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The Present Status of the Technological Development of Remote Monitoring Systems

Description: Let me begin with some comments about transparency. We all have some perception or vision about the use of transparency for nuclear technology and nuclear non-proliferation. Although we probably have some common understanding of what it implies, there is no precise definition that is agreed upon. One of the most significant ideas in transparency is that it is considered to be a voluntary or unilateral action. The party, or organization, or nation that wants its activities to be transparent voluntarily provides information to other parties with the expectation of receiving some acceptance or good will in return. The organization giving the information determines what information to provide, how much, how often, and when. This is in contrast to official treaties and monitoring regimes, in which specific verification information and activities are prescribed. This should have the advantage for the transparent organization of being less intrusive and less costly than a treaty monitoring regime. Information related to sensitive nuclear technology, proprietary processes, and physical security is more easily protected. The difficultly for both parties, the transparent organization and the information recipients, is in determining what information is necessary for the desired confidence building. It must be recognized that this state of transparency or confidence will only be achieved over an extended period of time, when history confirms that the information was reliable in conveying the true picture.
Date: January 28, 1999
Creator: Matter, J.C.
Partner: UNT Libraries Government Documents Department

Development and Operation of a Passive-Flow Treatment System for (Sup 90)Sr-Contaminated Groundwater

Description: Seep C was a free-flowing stream of groundwater that emerged in a narrow valley below the old low-level waste (LLW) disposal trenches in Solid Waste Storage Area 5 (SWSA 5) at Oak Ridge National Laboratory (ORNL). The flow rate of the seep water was strongly influenced by rainfall, and typically ranged from 0.5 to 8 L/min. The seep water entered Melton Branch, a small stream that joins White Oak Creek before exiting the ORNL boundary. The seep water contained high concentrations of {sup 90}Sr (10,000 to 20,000 Bq/L) and, before the full-scale treatment system was installed, contributed about 25% of all the {sup 90}Sr leaving ORNL. Seep C was identified as a primary source of off-site contaminant transport and was designated for an early removal action under the Comprehensive Environmental Response and Liability Act (CERCLA). A passive flow treatment system was chosen as the most cost-effective method for treating the water.
Date: February 28, 1999
Creator: Kirkham, P.S. & Taylor, P.A.
Partner: UNT Libraries Government Documents Department

A Coherent FMCW LIDAR Mapping System for Automated Tissue Debridment

Description: The Oak Ridge National Laboratory (ORNL) is developing a prototype 850-nm FMCW lidar system for mapping tissue damage in burn cases for the US Army Medical Research and Material Command. The laser system will provide a 3D-image map of the burn and surrounding area and provide tissue damage assessment.
Date: June 28, 1999
Creator: Allgood, G.O.; Hutchinson, D.P. & Richards, R.K.
Partner: UNT Libraries Government Documents Department

Robocasting of Ceramics and Composites Using Fine Particle Suspensions

Description: Solid freeform fabrication is the near-net-shape manufacturing of components by sequentially stacking thin layers of material until complicated three dimensional shapes are produced. The operation is computer controlled and requires no molds. This exciting new field of technology provides engineers with the ability to rapidly produce prototype parts directly from CAD drawings and oftentimes little or no machining is necessary after fabrication. Techniques for freeform fabrication with several types of plastics and metals are already quite advanced and maybe reviewed in references 1 and 2. Very complicated plastic models can be fabricated by stereolithography, selective laser sintering, fused deposition modeling, or three-dimensional ink jet printing. Metals may be freeformed by the LENS{trademark} technique and porous ceramic bodies by three dimensional printing into a porous powder bed. However, methods for freeform fabrication that utilize particulate slurries to build dense ceramics and composites are not as well developed. The techniques that are being developed for the freeform fabrication of dense structural ceramics primarily revolve around the sequential layering of ceramic loaded polymers or waxes. Laminated Object Manufacturing and CAM-LEM processing use controlled stacking and laser cutting of ceramic tapes [2,3]. Similar to fused deposition modeling, ceramic loaded polymer/wax filaments are being used for the fused deposition of ceramics [2,4]. Extrusion freeform fabrication uses high pressure extrusion to deposit layers of ceramic loaded polymer/wax systems[1]. Modified stereolithographic techniques are also being developed using ceramic loaded ultraviolet curable resins [2]. Pre-sintered parts made with any of these techniques typically have 40-55 vol.% polymeric binder. In this regard, these techniques are analogous to powder injection molding of ceramics. Very long and complicated burnout heat treatments are necessary to produce a dense ceramic, free of organics. Heating rates of 0.2 degrees Celsius per minute are common. [5] Thus, while a part maybe rapidly prototype within a ...
Date: October 28, 1999
Creator: CESARANO III,JOSEPH
Partner: UNT Libraries Government Documents Department

