Engineering Commons^™

Point Heat Source Correlation To Microstructural Evolution In Advanced Manufacturing, Mark Anderson

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Although there are different ways that advanced manufacturing can be performed, the use of single-point heat sources has become the standard to control a final product’s properties. It is imperative to understand how the heat source used in the different advanced manufacturing processes affect the microstructure of interest. The intimate relationship between the heat source and microstructure allows for controlling and tailoring a part’s properties. Utilizing different microstructural analysis, the cross-correlation of various point heat sources to developed microstructure was conducted in this dissertation.

Laser powder bed fusion allows for unique print-to-part protocols, but the dynamics of the process makes …

Trace Dna Detection Using Diamond Dye: A Recovery Technique To Yield More Dna, Leah Davis

Master's Theses

This study aspires to find a new screening approach to trace DNA recovery techniques to yield a higher quantity of trace DNA from larger items of evidence. It takes the path of visualizing trace DNA on items of evidence with potential DNA so analysts can swab a more localized area rather than attempting to recover trace DNA through the general swabbing technique currently used for trace DNA recovery. The first and second parts consisted of observing trace DNA interaction with Diamond Dye on porous and non-porous surfaces.

The third part involved applying the Diamond Dye solution by spraying it onto …

Characterizing Energy Dissipation Of Shallow-Water Wave Breaking In A Storm Surge, Hunter Boswell, Guirong Grace Yan, Wouter Mostert

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

While understanding breaking waves is crucial for the development of parametrizations used in ocean wave modeling for both deep and shallow water, the complete process of wave breaking is not well understood. Here we present direct numerical simulations of two-dimensional solitary waves that shoal and break on a uniform beach in shallow water, with the presence of storm surge represented by an inshore region. The storm surge depth, beach slope, and wave amplitude are varied to study the dependence of energy dissipation in the breaker on wave and bathymetric parameters. We classify wave breaker types and find a separation between …

Cycle Time Reduction In Additive Manufacturing Using Peltier Thermoelectric Cooling Devices, Trevor Carlton

Honors College Theses

Thermoelectric cooling and the Peltier effect were discovered in 1834, over 188 years ago. Additionally, the first iterations of additive manufacturing (i.e., 3D printing) began in the early 1980s, more than 40 years ago. Despite these technologies’ age and years of advancements, the application of Peltier cooling-based devices in additive manufacturing has not yet been realized. These devices can be used for the active thermal management of print beds in 3D printers. Developing a mechanism to heat and cool a print bed can reduce the cycle time to manufacture a part. In 3D printing, waiting for the heated bed to …

Comparative Design Space For Bistable Composites: An Integrated Framework Of Optimization, Finite Element Analysis, And Experimental Testing, Jonathan Bolanos

All Theses

Bistable composites are a class of advanced materials that can actuate between two stable shapes, making them attractive for a wide range of engineering applications. However, designing these composites to achieve optimal performance remains a challenging task. To address the challenge, this research develops an integrated framework that combines a genetic algorithm optimization technique, finite element analysis in Abaqus, and experimental testing to explore the design comparative space for square bistable composites composed of DA 409 carbon fibers. This leads to the study of generating an optimization algorithm to account for the relationship between the chances of a successful maximum …

Fusion Bonding Behavior Of 3d Printed Pa6/Cf Composites Via Post Fabrication Compaction, Gonzalo Fernandez Mediavilla

Mechanical & Aerospace Engineering Theses & Dissertations

Additive manufacturing (AM) is becoming a robust production technology for aerospace, healthcare, and construction industries among others. Fused Deposition Modelling (FDM) is one of the methods most used to 3D print products. FDM has limitation due to interlayer adhesion and restriction imposed by the printing direction. Specially with AM composites, as reinforced nylon PA6 with short fibers, parts show more strength along the direction of the filament due to the alignment of the carbon fibers, but weaker in other directions. The proposed method to solve this issue is to print parts separately and join them together by fusion bonding. PA6/CF …

Fabrication Of Solid Oxide Fuel Cell Components Using Stereolithography 3d Printing, Hannah Dyer

