Engineering Commons^™

Source Code Retrieval From Large Software Libraries For Automatic Bug Localization, Bunyamin Sisman

Open Access Dissertations

This dissertation advances the state-of-the-art in information retrieval (IR) based approaches to automatic bug localization in software. In an IR-based approach, one first creates a search engine using a probabilistic or a deterministic model for the files in a software library. Subsequently, a bug report is treated as a query to the search engine for retrieving the files relevant to the bug. With regard to the new work presented, we first demonstrate the importance of taking version histories of the files into account for achieving significant improvements in the precision with which the files related to a bug are located. …

Mechanisms Of Microstructure Formation Under The Influence Of Ultrasonic Vibrations, Milan Rakita

Open Access Dissertations

Positive effects of ultrasound on crystallization have been known for almost 90 years. Application of ultrasound has been very successful in many industries, most notably in chemistry, creating a new branch of science - sonochemistry. However, ultrasonication has not found wide commercial application in the solidification processing. The reason for that is the complexity of underlying phenomena and the lack of predicting models which correlate processing parameters with the properties of a product. The purpose of this study is to give some contribution toward better understanding of mechanisms that lead to changes in the solidifying microstructure. It has been found …

Design, Development, And Testing Of A Conformal Power Control Interface For Thrust Vectoring Aircraft, David Rozovski

Open Access Dissertations

Over the last five years, a new power control inceptor for tiltrotor aircraft, known as the Rotational Throttle Interface (RTI) was designed and built. Prior to the RTI, no tiltrotor inceptor had been able to simultaneously indicate both the direction and magnitude of thrust conformally. The purpose of the RTI is to provide an interface that maps to the intended vehicle response throughout ALL ranges of operation. Doing so is expected to reduce confusion that may have contributed to several tiltrotor accidents

Two tests were conducted with the RTI, one at the NASA Vertical Motion Simulator, and one at Canada's …

Redefining The Operation And Design Considerations Of Organic Solar Cells: Role Of Morphology And Defect States, Biswajit Ray

Open Access Dissertations

Organic photovoltaic (OPV) technology is currently a topic of great interest for potentially low cost solar energy conversion and possibility of many novel PV applications (e.g., building-integrated PV, portable solar cells). Successful commercialization of this technology, however, will require significant improvement in efficiency and lifetime. In the last few years, innovation in novel polymer synthesis has raised the efficiency of OPV above 10%, at par with a-Si and earth-abundant solar cells. Further improvement in performance relies on breakthroughs in device design, which requires profound understanding of the physics of device operation. A major challenge in the design of the state …

Influence Of Strand Debonding On The Shear Strength Of Prestressed Concrete, Michael David Wesson

Open Access Dissertations

Strand debonding is a common method used to reduce flexural stresses caused by prestress transfer in the end regions of pretensioned concrete beams. Debonding is especially useful when section geometries prohibit draping such as U-beams. Based on concerns regarding shear strength, the AASHTO bridge design specification currently limits the percentage of strands that can be debonded. These limits have been found in practice to limit both the efficiency and economy of bridge girders. For this reason, a number of states chose to ignore these limits. The objective of this research is to improve the understanding of the influence of debonding …

Filter Synthesis And Design Techniques For Highly Adaptable Systems, Eric James Naglich

Open Access Dissertations

Software defined radio and cognitive radio (SDR/CR) are promising concepts toward more optimally using the electromagnetic spectrum for communications and data transfer. These systems are highly agile in terms of modulation technique and frequency of operation due to early digitization and software processing of received radio frequency signals. However, the front ends of SDR/CR systems often use static antennas and switched banks of static, wide bandwidth filters before the digitization process. These components limit the ability of SDR/CR systems to operate in environments with high levels of interference and are therefore a bottleneck in the path to achieving optimal adaptation …

Utilizing Electron Microscopy And Spectroscopy Methods To Understand Water Structure And Water Doping, Lior Miller

Open Access Dissertations

Water is the second most common element in the universe and the most studied material on earth. Most of the studies concerning water are from the fields of chemistry and biology. Hence, the structure of water molecules and short range order and interactions are well characterized and understood. However, the collective arrangement of water molecules and the long range order are still missing. Understanding of this long range order in water is needed, as it is the key to many water activities.

