Engineering Commons^™

Hemodynamic Assessment Of Y-Incision Aortic Root Enlargement Using Computational Simulations, Astitwa Ghimire

Electronic Theses and Dissertations

The Yang procedure is a new aortic root enlargement technique used to enlarge the aortic annulus by multiple valve sizes. The procedure prevents patient prosthesis mismatch and establishes a viable platform for future valve-in-valve implantation. This study used the Yang procedure to investigate the hemodynamics in the aortic root and bioprosthetic valve regions after aortic root enlargement. Results indicate the velocity magnitude at the sinus regions of a patient who underwent the Yang procedure was slower, indicating risks of flow stasis and thrombosis. Simulation results denote computational models can be created for optimization of surgical procedures.

Machine Learning Based Average Pressure Coefficient Prediction For Isolated High-Rise Buildings, Shiva Sai Reddy Marapakala

ETD Archive

In structural design, the distribution of wind-induced pressure exerted on structures is crucial. The pressure distribution for a particular building is often determined by scale model tests in boundary layer wind tunnels (BLWTs). For all combinations of interesting building shapes and wind factors, experiments with BLWTs must be done. Resource or physical testing restrictions may limit the acquisition of needed data because this procedure might be time-and resource-intensive. Finding a trustworthy method to cyber-enhance data-collecting operations in BLWTs is therefore sought.

This research analyzes how machine learning approaches may improve traditional BLWT modeling to increase the information obtained from tests …

High Magnification Surface Topography Based Digital Image Correlation (Dic) For Identifying Damage Accumulation And Crack Growth In Polycrystalline Nickel, Arash Valiollahi

Mechanical and Aerospace Engineering Dissertations - Archive

Damage index parameters that have been formulated to identify damage localization in plastically deformed materials typically require all six stress or strain components. Recently, simulations through Crystal Plasticity Finite Element Method (CPFEM) have been widely used to extract damage initiation parameters. However, these models are rarely verified due to the challenges in measuring the out-of-plane deformation/strain experimentally. A damage index combining the effective plastic strain and surface roughness change is investigated for identifying damage accumulation sites and predicting crack propagation path in polycrystalline pure Nickel. A novel Digital Image Correlation (DIC) technique is developed to measure both in-plane and out-of-plane …

Investigation Of Thermal Performance Enhancement And Thermo-Mechanical Assessment Of Ite Using Single-Phase Immersion Cooling Technology, Pratik Bansode

Mechanical and Aerospace Engineering Dissertations - Archive

The use of air-cooling as a thermal management technique in data centers has consistently maintained its importance, however its efficacy is limited to CPUs with lower power requirements. The expenses and energy use related to the air circulation process for high-power density racks are deemed excessively costly. The limits of air cooling have aroused concerns owing to its low specific heat capacity and poor thermal conductivity, which result in reduced effectiveness. Consequently, a substantial discourse has emerged about alternate and effective cooling methods that provide supplementary advantages, such as the recuperation of waste heat. In light of the limitations associated …

Optimal Aggressive Constrained Trajectory Synthesis And Control For Multi-Copters, Tsung-Liang Liu

Mechanical and Aerospace Engineering Dissertations - Archive

Multi-copters have become increasingly popular in recent years due to their availability, mobility, agility, and flexibility. They serve as excellent platforms for control experiments and various applications. Their characteristics also make them an attractive choice for high-speed aerial navigation in complex environments. Numerous studies have been conducted on aggressive trajectory generation and maneuver tracking. However, the level of aggressiveness achievable depends on the optimality of the trajectory plan and the dynamic capabilities of the vehicle. It would be valuable if one can generate a trajectory that fully utilizes the dynamic capabilities of the multi-copter while accommodating specific maneuvers at predetermined …

Analyzing The Thermomechanical Performance Of Tg400g Material Substrate Core Under Immersion Cooling, Venkateswar Vishnu Tirupati Venkatachal

Mechanical and Aerospace Engineering Theses - Archive

The relentless surge in demand for seamless information exchange through consumer electronics, driven by the indispensable role of the Internet, has given rise to an unprecedented need for data centres. Yet, the energy consumption of conventional data centres, where a significant one-third of energy usage is attributed solely to cooling, has triggered an urgent quest for energy-efficient solutions. Immersion cooling technology appears as a promising contender due to its exceptional prowess in managing thermal energy. However, its potential impact on the reliability of IT equipment needs a more profound exploration before widespread adoption can be realized. This study embarks on …

Vibration Fatigue Of Leaded Solder Joint Interconnects For Pcb Electronics, John Crowder

All Theses

With the increasing prevalence of electronic equipment worldwide, there is also a decrease in the size of the components on their printed circuit boards (PCBs), leading to an increase in the density of these components. A significant amount of failure in electronic equipment is vibration fatigue of solder joints and their attachments. However, the complexity of these PCBs and their components has made finite element modeling (FEM) more complex, adding considerable time to create and analyze a model.

