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Articles 451 - 475 of 475
Full-Text Articles in Engineering
Scalable Communication Frameworks For Multi-Agency Data Sharing, Shafaq Chaudhry
Scalable Communication Frameworks For Multi-Agency Data Sharing, Shafaq Chaudhry
Electronic Theses and Dissertations, 2020-
With the rise in frequency and magnitude of natural disasters, there is a need to break down monolithic organizational barriers and engage with community volunteers. This calls for ease of systems interoperability to facilitate communication, data-sharing and scalability of real-time response, essential for crisis communications. We propose two scalable frameworks that enable multi-agency interoperability and real-time data-sharing. The first framework harnesses the power of social media, artificial intelligence, and community volunteers to form an extended rescue-and-response network that alleviates call center burden and augments the finite capacity of dispatch units. Through an "online 9-1-1" service, affected people can request help …
Detecting Small Moving Targets In Infrared Imagery, Adam Cuellar
Detecting Small Moving Targets In Infrared Imagery, Adam Cuellar
Electronic Theses and Dissertations, 2020-
Deep convolutional neural networks have achieved remarkable results for detecting large and medium sized objects in images. However, the ability to detect smallobjects has yet to achieve the same level performance. Our focus is on applications that require the accurate detection and localization of small moving objects that are distantfrom the sensor. We first examine the ability of several state-of-the-art object detection networks (YOLOv3 and Mask R-CNN) to find small moving targets in infraredimagery using a publicly released dataset by the US Army Night Vision and Electronic Sensors Directorate. We then introduce a novel Moving Target Indicator Network (MTINet) and …
Hybrid Physics-Informed Neural Networks For Dynamical Systems, Renato Giorgiani Do Nascimento
Hybrid Physics-Informed Neural Networks For Dynamical Systems, Renato Giorgiani Do Nascimento
Electronic Theses and Dissertations, 2020-
Ordinary differential equations can describe many dynamic systems. When physics is well understood, the time-dependent responses are easily obtained numerically. The particular numerical method used for integration depends on the application. Unfortunately, when physics is not fully understood, the discrepancies between predictions and observed responses can be large and unacceptable. In this thesis, we show how to directly implement integration of ordinary differential equations through recurrent neural networks using Python. We leveraged modern machine learning frameworks, such as TensorFlow and Keras. Besides offering basic models capabilities (such as multilayer perceptrons and recurrent neural networks) and optimization methods, these frameworks offer …
Tip Clearance Effect On Convective Heat Transfer In Micro Scale Pin Fins, Hanieh Tabkhivayghan
Tip Clearance Effect On Convective Heat Transfer In Micro Scale Pin Fins, Hanieh Tabkhivayghan
Electronic Theses and Dissertations, 2020-
Fluid flow and local heat transfer in a microchannel with single and array of pin fins have been studied. For the single pin fin case, a microchannel with a 150-µm diameter pin fin with a tip clearance was experimentally and numerically studied for three Reynolds numbers in laminar regime. Tip clearances of 0, 30, 45 and 100 µm in a 200-µm high microchannel. Experimental and numerical local temperatures and the corresponding Nusselt numbers along the centerline of the pin fin were presented and discussed. Local temperatures were measured on top of the heater surface and downstream the pin fin through …
Deep Hashing For Image Similarity Search, Ali Al Kobaisi
Deep Hashing For Image Similarity Search, Ali Al Kobaisi
Electronic Theses and Dissertations, 2020-
Hashing for similarity search is one of the most widely used methods to solve the approximate nearest neighbor search problem. In this method, one first maps data items from a real valued high-dimensional space to a suitable low dimensional binary code space and then performs the approximate nearest neighbor search in this code space instead. This is beneficial because the search in the code space can be solved more efficiently in terms of runtime complexity and storage consumption. Obviously, for this method to succeed, it is necessary that similar data items be mapped to binary code words that have small …
High-Speed Interferometry And Visible Videography For Meniscus Curvature Analysis During Anisotropic Hemiwicking, John Bal
Electronic Theses and Dissertations, 2020-
