Digital Commons Network^™

Comparative Study Of Power Semiconductor Devices In A Multilevel Cascaded H-Bridge Inverter, Kenneth Mordi

Graduate Theses and Dissertations

This thesis compares the performance of a nine-level transformerless cascaded H-bridge (CHB) inverter with integrated battery energy storage system (BESS) using SiC power MOSFETs and Si IGBTs. Two crucial performance drivers for inverter applications are power loss and efficiency. Both of these are investigated in this thesis. Power devices with similar voltage and current ratings are used in the same inverter topology, and the performance of each device is analyzed with respect to switching frequency and operating temperature. The loss measurements and characteristics within the inverter are discussed. The Saber® simulation software was used for the comparisons. The power MOSFET …

Geophysical Assessment Of Subsurface Soil Conditions Using Capacitively Coupled Resistivity, Folaseye Coker

Graduate Theses and Dissertations

The purpose of this research is to explore the applicability of Capacitively-Coupled Resistivity (CCR) as an improvement on traditional drilling and sampling methods for subsurface soil investigations. The CCR method could be used to identify critical locations for drilling and sampling such as expansive clay layers and anomalies (sinkholes, unknown landfills, etc.) rather than uniformly sampling across a site. CCR surveys were performed at Alpena, Arkansas along a highway expansion project changing US 62 from a two lane to four lane highway, and at Alton, Illinois along the Mel Price Levee, a 5.2 mile levee along a portion of the …

Computer Modeling Of Close-To-Ground Tornado Wind-Fields For Different Tornado Widths, Mohammadhossein Kashefizadeh

Graduate Theses and Dissertations

Tornadoes induce different wind forces on buildings than straight-line (SL) winds. The tangential velocity (Vθ) of tornados is the main parameter that causes damage to the buildings. In-field tornado measurements cannot evaluate the tornado’s Vθ at less than 20m above ground level (AGL). The laboratory tornado simulators suggest that the Swirl ratio (S) and the radius (ro) are the most influential factors affecting Vθ. However, due to scaling problems, laboratory simulators cannot report the Vθ for elevations less than 10m AGL. Well refined computational fluid dynamics (CFD) models can evaluate the Vθ at less than 10m AGL. However, the CFD …

Proposed Astm Standard For The Stokoe-Type Resonant Column Torsional Shear Device, Anh Tuan Tran

Graduate Theses and Dissertations

Resonant Column Torsional Shear (RCTS) testing has become one of the most commonly used methods for determining laboratory soil stiffness and soil damping. The RCTS test has been accepted and is commonly utilized during the permitting of new nuclear facilities. However, there is still no available public standard for performing RCTS tests using the Stokoe-type device. Therefore, an ASTM standard for calibration and performance of RCTS tests using the Stokoe-type RCTS device is presented herein. Data collected using the Stokoe-type RCTS devices at the University of Arkansas (UofA) and at the Norwegian Geotechnical Institute (NGI) also aided in the development …

Testing And Development Of Pre-Stressed Cfrp Retrofit Strategies For Controlling Fatigue Cracking In Steel Waterway Lock Gate Structures, Maggie Langston

Graduate Theses and Dissertations

Steel waterway lock gates across the national inland waterway transportation network are reaching and exceeding their intended service life, often experiencing component failures that lead to service interruptions. Unscheduled maintenance and repair of lock gates can be expensive and cause economic ripples throughout the entire inland waterway network. These lock gate component failures are often caused by fatigue cracking from repeated loading during operation. This thesis develops and tests a prestressed carbon fiber reinforced polymer (CFRP) fatigue retrofit for controlling fatigue demands within lock gate components. The study expands upon a recent analytical work by Lozano (2017) by experimentally investigating …

Aiding Growers’ Decisions: Describing Arkansas Blackberry Growers’ Resources And Needs Regarding Blackberry Production, Lesley Marie Smith

Graduate Theses and Dissertations

This study was a census of blackberry growers who attended the Blackberry Growers Association informal interest meetings held throughout the state during the month of April. The purpose of this study was to describe blackberry operations in Arkansas, describe the ideal blackberry cultivar growers want to produce, describe resources they use to research production information, and describe what changes to current resources growers would like to have. Questionnaire responses regarding blackberry production of 18 blackberry growers in the state of Arkansas were analyzed. Three growers elected to not participate resulting in an 86% response rate. The researcher hopes that this …

