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Pre-conceptual Design of a Rapid Cycling Medical Synchrotron
N/A
Date:
October 1, 1999
Creator:
A., Favale; Myers, T.; Rathke, J.; Sredniawski, J.; Todd, A.; Barton, D. et al.
Object Type:
Report
System:
The UNT Digital Library
Can Data Recognize Its Parent Distribution?
This study is concerned with model selection of lifetime and survival distributions arising in engineering reliability or in the medical sciences. We compare various distributions, including the gamma, Weibull and lognormal, with a new distribution called geometric extreme exponential. Except for the lognormal distribution, the other three distributions all have the exponential distribution as special cases. A Monte Carlo simulation was performed to determine sample sizes for which survival distributions can distinguish data generated by their own families. Two methods for decision are by maximum likelihood and by Kolmogorov distance. Neither method is uniformly best. The probability of correct selection with more than one alternative shows some surprising results when the choices are close to the exponential distribution.
Date:
May 1, 1999
Creator:
A.W.Marshall; J.C.Meza & Olkin, and I.
Object Type:
Report
System:
The UNT Digital Library
Periodic Boundary Conditions in the ALEGRA Finite Element Code
This document describes the implementation of periodic boundary conditions in the ALEGRA finite element code. ALEGRA is an arbitrary Lagrangian-Eulerian multi-physics code with both explicit and implicit numerical algorithms. The periodic boundary implementation requires a consistent set of boundary input sets which are used to describe virtual periodic regions. The implementation is noninvasive to the majority of the ALEGRA coding and is based on the distributed memory parallel framework in ALEGRA. The technique involves extending the ghost element concept for interprocessor boundary communications in ALEGRA to additionally support on- and off-processor periodic boundary communications. The user interface, algorithmic details and sample computations are given.
Date:
November 1, 1999
Creator:
AIDUN,JOHN B.; ROBINSON,ALLEN C. & WEATHERBY,JOE R.
Object Type:
Report
System:
The UNT Digital Library
Representative volume size: A comparison of statistical continuum mechanics and statistical physics
In this combination background and position paper, the authors argue that careful work is needed to develop accurate methods for relating the results of fine-scale numerical simulations of material processes to meaningful values of macroscopic properties for use in constitutive models suitable for finite element solid mechanics simulations. To provide a definite context for this discussion, the problem is couched in terms of the lack of general objective criteria for identifying the size of the representative volume (RV) of a material. The objective of this report is to lay out at least the beginnings of an approach for applying results and methods from statistical physics to develop concepts and tools necessary for determining the RV size, as well as alternatives to RV volume-averaging for situations in which the RV is unmanageably large. The background necessary to understand the pertinent issues and statistical physics concepts is presented.
Date:
May 1, 1999
Creator:
AIDUN,JOHN B.; TRUCANO,TIMOTHY G.; LO,CHI S. & FYE,RICHARD M.
Object Type:
Report
System:
The UNT Digital Library
Analysis of Tracer Tests with Multirate Diffusion Models: Recent Results and Future Directions within the WIPP Project
A series of single-well injection-withdrawal (SWIW) and two-well convergent-flow (TWCF) tracer tests were conducted in the Culebra dolomite at the WIPP site in late 1995 and early 1996. Modeling analyses over the past year have focused on reproducing the observed mass-recovery curves and understanding the basic physical processes controlling tracer transport in SWIW and TWCF tests. To date, specific modeling efforts have focused on five SWIW tests and one TWCF pathway at each of two different locations (H-11 and H-19 hydropads). An inverse parameter-estimation procedure was implemented to model the SWIW and TWCF tests with both traditional and multirate double-porosity formulations. The traditional model assumes a single diffusion rate while the multirate model uses a first-order approximation to model a continuous distribution of diffusion coefficients. Conceptually, the multirate model represents variable matrix block sizes within the Culebra as observed in geologic investigations and also variability in diffusion rates within the matrix blocks as observed with X-ray imaging in the laboratory. Single-rate double-porosity models cannot provide an adequate match to the SWIW data. Multirate double-porosity models provide excellent fits to all five SWIW mass-recovery curves. Models of the TWCF tests show that, at one location, the tracer test can be modeled …
Date:
October 1, 1999
Creator:
ALTMAN, SUSAN J.; HAGGERTY, ROY; MCKENNA, SEAN A. & MEIGS, LUCY C.
