Digital Commons Network^™

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 …

Metastability And Degradation In Cu(In,Ga)Se2 Thin-Film Solar Cells, Mohsen Jahandardoost

UNLV Theses, Dissertations, Professional Papers, and Capstones

Cu(In,Ga)(S,Se)2 or CIGS is a thin-film semiconductor that has shown a device efficiency of 23.35% and 24.2% for single-junction and perovskite/CIGS tandem solar cells, respectively. CIGS offers promising properties such as tunable bandgap and ease of processing making them great candidates for thin-film tandem devices. However, knowledge of the effect of material defects, buffer materials, and post-deposition treatment (PDT) on degradation and metastability behavior in these devices is not well understood.In this dissertation, metastability and long-term degradation of CIGS thin-film solar cells have been investigated under combinatorial stress factors of heat, light, and voltage bias to systematically understand the effect …

Dynamic Surface Tension Of Surfactants Through Separation Of Diffusion And Dilation Effects, Brandon Ortiz

UNLV Theses, Dissertations, Professional Papers, and Capstones

Surfactants are biphilic monomers that adsorb to interfaces and have the ability to reduce interfacial tension. From this reduction in interfacial tension, surfactants are able to function as emulsifiers, detergents, and wetting agents among a variety of other things. Despite their ubiquity surfactants and surfactant behaviors, in particular those in highly dynamic environments, are not yet well characterized. In these environments, surfactants undergo significant distortions to droplet, bubble, and foam geometries which induce changes to the surface tension. This establishes a need to understand how surfactants respond to distortions of geometry through diffusion and dilational effects. To address this need, …

Mechanoelectrical Behavior In Polyvinyl Chloride (Pvc) Based Soft Polymer Gel Smart Sensors For Soft Robotic Applications, Justin Neubauer

UNLV Theses, Dissertations, Professional Papers, and Capstones

Polyvinyl chloride (PVC) gels are a class of electroactive polymer that contain a PVC-based polymeric lattice and various amounts of plasticizer. PVC and plasticizer are industrially available and are commonly used in a wide range of applications including cable insulation, flexible hosing, and healthcare equipment. There are many plasticizer types available, some being extremely biocompatible with implementations in food-safe applications and even food additives for human consumption. Plasticizer weakly bonds to the long polymerized chains of the polymer lattice decreasing the modulus of the composite material. By adding excessive amounts of plasticizer, the bonding sites of these long carbon chains …

How Dynamic Adsorption Controls Surfactant‑Enhanced Boiling, Mario R. Mata, Brandon Ortiz, Dhruv Luhar, Vesper Evereux, H. Jeremy Cho

Mechanical Engineering Faculty Research

No abstract provided.

Enhancements To Nuclear Thermal Propulsion Rockets, Kimberly Gonzalez

UNLV Theses, Dissertations, Professional Papers, and Capstones

Nuclear thermal rocket propulsion has been proposed as a highly efficient technology for space vehicles traveling from earth orbit to the moon, Mars, and other locations in the solar system. With twice the performance of a chemical rocket, nuclear thermal propulsion (NTP) uses the thrust produced by heating hydrogen gas within a thermal nuclear reactor where the exhaust is then passed through a de Laval nozzle to produce supersonic flow. NTP engines were the subject ofthe NERVA experiments at the Nevada Test Site in the 1970’s, and they produced a specific impulse of up to 900 seconds which is almost …

Mobile 3d Printing Of Rail Track Surface For Rapid Repai, Ershad Mortazavian

UNLV Theses, Dissertations, Professional Papers, and Capstones

The frequent replacement of worn rails on tracks brings an immense economic burden on the railroad industry, and also causes significant interruptions to railroad operation. Restoration of worn rails via additive manufacturing, i.e., 3D printing, can considerably reduce the associated maintenance costs.The scope of this dissertation is to utilize metal additive manufacturing (AM) technology to repair worn rails that are used in the U.S. railway transportation system (e.g. 75-lb/yd light transit rails, or 136-lb/yd heavy freight rails). More specifically, this study aims to understand the interactive mechanisms between the deposited materials and the high-carbon rail steel to identify and alleviate …

Towards High-Efficient Broadband Omnidirectional Light-Trapping: Discrepancy-Assisted 2d/3d Deterministic Quasi-Random Nanostructure Design, Optimization, And Fabrication, Yihong Zhao

