Engineering Commons^™

Development Of A Dsm-Based Model For Managing The Design Of Complex Systems Considering The Impact Of Technological Obsolescence, Gershom Kwaku Obeng

Mechanical & Aerospace Engineering Theses & Dissertations

Obsolescence has been a constant issue for process planners and designers and if not properly accounted for, obsolescence can become an expensive issue. As systems become more complex, interconnected, and nonhomogeneous, separate studies of single groups of equipment are no longer sufficient in modeling the obsolescence of the systems that they make up. The purpose of this dissertation is to model the likelihood of a process's design becoming obsolescent given the obsolescent behavior of the equipment used to complete the process. The methodology discussed in this work is based on a combination of using a systems engineering tool called the …

Systems Theory Based Architecture Framework For Complex System Governance, Bry Carter

Engineering Management & Systems Engineering Theses & Dissertations

The purpose of this research was to develop a systems theory based framework for complex system governance using grounded theory approach. Motivation for this research includes: 1) the lack of research that identifies modeling characteristics for complex system governance, 2) the lack of a framework rooted in systems theory to support performance of complex system governance functions for maintaining system viability.

This research focused on answering: What systems theoretic framework can be developed to inform complex system governance and enable articulation of governance function performance? The grounded theory research approach utilized three phases. First, the literature in systems theory, management …

Testing And Analysis Of An Exergetically Efficient 4 K To 2 K Helium Heat Exchanger, Peter N. Knudsen

Mechanical & Aerospace Engineering Theses & Dissertations

Modern experimental nuclear physics programs that utilize advanced superconducting devices require refrigeration below the lambda temperature of helium (2.1768 K) and involve sub-atmospheric helium at some point in the process. They typically operate between 1.8 and 2.1 K (16 to 40 mbar) and can require refrigeration ranging from tens to thousands of watts. These processes are very energy intensive, requiring roughly 850 W/W even for large and well-designed refrigerators, though they can easily require much more. Adiabatic expansion of sub-cooled liquid helium to these sub-atmospheric pressures will result in a two-phase mixture with a large liquid to vapor density ratio. …

Dynamic Elasto-Plastic Behavior Of Steel Building Sub-Assemblage Including Cfrp Retrofitting Under Impact Load, Ali Mohammed Salih Aloosi

Civil & Environmental Engineering Theses & Dissertations

This dissertation presents the outcome of a theoretical and experimental study of the dynamic as well as the quasi-static elasto-plastic behavior of a steel building sub-assemblage including carbon fiber reinforced polymer (CFRP) retrofitting. The steel sub-assemblage consists of a beam-column attached to a pair of beams at its top end while its bottom end is fixed. An apparatus is constructed and used for conducting a series of experiments by applying a lateral impact load on the beam-column in the presence or absence of a static axial load. An innovative procedure for determining the shape of the forcing function caused by …

Changing Trends In Wave Heights In The U.S. Mid-Atlantic Region, Hillary Lane

Civil & Environmental Engineering Theses & Dissertations

The pace and effects of climate change are an area of constant focus for coastal engineers as evolving patterns in the atmosphere worldwide affect the oceans and coasts on a regional and global scale. Surface waves respond to changing wind patterns both locally and from propagating swell, and the difficulty in predicting future wind patterns is well-established. Expectations that climate change will result in more frequent and intense coastal storms and consequently greater wave heights in the North Atlantic are still unrealized, and recent forecasts from a variety of atmosphere-ocean coupled global climate models instead predict decreasing wave heights through …

A General Theory Of Emergence In Engineered Systems, John J. Johnson Iv

Engineering Management & Systems Engineering Theses & Dissertations

Engineered systems are designed to satisfy specific needs and produce explainable/predictable results. But despite this intent, engineered systems don’t always do what they are designed to do once they are implemented. Some engineered systems produce properties and behaviors that are not clearly explainable or predictable by the properties of their components. This is a problem recognized in government and private sectors as having broad ranging financial and security consequences. It is also the essence of the emergence phenomena. A review of the literature reveals two significant gaps in the current body of knowledge on emergence as it pertains to engineered …

Thermo-Mechanical System Identification Of A Shape Memory Alloy Actuated Mechanism, Cody Alexander Wright