Mask substrate requirements and development for extreme ultraviolet lithography (EUVL)

Description: The mask is deemed one of the areas that require significant research and development in EUVL. Silicon wafers will be used for mask substrates for an alpha-class EUVL exposure tool due to their low-defect levels and high quality surface finish. However, silicon has a large coefficient of thermal expansion that leads to unacceptable image distortion due to absorption of EUV light. A low thermal expansion glass or glass-ceramic is likely to be required in order to meet error budgets for the 70nm node and beyond. Since EUVL masks are used in reflection, they are coated with multilayers prior to patterning. Surface imperfections, such as polishing marks, particles, scratches, or digs, are potential nucleation sites for defects in the multilayer coating, which could result in the printed defects. Therefore we are accelerating developments in the defect reduction and surface finishing of low thermal expansion mask substrates in order to understand long-term issues in controlling printable defects, and to establish the infrastructure for supplying masks. In this paper, we explain the technical requirements for EUVL mask substrates and describe our efforts in establishing a SEMI standard for EUVL masks. We will also report on the early progress of our suppliers in producing low thermal-expansion mask substrates for our development activities.
Date: September 28, 1999
Creator: Hector, S D; Shell, M; Taylor, J S & Tong, W M
Partner: UNT Libraries Government Documents Department

Discussion of Comments from a Peer Review of A Technique for Human Event Anlysis (ATHEANA)

Description: In May of 1998, a technical basis and implementation guidelines document for A Technique for Human Event Analysis (ATHEANA) was issued as a draft report for public comment (NUREG-1624). In conjunction with the release of draft NUREG- 1624, a peer review of the new human reliability analysis method its documentation and the results of an initial test of the method was held over a two-day period in June 1998 in Seattle, Washington. Four internationally known and respected experts in HK4 or probabilistic risk assessment were selected to serve as the peer reviewers. In addition, approximately 20 other individuals with an interest in HRA and ATHEANA also attended the peer and were invited to provide comments. The peer review team was asked to comment on any aspect of the method or the report in which improvements could be made and to discuss its strengths and weaknesses. They were asked to focus on two major aspects: Are the basic premises of ATHEANA on solid ground and is the conceptual basis adequate? Is the ATHEANA implementation process adequate given the description of the intended users in the documentation? The four peer reviewers asked questions and provided oral comments during the peer review meeting and provided written comments approximately two weeks after the completion of the meeting. This paper discusses their major comments.
Date: January 28, 1999
Creator: Bley, D.C.; Cooper, S.E.; Forester, J.A.; Kolaczkowski, A.M.; Ramey-Smith, A, & J., Wreathall
Partner: UNT Libraries Government Documents Department

Effects of Platinum Additions and Sulfur Impurities on the Microstructure and Scale Adhesion Behavior of Single-Phase CVD Aluminide Bond Coatings

