Digital Commons Network^™

Genomic And Physiological Bioremediation Characteristics Of The Actinobacteria Frankia, Erik Swanson

Doctoral Dissertations

Introduction: Frankia is a genus of symbiotic, nitrogen fixing actinobacteria found in the soil and root tissue of actinorhizal plants throughout the world. Both Frankia and actinorhizal plants are resistant to a wide range of environmental and chemical stresses including heavy metals, high salinity, and drought. This makes Frankia and the actinorhizal symbiosis an interesting candidate for bioremediation applications. However, the microbial community found in the actinorhizal rhizosphere and surrounding soil has been implicated in some of the symbiotic and resistance traits attributed to Frankia. This necessitates thorough investigation of the genomic and genetic components of any bioremediation traits possessed …

Micromechanical Modeling And Evaluation Of Process-Induced Residual Stresses In 3d Woven Composites, Kostiantyn Vasylevskyi

Doctoral Dissertations

3D woven carbon/epoxy composites are high-performance materials with superior thermo-mechanical and physical properties making them an integral part of the aerospace, energy and automotive industries. However, under certain manufacturing conditions, these composites may accumulate severe intrinsic manufacturing-induced residual stresses which can even lead to microcracking. The complex reinforcement architecture makes analytical, numerical and experimental analysis of these composites challenging. This research has been focused on micromechanical analysis, computational modeling, and experimental characterization of 3D woven carbon/epoxy composites aiming to evaluate the manufacturing-induced residual stresses and enable mitigation of their negative impact on the resulting performance. A procedure to develop high-fidelity …

Investigation Of Parameter Effects On Impact Welding And Modelling Of Process, Shunyi Zhang

Doctoral Dissertations

There is a growing interest in creating light weight structures in various industries such as automobile, electronics, and aerospace in order to reduce energy consumption. One means to achieve mass reductions is to join or weld dissimilar materials to create lightweight structures. However, traditional fusion welding processes cannot be used for such dissimilar materials applications due to differences in material characteristics and the tendency to form brittle intermetallic compounds. One approach to join dissimilar materials is through high speed impact welding. With appropriate process parameters, a wavy interfacial morphology is commonly obtained at the interface of the two impact welded …

Characterizing Forest Stands Using Unmanned Aerial Systems (Uas) Digital Photogrammetry: Advancements And Challenges In Monitoring Local Scale Forest Composition, Structure, And Health, Benjamin T. Fraser

Doctoral Dissertations

Present-day forests provide a wide variety of ecosystem services to the communities that rely on them. At the same time, these environments face routine and substantial disturbances that direct the need for site-specific, timely, and accurate monitoring/management (i.e., precision forestry). Unmanned Aerial Systems (UAS or UAV) and their associated technologies offer a promising tool for conducting such precision forestry. Now, even with only natural color, uncalibrated, UAS imagery, software workflows involving Structure from Motion (SfM) (i.e., digital photogrammetry) modelling and segmentation can be used to characterize the features of individual trees or forest communities. In this research, we tested the …

Becoming Scientists: Undergraduate Students' Literacy Activities In Laboratory Education, Allison Giannotti

Doctoral Dissertations

In laboratory courses across universities, undergraduate students are learning to act, think, and write like professional scientists. Yet, despite the centrality of language and literacy in laboratory experiments, the process of becoming scientifically literate remains ambiguous. Thus, my dissertation examines how university laboratory courses foster undergraduate students’ emergence as literate professionals and competent communicators in science, technology, engineering, and math (STEM) fields. In particular, it examines undergraduate students’ literate practices, how they change over time, and how they are affected by material and experimental processes in three sequenced, chemistry laboratory courses. Through laboratory observations and interviews with undergraduate students, faculty, …

Implementing Socially Just Climate Adaptation: A Case Study Of Boston, Massachusetts, Jeffrey Thomas Malloy

Doctoral Dissertations

The urgency to adapt to climate change presents important questions about who stands to benefit from these efforts. The previous two decades of scholarship devoted to social justice in climate adaptation has established an important theoretical basis to evaluate these questions. Less understood however, is how and under what conditions climate adaptation policy implementation promotes or inhibits justice for socially vulnerable populations. This work draws upon the disciplines of urban climate change governance, climate adaptation, urban planning, social justice theory, and policy implementation, to evaluate ongoing climate adaptation policy initiatives in Boston, Massachusetts. Through a case study approach, this dissertation …

