Engineering Commons^™

Experimental Investigation Of Ultrawideband Wireless Systems: Waveform Generation, Propagation Estimation, And Dispersion Compensation, Amir Dezfooliyan

Open Access Dissertations

Ultrawideband (UWB) is an emerging technology for the future high-speed wireless communication systems. Although this technology offers several unique advantages like robustness to fading, large channel capacity and strong anti-jamming ability, there are a number of practical challenges which are topics of current research. One key challenge is the increased multipath dispersion which results because of the fine temporal resolution. The received response consists of different components, which have certain delays and attenuations due to the paths they took in their propagation from the transmitter to the receiver. Although such challenges have been investigated to some extent, they have not …

Semiconductor Nanomaterial Development For Photovoltaic And Thermoelectric Applications, Liangliang Chen

Open Access Dissertations

Today's world is frequently going through fossil energy shortage and environmental consequences brought by the over-emission of greenhouse gas from burning fossil fuels. Therefore, it is urgent now more than ever to discover or develop clean and sustainable power generation approaches. Among various approaches, photovoltaics and thermoelectrics have been more and more attentive both in academia and industry. Photovoltaic power generators can significantly decrease carbon dioxide emission by directly converting sunlight into electricity, and thermoelectric power generators can increase energy use efficiency by recycling waste heat into electricity. This research seeks to gain a better understanding of the mechanism that …

High-Power Microwave/ Radio-Frequency Components, Circuits, And Subsystems For Next-Generation Wireless Radio Front-Ends, Kenle Chen

Open Access Dissertations

As the wireless communication systems evolve toward the future generation, intelligence will be the main signature/trend, well known as the concepts of cognitive and software-defined radios which offer ultimate data transmission speed, spectrum access, and user capacity. During this evolution, the human society may experience another round of `information revolution'. However, one of the major bottlenecks of this promotion lies in hardware realization, since all the aforementioned intelligent systems are required to cover a broad frequency range to support multiple communication bands and dissimilar standards. As the essential part of the hardware, power amplifiers (PAs) capable of operating over a …

Atomic Level Study Of Water-Gas Shift Catalysts Via Transmission Electron Microscopy And X-Ray Spectroscopy, Mehmed Cem Akatay

Open Access Dissertations

Water-gas shift (WGS), CO + H₂ O [Special characters omitted.] CO₂ + H₂ (ΔH° = -41 kJ mol ^-1 ), is an industrially important reaction for the production of high purity hydrogen. Commercial Cu/ZnO/Al₂ O₃ catalystsare employed to accelerate this reaction, yet these catalysts suffer from certain drawbacks, including costly regeneration processes and sulfur poisoning. Extensive research is focused on developing new catalysts to replace the current technology. Supported noble metals stand out as promising candidates, yet comprise intricate nanostructures complicating the understanding of their working mechanism.

In this study, the structure of the supported …

Spectroscopic And Kinetic Study Of Copper-Exchanged Zeolites For The Selective Catalytic Reduction Of Nox With Ammonia, Shane Adam Bates

Open Access Dissertations

The recent application of metal-exchanged, small-pore zeolites for use in the selective catalytic reduction (SCR) of NO_x with ammonia NH₃ for automotive deNO_x applications has been a great stride in achieving emission standard goals. Copper-exchanged SSZ-13 (Cu-SSZ-13), the small-pore zeolite in this study, has been shown to be very hydrothermally stable and active under conditions presented in the exhaust of the lean-burn diesel engine. In this work, detailed studies were performed to identify many aspects of the active site(s) in Cu-SSZ-13 in order to learn about the standard SCR mechanism.

A series of seven Cu-SSZ-13 samples were …

Effects Of Hearing Aid Amplification On Robust Neural Coding Of Speech, Jonathan Daniel Boley

Open Access Dissertations

Hearing aids are able to restore some hearing abilities for people with auditory impairments, but background noise remains a significant problem. Unfortunately, we know very little about how speech is encoded in the auditory system, particularly in impaired systems with prosthetic amplifiers. There is growing evidence that relative timing in the neural signals (known as spatiotemporal coding) is important for speech perception, but there is little research that relates spatiotemporal coding and hearing aid amplification.

