Engineering Commons^™

Airport Security Investment Model, Joshua Daniel Bolton

Graduate Theses and Dissertations

In an increasingly mobile and diverse world, it is difficult to quantify the risk, or danger, associated with traveling. Airports have suffered greatly for being unable to define potential risks and protect against them. Intelligent adversary risk is a complicated high-level issue for many airports. Airports are targeted because of the large amount of people in a confined space and the social, economic, and psychological impact of terrorist attacks on the American people. In the months following September 11th, 2001, the airline industry in the United States lost $1.1 billion in revenue. The American people stayed grounded, for fear of …

Development Of Pre-Stressed Retrofit Strategies For Mitigating Fatigue Cracking In Steel Waterway Lock Gate Components, Christine Michelle Lozano

Graduate Theses and Dissertations

Lock gates are an important part of the transportation infrastructure within the United States (US), having many economic, safety, and environmental benefits over rail and highway transportation systems. Unfortunately, many existing lock gates throughout the US have reached or exceeded their initial design life and require frequent repairs to remain in service. Unscheduled repairs often increase as gates age, having a local economic impact on freight transport which can create economic ripples throughout the nation. Fatigue and corrosion are key causes of unscheduled service interruptions, degrading lock gate components over time. Additionally, because lock gates are submerged during operation, crack …

Coupling K-12 Music Education With Science, Technology, Engineering And Math (Stem) Curricula: Implementation Of A Stemusic Outreach Program, Mallory Maestri

Civil Engineering Undergraduate Honors Theses

Many studies have investigated the effects of music on evoking human emotions and diverse types of brain responses. One study by Juslin and Vastfjall indicates that hearing music can stimulate brain stem reflexes, create emotional contagion, recall episodic memories and provoke visual imagery. Due to the influence music has on human brain waves, researchers have been studying the effect of music on enhancing the spatial abilities of young students. Science, Technology, Engineering and Math (STEM) professions rely heavily on spatial skills. Research on the connection of music with spatial skills proposes that when the brain processes rhythm a “mental rotation” …

Measurement Of Peptoid Concentration Using Uv Spectroscopy, Katie Holland

Chemical Engineering Undergraduate Honors Theses

The goal of this research is to establish a relationship between ultraviolet adsorption and peptiod concentration to be used to determine the concentration of an unknown peptoid sample. This will allow for the measurement of concentration differences of peptoid samples before and after incubation with membrane surfaces. Samples were prepared nine know concentrations and diluted 50 fold. The UV absorbances of each sample was measured using a UV spectrophotometer at wavelengths from 200 to 450 nanometers. This process was repeated, and the maximum absorbance of each replicate was averaged to yield an absorbance value for each concentration of peptoid. …

A Risk-Based Method For Estimating The Carbon Sequestration Budget For A Mixed Hardwood Forest, Erin Cooper

Chemical Engineering Undergraduate Honors Theses

Carbon Dioxide (CO₂) levels in the atmosphere have risen from approximately 310 ppm in the 1950’s to over 400 ppm as of 2015. This rise in CO₂ has likely resulted in the observed warming trend of the earth’s atmosphere in the same time frame, causing significant concern in the scientific community. Several mitigation strategies have arisen to combat the upward trend of CO₂ emissions in recent decades, among them being carbon sequestration- the process of capturing CO₂ from the atmosphere and holding it for an extended period of time. This study used the U.S. Forest …

Mppt Control For Solar Splash Photovoltaic Array, Kelsey Zenko

Mechanical Engineering Undergraduate Honors Theses

This thesis demonstrates the ability to model and simulate the operation of Maximum Power Point Tracking, MPPT. Moreover, the MPPT technology is contextualized within the confines of the Solar Splash competition to provide the foundation for future model development and simulation for optimal competition performance. MatLab Simulink was used to model the solar panel's operation. A MPPT algorithm was written using the perturb and observe method and was implemented in the model using a buck DC to DC converter. The performance of the model with hardware in the loop using Typhoon and dSPACE, which demonstrated how the actual hardware would …

Structural And Elastic Properties Of Degenerate Sno Monolayers At Finite Temperature, Afsana Sharmin