Object Type:
Article
System:
The UNT Digital Library
A Numerical Feasibility Study of Three-Component Induction Logging for Three Dimensional Imaging About a Single Borehole
A theoretical analysis has been completed for a proposed induction logging tool designed to yield data which are used to generate three dimensional images of the region surrounding a well bore. The proposed tool consists of three mutually orthogonal magnetic dipole sources and multiple 3 component magnetic field receivers offset at different distances from the source. The initial study employs sensitivity functions which are derived by applying the Born Approximation to the integral equation that governs the magnetic fields generated by a magnetic dipole source located within an inhomogeneous medium. The analysis has shown that the standard coaxial configuration, where the magnetic moments of both the source and the receiver are aligned with the axis of the well bore, offers the greatest depth of sensitivity away from the borehole compared to any other source-receiver combination. In addition this configuration offers the best signal-to-noise characteristics. Due to the cylindrically symmetric nature of the tool sensitivity about the borehole, the data generated by this configuration can only be interpreted in terms of a two-dimensional cylindrical model. For a fill 3D interpretation the two radial components of the magnetic field that are orthogonal to each other must be measured. Coil configurations where both …
Date:
August 1, 1999
Creator:
ALUMBAUGH, DAVID L. & WILT, MICHAEL J.
Object Type:
Report
System:
The UNT Digital Library
Salinas - User's Notes
Salinas provides a massively parallel implementation of structural dynamics finite element analysis, required for high fidelity, validated models used in modal, vibration, static and shock analysis of weapons systems. This document provides a users guide to the input for Salinas. Details of input specifications for the different solution types, output options, element types and parameters are included. The appendices contain detailed examples, and instructions for running the software on parallel platforms.
Date:
November 1, 1999
Creator:
ALVIN,KENNETH F.; BHARDWAJ,MANOJ K.; DRIESSEN,BRIAN; REESE,GARTH M. & SEGALMAN,DANIEL J.
Object Type:
Report
System:
The UNT Digital Library
DESIGN AND ANALYSIS OF THE SNS CCL HOT MODEL WATER COOLING SYSTEM USING THE SINDA/FLUINT NETWORK MODELING TOOL
This report presents results for design and analysis of the hot model water cooling system for the Spallation Neutron Source (SNS) coupled-cavity linac (CCL). The hot model, when completed, will include segments for both the CCL and coupled-cavity drift-tube linac (CCDTL). The scope of this report encompasses the modeling effort for the CCL portion of the hot model. This modeling effort employed the SINDA/FLUINT network modeling tool. This report begins with an introduction of the SNS hot model and network modeling using SINDA/FLUINT. Next, the development and operation of the SINDA/FLUINT model are discussed. Finally, the results of the SINDA/FLUINT modeling effort are presented and discussed.
Date:
November 1, 1999
Creator:
AMMERMAN, C. & BERNARDIN, J.