Mechanical & Aerospace Engineering Theses & Dissertations

Transitioning from fossil fuel supplied energy to renewable technology must meet cost efficient parameters throughout the manufacturing process while possessing the characteristics of a functioning and reliable power source. With a significant demand in renewable energy products, developmental techniques require adaptive approaches and procedures for novel materials in the manufacturing phase. This report proposes how a solid oxide fuel cell (SOFC), a renewable energy system, can employ additive manufacturing for directly 3D printing its components by utilizing stereolithography (SLA) 3D printing techniques. Fabrication of the printed components from the mixtures were first mixed with varying concentrations of ceramic powder and …

Roboretrieve--In A Dual Role As A Hand-Held Surgical Robot And A Collaborative Robot End-Effector To Perform Spillage-Free Specimen Retrieval In Laparoscopy, Siqin Dong

Mechanical & Aerospace Engineering Theses & Dissertations

Recent advances in surgical robotics attempt to overcome limitations of manual surgery by augmenting the surgeon’s capabilities while performing suturing, incision, retraction, and retrieval tasks. This dissertation presents novel approaches for spillage-free specimen retrieval in confined spaces, targeted toward the surgical domain of minimally invasive robotic surgery. The retrieval task involves extraction of a resected specimen, residing in the abdominal cavity, completely outside of the patient’s body. A major challenge in this context is the spillage of content being retrieved, which may cause dissemination of malignancy. To address this challenge, this dissertation develops RoboRetrieve, a portable hand-held robot that …

E-Cadherin Force Transmission And Stiffness Sensing, Mazen Mezher

Mechanical & Aerospace Engineering Theses & Dissertations

E-cadherin is the chief mediator of cell-cell adhesion between epithelial cells and is a known mechanosensor. Force transmission and stiffness sensing are two crucial aspects of E-cadherin mechanobiology.

E-cadherin has an extracellular adhesive region, a transmembrane region and an intracellular region that binds to adhesion-associated proteins. Here, we assessed how different factors affect the level of force transmission (i) from inside the cell such as adhesion-associated proteins, (ii) on the cell membrane, such as growth factor receptors and (iii) outside the cell, such as different binding partners in adhesion. To study the level of force transmission inside the cell, we …

Engineered Material Systems For Mimicking Tissue And Disease, Margrethe Ruding

McKelvey School of Engineering Graduate Student Theses & Dissertations

This thesis comprises two studies involving design and application of soft material systems. The goal of the first study was to design, fabricate, and characterize hydrogel lattice structures with consistent, controllable, anisotropic mechanical properties. Lattices, based on four types of unit cells (cubic, diamond, vintile, and Weaire-Phelan), were printed using stereolithography (SLA) of polyethylene glycol diacrylate (PEGDA). In order to create structural anisotropy in the lattices, unit cell design files were scaled in one direction by a factor of two in each layer and then printed. The mechanical properties of the scaled lattices were measured in shear and compression and …

A Proof Of Concept For Detection Of Palato-Lingual Contact Without Intraoral Electrodes In A Human Participant, Amitava Biswas

Master's Theses

The author of this thesis conceived and investigated an unexpected electrical signal that may not be noticed during regular electroglottography (EGG) when electrodes are conventionally placed on the anterior surface of the throat. It appears that there is a measurable electrical signal from the EGG equipment when electrodes are placed over the frontal cheek (belly of zygomatic muscle), and the tongue is elevated to contact the hard palate, or the tongue is lowered to break the contact. Therefore, this phenomenon is designated as unconventional electroglottography (UEGG, Dr. Steven Cloud, private communication, July 17, 2022).

Two distinctive patterns of waveforms were …

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 …

A Unified Understanding Of Minimum Lattice Thermal Conductivity, Yi Xia, Dale Gaines, Jiangang He, Koushik Pal, Zhi Li, Mercouri G. Kanatzidis, Vidvuds Ozolinš, Chris Wolverton

Mechanical and Materials Engineering Faculty Publications and Presentations

We propose a first-principles model of minimum lattice thermal conductivity based on a unified theoretical treatment of thermal transport in crystals and glasses.

