Engineering Commons^™

Tip Clearance Effect On Convective Heat Transfer In Micro Scale Pin Fins, Hanieh Tabkhivayghan

Electronic Theses and Dissertations, 2020-2023

Fluid flow and local heat transfer in a microchannel with single and array of pin fins have been studied. For the single pin fin case, a microchannel with a 150-µm diameter pin fin with a tip clearance was experimentally and numerically studied for three Reynolds numbers in laminar regime. Tip clearances of 0, 30, 45 and 100 µm in a 200-µm high microchannel. Experimental and numerical local temperatures and the corresponding Nusselt numbers along the centerline of the pin fin were presented and discussed. Local temperatures were measured on top of the heater surface and downstream the pin fin through …

Seismocardiography - Genesis, And Utilization Of Machine Learning For Variability Reduction And Improved Cardiac Health Monitoring, Peshala Thibbotuwawa Gamage

Electronic Theses and Dissertations, 2020-2023

Seismocardiography (SCG) is the measured chest surface vibrations resulting from cardiac activity. Although SCG can contain information that correlate with cardiac health, its utility may be limited by lack of understanding of the signal genesis and a variability that can mask subtle SCG changes. The current research utilized medical imaging reconstruction and finite element method (FEM) to simulate SCG by modeling the propagation of myocardial movements to the chest surface. FEM analysis provided a link between myocardial movements and the SCG signals measured at the chest surface and suggested that myocardial movement is a primary source of SCG. Increased understanding …

A Facile, Fast, And Low-Cost Method For Fabrication Of Micro/Nano-Textured Superhydrophobic Surfaces, Amir Esmaeili, Noshin Mir, Reza Mohammadi

Graduate Research Posters

Background

Alkyl ketene dimer (AKD) is frequently used in paper industry as an inexpensive sizing agent. The formation of a fractal structure after curing the solidified AKD for an extra-long time (4 - 6 days) results in superhydrophobicity. In this study, a facile and low-cost method was utilized to turn AKD’s surface superhydrophobic in a very short period of time.

Method

We fabricated a superhydrophobic layer by dipping glass and paper substrates in molten AKD and then treating them with ethanol after solidification. The samples were characterized by X-ray diffraction, Scanning electron microscopy, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, Confocal …

Dose Deposition And Electrostatic Charging Of Kapton Films Irradiated With Electrons, Youssef Abouhussien, Gennady Miloshevsky

Graduate Research Posters

Kapton films are widely utilized in harsh radiation environments where radiation resistant insulating materials are required. For space applications, Kapton polymers are used on satellites as substrates for solar arrays and outer layers of thermal systems. Kapton is also used in nuclear power plants as wire insulation. Kapton materials can be exposed in nuclear reactors to a reactive chemical environment in addition to severe radiation. It is of utmost important to understand how Kapton materials behave under high irradiation conditions and mitigate radiation damage effects. High-energy electrons can deposit ionizing dose and electric charge deeply inside Kapton materials. The charge …

Photolithographic Micropatterning Of Organic, Flexible Biomaterials And Its Applications, Sayantan Pradhan, Sayantan Pradhan, Meng Xu, Vamsi K. Yadavalli

Graduate Research Posters

A current trend in biodevices has involved a shift from traditional rigid platforms to flexible and stretchable formats. These flexible devices are expected to have a significant impact on future healthcare, disease diagnostics and therapeutics. However, the fabrication of such flexible devices has been limited by the choice of materials. Biomimetic composites of naturally derived and synthetic polymers provide exciting opportunities to develop mechanically flexible, physiologically compliant, and degradable bioelectronic systems. Advantages include the ability to provide conformal contact at non-planar biointerfaces, being able to be degraded at controllable rate, and invoking minimal reactions within the body. These factors present …

Jxb Force Effects On Beryllium Melt Splashing In Fusion Devices, Cheng Zhang, Gennady Miloshevsky

Graduate Research Posters

Instability and disruption of high-temperature plasma in fusion devices may result in the edge-localized modes (ELMs) and lead to melting of plasma facing components (PFCs) causing their damage. Beryllium (Be) is used as a first wall for PFCs due to its low density, high strength, and high thermal conductivity. However, melting of Be on the surface of first wall is of a great concern as splashing of a molten Be layer will result in the plasma contamination and termination of fusion reaction. Therefore, it is important to understand the physics mechanisms characterizing the splashing of Be from a pool under …

Evaluating The Effectiveness Of Shielding Material, Vehicle Shape And Astronaut Position For Deep Space Travel, Daniel Bond, Braden Goddard, Robert Singleterry, Sama Bilbao Y Leon

Graduate Research Posters

Background: As future crewed, deep space missions are being planned, it is important to assess how spacecraft design can be used to minimize radiation exposure. Collectively with shielding material, vehicle shape and astronaut position must be used to protect astronauts from the two primary sources of space radiation: Galactic Cosmic Rays (GCRs) and Solar Particle Events (SPEs).