Description: The adhesion of alumina scales to aluminide bond coats is a life-limiting factor for some advanced thermal barrier coating systems. This study investigated the effects of aluminide bond coat sulfur and platinum contents on alumina scale adhesion and coating microstructural evolution during isothermal and cyclic oxidation testing at 1150 C. Low-sulfur NiAl and NiPtAl bond coats were fabricated by chemical vapor deposition (CVD). Lowering the sulfur contents of CVD NiAl bond coatings significantly improved scale adhesion, but localized scale spallation eventually initiated along coating grain boundaries. Further improvements in scale adhesion were obtained with Pt additions. The observed influences of Pt additions included: (1) mitigation of the detrimental effects of high sulfur levels, (2) drastic reductions in void growth along the scale-metal interface, (3) alteration of the oxide-metal interface morphology, and (4) elimination of Ta-rich oxides in the Al{sub 2}O{sub 3} scales during thermal cycling. The results of this study also suggested that the microstructure (especially the grain size) of CVD aluminide bond coatings plays a significant role in scale adhesion.
Date: February 28, 1999
Creator: Cooley, K.M.; Haynes, J.A.; Lee, W.Y.; Pint, B.A.; Wright, I.G. & Zhang, Y.
Partner: UNT Libraries Government Documents Department

The Life Cycle Analysis Toolbox

Description: The life cycle analysis toolbox is a valuable integration of decision-making tools and supporting materials developed by Oak Ridge National Laboratory (ORNL) to help Department of Energy managers improve environmental quality, reduce costs, and minimize risk. The toolbox provides decision-makers access to a wide variety of proven tools for pollution prevention (P2) and waste minimization (WMin), as well as ORNL expertise to select from this toolbox exactly the right tool to solve any given P2/WMin problem. The central element of the toolbox is a multiple criteria approach to life cycle analysis developed specifically to aid P2/WMin decision-making. ORNL has developed numerous tools that support this life cycle analysis approach. Tools are available to help model P2/WMin processes, estimate human health risks, estimate costs, and represent and manipulate uncertainties. Tools are available to help document P2/WMin decision-making and implement programs. Tools are also available to help track potential future environmental regulations that could impact P2/WMin programs and current regulations that must be followed. An Internet-site will provide broad access to the tools.
Date: February 28, 1999
Creator: Bishop, L.; Tonn, B.E.; Williams, K.A.; Yerace, P. & Yuracko, K.L.
Partner: UNT Libraries Government Documents Department

Atom Probe Field Ion Microscopy of Zr-Doped Polysynthetically Twinned Titanium Aluminide

Description: Interracial segregation and partitioning in a polysynthetically twinned Ti-48.4 at.% Al-0.6% Zr alloy were investigated by atom probe field ion microscopy and atom probe tomography. The compositions of the {gamma} and {alpha}{sub 2} phases were determined to be Ti-47.5% Al-O.71% Zr-0.06% O and Ti-31.6% Al-0.68% Zr-2.4% O, respectively. These results indicate a high concentration of zirconium in both matrix phases, confirming a strength increase through solid-solution strengthening, but no significant zirconium partitioning to either phase. Although zirconium additions produced a refined lamellar microstructure in this material, compositional analysis of {gamma}/{gamma} and {gamma}/{alpha}{sub 2} interfaces showed no evidence of significant zirconium segregation. This suggests that zirconium additions may produce a refined lamellar microstructure, but may not be effective at providing resistance to growth and coarsening.
Date: February 28, 1999
Creator: Inui, H.; Larson, D.J.; Miller, M.K. & Yamaguchi, M.
Partner: UNT Libraries Government Documents Department

Micromechanisms of Twin Nucleation in TiAl: Effects of Neutron Irradiation

Description: The so-called radiation-induced ductility (RID) reported in neutron-irradiated 47at%Al alloys is attributed to the formation of effective twin embryos in the presence of interstitial-type Frank loops in {gamma}-TiAl and the subsequent nucleation and growth of microtwins during post-irradiation tensile deformation. The stability of large faulted Frank loops is explained in terms of the repulsive interaction between Shockley and Frank partials. Interaction of only six ordinary slip dislocations with a Frank loop can facilitate a pole mechanism for twin formation to work. The relative ease of heterogeneous twin nucleation is the reason for the RID and the lack of changes in yield strength and work hardening.
Date: January 28, 1999
Creator: Hishinuma, A. & Yoo, M.H.
Partner: UNT Libraries Government Documents Department

