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Production of Neutral Photopions as a Function of Atomic Weight (open access)

Production of Neutral Photopions as a Function of Atomic Weight

Thesis discussing the relative yield of neutral pions from elements in a reaction "as a function of the quantum-limit energy (the maximum energy of the quanta in the bremsstrahlung beam) of the Berkeley synchrotron." Interpretation of the results leads to values for the mean free path for absorption of the neutral pions in nuclear matter.
Date: May 28, 1956
Creator: Anderson, John David
System: The UNT Digital Library
Encapsulation of Hazardous Wastes Into Agglomerates (open access)

Encapsulation of Hazardous Wastes Into Agglomerates

The objective of this study was to investigate the feasibility of using the cementitious properties and agglomeration characteristics of coal conversion byproducts to encapsulate and immobilize hazardous waste materials. The intention was to establish an economical way of co-utilization and co-disposal of wastes. In addition, it may aid in the eradication of air pollution problems associated with the fine-powdery nature of fly ash. Encapsulation into agglomerates is a novel approach of treating toxic waste. Although encapsulation itself is not a new concept, existing methods employ high-cost resins that render them economically unfeasible. In this investigation, the toxic waste was contained in a concrete-like matrix whereby fly ash and other cementitious waste materials were utilized. The method incorporates the principles of solidification, stabilization and agglomeration. Another aspect of the study is the evaluation of the agglomeration as possible lightweight aggregates. Since fly ash is commercially used as an aggregate, it would be interesting to study the effect of incorporating toxic wastes in the strength development of the granules. In the investigation, the fly ash self-cementation process was applied to electroplating sludges as the toxic waste. The process hoped to provide a basis for delisting of the waste as hazardous and, thereby …
Date: January 28, 1992
Creator: Guloy, Aida
System: The UNT Digital Library
TRISO Fuel Performance: Modeling, Integration into Mainstream Design Studies, and Application to a Thorium-fueled Fusion-Fission Hybrid Blanket (open access)

TRISO Fuel Performance: Modeling, Integration into Mainstream Design Studies, and Application to a Thorium-fueled Fusion-Fission Hybrid Blanket

This study focused on creating a new tristructural isotropic (TRISO) coated particle fuel performance model and demonstrating the integration of this model into an existing system of neutronics and heat transfer codes, creating a user-friendly option for including fuel performance analysis within system design optimization and system-level trade-off studies. The end product enables both a deeper understanding and better overall system performance of nuclear energy systems limited or greatly impacted by TRISO fuel performance. A thorium-fueled hybrid fusion-fission Laser Inertial Fusion Energy (LIFE) blanket design was used for illustrating the application of this new capability and demonstrated both the importance of integrating fuel performance calculations into mainstream design studies and the impact that this new integrated analysis had on system-level design decisions. A new TRISO fuel performance model named TRIUNE was developed and verified and validated during this work with a novel methodology established for simulating the actual lifetime of a TRISO particle during repeated passes through a pebble bed. In addition, integrated self-consistent calculations were performed for neutronics depletion analysis, heat transfer calculations, and then fuel performance modeling for a full parametric study that encompassed over 80 different design options that went through all three phases of analysis. Lastly, …
Date: November 28, 2011
Creator: Powers, J J
System: The UNT Digital Library
Suppressed Charmed B Decay (open access)

Suppressed Charmed B Decay

This thesis describes the measurement of the branching fractions of the suppressed charmed B{sup 0} {yields} D{sup (*)-} a{sub 0}{sup +} decays and the non-resonant B{sup 0} {yields} D{sup (*)-} {eta}{pi}{sup +} decays in approximately 230 million {Upsilon}(4S) {yields} B{bar B} events. The data have been collected with the BABAR detector at the PEP-II B factory at the Stanford Linear Accelerator Center in California. Theoretical predictions of the branching fraction of the B{sup 0} {yields} D{sup (*)-} a{sub 0}{sup +} decays show large QCD model dependent uncertainties. Non-factorizing terms, in the naive factorization model, that can be calculated by QCD factorizing models have a large impact on the branching fraction of these decay modes. The predictions of the branching fractions are of the order of 10{sup -6}. The measurement of the branching fraction gives more insight into the theoretical models. In general a better understanding of QCD models will be necessary to conduct weak interaction physics at the next level. The presence of CP violation in electroweak interactions allows the differentiation between matter and antimatter in the laws of physics. In the Standard Model, CP violation is incorporated in the CKM matrix that describes the weak interaction between quarks. Relations …
Date: November 28, 2011
Creator: Snoek, Hella Leonie & /Vrije U., Amsterdam
System: The UNT Digital Library
Magnetic spectroscopy and microscopy of functional materials (open access)

