Modeling Free Convection Flow of Liquid Hydrogen within a Cylindrical Heat Exchanger Cooled to 14 K (open access)

Modeling Free Convection Flow of Liquid Hydrogen within a Cylindrical Heat Exchanger Cooled to 14 K

None
Date: May 8, 2004
Creator: Green, Michael A.; Yang, S. W.; Green, M. A. & Lau, W.
Object Type: Article
System: The UNT Digital Library
Modeling Free Convection Flow of Liquid Hydrogen within a Cylindrical Heat Exchanger Cooled to 14 K (open access)

Modeling Free Convection Flow of Liquid Hydrogen within a Cylindrical Heat Exchanger Cooled to 14 K

A liquid hydrogen in a absorber for muon cooling requires that up to 300 W be removed from 20 liters of liquid hydrogen. The wall of the container is a heat exchanger between the hydrogen and 14 K helium gas in channels within the wall. The warm liquid hydrogen is circulated down the cylindrical walls of the absorber by free convection. The flow of the hydrogen is studied using FEA methods for two cases and the heat transfer coefficient to the wall is calculated. The first case is when the wall is bare. The second case is when there is a duct some distance inside the cooled wall.
Date: May 8, 2004
Creator: Green, Michael A.; Yang, S. W.; Green, M. A. & Lau, W.
Object Type: Article
System: The UNT Digital Library
Comments on Shimony's 'An Analysis of Stapp's 'A bell-type theoremwithout hidden variables'' (open access)

Comments on Shimony's 'An Analysis of Stapp's 'A bell-type theoremwithout hidden variables''

The hidden-variable theorems of Bell and followers depend upon an assumption, namely the hidden-variable assumption, that conflicts with the precepts of quantum philosophy. Hence from an orthodox quantum perspective those theorems entail no faster-than-light transfer of information. They merely reinforce the ban on hidden variables. The need for some sort of faster-than-light information transfer can be shown by using counterfactuals instead of hidden variables. Shimony's criticism of that argument fails to take into account the distinction between no-faster-than-light connection in one direction and that same condition in both directions. The argument can be cleanly formulated within the framework of a fixed past, open future interpretation of quantum theory, which neatly accommodates the critical assumptions that the experimenters are free to choose which experiments they will perform. The assumptions are compatible with the Tomonaga-Schwinger formulation of quantum field theory, and hence with orthodox quantum precepts, and with the relativistic requirement that no prediction pertaining to an outcome in one region can depend upon a free choice made in a region spacelike-separated from the first.
Date: September 8, 2004
Creator: Stapp, Henry P.
Object Type: Article
System: The UNT Digital Library
Transition to Turbulence and Effect of Initial Conditions on 3D Compressible Mixing in Planar Blast-wave-driven Systems (open access)

Transition to Turbulence and Effect of Initial Conditions on 3D Compressible Mixing in Planar Blast-wave-driven Systems

Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, results from three-dimensional numerical simulations of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams, 9(2), 209 (1991)] are presented. Using the multi-physics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J.A. Greenough, J. Comp. Phys. 184, 53 (2003)], the late nonlinear instability evolution, including transition to turbulence, is considered for various multimode perturbation spectra. The 3D post-transition state differs from the 2D result, but the process of transition proceeds similarly in both 2D and 3D. The turbulent mixing transition results in a reduction in the growth rate of the mixing layer relative to its pre-transition value and, in the case of the bubble front, relative to the 2D result. The post-transition spike front velocity is approximately the same in 2D and 3D. Implications for hydrodynamic mixing in core-collapse supernova are discussed.
Date: November 8, 2004
Creator: Miles, A R; Edwards, M J & Greenough, J A
Object Type: Article
System: The UNT Digital Library
Use of Conducting Polymers for Electronic Communication with Redox Active Nanoparticles (open access)

Use of Conducting Polymers for Electronic Communication with Redox Active Nanoparticles

