The CDF Silicon Vertex Detector for Run II (open access)

The CDF Silicon Vertex Detector for Run II

The 8 layer, 720k channel CDF Run II silicon detector is an essential part of the heavy flavor tagging and forward tracking capabilities of the CDF experiment. A summary of the experience in commissioning and operating this double-sided detector during the first 2 years of Run II is presented. The performances of the silicon in term of resolution, efficiency are also described. The results of the studies of radiation damage and the expected operational limits are discussed. A short description of the SVT, the Level 2 Silicon Vertex Trigger, one of the major upgrades related to the new silicon device is also presented. Finally, some of the many physics results achieved by means of the new Silicon+SVT machinery are also reviewed.
Date: January 6, 2004
Creator: Rossin, R.
Object Type: Article
System: The UNT Digital Library
The CDF Time of Flight Detector (open access)

The CDF Time of Flight Detector

A new Time of Flight (TOF) detector based on scintillator bars with fine-mesh photomultipliers at both ends has been in operation since 2001 in the CDF experiment. With a design resolution of 100 ps, the TOF can provide separation between K{sup +-} and {pi}{sup +-} in p{bar p} collisions at the 2{omega} level for low momentum, which enhances b flavor tagging capabilities. Because of its very fast response, the TOF is an excellent triggering device, and it is used to trigger on highly ionizing particles, multiple minimum ionizing particles and cosmic rays. Particle identification is achieved by comparing the time-of-flight of the particle measured by the TOF to the time expected for a given mass hypothesis. In order to obtain the resolution necessary for particle ID, optimal calibrations are critical. This paper describes the TOF detector, its calibration procedure, the achieved resolution, the long term operation performances and some of the first results from data analysis using this detector.
Date: January 6, 2004
Creator: al., S. Cabrera et
Object Type: Article
System: The UNT Digital Library
A Contamination Vulnerability Assessment for the Santa Clara and San Mateo County Groundwater Basins (open access)

A Contamination Vulnerability Assessment for the Santa Clara and San Mateo County Groundwater Basins

In response to concerns expressed by the California Legislature and the citizenry of the State of California, the State Water Resources Control Board (SWRCB), implemented a program to assess groundwater quality, and provide a predictive capability for identifying areas that are vulnerable to contamination. The program was initiated in response to concern over public supply well closures due to contamination by chemicals such as MtBE from gasoline, and solvents from industrial operations. As a result of this increased awareness regarding groundwater quality, the Supplemental Report of the 1999 Budget Act mandated the SWRCB to develop a comprehensive ambient groundwater-monitoring plan, and led to the initiation of the Ambient Groundwater Monitoring and Assessment (GAMA) Program. The primary objective of the GAMA Program is to assess the water quality and to predict the relative susceptibility to contamination of groundwater resources throughout the state of California. Under the GAMA program, scientists from Lawrence Livermore National Laboratory (LLNL) collaborate with the SWRCB, the U.S. Geological Survey, the California Department of Health Services (DHS), and the California Department of Water Resources (DWR) to implement this groundwater assessment program. In 2001 and 2002, LLNL carried out this vulnerability study in the groundwater basins of Santa Clara …
Date: January 6, 2004
Creator: Moran, J. E.; Hudson, G. B.; Eaton, G. F. & Leif, R.
Object Type: Report
System: The UNT Digital Library
ECR Browser: A Tool For Visualizing And Accessing Data From Comparisons Of Multiple Vertebrate Genomes (open access)

ECR Browser: A Tool For Visualizing And Accessing Data From Comparisons Of Multiple Vertebrate Genomes

