Studies in ion source development for application in heavy ion fusion (open access)

Studies in ion source development for application in heavy ion fusion

The overall purpose of these experiments is to contribute to the development of ion injector technology in order to produce a driver for use in a heavy-ion-fusion (HIF) power generating facility. The overall beam requirements for HIF are quite demanding; a short list of the constraints is the following: (1) Low cost (a large portion of overall cost will come from the beam system); (2) Bright, low emittance beam; (3) Total beam energy 5MJ; (4) Spot size 3mm (radius); (5) Pulse Duration 10ns; (6) Current on target 40kA; (7) Repetition Rate 5Hz; (8) Standoff from target 5m; and (9) Transverse Temp < 1 keV. The reasons for employing ion beams in inertial fusion systems become obvious when the repetition rate required is considered. While laser drivers are useful in producing a proof-of-concept, they will be incapable of application in power generation. Consequently attempts in the U.S. to achieve a power generating system make use of linear ion accelerators. It is apparent that the accelerator system requires the highest quality input as obtainable. Therefore injector design is an essential portion of the entire inertial fusion system. At Lawrence Berkeley and Lawrence Livermore National Laboratories experiments are being conducted using two injector …
Date: May 30, 2004
Creator: Kapica, Jonathan G.
System: The UNT Digital Library
Diffusion in silicon isotope heterostructures (open access)

Diffusion in silicon isotope heterostructures

The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and {sup 28}Si enriched layers, enables the observation of {sup 30}Si self-diffusion from the natural layers into the {sup 28}Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale …
Date: May 14, 2004
Creator: Silvestri, Hughes Howland
System: The UNT Digital Library
Recombination and propagation of quasiparticles in cuprate superconductors (open access)

Recombination and propagation of quasiparticles in cuprate superconductors

Rapid developments in time-resolved optical spectroscopy have led to renewed interest in the nonequilibrium state of superconductors and other highly correlated electron materials. In these experiments, the nonequilibrium state is prepared by the absorption of short (less than 100 fs) laser pulses, typically in the near-infrared, that perturb the density and energy distribution of quasiparticles. The evolution of the nonequilibrium state is probed by time resolving the changes in the optical response functions of the medium that take place after photoexcitation. Ultimately, the goal of such experiments is to understand not only the nonequilibrium state, but to shed light on the still poorly understood equilibrium properties of these materials. We report nonequilibrium experiments that have revealed aspects of the cup rates that have been inaccessible by other techniques. Namely, the diffusion and recombination coefficients of quasiparticles have been measured in both YBa{sub 2}Cu{sub 3}O{sub 6.5} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} using time-resolved optical spectroscopy. Dependence of these measurements on doping, temperature and laser intensity is also obtained. To study the recombination of quasiparticles, we measure the change in reflectivity {Delta}R which is directly proportional to the nonequilibrium quasiparticle density created by the laser. From the intensity dependence, we estimate …
Date: May 20, 2004
Creator: Gedik, Nuh
System: The UNT Digital Library
Aspherical supernovae (open access)

Aspherical supernovae

Although we know that many supernovae are aspherical, the exact nature of their geometry is undetermined. Because all the supernovae we observe are too distant to be resolved, the ejecta structure can't be directly imaged, and asymmetry must be inferred from signatures in the spectral features and polarization of the supernova light. The empirical interpretation of this data, however, is rather limited--to learn more about the detailed supernova geometry, theoretical modeling must been undertaken. One expects the geometry to be closely tied to the explosion mechanism and the progenitor star system, both of which are still under debate. Studying the 3-dimensional structure of supernovae should therefore provide new break throughs in our understanding. The goal of this thesis is to advance new techniques for calculating radiative transfer in 3-dimensional expanding atmospheres, and use them to study the flux and polarization signatures of aspherical supernovae. We develop a 3-D Monte Carlo transfer code and use it to directly fit recent spectropolarimetric observations, as well as calculate the observable properties of detailed multi-dimensional hydrodynamical explosion simulations. While previous theoretical efforts have been restricted to ellipsoidal models, we study several more complicated configurations that are tied to specific physical scenarios. We explore clumpy …
Date: May 21, 2004
Creator: Kasen, Daniel Nathan
System: The UNT Digital Library
Density, Distribution and Habitat Requirements for the Ozark Pocket Gopher (Geomys Bursarius Ozarkensis) (open access)

