Search Results

open access

Academic Reading Online: Digital Reading Strategies of Graduate-level English Language Learners

Description: English language learners (ELLs) face many linguistic and cultural challenges in their attempts to succeed academically. They encounter complex academic text, which is increasingly presented online. Although some research has addressed the challenges that university-level ELLs face when reading online texts, almost all of this prior work has focused on undergraduates. The purpose of the current study was to investigate the reading strategies employed by graduate-level ELLs when reading an academic English text online. Participating in the study were four foreign-born doctoral students from different first-language backgrounds—Arabic, Korean, Urdu, and Vietnamese—and the focus was on commonalities as well as differences among them. All four were enrolled in the same doctoral-level course, which included the reading of a specific online academic article as a course requirement. When reading this text individually, each student participated in a think-aloud procedure, followed by post-reading and discourse-based interviews. Analyses included unitizing data from the think-aloud protocols, coding units for strategies employed, and considering related interview commentary and classroom contributions. In their reading, these students made major use of problem-solving strategies, especially reading segments aloud and questioning. They also employed evaluative strategies as well as metacognitive strategies, which included affirming their understanding or indicating lack of understanding. With respect to global strategies, all made use of the article’s abstract and used the cursor to scroll forward to preview the article. In contrast to previous research with undergraduates, these students made little use of support strategies that involved translation websites. Instead, their major support strategies were navigating to web-based tools, particularly online encyclopedias in English. Despite prior theory and research suggesting the importance of sociorhetorical strategies in academic reading, only one student directed much attention to the authors of the article and to authorial intent. Although all four participants were students in the same doctoral course and …
Date: May 2015
Creator: Knezek, Lois Ann
Partner: UNT Libraries
open access

Academic, Social and Emotional Functioning of College Students with Attention-Deficit/Hyperactivity Disorder (ADHD)

Description: Attention deficit/hyperactivity disorder (ADHD) is frequently associated with negative occupational, social and psychological outcomes among community samples of adults; as such, it is expected that college students with ADHD face similar struggles. The research targeting this group of individuals, however, is sparse and tempered by significant limitations. The current study aimed to address methodological limitations in the current literature by including instruments to formally diagnosis ADHD and comorbid disorders, utilizing psychometrically sound instruments and comparing functioning of college students with ADHD across gender and subtype. It was hypothesized that participants with ADHD would report lower GPAs, higher levels of emotional distress and negative relationship characteristics than participants without ADHD. It was also hypothesized that participants with ADHD-combined type (ADHD-C) would report higher levels of substance and alcohol use than participants with ADHD-predominately inattentive type (ADHD-I), and that participants with ADHD-I would report higher levels of anxiety and depression than participants with ADHD-C. Women diagnosed with ADHD were expected to report higher levels of anxiety and depression than men diagnosed with ADHD; whereas, men diagnosed with ADHD were expected to report higher levels of substance and alcohol use than women. MANOVA, ANOVA and Mann-Whitney U tests were conducted to test hypotheses. Results revealed no significant differences between the ADHD and comparison group on GPA and relationship characteristics. Participants diagnosed with ADHD did report significantly higher emotional distress than participants in the comparison group. No differences in GPA or relationship characteristics were found across ADHD subtype or gender. Overall, these findings provide evidence to suggest that college students with ADHD are functioning relatively well compared to their non-ADHD peers.
Date: August 2015
Creator: McKelvy, Tara N.
Partner: UNT Libraries
open access

An Accelerometer-based Gesture Recognition System for a Tactical Communications Application