The increasing number of vertebrate genomes being sequenced in draft or finished form provide a unique opportunity to study and decode the language of DNA sequence through comparative genome alignments. However, novel tools and strategies are required to accommodate this increasing volume of genomic information and to facilitate experimental annotation of genome function. Here we present the ECR Browser, a tool that provides an easy and dynamic access to whole genome alignments of human, mouse, rat and fish sequences. This web-based tool (http://ecrbrowser.dcode.org) provides the starting point for discovery of novel genes, identification of distant gene regulatory elements and prediction of transcription factor binding sites. The genome alignment portal of the ECR Browser also permits fast and automated alignment of any user-submitted sequence to the genome of choice. The interconnection of the ECR browser with other DNA sequence analysis tools creates a unique portal for studying and exploring vertebrate genomes.
Date: January 6, 2004
Creator: Loots, G G; Ovcharenko, I; Stubbs, L & Nobrega, M A
Object Type: Article
System: The UNT Digital Library
Electron exchange along the tercyclopentadienyltrimetallic scaffold: Kinetics, equilibria, and bond strengths (open access)

Electron exchange along the tercyclopentadienyltrimetallic scaffold: Kinetics, equilibria, and bond strengths

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Date: January 6, 2004
Creator: Cammack, J. Kevin; Amouri, Hani; Leonard, Philip W.; Myrabo, Randy L. & Vollhardt, Peter C.
Object Type: Article
System: The UNT Digital Library
Human intake fraction of toxic pollutants: a model comparison between caltox and uses-lca (open access)

Human intake fraction of toxic pollutants: a model comparison between caltox and uses-lca

In Life Cycle Assessment and Comparative Risk Assessment potential human exposure to toxic pollutants can be expressed as the human intake fraction (iF), representing the fraction of the quantity emitted that enters the human population. To assess model uncertainty in the human intake fraction, ingestion and inhalation iFs of 367 substances emitted to air and freshwater were calculated with two commonly applied multi-media fate and exposure models, CalTOX and USES-LCA. Comparison of the model outcomes reveal that uncertainty in the ingestion iFs was up to a factor of 70. The uncertainty in the inhalation iFs was up to a factor of 865,000. The comparison showed that relatively few model differences account for the uncertainties found. An optimal model structure in the calculation of human intake fractions can be achieved by including (1) rain and no-rain scenarios, (2) a continental sea water compartment, (3) drinking water purification, (4) pH-correction of chemical properties, and (5) aerosol-associated deposition on plants. Finally, vertical stratification of the soil compartment combined with a chemical-dependent soil depth may be considered in future intake fraction calculations.
Date: January 6, 2004
Creator: Huijbregts, Mark A.J.; Geelen, Loes M.J.; Hertwich, Edgar G.; McKone, Thomas E. & van de Meent, Dik
Object Type: Article
System: The UNT Digital Library
Method for making devices having intermetallic structures and intermetallic devices made thereby (open access)

Method for making devices having intermetallic structures and intermetallic devices made thereby

A method and system for making a monolithic intermetallic structure are presented. The structure is made from lamina blanks which comprise multiple layers of metals which are patternable, or intermetallic lamina blanks that are patternable. Lamina blanks are patterned, stacked and registered, and processed to form a monolithic intermetallic structure. The advantages of a patterned monolithic intermetallic structure include physical characteristics such as melting temperature, thermal conductivity, and corrosion resistance. Applications are broad, and include among others, use as a microreactor, heat recycling device, and apparatus for producing superheated steam. Monolithic intermetallic structures may contain one or more catalysts within the internal features.
Date: January 6, 2004
Creator: Paul, Brian Kevin; Wilson, Rick D. & Alman, David E.
Object Type: Patent
System: The UNT Digital Library
Methods for Calculating a Simplified Hydrologic Source Term for Frenchman Flat Sensitivity Studies of Radionuclide Transport Away from Underground Nuclear Tests (open access)

Methods for Calculating a Simplified Hydrologic Source Term for Frenchman Flat Sensitivity Studies of Radionuclide Transport Away from Underground Nuclear Tests

