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Graduate Theses and Dissertations

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Full-Text Articles in Engineering

Understanding Peripheral Blood Pressure Signals: A Statistical Learning Approach, Md Abul Hayat Aug 2023

Understanding Peripheral Blood Pressure Signals: A Statistical Learning Approach, Md Abul Hayat

Graduate Theses and Dissertations

Proper estimation of body fluid status for human or animal subjects has always been a challenging problem. Accurate and timely estimate of body fluid can prevent life threatening conditions under trauma and severe dehydration. The main objective of this research is the estimation, classification and detection of dehydration in human and animal subjects using peripheral blood pressure (PBP) signals. Peripheral venous pressure (PVP) and peripheral arterial pressure (PAP) signals have been investigated in this research. Both PVP and PAP signals are PBP signals. A dataset of PVP signals was collected using standard peripheral intravenous catheters from human subjects suffering from …


Verification Of Astm Centrifugation Equations For Soil Suction Determination, Esteban Maclein Miranda Pinzon Aug 2023

Verification Of Astm Centrifugation Equations For Soil Suction Determination, Esteban Maclein Miranda Pinzon

Graduate Theses and Dissertations

The unit correction constant (B) in the ASTM D6836 standard needs to be evaluated. The B-value was proposed to be 0.00548 instead of 0.00553. This apparent discrepancy led to an investigation comparing the predicted and measured suction values for high air entry (HAE) ceramic disks. A Beckman-Coulter Model J6-MI six-bay centrifuge and a WP4C Dewpoint Potentiameter were used in the testing program. HAE ceramic disks rated with bubbling pressures of 3-bar and 5-bar were used as analogue soil specimens. The HAE ceramic disks were spun in the small-scale centrifuge to apply prescribed suction amounts and then placed in the WP4C …


Achieving High Renewable Energy Integration In Smart Grids With Machine Learning, Yaze Li Aug 2023

Achieving High Renewable Energy Integration In Smart Grids With Machine Learning, Yaze Li

Graduate Theses and Dissertations

The integration of high levels of renewable energy into smart grids is crucial for achieving a sustainable and efficient energy infrastructure. However, this integration presents significant technical and operational challenges due to the intermittent nature and inherent uncertainty of renewable energy sources (RES). Therefore, the energy storage system (ESS) has always been bound to renewable energy, and its charge and discharge control has become an important part of the integration. The addition of RES and ESS comes with their complex control, communication, and monitor capabilities, which also makes the grid more vulnerable to attacks, brings new challenges to the cybersecurity. …


Double-Sided Cooled Power Modules For Electric Vehicles, Riya Paul Aug 2023

Double-Sided Cooled Power Modules For Electric Vehicles, Riya Paul

Graduate Theses and Dissertations

Double-sided cooled (DSC) power modules in conjunction with Silicon Carbide (SiC) power devices are expected to significantly elevate the performance of the next-generation electric vehicle power inverters. The double-sided cooling enables maximum heat dissipation, resulting in higher power density. SiC power devices, with their fast-switching speeds, reduce the power losses for higher efficiency. A half-bridge power module consisting of 13 mΩ 1.2 kV SiC devices is used for this work. A baseline DSC power module was designed, fabricated, and tested. This unique design uses truncated rectangular copper connection blocks for better heat dissipation from the device top side compared to …


Non-Energy Circular Economy Potential Of Rice Husks: A Techno-Eco-Environmental Assessment, Winfred Oppong Yeboah Aug 2023

Non-Energy Circular Economy Potential Of Rice Husks: A Techno-Eco-Environmental Assessment, Winfred Oppong Yeboah

Graduate Theses and Dissertations

The non-energy circular bioeconomy potential of rice husks was examined via sustainability assessments, namely life cycle assessment (LCA), life cycle impact cost assessment (LCICA), and techno-economic assessment (TEA). The study was conducted with three objectives. The first objective was to review previous studies on the non-energy utilization potential of rice husks by the method of meta-analysis. This review followed a systematic approach where research papers were collected following a defined set of criteria. The study revealed 16 key utilization pathways, all of which showed promising results. However, a comprehensive sustainability assessment was lacking in all of the pathways. The second …


