Superlattice Photocathodes for Accelerator-Based Polarized Electron Source Applications (open access)

Superlattice Photocathodes for Accelerator-Based Polarized Electron Source Applications

A major improvement in the performance of the SLC was achieved with the introduction of thin strained-layer semiconductor crystals. After some optimization, polarizations of 75-85% became standard with lifetimes that were equal to or better than that of thick unstrained crystals. Other accelerators of polarized electrons, generally operating with a much higher duty factor, have now successfully utilized similar photocathodes. For future colliders, the principal remaining problem is the limit on the total charge that can be extracted in a time scale of 10 to 100 ns. In addition, higher polarization is critical for exploring new physics, especially supersymmetry. However, it appears that strained-layer crystals have reached the limit of their optimization. Today strained superlattice crystals are the most promising candidates for better performance. The individual layers of the superlattice can be designed to be below the critical thickness for strain relaxation, thus in principle improving the polarization. Thin layers also promote high electron conduction to the surface. In addition the potential barriers at the surface for both emission of conduction-band electrons to vacuum and for tunneling of valence-band holes to the surface can be significantly less than for single strained-layer crystals, thus enhancing both the yield at any intensity …
Date: March 22, 1999
Creator: Clendenin, James E
Object Type: Report
System: The UNT Digital Library
Probing coal reactivity by time-resolved small angle x-ray scattering. (open access)

Probing coal reactivity by time-resolved small angle x-ray scattering.

The objective of this study is to observe changes in coal structure in situ with small angle X-ray scattering (SAXS) during solvent swelling and during pyrolysis. We have built a SAXS instrument at the Basic Energy Sciences Synchrotrons Research Center at the Advanced Photon Source that allows us to obtain scattering patterns in the millisecond time domain. The eight Argonne Premium Coal samples were used in this study. The information that can be derived from these experiments, such as changes in fractal dimensionality and in size and type of porosity, was found to be very rank-dependent. In the swelling experiments, it was noted that for certain coals, structural changes occurred in just a few minutes.
Date: January 22, 1999
Creator: Winans, R. E.
Object Type: Article
System: The UNT Digital Library
Ordering in classical Coulombic systems. (open access)

Ordering in classical Coulombic systems.

The author discusses the properties of classical Coulombic matter at low temperatures. It has been well known for some time [1,2] that infinite Coulombic matter will crystallize in body-centered cubic form when the quantity {Lambda} (the dimensionless ratio of the average two-particle Coulomb energy to the kinetic energy per particle) is larger than {approximately}175. But the systems of such particles that have been produced in the laboratory in ion traps, or ion beams, are finite with surfaces defined by the boundary conditions that have to be satisfied. This results in ion clouds with sharply defined curved surfaces, and interior structures that show up as a set of concentric layers that are parallel to the outer surface. The ordering does not appear to be cubic, but the charges on each shell exhibit a ''hexatic'' pattern of equilateral triangles that is the characteristic of liquid crystals. The curvature of the surfaces prevents the structures on successive shells from interlocking in any simple fashion. This class of structures was first found in simulations [3] and later in experiments [4].
Date: January 22, 1998
Creator: Schiffer, J. P.
Object Type: Article
System: The UNT Digital Library
Management of offshore wastes in the United States. (open access)

Management of offshore wastes in the United States.

During the process of finding and producing oil and gas in the offshore environment operators generate a variety of liquid and solid wastes. Some of these wastes are directly related to exploration and production activities (e.g., drilling wastes, produced water, treatment workover, and completion fluids) while other types of wastes are associated with human occupation of the offshore platforms (e.g., sanitary and domestic wastes, trash). Still other types of wastes can be considered generic industrial wastes (e.g., scrap metal and wood, wastes paints and chemicals, sand blasting residues). Finally, the offshore platforms themselves can be considered waste materials when their useful life span has been reached. Generally, offshore wastes are managed in one of three ways--onsite discharge, injection, or transportation to shore. This paper describes the regulatory requirements imposed by the government and the approaches used by offshore operators to manage and dispose of wastes in the US.
Date: October 22, 1998
Creator: Veil, J. A.
Object Type: Article
System: The UNT Digital Library
Hierarchies Without Symmetries from Extra Dimensions (open access)

