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Open Access Dissertations

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Full-Text Articles in Engineering

Conceptual Understanding Of Threshold Concepts Of Electrical Phenomena: Mental Models Of Senior Undergraduates In Electrical Engineering, Mark T. Carnes Dec 2016

Conceptual Understanding Of Threshold Concepts Of Electrical Phenomena: Mental Models Of Senior Undergraduates In Electrical Engineering, Mark T. Carnes

Open Access Dissertations

Every field of study has a set of domain-specific concepts that anyone who desires to work in that field must know and understand. Most students who pursue university degrees in engineering trust that their education is designed to provide them with this knowledge. But does it? In electrical engineering (EE), conceptual understanding of electrical phenomena has rarely been addressed. Even though the presumed goal of instructors and students alike is to learn the concepts of electrical phenomena well enough to be able to use the concepts to design useful things, it is difficult to determine whether this goal is being ...


Wave Propagation And Imaging In Structured Optical Media, Zun Huang Dec 2016

Wave Propagation And Imaging In Structured Optical Media, Zun Huang

Open Access Dissertations

Structured optical media, usually characterized by periodic patterns of inhomogeneities in bulk materials, provide a new approach to ultimate control of wave propagation with possible practical applications: from distributed feedback lasers by diffraction gratings, to highly nonlinear performance for super-continuum generation, to fiber-optic telecommunications by microstructured photonic crystal fibers, to invisibility cloaking, to super-resolution imaging with metamaterials etc.

In particular, structured optical media allow to manipulate the wave propagation and dispersion. In this thesis, we focus on engineering the propagation phase dispersion by modulating the compositions and dimensions of the periodic elements. By tailoring the dispersion in momentum space, we ...


A Method For Selecting Hvac Retrofit Solutions For Existing Small- And Medium-Sized Commercial Buildings, Bonggil Jeon Dec 2016

A Method For Selecting Hvac Retrofit Solutions For Existing Small- And Medium-Sized Commercial Buildings, Bonggil Jeon

Open Access Dissertations

The primary purpose of the present study is to develop a framework and methodology for evaluating appropriate Heating, Ventilating, and Air Conditioning (HVAC) retrofit solutions that can be effectively retrofitted into different types of small- and medium-sized commercial buildings (SMSCB). Additionally, development of an advanced data-driven decision-making tool is introduced as a benefit of proposed framework. In recent years, considerable attention has been focused on retrofits of existing commercial buildings (IBE, 2013b). In fact, the Commercial Building Energy Consumption Survey (CBECS) 2003 (EIA, 2006) indicates that over 70% of existing commercial buildings across the United States are more than twenty ...


Plasmonic Devices Based On Transparent Conducting Oxides For Near Infrared Applications, Kim Jongbum Dec 2016

Plasmonic Devices Based On Transparent Conducting Oxides For Near Infrared Applications, Kim Jongbum

Open Access Dissertations

In the past decade, there have been many breakthroughs in the field of plasmonics and nanophotonics that have enabled optical devices with unprecedented functionalities. Even though remarkable demonstration of at photonic devices has been reported, constituent materials are limited to the noble metals such as gold (Au) and silver (Ag) due to their abundance of free electrons which enable the support of plasmon resonances in the visible range. With the strong demand for extension of the optical range of plasmonic applications, it is now a necessity to explore and develop alternative materials which can overcome intrinsic issues of noble metals ...


Numerical Investigation Of Crossflow Instability On The Hifire-5, Matthew T. Lakebrink Dec 2016

Numerical Investigation Of Crossflow Instability On The Hifire-5, Matthew T. Lakebrink

Open Access Dissertations

Stability analysis was performed with the Langley Stability and Transition Analysis Code (LASTRAC) on a 38.1% scale model of the HIFiRE-5 elliptic-cone forebody to study crossflow-induced transition in hypersonic boundary layers. A resolution study consisting of three grids (30e6, 45e6, and 91e6 points) indicated that the fine grid was sufficiently resolved. Results were largely insensitive to grid resolution over the acreage and near the attachment line. The percent variation in second-mode properties along the semi-minor axis was less than 1% between the medium and fine grids. The variation in crossflow-wave properties was less than 0.04% between the medium ...


