Digital Commons Network^™

Prestress Losses In Lightweight Self-Consolidating Concrete, Jared Bymaster

Graduate Theses and Dissertations

While much research has been performed on lightweight concrete and self-consolidating concrete (SCC), the knowledge of prestress losses in lightweight self-consolidating concrete (LWSCC) is still limited. LWSCC has the benefits of increased flowability, reduced placement labor, and decreased shipping cost compared to conventional concrete. This research program included the study of 14 SCC beams cast with expanded clay, expanded shale, and limestone aggregates. Strains in the beams were measured with vibrating-wire strain gages, and the measured prestress losses were compared with current AASHTO methods for calculating prestress losses. The AASHTO approximate method better predicted actual losses than did the AASHTO …

Development Of Mems-Based Corrosion Sensor, Feng Pan

Graduate Theses and Dissertations

This research is to develop a MEMS-based corrosion sensor, which is used for monitoring uniform, galvanic corrosion occurring in infrastructures such as buildings, bridges. The corrosion sensor is made up of the composite of micro/nano metal particles with elastomers. The mechanism of corrosion sensor is based on the mass transport of corrosive species through the sensor matrix. When the metal particles in the matrix corrode, the electrical resistivity of the material increases due to increasing particle resistances or reduction of conducting pathways. The corrosion rate can be monitored by detecting the resistivity change in sensing elements. The life span of …

Silica Nanoparticle-Based Coatings With Superhydrophilic And Superhydrophobic Properties, Robert Andrew Fleming

Graduate Theses and Dissertations

Superhydrophilic and superhydrophobic surfaces have potential for implementation into a variety of fields, including self-cleaning surfaces, anti-fogging transparent materials, and biomedical applications. In this study, sandblasting, oxygen plasma treatments, silica nanoparticle films, and a low surface energy fluorocarbon film were employed to change the natural surface wettability of titanium, glass, and polyethylene terephthalate (PET) substrates, with an aim to produce superhydrophilic and superhydrophobic behavior. The effects of these surface modifications are characterized by water contact angles (WCAs), surface wetting stability, surface morphology and roughness, surface elemental composition, and optical transmittance measurements. The results show that stable superhydrophilic and superhydrophobic surfaces …

Distribution Map Of Multi-Walled Carbon Nanotubes In A Refrigerant/Oil Mixture Within A 2.5 Ton Unitary Air-Conditioner, Warren Russell Long

Graduate Theses and Dissertations

In recent years, nanoparticles have received considerable attention as a potential additive to heat transfer fluids (i.e. refrigerant) in order to increase the heat transfer capabilities of these fluids. The potential of carbon nanotubes (CNTs) to exit the compressor, migrate throughout a vapor compression air conditioning system, and possibly foul the components of such a system was experimentally investigated in this research. Six grams of CNTs were dispersed in the polyol ester oil used by a 2.5 ton (8.79 kW) unitary air conditioning system, which was continuously operated for 168 hours. After this time, the unit was shut down and …

Resistance Screening And Control Options For Glyphosate-Resistant Palmer Amaranth (Amaranthus Palmeri) In Cotton (Gossypium Hirsutum), Ryan Christopher Doherty

Graduate Theses and Dissertations

In the mid-2000's, glyphosate-resistant Palmer amaranth biotypes began to emerge in many southern states. In 2006, glyphosate-resistant Palmer amaranth was identified in a field in Mississippi County, Arkansas. A greenhouse experiment was conducted in 2008 to screen Palmer amaranth accessions, collected in this survey, for glyphosate resistance. Inflorescence were collected from a total of 276 plants from fields were glyphosate failure occurred, representing 74 accessions in 14 counties, including Clay, Craighead, Crittenden, Greene, Jackson, Jefferson, Lawrence, Lee, Mississippi, Phillips, Poinsett, Randolph, St. Francis, and White Counties. Eight of the 74 accessions did not produce viable seed. In the greenhouse, 32 …

Comprehensive Drainage Study Of The Upper Reach Of College Branch In Fayetteville, Arkansas, Kathryn Lea Mccoy

Graduate Theses and Dissertations

College Branch is a stream with headwaters located on the University of Arkansas campus. The stream flows through much of the west side of campus, gaining discharge and enlarging its channel as it meanders to the south. College Branch has experienced erosion and flooding issues in recent years due to increased urbanization of its watershed and increased runoff volume.