Graduate Theses and Dissertations

Chalcogen-based layered superconductors with a litharge structure such as FeS and FeSe mono-layers undergo structural and superconducting phase transitions that are tunable by doping. Representing another material platform with a litharge structure but without valence d-electrons, SnO monolayers also display a structural ground state with a degenerate rectangular unit cell at zero temperature and a charge-tunable energy barrier that leads to a thermally-controllable structural phase change. Doped SnO monolayers with rectangular degenerate unit cells give rise to two-dimensional multiferroicity. Their two-dimensional elastic energy landscape adopts a basic analytic expression that is employed to discuss this structural transition. The results contained …

Analyzing The Fundamental Aspects And Developing A Forecasting Model To Enhance The Student Admission And Enrollment System Of Msom Program, Sultanul Nahian Hasnat

Graduate Theses and Dissertations

A forecasting model, associated with predictive analysis, is an elementary requirement for academic leaders to plan course requirements. The M.S. in Operations Management (MSOM) program at the University of Arkansas desires to understand future student enrollment more accurately. The available literature shows that there is an absence of forecasting models based on quantitative, qualitative and predictive analysis. This study develops a combined forecasting model focusing on three admission stages. The research uses simple regression, Delphi analysis, Analysis of Variance (ANOVA), and classification tree system to develop the models. It predicts that 272, 173, and 136 new students will apply, matriculate …

Free-Space Measurements Of Dielectrics And Three-Dimensional Periodic Metamaterials, Clifford E. Kintner

Graduate Theses and Dissertations

This thesis presents the free-space measurements of a periodic metamaterial structure. The metamaterial unit cell consists of two dielectric sheets intersecting at 90 degrees. The dielectric is a polyetherimide-based material 0.001” thick. Each sheet has a copper capacitively-loaded loop (CLL) structure on the front and a cut-wire structure on the back. Foam material is used to support the unit cells. The unit cell repeats 40 times in the x-direction, 58 times in the y-direction and 5 times in the z-direction. The sample measures 12” × 12” × 1” in total. We use a free-space broadband system comprised of a pair …

Asynchronous 3d (Async3d): Design Methodology And Analysis Of 3d Asynchronous Circuits, Francis Corpuz Sabado

Graduate Theses and Dissertations

This dissertation focuses on the application of 3D integrated circuit (IC) technology on asynchronous logic paradigms, mainly NULL Convention Logic (NCL) and Multi-Threshold NCL (MTNCL). It presents the Async3D tool flow and library for NCL and MTNCL 3D ICs. It also analyzes NCL and MTNCL circuits in 3D IC. Several FIR filter designs were implement in NCL, MTNCL, and synchronous architecture to compare synchronous and asynchronous circuits in 2D and 3D ICs. The designs were normalized based on performance and several metrics were measured for comparison. Area, interconnect length, power consumption, and power density were compared among NCL, MTNCL, and …

Using Historic Pavement Performance Data To Identify And Select Sites For Asphalt Mixture Design Studies, Allyson Richey

Civil Engineering Undergraduate Honors Theses

Since 1997 Arkansas asphalt mixtures have been designed using a procedure commonly known as ‘Superpave’. In a traditional Superpave mix design, the design considers only traditional volumetric parameters; however, recent advances in mix design technology emphasize mixture’s ability to perform in its environment. There are numerous factors which affect the performance characteristics of an asphalt mix. Certainly, the asphalt binder’s performance is a critical variable in this system. Asphalt binders are sensitive to temperature, so much so that their primary parameter on which they are recommended is a function of both temperature and the geographic latitude in which the pavement …

A Silicon Carbide Power Management Solution For High Temperature Applications, Robert Murphree

Graduate Theses and Dissertations

The increasing demand for discrete power devices capable of operating in high temperature and high voltage applications has spurred on the research of semiconductor materials with the potential of breaking through the limitations of traditional silicon. Gallium nitride (GaN) and silicon carbide (SiC), both of which are wide bandgap materials, have garnered the attention of researchers and gradually gained market share. Although these wide bandgap power devices enable more ambitious commercial applications compared to their silicon-based counterparts, reaching their potential is contingent upon developing integrated circuits (ICs) capable of operating in similar environments.