Hierarchies Without Symmetries from Extra Dimensions

It is commonly thought that small couplings in a low-energy theory, such as those needed for the fermion mass hierarchy or proton stability, must originate from symmetries in a high-energy theory. We show that this expectation is violated in theories where the Standard Model fields are confined to a thick wall in extra dimensions, with the fermions ''stuck'' at different points in the wall. Couplings between them are then suppressed due to the exponentially small overlaps of their wave functions. This provides a framework for understanding both the fermion mass hierarchy and proton stability without imposing symmetries, but rather in terms of higher dimensional geography. A model independent prediction of this scenario is non-universal couplings of the Standard Model fermions to the ''Kaluza-Klein'' excitations of the gauge fields. This allows a measurement of the fermion locations in the extra dimensions at the LHC or NLC if the wall thickness is close to the TeV scale.
Date: March 22, 1999
Creator: Arkani-Hamed, Nima
Object Type: Report
System: The UNT Digital Library
Nucleon decay in Soudan 2. (open access)

Nucleon decay in Soudan 2.

The Soudan 2 detector is used to search for evidence of nucleon decay. Particular emphasis is put on searches for modes with multiple-charged particles in the final state, and for modes suggested by super-symmetric theories.
Date: June 22, 1999
Creator: Goodman, M. C.
Object Type: Article
System: The UNT Digital Library
Increasing Waterflood Reserves in the Wilmington Oil Field Through Improved Reservoir Characterization and Reservoir Management (open access)

Increasing Waterflood Reserves in the Wilmington Oil Field Through Improved Reservoir Characterization and Reservoir Management

The objectives of this quarterly report are to summarize the work conducted under each task during the reporting period January - March 1998 and to report all technical data and findings as specified in the "Federal Assistance Reporting Checklist". The main objective of this project is the transfer of technologies, methodologies, and findings developed and applied in this project to other operators of Slope and Basin Clastic Reservoirs. This project will study methods to identify sands with high remaining oil saturation and to recomplete existing wells using advanced completion technology. The identification of the sands with high remaining oil saturation will be accomplished by developing a deterministic three dimensional (3-D) geologic model and by using a state of the art reservoir management computer software. The wells identified by the geologic and reservoir engineering work as having the best potential will be logged with cased-hole logging tools. The application of the logging tools will be optimized in the lab by developing a rock-log model. This rock-log model will allow us to translate measurements through casing into effective porosity and hydrocarbon saturation. The wells that are shown to have the best oil production potential will be recompleted. The recompletions will be optimized …
Date: April 22, 1998
Creator: Phillips, Chris; Moos, Dan; Clarke, Don; Nguyen, John; Tagbor, Kwasi; Koerner, Roy et al.
Object Type: Report
System: The UNT Digital Library
Enigmatic electrons, photons, and ``empty`` waves (open access)

Enigmatic electrons, photons, and ``empty`` waves

A spectroscopic analysis is made of electrons and photons from the standpoint of physical realism. In this conceptual framework, moving particles are portrayed as localized entities which are surrounded by ``empty`` waves. A spectroscopic model for the electron Stands as a guide for a somewhat similar, but in essential respects radically different, model for the photon. This leads in turn to a model for the ``zeron``. the quantum of the empty wave. The properties of these quanta mandate new basis states, and hence an extension of our customary framework for dealing with them. The zeron wave field of a photon differs in one important respect from the standard formalism for an electromagnetic wave. The vacuum state emerges as more than just a passive bystander. Its polarization properties provide wave stabilization, particle probability distributions, and orbit quantization. Questions with regard to special relativity are discussed.
Date: August 22, 1995
Creator: MacGregor, M.H.
Object Type: Article
System: The UNT Digital Library
Deposition and Characterization of Highly Oriented Mg(3)(VO(4))(2) Thin Film Catalyst (open access)