Nanoscale materials provide unique properties that will enable new technologies and enhance older ones. One area of intense activity in which nanoscale materials are being used is in the development of new functional materials for battery applications.1-4 This effort promises superior materials with properties that circumvent many of the problems associated with traditional battery materials. Previously we have worked on several approaches for using nanoscale materials for application as cathode materials in rechargeable Li batteries.5-11 Our recent work has focused on synthesizing MnO2 nanoparticles and using conducting polymers to electronically address these particles in nanoparticle assemblies. This presentation will focus on those efforts. MnO2 nanoparticles that are encapsulated with poly(3,4-ethylenedioxythiophene) (PEDOT) are prepared using 3,4-ethylenedioxythiophene (EDOT) as a chemical reductant for permanganate anion. This non-aqueous preparation is based on a recent report of a similar method for preparation of PEDOT-encapsulated Au nanoparticles.12 We also describe the synthesis of MnO2 colloidal nanoparticles prepared using an aqueous route involving reduction of permanganate anion with butanol using a previously described route.13 We report the synthesis and characterization of the PEDOT material, and the aqueous colloidal material. We show that the aqueous colloidal nanoparticles can be trapped in thin films using a layer-by-layer deposition …
Date: August 8, 2004
Creator: Bazito, Fernanda; O'Brien, Robert & Buttry, Daniel A.
Object Type: Article
System: The UNT Digital Library
Defects in p-GaN and their atomic structure (open access)

Defects in p-GaN and their atomic structure

In this paper defects formed in p-doped GaN:Mg grown with Ga polarity will be discussed. The atomic structure of these characteristic defects (Mg-rich hexagonal pyramids and truncated pyramids) in bulk and thin GaN:Mg films grown with Ga polarity was determined at atomic resolution by direct reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities were present inside the defects. The inside walls of the cavities were covered by GaN which grew with reverse polarity compared to the matrix. It was proposed that lateral overgrowth of the cavities restores matrix polarity on the defect base. Exchange of Ga and N sublattices within the defect compared to the matrix lead to a 0.6 {+-} 0.2 {angstrom} displacement between the Ga sublattices of these two areas. A [1{und 1}00]/3 shift with change from AB stacking in the matrix to BC within the entire pyramid is observed
Date: October 8, 2004
Creator: Liliental-Weber, Z.; Tomaszewicz, T.; Zakharov, D.; Jasinski, J. & and O'Keefe, M.
Object Type: Article
System: The UNT Digital Library
Wintertime pytoplankton bloom in the Subarctic Pacific supportedby continental margin iron (open access)

Wintertime pytoplankton bloom in the Subarctic Pacific supportedby continental margin iron

Heightened biological activity was observed in February 1996in the high-nutrient low-chlorophyll (HNLC) subarctic North PacificOcean, a region that is thought to beiron-limited. Here we provideevidence supporting the hypothesis that Ocean Station Papa (OSP) in thesubarctic Pacific received a lateral supply of particulate iron from thecontinental margin off the Aleutian Islands in the winter, coincidentwith the observed biological bloom. Synchrotron X-ray analysis was usedto describe the physical form, chemistry, and depth distributions of ironin size fractionated particulate matter samples. The analysis revealsthat discrete micron-sized iron-rich hotspots are ubiquitous in the upper200m at OSP, more than 900km from the closest coast. The specifics of thechemistry and depth profiles of the Fe hot spots trace them to thecontinental margins. We thus hypothesize that iron hotspots are a markerfor the delivery of iron from the continental margin. We confirm thedelivery of continental margin iron to the open ocean using an oceangeneral circulation model with an iron-like tracer source at thecontinental margin. We suggest that iron from the continental marginstimulated a wintertime phytoplankton bloom, partially relieving the HNLCcondition.
Date: June 8, 2004
Creator: Lam, Phoebe J.; Bishop, James K.B.; Henning, Cara C.; Marcus,Matthew A.; Waychunas, Glenn A. & Fung, Inez
Object Type: Article
System: The UNT Digital Library
Formulation of the Linear Response Theory in Relativistic LAPW Method. Calculation of Forces in Alpha-Pu (open access)

Formulation of the Linear Response Theory in Relativistic LAPW Method. Calculation of Forces in Alpha-Pu

