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Articles 1 - 30 of 43
Full-Text Articles in Engineering
Modeling Response Of Water Quality To Land-Use And Climate Change In Lake Auburn, Me, Nicholas Messina
Modeling Response Of Water Quality To Land-Use And Climate Change In Lake Auburn, Me, Nicholas Messina
Electronic Theses and Dissertations
Lake Auburn, Maine, USA, is a historically unproductive lake that has experienced multiple algal blooms since 2011. The lake is the water supply source for a population of ~60,000. We modeled past temperature, and concentrations of dissolved oxygen (DO) and phosphorus (P) in Lake Auburn by considering the watershed and internal contributions of P as well as atmospheric factors, and predicted the change in lake water quality in response to future climate and land-use changes. A stream hydrology and P-loading model (SimplyP) was used to generate input from two major tributaries into a lake model (MyLake) to simulate physical mixing, …
Formally Designing And Implementing Cyber Security Mechanisms In Industrial Control Networks., Mehdi Sabraoui
Formally Designing And Implementing Cyber Security Mechanisms In Industrial Control Networks., Mehdi Sabraoui
Electronic Theses and Dissertations
This dissertation describes progress in the state-of-the-art for developing and deploying formally verified cyber security devices in industrial control networks. It begins by detailing the unique struggles that are faced in industrial control networks and why concepts and technologies developed for securing traditional networks might not be appropriate. It uses these unique struggles and examples of contemporary cyber-attacks targeting control systems to argue that progress in securing control systems is best met with formal verification of systems, their specifications, and their security properties. This dissertation then presents a development process and identifies two technologies, TLA+ and seL4, that can be …
Tide And Storm Surge Dynamics In Estuaries Of Variable Morphology, Preston Spicer
Tide And Storm Surge Dynamics In Estuaries Of Variable Morphology, Preston Spicer
Electronic Theses and Dissertations
Storm surges are the most destructive component of coastal storms, and climate change is predicted to enhance the frequency of intense storm events in the future. Currently, most storm surge forecasting assumes linear surges and the extent to which this assumption leads to model inaccuracies is currently unknown. The goals of this research are to characterize storm surge in estuaries and determine the contribution of nonlinear tide-surge interaction to total inland surges. A citizen science experiment was conducted in four estuaries in Maine. Results show the estuary shape influences surges through convergence, friction and man-made constrictions. These mechanisms modified total …
Perspectives On Water Resources Risk, Policy, And Stewardship, Anne Marie Lausier
Perspectives On Water Resources Risk, Policy, And Stewardship, Anne Marie Lausier
Electronic Theses and Dissertations
Water management approaches have historically optimized water for human use and placed lower emphasis on the relationship between ecosystems and humans. Despite efforts to balance human and ecosystem needs, existing management approaches tend to prioritize some needs, knowledges, and values over others. Natural and anthropogenic changes pose challenges to water governance institutions due to policy inflexibility, and may lead to ecosystem degradation, water stress, and conflict among water users. This work seeks to redress these shortcomings through three scholarly contributions. First, a conceptual framework for Water Resources Stewardship is developed in support of equitable and adaptive solutions under changing conditions. …
Analysis Of Hydrodynamic And Bathymetric Gradients In Canaveral National Seashore Following Living Shoreline And Oyster Restorations, David Spiering
Analysis Of Hydrodynamic And Bathymetric Gradients In Canaveral National Seashore Following Living Shoreline And Oyster Restorations, David Spiering
Electronic Theses and Dissertations
Coastal vulnerability has been gaining recognition as a critical issue, especially with the increasing predictions of sea level rise. Susceptibility to extreme events, eutrophication, and shoreline modification has left many coastal regions in a degraded state. Shoreline protection has traditionally taken the form of seawalls and offshore breakwaters which can be detrimental to both the local ecosystems and adjoining shorelines. The objective of this thesis is to analyze the hydrodynamic and bathymetric variation that occurs within Mosquito Lagoon, Florida following living shoreline and oyster reef restorations. The shoreline sites were sampled using a Before-After-Control-Impact (BACI) design and data were analyzed …