Hydrodynamics Of Swimming Microorganisms In Complex Fluids, Gaojin Li Dec 2016

Hydrodynamics Of Swimming Microorganisms In Complex Fluids, Gaojin Li

Open Access Dissertations

Swimming motion of microorganisms, such as spermatozoa, plankton, algae and bacteria, etc., ubiquitously occurs in nature. It affects many biological processes, including reproduction, infection and the marine life ecosystem. The hydrodynamic effects are important in microorganism swimming, their nutrient uptake, fertilization, collective motions and formation of colonies. In nature, microorganisms have evolved to use various fascinating ways for locomotion and transport. Different designs are also developed for the locomotion of artificial nano- and microswimmers. In this study, we use several different computational models to investigate the behavior of microswimmers.

Microorganisms typically swim in the low Reynolds number regime, where inertia ...


Race, Class And Gender In Engineering Education: A Quantitative Investigation Of First Year Enrollment, Canek Moises Luna Phillips Dec 2016

Race, Class And Gender In Engineering Education: A Quantitative Investigation Of First Year Enrollment, Canek Moises Luna Phillips

Open Access Dissertations

Research explanations for the disparity across both race and gender in engineering education has typically relied on a deficit model, whereby women and people of color lack the requisite knowledge or psychological characteristics that Whites and men have to become engineers in sufficient numbers. Instead of using a deficit model approach to explain gender and race disparity, in the three studies conducted for this dissertation, I approach gender and race disparity as the result of processes of segregation linked to the historic and on-going perpetuation of systemic sources of oppression in the United States. In the first study, I investigate ...


Fracture Analysis In Biomimetic Bouligand Architectures, Nobphadon Suksanqpanya Dec 2016

Fracture Analysis In Biomimetic Bouligand Architectures, Nobphadon Suksanqpanya

Open Access Dissertations

The Bouligand structure, which is found in many biological materials, is a hierarchical architecture that features uniaxial fiber layers assembled periodically into a helicoidal pattern. Many studies have highlighted the high damage-resistant performance of Bouligand structures and its biomimetic materials. One of the outstanding species with the Bouligand structures is the smashing Mantis Shrimp, Odontodactylus Scyllarus, (or stomatopod) due to its capability of generating high speed, high acceleration blows using its raptorial appendage to defeat highly armored preys. The load-bearing part of this appendage, the dactyl club, contains an interior region, which is mainly characterized by the Bouligand structure. This ...


Geometric Accuracy Evaluation Of Mobile Terrestrial Lidar Surveys With Supporting Algorithms, Chisaphat Supunyachotsakul Dec 2016

Geometric Accuracy Evaluation Of Mobile Terrestrial Lidar Surveys With Supporting Algorithms, Chisaphat Supunyachotsakul

Open Access Dissertations

Mobile Mapping System (MMS) technology is widely used for many applications, hence quantifying its accuracy is a very important and essential task and is a primary focus of this research. In general, to perfrom geometric accuracy evaluation of MMS data, validation points/features are needed. A method is needed to capture a point feature off the roadway in a position where a target on the ground surface would not be visible to the scanner. In this study, eight sphere targets with 14" diameter were placed on the shoulder of the roadway over validation points on the ground. The sphere targets ...


Clustered-Dot Periodic Halftone Screen Design And Icc Profile Color Table Compression, Chuohao Tang Dec 2016

Clustered-Dot Periodic Halftone Screen Design And Icc Profile Color Table Compression, Chuohao Tang

Open Access Dissertations

This dissertation studies image quality problems associated with rendering images in devices like printing or displaying. It mainly includes two parts: clustered-dot periodic halftone screen design, and color table compression.

Screening is a widely used halftoning method. As a consequence of the lower resolution of digital presses and printers, the number of printer-addressable dots or holes in each microcell may be too few to provide the requisite number of tone lev- els between paper white and full colorant coverage. To address this limitation, the microcells can be grouped into supercells. The challenge is then to determine the desired supercell shape ...