Alkali Silica Reaction Mitigation Using Glycerin, Ana Laura Errigo Chanis Aug 2023

Alkali Silica Reaction Mitigation Using Glycerin, Ana Laura Errigo Chanis

Graduate Theses and Dissertations

The use of glycerin as a concrete additive to reduce alkali silica reaction (ASR), was evaluated and is presented in this study. Specifically, the United States Army Corps of Engineers (USACE) ultra-accelerated alkali silica reaction testing procedure by means of autoclaving was employed to examine the use of glycerin for ASR mitigation or reduction by analyzing mortar bar expansion data. The fine aggregates used in this investigation consisted of highly reactive Jobe Sand or Los Lunas Sand with an autoclave expansion of 0.5 and 0.4 percent, respectively. The laboratory investigation was performed by recording the amount of expansion of the …


Modeling And Control Strategies For A Two-Wheel Balancing Mobile Robot, John Alan Moritz May 2023

Modeling And Control Strategies For A Two-Wheel Balancing Mobile Robot, John Alan Moritz

Graduate Theses and Dissertations

The problem of balancing and autonomously navigating a two-wheel mobile robot is an increasingly active area of research, due to its potential applications in last-mile delivery, pedestrian transportation, warehouse automation, parts supply, agriculture, surveillance, and monitoring. This thesis investigates the design and control of a two-wheel balancing mobile robot using three different control strategies: Proportional Integral Derivative (PID) controllers, Sliding Mode Control, and Deep Q-Learning methodology. The mobile robot is modeled using a dynamic and kinematic model, and its motion is simulated in a custom MATLAB/Simulink environment. The first part of the thesis focuses on developing a dynamic and kinematic …


On The Feasibility Of Embedding Fe-Sma Short-Fibers In Ultra-High-Performance Concrete For Self Prestressing, Gavin Briggs May 2023

On The Feasibility Of Embedding Fe-Sma Short-Fibers In Ultra-High-Performance Concrete For Self Prestressing, Gavin Briggs

Graduate Theses and Dissertations

Prestressing concrete is common practice in the construction industry. Current prestressing methods are often used for large, straight members and come with geometric limitations for curved or thin-walled members. Shape memory alloy short fibers embedded within concrete mixes may allow for the prestressing of geometries not possible with traditional methods. This study reviews past research on prestressing concrete with shape memory alloys, evaluates the achievable recovery stress within an Fe-SMA (when deformed at room temperature), and examines the mechanical behavior of Ductal dark grey UHPC when heated to 250 °C. The flexural behavior, compressive strength, and fiber-to-concrete bond strength of …


Demand Prediction And Inventory Management Of Surgical Supplies, Rajon Paul Pantha May 2023

Demand Prediction And Inventory Management Of Surgical Supplies, Rajon Paul Pantha

Graduate Theses and Dissertations

Effective supply chain management is critical to operations in various industries, including healthcare. Demand prediction and inventory management are essential parts of healthcare supply chain management for ensuring optimal patient outcomes, controlling costs, and minimizing waste. The advances in data analytics and technology have enabled many sophisticated approaches to demand forecasting and inventory control. This study aims to leverage these advancements to accurately predict demand and manage the inventory of surgical supplies to reduce costs and provide better services to patients. In order to achieve this objective, a Long Short-Term Memory (LSTM) model is developed to predict the demand for …


Ranking Highway Transportation Asset Criticality Through Stakeholder Input Using The Analytical Hierarchy Process (Ahp), Kwadwo Amankwah-Nkyi May 2023

Ranking Highway Transportation Asset Criticality Through Stakeholder Input Using The Analytical Hierarchy Process (Ahp), Kwadwo Amankwah-Nkyi

Graduate Theses and Dissertations

The transportation system is especially vulnerable to natural and human-made disasters which can have effects on mobility, safety, and the economy. This thesis presents a method to rank transportation assets based on their criticality to the transportation system by uniquely gathering stakeholder input on criticality criteria weights. This serves as a typical first step in vulnerability and resilience assessments. Six criteria were used to estimate asset criticality: Annual Average Daily Traffic (AADT), roadway classification, freight output, tourism output, Social Vulnerability Index (SoVI), and redundancy. Then, the criteria are combined via stakeholder input using a weighted ranking scheme called the Analytical …