Lithium Molybdate-Sulfur Battery., Ruchira Ravinath Dharmasena
Lithium Molybdate-Sulfur Battery., Ruchira Ravinath Dharmasena
Electronic Theses and Dissertations
Rechargeable energy storage systems play a vital role in today’s automobile industry with the emergence of electric vehicles (EVs). In order to meet the targets set by the department of energy (DOE), there is an immediate need of new battery chemistries with higher energy density than the current Li- ion technology. Lithium–sulfur (Li–S) batteries have attracted enormous attention in the energy-storage, due to their high specific energy density of 2600 Wh kg-1 and operational voltage of 2.0 V. Despite the promising electrochemical characteristics, Li-S batteries suffer from serious technical challenges such as dissolution of polysulfides Li2Sx …
An Explainable Sequence-Based Deep Learning Predictor With Applications To Song Recommendation And Text Classification., Khalil Damak
An Explainable Sequence-Based Deep Learning Predictor With Applications To Song Recommendation And Text Classification., Khalil Damak
Electronic Theses and Dissertations
Streaming applications are now the predominant tools for listening to music. What makes the success of such software is the availability of songs and especially their ability to provide users with relevant personalized recommendations. State of the art music recommender systems mainly rely on either Matrix factorization-based collaborative filtering approaches or deep learning architectures. Deep learning models usually use metadata for content-based filtering or predict the next user interaction (listening to a song) using a memory-based deep learning structure that learns from temporal sequences of user actions. Despite advances in deep learning models for song recommendation systems, none has taken …
High Performance Liquid Crystal Devices For Augmented Reality And Virtual Reality, Md Javed Rouf Talukder
High Performance Liquid Crystal Devices For Augmented Reality And Virtual Reality, Md Javed Rouf Talukder
Electronic Theses and Dissertations
See-through augmented reality and virtual reality displays are emerging due to their widespread applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment. For augmented reality and virtual reality displays, high-resolution density, high luminance, fast response time and high ambient contrast ratio are critically needed. High-resolution density helps eliminate the screen-door effect, high luminance and fast response time enable low duty ratio operation, which plays a key role for suppressing image blurs. A dimmer placed in front of AR display helps to control the incident background light, which in turn improves the image contrast. In this dissertation, …
Processing Of Advanced Infrared Materials, Daniel Mcgill
Processing Of Advanced Infrared Materials, Daniel Mcgill
Electronic Theses and Dissertations
Infrared transparent glassy and crystalline materials often have unique and complex processing requirements but are an important class of materials for such applications as optical windows, lenses, waveplates, polarizers and beam splitters. This thesis investigates two specific materials, one amorphous and one crystalline, that are candidates for use in the short and midwave-infrared and mid and longwave infrared, respectively. It is demonstrated that an innovative uniaxial sintering process, which uses a sacrificial pressure-transmitting medium, can be used to fully densify a 70TeO2-20WO3-10La2O3 (TWL) glass powder. The characteristics of the sintered TWL glass is compared to that of a parent glass …
Broadband Mid-Infrared Frequency Combs Generated Via Frequency Division, Qitian Ru
Broadband Mid-Infrared Frequency Combs Generated Via Frequency Division, Qitian Ru
Electronic Theses and Dissertations
Frequency combs have revolutionized metrology and demonstrated numerous applications in science and technology. Combs operating in the mid-infrared region could be beneficial for molecular spectroscopy for several reasons. First, numerous molecules have their spectroscopic signatures in this region. Furthermore, the atmospheric window (3-5μm and 8-14μm) is located here. Additionally, a mid-infrared frequency comb could be employed as a diagnostic tool for the many components of human breath, as well as for detection of harmful gases and contaminants in the atmosphere. In this thesis, I used synchronously pumped subharmonic optical parametric oscillators (OPOs) operating at degeneracy to produce ultra-broadband outputs near …
