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Compact D-D/D-T neutron generators and their applications

Description: Neutron generators based on the {sup 2}H(d,n){sup 3}He and {sup 3}H(d,n){sup 4}He fusion reactions are the most commonly available neutron sources. The applications of current commercial neutron generators are often limited by their low neutron yield and their short operational lifetime. A new generation of D-D/D-T fusion-based neutron generators has been designed at Lawrence Berkeley National Laboratory (LBNL) by using high current ion beams hitting on a self-loading target that has a large surface area to dissipate the heat load. This thesis describes the rationale behind the new designs and their potential applications. A survey of other neutron sources is presented to show their advantages and disadvantages compared to the fusion-based neutron generator. A prototype neutron facility was built at LBNL to test these neutron generators. High current ion beams were extracted from an RF-driven ion source to produce neutrons. With an average deuteron beam current of 24 mA and an energy of 100 keV, a neutron yield of >10{sup 9} n/s has been obtained with a D-D coaxial neutron source. Several potential applications were investigated by using computer simulations. The computer code used for simulations and the variance reduction techniques employed were discussed. A study was carried out to determine the neutron flux and resolution of a D-T neutron source in thermal neutron scattering applications for condensed matter experiments. An error analysis was performed to validate the scheme used to predict the resolution. With a D-T neutron yield of 10{sup 14} n/s, the thermal neutron flux at the sample was predicted to be 7.3 x 10{sup 5} n/cm{sup 2}s. It was found that the resolution of cold neutrons was better than that of thermal neutrons when the duty factor is high. This neutron generator could be efficiently used for research and educational purposes at universities. Additional applications studied were ...
Date: May 1, 2003
Creator: Lou, Tak Pui
Partner: UNT Libraries Government Documents Department

Fluid Dynamics of Carbon Dioxide Disposal into Saline Aquifers

Description: Injection of carbon dioxide (CO{sub 2}) into saline aquifers has been proposed as a means to reduce greenhouse gas emissions (geological carbon sequestration). Large-scale injection of CO{sub 2} will induce a variety of coupled physical and chemical processes, including multiphase fluid flow, fluid pressurization and changes in effective stress, solute transport, and chemical reactions between fluids and formation minerals. This work addresses some of these issues with special emphasis given to the physics of fluid flow in brine formations. An investigation of the thermophysical properties of pure carbon dioxide, water and aqueous solutions of CO{sub 2} and NaCl has been conducted. As a result, accurate representations and models for predicting the overall thermophysical behavior of the system CO{sub 2}-H{sub 2}O-NaCl are proposed and incorporated into the numerical simulator TOUGH2/ECO{sub 2}. The basic problem of CO{sub 2} injection into a radially symmetric brine aquifer is used to validate the results of TOUGH2/ECO2. The numerical simulator has been applied to more complex flow problem including the CO{sub 2} injection project at the Sleipner Vest Field in the Norwegian sector of the North Sea and the evaluation of fluid flow dynamics effects of CO{sub 2} injection into aquifers. Numerical simulation results show that the transport at Sleipner is dominated by buoyancy effects and that shale layers control vertical migration of CO{sub 2}. These results are in good qualitative agreement with time lapse surveys performed at the site. High-resolution numerical simulation experiments have been conducted to study the onset of instabilities (viscous fingering) during injection of CO{sub 2} into saline aquifers. The injection process can be classified as immiscible displacement of an aqueous phase by a less dense and less viscous gas phase. Under disposal conditions (supercritical CO{sub 2}) the viscosity of carbon dioxide can be less than the viscosity of the aqueous phase ...
Date: December 18, 2003
Creator: Garcia, Julio Enrique
Partner: UNT Libraries Government Documents Department