Approximate Computing: An Integrated Cross-Layer Framework, Swagath Venkataramani Dec 2016

Approximate Computing: An Integrated Cross-Layer Framework, Swagath Venkataramani

Open Access Dissertations

A new design approach, called approximate computing (AxC), leverages the flexibility provided by intrinsic application resilience to realize hardware or software implementations that are more efficient in energy or performance. Approximate computing techniques forsake exact (numerical or Boolean) equivalence in the execution of some of the application’s computations, while ensuring that the output quality is acceptable. While early efforts in approximate computing have demonstrated great potential, they consist of ad hoc techniques applied to a very narrow set of applications, leaving in question the applicability of approximate computing in a broader context.

The primary objective of this thesis is ...


A Unicorn's Tale: Examining The Experiences Of Black Women In Engineering Industry, Monique S. Ross Dec 2016

A Unicorn's Tale: Examining The Experiences Of Black Women In Engineering Industry, Monique S. Ross

Open Access Dissertations

Black women have recently been identified as the most educated demographic in the United States, and yet they are grossly underrepresented in engineering. They comprise 6.4 % of the U.S. population and only 0.72 % of engineering industry. Meanwhile, engineers have been identified as the key to the United States’ ability to maintain its prominence and leadership in a competitive global economy due to their contribution to maintaining and improving our infrastructures and standard of living. This significance to society has spawned national initiatives geared towards broadening participation in engineering. This research study was designed to explore the experiences ...


Fea Methodology For System-Level Redundancy Evaluation: Application To Non-Composite Steel Bridges, Francisco Javier Bonachera Martin Dec 2016

Fea Methodology For System-Level Redundancy Evaluation: Application To Non-Composite Steel Bridges, Francisco Javier Bonachera Martin

Open Access Dissertations

Currently, all steel bridges with members designated as Fracture Critical Members (FCMs) are required to undergo hands-on inspections every 24 months. A FCM is a primary steel tension member (or portion of) which failure results in collapse or loss of serviceability of a bridge. However, presently, there are no codified procedures used to evaluate system-level redundancy in steel bridges. In this dissertation, finite element analysis (FEA) procedures, techniques and inputs were researched in order to develop bridge models that account for the mechanisms that lead to redundant capacity after the failure of a primary steel member. These mechanisms include partial ...


Energy Localization And Heat Generation In Composite Energetic Systems Under High-Frequency Mechanical Excitation, Jesus O. Mares Dec 2016

Energy Localization And Heat Generation In Composite Energetic Systems Under High-Frequency Mechanical Excitation, Jesus O. Mares

Open Access Dissertations

In this work, the ability to use high frequency mechanical excitation to generate significant heating within plastic bonded explosives, as well as single energetic particles embedded within a viscoelastic binder, is studied. In this work, the fundamental mechanisms associated with the conversion of high-frequency mechanical excitation to heat as applied to these composite energetic systems are thoroughly investigated.

High-frequency contact excitation has been used to generate a significant amount of heat within samples of PBX 9501 and representative inert mock materials. Surface temperature rises on the order of 10 °C were observed at certain frequencies over a range from 50 ...


What Broke Where For Distributed And Parallel Applications — A Whodunit Story, Subrata Mitra Dec 2016

What Broke Where For Distributed And Parallel Applications — A Whodunit Story, Subrata Mitra

Open Access Dissertations

Detection, diagnosis and mitigation of performance problems in today's large-scale distributed and parallel systems is a difficult task. These large distributed and parallel systems are composed of various complex software and hardware components. When the system experiences some performance or correctness problem, developers struggle to understand the root cause of the problem and fix in a timely manner. In my thesis, I address these three components of the performance problems in computer systems. First, we focus on diagnosing performance problems in large-scale parallel applications running on supercomputers. We developed techniques to localize the performance problem for root-cause analysis. Parallel ...


