Digital Commons Network^™

Machine Learning-Based Modeling And Optimization Of Nitrogen Removal In Wastewater Treatment Under Highly Variable Operating Conditions, Rebecca L. Rubinstein

Doctoral Dissertations

Robust and effective nutrient removal in wastewater treatment is critical to protection of human health and the environment. However, it can be very challenging under variable influent conditions such as those experienced at the University of Connecticut (UConn) Water Pollution Control Facility. The highly seasonal nature of the UConn student population results in rapid transitions between very high and very low loading rates, which can cause short-term permit violations while the system adjusts. The microbial community responsible for most nutrient removal at this and many other facilities is complex and very responsive to influent and environmental conditions. This responsiveness allows …

Lattice Dynamics Studies Of Negative Thermal Expansion Due To Two Low-Temperature Lattice Instabilities., Sahan Uddika Handunkanda

Doctoral Dissertations

Here I present a complete study of lattice dynamics of negative thermal expansion (NTE) material Scandium trifluoride (ScF₃) and discovery of NTE in mercurous iodide (Hg₂I₂). An inelastic x-ray scattering (IXS) study of ScF₃ reveals copious evidence of an incipient soft-mode instability indicating that the T=0 state of ScF₃ is very close to a structural quantum phase transition (SQPT). Is the anomalously strong and thermally persistent NTE behavior of ScF₃ a consequence of the SQPT? In order to address that, we have explored the coefficient of thermal expansion (CTE) and soft …

Planning, Operation, Protection And Restoration Strategies For Microgrids With Distributed Energy Resources, Wei Kou

Doctoral Dissertations

Integration or interconnection of distributed energy resources (DER) is evolving as an emerging power scenario for electric power generation, transmission and distribution infrastructure globally. As DER applications penetrates into the conventional bulk power systems, the following technical problems and challenges have been considered by the utility operators and DER providers: 1) sizing and locating for DERs in the planning stage; 2) demand-side management for DER-dominated microgrid in the steady-state operation stage; 3) protection control for inverter-interfaced DER in the transient dynamic stage; and 4) restoration service with DER participants in the restoration stage. To overcome the above difficulties, four novel …

Understanding Of The Nucleation Induced Cooperative Behavior In Complex Macromolecular Systems, Hailin Fu

Doctoral Dissertations

Archival abstract submitted

In Situ Investigation Of Thermally Activated Processes Using Mems-Based Devices: Practical Challenges & Applications, Sriram Vijayan

Doctoral Dissertations

In situ heating holders offer the possibility of studying thermally activated processes by performing real time, high temperature experiments inside the transmission electron microscope. The poor thermal stability of traditional furnace-type heating holders limits their use to a narrow range of materials and processes. Modern micro electro mechanical system (MEMS) based heating holders have significantly improved the ability to perform such experiments and have led to a revival in the field of in situ TEM. The excellent thermal stability of the MEMS devices allows us to carry out controlled heating and cooling experiments on both particulate and bulk samples at …

Tailoring Electrospun Carbon Nanofiber Properties For Improving Chemical Sorption, Yi Han

Doctoral Dissertations

Activated carbon nanofiber (ACNF), as a novel electrospun polyacrylonitrile-based sorptive material, takes advantage of nanoscale fabrication to reduce mass transfer limitations while maintaining a membrane structure. Steam activated ACNF has been compared with commercial activated carbons and exhibits fast sorption rates and capacity for polycyclic aromatic hydrocarbons. However, to increase effectiveness for difficult to remove micropollutants, changes to the surface chemistry was required. For the initial modification to introduce carboxylic acids on the surface, a range of oxidants were compared including nitric acid, nitric acid and sulfuric acid, potassium permanganate, osmium tetroxide followed with potassium permanganate or oxone®, and ruthenium …

Characterization Of Nanomaterials For Thermal Management Of Electronics, Amit Rai