Experimental Characterization And Crystal Plasticity Modeling Of Mechanical Properties And Microstructure Evolution Of Additively Manufactured Inconel 718 Superalloy, Saeede Ghorbanpour

Doctoral Dissertations

In this thesis, the mechanical behavior of the additively manufactured (AM) IN718 nickel-based superalloy and their correlations with the evolution of microstructure are studied comprehensively. The effects of manufacturing parameters, build orientations, and post processing procedures, i.e. standard heat treatment and hot isostatic pressing (HIP), on various mechanical properties including monotonic compression and tension strength, low cyclic fatigue performance, high cyclic fatigue behaviour, and fatigue crack growth behavior are investigated. Due to the high temperature applications of the IN718 alloy, elevated temperature properties are examined as well. Electron Backscattered Diffraction (EBSD) technique is employed to measure the initial and deformed …

A High-Performance Full-Field Crystal Plasticity Solver Within Finite Elements For Micromechanical Simulation Of Metallic Components Under Large Deformations, Adnan Eghtesad

Doctoral Dissertations

It is undeniable that metals and metallic alloys are of great significance in automotive and aerospace industry. Metallic materials are aggregates of grains (i.e., crystals) in orders of microns. Understanding the behavior of multi-phase metallic structures plays a vital role in automotive and aerospace design and manufacturing industries. Work presented in this dissertation presents a high-performance crystal plasticity solver, capable of performing simulations of massively large data sets in order of few hours instead of months of run. The developed accelerated solver is capable of performing simulations of massively large data sets representing very high-resolution microstructures with tens of millions …

Metareasoning For Heuristic Search Using Uncertainty, Tianyi Gu

Doctoral Dissertations

Heuristic search methods are widely used in many real-world autonomous systems. Yet, people always want to solve search problems that are larger than time allows. To address these challenging problems, even suboptimally, a planning agent should be smart enough to intelligently allocate its computational resources, to think carefully about where in the state space it should spend time searching. For finding optimal solutions, we must examine every node that is not provably too expensive. In contrast, to find suboptimal solutions when under time pressure, we need to be very selective about which nodes to examine. In this dissertation, we will …

Synthesis Of Thioacids And Dicarboxylic Acids Derived From Open Β-Lactams For Inhibition Of Metallo-Β-Lactamases, Junfu Chen

Doctoral Dissertations

Antibiotics are important substances that have been used in clinical treatment for over 70 years. Because of overuse and misuse of antibiotics, bacteria developed resistance. However, bacterial resistance towards antibiotics, especially the β-lactam antibiotics, is becoming increasingly threat. Currently, the β-lactam antibiotics are seriously threatened by β-lactamases. Metallo-β-lactamases (MBLs), a sub-class of β-lactamases, have been found in several bacteria since they confer resistance to many different β-lactams, and as a result, the bacteria survive in their presence. A potential treatment is to synthesize inhibitors of MBLs, however, there are no inhibitors synthesized in clinical use. The goal of this project …

High Level Learning Using The Temporal Features Of Human Demonstrated Sequential Tasks, Madison Brandywine Clark-Turner

Doctoral Dissertations

Modelling human-led demonstrations of high-level sequential tasks is fundamental to a number of practical inference applications including vision-based policy learning and activity recognition. Demonstrations of these tasks are captured as videos with long durations and similar spatial contents. Learning from this data is challenging since inference cannot be conducted solely on spatial feature presence and must instead consider how spatial features play out across time. To be successful these temporal representations must generalize to variations in the duration of activities and be able to capture relationships between events expressed across the scale of an entire video.

Contemporary deep learning architectures …

Molecular Architecture Of Rod Photoreceptor Phosphodiesterase In Its Nonactivated And G-Protein Activated States, Michael Irwin

Doctoral Dissertations

The photoreceptor phosphodiesterase (PDE6) plays an important role in the G-protein coupled visual signaling pathway which uses cGMP as a second messenger to convert light stimuli into electrical signals. PDE6 is a tetrameric peripheral membrane protein consisting of two catalytic subunits and two inhibitory subunits and is localized to the outer segment membranes of rod and cone photoreceptors. Mutations in this enzyme are one cause of retinitis pigmentosa and other retinal degenerative diseases resulting in blindness or visual dysfunction that lack adequate therapeutic intervention due to inadequate knowledge of PDE6 structure and regulation PDE6 is tightly regulated in the nonactivated …