Methods: The On-Line Tool for the Assessment of Radiation in Space (OLTARIS) version 4.1 analysis package is used to evaluate and analyze this detailed radiation field. Developed by the National Aeronautics and Space Administration's (NASA) Langley Research Center, the tool enables engineering and …

Elastic Foundations As Heterogeneous Adventitial Boundary Condition For The Assessment Of Aortic Wall And Peri-Aortic Stiffness From Dense-Mri Data Using Inverse Fem Approach, Johane H. Bracamonte, John S. Wilson, Joao S. Soares

Graduate Research Posters

Background: The establishment of in vivo, patient-specific, and regionally resolved techniques to quantify aortic properties is key for improving risk assessment in clinical practice and scientific understanding of cardiovascular growth and remodeling. Many in vivo studies quantify vascular stiffness using Pulse Wave Velocity. This method provides an averaged measure of stiffness for the entire aorta, ignoring variations in wall stiffness and boundary conditions. Previous studies using Displacement Encoding with Stimulated Echoes Magnetic Resonance Imaging (DENSE-MRI) suggested that the infrarenal abdominal aorta (IAA) deforms heterogeneously throughout the cardiac cycle.

Method: Herein, we hypothesize that the aortic wall strain heterogeneity is driven …

Spatio-Temporal Evolution Of Warm Dense Plasmas: Molecular Dynamics Modeling, Harrison Wenzel, Gennady Miloshevsky

Graduate Research Posters

SPATIO-TEMPORAL EVOLUTION OF WARM DENSE PLASMAS: MOLECULAR

DYNAMICS MODELING Cole Wenzel and Gennady Miloshevsky

Virginia Commonwealth University, Department of Mechanical and Nuclear Engineering, 401

West Main St, Richmond, VA 23284-3015

The exo-atmospheric detonation of nuclear device would be of great impact on the material integrity of orbiting satellites. The spectral energy distribution of high intensity X-ray flux, ~10 28 -10 35 photons/(cm 2 ∙s), originating from a nuclear blast is described by the Planck's blackbody function with the temperature from 0.1 keV to 10 keV. Particular damage would occur to the multi-layered, solar cell panels of satellites. However, the X-ray …

Dynamics Within A Tunable Harmonic/Quartic Waveguide, Rudolph N. Kohn Jr., James A. Stickney

Space Dynamics Laboratory Publications

We present an analytical solution to the dynamics of a noninteracting cloud of thermal atoms in a cigar-shaped harmonic trap with a quartic perturbation along the axial direction. We calculate the first and second moments of position, which are sufficient to characterize the trap. The dynamics of the thermal cloud differ notably from those of a single particle, with an offset to the oscillation frequency that persists even as the oscillation amplitude approaches zero. We also present some numerical results that describe the effects of time-of-flight on the behavior of the cloud in order to better understand the results of …

Time- And Space-Dependent Uncertainty Analysis And Its Application In Lunar Plasma Environment Modeling, Xinpeng Wei

Doctoral Dissertations

”During an engineering system design, engineers usually encounter uncertainties that ubiquitously exist, such as material properties, dimensions of components, and random loads. Some of these parameters do not change with time or space and hence are time- and space-independent. However, in many engineering applications, the more general time- and space-dependent uncertainty is frequently encountered. Consequently, the system exhibits random time- and space-dependent behaviors, which may result in a higher probability of failure, lower average lifetime, and/or worse robustness. Therefore, it is critical to quantify uncertainty and predict how the system behaves under time- and space- dependent uncertainty. The objective of …

Fault Identification On Electrical Transmission Lines Using Artificial Neural Networks, Christopher W. Asbery

Theses and Dissertations--Electrical and Computer Engineering

Transmission lines are designed to transport large amounts of electrical power from the point of generation to the point of consumption. Since transmission lines are built to span over long distances, they are frequently exposed to many different situations that can cause abnormal conditions known as electrical faults. Electrical faults, when isolated, can cripple the transmission system as power flows are directed around these faults therefore leading to other numerous potential issues such as thermal and voltage violations, customer interruptions, or cascading events. When faults occur, protection systems installed near the faulted transmission lines will isolate these faults from the …