Doctoral Dissertations

Recently, there has been a growing interest in flexible electronic devices as they are light, highly flexible, robust, and use less expensive substrate materials. Such devices are affected by thermal management issues that can reduce the device’s performance and reliability. Therefore, this work is focused on the study of the thermal properties of nanomaterials and the methods to address such issues. The goal is to enhance the effective thermal conductivity by adding nanomaterials to the polymer matrix or by structural modification of nanomaterials. The thermal conductivity of copper nanowire/polydimethylsiloxane and copper nanowire/polyurethane composites were measured and showed more than threefold …

Nanoparticle Catalytic Enhancement Of Carbon Dioxide Reforming Of Methane For Hydrogen Production, Nicholas Groden

Doctoral Dissertations

The U.S. produces 5559.6 million metric tons of carbon dioxide annually, of which 21% is produced by industrial processes. Steam reforming, an industrial process that accounts for 95% of all hydrogen production in industry, produces 134.5 million metric tons of carbon dioxide or around 11% of the total carbon dioxide produced by industry. This carbon dioxide is then either emitted or goes through a sequestration process that accounts for 75% of the plant's operational costs. An alternative reaction to steam reforming is dry reforming, which utilizes carbon dioxide rather than emitting it and can be used in conjunction with current …

Electrical Characterization Of Graphene And Nanodiamond Nanostructures, A Z M Nowzesh Hasan

Doctoral Dissertations

The electrical characterization on two-dimensional carbon-based graphene and nanodiamond materials was performed to improve charge transport properties for the label-free electrical biosensors. The charge transport in solution-gated graphene devices is affected by the impurities and disorders of the underlying dielectric interface and its interaction with the electrolytes. Advancement in field-effect ion sensing by introducing a dielectric isomorph, hexagonal boron nitride between graphene and silicon dioxide of a solution-gated graphene field-effect transistor was investigated. Increased transconductance due to increased charge carrier mobility is accompanied with larger ionic sensitivity. These findings define a standard to construct future graphene devices for biosensing and …

Understanding Why Students Take Industry-Based Credentialing Examinations: Instrument Development And Pilot Study, Jennifer H. Lawrence

Doctoral Dissertations

Educational credentialing is complicated for students with the addition of industry-based credentialing (IBC) in traditional academic and career and technical fields (Bahr, 2015; Lumina Foundation, 2015; Xu & Ran, 2015). Human Capital Theory and Cognitive Engagement Theory framed this study which looked at IBC training from the student point of view (Grisham, 2013; Saldana, 2016; Walters, 2004). The body of literature on credential training is sparse and largely focused on institutional policy rather than student perception and participation (Bahr, 2015; Xu & Ran, 2015). There is evidence that salaries are positively correlated with IBCs and studies show that employers pay …

Multidimensional Feature Engineering For Post-Translational Modification Prediction Problems, Norman Mapes Jr.

Doctoral Dissertations

Protein sequence data has been produced at an astounding speed. This creates an opportunity to characterize these proteins for the treatment of illness. A crucial characterization of proteins is their post translational modifications (PTM). There are 20 amino acids coded by DNA after coding (translation) nearly every protein is modified at an amino acid level. We focus on three specific PTMs. First is the bonding formed between two cysteine amino acids, thus introducing a loop to the straight chain of a protein. Second, we predict which cysteines can generally be modified (oxidized). Finally, we predict which lysine amino acids are …

Electromagnetic Wave-Matter Interactions In Complex Opto-Electronic Materials And Devices, Raj Kumar Vinnakota

Doctoral Dissertations

This dissertation explores the fundamentals of light-matter interaction towards applications in the field of Opto-electronic and plasmonic devices. In its core, this dissertation attempts and succeeds in the the modeling of light-matter interactions, which is of high importance for better understanding the rich physics underlying the dynamics of electromagnetic field interactions with charged particles. Here, we have developed a self-consistent multi-physics model of electromagnetism, semiconductor physics and thermal effects which can be readily applied to the field of plasmotronics and Selective Laser Melting (SLM). Plasmotronics; a sub-field of photonics has experienced a renaissance in recent years by providing a large …