Deposition and Characterization of Highly Oriented Mg(3)(VO(4))(2) Thin Film Catalyst

Magnesium vanadates are potentially important catalytic materials for the conversion of alkanes to alkenes via oxidative dehydrogenation. However, little is known about the active sites at which the catalytic reactions take place. It may be possible to obtain a significant increase in the catalytic efficiency if the effects of certain material properties on the surface reactions could be quantified and optimized through the use of appropriate preparation techniques. Given that surface reactivity is often dependent upon surface structure and that the atomic level structure of the active sites in these catalysts is virtually unknown, we desire thin film samples consisting of a single magnesium vanadate phase and a well defined crystallographic orientation in order to reduce complexity and simplify the study of active sites. We report on the use of reactive RF sputter deposition to fabricate very highly oriented, stoichiometric Mg{sub 3}(VO{sub 4}){sub 2} thin films for use in these surface analysis studies. Deposition of samples onto amorphous substrates resulted in very poor crystallinity. However, deposition of Mg{sub 3}(VO{sub 4}){sub 2} onto well-oriented, lattice-matched thin film ''seed'' layers such as Ti(0001), Au(111), or Pt(111) resulted in very strong preferential (042) crystallographic orientation (pseudo-hexagonal oxygen planes parallel to the substrate). This …
Date: October 22, 1999
Creator: Rodriguez, Mark A.; Ruffner, Judith A.; Sault, Allen G. & Tissot, Ralph G., Jr.
Object Type: Article
System: The UNT Digital Library
Mixed-conducting dense ceramics for gas separation applications. (open access)

Mixed-conducting dense ceramics for gas separation applications.

Mixed-conducting (electronic and ionic conducting) dense ceramics are used in many applications, including fuel cells, gas separation membranes, batteries, sensors, and electrocatalysis. This paper describes mixed-conducting ceramic membranes that are being developed to selectively remove oxygen and hydrogen from gas streams in a nongalvanic mode of operation (i.e., with no electrodes or external power supply). Ceramic membranes made of Sr-Fe-Co oxide (SFC), which exhibits high combined electronic and oxygen ionic conductivities, can be used for high-purity oxygen separation and/or partial oxidation of methane to synthesis gas (syngas, a mixture of CO and H{sub 2}). The electronic and ionic conductivities of SFC were found to be comparable in magnitude. Steady-state oxygen permeability of SFC has been measured as a function of oxygen-partial-pressure gradient and temperature. For an {approx}3-mm-thick membrane, the oxygen permeability was {approx}2.5 scc{center_dot}cm{sup {minus}2}{center_dot}min{sup {minus}1} at 900 C. Oxygen permeation increases as membrane thickness decreases. Tubular SFC membranes have been fabricated and operated at 900 C for {approx}1000 h in converting methane into syngas. The oxygen permeated through the membrane reacted with methane in the presence of a catalyst and produced syngas. We also studied the transport properties of yttria-doped BaCeO{sub 3{minus}{delta}} (BCY) by impedance spectroscopy and open-cell voltage …
Date: June 22, 1999
Creator: Balachandran, U.; Dorris, S. E.; Dusek, J. T.; Guan, J.; Liu, M.; Ma, B. et al.
Object Type: Article
System: The UNT Digital Library
Online modeling of the Fermilab accelerators (open access)

Online modeling of the Fermilab accelerators

Access through the Fermilab control system to beam physics models of the Fermilab accelerators has been implemented. The models run on Unix workstations, communicating with legacy VMS-based controls consoles via a relational database and TCP/IP.The client side (VMS) and the server side (Unix) are both implemented in object-oriented C++. The models allow scientists and operators in the control room to do beam physics calculations. Settings of real devices as input to the model are supported, and readings from beam diagnostics may be compared with model predictions.
Date: November 22, 1999
Creator: E. McCrory, O. Krivosheev, L. Michelotti and J-F. Ostiguy
Object Type: Article
System: The UNT Digital Library
HIGH RESOLUTION MICROTOMOGRAPHY FOR DENSITY AND SPATIAL INFORMATION ABOUT WOOD STRUCTURES. (open access)

HIGH RESOLUTION MICROTOMOGRAPHY FOR DENSITY AND SPATIAL INFORMATION ABOUT WOOD STRUCTURES.

