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Mesh considerations for finite element structural dynamic applications

Description: Three factors relating to a finite element mesh and discretization scheme are discussed: the geometric accuracy of the node locations, the amount of warp of a quadrilateral shell element, and the directional biasing effect of similarly oriented triangular elements. These factors can have a significant effect on the accuracy of a finite element structural dynamic analysis. Two finite element models that illustrate these effects are described.
Date: November 1, 1990
Creator: Stevens, R.R.
Partner: UNT Libraries Government Documents Department

The use of the case study method in radiation worker continuing training

Description: Typical methods of continuing training are often viewed by employees as boring, redundant and unnecessary. It is hoped that the operating experience lesson in the required course, Radiation Worker Requalification, will be well received by employees because actual RFP events will be presented as case studies. The interactive learning atmosphere created by the case study method stimulates discussion, develops analytical abilities, and motivates employees to use lessons learned in the workplace. This problem solving approach to continuing training incorporates cause and effect analysis, a technique which is also used at RFP to investigate events. A method of designing the operating experience lesson in the Radiation Worker Requalification course is described in this paper. 7 refs., 2 figs.
Date: January 1, 1990
Creator: Stevens, R.D.
Partner: UNT Libraries Government Documents Department

Verification of the W76-1 hostile environments model

Description: Demonstrating mesh convergence for a finite element analysis requires multiple meshes, but creating high quality meshes is a time-consuming task. Furthermore, estimates of the amount of error caused by mesh refinement are difficult to make for a sequence of unrelated, unstructured finite element meshes. A solution for both of these problems is to automatically generate a refined mesh by subdividing every element in the original mesh. The resulting refined mesh has a uniform 'mesh refinement ratio' (relative to the original mesh), so established mesh convergence error estimators, such as Roache's Grid Convergence Indicator (GCI), can be applied. This presentation will cover the process of automatically generating a refined mesh, and discuss the Grid Convergence Indicator (GCI) error metric. The GCI will be applied to two models subjected to transient loadings: a simple test problem and a high-fidelity model of an unclassified W76 component. The mesh convergence exhibited by the analysis code DYNA3D will be discussed.
Date: January 1, 2002
Creator: Stevens, R. Robert
Partner: UNT Libraries Government Documents Department

Studies on the Alkalinity of Some Silicate Minerals

Description: Abstract: By grinding minerals under water it has been found that they yield relative and reproducible measurements of the hydrogenion concentration resulting from their hydrolysis. Many silicate minerals and two glasses have been studied in this way by a colorimetric method of determining hydrogen-ion concentration, and some of them have been studied more quantitatively by means of the hydrogen electrode. The results of these tests are a rough index of the weathering qualities of different silicate minerals. The effect of silicate minerals on underground waters and upon geochemical changes is discussed.
Date: 1934
Creator: Stevens, R. E.
Partner: UNT Libraries Government Documents Department

Development of a force specification for a force-limited random vibration test

Description: Vibration testing, techniques have been developed and employed that reduce the overtesting caused by the essentially infinite mechanical impedance of the shaker in conventional vibration tests. With these ``force-limiting`` techniques, two vibration test specifications are used: the conventional acceleration specification, and an interface force specification. The vibration level of the shake table is controlled such that neither the table acceleration nor the force transmitted to the test item exceeds its specification, hence the name ``dual control`` vibration test. The effect of limiting the shake table vibration to the force specification is to reduce (``notch``) the shaker acceleration near some of the test item`s resonance frequencies. Several methods of deriving the force specification have been described in the literature. A new method is proposed in this paper that is based on a modal method of coupling two dynamic systems, in this case the ``source`` or launch vehicle, and the ``load`` or payload. The only information that is required is an experimentally-measurable frequency-response function (FRF) called the dynamic mass for both the source and the load. The method, referred to as the coupled system, modal approach (CSMA) method, is summarized and compared to an existing method of determining the force specification for force-limited vibration testing.
Date: February 1, 1996
Creator: Stevens, R.R.
Partner: UNT Libraries Government Documents Department

Development of a multicusp H/sup -/ ion source for accelerator applications

Description: The development of a multicusp surface-production H/sup -/ ion source (Berkeley concept) designed specifically for accelerator use is described. The goal of this development effort has been to provide a suitable H/sup -/ ion source for the Proton Storage Ring now being constructed at LAMPF. The ion source that has been developed is now capable of long-term operation at 20 mA of H/sup -/ current at 10% duty factor and with normalized beam emittance of 0.13 cm-mrad (95% beam fraction). The development program will be described with particular emphasis on beam emittance measurements.
Date: January 1, 1983
Creator: York, R.L. & Stevens, R.R. Jr.
Partner: UNT Libraries Government Documents Department

