spectrometry (MIMS) in environmental, and specifically in Mixed Waste, monitoring and characterization applications. Membrane introduction mass spectrometry (MIMS) functions as a near real-time monitor: there is little to no sample preparation and t analysis time is seconds to minutes. MIMS can be implemented as a flow injection technique, where samples, standards, and method blanks can be sequentially analyzed in a continuous fashion. The membrane acts as an interface between the sample (air or water) and the vacuum of the mass spectrometer. Transport of the analyte through the membrane occurs by the process of pervaporation. This process is described by adsorption to the outer surface of the membrane, diffusion through the membrane, and desorption from the inner membrane surface into a helium gas flow or into vacuum. The driving force for this work is the need for a rapid, sensitive, and broadly applicable tool for characterizing organic and metal-containing contaminants in a variety of DOE (and other) waste streams. In all characterization scenarios, a balance must be struck between evaluation of the hazards and their extent at a waste site, …
Date:
December 31, 2000
Creator:
Wilkerson Jr., Charles W.
Object Type:
Report
System:
The UNT Digital Library
Risk Reduction With a Fuzzy Expert Exploration Tool
Incomplete or sparse information on types of data such as geologic or formation characteristics introduces a high level of risk for oil exploration and development projects. ''Expert'' systems developed and used in several disciplines and industries, including medical diagnostics, have demonstrated beneficial results. A state-of-the-art exploration ''expert'' tool, relying on a computerized data base and computer maps generated by neural networks, is proposed for development through the use of ''fuzzy'' logic, a relatively new mathematical treatment of imprecise or non-explicit parameters and values. Oil prospecting risk can be reduced with the use of a properly developed and validated ''Fuzzy Expert Exploration (FEE) Tool.'' This tool will be beneficial in many regions of the US, enabling risk reduction in oil and gas prospecting and decreased prospecting and development costs. In the 1998-1999 oil industry environment, many smaller exploration companies lacked the resources of a pool of expert exploration personnel. Downsizing, low oil prices and scarcity of exploration funds have also affected larger companies, and will, with time, affect the end users of oil industry products in the US as reserves are depleted. The proposed expert exploration tool will benefit a diverse group in the US, leading to a more efficient use …
Date:
December 31, 2000
Creator:
Weiss, William W.
Object Type:
Report
System:
The UNT Digital Library
Second Generation Advanced Reburning for High Efficiency NOx Control
This project is designed to develop a family of novel NO{sub x} control technologies, called Second Generation Advanced Reburning (SGAR) which has the potential to achieve 90+% NO{sub x} control in coal-fired boilers at a significantly lower cost than SCR. The thirteenth reporting period in Phase II (October 1-December 31, 2000) included SGAR tests in which coal was used as the reburning fuel. All test work was conducted at GE-EER's 1.0 MMBtu/hr Boiler Simulator Facility. Three test series were performed including AR-Lean, AR-Rich, and reburning + SNCR. Tests demonstrated that over 90% NO{sub x} reduction could be achieved with utilization of coal as a reburning fuel in SGAR. The most effective SGAR variant is reburning + SNCR followed by AR-Lean and AR-Rich.
Date:
December 31, 2000
Creator:
Zamansky, Vladimir M.; Maly, Pete M. & Lissianski, Vitali V.
Object Type:
Report
System:
The UNT Digital Library
Selective excitation of the yellow and blue luminescence in n- and p-doped Gallium Nitride
GaN is an interesting material: technologically very useful, but still having many unexplained features. Two such features are the broad defect-related luminescence bands: the YL of n-type GaN and the BL of Mg-doped p-type GaN. We have employed selective excitation to investigate these bands. In the case of the YL, most of the previous evidence has supported a recombination model between distant donors and acceptors, most likely a transition involving a shallow donor to a deep acceptor. Our selective excitation experiments have resolved finer structures within the YL. Our results indicate that the YL in bulk samples is related to the YL in film samples. We suggest that selectively excited YL involves recombination at DAP complexes, rather than between spatially distant DAPs (however other recombination channels, including that of distant DAPs may become significant under other excitation conditions). Characteristics of the DAP complexes within our YL model include (a) an electron localization energy of around 60-70 meV, (b) a localized phonon energy of around 40 meV, and (c) excited states of the complex at 200 and 370 meV above the ground state. In the case of the BL, the deep defect responsible for the BL is unknown, and there may …
Date:
December 31, 2000
Creator:
Colton, John S.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Selectively excited blue luminescence in heavily Mg doped p-type GaN
The emission at {approx}2.8 eV from heavily doped p-GaN, known as the blue luminescence (BL), has been studied by selective excitation using a dye laser tunable between 2.7-3.0 eV. The peak position and intensity of the BL are found to exhibit an unusual dependence on the excitation photon energy. We have explained our results with a shallow-donor and deep-acceptors pair recombination model which includes potential fluctuations induced by heavy doping. We found a ''critical energy'' of {approx}2.8 eV for the BL. Electron-hole pairs with energies above this energy are able to achieve quasi-thermal equilibrium while those with energies below 2.8 eV are strongly ''localized''.
Date:
December 31, 2000
Creator:
Colton, John S. & Yu, Peter Y.
Object Type:
Article
System:
The UNT Digital Library
Seminole Sentinel (Seminole, Tex.), Vol. 94, No. 22, Ed. 1 Sunday, December 31, 2000
Semiweekly newspaper from Seminole, Texas that includes local, state, and national news along with advertising.
Date:
December 31, 2000
Creator:
Dow, M. Gene & Fisher, David
Object Type:
Newspaper
System:
The Portal to Texas History
[Shark dives down past the aquarium window]
A shark dives down past the aquarium window.
Date:
December 31, 2000
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library
[Shark swims against a background of green]
A shark swims overhead against a background of plants and rocks.
Date:
December 31, 2000
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library
[Shark swims against a background of rock]
Photograph of a grey shark swimming by a background of brown rock.
Date:
December 31, 2000
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library
[Shark swims below]
A shark swims below the photographer, looking very black against the reflection of the aquarium bottom.
Date:
December 31, 2000
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library
[Shark swims by with his eye visible]
As a shark swims past the viewer, his eye is visible.
Date:
December 31, 2000
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library
[Shark swims downward]
A shark swims downward in the aquarium, past the viewer.
Date:
December 31, 2000
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library
[Shark swims overhead]
A shark swims in the aquarium over the head of the viewer.
Date:
December 31, 2000
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library
[Shark swims parallel to the aquarium window]
A shark swims parallel to the aquarium window.
Date:
December 31, 2000
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library
[Small boy reaches out to touch the glass where several fish swim]
A small boy in a yellow shirt reaches out to touch the glass while several fish swim nearby.
Date:
December 31, 2000
Creator:
Castillo, José L.
Object Type:
Photograph
System:
The UNT Digital Library