Engineering Commons^™

The Challenges Of Low-Energy Secondary Electron Emission Measurement, Matthew J. Vincie

Theses and Dissertations

The phenomena known as secondary electron emission was discovered over a century ago. Yet it remains very difficult to model accurately due to the limited availability of reliable experimental data. With the growing use of computer simulations in hardware development, the need for accurate models has increased. This research focused on determining what factors may be causing measurement discrepancies and methods for increasing the accuracy of measurements. It was found that several assumptions are commonly invoked when these measurements are performed that may not always be consistent with reality. The violation of these assumptions leads to measurement bias that is …

Development Of Cislunar Space Logistics Networks For Satellite Constellation Support Using Event-Driven Generalized Multi-Commodity Network Flows, Alexander R. Collins

Theses and Dissertations

As space becomes an increasingly congested domain, the risk of damage to satellite constellations is increasing. In response, there is an increasing need for capabilities for unmanned repair, refueling, and reconstitution (R3) of those constellations. Cislunar orbits offer a promising storage and low-cost transfer solution for on-orbit service vehicles and replacement satellites to leverage those capabilities. This research makes use of mixed-integer linear programming-based logistics models to determine the situations in which a cislunar mission architecture would offer a cost-effective alternative to Earth-based R3. The network models presented in this research make use of the latest developments in Event-Driven Generalized …

An Experimental And Theoretical Investigation Of Internal Wave Kinetic Energy Density In Variable Stratifications, Allison Marie Lee

Theses and Dissertations

Internal waves are generated in a fluid if the density increases continuously with depth. The variation in density with depth, or stratification, defines the natural frequency of the fluid N. Two common examples of stratified fluids are the ocean and atmosphere; internal waves are generated continuously in both mediums. Although there are many internal wave generation mechanisms, one common and frequently studied method is tidal flow over oceanic bathymetry. If the local natural frequency of the water near the topography is greater than the tidal frequencyω, internal waves will be generated by the tidal flow over the topography. If N=ω, …

Groundwater Level Mapping Tool: Development Of A Web Application To Effectively Characterize Groundwater Resources, Steven William Evans

Theses and Dissertations

Groundwater is used worldwide as a major source for agricultural irrigation, industrial processes, mining, and drinking water. An accurate understanding of groundwater levels and trends is essential for decision makers to effectively manage groundwater resources throughout an aquifer, ensuring its sustainable development and usage. Unfortunately, groundwater is one of the most challenging and expensive water resources to characterize, quantify, and monitor on a regional basis. Data, though present, are often limited or sporadic, and are generally not used to their full potential to aid decision makers in their groundwater management.This thesis presents a solution to this under-utilization of available data …

Design And Measurement Of Strongarm Comparators, Nathan Robert Whitehead

Theses and Dissertations

The StrongARM comparator is utilized in many analog-to-digital converters (ADCs) because of its high power efficiency and rail-to-rail outputs. The performance of the comparator directly affects the speed, power, and accuracy of an ADC. However, the StrongARM comparator performance parameters such as delay, noise, and offset measured directly from silicon prototypes are rare in literature and often consist of small sample sets. In addition, existing techniques to measure the comparator require large chip areas, making it impractical to characterize a large number of comparators to obtain stochastic parameters such as offset and noise. This work presents novel circuit techniques to …

A Novel Gripping System For Corrugated Box Grasping And Manipulation For Unmanned Aerial Vehicles, Trigun Maroo

Theses and Dissertations

An Unmanned Aerial Vehicle (UAV) can carry packages to locations that are unreachable by an autonomous ground vehicle (AGV) using a suitable gripper system. A novel gripping system for grasping corrugated boxes which has the potential to be mounted on a UAV is presented. The proposed gripping system uses two pairs of perpendicularly mounted linear actuators to move the end effectors, geared such that they are operated with a single control input. The mechanism is designed to handle position and orientation errors of the target object automatically in the specified grasping zone without the need of a control system. The …

Collaborative Uav Planning, Mapping, And Exploration In Gps-Denied Environments, Jacob Moroni Olson