Mechanical & Aerospace Engineering Theses & Dissertations

Shape memory alloy (SMA) actuators paired in an antagonistic arrangement can be used to produce mechanisms that replicate human biomechanics. To investigate this proposal, the biomechanical articulation of the elbow by means of the biceps brachii muscle is compared with that of a SMA actuated arm. This is accomplished by parametric analysis of a crank-slider kinematic mechanism actuated, first, with an experimentally characterized SMA wire and then an idealized musculotendon actuator based on actuation properties of muscles published in the literature. Next, equations of motion for the system dynamics of the SMA actuated mechanism are derived and phase portrait analysis …

Region-Based Approach For Single Image Super-Resolution, Min Zhang

Electrical & Computer Engineering Theses & Dissertations

Single image super-resolution (SR) is a technique that generates a high- resolution image from a single low-resolution image [1,2,10,11]. Single image super- resolution can be generally classified into two groups: example-based and self-similarity based SR algorithms. The performance of the example-based SR algorithm depends on the similarity between testing data and the database. Usually, a large database is needed for better performance in general. This would result in heavy computational cost. The self-similarity based SR algorithm can generate a high-resolution (HR) image with sharper edges and fewer ringing artifacts if there is sufficient recurrence within or across scales of the …

Physical Layer Secret Key Agreement Using One-Bit Quantization And Low-Density Parity-Check Codes, John A. Snoap

Electrical & Computer Engineering Theses & Dissertations

Physical layer approaches for generating secret encryption keys for wireless systems using channel information have attracted increased interest from researchers in recent years. This paper presents a new approach for calculating log-likelihood ratios (LLRs) for secret key generation that is based on one-bit quantization of channel measurements and the difference between channel estimates at legitimate reciprocal nodes. The studied secret key agreement approach, which implements advantage distillation along with information reconciliation using Slepian-Wolf low-density parity-check (LDPC) codes, is discussed and illustrated with numerical results obtained from simulations. These results show the probability of bit disagreement for keys generated using the …

Improvement Of Work Process Performance With Task Assignments And Mental Workload Balancing, Cansu Kandemir

Engineering Management & Systems Engineering Theses & Dissertations

The outcome of a work process depends heavily on which tasks assigned to which employees. However, sometimes-optimized assignments based on employees’ qualifications may result in an uneven and ineffective workload distribution among them. Likewise, an even workload distribution without considering the employee's qualifications may cause unproductive employee-task matching that results in low performance of employees. This trade-off is even more noticeable for work processes during critical time junctions, such as in military command centers and emergency rooms that require being fast and effective without making errors.

This study proposes that optimizing task-employee assignments according to their capabilities while also keeping …

Longitudinal Tidal Dispersion Coefficient Estimation And Total Suspended Solids Transport Characterization In The James River, Beatriz Eugenia Patino

Civil & Environmental Engineering Theses & Dissertations

The longitudinal dispersion coefficient is a parameter used to evaluate the effect of cross-sectional variations on substance mixing mechanisms in estuaries influenced by tide, wind and internal density variations. Considering a two dimensional approach, this study aims at evaluating a tidal area of the lower James River at approximately 19 miles upstream from the mouth at the Chesapeake Bay, in the City of Newport News, and applies an experimental procedure based on in-situ salinity concentrations to estimate the dispersion coefficient in the area where receives a discharge from the HRSD James River Wastewater Treatment Plant, and further characterizes Total Suspended …

An Examination Of The Indentation Size Effect In Fcc Metals And Alloys From A Kinetics Based Perspective Using Nanoindentation, David Earl Stegall

Mechanical & Aerospace Engineering Theses & Dissertations

The indentation size effect (ISE) in metals is described as the rise in hardness with decreasing depth of indentation and contradicts conventional plasticity behavior. The goal of this dissertation is to further examine the fundamental dislocation mechanisms that may be contributing to the so-called indentation size effect. In this work, we examined several metals and alloys including 99.999% Aluminum (SFE ~200 mJ/m²), 99.95% Nickel (SFE ~125 mJ/m²), 99.95% Silver (SFE ~22 mJ/m²⁾, and three alloys, alpha brass 70/30 (SFE >10 mJ/m²), 70/30 nickel copper (SFE ~100 mJ/ …

Efficient Domain Decomposition Algorithms And Applications In Transportation And Structural Engineering, Paul W. Johnson Iii