Preliminary Report on Methods of Analysis for very Small Percentages of Uranium

Description: Abstract: Procedures are presented in detail of two methods for the determination of very small percentages or uranium (down to 0.0025). The methods are applicable to a wide variety of materials. Notes on the methods and confirmatory experiments are also given.
Date: August 8, 1983
Creator: Foster, H. D.; Grimaldi, F. S. & Stevens, R. M.
Partner: UNT Libraries Government Documents Department

Containment vessel dynamic analysis. Part 1: Base configuration

Description: This report describes the approach and methods used in the analysis of a containment vessel that is being designed for use at the Dual-Axis Radiographic Hydrodynamic Test Facility (DARHT). The vessel will be subjected to transient pressure loads during explosive tests conducted at the facility and is required to contain all of the products of these tests. Computational simulations of the structural response of the vessel have been made using a combination of two numerical techniques: the transient pressure histories acting on the inner surfaces of the vessel were computed using an Eulerian hydrodynamics code, and the vessel`s structural response to these pressures was analyzed using an explicit finite element code. The methods and approximations involved in combining these two numerical analysis tools will be discussed, and the stresses produced in the vessel and important measures of the dynamic response will be presented.
Date: February 1, 1997
Creator: Stevens, R.R. & Benner, J.
Partner: UNT Libraries Government Documents Department

Force-limited vibration tests aplied to the FORTE` satellite

Description: A force limited random vibration test was conducted on a small satellite called FORTE{prime}. This type of vibration test reduces the over testing that can occur in a conventional vibration test. Two vibration specifications were used in the test: The conventional base acceleration specification, and an interface force specification. The vibration level of the shaker was controlled such that neither the table acceleration nor the force transmitted to the test item exceeded its specification. The effect of limiting the shake table vibration to the force specification was to reduce (or ``notch``) the shaker acceleration near some of the satellite`s resonance frequencies. This paper describes the force limited test conducted for the FORTE{prime} satellite. The satellite and its dynamic properties are discussed, and the concepts of force limiting theory are summarized. The hardware and setup of the test are then described, and the results of the force limited vibration test are discussed.
Date: February 1, 1996
Creator: Stevens, R.R. & Butler, T.A.
Partner: UNT Libraries Government Documents Department

Implementation of a distributed multiterabyte storage system

Description: The University of Chicago and Argonne National Laboratory are building a highly distributed storage system to meet the needs of a cross-disciplinary group of scientists and to investigate the issues involved in implementing such a system. The storage system is based on IBM 3590/3494 tape technology managed by ADSM software. High-speed wide-area networking is required to support the distributed user community. NFS, DFS, FTP, and other user access methods are supported. A simulation project undertaken to guide system development has provided useful insights even in the calibration and design phases.
Date: November 24, 1999
Creator: Hereld, M.; Nickless, B. & Stevens, R.
Partner: UNT Libraries Government Documents Department

Neutron diffraction analysis of HRh(P(C/sub 6/H/sub 5/)/sub 3/)/sub 4/

Description: We have collected neutron diffraction data on a large single crystal of the title compound. The most surprising result is an extremely short Rh-H distance of 1.31(8) A, presumably caused by steric interactions involving the bulky triphenyl phosphine ligands. Crystallographic details: HRh(P(C/sub 6/H/sub 5/)/sub 3/)/sub 4/ . /sup 1///sub 2/C/sub 6/H/sub 6/ crystallizes in the space group Pa3, with a = b = c = 22.776(3) A, Z = 8. Data were collected at the Brookhaven High Flux Beam reactor at a temperature of -23/sup 0/C, lambda = 1.15882(7) A/sup -1/. Least-squares refinement (in which the phenyl rings were treated as rigid groups) resulted in an R factor (based on data with f > 4sigma(F)) of 0.12 for 914 reflections and 95 parameters. 10 refs.
Date: January 1, 1987
Creator: Bau, R.; Stevens, R.C.; McLean, M. & Koetzle, T.F.
Partner: UNT Libraries Government Documents Department

High-current negative-ion beam transport

Description: The requirements for transporting high-current, negative-ion beams are presented with particular emphasis on applications involving negative-hydrogen-ion beams. In addition to the usual matching and steering problems, particular attention must be paid to beam emittance growth in the transport system. Depending on the application, a number of approaches have been developed using both magnetic and electric lenses. I discuss the design considerations for transporting and matching these beams to radiofrequency quadrupole accelerators, and present a survey of the various types of beamlines now used for negative-ion beams.
Date: January 1, 1993
Creator: Stevens, R.R. Jr.
Partner: UNT Libraries Government Documents Department