Description: In modern society, computers are primarily interacted with via keyboards, touch screens, voice recognition, video analysis, and many others. For certain applications, these methods may be the most efficient interface. However, there are applications that we can conceive where a more natural interface could be convenient and connect humans and computers in a more intuitive and natural way. These applications are gesture recognition systems and range from the interpretation of sign language by a computer to virtual reality control. This Thesis proposes a gesture recognition system that primarily uses accelerometers to capture gestures from a tactical communications application. A segmentation algorithm is developed based on the accelerometer energy to segment these gestures from an input sequence. Using signal processing and machine learning techniques, the segments are reduced to mathematical features and classified with support vector machines. Experimental results show that the system achieves an overall gesture recognition accuracy of 98.9%. Additional methods, such as non-gesture recognition/suppression, are also proposed and tested.
Date: December 2015
Creator: Tidwell, Robert S., Jr.
Partner: UNT Libraries
open access

Acceptance Theories for Behavior in Conducting Research: Instructors in the Rajabhat University System, Thailand

Description: Responding to globalization and its effects on education and research development, the Thai government decided to push all public universities to become autonomous and establish a system of quality assurances. The establishment of quality assurances has had a large impact on many Thai instructors, especially in new public universities. Thai instructors are now forced to more focus on conducting research because the number of research publications is regarded as one of the main criteria for quality universities. The purpose of this study is to investigate the key factors, at the individual and university levels, which impact on the instructors' behavior in conducting research of the full-time instructors in the faculty of Management Science from the Rajabhat Universities in Thailand. The current study will help explain how and why the instructors accept or refuse to conduct research and provide insight into the salient factors motivating the instructors to produce more research by conducting HLM. Data were collected from 694 participants at 37 institutions via a questionnaire survey. The findings revealed that there was no difference among these 37 universities on behavior in conducting research. The key factors statistically influencing behavior in conducting research of the instructors were facilitating conditions, academic degree, social influence, and usefulness as well as ease of conducting research that the instructors perceived. This study gained 46% of effect size.
Date: December 2015
Creator: Laksaniyanon, Benchamat
Partner: UNT Libraries
open access

Accurate Energetics Across the Periodic Table Via Quantum Chemistry

Description: Greater understanding and accurate predictions of structural, thermochemical, and spectroscopic properties of chemical compounds is critical for the advancements of not only basic science, but also in applications needed for the growth and health of the U.S. economy. This dissertation includes new ab initio composite approaches to predict accurate energetics of lanthanide-containing compounds including relativistic effects, and optimization of parameters for semi-empirical methods for transition metals. Studies of properties and energetics of chemical compounds through various computational methods are also the focus of this research, including the C-O bond cleavage of dimethyl ether by transition metal ions, the study of thermochemical and structural properties of small silicon containing compounds with the Multi-Reference correlation consistent Composite Approach, the development of a composite method for heavy element systems, spectroscopic of compounds containing noble gases and metals (ArxZn and ArxAg+ where x = 1, 2), and the effects due to Basis Set Superposition Error (BSSE) on these van der Waals complexes.
Date: December 2015
Creator: Peterson, Charles Campbell
Partner: UNT Libraries
open access

Act Like a Punk, Sing Like a Feminist: A Longitudinal Content Analysis of Feminist Themes in Punk Rock Song Lyrics, 1970-2009

Description: Punk rock music has long been labeled sexist as copious media-generated accounts and reports of the genre concentrate on male artists, hyper-masculine performances, and lyrics considered to be aggressive, sexist, and misogynist. However, scholars have rarely examined punk rock music longitudinally, focusing heavily on 1980s and 1990s manifestations of the genre. Furthermore, few systematic content analyses of feminist themes in punk rock song lyrics have been conducted. The present research is a longitudinal content analysis of lyrics of 600 punk rock songs released for four decades between 1970 and 2009 to examine the prevalence of and longitudinal shifts in antiestablishment themes, the prevalence of and longitudinal shifts in sexist themes relative to feminist themes, the prevalence of and longitudinal shifts in specific feminist branches, and what factors are related to feminism. Using top-rated albums retrieved from Sputnik Music’s “Best Punk Albums” charts, systematic random sampling was applied to select 50 songs for each combination of three gender types and four decades. Sexism and feminism were then operationalized to construct a coding sheet to examine relevant dimensions. While the present study found no significant patterns of longitudinal increase or decrease in feminist or sexist themes, it revealed that feminist themes were consistently high across four decades and, furthermore, indicated a phenomenon of post-modern hybridity.
Date: May 2015
Creator: Levine, Lauren E.
Partner: UNT Libraries
open access