The foundation of any electrical system is …

Power Interface Design And System Stability Analysis For 400 V Dc-Powered Data Centers, Yuzhi Zhang

Graduate Theses and Dissertations

The demands of high performance cloud computation and internet services have increased in recent decades. These demands have driven the expansion of existing data centers and the construction of new data centers. The high costs of data center downtime are pushing designers to provide high reliability power supplies. Thus, there are significant research questions and challenges to design efficient and environmentally friendly data centers with address increasing energy prices and distributed energy developments.

This dissertation work aims to study and investigate the suitable technologies of power interface and system level configuration for high efficiency and reliable data centers.

A 400 …

Energy-Aware Sparse Sensing Of Spatial-Temporally Correlated Random Fields, Zuoen Wang

Graduate Theses and Dissertations

This dissertation focuses on the development of theories and practices of energy aware sparse sensing schemes of random fields that are correlated in the space and/or time domains. The objective of sparse sensing is to reduce the number of sensing samples in the space and/or time domains, thus reduce the energy consumption and complexity of the sensing system. Both centralized and decentralized sensing schemes are considered in this dissertation.

Firstly we study the problem of energy efficient Level set estimation (LSE) of random fields correlated in time and/or space under a total power constraint. We consider uniform sampling schemes of …

Peptoid-Modified Bicelles As Surrogate Cell Membranes For Membrane Protein Sensors And Analytics, Helya Najafi

Graduate Theses and Dissertations

Membrane-affiliated interactions are significant in understanding cell function, detecting biomarkers to diagnose disease, and in testing the efficiency of new therapeutic targets. Model membrane systems have been developed to study membrane proteins, allowing for stable protein structure and maintaining native activity. Bicelles, disc-shaped lipid bilayers created by combining long- and short-chain phospholipids, are the model membrane system of focus in this study. Bicelles are accessible from both sides and have a wide size range, which make them attractive for studying membrane proteins without affecting function. In this work, bicelles were functionalized with two peptoids to alter the edge and face …

Energy Shaping Control For Stabilization Of Interconnected Voltage Source Converters In Weakly-Connected Ac Microgrid Systems, Nadia Lenora Carmita Smith

Graduate Theses and Dissertations

With the ubiquitous installations of renewable energy resources such as solar and wind, for decentralized power applications across the United States, microgrids are being viewed as an avenue for achieving this goal. Various independent system operators and regional transmission operators such as Southwest Power Pool (SPP), Midcontinent System Operator (MISO), PJM Interconnection and Electric Reliability Council of Texas (ERCOT) manage the transmission and generation systems that host the distributed energy resources (DERs). Voltage source converters typically interconnect the DERs to the utility system and used in High voltage dc (HVDC) systems for transmitting power throughout the United States. A microgrid …

Modeling And Simulation Of Iii-Nitride-Based Solar Cells Using Nextnano®, Malak Refaei

Graduate Theses and Dissertations

Nextnano³ software is a well-known package for simulating semiconductor band-structures at the nanoscale and predicting the general electronic structure. In this work, it is further demonstrated as a viable tool for the simulation of III-nitride solar cells. In order to prove this feasibility, the generally accepted solar cell simulation package, PC1D, was chosen for comparison. To critique the results from both PC1D and Nextnano3, the fundamental drift-diffusion equations were used to calculate the performance of a simple p-n homojunction solar cell device analytically. Silicon was picked as the material for this comparison between the outputs of the two simulators as …

Methodologies For Solving Integrated Transportation And Scheduling Problems, Fereydoun Adbesh

Graduate Theses and Dissertations

This research proposes novel solution techniques to optimize two real-world problems in the area of scheduling and transportation. We first consider a model for optimizing the operations of dredges. In this problem, scheduling and assignment decisions are integrated across a finite planning horizon. Additional constraints and problem elements explicitly considered include, but are not limited, to environmental work window restrictions, budget limitations, dredge operation rates and schedule-dependent dredge availability. Our approach makes use of Constraint Programming (CP) to obtain quality and robust solutions within an amount of time small enough to be useful to practitioners. The expanded feature set of …

