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Articles 1351 - 1380 of 4566

Full-Text Articles in Engineering

An Integrated Hydrodynamic-Marsh Model With Applications In Fluvial, Marine, And Mixed Estuarine Systems, Karim Alizad Jan 2016

An Integrated Hydrodynamic-Marsh Model With Applications In Fluvial, Marine, And Mixed Estuarine Systems, Karim Alizad

Electronic Theses and Dissertations

Coastal wetlands experience fluctuating productivity when subjected to various stressors. One of the most impactful stressors is sea level rise (SLR) associated with global warming. Research has shown that under SLR, salt marshes may not have time to establish an equilibrium with sea level and may migrate landward or become open water. Salt marsh systems play an important role in the coastal ecosystem by providing intertidal habitats and food for birds, fish, crabs, mussels, and other animals. They also protect shorelines by dissipating flow and damping wave energy through an increase in drag forces. Due to the serious consequences of …

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A New Path Planning Guidance Law For Improved Impact Time Control Of Missiles And Precision Munitions, Mark Snyder Jan 2016

A New Path Planning Guidance Law For Improved Impact Time Control Of Missiles And Precision Munitions, Mark Snyder

Electronic Theses and Dissertations

A new missile guidance law is proposed for the control of impact time which provides an improved time-to-go calculation by removing error due to trajectory curvature and also provides a family of trajectories for trajectory planning purposes. Unlike conventional optimal guidance laws, the proposed law is non explicit in time-to-go and the linearization of the engagement kinematics in order to gain a closed form solution is not necessary.

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Uncooled Infrared Detector Featuring Silicon Based Nanoscale Thermocouple, Mohammad Modarres-Zadeh Jan 2016

Uncooled Infrared Detector Featuring Silicon Based Nanoscale Thermocouple, Mohammad Modarres-Zadeh

Electronic Theses and Dissertations

The main focus of this dissertation is to improve the performance of thermoelectric (TE) infrared (IR) detectors. TE IR detectors are part of uncooled detectors that can operate at room temperature. These detectors have been around for many years, however, their performance has been lower than their contesting technologies. A novel high-responsivity uncooled thermoelectric infrared detector is designed, fabricated, and characterized. This detector features a single standalone polysilicon-based thermocouple (without a supporting membrane) covered by an umbrellalike optical-cavity IR absorber. It is proved that the highest responsivity in the developed detectors can be achieved with only one thermocouple. Since the …

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Getting To Net Zero Energy Buildings: A Holistic Techno-Ecological Modeling Approach, Mehdi Alirezaei Jan 2016

Getting To Net Zero Energy Buildings: A Holistic Techno-Ecological Modeling Approach, Mehdi Alirezaei

Electronic Theses and Dissertations

Buildings in the United States are responsible for more than 40% of the primary energy and 70% of electricity usage and greatly in CO2 emission by about 39%, more than any other sector including transportation and industry sectors. This energy consumption is expected to grow mainly due to increasing trends in new buildings construction. Rising energy prices alongside with energy independencies, limited resources, and climate change have made the current situation even worse. An Energy Efficient (EE) building is able to reduce the heating and cooling load significantly compared with a code compliant building. Furthermore, integrating renewable energy sources in …

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Transient Cfd Analysis Of Autorotation Using Hybrid Les And Adaptive Mesh Morphing Techniques, Patricia Coronado Domenge Jan 2016

Transient Cfd Analysis Of Autorotation Using Hybrid Les And Adaptive Mesh Morphing Techniques, Patricia Coronado Domenge

Electronic Theses and Dissertations

Large-Eddy Simulation (LES) based turbulence modeling is a developing area of research in Fluid-Structure Interaction (FSI). There is considerable scope for further scientific research in this field and this dissertation aims to extend it to the study of flow-induced motion. The emphasis of this work is on autorotation, an important category of flow-induced motion that is commonly seen in energy applications such as wind turbines and in aviation applications such as the autogyro. In contrast to existing works on FSI that typically assume prescribed motion of structures in a flow field, this research develops LES based FSI studies for large-scale …