To fill this gap, this study utilizes a new direct method for characterization of water in the vapor …

The Effect Of Composition On The Linear And Nonlinear Mechanical Properties Of Particulate Filled Elastomers, Oluwaseyi Ogebule

Open Access Dissertations

Engineering elastomers are materials capable of undergoing large deformation upon load application and recovering upon load removal. From car tires to building vibration isolator systems, elastomers are the most versatile of engineering materials. The inclusion of particulate fillers into elastomers enhances their mechanical properties (modulus, tensile strength, toughness, tear resistance, etc) thereby extending their applicability to more demanding functions. The automotive, healthcare, construction, adhesives and consumer products are some of the many industries that produce finished goods containing elastomeric parts.

Despite the various concepts on reinforcement in filled elastomers, a complete understanding of their linear viscoelastic properties and the nonlinear …

Energy Systems Analysis For A Solar Economy, Dharik Sanchan Mallapragada

Open Access Dissertations

The use of solar energy for human needs faces challenges owing to its relatively low energy intensity and intermittent availability, coupled with the constrained availability of renewable carbon and land resources. This study uses systems analysis tools to identify carbon and energy efficient transformations of solar energy for different purposes, including transportation fuels and grid-scale energy storage. These efforts have been complemented with a feasibility analysis of existing fossil-energy and other hybrid pathways.

In an era of limited fossil resources, liquid fuels from sustainably available (SA) biomass could meet the energy needs of the transportation sector. We present a method …

Mispronunciation Detection For Language Learning And Speech Recognition Adaptation, Zhenhao Ge

Open Access Dissertations

The areas of "mispronunciation detection" (or "accent detection" more specifically) within the speech recognition community are receiving increased attention now. Two application areas, namely language learning and speech recognition adaptation, are largely driving this research interest and are the focal points of this work.

There are a number of Computer Aided Language Learning (CALL) systems with Computer Aided Pronunciation Training (CAPT) techniques that have been developed. In this thesis, a new HMM-based text-dependent mispronunciation system is introduced using text Adaptive Frequency Cepstral Coefficients (AFCCs). It is shown that this system outperforms the conventional HMM method based on Mel Frequency Cepstral …

Image Reconstruction For X-Ray Computed Tomography In Security Screening Applications, Sherman Jordan Kisner

Open Access Dissertations

X-ray tomographic systems have increasingly widespread use in security screening applications. For example, most major airports now utilize X-ray CT

systems for efficient screening of baggage and cargo. While decades of research has benefited CT for medical diagnostics, a number of practical differences in the security application present a new set of challenges for the reconstruction problem. For example, the size and composition of the scan subjects, the throughput requirements, and the measure of image quality are

all factors that lead to a different set of design considerations. This thesis investigates the application of model-based iterative reconstruction (MBIR) methods for …

Spacecraft Orbit Design In The Circular Restricted Three-Body Problem Using Higher-Dimensional Poincaré Maps, Christopher D. Geisel

Open Access Dissertations

Strategies for designing three-dimensional spacecraft trajectories in a multi-body dynamical environment are investigated using four-dimensional Poincaré maps. Unlike the planar circular restricted three-body problem, where a two-dimensional map provides a simplified view of a portion of the vast and often chaotic design space, the spatial problem requires a four-dimensional map to achieve an equivalent perspective. Such higher-dimensional maps present a visualization challenge. Furthermore, a spacecraft in the spatial problem can exhibit fundamentally more diverse and complex behavior than in the planar problem. A novel approach to four-dimensional-map-based design in the spatial circular restricted three-body problem is developed and applied to …

Ant: A Framework For Increasing The Efficiency Of Sequential Debugging Techniques With Parallel Programs, Jae-Woo Lee

Open Access Dissertations

Bugs in sequential programs cost the software industry billions of dollars in lost productivity each year. Even if simple parallel programming models are created, they will not reduce the level of sequential bugs in programs below that of sequential programs. It can be argued that the complexity of current parallel programming models may increase the number of sequential bugs in parallel programs because they distract the programmer from the core logic of the program.