Modifying Burning Rate And Agglomeration Size In Aluminized Composite Solid Propellants Using Mechanically Activated Metals, Hatem Mohamed Belal Dec 2016

Modifying Burning Rate And Agglomeration Size In Aluminized Composite Solid Propellants Using Mechanically Activated Metals, Hatem Mohamed Belal

Open Access Dissertations

Agglomeration reduction techniques are important field in solid propellant industry, Large agglomeration results in excessive two phase losses. Tailored composite particles has been applied to tailor aluminum particle ignition and combustion. In this research, mechanical activated aluminum magnesium powders are synthesized, tested in both laser ignition using CO2 and propellant. Prepared powders categorized into particle size that suitable for propellant application. Laser ignition tests showed that the prepared powder are more reactive than magnalium which has the same Al:Mg weight ratio. Agglomeration capturing showed that the prepared powder produce much less than neat aluminum or even similar physical mixture ...


Bridge Maintenance To Enhance Corrosion Resistance And Performance Of Steel Girder Bridges, Luis M. Moran Yanez Dec 2016

Bridge Maintenance To Enhance Corrosion Resistance And Performance Of Steel Girder Bridges, Luis M. Moran Yanez

Open Access Dissertations

The integrity and efficiency of any national highway system relies on the condition of the various components. Bridges are fundamental elements of a highway system, representing an important investment and a strategic link that facilitates the transport of persons and goods. The cost to rehabilitate or replace a highway bridge represents an important expenditure to the owner, who needs to evaluate the correct time to assume that cost. Among the several factors that affect the condition of steel highway bridges, corrosion is identified as the main problem. In the USA corrosion is the primary cause of structurally deficient steel bridges ...


Impact Of Rfid Information-Sharing Coordination Over A Supply Chain With Reverse Logistics, Juan Jose Nativi Nicolau Dec 2016

Impact Of Rfid Information-Sharing Coordination Over A Supply Chain With Reverse Logistics, Juan Jose Nativi Nicolau

Open Access Dissertations

Companies have adopted environmental practices such as reverse logistics over the past few decades. However, studies show that aligning partners inside the green supply chain can be a substantial problem. This lack of coordination can increase overall supply chain cost. Information technology such as Radio Frequency Identification (RFID) has the potential to enable decentralized supply chain coordinate their information. Even though there are research that address RFID on traditional supply chain, few researches address how to coordinate RFID information sharing in a green supply chain. We study, through simulation experiments, two types of RFID information-sharing coordination under different configurations related ...


Matrix-Free Time-Domain Methods For General Electromagnetic Analysis, Jin Yan Dec 2016

Matrix-Free Time-Domain Methods For General Electromagnetic Analysis, Jin Yan

Open Access Dissertations

Many engineering challenges demand an efficient computational solution of large-scale problems. If a computational method can be made free of matrix solutions, then it has a potential of solving very large scale problems. Among existing computational electromagnetic methods, the explicit finite-difference time-domain (FDTD) method is free of matrix solutions. However, it requires a structured orthogonal grid for space discretization. In this work, we develop a new time-domain method that naturally requires no matrix solution, regardless of whether the discretization is a structured grid or an unstructured mesh. No dual mesh, interpolation, projection and mass lumping are needed. Furthermore, a time-marching ...


Computer Vision-Based Structural Assessment Exploiting Large Volumes Of Images, Chul Min Yeum Dec 2016

Computer Vision-Based Structural Assessment Exploiting Large Volumes Of Images, Chul Min Yeum

Open Access Dissertations

Visual assessment is a process to understand the state of a structure based on evaluations originating from visual information. Recent advances in computer vision to explore new sensors, sensing platforms and high-performance computing have shed light on the potential for vision-based visual assessment in civil engineering structures. The use of low-cost, high-resolution visual sensors in conjunction with mobile and aerial platforms can overcome spatial and temporal limitations typically associated with other forms of sensing in civil structures. Also, GPU-accelerated and parallel computing offer unprecedented speed and performance, accelerating processing the collected visual data. However, despite the enormous endeavor in past ...