Green Chemistry Oxidative Modification Of Peptoids Utilizing Bleach And Tempo, Jesse Leland Roberts

Graduate Theses and Dissertations

Biotherapeutic drugs, derived from biological molecules such as proteins and DNA, are becoming an integral and exceptionally critical aspect of modern medicine. Compared to common pharmaceutical drugs, biotherapeutics are much larger in size and have greater target specificity, allowing them to treat many chronic diseases ranging from cancer to rheumatoid arthritis. The major issue with protein based therapeutics is that they readily undergo proteolysis, or enzymatic degradation, when administered through subcutaneous injections. Traditionally, biotherapeutic modification procedures have centered on the use of PEG derivatives. This process, called PEGylation, is unfavorable due to the increases in molecular weights of the proteins …

The Development Of Novel Interconnection Technologies For 3d Packaging Of Wire Bondless Silicon Carbide Power Modules, Sayan Seal

Graduate Theses and Dissertations

This dissertation advances the cause for the 3D packaging and integration of silicon carbide power modules. 3D wire bondless approaches adopted for enhancing the performance of silicon power modules were surveyed, and their merits were assessed to serve as a vision for the future of SiC power packaging. Current efforts pursuing 3D wire bondless SiC power modules were investigated, and the concept for a novel SiC power module was discussed. This highly-integrated SiC power module was assessed for feasibility, with a focus on achieving ultralow parasitic inductances in the critical switching loops. This will enable higher switching frequencies, leading to …

Developing Methods Of Obtaining Quality Failure Information From Complex Systems, Oladapo Olalekan Bello

Graduate Theses and Dissertations

The complexity in most engineering systems is constantly growing due to ever-increasing technological advancements. This result in a corresponding need for methods that adequately account for the reliability of such systems based on failure information from components that make up these systems.

This dissertation presents an approach to validating qualitative function failure results from model abstraction details. The impact of the level of detail available to a system designer during conceptual stages of design is considered for failure space exploration in a complex system. Specifically, the study develops an efficient approach towards detailed function and behavior modeling required for complex …

Deformation Behavior Of Al/A-Si Core-Shell Nanostructures, Robert Andrew Fleming

Graduate Theses and Dissertations

Al/a-Si core-shell nanostructures (CSNs), consisting of a hemispherical Al core surrounded by a hard shell of a-Si, have been shown to display unusual mechanical behavior in response to compression loading. Most notably, these nanostructures exhibit substantial deformation recovery, even when loaded much beyond the elastic limit. Nanoindentation measurements revealed a unique mechanical response characterized by discontinuous signatures in the load-displacement data. In conjunction with the indentation signatures, nearly complete deformation recovery is observed. This behavior is attributed to dislocation nucleation and annihilation events enabled by the 3-dimensional confinement of the Al core. As the core confinement is reduced, either through …

Soil-Structure Interaction Effects On The Seismic Response Of Low-Rise Eccentrically Braced Frames, Luis Gerardo Buitrago Goyez

Graduate Theses and Dissertations

The importance of soil-structure interaction (SSI) effects on the seismic response of buildings has been long recognized and has been researched for over 40 years. However, SSI analysis has only been applied in a few building projects because the fixed base condition is considered to provide a conservative estimation for the response of buildings under seismic loads. This assumption of a fixed base condition adopted by practitioners is not always conservative or cost-effective, especially for rigid buildings over soft soils. Additionally, for the case of ductile steel frames with eccentric configurations, the influence of SSI on their seismic performance has …

A Spreadsheet Algorithm For Determining The Economic Feasibility Of Micro-Chp Systems In The Arkansas Manufacturing Sector, Ford R. Lewallen

Graduate Theses and Dissertations

Combined heat and power (CHP) systems are not new to the market. However, advances in technology, specifically MicroTurbines, have presented new opportunities for installations of micro-CHP units - defined as 50 kWe to 300 kWe, specifically at small- to medium-sized industrial facilities. One pressing concern is whether or not an industrial plant has a high enough process thermal load requirement to fully utilize the energy output.

