System-Layout-Dependent Thermally Induced Solder Stress & Reliability Implications, Ange C. Iradukunda

Mechanical Engineering Undergraduate Honors Theses

Electronic flip chip assemblies consist of dissimilar component materials, which exhibit different CTE. Under thermal cyclic operating conditions, this CTE mismatch produces interfacial and interconnect stresses, which are highly dependent on system layout. In this paper, sensitivity analyses are performed using ANSYS FEA to establish how the proximity and arrangement of neighboring devices affect interconnect stress. Flip chip alignment modes ranging from edge-to-edge to corner-to-corner are studied. Results of these FEA studies, demonstrated that closely packing devices together has the effect of making them act as one. This results in a significant increase in the thermomechanical stresses induced on peripheral …

Determining Drag Forces On 3d Printed Shark Skin And The Conditions In Which Drag Forces Are Reduced, Kayla M. Bartnicke

Mechanical Engineering Undergraduate Honors Theses

ABSTRACT

This project was conducted at the University of Arkansas with access to 3D printers and a water tunnel. The project examines drag forces over 3D-printed shark skin. Shark skin was chosen to be studied because of its unique three-pronged denticle shape and the assumption that this unique shape has a purpose, such as drag reduction.

A shark denticle was designed using SolidWorks software, multiplied 164 times creating a total skin area of 17.5 in², and printed using both a MakerBot Replicator 2 3D printer and an Ultimaker 2 Go 3D printer. The shark skin was initially printed …

Exploiting Hardware Abstraction For Parallel Programming Framework: Platform And Multitasking, Hongyuan Ding

Graduate Theses and Dissertations

With the help of the parallelism provided by the fine-grained architecture, hardware accelerators on Field Programmable Gate Arrays (FPGAs) can significantly improve the performance of many applications. However, designers are required to have excellent hardware programming skills and unique optimization techniques to explore the potential of FPGA resources fully. Intermediate frameworks above hardware circuits are proposed to improve either performance or productivity by leveraging parallel programming models beyond the multi-core era.

In this work, we propose the PolyPC (Polymorphic Parallel Computing) framework, which targets enhancing productivity without losing performance. It helps designers develop parallelized applications and implement them on FPGAs. …

Effects Of Wash Water On The Compressive Strength Of Concrete, Gabriel W. Cook

Civil Engineering Undergraduate Honors Theses

Due to the scale of concrete production throughout the world, there is potential for implementing methodologies that reduce the environmental impact of concrete processes. One intriguing solution is utilizing concrete wash water as mixing water. Concrete wash water is the water created by concrete production. If wash water can be reused, this would provide a safe disposal of the water and save millions of gallons of potable water per year (Indiana, 2014). For this to become a realistic option for concrete plants, it is important that the wash water does not decrease the compressive strength of concrete, otherwise the cost …

Linear Quadratic Optimal Control For A Cascaded Converters-Based Microgrid, Amlam Niragire

Graduate Theses and Dissertations

There is a constant transformation of the electric grid due to an ongoing interest in the deployment of renewable energy resources and electric microgrid formation. This transformation, though advantageous in many ways, poses great challenges for the energy industry and there must be a constant improvement in modeling, simulation, analysis and control techniques in order to characterize and optimize the system design and operation. In this light, the scope of this thesis is focused on developing a linear model, analyzing the stability and designing an optimal linear quadratic regulator (LQR) for a microgrid system. The microgrid system used is inspired …

Service Consistency In Vehicle Routing, Kunlei Lian

Graduate Theses and Dissertations

This thesis studies service consistency in the context of multi-period vehicle routing problems (VRP) in which customers require repeatable services over a planning horizon of multiple days. Two types of service consistency are considered, namely, driver consistency and time consistency. Driver consistency refers to using the fewest number of different drivers to perform all of the visits required by a customer over a planning horizon and time consistency refers to visiting a customer at roughly the same time on each day he/she needs service. First, the multi-objective consistent VRP is defined to explore the trade-offs between the objectives of travel …

Applications Of Krylov Subspace And Balanced Truncation Model Order Reduction In Power Systems, Sebastian Emanuel Garrido

Graduate Theses and Dissertations

Dynamic representations of power systems usually result in the order of hundreds or even thousands of buses. Therefore, reduction of these dynamic representations is convenient. Two applications of model order reduction in power systems are discussed in this thesis. First, Krylov subspace-based method is applied to the IEEE-123 Node Test Feeder in the context of distribution-level power systems simulation. Second, a Balanced Truncation-based model reduction is implemented in the 3-Machine 9-Bus system for designing a power system controller in the context of generation- and transmission-level power systems.

