Engineering Commons^™

An Exploratory Study Of Engineering Identity Development In African American Youth, Coletta Elayne Johnson Bey

Engineering Management & Systems Engineering Theses & Dissertations

Over the next ten years, the United State government forecasted a shortage of one million science, technology, engineering and mathematic (STEM) workers. This shortage of STEM workers can adversely impact the global competitiveness and sustainability of America. Within the workforce, African Americans are grossly underrepresented. The emerging body of knowledge has derived a process by which potential engineers make be identified. There is wide recognition in the body of knowledge that developing engineers have growth mindsets; strong math and science skills; and associate in engineering communities of practice. Authors of published research also agree that parents influence their child(ren)’s career …

Identifying And Quantifying Personnel Skills Gaps, Martin Joseph Mckenney

Engineering Management & Systems Engineering Theses & Dissertations

One of the issues organizations face is identifying the required skills needed for a position and then evaluating whether their personnel have these skills or if there is a “skills gap”. The skills gap is the distance between the position requirements and the skills currently possessed by the worker in that position. While multiple models have been created over the years to address facets of the problem, none of them provide a comprehensive framework to clearly identify the required skills and worker qualifications and then evaluate the degree of similarity. A composite skills gap model has been developed using the …

Spatiotemporal Downscaling Rainfall Predictions Of North American Regional Climate Change Assessment Program For Entire Virginia, Zhaoyi Cai

Civil & Environmental Engineering Theses & Dissertations

This thesis developed a statistical downscaling approach, which consists of a series of linear regression equations, to spatiotemporally downscale the rainfall predictions from North American Regional Climate Change Assessment Program (NARCCAP) in accordance with the 15-min observed rainfall data at the rain gauges across the state of Virginia. NARCCAP has generated twelve different region-global climate models (RCM-GCMs) with a temporal resolution of 3 hr and a spatial resolution of 50 km over the entire America. Although it has been downscaled already, such resolutions are still too coarse to represent the rain gauges. This means that the RCM-GCMs’ predictions need to …

Enhanced Sensing Performance Of Novel Nanostructured Zno Gas Sensors In Ethanol Vapor Concentration Detection Applications, Pengtao Lin

Electrical & Computer Engineering Theses & Dissertations

Sensors are devices which have been commonly used to measure the functional dependence and the variability of physical parameters like temperature, pressure, pH, voltage, current, concentration, and others. Among the numerous kinds of sensors in different areas, gas sensors have been widely used and investigated for gas monitoring. Gas sensors are of crucial importance for the detection of hazardous atmospheres, because toxic gases are frequently odorless, colorless, invisible, rapidly evaporating, and flammable, and would otherwise go unnoticed. Gas sensors have been used in a variety of applications among others for the detection of specific gas species and the detection of …

Challenges Of Designing And Operating A Pilot Scale Short Residence Time Continuous Hydrothermal Flash Hydrolysis Reactor For High Slurry Load Biomass Processing, Mason James Martin

Civil & Environmental Engineering Theses & Dissertations

Increasing demand for renewable energy, fuels, and bioproducts has resulted in a push for increasingly efficient and economically favorable biomass pretreatment methods. Flash Hydrolysis, (FH) a promising biomass pretreatment method, has been extensively studied at a laboratory scale. FH employs a continuous subcritical hydrothermal process capable of fractionating microalgae for lipid and protein recovery. FH is unique in that the residence time is very short (~ 10 s). Maintaining this residence time was key in designing a scaled pilot flash hydrolyzing unit (FHU). We have developed a one of its kind pilot FHU capable of increasing the processing output of …

Pulse Power Effects On Transient Plasma Ignition For Combustion, David Wayne Alderman Ii

Electrical & Computer Engineering Theses & Dissertations

Transient plasma ignition (TPI) uses highly non-equilibrium plasmas, driven by less than 100 nanosecond, high-voltage pulses, to initiate combustion. The effects of pulse repetition frequency (PRF) and ultrashort nanosecond rise times on TPI are investigated in this work using lean, stoichiometric, and rich air-fuel mixtures at atmospheric pressure. Experimental data show the transient plasmas driven by ultrashort rise time, high voltage pulses at high PRF’s enhance the combustion of lean or stoichiometric air-methane mixtures in a static chamber. In particular, increasing PRF enhances the combustion performance by means of reduced delay times independent of the equivalence ratio of the air-fuel …