Theses and Dissertations

The use of multirotor UAVs to map GPS-degraded environments is useful for many purposes ranging from routine structural inspections to post-disaster exploration to search for survivors and evaluate structural integrity. Multirotor UAVs are able to reach many areas that humans and other robots cannot safely access. Because of their relatively short operational flight time compared to other robotic applications, using multiple UAVs to collaboratively map these environments can streamline the mapping process significantly. This research focuses on four primary areas regarding autonomous mapping and navigation with multiple UAVs in complex unknown or partially unknown GPS-denied environments: The first area is …

Mobile Ad Hoc Networks In Transportation Data Collection And Dissemination, Kardigue Konte

Theses and Dissertations

The field of transportation is rapidly changing with new opportunities for systems solutions and emerging technologies. The global economic impact of congestion and accidents are significant. Improved means are needed to solve them. Combined with the increasing numbers of vehicles on the road, the net economic impact is measured in the many billions of dollars. Promising methodologies explored in this thesis include the use of the Internet of Things (IoT) and Mobile Ad Hoc Networks (MANET). Interconnecting vehicles using Dedicated Short Range Communication technology (DSRC) brings many benefits. Integrating DSRC into roadway vehicles offers the promise of reducing the problems …

Exploring Intercultural Wonderment As A Mediator For Global Perspective Development In Engineering Students, John A. Schneider

Theses and Dissertations

The purpose of this study is to investigate the mediatory role intercultural wonderment plays in global learning during engineering students' international experiences. Engberg and colleagues have posited a connection between the programmatic components of an international experience (i.e., study abroad) and global learning, with international wonderment serving as a conduit for that connection. Qualitative and quantitative data were collected under an NSF multi-institutional grant that focused on identifying ways global preparedness can be developed in and out of formal curricula. Data included semi-structured, student interviews, student background data, and global perspective scores as measured by the Global Perspective Inventory (GPI). …

Prodhimi I Çimentos, Donika Musliu

Theses and Dissertations

Ky studim përfshin prodhimin e çimentos. Qëllimi i këtij punimi është që të zgjerojm njohurit e përgjithshme mbi teknologjin e prodhimit të çimentos. Cimento eshte pluhur i thate i cili formohet me kombinimin e materialeve te ndryshme , si guri gelqerore, argjila, shkumesi, oksidet e ndryshme etj. Cimentoja eshte nje material ndertimi shum i rendesishme.Hapi i pare ne prodhimin e cimentos eshte te kombinoje nje shumellojshmeri perberesish te paperpunuar ne menyre qe cimentoja qe rezulton te kete perberjen e deshiruar kimike. Këtu përshkruhet në mënyrë të detajuar proceset kryesore siç janë: Procesi i thatë dhe i lagësht i lëndës së …

Shqyrtimet Nga Materialet E Ndërtimit Ne Laboratorin E Qendrës Se Kompetencës-Skenderaj, Gëzim Bajraktari

Theses and Dissertations

Shqyrtimet e materialeve ndërtimore për caktimin e cilësisë se tyre kërkon një përkushtim dhe një punë te madhe, ne ketë teme do te fokusohemi ne shqyrtimin e materialeve ndërtimore me fokus te veçantë materialeve për përfitimin e betonit, shqyrtime këto qe realizohen ne laboratorin e Qendrës se Kompetencës në Skenderaj. Materialet konkrete qe do te jene ne fokus janë kryesisht materialet apo komponentët përbërëse te betonit, siç janë agregati, çimentoja dhe uji. Llojet e agregatit mënyrat e përfitimit dhe vetitë e agregateve, mënyrat e ekzaminimit te tije. Caktimi i fraksioneve te agregatit dhe rëndësia e fraksionizmit, mënyrat e fraksionizmit dhe …

Rregullimi I Parkingut Për Mjetet Më Bashkëkohore Për Parkim Te Kategorisë “B”, Teuta Ukoshata

Theses and Dissertations

No abstract provided.