Engineered Coating Of Natural Fibers And Oil-Water Interfaces With Self-Assembly Of Clay Nanotubes, Abhishek Panchal

Doctoral Dissertations

Taking into consideration two different types of surfaces, this dissertation proposes techniques to coat the surface of natural fibers and oil-water interfaces by spontaneous self-assembly of halloysite clay nanotubes. The material of choice, halloysite clay, is a widely available natural resource and can be used after minimal processing. In regards to chemical composition, halloysite clay resembles aluminosilicate mineral kaolin; physically, a defect in the crystal structure ordering causes the sheets of kaolinite to roll into halloysite nanotubes. The dimensions of halloysite nanotubes are dependent on the source, but generally vary from 200 nm to 3 µm in length, 100-150 nm …

Effective Magnetic And Electric Response Of Composite Materials, Mona Hassan Alsaleh

Doctoral Dissertations

Metamaterials (MMs) are nanocomposite materials consisting of metal-dielectric resonators much smaller in size than the wavelength of the incident light. Common examples of metamaterials are based on split ring resonators (SRRs), parallel wires or strips and fishnet structures. These types of materials are designed and fabricated in order to provide unique optical responses to the incident electromagnetic radiation that are not available in naturally existing materials. The MMs can exhibit unusual properties such as strong magnetism at terahertz (THz) and optical frequencies. Additionally, negative index materials (NIMs) can provide negative index of refraction which can be used in many applications …

Investigating High Energy Mixing In Cement-Based Materials, Aileen Vandenberg

Doctoral Dissertations

One of the current challenges to nano-engineering cementitious composite materials is obtaining properly dispersed nano-sized particles in the cementitious composite matrix. Properly dispersed nanoparticles can lead to an improved particle packing density, a key parameter to improving the mechanical, chemical, and sustainable properties of the cementitious composite. Broadening the particle size distributions of cementitious materials, such as ultra-high performance concrete (UHPC), to include additional nano-sized particles is a challenge that requires a better understanding of how they self-assemble in the cementitious matrix. Thus, the purpose of this research is to investigate the role mixing plays in multi-scale, multi-phase self-assembling cement-based …

Phonon Dispersion And Band Gap Engineering Of Strained And Isotopically Enriched Atomically Thin Transition Metal Dichalcogenide Semiconductors, Wei Wu

Doctoral Dissertations

Transition metal dichalcogenide (TMD) materials consist of strong intra-layer covalently bonded and weak inter-layer van der Waals bonded layers, which enable the preparation of atomically thin devices by either mechanical exfoliation or chemical vapor deposition (CVD). As a certain group of TMDs MX₂ (M=Mo, W; X=S, Se, Te) are scaled to the thickness of one three-atom-thick layer, the electronic dispersion undergoes a transition from an indirect to a direct band gap due to quantum confinement effects. The mechanical flexibility can be also enhanced by reducing layer number in TMDs. In view of these extraordinary properties, TMDs have been proposed …

Imaging Innovations For Whole-Slide And Hyperspectral Microscopy, Jun Liao

Doctoral Dissertations

Digital pathology via whole-slide imaging (WSI) systems has recently been approved for the primary diagnostic use in the US. A critical challenge of WSI is to perform accurate focusing in high speed. Traditional systems create a focus map prior to scanning. For each focus point on the map, a sample needs to be static in the x-y plane, and axial scanning is needed to maximize the contrast. Here I report a novel focus map surveying method for WSI. In this method, I use two LEDs to illuminate the sample and recover the focus points based on 1D autocorrelation analysis. The …

A Complete Characterization Of Near Outer-Planar Graphs, Tanya Allen Lueder Genannt Luehr