Recent advancements in microelectronics have increased the need for thermal management systems capable of high heat flux dissipation within significant spatial constraints. One method of increasing local heat fluxes is the fabrication of superhydrophilic materials via micro/nanostructuring of the surface. Superhydrophilic surfaces act in a self-pumping capacity, spreading fluid beyond its intrinsic meniscus length to form thin-films, a process known as "hemiwicking", with practical applications in evaporative cooling, as well as flow, pool, and thin-film boiling. Of particular interest is anisotropic hemiwicking via asymmetric microstructuring. The microscopic asymmetricity of the design induces a macroscopically preferred direction of wicking, which has …
Monolithic Thin-Film Lithium Niobate Scanning Micromirror: Design And Simulation, Abimanyu Veerappan
Monolithic Thin-Film Lithium Niobate Scanning Micromirror: Design And Simulation, Abimanyu Veerappan
Electronic Theses and Dissertations, 2020-
In this thesis, a novel scanning micromirror is introduced in which a thin layer of lithium niobate (few micrometer thick) is utilized as both as the structural material and the actuating piezoelectric medium. In this novel monolithic design, the conventional composite torsional hinges are avoided. The finite element simulations performed and reported in here indicate that the proposed design offers a superior performance in terms of higher scan angle and linear angle control compared to the existing solutions for the same dimensions. The simulation results predict an optical scan angle of 125.6° at a resonant frequency of 550 Hz using …
Experimental Investigation Of The Laminar Burning Velocities Of High-Performance Co-Optima Biofuels, Gihun Kim
Experimental Investigation Of The Laminar Burning Velocities Of High-Performance Co-Optima Biofuels, Gihun Kim
Electronic Theses and Dissertations, 2020-
Co-Optimization of Fuels and Engines (Co-Optima) initiative of the U.S Department of Energy (DOE) started research on biofuel and biodiesel to replace the gasoline (petrol) and diesel for over the road internal combustion engines. From an initial list of thousands of fuels, selected bio-fuels and biodiesels were investigated for further combustion studies following the implementation of screening, which consisted of biodegrading, toxicity, flash point, research octane number, motor octane numbers, cetane number, and economic effect, etc. Experimental measurements of laminar burning velocity (LBV) are key parameters to understand fuel performance and applicability in engines. Furthermore, knowledge of LBV is required …
Distributed Multi-Agent Optimization And Control With Applications In Smart Grid, Towfiq Rahman
Distributed Multi-Agent Optimization And Control With Applications In Smart Grid, Towfiq Rahman
Electronic Theses and Dissertations, 2020-
With recent advancements in network technologies like 5G and Internet of Things (IoT), the size and complexity of networked interconnected agents have increased rapidly. Although centralized schemes have simpler algorithm design, in practicality, it creates high computational complexity and requires high bandwidth for centralized data pooling. In this dissertation, for distributed optimization of networked multi-agent architecture, the Alternating Direction Method of Multipliers (ADMM) is investigated. In particular, a new adaptive-gain ADMM algorithm is derived in closed form and under the standard convex property to greatly speed up the convergence of ADMM-based distributed optimization. Using the Lyapunov direct approach, the proposed …
Bias And Sensitivity Of Nonlinear Models For Seismic Response Of Ordinary Standard Bridges, Andres Rodriguez Caballero
Bias And Sensitivity Of Nonlinear Models For Seismic Response Of Ordinary Standard Bridges, Andres Rodriguez Caballero
Electronic Theses and Dissertations, 2020-
The implementation of nonlinear structural analysis under large deformation demands has enabled more realistic response prediction in comparison with the classical linear approaches. However, the sensitivity to modeling assumptions, element and material formulations, implementations, and parameter selection may lead to unreliable results. While previous works have led to a better understanding of how to best model nonlinear static responses of bridge components and systems, the introduction of dynamic loads and the corresponding material hysteresis presents an additional source of variability in the nonlinear responses. The current research involves the analysis of two ordinary standard bridges in California under seismic load …
Viscoelastic Analysis Of High Strain Composites For Deployable Structures In Space Applications, Andrew Gomez-Delrio
