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429 Matching Results

Start Over Year 2001 Day 29th Language English

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Results: 1 - 24 of 429 next

(open access)

Unquenched Studies Using the Truncated Determinant Algorithm

A truncated determinant algorithm is used to study the physical effects of the quark eigenmodes associated with eigenvalues below 420 MeV. This initial high statistics study focuses on coarse (6{sup 4}) lattices (with O(a{sup 2}) improved gauge action), light internal quark masses and large physical volumes. Three features of full QCD are examined: topological charge distributions, string breaking as observed in the static energy and the eta prime mass.

Date: November 29, 2001

Creator: A. Duncan, E. Eichten and H. Thacker

Object Type: Article

System: The UNT Digital Library

(open access)

Global Climate Change: Selected Legal Questions About the Kyoto Protocol

This report addresses legal issues after the United States signed the Kyoto Protocol to the UnitedNations Framework Convention on Climate Change. The protocol is not yet in effect internationally and cannot be legally binding on the U.S. unless and until the Senate gives its advice and consent.

Date: March 29, 2001

Creator: Ackerman, David M.

Object Type: Report

System: The UNT Digital Library

(open access)

High Temperature Surface Measurements Using Lifetime Imaging of Thermographic Phosphors: Bonding Tests

Temperature-sensitive paint (TSP) comprised of thermally sensitive phosphor can provide a viable means for noncontact thermometry in wind tunnel and other aeropropulsion applications. Described here are recent results aimed at developing a phosphor and binder system that will cover a wide temperature range, ambient to 1000 C. The phosphor/binder mixture is to be sprayed directly on the surface with an airbrush. Whereas many surfaces are candidates for various uses, the present effort concerned silicon carbide, silicon nitride and silica substrates. Initial tests show that a phosphor mixture with two water-soluble materials, designated LK and HPC and manufactured by ZYP Inc., adhered well to these substrates. This same material was earlier shown to function well on a high strength nickel alloy.

Date: October 29, 2001

Creator: Allison, S. W.

Object Type: Article

System: The UNT Digital Library

(open access)

High-Efficiency Target-Ion sources for RIB Generation

In this report, emphasis is placed on issues related to selection and design of high-temperature, ion sources that have demonstrated the high ionization efficiency, species versatility, and operational reliability required at ISOL based radioactive ion beam facilities. In designing sources for ISOL applications, careful attention must be given to the following: selecting the most appropriate materials of construction, coupling of the vapor transport system, ion optics, operational parameters, thermal transport properties, emittances, ionization efficiencies and engineering details for safe handling in the high-level radioactivity radiation fields incumbent at such facilities. Included in the article are descriptions and performance data for high temperature, positive (electron-impact and surface-ionization) and negative (kinetic-ejection and surface-ionization) ion sources, as well as, low temperature, batch-mode negative-ion sources, developed for processing long-lived isotopes, that have been principal contributors to recent successes held at the Holifield Radioactive Ion Beam Facility.

Date: June 29, 2001

Creator: Alton, G. D.

Object Type: Article

System: The UNT Digital Library

(open access)

Reducing ion beam noise of vacuum arc ion sources

Vacuum arc ion sources are known for delivering high currents of metal ion beams. By Langmuir probe and Faraday cup measurements it is shown that fluctuations of the ion beam current are due to the fluctuations of plasma density which in turn are due to the explosive nature of plasma production at cathode spots. Humphries and co-workers and later Oks and co-workers have shown that beam fluctuations can be reduced by inserting biased meshes in the plasma. Here, the idea of ion extraction at kV-level with post-acceleration is investigated. The high voltage allows us to use coarse, ridged meshes or grids. The combination of an extractor operating in the overdense plasma regime with post-acceleration lead to very reproducible, practically ''noiseless'' ion beams however at the expense of low ion current density. The noise reduction is due to ion optics effects. Although the current setup is not suitable for a heavy ion fusion injector due to the low beam current and the risk of extractor voltage breakdown, further development of the concept may lead to reproducible beam pulses of sufficiently high current and brightness.