High-current negative-ion beam transport

Description: The requirements for transporting high-current, negative-ion beams are presented with particular emphasis on applications involving negative-hydrogen-ion beams. In addition to the usual matching and steering problems, particular attention must be paid to beam emittance growth in the transport system. Depending on the application, a number of approaches have been developed using both magnetic and electric lenses. I discuss the design considerations for transporting and matching these beams to radiofrequency quadrupole accelerators, and present a survey of the various types of beamlines now used for negative-ion beams.
Date: April 1, 1993
Creator: Stevens, R. R. Jr.
Partner: UNT Libraries Government Documents Department

Direct Determination of the Phase Distributions of Semi-VolatilePolycyclic Aromatic Hydrocarbons Using Annular Denuders

Description: An annular denuder-based sampler, here called the integrated organic vapor/particle sampler (IOVPS), has been developed for direct determination of both gas and particulate semi-volatile organic species. The IOVPS uses a cyclone inlet for removal of particles greater than 2.5 micrometers from the airstream, followed by two or three sandblasted glass annular denuders coated with ground particles of an adsorbent resin. The denuders trap the gas phase species of interest before the airstream passes through a filter and a backup denuder. Extracts of the denuders and filters are analyzed for the semi-volatile species of interest. The IOVPS has been tested and validated for sampling semi-volatile polycyclic aromatic hydrocarbons (PAH) in indoor laboratory room air and environmental tobacco smoke (ETS). Ground XAD-4 was the adsorbent for these initial studies. Gas- and particulate-phase concentrations of semi-volatile PAH are presented for these two environments. The new sampler provides the means for directly determining phase distributions of PAH and other classes of semi-volatile organic species, rather than by difference or by techniques that are subject to large positive and negative artifacts. For example, the results obtained with the IOVPS indicate that the volatilization artifact ('blow-off') from particulate PAH collected in indoor laboratory room air with a conventional filter-sorbent bed sampler at face velocity of 33 cm sec-1 led to three-fold underestimation of the particulate fractions of phenanthrene, pyrene and chrysene. Phase distributions for PAH in ETS are also reported here.
Date: June 1, 1994
Creator: Gundel, L.A.; Lee, V.C.; Mahanama, K.R.R.; Stevens, R.K. & Daisey,J.M.
Partner: UNT Libraries Government Documents Department

Polycyclic Aromatic Hydrocarbons in Indoor Air and EnvironmentalTobacco Smoke Measured with a New Integrated Organic Vapor-ParticleSampler

Description: Sampling details. The novel aspect of the sampling equipment is the use of ground XAD-4 resin as a coating for annular denuders. Figure 1 shows a schematic diagram of one sampling configuration used for field testing the IOVPS in indoor air and ETS. Commercially available, single-channel glass denuders, 22 cm long, with a 1 mm annulus (University Research Glass, Carrboro, NC, USA were used with a Teflon- ) lined aluminum cyclone (cutoff 2.5 microns at 10 L mine ) preceding the first denuder. Three XAD-4-coated denuders were connected in series between the cyclone and a Teflon filter pack which contained a pre-extracted and pre-weighed Teflon-coated glass-fiber filter. (The three-denuder configuration was used for determining breakthrough of naphthalene and its methyl derivatives as a function of flow rate.) In some experiments, a coated denuder followed the filter pack. The parallel sorbent bed sampler used an aluminum open-face filter holder with a Teflon-coated glass-fiber filter, followed by a glass tube packed with 2.5 g cleaned XAD-4 resin. Flow rates, measured with a dry gas test meter, were 5, 10 and 20 L min-1 for field testing; sampling times varied from 3 to 22 hours. Indoor air with no combustion sources was sampled in an unoccupied room. Diluted sidestream smoke was sampled as a surrogate for ETS in an unventilated 20 m3 chamber at 5 L rnin-l for hour-long periods while a single-port smoking machine smoked 3 cigarettes. Ambient temperature varied between 22 and 26 C.
Date: January 1, 1993
Creator: Gundel, L.A.; Daisey, J.M.; Mahanama, K.R.R.; Lee, C.C. & Stevens,R.K.
Partner: UNT Libraries Government Documents Department

Systems Biology Knowledgebase for a New Era in Biology A Genomics:GTL Report from the May 2008 Workshop

Description: Biology has entered a systems-science era with the goal to establish a predictive understanding of the mechanisms of cellular function and the interactions of biological systems with their environment and with each other. Vast amounts of data on the composition, physiology, and function of complex biological systems and their natural environments are emerging from new analytical technologies. Effectively exploiting these data requires developing a new generation of capabilities for analyzing and managing the information. By revealing the core principles and processes conserved in collective genomes across all biology and by enabling insights into the interplay between an organism's genotype and its environment, systems biology will allow scientific breakthroughs in our ability to project behaviors of natural systems and to manipulate and engineer managed systems. These breakthroughs will benefit Department of Energy (DOE) missions in energy security, climate protection, and environmental remediation.
Date: March 1, 2009
Creator: Gregurick, S.; Fredrickson, J. K. & Stevens, R.
Partner: UNT Libraries Government Documents Department