Thin-Film Lithium Niobate Integrated Photonics On Silicon For Electro- And Nonlinear-Optic Applications, Amirmahdi Honardoost

Electronic Theses and Dissertations, 2020-2023

In order to overcome the drawbacks associated with conventional bulk lithium niobate photonic, thin-film lithium-niobate-on-silicon has been pursued recently. This work presents contributions made to electro-, and nonlinear-optic applications of this technology. For electrooptic applications, detailed modeling and design guidelines of optical and radio-frequency parameters of ultracompact modulators are developed and their accuracy in predicting the high-speed performance of such devices have been verified by comparison with experimental results. Novel design techniques and pathways for ultrahigh-speed (sub-terahertz) operation of such modulators, achieving up to 400 GHz modulation bandwidth, are also presented. For optical interconnect applications, novel structures for ultralow-power consumption …

Traffic Speed Prediction And Mobility Behavior Analysis Using On-Demand Ride-Hailing Service Data, Jiechao Zhang

Electronic Theses and Dissertations, 2020-2023

Providing accurate traffic speed prediction is essential for the success of Intelligent Transportation Systems (ITS) deployments. Accurate traffic speed prediction allows traffic managers take proper countermeasures when emergent changes happen in the transportation network. In this thesis, we present a computationally less expensive machine learning approach XGBoost to predict the future travel speed of a selected sub-network in Beijing's transportation network. We perform different experiments for predicting speed in the network from future 1 min to 20 min. We compare the XGBoost approach against other well-known machine learning and statistical models such as linear regression and decision tree, gradient boosting …

Prediction Of Pedestrians' Red Light Violations Using Deep Learning, Shile Zhang

Electronic Theses and Dissertations, 2020-2023

Pedestrians are regarded as Vulnerable Road Users (VRUs). Each year, thousands of pedestrians' deaths are caused by traffic crashes, which take up 16% of the total road fatalities and injuries in the U.S. (FHWA, 2018). Crashes can happen if there are interactions between VRUs and motorized transportation. And pedestrians' unexpected crossings, such as red-light violations at the signalized intersections, would expose them to motorized transportation and cause potential collisions. This thesis is intended to predict the pedestrians' red-light violation behaviors at the signalized crosswalks based on an LSTM (Long Short-term Memory) neural network. With video data collected from real traffic …

Optimization Studies For The Gas Atomization And Selective Laser Melting Processes Of Al10simg Alloy, Sharon Park

Electronic Theses and Dissertations, 2020-2023

Selective laser melting (SLM) is an additive manufacturing technology that can fabricate complex engineering components using a scanning laser beam to melt consecutive layers of powders with characteristics that significantly influence material properties. Present work investigates both the gas atomization and SLM processes for the Al10SiMg alloy with a focus on establishing the relationships among atomization parameters, powder characteristics, SLM parameters and materials properties. Al10SiMg alloy powders (Al-10wt.%Si-0.5wt.%Mg) were batch-produced through gas atomization by systematically varying the melt flow rate (0.012 - 0.037 kg/s), gas pressure (1.4 - 3.1 MPa), and melt temperature (850C -1000C). The highest yield of 80 …

Ultraviolet Irradiation Combined With Chlorine Dioxide Pre-Oxidation For Disinfection By-Product Control, Paula Campesino

Electronic Theses and Dissertations, 2020-2023

The use of ultraviolet (UV) light and chlorine dioxide (ClO2) as an advanced oxidation process (AOP) has been investigated at the bench-scale to understand the effects of their use on disinfection by-product (DBP) formation potential (FP) in chlorinated groundwater (GW) and surface water (SW) supplies. Two GWs and two SWs of varying qualities were subject to a series of AOP treatment sequences at the bench scale: sodium hypochlorite, to serve as a baseline; ClO2-Cl2, UV-Cl2, and UV-ClO2-Cl2. In these treatment sequences, Cl2 is used as a primary and secondary disinfectant. Several water quality parameters were measured throughout the experiments, including …

Study On Ductile Fracture With Anisotropic And Strain Rate Effects In Manufacturing Processes, Hao Pan

Electronic Theses and Dissertations, 2020-2023

Ductile fracture is a topic of great importance in automotive and aerospace industries. Prediction of ductile fracture in engineering structures relies on developing robust material models under complex loading conditions. This dissertation addresses the anisotropic and strain rate effects in constitutive and ductile fracture models of lightweight metals. In the present modeling framework, the anisotropic plasticity behavior is modeled by combination of an initial anisotropic yield function and an isotropic hardening correction by Lode dependence. A new all-strain based anisotropic fracture model is proposed based on the approach of linear transformation on plastic strain rate tensor. The strain rate effects …