Advanced Cmos Process For Submicron Silicon Carbide (Sic) Device, Niloy Saha May 2023

Advanced Cmos Process For Submicron Silicon Carbide (Sic) Device, Niloy Saha

Graduate Theses and Dissertations

Silicon carbide (SiC) is a wide semiconductor material with superior material properties compared to other rival materials. Due to its fewer dislocation defects than gallium nitride and its ability to form native oxides, this material possesses an advantage among wide band gap materials. Despite having several superior properties its low voltage application is less explored. CMOS is extremely important in low voltage areas and silicon is the dominant player in it for the last 50 years where scaling has contributed a major role in this flourishment. The channel length of silicon devices has reached 3 nm whereas SiC is still …


Modbus Rtu For Embedded Cyber Secure Inverter Controller, Brady Mcbride May 2023

Modbus Rtu For Embedded Cyber Secure Inverter Controller, Brady Mcbride

Graduate Theses and Dissertations

The Modbus communication protocol is a widely adopted communication standard in industrial control systems. This communication protocol is known for being reliable and straightforward to implement while being versatile in terms of its operating parameters while supporting multiple formats over various hardware infrastructures and architectures. Many intelligent devices such as Programmable Logic Controllers (PLCs), Human-Machine Interfaces (HMIs), Internet-of-Things (IoT), and various Operational Technologies (OT) utilize Modbus for their communication systems. These types of systems must communicate with each other through a standardized and central communication process. To support the integration of these modular systems, a Field-Programmable Gate Array (FPGA) can …


Pda/Ptfe Solid Lubricant Coating For 60niti Applications, Charles Richey Miller May 2023

Pda/Ptfe Solid Lubricant Coating For 60niti Applications, Charles Richey Miller

Graduate Theses and Dissertations

The intermetallic alloy 60NiTi has a unique combination of high hardness and low elastic modulus, which makes it highly resistant to dents. Additionally, 60NiTi is extremely corrosion resistant and chemically inert. These properties make 60NiTi a desirable material for challenging mechanical component applications with high contact stresses and in harsh environments. However, lubrication issues have hindered the use of 60NiTi because it has poor tribological performance if it is not properly lubricated. The mechanical properties of hardened 60NiTi and its microconstituents were studied by nanoindentation. This study showed that the bulk properties of 60NiTi are driven by the properties of …


Bond-Breaker Properties Of Different Media For Concrete Pavement Design, Andres Calzacorta May 2023

Bond-Breaker Properties Of Different Media For Concrete Pavement Design, Andres Calzacorta

Graduate Theses and Dissertations

Currently Arkansas requires a layer of asphalt as the main bond-breaker over cement treated base for rigid pavement design. The study presented in this paper aims to replicate the results from previous research which demonstrated the bond-breaker properties of concrete curing compounds and geotextiles. Bond-breakers are materials applied to the surface of stabilized bases to reduce the interaction between the base and a pavement cement concrete layer. The excessive interaction between these two layers can lead to cracking in the overlay and reduction of the serviceability life of concrete. The curing compound was applied in a single application (SA, 200 …


Tangential Flow Treatment Of Poultry Processing Wastewater Using Stainless Steel Ultrafiltration Membrane, Saubana Olorunsola Dada May 2023

Tangential Flow Treatment Of Poultry Processing Wastewater Using Stainless Steel Ultrafiltration Membrane, Saubana Olorunsola Dada

Graduate Theses and Dissertations

The current treatment of poultry processing wastewater (PPW) requires a large expanse of land, takes time, and requires chemical usage. The wastewater is typically treated prior to discharge. Apart from aiming to reuse the treated water for non-potable activities, this project aimed to reduce the footprint and time required for PPW treatment. To intensify the PPW treatment units, we studied the possibility of replacing dissolved air floatation (DAF) with a stainless steel ultrafiltration membrane (SSUF). Combined PPW from all processing units taken before the first DAF and the second DAF were used for this study with no pretreatment. The SSUF …