The Effect Of Edge-Of-Field Nutrient Management Practices On Microbial Concentrations In Subsurface Drainage Water And The Associated Risk Of Antibiotic Resistance Dissemination, Sara Mardani
Electronic Theses and Dissertations
Many in-field and edge-of-field management practices have been used to reduce nutrient loads from agricultural fields. The denitrification woodchip bioreactor (WB) is one edgeof- field management practice that has proven to be effective in removing nitrate from subsurface drainage water. The success in nitrate removal achieved with WBs has raised interest in expanding their capabilities for removing other agricultural pollutants, including phosphorus, by using other types of media like phosphorus-sorbing filters or combining these filters with woodchips to remove both nitrate and phosphorus as dual-nutrient removal systems. Despite the extensive research done on WBs and nutrient filter materials, little consideration …
A Study Of Several Applications Of Parallel Computing In The Sciences Using Petsc, Nicholas Stegmeier
A Study Of Several Applications Of Parallel Computing In The Sciences Using Petsc, Nicholas Stegmeier
Electronic Theses and Dissertations
The importance of computing in the natural sciences continues to grow as scientists strive to analyze complex phenomena. The dynamics of turbulence, astrophysics simulations, and climate change are just a few examples where computing is critical. These problems are computationally intractable on all computing platforms except supercomputers, necessitating the continued development of efficient algorithms and methodologies in parallel computing. This thesis investigates the use of parallel computing and mathematical modeling in the natural sciences through several applications, namely computational fluid dynamics for impinging jets in mechanical engineering, simulation of biofilms in an aqueous environment in mathematical biology, and the solution …
Holographic Optical Elements For Visible Light Applications In Photo-Thermo-Refractive Glass, Fedor Kompan
Holographic Optical Elements For Visible Light Applications In Photo-Thermo-Refractive Glass, Fedor Kompan
Electronic Theses and Dissertations
This dissertation reports on design and fabrication of various optical elements in Photo-thermo-refractive (PTR) glass. An ability to produce complex holographic optical elements (HOEs) for the visible spectral region appears very beneficial for variety of applications, however, it is limited due to photosensitivity of the glass confined within the UV region. First two parts of this dissertation present two independent approaches to the problem of holographic recording using visible radiation. The first method involves modification of the original PTR glass rendering it photosensitive to radiation in the visible spectral region and, thus, making possible the recording of holograms in PTR …
Imaging Through Glass-Air Anderson Localizing Optical Fiber, Jian Zhao
Imaging Through Glass-Air Anderson Localizing Optical Fiber, Jian Zhao
Electronic Theses and Dissertations
The fiber-optic imaging system enables imaging deeply into hollow tissue tracts or organs of biological objects in a minimally invasive way, which are inaccessible to conventional microscopy. It is the key technology to visualize biological objects in biomedical research and clinical applications. The fiber-optic imaging system should be able to deliver a high-quality image to resolve the details of cell morphology in vivo and in real time with a miniaturized imaging unit. It also has to be insensitive to environmental perturbations, such as mechanical bending or temperature variations. Besides, both coherent and incoherent light sources should be compatible with the …
Fundamental Properties Of Metallic Nanolasers, William Hayenga
Fundamental Properties Of Metallic Nanolasers, William Hayenga
Electronic Theses and Dissertations
The last two decades have witnessed tremendous advancements in the area of nanophotonics and plasmonics, which has helped propel the development of integrated photonic sources. Of central importance to such circuits is compact, scalable, low threshold, and efficient coherent sources that can be driven at high modulation frequencies. In this regard, metallic nanolasers offer a unique platform. Their introduction has enabled confinement of light at a subwavelength scale and the ultra-small size of the modes afforded by these structures allows for cavity enhancing effects that can help facilitate thresholdless lasing and large direct modulation bandwidths. In this report, I present …
Adsorption Capacity Assessment Of Advance Green Environmental Media To Remove Nutrients From Stormwater-Runoff, Hanan Elhakiem