Photoelectrochemical And Photophysical Studies Of Carbon Nanotube And Molybdenum Disulfide Based Light Harvesting Devices, Hanyu Zhang Dec 2016

Photoelectrochemical And Photophysical Studies Of Carbon Nanotube And Molybdenum Disulfide Based Light Harvesting Devices, Hanyu Zhang

Open Access Dissertations

There is a critical need in utilizing solar radiation as a renewable energy source. While photovoltaic solar cells are widely used, much attention has been devoted in the past decade to developing nanotechnology for potential cost reduction and improved device efficiency and reliability. Low-dimensional materials offer unique physical properties which may be exploited for solar energy harvesting and conversion. Understanding their fundamental properties and developing relevant manufacturing strategies will thus pave the road toward high-performance, cost-effective, light-harvesting devices.

This thesis has investigated single-wall carbon nanotubes (SWCNTs) and molybdenum disulfide (MoS2) nanolayers for their light-harvesting ability in donor-acceptor systems. These materials ...


Identifying And Prioritizing Critical Success Factors For Fixed Base Operators In The United States: A Mixed Method Approach, Yu Wang Dec 2016

Identifying And Prioritizing Critical Success Factors For Fixed Base Operators In The United States: A Mixed Method Approach, Yu Wang

Open Access Dissertations

Fixed Base Operators (FBOs) are major service providers for the general aviation (GA) sector, which closely connect the public with the aviation industry. However, over the past decade, the U.S. GA industry has experienced a decline in the numbers of registered aircraft, pilots, and airports. Due to the fact that FBOs significantly contribute to the aviation industry, further research studies regarding the FBO-sector at a national level are needed. The purpose of this dissertation was to identify and prioritize the critical success factors (CSFs) that promote the success of FBO operations in the United States.

The methodology consisted of ...


Fundamental Studies Of Flame Propagation In Lean-Burn Natural Gas Engines, Zhiyan Wang Dec 2016

Fundamental Studies Of Flame Propagation In Lean-Burn Natural Gas Engines, Zhiyan Wang

Open Access Dissertations

Lean-burn natural gas engines offer enhanced thermal efficiencies and reduced soot and NOx emissions. However, cycle-to-cycle variability in combustion that can result from unreliable ignition, variability in equivalence ratio and quenching is a challenge. Reliability of ignition can be improved by employing a dual-fuel ignition strategy in which a small quantity of diesel fuel is injected to initiate ignition. Computational studies of n-heptane/methane-air mixing layers are performed to provide insight into the fundamental physics of dual-fuel ignition. The results show that the characteristic time required for steady premixed flame propagation has three components: time for autoignition to occur, time ...


On The Use Of Mechanical And Acoustical Excitations For Selective Heat Generation In Polymer-Bonded Energetic Materials, Daniel C. Woods Dec 2016

On The Use Of Mechanical And Acoustical Excitations For Selective Heat Generation In Polymer-Bonded Energetic Materials, Daniel C. Woods

Open Access Dissertations

To address security issues in both military and civilian settings, there is a pressing need for improved explosives detection technologies suitable for trace vapor detection. In light of the strong dependence of vapor pressure on temperature, trace vapor detection capabilities may be enhanced by selectively heating target materials by external excitation. Moreover, polymer-bonded energetic materials may be particularly susceptible to heating by mechanical or acoustical excitation, due to the high levels of damping and low thermal conductivities of most polymers. In this work, the thermomechanical response of polymer-based energetic composites and methods for acoustical excitation are investigated in order to ...


Improving Programmability And Performance For Scientific Applications, Chenyang Liu Dec 2016

Improving Programmability And Performance For Scientific Applications, Chenyang Liu

Open Access Dissertations

With modern advancements in hardware and software technology scaling towards new limits, our compute machines are reaching new potentials to tackle more challenging problems. While the size and complexity of both the problems and solutions increases, the programming methodologies must remain at a level that can be understood by programmers and scientists alike. In our work, this problem is encountered when developing an optimized framework to best exploit the semantic properties of a finite-element solver. In efforts to address this problem, we explore programming and runtime models which decouple algorithmic complexity, parallelism concerns, and hardware mapping. We build upon these ...