Zona Libre: Conservatism, Urban Growth, And The Rise Of The New Economy In The San Diego Borderlands, Daniel Elkin

Graduate Theses and Dissertations

Both the rise of conservatism as well as the neoliberal turn of the twentieth century have received much scholarly attention in recent decades. Often, these two subjects are examined separately, with the former focusing on questions of party realignment in the United States and the latter on global economic shifts toward privatization, finance, and the segregation of labor types across international boundaries. As a result, efforts to trace the dual movement between questions of domestic politics and international economy are left underdeveloped. “Zona Libre: Conservatism, Urban Growth, and the Rise of the New Economy” remedies this gap by exploring the …

Efficacy Of Multi-Threshold Null Convention Logic In Low-Power Applications, Brent Bell

Graduate Theses and Dissertations

In order for an asynchronous design paradigm such as Multi-Threshold NULL Convention Logic (MTNCL) to be adopted by industry, it is important for circuit designers to be aware of its advantages and drawbacks especially with respect to power usage. The power tradeoff between MTNCL and synchronous designs depends on many different factors including design type, circuit size, process node, and pipeline granularity. Each of these design dimensions influences the active power and the leakage power comparisons. This dissertation analyzes the effects of different design dimensions on power consumption and the associated rational for these effects. Results show that while MTNCL …

Flow Regime Influences On Stream And Riparian Soil Carbon Dynamics In The Ozark Highlands And Boston Mountains Of Arkansas, Allyn Dodd

Graduate Theses and Dissertations

The natural flow regime exerts primacy over lotic ecosystem patterns and processes. However, little work has examined the influence of flow regime on instream and riparian carbon (C) dynamics in minimally-impacted, temperate forested systems. To date, most research efforts have focused on characterizing C movement and transformations across biomes and land use categories; however, flow regime represents an overlooked, finer level of detail that may drive differences in ecosystem function. My dissertation objective was to measure C fixation and movement within and across multiple environmental spheres (e.g. within stream channels, between stream surfaces and the atmosphere, and from riparian soils …

The Spatial Agency Of The Catacombs: An Analysis Of The Interventions Of Damasus I (305-384), Natalie A. Hall

Graduate Theses and Dissertations

Damasus I (305-384) ascended to the office of the Bishop of Rome after a bitter and bloody battle with Ursinus in 366 CE. The violence was a culmination of doctrinal squabbles and power contests which erupted in the Roman church over the course of the fourth century. Damasus engaged in a substantial program of physical renovation and enlargement of martyr sites and personally penned numerous epigrams both extolling the virtue of the honored dead and the patronage of the bishopric. Scholarship related to Damasus and his works is typically narrowly focused, considering motive(s) for his actions, his use of specific …

“There Goes That Relationship”: Journalistic Aggression And Political Equivocation In Joint Press Conferences, Nichole Anne Russell

Graduate Theses and Dissertations

This study evaluates the relationship between the press and political leaders during joint press conferences. Aggressive journalistic questioning in press conferences has increased over time (Clayman & Heritage, 2002; Clayman, Elliott, Heritage, & McDonald, 2004; Clayman, Elliott, Heritage, & McDonald, 2007), but recent scholarships shows that journalists present less aggressive questions when a foreign head of state is present (Banning & Billingsley, 2007). Joint press conferences hosted in the United States by President Donald Trump between Prime Minister Theresa May of the United Kingdom, Prime Minister Justin Trudeau of Canada, Prime Minister Benjamin Netanyahu of Israel, and Chancellor Angela Merkel …

Three Essays On Macroeconomics And Laboratory Experiments, Justin Leblanc

Graduate Theses and Dissertations

This dissertation examines two prominent macroeconomic models and their behavioral underpinnings in a laboratory setting. The first is that of state-dependent pricing models (i.e., “menu cost” models). Comparisons were made between laboratory results and a computer- simulated optimal behavior, and results indicate that subjects update prices too frequently resulting in statistically suboptimal profits due to subjects’ inability to clearly ascertain the optimal threshold at which to update prices. Second, the consumption predictions made under rational inattention theory were examined via a laboratory experiment. Results indicate that subjects’ behavior aligns well with predictions in that they consume stochastically, yet adjust their …