Ultrafast infrared studies of complex ligand rearrangements in solution

Description: The complete description of a chemical reaction in solution depends upon an understanding of the reactive molecule as well as its interactions with the surrounding solvent molecules. Using ultrafast infrared spectroscopy it is possible to observe both the solute-solvent interactions and the rearrangement steps which determine the overall course of a chemical reaction. The topics addressed in these studies focus on reaction mechanisms which require the rearrangement of complex ligands and the spectroscopic techniques necessary for the determination of these mechanisms. Ligand rearrangement is studied by considering two different reaction mechanisms for which the rearrangement of a complex ligand constitutes the most important step of the reaction. The first system concerns the rearrangement of a cyclopentadienyl ring as the response of an organometallic complex to a loss of electron density. This mechanism, commonly referred to as ''ring slip'', is frequently cited to explain reaction mechanisms. However, the ring slipped intermediate is too short-lived to be observed using conventional methods. Using a combination of ultrafast infrared spectroscopy and electronic structure calculations it has been shown that the intermediate exists, but does not form an eighteen-electron intermediate as suggested by traditional molecular orbital models. The second example examines the initial steps of alkyne polymerization. Group 6 (Cr, Mo, W) pentacarbonyl species are generated photolytically and used to catalyze the polymerization of unsaturated hydrocarbons through a series of coordination and rearrangement steps. Observing this reaction on the femto- to millisecond timescale indicates that the initial coordination of an alkyne solvent molecule to the metal center results in a stable intermediate that does not rearrange to form the polymer precursor. This suggests that polymerization requires the dissociation of additional carbonyl ligands before rearrangement can occur. Overall, this research demonstrates the importance of examining reaction dynamics on the ultrafast timescale. In the case of both ...
Date: Spring 2003
Creator: Payne, Christine K.
Partner: UNT Libraries Government Documents Department

A simulation-based study of HighSpeed TCP and its deployment

Description: The current congestion control mechanism used in TCP has difficulty reaching full utilization on high speed links, particularly on wide-area connections. For example, the packet drop rate needed to fill a Gigabit pipe using the present TCP protocol is below the currently achievable fiber optic error rates. HighSpeed TCP was recently proposed as a modification of TCP's congestion control mechanism to allow it to achieve reasonable performance in high speed wide-area links. In this research, simulation results showing the performance of HighSpeed TCP and the impact of its use on the present implementation of TCP are presented. Network conditions including different degrees of congestion, different levels of loss rate, different degrees of bursty traffic and two distinct router queue management policies were simulated. The performance and fairness of HighSpeed TCP were compared to the existing TCP and solutions for bulk-data transfer using parallel streams.
Date: April 29, 2003
Creator: Souza, Evandro de
Partner: UNT Libraries Government Documents Department

Maskless, resistless ion beam lithography

Description: As the dimensions of semiconductor devices are scaled down, in order to achieve higher levels of integration, optical lithography will no longer be sufficient for the needs of the semiconductor industry. Alternative next-generation lithography (NGL) approaches, such as extreme ultra-violet (EUV), X-ray, electron-beam, and ion projection lithography face some challenging issues with complicated mask technology and low throughput. Among the four major alternative NGL approaches, ion beam lithography is the only one that can provide both maskless and resistless patterning. As such, it can potentially make nano-fabrication much simpler. This thesis investigates a focused ion beam system for maskless, resistless patterning that can be made practical for high-volume production. In order to achieve maskless, resistless patterning, the ion source must be able to produce a variety of ion species. The compact FIB system being developed uses a multicusp plasma ion source, which can generate ion beams of various elements, such as O{sub 2}{sup +}, BF{sub 2}{sup +}, P{sup +} etc., for surface modification and doping applications. With optimized source condition, around 85% of BF{sub 2}{sup +}, over 90% of O{sub 2}{sup +} and P{sup +} have been achieved. The brightness of the multicusp-plasma ion source is a key issue for its application to maskless ion beam lithography. It can be substantially improved by optimizing the source configuration and extractor geometry. Measured brightness of 2 keV He{sup +} beam is as high as 440 A/cm{sup 2} {center_dot} Sr, which represents a 30x improvement over prior work. Direct patterning of Si thin film using a focused O{sub 2}{sup +} ion beam has been investigated. A thin surface oxide film can be selectively formed using 3 keV O{sub 2}{sup +} ions with the dose of 10{sup 15} cm{sup -2}. The oxide can then serve as a hard mask for patterning of the Si ...
Date: March 10, 2003
Creator: Ji, Qing
Partner: UNT Libraries Government Documents Department