Probabilistic Machine Learning For Battery State Of Health Prognostics, Charli Zaretsky

Honors Scholar Theses

The ability to understand and predict the state of health (SOH) of lithium-ion batteries is an integral component of their widespread commercial use. There are various methods through which SOH can be analyzed and predicted, and this paper discusses these different methods, and the strengths and weaknesses of each. This paper also details an analysis of lithium-ion battery SOH through two data-driven machine learning methods: XGBoost and Gaussian process regression. A comparison is made between each method’s accuracy in predicting next-cycle discharge capacity using electrochemical impedance spectroscopy (EIS) readings and battery charge and discharge rates, from a dataset given in …

Mechanical And Thermal Performance Of Additively Manufactured Digital Materials, Layth Muayyad Ahmad

Mechanical and Aerospace Engineering Theses - Archive

Over the past decades, additive manufacturing has become a critical material processing tool. All ranges of materials including polymers, composites, metals, and ceramics can be used to fabricate structures with complex geometries that are nearly impossible to build using conventional fabrication process. Recently, additive manufacturing methods to build polymeric structures have been advanced significantly. In particular, the emergence of multi-material printers has made it possible to seamlessly print hybrid and digital materials where materials components and compositions are digitally varied to construct fully tailored material system. In this work, using a commercially available polyjet printer (Stratasys J850 Prime 3D printer), …

Parametric Multi-Objective Optimization Of Cold Plate For Single-Phase Immersion Cooling, Geevarghese Joseph Nattasseriedathil

Mechanical and Aerospace Engineering Theses - Archive

The increasing demand for high performance computing in applications such as Internet of Things, Deep Learning, Big data for crypto-mining, virtual reality, healthcare research on genomic sequencing, cancer treatment etc. has led to the growth of hyper scale datacenters. To meet the cooling energy demands of HPC datacenters efficient cooling technologies must be adopted. Traditional air cooling, direct to chip liquid cooling and immersion are some of those methods. Among all, Liquid cooling is superior compared to various air-cooling methods in terms of energy consumption. Direct on-chip cooling using cold plate technology is one such method used in removing heat …

Computational Analysis Of Water Braking Phenomena For High-Speed Sled And Its Machine Learning Framework, Jose A. Terrazas

Open Access Theses & Dissertations

Specializing in high-speed testing, Holloman High-Speed Test Track (HHSTT) uses a process called "water braking" as a method to bring vehicles at the test track to a stop. This method takes advantage of the higher density of water, compared to air, to increase braking capability through momentum exchange. By studying water braking using Computational Fluid Dynamics (CFD), forces acting on track vehicles can be approximated and prepared for prior to the actual test. In this study, focus will be made on the brake component of the track sled that is responsible for interacting with the water for braking. By discretizing …

A Method For Measuring The Spectral Emissivity Of Metal Powders At Different Temperatures And Applications In Laser Powder Bed Fusion, Emmanuel Levario

Open Access Theses & Dissertations

Radiation thermometry monitoring methods used in powder bed fusion additive manufacturing (PBF-AM) are becoming increasingly more popular for quality assurance and repeatability. The dynamic nature of the PBF process and a lack of accuracy of metrics being captured for temperature monitoring lend great difficulty in the successful implementation of in-situ monitoring. There is currently no data on the emissivity, a metric used in non-contact temperature measurements, for metal powders used in AM. This work describes a method for measuring the spectral emissivity for metal powder sizes commonly used in AM using a multi-wavelength (MW), FMPI SpectroPyrometer, calibrated within the spectral …

Sensing Optimization Of Thermoplastics And Ceramics Fabricated Through Additive Manufacturing, Cory Marquez

Open Access Theses & Dissertations

The objective of this research is to fabricate and optimize thermoplastic and ceramic materials that can be fabricated for Laser Sintering (LS), Direct Ink Write (DIW), and Fused Filament Fabrication (FFF) 3D printing. The fabrication of High-Density Polyethylene (HDPE) thermoplastic particles into spherical allow for better flowability and packing density for LS printing which results in better printability and an increase in mechanical properties. The fabrication of clay ceramic allows the printability application for DIW with the implementation of an embedded wireless temperature and relative humidity sensor. The use of FFF multi-material printing allowed the capabilities of 3D printing a …