This research uses a combination of computational modeling and physiological experiments to characterize how hearing aids affect vowel coding in noise at the level of …

Spectroscopic And Kinetic Characterization Of Catalytic Materials For The Conversion Of Biomass-Derived Compounds, Paul James Dietrich

Open Access Dissertations

As economies look to transition away from petroleum for social, economic, and political reasons, biomass will continue to attract attention as a renewable feedstock for the fuels and chemicals industry. In order to turn biomass into end use fuels and chemicals, the oxygen content must be lowered significantly, requiring large hydrogen inputs. For these processes to be completely renewable, the hydrogen must come from biomass or biomass-derived compounds. In this work, catalysts for the aqueous phase reforming (APR) of biomass-derived sugars were characterized by a combination of reaction kinetics, X-ray spectroscopy, electron microscopy, and theoretical computation to determine the active …

Transmit Signal Design For Mimo Radar And Massive Mimo Channel Estimation, Andrew Jason Duly

Open Access Dissertations

The widespread availability of antenna arrays and the capability to independently control signal emissions from each antenna make transmit signal design increasingly important for radar and wireless communication systems. In the rst part of this work, we develop the framework for a MIMO radar transmit scheme which trades o waveform diversity for beampattern directivity. Time-division beamforming consists of a linear precoder that provides direct control of the transmit beampattern and is able to form multiple transmit beams in a single pulse. The MIMO receive ambiguity function, which incorporates the receiver structure, reveals a space and delay-Doppler separability that emphasizes the …

A Novel Multiblock Immersed Boundary Method Enabling High Order Large Eddy Simulation Of Pathological And Medical Device Hemodynamics, Anupindi Kameswararao

Open Access Dissertations

Computational fluid dynamics (CFD) simulations are becoming a reliable tool in understanding disease progression, investigating blood flow patterns and evaluating medical device performance such as stent grafts and mechanical heart valves. Previous studies indicate the presence of highly disturbed, transitional and mildly turbulent flow in healthy and pathological arteries. Accurate simulation of the transitional flow requires high order numerics together with a scale resolving turbulence model such as large eddy simulation (LES). This in turn limits one to use a structured fluid flow solver on which complex, branching arterial domains that are typical in the human blood circulatory system could …

Reasoning Across Language And Vision In Machines And Humans, Andrei Barbu

Open Access Dissertations

Humans not only outperform AI and computer-vision systems, but use an unknown computational mechanism to perform tasks for which no suitable approaches exist. I present work investigating both novel tasks and how humans approach them in the context of computer vision and linguistics. I demonstrate a system which, like children, acquires high-level linguistic knowledge about the world. Robots learn to play physically-instantiated board games and use that knowledge to engage in physical play. To further integrate language and vision I develop an approach which produces rich sentential descriptions of events depicted in videos. I then show how to simultaneously detect …

Advanced Control Strategies For Mobile Hydraulic Applications, Davide Cristofori

Open Access Dissertations

Mobile hydraulic machines are affected by numerous undesired dynamics, mainly discontinuous motion and vibrations. Over the years, many methods have been developed to limit the extent of those undesired dynamics and improve controllability and safety of operation of the machine. However, in most of the cases, today's methods do not significantly differ from those developed in a time when electronic controllers were slower and less reliable than they are today.

This dissertation addresses this aspect and presents a unique control method designed to be applicable to all mobile hydraulic machines controlled by proportional directional valves. In particular, the proposed control …

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 …

Improving Multicore Resource Efficiency And Performance, Syed Ali Raza Jafri

Open Access Dissertations

With clock speeds stagnating for the last few years and multi-cores having replaced uniprocessors, software development must now turn towards shared memory parallel programming to continue enhancing performance. Shared memory parallel programming; however is significantly more challenging than its sequential counterpart. Conventional shared memory parallel programs can fall victim to deadlocks, livelocks and data races which are hard to detect and debug. Aside from programming complexity chipmultiprocessors need a scalable, low latency, high bandwidth interconnect fabric to deliver performance. Conventional interconnects such as crossbars and buses can deliver low latency but do not scale with increasing number of cores. Researchers …

Direct And Indirect Greenhouse Gas Emissions From Biomass Storage: Implications For Life Cycle Assessment Of Biofuels, Isaac Robert Emery

Open Access Dissertations

Ethanol and other biofuels from cellulosic feedstocks are currently the most promising candidates to replace a large fraction of gasoline consumption in the United States and reduce greenhouse gas emissions. Gaps in current approaches to estimating the net greenhouse gas emissions from second-generation biofuels may lead to underestimation of the carbon intensity of these fuels. Current life cycle assessment models of biofuels do not sufficiently account for biomass losses and emissions associated with the harvest and storage of biomass feedstocks, which can require additional fuel and materials use on the farm as well as reducing the effective yield of a …

Automatically Optimizing Tree Traversal Algorithms, Youngjoon Jo

Open Access Dissertations

Many domains in computer science, from data-mining to graphics to computational astrophysics, focus heavily on irregular applications. In contrast to regular applications, which operate over dense matrices and arrays, irregular programs manipulate and traverse complex data structures like trees and graphs. As irregular applications operate on ever larger datasets, their performance suffers from poor locality and parallelism. Programmers are burdened with the arduous task of manually tuning such applications for better performance. Generally applicable techniques to optimize irregular applications are highly desired, yet scarce.