Measurement of the beta-neutrino correlation in laser trapped {sup 21}Na

Description: Trapped radioactive atoms are an appealing source for precise measurements of the beta-neutrino correlation coefficient, a, since the momentum of the neutrino can be inferred from the detection of the unperturbed low-energy recoil daughter nucleus. Sodium-21 is produced on-line at the 88'' cyclotron at Lawrence Berkeley National Laboratory, and 8e5 atoms have been maintained in a magneto-optical trap. A static electric field draws daughter Neon-21 ions to a microchannel plate detector and betas are detected in coincidence with a plastic scintillator beta detector. The Neon-21 time-of-flight distribution determines the beta neutrino correlation coefficient, a. The resulting charge-state distribution is compared to a simple model based on the sudden approximation which suggests a small but important contribution from nuclear recoil-induced ionization. A larger than expected fraction of the daughters are detected in positive charge-states, but no dependence on either the beta or recoil nucleus energy was observed. We find a = 0.5243 plus or minus 0.0092, which is in 3.6 sigma disagreement with the Standard Model prediction of a = 0.559 plus or minus 0.003. Aside from a deviation from the Standard Model, a possible explanation for the discrepancy is that the branching ratio to the first excited state is in error.
Date: June 1, 2003
Creator: Scielzo, Nicholas David
Partner: UNT Libraries Government Documents Department

Geometry, topology, and string theory

Description: A variety of scenarios are considered which shed light upon the uses and limitations of classical geometric and topological notions in string theory. The primary focus is on situations in which D-brane or string probes of a given classical space-time see the geometry quite differently than one might naively expect. In particular, situations in which extra dimensions, non-commutative geometries as well as other non-local structures emerge are explored in detail. Further, a preliminary exploration of such issues in Lorentzian space-times with non-trivial causal structures within string theory is initiated.
Date: July 10, 2003
Creator: Varadarajan, Uday
Partner: UNT Libraries Government Documents Department

High p<sub partial> inclusive charged hadron distributions in Au+Au collisions at square root(s<sub NN>) = 130 Gev at RHIC

Description: This thesis reports the measurement of the inclusive charged particle (h{sup +} + h{sup -}) p{perpendicular} spectra for 1.7 < p{perpendicular} < 6 GeV/c at midrapidity (|{eta}| < 0.5) as a function of various centrality classes in Au+Au collisions at {radical}s{sub NN} = 130 GeV. Hadron suppression is observed relative to both scaled NN and peripheral Au+Au reference data, possibly indicating non-Abelian radiative energy loss in a hot, dense medium.
Date: July 1, 2003
Creator: Choi, Bum
Partner: UNT Libraries Government Documents Department

Electron-positron production in ultra-peripheral heavy-ion collisions with the STAR experiment

Description: This thesis presents a measurement of the cross-section of the purely electromagnetic production of e{sup +}e{sup -} pairs accompanied by mutual nuclear Coulomb excitation AuAu {yields} Au*Au* + e{sup +}e{sup -}, in ultra-peripheral gold-gold collisions at RHIC at the center-of-mass collision energy of {radical}S{sub NN} = 200 GeV per nucleon. These reactions were selected by detecting neutron emission by the excited gold ions in the Zero Degree Calorimeters. The charged tracks in the e{sup +}e{sup -} events were reconstructed with the STAR Time Projection Chamber. The detector acceptance limits the kinematical range of the observed e{sup +}e{sup -} pairs; therefore the measured cross-section is extrapolated to 4{pi} with the use of Monte Carlo simulations. We have developed a Monte Carlo simulation for ultra-peripheral e{sup +}e{sup -} production at RHIC based on the Equivalent Photon Approximation, the lowest-order QED e{sup +}e{sup -} production cross-section by two real photons and the assumption that the mutual nuclear excitations and the e{sup +}e{sup -} production are independent (EPA model). We compare our experimental results to two models: the EPA model and a model based on full QED calculation of the e{sup +}e{sup -} production, taking the photon virtuality into account. The measured differential cross-section d{sigma}/dM{sub inv} (M{sub inv} - e{sup +}e{sup -} invariant mass) agrees well with both theoretical models. The measured differential cross-section d{sigma}/dp{sub {perpendicular}}{sup tot} (p{sub {perpendicular}}{sup tot} - e{sup +}e{sup -} total transverse momentum) favors the full QED calculation over the EPA model.
Date: August 1, 2003
Creator: Morozov, Vladimir Borisovitch
Partner: UNT Libraries Government Documents Department