The purpose of this report is to provide an approach for the development of a simplified unclassified hydrologic source term (HST) for the ten underground nuclear tests conducted in the Frenchman Flat Corrective Action Unit (CAU) at the Nevada Test Site (NTS). It is being prepared in an analytic form for incorporation into a GOLDSIM (Golder Associates, 2000) model of radionuclide release and migration in the Frenchman Flat CAU. This model will be used to explore, in an approximate and probabilistic fashion, sensitivities of the 1,000-year radionuclide contaminant boundary (FFACO, 1996; 2000) to hydrologic and other related parameters. The total inventory (or quantity) of radionuclides associated with each individual test, regardless of its form and distribution, is referred to as the radiologic source term (RST) of that test. The subsequent release of these radionuclides over time into groundwater is referred to as the hydrologic source term (HST) of that test (Tompson, et al., 2002). The basic elements of the simplified hydrologic source term model include: (1) Estimation of the volumes of geologic material physically affected by the tests. (2) Identification, quantification, and distribution of the radionuclides of importance. (3) Development of simplified release and retardation models for these radionuclides in …
Date: January 6, 2004
Creator: Tompson, A; Zavarin, M; Bruton, C J & Pawloski, G A
Object Type: Report
System: The UNT Digital Library
Multiscale Thermohydrologic Model Analyses of Heterogeneity and Thermal-Loading Factors for a Proposed Nuclear Waste Repository (open access)

Multiscale Thermohydrologic Model Analyses of Heterogeneity and Thermal-Loading Factors for a Proposed Nuclear Waste Repository

The MultiScale ThermoHydrologic Model is used to predict thermal-hydrologic conditions in emplacement drifts and the adjoining host-rock throughout a proposed nuclear waste repository. The presented modeling effort simulates a lower temperature operation mode with a different panel loading than the repository currently being considered for the Yucca Mountain license application. Simulations address the influence of repository-scale thermal-conductivity heterogeneity and the influence of pre-closure operational factors on thermal-loading conditions. MSTHM can accommodate a complex repository layout, a development that, along with other improvements, enables more rigorous analyses of preclosure operational factors. Differences in MSTHM output occurring with these new capabilities are noted for a new sequential waste-package loading technique compared to a standard simultaneous loading technique. Alternative approaches to modeling repository-scale thermal-conductivity heterogeneity in the host-rock units are investigated, and study incorporating geostatistically-varied host-rock thermal conductivity is discussed.
Date: January 6, 2004
Creator: Lee, K.; Buscheck, T. A.; Gansemer, J.; Glascoe, L. G. & Sun, Y.
Object Type: Article
System: The UNT Digital Library
Proceedings of Riken Bnl Research Center Workshop: Volume 56 Rbrc Scientific Review Committee Meeting. (open access)

Proceedings of Riken Bnl Research Center Workshop: Volume 56 Rbrc Scientific Review Committee Meeting.

The sixth evaluation of the RIKEN BNL Research Center (RBRC) took place on November 20-21, 2003, at Brookhaven National Laboratory. The present members of the Scientific Review Committee are Dr. Jean-Paul Blaizot, Professor Makoto Kobayashi, Dr. Akira Masaike, Professor Charles Young Prescott (absent), Professor Stephen Sharpe, and Professor Jack Sandweiss, Committee Chair. In order to illustrate the breadth and scope of the program, each member of the Center made a presentation on his research efforts. In addition, a special presentation was given jointly by our collaborators, Professors Norman Christ and Robert Mawhinney of Columbia University, on the progress and status of the IRBRC QCDSP/QCDOC Supercomputer program. A demonstration of a 64-node (64 Gflops peak speed) QCDOC machine in action followed. Although the main purpose of this review is a report to RIKEN Management (Dr. Ryoji Noyori, RIKEN President) on the health, scientific value, management and future prospects of the Center, the RBRC management felt that a compendium of the scientific presentations are of sufficient quality and interest that they warrant a wider distribution. Therefore we have made this compilation and present it to the community for its information and enlightenment.
Date: January 6, 2004
Creator: Samios, N. P. & Lee, T. D.
Object Type: Report
System: The UNT Digital Library
A process for reducing the licensing burden for new products containing depleted uranium. (open access)

A process for reducing the licensing burden for new products containing depleted uranium.