UNLV Theses, Dissertations, Professional Papers, and Capstones

Recently, nano-scaled surface decoration has brought significant advancement and exciting new possibilities to light management. Numerous nanostructure patterns have been explored, wherein the quasi-random nanostructures (QRNs) present a promising path in manipulating light to increase the photon flux over the broadband spectra for optical (e.g., photovoltaic) devices. However, due to the infinite number of QRNs, it is difficult to directly design and fabricate the exact QRN pattern as desired to achieve the optimized light-trapping capability. To overcome this obstacle, we 1) digitize the traditional continuous QRNs into meshes and then map the meshes to binary matrices, which can be deterministically …

Radiomic Features To Predict Overall Survival Time For Patients With Glioblastoma Brain Tumors Based On Machine Learning And Deep Learning Methods, Lina Chato

UNLV Theses, Dissertations, Professional Papers, and Capstones

Machine Learning (ML) methods including Deep Learning (DL) Methods have been employed in the medical field to improve diagnosis process and patient’s prognosis outcomes. Glioblastoma multiforme is an extremely aggressive Glioma brain tumor that has a poor survival rate. Understanding the behavior of the Glioblastoma brain tumor is still uncertain and some factors are still unrecognized. In fact, the tumor behavior is important to decide a proper treatment plan and to improve a patient’s health. The aim of this dissertation is to develop a Computer-Aided-Diagnosis system (CADiag) based on ML/DL methods to automatically estimate the Overall Survival Time (OST) for …

Carbon Fiber Coil Spring Characterization And Manufacturing, Cooper Madrazo

UNLV Theses, Dissertations, Professional Papers, and Capstones

Helical coil springs are used in many mechanical design applications including industrial machines, devices, and vehicle suspension systems. It is desirable to minimize the weight of vehicle suspension systems as this can improve performance and handling. Most vehicle suspension coil springs are made from solid steel alloys or other metallic materials. Significant weight savings could be achieved if the metallic material were replaced by high performance fiber reinforced polymer composites. However, the coil spring geometry is a difficult manufacturing challenge for composite materials. The goal of this thesis was to investigate efficient and low-cost manufacturing methods to produce light-weight polymer …

Fuel Injector Design Of A Hypersonic Jet Engine Using Computational Fluid Dynamics, Melissa Rose Mercado

UNLV Theses, Dissertations, Professional Papers, and Capstones

The development of hypersonic airbreathing engines, such as a supersonic combustion ramjet, or scramjet, are implemented for flight Mach numbers over 5 where combustion must occur in supersonic conditions. The advancement of scramjet propulsion has led to favored usage over rocket propulsion systems for in atmosphere applications due to their lighter weight, higher specific impulse, and greater maneuverability [1]. The combustor section of a scramjet engine houses the fuel injectors. Fuel is injected into the supersonic flow with the main objective of achieving rapid and thorough fuel-air mixing because the residence time in the combustion chamber has a timescale of …

Predicting The Progression Of Diabetes Mellitus Using Dynamic Plantar Pressure Parameters, Mathew Sunil Varre

UNLV Theses, Dissertations, Professional Papers, and Capstones

Introduction: Diabetic peripheral neuropathy is one of the common complications of type-2 diabetes mellitus (DM). Changes in the intrinsic plantar tissue coupled with repetitive mechanical loads and loss of sensation may lead to foot related complications (skin break down, ulcerations, and amputations) in persons with neuropathy if left untreated. The purpose of this dissertation was to stratify individuals with pre-diabetes, diabetes with and without neuropathy using dynamic plantar pressure parameters during walking, using machine learning algorithms.Methods: Plantar pressure data was collected from one hundred participants during walking with pressure measuring insoles fixed between the feet and thin socks. Simultaneously high-definition …

Transdisciplinarity In Experience Design: A Global Survey Of Higher Ed Programs In Exd/Xd, Yvonne Houy

Creative Collaborations

In our age of ubiquitous devices and digital media it is the perceived value of the end-to-end experience that brings people to a place. Designing inspiring and emotionally engaging end-to-end experiences requires experts in a wide range of disciplines committed to an interdisciplinary collaboration that can arrive at transdisciplinary design - the sum becomes greater than its parts.