Tools exist that identify statements related to sequential bugs and allow those bugs to be more quickly located and fixed. Their use in parallel programs will …

An Experimental Investigation Of Wind Turbine Aerodynamic Interaction, Brandon Lee Ennis

Open Access Dissertations

Wind turbines have become a viable component in the overall energy makeup of the United States due to improved economics where energy prices have risen and production costs dropped. For a fixed cost, the effectiveness of a wind turbine financially is highly related to its performance. Considering the size of current wind farms, a minor performance improvement will result in large additional sums of revenue. A problem that has received attention with wind farms is that while the fixed costs of the development do get spread out further to reduce the installed cost of each wind turbine, the wind turbines …

Wireless Sensors For Condition Monitoring Applications Operating In Complete Metallic Environment, Lokesh Anilkumar Gupta

Open Access Dissertations

Condition monitoring of machines is advantageous in predicting failure and estimating machine component lifetime. Continuous monitoring of parameters such as temperature, vibration, and strain using sensors and consequent data analysis can help in reducing machine downtime by taking corrective actions before failure. Various wireless and wired sensors may be attached to critical components such as bearings, gears, mechanical seals, shafts etc. for measurements. These sensors however are often inadequate solutions as wired sensors are dicult to mount on rotating components, especially in millimeter-size spaces that may exist in some of these components. Wireless sensors provide a viable solution for measurements …

Digitally-Assisted Rf Ic Design Techniques For Reliable Performance, Jang Joon Lee

Open Access Dissertations

Semiconductor industries have competitively scaled down CMOS devices to attain benefits of low cost, high performance, and high integration density in digital integrated circuits. On the other hand, deep scaled technologies inextricably accompany a large process variation, supply voltage scaling, and reduction in breakdown voltages of transistors. When it comes to RF/analog IC design, CMOS scaling adversely affects its reliability due to large performance variation and limited linearity. For addressing the issues related to variations and linearity, this research proposes the following digitally-assisted RF circuit design techniques: self-calibration system for RF phase shifters and wide dynamic range LNAs.

Due to …

Student Success: Approaches To Modeling Student Matriculation And Retention, Jien-Jou Lin

Open Access Dissertations

Every year a group of graduates from high schools enter the engineering programs across this country with remarkable academic record. However, as reported in numerous studies, the number of students switching out of engineering majors continues to be an important issue. Previous studies have suggested various factors as predictors for student retention in engineering. To assist the engineering students with timely advising early in their program, an effective prediction model of matriculation and retention in engineering that use available student data are highly desirable.

In the first part of this work, the author developed new prediction models of student retention …

Research On Print Defect Visibility And Evaluation, Xiaochen Jing

Open Access Dissertations

Banding is a well-known artifact produced by printing systems. It usually appears as lines perpendicular to the process direction of the print. Therefore, banding is an important print quality issue which has been analyzed and assessed by many researchers. However, little literature has focused on the study of the masking effect of content for this kind of print quality issue. Compared with other image and print quality research, our work is focused on the print quality of typical documents printed on a digital commercial printing press. In this paper, we propose a Masking Mediated Print Defect Visibility Predictor (MMPDVP) to …

Response Of Plasma Facing Components In Tokamaks Due To Intense Energy Deposition Using Particle-In-Cell(Pic) Methods, Filippo Genco