In this dissertation, we argue that, for an important subset of irregular programs which arises in …

Solution To Certain Problems In The Failure Of Composite Structures, Jonathan Goodsell

Open Access Dissertations

The present work contains the solution of two problems in composite structures. In the first, an approximate elasticity solution for prediction of the displacement, stress and strain fields within the m-layer, symmetric and balanced angle-ply composite laminate of finite-width subjected anticlastic bending deformation is developed. The solution is shown to recover classical laminated plate theory predictions at interior regions of the laminate and thereby illustrates the boundary layer character of this interlaminar phenomenon. The results exhibit the anticipated response in congruence with the solutions for uniform axial extension and uniform temperature change, where divergence of the interlaminar shearing stress is …

Multiscale Modeling Of The Hierarchical Structure Of Cellulose Nanocrystals, Fernando Luis Dri

Open Access Dissertations

Cellulose constitutes the most abundant renewable polymeric resource available today. It considered an almost inexhaustible source of raw material, and holds great promise in meeting increasing demands for environmentally friendly and biocompatible products. Key future applications are currently under development for the automotive, aerospace and textile industries. When cellulose fibers are subjected to acid hydrolysis, the fibers yield rod-like, highly crystalline residues called cellulose nanocrystals (CNCs). These particles show remarkable mechanical and chemical properties (e.g. Young Modulus ~200 GPa) within the range of other synthetically-developed reinforcement materials. Critical to the design of these materials are fundamental material properties, many of …

Characterization Of Fractures Subjected To Normal And Shear Stress, Min-Kwang Choi

Open Access Dissertations

Results from a series of laboratory experiments to determine fracture specific stiffness, for a fracture subjected to shear and normal stress, are presented and analyzed. The experimental work focuses on the determination of relations between normal and shear fracture specific stiffness and between spatial distribution of fracture specific stiffness and fluid flow through the fracture

The ratio of shear to normal fracture specific stiffness is experimentally investigated on a fracture subjected to shear as well as normal stress. Synthetic fractures made of gypsum and lucite were prepared with different fracture surface conditions: either well-mated or non-mated. For well-mated fracture surfaces, …

Variation-Derived Chip Security And Accelerated Simulation Of Variations, William Paul Griffin

Open Access Dissertations

In modern ICs, variations can be quite troublesome. Ensuring quality and yield requires careful and resource-intensive simulation under the effects of parameter variations. Threshold voltage approximation of parameter variations can help accelerate simulations, but it comes with unknown losses in quality. Instead, we propose a parameter reduction technique designed to minimize quality loss through careful analysis of the source transistor model and the set of input parameter variations. Using Pao-Sah's Double Integral model, we demonstrate the relative quality of our reduced parameter approach versus threshold voltage approximation.

Despite their negative role in circuitry, variations can be useful for security applications. …

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 …

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 …

Resource-Aware Distributed Particle Filtering For Cluster-Based Object Tracking In Wireless Camera Networks, Kihyun Hong

Open Access Dissertations

The proliferation of miniaturized low-power computing devices, advances in wireless communications, and the availability of inexpensive imaging sensors have enabled the development of wireless camera networks (WCN). In this dissertation, we consider the problem of real-time object tracking with a WCN. Existing object tracking methods designed for multi-camera systems do not take into account the unique constraints of WCNs. Specifically, an effective object tracking system for WCNs must anticipate unreliable network communication, limited memory, and limited computational power in each camera node. In particular, unreliable communication degrades the quality of the visual information shared by the cameras, which ultimately degrades …

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 …

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 …

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 …

Manifold Learning Based Spectral Unmixing Of Hyperspectral Remote Sensing Data, Jun-Hwa Chi

Open Access Dissertations

Nonlinear mixing effects inherent in hyperspectral data are not properly represented in linear spectral unmixing models. Although direct nonlinear unmixing models provide capability to capture nonlinear phenomena, they are difficult to formulate and the results are not always generalizable. Manifold learning based spectral unmixing accommodates nonlinearity in the data in the feature extraction stage followed by linear mixing, thereby incorporating some characteristics of nonlinearity while retaining advantages of linear unmixing approaches. Since endmember selection is critical to successful spectral unmixing, it is important to select proper endmembers from the manifold space. However, excessive computational burden hinders development of manifolds for …

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 …

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 …

Modeling The Atomic And Electronic Structure Of Metal-Metal, Metal-Semiconductor And Semiconductor-Oxide Interfaces, Ganesh Krishna Hegde

Open Access Dissertations

The continuous downward scaling of electronic devices has renewed attention on the importance of the role of material interfaces in the functioning of key components in electronic technology in recent times. It has also brought into focus the utility of

atomistic modeling in providing insights from a materials design perspective. In this thesis, a combination of Semi Empirical Tight-Binding (TB), first-principles Density

Functional Theory and Reactive Molecular Dynamics (MD) modeling is used to study aspects of the electronic and atomic structure of three such 'canonical' material interfaces - Metal-Metal, Metal-Semiconductor and Semiconductor oxide interfaces.

An important contribution of this thesis …

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 …