Adaptive Power Management for Autonomic Resource Configuration in Large-scale Computer Systems

Description: In order to run and manage resource-intensive high-performance applications, large-scale computing and storage platforms have been evolving rapidly in various domains in both academia and industry. The energy expenditure consumed to operate and maintain these cloud computing infrastructures is a major factor to influence the overall profit and efficiency for most cloud service providers. Moreover, considering the mitigation of environmental damage from excessive carbon dioxide emission, the amount of power consumed by enterprise-scale data centers should be constrained for protection of the environment.Generally speaking, there exists a trade-off between power consumption and application performance in large-scale computing systems and how to balance these two factors has become an important topic for researchers and engineers in cloud and HPC communities. Therefore, minimizing the power usage while satisfying the Service Level Agreements have become one of the most desirable objectives in cloud computing research and implementation. Since the fundamental feature of the cloud computing platform is hosting workloads with a variety of characteristics in a consolidated and on-demand manner, it is demanding to explore the inherent relationship between power usage and machine configurations. Subsequently, with an understanding of these inherent relationships, researchers are able to develop effective power management policies to optimize productivity by balancing power usage and system performance. In this dissertation, we develop an autonomic power-aware system management framework for large-scale computer systems. We propose a series of techniques including coarse-grain power profiling, VM power modelling, power-aware resource auto-configuration and full-system power usage simulator. These techniques help us to understand the characteristics of power consumption of various system components. Based on these techniques, we are able to test various job scheduling strategies and develop resource management approaches to enhance the systems' power efficiency.
Date: August 2015
Creator: Zhang, Ziming
Partner: UNT Libraries
open access

Addressing Multicultural Issues in the Counselor Education Classroom: a Phenomenological Analysis

Description: Multicultural education in counselor education is a popular topic among counselor educators and scholars. To date, scholars have focused on understanding the experiences of counselor educators who teach dedicated multicultural courses. However, less attention has been given to other counselor educators who are required by ethical and training standards to address multicultural issues across the curriculum. The purpose of this study was to understand counselor educators’ experiences addressing multicultural issues in courses that do not have a specific multicultural or diversity focus. I used phenomenological methodology to explore the experiences of counselor educators who hold doctoral degrees in counseling or a related field, have taken a multicultural/diversity course in their graduate training, are full-time clinical or tenure-line faculty members in CACREP-accredited programs, and have never taught courses dedicated to multicultural or diversity issues. Twelve participants (six men and six women), ranging in age ranged from 31 to 65, participated in the study. Ten participants identified as White, one African-American, and one Hispanic. The research team identified eight themes: (1) reasons for avoidance, (2) constraints, (3) qualities and practices, (4) educator as a factor in student development, (5) infusion, (6) personal background, (7) awareness of biases and assumptions, and (8) counselor educator responsibility/gatekeeping. Findings from this study will add to the literature regarding infusion of multicultural issues across the curriculum. Additionally, the implications offered will serve as a resource for counselor educators as they experience unique personal and professional challenges when addressing multicultural issues in classrooms beyond the main multicultural or diversity course offered in counseling programs. Implications for this study may lead to development of more focused guidelines on how to increase the increase the comfort of counselor educators as they facilitate multicultural discussions and assist counselors-in-training in working toward cultural competence.
Date: December 2015
Creator: Wagner, Terra M.
Partner: UNT Libraries
open access

Adult Attachment, Acculturation, and Help-seeking Attitudes of Latino College Students