The purpose of this project was to develop a comprehensive drainage study of College Branch on the University of Arkansas campus. Storm runoff and flood flow patterns were evaluated in order to understand the hydraulics and hydrology of the watershed and …

Implementing Conductive Concrete With Photovoltaic Energy To Develop Anti-Icing Airfield Runways, Adam Benjamin Osweiler

Graduate Theses and Dissertations

Snow and ice accumulation on airport runways force airports to cancel or significantly delay flights. Winter weather can also drastically affect airport safety during times of aircraft takeoff and landing. During these times, countless dollars are used to remove snow and return airports to their functional conditions. In this thesis, a conductive concrete solar energy system will be examined in order to prevent snow and ice accumulation. The objective of this research is to implement a conductive concrete overlay system on airport runways in conjunction with photovoltaic energy so that no frost precipitation accumulates on the runway surface.

Performance And Cost Analysis Of A Structured Concrete Thermocline Thermal Energy Storage System, Matt Nicholas Strasser

Graduate Theses and Dissertations

Increasing global energy demands and diminishing fossil fuel resources have raised increased interest in harvesting renewable energy resources. Solar energy is a promising candidate, as sufficient irradiance is incident to the Earth to supply the energy demands of all of its inhabitants. At the utility scale, concentrating solar power (CSP) plants provide the most cost-efficient method of harnessing solar energy for conversion to electrical energy. A major roadblock to the large-scale implementation of CSP plants is the lack of thermal energy storage (TES) that would allow the continued production of electricity during the absence of constant irradiance. Sensible heat TES …

The Design And Implementation Of A Mobile Game Engine For The Android Platform, Jon Hammer

Computer Science and Computer Engineering Undergraduate Honors Theses

In this thesis, a two-dimensional game engine is proposed for the Android mobile platform that facilitates rapid development of those games by individual developers or hobbyists. The essential elements of game design are presented so as to introduce the reader to the concepts that are crucial for comprehension of the paper. A brief overview of the Android Operating System is also included for those unfamiliar with it. Three primary design goals are identified, and a prototype solution is described in detail. The prototype is then evaluated against those design goals to see how well it accomplishes each task. The results …

Modeling, Fabrication And Characterization Of Scalable Electroless Gold Plated Nanostructures For Enhanced Surface Plasmon Resonance, Gyoung Gug Jang

Graduate Theses and Dissertations

The scientific and industrial demand for controllable thin gold (Au) film and Au nanostructures is increasing in many fields including opto-electronics, photovoltaics, MEMS devices, diagnostics, bio-molecular sensors, spectro-/microscopic surfaces and probes. In this study, a novel continuous flow electroless (CF-EL) Au plating method is developed to fabricate uniform Au thin films in ambient condition. The enhanced local mass transfer rate and continuous deposition resulting from CF-EL plating improved physical uniformity of deposited Au films and thermally transformed nanoparticles (NPs). Au films and NPs exhibited improved optical photoluminescence (PL) and surface plasmon resonance (SPR), respectively, relative to batch immersion EL (BI-EL) …

An Analysis Of The Legal Obstacles To State Pension Reform, Jeremy Stuart Buck

Graduate Theses and Dissertations

Public pension systems are underfunded, straining state budgets. Historically, many states have presumed that they can modify pension benefits only as to newly-hired employees, and that they must leave benefit accruals untouched for current workers. More recently, though, states have begun enacting more fundamental pension reform that modifies future accruals or even reduces cost-of-living allowances for retirees. Nearly all such new reforms have been the subject of one or more lawsuits alleging that the federal and/or state constitution bars the legislature from reducing benefits or accrual patterns. This dissertation examines the legal underpinnings for arguments made against pension reform, and …

Urbanism In The Northern Levant During The 4th Millennium Bce, Rasha El-Endari

Graduate Theses and Dissertations

The development of urbanism in the Near East during the 4thmillennium BCE has been an important debate for decades and with recent scientific findings, a revival of this intellectual discussion has come about. Many archaeologists suggested that urban societies first emerged in southern Mesopotamia, and then expanded to the north and northwest. With recent excavations in northern Mesopotamia, significant evidence has come to light with the finding of monumental architecture and city walls dated to the beginning of the 4th millennium BCE, well before southern Mesopotamian urban expansion. These discoveries reflect important administrative systems and stratified sociopolitical structures within these …