First, for the IEEE-123 Node Test Feeder, a two-sided Arnoldi algorithm is proposed …

Morphology Controlled Synthesis Of Copper Based Multimetallic Nanostructures And Their Electrocatalytic Properties For Methanol Oxidation Reaction, Leanne Elizabeth Mathurin

Graduate Theses and Dissertations

This research focuses on the development of shape-controlled synthesis of Cu NM, Cu-based bimetallic and trimetallic nanostructures, and their electrocatalytic properties for methanol oxidation reaction (MOR). Copper nanomaterials (Cu NM) with specific surface facets can tailor their catalytic activity. Understanding reagents responsible for Cu NM growth is important for morphology-controlled synthesis of the nanostructures. This research studies the halide influence on Cu NM growth and morphology in an oil-based synthesis. The morphology of the Cu NM varies with the halide type (i.e., Cl-, Br-, I-), and the halide concentration. Additionally, the type of Cu precursor also influenced the morphology of …

Investigation Of Fes2 Nanoparticles For Use In Optoelectronic And Thermoelectric Applications, Rick Tefal Eyi Nkoghe

Graduate Theses and Dissertations

Iron pyrite (FeS2) is the most abundant sulfide material on earth. This material has been widely investigated by researchers because of its optical properties. However, it has been difficult to produce High efficiency FeS2 based solar cells. This is due to many different impurities that arise when making the materials. The ability to synthesize pure pyrite FeS2 material is therefore critical for applications.

Pure Iron pyrite nanocrystals were synthesized using hot injection by mixing sulfur with an iron precursor in the presence of an amine. To improve the stability, shorter ligands replaced the native amines ligands. The stability of the …

Short-Circuit Protection For Low-Voltage Dc Distribution Systems Based On Solid-State Circuit Breakers, Sharthak Munasib

Graduate Theses and Dissertations

Proper short-circuit protection in dc distribution systems has provided an austere challenge to researchers as the development of commercially-viable equipment providing fast operation, coordination and reliability still continues. The objective of this thesis is to analyze issues associated with short-circuit protection of low-voltage dc (LVDC) distribution systems and propose a short-circuit protection methodology based on solid-state circuit breakers (SSCBs) that provides fault-current limiting (FCL). Simulation results for a simplified notional 1-kVdc distribution system, performed in MATLAB/SIMULINKTM, would be presented to illustrate that SSCB solutions based on reverse-blocking integrated gate-commutated thyristors (RB-IGCT) are feasible for low-voltage dc distribution systems but requires …

Power Efficient High Temperature Asynchronous Microcontroller Design, Nathan William Kuhns

Graduate Theses and Dissertations

There is an increasing demand for dependable and efficient digital circuitry capable of operating in high temperature environments. Extreme temperatures have adverse effects on traditional silicon synchronous systems because of the changes in delay and setup and hold times caused by the variances in each device’s threshold voltage. This dissertation focuses on the design of the major functionality of an asynchronous 8051 microcontroller in Raytheon’s high temperature Silicon Carbide process, rated for operation over 300ºC. The microcontroller is designed in NULL Convention Logic, for which the traditional bus architecture used for data transfer would consume a large amount of power. …

Silicon Germanium Bicmos Comparator Designed For Use In An Extreme Environment Analog To Digital Converter, Benjamin Riley Sissons

Graduate Theses and Dissertations

This thesis demonstrates the process of creating a radiation hardened and extreme temperature operating comparator from start to finish in the 90 nm SiGe 9HP process node. This includes the entire design flow from examining comparator topologies, to designing the initial comparator circuits, to simulating the comparator over a temperature range of -196°C to 125°C, and finally the testing of the fabricated circuit. To verify the circuit would work at low temperatures, several new device models were created that could be used for simulations at -196°C. In addition to its properties as a standalone comparator, the circuit was also used …