Microtomography has successfully been used to characterize loss of structural integrity of wood. Tomographic images were generated with the newly developed third generation x-ray computed microtomography (XCMT) instrument at the X27A beamline at the National Synchrotron Light Source (NSLS). The beamline is equipped with high-flux x-ray monochromator based on multilayer optics developed for this application. The sample is mounted on a translation stage with which to center the sample rotation, a rotation stage to perform the rotation during data collection and a motorized goniometer head for small alignment motions. The absorption image is recorded by a single-crystal scintillator, an optical microscope and a cooled CCD array detector. Data reconstruction has provided three-dimensional geometry of the heterogeneous wood matrix in microtomographic images. Wood is a heterogeneous material composed of long lignocellulose vessels. Although wood is a strong natural product, fungi have evolved chemical systems that weaken the strength properties of wood by degrading structural vessels. Tomographic images with a resolution of three microns were obtained nonintrusively to characterize the compromised structural integrity of wood. Computational tools developed by Lindquist et al (1996) applied to characterize the microstructure of the tomographic volumes.
Date: July 22, 1999
Creator: ILLMAN,B.
Object Type: Article
System: The UNT Digital Library
U.S. Atomic Energy Commission's Environmental Research Programs Established in the 1950s (open access)

U.S. Atomic Energy Commission's Environmental Research Programs Established in the 1950s

In 1946 the United States (U.S.) Congress passed the Atomic Energy Act and with it created the Atomic Energy Commission. For the ensuing half-century the AEC and its successors have pursued biological and environmental research with an unwavering mandate to exploit the use of fissionable and radioactive material for medical purposes and, at the same time, to ensure the health of it's workers, the public, and the environment during energy technology development and use (AEC. 1961; DOE 1983; DOE, 1997). The following pages are testimony to the success of this undeviating vision (Figure 1). From the early days of the AEC, cooperation has also linked researchers from the national laboratories, the academic community, and the private sector. The AEC-sponsored research both at national laboratories and universities, and also supported graduate students to develop a cadre of health physicists, radiation biologists, and nuclear engineers. Coordinating these diverse performers has been crucial to the unique teaming that has made many of the successes possible. The success of the biological and environmental research program has often been shared with other federal agencies. The future will demand even stronger and more substantive intraagency, interagency, and international collaborations.
Date: September 22, 1999
Creator: Reichle, D.E.
Object Type: Article
System: The UNT Digital Library
Optimization of a CNG series hybrid concept vehicle (open access)

Optimization of a CNG series hybrid concept vehicle

Compressed Natural Gas (CNG) has favorable characteristics as a vehicular fuel, in terms of fuel economy as well as emissions. Using CNG as a fuel in a series hybrid vehicle has the potential of resulting in very high fuel economy (between 26 and 30 km/liter, 60 to 70 mpg) and very low emissions (substantially lower than Federal Tier II or CARB ULEV). This paper uses a vehicle evaluation code and an optimizer to find a set of vehicle parameters that result in optimum vehicle fuel economy. The vehicle evaluation code used in this analysis estimates vehicle power performance, including engine efficiency and power, generator efficiency, energy storage device efficiency and state-of-charge, and motor and transmission efficiencies. Eight vehicle parameters are selected as free variables for the optimization. The optimum vehicle must also meet two perfect requirements: accelerate to 97 km/h in less than 10 s, and climb an infinitely long hill with a 6% slope at 97 km/h with a 272 kg (600 lb.) payload. The optimizer used in this work was originally developed in the magnetic fusion energy program, and has been used to optimize complex systems, such as magnetic and inertial fusion devices, neutron sources, and mil guns. …
Date: September 22, 1995
Creator: Aceves, S. M.; Smith, J. R.; Perkins, L. J.; Haney, S. W. & Flowers, D. L.
Object Type: Article
System: The UNT Digital Library
New Microscopic Model of the Staebler-Wronski Effect in Hydrogenated Amorphous Silicon (open access)