Coaching Behavior Preferences of Interscholastic Athletes

Description: The purpose of this study was to determine whether coaching behavior preferences of interscholastic athletes differ as a function of gender and type of sport. The Coaching Behavior Questionnaire (CBQ; Martin & Barnes, 1999) was administered to 372 interscholastic athletes. The mean scores of the participants' responses to each subscale on the CBQ were the dependent variables and gender and type of sport were the independent variables. Descriptive statistics revealed that female and male interscholastic athletes who perform on coactive, mixed, and interactive sport teams preferred coaches who engage in supportive and instructional behaviors, as opposed to non-responses or negative responses. A 2 (Gender) X 3 (Type of Sport) MANOVA and discriminant function analyses indicated that gender and the degree of interdependency between group members affects preferred coaching behavior. Thus, coaches should consider situational factors and personal characteristics when working with interscholastic athletes.
Date: May 2003
Creator: Kravig, Seth Dayton
Partner: UNT Libraries

Analysis and expression of the cotton gene for the D-12 fatty acid desaturases 2-4 (FAD2-4)

Description: A genomic clone containing a 16.9-kb segment of cotton DNA was found to encompass a D-12 fatty acid desaturases (FAD2-4) gene. The FAD2-4 gene has a single, large intron of 2,780 bp in its 5'-untranslated region, just 12 bp upstream from the ATG initiation codon of the FAD2-4 opening reading frame. A number of prospective promoter elements, including several light-responsive sequences, occur in the 5'-flanking region. The coding region of the gene is 1155 bp with no introns, and would encode a FAD2-4 polypeptide of 384 amino acids. The putative protein had four membrane-spanning helices, hallmarks of an integral membrane protein, and would probably be located in the endoplasmic reticulum. The FAD2-4 gene is indeed a functional gene, since yeast cells transformed with a plasmid containing the coding region of the gene synthesize an appreciable amount of linoleic acid (18:2), not normally made in wild-type yeast cells. The FAD2-4 gene has many structural similarities to the cotton FAD2-3 gene that was also analyzed in this laboratory.
Date: August 2003
Creator: Park, Stacy J.
Partner: UNT Libraries

Agent-Based Architecture for Web Deployment of Multi-Agents as Conversational Interfaces.

Description: Agent-based architecture explains the rationale and basis for developing agents that can interact with users through natural language query/answer patterns developed systematically using AIML (artificial intelligence mark-up language) scripts. This thesis research document also explains the architecture for VISTA (virtual interactive story-telling agents), which is used for interactive querying in educational and recreational purposes. Agents are very effective as conversational interfaces when used along side with graphical user interface (GUI) in applications and Web pages. This architecture platform can support multiple agents with or with out sharing of knowledgebase. They are very useful as chat robots for recreational purposes, customer service and educational purposes. This platform is powered by Java servlet implementation of Program D and contained in Apache Tomcat server. The AIML scripting language defined here in is a generic form of XML language and forms the knowledgebase of the bot. Animation is provided with Microsoft® Agent technology and text-to-speech support engine.
Date: May 2003
Creator: Pothuru, Ranjit Kumar
Partner: UNT Libraries

Analysis of Japanese Exports and Imports of Rice

Description: This research shows that the Japanese rice policy has affected the volume of exported and imported rice; moreover, multilateral and bilateral agreements have also affected Japanese rice policy. Japan's institution of subsidies and trade barriers has made its rice products too expensive for foreign trade and its domestic consumers. Since the WTO agreement has forced Japan to open its market gradually over six years, Japan may be unable to compete internationally because of its limited land, high labor costs, and the field utility fees.
Date: May 2003
Creator: Shiraiwa, Toshio
Partner: UNT Libraries

Deposition and Characterization of Pentacene Film.

