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25,827 Matching Results
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Laser-plasma interactions relevant to Inertial Confinement Fusion
Research into laser-driven inertial confinement fusion is now entering a critical juncture with the construction of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). Many of the remaining unanswered questions concerning NIF involve interactions between lasers and plasmas. With the eventual goal of fusion power in mind, laser-plasma interactions relevant to laser fusion schemes is an important topic in need of further research. This work experimentally addresses some potential shortcuts and pitfalls on the road to laser-driven fusion power. Current plans on NIF have 192 laser beams directed into a small cylindrical cavity which will contain the fusion fuel; to accomplish this the beams must cross in the entrance holes, and this intersection will be in the presence of outward-flowing plasma. To investigate the physics involved, interactions of crossing laser beams in flowing plasmas are investigated with experiments on the Nova laser facility at LLNL. It was found that in a flowing plasma, energy is transferred between two crossing laser beams, and this may have deleterious consequences for energy balance and ignition in NIF. Possible solutions to this problem are presented. A recently-proposed alternative to standard laser-driven fusion, the ''fast ignitor'' concept, is also experimentally addressed in …
Date:
November 2, 1998
Creator:
Wharton, Kenneth Bradford
System:
The UNT Digital Library
Design, Construction, and Application of an Electrostatic Quadrupole Doublet for Heavy Ion Nuclear Microprobe Research
A nuclear microprobe, typically consisting of 2 - 4 quadrupole magnetic lenses and apertures serving as objective and a collimating divergence slits, focuses MeV ions to approximately 1 x 1 μm for modification and analysis of materials. Although far less utilized, electrostatic quadrupole fields similarly afford strong focusing of ions and have the added benefit of doing so independent of ion mass. Instead, electrostatic quadrupole focusing exhibits energy dependence on focusing ions. A heavy ion microprobe could extend the spatial resolution of conventional microprobe techniques to masses untenable by quadrupole magnetic fields. An electrostatic quadrupole doublet focusing system has been designed and constructed using several non-conventional methods and materials for a wide range of microprobe applications. The system was modeled using the software package "Propagate Rays and Aberrations by Matrices" which quantifies system specific parameters such as demagnification and intrinsic aberrations. Direct experimental verification was obtained for several of the parameters associated with the system. Details of the project and with specific applications of the system are presented.
Date:
December 2017
Creator:
Manuel, Jack Elliot
System:
The UNT Digital Library
Children with Emotional and Behavioral Disorders in Saudi Arabia: A Preliminary Prevalence Screening
Education in Saudi Arabia, including the education of children with special needs, is developing rapidly. However, children with emotional and behavioral disorders are neither consistently identified nor adequately served in Saudi Arabia although they are recognized as a distinct category of children who require special education services. The goal of this study was to examine the prevalence of emotional and behavioral disorders among children in Saudi Arabia to assess the need for intervention services to help those children reach their potential. The current research identified the types of behaviors that are most evident in the study sample. Also, the relationship between demographics and emotional and behavioral disorders is studied to identify possible predictors of disruptive forms of behavior. Parents of children aged 4-17 years in Saudi Arabia were surveyed using the Strengths and Difficulties Questionnaire. The findings of the study suggest that children with emotional and behavioral disorders in Saudi Arabia may account for 20% of the population of children between the ages of 4 and 17. The findings also revealed that over 20% of children in Saudi Arabia have difficulties in peer relationship and lack the necessary prosocial behaviors. The parent reporting, child gender, child education type, the geographical …
Date:
December 2017
Creator:
Maajeeny, Hassan
System:
The UNT Digital Library
Homologs of Mammalian Lysosomal Lipase in Arabidopsis and Their Roles in Lipid Droplet Dynamics
Lipid droplets (LDs) are organelles with many functions in cells and numerous protein interactors facilitate their biogenesis, maintenance, and turnover. The mammalian lipase responsible for LD turnover during lipophagy, LipA, has two candidate homologs in Arabidopsis: MPL1 and LIP1. One or both of these plant homologs may function in a similar manner to mammalian LipA, providing an LD breakdown pathway. To test this hypothesis, wild type (WT) Arabidopsis plants, MPL1 over-expressing (OE) mutants, and T-DNA insertion mutants of MPL1 (mpl1) and LIP1 (lip1) were examined for LD phenotypes in normal conditions and in environments where LD numbers are known to fluctuate. Plants to be imaged by confocal microscopy were exposed to heat stress and wounding to increase LD accumulation, senescence was induced in leaves to deplete lipids, and LDs were imaged throughout the day/night period to observe their diurnal regulation. The mutation of both MPL1 and LIP1 lead to an increase in LDs within the leaf mesophyll cells, although the spatial distribution of the LDs differed between the two mutants. mpl1 mutants had disrupted diurnal regulation of their LDs, but lip1 mutants did not. Alternately, lip1 mutants retained LDs during dark-induced senescence, and mpl1 mutants did not. Together these results …
Date:
December 2017
Creator:
McClinchie, Elizabeth A
System:
The UNT Digital Library
"A Kind of Ghost"
A mosaic of past and present, mother and daughter, body and spirit: A Kind of Ghost inhabits memory and imagined spaces, haunting and begging to be remembered.