This report is intended to provide guidance on the process for petitioning the U.S. Nuclear Regulatory Commission (NRC) to initiate a rulemaking that could reduce the licensing burden for new products containing depleted uranium (DU), which are being investigated by the DU Uses Research and Development (R&D) Program at Oak Ridge National Laboratory (ORNL). The focus is on requirements of the NRC rulemaking process applicable to establishing new exemptions or general licenses for products and devices containing source material. NRC policies and guidance regarding such requirements are described, including a 1965 policy statement on approval of new exemptions for products containing radionuclides (''Federal Register'', Volume 30, page 3462 [30 FR 3462]; March 16, 1965) and Regulatory Guide 6.7, which addresses the contents of environmental reports that support rulemaking petitions seeking exemptions for radionuclide-containing products. Methodologies for calculating radiological and nonradiological impacts on human health (i.e., risks) associated with distributing, using, and disposing of DU-containing products are presented. Also, methodologies for completing assessments of the potential effects of accidents involving new DU-containing products and of product misuse are described. The report recommends that the U.S. Department of Energy formulate a regulatory plan for deployment of DU-containing products in areas that are …
Date: January 6, 2004
Creator: Ranek, N. L.; Kamboj, S.; Hartmann, H. M. & Avci, H.
Object Type: Report
System: The UNT Digital Library
Proteomic Dissection of the Mitochondrial DNA Metabolism Apparatus in Arabidopsis (open access)

Proteomic Dissection of the Mitochondrial DNA Metabolism Apparatus in Arabidopsis

This study involves the investigation of nuclear genetic components that regulate mitochondrial genome behavior in higher plants. The approach utilizes the advanced plant model system of Arabidopsis thaliana to identify and functionally characterize multiple components of the mitochondrial DNA replication, recombination and mismatch repair system and their interaction partners. The rationale for the research stems from the central importance of mitochondria to overall cellular metabolism and the essential nature of the mitochondrial genome to mitochondrial function. Relatively little is understood about mitochondrial DNA maintenance and transmission in higher eukaryotes, and the higher plant mitochondrial genome displays unique properties and behavior. This investigation has revealed at least three important properties of plant mitochondrial DNA metabolism components. (1) Many are dual targeted to mitochondrial and chloroplasts by novel mechanisms, suggesting that the mitochondria a nd chloroplast share their genome maintenance apparatus. (2)The MSH1 gene, originating as a component of mismatch repair, has evolved uniquely in plants to participate in differential replication of the mitochondrial genome. (3) This mitochondrial differential replication process, termed substoichiometric shifting and also involving a RecA-related gene, appears to represent an adaptive mechanism to expand plant reproductive capacity and is likely present throughout the plant kingdom.
Date: January 6, 2004
Creator: Mackenzie, SAlly A.
Object Type: Report
System: The UNT Digital Library
Quadratic Finite Element Method for 1D Deterministic Transport (open access)

Quadratic Finite Element Method for 1D Deterministic Transport

In the discrete ordinates, or SN, numerical solution of the transport equation, both the spatial ({und r}) and angular ({und {Omega}}) dependences on the angular flux {psi}{und r},{und {Omega}}are modeled discretely. While significant effort has been devoted toward improving the spatial discretization of the angular flux, we focus on improving the angular discretization of {psi}{und r},{und {Omega}}. Specifically, we employ a Petrov-Galerkin quadratic finite element approximation for the differencing of the angular variable ({mu}) in developing the one-dimensional (1D) spherical geometry S{sub N} equations. We develop an algorithm that shows faster convergence with angular resolution than conventional S{sub N} algorithms.
Date: January 6, 2004
Creator: Tolar, Jr., D R & Ferguson, J M
Object Type: Article
System: The UNT Digital Library
The Quest for Clouds and Volcanoes (open access)