The Growth And Characterization Of Inn Quantum Dots Using Droplets Epitaxy In Mbe, Malak Refaei May 2023

The Growth And Characterization Of Inn Quantum Dots Using Droplets Epitaxy In Mbe, Malak Refaei

Graduate Theses and Dissertations

III-nitride semiconductor material systems offer great potential for next-generation optoelectronic devices due to their direct bandgaps, which vary from 0.7 eV (InN) to 3.5 eV (GaN) to 6.2 eV (AlN), as well as their other unique properties. InN has gained much less attention than GaN and AlN within this family of semiconductors due to its complicated low-temperature growth. However, the prediction that an InN quantum well on GaN can become a two-dimensional (2D) topological insulator has resulted in expanding the research interest in InN. At the same time, this renewed interest has begun to reveal that the formation of an …


The Influence Of Pesticides On Us Corn Production Environmental Impact: A Comparative Life Cycle Assessment Of Dominant Production Practices, Kyle Marinoni Lawrence May 2023

The Influence Of Pesticides On Us Corn Production Environmental Impact: A Comparative Life Cycle Assessment Of Dominant Production Practices, Kyle Marinoni Lawrence

Graduate Theses and Dissertations

In recent years there has been increasing interest in reducing agricultural environmental footprints in the United States, particularly for commodity crops like corn grain. Pest management is one aspect of agricultural production that is often identified as having potential for improvement with regard to environmental impact, but there is not a robust body of literature to identify the wide-scale influence of pesticides on yield and environmental impact. In this study, we hypothesized that the use of different classifications of pesticides has a significant impact on the overall environmental impact. To test this, agricultural models were created to represent the dominant …


Geophysical Assessment Of Internal Erosion Damage At The Crawford County Levee, Samuel Ross Hokett May 2023

Geophysical Assessment Of Internal Erosion Damage At The Crawford County Levee, Samuel Ross Hokett

Graduate Theses and Dissertations

Levee failures during flooding events can result in catastrophic loss of life and property. Soil erosion during high water events is a primary cause of levee failures. Accordingly, this research focuses on the geophysical assessment of internal erosion damage in levees. This thesis presents a case study utilizing Capacitively Coupled Resistivity (CCR), Direct Current Electrical Resistivity Tomography (DC ERT), and Multichannel Analysis of Surface Waves (MASW) to assess internal erosion damage at the Crawford County Levee System in Van Buren, AR, that occurred during the 2019 Arkansas River flood. Geophysical surveys acquired included longitudinal CCR, DC ERT, and MASW lines …


Design Approaches To Enhance Power Density In Power Converters For Traction Applications, Shamar Christian May 2023

Design Approaches To Enhance Power Density In Power Converters For Traction Applications, Shamar Christian

Graduate Theses and Dissertations

This dissertation presents a design strategy to increase the power density for automotive Power Conversion Units (PCUs) consisting of DC-DC and DC-AC stages. The strategy significantly improves the volumetric power density, as evident by a proposed PCU constructed and tested having 55.6 kW/L, representing an 11.2 % improvement on the Department of Energy’s 2025 goal of 50 kW/L for the same power electronics architecture. The dissertation begins with a custom magnetic design procedure, based on optimization of a predetermined C-core geometrical relationship and custom Litz wire. It accounts for electrical and thermal tradeoffs to produce a magnetic structure to best …


Multiple Output Power Supply Using Toroidal Transformers For Medium Voltage Active Gate Drivers, Samhitha Venkata Machireddy May 2023

Multiple Output Power Supply Using Toroidal Transformers For Medium Voltage Active Gate Drivers, Samhitha Venkata Machireddy

Graduate Theses and Dissertations

When operating in high power applications, power devices dissipate tens or hundreds of watts of power in the form of heat. The ability of the power devices to withstand power and dissipation of heat across the power devices becomes a prominent requirement in designing the power converter. This challenge demands a power converter design to be more effective and consistent which factors in size, cost, weight, power density and reliability. This study aims to propose a gate driver isolated power supply design that can be used in medium voltage applications (e.g., up to 10 kV) while respecting the principle of …


Stream Processor Development Using Multi-Threshold Null Convention Logic Asynchronous Design Methodology, Wassim Khalil May 2023

