A 3D Contact Smoothing Method (open access)

A 3D Contact Smoothing Method

Smoothing of contact surfaces can be used to eliminate the chatter typically seen with node on facet contact and give a better representation of the actual contact surface. The latter affect is well demonstrated for problems with interference fits. In this work we present two methods for the smoothing of contact surfaces for 3D finite element contact. In the first method, we employ Gregory patches to smooth the faceted surface in a node on facet implementation. In the second method, we employ a Bezier interpolation of the faceted surface in a mortar method implementation of contact. As is well known, node on facet approaches can exhibit locking due to the failure of the Babuska-Brezzi condition and in some instances fail the patch test. The mortar method implementation is stable and provides optimal convergence in the energy of error. In the this work we demonstrate the superiority of the smoothed versus the non-smoothed node on facet implementations. We also show where the node on facet method fails and some results from the smoothed mortar method implementation.
Date: May 2, 2002
Creator: Puso, M. A. & Laursen, T. A.
Object Type: Article
System: The UNT Digital Library
Chemical separations schemes for partitioning and transmutation systems. (open access)

Chemical separations schemes for partitioning and transmutation systems.

In the initial phase of the U.S. Accelerator Transmutation of Waste (ATW) program, a single-tier system was foreseen in which the transuranics and long-lived fission products (specifically, {sup 99}Tc and {sup 129}I) recovered from spent LWR oxide fuel would be sent directly to an accelerator-driven transmuter reactor [1]. Because the quantity of fuel to be processed annually was so large (almost 1,500 tons per year), an aqueous solvent extraction process was chosen for LWR fuel processing. Without the need to separate transuranics from one another for feed to the transmuter, it became appropriate to develop an advanced aqueous separations method that became known as UREX. The UREX process employs an added reagent (acetohydroxamic acid) that suppresses the extraction of plutonium and promotes the extraction of technetium together with uranium. Technetium can then be efficiently removed from the uranium; the recovered uranium, being highly decontaminated, can be disposed of as a low-level waste or stored in an unshielded facility for future use. Plutonium and the other transuranic elements, plus the remaining fission products, are directed to the liquid waste stream. This stream is calcined, converting the transuranics and fission products to their oxides. The resulting oxide powder, now representing only about …
Date: May 2, 2002
Creator: Laidler, J.
Object Type: Article
System: The UNT Digital Library
Developing Countries: Switching Some Multilateral Loans to Grants Would Lesson Poor Country Debt Burdens (open access)

Developing Countries: Switching Some Multilateral Loans to Grants Would Lesson Poor Country Debt Burdens

Testimony issued by the General Accounting Office with an abstract that begins "Last year, President Bush proposed that the World Bank and other development banks replace half of all future loans to the world's poorest countries with grants. The goal of the proposal was to relieve poor countries' long term debt burdens. The World Bank estimates that the proposal would result in a financial loss of $100 billion dollars to it during the next 40 years. GAO found that the proposal would help poor countries reduce their debt burdens and that the World Bank would lose only $15.6 billion, which could be financed through relatively small increases in donor contributions. This testimony is based on an April report. (See GAO-02-593.)"
Date: May 2, 2002
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library
Electron cloud in linear collider damping rings (open access)

Electron cloud in linear collider damping rings

None
Date: May 2, 2002
Creator: Wolski, Andrzej
Object Type: Article
System: The UNT Digital Library
Employing Thin HPGe Detectors for Gamma-Ray Imaging (open access)