Viscoelastic Analysis Of High Strain Composites For Deployable Structures In Space Applications, Andrew Gomez-Delrio
Electronic Theses and Dissertations, 2020-
Thin-ply composite laminates capable of enduring high strains are currently under investigation for compliant deployable spacecraft structures. Deployable structures such as booms fabricated from these materials can be flattened and coiled to high curvatures, achieving a compact configuration for stowage. Once in orbit, they are released with minimal actuation for deployment, allowing the operational geometry to be recovered. Previous studies have shown that the viscoelastic properties of the composite epoxy matrix can negatively impact final shape accuracy due to stress relaxation during stowage. In addition, since the strain energy stored is relied upon for deployment, considerable relaxation can potentially result …
Data-Driven Nonlinear Control Designs For Constrained Systems, Roland Harvey
Data-Driven Nonlinear Control Designs For Constrained Systems, Roland Harvey
Electronic Theses and Dissertations, 2020-
Systems with nonlinear dynamics are theoretically constrained to the realm of nonlinear analysis and design, while explicit constraints are expressed as equalities or inequalities of state, input, and output vectors of differential equations. Few control designs exist for systems with such explicit constraints, and no generalized solution has been provided. This dissertation presents general techniques to design stabilizing controls for a specific class of nonlinear systems with constraints on input and output, and verifies that such designs are straightforward to implement in selected applications. Additionally, a closed-form technique for an open-loop problem with unsolvable dynamic equations is developed. Typical optimal …
Experimentation And Simulation Of Pulsed Eddy Current Thermography Of Subsurface Aircraft Corrosive Defects, Johnathan Hernandez
Experimentation And Simulation Of Pulsed Eddy Current Thermography Of Subsurface Aircraft Corrosive Defects, Johnathan Hernandez
Electronic Theses and Dissertations, 2020-
During the life cycle of aircraft, external structures are under constant attack from environmental degradation in the form of corrosion. Corrosive defects consist of multiple types of surface and subsurface damage that are often undetectable due to surface coatings or insulation leading to loss in structural integrity. Non-destructive techniques for corrosion detection typically require the removal of paint. Detection of corrosion under insulation (CUI) is highly valuable for cost and time effectiveness. Although techniques have been developed for detection of CUI, not many of these satisfy the criteria for portability and hangar operation. To address this, multiple techniques were investigated …
Engineering The Surface Chemistry And Surface Conditions To Optimize The Heat Removal Rate Of Various Surfaces, Thomas Germain
Engineering The Surface Chemistry And Surface Conditions To Optimize The Heat Removal Rate Of Various Surfaces, Thomas Germain
Electronic Theses and Dissertations, 2020-
As the demand for more powerful and smaller electronics rise, the need for creative cooling solutions to prevent burnout becomes increasingly paramount. In response to recent cooling needs, new cooling techniques, such as jet impingement cooling, spray cooling, and heat pipes, have risen in popularity for their simple design and efficiency in thermal transport. This interest has risen in both industry and academia, where research has been conducted to optimize the heat transfer performance for these systems and how these systems can be implemented in new technologies. One method that has risen in interest is affecting the surface, through physical …
Integrating Graphene Into Polymer Derived Ceramics Towards The Development Of New Thermoelectric Materials, Elizabeth Barrios
Integrating Graphene Into Polymer Derived Ceramics Towards The Development Of New Thermoelectric Materials, Elizabeth Barrios
Electronic Theses and Dissertations, 2020-
Radioisotope thermoelectric generators (RTGs) have been an enabling technology for the exploration of deep space since the dawn of the Space Age. Since its first deployment in a meteorological satellite in the late 1960's, RTGs have been used to provide solid-state, maintenance-free power to 27 American spacecraft and scientific instruments. While showing great success in the past, the future usage of thermoelectric devices is limited by the low operating efficiencies and the use of hazardous or expensive materials, limiting the use of thermoelectric technologies to niche applications such as space exploration. Current research efforts that address these disadvantages have focused …