Metal Fused Filament Fabrication: Distortion Compensation & Co2 Electrochemical Reduction, Jean Emmanuel Montes Ramirez

Open Access Theses & Dissertations

Metal fused filament fabrication (MF3) is a rapidly growing additive manufacturing technology that enables the creation of complex metal parts with high accuracy and precision. Copper, a highly conductive metal with various applications in industries such as electronics and aerospace, is a promising material for MF3. In this study, we investigated the use of MF3 copper parts to fabricate copper electrodes for CO2 electrochemical reduction. We examined the post-processing manufacturing process of debinding and sintering to obtain fully 3D printed copper parts in an air environment. Our results demonstrate that MF3 copper parts have high porosity, providing a larger active …

Convexity Applications In Single And Multi-Agent Control, Olli Nikodeemus Jansson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The focus of this dissertation is in the application of convexity for control problems; specifically, single-agent problems with linear or nonlinear dynamics and multi-agent problems with linear dynamics. A mixture of convex and non-convex constraints for optimal control problems is also considered. The main contributions of this dissertation include: 1) a convexification of single-agent problems with linear dynamics and annular control constraint, 2) a technique for controlling bounded nonlinear single-agent systems, and 3) a technique for solving multi-agent pursuit-evasion games with linear dynamics and convex control and state constraints. The first result shows that for annularly constrained linear systems, controllability …

High-Yield Bioinspired Atmospheric Water Capture Through Hydrogels, Yiwei Gao

UNLV Theses, Dissertations, Professional Papers, and Capstones

Water scarcity is a global issue affecting billions of people, and atmospheric water harvesting (AWH) technology has been identified as a potential solution. However, existing single-material AWH approaches have limited water harvesting yields due to alternated water capture, storage, and release stages, and only function within a high relative humidity range. In my doctoral research project, we developed a bio-inspired, hydrogel-based multi-layer AWH approach that allows for segregated capture, storage, and release stages, and is envisioned to have higher daily water harvesting efficiency even in low-humidity areas. My research began with understanding the relations between hydrogel mechanical stiffness, hydraulic permeability, …

Time-Dependent Wetting Behavior Of Hydrogels, Amir Kashani

UNLV Theses, Dissertations, Professional Papers, and Capstones

Hydrogels are 3-D polymers with hygroscopic properties that enable them to absorb and retain large amounts of water. In many applications such as biomedical applications, including drug delivery, wound healing, tissue engineering, biosensors, and contact lenses, agriculture, food and beverage, cosmetics, and environmental, hydrogels also need to maintain a high degree of wetting in order to ensure effective functionality and interaction with surrounding fluids or tissues in desired applications. The combination of wetting and absorptive behavior of hydrogels that are often encountered in biomedical, biological, industrial and the mentioned applications presents a challenging physical problem that is not completely understood. …

A One-Dimensional Analysis Of A Microbial Fuel Cell For Efficient Acetate Removal And Power Density Output, David Rouhani

UNLV Theses, Dissertations, Professional Papers, and Capstones

Microbial fuel cells (MFCs) are electrochemical devices that utilize microorganisms to convert organic matter into electrical energy. MFCs have been discussed to have potential application for sustainable wastewater treatment due to their ability to generate electricity while simultaneously treating contaminated water. To optimize MFC performance, numerical models can be used to understand the complex electrochemical and biological processes occurring in the system. In this study, a numerical model was developed to simulate the performance of MFCs under varying operating conditions and to investigate the performance of a MFC for treating wastewater fuel. More specifically, the MFC was modeled to oxidize …

Characterization And Manipulation Of Double-Stranded Dna Using Atomic Force Microscopy, Lauren Skartvedt