Employing Thin HPGe Detectors for Gamma-Ray Imaging

We have evaluated a collimator-less gamma-ray imaging system, which is based on thin layers of double-sided strip HPGe detectors. The positions of individual gamma-ray interactions will be deduced by the strip addresses and the Ge layers which fired. Therefore, high bandwidth pulse processing is not required as in thick Ge detectors. While the drawback of such a device is the increased number of electronics channels to be read out and processed, there are several advantages, which are particularly important for remote applications: the operational voltage can be greatly reduced to fully deplete the detector and no high bandwidth signal processing electronics is required to determine positions. Only a charge sensitive preamplifier, a slow pulse shaping amplifier, and a fast discriminator are required on a per channel basis in order to determine photon energy and interaction position in three dimensions. Therefore, the power consumption and circuit board real estate can be minimized. More importantly, since the high bandwidth signal shapes are not used to determine the depth position, lower energy signals can be processed. The processing of these lower energy signals increases the efficiency for the recovery of small angle scattering. Currently, we are studying systems consisting of up to ten …
Date: May 2, 2002
Creator: Vetter, K.; Mihailescu, L.; Ziock, K.; Burks, M.; Hull, E.; Madden, N. et al.
Object Type: Article
System: The UNT Digital Library
Estimating long-term surface hydrological components by coupling remote sensing observation with surface flux model. (open access)

Estimating long-term surface hydrological components by coupling remote sensing observation with surface flux model.

A model framework for parameterized subgrid-scale surface fluxes (PASS) has been applied to use satellite data, models, and routine surface observations to infer root-zone available moisture content and evapotranspiration rate with moderate spatial resolution within Walnut River Watershed in Kansas. Biweekly composite normalized difference vegetative index (NDVI) data are derived from observations by National Oceanic and Atmospheric Administration (NOAA) satellites. Local surface observations provide data on downwelling solar irradiance, air temperature, relative humidity, and wind speed. Surface parameters including roughness length, albedo, surface water conductance, and the ratio of soil heat flux to net radiation are estimated; pixel-specific near-surface meteorological conditions such as air temperature, vapor pressure, and wind speed are adjusted according to local surface forcing. The PASS modeling system makes effective use of satellite data and can be run for large areas for which flux data do not exist and surface meteorological data are available from only a limited number of ground stations. The long-term surface hydrological budget is evaluated using radar-derived precipitation estimates, surface meteorological observations, and satellite data. The modeled hydrological components in the Walnut River Watershed compare well with stream gauge data and observed surface fluxes during 1999.
Date: May 2, 2002
Creator: Song, J. & Wesely, M. L.
Object Type: Article
System: The UNT Digital Library
Evaluation of ZnO(Ga)Coatings as Alpha Particle Transducers Within a Neutron Generator (open access)

Evaluation of ZnO(Ga)Coatings as Alpha Particle Transducers Within a Neutron Generator

We report investigations and preliminary results from efforts to develop a recoil alpha particle detector for use in a portable neutron generator. The associated particle sealed tube neutron generator (APSTNG) will be used as an interrogation source for the Nuclear Materials Identification System (NMIS). With the emission of 14.1 MeV neutrons produced by the D-T reaction, associated 3.5 MeV alpha particles are emitted. These neutrons and alphas may then be correlated in time and direction, thus effectively ''tagging'' the neutrons of interest for subsequent use as an active nuclear materials interrogation source. The alpha particle detector uses a ZnO(Ga) scintillator coating applied to a fiber optic face plate. Gallium-doped zinc oxide is a fast (1.5 ns decay time), inorganic scintillator with a high melting point (1975C) and an absolute light yield of 1.5% of NaI(Tl). The scintillator is coated with a thin layer of nickel in order to screen out light produced in the tube and scattered deuterons and tritons. This coating also serves to prevent the buildup of charge on the detector surface. Results to date indicate promise as an effective alpha particle detector for the APSTNG for future use in the NMIS.
Date: May 2, 2002
Creator: Mihalczo, J. T.; Neal, J. S.; Cooper, J. C. & Koltick, D. S.
Object Type: Article
System: The UNT Digital Library
Executive and Independent Agency Publications: Where to Get Official Documents (open access)

Executive and Independent Agency Publications: Where to Get Official Documents

This is a directory of telephone numbers and addresses that congressional offices may use to obtain publications from the Executive Office of the President, the executive departments, and the independent agencies and commissions of the federal government. Electronic sources are included for locating copies of government publications on the Internet. The information for each agency was provided by the agency itself.
Date: May 2, 2002
Creator: Campos, Jesus
Object Type: Report
System: The UNT Digital Library
Force Structure: Air Force Needs a Periodic Total Force Assessment (open access)