The Quest for Clouds and Volcanoes

Elementary students are using the internet to experience virtual field trips to learn about areas that they are not able to experience in person. This poster presentation describes a virtual field trip taken by Mendoza Elementary School, Las Vegas, Nevada classes during the summer of 2003. The authors, who are DataStreme Learning Implementation Team members, drove from Las Vegas to Seattle for the annual DataStreme Summer Workshop. During the trip and in Seattle, the authors communicated through the internet with classrooms in Las Vegas. Weather information, pictures, and pertinent information about Seattle or the enroute area were sent to the classes each day. The students then compared the weather in Las Vegas with the weather and clouds from the communication. Fourth grade students were studying about volcanoes and were excited to hear about, and see pictures of, Mt. Shasta, Mt. Lassen, Mt. St. Helen and Mt. Rainier during the virtual field trip. Classes were able to track the route taken on a map during the virtual field trip.
Date: January 6, 2004
Creator: Blink, F. D. & Blink, J. A.
Object Type: Article
System: The UNT Digital Library
Recent results using all point quark propagators (open access)

Recent results using all point quark propagators

Pseudofermion methods for extracting all-point quark propagators are reviewed, with special emphasis on techniques for reducing or eliminating autocorrelations induced by low eigenmodes of the quark Dirac operator. Recent applications, including high statistics evaluations of hadronic current correlators and the pion form factor, are also described.
Date: January 6, 2004
Creator: Duncan, A. & Yoo, E. Eichten and J.
Object Type: Article
System: The UNT Digital Library
Single Molecule Studies of Chromatin (open access)

Single Molecule Studies of Chromatin

The DNA in eukaryotic cells is tightly packaged as chromatin through interactions with histone proteins to form nucleosomes. These nucleosomes are themselves packed together through interactions with linker histone and non-histone proteins. In order for processes such as DNA replication, DNA repair, and transcription to occur, the chromatin fiber must be remodeled such that the necessary enzymes can access the DNA. The structure of the chromatin fiber beyond the level of the single nucleosome and the structural changes which accompany the remodeling process are poorly understood. We are studying the structures and forces behind the remodeling process through the use of atomic force microscopy (AFM). This allows both high-resolution imaging of the chromatin, and manipulation of individual fibers. Pulling a single chromatin fiber apart using the AFM tip yields information on the forces which hold the structure together. We have isolated chromatin fibers from chicken erythrocytes and Chinese hamster ovary cell lines. AFM images of these fibers will be presented, along with preliminary data from the manipulation of these fibers using the AFM tip. The implications of these data for the structure of chromatin undergoing the remodeling process are discussed.
Date: January 6, 2004
Creator: Jeans, Christopher; Colvin, M. E.; Thelen, Michael P. & Noy, A.
Object Type: Article
System: The UNT Digital Library
Static hybrid quarkonium potential with improved staggered quarks (open access)

Static hybrid quarkonium potential with improved staggered quarks

The authors are studying the effects of light dynamical quarks on the excitation energies of a flux tube between a static quark and antiquark. They report preliminary results of an analysis of the ground state potential and the {Sigma}{prime}{sub g}{sup +} and II{sub u} potentials. They have measured these potentials on closely matched ensembles of gauge configurations, generated in the quenched approximation and with 2+1 flavors of Asqtad improved staggered quarks.
Date: January 6, 2004
Creator: Bernard, C.
Object Type: Article
System: The UNT Digital Library
Surface Structure and Chemical Switching of Thioctic Acid Adsorbed on Au(111) as Observed Using Near-Edge X-ray Absorption Fine Structure (open access)

Surface Structure and Chemical Switching of Thioctic Acid Adsorbed on Au(111) as Observed Using Near-Edge X-ray Absorption Fine Structure