This paper aims to provide a literature review for the vibration fatigue of leaded solder components, create a test setup, and validate …

Life Cycle Energy Assesment Of Advanced Fiber Reinforced Composite Design And Manufacturing Methodologies, Urjit Lad

All Theses

Automotive industry at large is focused on vehicle light-weighting since a 6%-8% increase in fuel efficiency can be achieved with a 10% reduction in vehicle weight [1]. With the growing demand for cost-effective and sustainable light weighting of automobile structures, interest has increased in the application of fiber reinforced plastic (FRP) composites for use in the Body-in-White (BiW), which can account for up to 40% of the total vehicle weight. Traditional FRP composite manufacturing processes like vacuum assisted resin transfer molding, autoclave consolidation or use of automated fiber placement have been successfully used for marine and aerospace applications. However, these …

Computational Comparison Of Medializing Tibial Tubercle Osteotomy And Trochleoplasty In Patients With Trochlear Dysplasia, Clare K. Fitzpatrick, Robert N. Steensen, Oliver Alvarez, Amy E. Holcomb, Paul J. Rullkoetter

Mechanical and Biomedical Engineering Faculty Publications and Presentations

Medial patellofemoral ligament reconstruction (MPFLR) has emerged as the procedure of choice for recurrent patellar dislocation. This addresses soft tissue injury but does not address underlying anatomic factors, including trochlear dysplasia, that are commonly present and increase risk of dislocation. Quantification of the stability offered by other surgical interventions, namely, medializing tibial tubercle osteotomy (mTTO) and trochleoplasty, with and without MPFLR, may provide insight for surgical choices in patients with trochlear dysplasia. We developed subject-specific finite element models based on magnetic resonance scans from a cohort of 20 patients with trochlear dysplasia and recurrent patellar dislocation. The objectives of this …

Experimental And Numerical Investigation Of Fluid Flow Behavior Through Fractured Wellbore Cement, Mahya Hatambeigi

Civil Engineering ETDs

Leakage from wellbores has been a major challenge in the energy industry, leading to groundwater contamination, reduced productivity, safety hazards, and increased operating costs. Cemented annulus fractures are a common type of leakage pathway in wellbores that can form due to various physical and chemical conditions. The number of wellbore leaks continues to increase globally, making it imperative to develop a better understanding of the complex mechanisms governing fluid flow through fractured wellbore cement. Understanding the behavior of fluid flow through a leaky cemented annulus is crucial for evaluating the leakage potential and risk assessments in wellbore systems, as well …

Laser-Induced Forward Transfer (Lift) Based Bioprinting Of The Collagen I With Retina Photoreceptor Cells, Md Shakil Arman, Ben Xu, Andrew Tsin, Jianzhi Li

Manufacturing & Industrial Engineering Faculty Publications

This study focuses on the 3D bioprinting of retina photoreceptor cells using a laser-induced forward transfer (LIFT) based bioprinting system. Bioprinting has a great potential to mimic and regenerate the human organoid system, and the LIFT technique has emerged as an efficient method for high-resolution micropatterning and microfabrication of biomaterials and cells due to its capability of creating precise, controlled microdroplets. In this study, the parameters for an effective femtosecond laser-based LIFT process for 3D bioprinting of collagen biomaterial were studied. Different concentrations of collagen I solutions were tested and 0.75 mg/ml to 1 mg/ml collagen Ⅰ was identified as …

The Influence Of Diversity Dimensions On Student’S Collaboration Success: What It Means For Workforce Development In Manufacturing, Oyinkansola Adeite

All Theses

Manufacturing productivity is measured by labor productivity which is the hourly output of the manufacturing economy. The recent reduction in productivity numbers by the United States Bureau of Labor Statistics emphasizes the need for workforce development. With globalization and technological advancements, diversity has emerged as a critical aspect for the workplace. By encompassing dimensions such as education, race, and age, diversity creates a tapestry of unique perspectives and experiences. This study’s aim is to figure out the effect of a diversity dimension on team performance using intelligent systems, and in addition, if extra dimensions of diversity further impact team performance. …

Healthcare Built Environment And The Covid-19 Pandemic, A Mixed-Method Study, Mohammad Saleh Nikooopayan Tak