Date:
December 2017
Creator:
Pilcher, Lauren
System:
The UNT Digital Library
Irradiation induced dislocation climb in Cu--Al alloys of different stacking fault energies
None
Date:
June 1, 1975
Creator:
Kosel, Thomas Hebert
System:
The UNT Digital Library
Cattle Capitalists: The XIT Empire in Texas and Montana
The Texas Constitution of 1876 set aside three million acres of Texas public land in exchange for construction of the monumental red granite Capitol that continues to house Texas state government today. The Capitol project and the land went to an Illinois syndicate led by men influential in business and politics. Austin's statehouse is a recognizable symbol of Texas around the world. So too, the massive Panhandle tract given in exchange -- what became the "fabulous" XIT Ranch -- has come to, for many, symbolize Texas and its role in the nineteenth century cattle boom. After finding sales prospects for the land, known as the Capitol Reservation, weak at the time, backed by British capital, the Illinois group, often called the Capitol Syndicate, turned their efforts to cattle ranching to satisfy investors until demand for the land increased. The operation included a satellite ranch in Montana to which two-year-old steers from Texas were sent for fattening, often "over the trail" on a route increasingly blocked by people and settlement. Rather than a study focused on ranching operations on the ground -- the roundups, the cattle drives, the cowboys -- this instead uncovers the business and political side of the Syndicate's …
Date:
December 2017
Creator:
Miller, Michael M.
System:
The UNT Digital Library
Niche Expansion of an Invasive Predator (Neovison vison), Prey Response, and Facilitative Interactions with Other Invasive Mammals at the Southern End of the Americas: Conservation Challenges and Potential Solutions
The Cape Horn Biosphere Reserve is located at the southern tip of South America. This large archipelago is considered one of the last pristine areas left on the world. Despite it being an unpopulated area with most of the native forest cover intact, it has not been exempt from biological invasions, one of the major drivers of biodiversity loss. Three species that naturally interact in their native range in North America – American beavers (Castor canadensis), muskrats (Ondatra zibethicus), and American mink (Neovison vison) – were independently introduced in this remote region. In my dissertation, I investigated (i) the hypothesis of niche expansion in the invasive mink population on Navarino Island towards terrestrial habitats; (ii) potential mink impact on breeding success of forest-bird populations; (iii) habitat selection of small-rodent species and their perception on the mink's novel predation risk; and (iv) the dynamics of multiple-species invasions under the hypothesis of an invasional meltdown. Additionally, I worked within the framework of environmental philosophy. I provide an example of combining ecological and cultural dimensions within the International Long-Term Ecological Research network to disentangle the ethical dilemmas that surround the management of invasive species. I finally proposed a management plan based on the …
Date:
December 2017
Creator:
Crego, Ramiro Daniel
System:
The UNT Digital Library
Surface Degradation Behavior of Bulk Metallic Glasses and High Entropy Alloys
In this study, the surface degradation behavior was studied for typical examples from bulk metallic glasses (BMGs), metallic glass composites (MGCs) and high entropy alloys (HEAs) alloy systems that are of scientific and commercial interest. The corrosion and wear behavior of two Zr-based bulk metallic glasses, Zr41.2Cu12.5Ni10Ti13.8Be22.5 and Zr57Cu15.4Ni12.6Al10Nb5, were evaluated in as-cast and thermally relaxed states. Significant improvement in corrosion rate, wear behavior, and friction coefficient was seen for both the alloys after thermal relaxation. Fully amorphous structure was retained with thermal relaxation below the glass transition temperature. This improvement in surface properties was explained by annihilation of free volume, the atomic scale defects in amorphous metals resulting from kinetic freezing. Recently developed MGCs, with in situ crystalline ductile phase, demonstrate a combination of mechanical properties and fracture behavior unseen in known structural metals. The composites showed higher wear rates but lower coefficient of friction compared to monolithic amorphous glasses. No tribolayer formation was seen for the composites in sharp contrast to that of the monolithic metallic glasses. Corrosion was evaluated by open circuit potential (OCP) analysis and potentiodynamic polarization. Site-specific corrosion behavior was studied by scanning vibration electrode technique (SVET) to identify formation of galvanic couples. Scanning kelvin …
Date:
December 2017
Creator:
Ayyagari, Venkata A
System:
The UNT Digital Library