Civil engineering, hospitality, business, psychology, digital User Experience (UX) design, and experience data analysis need to be seamless integrated with the fine and performing arts and design fields:

• Architecture, interior, landscape and sound design actively engage the senses.

• Graphic and fine arts …

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Polyvinyl Chloride Gels: Theoretical Modeling Of Their Actuation Mechanism And Characterization Of Their Properties, Zachary Frank

UNLV Theses, Dissertations, Professional Papers, and Capstones

Polyvinyl chloride (PVC) gels are an electroactive polymer smart material which has been considered in a variety of actuator applications. Their large deformation, fast response rates, optical transparency, and soft nature has made them a key area of interest in fields ranging from soft robotics to optics. PVC gels are made from PVC mixed with large quantities of plasticizer, such as dibutyl adipate (DBA). When a voltage is applied, the gel experiences an “anodophilic” deformation (in which it moves preferentially towards the anode). This unique characteristic is the result of a charge buildup near the anode surface, which creates electromechanical …

Computational Sodium Heat Pipe Simulation In Three Dimensions For Transient Nuclear Reactor Analysis With Variable Surface Heat Flux, Valerie Jean Lawdensky

UNLV Theses, Dissertations, Professional Papers, and Capstones

Heat pipes are used to transfer heat through phase change in a liquid/vapor contained in a metal tube. They are passive devices that require no pumps to circulate the fluid and can transfer heat far more efficiently than a solid copper rod of the same diameter. They are commonly used in laptop computers where copper heat pipes filled with water take heat away from the CPU and transfer the heat to air through a heat exchanger. Heat pipes were also used in the Kilopower nuclear reactor where higher temperatures required sodium as the working fluid with stainless steel tubes. Computer …

Modeling The Mechanical Behavior And Shock Propagation Of Metallic And Nanocomposite Materials, Pouya Shojaeishahmirzadi

UNLV Theses, Dissertations, Professional Papers, and Capstones

Evaluating the materials properties under different loading conditions is critical in various industries. Compared to quasi-static loading, predicting the behavior of structures under dynamic loads is more challenging. In this work, we will address multiple problems with strain rates varying from quasi-static to hypervelocity conditions. Computer simulation is increasingly used in the design and evaluation phases to improve the efficiency, cost-effectiveness, and flexibility. However, verification and validation of each simulation is necessary. Experiments are performed in all topics and the computational models are validated by comparing with the experiments. One of the most common types of connections in structures is …

Global 3d Radiation Hydrodynamic Simulations Of Proto-Jupiter’S Convective Envelope, Zhaohuan Zhu, Yan-Fei Jiang, Hans Baehr, Andrew N. Youdin, Philip J. Armitage, Rebecca G. Martin

Physics & Astronomy Faculty Research

The core accretion model of giant planet formation has been challenged by the discovery of recycling flows between the planetary envelope and the disc that can slow or stall envelope accretion. We carry out 3D radiation hydrodynamic simulations with an updated opacity compilation to model the proto-Jupiter’s envelope. To isolate the 3D effects of convection and recycling, we simulate both isolated spherical envelopes and envelopes embedded in discs. The envelopes are heated at given rates to achieve steady states, enabling comparisons with 1D models. We vary envelope properties to obtain both radiative and convective solutions. Using a passive scalar, we …

Use Of Pressure-Measuring Insoles To Characterize Gait Parameters In Simulated Reduced-Gravity Conditions, Christian Ison, Connor Neilsen, Jessica Deberardinis, Mohamed B. Trabia, Janet S. Dufek

Mechanical Engineering Faculty Research

Prior researchers have observed the effect of simulated reduced-gravity exercise. However, the extent to which lower-body positive-pressure treadmill (LBPPT) walking alters kinematic gait characteristics is not well understood. The purpose of the study was to investigate the effect of LBPPT walking on selected gait parameters in simulated reduced-gravity conditions. Twenty-nine college-aged volunteers participated in this cross-sectional study. Participants wore pressure-measuring insoles (Medilogic GmBH, Schönefeld, Germany) and completed three 3.5-min walking trials on the LBPPT (AlterG, Inc., Fremont, CA, USA) at 100% (normal gravity) as well as reduced-gravity conditions of 40% and 20% body weight (BW). The resulting insole data were …