A Laser Ion Source For Thin Film Deposition: Characterization Of Source And Growth Conditions, Md Mahmudur Rahman

Electrical & Computer Engineering Theses & Dissertations

Multicharged aluminum and carbon ions are generated by a laser-arc ion source. The design, construction, and testing of a compact laser ion source is demonstrated where the laser plasma is amplified by a high voltage spark-discharge. Optical emission and ion time-of-flight are measured for a spark-coupled laser aluminum plasma. A Q-switched Nd:YAG laser (wavelength λ = 1064 nm, pulse width τ ~7 ns, pulse energy E_p ≤ 260 mJ, intensity I ≤ 15 × 10⁹ W/cm²) generates the Al plasma, while a synchronized spark-discharge enhances the ion flux and charge state. Time-integrated, spatially resolved optical spectra …

A Multi-Agent Systems Approach For Analysis Of Stepping Stone Attacks, Marco Antonio Gamarra

Electrical & Computer Engineering Theses & Dissertations

Stepping stone attacks are one of the most sophisticated cyber-attacks, in which attackers make a chain of compromised hosts to reach a victim target. In this Dissertation, an analytic model with Multi-Agent systems approach has been proposed to analyze the propagation of stepping stones attacks in dynamic vulnerability graphs. Because the vulnerability configuration in a network is inherently dynamic, in this Dissertation a biased min-consensus technique for dynamic graphs with fixed and switching topology is proposed as a distributed technique to calculate the most vulnerable path for stepping stones attacks in dynamic vulnerability graphs. We use min-plus algebra to analyze …

Parallel Jacobi Transformation Algorithm For Generalized Eigen-Solution With Improved Damage Detection Of Truss/Bridge-Type Structures, Maryam Ehsaei

Civil & Environmental Engineering Theses & Dissertations

Serial Jacobi transformation algorithm for the solution of “standard eigen-problems” is re-visited to facilitate the explanation of the proposed parallel transformation algorithm, for which computational efficiency can be realized in this study through “pattern recognition” for the development and explanation of “explicit formulas” to avoid costly matrix time matrix operations. The proposed parallel Jacobi transformation for the solution of “generalized eigen-problems” has also been incorporated into the “improved damage detection” algorithm.

Computational efficiency and robust behaviors for the entire proposed procedures (eigen-solution, damage detection and damage quantification) can be validated through several academic and real-life numerical examples. Numerical results obtained …

Demonstration Of Visible And Near Infrared Raman Spectrometers And Improved Matched Filter Model For Analysis Of Combined Raman Signals, Alexander Matthew Atkinson

Electrical & Computer Engineering Theses & Dissertations

Raman spectroscopy is a powerful analysis technique that has found applications in fields such as analytical chemistry, planetary sciences, and medical diagnostics. Recent studies have shown that analysis of Raman spectral profiles can be greatly assisted by use of computational models with achievements including high accuracy pure sample classification with imbalanced data sets and detection of ideal sample deviations for pharmaceutical quality control. The adoption of automated methods is a necessary step in streamlining the analysis process as Raman hardware becomes more advanced. Due to limits in the architectures of current machine learning based Raman classification models, transfer from pure …

Application Of A Biodegradable And Recyclable Chelating Agent For Ash Removal From Algae, Temitope George Daramola

Civil & Environmental Engineering Theses & Dissertations

Ash is inherent in algae biomass and it causes operational difficulties, equipment failure, and disposal issues during biomass conversion to biofuels and bioproducts. The objectives of this study are to (i) investigate the use of the biodegradable chelating agent for reducing ash content of algae and (ii) evaluate the potential of regeneration and recycle of the chelating agent for multiple uses. Conventionally, ethylenediamine-tetraacetic acid (EDTA) has been studied extensively to remove ash from biomass. However, EDTA is non-biodegradable and causes environmental issues at the disposal.

Nitrilotriacetic acid (NTA) is a biodegradable chelating agent and was used in this study for …

Effect Of The Physical Micro-Environment On Cell Adhesion And Force Exertion, Mohamad Eftekharjoo

Mechanical & Aerospace Engineering Theses & Dissertations

Physical characteristics of the microenvironment, such as geometry and stiffness, influence cell adhesion and contractile forces. Here, we determined how these physical factors influenced cell force exertion and adhesion in two specific contexts that have broad relevance.