Refractive Index Chemical Sensing With Noble Metal Nanoparticles, Phillip Blake

Graduate Theses and Dissertations

Chemical sensing is a key component in modern society, especially in engineering applications. Because of their widespread impact, improvements to chemical sensors are a significant area of research. One class of sensors, plasmonic sensors, is being heavily researched because of their ability to detect low levels of analyte in near real time without destroying the analyte. This work studies a new class of plasmonic sensor that utilizes diffractive coupling to improve sensor performance. Specifically, this work outlines the first study of diffractive coupling sensors with typical nanoparticle shapes. Sensitivity of this new class of sensor is directly compared to typical …

Timing Of Castration, With Or Without Analgesia, On Growth Performance, Hematology, And Behavior Of Beef Calves, April C. Brown

Graduate Theses and Dissertations

Angus-sired (n = 30) and Hereford-sired (n = 32) bull calves were assigned randomly to 1 of 4 treatments. Treatments were 1) surgical castration near birth, 2) oral administration of the analgesic meloxicam (1 mg/kg of body weight) followed by surgical castration near birth, 3) surgical castration at weaning, or 4) surgical castration at weaning with oral administration of the analgesic meloxicam (1 mg/kg of body weight). Data was recorded for behavior, hematology, and growth at birth and weaning. Calf standing and lying activity was monitored at both stages by recording x and y axis positions of a data logger …

Do Honors Programs Make A Difference During The First Year Of College? The Development Of Critical Thinking Skills And Exposure To Good Practices In Undergraduate Education, Amanda Kay Moore

Graduate Theses and Dissertations

This longitudinal study analyzed pretest-posttest data to 1) examine the influence of honors programs on first-year college students' critical thinking skills, 2) to determine whether students in honors programs receive more exposure to good practices in undergraduate education than their non-honors peers, and 3) to assess the effect of good practices on critical thinking. The quasi-experimental study also investigated whether the influence of honors programs on critical thinking skills varied in direction and magnitude for male versus female students and White versus students of color. To replicate an earlier study conducted by Seifert et al. (2007), the current study utilized …

Prehistoric Human Ecodynamics In The Rub Al-Khali Desert: Results Of Remote Sensing And Excavations In Dubai, United Arab Emirates, Jason T. Herrmann

Graduate Theses and Dissertations

Archaeological investigations in the Emirate of Dubai, UAE conducted by the Dubai Department of Archaeology and the University of Arkansas demonstrate that the desert inland of the Oman Peninsula was occupied not only during the Arabian Neolithic (8000-4400 BC), when the region experienced a moist period referred to as the Holocene Climatic Optimum (HCO), but also during the more arid millennia following the decline of the HCO into the Christian Era. During this period, desert settlement clustered near a band of oases, in contrast to the more widespread spatial distribution of remains of nomadic pastoralists from the Neolithic. Excavations at …

The Relationship Of Peer Acceptance, Age, Gender, Ethnicity, And Appearance Among Preschoolers, Kora Klaire Stuffelbeam

Graduate Theses and Dissertations

The purpose of this study was to examine preschool children's acceptance of peers. The term peer acceptance is defined as "the degree a child is Socially accepted or rejected by his or her peer group." Johnson et al. (2002) found children between the ages of three and five were able to develop friendships and Social skills that would impact their acceptance among peers. The study determined if children based their choice of peers according to a child's age, gender, ethnicity, appearance, and/or Social skills. The subjects of this study were 31 children whose ages were three-, four-, and five-years-old who …

Preparedness To Implement Wellness Strategies: Perceptions Of School Counselors, Tena Burnett

Graduate Theses and Dissertations

The purpose of this study is to survey school counselors to determine their knowledge and perceived preparedness to implement wellness strategies in school counseling programs. Wellness plans are a requirement for thousands of public school districts in the United States. There are no established standards for the training of school counselors in the area of wellness. School counselors are in a unique position to positively impact students through the use of wellness programs and strategies. School counselors from a mid-south state (N = 156) completed an electronic survey to measure how they implement wellness strategies and their perceived preparedness in …