Biologically Inspired Computer Vision/ Applications Of Computational Models Of Primate Visual Systems In Computer Vision And Image Processing, Reza Hojjaty Saeedy

Doctoral Dissertations

Biologically Inspired Computer VisionApplications of Computational Models of Primate Visual Systems in Computer Vision and Image Processing Reza Hojjaty Saeedy Abstract Biological vision systems are remarkable at extracting and analyzing the information that is essential for vital functional needs. They perform all these tasks with both high sensitivity and strong reliability. They can efficiently and quickly solve most of the difficult computa- tional problems that are still challenging for artificial systems, such as scene segmentation, 3D/depth perception, motion recognition, etc. So it is no surprise that biological vision systems have been a source of inspiration for computer vision problems. In …

Cognitive Buffer-Aided Cooperative Networks: Scheduling, Resource Allocation, And Performance Analysis, Omid Moghimi Kandelusy

Doctoral Dissertations

Electromagnetic spectrum, as a limited resource, is prone to scarcity due to the astronomical growth in demands for ubiquitous wireless connectivity in the past few decades. Meeting such an ever-growing demand is contingent upon optimizing the spectrum utilization. In this context, dynamic spectrum access policies, such as spectrum sharing, are promising solutions to mitigate the spectrum gridlock. Spectrum sharing networks are allowed to operate on the licensed frequency bands as the secondary users of the spectrum provided that the licensed primary network is protected from any disruptive interference due to the coexistence. The stringent constraints on the secondary network for …

Multiscale Dynamics Of Energy Transfer Within The Electron Diffusion Region Of Magnetic Reconnection, Dominic Payne

Doctoral Dissertations

During the process of magnetic reconnection, anti-parallel magnetic fields with embedded plasma particles converge and undergo a dramatic topological reconfiguration in the electron diffusion region (EDR) while releasing some of the stored magnetic energy directly into the particles. This process is ubiquitous in natural plasmas, and is responsible for many of the explosive phenomena observed in the Earth's magnetosphere and on the sun. While it has long been established that magnetic reconnection is a plasma energization process, it is still unclear what mechanisms underlie the energy conversion from fields to particles, particularly in the EDR where magnetohydrodynamic (MHD) approximations are …

The Application Of Iron-Based Materials In Aqueous Energy Storage, Fenghua Guo

Doctoral Dissertations

Aqueous energy storage has been an important part of battery research for its cost-effective, environmentally benign, and robust nature. Iron-based materials, including iron hydroxides and iron oxides, are widely investigated as electrode materials for their extremely low cost and sufficient discharge capacity. Iron-based electrode materials were often operated in strong alkaline electrolytes, experiencing either slow reaction kinetics, severe side reactions, or significant capacity loss over cycling. This research focused on the application of iron-based materials in aqueous electrolytes with low alkalinity. This research showed that the synthesized γ-FeOOH measured with a cocktail electrolyte of sodium sulfate and sodium hydroxide demonstrated …

I. Incorporation Of Functionality At The Β-Position For The Zinc-Mediated Chain Extension Reaction Ii. Formal Synthesis Of Heliotridane And Pseudoheliotridane Through A Zinc-Mediated Chain Extension Approach, Nicholas Alexander Arnista

Doctoral Dissertations

The zinc-mediated chain extension reaction has been previously developed to incorporate alkyl or aryl substituents at the β position of the chain-extended product. The incorporation of heteroatom functionality at the β position of the chain-extended product was demonstrated through the use of a functionalized zinc carbenoid species. Silyl ether-functionalized geminal diiodides were used in the chain extension reaction with low to modest yields. Optimization of the chain extension reaction was performed by modification of solvent, reaction temperature, reaction time, and addition of diiodide. The chain extension reaction was performed on several different substrates, such as β-keto esters, β-keto amides, and …

Ligand Design In C-Functionalized Cobalt Cyclams For Hybrid Photocatalytic Co2 Reduction, Ethan Edward Jarvis

Doctoral Dissertations

Global climate change is one of the most significant risks to both the planet and all life on it. The largest contributor to this ever-growing threat is CO2 and its continued emission into the atmosphere. As a result, many scientists are researching CO2 reduction processes to help slow and potentially reverse the climate change by reducing the atmospheric levels of CO2. Ideally, these reduction processes convert CO2 into useful materials such as hydrocarbon-based fuels such as methanol or ethanol, which could also help remove our dependence on finite natural energy resources. CO2 reduction is challenging to do efficiently however, due …