Linear-response (LR) theory in combination with the first-principles band structure codes allows to calculate phonons in an efficient way. In this report a formalism which enables us to apply LR theory within an all-electron framework utilizing the relativistic full-potential linearized augmented plane-wave (RFLAPW) method is presented. As first part, the equations for the calculations of the atomic forces are given and they are used for the calculation of forces in {alpha}-Pu. As a second step, a complete set of formulaes for the dynamic matrices calculation is presented.
Date: January 8, 2004
Creator: Kutepov, A L
Object Type: Report
System: The UNT Digital Library
Probability Density Function for Waves Propagating in a Straight PEC Rough Wall Tunnel (open access)

Probability Density Function for Waves Propagating in a Straight PEC Rough Wall Tunnel

The probability density function for wave propagating in a straight perfect electrical conductor (PEC) rough wall tunnel is deduced from the mathematical models of the random electromagnetic fields. The field propagating in caves or tunnels is a complex-valued Gaussian random processing by the Central Limit Theorem. The probability density function for single modal field amplitude in such structure is Ricean. Since both expected value and standard deviation of this field depend only on radial position, the probability density function, which gives what is the power distribution, is a radially dependent function. The radio channel places fundamental limitations on the performance of wireless communication systems in tunnels and caves. The transmission path between the transmitter and receiver can vary from a simple direct line of sight to one that is severely obstructed by rough walls and corners. Unlike wired channels that are stationary and predictable, radio channels can be extremely random and difficult to analyze. In fact, modeling the radio channel has historically been one of the more challenging parts of any radio system design; this is often done using statistical methods. In this contribution, we present the most important statistic property, the field probability density function, of wave propagating in …
Date: November 8, 2004
Creator: Pao, H
Object Type: Article
System: The UNT Digital Library
Numerical Modeling of Nonlinear Thermodynamics in SMA Wires (open access)

Numerical Modeling of Nonlinear Thermodynamics in SMA Wires

We present a mathematical model describing the thermodynamic behavior of shape memory alloy wires, as well as a computational technique to solve the resulting system of partial differential equations. The model consists of conservation equations based on a new Helmholtz free energy potential. The computational technique introduces a viscosity-based continuation method, which allows the model to handle dynamic applications where the temporally local behavior of solutions is desired. Computational experiments document that this combination of modeling and solution techniques appropriately predicts the thermally- and stress-induced martensitic phase transitions, as well as the hysteretic behavior and production of latent heat associated with such materials.
Date: January 8, 2004
Creator: Reynolds, D R & Kloucek, P
Object Type: Article
System: The UNT Digital Library
A Comparison of Inexact Newton and Coordinate Descent Meshoptimization Technqiues (open access)

A Comparison of Inexact Newton and Coordinate Descent Meshoptimization Technqiues

We compare inexact Newton and coordinate descent methods for optimizing the quality of a mesh by repositioning the vertices, where quality is measured by the harmonic mean of the mean-ratio metric. The effects of problem size, element size heterogeneity, and various vertex displacement schemes on the performance of these algorithms are assessed for a series of tetrahedral meshes.
Date: July 8, 2004
Creator: Diachin, L F; Knupp, P; Munson, T & Shontz, S
Object Type: Article
System: The UNT Digital Library
SEISMIC DATA FOR NUCLEAR EXPLOSION MONITORING IN THE ARABIAN PENINSULA (open access)

SEISMIC DATA FOR NUCLEAR EXPLOSION MONITORING IN THE ARABIAN PENINSULA

We report results from the third and final year of our project (ROA0101-35) to collect seismic event and waveform data recorded in and around the Arabian Peninsula. This effort involves several elements. We are working with King Abdulaziz City for Science and Technology to collect data from the Saudi National Seismic Network, that consists of 38 digital three-component stations (27 broadband and 11 short-period). We have an ongoing collaboration with the Kuwait Institute for Scientific Research, which runs the eight station Kuwait National Seismic Network. We installed two temporary broadband stations in the United Arab Emirates (funded by NNSA NA-24 Office of Non-Proliferation & International Security). In this paper we present a summary of data collected under these efforts including integration of the raw data into LLNL's Seismic Research Database and preliminary analysis of souce parameters and earth structure.
Date: July 8, 2004
Creator: Rodgers, A. & Al-Amri, A.
Object Type: Article
System: The UNT Digital Library
No-Core Shell Model Calculations in Light Nuclei with Three-Nucleon Forces (open access)