Modeling And Validation Of 4h-Sic Low Voltage Mosfets For Integrated Circuit Design, Shamim Ahmed

Graduate Theses and Dissertations

Silicon Carbide is a promising wide bandgap material and gradually becoming the first choice of semiconductor for high density and high efficiency power electronics in medium voltage range (500-1500V). SiC has also excellent thermal conductivity and the devices fabricated with the material can operate at high temperature (~ 400 ⁰C). Thus, a power electronic system built with SiC devices requires less cooling requirement and saves board space and cost. The high temperature applications of SiC material can also be extended to space exploration, oil and gas rigging, aerospace and geothermal energy systems for data acquisition, sensing and instrumentation and power …

Design And Test Of A Gate Driver With Variable Drive And Self-Test Capability Implemented In A Silicon Carbide Cmos Process, Matthew Barlow

Graduate Theses and Dissertations

Discrete silicon carbide (SiC) power devices have long demonstrated abilities that outpace those of standard silicon (Si) parts. The improved physical characteristics allow for faster switching, lower on-resistance, and temperature performance. The capabilities unleashed by these devices allow for higher efficiency switch-mode converters as well as the advance of power electronics into new high-temperature regimes previously unimaginable with silicon devices. While SiC power devices have reached a relative level of maturity, recent work has pushed the temperature boundaries of control electronics further with silicon carbide integrated circuits.

The primary requirement to ensure rapid switching of power MOSFETs was a gate …

Plasmon-Mediated Energy Conversion In Metal Nanoparticle-Doped Hybrid Nanomaterials, Jeremy Dunklin

Graduate Theses and Dissertations

Climate change and population growth demand long-term solutions for clean water and energy. Plasmon-active nanomaterials offer a promising route towards improved energetics for efficient chemical separation and light harvesting schemes. Two material platforms featuring highly absorptive plasmonic gold nanoparticles (AuNPs) are advanced herein to maximize photon conversion into thermal or electronic energy. Optical extinction, attributable to diffraction-induced internal reflection, was enhanced up to 1.5-fold in three-dimensional polymer films containing AuNPs at interparticle separations approaching the resonant wavelength. Comprehensive methods developed to characterize heat dissipation following plasmonic absorption was extended beyond conventional optical and heat transfer descriptions, where good agreement was …

Controlled Synthesis And Utilization Of Metal And Oxide Hybrid Nanoparticles, Cameron Cowgur Crane

Graduate Theses and Dissertations

This dissertation reports the development of synthetic methods concerning rationally-designed, hybrid, and multifunctional nanomaterials. These methods are based on a wet chemical, solution phase approach that utilizes the knowledge of synthetic organic and inorganic chemistry to generate building blocks in solution for the growth of nanocrystals and hybrid nanostructures. This work builds on the prior knowledge of shape-controlled synthesis of noble metal nanocrystals and expands into the challenging realm of the more reactive first row transition metals. Specifically, a microemulsion sol-gel method was developed to synthesize Au-SiO2 dimers as precursors for the synthesis of segmented heterostructures of noble metals that …

Development Of An Oxygen Saturation Monitoring System By Embedded Electronics, Manikandan Venkatesan Gomathy

Graduate Theses and Dissertations

Measuring Oxygenation of blood (SaO2) plays a vital role in patient’s health monitoring. This is often measured by pulse oximeter, which is standard measure during anesthesia, asthma, operative and post-operative recoveries. Despite all, monitoring Oxygen level is necessary for infants with respiratory problems, old people, and pregnant women and in other critical situations.