Stream Processor Development Using Multi-Threshold Null Convention Logic Asynchronous Design Methodology, Wassim Khalil

Graduate Theses and Dissertations

Decreasing transistor feature size has led to an increase in the number of transistors in integrated circuits (IC), allowing for the implementation of more complex logic. However, such logic also requires more complex clock tree synthesis (CTS) to avoid timing violations as the clock must reach many more gates over larger areas. Thus, timing analysis requires significantly more computing power and designer involvement than in the past. For these reasons, IC designers have been pushed to nix conventional synchronous (SYNC) architecture and explore novel methodologies such as asynchronous, self-timed architecture. This dissertation evaluates the nominal active energy, voltage-scaled active energy, …


Dpd Guided Insight On The Formation Process Of Polyethersulfone Membranes By Nonsolvent Induced Phase Separation And The Effects Of Additives, Eric Ledieu May 2023

Dpd Guided Insight On The Formation Process Of Polyethersulfone Membranes By Nonsolvent Induced Phase Separation And The Effects Of Additives, Eric Ledieu

Graduate Theses and Dissertations

Dissipative particle dynamics (DPD), a coarse grain simulation method, was applied to the membrane formation process of non-solvent induced phase separation (NIPS) to gain further insight on the mechanism of certain variables and how they affect the final morphology. NIPS involves two solutions, an organic polymer dissolved in an organic solvent colloquially called the dope and an aqueous coagulation bath, brought into contact with one another. The solvents then mix, causing the polymer to fall out of solution as an asymmetric membrane with a dense surface layer and a more open subsurface layer in response to the decreasing solubility. Polyethersulfone …


Achieving Causal Fairness In Recommendation, Wen Huang May 2023

Achieving Causal Fairness In Recommendation, Wen Huang

Graduate Theses and Dissertations

Recommender systems provide personalized services for users seeking information and play an increasingly important role in online applications. While most research papers focus on inventing machine learning algorithms to fit user behavior data and maximizing predictive performance in recommendation, it is also very important to develop fairness-aware machine learning algorithms such that the decisions made by them are not only accurate but also meet desired fairness requirements. In personalized recommendation, although there are many works focusing on fairness and discrimination, how to achieve user-side fairness in bandit recommendation from a causal perspective still remains a challenging task. Besides, the deployed …


Polymeric Biomaterials Approaches For Engineering The In Vitro Cellular Microenvironment For Mscs, Mahsa Letter-Mahsa Haseli May 2023

Polymeric Biomaterials Approaches For Engineering The In Vitro Cellular Microenvironment For Mscs, Mahsa Letter-Mahsa Haseli

Graduate Theses and Dissertations

Cell therapy is a technology that relies on replacing diseased or dysfunctional cells with healthy functioning ones. One of the cells used for such advanced therapies are stem cells, owing to their ability to differentiate into specific cells required for repairing damaged or defective tissues or cells. The majority of cell-based products are intended to transiently persist in the patient, secreting factors which then allow the patient’s body to heal; in these products, the cells are subsequently eliminated from the body. Furthermore, unique manufacturing platforms, in addition to novel commercialization strategies, will be required to create a successful, sustainable cell …


Improving Tribological Properties Of Polydopamine/Polytetrafluoroethylene Coatings Through Incorporating Core-Shell Nanoparticles And Laser Surface Texturing, Firuze Soltani-Kordshuli May 2023

Improving Tribological Properties Of Polydopamine/Polytetrafluoroethylene Coatings Through Incorporating Core-Shell Nanoparticles And Laser Surface Texturing, Firuze Soltani-Kordshuli

Graduate Theses and Dissertations

Polytetrafluoroethylene (PTFE) is a widely used polymer that has unique properties such as chemical and temperature resistance, corrosion resistance, low maintenance cost, and a very low coefficient of friction (COF). These distinctive properties have made PTFE a promising candidate for industrial applications where surfaces are in relative motion. PTFE can be utilized as a thin film solid lubricant to significantly reduce the friction between moving surfaces. However, PTFE coatings have low cohesion and poor adhesion to the substrate resulting in its low wear resistance. This fact limits the application of PTFE coatings in load-bearing situations. To address these limitations, an …