Force Structure: Air Force Needs a Periodic Total Force Assessment

A letter report issued by the General Accounting Office with an abstract that begins "The Air Force began to test the force requirements in its manpower requirements-determination process in May 2000. The defense strategy envisions simultaneously fighting two major theater wars and conducting multiple contingency operations in peacetime. The Total Force Assessment was the Air Force's first evaluation of manpower adequacy in these contexts since 1995. Because the Total Force Assessment was not implemented as planned, the Air Force cannot demonstrate that it has the forces needed to carry out the full spectrum of military operations. Although intended to examine whether authorized Air Force personnel were sufficient to meet both the wartime and peacetime scenarios, the assessment only addressed the wartime scenario and did not address the adequacy of manpower for conducting multiple contingency operations in peacetime. Air Force officials concluded that manpower was adequate to support the wartime scenario but this assessment was inconclusive because the effort was discontinued before all discrepancies in the assessment's results were resolved. Although the Air Force spent considerable time and effort conducting at least a portion of its planned assessment, it has not used the results to the extent anticipated."
Date: May 2, 2002
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Global Climate Change: Market-Based Strategies to Reduce Greenhouse Gases (open access)

Global Climate Change: Market-Based Strategies to Reduce Greenhouse Gases

This report discusses global climate change and the possibility that human activities are releasing gases, including carbon dioxide (CO2), at rates that could affect global climate change.
Date: May 2, 2002
Creator: Parker, Larry
Object Type: Report
System: The UNT Digital Library
Human Cloning (open access)

Human Cloning

This report provides information about the Human Cloning where a human embryo produced via cloning involves the process called somatic cell nuclear transfer. The nuclear of the egg is removed and replaced with a mature body cell.
Date: May 2, 2002
Creator: Johnson, Judith A.
Object Type: Report
System: The UNT Digital Library
Information Security: Additional Actions Needed to Fully Implement Reform Legislation (open access)

Information Security: Additional Actions Needed to Fully Implement Reform Legislation

A letter report issued by the General Accounting Office with an abstract that begins "In March, GAO testified on the federal government's fiscal-year implementation of legislative provisions for government information security reform. (See GAO-02-470T.) GAO reported that implementation of the reforms addresses serious, pervasive information security weaknesses. GAO also noted the Office of Management and Budget needs to (1) further guide agencies and encourage them to implement the reform provision requirements and (2) provide Congress with the information it needs for overseeing agencies' implementation, compliance, and corrective actions, as well as for its related budget deliberations."
Date: May 2, 2002
Creator: United States. General Accounting Office.
Object Type: Report
System: The UNT Digital Library
Information Security: Comments on the Proposed Federal Information Security Management Act of 2002 (open access)

Information Security: Comments on the Proposed Federal Information Security Management Act of 2002

Testimony issued by the General Accounting Office with an abstract that begins "The Federal Information Security Management Act of 2002 reauthorizes and expands the information security, evaluation, and reporting requirements enacted in the National Defense Authorization Act for Fiscal Year 2001. Concerned that pervasive information security weaknesses place federal operations at significant risk of disruption, tampering, fraud, and inappropriate disclosures of sensitive information, Congress enacted the Government Security Reform Act (GISRA) for more effective oversight. The Federal Information Security Management Act also changes and clarifies information security issues noted in the first-year implementation of GISRA. In particular, the bill requires the development, promulgation of, and compliance with minimum mandatory management controls for securing information and information systems; requires annual agency reporting to both the Office of Management and Budget and the Comptroller General; and defines the evaluation responsibilities for national security systems. To ensure that information security receives appropriate attention and resources and that known deficiencies are addressed, it will be necessary to delineate the roles and responsibilities of the numerous entities involved; obtain adequate technical expertise to select, implement, and maintain controls; and allocate enough agency resources for information security."
Date: May 2, 2002
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library
Land-Surface Modeling and Climate Simulations: Results over the Autstralian Region from Sixteen AMIP2 Models (open access)