Description: Based on theoretical reasoning and empirical evidence, the present study examined the unique and shared effects of attachment anxiety, attachment avoidance, and acculturation on attitudes toward seeking professional help among Latino college students. The research participants included 149 bilingual Latino college students from a large, public southwestern university. Results of a multiple regression analysis indicated that attachment avoidance was positively associated with both the recognition of need for psychological help and stigma of seeking professional help. Acculturation to American society was found to be statistically insignificant in predicting help-seeking attitudes in this sample of the population. Findings from exploratory questions suggested that Latino individuals would most likely seek help from parents, close friends, and then professionals. This study suggested that Latino individuals with high attachment avoidance acknowledge the potential benefit of professional help-seeking but distrust the process of approaching others for help. Limitations, implications, and future research directions will be discussed.
Date: May 2015
Creator: Zamudio, Gabriel
Partner: UNT Libraries
open access

Advanced Power Amplifiers Design for Modern Wireless Communication

Description: Modern wireless communication systems use spectrally efficient modulation schemes to reach high data rate transmission. These schemes are generally involved with signals with high peak-to-average power ratio (PAPR). Moreover, the development of next generation wireless communication systems requires the power amplifiers to operate over a wide frequency band or multiple frequency bands to support different applications. These wide-band and multi-band solutions will lead to reductions in both the size and cost of the whole system. This dissertation presents several advanced power amplifier solutions to provide wide-band and multi-band operations with efficiency improvement at power back-offs.
Date: August 2015
Creator: Shao, Jin
Partner: UNT Libraries
open access

Airbourne WiFi Networks Through Directional Antenna: An Experimental Study

Description: In situations where information infrastructure is destroyed or not available, on-demand information infrastructure is pivotal for the success of rescue missions. In this paper, a drone-carried on demand information infrastructure for long-distance WiFi transmission system is developed. It can be used in the areas including emergency response, public event, and battlefield. The WiFi network can be connected to the Internet to extend WiFi access to areas where WiFi and other Internet infrastructures are not available. In order to establish a local area network to propagate WIFI service, directional antennas and wireless routers are used to create it. Due to unstable working condition on the flying drones, a precise heading turning stage is designed to maintain the two directional antennas facing to each other. Even if external interferences change the heading of the drones, the stages will automatically rotate back to where it should be to offset the bias. Also, to maintain the same flying altitude, a ground controller is designed to measure the height of the drones so that the directional antennas can communicate to each other successfully. To verify the design of the whole system, quite a few field experiments were performed. Experiments results indicates the design is reliable, viable and successful. Especially at disaster areas, it’ll help people a lot.
Date: May 2015
Creator: Gu, Yixin
Partner: UNT Libraries
open access

Algorithm Optimizations in Genomic Analysis Using Entropic Dissection

Description: In recent years, the collection of genomic data has skyrocketed and databases of genomic data are growing at a faster rate than ever before. Although many computational methods have been developed to interpret these data, they tend to struggle to process the ever increasing file sizes that are being produced and fail to take advantage of the advances in multi-core processors by using parallel processing. In some instances, loss of accuracy has been a necessary trade off to allow faster computation of the data. This thesis discusses one such algorithm that has been developed and how changes were made to allow larger input file sizes and reduce the time required to achieve a result without sacrificing accuracy. An information entropy based algorithm was used as a basis to demonstrate these techniques. The algorithm dissects the distinctive patterns underlying genomic data efficiently requiring no a priori knowledge, and thus is applicable in a variety of biological research applications. This research describes how parallel processing and object-oriented programming techniques were used to process larger files in less time and achieve a more accurate result from the algorithm. Through object oriented techniques, the maximum allowable input file size was significantly increased from 200 mb to 2000 mb. Using parallel processing techniques allowed the program to finish processing data in less than half the time of the sequential version. The accuracy of the algorithm was improved by reducing data loss throughout the algorithm. Finally, adding user-friendly options enabled the program to use requests more effectively and further customize the logic used within the algorithm.
Date: August 2015
Creator: Danks, Jacob R.
Partner: UNT Libraries
open access

Algorithmic Music Analysis: a Case Study of a Prelude From David Cope’s “From Darkness, Light”