Silk Fibroin Supraparticles Created By The Evaporation Of Colloidal Ouzo Droplets, Ashley Lamb, Fengjie He, Shengjie Zhai, Hui Zhao

Mechanical Engineering Faculty Research

Due to its high biocompatibility and biodegradability, supraparticles made from silk fibroin—produced from Bombyx mori (B. mori) cocoons—can find various applications in biomedical fields. The evaporation of Ouzo droplets by not requiring energy nor a surfactant is an environmentally friendly, easy, and cost-effective strategy to fabricate three-dimensional supraparticles, tackling the so-called “coffee ring effect” associated with droplet evaporation. Silk fibroins are dissolved into quaternary droplets, comprised of ultrapure water, ethanol, trans-anethole oil, and formic acid. The Ouzo droplet is able to form an oil ring that facilitates the droplet contraction to create a three-dimensional supraparticle. Using the Ouzo effect to …

Plasma Aerodynamics: Experimental Quantification Of The Lift Force Generated On An Airfoil Using Plasma Actuation To Estimate Power Requirements In Small Uav Applications, Getachew Ashenafi

UNLV Theses, Dissertations, Professional Papers, and Capstones

This research addressed the amount of electric power required to induce specific changes in lift force using a NACA 2127 airfoil with a chord length of ~28 mm, connected to a micro load cell, in a wind tunnel of 103 square centimeter cross-section. A DBD plasma actuator supplied by a ZVS driven high voltage pulsed DC circuit, operating at a frequency of 17.4 kHz, was utilized for voltages of up to 5000 V. Two configurations of electrode gapping were compared to determine the efficient use of power. The configuration with a gap of ~1 mm between the upstream and downstream …

Healthy Aging In Place: An Integrated Smart Home Using Alexa-Compatible Technology, Tyler Kryst

UNLV Theses, Dissertations, Professional Papers, and Capstones

The purpose of this research was to address current healthcare concerns among the aging population. Around the globe, the average life expectancy is projected to continue increasing resulting in a higher prevalence of age-related disease. With the ever-increasing capabilities of modern technology, it is necessary to apply this technology to increase the health and safety of older adults. This work had three objectives. The first objective was the establishment of an integrated smart home aimed at creating a healthy aging-in-place environment through the use of Alexa. The second objective was the development and integration of a completely custom health device …

A Hyperelastic Porous Media Framework For Ionic Polymer-Metal Composites And Characterization Of Transduction Phenomena Via Dimensional Analysis And Nonlinear Regression, Zakai J. Olsen

UNLV Theses, Dissertations, Professional Papers, and Capstones

Ionic polymer-metal composites (IPMC) are smart materials that exhibit large deformation in response to small applied voltages, and conversely generate detectable electrical signals in response to mechanical deformations. The study of IPMC materials is a rich field of research, and an interesting intersection of material science, electrochemistry, continuum mechanics, and thermodynamics. Due to their electromechanical and mechanoelectrical transduction capabilities, IPMCs find many applications in robotics, soft robotics, artificial muscles, and biomimetics. This study aims to investigate the dominating physical phenomena that underly the actuation and sensing behavior of IPMC materials. This analysis is made possible by developing a new, hyperelastic …

Patient-Specific Finite Element Analysis For Mandibular Fracture Fixation, Ethan Snyder

UNLV Theses, Dissertations, Professional Papers, and Capstones

This thesis proposes an approach for Finite Element Analysis (FEA) of mandibular fracture fixation. Using a Computerized Tomography (CT) scan of mandible obtained from a specific person, the material characteristics, density and modulus of elasticity, were determined from a set of discrete points within the mandible that are 1mm spaced based on the Hounsfield Units of these points. The mandible geometry was sectioned to simulate a fracture. Muscle and mastication forces were added to replicate post-surgery loading. Using a standard linear miniplate, this material model was compared with two commonly used mandibular cortical shell bone models: isotropic and orthotropic. A …

Toward The Use Of Drones For Photovoltaic Panel Inspection, Fausto Vega

Undergraduate Research Symposium Posters

The monitoring of photovoltaic panels is an essential task to maintain the efficiency of the power plant. The conventional form of inspection consists of manual inspection with a thermal camera which takes several days as fields contain thousands of panels. Solar panel installation is costly, and the installation does not guarantee maximum power generation without proper maintenance and handling. A drone with a thermal camera payload was developed to reduce labor costs as well as increase efficiency of the inspection as it can survey the field with a large field of view. Several image processing methods were used to process …