Fibroblasts are cells in connective tissues that interact with a fibrous extracellular matrix (ECM) that have a predominantly one-dimensional (1D) (fibrillar) geometry. However, it has been unclear as to how the 1D nature of the fibrillar ECM influences the forces exerted by fibroblasts. Here, we used fibroblast cells adherent on fibronectin lines on polyacrylamide (PAA) gels of stiffness 13 and 45 kPa to …

Catalytic Transfer Hydrogenation Reactions Of Lipids, Alexander Asiedu

Civil & Environmental Engineering Theses & Dissertations

Catalytic transfer hydrogenation (CTH) of lipids was investigated using 2-propanol as hydrogen donor for producing liquid hydrocarbons, e.g. jet fuels. The main sources of lipids selected in this study were waste cooking oil (WCO) and oil-laden algae-derived biofuel intermediate (BI). Two different catalysts were employed in this study, namely activated carbon and trimetallic-doped zeolite.

The CTH reaction was between WCO and 2-propanol in a continuous flow reactor over a packed-bed activated carbon at near atmospheric pressure. Results revealed a high level of alkenes and aromatics compounds, which are not stable and are not environmentally unfriendly. To reduce these compounds in …

Modeling Social Learning: An Agent-Based Approach, Erika G. Ardiles Cruz

Computational Modeling & Simulation Engineering Theses & Dissertations

Learning is the process of acquiring or modifying knowledge, behavior, or skills. The ability to learn is inherent to humans, animals, and plants, and even machines are provided with algorithms that could mimic in a restricted way the processes of learning. Humans learn from the time they are born until they die because of a continuous process of interaction between them and their environment. Behavioral Psychology Theories and Social Learning Theories study behavior learned from the environment and social interactions through stimulus-response. Some computer approaches to modeling human behavior attempted to represent the learning and decision-making processes using agent-based models. …

Extension Of A Penalty Method For Numerically Solving Constrained Multibody Dynamic Problems, Troy Newhart

Mechanical & Aerospace Engineering Theses & Dissertations

Numerical analysis of constrained static and multibody dynamic systems has become an integral part of engineering analysis with the continued improvements in technology and software availability. Many methods currently exist for numerically solving constrained static and dynamic systems. The applicability of a penalty method for constrained static solutions is observed in many academic texts and papers. The appeal for using a penalty method in statics pertains to its ease of implementation, computational suitability, and accuracy. This thesis extends a static penalty method for use with constrained multibody dynamics to observe if the penalty method’s benefits are similar for a dynamics …

Numerical Modeling And Field Investigation Of Nearshore Nonlinear Wave Propagation, Elham Sharifineyestani

Civil & Environmental Engineering Theses & Dissertations

First, a phase-resolving frequency-domain wave model that solves nonlinear wave-wave interactions is improved to account for wave dissipation and modulations over viscoelastic mud layer. Model results show satisfactory agreement with laboratory measurements. The model is then used to investigate the combined effect of mud viscoelasticity and nonlinear wave-wave interactions on surface wave evolution using cnoidal and random wave simulations. In general, qualitative measures such as shape of cnoidal waves or pattern of variation in H_rms of random waves are dictated by direct mud-induced damping which, due to resonance effects, has a substantially different structure over viscoelastic mud compared to …

Computational Analysis Of Antipode Algorithms For The Output Feedback Hopf Algebra, Lance Berlin

Electrical & Computer Engineering Theses & Dissertations

The feedback interconnection of two systems written in terms of Chen-Fliess series can be described explicitly in terms of the antipode of the output feedback Hopf algebra. At present, there are three known computational approaches to calculating this antipode: the left coproduct method, the right coproduct method, and the derivation method. Each of these algorithms is defined recursively, and thus becomes computationally expensive quite quickly. This motivates the need for a more complete understanding of the algorithmic complexity of these methods, as well as the development of new approaches for determining the Hopf algebra antipode. The main goals of this …

A Cfd Study Of Steady Fully Developed Laminar Flow Through A 90-Degree Bend Pipe With A Square Cross-Sectional Area, Subodh Sushant Toraskar