New Microscopic Model of the Staebler-Wronski Effect in Hydrogenated Amorphous Silicon

A new microscopic and kinetic model of light-induced metastability in hydrogenated amorphous silicon (a-Si:H) was recently proposed. Carrier recombination excites H from deep Si-H bonds into a mobile configuration, leaving a threefold-coordinated Si dangling bond (DB) defect at the site of excitation - a process long suspected to be an element of metastable DB production. Normally, mobile H are recaptured at DB defects and neither metastability nor net DB production results. However, when two mobile H collide, they form a metastable two-hydrogen complex and leave two spatially-uncorrelated Staebler-Wronski DBs. The model leads to differential equations describing the evolution of the mobile H and DB densities and a variety of new predictions. New directions for improving the stability of a-Si:H are discussed.
Date: October 22, 1998
Creator: Branz, H. M.
Object Type: Article
System: The UNT Digital Library
Preliminary design report of a relativistic-Klystron two-beam-accelerator based power source for a 1 TeV center-of-mass next linear collider (open access)

Preliminary design report of a relativistic-Klystron two-beam-accelerator based power source for a 1 TeV center-of-mass next linear collider

A preliminary point design for an 11.4 GHz power source for a 1 TeV center-of-mass Next Linear Collider (NLC) based on the Relativistic-Klystron Two-Beam-Accelerator (RK-TBA) concept is presented. The present report is the result of a joint LBL-LLNL systems study. consisting of three major thrust areas: physics, engineering, and costing. The new RK-TBA point design, together with our findings in each of these areas, are reported.
Date: February 22, 1995
Creator: Yu, S.; Goffeney, N. & Henestroza, E.
Object Type: Report
System: The UNT Digital Library
Buoyancy and Dissolution of the Floating Crust Layer in Tank 241-SY-101 During Transfer and Back-Dilution (open access)

Buoyancy and Dissolution of the Floating Crust Layer in Tank 241-SY-101 During Transfer and Back-Dilution

To remediate gas retention in the floating crust layer and the potential for buoyant displacement gas releases from below the crust, waste will be transferred out of Hanford Tank 241-SY-101 (SY-101) in the fall of 1999 and back-diluted with water in several steps of about 100,000 gallons each. To evaluate the effects of back-dilution on the crust a static buoyancy model is derived that predicts crust and liquid surface elevations as a function of mixing efficiency and volume of water added during transfer and back-dilution. Experimental results are presented that demonstrate the basic physics involved and verify the operation of the models. A dissolution model is also developed to evaluate the effects of dissolution of solids on crust flotation. The model includes dissolution of solids suspended in the slurry as well as in the crust layers. The inventory and location of insoluble solids after dissolution of the soluble fraction are also tracked. The buoyancy model is applied to predict the crust behavior for the first back-dilution step in SY-101. Specific concerns addressed include conditions that could cause the crust to sink and back-dilution requirements that keep the base of the crust well above the mixer pump inlet.
Date: November 22, 1999
Creator: Stewart, C. W.; Sukamto, J. H.; Cuta, J. M. & Rassat, S. D.
Object Type: Report
System: The UNT Digital Library
A Combined Statistical-Microstructural Model for Simulation of Sintering (open access)