Date: August 29, 2001

Creator: Anders, Andre & Hollinger, Ralph

Object Type: Article

System: The UNT Digital Library

(open access)

Atmospheric Radiation Measurement Program Facilities Newsletter, October 2001.

Monthly newsletter discussing news and activities related to the Atmospheric Radiation Measurement Program, articles about weather and atmospheric phenomena, and other related topics.

Date: October 29, 2001

Creator: Atmospheric Radiation Measurement Program (U.S.)

Object Type: Journal/Magazine/Newsletter

System: The UNT Digital Library

(open access)

Probabilistic Assessment of Weld Quality in Steel Piping Under Seismic Conditions

Seismic stress analyses of plant piping systems usually ignore the possibility of reduced joint strength due to weld imperfections. This paper presents a method that might be used to assess the impact of weld imperfections in a piping system, provided that limited destructive examination of welded joints is possible. A probability distribution function of weld quality is developed from the destructive examination, and this is combined with an experimentally determined relationship between weld quality and reduced strength. This latter is the result of uniaxial tensile testing of specimens with controlled imperfections. A seismic stress probability distribution function is determined by conventional seismic analysis. The above quantities are used to quantify the conditional failure probability of the imperfect weld. Effect of imperfection distribution within a given weld on the probability of failure is discussed.

Date: May 29, 2001

Creator: Awadalla, N.G.

Object Type: Article

System: The UNT Digital Library

(open access)

Expedited Procedures in the House: Variations Enacted Into Law

Congress enacts expedited, or fast-track, procedures into law when it wants to increase the likelihood that one or both houses of Congress will vote in a timely way on a certain measure or kind of measure. These procedures are enacted as rulemaking provisions of law pursuant to the constitutional power of each house to adopt its own rules. The house to which a set of expedited procedures applies may act unilaterally to waive, suspend, amend, or repeal them.

Date: January 29, 2001

Creator: Bach, Stanley

Object Type: Report

System: The UNT Digital Library

(open access)

Performance-Driven Robust Identification and Control of Uncertain Dynamical Systems

The grant DEFG02-97ER13939 from the Department of Energy has supported our research program on robust identification and control of uncertain dynamical systems, initially for the three-year period June 15, 1997-June 14, 2000, which was then extended on a no-cost basis for another year until June 14, 2001. This final report provides an overview of our research conducted during this period, along with a complete list of publications supported by the Grant. Within the scope of this project, we have studied fundamental issues that arise in modeling, identification, filtering, control, stabilization, control-based model reduction, decomposition and aggregation, and optimization of uncertain systems. The mathematical framework we have worked in has allowed the system dynamics to be only partially known (with the uncertainties being of both parametric or structural nature), and further the dynamics to be perturbed by unknown dynamic disturbances. Our research over these four years has generated a substantial body of new knowledge, and has led to new major developments in theory, applications, and computational algorithms. These have all been documented in various journal articles and book chapters, and have been presented at leading conferences, as to be described. A brief description of the results we have obtained within the …

Date: October 29, 2001

Creator: Basar, Tamer

Object Type: Report

System: The UNT Digital Library

(open access)

Determination of Free Acid by Standard Addition with Potassium Thiocyanate as Complexant

A method is described for determination of free acid in solutions containing the hydrolyzable ions Al (III), Cr(III), Fe(III), Hg(II), Ni(II), Th(IV), and U(VI). The concentration of the sample is calculated either by solving three simultaneous Nernst equations, by the Gran plot procedure, or by means of a microprocessor pH meter. Molar concentrations of metal ion up to 2.5 times that of the acid can be tolerated. The method has been applied to analysis of nuclear processing solutions that contain Pu(III), in addition to the ions listed above.

Date: May 29, 2001

Creator: Baumann, E. W.