Image Appraisal for 2D and 3D Electromagnetic Inversion

Description: Linearized methods are presented for appraising image resolution and parameter accuracy in images generated with two and three dimensional non-linear electromagnetic inversion schemes. When direct matrix inversion is employed, the model resolution and posterior model covariance matrices can be directly calculated. A method to examine how the horizontal and vertical resolution varies spatially within the electromagnetic property image is developed by examining the columns of the model resolution matrix. Plotting the square root of the diagonal of the model covariance matrix yields an estimate of how errors in the inversion process such as data noise and incorrect a priori assumptions about the imaged model map into parameter error. This type of image is shown to be useful in analyzing spatial variations in the image sensitivity to the data. A method is analyzed for statistically estimating the model covariance matrix when the conjugate gradient method is employed rather than a direct inversion technique (for example in 3D inversion). A method for calculating individual columns of the model resolution matrix using the conjugate gradient method is also developed. Examples of the image analysis techniques are provided on 2D and 3D synthetic cross well EM data sets, as well as a field data set collected at the Lost Hills Oil Field in Central California.
Date: January 28, 1999
Creator: Alumbaugh, D.L. & Newman, G.A.
Partner: UNT Libraries Government Documents Department

Liquid Permeability Measurements in Solidifying Aluminum-Copper Alloys

Description: Measurements of liquid permeability in the mushy zones of AI-15.42% Cu and Al-8.68% Cu alloy samples have been performed isothermally just above the eutectic temperature, using eutectic liquid as the fluid. A modified method has been developed to determine the specific permeability, K{sub s}, as a function of time during the test from the data collected on these alloys. Factors affecting permeability measurements are discussed. Permeabilities are observed to vary throughout the experiment. This is attributed to microstructural coarsening and channeling that occurs in the sample during the experiment. The permeability is related to the microstructure of the sample using the Kozeny-Carman equation. The correlation between the measured K{sub s}, liquid fraction, g{sub L} and the specific solid surface area, S{sub v}, improves markedly when compared to previous studies in which microstructural coarsening was ignored.
Date: February 28, 1999
Creator: Duncan, A.J.; Han, Q. & Viswanathan, S.
Partner: UNT Libraries Government Documents Department

Mercury Removal from Waste Organics

Description: Mercury was effectively removed from the oil via sorption using SAMMS.The method was demonstrated on a large scale using ORNL waste oil contaminated with mercury. This technology is ready for further demonstration and implementation when the SAMMS material is available in large quantities.
Date: February 28, 1999
Creator: Cummins, R.L.; Klasson, T. & Taylor, P.A.
Partner: UNT Libraries Government Documents Department

Hot Corrosion of Nickel-Base Alloys in Biomass-Derived Fuel Simulated Atmosphere

Description: Biomass fuels are considered to be a promising renewable source of energy. However, impurities present in the fuel may cause corrosion problems with the materials used in the hot sections of gas turbines and only limited data are available so far. As part of the Advanced Turbine Systems Program initiated by the U.S. Department of Energy, the present study provides initial data on the hot corrosion resistance of different nickel-base alloys against sodium sulfate-induced corrosion as a baseline, and against salt compositions simulating biomass-derived fuel deposits. Single crystal nickel-superalloy Rene N5, a cast NiCrAlY alloy, a NiCoCrAlY alloy representing industrially used overlay compositions, and a model {beta}NiAl+Hf alloy were tested in 1h thermal cycles at 950 C with different salt coatings deposited onto the surfaces. Whereas the NiCoCrAlY alloy exhibited reasonable resistance against pure sodium sulfate deposits, the NiCrAiY alloy and Rene N5 were attacked severely. Although considered to be an ideal alumina former in air and oxygen at higher temperatures, {beta}NiAl+Hf also suffered from rapid corrosion attack at 950 C when coated with sodium sulfate. The higher level of potassium present in biomass fuels compared with conventional fuels was addressed by testing a NiCoCrAlY alloy coated with salts of different K/Na atomic ratios. Starting at zero Na, the corrosion rate increased considerably when sodium was added to potassium sulfate. In an intermediate region the corrosion rate was initially insensitive to the K/Na ratio but accelerated when very Na-rich compositions were deposited. The key driver for corrosion of the NiCoCrAlY alloy was sodium sulfate rather than potassium sulfate, and no simple additive or synergistic effect of combining sodium and potassium was found.
Date: February 28, 1999
Creator: Leyens, C.; Pint, B.A. & Wright, I.G.
Partner: UNT Libraries Government Documents Department