Check Six: The Duke Cunningham Story, Ninette Del Rosario Sosa

Graduate Theses and Dissertations

This short documentary film is about one man’s ascent, descent and redemption for making an extremely poor personal decision that has impacted his entire adult life. Randall “Duke” Cunningham, 76, is a former U.S. Republican Congressman from California who was sentenced in 2005 to more than eight years in prison for accepting bribes totaling $2.4 million and tax evasion. He was released from an Arizona prison in 2013 and moved to Hot Springs Village, Arkansas because he had a brother and sister-in-law who lived there and they could assist him in getting settled. He said the area was quiet and …

Multiculturalism, Colorblindness, And Prejudice: Examining How Diversity Ideologies Impact Intergroup Attitudes, David Sparkman

Graduate Theses and Dissertations

The present research examined an underlying psychological process of the effect of diversity ideologies on prejudice among Whites. In one study, I tested whether colorblindness vs. multiculturalism affected perceptions of similarity vs. difference, outgroup perspective taking, and, in turn, prejudice. Using an experimental design, 341 total White participants from both an undergraduate (n = 151) and non-student adult sample (n = 190) were randomly assigned to a standard colorblind or multicultural condition. Participants then completed various measures of perceived similarities vs. differences (visual, interpersonal), outgroup perspective taking (egocentrism, perspective-taking scenario), and prejudice (explicit racial bias, symbolic racism). Results suggest the …

Essays On Performance Implications Of Social Media For Established And Nascent Firms, Alireza Golmohammadi

Graduate Theses and Dissertations

The possibility of large-scale communication with stakeholders brought about by social media has made these new channels of communication an important arena for spending marketing budgets. Despite the increasing share of social media in firms’ marketing budget, there is significant heterogeneity in firms’ social media communication practices even within the same venue and among firms from the same industry. As such, there is need for more research on how firms can leverage social media to achieve better performance. In order to address this broad question, two essays have been designed and executed.

The first essay utilizes integrated marketing communication as …

Gold Nanoparticles For Stem Cell Delivery In Myocardial Infarction: Analysis Of Toxicity And Development Of A Cell Culture Platform For Use In An In-Vitro Model Of Mi-Associated Ischemia/Reperfusion, Jeffrey Curran Henson

Graduate Theses and Dissertations

In this work, the potential for PEGylated gold nanoparticles for use as a platform for stem cell delivery in treatment of myocardial infarction (MI) is preliminarily investigated. Cardiovascular disease is currently the leading cause of death worldwide, with majority of mortality resulting from coronary artery disease and associated MI. The ensuing ischemic conditions resulting from MI cause substantial heart muscle tissue loss and scarring in the heart. Adverse tissue remodeling creates a significant loss in heart function that can result in the formation of cardiac hypertrophy, ventricular dilation and arrythmias. The long-term prognosis of patients who have suffered MI is …

Estimating Watershed Mercury Contribution To Lake Fort Smith State Park, Arkansas, Usa, William Miles Harmon

Graduate Theses and Dissertations

Mercury contamination associated with human activities poses global human health and environmental risks. A fish-consumption advisory has been in effect at Lake Fort Smith in central west Arkansas for more than a decade due to observed methylmercury concentrations in fish tissue. Lake Fort Smith is an important municipal drinking water supply and recreational resource. Water samples from the majority contributing tributary stream, Frog Bayou creek, were collected periodically, under differing hydrologic conditions in order to quantify the allochthonous mercury load delivered to the lake. Temperature, specific conductance, and turbidity data were collected and used to estimate dissolved organic carbon, methylmercury …

Mapping Lower Austin Chalk Secondary Porosity Using Modern 3-D Seismic And Well Log Methods In Zavala County, Texas, David Kilcoyne