Description: The use of algorithms in compositional practice has been in use for centuries. With the advent of computers, formalized procedures have become an important part of computer music. David Cope is an American composer that has pioneered systems that make use of artificial intelligence programming techniques. In this dissertation one of David Cope’s compositions that was generated with one of his processes is examined in detail. A general timeline of algorithmic compositional practice is outlined from a historical perspective, and realized in the Common Lisp programming language as a musicological tool. David Cope’s compositional output is summarized with an explanation of what types of systems he has utilized in the analyses of other composers’ music, and the composition of his own music. Twentieth century analyses techniques are formalized within Common Lisp as algorithmic analyses tools. The tools are then combined with techniques developed within other computational music analyses tools, and applied toward the analysis of Cope’s prelude. A traditional music theory analysis of the composition is provided, and outcomes of computational analyses augment the traditional analysis. The outcome of the computational analyses, or algorithmic analyses, is represented in statistical data, and corresponding probabilities. From the resulting data sets part of a machine-learning technique algorithm devises semantic networks. The semantic networks represent chord succession and voice leading rules that underlie the framework of Cope’s prelude.
Date: May 2015
Creator: Krämer, Reiner
Partner: UNT Libraries
open access

Alternative Certification Teaching Programs in Texas: A Historical Analysis

Description: Before 1984, nearly 975 of teachers entered the teaching profession after graduating from a traditional university-based program. However, beginning in the mid-1980s, alternative routes leading to teacher certification began to emerge in the United States. As of 2010, nearly one-third of all new teachers graduated from an alternative preparation program. As alternative certification (AC) routes approach 30 years since establishment, programs continue to evolve and increase in enrollment. This study focused on the changes that have come about in the maturation of alternative certification programs in Texas since legislation was passed in 1985. The purpose of the study was to delineate the evolution of AC programs using a historical approach, the study used both primary and secondary resources as research tools and employed the use of eight interviews and the literature review for the collection of data. The prediction of future teacher shortages, the need for diversity in the profession the political view to privatize education, and economic recessions were all motivating factors for establishing alternative teacher programs. In the beginning, graduation from AC programs were perceived as not authentic teachers and not as prepared for teaching as graduates from traditional programs. AC programs have become a legitimate and viable option for educator preparation programs as they offer greater flexibility, staff/instructor diversity, and multiple approaches to instruction. This data suggests that AC programs in Texas have emerged as a real and sustainable option to traditional certification programs leading to certification and licensure.
Date: May 2015
Creator: Etheredge, David K.
Partner: UNT Libraries
open access

Amarillo Globe-News: How Did Gene Howe and the Globe-News Help Guide Amarillo, Texas through the Dust Bowl and Great Depression?

Description: For many years newspapers were locally owned by editors and publishers. However, today many are run by corporations from out of state. As a result, many communities have lost the personal relationship between the family owned publication and the community. Gene Howe, who served as editor, publisher and columnist of the Amarillo Globe-News from 1926 until his death in 1952, believed the community was where the focus should be and the newspaper should do all that it can to help their readers. Despite the fact that Howe was not born in Amarillo, Texas, his passion and love for the city and its inhabitants compensated for it. During the Dust Bowl and Great Depression Howe and the Globe-News helped Amarillo survive the dust and economic storms that blew through the Texas Panhandle, an area that has not been written as much as other parts of Texas. Through his “Tactless Texan” column, which served as a pulpit to the community, to the various contests and promotions the newspaper sprang up, including the creation of Mother in Law Day, Gene Howe gave the newspaper another dimension little has been studied about, the role of the editor and publisher in guiding a community through a dramatic era. Understanding Howe’s ethos can allow others to examine the roles editors and newspapers play in communities throughout the country.
Date: May 2015
Creator: Hasman, Gregory R. C.
Partner: UNT Libraries
open access

An Analysis of Du cristal…à la fumée by Kaija Saariaho and Axiom Unearthed, Original Composition