Analysis of Solar Two Heliostat Tracking Error Sources

Description: This paper explores the geometrical errors that reduce heliostat tracking accuracy at Solar Two. The basic heliostat control architecture is described. Then, the three dominant error sources are described and their effect on heliostat tracking is visually illustrated. The strategy currently used to minimize, but not truly correct, these error sources is also shown. Finally, a novel approach to minimizing error is presented.
Date: January 28, 1999
Creator: Jones, S.A. & Stone, K.W.
Partner: UNT Libraries Government Documents Department

A Life Cycle Analysis System to Support D and D, Pollution Prevention, and Asset Recovery

Description: This paper describes a life cycle analysis system (LCAS) developed to support US Department of Energy (DOE) decision-making regarding deactivation and decommissioning (D and D), pollution prevention (P2), and asset recovery, and its deployment to analyze the disposition of facilities and capital assets. Originally developed for use at the Oak Ridge East Tennessee Technology Park, this approach has been refined through application at Ohio Operations Office sites and is now being deployed at a number of DOE sites. Programs such as National Metals Recycle, the D and D Focus Area, P2, and Asset Utilization are successfully using the system to make better decisions resulting in lower cost to the taxpayer and improved environmental quality. The LCAS consists of a user-friendly, cost-effective, and analytically-sound decision-aiding process and a complementary suite of automated tools to handle data administration and multiple criteria life cycle analysis (LCA). LCA is a systematic and comprehensive process for identifying, assessing, and comparing alternatives for D and D, P2, and asset recovery at government sites, and for selecting and documenting a preferred alternative. An LCA includes all of the impacts (benefits and costs) that result from a course of action over the entire period of time affected by the action. The system also includes visualizations that aid communication and help make decision-making transparent. The LCAS has three major components related to data collection, decision alternative assessment, and making the decisions. Each component is discussed in-depth using the example of deployment of the LCAS to support asset recovery.
Date: February 28, 1999
Creator: Bishop, L.; Tonn, B.E. & Yuracko, K.L.
Partner: UNT Libraries Government Documents Department

Processing and Characterizing Alumina/Aluminum Composites with Tailored Microstructures Formed by Reactive Metal Penetration

Description: In industry, the need to maximize energy efficiency depends on the availability of suitable advanced materials. Ceramic composites are exemplary materials for many advanced engineering applications because they exhibit good thermal stability, oxidation resistance and enhanced toughness. Presently, ceramic composite fabrication processes are costly, often requiring high temperatures and pressures to achieve reasonable densities. Our research is focused on developing a processing technique, that will allow production of alumina/aluminum composites using relatively low temperatures and without the application of an external force, thus reducing the processing costs. Our composites were formed using Reactive Metal Penetration (RMP), which is a process involving the reaction of molten Al with a dense ceramic preform. The result is a near net shape ceramic/metal composite with interpenetrating phases. The volume fraction of metal in the composites was varied by doping an aluminosilicate ceramic preform with silica. For this study we fabricated composites using pure mullite and mullite doped with 23 and 42 weight percent silica, yielding 18, 25, and 30 volume percent metal in the composites, respectively. Optical and Scanning Electron Microscopy were used to characterize the homogeneity and scale of the microstructure. The scale of the microstructure varied with preform composition, the reaction temperature and with secondary heat treatments. Four-point bend testing was used to evaluate the influence of microstructure on strength and reliability. During these studies a gradient in the microstructure was observed, which we further characterized using microhardness testing. Alumina/aluminum composites formed by RMP show higher toughness then monolithic alumina and have the potential for improved reliability when compared to monolithic ceramics.
Date: January 28, 1999
Creator: Corral, E.; Ellerby, D.; Ewsuk, K.; Fahrenholtz, B. & Loehman, R.
Partner: UNT Libraries Government Documents Department