Object Type:
Report
System:
The UNT Digital Library
Corrosion of Uranium in Desert Soil, with Application to GCD Source Term M
Uranium fragments from the Sandia Sled Track were studied as analogues for weapons components and depleted uranium buried at the Greater Confinement Disposal (GCD) site in Nevada. The Sled Track uranium fragments originated as weapons mockups and counterweights impacted on concrete and soil barriers, and experienced heating and fragmentation similar to processes thought to affect the Nuclear Weapons Accident Residues (NWAR) at GCD. Furthermore, the Sandia uranium was buried in unsaturated desert soils for 10 to 40 years, and has undergone weathering processes expected to affect the GCD wastes. Scanning electron microscopy, X-ray diffraction and microprobe analyses of the fragments show rapid alteration from metals to dominantly VI-valent oxy-hydroxides. Leaching studies of the samples give results consistent with published U-oxide dissolution rates, and suggest longer experimental periods (ca. 1 year) would be required to reach equilibrium solution concentrations. Thermochemical modeling with the EQ3/6 code indicates that the uranium concentrations in solutions saturated with becquerelite could increase as the pore waters evaporate, due to changes in carbonate equilibria and increased ionic strength.
Date:
September 1, 1999
Creator:
ANDERSON, HOWARD L.; BACA, JULIANNE; KRUMHANSL, JAMES L.; STOCKMAN, HARLAN W. & THOMPSON, MOLLIE E.
Object Type:
Report
System:
The UNT Digital Library
STATUS OF THE ACCELERATOR PRODUCTION OF TRITIUM (APT) PROJECT
None
Date:
November 1, 1999
Creator:
ANDERSON, J. L.; LISOWSKI, P. W. & AL, ET
Object Type:
Article
System:
The UNT Digital Library
DEVELOPMENT OF REMOTE MONITORING SYSTEM FOR THE UNATTENDED MODE NDA IN PFPF
None
Date:
November 1, 1999
Creator:
ASAKURA, K.; OHTANI, T. & AL, ET
Object Type:
Article
System:
The UNT Digital Library
Search for Squarks and Gluinos in Events Containing Jets and a Large Imbalance in Transverse Energy
Using data corresponding to an integrated luminosity of 79 pb{sup -1}, D0 has searched for events containing multiple jets and large missing transverse energy in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron collider. Observing no significant excess beyond what is expected from the standard model, they set limits on the masses of squarks and gluinos and on the model parameters m{sub 0} and m{sub 1/2}, in the framework of the minimal low-energy supergravity models of supersymmetry. For tan {beta} = 2 and A{sub 0} = 0, with {mu} < 0, they exclude all models with m{sub q} {approx} < 250 GeV/c{sup 2}. For models with equal squark and gluino masses, they exclude m < 260 GeV/c{sup 2}.
Date:
February 1, 1999
Creator:
Abbott, B.; Abolins, M.; Abramov, V.; Acharya, B. S.; Adam, I.; Adams, D. L. et al.
Object Type:
Article
System:
The UNT Digital Library
CODA performance in the real world
The most ambitious implementation of the Jefferson Lab data acquisition system (CODA) to date is for the CLAS spectrometer in Experimental Hall B. CLAS has over 40,000 instrumented channels and uses up to 30 front-end (FASTBUS/VME) crates in the DAQ subsystem. During the initial experiments the authors found that performance of the fully instrumented DAQ system did not scale as expected based on single point to point benchmarks. Over the past year the authors have been able to study various performance bottlenecks in the CLAS DAQ system including front-end real time performance, switched 100BaseT Ethernet data transport, and online data distribution and recording. Performance tuning was necessary for components on both real time (VxWorks) and UNIX (Solaris) operating systems. In addition, a new efficient Event Transfer System (ET) was developed to provide faster online monitoring while having minimal impact on data throughput to storage. They discuss these issues and efforts to overcome the real world problems associated with running a high performance DAQ system on a variety of commercial hardware and software.
Date:
June 1, 1999
Creator:
Abbott, D.J.; Heyes, W.G.; Jastrzembski, E.; MacLeod, R.W.; Timmer, C. & Wolin, E.