Civil & Environmental Engineering Theses & Dissertations

Domain decomposition is a divide-and-conquer strategy. In the first part of this dissertation, a new/simple/efficient domain decomposition partitioning algorithm is proposed to break a large domain into smaller sub-domains, in such a way as to minimize the number of system boundary nodes and to balance the work load for each sub-domain. This new domain decomposition algorithm is based on the network’s shortest path solution. Numerical results indicate that the new Shortest Distance Decomposition Algorithm outperformed the most widely used METIS algorithm in 21 out of 27 tested (transportation) examples. In the second part of this dissertation, another new/simple and highly …

Agenda, Hampton Roads Sea Level Rise/Flooding Adaptation Forum, Hr Adaptation Forum

September 29, 2016: Adaptive Structures and Innovative Solutions

Agenda for the Hampton Roads Sea Level Rise/Flooding Adaptation Forum on September 29, 2016 at the Hampton University Conference Room 204, the Bemis Laboratories, 713 Orchard Road, Hampton, VA.

Active Fault Tolerant Control For Vertical Tail Damaged Aircraft With Dissimilar Redundant Actuation System, Wang Jun, Wang Shaoping, Wang Xingjian, Shi Cun, Mileta M. Tomovic

Engineering Technology Faculty Publications

This paper proposes an active fault-tolerant control strategy for an aircraft with dissimilar redundant actuation system (DRAS) that has suffered from vertical tail damage. A damage degree coefficient based on the effective vertical tail area is introduced to parameterize the damaged flight dynamic model. The nonlinear relationship between the damage degree coefficient and the corresponding stability derivatives is considered. Furthermore, the performance degradation of new input channel with electro-hydrostatic actuator (EHA) is also taken into account in the damaged flight dynamic model. Based on the accurate damaged flight dynamic model, a composite method of linear quadratic regulator (LQR) integrating model …

Robust Algorithms For Estimating Vehicle Movement From Motion Sensors Within Smartphones, Ilyas Ustun

Computational Modeling & Simulation Engineering Theses & Dissertations

Building sustainable traffic control solutions for urban streets (e.g., eco-friendly signal control) and highways requires effective and reliable sensing capabilities for monitoring traffic flow conditions so that both the temporal and spatial extents of congestion are observed. This would enable optimal control strategies to be implemented for maximizing efficiency and for minimizing the environmental impacts of traffic. Various types of traffic detection systems, such as inductive loops, radar, and cameras have been used for these purposes. However, these systems are limited, both in scope and in time. Using GPS as an alternative method is not always viable because of problems …

Profit Based Simulation Model For The Rail Transportation Industry, Mark Patrick Doran

Engineering Management & Systems Engineering Theses & Dissertations

Schedules often conflict in the rail transportation industry. Operations managers assign resources and make scheduling decisions with no visibility of the revenue, cost, and profitability characteristics of the route they are manipulating. Transit speed decisions focus on ensuring trains safely reach their destination on time with little regard given to the actual service needs of the customer. Although all customers want on-time deliveries, few actually pay a premium to garner this level of preferential treatment. Operating in this type of environment results in decisions that severely erode profits.

In this dissertation, a simulation model referred to as the Rail Profit …

Constrained-Energy Cross-Well Actuation Of Bistable Structures, Masoud Zarepoor

Mechanical & Aerospace Engineering Theses & Dissertations

Bistable structures have two stable equilibrium positions and can be utilized to maintain a specific static shape with no energy consumption. This dissertation focuses on the minimum required energy for performing snap-through of a bistable structure. Snap-through is the motion of a bistable structure from one stable equilibrium position to the other. This research uses the Duffing-Holmes equation as a one-degree-of-freedom representative model of a bistable structure, and this nonlinear equation is solved to calculate the required energy for cross-well oscillation. The research identifies several unique features of the response of a bistable system subjected to force and energy constraints. …

Design Of Experiments Enhanced Statistical Process Control For Wind Tunnel Check Standard Testing, Ben D. Phillips