Expansion Of Human Induced Pluripotent Stem Cells On Synthetic Substrate In Defined Medium, Huantong Yao

Graduate Theses and Dissertations

Human induced pluripotent stem cells (hiPSCs) have the potential to generate patient-specific cells to treat many incurable diseases by cell replacement therapy. However, so far the culture of hiPSCs depends greatly on feeder cells or Matrigel which has safety issues. Thus, chemically defined substrates that could provide niches necessary for cell attachment and proliferation are preferred for clinical application of hiPSCs. Recently, Corning Life Sciences has developed synthetic peptide-functionalized cell culture surface, referred to as Corning® Synthemax that support self-renewal and differentiation of human embryonic stem cell (hESC). In this work, we have collaborated with Corning to investigate the attachment, …

Ideology In Popular Late Twentieth And Twenty-First Century Children's And Young Adult Literature And Film, Iris Grace Shepard

Graduate Theses and Dissertations

Texts created for the consumption of children and young adults are not simple texts made for the sole purpose of entertaining young audiences. In fact, these texts are complicated, multi-faceted texts that function both in the creation and performance of childhood. Children's and young adult literature and film disseminated mainstream ideology about young people's place in society and attempt to enculturate young readers and viewers in regards to race, gender, age, and Social class. However, by helping young people interact critically with these texts, critical thinking skills as well as a passion for reading can be fostered. In addition, by …

Breeding For Modified Seed Composition In Soybean: Selection Of Genotypes, Yield Stability, And Environmental Effects, Luciano Miguel Jaureguy

Graduate Theses and Dissertations

The development of cultivars with modified seed composition represents an excellent alternative to cope with the world's need for more nutritious food. Understanding the genetic and environmental factors controlling crop seed quality traits is of crucial importance for such an endeavor. The objectives of this study were: a) to evaluate the efficiency of phenotype and marker-assisted selection for low stachyose and low phytate soybean breeding lines, and their yield stability, b) to study the effect of management practices planting date and delayed harvest on soybean seed composition, and c) to study the potential association between soil properties and leaf chemical …

Influence Of Nutritional Modifications On Sow, Litter, And Nursery Performance, Benjamin Edward Bass

Graduate Theses and Dissertations

Two separate series of experiments were conducted to determine: 1) the influence of dietary arginine supplementation in late gestation on reproductive performance, and 2) the impact of a whole yeast product in gestation, lactation, and weaned pig diets on reproductive, growth, and immune parameters.

In the first study 99 sows were provided a control diet, or the control diet supplemented with 1% L-arginine from gestation d 93 to 110. Compared to control-fed sows, no differences were observed in reproductive parameters, however a tendency for increased gestational weight gain was observed for sows provided supplemental arginine.

In a second study, 98 …

Titanium Aluminum Nitride Films Deposited By Ac Reactive Magnetron Sputtering: Study Of Positioning Effect In An Inverted Cylindrical Magentron Sputtering System, George C. Vandross Ii

Graduate Theses and Dissertations

TiAlN films were deposited on glass substrates by AC magnetron sputtering at 2 kW with constant Argon and Nitrogen gas flow rates to study the effects of positioning on the deposited films. The deposition system used was an ICM-10 IsoFlux cylindrical magnetron sputtering chamber. The samples were placed in different positions and tilts with respect to the location of the Titanium and Aluminum targets in the chamber. It was found that with change in position and application of tilts, deposited films acquired different physical and chemical properties. It is believed that the differences in these properties were caused by to …

Master Principals' Perceptions Of The Impact Of The Arkansas Leadership Academy's Master Principal Program On Leadership Practices, School Cultures And Student Achievement, Diana Peer

Graduate Theses and Dissertations

A qualitative dissertation study was conducted to examine the impact of the Arkansas Leadership Academy's Master Principal Program through the perspective of those who have completed the entire program and attained designation as a Master Principal. A logic model for the Master Principal Program offered a context for the study. A review of relevant literature provided the identification of gaps in the research which included limited findings for a program comparable to the Master Principal Program. Research methods for this phenomenological study were explained. The research sample included Master Principals, as of 2011. Interviews and a focus group using collaborative …