Object Type:
Article
System:
The UNT Digital Library
Roles and Delegation of Authority (R/DA) System
The processes of defining managerial roles and providing for delegation of authority are essential to any enterprise. At most large organizations, these processes are defined in policy manuals and through sets of standard operating procedures for many, if not all, business and administrative functions. Many of these staff-initiated, administrative functions require the routing of documents for approval to one or more levels of management. These employee-oriented, back office types of workflows tend to require more flexibility in determining to whom these documents should go to, while, at the same time, providing the responsible parties with the flexibility to delegate their approval authority or allow others to review their work. Although this practice is commonplace in manual, paper-based processes that exist in many organizations, it is difficult to provide the same flexibility in the more structured, electronic-based, workflow systems. The purpose of this report is to present a framework or architecture for creating a R/DA system and provide some insights associated with its design and utilization. To improve understanding and clarify subsequent discussion, the goals and requirements for the major R/DA system components, namely, the database and interface modules, are initially presented along with the identification of important concepts and the …
Date:
November 1, 1999
Creator:
Abbott, John P.; Hutchins, James C. & Schoch, David G.
Object Type:
Report
System:
The UNT Digital Library
Screening Level Risk Assessment for the New Waste Calcining Facility
This screening level risk assessment evaluates potential adverse human health and ecological impacts resulting from continued operations of the calciner at the New Waste Calcining Facility (NWCF) at the Idaho Nuclear Technology and Engineering Center (INTEC), Idaho National Engineering and Environmental Laboratory (INEEL). The assessment was conducted in accordance with the Environmental Protection Agency (EPA) report, Guidance for Performing Screening Level Risk Analyses at Combustion Facilities Burning Hazardous Waste. This screening guidance is intended to give a conservative estimate of the potential risks to determine whether a more refined assessment is warranted. The NWCF uses a fluidized-bed combustor to solidify (calcine) liquid radioactive mixed waste from the INTEC Tank Farm facility. Calciner off volatilized metal species, trace organic compounds, and low-levels of radionuclides. Conservative stack emission rates were calculated based on maximum waste solution feed samples, conservative assumptions for off gas partitioning of metals and organics, stack gas sampling for mercury, and conservative measurements of contaminant removal (decontamination factors) in the off gas treatment system. Stack emissions were modeled using the ISC3 air dispersion model to predict maximum particulate and vapor air concentrations and ground deposition rates. Results demonstrate that NWCF emissions calculated from best-available process knowledge would result in …
Date:
May 1, 1999
Creator:
Abbott, M. L.; Keck, K. N.; Schindler, R. E.; VanHorn, R. L.; Hampton, N. L. & Heiser, M. B.
Object Type:
Report
System:
The UNT Digital Library
Air Dispersion Modeling of Mine Waste in the Southeast Missouri Old Lead Belt
Past lead ore processing conducted in the Southeast Missouri Old Lead Belt since the 1700s has left numerous large areas of lead contamination in elevated piles of fine gravel waste called “chat” and dried-out tailings ponds. Wind suspension and atmospheric dispersion are known to transport these materials to the surrounding communities where the lead could pose a human health threat through inhalation or ingestion of the deposited contamination. The purpose of this study was to estimate potential wind suspension rates, perform dispersion modeling of the tailings and chat sources, and determine ground surface deposition rates and potential soil concentrations of lead in the surrounding areas. The results can be used to prioritize soil sampling locations, site air monitors, help identify the source of soil lead contamination, and to help develop remediation plans. Numerous, large complex sources in the region were parameterized into 33 area sources with the aid of digital aerial photos, digitized typographic maps, Geographic Information Systems (GIS) software, and site inspections. An AP-42 particulate emission model was used to estimate lower- and upper-bound hourly emission rates using six years of hourly wind speed data obtained from the St. Louis Airport. The emissions model accounted for wind speed, precipitation, …
Date:
October 1, 1999
Creator:
Abbott, Michael Lehman
Object Type:
Report
System:
The UNT Digital Library
AmBe Waste Minimization Activities Annual Report
The CST-11 objective for the Radioactive Source Recovery Project is to evaluate a nitric acid-based flowsheet and alternatives for dissolution, separation, and recovery of americium from AmBe neutron source materials returned from private and governmental institutions. Specific tasks performed during FY97 and FY98 included the experimental investigation of material dissolution rate and efficiency as a function of time and temperature for nitric acid as compared to hydrochloric acid. Alkaline dissolution reaction conditions using sodium hydroxide and ammonium bifluoride were also investigated. In both the acidic and alkaline dissolution conditions, the objective was to effect an initial separation of the americium from the beryllium or vice versa. The process solution and remaining solids should also be amenable to further processing and purification schemes. This work was performed on actual AmBe neutron source material in order to demonstrate the feasibility of {sup 241}Am purification from dismantled neutron sources.
