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Articles 3361 - 3390 of 4180
Full-Text Articles in Engineering
A Comparative Analysis Of Green Roof Designs Including Depth Of Media, Drainage Layer Materials, And Pollution Control Media, Matt Kelly
Electronic Theses and Dissertations
Population growth has lead to an increase in development and impervious areas in urban settings. Post-development conditions cause several problems for stormwater management such as limited space for stormwater storage systems and the conveyance of pollution picked up by runoff to near by water bodies. Green Roofs with cisterns have been shown to attenuate the peak flow of storm events and reduce the pollution load leaving a site and entering nearby water bodies. The purpose of this research is to expand the available research data on green roofs with cisterns by investigating the water quality and hydrology effects of different …
Finite Element Modeling Of Tides And Currents Of The Pascagoula River, Qing Wang
Finite Element Modeling Of Tides And Currents Of The Pascagoula River, Qing Wang
Electronic Theses and Dissertations
This thesis focuses on the simulation of astronomic tides of the Pascagoula River. The work is comprised of five steps: 1) Production of a digital elevation model describing the entire Pascagoula River system; 2) Development of an inlet-based, unstructured mesh for inbank flow to better understand the basis of the hydrodynamics within the Pascagoula riverine system. In order to assist in the mesh development, a toolbox was constructed to implement one-dimensional river cross sections into the two-dimensional model; 3) Implementation of a sensitivity analysis of the Pascagoula River two inlet system to examine the inlet effects on tidal propagation; 4) …
Real-Time Trajectory Planning For Groundand Aerial Vehicles In A Dynamic Environment, Jian Yang
Real-Time Trajectory Planning For Groundand Aerial Vehicles In A Dynamic Environment, Jian Yang
Electronic Theses and Dissertations
In this dissertation, a novel and generic solution of trajectory generation is developed and evaluated for ground and aerial vehicles in a dynamic environment. By explicitly considering a kinematic model of the ground vehicles, the family of feasible trajectories and their corresponding steering controls are derived in a closed form and are expressed in terms of one adjustable parameter for the purpose of collision avoidance. A collision-avoidance condition is developed for the dynamically changing environment, which consists of a time criterion and a geometrical criterion. By imposing this condition, one can determine a family of collision-free paths in a closed …
Amorphous Phase Formation In Mechanically Alloyed Fe-Based Systems., Satyajeet Sharma
Amorphous Phase Formation In Mechanically Alloyed Fe-Based Systems., Satyajeet Sharma
Electronic Theses and Dissertations
Bulk metallic glasses have interesting combination of physical, chemical, mechanical, and magnetic properties which make them attractive for a variety of applications. Consequently there has been a lot of interest in understanding the structure and properties of these materials. More varied applications can be sought if one understands the reasons for glass formation and the methods to control them. The glass-forming ability (GFA) of alloys can be substantially increased by a proper selection of alloying elements and the chemical composition of the alloy. High GFA will enable in obtaining large section thickness of amorphous alloys. Ability to produce glassy alloys …
Drive-Based Modeling And Visualization Of Crew Race Strategy And Performance, Jeffrey Cornett
Drive-Based Modeling And Visualization Of Crew Race Strategy And Performance, Jeffrey Cornett
Electronic Theses and Dissertations
Crew race strategy is typically formulated by coaches based on rowing tradition and years of experience. However, coaching strategies are not generally supported by empirical evidence and decision-support models. Previous models of crew race strategy have been constrained by the sparse information published on crew race performance (quarterly 500-meter splits). Empirical research has merely summarized which quarterly splits averaged the fastest and slowest relative to the other splits and relative to the average speed of the other competitors. Video records of crew race world championships provide a rich source of data for those capable and patient enough to mine this …
Numerical Modeling Of Wave Propagation In Nonlinear Photonic Crystal Fiber, Md. Kaisar Khan
Numerical Modeling Of Wave Propagation In Nonlinear Photonic Crystal Fiber, Md. Kaisar Khan
Electronic Theses and Dissertations
In this dissertation, we propose numerical techniques to explain physical phenomenon of nonlinear photonic crystal fiber (PCF). We explain novel physical effects occurred in PCF subjected to very short duration pulses including soliton. To overcome the limitations in the analytical formulation for PCF, an accurate and efficient numerical analysis is required to explain both linear and nonlinear physical characteristics. A vector finite element based model was developed to precisely synthesize the guided modes in order to evaluate coupling coefficients, nonlinear coefficient and higher order dispersions of PCFs. This finite element model (FEM) is capable of evaluating coupling length of directional …