This paper discusses the process of calculating the level of oxygen in blood and heart-rate detection using a non-invasive photo plethysmography also called as pulsoximeter using the MSP430FG437 microcontroller (MCU). The probe uses infrared lights to measure and should be in physical contact with any peripheral points …

Effect Of Storage Temperature And Time On Lyophilized Water Bark Extract's Biological Activity, Jillian Schneider

Biological and Agricultural Engineering Undergraduate Honors Theses

Sweetgum bark extract has been known to show biological activities such as antimicrobial and antioxidant capabilities. The storage capacity of the extract, however, was unknown and previously thought to diminish over time. However, upon experimentation, the freeze-dried sweetgum bark extract showed no signs that storage time or storage temperature had any significant effect on the biological activities. There was no significant difference across storage temperature over time in the experiment (ANOVA RM, P0.05). Therefore, the antioxidant capabilities of the sweetgum extract were not affected by the storage time or temperature treatments studied in this work. For the antimicrobial experiment, there …

Analysis Of Lid Implementation To Combat Flooding And Erosion At The University Of Arkansas Campus, Madison E. Crowl

Biological and Agricultural Engineering Undergraduate Honors Theses

The city of Fayetteville, Arkansas has experienced rapid urbanization throughout recent years as it continues to grow. Within the city, the University of Arkansas has been constantly expanding, with increased impervious surfaces as more parking lots and facilities are built. This has caused issues including flooding and stream bank erosion, specifically in Mullins Creek, which receives runoff from a large part of campus. A portion of the creek was restored, but there are still downstream issues. Low Impact Development (LID) is a type of green infrastructure that has been shown to decrease runoff and increase infiltration. EPA SWMM, a hydrologic …

Transportation Engineering: Traffic Control Simulator, Sarah V. Hernandez, Karla Diaz-Corro, Taslima Akter, Magdalena Asborno, Fu Durandal

Civil Engineering Teaching and Learning

The purpose of these lesson plans is to introduce students to traffic signalization basics. Students will be lead through a series of mini-lectures on traffic control and signalization including a discussion on the limitations and benefits of traffic signalization. The lesson plans compliment a computer simulation “game” in which students act as manual operators for a single up to four by four gridded intersection. Students attempt to control the progression of signals to understand the relationship between signal timing and user delay. Through experimentation with the simulation, students generate a presentation discussing the benefits and drawbacks of signal timing and …

Journal Of The Arkansas Academy Of Science- Volume 71 2017, Academy Editors

Journal of the Arkansas Academy of Science

No abstract provided.

Restrained Shrinkage Of Fly Ash Based Geopolymer Concrete And Analysis Of Long Term Shrinkage Prediction Models, Md R. Islam, Mahbub K. Ahmed, Hosney Ara Begum, Erez N. Allouche

Journal of the Arkansas Academy of Science

The research presented in this manuscript describes the procedure to quantify the restrained shrinkage of geopolymer concrete (GPC) using ring specimen. Massive concrete structures are susceptible to shrinkage and thermal cracking. This cracking can increase the concrete permeability and decrease the strength and design life. This test is comprised of evaluating geopolymer concrete of six different mix designs including different activator solution to fly ash ratio and subjected to both restrained and free shrinkage. Test results obtained from this experimental setup was plotted along with the available empirical equation to observe the shrinkage strain of GPC and a model was …

An Acoustic-Based Approach For Condition Monitoring Of Pipes, Muhammad S. Khan, Turaj Ashuri, Mitchell Collins, Geoffrey Birkemeier, Emad Almohmmedali

Journal of the Arkansas Academy of Science

Polyvinyl chloride pipes are extensively used in municipal sewer systems. As the sewer system ages, polyvinyl chloride pipes become prone to developing cracks that can release toxic effluents into the environment. Traditionally, utility operators pass a close circuit television camera mounted on a guided vehicle through the pipe to monitor the defects. The video is observed by a trained operator who records the condition of the pipe. This arrangement has two major limitations. First, it is expensive due to complex set up. Second, if a pipe is blocked the guided vehicle cannot pass through its entire length. A more economical …

Time Domain Analysis Of Terahertz Photoconductive Antennas Using High- Frequency Structure Simulator (Hfss), David Carballo

Electrical Engineering Undergraduate Honors Theses

In this thesis, an in-depth guide and description on how to model and perform frequency and mainly time domain analysis of a THz photoconductive antenna using HFSS will be presented. The main purpose of this thesis is to master and document the procedures for transient domain analysis in HFSS to fill the lack of documentation about this topic. Moreover, another goal is to compare the results from HFSS with the ones from another program, COMSOL (conducted by a PhD student), in order to validate the correctness of the procedure.