Determination of toxic material penetrations for wildland respirator filters
Thousands of wildland firefighters are exposed to high levels of toxic materials every year. Carbon monoxide, formaldehyde and acrolein gases, along with high particulate concentrations, are the major toxics encountered. Currently, the only respiratory protection wildland firefighters use is a bandanna over the mouth and nose. In this study, a modem activated carbon cartridge with an electrostatic prefilter was compared to a typical bandanna for its ability to filter wildland smoke toxics such as formaldehyde and particulates. The results of the tests were disappointing; neither filter performed very well. The activated carbon cartridge and prefilter efficiently collected formaldehyde gas for up to 60 minutes; however, it only collected 85 percent of the challenge particulate. ]Me bandanna, as expected, was only partially effective at collecting smoke particulate and filtered no toxic gases.
Date:
May 1, 1994
Creator:
Foote, Kenneth Lawrence
System:
The UNT Digital Library
OPNET Based Design and Performance Evaluation of ZigBee Networks
ZigBee is a substandard of IEEE 802.15 family that is specially designed to take care of factors such as power, data rate and area that primarily affect network performance. This has controlling and monitoring capability, which finds potential applications in different sectors. ZigBee allows the concept of hybrid networks and mobility. A comprehensive analysis of ZigBee networks was carried out by constructing and simulating the networks to evaluate the performance in terms of throughput, delay, network load, and packets dropped. This research is aimed at evaluating the effect of network topology on the system performance. A careful review of simulation platforms brought the conclusion of using OPNET Modeler which has the required frame work. Different network topologies of simple and hybrid were built and simulated. Throughout the simulations, the best-case scenarios were drawn to the conclusion by the graphical analysis of parameters of evaluation. Mobile networks were constructed and simulated to investigate the effect of mobility on communication.
Date:
December 2017
Creator:
Nurubhashu, Mabusubhan Vali
System:
The UNT Digital Library
Psychopathy in Male and Female Offenders: Validating the CAPP-IRS and Investigating the Impact of Gender Role Conformity
Recent conceptualizations of psychopathy are moving toward more inclusive, purely trait-based models. However, researchers continue to heavily rely on assessments of psychopathy that include categorical behavioral elements. The newly developed Comprehensive Assessment of Psychopathic Personality – Institutional Rating Scale appears to be a promising interview-based measure of psychopathy, but research on its reliability and validity is in its infancy. As a second issue, the vast majority of research on psychopathy, particularly in offender populations, is conducted with male participants. Nonetheless, the growing body of literature involving incarcerated females suggests gender differences in the prevalence and manifestation of psychopathic traits. Reasons for these differences are unclear, but some have proposed socialized gender roles as a contributing factor. With a sample of 52 female 49 male offenders recruited from a large, metropolitan jail, this dissertation evaluated the construct validity of the CAPP-IRS and examined the effect of gender role conformity on the manifestation of psychopathic traits. Results indicated that a three-factor model of psychopathy represented by antagonistic interpersonal relations, restricted emotions, and disinhibited behavior best fit the data. Findings further suggested convergent and discriminant validity for the CAPP-IRS. Additionally, masculine and feminine gender role conformity differentially related to psychopathy, but generally accounted …
Date:
December 2017
Creator:
Carter, Rachel Marjann
System:
The UNT Digital Library
Postmodern Multiplicities in Three Original Works
My recent compositions are situated within a postmodern theoretical framework. The heterogeneity of materials and hybridity of musical formation in these works are interpreted and contextualized within a personal reading of postmodern theories. The critical essay traces my aesthetics through a historical investigation into the definition of musical postmodernism. Through extensive citation and analysis of the writings of Julius T. Fraser, Italo Calvino, and Richard Rorty, the essay aims to provide a theoretical context for the interpretation of the musical examples. The creative documentation contains three newly-composed musical works: Piano Trio from Opus 3/c, Opus 6 for Violin, and Opus 7 for Piccolo. The works' postmodern features include creative approaches to the fragmentation of musical time into separate levels, historical allusions, and the exploration of multiplicity.