Date:
May 1, 1999
Creator:
Abney, Kent D.; Svitra, Zita V. & Cisneros, Michael R.
Object Type:
Report
System:
The UNT Digital Library
Stable isotope investigations of chlorinated aliphatic hydrocarbons.
Stable isotope ratio measurements for carbon (C) and chlorine (Cl) can be used to elucidate the processes affecting transformation and transportation of chlorinated aliphatic hydrocarbons (CAHs) in the environment. Methods recently developed in our laboratory for isotopic analysis of CAHs have been applied to laboratory measurements of the kinetic isotope effects associated with aerobic degradation of dichloromethane (DCM) and with both anaerobic and aerobic cometabolic degradation of trichlomethene (TCE) in batch and column microbial cultures. These experimental determinations of fractionation factors are crucial for understanding the behavior of CAHs in complex natural systems, where the extent of biotransformation can be masked by dispersion and volatilization. We have also performed laboratory investigations of kinetic isotope effects accompanying evaporation of CAHs, as well as field investigations of natural attenuation and in situ remediation of CAHs in a number of contaminated shallow aquifers at sites operated by the federal government and the private sector.
Date:
June 1, 1999
Creator:
Abrajano, T.; Heraty, L. J.; Holt, B. D.; Huang, L. & Sturchio, N. C.
Object Type:
Article
System:
The UNT Digital Library
Field emission from carbon films deposited by VHF CVD on difference substrates
As previously demonstrated, non-diamond carbon (NDC) films deposited at low temperatures 200-300 C on silicon tips reduced the threshold of field emission. In this paper we will present the results of the study of field emission from flat NDC films prepared by VHF CVD. Emission measurements were performed in a diode configuration at approximately 10{sup {minus}10} Torr. NDC films were deposited on ceramic and on c-Si substrates sputter coated with layers of Ti, Cu, Ni and Pt. The back contact material influences the emission characteristics but not as a direct correlation to work function. A model of field emission from metal-NDC film structures will be discussed.
Date:
April 1, 1999
Creator:
Abramov, A A; Andronov, A N; Felter, T E; Ioffe, A F; Kosarev, A I; Shotov, M V et al.
Object Type:
Article
System:
The UNT Digital Library
The Migration and Entrapment of DNAPLs in Physically and Chemically Heterogeneous Porous Media
Dense nonaqueous phase liquids (DNAPLs) are common subsurface contaminants at many Department of Energy (DOE) hazardous waste sites. The migration and entrapment of DNAPLs at these sites is greatly influenced by subsurface heterogeneity, both physical and chemical. Unfortunately, the physics of DNAPL flow in chemically heterogeneous systems is poorly understood and, hence, multiphase flow simulators typically assume that subsurface soils are completely water-wet (chemically homogeneous). The primary objective of this research is to improve our understanding of and ability to simulate the influence of subsurface chemical heterogeneities on DNAPL flow and entrapment in the saturated zone. Laboratory and numerical investigations are being conducted for a matrix of organic contaminants and porous media encompassing a range of wettability characteristics. Specific project objectives include: (1) quantification of system wettability and interfacial tensions; (2) determination of hydraulic property relations; (3) investigation of DNAPL infiltration behavior in two-dimensional systems; (4) modification of a continuum based multiphase flow simulator to account for coupled physical and chemical heterogeneity; and (5) exploration of the migration of DNAPLs and the development of innovative remediation schemes under heterogeneous conditions using this model.