From this thesis, it can be concluded that in order to …

Development Of Breast Tissue Phantoms For Enhanced Terahertz Imaging Utilizing Microdiamond And Nano-Onion Particles, Alec Walter

Electrical Engineering Undergraduate Honors Theses

This thesis presents the work performed to develop tissue phantoms and a contrast agent that will be used in future research of terahertz time-domain imaging of breast tumor margins. Since an excised breast tumor can contain healthy fibrous and fatty tissues along with invasive ductal carcinoma (IDC), three phantom materials were developed. Solid phantom materials were made by using TX151 to solidify water in order to tune the refractive index and absorption coefficient of the fibrous tissue phantom and IDC phantom to the properties of freshly excised breast tissue. Various amounts of olive oil were added to the water prior …

Influence Of Concrete Compressive Strength On Transfer And Development Lengths Of Prestressed Concrete, Alberto Teodoro Ramirez-Garcia

Graduate Theses and Dissertations

This research examines the relationship between concrete compressive strength and strand bond. The goal of this research was to develop an equation that relates strand bond to concrete compressive strength at strand release (approximately 1 day of age) and at 28 days of age, and those equations are presented in this investigation. Strand bond is assessed by measuring the transfer length and development length for prestressed beams cast in the laboratory. In the U.S., strand bond is predicted using transfer length and development length equations provided by the American Concrete Institute (ACI-318) Building Code and American Association of State and …

Selective Resistive Sintering: A Novel Additive Manufacturing Process, Austin Bryan Van Horn

Graduate Theses and Dissertations

Selective laser sintering (SLS) is one of the most popular 3D printing methods that uses a laser to pattern energy and selectively sinter powder particles to build 3D geometries. However, this printing method is plagued by slow printing speeds, high power consumption, difficulty to scale, and high overhead expense. In this research, a new 3D printing method is proposed to overcome these limitations of SLS. Instead of using a laser to pattern energy, this new method, termed selective resistive sintering (SRS), uses an array of microheaters to pattern heat for selectively sintering materials. Using microheaters offers significant power savings, significantly …

Soil Moduli Obtained From A Back Pressure Constant Rate Of Strain Bender Element Consolidation Apparatus, Yi Zhao

Graduate Theses and Dissertations

A back-pressure saturated, constant-rate-of-strain consolidation device was modified to incorporate bender elements (BP-CRS-BE) and thus allowed for shear wave measurements during consolidation tests. This newly fabricated system has many advantages over other previous or current devices: 1) it can be utilized not only for laboratory prepared soil samples but also for field sampled soils such as Shelby tube samples, and 2) continuous compression curves, and continuous values of vertical hydraulic conductivity and coefficient of consolidation can be acquired with a significant reduction in testing time. Soil modulus values such as shear modulus and constrained modulus are also able to be …

Identifying Damage, Predicting Expansion, And Determining The Effectiveness Of Sealers On Concrete Affected By Alkali-Silica Reaction And Freeze-Thaw, Matthew Caleb Waidner

Graduate Theses and Dissertations

Premature cracking of the barrier wall and pavement on I-49 south of Fayetteville, Arkansas due to a combination of Alkali-Silica Reaction (ASR) and freeze-thaw has led to ASR and freeze-thaw research at the University of Arkansas. Potential for further expansion (PFET), Damage Rating Index (DRI), and mitigation of freeze-thaw and ASR with sealers testing and results are contained herein. PFET results indicated that the pavement will not continue to expand from ASR. With other interstate pavements deteriorating prematurely throughout Arkansas, DRI has shown that most are damaged not only by ASR but by freeze-thaw too. Recommendations for freeze-thaw’s inclusion into …

Effective Supplier Quality Practices In The Construction Industry, Ashleigh Hegwood

Industrial Engineering Undergraduate Honors Theses

The dynamic and irregular nature of projects in the construction industry causes the complexity of supplier quality management (SQM). The Construction Industry Institute (CII) Research Team (RT) 308 is focused on achieving zero rework through effective supplier quality practices.

This honors thesis is an extension of RT 308’s project work. Its purpose is to look at current supplier evaluation practices within the construction industry, confirm arecommended supplier cutoff rating through data analysis, and determine if outliers in the data set could be normalized. A survey was developed in Qualtrics (an online survey software tool) and sent to CII members for …