All Theses

The outbreak of COVID-19 presented an unparalleled risk to public health, leading to urgent scientific efforts in understanding transmission mechanisms and mitigating risks, especially in healthcare settings. This mixed-methods study examines knowledge advancement regarding indoor air quality in healthcare facilities during the pandemic. A systematic literature review of 163 post-COVID studies identifies key research thrusts and 31 recommendations related to building ventilation, air filtration, surface disinfection, and monitoring. Comparison with over 200 pre-pandemic publications reveals both reliance on established infection control principles and unique contributions, such as detecting viral RNA in air and surface samples indicating potential airborne and fomite …

Integrated Energy-Aware Motion Planning And Charge Scheduling Of Unmanned Aerial Vehicles, Hayleyesus Alemayehu

All Theses

The growing demand for unmanned aerial vehicles (UAVs) is driven by their operational convenience, cost-effectiveness, availability, and adaptability to various scenarios. In energy-constrained environments, optimizing energy consumption and ensuring a continuous power supply for UAVs is crucial for mission success. The objective of this thesis is to address this issue by integrating energy-aware motion planning and charge scheduling for UAVs by utilizing a charger hosted on an unmanned ground vehicle (UGV), whose rendezvous locations and routes are jointly computed to minimize overall energy consumption.

This thesis proposes a hierarchical trajectory and control framework comprising local and global planners for each …

The Effect Of Deployment And Optimal Dispatch Of Shared Electric Shuttles On The Energy Efficiency Of Campus Transit, Robert Smith

All Theses

A problem facing most public transit systems is low energy efficiency and the continued cycling of large transport vehicles such as buses at low occupancy when low demand for transport exists, wasting energy to no benefit. To remedy this issue, we propose a hybrid system consisting of existing diesel buses and automated electric shuttles to augment the system during off-peak hours. Due to their smaller size, higher occupancy, and more efficient powertrains, these shuttles could reduce the system energy used per passenger-mile-traveled. Automation removes the labor cost of drivers and, thus, eliminates the need to employ more drivers for the …

Influence Of Swirl And Turbulence In The Particle Removal Using Fog In A Pipe Flow, Nisarg T. Patel

All Theses

Fog-and-tube scrubbers are employed to remove harmful ultrafine aerosols, such as Diesel particulate matter (DPM), from an airflow. The underlying principle of this removal process involves enlarging the aerosol particles by coagulating them with fog drops, which are subsequently eliminated through inertial impaction onto the tube wall. Previous research conducted by Tabor et al. (2021) demonstrated an increase in scavenging of ultrafine DPM particles, ranging from 11.5 nm to 154 nm, by as large as 45% over the no fog case. This finding is crucial in addressing the challenges associated with conventional filtration methods for capturing ultrafine particles.

The present …

A Unit-Load Approach For Reliability-Based Design Optimization Of Linear Structures Under Random Loads And Boundary Conditions, Robert James Haupin, Gene Jean-Win Hou

Mechanical & Aerospace Engineering Faculty Publications

The low order Taylor’s series expansion was employed in this study to estimate the reliability indices of the failure criteria for reliability-based design optimization of a linear static structure subjected to random loads and boundary conditions. By taking the advantage of the linear superposition principle, only a few analyses of the structure subjected to unit-loads are needed through the entire optimization process to produce acceptable results. Two structural examples are presented in this study to illustrate the effectiveness of the proposed approach for reliability-based design optimization: one deals with a truss structure subjected to random multiple point constraints, and the …

Phase Stability Of Lead Phosphate Apatite, Jiahong Shen, Dale Gaines Ii, S. Shahabfar, Zi Li, Dohun Kang, Sean Griesemer, Adolfo Salgado-Casanova, Tzu-Chen Liu, Yi Xia, Multiple Additional Authors

Mechanical and Materials Engineering Faculty Publications and Presentations

Recently, Cu-substituted lead apatite LK-₉₉ was reported to have room-temperature ambientpressure superconductivity. Here we utilize density functional theory (DFT) total energy and harmonic phonon calculations to investigate the thermodynamic and dynamic stability of two lead phosphate apatites in their pure and Cu-substituted structures. Though Pb₁₀(PO₄)₆O and Pb₁₀(PO₄)₆(OH)₂ are found to be thermodynamically stable (i.e., on the T=₀K ground state convex hull), their Cu-substituted counterparts are above the convex hull. Harmonic phonon calculations reveal dynamic instabilities in all four of these structures. Oxygen vacancy formation …

Development Of Pre-Magnetized Magnetorheological Elastomer For Bidirectionally Variable Stiffness Applications, Choonghan Lee