Adsorption Capacity Assessment Of Advance Green Environmental Media To Remove Nutrients From Stormwater-Runoff, Hanan Elhakiem
Electronic Theses and Dissertations
Best Management Practices (BMPs) in stormwater treatment are a suite of treatment alternatives to deal with pollutant removal problems from stormwater runoff. Biosorption-activated media (BAM) are green sorption media consists of recycled materials have shown excellent nutrient removal as an effective BMP by enhancing physicochemical and microbiological processes. In this study, Iron-Filling Green Environmental Media (denoted as IFGEM-3) and Advanced Green Environmental Media 1 and 2 (denoted as AGEM-1 and AGEM-2) were produced and tested for their adsorption capacities as well as removal and recovery potential for phosphate, nitrate, and ammonia against natural soil (baseline) collected from a stormwater retention …
Hybrid Integration Of Second- And Third-Order Highly Nonlinear Waveguides On Silicon Substrates, Guillermo Fernando Camacho Gonzalez
Hybrid Integration Of Second- And Third-Order Highly Nonlinear Waveguides On Silicon Substrates, Guillermo Fernando Camacho Gonzalez
Electronic Theses and Dissertations
In order to extend the capabilities and applications of silicon photonics, other materials and compatible technologies have been developed and integrated on silicon substrates. A particular class of integrable materials are those with high second- and third-order nonlinear optical properties. This work presents contributions made to nonlinear integrated photonics on silicon substrates, including chalcogenide waveguides for over an octave supercontinuum generation, and rib-loaded thin-film lithium niobate waveguides for highly efficient second-harmonic generation. Through the pursuit of hybrid integration of the two types of waveguides for applications such as on-chip self-referenced optical frequency combs, we have experimentally demonstrated fabrication integrability of …
Third-Order Optical Nonlinearities For Integrated Microwave Photonics Applications, Marcin Malinowski
Third-Order Optical Nonlinearities For Integrated Microwave Photonics Applications, Marcin Malinowski
Electronic Theses and Dissertations
The field of integrated photonics aims at compressing large and environmentally-sensitive optical systems to micron-sized circuits that can be mass-produced through existing semiconductor fabrication facilities. The integration of optical components on single chips is pivotal to the realization of miniature systems with high degree of complexity. Such novel photonic chips find abundant applications in optical communication, spectroscopy and signal processing. This work concentrates on harnessing nonlinear phenomena to this avail. The first part of this dissertation discusses, both from component and system level, the development of a frequency comb source with a semiconductor mode-locked laser at its heart. New nonlinear …
Non-Hermitian And Space-Time Mode Management, Nicholas Nye
Non-Hermitian And Space-Time Mode Management, Nicholas Nye
Electronic Theses and Dissertations
In the last few years, optics has witnessed the emergence of two fields namely metasurfaces and parity-time (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. On the other hand, PT symmetry has emerged from quantum mechanics, when a new class of non-Hermitian Hamiltonian quantum systems was shown to have real eigenvalues. In this work, we demonstrate how PT-symmetric diffractive structures are capable of eliminating diffraction orders in specific directions, while maintaining/enhancing the remaining orders. In the second part of this work, we emphasize on supersymmetry (SUSY) and its applications in …
Variability Of E. Coli In Streambed Sediments And Its Implication For Water Quality, Sadia Salam
Variability Of E. Coli In Streambed Sediments And Its Implication For Water Quality, Sadia Salam
Electronic Theses and Dissertations
Fecal indicator bacteria (FIB), including E. coli, are the number one cause of water quality impairments in the United States according to the USEPA. FIB are used as a predictor to identify the possible presence of pathogens in waterbodies. E. coli is a useful indicator of gastrointestinal (GI) related illnesses from contact with fresh water. While surface water is routinely monitored for water quality, streambed sediments are rarely considered as a source of FIB to the overlying water column. This study focuses on understanding the variation of E. coli concentrations in streambed sediments and the potential impact of sediment sources …