Thioctic acid (alpha-lipoic acid) is a molecule with a large disulfide-containing base, a short alkyl-chain with four CH{sub 2} units, and a carboxyl termination. Self-assembled monolayer (SAM) films of thioctic acid adsorbed on Au(111) have been investigated with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy and x-ray photoelectron spectroscopy (XPS) to determine film quality, bonding and morphology. Using standard preparation protocols for SAMs, that is, dissolving thioctic acid in ethanol and exposing gold to the solution, results in poor films. These films are highly disordered, contain a mixture of carboxyl and carboxylate terminations, have more than monolayer coverage, and exhibit unbound disulfide. Conversely, forming films by dissolving 1 mmol thioctic acid into 5% acetic acid in ethanol (as previously reported with carboxyl-terminated alkyl-thiols) forms ordered monolayers with small amounts of unbound sulfur. NEXAFS indicates tilted over endgroups with the carboxyl group normal on average 38{sup o} from the surface normal. Slight dichroism in other features indicates alkyl chains statistically more upright than prostrate on the surface. Reflection-absorption Fourier transform infrared (RA-FTIR) spectra indicate hydrogen bonding between neighboring molecules. In such well-formed monolayers, a stark reorientation occurs upon deprotonation of the endgroup by rinsing in a KOH solution. The carboxylate plane …
Date: January 6, 2004
Creator: Meulenberg, R W; van Buuren, T; Vance, A L; Terminello, L J; Willey, T M; Bostedt, C et al.
Object Type: Article
System: The UNT Digital Library
Topological susceptibility with the improved Asqtad action (open access)

Topological susceptibility with the improved Asqtad action

As a test of the chiral properties of the improved Asqtad (staggered fermion) action, we have been measuring the topological susceptibility as a function of quark masses for 2 + 1 dynamical flavors. We report preliminary results, which show reasonable agreement with leading order chiral perturbation theory for lattice spacing less than 0.1 fm. The total topological charge, however, shows strong persistence over Monte Carlo time.
Date: January 6, 2004
Creator: Bernard, C.
Object Type: Article
System: The UNT Digital Library
Coral Radiocarbon Records of Indian Ocean Water Mass Mixing and Wind-Induced Upwelling Along the Coast of Sumatra, Indonesia (open access)

Coral Radiocarbon Records of Indian Ocean Water Mass Mixing and Wind-Induced Upwelling Along the Coast of Sumatra, Indonesia

Radiocarbon ({sup 14}C) in the skeletal aragonite of annually banded corals track radiocarbon concentrations in dissolved inorganic carbon (DIC) in surface seawater. As a result of nuclear weapons testing in the 1950s, oceanic uptake of excess {sup 14}C in the atmosphere has increased the contrast between surface and deep ocean {sup 14}C concentrations. We present accelerator mass spectrometric (AMS) measurements of radiocarbon isotope ({Delta}{sup 14}C) in Porites corals from the Mentawai Islands, Sumatra (0 S, 98 E) and Watamu, Kenya (3 S, 39 E) to document the temporal and spatial evolution of the {sup 14}C gradient in the tropical Indian Ocean. The rise in {Delta}{sup 14}C in the Sumatra coral, in response to the maximum in nuclear weapons testing, is delayed by 2-3 years relative to the rise in coral {Delta}{sup 14}C from the coast of Kenya. Kenya coral {Delta}{sup 14}C values rise quickly because surface waters are in prolonged contact with the atmosphere. In contrast, wind-induced upwelling and rapid mixing along the coast of Sumatra entrains {sup 14}C-depleted water from the subsurface, which dilutes the effect of the uptake of bomb-laden {sup 14}C by the surface-ocean. Bimonthly AMS {Delta}{sup 14}C measurements on the Mentawai coral reveal mainly interannual variability …
Date: February 6, 2004
Creator: Guilderson, T. P.; Grumet, N. S.; Abram, N. J.; Beck, J. W.; Dunbar, R. B.; Gagan, M. K. et al.
Object Type: Article
System: The UNT Digital Library
Corrosion Behavior of Nickel Alloys in Wet Hydrofluoric Acid (open access)

