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Inertial Conference Fusion Semiannual Report October 1999 - March 2000, Volume 1, Number 1

Description: This first issue of the ''ICF Semiannual Report'' contains articles whose diverse subjects attest to the broad technical and scientific challenges that are at the forefront of the ICF program at LLNL. The first article describes the progress being made at solving the surface roughness problem on capsule mandrels. All NIF capsule options, except machined beryllium, require a mandrel upon which the ablator is deposited. This mandrel sets the baseline sphericity of the final capsule. Problems invo… more
Date: March 1, 2000
Creator: Hammel, B. A.
Partner: UNT Libraries Government Documents Department
open access

Measurement of the neutron spin structure function at low Q{sup 2}

Description: The spin dependent cross sections, {sigma}{sup T}{sub 1/2} and {sigma}{sup T}{sub 3/2}, and asymmetries, A{sub {parallel}} and A{sub {perp}}, for {sup 3}He have been measured at the Jefferson Lab's Hall A facility. The inclusive scattering process {sup 3}{vec He}({vec e},e)X was performed for initial beam energies ranging from 0.86 to 5.1 GeV, at a scattering angle of 15.5°. Data includes measurements from the quasielastic peak, resonance region, and the deep inelastic regime. An approximation … more
Date: August 1, 2000
Creator: Jensen, John Steffen
Partner: UNT Libraries Government Documents Department
open access

XANES, EXAFS and Kbeta spectroscopic studies of the oxygen-evolving complex in Photosystem II

Description: A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S{sub 3} {r_arrow} [S{sub 4}] {r_arrow} S{sub 0} transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn K{beta} X-ray emission… more
Date: December 1, 2000
Creator: Robblee, John H.
Partner: UNT Libraries Government Documents Department
open access

The intergroup protocols: Scalable group communication for the internet

Description: Reliable group ordered delivery of multicast messages in a distributed system is a useful service that simplifies the programming of distributed applications. Such a service helps to maintain the consistency of replicated information and to coordinate the activities of the various processes. With the increasing popularity of the Internet, there is an increasing interest in scaling the protocols that provide this service to the environment of the Internet. The InterGroup protocol suite, describe… more
Date: November 1, 2000
Creator: Berket, K.
Partner: UNT Libraries Government Documents Department
open access

Study of the Axial Anomaly using the {gamma}p {yields} {pi}{sup +}P{pi}{sup 0} n Reaction Near Threshold

Description: This experiment was one of the first photoproduction experiments performed at Jefferson Lab using the CLAS and the Photon Tagger. The event reconstruction and the photon flux determination procedures have been developed and were proven to work well as we can see from the cross section measurement of the {gamma}p {yields} {pi}{sup +}n reaction. The preliminary results at CLAS for this reaction agree very well with previous world data. The analysis procedure has been developed to analyze the doub… more
Date: May 1, 2000
Creator: Asavapibhop, Burin
Partner: UNT Libraries Government Documents Department
open access

Object-oriented algorithmic laboratory for ordering sparse matrices

Description: We focus on two known NP-hard problems that have applications in sparse matrix computations: the envelope/wavefront reduction problem and the fill reduction problem. Envelope/wavefront reducing orderings have a wide range of applications including profile and frontal solvers, incomplete factorization preconditioning, graph reordering for cache performance, gene sequencing, and spatial databases. Fill reducing orderings are generally limited to--but an inextricable part of--sparse matrix factori… more
Date: May 1, 2000
Creator: Kumfert, G K
Partner: UNT Libraries Government Documents Department
open access

Water resources development in Santa Clara Valley, California: insights into the human-hydrologic relationship

Description: Groundwater irrigation is critical to food production and, in turn, to humankind's relationship with its environment. The development of groundwater in Santa Clara Valley, California during the early twentieth century is instructive because (1) responses to unsustainable resource use were largely successful; (2) the proposals for the physical management of the water, although not entirely novel, incorporated new approaches which reveal an evolving relationship between humans and the hydrologic … more
Date: June 1, 2000
Creator: Reynolds, Jesse L. & Narasimhan, T.N.
Partner: UNT Libraries Government Documents Department
open access