Post-Combustion and Pre-Combustion CO2 Capture Solid Sorbents

Description: Combustion of fossil fuels is one of the major sources of the greenhouse gas CO2. Pressure swing adsorption/sorption (PSA/PSS) and temperature swing adsorption/sorption (TSA/TSS) are some of the potential techniques that could be utilized for removal of CO2 from fuel gas streams. It is very important to develop sorbents to remove CO2 from fuel gas streams that are applicable for a wide range of temperatures. NETL researchers have developed novel CO2 capture sorbents for low, moderate, and high temperature applications. A novel liquid impregnated solid sorbent was developed for CO2 removal in the temperature range of ambient to 60 °C. The sorbent is regenerable at 60 – 80 °C. The sorbent formulations were prepared to be suitable for various reactor configurations (i.e., fixed and fluidized bed). Minimum fluidization gas velocities were also determined. Multi-cycle tests conducted in an atmospheric bench scale reactor with simulated flue gas indicated that the sorbent retains its CO2 sorption capacity with a CO2 removal efficiency of approximately 99% and was unaffected by presence of water vapor. The sorbent was subsequently commercially prepared by Süd Chemie to determine the viability of the sorbent for mass production. Subsequent testing showed that the commercially-synthesized sorbent possesses the same properties as the lab-synthesized equivalent. An innovative solid sorbent containing mixture of alkali earth and alkali compounds was developed for CO2 removal at 200 – 315°C from high pressure gas streams suitable for IGCC systems. The sorbent showed very high capacity for CO2 removal from a gas streams containing 28% CO2 at 200 °C and at 20 atm during a lab scale reactor test. This sorbent can be regenerated at 20 atm and at 375 °C utilizing a gas stream containing steam. High pressure enhanced the CO2 sorption process. Bench scale testing showed consistent capacities and regenerability. A unique high ...
Date: November 1, 2007
Creator: Siriwardane, R.V.; Stevens, R.W. & Robinson, Clark
Partner: UNT Libraries Government Documents Department

Solid Sorbents for CO2 Capture from Post-Combustion and Pre-Combustion Gas Streams

Description: A novel liquid impregnated solid sorbent was developed for CO2 removal in the temperature range of ambient to 60 °C for both fixed bed and fluidized bed reactor applications. The sorbent is regenerable at 60-80 °C. Multi-cycle tests conducted in an atmospheric bench scale reactor with simulated flue gas demonstrated that the sorbent retains its CO2 sorption capacity with CO2 removal efficiency of about 99%. A second, novel solid sorbent containing mixture of alkali earth and alkali compounds was developed for CO2 removal at 200-315 °C from high pressure gas streams (i.e., suitable for IGCC systems). The sorbent showed very high capacity for CO2 removal from gas streams containing 28% CO2 at 200 °C and 11.2 atm during lab-scale flow reactor tests as well as regenerability at 375 °C.
Date: August 1, 2007
Creator: Siriwardane, R.V.; Robinson, C. & Stevens, R.W.
Partner: UNT Libraries Government Documents Department

Confinement Vessel Dynamic Analysis

Description: A series of hydrodynamic and structural analyses of a spherical confinement vessel has been performed. The analyses used a hydrodynamic code to estimate the dynamic blast pressures at the vessel's internal surfaces caused by the detonation of a mass of high explosive, then used those blast pressures as applied loads in an explicit finite element model to simulate the vessel's structural response. Numerous load cases were considered. Particular attention was paid to the bolted port connections and the O-ring pressure seals. The analysis methods and results are discussed, and comparisons to experimental results are made.
Date: August 1, 1999
Creator: Stevens, R. Robert & Rojas, Stephen P.
Partner: UNT Libraries Government Documents Department

Virtual reality visualization of parallel molecular dynamics simulation

Description: When performing communications mapping experiments for massively parallel processors, it is important to be able to visualize the mappings and resulting communications. In a molecular dynamics model, visualization of the atom to atom interaction and the processor mappings provides insight into the effectiveness of the communications algorithms. The basic quantities available for visualization in a model of this type are the number of molecules per unit volume, the mass, and velocity of each molecule. The computational information available for visualization is the atom to atom interaction within each time step, the atom to processor mapping, and the energy resealing events. We use the CAVE (CAVE Automatic Virtual Environment) to provide interactive, immersive visualization experiences.
Date: December 31, 1995
Creator: Disz, T.; Papka, M.; Stevens, R.; Pellegrino, M. & Taylor, V.
Partner: UNT Libraries Government Documents Department