Instance Segmentation And Object Detection In Road Scenes Using Inverse Perspective Mapping Of 3d Point Clouds And 2d Images, Chungyup Lee
Instance Segmentation And Object Detection In Road Scenes Using Inverse Perspective Mapping Of 3d Point Clouds And 2d Images, Chungyup Lee
Electronic Theses and Dissertations
The instance segmentation and object detection are important tasks in smart car applications. Recently, a variety of neural network-based approaches have been proposed. One of the challenges is that there are various scales of objects in a scene, and it requires the neural network to have a large receptive field to deal with the scale variations. In other words, the neural network must have deep architectures which slow down computation. In smart car applications, the accuracy of detection and segmentation of vehicle and pedestrian is hugely critical. Besides, 2D images do not have distance information but enough visual appearance. On …
Natural Sunlight Photodegradation Of Halogenated Disinfection Byproducts In Water, Ibrahim Abusallout
Natural Sunlight Photodegradation Of Halogenated Disinfection Byproducts In Water, Ibrahim Abusallout
Electronic Theses and Dissertations
Disinfection byproducts (DBPs) presence in wastewater effluents and receiving waters may impact the quality of drinking water during water reuse practices. Natural solar photolysis is one of the biogeochemical processes that may lead to decreased DBPs concentrations in water. The purpose of this dissertation is to determine the fate of chlorinated, brominated and iodinated DBPs in surface water by natural sunlight photolysis and investigate the use of solar-based advanced oxidation processes (AOPs) for removal of DBPs in water. Total organic halogen (TOX) was used to measure total chlorinated- (TOCl), brominated- (TOBr) and iodinated-DBPs (TOI) in water. The first objective was …
A Policy Mechanism For Federal Recommendation Of Security Standards For Mobile Devices That Conduct Transactions, Ariel Huckabay
A Policy Mechanism For Federal Recommendation Of Security Standards For Mobile Devices That Conduct Transactions, Ariel Huckabay
Electronic Theses and Dissertations
The proliferation of mobile devices in the BRIC countries has prompted them to develop policies to manage the security of these devices. In China, mobile devices are a primary tool for payments. As a result, China instituted in 2017 a cyber security policy that applies to mobile devices giving China broad authority to manage cyber threats. The United States has a similar need for a cyber policy. Mobile devices are likely to become a primary payment tool in the United States soon. DHS has also identified a need for more effective security policy in mobile devices for government operations. This …
Use Of Seismic Refraction In Determining Rock Mass Anisotropy, Mohammad Najmush Sakib Oyan
Use Of Seismic Refraction In Determining Rock Mass Anisotropy, Mohammad Najmush Sakib Oyan
Electronic Theses and Dissertations
Seismic refraction is a popular method used by geological/geotechnical engineers to understand subsurface conditions. This method along with information collected from borings produce a realistic image of the ground beneath us. The goal of this study is to define and test a set of procedures to use seismic refraction alone to create high quality images of subsurface conditions. The focus is on areas with several meters of soil overlain by bedrock. The application of these procedures will minimize construction costs by eliminating the need for multiple boreholes. The results show that two important criteria must be met for successful application …
Computational Imaging Systems For High-Speed, Adaptive Sensing Applications, Yangyang Sun
Computational Imaging Systems For High-Speed, Adaptive Sensing Applications, Yangyang Sun
Electronic Theses and Dissertations
Driven by the advances in signal processing and ubiquitous availability of high-speed low-cost computing resources over the past decade, computational imaging has seen the growing interest. Improvements on spatial, temporal, and spectral resolutions have been made with novel designs of imaging systems and optimization methods. However, there are two limitations in computational imaging. 1), Computational imaging requires full knowledge and representation of the imaging system called the forward model to reconstruct the object of interest. This limits the applications in the systems with a parameterized unknown forward model such as range imaging systems. 2), the regularization in the optimization process …
Design And Fabrication Of Scalable Multifunctional Multimaterial Fibers And Textiles, Felix Tan
Design And Fabrication Of Scalable Multifunctional Multimaterial Fibers And Textiles, Felix Tan