Density, Distribution and Habitat Requirements for the Ozark Pocket Gopher (Geomys Bursarius Ozarkensis)

A new subspecies of the plains pocket gopher (Geomys bursarius ozarkensis), located in the Ozark Mountains of north central Arkansas, was recently described by Elrod et al. (2000). Current range for G. b. ozarkensis was established, habitat preference was assessed by analyzing soil samples, vegetation and distance to stream and potential pocket gopher habitat within the current range was identified. A census technique was used to estimate a total density of 3, 564 pocket gophers. Through automobile and aerial survey 51 known fields of inhabitance were located extending the range slightly. Soil analyses indicated loamy sand as the most common texture with a slightly acidic pH and a broad range of values for other measured soil parameters and 21 families of vegetation were identified. All inhabited fields were located within an average of 107.2m from waterways and over 1,600 hectares of possible suitable habitat was identified.
Date: May 2004
Creator: Kershen, Audrey Allbach
System: The UNT Digital Library
Mobile agent security through multi-agent cryptographic protocols. (open access)

Mobile agent security through multi-agent cryptographic protocols.

An increasingly promising and widespread topic of research in distributed computing is the mobile agent paradigm: code travelling and performing computations on remote hosts in an autonomous manner. One of the biggest challenges faced by this new paradigm is security. The issue of protecting sensitive code and data carried by a mobile agent against tampering from a malicious host is particularly hard but important. Based on secure multi-party computation, a recent research direction shows the feasibility of a software-only solution to this problem, which had been deemed impossible by some researchers previously. The best result prior to this dissertation is a single-agent protocol which requires the participation of a trusted third party. Our research employs multi-agent protocols to eliminate the trusted third party, resulting in a protocol with minimum trust assumptions. This dissertation presents one of the first formal definitions of secure mobile agent computation, in which the privacy and integrity of the agent code and data as well as the data provided by the host are all protected. We present secure protocols for mobile agent computation against static, semi-honest or malicious adversaries without relying on any third party or trusting any specific participant in the system. The security of …
Date: May 2004
Creator: Xu, Ke
System: The UNT Digital Library
Identification and quantification of lipid metabolites in cotton fibers: Reconciliation with metabolic pathway predictions from DNA databases. (open access)

Identification and quantification of lipid metabolites in cotton fibers: Reconciliation with metabolic pathway predictions from DNA databases.

The lipid composition of cotton (Gossypium hirsutum, L) fibers was determined. Fatty acid profiles revealed that linolenate and palmitate were the most abundant fatty acids present in fiber cells. Phosphatidylcholine was the predominant lipid class in fiber cells, while phosphatidylethanolamine, phosphatidylinositol and digalactosyldiacylglycerol were also prevalent. An unusually high amount of phosphatidic acid was observed in frozen cotton fibers. Phospholipase D activity assays revealed that this enzyme readily hydrolyzed radioactive phosphatidylcholine into phosphatidic acid. A profile of expressed sequence tags (ESTs) for genes involved in lipid metabolism in cotton fibers was also obtained. This EST profile along with our lipid metabolite data was used to predict lipid metabolic pathways in cotton fiber cells.
Date: May 2004
Creator: Wanjie, Sylvia W.
System: The UNT Digital Library
Colorful Diary (open access)

Colorful Diary

Chapter I describes how my works are grounded in a Chinese point of view, based on sociological and anthropological approaches as defined in my work. The questions in my Statement of Problem deal with how I use "imbalance" in my works, yet still find a way to make acceptable compositions to better tell my stories. I relate how my work constitutes a positive act or event in an evolving world culture. Chapter II discusses the work I focused around the questions posed in Chapter I. Chapter III expresses my conclusion about my work and my goals for the future.
Date: May 2004
Creator: Wang, Nanfei
System: The UNT Digital Library
Hydrophobic, fluorinated silica xerogel for low-k applications. (open access)

Hydrophobic, fluorinated silica xerogel for low-k applications.