Quantification Of Material Degradation For Material State Awareness Of Composite Materials., Vahid Tavaf

Theses and Dissertations

The objectives of this research are to develop a comprehensive method to quantify the material degradation of composite materials in the presence of distributed damages and predict the failure in the defected composites using the updated effective material properties. Defects can grow in composites at the macro scale caused by the microscale voids, matrix cracks, fiber breakages starting from manufacturing processes to the high and low cycle fatigue loads, high temperature, and high humidity during operation. Hence, to predict a more realistic failure model, it is necessary to consider the repercussions of degraded materials. The proposed research work is divided …

Developing Origami-Based Approaches To Realize Novel Architectures And Behaviors For Deployable Space Arrays, Nathan Alan Pehrson

Theses and Dissertations

Origami-based approaches for the folding of thick materials for specific application to large deployable space arrays is explored in this work. The folding approaches presented utilize strain energy, spatial kinematics, membranes, compliant mechanisms, and or in combination together to fold finite-thickness materials viewed through the lens of origami-based engineering. Novel architectures and behaviors of mechanisms are developed to achieve packaging efficiency, deployment, and self-stiffening. A method for the folding of monolithic thick-sheet materials is developed by incorporating compliant mechanisms into the material itself to strategically add degrees of freedom. The design and characterization of the compliant mechanisms with consideration to …

Characterization And Drying Of Oxyhydroxides On Aluminum Clad Spent Nuclear Fuel, Matthew Shalloo

Theses and Dissertations

Research reactors such as the Advanced Test Reactor (ATR) and the High Flux Isotope Reactor (HFIR) employ aluminum-clad fuel elements made up of many thin plates with uranium dispersed within. In most engineering applications, aluminum is considered to have favorable corrosion characteristics. It forms a thin oxide layer [Al2O3] under atmospheric conditions that is impenetrable to oxygen thus stopping any further corrosion. However, both aluminum metal and Al2O3 react with water to form hydrous oxides which are less protective against further corrosion and form significantly thicker layers than oxidation in dry air. As a result, aluminum-clad spent nuclear fuel (ASNF) …

Experimental Investigation Of Hydraulic Effects On Unsaturated Soils Behaviors, Muwafaq Awad

Theses and Dissertations

Geo-structures are frequently constructed in or on soils with unsaturated conditions and are subjected to variations of moisture contents due to seasonal changes. Even though unsaturated soil mechanics have been established for several decades, it has not been fully implemented in practice today because of a lack of understanding of the interaction between the soil, water, and air phases. Many experimental research studies have been conducted to improve the understanding of unsaturated behavior but these studies are typically limited to small soil elements tested under fully drained conditions. The goal of this research is to evaluate the effect of hydraulics …

A Non-Contacting System For Rail Neutral Temperature And Stress Measurements, Katelyn Knopf

Theses and Dissertations

Continuous Welded Rail (CWR) has become the standard in modern railway track construction around the world because it alleviates well-documented disadvantages of rail joints in a track. CWR practice results in long segments of continuous rail in the track that will develop significant thermal elongation. To avoid the use of impractical large thermal expansion joints and limit the expected thermal elongation, the rail is anchored to the ties. Consequently, the rail is exposed to higher thermal stress demands as the rail temperature varies. At the time a CWR is laid, the rail is free of thermal stresses; the temperature at …

Evaluating Measurement Of Strain Hardening Method For Mechanical Assessment Of Geomembrane Service Life In Msw Landfills, Alaa Alsharaballi

Theses and Dissertations

The increased household production result in more construction of municipal solid waste (MSW) landfills and lagoons. One major part of these engineering projects is high-density polyethylene (HDPE) geomembrane. Geomembrane is an impermeable layer that used along bottom and sides of landfills and lagoons to contain the leachate and to protect the groundwater. Although of their chemicals resistance and high strength, it can be aged under service conditions such as high temperature, ultraviolet (UV) light, and chemicals exposure. These conditions accelerate oxidation of geomembrane and lead to brittle behavior and stress cracking which reduce its service life.

Our objective in this …

Nonlinear Characterizing Of A New Titanium Nitride On Aluminum Oxide Metalens, Michael A. Cumming

Theses and Dissertations

A sample metalens generated from Titanium Nitride deposited onto Aluminum Oxide was designed to focus at 10 microns with a beam centered at 800nm, and when analyzed with high intensity illumination was found to have a focal length of 9.650 ±.003µm at an intensity of 16.93[MW/cm² ]. Analyzing this change by comparing it to a Fresnel Lens’ physics shows that for this lens, the effective nonlinear index of refraction is certainly greater than the nonlinear index of just Titanium Nitride itself, at −1.6239 × 10⁻¹⁵[m²/W] compared to the materials −1.3 × 10⁻¹⁵[m^{2 …}