No-Core Shell Model Calculations in Light Nuclei with Three-Nucleon Forces

The ab initio No-Core Shell Model (NCSM) has recently been expanded to include nucleon-nucleon (NN) and three-nucleon (3N) interactions at the three-body cluster level. Here it is used to predict binding energies and spectra of p-shell nuclei based on realistic NN and 3N interactions. It is shown that 3N force (3NF) properties can be studied in these nuclear systems. First results show that interactions based on chiral perturbation theory lead to a realistic description of {sup 6}Li.
Date: January 8, 2004
Creator: Barrett, B R; Vary, J P; Nogga, A; Navratil, P & Ormand, W E
Object Type: Article
System: The UNT Digital Library
LLNL Experimental Results on OMEGA: FY'04 (open access)

LLNL Experimental Results on OMEGA: FY'04

Lawrence Livermore National Laboratory (LLNL) conducted approximately 360 shots on Omega in FY04. Approximately half of the shots were devoted to ICF-relevant experiments. These are summarized as follows:
Date: September 8, 2004
Creator: Turner, R E
Object Type: Report
System: The UNT Digital Library
Fracture Permeability Evolution in Rock from the Desert Peak EGS Site (open access)

Fracture Permeability Evolution in Rock from the Desert Peak EGS Site

Fluid flow experiments are being conducted on core specimens of quartz monzonite retrieved from depths of about 1 km at the Desert Peak East EGS site in Churchill County, Nevada. Our immediate goal is to observe permeability evolution in fractures at pressure and temperature conditions appropriate to the Desert Peak geothermal site. Longer term, we aim to evaluate mechanisms that control the evolution of fracture permeability. In the experiments saline water is flowed through an artificial fracture at a constant rate of 0.02 ml/min over a period of several weeks. The constant flow tests are interrupted at selected times for shorter tests in which flow is either stopped or varied between 0 and 2.0 ml/min. The experiments to date were conducted at a confining pressure of 5.5 MPa, pore pressures of 1.38 MPa or 2.07 MPa and temperatures of 167- 169 C. Measurements include differential pressure and electrical resistance across the specimen. The short-term variable flow rate experiments allow us to calculate the effective hydraulic aperture of the fracture at various times during the experiment. Changes in electrical resistivity provide indirect evidence of ongoing mineral dissolution and precipitation processes that are expected to change fracture permeability over time. The early …
Date: April 8, 2004
Creator: Carlson, S. R.; Roberts, J. J.; Detwiler, R. L.; Burton, E. A.; Robertson-Tait, A.; Morris, C. et al.
Object Type: Article
System: The UNT Digital Library
Laboratory Measurements of Velocity and Attenuation in Sediments (open access)

Laboratory Measurements of Velocity and Attenuation in Sediments

Laboratory measurements are required to establish relationships between the physical properties of unconsolidated sediments and P- and S-wave propagation through them. Previous work has either focused on measurements of compressional wave properties at depths greater than 500 m for oil industry applications or on measurements of dynamic shear properties at pressures corresponding to depths of less than 50 m for geotechnical applications. Therefore, the effects of lithology, fluid saturation, and compaction on impedance and P- and S-wave velocities of shallow soils are largely unknown. We describe two state-of-the-art laboratory experiments. One setup allows us to measure ultrasonic P-wave velocities at very low pressures in unconsolidated sediments (up to 0.1 MPa). The other experiment allows P- and S-wave velocity measurements at low to medium pressures (up to 20 MPa). We summarize the main velocity and attenuation results on sands and sand - clay mixtures under partially saturated and fully saturated conditions in two ranges of pressures (0 - 0.1 MPa and 0.1 - 20 MPa) representative of the top few meters and the top 1 km, respectively. Under hydrostatic pressures of 0.1 to 20 MPa, our measurements demonstrate a P- and S-wave velocity-dependence in dry sands around a fourth root (0.23 …
Date: June 8, 2004
Creator: Zimmer, M A; Berge, P A; Bonner, B P & Prasad, M
Object Type: Article
System: The UNT Digital Library
What can we learn from neutrinoless double beta decay experiments? (open access)

What can we learn from neutrinoless double beta decay experiments?