A new hydrophobic hybrid silica film was synthesized by introducing one silicon precursor (as modifiers) into another precursor (network former). Hybrid films have improved properties. Hydrolysis and condensation of dimethyldiethoxysilane (DMDES) (solvent (EtOH) to DMDES molar ratio R = 4, water to DMDES molar ratio r = 4, 0.01 N HCl catalyst) was analyzed using high-resolution liquid 29Si NMR. It was found that after several hours, DMDES hydrolyzed and condensed into linear and cyclic species. Films from triethoxyfluorosilane (TEFS) have been shown to be promising interlayer dielectric materials for future integrated circuit applications due to their low dielectric constant and high mechanical properties (i.e., Young's modulus (E) and hardness (H)). Co-condensing with TEFS, linear structures from DMDES hydrolysis and condensation reactions rendered hybrid films hydrophobic, and cyclic structures induced the formation of pores. Hydrophobicity characterized by contact angle, thermal stability by thermogravimetric analysis (TGA), Fourier transform Infrared spectroscopy (FTIR), contact angle, and dynamic secondary ion mass spectroscopy (DSIMS), dielectric constant determined by impedance measurement, and mechanical properties (E and H) determined by nanoindentation of TEFS and TEFS + DMDES films were compared to study the effect of DMDES on the TEFS structure. Hybrid films were more hydrophobic and thermally stable. …
Date: May 2004
Creator: Zhang, Zhengping
System: The UNT Digital Library
A Detailed Proof of the Prime Number Theorem for Arithmetic Progressions (open access)

A Detailed Proof of the Prime Number Theorem for Arithmetic Progressions

We follow a research paper that J. Elstrodt published in 1998 to prove the Prime Number Theorem for arithmetic progressions. We will review basic results from Dirichlet characters and L-functions. Furthermore, we establish a weak version of the Wiener-Ikehara Tauberian Theorem, which is an essential tool for the proof of our main result.
Date: May 2004
Creator: Vlasic, Andrew
System: The UNT Digital Library
A Personal Expression (open access)

A Personal Expression

The problem involves developing a method that leaves conventional form and form making and moves toward a spontaneous and intuitive approach. The thesis is organized into 3 chapters. The first chapter includes an introduction, statement of the problem and methodology. The second chapter describes the work in eight movements. The third chapter answers questions posed by the problem and includes a summary and conclusion. The findings are that a spontaneous, impulsive, and intuitive approach to the medium, clay, is a productive and artistic method. The medium is responsive and telling of the method and art is produced.
Date: May 2004
Creator: Veatch, Nancy Carole Steveson
System: The UNT Digital Library
Studies in regiospecific oxidation reactions of 1-methyl-pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione. (open access)

Studies in regiospecific oxidation reactions of 1-methyl-pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione.

Baeyer-Villiger oxidation of 1-methylpentacyclo[5.4.0.02,6.03,10.05,9] undecane-8,11-dione, performed by using m-chloroperbenzoic acid in 1:1 molar ratio, resulted in the formation of monolactone. The corresponding dilactone, was synthesized by reacting 1-methyl-PCU-8,11-dione with m-chloroperbenzoic acid in 1:2 molar ratio. 6-Methyl-1,4,4a,8a-tetrahydro-1,4-methanonaphthalene-5,8-dione was converted into the corresponding exo-6,7-monoepoxide via treatment with 30% aqueous hydrogen peroxide. Epoxidation of this monoepoxide by using m-chloroperbenzoic acid afforded the corresponding bis-epoxide. Ceric ammonium nitrate (CAN) promoted oxidation of 1-methyl-PCU-8,11-dione afforded "methylated lactones" and a "methylated alkene."
Date: May 2004
Creator: Vappala, Indu
System: The UNT Digital Library
Simulation of local watershed nutrient and sediment delivery to Lake Texoma. (open access)

Simulation of local watershed nutrient and sediment delivery to Lake Texoma.