Land-Surface Modeling and Climate Simulations: Results over the Autstralian Region from Sixteen AMIP2 Models

This report presents analyses of sixteen models from the Atmospheric Model Intercomparison Project II (AMIP2) over the Australian region. It is focused on assessing how well surface climate and fluxes over this region are simulated in current Atmospheric General Circulation Models (AGCMs) forced by observed sea surface temperatures (SSTs). The importance of land-surface modeling on model predictability is also investigated. In this preliminary analysis, the Bureau of Meteorology (BoM) observational rainfall, temperature and surface evapotranspiration datasets are used in validating surface climatologies simulated by the 16 models. Specifically, the Linear Error in Probability Space (LEPS) score is calculated in assessing the skill of the models in simulating surface Climate anomalies for the 17-year period (1979 to 1995). Numerous model differences are seen with some aspects of the model performance being linked to the complexity of land-surface schemes used. The connection between model skill in simulating surface climate anomalies and surface flux anomalies is explored. Lag-correlation analysis is conducted. Results reveal that ''climatic memory'' derived from land-surface processes (e.g: soil moisture) has different features in the sixteen models: some models show rapid feedback processes between land-surface and the overlying atmosphere, while others show slowly varying processes in which anomalous surface conditions …
Date: May 2, 2002
Creator: Zhang, H; Henderson-Sellers, A; Irannejad, P; Sharmeen, S; Phillips, T & McGuffie, K
Object Type: Report
System: The UNT Digital Library
Managing Nuclear Waste: Options Considered (open access)

Managing Nuclear Waste: Options Considered

Starting in the 1950s, U.S. scientists began to research ways to manage highly radioactive materials accumulating at power plants and other sites nationwide. Long-term surface storage of these materials poses significant potential health, safety, and environmental risks. Scientists studied a broad range of options for managing spent nuclear fuel and high-level radioactive waste. The options included leaving it where it is, disposing of it in various ways, and making it safer through advanced technologies. International scientific consensus holds that these materials should eventually be disposed of deep underground in what is called a geologic repository. In a recent special report, the National Academy of Sciences summarized the various studies and emphasized that geologic disposal is ultimately necessary.
Date: May 2, 2002
Creator: United States. Department of Energy.
Object Type: Report
System: The UNT Digital Library
Mechanism of the Mg-chelatase step in chlorophyll biosynthesis. Final technical report (open access)

Mechanism of the Mg-chelatase step in chlorophyll biosynthesis. Final technical report

Mg-chelatase catalyzes the insertion of Mg2+ into protoporphyrin-IX (Proto) in the chlorophyll biosynthetic pathway. This is the first step unique to the chlorophyll pathway and is at the branchpoint between heme and chlorophyll biosynthesis. Previous work from our laboratory has shown that the enzyme from pea chloroplasts requires three distinct protein fractions (now known to contain the D, I and H subunits). The reaction requires ATP in two distinct steps: activation requiring two of the fractions (I and D) and metal ion insertion, requiring all three fractions. Work covered in this granting period includes the cloning and expression of the active form of one of the pea subunits and demonstration of the change in chromatographic behavior of the subunits upon activation with ATP.
Date: May 2, 2002
Creator: Weinstein, Jon
Object Type: Report
System: The UNT Digital Library
Multiscale finite element methods for miscible and immiscible flow in porous media (open access)

Multiscale finite element methods for miscible and immiscible flow in porous media

None
Date: May 2, 2002
Creator: Juanes, Ruben & Patzek, Tadeusz W.
Object Type: Article
System: The UNT Digital Library
Non-Equilibrium Zeldovich-Von Neumann-Doring Theory and Reactive Flow Modeling of Detonation (open access)

Non-Equilibrium Zeldovich-Von Neumann-Doring Theory and Reactive Flow Modeling of Detonation