UNLV Theses, Dissertations, Professional Papers, and Capstones

Magnetorheological elastomers (MREs) utilize magnetic forces between ferromagnetic particles to cause variable stiffness properties and damping with external magnetic fields. In the MREs, the particles are embedded in a cured elastomer matrix, and an external magnetic field makes the stiffness change due to induced magnetic forces among particles. A disadvantage of the conventional MREs is that they cannot be softened (reduced stiffness) under an external magnetic field. Considering that there are many engineering applications where fast changes of stiffness in both directions (stiffening and softening) are required, embedding magnetically biased particles in the MRE can provide potential solutions. In this …

Towards Cfd Investigations Into Particulate Air Pollution Of A Desert Urban Environment, Prosun Roy

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation has explored computational fluid dynamics (CFD) techniques for studying particulate air quality in the Las Vegas urban area. The dissertation is based on three research tasks:

• • High time-resolution fenceline air quality sensing and dispersion modeling for environmental justice-centered source attribution. (Chapter 2)
• • Pollen dispersion and deposition in real-world urban settings: A computational fluid dynamic study. (Chapter 3)
• • Effects of urban canopy parameterizations on modeling pollen dispersion and exposure. (Chapter 4)

In Chapter 2, we investigate the facilitation of low-cost air quality sensors (LCAQS) and CFD technique on exposure assessment of environmental justice (EJ) communities and …

Co-Simulation Of Active Magnetic Bearing Rotors Using Adams, Msc Apex, And Simulink, Shea A. Charkowsky

Master's Theses

Apex-Adams-Simulink co-simulation is applied to active magnetic bearing (AMB) rotors, demonstrating results unshown in literature, including continuous frequency response, and unavailable in known rotor dynamics software, including touchdown bearing impact. AMBs levitate rotors without contact, so they involve no friction, wear, lubrication, pollution, or shaft speed limits and are thus valuable for large, high-speed applications. Modeling of such rotors, necessary for safety and performance, simultaneously requires flexible body dynamics and advanced control design, but simulation programs tend to specialize in only one or the other. The co-simulation method combines multiple such programs—MSC Apex (finite element modeling), Adams (multibody dynamics), and …

Chemical And Physical Interaction Mechanisms And Multifunctional Properties Of Plant Based Graphene In Carbon Fiber Epoxy Composites, Daniel W. Mulqueen

Mechanical & Aerospace Engineering Theses & Dissertations

Graphene has generated substantial interest as a filler due to its exceptional strength, flexibility, and conductivity but faces obstacles in supply and implementation. A renewable, plant-based graphene nanoparticle (pGNP) presents a more accessible and sustainable filler with the same properties as mineral graphenes. In this study, the mechanisms of graphene reinforcement in carbon fiber reinforced plastic (CFRP) were examined, along with the resulting improvements to mechanical strength, resistance to crack propagation, electrical and thermal conductivity at elevated temperatures. pGNP, produced from renewable biomass, was shown to have a graphitic structure with flakes 3-10 layers thick and a median lateral size …

Development, Experimental Validation, And Progressive Failure Modeling Of An Ultra-Thin High Stiffness Deployable Composite Boom For In-Space Applications, Jimesh D. Bhagatji

Mechanical & Aerospace Engineering Theses & Dissertations

To maximize the capabilities of nano- and micro-class satellites, which are limited by their size, weight, and power, advancements in deployable mechanisms with a high deployable surface area to packaging volume ratio are necessary. Without progress in understanding the mechanics of high-strain materials and structures, the development of compact deployable mechanisms for this class of satellites would be difficult. This research focuses on fabrication, experimental testing, and progressive failure modelling to study the deformation of an ultra-thin composite beam. The research study examines deformation modes of a boom under repetitive pure bending loads using 4-point bending setup. The material and …

Study Of Microphonic Effects On The C100 Cryomodule For High Energy Electron Beam Accelerators, Caleb James Hull

Mechanical & Aerospace Engineering Theses & Dissertations

The Continuous Electron Beam Accelerator Facility (CEBAF) at Thomas Jefferson National Laboratory (JLab) is a particle accelerator which can accelerate an electron beam to relativistic speeds and apply the beam onto target samples. The C100 superconducting radio frequency (SRF) cavity is the primary accelerating structure of the C100 cryomodule, one of the many cryomodules which compose the CEBAF linear accelerator. SRF cavities are particularly sensitive to internal and external vibrations that can result in a phenomenon called microphonics which degrade the operational stability of a cryomodule.