Mechanical & Aerospace Engineering Theses & Dissertations

Fluid flow through a closed curved conduit has always been a topic of extensive research, as it has many practical and industrial applications. The flow is generally characterized by a presence of secondary flow, vortical motions and pressure losses for different flow regimes. These observed irregularities may positively or negatively impact the flow. They are beneficial for cases where mixing of fluids is required, usually observed for multiphase flow regimes or detrimental for cases involving particles in the fluid. There are also instances where a particle-laden fluid transported through the curved pipe was directly related to corrosion- erosion related problems. …

Communication Capability For A Simulation-Based Test And Evaluation Framework For Autonomous Systems, Ntiana Sakioti

Computational Modeling & Simulation Engineering Theses & Dissertations

The design and testing process for collaborative autonomous systems can be extremely complex and time-consuming, so it is advantageous to begin testing early in the design. A Test & Evaluation (T&E) Framework was previously developed to enable the testing of autonomous software at various levels of mixed reality. The Framework assumes a modular approach to autonomous software development, which introduces the possibility that components are not in the same stage of development. The T&E Framework allows testing to begin early in a simulated environment, with the autonomous software methodically migrating from virtual to augmented to physical environments as component development …

Laser-Spark Multicharged Ion Implantation System ‒ Application In Ion Implantation And Neural Deposition Of Carbon In Nickel (111), Oguzhan Balki

Electrical & Computer Engineering Theses & Dissertations

Carbon ions generated by ablation of a carbon target using an Nd:YAG laser pulse (wavelength λ = 1064 nm, pulse width τ = 7 ns, and laser fluence of 10-110 J/cm²) are characterized. Time-of-flight analyzer, a three-mesh retarding field analyzer, and an electrostatic ion energy analyzer are used to study the charge and energy of carbon ions generated by laser ablation. The dependencies of the ion signal on the laser fluence, laser focal point position relative to target surface, and the acceleration voltage are described. Up to C⁴⁺ are observed. When no acceleration voltage is applied between …

Numerical Modeling Of Shoreline Response To Storm Tides And Sea Level Rise, Akash Sahu

Civil & Environmental Engineering Theses & Dissertations

In this study, an integrated hydrodynamic, wave, and sediment transport modeling approach is developed for predicting the spatiotemporal variation of erosion of a sandy shoreline due to storm surge, wave action, tidal variations, and relative sea level rise (RSLR). The study site is located at the northern most portion of the city of Norfolk, Virginia, and it is of importance to the city, both in terms of tourism and for the protection that it provides for upland properties against storms. The region, in general, experiences the highest rate of RSLR on the U.S. East Coast which should result in high …

Gesture Based Control Of Semi-Autonomous Vehicles, Brian Sanders

Computational Modeling & Simulation Engineering Theses & Dissertations

The objective of this investigation is to explore the use of hand gestures to control semi-autonomous vehicles, such as quadcopters, using realistic, physics based simulations. This involves identifying natural gestures to control basic functions of a vehicle, such as maneuvering and onboard equipment operation, and building simulations using the Unity game engine to investigate preferred use of those gestures. In addition to creating a realistic operating experience, human factors associated with limitations on physical hand motion and information management are also considered in the simulation development process. Testing with external participants using a recreational quadcopter simulation built in Unity was …

A Comparison Of Multi-Attribute Utility Theory, The Analytic Hierarchy Process, The Analytic Network Process, And New Hybrid Approaches For A Case Study Involving Radon, Jesse Ray Toepfer

Engineering Management & Systems Engineering Theses & Dissertations

This dissertation focuses on the use of three new combinational hybrid approaches to solve a rational decision problem. Even though Multi-Attribute Utility Theory (MAUT) and the Analytic Hierarchy Process (AHP), and the Analytic Network Process (ANP), are all long established theories, their practical applications continue to grow and generate new knowledge. As a case study approach, there exists a knowledge gap concerning the use of these MCDM methods in the area of environmental remediation, and more especially, in situations that involve radioactive materials. From this, and as borne out by the literature review discussed herein, a problem statement is thus …

Adaptive Control Of Base Isolation Systems Using The Transmissibility-Based Semi-Active Controller, Ramin Rabiee

Civil & Environmental Engineering Theses & Dissertations

Base isolation system is one of the most effective seismic protection systems which is widely used to protect buildings of high importance against seismic hazards. However, the performance of these systems might be impaired under long-period earthquake ground motions due to the resonance effect. The main focus of this dissertation is the development of an adaptive semi-active control algorithm to improve the performance of conventional base isolation systems. The proposed control law works based on the transmissibility theory, called the transmissibility-based semi-active (TSA) controller, which can adaptively change the damping of the base-isolation system based on the response of the …