Doctoral Dissertations

A graph is outer-planar (OP) if it has a plane embedding in which all of the vertices lie on the boundary of the outer face. A graph is near outer-planar (NOP) if it is edgeless or has an edge whose deletion results in an outer-planar graph. An edge of a non outer-planar graph whose removal results in an outer-planar graph is a vulnerable edge. This dissertation focuses on near outer-planar (NOP) graphs. We describe the class of all such graphs in terms of a finite list of excluded graphs, in a manner similar to the well-known Kuratowski Theorem for planar …

Differences In Leadership Behaviors Of Principals And Success In The School Turnaround Processes, Annette Lee

Doctoral Dissertations

The purpose of this study was to examine leadership behaviors of principals associated with public elementary schools that were either in the school turnaround process or had already transitioned out of school academic turnaround from 2011 through 2016. Transformational leadership guided the study to determine whether leadership behaviors differed among leaders of schools associated with academic failure. School accountability data were initially gathered through the Louisiana Department of Education website. Academically unsuccessful schools (AUS) were identified. Schools that were deemed failing at least one time during the 2012-2016 timeframe were grouped as follows: (a) Group A consisted of two schools …

Aiming For Success: Evaluating Statistical And Machine Learning Methods To Predict High School Student Performance And Improve Early Warning Systems, David Alexandro

Doctoral Dissertations

In response to the high school dropout crisis, which comes with great economic and social costs, early warning systems (EWSs) have been developed to systematically predict and improve student outcomes. The purpose of this study is to evaluate different statistical and machine learning methods to predict high school student performance and improve EWSs. By improving education EWSs, this study aims to better identify those students in need of targeted support and inform on-the-ground practitioners who may intervene long before students may be dropping out.

The current study explores the aforementioned methods in the context of a cohort of 40,008 Connecticut …

Oxidative Modifications Of Pentafluorophenylporphyrin, Nisansala Pitiduwa Hewage

Doctoral Dissertations

Archival abstract submitted

Data Sampling And Reasoning: Harnessing Optimization And Machine Learning For Design And System Identification, Pei Cao

Doctoral Dissertations

The recently rapid advancements in sensing devices and computational power have caused paradigm shift in engineering analyses: data driven and sampling-based approaches play more and more important roles. For example, with sampling-based global optimization techniques, mechanical components can be refined and redesigned; system parameters can be accurately identified. With advancements in data mining and machine learning, underlying input and output relations of complex systems can be developed to make predictions with unseen data or to expedite analytical process. In this dissertation, advanced optimization and machine learning techniques are developed and employed to multi-facet engineering tasks from system design to identification. …

Mesoscale Modeling Of Short Fatigue Crack Behavior In Metallic Microstructure And Application To The Structural Components, Hao Yuan

Doctoral Dissertations

Many catastrophic failures of metallic structures were found to originate from fatigue damages in local details. Meanwhile, the associated environmental effects such as corrosion and high uncertainties from many aspects including material microstructure also make it difficult to quantify the fatigue life of the components or structures. Partially overcoming the limitation of current experimental means and custom fatigue assessment methods, this dissertation develops a probabilistic multi-scale fatigue damage modeling framework to comprehensively analyze the short fatigue crack behavior in mesoscale microstructure and propagate the damage to component level and structural level analysis.

For statistical volume element (SVE) in mesoscale, a …

Defining Neoepitopes That Contribute To Tumor Immunity, Cory Brennick

Doctoral Dissertations

Archive abstract submitted

Development And Characterization Of Inorganic Materials With Energy Sector Applications, Samuel J. Frueh

Doctoral Dissertations

Four classes of materials with energy sector applications have been developed or characterized herein. Processing requirements that lead to a toughened carbon fiber reinforced silicon carbide ceramic matrix composite with a compliant and oxidation resistance boron nitride interface coating were developed. Preliminary experiments resulted in highly brittle composites when BN was applied by CVD to as-received fiber. This led to a requirement of heat treating the carbon fiber to favorably modify the fiber surface prior to BN deposition. The compound ammonia borane was investigated as a potential chemical hydrogen storage material for hydrogen fuel cell applications. Two known thermal decomposition …