Object Type: Article

System: The UNT Digital Library

(open access)

A Tritiated-Water Detector with U-232/Th-228 Source

The detection capabilities of the new U-232/Th-228 source are comparable to those of the Na-24 source. The main benefit in using the new source is the ease of operation. Elimination of the neutron activation step required for Na-24 sources saves about 24 hours in planning, scheduling, and executing. With the new U-232/Th-228 source, the monitor can be put in operation in less than 15 minutes. The long half-life of the U-232/Th-228 source also eliminates the need to record calibration and measurement times, as required for decay corrections when using a Na-24 source.

Date: May 29, 2001

Creator: Baumann, N.P.

Object Type: Article

System: The UNT Digital Library

(open access)

Argonne National Laboratory institutional plan FY 2002 - FY 2007.

The national laboratory system provides a unique resource for addressing the national needs inherent in the mission of the Department of Energy. Argonne, which grew out of Enrico Fermi's pioneering work on the development of nuclear power, was the first national laboratory and, in many ways, has set the standard for those that followed. As the Laboratory's new director, I am pleased to present the Argonne National Laboratory Institutional Plan for FY 2002 through FY 2007 on behalf of the extraordinary group of scientists, engineers, technicians, administrators, and others who are responsible for the Laboratory's distinguished record of achievement. Like our sister DOE laboratories, Argonne uses a multifaceted approach to advance U.S. R and D priorities. First, we assemble interdisciplinary teams of scientists and engineers to address complex problems. For example, our initiative in Functional Genomics will bring together biologists, computer scientists, environmental scientists, and staff of the Advanced Photon Source to develop complete maps of cellular function. Second, we cultivate specific core competencies in science and technology; this Institutional Plan discusses the many ways in which our core competencies support DOE's four mission areas. Third, we serve the scientific community by designing, building, and operating world-class user facilities, such …

Date: November 29, 2001

Creator: Beggs, S. D.

Object Type: Report

System: The UNT Digital Library

(open access)

A Universal Method for Effusive-flow Characterization of Target/Vapor Transport Systems for RIB Generation

In this article, thermal modeling techniques are used to simulate ISOL targets irradiated with high power proton beams. Beam scattering effects, nuclear reactions and beam power deposition distributions in the target were computed with the Monte Carlo simulation code, GEANT4. The power density information was subsequently used as input to the finite element thermal analysis code, ANSYS, for extracting temperature distribution information for a variety of target materials. The principal objective of the studies was to evaluate techniques for more uniformly distributing beam deposited heat over the volumes of targets to levels compatible with their irradiation with the highest practical primary-beam power, and to use the preferred technique to design high power ISOL targets. The results suggest that radiation cooling, in combination, with primary beam manipulation, can be used to control temperatures in practically sized targets, to levels commensurate with irradiation with 1 GeV, 100 kW proton beams.

Date: June 29, 2001

Creator: Bilheux, J.-C.

Object Type: Article

System: The UNT Digital Library

(open access)

Variations in the Retention and Excretion of {sup 137}Cs with Age and Sex

This report discusses the effects of age and sex on the retention and excretion of {sup 137}Cs in the body in a cross section of the general population over a four-year period.

Date: August 29, 2001

Creator: Boni, A. L.

Object Type: Article

System: The UNT Digital Library

(open access)

Grandview Tribune (Grandview, Tex.), Vol. 106, No. 45, Ed. 1 Friday, June 29, 2001

Weekly newspaper from Grandview, Texas that includes local, state, and national news along with advertising.

Date: June 29, 2001

Creator: Bosher, Casey & Marten, Donna K.

Object Type: Newspaper

System: The Portal to Texas History

(open access)

Californium-252 Neutron Sources for Medical Applications

Californium-252 neutron sources are being prepared to investigate the value of this radionuclide in diagnosing and treating diseases. A source resembling a cell-loaded radium needle was developed for neutron therapy. Since therapy needles are normally implanted in the body, very conservative design criteria were established to prevent leakage of radioactive. Methods are being developed to prepare very intense californium sources that could be used eventually for neutron radiography and for diagnosis by neutron activation analysis. This paper discusses these methods.