Real-Time Measurement of Vehicle Exhaust Gas Flow

Description: A flow measurement system was developed to measure, in real-time, the exhaust gas flow from vehicies. This new system was based on the vortex shedding principle using ultrasonic detectors for sensing the shed vortices. The flow meter was designed to measure flow over a range of 1 to 366 Ips with an inaccuracy of ~1o/0 of reading. Additionally, the meter was engineered to cause minimal pressure drop (less than 125mm of water), to function in a high temperature environment (up to 650oC) with thermal transients of 15 oC/s, and to have a response time of 0.1 seconds for a 10% to 90!40 step change. The flow meter was also configured to measure hi-directional flow. Several flow meter prototypes were fabricated, tested, and calibrated in air, simulated exhaust gas, and actual exhaust gas. Testing included gas temperatures to 600oC, step response experiments, and flow rates from O to 360 lps in air and exhaust gas. Two prototypes have been tested extensively at NIST and two additional meters have been installed in exhaust gas flow lines for over one year. This new flow meter design has shown to be accurate, durabIe, fast responding, and to have a wide rangeabi~ity.
Date: June 28, 1999
Creator: Hardy, J.E.; Hylton, J.O.; Joy, R.D. & McKnight, T.E.
Partner: UNT Libraries Government Documents Department

Projection Methods for Interdendritic Flows

Description: In spite of recent advances in the mathematical modeling of fluid dynamics for materials processing applications, no significant advances have been made in the numerical discretization of these equations. In this work, the application of two-step projection methods for the numerical simulation of interdendritic flows is, discussed. Unlike previous methods, the methods presented here are constructed for the exact equations which are characterized by variable density and volumetric fraction of the liquid. The drag terms, which describe the momentum loss due to the flow around and through the dendrite structures, are treated implicitly. Numerical examples for shrinkage-induced flow during solidification of an AI-4.5% Cu alloy bar is used to illustrate the effectiveness of the proposed algorithm.
Date: February 28, 1999
Creator: Han, Q.; Sabau, A.S. & Viswanathan, S.
Partner: UNT Libraries Government Documents Department

Surface Engineering of Silicon and Carbon by Pulsed-Laser Ablation

Description: Experiments are described in which a focused pulsed-excimer laser beam is used either to ablate a graphite target and deposit hydrogen-free amorphous carbon films, or to directly texture a silicon surface and produce arrays of high-aspect-ratio silicon microcolumns. In the first case, diamond-like carbon (or tetrahedral amorphous carbon, ta-C) films were deposited with the experimental conditions selected so that the masses and kinetic energies of incident carbon species were reasonably well controlled. Striking systematic changes in ta-C film properties were found. The sp{sup 3}-bonded carbon fraction, the valence electron density, and the optical (Tauc) energy gap ail reach their maximum values in films deposited at a carbon ion kinetic energy of {approximately}90 eV. Tapping-mode atomic force microscope measurements also reveal that films deposited at 90 eV are extremely smooth (rms roughness {approximately}1 {angstrom} over several hundred nm) and relatively free of particulate, while the surface roughness increases in films deposited at significantly lower energies. In the second set of experiments, dense arrays of high-aspect-ratio silicon microcolumns {approximately}20-40 {micro}m tall and {approximately}2 {micro}m in diameter were formed by cumulative nanosecond pulsed excimer laser irradiation of silicon wafers in air and other oxygen-containing atmospheres. It is proposed that microcolumn growth occurs through a combination of pulsed-laser melting of the tips of the columns and preferential redeposition of silicon on the molten tips from the ablated flux of silicon-rich vapor. The common theme in this research is that a focused pulsed-laser beam can be used quite generally to create an energetic flux, either the energetic carbon ions needed to form sp{sup 3} (diamond-like) bonds or the overpressure of silicon-rich species needed for microcolumn growth. Thus, new materials synthesis opportunities result from the access to nonequilibrium growth conditions provided by pulsed-laser ablation.
Date: February 28, 1999
Creator: Fowlkes, J.D.; Geohegan, D.B.; Jellison, G.E., Jr.; Lowndes, D.H.; Merkulov, V.I.; Pedraza, A.J. et al.
Partner: UNT Libraries Government Documents Department

