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Combustion in Homogeneous Charge Compression Ignition Engines: Experiments and Detailed Chemical Kinetic Simulations

Description: Homogeneous charge compression ignition (HCCI) engines are being considered as an alternative to diesel engines. The HCCI concept involves premixing fuel and air prior to induction into the cylinder (as is done in current spark-ignition engine) then igniting the fuel-air mixture through the compression process (as is done in current diesel engines). The combustion occurring in an HCCI engine is fundamentally different from a spark-ignition or Diesel engine in that the heat release occurs as a g… more
Date: June 7, 2002
Creator: Flowers, D L
Partner: UNT Libraries Government Documents Department
open access

Superconducting High Energy Resolution Gamma-ray Spectrometers

Description: We have demonstrated that a bulk absorber coupled to a TES can serve as a good gamma-ray spectrometer. Our measured energy resolution of 70 eV at 60 keV is among the best measurements in this field. We have also shown excellent agreement between the noise predictions and measured noise. Despite this good result, we noted that our detector design has shortcomings with a low count rate and vulnerabilities with the linearity of energy response. We addressed these issues by implementation of an act… more
Date: February 22, 2002
Creator: Chow, Daniel Tun Lai
Partner: UNT Libraries Government Documents Department
open access

Aerosol Property Comparison Within and Above the ABL at the ARM Program SGP Site

Description: This thesis determines what, if any, measurements of aerosol properties made at the Earth surface are representative of those within the entire air column. Data from the Atmospheric Radiation Measurement site at the Southern Great Plains, the only location in the world where ground-based and in situ airborne measurements are routinely made. Flight legs during the one-year period from March 2000 were categorized as either within or above the atmospheric boundary layer (ABL) by use of an objectiv… more
Date: May 1, 2002
Creator: Delle Monache, L
Partner: UNT Libraries Government Documents Department
open access

Large-Eddy Simulation of the Evolving Stable Boundary Layer Over Flat Terrain

Description: The stable boundary layer (SBL) in the atmosphere is of considerable interest because it is often the worse case scenario for air pollution studies and health effect assessments associated with the accidental release of toxic material. Traditional modeling approaches used in such studies do not simulate the non-steady character of the velocity field, and hence often overpredict concentrations while underpredicting spatial coverage of potentially harmful concentrations of airborne material. The … more
Date: January 2, 2002
Creator: Townsend, Richard Townsend
Partner: UNT Libraries Government Documents Department
open access

Experimental Studies of the Stimulated Brillouin Scattering Instability in the Saturated Regime

Description: An experimental study of the stimulated Brillouin scattering (SBS) instability has investigated the effects of velocity gradients and kinetic effects on the saturation of ion-acoustic waves in a plasma. For intensities less than I < 1.5 x 10{sup 15} W cm{sup -2}, the SBS instability is moderated primarily by velocity gradients, and for intensities above this threshold, nonlinear trapping is invoked to saturate the instability. We report direct evidence of detuning of SBS by a velocity gradie… more
Date: October 29, 2002
Creator: Froula, D
Partner: UNT Libraries Government Documents Department
open access

Design and Evaluation of System Configurations for an EUV Mask Inspection Microscope

Description: This document is the third sub-report of the EUV AIM design study being conducted at LLNL on behalf of International Sematech (ISMT). The purpose of this study as identified in section 1.2 of the statement of work is to research the basic user requirements of an actinic defect characterization tool, potential design configurations and top-level specifications. The objectives of this design study specifically identified in section 1.3 of the statement of work were to: (1) Determine the user requ… more
Date: August 20, 2002
Creator: Barty, Anton; Taylor, John S.; Hudyma, Russell & Spiller, Eberhard
Partner: UNT Libraries Government Documents Department
open access

Level Densities and Radiative Strength Functions in 56FE and 57FE

Description: Understanding nuclear level densities and radiative strength functions is important for pure and applied nuclear physics. Recently, the Oslo Cyclotron Group has developed an experimental method to extract level densities and radiative strength functions simultaneously from the primary {gamma} rays after a light-ion reaction. A primary {gamma}-ray spectrum represents the {gamma}-decay probability distribution. The Oslo method is based on the Axel-Brink hypothesis, according to which the primary … more
Date: December 10, 2002
Creator: Tavukcu, E
Partner: UNT Libraries Government Documents Department
open access

Efficient Video Similarity Measurement and Search

Description: The amount of information on the world wide web has grown enormously since its creation in 1990. Duplication of content is inevitable because there is no central management on the web. Studies have shown that many similar versions of the same text documents can be found throughout the web. This redundancy problem is more severe for multimedia content such as web video sequences, as they are often stored in multiple locations and different formats to facilitate downloading and streaming. Similar… more
Date: December 19, 2002
Creator: Cheung, Sen-Cheng S.
Partner: UNT Libraries Government Documents Department
open access