A Combined Statistical-Microstructural Model for Simulation of Sintering

Sintering theory has been developed either as the application of complex diffusion mechanisms to a simple geometry or as the deformation and shrinkage of a continuum body. They present a model that can treat in detail both the evolution of microstructure and the sintering mechanisms, on the mesoscale, so that constitutive equations with detail microstructural information can be generated. The model is capable of simulating vacancy diffusion by grain boundary diffusion, annihilation of vacancies at grain boundaries resulting in densification, and coarsening of the microstructural features. In this paper, they review the stereological theory of sintering and its application to microstructural evolution and the diffusion mechanism, which lead to sintering. They then demonstrate how these stereological concepts and diffusion mechanisms were incorporated into a kinetic Monte Carlo model to simulate sintering. Finally, they discuss the limitations of this model.
Date: October 22, 1999
Creator: BRAGINSKY,MICHAEL V.; DEHOFF,ROBERT T.; OLEVSKY,EUGENE A. & TIKARE,VEENA
Object Type: Article
System: The UNT Digital Library
The Effect of Ramp Rate on the C49 to C54 Titanium Disilicide Phase Transformation from Ti and Ti(Ta) (open access)

The Effect of Ramp Rate on the C49 to C54 Titanium Disilicide Phase Transformation from Ti and Ti(Ta)

The C49 to C54 TiSi{sub 2} transformation temperature is shown to be reduced by increasing the ramp rate during rapid thermal processing and this effect is more pronounced for thinner initial Ti and Ti(Ta) films. Experiments were performed on blanket wafers and on wafers that had patterned polycrystalline Si lines with Si{sub 3}N{sub 4} sidewall spacers. Changing the ramp rate caused no change in the transformation temperature for 60 nm blanket Ti films. For blanket Ti films of 25 or 40 nm, however, increasing the ramp rate from 7 to 180 C/s decreased the transformation temperature by 15 C. Studies of patterned lines indicate that sheet resistance of narrow lines is reduced by increased ramp rates for both Ti and Ti(Ta) films, especially as the linewidths decrease below 0.4 {micro}m. This improvement is particularly pronounced for the thinnest Ti(Ta) films, which exhibited almost no linewidth effect after being annealed with a ramp rate of 75 C/s.
Date: September 22, 1999
Creator: BAILEY, GLENN A.; HU, YAO ZHI; SMITH, PAUL M. & TAY, SING PIN
Object Type: Article
System: The UNT Digital Library
Stress corrosion cracking of Ni-base and Ti alloys under controlled potential (open access)

Stress corrosion cracking of Ni-base and Ti alloys under controlled potential

Susceptibility to stress corrosion cracking (SCC) of alloy C-22 and Ti Gr-12, two candidate alloys for the inner-container of the multi-barrier nuclear waste package, was evaluated by using the slow-strain-rate (SSR) test technique in a deaerated acidic brine (pH {approx} 2.70) at 90 C. The strain rate used was 3.3 x 10{sup {minus}6} sec{sup {minus}1}. Prior to being tested in the acidic brine, specimens of each alloy were pulled inside the test chamber in the dry condition at room temperature (RT). Then specimens were exposed to the test solution while being strained under different controlled electrochemical potentials. The magnitude of the controlled potential was selected based on the corrosion potential measured in the test solution prior to straining of the specimen. Results indicate that, for Ti Gr-12, the times to failure were significantly shorter compared to those for alloy C-22. Furthermore, Ti Gr-12 showed reduced ductility in terms of percent reduction in area and true fracture stress, as the controlled potential became more cathodic. Results also indicate that the time-to-failure and percent elongation reached the minimum values when Ti Gr-12 was tested under impressed potential of {minus}1162 mV. Finally, metallographic examination was performed to evaluate the primary fracture, and the …
Date: October 22, 1998
Creator: Estill, J. C.; Gordon, S. R.; Logeteta, L. F. & Roy, A. K.
Object Type: Article
System: The UNT Digital Library
Basin Analysis of the Mississippi Interior Salt Basin and Petroleum System Modeling of the Jurassic Smackover Formation, Eastern Gulf Coastal Plain (open access)