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Shock Tube And Mid-Infrared Laser Absorption Measurements Of Ignition Delay Times And Species Time-Histories, Batikan Koroglu Jan 2016

Shock Tube And Mid-Infrared Laser Absorption Measurements Of Ignition Delay Times And Species Time-Histories, Batikan Koroglu

Electronic Theses and Dissertations

Energy consumption has increased dramatically as the world advances and becomes more industrialized. Over the next twenty five years, the U.S. Department of Energy expects the energy demand to increase by 29% with majority of the new energy coming from natural gas (methane). Another promising fuel source for power generation and transportation is the biofuels. The biofuel use in the US is shown to have increased substantially in the last decade. There are serious environmental concerns associated with greenhouse (e.g. carbon-dioxide) and toxic gas emissions (e.g. nitrogen oxides and aldehydes such as propanal) due to deriving energy from natural gas …

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Phase Transformation And Growth Kinetics In Reaction Zone Between Uranium Alloy And Zirconium Diffusion Barrier, Young Joo Park Jan 2016

Phase Transformation And Growth Kinetics In Reaction Zone Between Uranium Alloy And Zirconium Diffusion Barrier, Young Joo Park

Electronic Theses and Dissertations

U-10wt.%Mo (U10Mo) alloy as a part of monolithic fuel system is being developed under Material Management and Minimization Reactor Conversion (MMMRC) program, tasked with replacing high-enriched uranium (HEU) fuel with low-enriched uranium (LEU) fuel in civilian research and test reactors. Use of U10Mo fuel alloy entails a Zr diffusion barrier to avoid the undesirable interdiffusion and reactions between the U10Mo and Al-alloy cladding. To better understand the interaction between these fuel system constituents, microstructural development and diffusion kinetics in U-Mo-Zr, U-Zr and fuel plate assembly processed by co-rolling and hot isostatic pressing (HIP) were investigated using a variety of analytical …

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Estimating A Freight Mode Choice Model: A Case Study Of Commodity Flow Survey 2012, Nowreen Keya Jan 2016

Estimating A Freight Mode Choice Model: A Case Study Of Commodity Flow Survey 2012, Nowreen Keya

Electronic Theses and Dissertations

This research effort develops a national freight mode choice model employing data from the 2012 Commodity Flow Survey (CFS). While several research efforts have developed mode choice model with multiple modes in the passenger travel context, the literature is sparse in the freight context. The primary reasons being unavailability and/or the high cost associated with the acquisition of mode choice and level of service (LOS) measures – such as travel time and travel cost. The first contribution of the research effort is to develop travel time and cost measures for various modes reported in the CFS. The study considers five …

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Modeling And Compensation For Efficient Human Robot Interaction, Nicholas Paperno Jan 2016

Modeling And Compensation For Efficient Human Robot Interaction, Nicholas Paperno

Electronic Theses and Dissertations

The purpose of this research is to first: identify the important human factors to performance when operating an assistive robotic manipulator, second: develop a predictive model that will be able to determine a user's performance based on their known human factors, and third: develop compensators based on the determined important human factors that will help improve user performance and satisfaction. An extensive literature search led to the selection of ten potential human factors to be analyzed including reaction time, spatial abilities (orientation and visualization), working memory, visual perception, dexterity (gross and fine), depth perception, and visual acuity of both eyes …

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A Framework For Quantifying And Managing Overcrowding In Healthcare Facilities, Abdulrahman Albar Jan 2016

A Framework For Quantifying And Managing Overcrowding In Healthcare Facilities, Abdulrahman Albar

Electronic Theses and Dissertations

Emergency Departments (EDs) represent a crucial component of any healthcare infrastructure. In today's world, healthcare systems face growing challenges in delivering efficient and time-sensitive emergency care services to communities. Overcrowding within EDs represents one of the most significant challenges for healthcare quality that adversely impacts clinical outcomes, patient safety, and overall satisfaction. Research in this area has resulted in creating several ED crowding indices, such as National Emergency Department Overcrowding Scale (NEDOCS) and Emergency Department Work Index (EDWIN) that have been developed to provide measures aimed at mitigating overcrowding. Recently, efforts made by researchers to examine the validity and reproducibility …