Description: Beginning in the 1970s, and aided by the advancement and an increased prevalence of computers, spectral music emerged as an important development in twentieth century music. Spectral composers, as exemplified by Gérard Grisey and Tristan Murail, took the harmonic spectra of sounds as the fundamental materials of composition. The resulting music placed an emphasis on texture and gradually evolving forms. The generation of composers immediately following the spectralists assimilated their techniques into distinct and varying styles. Finnish composer Kaija Saariaho uses spectral techniques to create an aesthetic that generates form and progression from a sound/noise axis. In her piece Du cristal…à la fumée, a number of pendulum and half-pendulum gestures build up texture and form. The accompanying original composition Axiom Unearthed employs similar pendulum gestures and uses spectral techniques to generate melody and harmony in an aesthetic divergent from traditional spectral pieces.
Date: May 2015
Creator: Allen, John Clay
Partner: UNT Libraries
open access

An Analysis of Market Efficiency for Exchange-traded Foreign Exchange Options on an Intraday Basis

Description: This study examines the comparative magnitude of disturbances in intraday data for exchange traded foreign exchange (FX) options. An in-depth time series analysis on the frequency and extent of discrepancies in the disturbances is conducted. The purpose of this study is twofold. First, using intraday data and trading volume, this study attempts to determine whether both put-call parity and lower boundary conditions consistently hold for exchange traded options written on U.S. dollar denominated options on the Euro trading on the Philadelphia Stock Exchange (PHLX). Second, this study attempts to investigate the magnitude of any discrepancies that may exist due to a temporary cessation of either put-call parity or lower boundary conditions. Intraday (tick-by-tick) bid prices, ask prices, and trading volume on U.S. dollar denominated European style call options and put options on the Euro are obtained. Option data is collected through a Structured Query Language (SQL) request from the Bloomberg database. Corresponding tick-by-tick spot rates for the underlying exchange rate are obtained for the same time period. Tick-by-tick 3-month Treasury bill rates are obtained to for use as the relevant risk-free interest rate. The primary data set spans an approximate one month period from 11/1/2011 to 12/6/2011. Call and option pricing data for near-the-money exercise prices are obtained for options expiring in December 2011, January 2012, February 2012, March 2012, June 2012, and September 2012. A total of 7,212 ticks (minutes) are analyzed for the conversion strategy and 7,209 ticks are analyzed for the reversal strategy. The data is structured into an unbalanced panel data set (cross-sectional time series data) using put-call pairs as the cross sectional units and ticks as the time-series unit. To test the efficiency of the foreign exchange options market, lower boundary and put-call parity conditions were tested on tick-by-tick currency option data. Analysis shows that …
Date: May 2015
Creator: Ren, Peter
Partner: UNT Libraries
open access

Anger, Forgiveness and Mindfulness: Correlates of Perceived Stress in an LGB Sample

Description: A sexual minority is someone who identifies as lesbian, gay or bisexual (LGB). According to the Minority Stress Model (Meyer, 2003), sexual minorities encounter significant levels of stress due to their minority group status, thus they are more likely to experience perceived stress. Our cross-sectional, correlational study aimed to explore the relationships between forgiveness, mindfulness and anger and how they are related to perceived stress in a convenience sample of ethnically diverse LGB adults. We hypothesized that: 1) anger is positively associated with perceived stress; 2) forgiveness is negatively associated with perceived stress; 3) mindfulness is negatively associated with perceived stress; and 4) anger, forgiveness and mindfulness account for a significant proportion of the variance in perceived stress. 5) The relationship between anger and perceived stress is moderated by forgiveness. 6) The relationship between anger and perceived stress is moderated by mindfulness. Among LGB adults, the extant literature does not address these four variables in conjunction and the relationships between anger, forgiveness, mindfulness and stress has yet to be explored. Various statistical analyses were conducted, including a hierarchical linear regression to test our model. We found that our overall model accounted for 36% of the total variance in perceived stress (F(5, 142) = 17.31, p <.01) with anger (β = .31, t = 3.55, p = .001) and forgiveness (β = -.21, t = -2.56, p < .05) as the significant predictors. Contrary to prediction, forgiveness and mindfulness did not moderate the relationship between anger and perceived stress in our LGB sample. Limitations, strengths, future research and implications are discussed.
Date: December 2015
Creator: Schumacher, Matthew Robert
Partner: UNT Libraries
open access