Date:
December 2017
Creator:
Bejo, Ermir
System:
The UNT Digital Library
Emergent Functionality and Controllability in Beamforming System
This dissertation presents beamforming designs. Using novel techniques and methods, the performance of the beamforming is improved on dual-band, tri-band, flexible function, tunable function in THz, and dynamic controllability on incident wave.
Date:
December 2017
Creator:
Ren, Han
System:
The UNT Digital Library
Facets of Positive Affect and Risk for Bipolar Disorder: Role of the Behavioral Activation System
Bipolar disorder is characterized by disruptions in mood and affect that occur not only during mood episodes, but during euthymic periods as well. At the same time, sensitivity of the behavioral activation system (BAS) has been implicated in the disorder and is a risk marker for it. Less clear is the relationship between BAS sensitivity and positive affect, particularly lower level facets of positive affect. The aim of the present study was to examine the relationship between positive affect and vulnerability for mania as assessed using BAS sensitivity. Specifically, the link between daily levels and fluctuations of positive affect and baseline BAS sensitivity was examined. Following the hierarchical model of affect, this study also assessed the relationship between BAS sensitivity and the distinct facets of positive affect. Finally, this study examined whether BAS sensitivity moderates associations between daily rewards and positive affect. Undergraduates (N = 265) from a large university in the South were recruited to complete measures of BAS sensitivity, affect, and mood symptoms at baseline. Using ecological momentary assessment (EMA), participants completed daily surveys assessing affect and engagement with rewarding situations. An exploratory factory analysis revealed a four factor structure of positive affect, consisting of Serenity, Joviality, Attentiveness, …
Date:
December 2017
Creator:
Dornbach-Bender, Allison
System:
The UNT Digital Library
P-type Doping of Pulsed Laser Deposited WS2 with Nb
Layered transition metal dichalcogenides (TMDs) are potentially ideal semiconducting materials due to their in-plane carrier transport and tunable bandgaps, which are favorable properties for electrical and optoelectronic applications. However, the ability to make p-n junctions is the foundation of semiconductor devices, and therefore the ability to achieve reproducible p- and n-type doping in TMD semiconducting materials is critical. In this work, p-type substitutional doping of pulsed laser deposited WS2 films with niobium is reported. The synthesis technique of the PLD target with dopant incorporation which also ensures host material stoichiometry is presented. Hall electrical measurements confirmed stable p-type conductivity of the grown films. Structural characterization revealed that there was no segregation phase of niobium in the fabricated films and x-ray phtoelectron spectroscopy (xps) characterization suggest that the p-type doping is due to Nb4+ which results in p-type behavior. Stable hole concentrations as high as 10E21(cm-3) were achieved. The target fabrication and thin film deposition technique reported here can be used for substitutional doping of other 2D materials to obtain stable doping for device applications.
Date:
December 2017
Creator:
Egede, Eforma Justin
System:
The UNT Digital Library
Analysis and Performance of a Cyber-Human System and Protocols for Geographically Separated Collaborators
This dissertation provides an innovative mechanism to collaborate two geographically separated people on a physical task and a novel method to measure Complexity Index (CI) and calculate Minimal Complexity Index (MCI) of a collaboration protocol. The protocol is represented as a structure, and the information content of it is measured in bits to understand the complex nature of the protocol. Using the complexity metrics, one can analyze the performance of a collaborative system and a collaboration protocol. Security and privacy of the consumers are vital while seeking remote help; this dissertation also provides a novel authorization framework for dynamic access control of resources on an input-constrained appliance used for completing the physical task. Using the innovative Collaborative Appliance for REmote-help (CARE) and with the support of a remotely located expert, fifty-nine subjects with minimal or no prior mechanical knowledge are able to elevate a car for replacing a tire in an average time of six minutes and 53 seconds and with an average protocol complexity of 171.6 bits. Moreover, thirty subjects with minimal or no prior plumbing knowledge are able to change the cartridge of a faucet in an average time of ten minutes and with an average protocol complexity …
Date:
December 2017
Creator:
Jonnada, Srikanth
System:
The UNT Digital Library
Analysis of Behavioral Objectives with Implications for Pre-student Teaching Preparation
Zella Patterson writes an academic paper that supports the implications for pre-student teaching.