A hydrologic model and watershed export model was used to estimate the loading of nutrients and total suspended solids from un-gaged local watersheds associated with Lake Texoma. Discharge to the reservoir from local watersheds was predicted using a modification of the curve number method in HEC Hydrologic Modeling System (HEC-HMS). Event mean concentrations were applied to land use to estimate loadings of nutrients and TSS. Total discharge from the local watersheds was estimated to be 3.02 x 107 cubic meters for a study window of March 1 to May 31, 1997, less than 10 percent of the input to the lake from the Red River and Washita River systems. Loadings were estimated to be 33,553 kg nitrogen, 4,401 kg phosphorus, and 3,423,140 kg TSS. The models and results obtained from their application appear to have potential utility for use in a water quality management decision support system for the reservoir.
Date: May 2004
Creator: Upton, Alexandra C.
System: The UNT Digital Library
An Analysis of the Genesis of Motive, Rhythm, and Pitch in the First Movement of the Sonata for Two Pianos and Percussion by Béla Bartók. (open access)

An Analysis of the Genesis of Motive, Rhythm, and Pitch in the First Movement of the Sonata for Two Pianos and Percussion by Béla Bartók.

This dissertation presents evidence that Béla Bartók created his masterwork, the Sonata for Two Pianos and Percussion (1937), in a very complex period of his life. Since it was a mature piece, Bartók utilized typically "Bartókian" compositional techniques and styles. His ethnomusicological studies were also influential factors in the creation of the Sonata for Two Pianos and Percussion. We can be witness to how different the first draft was to the published version; the minor and major changes are revealed in the draft study of the Sonata for Two Pianos and Percussion 's first movement. These changes allow today's musicians to reconstruct the compositional process. The first movement introduces some interesting uses of sonata form, to be explored in more detail in the analysis. Starting with linear analysis, the basic motives and rhythmic patterns are discussed and supported with Bartók's own explanations. The conclusion of this study has important ramifications for performance: it eases up the pressure on the performers, since problematic passages are analyzed and explained - preparing the players' mentally for the performance. This is music which is hard to play and difficult to analyze. The analysis, combining the results of both theoretical and musicological studies, is intended …
Date: May 2004
Creator: Ujj-Hilliard, Emöke
System: The UNT Digital Library
New Reality Resembles Old: An Examination of the American Public's Social Construction of Reality Following September 11, 2001 Terrorist Attacks (open access)

New Reality Resembles Old: An Examination of the American Public's Social Construction of Reality Following September 11, 2001 Terrorist Attacks

This thesis examines whether the September 11, 2001 terrorist attacks caused a significant, lasting change in the American public's social construction of reality. A framework of everyday reality was created which focused on beliefs, behaviors, and cultural institutions in the United States. Data regarding specific beliefs and behaviors was collected from numerous survey sources, and content analysis was performed on media literature from September 11, 2001 to September 11, 2003. Findings from this study show that beliefs examined did change, while behaviors on similar topics did not. These finding represents an interesting paradox to be evaluated in future studies. Cultural institutions, as related to the public's knowledge of and relationship with each, also appeared little changed. Therefore, while some aspects displayed adjustment, this study cannot conclusively state that American public's social construction of reality experienced a "new reality" paradigm shift as proclaimed by the media immediately following the attacks.
Date: May 2004
Creator: Stoutmeyer, Stacie L.
System: The UNT Digital Library
Crystalline Surface Challenge (open access)

Crystalline Surface Challenge

Ever since I became interested in the world of ceramics, crystalline glazes have been the most fascinating and challenging to me. Even though crystalline glazes are the most difficult and elusive to potters, their spectacular results (when done right) keep me coming back. Over the last year I have developed a crystalline glaze that yields consistent and excellent results. During this period, I have worked with these glazes in the traditional manor, being that they are only applied to smooth porcelain vessels. My proposal will be to attempt crystalline glazes on different surface textures.
Date: May 2004
Creator: Rostagno, Nicholas
System: The UNT Digital Library
A Mythic Perspective of Commodification on the World Wide Web (open access)