Effect Of Human Decellularized Skeletal Muscle On Recovery From Volumetric Muscle Loss Injury, Jacob Schluns May 2023

Effect Of Human Decellularized Skeletal Muscle On Recovery From Volumetric Muscle Loss Injury, Jacob Schluns

Graduate Theses and Dissertations

Volumetric muscle loss (VML) overwhelms muscle’s robust capacity for regeneration. A key event in the etiology of VML injury is the bulk loss of structural cues provided by the underlying extracellular matrix (ECM). While muscle is a highly structured tissue, with cell and ECM alignment in the direction of contractile force production, the impact of scaffold alignment on recovery remains unclear. Bulk human decellularized skeletal muscle (DSM) tissues were sectioned into 10 x 1-2 mm fibers. VML defects were repaired using multi-fiber implants consisting of approximately 8 fibers per defect arranged into two layers. Fibers were oriented 1) to the …


Analysis Of An Isolated Bidirectional Ćuk Converter, Yeny Hau Chen May 2023

Analysis Of An Isolated Bidirectional Ćuk Converter, Yeny Hau Chen

Graduate Theses and Dissertations

The objective of this thesis is to perform an analysis of the isolated bidirectional Ćuk dc-dc converter topology and demonstrate the advantages and operation of this configuration through simulations using MATLAB/SimulinkTM and measurements collected from a 1.5-kW prototype tested at the Engineering Research Center (ENRC) laboratory of the University of Arkansas. The idea of integrating an active-clamp snubber circuit on each side of the converter, proposed by Dr. Sudip Mazumder from the University of Illinois, Chicago, limits the additional voltage stresses on the components due to the energy from the transformer’s leakage inductance. This is studied in this thesis to …


Understanding And Tuning Magnetism In Van Der Waals Magnetic Compounds, Rabindra Basnet May 2023

Understanding And Tuning Magnetism In Van Der Waals Magnetic Compounds, Rabindra Basnet

Graduate Theses and Dissertations

The recently discovered two-dimensional (2D) magnetism has attracted intensive attention due to possible magnetic phenomenon arising from 2D magnetism and their promising potential for spintronics applications. The advances in 2D magnetism have motivated the study of layered magnetic materials, and further enhanced our ability to tune their magnetic properties. Among various layered magnets, tunable magnetism has been widely investigated in metal thiophosphates MPX3. It is a class of magnetic van der Waals (vdW) materials with antiferromagnetic ordering persisting down to atomically thin limit. Their magnetism originates from the localized moments due to 3d electrons in transition metal ions. So, their …


Automation Of Life Cycle Assessment, Jacob Hickman May 2023

Automation Of Life Cycle Assessment, Jacob Hickman

Graduate Theses and Dissertations

An automation program, named Jacob LCA, was created to help perform life cycle assessment (LCA). The program uses a template file to perform controlled and consistently ordered actions with the LCA program, SimaPro, and effectively removes the need for manual user input. It can be set to run using data from one or more life cycle inventory (LCI) files, which allows for rapid iteration and testing of data. It also partially addresses some of the limitations of LCA by establishing a procedure through which temporal and spatial variations in data can be integrated into LCI files and then passed to …


On The Micro-Mechanical Property Characterization And Bulk-Volume Behavior Prediction Of Additively Manufactured 17-4 Ph Stainless Steels, David González-Niño May 2023

On The Micro-Mechanical Property Characterization And Bulk-Volume Behavior Prediction Of Additively Manufactured 17-4 Ph Stainless Steels, David González-Niño

Graduate Theses and Dissertations

Selective laser melting is an additive manufacturing technology that opens the possibility to manufacture components with complex geometries that are difficult with traditional manufacturing techniques which could benefit engineering applications such as aviation or structural engineering. However, the lack of a reliable universal predictive model for selective laser melting components could impede the full implementation in industrial applications. Therefore, this dissertation investigates the mechanical behavior of selective laser melting 17-4 PH stainless steel under ultra-low cycle fatigue regime and propose a novel micro-mechanical based modeling using statistical and representative volume element. The first phase of this project examined the mechanical …