Date:
1937
Creator:
Patterson, Zella
System:
The Gateway to Oklahoma History
After-Sales Service Contracting for Excellence in Life-Cycle Cost Management: Numerical Experiments and Systematic Review of Analytical Models
This research adds to the literature and provides insight to practice via three essays that increase understanding about the applications and consequences of the two new approaches to the after-sales service governance: warranty contract and performance-based contracts. First, we attempted to enhance our knowledge of the modeling of the after-sales service process. In the first essay, the research papers with analytical models of after-sales services to present current trends, issues, and future research directions in the literature are classified. In the second essay, the effect of the warranty contract on the supplier's product quality improvement efforts in the context of capital goods is examined. Three sets of optimization models reveal that the existence of a warranty improves product quality. In the third essay, the performance-based contract is examined in the context of the warranty contract. The numerical experimentations conducted demonstrate that the performance-based contract is superior to the warranty contract in terms of the supplier's product quality efforts and the customer's total cost of after-sales services. The alignment of incentives based on the product performance tackles the issues presented in the traditional after-sales service contracting. Collectively, the three studies presented in this research expand our understanding of after-sales service contracts. …
Date:
August 2020
Creator:
Küçük, Carullah Yavuz
System:
The UNT Digital Library
Centralizing the Voices and Experiences of Microaggressions of Queer Womxn of Color in Therapy
The purpose of this participatory action research study was to explore queer womxn of color's experiences of microaggressions in therapy. Due to the multifaceted and complex experiences of queer womxn of color, this study was informed by intersectionality theory and utilized photovoice methodology to answer the following question: How do queer womxn of color experience microaggressions in therapy? The seven queer womxn of color who participated in this study provided vivid, honest, and courageous portrayals of their experience of microaggressions in therapy. Six major themes were prominent in their photographs and narratives: (a) collective and pervasive experiences of oppression, (b) therapy as a tool of oppression, (c) impact of oppression in therapy, (d) strategies for survival, (e) healing for queer womxn of color, and (f) the power of sharing mi historia. Overall, co-researchers provided insight into their experiences of oppression in therapy, while highlighting clinical and research practices that may be healing and liberatory for queer womxn of color. Additionally, implications and conclusions drawn from the experiences of co-researchers provide recommendations for mental health professionals, educational programs, and researchers to consider when working with queer womxn of color.
Date:
August 2020
Creator:
Reyes, Ana Guadalupe
System:
The UNT Digital Library
Risky Business: A Sub-National Analysis of Violent Organized Crime and Foreign Direct Investment in Mexico
This dissertation examines the relationship between violent organized crime and foreign direct investment (FDI) through sub-national analysis focused on the case of Mexico. The results indicate that FDI decisions vary based on the type of violent organized crime.
Date:
August 2020
Creator:
Bennett, Amanda White
System:
The UNT Digital Library
Role of calcium carbonate precipitation in lake metabolism
None
Date:
January 1, 1974
Creator:
White, W. Sedgefield
System:
The UNT Digital Library
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
Coupled two-dimensional edge plasma and neutral gas modeling of tokamak scrape-off-layers
The objective of this study is to devise a detailed description of the tokamak scrape-off-layer (SOL), which includes the best available models of both the plasma and neutral species and the strong coupling between the two in many SOL regimes. A good estimate of both particle flux and heat flux profiles at the limiter/divertor target plates is desired. Peak heat flux is one of the limiting factors in determining the survival probability of plasma-facing-components at high power levels. Plate particle flux affects the neutral flux to the pump, which determines the particle exhaust rate. A technique which couples a two-dimensional (2-D) plasma and a 2-D neutral transport code has been developed (coupled code technique), but this procedure requires large amounts of computer time. Relevant physics has been added to an existing two-neutral-species model which takes the SOL plasma/neutral coupling into account in a simple manner (molecular physics model), and this model is compared with the coupled code technique mentioned above. The molecular physics model is benchmarked against experimental data from a divertor tokamak (DIII-D), and a similar model (single-species model) is benchmarked against data from a pump-limiter tokamak (Tore Supra). The models are then used to examine two key issues: …
Date:
August 1, 1992
Creator:
Maingi, R.
System:
The UNT Digital Library