A Mythic Perspective of Commodification on the World Wide Web

Capitalism's success, according to Karl Marx, is based on continued development of new markets and products. As globalization shrinks the world marketplace, corporations are forced to seek both new customers and products to sell. Commodification is the process of transforming objects, ideas and even people into merchandise. The recent growth of the World Wide Web has caught the attention of the corporate world, and they are attempting to convert a free-share-based medium into a profit-based outlet. To be successful, they must change Web users' perception about the nature of the Web itself. This study asks the question: Is there mythic evidence of commodification on the World Wide Web? It examines how the World Wide Web is presented to readers of three national publications-Wired, Newsweek, and Business Week-from 1993 to 2000. It uses Barthes' two-tiered model of myths to examine the descriptors used to modify and describe the World Wide Web. The descriptors were clustered into 11 general categories, including connectivity, social, being, scene, consumption, revolution, tool, value, biology, arena, and other. Wired articles did not demonstrate a trend in categorical change from 1993 to 2000; the category of choice shifted back and forth between Revolution, Connectivity, Scene, and Being. Newsweek …
Date: May 2004
Creator: Robinson, Glendal Paul
System: The UNT Digital Library
The Effects of Teacher Certification on Freshman High School Students' Algebra I Achievement (open access)

The Effects of Teacher Certification on Freshman High School Students' Algebra I Achievement

The purpose of this study was to determine whether students taught by certified teachers and those taught by uncertified teachers had significantly different achievement on a state Algebra I End of Course examination. The specific research questions were: (1) Does type of teacher certification impact Algebra I End of Course (EOC) Exam scores for high school freshman when controlling for students' past mathematics success as measured by 8th grade TAAS mathematics test scores and teachers' years of experience? (2) Does type of teacher certification impact Algebra I End of Course (EOC) Exam passage rates for high school freshman when controlling for students' past mathematics success as measured by 8th grade TAAS mathematics test scores, socio-economic status, ethnicity, gender, and teachers' years of experience? This research was conducted in a large north Texas suburban school district. The entire population (N=1,433) of freshman students enrolled in year-long Algebra I was included for this study. Three statistical tests were used in data analysis for the first question. Analysis of covariance using student as well as teacher as the unit of analysis and hierarchical multiple regression were used to analyze students' specific scores. Logistic regression was used for the second research question. This study …
Date: May 2004
Creator: Ringrose, Laura Chamberlin
System: The UNT Digital Library
A general purpose semantic parser using FrameNet and WordNet®. (open access)

A general purpose semantic parser using FrameNet and WordNet®.

Syntactic parsing is one of the best understood language processing applications. Since language and grammar have been formally defined, it is easy for computers to parse the syntactic structure of natural language text. Does meaning have structure as well? If it has, how can we analyze the structure? Previous systems rely on a one-to-one correspondence between syntactic rules and semantic rules. But such systems can only be applied to limited fragments of English. In this thesis, we propose a general-purpose shallow semantic parser which utilizes a semantic network (WordNet), and a frame dataset (FrameNet). Semantic relations recognized by the parser are based on how human beings represent knowledge of the world. Parsing semantic structure allows semantic units and constituents to be accessed and processed in a more meaningful way than syntactic parsing, moving the automation of understanding natural language text to a higher level.
Date: May 2004
Creator: Shi, Lei
System: The UNT Digital Library
A study of the technology leadership of Texas high school principals. (open access)

A study of the technology leadership of Texas high school principals.