This paper discusses the Non-Equilibrium Zeldovich - von Neumann - Doring (NEZND) theory of self-sustaining detonation waves and the Ignition and Growth reactive flow model of shock initiation and detonation wave propagation in solid explosives. The NEZND theory identified the non-equilibrium excitation processes that precede and follow the exothermic decomposition of a large high explosive molecule into several small reaction product molecules. The thermal energy deposited by the leading shock wave must be distributed to the vibrational modes of the explosive molecule before chemical reactions can occur. The induction time for the onset of the initial endothermic reactions can be calculated using high pressure, high temperature transition state theory. Since the chemical energy is released well behind the leading shock front of a detonation wave, a physical mechanism is required for this chemical energy to reinforce the leading shock front and maintain its overall constant velocity. This mechanism is the amplification of pressure wavelets in the reaction zone by the process of de-excitation of the initially highly vibrationally excited reaction product molecules. This process leads to the development of the three-dimensional structure of detonation waves observed for all explosives. For practical predictions of shock initiation and detonation in hydrodynamic codes, …
Date: May 2, 2002
Creator: Tarver, C M; Forbes, J W & Urtiew, P A
Object Type: Article
System: The UNT Digital Library
Operation of an aluminum-intensive vehicle : report on a six-year project. (open access)

Operation of an aluminum-intensive vehicle : report on a six-year project.

In 1994, Ford produced a small demonstration fleet of Mercury Sables with aluminum bodies. Argonne National Laboratory obtained one of these vehicles on a lease so that Laboratory staff could observe the wear characteristics of the body under normal operating conditions. The vehicle was placed in the transportation pool, parked outdoors, and used by staff members for both local and longer trips. The vehicle performed normally, except for having particularly good acceleration because of its light weight and highpower SHO engine. No significant problems were encountered that related to the Al body or engine. No special driving protocols were observed, but a log was kept of trip lengths and fuel purchases. Fuel economy was observed to be improved, compared with that of a similar conventional steel-bodied vehicle that was available for one year of the lease period. The vehicle was tested on a chassis dynamometer to obtain emissions and fuel economy over the federal test cycle. The impacts of further mass reduction were also simulated. At the end of the lease, the body was in excellent condition, which we documented with a set of detailed photographs before the vehicle was returned to Ford. There were minor imperfections in the painted …
Date: May 2, 2002
Creator: Gaines, L. L. & Cuenca, R. M.
Object Type: Article
System: The UNT Digital Library
Practical Issues Associated with Mortar Projections in Large Deformation Contact/Impact Analysis (open access)

Practical Issues Associated with Mortar Projections in Large Deformation Contact/Impact Analysis

Several recent works have considered variants of the mortar-finite element method for numerical treatment of contact phenomena. The method has shown considerable promise for the spatial discretization of contact interactions, particularly for kinematically linear applications where one or both of the contacting surfaces are flat. Desirable features already demonstrated for the method in this specialized setting include passage of patch tests, preservation of convergence rates that would be obtained with a perfectly conforming mesh, and accurate resolution of contact stresses on interfaces. This paper concerns itself with the successful extension of these methods to encompass contact of geometrically noncoincident surfaces. The issue of patch test passage over curved interfaces will be discussed. It will be shown that a generalization of the mortar projection method is required to pass patch tests in this instance. Issues relating to the exact numerical integration of the mortar projection integrals will also be outlined, and a convergence study for a mortar tying application will be presented.
Date: May 2, 2002
Creator: Laursen, T. A.; Puso, M. A. & Heinstein, M. W.
Object Type: Article
System: The UNT Digital Library
Practical superconductor development for electrical power applications : annual report for FY 2001. (open access)

Practical superconductor development for electrical power applications : annual report for FY 2001.