A High-Resolution Storm Surge Model For The Pascagoula Region, Mississippi, Naeko Takahashi
A High-Resolution Storm Surge Model For The Pascagoula Region, Mississippi, Naeko Takahashi
Electronic Theses and Dissertations
The city of Pascagoula and its coastal areas along the United States Gulf Coast have experienced many catastrophic hurricanes and were devastated by high storm surges caused by Hurricane Katrina (August 23 to 30, 2005). The National Hurricane Center reported high water marks exceeding 6 meters near the port of Pascagoula with a near 10-meter high water mark recorded near the Hurricane Katrina landfall location in Waveland, MS. Although the Pascagoula River is located 105 km east of the landfall location of Hurricane Katrina, the area was devastated by storm surge-induced inundation because of its low elevation. Building on a …
Phase-Shifting Haar Wavelets For Image-Based Rendering Applications, Mais Alnasser
Phase-Shifting Haar Wavelets For Image-Based Rendering Applications, Mais Alnasser
Electronic Theses and Dissertations
In this thesis, we establish the underlying research background necessary for tackling the problem of phase-shifting in the wavelet transform domain. Solving this problem is the key to reducing the redundancy and huge storage requirement in Image-Based Rendering (IBR) applications, which utilize wavelets. Image-based methods for rendering of dynamic glossy objects do not truly scale to all possible frequencies and high sampling rates without trading storage, glossiness, or computational time, while varying both lighting and viewpoint. This is due to the fact that current approaches are limited to precomputed radiance transfer (PRT), which is prohibitively expensive in terms of memory …
Improving Airline Schedule Reliability Using A Strategic Multi-Objective Runway Slot Assignment Search Heuristic, Florian Hafner
Improving Airline Schedule Reliability Using A Strategic Multi-Objective Runway Slot Assignment Search Heuristic, Florian Hafner
Electronic Theses and Dissertations
Improving the predictability of airline schedules in the National Airspace System (NAS) has been a constant endeavor, particularly as system delays grow with ever-increasing demand. Airline schedules need to be resistant to perturbations in the system including Ground Delay Programs (GDPs) and inclement weather. The strategic search heuristic proposed in this dissertation significantly improves airline schedule reliability by assigning airport departure and arrival slots to each flight in the schedule across a network of airports. This is performed using a multi-objective optimization approach that is primarily based on historical flight and taxi times but also includes certain airline, airport, and …
Optimizing The Level Of Customization For Products In Mass Customization Systems, Sami Spahi
Optimizing The Level Of Customization For Products In Mass Customization Systems, Sami Spahi
Electronic Theses and Dissertations
Mass customization (MC) was developed to capitalize on the combined benefits of economies of scale and economies of scope. Balancing the tradeoffs involved in an MC system warrants the determination of the degree or the extent of customization. Most of the literature views the degree of customization as how early or how far the customer is integrated in the production cycle, which is defined as the order decoupling point. In this study we are addressing the degree of customization from a product structural perspective. There are two objectives in this research. The first is to develop a unit of measurement …
A Customer Programmable Microfluidic System, Miao Liu
A Customer Programmable Microfluidic System, Miao Liu
Electronic Theses and Dissertations
Microfluidics is both a science and a technology offering great and perhaps even revolutionary capabilities to impact the society in the future. However, due to the scaling effects there are unknown phenomena and technology barriers about fluidics in microchannel, material properties in microscale and interactions with fluids are still missing. A systematic investigation has been performed aiming to develop "A Customer Programmable Microfluidic System". This innovative Polydimethylsiloxane (PDMS)-based microfluidic system provides a bio-compatible platform for bio-analysis systems such as Lab-on-a-chip, micro-total-analysis system and biosensors as well as the applications such as micromirrors. The system consists of an array of microfluidic …
Effect Of Pressure Gradient And Wake On Endwall Film Cooling Effectiveness, Sylvette Rodriguez
Effect Of Pressure Gradient And Wake On Endwall Film Cooling Effectiveness, Sylvette Rodriguez
Electronic Theses and Dissertations
Endwall film cooling is a necessity in modern gas turbines for safe and reliable operation. Performance of endwall film cooling is strongly influenced by the hot gas flow field, among other factors. For example, aerodynamic design determines secondary flow vortices such as passage vortices and corner vortices in the endwall region. Moreover blockage presented by the leading edge of the airfoil subjects the incoming flow to a stagnating pressure gradient leading to roll-up of the approaching boundary layer and horseshoe vortices. In addition, for a number of heavy frame power generation gas turbines that use cannular combustors, the hot and …
Optical Solitons In Periodic Structures, Konstantinos Makris