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A Neuroergonomics Study Of Brain Eeg's Activity During Manual Lifting Tasks, Awad Aljuaid Jan 2016

A Neuroergonomics Study Of Brain Eeg's Activity During Manual Lifting Tasks, Awad Aljuaid

Electronic Theses and Dissertations

Electroencephalography (EEG) has been shown to be a reliable tool in neuroergonomics studies due to the relatively low cost of brain data collection and limited body invasion. The application of EEG frequency bands (including theta, alpha and beta), enjoyed a wide range of interest in physical and cognitive ergonomics. The psychophysical approach has been used for decades to improve safe work practices by understanding human limitations in manual materials handling. The main objective of this research project was to study the brain's EEG activity expressed by the power spectral density during manual lifting tasks related to: 1) the maximum acceptable …

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Computational Methods For Comparative Non-Coding Rna Analysis: From Secondary Structures To Tertiary Structures, Ping Ge Jan 2016

Computational Methods For Comparative Non-Coding Rna Analysis: From Secondary Structures To Tertiary Structures, Ping Ge

Electronic Theses and Dissertations

Unlike message RNAs (mRNAs) whose information is encoded in the primary sequences, the cellular roles of non-coding RNAs (ncRNAs) originate from the structures. Therefore studying the structural conservation in ncRNAs is important to yield an in-depth understanding of their functionalities. In the past years, many computational methods have been proposed to analyze the common structural patterns in ncRNAs using comparative methods. However, the RNA structural comparison is not a trivial task, and the existing approaches still have numerous issues in efficiency and accuracy. In this dissertation, we will introduce a suite of novel computational tools that extend the classic models …

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Performance Evaluation Of Connectivity And Capacity Of Dynamic Spectrum Access Networks, Osama Al-Tameemi Jan 2016

Performance Evaluation Of Connectivity And Capacity Of Dynamic Spectrum Access Networks, Osama Al-Tameemi

Electronic Theses and Dissertations

Recent measurements on radio spectrum usage have revealed the abundance of under- utilized bands of spectrum that belong to licensed users. This necessitated the paradigm shift from static to dynamic spectrum access (DSA) where secondary networks utilize unused spectrum holes in the licensed bands without causing interference to the licensed user. However, wide scale deployment of these networks have been hindered due to lack of knowledge of expected performance in realistic environments and lack of cost-effective solutions for implementing spectrum database systems. In this dissertation, we address some of the fundamental challenges on how to improve the performance of DSA …

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Application Of Landfill Treatment Approaches For The Stabilization Of Municipal Solid Waste, Stephanie Bolyard Jan 2016

Application Of Landfill Treatment Approaches For The Stabilization Of Municipal Solid Waste, Stephanie Bolyard

Electronic Theses and Dissertations

This research focused on the fundamental requirements of stabilizing a mature landfill using three treatment approaches as well as the implications of discharging leachate organic matter (LOM) to wastewater treatment plants (WWTPs). Three treatment approaches aimed at removing releasable carbon and nitrogen from mature landfills including flushing with clean water, leachate recirculation with ex-situ chemical oxidation, and leachate recirculation with ex-situ chemical oxidation and in-situ aeration were evaluated. After extensive treatment of the waste in the flushing bioreactor (FB) scenarios, the overall biodegradable fraction was reduced relative to mature waste. Leachate quality improved for all FBs but through different mechanisms. …

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Structural Health Monitoring Of Composite Overwrapped Pressure Vessels, Luca Letizia Jan 2016

Structural Health Monitoring Of Composite Overwrapped Pressure Vessels, Luca Letizia

Honors Undergraduate Theses

This work is focusing to study the structural behavior of Composite Overwrapped Pressure Vessels (COPVs). These COPVs are found in many engineering applications. In the aerospace field, they are installed onto spaceships and aid the reorientation of the spacecraft in very far and airless, therefore frictionless, orbits to save energy and fuel. The intent of this research is to analyze the difference in performance of both perfectly intact and purposely damaged tanks. Understanding both the source and location of a structural fault will help NASA engineers predict the performance of COPVs subject to similar conditions, which could prevent failures of …