Corrosion Behavior of Nickel Alloys in Wet Hydrofluoric Acid

Hydrofluoric acid is a water solution of hydrogen fluoride (HF). Hydrofluoric acid is used widely in diverse types of industrial applications; traditionally, it is used in pickling solutions in the metal industry, in the fabrication of chlorofluorocarbon compounds, as an alkylation agent for gasoline and as an etching agent in the industry of glass. In recent years, hydrofluoric acid has extensively been used in the manufacture of semiconductors and microelectronics during the wet chemical cleaning of silicon wafers. Hydrofluoric acid can be considered a reducing acid and although it is chemically classified as weaker than, for example, sulfuric or hydrochloric acids, it is extremely corrosive. This acid is also particularly toxic and poses greater health hazard than most other acids. The corrosion behavior of metals in hydrofluoric acid has not been as systematic studied in the laboratory as for other common inorganic acids. This is largely because tests using hydrofluoric acid cannot be run in standard equipment and because of the toxic nature of this acid. Moreover, short-term weight loss laboratory corrosion tests in hydrofluoric acid can be frustrating since the results are not as highly reproducible as in the case of other acids such as sulfuric or hydrochloric. One …
Date: February 6, 2004
Creator: Rebak, R. B.
Object Type: Book
System: The UNT Digital Library
Crystal level simulations using Eulerian finite element methods (open access)

Crystal level simulations using Eulerian finite element methods

Over the last several years, significant progress has been made in the use of crystal level material models in simulations of forming operations. However, in Lagrangian finite element approaches simulation capabilities are limited in many cases by mesh distortion associated with deformation heterogeneity. Contexts in which such large distortions arise include: bulk deformation to strains approaching or exceeding unity, especially in highly anisotropic or multiphase materials; shear band formation and intersection of shear bands; and indentation with sharp indenters. Investigators have in the past used Eulerian finite element methods with material response determined from crystal aggregates to study steady state forming processes. However, Eulerian and Arbitrary Lagrangian-Eulerian (ALE) finite element methods have not been widely utilized for simulation of transient deformation processes at the crystal level. The advection schemes used in Eulerian and ALE codes control mesh distortion and allow for simulation of much larger total deformations. We will discuss material state representation issues related to advection and will present results from ALE simulations.
Date: February 6, 2004
Creator: Becker, R; Barton, N R & Benson, D J
Object Type: Article
System: The UNT Digital Library
Environmentally Assisted Cracking of Nickel Alloys (open access)

Environmentally Assisted Cracking of Nickel Alloys

Environmentally Assisted Cracking (EAC) is a general term that includes phenomena such as stress corrosion cracking (SCC), hydrogen embrittlement (HE), sulfide stress cracking (SSC), liquid metal embrittlement (LME), etc. EAC refers to a phenomenon by which a normally ductile metal looses its toughness (e.g. elongation to rupture) when it is subjected to mechanical stresses in presence of a specific corroding environment. For EAC to occur, three affecting factors must be present simultaneously. These include: (1) Mechanical tensile stresses, (2) A susceptible metal microstructure and (3) A specific aggressive environment. If any of these three factors is removed, EAC will not occur. That is, to mitigate the occurrence of EAC, engineers may for example eliminate residual stresses in a component or limit its application to certain chemicals (environment). The term environment not only includes chemical composition of the solution in contact with the component but also other variables such as temperature and applied potential. Nickel alloys are in general more resistant than stainless steels to EAC. For example, austenitic stainless steels (such as S30400) suffer SCC in presence of hot aqueous solutions containing chloride ions. Since chloride ions are ubiquitous in most industrial applications, the use of stressed stainless steels parts …
Date: February 6, 2004
Creator: Rebak, R. B.
Object Type: Book
System: The UNT Digital Library
FACTORS INFLUENCING THE FLOW AND FRACTURE OF SUPERPLASTIC CERAMICS: FINAL TECHNICAL REPORT (open access)

FACTORS INFLUENCING THE FLOW AND FRACTURE OF SUPERPLASTIC CERAMICS: FINAL TECHNICAL REPORT

This is the Final Technical Report describing the achievements on this DOE program. This research program was initiated with the objective of obtaining a better understanding of the flow, and especially the superplastic flow, of representative ceramics. Detailed experiments were undertaken on the yttria-stabilized tetragonal zirconia (Y-TZP) and on various composite materials containing Y-TZP and Al{sub 2}O{sub 3}. In addition, a comprehensive theoretical interpretation was developed which showed, for the first time, that the superplasticity of ceramic materials has very significant differences from the conventional superplastic flow in metals.
Date: February 6, 2004
Creator: Langdon, Terence G.
Object Type: Report
System: The UNT Digital Library