Magnetic spectroscopy and microscopy of functional materials

Heusler intermetallics Mn{sub 2}Y Ga and X{sub 2}MnGa (X; Y =Fe, Co, Ni) undergo tetragonal magnetostructural transitions that can result in half metallicity, magnetic shape memory, or the magnetocaloric effect. Understanding the magnetism and magnetic behavior in functional materials is often the most direct route to being able to optimize current materials for todays applications and to design novel ones for tomorrow. Synchrotron soft x-ray magnetic spectromicroscopy techniques are well suited to explore the the competing effects from the magnetization and the lattice parameters in these materials as they provide detailed element-, valence-, and site-specifc information on the coupling of crystallographic ordering and electronic structure as well as external parameters like temperature and pressure on the bonding and exchange. Fundamental work preparing the model systems of spintronic, multiferroic, and energy-related compositions is presented for context. The methodology of synchrotron spectroscopy is presented and applied to not only magnetic characterization but also of developing a systematic screening method for future examples of materials exhibiting any of the above effects. The chapter progression is as follows: an introduction to the concepts and materials under consideration (Chapter 1); an overview of sample preparation techniques and results, and the kinds of characterization methods employed …
Date: January 28, 2011
Creator: Jenkins, C.A.
System: The UNT Digital Library
Multicore Architecture-aware Scientific Applications (open access)

Multicore Architecture-aware Scientific Applications

Modern high performance systems are becoming increasingly complex and powerful due to advancements in processor and memory architecture. In order to keep up with this increasing complexity, applications have to be augmented with certain capabilities to fully exploit such systems. These may be at the application level, such as static or dynamic adaptations or at the system level, like having strategies in place to override some of the default operating system polices, the main objective being to improve computational performance of the application. The current work proposes two such capabilites with respect to multi-threaded scientific applications, in particular a large scale physics application computing ab-initio nuclear structure. The first involves using a middleware tool to invoke dynamic adaptations in the application, so as to be able to adjust to the changing computational resource availability at run-time. The second involves a strategy for effective placement of data in main memory, to optimize memory access latencies and bandwidth. These capabilties when included were found to have a significant impact on the application performance, resulting in average speedups of as much as two to four times.
Date: November 28, 2011
Creator: Srinivasa, Avinash
System: The UNT Digital Library
Structural and magnetic properties of transition metal substituted BaFe{sub 2}As{sub 2} compounds studied by x-ray and neutron scattering (open access)

Structural and magnetic properties of transition metal substituted BaFe{sub 2}As{sub 2} compounds studied by x-ray and neutron scattering

The purpose of my dissertation is to understand the structural and magnetic properties of the newly discovered FeAs-based superconductors and the interconnection between superconductivity, antiferromagnetism, and structure. X-ray and neutron scattering techniques are powerful tools to directly observe the structure and magnetism in this system. I used both xray and neutron scattering techniques on di#11;erent transition substituted BaFe2As2 compounds in order to investigate the substitution dependence of structural and magnetic transitions and try to understand the connections between them.
Date: August 28, 2012
Creator: Kim, Min Gyu
System: The UNT Digital Library
Fabrication of metal matrix composite by semi-solid powder processing (open access)

Fabrication of metal matrix composite by semi-solid powder processing

Various metal matrix composites (MMCs) are widely used in the automotive, aerospace and electrical industries due to their capability and flexibility in improving the mechanical, thermal and electrical properties of a component. However, current manufacturing technologies may suffer from insufficient process stability and reliability and inadequate economic efficiency and may not be able to satisfy the increasing demands placed on MMCs. Semi-solid powder processing (SPP), a technology that combines traditional powder metallurgy and semi-solid forming methods, has potential to produce MMCs with low cost and high efficiency. In this work, the analytical study and experimental investigation of SPP on the fabrication of MMCs were explored. An analytical model was developed to understand the deformation mechanism of the powder compact in the semi-solid state. The densification behavior of the Al6061 and SiC powder mixtures was investigated with different liquid fractions and SiC volume fractions. The limits of SPP were analyzed in terms of reinforcement phase loading and its impact on the composite microstructure. To explore adoption of new materials, carbon nanotube (CNT) was investigated as a reinforcing material in aluminum matrix using SPP. The process was successfully modeled for the mono-phase powder (Al6061) compaction and the density and density distribution were …
Date: November 28, 2012
Creator: Wu, Yufeng
System: The UNT Digital Library
Time-varying Reeb Graphs: A Topological Framework Supporting the Analysis of Continuous Time-varying Data (open access)