The Impacts Of Wave Energy Conversion On Coastal Morphodynamics In A Changing Climate, Cigdem Ozkan

Electronic Theses and Dissertations, 2020-2023

Fossil fuels, i.e., petroleum, natural gas, and coal, are the primary sources of global energy. Studies on the impacts of fossil fuels on climate change have shown the immediate need to reduce greenhouse gas emissions and adopt sustainable alternatives since these emissions result in warmer atmospheric temperatures, ocean acidification, glacier melting, sea level rise, and many other ramifications. In recent years, these alarming results have prompted governments worldwide to develop adaptation strategies for climate change, leading to increased investments in renewable energy resources. Globally, solar energy, wind energy, and hydropower have been the leading sources of renewable energy. Ocean wave …

Interfacial Properties Modulate Water Entry Dynamics For Spherical Projectiles, Daren Watson

Electronic Theses and Dissertations, 2020-2023

Rigid bodies impacting liquid pools incite splashing and air-entraining cavities that depend on impactor shape, entry speed, surface texture, and free surface conditions. In this body of work, we investigate the influence of interfacial properties on water entry dynamics for free-falling spherical projectiles. Our investigations translate to everyday fluid-structure interactions that are complex and generally conclude beyond the temporal acuity of the naked eye. High-speed videography between 1000 -- 3200 fps is used to digitize the water entry process and measure salient splash features under different initial conditions. We assess splashes arising from the impacts of free-falling hydrophilic spheres with …

Pathological Tremor As A Mechanical System: Modeling And Control Of Artificial Muscle-Based Tremor Suppression, Christopher Kelley

Electronic Theses and Dissertations, 2020-2023

Central nervous system disorders produce the undesired, approximately rhythmic movement of body parts known as pathological tremor. This undesired motion inhibits the patient's ability to perform tasks of daily living and participate in society. Typical treatments are medications and deep brain stimulation surgery, both of which include risks, side effects, and varying efficacy. Since the pathophysiology of tremor is not well understood, empirical investigation drives tremor treatment development. This dissertation explores tremor from a mechanical systems perspective to work towards theory-driven treatment design. The primary negative outcome of pathological tremor is the undesired movement of body parts: mechanically suppressing this …

The Reliability Of Through Glass Vias And Solder Joints For Three Dimensional Multi Functional Integrated Systems, Omar Ahmed

Electronic Theses and Dissertations, 2020-2023

Three-dimensional (3D) integration technologies, including interposer-based integration, are among the most promising solutions to meet the increased demand for high performance computing, high chip density, and small form factor. Key technologies that enable 3D integration include through-substrate vias and solder joints. Glass is considered as a promising substrate material for interposer-based 3D integration technology especially in radio frequency applications because of glass's high resistivity, low dielectric constant, low electrical loss, and the adjustable coefficient of thermal expansion (CTE). However, during fabrication or service, through-glass vias can suffer from interface delamination and substrate cracking. The problem of copper protrusion is also …

In Pursuit Of Low-Dimensional Manifold Structures In High-Dimensional Data, Mahlagha Sedghi

Electronic Theses and Dissertations, 2020-2023

The ever-increasing availability of large-scale and high-dimensional data offers unprecedented opportunities for data-driven studies across widely differing domains ranging from marketing and web mining, to bioinformatics and space exploration. Yet, it also poses formidable challenges in face of storing, organizing and analyzing such data. Often though, high-dimensional data tend to lie close to some low-dimensional structures. Aside from substantial computational and storage conservations, discovering such structures also contributes to improved learning and inference performance. A majority of existing work assume linear data models which fail to effectively capture the complex patterns of real-world problems. Non-linear models on the other hand …

Creation And Analysis Of An Enhanced Rascal-Lvc Framework Capable Of Simulating Ionizing Radiation Damage To Emergency Responders During A Nuclear Power Plant Disaster: A Case Study In Unmanned Aerial Vehicle Electronic System Survivability, Buder Shageer

Electronic Theses and Dissertations, 2020-2023

This study developed and analyzed the use of a live virtual constructive (LVC) framework capable of simulating ionizing radiation damage to Unmanned Aerial Vehicles (UAV) during a nuclear power plant disaster. UAV response promises greater safety to humans over helicopters as well as provides longer survivability in the presence of irradiated environments. However, electronics in unmanned systems are subject to radiation damage and over time eventual failure. A LVC simulation framework may offer an independent and low-cost assessment of equipment life expectancy. Knowing life expectancy of equipment for operational scenarios is critical for emergency management planners. This research creates an …