Basin Analysis of the Mississippi Interior Salt Basin and Petroleum System Modeling of the Jurassic Smackover Formation, Eastern Gulf Coastal Plain

The objective is to provide a comprehensive geologic analysis of the Mississippi Interior Salt Basin.
Date: December 22, 1997
Creator: Mancini, Ernest A.
Object Type: Report
System: The UNT Digital Library
Environmental Impact From Accelerator Operation at SLAC (open access)

Environmental Impact From Accelerator Operation at SLAC

Environmental impacts from electron accelerator operations at the Stanford Linear Accelerator Center, which is located near populated areas, are illustrated by using examples of three different accelerator facilities: the low power (a few watts) SSRL, the high power (a few kilowatts) PEP-II, and the 50-kW SLC. Three types of major impacts are discussed: (1) off-site doses from skyshine radiation, mainly neutrons, (2) off-site doses from radioactive air emission, mainly {sup 13}N, and (3) radioactivities, mainly {sup 3}H, produced in the groundwater. It was found that, from SSRL operation, the skyshine radiation result in a MEI (Maximum Exposed Individual) of 0.3 {mu}Sv/y while a conservative calculation using CAP88 showed a MEI of 0.36 {mu}Sv/y from radioactive air releases. The calculated MEI doses due to future PEP-II operation are 30 {mu}Sv/y from skyshine radiation and 2 {mu}Sv/y from air releases. The population doses due to radioactive air emission are 0.5 person-mSv from SSRL and 12 person-mSv from PEP-II. Because of the stronger decrease of skyshine dose as the distance increases, the population dose from skyshine radiation are smaller than that from air release. The third environmental impact, tritium activity produced in the groundwater, was also demonstrated to be acceptable from both the …
Date: March 22, 1999
Creator: Liu, James C
Object Type: Report
System: The UNT Digital Library
X-ray absorption near-edge spectroscopy of plutonium solid species. (open access)

X-ray absorption near-edge spectroscopy of plutonium solid species.

We present XANES at the L{sub III} edge for four plutonium solid phases: Pu(III)F{sub 3}, Pu(IV)O{sub 2}, NaPu(V)O{sub 2}CO{sub 3}, and Ba{sub 3}Pu(VI)O{sub 6}. These correspond to the four important oxidation states in the process chemistry and environmental chemistry of plutonium. By a fitting method that uses an arc tangent function and gaussian curves, it was possible to reproducibly determine the edge energy and distinguish among the four oxidation states. These data demonstrate a 1.85 {+-} 0.20 eV shift per oxidation state.
Date: October 22, 1998
Creator: Kropf, A. J.
Object Type: Article
System: The UNT Digital Library
Innovative regulatory approach for synthetic-based muds. (open access)

Innovative regulatory approach for synthetic-based muds.

The oil and gas industry has historically used water-based muds (WBMs) and oil-based muds (OBMs) in offshore drilling operations. WBMs are less expensive and are widely used. Both the WBMs and the associated drill cuttings maybe discharged from the platform to the sea provided that U.S. Environmental Protection Agency (EPA) discharge limitations are met. In some wells, however, difficult drilling conditions may force a switch from a WBM to an OBM. Neither the OBM nor the associated drill cuttings may be discharged. The OBM is hauled to shore, where it is processed for reuse, while the associated cuttings are injected in a disposal well at the platform or hauled to shore to a disposal facility. Both of these options are expensive. Synthetic-based muds (SBMs) are drilling fluids that use synthetic organic chemicals as base fluids. SBMs were developed to replace OBMs in difficult drilling situations. SBMs are more expensive than OBMs; however, they have superior environmental properties that may permit the cuttings to be discharged on-site. Like OBMs, SBMs are hauled ashore for processing and reuse after the well is drilled. The existing national effluent limitations guidelines (ELGs) for the offshore industry do not include requirements for SBM-cuttings since SBMs …
Date: October 22, 1998
Creator: Veil, J. A.
Object Type: Article
System: The UNT Digital Library