Digital Commons Network^™

The Separation Of Shear-Driven Liquid Films From A Sharp Corner, Zahra Sadeghizadeh

Doctoral Dissertations

"The separation of shear-driven liquid films occurs in many engineering applications such as port fuel injected engines, demisters, and gas transfer lines. Despite the importance of this problem, the details of the interaction between operating parameters such as liquid flow rate, gas velocities and liquid film properties on the forces at the expanding corner are still not clear. To enhance the insight on the complicated interaction between the gas and liquid phases, the shear-driven liquid flow around a corner has been studied both experimentally and analytically in this work. The effect of the complex liquid film structure on liquid mass …

The Significance Of Grouping And Missed Bubbles On Interfacial Area Concentration And Void Fraction, Chandller Stephen-Leslie Mills

Doctoral Dissertations

"The two-fluid model is used in nuclear reactor safety codes. Two of the important constitutive relations will be discussed in this study, the interfacial area concentration and void fraction. The Interfacial area concentration is directly affected by the number of bubbles and how these bubbles are categorized into groups. In this study, a new algorithm was implemented to account for trailing bubbles, bubbles with short response times, and the categorization of bubbles based upon diameter for all group 1 bubbles. The optical and conductivity probes were used to determine the void fraction and interfacial area concentration in a bubble column. …

Detecting Cells And Analyzing Their Behaviors In Microscopy Images Using Deep Neural Networks, Yunxiang Mao

Doctoral Dissertations

"The computer-aided analysis in the medical imaging field has attracted a lot of attention for the past decade. The goal of computer-vision based medical image analysis is to provide automated tools to relieve the burden of human experts such as radiologists and physicians. More specifically, these computer-aided methods are to help identify, classify and quantify patterns in medical images. Recent advances in machine learning, more specifically, in the way of deep learning, have made a big leap to boost the performance of various medical applications. The fundamental core of these advances is exploiting hierarchical feature representations by various deep learning …

Design And Characterization Of Multi-Spectral Underwater Beam-Port For Pool-Type Research Reactors, Meshari Mesfer Alqahtani

Doctoral Dissertations

“The beam-port is a cardinal facility at research reactors necessary for dry irradiation, testing and measurement experiments. The Missouri University of Science and Technology Reactor (MSTR) is one such reactor with a beam-port. Installation of additional beam-port in such reactor facilities can be prohibitive. A novel remedy to this is an underwater beam-port for pool-type reactors. The design and characterization of a conceptual underwater multi-spectral beam-port for neutron and gamma fluxes were completed for the MSTR. The neutron spectra from the MSTR were simulated using the Monte Carlo N-particle (MCNP). The determined neutron spectra were experimentally validated using SAND-II. The …

Mitigation Of Environmental Hazards Of Sulfide Mineral Flotation With An Insight Into Froth Stability And Flotation Performance, Muhammad Badar Hayat

Doctoral Dissertations

"Today's major challenges facing the flotation of sulfide minerals involve constant variability in the ore composition; environmental concerns; water scarcity and inefficient plant performance. The present work addresses these challenges faced by the flotation process of complex sulfide ore of Mississippi Valley type with an insight into the froth stability and the flotation performance. The first project in this study was aimed at finding the optimum conditions for the bulk flotation of galena (PbS) and chalcopyrite (CuFeS₂) through Response Surface Methodology (RSM). In the second project, an attempt was made to replace toxic sodium cyanide (NaCN) with the biodegradable chitosan …

Experiences Of Women Stem Professors Who Are Considering Leadership Positions At Research Universities, Cheri Liebow

Doctoral Dissertations

Empirical evidence is needed to discern the reasons for inequities among those with doctorates hired in science, technology, engineering, and mathematics (STEM) fields. It is necessary to create a successful and motivational atmosphere for various types of female leaders who are seeking opportunities to become leaders, especially in STEM fields. This qualitative-method study used an exploratory design. The study first sought to gather information about female STEM professors’ experiences through open-ended qualitative interviews to explain gaps in details of women’s experiences as professors in STEM departments of universities. Second, the researcher sought to discern common themes in interview responses for …