We assess how well next generation neutrinoless double beta decay and normal neutrino beta decay experiments can answer four fundamental questions. 1) If neutrinoless double beta decay searches do not detect a signal, and if the spectrum is known to be inverted hierarchy, can we conclude that neutrinos are Dirac particles? 2) If neutrinoless double beta decay searches are negative and a next generation ordinary beta decay experiment detects the neutrino mass scale, can we conclude that neutrinos are Dirac particles? 3) If neutrinoless double beta decay is observed with a large neutrino mass element, what is the total mass in neutrinos? 4) If neutrinoless double beta decay is observed but next generation beta decay searches for a neutrino mass only set a mass upper limit, can we establish whether the mass hierarchy is normal or inverted? We base our answers on the expected performance of next generation neutrinoless double beta decay experiments and on simulations of the accuracy of calculations of nuclear matrix elements.
Date: April 8, 2004
Creator: Bahcall, John N.; Murayama, Hitoshi & Pena-Garay, Carlos
Object Type: Article
System: The UNT Digital Library
Study of Dark Matter inspired cMSSM scenarios at a TeV-class Linear Collider (open access)

Study of Dark Matter inspired cMSSM scenarios at a TeV-class Linear Collider

The accuracy in the measurement of the masses of sleptons and heavy Higgs bosons in cMSSM scenarios, compatible with the WMAP result on cold dark matter, has been re-analysed in view of the requirements for predicting this density to a few percent level from SUSY measurements at the linear collider.
Date: October 8, 2004
Creator: Battaglia, Marco
Object Type: Article
System: The UNT Digital Library
New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells Quarterly Report: July-September 2004 (open access)

New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells Quarterly Report: July-September 2004

None
Date: November 8, 2004
Creator: Jacobson, Allan J.
Object Type: Report
System: The UNT Digital Library
BIOTIC INTEGRITY OF STREAMS IN THE SAVANNAH RIVER SITE INTEGRATOR OPERABLE UNITS, 1996 TO 2003 (open access)

BIOTIC INTEGRITY OF STREAMS IN THE SAVANNAH RIVER SITE INTEGRATOR OPERABLE UNITS, 1996 TO 2003

The Savannah River Site (SRS) has been divided into six Integrator Operable Units (IOUs) that correspond to the watersheds of the five major streams on the SRS (Upper Three Runs, Fourmile Branch, Pen Branch, Steel Creek, and Lower Three Runs) and the portions of the Savannah River and Savannah River Swamp associated with the SRS. The streams are the primary integrators within each IOU because they potentially receive, through surface or subsurface drainage, soluble contaminants from all waste sites within their watersheds. If these contaminants reach biologically significant levels, they would be expected to effect the numbers, types, and health of stream organisms. In this study, biological sampling was conducted within each IOU as a measure of the cumulative ecological effects of the waste sites within the IOUs. The use of information from biological sampling to assess environmental quality is often termed bioassessment. The IOU bioassessment program included 38 sites in SRS streams and nine sites in the Savannah River. Sampling was conducted in 1996 to 1998, 2000, and 2003. Four bioassessment methods were used to evaluate ecological conditions in the IOU streams: the Index of Biotic Integrity, the Fish Health Assessment Index, measurement of fish tissue contaminant levels, and …
Date: November 8, 2004
Creator: Paller, M & Susan Dyer, S
Object Type: Report
System: The UNT Digital Library
Fabrication and Characterization of Graded Cu-Doped Be Shells - Details and Documentation of Our First Attempt (open access)

Fabrication and Characterization of Graded Cu-Doped Be Shells - Details and Documentation of Our First Attempt