Date: August 29, 2001

Creator: Boulogne, A.R.

Object Type: Article

System: The UNT Digital Library

(open access)

Surface Depletion in the Vacuum Distillation of Metals from Bismuth

Surface depletion was investigated in laboratory- and plant-scale distillation units with mixing by natural convection or by mechanical surface agitation. A model was developed for predicting the degree of surface depletion during the distillation of metals from bismuth as a function of temperature, still pot dimensions, and degree of agitation. This paper discusses those findings.

Date: August 29, 2001

Creator: Bradley, R.F.

Object Type: Article

System: The UNT Digital Library

(open access)

Photocharge Transport and Recombination Measurements in Amorphous Silicon Films and Solar Cells by Photoconductive Frequency Mixing: Annual Subcontract Report, 20 April 1999 - 19 April 2000

This report describes research focused on improving the individual component cells from which the multijunction devices are fabricated. The Mid-Bandgap and Metastability subteam and the Low-Bandgap subteam have the responsibility to develop appropriate materials for the respective layer of the triple-junction solar cell. To this end, it is necessary to characterize the materials that are prepared for the appropriate layer to optimize the devices and to develop an understanding of the conditions responsible for light-induced degradation so as to develop means to mitigate the degradation. Using the photomixing technique, UCLA was able to determine the mobility and lifetime separately of a number of semiconductor materials. We have established that different kinetics of degradation occur for mobility and lifetime. We have found that the drift mobility is electric-field dependent, and we developed a model for the charge transport through long-range potential fluctuations that enable a determination of the range and the depth of these fluctuations for material in the annealed and light-soaked states. UCLA has continued to provide transport parameters for the Mid-Gap, Metastability, and Low-Band teams. The materials studied were prepared by various deposition techniques. In phase II of this program, we investigated in detail the charge-transport properties by photomixing …

Date: August 29, 2001

Creator: Braunstein, R.; Kathwinkel, A. & Sheng, S. R. (University of California/Los Angeles)

Object Type: Report

System: The UNT Digital Library

(open access)

The Goldthwaite Eagle (Goldthwaite, Tex.), Vol. 107, No. 20, Ed. 1 Thursday, November 29, 2001

Weekly newspaper from Goldthwaite, Texas that includes local, state, and national news along with extensive advertising.

Date: November 29, 2001

Creator: Bridges, G. Frank & Bridges, Georgie

Object Type: Newspaper

System: The Portal to Texas History

(open access)

Waste Characteristics of the Former S-3 Ponds and Outline of Uranium Chemistry Relevant to NABIR Field Research Center Studies

The Environmental Sciences Division at Oak Ridge National Laboratory (ORNL) was awarded the first Naturaland Accelerated Bioremediation Research (NABIR) Program, Field Research Center (FRC) based upon the recommendation of a review panel following a competitive peer-reviewed proposal process. The contaminated FRC site at ORNL is centered on groundwater plumes that originate from the former S-3 Waste Disposal Ponds located at the Y-12 Plant and the Y-12 Bone Yard/Bum Yard. Proposals for individual science research projects at the FRC were submitted in the spring of 2000 in response to a solicitation issued by the Department of Energy (DOE). Proposals selected for funding began work in Fiscal Year 2001 (October 1, 2000). The FRC staff have initiated several characterization efforts intended to support, inform, and educate individual FRC investigators, NABIR principal investigators (PIs), and the broader community of the specific conditions, opportunities, and challenges of this site. These efforts include both physical site characterization as well as numerical simulation (modeling) studies. Geochemical modeling has been conducted with the goal of: (1) providing a baseline understanding of the geochemical behavior of uranium (U); (2) examining the interaction of geochemistry and uranium transport in the subsurface; (3) elucidating some potential pitfalls for researchers with …

Date: June 29, 2001

Creator: Brooks, S. C.

Object Type: Report

System: The UNT Digital Library