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Smart Material Actuation And Morphing For Unmanned Aircraft Systems, Caio H. Da Silva Lima Jan 2016

Smart Material Actuation And Morphing For Unmanned Aircraft Systems, Caio H. Da Silva Lima

Honors Undergraduate Theses

The intent of this thesis is to outline the design, analysis, and characterization of an axially compressed piezocomposite actuator and, in particular, to determine the correlation and accuracy of two models used to predict deflection of an axially compressed piezocomposite bimorph. Restrictions in material properties lead to vehicle inefficiencies caused by the discontinuous geometry of deflected control surfaces in unmanned aircraft systems. This performance disadvantage in discrete control surfaces is caused in part by the sharp edges that are formed when the surface is pivoted. Flow continuity over the body of a vehicle is important in minimizing the effects of …

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An Experimental Investigation Of Heat Transfer For Arrays Of Impingement Jets Onto The Featured Surfaces With Cylindrical And Elliptical Raised Surfaces, Marc A. Medina Jan 2016

An Experimental Investigation Of Heat Transfer For Arrays Of Impingement Jets Onto The Featured Surfaces With Cylindrical And Elliptical Raised Surfaces, Marc A. Medina

Honors Undergraduate Theses

This study focuses on multi-jet impingement for gas turbine geometries in which the objective is to understand the influence of the roughness elements on a target surface to the heat transfer. Current work has proven that implementing roughness elements for multi-jet impingement target surfaces has increased heat transfer ranging anywhere from 10-30%. This study has chosen to investigate three different roughness elements, elliptical in cross-section, to compare to smooth surface geometries for multi-jet impingement. An experimental was taken for this study to extend the current knowledge of multi-jet impingement geometries and to further understand the heat transfer performance. A temperature …

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Conjugate Heat Transfer Analysis Of Combined Regenerative And Discrete Film Cooling In A Rocket Nozzle, Charlotte M. Pearce Jan 2016

Conjugate Heat Transfer Analysis Of Combined Regenerative And Discrete Film Cooling In A Rocket Nozzle, Charlotte M. Pearce

Honors Undergraduate Theses

Conjugate heat transfer analysis has been carried out on an 89kN thrust chamber in order to evaluate whether combined discrete film cooling and regenerative cooling in a rocket nozzle is feasible. Several cooling configurations were tested against a baseline design of regenerative cooling only. New designs include combined cooling channels with one row of discrete film cooling holes near the throat of the nozzle, and turbulated cooling channels combined with a row of discrete film cooling holes. Blowing ratio and channel mass flow rate were both varied for each design. The effectiveness of each configuration was measured via the maximum …

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Characterization Of Dispersion And Residual Stress In Nanoparticle Reinforced Hybrid Carbon Fiber Composites, Alex Selimov Jan 2016

Characterization Of Dispersion And Residual Stress In Nanoparticle Reinforced Hybrid Carbon Fiber Composites, Alex Selimov

Honors Undergraduate Theses

Hybrid carbon fiber reinforced composites are a new breed of materials that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress sensing capabilities can be achieved. In order to maximize these properties, it is necessary to achieve a homogeneous dispersion of particulate filler. Utilizing the photoluminescent properties of alumina, it is possible to compare local levels of particle concentration through emission intensities as a way to determine the effectiveness of the tested manufacturing parameters in increasing material homogeneity. Parameters of …

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The Mechanical Response And Parametric Optimization Of Ankle-Foot Devices, Kevin Smith Jan 2016

The Mechanical Response And Parametric Optimization Of Ankle-Foot Devices, Kevin Smith

Electronic Theses and Dissertations

To improve the mobility of lower limb amputees, many modern prosthetic ankle-foot devices utilize a so called energy storing and return (ESAR) design. This allows for elastically stored energy to be returned to the gait cycle as forward propulsion. While ESAR type feet have been well accepted by the prosthetic community, the design and selection of a prosthetic device for a specific individual is often based on clinical feedback rather than engineering design. This is due to an incomplete understanding of the role of prosthetic design characteristics (e.g. stiffness, roll-over shape, etc.) have on the gait pattern of an individual. …