We have fabricated by sputtering and characterized a set of step-graded Cu-doped Be capsules. The capsules were made with Cu doped layers of about 0.35 and 0.70 atom % Cu. The total thickness of the coating is about 100 {micro}m. Capsules were removed from the coater for characterization after each layer was deposited. Our ability to produce doped layers is confirmed, and our ability to control the level of doping is excellent. A variety of characterization techniques, both destructive and non-destructive were explored. The surface finish of the sample capsules removed after each layer progressively got rougher, it is likely that polishing will be necessary to produce capsules that will meet surface specifications. We have learned a great deal from this first effort, both in terms of coating technology and capsule characterization. We are now implementing several changes in the coating system based in part upon our experience with this first effort. The next graded capsule run should begin near the end of October.
Date: October 8, 2004
Creator: Gunther, J.; McElfresh, M.; Alford, C.; Huang, H. & Cook, R.
Object Type: Report
System: The UNT Digital Library
Antenna-coupled bolometer arrays using transition-edgesensors (open access)

Antenna-coupled bolometer arrays using transition-edgesensors

We describe the development of an antenna-coupled bolometer array for use in a Cosmic Microwave Background polarization experiment. Prototype single pixels using double-slot dipole antennas and integrated microstrip band defining filters have been built and tested. Preliminary results of optical testing and simulations are presented. A bolometer array design based on this pixel will also be shown and future plans for application of the technology will be discussed.
Date: June 8, 2004
Creator: Myers, Michael J.; Ade, Peter; Engargiola, Greg; Holzapfel,William; Lee,Adrian T.; O'Brient, Roger et al.
Object Type: Article
System: The UNT Digital Library
SATURATED ZONE IN-SITU TESTING (open access)

SATURATED ZONE IN-SITU TESTING

The purpose of this scientific analysis is to document the results and interpretations of field experiments that test and validate conceptual flow and radionuclide transport models in the saturated zone (SZ) near Yucca Mountain, Nevada. The test interpretations provide estimates of flow and transport parameters used in the development of parameter distributions for total system performance assessment (TSPA) calculations. These parameter distributions are documented in ''Site-Scale Saturated Zone Flow Model (BSC 2004 [DIRS 170037]), Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]), Saturated Zone Colloid Transport (BSC 2004 [DIRS 170006]), and ''Saturated Zone Flow and Transport Model Abstraction'' (BSC 2004 [DIRS 170042]). Specifically, this scientific analysis contributes the following to the assessment of the capability of the SZ to serve as part of a natural barrier for waste isolation for the Yucca Mountain repository system: (1) The bases for selection of conceptual flow and transport models in the saturated volcanics and the saturated alluvium located near Yucca Mountain. (2) Results and interpretations of hydraulic and tracer tests conducted in saturated fractured volcanics at the C-wells complex near Yucca Mountain. The test interpretations include estimates of hydraulic conductivities, anisotropy in hydraulic conductivity, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion …
Date: November 8, 2004
Creator: REIMUS, P.W.
Object Type: Report
System: The UNT Digital Library
Modeling Soil Quality Thresholds to Ecosystem Recovery at Fort Benning, Georgia, USA (open access)

Modeling Soil Quality Thresholds to Ecosystem Recovery at Fort Benning, Georgia, USA

The objective of this research was to use a simple model of soil C and N dynamics to predict nutrient thresholds to ecosystem recovery on degraded soils at Fort Benning, Georgia, in the southeastern USA. The model calculates aboveground and belowground biomass, soil C inputs and dynamics, soil N stocks and availability, and plant N requirements. A threshold is crossed when predicted soil N supplies fall short of predicted N required to sustain biomass accrual at a specified recovery rate. Four factors were important to development of thresholds to recovery: (1) initial amounts of aboveground biomass, (2) initial soil C stocks (i.e., soil quality), (3) relative recovery rates of biomass, and (4) soil sand content. Thresholds to ecosystem recovery predicted by the model should not be interpreted independent of a specified recovery rate. Initial soil C stocks influenced the predicted patterns of recovery by both old field and forest ecosystems. Forests and old fields on soils with varying sand content had different predicted thresholds to recovery. Soil C stocks at barren sites on Fort Benning generally lie below predicted thresholds to 100% recovery of desired future ecosystem conditions defined on the basis of aboveground biomass (18000 versus 360 g m{sup …
Date: March 8, 2004
Creator: Garten C.T. Jr.
Object Type: Report
System: The UNT Digital Library