Description: Many organic materials have been studied to be used as semiconductors, few of them being pentacene and polythiophene. Organic semiconductors have been investigated to make organic thin film transistors. Pentacene has been used in the active region of the transistors. Transistors fabricated with pentacene do not have very high mobility. But in some applications, high mobility is not needed. In such application other properties of organic transistors are used, such as, ease of production and flexibility. Organic thin film transistors (OTFT) can find use as low density storage devices, such as smart cards or I.D. tags, and displays. OTFT are compatible with polymeric substrates and hence can find use as flexible computer screens. This project aims at making 'smart clothes', the cheap way, with pentacene based OTFT. This problem in lieu of thesis describes a way to deposit pentacene films and characterize it. Pentacene films were deposited on substrates and characterized using x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The substrate used was ~1500Å platinum on silicon wafer or bare silicon wafer. was used. A deposition system for vacuum deposition of pentacene was assembled. The XRD data for deposited pentacene films shows the presence of two phases, single crystal phase (SCP) and thin film phase (TFP), and the increase in percentage of SCP with increase in substrate temperature during deposition or by annealing the deposited film, in vacuum, at 80°C.
Date: December 2003
Creator: Singh, Nidhi
Partner: UNT Libraries

Case-Based Reasoning for Children Story Selection in ASP.NET

Description: This paper describes the general architecture and function of a Case-Based Reasoning (CBR) system implemented with ASP.NET and C#. Microsoft Visual Studio .NET and XML Web Services provide a flexible, standards-based model that allows clients to access data. Web Form Pages offer a powerful programming model for Web-enabled user interface. The system provides a variety of mechanisms and services related to story retrieval and adaptation. Users may browse and search a library of text stories. More advanced CBR capabilities were also implemented, including a multi-factor distance-calculation for matching user interests with stories in the library, recommendations on optimizing search, and adaptation of stories to match user interests.
Date: December 2003
Creator: Hu, Demin
Partner: UNT Libraries

The aquatic insect communities of Holbrook Creek and Cochetopa Creek in Colorado.

Description: The first objective for this problem in lieu of thesis project was to gather, identify to the lowest practical taxonomic level and organize all available aquatic insects collected from high altitude Colorado aquatic systems during the summers of 1994, 1996, 1998, and 2002 for the University of North Texas Environmental Science Field Course (BIOL 5650). The curated collection will be housed in the Elm Fork Natural History Museum, located at the University of North Texas. The second objective was to provide a summary and discussion of the occurrence and distribution of the aquatic insects collected from Mt. Blanca in 1994, 1996, and 1998 and to create a taxa list of aquatic insects collected from Cochetopa Creek during the summer of 2002.
Date: December 2003
Creator: Wallace, Mark Allen
Partner: UNT Libraries

Content-Based Image Retrieval by Integration of Metadata Encoded Multimedia Features in Constructing a Video Summarizer Application.

Description: Content-based image retrieval (CBIR) is the retrieval of images from a collection by means of internal feature measures of the information content of the images. In CBIR systems, text media is usually used only to retrieve exemplar images for further searching by image feature content. This research work describes a new method for integrating multimedia text and image content features to increase the retrieval performance of the system. I am exploring the content-based features of an image extracted from a video to build a storyboard for search retrieval of images. Metadata encoded multimedia features include extracting primitive features like color, shape and text from an image. Histograms are built for all the features extracted and stored in a database. Images are searched based on comparing these histogram values of the extracted image with the stored values. These histogram values are used for extraction of keyframes from a collection of images parsed from a video file. Individual shots of images are extracted from a video clip and run through processes that extract the features and build the histogram values. A keyframe extraction algorithm is run to get the keyframes from the collection of images to build a storyboard of images. In video retrieval, speech recognition and other multimedia encoding could help improve the CBIR indexing technique and makes keyframe extraction and searching effective. Research in area of embedding sound and other multimedia could enhance effective video retrieval.
Date: May 2003
Creator: Anusuri, Ramprasad
Partner: UNT Libraries