This thesis will discuss simulations that were run on several actual electric and thermal load combinations, which correspond to types of manufacturing facilities commonly found in Arkansas. Analysis of the plant usage profiles will …

Laboratory Resistivity Measurements For Soil Characterization, Behdad Mofarraj Kouchaki

Graduate Theses and Dissertations

Field based electrical resistivity measurements, such as electrical resistivity tomography (ERT) and capacitively coupled resistivity (CCR), are geophysical methods that offer a non-destructive and rapid means to collect continuous data. As such, ERT and CCR are becoming increasingly popular tools for geotechnical engineers; however, it is challenging to derive geotechnical information such as soil type, density, and water content from the data. A laboratory geophysical investigation was carried out to gain a better understanding of the parameters that affect the electrical resistivity of soils and devise a relationship between resistivity and soil type or classification. In this study, a soil …

Development Of Deep Site Specific And Reference Shear Wave Velocity Profiles In The Canterbury Plains, New Zealand, Michael Ryan Deschenes

Graduate Theses and Dissertations

Deep (typically >1000 m) shear wave velocity profiles were developed across the Canterbury basin at nine strong motion stations using a combination of active and passive surface wave methods and horizontal to vertical spectral ratio measurements. A multi-mode, multi-method joint inversion process, which included Rayleigh and Love wave dispersion and horizontal to vertical spectral ratio data, was used to estimate the shear wave velocity profiles at each site. A-priori geologic information was utilized in defining preliminary constraints on the complex geologic layering of the Canterbury basin. At sites where interbedded layers were present, velocity reversals were considered in the inversion. …

Geophysical Assessment Of Kinion Lake Dam, Tim Allen Moody

Graduate Theses and Dissertations

Geophysical methods including Capacitively-Coupled Resistivity (CCR), Electrical Resistivity Tomography/Imaging (ERT/ERI), Multichannel Analysis of Surface Waves (MASW) with Love and Rayleigh waves and a Full-Waveform Inversion (FWI) were performed on Kinion Lake Dam, an earth-filled embankment dam that has historically experienced significant seepage and internal erosion issues. Surveys were completed along the crest and downstream toe of the dam. Results from the surveys indicate that each method is capable of resolving the bedrock depth within 1-2 m of locations shown on previous drilling logs, though some discrepancies between the methods exist. A weathered bedrock layer is believed to have led to …

Mitigation And Evaluation Of Alkali-Silica Reaction (Asr) And Freezing And Thawing In Concrete Transportation Structures, Richard Albert Deschenes Jr.

Graduate Theses and Dissertations

An evaluation of alkali-silica reaction (ASR) and freezing and thawing (F/T) in concrete transportation structures is presented along with mitigation methods for slowing the rate of deterioration in concrete. A combination of field and laboratory testing confirms ASR deterioration is exacerbated by exposure to F/T. Laboratory testing indicates an aggregate previously deemed inert to ASR, caused ASR deterioration in several concrete pavement and transportation structures. Existing standard test methods deem this aggregate safe for use in concrete. A modified test method shows the concrete can deteriorate rapidly when subjected to cycles of conditions promoting ASR and F/T. Several structures containing …

Optimization Of Concrete Mixtures For Use In Structural Elements, Waleed Almutairi

Graduate Theses and Dissertations

Portland cement is an essential ingredient in concrete. The use of cement is to enhance the strength as well as other hardened properties of concrete mixtures. Determining the accurate amount of cement is important because the required strength may not be achieved if not enough cement is used. By contrast, when using too much cement, concrete cracking may occur that leads to reducing durability. Researchers at the University of Arkansas (UA) have shown that many bridge decks achieve their 28 day design strength of 4000 psi by 7 days of age. Bridge decks having high strength may experience cracking, which …

A Comparative Analysis Of Feed And Environmental Factors On Broiler Growth In The United States, Alexandra Gulli

Graduate Theses and Dissertations

Broiler production in the United States has become an important industry within the last half century. As the demand for poultry continues to increase and the concern of climate change also increases, it will become an important part of the industry to become more sustainable. This study uses a feed optimization model, a broiler growth model, and a life cycle assessment (LCA) to determine how feed ingredients and the barn environment can affect the broiler’s growth and production emissions. A multi-criteria ration optimization model is used to produce feeds based on carbon footprint and cost. A growth model is used …