Time-varying Reeb Graphs: A Topological Framework Supporting the Analysis of Continuous Time-varying Data

I present time-varying Reeb graphs as a topological framework to support the analysis of continuous time-varying data. Such data is captured in many studies, including computational fluid dynamics, oceanography, medical imaging, and climate modeling, by measuring physical processes over time, or by modeling and simulating them on a computer. Analysis tools are applied to these data sets by scientists and engineers who seek to understand the underlying physical processes. A popular tool for analyzing scientific datasets is level sets, which are the points in space with a fixed data value s. Displaying level sets allows the user to study their geometry, their topological features such as connected components, handles, and voids, and to study the evolution of these features for varying s. For static data, the Reeb graph encodes the evolution of topological features and compactly represents topological information of all level sets. The Reeb graph essentially contracts each level set component to a point. It can be computed efficiently, and it has several uses: as a succinct summary of the data, as an interface to select meaningful level sets, as a data structure to accelerate level set extraction, and as a guide to remove noise. I extend these uses …
Date: November 28, 2006
Creator: Mascarenhas, A
System: The UNT Digital Library
SQUID magnetometry from nanometer to centimeter length scales (open access)

SQUID magnetometry from nanometer to centimeter length scales

The development of Superconducting QUantum Interference Device (SQUID)-based magnetometer for two applications, in vivo prepolarized, ultra-low field MRI of humans and dispersive readout of SQUIDs for micro- and nano-scale magnetometery, are the focus of this thesis.
Date: June 28, 2010
Creator: Hatridge, Michael J.
System: The UNT Digital Library
Fracture toughness of thin beryllium sheet (open access)

Fracture toughness of thin beryllium sheet

None
Date: February 28, 1974
Creator: Tardiff, G.E. Jr.
System: The UNT Digital Library
Measurement of Beam Current in the Bevatron by Induced Voltages (open access)

Measurement of Beam Current in the Bevatron by Induced Voltages

The Bevatron uses a system of electrodes through which the internal proton beam passes in order to continuously measure the magnitude and radial position of the beam. The bunched circulating beam induces a periodic voltage on the electrodes. This signal is amplified and displayed on an oscilloscope and also converted to direct current for operation of a recorder. Two types of electrode systems are used. The first is a large hollow box to provide beam magnitude signals for specialized monitoring and for primary calibration. The second system consists of two sets of smaller electrodes. One set provides beam radial-position information for tracking control, and the other provides beam magnitude information for magnitude control and for general distribution to experimenters associated with the Bevatron. A telemetering radio link is used to relay beam information to those in other areas. Problems associated with handling the beam signal are discussed, and the design principles involved in detection, amplification, and isolation of the signal are described. Calibration techniques, signal distribution facilities, and control features are also given. The systems described are stable and provide the desired information with a minimum of maintenance and operational difficulty. (auth)
Date: October 28, 1957
Creator: Lavrischeff, J. T.
System: The UNT Digital Library
Role of Li$sub 2$O on thermoluminescence in $sup 7$LiF (open access)

Role of Li$sub 2$O on thermoluminescence in $sup 7$LiF

None
Date: March 28, 1973
Creator: Toy, A.J.
System: The UNT Digital Library
A Cavity-Stabilized Oscillator With Two Feed-Back Circuits (open access)

A Cavity-Stabilized Oscillator With Two Feed-Back Circuits

None
Date: September 28, 1955
Creator: Franck, J. V.
System: The UNT Digital Library
Duality property for a hermitian scalar field (open access)

Duality property for a hermitian scalar field

None
Date: April 28, 1975
Creator: Bisognano, J.J.
System: The UNT Digital Library
THE TRIPLE--REGGE VERTEX. (open access)

THE TRIPLE--REGGE VERTEX.