Phenotypic Plasticity Of Rattlesnake Trophic Morphology, Matthew Thomas Smith

Graduate Theses and Dissertations

The trophic morphology of gape-limited predators constrains the shape and size of prey items they can ingest. Trophic morphology consists of any morphological feature that is involved in the handling and ingestion of food. Diet has a profound effect on the morphology of many gape-limited predators. Identifying how prey type and resource level affect the morphology of different populations is an essential step in understanding the mechanisms contributing to patterns of morphological diversity. Species interactions (Chapter 1) induce plasticity in morphology that can lead to increased fitness, morphological divergence, and eventually speciation.

In Chapter 2, a laboratory study tested the …

Community Structure And Ecological Specialization In Plant-Ant Interactions, Paola Barriga

Graduate Theses and Dissertations

Positive associations among species have contributed to the maintenance of biodiversity. These interactions are typically studied in pairwise fashion where two interacting organisms are the focus. This dissertation uses network theory to analyze positive plant-ant associations in three Neotropical forests. Obligate plant-ant mutualisms were used, where plants host the ants in domatia and provide food bodies while the ants protect the plants and can feed them. A network approach was used to depict all obligate plant-ant interactions within a community. The main questions asked at the community level were: 1) Do network structure and levels of specialization change geographically and, …

Effect Of Body Size And Exercise On Mood State, Alexandra Lachance

Graduate Theses and Dissertations

Exercising in the presence of nature (i.e., "green exercise"), has been shown to heighten the physiological and mental benefits of traditional exercise on non-obese individuals. The effects of green exercise on obese individuals are unknown. It is hypothesized that green exercise is more beneficial for obese (greater positive improvements in mental health scores), compared to non-obese individuals. For example, the benefits of green exercise could help lower feelings of depression, improve mood and self-esteem to increase the propensity of obese individuals to meet exercise recommendations. Accordingly, this study investigated the physiological and psychological effects of green exercise on 12 obese …

Analytical Research Topics In Sport Management, Gi-Yong Koo

Graduate Theses and Dissertations

The field of sport management has grown tremendously as an academic discipline. Researchers have continuously discussed the scope and direction of research and the importance of the diversity of research design. There have been a significant number of studies examining the scope and direction of research over the past few decades such as: the lack of diversity in methodology; the lack of diversity in research focus; the lack of importance of power analysis; and the lack of diversity in topic areas. Embracing a variety of research designs is an absolutely necessary condition for the growth and credibility of sport management …

Characterization And Epidemiology Of Soybean Vein Necrosis Associated Virus, Jing Zhou

Graduate Theses and Dissertations

Soybean vein necrosis disease (SVND) is widespread in major soybean-producing areas in the U.S. The typical disease symptoms exhibit as vein clearing along the main vein, which turn into chlorosis or necrosis as season progresses. Double-stranded RNA isolation and shot gun cloning of symptomatic tissues revealed the presence of a new tospovirus, provisionally named as Soybean vein necrosis associated virus (SVNaV). The presence of the virus has been confirmed in 12 states: Arkansas, Illinois, Missouri, Kansas, Tennessee, Kentucky, Mississippi, Maryland, Delaware, Virginia and New York. Symptomatic samples collected from eight states (AR, IL, MO, MS, KS, TN, MD and DE), …

Effects Of Associated Subcortical Beetles On Oviposition Behavior And Early-Stage Survival Of Sirex Nigricornis F. (Hymenoptera: Siricidae), Ace J. Lynn-Miller

Graduate Theses and Dissertations

Sirex (Hymenoptera: Siricidae) woodwasps develop within xylem of host conifers. Sirex females drill through the bark, phloem and into xylem tissues where they deposit eggs along with a symbiotic Amylostereum fungus. The presence of Amylostereum is necessary for successful development of Sirex immatures as the larvae are unable to derive adequate nutrition from xylem in the absence of the fungus. The Eurasian woodwasp, Sirex noctilio F., was discovered in northeastern North America in 2004. Sirex noctilio has caused significant economic damage in Pinus radiata D. Don plantations of the southern hemisphere, but is of little economic significance in its native …