Mechanical & Aerospace Engineering Theses & Dissertations

The current wind tunnel check standard testing program at NASA Langley Research Center is focused on increasing data quality, uncertainty quantification and overall control and improvement of wind tunnel measurement processes. The statistical process control (SPC) methodology employed in the check standard testing program allows for the tracking of variations in measurements over time as well as an overall assessment of facility health. While the SPC approach can and does provide researchers with valuable information, it has certain limitations in the areas of process improvement and uncertainty quantification. It is thought by utilizing design of experiments methodology in conjunction with …

Methodologies For Estimating Traffic Flow On Freeways Using Probe Vehicle Trajectory Data, Khairul Azfi Anuar

Civil & Environmental Engineering Theses & Dissertations

Probe vehicle data are increasingly becoming the primary source of traffic data. As probe vehicle data become more widespread, it is imperative that methods are developed so that traffic state estimators such as flow, density, and speed can be derived from such data. In this dissertation three different methodologies are proposed for predicting traffic flow or volume on a freeway. All of the proposed methodologies exploit several different traffic flow theories in conjunction with probe vehicle data to predict traffic flow. The first methodology takes advantage of the fundamental diagram or speed-flow relationship. The relationship states that flow can be …

Extension Of The Gravity Model: A Risk Integrated Approach Towards The Impact Analysis Of Mega Sports Events On Inbound Tourist Arrivals, Abdul Sami Stanekzai

Engineering Management & Systems Engineering Theses & Dissertations

Mega sports events such as the Olympics and the FIFA World Cup are highly attended and countries compete ferociously to host such events due to their perceived long term positive effects. Inbound tourist forecasting is an important aspect of the hosting decision both for the organizing committees and the hosting nations. As a precaution against letting the event fall into incapable hands, which can lead into chaos and mismanagement, measures needs to be taken. Capacity evaluation of interested parties is possible, only by knowing the number of people who may attend the event. However, due to the infrequent occurrence of …

Evaluation Of 4h-Sic Photoconductive Switches For Pulsed Power Applications Based On Numerical Simulations, Rajintha Tiskumara

Electrical & Computer Engineering Theses & Dissertations

Since the early studies by Auston, photoconductive semiconductor switches (PCSSs) have been investigated intensively for many applications owing to their unique advantages over conventional gas and mechanical switches. These advantages include high speeds, fast rise times, optical isolation, compact geometry, and negligible jitter. Another important requirement is the ability to operate at high repetition rates with long device lifetimes (i.e., good reliability without degradation). Photoconductive semiconductor switches (PCSSs) are low-jitter compact alternatives to traditional gas switches in pulsed power systems. The physical properties of Silicon Carbide (SiC), such as a large bandgap (3.1-3.35 eV), high avalanche breakdown field (~3 MV/cm), …

Computational Modeling Of Facial Response For Detecting Differential Traits In Autism Spectrum Disorders, Manar D. Samad

Electrical & Computer Engineering Theses & Dissertations

This dissertation proposes novel computational modeling and computer vision methods for the analysis and discovery of differential traits in subjects with Autism Spectrum Disorders (ASD) using video and three-dimensional (3D) images of face and facial expressions. ASD is a neurodevelopmental disorder that impairs an individual’s nonverbal communication skills. This work studies ASD from the pathophysiology of facial expressions which may manifest atypical responses in the face. State-of-the-art psychophysical studies mostly employ na¨ıve human raters to visually score atypical facial responses of individuals with ASD, which may be subjective, tedious, and error prone. A few quantitative studies use intrusive sensors on …

A Comparison Of Microstructure And Uniaxial Compressive Response Of Ice-Templated Porous Alumina Scaffolds Fabricated From Two Different Particle Sizes, Nikhil D. Dhavale

Mechanical & Aerospace Engineering Theses & Dissertations

Development of bio-inspired highly porous (>50 vol.%) cellular ceramics is crucial to meet the demand of high-performance lightweight and damage-tolerant materials for a number of cutting-edge applications including impact energy absorption, biomedical implants, and energy storage. A key design feature that is observed in many natural materials (e.g., nacre, bamboo, wood, etc.) is the presence of hierarchical microstructure that results in an excellent synergy of various material properties, which are otherwise considered as mutually exclusive in current paradigm of materials design. To this end, development of multilayered, interconnected and anisotropic cellular ceramics could benefit the aforementioned applications. However, mimicking …

Development Of The Compact Jet Engine Simulator From Concept To Useful Test Rig, Henry H. Haskin