Critical Peace Pedagogies At The American Center For Civil And Human Rights And The Canadian Museum For Human Rights: A Comparative Case Study, Ion Vlad

Doctoral Dissertations

The struggle for racial equity in the United States and Canada is ongoing. Troubled historical legacies in both countries have present-day implications. African Americans and Indigenous Canadians are still two of the most marginalized populations from the standpoint of socioeconomics and political representation (Giroux, 2013; Vickers, 2012). In order to redress these problems, human rights and peace education have to pose structural questions and expose systemic unbalances. In the recent past, neoliberalism has had a major influence on the organization and content of American and Canadian formal education, obscuring some of these structural questions (Ravitch, 2013). In this context, human …

Psychological Conditions That Promote Job Engagement: Test Of A Model, Zhuo Chen

Doctoral Dissertations

According to Kahn’s theoretical model (1990), the following three psychological conditions - meaningfulness, safety, and availability - are the key proximal predictors of job engagement. The current study examined the effects of these three psychological conditions (meaningfulness, safety, and availability) on three aspects of job engagement (JE), using both cross-sectional and daily diary data to examine between-person and within-person relationships among these variables. Psychological conditions were also examined as mediators of relationships between organizational and personal factors and job engagement. Furthermore, positive affect (PA) was tested as a moderator of the relationships between distal predictors and the three psychological conditions. …

Land-Atmosphere Interactions And Regional Climate In West Africa And South America, Amir Erfanian Javadian Entezar Yazd

Doctoral Dissertations

Land, atmosphere, and oceans interact with each other through energy, mass, and momentum exchanges. These interactions regulate climate variability and influence climate changes at the regional scale. One notable example of highly influential land-atmosphere-ocean interactions on regional climates is monsoonal systems that influence a substantial portion of the world’s population. In this dissertation, the present and future climates of West Africa (WA) and South America (SA), two important monsoon regions, were studied utilizing Regional and Global Climate Models (RCMs and GCMs), mathematical techniques and data mining tools, and observational data (in-situ, remote-sensing, and reanalysis). The objective is to advance our …

Genome Evolution In Najas And Hydrilla (Hydrocharitaceae)., Ursula King

Doctoral Dissertations

Archival abstract submitted

Emotionally And Socially Aware Approaches To Understanding And Changing Users’ Cybersecurity Behavior, Michael Fagan

Doctoral Dissertations

Security is a priority to most, but studies show that users commonly fail to adopt recommended cybersecurity behavior. Researchers have looked to user factors for explanations of this gap, finding security and convenience to be common considerations, along with perceptions of risks and past experiences. Some have tried to alter user behavior, but are targeted at specific advice and focused on rational motivations to persuade users.

In this thesis, three expertly recommended cybersecurity advice (i.e., updating software regularly, using two-factor authentication, using a secure password manager) are deeply explored. These results inform the design of videos in a systematic study …

Advanced Power Loss Modeling And Model-Based Control Of Three-Phase Induction Motor Drive Systems, Yiqi Liu

Doctoral Dissertations

Three-phase induction motor (IM) drive systems are the most important workhorses of many industries worldwide. This dissertation addresses improved modeling of three-phase IM drives and model-based control algorithms for the purpose of designing better IM drive systems. Enhancements of efficiency, availability, as well as performance of IMs, such as maximum torque-per-ampere capability, power density, and torque rating, are of major interest. An advanced power loss model of three-phase IM drives is proposed and comprehensively validated at different speed, load torque, flux and input voltage conditions. This model includes a core-loss model of three-phase IMs, a model of machine mechanical and …

Design And Fabrication Of Micro-Pillar Based Piezoresistive Flow Sensors, Adimali Piyadasa