Measuring Risks Of Interdependencies In Enterprise Systems: An Application To Ghana’S Salt Enterprise, Yaw Mensah

Engineering Management & Systems Engineering Theses & Dissertations

This dissertation describes the use of Functional Dependency Network Analysis (FDNA) for modeling risks resulting from dependencies among elements of enterprise systems with application to salt processing enterprise in Ghana. FDNA was developed to model dependencies among members of enterprise systems by highlighting two dimensions of dependency: strength and criticality. Nonetheless, the concepts and analytics for these two dimensions of dependencies needed further development and generalization in the context of project management and systems development in developing countries.

Managing risks within the interdependency in enterprise systems through integration will help improve global economic growth. Coherent theory for enterprise integration must …

A Study To Determine How To Measure The Laser Safety Climate At Academic Institutions, John Settlemyer

OTS Master's Level Projects & Papers

Statement of Problem

The purpose of this study was to determine if the laser safety climate can be measured at academic institutions and what factors would provide valid measures of the laser safety climate at academic institutions. Specifically, the study attempted to answer the following questions:

Research Questions

RQ1. Can laser safety climate be measured at academic institutions using a climate survey instrument?

RQ2. What factors should be measured by a laser safety climate instrument?

RQ3. What measures would provide actionable data for prescriptive intervention by laser safety professionals at academic institutions? (p. 4)

Periodic Orbit Analytic Construction In The Circular Restricted Three-Body Problem, Jay Shriram Suryawanshi

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis investigates an approximate analytic construction of halo-type periodic orbits about the collinear equilibrium points in the circular restricted three-body problem. The research follows a parallel approach to the one used by Ghazy and Newman, but the initial assumptions and utilized functions are unique to this thesis. A suppositional base solution constructed using Jacobi elliptic functions and satisfying Jacobi's integral equation is at the core of the analytic construction framework. The locus of this solution is a circle lying in the plane perpendicular to the line joining the primaries. The base solution elicits a closed-form expression for the period …

Reducing The Noise Impact Of Unmanned Aerial Vehicles By Flight Control System Augmentation, Matthew B. Galles

Mechanical & Aerospace Engineering Theses & Dissertations

The aim of this thesis is to explore methods to reduce the noise impact of unmanned aerial vehicles operating within acoustically sensitive environments by flight control system augmentation. Two methods are investigated and include: (i) reduction of sound generated by vehicle speed control while flying along a nominal path and (ii) reduction of acoustic exposure by vehicle path control while flying at a nominal speed. Both methods require incorporation of an acoustic model into the flight control system as an additional control objective and an acoustic metric to characterize primary noise sources dependent on vehicle state. An acoustic model was …

Using Feature Extraction From Deep Convolutional Neural Networks For Pathological Image Analysis And Its Visual Interpretability, Wei-Wen Hsu

Electrical & Computer Engineering Theses & Dissertations

This dissertation presents a computer-aided diagnosis (CAD) system using deep learning approaches for lesion detection and classification on whole-slide images (WSIs) with breast cancer. The deep features being distinguishing in classification from the convolutional neural networks (CNN) are demonstrated in this study to provide comprehensive interpretability for the proposed CAD system using the domain knowledge in pathology. In the experiment, a total of 186 slides of WSIs were collected and classified into three categories: Non-Carcinoma, Ductal Carcinoma in Situ (DCIS), and Invasive Ductal Carcinoma (IDC). Instead of conducting pixel-wise classification (segmentation) into three classes directly, a hierarchical framework with the …

Computational Analysis And Design Optimization Of Convective Pcr Devices, Jung Il Shu

Mechanical & Aerospace Engineering Theses & Dissertations

Polymerase Chain Reaction (PCR) is a relatively novel technique to amplify a few copies of DNA to a detectable level. PCR has already become common in biomedical research, criminal forensics, molecular archaeology, and so on. Many have attempted to develop PCR devices in numerous types for the purpose of the lab-on-chip (LOC) or point-of-care (POC). To use PCR devices for POC lab testing, the price must be lower, and the performance should be comparable to the lab devices. For current practices with the existing methods, the price is pushed up higher partially due to too much dependence on numerous developmental …