Animated Autoethnographies: Using Stop Motion Animation As a Catalyst for Self-acceptance in the Art Classroom

Description: As a doctoral student, I was asked to teach a course based on emerging technologies and postmodern methods of inquiry in the field of art education. The course was titled Issues and Applications of Technology in Art Education and I developed a method of inquiry called animated autoethnography for pre-service art educators while teaching this course. Through this dissertation, I describe, analyze, interrogate, value, contextualize, reflect on, and artistically react to the autoethnographic animated processes of five pre-service art educators who were enrolled in the course. I interviewed the five participants before and after the creation of their animated autoethnographies and incorporated actor-network theory within the theoretical analysis to study how the insights of my students’ autoethnographies related to my own animations and life narratives. The study also examines animated autoethnography as a method of inquiry that may develop or enhance future teaching practices and encourage empathic connections through researching the self. These selected students created animations that accessed significant life moments, personal struggles, and triumphs, and they exhibited unique representations of self. Pre-service art educators can use self-research to create narrative-based short animations and also use socio-emotional learning to encourage the development of empathy within the classroom. I show diverse student examples, compare them to my own animations, and present a new model of inquiry that encourages the development of self by finding place in chaos, loving the unknown, embracing uncertainty, and turning shame into a celebration of life.
Date: August 2015
Creator: Blair, Jeremy Michael
Partner: UNT Libraries
open access

Anisotropic Nature of Radially Strained Metal Tubes

Description: Metal pipes are sometimes swaged by a metal cone to enlarge them, which increases the strain in the material. The amount of strain is important because it affects the burst and collapse strength. Burst strength is the amount of internal pressure that a pipe can withstand before failure, while collapse strength is the amount of external pressure that a pipe can withstand before failure. If the burst or collapse strengths are exceeded, the pipe may fracture, causing critical failure. Such an event could cost the owners and their customers millions of dollars in clean up, repair, and lost time, in addition to the potential environmental damage. Therefore, a reliable way of estimating the burst and collapse strength of strained pipe is desired and valuable. The sponsor currently rates strained pipes using the properties of raw steel, because those properties are easily measured (for example, yield strength). In the past, the engineers assumed that the metal would be work-hardened when swaged, so that yield strength would increase. However, swaging introduces anisotropic strain, which may decrease the yield strength. This study measured the yield strength of strained material in the transverse and axial direction and compared them to raw material, to determine the amount of anisotropy. This information will be used to more accurately determine burst and collapse ratings for strained pipes. More accurate ratings mean safer products, which will minimize risk for the sponsor’s customers. Since the strained metal has a higher yield strength than the raw material, using the raw yield strength to calculate burst and collapse ratings is a conservative method. The metal has even higher yield strength after strain aging, which indicates that the stresses are relieved. Even with the 12% anisotropy in the strained and 9% anisotropy in the strain aged specimens, the raw yield strengths are …
Date: December 2015
Creator: Strickland, Julie N.
Partner: UNT Libraries
open access

Application of Cyclic Polarization of Aluminum 3003 Used in All-Aluminum Microchannel Heat Exchangers