Optical Solitons In Periodic Structures, Konstantinos Makris
Electronic Theses and Dissertations
By nature discrete solitons represent self-trapped wavepackets in nonlinear periodic structures and result from the interplay between lattice diffraction (or dispersion) and material nonlinearity. In optics, this class of self-localized states has been successfully observed in both one-and two-dimensional nonlinear waveguide arrays. In recent years such lattice structures have been implemented or induced in a variety of material systems including those with cubic (Kerr), quadratic, photorefractive, and liquid-crystal nonlinearities. In all cases the underlying periodicity or discreteness leads to new families of optical solitons that have no counterpart whatsoever in continuous systems. In the first part of this dissertation, a …
High Temperature Packaging For Wide Bandgap Semiconductor Devices, Brian Grummel
High Temperature Packaging For Wide Bandgap Semiconductor Devices, Brian Grummel
Electronic Theses and Dissertations
Currently, wide bandgap semiconductor devices feature increased efficiency, higher current handling capabilities, and higher reverse blocking voltages than silicon devices while recent fabrication advances have them drawing near to the marketplace. However these new semiconductors are in need of new packaging that will allow for their application in several important uses including hybrid electrical vehicles, new and existing energy sources, and increased efficiency in multiple new and existing technologies. Also, current power module designs for silicon devices are rife with problems that must be enhanced to improve reliability. This thesis introduces new packaging that is thermally resilient and has reduced …
Design And Optimization Of Nanostructured Optical Filters, Jeremiah Brown
Design And Optimization Of Nanostructured Optical Filters, Jeremiah Brown
Electronic Theses and Dissertations
Optical filters encompass a vast array of devices and structures for a wide variety of applications. Generally speaking, an optical filter is some structure that applies a designed amplitude and phase transform to an incident signal. Different classes of filters have vastly divergent characteristics, and one of the challenges in the optical design process is identifying the ideal filter for a given application and optimizing it to obtain a specific response. In particular, it is highly advantageous to obtain a filter that can be seamlessly integrated into an overall device package without requiring exotic fabrication steps, extremely sensitive alignments, or …
Value Mapping Framework Involving Stakeholders For Supply Chain Improvement When Implementing Information Technology Projects, Karla Moore
Electronic Theses and Dissertations
Successful Supply Chain Management (SCM) depends on how well an organization performs internal and external communications with trading partners, executes the logistics component, and understands/monitors related costs of conducting its business. The use of information technology (IT) is considered a prerequisite for the effective control of today's complex supply chains. Increased communication technology has redefined how businesses work together, raised customer expectations, and placed new demands on supply chain performance. IT components with proven and rapid return-on-investment are favored to support critical supply chain processes such as leaner manufacturing processes, consumer-driven supply chains, and customer responsiveness. The use of IT …
Design Of An Adaptive Autopilot For An Expendable Launch Vehicle, Clinton Plaisted
Design Of An Adaptive Autopilot For An Expendable Launch Vehicle, Clinton Plaisted
Electronic Theses and Dissertations
This study investigates the use of a Model Reference Adaptive Control (MRAC) direct approach to solve the attitude control problem of an Expendable Launch Vehicle (ELV) during its boost phase of flight. The adaptive autopilot design is based on Lyapunov Stability Theory and provides a useful means for controlling the ELV in the presence of environmental and dynamical uncertainties. Several different basis functions are employed to approximate the nonlinear parametric uncertainties in the system dynamics. The control system is designed so that the desire dresponse to a reference model would be tracked by the closed-loop system. The reference model is …
An Adaptive Multiobjective Evolutionary Approach To Optimize Artmap Neural Networks, Assem Kaylani
An Adaptive Multiobjective Evolutionary Approach To Optimize Artmap Neural Networks, Assem Kaylani
Electronic Theses and Dissertations
This dissertation deals with the evolutionary optimization of ART neural network architectures. ART (adaptive resonance theory) was introduced by a Grossberg in 1976. In the last 20 years (1987-2007) a number of ART neural network architectures were introduced into the literature (Fuzzy ARTMAP (1992), Gaussian ARTMAP (1996 and 1997) and Ellipsoidal ARTMAP (2001)). In this dissertation, we focus on the evolutionary optimization of ART neural network architectures with the intent of optimizing the size and the generalization performance of the ART neural network. A number of researchers have focused on the evolutionary optimization of neural networks, but no research has …