Comparison of Aerosol Properties Within and Above the ABL at the ARM Program's SGP Site

Description: The goal of this thesis is to determine under what conditions, if any, measurements of aerosol properties made at the Earth's surface are representative of aerosol properties within the column of air above the surface. This thesis will use data from the Atmospheric Radiation Measurement (ARM) site at the Southern Great Plains (SGP) which is the only location in the world where ground-based and in situ airborne measurements are made on a routine basis. All flight legs in the one-year period from… more
Date: May 1, 2002
Creator: Delle Monache, L
Partner: UNT Libraries Government Documents Department
open access

Reflectance, Optical Properties, and Stability of Molybdenum/Strontium and Molybdenum/Yttrium Multilayer Mirrors

Description: The motivation of this work is to develop high reflectance normal-incidence multilayer mirrors in the 8-12 nm wavelength region for applications in astronomy and extreme ultraviolet lithography. To achieve this goal, Mo/Sr and Mo/Y multilayers were studied. These multilayers were deposited with a UHV magnetron sputtering system and their reflectances were measured with synchrotron radiation. High normal-incidence reflectances of 23% at 8.8 nm, 40.8% at 9.4 nm, and 48.3% at 10.5 nm were achieved… more
Date: September 1, 2002
Creator: Kjornrattanawanich, B
Partner: UNT Libraries Government Documents Department
open access

Polarization-Modulated Second Harmonic Generation Microscopy in Collagen

Description: Collagen is a key structural protein in the body; several pathological conditions lead to changes in collagen. Among imaging modalities that can be used in vivo, second harmonic generation (SHG) microscopy has a key advantage: it provides {approx}1 {micro}m resolution information about collagen structure as a function of depth. A new technique--polarization-modulated SHG--is presented: it permits simultaneous measurement of collagen orientation, of a lower bound on the magnitude of the second o… more
Date: September 30, 2002
Creator: Stoller, P. C.
Partner: UNT Libraries Government Documents Department
open access

Studies in High Current Density Ion Sources for Heavy Ion FusionApplications

Description: This dissertation develops diverse research on small (diameter {approx} few mm), high current density (J {approx} several tens of mA/cm{sup 2}) heavy ion sources. The research has been developed in the context of a programmatic interest within the Heavy Ion Fusion (HIF) Program to explore alternative architectures in the beam injection systems that use the merging of small, bright beams. An ion gun was designed and built for these experiments. Results of average current density yield (<J>… more
Date: June 1, 2002
Creator: Chacon-Golcher, E.
Partner: UNT Libraries Government Documents Department
open access

Topics in Hadronic Physics

Description: Hadron production cross sections are calculated in the perturbative QCD frame work. Parton distribution functions are obtained from a strip-soliton model. The fragmentation functions are derived from the Lund model of string breaking.
Date: August 1, 2002
Creator: Tang, Alfred
Partner: UNT Libraries Government Documents Department
open access

Microearthquake Study of the Salton Sea Geothermal Field, California: Evidence of Stress Triggering

Description: A digital network of 24 seismograph stations was operated from September 15, 1987 to September 30, 1988, by Lawrence Livermore National Laboratory and Unocal as part of the Salton Sea Scientific Drilling Project to study seismicity related to tectonics and geothermal activity near the drilling site. More than 2001 microearthquakes were relocated in this study in order to image any pervasive structures that may exist within the Salton Sea geothermal field. First, detailed velocity models were ob… more
Date: February 1, 2002
Creator: Holland, Austin Adams
Partner: UNT Libraries Government Documents Department
open access

Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

Description: Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish a… more
Date: September 18, 2002
Creator: Wang, Tong
Partner: UNT Libraries Government Documents Department
open access

Constructing Predictive Estimates for Worker Exposure to Radioactivity During Decommissioning: Analysis of Completed Decommissioning Projects

Description: An analysis of completed decommissioning projects is used to construct predictive estimates for worker exposure to radioactivity during decommissioning activities. The preferred organizational method for the completed decommissioning project data is to divide the data by type of facility, whether decommissioning was performed on part of the facility or the complete facility, and the level of radiation within the facility prior to decommissioning (low, medium, or high). Additional data analysis … more
Date: October 1, 2002
Creator: Dettmers, Dana Lee & Eide, Steven Arvid
Partner: UNT Libraries Government Documents Department
open access

A study of B(s)0 to J/psi phi in the D0 experiment and an example of HEP technology transfer