Doctoral Dissertations

This study is focused on developing a new type of micro-scale gas flow sensors to be used in critical environments such as combustion engines with high pressure high temperature gas flow and integrated micro electro mechanical applications such as lab-on-chip devices. Proposed flow sensor is based on piezoresistivity of Silicon micro column cantilever. Change in resistivity tensor due to gas flow induced stress in the piezoresistive layer results in generating of an output voltage proportional to the gas flow rate in the channel. Current results show that the anisotropic properties of the Silicon can be successfully used in the gas …

Modeling Iron Oxide Reactivity In The Environment, Nefeli Maria Bompoti

Doctoral Dissertations

Iron oxides and hydroxides are highly reactive mineral phases in natural systems since they interact with pollutants, controlling their fate and transport in the environment. Goethite (GH) and hematite (HT) are the most abundant iron minerals in nature, while ferrihydrite (FH) is a nanomineral with high surface reactivity. Subsurface transport modeling has usually represented the adsorption processes by empirical relationships, such as distribution coefficients (K_d) or isotherm equations. However, empirical approaches cannot account for variable geochemical conditions. These effects can be addressed by the mechanistic surface complexation models (SCMs). So far, the application of SCMs has been limited …

Computational Framework For Modeling Adhesion Of The Red Blood Cell Membrane Using Impetus, Vi Quoc Ha

Doctoral Dissertations

Modeling multiple receptor-ligand interactions, where receptors are distributed on a fluctuating membrane, is challenging since it involves two very distinct timescales. We overcame this obstacle by introducing an essentially time coarse-graining algorithm by employing a stochastic methodology to compute the probability of the bond remaining intact at specific time step. We developed a computational framework to model the complex receptor and ligand interaction by using a survival probability function. Using the model, we studied how membrane oscillations are affected by adhesion between substrate ligands and membrane receptors, and how diffusion of membrane receptors depends on ligand-receptor adhesion.

In order to …

Resilient Microgrids Through Software-Defined Networking, Lingyu Ren

Doctoral Dissertations

Multiple major blackouts had occurred in the U.S. power distribution system highlighting the importance of enhancing electricity resiliency. Microgrid is the new paradigm incorporating high flexibility and reliability in power supply. It allows various distributed energy resources and loads to be integrated and coordinated as an intelligent entity through control and communication infrastructure. Microgrid control technologies have been continuously developed over 20 years. However, there is still a lack of communication architecture that is able to provide fast, reliable and elastic services for multi-level data transmission and adaptable network management. This dissertation solves this intractable problem by integrating programmable networks …

Lyme Disease Ecology: Effects Of Habitat And Hosts On The Density And Distribution Of Borrelia Burgdorferi-Infected Ixodes Scapularis, Megan Ainsley Linske

Doctoral Dissertations

The research discussed in this dissertation examined host and habitat composition in Connecticut and their effect on the ecology of Lyme disease. Previous studies on management strategies sought a one-size-fits-all solution. However, Connecticut may require its own implementation of management strategies supported by research executed in its respective environment. Therefore, a novel approach that addresses the key components of a particular habitat, in this case Connecticut’s northern hardwood forests with an invasive plant understory, may yield better results than a “silver bullet” solution produced by a model or conducted in a different geographic location.

My research is conducted in Connecticut …

Optimizing Fabrication And Modeling Of Quantum Dot Superlattice For Fets And Nonvolatile Memories, Pial Mirdha

Doctoral Dissertations

Quantum Dot Superlattice (QDSL) are novel structures which can be applied to transistors and memory devices to produce unique current voltage characteristics. QDSL are made of Silicon and Germanium with an inner intrinsic layer surrounded by their respective oxides and in the single digit nanometer range. When used in transistors they have shown to induce 3 to 4 states for Multi-Valued Logic (MVL). When applied to memory they have been demonstrated to retain 2 bits of charge which instantly double the memory density. For commercial application they must produce consistent and repeatable current voltage characteristics, the current QDSL structures consist …

Gender And Domain Differences In College Students’ Responses To Success And Failure, Elizabeth K. Lawner