Prevention Of Environmentally Induced Degradation In Carbon/Epoxy Composite Material Via Implementation Of A Polymer Based Coati, Bradford Tipton
Prevention Of Environmentally Induced Degradation In Carbon/Epoxy Composite Material Via Implementation Of A Polymer Based Coati, Bradford Tipton
Electronic Theses and Dissertations
As the use of fiber reinforced plastics increases in such industries as aerospace, wind energy, and sporting goods, factors effecting long-term durability, such as environmental exposure, are of increasing interest. The primary objectives of this study were to examine the effects of extensive environmental exposure (specifically UV radiation and moisture) on carbon/epoxy composite laminate structures and to determine the relative effectiveness of polymer-based coatings at mitigating degradation incurred due to such exposure. Carbon/epoxy composite specimens, both coated and uncoated, were subjected to accelerated weathering in which prolonged outdoor exposure was simulated by controlling the radiation wavelength (in the UV region), …
Improving Business Performance Through The Integration Of Human Factors Engineering Into Organizations Using A Systems Engineeri, Monica Philippart
Improving Business Performance Through The Integration Of Human Factors Engineering Into Organizations Using A Systems Engineeri, Monica Philippart
Electronic Theses and Dissertations
Most organizations today understand the valuable contribution employees as people (rather than simply bodies) provide to their overall performance. Although efforts are made to make the most of the human in organizations, there is still much room for improvement. Focus in the reduction of employee injuries such as cumulative trauma disorders rose in the 80 s. Attempts at increasing performance by addressing employee satisfaction through various methods have also been ongoing for several years now. Knowledge Management is one of the most recent attempts at controlling and making the best use of employees knowledge. All of these efforts and more …
Low Reynolds Number Water Flow Characteristics Through Rectangular Micro Diffusers/Nozzles With A Primary Focus On Major/Minor P, Kyle Hallenbeck
Low Reynolds Number Water Flow Characteristics Through Rectangular Micro Diffusers/Nozzles With A Primary Focus On Major/Minor P, Kyle Hallenbeck
Electronic Theses and Dissertations
The field of microfluidics has recently been gathering a lot of attention due to the enormous demand for devices that work in the micro scale. The problem facing many researchers and designers is the uncertainty in using macro scaled theory, as it seems in some situations they are incorrect. The general idea of this work was to decide whether or not the flow through micro diffusers and nozzles follow the same trends seen in macro scale theory. Four testing wafers were fabricated using PDMS soft lithography including 38 diffuser/nozzle channels a piece. Each nozzle and diffuser consisted of a throat …
Empirical Relationships Betweenload Test Data And Predicted Compression Capacity Of Augered Cast-In-Place Piles In Predominantly, Donald Mccarthy
Empirical Relationships Betweenload Test Data And Predicted Compression Capacity Of Augered Cast-In-Place Piles In Predominantly, Donald Mccarthy
Electronic Theses and Dissertations
Augered Cast-In-Place (ACIP) Piles are used in areas were the loading from a superstructure exceeds the soil bearing capacity for usage of a shallow foundation. In Northwest Florida and along the Gulf Coast, ACIP piles are often utilized as foundation alternatives for multi-story condominium projects. Data from 25 compression load tests at 13 different project sites in Florida and Alabama were analyzed to determine their individual relationships between anticipated and determined compression load capacity. The anticipated capacity of the ACIP pile is routinely overestimated due to uncertainties involved with the process of estimating the compressive capacity and procedures of placing …
Low Noise, High Repetition Rate Semiconductor-Based Mode-Locked Lasers For Signal Processing And Coherent Communications, Franklyn Quinlan
Low Noise, High Repetition Rate Semiconductor-Based Mode-Locked Lasers For Signal Processing And Coherent Communications, Franklyn Quinlan
Electronic Theses and Dissertations
This dissertation details work on high repetition rate semiconductor mode-locked lasers. The qualities of stable pulse trains and stable optical frequency content are the focus of the work performed. First, applications of such lasers are reviewed with particular attention to applications only realizable with laser performance such as presented in this dissertation. Sources of timing jitter are also reviewed, as are techniques by which the timing jitter of a 10 GHz optical pulse train may be measured. Experimental results begin with an exploration of the consequences on the timing and amplitude jitter of the phase noise of an RF source …
Ultrashort Laser Pulse Interaction With Photo-Thermo-Refractive Glass, Leo Siiman
Ultrashort Laser Pulse Interaction With Photo-Thermo-Refractive Glass, Leo Siiman
Electronic Theses and Dissertations