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Intrinsic Modulation Response Modeling And Analysis For Lithographic Vertical-Cavity Surface-Emitting Lasers, Mingxin Li Jan 2016

Intrinsic Modulation Response Modeling And Analysis For Lithographic Vertical-Cavity Surface-Emitting Lasers, Mingxin Li

Electronic Theses and Dissertations

Vertical-cavity surface-emitting lasers (VCSELs) have been greatly improved and successfully commercialized over the past few decades owing to their ability to provide both mode and current confinement that enables low energy consumption, high efficiency and high modulation speed. However, further improvement of oxide VCSELs is limited by the nature of the oxide aperture because of self-heating, internal strain and difficulties in precise size control. In this dissertation, VCSELs using lithographic approach are demonstrated to overcome the limitations of oxide VCSELs, in which an intra-cavity phase shifting mesa is applied to define the device size and provide optical mode and electrical …

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The Woz Recognizer: A Tool For Understanding User Perceptions Of Sketch-Based Interfaces, Jared Bott Jan 2016

The Woz Recognizer: A Tool For Understanding User Perceptions Of Sketch-Based Interfaces, Jared Bott

Electronic Theses and Dissertations

Sketch recognition has the potential to be an important input method for computers in the coming years; however, designing and building an accurate and sophisticated sketch recognition system is a time consuming and daunting task. Since sketch recognition is still at a level where mistakes are common, it is important to understand how users perceive and tolerate recognition errors and other user interface elements with these imperfect systems. A problem in performing this type of research is that we cannot easily control aspects of recognition in order to rigorously study the systems. We performed a study examining user perceptions of …

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Broad Bandwidth Optical Frequency Combs From Low Noise, High Repetition Rate Semiconductor Mode-Locked Lasers, Anthony Klee Jan 2016

Broad Bandwidth Optical Frequency Combs From Low Noise, High Repetition Rate Semiconductor Mode-Locked Lasers, Anthony Klee

Electronic Theses and Dissertations

Mode-locked lasers have numerous applications in the areas of communications, spectroscopy, and frequency metrology. Harmonically mode-locked semiconductor lasers with external ring cavities offer a unique combination of benefits in that they can produce high repetition rate pulse trains with low timing jitter, achieve narrow axial mode linewidths, have the potential for entire monolithic integration on-chip, feature high wall-plug efficiency due to direct electrical pumping, and can be engineered to operate in different wavelength bands of interest. However, lasers based on InP/InGaAsP quantum well devices which operate in the important telecom C-band have thus far been relatively limited in bandwidth as …

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Advanced Blue Phase Liquid Crystal Displays, Daming Xu Jan 2016

Advanced Blue Phase Liquid Crystal Displays, Daming Xu

Electronic Theses and Dissertations

Thin-film transistor (TFT) liquid crystal displays (LCDs) have become indispensable in our daily lives. Their widespread applications range from smartphones, laptops, TVs to navigational devices, data projectors and wearable displays. Over past decades, massive efforts have been invested in device development, material characterization and manufacturing technology. As a result, the performance of LCDs, such as viewing angle, contrast ratio, color gamut and resolution, have been improved significantly. Nonetheless, there are still urgent needs for fast response time and low power consumption. Fast response time helps reduce motion image blurs and enable color sequential displays. The latter is particularly attractive since …

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Dynamic Modeling Of Autorotation For Simultaneous Lift And Wind Energy Extraction, Sadaf Mackertich Jan 2016

Dynamic Modeling Of Autorotation For Simultaneous Lift And Wind Energy Extraction, Sadaf Mackertich

Electronic Theses and Dissertations

The goal of this thesis is to develop a multi-body dynamics model of autorotation with the objective of studying its application in energy harvesting. A rotor undergoing autorotation is termed an Autogyro. In the autorotation mode, the rotor is unpowered and its interaction with the wind causes an upward thrust force. The theory of an autorotating rotorcraft was originally studied for achieving safe flight at low speeds and later used for safe descent of helicopters under engine failure. The concept can potentially be used as a means to collect high-altitude wind energy. Autorotation is inherently a dynamic process and requires …