Doctoral Dissertations

Four studies examined perceptions of STEM and non-STEM college courses, gender and domain differences in responses to success and failure, and whether interventions to make failure seem normative could ameliorate negative responses to failure, particularly among women. Study 1 found that college students perceive STEM courses as more difficult than non-STEM courses, and believe that introductory STEM courses are used to remove students from those fields. Moreover, the difference in perceptions of STEM and non-STEM courses was larger for women. Study 2 piloted a novel task that was used in Studies 3 and 4. These studies did not support the …

Development Of Molecular Catalysts For Co2 Reduction And Nanomaterial Catalysts For Oxidation Reactions, Kankana Mullick

Doctoral Dissertations

The thesis presented here is focused on two aspects of transition metal mediated catalysis research- one is designing homogeneous rhenium complex with suitable ligand framework for electrochemical reduction of carbon dioxide to address dual issues regarding green house gas removal and hydrocarbon fuel production; another being fabrication of heterogeneous mesoporous manganese oxide to catalyze organic fine chemical synthesis under aerobic atmospheric condition. The quest for conquering fossil fuel energy dependence leads us to develop methodologies for using CO₂ as a renewable resource. Electrochemical reduction of CO₂ has been considered as a promising procedure for this purpose. Coordination complexes …

Social Movements And Mainstream Media: Framing Processes In An Ideologically Segmented Tv News Field, Malaena J. Taylor

Doctoral Dissertations

This dissertation examines television news coverage of the Tea Party and Occupy Wall Street movements. Theories regarding the relationship between media and social movements are mostly based on outdated models of media and journalistic norms. In addition, the literature on framing is underdeveloped in that it has focused on the process of creating frames and the implications of collective action framing; less is known about the process of frame usage in non-print media. My dissertation addresses these two problems. I develop the partisan media paradigm, an improved framework for understanding media coverage of social movements, by reformulating a dominant theory …

Diffusion On Silver Nanorod Surfaces: Mechanisms Of Fast Diffusion At Low Temperature, Lou Bachenheimer

Doctoral Dissertations

Ag nanorods may serve as sensors in the detection of trace amounts of chemical agents, even single molecules, through surface enhanced Raman spectroscopy (SERS). However, thermal coarsening of Ag nanorods near room temperature limits their applications. In this work, we examine this thermal instability through molecular dynamics simulations and molecular statics calculations in order to elucidate the process. From these computational methods, it is realized that the thermal instability of Ag nanorods is the result of rapid surface diffusion, and we hypothesize that the thermal stability can be enhanced by the addition of a thin dielectric cap. This hypothesis is …

Compact And Robust Ultrasound-Guided Diffuse Optical Tomography For Breast Imaging: System And Algorithm Developments, Hamed Vavadi

Doctoral Dissertations

According to the World Health Organization, breast cancer is the most common cancer among women worldwide, claiming lives of hundreds of thousands of women each year. Mammography, ultrasound (US) and magnetic resonance imaging (MRI) are widely used to detect and diagnose breast lesions and each of them have some disadvantages which motivates researchers to find a new and high sensitive imaging method. Diffuse optical tomography (DOT) is a noninvasive functional imaging modality that utilizes near-infrared (NIR) light to probe tissue optical properties. Minimal light absorption in the NIR spectrum allows for several centimeters of light penetration in soft tissue. NIR …

Model Reduction And Dynamic Adaptive Hybrid Integration For Efficient Combustion Simulations, Yang Gao

Doctoral Dissertations

Large-scale high-fidelity numerical simulation with detailed chemistry is an important approach to the study of combustion problems, which may involve turbulence and complex chemical reactions. However, detailed chemistry can involve a large number of species and reactions as well as severe chemical stiffness, resulting in high computational cost. This thesis presents a systematic study on reducing the computational cost of reacting flow simulations when detailed chemistry is involved. The effort includes reduction of chemical kinetic models and molecular diffusion, as well as development of advanced stiff chemistry solvers. First, a reduced kinetic model for ethylene/air with polycyclic aromatic hydrocarbons (PAHs) …

The Impact Of Cause-Related Marketing On Global Consumers: A Meta-Analysis, Michelle Morin Rego