Date:
June 1, 1999
Creator:
Abriola, Linda M.; Demond, Avery H. & Glass, Robert
Object Type:
Report
System:
The UNT Digital Library
Changes in Gas Bubble Disease Signs for Migrating Juvenile Salmonids Experimentally Exposed to Supersaturated Gasses, 1996-1997 Progress Report.
This study was designed to answer the question of whether gas bubble disease (GBD) signs change as a result of the hydrostatic conditions juvenile salmonids encounter when they enter the turbine intake of hydroelectric projects during their downstream migration.
Date:
March 1, 1999
Creator:
Absolon, Randall F.
Object Type:
Report
System:
The UNT Digital Library
Analysis of heat transfer during quenching of a gear blank
This paper presents experimental and numerical results for the quench of a gear blank in agitated and stagnant oil. Heat transfer within the gear blank is analyzed with a whole domain-optimizer technique inverse solution method, to calculate the time history at every point in the gear blank. The development of this procedure represents the first stage in an overall analysis of the quench process that will later include material phase transformations and deformation. The paper presents ten variations in setting up the inverse problem, to analyze which combination of independent variables and decision variables results in the best match between experimental and numerical results. The results indicate that dividing the boundary of the gear blank into four zones and assigning a fixed heat transfer coefficient or heat flux to each zone yields an average RMS error (average difference between experimental and numerical results) of the order of 40 K. This error can be reduced by either increasing the number of zones, by reducing the number of thermocouples being matched, or by allowing the heat transfer or heat flux to vary within the zones. Of these possibilities, variation of heat transfer within the zones gives the best improvement in the quality …
Date:
March 1, 1999
Creator:
Aceves, S M & Sahai, V
Object Type:
Article
System:
The UNT Digital Library
Evaluation of insulated pressure vessels for cryogenic hydrogen storage
This paper presents an analytical and experimental evaluation of the applicability of insulated pressure vessels for hydrogen-fueled light-duty vehicles. Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen (LH?) or ambient-temperature compressed hydrogen (CH2). Insulated pressure vessels offer the advantages of liquid hydrogen tanks (low weight and volume), with reduced disadvantages (lower energy requirement for hydrogen liquefaction and reduced evaporative losses). The purpose of this work is to verify that commercially available aluminum-lined, fiber- wrapped vessels can be used for cryogenic hydrogen storage. The paper reports on previous and ongoing tests and analyses that have the purpose of improving the system design and assure its safety.
Date:
March 1, 1999
Creator:
Aceves, S M; Garcia-Villazana, O & Martinez-Frias, J
Object Type:
Article
System:
The UNT Digital Library
An Accuracy Evaluation for the Madejski Splat-Quench Solidification Model
Development of methods to spray form materials by precisely controlled deposition of droplets can result in new manufacturing processes which offer improved metallurgical performance and reduced production costs. These processes require a more detailed knowledge of the fluid mechanics, heat transfer and solidification that occur during droplet spreading. Previous work using computer simulations of this process have been difficult to implement and have required long running times. This paper examines the use of an alternative, simplified, method developed by Madjeski for solving for the problem of droplet spreading and solidification. These simplifications reduce the overall splat spreading and solidification problem to a closed-form differential equation. This differential equation is then solved under various conditions as reported from recent publications of experimental and numerical results of drop analysis. The results from the model are compared in terms of maximum spl at diameter, minimum splat thickness, and time for the droplet spreading to reach 95% of the maximum diameter. The results indicate that the accuracy of the model can be improved by accounting for energy losses in the initial rate of droplet spreading. The model results show that the predictions of experimental results are improved to within 30% over a wide range …
Date:
March 1, 1999
Creator:
Aceves, S. M.; Sahai, V. & Shapiro, A. B.
Object Type:
Article
System:
The UNT Digital Library