Advanced Control Design For Power Capture Enhancement And Load Mitigation Of Wind Turbines, Yuan Yuan

Doctoral Dissertations

Wind energy is commonly recognized as a major environmentally friendly renewable energy source. Modern wind turbines are large, flexible structures that may suffer from reduced life owing to extreme loads and fatigue when operated under highly turbulent wind field. In this dissertation, advanced controllers are synthesized to reduce overall cost of wind energy production by regulating power capture and at the same time decreasing the structural loading to enhance the durability of turbine components.

First, collective pitch control (CPC) methods are investigated to regulate speed and power, and to mitigate symmetric loads in high wind speeds. A new adaptive control …

Bdnf-Induced Release Of Endogenous Cannabinoids At Inhibitory And Excitatory Synapses, Rajamani Selvam

Doctoral Dissertations

Endocannabinoids (eCBs) are important mediators of synaptic plasticity, acting as retrograde messengers because they are released on demand from postsynaptic sites and activate presynaptic type I cannabinoid (CB1) receptors to suppress neurotransmitter release at both excitatory and inhibitory synapses. Similarly, brain derived neurotrophic factor (BDNF) is also a potent neuromodulator of synaptic transmission. The effect of BDNF on synaptic transmission is mediated by tropomyosin receptor kinase B (trkB) receptors. Both CB1 and trkB receptors are highly expressed at synapses throughout the neocortex and hippocampus. There is a growing evidence of cross talk between eCB and BDNF signaling. In particular, studies …

Mismatch Repair Processing Of Dna Damage Causes Replication Stress, Dipika Gupta

Doctoral Dissertations

The DNA mismatch repair (MMR) pathway, a crucial post-replicative repair pathway, is essential to the maintenance of genomic stability. Consequentially, loss of MMR increases mutation frequency, promoting tumorigenesis. However, if and how MMR activity coordinates with cellular replication forks is unclear. Particularly, at forks encountering lesions that cannot be faithfully replicated, like O6-methylguanine (^MeG) lesions created by DNA alkylating agents, MMR-directed processing of resultant mismatches could disrupt fork progression. Yet the events following lesion recognition remain elusive. In transformed cells MMR-dependent ^MeG/T recognition in the first S phase elicits a permanent G₂ arrest in the subsequent …

Structural Health Monitoring Of Critical Load-Carrying Members, Rosana E. Martínez-Castro

Doctoral Dissertations

The structural integrity of transportation infrastructure relies greatly on the condition of critical load-carrying members. Many in-service highway bridges use primary beams with welded cover plates that provide greater flexural capacity in regions of high-applied moment. The cyclic loading pattern of a bridge induces fatigue damage starting from the toe of the welds due to high stress concentrations. The crack propagates well into the beam’s web, reducing flexural capacity. This behavior is present in other typical connection details where stress concentrates greatly, such as floor-beams to main truss connections, diaphragms and cross-bracing connections, copied and cut-short beam ends, and stringer-to-floor …

Methods Of Storm Wind-Speed Prediction Applied To The Northeast United States, Jaemo Yang

Doctoral Dissertations

Weather forecasting of extreme weather events has evolved with the use of various techniques in an attempt to improve the forecast skill (e.g. multi/single model ensemble, data assimilation and high-resolution techniques). Despite the noted improvements, inaccuracies caused by random and systematic errors are a continuous topic for research. Statistical post-processing techniques that are computationally inexpensive play a useful role to address this issue and contribute to the reduction of prediction errors. In this research, statistical post-processing methods using numerical weather prediction models and single-model ensemble techniques are implemented to improve the prediction of storms (e.g. tropical storm, thunderstorm, rain/wind events) …