Description: After years of preparation, data taking with the upgraded D0 detector at the Tevatron proton-antiproton collider has begun. The large amount of data produced in a p{bar p}-collider requires sophisticated triggers to filter out the interesting events. Described in this thesis is the development of trigger software for the newly implemented Silicon Microstrip Tracker. D0 is a multi-purpose detector with a broad physics program. one area being studied at D0 is B mesons. An algorithm for reconstruc… more
Date: January 1, 2002
Creator: Bauer, Daniela Ursula
Partner: UNT Libraries Government Documents Department
open access

Development of trigger software for the silicon and fibre trackers and a study of B meson lifetimes for the D0 experiment

Description: The D0 detector has recently undergone a major upgrade to maximize its potential to fully exploit Run II at the Tevatron 2 TeV proton-antiproton collider. The upgrade includes a completely new central tracking system with an outer scintillating fiber tracker and an inner silicon vertex detector. This thesis describes the development of the software to ''unpack'' the raw data from the central tracking detectors into a useful form, and the development of the Level 3 trigger algorithms to cluster … more
Date: January 1, 2002
Creator: Illingworth, Robert Arthur
Partner: UNT Libraries Government Documents Department
open access

Evaluating Radionuclide Air Emission Stack Sampling Systems

Description: The Pacific Northwest National Laboratory (PNNL) operates a number of research and development (R&D) facilities for the U.S. Department of Energy at the Hanford Site, Washington. These facilities are subject to Clean Air Act regulations that require sampling of radionuclide air emissions from some of these facilities. A revision to an American National Standards Institute (ANSI) standard on sampling radioactive air emissions has recently been incorporated into federal and state regulations and … more
Date: December 16, 2002
Creator: Ballinger, Marcel Y.
Partner: UNT Libraries Government Documents Department
open access

Measurement of the neutron ({sup 3}He) spin structure functions at low Q{sup 2}: A CONNECTION BETWEEN THE BJORKEN AND GERASIMOV-DRELL-HEARN SUM RULE

Description: This dissertation presents results of experiment E94-010 performed at Jefferson Laboratory (simply known as JLab) in Hall A. The experiment aimed to measure the low Q{sup 2} evolution of the Gerasimov-Drell-Hearn (GDH) integral from Q{sup 2} = 0.1 to 0.9 GeV{sup 2}. The GDH sum rule at the real photon point provides an important test of Quantum Chromodynamics (QCD). The low Q{sup 2} evolution of the GDH integral contests various resonance models, Chiral Perturbation Theory ({chi}#31;PT) and lat… more
Date: December 1, 2002
Creator: Djawotho, Pibero
Partner: UNT Libraries Government Documents Department
open access

Near Threshold electroproduction of the Omega Meson at Momentum Transfer Q2=0.5 (GeV/c)2

Description: Jefferson Lab kaon experiments E91016/E93018 produced data on both strangeness and vector meson electroproduction. The latter part of the experiments was focused on the electroproduction of the omega meson for momentum transfer Q 2 near 0.5 (GeV/c) 2. This reaction was selected from the inelastic ep channel, H-1 (e, e' p)X, by performing involved signal background separation. Tagging the omega meson production only on electron and proton not only introduced appreciable statistical error but als… more
Date: January 1, 2002
Creator: Ambrosewicz, P.
Partner: UNT Libraries Government Documents Department
open access

High Precision Hypernuclear Spectroscopy Study by the (e,e'K) Reaction

Description: Jefferson Lab experiment E89009 is the first experiment to study hypernuclear spectroscopy by (e,e' K{sup +}) reaction. The 12 / LambdaB spectrum was observed from carbon target with the best energy resolution ever achieved from direct measurement of hypernuclear spectrum. The comparisons of the 12 / LambdaB spectrum with theoretical predictions were provided in terms of excitation strength and level separations. The overall excitation is in accord with theoretical calculations. The binding ene… more
Date: August 1, 2002
Creator: Yuan, Lulin
Partner: UNT Libraries Government Documents Department
open access

Study of the Delta (1232) Using Double Polarization Asymmetries

Description: An extensive experimental program to measure the spin structure of the nucleus is underway in Hall B at Jefferson Lab using a polarized electron beam incident on a polarized target. Spin degrees of freedom offer the possibility to test, in an independent way, existing models of resonance electro-production. The present analysis selects the Delta{sup +} (1232) in the exclusive channel {rvec p}({rvec e}, e'p)pi{sup 0} from data of the EG1 run period, taken in the Fall of 1998, to extract single a… more
Date: March 1, 2002
Creator: Biselli, Angela
Partner: UNT Libraries Government Documents Department
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