Description: All-aluminum microchannel heat exchangers are designed to significantly reduce refrigerant charge requirements, weight, reduced brazed joints, and decreased potential for leakage by increasing reliability. Al 3003 alloy is corrosion resistant and can be formed, welded, and brazed but the issue with all-aluminum heat exchangers is localized corrosion (pitting) in corrosive environments. Currently, there is no universally accepted corrosion test that all coil manufacturers use to characterize their products. Electrochemical testing method of cyclic polarization was employed in this investigation and relevant parameters including electrolyte corrosive agent and its concentration, electrolyte pH, and applied potential scan rate was varied to find an optimal set of parameters. Results of cyclic polarization of Al 3003 in electrolytes containing various concentrations of NaCl were compared with those of the tests in Sea Water Acidified Accelerated Test (SWAAT) electrolyte and it is shown the SWAAT electrolyte (4.2% sea salt acidified to pH of 2.9) is by far stronger (in terms of corrosivity) than typical 3.5% NaCl solution used in most corrosion testing. Corrosion rates (g/m2yr) of Al 3003 measured in this investigation were comparable to those provided by ISO 9223 standard corresponding to C1 through CX categories. Duration of cyclic polarization test is much shorter than that of SWAAT and results obtained in this test is more reproducible compared to those of SWAAT. Scanning electron microscopy micrographs show typical pit depths of about 50 μm.
Date: May 2015
Creator: Barnes, Javier
Partner: UNT Libraries
open access

An Application of Marxian and Weberian Theories of Capitalism: the Emergence of Big Businesses in the United States, 1861 to 1890

Description: This study was an examination of businesses that became big businesses in the United States during the time period between the years of 1861 and 1890, a period of time frequently referred to as the “big business era.” The purpose of the study was to identify actions taken by businesses that enabled them to become and remain big businesses. A secondary purpose of the study was to show that these actions were explained by theories of Karl Marx and Max Weber. The results of the study showed that businesses which took specific actions were able to become and remain big businesses and these actions were explained by the theories of Marx and Weber. The results of the study demonstrate the ability of classical sociological theory to explain macro-level social change.
Date: May 2015
Creator: Magness, Penny J.
Partner: UNT Libraries
open access

Application of the Correlation Consistent Composite Approach to Biological Systems and Noncovalent Interactions

Description: Advances in computing capabilities have facilitated the application of quantum mechanical methods to increasingly larger and more complex chemical systems, including weakly interacting and biologically relevant species. One such ab initio-based composite methodology, the correlation consistent composite approach (ccCA), has been shown to be reliable for the prediction of enthalpies of formation and reaction energies of main group species in the gas phase to within 1 kcal mol-1, on average, of well-established experiment, without dependence on experimental parameterization or empirical corrections. In this collection of work, ccCA has been utilized to determine the proton affinities of deoxyribonucleosides within an ONIOM framework (ONIOM-ccCA) and to predict accurate enthalpies of formation for organophosphorus compounds. Despite the complexity of these systems, ccCA is shown to result in enthalpies of formation to within ~2 kcal mol-1 of experiment and predict reliable reaction energies for systems with little to no experimental data. New applications for the ccCA method have also been introduced, expanding the utility of ccCA to solvated systems and complexes with significant noncovalent interactions. By incorporating the SMD solvation model into the ccCA formulation, the Solv-ccCA method is able to predict the pKa values of nitrogen systems to within 0.7 pKa unit (less than 1.0 kcal mol-1), overall. A hydrogen bonding constant has also been developed for use with weakly interacting dimers and small cluster compounds, resulting in ccCA interaction energies for water clusters and dimers of the S66 set to within 1.0 kcal mol-1 of well-established theoretical values.
Date: May 2015
Creator: Riojas, Amanda G.
Partner: UNT Libraries
open access

Applications of Single Reference Methods to Multi-Reference Problems

Description: Density functional theory is an efficient and useful method of solving single-reference computational chemistry problems, however it struggles with multi-reference systems. Modifications have been developed in order to improve the capabilities of density functional theory. In this work, density functional theory has been successfully applied to solve multi-reference systems with large amounts of non-dynamical correlation by use of modifications. It has also been successfully applied for geometry optimizations for lanthanide trifluorides.
Date: May 2015
Creator: Jeffrey, Chris C.
Partner: UNT Libraries
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