Graduate Theses and Dissertations

Establishing fracture distribution and porosity trends is key to successful well design in a majority of unconventional plays. The Austin Chalk has historically been referred to as an unpredictable producer due to high fracture concentration and lateral variation in stratigraphy, however recent drilling activity targeting the lower Austin Chalk has been very successful. The Upper Cretaceous Austin Chalk (AC) and underlying Eagle Ford (EF) units are considered by many to act as a single hydrocarbon system, with communication between these two units largely through expulsion or dewatering fractures, extensional faults or along the AC/EF unconformity. Total porosity for the Eagle …

Scattering Of Few Photon Fields By Two Level Systems In A One Dimensional Geometry, William Konyk

Graduate Theses and Dissertations

Recent experimental progress has realized strong, efficient coupling of effective two level systems to waveguides. We study the scattering of multimode photons from such emitters coupled losslessly to the confined geometry of a one dimensional waveguide. We develop novel techniques for describing the scattered state of both single and multi-photon wavepackets and explore how such wavepackets interact with arrays of emitters coupled to a one dimensional waveguide. Finally, we apply these techniques and analyze the capability of two particular systems to act as a quantum conditional logic gate.

Predicting Changes In Earnings: A Walk Through A Random Forest, Joshua Hunt

Graduate Theses and Dissertations

This paper investigates whether the accuracy of models used in accounting research to predict categorical dependent variables (classification) can be improved by using a data analytics approach. This topic is important because accounting research makes extensive use of classification in many different research streams that are likely to benefit from improved accuracy. Specifically, this paper investigates whether the out-of-sample accuracy of models used to predict future changes in earnings can be improved by considering whether the assumptions of the models are likely to be violated and whether alternative techniques have strengths that are likely to make them a better choice …

Establishing Influence And Authority In Ancient Civilizations And Modern Politics: The Rhetoric Of Oracles And The Oracular Maneuvers Of Political Action Committees, Michel C. Lacrue

Graduate Theses and Dissertations

While most animals communicate in order to convey environmental information such as danger or where food is located, humans have evolved and developed an articulated language for a myriad of uses, and our language is the basis for how we shape and maintain reality. Language can be used to teach, express an attitude or affiliation to a group, and give us a sense of our state of being, but it can also be used to manipulate a narrative in order to gain power over others. This project argues that Political Action Committees (PACs), and the language that they use in …

Strong Evidence For The Density-Wave Theory Of Spiral Structure From A Multi-Wavelength Study Of Disk Galaxies, Hamed Pour-Imani

Graduate Theses and Dissertations

The density-wave theory of spiral structure, though first proposed as long ago as the mid-1960s by C.C. Lin and F. Shu (Lin & Shu, 1964; Bertin & Lin, 1996; Shu, 2016), continues to be challenged by rival theories, such as the manifold theory. One test of these theories which has been proposed is that the pitch angle of spiral arms for galaxies should vary with the wavelength of the image in the density-wave theory, but not in the manifold theory. The reason is that stars are born in the density wave but move out of it as they age. In …

A Multimodal Assessment Of Disgust In Response To Traumatic Event Reminders Among Adolescents, Teah-Marie R. Bynion

Graduate Theses and Dissertations

The majority of youth will report traumatic event exposure by the time they reach adulthood. Research suggests exposure to such events is linked to myriad negative outcomes. Not all traumatic events are alike, however; evidence suggests that, compared to non-interpersonal events, interpersonal events in which another person intentionally perpetrates harm are linked to elevations in the likelihood of negative outcomes, including posttraumatic stress disorder (PTSD). One reason for this discrepancy is that interpersonal traumatic events may elicit greater levels of disgust. However, this is a very under-developed research base, no study has examined this question among youth. The current study …

Activating Schemata In Esl Writing, Uyen Dang

Graduate Theses and Dissertations

My research aims at exploring the contribution of various types of schemata to leaners’ text comprehension and text production, especially ESL (English as a Second Language) writing, to better understand how ESL learners, especially Vietnamese graduate students, use diverse resources in schema activation to facilitate their processes of learning to write in the academic setting. To better understand these processes, the researcher synthesized previous studies together with conducting interviews with four Vietnamese graduate students and analyzing their writing samples to investigate the relationships among types of schemata: formal, content, and rhetorical schemata, which can be significant in ESL writing and …