None
Date: April 28, 1970
Creator: Misheloff, M. N.
System: The UNT Digital Library
A Study of Selected Properties and Applications of AlMgB14 and Related Composites: Ultra-Hard Materials (open access)

A Study of Selected Properties and Applications of AlMgB14 and Related Composites: Ultra-Hard Materials

This research presents a study of the hardness, electrical, and thermal properties AlMgB{sub 14} containing Al{sub 2}MgO{sub 4} spinel. This research also investigated how much Al{sub 2}MgO{sub 4} spinel consistently forms with AlMgB{sub 14}, if AlMgB{sub 14} materials can be produced by hot isostatic pressing (HIP), what effects TiC and TiB{sub 2} have on this composite material, and the importance of mechanical alloying. Included also is a study of the variation in hardness measurements and how they relate to SI units. Heretofore, all ultra-hard materials (hardness > 40 GPA) have been found to be cubic in structure, electrical insulators, and expensive; the behavior of AlMgB{sub 14}, which in certain specimens and compositions can have hardness values greater than 40 GPa, is therefore quite unusual since it is non-cubic, conductive, and moderate in cost. This offers an opportunity to investigate the relationship between hardness, thermal, and electrical properties from a new perspective. The main purpose of this project was to characterize the different properties of the AlMgB{sub 14} materials and to demonstrate that this material can be made in bulk. The technologies used for this study include microhardness measurement techniques, scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction spectroscopy, x-ray diffraction …
Date: May 28, 2002
Creator: Lewis, Theron L.
System: The UNT Digital Library
Two-dimensional NMR investigations of the dynamic conformations of phospholipids and liquid crystals (open access)

Two-dimensional NMR investigations of the dynamic conformations of phospholipids and liquid crystals

None
Date: May 28, 1996
Creator: Hong, Mei
System: The UNT Digital Library
Solid state nuclear magnetic resonance studies of prion peptides and proteins (open access)

Solid state nuclear magnetic resonance studies of prion peptides and proteins

None
Date: August 28, 1997
Creator: Heller, J.
System: The UNT Digital Library
Efficient biased random bit generation for parallel processing (open access)

Efficient biased random bit generation for parallel processing

A lattice gas automaton was implemented on a massively parallel machine (the BBN TC2000) and a vector supercomputer (the CRAY C90). The automaton models Burgers equation {rho}t + {rho}{rho}{sub x} = {nu}{rho}{sub xx} in 1 dimension. The lattice gas evolves by advecting and colliding pseudo-particles on a 1-dimensional, periodic grid. The specific rules for colliding particles are stochastic in nature and require the generation of many billions of random numbers to create the random bits necessary for the lattice gas. The goal of the thesis was to speed up the process of generating the random bits and thereby lessen the computational bottleneck of the automaton.
Date: September 28, 1994
Creator: Slone, D.M.
System: The UNT Digital Library
Synthesis of higher alcohols from carbon monoxide and hydrogen in a slurry reactor (open access)

Synthesis of higher alcohols from carbon monoxide and hydrogen in a slurry reactor

Higher, i.e. C{sub 2{sup +}}, alcohols are desired as gasoline additives, feedstocks for producing ethers and as alternative fuels for automobiles. In all cases, the backbone branching of an alcohol improves octane rating, which is essential for good engine performance. These types of branched, higher alcohols are the desired products for a process converting synthesis gas, a CO and H{sub 2} mixture, often generated from coal gasification. Based on this premise, promoted ZnCr oxide catalysts appear to be as one of the best avenues for further investigation. Once this investigation is complete, a natural extension is to replace the Cr in the ZnCr oxide catalyst with Mo and W, both in the same elemental triad with Cr. Mo has already been shown as an active HAS catalyst, both on a SiO{sub 2} support and in the MoS{sub 2} form. The three catalyst combinations, ZnMo, ZnW, and MnCr oxides will be tested in the stirred autoclave system. However, if none of the three indicate any comparable activity and/or selectivity toward higher alcohols as compared with other HAS catalysts, then an investigation of the effects of Cs promotion on the ZnCr oxide methanol catalysts will be executed.
Date: August 28, 1992
Creator: McCutchen, M. S.
System: The UNT Digital Library