Understanding The Socio-Infrastructure Systems During Disaster From Social Media Data, Kamol Chandra Roy
Understanding The Socio-Infrastructure Systems During Disaster From Social Media Data, Kamol Chandra Roy
Electronic Theses and Dissertations, 2020-
Our socio-infrastructure systems are becoming more and more vulnerable due to the increased severity and frequency of extreme events every year. Effective disaster management can minimize the damaging impacts of a disaster to a large extent. The ubiquitous use of social media platforms in GPS enabled smartphones offers a unique opportunity to observe, model, and predict human behavior during a disaster. This dissertation explores the opportunity of using social media data and different modeling techniques towards understanding and managing disaster more dynamically. In this dissertation, we focus on four objectives. First, we develop a method to infer individual evacuation behaviors …
Advanced Econometic Models For Modeling Flows: Application To Shared Economy, Bibhas Dey
Advanced Econometic Models For Modeling Flows: Application To Shared Economy, Bibhas Dey
Electronic Theses and Dissertations, 2020-
Travel and tourism industry is undergoing transformation with the flourishing of online sharing economy marketplaces such as Bike Share services, Uber/Lyft (for taxi services), Eatwith (for community restaurants), and AirBnB (for accommodation). The current research effort contributes to literature on sharing economy service flow analysis by formulating and estiamting econometric approaches for analyzing frequency variables. The sharing economy alternatives investigated include: (a) accommodation service (AirBnB), (b) bikeshare service (Citi bike, NYC) and (c) ride hailing service (UBER/LYFT/Taxi). In the first part of the dissertation, we develop a copula based negative binomial count model framework to count AirBnB listings at census …
Ultraviolet Irradiation Combined With Chlorine Dioxide Pre-Oxidation For Disinfection By-Product Control, Paula Campesino
Ultraviolet Irradiation Combined With Chlorine Dioxide Pre-Oxidation For Disinfection By-Product Control, Paula Campesino
Electronic Theses and Dissertations, 2020-
The use of ultraviolet (UV) light and chlorine dioxide (ClO2) as an advanced oxidation process (AOP) has been investigated at the bench-scale to understand the effects of their use on disinfection by-product (DBP) formation potential (FP) in chlorinated groundwater (GW) and surface water (SW) supplies. Two GWs and two SWs of varying qualities were subject to a series of AOP treatment sequences at the bench scale: sodium hypochlorite, to serve as a baseline; ClO2-Cl2, UV-Cl2, and UV-ClO2-Cl2. In these treatment sequences, Cl2 is used as a primary and secondary disinfectant. Several water quality parameters were measured throughout the experiments, including …
Seismocardiography - Genesis, And Utilization Of Machine Learning For Variability Reduction And Improved Cardiac Health Monitoring, Peshala Thibbotuwawa Gamage
Seismocardiography - Genesis, And Utilization Of Machine Learning For Variability Reduction And Improved Cardiac Health Monitoring, Peshala Thibbotuwawa Gamage
Electronic Theses and Dissertations, 2020-
Seismocardiography (SCG) is the measured chest surface vibrations resulting from cardiac activity. Although SCG can contain information that correlate with cardiac health, its utility may be limited by lack of understanding of the signal genesis and a variability that can mask subtle SCG changes. The current research utilized medical imaging reconstruction and finite element method (FEM) to simulate SCG by modeling the propagation of myocardial movements to the chest surface. FEM analysis provided a link between myocardial movements and the SCG signals measured at the chest surface and suggested that myocardial movement is a primary source of SCG. Increased understanding …
Thin-Film Lithium Niobate Integrated Photonics On Silicon For Electro- And Nonlinear-Optic Applications, Amirmahdi Honardoost
Thin-Film Lithium Niobate Integrated Photonics On Silicon For Electro- And Nonlinear-Optic Applications, Amirmahdi Honardoost
Electronic Theses and Dissertations, 2020-
In order to overcome the drawbacks associated with conventional bulk lithium niobate photonic, thin-film lithium-niobate-on-silicon has been pursued recently. This work presents contributions made to electro-, and nonlinear-optic applications of this technology. For electrooptic applications, detailed modeling and design guidelines of optical and radio-frequency parameters of ultracompact modulators are developed and their accuracy in predicting the high-speed performance of such devices have been verified by comparison with experimental results. Novel design techniques and pathways for ultrahigh-speed (sub-terahertz) operation of such modulators, achieving up to 400 GHz modulation bandwidth, are also presented. For optical interconnect applications, novel structures for ultralow-power consumption …