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A Holistic Framework For Effective Engineering Leadership Development Using 3d Virtual World Simulation, Hamed Almalki Jan 2016

A Holistic Framework For Effective Engineering Leadership Development Using 3d Virtual World Simulation, Hamed Almalki

Electronic Theses and Dissertations

Problems associated with the limited success of traditional engineering leadership development are the absence of embedded real-life industry case studies in leadership development and incorrect applications of leadership strategies in the various contexts. Though recommended programs for enhancing leadership development exist, they lack an examined framework, especially when it comes to leadership development of undergraduate engineering students. In this research effort, the impact of a framework using 3D virtual world simulation and the 4-D Leadership System to enhance the leadership abilities of undergraduate engineering students at the individual and team levels based on industrial leadership case studies was investigated. The …

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Multi-Purpose Device For Analyzing And Measuring Ultra-Short Pulses, Naman Anilkumar Mehta Jan 2016

Multi-Purpose Device For Analyzing And Measuring Ultra-Short Pulses, Naman Anilkumar Mehta

Electronic Theses and Dissertations

Intensity auto correlator is device to measure pulse widths of ultrashort pulses on the order of picoseconds and femtoseconds. I have built an in-house, compact, portable, industry standard intensity auto correlator for measuring ultrashort pulse-widths. My device is suitable for pulse-widths from 500 ps to 50 fs. The impetus for developing this instrument stemmed from our development of a multicore-fiber laser for high power laser applications, which also produces very short pulses that cannot be measured with an oscilloscope. As techniques for measuring short pulse-widths have been well studied, what made my journey exciting was the process of taking an …

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Stress-Induced Phase Change Sintering: A Novel Approach To The Fabrication Of Barium Chloride Transparent Ceramic Scintillators, William Shoulders Jan 2016

Stress-Induced Phase Change Sintering: A Novel Approach To The Fabrication Of Barium Chloride Transparent Ceramic Scintillators, William Shoulders

Electronic Theses and Dissertations

For the precise in-field identification of dangerous radioisotopes, the desire for higher resolution, cheaper, and more rugged gamma-ray scintillator detectors has pushed the materials science community to investigate new compounds and processing techniques.  One particular solution is Eu:BaCl2 transparent ceramics processed by the novel phase-change sintering technique. Typically, optical transparency in BaCl2 would be limited by birefringence scattering at grain boundaries due to mismatch in refractive index. Traditional ceramic processing routes would also predispose this volatile and hygroscopic material to the formation of defects, which interrupt the energy transfer in the scintillation process. Literature shows that these challenges have prevented …

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Study Of Novel Power Semiconductor Devices For Performance And Reliability., Karthik Padmanabhan Jan 2016

Study Of Novel Power Semiconductor Devices For Performance And Reliability., Karthik Padmanabhan

Electronic Theses and Dissertations

Power Semiconductor Devices are crucial components in present day power electronic systems. The performance and efficiency of the devices have a direct correlation with the power system efficiency. This dissertation will examine some of the components that are commonly used in a power system, with emphasis on their performance characteristics and reliability. In recent times, there has a proliferation of charge balance devices in high voltage discrete power devices. We examine the same charge balance concept in a fast recovery diode and a MOSFET. This is crucial in the extending system performance at compact dimensions. At smaller device and system …

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Impact Of Wireless Channel Uncertainty Upon M-Ary Distributed Detection Systems., Zahra Hajibabaei Najafabadi Jan 2016

Impact Of Wireless Channel Uncertainty Upon M-Ary Distributed Detection Systems., Zahra Hajibabaei Najafabadi

Electronic Theses and Dissertations

We consider a wireless sensor network (WSN), consisting of several sensors and a fusion center (FC), which is tasked with solving an $M$-ary hypothesis testing problem. Sensors make $M$-ary decisions and transmit their digitally modulated decisions over orthogonal channels, which are subject to Rayleigh fading and noise, to the FC. Adopting Bayesian optimality criterion, we consider training and non-training based distributed detection systems and investigate the effect of imperfect channel state information (CSI) on the optimal maximum a posteriori probability (MAP) fusion rules and detection performance, when the sum of training and data symbol transmit powers is fixed. Our results …

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