Adapting To Sparsity And Heavy Tailed Data, Mohamed Abdelkader Abba

Graduate Theses and Dissertations

The Lasso and the Horseshoe, gold-standards in the frequentist and Bayesian paradigms, critically depend on learning the error variance. This causes a lack of scale invariance and adaptability to heavy-tailed data. The √ Lasso [Belloni et al., 2011] attempt to correct this by using the `1 norm on both the likelihood and the penalty for the objective function. In contrast, there is essentially no methods for uncertainty quantification or automatic parameter tuning via a formal Bayesian treatment of an unknown error distribution. On the other hand, Bayesian shrinkage priors lacking a local shrinkage term fails to adapt to the large …

Can Social Capital Boost Irrigation Capital: Empirical Evidence From North China, Yefan Nian

Graduate Theses and Dissertations

Using data from China Water Institution and Management (CWIM) survey, the study first constructs measures of all three most studied dimensions of social capital: trust, networks, and norms. The study then examines if social capital has any predictive powers of individual farmers’ contribution decisions as well as farmers’ contributions aggregated at the village level. Farmers’ choices between different forms of contributions (labor versus cash) are also analyzed. Our results suggest that all three dimensions of social capital explain farmers’ contribution decisions. Governance quality of local irrigation systems and the norm of cooperation have strong predictive powers of farmers’ decisions to …

Are Unicorns Extinct In The Modern World?: Directing Tennessee Williams' The Glass Menagerie In 2017, Jon Cole Wimpee

Graduate Theses and Dissertations

What follows is a description of my process directing The Glass Menagerie by Tennessee Williams.

I’ve made an effort to track the journey I undertook starting from my earliest encounter with the play and the selection of the story as a thesis project. This document contains my initial script analysis, notes from design meeting collaborations, casting decisions, general research approaches, the rehearsal process, performance insights, and evaluations after completion. This document will also provide, intermittently, additional reflections on my critical attitudes towards this play and production, as well as self-assessments related to notable lessons, successes, failures, and discoveries pertinent to …

Introducing The Academic Discipline Of Agricultural Communications To The United Kingdom: A Needs Analysis, Sara Kathryn Maples

Graduate Theses and Dissertations

There is a current need to identify and describe opinions of prospective employers and current agricultural students about the prospects of developing an agricultural communications academic discipline in the U.K. An understanding of the competencies employers would expect of agricultural communications graduates, as well as an understanding of what students would expect to learn, would form the conceptualization and development of the discipline in the U.K. A total of 22 agricultural communications professionals and 67 agricultural students from across the United Kingdom completed the survey. Collected data showed agricultural students and agricultural communications professionals answers overall were not statistically different. …

Comparison Of Correlation, Partial Correlation, And Conditional Mutual Information For Interaction Effects Screening In Generalized Linear Models, Ji Li

Graduate Theses and Dissertations

Numerous screening techniques have been developed in recent years for genome-wide association studies (GWASs) (Moore et al., 2010). In this thesis, a novel model-free screening method was developed and validated by an extensive simulation study. Many screening methods were mainly focused on main effects, while very few studies considered the models containing both main effects and interaction effects. In this work, the interaction effects were fully considered and three different methods (Pearson’s Correlation Coefficient, Partial Correlation, and Conditional Mutual Information) were tested and their prediction accuracies were compared.

Pearson’s Correlation Coefficient method, which is a direct interaction screening (DIS) procedure, …

The Effects Of Consuming Eggs On The Physical And Cognitive Development Of Food-Insecure Haitian Children, Monica Elaine Stewart

Graduate Theses and Dissertations

Within Latin America and the Caribbean, severe food insecurity is highest in Haiti. Fifty-five percent of the population lives below the poverty line with approximately 50% of the population undernourished. Given the typical diet in the developing world is primarily plant-based, the two studies presented in this thesis examine how eggs, a locally available animal protein, impact physical growth, cognitive development, and motor skills of food-insecure children from a single orphanage in Leogane, Haiti when added to the diet.

In the first study, growth parameters in children ages 3-8 years old were measured at baseline, six months, and one year. …