Spike Nozzle Design For Use In Nanosat Orbital Maneuvering, Drew Nemeth

Undergraduate Research Symposium Podium Presentations

Annular spike nozzle engines have long been the holy grail of rocket engine design, promising superior performance in a smaller footprint when compared to conventional bell nozzles. However, flaws inherent to the design of spike nozzles have prevented widespread adoption and testing. As a result, research on potential applications has been quite sparse. This project aims to further spike nozzle research by investigating rarely tested materials that literature suggests have potential for use in a spike nozzle design. The goal of the overall research project is to examine 3D printed polycarbonate component longevity under conditions representative of a small satellite …

Foot Contact Dynamics And Fall Risk Among Children Diagnosed With Idiopathic Toe Walking, Rahul Soangra, Michael Shiraishi, Richard Beuttler, Michelle Gwerder, Lou Anne Boyd, Venkatesan Muthukumar, Mohamed Trabia, Afshin Aminian, Marybeth Grant-Beuttler

Electrical & Computer Engineering Faculty Research

Children that are diagnosed with Idiopathic Toe walking (cITW) are characterized by persistent toe-to-toe contacts. The objective of this study was to explore whether typical foot contact dynamics during walking predisposes cITW to a higher risk of falling. Twenty cITW and age-matched controls performed typical and toe walking trials. The gait parameters related to foot contact dynamics, vertical force impulses during stance, slip, and trip risk were compared for both groups. We found that cITW manifest less stable gait and produced significantly higher force impulses during push-off. Additionally, we found that cITW had a higher slip-initiation risk that was associated …

Morphology Control Of One-Dimensional Gallium Nitride Nanostructures By Modulating The Crystallinity Of Sacrificial Gallium Oxide Templates, Yun Taek Ko, Mijeong Park, Jingyeong Park, Jaeyun Moon, Yong Ho Choa, Young In Lee

Mechanical Engineering Faculty Research

In this study, we demonstrated a method of controllably synthesizing one-dimensional nanostructures having a dense or a hollow structure using fibrous sacrificial templates with tunable crystallinity. The fibrous ga2o3 templates were prepared by calcining the polymer/gallium precursor nanofiber synthesized by an electrospinning process, and their crystallinity was varied by controlling the calcination temperature from 500oC to 900oC. gaN nanostructures were transformed by nitriding the ga2o3 nanofibers using NH3 gas. All of the transformed gaN nanostructures maintained a one-dimensional structure well and exhibited a diameter of about 50 nm, but their morphology was clearly distinguished according to the crystallinity of the …

Direct Energy Deposition Of Mo Powder Prepared By Electrode Induction Melting Gas Atomization, Goo Won Roh, Eun Soo Park, Jaeyun Moon, Hojun Lee, Jongmin Byun

Mechanical Engineering Faculty Research

Molybdenum (Mo) is used to form a barrier layer for metal wiring in displays or semiconductor devices. Recently, researches have been continuously attempted to fabricate Mo sputtering targets through additive manufacturing. in this study, spherical Mo powders with an average particle size of about 37 um were manufactured by electrode induction melting gas atomization. Subsequently, Mo layer with a thickness of 0.25 mm was formed by direct energy deposition in which the scan speed was set as a variable. According to the change of the scan speed, pores or cracks were found in the Mo deposition layer. Mo layer deposited …

Effect Of Heat Treatment On Microstructure And Hardness Of A Worn Rail Repaired Using Laser Powder Deposition, Ershad Mortazavian, Zhiyong Wang, Hualiang Teng

Mechanical Engineering Faculty Research

The frequent replacement of worn rails on tracks brings an immense economic burden on the railroad industry, and also causes significant interruptions to railroad operation. Restoration of worn rails via laser powder deposition (LPD) can considerably reduce the associated maintenance costs. This study was focused on the use of LPD to repair the worn profile of a standard U.S. rail. The microstructure of the 304L stainless steel deposits with a minimum hardness of 85 HRB was composed of austenite, δ-ferrite, and sigma. Micropores were dispersed throughout the deposit, and microcracks were found at the rail-deposition interface. The pearlitic rail substrate …