Mechanical Engineering Undergraduate Honors Theses

An atomic force microscope (AFM) is used to scan high-resolution images on the nano scale. The lambda DNA used for this project are 48,502 base pairs in length and are double-stranded. This project utilizes the NanoSurf Core AFM in order to characterize and manipulate strands of lambda DNA which have been deposited on a mica surface. The deposition process of the DNA on the mica surface was developed by the National Institute of Standards and Technology and the University of Colorado - Boulder. The AFM is used in imaging mode to scan the mica surface to locate the DNA. When …

A Systematic Study Into The Design And Utilization Of Burn Wire As A Means Of Tensioning And Releasing Spacecraft Mechanisms Through Applied Joule Heating, Chandler Dye

Mechanical Engineering Undergraduate Honors Theses

The joule heating characteristics of Nichrome burn wires, often used as a thermal cutting device in mechanisms designed to fasten and release CubeSat deployables, are examined in the following thesis. Wires ranging from 0.125 inches to 2 inches long, and diameters of 30 Ga and 40 Ga, are investigated through analytical calculations and thermal simulations based on heat transfer due to joule heating, and through physical circuitry-based experiments. The temperature data is used to generate heating curves to predict the time it takes for Nichrome wires to fail under varying testing parameters. This research aims to catalog a series of …

Using Actor-Critic Reinforcement Learning For Control Of A Quadrotor Dynamics, Edgar Adrian Torres

Theses and Dissertations

This paper presents a quadrotor controller using reinforcement learning to generate near-optimal control signals. Two actor-critic algorithms are trained to control quadrotor dynamics. The dynamics are further simplified using small angle approximation. The actor-critic algorithm’s control policy is derived from Bellman’s equation providing a sufficient condition to optimality. Additionally, a smoother converter is implemented into the trajectory providing more reliable results. This paper provides derivations to the quadrotor’s dynamics and explains the control using the actor-critic algorithm. The results and simulations are compared to solutions from a commercial, optimal control solver, called DIDO.

Reynolds-Averaged Navier-Stokes Cfd Simulation Of High-Speed Boundary Layers, Michael Tullis

Mechanical Engineering Undergraduate Honors Theses

This paper presents an investigation of Reynolds-averaged Navier-Stokes (RANS) turbulence models used in computational fluid dynamics (CFD) simulations of boundary layer flow and heat transfer in high Mach number flows. This study evaluates an industry standard RANS turbulence model (k-omega SST) and a recently proposed modification to that model (Danis and Durbin [1]), and quantifies the accuracy for predicting high Mach number boundary layer flow. The test cases were previously documented by Duan et al. (2018), who used direct numerical simulation (DNS) to calculate boundary layer flow of an ideal gas over a flat plate at freestream Mach numbers ranging …

Investigation Of Dynamic Hybrid Rans-Les Turbulence Modeling For Cfd Simulation Of A Normal Jet In Crossflow, Cole Simmonds

Mechanical Engineering Undergraduate Honors Theses

The jet in crossflow is a canonical flow feature in many natural and engineered systems, ranging from pollutant dispersal in exhaust discharge to film cooling of high-temperature components in modern propulsion systems. The ability to computationally predict the flow features of jets in crossflow accurately and efficiently is therefore important for analysis and design for a wide variety of applications. In this study the capabilities of the dynamic hybrid RANS-LES (DHRL) turbulence modeling technique are investigated and compared to an industry standard Reynolds-averaged Navier-Stokes model (k-omega SST) in order to quantify the accuracy and computational cost of the two approaches. …

Study Of Different Heat Treatments And Aging Conditions For Observing Microstructures And Mechanical Properties Of Lpbf Fabricated F357 Alloy, Victor Adrian Medrano Balderas

Open Access Theses & Dissertations

Aluminum F357 is a widely used material for casting in the aerospace and additive manufacturing industry. Heat treatments are commonly applied to some aluminum alloys to modify their properties. With a further study on the aging and performance of the F357 with 3D printing technology, several industries benefit from this; military, automotive, and aerospace are some examples because of the numerous components cast in service. This work presents the mechanical properties of F357 specimens fabricated with EOS technology and subjected to heat treatments. Heat treatment conditions were applied to tensile specimens and tested. Furthermore, the specimens were subjected to artificial …