Most large-scale applications of high-critical-temperature superconductors will require wires or tapes that can carry large current in applied magnetic fields. This report describes research and development efforts at Argonne National Laboratory (ANL) aimed at producing practical superconducting components and devices using the Y-Ba-Cu-O and Bi-(Pb)-Sr-Ca-Cu-O systems. Topics discussed include various methods of forming second- and first-generation composite conductors, characterization of their structures and superconducting and mechanical properties, modeling of grain-boundary current transport, and the testing and modeling of a superconducting fault current limiter.
Date: May 2, 2002
Creator: Cha, Y. S.; Dorris, S. E.; Dusek, J. T.; Emerson, J. E.; Erck, R. A.; Fisher, B. L. et al.
Object Type: Report
System: The UNT Digital Library
Prediction of Carbon Monoxide and Hydrocarbon Emissions in Isooctane HCCI Engine Combustion Using Multi-Zone Simulations (open access)

Prediction of Carbon Monoxide and Hydrocarbon Emissions in Isooctane HCCI Engine Combustion Using Multi-Zone Simulations

Homogeneous Charge Compression Ignitions (HCCI) engines show promise as an alternative to Diesel engines, yet research remains: development of practical HCCI engines will be aided greatly by accurate modeling tools. A novel detailed chemical kinetic model that incorporates information from a computational fluid mechanics code has been developed to simulate HCCI combustion. This model very accurately predicts many aspects of the HCCI combustion process. High-resolution computational grids can be used for the fluid mechanics portion of the simulation, but the chemical kinetics portion of the simulation can be reduced to a handful of computational zones (for all previous work 10 zones have been used). While overall this model has demonstrated a very good predictive capability for HCCI combustion, previous simulations using this model have tended to underpredict carbon monoxide emissions by an order of magnitude. A factor in the underprediction of carbon monoxide may be that all previous simulations have been conducted with 10 chemical kinetic zones. The chemistry that results in carbon monoxide emissions is very sensitive to small changes in temperature within the engine. The resolution in temperature is determined directly by the number of zones. This paper investigates how the number of zones (i.e. temperature resolution) affects …
Date: May 2, 2002
Creator: Flowers, D; Aceves, S M; Martinez-Frias, J & Dibble, R
Object Type: Article
System: The UNT Digital Library
Radiological considerations for the operation of the Advanced Photon Source storage ring (revised). (open access)

Radiological considerations for the operation of the Advanced Photon Source storage ring (revised).

This report deals with the radiological considerations of operations using 7700-MeV positron and electron beams in the storage ring (SR) tunnel. The radiological considerations addressed include the following: prompt secondary radiation (bremsstrahlung, giant resonance neutrons, medium and high energy neutrons, and muons) produced by electrons/positrons interacting in a beam stop or by particle losses in the component structures; skyshine radiation, which produces a radiation field in nearby areas and at the nearest off-site location; radioactive gases produced by neutron irradiation of air in the vicinity of a particle loss site; noxious gases (ozone and others) produced in air by the escaping bremsstrahlung radiation that results from absorbing particles in the components or by synchrotron radiation escaping into the tunnel; activation of the storage ring components that results in a residual radiation field in the vicinity of these materials following shutdown; potential activation of water used for cooling the magnets and other purposes in the SR tunnel; evaluation of the radiation fields due to escaping synchrotron radiation and gas bremsstrahlung. Estimated dose rates outside of the tunnel, in the early assembly area (EAA), and in the Experiment Hall for several modes of operation (including potential safety envelope beam power, normal beam …
Date: May 2, 2002
Creator: Moe, H. J.
Object Type: Report
System: The UNT Digital Library
Social Security Administration: Agency Must Position Itself Now to Meet Profound Challenges (open access)

Social Security Administration: Agency Must Position Itself Now to Meet Profound Challenges

Testimony issued by the General Accounting Office with an abstract that begins "The Social Security Administration (SSA) provided $450 billion in benefits to 50 million recipients in fiscal year 2001. Since 1995, when SSA became an independent agency, GAO has called for effective leadership and sustained management attention to several unresolved management challenges, including the redesign of its disability claims process, management and oversight problems with its SSI program, future service delivery demands, and implementing its information technology and research and policy development capacity. SSA has much more to do and will need to take bolder action or make more fundamental changes to existing programs."
Date: May 2, 2002
Creator: United States. General Accounting Office.
Object Type: Text
System: The UNT Digital Library