Open Access Dissertations

Damage to plasma-facing components (PFC) due to various plasma instabilities is still a major concern for the successful development of fusion energy and represents a significant research obstacle in the community. It is of great importance to fully understand the behavior and lifetime expectancy of PFC under both low energy cycles during normal events and highly energetic events as disruptions, Edge-Localized Modes (ELM), Vertical Displacement Events (VDE), and Run-away electron (RE). The consequences of these high energetic dumps with energy fluxes ranging from 10 MJ/m2 up to 200 MJ/m2 applied in very short periods (0.1 to 5 ms) can be …

Electric Machine Differential For Vehicle Traction Control And Stability Control, Sandun Shivantha Kuruppu

Open Access Dissertations

Evolving requirements in energy efficiency and tightening regulations for reliable electric drivetrains drive the advancement of the hybrid electric (HEV) and full electric vehicle (EV) technology. Different configurations of EV and HEV architectures are evaluated for their performance. The future technology is trending towards utilizing distinctive properties in electric machines to not only to improve efficiency but also to realize advanced road adhesion controls and vehicle stability controls. Electric machine differential (EMD) is such a concept under current investigation for applications in the near future. Reliability of a power train is critical. Therefore, sophisticated fault detection schemes are essential in …

Algorithmic And Mathematical Programming Approaches To Scheduling Problems With Energy-Based Objectives, Kan Fang

Open Access Dissertations

This dissertation studies scheduling as a means to address the increasing concerns related to energy consumption and electricity cost in manufacturing enterprises. Two classes of problems are considered in this dissertation: (i) minimizing the makespan in a permutation flow shop with peak power consumption constraints (the PFSPP problem for short) and (ii) minimizing the total electricity cost on a single machine under time-of-use tariffs (the SMSEC problem for short). We incorporate the technology of dynamic speed scaling and the variable pricing of electricity into these scheduling problems to improve energy efficiency in manufacturing.The challenge in the PFSPP problem is to …

Human Cognitive Performance In Healthcare Information System Environment And Its Application On Nursing Tasks, Byung Cheol Lee

Open Access Dissertations

The US healthcare system has serious issues in care quality and patient safety. Patients often do not receive the care they need or the given care service cause harm. In addition, the significant amounts of medical and medication errors occur, and recurring adverse drug events due to damaging side effects from medications threaten patient safety. To solve these issues, healthcare information systems (HIS) have been recommended in various care processes. Though several studies have confirmed the benefits and usefulness of the systems (Cordero, Kuehn, Kumar, & Mekhjian, 2004; Kohn, Corrigan, & Donaldson, 2000; Sittig, Krall, Kaalaas-Sittig, & Ash, 2005; Weiner …

Engineering Students At Typically Invisible Transition Points: A Focus On Admissions And The Sophomore Year, Elizabeth M. Holloway

Open Access Dissertations

As of 2012, women are approximately 19% of all engineering undergraduate students nationally (American Society for Engineering Education, 2012). Women's representation in engineering has not changed significantly over the last 20 years, despite increased attention, increased funding, and increased programmatic activities intended to encourage more women to become engineers. Research around the world continues to seek identification of the reasons for the underrepresentation of women in engineering. This prior work has focused primarily on two broad areas: recruiting, that is, preparation, socialization, exposure, and experiences prior to college; and retention, that is, experiences in higher education. Retention studies and programmatic …

Near-Field Pressure Distributions To Enhance Sound Transmission Into Multi-Layer Materials, Andrew Martin Jessop

Open Access Dissertations

The large impedance difference between air and most solids prevents significant energy transfer from incident acoustic waves across the air-material interface. Refraction also plays a role in preventing acoustic transmission, as the wave speed difference between air and solid materials results in an increase of the resulting propagation angles, creating near-field pressure distributions in the solid material. By utilizing evanescent pressure distributions, which decay normal to the usual direction of propagation and are represented as plane waves propagating with complex angles, energy propagation through the interface can be increased in the subsonic region of wave propagation: i.e., where waves typically …