Mechanical & Aerospace Engineering Theses & Dissertations

Two Compact Jet Engine Simulator (CJES) units were designed for integrated wind tunnel acoustic experiments involving a Hybrid Wing Body (HWB) vehicle. To meet the 5.8% scale of the HWB model, Ultra Compact Combustor technology from the Air Force Research Laboratory was used. The CJES units were built and integrated with a control system in the NASA Langley Low Speed Aero acoustic Wind Tunnel. The combustor liners, plug—vane and flow conditioner components were built in-house at Langley Research Center. The operation of the CJES units was mapped and fixes found for combustor instability tones and rig flow noise. The original …

Development And Implementation Of A Propeller Test Capability For Gl-10 "Greased Lightning" Propeller Design, Brian Edward Duvall

Mechanical & Aerospace Engineering Theses & Dissertations

Interest in small unmanned aerial vehicles has increased dramatically in recent years. Hybrid vehicles which allow forward flight as a fixed wing aircraft and a true vertical landing capability have always had applications. Management of the available energy and noise associated with electric propeller propulsion systems presents many challenges. NASA Langley has developed the Greased Lightning 10 (GL-10) vertical takeoff, unmanned aerial vehicle with ten individual motors and propellers. All are used for propulsion during takeoff and contribute to acoustic noise pollution which is an identified nuisance to the surrounding users. A propeller test capability was developed to gain an …

Detecting And Resolving Air Traffic Conflicts Using A Point Of Closest Approach Method, Marc S. Easton

Mechanical & Aerospace Engineering Theses & Dissertations

A geometrical point of closest approach method is used to solve air traffic conflict detection/resolution problems with a single conflict vehicle that is unaware or unable to aid in resolving the conflict. Nonlinear, three degree of freedom equations of motion for a point-mass vehicle are derived and formulated to allow commanded trajectories to steer the vehicle to a desired location. A dynamic model is developed to propagate the vehicle in three dimensions. A closed-loop model implementing a negative feedback controller using a Proportional-Integral-Derivative control scheme is used to drive the vehicle to match the commanded trajectories. A conflict detection/resolution algorithm …

Development Of Visualization-Animation Software For Learning Transportation Algorithms, Ivan P. Makohon

Computational Modeling & Simulation Engineering Theses & Dissertations

Recognizing the steady decline in US Science Technology Engineering Mathematics (STEM) interests and enrollments, the National Science Foundation (NSF) and the White House have developed national strategies and provided significant budget resources to STEM education research [1-2] in the past years, with the ultimate goals being to improve both the quality and number of highly trained US educators, student workforce in STEM topics, in today’s highly competitive global markets. With the explosion of the internet’s capability and availability, it is even more critical to effectively train this future USA-STEM work-force and/or to develop effective STEM related teaching tools to reach …

Toward Simulation-Based Training Validation Protocols: Exploring 3d Stereo With Incremental Rehearsal And Partial Occlusion To Instigate And Modulate Smooth Pursuit And Saccade Responses In Baseball Batting, Ricardo A. Roca

Computational Modeling & Simulation Engineering Theses & Dissertations

“Keeping your eye on the ball” is a long-standing tenet in baseball batting. And yet, there are no protocols for objectively conditioning, measuring, and/or evaluating eye-on-ball coordination performance relative to baseball-pitch trajectories. Although video games and other virtual simulation technologies offer alternatives for training and obtaining objective measures, baseball batting instruction has relied on traditional eye-pitch coordination exercises with qualitative “face validation”, statistics of whole-task batting performance, and/or subjective batter-interrogation methods, rather than on direct, quantitative eye-movement performance evaluations. Further, protocols for validating transfer-of-training (ToT) for video games and other simulation-based training have not been established in general ― or …

Analysis And Implementation Of Communications Systems For Small Satellite Missions, Jason S. Harris

Electrical & Computer Engineering Theses & Dissertations

Nano satellites are becoming more and more popular space platforms due to their relatively low cost. Constellations of many of these small satellites are being launched for scientific and research purposes. This thesis has examined implementing a communications system for small satellites that can be used to maintain constant contact with satellites as they orbit the Earth. It analyzes the various components of a small satellite and how they integrate. It then discusses the different abstraction layers that will be required in order to support the same software architecture across various types of hardware. An orbital analysis was performed to …