Quantifying And Elucidating The Effect Of Co2 On The Thermodynamics, Kinetics And Charge Transport Of Aemfcs, Yiwei Zheng

Theses and Dissertations

Anion exchange membrane fuel cells (AEMFCs) have shown significant promise to provide clean, sustainable energy for grid and transportation applications – and at a lower theoretical cost than more established proton exchange membrane fuel cells (PEMFCs). Adding to the excitement around AEMFCs is the extremely high peak power that can now be obtained (> 3 W cm-2) and continuously improving durability (1000+ h), which has made the future deployment of AEMFCs in real-world applications a serious consideration. For some applications (e.g. automotive), the most critical remaining practical issue with AEMFCs is understanding and mitigating the effects of atmospheric CO2 (in …

Enhanced Heat Transfer In Spray Cooling Through Surface Modifications: An Experimental And Computational Study, Azzam Saadi Salman

Theses and Dissertations

Today, dissipating high heat flux safely is one of the greatest challenges for thermal engineers in thermal management systems, and it becomes a critical barrier to technological developments for many engineering applications. Due to technological advances and aggressive micro-miniaturization of electronic components, the surface area of most devices has shrunk while the computational power increased exponentially. Therefore, the amount of heat dissipated from surfaces has increased significantly. Numerous cooling techniques have been introduced to replace the traditional air cooling systems and to maintain the efficiency and reliability of electronic components. Microelectronics work efficiently and safely at surface temperatures of < 100 ℃ and 125 ℃ for general and defense applications, respectively. One of the proposed alternative schemes is spray cooling, which is considered one of the most advanced cooling methods. It is used for high and ultra-high heat flux dissipation, as it can dissipate 150-200 W/cm2 while maintaining the surface temperature within this range. Also, spray cooling removes a large amount of energy at a lower liquid flow rate compared to other cooling techniques, such as jet impingement and microchannel heat sink. The thermal performance of spray cooling systems can be enhanced either actively or passively. Active enhancement is a very efficient technique; however, it adds more pumping power. The present work focuses on three main objectives: evaluating and analyzing spray cooling performance, developing a three-dimensional numerical multi-phase model for heat transfer process in spray cooling and enhancing the thermal performance of spray cooling passively.

First, …

Computational Wave Field Modeling In Anisotropic Media, Sajan Shrestha

Theses and Dissertations

In this thesis, a meshless semi-analytical computational method is presented to compute the ultrasonic wave field in generalized anisotropic material while understanding the physics of wave propagation in detail. To understand the wave-damage interaction in an anisotropic material, it is neither feasible nor cost-effective to perform multiple experiments in the laboratory. Hence, recently the computational nondestructive evaluation (CNDE) received much attention to performing the NDE experiments in a virtual environment. In this thesis, a fundamental framework is constructed to perform the CNDE experiment of a thick composite specimen in a Pulse-Echo (PE) and through-transmission mode. To achieve the target, the …

Molecular Modeling Of Tethered Polyelectrolytes For Novel Biomedical Applications, Merina Jahan

Theses and Dissertations

Current research trends throughout the world focus on designing intelligent materi- als and systems for diverse applications in all courses of life. Biomaterials research encompasses a major part in this revolution due to the increased effort in fulfilling unmet medical needs to treat complex physiological and neurodegenerative disorders. Polymers play inevitable roles in these research endeavors for their ubiquitous pres- ence in biological systems. Therefore, it is crucial to understand how the polymeric molecules interact within diverse biological environments, to efficiently engineer them for various drug delivery and biosensing systems. The use of experimental design and selection of different polymers …

Using A Nondispersive Wave Propagation For Measuring Dynamic Fracture Initiation Toughness Of Materials: Experimental And Numerical Based Study, Ali Fahad Fahem

Theses and Dissertations

Fracture mechanics has been a subject of great interest in the engineering community for decades. During this period, fracture parameters such as Stress Intensity Factor (SIF), J-integral, and Crack-Tip Opening Displacement (CTOD) have been developed and used to characterize the fracture properties of most engineering materials under quasi-static loading condition. Usually, these properties are obtained experimentally by using standard methods such as ASTM E399, E1820 or E1920 to evaluate the stress intensity factor ������ ������������, elastic-plastic toughness ������ ������������ and crack tip opening displacement (CTOD) respectively. Conversely, most critical engineering applications are subjected to a sudden or high strain rate …