The Gamification Framework Of Military Flight Simulator For Effective Learning And Training Environment, Daeho Noh

Electronic Theses and Dissertations, 2020-2023

The purpose of this thesis is to develop a framework for the gamification of flight simulators to provide an active learning and training environment for military jet pilots. Currently, with the development of visual displays and computer processing capabilities, the modern simulator has made great progress in visual and auditory terms that is incomparable to the past. In addition, functions that were previously implemented through supercomputers and complex hardware devices are now available through desktop computers at an affordable cost. Despite these advances, the simulators so far are thought to have been negligent in building an active learning and training …

Mispronunciation Detection And Diagnosis In Mandarin Accented English Speech, Subash Khanal

Theses and Dissertations--Electrical and Computer Engineering

This work presents the development, implementation, and evaluation of a Mispronunciation Detection and Diagnosis (MDD) system, with application to pronunciation evaluation of Mandarin-accented English speech. A comprehensive detection and diagnosis of errors in the Electromagnetic Articulography corpus of Mandarin-Accented English (EMA-MAE) was performed by using the expert phonetic transcripts and an Automatic Speech Recognition (ASR) system. Articulatory features derived from the parallel kinematic data available in the EMA-MAE corpus were used to identify the most significant articulatory error patterns seen in L2 speakers during common mispronunciations. Using both acoustic and articulatory information, an ASR based Mispronunciation Detection and Diagnosis (MDD) …

Investigation Of Via Extrusion And The Effect Of Cap Layer For 3d Integrated Circuits, Golareh Jalilvand

Electronic Theses and Dissertations, 2020-2023

Copper (Cu) through-silicon via (TSV) is an essential structural and functional element in three-dimensional integration circuits (3D ICs), which offers substantial improvements in integration density, form factor, device performance, and power efficiency. However, Cu-filled TSVs are exposed to multiple thermal cycles during fabrication, test and operation, which lead to the development of considerable thermal stresses, in and around the vias, due to the large mismatch of the coefficient of thermal expansion (CTE) between Cu and silicon (Si). The stress subsequently raises reliability concerns, among which, via extrusion is an important one. Via extrusion can damage the adjacent components, in particular …

A Study Into Validating A Coupled Method Of Characteristics And Direct Simulation Monte Carlo Method Against Empirical Data, Andrew Brown

Electronic Theses and Dissertations, 2020-2023

The following will outline the methodology and results of validating a coupled Method of Characteristics (MOC) and Direct Simulation Monte Carlo (DSMC) method. This research focused specifically on modeling plume impingement, induced by Reaction Control System (RCS) thrusters that flew on the National Aeronautics and Space Administration's (NASA's) space shuttle Discovery. For each simulation, the continuum portion of the RCS thruster was simulated using MOC for solving hyperbolic Partial Differential Equations (PDEs) and computed with the NASA code, Reacting and Multi-phase Program (RAMP). The solution was then implemented as a starting condition into the NASA DSMC code, Direct Simulation and …

Human Performance In Virtual Reality Environments And Its Exploration With Engineering Analytics, Fahad Alasim

Electronic Theses and Dissertations, 2020-2023

Engineering Analytics (EA) is a technique used to derive meaningful insight from gathered data. It is an approach that has arisen, and it includes the process of analyzing data using analytics tools from fields such as Big Data, Machine Learning (ML), traditional operations research, statistics, and numerical methods. Industrial Engineering is an engineering field concerned with how to design better, improve, and install integrated systems, uses EA to understand and continually improve, innovate, and build new processes. Therefore, EA and Virtual Reality (VR) technology can be used in combination with Electroencephalography (EEG), a physiological measurement, to investigate human areas. The …

The Impact Of Work Environment On Successful Implementation Of Lean Six Sigma In Emergency Department, Elaf Makkawi

Electronic Theses and Dissertations, 2020-2023

Continuous improvement (CI) is an initiative to improve the performance of processes in alignment with the customer needs and organizational strategy. Lean Six Sigma (LSS) is one of the most successful CI techniques in redesigning and improving significant processes to improve quality and eliminate waste. The healthcare sector has benefited from applying LSS due to its complicated work practices that face many challenges including increased expenditures and difficulties related to individual or community access to appropriate care. In particular, Emergency Departments (ED) have an important unit within healthcare organizations due to their essential role in providing urgent medical care services …