Doctoral Dissertations

Cause-related marketing (CRM) is a growing area of corporate social responsibility that involves a joint venture between a for-profit brand and a nonprofit organization. Over the past 30 years, cause-related marketing research has expanded to all corners of the globe. Themes in CRM research include cause-brand fit, cause involvement, cultural values and beliefs, and the influence of CRM on consumer attitudes and purchase intentions. A series of bivariate meta-analyses were conducted using a random effects assumption to determine effect sizes in this field, and explain the variance in effects across a global body of literature. Results include the effect of …

Probabilistic Controlled Airspace Infringement Tool And Conflict Resolution, Yousra Almathami

Doctoral Dissertations

A current ground based safety net called Controlled Airspace infringement Tool (CAIT) is used by Air Traffic Controllers (ATCs). It warns them if any aircraft within uncontrolled airspace penetrates the Controlled airspace (CAS) without an advance clearance from the ATC. This penetration or ‘Infringement’ is considered as a major concern to ATCs where it may cause a possible conflict or mid- air collision. A conflict is an event which one aircraft loses its minimum separation to another. The downside of CAIT is that it only warns ATCs if the aircraft has already infringed CAS, this gives the ATC minimum time …

Spatiotemporal Subspace Feature Tracking By Mining Discriminatory Characteristics, Richard D. Appiah

Doctoral Dissertations

Recent advancements in data collection technologies have made it possible to collect heterogeneous data at complex levels of abstraction, and at an alarming pace and volume. Data mining, and most recently data science seek to discover hidden patterns and insights from these data by employing a variety of knowledge discovery techniques. At the core of these techniques is the selection and use of features, variables or properties upon which the data were acquired to facilitate effective data modeling. Selecting relevant features in data modeling is critical to ensure an overall model accuracy and optimal predictive performance of future effects. The …

Resonant-Cavity Optoelectronic Devices For Optical Interconnects, Brian Pile

Doctoral Dissertations

Internet traffic is increasing exponentially with the continued growth of online streaming, cloud computing, and social media services. This increases demand on data centers that must handle the transmission, routing, and storage of the data. As bandwidth is scaled up, more power efficient systems are required to reduce cost and power consumption, while maintaining thermal requirements. Gigabit connections between the labyrinth of network servers are traditionally made of copper, but link distances are typically limited to ten meters, and the required electronic equalizations add to the power budget. To achieve high bitrates with low energy per bit, optical interconnects are …

Electrosprayed Polymerization: A Green, Additive Approach For Making Highly Tunable Polyamide Films For Desalination, Md Maqsudur Rahman Chowdhury

Doctoral Dissertations

In membrane based desalination processes, the thin film composite (TFC) membrane is an industry standard which uses interfacial polymerization technique to form an ultra-thin polyamide layer on the surface of polymeric substrates. Remarkably, in 30 years of using this approach, the RO industry has yet to create a polyamide film onto a supporting membrane with controllable thickness, roughness and properties that are independent from the substrate properties. While the film formation essentially is “self-controlled”, the reaction itself is simply allowed to proceed uncontrolled. Thickness and roughness impact membrane permeance and fouling propensity, respectively, and controlling these parameters could greatly benefit …

Protein-Based Autofluorescent Hydrogel And Nano/Micro-Particles For Bio-Imaging Applications, Xiaoyu Ma

Doctoral Dissertations

Fluorescent polymeric materials such as hydrogels and polymeric particles have been attracting attention in many biomedical applications including bio-imaging, optical sensing, tissue engineering and therapy, due to their good biocompatibility, biodegradability, and advanced optical property. This PhD project aims at developing novel autofluorescent protein materials in different configurations with good biocompatibility and biodegradability for bio-imaging applications.

Early research focused on the development of autofluorescent protein hydrogels for in vivo bio-imaging application. Glutaraldehyde cross-linked Bovine Serum Albumin (BSA) hydrogel were facilely prepared. Various advanced techniques were employed to characterize the as-prepared material. SEM study clearly revealed its 3-dimentional pore structure, while …