Three Essays In Applied Microeconomics: Spillover Effects Of Anti Discrimination And Anti Violence Policies, Gokhan Kumpas

Doctoral Dissertations

In this research, I examine the intended and unintended consequences of three highly debated policies at the state and federal level: enactment of Title IX, state anti-bullying laws, and warrantless arrest laws aimed at curbing domestic violence. My first essay examines the causal relationship between athletic participation and means-tested program participation. I use the variation in the implementation of Title IX and find that a 30 percentage-point increase in female athletic participation induced by Title IX increased program participation among 25 to 40-year-old females by 2.8 percentage-points. This effect persists across SNAP, TANF, and Medicaid recipiency. Event study analysis and …

The Effect Of Deep-Water Multibeam Mapping Activity On The Foraging Behavior Of Cuvier’S Beaked Whales And The Marine Acoustic Environment, Hilary Suzanne Curran Kates Varghese

Doctoral Dissertations

Sound can propagate great distances underwater and is an important mode for marine life to obtain information. Human activities in the ocean such as global shipping, coastal construction, gas and oil exploration, and mapping navigation routes intentionally and unintentionally emit sound into the ocean, potentially interacting with marine life. Therefore, it is essential that the effects of anthropogenic noise on marine life and the ambient marine acoustic environment be understood. Most of the work, to date, has focused on the impact of low-frequency (<1 kHz) sources such as shipping noise, which is ubiquitous in the ocean, and mid-frequency (1-10 kHz) sources such as naval sonar, to which many marine mammals have shown to be sensitive. The effect of these sources can be as salient as a mass stranding event or as benign as an animal swimming away from a source of noise with no other effect. Less work has focused on higher frequency sources (>10 kHz), including ocean-mapping sonar systems. However, most marine mammals, namely toothed whales (odontocetes), are capable …

Investigation Of Anomalous Data Trends During Coal Dust Explosibilty Testing, Jacob Lee Miller

Doctoral Dissertations

Coal dust explosibility is a health and safety concern that has been a recognized hazard for over 100 years. Initial testing by the Author using a Siwek 20L apparatus recorded a secondary maximum pressure at higher dust concentrations (1,000-7,000g/m³) with Pulverized Pittsburgh Coal (PCC). Higher dust concentrations are beyond the typical ASTM E1226 testing procedure but are possible in mining and processing scenarios. No reference documents have been discovered that show a secondary maximum pressure at higher dust concentrations. Literature reviewed identified that once a coal dust concertation generates a peak pressure, the pressure remains constant or decreases …

Development Of In-Situ Radiometric Inspection Methods For Quality Assurance In Laser Powder Bed Fusion, Cody S. Lough

Doctoral Dissertations

“Laser Powder Bed Fusion (LPBF) metal Additive Manufacturing (AM) fabricates 3D metal parts layer-by-layer. The process enables production of geometrically complex parts that are difficult to inspect with traditional methods. The LPBF parts experience significant geometry driven thermal variations during manufacturing. This creates microstructure and mechanical property inhomogeneities and can stochastically cause defects. Mission critical applications require part qualification by measuring the defects non-destructively. The layer-to-layer nature of LPBF permits non-intrusive measurement of radiometric signals for a part’s entire volume. These measurements provide thermal features that correlate with the local part health. This research establishes Optical Emission Spectroscopy (OES) and …

Novel Piezo Actuators For Surface Cleaning, Yezad H. Anklesaria

Doctoral Dissertations

"Optical cameras are becoming increasingly common and are used in a variety of applications. With recent progress and transition toward more autonomous systems, the usage of optical systems will be common and widespread. Applications of the optical systems range from autonomous vehicles, home security systems, aviation, extraterrestrial vehicles, spacecraft, and satellites. Imaging systems are used in decision-making in many of these applications. Fouling of the field of view of the imaging system can impede the decision process. An active autonomous cleaning method for the optical surface of the optical systems reliably would be advantageous. The research work focuses on developing …

Fabrication, Characterization Of High-Entropy Alloys And Deep Learning-Based Inspection In Metal Additive Manufacturing, Wenyuan Cui