Laser-Processed Parchment Paper For Fabrication Of Chronic Wound Dressings With Selective Oxygenation, Manuel Ochoa Dec 2016

Laser-Processed Parchment Paper For Fabrication Of Chronic Wound Dressings With Selective Oxygenation, Manuel Ochoa

Open Access Dissertations

Chronic non-healing wounds (e.g., diabetic foot ulcers and bed sores) impact over 6.5 million Americans per year, costs in excess of $25 billion to treat on an annual basis, and are on the rise due to increasing levels of obesity and diabetes compounded by an aging population. A major inhibitor of healing is suboptimal oxygenation of the wound bed. Unlike acute injuries that receive sufficient oxygen via a functional blood vessel network, chronic wounds often suffer from the lack of a proper vascular network; thus being incapable of providing sufficient oxygen for tissue growth. Typical medical treatment of ...


Development Of Inverse Methods For Reconstruction Of Flight Environments On Ablators, A. Brandon Oliver Dec 2016

Development Of Inverse Methods For Reconstruction Of Flight Environments On Ablators, A. Brandon Oliver

Open Access Dissertations

Obtaining measurements of flight environments on ablative heatshields is both critical for spacecraft development and extremely challenging due to the harsh heating environment and surface recession. Thermocouples installed several millimeters below the surface are commonly used to measure the heatshield temperature response, but an ill-posed inverse heat conduction problem must be solved to reconstruct the surface heating environment from the embedded thermocouple measurements. The material properties of typical ablators make the reconstruction process more challenging when the measurements are deep, but measurements often must be located deep to allow for surface recession. Compounding the complexity of the surface reconstruction problem ...


Thermomechanical Properties Of Novel Lanthanum Zirconate Based Thermal Barrier Coatings - An Integrated Experimental And Modeling Study, Xingye Guo Dec 2016

Thermomechanical Properties Of Novel Lanthanum Zirconate Based Thermal Barrier Coatings - An Integrated Experimental And Modeling Study, Xingye Guo

Open Access Dissertations

Thermal barrier coatings (TBCs) are refractory materials deposited on gas turbine components, which provide thermal protection for metallic components at operating conditions. The current state-of-art TBC material is yttria-stabilized zirconia (YSZ), whose service temperature is limited to 1200 celsius, due to sintering and phase transition at higher temperatures. In comparison, lanthanum zirconate (La2Zr2O7, LZ) has become a promising candidate material for TBCs due to its lower thermal conductivity and higher phase stability compared to YSZ.

The primary objective of this thesis is to design a novel robust LZ-based TBC system suitable for applications beyond 1200 celsius. Due to LZ’s ...


Modeling Methods For Merging Computational And Experimental Aerodynamic Pressure Data, Jacob Courtney Haderlie Dec 2016

Modeling Methods For Merging Computational And Experimental Aerodynamic Pressure Data, Jacob Courtney Haderlie

Open Access Dissertations

This research describes a process to model surface pressure data sets as a function of wing geometry from computational and wind tunnel sources and then merge them into a single predicted value. The described merging process will enable engineers to integrate these data sets with the goal of utilizing the advantages of each data source while overcoming the limitations of both; this provides a single, combined data set to support analysis and design. The main challenge with this process is accurately representing each data source everywhere on the wing. Additionally, this effort demonstrates methods to model wind tunnel pressure data ...


Statistical Modeling And Simulation Of Variability And Reliability Of Cmos Technology, Khaled Hassan Md Dec 2016

Statistical Modeling And Simulation Of Variability And Reliability Of Cmos Technology, Khaled Hassan Md

Open Access Dissertations

The introduction of High-κ Metal Gate transistors led to higher integration density, low leakage current, and faster switching speed. However, this transition in technology roadmap brought about new failure mechanisms such as Positive Bias Temperature Instability and Stress Induced Leakage Current. In addition, the relentless downscaling of devices to keep up with Moore's law has significantly increased the time-zero variability caused by Random Dopant Fluctuation, Mean Gate Length Deviation, and Line Edge Roughness. Because of their possible correlation with time dependent aging effects, the quantification of reliability has become more complex than ever. To that effect, we propose a ...