Wind Turbine Generator Overheating Solution, Gopal Singh
Wind Turbine Generator Overheating Solution, Gopal Singh
Electronic Theses and Dissertations, 2020-
An increase in the demand for electrical power and tremendous growth of renewable energy sources has been seen in the last decade, which resulted in designing the wind turbine system components for higher load point performance, resulting in higher annual energy production. Cost optimization, weight reduction, and lower non-conformance cost are some of the expectations that the wind turbine needs to meet in the present stringent market condition. Overheating of the wind turbine system components is one of the primary challenges to overcome when the system operates at a higher load point. The overheating issue of the wind turbine generator …
Mfpa: Mixed-Signal Field Programmable Array For Energy-Aware Compressive Signal Processing, Adrian Tatulian
Mfpa: Mixed-Signal Field Programmable Array For Energy-Aware Compressive Signal Processing, Adrian Tatulian
Electronic Theses and Dissertations, 2020-
Compressive Sensing (CS) is a signal processing technique which reduces the number of samples taken per frame to decrease energy, storage, and data transmission overheads, as well as reducing time taken for data acquisition in time-critical applications. The tradeoff in such an approach is increased complexity of signal reconstruction. While several algorithms have been developed for CS signal reconstruction, hardware implementation of these algorithms is still an area of active research. Prior work has sought to utilize parallelism available in reconstruction algorithms to minimize hardware overheads; however, such approaches are limited by the underlying limitations in CMOS technology. Herein, the …
Parallelized X-Ray Tracing With Gpu Ray-Tracing Engine, Joseph Ulseth
Parallelized X-Ray Tracing With Gpu Ray-Tracing Engine, Joseph Ulseth
Electronic Theses and Dissertations, 2020-
X-ray diffraction tomography (XDT) is used to probe material composition of objects, providing improved contrast between materials compared to conventional transmission based computed tomography (CT). In this work, a small angle approximation to Bragg's Equation of diffraction is coupled with parallelized computing using Graphics Processing Units (GPUs) to accelerate XDT simulations. The approximation gives rise to a simple yet useful proportionality between momentum transfer, radial distance of diffracted signal with respect to incoming beam's location, and depth of material, so that ray tracing may be parallelized. NVIDIA's OptiX ray-tracing engine, a parallelized pipeline for GPUs, is employed to perform XDT …
Study On Ductile Fracture With Anisotropic And Strain Rate Effects In Manufacturing Processes, Hao Pan
Study On Ductile Fracture With Anisotropic And Strain Rate Effects In Manufacturing Processes, Hao Pan
Electronic Theses and Dissertations, 2020-
Ductile fracture is a topic of great importance in automotive and aerospace industries. Prediction of ductile fracture in engineering structures relies on developing robust material models under complex loading conditions. This dissertation addresses the anisotropic and strain rate effects in constitutive and ductile fracture models of lightweight metals. In the present modeling framework, the anisotropic plasticity behavior is modeled by combination of an initial anisotropic yield function and an isotropic hardening correction by Lode dependence. A new all-strain based anisotropic fracture model is proposed based on the approach of linear transformation on plastic strain rate tensor. The strain rate effects …
Pervasive Spectrum Sharing For Improved Wireless Experience, Mostafizur Rahman
Pervasive Spectrum Sharing For Improved Wireless Experience, Mostafizur Rahman
Electronic Theses and Dissertations, 2020-
Spectrum sharing among cellular users has been a promising approach to attain better efficiency in the use of the limited spectral bands. The existing dynamic spectrum access techniques include sharing of the licensed spectrum bands by allowing other 'secondary' users to use the bands if the licensee 'primary' user is idle. This primary-secondary spectrum sharing is limited in terms of design space, and may not be sufficient to meet the ever-increasing demand of connectivity and high signal quality to improve the end-users' wireless experience. The next step to increase spectrum efficiency is to design markets where sharing takes place pervasively …