Hybrid And Smart Topologically Interlocking Materials, Somesh Khandelwal

Open Access Dissertations

This thesis explores the mechanical properties of a new class of multifunctional architectured materials, Topologically Interlocking Materials (TIMs). These materials are created as an assembly of unit elements arranged in an interlocking pattern such that the load transfer between unit elements occurs by contact only. In the absence of adhesive interaction, the tensile component of the load is carried by complementary tensile elements in the form of external constraints or integrated filaments. By virtue of the bottom up design used in creating these materials, their mechanical properties are influenced by a number of controllable parameters including shape, confinement force, scale, …

Multiscale Simulation Of Thermocline Energy Storage For Concentrating Solar Power, Scott Michael Flueckiger

Open Access Dissertations

Concentrating solar power (CSP) is a renewable and demonstrated technology for large-scale power generation but requires multiple engineering advancements to achieve grid parity with conventional fossil fuels. Part of this advancement includes novel and inexpensive thermal energy systems to decouple daily power production from intermittent solar collection. Dual-media thermocline tanks, composed of molten salt and solid rock filler, offer low-cost storage capability but the concept has experienced limited deployment in CSP plants due to unresolved concerns about long-term thermal and structural stability. The main objective of the present work is to advance the understanding of thermocline storage design and operation …

The Application And Analysis Of Automated Triangulation Of Video Imagery By Successive Relative Orientation, Jae Sung Kim

Open Access Dissertations

The purpose of this thesis is the analysis and evaluation of methods to orient a strip of images using an automated approach. Automatic orientation of strips of video frame imagery would facilitate the construction of three dimensional models with less demand on a human operator for tedious measurement. Often one has no control points, so only relative orientation is possible. The relative orientation process gives camera parameters such as attitudes and selected baseline components and it can be implemented by using either collinearity or coplanarity equations. To automate the point selection, the pass and/or tie points were detected by the …

Using X-Ray Imaging Techniques To Determine Density Of Foods, Shivangi Mohan Kelkar

Open Access Dissertations

Density depends on the experimental technique and structural properties of food. True, apparent and bulk are different types of densities. For porous foods such as baked food products and complex food systems, accurate measurement of density is challenging. Empirical correlations dependent on composition and temperature exist to calculate true density. Thus if composition and apparent density are known, porosity can be calculated, porosity = [1 - (apparent density/ true density)]. Various non-destructive diagnostic tools have been employed to study food microstructure. Among these, computed tomography (CT) and digital radiography (DR) utilizing x-ray imaging showed greater capability for evaluation of food …

Developing A Drug Delivery System For Treatment Of Vocal Fold Scarring, Aaron Michael Kosinski

Open Access Dissertations

Vocal fold scarring is an affliction that results in the formation of a disorganized and stiff extracellular matrix (ECM) with abnormal ECM component densities & structures including a significant increase in collagen deposition. It is caused by improper healing post injury and results in profound changes in the biomechanical properties of the vocal folds impairing their ability to generate a normal mucosal wave during phonation.

Finding an effective treatment for vocal fold scarring has been elusive. Currently, treatments seek temporary solutions that correct glottal incompetence and reduce stiffness caused by the scar through the augmentation of the vocal folds using …

Graphene Decorated Substrates And Their Interfacial Characteristics, Anurag Kumar

Open Access Dissertations

Carbon nanotubes and graphene have been extensively studied for their excellent properties. As research on carbon expands, two major issues face the scientific community: (i) Expanding the scale of synthesis and (ii) Integration of different carbon structures for improved functionality. While significant advancements have been made in large-scale synthesis, room for improvement remains. As the scale of production increases, issues such as time, cost and energy that may otherwise not be very significant, begin to play greater roles. Thus, in order to effectively transition from laboratory prototypes to industrial products, a synthesis method that can address these issues is strongly …