Doctoral Dissertations

"Alloying has been used to confer desirable properties to materials. It typically involves the addition of small amounts of secondary elements to a primary element. In the past decade, however, a new alloying strategy that involves the combination of multiple principal elements in high concentrations to create new materials called high- entropy alloys (HEAs) has been in vogue. In the first part, the investigation focused on the fabrication process and property assessment of the additive manufactured HEA to broaden its engineering applications. Additive manufacturing (AM) is based on manufacturing philosophy through the layer-by-layer method and accomplish the near net-shaped components …

Contributions To The Performance Of Thin Film Capacitors For High Reliability Applications, Daniel Krueger

Doctoral Dissertations

"Capacitors are critical devices in microelectronic assemblies that must be incorporated into electronic systems through a variety of ways such as integrated or discrete devices. This work has developed new thin film capacitors deposited directly onto multichip module or printed circuit board surfaces to benefit from closer integration that enhances system performance for use in high reliability applications. The capacitors serve as filters or provide tuning and energy storage functions. Unexpected performance was observed during development that included low adhesion of the films to the substrates, higher effective dielectric constants than reported in literature, and low yields. Three publications resulted …

Collaborative Planning In The Construction Industry: A Holistic Framework For Assessing Collaborative Planning Practices And Predicting Project Performance, Amr Elsayegh

Doctoral Dissertations

"The fragmentation of the construction industry prompted developing novel methods such as collaborative planning, lean construction, advancements in technology, integrated project delivery, and relational contracting. Current research focused on specific facets of collaborative planning without presenting a comprehensive analysis of its factors. As such, the goal of this research is to develop a holistic framework that studies and evaluates collaborative planning practices in construction projects. This research offers significant addition to the body of knowledge through various theoretical and practical contributions. In relation to that, this research developed a comprehensive framework by (1) identifying a comprehensive list of factors influencing …

Advanced Battery Modeling For Interfacial Phenomena And Optimal Charging, Yaqi Zhu

Doctoral Dissertations

"Lithium-ion batteries are one of the most promising energy storage systems for portable devices, transportation, and renewable grids. To meet the increasing requirements of these applications, higher energy density and areal capacity, long cycle life, fast charging rate and enhanced safety for lithium-ion battery (LIBs) are urgently needed. To solve these challenges, the relevant physics at different length scale need to be understood. However, experimental study is time consuming and limited in small scale’s study. Modeling techniques provide us powerful tools to get a deep understanding of the relevant physics and find optimal solutions. This work focuses on studying the …

Infrastructure Systems Modeling Using Data Visualization And Trend Extraction, Jacob Marshal Hale

Doctoral Dissertations

“Current infrastructure systems modeling literature lacks frameworks that integrate data visualization and trend extraction needed for complex systems decision making and planning. Critical infrastructures such as transportation and energy systems contain interdependencies that cannot be properly characterized without considering data visualization and trend extraction.

This dissertation presents two case analyses to showcase the effectiveness and improvements that can be made using these techniques. Case one examines flood management and mitigation of disruption impacts using geospatial characteristics as part of data visualization. Case two incorporates trend analysis and sustainability assessment into energy portfolio transitions.

Four distinct contributions are made in this …

Scaling, Experiments, And Simulations Of Condensation Heat Transfer For Advanced Nuclear Reactors Safety, Palash Kumar Bhowmik

Doctoral Dissertations

“The purpose of this research was to perform scaled experiments and simulations to validate computational fluid dynamics (CFD) and empirical models of condensation heat transfer (CHT) for the passive containment cooling system (PCCS) of Small Modular Reactors (SMRs). SMRs are the futuristic candidates for clean, economic, and safe energy generation; however, reactor licensing requires safety system evaluations, such as PCCS. The knowledge in the reviewed relevant literature showed a gap in experimental data for scaling SMR’s safety systems and validating computational models. The previously available test data were inconsistent due to unscaled geometric and varying physics conditions. These inconsistencies lead …

Parental Involvement In Support Of African American Families, September Rose

Doctoral Dissertations

Meaningful parental engagement has historically been identified as the root cause of the United States’ academic achievement gap in African American education. However, the systematic structures that impose difficulties for African American’s access to education in school and other aspects of their social development must be addressed to gain a deeper understanding of the challenges these African American families face. Society must consider the perpetual marginalization of not only African American students’ academic experiences, but also their professional and personal development as well. The parental engagement with educators in the San Francisco K-8 schools, has not been studied. The purpose …