The Creation of Modern Fashions through the Merging of Eastern and Western culture: Spring Message

Description: I have always believed the design of clothes should not try to conceal the naked body but should act as a catalyst that reveals the existence and strength of the individual. Spring Message includes three phases, Spring Message, Mystification, and My Paradise to reflect my three life experiences. Spring Message is an attempt to express my thoughts and ideas though designs in fashion, which were derived from the ancient beliefs, traditions, and western influence I have experienced. Through my individual pieces and creations I hope the viewer will be able to see who I am, where I came from, and understand the happiness and changes in my life.
Date: May 2003
Creator: Cui, Yan
Partner: UNT Libraries

Enigmatic Realms

Description: The use of copper in my work has opened up an entirely new conceptual and esthetic world. I have expanded my vocabulary of visual imagery based on the nature of how copper reacts with fire. The organic beauty harmonizes so gracefully with the manufactured material. This new material has certainly opened up a refreshing platform on which to further develop my ideas.
Date: December 2003
Creator: Malik, Irum
Partner: UNT Libraries

Fashion Circles

Description: Through this body of work and this paper the possibilities of using Fashion Design to express the concepts of the circle has been explored. This was done with three questions in mind: How can I use the shape of the circle as inspiration for fashion design? How can I express related words and phrases in my design? and How can I use the colors black and white to emphasize the concept of my design. To answer these questions I have created two groups of garments: one was inspired by circular objects, such as cherries and drops, and the other starting from words and phrases such as "study circle" and "circle the wagons." In the first group the emphasis was on the aesthetics of the garment while the second group was more focused on meaning. All garments are black and white.
Date: December 2003
Creator: Öhrn, Linda
Partner: UNT Libraries

The Feasibility of Multicasting in RMI

Description: Due to the growing need of the Internet and networking technologies, simple, powerful, easily maintained distributed applications needed to be developed. These kinds of applications can benefit greatly from distributed computing concepts. Despite its powerful mechanisms, Jini has yet to be accepted in mainstream Java development. Until that happens, we need to find better Remote Method Invocation (RMI) solutions. Feasibility of implementation of Multicasting in RMI is worked in this paper. Multicasting capability can be used in RMI using Jini-like technique. Support of Multicast over Unicast reference layer is also studied. A piece of code explaining how it can be done, is added.
Date: May 2003
Creator: Ujjinihavildar, Vinay
Partner: UNT Libraries

OLAP Services

Description: On-line Analytical Processing (OLAP) is a very interesting platform to provide analytical power to the data present in the database. This paper discusses the system designed which handles integration of data from two remote legacy reservation systems to merge as one Integrated database server and also the design of an OLAP database and building an OLAP cube for the data warehousing. OLAP cube is useful for analysis of data and also for making various business decisions. The Data Transformation Services (DTS) in the Microsoft® SQL Server 2000 is used to integrate as a package the collection of data and also for refreshing data in the databases. On-line Analytical Processing (OLAP) cube is designed using Microsoft® Analysis Server.
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Date: December 2003
Creator: Sanghvi, Rajendra
Partner: UNT Libraries

Painting with Clay

Description: The body of work created during this exploration indicates that painting approach can actively integrate with the clay element. The main point is the surface manipulation during this process. There are four factors relate to this manipulation: timing, action, style, and size. Overall, the painting approach can be modified to create a truly active relationship with clay element. The final touch by the fire and glazing techniques reflect paintings approach may be used in a variety way to decorate the clay element without any limits. Moreover, the painting approach need not be subordinate to the clay element. It can be used not only to complement the clay, but also to enhance any given clay pieces no matter what the shape is.
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Date: December 2003
Creator: Pan, Yi-Tze
Partner: UNT Libraries