The purpose of this thesis is to investigate the significance of mechanical disturbances on …

Data-Driven Predictive Modeling To Enhance Search Efficiency Of Glowworm-Inspired Robotic Swarms In Multiple Emission Source Localization Tasks, Payal Nandi

Mechanical & Aerospace Engineering Theses & Dissertations

In time-sensitive search and rescue applications, a team of multiple mobile robots broadens the scope of operational capabilities. Scaling multi-robot systems (< 10 agents) to larger robot teams (10 – 100 agents) using centralized coordination schemes becomes computationally intractable during runtime. One solution to this problem is inspired by swarm intelligence principles found in nature, offering the benefits of decentralized control, fault tolerance to individual failures, and self-organizing adaptability. Glowworm swarm optimization (GSO) is unique among swarm-based algorithms as it simultaneously focuses on searching for multiple targets. This thesis presents GPR-GSO—a modification to the GSO algorithm that incorporates Gaussian Process Regression (GPR) based data-driven predictive modeling—to improve the search efficiency of robotic swarms in multiple emission source localization tasks. The problem formulation and methods are presented, followed by numerical simulations to illustrate the working of the algorithm. Results from a comparative analysis show that the GPR-GSO algorithm exceeds the performance of the benchmark GSO algorithm on evaluation metrics of swarm size, search completion time, and travel distance.

Measurement Of Conduction, Radiation, And Convection Thermal Energy To Assess Baking Performance In Residential Ovens., Sean Simpson

Electronic Theses and Dissertations

Residential ovens are complicated thermal environments capable of delivering convection, conduction, and radiation heat transfer to food. The amount and mode of heat transfer can change based on the design of the oven cavity, cooling systems, and oven cycle algorithms. Studies have shown that the changes in one heat transfer mode can have an impact on the quality of baked goods. The many variables involved make designing residential ovens a time consuming and costly process. The goal of this study is to adapt thermal energy sensing technology to collect energy data from a residential oven and develop correlations to quality …

Aerodynamic Flow Control Using Micro Rotating Cylinders, Alejandro Daniel Carrizales

Theses and Dissertations

This research investigates the aerodynamic and flow field characteristics of a NACA 0010 airfoil equipped with rotating cylinders near the leading edge, subjected to a flow with a freestream turbulence intensity of 4.3%. The airfoil was modified to integrate five micro-DC motors positioned at 14.5% of the chord length from the leading edge. The cylinders, with dimensions of 0.75 inches in diameter and 0.5 inches in width, exposed 3mm of their length to the incoming flow. A modified leading edge with eight sinusoidal protrusions (tubercles) was employed to compare the performance of the micro-rotating cylinder airfoil with an unmodified baseline …

Double Cantilever Beam Mode-I Testing Validation In Large-Scale Additive Manufacturing Carbon Composite, Luis Alfonso Camacho

Open Access Theses & Dissertations

Testing for mechanical properties for additive manufacturing has been based on already existing standards for traditional manufacturing methods. For composites in large scale additive manufacturing there is a research gap in bond strength and fracture toughness for a single layer interface. By using Double cantilever beam Mode I, this thesis manuscript validates testing parameters and protocols to describe the intricacies of ABS matrix 20 wt.% carbon filled composite, specifically on the layer-to-layer interface. Studies suggest that fracture toughness is sensitive to process parameters, like deflection speed and sharpened crack tip at the layer interface of BAAM 3D printed part and …

Measurement Of Vapour Pressure, Miscibility And Thermal Conductivity For Binary And Ternary Refrigerant Lubricant Mixtures In The Context Of Heat Pump Tumble Dryers, Katharina Stockel, Ramona Nosbers, Riley Barta, Christiane Thomas

School of Mechanical Engineering Faculty Publications

Household appliances need to be both efficient and cost-effective. As a result, electrically driven tumble dryers were converted to heat pump driven ones several years ago in order to comply with energy directives, in this case in Germany. In order to increase the efficiency of heat pumps of different performance classes, the use of zeotropic refrigerant mixtures can be useful, since the temperature glide during the phase change of the refrigerant mixture can be adapted to the temperature gradients of the secondary fluids. In order to take advantage of this unique property, a refrigerant mixture selection was carried out by …

Design And Implementation Of A Load Sensor In A Bearing Adapter Assembly For Freight Railcar Applications, Prince E. Mensah

Theses and Dissertations

The U.S. freight rail network, which covers approximately 140,000 route miles, is commonly regarded as the largest, safest, and most economical freight system in the world. It generates more than 167,000 jobs nationwide and has additional advantages over other modes of transportation, such as lower costs for logistics, public infrastructure upkeep, and decreases in traffic congestion, highway deaths, fuel consumption, and greenhouse gas emissions. Knowing the exact weight of cargo hauled by freight railcars can help avoid exceeding the loading thresholds set by the Association of American Railroads (AAR). Moreover, knowing the exact load applied to each bearing on the …