Electronic Theses and Dissertations
Multimaterial fibers eschew the traditional mono-material structures typical of traditional optical fibers for novel internal architectures that combine disparate materials with distinct optical, mechanical, and electronic properties, thereby enabling novel optoelectronic functionalities delivered in the form factor of an extended fiber. This new class of fibers developed over the past two decades is attracting interest from researchers in such different fields as optics, textiles, and biomedicine. The juxtaposition of multiple materials integrated at micro- and nanoscales in complex geometries while ensuring intimate smooth interfaces extending continuously for kilometers facilitates unique applications such as non-invasive laser surgery, self-monitoring fibers, e-textiles, and …
Stable, Highly Luminescent Perovskite-Polymer Composites For Photonics Applications, Juan He
Stable, Highly Luminescent Perovskite-Polymer Composites For Photonics Applications, Juan He
Electronic Theses and Dissertations
Metal halide perovskites (simplified as perovskites as below), particularly those in nanocrystal forms, have recently emerged as highly efficient, bandgap tunable photonics materials that can be easily solution processed at low cost for display, lighting or other energy conversion applications. However, the quick degradation of perovskite nanocrystals under external stresses or upon colloidal aggregations has been a major challenge for most applications where high reliability is normally required. In this thesis, we have explored a polymer swelling-deswelling microencapsulation (SDM) process that enables the dispersion, in-situ crystallization and subsequent surface passivation of perovskite nanocrystals in polymer matrices, and leads to ultrastable …
Assessment Of A Surface Water Supply For Source And Treated Distribution System Quality, Angela Rodriguez
Assessment Of A Surface Water Supply For Source And Treated Distribution System Quality, Angela Rodriguez
Electronic Theses and Dissertations
This study focused on providing a source to tap assessment of surface water systems with respect to (i) the use of alternative biomonitoring tools, (ii) disinfection byproduct (DBP) formation and control, and (iii) corrosion control. In the first study component, two water systems were microbiologically evaluated using adenosine triphosphate (ATP) bioluminescence technology. It was determined that microbial ATP was useful as a surrogate for biomonitoring within a surface water system when paired with traditional methods. Although microbial activity differed between distribution systems that used either chloramine or chlorine disinfectant, in both cases flowrate and season affected microbial ATP values. In …
An Assessment Of Biosorption Activated Media For The Removal Of Pollutants In Up-Flow Stormwater Treatment Systems, Andrew Hood
An Assessment Of Biosorption Activated Media For The Removal Of Pollutants In Up-Flow Stormwater Treatment Systems, Andrew Hood
Electronic Theses and Dissertations
Nitrogen and phosphorus are often the limiting nutrients for marine and freshwater systems respectively. Additionally, stormwater often contains elevated levels of pathogens which can pollute the receiving water body and impact reuse applications [1-4]. The reduction of limiting nutrients and pathogens is a common primary target for stormwater best management practices (BMPs) [5]. Traditional BMPs, such as retention/detention treatment ponds require large footprints and may not be practical in ultra-urban environments where above ground space is limited. Upflow filters utilizing biosorption activated media (BAM) that can be placed underground offer a small footprint alternative. Additionally, BAM upflow filters can be …
A Study Of Perceptions On Incident Response Exercises, Information Sharing, Situational Awareness, And Incident Response Planning In Power Grid Utilities, Joseph Garmon
Electronic Theses and Dissertations
The power grid is facing increasing risks from a cybersecurity attack. Attacks that shut off electricity in Ukraine have already occurred, and successful compromises of the power grid that did not shut off electricity to customers have been privately disclosed in North America. The objective of this study is to identify how perceptions of various factors emphasized in the electric sector affect incident response planning. Methods used include a survey of 229 power grid personnel and the use of partial least squares structural equation modeling to identify causal relationships. This study reveals the relationships between perceptions by personnel responsible for …