Rapid Sampling from Sealed Containers

Description: The authors have developed several different types of tools for sampling from sealed containers. These tools allow the user to rapidly drill into a closed container, extract a sample of its contents (gas, liquid, or free-flowing powder), and permanently reseal the point of entry. This is accomplished without exposing the user or the environment to the container contents, even while drilling. The entire process is completed in less than 15 seconds for a 55 gallon drum. Almost any kind of container can be sampled (regardless of the materials) with wall thicknesses up to 1.3 cm and internal pressures up to 8 atm. Samples can be taken from the top, sides, or bottom of a container. The sampling tools are inexpensive, small, and easy to use. They work with any battery-powered hand drill. This allows considerable safety, speed, flexibility, and maneuverability. The tools also permit the user to rapidly attach plumbing, a pressure relief valve, alarms, or other instrumentation to a container. Possible applications include drum venting, liquid transfer, container flushing, waste characterization, monitoring, sampling for archival or quality control purposes, emergency sampling by rapid response teams, counter-terrorism, non-proliferation and treaty verification, and use by law enforcement personnel during drug or environmental raids.
Date: February 28, 1999
Creator: Johnston, R.G.; Garcia, A.R.E.; Martinez, R.K. & Baca, E.T.
Partner: UNT Libraries Government Documents Department

Studies of the top quark at the Tevatron

Description: We report on studies of the top quark, beyond the measurements of its mass and produciton cross section, which have been carried out recently by the CDF and D0 collaborations, based on {approximately}110{+-}6 pb{sup -1} of proton-antiproton collisions at a center-of-mass energy of 1.8 TeV. Each experiment has searched for t{yields}H{sup +}b decays and, from the lack of observable signal, excluded previously unexplored regions of the [M{sub H+},tan{beta}] parameter space. D0 has studied the correlation between the spin states of pair-produced top quarks, and CDF has studied the helicity of the W bosons produced in the decay of top quarks. Within large statistical uncertainties, both measurements agree with predictions of the standard model.
Date: May 28, 1999
Creator: Chakraborty, Dhiman
Partner: UNT Libraries Government Documents Department

Effects of nonlocal one-pion-exchange potential in deuteron

Description: The off-shell aspects of the one-pion-exchange potential (OPEP) are discussed. Relativistic Hamiltonians containing relativistic kinetic energy, relativistic OPEP with various off-shell behaviors and Argonne v{sub 18} short-range parameterization are used to study the deuteron properties. The OPEP off-shell behaviors depend on whether a pseudovector or pseudoscalar pion-nucleon coupling is used and are characterized by a parameter {mu}. The authors study potentials having {mu} = {minus}1, 0 and +1 and they find that they are nearly unitarily equivalent. They also find that a nonrelativistic Hamiltonian containing local potentials and nonrelativistic kinetic energy provides a good approximation to a Hamiltonian containing a relativistic OPEP based on pseudovector pion-nucleon coupling and relativistic kinetic energy.
Date: May 28, 1999
Creator: Forest, J.L.
Partner: UNT Libraries Government Documents Department