Multi-atom resonant photoemission and the development of next-generation software and high-speed detectors for electron spectroscopy

Description: This dissertation has involved the exploration of a new effect in photoelectron emission, multi-atom resonant photoemission (MARPE), as well as the development of new software, data analysis techniques, and detectors of general use in such research. We present experimental and theoretical results related to MARPE, in which the photoelectron intensity from a core level on one atom is influenced by a core-level absorption resonance on another. We point out that some of our and others prior experi… more
Date: September 1, 2000
Creator: Kay, Alexander William
Partner: UNT Libraries Government Documents Department
open access

Image reconstruction for a Positron Emission Tomograph optimized for breast cancer imaging

Description: The author performs image reconstruction for a novel Positron Emission Tomography camera that is optimized for breast cancer imaging. This work addresses for the first time, the problem of fully-3D, tomographic reconstruction using a septa-less, stationary, (i.e. no rotation or linear motion), and rectangular camera whose Field of View (FOV) encompasses the entire volume enclosed by detector modules capable of measuring Depth of Interaction (DOI) information. The camera is rectangular in shape … more
Date: April 1, 2000
Creator: Virador, Patrick R.G.
Partner: UNT Libraries Government Documents Department
open access

Kinetics of (beta)(right arrow)(delta) Solid-Solid Phase Transition of HMX

Description: In order to calculate the kinetic parameters from DSC data, we have used the generally accepted methods of Bershtein [13]. We have calculated the rate constants for 4 temperatures and the activation energy based on the shift in the transition temperature, {beta} {yields} {delta} for HMX. The values of E{sub a} from this work is 402 kJ/mol compared to previous results by Brill [9] of 204 kJ/mol. Brill and associates measured the phase transition of HMX using FTIR, sodium chloride plates and sili… more
Date: September 1, 2000
Creator: Weese, R K
Partner: UNT Libraries Government Documents Department
open access

Development and Implementation of Photonuclear Cross-Section Data for Mutually Coupled Neutron-Photon Transport Calculations in the Monte Carlo N-Particle (MCNP) Radiation Transport Code

Description: The fundamental motivation for the research presented in this dissertation was the need to development a more accurate prediction method for characterization of mixed radiation fields around medical electron accelerators (MEAs). Specifically, a model is developed for simulation of neutron and other particle production from photonuclear reactions and incorporated in the Monte Carlo N-Particle (MCNP) radiation transport code. This extension of the capability within the MCNP code provides for the … more
Date: July 1, 2000
Creator: White, Morgan C.
Partner: UNT Libraries Government Documents Department
open access

Novel nuclear magnetic resonance techniques for studying biological molecules

Description: Over the fifty-five year history of Nuclear Magnetic Resonance (NMR), considerable progress has been made in the development of techniques for studying the structure, function, and dynamics of biological molecules. The majority of this research has involved the development of multi-dimensional NMR experiments for studying molecules in solution, although in recent years a number of groups have begun to explore NMR methods for studying biological systems in the solid-state. Despite this new effor… more
Date: June 1, 2000
Creator: Laws, David D.
Partner: UNT Libraries Government Documents Department
open access

Fidelity of a Finite Element Model for Longitudinal Wave Propagation in Thick Cylindrical Wave Guides

Description: The ability to model wave propagation in circular cylindrical bars of finite length numerically or analytically has many applications. In this thesis the capability of an explicit finite element method to model longitudinal waves in cylindrical rods with circular cross-sections is explored. Dispersion curves for the first four modes are compared to the analytical solution to determine the accuracy of various element sizes and time steps. Values for the time step and element size are determined … more
Date: September 1, 2000
Creator: Puckett, A.D.
Partner: UNT Libraries Government Documents Department
open access

Development of techniques in magnetic resonance and structural studies of the prion protein