Photo-thermo-refractive (PTR) glass is an ideal photosensitive material for recording phase volume holograms. It is a homogeneous multi-component silicate glass that demonstrates all the advantages of optical glass: thermal stability, high laser damage threshold, and a wide transparency range. Moreover the ability to record phase patterns (i.e. spatial refractive index variations) into PTR glass has resulted in the fabrication of volume holograms with diffraction efficiency greater than 99%. The conventional method of recording a hologram in PTR glass relies on exposure to continuous-wave ultraviolet laser radiation. In this dissertation the interaction between infrared ultrashort laser pulses and PTR glass is …
Cholesteric Liquid Crystal Photonic Crystal Lasers And Photonic Devices, Ying Zhou
Cholesteric Liquid Crystal Photonic Crystal Lasers And Photonic Devices, Ying Zhou
Electronic Theses and Dissertations
This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is …
Integrated Optical Spr (Surface Plasmon Resonance) Sensor Based On Optoelectronic Platform, Hyungseok Bang
Integrated Optical Spr (Surface Plasmon Resonance) Sensor Based On Optoelectronic Platform, Hyungseok Bang
Electronic Theses and Dissertations
Current major demands in SPR sensor development are system miniaturization and throughput improvement. Structuring an array of integrated optical SPR sensor heads on a semiconductor based optoelectronic platform could be a promising solution for those issues, since integrated optical waveguides have highly miniaturized dimension and the optoelectronic platform enables on-chip optical-to-electrical signal conversion. Utilizing a semiconductor based platform to achieve optoelectronic functionality poses requirements to the senor head; the sensor head needs to have reasonably small size while it should have reasonable sensitivity and fabrication tolerance. This research proposes a novel type of SPR sensor head and demonstrates a fabricated …
Extended Focus Range High Resolution Endoscopic Optical Coherence Tomography, Kye-Sung Lee
Extended Focus Range High Resolution Endoscopic Optical Coherence Tomography, Kye-Sung Lee
Electronic Theses and Dissertations
Today, medical imaging is playing an important role in medicine as it provides the techniques and processes used to create images of the human body or parts thereof for clinical purposes (medical procedures seeking to reveal, diagnose or examine disease) or medical science (including the study of normal anatomy and function). Modalities are developing over time to achieve the highest possible resolution, speed of image acquisition, sensitivity, and specificity. In the past decade, advances in optics, fiber, as well as laser technology have enabled the development of noninvasive optical biomedical imaging technology that can also be applied to endoscopy to …
Design Of An Active Orthotic Device For Joint Management., Steven Clayton Anderson
Design Of An Active Orthotic Device For Joint Management., Steven Clayton Anderson
Electronic Theses and Dissertations
Existing treatment programs and procedures are incapable of addressing the complications encountered with patients who experience spasticity and hypertonia related joint contractures. Current passive therapy procedures and devices are only capable of managing the extent of joint contractures on patients with chronic and acute onset severe neurological disorders. The project was conceived as a means to develop an active device that is capable of adapting to the state of the joint to mange the extent of contractures and to permit consideration for the prevalence of spastic activity episodes and hypertonia. The project focused on the design of the physical prototype …
Risk Assessment For Hazardous Materials Incident, Washington County, Tennessee: Road Transportation, Rail Transportation, And Hazardous Materials Storage., Steed Kenlee Stagnolia
Risk Assessment For Hazardous Materials Incident, Washington County, Tennessee: Road Transportation, Rail Transportation, And Hazardous Materials Storage., Steed Kenlee Stagnolia
Electronic Theses and Dissertations
This study was conducted to provide a quantitative risk assessment for road transportation, railway transportation, and storage of hazardous materials in Washington County, Tennessee. A roadside survey, railroad hazardous materials survey, and a chemical inventory were conducted. It revealed an estimated 267,858 HAZMAT shipments per year on primary and secondary roadways and an estimated total of 9.4 x 109 tons of HAZMAT shipped by rail per year. There are 49 facilities that store a daily average of 33,722,700 lbs of HAZMAT. The risk of a hazardous materials incident occurring in Washington County is highest for Interstate transportation. The risk for …
Intrusion Detection And Response Model For Mobile Ad Hoc Networks., Sathishkumar Alampalayam 1974-
Intrusion Detection And Response Model For Mobile Ad Hoc Networks., Sathishkumar Alampalayam 1974-
Electronic Theses and Dissertations
This dissertation presents a research whose objective is to design and develop an intrusion detection and response model for Mobile Ad hoc NETworks (MANET). Mobile ad hoc networks are infrastructure-free, pervasive and ubiquitous in nature, without any centralized authority. These unique MANET characteristics present several changes to secure them. The proposed security model is called the Intrusion Detection and Response for Mobile Ad hoc Networks (IDRMAN). The goal of the proposed model is to provide a security framework that will detect various attacks and take appropriate measures to control the attack automatically. This model is based on identifying critical system …