A Novel And Inexpensive Solution To Build Autonomous Surface Vehicles Capable Of Negotiating Highly Disturbed Environments, Jason Moulton

Theses and Dissertations

This dissertation has four main contributions. The first contribution is the design and build of a fleet of long-range, medium-duration deployable autonomous surface vehicles (ASV). The second is the development, implementation, and testing of inex-pensive sensors to accurately measure wind, current, and depth environmental vari- ables. The third leverages the first two contributions, and is modeling the effects of environmental variables on an ASV, finally leading to the development of a dynamic controller enabling deployment in more uncertain conditions.

The motivation for designing and building a new ASV comes from the lack of availability of a flexible and modular platform …

Cybersecurity Issues In The Context Of Cryptographic Shuffling Algorithms And Concept Drift: Challenges And Solutions, Hatim Alsuwat

Theses and Dissertations

In this dissertation, we investigate and address two kinds of data integrity threats. We first study the limitations of secure cryptographic shuffling algorithms regarding preservation of data dependencies. We then study the limitations of machine learning models regarding concept drift detection. We propose solutions to address these threats.

Shuffling Algorithms have been used to protect the confidentiality of sensitive data. However, these algorithms may not preserve data dependencies, such as functional de- pendencies and data-driven associations. We present two solutions for addressing these shortcomings: (1) Functional dependencies preserving shuffle, and (2) Data-driven asso- ciations preserving shuffle. For preserving functional dependencies, …

Challenges In Large-Scale Machine Learning Systems: Security And Correctness, Emad Alsuwat

Theses and Dissertations

In this research, we address the impact of data integrity on machine learning algorithms. We study how an adversary could corrupt Bayesian network structure learning algorithms by inserting contaminated data items. We investigate the resilience of two commonly used Bayesian network structure learning algorithms, namely the PC and LCD algorithms, against data poisoning attacks that aim to corrupt the learned Bayesian network model.

Data poisoning attacks are one of the most important emerging security threats against machine learning systems. These attacks aim to corrupt machine learning models by con- taminating datasets in the training phase. The lack of resilience of …

Experimental Investigations Of Levee Breach Flows, Ibrahim Adil Ibrahim

Theses and Dissertations

Two individual but related problems involving levee breach flow are studied. The first one involves experimental and dynamic modeling of steady flow through a levee breach, and the second one involves experimental investigation of flood management by an engineered levee breach. Both studies are conducted in the Hydraulics Laboratory, the University of South Carolina.

In the first problem, an idealized levee breach on a trapezoidal embankment was studied. Flow data including water depths, surface velocities, and flow discharges were collected from 28 experiments considering different cases of breach width and downstream water depth. Ultrasonic sensors were used to record the …

Stacked Modelling Framework, Kareem Abdelfatah

Theses and Dissertations

The thesis develops a predictive modeling framework based on stacked Gaussian processes and applies it to two main applications in environmental and chemical en- gineering. First, a network of independently trained Gaussian processes (StackedGP) is introduced to obtain analytical predictions of quantities of interest (model out- puts) with quantified uncertainties. StackedGP framework supports component- based modeling in different fields such as environmental and chemical science, en- hances predictions of quantities of interest through a cascade of intermediate predic- tions usually addressed by cokriging, and propagates uncertainties through emulated dynamical systems driven by uncertain forcing variables. By using analytical first and …

Properties, Learning Algorithms, And Applications Of Chain Graphs And Bayesian Hypergraphs, Mohammad Ali Javidian

Theses and Dissertations

Probabilistic graphical models (PGMs) use graphs, either undirected, directed, or mixed, to represent possible dependencies among the variables of a multivariate probability distri- bution. PGMs, such as Bayesian networks and Markov networks, are now widely accepted as a powerful and mature framework for reasoning and decision making under uncertainty in knowledge-based systems. With the increase of their popularity, the range of graphical models being investigated and used has also expanded. Several types of graphs with dif- ferent conditional independence interpretations - also known as Markov properties - have been proposed and used in graphical models.

The graphical structure of a …