Description: Magnetic resonance is the most powerful analytical tool used by chemists today. Its applications range from determining structures of large biomolecules to imaging of human brains. Nevertheless, magnetic resonance remains a relatively young field, in which many techniques are currently being developed that have broad applications. In this dissertation, two new techniques are presented, one that enables the determination of torsion angles in solid-state peptides and proteins, and another that in… more
Date: July 1, 2000
Creator: Bitter, Hans-Marcus L.
Partner: UNT Libraries Government Documents Department
open access

Open cycle thermoacoustics

Description: A new type of thermodynamic device combining a thermodynamic cycle with the externally applied steady flow of an open thermodynamic process is discussed and experimentally demonstrated. The gas flowing through this device can be heated or cooled in a series of semi-open cyclic steps. The combination of open and cyclic flows makes possible the elimination of some or all of the heat exchangers (with their associated irreversibility). Heat is directly exchanged with the process fluid as it flows t… more
Date: January 1, 2000
Creator: Reid, Robert Stowers
Partner: UNT Libraries Government Documents Department
open access

A Spatial Discretization Scheme for Solving the Transport Equation on Unstructured Grids of Polyhedra

Description: In this work, we develop a new spatial discretization scheme that may be used to numerically solve the neutron transport equation. This new discretization extends the family of corner balance spatial discretizations to include spatial grids of arbitrary polyhedra. This scheme enforces balance on subcell volumes called corners. It produces a lower triangular matrix for sweeping, is algebraically linear, is non-negative in a source-free absorber, and produces a robust and accurate solution in thi… more
Date: November 1, 2000
Creator: Thompson, Kelly Glen
Partner: UNT Libraries Government Documents Department
open access

An implicit Smooth Particle Hydrodynamic code

Description: An implicit version of the Smooth Particle Hydrodynamic (SPH) code SPHINX has been written and is working. In conjunction with the SPHINX code the new implicit code models fluids and solids under a wide range of conditions. SPH codes are Lagrangian, meshless and use particles to model the fluids and solids. The implicit code makes use of the Krylov iterative techniques for solving large linear-systems and a Newton-Raphson method for non-linear corrections. It uses numerical derivatives to const… more
Date: April 1, 2000
Creator: Knapp, Charles E.
Partner: UNT Libraries Government Documents Department
open access

Measurement of a Weak Polarization Sensitivity to the Beam Orbit of the CEBAF Accelerator

Description: An accelerator-based experiment was performed using the CEBAF accelerator of the Thomas Jefferson National Accelerator Facility to investigate a predicted sensitivity of the beam polarization to the vertical betatron orbit in the recirculation arcs. This is the first measurement of any such effect at CEBAF, and provides information about the polarized beam delivery performance of the accelerator. A brief description of the accelerator is given, followed by the experimental methods used and the … more
Date: April 1, 2000
Creator: Grames, Joseph
Partner: UNT Libraries Government Documents Department
open access

Gradient Effects on the Fracture of Inhomogeneous Materials

Description: Functionally Graded Materials (FGMs) have a spatial variation in physical properties that can be tailored to meet the needs of a specific application and/or to minimize internal stresses arising from thermal and elastic mismatch. Modeling these materials as inhomogeneous continua allows assessment of the role of the gradient without requiring detailed knowledge of the microstructure. Motivated by the relative difficulty of obtaining analytical solutions to boundary value problems for FGMs, an a… more
Date: May 1, 2000
Creator: Becker, Terrence Lee
Partner: UNT Libraries Government Documents Department
open access

Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

Description: The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby… more
Date: May 1, 2000
Creator: Roberts, J.G.
Partner: UNT Libraries Government Documents Department
open access

The ideal strength and mechanical hardness of solids

Description: Relationships between intrinsic mechanical hardness and atomic-scale properties are reviewed, Hardness scales closely and linearly with shear modulus for a given class of material (covalent, ionic or metallic). A two-parameter fit and a Peierls-stress model produce a more universal scaling relationship, but no model can explain differences in hardness between the transition metal carbides and nitrides. Calculations of ''ideal strength'' (defined by the limit of elastic stability of a perfect cr… more
Date: April 1, 2000
Creator: Krenn, Christopher
Partner: UNT Libraries Government Documents Department
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