Effectively integrating technology into school requires the presence of informed and visionary leadership. Past research on change in schools demonstrates the importance of the principal to that process. In that research it is obvious that the principal must possess more than skills and knowledge about the change, he or she must also possess leadership skills to lead the campus through the change. Despite this finding, very little research has been attempted to determine the leadership knowledge and skills of principals for technology integration. This study attempts to investigate the technology leadership of high school principals in Texas using the National Educational Technology Standards for Administrators (NETS*A). In addition, this study compares technology leadership among principals who have attended the Technology Leadership Academy with those who have not attended this training. The two questions that guided this study are: (1) What are the technology leadership actions of Texas' high school principals in each of the six technology leadership standards identified by the NETS*A standard document? (2) How are the technology leadership practices of high school principals who participated in the Technology Leadership Academy sponsored by TASA and TBEC different from those who have not participated in the training? Because no existing …
Date: May 2004
Creator: Seay, D. Alan
System: The UNT Digital Library
The Effects of Sign Language on the Vocal Responses of a Child with Autism. (open access)

The Effects of Sign Language on the Vocal Responses of a Child with Autism.

Sign language is an effective form of alternative communication for persons with autism and other developmental disabilities. Only a few studies have systematically measured the effects of sign language on the vocal responses of its users. This study employed a multiple baseline design to evaluate the effects of sign language on the vocal responses of a four-year-old boy with autism. Results indicate that a reinforcement contingency placed only on sign responses is inadequate for maintaining vocal responses. When a reinforcement contingency is placed on sign responses as well as vocal responses that the user is capable of emitting in verbal imitation, both sign and vocal responses are maintained. Results are discussed in terms of the need for a reinforcement contingency placed on vocal and sign responses, the effects of teaching procedures on response variability, and the need for future research to examine procedures utilized to teach sign language to persons within the developmental disabilities population.
Date: May 2004
Creator: Scarbro-McLaury, Jill
System: The UNT Digital Library
Some String or Another: Fiction and Nonfiction Stories of Connection (open access)

Some String or Another: Fiction and Nonfiction Stories of Connection

Some String or Another: Fiction and Nonfiction Stories of Connection, a creative thesis, explores patterns of change in stories from the perspective of connection and disconnection. The preface examines the effects of temporal disconnection, the relationship of conflict and connection to narrative rhythm, and the webs of connection formed during the process of creation. Included in the body of the work are six fiction stories, one metafiction story, and two nonfiction essays.
Date: May 2004
Creator: Salts, Diane Michelle
System: The UNT Digital Library
Judicial Enforcers? Exploring Lower Federal Court Compliance in Regulating the Obscene (open access)

Judicial Enforcers? Exploring Lower Federal Court Compliance in Regulating the Obscene

Although federal circuit and district court judges are placed within a federal hierarchy, and receive legal and judicial training that emphasizes the importance of the judicial framework and its structure, such judges are also subjected to other pressures such as the types of litigants within the courtrooms as well as their local political environment. Furthermore, such judges are apt to form their own views about politics and legal policy and are often appointed by presidents who approve of their ideological leanings. Thus, federal courts are caught between competing goals such as their willingness to maximize their preferred legal policy, and their place within the judicial hierarchy. This dissertation applies hierarchy and impact theory to assess the importance of the judicial framework and its socialization, by analyzing both the judicial opinions and votes of federal circuit and district court judges in obscenity cases during a four-decade period (1957-1998). The research presented here finds the influence of higher court precedent to correspond in part with the conception of a judicial hierarchy. An analysis of citations of Supreme Court precedent (Roth v. United States (1957) and Miller v. California (1973)) in lower court majority opinions suggests low levels of compliance: lower courts at …
Date: May 2004
Creator: Ryan, John Francis
System: The UNT Digital Library
On the Relation between Stimulus Equivalence and Extension of Stimulus Function (open access)

On the Relation between Stimulus Equivalence and Extension of Stimulus Function

The purpose of this study was to examine the relation between stimulus equivalence (briefly, networks of relations among stimuli) and the extension of stimulus function (briefly, spread of effect across network) more closely than has been possible before. The traditional view of this relation suggests that equivalence classes mediate the extension of stimulus function and are, therefore, necessary for any extension to occur. This study used a preparation in which the conditional discriminations required for the development of equivalence classes and the simple discriminations required for the extension of function were trained or tested simultaneously. Results suggest that equivalence are not necessary for the extension of stimulus function though they may be sufficient.
Date: May 2004
Creator: Hartman, Carrie
System: The UNT Digital Library